This is the session 1 of the 2013 Microbotics Summer Workshop organized by the Electronic Technology department at University of Malaga. In this session, a printable modular snake robot, consisting of 9 modules is assembled and the main locomotion principles are presented.

1. Let's build
a modular snake robot!
Dr. Juan González-Gómez
July-2nd-2013
1

2. Let's build a modular snake robot!
Agenda
1.
Introduction
2. Modules
3. Locomotion in 1D
4. Locomotion in 2D
2

3. Modular robots
One module to rule them all!!
Multiple configurations
3

4. Morphology
1D topology
2D topology
3D topology
Snake robots
Pitch-pitch
Yaw-yaw
Pitch-yaw
4

5. Controller
How to generate the snake motion?
Bio-inspired
Classic
●
●
●
Mathematical models
Inverse kinematics
Depend on the morphology
●
●
Nature imitation
Central pattern
generators (CPG)
CPG
CPG
CPG
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6. Controller for snake robots
●
Replace the CPGs by sinusoidal oscillators
CPG
●
CPG
CPG
Sinusoidal oscillators:
φ i (t )= Ai sin(
2π
t + ψi)+ Oi
T
Advantages:
● Very few resources are
needed
for
their
implementation
6

7. Software architecture
Locomotion layer
Oscillator layer
Servo layer
Pw
m
7

8. Robotics is interdisciplinary
Software
s
ic
on
M
ec
ha
tr
ec
El
ni
cs
Robotics
8

9. Let's build a modular snake robot!
Agenda
1. Introduction
2.
Modules
3. Locomotion in 1D
4. Locomotion in 2D
9

10. Y1 modules family
●
One degree of freedom
●
Easy to build
●
Servo: Futaba 3003
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Size: 52x52x72mm
●
Types of connection
Open source
Y1
Repy1
MY1
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11. REPYZ modules
●
The latest version
●
3D Printed
●
Easy to clone
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Easy to modify
●
Designed in Openscad
●
Open source
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12. New age: 3D printing!
You can convert ideas
into real objects!!
●
EASY
●
FAST
●
CHEAP
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13. RepRap: Open source 3D printers
Demo
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14. REPYZ (II)
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Freecad
Module in Freecad (an open source CAD tool)
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15. REPYZ (III)
●
Designed in Openscad (Another open source tool)
●
Openscad
The module is code! Like programming!
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16. REPYZ. Assembling (I)
●
REPYZ exploded view
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17. REPYZ. Assembling (II)
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REPYZ: Bill of materials
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18. REPYZ. Assembling (III)
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Embed four M3 nuts
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19. REPYZ. Assembling (IV)
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Change the servo lower cover by the new one
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20. REPYZ. Assembling (VI)
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Screw the servo to the body part
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21. REPYZ. Assembling (VI)
●
Prepare the module head
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22. REPYZ. Assembling (VII)
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Join the body and the head
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23. REPYZ. Assembling (VIII)
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Add the 608 bearing
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24. REPYZ. Assembling (XI)
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Tighten the servo horn
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25. REPYZ (X)
●
The module is ready!
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26. Oscillations (I)
TASK:
●
●
●
Insert the battery packs into the holders
Screws the electronics with 20mm in length spacers
Connect one servo to the SERVO 2 connector
26

27. Module oscillation
Demo
φ (t )= Asin(
Bending angle
2π
t +Φ)+ O
T
Sinusoidal oscillator
Parameters:
●
Amplitude: A
●
Period: T
●
Offset: O
27

28. Oscillation of two modules
φ 1 (t )= A sin(
2π
+ Φ0 )
T
φ 2 (t )= A sin(
Demo
2π
+Δ Φ +Φ 0 )
T
ΔΦ
New parameter:
●
Phase difference:
ΔΦ
It determines how a module oscillates in relation to other
28

29. Experiment I: the wave
Demo
TASK:
●
●
●
●
Create “the wave” using 9 REPYZ modules
Amplitude, offset and period are fixed
See what happens for different phase differences
Fundamental equation:
360
Δ Φ= k
M
●
●
●
Degrees
●
●
K number of waves
M number of modules
M = 9, k = 1 ===> 40
M = 9, k = 2 ===> 80
M = 9, k = 3 ===> 120
29

30. Let's build a modular snake robot!
Agenda
1. Introduction
2. Modules
3.
Locomotion in 1D
4. Locomotion in 2D
30

31. Control model
31

32. Minimal configuration
TASK:
●
●
●
Build 3 minimal configuration
Each one consist of 2 modules
Test the locomotion for different oscillator parameters
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33. 3 module configuration
TASK:
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Build 3 configurations composed of 3 modules each
Test the locomotion for different oscillator parameters
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34. 6 modules configuration
TASK:
●
●
Build 1 configurations composed of 6 modules
Test the locomotion for different oscillator parameters
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35. 9 modules configuration
TASK:
●
●
Build 1 configurations composed of 9 modules
Test the locomotion for different oscillator parameters
35

36. Let's build a modular snake robot!
Agenda
1. Introduction
2. Modules
3. Locomotion in 1D
4.
Locomotion in 2D
36

37. Control model
37

38. Locomotion gaits
Straight
Av =40, Ah=0
 v =120
Sideways
Av = Ah40
 vh =90,  v=0
Av = Ah60
turning
Rotating
Av =40, Ah=0
Oh =30, v =120
Rolling
Av =10, Ah=40
 vh =90,  v=180
 vh =90,  v=0
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39. Minimal configuration
TASK:
●
●
Build 3 PYP configurations composed of 3 modules
Test the different locomotion gaits
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40. 6 module configuration
TASK:
●
●
Build 1 pith-yaw configuration composed of 6 modules
Test the different locomotion gaits
40

41. Locomotion gaits
Sidewinding
Straight
Rotating
v 0, k v =k h ,  vh=90
k h=1
v =40 , k v =2
h =0
Rolling
Turning
 v  0,k v=2kh ,  vh =0
 v  0,  vh =90
v =40 , k v =3
 h ≠0
41

42. Let's build
a modular snake robot!
Dr. Juan González-Gómez
July-2nd-2013
42