Angular rate sensor

Claim 2

Angular rate sensor of the class wherein two electro- magnetic waves travel in opposite directions, each wave substantially traveling about a closed-loop path, wherein the frequency of each of said waves is a function of the rate of rotation of said closed-loop path, and there being a corresponding phase relationship established between said waves also being a function of the rate of rotation of said closed-loop path, and wherein said sensor generates a first sensor signal related to the true angle of rotation of said sensor but which includes lock-in error inherent in said sensor, characterized by: biasing means (30, 32) capable of varying at least one of said waves such that the phase, of said phase relationship between said waves takes on alternately at least first and second values at selected occurrences of those times when selected values of dY/dt occur thereby substantially reducing said lock-in error in said first sensor signal.

Claim 3

Sensor according to claim 1, characterized by said biasing means (30, 1130) being capable of producing, in response to a control signal, rotational oscillations of said closed-loop path relative to a fixed reference axis so as to vary the frequency of each of said waves, and said corresponding phase relationship therebetween, in a manner to cause the sign of the frequency difference between said waves to periodically alternate, said bias control signal capable of ) (i) directing said rotational oscillations at substantially a first frequency, and (ii) directing the peak clockwise and counterclockwise amplitude values of said rotational oscillations about said fixed reference axis so as to alter the phase of said phase relationship between said waves substantially at occurrences of selected values of dψ/dt; bias control signal generating means (32) for producing said bias control signal (33) for directing said biasing means so that said phase, ψ, of said phase relationship between said waves takes on selected phase values at selected occurrences of those times when selected values of dY/dt occur, said selected phase values having a predetermined relationship which reduces said lock-in error in said first sensor signal.

Claim 4

Sensor according to claim 1, character- ized by said biasing means (30, 1130) being capable of producing, in response to a control signal, rotational oscillations of said closed-loop path relative to a fixed reference axis so as to vary the frequency of each of said waves and said corresponding phase relationship therebetween in a manner to cause the sign of the frequency difference between said waves to periodically alternate, said bias control signal capable of (i) directing said rotational oscillations at substantially a first frequency, and (ii) directing the peak clockwise and counterclockwise amplitude values of said rotational oscillations about said fixed reference axis so as to alter the phase, ψ, of said phase relationship between said waves substantially at occurrences of selected values of dψ/dt; bias control signal generatina means (32) for producing said bias control signal (33) for directing said biasing means so that said phase, Y , of said phase relationship between said waves, takes on selected phase values at successive occurrences of a group of successive occurrences of those times when dψ/dt is zero and the value of d 2 ψ/dt 2 is of the same polarity, said selected phase values of each of said group having a predetermined relationship which reduces said lock-in error in said first sensor signal.

Claim 5

Sensor according to claim 1, character- ized by said biasing means (30, 1130) being capable of producing, in response to a bias control signal (33), rotational oscillations of said closed-loop path relative to a fixed reference axis so as to vary the frequency of each of said waves, and said corresponding phase relationship therebetween, in a manner to cause the sign of the frequency difference between said waves to periodically alternate, said bias control signal capable of (i) directing said rotational oscillations at substantially a first frequency, and (ii) directing peak clockwise and counterclockwise amplitude values of said rotational oscillations about said fixed reference axis, each of said peak amplitudes having a corresponding instantaneous phase value of said phase relationship, associated therewith; bias control signal generating means (32) for producing said bias control signal (33) for directing said biasing means so that (i) successive peak clockwise amplitudes of successive groups of successive peak clockwise amplitudes of said rotational oscillations take on selected amplitude values, and (ii) successive peak counterclockwise amplitudes of successive groups of successive peak counterclockwise amplitudes take on selected amplitude values such that said lock-in error in said first sensor signal is reduced.

Claim 6

Sensor according to claim 3, character- ized in that said bias control signal generating means comprises: first means (34) for providing a first signal component of said bias control signal for periodically varying said frequency of at least one of said waves such that the frequency difference between said waves periodically varies by a selected magnitude at a first frequency; second means (35) for providing a second signal component of said bias control signal for periodically varying said frequency of at least one of said waves such that the frequency difference between said waves periodically varies by a selected magnitude at a second frequency; and said first and second signal components of said bias control signal having selected magnitudes for affecting said phase such that said phase takes on said at least first and second values at selected occurrences of those times when dψ/dt is zero thereby substantially reducing said lock-in error in said first sensor signal.

