1 Design of a controller for sitting of infants Semester Project July 5, 2007 Supervised by: Ludovic Righetti Prof. Auke J. Ijspeert Presented by: Neha

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Design of a controller for Design of a controller for sitting of infantssitting of infants

Semester ProjectSemester ProjectJuly 5, 2007July 5, 2007

Supervised by:Supervised by:Ludovic RighettiLudovic RighettiProf. Auke J. IjspeertProf. Auke J. Ijspeert

Presented by:Presented by:Neha P. GargNeha P. Garg

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Content

Introduction & Motivation

Observations

Hand Made trajectory

Analysis of trajectory

Dynamical System

Further Work

Conclusions

• Introduction & Motivation

• Observations

• Hand Made Trajectory

• Analysis of trajectory

• Dynamical System

• Further Work

• Conclusions

3

RobotCub Project

Aim: study cognitive abilities of a child

How: by building a 2 year old infant-like

humanoid robot ICUB


• Observations




• Further Work

• Conclusions

4

Need for Locomotion

Cognitive Development

Explore Environment

Locomotion


• Observations




• Further Work

• Conclusions

5

Real Infants

Two main phases of sitting

Bringing of one leg forward

Movement of arm to sit on hip


• Observations




• Further Work

• Conclusions

6

Demonstration


• Observations




• Further Work

• Conclusions

Video of hand-made trajectory

7

Main Characteristics

Torso Movement Leg Movement First Phase Complete

Second Phase Start Arm Movement Sitting


• Observations




• Further Work

• Conclusions

Critical Phase

8

The Trajectory


• Observations




• Further Work

• Conclusions

9

Robustness

Checked in only critical period

Variation of the points specified for DOFs that effect critical period

Trajectory is quiet robust


• Observations




• Further Work

• Conclusions

10

Robustness

Right Arm


• Observations




• Further Work

• Conclusions

Point 6

Point 7

11

Robustness

Torso


• Observations




• Further Work

• Conclusions

Point 6

Point 7

12

Robustness

Right Leg


• Observations




• Further Work

• Conclusions

Point 3

Point 4

13

Center of Mass


• Observations




• Further Work

• Conclusions

Can information about projection of CM during sitting can be used to classify transitions as good or bad?

Defining stability measure as integration of distance of center of mass from support polygon with time during sitting

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Center of Mass


• Observations




• Further Work

• Conclusions

15

Torso Speed

Can we predict sitting/falling before critical period ?


• Observations




• Further Work

• Conclusions

16

Observations from analysis

Clear division of sitting in two phases

Robot unstable in the second phase

Robustness more important than stability

Some amount of instability required for sitting

Torso speed cannot be used to predict sitting/falling


• Observations




• Further Work

• Conclusions

17

Two Main Tasks

Switching from crawling to sitting

Designing mathematical equations for sitting trajectories


• Observations




• Further Work

• Conclusions

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When an external signal S is given, robot should switch from crawling to sitting

This can be done by:


• Observations




• Further Work

• Conclusions

),()1(

),()1(

crawlingFor

2

1

cycxfScy

cycxfScx

dd

dd

),(

),(

sittingFor

4

3

sysxfSsy

sysxfSsx

dd

dd

ddd sxcxx

19


This may cause abrupt shift from crawling to sitting

Switching should occur only when while crawling hip and shoulder joints are moving in the same direction as they will move after shifting

For this we replace S by


• Observations




• Further Work

• Conclusions

icyDie

SS

1

1.'

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• Observations




• Further Work

• Conclusions

21

Dynamical System for Sitting

For all of the trajectories except Left Leg (Abduc /Adduc and Rotation) the following equation can be used:

Where parameter P decides when the system should start and when the system starts it goes towards

can also be changed if required


• Observations




• Further Work

• Conclusions

))0(.( dddddd

dd

yxxPy

yPx

dx0

dx0

22


For example: for torso pitch

P = 1

=

Where S1 becomes 1 when second phase starts

And is calculated as:


• Observations




• Further Work

• Conclusions

dx0 )12.(11 valvalSval

)2.01*(1000

)2.01*(1000

11

P

P

e

eS

)_0_()_0_(100)3__()3__(1001

1

1

11

kneeleftxkneeleftxkneeleftxkneeleftxlegleftxlegleftxee

P

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For example: for left knee


• Observations




• Further Work

• Conclusions

10 valx d

)2_08.02_(1001

1torsoxtorsox

eP

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For Left Leg (Abduc/Adduc and Rotation), the movement has to be synchronized with left knee


• Observations




• Further Work

• Conclusions

2__,3__1

11

1

))0()0((

__100

)2_08.02_(100

__21

legleftlegleftbecande

K

eTwhere

xxxxcxcKTx

kneeleftykneelefty

torsoxtorsox

ddkneeleftkneeleftdd

25



• Observations




• Further Work

• Conclusions

26



• Observations




• Further Work

• Conclusions

27



• Observations




• Further Work

• Conclusions

28



• Observations




• Further Work

• Conclusions

29



• Observations




• Further Work

• Conclusions

30

Demonstration

Crawling and Sitting using Dynamical System


• Observations




• Further Work

• Conclusions

31

Further Work

Addition of sensory feedback while sitting Robot Falling

Collection of biological data to know whether the movements while sitting are controlled by brain or spinal cord

Development of controller for transition from sitting to crawling

Increase in the limit up to which hip joint can be extended


• Observations




• Further Work

• Conclusions

32

Conclusions

Main characteristics of sitting behavior of infants and the period of instability have been identified

A controller for sitting of the robot in the same way as infants has been implemented

Sensory feedback can be easily integrated by modifying values of parameter (P) according to sensory input

Robot can be switched from crawling to sitting by providing an external signal


• Observations




• Further Work

• Conclusions

33

Thanks a lot!

Questions?


• Observations




• Further Work

• Conclusions

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References[1] G. Sandini, G. Metta, and D. Vernon, “Robotcub: an open framework for

research in embodied cognition,” 2004, paper presented at the IEEE RAS/RJS International Conference on Humanoid Robotics, Santa Monica, CA.

[2] L. Righetti and A.J. Ijspeert. “Design methodologies for central pattern generators: an application to crawling humanoids”, Proceedings of Robotics: Science and Systems 2006, Philadelphia, USA

[3] Michel, O. “Webots:Professional Mobile Robot Simulation.”Int. J. of Advances Robotic Systems, 2004, pages:39-42,vol.1

[4] G. Metta, G. Sandini, D. Vernon, D. Caldwell, N. Tsagarakis, R. Beira, J. Santos-Victor, A. Ijspeert, L. Righetti, G. Cappiello, G. Stellin, F. and Becchi. “The RobotCub project - an open framework for research in embodied cognition”, Humanoids Workshop, Proceedings of the IEEE -RAS International Conference on Humanoid Robots, December 2005

[5] MATLAB Function pchip: Fritsch, F. N. and R. E. Carlson, "Monotone Piecewise Cubic Interpolation," SIAM J. Numerical Analysis, Vol. 17, 1980, pp.238-246


• Observations




• Further Work

• Conclusions

Documents

1 Design of a controller for sitting of infants Semester Project July 5, 2007 Supervised by: Ludovic Righetti Prof. Auke J. Ijspeert Presented by: Neha