Development of Electric Vehicles in Nagaoka University of Technology

Transcription

1 Development of Electric Vehicles in Nagaoka University of echnology Kazuo Saito and oshihiko Noguchi Department of Electric, Electronics, and Information Engineering Nagaoka University of echnology 1631 Kamitomioka, Nagaoka, Niigata , Japan Abstract his paper describes four types of electric vehicles (EV) which have been developed in Nagaoka University of echnology. hese EVs are named NEVI, II, III, and NEV4. NEVI and NEVII are converted from commercial cars, driven by a DC motor or an induction motor, respectively. NEVIII is an original EV with in motor drive, which has innovative structure and some unique driving modes as well as automatic drive. NEV4 has been improved to achieve high performances of running stabilization. hese four EVs possess proper features, and they have been investigated for each appropriate viewpoint. According to calculated and experimental results, it is verified that these EVs have their own essential performances. II. FEAUES AND PEFOMANCES OF HE ELECIC VEHICLES A. NEVI (Converted EV) [4], [5] NEVI is the first EV developed in Nagaoka Univ. of ech., which was made in his EV was converted from a commercial car with gasoline engine (55cc). Fig. 1 and able 1 show a picture and main specifications of NEVI. For the drive motor, a DC motor was adopted, because it was thought that DC motor drive by a chopper circuit was easy to produce an EV as the first step. Indeed, a commercial car was converted to the EV in three months. Keywords electric vehicle, DC motor, induction motor, in motor, chopper, inverter, steerbywire, special driving mode, automatic drive, running stabilization, yawmoment, cornering stiffness I. INODUCION In these days, topics of EVs (i. e., battery cars) as well as hybrid cars, fuelcell cars, and some kinds of ecofriendly cars have been increased amazingly. Different styles of EVs have been produced in Japan. Also, there are many discussions on drive motor, control system, battery, and etc. Even though, the specialties of most EVs are not utilized very well. [1] [3] he authors have developed four types of EVs called NEV to improve their performances and challenge to new technologies since he name of NEV is derived from Nagaoka and Electric Vehicle. he study started with converted EVs, i.e., NEVI and NEVII. Following them, NEVIII was designed and produced as a newtype EV. Lately, NEV4 becomes a main subject, and its running stabilization control systems have been examined. In this paper, the points of the features of these EVs and their particular characteristics are introduced, and the performances of them are investigated. Fig. 1 NEVI able 1 Specifications ( NEVI ) Seating capacity (L), 1395 (W) 1335 (H) mm Motor DC motor (rating: 3.5kW) Drive system Chopper circuit Battery 12V (Leadacid) Maximum speed 6km/h 1

2 As shown in able 1, the seating capacity was changed to two persons from four because of setting batteries in the rear seat position. Fig. 2 (a) and (b) show the engine room (before and after remodeling). Battery arrangement and the layout of main components are shown in Fig. 3 and Fig. 4, respectively. Fig. 5 shows the drive system using a chopper circuit. It has the motoring and the regeneration modes, then regenerative charges batteries when the EV brakes. In case the acceleration and the brake signal are both given, the brake precedes. Fig. 6 shows running data of the EV. ransmission was shifted from the 1st to the 4th, finally braking. he vehicle speed reached about 5 km/h, and regeneration was observed when the brake operated. Cooling fan DC motor Accelerator and brake mechanism Main battery DC12[V] ransmission Vacuum pump Main switch (SW1) Subswitch (SW2) Switching power supply Charging circuit Circuit box Subbattery DC12[V] Defroster Socket for charge Fig. 4 Layout of main components ( NEVI ) (a) Before remodeling Accelerator E i 1kHz Current feedback Control circuit 12V Drive circuit Motoring Drive circuit egeneration IGB1 L DCC IGB2 C IGB Chopper circuit DC M Fig. 5 Motor drive system ( NEVI ) (b) After remodeling Fig. 2 Engine room ( NEVI ) Fig. 3 Battery arrangement ( NEVI ) Armature [A] erminal voltage [V] Motor speed [rpm] [%] [%] Vehicle speed [km/h] egenerative 1st 2nd 3rd 4th time [s] Fig. 6 unning characteristics ( NEVI ) 2

