In order to realise the prediction of the diffusion trend of chemical gases under toxic, flammable, and explosive conditions, this article used a multiple regression model and a back propagation (BP) neural network model, established two kinds of leakage gas diffusion models based on Fluent simulation data. First, the multivariate function relation between multiple influencing factors and diffusion concentration is established by using linear fitting method, i.e. multivariate regression model. Second, according to the large number and non-linearity of Fluent simulation data of leakage gas, a three-layer BP neural network prediction model for leakage gas, wind speed, X-axis diffusion distance, and Y-axis diffusion distance was established by using BP neural network algorithm. Under the same data conditions, the prediction error of BP neural network prediction model is smaller than that of multivariate reversion model, and the fitting degree is high, but the stability of multiple linear regression is better.

An online modelling method for secondary path of two distinct variable step-size strategies based on the filtered-x least square (FXLMS) algorithm is proposed. In this method, the variable step-size strategy with two distinct steps is used, and two variable step-size strategies are used before and after the secondary path modelling process converges, so that the convergence rate is guaranteed. At the same time, it can effectively avoid the fluctuation after the system converges and improve the stability and modelling accuracy of the system. Due to the white noise, the signal of secondary path modelling will affect the control part. A white noise control strategy is proposed to adjust the white noise according to the change of the step-size of the secondary path. On the premise of ensuring identification speed and precision, the influence of white noise on the control part is eliminated as far as possible. Compared to the existing methods, the simulation result shows that the proposed method can significantly improve the modelling accuracy of the secondary path while ensuring the convergence speed and has a better performance in vibration control effects.

The non-metallic valve spool has the advantages of safety, stability, and biocompatibility. In order to expand the application of non-metallic elastic valve spool in medical water jet, a check valve spool structure with double-protrusion structure of polyurethane is designed to replace the metal valve spool and the spring thus achieves control of the fluid. Based on the non-linear mechanical response of elastic materials, ANSYS Workbench was used to calculate the stress and deformation under the different friction coefficient and pre-compression. The results show that the static sealing effect of the valve spool is best when the pre-compression is 0.1 mm and the friction coefficient between the spool and the valve sleeve is 0.2. Then, based on bidirectional fluid–solid coupling analysis through Fluent, the flow field changes during the interaction between fluid and elastic material and the key bearing position of the valve spool are clarified. The results shows that size, processing quality, and material properties of the inner ring protrusion will determine the dynamic sealing performance of elastic valve spool.

In order to study the lubrication and anti-wear mechanism of the pit-type bionic non-smooth surface used in the low-speed and high-torque seawater hydraulic motor valve plate pair, the discrete phase models of the four pits are simulated under different working conditions. In this study, the trajectories of different diameters particles in the hemispherical pits are analysed, which can reflect the movement of different sizes and masses wear debris in the pits. The discrete phase concentration distributions of the four-kind pits, hemispherical pits, cylindrical pits, four-prism pits and tri-prism pits, are simulation under the same working conditions, which reflects the effect of pit geometry on the movement of wear debris. The discrete phase concentration distributions of four pits moving at different rotation speeds and different rotation radii are calculated, which indicates that the rotation speed of the motor and the distribution of pits on the valve plate will affect the ability of the pit to store wear debris.

In order to eliminate the plug stem phenomenon and reduce the transmission power consumption of the self-developed integrated tobacco stalk pull-out crusher transmission mechanism when the culms are pulled out at high speed in the field, based on the analysis of the reasons of plug stem, a new rubber-type roller pair transmission mechanism with easy disassembly and adjustable spacing was designed. Through the force analysis, the mathematical model of the force, deformation and transmission power of the tobacco stalk during the extrusion and transportation phase was obtained, and the test platform of the tobacco stalk pull-out crusher transmission mechanism was built to carry out the orthogonal rotation combination test. The test results show that the optimal working parameter combination within the range of test factors is: the roller speed is 530 r/min, the II pair of roller spacing is 90 mm, the III pair of roller spacing is 30 mm, and the tobacco stalk feeding rate is 1.5 s/n. At this time, the plugging rate of stem is 2.22%, the transmission power consumption is 645 W, and the actual average leak stalk rate obtained by repeating 10 tests under this parameter is 3.33%, and the actual transmission power consumption is 684 W, the actual plugging rate of stem and transmission power are basically consistent with the optimized values, indicating that the improved design structure is reasonable, and the established regression model is basically reliable.

The lifting mechanism on the transfer vehicle is a common electromechanical–hydraulic system. In order to overcome the non-linear and interference that exist in the hydraulic boom combined motion process, a dynamic surface adaptive fuzzy sliding mode control method is proposed. The Lyapunov function and virtual control base on inversion of the sliding mode control are designed, the dynamic surface control is used to calculate the derivative of the virtual control, and the adaptive control is applied to estimate the parameter. Furthermore, the fuzzy control is applied to fuzzification the switching item of the sliding surface. Verified by simulation, the designed sliding mode controller has high control accuracy and strong robustness and eliminates system chatter.

Based on the mixed-lubrication theory, a numerical simulation model of a reciprocating seal is established. The model includes finite element, fluid mechanics, contact mechanics and deformation mechanics analyses. The hydrodynamic analysis uses elastohydrodynamic lubrication theory and inverse hydrodynamic lubrication to obtain the relationship between fluid pressure and film thickness, while the contact mechanics analysis obtains the relationship between the asperity contact pressure and film thickness. The influence of the coefficient matrix and static contact pressure is calculated by the finite element analysis. The coupling relationship among the fluid pressure, asperity contact pressure and static contact pressure is provided by the influence coefficient method of the deformation mechanics analysis. The calculation results of the numerical model are verified by experimental results, which are measured by the bench test developed by the authors.

The velocity of the free-piston assembly (FPA) of the hydraulic free-piston engine (HFPE) is very high, which is up to 10 m/s. In order to avoid the collision of the FPA to the cylinder head when the FPA moves towards the dead centres, the cushioning device must be involved. A cushioning structure which combines the sidestep-shape cushion and flute-shape cushion is proposed according to the working principle of the HFPE. The mathematical model of the cushioning is set up, and key parameters are obtained. AMESim is employed to analyse the cushioning process and the influence of the key parameters on the cushioning process. The optimised parameters are obtained according to the simulation. The test rig is established to verify the effectiveness of the cushioning structure according to the optimised parameters. The experiment results show that the proposed cushioning structure is reliable. The maximum pressure during the cushioning process is 19 MPa, and cushioning time is 12 ms. The cushioning structure has little influence on the starting process of HFPE.

In order to improve the robustness and low-speed performance of continuous rotary electro-hydraulic servo system under influences of dynamic uncertainties, parametric perturbation, friction, other non-linear properties, and uncertainties, the robust control strategy was proposed with Adaboost prediction. Firstly, basing on the system mathematic model, the model with structured uncertainty and generalised state equation was established with parametric perturbation and external disturbances, and then the robust controller was developed by adopting theory. Furthermore, Adaboost algorithm based on radial basis function (RBF) neural network was applied to design the system feedback mechanism, so the multiple weak neural network learners were obtained by using Adaboost algorithm to train system actual output and input. Also, these weak neural network learners constituted a strong learner to predict the electro-hydraulic servo system output and calculate the predictive error so as to adjust the system robust control output, so the real-time control was carried out by the robust controller. Some comparative simulated results are obtained to verify the proposed controller guarantees performances of low speed, tracking accuracy, and ability of anti-interference, which greatly expands the band of frequency response and improve the system robustness.

