| Multi-body interactions and environmental contacts in robotic systems make the analysis of such systems challenging. We present an approach for kinematics and dynamics analysis of robotic systems that exposes the critical design issues. We demonstrate that the approach is generic, and amenable for control synthesis.; We start out with the development of a team of mobile robots in which the robots physically cooperative to improve mobility for search and rescue missions. Understanding the specific needs of such missions we introduce the idea of using robot wheel torques to achieve cooperation thus avoiding the need for additional actuation. To this end we propose a novel connecting link mechanism and we demonstrate cooperative maneuvers involving two robots with a prototype hardware system. Using the hardware and the analytical models we expose critical design issues related to the cooperation. Specifically, we prove that in order to achieve cooperative behaviors high friction is necessary at the points of contact of robots with the environment; and that robot system dynamics can be exploited to relax the stringent friction requirements.; To systematically analyze and design cooperative behaviors, and to be able to generalize the ideas of cooperative mobility, we developed a method called P-Robot, Method. By treating the linked bodies of mobile robots as a multiple degree-of-freedom object comprising an articulated open kinematic chain, and by introducing the concept of pseudo robots at the ground interaction points, the P-robot Method allows for a decoupled approach to analyzing a team of mobile robots. Using the P-robot Method, we have carried out statics as well as dynamics analysis for the 2-robot and 3-robot cooperation cases.; Applicability of the P-robot Method is extendible to general robotic systems. We demonstrate this by employing the method to analyze four examples of mechanical systems that are representative of many classes of robotic systems. The analysis of each example requires some modification of the method, and leads to interesting insights into the respective system, and the method itself. We propose and demonstrate with two examples that controllers can be designed for robotic systems based on kinematics and dynamics analysis using the P-robot Method. |
