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					             AUTOMATIC GUIDED FUTURE VEHICLES

Abstract :Four technologies, combining mainly innovative solutions,
offer the possibility of clean and flexible vehicles, all using only
electricity. The main common components are contact-free energy
transmission, storage on super-capacitors, holonome axles integrating
wheel-motors and automatic guiding. Moreover, the complete
energetic chain is managed by power electronics. Their applications
are mainly in the field of public and industrial transportation. Several
applications are described: electric busses, automatic guided
 vehicles for container handling, automatic people movers and
automatic surveillance vehicles.

applications are described: electric busses, automatic guided vehicles
for container handling, automatic people movers and automatic
surveillance vehicles.
                                                                           Fig. 1. From Swissmetro project to specific technologies

                                                                           Fig. 2. Contact-free energy transmission - Principle

                                                                           III.CONTACT-FREE                  ELECTRICAL                  ENERGY
                                                                           TRANSFER

                                                                           A. Principle
                                                                           This technique [2-7] offers the possibility to transfer electrical energy
                                                                           from a fixed coil on or in the ground to Moving coil linked to the
                                                                           vehicle Fixed coil in the ground an other coil placed under a vehicle.
                                                              I.           The process is realized without iron magnetic circuit, in the air. On
INTRODUCTION                                                               Figure 2 the principle is illustrated. In order to reach this ironless
A new generation of vehicles, mainly based on 4 different                  magnetic coupling, a high frequency is necessary (>>50 Hz).
technologies, is presently in development for good or passenger            Effectively, from the back-EMF equation it is possible to write:
transportation or special applications.These technologies are              Ui=d/dt =back EMF
- Contact-freeenergy transmission                                          =total flux = N
- Wheel-motor with an external rotor                                       N = coil number of turns
- Energy storage on super-capacitances                                     B = magnetic flux density
-The use of an energy chain based on power electronics and control,        Sair= magnetic air section
from the ground to the motors.                                             So the back-EMF equation becomes :
The main applications are :                                                Ui  N.f.B.Sair
- An automatic guided vehicle (AGV) for container transportation           By increasing the frequency and the magnetic section, it is possible to
and handling                                                               reduce the flux density B and the copper volume by reducing the
- An automatic people mover at 15 km/h                                     number of turns N. Thus, it is possible to suppress the iron magnetic
- An automatic safety and control vehicle                                  circuit, using air instead. An optimisation software, aiming to reduce
- An electric city bus                                                     the copper volume, to reach a transmission efficiency > 98 % and to
II. AIM                                                                    minimise the electromagnetic radiation has been developed and
Starting from different technologies developed for the high speed          applied. A system for a total power of 120 kW (Fig 3) has been
Maglev Swissmetro (Fig 1 ) [1], the approach of technology transfer        designed and built with the corresponding power electronic to
has been to apply one or several components to innovative vehicles         generate the high frequency and a controlled rectifier on the vehicle .
,responding to specific constraints and criteria:                          A global maximum efficiency of 95 % has been measured at 110 kW.
- High flexibility of exploitation
- Clean, quiet and sustainable ;
- High automation and control with or without driver;
- Low investment in infrastructure;
- Low maintenance costs.
In order to reach these goals, specifically in the range of speeds
between 10 and 100 km/h, one more device had to be implemented :
the direct drive wheel-motor with external rotor, also developed at
EPFL.



