biomedical engineering design - lecture 7. example - rehabilitation
TRANSCRIPT
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
BackgroundBackground
WILMER, NetherlandsHosmer Dorrance, USAOtto Bock Healthcare GmbHMotion Control, USA
BackgroundBackground
Many different types of prostheses availableBut all fail to comply with the basic requirements
BackgroundBackground
RSL-Steeper, UK
Centri AG, Sweden
Otto Bock Healthcare GmbH
VASI Inc., Canada
BackgroundBackground
Disadvantages electric actuation:– Mass– Speed– Vulnerable– Size
RSL-Steeper, UK
BackgroundBackground
Pneumatic actuation:– Light– Fast– Reliable– Small
History of pneumatic actuationHistory of pneumatic actuation
Dates back to 1877!
History of pneumatic actuationHistory of pneumatic actuation
Dates back to 1877!
Dalish, 1877
History of pneumatic actuationHistory of pneumatic actuation
Anonymous, ±1919
History of pneumatic actuationHistory of pneumatic actuation
Dates back to 1877!Boosted in mid 20th
century: Thalidomide!
History of pneumatic actuationHistory of pneumatic actuation
Dates back to 1877!Boosted in mid 20th
century: Thalidomide!
History of pneumatic actuationHistory of pneumatic actuation
Dates back to 1877!Boosted in mid 20th
century: Thalidomide!
History of pneumatic actuationHistory of pneumatic actuation
Dates back to 1877!Boosted in mid 20th
century: Thalidomide!
Heidelberg, 1949+
History of pneumatic actuationHistory of pneumatic actuation
Steeper, 1964
History of pneumatic actuationHistory of pneumatic actuation
Otto Bock, 1970+
History of pneumatic actuationHistory of pneumatic actuation
Edinburgh, 1963 - 1977
History of pneumatic actuationHistory of pneumatic actuation
Never successful:– Gas containers– Gas consumption– Overall mass
History of pneumatic actuationHistory of pneumatic actuation
History of pneumatic actuationHistory of pneumatic actuation
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
Method Method –– system choicesystem choice
‘Bi-phasic’ operation
0 max. hand opening width
cont
rol f
orce
max.
object size
prehension phase
pinching phase
Method Method –– system choicesystem choice
‘Bi-phasic’ operationpinching motorpinching spring
closing springprehension motor
locking mechanism
Method Method –– system choicesystem choice
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
Method Method –– system choicesystem choice
thu m
b m
omen
t
0
compensation mechanismcharacteristic of
ϕ
resulting characteristic
cosmetic glovecharacteristic of
max. thumb angle
Method Method –– system choicesystem choice
II
I
thumb closed
+ϕ
thumb open
Method Method –– system choicesystem choice
-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
Method Method –– system choicesystem choice
Method Method –– system choicesystem choice
0 max. hand opening width
cont
rol f
orce
max.
object size
prehension phase
pinching phase
Pinching Phase Mechanism
Method Method –– system choicesystem choice
0x
F
1
2
3x, F
Force delivered bySprings 1 and 2
Force needed tocompress Spring 3
F
F
Method Method –– system choicesystem choice
05
1015
20253035
0 2 4 6 8
Thumb tip displacement [mm]
Pinc
hing
forc
e [N
]
Method Method –– system choicesystem choice
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
Method Method –– system choicesystem choice
Locking mechanism:– Continuously adjustable– Friction free– Rigid– Fast switching– Low energy– No backlash– Quiet– Overload protection
Method Method –– system choicesystem choice
Logical circuit
pinching motor
locking motor
object sensor
prehension motor
p /p in out
state sensor pinching motor
state sensorslocking motor
Method Method –– system choicesystem choice
Method Method –– friction lossesfriction losses
Pivot point friction:– Journal bearings– Ball bearings– Flexible pivots– Gas bearings
Method Method –– friction lossesfriction losses
Pivot point friction:– Journal bearings
2d
FfT rf ⋅⋅=
Method Method –– friction lossesfriction losses
Pivot point friction:– Ball bearings
m113m0
7f dPfdf10160T ⋅⋅+⋅⋅⋅= −
Method Method –– friction lossesfriction losses
Pivot point friction:– Flexible pivot
2r
z 4dF
Tπ⋅
ϕ⋅⋅=
Method Method –– friction lossesfriction losses
Pivot point friction:– Gas bearings
zpdF
4T
2r
fω
⋅Δ⋅α
⋅⋅η⋅
π=
Method Method –– friction lossesfriction losses
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
Method Method –– friction lossesfriction losses
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
Method Method –– friction lossesfriction losses
Pneumatic seal friction:– Piston motor– O-ring seals
Method Method –– friction lossesfriction losses
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
Method Method –– supply pressuresupply pressure
[ ] ⎥⎦⎤
⎢⎣⎡ ⋅+⋅⋅
π⋅ρ=+⋅ρ= c
2cphc AxLd
4VVm
L
d
x max
x
ps
Method Method –– supply pressuresupply pressure
[ ] ⎥⎦⎤
⎢⎣⎡ ⋅+⋅⋅
π⋅ρ=+⋅ρ= c
2cphc AxLd
4VVm
Optimal supply pressure level from:
0AxLd4dp
ddp
dmc
2
ss
hc =⎥⎦
⎤⎢⎣
⎡⎥⎦⎤
⎢⎣⎡ ⋅+⋅⋅π
⋅ρ=
Method Method –– supply pressuresupply pressure
( )
( )
( ) ( )[ ]
( ) ( ) ( ) ( )[ ]
( ) ( ) ( )[ ]
+
⎥⎥⎥⎥⎥⎥
⎦
⎤
⎢⎢⎢⎢⎢⎢
⎣
⎡
⎥⎥⎦
⎤
⎢⎢⎣
⎡
++⋅
+⋅
⎥⎥⎦
⎤
⎢⎢⎣
⎡
⋅−
⋅
+⋅⋅+
+⎥⎥⎦
⎤
⎢⎢⎣
⎡
−+⋅
−⋅
⎥⎥⎦
⎤
⎢⎢⎣
⎡
⋅+
⋅
−⋅⋅
⋅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 =⎥⎥⎦
⎤
⎢⎢⎣
⎡
+⋅−+⋅−⋅⋅⋅
⋅⋅⋅⋅−⋅+⋅⋅⋅++⋅⋅+⋅⋅
⋅+
Method Method –– supply pressuresupply pressure
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
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
Logical circuit
Results IResults I
‘Old timer’ check valve
Results IResults I
Pneumatic switch
Results IResults I
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]
Method Method –– prototype IIprototype II
Method Method –– prototype IIprototype II
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]
Method Method –– prototype IIprototype II
Method Method –– prototype IIprototype II
Method Method –– prototype IIprototype II
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
Method Method –– prototype IIprototype II
Pneumatic relay:
- Ø 3.5 x 8.15 mm
- ΔP = 0.4 MPa
- Q = 74.2 ltr/hr
- m = 0.66 g
Method Method –– prototype IIprototype II
Method Method –– prototype IIprototype II
Pneumatic switch:
- Ø 3.0 x 4.3 mm
- F = 0.6 N
- Q = 97.0 ltr/hr
- m = 0.19 g
Method Method –– prototype IIprototype II
Method Method –– prototype IIprototype II
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