Presence detection sensors and apparatuses

Abstract

The invention relates to a presence detection sensor (1) for unlocking an opening member of a motor vehicle, said sensor (1) comprising: a microcontroller (10) implementing an analog-to-digital converter (ADC) and comprising a first input (E1), a second input (E2) constituting a voltage reference of said analog-to-digital converter (ADC), a third input (E3) for feeding a voltage to the microcontroller (10) and a plurality of input outputs (S1, S2, S3), and a capacitive voltage divider (20) connected to at least one input output (S1, S2, S3) of the plurality of input outputs (S1, S2, S3). The sensor (1) comprises a resistive module (Rin) connected between the first input (E1) and the second input (E2) of the microcontroller (10) and a capacitive module (Cin) connected between the second input (E2) of the microcontroller (10) and ground (M).

Description

TECHNICAL FIELD

[0001] The present invention relates to the field of motor vehicles, and more particularly to unlocking access to a motor vehicle. The subject of the invention is a method and a sensor for detecting the presence of a user in the vicinity of a vehicle, and a vehicle comprising such a sensor.

[0002] The invention aims in particular to improve the sensitivity of existing CVD and DCVD type sensors. BACKGROUND

[0003] In motor vehicles, it is known to use access unlocking systems comprising a sensor for detecting the presence of a user. Such a sensor is known in the form of a capacitive proximity sensor which makes it possible to detect the presence of a user's hand on a vehicle door handle in order to unlock the door, or to detect the passage of a user's foot under a vehicle trunk in order to unlock the trunk. In particular, when a user moves a hand from a first position, for example far from the vehicle door handle, to a second position on said handle, the sensor detects this presence, resulting in the unlocking of the door.

[0004] In a known solution called CVD (for Capacitive Voltage Divider, or capacitive voltage divider), the detection sensor comprises a printed circuit comprising a so-called "detection" capacitor forming a first electrode and a so-called "storage" capacitor connected by a switch to a voltage generator and to a microcontroller implementing an analog-digital converter, thus making it possible to quantify the charge stored in the storage capacitor.

[0005] In the absence of a user in the vicinity of the sensor, the storage capacitor is charged with a nominal charge which defines a nominal storage voltage. When a user's hand is located in the vicinity of the electrode, the user acts as a second electrode connected to ground, which causes the capacitance value of the detection capacitor to increase beyond its nominal capacitance value measured in the absence of a user.

[0006] In order to detect the presence of a user, the sensor first comprises an acquisition phase which makes it possible to charge the storage capacitor, in which said capacitor is previously discharged. This acquisition phase first comprises the charging of the detection capacitor by the voltage generator, and secondly the conduction of the current from the charge stored in the detection capacitor to the storage capacitor. The voltage across the storage capacitor is then measured in a second phase called the measurement phase.

[0007] When the storage capacitor is charged in the absence of any user in the vicinity of the sensor, its charge at the end of the acquisition phase corresponds to its nominal charge value and the storage voltage across it thus corresponds to the nominal storage voltage. To the contrary, when a user is in the vicinity of the sensor during the acquisition phase, the presence of the user causes the capacitance value of the detection capacitor to increase, which results in a voltage defined across the storage capacitor at the end of the acquisition phase that is higher than the voltage defined by the nominal charge measured in the absence of any user in the vicinity of the sensor. In this case, the voltage across the storage capacitor is equal to the detection voltage, which is higher than the nominal storage voltage. Once the user is detected, the microcontroller sends a detection signal to the electronic computer of the vehicle, so that the electronic computer authenticates the user and unlocks one or more opening parts in appropriate cases.

[0008] This CVD type solution makes it possible to measure and quickly detect the presence of a user. However, it has been noted that this operation can generate very high electromagnetic interferences, in particular low-frequency noise, which can disturb other electronic devices of the vehicle. Furthermore, the sensitivity of such a sensor can be relatively low, which means a short detection distance.