Steering differential performance is an important factor affecting the driving performance of the vehicle. A hydraulic control method is proposed for the differential system of the hydraulic wheel-driving off-road vehicle, and the driving force equalisation technique is adopted to realise the adaptive steering differential under the different speed modes. Based on the analysis of the working principle of static pressure driving steering differential, the mathematical model of the steering differential system is derived by using kinematics and dynamics theory. The hydraulic driving system and multibody dynamics model are established by AMESim and LMS Virtual.Lab Motion, respectively, and joint simulation is carried out. The experimental scheme is designed for the typical working conditions in the simulation, and the rotation speed and the pressure differential of the motor in the steady state are analysed. The experimental results are consistent with the theoretical analysis and simulation results, which indicate that the system can achieve a better steering differential performance. This research provides a new idea for the study of the steering performance of the hydraulic wheel-driving walking system, which is of great practical significance to improve the driving performance of off-road vehicles under the complex terrain.

The force of a lifting cylinder is the main factor of the alternating stress of scissors arms in a scissors aerial work platform, which seriously affects the fatigue life of structures. Aiming at this problem, the installation position parameters that affect the force of the lifting cylinder was simulated and optimised. First, the mechanical model of the lifting system was established based on the principle of virtual work, and the position parameters that affect the force of lifting cylinder were determined. Then, the advanced modeling environment for performing simulation of engineering systems (AMESim) simulation model was used to simulate the lifting process of the lifting system, and the reliability of the simulation model was verified by the pressure test of the hydraulic system. Finally, based on the simulation model, the design of experiment method was used to optimise the installation position of the lifting cylinder in the design and development environment of AMESim, and the optimisation effect was verified through the test on a real vehicle. The result shows that the peak load of the lifting cylinder is reduced by ∼12%, and the average of the steady-state value decreases by ∼20% after the installation position is optimised.

Aiming at solving the problem of low unloading sensitivity, bad dynamic performance and poor stability of high-pressure and large-flow relief valve in hydraulic support system, a new differential type of high-pressure and large-flow relief valve, functioned by high water-based hydraulic medium, is designed. Through analysing the influence of spool form, elastic element, and working principle on valve performance, a structural scheme of large-flow and high-pressure safety valve is put forward. The three-dimensional fluid–solid coupling model of differential safety valve is established; through ADINA software, three-dimensional fluid–solid coupling simulation of relief valve's orifice from shutdown to full opening is carried out to analyse the distribution of internal pressure in the flow field of the safety valve and the pressure change of the structure field. The physical simulation model of safety valve is established by using AMESim software, and the dynamic performance of safety valve is simulated under the given signal of nominal flow and small flow. According to the design structure, the safety valve with the rated flow of 3000 L/min is manufactured and tested. The simulation and experimental results show that the safety valve has good dynamic performance and high sensitivity..

In order to analyse the influence of different performance indexes on the working reliability of a tractor multi-way valve. The grey correlation theory is introduced into the reliability analysis of multi-way valves. Combined with the multi-way valve failure mode, the reliability index is proposed, and then a grey relational model and the reliability evaluation sequence of multi-way valves are established. The reliability of multi-way valve is analysed by traditional grey relational analysis and improved weighted grey correlation analysis, respectively. Although both methods produced the same optimal prototype, the dynamic identification coefficient introduced by the latter can effectively suppress the influence of singular values on the correlation sequence in the prototype sequence. The analysis process is simplified, and the accuracy of calculation is improved. Meanwhile, the identification degree of the sequence of the prototype is increased. In addition, the improved weighted grey relational analysis method uses the entropy weight method to assign weight coefficients. This method can reflect the influence degree of different sequence points on the overall correlation degree objectively and improve the reliability of the analysis results. Finally, the correctness of the optimal prototype is verified by comparing the experimental data. The reliability evaluation standard of the tractor multi-way valve is obtained.

It is generally difficult to obtain accurate optimisation functions during parameters matching and optimisation process of the hybrid system, especially in the optimisation variable field containing both a continuous set and a discontinuous set and when the control strategy has an important influence on the system performance. To aim at the fuel economy of the parallel hydraulic hybrid system, a global parameter matching and control strategy based on the simulation model were proposed. The AMESim simulation model as the judgment module of the optimisation algorithm was used to match and optimise the main parameters and control strategies in the hybrid system. The communication of underlying parameters was developed by the VBA in EXCEL platform. Parameters match was implemented on a truck crane chassis in practice. The test results indicated that the rate of fuel saving reached 15.2%, which was generally consistent with the theoretical analysis. The parameters were met the energy-saving requirements of hybrid vehicles.

This study proposes an active-controlled hydraulic low-frequency vibration isolator. The vibration isolator can achieve large equivalent mass and quasi-zero dynamic stiffness by combining the fluid inerter with the hydraulic active compensation. Thus, good vibration isolation performance at ultra-low frequency can be realised. The model for the dynamics of the device is set up. The principle of low-frequency vibration isolation is explicated. The natural frequency and its influencing factors are analysed. Finally, preliminary experimental research works are carried out. The results indicate that low-frequency vibration can be effectively isolated by the device proposed in this study.

The effect of cavitation on vibration characteristics of a two-stage throttle valve is experimentally studied by changing inlet pressure, outlet pressure and opening. The shadow photograph of the flow field in the throttle is obtained by a high-speed camera, and the signal of vibration induced by cavitation of the two-stage throttle is obtained by an acceleration sensor. It can be concluded that the fixed cavitation and the travelling cavitation in the two-stage throttle valve occur at the back of the throttle orifice. The effect of cavitation on vibration intensity and power spectral density is obvious. There are two frequency peaks in the spectrum, which are located in the vicinity of 7.5 and 12.5 kHz, respectively. These peaks correspond to travelling cavitation and fixed cavitation. The cavitation vibration intensity increases with the increase in the cavitation intensity, and the centre frequency of the signal peak near 7.5 kHZ is also moving towards the low frequency.

This paper proposed a new method of fault diagnosis based on Noise Assisted Multivariate Empirical Mode Decomposition (NA-MEMD) and Fuzzy Recurrent Cerebellar Model Articulation Controller (FRCMAC) Neural Networks. Aiming at the problem that during the use of the NA-MEMD method, the white noise amplitude parameter needs to be selected by artificial experience, a method of using Genetic Algorithm (GA) to optimize its auxiliary white noise parameters is proposed, which facilitates the use of NA-MEMD. We proposed a novel FRCMAC structure which improved Learning efficiency and dynamic response speed than traditional CMAC structure. First, the GA-NA-MEMD method is applied to process the vibration signals of rolling bearings, and the signals are decomposed into a group of Intrinsic Mode Functions (IMFs). Then use energy moments of IMFs as fault feature vectors to train FRCMAC neural network, a neural network structure suitable for rolling bearing fault diagnosis is obtained. Finally, the data from bearing data center of Case Western Reserve University is used to prove that the fault diagnosis method proposed in this paper is superior to other methods in diagnosis time and precision, which can meet the training requirements more quickly with limited training samples and fault diagnosis results more accurate.

In order to improve the pressure distribution, the aerostatic circular thrust bearing with single supply hole was studied. In the computational fluid dynamics (CFD) simulation, the laminar model, the turbulent model, the mixture model of laminar and turbulent were used simultaneously. The micro-characteristics of the gas flows were analysed based on the simulation results. One test rig was built for measuring the pressure distribution with the single test hole, and the calculated and experimental results were compared. The results showed that when the gas film clearance is small and the gas flow is subsonic completely, the whole gas flow is laminar flow, which should be calculated based on the laminar model and when the gas film thickness is large and there is supersonic flow in some region, which should be calculated according to the mixture model; at the same time, there is no surface of discontinuity for Mach number and pressure distribution, and no shock, and the pressure is recovered due to the boundary layer separation, the change of the flow state and the change of viscosity. The method for testing the pressure distributions with a single test hole is effective.

