Meaning
Real-time adjustment of the vertical positioning system in a precision instrument counteracts the effects of thermal expansion or mechanical settling. High-precision systems utilize z axis drift compensation to maintain the focal plane or the probe height during long-duration operations. Sensors monitor the distance to the workpiece and send feedback to the motion controller to make micro-adjustments.
Mechanical Compensation
Physical changes in the machine structure are corrected by small movements of the lead screw or a piezo actuator. Because z axis drift compensation happens in real-time, it can account for changes that occur as the machine warms up during the first hour of use. These adjustments are typically in the nanometer or micrometer range.
Feedback Loop
Continuous monitoring of the vertical offset ensures that the system remains at the desired setpoint despite external changes. Integration of z axis drift compensation into the control algorithm allows for a faster response than manual correction could ever achieve. The loop must be tuned to avoid oscillation, which would introduce more error than the drift itself.
Precision encoders provide the high-resolution data needed for this level of control.
System Stability
Long-term performance of the instrument depends on its ability to stay within a tight tolerance band throughout the entire shift. Successful z axis drift compensation reduces the need for frequent manual recalibration and allows for overnight automated runs. The effectiveness of the system is measured by the repeatability of measurements over a twenty-four-hour period.
