IFAC-PapersOnLine 49-18 (2016) 098–103 ScienceDirect Available online at www.sciencedirect.com 2405-8963 © 2016, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved. Peer review under responsibility of International Federation of Automatic Control. 10.1016/j.ifacol.2016.10.146 © 2016, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved. Keywords: Adaptive sliding-mode control, parameter estimation, nonlinear control, engine cooling control. 1. INTRODUCTION Considering the growing environmental impact of green- house gases, increasingly stricter regulations for a cleaner environment and the depletion of the natural reservoirs of fossil fuels, efficient fuel consumption combined with low exhaust emission of road vehicles is of high importance. Moreover, the use of vehicles has increased conspicuously in the urban traffic, where the engine is mostly operated in part load conditions, see Arici et al. (1999). The partly loaded engine results in an increase in the pollutant emis- sion and the fuel consumption, which adversely affect the efficiency of the combustion engine, cf. Heywood (1988). The potential for a further reduction of the fuel consump- tion related to turbocharger, diesel particulate filter, se- lective catalytic reduction and other peripheries is getting smaller. However, there still exist other possibilities for fuel efficient operation. One of the research areas to maximize the efficiency of the engine is related to the electrification of an engine cooling system. On the one hand, a properly designed engine cooling system contributes to an improved temperature control and a reduced heating-up time, on the other hand, it leads to an increase in the durability and reliability of the engine, cf. Page et al. (2005). A conventional engine cooling system, cf. Zou et al. (1999), consists of an internal combustion engine, a belt-driven centrifugal pump, a radiator-fan unit, a thermostat, and mechanically operated bypass valve, see Fig. 1. Recent research on energy savings and an electrification of the automotive cooling system has been published in several contributions, see Salah et al. (2008); Wang and Wag- ner (2015); Butt et al. (2014). In Salah et al. (2008), a detailed dynamic model of each component within an engine cooling system is described. According to Wang and Wagner (2015), a considerable amount of energy is needed Radiator Engine Thermostat Bypass Fan Fig. 1. Structure of an engine cooling system. to operate the radiator fan(s) in comparison to the electric bypass valve and the electrically actuated pump. The pro- posed nonlinear control-oriented model is of second-order. Furthermore, the resulting mathematical description of the engine cooling system reveals that it is under the influence of both matched lumped disturbance as well as mismatched lumped disturbances. In some of the recent publications, the tracking control problem with lumped disturbances is addressed by combining different nonlinear model-based control strategies, e.g., integral sliding-mode control, dynamic sliding-mode control, and flatness-based control, together with a nonlinear state and disturbance estimator, for example, an extended Kalman filter and a gain-scheduled modified Utkin observer, cf. Aschemann et al. (2011); Butt et al. (2015a,b). From a theoretical point of view, a stability proof for the overall closed-loop system is of important concern. To address this issue, a novel adaptive sliding-mode control with observer-like parameter update laws is proposed in this contribution. The underlying idea of an adaptive sliding-mode control Abstract: This paper proposes a novel adaptive sliding-mode control for an innovative engine cooling system under the influence of both matched and mismatched lumped disturbances. The parameter update laws resemble a nonlinear reduced-order disturbance observer and guarantee the convergence of the estimated parameter values to the real ones. Experiments on a dedicated test rig highlight the effectiveness of the proposed novel adaptive sliding-mode control in terms of asymptotic tracking, global stability and guaranteed parameter convergence. The closed-loop stability of the overall system is established by using Lyapunov’s direct method. To provide a fair comparison, the performance of the proposed controller is compared with a PI-controller. * Chair of Mechatronics, University of Rostock, D-18059 Rostock, Germany (e-mail: {Saif.Butt, Robert.Prabel, Jisheng.Zhang, Harald.Aschemann}@uni-rostock.de) Saif S. Butt * , Robert Prabel * , Jisheng Zhang * , Harald Aschemann * Adaptive Sliding-Mode Control of an Innovative Engine Cooling System