The goal of this paper is to suggest suitable method for angle measuring of mobile robot. There are being analyzed 3 different sensors – gyroscope, accelerometer and electronic compass in the prologue. Their advantages and disadvantages in the theoretical way are being explained in this part and also their opportunities of use in the practical way. In the following parts the work is focused on MEMS gyroscopes and their opportunities of use in the practical way with regard to achievable exactness and to the application for development of its exactness. The application of device together with main SW for microcontroller and the valuation of achievable exactness and determined facts are being described in the conclusion part.

Vehicle classification data especially trucks has an important role in both pavement maintenance and highway planning strategy. An advanced microelectromechanical system (MEMS) accelerometer for vehicle classification based on axle count and spacing was designed, tested, and applied to the pavement. Vehicle-pavement interaction was collected by the vibration sensor while vehicle axle count and spacing were calibrated later. Collected vibration data also used to analyze the pavement surface condition and compared with simulation using dynamic loading analysis. Laboratory tests using MMLS3 device to verify the accuracy of MEMS accelerometer and reaction under different surface condition were tested. An algorithm for calculating axle spacing and axle count was developed. Acceleration of different pavement surface condition were analyzed and compared with simulation results, the influence of surface condition to the pavement acceleration was concluded. / Master of Science

abstract: The applications which use MEMS accelerometer have been on rise and many new fields which are using the MEMS devices have been on rise. The industry is trying to reduce the cost of production of these MEMS devices. These devices are manufactured using micromachining and the interface circuitry is manufactured using CMOS and the final product is integrated on to a single chip. Amount spent on testing of the MEMS devices make up a considerable share of the total final cost of the device. In order to save the cost and time spent on testing, researchers have been trying to develop different methodologies. At present, MEMS devices are tested using mechanical stimuli to measure the device parameters and for calibration the device. This testing is necessary since the MEMS process is not a very well controlled process unlike CMOS. This is done using an ATE and the cost of using ATE (automatic testing equipment) contribute to 30-40% of the devices final cost. This thesis proposes an architecture which can use an Electrical Signal to stimulate the MEMS device and use the data from the MEMS response in approximating the calibration coefficients efficiently. As a proof of concept, we have designed a BIST (Built-in self-test) circuit for MEMS accelerometer. The BIST has an electrical stimulus generator, Capacitance-to-voltage converter, ∑ ∆ ADC. This thesis explains in detail the design of the Electrical stimulus generator. We have also designed a technique to correlate the parameters obtained from electrical stimuli to those obtained by mechanical stimuli. This method is cost effective since the additional circuitry needed to implement BIST is less since the technique utilizes most of the existing standard readout circuitry already present. / Dissertation/Thesis / M.S. Electrical Engineering 2014

No description available.

Over the past two decades, Micro-Electro-Mechanical System (MEMS) based accelerometers, benefiting from relatively simple structure, low-power consumption, high sensitivity, and easy integration, have been widely used in many industrial and consumer electronics applications. For the high precision accelerometers, a significant technical challenge is to design a low-noise readout circuit to guarantee the required high resolution of the entire integrated system. There are three main approaches for improvement of the noise and offset of the readout circuit, namely auto-zero (AZ) and correlated double sampling (CDS) for the switched- capacitor (SC) circuit and chopper stabilization (CHS) for the continuous-time circuit. This thesis investigates the merits and drawbacks of all three techniques for reading the capacitance of a low noise MEMS accelerometer developed in our group. After that, we compare the different effects of the three technologies on noise, offset, output range, linearity, dynamic range, and gain. Next, we present the design of the most suitable structure for our sensor to achieve low noise, low offset, and high precision within the working frequency. In this thesis, the design and post-layout simulation of the circuit is proposed, and the fabrication is currently in progress. The readout circuit has reached the noise floor of the sub-μg, which meets the strict requirements of low noise MEMS capacitance-to-voltage converter. A high-performance accelerometer system is regarded as the core of a low-noise, high-resolution geophone. We show that together with the MEMS accelerometer sensor, the readout circuit provides competitive overall system noise and guarantees the required resolution.

