Coordinated control of two robot arms by nonlinear feedback

When two robot arms work on the same object in their common work space, the control coordination between them is essential to fulfill the task. We have proposed two formulations for the coordinated control of two robot arms. The first formulation achieves the coordination by monitoring the interaction forces and moments between the two robots, while the second formulation handles the coordination by considering the two robot arms as a single closed chain mechanical system to be modeled and controlled. We have also developed a new treatment for the robot force control. The resultant force feedback control algorithm makes rigorous use of the nonlinear dynamics of robot arms and is independent of tasks. The control method is so general that it covers pure position control, hybrid position/force control, and pure force control. The results on simultaneous total linearization and output block decomposition of time-varying nonlinear systems developed in this dissertation have been utilized to simplify the controller design process. Computer simulations conducted for each proposed controller design showed the effectiveness and feasibility of the control method. Finally we discuss some issues associated with implementation and suggest possible future research topics.