Fig 1.
Test stand with strain gauges W1–W4 and the reaction force at the supports of the weighing scale platform R1–R4.
Fig 2.
Diagram including data for determining the position of the centre of gravity, where: CG—Centre of gravity, πi—One of four side planes, Ri—Reaction of the support of the weighing scale platform, fij−position of the centre of gravity on one of the side planes, L—Platform length, H—Platform width.
Fig 3.
Diagram representing the ellipse used to determine the variability of the position of the centre of gravity of the human body based on the measured points of the position of the centre of gravity, where α—Inclination of the axis of the ellipse, a—Semimajor axis, b—Semiminor axis.
Fig 4.
Test stand for simulating operating conditions and measuring dynamic parameters of a wheelchair, see description in the article, where A—Weighing scale platform, B—Strain gauges, C—Electric motors, D—Traction rollers, E—Incremental encoders, F—Tilting arm.
Fig 5.
Tested wheelchair at the test stand, where A—Multispeed hub gearbox.
Table 1.
Test configurations: Velocity vi, wheelchair tilt angle ki and gear ratio pi.
Fig 6.
Diagrams of regions of the position of the centre of gravity for three gears ratios p1–i = 1.96 (A), p2–i = 1 (B), p3–i = 0.51 (C), medium regions of the position of the centre of gravity (D) and location of medium centre of gravity (E), where test—Independent measuring test.
Fig 7.
Diagrams of regions of the position of the centre of gravity for three propulsion velocities v1–v = 40 ppm (A), v2–v = 45 ppm (B), v3–v = 50 ppm (C), medium regions of the position of the centre of gravity (D) and location of medium centre of gravity (E), where test—Independent measuring test.
Fig 8.
Diagrams of three regions of the position of the centre of gravity at three wheelchair tilt angle k1–β = 0° (A), k2–β = 1.5° (B), k3–β = 5.4° (C), medium regions of the position of the centre of gravity (D) and location of medium centre of gravity (E), where test—Independent measuring test.
Table 2.
Parameters of the ellipses describing the region of variability of the position of the centre of gravity for selected operational parameters of the wheelchair and three gear ratios, where i—Gearbox ratio, test—Independent measuring test, α—Inclination of the axis of the ellipse, a—Horizontal axis of the ellipse, b—Vertical axis of the ellipse, M—Average value, SD—Standard deviation, xCG—Average position of the centre of gravity on x-axis, yCG—Average position of the centre of gravity on y-axis, ρ—The number of measured points inside the ellipse.
Table 3.
Parameters of the ellipse describing the region of variability of the position of the centre of gravity for the selected operational parameters of the wheelchair and three propulsion velocities, where v—Frequency of push, test—Independent measuring test, α—Inclination of the axis of the ellipse, a—Horizontal axis of the ellipse, b—Vertical axis of the ellipse, M—Average value, SD—Standard deviation, xCG—Average position of the centre of gravity on x-axis, yCG—Average position of the centre of gravity on y-axis, ρ—The number of measured points inside the ellipse.
Table 4.
Parameters of the ellipses describing the region of variability of the position of the centre of gravity for selected operational parameters of the wheelchairs and three wheelchair tilt angles β, where test—Independent measuring test, α—Inclination of the axis of the ellipse, a—Horizontal axis of the ellipse, b—Vertical axis of the ellipse, M—Average value, SD—Standard deviation, xCG—Average position of the centre of gravity on x-axis, yCG—Average position of the centre of gravity on y-axis, ρ—The number of measured points inside the ellipse.