A high temperature and low power SOI CMOS MEMS based thermal conductivity gas sensor

The design, 3D FEM modelling and measurement results of a novel high temperature, low power SOI CMOS MEMS thermal conductivity gas sensor are presented here. The sensor consists of a circular membrane with an embedded tungsten micro-heater. The high sensing capability is based on the temperature sensitivity of the resistive heating element. The sensor was fabricated at a commercial foundry using a 1 μm process and measures only 1×1 mm 2. The circular membrane has a 600 μm diameter while the heating element has a 320 μm diameter. Measurement results show that for a constant power consumption of 75 mW the heater temperature was 562.4°C in air, 565.9°C in N2, 592.5°C for 1 % H2 in Ar and 599.5°C in Ar. © 2013 IEEE.

A thermopile based SOI CMOS MEMS wall shear stress sensor

In this paper we present for the first time, a novel silicon on insulator (SOI) complementary metal oxide semiconductor (CMOS) MEMS thermal wall shear stress sensor based on a tungsten hot-film and three thermopiles. These devices have been fabricated using a commercial 1 μm SOI-CMOS process followed by a deep reactive ion etch (DRIE) back-etch step to create silicon oxide membranes under the hot-film for effective thermal isolation. The sensors show an excellent repeatability of electro-thermal characteristics and can be used to measure wall shear stress in both constant current anemometric as well as calorimetric modes. The sensors have been calibrated for wall shear stress measurement of air in the range of 0-0.48 Pa using a suction type, 2-D flow wind tunnel. The calibration results show that the sensors have a higher sensitivity (up to four times) in calorimetric mode compared to anemometric mode for wall shear stress lower than 0.3 Pa. © 2013 IEEE.

A dual mode SOI CMOS MEMS based thermal conductivity and IR absorption gas sensor

Design, FEM modelling and characterization of a novel dual mode thermal conductivity and infrared absorption sensor using SOI CMOS technology is reported. The dual mode sensing capability is based on the temperature sensitivity and wideband infrared radiation emission of the resistive heating element. The sensor was fabricated at a commercial foundry using a 1 μm process and measures only 1×1 mm2. Infrared detectors usually use thermopiles in addition to a separate IR source. A single highly responsive dual mode source and sensing element targeting not only low molecular mass gases but also greenhouse gases, while consuming 40 mW power at 700°C in synthetic air, thus makes this sensor particularly viable for battery powered handheld devices. © 2013 IEEE.

A 1,000 Frames/s Programmable Vision Chip with Variable Resolution and Row-Pixel-Mixed Parallel Image Processors

A programmable vision chip with variable resolution and row-pixel-mixed parallel image processors is presented. The chip consists of a CMOS sensor array, with row-parallel 6-bit Algorithmic ADCs, row-parallel gray-scale image processors, pixel-parallel SIMD Processing Element (PE) array, and instruction controller. The resolution of the image in the chip is variable: high resolution for a focused area and low resolution for general view. It implements gray-scale and binary mathematical morphology algorithms in series to carry out low-level and mid-level image processing and sends out features of the image for various applications. It can perform image processing at over 1,000 frames/s (fps). A prototype chip with 64 x 64 pixels resolution and 6-bit gray-scale image is fabricated in 0.18 mu m Standard CMOS process. The area size of chip is 1.5 mm x 3.5 mm. Each pixel size is 9.5 mu m x 9.5 mu m and each processing element size is 23 mu m x 29 mu m. The experiment results demonstrate that the chip can perform low-level and mid-level image processing and it can be applied in the real-time vision applications, such as high speed target tracking.

Land cover classification of Lago Grande de Curuai floodplain (Amazon, Brazil) using multi-sensor and image fusion techniques

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Design of a Wireless Vision Sensor for Object Tracking in Wireless Vision Sensor Networks

The integration of CMOS cameras with embedded processors and wireless communication devices has enabled the development of distributed wireless vision systems. Wireless Vision Sensor Networks (WVSNs), which consist of wirelessly connected embedded systems with vision and sensing capabilities, provide wide variety of application areas that have not been possible to realize with the wall-powered vision systems with wired links or scalar-data based wireless sensor networks. In this paper, the design of a middleware for a wireless vision sensor node is presented for the realization of WVSNs. The implemented wireless vision sensor node is tested through a simple vision application to study and analyze its capabilities, and determine the challenges in distributed vision applications through a wireless network of low-power embedded devices. The results of this paper highlight the practical concerns for the development of efficient image processing and communication solutions for WVSNs and emphasize the need for cross-layer solutions that unify these two so-far-independent research areas.

