Int. J. Modelling, Identification and Control, Vol. 29, No. 2, 2018 127 Copyright © 2018 Inderscience Enterprises Ltd. A novel sliding mode controller scheme for a class of nonlinear uncertain systems Jalel Ghabi LARATSI, ENIM, University of Monastir, Tunisia and Department of Electrical Engineering, ISSATK, University of Kairouan, Tunisia Email: jalel.ghabi@yahoo.fr Abstract: This paper considers a continuous sliding mode control for a class of nonlinear systems with uncertainties including both parameter variations and external disturbances. Under the framework of sliding mode and using the upper bounds of the uncertainties, the proposed controller is derived to guarantee the stability of an overall closed-loop system and ensure robustness against modelling errors, parameter uncertainties and external disturbances. As for chattering elimination in sliding mode control, a boundary layer around the sliding surface is used and the continuous control is applied within the boundary. Moreover, an extended schema of a higher-order sliding mode controller is developed in this paper as another solution to avoid the problem of chattering effect. Simulation results demonstrate the efficacy of the proposed control methodology to stabilise an inverted pendulum, which is a standard nonlinear benchmark system. The applicability of the proposed algorithm will be extended, via suitable modifications, to the case of multivariable nonlinear systems with uncertainties of more general type, covering a wide class of processes. Keywords: nonlinear systems; uncertainty; sliding mode control; stability; robustness; inverted pendulum; higher-order sliding mode. Reference to this paper should be made as follows: Ghabi, J. (2018) ‘A novel sliding mode controller scheme for a class of nonlinear uncertain systems’, Int. J. Modelling, Identification and Control, Vol. 29, No. 2, pp.127–135. Biographical notes: Jalel Ghabi received his Master in Automatic Control and Industrial Computing from National Engineering School of Sfax (ENIS) in 2003 and PhD in Automatic Control from National Engineering School of Monastir (ENIM) in 2009. Currently, he is an Associate Professor at ISSATK, University of Kairouan. His research is related to sliding mode control and robust predictive control of nonlinear uncertain systems. This paper is a revised and expanded version of a paper entitled ‘A sliding mode controller schema for nonlinear uncertain systems’ presented at the Third International Conference on Automation, Control, Engineering and Computer Science (ACECS2016), Hammamet, Tunisia, 20–22 March 2016. 1 Introduction Recently, sliding mode control (SMC) has received considerable amount of researches in automatic control and has found a number of industrial applications owing to its good performance (Utkin and Chang, 2002; Utkin, 1992; Levant, 2001; Edwards and Spurgeon, 1998; Young et al., 1999; Rhif, 2014; Kolsi et al., 2015; Zarrabi et al., 2015; Vaidyanathan et al., 2015; Yue and Zhang, 2016; Boujelben et al., 2016). This approach is recognised as one of the efficient tools to design robust controllers for complex high- order nonlinear dynamic plants operating under uncertainty conditions. In the continuous-time, SMC provides invariance and robustness properties to uncertainties including modelling errors and external disturbances (Utkin et al., 1977; Utkin, 1984; Hung et al., 1993). This is achieved by assuming that infinitely fast switching between two different control structures is possible, and that the uncertainties are bounded. SMC has other advantages as well, like ease of implementation, fast dynamic responses and good transient performance. Moreover, the dynamic performance of a system under SMC method can be shaped according to the system specification by an appropriate choice of switching function. SMC consists of two phases. The first phase is the design of a sliding surface along which the process can slide to find its desired final value. The second one is the synthesis of the control law in such a way that any state outside the sliding surface is forced to reach the desired sliding manifold in finite time and stay on it. The control