Biomedical Engineering Design - Lecture 7. Example - rehabilitation

BIOMEDICALBIOMEDICALENGINEERING DESIGNENGINEERING DESIGN

WB2308WB2308

LECTURE STRUCTURE1. INTRODUCTION

CLINICALLY DRIVEN PROBLEM ANALYSISASSIGNMENT

3. BASIC REQUIREMENTS: ORTHOPAEDICS4. PROBLEM ANALYSIS: STUDENT PRESENTATIONS5. DESIGN ENGINEERING: THE CREATIVE PROCESS

6. DESIGN ENGINEERING PRINCIPLES

2. BASIC REQUIREMENTS: REHABILITATION

7. EXAMPLES: REHABILITATIONORTHOPAEDICS

Presentation overviewPresentation overview

BackgroundHistory of pneumatic actuationProject goalsMethodsResultsConcluding remarks

BackgroundBackground

Many different types of prostheses available


WILMER, NetherlandsHosmer Dorrance, USAOtto Bock Healthcare GmbHMotion Control, USA


Many different types of prostheses availableBut all fail to comply with the basic requirements


RSL-Steeper, UK

Centri AG, Sweden

Otto Bock Healthcare GmbH

VASI Inc., Canada


Disadvantages electric actuation:– Mass– Speed– Vulnerable– Size

RSL-Steeper, UK


Pneumatic actuation:– Light– Fast– Reliable– Small

History of pneumatic actuationHistory of pneumatic actuation

Dates back to 1877!


Dates back to 1877!

Dalish, 1877


Anonymous, ±1919


Dates back to 1877!Boosted in mid 20th

century: Thalidomide!


Dates back to 1877!Boosted in mid 20th

century: Thalidomide!

Heidelberg, 1949+


Steeper, 1964


Otto Bock, 1970+


Edinburgh, 1963 - 1977


Never successful:– Gas containers– Gas consumption– Overall mass

Project goalsProject goals

Re-assessment pneumatic actuation:– Light?– Fast?– Reliable?– Small?

MethodMethod

Minimize gas consumption by– System choice– Reduction of friction losses– Reduction of dead space– Supply pressure

Prototypes

Method Method –– system choicesystem choice

‘Standard’ operation

0 max. hand opening widthpi

nchi

ng fo

rce


‘Bi-phasic’ operation

0 max. hand opening width

cont

rol f

orce

max.

object size

prehension phase

pinching phase


‘Bi-phasic’ operationpinching motorpinching spring

closing springprehension motor

locking mechanism


Glove compensation

0max. thumb angle

thum

b m

o men

t M

characteristic ofcosmetic glove

resulting characteristic

characteristic ofcompensation mechanism

φ

-250

-200

-150

-100

-50

0

50

100

150

200

250

300

0 5 10 15 20 25 30 35

thumb opening angle ϕ [°]

mom

ent t

hum

b ax

is [N

mm

]

M open

M close


thu m

b m

omen

t

0

compensation mechanismcharacteristic of

ϕ

resulting characteristic

cosmetic glovecharacteristic of

max. thumb angle


II

I

thumb closed

+ϕ

thumb open


-300

-200

-100

0

100

200

300

0 5 10 15 20 25 30 35

thumb opening angle ϕ [°]

mom

ent t

hum

b ax

is [N

mm

] M open

M close

compensation moment

remaining closing moment

remaining openingmoment



0 max. hand opening width

cont

rol f

orce

max.

object size

prehension phase

pinching phase

Pinching Phase Mechanism


0x

F

1

2

3x, F

Force delivered bySprings 1 and 2

Force needed tocompress Spring 3

F

F


05

1015

20253035

0 2 4 6 8

Thumb tip displacement [mm]

Pinc

hing

forc

e [N

]


Thumb tip displacement

0

5

10

15

20

25

30

35

40

0 2 4 6 8

Thumb tip displacement [mm]

Pinc

hing

forc

e [N

]

desired pinchingforce

resulting pinchingforce


Locking mechanism:– Continuously adjustable– Friction free– Rigid– Fast switching– Low energy– No backlash– Quiet– Overload protection


Logical circuit

pinching motor

locking motor

object sensor

prehension motor

p /p in out

state sensor pinching motor

state sensorslocking motor

Method Method –– friction lossesfriction losses

Pivot point friction:– Journal bearings– Ball bearings– Flexible pivots– Gas bearings


