WO2015063541A1

WO2015063541A1 - Apparatus and algorithm for the detection of capacitive button events

Info

Publication number: WO2015063541A1
Application number: PCT/IB2013/059740
Authority: WO
Inventors: Christian Schenkewitz
Original assignee: Continental Automotive Gmbh
Priority date: 2013-10-29
Filing date: 2013-10-29
Publication date: 2015-05-07

Abstract

The application provides a capacitive button arrangement for a faceplate of an automobile. The capacitive button arrangement includes a guided plate unit and an evaluation unit. The guided plate unit comprises at least two capacitive buttons. Each capacitive button includes a capacitive sensor for transmitting a primary detection signal. The guided plate unit comprises a guided plate for transmitting a secondary detection signal. The evaluation unit is electrically connected to the capacitive sensors of the capacitive buttons for receiving the primary detection signals from the capacitive sensors and is electrically connected to the guided plate for receiving the secondary detection signal.

Description

APPARATUS AND ALGORITHM FOR THE DETECTION OF CAPACITIVE BUTTON EVENTS

This application relates to capacitive buttons for a face- plate of an automobile.

EP 1253717 A2 discloses that a key pad can have one or more keys behind a protective cover, which carries on the inner surface a dielectric material. The individual keys are formed of a central key section encircled by a reference section, both of conductive material. With the aid of changeover switches, amplifier, evaluator, and dc supply tests can be carried out by comparison of reference and key sections, to determine whether the keys are functioning correctly.

US 20090107737 Al discloses methods for determining actuation of a capacitive button having at least three sensor electrode elements associated with at least three distinct sensor elec^¬ trodes. In one embodiment, indicia from the at least three distinct sensor electrodes associated with the at least three sensor electrode elements comprising the capacitive button are received. At least three electrode values are generated from the indicia. The at least three electrode values are then utilized to determine actuation of the capacitive but- ton.

It is an object of the application to provide an improved ca^¬ pacitive buttons. The application provides an improved capacitive button ar^¬ rangement for a faceplate of a component of an automobile. The automobile is used for transporting people or goods. The faceplate is also called a console. It is often placed inside the automobile as part of a dashboard. Examples of the auto^¬ mobile component include an entertainment device, such as a radio and an air conditioning unit.

The capacitive button arrangement includes a guided plate unit and an evaluation unit. The guided plate unit includes at least two capacitive but^¬ tons and a guided plate for receiving a user touch.

The capacitive button acts a node for receiving the user touch. Each capacitive button includes a capacitive sensor for detecting the user touch and for transmitting a primary detection signal that corresponds to the user touch.

When the user touches one capacitive sensor, the touch chang^¬ es the capacitance of the touched capacitive sensor. The touched capacitive sensor then transmits a primary detection signal with a signal strength that corresponds to the user touch .

The neighbouring capacitive sensors, which are not touched, generate pseudo signals. These neighbouring capacitive sen^¬ sors experience a weaker change of capacitances. These touch capacitive sensors then send primary detection signals with weak signal strengths. The guided plate acts as a carrier for the capacitive but^¬ tons. The guided plate is provided for transmitting a second^¬ ary detection signal upon receiving the user touch. The touch moves the guided plate, wherein the movement then activates and generates the secondary detection signal.

In one implementation, the guided plate includes a button or switch. The button is mounted on the guided plate although it can also be mounted on a base plate. Movement of the guided plate actuates the button such that the button transmits a secondary detection signal. Referring to the evaluation unit, it is electrically connect^¬ ed to the capacitive sensors of the capacitive buttons for receiving the primary detection signals from the capacitive sensors. It is also electrically connected to the guided plate for receiving the secondary detection signal.

The primary detection signal can reach the evaluation unit before or after the secondary detection reaches the evalua^¬ tion unit. The order in which these signals reach the evalua^¬ tion unit is not important here.

The evaluation unit is configured to determine which of the primary detection signals from the capacitive sensors com^¬ prises the strongest signal strength. The primary detection signal with the strongest signal strength corresponds to the touched capacitive sensor, as explained above.

The evaluation unit then generates a button pressed signal that corresponds to the primary detection signal with the strongest signal strength and that corresponds to the second- ary detection signal to the automobile component.

