Microelectromechanical systems vibration powered electromagnetic generator for wireless sensor applications

This paper presents a silicon microgenerator, fabricated using standard silicon micromachining techniques, which converts external ambient vibrations into electrical energy. Power is generated by an electromagnetic transduction mechanism with static magnets positioned on either side of a moving coil, which is located on a silicon structure designed to resonate laterally in the plane of the chip. The volume of this device is approximately 100 mm³. ANSYS finite element analysis (FEA) has been used to determine the optimum geometry for the microgenerator. Electromagnetic FEA simulations using Ansoft’s Maxwell 3D software have been performed to determine the voltage generated from a single beam generator design. The predicted voltage levels of 0.7–4.15 V can be generated for a two-pole arrangement by tuning the damping factor to achieve maximum displacement for a given input excitation. Experimental results from the microgenerator demonstrate a maximum power output of 104 nW for 0.4g (g=9.81 m s⁻¹) input acceleration at 1.615 kHz. Other frequencies can be achieved by employing different geometries or materials.

     

Microelectromechanical systems vibration powered electromagnetic generator for wireless sensor applications

This paper presents a silicon microgenerator, fabricated using standard silicon micromachining techniques, which converts external ambient vibrations into electrical energy. Power is generated by an electromagnetic transduction mechanism with static magnets positioned on either side of a moving coil, which is located on a silicon structure designed to resonate laterally in the plane of the chip. The volume of this device is approximately 100 mm³. ANSYS finite element analysis (FEA) has been used to determine the optimum geometry for the microgenerator. Electromagnetic FEA simulations using Ansoft’s Maxwell 3D software have been performed to determine the voltage generated from a single beam generator design. The predicted voltage levels of 0.7–4.15 V can be generated for a two-pole arrangement by tuning the damping factor to achieve maximum displacement for a given input excitation. Experimental results from the microgenerator demonstrate a maximum power output of 104 nW for 0.4g (g=9.81 m s^?1) input acceleration at 1.615 kHz. Other frequencies can be achieved by employing different geometries or materials.     

Comparison of energy harvesting systems for wireless sensor networks

Wireless sensor networks (WSNs) offer an attractive solution to many environmental, security, and process monitoring problems. However, one barrier to their fuller adoption is the need to supply electrical power over extended periods of time without the need for dedicated wiring. Energy harvesting provides a potential solution to this problem in many applications. This paper reviews the characteristics and energy requirements of typical sensor network nodes, assesses a range of potential ambient energy sources, and outlines the characteristics of a wide range of energy conversion devices. It then proposes a method to compare these diverse sources and conversion mechanisms in terms of their normalised power density.     

An investigation of self-powered systems for condition monitoring applications

Over recent years there has been a growing interest in the field of micro-systems and their applications across a wide range of areas, including sensor-based systems able to operate with full galvanic isolation. This paper details the development of a self-powered system, specifically for sensor applications that can be energised on a test rig by an electromagnetic vibration-powered generator. This enables wireless operation without the use of a battery with a finite service life. The results of two systems designed for remote sensing in condition monitoring applications are discussed. The first system uses a liquid crystal display to provide the system output; the second uses an infra-red link to transmit the data output.     

An efficient electromagnetic power harvesting device for low-frequency applications

Mechanical energy in the form of low frequency vibrations (1-100 Hz) can be commonly available and this energy type can be advantageously converted to electrical one by exploiting energy harvesting techniques. At the same time, in many applications, the devices that convert low frequency mechanical energy to electrical one should have a small size. An electromechanical power generator is proposed for converting mechanical energy in the form of low-frequency vibrations, available in the measurement environment, into electrical energy. The intended applications for the proposed electromechanical power generator, described in this paper, are for examples mechanical systems with low frequency vibrations (1-100 Hz). The operating principle is based on the relative movement of a planar inductor with respect to permanent magnets. The generator implements a novel configuration of magnets that is proposed and analyzed with the aim to improve the conversion efficiency, increasing the spatial variation of magnetic flux. Furthermore, the generator uses polymeric material as resonators, which have low-frequency mechanical resonances due to the low Young's modulus of the materials by which they are made. The different materials, with which the suspensions for the planar inductor were made, have allowed to compare different behaviors of the resonators: linear and nonlinear. The experimental results have shown, for a linear resonator, a vibration frequency of about 100 Hz with generated powers of about 290 μW and a harvesting effectiveness of 0.5%, while, for the polymeric resonator made by Latex, the vibration frequency is around 40 Hz with a maximum power of 153 μW and a harvesting effectiveness of 3.3%. The proposed configuration can be adopted for its low profile, modularity and low-frequency vibrations in many applications from industrial to medical.     

Double permanent magnet vibration power generator for smart hip prosthesis

Ever since the first studies about biomedical implantable devices, the problem of how to energize them has stood out as both important and notoriously difficult to solve. In order to extend the lifetime of implants, it is imperative to develop power generators that are autonomous, safe and maintenance-free. Energy harvesting is a natural way of meeting these requirements. First, the energy source is theoretically everlasting, a fact that helps to guarantee the autonomy. Second, the energy is obtained from the environment of the application itself, contributing to its safety. Finally, a properly designed energy harvesting system is very unlikely to ever require maintenance. This paper follows this line and describes an electromagnetic power transducer that harvests electrical energy from the human gait and stores it. An efficient power management module uses the stored energy to energize the telemetric system of a smart hip prosthesis implant, enabling the early detection of loosening, the target application of this work. The system is able to extract a total 1912.5 μJ of usable energy under normal walking conditions.     

Electromagnetic generator for harvesting energy from human motion

This paper presents an electromagnetic based generator which is suitable for supplying generating power from human body motion and has application in providing energy for body worn sensors or electronics devices. A prototype generator has been built and tested both by a shaker at resonance condition and also by human body motion during walking and slow running. The experimental results will show that the prototype could generate 300 μW to 2.5 mW power from human body motion. The measured results are analyzed and compared with the theoretical model.     

Information-control aspects of sensor systems for intelligent robotics

In order to discuss sensor systems in intelligent robotics or manufacturing systems, it is necessary to classify tasks, controller requirements, as well as the information-control aspects. This paper classifies tasks as deterministic (principally driven by geometry considerations) and non-deterministic. The latter are the problems done by people requiring skill involving processes whose process models either do not exist or are poorly understood. Other non-deterministic tasks involve inspection or data interpretation. The process tasks require adaptive-learning type control systems and are rich in sensor needs. Automated inspection tasks can be implemented by Engineering-Based Expert systems with more modest sensor system requirements.     

An intelligent sensor for detection of milling chatter

In this paper, a new real-time sensor system has been developed to detect chatter in milling operations. In the developed sensor system, a pattern recognition technique based on an unsupervised neural network using the adaptive resonance theory (ART) is adopted for detection of milling chatter. The features on the cutting force spectrum are fed into the sensor system to classify the milling process with or without chatter. The experimental results indicate that the proposed sensor system can accurately detect milling chatter regardless of the variation in cutting conditions.     

An automata-theoretic framework for intelligent systems

A theoretical framework for the analysis and synthesis of intelligent systems is presented. The basic models of automata theory and adaptive systems are highlighted, then extended and interpreted in the context of intelligent system design. In particular, the basic models are generalized to intelligent systems incorporating self-learning behavior. The utility of this approach is demonstrated by its use as a rigorous basis for (1) the discussion of information minimization in automatic systems, (2) the formal structure of adaptive systems and (3) implications for a general theory of intelligent systems.