Litton Systems, Inc.

Northrop Grumman Systems Corporation

Litef Gmbh

Northrop Grumman Guidance and Electronics Company, Inc.

John G Mark

Daniel A Tazartes

David I Tazartes

Tae W Hahn

Amado Cordova

Brian T Lottman

Agop Hygasov Cherbettchian

Anthony Robert Matthews

Robert E Ebner

Daniel P Wiener

Michael W Denice, Jr

Dean E Lottman

David Barnett Hall

Eric Lee Goldner

George A Pavlath

Stanley F Wyse

Donald A Frederick

Edward Kanegsberg

Robert John Buchler

Alison K Brown

James R Steele

Daniel Perrine McLane

Arnold E Goldman

Albert V Scappaticci

Juergen K Flamm

Peter Kyriacou

Bruce C Grover

Ray D Dykeman

John E Higbee

Ike J Song

Shaw-Wen Fann

James G Welker

K Juergen Flamm

Anthony Mathews

Mauricio Ribes

Daniel A Tarzartes

William B Ware

Jacque A Tazartes

Shaw W Fann

Nibir K Datta

Neal J Dahlen

Yumi Yoshida

Roger L Meyer

G Kevin Liu

Craig C Hansen

Jonathan A Lincoln

Yury A Litmanovich

Philip T Kent

Larry R Moeller

Robert J Buchler

A method of distinguishing an analog drive signal from a pickoff signal for attenuating the effect of electrical cross-coupling between the analog drive signal and the pickoff signal. The method may include receiving a periodic digital signal at a first frequency in the form of a stream of digital data values, randomly inverting at least one of the digital data values and converting the stream of digital data values to a stream of analog data values to form an analog drive signal. The method may also include driving a sensor, physically coupled to a resonant member configured to oscillate at a second frequency, using the analog drive signal and sensing changes in the movement of the resonant member detected by the sensor for producing a pickoff signal.

Modulation method for signal crosstalk mitigation in electrostatically driven devices

System and method for measuring force-dependent gyroscopic sensitivity. A force-effect model of the effects of acceleration on the output of a gyro triad is determined. Rotation sequences are then devised to permit excitation and observation of force-effect model parameters in order to provide calibration information for these parameters. A state diagram containing the gyro triad force-effect model parameters is derived from the force-effect model, where moving from one position in the state diagram to another position indicates the gyro triad error which would occur in rotating the gyro triad according to a corresponding motion. Searching for all possible closed loop paths achievable through the state diagram, by a multiple-axes rate table with a specified number of rotations, to separate gyro triad error calibration from the accelerometer calibration. Closed loop paths having minimal lengths and exhibiting larger error sensitivity are chosen to perform error parameter calibration and reduce force-dependent gyroscopic sensitivity.

Method for measuring force-dependent gyroscope sensitivity

Multiple isolators are configured with respect to an assembly (), such as a sensor assembly in an inertial navigation system or other system where cross-axis acceleration or rotation coupling is undesirable. The system utilizes a set of isolators (andorand) that are substantially matched to each other, but may have uncorrelated axial stiffness and radial stiffness. The system configuration does not introduce cross-axis coupling, such as cross-axis translational coupling and cross-axis rotational coupling.

Isolator and assembly configuration

The invention is a method and apparatus for repetitively executing a plurality of software packages at a plurality of rates utilizing a common set of computational resources. The method consists of counting contiguous time increments and executing a plurality of software packages. Each software package is executed during each time increment in one or more sequences of time increments. The time increments in each sequence recur at a predetermined rate, and the time increments assigned to one software package do not overlap the time increments assigned to any other of the plurality of software packages.

Partitioned executive structure for real-time programs

A sleeve ( ) enables attachment of an optic fiber ( ) to a multi-integrated optic chip ( ) in optical communication therewith, and maintains alignment of the fiber at its end adjacent the chip. The sleeve includes a symmetrically-shaped cavity ( ) bounded by termini ( ) which are respectively disposed to fit onto the chip and to accept the fiber. An adhesive ( ) within the cavity symmetrically bonds the fiber to the chip. The adhesive cures symmetrically in the cavity, to eliminate undesired motion of the fiber from its preferred alignment position vis-a-vis the chip connection point ( ) or to provide a repeatable motion to achieve the optimum alignment position of the fiber with respect to the chip. The sleeve may be left in place or, alternatively, it may be removed. The sleeve controls, defines and confines the index matching adhesive and/or fluid between fiber end ( ) and connection point ( ) by defining the areas and volume actually in contact with the adhesive or fluid. Symmetry is preserved over the effects of gravity and wicking which heretofore have prevented a very symmetrical pigtail which is necessary for performance and repeatability.

