Abstract: During the course of electric steering engine’s transmission experiment, the measuring errors generated from mechanical installation, bearing friction and electrical machine drivers’ nonlinearities are likely to be converted to ratio’s measurement error, and decrease precision. Subjected to the speed reducer, the mathematical model of such system is established by means of dynamics equations, the measurement errors generated from mechanical installation and bearing friction are regarded as determined system error by theoretical analysis, and a new method is provided of preprocessing actual measuring data and improving ratio precision according to simulation results. The calculated results imply this method is to some extent able to compensate the measurement errors from electrical machine driver nonlinearities.

Key words: Speed reducer of the electric steering engine, Transmission characteristics, Error analysis, Compensation