THREE DIMENSIONAL RECONSTRUCTION OF EXOSKELETONBY CONFOCAL MICROSCOPY

Confocal microscopy:DAVID NEFFLAURA QUIMBYFAITH FRAZIER

TROCHANTER OF FRONT LEG

CONVERTING CONFOCAL MODELS OF EXOSKELETONTO MODELS FOR FINITE ELEMENT ANALYSIS

CLAY FLANNIGAN, CASE WESTERN

TROCHANTER OF HINDLEG

PEGLEG EXPERIMENTS: PHYSIOLOGY ANDFINITE ELEMENT ANALYSIS STUDIES

P

PEG LEG TESTS ON HINDLEG Clay Flannigan, Case Western

RESULTS- RECEPTORS SIGNAL FORCESAS AN ARRAY- SOME GROUPS ARE EXCITED BYEXTERNAL LOAD AND MUSCLE CONTRACTIONS AND CAN PROVIDE POSITIVE FEEDBACK

FORCE FLEX FORCE EXTEND

TROCHANTERAL GROUP 3 SENSILLA ENCODEFORCED FLEXIONS: PHYSIOLOGY ABLATION EXPERIMENTS

STRAINS PRODUCED BY EXTENSOR MUSCLE CONTRACTIONS: SOME GROUPS CAN

MEDIATE POSITIVE FEEDBACK

POSITIVE FEEDBACK DECLINES AS LEG IS EXTENDED

Femur and Tibia Attached to Trochanter - FT Joint Angle from Kinematic Studies, Forces applied at Levels (Fx, Fy, Fz) for early, middle and late stance.(Kinematic Data from J. Watson, R. Ritzmann; Force Data from R. Full)

STRAINS DURING STANCE PHASE:S. Ramasubramanian, G. Nelson, Case Western

Fy

Fz

Fx

STRAINS DURING MIDSTANCE PHASE:S. Ramasubramanian, Case Western

LEG LOADING

RESULTS-ARRAY ENCODES FORCE DIRECTION(FORCE POSTERIOR, FLEXION)-ARRAY ENCODES FORCE MAGNITUDE

TROCHANTERAL FORCE SENSORS AS LOAD CELL: Fx, Fy and Fz INDEPENDENTLY VARIED

ARRAY CAN DETECT INCREASES IN FORCE VECTORS

Summary:

ENCODING PROPERTIES OF CAMPANIFORM SENSILLA- signal level of load rate of change of force, provide active signal for sudden decreasesMODELING THROUGH FINITE ELEMENT ANALYSIS - trochanteral campaniform sensilla encode forces as a array; some groups provide positive feedback in limited ranges of joint anglesLEG DESIGN/ANATOMY DETERMINES SPECIFICITY OF AFFERENT INPUTS

1- Exoskeleton is a tubular structure that is rigid (modulus =3160 N/mm^2);fixed beam analysis is useful

2- Receptors located on proximal ends of segments and are subject to large bending forces when end of leg ispushed against substrate

FEA Modeling Studies:Strain in Exoskeleton

3- Strains also result from muscle contractions:• Muscles with insertions near receptors produce strains; locally distribution depends upon shape• Muscles located close to body can produce bending along length of leg

TIBIAL EXTENSORMUSCLE

TROCHANTERALEXTENSORMUSCLE

TIBIAL SENSILLA

TROCHANTERAL SENSILLA

Three Dimensional Reconstruction of Exoskeleton by Confocal Microscopy Converted to FEA Model

Confocal microscopy:DAVID NEFFLAURA QUIMBYFAITH FRAZIER

CLAY FLANNIGAN, ROGER QUINNCASE WESTERN RESERVE

FEA MODEL

The trochanteral segment contains the largest number of strain sensing campaniform sensilla in the leg.

These receptors have been characterized physiologically and their responses have been modeled by Finite Element Analysis.

The trochanteral receptors can provide precise information about the magnitude, direction and rate of forces applied to the femur.

FORCE RECEPTORS ONTROCHANTER

Insect-Like Hexapods

•Robot II - “stick insect”

•6 symmetric 3 DOF Legs - 18DOF

•Locomotion controller uses network of inter-leg influences

•Able to walk over rough and unstable terrain Robot II

Robot III

•Robot III - cockroach•Pneumatic actuation•24 DOF: 5 front, 4 middle, 3 rear•Currently shows high power (30lb payload) and robust posture control

Cockroach Anatomy

•5 leg segments: coxa, trochanter, femur, tibia, tarsus

•CT, FT are 1 DOF, hinge-like and articulate about 2 condyles

•Large muscles of the coxa insert on the trochanter

•Trochanter is heavily loaded during stance

Coxa

Trochanter

Femur

Tibia

Tarsus

Cockroach Leg

Muscle Definition

Trochanter

•Approximately 2.5 mm in length for the adult P. americana•Outer surface is smooth; inner surface has variable topology •Coxa attaches via 2 condyles on the anterior and posterior sides•Femur attaches via 2 condyles on the distal anterior surface

