Minimum-time control of magnetic head flux

This paper presents an optimal shape for a wave traversing a transmission line, incident to a magnetic head's write element, that gives minimum-time control of a magnetic head's yoke flux. The control waveform allows for the effects of the magnetic head's eddy currents as well as of the wave that reflects from the time-varying impedance of the magnetic head write element. It is shown that bringing all magnetic head states to equilibrium for minimum nonlinear transition shift requires excessive time. The preferred solution is to quickly achieve a value of desired yoke flux in minimum time and then to use a subsequent control that maintains the desired flux level in the presence of continuing response from yoke eddy currents. The analysis of a transmission line terminated in a simple RLC magnetic head model gives insight to the choice of transmission line impedance.