Multiplexed fiberoptic gyro control

• US 5,033,854 A
• Filed: 12/06/1989
• Issued: 07/23/1991
• Est. Priority Date: 12/06/1989
• Status: Expired due to Term

• Current Assignee: Litton Systems Incorporated (Northrop Grumman Corporation)
• Original Assignee: Litton Systems Incorporated (Northrop Grumman Corporation)
• Inventors: Matthews, Anthony, Darling, J. Scott, Varty, Guy T.
• Primary Examiner(s): TURNER, SAMUEL A
• Application Number:
  US07/447,560
• Time in Patent Office: 594 Days
• Field of Search: 356/350, 372/94
• US Class Current: 356/462
• CPC Class Codes: G01C 19/721 Details
• CPC Class Codes: G01C 19/728 Assemblies for measuring along different axes, e.g. triads

Abstract

Apparatus and methods are disclosed for the time division multiplexing of fiberoptic gyros to reduce the amount of control electronics required. Each of a plurality of gyros is sampled at a rate of nτ, where τ is the gyro optical transit time and n is an integer. The sampled signal is fed to a digital signal processor (DSP) for processing and used to form a rate feedback signal. The rate feedback signal is converted to analog form to drive the phase modulator drive of each gyro. In preferred embodiments the multiplexed sample rate is at least ten times the bandwidth of the gyros. The rate data can be filtered and output by the DSP and the DSP can integrate the rate data to give angle data. The use of precision analog circuits is avoided.

Claims

1. A method of controlling a plurality of fiberoptic gyros comprising:

connecting an undemodulated, non-integrated, preamplified electrical output of each of said gyros to a multiplexing means, said multiplexing means having an output at which an electrical signal from only one of said gyros appears;

connecting said output of said multiplexing means to an input of a gyros controller;

alternately switching, with said multiplexing means, from one gyro output to another in a predetermined sequence;

operating on said electrical signal, after converting said electrical signal to a digital signal, from said one of said gyros with a digital processor to produce a modulation and rate feedback signal, and, optionally, an angular rate signal, an angle signal or both; and

applying said modulation and rate feedback signal to an input of each of said gyros to drive a phase modulator included in each of said gyros.

2. A method of controlling a plurality of fiberoptic gyros with a single set of multiplexing control electronics, each said gyro providing an undemodulated, non-integrated electrical signal at an output which is fed to an associated preamplifier, comprising:

connecting a preamplified signal output of each of said preamplifiers to a multiplexing means, said multiplexing means having an output at which a preamplified signal from only one of said gyros appears;

selecting one of said gyros so that said preamplified signal corresponds to its output;

gating said preamplifier associated with said one gyro with a gating signal to select portions of said preamplified signals to be passed;

connecting said output of said multiplexing means to an input of an analog-to-digital converter;

sampling said preamplified signal with said analog-to-digital converter to produce a corresponding digital signal;

operating one said digital signal with a digital signal processor to produce a digital modulation and rate feedback signal, said gating signal, and, optionally, an angular rate signal, an angle signal, or both;

converting said digital modulation and rate feedback signal to a corresponding analog signal;

applying said corresponding analog signal to an input of a phase modulator included in said one of said gyros;

repeating the sequence of above steps for each of the remaining gyros in said plurality of gyros; and

repeating the sequence of above steps as long as operation of the gyros is desired.

3. An apparatus for controlling a plurality of fiberoptic gyros, comprising:

multiplexing means having a plurality of amplified electrical inputs from said fiberoptic gyros and having an undemodulated, non-integrated, preamplified output at which an electrical signal from only one of said gyros appears;

gyro controller means having an input connected to said output of said multiplexing means, for operating on said electrical signal of said one of said gyros with a digital signal processing means to produce a modulation and rate feedback signal, and, optionally, an angular rate signal, an angle signal, or both; and

means for applying said modulation and rate feedback signal to an input of each of said gyros to drive a phase modulator included in each of said gyros.

4. The apparatus of claim 3 wherein said gyro controller means comprises:

sampling means having an input connected to said output of said multiplexing means, for converting said electrical signal to a corresponding digital signal at an output;

said digital signal processing means being connected to said output of said sampling means for operating on said digital signal to produce a digital modulation and rate feedback signal at a first output, an angular rate signal at a second output, an angle signal at a third output, and a gating signal at a fourth output for gating said inputs to said multiplexing means;

digital-to-analog conversion means connected to said first output of said digital signal processing means, for converting said digital modulation and rate feedback signal to a corresponding analog signal at an output; and

phase modulation drive selection means having an input responsive to said corresponding analog signal for applying said corresponding analog signal to an input of said phase modulator included in said gyro.

5. The apparatus of claim 3 wherein said multiplexing means includes channel selection means for periodically selecting one of said gyros to which said electrical signal at said output of said multiplexing means corresponds, operatively connected to said multiplexing means;

and wherein said digital signal processing means provides a channel-selection signal at a fourth output connected to said multiplexing means.

6. The apparatus of claim 3 further comprising a plurality of gated preamplification means, each preamplification means having a first input from a photodetection means in a corresponding one of said gyros, a second input from said signal processing means, and having an output connected to a corresponding input of said multiplexing means.

7. The apparatus of claim 3 further comprising a single gated preamplification means for amplifying selected portions of an input signal, having a first input from said output of said multiplexing means, a second input from said signal processing means, and having an output connected to said input of said flash analog-to-digital conversion means.

8. An apparatus for controlling a plurality of fiberoptic gyros, comprising:

multiplexing means having a plurality of gated preamplified undemodulated, non-integrated inputs from said fiberoptic gyros and having an output at which an electrical signal from only one of said gyros appears;

sampling means having an input connected to said output of said multiplexing means, for converting said electrical signal to a corresponding digital signal at an output;

digital signal processing means connected to said output of said sampling means for operating on said digital signal to produce a digital modulation and rate feedback signal at a first output, an angular rate signal as desired at a second output, an angle signal as desired at a third output, and a gating signal at a fourth output for gating said preamplified inputs to said multiplexing means;

digital-to-analog conversion means connected to said first output of said digital signal processing means, for converting said digital modulation and rate feedback signal to a corresponding analog signal at an output; and

phase modulation drive selection means having an input responsive to said corresponding analog signal for applying said corresponding analog signal to an input of said phase modulator included in said gyro.

9. The apparatus of claim 8 further comprising a plurality of gated preampification means, each preamplification means having a first input from a photodetection means in a corresponding one of said gyros, a second input from said signal processing means, and having an output connected to a corresponding input of said multiplexing means.

10. The apparatus of claim 8 wherein said multiplexing means includes channel selection means for periodically selecting one of said gyros to which said electrical signal at said output of said multiplexing means corresponds, operatively connected to said multiplexing means;

and wherein said digital signal processing means provides a channel-selection signal at a fourth output connected to said multiplexing means.

11. The apparatus of claim 8 wherein said sampling means comprises a flash analog-to-digital converter.

12. The apparatus of claim 8 wherein said multiplexing means comprises:

a plurality of electronic switching means, each said switching means having one side connected to one of said gated preamplified inputs and another side connected to said output, for connecting said an input of said switching means with said output; and

a plurality of channel-selection control means, each said means controlling one of said electronic switching means, operatively connected to said one of said switching means.

13. The apparatus of claim 12 wherein each of said electronic switching means comprises a normally open single-pole, double-throw switch.