In order to determine the significance and importance order of the jet performance caused by fan nozzle's geometric parameters of aero-engine online cleaning equipment, the orthogonal experiment method, standard k–ɛ turbulence model and volume of fluid (VOF) two-phase flow algorithm are used to research the jet of fan nozzle. The sensitivity of nozzle contraction angle, nozzle area ratio, nozzle incision angle, nozzle exit thickness and offset to the influence of fan nozzle spray angle was verified by range analysis and variance analysis. The results of the two analysis methods consistently show that the main order of influence of the geometric parameters of fan nozzle on spray angle is nozzle area ratio, nozzle incision angle, nozzle exit thickness, offset and nozzle convergence angle. The former two have more influence on the spray angle than the others. Finally, the simulation results and orthogonal test results are verified by the injection experiment of the fan nozzle. The jet shape is mainly determined by the nozzle area ratio and incision angle. The larger the incision angle and the nozzle area ratio are, the smaller the spray angle becomes.

Based on the theories of heat transfer and the method of computational fluid dynamics, a liquid–solid mathematical model of heat transfer of an axial piston hydraulic motor pump is constructed in this study. Through the finite volume method, the model with different cooling runners has been solved. Meanwhile, the oil flow regularity of runner and temperature distribution of the motor pump and oil duct has been obtained. On the basis of the model of long-strip runner, the influence of ambient temperature on the motor pump's temperature rise has been analysed. The result shows that the cooling channels on the housing of the hydraulic motor pump effectively reduce the temperature rise, and a long-strip channel is for optimum cooling. The average temperature rise of the motor pump increases linearly with the increase of ambient temperature.

If the magnetic resonance coupling-based wireless power transmission system has multiple receivers, cross-coupling will occur between the transmitter and the receiver, resulting in the variation of transmission characteristics when compared with the case of a single receiver. To solve this problem, a mutual inductance coupling circuit model for double-relay and multi-load transmission system and a calculation model for mutual inductance between solenoid coils in the same plane have been built to study the transmission characteristics of the system through simulation and testing. The study results show that: the cross-coupling effect between the transmitter and the receiver will cause resonance frequency shift, or even lead to the variation of resonance frequency splitting characteristic; when compared with a single-load system, the multi-load system may increase in total transmission power and efficiency; generally, with the introduction of additional receivers, the receiving power and efficiency of the original loads will decrease; along with the increase in circuit spacing and the decrease in cross-coupling, the transmission characteristics will gradually regress to the state of a single-load system. In this article, the calculation model for mutual inductance is correct and the maximum relative error in these calculating examples is 5.28%.

Due to the uncertainties caused by high non-linearity, friction, leakage and other external factors existing in the flight simulator with continuous rotary electro-hydraulic servo motor and the traditional control strategies discontenting with the high-performance requirements, the mathematical model of continuous rotary electro-hydraulic position servo system is established and the compound control theory combining proportional-integral-derivative (PID) and the predictive function control (PFC) method is proposed. In order to enable the servo system to estimate the influence of uncertainties and correct it by repeating online optimisation continuously, PID–PFC compound controller basing on the structure of internal model control is designed and then applied to continuous rotary electro hydraulic servo system. The simulation results show that compared with the traditional PID, PFC controller, PID–PFC compound control can effectively inhibit the interferences of the electro-hydraulic servo system, and greatly improve the response speed and tracking performances and expanding the system frequency band width. The accurate control of motor's position can be realised by applying PID–PFC compound control, which can make the servo system has stronger robustness.

A set of semi-physical simulation system based on real-time working simulation platform tools (Matlab/RTW) was established for electro-hydraulic proportional position servo system in the development of missile weapons and other equipment. The system is mainly composed of hydraulic system consisting of hydraulic actuators and Simulink simulation model. It is a closed-loop real-time simulation system of physical equipment in the loop. The simulation and experiment of proportional servo control system show that the system has high simulation real-time performance, the positioning accuracy and control stability. Two controllers are designed for different application conditions, which can obtain the good practicality and feasibility.

Fire water monitor is an important part of a sprinkler system. In this study, the jet flow characteristics of the external jet of the fire water monitor are studied. The water jet system is used to launch the water jet experiment under six pressures. A high-speed camera is used to obtain the water jet images. The feature extraction of water jet is obtained based on image processing technology, and it is used to study the jet diffusion angle and bundling of the fire water monitor under different pressures. The results of this study show that the jet pressure is an important parameter, which has a great influence on the cluster and surface characteristics of the jet. The fire water monitor has a limited range of pressure. When the pressure is constant, the jet distance determines the size of the air acting on water column, so the cluster and surface characteristics of the water column have changed obviously with the jet distance.

In order to investigate the internal flow field of an axial blood pump, two-dimensional (2D) particle image velocimetry (PIV) was applied to test the blood pump under three different conditions. Acquiring the images of inlet, front guide vane, impeller, back guide vane and outlet area, the distribution of internal flow field was then analysed. The rotation speed of the blood pump was set to 6000, 7000 and 8000 r/min, respectively. The results show that the flow field of blood pump is stable relatively at the inlet area. Some vortices and reflux existed due to the block of guide vane in the import and impeller area. With the increase of rotating speed, the overall disturbance degree of flow field increases. Under the condition of low rotation speed, the flow field acceleration is insufficient. Under the medium rotation speed condition, the flow field is stable and the velocity distribution is even. Under the condition of high rotating speed, the number of vortices in the flow field increased significantly, the flow separation phenomenon at the impeller was obvious and more unstable flow appeared at the back guide vanes and outlet area.

In civil aviation ground deicing system, the traditional reciprocating pump is often used as the power supply device to ensure the physical and chemical properties of high viscosity deicing fluid. The traditional reciprocating pump exist the problem of flow fluctuation. A new horizontal space multiphase crankshaft pump is proposed to suppress the flow fluctuation. The new type of pump adopts segmented crankshaft: each crank pin on the crankshaft drives two connecting rods simultaneously. The connecting rod drives the pistons distributed on both sides of the crankshaft to achieve linear reciprocating motion. Three sections of the crank pin are arranged by 120° phase space circular, and this kind of crankshaft implements multiple phase coupling of piston movement. The hydraulic cylinder adopts the horizontal layout, so the machine structure presents spatial symmetry. A mathematical model of two connecting rods driven by crankpin is established for the new type of pump. The kinematics equation of the piston is solved by the analytical method and then the flow rate of the pump is calculated. In contrast with the experimental data, the new pump can effectively reduce the flow fluctuation.

Cavitation is a common phenomenon in industrial control valves, which has a strong influence on the internal flow. Herein, characteristics of cavitation flow inside conical throttle valve have been numerically analysed using a two-phase mixture model via computational fluid dynamics software firstly. The accuracy of the numerical model is proven by comparing the numerical results with the experimental data recorded by high-speed camera. Then, the development of cavitation and the relationship between cavitation, pressure and velocity have also been discussed. The effects of cone angle on the flow and cavitation characteristics have been investigated in detail. The results reveal that under different cone angle conditions, cavitation process and flow field physical parameters are similar. The highest velocity and lowest pressure of the oil is located at the orifice, which is the main area cavitation occurs. Meanwhile, with decreasing cone angle valve, the range of low pressure increases gradually also the highest velocity. It is concluded from the results that the decreasing cone angle will be beneficial for the anti-cavitation and anti-erosion of throttle valve. The authors’ conclusions could provide theoretical help for designing high-performance hydraulic valves.