A skin surface characterization system based on capacitive image analysis

During the last few years, several methods have been proposed in order to study and to evaluate characteristic properties of the human skin by using non-invasive approaches. Mostly, these methods cover aspects related to either dermatology, to analyze skin physiology and to evaluate the effectiveness of medical treatments in skin diseases, or dermocosmetics and cosmetic science to evaluate, for example, the effectiveness of anti-aging treatments. To these purposes a routine approach must be followed. Although very accurate and high resolution measurements can be achieved by using conventional methods, such as optical or mechanical profilometry for example, their use is quite limited primarily to the high cost of the instrumentation required, which in turn is usually cumbersome, highlighting some of the limitations for a routine based analysis. This thesis aims to investigate the feasibility of a noninvasive skin characterization system based on the analysis of capacitive images of the skin surface. The system relies on a CMOS portable capacitive device which gives 50 micron/pixel resolution capacitance map of the skin micro-relief. In order to extract characteristic features of the skin topography, image analysis techniques, such as watershed segmentation and wavelet analysis, have been used to detect the main structures of interest: wrinkles and plateau of the typical micro-relief pattern. In order to validate the method, the features extracted from a dataset of skin capacitive images acquired during dermatological examinations of a healthy group of volunteers have been compared with the age of the subjects involved, showing good correlation with the skin ageing effect. Detailed analysis of the output of the capacitive sensor compared with optical profilometry of silicone replica of the same skin area has revealed potentiality and some limitations of this technology. Also, applications to follow-up studies, as needed to objectively evaluate the effectiveness of treatments in a routine manner, are discussed.

Improved Space Object Orbit Determination Using CMOS Detectors

CMOS-sensors, or in general Active Pixel Sensors (APS), are rapidly replacing CCDs in the consumer camera market. Due to significant technological advances during the past years these devices start to compete with CCDs also for demanding scientific imaging applications, in particular in the astronomy community. CMOS detectors offer a series of inherent advantages compared to CCDs, due to the structure of their basic pixel cells, which each contains their own amplifier and readout electronics. The most prominent advantages for space object observations are the extremely fast and flexible readout capabilities, feasibility for electronic shuttering and precise epoch registration,and the potential to perform image processing operations on-chip and in real-time. Here, the major challenges and design drivers for ground-based and space-based optical observation strategies for objects in Earth orbit have been analyzed. CMOS detector characteristics were critically evaluated and compared with the established CCD technology, especially with respect to the above mentioned observations. Finally, we simulated several observation scenarios for ground- and space-based sensor by assuming different observation and sensor properties. We will introduce the analyzed end-to-end simulations of the ground- and spacebased strategies in order to investigate the orbit determination accuracy and its sensitivity which may result from different values for the frame-rate, pixel scale, astrometric and epoch registration accuracies. Two cases were simulated, a survey assuming a ground-based sensor to observe objects in LEO for surveillance applications, and a statistical survey with a space-based sensor orbiting in LEO observing small-size debris in LEO. The ground-based LEO survey uses a dynamical fence close to the Earth shadow a few hours after sunset. For the space-based scenario a sensor in a sun-synchronous LEO orbit, always pointing in the anti-sun direction to achieve optimum illumination conditions for small LEO debris was simulated.

Diseño, Implementación y Verificación de un Sensor de Temperatura CMOS de Bajo Coste y Alta Funcionalidad

En este proyecto, se presenta un sensor de temperatura integrado CMOS basado en la medida de una variable secundaria, cuyo valor es dependiente de la temperatura, como es el tiempo de subida que presenta una señal eléctrica en sus flancos de subida. Con el objetivo de reducir coste y potencia consumida, el sensor integrado de temperatura propuesto genera un pulso con un ancho proporcional a la temperatura medida. Este sensor para realizar la medida elimina la necesidad de tener una señal que sirva de referencia. El área ocupada por este modelo de sensor es de 1.8967mm2, siendo éste fabricado en tecnología CMOS de 0.35µm de 4 capas de metal. Gracias a la excelente linealidad que presenta la salida digital del sensor, el error de medida alcanzado es como máximo de ±0.520ºC. La resolución efectiva mostrada en el caso peor es de 0.7ºC, y el consumo de potencia se encuentra por debajo de los 263µW, con una velocidad de realización de medidas que puede llegar a alcanzar las 1.5x10^6 medidas por segundo.

A built-in CMOS Total Ionization Dose smart sensor

Total Ionization Dose (TID) is traditionally measured by radiation sensitive FETs (RADFETs) that require a radiation hardened Analog-to-Digital Converter (ADC) stage. This work introduces a TID sensor based on a delay path whose propagation time is sensitive to the absorbed radiation. It presents the following advantages: it is a digital sensor able to be integrated in CMOS circuits and programmable systems such as FPGAs; it has a configurable sensitivity that allows to use this device for radiation doses ranging from very low to relatively high levels; its interface helps to integrate this sensor in a multidisciplinary sensor network; it is self-timed, hence it does not need a clock signal that can degrade its accuracy. The sensor has been prototyped in a 0.35μm technology, has an area of 0.047mm2, of which 22% is dedicated to measuring radiation, and an energy per conversion of 463pJ. Experimental irradiation tests have validated the correct response of the proposed TID sensor.

