Incremental Multi-Objective Motion Control of Nonholonomic Mobile Robots

This paper describes a motion controller which issues incremental velocity commands to a nonholonomic mobile robot guided by a holonomic path planner. The controller finds the best pair of rotational and translational velocities through discrete optimization of a multi-criteria objective function. Valid velocity choices are restricted within the dynamic velocity window as determined by the current velocities and the maximum acceleration and deceleration ability of the robot (smoothness criterion). In addition, for each choice the objective function examines the proximity of the resulting stopping configuration to the current goal set by the planner (accuracy criterion). Finally, it takes into account the potential of unforeseen, perhaps unavoidable, collisions due to dynamic obstacles or due to the holonomic nature of the path planner (safety criterion). The controller issues commands which balance these criteria as determined by the user. The proposed controller has been implemented and tested on a Nomad 200 mobile robot achieving smooth, accurate, and safe motion control both in simulated and in real environments