The document describes the development of an automatic teaching method using a stereo camera for SCARA robots. The method involves building a camera-robot system with hardware including a stereo camera and SCARA robot. Software algorithms are designed for position calculation, end-effector angle updating, and communication between the PC and robot controller. Experiments are conducted to evaluate repeatability, distance correlation, feedback position accuracy, and overall system operability. The automatic teaching method shows potential but could be improved with marker redesign and synchronization optimization.

1. VIETNAM NATIONAL UNIVERSITY HO CHI MINH CITY
HO CHI MINH UNIVERSITY OF TECHNOLOGY
FACULTY OF ELECTRICAL AND ELECTRONICS ENGINEERING
DEPT OF CONTROL ENGINEERING AND AUTOMATION
GRADUATION ESSAY
DEVELOPMENT OF AUTOMATIC TEACHING METHOD
USING STEREO CAMERA FOR SCARA ROBOTS
SVTH:
Phạm Phước Dũng 1710875
GVHD:
TS. Nguyễn Hoàng Giáp
26/12/2022

2. Content
Introduction
01
Hardware
System
Design
02
Software
Design
03
Experiments
and
Evaluation
04
Conclusion
and
Development
direction
05
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3. Introduction
System overview
01
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4. 01 Introduction
Reasons for choosing
the topic
Thesis objectives System overview
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5. 01 Introduction
1.1. Reasons for choosing the topic
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6. 1.1. Reasons for choosing the topic
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 The teaching-less method for robots is being strongly developed in the world because
of the advantages compared to the traditional teaching ones.
 The successful development of this topic will increase the diversity of robot applications
by solving problems that cannot be solved by traditional teaching methods.
Remote robot-assisted surgery
Robot welding

7. 01 Introduction
1.2. Thesis objectives
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8. 1.2. Thesis objectives
 Develop a teaching-less method using stereo camera for SCARA robot to perform the
pick-and-place feature with high precision.
 Build a camera - robot system which can operate based on designed algorithms and
principles.
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Pick-and-place feature with high precision Force Torque Sensor required

9. 01 Introduction
1.3. System overview
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10. 1.3. System overview
 Principle of system operation
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11. 1.3. System overview
 Hardware system structure
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12. 1.3. System overview
 Principle of component operation
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13. Hardware System Design
Design and build hardware system
02
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14. 02 Hardware System Design
Marker
 Passive marker
Stereo camera
 Stereo camera
mounted from 2 Basler
Dart daA1600-60um
 Module emits IR
 IR Filter
Hệ robot SCARA
 Robot SCARA Epson
EC251S
 DTP7H-coreCon robot
controller
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15. 02 Hardware System Design
2.1. Marker
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16. 2.1. Marker
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Robot Marker
 Passive marker
Setpoint Marker
Robot Marker Setpoint Marker
Length (mm) 60 98.2
Width (mm) 60 87
Height (mm) 75 22.7
Marker’s size

17. 02 Hardware System Design
2.2. Stereo camera
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18. 2.2. Stereo camera
Stereo camera mounted from 2 Basler Dart daA1600-60um
 Resolution: 2x(640x480) pixel.
 Max Frame: 45FPS.
 Accuracy: 0.25mm RMS
 Operating distance: 500mm to 1500mm
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19. 02 Hardware System Design
2.3. Robot SCARA
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20. 2.3. Robot SCARA
Robot SCARA EC251S DTP7H-coreCon robot controller
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21. Software Design
Build algorithms and principles for model
03
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22. 03 Software Design
Algorithm design
 Thread for position calculating
 Thread for end-effector's angle
updating
 Thread for communication
between PC and robot controller
 Convert distance
User interface design
 Main program
 Error evaluation experimental
program
Communicate with PC
using robot controller
 Setup communication protocol
on robot controller
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23. 03 Software Design
3.1. Algorithm design
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24. 3.1. Algorithm design
 Thread for position calculating
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𝛥𝐷𝑖𝑠𝑡𝑎𝑛𝑐𝑒 = (𝑥𝑠𝑒𝑡𝑝𝑜𝑖𝑛𝑡 − 𝑥𝑟𝑜𝑏𝑜𝑡)2+ (𝑦𝑠𝑒𝑡𝑝𝑜𝑖𝑛𝑡 − 𝑦𝑟𝑜𝑏𝑜𝑡)2+ (𝑧𝑠𝑒𝑡𝑝𝑜𝑖𝑛𝑡 − 𝑧𝑟𝑜𝑏𝑜𝑡)2

