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8/9/2019 Task a Report
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PICK AND PLACE ROBOTTASK A
Group Members:
Mohammad Johirul Islam
(245185)
Samuel Olaiya Afolaranmi
(245179)
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Table of Contents
Introduction.............................................................................................................................................................................. 2
Components Used.................................................................................................................................................................. 2
Building the Model................................................................................................................................................................. 3
Program Algorithm:............................................................................................................................................................... 5
Flow Chart................................................................................................................................................................................ 6
Full System PICs...................................................................................................................................................................... 6
System Running (Video)....................................................................................................................................................... 8
Challenges Faced.................................................................................................................................................................... 8
Remedy ..................................................................................................................................................................................... 8
Limitations of the Systemand Further Recommendations:........................................................................................ 8
FiguresFig 1: Robot ARM .3
Fig 2: Gear assembly .3
Fig 3: Input buffer .4
Fig 4: Output Buffer .4
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IntroductionPick and Place is a very common function in Robotics industries. In industries many robots are used
in different work cells to pick up the objects from the production line and place it to buffer zone or
deliver it to packaging area.
This Pick up and Placing has been done by Robot Arms. There are also different type of manipulator
to hold the objects. There is one motor require to pick up and placing and one required for
transportation. The sorting in the output buffer can be done depending on size, color. We have sorted
here depending on color (2 color)
Components UsedItem Name Type Port Used Quantity Description
1 Lego
NXT Motor
Servo
OUTPUT
A
&
C
2 This motor is specific to the NXT set.
Includes a rotation encoder, returning
to the NXT the position of the shaft
with 1 resolution.
2 Light Sensor INPUT 2 1 The Light Sensor reads the light
intensity of an object to distinguish
values of the light and dark, shades of
gray.
3 Lego
Touch Sensor
INPUT 1 1 The touch sensor detects when an
object touches the endpoint of the
sensor, or when the sensor is released
again.
4 Lego
Programming
Brick
CONTRO
LLER
N/A 1 Real brain of your robot, the NXT
brick centralizes information from the
sensors, calculates and issues
commands to actuators.
5 4X2 bricks Objects N/A 4 Two of blue color and two of Yellow
color.
6 Lego Blocks Building
Blocks
N/A Many These has been used to build the
model
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Building the Model
The first step of the project is to design the model and building it.
We had to build One Pick and Place Robot, One Input Buffer and Two Output buffers.
We followed the design of the sample PnP Robot model given as sample for this project.
We used Lego Digital Designer to analyze the design of the sample.
Fig 1: Robot ARM
We went to Building guide mode to follow building step by step as it was the first time for us
with these lego.
Here we assigned the lower servo as Motor A and the upper one as Motor B
Motor A is responsible for the rotational motion of the arm. We can also call it the translationmotion from one place to another.
Motor B is responsible for the vertical movement of the arm to pick au and placing the blocks.
Later we developed one input buffer and two output buffers.
One of the important consideration of building the robot is Motor A carries all the loads of
the arm and to have a steady motion a bigger gear is introduced as driven gear. This gives
lower speed of the arm but higher torque for the Motor A.
Fig 2: Gear assembly
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The light sensor has been placed with the input buffer in such a way that it can sense the light
reflection value on the way of ascendance of the arm.
Fig 3: Input buffer
Two output buffers are built in basic ways. But important consideration of these buffers is
their front legs. They are needed to design in such a way that it does not make any obstacle
for the Robot arm.
Fig 4: Output Buffer
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Program Algorithm:The programming part has been done in LEGO MINDSTORM NXT 2.0
Motor A moves 0.5 clockwise rotation and this lead the Robot Arm under the input Buffer.
Then Motor C makes a 54 degree of rotation which creates a vertical motion of the arm.
This 54 degree motion make the arm reach near the light sensor.
The sensor differentiate the color depending on reflection intensity.
If the intensity is less than 40% than the block will be consider as blue.
Else the block will be consider as yellow.
For the Blue Block the Motor A will give 1 full clockwise rotation to achieve the position of
the arm tip over the Blue output buffer.
Then Motor C will descend gradually 94 degree so that it can easily place the block over the
output buffer and arm reaches to its vertical initial position.
To get to its horizontal initial position, Motor A give 1.5 anticlockwise rotation.
For the Yellow Block the Motor A will give 2 full clockwise rotation to achieve the position
of the arm tip over the Yellow output buffer.
Then Motor C will descend gradually 94 degree so that it can easily place the block over the
output buffer and arm reaches to its vertical initial position.
To get to its horizontal initial position, Motor A give 2.5 anticlockwise rotation.
The whole process is in an infinite loop for continuous operation.
The touch sensor is used as emergency stop.
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Flow Chart
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Full System PICs
Fig: Robot in Initial Position
Fig: After Completion of a Full Cycle.
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System Running (Video)http://youtu.be/Ko5O8hePU4w
Challenges Faced
Firstly, we faced a challenge of getting familiarize with the commands and user interface of
the NXT 2.0
While building the model, we have found that there was many blocks missing, which actually
forced us to improvise alternative designs with available lego blocks.
Finally a great challenge we have faced on the demonstration day that the Robot and the input
buffer and the output buffers are not be able to fixed in its own position due to lack of base
lego brick.
We have to identify the input buffer and the output buffers each time we change the position
of the robot. And it was really very hard as there is no scaling system about the positions of
the buffers.
Remedy
We used the some NXT tutorials and help files to familiarize with the NXT interface and the
commands.
We tried to find the missing blocks that we need in the lab, if not found the design need to be
modified.
To restrict the slipping of the robot and the buffers we used some adhesive tapes so that they
can be fixed to their positions.
Limitations of the System and Further Recommendations:
The light sensor can detect depending on the reflection intensity. So it cannot detect more than
two color. Using color sensor can solve the problem.
In our system there was no sensor to detect the condition of the input buffer as if it is emptyor full. An ultrasonic sensor can be used to solve this issue.
The light sensor can be fixed with the Arm, then we would not have to wait for sensing.
A conveyor in the output buffer can make the system more live.
http://youtu.be/Ko5O8hePU4whttp://youtu.be/Ko5O8hePU4whttp://youtu.be/Ko5O8hePU4w