Wireless Sensors and Actuators for Structural Health Monitoring of Fiber Composite Materials

This work evaluates and investigates the wireless generation and detection of Lamb-waves on fiber-reinforced materials using surface applied or embedded piezo elements. The general target is to achieve wireless systems or sensor networks for Structural Health Monitoring (SHM), a type of Non-Destructive-Evaluation (NDE). In this sense, a fully wireless measurement system that achieves power transmission implementing inductive coils is reported. This system allows a reduction of total system weight as well as better integration in the structure. A great concern is the characteristics of the material, in which the system is integrated, because the properties can have a direct impact on the strength of the magnetic field. Carbon-Fiber-Reinforced-Polymer (CFRP) is known to behave as an electrical conductor, shielding radio waves with increasing worse effects at higher frequencies. Due to the need of high power and voltage, interest is raised to evaluate the operation of piezo as actuators at the lower frequency ranges. To this end, actuating occurs at the International Scientific and Medical (ISM) band of 125 kHz or low-frequency (LF) range. The feasibility of such system is evaluated extensively in this work. Direct excitation, is done by combining the actuator bonded to the surface or embedded in the material with an inductive LF coil and setting the circuit in resonance. A more controlled possibility, also explored, is the use of electronics to generate a Hanning-windowed-sine to excite the PWAS in a narrow spectrum. In this case, only wireless power is transmitted to the actuator node, and this lastly implements a Piezo-driver to independently excite Lamb-waves. Sensing and data transfer, on the other hand, is done using the high-frequency (HF) 13.56 MHz. The HF range covers the requirements of faster sampling rate and lower energy content. A re-tuning of the antenna coils is performed to obtain better transmission qualities when the system is implemented in CFRP. Several quasi-isotropic (QI) CFRP plates with sensor and actuator nodes were made to measure the quality of transmission and the necessary energy to stimulate the actuator-sensor system. In order to produce baselines, measurements are prepared from a healthy plate under specific temperature and humidity conditions. The signals are evaluated to verify the functionality in the presence of defects. The measurements demonstrate that it is possible to wirelessly generate Lamb-waves while early results show the feasibility to determine the presence of structural failure. For instance, progress has been achieved detecting the presence of a failure in the form of drilled holes introduced to the structure. This work shows a complete set of experimental results of different sensor/-actuator nodes

Catching particles by atomic spectrometry: Benefits and limitations of single particle - inductively coupled plasma mass spectrometry

Single particle inductively coupled plasma mass spectrometry (SP-ICP-MS) has led ICP-MS into a new dimension, turning an ensemble technique for elemental and isotope ratio analysis into a particle counting technique and well beyond. SP-ICP-MS allows the detection of particles, their size characterization and the quantification of their number and mass concentrations, as well as the dissolved forms of the target element(s). Although the technique is mostly applied to metal- and metalloid-based nanoparticles, its application to microparticles and carbon-based particles are emerging. After twenty years since the first publications and more than ten years of ongoing development, SP-ICP-MS has reached a high degree of maturity, with an increasing number of applications in a wide range of fields. Despite this trend, there are aspects related to the fundamentals of the technique that still require further studies. This review is organized around the fundamentals of the technique along with the different steps and processes involved, from the sample introduction to the signal processing, offering an updated view of these topics, focusing on the benefits and current limitations of the technique, as well as its future perspectives

Advances in power quality analysis techniques for electrical machines and drives: a review

The electric machines are the elements most used at an industry level, and they represent the major power consumption of the productive processes. Particularly speaking, among all electric machines, the motors and their drives play a key role since they literally allow the motion interchange in the industrial processes; it could be said that they are the medullar column for moving the rest of the mechanical parts. Hence, their proper operation must be guaranteed in order to raise, as much as possible, their efficiency, and, as consequence, bring out the economic benefits. This review presents a general overview of the reported works that address the efficiency topic in motors and drives and in the power quality of the electric grid. This study speaks about the relationship existing between the motors and drives that induces electric disturbances into the grid, affecting its power quality, and also how these power disturbances present in the electrical network adversely affect, in turn, the motors and drives. In addition, the reported techniques that tackle the detection, classification, and mitigations of power quality disturbances are discussed. Additionally, several works are reviewed in order to present the panorama that show the evolution and advances in the techniques and tendencies in both senses: motors and drives affecting the power source quality and the power quality disturbances affecting the efficiency of motors and drives. A discussion of trends in techniques and future work about power quality analysis from the motors and drives efficiency viewpoint is provided. Finally, some prompts are made about alternative methods that could help in overcome the gaps until now detected in the reported approaches referring to the detection, classification and mitigation of power disturbances with views toward the improvement of the efficiency of motors and drives.Peer ReviewedPostprint (published version