Claim 7

Sensor according to claim 1, character- ized by said biasing means (1130) being capable of producing rotational oscillations of said closed-loop path relative to a fixed reference axis so as to vary the frequency of each of said waves to cause the sign of the frequency difference between said waves to periodically alternate, said biasing means adapted to receive a bias control signal capable of (i) directing said rotational oscillations at substantially a first frequency, and (ii) directing the peak clockwise and counterclockwise amplitudes of said rotational oscillations about said fixed- reference axis, each of said peak amplitudes having a corresponding instantaneous phase value of said phase relationship associated therewith; rotational amplitude detecting means (1140), responsive to rotational motion of said sensor about said fixed reference axis, capable of producing an output signal indicative of the values of successive peak clockwise and counterclockwise amplitudes about said fixed reference axis; rate indicating means (1124) responsive to said propagating waves for providing an output signal indicative of the rate of rotation of said closed-loop path; bias control signal generating means (1150), responsive to said rate detecting means output signal and said amplitude detecting means output signal, for producing said bias control signal, for directing said peak clockwise and counterclockwise amplitudes so that the phase, ψ, of said phase relationship, at selected occurrences of those times when selected values of dψ/dt occur, takes on selected phase values which satisfy a predetermined relationship such that said lock-in error in said first sensor signal is reduced.

Claim 8

Sensor according to claim 1, characterized in that each of said selected values of dψ/dt is zero and said phase takes on said first value at a first occurrence of a first one of said selected values of dψ/dt, and said phase takes on said second value at a second occurrence of a second one of said selected values of d*/dt, said first and second ones of said selected values of dψ/dt being successive zeroes having corresponding second derivative values, d 2 ψ/dt 2 , being of the same polarity..

Claim 9

Sensor according to claim 1 or one of the following claims, characterized in that said values of said phase differ by a predetermined value.

Claim 10

Sensor according to claim 8, characterized in that said predetermined value is π radians.

Claim 11

Sensor according to claim 7, characterized in that said values of said phase are such that the sum of the sine function value of said first phase value and the sine function value of said second phase value are substantially zero, and wherein the sum of the cosine function value of said first phase value and the cosine function value of said second phase value are substantially zero.

Claim 12

Sensor according to claim 1 or one of the following claims, characterized in that said biasing means includes means (34, 634a) for periodically varying the frequency of at least one of said waves such that the frequency difference between the frequencies of said waves periodically alternates in sign.

Claim 13

Sensor according to claim 11, character- ized in that said biasing means includes rotating means (1130) for mechanically oscillating said sensor in a rotational mode back and forth thereby periodically varying the frequency of at least one of said waves and thereby periodically alternate said sign of said frequency difference.

Claim 14

Sensor according to claim 1 or one of the following claims, characterized in that a plurality of phase values is substantially determined by: where M = number of said plurality of phase values corresponding to those times that selected values of dψ/dt occur, A. = i th value of said phase of said plurality of phase values, and A = a constant initial phase value.

Claim 15

Sensor according to claim 13, character- ized in that said selected occurrences are M successive values of dψ/dt being zero and the corresponding second derivative, d 2 ψ/dt 2 , being of the same 5 polarity at each of said successive selected values of dY/dt being zero.

Claim 16

Sensor according to claim 4, characterized in that: said successive groups of successive peak clockwise amplitudes consist of a pair of selected amplitude values differing by a selected first difference value; and said successive groups of successive peak counterclockwise amplitudes consists of a pair of said selected amplitude values differing by a second selected difference value.

Claim 17

Sensor according to claim 15, character- ized in that said first and second selected difference values are such that said corresponding instantaneous phase values differ substantially by ± π radians.

Claim 18

17 - Sensor according to claim 4, 15 or 16, charac- terized in that said bias control signal generating means includes means (634b) for directing said biasing means to cause at least one of said selected amplitude values of said peak clockwise and counterclockwise amplitude values in said group to have a random value, and remaining ones of said selected amplitude values of said group having a predetermined relationship to at least one other of said selected amplitude values.

Claim 19

Sensor according to claim 2 or 3, character- ized in that said bias control signal generating means includes means (634b) for directing said biasing means to cause at least one of said selected phase values to have a random value, and remaining ones of said selected phase values having a predetermined relationship to at least one other of said selected i phase values.

Claim 20

Sensor according to claim 2, 3 or 4, character- ized in that said bias control signal generating means includes: means for generating a signal component of said bias control signal including a series of pulses (537) substantially synchronized with said first frequency for directing said clockwise and counterclockwise peak amplitudes so that said phase takes on said selected phase values.

Claim 21

Sensor according to claim 2, 3 or 4, charac- terized in that said bias control signal generating means includes: means (34) for providing a first signal component of said bias control signal for periodically varying the frequency of at least one of said waves so that the frequency difference between said waves periodically varies at said first frequency; means (35) for providing a second signal component of said bias control signal for periodically varying said frequency of at least one of said waves such that the frequency difference between said waves periodically varies at a second frequency different than said first frequency so that said peak clockwise and counterclockwise amplitudes take on said selected phase values.

