Passenger car testing: acceleration measurement on dynamometer and road

The accurate simulation of road conditions on chassis dynamometers requires the separate evaluation of both dissipative and inertial components of vehicle loading in the laboratory and on the road. This requires the measurement of transient driving force, speed and acceleration by techniques which are equally applicable to laboratory and road. The paper reviews techniques for measuring vehicle speed and acceleration, and examines the characteristics of a pulse generator on the drive–shaft in detail. The precision of velocity and acceleration data is related to the bandwidth required, and the central role of the distance increment per pulse is studied. The change in the distance increment per pulse is presented as a function of speed and lyre inflation pressure, and its effect on the speed and acceleration data is identified. Variations in the sampling interval of approximately 0.1% are shown to have an appreciable effect on the precision of acceleration data, and a technique for overcoming this problem is presented.