3 B. NEVII (Converted EV) [6] NEVII was produced in 1997 followed by NEVI to make a comparison between DC motor and AC motor drive systems. herefore, the structures of these two EVs including the layout of main components are almost the same, as known from Fig. 7 and Fig. 8. he original car of NEVII is selected the same type of NEVI. But, as shown in able 2, the motor adopted in NEVII is an induction motor, which is altered from a commercial motor (rating: 3.7kW) to increase the rating output (4.5kW). he motor drive system is made up of a PWM inverter with quickresponse and highefficiency control which called direct torque control (DC) method. [7] he drive system is illustrated in Fig. 9. DC method has equivalent characteristics of fieldoriented control, but it doesn t need a position sensor attached on a motor. hen the system can be composed easily and at low cost. Fieldweakening control is applied to the motor to increase its speed. As a result, the vehicle speed reached about 9km/h, as shown in Fig. 1. Besides, Fig. 11 shows actual brake function. he vehicle speed decreases quickly from to around 5 seconds. It means regeneration of the motor assists the mechanical brake. he effect corresponds to the regenerative shown in Fig V Voltage Source PWM Inverter S a S b S c Switching able τ φ v 1 v 3φ 2φ v 1 v i ) dt ( i IM 3φ 2φ i 1 i 1 1 i1 1i1 Fig. 7 NEVII able 2 Specifications ( NEVII ) Seating capacity (L), 1395 (W) 1335 (H) mm Motor Induction motor (rating: 4.5kW) Drive system PWM inverter with DC Battery 24V (Leadacid) Maintenance free battery Maximum speed 9km/h orque Armature Vehicle speed 1 Discriminator Fig. 9 Motor drive system ( NEVII ) 1st 2nd 3rd 4th 5th 5s egenerative Fieldweakening 2V 5V 2V 2A 5km/h Fig. 1 unning characteristics ( NEVII ) Fig. 8 Engine room ( NEVII) Vehicle speed [km/h] ime [s] Fig. 11 Experiment of brake function ( NEVII ) 3

4 C. NEVIII (Original EV) [8], [9] NEVIII is an original EV, and it has many unique features. he prototype of the EV was made in Fig. 12 and able 3 indicate the basic character of the EV; three s arranged like a triangle shape, drive by an in motor (PM motor) installed in the rear, etc. One of the merits of NEVIII is to have special driving modes, as illustrated in Fig. 13 (a), (b) and (c). he modes are slide move, pivot, and brake arranged the direction angles of three s. hese modes can be also utilized when automatic drive is carried out without a driver. Fig. 14 shows the servo steering system of NEVIII. here are three kinds of steering devices, as shown in Fig. 12, too. A steering is used for normal driving mode which is the same style drive of conventional cars. wo joy sticks are the devices for special driving modes. Moreover, a magnetic sensor is used for automatic drive. Each servo steering system controls the direction angles of the three s independently, using steerbywire. he angles are detected by potentiometers all the time, and compared with the signal given by one of the steering devices. hen the s are turned toward proper directions by DC servo motors. Steering Wheel DC 12V Servo Control (Leftside Wheel) θ 1 (Wheel Angle) Control circuit Chopper Potentiometer DCC i 1 DC M Gear Joysticks (two) Magnetic Sensor S 1 Steering ( Angle ( i 1 Personal Computer (Motor Current) 2 3 ire Servo Control (ightside Wheel) Servo Control (ear Wheel) Fig. 12 NEVIII able 3 Specifications ( NEVIII ) Seating capacity (L), 156 (W) 157 (H) mm Drive Circuit Quasisource inverter Motor In motor (rating: 2kW) Circuit 4quadrant chopper Steering DC servo motor Motor Front; ear; 11W 3W Battery 12V (Leadacid) Maximum speed 4km/h (design value) kg 13kg 5cm/div Fig. 14 Servo steering system ( NEVIII ) (a) Slide move Front ear kg 5cm/div 13kg (b) pivot Front ear Fig. 15 Experiment of special driving modes ( NEVIII ) Control signal (Accelerator) Starting signal 2s 5V 5V Front Driver's position ear command command Chopper egenerative 1A 1A 1A Side direction (a) Slide move (b) Pivot (c) Fig. 13 Special driving modes ( NEVIII ) Motor speed Start Low speed stage Constant speed eacceleration & constant speed Free run High speed stage Deceleration Stop Low speed stage Fig. 16 unning characteristics ( NEVIII ) 2rpm 4

