Group-based common-mode rejection of proximity switch arrangements

Abstract

Method for activating a proximity circuit arrangement (20), comprising a common-mode drift suppression routine (430) for dealing with the presence of electrical drift, the method comprising: Generating activation fields (32) with a plurality of proximity sensors (24) associated with a plurality of proximity switches (22); wherein the common-mode drift suppression routine (430) monitors the amplitude of a signal (50A, 50B, 50C) generated in response to each of the activation fields (32), to detect a common-mode signal, which is the signal (50A, 50B, 50C) with the lowest amplitude, associated with the proximity sensors (24) to compensate for drift that may be caused by electromagnetic interference or other internal drift, and to subtract the common-mode signal from each of the other signals (50A, 50B, 50C) before determining activation of one of the plurality of proximity switches (22) based on the subtracted signals; wherein the proximity switch arrangement (20) provides a plurality of groups (22A, 22B, 22C) of proximity sensors (22), wherein each of the groups (22A, 22B, 22C) subtracts only the common-mode signal associated with that group (22A, 22B, 22C).

Description

CROSS-REFERENCE TO RELATED REGISTRATIONS

[0001] This application is a partial continuation of US patent application no. 13 / 721,886, filed on December 20, 2012, entitled “PROXIMITY SWITCH ASSEMBLY AND ACTIVATION METHOD USING RATE MONITORING”, which is a partial continuation of US patent application no. 13 / 444,374, filed on April 11, 2012, entitled “PROXIMITY SWITCH ASSEMBLY AND ACTIVATION METHOD”. AREA OF INVENTION

[0002] The present invention relates generally to switches, and in particular to proximity switches with an improved switch activation determination. BACKGROUND OF THE INVENTION

[0003] Motor vehicles are typically equipped with various user-operated switches, such as those for operating features including power windows, headlights, windshield wipers, sunroofs or sunroofs, interior lights, radio and infotainment systems, and various other devices. Generally, these types of switches require user action to activate or deactivate a feature or perform some type of control function. Proximity switches, such as capacitive switches, employ one or more proximity sensors to create a detection activation field and to detect changes in the activation field that indicate user action on the switch, typically caused by a user's finger in close proximity to or in contact with the switch.Capacitive switches are typically configured to detect user actuation of the switch based on a comparison of the scanning activation field with a threshold.

[0004] Switch arrangements often employ multiple capacitive switches in close proximity and generally require a user to select a single desired capacitive switch to perform the intended operation. In some applications, such as use in a motor vehicle, the driver's ability to see the switches is limited due to driver distraction. In such applications, it is desirable to allow the user to scan the switch arrangement for a specific button while preventing premature switch activation. It is therefore desirable to distinguish whether the user intends to activate a switch, is merely searching for a specific switch button while focused on a higher-priority task such as driving, or has no intention of activating a switch.

[0005] Capacitive switches can be manufactured using thin-film technology, where a conductive ink mixed with a solvent is printed and cured to create an electrical circuit layout. Capacitive switches can be affected by condensation. For example, changes in condensation due to fluctuating humidity can alter the capacitive signal. These changes in condensation may be sufficient to trigger a false activation.

[0006] Electrical drift of sensor signals can be caused by electromagnetic interference and internal drift resulting from interactions between internal components, typically occurring very rapidly. The magnitude of such electrical drift can depend on the circuit design and the strength and frequency of the interfering radiation. The relatively rapid change in the signal due to electromagnetic interference and internal drift, which disrupt the capacitive electric field, can impair the ability of capacitive sensors and switches to function correctly.

[0007] Methods for activating a proximity circuit arrangement, proximity switch arrangements and methods for suppressing noise for a plurality of proximity sensors can be found in US 2014 / 0 210 257 A1 and DE 10 2014 212 355 A1.

[0008] Accordingly, it is desirable to provide a proximity switch arrangement that improves the usability of proximity switches by a person, such as a vehicle driver. It is further desirable to provide a proximity switch arrangement that reduces or prevents false activations due to environmental changes, such as condensation events, electromagnetic interference, and internal drift. BRIEF SUMMARY OF THE INVENTION

[0009] Based on this prior art, a method for activating a proximity circuit arrangement according to claim 1 is proposed according to the invention. Advantageous embodiments of the invention will become apparent from the dependent claims and the following description.

[0010] According to an aspect not covered by the invention, a method for activating a proximity switch arrangement is provided. The method comprises the steps of generating activation fields with a plurality of proximity sensors associated with a plurality of proximity switches, and monitoring the amplitude of a signal generated in response to each of the activation fields. The method further comprises the steps of subtracting the smallest signal from each of the other signals and determining the activation of one of the plurality of proximity switches based on the subtracted signals.The majority of proximity sensors are associated with a first group of proximity switches, wherein the proximity switch arrangement includes a second group of proximity switches, the smallest signal from each of the other signals of the first group of proximity switches being subtracted from other signals of the first group of proximity switches.

[0011] According to another aspect not covered by the invention, a proximity switch arrangement is provided. The proximity switch arrangement comprises a plurality of proximity switches, each including a proximity sensor for providing a detection activation field. The proximity switch arrangement also includes a control circuit arrangement that processes the activation field of each proximity switch to detect activation. The control circuit arrangement monitors the amplitude of a signal generated in response to each of the activation fields, subtracts the smallest signal from each of the other signals, and determines the activation of one of the plurality of proximity switches based on the subtracted signals.The majority of proximity switches comprise a first group of proximity switches and a second group of proximity switches, with the smallest signal being subtracted from each of the other signals of the first group of proximity switches.

[0012] According to a further aspect not covered by the invention, a method for suppressing noise for a plurality of proximity sensors is provided. The method comprises the steps of generating activation fields with the plurality of proximity sensors, monitoring the amplitude of a signal generated in response to each of the activation fields, subtracting the smallest signal from each of the other signals, and determining the activation of one of the plurality of proximity sensors based on the subtracted signals.The majority of proximity sensors are associated with a first group and a second group, wherein the smallest signal from each of the other signals of the first group of proximity sensors is subtracted from other signals of the first group of proximity sensors, and wherein the smallest signal from each of the other signals of the second group of proximity sensors is subtracted from other signals of the second group of proximity sensors.

