Development of Automatic
Steering & Battery PoweredAutomated People Mover
HIROSHI OGAWA*1
MASAHIRO YAMAGUCHI*2
KATSUAKI MORITA*2

MITSUAKI HOSHI* 1
HIROYUKI KONO*2
MASAYA MITAKE*2

In today's world where environmental problems draw great attention, guideway transportation systems are popular because of their environmentally friendly features. Introducing an actuator-driven automatic steering mechanism simplifies the guiding system which is laid on the guideway. In addition, by fitting a battery system to thevehicle, we can eliminate the power rail supplying electric power, realizing a compact guideway, and reducing theconstruction costs. Further, the kinetic energy of the vehicles can efficiently recharge the batteries. Mitsubishi
Heavy Industries, Ltd. (MHI) has developed this automatic steering and battery powered APM (automated peoplemover) to realize a ground transportation system which can satisfy society's needs.

struction period. Further, from the standpoint of energy saving, the kinetic energy can be efficiently
recharged to the battery during braking. This paper
outlines the concept of the new system and the resultsof the practical running performance of a test vehicle.

1. Introduction
New transportation systems have been increasingly
introduced in various parts of the world. MHI has also
been developing safe and comfortable ground transportation systems such as the APM (automated peoplemover) which is a new, rubber tire transportation system, the steel wheel LRT (light rail transit), monorailsystems, and Skyrail systems. Further, as environmental issues are increasingly a global concern, there is abigger demand for new energy-saving transportation systems which are compact and environmentally friendly.
Accordingly, MHI has developed an automatic steering,battery powered APM by adopting a new concept to satisfy our customers' needs. The automatic steeringsystem, by using an actuator steering mechanism, simplifies the guidance system which is laid on the guideway.
Also, as a battery system is installed on the vehicle, iteliminates the power rail which supplies electric power,
contributing to a compact guideway configuration. It
also reduces construction costs and shortens the con-2. Conventional system
2.1 Guiding system
A conventional APM uses the typical side guided system shown in Fig. 1
1. The four-wheel steering running
wheels and the guiding devices fitted with guide wheels
on both sides are located at the front and rear of thevehicle, and are mechanically connected via a link mechanism. When the vehicle starts to move, the guide wheels
come in contact with the guide rails on both sides of theguideway, generating a reaction force which steers therunning wheels and guides the vehicle along the guiderails.
Also, as both the front and rear wheels of the vehicle
need to run on the same trajectory, the front and rear
wheels are steered in opposite directions. In order toachieve this mechanism a steering reverser is installed
between the guiding device and the axle steering arms.
2.2 Electric power supply system
As for electric power supply, power rails are laid along
the guideway and the vehicle receives electric power by
the pantograph on the vehicle being in constant contact
with the power rail.
As explained above, in the conventional system theguide rails and power rails are laid on either side of theguideway throughout the whole line. Therefore, as thecross-sectional area of the track becomes larger and alonger construction period is required to lay the guiderails and power rails.

Guidingmechanism
Running wheels
Guide rail

Guide wheels

Fig. 1 Side guided system

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 44 No. 2 (Jul. 2007)*1 Plant and Transportation Systems Engineering & Construction Center*2 Hiroshima Research & Development Center, Technical Headquarters1

3. Concept of Automatic Steering & Battery Powered
APM

Powerrail

Figure 2 shows a comparison of the conventional APM
and the new system. As the new system can eliminate
the guide rails and power rails, the track becomes narrower in width, and the structure becomes simplified.
3.1 Automatic steering system
The automatic steering system determines the running pattern of the guideway from the real time vehicle
position, alignment database and operational data, anduses them to control the steering of the vehicle. An active control type four-wheel steering system using an
actuator is adopted for steering. The steering of eachvehicle is controlled so that the front and rear wheels
run on the same trajectory on the guideway, making thesystem suitable for single vehicles and also for multivehicle combinations.
The automatic steering system consists of an automatic steering control device, an actuator, and rods whichtransmit the actuator movement to the running wheels,and neither a guiding device or a steering reverser arerequired. This contributes to the weight reduction ofthe bogie. This does not involve any revisions to thesuspension mechanism, the axle and the running wheels,
which have a long-proven record in the conventional
APM.
In addition, the backup-wheel mechanism shown inFig. 3 is used as a fail-safe backup system. The backupwheel mechanism comprises of a backup-wheel guide on
the running track and a backup-wheel device for thevehicle, where the guide width is determined to ensure
a specified clearance between the backup-wheels and thebackup-wheel guide.
Therefore, in the normal condition, the backup-wheels

