A quasi-static state examination of handle forces and translational acceleration at impending planar motion for the four-caster manually manoeuvred vehicle

Abstract

Motion resistance, handle forces, and translational acceleration of a four-caster manually manoeuvred vehicle (FMV) are examined at impending planar motion. FMV-wheel angular acceleration directions occur in polygon regions of the FMV-body translational acceleration. The mass centre force and torque, which balance motion resistance, using a Coulomb model, are non-linear and discontinuous functions of FMV-body acceleration. The transformation from mass centre force and torque to a dynamically equivalent handle-force measure is examined. A reference manoeuvre with a single set of caster orientations shows that FMV-body translational acceleration has a substantial effect on handle-force measure variation: an almost three-fold variation exists. The reference manoeuvre analysis is repeated with a representative sample of all caster orientations. The mean handle-force measure for this sample also shows a substantial handle-force measure variation, e.g. relatively high handle forces occur when the translational acceleration is directed as the impending change of FMV heading. This effect is independent of motion resistance values. As the handle forces required to balance motion resistance vary substantially depending on FMV-body translational acceleration, spatial constraints may have a substantial effect on handle forces. A relationship between handle forces and spatial constraints indicates that architectural planning has health and safety implications for the FMV operator.