Farbod Khameneifar

A Piezoelectric Energy Harvester for Rotary Motion Applications: Design and Experiments

This paper investigates the analysis and design of a vibration-based energy harvester for rotary motion applications. The energy harvester consists of a cantilever beam with a tip mass and a piezoelectric ceramic attached along the beam that is mounted on a rotating shaft. Using this system, mechanical vibration energy is induced in the flexible beam due to the gravitational force applied to the tip mass while the hub is rotating. The piezoelectric transducer is used to convert the induced mechanical vibration energy into electricity. The equations of motion of the flexible structure are utilized along with the physical characteristics of the piezoelectric transducer to derive expressions for the electrical power. Furthermore, expressions for the optimum load resistance and maximum output power are obtained and validated experimentally using PVDF and PZT transducers. The results indicate that a maximum power of 6.4 mW at a shaft speed of 138 rad/s can be extracted by using a PZT transducer with dimensions 50.8 mm × 38.1 mm × 0.13 mm. This amount of power is sufficient to provide power for typical wireless sensors such as accelerometers and strain gauges.

Modeling and Analysis of a Piezoelectric Energy Scavenger for Rotary Motion Applications

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.

Energy Harvesting From Pneumatic Tires Using Piezoelectric Transducers

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.Copyright

Vibration Energy Harvesting From a Hydraulic Engine Mount via PZT Decoupler

Engine is one of the major sources of vibration in a vehicle. An engine mount is the device for isolating the body of vehicles from these vibrations. Harvesting the ambient energy of the vibrating fluid inside a hydraulic engine mount and converting it to the electricity is discussed in this paper. The energy harvester mechanism consists of two piezoelectric bimorph cantilevers with tuning tip masses with the beams covered by a thin layer of rubber. The deflections of the thin rubber layer induce vibrations in the beams which result in electrical power to be generated through the piezoelectric beams. The generated power can be used to recharge the battery for pressure sensors inside the engine mount. This novel harvester is tuned to work in the low frequency, high amplitude excitation environment of the engine. A mathematical model for this energy harvesting application is derived in this paper. Based on this model, the optimum load of the electrical circuit is also obtained. Simulation studies demonstrate performance of the energy harvester and predict the output voltage and maximum power which can be extracted from the energy scavenging device.Copyright

Piezo-Actuated Active Decoupler Hydraulic Engine Mount

Hydraulic mounts are widely used in the automotive industry to isolate the engine and chassis from each other. For these passive economic vibration isolators the parameter values and characteristics are fixed. As a result, they cannot properly attenuate the complicated vibration transmitted from the engine. In this paper development of a new active mount using piezoelectric materials is described. The typical decoupler of the mount has been replaced by a set of piezoelectric actuators. The actuator consists of two piezoelectric bimorph cantilevers and the beams are covered by a thin rubber layer. The actuator moves upon receiving the signal from the controller, and it changes the dynamic performance of the mount accordingly. Mathematical modeling of the active mount is derived and the simulated results are presented for different voltage signals. Simulations demonstrate the performance of the designed active engine mount to deal with complicated vibration patterns.Copyright

Extracting sectional contours from scanned point clouds via adaptive surface projection

This paper presents a new and fully automatic method to extract cross-sectional contour profiles of a physical object from the point cloud data scanned from its surface. Correctly extracting the sectional contours is of particular importance in the quality inspection of airfoil blades as the tolerances specified on a manufactured aero-engine blade are generally imposed at specific blade sections. The collected point cloud via 3D laser scanning is, however, distributed all over the blade surface rather than at the desired specific sections. In fact, no point in the point cloud is located exactly on the sectional planes. The desired sectional data have to be extracted from the nearby data points. If the underlying smooth surface geometry of the point cloud in the vicinity of a nearby data point can be approximated by a mathematical function, the approximated local surface formulation can be used to project the nearby point onto the desired sectional plane along a curvilinear trajectory. This is achieved in this work by fitting a local quadric surface to the neighbouring points of the point of interest. A systematic approach to establish a balanced set of neighbouring points is employed to avoid bias in fitting the local quadric surface as well as to guide the selection of points to be projected onto the sectional plane. The projected points are then used to construct the desired sectional contour profile. Implementation results have demonstrated the superior performance of the proposed fully automatic method in comparison with the existing methods.

Establishing a balanced neighborhood of discrete points for local quadric surface fitting

Abstract This paper presents a novel algorithm to establish a balanced neighborhood of points for reliable local quadric surface fitting, a common task in point cloud data processing. The underlying smooth surface geometry of a point cloud in the vicinity of a point can be locally approximated by the best fitted quadric surface at the point. The quality of the fitted surface considerably depends on what neighboring points are selected for the fitting. Specifically, if the selected neighboring points carry a biased distribution, the fitted geometry becomes biased, resulting in loss of accuracy in the fitting. The presented algorithm in this paper is able to reliably select neighboring points considering measures of both distance and direction. The main feature is the development of a geometric relationship, named as Territory Claiming, between the selected and the candidate neighboring points. The fundamental principle is for the selected point set to cover the whole neighborhood domain without redundancy. The selection procedure starts with a distance-based sequence of neighboring points with the territory claiming relationship functioning as a filter to establish a well-balanced neighborhood. The neighborhood can be expanded to incorporate sufficient number of points for the quadric surface fitting while maintaining the balance of the overall neighborhood. The implementation results have demonstrated that the presented method is robust and selects local neighboring points with superior fitting performance in comparison with the distance-based neighbors, mesh neighbors, and elliptic Gabriel graph neighbors.

Section-specific geometric error evaluation of airfoil blades based on digitized surface data

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