MAXIMIZING OUTPUT VOLTAGE OF A PIEZOELECTRIC ENERGY HARVESTER VIA BEAM DEFLECTION METHOD FOR LOW-FREQUENCY INPUTS

In micro-scale energy harvesting, piezoelectric (PZT) energy harvesters can adequately convert kinetic energy from ambient vibration to electrical energy. However, due to the random motion and frequency of human motion, the piezoelectric beam cannot efficiently harvest energy from ambient sources. This research highlights the ability of piezoelectric energy harvester constructed using a PZT-5H cantilever beam to generate voltage at any input frequency from human motion. An eccentric mass is used to convert the linear motion of human movement to angular motion. Then, using a magnetic plucking technique, the piezoelectric beam is deflected to its maximum possible deflection each time the eccentric mass oscillates past the beam, ensuring the highest stress is induced and hence the highest current is generated. For testing works, the frequency of oscillation of the eccentric mass is controlled using an Arduino Uno microcontroller. In this work, it is found that when given any input frequencies, the energy harvester produced a consistent AC voltage peak around 5.8 Vac. On the other hand, the DC voltage produced varies with respect to the input frequency due to the number of times the peak AC signal is generated. The highest DC voltage produced in this work is 3.7 Vdc, at 5 Hz, which is within the frequency range of human motion. This research demonstrated that energy can still be effectively harvested at any given low-frequency input, in the condition that the piezoelectric beam is being deflected at its maximum. ABSTRAK: Piezoelektrik dapat mengubah tenaga kinetik daripada getaran persekitaran kepada tenaga elektrik melalui penjanaan tenaga berskala mikro. Namun, PZT tidak dapat menjana tenaga dengan berkesan dari sumber persekitaran kerana pergerakan dan kekerapan pergerakan manusia adalah rawak. Kajian ini adalah mengenai keupayaan penuai tenaga piezoelektrik menggunakan bilah kantilever PZT-5H bagi menjana voltan pada sebarang frekuensi menerusi gerakan manusia. Jisim eksentrik digunakan bagi menukar gerakan linear manusia kepada gerakan putaran. Kemudian, teknik penjanaan piezoelektrik secara magnetik digunakan bagi memesongkan bilah piezoelektrik ke tahap maksimum. Bagi memastikan tenaga tertinggi dihasilkan, jisim eksentrik perlu berayun melepasi bilah PZT. Ayunan frekuensi jisim eksentrik ini dikawal melalui kawalan mikro Arduino Uno. Dapatan kajian menunjukkan bagi setiap frekuensi input, PZT ini dapat menghasilkan voltan AC yang konsisten, iaitu sekitar 5.8 Vac. Namun, voltan DC maksimum yang terhasil adalah berbeza-beza bagi setiap frekuensi input, iaitu berdasarkan bilangan kekerapan maksimum isyarat AC yang terhasil. Voltan DC tertinggi ialah 3.7 Vdc, pada 5 Hz, iaitu pada kadar frekuensi gerakan manusia. Ini menunjukkan bahawa tenaga masih dapat dihasilkan secara berkesan pada frekuensi rendah, dengan syarat bilah piezoelektrik terpesong pada tahap maksimum.

Barium titanate piezoelectric-film-based beam-array airflow sensor for wearable breath-monitoring application

This study presents a barium titanate (BaTiO3) film-based piezoelectric airflow sensor. This sensor integrated a piezoelectric beam array with a poly(dimethylsiloxane) orifice membrane as the core sensing component. The compact size of the micromachined device fit the requirements for a wearable device. The hydrothermally grown barium titanate film exhibited an orthorhombic crystal structure with good piezoelectric properties. We propose an algorithm to determine the airflow sensor performance using data from the measured piezoelectric signal and the displacement of the piezoelectric beam. This algorithm correlates the discharge coefficient of the core sensing component, Reynold’s number, airflow velocity, pressure difference across the component, displacement of the piezoelectric beam, strain of the barium titanate film, and generated charge from the sensor, which is rarely reported in the literature. The Young’s modulus and piezoelectric constant of the barium titanate film could also be derived as 100 GPa and 8 pC/N, respectively. Utilizing this algorithm and the generated piezoelectric signal of the sensor, important breath parameters of a young male subject at rest were monitored.

