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| Silicon Sensing Systems Japan Ltd.[31] | |
| The rate gyroscope uses Coriolis effect of sensor element(vibrating resonator chip) to sense the speed of rotation(rate of turn). The new concept ring-shaped micro-machined resonator shows distinguished resistance against external shocks and vibrations over a wide range of temperature. Prefered by the customers of different applications due to its reliability compared to other gyros, about 4 million have thus been produced here at Amagasaki-Japan as of October 2002. | |
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| Electrostatically levitating micromotor for inertia measurement system[32] | |
An electrostatically levitating micromotor has been developed for an high precision inertia measurement system (not only two-axis gyroscope but also three-axis accelerometer)[53]. The rotor is fabricated using the deep RIE of silicon. The levitation is performed by force balancing in all direction using capacitive displacement sensing and electrostatic actuation. A silicon rotor is packaged in a vacuum cavity and the gaps between the silicon rotor and the electrodes on the glasses are 5um. The levitation and rotation (1000 rpm/min) were successfully demonstrated. |
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| Resonating angular rate sensor[33] | |
Small size resonant angular rate sensors(i.e. gyroscopes have been developed). The sensor shown(right) has a resonator which is driven electrostatically in lateral direction. When it is rotated, the resonator causes a vibration in perpendicular direction by the Corioli’s force and it is detected capacitively. The beam size is precisely controlled using following advanced dry etching process. Silicon is etched vertically using the deep RIE and the etched side wall is oxidized. Silicon is etched using the XeF2 etching and such structure shown(left) is obtained. Finally the side wall oxide is etched out.  |
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| Henry Samueli School of Engineering - Inertial Micro-Electro-Mechanical Systems[34] | |
| MEMS gyroscopes are probably the most challenging type of transducers ever attempted to be designed in micro-world. A nail size dynamic system integrated with control electronics on the same silicon chip is designed to be a very sensitive sensor which is able to detect maneuvers and motions that are even beyond human perception. Along with exciting opportunities which MEMS gyroscopes could bring to our everyday life, the miniaturization introduces many technical challenges in the design, analysis, and control. Development of such systems is currently an active area of research. Silicon micromachined Z-axis gyroscope for angle measurement (patent pending). The chip is fabricated using Sandia National Lab iMEMS technology. MEMS gyroscopes are vibratory systems operating on the principle of induced motion by the inertial Coriolis force. |
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| The following three pictures illustrate a design of silicon micromachined string gyroscope and a gyroscope packaged in a standard 24-pin ceramic IC package. | |
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| Radial Comb Drive[35] | |
An eight segment, radial comb drive centrally supported via a spiral spring. The eight radial elements are grouped into four pairs supported, each on a common arm connected to the outer ring of the spiral spring. Potential differences are applied alternately between each pair, the electrostatic attraction resulting in the the support arms being rotated clockwise or counterclockwise. The spiral spring provides the restoring force. The device is thus set into oscillation at a characteristic frequency, largely determined by the stiffness of the support spring, the mass of the sprung weight and damping from the surrounding medium. The following image shows the complete 2-D layout of the device shown in MEMS Pro (courtesy MEMSCAP S.A.).
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| A Resonating Comb/Ring Angular Rate Sensor Vacuum Packaged Via Wafer Bonding[35] | |
| A scanning electron photomicrograph of the earliest version of the sensor element is shown(left). Semi-circular springs support the 1 mm diameter ring and store the vibrational energy. The springs are attached to the substrate with a symmetric post. The post/spring design greatly reduces the effect of packaging stresses on the sensor. Package-induced stress has been a long-standing problem for many other sensor programs. The micromachined structure shown(right) is the result of merging the ring device and comb structure. Adding the comb obviously increases the signal size obtained from the vibrating ring.   |
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