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This paper presents modeling and analysis of a piezoelectric mounted rotary flexible beam that can be used as an energy scavenger for rotary motion applications. The energy harvester system consists of a piezoelectric bimorph cantilever beam with a tip mass mounted on a rotating hub. Assuming Euler-Bernoulli beam equations and considering the effect of a piezoelectric transducer, equations of motion are derived using the Lagrangian approach followed by relationships describing the harvested power. The equations provide a quantitative description of how the hub acceleration and gravity due to the tip mass contribute power to the energy harvester. In particular, expressions describing optimum load resistance and the maximum power that can be harvested using the proposed system are derived. Numerical simulations are performed to show the performance of the harvester by obtaining tip velocities and electrical output voltages for a range of electrical load resistances and rotational speeds. It is shown that by proper sizing and parameter selection, the proposed system can supply enough energy for operating wireless sensors in rotating mechanisms such as tires and turbines.

The concept of harvesting energy in our surrounding has recently drawn global attention. Harvesting the ambient energy of the deflected tire and convert it to electricity is discussed in this paper. An Elastic pneumatic tire deflects due to the load it carries. This deflection appears as a contact patch to the road surface. Initially, the concept of the tire deflection will be discussed. This deflection is then related to the wasted energy used for deflection. The dependency of this energy to some important parameters such as the tire air pressure, vehicle speed and tire geometry and forces are primarily discussed. To harvest the deflection energy different well established methods are exists. Due to the tire environment, piezoelectric transducers can serve as the best option. Those transducers are traditionally used to produce mechanical motion due to the applied electrical charges. This material is also capable of generating electrical charges by mechanical motion and deflections. For the tire energy harvesting application, the piezoelectric stacks can be mounted inside a tire structure such that electric charge is generated therein as the wheel assembly moves along a ground surface. For this application, lead-zirconate-titanate (PZT) is selected. The PZT inside the tire is modeled as a cantilever beam vibration in its first mode of vibration. The frequency of vibration is calculated based on the car speed, tire size, and PZT stack length. A mathematical model for this energy harvesting application is derived. Based on this model, the optimum load of the electrical circuit is also found. Finally the amount of energy harvested from tire using PZT is calculated. Although this energy is not significantly high, it will be enough to provide power for wireless sensors applications.

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