A ClosedLoop Controller for CableDriven HyperRedundant Manipulator with Joint Angle Sensors * A cabledriven hyperredundant manipulator is especially suited for manipulations in confined spaces. In most of the existing approaches, a controller is often designed to actuate the joints by pulling the corresponding cables without the feedback from remote sensors at the joints. The unmodeled elongations of these cables due to unknown tensions often cause a decrease in control precision. To improve the performance of such a manipulator, this paper presents an investigation where miniature potentiometers are integrated into the joints for angle feedback. Furthermore, a pullerfollower controller is developed to control the three cables of a universal joint for not only closed loop joint angle control but also cable tension preservation. Applying the Hookexe2x80x99s Law, the cable tension is represented by its deformation. In this way, the controller is designed to realize both the desired angles and the cable deformations, without force sensing on the cables. Finally, experiments on a single joint and multiple joints were conducted to verify the effectiveness of this proposed controller.

A Novel Control Strategy for CableDriven Parallel Robots with Unknown Jacobians Cabledriven parallel robots (CDPRs) have been studied by many researchers in the past decades. Due to the inconsistency among setups of a CDPR in some applications, such as rehabilitation, the Jacobian of the CDPR may not be known for a setup. In order to control a CDPR with unknown Jacobian, a novel control strategy named the PIDFNN control strategy is proposed in this paper. The control strategy consists of a PID controller and a feedforward neural network (FNN). The FNN takes over the role of the Jacobian by mapping a wrench applied on the endeffector of the CDPR at a pose in the task space to a set of cable tensions in the joint space. In this way, the CDPR is controlled by cable tensions computed by solving the inverse dynamics problem using such a mapping, rather than the Jacobian. Simulation results show that the PIDFNN control strategy works as expected in controlling an example CDPR with four cables, three degrees of freedom, and unknown Jacobian.