The Use of Magnetorheological Fluid Dampers to Reduce Servo Drive Velocity Jumps due to Load Changes

A problem of velocity control of servo drives in the presence of high load changes is described and studied in this article. The rapid fall of load causes an unexpected jump of the movable elements of the machine. The increase of velocity is harmful and may be reduced by usage of electrically controllable dampers. Such dampers employ a magnetorheological fluid that changes its properties in the presence of a magnetic field. This results in a damper whose characteristics may by adapted in real time to the user’s requirements. In this article the construction of such a damper is described and a machine tool servo drive with an MRF damper is presented. Its simulation model is proposed and some simulation and control analyses are made. Finally experimental results of servo drive velocity control in the presence of load changes are presented. The article is focused on velocity jump reduction which is caused by load decrease.