Minimum-time control of magnetic head flux

This paper presents an optimal shape for a wave traversing a transmission l ine, incident to a magnetic head's write element, that gives minimum-time c ontrol 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 re flects from the time-varying impedance of the magnetic head write element. It is shown that bringing all magnetic head states to equilibrium for minim um nonlinear transition shift requires excessive time, The preferred soluti on is to quickly achieve a value of desired yoke flux in minimum time and t hen to use a subsequent control that maintains the desired flux level in th e presence of continuing response from yoke eddy currents. The analysis of a transmission line terminated in a simple RI;C magnetic head model gives i nsight to the choice of transmission line impedance.