Sliding Mode Control Strategies for Positioning System

Lim, Chin Chen (2026) Sliding Mode Control Strategies for Positioning System. Final Year Project (Bachelor), Tunku Abdul Rahman University of Management and Technology.

Text Lim Chin Chen_Full Text.pdf Restricted to Registered users only Download (10MB)

Abstract

Machine tool accuracy is a critical requirement for high-performance manufacturing systems, where drive control strategies must handle nonlinear dynamics and external disturbances. Sliding Mode Control (SMC) is awell-established robust technique, but its discontinuous switching law causes severe chattering, which limits precision. The Super-Twisting Sliding Mode Control (ST-SMC) improves on classical SMC by enhancing tracking performance and disturbance rejection, though residual high-frequency chattering remains. To address this issue, this study proposes and evaluates an Integral Super-Twisting Sliding Mode Control (IST-SMC) for machine tool positioning applications. A direct-drive single-axis positioning system was modelled in MATLAB/Simulink, with realistic disturbances introduced via measured cutting-force signals collected using a Neo-MoMac dynamometer during milling at depths of cut (DOC) of 0.5 mm, 1.0 mm, and 1.5 mm. Performance was evaluated using Maximum Tracking Error (MTE), Root Mean Square Error (RMSE), frequency-domain analysis of tracking errors, and chattering inspection of control inputs. Results show that both advanced controllers outperform classical SMC. ST-SMC reduces MTE by ∼10% and RMSE by up to 91%, while IST-SMC achieves consistent improvements of ∼23–24% in MTE and ∼83–93% in RMSE across all DOC levels. Frequency-domain analysis confirms IST-SMC delivers the strongest suppression of cutting-related harmonics, while controlinput analysis demonstrates the lowest chattering, even at the highest DOC. Overall, IST-SMC provides the most effective balance of disturbance rejection, tracking accuracy, and smooth control action, making it a promising control strategy for precision machine tool systems