Analysis of Sliding-Mode Control Systems with Unmatched Disturbances Altering the Relative Degree⁎The authors kindly acknowledge support by the European Union Horizon 2020 research and innovation program under Marie Skłodowska-Curie grant agreement No. 734832. Issue 2 (2020)

• Record Type: Journal Article
• Authors: Posielek, Tobias; Wulff, Kai; Reger, Johann
• Is Part Of: IFAC-PapersOnLine. Volume 53:Issue 2(2020)
• Page Start: 5122
• Page End: 5128
• Publication Date: 2020
• Subjects: Sliding-mode control -- Unmatched disturbances -- Relative degree; Automatic control -- Periodicals; 629.805
• DOI: 10.1016/j.ifacol.2020.12.1149
• Languages: English
• ISSNs: 2405-8963

Abstract

Abstract: We consider sliding-mode control systems subject to unmatched disturbances. Classical first-order sliding-mode techniques are capable to compensate unmatched disturbances if differentiations of the output of sufficiently high order are included in the sliding variable. For such disturbances it is commonly assumed that they do not affect the relative degree of the system. In this contribution we consider disturbances that alter the relative degree of the process and study their impact on the closed-loop control system with the classical first-order sliding-mode design. We analyse the reaching and sliding phase of the resulting closed-loop system. We show that uniqueness of the solution may be lost and derive conditions for such behaviour. We present conditions for the stability of the sliding-mode dynamics and analyse the disturbance rejection properties. A simulation case study of a two-mass spring-damper system illustrates the various closed-loop behaviours.