Abstract: 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.

Abstract: Multiple isolators are configured with respect to an assembly (101), 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 (203, 209, 215, and 221; 305, 307, 311, 313, 317, 319, 323, 325; or 403, 405, 407, 411, 413, and 415) 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.

Abstract: 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.

Abstract: A sleeve (22) enables attachment of an optic fiber (14) to a multi-integrated optic chip (10) in optical communication therewith, and maintains alignment of the fiber at its end adjacent the chip. The sleeve includes a symmetrically-shaped cavity (26) bounded by termini (30, 32) which are respectively disposed to fit onto the chip and to accept the fiber. An adhesive (46) 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 (12) 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 (44) and connection point (12) by defining the areas and volume actually in contact with the adhesive or fluid.

Abstract: 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.

Abstract: Multiple isolators are configured with respect to an assembly (101), 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 (203, 209, 215, and 221; 305, 307, 311, 313, 317, 319, 323, 325; or 403, 405, 407, 411, 413, and 415) 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.

Abstract: The invention is a method and apparatus for processing signals with frequencies fL and fR from a multioscillator ring laser gyro, the method being repeated at regular time intervals. The difference f&Dgr;&thgr;, of fL and fR is a measure of the angular rotation rate of the ring laser gyro and the sum fF of fL and fR divided by 2 is the Faraday bias frequency. The first step of the method comprises determining two or more of the values MLP, MRP, MFP, and M&Dgr;&thgr;P of a set of functions ML(fL), MR(fR), MF(fF), and M&Dgr;&thgr;(f&Dgr;&thgr;). The second step comprises storing two or more processed values MLS, MRS, MFS, and M&Dgr;&thgr;S of the functions ML(fL), MR(fR), MF(fF), and M&Dgr;&thgr;(f&Dgr;&thgr;) if the corresponding values of MLP, MRP, MFP, and M&Dgr;&thgr;P 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.

Abstract: 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.

Abstract: A sleeve (22) enables attachment of an optic fiber (14) to a multi-integrated optic chip (10) in optical communication therewith, and maintains alignment of the fiber at its end adjacent the chip. The sleeve includes a symmetrically-shaped cavity (26) bounded by termini (30, 32) which are respectively disposed to fit onto the chip and to accept the fiber. An adhesive (46) 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 (12) 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 (44) and connection point (12) by defining the areas and volume actually in contact with the adhesive or fluid.

Abstract: 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.

Abstract: The invention is a method and apparatus for generating a pseudorandom sequence of bits. The method comprises the steps of (1) selecting a “0” or a “1” 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.

Abstract: 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.

Abstract: 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.

Abstract: The invention is a method and apparatus for obtaining an accurate value x1c of a variable x1 based on an estimate x1e that is a function of K variables x1, x2, . . . , xk, . . . , xK. The method comprises the steps of (a) obtaining a plurality of estimates x1e, x2e, . . . , xke, . . . , xKe of the variables x1, x2, . . . , xk, . . . , xK over a method-execution time period, the values of the variables x1, x2, . . . , xk, . . . , xK changing or being changed during the method-execution time period; (b) obtaining from an external source the actual values x1a of x1 during the method-execution time period; (c) defining a compensation model &dgr;x1 that is a function of one or more of the estimates x1e, x2e, . . . , xke, . . . xKe of the variables x1, x2, . . . , xk, . . . , xK, the compensation model being further defined by I unknown constants a1, a2, . . . , ai, . . . , aI; (d) applying an operator G to the values of x1e−x1a and &dgr;x1; (e) determining the values of a1, a2, . . . , ai, . . .

Abstract: 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.

Abstract: 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.

Abstract: The invention is a method continuing over a plurality of time periods for compensating for the output error in each of one or more navigation instruments in a system comprising a plurality of navigation instruments after the system is introduced into its operating environment. The practice of the method begins with determining the values of one or more of a set of coordinates that specify the position, velocity, and orientation of the system in space together with the error in a compensated output for each of the one or more navigation instruments. The method continues with determining a compensation model for each of the one or more navigation instruments. A compensation model specifies for a current time period an adjustment in amplitude of the output of a navigation instrument as a function of time and temperature.

Abstract: The invention is a method and apparatus for determining the rotation of a medium through which a light beam propagates by modulating the light beam with a pseudorandom sequence of bits. The method comprises the steps of (1) selecting a "0" or a "1" 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.

Abstract: The invention is a method and apparatus for determining the rotation of a medium through which a light beam propagates by modulating the light beam with 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.

Abstract: The invention is a method for compensating for fringe visibility errors in a fiber-optic gyro. The light beam phase is modulated utilizing a phase-modulation generating function comprising a stepped waveform with steps of height 2.pi.k-.phi..sub.SE +j.phi..sub.M -.gamma..sub.ZS at time intervals .tau. where a phase step .phi. specified by the phase-modulation generating function is transformed into a change in light-beam phase of (.phi..sub.X /X).phi..sub.X where .phi..sub.X is the change in light phase produced by a phase step X. The integer k takes on the value -1, 0, or 1, j takes on the value -1 or 1, .phi..sub.SE is a phase determined by the fiber-optic gyro, .phi..sub.M is a predetermined phase value, and .gamma..sub.ZS is a phase designed to compensate for the fringe visibility errors. The phase .gamma..sub.