Servo system

Apparatus for controlling the position of a motor according to a predetermined velocity profile including changes of velocity the position control being at a rate independent of the magnitude of its departure from the profile;

• including
• a. means for producing output pulses characteristic of predetermined units of change of motor position,
• b. storage means for storing said predetermined velocity profile,
• c. first counter means for counting the output pulses to determine the position of the motor and for causing the storage means to produce at its output, for each said output pulse, an output signal which is characteristic of the nominal velocity value of the motor as defined by the profile;
• d. means response to the output pulses for providing an indication of the actual velocity of the motor for each said output pulse;
• e. comparator means for comparing for each said output pulse the storage means output defining a nominal velocity as defined by the profile for each output pulse, with the actual velocity as determined for the same output pulse to produce a first indication if the actual velocity is above the nominal value as defined by the profile, and a second indication if the actual velocity is below the nominal value as defined by the profile,
• f. means for stepwise varying the energising current input for the motor, and
• g. means for controlling the stepwise variation for each said decoder output pulse, which means is responsive to each of the first indications to change the current input by one of said steps as to cause the velocity value to be reduced, and is responsive to each of the second indications to cause the velocity to be increased.