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Hydraulic Ankle Foot Orthosis: First Platform. Torque: 90 N-m (600 lbs force for a 3cm moment arm) Small packaging space Weight: < 1 kg Portability: untethered Longevity: 10,000 steps Peak power: 250 W. Artist rendering. - PowerPoint PPT Presentation
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Hydraulic Ankle Foot Orthosis: First Platform
Torque: 90 N-m(600 lbs force for a 3cm moment arm)
Small packaging space
Weight: < 1 kg
Portability: untethered
Longevity: 10,000 steps
Peak power: 250 W
Artist rendering
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Pump Conduits ActuatorsBatteryElectric Motor
Linear?orRotary?
Long?orShort?
Piston?or
Vane?
Gearhead?or
Not?
Many System Level Questions Need to Be Answered Before Specifying Each Component
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0 200 400 600 800 10000
20
40
60
80
100
Gear ratio
Gea
rhea
d ef
ficie
ncy
(%)
1 2 3 4 5 6 7 8 9 1040
50
60
70
80
90
Pump displacement (cc/rev)
Pu
mp
effi
cie
ncy
(%
)
The Efficiency and Weight of Each Component Can Be Modeled Analytically
Electric DC Motor Weight
Gear-head Efficiency
Hydraulic Cylinder Weight
Axial-Piston Pump Efficiency
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The Established Efficiency and Weight Models Can Identify the AFO Configuration
Power Pack
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2pp
outoutth P
TV
Pump displacement (cc/rev):
tan2
p
thp Rz
VAPump piston area (m^2):
pp Ad 4
Pump piston bore (m):
z
pR
Num. of pistons
Pitch radius
Swash-plate angle
),,,( pppthp PdVf Pump efficiency:
Design Variables Can Be Expressed by Known Parameters*
* Key pump design variable: pump displacement, pump piston bore and pump efficiency. To simplify the design problem, other pump parameters were adopted from the three-piston Oildyne pump.
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100
100
100
120
120
120
120
140
140
140140
160
160
160
160
180
180
180
200
200
200
220
220
220
240
240
240
260
280
10
10
10
10
15
15
1515
20
2020
252525
303035
0.5
0.5
0.5
0.5
1
11
11.5
1.5 1.5222
2.52.5
33 3.544.55
15 15 15
20 20 20
25 25 2530 30 30
35 35 3540 40 40
240
260
260
260
260
280280
280
280
280
280280300 300
300
300300
300
320 320320
320320
320
340 340360 360380400
Pump shaft speed (rpm)
Pu
mp
ou
tlet
pre
ssu
re (
MP
a)
1200 1400 1600 1800 2000 2200 2400 2600 2800 3000
5
10
15
20 Desired DC motor T (mNm)Pump cylinder bore (mm)Pump displacement (cc/rev)Cylinder bore (mm)Battery weight (g)
Design Variables Can Be Plotted on P-n Plot
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Component Part Number Wt (g) Dia (mm) Len (mm)
Actuator Package
PF Cylinder Custom part 165 17.2 100
DF Cylinder Custom part 23 7 100
Joint Pulley Custom part TBD 60 NA
Total 188 72 130
Power Source
Valves TBD
Pump Custom part 190 32 53
Gear Head Maxon 166930 118 32 27
DC Motor Maxon 397172 141 45 27
Total 449 45 107
Energy Source
Battery TP2700-6SPL25 465 50 x 34 x 102
The Hydraulic AFO Components Can Be Specified Based on the Design Map
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1. System level analyses are necessary to identify the design guidelines for the hydraulic AFO.
2. The analytical efficiency and weight models for the system level analyses are achievable.
3. For the hydraulic AFO, the actuators would better be separated from the power source, similar to an excavator.
4. The analytical efficiency and weight models are also needed to specify each component in the hydraulic AFO system.
Conclusions
