Designing an Electromagnetic Damper

When it comes to active or semi-active suspension, one of many design challenges is the ability to dynamically change the damping rate of a shock absorber. Two fundamental means of accomplishing variable damping are by changing the restriction imposed on the fluid or changing the viscosity of the fluid. One way to change the restriction imposed on the fluid is by using a valve controlled by a solenoid. As more current flows through the solenoid a plunger gets pulled into the center of the coil, which acts against a mechanical spring that pushes it to a default state. There are specific kinds of fluids, such as ferrofluids or magnetorheological fluids, that change their viscosity in the presence of magnetic fields. This paper aims to guide the reader through the design of an electromagnetic damper, how to derive theoretical performance criteria from a semi-active suspension system, and design optimization considerations. The design will test three different coil specifications, including size, wire size, location, applied voltage, and amperage. The experimental evaluation was conducted as a qualitative proof-of-concept to verify the presence of field-dependent viscosity and damping behavior under low-frequency manual excitation. Quantitative performance assessment was performed using analytical and numerical modeling to determine whether the proposed design satisfies semi-active suspension damping requirements.