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A methodology for measuring rearward amplification

In: Proceedings, International Symposium on Heavy Vehicle Weights and Dimensions, 3rd, 28 June - 2 July 1992, Cambridge, England.

Authors: Paul Fancher, C. B. Winkler

A new type of objective test procedure for assessing the obstacle avoidance capabilities of articulated vehicles is described in this paper. The method quantifies rearward amplification. The measurement method involves driving the lorry round a test course which has been laid out to excite the rearward amplification tendencies of multi- articulated heavy lorries. The lorry is instrumented to measure lateral accelerations at the tractor's front axle and at the centre of gravity of the sprung mass of the last trailer. The rearward amplification (RA) is the ratio of a) the "output" divided by b) the "input". The output is obtained by measuring the maximum absolute value of the lateral acceleration of the last trailer. The "input" is quantified by computing the root mean square value of the lateral acceleration value over the lateral manoeuvring section of the test course. The value of the input is obtained by multiplying the root mean square value of the input by the square root of 2 to provide an estimate of the amplitude of an equivalent sinusoid of lateral acceleration. The measures of rearward amplification determined by this procedure are in close agreement with those predicted by the yaw/roll simulation.