The International Workshop on Mechatronics 2006
December 12-13, 2006, Supalai Resort, Saraburi, Thailand

Development of Electric Wheelchair Using PEM Fuel Cell
Kazuo Saito, Chan Anyapo, and Toshihiko Noguchi
Department of Electrical Engineering, Faculty of Engineering,
Nagaoka University of Technology, 1603-1 Kamitomioka, Nagaoka, Niigata 940-2188, Japan
Tel/Fax: 81-258-47-9541, E-mail: saito@vos.nagaokaut.ac.jp

Abstract
This paper presents a developed electric wheelchairusing a PEM fuel cell as a power supply. In addition, it
has an EDLC bank for an energy buffer. Two DC motorsof the wheelchair are driven by a newly designed fourquadrant DC chopper. Performances of the fuel cell andthe wheelchair have been examined by experiments.
Then, it is clarified that the PEM fuel cell has enoughcapability and is appropriate for the electric wheelchair.
Keywords: wheelchair, PEM fuel cell, EDLC, DC motor,
four-quadrant DC chopper
1. Introduction
Effective applications of fuel cells have amazingly
been discussed in recent years. Meanwhile, many typesof electric vehicles have already been developed bymanufactures and research agencies in Japan. Therefore,
combination of a fuel cell and an electric vehicle is aworthwhile topic for the future transportation [1].
This paper introduces an electric wheelchair using aPEM (Proton Exchange Membrane) fuel cell. Thewheelchair also has an EDLC (Electric Double Layer
Capacitor) bank for an energy buffer, and a four-quadrant
DC chopper to drive two DC motors installed inside eachwheel. Moreover, basic characteristics of the fuel celland the electric wheelchair are shown in the paper.
2. Configuration of wheelchair
Figure 1 shows the developed electric wheelchair.
The original one has the following specifications;diameter of drive wheels is 22 inches, maximum speed is
6km/h, output power of each DC motor is 90W, power
supply is a Li-ion battery (25.9V/6Ah).
The electric wheelchair has been improved on
several points. In particular, its power supply is replacedby the PEM fuel cell, the two DC motors are driven byFigure 1. Developed electric wheelchair.

the newly designed DC chopper, and the EDLC bank isemployed as the energy buffer.
Figure 2 illustrates the motor drive system of theelectric wheelchair. Regarding the fuel cell, hydrogen issupplied from a hydrogen storage alloy, and oxygen in
air is inhaled by a blower. The EDLC can be charged ordischarged depending on the drive condition of thewheelchair. For example, the EDLC supplies energy if
the fuel cell lacks its output power for driving the two
DC motors. When regeneration of the motors occurs, adischarging resistor dissipates energy if the EDCL isfully charged. Major specifications of these equipments
are as follows;(1) PEM fuel cell: 200W/24V (output), 41 cells (stack),(2) Hydrogen storage alloy: 500ℓ (capacity of H2),(3) EDLC: 1350F/2.7V (capability),(4) DC motor: 90W (identical to the original one).
3. Characteristics of PEM fuel cell
There are several kinds of fuel cells, and the PEM
fuel cell is the most suitable for the developed electricwheelchair. Because the PEM fuel cell can be used atroom temperature, and its size is compact [2].

Q 10

PEM Fuel Cell

D

Fuel Cell+
M3 24V• Stack
41 Cells• Output
200W /24VR

Q7

C1BlowerLQ9
D9VB

D7Q8

D8Q3

D1-- M2 +Left
MotorRight
Motor+EDLC
C2Q2

D3M1

D2Q4

D4Q5

D5Q6

D6BlowerOxygen
SteamGauge

Q1EDLC

HydrogenHydrogen
Storage Alloy

Discharging
Resistor

Fuel Cell

Electric Double
Layer Capacitor

DCMotors

Figure 2. Motor drive system of electric wheelchair.

200

Voltage

25Power

20150

100oTemperature: 23 C
Humidity: 81%

15005

10

Output power (W)Output voltage (V)3050015

Output current (A)Figure 3. Characteristics of PEM fuel cell.

