Inertially decoupled strapdown system

• US 4,262,861 A
• Filed: 10/16/1978
• Issued: 04/21/1981
• Est. Priority Date: 10/16/1978
• Status: Expired due to Term

• Current Assignee: Kearfott Guidance and Navigation Corporation
• Original Assignee: Singer PLC (Hayleys Plc)
• Inventors: Goldstein, Murray S.
• Primary Examiner(s): Blum, Theodore M.
• Application Number:
  US05/952,016
• Time in Patent Office: 918 Days
• Field of Search: 244/3.2, 244/175, 102/DIG. 3, 364/453
• US Class Current: 244/3.2
• CPC Class Codes: G01C 21/166 Mechanical, construction or arrangement details of inertial navigation systems
• CPC Class Codes: G01C 21/183 Compensation of inertial measurements, e.g. for temperature effects

Abstract

The invention comprises a novel strapdown gyro inertial system having a single degree of freedom between it and the vehicle upon which it is mounted. An angular transducer having a low friction bearing is mounted on the vehicle along the vehicle roll axis bearing and supports the strapdown gyros and accelerometers that are skewed with respect to the roll axis. The method of determining the total vehicle attitude employs the gyros so that the vehicle rate around each gyro axis is integrated and combined with the vehicle angular roll to obtain the total attitude. The inertial momentum of the sensor block, electrically enhanced or strictly dependent upon its mass, decouples high acceleration inputs along the free axis and thus reduces the dynamic rate sensing requirement along the free axis. Also the novel configuration of the sensors skewed with respect to the free axis, permits easy calibration of gyro scale factors and other inertial parameters which are characteristics of gyroscopes and accelerometers. The calibration is attainable in the factory or in the field.

Claims

1. A strapdown gyro inertial system comprising:

means for transporting said strapdown inertial system,

means affixed to said transporting means and mounted along the roll axis thereof,

means having angular rotation along said roll axis mounted to said fixed means, and

gyro means skewedly mounted with respect to said roll axis on said means having angular rotation whereby said means having angular rotation provides angular readout to add to gyro output and provides a reference for calibration of said strapdown gyro inertial system.

2. The strapdown gyro inertial system of claim 1 wherein said means having angular rotation along said roll axis comprises:

an angular transducer having low friction bearing said angular transducer reducing the total angular rate which said gyro means must sense and reducing the total angular rate range which said gyro means must accurately sense.

3. The strapdown gyro inertial system of claim 2 wherein said gyro means comprises:

strapdown gyros and accelerometers skewedly mounted on said angular transducer with respect to said roll axis so that each axis of said gyros sensor can sense rotation about said roll axis and so that said skewing further reduces the total roll angular rate sensed by the gyros whereby the dynamic measuring range of said strapdown gyro inertial is further reduced.

4. A strapdown gyro inertial system comprising:

a vehicle supporting said gyro inertial system,

an angular transducer mounted on said vehicle and having angular rotation along the roll axis of said vehicle, and

strapdown gyros and accelerometers skewedly mounted on said angular transducer with respect to said roll axis so that each axis of said gyro sensor can sense rotation about said roll axis and so that said skewing further reduces the total roll angular rate sensed by said gyros whereby the dynamic measuring range of said strapdown gyro system is further reduced.

5. The strapdown gyro inertial system of claim 4 comprising:

means for converting the measured roll angle signal from said angle transducer and the rate signals from said gyros and accelerometers into digital signals.

6. A strapdown gyro inertial system comprising:

a vehicle supporting said gyro inertial system,

an angular transducer mounted on said vehicle and having angular rotation along the roll axis of said vehicle,

strapdown gyros and accelerometers skewedly mounted on said angular transducer with respect to the roll axis of said vehicle so that each axis of said gyro sensors can sense rotation about the roll axis and so that said skewing further reduces the total roll angular rate sensed by said gyros, whereby the dynamic measuring range of said strapdown gyro system is further reduced,

means for converting the measured roll angle signal from said angle transducer and the rate signals from said gyros and accelerometers into digital signals, and

means for providing a compensated roll output that is combined with the integrated rate output of said gyros so that said roll output is decoupled along said roll axis.

7. The strapdown gyro inertial system of claim 6 comprising:

means for transforming the compensated acceleration signals from body coordinate to inertial coordinate signals.

8. The strapdown gyro inertial system of claim 7 comprising:

means operative on said inertial coordinate signals for providing system velocity signals.

9. The strapdown gyro inertial system of claim 8 comprising:

means operative on said velocity signals for providing system position output signals.

10. A strapdown gyro inertial system comprising:

a vehicle supporting said gyro inertial system,

an angular transducer mounted to said vehicle having angular rotation along the roll axis of said vehicle,

a plurality of strapdown gyros each oriented along three approximately orthogonal axes skewedly mounted on said angular transducer with respect to said roll axis,

a plurality of accelerometers each oriented along the three orthogonal axes of said gyros also skewedly mounted on said angular transducer with respect to said roll axis,

a digital converter for converting the measured roll angle signal from said angle transducer and the rate signals from said gyros and accelerometers into digital signals,

a differentiator and compensation network for providing a compensated roll output signal that is combined with the rate and integrated rate output of said gyros,

a body transform matrix for transforming the compensated signals from body coordinates to inertial coordinate signals,

a first computation and integration network for converting said inertial coordinate signals into system velocity,

a second computation and integration network operative upon the output of said first computation and integration network for providing system position, whereby the pg,19 single degree of freedom provided by said angle transducer and said skewing further reduces the total roll angular rate sensed by the roll gyro resulting in the dynamic measuring range of said strapdown gyro inertial system being reduced.