Zhenhua Zhao

Composite predictive flight control for airbreathing hypersonic vehicles

The robust optimised tracking control problem for a generic airbreathing hypersonic vehicle (AHV) subject to nonvanishing mismatched disturbances/uncertainties is investigated in this paper. A baseline nonlinear model predictive control (MPC) method is firstly introduced for optimised tracking control of the nominal dynamics. A nonlinear-disturbance-observer-based control law is then developed for robustness enhancement in the presence of both external disturbances and uncertainties. Compared with the existing robust tracking control methods for AHVs, the proposed composite nonlinear MPC method obtains not only promising robustness and disturbance rejection performance but also optimised nominal tracking control performance. The merits of the proposed method are validated by implementing simulation studies on the AHV system.

Finite-time super-twisting sliding mode control for Mars entry trajectory tracking

Abstract The robust tracking control problem for Mars entry vehicles subject to parameter perturbations, external disturbances and initial state errors during the entry phase is investigated in this paper. A new finite-time super-twisting (FTSTW) control law is proposed by designing a nonsingular terminal sliding mode (NTSM) surface for Mars entry trajectory tracking. The proposed FTSTW controller exhibits not only strong robustness against parameter perturbations, external disturbances and initial state errors but also the property of finite-time convergence of tracking error. Moreover, compared with traditional sliding mode control method, the control input (namely, the bank angle) of the proposed control approach is continuous which effectively avoids high-frequency switching and sharp change of control action. The merits of the proposed method are validated by implementing simulation studies on Mars entry vehicle system with disturbances and uncertainties. The results of a 500-run Monte Carlo simulation show that the proposed controller provides a promising solution for high-precision Mars entry trajectory tracking.

Continuous terminal sliding mode control with extended state observer for PMSM speed regulation system

In this paper, we discuss the speed regulation problem of permanent magnet synchronous motor (PMSM) servo systems. Firstly, a continuous terminal sliding mode control (CTSMC) method is introduced for speed loops to eliminate the chattering phenomenon while still ensuring a strong disturbance rejection ability for the closed-loop system. However, in the presence of strong disturbances, the CTSMC law still needs to select high gain which may result in large steady-state speed fluctuations for the PMSM control system. To this end, an extended state observer (ESO)-based continuous terminal sliding mode control method is proposed. The ESO is employed to estimate system disturbances and the estimation is employed by the speed controller as a feed-forward compensation for disturbances. Compared to the conventional sliding mode control method, the proposed composite sliding control method obtains a faster convergence and better tracking performance. Also, by feed-forward compensating system disturbances and tuning down the gain of the CTSMC law, the fluctuation of steady-state speed of the closed-loop system is reduced while the disturbance rejection capability of the PMSM system is still maintained. Simulation and experimental results are provided to demonstrate the superior properties of the proposed control method.

Continuous Output Feedback TSM Control for Uncertain Systems With a DC–AC Inverter Example

This brief proposes a continuous output feedback terminal sliding mode (TSM) control method for the output tracking problem of nonlinear systems with mismatched uncertainties. This method is developed by two consecutive steps: 1) design a sliding mode observer to estimate the derivative and high-order derivatives of system output and 2) construct a continuous TSM controller based on system output and the estimations of its high-order derivatives. The proposed controller not only guarantees system output converges to its reference in finite time but also keeps the continuity of control action. Experiments on single-phase dc–ac inverter circuits are also carried out to show the effectiveness of the proposed controller.

Design and implementation of chattering free sliding mode control method for PMSM speed regulation system

The speed regulation problem for permanent magnet synchronous motor (PMSM) servo system is studied in this paper. In order to eliminate the chattering phenomenon caused by high switching gain, a composite sliding mode controller is designed for the speed loop. Firstly, a continuous chattering free sliding mode control (CFSMC) method is proposed to ensure the performance of the closed-loop system. Then, an extended state observer (ESO) is used to estimate the disturbances of system and the estimated value is designed as feed-forward compensation, which helps to enhance the disturbance rejection performance. The proposed composite controller combines the merits of both methods. Matlab simulation and TMS320F2808 DSP experiment results indicate the superiority of the proposed method.

Continuous finite-time sliding mode control for output voltage regulation of DC-AC inverters with mismatched disturbances

A continuous finite-time sliding mode control method based on finite-time disturbance observer is designed for DC-AC inverters with matched/mismatched disturbances. First of all, a finite-time disturbance observer is introduced for the estimations of disturbances and their derivatives. And then, the estimation information of disturbances and their derivatives are utilized to construct a new dynamic sliding surface. To eliminate the chattering phenomenon of sliding mode control, the switching terms of proposed method is designed to appear only in the derivative of control. Finally, the robustness of proposed controller to parameter perturbations and external input voltage disturbances is demonstrated by simulation results.