Zisen Hua,∗,∗∗ Xuewen Rong,∗∗∗ Yaru Sun,∗,∗∗ Yibin Li,∗∗∗ Hui Chai,∗∗∗ and Chengjun Wang∗,∗∗
Hydraulic actuator, passive compliance, quadruped robot, impact force
Impact forces are inevitably generated between the feet and the ground while legged robots are moving, and the hydraulic servo actuator with the original structure cannot respond to such impact forces in a timely manner though it is controlled by the hydraulic servo valve with high performance. A novel passive compliance method is proposed for quadruped robots, aiming to improve the output characteristics of the hydraulic servo actuator and reduce the impact. Firstly, the hydraulic principle of the actuator with the improve structure is proposed, which is characterized using the accumulator as an elastic element and adding some auxiliary oil circuits and control valves to improve the output performance of the actuator. Then the mathematical model of the actuator is deduced and built by Simulink. After that, the active and passive performances of the actuator are simulated. Furthermore, the single-leg test bench is designed and effectiveness of the method is validated through the experiments. It can be demonstrated that the actuator not only has better output performance but also shows an ideal passive compliance based on the simulations and experiments.
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