Development of a Pipe Positioning System Using a 5-DOF Suspension Mechanism

Abstract

Abstract Decreasing the number of skilled workers and utilization of automated machines is becoming a general trend at plant construction sites. For this reason, an automated pipe positioning system using a 5-DOF suspension mechanism has been developed as an important automated tool for power plant construction sites. This device is expected to be used for not only assisting less skilled operators, but also making operations more efficient at plant construction sites. This paper mainly focuses on the control system design and the control performance of the proposed positioning system. The controller is designed based on the disturbance observer concept. The pipe positioning system has a 5-DOF suspension mechanism which consists of five stepping motors and chains. A relationship between the actuator space (chain length) and the task space (position and attitude of the pipe center of gravity) is expressed using the Jacobian matrix, and each element of this Jacobian matrix is generally a nonlinear function in space. Therefore the plant in this system is nonlinear. In this study, a disturbance observer concept is used to remove this nonlinearlity, then a conventional linear feedback control low is applied to the control system. The control performance is verified through experiments using a pipe with a diameter of 0.3m. In the experiments, trajectories of the pipe center of gravity with the Jacobian nonlinearly compensation is compared to the trajectories without Jacobian compensation case, and the effectiveness of this pipe positioning system is shown.