In this paper, a first attempt is made to deal with the motion tracking problem for a hydraulic system in the existence of input saturation, unknown valve dead-zone, parametric uncertainties, and uncertain disturbances. To address the problem of input saturation and valve dead-zone simultaneously, the designed anti-windup is integrated with the compensation of the dead-zone nonlinearity effectively via a combined and comprehensive inverse model. A dynamic auxiliary system and a smooth dead-zone inverse model, which are utilized to attenuate input saturation and compensate the nonlinearity of dead-zone, are synthesized into the design of the robust adaptive controller based on the backstepping technology. Meanwhile, the adaptive law and the nonlinear robust control law are conducted to handle parametric uncertainties and various disturbances. Based on the Lyapunov stability theory, the closed-loop asymptotic stability of the designed control strategy is proved, and the boundedness of all the signals are ensured. The excellent performance of the proposed control scheme is verified by comparative experimental results.

Traditional control methods for precise motion control of electro-hydraulic servo systems are primarily based on rigid-body dynamics of the system. Considering that structural flexibility of the mechanical components have a certain impact on all drive systems, the neglected high-frequency dynamics caused by structural flexibility have become one of the major obstacles when developing better control performance. In this paper, a high-accuracy tracking control is concerned for hydraulic actuators with unmodeled flexible dynamics. Firstly, a damping term is utilized to counterweigh the unmodeled nonlinear flexible function and a dynamic signal is designed to control the dynamic flexible disturbance. Then, in order to process parametric uncertainties along with unmodeled flexible dynamics, an adaptive backstepping controller is proposed. The controller theoretically guarantees global bounded tracking performance via Lyapunov analysis. The experimental and simulation results illustrate the high-performance nature of the proposed controller.

Unlike the roll motion of the unmanned aerial vehicle (UAV) controlled by the ailerons, the moving-mass actuated unmanned aerial vehicle (MAUAV) uses the motion of the mass block inside the wing to generate the roll moment. The light weight and severe coupling of lateral and longitudinal motion of this type of small UAV make its landing control a challenging task. Considering the above problems, the dynamic models of MAUAV are first established. Then, forward velocity, altitude, attitude, and moving-mass position controllers are designed separately to make the MAUAV track a given path during the landing process. Linear active disturbance rejection control (LADRC) is introduced in the design process of all four controllers, compensating for unknown disturbances in the system. Simulation results show that the proposed control scheme can achieve fast and accurate tracking of forward velocity and flight trajectory commands with good robustness to model uncertainties.

This paper concerns high-accuracy roll control for single moving-mass controlled reentry vehicle. Considering the simultaneous existence of matched and mismatched uncertainties in the reentry vehicle system, a continuous integral robust control strategy is proposed based on the backstepping design framework. The controller uses the error transformation method to transfer the mismatched modeling uncertainty to the control input channel, and then a robust structure constructed in the controller can handle it together with the matched modeling uncertainty. The final control input is continuously differentiable, which is benefit for tracking performance improvement and practical controller implementation. The proposed controller theoretically guarantees asymptotic tracking performance via Lyapunov analysis. Finally, simulation results are given to illustrate the efficiency of the proposed approach.

The presence of both additive disturbances and parameter uncertainties is common in reentry systems. In order to solve these two problems at the same time, an asymptotic adaptive roll tracking control is concerned in this article. The disturbances are estimated through an adaptive-gain disturbance observer. Meanwhile, the controller uses a parametric adaptive law to handle the parametric uncertainties. Through the backstepping design framework and Lyapunov analysis, the proposed controller guarantees asymptotic tracking performance based on the integrated design of adaptive-gain disturbance observer and parametric adaption technique. Finally, simulation results including the comparison with traditional algorithm are demonstrated to verify the effect of the designed method.