LOADS IN PUSHING PULLING ATTENDANTPROPELLED WHEELCHAIRS DURING FORWARD WALKING ON UPWARD AND DOWNWARD SLOPES Tatsuto Suzuki Maizuru National College of Technology Japan ID: 555161
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EVALUATION OF JOINT LOADS IN PUSHING / PULLING ATTENDANT-PROPELLED WHEELCHAIRS DURING FORWARD WALKING ON UPWARD AND DOWNWARD SLOPES
Tatsuto Suzuki, Maizuru National College of Technology, JapanHironobu Uchiyama, Kansai University, JapanCatherine Holloway, University College London, UKNick Tyler, University College London, UKSlide2
BackgroundThe pushing and pulling cart are well met tasks in daily life.Typical pushing and pulling wheel cartsAttendant propelled wheelchair (80kg)Shopping cart (30kg)Baby pushchair (25kg)
Medical stretcher (140kg)Trolley aboard aircraft (85kg)Industrial cart (up to 400kg)Slide3
Workload factorsAttendant - Push/pull performance - Age - Gender
Wheelchair - Weight - Rolling resistance - Dimensions
Environment
- longitudinal and cross slopes
-
Kerbs
- Gaps
- Roughness of road surfaces
Provided capability
by person
Required capability
by wheelchair and environmentsSlide4
Problems1. Pushing/pulling is very hard task2. Pushing/pulling is a known risk factor for musculoskeletal disorders (Back pain, joint strain, sprains)
3. Cause of musculoskeletal disorders- Peak and cumulative forces- duration and repetition,- Continuous tense non-neutral posture Slide5
Objectives1. How hard are pushing/pulling tasks?-> How large is the required capability in power?2. How to adapt push/pull style against the increase of load?-> How to change push/pull posture?3. How hard are shoulder and elbow?-> How large are the joint torque in shoulder and elbow?Slide6
Methodology1. Change slope angles Longitudinal slope angle:+00, +6.5%, +9%, and 12%2. Change the weight of a wheelchair Wheelchair weight: 36Kg + 00, 20, 40, and 60kg3.
Subjects Ablebodied five patiripants Average age: 33years oldSlide7
Longitudinal slopesUCL Pamela platform - Each plate size: 1200 x 1200mm - Maximum height difference: 300mm - Slope conditions: 0%, 6.5%, 9.0%, 12%
9.0%
6.5%
12%
0%Slide8
Attendant propelled wheelchairForce measurement: 6-axis load cell at both gripsVelocity measurement: Rotary encoder at both wheelsMain specifications Wheelchair weight: 36kg Grip height: 0.95m
Additional weight: +00, +20, +40, +60kgSlide9
Joint position measurementTwo dimensional measurement - One camera and reflective markers - Marker tracking softwareSlide10
Joint torque calculationFigure 1 (a) Experimental system with seven link model to analyse joint torques. (b) Each link difinition
in multibody dynamics Slide11
Joint torque calculation
System mass matrix: Mi = diag [mi, mi,
μ
i
]
System state vector:
q
i
= [
x
i
, yi, ϕ
i ]External force vector: gi = [ge
xi
,
g
e
yi
-
m
i
g
,
g
e
ni
]
Jacobian
matrix:
Φ
q
i
= [1 0; 0 1; -(
y
Pa
-
y
i
) (
x
Pa
-
x
i ) ]Reaction force vector by constraint: λi = [λxi, λyi ]The external force vector gi was described next equation. gexi = fxi - λx(i-1) geyi = fyi - λy(i-1) (2) geni = τa – τb + (rPb - ri ) x [gxi, gyi ]Twhere, the subscript i of each variables is link number. Slide12
Change of push/pull force and velocity
Figure 2 Averaged propelling forces and wheelchair velocities in ascending and descending under four weight and slope conditions. Slide13
Change of push/pull force and velocity
Figure 2 Averaged propelling forces and wheelchair velocities in ascending and descending under four weight and slope conditions.
Light load
Heavy load
Heavy loadSlide14
Push/pull powerSlide15
Push/pull power
Light load
Heavy load
Heavy loadSlide16
Posture in push/pull
(
a)
(
b
)
(
c
)
Figure
3 The difference of propelling postures during stance
phase.(participant
one) (a) Propelling at a level. (
b
) Ascend propelling at +9.0%. (
c
) Descent propelling at -9.0%. Each first frame is the beginning of the stance phase, and last frame is the end of the phase. The time interval between two frames is 25% of the phase. All weight conditions are W = 60kg.
Slide17
Posture in push/pull
(
a)
(
b
)
(
c
)
Figure
3 The difference of propelling postures during stance
phase.(participant
one) (a) Propelling at a level. (
b
) Ascend propelling at +9.0%. (
c
) Descent propelling at -9.0%. Each first frame is the beginning of the stance phase, and last frame is the end of the phase. The time interval between two frames is 25% of the phase. All weight conditions are W = 60kg.
Heavy push
Light push
Heavy pull
Lean forward
Lean BackwardSlide18
Joint angle in shoulder and elbow
Figure 4 Averaged shoulder and elbow angle during stance phase. The joint angles were measured based on the medical definition.Slide19
Joint angle in shoulder and elbow
Figure 4 Averaged shoulder and elbow angle during stance phase. The joint angles were measured based on the medical definition.
Extension
with the increase of load
Flexion
with the increase of loadSlide20
Joint torque in shoulder and elbow
Figure 5 Averaged shoulder and elbow torque during stance phase. The calculation was carried out with the model in Figure 1.Slide21
Joint torque in shoulder and elbow
Figure 5 Averaged shoulder and elbow torque during stance phase. The calculation was carried out with the model in Figure 1.
Push: Shoulder torque increased
Elbow torque increased
Push: Low shoulder torque
Large pull torqueSlide22
Discussions1. Maximum workload at push/pull around 60W - The same as electric bulbs! - Over 60W in required capability is quite hard to push/pullSlide23
Discussions2. Posture Change with the increase of load - lean forward (Push) - lean backward (Pull) - Need to keep balance to apply push/pull force3
. Joint torque in shoulder and elbow - Shoulder in push is harder than in pull - Elbow in pull is harder than in push - Elbow in pull on 12% slope is quite hardSlide24
Future works1. Calculate joint power2. Assisting system for attendants!