An asymmetric magnetic-coupled bending-torsion piezoelectric energy harvester: modeling and experimental investigation

This paper presents a detailed investigation on an asymmetric magnetic-coupled bending-torsion piezoelectric energy harvester based on harmonic excitation. There is an eccentricity between the shape center of moving magnets and the axis of the piezoelectric beam, which results in the bending and torsion simultaneously in working condition. The distributed mathematical model is derived from the energy method to describe the dynamic characteristics of the harvester, and the correctness of the model is verified by experiments. To further demonstrate the improvement performance of the proposed energy harvester, the bending-torsion energy harvester (i.e. magnetic-coupled was not configured) is experimented and compared. The theoretical and experimental results indicate that the average power increases about 300% but the resonance frequency decreases approximately 2 Hz comparing to the harvester without magnetic-coupled. According to the characteristic of distributed parameter model, the magnetic force and the size of the piezoelectric beam are investigated respectively. And the lumped-parameter model is introduced to analyze the steady-state characteristic. Accordingly, this paper provides a feasible method to improve performance for piezoelectric energy harvester.

On the consistency of two-phase local/nonlocal piezoelectric integral model

In this paper, we propose general strain- and stress-driven two-phase local/nonlocal piezoelectric integral models, which can distinguish the difference of nonlocal effects on the elastic and piezoelectric behaviors of nanostructures. The nonlocal piezoelectric model is transformed from integral to an equivalent differential form with four constitutive boundary conditions due to the difficulty in solving intergro-differential equations directly. The nonlocal piezoelectric integral models are used to model the static bending of the Euler-Bernoulli piezoelectric beam on the assumption that the nonlocal elastic and piezoelectric parameters are coincident with each other. The governing differential equations as well as constitutive and standard boundary conditions are deduced. It is found that purely strain- and stress-driven nonlocal piezoelectric integral models are ill-posed, because the total number of differential orders for governing equations is less than that of boundary conditions. Meanwhile, the traditional nonlocal piezoelectric differential model would lead to inconsistent bending response for Euler-Bernoulli piezoelectric beam under different boundary and loading conditions. Several nominal variables are introduced to normalize the governing equations and boundary conditions, and the general differential quadrature method (GDQM) is used to obtain the numerical solutions. The results from current models are validated against results in the literature. It is clearly established that a consistent softening and toughening effects can be obtained for static bending of the Euler-Bernoulli beam based on the general strain- and stress-driven local/nonlocal piezoelectric integral models, respectively.

Assessment of Miniature Piezoelectric Travelling-Wave Beam and Plate Robots

Different up-to-date utilizations have found several benefits in condensing the size of autonomous robots. Miniature traveling wave piezoelectric robots have proven to be appropriate for many of these applications. The principles of locomotion embraced in these robots are mainly inspired by natural biological locomotion and could be categorized by their movement through a specific medium. In this article, after having highlighted the amplifying effect of piezoelectric actuators generating the locomotion necessary for robotic requests, we will review the different types of such locomotion. Next, we will discuss the traveling wave piezoelectric resonant robots. Succeeding, we will look at the operation and usages of piezoelectric beam and plate robots. Finally, we will discuss the modeling aspects implicated in these robots and more generally, the modeling of piezoelectric patches stuck on thin structures. Keywords: piezoelectric, miniature, travelling-wave, locomotion, beam and plate robots

Piezoelectric Beam Finite Element Model and Its Reduction and Control

The paper deals with the development of the finite element method (FEM) model of piezoelectric beam elements, where the piezoelectric layers are located on the outer surfaces of the beam core, which is made of functionally graded material. The created FEM model of piezoelectric beam structure is reduced using the modal truncation method, which is one of model order reduction (MOR) method. The results obtain from reduced state-space model are compared with results obtain from finite element model. MOR state-space model is also used in the design of the linear quadratic regulator (LQR). Created reduced state-space model with feedback with the LQR controller is analysed and compared with the results from FEM model.