G. Uma

Pyroelectric-Based Solar and Wind Energy Harvesting System

Inherent scarcity of thermal sources with a time varying temperature profile is the reason why the pyroelectric-based energy harvesting is not as prominent as its counterpart, thermoelectric generators, in the thermal energy harvesting domain. In this paper, a practical solution for generating thermal oscillations required for sustainable pyroelectric-based energy harvesting from the solar and wind energies, is presented. The main focus of the work is to modulate the concentrated solar radiation using a vertical axis wind turbine for producing higher rate of change of temperature on the pyroelectric material. The maximum energy and power density produced by the prototype device using PZT-5H as pyroelectric material are 6.927 mJ/cm3/cycle and 421.18 μW/cm3, respectively, and on average it can produce a power density of 304.78 μW/cm3, which concurs with the theoretical model.

A New Resonance-Based Method for the Measurement of Nonmagnetic-Conducting-Sheet Thickness

A measurement system to measure the thickness of a nonmagnetic conducting sheet is designed, simulated, developed, and tested. The measurement system is designed as a resonant system with a cantilever being a resonating structure with piezoelectric excitation and detection. The permanent magnets at the tip of the cantilever beams produces an oscillating magnetic field, and the insertion of the conducting sheet in the magnetic field produces eddy current on it. The magnetic field produced due to eddy current alters the magnetic field produced by the permanent magnet. This alters the natural frequency of the measurement system as the stiffness due to the magnetic force varies with thickness. The simulation and experimental results show that the resonant frequency of the measurement system varies linearly with thickness and sensitivity is found to be higher for the material having higher conductivity.

Design of Microcontroller Based Resonant Sensor with Piezoelectric Excitation and Detection

Abstract This paper presents design, development, and testing of a resonant sensor to measure mass in the range of 0–10 grams. The main feature of the proposed sensor is the microcontroller based closed loop electronics. The advantage of using the microcontroller is that the method can be easily extended for any range of measurand.

Design and Simulation of MEMS Devices using Interval Analysis

Modeling and simulation of MEMS devices are used to optimize the design, to improve the performance of the device, to reduce time to market, to minimize development time and cost by avoiding unnecessary design cycles and foundry runs. The major design objectives in any device design, is to meet the required functional parameters and the reliability of the device. The functional parameters depend on the geometry of the structure, material properties and process parameters. All model parameters act as input to optimize the functional parameters. The major difficulty the designer faces is the dimensions and properties used in the simulation of the MEMS devices can not be exactly followed during fabrication. In order to overcome this problem, the designer must test the device in simulation for bound of parameters involved in it. The paper demonstrates the use of interval methods to assess the electromechanical behaviour of micro electromechanical systems (MEMS) under the presence of manufacturing and process uncertainties. Interval method guides the design of pullin voltage analysis of fixed-fixed beam to achieve a robust and reliable design in a most efficient way. The methods are implemented numerically using Coventorware and analytically using Intlab.

Cantilever piezoelectric energy harvester with multiple cavities

Energy harvesting employing piezoelectric materials in mechanical structures such as cantilever beams, plates, diaphragms, etc, has been an emerging area of research in recent years. The research in this area is also focused on structural tailoring to improve the harvested power from the energy harvesters. Towards this aim, this paper presents a method for improving the harvested power from a cantilever piezoelectric energy harvester by introducing multiple rectangular cavities. A generalized model for a piezoelectric energy harvester with multiple rectangular cavities at a single section and two sections is developed. A method is suggested to optimize the thickness of the cavities and the number of cavities required to generate a higher output voltage for a given cantilever beam structure. The performance of the optimized energy harvesters is evaluated analytically and through experimentation. The simulation and experimental results show that the performance of the energy harvester can be increased with multiple cavities compared to the harvester with a single cavity.

Normal limits of ECG measurements related to atrial activity using a modified limb lead system.

