Disturbance Force Compensation Using Robust Controller in Linear Drive Positioning System

Chua, Chong Joe (2022) Disturbance Force Compensation Using Robust Controller in Linear Drive Positioning System. Final Year Project (Bachelor), Tunku Abdul Rahman University College.

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Abstract

The milling machine can carry out many types of machining operations such as end milling, thread milling, gear milling and angular milling that require high accuracy and precision. However, the performance of these machine tools is limited by the presence of undesirable disturbances during the machining processes. The typical disturbance forces occurred in machining are the friction force and cutting forces, which exhibit nonlinear behaviours. These forces affected the precision and accuracy of the linear drive system, causing tracking errors that led to low quality of products such as poor surface roughness. One of the usual methods in solving the disturbances is the application of controllers such as H infinity robust controller, nonlinear PID and PID controller. The application of H-infinity controller in machine tools was constrained by its complex design procedure. However, H-infinity controller has a high degree of freedom in setting parameters and simple mathematical calculation. Parameters with high degree of freedom can produce high stability and immunity from external interference. These methods are expected to produce good steady state tracking and disturbance rejection properties and would be simulated using MATLAB software. Performances of designed controller would be analysed based on collected tracking error signals reduction, maximum tracking error and disturbance rejection. In conclusion, H-infinity controller outperforms compare to PID and NPID controllers in terms of tracking error reduction and disturbance rejection. As a result, the maximum and minimum improvement of cutting force rejection of H-infinity controller is 99.50 % and 91.05 % respectively. Furthermore, H-infinity controller had effetely reduced the tracking error almost 100% without cutting force and with 1000 rpm, 1500 rpm and 2000 rpm of cutting force. Lastly, the H-infinity controller has effectively reduced the maximum tracking error by maximum of 98.75% with 2000 rpm of cutting force and minimum of 91.10% with 1500 rpm of cutting force. Hence, in terms of tracking error reduction and disturbance rejection, the H-infinity controller outperforms the PID and NPID controllers. Because the H-infinity controller has a reduced tracking error, the output is more precise or accurate when compared to the reference input.