Rate gyro error correction and use as heading source
First Claim
1. An error-corrected rate gyro apparatus comprising:
- a rate gyro providing an output that is compensated for error by subtraction of an error signal; and
an error signal generation circuit including (a) an amplitude clamp connected to receive the error-compensated rate gyro output and to provide an amplitude-clamped output and (b) an integrator connected to receive and integrate said amplitude-clamped output to provide an updated value for said error signal.
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Accused Products
Abstract
A simple accelerometer economically corrects the output of a yaw rate transducer for (a) vibration-induced noise and (b) aircraft bank angle (e.g., by using the accelerometer to measure apparent gravity forces which are a function of aircraft bank angle) to create a heading source. The exemplary embodiment utilizes a programmed digital signal processor in conjunction with suitable transducers and may be installed in an aircraft for measuring heading changes of banked and turning aircraft in flight (typically used by aircraft navigation and/or whether display apparatus). A long-running (e.g., continuous) integrator is used in a current balance circuit to provide enhanced measurement precision. Severely limited dynamic range of periodic heading change update signals for use in generating an error-compensation signal greatly reduces the influence of turbulence-induced errors and acts to continually increase the rate of convergence to true aircraft heading change outputs. Transducer offset measure and compensation is preferably operated at a first relatively high aggressive rate at instrument turn-on conditions when the aircraft is assumed to be stationary and then at a slower less aggressive rate thereafter.
40 Citations
58 Claims
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1. An error-corrected rate gyro apparatus comprising:
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a rate gyro providing an output that is compensated for error by subtraction of an error signal; and an error signal generation circuit including (a) an amplitude clamp connected to receive the error-compensated rate gyro output and to provide an amplitude-clamped output and (b) an integrator connected to receive and integrate said amplitude-clamped output to provide an updated value for said error signal. - View Dependent Claims (2)
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3. Rate gyro heading apparatus to be installed in a vehicle for measuring heading changes of a banked and turning vehicle, said apparatus comprising:
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a yaw rate transducer; a bank angle transducer; and a signal combining circuit connected to receive, process and combine outputs from both of said transducers thereby providing an vehicle heading output signal representative of vehicle heading changes. - View Dependent Claims (4, 5, 6)
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7. Rate gyro heading apparatus to be installed in a vehicle for measuring heading changes of a banked and turning vehicle, said apparatus comprising:
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a yaw rate transducer; a bank angle transducer; a signal combining circuit connected to receive, process and combine outputs from both of said transducers thereby providing a vehicle heading output signal representative of vehicle heading changes, wherein said yaw rate transducer comprises; a yaw rate gyro; and a substantially continuously operating current balance circuit connected to an output of the yaw rate gyro and to a reference current source.
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8. Rate gyro heading apparatus to be installed in a vehicle for measuring heading changes of a banked and turning vehicle, said apparatus comprising:
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a yaw rate transducer; a bank angle transducer; a signal combining circuit connected to receive, process and combine outputs from both of said transducers thereby providing a vehicle heading output signal representative of vehicle heading changes, wherein said signal combining circuit comprises a programmed digital signal processor; and wherein said programmed digital signal processor generates a pair of quadrature-phase step motor drive signals.
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9. Rate gyro heading apparatus to be installed in a vehicle for measuring heading changes of a banked and turning vehicle, said apparatus comprising:
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a yaw rate transducer; a bank angle transducer; a signal combining circuit connected to receive, process and combine outputs from both of said transducers thereby providing a vehicle heading output signal representative of vehicle heading changes, and a dynamic range signal limiter connected to limit the dynamic range of periodic changes made to a yaw-rate error signal based on a long term average of the raw yaw-rate measurement thereby reducing the significance of turbulence-related noise components affecting the heading output signal.
