Servo system with noise cancellation

Claim 2

In a servo system including drive means for controlling output means in response to an error, said output means including feedback signal means to reduce said error, the combination comprising: fourth means for providing second and third signals indicative respectively of the magnitude and polarity of said error; fifth means coupled to said drive means and responsive to said third signal for controlling the direction of movement of said drive means; sixth means coupled to said drive means and responsive to said second signal for providing continuously an energizing signal for said drive means, said sixth means including rate control means for establishing a given minimum rate of said drive means; and further means coupled to said sixth means and responsive to said third signal for limiting the rate of said drive means to said given minimum rate in the presence of error polarity reversal indications of said third signal.

Claim 3

The invention according to claim 1, wherein: said drive means comprises means rotatable at a controlled rate said sixth means includes rotational rate control means for establishing a minimum rotational rate for said drive means, error magnitude signal averaging means coupled to said rotational rate control means for varying said rotational rate above said minimum rate in response to said second signal, and said further means includes means for controlling the variation of said rotational rate by said averaging means irrespective of the value of said second signal.

Claim 4

The combination with a servo system including rotatable drive means for controlling output means in response to first and second signals indicative respectively of magnitude and polarity of an error, including feedback signal means to reduce said error comprising: generating means continuously operable to provide a periodic energizing signal at a predetermined rate which determines the rotational speed of said drive means, said generating means including means for increasing said rate with respect to said predetermined rate in response to an input applied thereto, means responsive to said first signal for applying to the input of said energizing means a third signal in accordance with the magnitude of said error, further means responsive to said second signal for applying said energizing signal to said driven means in a manner to provide controlled rotation in a direction in accordance with the indication of polarity error of said second signal, sensing means responsive to said second signal for providing a further signal indicative of reversals of the error polarity information of said second signaL, and means responsive to occurrence of said further signal for modifying said third signal as applied to said energizing means.

Claim 5

The combination with a servo system including rotatable drive means for controlling output means in response to first and second signals indicative respectively of magnitude and polarity of an error, including feedback signal means to reduce said error comprising: generating means continuously operable to provide a periodic energizing signal at a predetermined rate which determines the rotational speed of said drive means, said generating means including means for increasing said rate with respect to said predetermined rate in response to an input applied thereto, means responsive to said first signal for applying to the input of said energizing means a third signal in accordance with the magnitude of said error, further means responsive to said second signal for applying said energizing signal to said driven means in a manner to provide controlled rotation in a direction in accordance with the indication of polarity error of said second signal, sensing means responsive to said second signal for providing a further signal indicative of reversals of the error polarity information of said second signaL, and means responsive to occurrence of said further signal for modifying said third signal as applied to said energizing means.

Claim 6

The invention according to claim 3, wherein said last mentioned means includes signal averaging means and means for disabling the input to said signal averaging means in response to said further signal.

Claim 7

The invention according to claim 3, wherein said last mentioned means includes means operable to limit the value of said third signal and therefore the rate of said energizing signal to a desired value.

Claim 8

The invention according to claim 3, and further including means for selectively controlling the duration of the modification of said third signal in response to the occurrence of said further signal.

Claim 9

The invention according to claim 3, wherein: said drive means comprises a motor having a plurality of winding capable of being selectively energized to control the direction of rotation of said drive means; said further means includes logic means coupled to said energizing means and responsive to said second signal, for generating direction control signals corresponding with the presence of indicated polarity error of said second signal and for selectively applying said energizing signal to said windings in accordance with the presence of said direction control signals.

Claim 10

In combination, a servo system including rotatable drive means for positioning an output means in response to the phase difference between first and second inputs, comprising: variable phase shifting means responsive to said first input for providing a third signal phase shifted by an amount in accordance with a control input of said shifting means; phase difference sensing means responsive to said second and third signals for providing fourth and fifth signals in response respectively to the magnitude and relative polarity of the phase difference between the inputs thereto; pulse generating means for continuously providing an energizing signal for said drive means at a pulse repetition rate at least equal to a given rate; first control means responsive to said fourth signal for varying the rate of said energizing signal above said given rate in response to the magnitude of said phase error; second control means coupled to said pulse generating means and responsive to said fifth signal for enabling rotation of said drive means in a given direction in accordance with the presence of relative polarity phase error between said third signal and said second signal, means coupling said output means and the control input of said phase shifting means to said drive means and responsive to the rotation thereof for shifting said first signal in a manner to reduce the phase difference between said second and third signals, and means coupled to said second control means and responsive to reversals of the relative polarity of said phase error for disabling the operation of said first control means.

Claim 11

In combination, a servo system including rotatable drive means for positioning an output means in response to the phase difference between first and second inputs, comprising: variable phase shifting means responsive to said first input for providing a third signal phase shifted by an amount in accordance with a control input of said shifting means; phase difference sensing means responsive to said second and third signals for providing fourth and fifth signals in response respectively to the magnitude and relative polarity of the phase difference between the inputs thereto; pulse generating means for continuously providing an energizing signal for said drive means at a pulse repetition rate at least equal to a given rate; first control means responsive to said fourth signal for varying the rate of said energizing signal above said given rate in response to the magnitude of said phase error; second control means coupled to said pulse generating means and responsive to said fifth signal for enabling rotation of said drive means in a given direction in accordance with the presence of relative polarity phase error between said third signal and said second signal, means coupling said output means and the control input of said phase shifting means to said drive means and responsive to the rotation thereof for shifting said first signal in a manner to reduce the phase difference between said second and third signals, and means coupled to said second control means and responsive to reversals of the relative polarity of said phase error for disabling the operation of said first control means.

Claim 12

The invention according to claim 8, wherein: said drive means is a stepping motor having a plurality of energizable windings; said first control means includes, filter means for averaging the magnitude of said phase error as applied to said pulse generating means; said second control means includes, first switching means for selectively enabling said motor windings in a controlled sequence, logic means responsive to the relative polarity of said phase error for controlling said first switching means; and said last mentioned means includes, further switching means operable in a first condition to disable the input to said filter means, and means including further logic means responsive to said polarity reversals of said phase error for disposing said further switching means in said first condition for a given duration.