A Proposal on the Dither

Abstract

The technics of adopting a dither to eliminate the dead zone or hysteresis caused by the static friction have often been used for a long time in measuring or indicating instruments. In spite of this fact, there has been no reasonable standard to select the optimal dither for electro-hydraulic servovalves up to now. In this paper, therefore, the nonlinear second order system with static and Coulomb friction was considered as a mechanical model to represent the mechanical characteristics (excluding the electromagnetic characteris tics) of the servovalves and the effects given to the system by the dither were analyzed. In consequence, several important points in selection of the dither were found by this analysis and they were proposed as a standard to give an adequate dither to the system for eliminating the dead zone or hysteresis due to the static friction. The effects of the dither exerted upon the electromagnetic and dynamic characteristics were not touched in this paper.