A COMPLIANT HAND BASED ON A PNEUMATIC ACTUATORDr. Oliver Brock team from TU Berlin

PneuFlex actuator

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TABLE OF CONTENT

Related works Basic idea Design + Manufacturing process Controlling Experiment Applications

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RELATED WORKS

Starfish gripper Harvard university made of silicone symmetric design same principle of RBO hand

Positive pressure gripper university of Chicago rubber balloon, filled with ground coffee Can match relative small object Need a supporting surface, cannot free grasping

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RELATED WORKS

SDM hand developed by Harvard +Yale rigid finger links opposing finger configuration mechanical coupling through tendons

Pneumatic Anthropomorphic hand rigid finger links hinge joints inflatable chamber to actuate(-)reduce ability to match the shape(?) did not mention to the effect of

compliance in subsequence research 4

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BASIC IDEA

Passive compliance Finger that effort shape matching without

sensing and controlling Improving grasp success/robustness under

uncertainty easy to mass-production Fast manufacturing turn-around

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DESIGNING

use of soft materials such as rubber or silicone Reinforce by steel helix Operate using pneumatic mechanism

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DESIGNING Active layer Passive layer Reinforcement helix

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palm

DESIGNING

Active layero Hollow silicone rubber Air Chamber can be

inflated or deflatedo More elongating than passive layer o Transparent square tube with closed end

Passive layero Flat piece of Polymer fiber (Polyethylene

terephthalate-PET) attach at 1 side of the rubber part reinforce rubber substrate enable bending without significant elongation create anisotropic elasticity ( need (1) )

Reinforcement helix (1)• Sheet of steel fabric is woven along the

passive layer

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MANUFACTURINGActive layer casting

Reinforcement helix winding

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MANUFACTURING

Passive layer casting

Airchamber attaching

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IMPLEMENTING

3 finger palms – each: 2 actuatorstotal length 130mm

2/3 fingers are split up

Finger made from 2 sectionspalm, bending rubber pad

Air chamber: split up 2 segments 35 +45 mm

Fingers are mounted to metacarpal 300

Posture – 2 supply tubes

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80x80x3 Rubber

Palm

CONTROLLING

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CONTROLLING

The simplest controlling system :Solenoid valvesDarlington transistor circuit (TIP121)Valves are controlled using the IO ports of an Arduino, Raspberry Pi, or any other embedded system.

A direct acting solenoid valve typically operates in 5 to 10 milliseconds

Angular deformation of palm can be various by changing the thickness of passive layer/ changing material

Max load: 0.5kg

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EXPERIMENT SETTING UP

Vary object types – 10 2 spatial variables (x,y) – 1204 trials Fixed action sequence – 2 different grasps:

Sliding grasping: objects were grasped from the side along a horizontal support surface

Surface constrained grasping: the hand is positioned above the object and approaches the table surface from top down, with the palm pitched at 45◦

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EXPERIMENTAL RESULTS

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EXPERIMENTAL RESULTS

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APPLICABILITY

Compliance & low inertia Safe for human interaction Fit for outdoor applications/ medical Rubber fragile for sharp object

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REFERENCES http://www.robotics.tu-berlin.de/menue/research/compliant_

manipulators/pneuflex_tutorial/ Pneuflex actuator

http://www.hizook.com/blog/2012/12/05/new-underactuated-robot-hands-lacquey-and-willow-garage SDM hand

http://gmwgroup.harvard.edu/research/index.php?page=23 starfish gripper

http://creativemachines.cornell.edu/positive_pressure_gripper

http://elib.dlr.de/78735/ Awiwi http://en.wikipedia.org/wiki/Darlington_transistor darlington

transistor circuit http://www.youtube.com/watch?v=SwqM8zpmAD8 solenoid

valve animation 18

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THANKS FOR W@TCHING!

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ductoanhcm@gmail.com

QUESTIONS AND ANSWERS

How to make sure that palm bend down on the specific side? Passive layer cannot extend+ attach along 1 side of

active layer palm bends down in the direction of the passive side.

Why really need steel fabric? to force the palm not bend aside

Maximum pressure 120kpa

Key ideas behinds all these hands Shape matching

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QUESTIONS AND ANSWERS

Summary ? Key techno: passive helix with steel fabric

Could normal position of hand be curve, not linear? Could be, currently there’s another research by TU

Berlin Real applications

SDM PR2 PPG  Solid Phase Extraction system http://

www.zinsserna.com/speedy.htm Starfish PAH Asimo, Azzurra (really important for hand

manipulation) for dangerous experiments) Pneuflex not yet

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