5 ear tire (Center) 5cm/div ear tire (Center) 5cm/div Magnetic sensor Iron sheet (a) Only rear control Magnetic sensor (b) hree control Iron sheet =23cm max. deviation : 39cm =23cm max. deviation : 13cm Fig. 17 Experiment of automatic drive ( NEVIII ) he automatic drive is possible by employing an original magnetic sensor. As the running course, thin iron sheet (thickness: 1mm, width: 12mm) is put on the ground. he magnetic sensor designed and made originally is attached on the bottom of the chassis at front side of NEVIII, and it detects the course. Fig. 15, 16, and 17 show typical experimental results of NEVIII. Firstly, examples of special driving modes comparing between the two different load conditions (kg and 13kg) are shown in Fig.15 (a) and (b). he maximum deviation from the ideal trace was less than 1cm when 13kg weight was loaded. It is probably no problem for real drive. Secondly, running characteristics for normal driving mode are shown in Fig. 16. he experiment carried out on several conditions continuously; acceleration, constant speed, reacceleration and constant speed, free run, deceleration, and stop. he maximum vehicle speed reached at 15km/h in this experiment. hirdly, Fig. 17 (a) and (b) show the results of automatic drive. wo ways were examined, one is only rear control, and the other is three control simultaneously. he maximum deviation of the rear tire from the ideal trace was 39mm and 13mm, respectively. It is clear that the latter is superior to the former. In this figure, the trace line of the magnetic sensor means the frontside center of the EV. When one of the three steering devices gives the directional reference, NEVIII moves properly for any driving modes. According to these experimental results, it is known that the EV is appropriate to drive in small place, also it can contribute to unskilled driver. In addition, concept of the technological design of NEVIII will be able to utilize for future vehicles. D. NEV4 (Improved EV) [1] his is an EV with two in motors in rear s originally, as shown in Fig. 18 and able 4. NEV4 has been improved to achieve high performances since 22. As the first strep, running stabilization control for yaw motion has been studied. Fig. 19 and Fig. 2 show the novel direct yawmoment control (DYC) systems. In addition, new antislip control is utilized as innerloop system to control longitudinal motion. First, a simple DYC system with yawmoment observer (YMO), as outerloop lateral controller, is shown in Fig.19. his observer can nominalize the yawing dynamics by compensating the unknown nonlinear lateral force and yawmoment as lumped disturbance. On the other hand, an advanced DYC is proposed with road condition estimation, as shown in Fig. 2. In this scheme, an immeasurable parameter known as cornering stiffness is estimated from the detected yawrate, steering angle, speed, and yawmoment observer output in realtime. Fig. 21 (a) and (b) show the experimental results of stabilization control on dry and snowy terrain conditions. he proposed adaptive control was compared with the robust control based on YMO when the sinusoidal steering reference was provided. he experimental results show that the yawrate error (γ error ) is well attenuated by these control systems. he technologies applied to NEV4 are very important components for safe drive, especially on snowy or iced road. Fig. 18 NEV4 able 4 Specifications ( NEV4 ) Seating capacity (L), 955 (W) 16 (H) mm Motor wo in motors (max.: each 2.kW) Drive system PWM inverter with stabilization control Battery 72V (Leadacid) Maximum speed 5km/h 5

