This study proposes a fractional-order (FO) improved fast terminal sliding mode controller for permanent-magnet synchronous motor speed regulation system. By designing an FO proportional–integral controller for current loops, an FO model between reference q-axis current and speed output is proposed. By introducing an FO terminal sliding mode surface, a novel FO terminal sliding mode controller is designed for speed loop to improve the speed tracking performance. The proposed FO controller can make speed reach reference value in finite time. Moreover, it is proved that the control time of the FO sliding mode controller is shorter than integer-order (IO) sliding mode controller. To further enhance the convergence speed, the fast terminal sliding mode control method is used. Meanwhile, FO disturbance observer is utilised to enhance the disturbance-rejection ability. The control law of the proposed controller is designed according to Lyapunov stability theorem. Finally, Simulation and experimental results demonstrate the effectiveness, high control performance and high disturbance-rejection ability of the proposed composite FO controller in comparison with IO controller.

This study investigates the problem of distributed receding horizon control (DRHC) for constrained networked systems with polytopic uncertainty description, subject to time delays. Considering the limited communication capacity of the network and computational complexity, the approach of this study is based on a synchronous and non-iterative structure. Thus, for each subsystem, assumed predictive state evolutions of the neighbours are used. To restrict the assumed evolutions not deviating much from the true ones, the compatibility condition is derived concerning global stability. Time delays are handled by introducing an augmented polytopic uncertainty description, and the local optimisation problem is properly formulated by means of the robust receding horizon control technique. Applying the DRHC approach of this study, the recursive feasibility of the optimisation problem and exponential stability of the global system are guaranteed. An example is provided to illustrate the effectiveness of the proposed approach.

The uncertainty and disturbance estimator (UDE)-based robust control approach is widely investigated and applied due to its excellent performance and simple implementation. However, its stabilisability of unstable systems has not been documented. In this study, the sufficient and necessary stabilisability conditions of the UDE-based robust control are investigated. According to the stabilisability conditions, a systematical design method is presented for the reference model based on the controllable canonical transformation and pole placement. This is then applied to a magnetic levitation system (MagLev) subject to model uncertainties and external disturbance as an example. Simulation results are presented to illustrate the effectiveness of the proposed control approach with respect to matched uncertainties.

This study addresses robust QSR-dissipativity and feedback dissipation of a class of fractional-order (FO) uncertain linear systems. Both the state and controlled output matrices are with time-varying norm-bounded parameter uncertainties. Firstly, some new notions of QSR-dissipativity and passivity for FO systems are introduced, the relationship between QSR-dissipativity and asymptotic stability and input–output stability are discussed, respectively. Then, a sufficient condition in the form of linear matrix inequality (LMI) is proposed to ensure that such system is robustly QSR-dissipative. According to this condition, a state feedback controller is proposed when the full states can be measured. Secondly, by employing LMI techniques and matrices singular value decomposition, sufficient conditions for the existence and a robust dissipation synthesis method are derived, respectively. Thirdly, a design method of dynamic output feedback controller is developed in order to guarantee that the closed-loop system is dissipative. Finally, some numerical examples are provided to show the application of the proposed methods.

In this study, a new adaptive controller is introduced for the induction motors (IMs) based on immersion and invariance (I&I) technique. The dynamics of the IM system are perturbed by some disturbances such as time-varying rotor resistance and load torque. Accordingly, an adaptive controller is designed and the uncertain parameters are online estimated. The adaptation laws are obtained from the stability analysis based on I&I method. The simulation results verified the effectiveness of the proposed control method. It is revealed that the outputs of the IM could track the desired signals in the presence of the mentioned disturbances. Also, the results are compared with the conventional control methods and it is concluded that the proposed control approach resulted in better performance.