INDUCTIVE SENSOR ARRANGEMENT FOR DETECTING A CHANGE IN THE POSITION OF AN ACTUATOR ELEMENT

Description

[0001] The invention relates to an inductive sensor arrangement. The invention also relates to an actuating arrangement.

[0002] Inductive sensor systems are playing an increasingly important role in modern vehicles, for example, in detecting the actuation of a so-called fixed door handle and the resulting activation of the door opening mechanism. The operating principle of inductive sensor systems is based on the detection of a change in an electromagnetic field when a metallic or ferromagnetic actuating element moves within that field. The underlying physical effect is the change in inductance and / or the quality factor of the inductance due to a change in the position of the conductive and / or ferromagnetic element relative to the component generating the inductance. The conductive or ferromagnetic element could, for example, be the actuating area of ​​a door handle or a part of the actuating area of ​​the door handle.Because inductive sensors can detect even slight changes in position, for example in the micrometer range, the use of inductive sensors is particularly interesting for the increasingly used so-called fixed door handles.

[0003] When providing actuation systems with inductive sensor arrays, reliable detection of changes in the position of a metallic actuating element is important. Furthermore, it is desirable that the actuation system be economically manufacturable.

[0004] GB 2 494 183 A describes an effects unit for generating an output signal from an input signal originating from an electronic musical instrument or a microphone. GB 2 494 183 A describes, among other things, the use of a resonant circuit, also including an inductive coil.

[0005] US 2019 / 094404 A1 describes a proximity sensor that detects and outputs the presence or absence of an object.

[0006] US Patent 10,428,562 B2 discloses a device for detecting the presence of a user and a vehicle door handle that includes this device.

[0007] WO 2019 / 122867 A1 discloses recording systems and methods for keyboards, for example for musical instruments.

[0008] The object of the invention is to provide an alternative to existing actuation arrangements. The considerations to be found should enable sufficiently reliable detection of a change in the position of an actuating element and allow the production of an actuation arrangement with reasonable economic efficiency.

[0009] The problem is solved by a motor vehicle with an actuating arrangement, wherein the actuating arrangement comprises an inductive sensor arrangement, with the features of claim 1.

[0010] An inductive sensor arrangement is provided for detecting a change in the position of a metallic actuating element. The sensor arrangement comprises at least the following components: an LC resonant circuit with an inductive element (L), preferably a coil or a combination of several coils, and with a capacitive element (C), for example a capacitor or several capacitors; an excitation supply which is coupled to the LC resonant circuit with an excitation voltage (U) for exciting the LC resonant circuit, a decoupling element arranged between the excitation supply and the LC resonant circuit, an evaluation arrangement for evaluating the signal falling across the resonant circuit.

[0011] A high-impedance series resistor can be used as a decoupling element, connected between the excitation power supply and the resonant circuit. This high-impedance series resistor can, for example, have a resistance value between 1 kΩ and 10 kΩ, preferably between 3 kΩ and 7 kΩ. Of course, the decoupling element can also comprise more than one component; the essential requirement is the functionality of the high-impedance decoupling.

[0012] The excitation voltage is preferably output by the excitation supply as a sequence of voltage pulses, particularly preferably as a sequence of square wave pulses. The voltage pulses can be output, for example, at an operating frequency between 1 MHz and 10 MHz, preferably 5 MHz to 10 MHz, and particularly preferably 7 MHz to 9 MHz. Alternatively, other excitation voltage variants are also conceivable, for example, excitation by means of an excitation signal that follows a sinusoidal waveform, that is, with an excitation voltage that can be described as a sine function or sinusoidal oscillation as a function of time. In this case, the operating frequencies can also be between 1 MHz and 10 MHz, preferably 5 MHz to 10 MHz, and particularly preferably 7 MHz to 9 MHz.

[0013] For example, a NOC can act as a stimulus provider, numerically controlled oscillator, often also called DCO digitally controlled oscillator, This allows for the use of a timer required for outputting voltage pulses, which has the advantage that it is already integrated into the excitation power supply. The excitation power supply can also be referred to as a signal source; the term "signal source" is commonly used in the context of operating a resonant circuit.

[0014] The LC resonant circuit is preferably a parallel resonant circuit, but the sensor arrangement is also functional in principle with an LC resonant circuit designed as a series resonant circuit.

