This paper presents a structural improvement method for temperature coefficient of resonance frequency (TCF) in resonant silicon sensors. A silicon resonator, whose mass was suspended by a slanted flexible beam, was adopted in this study. The slanted suspension beam was formed by (1 0 0) and (1 1 1) crystal planes and fabricated by anisotropic wet etching. We propose a stress buffer structure to improve the robustness of resonance frequency against temperature variations. Theoretical considerations of the tested resonator are proposed to augment the effect of the buffer structure. The temperature dependence of the resonance frequency is experimentally characterized over the range −40°C to 60°C. The TCF of the original resonators with no stress buffer structure was linearly fitted to be 36 and 40 ppm/°C . After using an appropriate stress buffer structure, the TCF is linearly fitted to be −0.98 and 0.36 ppm/°C . The experimental results suggest that the TCF of the resonator is improved to sub-ppm/°C level by using a stress buffer structure, which has more than an order of magnitude improvement comparing to the original one. The small range of TCF is much more convenient to be compensated by electrical ways.
We present a dynamic electrical balancing of coupling stiffness for improving the bias stability of micromachined gyroscopes, which embeds the coupling stiffness in a closed-loop system to make the micromachined gyroscope possess more robust bias stability by suppressing the variation of coupling stiffness. The effect of the dynamic electrical balancing control is theoretically analyzed and implemented using a silicon micromachined gyroscope as an example case. It has been experimentally shown that, comparing with open loop detection, the proposed method increased the stability of the amplitude of the mechanical quadrature signal by 38 times, and therefore improved the bias stability by 5.2 times from 89 to 17 deg/h , and the temperature stability of scale factor by 2.7 times from 622 to 231 ppm/°C . Experimental results effectively indicated the theoretical model of dynamic electrical balancing of coupling stiffness.
In order to improve its structural sensitivity, a vibratory microgyroscope is commonly sealed in high vacuum to increase the drive mode quality factor. The sense mode quality factor of the microgyroscope will also increase simultaneously after vacuum sealing, which will lead to a long decay time of free response and even self-oscillation of the sense mode. As a result, the mechanical performance of the microgyroscope will be seriously degraded. In order to solve this problem, a closed-loop control technique is presented to adjust and optimize the sense mode quality factor. A velocity feedback loop was designed to increase the electric damping of the sense mode vibration. A circuit was fabricated based on this technique, and experimental results indicate that the sense mode quality factor of the microgyroscope was adjusted from 8052 to 428. The decay time of the sense mode free response was shortened from 3 to 0.5 s, and the vibration-rejecting ability of the microgyroscope was improved obviously without sensitivity degradation.
For capacitive micromahcined accelerometers, in order to measure external acceleration, forces balance is usually introduced in the device. According to the conditioning circuitry adopted, this paper identifies three kinds of forces balance in the micromahcined accelerometer, namely, elastic forces balance, electrostatic forces balance and combination forces balance. Their performances such as linearity and frequency response are analyzed respectively
This paper presents a five DOF parallel manipulator. It consists of a four-DOF parallel manipulator and a rotate table. This kind of manipulator can be used in the field of micro machining and micro assembly. It owns all the advantage of parallel structure such as high stiffness, small dimension, low cost and high accuracy. Commonly the direct kinematics solution of a parallel structure is very difficult to solve, because it comes down to getting the answers of several connected nonlinear equations. While that problem becomes very easy for our five DOF parallel machine tool because we use some special parameters to determine the spatial position of the end-effector. That results in the convenience of analyzing the kinematical characteristic.
KEYWORDS: Sensors, Information fusion, Probability theory, Data processing, Intelligence systems, Information theory, Data fusion, Distance measurement, Operational intelligence, Automatic target recognition
In the operation of an intelligent system, the role of multi-sensor integration and fusion can best be understood with reference to the type of information that the integrated multi-sensor can uniquely provide the system. The potential advantages gained through the synergistic use of this multi-sensor information can be decomposed into a combination of four fundamental aspects: the redundancy, complementarily, timeliness, and cost of the information. In this paper, the concept of fusion entropy is presented by generalizing the entropy theory, it is defined to be the posterior entropy of the fusion system. The validity of multi-sensor fusion is proved based on the transition of fusion entropy in information process; the result shows that the uncertainty in the output of a multi-sensor system is less than that in the output of a single sensor system. And then the rule to choose the multi-sensor is presented by the theorem.
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