Analysis and control of a cable-driven 3-DOF manipulator with joint angle feedback

This paper presents the control of a 3-DOF manipulator with joint angle feedback, the function of which was achieved by three mutually perpendicular joints intersecting at one point actuated by four parallel pulling force. Encoders were installed on each joint to obtain the control error caused by elasticity of cables and mechanism installation. Due to the output coupling problem of parallel mechanism, a linear position interpolation algorithm was proposed with real-time computation of inverse kinematics and online error compensation. Besides, an optimal tension distribution algorithm evading tension limits was proposed to solve the tension dramatic changes and oscillation problems, in which the linear programming method was used and two new variables were introduced for tension optimization. The real time control system based on PC and motion controller was designed and experiments were carried out to demonstrate the correctness of the algorithm and the effectiveness of the control system.