Cooperative attitude control for a wheel-legged robot

Robot systems are complex systems which include many CPUs and communication networks. In order to control attitude of a wheel-legged robot, a cooperative control framework is designed. The wheel-legged robot has four legs and four wheels, and the wheels are installed on the foot. The wheel-legged robot can adjust its attitude by controlling the position of each leg when it is walking with wheels. In addition, in order to avoid the wheels dangling during the driving of the robot, an impedance control based on force method is applied. Moreover, the centroid height of the robot is controlled to guarantee that the robot has maximum motion space. The cooperative control framework is implemented in a host CPU and four slave CPUs. The host CPU calculates the position of each leg by combining the control variables of attitude controller, centroid height controller and impedance controller based on force. The slave CPUs receive the position command, and then control the position of each leg with active disturbance rejection control (ADRC). ADRC can deal with the internal modeling uncertainty and external disturbances. The application of the proposed method is illustrated in the electric parallel wheel-leg robot system. Experimental results are provided to verify the effectiveness of the proposed method.