Claim 22

Sensor according to claim 20, character- ized in that said second frequency is one-half of said first frequency thereby causing said peak clockwise and counterclockwise amplitudes to periodically alternate in value.

Claim 23

Sensor according to claim 20, character- ized in that said bias control signal generating means further includes a random noise generator (634b) for providing a random signal component of said bias control signal so as to periodically randomize at least one of said peak clockwise and peak counterclockwise amplitudes.

Claim 24

Sensor according to claim 5, characterized in that said first frequency is twice the value of said second frequency.

Claim 25

Sensor according to claim 2, characterized in that said bias control signal generating means includes: means (804, 805) responsive to an output signal of a phase angle detector means (22) for determining at least a first phase value of said phase relationship at an occurrence of a first selected value of dψ/dt; means responsive to said first phase value for determining at least one signal component of said bias control signal such that said bias control signal causes said biasing means to produce a second and a third phase value of said phase relationship at a subsequent occurrence of a second and a third selected value of dψ/dt such that said second phase value and said third phase value differ by substantially a selected difference value such that the lock-in error associated with said sensor signal is reduced.

Claim 26

Sensor according to claim 24, characterized in that said phase angle detector means (22) 5 includes at least a first transducer (22a) adapted to provide an output signal in response to an interference pattern generated by optically combined portions of said two waves, said first transducer providing said phase angle detector means output signal.

Claim 27

Sensor according to claim 2, characterized in that said bias control signal generating means includes: error signal means (900) responsive to an output signal 5 of a phase angle detector means (22) for generating at least a first error signal indicative of a first function of past phase values, including said at least a first phase value, at said selected occurrences of selected values of dψ/dt; first means (834) for providing a first signal component of said bias control signal for.periodically varying said frequency of at least one of said waves such that the frequency difference between said waves periodically varies at a first frequency; second means (835) responsive to said at least a first error signal for providing a second component of said bias control signal thereby affecting said biasing means for affecting said phase of said phase relationship such that said phase, associated with selected subsequent pairs of successive occurrences of said selected values of dt/dt having the same polarity of d 2 ψ/dt 2 , takes on first and second values, which differ by a selected phase difference such that the lock-in error associated with said sensor signal is reduced.

Claim 28

Sensor according to claim 26, characterized in that said second error signal means is further capable of generating a second error signal indicative of a second function of past phase values at selected occurrences of selected values of dψ/dt.

Claim 29

Sensor according to claim 26, characterized in that said second means providing said second signal component of said bias control signal comprises: pulsing means (835) for providing a component of said second signal component comprising a first series of pulses in time relationship to occurrences of a selected value of dψ/dt, selected ones of said first series of pulses having a magnitude of energy related to said first error signal.

Claim 30

Sensor according to claim 26, characterized in that : said error signal means (900) is capable of generating a second error signal indicative of a second function of past phase values, including said at least a first phase value, at selected occurrences of selected values of dψ/dt; and said second means for providing said second signal component includes: pulsing means (835) capable of providing a component of said second signal component comprising a first series of pulses in time relationship to occurrences of a selected value of dV/dt, and a first polarity of d 2 ψ/dt 2 , selected ones of said first series of pulses having a magnitude of energy related to said first error signal, and said pulsing means (837) capable of providing a component of said second signal component comprising a second series of pulses in time relationship to occurrences of a selected value of dψ/dt and a second polarity of d 2 ψ/dt 2 , selected ones of said second series of pulses having a magnitude of energy responsive to said second error signal.

Claim 31

Sensor according to claim 29, character- ized in that said first series of pulses consists of a repetition of pulses defined by: a first pulse of random magnitude applied before dψ/dt. is zero and d 2 ψ/dt 2 being of a first polarity, and a second pulse having a magnitude dependent on said first error signal and applied before a successive occurrence of dψ/dt being zero and d 2 ψ/dt 2 being of said first polarity; and said second series of pulses consists of a repetition of pulses defined by: i a first pulse having a magnitude dependent on said second error signal applied before dψ/dt is zero and d 2 ψ/dt 2 being of a second polarity and following said first pulse, and a second pulse being substantially the magnitude of said i first pulse of said second series of pulses applied before dψ/dt is zero and d 2 ψ/dt 2 being of a second polarity and following said second pulse of said first series of pulses.

Claim 32

Sensor according to claim 25, character- ized in that said phase detector means (22) includes a second transducer (226) having an output signal responsive to said interference pattern but which responds to a different portion of said interference pattern than said first transducer.