Guide rail
Conventional APM

Automatic steering,battery powered APM

Fig. 2 Conventional APM and automatic steering, battery
powered APM

move in conjunction with the steering mechanism of therunning wheels without touching the guide. In the eventof a control failure, the backup-wheels can guide thevehicle along the backup-wheel guide, which serves as afail-safe system.
3.2 Concept of battery system
The battery system eliminates the conventional power
supply from power rails, and the vehicle is driven bybatteries mounted on the vehicle. During braking, thekinetic energy is efficiently recharged back to the battery. As an APM is restricted in terms of vehicle space
and weight, the use of high-performance batteries is required. The battery system needs to have at least enoughenergy capacity to cover the distance between two stations and the energy consumed during traveling needs
to be quickly re-charged while stopped at the station.
In consideration of these requirements, high performance, high output lithium ion secondary batteries which
realize high acceleration and high speed running havebeen adopted.

Real time vehicle position, alignment database, operational database
Steering commandController

Tire

Backup-wheel guide

Backup-wheel
deviceActuator

Fig. 3 Configuration of automatic steering system

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 44 No. 2 (Jul. 2007)2circuit. The batteries, in order to cope with the conditions under the floor, such as rain and direct sunlight,
are structured to have good waterproof properties. Thesystem is also equipped with a fan cooling device to prevent temperature rises. Due to vehicle space restrictions,particular consideration was given to the on board design so that the batteries could be mounted compactly
under the floor. In system operation, in order to prevent
over-charging or over-discharging, the voltage is adjusted
so that the battery charging condition is held within aspecified range and the current does not exceed the allowable limits of the batteries.

4. Vehicle testing
In order to use it as a test vehicle (the photograph on
page 1), MHI's existing experimental vehicle was
equipped with the automatic steering and battery systems described above.
Figure 4 shows an actual test conducted on the test
line at our Plant and Transportation Systems Engineering & Construction Center (Mihara).
4.1 Automatic steering system
The vehicle is equipped with the actuator, controller,
and fail-safe system necessary for the automatic steering system, while the backup-wheel guide is built into
the guideway. The fail-safe system is a backup mechanism, and works in conjunction with the running wheels
steering mechanism so that the backup-wheels do nottouch the guide under normal conditions.
4.2 Battery system
Figure 5 shows the configuration of the battery system. Lithium ion secondary batteries are mounted underthe vehicle floor and are connected to the main vehicle

5. Test Results
The running tests were conducted on our test line
combining straight and curved sections, where the automatic steering, battery power system achieved practical
speeds over the line. All tests were conducted by using
batteries as the power source, during which no trouble
was reported.
Some examples from the tests results are illustrated
as follows. Figure 6 shows photos of the backup-wheels
taken during a high speed run along a straight line.

Operation panel
Induction
motorHigh-speed circuit breakerIMVVVF
inverterTo SIVIM

Lithium ion
battery box
Fig. 4 Test scene

Lithium ion
battery box

Fig. 5 Configuration of battery system

Backup-wheel guideClearance
Backupwheels(a) Backup-wheels during a high speed run on
the straight line(b) Positions of backup-wheels

Fig. 6 (a) Backup-wheels during a high speed run on the straight line (b) Positions of backup-wheels

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 44 No. 2 (Jul. 2007)

3

Fig. 7 Backup-wheels along small curve

Figure 7 shows the behavior of the front backupwheels during a run on a small curved line. Figure 8shows an outside view taken from the vehicle during arun on the small curved line. It was verified that thevehicle was steered along the curved guideway also on
the curved section and the backup-wheels did not touchthe backup-wheel guide.

6. Conclusion
Based on the concept of an environmentally friendly
APM which is compact and easy to construct, MHI has
worked on the development of a new, energy-savingtransportation system with a compact guideway whichis unique and innovative. The automatic steering, battery powered APM is an unsurpassed urban
transportation system which meets the above concept.
MHI has completed internal running tests at the practical operational level and is expecting the earliest possibledelivery of this system to our customers.
We would like to express our sincere gratitude to allparties concerned for their guidance and cooperation
extended to us in the course of the development of thisautomatic steering, battery powered APM.

Fig. 8 Outside view taken from vehicle during along run small
curve

Hiroshi Ogawa

Mitsuaki Hoshi

Masahiro Yamaguchi

Hiroyuki Kono

Katsuaki Morita

Masaya Mitake

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 44 No. 2 (Jul. 2007)4