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CORNER Sébastien
Project Report Robot
Academic Year : Fall 2009
1
Contents
Introduction: ........................................................................................................................................ 3
I-Components of the Robot...................................................................................................................... 4
A - Motor ............................................................................................................................................ 4
B – Driver ........................................................................................................................................... 5
C – Arduino card ................................................................................................................................. 6
D - Camera used for detection............................................................................................................. 7
E - . Connection................................................................................................................................... 7
II - Working of the Robot ........................................................................................................................ 8
Working .............................................................................................................................................. 8
Direction: ............................................................................................................................................ 9
Enable: ................................................................................................................................................ 9
Pulse: ................................................................................................................................................ 10
Speed ................................................................................................................................................. 10
The orientation of the robot with respect to the starting position: ......................................................... 11
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Introduction:
This report shall explain the main functions and the working of the robot. Our aim
was to build a robot which will participate in the robotics competition.
Our main objective this semester was to find methods which would:
1. Enable the robot to maintain a constant speed
2. Define the coordinates of the robot so that it doesn't deviate from its intended
path.
3. Enable the robot Identify the objects
By the end of the semester, we were able to achieve the first two objectives. The
details are explained in the following pages.
We have the camera which would enable the robot to identify the various objects but
are working on the program to integrate it in the robot and modifying it according to
our needs.
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I.
Components of the Robot
A - Motor
The M4 42 051 bipolar motor with permanent magnetism is used.
The M4 42 051 motor works with at least two spools. It functions in a step by step
manner, i.e. with each pulse, it rotates by an angle of 1.8 degrees. We can use a
maximum of 4 different steps.
Step 1 : A rotation of 1.8 degrees
Step 2 : Dividing the rotation by 2 thus obtaining a rotation of 0.9 degrees
Step 3 : Dividing the rotation by 4 thus obtaining a rotation of 0.45 degrees
Step 4 : Dividing the rotation by 8 thus obtaining a rotation of 0.225 degrees
thus with each reduction in the degree of rotation, we increase the precision but reduce
the speed by the times the degree of rotation was reduced.
The motor needs to a current of 0,6 ampere and 7 ohm resistance. Thus consuming less
energy thereby reducing the costs.
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B – Driver
A M325 micro step driver has high performance and low cost. It has an area of 47.3 cm²
and a size of 2.05 cm. It supplies voltage in a range from 12 to 24 volt, and it's possible to
adjust the current from 0.39A to 2.5 A with the help of three current control buttons. The
pulse frequency can go up to 100 Khz and we dispose of 4 selectable micro step
resolutions.
We have realized an experience aiming to determinate what step and which current we
would use. The results of the manipulation show that the step 2 and the 4msec timer is
most stable with a current of 0,6 amperer.
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C – Arduino card
As the Arduino card is easily programmed it is the most viable option.
It has an area of 38,5 cm² a of thickness of 1.5cm and is equipped with a micro controller
Atmel AVR of 8bits.
A micro controller allows the card to carry out different instructions and also has an
internal memory. It's an integrated circuit which gathers the essential elements of a
computer. It is connected to the computer with the help of a USB connection and needs
an external power source.
The various software characteristics of the card are:
1. A Code Editor
2. A Compile function
3. A debug and run file function.
4. A simplified language and good bibliographies which improve the capacity of the
micro controller.
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D - Camera used for detection
Pob Eye II
P
•
USB port
•
Serial port
•
Zigbee port (option)
•
Micro camera 160x120 of color revolution
E - . Connection
Le POB-Eye II can be used to work with Xbee, Seial connection and Bluetooth .
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II.
Working of the Robot
A. Working
The main parts of the robot are the two servo motors and the Arduino circuit board. These three
component help us to govern the various functions such as the direction, speed and the positioning of the
robot . The connections are as shown below.
Figure 1 : Servo Motor - Arduino CARD CONNECTION
For Motor 1, the direction, the pulse and the Enable cables are connected to the pins 13, 8 and 11 and for
the Motor 2 the direction, the pulse and the Enable cables are connected to pins 12, 9 and 10 of the
Arduino card respectively.
