Development and analysis of a wire-based robot with twin direct-drive motor system

In this paper, a sensorless wire rope tension control is introduced and analyzed to implement a wire-based robot with twin direct-drive motor system. Two of the same direct-drive motors are required and connected by wire rope mechanism. In the controller design, dual disturbance observers with respect to two control modes, namely the common mode and the differential mode are designed and applied for control of motion and wire rope tension. The wire rope tension in the common mode is controlled in order to regulate the mechanical bandwidth of the system. From the identification results, the high-tension of wire rope system is obtained a high mechanical bandwidth in the robot systems. The disturbance observer-based eliminates the need for the tension sensors, and may also be used to achieve the precise velocity and position control with the vibration-free performance in the differential mode. The effectiveness of the proposed method is verified by experimental results. It is shown that the high frequency responses are obtained by using high-tension of wire rope. The control performance may improve during the robot operation and, therefore, it is useful to compensate for the vibration effect.