Driving Torque Distribution Method for Front-And- Rear- Wheel-Independent-Drive-Type Electric Vehicles (FRID Evs) at the Time of Cornering

EVS25 Shenzhen, China, Nov 5-9, 2010

Driving Torque Distribution Method for Front-and- Rear- Wheel-Independent-Drive-Type Electric Vehicles (FRID EVs) at the Time of Cornering

Nobuyoshi Mutoh1 Osamu Nishida1, Tatsuya Takayanagi1, Tadahiko Kato2, Kazutoshi Murakami2 1 Graduate School of Tokyo Metropolitan University 6-6, Asahigaoka, Hino-shi, Tokyo, Japan [email protected] 2 Univance Corporations, 2418 Washes, Kisi-shi, Shizuoka, Japan

Abstract This paper describes a driving torque distribution method for front–and-rear-wheel-independent-drive- type electric vehicles (FRID EVs) in which it is possible to get stable steering on a low friction coefficient road surface. This method is characterized by distributing driving torque to the left and right wheels of the front and rear wheels, considering not only load movement of the longitudinal direction but also load movement of the lateral direction which is generated at cornering. The load movements are estimated by detecting components of the 3-axis directions, i.e., longitudinal and lateral accelerations and yaw rate, and the steering angle and friction coefficient of the road surface. The effectiveness of the proposed driving torque distribution method was verified using simulators equivalent to the prototype FRID EV simulated with Matlab/Simulink and CarSim software. This method is expected to be indispensable to improving running performance of FRID EVs.

Keywords: EV (electric vehicle), front–and-rear-wheel-independent-drive-type electric vehicles (FRID EVs), load movement, driving torque distribution, cornering, friction coefficient.

performance, has been investigated. Many studies on front or rear one-motor-drive-type EVs (Fig. 1 Introduction 1(a)) have been done from the viewpoint of Electric vehicles (EVs) are becoming economical efficiency [2] and these EVs are important not only as an environmental measure already being marketed commercially [2]. against global warming, but also as an industrial Moreover, studies on two or four in-wheel motor- policy [1]. In order for EVs to be used widely, drive-type EVs (Figs. 1(b) and (c)) have also been the development of the next generation EVs with done from the viewpoints of the control technique compatible in safety and running performance is [3], [4], [5] and packaging [6], [7]. First, by indispensable. To meet such social requirements, focusing on the running performance, EVs of Figs. the conventional propulsion force generation 1 (a) and (b) cannot cope with such dangerous mechanism, i. e. motor-drive structure, which vehicle problems as wheel spin and wheel lock strongly influences the safety and running which are caused by the load movement always

generated when accelerating or decelerating [7]. When attention is paid to the safety at the time of failure, EVs of Fig. 1 (c) have difficulties with Fr Re ont INV ont Fron ar INV Fro Re

steering ability [8]. Since EVs of Fig.1(c) have ar ar DSP nt nt DSP t more drive structures as compared with other Re EVs, economical efficiency and maintenance is not good, and a reliability issue may be aggravated.

