Robotic Arm to Sort different Objects

Abdulrahman Albanyan

201500006

Robotic Arm to Sort different Objects

In recent years, robotics systems become more and more accurate to solve more complex tasks, it also became cheaper. But the problem in these systems is the mostly designed for heavy duty tasks, which needs a large area and permanent position to work on. Also, it is dangerous for a human to work alongside with them, because they are heavy and move too fast. The aim of this project to create a light duty robot to sort a large scale of mixed objects in reasonable amount of time.

Table of content:

Introduction …………………………………………… 2

Motivation ……………………………………………..3

Project summary………………………………………..4

Project details:

A-Components…………………………………4

B-Layout:

-The arm……………………………….5

- End-effector ………………………...5

- How will it work? ..............................7

-Over all view of the whole system…...9

C- Implementations issue and challenges…………10

D-Timeline …………………………………………..11

Conclusion …………………………………………………..11

References……………………………………………………12

Motivation:

This problem occurs in many situations, for example a junk yard. In a junk yard you will have many mixed parts sits on top of each others, and this will the owner un aware with the useful parts! Or in light duty work places such as a food warehouses. In warehouses, accidents occurs all the times, and that would causes a lot of chaos, such as products will be on top of each others. After any accident, the company needs to fix the warehouse in order to function again. The project will help the company to sort the product into categories which will speed up warehouse return to function.

Project summary:

By using a camera and computer vision techniques, the robotic arm will be able to sort four different types of mixed objects into four separated boxes.

Project details:

A- Components:

1- Raspberry pi.

2- 4 Stepper motor.

3- Camera.

4- Sonar sensor.

5- Relay.

6- Compressor.

7- Keras Library.

8- OpenCV Library.

In this project, the main programming language will be Python. We will also going to use MATLAB for the camera.

B-Layout:

-The Arm:

The arm consists of a body, 3 links and 3 joints. Joint 1 connect the body with link 1. Joint 2 connect link 1 and link 2. Joint 3 connect link 2 and link 3 as it shown in figure 1.

Figure 1: Overview of the robot.

-End-effector:

The End-effector will be a soft robot. A soft robot is a robot that built by a compliant materials. By using a compressor, the air will flow through the compliant material and it going to make it move in a predictable motion. This motion will works as a human fingers or as it shown in figure 2. The soft robot will be made from silicon. Shaping the robot by milting the silicon and pouring it in a 3D printed frame, as it shown in figure 3. The air will be provided by a small compressor which is going to be controlled by a relay.

Figure 2: A soft robot fetch a ball.

.

Figure 3: soft robot structure.

-How will its work?

Lets cosider the next graph, the point p will have (15,20) as its coordinate plot in the cartesian system:

Figure 4

First, we need to sit joint 1 angle, joint will decide what dirction the arm is pointing to. To determin the dirction, convert x into Θ by using the polar equation: Θ = arctan(y/x) = 53.13º. After determining the direction, the arm should adjust joint 2, 3 and 4 angles to point the end-effector to object in space. The way to achieve that is by using trigonometry as it shown in figure 5 and 6. Figure 5 shows a cylindrical robot pointing into point P. To turn this robot form cylindrical to articulated robot, connect the base to the horizontal line, and the horizontal line to the point P, as it shown in figure 6:

Figure 5: a cylindrical robotic arm side view (2D).

Figure 6.

By connecting those lines –r1 and r2-, there will be two right triangles. The lines r1 and r2 will represent the robot’s links, theta 1 and theta 2 will be the angles which the joints would rotate to point the arm to point P. To get theta 1, we need to get theta a, to get theta a we must have all the sides – y1-. y1 = √ (r1)2 – (h1)2. Now Θa = arctan(y1/h1).

Θ 1= 90 – Θa , because h1 is perpendicular to the base. By that we obtained joint 1 angle.

Joint 2 angle - Θ2- can be obtain by this relation: Θ2 = 180- Θb –Θc.

Θb = 180 – 90 – Θa. But to get Θc, we need all sides Z and y2. y2 = h2-y1.

Z = √ (r2)2 – (y2)2. After obtaining all sides, now we can get Θc. Θc = arctan(Z/y2).

Θ2 = 180-Θc-Θb.

Now we have Θ1 and Θ2.

-Over all view of the whole system:

Figure 6: view of the system

C- Implementations issue and challenges:

Last section explains how the system is going to convert cartesian to polar, but the qustion is how to get the cartisian plots? In the design, the plot will be fetch by using a camera that perpendiclur to the coodinate system -The box which the objects lay in it-, but how can that happen? By creating a mapping function that map each pixel into a square unit, which described in this relation: m = pn/un.

Any inaccuracy means the end-effector will miss the object. This unaccurcy might happen because the camera in not really perpendiclur to the coordinate system -The box which the objects lay in it-, or the the mapping function is to good.

Also the ligthing might effact the camera to recognize the objects because of the shadow.

D- Timeline

Week#

Delivary

3

Finalize the design – ordring components – testing software

4

Testing hardware componts – re-test software(if there is any problem)

5

Buliding and printing 3D module for the robot

6

Assembling the arm

7

Building and testing end-effector

8

Report to the proffessor

9

Assembling the arm with end-effector

10

Building the entier system (Boxes, camera, arm, end-effector, etc…)

11

Testing the entire system

12

Testing the entire system

13

Testing the entire system – submission

Concluion:

This project will be designed for light-duty tasks, it helps by sorting mixed objects in a large scale. By mapping the camera to the sufface which the object operate on, the robot can easily find the object coordinate and fetch it with help from the end-effector. The robot will function by a design the created but the students from their mathematical knowledge.

References:

· Image from ronohub.

https://robohub.org/soft-robots-that-can-sense-touch-pressure-movement-and-temperature/

Examples for some similar robots:

· Rethink Robotics.

· Elephant Robotics.

· Computerphile: Soft Robotics:

https://www.youtube.com/watch?v=BLE5yhS3k3I&t=314s

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