A Multi-Resonant Speed Piezoelectric Beam Device for Harvesting Energy from Vehicle Wheels 2020-01-1236
This work analyzes a cantilevered piezoelectric beam device for harvesting energy from the simultaneous rotation and translational vibration of vehicle wheels. The device attaches to the wheel rim so that it displaces tangentially during operation. A lumped-parameter analytical model for the coupled electromechanical system is derived. The device has one natural frequency that is speed-dependent because of centripetal acceleration affecting the total stiffness of the device. Even though the device has one natural frequency, it experiences three resonances as the rotation speed varies. One resonance occurs when the rotation speed coincides with the speed-dependent natural frequency of the device. The other two resonances are associated with excitations from the vibration of the vehicle wheel. The device’s parameters are chosen so that these three resonances occur when the wheel travels near 30 mph, 55 mph, and 70 mph. There are two excitation frequencies that give these resonant speeds, and both choices differ from the conventional selection of the device’s natural frequency to match the excitation frequency. Instead, the device’s natural frequency must be either above or below the natural frequency for these resonances to occur at the intended speeds. The maximum energy harvested by the device is more than 45 milliwatts at each resonance. The speed bandwidths are quantified near each resonance, and, even though the resonances are linear, bandwidths of a few mph demonstrate the robustness of the device to changing vehicle speeds. The sensitivity of the power harvested by the device to the input vibration frequency and equivalent resistance of the electrical load is numerically examined. The power harvested by this device is sufficiently large to permit sensing and communication for next generation intelligent tire applications.