[0013] According to one aspect of the present invention, a proximity sensor arrangement is provided. The proximity sensor arrangement comprises a plurality of proximity sensors, each providing a detection activation field, and a control circuit arrangement for processing the activation field of each proximity sensor to detect activation. The control circuit arrangement monitors the amplitude of a signal generated in response to each of the activation fields, subtracts the smallest signal from each of the other signals, and determines the activation of one of the plurality of proximity sensors based on the subtracted signals. A common-mode signal is the signal with the lowest amplitude associated with the proximity sensors to compensate for drift that may be caused by electromagnetic interference or other internal drift.The proximity switch arrangement provides a plurality of groups of proximity sensors, with each group subtracting only the common-mode signal associated with that group.

[0014] These and other aspects, tasks and features of the present invention are comprehensible and apparent to those skilled in the art upon examination of the present specification, the claims and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The drawings are Fig. 1 a perspective view of a passenger compartment of a motor vehicle with a roof console with a proximity switch arrangement according to an embodiment; Fig. 2 An enlarged view of the roof console and proximity switch assembly, which is shown in Fig. 1 are shown; Fig. 3 an enlarged cross-sectional view along line III-III of Fig. 2, which represents a series of proximity switches in relation to a user's finger; Fig. 4 A schematic representation of a capacitive sensor used in each of the capacitive switches described in Fig. 3 are shown; Fig. 5 a block diagram illustrating the proximity switch arrangement according to one embodiment; Fig. 6 a graph illustrating the signal count for a channel associated with a capacitive sensor and representing an activation motion profile; Fig. 7 a graph illustrating the signal count for two channels associated with the capacitive sensors and showing a search / probing glide motion profile; Fig. 8 a graph illustrating the signal count for a signal channel associated with the capacitive sensors and showing a profile of slow activation movement; Fig. 9 a graph illustrating the signal count for two channels associated with the capacitive sensors and showing a profile of fast search / probing glide motion; Fig. 10 a graph illustrating the signal count for three channels associated with the capacitive sensors in a search / probing mode and representing activation at constant pressure on the tip according to one embodiment; Fig. 11 a graph illustrating the signal count for three channels associated with the capacitive sensors in a search / probing mode and representing activation at constant pressure when the signal drops below the tip according to another embodiment; Fig. 12 a graph illustrating the signal count for three channels associated with the capacitive sensors in a search / probing mode and representing an increased constant pressure on a contact surface to activate a switch according to a further embodiment; Fig. 13 a graph illustrating the signal count for three channels associated with the capacitive sensors in a search mode and showing an increased constant pressure and selection of a contact area based on the increased constant pressure according to a further embodiment; Fig. 14 a state diagram illustrating five states of the capacitive switch arrangement implemented with a state machine according to one embodiment; Fig. 15 a flowchart illustrating a routine for performing a procedure to activate a switch of the switch arrangement according to an embodiment; Fig. 16 a flowchart illustrating the processing of switch activation and switch release; Fig. 17 a flowchart illustrating the logic for switching between the no-switch and switch-active states; Fig. 18 a flowchart illustrating the logic for changing from the active switch state to the no-switch or switch threshold state; Fig. 19 a flowchart illustrating a routine for switching between the switch threshold and switch probe states; Fig. 20 a flowchart illustrating a virtual button procedure that implements the switch probing state; Fig. 21 a graph illustrating the signal count for a signal channel associated with a capacitive sensor experiencing condensation effects; Fig. 22 a graph illustrating the signal count for a signal channel associated with a capacitive sensor using threshold-based rate monitoring according to an embodiment; Fig. 23 a flowchart illustrating a routine for performing rate monitoring to enable the activation of a proximity switch according to one embodiment; Fig. 24A a graph illustrating the signal count for three signal channels that experience electrical drift due to electromagnetic interference, for example, according to an example; Fig. 24B a graph showing the signal count for the three signal channels that are in Fig. 24A are shown, illustrating common-mode drift suppression according to one embodiment; Fig. 25A a graph illustrating the signal count for three signal channels experiencing electrical drift, according to an example; Fig. 25B a graph showing the signal count for the three signal channels that are in Fig. 25A are shown, illustrated using common-mode drift suppression; Fig. 26A a graph illustrating three signal channels experiencing electrical drift, according to an example; Fig. 26B a graph showing the signal counts for the three signals that are in Fig. 26A are shown, illustrated using common-mode drift suppression; Fig. 27 a flowchart illustrating a simplified switch activation routine which uses the common-mode drift suppression routine according to one embodiment; Fig. 28 a flowchart illustrating the common-mode drift suppression routine according to one embodiment; and Fig. 29 a flowchart illustrating a routine for implementing common-mode drift suppression based on groups of sensors according to a further embodiment. DETAILED DESCRIPTION OF PREFERRED EXECUTION FORMS

[0016] As necessary, detailed embodiments of the present invention are disclosed herein; however, it is understood that the disclosed embodiments are purely exemplary of the invention, which can be implemented in various and alternative forms. The figures are not necessarily detailed representations; some schematic representations may be exaggerated or minimized to provide an overview of the functions. The specific structural and functional details disclosed herein should therefore not be interpreted as limiting, but merely as a representative basis for teaching a person skilled in the art how the present invention can be carried out in various ways.

[0017] With reference to Fig. 1 and Fig. Figure 2 illustrates the interior of a motor vehicle 10, generally comprising a passenger compartment and a switch arrangement 20 which, according to one embodiment, employs a plurality of proximity switches 22 with switch activation monitoring and determination. The vehicle 10 generally includes a roof console 12, which is mounted on the headliner on the underside of the roof or ceiling, generally above the front passenger seating area at the upper end of the vehicle's passenger compartment. The switch arrangement 20 comprises a plurality of proximity switches 22, which, according to one embodiment, are arranged close together in the roof console 12.The various proximity switches 22 can each control a number of vehicle features and functions, such as controlling the movement of a sliding or sunroof 16, controlling the movement of a sunroof shade 18, controlling the activation of one or more lighting devices, such as (map) reading interior and overhead lights 30, and various other features and functions. However, it is understood that, depending on the vehicle application, the proximity switches 22 may also be located elsewhere in the vehicle 10, such as on the instrument panel, on other consoles, such as on the center console, integrated into a touchscreen display 14 for a radio or infotainment system, such as a navigation and / or audio display, or elsewhere on board the vehicle 10.