[0009] Furthermore, to at least partially remedy these drawbacks, it is known to use an alternative solution called DCVD (for Differential Capacitive Voltage Divider, or differential capacitive voltage divider). In this solution, the detection sensor is identical to that of the CVD solution, but comprises a different switching arrangement to make it operate differently. This solution first comprises a first acquisition phase identical to that of the CVD solution, followed by a second acquisition phase comprising charging the storage capacitor from a voltage delivered by a voltage generator, then discharging the storage capacitor into the detection capacitor.

[0010] When the detection capacitor is charged in the absence of any user in the vicinity of the sensor, the charge of the detection capacitor at the end of the second acquisition phase corresponds to its nominal charge value and the storage voltage across it thus corresponds to the nominal storage voltage. To the contrary, when a user is present in the vicinity of the sensor during the second acquisition phase, the capacitance value of the detection capacitor increases, so that the voltage defined across it at the end of the acquisition phase is lower than the voltage defined by the nominal charge measured in the absence of any user in the vicinity of the sensor.

[0011] Once the first and second acquisition phases are completed, the microcontroller analyzes the difference between the voltage measured during the first acquisition phase, which increases in the presence of a user near the sensor, and the voltage measured during the second acquisition phase, which decreases in the presence of a user near the sensor. The concatenation of these two acquisition phases can significantly increase the measurement duration, making the detection of the presence of a user near the sensor particularly time-consuming, which is a major drawback.

[0012] The DCVD capacitance measurement uses the principle of a capacitive voltage divider: the voltage measured across an electrode capacitor is linked to its own capacitance. In order to have a satisfactory sensitivity, this voltage measurement, performed by the analog-to-digital converter of the microcontroller, must have the best possible resolution, i.e. a numerical variation of the digital value measured by the analog-to-digital converter corresponds to the lowest possible variation of voltage.

[0013] The voltage corresponding to a number is given by the following formula:

[0014] [mathematical formula 1]

[0015] where ADC bit corresponds to the number of bits of the analog-to-digital converter, and V ref_ADC corresponds to the reference voltage of the analog-to-digital converter.

[0016] The sensitivity can thus be reduced by reducing V ref_ADC or by increasing ADC bit .

[0017] It is known in the prior art to adjust the reference voltage V ref_ADC of the analog-to-digital converter by using a resistive voltage divider at the input of the microcontroller, so as to adapt the reference voltage V ref_ADC of the analog-to-digital converter as closely as possible to the working zone of the sensor. This reference voltage V ref_ADC should be adjusted so that it is always higher than the voltage to be measured, otherwise the measurement would saturate.

[0018] However, it turns out that for such a circuit, the capacitive DCVD signal is sometimes too weak to have a satisfactory sensitivity. In addition, adjusting the reference voltage V ref_ADC by a resistive voltage divider does not maximize the resolution of the analog-to-digital converter, since in order to avoid saturation in the worst case, it is then necessary to overestimate the reference voltage V ref_ADC .

[0019] There is therefore a need for a simple, reliable and effective solution that makes it possible to at least partially remedy these drawbacks and which is in particular intended to improve the sensitivity of existing detection sensors. SUMMARY

[0020] To this end, the subject of the application is first of all a presence detection sensor for unlocking an opening member of a motor vehicle, said sensor comprising:

[0021] - a microcontroller comprising an analog-digital converter, a first input-output port, a second input-output port constituting a voltage reference of said analog-digital converter, a third input-output port feeding a voltage to the microcontroller, a fourth input-output port called "connection input-output port" and a fifth input-output port,

[0022] - a capacitive divider connected to said connection input-output port and comprising at least one detection capacitor and at least one storage capacitor,

[0023] The sensor is characterized in that it comprises a resistive module connected between the first input-output port and the second input-output port of the microcontroller and a capacitive module connected between the second input-output port of the microcontroller and the ground, and in that the microcontroller is configured to connect the first input-output port and the third input-output port in an internal way for a predetermined duration called "charging duration" of the capacitive module, to dynamically establish the reference voltage of the analog-digital converter. "Input-output" means input, or output, or simultaneously input and output if applicable.

