Position Tracking Control of Dual-Rope Winch Robot with Rope Slip Compensation

Abstract

This paper presents the design and position tracking control of a novel two-degree-of-freedom dual-rope winch robot. It is designed to be facilely installed at both corners of a building using two synthetic ropes and to move freely on the wall plane using the ropes to perform building maintenance work. This robot consists of a dual-rope winch system responsible for its movement on a plane and a thrust module that allows the robot to remain close to the wall through the force of the propeller. In the dual-rope winch system, ascending modules driven by two pulleys and connected by differential gears are arranged symmetrically; the position and posture on the plane can be determined by controlling the ropes. The position of the robot can be calculated by measuring the angle from the installation point of the rope, and an inertial measurement unit sensor is employed to reduce the position-measurement error. The robot winds a synthetic rope around the pulley to support the load with frictional force. Precise position control is difficult to implement because of the elasticity of the rope and the slip around the pulley. Therefore, in this paper, a feedforward control to predict and compensate for the slip length of the rope and a proportional integral controller to regulate the position error owing to the dynamic characteristics of the rope are proposed. Experiments to verify the performance of the controller for various trajectories were performed on the test bench. It was confirmed that the actual trajectory deviation is within 0.5 % of the target trajectory. IEEE