[0018] The proximity switches 22 are presented and described herein as capacitive switches according to one embodiment. Each proximity switch 22 comprises at least one proximity sensor that provides a detection activation field for sensing contact or immediate proximity (e.g., within one millimeter) of a user to the one or more proximity sensors, such as a glancing movement of the user's finger. Accordingly, in the exemplary embodiment, the detection activation field of each proximity switch 22 is a capacitive field, and the user's finger exhibits electrical conductivity and dielectric properties that cause a change or disturbance of the detection activation field, as should be apparent to those skilled in the art.However, experts should also recognize that additional or alternative types of proximity sensors can be used, such as, but not limited to, inductive sensors, optical sensors, temperature sensors, resistance sensors, and the like, or a combination thereof. Examples of proximity sensors are described in the ATMEL Touch Sensor Design Guide. ® Touch Sensors Design Guide, 10620 D-AT42-04 / 09, edition of April 9, 2009, described, which is hereby incorporated herein in its entirety by reference.

[0019] The proximity sensors 24, which are in Fig. 1 and Fig. The proximity switches 22 shown in Figure 2 each provide control of a vehicle component or device, or they provide a defined control function. One or more of the proximity switches 22 can be dedicated to controlling the movement of a sliding or sunroof 16, in order to cause the sunroof 16 to move in an opening or closing direction, to tilt the sunroof, or to stop its movement based on a control algorithm. One or more of the proximity switches 22 can be dedicated to controlling the movement of a sunroof shade 18 between open and closed positions. Each of the sunroof 16 and the shade 18 can be actuated by an electric motor in response to the actuation of the corresponding proximity switch 22.Other proximity switches 22 can be dedicated to controlling other devices, such as switching on or off an interior (map) reading light 30, switching a ceiling light on or off, unlocking a trunk, opening a tailgate, or overriding a door light switch. Additional controls via the proximity switches 22 can include raising and lowering electric door windows. Various other vehicle controls can be operated by the proximity switches 22 described herein.

[0020] In Fig. Figure 2 also shows three groupings of proximity switches 22, designated as a first group 22A, a second group 22B, and a third group 22C. Each of the groupings 22A to 22C has a plurality of proximity switches, each of which has corresponding proximity sensors. The proximity switches 22 within each of the respective groupings 22A to 22C are shown with three switches and are arranged relatively close to each other. Each of the groupings 22A to 22C can have closely spaced interface contact surfaces and / or a relatively densely packed electrical circuit arrangement, such that electromagnetic interference or other internal drift within the switch arrangement can have a similar effect on all of the switches 22 within the same grouping.The proximity switch arrangement can compensate for electrical drift of the sensor signals caused by electromagnetic interference or other internal drift for all of the proximity switches 22 or for the proximity switches within one or more groups.

[0021] With reference to Fig. Figure 3 illustrates a section of the proximity switch arrangement 20 with a series of serially arranged proximity switches 22 in close relation to one another with respect to a user's finger 34 during use of the switch arrangement 20. Each proximity switch 22 includes one or more proximity sensors 24 for generating a detection activation field. According to one embodiment, each of the proximity sensors 24 can be formed by printing conductive ink onto the upper surface of the polymer roof console 12. An example of a proximity sensor 24 made of printed ink is shown in Fig. Figure 4 shows a control electrode 26 and a receiving electrode 28, each having interlocking fingers for generating a capacitive field 32. It is understood that each of the proximity sensors 24 can also be configured differently according to other embodiments, for example by mounting a pre-formed conductor track on a substrate. The control electrode 26 receives square-wave control pulses at a voltage V. I The receiving electrode 28 has an output for generating an output voltage V. O It is understood that the electrodes 26 and 28 can be arranged in various other configurations to generate the capacitive field as activation field 32.

[0022] In the embodiment shown and described herein, an input voltage V is applied to the control electrode 26 of each proximity sensor 24. IThe signal is applied as rectangular wave pulses with a charging pulse cycle sufficient to charge the receiving electrode 28 to a desired voltage. The receiving electrode 28 serves as a measuring electrode. In the illustrated embodiment, adjacent detection activation fields 32, generated by adjacent proximity switches 22, overlap slightly, whereas in other embodiments, no overlap is required. When a user or operator, such as the user's finger 34, enters an activation field 32, the proximity switch arrangement 20 detects the disturbance caused by the finger 34 in the activation field 32 and determines whether the disturbance is sufficient to activate the corresponding proximity switch 22. The disturbance of the activation field 32 is detected by processing the charging pulse signal associated with the corresponding signal channel.When the user's finger 34 touches two activation fields 32, the proximity switch arrangement 20 detects the disturbance of both touched activation fields 32 via separate signal channels. Each proximity switch 22 has its own dedicated signal channel that generates charge pulse counts, which are processed as discussed herein.

[0023] With reference to Fig. Figure 5 illustrates the proximity switch arrangement 20 according to one embodiment. A plurality of proximity sensors 24 are shown to provide inputs to a controller 40, such as a microcontroller. The controller 40 may include a control circuit arrangement, such as a microprocessor 42 and a memory 48. The control circuit arrangement may include a detection control circuit arrangement that processes the activation field of each sensor 22 to detect user activation of the corresponding switch by comparing the activation field signal with one or more thresholds according to one or more control routines. It is understood that other analog and / or digital control circuit arrangements may be used to process each activation field, determine user activation, and trigger an action.According to one embodiment, the controller 40 can employ a QMatrix acquisition method provided by ATMEL. ® is available. The ATMEL data acquisition method uses a WINDOWS system to simplify development. ® -hosted WinAVR compiler and debugger for C / C++ and, for testing, the Hawkeye utility, which allows monitoring of the internal state of critical software variables in real time as well as collecting logs of data for post-processing.

[0024] The controller 40 transmits an output signal to one or more devices configured to perform dedicated actions in response to the correct activation of a proximity switch. For example, the one or more devices may include a sunroof 16 with a motor for moving a sunroof panel between open, closed, and tilted positions; a sunroof visor 18 that moves between open and closed positions; and lighting devices 30 that can be switched on and off. Other devices, such as a radio for performing on / off functions, volume control, station search, and other types of devices for performing other dedicated functions, may also be controlled.One of the proximity switches 22 can be dedicated to actuating the sunroof to close it, another proximity switch 22 can be dedicated to actuating the sunroof to open it, and yet another switch 22 can be dedicated to actuating the sunroof into a tilted position, all of them causing a motor to move the sunroof into the desired position. The sunroof visor 18 can be opened in response to one proximity switch 22, and it can be closed in response to another proximity switch 22.