[0024] In this way, the microcontroller can manipulate the charging of the capacitive module via the resistive module to dynamically set the reference voltage of the analog-digital converter, thus optimizing the sensitivity of the sensor. In other words, such a manipulation makes it possible to use an optimal reference voltage, thus making it possible to improve the performance of the sensor in terms of sensitivity. Furthermore, using a microcontroller that can dynamically manipulate the capacitive module that it charges makes it possible to reduce the power consumption of the sensor, which would not be the case if the microcontroller permanently manipulated the reference voltage. Furthermore, using a resistive module and a capacitive module makes it possible to reduce the number of components and resources required compared to existing solutions, in particular in "Vref hopping" type architectures, the principle of which is known to those skilled in the art.

[0025] Preferably, the resistive module is constituted by a single resistor, called "input resistor", to simplify the architecture of the sensor. For example, the value of the input resistor is approximately 500 ohms.

[0026] Still preferably, the capacitive module is constituted by a single capacitor, called "input capacitor", for example with a value of approximately 220 nF, to simplify the architecture of the sensor.

[0027] The capacitive divider can be either of the CVD type or of the DCVD type.

[0028] The application also relates to a motor vehicle comprising at least one sensor as described above.

[0029] Finally, the application relates to a method for detecting the presence of a user in the vicinity of a sensor as described above, said method comprising:

[0030] - an initialization phase, during which the microcontroller first charges the capacitive module to the feed voltage by connecting the first input-output port to the third input-output port for a charging duration, then the microcontroller performs a capacitive measurement after the end of the charging to derive therefrom an optimal reference voltage and the charging time required to obtain this optimal reference voltage,

[0031] - a reference obtaining phase, during which the microcontroller controls the capacitive divider to perform a series of capacitive measurements at the optimal reference voltage determined during the initialization phase in order to obtain a reference value of the measured capacitive signal, for example a digital value corresponding to the average of the successive capacitive measurements performed (for example between 4 and 8 acquisitions),

[0032] - a measurement phase, during which the microcontroller controls the capacitive divider to the determined optimal reference voltage and said capacitive divider periodically measures the voltage value across the storage capacitor to detect the presence or not of a person in the vicinity of the sensor.

[0033] The term "capacitive measurement" means measuring the voltage defined across the storage capacitor.

[0034] According to one aspect of the application, when the microcontroller detects saturation of the analog-digital converter during the measurement phase, then the microcontroller performs again the initialization phase and the reference obtaining phase to modify the optimal reference voltage and the capacitive signal reference, then resumes the measurement phase.

[0035] Preferably, the optimal reference voltage is higher than the voltage measured across the storage capacitor by 10% to 20% to avoid saturation of said voltage signal when the sensor is nominally operated, for example in the case of a handle sensor with a hand placed on the handle of the opening member, the palm on the entire unlocking area, or a finger pressed on the locking area.

[0036] In one embodiment, the method comprises between the reference obtaining phase and the measurement phase a determination phase, during which the microcontroller determines at least one detection threshold for detecting the presence of a person based on the reference capacitive signal, then performs the measurement phase in order to detect the presence or not of a person in the vicinity of the sensor according to the determined at least one detection threshold. BRIEF DESCRIPTION OF DRAWINGS

[0037] Further features and advantages of the application will appear further on reading the following description. This description is purely illustrative and should be read in conjunction with the appended drawings wherein:

[0038] Figure 1A first embodiment of a sensor according to the application is shown;

[0039] Figure 2 A second embodiment of a sensor according to the application is shown;

[0040] Figure 3 An embodiment of a method according to the application is shown. DETAILED DESCRIPTION

[0041] The sensor according to the application is intended to be installed in a motor vehicle and more particularly in a door handle or in the vicinity of the trunk of a motor vehicle in order to detect the presence of a user, for example, so as to enable the opening members of the vehicle to be unlocked.

[0042] Figure 1 An example of the electronic circuit of the sensor 1 according to the application is shown in the figure. The sensor 1 comprises a microcontroller 10 and a capacitive divider 20.

[0043] The microcontroller 10 comprises an analog-to-digital converter ADC, a first input-output port E1, a second input-output port E2, a third input-output port E3, a fourth input-output port S1 and a fifth input-output port S2, the latter two ports representing a connection input-output port S1, S2. The term "the microcontroller 10 comprises an analog-to-digital converter ADC" means that the microcontroller 10 implements a hardware analog-to-digital converter ADC or is configured to implement an analog-to-digital converter ADC in software.