This capacitive button arrangement has an advantage of pre^¬ venting false pressed button detection signal since the de- tection of the pressed button is dependent on both the prima^¬ ry detection signal and the secondary detection signal.

Different implementations of the evaluation unit are possi- ble. In one implementation, the evaluation unit determines which of the primary detection signals from the capacitive sensors comprises the strongest signal strength, only upon receiving the secondary detection signal. Put differently, the evaluation unit only analyses the primary detection sig- nal only after receiving the secondary detection signal.

The evaluation unit can generate the button pressed signal only if the strength of the strongest primary detection signal exceeds a pre-determined threshold value. This has an ad- vantage of preventing electrical noise from generating the button pressed signal.

Different arrangements of the capacitive buttons are possi^¬ ble .

The capacitive buttons can be provided next to the guided plate for easy implementation of the button arrangement.

The capacitive buttons can also be mounted on the guided plate or be attached to the guided plate.

The capacitive buttons can be provided by areas of a touch screen . The capacitive buttons can also be provided by a keypad.

The guided plate unit often includes a tactile unit for providing a user sensation for overcoming a detectable force threshold for switching. In other words, the tactile unit provides a haptic sensation.

The tactile unit can include a push button for transmitting the secondary detection signal.

The tactile unit can also include a spring unit for providing a user sensation. The guided plate unit can include a base plate for supporting the guided plate. The base plate is also called a supporting plate .

The tactile unit can be placed between the base plate and the guided plate for easy design of the capacitive button ar^¬ rangement .

The guided plate unit often comprises a guiding means for keeping the guided plate level when the guided plate is pressed. Without the guided means, the guided plate unit can tilt when it receives a user touch at one end of the guided plate unit.

In one implementation, the guiding means is provided at end parts of the guided plate.

The guided plate unit can include an optical sensor for providing the secondary detection signal. The optical sensor is used for detecting a movement of the guided plate when a user presses the guided plate.

A light barrier unit can provide a transmitter for emitting a light ray and an optical sensor for receiving the light ray. The movement of the guided plate can block the light ray, wherein the optical sensor then sends a detection signal to indicate the movement of the guided pate. The application also provides a faceplate for an automobile. The faceplate includes at least one of the above capacitive button arrangement for detecting a user touch and for sending a corresponding button pressed signal to a component of the automobile .

The application also discloses an automobile. The automobile comprises at least one component and the above faceplate. The faceplate comprises at least one capacitive button arrange^¬ ment being connected to the at least one component for de- tecting a user touch and for sending a corresponding button pressed signal to the component.

The application also provides a method of operating a capaci^¬ tive button arrangement for a faceplate of an automobile. The capacitive button arrangement includes at least two capaci^¬ tive buttons with capacitive sensors and a guided plate.

The method includes a step of the capacitive sensor providing a primary detection signal and a step of the guided plate providing a secondary detection signal.

After this, a determination of which of the primary button detection signals from the capacitive sensors comprises the strongest signal strength is performed.

A button pressed signal corresponding to the primary detection signal with the strongest signal strength and corre^¬ sponding to the secondary detection signal is then generated. Fig. 1 illustrates an arrangement of capacitive buttons on a guided plate,

Fig. 2 illustrates a flow diagram of a method of operating the capacitive buttons of Fig. 1,

Fig. 3 illustrates signal strengths of the capacitive but^¬ tons of Fig. 1 under normal conditions,

Fig. 4 illustrates signal strengths of the capacitive but^¬ tons of Fig. 1 under adverse conditions,

Fig. 5 illustrates another flow diagram of a further method of operating the capacitive buttons of Fig. 1,

Fig. 6 illustrates a passenger compartment of a car with control panels having the capacitive buttons of Fig. 1,

Fig. 7 illustrates a graph of a force versus distance of a tact switch of push button of the capacitive but^¬ tons of Fig. 1, and

Fig. 8 illustrates a further arrangement of capacitive

buttons on a guided plate.

In the following description, details are provided to de^¬ scribe embodiments of the application. It shall be apparent to one skilled in the art, however, that the embodiments may be practiced without such details.

Some parts of the embodiments have similar parts. The simila parts may have the same names or similar part numbers. The description of one part applies by reference to another simi lar part, where appropriate, thereby reducing repetition of text without limiting the disclosure.