Thus, after proposing front and rear wheel Figure 2. Front-and-rear-wheel-independent- independent drive type electric vehicles FRID drive-type EV (FRID EV). EVs (Fig. 2) compatible in safety and running performance [9], their research is being done U nder from various angles by positioning them as a - stee ring next-generation EV. It has been clarified through (US) N vehicle dynamics analysis experiments that eutra l -ste outstanding running performance is obtained ering (NS) using a structural feature which can freely control longitudinal force of the front and rear wheels according to the running and road surface conditions [10]. In FRID EVs, distribution of the Start ) cornering (OS ering lateral force to the right and left tires of a front r-ste wheel and a rear wheel is performed through a Ove differential gear like in ordinary gas-powered vehicles. Accordingly, in currently available vehicles, since sufficient lateral force required Figure 3. Situations caused by steering operations for revolution cannot be secured, under-steering at the time of cornering. (Fig. 3) is apt to be caused when cornering on a low -road or when cornering at high speed on a 2. Driving Torque Distribution dry road. It is only the four in-wheel-motor- drive-type EV (Fig. 1 (c)) that can directly Method at the Time of Cornering handle the longitudinal and lateral forces of four wheels [11]. However, in-wheel-motor-drive- 2.1 Principal of Driving Torque type EVs have the serious problems cited above Distribution at the Time of Cornering as a next generation EV. Thus, a driving torque distribution method When vehicle speed is in a steady state (which suitable for FRID EVs which can secure can include the standstill state), front and rear tire sufficient lateral forces of the front and rear loads (normal forces) Fzd_f and Fzd_r act on each wheels is proposed here. The lateral forces tire of the front and rear wheels. In this case, the required for revolution are estimated based on vehicle is driven by the front and rear driving the conditions regarding the friction circle in forces Fxd_f and Fxd_r which are supplied from front consideration of the longitudinal and lateral load and rear motors, respectively. Shifting to an movements. Here, the effectiveness of the acceleration mode, the longitudinal load movement proposed driving torque distribution method is z to the rear wheels from the front wheels is verified using a simulator equivalent to an actual x prototype FRID EV. generated. As a result, front and rear tire loads Fzd_f and Fzd_r are changed to Fz_f (=Fzd_f - zx) and Fz_r (=Fzd_r + zx) by zx (Fig.4(b)). Therefore, in Front Front Front order for the vehicle to maintain ideal running M M based on vehicle dynamics, driving torque distribution to the front and rear wheels should be M done so that the front and rear motors can generate the proper driving forces F and F M M M M x_f x_r Rear Rear Rear corresponding to the front and rear tire loads Fz_f and Fz_r which are changed by the load movement.

(a) Front or (b) Front or rear (c) Four in- Next, when starting cornering, the new lateral rear wheel two in-wheel wheel drive load movement zy takes place between the left and drive type EV drive type EV type EV right wheels. Front and rear tire loads Fz_f and Fz_r are further changed by the produced load Figure 1. EVs with various conventional motor movement zy. For example, when cornering to the drive structures. left, the left and right tire loads Fz_fl and Fz_fr , Fz_fl

and Fz_fr which act on the left and right tires of Finally, in order to secure the stability of the front the front and rear wheels are changed to (Fz_fl + and rear wheels the above driving torque * * zy ) and (Fz_fr - zy), ( Fz_rl + zy ) and (Fz_rr- zy), references Rf and Rr are compensated for respectively. Here, subscripts l and r indicate left according to the following slip ratio conditions and right tires, respectively. Thus, in order for (Fig. 5). vehicles to corner stably, it is necessary to * always secure the front and rear lateral forces if _ lf sors _ rf ,2.0,, then Rf ,0 corresponding to lateral load movement zy. To do so, driving torque distribution should be where _ ( _ lfefflf ) rVrs _ lfeff ;/ performed according to the fact that each of the (6) _ (rs _ rfeffrf ) rV _ rfeff ./ driving and braking forces and the cornering * force cannot exceed the friction force W(: if _ lr sors _ rr ,2.0,, then Rr ,0 friction coefficient, W: tire load) (Fig. 4(a)). That

is, specifically, after securing lateral force where _ _ )( rVrs _ lrefflrefflr ;/ required for revolution, in a friction circle, the (7) _ (rs _ rreffrr ) rV _ rreff ./ maximum Fx_j_max of the longitudinal force needed to propel the vehicle is secured by Here reff is effective radius of a tire; V is vehicle

