When designing a performance involving people and mobile robots, we must consider the required functions and shape of the robot. However, it can be difficult to account for all of the requirements. In this paper, we discuss a mobile robot in the shape of a ball that is used in theatrical performances. Such a spherical robot should be agile and be able to roll like a ball. However, it is difficult to create a robot with all of these characteristics. Instead, we propose a mobile robot that can give the audience the optical illusion of the unique movements of a sphere by mounting a spherical LED display on a high-agility wheeled robot. The results of an experiment using a prototype indicate that this sort of robot can broaden the range of possible performances by giving the optical illusion of being a rolling sphere.

1. Mimebot: Sphere-shaped Mobile Robot
Imitating Rotational Movement
Shuhei Tsuchida†1, Tatsuya Takemori†2,
Tsutomu Terada†1†3, Masahiko Tsukamoto†1
†1 Kobe University
†2 Kyoto University
†3 PRESTO, JST

2. Demo Movie 2

3. 1. Background
2. Research Purpose
3. Proposed Method
4. Preliminary Study
5. Improvement of System and Evaluation
6. Testing the ability of the proposed system
7. Summarize

4. 1. Background
2. Research Purpose
3. Proposed Method
4. Preliminary Study
5. Improvement of System and Evaluation
6. Testing the ability of the proposed system
7. Summarize

5. 5
A performance involving people and mobile robots
Reference: Dance with Drones, https://www.youtube.com/watch?v=HQLORg5COiU
Problem
・Noisy
・Risk of Crash
・Control difficulty
Background

6. 6
Problem
・Posture deviation
・Low agility
Background

7. 7
How to provide a stable system
Function
・Failsafe
・Multiplexing
For a general system
System User
Dependability
Background

8. 8
System Performer /
Stage director
Function Stage effects
Audience
How to provide a stable system
For a stage effect system
Background

9. 9
System Performer /
Stage director
Function Stage effects
Audience
How to provide a stable system
For a stage effect system
Background
Dependability

10. 10
System Performer /
Stage director
Function Stage effects
Audience
How to provide a stable system
For a stage effect system
Background
Dependability Appearance Dependability
Stabilize the function with the same stage effect

11. 11
Performance involving objects flying in the air
Ex.
Background

12. 12
Performance involving objects flying in the air
Ex.
Background
Wire

13. 13
Performance involving objects flying in the air
Ex.
Background
Wire

14. 14
Performance involving objects flying in the air
Ex.
Background
Drone Using Wire
Cost High Low
Stability Low High
Audience Satisfaction ◎ ◎

15. 15
Construct a alternative mechanism to d
stage effects equivalent to
real objects.
Research Purpose

16. 1. Background
2. Research Purpose
3. Proposed Method
4. Preliminary Study
5. Improvement of System and Evaluation
6. Testing the ability of the proposed system
7. Summarize

17. Problem of a rolling robot 17
Expression of
rotational movement
Agility
Accuracy of
posture estimation

18. Problem of a rolling robot 18
Expression of
rotational movement
Agility
Accuracy of
posture estimation
Cross section
Actual appearance

19. Problem of a rolling robot 19
Expression of
rotational movement
Agility
Accuracy of
posture estimation
Cannot increase acceleration
Cannot make a sudden turn
by centrifugal force

20. Problem of a rolling robot 20
Expression of
rotational movement
Agility
Accuracy of
posture estimation Cannot attach a marker for
motion capture to
the outer surface

21. Problem of a rolling robot 21
Expression of
rotational movement
Agility
Accuracy of
posture estimation
High-agility mobile wheeled rob

22. Problem of a rolling robot 22
Expression of
rotational movement
Agility
Accuracy of
posture estimation
High-agility mobile wheeled rob
Spherical LED display visually
reproduces rotational moveme

23. 1. Background
2. Research Purpose
3. Proposed Method
4. Preliminary Study
5. Improvement of System and Evaluation
6. Testing the ability of the proposed system
7. Summarize

24. Preliminary Investigation on Rotational Movement
Expression of a Sphereical LED Display 24
Purpose
Built a mobile robot equipped
with a spherical LED display
and evaluate its visual effect.

