A Novel Extension Of Generalize Maxwell Slip Friction Model In Combination With Super-Twisting Sliding Mode Controller

Jamaludin, Zamberi and Jafar, Fairul Azni and Bani Hashim, Ahmad Yusairi and Rafan, Nur Aidawaty and Halim, Mohd Faizal and Md Ghazaly, Mariam and Abd Rahman, Md Nizam (2019) A Novel Extension Of Generalize Maxwell Slip Friction Model In Combination With Super-Twisting Sliding Mode Controller. Project Report. UTeM, Melaka, Malaysia. (Submitted)

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Abstract

Great demands for accuracy and precision as well as global concerns on sustainability have stimulated research on disturbance compensation to improve position tracking performance of machine tools. Disturbance force such as friction has become the main interest of research for many years as it affects tracking performance of machine tools that ultimately produces position errors and poor surface finish. Friction force especially at velocity reversal is a natural and undesired phenomenon ([1 ],[2]) that existed in the feed drive system as internal disturbance. It is the main cause of the formation of quadrant glitches during milling cutting process. Many friction models have been developed and applied in literature such as static friction model, Dahl model, LuGre model [3], and recently the Generalized Maxwell Slip (GMS) model [4-5]. These models were able to characterize the behaviour of friction forces in drive system to some extent. However, the presence of discontinuous switching between pre-sliding and sliding regimes in the GMS model has affected its overall effective [6]. A smoothening function was implemented to improve switching between pre-sliding and sliding regimes without affecting its ability in characterizing the highly nonlinear frictional behaviour near the zero velocity region [7]. The main objective of this research was to synthesis a new version of the GMS friction model with modified switching function in application with a Super Twisting Sliding Mode position controller (ST-SMC). Two models of friction forces named Sigmoid-Like-Curve-Slip (SLCS) model and the Pseudo-Like-Curve-Slip (PLCS) model were introduced and were validated against GMS friction model. The SLCS model managed to produce a 99% reduction in the magnitude of the quadrant glitches when combined with cascade P/PI position controller at tracking velocity of 2 mm/s. Generally, the new models were able to accurately describe friction behaviour in pre-sliding regime by providing smooth transition between pre-sliding and sliding regimes. For position control, ST-SMC becomes attractive for its ability to meet complex demands on system performance where classical controllers have failed to meet. However, chattering still exist as an issue in application of STSMC. Two variants of ST-SMC were formulated based on modifications of the control laws of original ST-SMC; where the signum function was replaced by either a hyperbolic tangent function or an arc-tangent smoothening function to a form hyperbolic ST-SMC (HST-SMC) and an arctangent ST-SMC (Arc-ST-SMC) respectively. Control performances were validated on a single axis sliding unit. Results were analyzed with respect to tracking accuracy, chattering suppression, and robustness against input disturbance and system dynamics variation. Results showed that optimized ST-SMC produced the best overall control performance with improvement of 9.6% (RMSE), 3.9% (disturbance rejection), and 13.4% (robustness). However, HST-SMC offers a fair trade-off in control performance between tracking accuracy, disturbance rejection and chattering attenuation.

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