Transition control of a quadruped robot from quadruped to biped locomotion

ZHOU Kun-ling， ZHANG Xiu-li， GONG Jia-qing
（School of Mechanical， Electronic and Control Engineering， Beijing Jiaotong University， Beijing 100044， China）

Abstract： Aiming at the problem that extending the locomotion performance and environmental adaptability of quadruped bionic robot，a method was proposed that combining biologically-inspired trajectory-planning and zero moment point（ZMP） stability controlling to realize a quadruped robot "Babybot" transition from quadruped to biped locomotion. Firstly，the motion trajectories of the quadruped robot from quadruped to biped locomotion by mimicking human's standing-up motion were planned. Secondly，the key postures using static balance principle and multivariable optimization approach were determined. Finally，transition between of the key postures using ZMP-based linear interpolation was executed，and dynamic simulation of robot from quadruped to biped locomotion was done，dynamic simulations show that the "Babybot" spends 9.5 seconds to complete the transition  from quadruped to bipedal locomotion smoothly. The results indicate that the proposed control method that combining biologically-inspired trajectory-planning and ZMP stability controlling has effect on the transition from quadruped to biped locomotion，and provides a reference for other performance of quadruped robot.
Key words： quadruped robot； quadruped to bipedal locomotion transition； trajectory planning； balance control； zero moment point（ZMP）