The hydrogen storage alloy is connected with thefuel cell, as shown in Figure 2. The figure also illustrates
the flow of hydrogen and oxygen. Figure 3 demonstrates
the key characteristics of the PEM fuel cell obtained
from experimental results. By increasing output current,
output voltage has a droop characteristic, meanwhile themaximum output power reaches around 200W [3, 4].
4. Performances of wheelchair
The developed electric wheelchair has several drive
modes, i. e., forward, backward, right or left turn, andpivot. The two DC motors installed inside the wheels aredriven by a four-quadrant DC chopper which is speciallydesigned to simplify the drive system. According to theexperimental results, it is cleared that the PEM fuel cell
has enough output power to drive the two DC motors [5].
4.1 Four-quadrant DC chopper
The four-quadrant DC chopper has a combined

structure of two full-bridge chopper circuits. Thus, thenumber of switching device (MOSFET) can be reduced
from eight to six, as indicated in Figure 4.
Figure 4 also explains an operating condition of theDC chopper when the forward drive mode is carried out.
Thick arrows stand for the current path of the two DC
motors and the switching devices.
Figure 5 shows the gate signals of the MOSFETs,
the waveforms of voltages and currents of the two DCmotors. The PWM switching frequency of Q1, Q2, Q5, Q6
is 10kHz, and that of Q3, Q4 is 1kHz. When Q4 is ON,
and Q1 and Q5 are in switching operations, the two DC
motors rotate in forward direction at once. It means theelectric wheelchair moves ahead. For the other drive
modes, appropriate PWM switching is selected, too. For
example, in the case of the left turn drive mode, only theright motor (M2) rotates in forward direction, and the left
motor (M1) doesn’t operate. For the pivot drive mode,
M1 and M2 rotate in reverse directions each other.
4.2 Experimental results of wheelchair
Figure 6 demonstrates the experimental results forthe output power of the fuel cell, when the forward drivemode and the left turn drive mode are carried out.
As shown in Figure 6 (a), the maximum instantaneous output power reaches about 100W, and the steadystate value of it is below 60W. Whereas, for Figure 6 (b),the correspondent values are 105W and 50W, respectively. Besides, the output power is around 30W when thetwo motors don’t operate. The reason of the phenomenon
is to work the blower which inhales oxygen from air, i. e.,
the output of the fuel cell is simultaneously used as apower supply of the blower.
Regarding the other drive modes, experimental data

120
D1Q3+

M1-Right Motor

Q4Q2
D2D5Q5- M2 +Left Motor

OFFD3Q6D4D6OFF

100

Output power (W)Q1806040
20000.5

1.01.5Figure 4. Operation of chopper (forward drive mode).
StopQ1Q2(V)
5Output power (W)100

50vLvR

5024024

Stop120

5Q5 0Q6Forward(a) Forward drive mode.

050
5Q30

Q4

2.0Time(s)

iL

80
60
40
20
00

0.5

1.0

1.5

2.0Time(s)

iR0

Stop

Left turnStop(b) Left turn drive mode.

Figure 5. Waveforms of chopper (forward drive mode).

Figure 6. Experimental data of output power.

have been obtained. Measured values for the backwardmode and the right turn mode are almost the same withthe forward mode and the left turn mode, respectively.

Co., Ltd. for providing the EDLCs, and Q M Soft Co.,
Ltd. for supporting on the PEM fuel cell.

5. Conclusion
The new electric wheelchair using the PEM fuel cellhas been developed. Additional ideas are applying theEDLC bank and the newly designed DC chopper. The
performance of the electric wheelchair was examined byexperiments. On the other hand, the characteristics of thefuel cell were investigated. As a result, it is clarified thatthe PEM fuel cell is adaptable to the electric wheelchair,and the basic movements of it have been achieved. In
addition, it is necessary to examine the management ofpower flow of the motor drive system in the near future.
Acknowledgements
The authors would like to thank Power Systems

References[1] Iizuka, S., 2006. Possibility of Fuel Cell Cars andElectric Vehicles. Grand Prix Pub. Co., Ltd., Japan.
[2] Larminie, J., and Dicks, A., 2003. Fuel Cell Systems
Explained (2nd edition). John Wiley & Sons Ltd., UK.
[3] Nakai, K., Saito, K., and Noguchi, T., 2004. Evaluation of Characteristics of a PEM Fuel Cell. Niigata
Branch of IEEJ, P-38, November 20, p. 118.
[4] Nakai, K., Saito, K., and Noguchi, T., 2005. Study on
Dynamic Characteristics of a Polymer Electrolyte
Fuel Cell. National Convention Record IEEJ, No.
4-216, March 17-19, p. 346.
[5] Anyapo, C., Saito, K., and Noguchi, T., 2006. Development of Electric Wheelchair Using Fuel Cell.
Niigata Branch of IEEJ, November 18.