Fig. 1 shows a button arrangement 10 for a console of a car. The button arrangement 10 includes capacitive buttons 11, 12, 13, and 14 on a guided plate 15 with a mechanical tact switch unit 16, and an electronic evaluation unit 21. The electronic evaluation unit 21 is connected electrically to the capacitive buttons 11, 12, 13, and 14 and to the switch unit 16. The guided plate 15 is placed between the ca^¬ pacitive buttons 11, 12, 13, and 14 and the tact switch unit 16.

Referring to the capacitive buttons 11, 12, 13, and 14, they are mounted on the guided plate 15. The capacitive buttons 11, 12, 13, and 14 comprise capacitive sensors or sensing ar^¬ eas 17, 18, 19, and 20, respectively, wherein the capacitive sensors 17, 18, 19, and 20 are connected to the evaluation unit 21.

An upper major surface of the guided plate 15 is placed below the capacitive buttons 11, 12, 13, and 14, wherein the capac- itive buttons 11, 12, 13, and 14 are mounted on the major surface .

The tact switch 16 is mounted on a supporting plate 24. The tact switch 16 is placed between the guided plate 15 and the supporting plate 24. The tact switch unit 16 includes a spring 22 and a push button 23, wherein the push button 23 is placed inside the spring 22. The push button 23 is mounted to the supporting plate 24 and is electrically connected to the evaluation unit 21.

In a general sense, the spring 22 and the push button 23 can be replaced by a tact switch, which is spring loaded. A guiding mechanism 26 connects outer parts of the guided plate 15 to outer parts of the supporting plate 24.

In use, the capacitive sensors 17, 18, 19, and 20 of the ca- pacitive buttons 11, 12, 13, and 14 serve as capacitance- sensing nodes. These capacitance-sensing nodes act to receive a touch from a user. The touch alters capacitance of the touched capacitance-sensing nodes. The touched capacitance- sensing nodes then generate electrical primary detection sig- nals, which correspond to the touch, to the evaluation unit 21.

When one capacitive button 11, 12, 13, and 14 is touched, its capacitance is changed. The touched capacitive button 11, 12, 13, and 14 then sends a touch primary detection signal, corresponding to its capacitance, to the evaluation unit 21.

The other capacitive buttons 11, 12, 13, and 14, which are not touched, generate pseudo signals. These other capacitive buttons 11, 12, 13, and 14 also experience a weaker change of capacitances. These other capacitive buttons 11, 12, 13, and 14 later sends weaker primary detection signals, corresponding to their capacitances, to the evaluation unit 21. The switch unit 16 acts to provide a haptic sensation to the user and to provide an electrical secondary detection signal to the evaluation unit 21. When the user touches one of the capacitive buttons 11, 12, 13, and 14, the touching also presses the capacitive button 11, 12, 13, and 14 and presses the guided plate 15 towards the supporting plate 24. The guided plate 15 then moves towards the supporting plate 24 against the force of a spring 22, thereby providing a haptic sensation to the user. This moving of the guided plate 15 to- wards the supporting plate 24 also actuates the push button 23.

The push button 23 has an "ON" state and an "OFF" state. The "ON" state is illustrated by "S = 1" and the OFF state is il^¬ lustrated by "S = 0" in Fig. 7.

When a force F is applied on the guided plate 15, the guided plate 15 travels by a distance d, as illustrated in Fig. 1 and 7. When the distance d reaches a threshold dl, the push button 23 switches from the OFF state to the ON state and the distance d snaps back to zero, thereby providing a user sen^¬ sation. The actuated push button 23 then sends a secondary detection signal to the evaluation unit 21.

The evaluation unit 21 comprises an electronic circuit and/or an Application Specific Integrated Circuits (ASIC) to act as data processor for evaluating the primary detection signals from the capacitive sensors 17, 18, 19, and 20 and for evalu^¬ ating the secondary detection signal from the switch unit 16.

In a general sense, a light barrier or curtain unit can re- place the switch unit 16. The light barrier unit provides a transmitter for emitting a light ray and a receiver for receiving the light ray, wherein the light barrier unit pro^¬ vides a detection signal when the emission of the light ray from the transmitter to the receiver is blocked by an object, such as the guided plate 15.