This thesis presents a detailed SIMULINK model for a conventional capacitive &amp / #931 / -&amp / #916 / accelerometer system consisting of a MEMS accelerometer, closed-loop readout electronics, and signal processing units (e.g. decimation filters). By using this model, it is possible to estimate the performance of the full accelerometer system including individual noise components, operation range, open loop sensitivity, scale factor, etc. The developed model has been verified through test results using a capacitive MEMS accelerometer, full-custom designed readout electronics, and signal processing unit implemented on a FPGA. Conventional accelerometer system with force-feedback is used in this thesis. The sensor is a typical capacitive lateral accelerometer. The readout electronics form a 2nd order electromechanical &amp / #931 / -&amp / #916 / modulator together with the accelerometer, and provide a single-bit PDM output, which is decimated and filtered with a signal processing unit, software implemented on a FPGA. The whole system is modeled in MATLAB-SIMULINK since it has both mechanical and electrical parts. To verify the model, two accelerometer systems are implemented. Each accelerometer system is composed of a MEMS accelerometer, readout circuit, and decimation filters. These two different designs are implemented and simulation and test results are compared in terms of output noise, operational range, open loop sensitivity, and scale factor. The first design operates at 500 kHz sampling rate and has 0.48 V/g open-loop sensitivity, 58.7 &micro / g/&amp / #8730 / Hz resolution, &plusmn / 12g operation range, and 0.97*10-6 g/(output units) scale factor, where these numbers are in close agreement with the estimated results found with simulations. Similarly, the second design operates at 500 kHz sampling rate and has 0.45 V/g open-loop sensitivity, 373.3 &micro / g/&amp / #8730 / Hz resolution, &plusmn / 31g operation range, and 2.933*10-6 g/(output units) scale factor, where these numbers are also close to the estimated results found with simulations. Within this thesis study, an accelerometer sensing element design algorithm is also proposed which is based on the theoretical background obtained in accelerometer system SIMULINK model. This algorithm takes the requirements of the desired accelerometer as input and outputs the dimensions of the minimum noise accelerometer satisfying these requirements. The algorithm is extended to design three different accelerometer structures. An accelerometer sensing element is designed using the proposed design algorithm and tested in order to see performance matching of the algorithm. The designed accelerometer has &plusmn / 33.02g operational range and 155&micro / g/&amp / #8730 / Hz noise where these numbers matches with the values found by the algorithm

Micromachining technologies enabled the use of miniaturized transducers in many high technology sensing systems. These transducers have many advantages like small-size, low-cost and high-reliability. One of the applications micro-machined transducers are used is inertial navigation systems, where the exact position of a moving frame is continuously monitored by tracking the linear and angular motions of the frame. Other than navigation applications, inertial sensors are used in health and military applications as well as consumer electronics. Today accelerometers capable of measuring accelerations from 0.5g-1g range up to several thousand g&rsquo / s are commercially available in the market which have been fabricated using micromachining technologies. The aim of this research is to develop such a state-of-the-art micro-machined accelerometer system, whose performance is expected to reach tactical-grade level. In order to achieve these performance values a MATLAB algorithm is developed to optimize the accelerometer performances in the desired levels. Expected performance parameters of the designed accelerometer structures are extracted from the simulations done by both Coventorware finite element modeling tool and MATLAB. Designed structures are then fabricated with silicon-on-glass, dissolved wafer and dissolved epitaxial wafer processes. These fabrication results are compared and it is observed that highest yield accelerometers are fabricated with the SOG process. But these accelerometers could not be able to satisfy tactical grade performance parameters. Best performances are obtained with DWP, but due to high internal stress, yield of the sensors were very low. DEWP increased the yield of this process from 2-3% to 45-50% but the expected operation range of the designs dropped to &plusmn / 12.5g range. Using the fabricated accelerometers in DEWP a three axial accelerometer package is prepared and tests results proved that this three axial accelerometer system was satisfying the tactical grade requirements. In addition to these a three axial monolithic accelerometer fabrication technique is proposed and sensors are designed which are suitable for this process. Best performances achieved with single axis accelerometers were 153&micro / g/&radic / Hz noise floor, 50&micro / g bias drift, 0.38% non-linearity and a maximum operation range of 33.5g which has the higher dynamic range among its counterparts in the literature. Performance results achieved with the three axes accelerometer were ~150&micro / g bias drift, &lt / 200&micro / g/&radic / Hz noise density, ~0.4% non-linearity with higher than &plusmn / 10g operation range.

