SPEED SENSOR

Abstract

A speed sensor for detecting a speed of a magnetizable object. The speed sensor (100) can be supplied with an electric alternating signal with a first frequency by an electric signal source. The speed sensor including: a primary coil for generating a magnetic alternating field with the first frequency; first and second secondary coils. The first and second secondary coils can each be magnetically coupled to the primary coil via a magnetizable object. First and second electric signals induced in the first and second secondary coils respectively by the generated magnetic alternating field; a Goertzel filter bank detects first and second amplitude values of respective spectral components of the induced first and second electric signals in the event of a second frequency which differs from the first frequency. A processor determines the speed of the magnetizable object depending on the detected first amplitude value and the detected second amplitude value.

Claims

1. A speed sensor for sensing a speed of a magnetizing object, the speed sensor being able to be supplied with an electrical alternating signal at a first frequency by an electrical signal source, comprising: a primary coil for generating an alternating magnetic field at the first frequency; a first secondary coil and a second secondary coil, the first secondary coil and the second secondary coil each being able to be magnetically coupled to the primary coil by a magnetizable object, and a first electrical signal being able to be induced in the first secondary coil and a second electrical signal being able to be induced in the second secondary coil by the alternating magnetic field which is generated; a Goertzel filter bank for recording a first amplitude value of a spectral component of the induced first electrical signal and a second amplitude value of a spectral component of the induced second electrical signal at a second frequency which differs from the first frequency; and a processor for determining the speed of the magnetizing object on the basis of the recorded first amplitude value and the recorded second amplitude value.

2. The speed sensor as claimed in claim 1, the recorded respective amplitude value being a voltage value or a current value of the respective electrical signal.

3. The speed sensor as claimed in claim 1, the processor being designed to determine a difference between the recorded respective amplitude values in order to determine the speed of the magnetizing object.

4. The speed sensor as claimed in claim 1, the processor being designed to determine a Fourier coefficient on the basis of the recorded respective amplitude values in order to determine the speed of the magnetizing object.

5. The speed sensor as claimed in claim 1, having a memory in which calibration data are prestored, the processor being designed to determine the speed of the magnetizing object on the basis of the recorded respective amplitude values and the calibration data.

6. The speed sensor as claimed in claim 5, the calibration data being prestored in the memory in the form of a look-up table.

7. The speed sensor as claimed in claim 6, the processor also being designed to determine a difference between the recorded respective amplitude values, and a difference between the recorded respective amplitude values being assigned to a speed of the magnetizing object in the look-up table.

8. The speed sensor as claimed in claim 1, further comprising an analog/digital converter being connected upstream of the Goertzel filter bank.

9. The speed sensor as claimed in claim 1, further comprising a window device for signal windowing being connected upstream of the Goertzel filter bank.

10. The speed sensor as claimed in claim 1, the Goertzel filter bank comprising a further electrical signal source for generating a reference signal at the second frequency.

11. The speed sensor as claimed in claim 1, the second frequency being twice the first frequency, and the Goertzel filter bank comprising a frequency doubler for generating a reference signal at the second frequency.

12. The speed sensor as claimed in claim 1, the Goertzel filter bank comprising a first Goertzel filter for recording the first amplitude value and a second Goertzel filter for recording the second amplitude value.

13. The speed sensor as claimed in claim 1, the first frequency being in the range between 5 kHz and 20 kHz.

14. The speed sensor as claimed in claim 1, further comprising having-a further Goertzel filter bank for recording a further amplitude value of a further spectral component of the induced first electrical signal or of the induced second electrical signal at the first frequency, the processor also being designed to determine a position of the magnetizing object on the basis of the recorded further amplitude value.

15. The speed sensor as claimed in claim 1, further comprising a further Goertzel filter bank for recording a further amplitude value of a further spectral component of the induced first electrical signal or of the induced second electrical signal at a third frequency which differs from the first frequency and from the second frequency, the processor also being designed to determine an acceleration of the magnetizing object on the basis of the recorded further amplitude value.

16. The speed sensor as claimed in claim 2, the processor being designed to determine a difference between the recorded respective amplitude values in order to determine the speed of the magnetizing object.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Exemplary embodiments of the invention are illustrated in the drawing and are described in more detail below.