Detecting and locating electronic devices using their unintended electromagnetic emissions

Electronically-initiated explosives can have unintended electromagnetic emissions which propagate through walls and sealed containers. These emissions, if properly characterized, enable the prompt and accurate detection of explosive threats. The following dissertation develops and evaluates techniques for detecting and locating common electronic initiators. The unintended emissions of radio receivers and microcontrollers are analyzed. These emissions are low-power radio signals that result from the device\u27s normal operation. In the first section, it is demonstrated that arbitrary signals can be injected into a radio receiver\u27s unintended emissions using a relatively weak stimulation signal. This effect is called stimulated emissions. The performance of stimulated emissions is compared to passive detection techniques. The novel technique offers a 5 to 10 dB sensitivity improvement over passive methods for detecting radio receivers. The second section develops a radar-like technique for accurately locating radio receivers. The radar utilizes the stimulated emissions technique with wideband signals. A radar-like system is designed and implemented in hardware. Its accuracy tested in a noisy, multipath-rich, indoor environment. The proposed radar can locate superheterodyne radio receivers with a root mean square position error less than 5 meters when the SNR is 15 dB or above. In the third section, an analytic model is developed for the unintended emissions of microcontrollers. It is demonstrated that these emissions consist of a periodic train of impulses. Measurements of an 8051 microcontroller validate this model. The model is used to evaluate the noise performance of several existing algorithms. Results indicate that the pitch estimation techniques have a 4 dB sensitivity improvement over epoch folding algorithms --Abstract, page iii

On-die transient event sensors and system-level ESD testing

System level electrostatic discharge (ESD) testing of electronic products is a critical part of product certification. Test methods were investigated to develop system level ESD simulation models to predict soft-failures in a system with multiple sensors. These methods rely completely on measurements. The model developed was valid only for the linear operation range of devices within the system. These methods were applied to a commercial product and used to rapidly determine when a soft failure would occur. Attaching cables and probes to determine stress voltages and currents within a system, as in the previous study, is time-consuming and can alter the test results. On-chip sensors have been developed which allow the user to avoid using cables and probes and can detect an event along with the level, polarity, and location of a transient event seen at the I/O pad. The sensors were implemented with minimum area consumption and can be implemented within the spacer cell of an I/O pad. Some of the proposed sensors were implemented in a commercial test microcontroller and have been tested to successfully record the event occurrence, location, level, and polarity on that test microcontroller. System level tests were then performed on a pseudo-wearable device using the on-chip sensors. The measurements were successful in capturing the peak disturbance and counting the number of ESD events without the addition of any external measurement equipment. A modification of the sensors was also designed to measure the peak voltage on a trace or pin inside a complex electronic product. The peak current can also be found when the sensor is placed across a transient voltage suppressor with a known I-V curve. The peak level is transmitted wirelessly to a receiver outside the system using frequency-modulated magnetic or electric fields, thus allowing multiple measurements to be made without opening the enclosure or otherwise modifying the system. Simulations demonstrate the sensors can accurately detect the peak transient voltage and transmit the level to an external receiver --Abstract, page iv

Design and development of safety systems for high frequency inductive power transfer

As wireless charging is gaining its popularity among consumer electronics, e.g., phones, smart wearables, electric toothbrushes, etc., there has been a trend of expanding this technology into a wider range of applications e.g. drones, robots, electric vehicles etc.. To achieve this, both the charging power and range need to be increased. This thesis discusses the limitations of widely used kHz inductive power transfer systems and emphasises the challenge of deploying into a wider range of applications. High-frequency inductive power transfer (HF-IPT) systems are then discussed with two real-world applications presented to showcase HF-IPT’s potential over kHz IPT systems. Some of the benefits of the HF-IPT, e.g., the large air gap and tolerance to misalignment, could increase the chances for live or other unintended objects to be coupled into the wireless charging system, which could cause safety hazards if the system was not designed carefully. This thesis, therefore, focuses on the safety systems design and development for HF-IPT systems. A number of existing and potential foreign and live object detection methods (FOD/LOD) including a new FOD/LOD method based on reflected impedance are introduced. The proposed method can operate without additional sensors, and without a communication link between IPT transmitter and receiver. A detection accuracy of 95% is achieved by implementing such FOD/LOD method. In addition, a FOD/LOD technique based on a mmWave radar sensor is also introduced. Differing from typical radar applications, the proposed method leverages machine learning techniques to perform object recognition to reduce the false detection rate. The developed FOD/LOD system could classify six different charging scenarios with an average accuracy of 96%. For applications that do not involve any live or unintended objects, this thesis also introduces a localisation technique based on the IPT system to help guide a drone or robot to a specific location e.g. a wireless charging point. Such a system was designed to reduce the risk of charging by minimising human’s involvement.Open Acces

