DEVICE FOR SYNCHRONIZED ROTATION

Shuh Jing Ying, Rufael Berhane and Rajiv Dubey

Department of Mechanical Engineering

University of South Florida

Tampa, Florida, U.S.A.

Keywords: Synchronization, Synchronized rotation.

Abstract: This device makes two shafts rotating in synchronized angular displacement. The sensors are potentiometers.

The device is designed for use in a driving simulator. The first shaft is connected to a steering wheel and

controlled by a driver so this shaft is the master, the second shaft is connected to the computer software that

displays the surrounding sceneries, therefore this shaft is the follower. The two shafts must be rotated in

synchronized mode and accurately. Major components in this device are operational amplifiers, NAND

gates, power MOFET and relays. Details in design and manufacturing are reported in this paper. This device

may be used for any place that requires two shafts rotating synchronically.

1 INTRODUCTION

Electronic Mobility Control Co.(EMC) developed an

Advanced Electronic Vehicle Interface Technology

(AVEIT) that converted the steering wheel, gas

pedal and brake pedal in a car into one joystick.

Based on the EMC system, we are building a driving

simulator for training disabled person to drive by

using a joystick for gas, brake and steering. The

forward movement of joystick is for gas pedal,

backward for brake, and right and left for steering.

However it is really difficulty for a person to drive a

real car without going through a simulator. A

simulator to be built is similar to an airplane

simulator for training pilot to drive an airplane. But

it is not so simple to build a driving simulator, many

man powers are required to work on the project from

design, computer software, and manufacturing.

Because of the limited man power and financial

resources, we bought a regular car simulator from

Simulator Systems International (SSI). It has three

screens to show the surrounding sceneries for the

driver to see. We hope to build a device that can

make EMC and SSI systems working

simultaneously. That is the whole purpose of this

project.

There are two possibilities for reaching the

synchronized rotation, mechanical and electrical

devices. After a length consideration the final

decision was on electrical approach.

Once electrical device is chosen we looked into

existing literature but to our surprise we could not

find any in our library or any nearby libraries.

Although we were pretty certain that synchronized

motors have been used in large airplanes but no

information is found. Anyway the existing device

may not fit what we need.

So we start to design a circuit for our purpose

and we build the device exactly as we want. The

details are given in this paper. After the device is

completed certainly we had quite extensive test to

check out every part. However we have not reached

to the point to train a disabled person actually to

drive.

2 DESIGN OF THE CIRCUIT

The circuit required is to operate a motor which has

enough power to rotate the steering mechanism of

the SSI system. The directions of rotation can be

clockwise and counterclockwise. The size of motor

is chosen to be similar to the servomotor used in the

EMC system. The input power of the motor is 93

watts with torque of 8.7 n-m. The motor is a geared

DC motor. Because there is no precise position

required in the operation analogue circuit is chosen

in the design. Potentiometers are used for the

position indicators and relays are used for the

control of the motor.

339

Ying S., Berhane R. and Dubey R. (2009).

DEVICE FOR SYNCHRONIZED ROTATION.

In Proceedings of the International Conference on Biomedical Electronics and Devices, pages 339-342

DOI: 10.5220/0001431903390342

 SciTePress

2.1 Differential Amplifier

The difference of the voltage signals from the

potentiometers are to be amplified. Positive signal

will make the motor to rotate in one direction and

negative signal then will rotate in the other direction.

A bipolar op amp, AD706, is chosen to build a

differential amplifier. The schematic circuit diagram

is shown below.

It will be idea if the amplifier is very sensitive to

the input voltage and the dissipation power is not

very large as compared to the motor power. The

output voltage is given by

()

#1 #2

14 23

out in in

VVV

for R R and R R

⎡⎤

=− +

⎢⎥

⎣⎦

Figure 1: Differential Amplifier.

See Ref. 3 for details. The specification of AD706 is

given in Appendix.

2.2 NAND Gate

Because the output voltage of AD706 is not high

enough to turn on the power MOSFET to operate the

relay, a NAND gate is used to further amplify the

positive signal. NTC4011B is chosen for achieving

this purpose. NTC 4011B is a 2 input positive logic

NAND gate. There are four NAND gates in one IC.

The specification of NTE4011B is given in

Appendix. One input of the first NAND gate is

connected to a fixed positive voltage, hence only

positive signal will go through the first NAND gate.

Two of the 4 NAND gates are used for amplifying

the positive signals when the output of AD706 is

positive. However when the output of AD706 is

negative we must lead the signal to go to other

branch and to make the motor to turn in another

direction. A negative latch is used for that purpose.

2.3 Negative Latch

A negative latch is a resetable memory block. The

output goes to high as soon as the input signal goes

to negative. This is exactly we need for the output of

AD706 goes to negative.

Two NAND gates are needed. The circuit

diagram is given as follows

Figure 2: Negative Latch.

2.4 Power MOSFET

A power MOSFET is a specific type of Metal Oxide

Semiconductor Field-Effect Transistor. It is

designed to handle large power. IRFP250N is

chosen for this circuit. When the voltage applied to

G reaches 12 v, the switch is turned on from S to D.

The specification of IRFP250N is given in appendix.

2.5 The Circuit Diagram

With some details given above, the whole circuit can

be presented as shown in Fig 3. The input signals are

from the potentiometers, one is connected to the

EMC system and one is with SSI system. These

signals go through the differential amplifier AD706.

