Transducer positioning system

Apparatus for generating an indication of position with respect to a predetermined path, comprising:

• a first track adjacent one side of said path comprising long magnetic segments magnetized in a first direction interrupted by short magnetic segments magnetized in the opposite second direction,
• a second track adjacent the other side of said path and comprising long magnetic segments energized in said second direction interrupted by short magnetic segments magnetized in said first direction, said short magnetic segments in said second path appearing opposite said long magnetic segments in said first path,
• a magnetic head for detecting said magnetic segments as the segments move with respect to the head whereby the head produces an output signal comprising a fundamental signal and a second harmonic signal which varies in amplitude as said head moves across said tracks, and
• means for determining when the amplitude of said second harmonic is at a predetermined value so as to thereby determine when said head has moved to a predetermined position with respect to said two tracks.

In a method for generating an indication of position with respect to a predetermined path, the steps which comprise:

• providing a first track adjacent one side of said path comprising long magnetic segments energized in a first direction interrupted by short magnetic segments magnetized in the opposite second direction,
• providing a second track adjacent the other side of said path and comprising long magnetic segments energized in said second direction interrupted by short magnetic segments magnetized in said first direction, said short magnetic segments in said second path appearing opposite said long magnetic segments in said first path,
• detecting said segments by means of a transducing means positioned in information transferring relationship with respect to said tracks to produce a composite signal comprising a fundamental signal and a second harmonic signal which varies in amplitude as said transducing means moves across said tracks, and
• providing a steady state position error signal, the amplitude of which varies with the amplitude of said second harmonic signal so as to thereby indicate the position of said transducing means with respect to said tracks.

In a method for generating an indication of position with respect to a predetermined circular path on a magnetic disk, the steps which comprise:

• providing a first circular track on said disk adjacent one side of said path comprising long magnetic segments energized in a first direction interrupted by short magnetic segments magnetized in the opposite second direction,
• providing a second circular track adjacent the other side of said path and comprising long magnetic segments energized in said second direction interrupted by short magnetic segments magnetized in said first direction, said short segments of said first track being centered on radial lines of said disk with respect to said long segments of said second track and said short segments of said second track being centered on radial lines of the disk with respect to long segments of said first track,
• detecting said magnetic segments by means of a transducer positioned in information transferring relationship with respect to said tracks as said disk and the segments rotate with respect to the transducer whereby the transducer produces an output signal comprising a fundamental signal and a second harmonic signal which varies in amplitude as said transducer moves across said tracks,
• producing a uniform frequency and amplitude reference signal at twice the frequency of said fundamental signal,
• producing an analog signal at the frequency and with the amplitude of said second harmonic signal,
• multiplying said reference signal and said analog signal together to thereby produce a pulsating unidirectional output signal, the amplitude of which varies with the amplitude of said second harmonic signal, and
• averaging said pulsating signal so as to thereby produce a steady state signal which thereby constitutes a position error signal indicating the position of said transducer with respect to said tracks.