Cooperative Object Manipulation by Suspended Wheeled Mobile Manipulators

Mobile platforms with one or more manipulators are of great interest for their wide area of applications and dexterity. Including a suspension system in such mobile platforms will certainly add to their maneuverability, though causes more complexity. In this paper, a suspended mobile platform with two 6-DOF manipulators is used to manipulate an object in a mixed circular-straight path. The Multiple Impedance Control (MIC) as a Model-Based algorithm, enforces the same impedance law both on the robotic system, and the manipulated object level. To apply model-based control laws, however, it is needed to extract system dynamics equations. For such highly nonlinear dynamical systems, it is necessary to have a concise set of dynamic equations with as few as possible mathematical calculations. Therefore, concept of Direct Path Method, is extended to derive explicit dynamics modeling for such challenging systems. Then non-holonomic constraint of the wheeled platform is discussed, and obtained dynamics model is reformatted to become more concise using Natural Orthogonal Complement Method. Next, the MIC law is applied to cooperative manipulation of an object by the two manipulators. The obtained results reveal the success of the suspended mobile robot in its defined mission.