6 k f f s 1 I n s N in N z Nˆ dt r ASC r N d eal vehicle DL ac ASC l l I n s c DL:orque Distribution Law s c ASC:Anti Slip Controller Fig. 19 DYC based on yaw moment observer ( NEV4 ) k f f s 1 Ĉ ˆ N dt N tc I n s ˆ ˆ C C e N in N z Nˆtc Nˆ dt r N d r eal ASC vehicle DL ac ASC l l I n s c DL:orque Distribution Law s c ASC:Anti Slip Controller Fig. 2 Proposed DYC with cornering stiffness estimation ( NEV4 ) (rad/s) error (rad/s) ^ C (N/rad) (rad/s) error (rad/s) ^ C (N/rad) YMO method proposed method ime (s) (a) Dry terrain YMO method proposed method ime (s) (b) Snowy terrain Fig. 21 Experiment of stabilization control ( NEV4 ) III. CONCLUSIONS he different types of EVs developed in Nagaoka Univ. of ech. have each meaningful feature. NEVI has the simplest drive system among the four, and this EV has passed the automobile safety inspection of Japanese Standards since 1997 until now. NEVII has higher maximum speed than that of NEVI, because it is driven by the induction motor with fieldweakening control. NEVIII is using steerbywire control for three s, therefore it has peculiar performances. NEV4 is going on study; the novel direct yawmoment control systems have accomplished already, and next challenge is examined. Small EVs, exampled in this paper, are expected for new transport, e.g., commuter car, second car, delivery service car, vehicle for elderly people, etc. We hope that the new technologies applying to these four NEVs would contribute to the design of future vehicles. ACKNOWLEDGEMENS We would like to thank the staff of the Power Electronics Laboratory in Nagaoka Univ. of ech. for their assistance and helpful discussions. Special thanks are due to Dr. Isao akahashi. EFEENCES [1] I. akahashi, et al., he Latest echnology of Electric Vehicles, Ohmsha, Japan, [2] M. H. Westbrook, he Electric Car, he Institution of EE, UK, and Society of Automotive Engineers, USA, 21. [3] Y. Hori,. eratani, and. Masaki, Motor echnology of Automobiles, Nikkankogyo Shinbunsha, Japan, 23. [4] K. Saito, et al., Development of an Electric Vehicle NEVI and Its unning Performances, Proceedings of the Japan Industry Society Conference, pp , [5] I. akahashi, M. Sekimoto, and K. Saito, et al., Development of a Fly Energy Storage System for a Hybrid Electric Vehicle, Journal of Asian Electric Vehicles, Vol. 1, No. 1, pp , 23 [6] K. Saito and I. akahashi, Application of Direct orque Control Method to an Electric Vehicle, Journal of Asian Electric Vehicles, Vol. 1, No. 2, pp , 23. [7] I. akahashi and. Noguchi, A New Quickesponse and HighEfficiency Control Strategy of an Induction Motor, IEEE rans. on Industry Applications, Vol. IA22, No. 5, pp , [8] K. Saito and I. akahashi, Development of an Electric Vehicle Having hree Wheels and One Motor Drive, INEMAC Joint echnical Conference, Japan (CD OM), OSV5 (OSE5), 21 [9] K. Saito,. Masuda, and I. akahashi, Characteristics of an Electric Vehicle with hree Wheels and One Wheelinmotor, Journal of Asian Electric Vehicles, Vol. 1, No. 2, pp , 23. [1] A. sumasaka, H. Fujimoto, and. Noguchi, unning Stabilization Control of Electric Vehicle Based on Cornering Stiffness Estimation, he Papers of echinical Meeting on Vehicle echnology, IEE Japan, V514, pp. 7782, 25. 6