Motion control of differential wheeled robots with joint limit constraints

The motion of wheeled mobile robots is inherently based on their wheels´ rolling capabilities. The assumption is that each wheel can rotate indefinitely, backwards or forward. This is the starting point for all motion control mechanisms of wheeled robots. In this paper, a new motion capability of differential mobile robots with limited wheel rotation capabilities is presented. The robot will be able to travel any distance and change its direction of movement even if its wheels can not rotate within more than a certain range of angles. The proposed solution is based on the bio-inspired controller principles used for modular and legged robots, in which oscillations are generated for achieving motion. A total of two oscillators, one per wheel, are enough to generate well-coordinated rhythms on the wheels to control the robot motion. The kinematics of this new type of mobile robot motion is presented, and the relation between the oscillator´s parameters and the trajectory is studied. Experiments with real robots will demonstrate the viability of this new locomotion gait.