Control System Development for Tethered Mobile Robot for Automating Highway Maintenance Operation

A new concept, the use of a self-propelled mobile robot working in close proximity to a support vehicle for purposes of power, materials, etc., has been proposed for highway maintenance operations which require positioning equipment within close proximity to a support vehicle and almost always demand an end-effector to follow a specific path with precise path following requirements. This mobile robot system has been termed the Tethered Mobile Robot (TMR), and such an approach has the potential of use in a wide variety of applications as a positioning module. This report discusses the control system development of the TMR including various tracking control modes and controller hardware for their implementation.

A new non-linear path tracking control algorithm for a 2 DOF differentially steered mobile robot is presented and its exponential stability is proved. There have been no papers that have applied the feedback linearization for non-holonomic mobile robot control problem due to non-square nature of its equations of motion. A new idea is proposed to overcome the inherent problem and an exponentially stable non-linear control law is successfully derived using the feedback linearization.

In the TMR control, the biggest concerns are the non-linear terms due to centrifugal force and routing force that is very hard to estimate. However, the upper and lower bounds of the fluctuating routing force can be determined using an appropriate experimental method. Therefore, the robust control using the sliding mode technique is appropriate to the TMR control problem. The sliding mode control for wheeled mobile robot is formulated and this is a unique control strategy for the TMR and general wheeled mobile robot.

To implement the developed algorithms, a new mobile robot controller is optimally designed using 80486 CPU and the motor controller equipped with the Flexible Servo Controller (FSC). The motor controller board is fabricated with the Printed Circtui Board CAD. This motor controller is the first application of the FSC chip. The TMR controller has unique features utilizing the advantages of the developed servo motor controller.