1. Dr. Juan González-Gómez
Let's build
a modular snake robot!
Agradecimientos:
Jesús Ernesto Zavala
Ana Cecilia Ruiz
Dr. Juan González-Gómez
July-2nd-2013

2. Agenda Modules Locomotion in 1D Locomotion in 2D Agradecimientos:
Let's build a modular snake robot!
Agenda
Introduction
Modules
Locomotion in 1D
Locomotion in 2D
Agradecimientos:
Jesús Ernesto Zavala
Ana Cecilia Ruiz

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

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

5. Controller How to generate the snake motion? Classic Bio-inspired
Nature imitation
Central pattern generators (CPG)
Mathematical models
Inverse kinematics
Depend on the morphology
CPG

6. Controller for snake robots
Replace the CPGs by sinusoidal oscillators
CPG
Sinusoidal oscillators:
φ 𝑖 𝑡 = 𝐴 𝑖 sin 2π 𝑇 𝑡+ ψ 𝑖 + 𝑂 𝑖
Advantages:
Very few resources are needed for their implementation

7. Software architecture
Locomotion layer
Oscillator layer
Servo layer
Pwm

8. Robotics is interdisciplinary
Software
Robotics
Electronics
Mechanics

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

10. Y1 modules family One degree of freedom Easy to build
Servo: Futaba 3003
Size: 52x52x72mm
Open source
Types of connection
MY1
Repy1 Y1

11. REPYZ modules The latest version 3D Printed Easy to clone
Easy to modify
Designed in Openscad
Open source

12. New age: 3D printing! FAST CHEAP
You can convert ideas into real objects!!
EASY
FAST
CHEAP

13. RepRap: Open source 3D printers
Demo

14. REPYZ (II)
Freecad
Module in Freecad (an open source CAD tool)

15. REPYZ (III) Openscad Designed in Openscad (Another open source tool)
The module is code! Like programming!

16. REPYZ. Assembling (I)
REPYZ exploded view

17. REPYZ. Assembling (II)
REPYZ: Bill of materials

18. REPYZ. Assembling (III)
Embed four M3 nuts

19. REPYZ. Assembling (IV)
Change the servo lower cover by the new one

20. REPYZ. Assembling (VI)
Screw the servo to the body part

21. REPYZ. Assembling (VI)
Prepare the module head

22. REPYZ. Assembling (VII)
Join the body and the head

23. REPYZ. Assembling (VIII)
Add the 608 bearing

24. REPYZ. Assembling (XI)
Tighten the servo horn

25. REPYZ (X)
The module is ready!

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

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

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

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:
ΔΦ= 360 𝑀 𝑘
K number of waves
M number of modules
Degrees
M = 9, k = 1 ===> 40
M = 9, k = 2 ===> 80
M = 9, k = 3 ===> 120

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

31. Control model

32. Minimal configuration
TASK:
Build 3 minimal configuration
Each one consist of 2 modules
Test the locomotion for different oscillator parameters

33. 3 module configuration TASK:
Build 3 configurations composed of 3 modules each
Test the locomotion for different oscillator parameters

34. 6 modules configuration
TASK:
Build 1 configurations composed of 6 modules
Test the locomotion for different oscillator parameters

35. 9 modules configuration
TASK:
Build 1 configurations composed of 9 modules
Test the locomotion for different oscillator parameters

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

37. Control model

38. Locomotion gaits Rolling Straight Sideways 𝐴 𝑣 =40, 𝐴 ℎ =0
Δ Φ 𝑣 =120
Rolling
𝐴 𝑣 = 𝐴 ℎ >60
Δ Φ 𝑣ℎ =90,Δ Φ 𝑣 =0
Sideways
𝐴 𝑣 = 𝐴 ℎ <40
Δ Φ 𝑣ℎ =90,Δ Φ 𝑣 =0
turning
Rotating
𝐴 𝑣 =10, 𝐴 ℎ =40
Δ Φ 𝑣ℎ =90,Δ Φ 𝑣 =180
𝐴 𝑣 =40, 𝐴 ℎ =0
𝑂 ℎ =30,Δ Φ 𝑣 =120

39. Minimal configuration
TASK:
Build 3 PYP configurations composed of 3 modules
Test the different locomotion gaits

40. 6 module configuration TASK:
Build 1 pith-yaw configuration composed of 6 modules
Test the different locomotion gaits

41. Locomotion gaits Sidewinding Rotating Straight
α 𝑣 →0, 𝑘 𝑣 = 2k ℎ ,Δ Φ 𝑣ℎ =0
Straight
α 𝑣 →0, 𝑘 𝑣 = 𝑘 ℎ ,Δ Φ 𝑣ℎ =90
k ℎ =1
α 𝑣 =40, 𝑘 𝑣 =2
α ℎ =0
Turning
α 𝑣 =40, 𝑘 𝑣 =3
ϕ ℎ ≠0
Rolling
α 𝑣 →0,Δ Φ 𝑣ℎ =90

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