Kinematics Modeling and Control of Spherical Rolling Contact Joint and Manipulator

Rolling contact joints are attracting increasing interest in applications to robotic fingers and manipulators, due to the potential of the absence of abrasion wear, the simplification of the controller, and the enlargement of reachable configurations. This article first proposes a novel two-degree-of-freedom (DOF) spherical rolling contact (SRC) joint, with the joint model elements being formulated, including rotation matrix, position vector, and free modes, as with those of classic joints. As an application, a new kind of serial manipulator formed by the SRC joints is presented, and its forward and inverse kinematics are modeled. The motions of the two-DOF SRC joint and manipulator are implemented using the FreeBOT, and the control method is proposed for the FreeBOT, such that the SRC joint and manipulator realize the motion control. The kinematics and control of the two-DOF SRC joint and manipulator are validated using physics simulations and on a real manipulator formed by FreeBOTs.