Six Degree of Freedom Force/Torque Sensor

The use of robots and manipulators in many kind of applications, such as scientific, medical or industrial ones, requires efficient multi-component force sensing schemes to control the force exerted by the robot end-effector on a human or an object. A multiaxis force sensor can be used to measure the contact force as accurately as possible, and to feed it back to the command signal so that the robot can achieve the pre-specified contact force. As the commercial force sensors are complex and expensive, the goal of this work is to make a multiaxis force sensor that could rThis work describes the design, development and calibration of a complete six?degree-of-freedom force and torque sensor. Compared to commercial sensors, this design has the advantage of simplicity and low cost. The sensor was machined from aluminium, and sensed by an array of commercial low-cost strain gauges. As a sensor, it could be applied in multi-DOF industrial, scientific and medical robotic systems, for instance

Multi-scale Structural Health Monitoring using Wireless Smart Sensors

Tremendous progress has been made in recent years in the wireless smart sensor (WSS) technology to monitor civil infrastructures, shifting focus away from traditional wired methods. Successful implementations of such WSS networks for full-scale SHM have demonstrated the feasible use of the technology. Much of the previous research and application efforts have been directed toward single-metric applications. Multi-metric monitoring, in combination with physics-based models, has great potential to enhance SHM methods; however, the efficacy of the multi-metric SHM has not been illustrated using WSS networks to date, due primarily to limited hardware capabilities of currently available smart sensors and lack of effective algorithms. This research seeks to develop multi-scale WSSN strategies for advanced SHM in cost effective manner by considering: (1) the development of hybrid SHM method, which combine numerical modeling and multi-metric physical monitoring, (2) multi-metric and high-sensitivity hardware developments for use in WSSNs, (3) network software developments for robust WSSN, (4) algorithms development to better utilize the outcomes from SHM system, and (5) fullscale experimental validation of proposed research. The completion of this research will result in an advanced multi-scale WSS framework to provide innovate ways civil infrastructure is monitored.Financial support for this research was provided in part by the National Science Foundation under NSF Grants No. CMS-0600433 and CMMI-0928886.Ope

Portable High Throughput Digital Microfluidics and On-Chip Bacteria Cultures

An intelligent, portable, and high throughput digital microfluidic (DMF) system is developed. Chapter 1 introduces microfluidics and DMF systems. In Chapter 2, a low-cost and high resolution capacitive-to-digital converter integrated circuit is used for droplet position detection. A field-programmable gate array FPGA is used as the integrated logic hub of the system for highly reliable and efficient control of the circuit. In this chapter a fast-fabricating PCB (printed circuit board) substrate microfluidic system is proposed. Smaller actuation threshold voltages than those previously reported are obtained. Droplets (3 µL) are actuated using 200 V, 500 Hz DC pulses. Droplet positions can be detected and displayed on a PC-based 3D animation in real time. The actuators and the capacitance sensing circuits are implemented on one PCB to reduce the size of the system. In Chapter 3, an intelligent EWOD (electrowetting on dielectric) top plate control system is proposed. The dynamic top plate is controlled by a piezoelectric (PZT) cantilever structure. A high resolution laser displacement sensor is used to monitor the deflection of the top plate. The gap height optimization and the harmonic vibration significantly improve the droplet velocity and decrease the droplet minimum threshold actuation voltage. The top plate vibration induced actuation improvement is magnitude and frequency dependent. 100 µm and 200 µm vibrations are tested at 25 Hz. Vibration frequencies at 5 Hz, 10 Hz, and 20 Hz are tested while the magnitude is 200 µm. Results show greater improvements are achieved at larger vibration magnitudes and higher vibration frequencies. With a vibrated top plate, the largest reduction of the actuation voltage is 76 VRMS for a 2.0 µl DI water droplet. The maximum droplet instantaneous velocity is around 9.3 mm/s, which is almost 3 times faster than the droplet velocity without top plate vibration. Liquid that has different hysteresis such as acetonitrile with various concentrations are used as a control to show its compatibility with the proposed DMF chip. Contact line depinning under top plate vibration is observed, which indicates the underlying mechanism for the improvements in actuation velocity and threshold voltage. The top plate control technique reported in this study makes EWOD DMF chips more reliable for point of care diagnostics. In Chapter 4, the mechanisms of the improvements were investigated by observing the detailed changes in the contact angle hysteresis using both parallel and nonparallel top plates. In Chapter 5, on-chip cell cultures are used for anti-biotic resistant bacteria detection. The passively dispensed on-chip cell cultures realize the isolated micro environment electrochemistry measurement, shorten the culturing time, and reduce the required sample volume. The design of the next generation ultra-portable DMF system is covered in the Appendix. Detailed technical notes and hardware design is covered in the Appendix. The proposed portable and high throughput DMF system with on-chip cell cultures have a great potential to change the standards for micro-environment culturing technologies, which will significantly improve the efficiency of actuation, sensing, and detecting performance of the DMF systems