Each of the pins has to be set on the output mode and switched to the High output setting.
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B. Direction:
The function ‘direction _robot’ is responsible to control the moving and direction of the robot.
If the direction pin of the motor is configured to the High mode, the motor moves in the forward direction
and conversely if it is configured to the low output mode it moves in the backward direction.
Thus:
1.
2.
3.
4.
If both the motors are set to function in the High mode, the robot moves forward.
If both the motors are set to function in the low mode, the robot moves backwards.
If the right motor is set to High and the left to low mode, the robot turns left.
If the left motor is set to high and the right to low mode, the motor turns right.
Right Motor
High
Low
High
Forward
Right
Low
Left
Backward
Left Motor
The configuration of the left and right motors can be controlled by the variable ‘Consigne.Left’ and
‘Consigne.Right’ respectively.
C. Enable:
The enable port acts as an electronic switch. When it is configured to the High output mode the robot is
on and when it is configured to the low output mode, the robot is off. It is thus always set to the high
output configuration during normal circumstances and is set to the low output configuration when the
robot needs to be stopped by urgency.
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D. Pulse:
The pulses are in the forms of square waves. With each pulse the motor makes a rotation of 1.8 mille
radians (with step 1).. Thus by controlling the time between two consecutive pulses, the speed of the robot
can be controlled. The lesser the time is the faster the robot is and vice versa.
Figure 2 : Pulse time
There has to be a minimum time difference of 20 micro seconds between the initiations
initiations of two
consecutive pulses as that is the time period of one pulse.
Speed
As stated above the speed of the robot can be controlled by controlling the time difference between two
consecutive pulses.
In order to do so, a program named feedback is
is used which acts as a time counter. This program is
repeated after every 1 mille seconds. This program contains a sub-program
sub program called the creneau pulse which
is responsible to initiate the pulse. The time difference between each creneau pulse function can be
modified by changing the value of the variable ‘consigne.seuil’ thus varying the speed of the robot.
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III.
The orientation of the robot with respect to the starting
position:
With the help of experiments we know that with each pulse the robot moves 170 micro meters in the
forward or the backward direction and in the case of turning, it rotates by an angle of 1.5 radians. In order
to determine the position of the robot with respect to the origin, two frames of references are used. One of
them is a fixed reference (X-Y)and
Y)and the other is a moving frame of reference (er – eѲ).
Figure 3 : Frames of References
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The frame ‘er-eѲ’ move along with the robot. The following programs are used to determine the position
of the robot wrt the two frames of references:
1. Robo.R – gives the position of the robot from the last turn it made with respect to the‘er-eѲ’
frame of reference.
2. Robo.teta – gives the angle between the axis of the robot and the er axis.
3. Robo.X – gives the position of the ‘er-eѲ’ frame of reference with respect to the fixed X axis.
4. Robo.Y – gives the position of the ‘er-eѲ’ frame of reference with respect to the fixed Y axis.
Finally as we now know how to define the coordinates of the robot, we can program it to go from one
point to another and move back on its intended path in case of any deviations.
If the robot is located at a position X1, Y1 making at an angle +Ѳ from the horizontal and it has to go to a
position X2, Y2 making an angle –β from the horizontal from its current position, the program will
accordingly make the robot rotate by an angle ‘Ѳ+β’ in the clockwise direction and then will make it
proceed to its destination X2, Y2.
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Conclusion
This report explains how the robot is able to move from one point to another.
With the help of the processing software, the robot can move to any desired location by
clicking on the green square, which represents the testing table using for our experience.
Apart from the above-mentioned program, we have done another program using which we
can control the robot with the arrow keys. The acceleration is controlled by the key 'Z' , the
deceleration with the key 'A' and 'S' to stop. Both program and video demonstration are
available in our website (wwww.pobot.org).
The next step will be to study the working of the camera in order for the robot to recognize
objects and thus automatically give the coordinates of the desired destination.
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