25. 25
Device
miniUSB
Multi plug
Breadboard
Spherical
LED display
Cover
Mobile robot
Preliminary Investigation on Rotational Movement
Expression of a Sphereical LED Display

26. 26
Device
miniUSB
Multi plug
Breadboard
Spherical
LED display
Cover
Mobile robot
Before coating After coating
Inside of the sphere
Preliminary Investigation on Rotational Movement
Expression of a Sphereical LED Display

27. 27
Device
Spherical
LED display
Mobile robot
Diameter Φ350mm
Weight 3500g
Speed 0.42m/sec
Preliminary Investigation on Rotational Movement
Expression of a Sphereical LED Display
miniUSB
Multi plug
Breadboard Cover

28. 28
Device
miniUSB
Multi plug
Breadboard
Spherical
LED display
Cover
Mobile robot
Preliminary Investigation on Rotational Movement
Expression of a Sphereical LED Display

29. 29
Application
1つ1つがLEDと対応
Preliminary Investigation on Rotational Movement
Expression of a Sphereical LED Display

30. 30
Experiment
Preliminary Investigation on Rotational Movement
Expression of a Sphereical LED Display

31. 31
・The larger the surface area to light the light,
the larger the variation of the pattern,
the tendency to increase the illusion effect was observed.
・Nine out of the eleven participants noticed that
the velocity of the sphere and the rotational speed of
the lights were not the same and commented on it.
Result
Preliminary Investigation on Rotational Movement
Expression of a Sphereical LED Display

32. 1. Background
2. Research Purpose
3. Proposed Method
4. Preliminary Study
5. Improvement of System and Evaluation
6. Testing the ability of the proposed system
7. Summarize

33. Improvement of System 33
・Synchronize the rotation of the lights
of the spherical LED display
with the distance moved by the robot．
・In consideration of an actual stage
performance, the driving part should
be as low and as small as possible.
Improvement point
＝

34. 34
System configuration
Before Improvement
PC
Mobile robot
Spherical
LED
display
Command
Arduino nano
12
Control
the lights
Lighting
Patterns
Improvement of System

35. 35
System configuration
PC
Mobile robot
Spherical
LED
display
Command
Arduino nano
12
Control
the lights
Lighting
Patterns
Improvement of System
mbed x 1
Velocity
There is no difference between the movement distance of
the mobile robot and the rotation amount of light
After Improvement

36. 36
Motor cover Battery
mbed
Xbee Cover
Spherical LED
display
Mobile robot
Device
Disassembled Assembled
Improvement of System

37. 37
Motor cover Battery
mbed
Xbee
Spherical LED
display
Mobile robot
Device
Disassembled
Improvement of System
Previous New device
Diamete
r
350mm 200mm
Height 110mm 60mm
Weight 3500g 600g
CPU H8/36064 STM32F405
Table: Spec

38. 38
Acceleration comparison test of spherical mobile robots
the arrival times
for a distance
of 1.0 m
・Sphero
1.39 sec
・Propsed Robot
1.00 sec
Improvement of System

39. Experiment 41
Experiment items
1. Whether participants who did not see the movements of
the spherical mobile robot experience the optical illusion of a
rolling spheres.
2. The relationship between the velocity of the robot and the
perception of the optical illusion.
3. Influence of the deviation between the amount of rotation
and the moving distance on the illusion.
Participants
12 males (Average age 22.7)
→Possibility of alternative mechanism
→Allowable range of alternative mechanism
→Allowable range of alternative mechanism

40. 42
Experiment procedure
Step 1 → Step 2 → Step 3 → Step 4
4.4 m
2 m
0.5 m
0.23 m
View point
Experiment
6 m

41. 43
Experiment procedure
Step 1 → Step 2 → Step 3 → Step 4
6 m
4.4 m
2 m
0.5 m
0.23 m
Experiment
A participant watches a
performance involving
the mobile robot equipped
with a spherical LED display
and has no knowledge about
how it operates.
Performer
Par$cipant

42. 44
Experiment procedure
Step 1 → Step 2 → Step 3 → Step 4
6 m
4.4 m
2 m
0.5 m
0.23 m
Experiment
Performer
Participant

43. 45
Experiment procedure
Step 1 → Step 2 → Step 3 → Step 4
6 m
4.4 m
2 m
0.5 m
0.23 m
Experiment
Performer
Par$cipant

44. 46
Experiment procedure
Step 1 → Step 2 → Step 3 → Step 4
Experiment
・a spherical LED display presents the rotation (0.6 m/s).
・After the presentation, an experimenter orally asks the
participant two questions:．
Q1: Did the sphere appear to be rolling?
Q2: What mechanism do you think makes the sphere moves?

