Micromachined accelerometers have found large attention in recent years due
to their low-cost and small size. There are extensive studies with different
approaches to implement accelerometers with increased performance for a number of
military and industrial applications, such as guidance control of missiles, active
suspension control in automobiles, and various consumer electronics devices. This
thesis reports the development of various capacitive micromachined accelerometers
and various integrated CMOS readout circuits that can be hybrid-connected to
accelerometers to implement low-cost accelerometer systems.
Various micromachined accelerometer prototypes are designed and optimized
with the finite element (FEM) simulation program, COVENTORWARE, considering
a simple 3-mask surface micromachining process, where electroplated nickel is used
as the structural layer. There are 8 different accelerometer prototypes with a total of
65 different structures that are fabricated and tested. These accelerometer structures occupy areas ranging from 0.2 mm2 to 0.9 mm2 and provide sensitivities in the range
of 1-69 fF/g.
Various capacitive readout circuits for micromachined accelerometers are
designed and fabricated using the AMS 0.8 µ / m n-well CMOS process, including a
single-ended and a fully-differential switched-capacitor readout circuits that can
operate in both open-loop and close-loop. Using the same process, a buffer circuit
with 2.26fF input capacitance is also implemented to be used with micromachined
gyroscopes. A single-ended readout circuit is hybrid connected to a fabricated
accelerometer to implement an open-loop accelerometer system, which occupies an
area less than 1 cm2 and weighs less than 5 gr. The system operation is verified with
various tests, which show that the system has a voltage sensitivity of 15.7 mV/g, a
nonlinearity of 0.29 %, a noise floor of 487 Hz µ / g , and a bias instability of 13.9
mg, while dissipating less than 20 mW power from a 5 V supply. The system
presented in this research is the first accelerometer system developed in Turkey, and
this research is a part of the study to implement a national inertial measurement unit
composed of low-cost micromachined accelerometers and gyroscopes.
| Identifer | oai:union.ndltd.org:METU/oai:etd.lib.metu.edu.tr:http://etd.lib.metu.edu.tr/upload/1093475/index.pdf |
| Date | 01 January 2003 |
| Creators | Yazicioglu, Refet Firat |
| Contributors | Akin, Tayfun |
| Publisher | METU |
| Source Sets | Middle East Technical Univ. |
| Language | English |
| Detected Language | English |
| Type | M.S. Thesis |
| Format | text/pdf |
| Rights | To liberate the content for public access |
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