A Closed-Loop Controller for Cable-Driven Hyper-Redundant Manipulator with Joint Angle Sensors

Abstract

A cable-driven hyper-redundant 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 un-modeled 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 puller-follower 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 Hooke’s 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.