Objective: The present study was designed to derive the normal limits of a new ECG lead system aimed at enhancing the amplitude of atrial potentials through the use of bipolar chest leads. Methods: Sixty healthy male subjects, mean age 38.85±8.76 years (range 25 to 58 years) were included in this study. In addition to a standard 12-lead ECG, a modified limb lead (MLL) ECG was recorded for 60 sec with the RA electrode placed in the 3rd right intercostal space slightly to the left of the mid-clavicular line, the LA electrode placed in the 5th right intercostal space slightly to the right of the mid-clavicular line and the LL electrode placed in the 5th right intercostal space on the mid- clavicular line. Results: In the frontal plane, the modification of limb electrode positions produced significant changes compared to standard limb lead I and II. The mean P wave amplitude was 111±17μV in MLL I and 64±16μV in standard limb lead (SLL) I (p<0.001). Similarly it was 118±22μV in MLL II and 100±27μV in SLL II. No statistically significant changes were seen in V1-V6 due to modification of the Wilson central terminal electrode positions. Conclusion: The modification of limb electrode placement leads to changes in the amplitude of the P waves in the MLL leads I and II compared to SLL leads I and II in healthy subjects. These changes may be of importance in the detection of atrial electrical activity.

Simple liquid pumping system using piezoelectric actuated cantilever beam

A simple liquid pumping system is designed using a piezoelectric actuated cantilever beam with a glass tube attached to its tip. The flowrate of the pump is proportional to the tip displacement and vibrating frequency of the cantilever beam. The flowrate linearly increases up to 0.53 mL/s for water with actuation voltage (with amplitudes up to 300 V(p-p)) applied to the piezoelectric actuator. The effect of other important parameters such as viscosity of the liquid, level of the liquid in the vessel and tube diameter on the flowrate of the pump is experimentally evaluated. The results demonstrate that the proposed pump is applicable to liquids with viscosity ranging from 0.23 to 170 mPa s.

New observation on automatic phase adjustment of a smart cantilever resonator

The condition for producing sustained oscillation during the placement of additional mass on a piezo sensed/actuated cantilever beam and diaphragm structure is derived. The phase condition for continuous oscillation of these structures is met automatically by adjusting the phase angle of the vibrating structure with a resistor–capacitor network in feedback. The concept is evaluated for the measurement of mass analytically, through numerical simulation, and is verified experimentally.

Piezoelectric Energy Harvester With Shape Memory Alloy Actuator Using Solar Energy

A piezoelectric cantilever beam-based energy harvester working with solar energy is proposed in this paper. The piezoelectric cantilever beam is excited by a shape memory alloy (SMA) spring actuator. The heating and cooling of the SMA actuator is done by designing an appropriate piping and transport system with water as a working fluid. The frequency and amplitude of excitation force exerted by an SMA actuator to the piezoelectric cantilever beam depend on the flow rate of water used for heating and cooling of SMA and the temperature of the water. The energy harvester is modeled analytically and fabricated to evaluate its performance in the laboratory. The analytical and experimental results show that higher output voltage from the energy harvester can be obtained with higher water temperature and frequency of the output voltage is limited to the dynamics of the SMA actuator. The voltage generated with the proposed energy harvester at the flow rate of 24 ml/s with the temperature of 70 °C is found to be 12 V. The harvester utilizes only the solar energy for its operation and hence the proposed design is a new addition to the area of energy harvesting using piezoelectric cantilever beam.

A new self-sensing electronics for piezoelectric resonance sensor

A new self-sensing electronics for a piezoelectric-excited and piezoelectric-sensed cantilever-based resonant sensor is proposed. The self-sensing is achieved by using the positive half cycle of the excitation signal for actuation and sensing during negative half cycle. The proposed self-sensing electronics has been proven effective to track the variation in resonance frequency in a mass-sensitive resonant sensor. The concept is proved by analytical and numerical simulation; experimentation is carried out to test the practicability and applicability of the proposed electronics. The proposed electronics will ease the trend of miniaturizing a piezoelectric-excited/detected resonant sensor as the need for a single piezo for sensing and excitation has increased.