Cylindrical Cam Electromagnetic Vibration Damper Utilizing Negative Shunt Resistance

Two common problems in utilizing electromagnetic dampers are addressed in this article. The first problem is the maximum available damping that can be created in an electromagnetic actuator using a positive resistive load. Maximum damping is achieved when the motor terminals are placed in a short circuit configuration, but it might not be enough in certain applications. As a solution, a method to produce negative resistance using power electronics and control techniques is presented in this article. The negative resistance cancels part of the resistance of the electromagnetic machine, which leads to producing larger electrical current in the actuator coils. As a result, higher damping levels are generated. The other contribution of this article is devising an effective motion rectification mechanism for converting the translational motion into rotary motion that drives an electric machine. To this end, a cylindrical cam mechanism is proposed which can provide longer strokes while keeping the geometry and size of the damper similar to the axial dampers used in automotive and bicycle dampers. The mechanism shows longer values for the ratio of stroke to maximum length compared to other designs reported in the literature.