The button arrangement 10 has an advantage of low cost in that all capacitive buttons 11, 12, 13, and 14 has only one tact switch unit 16 for providing haptic sensation for to the user. This is unlike other button arrangement where each a capacitive button has an individual tact switch for providing the haptic sensation.

The guiding mechanism 26 keeps the guided plate 15 essential^¬ ly parallel to the supporting plate 24. It also allows the guided plate 15 to move towards the supporting plate 24 when a user pushes the capacitive buttons 11, 12, 13, and 14 and allows the guided plate 15 to move away from the supporting plate 24 when the cease pushing the capacitive buttons 11,

12, 13, and 14.

Fig. 2 shows a flow chart 30 of a method of determining a pressing of the capacitive buttons 11, 12, 13, and 14.

The button press can occur under good conditions or under adverse conditions. The adverse conditions refer to reduced sensitivity of the capacitive buttons 11, 12, 13, and 14, which can occur when a user wears gloves for touching the capacitive buttons 11, 12, 13, and 14.

Upon the user pressing one of the capacitive buttons 11, 12,

13, and 14, the evaluation unit 21 later receives a secondary detection signal from the switch unit 16. The evaluation unit

21 then analyses the secondary detection signal from the switch unit 16, in a process step 31

The evaluation unit 21 then analyses the primary detection signal from the capacitive buttons 11, 12, 13, and 14, in a process step 32. The capacitive buttons 11, 12, 13, and 14 can generate the primary detection signals under good conditions or under adverse conditions. Fig. 3 shows an example of signal strengths 111, 112, 113, and 114 of the primary detection signals of the capacitive buttons 11, 12, 13, and 14 respectively, which are generated under good conditions. The signal strength 113 exceeds a pre-determined threshold, which is shown by a dashed line in Fig. 3. In contrast, the other signal strengths 111, 112, and 114 are less than the pre-determined threshold. Fig. 4 shows an example of signal strengths 211, 212, 213, and 214 of the primary detection signals of the capacitive buttons 11, 12, 13, and 14 respectively, which are generated under adverse conditions. A user wears gloves to press the capacitive button 13. The pressed capacitive button 13 generates a primary detection signal with a weak signal strength 213 that is less than the pre-determined threshold. The other capacitive buttons 11, 12, and 14 also generate primary detection signals with weak signal strengths 211, 212, and 214 respectively, which also are less than the pre-determined threshold and also less than the signal strength 213. The signal strength 213 exceeds the signal strengths 211, 212, and 214 because the user touches the capacitive button 13.

The evaluation unit 21 then determines which primary detection signal has the maximum signal strength or has the strongest signal, in a process step 33. After this, a button detection signal that corresponds to the button 13 with the strongest signal is generated, in a pro^¬ cess step 34.

If two or more equally strong signals are detected, the eval^¬ uation unit 21 does not generate any button detection signal. The evaluation unit 21 may furthermore be configured such that no detection signal is generated when the strongest sig- nal is below a pre-determined low threshold.

The method has an advantage in that, by gating a detection of the pressed button on the presence of both the primary detec^¬ tion signal and the secondary detection signal, a false but- ton detection signal is largely prevented.

The method has a further advantage of robustness in that it is able to detect the pressed button under both good and ad^¬ verse conditions. This is unlike other methods, which works only under good conditions.

Furthermore, the evaluation unit 21 may save electric energy by powering the button capacitive sensors 17, 18, 19, and 20 only when the secondary detection signal is detected. The de- tection signal is used to as a wake up event to activate the evaluation unit 21 from a sleep mode.

Fig. 5 shows another flow chart 50 of a further method of de^¬ termining a pressing of the capacitive buttons 11, 12, 13, and 14, which can occur under good conditions or under adverse conditions. The flow chart 50 includes a process step 35 of the evalua^¬ tion unit 21 analysing primary detection signals from the ca- pacitive buttons 11, 12, 13, and 14. When the analysis determines that the primary detection sig^¬ nals are present, these primary detection signals are com^¬ pared with a pre-determined detection threshold, in a deci^¬ sion step 36. If the pre-determined detection threshold is exceeded by any of the primary detection signals, a button pressed signal that corresponds to the exceeded primary detection signal is then sent, in a process step 37. The above step 35 is later performed .

If, on the other hand, the pre-determined detection threshold is not exceeded by any of the primary detection signals, a presence of a secondary detection signal is afterward evalu^¬ ated, in a decision step 38.