[0044] The microcontroller 10 is configured to internally electrically connect the first input-output port E1 and the third input-output port E3 so that they are at the same potential and to internally electrically disconnect the first input-output port E1 and the third input-output port E3. The second input-output port E2 constitutes the voltage reference of the analog-to-digital converter ADC. The third input-output port E3 is an input for feeding the microcontroller 10 with a supply voltage Vcc, which is known per se.

[0045] In the example described next, the sensor 1 is a CVD (Capacitive Voltage Divider Differential) type sensor, but in another embodiment, it can equally be a DCVD (Capacitive Voltage Divider) type sensor.

[0046] The capacitive voltage divider 20 includes a first detection capacitor Ce and a first storage capacitor Cext. Each terminal of the first storage capacitor Cext is electrically connected to the input / output ports S1 and S2, respectively. A resistor R1 is connected between the fourth input / output port S1 and the terminal of the first detection capacitor Ce, which is connected to the feed voltage Vcc. The first detection capacitor Ce represents the equivalent capacitance of the electrodes of the sensor 1, which changes as a user's body part (e.g., hand) approaches. In order to charge the first detection capacitor Ce and detect its presence in CVD or DCVD mode, the first detection capacitor Ce can be intermittently connected to the feed voltage Vcc in a manner known per se (via a switch, not shown).

[0047] Sensor 1 includes a resistor module Rin connected between a first input / output port E1 and a second input / output port E2 of microcontroller 10, and a capacitor module Cin connected between the second input / output port E2 of microcontroller 10 and ground M. In this preferred example, the resistor module Rin consists of a single resistor, referred to as the "input resistor," and the capacitor module Cin consists of a single capacitor, referred to as the "input capacitor." In another embodiment, the resistor module Rin may include multiple resistors and the capacitor module Cin may include multiple capacitors.

[0048] The microcontroller 10 is configured to internally connect the first input / output port E1 and the third input / output port E3 for a predetermined duration, referred to as the "charging duration," to charge the capacitor module Cin, thereby dynamically establishing the reference voltage for the analog-to-digital converter (ADC).

[0049] exist Figure 2 In the second embodiment shown, the microcontroller 10 further includes a sixth input / output port S3 (referred to as the "connection input / output port", like the fourth input / output port S1 and the fifth input / output port S2), and the capacitor divider 20 includes, in addition to the components already present in the first embodiment, a first filter capacitor C1, a second storage capacitor Cext2, a second filter capacitor C2, a second resistor R2, and a second detection capacitor Ce2.

[0050] A first filter capacitor C1 is connected between the first input / output port S1 of the microcontroller 10 and ground M, enabling the filtering of the current signal flowing between the first input / output port S1 and the first detection capacitor Ce via the first resistor R1. The first resistor R1 is connected between the first input / output port S1 of the microcontroller 10 and the unlock terminal (labeled "unlock"), which represents the electrode for unlocking the vehicle's opening mechanism and is indicated by the first detection capacitor Ce. In other words, a user's unlocking request is detected when the voltage measured at the "unlock" terminal exceeds a predetermined threshold.

[0051] The second storage capacitor Cext2 is connected between the fifth input-output port S2 and the sixth input-output port S3 of the microcontroller 10. The second filter capacitor C2 is connected between the sixth input-output port S3 of the microcontroller 10 and the ground M and makes it possible to filter the current signal flowing between the sixth input-output port S3 and the second detection capacitor Ce2 via the second resistor R2. The second resistor R2 is connected between the third input-output port S3 of the microcontroller and a lock terminal (labeled "Lock"), which is intended to embody an electrode for locking the opening means of the vehicle, represented by the second detection capacitor Ce2, different from the unlocking electrode. In other words, when the voltage measured on the lock terminal "Lock" exceeds a predetermined threshold, a lock request detection by the user is detected.

[0052] As a variant, it is pointed out that the capacitive divider 20 can comprise a different number and different types of components and / or be arranged in a different way while implementing the same functions.

