This paper focuses on active compliance control of hydraulic quadruped robot, especially the analysis of the inner-loop of the coupled system. Current researches on active compliance control regard the bandwidth of the inner loop of the system as infinite, while ignoring that the extra-load will cause the inner-loop response characteristics to deteriorate when the leg is in the stance phase. In this work, we first briefly introduced the structure of the robot, and its kinematics and dynamics are analyzed. Next, the robot’s active compliance control framework is established, and the inner-loop two-cylinder coupling system is analyzed in depth. It can be concluded that the existence of low frequency poles in the system is the main reason for the poor response characteristics. Then through the analysis of the state equation and transfer function matrix of the multi-input multi-output system, we show that the equivalent hydraulic spring stiffness (EHSS) is the main factor affecting the zero-pole distribution. Furthermore, we optimize the structure to increase the EHSS to improve the response characteristics of the system. Finally, the co-simulation platform and single-leg experiment bench are introduced. The simulation and experimental results show that the response speed of the inner-loop control is significantly improved after optimization, and the robot with active compliance control strategies can significantly reduce the impact of the foot.

本文着重于液压四足机器人的主动柔量控制，尤其是对耦合系统内环的分析。当前关于主动顺应性控制的研究认为系统内环的带宽是无限的，而忽略了额外的负载会导致腿处于站立状态时内环的响应特性恶化。在这项工作中，我们首先简要介绍了机器人的结构，并分析了它的运动学和动力学。接下来，建立机器人的主动顺应性控制框架，并深入分析内环两缸耦合系统。可以得出结论，系统中低频极点的存在是响应特性较差的主要原因。然后通过对多输入多输出系统的状态方程和传递函数矩阵的分析，表明等效液压弹簧刚度（EHSS）是影响零极点分布的主要因素。此外，我们优化结构以增加EHSS，以改善系统的响应特性。最后，介绍了协同仿真平台和单腿实验台。仿真和实验结果表明，优化后内环控制的响应速度明显提高，具有主动柔度控制策略的机器人可以显着减少脚的冲击。我们优化结构以增加EHSS，以改善系统的响应特性。最后，介绍了协同仿真平台和单腿实验台。仿真和实验结果表明，优化后内环控制的响应速度明显提高，具有主动柔度控制策略的机器人可以显着减少脚的冲击。我们优化结构以增加EHSS，以改善系统的响应特性。最后，介绍了协同仿真平台和单腿实验台。仿真和实验结果表明，优化后内环控制的响应速度明显提高，具有主动柔度控制策略的机器人可以显着减少脚的冲击。