Theory and validation of the motion resistance mechanism of four-caster manual vehicles

Abstract

The four-caster manually manoeuvred vehicle is a crucial device for goods movement and disability transport. While there are manual handling related health and safety concerns, no dynamical theoretical-empirical investigation exists. Theoretical examination demonstrates that, in loose terms, the motion resistance effects are affected by vehicle-frame translational velocity direction: the proportion of the moment effect to translational effect produced by motion resistance varies in a highly non-linear way depending on the vehicle-frame velocity direction. An empirical study is devised from the theory. As the intention was to investigate the presence of this phenomenon in real use, human operators were used: they made planar manoeuvres from static equilibrium with a self-selected load while attempting to maintain 11 (maximum) different centres of zero velocity which related to the velocity directions. Results demonstrate that (1) the proportion of moment motion resistance effect to translational motion resistance effect does vary and (2) it is motion resistance rather than inertial forces which are the first-order effect. These results are an essential first step in understanding the manoeuvring difficulties and health and safety issues which arise with these vehicles.

A novel four-caster manual vehicle manoeuvring investigation: Higher loading-weights require larger turning spaces

“…As experimental development and results are the focus of this work, a qualitative account is provided: the aim is to provide a useful, plausible explanation and avoid lengthy text. The interested reader will find initial treatment in Abraham and Johnson, 1 a complete account in Abraham 18 and a validation of the kinematic–dynamics relationship in Abraham et al 16…”

“…The proportion of these two motion resistance effects varies if the centre of zero velocity is varied: this is predicted by theory and has been demonstrated empirically. 16…”

“…First, it has been shown that the initial centre of zero velocity for a standard wheelchair is described by a point anywhere on a line, whereas for the four-caster vehicle, the initial centre of zero velocity is described by a point anywhere on a plane. 16 Second, the four-caster vehicle has two more casters than the standard wheelchair and each caster can be set to any initial orientation. While the dimensions of manoeuvring spaces in buildings have been determined experimentally, 17 such empirical data on its own do not guarantee an understanding of the four-caster vehicle.…”

“…The useful centres of zero velocity, that is, those that avoid collisions, are determined by the relative positions of walls, fixtures and vehicle, with load or occupant size. It has been shown that the centres of zero velocity have a substantial effect on motion resistance 16 and consequentially on the operator’s maximum comfortable loading weight (definition to follow). 18 The relationship between wall positions and maximum comfortable loading-weight is therefore of investigative interest for two reasons.…”

Posters

“…A novel tool, constrained-outlines (Abraham and Johnson 2006), is being developed for many types of wheelchairs and wheeled disability vehicles by the application of engineering science (Abraham 2012, Abraham et al 2013. Occupational therapists can use these research based tools by following a few straightforward rules (Abraham et al, In press).…”