25. 3.1. Algorithm design
 Thread for end-effector's angle updating
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26. 3.1. Algorithm design
 Thread for end-effector's angle updating
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Rotation matrix obtained from Homogeneous matrix𝑐𝑎𝑚𝑒𝑟𝑎
𝑟𝑜𝑏𝑜𝑡𝑇𝑋𝑌𝑍 :
𝑐𝑎𝑚𝑒𝑟𝑎
𝑟𝑜𝑏𝑜𝑡
𝑅𝑋𝑌𝑍(, , ) =
𝑟11 𝑟12 𝑟13
𝑟21 𝑟22 𝑟23
𝑟31 𝑟23 𝑟33
So the pitch angle is:
 = arctan(−𝑟31, 𝑟32
2
+ 𝑟33
2
) (rad)
Calculation of rotation angle difference between two markers:
𝛥𝐴𝑛𝑔𝑙𝑒 =
180 ∗ (𝐻𝑜𝑚𝑒− 𝑆𝑒𝑡𝑝𝑜𝑖𝑛𝑡)
𝜋
(degree)

27. 3.1. Algorithm design
 Thread for communication between PC and robot controller
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28. 3.1. Algorithm design
 Thread for communication between PC and robot controller
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Time delay for robot moving to Setpoint position:
∆𝑇𝑀𝑜𝑣𝑖𝑛𝑔 𝑚𝑠 =
∆𝐷𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑚𝑚
𝑆𝑝𝑒𝑒𝑑
100
∗ 𝑅𝑜𝑏𝑜𝑡 𝑚𝑎𝑥𝑖𝑚𝑢𝑚 𝑚𝑜𝑣𝑖𝑛𝑔 𝑠𝑝𝑒𝑒𝑑
𝑚𝑚
𝑠
∗ 1000 + 500
- Robot maximum moving speed is set in robot controller to 1000 (mm/s).
- Speed ​​entered by the user, default will be 10 (%).
- Since the robot has time to accelerate and decelerate in each movement and this value cannot
be interfered with or measured, so in this project, I will use 500 (ms) to characterize this time
value.

29. 3.1. Algorithm design
 Convert distance using equivalent coordinate system
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Incremental value xRobot = - Incremental value xCamera
Incremental value yRobot = - Incremental value zCamera
Incremental value zRobot = Incremental value yCamera

30. 03 Software Design
3.2. User interface design
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31. 3.2. User interface design
 Main program
Module Tracker Module Pick Place App
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32. 3.2. User interface design
 Error evaluation experimental program
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33. 03 Software Design
3.3. Communicate with PC using robot controller
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34. 3.3. Communicate with PC using robot controller
 Config IP Address and Port on robot controller
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Programing on robot controller
Config IP Address

35. Experiments and Evaluation
Experimental results to verify the operability of model
04
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36. 04 Experiments and Evaluation
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Setup camera
Setup robot and experimental platform

37. 04 Experiments and Evaluation
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Setup experimental environment

38. 04 Experiments and Evaluation
Determining
repeatability
Checking
distance
correlation
Comparing
feedback
position
Evaluating the
operability of
model
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39. 04 Experiments and Evaluation
4.1. Determining repeatability
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40. 4.1. Determining repeatability
Mica panel with holes cut by laser
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Marker fit perfectly inside mica panel

