Roll Torque Vibration Isolation Control on Parallel Active Suspension System via Impedance-Based MPC for Vehicular Terminal

To improve the stability of vehicle body dynamics on rugged roads, the majority of researchers have studied vertical force control at the terminal of the vehicle utilizing an active suspension system. However, terminal disturbance roll torque can also have a negative impact on the stability of the vehicle’s state. In this paper, a terminal roll torque control strategy (TRTCS) is proposed to enhance the stability of body attitude by controlling terminal roll torque in wheeled motion. The strategy includes impedance-based model predictive control (IMPC) and terminal posture return controller (TPRC). Firstly, IMPC analyzes the single-leg dynamic model embedded with torque impedance at the terminal. Then, the controller iterates through quadratic optimization to obtain an optimal impedance target torque that can efficiently mitigate terminal disturbance roll torque while stabilizing the terminal roll velocity, acceleration, and force on each electric cylinder. Then, TPRC generates additional smooth return speed for the terminal roll angle to the initial value through the Bezier curve and event-trigger mechanisms to estimate the terminal contact state to the ground. TPRC aims to compensate for low angular return speed due to insufficient measured torque on the suspending terminal during the downhill process. Finally, through simulation and experiment, TRTCS significantly diminishes the deviation of terminal roll torque and body attitude from target value to 25.2% and 35.8% respectively when a vehicle crosses multi-slopes compared with traditional torque impedance.Note to Practitioners—The motivation for this work is that the vibration isolation control on vehicles or wheeled robots often neglects the disturbance of the roll torque on their feet on rough roads. Unfortunately, this can damage the leg actuators of vehicles or robots, and even have a negative impact on the steadiness of the body posture. Therefore, this paper proposes a TRTCS, which controls the terminal roll torque by rotating its roll angle with high dynamic stability. The control framework has the following functionalities: 1). The terminal roll angular velocity is obtained based on an optimization function that can make the terminal torque converge smoothly to the target value and the leg actuator subjected to more distributed force. 2). A smooth roll angle correction additional speed is generated based on the Bezier curve to compensate for the slow roll angle correction speed caused by insufficient correction roll torque during the downhill phase. A series of simulations and experiments have verified that the control method has a small steady-state error in controlling the roll torque at the terminal. At the same time, under TRTCS, the peak force on the leg actuator is significantly reduced, which has a significant inhibitory effect on the actuator loss and unsteadiness of the body posture. In future research, we will further investigate the control of terminal pitch and yaw torque.