Variable speed closed loop digital servosystem

Claim 2

A variable speed closed loop digital servo system comprising: an electrical stepper motor having an output shaft; means for deriving a first analog electrical signal related to the instantaneous angular position of said shaft; means for generating a second analog electrical signal related to the desired instantaneous angular position of said shaft; means for generating an analog electrical error signal continuously related to the difference in amplitude between said first and said second electrical signals; means for generating a series of electrical pulses having a rate of recurrence continuously related to the amplitude of said analog error signal; circuit means for applying a driving pulse to said stepper motor in response to each pulse in said series of electrical pulses whereby the rate of change in the angular position of the shaft of said stepper motor is continuously related to the amplitude of said analog error signal; and low pass filter means connected to said electrical pulse generating means for limiting the rate of increase in the recurrence rate of the pulse in said series of electrical pulses to thereby reduce the tendency of said motor to oscillate in response to an abrupt increase in the recurrence rate of the pulses in said series of electrical pulses.

Claim 3

A variable speed closed loop digital servo system comprising: an electrical stepper motor having an output shaft; means for deriving a first analog electrical signal related to the instantaneous angular position of said shaft; means for generating a second analog electrical signal related to the desired instantaneous angular position of said shaft; means for generating an analog electrical error signal continuously related to the difference in amplitude between said first and said second electrical signals; means for generating a series of electrical pulses having a rate of recurrence continuously related to the amplitude of said analog error signal; circuit means for applying a driving pulse to said stepper motor in response to each pulse in said series of electrical pulses whereby the rate of change in the angular position of the shaft of said stepper motor is continuously related to the amplitude of said first gate means interconnected between said pulse generating means and said circuit means for passing pulses in said series of electrical pulses from said pulse generating means to said circuit means when enabled and for otherwise blocking the passage of pulses in said series of electrical pulses; and means responsive to the amplitude of said error signal for enabling said gate means.

Claim 4

A variable speed closed loop digital servo system comprising: an electrical stepper motor having an output shaft; means for deriving a first analog electrical signal related to the instantaneous angular position of said shaft; means for generating a second analog electrical signal related to the desired instantaneous angular position of said shaft; means for generating an analog electrical error signal continuously related to the difference in amplitude between said first and said second electrical signals; means for generating a series of electrical pulses having a rate of recurrence continuously related to the amplitude of said analog error signal; circuit means for applying a driving pulse to said stepper motor in response to each pulse in said series of electrical pulses whereby the rate of change in the angular position of the shaft of said stepper motor is continuously related to the amplitude of said first gate means interconnected between said pulse generating means and said circuit means for passing pulses in said series of electrical pulses from said pulse generating means to said circuit means when enabled and for otherwise blocking the passage of pulses in said series of electrical pulses; and means responsive to the amplitude of said error signal for enabling said gate means.

Claim 5

The servo system of claim 2 including a second gate means connected between said pulse generating means and said circuit means for passing pulses in said series of electrical pulses to said circuit means when enabled and for otherwise blocking the passage of pulses in said series of electrical pulses; and first and second threshold comparators connected one each between said error signal generating means and said first and second gate means respectively, said first comparator enabling said first gate means in response to error signals of one polarity having an amplitude greater than a predetermined value, said second comparator enabling said second gate means in response to error signals of the other polarity having an amplitude greater than a predetermined value; and wherein circuit means includes means for driving said stepper motor to change the position of said shaft in one direction in response to a pulse from said first gate means and for driving said stepper motor to change the position of said shaft in the opposite direction in response to a pulse from said second gate means.

Claim 6

A variable speed closed loop digital servo system comprising: an electrical stepper motor having an output shaft; means for deriving a first analog electrical signal related to the instantaneous angular position of said shaft; means for generating a second analog electrical signal related to the desired instantaneous angular position of said shaft; means for generating an analog electrical error signal continuously related to the difference in amplitude between said first and said second electrical signals; means for generating a series of electrical pulses having a rate of recurrence continuously related to the amplitude of said analog error signal; circuit means for applying a driving pulse to said stepper motor in response to each pulse in said series of electrical pulses whereby the rate of change in the angular position of the shaft of said stepper motor is continuously related to the amplitude of said analog error signal; absolute value means connected between said error signal generating means and said pulse generating means for deriving the absolute value of said instantaneous error signal whereby said pulse generating means is nonresponsive to the polarity of said error signal; and low-pass filter means connected between said absolute value means and said pulse generating means for limiting the rate of change of the analog signal applied to said pulse generating means.

Claim 7

A variable speed closed loop digital servo system comprising: an electrical stepper motor having an output shaft; means for deriving a first analog electrical signal related to the instantaneous angular position of said shaft; means for generating a second analog electrical signal related to the desired instantaneous angular position of said shaft; means for generating an analog electrical error signal continuously related to the difference in amplitude between said first and said second electrical signals; means for generating a series of electrical pulses having a rate of recurrence continuously related to the amplitude of said analog error signal; circuit means for applying a driving pulse to said stepper motor in response to each pulse in said series of electrical pulses whereby the rate of change in the angular position of the shaft of said stepper motor is continuously related to the amplitude of said analog error signal; absolute value means connected between said error signal generating means and said pulse generating means for deriving the absolute value of said instantaneous error signal whereby said pulse generating means is nonresponsive to the polarity of said error signal; and low-pass filter means connected between said absolute value means and said pulse generating means for limiting the rate of change of the analog signal applied to said pulse generating means.