                                                                           Fig.3. Contact-free energy transmission – 120 kW test facility

                                                                           B. Magnetic field
A specific problem of inductive energy transfer is the
magnetic field radiation, limited by normalization, according
to the frequency. The solution to reduce the intensity of
radiation for passengers in the vehicle and nearby is to design
the system using 3 safety elements:
- To switch on the primary coil only when the secondary coil
(i.e. the vehicle) is correctly positioned.
- To place a magnetic shield on the vehicle floor (a thin
lamination)
- To impose the same current volume for the primary and the
secondary coils This last condition has been applied to an          Fig.6. Relative flux density distribution on a level of 1.2 m
energy transfer system corresponding to the following               above the
conditions:                                                         IV. ENERGY STORAGE ON SUPERCAPACITORS
- Power transferred : 108 kW                                        Energy transfer can be done continuously from the ground to
- Coil sizes : 4*2 m                                                a vehicle, using a continuous succession of coils (Fig.7) . This
- Distance d : 0.115 m                                              presents two drawbacks: the investment cost and the absence
- Primary voltage: 500 V                                            of track flexibility.
- Floor level above primary coil : 0.3 m
With current volume opposition, the magnetic field levels
without shielding are represented on graphics, in relative
values, referred to the earth magnetic field. On Fig. 4, the
relative flux density is calculated above the middle of the
coils, on a vertical axis (yy), from the vehicle floor level (0.3
m) up to 2 m. On the vehicle floor, the relative amplitude is
0.3.




                                                                    Fig.7.Continuous coil track
                                                                    As a variant, contact-free energy transmission with
                                                                    intermediate fast storage on ultra-capacitors [8,9] is a very
                                                                    interesting solution. It allows an autonomy of track with a
                                                                    reduced investment. This solution requires an autonomy in the
Fig.4. Relative flux density distribution above the coil centre,    range of 2.5 to three times the distance between two loading
on a                                                                stations. On Fig.8, the global electrical scheme of such a
On Fig.5, the same relative flux density is represented on the      solution is presented, including the energy transmission
floor level (yy= 0.3m) on an horizontal axis, from the coil         system and ultra-capacitor loading control. The rapid loading
centre laterally up to 2m; xx = 1 m corresponds to the coil         operation requires an important peak power. Thus, an
side level. The peak value is 0.75 above the coils.                 interesting solution is to equip a station also with an ultra-
                                                                    capacitor intermediate storage, such as to have the possibility
                                                                    to smooth down the main power (see Fig. 18).
                                                                    V. WHEEL-MOTOR
                                                                    For the different categories of vehicles presented hereafter,
                                                                    the electric drive solution has been focused on direct wheel
                                                                    motor drive characterized by:
                                                                    - No gear transmission
                                                                    - Brushless DC motors
                                                                    - External rotor
Fig.5. Relative flux density distribution on the vehicle floor      The absence of transmission leads to a heavier motor. But the
level, from                                                         solution with external rotor [10] allows a better integration
the centre to 2 m – 108 kW power – 4*2 m coils                      directly in the wheel and not laterally to the wheel (Fig 9) as
On Fig.6, the same relative flux density is represented on the      sometimes realized. Fig 10 shows a wheel motor according to
on a level of yy=1.2m, on an horizontal axis, from the coil         the proposed solution. An optimized design software leads to
centre laterally up to 2m; xx = 1 m corresponds to the coil         an acceptable mass with an important free volume at the
side level. The peak value is 0.1m above the coil centre.           inside.
Fig.8.Electric scheme of energy transfer system and storage
on ultracapacitors




                                                                   Fig.12.Vehicle axle with 2 wheel motors and a steering motor.
                                                                   The
                                                                   damping elements are integrated in the motor itself.



Fig.9.Electric drive for wheel with classical gear transmission
Fig 11 shows the stator (left) and the rotor (right) of such a
motor for a rating torque of 4000 Nm. Based on such motors,
vehicle axles with 2 wheels have been developed, with
integrated steering motor allowing a very important angle of
rotation until ± 90o (Fig 12). In this case, the damping devices
have been integrated in the free space internal to the motors.
Such an axle has been realized for the vehicle of Fig.14.



                                                                   Fig.13.Automatic Guided Vehicle for 40 T containers -120
                                                                   kW powerat 25km/h.
                                                                   VI. VEHICLES INTEGRATING THE DIFFERENT
                                                                   TECHNOLOGIES
                                                                   Automatic guided vehicles for container handling:
                                                                   An automatic guided vehicle for container handling has been
                                                                   developed tire d integrating the following technologies:
                                                                   - Contact-free energy transmission
                                                                   - Motor wheel axles
                                                                   - Energy storage on super-capacitors
                                                                   - Automatic guiding
                                                                   The transportation capacity is designed for 40 T containers.
Fig.10.wheel motor with external rotor                             The maximum power is 120 kW with a maximum speed of
                                                                   25km/h. On Fig.13, a picture of the final vehicle is presented.
                                                                   On Fig 14, the first prototype vehicle is represented. It is
                                                                   supplied by the coil system of Fig.3.




