Nonelectric variables control
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An 80-mg double piezo-actuated insect-inspired flapping-wing robot is presented in this Letter. With the design of the two piezoelectric actuators placed back to back, each wing of this robot is independently driven and controlled, giving this robot the ability to achieve asymmetric flapping of the two wings to generate torques for steering. The piezoelectric actuators are designed with electrical insulation and structural reinforcement to improve the reliability under high-voltage and high-frequency drive mode. Fibre directions of each component of the robot are reasonably designed to enhance strength and stiffness. The average lift generated by the robot is measured by a customised lift measurement system found to be proportional to the square of the input voltage amplitude. The three steering torques generated by the robot are measured separately by a customised lift measurement system. Each steering torque can only be linearly modulated by its specific control variable of the input voltages. With a total weight of 80 mg and a wingspan of 3.5 cm, this robot can generate sufficient lift to take off and independently modulate all three steering torques with good decoupling, which is vital for the further controlled flight.
Currently, majorities of the robust H ∞ control methods are designed for active suspensions, and seldom take the active control of the in-wheel-motor (IWM) into consideration for IWM driven electric vehicles (EVs). In this study, a robust fault-tolerant H ∞ output feedback control strategy with finite-frequency constraint is proposed to synchronously control the active suspension and dynamic vibration absorber (DVA) for IWM driven EVs. Firstly, a DVA-based electric wheel model is developed, in which the IWM is designed as DVA. Furthermore, the spring-damper parameters of the DVA are matched by using particle swarm optimisation (PSO). Then, the robust fault-tolerant H ∞ output feedback control strategy is developed based on linear matrix inequality, in which the finite-frequency constraint is designed in the resonance frequency range of sprung mass. Finally, simulation results validate that the PSO can effectively optimise the spring-damper parameters of the DVA. The robust fault-tolerant H ∞ output feedback control with finite-frequency constraint can effectively improve the ride comfort and suppress the vertical vibration caused by IWM compared with entire frequency constraint. Meanwhile, the fault-tolerant effectiveness of the proposed method is demonstrated under the actuator faults concerning the actuator force noises and losses.
This study proposes a dynamic motion planner with trajectory optimisation for automated highway lane-changing driving. Owing to the connected and automated vehicles (CAVs) technology that the real-time traffic information can be obtained, alternative trajectories can be generated to satisfy the vehicle kinematic constraints and avoid many types of potential collisions. An optimal control theory is adopted to select an optimal lane-changing path from the finite path set, and the appropriate acceleration and speed for the execution path are also determined. In order to avoid unnecessary motion re-planning process, this study puts forward a collision-avoidance monitoring algorithm to reduce the time consumption costs of the motion planner. Moreover, an online planning framework based on ‘decision-execution’ is explored. Applying this timeline framework can not only help to evaluate the dynamic planner's online performance, but also reduce the deviation between the online calculation and the actual execution caused by the time consumption. The simulations are performed in PreScan-Simulink platform and the experimental results show that the presented dynamic planner can complete the lane-changing manoeuvre safely and effectively in a high-speed environment.
This article studies the problem of event-triggered distributed adaptive bipartite consensus control for multiple autonomous underwater vehicle (AUV) systems with a fixed topology. Different from the existing literature on multiple AUV systems, the competitive relationship among AUVs is taken into consideration. In this situation, the bipartite consensus control is implemented to complete the controller design. Furthermore, combing the relative threshold strategy and the backstepping method, an adaptive event-triggered control scheme is developed to decrease the updating frequency of control input. Through the Lyapunov analysis, the proposed protocol ensures that the position tracking error of the considered system converges to a small neighbourhood near the origin. Finally, a simulation example is given to show the effectiveness of the control scheme.
For scanning applications, damping and tracking controllers are employed in a dual-loop fashion. Whilst these damping and tracking controllers are designed sequentially in literature (damping first, tracking later), it has been found that the tracking controller (typically integral or proportional–integral) influences the 'desired' pole locations (and thereby its damping performance) achieved by the positive acceleration, velocity and position feedback (PAVPF) damping controller. This work starts by first highlighting this unwanted effect that results in low positioning bandwidth. To address this drawback, this work presents the design, analysis and experimental validation of the simultaneous design method for the PAVPF control-based combined damping and tracking scheme, aimed at achieving accurate, high-bandwidth nanopositioning. It also details a recursive analytical method to simultaneously optimise the damping and tracking controller parameters resulting in almost a three-fold increase in closed-loop bandwidth when compared with the traditional sequential method. To further confirm the advantages of the proposed simultaneous design method, comparative experimental results conducted on one axis of a piezo-actuated nanopositioner are presented. Significant improvements in the steady-state positioning as well as transient response are noted. These improvements combined, result in significant gains in the raster scanning performance of nanopositioning stages.
