Chitta Saha

A micro electromagnetic generator for vibration energy harvesting

Vibration energy harvesting is receiving a considerable amount of interest as a means for powering wireless sensor nodes. This paper presents a small (component volume 0.1 cm3, practical volume 0.15 cm3) electromagnetic generator utilizing discrete components and optimized for a low ambient vibration level based upon real application data. The generator uses four magnets arranged on an etched cantilever with a wound coil located within the moving magnetic field. Magnet size and coil properties were optimized, with the final device producing 46 µW in a resistive load of 4 k? from just 0.59 m s-2 acceleration levels at its resonant frequency of 52 Hz. A voltage of 428 mVrms was obtained from the generator with a 2300 turn coil which has proved sufficient for subsequent rectification and voltage step-up circuitry. The generator delivers 30% of the power supplied from the environment to useful electrical power in the load. This generator compares very favourably with other demonstrated examples in the literature, both in terms of normalized power density and efficiency.

Optimization of an Electromagnetic Energy Harvesting Device

This paper presents the modeling and optimization of an electromagnetic-based generator for generating power from ambient vibrations. Basic equations describing such generators are presented and the conditions for maximum power generation are described. Two-centimeter scale prototype generators, which consist of magnets suspended on a beam vibrating relative to a coil, have been built and tested. The measured power and modeled results are compared. It is shown that the experimental results confirm the optimization theory

FPGA implementation of spiking neural networks - an initial step towards building tangible collaborative autonomous agents

This work contains the results of an initial study into the FPGA implementation of a spiking neural network. This work was undertaken as a task in a project that aims to design and develop a new kind of tangible collaborative autonomous agent. The project intends to exploit/investigate methods for engineering emergent collective behaviour in large societies of actual miniature agents that can learn and evolve. Such multi-agent systems could be used to detect and collectively repair faults in a variety of applications where it is difficult for humans to gain access, such as fluidic environments found in critical components of material/industrial systems. The initial achievement of implementation of a spiking neural network on a FPGA hardware platform and results of a robotic wall following task are discussed by comparison with software driven robots and simulations.

Design and performance of a microelectromagnetic vibration powered generator

In this paper we, report on the design, simulation and initial results of a microgenerator, which converts external vibrations into electrical energy. Power is generated by means of electromagnetic transduction with static magnets positioned either side of a moving coil located on a silicon structure designed to resonate laterally in the plane of the chip. The development and fabrication of a micromachined microgenerator that uses standard silicon based fabrication techniques and a low cost, batch process is presented. Finite element simulations have been carried out using ANSYS to determine an optimum geometry for the microgenerator. Electromagnetic FEA simulations using Ansofts Maxwell 2D software have shown voltage levels of 4 to 9 V can be generated from the single beam generator designs. Initial results at atmospheric pressure yield 0.5 /spl mu/W at 9.81 ms/sup -2/ and 9.5 kHz and emphasise the importance of reducing unwanted loss mechanisms such as air damping.

Designing a Low-Cost, Electricity-Generating Cooking Stove

Over two billion people world-wide cook on an open fire stove [1], do not have access to electricity, and would benefit from an off-grid electrical supply [2], [3]. Score, www.score.uk.com, is a

Performance enhancement defect tolerance in the cell matrix architecture

4M, fiveyear project to research a cooking stove that will generate electricity and cooling and is aimed primarily at poor people in developing countries in sub-Saharan Africa, the Indian Sub-continent, and South America. The technology chosen for the design is based on the Thermo-acoustic work at Los Alamos Laboratories [4].

Modelling Theory and Applications of the Electromagnetic Vibrational Generator

This research concentrates on the area of fault tolerant circuit implementation in a field programmable type architecture, In particular, an architecture called the Cell Matrix, presented as a fault tolerant alternative to field programmable gate arrays using their Supercell approach, is studied. Architectural constraints to implement fault tolerant circuit design in this architecture are discussed. Some modifications of its basic Structure, such as the integration of circuitry for error correction and scan path, to enhance fault tolerant circuits design are introduced and are compared to the Supercell approach.

Wireless power transfer using relay resonators

There is rapidly growing interest over the last decade on the topics of energy harvesting devices as a means to provide an alternative to batteries as a power source for medical implants, embedded sensor applications such as buildings or in difficult to access or remote places where wired power supplies would be difficult [1-13]. There are several possible sources of ambient energy including vibrational, solar, thermal gradients, acoustic, RF, etc that can be used to power the sensor modules or portable electronic devices. The most promising ambient energy sources of these are solar, thermo-electric and vibrational. A significant amount of research has already been done in this area over the past few years and several energy scavenger products are already available in the market such as the solar calculator, thermoelectric wristwatch and wireless push button switches etc. The Solar energy is a mature technology and represents a very straight forward approach to generate energy from ambient light. However, solar cell is not cost effective and devices using solar cell need larger areas which would not be compatible with small MEMS powering. Furthermore sufficient sunlight is necessary which also limits the application areas. In thermoelectric generators, large thermal gradients are essential to generate practical levels of voltage and power. It would be very difficult to get more than 10°C in a MEMS compatible device. On the other hand, vibrational energy scavenger could be a reliable option for autonomous sensor modules or body-worn sensor, in automotive, industrial machine monitoring or other applications where ambient vibrational energy is available. This vibrational energy can be converted into electrical energy using three different principles: electromagnetic, electrostatic and piezoelectric.

Suspension Design, Modeling, and Testing of a Thermo-Acoustic-Driven Linear Alternator

This paper presents an advanced design configuration of a wireless power transfer system using overlapping relay coil techniques for free loading position. The work undertaken investigates the tuning position of prototype relay coils in a horizontal configuration in order to evaluate power transfer efficiency versus increasing operating distance between the transmitter and receiver coils. A prototype relay coil system was evaluated to determine the optimum distance between the transmitter and receiver. Finite element magnetic simulation was used to appraise the magnetic field distribution and power transfer efficiency with respect to a strongly coupled magnetic resonance condition. Experimental and simulation results analysis suggest that the proposed design could achieve 85%–90% efficiency within a 4 cm operational distance. Finally, the experimental results were analyzed and compared with the simulation results.This paper presents an advanced design configuration of a wireless power transfer system using overlapping relay coil techniques for free loading position. The work undertaken investigates the tuning position of prototype relay coils in a horizontal configuration in order to evaluate power transfer efficiency versus increasing operating distance between the transmitter and receiver coils. A prototype relay coil system was evaluated to determine the optimum distance between the transmitter and receiver. Finite element magnetic simulation was used to appraise the magnetic field distribution and power transfer efficiency with respect to a strongly coupled magnetic resonance condition. Experimental and simulation results analysis suggest that the proposed design could achieve 85%–90% efficiency within a 4 cm operational distance. Finally, the experimental results were analyzed and compared with the simulation results.

Modelling and performance analysis of a silicon PV module

The Score-Stove™ generates electricity from a wood-burning cooking stove using a thermo-acoustic engine (TAE) that converts heat to sound through a linear alternator (LA). This paper introduces a prototype hemitoroidal suspension that was refined into a segmented trapezoidal shape that gave a higher cyclic life for the LA and includes a critical evaluation that compares a theoretical analysis with experimental results. The results show an improvement from the 40% efficiency of a standard loudspeaker used in reverse as an LA to 70–80% efficiency with the new suspension and a double Halbach array magnetic topology.