Design and Analysis of a Wheel-pendulum Driven Spherical Robot

In this paper, a wheel-pendulum driven spherical robot is proposed to overcome the shortcomings of the spherical robots with traditional configurations regarding continuous motion ability and pose adjustment ability. Firstly, the electro-mechanical system of the spherical robot is designed. Then, the kinetic energy and potential energy of each part of the spherical robot are calculated, and its kinetics are modeled according to the Lagrange equation method. The driving process of the spherical robot is solved into the torque control and speed control of motors and servos according to the results of the kinetics model. Finally, a cascade PID based motion controller is designed and tested for the spherical robot: the control error of the motor speed closed-loop controller is no more than 3%, the angle control speed of the pitch angle closed-loop controller is 8.33dps, the yaw angle closed-loop controller is up to 180dps, the angle control speed of the roll angle closed-loop controller is 3.57dps, and the yaw distance of the auto-tracking direction closed-loop controller is not more than the target track ±1cm. The effects of the above controllers can meet the requirements of the actual working conditions, and the wheel-pendulum driven spherical robot has good continuous motion ability and pose adjustment ability.