[0033] In the drawing:

[0034] FIG. 1 shows a schematic illustration of a speed sensor according to one embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0035] FIG. 1 shows a schematic illustration of a speed sensor 100 according to one embodiment. The speed sensor 100 comprises a primary coil 101, a first secondary coil 103, a second secondary coil 105, a Goertzel filter bank 107 and a processor 109.

[0036] The speed sensor 100 for sensing a speed of a magnetizing object, the speed sensor 100 being able to be supplied with an electrical alternating signal at a first frequency by an electrical signal source, can be designed with: the primary coil 101 for generating an alternating magnetic field at the first frequency; the first secondary coil 103 and the second secondary coil 105, the first secondary coil 103 and the second secondary coil 105 each being able to be magnetically coupled to the primary coil 101 by means of a magnetizable object, and a first electrical signal being able to be induced in the first secondary coil 103 and a second electrical signal being able to be induced in the second secondary coil 105 by the alternating magnetic field which is generated; the Goertzel filter bank 107 for recording a first amplitude value of a spectral component of the induced first electrical signal and a second amplitude value of a spectral component of the induced second electrical signal at a second frequency which differs from the first frequency; and the processor 109 for determining the speed of the magnetizing object on the basis of the recorded first amplitude value and the recorded second amplitude value.

[0037] The magnetizable object may comprise a soft-magnetic element or may be formed by a soft-magnetic element. The magnetizing object may also be an element of a movable piston.

[0038] The electrical signal source may be an AC voltage source or an alternating current source. The electrical signal source may also comprise a frequency generator, a resonant circuit and/or a voltage-controlled oscillator (VCO).

[0039] The first frequency may be predetermined or can be adjusted by means of an actuation element, such as a pushbutton, a rotary knob or a dual in-line package (DIP) switching element, of the electrical signal source. For example, the first frequency is 1 Hz, 10 Hz, 100 Hz, 1 kHz, 10 kHz, 100 kHz, 1 MHz, 10 MHz or 100 MHz. According to one embodiment, the second frequency can be twice the first frequency.

[0040] The primary coil 101 and the respective secondary coils 103, 105 may form a differential transformer or may be included in a differential transformer. The primary coil 101 and the respective secondary coils 103, 105 may also be elements of a linear inductive position sensor (LIPS).

[0041] The Goertzel filter bank 107 may also comprise a filter element, such as a Goertzel filter, for filtering the first electrical signal and/or the second electrical signal according to the Goertzel algorithm. Such a filter element can be used to sense an amplitude of the electrical signal at a predetermined frequency, such as the second frequency.

[0042] According to one advantageous embodiment, the speed sensor 100 or a linear inductive position sensor (LIPS) may comprise a differential transformer which is operated at a defined application frequency, such as the first frequency. The respective electrical signals induced or produced in this case in the respective secondary coils 103, 105, such as respective secondary voltages, can be evaluated in a frequency-selective manner. In this case, the frequency selectivity can be achieved using a Goertzel filter. For this purpose, the Goertzel filter uses a method based on a Fourier transform, but, in contrast to a Fourier transform, the amplitudes of the frequencies of an entire spectrum are not determined, but rather only the amplitude at one frequency, namely the excitation frequency, such as the first frequency. The difference between the respective secondary amplitudes, which is determined using this method, is a measure of the position of the magnetizing object, such as a magnet.

[0043] According to another advantageous embodiment, the speed sensor 100 can be operated at the first frequency, such as a frequency f, and the secondary voltages can be evaluated at the second frequency, such as twice the frequency. In this case, the second Fourier coefficient can be determined. This coefficient is proportional to the rate of change of the respective electrical signals and can therefore represent a measure of the speed at which the magnetizing object, such as a magnetic target, is moving. This makes it possible to simultaneously sense the position and the speed of the magnetizing object, such as a magnetic target.

[0044] According to another advantageous embodiment, an acceleration of the magnetizing object can be sensed when evaluating the respective electrical signals, such as the respective secondary voltages, at the third frequency, such as three times the frequency.

LIST OF REFERENCE SYMBOLS

[0045] 100 Speed sensor

[0046] 101 Primary coil

[0047] 103 First secondary coil

[0048] 105 Second secondary coil

[0049] 107 Goertzel filter bank

[0050] 109 Processor