[0053] An embodiment of the method according to the application will now be described, with particular reference to Figure 3

[0054] First, the microcontroller 10 electrically connects the first input-output port E1 with the third input-output port E3, so that the voltage defined between the first input-output port E1 and the ground M is equal to the supply voltage Vcc of the microcontroller 10, which is itself defined between the third input-output port E3 and the ground M.

[0055] This voltage defined between the first input-output port E1 and the ground M makes it possible to charge the input capacitor of the capacitive module Cin via the input resistor of the resistive module Rin and at the second input-output port E2, which constitutes the reference voltage of the analog-to-digital converter ADC. The time of electrical connection between the first input-output port E1 and the third input-output port E3 then defines the charging time of the input capacitor of the capacitive module Cin. In this way, the microcontroller 10 can adjust the reference voltage of the analog-to-digital converter ADC by adjusting the charging time t according to the following formula:

[0056]

Mathematical formula 2

[0057] ,

[0058] where V ref_ADC is the reference voltage of the analog-to-digital converter ADC, Vcc is the supply voltage of the microcontroller 10, "Rin" is the value of the input resistor of the resistive module Rin and "Cin" is the value of the input capacitor of the capacitive module Cin.

[0059] ​At the end of the charging duration, the microcontroller 10 electrically disconnects the first input / output port E1 and the third input / output port E3, thereby setting and stabilizing the voltage across the input capacitor of the capacitor module Cin. The microcontroller 10 then measures the voltage defined between the fourth input / output port S1 and ground M, i.e., the voltage defined across the first storage capacitor Cext, the change of which reflects the change of the first detection capacitor Ce.

[0060] Once fully charged, the microcontroller 10 uses the capacitor divider 20 to perform a capacitance measurement on the voltage across the storage capacitor Cext in order to derive an optimal reference voltage that is slightly higher than the measured voltage, for example, 10% higher, and to derive the charging time required to obtain this optimal reference voltage.

[0061] Subsequently, in the reference acquisition phase PH2, the microcontroller 10 controls the capacitor divider 20 to perform a series of capacitance measurements at the optimal reference voltage determined during the initialization phase PH1 to obtain a reference value for the capacitance signal, which will then enable the determination of the detection threshold to be used as the detection criterion in a manner known per se.

[0062] Next, in the measurement phase PH3, the microcontroller 10 controls the capacitive voltage divider 20 to periodically measure the voltage value (the voltage across the first storage capacitor Cext) defined between the fourth input / output port S1 and ground M and compares it with the optimal reference voltage determined during the reference acquisition phase PH2 in order to detect whether a person (e.g., a hand) is present near the sensor.

[0063] If the microcontroller 10 does not detect ADC saturation, that is, the output value of the ADC is lower than (2... ADC_bits – margin), where ADC_bits is the number of bits of the analog-to-digital converter ADC, then the microcontroller 10 continues to use the value of the optimal reference voltage defined during the initialization phase PH1.

[0064] If the microcontroller 10 detects that the analog-to-digital converter (ADC) is saturated, that is, the output value of the ADC is higher than (2... ADC_bits – margin), then the microcontroller 10 executes the initialization phase PH1 and the reference acquisition phase PH2 again to modify the optimal reference voltage and capacitor signal reference, and then periodically executes phase PH3 again.

[0065] The example above is provided for detecting the presence of the unlocked component. See also... Figure 1 and Figure 2 (especially) Figure 2 The terminal is "unlocked"), but these examples also apply to detecting the presence of the locked opening component, while referring toFigure 1 and Figure 2 in particular Figure 2 the terminals "lock").

[0066] In this way, the method according to the present application enables the microcontroller 10 to adapt the reference voltage V ref_ADC of the analog-to-digital converter ADC in order to optimize the use of the sensor 1 and thus to improve its nominal performance.

[0067] In the "reference voltage jump" type architecture, the present application enables, in particular, to reduce the types of components in order to define the level of the "reference voltage jump" in a manner known to the person skilled in the art, by enabling to manipulate the reference voltage on the basis of the charge of the capacitive module Cin.

