Stability Improvement of Mobile Robot with Mutative Driving Axial Distance Omni-Directional Wheels

The omni-directional mobile robot has three degrees of freedom in the plane. It has high flexibility and is also suitable for transport and operation in crowded and narrow environments. The work focuses on detailed analysis of the driving mode of the driving wheel and the changing process of the driving axial distance. In accordance with the driving axial distance, the omni-directional wheels are divided into two types: mutative driving axial distance wheels and fixed driving axial distance wheels. The mecanum wheel, alternate wheel and the MY3 wheel belong to the mutative driving axial distance wheel. The causes of the abrupt change of ground distance of the robot and the influence of the mutation on the stability of the robot are analyzed. In order to improve the stability, the relationship between the ground distance and the rotation angle of MY3 robot is analyzed. Two functions are proposed: The sinusoidal gradual- change function and The polynomial gradual-change function. Synthesizing the trajectory, kinematics and dynamics models, the minimum value of the gradual coefficient is obtained and the trajectory accuracy is improved. The simulation results show that both the functions can eliminate mutations of the speed and torque of the motor, but the trajectory errors of the sinusoidal gradual-change function are smaller.