45. 47
Participant
Experimenter
Experiment procedure
Step 1 → Step 2 → Step 3 → Step 4
Experiment

46. 48
Participant
Experimenter
Experiment procedure
Step 1 → Step 2 → Step 3 → Step 4
Experiment

47. 49
Participant
Experimenter
Experiment procedure
Step 1 → Step 2 → Step 3 → Step 4
Experiment
・Explain the mechanism
of the mobile robot．
・Orally confirms whether
or not the participant
recognized the mechanism．

48. 50
Experiment procedure
Step 1 → Step 2 → Step 3 → Step 4
Experiment
Participant
・Participants confirm
the actual LED ball
rolling from the same
position as in Step 1.

49. 51
Experiment procedure
Step 1 → Step 2 → Step 3 → Step 4
Experiment
Participant
・Participants confirm
the actual LED ball
rolling from the same
position as in Step 1.
被験者
Actual LED ball
Spherical LED display

50. 52
・The LED display shows showed the following
7 visual effect patterns.
Velocity:
0.3, 0.6, 0.9, 1.2 [m/s]
Amount of rotation of lights with respect to the moving
distance:
0.5, 1.5, 2.0 (velocity 0.6 m/s)
Experiment procedure
Step 1 → Step 2 → Step 3 → Step 4
Experiment

51. 53
Experiment
Results and Consideration
Step 1 → Step 2 → Step 3 → Step 4

52. 54
Q1: Did the sphere appear to be rolling?
Experiment
Step 1 → Step 2 → Step 3 → Step 4
Yes
12 participants
11
Results and Consideration

53. 55
Experiment
Step 1 → Step 2 → Step 3 → Step 4
Results and Consideration
Q2: What mechanism do you think makes the sphere moves?
「I thought that the sphere was just rolling. 」
「I thought that the LED ball was rolling by running on electric rails. 」
「I thought there was a driving part inside the LED ball and
that the LED ball was rolling because its center of gravity
was moving. 」

54. 56
Experiment
Step 1 → Step 2 → Step 3 → Step 4
Results and Consideration
Q2: What mechanism do you think makes the sphere moves?
「I thought that the sphere was just rolling. 」
「I thought that the LED ball was rolling by running on electric rails. 」
「I thought there was a driving part inside the LED ball and
that the LED ball was rolling because its center of gravity
was moving. 」
These answers confirmed that the
participants perceived the sphere to be
physically rolling.

55. 57
Experiment
Step 1 → Step 2 → Step 3 → Step 4
Results and Consideration
Participants didn’t notice
・We explained the mechanism and confirmed whether
the participants had noticed the mechanism.
12 participants
12

56. 58
Experiment
Experiment items
1. Whether or not participants who did not see the movements
of the spherical mobile robot
experience the optical illusion of a rolling spheres.
2. The relationship between the velocity of the robot and the
perception of the optical illusion.
3. Influence of the deviation between the amount of rotation
and the moving distance on the illusion.

57. 59
Experiment
Experiment items
Participants feel the ball is actually rolling.
1. Whether or not participants who did not see the movements
of the spherical mobile robot
experience the optical illusion of a rolling spheres.
2. The relationship between the velocity of the robot and the
perception of the optical illusion.
3. Influence of the deviation between the amount of rotation
and the moving distance on the illusion.

