Anti-disturbance vibration control is a crucial component in a hydraulic suspension system. However, random input excitation and prolonged service can cause hydraulic suspension system parameters to drift, leading to system vibration with suppression failure. The resulting states of nonlinearity and disturbance will lead to a gradual deterioration of pressure control. Therefore, designing a viable controller for a hydraulic suspension system that considers system nonlinearity, computing capacity, and sensor configuration is essential. To address this need, we present a double-layer control strategy in this work. A hybrid sliding mode control algorithm based on the reference skyhook and groundhook model is proposed to regulate the expected force of reverse compensation. An output controller is then applied based on the expected force observer to mitigate low-frequency vibrations to realize a steady state. A logic rule is designed to ensure that the two controllers work to suppress sprung mass vibration, and a comprehensive system model is derived to help characterize system nonlinearities and design the hybrid sliding model controller. Numerical and physical validations are then carried out to demonstrate the feasibility of the strategy and test the performance of the controller. The experimental results show that the hybrid sliding mode controller can suppress vibration under disturbance excitation and reduce the vibration acceleration to a 2.3 m/s2 random response when system parameters vary.
Tractors transporting heavy hitches tend to tilt severely, resulting in significant dynamic loads on the front axle and affecting handling stability. Tractors and rear hitches can be considered vibration systems with two coupled masses. Thus, active damping control strategies between tractors and rear hitches are proposed in this study. The complexity and versatility of tractor hydraulic hitching during tractor transit transport are considered. A method of improving the tractor hydraulic hitch damping ratio with pressure feedback is proposed. The dynamic characteristics of the pressure feedback hydraulic hitch system are analyzed. A dynamic model of the tractor transfer transport unit is established, and a numerical simulation is carried out to verify the effectiveness of the proposed hydraulic hitch vibration reduction control strategy based on pressure feedback. A real test platform for tractor vibration reduction control is built. The test results show that the pressure feedback vibration reduction control method proposed in this paper affects tractor pitching motion suppression. In addition, the proposed control strategy does not require a force pin sensor. Tractor hydraulic hitch damping control costs are reduced. The vibration reduction control strategy proposed in this study has high reliability and can be used as a reference for non-road-vehicle vibration reduction control.
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