Method of and device for contactless measurement of rotary speed of direct current motor by forming autocorrelation sequence

Claim 3

A method as defined in claim 1, wherein said determining the rotary speed includes determining a rotary speed from a distance between two neighboring maxima of the auto-correlation sequence.

Claim 4

A method as defined in claim 1, wherein said determining the rotary speed includes determining a rotary speed from a distance between two neighboring minima of the auto-correlation sequence.

Claim 5

A method as defined in claim 1, wherein the rotating part is an armature of an electric fuel pump.

Claim 6

A method as defined in claim 4, wherein the signal is a current signal of the electric fuel pump.

Claim 7

A method as defined in claim 4, wherein the signal is a magnetic signal of the electric fuel pump.

Claim 8

A method as defined in claim 1, wherein said forming includes forming an auto-correlation sequence in a computer.

Claim 9

A method as defined in claim 7, wherein the computer is a microcomputer.

Claim 10

A method as defined in claim 1; and further comprising the step of using the determined rotary speed as an estimate rate which is used for determination of a sensing rate with which the current signal is evaluated in a next evaluation.

Claim 11

A method as defined in claim 9, wherein said forming includes twice fourier transforming the signal for producing a spectrum, determining the rotary speed by evaluating of an absolute maximum available in the twice fourier transformed spectrum, and taking into consideration a parameter of the fourier transformation of the previously determined rotary speed estimate rate to form the auto-correlation sequence.

Claim 12

A method as defined in claim 10, wherein the rotary speed is determined by determination of a time associated with the maximum which is inversely proportional to the rotary speed.

Claim 13

An arrangement for measuring a rotary speed of a rotatable part to which a current signal is fed to activate a rotation and which is surrounded by a housing, comprising a measuring device for measuring the current signal I(t) and producing from said measured current signal a signal dependent on the rotary speed of said rotatable part; means for filtering the produced signal; means for sensing said filtered signals at a selected rate and digitalizing the filtered signal to form a plurality of sensed values of the digitalized signal; computing means for forming from the digitalized signals an auto-correlation sequence having maxima and minima; means for selecting a number of the sensed values of the digitalized signal in dependence on a desired accuracy and availability of a computer capacity; and means for determining the rotary speed from the maxima or minima of the auto-correlation sequence by evaluating a distance between at least two successive maxima or minima of the selected sensed values.

Claim 14

An arrangement for measuring a rotary speed of a rotatable part to which a current signal is fed to activate a rotation and which is surrounded by a housing, comprising a measuring device for measuring the current signal I(t) and producing from said measured current signal a signal dependent on the rotary speed of said rotatable part; means for filtering the produced signal; means for sensing said filtered signals at a selected rate and digitalizing the filtered signal to form a plurality of sensed values of the digitalized signal; computing means for forming from the digitalized signals an auto-correlation sequence having maxima and minima; means for selecting a number of the sensed values of the digitalized signal in dependence on a desired accuracy and availability of a computer capacity; and means for determining the rotary speed from the maxima or minima of the auto-correlation sequence by evaluating a distance between at least two successive maxima or minima of the selected sensed values.

Claim 15

An arrangement as defined in claim 12, wherein said device for producing signals is a current measuring device, said filtering means is a band pass filter, said digitalizing means is analog-digital converter, and said computing means is a computer.

Claim 16

An arrangement as defined in claim 13; and further comprising an amplifier provided between said band pass filter and said analog/digital converter.

Claim 17

An arrangement as defined in claim 13; and further comprising an output unit connected with said computer for outputting the rotary speed.

Claim 18

An arrangement as defined in claim 13, wherein said computer has a region for forming the auto-correlation sequence and a region for performing fourier transformations.