Dynamic hopping height control of single-legged hopping robot

Abstract

In order to control the vertical hopping height of two degree-of-freedom articulated single-legged hopping robot, a hopping height control scheme based on the energy conservation in the course of hopping was proposed. The kinematic model of the legged hopping robot and the hybrid dynamic model on flight and stance phase according to the different constraint condition was established, and the ground contact model based on the impact collisions between end-effector and ground was analyzed. On the one hand when robot was controlled to hop higher, energy was imparted into the robot system by increasing the pre-compressed length of the virtual spring. On the other hand, when robot was controlled to hop lower, the redundant energy of the robot system was dissipated by the inelastic collisions when the end-effector touched down the ground. The control scheme is demonstrated by the simulation experiment of hopping height control implemented in MATLAB/Simulink. The robot’s hopping height increases from 0.55 to 0.8 m and then decreases from 0.8 to 0.55 m with 0.05 m intervals. The phase plot shows that the dynamic hopping with different height approaches respective periodic and stable orbit. And the time domain hopping plot shows that the control scheme has fast dynamic response and nearly no steady-state error. The experiment result shows great efficiency of the control scheme proposed here.