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GECKO-LIKE “STICKYBOT III” BME500 Biomechanics and Biorobotics Rano Sidhu & Raul Soto http://roboticsnedir.com/2010/08/27/gecko- robot-gives-spiderman-some-tough- competition/

Gecko climbing robots

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Page 1: Gecko climbing robots

GECKO-LIKE “STICKYBOT III”

BME500 Biomechanics and Biorobotics

Rano Sidhu & Raul Soto

http://roboticsnedir.com/2010/08/27/gecko-robot-gives-spiderman-some-tough-competition/

Page 2: Gecko climbing robots

Purpose Mobile robots able to

climb and maneuver on vertical surfaces are useful for inspection, surveillance, and disaster relief applications

Kim (2008)

Page 3: Gecko climbing robots

http://media.treehugger.com

/assets/images/2011/10/gecko-foot.jpg

http://www.sciencephoto.com/media/344470/enlarge

Stickybot III

Gecko

• High sticking power

• Easy to peel off

Page 5: Gecko climbing robots

Stickybot III Four legs, Each with four degrees of freedom Actuation at the wrist to expand beyond

vertical-only climbing of the first platform.

At the body level, Stickybot has 12 servomotors

32 degrees of freedom (DOFs), making it highly underactuated.

Page 6: Gecko climbing robots

Sickybot III Each motor has a local microprocessor-

based servo controller. The feet are detachable. Stickybot III can currently climb at 5 cm/sec. The robot has a snout-vent length of 36 cm,

and the tail adds an additional 40 cm. The smoother the surface is, the easier

Stickybot III can climb it

Page 7: Gecko climbing robots

Sickybot III The robot has rotatable ankles. When a gecko goes down a wall upside-down, it

will reverse its back feet such that they point upward.

All computation is done on the robot using a 40 MHz PIC microcontroller.

A computer can send commands such as 'start' and 'stop' over a Bluetooth connection, but the robot does not require an external computer or sensors.

Page 8: Gecko climbing robots

Leg Mechanics Bar mechanism to keep the

stroke and elbow servos close to the body.

The red joints are active; green joints are passive.

The ankle motor is intended to keep the feet aligned so that tangential forces are in the correct direction for the directional adhesives.

Rotates in and out of the plane of the screen using another "wing angle" servo motor

http://bdml.stanford.edu/pmwiki

Page 9: Gecko climbing robots

Servos The wing moves

the foot towards or away from the wall.

The wing servo rotates a carriage that holds the stroke and elbow servos.

Page 10: Gecko climbing robots

Tail Helps reduce the pitch-

back torque on the robot. The lowest point on the

robot presses into the window since the center-of-mass is a significant distance from the wall.

Using a tail means the back feet can act as adhesives.

Without a tail, only the front feet would be adhering to the window in tension and the back feet would be in compression.

Page 11: Gecko climbing robots

Tail The tail and body are held

together using strong magnets.

This allows the tail to break-away during a fall, but also detach for storage as well as for demonstrations on the utility of the tail.

The tail's hinge has a thumb-screw to adjust the angle and interchangeable springs to adjust the stiffness.

Page 12: Gecko climbing robots

Elements of hierarchical compliance

Page 13: Gecko climbing robots

Toe Fabrication Four segmented toes

molded with two grades of polyurethane that sandwich a thin polyester fabric

The fabric flexes easily, but is relatively inextensible

Transmits shear stresses across the surface of the foot

Avoids the buildup of stress concentrations

Peeling, at the proximal regions of the toes.

Kim, S. et al. 2007

Page 14: Gecko climbing robots

Bent Toes Conform to gently

curved surfaces. Peel backward in a

motion like hyperextension of

geckos toes detachment. Servomotor connected

via push–pull cables in sleeves,

Attached to a rocker–bogie linkage located at the foot

Page 15: Gecko climbing robots

Cable Profiles Uniform stress

distribution when the toes are deployed on a flat surface

Page 16: Gecko climbing robots

DIRECTIONAL FRICTION AND ADHESION

Anisotropic hairs comprised of Shore-A polyurethane.

Hairs measure 380 μm in diameter at the base.

