Control of suspended wheeled mobile robots with multiple arms during object manipulation tasks

In this paper, a suspended mobile platform with two 3 DOF manipulators, is used to manipulate an object in a combined circular-straight path. The multiple impedance control (MIC) is used as a model-based algorithm which has been shown to have desirable performance in case of impact with an obstacle and system flexibility. The MIC enforces same impedance law both on the robotic system, and the manipulated object level. However, to apply model-based control laws, it is needed to extract system dynamics model. For such complicated robotic systems with suspension system, it is necessary to have a concise set of dynamic equations of motion with few mathematical calculations. Therefore, the concept of direct path method is extended to derive explicit dynamics modeling for such challenging systems. Then, non-holonomic constraint of the wheeled system is derived, and the obtained dynamics model is reformatted to become a more concise one using natural orthogonal complement method. Next, the MIC law is applied to cooperative manipulation of an object by two manipulators mounted on a suspended wheeled robotic system. The obtained results reveal a smooth system performance, i.e. negligible small tracking errors in the presence of impacts with obstacles and significant disturbances.