Fig.11.Stator (left) and rotor of a wheel motor of 4000 Nm




                                                                   Fig.14.Automatic Guided Vehicle for 40 T containers – First
                                                                   prototype
A first series of such vehicles will be built and tested in a
harbor at the end of 2008.
Low floor electric bus :
The same technology of energy transmission system and axles
with wheel motors can be applied to busses with a very low
floor, according to the integrated wheel realization . The
possibility to move the wheels independently (but in
coordination) offers the advantage to reduce the stop area
length. A test realization is foreseen for 2009.

                                                                    Fig.18.Automatic people mover with energetic chain and
                                                                    loading station
                                                                    1-Vehicle structure 2-Loading station with intermediate
                                                                    storage
                                                                    3-Power electronics 4-Super-capacitors 5-Obstacle detection
                                                                    6-Primary coil 7-Secondary coil
Fig.15.Bus with independent wheel axles and very low floor          Automatic surveillance vehicle:
                                                                    Many different installations or situations require safety
Automatic people mover:                                             surveillance and reconnaissance. They are generally known
Automatic people mover (APM) are small vehicles with a              under the name of Mobile Detection Assessment Response
capacity of 8 to 10 people (1200 kg) with a speed of 15 km/h        System (MDARS).Automatic systems based on the same
(Fig 16). The rating power is 14 kW with a maximum slope of         energetic chain as the APM system have the advantage of
16%. The peak power for the energy transfer is 50 kW. This          reliability, absence of noise, insensitivity to any type of
allows a loading time of maximum 10 seconds for an                  pollution and a smaller size. Such a vehicle has been designed
autonomy of 1 km (Fig 17). In order to avoid such peak              and will be equipped with devices such as radar, NBC
energy consumption on the main, an intermediate energy              sensors, IR camera, etc. Among the characteristic
storage at each loading station is introdu ced (Fig 18). So the     applications: airports, nuclear power plants, gas and fuel
power request on the main is smoothed. Such transportation          production, high or low temperature environment, catastrophe
system can be applied to pedestrian streets, airports, large        evaluation and rescue, military investigation, etc. Such a
parking areas, exhibition centers, university campus, large         vehicle, based on similar technologies as AGV and APM,
factories, etc. Two test vehicles are in construction and a first   have the advantage of no noise, no pollution and high
pilot track is foreseen for 2009, in Lausanne.                      flexibility. A first prototype will be built soon. On Fig 19, the
                                                                    vehicle design is represented.
                                                                    VII. ENERGETIC CHAIN
                                                                    All these different vehicles use basically the same energetic
                                                                    chain, with powers from 10 kW to 250 kW. For these
                                                                    developments, power electronics is a key factor, mainly for
                                                                    the following functions:
                                                                    -High frequency supply generator for energy 53.
                                                                    transmission, with a high efficiency
                                                                    - Super-capacitors load and control
                                                                    - Propulsion and steering motor control and drive
Fig.16.Automatic people mover vehicle




                                                                    Fig 20 describes the complete energetic chain.

                                                                    CONCLUSION :
                                                                    Infrastructure is an important determinant of transport costs,
Fig.17.Automatic people mover system with loading stations          especially for densely populated locked countries like India..
every                                                               Almost two-third of deaths in our country is due to road
400 m                                                               accidents. Obviously, many drawbacks of conventional mode
                                                                    of transportation in our country would be avoided, on
    implementing this idea We move for automation to dispel
    manual errors.    Also we could create pollution free
    environment zone and safety mean of transportation.

    REFERENCE:
                  “Theory of machines” Khurmi Gupta,
                  “ Electrical machines “Nagarath & Kothari ,
                  www.numexia.com.

				
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posted:8/26/2012
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