The influence of inclined angle on the flow characteristics of angle seat valve is investigated by the numerical and experimental study. The accuracy of numerical modelling and calculation is verified by comparing the flow coefficients obtained from numerical simulation and experiments under the different pressure difference at the inclined angle of 45° and 60°. The experiment results showed that the highest flow velocity, the maximum flow coefficient, and the minimum flow resistance exist as the inclined angle is 45°. The flow coefficient increases as the increase of inclined angle when it ranges from 45° to 60°, and the flow resistance decreases correspondingly. The observed result is discussed and explained by the computational fluid dynamics (CFD) method. The calculation results indicated that the flow coefficient mainly depends on the maximum flow velocity in the angle seat valve. Moreover, the flow capacity is also affected by the flow direction near the sealing surface, and the number, locations and intensities of flow vortex.

This study concerns adaptive feedforward and hybrid (combined feedback and feedforward) control systems for active vibration suppression of smart flexible beam with a tip mass. By analysing traditional feedforward filtered-X least mean square (FXLMS) algorithm and filtered-X variable step size least mean square (FX-VSSLMS) algorithm, a new hybrid FX-VSSLMS algorithm is developed to improve the control performance of feedforward controllers. A stainless steel beam with a tip mass is employed to simulate flexible robot arm with varying loads. Piezoelectric actuators and sensors are attached to the surface of the beam. Comparison experiments show the effectiveness and benefits of the proposed hybrid FX-VSSLMS method.

Microelectromechanical system (MEMS) accelerometers are small in size, low in power consumption and easily integrated. They can be used in intelligent hydraulic components to obtain the dynamic acceleration of the system and monitor the operating status of the system. In this study, based on the noise characteristics of MEMS accelerometer output signals, a wavelet modulus maxima denoising algorithm based on adaptive threshold estimation is proposed, in which SureShrink threshold estimation is used to choose the right modulus maxima. Then, the signal-to-noise ratio and mean-square-error are used as the evaluating indices of the denoising performance for the wavelet modulus maxima denoising based on SureShrink threshold estimation, the wavelet modulus maxima denoising based on BayesShrink threshold estimation and the normal wavelet modulus maxima denoising. The simulation results show that the wavelet modulus maxima denoising based on SureShrink threshold estimation has better denoising performance than the normal modulus maxima denoising and the wavelet modulus maxima method based on BayesShrink threshold estimation, and effectively eliminates the noise of MEMS accelerometer output signals.

In this study, biological characteristic of manpower is analysed and then the structural of exoskeleton rehabilitation manipulator is designed base on the thought of modular. First, the overall assembly drawing is drawn by SolidWorks. Second, the controlled pneumatic system is designed. The mainly contents are selecting mini pneumatic cylinder as a driver and controlling electromagnetic reversing valve which can lead to the piston movement of cylinder by STM32F429 microcontroller. At last, the movement simulation of exoskeleton rehabilitation manipulator is done and analysed by ADAMS, and then the experimental research of the same move pattern with simulation is carried out. It is proved that the pneumatic exoskeleton rehabilitation manipulator system has certain reliability and feasibility. Furthermore, it has the ability to meet the rehabilitation needs of patients with finger movement disorders.

In this article, the mechanical properties of large-scale rack structures are analysed by MSC Marc analysis software is verified through the modal test. The modal frequency and modal shape are obtained through the finite element analysis and LMS data acquisition system for modal test verification. It is showed that the modal shape of the modal test and the calculation by finite element analysis are consistent, which verifies the inherent characteristics of the frame structure effectively and provides reliability parameters of the manipulator for the space station in the zero-gravity test.

The pumping unit is the main equipment for oil production in the oilfield. However, its serious energy consumption has greatly increased the cost of oil extraction. The reason of this phenomenon is the undesirable primary and secondary balance cannot make the motor run steadily in the high efficiency load rate interval, leading to low efficiency and great loss of the motor. In this paper, the secondary balance system for hydraulic hybrid power of pumping unit is developed, which can store the potential energy of the lower stroke in the accumulator and release it in the up stroke. It can effectively fill and reduce the wave valley and peak of the load rate curve, so that the motor can run in the high efficiency for a long time. The controller of the secondary balance system has a self-learning method based on the multiple populations' genetic algorithms. It can reflect the real load by detecting the motor operating parameters, improving the response speed. At last, use AMEsim to simulate the hydraulic system, and compare the load fluctuation and motor energy consumption before and after setting energy-saving system. It is proved that the energy saving effect of the system is extremely remarkable.

For the transport of large-tonnage equipment and structures, most of them use multiple hydraulic trucks to combine. The coordinated control of the hydraulic trucks’ hydraulic system groups is particularly important. The coordinated control of two hydraulic trucks from a company was studied during the steering of combined transportation. First, the hydraulic steering mechanism was analysed, and the functional relationship between steering angle and hydraulic cylinder stroke was obtained. Then, the synchronisation control strategy was compared and analysed, and the synchronous control mode with higher precision was selected. The mathematical model of the steering system was established, and the AMESim model and Simulink model were established to verify the feasibility of the control strategy. Finally, the steering tests of no load and full load were carried out. It was found that the actual test results were basically consistent with the simulation results. It was verified that the steering system with load-sensing pump and master–slave coordinated PID control strategy can better realise coordinated steering action.

The hydraulic lifting system is the key part of the crane. A sliding mode control method based on the cerebella neural network is proposed to solve the problem that the robustness of the traditional control method is poor in view of the problem of the synchronous error of the double motor in the lifting process of the crane. On the basis of the master and slave control, the outlet pressure of the hydraulic pump and the angle of the hook are simulated as the control index. Finally, the experimental study is carried out on the lifting condition. The results show that, compared with the traditional method, the proposed control strategy can effectively improve the synchronisation control precision of two motors, strong anti-interference ability and good robust performance.

A novel anti-resonant hydropneumatic suspension system was presented in this study. The mathematical model of the presented suspension system was derived and the theoretical analysis was carried out. For lower frequency vibrations, the presented suspension system can achieve better vibration isolation performance comparing with the traditional hydropneumatic suspension system. The frequency spectrum on which the presented suspension achieves better vibration isolation performances can be widened by adjusting the length of the oil tube. Therefore, it is possible for the presented suspension system to achieve better vibration isolation performance on different road conditions.

Ceramic roller is more reliable than metal roller. However, ceramic materials are difficult to process due to their high hardness and great brittleness. They are easy to crack and easy to damage cutting tools. To batch processing of ceramic roller blanks (CRBs), a special ceramic roller cutting equipment (SCRCE) is designed to deal with CRBs of different diameters and lengths. To avoid clamping damage to CRBs, the SCRCE adopts the new clamping mechanism. The blanks are orientated to double rotating shafts with V-type sleeves to reduce friction. Moreover, the SCRCE adopts a new ring-cut method. The ring-shape cutting is used. The cutting spindle and the blanks are revolving at the same time in cutting processing. The design and modelling of the special cutting equipment is also finished. To analysis the axial displacement of CRBs while cutting, the simulation model with ADAMS is built and the related characteristic is simulated. The test result shows that the new type cutting machine is suitable for ceramic roller blank cutting process.

Real-time fault prevention and diagnosis in hydraulic systems is one of the challenges in engineering applications. In order to solve the problems of feature extraction and pattern recognition of different types of fault signals such as leakage, blockage, and cavitation in the hydraulic system, this paper presents a fault diagnosis method based on a multi-feature fusion support vector machine. This method first extracts the typical features of the fault signal from the time domain, frequency domain, and time−frequency domain. Then use the information entropy to calculate the weight of each feature, select the feature with the larger weight to participate in the stock index diagnosis. Finally, a multi-classifier based on the support vector machine is used to realise the fault diagnosis of the hydraulic system. The experimental results show that this method can achieve high accuracy in the hydraulic system fault diagnosis when the Gaussian radial basis function is selected. Also, compared with the commonly used improved back-projection neural network fault diagnosis method, this method has more excellent diagnostic performance.