[0025] The controller 40 is further shown with an analog-to-digital (A / D) comparator 44, which is coupled to the microprocessor 42. The A / D comparator 44 receives the output voltage V. OThe controller 40 converts the analog signal from each of the proximity switches 22 into a digital signal and transmits the digital signal to the microprocessor 42. The controller 40 also includes a pulse counter 46, which is coupled to the microprocessor 42. The pulse counter 46 counts the charging signal pulses applied to each drive electrode of each proximity sensor and counts the pulses required to charge the capacitor until the output voltage V is reached. O A predetermined voltage is reached, and the count is transmitted to the microprocessor 42. The pulse count indicates the change in capacitance of the corresponding capacitive sensor. The controller 40 is further shown communicating with a pulse-width modulated drive buffer 15. The controller 40 transmits a pulse-width modulated signal to the pulse-width modulated drive buffer 15 to generate a square-wave pulse train V. Ito generate a signal that is applied to each control electrode of each proximity sensor / switch 22. The controller 40 processes one or more control routines 100 stored in memory to monitor and determine whether to activate one of the proximity switches. The control routines may include a routine for executing a procedure to activate a proximity switch using rate monitoring to reduce or eliminate adverse effects caused by condensation.

[0026] Furthermore, a common-mode drift suppression routine 420 is shown stored in memory 48. Routine 420 can also be executed by the microprocessor 42. Advantageously, the common-mode drift suppression routine 420 subtracts from each sensor signal a common-mode signal, which is the signal with the lowest amplitude associated with the proximity sensors, to compensate for drift that may be caused by electromagnetic interference or other internal drift. The common-mode drift suppression can compensate for drift within all of the proximity sensors or within one or more groups of proximity sensors. The common-mode drift suppression can be used to eliminate electrical drift of the sensors for either a sensor or a switch application.

[0027] In Fig. 6 to 13 is the change in the sensor charge pulse counts, represented as Δ sensor counts, for a plurality of signal channels connected to a plurality of proximity switches 22, such as the three in Fig. The three switches 22 shown are associated with each other, as illustrated by various examples. The change in the sensor charge pulse count is the difference between a preset reference count value without any fingers or other objects present in the activation field and the corresponding sensor reading. In these examples, the user's finger enters the activation fields 32 associated with each of the three proximity switches 22, generally one detection activation field each, with overlap between adjacent activation fields 32 as the user's finger moves across the row of switches.Channel 1 is the change (Δ) in the sensor charge pulse count associated with a first capacitive sensor 24, channel 2 is the change in the sensor charge pulse count associated with the adjacent capacitive sensor 24, and channel 3 is the change in the sensor charge pulse count associated with the third capacitive sensor 24 adjacent to the second capacitive sensor. In the disclosed embodiment, the proximity sensors 24 are capacitive sensors. When a user's finger is in contact with or in close proximity to a sensor 24, the finger changes the capacitance measured at the corresponding sensor 24. This capacitance is parallel to the parasitic capacitance of the untouched sensor contact area and is measured accordingly as an offset.The capacitance induced by the user or operator is proportional to the dielectric constant of the user's finger or other body part, the surface in contact with the capacitive contact area, and inversely proportional to the distance of the user's limb from the switch button. According to one embodiment, each sensor is excited by pulse-width modulation (PWM) electronics with a series of voltage pulses until the sensor is charged to a predetermined voltage potential. Such a sensing method charges the receiving electrode 28 to a known voltage potential. The cycle is repeated until the voltage across the measuring capacitor reaches a predetermined voltage.Placing a user's finger on the contact surface of switch 24 introduces external capacitance, which increases the amount of charge transferred each cycle, thereby reducing the total number of cycles required for the sensor capacitance to reach the predetermined voltage. The user's finger causes the change in the sensor charge pulse count to increase, as this value is based on the preset reference count minus the sensor reading.

[0028] The proximity switch arrangement 20 is capable of detecting the user's hand movement when the hand, in particular a finger, is in close proximity to the proximity switches 22. This allows the arrangement to distinguish whether the user intends to activate a switch 22, to search for a specific switch button while concentrating on higher-priority tasks such as driving, or to perform a task, such as adjusting the rearview mirror, which is unrelated to actuating a proximity switch 22. The proximity switch arrangement 20 can operate in a search or probing mode, which enables the user to scan the keypads or buttons by passing or sliding a finger in close proximity to the switches without triggering any switch activation, until the user's intention is determined.The proximity switch arrangement 20 monitors the amplitude of a signal generated in response to the activation field, determines a differential change in the generated signal, and generates an activation output when the differential signal exceeds a threshold. As a result, scanning of the proximity switch arrangement 20 is permitted, allowing users to freely scan the switch interface contact surface with their fingers without unintentionally triggering an event. The interface response time is fast, activation occurs when the finger touches a surface field, and unintentional activation of the switch is prevented or reduced.

[0029] If, with reference to Fig. When the user's finger 34 approaches a switch 22 associated with signal channel 1, the finger 34 enters the activation field 32 associated with sensor 24, causing an interruption of the capacitance and thus resulting in a sensor count increase, as represented by signal 50A with a typical activation motion profile. An input ramp rise method can be used to determine whether the operator intends to press a button or scan the interface based on the rise of the input ramp of signal 50A of the channel 1 signal, which increases from point 52, where signal 50A exceeds the active level (LVL_ACTIVE) count, to point 54, where signal 50A exceeds the threshold level (LVL_THRESHOLD) count. The input ramp rise is the differential change in the generated signal between points 52 and 54 during the time period between the times t. th and t actook place. Since the counter level threshold - level-active generally only changes when the presence of gloves is detected, but is otherwise a constant, the increase can be calculated as exactly the time it takes to transition from level-active to level threshold, and which is called t active2threshold is denoted as the difference between time t th and t ac This involves directly pressing a switch contact surface, which can typically be described as t directpush The specified time period is in the range of approximately 40 to 60 milliseconds. If the time t active2threshold shorter than or equal to the direct printing time t directpush If the condition is met, then it is determined that the switch is activated. Otherwise, it is determined that the switch is in search mode.

[0030] According to another embodiment, the rise of the input ramp can be defined as the difference in time from time t. acat point 52 up to time t pk to reach the peak count at point 56, which is calculated as time t active2peak is referred to as time t. active2peak can be used with a as t direct_push_pk The designated direct pressure tip can be compared, which, according to one embodiment, can have a value of 100 milliseconds. If the time t active2peak shorter than or equal to t direct_push_pk If the condition is met, the system determines that the switch will be activated. Otherwise, it determines that the switch arrangement will operate in a search mode.