When the difference is positive, the signal goes

through the upper branch in the circuit diagram

because one of the inputs in the NAND gate TC4011

is set to +5Vdc. This positive signal then turn on the

power MOSFET and make the motor to rotate. As

the output of AD706 is negative, the signal triggers

the negative latch and the power MOSFET in the

lower branch in the diagram is turned on

consequently the motor is turning in the another

direction.

However, when the circuit was tested, the motor

will rotate back and forth as the input difference of

AD706 is nearly zero. This will severely shorten the

life of the motor. The power supplies in the circuit

are using voltage dividers. This is only for the

saving of space in the device.

Also we experienced the lives of IC’s are very

sensitive to the voltages applied. Follow the

specifications carefully, is very important. That is

why all the specification are attached in appendix.

BIODEVICES 2009 - International Conference on Biomedical Electronics and Devices

340

Figure 3: Circuit Diagram for Synchronized Rotation.

Figure 4: Modified Input Circuit.

2.6 Modified Input Circuit

To stop the rotation of the motor as the input of

AD706 is nearly zero. The outputs of NAND gates

and the inputs of the power MOSFETs are

disconnected The connection of these wires are

controlled by this modified input circuit that is

shown in Fig 4. Note that in this circuit the input to

IC AD706 is through a full wave rectifier. When the

signal is nearly zero, the voltage is not strong

enough to trigger the relay in this circuit so that the

relay in the previous diagram will not be turned on.

Consequently the motor will not be turned on. Now

as the EMC steering wheel rotates approximately

, the motor will start to rotate in the same

direction. And the motor will stop as the difference

between the potentiometers is within 45

. This

operation is considered as perfect.

3 CONCLUSIONS

Although this device is aimed originally for the use

of the synchronized rotation in a driving simulator,

actually it can be used in many other places

requiring a synchronized rotation. Because of this,

the information presented here could be invaluable

to many research workers in this community. On the

other hand this circuit is rather simple and easy to

follow, mechanical engineers can use it. The device

has been tested extensively in the simulator and it is

working perfectly well. However, the simulator has

not been used for training disabled person to drive.

This is considered as the next phase of our work.

Just to make the information completely presented.

The specifications of IC’s are given in appendix.

DEVICE FOR SYNCHRONIZED ROTATION

341

REFERENCES

Narsingh Deo, 1983, System Simulation with Digital

Computer, Prentice-Hall Englewood Cliffs, N. J.

Geert Van der Plas, Georges Gielen and Willy Sansen,

2002, A computer-aided design and synthesis for

Analog Integrated Circuits, Kluwer Academic

Publishers, Boston, MA.

Amplifier Reference Manual, 1992, Analog Devices

Norwood, MA.

The ARRL Handbook for radio 2006, 2005 83

Edition A.

R. R. L.

Ying, Shuh Jing, Patti Barrett, and Stephen Sundarrao,

2008, A Device Turning on Strobe Light from Horn

Signal, BMES Annual Fall Meeting, St.Louis, MO

Ying, Shuh Jing and Stephen Sundarrao, 2007 Design and

Manufacturing of A Wheel Chair Treadmill, RESNA

2007

APPENDIX

AD706 – SPECIFICATIONS

Features:

High DC precision.

100µV max offset voltage

1.5 µV/

C max offset drift

200 pA max input bias current

0.5 µV p-p voltage noise, 0.1 Hz to 10 Hz

750 µA supply current

Maximum Ratings:

Supply Voltage………………………….…....…18V

Internal Power Dissipation

(Total: Both Amplifiers)……...….650mW

Input Voltage…….………………..……...….…....V

Differential Input Voltage…….….……….....…0.7V

Output Short Circuit Duration……….........Indefinite

Storage Temperature Range……...….-65

to +125

Operating Temperature Range

AD706J……….………….…........…0 to +70

AD706A…………….……….…...-40 to +85

Lead Temperature(Soldering 10sec).…….......300

Notes:

Stresses above the maximum ratings may cause

permanent damage to the device. This is a stress

rating only. Exposure to max rating conditions for

extended periods may affect device reliability. The

input pins of this amplifier are protected by back–

to–back diodes. If the differential voltage

exceeds 0.7

V, external series protection resistors should be added to

limit the input current to less than 25 mA.

TC4011-SPECIFICATIONS

The TC4011B is a quad 2 input NAND gate.

Maximum Ratings:

DC Supply voltage………….……..........…….18 V

Input voltage…….……………………….…18.5 V

Output Voltage….…………………………..18.5 V

DC input current……….……………..……..10 mA

Power dissipation…………………..……... 300 mW

Operation Temperature range………...... -40 to 85

Storage Temperature range…………… -65 to 150

IRFP250N-SPECIFICATIONS

Maximum

Ratings:

continuous drain current…..…..……...…..… 30A

DM,

pulsed drain current……..….…………..…120A

Power dissipation……….…………….....………….214W

Gate to source voltage…….…………..……..……….20V

Single pulse avalanche energy………………..……315mJ

Avalanche current……..…………………..…..……..30A

Repetitive avalanche energy…….………....……….21mJ

Peak diode recovery…….………..…...…………..8.6V/ns

Operating temperature range……….....…….-55 to 175

Soldering Temperature (10 sec)……………………300

Mounting Torque…… ..….…. 1.1 N-m (10 lbf-in)

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