Abstract
Mobile robots are increasingly being used in challenging outdoor environments for applications that include construction, mining, agriculture, military and planetary exploration. In order to accomplish the planned task, it is critical that the motion control system ensure accuracy and robustness. The achievement of high performance on rough terrain is tightly connected with the minimization of vehicle-terrain dynamics effects such as slipping and skidding. This paper presents a cross-coupled controller for a 4-wheel-drive/4-wheel-steer robot, which optimizes the wheel motors' control algorithm to reduce synchronization errors that would otherwise result in wheel slip with conventional controllers. Experimental results, obtained with an all-terrain rover operating on agricultural terrain, are presented to validate the system. It is shown that the proposed approach is effective in reducing slippage and vehicle posture errors.
Highlights
For mobile robots driving across challenging terrains, the greatest enemy of motion accuracy is wheel slippage
Other examples of mobile robots with over-constrained drive systems are the six-wheeled Shrimp [2], the Nomad Arctic traverse robot developed at Carnegie Mellon University [3], wheeled snake-type robots like the ones developed by Hirose et al [4], and hybrid leg/wheel systems [5]
It was demonstrated that during single straight-line and turning maneuvers, the orientation error and the tracking error were significantly reduced to maximum values of
Summary
For mobile robots driving across challenging terrains, the greatest enemy of motion accuracy is wheel slippage. Other examples of mobile robots with over-constrained drive systems are the six-wheeled Shrimp [2], the Nomad Arctic traverse robot developed at Carnegie Mellon University [3], wheeled snake-type robots like the ones developed by Hirose et al [4], and hybrid leg/wheel systems [5] For all of these vehicles the designers accept the reduction of motion accuracy in their over-constrained systems as a tradeoff for enhanced mobility. Shown, is an independently controlled four-wheel-drive/four-wheel steer mobile robot, featuring a rocker-type suspension system. This architecture provides a high degree of mobility, allowing the robot to safely traverse rocks over one and half its wheel diameter and to perform special maneuvers such as crab and turn-on the spot motion.
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