Multi-layered control of a four-degree-of-freedom mobile robot with compliant linkage

An approach to the design and control of a four-degree-of-freedom (4DOF) vehicle is presented. Existing 4DOF vehicles are difficult to control because of their overconstrained nature. These difficulties translate into severe wheel slippage or jerky motion under certain driving conditions. The author´s approach overcomes these difficulties by introducing compliant linkage in the control and kinematic design of 4DOF mobile robots. Compliant linkage provides compliance between the drive wheels or drive axles of a vehicle in order to accommodate control errors which would otherwise cause wheel slippage. A three-level control system comprising of a wheel-level, a vehicle-level, and a trajectory-level controller is described. Experimental results are presented and show that control errors are effectively absorbed by the compliant linkage, resulting in smooth and precise motion