Method for filtering digital signals which varies the filter length
AssigneeSiemens Aktiengesellschaft
InventorGerd Hoos
Life of this patent
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Abstract
Digital signals V(K), for use in numerical control of machine tools or robots, for example, are smoothed by means of digital filters to avoid sudden load changes on the axes. As a result, different filter lengths (N') can be used during an axial movement to accommodate varying loads on the axis. This is achieved by presetting modified discontinuous signals V'(K), whose value is determined by doubling the signal difference (D), and then dividing it by the altered filter length (N') less one, in the filter when changing the filter length.
Claims28
A numerical control method for controlling a velocity of a numerically controlled machine, comprising the steps of:
- a) producing velocity signals as digital inputs signals (V(K)) of a filter using an interpolator;
- b) storing a number of the digital input signals (V(K)) corresponding to a specifiable filter length (N) in the filter;
- c) generating an output signal (V(K) of the filter from a sum of a number of the input signals (V(K)), divided by the filter length (N);
- d) calculating a signal difference (D) between each digital input signal (V(K)) and its corresponding output signal (V(K));
- e) storing the signal difference (D) in a storage medium;
- f) modifying the filter length (N) to a modified filter length (N');
- g) determining values of a plurality of modified digital signals V'(K)) when a specifiable change occurs in the filter length to the modified filter length (N') in response to the modifying step f) by doubling the signal difference (D) stored in the storage medium, and then dividing the result by the modified filter length (N') less one;
- h) storing a number, corresponding to the modified filter length (N'), of said plurality of modified digital signals (V'(K)) in the filter;
- and
- i) providing the numerically controlled machine with the output signals (V(K)) to control the velocity of the numerically controlled machine;
- j) controlling the velocity of the numerically controlled machine using the output signals V(K).
A numerical control system for controlling a velocity of a numerically controlled machine, comprising:
- an interpolator producing digital velocity signals (V(K));
- a filter receiving the digital velocity signals (V(K)) produced by the interpolator as digital input signals (V(K)) of the filter, said filter including a means for storing a number of the digital input signals (V(K)) corresponding to a specifiable filter length (N), said filter generating an output signal (V(K)) from a sum of a number of the input signals (V(K)), divided by the filter length (N), said filter modifying the filter length (N) to a modified filter length (N');
- means for calculating a signal difference (D) between each digital input signal (V(K)) and its corresponding output signal (V(K));
- a storage medium storing the calculated signal difference (D);
- and
- means for determining values of a plurality of modified digital signals (V'(K)) when a specifiable change occurs in the filter length to the modified filter length (N') in response to the modifying of the filter length (N) by doubling the signal difference (D) stored in the storage medium, and then dividing the result by the modified filter length (N') less one;
- wherein a number corresponding to the modified filter length (N') of said plurality of modified digital signals V'(K)) is stored in the filter;
- and
- wherein the output signals (V(K)) are provided to the numerically controlled machine to control the velocity of the numerically controlled machine.
Dependencies are inferred from the claim text.