MEMS accelerometers are quickly approaching navigation grade performance and navigation market for MEMS accelerometer systems are expected to grow in the recent years. Compared to conventional accelerometers, these micromachined sensors are smaller and more durable but are generally worse in terms of noise and dynamic range performance. Since MEMS accelerometers are already dominant in the tactical and consumer electronics market, as they are in all modern smart phones today, there is significant demand for MEMS accelerometers that can reach navigation grade performance without significantly altering the developed process technologies. This research aims to improve the performance of previously fabricated and well-known MEMS capacitive closed loop &Sigma / &Delta / accelerometer systems to navigation grade performance levels. This goal will be achieved by reducing accelerometer noise level through significant changes in the system architecture and implementation of a new electronic interface readout ASIC. A flexible fourth order &Sigma / &Delta / modulator was chosen as the implementation of the electro-mechanical closed loop system, and the burden of noise shaping in the modulator was shifted from the mechanical sensor to the programmable electronic readout. A novel operational transconductance amplifier (OTA) was also designed for circuit implementation of the electronic interface readout. Design and fabrication of the readout was done in a standard 0.35 &micro / m CMOS technology. With the newly designed and fabricated readout, single-axis accelerometers were implemented and tested for performance levels in 1g range. The implemented system achieves 5.95 &micro / g/sqrt Hz, 6.4 &micro / g bias drift, 131.7 dB dynamic range and up to 37.2 g full scale range with previously fabricated dissolved epitaxial wafer process (DEWP) accelerometers in METU MEMS facilities. Compared to a previous implementation with the same accelerometer element reporting 153 &micro / g/sqrtHz, 50 &micro / g bias drift, 106.8 dB dynamic range and 33.5 g full scale range / this research reports a 25 fold improvement in noise, 24 dB improvement in dynamic range and removal of the deadzone region.

The healthy condition of a rotating machine leads to safe and cheap operation of almost all industrial facilities and mechanical systems. To achieve such a goal, vibration-based condition monitoring has proved to be a well-accepted technique that detects incipient fault symptoms. The conventional way of On-Bearing Vibration Measurement (OBVM) captures symptoms of different faults, however, it requires a relatively expensive setup, an additional space for the auxiliary devices and cabling in addition to an experienced analyst. On-Shaft Vibration Measurement (OSVM) is an emerging method proposed to offer more reliable Faults Diagnosis (FD) tools with less number of sensors, minimal processing time and lower system and maintenance costs. The advancement in sensor and wireless communications technologies enables attaching a MEMS accelerometer with a miniaturised wireless data acquisition unit directly to the rotor without altering the machine dynamics. In this study, OSVM is analysed during constant speed and run-up operations of a test rig. The observations showed response modulation, hence, a Finite Element (FE) analysis has been carried out to help interpret the experimental observations. The FE analysis confirmed that the modulation is due to the rotary motion of the on-shaft sensor. A demodulation method has been developed to solve this problem. The FD capability of OSVM has been compared to that of OBVM using conventional analysis where the former provided more efficient diagnosis with less number of sensors. To incorporate more features, a method has been developed to diagnose faults based on Principal Component Analysis and Nearest Neighbour classifier. Furthermore, the method is enhanced using Linear Discriminant Analysis to do the diagnosis without the need for a classifier. Another faults diagnosis method has been developed that ensures the generalisation of extracted faults features from OSVM data of a specific machine to similar machines mounted on different foundations.

This paper reports the evaluation results of the mechanical structures of MEMS (micro electro mechanical systems) sensor implemented in the integrated MEMS inertial sensor for a wide sensing range from below 0.1 G to 20 G (1 G = 9.8 m/s^2). To investigate the mechanical tolerance, a maximum target acceleration of 20G was applied to the sub-1G sensor which had the heaviest proof mass of all that sensors had. The structure stability of Ti/Au multi-layered structures was also examined by using Ti/Au micro cantilevers. The results showed that the stoppers effectively functioned to prevent the proof mass and the springs from self-destruction, and that the stability of Ti/Au structures increased with an increase in width. Those results suggest that the proposed stopper and spring structures could be promising to realize MEMS sensors.