[0031] In the Fig. In the example shown in Figure 6, the channel 1 signal is represented such that it increases with increasing capacitance disturbance and rises rapidly from point 52 to the peak value at point 56. The proximity switch arrangement 20 determines the rise of the input ramp either as a time period t active2threshold or t active2peak, so that the signal rises from the first threshold point 52 either to the second threshold at point 54 or to the peak threshold at point 56. The rise or the change in the difference of the generated signal is then compared with a representative direct pressure threshold t. direct_push or t direct_push_pk Used to determine the activation of the proximity switch. Specifically, the switch is activated when the time t active2peak shorter than t direct_push is, or t active2threshold shorter than t direct_push is. Otherwise, the switch configuration remains in search mode.

[0032] With reference to Fig. Figure 7 illustrates an example of a gliding / searching motion across two switches when the finger passes or glides through the activation field of two adjacent proximity sensors, represented as signal channel 1 labeled 50A and signal channel 2 labeled 50B. As the user's finger approaches a first switch, the finger enters the activation field associated with the first switch sensor, causing the sensor count at signal 50A to increase at a slower rate, resulting in a smaller differential change in the generated signal. In this example, the profile of signal channel 1 undergoes a change over time t. active2peak , which are not shorter than or equal to t direct_push is to thereby lead to entry into probing or search mode. Since t active2thresholdAccording to one embodiment, if a slow differential change of the generated signal is indicated, no activation of the switch button is initiated. According to another embodiment, since the time t active2peak not shorter than or equal to t direct_push_pk This indicates a slow differential change of a generated signal; according to another embodiment, no activation is initiated. The second signal channel, labeled 50B, is depicted such that at transition point 58 it becomes the maximum signal and exhibits a rise in the Δ-sensor count with a differential change of the signal similar to that of signal 50A. Consequently, the first and second channels 50A and 50B reflect a sliding movement of the finger across two capacitive sensors in search mode, resulting in no activation of either switch. Using the time period t active2threshold or t active2peakA decision can be made to activate a proximity switch or not when its capacitance level reaches the signal peak.

[0033] For a slow direct pressing motion, such as in Fig. As shown in Figure 8, additional processing can be used to ensure that no activation is intended. As shown in Fig. As can be seen in Figure 8, signal channel 1, designated as signal 50A, is shown in such a way that it either during the time period t active2threshold or t active2peak increases more slowly, which would lead to entering search mode. Upon detection of such a gliding / search state, where time t active2threshold longer than t direct_pushIf the channel that falls out of the state was the first channel to enter search mode, and it is still the maximum channel (channel with the highest intensity) when its capacity drops below LVL_KEYUP_Threshold at point 60, activation of the switch is initiated.

[0034] With reference to Fig. Figure 9 illustrates a rapid movement of a user's finger across the proximity switch arrangement without activating the switches. In this example, the relatively large differential change in the generated signal for channels 1 and 2 is detected for both channels 1 and 2, represented by lines 50A and 50B, respectively. The switch arrangement employs a delay period to postpone activation of a decision until transition point 58, at which the second signal channel 50B rises above the first signal channel 50A. According to one embodiment, the time delay could be equal to the time threshold t.direct_push_pk This can be defined. Accordingly, by introducing a delay period before determining the activation of a switch, the very rapid scanning of the proximity keypads prevents unintentional activation of a switch. Introducing this time delay in the response can result in the interface responding less frequently and functioning better when the operator's finger movement is essentially uniform.

[0035] If a previous threshold event that did not result in activation has recently been detected, one embodiment allows the system to automatically enter search mode. Consequently, greater caution can be exercised for a period of time in search mode, allowing for the detection and suppression of any unintended activation.

[0036] Another way to enable an operator to enter search mode is to use one or more appropriately marked and / or textured areas or contact surfaces on the switch panel surface associated with the dedicated proximity switches. These areas signal the operator's intention to search blindly to the proximity switch arrangement. The one or more search engagement contact surfaces can be located in an easily accessible area where activity from other signal channels is unlikely to occur. Alternatively, a larger, unmarked search engagement contact surface can be used, surrounding the entire switch interface.The operator's hand would probably first encounter such a search contact surface when gliding over the roof console's trim in search of a reference point from which to begin a blind search of the proximity switch arrangement.

[0037] Once the proximity sensor array determines whether an increase in the change in the sensor count is a switch activation or the result of a search movement, the array proceeds to determine whether and how the search movement should result in a proximity switch activation. According to one embodiment, the proximity switch array searches for a constant pressing of a switch button for at least a predetermined duration. In a specific embodiment, the predetermined duration is equal to or longer than 50 milliseconds and is preferably about 80 milliseconds. Examples of switch array operation employing a constant-time methodology are described in Fig. Illustrated in sections 10 to 13.

[0038] With reference to Fig. Figure 10 illustrates the scanning of three proximity switches, corresponding to signal channels 1 to 3 designated as signals 50A to 50C, while a finger in search mode glides over the first and second switches and then activates the third switch, associated with signal channel 3. When the finger scans the first and second switches associated with channels 1 and 2, no activation is determined due to the absence of a constant signal on lines 50A and 50B. The signal on line 50A for channel 1 starts as the maximum signal value until channel 2 on line 50B becomes the maximum value, and finally channel 3 becomes the maximum value. Signal channel 3 is represented as carrying a constant change in the sensor count near the peak value for a sufficient time period t. stable,such as 80 milliseconds, which is sufficient to initiate activation of the corresponding proximity switch. If the level threshold trigger condition is met and a peak has been reached, the constant level method activates the switch after the level at the switch has been maintained for at least the time period t. stable was fixed in a narrow area. This allows the operator to scan the various proximity switches and activate a desired switch as soon as it is found by monitoring the position of the user's finger in close proximity to the switch for a constant time period t. stable will be maintained.

[0039] With reference to Fig. Figure 11 illustrates another embodiment of the constant-level method, wherein the third signal channel on line 50C exhibits a change in the sensor count that has a constant state as the signal falls. In this example, the change in the sensor count for the third channel exceeds the level threshold and exhibits a constant pressure that lasts for the time period t. stable It is detected in such a way that the activation of the third switch is determined.

[0040] According to another embodiment, the proximity switch arrangement can employ a virtual button method that searches for an initial peak value in the change in the sensor count, while in search mode, followed by an additional sustained increase in the change in the sensor count to determine whether to activate the switch, as shown in Fig. 12 and Fig. 13 shown. Fig. 12. The third signal channel on line 50C rises to an initial peak value and then increases due to a change in sensor count C. vb Furthermore, this corresponds to a user's finger gently gliding across the surface of the switch assembly, reaching the desired key, and then depressing the virtual mechanical switch, such that the user's finger presses against the switch contact surface, increasing the volume of the finger closer to the switch. The increase in capacitance is brought about by the enlarged surface area of ​​the fingertip as it is compressed against the contact surface. The increased capacitance can occur immediately after detecting a peak value, as in Fig. 12 is shown, or it may occur after a decrease in the sensor count change, as in Fig. Figure 13 shows the proximity switch arrangement detecting an initial peak value, followed by a further larger change in the sensor count, which is caused by the capacitance C. vb at a constant level or in a constant time period t stable is displayed. A constant detection level generally means no change in the sensor count in the absence of noise, or a small change in the sensor count in the absence of noise, which can be determined during calibration.

