A piezoelectric device is introduced and modeled to directly interact with the tires of passing vehicles and generate electrical power for roadside applications. Piezoelectric beams are vertically placed on the surface of the road to generate energy from the load of passing vehices. A metal cap is connected to the top end of the bimorphs. The vertical motion of the metal cap is limited by the containing fixture of the device. Tires of the passing vehicles pass over the metal cap and force the bimorph into buckling. The buckling of the piezoelectric beam generates significant amount of power. By controlling the extent of deformation of the beam we make sure that the beam is not damaged by the buckling. To this end, the amount of axial recession of the metal cap (equal to axial deformation of the beam) is precision controlled by the containing fixture. When the beam deflects it axially shrinks due to geometric nonlinearities. This lowers the metal cap. After a certain amount of deformation the metal cap rests on the containing fixture and the tire load is no more transmitted to the piezoelectric beam.
In this paper the performance of the proposed energy harvesting device is analytically modeled. Geometric nonlinearities and piezoelectric couplings have been included in the model. The vibrations of the device are transient. Power is generated when the tire pushes down the metal cap and when the metal cap springs back after the tire has passed. The design criteria for the device are discussed. It is demonstrated that the device can be realized with commonly used piezoelectric patches and can generate hundreds of milliwatts from the moving traffic. The device is not prone to resonance and generates notable amounts of power from passing of each tire. It therefore can be used as a self-sufficient sensor for traffic control.