Sleeve for pig-tailing optical fiber

Apparatus and a method for compensating production or operationally-induced inaccuracies in the binary-weighted electrodes of a high-resolution digital phase modulator of, for example, a fiber optic gyroscope. Programmable correction values are employed to increase the accuracy of each binary-weighted planar electrode. In the invention, a less significant component of the binary drive signal, if appropriate after compensation in a low resolution digital-to-analog converter, is converted into an analog signal that is applied to a specific or a separate additional electrode of the digital phase modulator.

Digital phase modulator

The invention is a method and apparatus for processing signals with frequencies f and f from a multioscillator ring laser gyro, the method being repeated at regular time intervals. The difference f , of f and f is a measure of the angular rotation rate of the ring laser gyro and the sum f of f and f divided by 2 is the Faraday bias frequency. The first step of the method comprises determining two or more of the values M , M , M , and M of a set of functions M (f ), M (f ), M (f ), and M (f ). The second step comprises storing two or more processed values M , M , M , and M of the functions M (f ), M (f ), M (f ), and M (f ) if the corresponding values of M , M , M , and M are valid. A processed value is derived from the value for the present time interval and zero or more processed values for prior time intervals. The third step comprises determining f or a function thereof from zero or more valid function values obtained as a result of executing the first step during the current time interval, zero or more processed values obtained as a result of executing the second step during a prior time interval, and zero or more extrapolated values obtained by extrapolating the processed values obtained as a result of executing the second step during a prior time interval to the present time interval.

Shock-tolerant multioscillator ring laser gyro

A system and method for controlling the cavity length of a ring laser gyroscope to properly tune the resonant wavelengths of the ring laser gyroscope during moments when experiencing sudden shocks or high g force accelerations. The system controls the position of a movable mirror in the laser cavity of the gyroscope to control the length of the laser cavity. The system measures the acceleration experienced by the laser cavity, wherein the position of the movable mirror is adjusted to counteract the effects of the acceleration on the movable mirror in a real-time response to the measured acceleration. By adjusting the position of the movable mirror, the resonant wavelengths propagating in the ring laser gyroscope will be maintained at their desired intensity and continue to lase even after experiencing this acceleration. The system may further include a control servo-loop for providing additional cavity length control in order to maintain the desired intensity of the wavelengths propagating within the gyroscope.

System and method for providing cavity length control of a ring laser gyroscope

A closed loop accelerometer includes apparatus within an associated digital rebalance loop for reducing the presence of low frequency moding noise in the accelerometer output. In one embodiment, the digitized corrective signal is applied to a moving average filter. In a second embodiment, the corrective signal is modulated with a random function and, in a third embodiment, the digitized corrective signal is both randomized and applied to a moving average filter. In each embodiment, the periodic moding noise that results from the analog-to-digital conversion within the rebalance loop is significantly reduced from that observed in prior art systems.

Method and apparatus reducing output noise in a digitally rebalanced accelerometer

The invention is a method and apparatus for generating a pseudorandom sequence of bits. The method comprises the steps of (1) selecting a &ldquo;0&rdquo; or a &ldquo;1&rdquo; as the next bit of the modified pseudorandom bit sequence if one or more criteria are satisfied, the criteria being based on the measured properties of a plurality of prior bits of the modified pseudorandom bit sequence; otherwise: (2) selecting the next bit of an initial pseudorandom bit sequence as the next bit of the modified pseudorandom bit sequence, the next bit of the initial pseudorandom bit sequence being a function of one or more prior bits of the initial pseudorandom bit sequence.

Pseudorandom bit sequence generation

The invention is a method and apparatus for generating a primary pseudorandom bit sequence consisting of a plurality of contiguous P subsequences. Each P subsequence consists of a start sequence of predetermined length followed by a sequence of trailing bits. The method comprises three steps. The first step consists of deriving a feedback bit from each generating sequence in a P subsequence in accordance with a specified rule where a generating sequence is any sequence of contiguous bits in the P subsequence having the same length as the start sequence. The bit that follows a generating sequence is called the trailing bit for that generating sequence. The second step of the method consists of determining a sequence of one or more modifier bits to be used in modifying the P subsequence. The third step of the method consists of modifying the P subsequence utilizing the one or more modifier bits.

