Position measuring method and apparatus
First Claim
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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Abstract
A process and apparatus for obtaining harmonic-free periodic signals in an incremental measuring system is disclosed in which a graduation having a graduation period P is scanned by at least six scanning elements (for the case in which the previously determined bandwidth N of the analog signals obtained in scanning the graduation N is equal to 3). The periodic analog signals generated by the scanning elements are subjected to a Fourier analysis for the determination of the Fourier coefficients of the base or fundamental wave of the periodic analog signals. These Fourier coefficients are then evaluated as harmonic-free periodic signals for the formation of position measuring values.
43 Citations
13 Claims
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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:
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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; anddetermining 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. - View Dependent Claims (2, 3)
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4. In a position measuring system comprising a measuring scale which comprises a periodic graduation and a scanning unit adapted to scan the measuring scale, the improvement comprising:
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at least 2N scanning elements, each included in the scanning unit to scan the periodic graduation and to generate a respective periodic scanning signal in response thereto, each of said scanning signals including a fundamental component and (N-1) harmonic components; means for performing a Fourier analysis on the scanning signals to determine at least a pair of Fourier coefficients a1, b1 ;
Ua, Ub . . . characteristic of the fundamental component of the scanning signals; andmeans for evaluating the at least a pair of Fourier coefficients a1, b1 ;
Ua, Ub . . . to determine the position of the scanning unit with respect to the measuring scale. - View Dependent Claims (5, 6, 7, 8, 9, 10, 11, 12, 13)
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Specification