Advances in Modelling and Control of Wind and Hydrogenerators

Rapid deployment of wind and solar energy generation is going to result in a series of new problems with regards to the reliability of our electrical grid in terms of outages, cost, and life-time, forcing us to promptly deal with the challenging restructuring of our energy systems. Increased penetration of fluctuating renewable energy resources is a challenge for the electrical grid. Proposing solutions to deal with this problem also impacts the functionality of large generators. The power electronic generator interactions, multi-domain modelling, and reliable monitoring systems are examples of new challenges in this field. This book presents some new modelling methods and technologies for renewable energy generators including wind, ocean, and hydropower systems

Advances in Modelling and Control of Wind and Hydrogenerators

Rapid deployment of wind and solar energy generation is going to result in a series of new problems with regards to the reliability of our electrical grid in terms of outages, cost, and life-time, forcing us to promptly deal with the challenging restructuring of our energy systems. Increased penetration of fluctuating renewable energy resources is a challenge for the electrical grid. Proposing solutions to deal with this problem also impacts the functionality of large generators. The power electronic generator interactions, multi-domain modelling, and reliable monitoring systems are examples of new challenges in this field. This book presents some new modelling methods and technologies for renewable energy generators including wind, ocean, and hydropower systems

Soft Tactile Sensors for Mechanical Imaging

Tactile sensing aims to electronically capture physical attributes of an object via mechanical contact. It proves indispensable to many engineering tasks and systems, in areas ranging from manufacturing to medicine and autonomous robotics. Biological skin, which is highly compliant, is able to perform sensing under challenging and highly variable conditions with levels of performance that far exceed what is possible with conventional tactile sensors, which are normally fabricated with non-conforming materials. The development of stretchable, skin-like tactile sensors has, as a result, remained a longstanding goal of engineering. However, to date, artificial tactile sensors that might mimic both the mechanical and multimodal tactile sensory capabilities of biological skin remain far from realization, due to the challenges of fabricating spatially dense, mechanically robust, and compliant sensors in elastic media. Inspired by these demands, this dissertation addresses many aspects of the challenging problem of engineering skin-like electronic sensors. In the first part of the thesis, new methods for the design and fabrication of thin, highly deformable, high resolution tactile sensors are presented. The approach is based on a novel configuration of arrays of microfluidic channels embedded in thin elastomer membranes. To form electrodes, these channels are filled with a metal alloy, eutectic Gallium Indium, that remains liquid at room temperature. Using capacitance sensing techniques, this approach achieves sensing resolutions of 1 mm$^{-1}$. To fabricate these devices, an efficient and robust soft lithography method is introduced, based on a single step cast. An analytical model for the performance of these devices is derived from electrostatic theory and continuum mechanics, and is demonstrated to yield excellent agreement with measured performance. This part of the investigation identified fundamental limitations, in the form of nonmonotonic behavior at low strains, that is demonstrated to generically affect solid cast soft capacitive sensors. The next part of the thesis is an investigation of new methods for designing soft tactile sensors based on multi-layer heterogeneous 3D structures that combine active layers, containing embedded liquid metal electrodes, with passive and mechanically tunable layers, containing air cavities and micropillar geometric supports. In tandem with analytical and computational modeling, these methods are demonstrated to facilitate greater control over mechanical and electronic performance. A new soft lithography fabrication method is also presented, based on the casting, alignment, and fusion of multiple functional layers in a soft polymer substrate. Measurements indicate that the resulting devices achieve excellent performance specifications, and avoid the limiting nonmonotonic behavior identified in the first part of the thesis. In order to demonstrate the practical utility of the devices, we used them to perform dynamic two-dimensional tactile imaging under distributed indentation loads. The results reflect the excellent static and dynamic performance of these devices. The final part of the thesis investigates the utility of the tactile sensing methods pursued here for imaging lumps embedded in simulated tissue. In order to facilitate real-time sensing, an electronic system for fast, array based measurement of small, sub-picofarad (pF) capacitance levels was developed. Using this system, we demonstrated that it is possible to accurately capture strain images depicting small lumps embedded in simulated tissue with either an electronic imaging system or a sensor worn on the finger, supporting the viability of wearable sensors for tactile imaging in medicine. In conclusion, this dissertation confronts many of the most vexing problems arising in the pursuit of skin-like electronic sensors, including fundamental operating principles, structural and functional electronic design, mechanical and electronic modeling, fabrication, and applications to biomedical imaging. The thesis also contributes knowledge needed to enable applications of tactile sensing in medicine, an area that has served as a key source of motivation for this work, and aims to facilitate other applications in areas such as manufacturing, robotics, and consumer electronics.Ph.D., Electrical Engineering -- Drexel University, 201

