Abstract: An apparatus and/or method that corrects for tuning errors in vibrating structure gyroscopes that are configured to be driven along a plurality of axes without the need for dedicated torque elements. The correction is accomplished by introducing a phase offset in the drive signal of one or more of the drive elements relative to other drive elements to minimize or reduce the quadrature signal. The tuning may be accomplished as a one time “set and forget” adjustment, as a manual adjustment performed at the discretion of the user, or as a closed loop active correction system. The technique improves the tuning of the resonator assembly, rather than merely compensating for the mistuning. Accordingly, for various embodiments of the invention, the destructive interference between the plurality of drive axes is reduced. Conservation of vibrational energy present in the resonator is thus enhanced, with less vibrational energy transferred to the support structure.

Abstract: An apparatus and method for compensation of the effects of various bias errors encountered by inertial rate gyroscopes, particularly vibrating element gyroscopes, configured to detect heading relative to true north. Certain embodiments are suitable for reducing rotational dynamic errors associated with rotating gyroscopes. Other embodiments may include compensation of biases not related to rotational dynamics, such as thermal drift. The various methods disclosed may also account for the bias by sampling the rotational vector of the earth at an arbitrary heading, and at a heading that is 180° offset from the arbitrary heading. The sequence may be repeated numerous times to compensate for bias drift. The bias drift may be constant with respect to time (linear) or changing over time (non-linear) during the data acquisition sequence. Some embodiments include methods that utilize data from accelerometers to infer the bank and elevation angles as well as earth latitude location relative to the equator.

Abstract: A method for compensating for bias and scale factor errors in vibrating structure gyroscopes. Certain embodiments utilize the functional relationship that bias and scale factor errors have with resonant frequency of vibration in the main vibrating body. Other embodiments utilize the functional relationships that other drive parameters of vibrating structure gyroscopes, such as drive voltage, have with bias and scale factor errors. The various methods may be used repeatedly during normal gyroscope operation in order to continually compensate for the bias and scale factor errors.

Abstract: A vibrating inertial rate sensor has operational elements that define axes that are rotationally offset or “skewed” from a node or anti-node reference axis. The skew may be relative to separate node or anti-node reference axes, or take the form of an element that is “split” about the same node axis. Both the drive signal and the sense signal may be resolved from a common set of sensing elements. The drive elements may also operate on a skewed axis angle to rotationally offset the vibration pattern to affect active torquing of the gyroscope. Skewed drive elements may be combined with skewed or split elements on the same device. The skewed sensing scheme may be applied to vibratory systems having one or more node axes. The skewed drive scheme may be applied to vibratory systems having two or more node axes to affect active torquing.

Abstract: A vibrating inertial rate sensor has sense elements that operate on axes that are rotationally skewed from a node reference axis, enabling both a rate sense and a drive sense determination. Alternatively, the skew may be applied to rotationally offset the drive elements from antinode reference axes to affect active torquing of the gyroscope. The skewed sensing scheme may be applied to vibratory systems having one or more node axes. The skewed drive scheme may be applied to vibratory systems having two or more node axes to affect active torquing.

Abstract: A drive circuit apparatus for use in generating a drive signal for energizing an actuator about a natural resonant frequency is disclosed. The circuit has a counter that generates a count sequence derived from a drive sense signal. Additionally, a demodulator is further coupled to the counter and generates a voltage level signal from the drive sense signal based on the count sequence. A digital to analog (D/A) converter is coupled to both the counter and demodulator. The D/A converter generates the drive signal in a substantially constant phase relationship with respect to the drive sense signal as derived from the voltage level signal and based on the count sequence. In addition, a method of generating a drive signal for energizing an actuator about a natural resonant frequency is provided.

Abstract: A drive circuit apparatus for use in generating a drive signal for energizing an actuator about a natural resonant frequency is disclosed. The circuit has a counter that generates a count sequence derived from a drive sense signal. Additionally, a demodulator is further coupled to the counter and generates a voltage level signal from the drive sense signal based on the count sequence. A digital to analog (D/A) converter is coupled to both the counter and demodulator. The D/A converter generates the drive signal in a substantially constant phase relationship with respect to the drive sense signal as derived from the voltage level signal and based on the count sequence. In addition, a method of generating a drive signal for energizing an actuator about a natural resonant frequency is provided.