[0041] It is understood that a shorter time period t stable which can lead to accidental activations, especially after a reversal of the direction of finger movement, and that a longer period of time t stable which can lead to an interface that is less responsive.

[0042] It is understood that both the constant-value method and the virtual button method can be active simultaneously. The constant time t can be... stable The timer can be shortened to be longer, for example one second, because the operator can always trigger the button by using the virtual button method without waiting for the time to elapse after constant pressing.

[0043] The proximity switch arrangement can also employ robust noise suppression to prevent annoying unintentional activations. For example, in the case of a roof console, accidental opening and closing of the sunroof should be prevented. Excessive noise suppression can lead to the suppression of intended activations, which should be avoided. One approach to noise suppression is to consider whether multiple adjacent channels are reporting simultaneous trigger events and, if so, to select and activate the signal channel with the highest signal, thereby ignoring all other signal channels until the selected channel is released.

[0044] The proximity switch arrangement 20 can include a signature noise reduction method based on two parameters: a signature parameter, which is the ratio between the channel with the highest intensity (max_channel) and the cumulative total level (sum_channel), and the DAC parameter, which is the number of channels that are at least a certain ratio of max_channel. In one embodiment, DAC α dac =0.5. The signature parameter can be defined by the following equation: Signature=max_channelsum_channel=maxi=0,nchanneli∑i=0,nchanneli

[0045] The DAC parameter can be defined by the following equation: DAC=∀channelsi>αdacmax_channel.

[0046] Depending on the DAC, in order for a detected activation not to be suppressed, the channel must generally be clean, i.e., the signature must be above a predefined threshold. In one embodiment, α dac=1 = 0.4 and α dac=2 = 0.67. If DAC is higher than 2, activation is suppressed according to one embodiment.

[0047] If no decision is made to activate a switch during the downward phase of the profile, then instead of max_channel and sum_channel, their peak values ​​peak_max_channel and peak_sum_channel can be used to calculate the signature. The signature has the following equation: Signature=peak_max_channelpeak_sum_channel=max(max_channel(t))max(sum_channel(t)).

[0048] Noise reduction can be used, which triggers a probing mode. If a detected activation is suppressed due to an impure signature, the probing or search mode should be automatically activated. Consequently, a user might attempt to establish a reference frame from which to begin probing while blindly extending all fingers. This could trigger multiple channels simultaneously, resulting in a poor signature.

[0049] With reference to Fig. Figure 14 shows a state diagram for the proximity switch arrangement 20 in a state machine implementation according to one embodiment. The state machine implementation is shown with five states, comprising a SW_NONE state 70, a SW_ACTIVE state 72, a SW_THRESHOLD state 74, a SW_HUNTING state 76, and a SWITCH_ACTIVATED state 78. The SW_NONE state 70 is the state in which no sensor activity is detected. The SW_ACTIVE state is the state in which some activity is detected by the sensor, but not enough to trigger activation of the switch at that time. The SW_THRESHOLD state is the state in which activity, as determined by the sensor, is high enough to ensure activation, probing / scanning, or random movement of the switch arrangement.SW_HUNTING state 76 is entered when the activity pattern, as determined by the switch arrangement, is compatible with the search / probing interaction. SWITCH_ACTIVATED state 78 is the state in which activation of a switch has been identified. In SWITCH_ACTIVATED state 78, the switch button remains active, and no other selection is possible until the corresponding switch is released.

[0050] The state of the proximity switch assembly 20 changes depending on the detection and processing of the detected signals. When in SW_NONE state 70, system 20 can transition to SW_ACTIVE state 72 if some activity is detected by one or more sensors. If enough activity is detected to warrant activation, probing, or random movement, system 20 can transition directly to SW_THRESHOLD state 74. While in SW_THRESHOLD state 74, system 20 can transition to SW_HUNTING state 76 if a pattern indicating a search is detected, or directly to SWITCH-ACTIVATED state 78. If a switch activation is present in SW_HUNTING state, activation of the switch to transition to SWITCH-ACTIVATED state 78 can be detected. If the signal is suppressed and an unintended action is detected, system 20 can return to SW_NONE state 70.

[0051] With reference to Fig. Figure 15 describes the main method 100 for monitoring and determining when to generate an activation output with the proximity switch arrangement, according to one embodiment. Method 100 begins at step 102 and proceeds to step 104 to perform an initial calibration, which may be performed only once. In step 106, the calibrated signal channel values ​​are calculated from raw channel data, and calibrated reference values ​​are calculated by subtracting the reference value from the raw data. Method 100 may then proceed to step 107 to perform common-mode drift suppression. Common-mode drift suppression subtracts the smallest signal from each of the other signals associated with the proximity sensors or groups of proximity sensors to compensate for electromagnetic interference and other internal drift.Next, in step 108, the highest count value, denoted as max_channel, and the sum of all channel sensor measurements, denoted as sum_channel, are calculated from all signal channel sensor readings. The number of active channels is also determined. In step 110, procedure 100 calculates the most recent range of max_channel and sum_channel to later determine whether motion is in progress.

[0052] After step 110, procedure 100 proceeds to decision step 112 to determine if any of the switches are active. If no switch is active, procedure 100 proceeds to step 114 to perform an online real-time calibration. Otherwise, in step 116, procedure 100 processes the switch enable. If a switch was already active, procedure 100 proceeds to a module where it waits and blocks any activity until it is enabled.

[0053] After real-time calibration, procedure 100 proceeds to decision step 118 to determine if there is a channel block indicating recent activation. If so, it proceeds to step 120 to decrement the channel block timer. If no channel blocks are detected, procedure 100 proceeds to decision step 122 to search for a new max_channel. If the current max_channel has changed, resulting in a new max_channel, procedure 100 proceeds to step 124 to reset max_channel, sum the ranges, and set the threshold levels. Therefore, if a new max_channel is identified, the procedure resets the recent signal ranges and updates the probe / search parameters as needed. If switch_status is less than SW_ACTIVE, the probe / search flag is set to true, and the switch status is set to SW_NONE.Additionally, the rate flag is reset in step 124. After step 124, routine 100 proceeds to step 131 to update the rate flag. The rate flag allows the switch to be activated when the monitored rate of change of the delta signal count, such as a mean rate of change, exceeds a valid activation rate, thus preventing false activations due to condensation changes. If the rate flag is set, activation of the switch is permitted. If the rate flag is not set, activation of the switch is prevented.

