INDUCTIVE POSITION DETERMINATION

Abstract

A device for the inductive positioning comprises a signal generator, a coil connected with the signal generator, an element for influencing the inductance of the coil depending on its distance to the coil and an evaluator to determine the position of the element with regard to the coil on the basis of a voltage on the coil. The signal generator thereby provides a square wave signal.

Claims

1. A device for the inductive positioning, comprising: a signal generator; a coil connected with the signal generator; an element for influencing the inductance of the coil depending on its distance to the coil; an evaluation to determine the position of the element with regard to the coil on the basis of a voltage on the coil, wherein the signal generator provides a square wave signal.

2. The device according to claim 1, wherein the voltage on the coil comprises an alternating voltage with the frequency of the square wave signal and at least one more alternating voltage with an integral multiple frequency of the square wave signal.

3. The device according to claim 1, wherein an alternating voltage applied to the coil is integrated in a DC voltage by a low-pass filter.

4. The device according to claim 1, wherein the coil is a planar coil.

5. The device according to claim 1, further comprising a controllable switching mechanism to connect one end of the coil with a predetermined potential.

6. The device according to claim 5, wherein several coils are included each with respectively assigned switching mechanisms.

7. The device according to claim 6, wherein a control device is included which is equipped to always just close one of the switching mechanisms to perform a positioning with respect to the coil assigned to the switching mechanism that is being closed.

8. The device according to claim 1, wherein the evaluator comprises an analog-digital converter and a microcomputer and the microcomputer comprises a digital output that is set up to provide the square wave signal.

9. The device according to claim 1, wherein the element comprises an electrically conductive attenuator.

10. The device according to claim 1, wherein the element comprises a ferromagnetic and electrically insulating amplifying element.

11. The device according to claim 1, wherein the signal generator provides the square wave signal for the excitation of the coil.

12. The device according to claim 1, wherein the square wave signal of the signal generator can supply the coil directly and by means of exclusively passive electrical components.

13. The device according to claim 1, wherein a resistor is installed downstream in series with the coil for the current limitation.

14. The device according to claim 1, wherein the coil is designed as a single-layer planar coil.

15. A switching device for selecting a gear of a motor vehicle comprising a device according to claim 1.

16. The device according to claim 1, wherein the square wave signal of the signal generator can supply the coil directly or by means of exclusively passive electrical components.

17. The device according to claim 3, further comprising a diode positioned between the coil and the low-pass filter.

18. The device according to claim 5, wherein the switching mechanism is formed through a transistor.

19. The device according to claim 6, wherein the element comprises several elements, each corresponding to one of the several coils.

20. The device according to claim 1, wherein a measurement phase of an inductive positioning measuring process carried out by the device is performed in about 10 to 20 microseconds.

Description

[0021] The disclosure is now described in greater detail by means of the enclosed figures, in which:

[0022] FIG. 1 shows a diagram of a device for the inductive positioning; and

[0023] FIG. 2 shows a diagram of an expanded device according to the example of FIG. 1.

[0024] FIG. 1 shows a device 100 for the inductive determination of the positioning of an element 105. The device can be used aboard a motor vehicle, in particular, to determine a position or place of a mobile element. For example, the position of a gear lever can be scanned for a gear of a transmission in respect of a console. In another embodiment, a turning angle can be determined between the motor vehicle and a trailer coupled by means of a trailer hitch. The magnetic element 105 is generally an element which influences a magnetic alternating field that it is exposed to. The element 105 can thereby be especially electrically conductive to weaken the magnetic alternating field in the area of the coil 115, or ferromagnetically and electrically insulating to amplify the magnetic alternating field in the area of the coil 115. In one case, the element 105 can comprise copper or aluminum, for instance, in the second case, iron, nickel, or cobalt, for example. In addition to the element 105, the device 100 comprises a signal generator 110 to provide for a square wave signal, a coil 115 and an evaluator 120, and a resistor R for the current limitation, which is installed downstream with the signal generator 110 in sequence with the coil 115. The current that flows through the coil 115 can thus be limited to a preset maximum current value, and the service life of the device can be increased.

