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The impact vibration caused by sudden changes in the external load of hydraulic actuators, which reduces the service life of hydraulic components and limits the high-precision applications of hydraulic actuators. So to improve the underdamped characteristics and impact resistance of valve-controlled cylinder systems, a semi-active impact resistance control of hydraulic actuator based on Magnetorheological Damper (MRD) is proposed. Firstly, based on the shear force characteristics of magnetorheological, a multi-stage flow channel MRD is designed with high output force, which is connected in series with the hydraulic actuator to form a Hydraulic Damping Actuator (HDA). While, based on the universal material machine to test the mechanical performance of the HDA, and using the displacement-velocity-damping force experimental data, the parameters of MRD dynamic model are identified to ensure the accuracy of MRD output force. Secondly, a drop weight impact model is established to simulate the impact process of sudden changes in the external load, and based on the mechanical model of the valve-controlled cylinder system and the MRD, a sliding mode controller with real-time tracking current control is designed, which realizes the resistant force coupling between the MRD and the hydraulic actuator, with the goal of improving the impact resistance control effect. Then the dynamic performance test and impact resistance simulation program are established to verify the excellent dynamic performance and impact resistance effect of the HDA with the cooperation of the sliding mode controller, by comparing the displacement tracking effect and current output under constant and variable current. Finally, the drop weight impact experimental platform is built, and the reasonability of HDA series structure and excellent real-time tracking performance are verified by using sinusoid and step signal. While, the height of the impact and weight of the mass block are set at 200 mm and 50 kg, respectively, the dynamic offset of the HDA is only -1.14 mm, and the time to return to the original position is 0.07 s. This is the optimal impact resistance effect in the drop weight test, which confirms that the design can improve the underdamped characteristic of the valve-controlled cylinder system and the dynamic response performance of the hydraulic actuator.

Magnetorheological damper; Hydraulic actuator; Underdamped characteristic; Impact resistance; Sliding mode control