Vibratory Rate Research Articles

Vibration Characteristics of Twin Resonance Tuning-Fork Type Gyro. 1st Report, Method of Fine Tuning for making to High Gain.

Vibratory Rate Gyroscopes have a number of advantages, such as simple structure, stoutness, longlife and quick response, owing to the mechanism of the vibrating body and the absence of the bearings by comparison with the conventional rotating wheel gyro, and are available for a low price angular velocity sensor. However, Coriolis'force with the lower range of angular velocity for sensing is very small, much more the torsional vibration of the suspension mechanism for sensing. Therefore, this paper discribes an experimental study of the mechanical fine tuning for making the higher gain about twin resonance tuning-fork type gyro, and reports on the method of obtaining the resonance to which the torsional vibration system is stabilized.

Laterally oscillated and force-balanced micro vibratory rate gyroscope supported by fish-hook-shaped springs

A new concept for a micro vibratory rate gyroscope supported by fish-hook-shaped springs, where the oscillating position sensing and force balancing take place on the wafer surface, has been developed. The gyroscope consists of a grid-type planar mass, LT-shaped position-sensing electrodes to detect the Coriolis motion, pairs of force-balancing electrodes to improve the linearity and dynamic range, prominence-shaped comb-drive electrodes to improve the resolution by increasing the oscillating displacement, and fish-hook-shaped springs to match the first and second modes with the mass oscillating and position-sensing modes, respectively. Due to the relatively high stiffness of the proposed fish-hook-shaped springs except in the desired directions, the gyroscope tends to be quite insensitive to environmental vibrations or shocks, maintaining the electromechanical stability. Also the resonance frequencies associated with lateral vibration modes are independent of the change in thickness of the polysilicon structure, which guarantees a uniform sensitivity of the products. Experimental results show that the gyroscope has an equivalent noise level of 0.1 ° s −1 at 2 Hz, a bandwidth of 100 Hz, and a dynamic range of 90 ° s −1.

Preliminary results on a silicon gyrometer based on acoustic mode coupling in small cavities

A silicon vibratory gas angular rate sensor has been developed by means of micromachining techniques. It is a shockproof sensor because it has no movable part. This device is a miniaturized form of an instrument, which has been previously fabricated in a conventional technology format and called the acoustic gyrometer. The working principle of this sensor is based on acoustic coupling between two orthogonal modes of a closed cavity, due to Coriolis forces effect on vibrating gas particles. The gyrometer, which is presented in this paper, was fabricated by a silicon process. It is constituted by an acoustic cavity and four microphones: one to generate an acoustic wave, one to slave the cavity at its first resonance frequency, and two for the measurement of the angular rate effect. Finite element modeling (FEM) modal analyses were performed on two cavity shapes: cylindrical and trapezoidal, corresponding to the fabricated devices. The results are compared with available analytic solutions and with measurements.

Multimode digital control of a suspended polysilicon microstructure

Digital control of a suspended 350 /spl mu/m/spl times/380 /spl mu/m/spl times/1.6 /spl mu/m-thick surface-micromachined polysilicon plate is demonstrated in three degrees of freedom, with application to multimode accelerometers, vibratory rate gyroscopes, and actively positioned micromirrors. Plate displacement about the 2.2 /spl mu/m nominal position above the substrate is measured with shielded capacitive sensors connected to CMOS buffer circuits fabricated adjacent to the microstructure. Four micromechanical sigma-delta loops are used to control eight electrostatic actuators that drive the plate vertically (z) and in out-of-plane rotation (/spl theta/ and /spl phi/). Resonant frequencies are 2.7 kHz for the /spl theta/ rotational mode and 3.7 kHz for both z and /spl phi/ modes. The system is evaluated using a mixed mechanical/electromechanical/circuit simulation in SPICE. Closed-loop transient simulation of a 150-Hz square-wave position input signal is in good agreement with experimental results. Squeeze-film damping limits the plate slew rate to 0.83 mm/s in air. Position is controlled to within /spl plusmn/25 mm, being limited by quantization noise at the 50 kHz sampling rate.

A Novel Vibratory Device for Angular Rate Measurement

A vibratory angular rate sensor includes a vibrating element instead of a rotating element as in gyroscopes. The vibratory sensor can withstand high accelerations, has long operating life, and is not costly. A new configuration for a vibratory sensor is proposed and analyzed. The proposed scheme has high mechanical gain and low sensitivity to changes in its parameters. An experimental prototype was built and tested, and the results show good agreement with the analysis.

A review of vibratory gyroscopes

This paper describes the mechanical design of some vibratory rate gyroscopes. The principal commercial designs are identified and their operating principles are described. Only two designs based upon micromechanical methods of manufacture have been produced and these are still at an early stage of development. These designs are described and discussed.

振動ジャイロの位相特性 角速度の検出感度について

This paper describes the sensitivity of vibratory rate gyro as a sensor of angular velocity, which is detected by phase difference method. In a vibratory rate gyro, subvibration occurs due to the Coriolis' force, when the gyro is rotated around its longitudinal axis. The sensitivity depends on the angle between a straight line connecting the position of detector for subvibration to center of the gyro and the direction of mainvibration, and increases as the angle increases up to 90 degrees. Also the sensitivity depends on the difference between the two resonance frequencies of main- and subvibration, and increases as the difference becomes smaller.

The Dynamics of a Thin Piezoelectric Cylinder Gyroscope

The paper considers the theory of a new type of vibratory rate gyroscope. The design considered is based upon a thin cylindrical shell of radially polarized lead zirconate titanate on which are deposited drive and pick-off electrodes. The equations of motion of the cylindrical shell are derived and the response of the gyroscope to constant and harmonic rates of turn is determined.

The Theory of a Piezoelectric Disc Gyroscope

The theory of a new type of vibratory rate gyroscope is considered. The design considered is based upon a disc of piezoelectric material on which are deposited drive and pick-off electrodes. The equations of motion of the disc are derived and the response of the gyroscope to constant and harmonic rates of turn determined.

The effect of rotation on the steady state response of a spring-mass system under harmonic excitation

A two degree-of-freedom system, consisting of a point mass which is constrained to move in one plane, is considered. The motion is controlled by linear springs and viscous damping. A constant amplitude harmonic force is applied along one axis in the plane, which is rotating at a constant angular velocity about an axis perpendicular to the plane. Due to the rotation, oscillation takes place in the direction perpendicular to, as well as along, the axis of excitation. The amplitude and phase of the steady state vibrations are derived as a function of the excitation frequency and the rate of turn. For rates of turn very much less than the system natural frequencies, this theory covers the principles of vibratory rate sensors such as the tuning fork; however, the emphasis here is on the performance of the system when the angular velocity is of the same order as the natural frequencies of the system.

Comparison of vibratory and rotating-wheel gyroscopic rate indicators

RECENT ADVANCES in atmospheric and space flight have increased the need for reliable and accurate instrumentation for sensing the angular motions of aircraft, missiles, and space ships. Such measurements are especially needed for guidance and control purposes. At the present time, the preferred devices for measuring angular motion are based on the rotating-wheel gyroscope. By the expenditure of much research and development effort these gyroscopic devices have been brought to a state of perfection which makes inertial navigation technically feasible but very expensive. The present reliance on the rotating wheel does not mean that other devices have not been considered. Over the years a number of alternatives to the rotating wheel have been devised and some of these have been developed to the point where practical limitations on performance were found. In general, however, the total research and development effort that has been devoted to these alternatives has been rather small compared with the effort that has been expended in the refinement of the rotating-wheel gyroscope.