Self-regulating electronic tachometer

In apparatus having a load driven by an actuator for moving the load from a present position to a desired position at desired velocity and including means for receiving an input command signal for driving the load, transducer means coupled to the load for providing a feedback signal indicative of the motion of the load, and means for combining the input command and feedback signals to produce a control signal for application to the actuator to control the load to move at desired velocity, the improvement comprising:

• means including a velocity indicating integrator coupled to the input of a variable gain amplifier for receiving at the input of said velocity indicating integrator a signal indicative of the acceleration of said load to produce a coarse velocity signal at the output of said variable gain amplifier indicative of the velocity of said load,
• means including a distance indicating integrator coupled to receive the coarse velocity signal for producing a coarse distance signal which is referenced to a distance signal value representative of actual distance traversed by the load to provide a distance error signal indicative of error in the coarse velocity signal,
• means responsive to the distance error signal for changing the control signal applied to the actuator so the load moves at desired velocity irrespective of the error in the coarse velocity signal,
• said transducer means coupled to the load being further operative to provide distance marker signals indicative of position increments traversed by the load,
• said means including a distance indicating integrator being responsive to distance marker signals for resetting said distance indicating integrator to an initial value,
• said distance signal, value representative of actual distance traversed by the load being representative of distance between distance marker signals, and
• said means responsive to the distance error signal including sampling means actuatable by the distance marker signal for sampling the distance error signal prior to resetting of said distance indicating integrator and holding each such sampled value until the occurrence of a subsequent marker signal for effectuating the change of the control signal applied to the actuator.

Electronic tachometer apparatus for providing an indication of the velocity of an actuator driven load comprising:

• coarse velocity signal producing means coupled to receive a signal representative of energization applied to the actuator for controlling the velocity of the load to produce a coarse velocity signal indicative of the coarse velocity of said load,
• said coarse velocity signal producing means including a velocity indicating integrator coupled to the input of a variable gain amplifier which provides the coarse velocity signal at its output,
• said coarse velocity signal being adjustable by adjustment of the gain of said variable gain amplifier,
• means including a distance indicating integrator coupled to receive the coarse velocity signal for producing a coarse distance signal which is referenced to a distance signal value representative of actual distance traversed by the load to provide a distance error signal indicative of error in the coarse velocity signal,
• means responsive to the distance error signal and coupled to the coarse velocity signal producing means for producing a coarse velocity gain indicative signal which adjusts the gain of said coarse velocity signal producing means so as to null the distance error signal,
• additional means responsive to the distance error signal for supplying an accumulative error compensating signal to the input of said velocity indicating integrator of said coarse velocity signal producing means with a predetermined gain to compensate for accumulative error in the coarse velocity signal such as to reduce the accumulative error substantially to zero so that said coarse velocity signal producing means is able to operate in its dynamic operating range,
• means coupled to the load for providing distance marker signals indicative of position increments traversed by the load,
• said means including a distance indicating integrator being responsive to distance marker signals for resetting said distance indicating integrator to an initial value,
• said distance signal value representative of actual distance traversed by the load being representative of distance between distance maker signals, and
• said means responsive to the distance error signal including sample and hold means actuatable by the distance marker signals for sampling the distance error signal prior to resetting of said distance indicating integrator and holding such sampled value until the occurrence of a subsequent marker signal, the sampling rate being variable as a result of the variable velocity of the load, and the sampled value of the distance error signal being used for adjusting the gain of the variable gain amplifier to null the distance error signal.