A disc drive controller circuit for an actuator receives reference data indicating a desired actuator position ".theta..sub.d", error data indicating a difference "e" between the desired actuator position and a sensed actuator position ".theta.", and adaptive parameter data "A". The controller circuit calculates a circuit output "u" that drives the actuator. The controller circuit derives the circuit output "u" according to a formula:.function..theta..times..times..lamda..times..times..lamda..- times..function..times..times..lamda..times..times..lamda..times..intg..ti- mes..times..times.d.tau. ##EQU00001## in which ".lamda." is a controller zero value and "k" is a controller gain value and "t" is time. The adaptive parameter A is updated in general accordance with the formula: A(k)=e.sub.1e.sub.2.DELTA.t+A(k-1).