Thus the number of steps required to adjust
the seat need to be low, so that the seat adjustment is fast.
Two pictures of the suspension seat prototype (third version),
with its adjustment controls, are shown in Figs. 1 and 2. A
lever allows for the simultaneous adjustment of the seat rotation
(40° to the right and 40° to the left, by increment of 8°),
backward and forward translation (16 cm total) as well as
lateral translation (18 cm total). A switch allows for a total
height adjustment of 15 cm, by adding or removing air from
the suspension bladder. However, by leaving 3 cm at each
end to avoid end-stop impacts, a remaining 9 cm is usable as
total height adjustment. The selection of the cushion and suspension
have been previously optimized to minimize the SEAT
value for the MR-73 motor car vibration spectra10). Indeed,
the cushion has a resonance around 6 Hz, amplifying by more
than a factor of 2 the vertical vibration. The suspension is
attenuating that same frequency component, resulting in an
optimum cushion/suspension combination10). To allow the
suspension implementation in the small space of the operator
cab, the suspension has been rotated by 90°, fitting the suspension
largest dimension in the lateral direction of the cab,
or in the y-axis direction during laboratory testing.