Study On The Control Strategy For A Quadruped Robot Walking In Trot Gait Under External Disturbance

Quadruped robot that take advantage of high dynamic, high adaptability and high load has become a hot spot of the research. Conventional motion control method based on trajectory planning cannot ensure the quadruped robot adapt to rough terrain and resist external impact. This thesis mainly focuses on the issue of control strategy for a quadruped robot walking in trot gait under external disturbance. A compliant gait motion control method is proposed based on virtual model. The control strategy for rough terrain disturbance and external lateral impact is carried out. Simulation platform is built to conduct simulation verification of proposed strategy. The main work of the dissertation is as follows:Firstly, mathematical analysis model is established. Kinematics and dynamics analysis are carried out. The robot kinematics equation and dynamics equation are deduced. Forward and lateral stability is analyzed based on SLIP model.Secondly, the compliant gait locomotion method of the quadruped robot is represented using virtual model based on a mass-spring-damper model. The locomotion task of the quadruped robot is represented using virtual forces acting on the mass centre of the body. A principle that all feet of the quadruped robot have balanced equivalent torques is assumed, based on which the virtual force is distributed to all supporting feet. The Jacobian matrix for each single leg is employed to convert the foot forces in the Cartesian space to joint torques in the joint space. Control strategies for forward velocity, lateral velocity and yaw angle of quadruped robot are proposed.Thirdly, the control strategy of inertial forces under rough terrain disturbance and external lateral impact disturbance is carried out using force compensation.Lastly, a simulation platform for quadruped robot is built based on SCS. The control strategy of forward velocity, lateral velocity and yaw angle is verified. Then the proposed balance recovery algorithm is verified through simulation. The simulation result indicated the validity and rationality of the proposed compliant gait generation method and the balance recovery algorithm.