Wheelchair Forces. The Forces And Kinematics Involved In Self Propelling A Wheelchair - Essay Example

1 Methodology 1 Hypothesis and Experimental Design The overall aim of the study was to better understand the forces and kinematics involved in selfpropelling a wheelchair. This is in relation to the castor forces and hand rim forces generated through pushing. From the literature gathered as summarised in the Literature Review, the hypotheses of the study are: Hypothesis 1: H0: There is no significant difference in the castor forces generated during functional mobility tasks when the rear axle is moved forward. H1: There are significantly less castor forces generated when the rear axle is moved forward (less stable) during functional mobility Hypothesis 2: H0: There is no significant difference in push rim forces (Peak Mz) when the rear axle is moved forward during functional mobility. H1: There are significantly less push rim forces generated (Peak Mz) during functional mobility task when the rear wheel is moved forward. No need for assumptions since hypothesis was already used 1.2 Ethical Approval The study took place at the Stanmore Clinical Research Facility (SCRF) at the Royal National Orthopaedic Hospital (RNOH), Stanmore. All participants gave informed consent to participate in the study. (Refer to Appendix __ ). The proposal for the study was approved by the joint RNOH and Institute of Orthopaedic and Musculoskeletal NHS Local Research Ethics Committee. 1.3 Dynamic Stability Measurement 1.3.1 Study Design A quantitative analytical research was undertaken to establish forces generated by wheelchair users when performing a series of functional mobility tasks. The generation of forces were gathered through the front castors of the wheelchair and through the push rim. The forces generated are then recorded and analysed to investigate the hypothesis stated. The wheelchair users P:C Ratio was then calculated to establish whether the users exceeded their capacity when performing such tasks and whether Rear Axle Position (RAP) was found to influence this. 1.3.2 Control Wheelchair As there are no existing methods for testing dynamic wheelchair stability of a manual wheelchair, an instrument was developed. Consequently, a force sensitive castor was designed to look at this pattern in more detail. The chosen model was a 17" Quickie GPV, rigid frame lightweight wheelchair. The model was chosen as the most adaptable size for most test participants and was then configured to suit each individual's needs. The wheelchair weighs 18kg with nearly 7kg of added weight due to an attached equipment. The wheelchair is fitted with 25" solid tyres to accommodate the Smart Wheel technology and 5" solid castors. There is a 3-degree camber on the rear wheels. Figure 1. Quickie GPV Wheelchair Each participant was set up in the Laboratory's test wheelchair. Only one wheelchair could be used as the instrumentation was not interchangeable between wheelchairs. 1.3.3 Development of the Castor Force Transducer An earlier work at ACDS (spell out acronym) (WOWSUP, 2005) using a wheelchair Ergometer showed that there was a substantial weight shift between castors and rear wheels during the propulsion cycle, which subsequently increased with the pushing resistance. The Ergomenter used force plates beneath the front castors during propulsion. The study explored what happened to the Ergometer when users propelled their wheelchairs to perform functional activities. A force sensor was integrated into the castor stem of the wheelchair to examine weight shift during functional mobility. This was initially constructed in combination with the castor stem and a number of washers to accommodate its size. Figure 2. The Wheelchair Ergometer 1.3.4 Calibration of the castor force transducer This was completed by loading the wheelchair with known masses and recording the voltage output from both the force transducer in the castor and the force plate underneath it (force plates already calibrated for previous testing). This calibration produced 2 curves in order to demonstrate whether a linear relationship was achievable between the output and the masses. Initial testing was done on the Ergometer in a semi - static position. This testing allowed the researcher to examine in detail, how the weight distribution changes during a propulsion stroke, both through the force plates under each castor and also through the dynamic castors themselves. Once data was collated and transferred into Excel for analysis, it allowed the researcher to plot the information, using a scatter graph, to generate a calibration curve. However, a conversion equation was not established as the initial readings were unacceptable. Figure 3. Scatter graph of initial readings The graph shows the recorded propulsion cycle for the right force plate and the right castor. It has been labelled to show the direction of the propulsion cycle. Read More