Control of nonholonomic mobile manipulators for cooperative object transportation

In this paper, a methodology for transporting objects with a group of wheeled nonholonomic mobile manipulators is presented. A full dynamic model of a mobile manipulator with a three wheeled mobile base and a three DOF manipulator is derived using the Gibbs-Appell method. Since the dynamical equations of a mobile robot are highly nonlinear, an input-output linearization technique is used to control individual robots. Transporting the object is divided into two steps. First, the robots use a decentralized behavior-based method to approach and surround the object. Then, a virtual structure method is used to control the robots to transport the object cooperatively. A numerical simulation study is performed to show the eectiveness of the control methodology. The results show that robots together are capable of approaching and grasping unknown shapes and can also manipulate objects in various ways.