This paper studies the issue of input saturation in tracking control of differential drive robots. Although the structure of control strategy is a determinant factor for the occurrence of saturation phenomena, having a trajectory for the robot that is compatible with the bounds on the inputs is a necessary condition for avoiding saturation. In this study, analytic conditions for determining the compatibility of a trajectory with the input constraints are derived. Moreover, the problem of refining an incompatible trajectory to make it consistent with the input constraints is studied. This paper also proposes a novel control strategy for trajectory tracking of differential drive robots which can guarantee tracking and preservation of the input constraints provided that the desired trajectory satisfy compatibility conditions. In case of incompatibility of desired trajectory the proposed controller can simultaneously refine the trajectory and use the adjusted version for robot control, guaranteeing convergence of the robot to the geometric profile of trajectory. To demonstrate the power of developed theory, the problem of cooperative load carrying for two input-constrained differential robots has been studied. Simulation results show the validity of the derived control strategy.
['Amin Zeiaee', 'Rana Soltani-Zarrin', 'Reza Langari']
A novel approach for tracking control of differential drive robots subject to hard input constraints