Multi-Layered Control of a Four-Degree-of-Freedom Mobile Robot with Compliant Linkage

This paper introduces a new approach to the design and control of a four-degree-of-freedom (4DOF) vehicle. This vehicle can travel sideways and it can negotiate tight turns easily. Existing 4DOF vehicles have been found difficult to control 2. The compliant linkage because of their overcon-strained nature. These difficulties As explained above, the key element in any workable MDOF translate into severe wheel slippage or jerky motion under design must be the provision of mechanical compliance certain driving conditions. [Borenstein, 1992]. One possible kinematic design for an MDOF Our approach overcomes these difficulties by introducing vehicle is shown in Fig. 1. compliant linkage, a new concept in the control and kinematic design of 4DOF mobile robots. As the name implies, compliant linkage provides compliance between the drive wheels or drive axles of a vehicle, to accommodate control errors which would otherwise cause wheel slippage. We describe a three-level control system comprising of a wheel-level, a vehicle-level, and a trajectory-level controller. Experimental results are presented and show that control errors are effectively absorbed by the compliant linkage, resulting in smooth and precise motion.