Pivot point friction:– Journal bearings

2d

FfT rf ⋅⋅=


Pivot point friction:– Ball bearings

m113m0

7f dPfdf10160T ⋅⋅+⋅⋅⋅= −


Pivot point friction:– Flexible pivot

2r

z 4dF

Tπ⋅

ϕ⋅⋅=


Pivot point friction:– Gas bearings

zpdF

4T

2r

fω

⋅Δ⋅α

⋅⋅η⋅

π=


Pivot point friction assumptions:all pivots are loaded with the same force Fr

the axis diameter d is the same for all pivot pointsthe rotation angle ϕ = 30°, to be travelled in Δt = 0.1 s


Pivot point friction:– Journal bearings Tf = 0.05•Fr•d– Ball bearings Tf ~ 0.0018•Fr•d– Flexible pivots Tf = 0.013•Fr•d– Gas bearings Tf = 1•10-7•Fr•d2


Pneumatic seal friction:– Piston motor– O-ring seals


O-ring seal friction: [ ] [ ]AfLfF hcf ⋅+⋅=

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0 5 10 15 20 25

O-ring compression [%]

f c [N

/mm

]

70° shore

80° shore

90° shore

0

100

200

300

400

500

600

0 5 10 15 20 25

pressure [MPa]

f h [k

Pa]

Method Method –– dead spacedead space

Qp = ρ•Vds

Qp friction losses?

Qp leakage?

Method Method –– dead spacedead space

0

0.2

0.4

0.6

0.8

1

1.2

0 0.2 0.4 0.6 0.8 1 1.2

dimensional scale factor

para

siti

c ga

s co

nsum

ptio

nsc

ale

fact

or

dead space volumeO-ring frictionorificeball bearing frictionannular orifice

Method Method –– supply pressuresupply pressure

L

d

x max

x

ps


[ ] ⎥⎦⎤

⎢⎣⎡ ⋅+⋅⋅

π⋅ρ=+⋅ρ= c

2cphc AxLd

4VVm

L

d

x max

x

ps


[ ] ⎥⎦⎤

⎢⎣⎡ ⋅+⋅⋅

π⋅ρ=+⋅ρ= c

2cphc AxLd

4VVm

Optimal supply pressure level from:

0AxLd4dp

ddp

dmc

2

ss

hc =⎥⎦

⎤⎢⎣

⎡⎥⎦⎤

⎢⎣⎡ ⋅+⋅⋅π

⋅ρ=


( )

( )

( ) ( )[ ]

( ) ( ) ( ) ( )[ ]

( ) ( ) ( )[ ]

