Adaptive servo control system

An adaptive servo control system comprising:

• first stage means for positioning a work piece relative to a work apparatus;
• first drive means responsive to a first drive signal and operative to drive said first stage means in a first direction;
• first position detector means for monitoring the position of said first stage means and for developing a first actual position signal commensurate therewith;
• first input means for generating a first desired position signal corresponding to a position to which said first stage means is to be driven;
• and
• first stage position control means including,
• first comparator means for comparing said first actual position signal to said first desired position signal and for developing
• a first output signal when said first desired position signal equals said first actual position signal,
• a second output signal when said first desired position signal is greater than said first actual signal,
• a third output signal when said first desired position signal is less than first actual signal and
• a fourth output signal when the absolute value of the difference between said first desired position signal and said first actual position signal is less than a predetermined number,
• first tachometer means driven by said first drive means and operative to develop a first rate feedback signal,
• first servo amplifier means responsive to a first servo input signal and operative to develop said first drive signal,
• first variable attenuator means responsive to said fourth output signal and operative to attenuate said first rate feedback signal,
• first inverter means for inverting said third output signal,
• first circuit node means for variously adding together said inverted third signal, said second output signal and said attenuated first rate feedback signal to develop said first servo input signal, and
• means responsive to said first output signal and operative to couple a dc signal commensurate with said first position signal to said first node means for inclusion in said first servo input signal;
• whereby in response to said first desired position signal said first stage means is driven at a first rate toward said desired position and is then driven at a second rate as it approaches the desired position.