22 2 speed; f_l and f_r are angular speeds of the left F jx max__ FW jy max__ )(- ,:( rearrfrontfj ): (1) and right tires of the front wheels; and and r_l r_r are angular speeds of the left and right tires of the where F max(FF , )( lleftrright : , : ), yj__max yj_ l yjr_ rear wheels. Under the slip ratio conditions of * 0 FF . other than (6) and (7), the torque referencesRf and jxjx max___ * to satisfy the procedures of (4) and (5) become Rr the actual torque references for the front and rear Hereafter, in this study, the driving torque torque controllers. distribution uses the assumption that if slip angle As shown in the flow chart of Fig. 6, according is small, the lateral force almost agrees with the to the steering angle, the driving torque cornering force. The maximum longitudinal force references are distributed to the front and rear F (j = l: front, j = r: rear) obtained for each x_j_max wheels, dividing the two driving torque of the front and rear wheels is converted by distribution procedures into a procedure to

determine the distribution from longitudinal forces Fk . (2) _ _ jxjjx based on the torque reference generated from

accelerator. Hereafter, each procedure is described Here k (j = l and r) is a torque conversion gain j in detail. for front and rear wheels that get a match with

the torque reference R for the whole vehicle as Fx generated from an accelerator which is split A1 B Fx_max1 W between the front and rear wheels by A2 Fx_max2

Fy F x_r RfR Rr . (3) Fy_max1 Fy_max2 x_r ar F y_r D-G e t Fron r M oto Here, Rf and Rr are the front and rear torque R ear r M oto ar references split from R based on the load D-G e C ornering movement. The front and rear driving torque (a) Friction circle * * +Z-Zx references and are determined through δ Rf Rr Steer Angle F x_r x_r ≠ 0 x_l comparisons between Rf and x_f, and between Steer Angle D-Gear F y_r Going-straight Front and by the next procedures: ＝ 0 Motor Rr x_r x Load Movement Rear Steady State y Due to Acceleration A cceleration State Motor * D-Gear F F Rf ,min _ fxRf (4) zd_r F zd_f F z_r z_f

+Zx -Zx F F xd_f F x_f xd_r F x_r * (5) Rr ,min _ rxRr (b) Difference of the torque distribution when where x_f and x_r are the front and rear driving going straight and cornering references determined from the front and rear Figure 4. Basic points which should be taken into lateral forces F and F . y_f y_r consideration when distributing driving torque.

Slip Regions Suitable for using a moment diagram of forces acting on a Driving Control 1.0 vehicle which is in a standstill state (Fig. 7(a)) and Roads with High Friction Coefficient 0.8 an accelerating state (Fig. 7(b)). In a standstill state, the vehicle load which acts on the center of gravity 0.6 Asphalt is distributed to the normal forces F and F on zd_f zd_r 0.4 Wet Road the front and rear tires by Frozen Road 0.2 L L Roads with Low F r ,FF f F . Braking Regions Friction Coefficient _ fZd _rZdmg mg (8) Lcar Lcar -1.0 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1.0 -0.2 SLIP RATIO When vehicles are accelerated, the force moments Driving Regions acting on the contacting points (X and Y) of the -0.4 front-and-rear wheels are given by -0.6 Fmg -0.8 FLFL H 0 (9) _ mgrfzcar g carcar

-1.0 Slip Regions Suitable for and Braking Control Fmg Figure 5. Stability operation domain of slip ratio. L FLF _ rzcarmgf H carcar 0 (10) g

where vehicle weight F = mg (m: vehicle mass, mg g: acceleration due to gravity); car: longitudinal acceleration; Hcar: height of the center of gravity; Lcar: wheelbase of a vehicle; and Lf: length between the axles of the front wheels and the center of gravity. Therefore, the normal forces (Fz_f and Fz_r ) which act on the tire of the front and rear wheels are expressed by

Hcar car _ FF _ fZdfz F _ zF xfZdmg (11) car gL and

Hcar car FF __ rzdrz F _ zF xrzdmg (12) car gL

HH where zFcar car car F ()FM . x Lgmg Lcar car car car car car Using Fz_f , Fz_r and friction coefficient of a road surface, the longitudinal forces (Fx_f and Fx_r) acting between road surfaces and the tires of the front and rear wheels are given by