Abstract: A structure and arrangement for improving the accuracy and efficiency of an angular rate sensing gyroscope is herein disclosed. Voltage pick-off conductors are applied to an area of the surface of a resonating element of an angular rate sensing gyroscope that is subject to substantially zero stress when the gyroscope is rotationally stationary. Actuator conductors are similarly applied to a resonating element at a location bounded by areas of the resonating element subject to substantially uniform levels of stress when the gyroscope is rotationally stationary. A method for improving the voltage response of a piezoelectric resonating element is also disclosed.

Abstract: A structure and arrangement for improving the accuracy and efficiency of an angular rate sensing gyroscope is herein disclosed. Voltage pick-off conductors are applied to an area of the surface of a resonating element of an angular rate sensing gyroscope that is subject to substantially zero stress when the gyroscope is rotationally stationary. Actuator conductors are similarly applied to a resonating element at a location bounded by areas of the resonating element subject to substantially uniform levels of stress when the gyroscope is rotationally stationary. A method for improving the voltage response of a piezoelectric resonating element is also disclosed.

Abstract: A feedback circuit for generating an output signal from a sensor that makes changing electrical and temperature characteristics of the sensor and any sensing medium irrelevant. The sensor is placed in the forward loop of the circuit to make the output depend on the area of the parallel plates the sensor, not on any electrical or temperature characteristics of the sensor or sensing medium. A liquid filled sensor having parallel conducting plates, one solid and the other being split into two differential plate sections may be used in the forward loop as a liquid level sensor or an inclinometer. Alternative sensors such as inductive sensors may also be used.

Abstract: An angular rate sensor system [10] comprising a vibratory sensing element [12] and signal processing circuit [14]. The element [12] is preferably a polymorphic rectangular bar fabricated from two layers of piezoceramic material [26, 28] divided by a thin center electrode [E.sub.c ], and a plurality of electrodes [E.sub.1 -E.sub.4 ] scored onto the planar conductive surfaces [30, 32]. The element [12] is suspended at its acoustic nodes [N, N'] to vibrate in one direction [V] normal to the physical plane of the electrodes [E.sub.c, E.sub.1 -E.sub.4 ] using any suitable mounting structure such as parallel crossed filaments [34] or inwardly angled support arms [64] that provide predetermined degrees of lateral [S'] and longitudinal [S] stiffness. The circuit [14] may optionally constitute totally shared [FIG. 7], partially shared [FIG. 8], or totally isolated [FIG. 9] driving and sensing functions, the corresponding element [12] being configured with dual-pair, single-pair, or single-triple outer electrodes [E.

Abstract: An angular rate sensor system preferably comprising closely spaced vibrating drive and sensing elements in a paired tuning fork configuration mounted to rotate about a rotational axis oriented perpendicular to the sensitive axes. The rotational drive assembly includes an encoder to modulate sensing element orientation, and coupling means to transmit drive and output signals to and from the rotating elements. Each pair of sense and drive elements are disposed in non-aligned parallel side-by-side opposition across the axis of rotation. The elements may be carried on torsional masses including a resilient coupling therebetween. The angular rate sensor system may be utilized as a north-seeking gyroscope in applications such as mining, surveying, or artillery. The phase of the sinusoidal sensor output signal corresponds to the orientation between the sensitive axis of the sensing elements and the earth's angular rate vector to produce a reference to geographic north.

Abstract: A single core triaxial flux-gate magnetometer including a tall-toroidal core having a radial excitation winding, two orthogonal sets of axial or circumferential output windings, and an equatorial output winding oriented orthogonal to both axial output windings. The core is fabricated from a strip of magnetic tape material wrapped to form a toroid having a height approximately equal to its diameter. Each end of the strip is uniformly tapered along the top and bottom edges such that the tapered segments extend around an integer multiple of complete revolutions of the wrapping, the length of each tapered segment thereby being equal to the inner or outer circumference of the toroid or an integer multiple thereof.

