Song et al. / J Zhejiang Univ-Sci A (Appl Phys & Eng) 2014 15(9):681-693 681 A terminal sliding mode based torque distribution control for an individual-wheel-drive vehicle * Pan SONG 1,2 , Chang-fu ZONG †‡1 , Masayoshi TOMIZUKA 2 ( 1 State Key Laboratory of Automotive Simulation and Control, Jilin University, Changchun 130025, China) ( 2 Department of Mechanical Engineering, University of California, Berkeley, California 94720, USA) † E-mail: zongcf@jlu.edu.cn Received Apr. 16, 2014; Revision accepted Aug. 14, 2014; Crosschecked Aug. 22, 2014 Abstract: This paper presents a torque distribution method for an individual-wheel drive vehicle, in which each wheel is con- trolled individually by its own electric motor. The terminal sliding mode technique is employed for the motion control so as to track the desired vehicle motion obtained by interpreting the driver’s commands. Thus, finite-time convergence of the system’s dynamic errors can be achieved on the terminal sliding manifolds, as compared to the well-used linear sliding surface. By con- sidering nonlinear constraints of the tire adhesive limits, a simple yet effective distribution strategy is introduced to allocate the motion control efforts to each of the four wheels. Through the use of a high-fidelity CarSim full-vehicle model, vehicle stability and handling performance of the proposed controller is evaluated in both open- and closed-loop simulations. Key words: Vehicle dynamics, Integrated control, Driver model, Sliding mode control, Control allocation doi:10.1631/jzus.A1400101 Document code: A CLC number: U461.1 1 Introduction With the rapid development of electric motors and electronic communications, there is a trend in the automotive industry towards the use of electri- fied propulsion systems together with electronic control systems to achieve fuel efficiency and to improve handling performance. Almost all au- tomakers throughout the world have been studying and promoting electric vehicles (EVs) for energy and environmental considerations. Individual-wheel drive (IWD) is a promising technique for EVs in which all wheels are controlled independently by their own in-wheel/hub motors (Hori, 2004). Because of the inherent characteristics of elec- tric motors in which the torque can be negative, it is necessary for the global chassis control (GCC) sys- tem to coordinate the individual traction and braking actions of the four wheels. There are two main tasks in the GCC system (Johansen and Fossen, 2013). The first one is to compute a vector of virtual inputs to be applied to the vehicle so as to meet the motion control objectives of a given application. The other is to allocate these efforts to the individual actuators such that the total forces and moments generated by all actuators amount to the motion control efforts. In the design of the motion controller, the nonlinearity of the vehicle dynamics is usually handled by em- ploying the sliding mode control (SMC) method (Mokhiamar and Abe, 2004; Li et al., 2008; Wang and Longoria, 2009). A terminal sliding mode con- trol (TSMC) is a type of sliding control, in which the finite-time convergence and quick responsiveness can be achieved on the terminal sliding manifold (Liu and Wang, 2012). It has been successfully Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering) ISSN 1673-565X (Print); ISSN 1862-1775 (Online) www.zju.edu.cn/jzus; www.springerlink.com E-mail: jzus@zju.edu.cn ‡ Corresponding author * Project supported by the Open Fund Project of the State Key La- boratory of Automotive Simulation and Control (No. 20120111), and the China Scholarship Council (No. 201306170075) © Zhejiang University and Springer-Verlag Berlin Heidelberg 2014