Figure 6. Flow chart explaining the basic principal of HF carcar _ FF _ xfzdfx ()( Fz _ fzd ) (13) the driving torque distribution method. Lcar

and

HF carcar _ FF _ xrzdrx ()( Fz _ rzd ). (14) 2.2 A Procedure to Determine Driving Lcar Torque Distributed to the Front and Then, so that the front and rear motors can Rear Wheels Based on Torque Reference generate the driving torques corresponding to these Obtained from the Accelerator longitudinal forces, torque references Rf and Rr The main point of this procedure is to are distributed to the front and rear torque distribute longitudinal forces to the front and rear controllers by wheels in consideration of load movement Rk caused by acceleration and deceleration. Then, RffRf (15)

first, longitudinal load movement zx is derived

and z 2 y _ LFI ff 2cos _ LF rry (19)

k R rRrrRr RR f ).1( (16) where Iz is yaw moment of inertia about the z-axis. Here the front distribution ratio Rf is given by Solving (18) and (19) about Fy_f and Fy_r, the front and rear lateral forces are derived as r 1 RR f F _ fx _ zF xfzd )( zgM xf (17) Rf . IMz caryrL FF __ rxfx Mcar car gM F (20) yf_ 2(LL )cos fr and

- I z MLcaryf F yr _ (21) 2(LLfr )

Next, the lateral load movement zy appearing during cornering is obtained by considering roll

moment at the center of gravity of the vehicle shown in Fig. 9. Moment balance at the center of gravity of the vehicle yields the equation for the

(a) Standstill normal force Fz_l on the left tires of the front and rear wheels as

car car HFgM car F _ lz . (22) 2 b x * x Front Fx_f

y Yf Fy_f y*

Lf V (b)Accelerating state. xx y G y Figure 7. Moment diagram of forces acting on a z vehicle. x* x Lr Fx_r

2.3 A Procedure to Determine Driving Yr y (~Fy_r)

Torque Distribution Based on Lateral * y Fy_r Force Required for Cornering Rear Here, using Fig. 8, movement of vehicles is described, by transposing to a two-wheel model Figure 8. Two-wheel vehicle model equivalent to a four-wheel vehicle (left turn). equivalent to the four-wheel model of vehicles in general. Assuming that the steering angle and Lateral Acceleration the slip angle of vehicle are small, the lateral y motion of the vehicle and the yaw dynamics at Tread Width the center of gravity of the vehicle are studied b that can be handled using longitudinal and lateral accelerations x and y, and yaw rate detected from the 3-axis acceleration sensor installed at y MF car y the center of gravity of the vehicle. The lateral car gM H motion for front and rear wheels is expressed by car

Fy_l Fy_r M F _ fyycar F _ ry .2cos2 (18) -zy +zy Fz_l Fz_r Taking the moment balance about the z-axis into Zy=(Hcar/b)Mcar y consideration, the equation for yaw dynamics is

given by Figure 9. Roll moment which acts at the time of a left turn.

F _ rlz _ 2 FF _ ryrly . (31) FF __ rrzrlz

3. Verification of the Proposed Driving Torque Distribution Method by Simulations

Simulations are performed using a prototype Figure 10. Control block diagram of the torque controller when the proposed driving torque FRID EV with the following specifications. m: distribution method is applied to the FRID EV. 1900 kg; Hcar: 670 mm; Lf:1500 mm, Lr:1125 mm; Lcar: 2625 mm. Fig. 12 shows simulation results when turning toward the left on a low -road ( = Accordingly, using the obtained Fz_l and (9), the 0. 2) with a 3-deg steering angle at 3 s after lateral load movement zy is obtained by accelerating. First, the proposed driving torque distribution method is evaluated through HM carycar (23) simulations under the severe driving condition of Fz zy _ -WF ll ( carl gMW ).2/ b turning to the left on the low - road. When the By using the derived zy, the left-and-right- proposed method is not applied (Fig. 12(a)), at normal forces Fz_fl and Fz_fr on tires for the front around 2 s after stating cornering the slip angle of

wheels, and the left-and-right-normal forces Fz_rl Start 60 Cornering and Fz_rr on tires for the rear wheels are given as hicle 40 t1

Speed [km/h] follows: Ve 20 0 024681012 200 Rear Wheel

-( LM Hg xcarrcar )- H car Front Wheel _ ( _ ) zzFF yxfzdflz M ycar , [Nm] 100 Motor Lcar b Torque (24) 0 024681012 0 Rear Wheel ( LM rcar g car aH x )- H car (25) -1

