Slip Suppression of Electric Vehicles using Model Predictive PID Controller Tohru Kawabe Abstract—In this paper, a new model predictive PID controller design method for the slip suppression control of EVs (electric vehicles) is proposed. The proposed method aims to improve the maneuverability and the stability of EVs by controlling the wheel slip ratio. The optimal control gains of PID framework are derived by the model predictive control (MPC) algorithm. There also include numerical simulation results to demonstrate the effectiveness of the method. Keywords—Model Predictive Control, PID controller, Electric Vehicle, Slip suppression I. I NTRODUCTION E LECTRIC vehicles (EVs) have received much attention in recent years as a countermeasure to global warming and for being Eco friendly [1], [2], [3], [4]. EVs are automobiles which are propelled by electric motors, using electrical energy stored in batteries or another energy storage devices. Electric motors have several advan- tages over (internal-combustion engines) ICEs: • Energy efficient. Electric motors convert 75% of the chemical energy from the batteries to power the wheels - ICEs only convert 20% of the energy stored in gasoline. • Environmentally friendly. EVs emit no tailpipe pollu- tants, although the power plant producing the electricity may emit them. Electricity from nuclear-, hydro-, solar-, or wind-powered plants causes no air pollutants. • Performance benefits. Electric motors provide quiet, smooth operation and stronger acceleration and require less maintenance than ICEs. • Reduce energy dependence. Electricity is a domestic energy source. The travel distance per charge for EV has been increased through battery improvements and using regeneration brakes, and attention has been focused on improving motor perfor- mance. The following facts are viewed as relatively easy ways to improve maneuverability and stability of EVs. 1) The input/output response is faster than for gaso- line/diesel engines. 2) The torque generated in the wheels can be detected relatively accurately 3) Vehicles can be made smaller by using multiple motors placed closer to the wheels. Much research has been done on the stability of gen- eral automobiles, for example, ABS (Anti-lock-Braking Sys- tems), TCS (Traction-Control-Systems), and ESC (Electric- Stability-Control)[5] as well as VSA (Vehicle-Stability- Assist)[6] and AWC (All-Wheel-Control) [7]. What all of T. Kawabe is with the Division of Information Engineering, Faculty of Engineering, Information and Systems University of Tsukuba, Tsukuba 305- 8573 JAPAN (phone: +81-29-853-5507; e-mail: kawabe@cs.tsukuba.a.jp). these have in common is that they maintain a suitable tire grip margin and reduce drive force loss to stabilize the vehicle be- havior and improve drive performance. With gasoline/diesel engines, however, the response time from accelerator input until the drive force is transmitted to the wheels is slow and it is difficult to accurately determine the drive torque, which limits the vehicle’s control performance. This paper deals with the slip suppression of EV for controlling the wheel slip ratio. Conventional gasoline/diesel vehicles are equipped with a TCS, which requires expensive sensors and additional equipment, but, as mentioned above, EV have a fast torque response and the motor characteristics can be used to accurately determine the torque, which makes it relatively easy and inexpensive to realize high-performance traction control. This is expected to improve the maneu- verability and stability of EV. It’s, therefore, important to research and development to achieve high-performance EV traction control with slip suppression. Various proposals have been made for EV traction control, such as a system based on motor torque current dropping characteristics[8], a system that utilizes a nonlinear controller[9], and a system that controls the slip ratio with wheel control [10], but this paper proposes a PID control method based on model predicative control (MPC). PID controllers have a simple construction and have been proved to be practical and highly reliable in many industrial fields[11], [12]. The proposed method determines the PID controller gain using an MPC algorithm to utilize the capability of explicitly considering the constraints, which is one of the advantages of MPC, to achieve a more advanced and flexible control method[13], [14], [15]. Specifically, the optimum control input is calculated by the MPC explicitly considering the constraints and the PID gain for realizing this is derived in advance newline and used. For this reason, various road surfaces the vehicle will travel on are presumed, the optimum PID for each of them derived, and the creation for a look up table for these is envisioned. During actual driving, the values of PID gains in the look up table are referenced according to the conditions to be able to support a vehicle with fast-moving dynamic characteristics. This is based on the explicit-MPC concept[16]. The advantages of this method are that the structure is simple, that is uses a proved and reliable PID controller, and that it achieves flexible, high-performance control by explicitly considering the constructions the same as for MPC. Numerical examples are used to compare the proposed method to conventional methods and to verify the effectiveness of the proposed method. World Academy of Science, Engineering and Technology International Journal of Electrical and Information Engineering Vol:6, No:7, 2012 649 International Scholarly and Scientific Research & Innovation 6(7) 2012 ISNI:0000000091950263 Open Science Index, Electrical and Information Engineering Vol:6, No:7, 2012 publications.waset.org/13878/pdf