Control of the compass gait biped robot

Abstract

In this paper, two different controllers have been designed to follow the desired trajectory. The robot, known as Compass Gait Biped Robot (or Underactuated Biped Robot), is assumed to have 2 legs known as the stance leg and the swing leg. Both legs have the same mass, with each center of mass located at the midpoint of the leg. The hip’s mass is assumed to represent the weight of the entire upper body. The locomotion of this kind of robot is constrained in the sagittal plane, where the friction between links and the energy lost at the impact are ignored. The dynamic model of the system (i.e. the equation of motion) is obtained, and is validated by analyzing the kinetic and potential energy. Trajectory is generated by Cubic Spline Method, and the desired joint velocity and acceleration are obtained by inverse kinematics. Controller design involves the comparison between the Proportional Integral and Derivative (PID) controller and the Computed Torque Control (CTC), which indicate that the CTC method is better for tracking the generated trajectory.