When the presence of the secondary detection signal is de^¬ tected, the primary detection signals are evaluated, in a process step 32, and the strongest signal of the primary de^¬ tection signals is determined, in a process step 33. A button pressed signal, which corresponds to the button with the strongest signal, is then generated, in a process step 34. Later, the above step 35 is then performed.

On the other hand, when the presence of the secondary detec- tion signal is not detected, the above step 35 is later per^¬ formed . The method of determining the pressing of the capacitive but^¬ tons 11, 12, 13 can include other steps. Examples of the oth^¬ er steps include switching manually between a threshold com^¬ parison step and a maximum signal strength determination step, and automatic switching of these steps based on a pre^¬ determined criterion, such as an interior temperature of a car or a sensitivity estimate of the capacitive sensors.

Fig. 6 shows a dashboard 40 of a passenger compartment of a car having the capacitive buttons 11, 12, 13, and 14.fvwa

A middle console 41 of the dashboard 40 is equipped with a first control panel 42 for a car entertainment system and with a second control panel 43 for a heating ventilation and air conditioning (HVAC) system. The first control panel 42 and the second control panel 43 comprise the above capacitive buttons 11, 12, 13, and 14.

The car entertainment system comprises, among others, a radio cum CD player 44. The HVAC system provides ventilation, heating and air conditioning through ventilation openings such as ventilation openings 45 in the middle console and ventilation openings 46 on the side of the driver. While this embodiment shows a passenger car, the capacitive buttons may also be used for interior compartments of other motor vehicles, such as tractors and other farming vehicles, forestry vehicles and construction site vehicles. In cold en^¬ vironments, a driver of these vehicles can use gloves and furthermore, sources of sensor contamination, such as sand and earth, can exist.

Fig. 8 shows a further button arrangement 10' . The button arrangement 10' includes capacitive buttons 11, 12, 13, and 14 on a guided plate 15 with a mechanical tact switch unit 16, and an electronic evaluation unit 21 of the button arrangement 10 of Fig. 1. The tact switch 16 is mount^¬ ed on the guided plate 15 and is placed between the guided plate 15 and a supporting plate 24.

The embodiments can also be described with the following lists of features or elements being organized into an item list. The respective combinations of features, which are dis^¬ closed in the item list, are regarded as independent subject matter, respectively, that can also be combined with other features of the application.

1. A capacitive button arrangement for a faceplate of an automobile, the capacitive button arrangement comprising a guided plate unit comprising

at least two capacitive buttons, each capaci^¬ tive button comprising a capacitive sensor for transmitting a primary detection signal, and a guided plate for transmitting a secondary detection signal,

an evaluation unit being electrically connected to the capacitive sensors of the capacitive buttons for re^¬ ceiving the primary detection signals from the capacitive sensors and being electrically connected to the guided plate for receiving the secondary detection signal,

wherein the evaluation unit determines which of the primary detection signals from the capacitive sensors com^¬ prises the strongest signal strength, and generates a button pressed signal corresponding to the primary de- tection signal with the strongest signal strength and corresponding to the secondary detection signal. The capacitive button arrangement according to item 1, wherein

the evaluation unit, only upon receiving the secondary detection signal, then determines which of the primary detection signals from the capacitive sensors comprises the strongest signal strength. The capacitive button arrangement according to item 1 or 2, wherein

the evaluation unit generates the button pressed signal only if the strength of the strongest primary detection signal exceeds a pre-determined threshold value. The capacitive button arrangement according to one of the above-mentioned items, wherein

the capacitive buttons are provided next to the guided plate . The capacitive button arrangement according to one of above-mentioned items, wherein

the capacitive buttons are provided by areas of a touch screen . The capacitive button arrangement according to one of items 1 to 4, wherein

the capacitive buttons are provided by a keypad.

The capacitive button arrangement according to one of the above-mentioned items, wherein the guided plate unit further comprises a tactile unit for providing a user sensation for overcoming a detectable force threshold for switching.

The capacitive button arrangement according to item 7, wherein

the tactile unit comprises a push button for transmit^¬ ting the secondary detection signal.

The capacitive button arrangement according to item 7 or 8, wherein

the tactile unit comprises a spring unit for providing a user sensation.

