Smooth Transition Method from Compliance Control to Position Control for One Legged Hopping Robot

Abstract

Walking motion is approximately accomplished by conventional researches. In the next stage for legged robots, it is required to move fast and get over high obstacles. Hopping motion enables a legged robot to move like that. Therefore, hopping motion must be considered. In landing phase of the hopping cycle, the robot is affected by reaction force from the ground. There is a possibility for robots to upset and to be damaged because of reaction force at landing moment. In order to reduce reaction force, variable compliance control was proposed. However, the robot is not able to achieve desired motion at bottom with conventional variable compliance control, since command values of variable compliance controller are not equal to zero at bottom. In this paper, we propose a transition method from compliance control to position control for hopping robot to achieve the desired position of COG (center of gravity) at bottom. It is important for a hopping robot to achieve a desired position at bottom since the robot must prepare for a next hop. With the proposed method, the transition from compliance control to position control is appropriately achieved, and a phase shifts smoothly from landing phase to thrusting phase. Therefore, a desired position at bottom is achieved. The effectiveness of the proposed method is confirmed by experimental results.