Claim 33

Sensor according to claim 6, character- ized in that said bias control signal generating means includes: means (1380) for generating a first signal component of said bias control signal for producing said rotational oscillations at said first frequency; and means (1300) for generating a second signal component of said bias control signal substantially synchronized with said first frequency for directing values of said clockwise and counterclockwise peak amplitudes, in response to said rate indicating means output signal and said rotational amplitude detecting means output signal, so that said phase takes on said selected phase values.

Claim 34

Sensor according to claim 32, characterized in that said means for generating said second signal component comprises signal processing means including: means (1310) for storing values of selected ones of successive clockwise and counterclockwise peak amplitudes occurring in at least a first pair of successive cycles of said rotational oscillations; means (1325) responsive to said stored peak amplitudes for generating at least a first error signal being a function of said stored peak amplitudes; means (1331) responsive to said at least first error signal for determining said second signal component.

Claim 35

Sensor according to claim 33, characterized in that said signal processing.means further includes: means (1331) for generating a series of pulses being a component part of said second signal component, selected ones of said series of pulses having a magnitude of energy related to said at least first error signal; synchronizing means (1350) for synchronizing said series of pulses in synchronization with said first frequency and occurring substantially during at least a second pair of complete cycles of said rotational oscillations successively following said at least a first pair of . cycles.

Claim 36

Sensor according to claim 34, character- ized in that said series of pulses comprises a repetitive series of at least first and second pulses, (i) said first pulse having a random magnitude and applied during a first portion of said second pair of cycles, (ii) said second pulse having a value substantially defined by: where 5 y = said first error signal.

Claim 37

Sensor according to claim 32, character- ized in that said means for generating said series of pulses includes signal processing means 0 having, means (1310) for storing values of successive clockwise and counterclockwise peak amplitudes occurring in at least a first pair of two successive cycles of said rotational oscillations; 5 means (1325) responsive to said stored peak amplitudes for generating a first error signal being a first function of said stored peak amplitudes; means (1320) responsive to selected ones of said stored peak amplitudes'and said rate indicating means output signal for generating a second error signal being a function of said selected ones of said stored peak amplitudes and said rate indicating means output signal; i means (1330, 1331) responsive to said first and second error signals for determining said second signal component.

Claim 38

Sensor according to claim 36, character- ized in that said means for generating said second signal component further includes: means for generating a series of pulses being a component part of said second signal component, selected ones of said series of pulses having a magnitude of energy i related to said at least a first error signal and different ones of said series of pulses having a magnitude of energy related to said second error signal; synchronizing means (1350) for synchronizing said series of pulses in synchronization with said first frequency and occurring substantially during at least a second pair of complete cycles of said rotational oscillations successively following said at least a first pair of cycles.

Claim 39

Sensor according to claim 37, character- ized in that said series of pulses comprises a repetitive series of at least a first, second, third and fourth pulses occurring during a second pair of complete cycles of said rotational oscillations following ) said at least a first pair of cycles, (i) said first pulse having a random magnitude and occurring prior to a first peak clockwise rotational amplitude, (ii) said second pulse having a magnitude substantially defined by: where y = said second error signal, said second pulse occurring prior to a first peak counterclockwise rotational amplitude following said first peak clockwise rotational amplitude, (iii) said third pulse being substantially defined by: where x = said first error signal, said third pulse occurring prior to a second peak clockwise rotational amplitude following said first peak counterclockwise rotational amplitude, said second pulse having a polarity related to the polarity of said first pulse, and (iv) said fourth pulse being substantially the same magnitude as said second pulse but which occurs prior to a second counterclockwise peak rotational amplitude following said second peak clockwise rotational amplitude, the polarity of said fourth pulse being related to said second pulse.

Claim 40

Sensor according to claim 35, characterized in that said first error signal is substantially defined by: where R = said rate detecting means output signal D1, D2, D3 and D4 = are the values of successive peak amplitudes of said first pair of cycles.

Claim 41

Sensor according to claim 37, character- ized in that : said first error signal is substantially defined by: and said second error signal is substantially defined by: where R = said rate detecting means output signal D1,D2,D3 and D4 = are the values of successive peak amplitudes of said first pair of cycles. Sensor according to claim 2, 3 or 6, charac- terized in that said selected phase values satisfy the relationship: where M= number of said selected phase values ψ m , and ψ = phase value at said selected values of dψ/dt. . Sensor according to claim 4, character- ized in that said corresponding instantaneous phase values corresponding to said selected amplitude values satisfy the relationship: M = number of peak clockwise and counterclockwise peak amplitude values, and ψ m = said phase values corresponding to said peak amplitudes.