[0015] A structurally simple variant is preferred, in which exactly one coil acts as the inductive element and exactly one capacitor as the capacitive element, forming the LC resonant circuit. Alternatively, it is also possible to provide for several inductive components and / or several capacitive components, whereby the capacitive element then represents the total capacitive effect and the inductive element the total inductive effect within the framework of an equivalent circuit diagram.

[0016] In particular, it can be provided that at least the excitation power supply, the resonant circuit, the transmission line, and / or the decoupling element are contained in the same microcontroller, preferably also the evaluation arrangement. Providing all or many functionalities of the sensor arrangement within a single microcontroller means that the sensor arrangement can be provided very cost-effectively by programming a single microcontroller.

[0017] In one embodiment, the evaluation arrangement includes a rectifier circuit.

[0018] An inductive sensor arrangement is proposed for detecting changes in the position of an actuating element. To determine the change in position of the actuating element, the electromagnetic properties of the LC resonant circuit are measured, whereby a change in the position of the LC resonant circuit causes a detuning of the LC resonant circuit. An LC resonant circuit comprising an inductive element (L) and a capacitive element (C). An excitation supply coupled to the LC resonant circuit with an excitation voltage (U) for excitation. Preferably, the excitation supply is a pin controller whose output pin is coupled to the LC resonant circuit via a conductor, wherein a decoupling resistor with a high resistance value, for example between 1 kΩ and 10 kΩ, preferably between 4 kΩ and 6 kΩ, is arranged between the output pin and the LC resonant circuit. An evaluation arrangement for evaluating the signal across the resonant circuit. Preferably, the evaluation arrangement is a series connection of a rectifier circuit and an ADC, wherein the rectifier circuit and ADC are particularly preferably combined for signal smoothing via a further capacitive element, optionally additionally via a high-resistance resistor.

[0019] The rectifier circuit results in a DC voltage signal being present instead of a high-frequency AC voltage. In the preferred embodiment, where the rectifier circuit consists of a diode and a capacitor arranged in parallel with the resonant circuit, the voltage across the rectifier capacitor is a measure of the AC voltage amplitude. This, of course, requires that the capacitor be sufficiently large, which is the responsibility of the person skilled in the art during the design process. The voltage across the capacitor is measured at the ADC and, for example, compared with a target value and / or checked for falling below a lower threshold and / or exceeding an upper threshold. This is the evaluation of the signal across the resonant circuit, indirectly via the rectified voltage value, as performed in the present application.If one or more of the conditions are met in a predefined manner, dependent on the specific design of the sensor arrangement, the actuating element is recognized as deviating from its unactuated position, thereby triggering an actuation signal. This can cause a trigger circuit coupled to the evaluation arrangement to output an actuation signal.

[0020] A major advantage of the described approach is that the complex and error-prone time-resolved measurement of a high-frequency, time-dependent voltage is reduced to the measurement of a rectified—and therefore significantly less time-dependent—signal. Implementing this measurement results in a robust detection of position changes that is less dependent on deviations in timing or the accuracy of a timer.

[0021] In a preferred embodiment, the excitation supply is configured to output the excitation voltage at an operating frequency that corresponds to or is tuned to the resonant frequency of the resonant circuit. Being tuned to the resonant frequency preferably means that an excitation voltage is empirically found which produces noticeable effects even with minimal changes in position. Specifically, this means, for example, finding an operating point for the excitation voltage that exhibits the steepest possible slope on the signal-frequency curve (with the signal on the y-axis). Typically, this is a frequency close to the resonant frequency. For example, the excitation voltage may be designed to deviate from the resonant circuit's resonant frequency by less than 5 percent.An operating frequency close to the resonant frequency of the resonant circuit means that even a small change in the inductance of the inductive element and / or its quality factor leads to a significant change in the signal across the resonant circuit, resulting in high measurement sensitivity of the inductive sensor arrangement. Particularly in an embodiment according to the invention, which includes a rectifier circuit as part of the evaluation arrangement, it is advantageous to evaluate a parameter that depends on the rectified signal. Preferably, a rectified voltage is measured. It is advantageous to perform such an evaluation only after the rectified signal has saturated, for example, after at least five, preferably at least ten, excitation periods.

