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Position measuring method and apparatus

  • US 4,595,991 A
  • Filed: 09/21/1983
  • Issued: 06/17/1986
  • Est. Priority Date: 10/22/1982
  • Status: Expired due to Term
First Claim
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1. A method for generating harmonic-free periodic signals in an incremental or absolute measuring system comprising a scale which defines a graduation having a period P and a scanning unit which generates at least one scanning signal and scans the scale, said method comprising the following steps:

  • determining a band width N characteristic of the at least one scanning signal;

    providing at least 2N scanning elements in the scanning unit to scan the period P of the graduation, each of which generates a respective scanning signal Sn in response thereto;

    performing a Fourier analysis on the scanning signals to determine at least a pair of Fourier coefficients a1, b1 ;

    Ua, Ub . . . characteristic of a lowest frequency Fourier component of the at least one scanning signal; and

    determining by means of an evaluation unit the position of the scanning unit with respect to the scale from an evaluation of the at least a pair of Fourier coeffients a1, b1 ;

    Ua, Ub . . . as harmonic-free periodic signals.

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