The capacitive button arrangement according to one of the above-mentioned items, wherein

the guided plate unit further comprises a base plate for supporting the guided plate.

The capacitive button arrangement according to one the above-mentioned items, wherein

the guided plate unit further comprises a guiding for keeping the guided plate level.

the guided plate unit comprises an optical sensor providing the secondary detection signal.

13. faceplate for an automobile comprising

at least one capacitive button arrangement accord to one of the above-mentioned items for detecting user touch and for sending a corresponding button pressed signal to a component of the automobile.

An automobile comprising

at least one component and

a faceplate according to item 13 that comprises at least one capacitive button arrangement being connected to the at least one component for detecting a user touch and for sending a corresponding button pressed signal to the component .

A method of operating a capacitive button arrangement for a faceplate of an automobile, the capacitive button arrangement comprising at least two capacitive buttons with capacitive sensors and a guided plate,

the method comprising

the capacitive sensor providing a primary detection signal ,

the guided plate providing a secondary detection signal ,

determining which of the primary button detection signals from the capacitive sensors comprises the strongest signal strength, and

generating a button pressed signal corresponding to the primary detection signal with the strongest signal strength and corresponding to the secondary detection signal .

Although the above description contains much specificity, this should not be construed as limiting the scope of the em' bodiments but merely providing illustration of the foreseea^¬ ble embodiments. The above stated advantages of the embodi^¬ ments should not be construed especially as limiting the scope of the embodiments but merely to explain possible achievements if the described embodiments are put into prac^¬ tice. Thus, the scope of the embodiments should be determined by the claims and their equivalents, rather than by the exam- pies given.

REFERENCE LIST

10 arrangement

10' arrangement

11 button

12 button

13 button

14 button

15 guided plate

16 switch unit

17 sensing area

18 sensing area

19 sensing area

20 sensing area

21 evaluation unit

22 spring

23 push button

24 supporting plate

26 guiding mechanism

30 flow chart

31 process step

32 process step

33 process step

34 process step

35 process step

36 decision step

37 process step

38 decision step

40 dashboard

41 middle console

42 first control panel

43 second control panel

45 ventilation opening

46 ventilation opening flow chart signal strength signal strength signal strength signal strength signal strength signal strength signal strength signal strength

Claims

wherein the evaluation unit determines which of the primary detection signals from the capacitive sensors com^¬ prises the strongest signal strength, and generates a button pressed signal corresponding to the primary detection signal with the strongest signal strength and corresponding to the secondary detection signal.

2. The capacitive button arrangement according to claim 1, wherein

the evaluation unit, only upon receiving the secondary detection signal, then determines which of the primary detection signals from the capacitive sensors comprises the strongest signal strength.

3. The capacitive button arrangement according to claim 1, wherein the evaluation unit generates the button pressed signal only if the strength of the strongest primary detection signal exceeds a pre-determined threshold value.

4. The capacitive button arrangement according to claim 1, wherein

the capacitive buttons are provided next to the guided plate .

5. The capacitive button arrangement according to claim 1, wherein

the capacitive buttons are provided by areas of a touch screen .

6. The capacitive button arrangement according to claim 1, wherein

the capacitive buttons are provided by a keypad.

7. The capacitive button arrangement according to claim 1, wherein

the guided plate unit further comprises a tactile unit for providing a user sensation for overcoming a detectable force threshold for switching.

8. The capacitive button arrangement according to claim 7, wherein

9. The capacitive button arrangement according to claim 7, wherein

the tactile unit comprises a spring unit for providing a user sensation. The capacitive button arrangement according to claim 1, wherein

The capacitive button arrangement according to claim 1, wherein

the guided plate unit further comprises a guiding means for keeping the guided plate level.

The capacitive button arrangement according to claim 1, wherein

the guided plate unit comprises an optical sensor for providing the secondary detection signal.

A faceplate for an automobile comprising

at least one capacitive button arrangement accord^¬ ing to claim 1 for detecting a user touch and for sending a corresponding button pressed signal to a component of the automobile.

An automobile comprising

at least one component and

a faceplate according to claim 13 that comprises at least one capacitive button arrangement being connected to the at least one component for detecting a user touch and for sending a corresponding button pressed signal to the component .

the method comprising

the capacitive sensor providing a primary detection signal,

the guided plate providing a secondary detection signal ,