Dither circuit

Claim 1

An apparatus for use with a servomechanism of the type having a feedback element connected to a movable element and producing a quantized feedback signal, said feedback signal causing the servomechanism to limit cycle the movable element about a desired position, wherein the improvement comprises: a. means for producing a dither signal having a phase component thereof cyclically changing the time and having a frequency substantially greater than the limit cycle frequency of the element; and b. means responsive to the dither signal and the feedback signals for generating a new feedback signal, said new feedback signal causing the servomechanism to limit cycle at a frequency approximately equal to the dither frequency thereby eliminating the limit cycle of the movable element.

Claim 2

An apparatus for use with a servomechanism of the type having a feedback element connected to a movable element and producing a quantized feedback signal, said feedback signal causing the servomechanism to limit cycle the movable element about a desired position, wherein the improvement comprises: a. means for producing a dither signal having a phase component thereof cyclically changing the time and having a frequency substantially greater than the limit cycle frequency of the element; and b. means responsive to the dither signal and the feedback signals for generating a new feedback signal, said new feedback signal causing the servomechanism to limit cycle at a frequency approximately equal to the dither frequency thereby eliminating the limit cycle of the movable element.

Claim 3

An apparatus for use with a servomechanism of the type having a feedback element connected to a movable element and producing a quantized feedback signal, said feedback signal causing the servomechanism to limit cycle the movable element about a desired position, wherein the improvement comprises: a. means for producing reference signals representing trigonometric functions, each of said reference signals having a phase component oscillating between two predetermined angular values and said phase oscillation occurring at a frequency substantially greater than the limit cycle frequency of the movable element; and b. means responsive to the feedback signal and the reference signals for superimposiNg the reference signal on the feedback signal to cause the servomechanism to limit cycle at a frequency approximately equal to the reference signal frequency thereby eliminating the limit cycle of the movable element.

Claim 4

An apparatus for use with a servomechanism of the type having a feedback element connected to a movable element and producing a quantized feedback signal, said feedback signal causing the servomechanism to limit cycle the movable element about a desired position, wherein the improvement comprises: a. means for producing reference signals representing trigonometric functions, each of said reference signals having a phase component oscillating between two predetermined angular values and said phase oscillation occurring at a frequency substantially greater than the limit cycle frequency of the movable element; and b. means responsive to the feedback signal and the reference signals for superimposiNg the reference signal on the feedback signal to cause the servomechanism to limit cycle at a frequency approximately equal to the reference signal frequency thereby eliminating the limit cycle of the movable element.

Claim 5

An apparatus for use with a servomechanism of the type having a feedback element connected to a movable element and producing quantized feedback signals, one of said feedback signals representing a sine value of a position angle relating to the position of the feedback element, and the other feedback signal representing a cosine value of the position angle, said feedback signals causing the servomechanism to limit cycle the movable element about a desired position, wherein the improvement comprises: a. means for producing a first reference signal representing a cosine value of a reference angle varying between a first two predetermined angular values and a second reference signal representing a sine value of the reference angle varying between a second two predetermined angular values; and b. means responsive to the feedback signals and the reference signals for producing a first new feedback signal representing the sine value of the sum of the position angle and the reference angle and a second new feedback signal representing the cosine value of the sum of the position angle and the reference angle, said signals causing the servomechanism to limit cycle without changing the position of the movable element.

Claim 6

An apparatus for use with a servomechanism of the type having a feedback element connected to a movable element and producing quantized feedback signals, one of said feedback signals representing a sine value of a position angle relating to the position of the feedback element, and the other feedback signal representing a cosine value of the position angle, said feedback signals causing the servomechanism to limit cycle the movable element about a desired position, wherein the improvement comprises: a. means for producing a first reference signal representing a cosine value of a reference angle varying between a first two predetermined angular values and a second reference signal representing a sine value of the reference angle varying between a second two predetermined angular values; and b. means responsive to the feedback signals and the reference signals for producing a first new feedback signal representing the sine value of the sum of the position angle and the reference angle and a second new feedback signal representing the cosine value of the sum of the position angle and the reference angle, said signals causing the servomechanism to limit cycle without changing the position of the movable element.

Claim 7

An apparatus for use with a servomechanism of the type having a feedback element connected to a movable element and producing two quantized feedback signals, a first feedback signal representing a sine value of a position angle relating to the position of the feedback element and a second feedback signal representing a cosine value of the position angle, said feedback signals causing the servomechanism to limit cycle the movable element about a desired position, wherein the improvement comprises: a. means for producing a first reference signal representing a cosine value of a reference angle varying between a first two predetermined angular values and a second reference signal representing a sine value of a reference angle varying between a second two predetermined angular values; b. a first multiplier responsive to the first feedback signal and the first reference signal for multiplying said signals to produce a first output signal; c. a second multiplier responsive to the second feedback signal and the second reference signal for multiplying said signals to produce a second output signal; d. a summing amplifier responsive to the first and second output signals for summing said signals to produce a first new feedback signal; e. a third multiplier responsive to the second reference signal and the first feedback signal for multiplying said signals to produce a third output signal; f. a fourth multiplier responsive to the first reference signal and the second feedback signal for multiplying said signals to produce a fourth output signal; and g. a summing amplifier responsive to the third and fourth output signals for summing said signals to produce a second new feedback signal.

Claim 8

An apparatus for use with a servomechanism of the type having a feedback element connected to a movable element and producing two quantized feedback signals, a first feedback signal representing a sine value of a position angle relating to the position of the feedback element and a second feedback signal representing a cosine value of the position angle, said feedback signals causing the servomechanism to limit cycle the movable element about a desired position, wherein the improvement comprises: a. means for producing a first reference signal representing a cosine value of a reference angle varying between a first two predetermined angular values and a second reference signal representing a sine value of a reference angle varying between a second two predetermined angular values; b. a first multiplier responsive to the first feedback signal and the first reference signal for multiplying said signals to produce a first output signal; c. a second multiplier responsive to the second feedback signal and the second reference signal for multiplying said signals to produce a second output signal; d. a summing amplifier responsive to the first and second output signals for summing said signals to produce a first new feedback signal; e. a third multiplier responsive to the second reference signal and the first feedback signal for multiplying said signals to produce a third output signal; f. a fourth multiplier responsive to the first reference signal and the second feedback signal for multiplying said signals to produce a fourth output signal; and g. a summing amplifier responsive to the third and fourth output signals for summing said signals to produce a second new feedback signal.