The extremely dangerous and complex environment caused by tremendous earthquakes or unnatural disasters usually brings great danger to survivors and salvagers. Therefore, search and rescue missions after any disaster indicate a huge need in special access to reduce the loss for human beings and, at the same time, to improve the capability of performing the tasks. In terms of the miniature robots which can go into the confined zone for the searching tasks, this project focuses specially on analysing climbing obstacle capability of the miniature robots, and introduces a new concept composed of a jumping robot which is mounted on a tracked mobile base. To design, calculate, and analyse this system, an appropriate mechanism, geometric dimensions, and specific properties are detailed, which include a dual-tracked articulated transformable locomotion system, a transmission system with a sleeve shaft, an incomplete gear jumping mechanism, and the selection and calculation of power system motors. To complete the design procedure, a three-dimensional sketch of each component of the robot was generated by means of Solidworks.

Time-varying contact line and mesh stiffness are important parameters for dynamic investigation of helical gear pair with profile modification; however, the calculation methods of the time-varying mesh with high accuracy and high efficiency are also very limited currently. A new mesh stiffness calculation method for helical gear pairs with profile modification is proposed. The new method is conducted by cutting the helical gear tooth into slices to obtain the change of the contact line and the time-varying mesh stiffness with considering the change of each slice's engagement performance introduced by the profile modification. Then, the mesh stiffness of the assumed three different modification cases is calculated by using the proposed method. The calculated results indicate that the proposed method can be used to calculate the mesh stiffness of helical gear pairs, especially of those with tooth profile modification.

Aiming at the complicated internal flow state of hydraulic cone valve and the effect of fluid force on the performance, radial offset was seldom considered in the research of cone valve, so the inner flow field model of cone valve was established by UG software, and the mesh model was divided by ICEM CFD software. Then, the simulation calculation was carried out by FLUENT. The distribution of steady-state flow force, pressure field, and velocity field under the different opening of the cone valve was obtained. In order to verify the correctness of radial offset, the hydraulic simulation under the same working condition was carried out by AMESim software. Finally, the radial force on both sides of valve core was calculated on the basis of the pressure field on both sides of the valve core. The results show that the radial force difference on both sides of the spool is small when the valve port is small. With the increase of the valve port opening, the radial force difference between the two sides of the valve core changes larger, and finally fluctuating within a certain range. Then, the radial offset value can be calculated by the radial force formula. According to the obtained offset, the simulation and experimental study on the cavitation of the cone valve are carried out. The simulation results of radial offset are verified according to the distribution position of the cavitation, which lay the foundation for the design and performance research of the hydraulic poppet valve.

The high-speed train transmission system is a complex electromechanical coupling system, which consists of a motor, a universal shaft, a gearbox, and a wheel set. In order to solve dynamic problems such as torsion vibration caused by a high-speed train transmission system, the simplified model and equivalent mechanics model of the system were established, the natural vibration frequency was solved, and the simulation results of the system under a fixed torque input were analysed. The results showed that the natural vibration frequency of the universal shaft was 4.19 Hz, the natural vibration frequency of the pinion was 7.54 Hz, the natural vibration frequency of the big gear was 35.6 Hz, and the natural vibration frequency of the wheel set was 107.45 Hz. The natural vibration frequency of each part of the system increased gradually during the transmission from the motor to the wheel set. A fixed torque was added to the input end of the simulation model. The simulation results showed that the change amplitude of the torsion angle displacement of the big gear and the wheel set decreases. It is known that the angular displacement caused by the torsional vibration is weakened by the larger torsion stiffness of the axle.

This article focuses on the behaviour analysis of an unimorph ring-shaped piezoelectric plate that is used as an actuator in a fluidic valve. First, the system modelling is discussed by using the material mechanical properties of the piezoelectric plate and the non-piezoelectric substrate. That is, two differential equations are established for the displacements along the radial and transverse directions. After that, based on the clamped edge conditions, the transverse displacement solution is obtained as an explicit function of the applied voltage. On this basis, the analytical relationship between the transverse displacement and the applied voltage is displayed. Finally, three different voltages are applied to the ring-shaped piezoelectric plate of a fluidic valve. The measured experimental results are almost consistent to the analytical results, which illustrates the validity of the established system model.

It is difficult to accurately calculate the working load of the multi-way valve of the crawler tractor in the traditional method. In practice, the spool and valve body are prone to over-standard leakage and clamping problems in relative movement. This study analyses the mechanism of clamp and leakage problems caused by deformation, considering the influence of gradual change of oil channel diameter and direction change in the valve body caused by the throttling of the spool. Numerical simulation of heat–fluid–solid coupling for multi-way valves is carried out. Under the condition of maximum pressure, the characteristic curve of material deformation of different spool and valve body changes with oil temperature is obtained. By evaluating the fitting characteristics of the spool and valve body of common materials, the optimal fit clearance is determined accurately. This effectively solves the contradiction between the clamping and leakage of the multi-way valve and improves the performance of the multi-way valve.

In this study, a spool actuating mechanism using controlled pressure difference is proposed for a large hydraulic servo valve. The actuating mechanism is accomplished by tuning magneto-rheological (MR) fluid flow. The relationship between the flow rate and the controlled chamber pressure is obtained based on a non-convex constitutive relation of the MR fluid. The control of the pressure difference by tuning the electrical flow is simulated. A series of experiments are carried out on a prototype system; the numerical and experimental results show that the proposed system can produce a very quick pressure change, which can be used to actuate the spool of the hydraulic servo valves for large flow rate applications.

The problem of tracking control for piezoelectric actuator (PEA) is investigated in this article. In consideration of that, the control precision of PEA is being restricted due to the hysteretic effect. For the purpose of improving the tracking performance, two issues are, respectively, taken into account – the compensation of the hysteretic effect and the controller design for the PEA system. To solve these problems, first, a new hysteresis observer based on sliding mode control theory is established. The design of the observer has considered the uncertainty in PEA modelling and the exogenous disturbance. Besides, according to Lyapunov theory, the hysteresis observer can asymptotically estimate the hysteretic character with performance. Second, a fault-tolerant controller based on robust backstepping control theory is presented to make the PEA system to track the desire input. At last, numerical examples are given to verify the effectiveness of the proposed methods.

A lithium-ion battery package model was established. The influence of inlet velocity, inlet angle and battery space on the heat dissipation capacity of the lithium-ion battery pack was studied by the method of computational fluid dynamics. The single factor analysis and orthogonal test were used to optimise the lithium-ion battery package. The results showed that the best cooling effect was obtained under the conditions of 15 m/s wind speed, 8° inlet angle and equal battery spacing; the maximum temperature and temperature difference were reduced by 11.81% and 35%, respectively.

A certain type of crawler loader often appears flameout in unilateral steering, which makes the performance of the whole machine greatly affected. By analysing the dynamic characteristics of the load-sensitive drive system, it is found that the hydraulic fluctuation and the power matching between the hydraulic pump and the engine are the fundamental reasons for the failure. In order to solve this problem, a simple and easy improvement scheme is designed on the premise of not affecting the engine efficiency: a suitable size damping is connected in the middle of the two load feedback lines of the drive system to solve the power matching between the engine and the hydraulic pump and reduce the hydraulic fluctuation of the system. Simulation and experimental results show that this method can effectively solve the problem of stalling in the steering process of loaders and greatly improve the dynamic performance of the system.