[0025] The signal generator 110 provides a square wave voltage on its output with respect to a fixed potential reference in the representation of FIG. 1 as regards to ground. The coil 115 is connected with the output of the signal generator 110 with a first end, and with another fixed potential with the other end, which can correspond to the other fixed potential. The evaluator 120 is connected with the coil 115 and is set up to scan a voltage generated on the coil 115 depending on the square wave signal of the signal generator 110. An integrator or low-pass filter 125 is therefore preferably intended between the coil 115 and the evaluator 120. A diode 130 can optionally lead in forward direction from the coil 115 to the low-pass filter 125. The low-pass filter 125 integrates high-frequency signals on the coil 115 over a predetermined period of time and provides the evaluator 120 with a respective voltage.

[0026] The position of the element 105 with regard to the coil 115 influences its inductance. Depending on the material of the element 105, the inductance of the coil 115 can be increased or reduced during the approximation of the element 105 to the coil 105. The coil 115 is preferably designed as a flat coil, whereby it has a limited extension to remain manageable. The inductance of the coil 115 is therefore relatively low. The expansion of the element 105 is usually in the area of the extension of the flat coil 115.

[0027] The square wave signal 110 can be considered a superimposition of sine or cosine signals of different frequencies and amplitudes. A first sine signal has the frequency of the square wave signal as a basic frequency. Additional sinusoidal signals have frequencies that correspond to integer multiples of the basic frequency. The higher the frequency, the lower the amplitude of the frequency in the normal case.

[0028] Odd multiples of the basic frequency have an amplifying effect towards each other, so that the coil 15, especially when its inductance is low, can react to several of the sine signals so that its voltage drop can be influenced by the position of the element 105 multiple times right away. A voltage difference on the coil 115 with a present and absent element 105 can therefore be maximized. The measurement signal can have an improved signal-to-noise ratio and an amplifier for the measurement signal can be saved.

[0029] The evaluator 120 can especially comprise a digital-to-analog converter. This can provide a numerical value on a programmable microcomputer, for example. A different signal processing of the measuring voltage is however also possible.

[0030] FIG. 2 shows a diagram of an expanded device 100 according to the example of FIG. 1. Several coils 115 are provided for, whose respective one end is connected with the signal generator 110 through the resistor R. The respective other end is connected by means of a switching mechanism 205 with the predetermined constant potential. The switching mechanisms 205 can particularly be formed through transistors. Since the switching mechanisms 205 do not have to transmit any high frequencies regardless of the frequency of the square wave signal of the signal generator 110, cost-effective low-frequency transistors can be used for this purpose, for example.

[0031] The switching mechanisms 205 are controlled by a control device 210 which can comprise a programmable microcomputer, in particular. The control device 210 is set up to close just one of the switching mechanisms 205 at any time to perform a measurement of the position of the element 105 or several elements 105 with respect to the respective assigned coil 115. The control device 210 can also perform further processing of the voltage specified by means of the evaluator 120. The evaluation can comprise numerical or statistical operations especially when the control device 210 is designed as a programmable microcomputer.

[0032] In the embodiment shown, the control device 210 is also designed to provide the square wave signal and it therefore also works as a signal generator 110. For example, a serial or parallel interface of the control device 210 can be used to provide the square wave signal with a relatively high amplitude, such as between 0 and 3.3 volt or between 0 and 5 volt. Limiters or amplifiers can be used for other voltages accordingly.

[0033] The square wave signal described above can result in short signal times of the coils 115. This means that a voltage obtainable from the coil 115 can point out the presence or absence of the element 105 faster than with a sine signal. A measuring process with a single coil 115 can thus be performed relatively quickly, such as during a measurement phase of about 10 to 20 microseconds. A measurement pause may be taken between individual measurement phases with different coils 115 each, which can be of similar duration. Due to the short measurement periods, many coils 115 can be queried by the control device 210 one after the other so that a safe and rapid positioning is also possible with a low processing capacity of the control device 210. The control device 210 in a usual application with up to about 20 coils 115 can comprise a customary 8-bit microcomputer. A 32-bit microcomputer as is necessary for measurement methods based on sine signals can be saved.

[0034] The element 105 can be designed in its dimensions with respect to the arrangement of coils 115 so that it can influence several coils 115 simultaneously. As the inductance of each coil 115 is influenced to a greater or lesser extent depending on the respective distance of the element 105, the exact position of the element 105 can then be assessed based on ratios of the voltages provided on the low-pass filters 125 influenced by the coils 115.

REFERENCE SIGNS

[0035] 100 Device [0036] 105 Element [0037] 110 Signal generator [0038] 115 Coil [0039] 120 Evaluator [0040] 125 Low-pass filter [0041] 130 Diode [0042] 205 Switching mechanism [0043] 210 Control device [0044] R Resistor