In this study, a fault-tolerant position tracking control of a quadrotor unmanned aerial vehicle (UAV) is addressed by proposing a model reference interval type-2 (IT-2) fuzzy-model-based sliding mode tracking control methodology. Considering the underactuated characteristic of the quadrotor UAV, first, the authors separate the overall dynamics of the quadrotor into the attitude, altitude, and position subsystems. Moreover, each of them is represented via IT-2 fuzzy model to deal with uncertainties of its membership functions. After then, a linear reference model supposed to be tracked by each subsystem is designed, on which each tracking error dynamics is derived. Given the tracking error dynamics and additive actuator faults, an IT-2 integral fuzzy sliding surface is proposed to enhance the robust tracking performance of the entire system. As a result, a linear matrix inequality-based sufficient condition is derived to guarantee the asymptotic stabilisation as well as satisfying an tracking performance. Furthermore, a reachability condition of the designed sliding surface is also proposed. Finally, the authors provide design examples to demonstrate the effectiveness of the proposed position tracking control methodology.
This study presents a linear parameter varying (LPV) approach for the lateral control of autonomous vehicles, in order to take into account the whole operating domain of longitudinal speeds, as well as the variation of the look-ahead distance. Combining a dynamical vehicle model with look-ahead dynamics, together with an identified actuator model including an input delay, the closed-loop performances can be achieved and the tracking capabilities can be improved for every speed. This is obtained in particular through ad hoc representation of the look-ahead time as a parameter-dependent function. An LPV control problem is formulated considering parameter-dependent weighting functions, allowing the control adaptation for all speeds. The synthesis is performed using the gridding approach, in order to account for varying parameter rate. The proposed steering control system has been implemented on a real electric Renault Zoe car. The performances are therefore assessed experimentally on a real test track with a varying longitudinal speed profile, and compared with a classical LPV polytopic controller, which proves the advanced lane-tracking capabilities of the proposed methodology.
This study presents an integrated control scheme of a diesel engine which aims to ensure quick torque response while limiting the average NOx emission below the certain specification. To start with, the sensitivity analysis is performed to recognize the key factors determined to balance emission, torque and fuel consumption. Considering the strong nonlinearity of the diesel engine, a multi-input multi-output (MIMO) linear parameter varying (LPV) model is developed. Unlike the conventional state-depended LPV modelling process, the proposed LPV model is built based on a kernel function with a novel form of state-free predictive equation so that the system outputs are directly computed. The control objective of coordinating torque tracking and emission reduction is then accomplished by designing a model predictive controller that regulates the fuel injection quantity, fuel injection angle, exhaust gas recirculation (EGR) rate and the opening degree of variable geometry turbine (VGT) valve. Finally, the developed LPV model and the MPC controller are testified with a high-fidelity commercial diesel engine model. The results show that the LPV-MPC controller is able to satisfy the NOx emission specification and the engine torque tracks the desired reference fast in transients, while the control variables are suitably actuated within the actuator constraints.
This study introduces a new switching scheme for nine-level cascaded H-bridge (CHB) inverter to comply with the harmonic standards (IEC 61000-2-12, IEC 61000-3-6, and ER G4/5) using an improved selective harmonic minimisation pulse amplitude modulation (SHM-PAM) scheme. In this scheme, the optimised switching instances and variable DC-link voltages are determined by solving some new constraints based cost functions using particle swarm optimisation (PSO) technique. The theoretical analysis and optimisation results of the proposed modulation scheme are validated through MATLAB simulations and experimentally on a laboratory-scale prototype of CHB inverter. The proposed modulation scheme utilises a minimal number of switching instances in a fundamental period and optimisation variables in the problem formulation in comparison to conventional SHE-PWM and SHE-PAM schemes. The key performance of the proposed scheme in terms of harmonic and loss analysis is evaluated over the wide range of the power factors and modulation index. Finally, the suitability of the proposed scheme is tested for the closed-loop speed control of a 5 hp, 415 V three-phase induction motor.
In this study, the non-linear deadbeat direct torque and flux control (N-DB-DTFC) scheme is proposed for switched reluctance motor (SRM) to achieve torque and flux precise control. For torque control part, the Fourier series form of inductance is used to establish the non-linear torque model of SRM. As for the flux control, stator flux-oriented is adopted to achieve the flux control and simplified calculation in N-DB-DTFC. In addition, the synthetic voltage vectors are applied by pulse-width modulation. In order to assess the performance of N-DB-DTFC, the comparison of torque ripple is analysed among the traditional deadbeat controls in the simulation and experiment. Although, for the torque transient response, three deadbeat controls show the strong robustness and adaptability. In the results, the proposed N-DB-DTFC strategy shows better reflection in terms of lower torque ripple. Moreover, the results of simulation and experiment are based on a three-phase 12/8-poles SRM.
