Vertebrate- or snake-like soft robot based on tensegrity principle

Présentation GT5,

vendredi 28 novembre 2014

Alex Pitti, phDMaître de Conférence, chaire d'excellence UCP-CNRS

Laboratoire ETIS CNRS, ENSEA, Cergy-Pontoise University

Research aims

Biologically-inspired solutions to challenge control of dexterous robots

- dimensionality (high number of DoF)

- exploiting the physics of the material (elasticity, friction) and of the robot morphology

- large repertoire of behaviors (walking, breaking, jumping, postural control)

Some solutions I attempt to propose:

Mechanism of phase synchronization in dynamical systems

- control the system's global dynamics- “tuning” to the material property and system morphology- applied to high dimensional system

The body design to process morphological computations

- geometry, structure

- material properties

based on previous works [Pitti, 2005~]

the controller

the robot

Hard materials are Hookean (mostly linear)Soft tissues are non-Hookean (visco-elastic)

'' always in tension (pre-stressed, muscle tone)

[Gordon : « Structures or why things don't fall down »]

The body's material properties are soft (muscles tissues and bones),≠ actual robot are engineered with hard materials (steel, plastic)

The robot : physical embodiment 1, material

[Tulving, 2005]

[Gordon : « Structures or why things don't fall down »]

[Gordon, 1994]

physical embodiment 2, the structure

The body structure (morphology) plays a role of a function in behavior→”morphological computations”, [R. Pfeifer]

Actual robot designer starts to have these considerations in mind.

[Lipson, 2004]

Changing the paradigmWe may see the musculo-skeletal system as a network of tension links (muscles, tendons) connected to compression structures (bones) : Pre-stressed structure.

Pretty much-like tensile structures.

Tensegrity structureTensegrity = integrity of tension proposed by B. Fuller & Sneil

network of tension and compression structure.

[Fuller and Sneil]

Tensegrity structureTensegrity = integrity of tension proposed by B. Fuller & Sneil

network of tension and compression structure.

➔ No momentum (no tangential force ≠ Newton laws & actual robots)➔ Ecological distribution of forces on all the structure:

➔ less power consumption to move➔ Exploit fully the physic of the structure:

➔ Light-weight structure➔ Self-replicative with lots of redundancy

➔ More robust & solid to defects/shocks➔ Self-Balance and neutral posture:

➔ return back to its own stable equilibrium

for arbitrarily small perturbations

[Tulvey 2013]

Tensegrity structure in biology Tensile links (muscles) support the structure weights (bones), not the

reverse

Shun Izawaya[Pfeifer Pitti 2012]

[Flemons, 2006]

Tensegrity robots

[Riesel 2012]

Nasa satellite antenna[SunSpiral, 2012]

[Shibata 2009]

design principles: – Muscles redundancy for compliance– Morphological computations: structure = function– Weak and loosely distributed units

Prototypes done [2011~]➔ Joint link device

➔ Snake-like or trunk-like tensile robot

Current snake prototype➔ Snake-like or trunk-like tensile robot

Anguilliform models

Representation of the swimmer as a chain ofinterconnected links. [McMillen 2008]

Snake skeleton

A proposed model of CPGs for multi-DOFs

Chaotic systemUnknown dissipative system

?

γ is a global parameter to control synchronization (motor synergy)State of feedback resonance in the dissipative system [Fradkov, 1999]

Model-free mechanism

For some specific coupling, Chaotic systems will match the system dynamics

1 Perturbation

2 Feedback

4 Resonance

3 Synchronization

[Pitti, 2005-2011]

Simulations of multi-DOF robotsRing-like mass-spring damper system (30 DoF) [Pitti, 2005]

Dog-like system (2 DoF) [Pitti, 2006]

Fréquence (H

z)

Control Parameter

Frog-like systems[Niiyama, Pitti, 2009]

chaoticcontrolers

Snake-like robotModel with 10 servos and 200ms delay sinusoidal oscillators with 5 segments

[done with Julien Abadji]

top view side view

Snake-like robot, current versionModel with solenoids (electro-magnets) and chaotic controllers (logistic map)

electro-magnets chaotic controller

body

Morphological computationown facial somatopic information

Ear 3D printed

Micro

[Pitti, 2012]

Audio spectral filtering done by shape of the ear

Time [s]

Fre

q [H

z]

… can serve for facial processing

[Pitti, 2013]

to conclude

How to make a robot that perceives like humans?

Understanding human intelligence(s) by synthetic or constructive approaches.

- To bridge the level of explanations

between Engineering, Biomechanics

Robotics/Comp. Science/Info. Theory

Developmental Psychology

Cognitive Neuroscience

- Seeking for design principles

- Reproducing it with robots Rolf Pfeifer and Alex Pitti

Manuella Editions, 2012

Rolf Pfeifer, ETH Zurichmoves

thinks

Save the date:

Journée GT8 Robotique et Neuroscience 17 décembre, UPMC

Cognitive Robotics and Enactive Systems

co-organizers

Benoît Girard, Medhi Kamassi, Ghilès Mostafaoui, Alex Pitti

Thank you

Architect projectJB Mouret, 2014