Pseudorandom bit sequence generator

A system and method for improving the accuracy of altitude determinations in an inertial navigation system. The system utilizes pressure measurements which are taken by a barometric altimeter and converted into an estimated pressure altitude using any known pressure-to-altitude conversion. A pressure correction value is then generated using a correction value generating formula that is a function of altitude. The pressure correction value is then multiplied by a pressure offset value for the barometric altimeter to generate a pressure offset error for the barometric altimeter. This pressure offset error is used in the present invention to modify the pressure altitude estimation in order to generate an altitude determination having an improved accuracy. The present invention further determines an amount of observation noise in the barometric altimeter that is a function of pressure noise and altitude, where the altitude estimation is further modified to account for the observation noise. Thus, the system and method of the present invention improves the accuracy of altitude determinations in inertial navigation system over prior systems by directly accounting for errors in pressure measurements taken by a barometric altimeter due to offset and noise.

System and method of compensating for pressure sensor errors and noise in inertial vertical loop data

The invention is a method and apparatus for obtaining an accurate value x,of a variable x,based on an estimate x,that is a function of K variables x,, x,, . . . , x,, . . . , x,. The method comprises the steps of (a) obtaining a plurality of estimates x,, x,, . . . , x,, . . . , x,of the variables x,, x,, . . . , x,, . . . , x,over a method-execution time period, the values of the variables x,, x,, . . . , x,, . . . , x,changing or being changed during the method-execution time period; (b) obtaining from an external source the actual values x,of x,during the method-execution time period; (c) defining a compensation model &dgr;x,that is a function of one or more of the estimates x,, x,, . . . , x,, . . . x,of the variables x,, x,, . . . , x,, . . . , x,, the compensation model being further defined by I unknown constants a,, a,, . . . , a,, . . . , a,; (d) applying an operator G to the values of x,&minus;x,and &dgr;x,; (e) determining the values of a,, a,, . . . , a,, . . . , a,; and (f) determining the value of x,.

Compensation system

A system and method for improving the accuracy of altitude determinations in an inertial navigation system. Pressure measurements available to the inertial navigation system are used to initially calculate an estimated pressure altitude using the standard day model for the atmosphere. Temperature measurements are further utilized in the physical relationship between temperature, pressure, and altitude to compute a second computed altitude. A change between subsequent second computed altitudes is calculated and compared with a respective change in the computed pressure altitude in order to generate a correction value. The correction value is then used to modify the computed pressure altitude to generate a more accurate determination of the absolute altitude of the inertial navigation system. The correction value is utilized to account for changes in atmospheric conditions which may be encountered by an aircraft and to further reduce the effects of erroneous temperature and pressure measurements in subsequent altitude determinations. Thus, the system and method of the present invention provides an absolute altitude determination having improved stability and improved accuracy over prior systems.

System and method for improving the accuracy of pressure altitude determinations in an inertial navigation system

The invention is a method and apparatus for updating the attitude of a body by utilizing a plurality of gyros to measure as a function of time the angular rate vector or the integrated angular rate vector for the body. The method comprises the steps of (1) obtaining measured values of the angular rate vector at a plurality of readout intervals, (2) obtaining a smoothed value of each of one or more smoothed representations of the angular rate vector at the end of each of a plurality of smoothing intervals, and (3) obtaining the updated attitude of the body at the end of an update interval by utilizing the attitude at the beginning of the update interval and the smoothed values of the smoothed representations of the angular rate vector obtained during the update interval. A smoothed representation is a weighted sum of the measured values obtained during a smoothing interval. The attitude is updated at the end of an update interval by applying a rotation vector to the attitude at the end of the prior update interval, the rotation vector being a weighted sum of (1) a plurality of the smoothed values and (2) the values of a plurality of cross-products of the smoothed values, the smoothed values having been obtained during the update interval.

Method and apparatus for obtaining attitude updates in a strapdown inertial navigation system

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Pasadena, CA, United States of America

John G Mark