Pneumatic actuators (referred to as pneu-nets) are drawing increasing attention due to their high customisability, ease of fabrication and innate softness. The actuator's ability to bend is one of the important parameters characterising its performance and related to its structure. Some structures are developed. In this work, a new structure (NS) pneu-nets is developed, and its bending ability is compared with the currently common Mosadegh pneu-nets structure (developed by Mosadegh). These two are analysed in two aspects: the trajectories of the pneu-nets actuator's tip, and the defined angle of bending. The results indicate that the NS pneu-nets actuators are able to achieve greater bending at higher pressures and can be lightweight. These pneumatic actuators provide improved structure for soft robotics.

At present, there is a little research on the workspace of the hybrid mechanism, and the further development of the engraving plotter is hindered due to the limitation of the workspace. In order to clearly understand the workspace of the hybrid engraving plotter, and verify whether the workspace meets the industrial production needs, the five degrees of freedom hybrid engraving plotter is analysed and studied. First, the structure of the engraving plotter is analysed and simplified, and then the direct equation is deduced by the analytic method. Second, according to the engraving plotter direct solution equation, the boundary of workspace is determined and the volume is calculated by using the optimisation algorithm. In order to understand the change of workspace in different z planes, the workspace of the parallel part is intercepted by some planes, which are parallel to XOY; thus, the authors know that the cut plane area of the workspace increases with the increase of Z values. Finally, the influence of the mechanism parameters is discussed on the dexterity. These theoretical knowledge will make important research significance for guiding engineering practice.

Planetary gear train (PGT) is widely used in a variety of fields such as helicopters and aircraft engines. The failure of meshing gear often happens in the PGT due to the working condition of high speed, variable load, high-frequency excitation, assembly error etc. However, the causes of gear failure are still insufficiency, especially in the condition of high speed and high-frequency excitation. In this work, the engaging force between gear meshing pair of the PGT under high-frequency excitation is studied using the proposed position-correlated modal properties calculation method, which is established by incorporating the effect of meshing position and meshing phase difference of each contact pair into the free vibration model to study the modal properties of the PGT at different meshing positions. The corresponding engaging force responses based on the position-correlated modal properties are investigated. The simulation results show that the higher-order natural frequencies of the system are greatly affected by the meshing position. The peaks of engaging force occur at meshing positions where the natural frequencies are equal to the excitation frequency, which can be the potential cause of the gear damage.

The magnetic-liquid suspension guide-way (MLSG) adopts the double support form of permanent magnetic suspension and hydrostatic pressure. It can greatly enhance the bearing capacity and rigidity of the guide-way system. The liquid film thickness is the main influencing factor on both the bearing capacity of the hydrostatic system and the permanent magnetic force. This paper analysed the effect of liquid film thickness on the static, dynamic and vibration index of MLSG. Firstly, this paper introduced the structural characteristics and supporting mechanism of MLSG. Secondly, based on flow equation, the static pressure equation, the permanent magnetic force equation and the force balance equation, the transfer function of single DOF supporting system of MLSG in constant flow supply mode is presented, and analysed the influence of the thickness of liquid film on single DOF supporting performance of MLSG. The results show that with the increase of the thickness of the liquid film, the bearing capacity of guide-way, the static stiffness, the dynamic stiffness and the natural frequency decrease, and the adjust time, the total power loss, the amplitude amplification coefficient increases, the phase margin is almost unchanged. The study can provide a theoretical basis for the design of MLGS in engineering practice.

A highly efficient integrated transmission unit – external generating wave movable teeth transmission − was proposed and two kinds of typical transmission types were researched. Fixed and moving coordinate systems were established based on movable teeth transmission theory. On the basis of the profile of a wave generator, the teeth profile equations of ring gear were deduced by using the transform matrix and profile enveloping principle. The effects of the teeth number of the ring gear, generating wave coefficient, and tooth profile coefficient on the profile of the ring gear were investigated. The formula for calculating curvature radius of the ring gear was given. The pressure angle formulas were deduced, and the change rule of the pressure angle extremum was researched to obtain a continuous transmission condition. The relationship between design parameters and performance effect was analysed based on the analysis of the curvature and pressure angle. The results show that the transmission precision reached 97.67%, and the proper design parameters could guarantee transmission performance. Those researches lay a theoretical foundation for the design and application of an external generating wave movable teeth title.

This study presents an ultrahigh internal pressure compound booster cylinder and analyses the structure and principle of the cylinder. Its advantages include low input, high pressure output, and direct action on the execution cylinder. The model of the ultrahigh internal pressure compound booster cylinder is constructed by AMESim, and the result is analysed. By analysing the research and simulation results for this cylinder, the authors eventually designed an integrated composite hydraulic cylinder assembly that can realise the large pressure output of fast-forward and quick return actions.

To handle the increasingly serious air pollution issue, the concept of atmospheric air purification tower already has been proposed. The first prototype of such a novel system had been built in Xi'an, China. The aim of this study is to numerically study how the crosswind affects the dust removal performance of the atmospheric air purification tower and which counter-wind strategy is optimal choice. To achieve that, a three-dimensional model considering the external environment was developed in ANSYS Fluent. With the help of the proposed model, the benefits of three wind breaking designs were quantified and compared. The results showed that the design with inner union-jack shaped wind break walls is the optimal for the atmospheric air purification tower. It can maintain the dust removal rate of the system at relatively high level (3.5 kg/h) no matter what crosswind intensity is.

Model set of a valve-controlled asymmetric hydraulic system was built, and uniform switched control (USC) strategy was proposed for multi-model set hydraulic system. Aiming at each subsystem model, the uniform feedback linearisation control (FLC) structure was put forward based on the FLC method, and switch control strategy was used by adjusting switch gain between different sub-models. The boundary layer function was designed in order to enhance the system robustness and to reduce oscillation which is caused by discontinuous item. Furthermore, the switch control gain was further revised according to different load condition. At last, the USC, FLC control, and proportional differential (PD) control strategy was carried out by experiment, and the results show that the maximum speed tracking error of PD and FLC control was 1.1 and 1 mm/s, respectively. The USC strategy speed error is <0.25 mm/s. Compared with the PD and the FLC, the USC was found to be more speed accuracy in multiple state hydraulic system control.

According to the cone-type throttle valve is prone to cavitation, resulting in the reduction in the performance of the cone throttle valve. Here, a visual experimental platform for hydraulic cavitation is built, and the cavitation number of the conical throttle valve under different working pressure, opening degree, and different back pressure is studied. The cavitation image under different conditions is obtained. The research shows that properly increasing back pressure, reducing system working pressure, and keeping small opening of the valve port can restrain cavitation.

The performance of non-linear absorbers for suppression of the structure vibrations depends on the setting of the absorbers' parameters to a certain extent. A slowly varying dynamical system under investigation in the existing work is comprised of a linear oscillator coupled with an attached non-linear absorber called non-linear energy sink (NES). Slowly varying equations of the coupled system are achieved first by using the complex averaging method, and trajectory features of the slowly varying system are analysed. On that basis, the non-linear cubic stiffness design method is proposed. Considering that different damping coefficients of the NES impose a large impact on both system energy transfer and energy dissipation between the main structure and the NES, necessary damping conditions for the targeted energy transfer (TET) are obtained by using the phase trajectory analysis. With the proposed method, structure parameters of the NES are designed to get maximum absorbing effects. Finally, all these conclusions about parameters design for the NES are verified by simulation analysis. The simulation results demonstrate that the optimal vibration reduction effectiveness can be achieved with reasonably designed stiffness and damping.

