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EVALUATION OF JOINT LOADS IN PUSHING / PULLING ATTENDANT-PROPELLED WHEELCHAIRS DURING FORWARD WALKING ON UPWARD AND DOWNWARD SLOPES PowerPoint PPT Presentation


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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, Japan Hironobu Uchiyama, Kansai University, Japan

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EVALUATION OF JOINT LOADS IN PUSHING / PULLING ATTENDANT-PROPELLED WHEELCHAIRS DURING FORWARD WALKING ON UPWARD AND DOWNWARD SLOPES

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EVALUATION OF JOINT LOADSIN PUSHING / PULLINGATTENDANT-PROPELLED WHEELCHAIRS DURING FORWARD WALKING ONUPWARD AND DOWNWARD SLOPES

Tatsuto Suzuki, Maizuru National College of Technology, Japan

Hironobu Uchiyama, Kansai University, Japan

Catherine Holloway, University College London, UK

Nick Tyler, University College London, UK


Background

The pushing and pulling cart are

well met tasks in daily life.

Typical pushing and pulling wheel carts

  • Attendant propelled wheelchair (80kg)

  • Shopping cart (30kg)

  • Baby pushchair (25kg)

  • Medical stretcher (140kg)

  • Trolley aboard aircraft (85kg)

  • Industrial cart (up to 400kg)


Workload factors

Required capability

by wheelchair and environments

Provided capability

by person

Attendant

- Push/pull performance

- Age

- Gender

Wheelchair

- Weight

- Rolling resistance

- Dimensions

Environment

- longitudinal and cross slopes

- Kerbs

- Gaps

- Roughness of road surfaces


Problems

1. Pushing/pulling is very hard task

2. 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


Objectives

1. 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?


Methodology

1. 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 60kg

3. Subjects

Ablebodied five patiripants

Average age: 33years old


Longitudinal slopes

UCL Pamela platform

- Each plate size: 1200 x 1200mm

- Maximum height difference: 300mm

- Slope conditions: 0%, 6.5%, 9.0%, 12%

12%

9.0%

6.5%

0%


Attendant propelled wheelchair

Force measurement:

6-axis load cell at both grips

Velocity measurement:

Rotary encoder at both wheels

Main specifications

Wheelchair weight: 36kg

Grip height: 0.95m

Additional weight:

+00, +20, +40, +60kg


Joint position measurement

Two dimensional measurement

- One camera and reflective markers

- Marker tracking software


Joint torque calculation

Figure 1 (a) Experimental system with seven link model to analyse joint torques.

(b) Each link difinition in multibody dynamics


Joint torque calculation

System mass matrix: Mi = diag [mi, mi, μi ]

System state vector: qi = [xi, yi, ϕi ]

External force vector: gi = [gexi, geyi - mig, geni ]

Jacobian matrix: Φqi = [1 0; 0 1; -(yPa-yi) (xPa - xi ) ]

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 ]T

where, the subscript i of each variables is link number.


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.


Change of push/pull force and velocity

Heavy load

Figure 2 Averaged propelling forces and wheelchair velocities in ascending and descending under four weight and slope conditions.

Light load

Heavy load


Push/pull power


Push/pull power

Heavy load

Light load

Heavy load


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.


Posture in push/pull

Lean forward

Lean Backward

(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 pull

Heavy push

Light push


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.


Joint angle in shoulder and elbow

Extension

with the increase of load

Figure 4 Averaged shoulder and elbow angle during stance phase. The joint angles were measured based on the medical definition.

Flexion

with the increase of load


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.


Joint torque in shoulder and elbow

Push: Shoulder torque increased

Figure 5 Averaged shoulder and elbow torque during stance phase. The calculation was carried out with the model in Figure 1.

Push: Low shoulder torque

Large pull torque

Elbow torque increased


Discussions

1. Maximum workload at push/pull

around 60W

- The same as electric bulbs!

- Over 60W in required capability is quite hard to push/pull


Discussions

2. Posture Change with the increase of load

- lean forward (Push)

- lean backward (Pull)

- Need to keep balance to apply push/pull force

3. 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 hard


Future works

1. Calculate joint power

2. Assisting system for attendants!


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