Automatic calibration and servo control scheme for offsetting mechanical and electronic component variances

In a pen plotter in which a member is moved between multiple positions by an electrical actuator through a mechanical linkage, apparatus for compensating for changes in system gain to allow precision movement comprising:

• a) a sensor for accurately determining positions of the member;
• b) control logic connected to provide a control signal to the actuator;
• c) adjustable gain control means for adjusting gain of said control signal;
• and,
• d) compensation logic means connected to receive positional signals from said sensor for applying a control signal to the actuator to move the member to a target position closest to a desired final position, for adjusting said gain of said control signal with said adjustable gain control means until the member is located at said target position within an acceptable positional accuracy, and for then employing that gain to move the member to said desired final position.

In a pen plotter in which a member is moved between multiple positions by an electrical actuator through a mechanical linkage, a method for compensating for changes in system gain to allow precision movement comprising the steps of:

• a) providing a sensor for accurately determining positions of the member;
• b) connecting control logic to provide a control signal to the actuator;
• c) providing adjustable gain control means for adjusting gain of said control signal;
• d) applying a control signal to the actuator to move the member to a target position closest to a desired final position;
• e) adjusting said gain of said control signal with the adjustable gain control means until the member is located at the target position within an acceptable positional accuracy;
• and,
• f) employing that gain to move the member to said desired final position.

In a pen plotter in which a member is moved between multiple positions by an electrical actuator through a mechanical linkage, a method for compensating for changes in system gain to allow precision movement comprising the steps of:

• a) providing a sensor for accurately determining positions of the member;
• b) connecting control logic to provide a control signal to the actuator;
• c) providing adjustable gain control means for adjusting gain of said control signal;
• d) providing a look-up table for containing a plurality of pre-established gains associated with respective ones of a plurality of target positions;
• e) prior to plotting, pre-calibrating the look-up table by,
• e1) applying a control signal to the actuator to move the member to a target position closest to a desired final position,
• e2) adjusting said gain of said control signal with the adjustable gain control means until the member is located at the target position within an acceptable positional accuracy,
• e3) storing the gain in the look-up table for its associated target position, and
• e4) repeating steps (e1) through (e3) for each of the plurality of target positions;
• and,
• f) at a time of plotting,
• f1) selecting a gain from the look-up table associated with a target position closest to a desired final position, and
• f2) employing that gain from the look-up table to move the member to said desired final position.