Design and Fabrication of an Instrumented Handrim to Measure the Kinetic and Kinematic Information by the Hand of User for 3D Analysis of Manual Wheelchair Propulsion Dynamics

Abstract

The repetitious nature of propelling a wheelchair has been associated with the high incidence of injury among manual wheelchair users (MWUs), mainly in the shoulder, elbow and wrist. Recent literature has found a link between handrim biomechanics and risk of injury to the upper extremity. The valid measurement of three-dimensional net joint forces and torques, however, can lead to a better understanding of the mechanisms of injury, the development of prevention techniques, and the reduction of serious injuries to the joints. In this project, an instrumented wheel system was developed to measure the applied loads dynamically by the hand of the user and the angular position of the wheelchair user's hand on the handrim during the propulsion phase. The system is composed of an experimental six-axis load cell, and a wireless eight channel data logger mounted on a wheel hub. The angular position of the wheel is measured by an absolute magnetic encoder. The angular position of the wheelchair user's hand on the handrim during the propulsion phase (ɸ) or point of force application (PFA) is calculated by means of a new-experimental method using 36 pairs of infrared emitter/receiver diodes mounted around the handrim. In this regard, the observed data extracted from an inexperienced able-bodied subject pushed a wheelchair with the instrumented handrim are presented to show the output behavior of the instrumented handrim. The recorded forces and torques were in agreement with previously reported magnitudes. However, this paper can provide readers with some technical insights into possible solutions for measuring the manual wheelchair propulsion biomechanical data.

Keywords: Biomechanics; handrim; instrumented wheel system; kinetic and kinematic; manual wheelchairs; propulsion analysis; six-axis load cell.

Figure 1

(a) The components of the instrumented wheel system (IWS). (A) wheel, (B) handrim, (C) retainer, (D) wheel hub, (E) experimental sis-axis load cell, (F) plexiglas disc, (G) L-shaped slotted beam. (b) The assembly of the IWS. (c) An inexperienced able-bodied subject pushed a wheelchair with the instrumented handrim

Figure 2

A layout represents how the encoder was assembled (A) retainer, (B) bush, (C) wheel axle, (D) allen screw, (E) magnet, (F) AS5045, (G) circuit board of AS5045, (H) load cell

Figure 3

Signal flow cycle of the instrumented handrim

Figure 4

(a) Global and load cell coordinate systems. (b) Hand coordinate system on the handrim

Figure 5

Illustration of forces and torques applied on the handrim. (a) Side view, (b) Back view

Figure 6

Flowchart of the hand-handrim positioning system program

Figure 7

Circuit diagram for coupling diode, D1 is emitter diode, D2 is receiver diode

Figure 8

The angles α, wi, φs, φe for a complete stroke cycle of the manual wheelchair propulsion

Figure 9

Propulsion force components with respect to global and hand coordinate systems

Figure 10

Propulsion torque components with respect to global coordinate system

Figure 11

Angular position of the hand on the handrim (φ) and wheel rotation angle (α) with respect to global coordinate system for two strokes

Figure 12

Propulsion torque components with respect to hand coordinate system

Figure 13

The total force (F_total) and the total effective force

Figure 14

The fractional effective force during the propulsion phase