Variable Impedance Control of Quadruped Robot

Abstract

The research in this thesis aims to realize stable trot of aquadruped robot on irregular terrain. Trotting on irregular terrain is difficult as undesirable impulse force by collision between the foot and an obstacle makes the robot unstable. To cope with the problem, it is necessary to adjust the interaction characteristic of the robot feet and the ground when terrain condition and locomotion phase are changed. The interaction characteristic can be modeled as an impedance model, which includes mass, spring, and damper. In this paper, variable impedance con-trol algorithm changing leg impedance parameters according to the change of finite states of quadruped trot is proposed. The state of quadruped trot is divided into five phases and the impedance parameters are changed to generate adequate response to the contact force in each contact phase. Simulation of trotting on irregular terrain with half-ellipsoidal trajectory has been performed with the control groups, which are the simulations without impedance control and with fixed impedance control. The simulations have verified that proposed control method shows outstanding per-formance and better stability for trotting on the highly irregular terrain. This thesis also contains hardware development of HUNTER, which is aquadruped robot based on the biological analogous of areal dog. HUNTER was built up with network-based sensors and actuators and asoftware guaranteeing real time process of control thread was built. With asimple experiment on trot, the feasibility of network-based actuators and control software for HUNTER has been verified.