Digital control system for a vibrating structure gyroscope

• US 6,276,204 B1
• Filed: 09/15/1999
• Issued: 08/21/2001
• Est. Priority Date: 09/18/1997
• Status: Expired due to Term

• Current Assignee: Atlantic Inertial Systems Ltd (Rtx Corporation)
• Original Assignee: BAE Systems Plc
• Inventors: Townsend, Kevin
• Primary Examiner(s): KWOK, HELEN C
• Application Number:
  US09/396,443
• Time in Patent Office: 706 Days
• Field of Search: 735/040.2, 735/040.3, 735/040.4, 735/041.2, 735/041.3, 735/041.4, 735/041.5, 735/041.6, 73/13.7, 702/145, 702/147
• US Class Current: 73/504.12
• CPC Class Codes: G01C 19/56 Turn-sensitive devices using vibrating masses, e.g. vibratory angular rate sensors based on Coriolis forces

Abstract

A digital control system for a vibrating structure gyroscope having a vibrating structure (3), at least a primary drive (4) for putting and maintaining the vibrating structure (3) in vibratory resonance, and at least a primary pickoff (2) for detecting vibration of the vibrating structure (3), includes a digital processing unit (22) for receiving output signals from the pickoff (2) for processing the received signals and for passing them to the primary drive (4) via digital to analogue converters (20). The system includes sampling at selected intervals of time the output signals before passage to the digital processing unit (22) and a variable frequency oscillator (23) connected to and under the control of the digital processing unit (22) for controlling the sampling intervals.

Claims

1. A digital control system for a vibrating structure gyroscope having a vibrating structure, a primary drive for putting and maintaining the vibrating structure in vibratory resonance and a primary pick off for detecting vibration of the vibrating structure and providing detection output signals, which system includes:

a digital processing unit for receiving said output signals from the primary pick off, for processing and passing the received signals to the primary drive via digital to analogue converters,

a sampler for sampling at selected intervals of time said output signals before passage to the digital processing unit; and

a variable frequency oscillator connected to and under the control of the digital processing unit for controlling the sampling intervals of said sampler.

2. A digital control system according to claim 1, including a secondary drive for putting and maintaining the vibrating structure in vibratory resonance and a secondary pick-off for detecting vibration of the vibrating structure and providing detection output signals.

3. A digital control system according to claim 1, wherein the digital processing unit is operable to adjust the frequency of the variable frequency oscillator to a frequency which is a multiple of the resonant frequency of the vibrating structure based upon the output signals received by the digital processing unit from the primary pick off.

4. A digital control system according to claim 2, wherein the variable frequency oscillator is operable to generate a processor interrupt signal for synchronising loop filtering and control within the digital processing unit with the output signals received from one or more analogue to digital converters connected to receive the output signals from the primary and secondary pickoffs, which one or more analogue to digital converters form part of the sampler for sampling at selected intervals of time said output signals before passing to the digital processing unit.

5. A digital control system according to claim 4, including two analogue to digital converters, wherein the variable frequency oscillator is arranged to operate at substantially four times the natural resonant frequency of the vibrating structure to ensure sampling of the primary and secondary pickoff output signals over each quarter cycle of the output signals to the analogue to digital converters from the primary and second pickoffs.

6. A digital control system according to claim 4, wherein the sampler includes two or more sample and hold devices for each output signal channel from the primary and secondary pickoffs to provide interleaving of the samples.

7. A digital control system according to claim 6, including a data buffer for receiving data from the analogue to digital converter or converters after each quarter cycle and storing the data to enable the digital processing unit to receive data from the buffer over complete cycles of the primary and secondary pickoff output signals.

8. A digital control system according to claim 2, wherein the digital to analogue converters generate a drive waveform for passage to the primary and secondary drives to excite the vibrating structure into vibratory resonance, which digital to analogue converters are synchronised to the variable frequency oscillator.

9. A digital control system according to claim 2, wherein the sampler samples at selected intervals of time said output signals before passage to the data processing unit, includes two or more sigma delta analogue to digital converters arranged to receive the output signals from the primary and secondary pickoffs to integrate a waveform of the output signals over the sample intervals.

10. A vibrating structure gyroscope having a digital control system according claim 1.