In this paper, an energy saving variable damping seat suspension system is designed, manufactured, modeled, and validated. A continuously controllable electromagnetic damper (EMD) system, which consists of a permanent magnet synchronous motor, a three-phase rectifier, a metal-oxide-semiconductor field-effect transistor (MOSFET) switch, and an external resistor, is built and tested first. Its model parameters have been identified based on the test results. The EMD's damping property can be controlled by exerting pulsewidth modulation (PWM) signal with different duty cycles on the MOSFET switch. The EMD is integrated with a planetary gearbox to amplify its torque output, and the formed variable damper is installed on the center of the scissors structure of a seat suspension. By analyzing the EMD test results and the seat suspension's kinematic, the controllable damping of the proposed seat suspension is derived as 112 to 746 N·s/m. A control method for vibration isolation is proposed based on the system model. The proposed variable damping seat suspension and its controller are validated on a six-degrees-of-freedom vibration platform in both frequency domain and time domain; a well-tuned commercial passive seat suspension is also tested for comparison. The test results show that the controlled variable damping seat suspension has better performance in vibration isolation than the proposed seat with highest and lowest damping, and the conventional passive one. In the meantime, the RMS value of the system harvestable power is 1.492 W, and the power consumption of the PWM control signal is small. Therefore, this variable damping seat suspension can improve ride comfort with ignorable energy cost.
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