[0068] Reference Signs

[0069] 1 : sensor

[0070] 10: microcontroller

[0071] 20: capacitive divider

[0072] ADC: analog-to-digital converter

[0073] E1 : first input-output port

[0074] E2: second input-output port

[0075] E3: third input-output port

[0076] S1 : fourth input-output port (called "connection input-output port")

[0077] S2: fifth input-output port (called "connection input-output port")

[0078] Vcc: supply voltage

[0079] Ce: first detection capacitor

[0080] Cext: first storage capacitor

[0081] R1 : resistor

[0082] M: ground

[0083] Rin: resistance module

[0084] Cin: capacitance module

[0085] S3: sixth input-output port (called "connection input-output port")

[0086] C1 : first filtering capacitor

[0087] Cext2: second storage capacitor

[0088] C2: second filter capacitor

[0089] R2: second resistor

[0090] Ce2: second detection capacitor

[0091] Unlock: unlock terminal

[0092] Lock: lock terminal

Claims

1. Presence detection sensor (1) for unlocking opening members of a motor vehicle, said sensor (1) comprising: - a microcontroller (10) comprising an analog-to-digital converter (ADC), a first input-output port (El), a second input-output port (E2) constituting a voltage reference for the analog-to-digital converter (ADC), a third input-output port (E3) feeding a voltage (Vcc) for the microcontroller (10), a fourth input-output port (SI) called "connection input-output port" and a fifth input-output port (S2), - a capacitive voltage divider (20) connected to said connection input-output ports (SI, S2) and comprising at least one detection capacitor (Ce, Ce2) and at least one storage capacitor (Cext, Cext2), the sensor (1) being characterized in that it comprises a resistance module (Rin) connected between the first input-output port (El) and the second input-output port (E2) of the microcontroller (10) and a capacitance module (Cin) connected between the second input-output port (E2) of the microcontroller (10) and ground (M), and in that the microcontroller (10) is configured to connect the first input-output port (El) and the third input-output port (E3) in an internal manner for a predetermined duration called "charging duration" of the capacitance module (Cin) to dynamically establish the reference voltage of the analog-to-digital converter (ADC).

2. The sensor (1) according to claim 1, wherein The resistance module (Rin) is constituted by a single resistor.

3. The sensor (1) according to claim 2, wherein The value of the resistor is approximately 500 ohms.

4. The sensor (1) according to any one of claims 1 to 3, wherein The capacitance module (Cin) is constituted by a single capacitor.

5. The sensor (1) according to claim 4, wherein The value of the capacitor is approximately 220 nF.

6. The sensor (1) according to any one of claims 1 to 3, wherein The capacitive voltage divider (20) is of CVD or DCVD type.

7. Motor vehicle comprising at least one sensor (1) according to any one of the preceding claims.

8. Method for detecting the presence of a user in the vicinity of a sensor (1) according to any one of claims 1 to 6, said method comprising: - an initialization phase (PH1) during which the microcontroller (10) first charges the capacitance module (Cin) to the feeding voltage (Vcc) by connecting the first input-output port (El) to the third input-output port (E3) for the charging duration, then the microcontroller (10) performs a capacitance measurement after the end of the charging to deduce therefrom the optimal reference voltage and the charging time necessary to obtain this optimal reference voltage, - a reference obtaining phase (PH2) during which the microcontroller (10) controls the capacitive voltage divider (20) to perform a series of capacitance measurements at the optimal reference voltage determined during the initialization phase (PH1) in order to obtain the reference value of the measured capacitance signal, - a measurement phase (PH3) during which the microcontroller (10) controls the capacitive voltage divider (20) to the determined optimal reference voltage and said capacitive voltage divider (20) periodically measures the voltage value across the storage capacitor (Cext, Cext2) to detect the presence of a person in the vicinity of the sensor (1).

9. The method of claim 8, wherein, When the microcontroller (10) detects an analog-to-digital converter (ADC) saturation during the measurement phase (PH3), the microcontroller (10) again performs the initialization phase (PH1) and the reference acquisition phase (PH2) to modify the optimal reference voltage and the capacitance signal reference, then resumes the measurement phase (PH3).

10. The method of any one of claims 8 or 9, wherein, The optimal reference voltage is 10% to 20% higher than the voltage measured across the storage capacitor (Cext, Cext2).

Images