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10. Rate gyro heading apparatus to be installed in a vehicle for measuring heading changes of a turning vehicle, said apparatus comprising:
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a turn rate transducer having an output with a vehicle turn rate component related to vehicle turn rate but also including a noise component that is typically larger in magnitude than the vehicle turn rate component; and a dynamic range signal limiter connected to receive and process said transducer output to produce a yaw-rate error-compensation signal. - View Dependent Claims (11, 12, 13, 14, 15, 16)
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17. Apparatus to be installed in a vehicle for measuring heading changes of a banked and turning a vehicle, said apparatus comprising:
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a one-dimensional accelerometer aligned with the vehicle yaw axis; a one-dimensional rate gyro aligned with the vehicle yaw axis; and a multiplication and integration circuit connected to receive the outputs of said accelerometer and said gyro and to integrate the product thereof. - View Dependent Claims (18)
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19. Apparatus to be installed in a vehicle for measuring heading changes of a banked and turning vehicle, said apparatus comprising:
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a yaw rate transducer which provides a measured vehicle yaw-rate signal related jointly to vehicle turn rate and bank angle; a bank angle transducer which provides a measured bank angle signal related to vehicle bank angle; and signal processing circuits connected to receive said yaw rate signal and said bank angle signal and to provide a vehicle heading output signal representative of vehicle heading changes. - View Dependent Claims (20, 21, 22, 23, 24)
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25. Apparatus to be installed in a vehicle for measuring heading changes of a banked and turning vehicle, said apparatus comprising:
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a yaw rate transducer which provides a measured vehicle yaw-rate signal related jointly to vehicle turn rate and bank angle; a bank angle transducer which provides a measured bank angle signal related to vehicle bank angle; signal processing circuits connected to receive said yaw rate signal and said bank angle signal and to provide a vehicle heading output signal representative of vehicle heading changes, and wherein said yaw rate transducer comprises; a yaw rate gyro having an analog output signal; a reference current source providing a reference current signal; and a current balance circuit having one input connected to receive said analog output signal and another input connected to receive said reference current signal. - View Dependent Claims (26, 27, 28, 29, 30)
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31. Apparatus to be installed in a vehicle for measuring heading changes of a banked and turning vehicle, said apparatus comprising:
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a yaw rate transducer which provides a measured vehicle yaw-rate signal related jointly to vehicle turn rate and bank angle; a bank angle transducer which provides a measured bank angle signal related to vehicle bank angle; signal processing circuits connected to receive said yaw rate signal and said bank angle signal and to provide a vehicle heading output signal representative of vehicle heading changes, and wherein said signal processing circuits periodically accumulate signals representing changes in vehicle yaw-rate that have been limited in dynamic range to generate an error-compensation signal that is subtracted from the measured yaw-rate to improve the signal-to-noise ratio in the vehicle heading output signal while also increasing its rate of correction for any offset error in the yaw rate signal from the yaw rate transducer. - View Dependent Claims (32, 33, 34, 35)
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36. Apparatus to be installed in a vehicle for measuring heading changes of a banked and turning vehicle, said apparatus comprising:
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a yaw rate transducer which provides a measured vehicle yaw-rate signal related jointly to vehicle turn rate and bank angle; a bank angle transducer which provides a measured bank angle signal related to vehicle bank angle; signal processing circuits connected to receive said yaw rate signal and said bank angle signal and to provide a vehicle heading output signal representative of vehicle heading changes, and wherein said signal processing circuits, upon being initialized, are conditioned to effect transducer offset error correction using a first clipped dynamic range for an initial time period while the aircraft is assumed to be substantially stationary and thereafter at a second clipped dynamic range which is lower than said first range.
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37. A method for error-correcting the output of a rate-gyro, said method comprising the steps of:
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using an error signal derived from the rate gyro output to derive an error-corrected rate gyro output; amplitude clamping the error-corrected rate gyro output; and integrating the clamped signal to provide said error signal. - View Dependent Claims (38, 39, 40, 41)
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42. A method for measuring heading changes of a banked and turning vehicle, said method comprising:
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measuring yaw-rate of the vehicle with a yaw-rate transducer; measuring the vehicle bank angle with a one-dimensional accelerometer transducer; and combining outputs from both of said transducers to provide a heading output signal representative of vehicle heading changes. - View Dependent Claims (43, 44, 45, 46)
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47. A method for measuring heading changes of a banked and turning vehicle, said method comprising:
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measuring yaw-rate of the vehicle with a yaw-rate transducer; measuring the vehicle bank angle with a one-dimensional accelerometer transducer; combining outputs from both of said transducers to provide a heading output signal representative of vehicle heading changes; wherein combining step is performed within a programmed digital signal processor, and wherein said programmed digital signal processor generates a pair of quadrature-phase step motor drive signals.
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48. A method for measuring heading changes of a banked and turning vehicle, said method comprising:
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measuring yaw-rate of the vehicle with a yaw-rate transducer; measuring the vehicle bank angle with a one-dimensional accelerometer transducer; combining outputs from both of said transducers to provide a heading output signal representative of vehicle heading changes, and limiting the dynamic range of periodic changes made to an error-compensation signal based on an accumulation of measured yaw-rate signals thereby reducing the significance of turbulence-related noise components affecting the heading output signal.
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49. A method for measuring heading changes of a turning vehicle, said method comprising:
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measuring vehicle turn rate using a transducer having an output with a vehicle turn rate component related to vehicle turn rate but also including a noise component that is typically larger in magnitude than the vehicle turn rate component; and limiting the dynamic range of said transducer output to produce an error-compensation signal. - View Dependent Claims (50, 51, 52, 53, 54, 55)
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56. A method for measuring heading changes of a banked and turning vehicle, said method comprising:
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measuring one-dimensional acceleration aligned with the vehicle yaw axis; measuring one-dimensional yaw-rate aligned with the vehicle yaw axis; and multiplying said measurements and integrating the product thereof. - View Dependent Claims (57)
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58. A method for measuring heading changes of a banked and turning vehicle, said method comprising:
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measuring vehicle yaw-rate by deriving signal related jointly to vehicle turn rate and bank angle; measuring bank angle by deriving a signal related to vehicle bank angle; and combining said measured signals to provide an vehicle heading output signal representative of vehicle heading changes.
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Specification