A nonlinearity specification for constructing the servo position error signal

A high performance disk file actuator servo requires a position transducer whose response is linear with displacement. Two concerns that detrimentally affect positional linearity are the nonlinear response of the burst detector to burst amplitude and the nonuniform sensitivity of the magnetic read element across its pole faces. Nonuniform field sensitivity is of particular concern with the advent of magneto resistive heads for embedded servo systems, and this paper gives specification for both for good actuator positioning.