A nonlinear integrator for servomechanisms

INTEGRATION in the forward part of a servomechanism loop has long been known to reduce steady-state errors. With one perfect integrator, there will be no steady-state error following a simple step-function input; with two tandem integrators there will be no steady-state error due to a ramp input, etc. The major drawback to the linear integrator is the time delay involved. Each linear integrator introduces 90 degrees of phase lag at all frequencies, and so it takes only two integrators to make a basically unstable system. A nonlinear integrator is to be described which is superior in this respect to a linear type.