This study revisits the problem of attitude stabilisation for rigid spacecraft with actuator constraints in the framework of non-linear proportional–derivative (PD) control methodology. A simple single saturated PD (SSPD) control is proposed. The most appealing features of the proposed SSPD control are that it completely embeds the control action within only a single saturation function for every actuator and omits the elaborate discrimination of the terms that shall be bounded for the commonly-used saturated control and hence it is easy for practical implementation with an improved performance. Lyapunov's direct method is employed to show asymptotic attitude stabilisation. Two illustrative examples are presented to demonstrate the improved performance of the proposed approach.
In this study, adaptive prescribed finite-time stabilisation of uncertain single-input and single-output non-linear systems is considered in the presence of unknown states, unknown parameters, external load disturbance, and non-symmetric input saturation. A prescribed finite time disturbance observer is designed to approximate the unmeasured external disturbance. Also, a non-singular prescribed finite time terminal sliding mode control is proposed for the closed-loop control of the system with the non-symmetric input saturation. Extended Kalman filter algorithm is employed for the real-time estimations of the states and unknown parameters of the system. Moreover, a particle swarm optimisation algorithm is used to obtain the design parameters of the proposed disturbance observer and controller. To show the performance of designed control scheme, the proposed approach is employed to guarantee prescribed finite time stabilisation of non-linear vibration of a non-local strain gradient nanobeam. The Galerkin projection method is used to reduce the non-dimensional form of the governing non-linear partial differential equation of Euler–Bernoulli nanobeam to the ordinary differential equation. Finally, numerical simulations are performed to illustrate the effectiveness and performance of the developed adaptive control scheme for the vibration control of nanobeam in comparison with the conventional sliding mode control.
This study proposes a new active fault-tolerant control (FTC) and fault estimation scheme for a non-linear octorotor system. The proposed method utilises the idea of an online control allocation (CA) scheme to fully engage the rotors redundancy based on the information from the fault estimation unit. The nominal performance is first achieved using non-linear dynamic inversion (NDI) technique and then to incorporate the robustness, an adaptive non-linear sliding mode control is united with a baseline NDI controller. The proposed method is used to attain the desired altitude and attitude tracking control of an octorotor system. Furthermore, to control the un-actuated states (called internal dynamics) of octorotor system, a separate integral sliding mode-based NDI controller is designed that provides the translational axes control by generating the desired roll and pitch commands. Simulations on the non-linear model of octorotor system validate the dominant performance of the proposed scheme compared to the existing methods in the literature.
This work presents a new algorithm for flocking with a virtual leader by introducing a new sampling scenario, so-called multi-rate sampling. In the multi-rate sampling, the period of receiving data from different sources is different, but the updating time for all individuals is the same. Here, the authors assume that the period of receiving data from neighbour agents is T , and that from the virtual leader is an integer multiple of it, that is, mT . An upper bound for period T is attained from the upper bound of the energy function that guarantees the neighbouring network to be connected and collision to be avoided between agents. Also, an upper bound on m , which ensures the velocity of informed and uninformed agents to tend the virtual leader's velocity, is derived. The convergence analysis demonstrates that whatever the acquiring period of the virtual leader's information mT is further, then the convergence rate of the group's velocity to the virtual leader's velocity will be greater. Finally, to show the validity of the results, they present a simulation.
The safety of a vehicular platoon is seriously threatened in the presence of actuator saturations, (possibly fast) time-varying non-linear uncertainties. Meanwhile, the string stability and the strong string stability cannot eliminate the potential safety hazard caused by large initial error conditions. This study focuses on safety-guaranteed distributed control of the vehicular platoon with a bidirectional communication topology and the constant time headway policy. The authors formulate bilateral inequality constraints on the spacing error between adjacent vehicles to represent the collision-avoidance and compact formation performance. A novel state transformation technique is proposed to convert the bounded spacing error space to an unconstrained state space. On the basis, Comprehensive equality constraints for the transformed states are established by integrating the information of proximal (preceding and following) vehicles. In addition, an anti-windup compensation method is utilised to handle actuator saturations. Then an adaptive constraint-following controller is designed to render the uniform boundedness and uniform ultimate boundedness performance of the transformed state. As a result, the string stability, the strong string stability, the collision-avoidance and compact formation are guaranteed despite the presence of actuator saturations and complex uncertainties. Numerical simulations are performed to validate the effectiveness of the proposed control scheme.
