Abstract: The mathematic model of hydraulic drive unit of quadruped bionic robot is founded. Time and frequency domain equations are shown to describe the dynamic characteristics of hydraulic drive unit. The accuracy of mathematic model is proved by comparing model curve and experimental curve in specific conditions. Based on the state equations of hydraulic drive unit, the trajectory sensitivity equations are derived. By solving the step response displacement of hydraulic drive unit of the sensitivity function curves corresponding to its structural parameters, operating parameters and PID controller gains, the impact on output characteristics is researched. The influence degree of each parameter variation is analyzed by percentage change of step response displacement. Then the main factors and secondary factors which affect the dynamic characteristics are given. All the research above can provide theoretical basis for structure optimization design and optimal control of hydraulic drive unit.

Key words: Hydraulic drive unit, Matlab, Quadruped bionic robot, Trajectory sensitivity analysis