The base angle is 20◦ and the tip angle is 45◦.

Page 17: Gecko climbing robots

DISTRIBUTED FORCE CONTROL

Page 18: Gecko climbing robots

Weight Transfer During Trot

1 2

3 4

Not in contact with the wallIn contact with the wall

• Legs 1 and 4 make contact with the wall. • Weight is transferred from one pair to the other.• Legs 2 and 3 release from the wall.

Page 19: Gecko climbing robots

Gecko Feet 5 highly flexible digits Each has toe pads with hundreds of thousands of

setae Each seta has a stalk of hundreds of 200 nm – wide

spatular tips Adhesion via Van Der Waals forces!

Autumn (2006)

Page 20: Gecko climbing robots

http://www.youtube.com/watch?v=OoYeIsSkafI

http://www.psmicrographs.co.uk/gecko-foot/science-image/80016951http://robotics.eecs.berkeley.edu/~ronf/Gecko/interface08.html

http://www.psmicrographs.co.uk/_assets/uploads/moorish-gecko-foot-hairs--tarentola-mauritanica--80016981-l.jpg

Page 21: Gecko climbing robots

How Gecko Feet Attach to Surfaces 6 mechanical properties Useful for attaching / detaching in energy-

efficient manner Cantilever Effect Lever Effect Footprint Effect Peeling Effect Stiffness Asymmetry Momentum Distribution

Autumn (2006)

Page 22: Gecko climbing robots

Cantilever Effect Cantilever-shaped hairs enable robust grip on

irregular surfaces

Berenguer (2007)

Page 23: Gecko climbing robots

Lever Effect Lever principle : the

longer the hair, the lesser the force needed

Detachment occurs in path of least effort

First rotation of hair, then peeling

MR > Madh : moment due to external force applied to hair > moment over rotation axis due to adhesion force

Berenguer (2007)

Page 24: Gecko climbing robots

Footprint Effect ML : maximum load a hair

can support MR and ML depend on

shape of footprint Different footprint shapes =

different MR / ML ratios High MR / ML ratio : support

higher load, lower release force needed

Triangle-shaped footprint has higher MR / ML ratio, for a constant area, length, adhesion pressure

Berenguer (2007)

Page 25: Gecko climbing robots

Peeling Effect When load acts on lower

extreme of setae, hairs detach one by one in a coordinated way

The more contact points => more efficient adhesion system

Peak detachment force and maximum load capacity are proportional to the number of contact points

Berenguer (2007)

Page 26: Gecko climbing robots

Stiffness Asymmetry Effect Due to curvature of the hairs Stiffer hairs are easier to

detach from non-flat surface (+/-) Δx: decrease/increase

distance d between load cell and stage

(+/-) y: hair in tension / compression

When hair changes from tension to compression, its stiffness increases by almost 3x kT = 1.5 g/m => kC = 4 g/m

Berenguer (2007)

Page 27: Gecko climbing robots

Moment Distribution Effect Ability to distribute a big load into smaller loads to

each hair Curved shape of gecko hairs distribute loads and

tensions homogeneously If forces and tensions are not distributed

homogeneously, some hairs will detach => peeling crack will propagate => loss of adhesion in whole foot

Page 28: Gecko climbing robots

Robot Adhesion Mechanisms

Page 29: Gecko climbing robots

References Autumn, K. et al. 2006. Effective Elastic Modulus of Isolated Gecko Setal Arrays.

Journal of Experimental Biology. 209:3558-3568. Autumn, K. et al. 2006. Frictional Adhesion: A New Angle on Gecko Attachment.

Journal of Experimental Biology. 209:3569-3579. Berengueres, J. et al. 2007. Structural Properties of a Scales Gecko Foot-Hair.

Bioinsp. Biomim. 2:1-8. Kim, S. et al. 2007. Whole Body Adhesion: Hierarchival, directional and

distributed control of adhesive forces for a climbing robot. 2007 IEEE International Conference on Robotics and Automation. 10-14 April 2007.

Kim, S. et al. 2008. Smooth Vertical Surface Climbing With Directional Adhesion. IEEE Transactions on Robotics. 24(1):65-74.

http://bdml.stanford.edu/pmwiki