Compliant landing control of a trotting quadruped robot on unknown rough terrains

This paper presents a compliant landing control strategy for a trotting quadruped robot on unknown rough terrains based on contact force distribution/control algorithm. As joint actuator, the model of hydraulic cylinder is identified by using frequency response method. The compliant control strategy consists of three control loop: outer-loop is position and orientation of body control loop, in which friction cone constraint is considered; mid-loop is contact force control loop; inner-loop is joint torque control loop. In order to rapidly reduce disturbance caused by landing impact force, a landing phase is added between swing phase and stance phase based on contact force control. Finally, a trotting experiment is performed on a rough terrain to validate the effectiveness of the proposed method.