+

⎥⎥⎥⎥⎥⎥

⎦

⎤

⎢⎢⎢⎢⎢⎢

⎣

⎡

⎥⎥⎦

⎤

⎢⎢⎣

⎡

++⋅

+⋅

⎥⎥⎦

⎤

⎢⎢⎣

⎡

⋅−

⋅

+⋅⋅+

+⎥⎥⎦

⎤

⎢⎢⎣

⎡

−+⋅

−⋅

⎥⎥⎦

⎤

⎢⎢⎣

⎡

⋅+

⋅

−⋅⋅

⋅π⋅η⋅

⋅+⋅−+⋅−⋅⋅⋅

⎥⎥⎥⎥⎥⎥

⎦

⎤

⎢⎢⎢⎢⎢⎢

⎣

⎡

+⋅−+⋅−⋅⋅⋅⋅⎥⎥⎦

⎤

⎢⎢⎣

⎡

⎥⎥⎦

⎤

⎢⎢⎣

⎡

++⋅

+⋅

⋅

+⋅⋅+

⎥⎥⎦

⎤

⎢⎢⎣

⎡

−+⋅

−⋅

⋅

−⋅⋅⋅+−

−⎥⎥⎦

⎤

⎢⎢⎣

⎡

⎥⎥⎦

⎤

⎢⎢⎣

⎡

++⋅

+⋅

⎥⎥⎦

⎤

⎢⎢⎣

⎡

⋅−

⋅

+⋅⋅+

⎥⎥⎦

⎤

⎢⎢⎣

⎡

−+⋅

−⋅

⎥⎥⎦

⎤

⎢⎢⎣

⎡

⋅+

⋅

−⋅⋅⋅+⋅+⋅⋅⋅

⋅⋅⋅⋅η⋅

=

top0

top0333.32

s

0toptop

top0

top0333.32

s

0toptop

22asas

333.3

2asas

333.3

top0

top03s

0toptop

top0

top03s

0toptopas

top0

top0333.32

s

0toptop

top0

top0333.32

s

0toptop2as

333.3

333.32

s

s

FFxc

FFln

)T01.0(

517.57

pc

)FF2(F

FFxc

FFln

)T01.0(

483.107

pc

)FF2(F

tL128

pp4915.12pp5.82T01.0TR

pp4915.12pp5.82T01.0TRFFxc

FFln

pc

)FF2(F

FFxc

FFln

pc

)FF2(Fpp

FFxc

FFln

)T01.0(517.57

pc

)FF2(F

FFxc

FFln

)T01.0(483.107

pc

)FF2(Fpp4915.12T01.0TR

T01.0t

L32

dppdm

( ) ( ) ( ) ( ) ( ) ( )[ ]( ) ( ) ( )[ ] 0

pp4915.12pp5.82T01.0TR

T01.0TRpp4915.125.82T01.0ppT01.0pp4915.12

p

Fx22

asas333.3

2333.3as

333.32as

333.33as

2s

top =⎥⎥⎦

⎤

⎢⎢⎣

⎡

+⋅−+⋅−⋅⋅⋅

⋅⋅⋅⋅−⋅+⋅⋅⋅++⋅⋅+⋅⋅

⋅+


Ps, opt = 1.2 MPa

Independent of:Δt, L, Fs, and x

0

2

4

6

8

10

12

14

16

18

20

0 1 2 3

supply pressure [MPa]

gas

cons

umpt

ion

[mg]

Method Method –– prototype Iprototype I

Results IResults I

Results IResults I

Addition of check valvesPneumatic switchGlove compensation

Results IResults I

Logical circuit

pinching motor

locking motor

object sensor

prehension motor

p /p in out

state sensor pinching motor

state sensorslocking motor

Results IResults I

Logical circuit

Results IResults I

‘Old timer’ check valve

Results IResults I

Pneumatic switch

Results IResults I

-250

-150

-50

50

150

250

350

0 0.1 0.2 0.3 0.4 0.5 0.6

thumb angle [rad]

glov

e to

rque

[Nm

m]

Glove compensation

Results IResults I

Results IResults I

Endurance test: 77000 cycles

Results IResults I

Method Method –– prototype IIprototype II

Glove compensationMass of framePneumatical switchCheck valve

-250

-150

-50

50

150

250

350

0 0.1 0.2 0.3 0.4 0.5 0.6

thumb angle [rad]

glov

e to

rque

[Nm

m]



0 mm10

-250

-150

-50

50

150

250

350

0 0.1 0.2 0.3 0.4 0.5 0.6

thumb angle [rad]

glov

e to

rque

[Nm

m]

-250

-150

-50

50

150

250

350

0 0.1 0.2 0.3 0.4 0.5 0.6

thumb angle [rad]

glov

e to

rque

[Nm

m]


Δpcontrol

Δpcontrol

patm patm patm

phand mechanism

psupply

I II III IV

p

controlΔp

patm

supply

hand mechanismp

psupply

hand mechanism

atmppatm

p

Δpcontrol

a

b

c


Pneumatic relay:

- Ø 3.5 x 8.15 mm

- ΔP = 0.4 MPa

- Q = 74.2 ltr/hr

- m = 0.66 g


Pneumatic switch:

- Ø 3.0 x 4.3 mm

- F = 0.6 N

- Q = 97.0 ltr/hr

- m = 0.19 g


Check valve:

- Ø 1.5 x 2.8 mm

- ΔP = 48 kPa

- Q ≥ 120.0 ltr/hr

- m = 0.05 g

Results IIResults II

Concluding remarksConcluding remarks

Pneumatic actuation excels electrical actuation:– Low in mass– Fast– Reliable– Small

Concluding remarksConcluding remarks

Clinical evaluationPneumatic servo mechanismMiniature pneumatic components

Delft Delft InstituteInstitute of of ProstheticsProsthetics and and OrthoticsOrthotics

ADVANCED REHABILITATION TECHNOLOGYD E L F T U N I V E R S I T Y O F T E C H N O L O G Y

T H E N E T H E R L A N D S

Biomedical Engineering Design - Lecture 7. Example - rehabilitation

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Transcript of Biomedical Engineering Design - Lecture 7. Example - rehabilitation