Laser gyro dither strippr gain correction method and apparatus

A dither signal stripper apparatus for a ring laser gyro, the ring laser gyro having a dither pickoff, wherein the dither pickoff has a dither pickoff output, the dither pickoff output includes a plurality of zero crossings and peaks, the dither signal stripper apparatus comprising:

• (a) control means for deriving a stripped gyro angle signal having a control output which is activated at each of the plurality of zero crossings and peaks of the dither pickoff output;
• (b) first analog to digital conversion means for converting the dither pickoff output to a first digital dither pickoff output, wherein the first analog to digital conversion means is coupled to the control output and is responsive to the control output so as to be activated at zero crossings and peaks of the dither pickoff output;
• and
• (c) second analog to digital conversion means for converting the dither pickoff output to a second digital dither pickoff output.

An apparatus for generating a dither stripper gain factor for use in a ring laser gyro, the apparatus for generating comprising:

• (a) a means for providing a dither signal on a dither signal output;
• (b) means for amplifying connected at an input to the dither signal output, the amplifying means having an amplified output;
• (c) means for analog-to-digital conversion having an input connected to receive the amplified output and having a digital output which supplies a digital signal representative of the amplified output;
• (d) means for adding gain having a first input connected to the digital output and having a gain output, the gain adding means operating so as to multiply a value of the digital output by a gain factor, wherein the means for adding gain also has a gain factor input;
• (e) means for scaling having an input connected to the gain output and having a dither angle output;
• (f) means for providing a nonlinearity correction connected to the dither angle output having a nonlinearity corrected dither angle output;
• (g) first means for subtracting a previous dither angle from the nonlinearity corrected dither angle output, the first means for subtracting including an input connected to receive the nonlinearity corrected dither angle output and having a first difference value output;
• (h) second means for subtracting a current gyro angle and adding a previous gyro angle, the second subtracting means including an input connected to the first difference value output and having a second difference value output;
• (i) a gain multiplier means for multiplying having an input connected to the second difference value output and having a switched output wherein the gain multiplier means multiplies the second difference value output to produce a gain correction factor at a gain correction factor output switch wherein a polarity of the gain correction factor is switched to follow the polarity of the dither angle output;
• and
• (j) means, connected to the gain correction factor output switch, for transferring the gain correction factor to the means for adding gain by connection to the gain factor input.

An apparatus for measuring a phase error angle for use in a ring laser gyro, the apparatus for measuring comprising:

• (a) a means for providing a dither signal on a dither signal output;
• (b) means for amplifying connected at an input to the dither signal output, the amplifying means having an amplified output;
• (c) means for analog-to-digital conversion having an input connected to receive the amplified output and having a digital output which supplies a digital signal representative of the amplified output;
• (d) means for adding gain having a first input connected to the digital output and having a gain output, the gain adding means operating so as to multiply a value of the digital output by a gain factor;
• (e) means for scaling having an input connected to the gain output and having a dither angle output;
• (f) means for providing an error angle correction connected to the dither angle output having an error angle corrected dither angle output and having an error angle correction input;
• (g) means for subtracting a previous dither angle from the error angle corrected dither angle output, the means for subtracting including an input connected to receive the error angle corrected dither angle output and having a difference value output;
• (h) means for subtracting a current gyro angle and adding a previous gyro angle, the subtracting and adding means including an input connected to the difference value output and having a summing output;
• (i) a gain multiplier means for multiplying having an input connected to the summing output and having a switched output wherein the gain multiplier means multiplies the difference value to produce a phase error angle at an output switch wherein a polarity of the phase error angle is switched to follow a polarity of the dither angle output;
• and
• (j) means connected to the output switch for transferring the phase error angle to the means for providing an error angle correction.

A method for determining a stripped gyro angle comprising the steps of:

• (a) sensing a plurality of peak amplitudes P.sub.1, P.sub.2, P.sub.3 . . . P.sub.n from a dither drive signal wherein each of the plurality of peak amplitudes has corresponding times t.sub.1, t.sub.2, t.sub.3 . . . t.sub.n ;
• (b) simultaneously sensing a plurality of ring laser gyro output angles at each of the corresponding times t.sub.1, t.sub.2, t.sub.3 . . . t.sub.n ;
• and
• (c) determining a stripped gyro angle, .phi..sub.g, according to a relationship wherein .phi..sub.g =.phi..sub.n -.alpha..sub.n K, where K is a correction factor, .phi..sub.n is an unstripped gyro angle sampled at time t.sub.n and .alpha..sub.n is a dither angle at time t.sub.n.

A method for determining a stripped gyro angle comprising the steps of:

• (a) sensing a plurality of peak amplitudes P.sub.1, P.sub.2, P.sub.3 . . . P.sub.n from a dither drive signal wherein each of the plurality of peak amplitudes has corresponding times t.sub.1, t.sub.2, t.sub.3 . . . t.sub.n ;
• (b) simultaneously sensing a plurality of ring laser gyro output angles at each of the corresponding times t.sub.1, t.sub.2, t.sub.3 . . . t.sub.n ;
• and
• (c) determining a stripped gyro angle, .phi., according to a relationship wherein .phi.=.phi..sub.n -.alpha..sub.n K, where K is a correction factor, .phi..sub.n is an unstripped gyro angle sampled at time t.sub.n and .alpha..sub.n is a dither angle at time t.sub.n.

An apparatus for generating a dither stripper gain factor for use in a ring laser gyro, the apparatus for generating comprising:

• (a) a means for providing a dither signal on a dither signal output;
• (b) means for amplifying connected at an input to the dither signal output, the amplifying means having an amplified output;
• (c) means for analog-to-digital conversion having an input connected to receive the amplified output and having a digital output which supplies a digital signal representative of the amplified output;
• (d) means for adding gain having a first input connected to the digital output and having a gain output, the gain adding means operating so as to multiply a value of the digital output by a gain factor, wherein the means for adding gain also has a gain factor input;
• (e) means for scaling having an input connected to the gain output and having a dither angle output;
• (f) means for providing a nonlinearity correction connected to the dither angle output having a nonlinearity corrected dither angle output;
• (g) a gain multiplier means for multiplying having an input connected to the nonlinearity corrected dither angle output and having a switched output wherein the gain multiplier means multiplies the nonlinearity corrected dither angle output to produce a gain factor correction at a gain correction factor output switch wherein a polarity of the gain correction factor is switched to follow the polarity of the dither angle output;
• and
• (h) means, connected to the gain correction factor output switch, for transferring the gain correction factor to the means for adding gain by connection to the gain factor input.

An apparatus for measuring a phase error angle for use in a ring laser gyro, the apparatus for measuring comprising:

• (a) a means for providing a dither signal on a dither signal output;
• (b) means for amplifying connected at an input to the dither signal output, the amplifying means having an amplified output;
• (c) means for analog-to-digital conversion having an input connected to receive the amplified output and having a digital output which supplies a digital signal representative of the amplified output;
• (d) means for adding gain having a first input connected to the digital output and having a gain output, the gain adding means operating so as to multiply a value of the digital output by a gain factor;
• (e) means for scaling having an input connected to the gain output and having a dither angle output;
• (f) means for providing an error angle correction connected to the dither angle output having an error angle corrected dither angle output and having an error angle correction input;
• and
• (g) means connected to the error angle corrected dither angle output for transferring the phase error angle to the means for providing an error angle correction.