[0054] If the current max_channel has not changed, procedure 100 proceeds to step 126 to process the max_channel bare-fingered (no glove) state. This may involve processing the logic between the different states, as shown in the state diagram of Fig. Figure 14 illustrates this. After step 126, procedure 100 proceeds to decision step 128 to determine if any switches are active. If no switch activation is detected, procedure 100 proceeds to step 130 to detect the possible presence of a glove on the user's hand. The presence of a glove can be detected based on a reduced capacity change count value. Procedure 100 then proceeds to step 131 to update the rate flag, and then to step 132 to update the historical history of max_channel and sum_channel. The index of the active switch, if any, is then output to the software-hardware module at step 134, before the procedure terminates at step 136.

[0055] When a switch is active, a switch enable processing routine is activated, which is located in Fig. Figure 16 illustrates this. The switch enable processing routine 116 begins at step 140 and proceeds to decision step 142 to determine if the active channel is less than LVL_RELEASE, and ends at step 152 if it is. If the active channel is not less than LVL_RELEASE, then routine 116 proceeds to decision step 144 to determine if LVL_DELTA_THRESHOLD is greater than 0, and if it is not, it proceeds to step 146 to raise the threshold level if the signal is stronger. This can be achieved by lowering LVL_DELTA_THRESHOLD. Step 146 also sets the threshold, enable, and active levels. Routine 116 then proceeds to step 148 to reset the channel max and sum timers for probe / search parameters for a long, constant signal. The switch status is set to SW_NONE at step 150, before the routine ends at step 152.To exit the switch release processing module, the signal on the active channel must drop below LVL_RELEASE, which is an adaptive threshold that changes when glove interaction is detected. Once the switch is released, all internal parameters are reset, and the blocking timer is started to prevent further activations until a specified delay, such as 100 milliseconds, has elapsed. Additionally, the threshold levels are adjusted depending on whether gloves are present.

[0056] With reference to Fig. Figure 17 illustrates a routine 200 for determining a status change from the SW_NONE state to the SW_ACTIVE state according to one embodiment. Routine 200 begins at step 202 to process the SW_NONE state and then proceeds to decision step 204 to determine if max_channel is greater than LVL_ACTIVE. If max_channel is greater than LVL_ACTIVE, the proximity switch arrangement changes the state from the SW_NONE state to the SW_ACTIVE state, and the routine ends at step 210. If max_channel is not greater than LVL_ACTIVE, routine 200 checks at step 208 whether the probe flag should be reset before ending at step 210. Therefore, the status changes from the SW_NONE state to the SW_ACTIVE state when max_channel triggers above LVL_ACTIVE.If the channels remain below this level, the probing flag, if set, will be set to "Do not probing" after a certain waiting period, which is a way to exit probing mode.

[0057] With reference to Fig. Figure 18 illustrates a method 220 for processing the state of the SW_ACTIVE state, which transitions to either the SW_THRESHOLD or the SW_NONE state, according to one embodiment. Method 220 begins at step 222 and proceeds to decision step 224. If max_channel is not greater than LVL_THRESHOLD, then method 220 proceeds to step 226 to determine if max_channel is less than LVL_ACTIVE, and if so, it proceeds to step 228 to change the switch state to SW_NONE. Accordingly, the state machine state transitions from the SW_ACTIVE state to the SW_NONE state when the max_channel signal falls below LVL_ACTIVE. Additionally, a delta value can be subtracted from LVL_ACTIVE to introduce some hysteresis.If max_channel is greater than LVL_THRESHOLD, routine 220 proceeds to decision step 230 to determine whether a recent threshold event or a glove has been detected. If so, in step 232, it sets the probing-on flag to true. In step 234, procedure 220 sets the status to the SW_THRESHOLD state before ending in step 236. Therefore, if max_channel triggers above LVL_THRESHOLD, the status changes to the SW_THRESHOLD state. If gloves are detected, or a previous threshold event that did not trigger has recently been detected, entry into probing / search mode can occur automatically.

[0058] With reference to Fig. Figure 19 illustrates a method 240 for determining the activation of a switch from the SW_THRESHOLD state according to one embodiment. Method 240 begins at step 242 to process the SW_THRESHOLD state and proceeds to decision block 244 to determine whether the signal is constant or whether the signal channel is on a peak, ending at step 256 if neither is the case. If either the signal is constant or the signal channel is on a peak, then method 240 proceeds to decision step 246 to determine whether the probing or search mode is active and jumps to step 250 if so.If the probing or search mode is not active, procedure 240 proceeds to decision step 248 to determine if the signal channel is clean and fast-active is greater than a threshold. If so, it proceeds to decision step 249 to determine if the rate flag is set and, if so, sets switch-active at step 250 to the maximum channel value. If the signal channel is not clean and fast-active is not greater than the threshold, procedure 240 proceeds directly to step 252. Similarly, procedure 240 proceeds directly to step 252 if the rate flag is not set. At decision block 252, procedure 240 determines if there is an active switch and terminates at step 256 if there is.If there is no active switch, procedure 240 proceeds to step 254 to initialize the probe variables SWITCH_STATUS, which is set to SWITCH_HUNTING, and PEAK_MAX_BASE, which is set to MAX_CHANNELS, before ending at step 256.

[0059] In the SW_THRESHOLD state, no decision is made until a spike in MAX_CHANNEL is detected. Spike detection requires either a reversal of the signal's direction or that both MAX_CHANNEL and SUM_CHANNEL remain constant (fixed within a range) for at least a specified interval, such as 60 milliseconds. Once the spike is detected, the probing flag is checked. If probing mode is disabled, the input ramp-up method is applied. If SW_ACTIVE in SW_THRESHOLD was below a threshold, such as 16 milliseconds, and the noise signature suppression method identifies it as a valid trigger event, the state is changed to SWITCH_ACTIVE, and the process is transferred to the PROCESS_SWITCH_RELEASE module; otherwise, the probing flag is set to true.If the activation delay method is used instead of immediate activation of the switch, the state is changed to SW_DELAYED_ACTIVATION, forcing a delay at the end of which the button is activated if the MAX_CHANNEL index has not changed.

