Lecture 02: Locomotion

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Transcript of Lecture 02: Locomotion

  • 1. Introduction to RoboticsLocomotion
    CSCI4830/7000
    August 30, 2010
    NikolausCorrell

2. Last Lecture
Robots
Sense
Compute
Actuate
Communicate
If they dont they are just automatons (but the boundary is vague)
3. Last weeks exercise
Intro to Webots
How to create a wall
What you see / what the robot sees
Sensors: distance & camera
Physics
4. What is locomotion?
Latin: moving from place to place
Crawling
Sliding
Running
Jumping
Walking
Rolling
5. Other forms of locomotion
Swimming
Gliding
Flying
Propulsion
6. Locomotion relationships
Swimming to walking
Walking to rolling
Gliding to flying
Running to jumping
A.J. Ijspeert, A. Crespi, D. Ryczko, and J.M. Cabelguen. From swimming to walking with a salamander robot driven by a spinal cord model. Science, 9 March 2007, Vol. 315. no. 5817, pp. 1416 - 1420, 2007.
7. Nature vs. Technology
Robots become more and more capable of imitating natural locomotion schemes
Nature did not evolve rotating shafts / rotational joints
Hinge joint
Ball and socket joint
8. Walking vs. rolling
If the terrain allows, rolling is more efficient
Walking requires more
Structural complexity
Joints
Control
9. Characterization of locomotion
Stability
Number of contact points
Center of gravity
Static/Dynamic Stabilization
Inclination of terrain
Contact
Point vs. Area
Friction vs. grasp
3-Point rule
3 legs : static stability
6 legs : static walking
10. Walking
2-DOF
4-DOF
6-DOF
How many DOF are needed?
11. Gait
Sequence of event sequence
Event: leg up or down
Possible number of gaits N=(2k-1)!
Most efficient gait is a function of speed!
12. Horse Gait (Gallop)
167 different gaits observed in a horse!
13. Industry
2-legged locomotion
popular because suited to human environment
hardest to control
Commercial prototypes
4-legged locomotion
Not statically stable
Commercial prototypes
6-legged locomotion
Statically stable
Forestry
http://www.youtube.com/watch?v=FAcgSi6pzv4
http://www.youtube.com/watch?v=CD2V8GFqk_Y
14. Wheeled locomotion
Most appropriate for most applications
Stable with at least 3 wheels
Steered wheels make control more complex pretty quickly
Stable zone
15. Wheel suspension
Suspension consists of a spring and damper
The damper absorbs shock
The spring counteracts the shock
Result:
wheel remains on ground
Better traction
Better control
16. Omni-Directional Drive
Swedish Wheel
Rotation around wheel axle
Rotation around the rollers
Rotation around contact point
Uranus, CMU
17. Climbing with wheels
Friction-based
Center-of-gravity
based
Suspension-based
18. Dynamic Stability
The system has to move in order not to fall over
Active balance
Inertia is used to overcome unstable states
Examples are
Running
Getting up
Inverted Pendulum
19. Design
Lets design robots that
Crawl
Slide
Gallop
Jump
Walk
Roll
Crawling
Sliding
Running
Jumping
Walking
Rolling
20. 21. Crawling
Mechanics of Soft Materials Laboratory
http://ase.tufts.edu/msml/researchInchBot.asp
22. Sliding
Gavin Miller
Hirose-Fukushima lab
http://www-robot.mes.titech.ac.jp/robot_e.html
23. Running
Scout II, McGill University
24. Jumping
Laboratory of Intelligent Systems, EPFL
http://lis.epfl.ch/?content=research/projects/SelfDeployingMicroglider/
25. Rolling
http://modlabupenn.org
26. Homework
Chapter 3
Required for exercise in Week 4
Read till September 13
No class next week!
Hints
read the questions first
Skip: 3.2.3.4-5
Skim: 3.2.4-3.3.3
Understand what Maneuverability (Mobility and Steerability is) conceptionally
Goal: determine the speed of your robots motors so that it can follow a desired trajectory
27. Next exercise
Locomotion (Wednesday)
Play with different locomotion concepts in Webots
Understand various gaits and implement your own