Dual loop control in positioning system

• Main Author: Lok, Weng Hoo.
• Other Authors: Lau Wai Shing, Michael
• Format: Final Year Project
• Language: English
• Published: 2009
• Subjects: DRNTU::Engineering::Mechanical engineering::Control engineering
• Online Access: http://hdl.handle.net/10356/17171
• Institution: Nanyang Technological University

Backlash is a common phenomenon in motion control process. It happens when there is a delay between the motion on the load side and the motor side, which may lead to a loss in position accuracy and system instability. When this happens, a motion control process employing only one encoder, normally rotary encoder placed at motor position for system stability purposes, is not able to achieve load position accuracy as backlash is not accounted for in the process. In order to overcome this phenomenon, the motion control analysis in this project employs two encoders; rotary encoder placed at motor position and linear encoder placed at load position. Given this addition, it is then necessary to develop a dual loop motion control program to implement the changes. This dual loop motion control program is created using LabVIEW, a platform and development environment for graphical programming language named “G”. A single loop motion control program is also created and data collected using similar inputs are compared for both motion control system to determine the benefits of dual loop motion control. The data obtained shows the existence of oscillation in ‘voltage output’ and ‘set point – process variable’ of the controllers in both motion control program, with dual loop motion control program having a smaller magnitude of oscillation. Backlash is also observed in all the sets of data obtained. When no condition is set for the load to stop, only the load in the dual loop motion control is able to achieve a zero error load position. Thus, it can be concluded that dual loop motion control process is able to achieve a more stable operation and a higher degree of accuracy.