Effect of Electromagnetic Damping on System Performance of Voice-Coil Actuator Applied to Balancing-Type Scale

Changing a time-varying magnetic field induces an electromotive force (EMF) in non-magnetic conductive materials, resulting in an eddy current across the conductor. Thus, electromagnetic damping can be used as viscous damping. This study theoretically and experimentally investigates the electromagnetic damping characteristics of a bobbin-wounded coil with an attached cantilever beam floating over a permanent magnet; the beam is balanced by electromagnetic force compensation (EMFC) instead of applied weight. System identification is carried out for the mass (m), damping coefficient (c), and spring constant (k) values. The presence of a back EMF seen in either conductive or non-conductive material responses in the experiments includes the step input and corresponding output responses to measure the electromagnetic damping force with and without a voice-coil actuator (VCA). The results were validated using bobbins of conductive (aluminum) and non-conductive (plastic) materials. The experimental results for the conductive material show that the electromagnetic damping force is 10 times greater than that of the non-conductive material; the opposite was true in the case without a VCA, where the force was almost zero for the non-conductive material. In conclusion, conductivity is directly related to the electromagnetic damping force, which affects the performance of a VCA.