58. 60
・Participants watch an actual rolling LED ball.
（For evaluation criteria）．
Experiment
Step 1 → Step 2 → Step 3 → Step 4
Results and Consideration

59. 61
・Participants watches 7 patterns．
Experiment
Step 1 → Step 2 → Step 3 → Step 4
Results and Consideration

60. 62
Q: Did the sphere appear to be rolling?
・The relationship between the velocity of the robot
and the perception of the optical illusion.
Figure: Average value of the evaluation of 12 participants.
When the speed was extremely fast / slow,
the illusion effect tended to weaken.
Experiment
Results and Consideration

61. 63
Experiment
Experiment items
1. Whether or not participants who did not see the movements
of the spherical mobile robot
experience the optical illusion of a rolling spheres.
2. The relationship between the velocity of the robot and the
perception of the optical illusion.
3. Influence of the deviation between the amount of rotation
and the moving distance on the illusion.
Participants feel the ball is actually rolling.
When the speed was extremely fast / slow,
the illusion effect tended to weaken.

62. 64
・Influence of the deviation between the amount of
rotation and the moving distance on the illusion.
🦐 🦐 p < .05
Experiment
Results and Consideration
Q: Did the sphere appear to be rolling?
Figure: Average value of the evaluation of 12 participants.
Ｔhe amount of rotation [m] / The moving distance [m]

63. 65
Experiment
Experiment items
1. Whether or not participants who did not see the movements
of the spherical mobile robot
experience the optical illusion of a rolling spheres.
2. The relationship between the velocity of the robot and the
perception of the optical illusion.
3. Influence of the deviation between the amount of rotation
and the moving distance on the illusion.
Participants feel the ball is actually rolling.
When the speed was extremely fast / slow,
the illusion effect tended to weaken.
The illusion effect diminishes as the rotation amount is
increased with respect to the movement distance.

64. 66
Experiment
Experiment summary
• Eleven out of twelve participants believed the illusion that the
sphere was rolling when they watched the performance,
which is surprising.
• The improved hardware and software made the illusion
possible even when the LED ball moved too slowly or too
quickly.
• We found that attention needs to be paid to the relationship
between rotation and moving distance when setting up a
performance.

65. 1. Background
2. Research Purpose
3. Proposed Method
4. Preliminary Study
5. Improvement of System and Evaluation
6. Testing the ability of the proposed system
7. Summarize

66. 68
Testing the abilities of
the sphere-shaped mobile robot
Improvement of the system

67. 69
Testing the abilities of
the sphere-shaped mobile robot
Performance

68. 70
Experiment
Comments by Performer
• Until being told how the mechanism worked, I was convinced that
the sphere was physically rotating on its own.
• It looked as if the sphere was attached to the wall, and rolling on it.
• It seemed that the camera angle was changing, which was very
interesting.
• It looked as if the robot was surprised.
• It looked as if the video’s playback speed was changing.
• In one scene the robot was gentlemanlike.
Comments by Audience
A spherical robot on a moving stand demonstrated higher power
output and mobility than expected.
It was able to move very naturally during scenes such as when it
pushed against a wall without appearing too burdened.

69. 1. Background
2. Research Purpose
3. Proposed Method
4. Preliminary Study
5. Improvement of System and Evaluation
6. Testing the ability of the proposed system
7. Summarize

70. Summarize 72
・We propose the concept of using pseudo-physical
movements in performances with robots.
・We built a robot that visually reproduces
the movements of a rolling sphere and is capable of
faster movements and easier position estimations in
comparison with previous spherical robots.
・We created a performance that included the robot
interacting with a professional performer.

71. 73

72. 今後の課題 74
超現実表現
坂道を上る 逆⾛
急加速 急停止

73. 今後の課題 75
環境の錯視
凸凹な床 壁 つるつるの床

74. 今後の課題 76
パフォーマンス以外の利⽤
スポーツ 情報提示装置

75. まとめ 77
・球状LEDテ ィスフ レ イを搭載した移動ロホ ットを
提案．
・光を用いた視覚効果について調査．
・視覚効果による回転移動の錯視を確認．
・光の回転量に対する移動距離のずれが
錯視効果を弱めることを確認．

76. まとめ 78
・球状LEDテ ィスフ レ イを搭載した移動ロホ ットを
提案．
・光を用いた視覚効果について調査．
・視覚効果による回転移動の錯視を確認．
・光の回転量に対する移動距離のずれが
錯視効果を弱めることを確認．
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