Design of Hopping Robot Model for Improving Stability on Hopping Locomotion Control

This paper investigates the influence of the link length of hopping robot on the control performance of the robot attitude by simulation in order to improve the stability of the robot. The simulation model is a bipide hopping robot with springs and closed link mechanism. The springs are attached to the closed link legs horizontally, and the hopping motion is realized by opening and closing the link legs. The robot’s body has an inertial rotor, which improves the stability of attitude control. Attitude stabilization is conducted in combination with the swinging control of the legs and inertial rotor control. The mathematical model of the robot is derived separately for the state where the robot is on the ground and in the air by Lagrangian equation of motion. In order to realize the hopping motion, the periodic energy storage and release of the spring are used and the control input to the closed link of the leg is calculated using the vibration phase of the spring. The robot attitude control for stable locomotion control is designed by integral-type optimum servo with LQR method. This controller has a wide stability margin and robustness against modeling errors. Simulation analyses are conducted using robot models with three different leg link lengths by Simscape Multibody in MATLAB/Simulink. Guideline for designing link length of hopping locomotion control on an actual robot is discussed.