MLS MMLS3, Operator'S Manual

Page: 36 / 48

MLS Test Systems Pty Ltd
Revised: April 2013
34
APPENDIX B: The lateral displacement system
The purpose of the system is to spread the wheel loads on the pavement
in the lateral direction from the centreline of the track by moving the
entire machine. It consists of the following parts:
1. Two base plates that can be anchored to the pavement
2.
Two “skate boards”. These fit under the adjustable legs of the
machine and each has four rollers that run on the base plates in a
lateral direction.
3. A small electric servo motor with a gearbox to drive the system.
The feedback potentiometer is mounted on the output shaft of
the gearbox inside a watertight cover.
4. An electronic control system that is mounted with the other
controls in the orange control box. The cable with the blue 3-
pin connector feeds current to the 12 Volt servomotor, while the
feedback signal runs through the cable with the small black 6-
pin connector.
The maximum displacement is 75mm (3”) to each side of the centre line.
This is infinitely adjustable down to zero by the multi-turn control knob
to the right of the counter in the control box. With a tire width of 80 mm
the total maximum track width is thus 230mm. Although the knob is
scaled from 0 to 100, it is only used up to a setting of 75.
To achieve a normal lateral distribution of the wheel loads, the wheels
spend more time near the centreline of the track than at the edges.
Displacement increments take place at constant intervals (about 25 sec.)
while the increments are varied to achieve the normal distribution. At
the maximum setting of the track width the wheels will spend about the
same time at each of the following distances from the centreline:
2.7mm, 8.5mm, 14.4mm, 20.7mm, 27.4mm, 36.1mm, 48.0mm and 75.0
mm. This approaches a normal distribution:
Y = (1/sqrt(2 * PI))* exp. (-z*z/2), with the 75mm position at z = 3.