The aircraft braking system is a critical system used to slow down and stop the aircraft. Typically, the aircraft braking system usually uses the electro-hydraulic pressure servo-valve (EHPSV) to regulate the braking pressure of the aircraft. However, the pilot stage of EHPSV which has very precise orifice is easy to be blocked and leads to terrible fault. The on / off valve is robust to oil contamination and has better stability, but it is challenging to achieve high-precision pressure regulation. In order to guarantee the braking efficiency of aircraft, a high-precision pressure regulation algorithm is required. In this study, a algorithm with on / off valve array unit is studied to optimize the pressure regulation performance. The characteristics of the on / off valve under different actuation times and pressures are derived. Based on this characteristics, a novel algorithm which can predict the required number of on / off valves and actuation time obtained by the unknown input state observer. Then the proposed algorithm is validated both by simulations and experiments. The results show that the proposed regulation algorithm in this study can achieve high-precision pressure regulation for aircraft braking application, which the regulation precision is better than 0.2 MPa, and the overshoot is less than 2.5%.

To overcome the adverse effects of time-varying parametric uncertainties and strong disturbances in aircraft antiskid braking systems (ABS), achieving efficient antiskid braking control and shortening the braking distance. This article proposes a modified super-twisting sliding mode control (MSSMC)-based aircraft ABS controller with gain adaptive schedule and disturbance compensation. In this article, MSSMC is obtained by substituting the discontinuous term in the conventional super-twisting sliding mode control (SSMC) with a continuous fractional power term, which can alleviate the chattering and improve the tracking performance. The developed controller is derived by effectively integrating MSSMC, extended state observer (ESO) and gain adaptive techniques, preserving the advantages of these approaches while effectively overcoming their practical performance limitations. The time-varying disturbances and unmodeled dynamics in aircraft ABS are estimated by ESO and compensated in a feedforward way, which significantly decreases the residual uncertainties handled by the MSSMC, thus alleviating the burden on the MSSMC and avoiding the high-gain feedback. In addition, a novel gain adaptive protocol for MSSMC is proposed, which can minimize the control gain and the chattering amplitude without the prerequisite of uncertain upper boundary required for conventional SSMC. Theoretical analysis based on the Lyapunov approach shows that the designed ABS controller ensures that the sliding variable converges to the desired accuracy near the origin in a finite time. Comparative experimental results demonstrate the effectiveness of the proposed approach.

The hydraulic flight motion simulator (HFMS) is the key equipment for the hardware-in-the-loop simulation in the field of aerospace and has been widely used on occasions requiring high maneuverability and large power. However, three mismatched uncertainties, including nonlinear friction torque, unbalanced gravity torque, and unknown inertia, bring some certain difficulties for receiving the high-precision outer frame position control of the HFMS. In this article, first, by means of an ingenious experimental design, the coupled friction torque and gravity torque were identified separately. Subsequently, through combining the established mathematical model and identification results, an adaptive robust controller with model compensation was investigated in which adaptive controller is not only used to estimate unknown system parameters but also able to online correct identified parameters, and the robust controller is able to guarantee the stability of the whole system. Additionally, the zero bias of the servo valve was also introduced to assist controller implementation. Finally, experimental results show that by using the method of torque identification to improve the model accuracy, the burden of parameter adaptation and robust items can be effectively alleviated, and the high-precision outer frame position control of HFMS can be realized.

Hydraulic servomotor is a common energy-saving hydraulic power component that can switch between pump and motor operating conditions. Precise displacement control of hydraulic servomotors is crucial for minimizing throttling losses and enhancing overall efficiency. Nonetheless, the accuracy of hydraulic servomotor displacement control is negatively impacted by high-frequency uncertainty disturbances in swashplate moment. Traditional adaptive robust control methods have overlooked this factor, resulting in suboptimal displacement control effectiveness. To address this issue, a swashplate disturbance compensation robust control approach is introduced in this article, aiming to enhance the control accuracy of hydraulic servomotor displacement under high-frequency uncertainty disturbances. In the article, a mathematical model for the servomotor displacement adjustment system is formulated, and an average disturbance model for the moment of a swashplate is developed to account for periodic disturbances and uncertainties. Comparing experimental results of sine commands at different frequencies reveals that the proposed method achieves a substantial enhancement in displacement control accuracy. Specifically, the proposed method demonstrates a maximum improvement of 39.2% and 27.4% in displacement control accuracy compared to the PID method and traditional adaptive robust control, respectively.