[0022] According to the invention, the rectifier circuit comprises a diode and a capacitor (C_D), preferably connected in parallel to the resonant circuit. This design has the advantage of being particularly simple and therefore cost-effective.

[0023] According to the invention, the rectifier circuit is arranged between the LC resonant circuit and an ADC of the evaluation arrangement, wherein the evaluation arrangement is configured to detect a voltage value rectified at the rectifier with the ADC and to recognize a change in position as present depending on the detected voltage value.

[0024] Preferably, the evaluation arrangement is an ADC present in the microcontroller, or alternatively, includes an ADC as a component.

[0025] The evaluation arrangement is particularly preferably configured to recognize a change in position when an upper threshold voltage value is exceeded or when a lower threshold voltage value is undershot.

[0026] According to one embodiment of the sensor arrangement, the evaluation arrangement is configured to detect a change in position precisely when an upper threshold voltage value is exceeded or when a lower threshold voltage value is undershot. In particular, it can be provided that the change in position is detected precisely when an upper threshold voltage value is exceeded or when a lower threshold voltage value is undershot.

[0027] In an alternative embodiment of the invention, the evaluation arrangement does not include a rectifier circuit, and an ADC of the evaluation arrangement detects a voltage drop across the resonant circuit. In this embodiment, it is essential that the inertia of the ADC is adapted to the operating frequency of the excitation supply such that the minimum measurement duration of the ADC lasts at least one period of the resonant circuit excitation, preferably between 5 and 1000 periods of resonant circuit excitation, particularly preferably between 5 and 100 periods of resonant circuit excitation, and even more preferably between 5 and 20 periods of resonant circuit excitation. In simulations, 10 periods of resonant circuit excitation and adjacent values ​​have proven to be particularly suitable.This means that the ADC cannot track the time-dependent voltage change, but instead, for the ADC, the time-dependent voltage results in an essentially time-independent measured voltage value. This design thus exploits a disadvantage of relatively inexpensive ADCs, namely their poor time resolution.

[0028] According to the invention, an actuating arrangement is provided on a motor vehicle, wherein the actuating arrangement comprises a sensor arrangement according to one of the preceding claims and a metallic actuating element, wherein the metallic actuating element undergoes a change of position relative to the inductive element when actuated.

[0029] The metallic actuating element is movable or deformable relative to the electromagnetic field of the inductive element, both of which are encompassed by the general term "change in position." This change in position results in the previously explained change in the inductance and / or equivalent inductance and / or quality factor of the inductive element, which in turn causes a detuning of the LC resonant circuit and thus alters the value of the rectified voltage amplitude compared to the voltage amplitude present in the equilibrium state. The change in the voltage amplitude then directly indicates the change in position of the metallic actuating element.A change in position can be interpreted as present by the evaluation arrangement, for example, if an upper threshold voltage, determined by the person skilled in the art depending on the required accuracy and / or the tolerated false-positive measurements, is exceeded and / or a lower threshold voltage is undershot.

[0030] The term "metallic actuating element" refers to the property of influencing the electromagnetic field generated by the inductive link, and thus, for example, the quality factor of the inductive link's inductance. For this purpose, the metallic actuating element can be made of or contain a metal, but it can also be qualified as a metallic actuating element by using materials other than metals, such as a material that exhibits sufficiently metallic conductivity to influence the electromagnetic field, as is the case with some transition metal nitrides, such as titanium nitride.

[0031] It is naturally the responsibility of the person skilled in the art, tasked with carrying out the invention, to adapt the dimensions of the resonant circuit and excitation voltage on the one hand, and the design and positioning of the actuating element on the other, and to coordinate both with a minimal change in the voltage curve at the output of the rectifier circuit, from which a change in the position of the actuating element can or should be assumed. However, this is not essential for the fundamental functioning of the present invention, as long as the actuating element, when changing position within predetermined parameters, influences the electromagnetic field of the actuating element and this influence leads in a reproducible manner to a reliably detectable phase shift, which, above a value determined by the person skilled in the art, is considered as the detection of the actuation of the change in position.Such an interpretation in itself does not pose any fundamental challenges for the expert, but rather requires making standard technical considerations, for example between the required sensitivity of detecting changes in position on the one hand and the tolerated extent of false positive detections on the other.