Centrifugal fan in series is the core facility for pneumatic transportation. Its operation is required to be adjusted real time as the flow rate of transported materials changes. For optimisation performance, internal flow of a type 700 three-stage fan at rated rotation speed is analysed with FLUENT6.3 for various total pressure. Multiple reference frame (MRF) model is used for the impellers rotation in simulation, and Re-Normalisation group (RNG) κ-ɛ turbulence model and Roe-FDS flux type with first-order upwind difference scheme are used for calculation of compressible flow under various total pressure. Flow characteristics are obtained and differences of total pressure and velocity distribution in every impeller are analysed in different conditions, and velocity distribution on meridian plane as well as section of wind guide plates and volute are compared. Results show that there are many vortexes and backflows in fan with higher total pressure, and the lower pressure, the more smoothly flows, besides flow at inlet and outlet of impellers and in guide plates is seriously influenced by total pressure. Curves of P-Q and P-η at 4600 r/min are predicted based on simulation, which is helpful reducing the impact caused by off-design operation and improving efficiency.

Owing to the modal analysis of complex structure system exist in the problems such as the local mode cannot be identified and the overall modal vibration mode cannot be extracted, this study deduces a formula of modal effective parameters based on the kinetic energy and introduces to the simulation of mechanical characteristics of the SCK230 CNC pipe thread repair the lathe bed. The simulation shows that this method can identify the local mode of three directions effectively, and determines whether the numbers of solved modalities satisfy the requirement of precision. In order to improve the natural frequencies of the bed and analyse the influence of the opening of the bed on its dynamic performance, three optimisation schemes are proposed based on this, and verified the feasibility of the optimisation scheme. Through structural optimisation, improve the dynamic characteristic of the lathe bed and reduce the manufacturing cost, and the optimisation of the structure can be achieved without experimental modal analysis.

In the process of lead electrolysis, due to its production characteristics, it is necessary to extract and collect the cathode conductive rod on the cathode plate after electrolysis, so as to make it reusable. At present, most of the lead electrolytic manufacturers in China still rely on manual extraction in this process. In this study, a rapid, stable and effective cathode rod extraction equipment for lead electrolysis is designed by means of electro-hydraulic proportional technology. AMESim simulation and experimental research on the equipment are also carried out.

A vehicle-integrated transmission system is a complex system composed of mechanical, electronic, and hydraulic systems whose components work together. The hydraulic system of a vehicle shift is an important part of the vehicle-integrated transmission system. In order to improve the efficiency of the building model, the hydraulic system of a vehicle shift is analysed in detail using the modularisation theory. Also, the modularised simulation model of the system is obtained based on AMESim. The correctness of the module simulation model is verified by building a single-hydraulic-circuit test platform.

A new variable displacement oil pump has been modelled and simulated by using AMESim. Through the comparison and analysis of the simulation curve and the test data of this pump, it is found that the volume efficiency of it is unsatisfactory when the rotational speed is too high. The mechanical structure model of the pump was established by using ADAMS to confirm that the cause of the problem is redundant force on the variable device. On this basis, the redundant force acting on the variable device is theoretically deduced to prepare for the improvement of the pump.

This article proposes a planar-coil linear time grating displacement sensor. Compared with the existing magnetic field-type linear time grating, the structure without tooth and slot improves the velocity uniformity of travelling wave magnetic field and the measurement accuracy can be greatly improved. The two-phase excitation coils are arranged to form a plane coil array, and the travelling wave magnetic field is generated after the two-phase orthogonal signals are entered, respectively. Then, the electric travelling wave signal is induced by the pickup coils, and the displacement is obtained after processing. The signal processing circuit is designed to amplify and filter the electric travelling wave signal, and the accuracy experiment is carried out. Result shows that in the range of 240 mm (full-scale), the measurement accuracy can achieve ±0.8 μm.

In order to improve the precision of the extrusion speed control of the large hydraulic press and improve the quality of the extruding work piece, an experimental system was designed to simulate the throttle system of the hydraulic press. In order to simulate the transient heavy load and the fluctuating load characteristics of the throttle system, two pumps were used to supply the oil in the two chambers of the load cylinder separately, and the pressure of the two cavity of the load cylinder is controlled by two proportional relief valves. The force of the throttle spool driving cylinder can be controlled by controlling the pressure of the two chambers in closed loop, and the load state can be quickly changed. Experiments show that the load simulator can simulate the load form of the hydraulic press very well.

Comparative investigation on friction and wear properties of SiC, Si₃N₄, Al₂O₃, and ZrO₂ lubricated with seawater was carried out on a ring-on-ring contacted tribological test apparatus, and their worn surfaces were observed by an ultra-depth optical microscope. The results reveal that the friction coefficients of Si₃N₄ and SiC are obviously lower than those of Al₂O₃ and ZrO₂ when they slide against the polyetheretherketone (PEEK) composite in seawater, and the friction stability of ZrO₂ is so poor that it is not suitable for seawater hydraulic piston pumps. When the contacted load increases from 400 to 1000 N, the wear rate of Al₂O₃ is still the highest, while the wear rates of SiC and Si₃N₄ change from positive to negative, which indicates that plastic transfer is occurred under a heavier load. When they slide against the PEEK in seawater, the main tribological mechanism of SiC, Si₃N₄, and Al₂O₃ is slightly abrasive wear, while both abrasive wear and adhesive wear occur for ZrO₂. Generally, both SiC and Si₃N₄ have wide prospect applied in seawater hydraulic piston pumps, and particularly Si₃N₄ exhibits excellent friction and wear properties in seawater.

This study was to predict the optimum condition for leaf flavouring in cigarette manufacturing. To this purpose, an integrated research was used by using response surface and artificial neural network. A series of tobacco flavouring experiment's factors were designed by Experimental Design software. The MATLAB software's Neural Network function was used to forecast the responses, and the optimal solution configuration was coming out from the Response Surface Analysis Method. In the optimum condition, moisture removal opening, roller speed and tobacco process flow, pressure and feed liquid gas ejector flow are 18.60%, 10.74 rpm, 5314.11 kg/h, 3.70 bar and 243.63 kg/h, uniformity of the evaluation index and the utilization rate of material liquid distribution are 93.088% and 98.694%. With the corresponding experimental, results are consistent, under the condition of the error to less 7%, the test results show that through a few experimental data of predictive results of the neural network and response surface design has a certain practicability.

Sabot asymmetric discard after the projectile being launched from the muzzle at various angles of attack and 4Ma is investigated. This is implemented by the coupling computational fluid dynamics (CFD) and six degrees-of-freedom exterior ballistic code through the unstructured dynamic mesh and user defined function. The flow field characteristics during sabot discard process and the trajectory parameters of all three sabots have been obtained. In addition, the aerodynamic coefficients of the projectile are also obtained. The numerical results show that the asymmetric discard of sabot is more obvious along with the increasing angle of attack. Moreover, the aerodynamic forces of projectile have a larger change and the pressure distribution of its surface is more asymmetric and complex. This means the aerodynamic interference at a non-zero angle of attack contributes more significantly to shooting dispersion and flight stability than that at zero angle of attack and the influence increases as the angle of attack increases.

The structural characteristics and modes of the Stewart platform driven by electric cylinders are briefly introduced. Based on Simulink, the modelling method of the platform is analysed. To obtain the coordinate transformation of Stewart platform, the rotation matrix and homogeneous transformation are resolved, and the mathematical model of the electric-driven Stewart platform is established related to the structural characteristics. The simulation model of input and output signals is constructed by using graphical user interface (GUI) module provided by Simulink. The motion simulation curves of six electric actuators under different position and posture are obtained, which gives benefit to understand and control the different motion states of the electric-driven Stewart platform.

