Plasma arc torch position control

A torch height control system maintains a substantially constant operating parameter of the arc during processing of a workpiece by measuring the operating parameter, comparing the operating parameter to a reference value to generate a deviation, adjusting a standoff between the torch and the workpiece by moving the torch relative to the workpiece at a rate which increases with an increase in the deviation to minimize the deviation, and clamping the rate of torch movement relative to the workpiece when the deviation exceeds a predetermined value.