Energy-efficient data converter design in scaled CMOS technology

Data converters bridge the physical and digital worlds. They have been the crucial building blocks in modern electronic systems, and are expected to have a growing significance in the booming era of Internet-of-Things (IoT) and 5G communications. The applications raise energy-efficiency requirements for both low-speed and high-speed converters since they are widely deployed in wireless sensor nodes and portable devices. To explore the solutions, the author worked on three directions: 1) techniques to improve the efficiency of the low-speed converters including the comparator; 2) techniques to develop high-speed data converters including the reference stabilization; 3) new architecture to improve the efficiency of the capacitance-to-digital converter (CDC). In the first part, a power-efficient 10-bit SAR ADC featured with a gain-boosted dynamic comparator is presented. In energy-constrained applications, the converter is usually supplied with low supply voltage (e.g., 0.3 V-0.5 V), which reduces the comparator pre-amplifier (pre-amp) gain and results in higher noise. A novel comparator topology with a dynamic common-gate stage is proposed to increase the pre-amplification gain, thereby reducing noise and offset. Besides, statistical estimation and loading switching techniques are combined to further improve energy efficiency. A 40-nm CMOS prototype achieves a Walden FoM of 1.5 fJ/conversion-step while operating at 100-kS/s from a 0.5-V supply. To further improve the energy-efficiency of the comparator, a novel dynamic pre-amp is proposed. By using an inverter-based input pair powered by a floating reservoir capacitor, the pre-amp realizes both current reuse and dynamic bias, thereby significantly boosting g [subscript m] /I [subscript D] and reducing noise. Moreover, it greatly reduces the influence of the input common-mode (CM) voltage on the comparator performance, including noise, offset, and delay. A prototype comparator in 180-nm achieves 46-μV input-referred noise while consuming only 1 pJ per comparison under 1.2-V supply, which represents greater than 7 times energy efficiency boost compared to that of a Strong-Arm (SA) latch. The second part of this dissertation focuses on high-speed data converter techniques. A 10-bit high-speed two-stage loop-unrolled SAR ADC is presented. To reduce the SAR logic delay and power, each bit uses a dedicated comparator to store its output and generate an asynchronous clock for the next comparison. To suppress the comparator offset mismatch induced non-linearity, a shared pre-amp are employed in the second fine stage, which is implemented by a dynamic latch to avoid static power consumption. The prototype ADC in 40-nm CMOS achieves 55-dB peak SNDR at 200-MS/s sampling rate without any calibration. A key limiting factor for the SAR ADC to simultaneously achieve high speed and high resolution is the reference ripple settling problem caused by DAC switching. Unlike prior techniques that aim to minimize the reference ripple which requires large reference buffer power or on-chip decoupling capacitance area, this work proposes a new perspective: it provides an extra path for the full-sized reference ripple to couple to the comparator but with an opposite polarity, so that the effect of the reference ripple is canceled out, thus ensuring an accurate conversion result. The prototype 10-bit 120-MS/s SAR ADC is fabricated in 40-nm CMOS process and achieves an SNDR of 55 dB with only 3 pF reference decoupling capacitor. Finally, this dissertation also presents the design of an incremental time-domain two-step CDC. Unlike the classic two-step CDC, this work replaces the OTA-based active-RC integrator with a VCO-based integrator and performs time domain (TD) ΔΣ modulation. The VCO is mostly digital and consumes low power. Featuring the infinite DC gain in phase domain and intrinsic spatial phase quantization, this TDΔΣ enables a CDC design, achieving 85-dB SQNR by having only a 4-bit quantizer, a 1st-order loop and a low OSR of 15. The prototype fabricated in 40-nm CMOS achieves a resolution of 0.29 fF while dissipating only 0.083 nJ per conversion, which improves the energy efficiency by greater than 2 times comparing to that of state-of-the-art CDCsElectrical and Computer Engineerin

Advances in Modelling and Control of Wind and Hydrogenerators

Rapid deployment of wind and solar energy generation is going to result in a series of new problems with regards to the reliability of our electrical grid in terms of outages, cost, and life-time, forcing us to promptly deal with the challenging restructuring of our energy systems. Increased penetration of fluctuating renewable energy resources is a challenge for the electrical grid. Proposing solutions to deal with this problem also impacts the functionality of large generators. The power electronic generator interactions, multi-domain modelling, and reliable monitoring systems are examples of new challenges in this field. This book presents some new modelling methods and technologies for renewable energy generators including wind, ocean, and hydropower systems

Vibration Energy Harvesting for Wireless Sensors

Kinetic energy harvesters are a viable means of supplying low-power autonomous electronic systems for the remote sensing of operations. In this Special Issue, through twelve diverse contributions, some of the contemporary challenges, solutions and insights around the outlined issues are captured describing a variety of energy harvesting sources, as well as the need to create numerical and experimental evidence based around them. The breadth and interdisciplinarity of the sector are clearly observed, providing the basis for the development of new sensors, methods of measurement, and importantly, for their potential applications in a wide range of technical sectors