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Analysis and Optimization of an Inductive Power Transfer With a Randomized Method

This paper introduces the analysis of the efficiency and transferred power of an inductive link circuit with different network configurations of capacitors connected to primary and secondary coils. The best performance for both cited objective functions was observed with two capacitors connected to the input coil and two capacitors connected to the output coil. However, the output equations in this circuit configuration for both efficiency and output power are very complex and a numerical method had to be applied to compute the capacitors values. Since an exhaustive search would be long, some simplifications were assumed to reduce the search space and the processing time. Thus, a search algorithm based on a randomized method was developed and successfully applied. The results for both efficiency and output power of four capacitors configuration were compared with other usual approaches, such as the single and two capacitors compensation. Finally, a basic prototype was built and the theoretical results were validated. Both simulated and experimental results of the four capacitor configuration showed a significant improvement on the efficiency and output power of the inductive link.

Fine Tuning of an Inductive Link Through a Voltage-Controlled Capacitance

Wireless power transfer is a technique usually based on an inductive link, used for delivering energy to remote devices. The power of different applications ranges from microwatts to hundreds of kilowatts, e.g., in biomedical implants and electric vehicles. The transferred power is highly dependent on the relative position between the inductive link coils. Many studies have been presented considering static or quasi-static conditions, based on a fixed tuned circuit. However, when the coils are not stationary, the inductive link must be dynamically tuned to keep the designed output power. This paper presents a methodology for dynamically tune the inductive link by means of a variable capacitance. A voltage-controlled capacitance using concepts of the negative impedance converter and capacitance multiplier is proposed. The phase angle between the input voltage and current is used as the error signal to control the variable capacitance and keep the output power operating point. The experimental evaluation shows that the proposed methodology can significantly improve the power delivered to the load in comparison to a fixed inductive link.

Parameter Identification and Analysis of Uncertainties in Measurements of Lead–Acid Batteries

This paper is devoted to impedance measurements over the frequency band corresponding to the Randles model of the first order. An estimation technique is proposed to assess the state of charge of a battery using a developed experimental system. Randles parameter identification is carried out based on frequency response. This paper focuses on the analysis of the propagated uncertainty of input variables determining the measurement accuracy of battery parameters.

Power Transfer With an Inductive Link and Wireless Tuning

This paper presents the analysis of two air-coupled coils used to transfer energy to charge a battery. This battery is used to power an electronic device designed to monitor variables such as impact strength, range of temperature, and humidity associated with the transport of fruits. The device is inside a sealed enclosure that cannot be opened for recharging the battery. The study shows that the coupled coils need to work with a resonance capacitor, at least on the secondary coil. However, the resonance frequency also depends on the coupling factor k. Therefore, this work proposes a monitoring system with a closed loop for fine-tuning the resonance frequency of the secondary coil circuit. Before starting charging the battery, the system scans the resonance frequency on the primary coil and measures the output power on the secondary coil looking for the optimal point. This procedure reduces problems of coupling factor variations with positioning of the coils during the battery charging.

Eddy Current Probe Identification and Analysis

This paper presents a new approach to the classical method for failure detection with eddy currents. In contrast to traditional methods of measuring reflected impedance on the probe circuit, this paper uses concepts of identification theory to find a transfer function that characterizes the dynamics of the measuring system by eddy currents. The transfer function represents the admittance of the input equivalent circuit. The estimated parameters of the transfer function were used to compute the inductive time constant of equivalent circuit of the metal specimen. The results of the time constant variation of the equivalent circuit of the sample were compared with the equivalent input impedance variation. A preliminary analysis is done in a simple case study, which has shown that the inductive time constant is more sensitive than the reflected impedance on the probe circuit, especially at low frequencies. Moreover, the estimated time constant is independent of the excitation frequency and mutual inductance.

