Regenerative Brake and Slip Angle Control o f Electric Vehicle with In-wheel Motor and Active Front Steering Hiroshi Fujimoto1) 1) The University of Tokyo, Graduate School of Frontier Sciences Transdisciplinary Sciences Bldg. 613, 5-1-5, Kashiwanoha, Kashiwa, Chiba, 227-8561, Japan (E-mail: [email protected]) Received on March 31st, 2011 Presented at the JSAE Annual Congress on May 17th, 2011 ABSTRACT : Electric vehicles (EVs) have attractive potential not only for energy and environmental performance but also for vehicle motion control because electric motors have quick and measurable torque response. Recently, the authors’ laboratory has developed a completely original EV which has active front and rear steering systems and high-torque direct- drive in-wheel motors in the all wheels. In this paper, the main features of this vehicle are briefly introduced and our recent studies on pitching control, slip-ratio control, and yaw-rate and slip-angle control with lateral force sensors are explainedwith experimental results. KEY WORDS : Electric vehicle, In-wheel motors, Pitching and Slip ratio Control, Active steering 1.Introduction As a solution of energy and environmental problems, elec- tric vehicles (EVs) is paid to attention. In addition, from the point of view of control engineering, EVs including bat- tery, fuel-cell, and (plug-in) hybrid vehicles have very at- tractive potential. Since electric motors and inverters areutilized in drive system, they have great advantages over internal combustion engine vehicles (ICEVs). These ad- vantages can be summarized as follows, 1) Quick torque response The torque response of electric motors is 100-500 times as fast as that of ICEVs. 2) Measurable motor torque In ICEVs, it is difficult to accurately measure their out- put torque. On the other hand, the output torque of elec- tric motor can be measured easily from current. There- fore, the state of the road can be estimated precisely. 3) Individual wheels control By using in-wheel motors, each wheel can be indepen- dently driven. Then, individual wheel control can en- hance the vehicle stability. These advantages of electric motor enhance vehicle motion control in EVs (1)ʙ(3). Our research group focus the mer- its of motors and we are researching on the motion con- trol for the electric vehicles to achieve safety and comfort driving(4). In this paper, our recent researches on pitch- ing control for comfort braking(5)and slip-ratio control for emergent braking(6)are briefly introduced by using the re- generative brake of in-wheel motors. Finally, the advanced vehicle stability control method by active front steering(7) is explained. Fig. 1 Experimental vehicle 2.Experimental vehicle To verify the proposed control algorithm, an original elec- tric vehicle ‘FPEV2-Kanon’ developed in our laboratory is used for the test vehicle. Fig. 1 and Fig. 2 show the testvehicle and its configuration. 2.1. In-wheel motors The outer rotor type in-wheel motors made by Toyo Denki Seizo K.K., Ltd. are installed in two rear wheelsas driving power-train. Table 1 shows the specification of the in-wheel motors. Because this motor adopts the direct drive system, the reaction force from the road is directly transfered to the motor without gear reduction and back- lash. Then it can be said that this vehicle is ideal to ex-amine the proposed estimation and control methods. Fig. 3 shows in-wheel motor and Fig. 4 shows motor configura- tion. Recently, we installed in-wheel motors with much higher torque into two front wheels to develop control methodsfor 4WD EVs. However in this paper, only the results with rear in-wheel motors will be introduced for 2 wheels indi- vidual drive EVs. 2.2. Energy Storage The Li-ion battery is used for the energy storage. In this Copyright c/circlecopyrt2010 Society of Automotive Engineers of Japan, Inc. All rights reservedL motorR motor yaw-rate sensor steering angle sensora ,axy γ δ L inverterR inverterLi-ion Battery 15V 10 Chopp