Patent ID: 11946779
Assignee: DMG MORI CO., LTD.
Field: Measurement (Instruments)
Classification: CPC G | IPC G

Claim 3:
4. A position detection apparatus according to claim 1, comprising:
an absolute track in which a first binary sequence generated from a second binary sequence is recorded; and
an absolute sensor unit that reads the first binary sequence from said absolute track,
wherein the first binary sequence consists of 0s and 1s and is generated by replacing 0 in the second binary sequence with 10 and 1 in the second binary sequence with 01, or by replacing 0 in the second binary sequence with 01 and 1 in the second binary sequence with 10,
wherein when reading, values in the second binary sequence are replaced with 1s and 0s in accordance with not a positive/negative of magnetism but a direction of inversion from positive to negative or from negative to positive,
wherein said absolute sensor unit includes two sensor elements arranged at an interval of λ/2 or less than λ/2 of a recording pitch λ, of the first binary sequence, and
wherein said absolute sensor unit detects every other term of a sequence of at least N terms from the first binary sequence, and
the apparatus further comprises:
an incremental track communicating with an incremental sensor unit operating as a fore and rear detector that detects which one of the two values of the first binary sequence corresponds to the position that said absolute sensor unit faces;
an inverter that generates an inverted sequence by bit-inverting a detected sequence detected by said absolute sensor unit;
a discriminator that discriminates, based on fore and rear positions detected by the fore and rear detector, which one of the detected sequence and the inverted sequence should be searched for;
a searcher that searches the second binary sequence for the detected sequence or the inverted sequence discriminated by the discriminator; and
a position detector that converts, based on a correspondence relationship between the first binary sequence and the second binary sequence, the sequence detected by said absolute sensor unit, and detects a position of said absolute sensor unit based on the position of the detected sequence or the inverted sequence found by said searcher in the second binary sequence after the conversion and the fore and rear positions detected by said fore and rear detector.