Abstract: Angular rate sensors are disclosed. Each sensor includes a forked vibrating element having two tines extending from a base end to a free end. Each of the tines are magnetized to have two regions of opposing magnetic polarity, with the polarity of corresponding regions between the different tines being opposite. In a first embodiment, the tines are driven in complementary resonant vibration by a pair of drive coils positioned about the tines near the free ends thereof. In a second embodiment, the drive coils are located about the tines at the junction of the regions of magnetization mid-element. In the first embodiment, sense motions are detected by a pair of sense coils positioned about mid-element near the junction of the first and second regions of magnetization. In the second embodiment, sense motions are detected by capacitive sensing, which consists of two parallel plate capacitors formed of the tines and additional plates, which are connected for differential sensing.

Abstract: An angular rate sensor structure displaying high immunity to noise and feedback vibration is disclosed. Mounting elements (15) support a pair of matched vibratory piezoelectric bender elements (10) in symmetrical opposed alignment about a nodal axis (20). Each vibratory element includes a drive element (10A) and sense element (10B) connected to and for operative movement with the drive element. Resonance drive element (30) moves the vibratory elements (10) in a first mode of movement, in dirct opposition to one another about the nodal axis. The sensing members (10B) detect movement of the vibratory elements in directions other than in the first mode of movement resulting from application of external angular rate forces applied to the vibratory elements.

Abstract: An electronic drive circuit for driving an actuator mass for a sensor apparatus is disclosed. The driver requires no compensation or bridge elements. The actuator mass is directly driven by a square wave drive signal such that all of the capacitors loading errors associated with the driven actuator means are concentrated in time to that time interval in which the drive signal traverses between its two stable states. A sensor circuit connected to monitor the sensor output response signal is blanked out during the drive signal transition time interval, which effectively eliminates the transition drive noise energy from the sensed output signal.

Abstract: A method and apparatus for removing quadrature error signal components from synchronous AM demodulation signals are disclosed. A synchronous AM demodulator processes a synchronous sensor output signal in phase relation to a phase reference signal. Means are provided for dynamically producing a counteracting signal that is stably phase related to the system reference signal. The counteracting signal is in phase with the quadrature component of the synchronous signal such that when added to the synchronous signal, the quadrature component thereof is minimized or eliminated.

Abstract: A structure and arrangement for improving the accuracy and efficiency of an angular rate sensing gyroscope is herein disclosed. Voltage pick-off conductors are applied to an area of the surface of a resonating element of an angular rate sensing gyroscope that is subject to substantially zero stress when the gyroscope is rotationally stationary. Actuator conductors are similarly applied to a resonating element at a location bounded by areas of the resonating element subject to substantially uniform levels of stress when the gyroscope is rotationally stationary. A method for improving the voltage response of a piezoelectric resonating element is also disclosed.

Abstract: An angular rate sensor system [10] comprising a vibratory sensing element [12] and signal processing circuit [14]. The element [12] is preferably a polymorphic rectangular bar fabricated from two layers of piezoceramic material [26, 28] divided by a thin center electrode [Ec], and a plurality of electrodes [E1-E4] scored onto the planar conductive surfaces [30, 32]. The element [12] is suspended at its acoustic nodes [N, N?] to vibrate in one direction [V] normal to the physical plane of the electrodes [Ec, E1-E4] using any suitable mounting structure such as parallel crossed filaments [34] or inwardly angled support arms [64] that provide predetermined degrees of lateral [S?] and longitudinal [S] stiffness. The circuit [14] may optionally constitute totally shared [FIG. 7], partially shared [FIG. 8], or totally isolated [FIG. 9] driving and sensing functions, the corresponding element [12] being configured with dual-pair, single-pair, or single-triple outer electrodes [E1-E4], respectively.

Abstract: A structure and arrangement for improving the accuracy and efficiency of an angular rate sensing gyroscope is herein disclosed. Voltage pick-off conductors are applied to an area of the surface of a resonating element of an angular rate sensing gyroscope that is subject to substantially zero stress when the gyroscope is rotationally stationary. Actuator conductors are similarly applied to a resonating element at a location bounded by areas of the resonating element subject to substantially uniform levels of stress when the gyroscope is rotationally stationary. A method for improving the voltage response of a piezoelectric resonating element is also disclosed.