F _ frz - M ycar , [deg] L b -2 Front Wheel car Angle Slip -3 0246810 12 ( LM Hg ) H 1600 Left- Front Wheel Right- Front Wheel fcar car x car 1200 _ _ )( zzFF yxrzdrlz M ycar , Right- Rear Wheel Right- Rear Wheel [N]

800 L car b Force Lateral 400 0 (26) 024681012 Time[s] and (a)When lateral force is not distributed to the ( LM fcar Hg xcar ) H front and rear wheels properly. F - car M . _ rrz L b ycar car (27) Start 60 Cornering 40 t1

Speed

Considering that the front and rear lateral forces [km/h] 20 Vehicle 0 2Fy_f and 2Fy_r of (20) and (21) are divided with 0246810 12 200 ratios of Fz_fl : Fz_fr, and Fz_rl : Fz_rr,, respectively, Rear Wheel 100

[Nm] Motor the left and right lateral forces Fy_fl and Fy_fr of Torque Front Wheel 0 024681012 the front wheels and the left and right lateral 0

forces Fy_rl and Fy_rr of the rear wheels are -1

Slip [deg]

Angle expressed by -2 -3 0246810 12 1600

l Left-Front Wheel Right-Front Wheel F _ flz 1200 Left-Rear Wheel _ 2 FF _ fyfly , (28) 800

FF [N] Right-Rear Wheel __ frzflz Force 400 Latera 0 024681012 F _ frz Time[s] _ 2 FF _ fyfry , (29) _ FF _ frzflz (b)When lateral force is distributed to the front and rear wheels properly.

F _ rrz Figure 12. Effects of the proposed driving torque _ 2 FF _ ryrry , (30) FF __ rrzrlz distribution method on a very low -road when

cornering on a low -load ( = 0.2) at steering angle and 3 deg.

Start to L the front wheels is increasing gradually and the 40 o s accelerate s p e hicle e e d

Speed

[km/h] 20 front and rear lateral forces are saturated. As a Ve t 1 0 0 5101520 result, the vehicle shifts from the travelling lane, 200 160 Rear W heel 120 without the ability to corner (Fig.13). On the [Nm] 80 Motor Torque 40 Front Wheel 0 other hand, when the proposed method is applied, 0 0 5101520 Front Wheel -5 Rear Wheel

the saturation of lateral forces is suppressed by Slip [deg] Angle -10 -15 making driving forces of the front and rear 0 5101520 1 0.8 0.6 wheels decrease with cornering. Since the lateral Slip Ratio 0.4 0.2 forces required for cornering are secured (Fig. 0 0 5101520 500 12(b)), the vehicle can turn to the left along the 300 [N] Force

Lateral Lateral 100 0 travelling lane (Fig.13). 0 5101520

TIME[s] Next, the proposed method is evaluated under (a)Without proposed torque distribution method. severer conditions that make the vehicle

Stat to accelerate while cornering on an ultra low - 40 accelerate road ( = 0. 1). The difference in the cornering hicle 20 t 1 Speed [km/h] Ve 0 performance between the proposed method and 0 510 15 20 200

12 0

the conventional slip control is also made clear. Motor Torque [Nm] 40 0 Fig. 14 shows the simulation results under the 0 5 10 15 20 0 -5 conditions that the vehicle turns to the left at a 3- [deg] -10 deg steering angle while accelerating on the ultra Slip Angle -15 0 5101520 1

0.6

low -road at time t1 at about 10 s after stating. Slip Ratio 0.2 0 When the proposed method is not applied (Fig. 0 5 10 15 20 500 14(a)), the slip ratio immediately increases to 1. 300

Lateral 100 Force[N] 0510 15 20 Then, the wheel spin occurs, and a skid is caused. Time[s] Since sufficient lateral forces required for (b) With proposed torque distribution method revolution cannot be secured, the vehicle 40 S tart to accelerate

hicle 20 t 1 Speed [km/h]