[0032] Preferably, the actuating arrangement is a door handle of a vehicle door or a vehicle hatch, wherein the inductive sensor arrangement is arranged within the door handle. Particularly preferably, the actuating element is arranged on the door handle or is a component of the door handle, preferably a component of a section of the door handle's casing. Fig. 1a und 1b : Schematic diagrams of an actuation arrangement 1; Fig. 2 : schematic circuit diagram of an inductive sensor arrangement;

[0033] In Fig. 1a Figure 1 shows a schematic cross-sectional view of an actuating arrangement 1 of a motor vehicle. In the exemplary embodiment shown, the actuating arrangement 1 is a door handle, which is shown in cross-section. An inductive sensor arrangement 2 is shown within the handle 1, and in the illustrated embodiment, the entire assembly is mounted on a circuit board. The inductive sensor arrangement comprises a resonant circuit with a coil L. A metallic actuating element 4, designed as a metal foil, is arranged on the outer section of the door handle and on the inside of the door handle. The metallic actuating element 4 is positioned opposite the coil L of the inductive sensor arrangement 2. Due to the elastic behavior of the outer section of the door handle, the metallic actuating element 4 is movable relative to the sensor arrangement 2.

[0034] In Fig. 1b Figure 3 illustrates how the application of force (symbolized by arrow 3) causes an effect on the shell section. As a result of this force, the metallic actuating element 4, designed as a metal foil, has undergone a change in position. This change in position is a consequence of a section-by-section displacement of the actuating element 4 relative to the sensor arrangement 2, resulting from the deformation of the actuating element. 4. The change in position of the actuating element also occurred, in particular, relative to the coil L of the sensor arrangement 2. The sensor arrangement 2 serves the purpose of detecting the actuation manifested in the deformation of the actuating element 4.

[0035] In Fig. 2An embodiment of an inductive sensor arrangement according to the invention is shown. The sensor arrangement comprises an LC resonant circuit 5, which includes the inductive element L and the capacitive element C. The inductive element represents the component of the sensor arrangement that provides the functionality for detecting changes in the position of a metallic and / or ferromagnetic actuating element. In the illustrated embodiment, the resonant circuit 5 is a parallel resonant circuit that is coupled to the excitation supply 6 via the decoupling resistor 7. The excitation supply 6 is a pin controller whose output pin provides the excitation signal for the resonant circuit 5. In the illustration, the decoupling resistor has a resistance value of 5 kΩ.The evaluation arrangement for evaluating the signal falling across the resonant circuit is formed from the rectifier 8, the capacitor CD (also referred to as C_D), which together form the rectifier circuit, together with the ADC 10 and resistor 9 and capacitor CG, which are used for signal smoothing, but are not absolutely necessary for the actual functionality.

Claims

1. Motor vehicle with an actuating arrangement, wherein the actuating arrangement comprises an inductive sensor arrangement (2) for detecting a change in position of a metallic actuating element and the metallic actuating element (4), wherein the metallic actuating element (4) undergoes a change in position relative to an inductive member (L) when actuated, wherein the sensor arrangement comprises: - an LC resonant circuit with the inductive member (L) and with a capacitive member (C), - an excitation supply which is coupled to the LC resonant circuit with an excitation voltage (U) for exciting the LC resonant circuit, - a decoupling element arranged between the excitation supply and the LC resonant circuit, - an evaluation arrangement for evaluating the signal falling across the resonant circuit, wherein the evaluation arrangement has a rectifier circuit, wherein the rectifier circuit has a diode and a capacitance (C_D) connected preferably in parallel to the resonant circuit, wherein the rectifier circuit is arranged between the LC resonant circuit and an ADC of the evaluation arrangement, wherein the evaluation arrangement is designed to detect a voltage value rectified at the rectifier with the ADC and to recognise a change in position as present depending on the detected voltage value.

2. Motor vehicle according to claim 1, wherein the excitation supply is designed to output the excitation voltage (U) at a working frequency (f) which corresponds to or is tuned to the natural frequency of the resonant circuit.

3. Motor vehicle according to claim 1 or claim 2, wherein the evaluation arrangement is configured to detect a change in position as present when an upper threshold voltage value is exceeded or when a lower threshold voltage value is undershot.