Locomotion Control For A Quadruped Trot Based On3D Simplified Model

Quadruped robot has attracted lots of attention from scholars because of its highcarrying capacity, good stability, low redundancy and complexity. Trot gait, as a mediumspeed gait with high energy efficiency, has been widely applied in quadruped robots.Existing control methods for quadruped trot are mostly based on planar model, becauseplanar model only needs to consider three degrees of freedom of the robot’s body whichis forward speed, pitch angle and hopping height while the other degrees of freedom arerestrained. So it’s easy to design and analyze control methods based on planar model. Butin order to make quadruped trot meet the requirements of practical application, runningfree in the wild, the other degrees of freedom of the robot’s body need to be controlled.Therefore, the study of quadruped trot’s3D control method has important practicalsignificance.The thesis is supported by National Hi-tech Research and Development Program ofChina(863Program, Grant No.2011AA040701). Based on3D simplified quadrupedmodel, quadruped trot’s3D control method has been deeply researched on the combinedsimulation platform of virtual prototype and control system via analyzing the dynamicsof animals’ running.Firstly, the3D simplified quadruped model is built, and its kinematic equations arederived. Some needed variables are defined and its formula is derived, such as the heightof robot’s body and the inclination angle of ground. By observing the trot running ofanimals, the motion state of quadruped trot is designed and the motions of legs duringeach state are defined.Secondly, by analyzing the dynamics of spring loaded inverted pendulum(SLIP), thecontrol method for3D quadruped trot has been designed and the robot can run on the flatroad. In order to elevate the control performance of yaw motion, two strategies forcompensating the lateral speed and adjusting the roll angle have been proposed. Thismethod is combined with virtual model control method, so the robot can run like theanimals’ SLIP model and has high adaptation on tough road and good agility facingemergency.At last, a combined simulation platform has been built, composed by virtualprototype built by ADAMS software and control system built by MATLAB software. Aseries of simulation experiments has been carried out on the platform, including straightforward running and turning on flat road, climbing up and down the step and slope, andresisting the lateral disturb. By analyzing the result of these simulation experiments, thecontrol method has been proved effective and can be referred by actual robots.