摘要:
Micromachined, thermally insensitive silicon resonators are provided having accuracy equivalent or superior to that of quartz resonators, and are fabricated from a micromechanical, silicon-on-glass process. In one embodiment, such a resonator is realized using a tuning fork gyroscope (4). Radiation-hard precision voltage references (PVRs) are enabled using the silicon resonators. Thermal sensitivity is reduced relative to that of a silicon-on-silicon process oscillator, providing a thermal sensitivity comparable to that of a quartz oscillator. By employing a micromechanical device based upon a tuning fork gyroscope (4), resonators are made from either or both of the gyro drive and sense axes. A resonator constructed as an oscillator loop (8) whose resonant frequency is compared to a frequency standard provides a bias voltage as a reference voltage (Vref).
摘要:
Guard bands (20a, 20b, 20c, 20d) in a tuning fork gyroscope reduce or eliminate force and sensitivity associated with proof mass (13) motion normal to the substrate (22) as a result of voltage transients. The guard bands reduce the undesired effects of transient voltages on electrostatic coupling of interleaved comb electrodes (12a, 18a; 14a, 18b; 14b, 18c; 12d, 18d). The guard bands are biased to reduce the coupling ratio to zero and thereby enable starting and improved performance. Various configurations of guard bands may be employed including distinct inner (20b, 20c) and outer (20a, 20d) guard bands, distinct inner guard bands only, extended sense electrodes below inner sensing combs with no outer guards, distinct outer guard bands with extended sense electrodes, and sense electrodes extended beneath both drive and sensing combs.
摘要:
A micromechanical tuning fork gyro having two center electrodes (9a, 9b). The two center electrodes are excited with bias potentials of opposite polarity. The oppositely biased center electrodes provide electrical symmetry across the gyroscope and thereby reduce charge transients and sensitivity to vertical translation. Currents injected directly into the proof masses (3a, 3b) are equal and opposite and thus cancel. Motor lift forces acting on the proof masses and interleaved electrodes equal, hence the proof masses move in pure translation, thereby reducing in-phase bias. Further, any pure translation normal to the plane of the gyroscope does not effect sense axis output signals.
摘要:
Dynamic balancing reduces quadrature bias in microfabricated vibrating instruments such as tuning fork gyros so that a purity of motion is achieved in the absence of any angular rate input. Balancing is achieved by ablating (74) or depositing (72) onto support structures (62) for a tuning fork gyroscope rather than the proof mass (60) itself by melting and moving material on a tuning fork beam (62). Such adjusting is advantageously done during actual operation of the gyro by laser beam application through an encapsulating transparent cover which can be either part of the chip die or an external package.
摘要:
A micromechanical tuning fork gyroscope comprises an input axis (38) which is out-of-plane of the structure, parallel capacitor strips (42, 43) beneath a pair of apertured, planar proof masses (10) suspended from a substrate (22) by a support structure (16), wherein the proof masses are set in opposed vibrational motion by an electrostatic comb drive (12, 14), whereby in response to an input angular rate, the proof masses (10) translate with respect to the striped capacitors (42, 43), thereby varying the capacitance between the strips and the proof masses as a function of the input rate.