M. Umapathy

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.

Design and experimental evaluation of piecewise output feedback control for structural vibration suppression

This paper presents the design and the experimental implementation of fast and periodic output feedback controllers to minimize structural vibration, using collocated piezoelectric actuators and sensors. A linear dynamic model of the smart cantilever beam is obtained using online recursive least squares parameter estimation. A digital control system that consists of simulink modeling software and a dSPACE1104 controller board has been used for identification and control. The effectiveness of the controllers is shown experimentally by exciting the structure at resonance.

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.

Experimental evaluation of a shape memory alloy wire actuator with a modulated adaptive controller for position control

This paper presents an experimental investigation of position control of a shape memory alloy (SMA) wire actuator with adaptive and modulated adaptive controllers. The transfer function model of the SMA wire actuator is determined from the experimental open loop response. Adaptive controllers, namely LMS–GSPI, RLS–GSPI and Kalman–GSPI, and modulated adaptive controllers using pulse width modulation (PWM) are designed. The performances of these controllers are experimentally investigated for the position control of an SMA wire actuator with and without thermal disturbance. Experimental results demonstrate that the modulated adaptive controllers outperform adaptive controllers.

Active Vibration Control of SMA Actuated Structures using Fast Output Sampling Based Sliding Mode Control

Abstract Fast Output Sampling (FOS) based discrete sliding mode control is designed for Shape Memory Alloy (SMA) actuated structures to suppress the structural vibration. For the design of discrete sliding mode control the reaching law, method proposed by W. Gao is used. The simulation results demonstrate the performance of the controller. The proposed control technique achieves good vibration suppression. This methodology is more practical and easier to implement, since the measurement or estimation of the system states is not needed for designing the controller.

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.

Improved energy harvesting from vibration by introducing cavity in a cantilever beam

This paper presents modeling and experimental evaluation of a cantilever-based piezoelectric energy harvester with cavity. The introduction of cavity in the beam shifts the neutral axis of the beam away from the surface of the piezoelectric element which in turn increases the strain and generated voltage. The generated voltage from the cantilever beam with cavity is higher when compared to the beam without cavity and is found to vary with its position and thickness. The analytical and experimental results are in close agreement. The cantilever beam with cavity generates 75% higher voltage than the voltage generated from the beam without cavity.

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.

Design of Industrial Vibration Transmitter Using MEMS Accelerometer

This paper presents the overall design of an industrial vibration transmitter using Micro Electro Mechanical System (MEMS) capacitive accelerometer. It describes the accelerometer sensor interfacing circuit, rms-to-dc converter and voltage to current loop converter circuit design, calibration procedure and mounting methods. The industrial vibration transmitter output can be customized to obtain either acceleration or velocity with root mean square (rms) or peak (pk) value signal. The electronic circuit was designed to measure vibration in motion. The output of the transmitter is a current signal (4-20mA) which is proportional to input acceleration (0-10g rms). The AC coupling circuit for accelerometer sensor interfacing, RMS detector and industrial current loop converter circuit are implemented in a single printed circuit board. The prototype consists of 2 pin top connector for power input (24VDC), current output signal and stainless steel mechanical housing assembly with bottom thread connection for mounting. The loop powered acceleration vibration transmitter is employed for vibration monitoring and control applications. Keywords: Vibration transmitter, MEMS, capacitive accelerometer, AC coupling, RMS detector, current loop converter, condition monitoring.