Sensor fusion methods for reducing false alarms in heart rate monitoring

Automatic patient monitoring is an essential resource in hospitals for good health care management. While alarms caused by abnormal physiological conditions are important for the delivery of fast treatment, they can be also a source of unnecessary noise because of false alarms caused by electromagnetic interference or motion artifacts. One significant source of false alarms is related to heart rate, which is triggered when the heart rhythm of the patient is too fast or too slow. In this work, the fusion of different physiological sensors is explored in order to create a robust heart rate estimation. A set of algorithms using heart rate variability index, Bayesian inference, neural networks, fuzzy logic and majority voting is proposed to fuse the information from the electrocardiogram, arterial blood pressure and photoplethysmogram. Three kinds of information are extracted from each source, namely, heart rate variability, the heart rate difference between sensors and the spectral analysis of low and high noise of each sensor. This information is used as input to the algorithms. Twenty recordings selected from the MIMIC database were used to validate the system. The results showed that neural networks fusion had the best false alarm reduction of 92.5 %, while the Bayesian technique had a reduction of 84.3 %, fuzzy logic 80.6 %, majority voter 72.5 % and the heart rate variability index 67.5 %. Therefore, the proposed algorithms showed good performance and could be useful in bedside monitors.

Load cells in force sensing analysis -- theory and a novel application

Load cells have long been used to sense and measure force and torque. When properly designed and used, they are very accurate and reliable sensors. Load cells are applied in several different fields, usually for weighing measurements. Among many other things, food, vehicles, and animals are weighed daily with load cells. The gripper of a robotic arm that picks up an object can be equipped with load cells in order to provide compression force feedback to the control system to prevent the object from being damaged or released too early. Also, load cells can be used to sense the compression forces during a robot's walk to provide data for the equilibrium-controlling system. In industrial machinery, rods, beams, wheels and bars are instrumented in order to check the forces exerted on them. The volume or level of a tank can be measured indirectly by means of a load cell that monitors the total weight. Lift units can also have a load's total weight measured to prevent overload. Because of such a variety of possible applications, load cells are very important. This paper describes some of the theory and practice of load cells, including their basic elements and the electronics necessary for measurement. As an application example, the development of a 3-ring spherical load cell is presented which can be used to measure compression forces on fruit during storage and transportation is presented.

Design and characterization of a power transfer inductive link for wireless sensor network nodes

This paper describes a design of a power transfer inductive link for charging batteries of wireless sensor network nodes. The application physical constraints imposes a maximum size for the coils and demands a design methodology to maximize output power delivered to the load and energy transmission efficiency. This paper presents a complete methodology for designing the coils of wireless power transfer systems applied to rechargeable batteries of wireless sensor network nodes. The design of an inductive link is presented as a case study, in which two planar coils are built in order to validate the proposed method. Moreover, a complete wireless power transfer system is developed for the proposal, including coils, primary power source, capacitor network compensation, and secondary power management, with rectification, filtering, regulation, and battery charge control. The experimental results for working distances between the coils from 1 mm to 10 mm are reported as well as the frequency response of the entire system.

Authors: Rodrigo W. Porto ; Valner J. Brusamarello ; Ivan Müller ; Fernando R. de Sousa

2015 IEEE International Instrumentation and Measurement Technology Conference (I2MTC) Proceedings

Conference Location: Pisa
Publication Year: 2015, Page(s): 1261 - 1266
DOI: 10.1109/I2MTC.2015.7151454

Energy consumption estimation for TDMA-based industrial wireless sensor networks

Industrial wireless sensor networks make use of batteries to provide mobility and low maintenance. The available energy depends of battery specification, electrical characteristics of the device, communication protocol and process variable update rate. The development of industrial field devices and communication protocols demands solutions to verify the expended energy along the time which can be used to predict battery life and to provide a balanced network for messages routing. In this work, an energy measurement circuit is developed for TDMA-based industrial wireless field devices such as WirelessHART and ISA SP100.11 and it is used as a reference to correct an embedded energy estimation algorithm. The overall idea is to certify the algorithm embedded by the electronic measurement, further substituted by simple functions that calculate the expended energy. The results presented a 2.5% in most cases and 3.5% worst case errors by the estimation algorithm when compared to the reference circuit, used for measuring the total energy of the sensor node during a predefined communication period.

Contactless battery charger controller for wireless sensor node

Wireless sensor network nodes have been used to collect data from processes in several different areas. In most cases, these sensors and their batteries need to be recharged regularly. However, these sensors are often deployed in harsh environments that can damage them with moist and dust particles. Therefore this work aims to present a contactless inductive charger developed to avoid jack or plug holes on the sensor casing in order to prevent damage to its circuitry. This battery charger uses a resonant topology circuit and an algorithm to adjust the resonant frequency. Unlike a previous work, it measures the current through the primary coil to determine the optimal point, which yields a simpler solution. The concept has been proven to be effective while keeping low cost and simplicity, which are important aspects to wireless sensor networks.