Without the proposed driving Ve 0 50 torque distribution method 0 510 15 20 200 Front Road Rear 120 Wheel [Nm]

width Motor Wheel 40 Torque 40 With the proposed 0 048121620 driving torque 0 -5

30 Slip ] [deg] distribution method Angle -10

-15

Y[m 0 5 10 15 20 20 1

0.6 Slip

Ratio 0.2 10 0 0 5 10 15 20 500 300

0 [N] 100 0 10 20 30 40 50 60 70 80 0 0 5 10 15 20 X[ m] Force Lateral Time[s]

(a)Vehicle trajectories (c) With proposed torque distribution method

100 With only the slip ratio control 80 With the proposed driving torque

m] 60 distribution Y[ method 40

20 Without the proposed driving torque 0 distribution method -10 010203040506070 X[m]

(d) Vehicle trajectories when cornering while (b)Road condition used for simulations accelerating

Figure 13. Effects of the proposed driving torque Figure 14. Effects of the proposed driving torque distribution method on vehicle trajectories under distribution method when starting at a corner on an the same simulation conditions as Fig.12. ultra low -road while accelerating ( = 0.1, steering angle =3 deg).

strays from the travelling lane without being able wheel spin state is avoided. However, the slip to corner (Fig. 14(d)). Moving to the case of the angle increased gradually (Fig. 14(a)), and slip ratio control, when making a vehicle eventually, the vehicle cannot turn to the left (Fig. accelerate, slip ratios are soon increased to 1, and 14 (d)). On the other hand, when the proper although once they lead to the wheel spin state, driving torque is applied to front and rear wheels they are suppressed to less than 0. 2 and then the using the proposed driving torque distribution method, the slip ratio is kept at a value near zero

80 Start Cornering and skidding is also not seen. Then, lateral forces

t1 Speed 40 [km/h] Vehicle required for revolution are also secured, and the 0 0 5101520 vehicle can turn to the left properly along the 200 Rear Wheel traveling lane (Figs. 14 (c) and (d)). 160 Front Wheel 120 Finally, the effects when turning to the left at [Nm]

Motor 80 Torque 40 high speeds on the high -road ( = 0. 75) are 0 0 5101520 0 investigated under the conditions of beginning to

-2 Rear Wheel turn to the left at the time t1 while accelerating. -4 [deg] Front Wheel Angle Slip -6 When the proposed driving torque distribution -8 0 5101520 method is not applied, the vehicle can turn to the

6000 Right-Rear Wheel left properly up to corner B along the traveling 4000 Right-Front Wheel

teral Left-Rear Wheel lane, 10 s after starting to accelerate (Figs. 15(a)

La 2000

Force[N] Left-Front Wheel 0 and (c)).However, it is impossible to secure the 0 5101520 Time[s] lateral forces required for revolution because they are gradually saturated after passing B point. As a (a)Without the proposed torque distribution result, the vehicle cannot run along the road, and it method is accelerating too much. 80 Start On the other hand, when the proposed driving

icle Cornering

40 t1 torque distribution method is applied, lateral forces Speed [km/h] Veh 0 0 5101520 required for revolution are secured by decreasing 200 160 Rear Wheel the front and rear motor torques in accordance with 120 80 Front Wheel increase in speeds, and the turn to the left can be [Nm]

Motor 40 Torque 0 effectively carried out to bring the vehicle to the 0 5101520 0 final destination. -2 Rear Wheel Front

Slip -4 [deg] Angle -6 Wheel -8 0 5101520 4. Conclusion 6000 R ight-Rear W heel Left-Front When cornering on low -roads or at high 4000 Right-Front Wheel Wheel 2000 Left-Rear Wheel speeds, it is very difficult for all conventional Lateral Force [N] Force 00 5101520 vehicles to perform steering for revolution. This Time[s] paper described a driving torque distribution

(b)With the proposed torque distribution method method to solve these problems using the FRID EV structural feature that it can freely distribute 120 driving forces to the front and rear wheels W ith the t 80 1 proposed according to road surface and running conditions. B driving The driving torque distribution method is 40 torque Start distribution characterized by distributing the front and rear Point method torques to the front and rear motors so that lateral 0 A Y[m] forces required for revolution can be secured based -40 W ithout the proposed on the information about steering angle, friction driving torque -80 distribution method coefficient, and the lateral and longitudinal

-120 accelerations. The effectiveness of the proposed -40 0 40 80 120 driving torque distribution method was verified X[ m] through simulations about the cornering (c)Vehicle trajectories performance on low -roads and at high speeds.