The fixed-time master–slave trajectory tracking control problem of the human-in-the-loop teleoperation systems with mixed communication delays (including time-varying delays and random delays), parametric uncertainties, and external disturbances is discussed in this study. Based on the non-singular terminal sliding mode control technique, a novel neuro-adaptive fixed-time control algorithm is designed to solve the above-mentioned problem. Moreover, to improve the steady-state performance of the presented control algorithm, the combination of the radial basis function neural networks, parametric adaptive laws and fixed-time control method is newly-designed and used to reduce the effects of parametric uncertainties and external disturbances. By employing the Lyapunov argument, the sufficient conditions on the control parameters for guaranteeing the fixed-time stability of the controlled teleoperation system are derived. Besides, the authors also present the upper bound of the settling time and prove that it is independent of the initial condition. Finally, several simulation examples are performed to verify the effectiveness of the theoretical results.
This study proposes a model predictive control (MPC) method with a fixed weighting factor for three-phase four-switch inverter-fed permanent magnet synchronous motor drives to suppress the capacitor voltage offset. The prediction model of the capacitor voltage difference is obtained based on the relationship between capacitor voltage and phase current. Then by analysing the relationship between basic voltage vector, electromagnetic torque and flux amplitude, the control of electromagnetic torque and flux in the model predictive torque control is transformed into the control of the voltage vector. The dimension of the capacitor voltage difference is the same as that of the voltage vector, hence the cost function with the fixed weighting factor is defined with the consideration of the capacitor voltage offset suppression. The effectiveness of the proposed MPC method is validated by the simulation and experiment.
Classical artificial potential approach of motion planning is extended for emulating human driving behaviour in two dimensions. Different stimulus parameters including type of ego-vehicle, type of obstacles, relative velocity, relative acceleration, and lane offset are used. All the surrounding vehicles are considered to influence drivers' decisions. No emphasis is laid on vehicle control; instead, an ego vehicle is assumed to reach the desired state. The study is on human-like driving behaviour modelling. The developed motion planning algorithm formulates repulsive and attractive potentials in a data-driven way in contrast to the classical arbitrary formulation. Interaction between the stimulus parameters is explicitly considered by using multivariate cumulative distribution functions. Comparison of two-dimensional (lateral and longitudinal) performance indicators with a baseline model and generative adversarial networks indicate the effectiveness and suitability of the developed motion planning algorithm in the mixed traffic environment.
A novel concept of a dual-layer-oriented control strategy for fully automated vehicles’ lane-keeping system is proposed which consists of an inner controller with a modified preview driver model and an outer cooperative copilot controller. With designed weighting function of displacement error based on a hyperbolic tangent and adjustable preview horizon according to road geometry, the inner controller is supposed to track the lane centreline precisely and efficiently through optimal control framework. The outer controller is specially designed for situations where the vehicle may run out of the lane and cause a collision. Only when the vehicle is at high risk of lane-crossing, the outer controller is activated to guide the vehicle back to lane centreline by exerting proper steering command, which is calculated by solving a model predictive control-based constrained optimisation problem with a designed quadratic cost function. Finally, simulation tests based on CarSim-Matlab joint platform are carried out to verify the proposed strategy. Results demonstrate that the modified preview driver model is able to improve path following performance and the dual-layer-oriented control strategy with less computational burden can effectively prevent the vehicle from crossing lane boundaries.
The development of connected and automated vehicle technologies allows for cooperative control of vehicles and traffic signals at intersections. This study aims at exploring the cooperation between traffic signal control and eco-driving control for a connected hybrid electric vehicle (HEV) system. A two-level cooperative control method for integrating traffic signal control, vehicle speed control, and energy management is proposed with the objective of improving both traffic and fuel efficiency for HEVs at isolated intersections. In view of the energy management and recuperation system of HEV, the vehicle energy consumption characteristic is considered in the proposed method. More specifically, at the traffic level, a traffic signal control strategy is designed to minimise the total travel time and fuel consumption of all HEVs using dynamic programming, which explicitly considers the arrival time and recuperation information of vehicles. At the vehicle level, a hierarchical control architecture is applied to optimise the speed trajectories and powertrain of each HEV using model predictive control and adaptive equivalent consumption minimisation strategy. Simulation results show that compared with the fixed-time and cycle-based signal control strategies with eco-driving, the proposed method can significantly reduce the travel time and fuel consumption by up to 27 and 24%, respectively.