Position and tension control of a 2-DOF cable driven parallel mechanism

• Main Author: Ng, Shie Chen.
• Other Authors: Yeo Song Huat
• Format: Final Year Project
• Language: English
• Published: 2011
• Subjects: DRNTU::Engineering::Mechanical engineering::Robots
• Online Access: http://hdl.handle.net/10356/45090
• Institution: Nanyang Technological University

Cable driven Parallel mechanism (CDPM) is a special type of parallel mechanism that replaces the rigid links with cables. It has the advantages of large workspace and light structure. Due to the unilateral property of cables, the driving cables must always maintain tension. Therefore, the number of cable required to control the CDPM has to be more than its degrees of freedom. The objective of this project is to implement both position control loop and cable tension control loop in a 2-DOF CDPM. The 2-DOF CDPM is driven by 4 cables with universal joint between the links. A position control loop and cable tension control loops are set up for the controller design. The design of the position and cable tension control loops are done by using software LabVIEW. While the PID tunings were done for both position and cable tension control loops to choose the suitable PID parameters. In order to check the workability of both position and cable tension control loops, several tests are done for 1-DOF CDPM before implementing into the 2-DOF CDPM. Besides, the cable tensions of 2-DOF CDPM are computed by using linear programming. For the 1-DOF CDPM, the performance of position-position and position-tension control method are compared and evaluated. The position-tension control method is preferable as pre-tension is not required in order to maintain the cable tension during motion.