Anterior view trochanter

Femur

Femoral Condyles

Coxal Condyles

Distal Proximal

Dorsal

Ventral

Trochantery

x

Campaniform Sensilla

•Campaniform Sensilla (CS) are cuticular caps in the exoskeleton innervated by a single nerve

•Ellipsoidal with long-axis length from 6 to 24 m

•Have been shown to respond to cuticular compressive strains perpendicular to the long-axis (short axis strains)

•Directionally sensitive

Cuticle Cap

Dendrite

Sensory NeuronAxon

Campaniform sensilla structure

TrochanteralCampaniform Sensilla

•CS found in 6 groups on the leg (10-15 in a group)

•Within groups the CS are similarly oriented

•4 groups on the trochanter - 3 on the anterior 1 on the posterior

•Notice the ridge structures and ring of the interior surface

Anterior campaniform sensilla groups

Posterior campaniform sensilla group

Group 2

Group 1

Group 3Group 4

Confocal Modeling(Zill Lab)

•Confocal microscope used to optically section the trochanter•Irradiation of the specimen with UV Light causes the cuticle to fluoresce

•Microscope indexes its focal plane through the trochanter•Result: A series of bitmap images, when combined using specialized software, creates 3-D model of the trochanter

Confocal Sections

Meshed Trochanter

Anterior

Posterior

Thickness Scale:red 6mblue

265m

Trochanter-Femur Model

Forced Flexion

•Von Mises strain:

VM 1/ 2(( x y )2 ( y z )2 ( z x )2 ) 3( xy2 yz

2 zx2 )

Anterior Posterior

FUNCTIONLIKE STRAIN GAUGES

DETECT STRAININ EXOSKELETON -COMPRESSIONSPERPENDICULARTO CAP LONG AXISEXCITE RECEPTOR

STRUCTURE AND LOCATION OF CAMPANIFORM SENSILLA

TROCHANTERAL CAMPANIFORM SENSILLA:

IMAGING BY CONFOCAL MICROSCOPY

1) OCCUR AS FOUR GROUPS (Gp1-4)2) EACH GROUP HAS CONSISTENT ORIENTATION3) GROUPS ARE ASSOCIATED WITH INTERNAL BUTTRESSES OR THICKENINGS OF EXOSKELETON

CONFOCAL IMAGES OF CUTICLE

INNER SURFACEOUTER SURFACE

diI OUTFILL

THREE DIMENSIONAL RECONSTRUCTION OF EXOSKELETON BY CONFOCAL MICROSCOPY

Confocal microscopy:DAVID NEFFLAURA QUIMBYFAITH FRAZIER

TROCHANTER OF FRONT LEG

ACCURACY CONFIRMED BY SECTIONING MODEL/ORIGINAL

TROCHANTER

SEM

3D RECONSTRUCTION

Confocal model FEA model

Overlay comparison

CONFOCAL and FEA models

ACTIVITIES OF CAMPANIFORM SENSILLA ARE EVALUATED BY STRAINS

AT LOCATION OF CUTICULAR CAPS

- nodes corresponding to CS are located on the finite element model

- Compressions (negative strain values) excite receptors

Group 1, posterior trochanter Groups 2,3,4, anterior trochanter

FEA PEGLEG EXPERIMENT

BEHAVIORAL PARADIGM PHYSIOLOGY PARADIGM

ATTACHPEG LEG

BEND FEMUR

FEA PEGLEG

APPLY FORCESTO ATTACHEDFEMUR, POINTSOF MUSCLEINSERTIONS

SENSORYRECORDING

PEG LEG TEST ON Blaberus Discoidalis FRONT LEG

RESULTS:Campaniform Sensilla- Function as a strain gauge array signals forces in all directions of load- Can provide positive feedback

Group 3 short axis strain Group 4 short axis strain

FORCE FLEX FORCE EXTEND

Mid-stance

Fx

Fz

Fy

Late stance

FINITE ELEMENT MODELLING OF STRAINS DURING WALKING

High speed video:Adam NoahAngela Ridgel

SENSORY ACTIVATION PATTERNS DUE TO GROUND REACTION FORCES DURING

STANCE

Mid Stance

-1.00E-03

-8.00E-04

-6.00E-04

-4.00E-04

-2.00E-04

0.00E+00

2.00E-04

4.00E-04

6.00E-04

8.00E-04

1.00E-03

0 1 2 3 4 5

Group

Sh

ort

Axi

s S

trai

n

•Groups 1 and 4 show excitation due to ground reaction forces throughout stance.

•These sensilla groups could be responsible for signaling that leg is on substrate and bearing load.