41. 4.1. Determining repeatability
Marker’s position unchanged
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Capture marker’s position using software

42. 4.1. Determining repeatability
Deviation from the standard position (mm) Repeatability
(mm)
Min Max
1 0.012 0.088 0.045
2 0.016 0.273 0.078
3 0.022 0.116 0.051
Experiment results
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43. 04 Experiments and Evaluation
4.2. Checking distance correlation
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44. 4.2. Checking distance correlation
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Fixed marker to robot end-effector Get end-effector’s position
from robot controller Get marker’s position
from software

45. 4.2. Checking distance correlation
Experiment results
Distance difference between 2 points
determined by robot controller
𝒅𝒓 (mm)
Distance difference between 2
points determined by software
𝒅𝒄 (mm)
Error
(mm)
Mean Error
(mm)
RMS Error
(mm)
1 21.723 21.647 0.076
0.156 0.195
2 11.099 11.134 0.035
3 37.729 38.056 0.327
4 15.519 15.501 0.017
5 17.402 17.413 0.011
6 39.562 39.457 0.105
7 33.119 32.774 0.345
8 24.685 24.418 0.268
9 40.316 40.450 0.134
10 35.143 34.942 0.200
11 21.504 21.506 0.001
12 30.915 31.158 0.242
13 25.841 25.630 0.210
14 23.920 23.616 0.304
15 11.234 11.297 0.063
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46. 04 Experiments and Evaluation
4.3. Comparing feedback position
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47. 4.3. Comparing feedback position
Compare Setpoint’s position sent and Robot’s position received
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Graphing and calculating errors

48. 4.3. Comparing feedback position
Experiment results
 With 4 Setpoint unchanged position
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49. 4.3. Comparing feedback position
Experiment results
 With 4 Setpoint unchanged position
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50. 4.3. Comparing feedback position
Experiment results
 With 4 Setpoint unchanged position
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51. 4.3. Comparing feedback position
Experiment results
 With 4 Setpoint unchanged position
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52. 04 Experiments and Evaluation
4.4. Evaluating the operability of model
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53. 4.4. Evaluating the operability of model
 Video to demo the operability of model
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54. Conclusion and Development direction
Evaluate the completeness and feasibility of the model
05
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55. 05 Conclusion and Development direction
Conclusion Development direction
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56. 05 Conclusion and Development direction
5.1. Conclusion
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57. 5.1. Conclusion
 Achievements
 Complete the algorithm to calculate the displacement distance and update the rotation
angle of SCARA robot.
 Complete the system with Master and Slave stations to perform the pick-and-place
feature with SCARA robot.
 Complete the communication protocol between PC and SCARA robot controller.
 Complete user interface.
 Complete experiments to verify the operability of model.
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58. 5.1. Conclusion
 Difficulties
 Due to limitation on the marker’s surface which can reflect IR (3 out of 4), in case
SCARA robot rotate Robot Marker with the blind surface (the surface have no reflecting
point) toward camera, sorfware will unable to calculate and update the end-effector’s
rotation angle.
 Haven’t optimized the synchronization solution between the robot's moving time and
the camera’s capture time to update the robot's rotation angle.
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59. 05 Conclusion and Development direction
5.2. Development direction
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60. 5.2. Development direction
 Optimize the synchronization solution between the robot's moving time and the
camera’s capture time.
 Replace the other marker with no blind surface.
 Upgrade the robot system (controller, driver, robot) to minimize the mechanical error.
 Build a response system from Slave to Master to inform the current status of robot
(position, velocity, rotation,…).
 Build a controller mounted directly to camera in order to reduce system’s size.
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61. Thank you so much
for your interest and attention!

62. Principle of marker recognition
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3D reconstruction of
balls in DRB
: Comparing geometry consists of balls in
DRB
-> Center position, distance between
closer balls, etc.
Rom file data of
balls in DRB
(DRB)