evaluation of joint loads in pushing / pulling attendant-propelled wheelchairs during forward...
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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 - PowerPoint PPT PresentationTRANSCRIPT
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, 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
Attendant - 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 environments
Problems1. 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
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?
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 60kg
3. Subjects Ablebodied five patiripants Average age: 33years old
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%
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, +60kg
Joint position measurementTwo 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 = [ge
xi, geyi - mig, ge
ni ]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
Figure 2 Averaged propelling forces and wheelchair velocities in ascending and descending under four weight and slope conditions.
Light load
Heavy load
Heavy load
Push/pull power
Push/pull power
Light load
Heavy 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
(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 pushLight push Heavy pull
Lean forward Lean Backward
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
Figure 4 Averaged shoulder and elbow angle during stance phase. The joint angles were measured based on the medical definition.
Extensionwith the increase of load
Flexionwith 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
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 torque
Discussions1. Maximum workload at push/pull
around 60W
- The same as electric bulbs! - Over 60W in required capability is quite hard to push/pull
Discussions2. 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 works1. Calculate joint power2. Assisting system for attendants!