Spatial and temporal measurements using polyoxometalate, enzymatic and biofilm layers on a CMOS 0.35 μm 64 X 64-pixel I.S.F.E.T. array sensor

This thesis presents the achievements and scientific work conducted using a previously designed and fabricated 64 x 64-pixel ion camera with the use of a 0.35 μm CMOS technology. We used an array of Ion Sensitive Field Effect Transistors (ISFETs) to monitor and measure chemical and biochemical reactions in real time. The area of our observation was a 4.2 x 4.3 mm silicon chip while the actual ISFET array covered an area of 715.8 x 715.8 μm consisting of 4096 ISFET pixels in total with a 1 μm separation space among them. The ion sensitive layer, the locus where all reactions took place was a silicon nitride layer, the final top layer of the austriamicrosystems 0.35 μm CMOS technology used. Our final measurements presented an average sensitivity of 30 mV/pH. With the addition of extra layers we were able to monitor a 65 mV voltage difference during our experiments with glucose and hexokinase, whereas a difference of 85 mV was detected for a similar glucose reaction mentioned in literature, and a 55 mV voltage difference while performing photosynthesis experiments with a biofilm made from cyanobacteria, whereas a voltage difference of 33.7 mV was detected as presented in literature for a similar cyanobacterial species using voltamemtric methods for detection. To monitor our experiments PXIe-6358 measurement cards were used and measurements were controlled by LabVIEW software. The chip was packaged and encapsulated using a PGA-100 chip carrier and a two-component commercial epoxy. Printed circuit board (PCB) has also been previously designed to provide interface between the chip and the measurement cards.

Robot navigation in sensor space

This thesis investigates the problem of robot navigation using only landmark bearings. The proposed system allows a robot to move to a ground target location specified by the sensor values observed at this ground target posi- tion. The control actions are computed based on the difference between the current landmark bearings and the target landmark bearings. No Cartesian coordinates with respect to the ground are computed by the control system. The robot navigates using solely information from the bearing sensor space. Most existing robot navigation systems require a ground frame (2D Cartesian coordinate system) in order to navigate from a ground point A to a ground point B. The commonly used sensors such as laser range scanner, sonar, infrared, and vision do not directly provide the 2D ground coordi- nates of the robot. The existing systems use the sensor measurements to localise the robot with respect to a map, a set of 2D coordinates of the objects of interest. It is more natural to navigate between the points in the sensor space corresponding to A and B without requiring the Cartesian map and the localisation process. Research on animals has revealed how insects are able to exploit very limited computational and memory resources to successfully navigate to a desired destination without computing Cartesian positions. For example, a honeybee balances the left and right optical flows to navigate in a nar- row corridor. Unlike many other ants, Cataglyphis bicolor does not secrete pheromone trails in order to find its way home but instead uses the sun as a compass to keep track of its home direction vector. The home vector can be inaccurate, so the ant also uses landmark recognition. More precisely, it takes snapshots and compass headings of some landmarks. To return home, the ant tries to line up the landmarks exactly as they were before it started wandering. This thesis introduces a navigation method based on reflex actions in sensor space. The sensor vector is made of the bearings of some landmarks, and the reflex action is a gradient descent with respect to the distance in sensor space between the current sensor vector and the target sensor vec- tor. Our theoretical analysis shows that except for some fully characterized pathological cases, any point is reachable from any other point by reflex action in the bearing sensor space provided the environment contains three landmarks and is free of obstacles. The trajectories of a robot using reflex navigation, like other image- based visual control strategies, do not correspond necessarily to the shortest paths on the ground, because the sensor error is minimized, not the moving distance on the ground. However, we show that the use of a sequence of waypoints in sensor space can address this problem. In order to identify relevant waypoints, we train a Self Organising Map (SOM) from a set of observations uniformly distributed with respect to the ground. This SOM provides a sense of location to the robot, and allows a form of path planning in sensor space. The navigation proposed system is analysed theoretically, and evaluated both in simulation and with experiments on a real robot.

Design and evaluation of an image analysis platform for low-power, low-bandwidth camera networks

We describe the design and evaluation of a platform for networks of cameras in low-bandwidth, low-power sensor networks. In our work to date we have investigated two different DSP hardware/software platforms for undertaking the tasks of compression and object detection and tracking. We compare the relative merits of each of the hardware and software platforms in terms of both performance and energy consumption. Finally we discuss what we believe are the ongoing research questions for image processing in WSNs.