SQUIDs in biomagnetism : A roadmap towards improved healthcare

This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 686865.Peer reviewedPublisher PD

Automotive Inductive Position Sensor

Inductive angular position sensors (IAPS) are widely used for high accuracy and low cost angular position sensing in harsh automotive environments, such as suspension height sensor and throttle body position sensor. These sensors ensure high resolution and long lifetime due to their contactless sensing mode and their simple structure. Furthermore, they are suitable for wider application areas. For instance, they can be miniaturized to fit into a compact packaging space, or be adopted to measure the relative angle of multiple rotating targets for the purposes of torque sensing. In this work, a detailed SIMULINK model of an IAPS is first proposed in order to study and characterize the sensor performance. The model is validated by finite element analysis and circuit simulation, which provides a powerful design tool for sensor performance analysis. The sensor error introduced by geometry imperfection is thoroughly investigated for two-phase and three-phase configurations, and a corresponding correction method to improve the accuracy is proposed. A design optimization method based on the response surface methodology is also developed and used in the sensor development. Three types of sensors are developed to demonstrate the inductive sensor technology. The first type is the miniaturized inductive sensor. To compensate for the weak signal strength and the reduced quality (Q) factor due to the scaling down effect, a resonant rotor is developed for this type of sensor. This sensor is fabricated by using the electrodeposition technique. The prototype shows an 8mm diameter sensor can function well at 1.5mm air gap. The second type is a steering torque sensor, which is designed to detect the relative torsional angle of a rotating torsional shaft. It demonstrates the mutual coupling of multiple inductive sensors. By selecting a proper layout and compensation algorithm, the torque sensor can achieve 0.1 degree accuracy. The third type is a passive inductive sensor, which is designed to reduce power consumption and electromagnetic emissions. The realization and excellent performance of these three types of sensors have shown the robustness of the inductive sensor technology and its potential applications. The research conducted in this dissertation is expected to improve understanding of the performance analysis of IAPS and provide useful guidelines for the design and performance optimization of inductive sensors

New Cost-effective Method for Monitoring Wideband Disturbances at Secondary Substation

Modern societies are becoming increasingly dependent on reliable and continuous supply of high quality electricity. Maintaining continuous supply of electricity round the clock depends heavily on the efficient and reliable operation of distribution system components. On the other hand, large-scale power outages are increasing in overhead lines due to extreme weather condition i.e. heavy storms and snowfalls. Distribution network operators (DNOs) are facing considerable network investments in the near future due to the ongoing trend of cabling. At the same time, the long fault location and repair times in aging cable networks set new demands for condition monitoring and fault prevention through preventive maintenance. Partial discharge (PD) monitoring is an excellent way to determine the overall health of the MV components and detect developing faults in underground cables. On the other hand, the proliferation of e.g. distributed generation and electronic loads poses new challenges to maintain the power quality (PQ) in distribution networks. Utilizing network condition and power quality information together would improve the allocation accuracy and benefit-cost ratio of network maintenance and renewals. Thus, the importance of condition monitoring is increasing in the distribution networks to facilitate online diagnostic, preventive maintenance, forecasting risk of failure and minimizing outages.Secondary substations seldom have any remotely readable measurement and control units and the existing measurements in the network are limited to only power quality and MV fault management due to low sampling rate (some kHz). There are also commercially available devices for PD monitoring of underground cables but those capable of continuous on-line monitoring are still relatively expensive and as such, more suited for critical and high risk location. Currently, there are no cost-effective wideband multifunction devices suitable for continuous on-line PD monitoring, PQ monitoring, disturbance recording (DR) and fault location at secondary substation.This thesis proposes a novel cost-effective secondary substation monitoring solution which includes the monitoring system as well as the monitoring concept to measure various quantities at LV and MV side of secondary substation. Additionally, it can be used in fundamental frequency metering and can be used as disturbance recorder as well. It also locates earth fault which is demonstrated as an application of disturbance recording function. The architecture of the monitoring system includes high frequency current transformer (HFCT) sensors for current measurements at MV side, resistive divider for voltage measurements at LV side, filter & amplifier unit and multichannel data acquisition & processing unit. HFCT sensors not only measure PD but also PQ at the MV side of secondary substation, which is a novel approach. Hence, no sensor having expensive high voltage insulations is needed, which makes the solution cost-effective and reliable. The overall concept is tested and verified through prototype systems in the laboratory and in the field. Secondary substation monitoring solution provides a platform on which various monitoring, control and network automation applications can be built