Figure 15. Effects of the proposed driving torque Furthermore, in addition to the method of distribution method when cornering on a high - controlling the FRID EVs which was previously road while accelerating (steering angle= 3 deg, developed, the method proposed here has added a

=0.75).

still more powerful function to FRID EVs from Authors the viewpoints of safety and running Dr. Nobuyoshi Mutoh, Professor, performance. Graduate School of Tokyo Metropolitan University, Major fields References are advanced echo-machine control systems such as EVs. PV, wind power [1] K. T. Chua, C. C. Chan, and C. Liu, “Overview of and fuel cells. IEEE senior member, permanent-magnet brushless drives for electric and Professional Engineer (Electronics hybrid electric vehicles,” IEEE Trans. Ind. and Electronics) Electron., vol. 55, no. 6, pp. 2246–2257, 2008.

[2] Mitsubishi innovative Electric Vehicle, “imides”, Mr. Osamu Nishida http://www.mitsubishi- Honda Motors Co. Ltd. He received motors.co.jp/corporate/technology/environment/mi the BS degree in the Department of ev.html. Systems, Tokyo Metropolitan [3] Y. E. Zhao, J. W. Zhang, and X. Q. Guan, University. His area of research is EV “Modeling and simulation of electronic control system. differential system for an electric vehicle with

two-motor-wheel drive,” IEEE Intelligent Mr, Tatsuya Takayanagi Vehicles Symposium 2009, 3–5 June 2009, Xi’an, He is currently working towards the China, pp. 1209–1214. M.S degree in the Development of [4] F. Tahami, R. Kazemi, and S. Farhanhi, “A novel Systems Design of Graduate School, driver assist system for all-wheel-drive electric Tokyo Metropolitan University, vehicles,” IEEE Trans. on VT, vol. 52, no. 2, pp. Tokyo, Japan. 683–692, 2003. [5] M. Terashima, T. Ashikaga, T. Mizuno, K. Natori, N. Fujiwara, and M. Yada, “Novel motors and Mr. Tadahiko Kato controllers for high performance electric vehicle Fellow, General Manager, Advanced with four in-wheel motors,” IEEE Trans. Ind. Product Development Department, Electron., vol. 44, no. 1, pp. 28–38, 1997. Univance Co. [6] H. Shimizu, J. Harada, C. Bland, K. Kawakami, and L. Chan, “Advanced Concepts in Electric Vehicle Design,” IEEE Trans. Ind. Electron., vol. 44, no. 1, pp. 14–18, 1997. Mr. Kazutoshi Murakami [7] N. Mutoh, Y. Hayano, H. Yahagi, and K. Takita, Manager, DT Promotion Section, “Electric Braking Control Methods for Electric Advanced Product Development Vehicles With Independently Driven Front and Department, Univance Co. Rear Wheels,” IEEE Trans. on IES, Vol. 54, No. 2, 2007. [8] N. Mutoh, Y. Takahashi, and Y. Tomita, “Failsafe drive performance of FRID electric vehicles with the structure driven by the front and rear wheels independently,” IEEE Trans. Ind. Electron., vol. 55, no. 6, pp. 2306–2315, 2008. [9] N. Mutoh, Y. Miyazaki, R. Masaki, F. Tajima, and T. Ohmae, “Electric drive system and drive method”, U.S Patent 5549172. [10] N. Mutoh and Y. Takahashi, “Front-and-rear- wheel-independent-drive type electric vehicle (FRID EV) with the outstanding driving performance suitable for next-generation

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