Vehicle aerodynamic shape optimisation is a typical non-linear and computationally expensive black box problem, which is severely limited by time and cost of the objective function evaluations during the global optimisation process. To solve the shortcomings of low efficiency and high cost of the existing vehicle drag reduction method, an improved efficient global optimisation (EGO) algorithm is used to optimise a four-dimensional aerodynamic drag reduction design of a vehicle combined with computational fluid dynamics numerical simulation technology. Moreover, data mining technologies are used to reveal the influence mechanisms of design variables on aerodynamic drag and to analyse the relationship between the variables. It is demonstrated that the improved EGO algorithm, based on the kriging response surface and expected improvement function, can achieve the global optimum with minimum function evaluations. The aerodynamic drag of the optimal design is 1.56% lower than that of the original vehicle. The data mining results showed that the engine hood inclination and the tail upturn angle play a leading role in the vehicle's aerodynamic drag, and the hood inclination has the greatest impact.

The pivotal steering ability of vehicles is important in the case of narrow steering space. In this study, a pivot steering system for the rescue vehicle is designed, and the 1D + 3D co-simulation model is established based on automatic dynamic analysis of mechanical systems (Adams) and advanced modelling environment for performing simulation of engineering systems (AMESim). The dynamic analysis of the pivot steering system has been compared with the theoretical calculations, which proved the correction of the model. In addition, through the simulation, the authors can hold the conclusion that the tyre cornering stiffness has a great influence on the pivot steering system.

The aero-engine to be cleaned online can significantly improve compressor performance and increase maintenance intervals, but the cleaning online cannot achieve the anticipated effects due to the lack of cognisance of the internal multiphase flow field. In order to explore the characteristics of the compressor's internal flow field, a compressor and nozzle's flow channel model was established based on the data of the Rotor36 compressor blades published by NASA. The fluid simulation software was used to analyse the effects of circumferential vortex and axial vortex on the wall surface at different jet parameters and characteristics of the gas–liquid flow field formed by the compressor blades at different rotation speeds. It is concluded that the flow field formed at a jet pressure of 5 atm and a rotational speed of 2880 rpm is more favourable to the removal of fouling.

As a supplement to physical stores and online stores, vending machines are gradually becoming the third largest consumption mode. This article aims to design a removable vending machine, which can automatically move in front of the users to meet their demands, so as to realise a better shopping experience for people. The network structure for the vending machine was analysed and designed, and research on the wireless location technology and route planning of the vending machine is hoped to provide some reference value for the mobile technology of the vending machine.

Aiming at the fault diagnosis and remaining useful life (RUL) prediction of fatigue cracks of a helicopter main gearbox planet carrier, this article proposes a hidden semi-Markov model (HSMM) methodology, which introduces the explicit state durational distribution parameters into the traditional hidden Markov model (HMM), thus overcoming the limitation of exponential distribution in HMM, retaining strong pattern recognition and classification ability, and improving the diagnostic and prognostic accuracy, and the effectiveness of the method was verified through experiments.

The motion mechanism of the single droplet during wing cleaning of aeroengine is studied, and the force acting on the droplet entering the fan at low speed is analysed, and the motion model of a single droplet in swirl field is established. The influence of the main parameters such as droplet diameter, incident velocity and incidence angle on the droplet trajectory is analysed. The mechanism of droplet movement in the fan is described qualitatively.

Compared with the traditional hydraulic hybrid system, step variable hydraulic hybrid power system has the advantages of low cost, fast response and pollution resistance. However, the existing variable elements are heavy, and the control valve group has the disadvantages of insufficient through-flow capacity, large flow resistance, large leakage and reversing impact. In this study, the hydraulic components integrated by the cartridge valve group which can replace the traditional three-position four-way valve group are applied to the hydraulic hybrid power system. The AMESim simulation models of directional cartridge valve and the step variable hydraulic hybrid power system are established in this study. Through simulation analysis, it is verified that the cartridge valve integrated element can replace the traditional reversing valve to solve the defects of cumbersome components and insufficient through-flow capacity. Some important parameters of the system components are simulated and analysed. The simulation results can be used to improve the design efficiency and ensure the design quality.

Various gust alleviation technologies including passive and active methods have been investigated. This research is focused on the gust response analysis of the flying-wing aircraft with a gust alleviation device. Both passive and active approaches are investigated. Longitudinal analysis is involved in the gust response analysis. The model is longitudinally trimmed before gust response analysis. The result shows that efficiency is related to the frequency of deflection motion. The active control approach is more efficient than the passive gust control approach.

This study is focused on the superelastic Ni-based shape memory alloy (SMA) for finite-element applications. SMA has presented excellent characterisations in biomedical application, mechanical application, aerospace application, seismic prevention, disaster reduction and so on. In this study, a SMA constitutive model is proposed that is capable of describing SMA superelastic features and its plasticity effects. Finally, the analysed results show good ability to predict the experimental data.

The main executive element of the retractable landing gear is the hydraulic cylinder, and its common fault is caused by the leakage of the hydraulic cylinder. In this study, the mathematical model of the energy entropy of the wavelet packet is constructed according to the fault characteristic information, and the hydraulic system is modelled by the Amesim software. Through the simulation calculation of the leakage and leakage of the hydraulic cylinder, the fault characteristic parameters such as displacement and pressure are extracted. Wavelet packet transform is used to obtain the energy entropy of the wavelet packet, and a mapping relationship between the leakage of the hydraulic cylinder and the energy entropy is established. The research shows that the leakage fault diagnosis method based on wavelet packet can effectively predict the failure of the hydraulic cylinder of the landing gear, and it is effective and practical for guiding the fault prediction and intelligent maintenance of the hydraulic system of the aircraft.

With the use of large eddy simulation (LES), the initial structure and mixing characteristics of both the subsonic and supersonic circular jets are studied, respectively. The stretched-vortex model combined with the high-order hybrid scheme is employed to solve the LES equations. The typical structures of the initial jet at different conditions have been presented and discussed. The formation and evolution process of the vortex ring has been displayed in detail, and the unique characteristics of a compressible vortex ring generated by the unsteady jet have been identified. Furthermore, the engulfment and mixture of ambient gas with the jet gases have been discussed, the different mixing processes of both subsonic and supersonic jets, especially the shock wave effect in a supersonic jet on mixing process, have been illustrated.

Piezopositioning stage is widely used in the field of precision positioning. However, the positioning accuracy of the stage is primarily affected by the hysteresis property and dynamic property. In order to obtain high positioning precision, a mathematical model of the micro-displacement stage needs to be accurately modelled. They take a comprehensive consideration of the hysteresis property and dynamic property of stage and then build a mathematical model by combining these two properties, which can reflect both of the two properties. PI model is adopted to model the hysteresis property, the threshold r is determined by the non-uniform threshold method, and weight coefficient w is firstly identified by fitting the initial curve under the condition of off-line, and then on-line modified when the stage works. Dynamic modelling adopts a second-order system whose parameters of transfer function model are determined by the frequency analysis method. Comparing with the experiment results and the simulation, the maximum error and the mean error of this model are, respectively, 0.124 and 0.061 µm when the positioning range is 10 V. It indicates that this mathematical model of piezopositioning stage can meet the needs of the precision positioning of the micro-displacement stage.

The five-degree-of-freedom double-legged wall-climbing robot is the most straightforward structure with the promising application because the minimum degree-of-freedom of the foot-type climbing robot with continuous movement and obstacle-overcoming capability on the vertical wall is five. Based on the prototype of the wall-climbing robot, the parameter table of the Denavit-Hartenberg (DH) model is given out, and then the positive and inverse solutions of kinematics analysis of wall-climbing robot are derived. Secondly, the system dynamics model is established based on the Lagrange equation, and the weights of inertial load acceleration torque, Coriolis force torque, centrifugal force torque and gravity torque in the dynamic equation are analysed. The design ideas of compensation gravity load and inertial load adaptive proportional differential controller is proposed according to the analysis results, and the gravity torque compensation function and general nonlinear mass function are given correspondingly to provide theoretical support to adaptive controller design. Finally, the effectiveness of the control strategy was verified by the actual control of the knee joint and ankle joint.