[0060] With reference to Fig. Figure 20 illustrates a virtual key method according to one embodiment that implements the SW_HUNTING state. Method 260 begins at step 262 to process the SW_HUNTING state and proceeds to decision step 264 to determine if MAX_CHANNEL has fallen below LVL_KEYUP_THRESHOLD. If so, at step 272, it sets MAX_PEAK_BASE to MIN(MAX_PEAK_BASE, MAX_CHANNEL). If MAX_CHANNEL has fallen below LVL_KEYUP_THRESHOLD, then method 260 proceeds to step 266 to use the first channel probing procedure to check if the event should trigger key activation. This is determined by ascertaining whether the first and only channel is traversed and the signal is pure.If this is the case, procedure 260 proceeds to decision step 269 to determine if the Rate flag is set, and if so, sets Switch_Active to the maximum channel at step 270 before ending at step 282. Procedure 260 ends at step 282 if the Rate flag is not set. If the first and only channel is not traversed, or if the signal is not pure, procedure 260 proceeds to step 268 to abandon and determine an unintended activation, setting SWITCH_STATUS to the SW_NONE state before ending at step 282.

[0061] After step 272, procedure 260 proceeds to decision step 274 to determine if the channel has clicked. This can be determined by whether MAX_CHANNEL is greater than MAX_PEAK_BASE plus the delta. If the channel has clicked, procedure 260 proceeds to decision step 276 to determine if the signal is constant and pure. If so, it proceeds to decision step 279 to determine if the rate flag is set. If so, it sets the switch-active state to the maximum channel at step 280 before concluding at step 282.If the channel has not clicked, procedure 260 proceeds to decision step 278 to check if the signal is long, constant, and pure. If so, it proceeds to decision step 279 to determine if the rate flag is set. If so, it proceeds to step 280 to set switch-active to the maximum channel before ending at step 282. Procedure 260 ends at step 282 if the rate flag is not set.

[0062] Accordingly, the proximity switch monitoring and detection routine advantageously determines the activation of the proximity switches. The routine advantageously allows a user to scan the proximity switch contact surfaces, which can be particularly useful in a motor vehicle application where driver distraction can be avoided.

[0063] Proximity sensors can be manufactured using thin-film technology, which may involve printing a conductive ink mixed with a solvent to achieve a desired electrical circuit layout. The printed ink can be formed into a film that is cured in a curing process using controlled heating and light / heat exposure to remove the solvent. Variations in existing curing processes can lead to residual solvent becoming trapped in the electrical traces, resulting in sensors that are sensitive to temperature and humidity changes. Condensation forming on a proximity sensor can alter the raw capacitive signal and the delta signal count.Condensation can occur in a vehicle, for example, if the vehicle is driven during a rainstorm before the windshield defroster is switched on, or if the vehicle is entered on a hot, humid summer day and the HVAC blower directs moisture onto the switches. Similarly, the capacitive raw signal and the delta signal count can change in the opposite direction as the condensation dries. An example of a delta signal count variation during a change in condensation is shown in [reference missing]. Fig. Figure 21 illustrates that signal 50 increases in value as a result of changes in condensation, such as a decrease in condensation, which can trigger a false activation event when signal 50 reaches a certain threshold. Similarly, the Δ-sensor count signal 50 decreases as condensation increases, which can also trigger a false activation event. To compensate for condensation and prevent or reduce false activations, the proximity switch arrangement 20 and method 100 employ a rate monitoring routine to determine valid switch activations from false events caused by condensation.

[0064] With reference to Fig. Figure 22 illustrates the Δ-sensor count signal 50 during a potential switch activation and with a specific signal sampling rate for successive detected signal samples. The signal samples include the current signal sample C0 and the previously monitored signal sample C. -1 , the next previously monitored signal sample value C -2 and the next previous signal sample value C -3Consequently, a history of samples from Δ-sensor count signals 50 is monitored and used by the rate monitoring routine. The rate monitoring routine monitors the amplitude of a signal generated in response to the activation field, determines a rate of change of the generated signal, compares the rate of change to a threshold rate, and generates an output based on the rate of change exceeding the threshold rate. The generated output is then used by a method to activate a proximity sensor. In one embodiment, the rate flag enables activation of the proximity switch when set and prevents activation of the proximity switch when the rate flag is not set. The rate of change can be a moving average rate of change calculated over more than two signal samples, such as samples C0 to C1. -3, is recorded. To eliminate or remove noise from the signal rise estimation, the moving average can be calculated, for example, using a low-pass filter to enable sensor activation and prevent false activation due to condensation. The moving average can be calculated by determining the difference between a first count signal and a second count signal, where the first and second count values ​​are acquired over a time period encompassing more than two samples. Additionally, the rate monitoring routine can calculate incremental rate-of-change values ​​between successive signal samples, such as samples C0 and C1. -1, determine and furthermore compare the successive rate of change values ​​with a step rate threshold, whereby the activation output is generated if the successive rate of change signals exceed the step rate threshold. Furthermore, the rate of change of the generated signal can be the difference between two successive signal counts, such as the sample values ​​C -0 and C -1 , which, according to one embodiment, is compared to a fast activation rate. It is generally known that condensation increases at a slower rate than activation by a user, such that slower activation rates prevent the sensor from activating when the threshold value is reached due to condensation.

[0065] The rate monitoring routine 300, which is in Fig. The routine shown in Figure 23 is implemented as an update rate flag routine that starts at step 302. Routine 300 proceeds to decision step 304 to calculate the difference between the current maximum Δ sensor count MAX_CH(t) and a previously determined maximum Δ sensor count MAX_CH(t-3), and to determine whether the calculated difference is greater than a valid activation rate. The difference between the maximum Δ sensor counts over a plurality of signal samples, such as four samples C0 to C1, is used to calculate the update rate. -3The Δ sensor count is acquired at successive sampling times t, t-1, t-2, and t-3. The difference between these values ​​provides a moving average of the Δ sensor count. If the moving average is greater than the activation rate, procedure 300 proceeds to decision step 306. In decision step 306, routine 300 compares each of the incremental changes in the Δ sensor count signals MAX_CH(t) between successive monitored samples and compares the incremental differences to a step rate value.This involves comparing the current maximum channel signal MAX_CH(t) with the previous maximum channel signal MAX_CH(t-1) to check if the difference is greater than the step rate; comparing the previous maximum channel signal MAX_CH(t-1) with the second previous maximum channel signal MAX_CH(t-2) to check if the difference is greater than the step rate; and comparing the second previous maximum channel signal MAX_CH(t-2) with the third previous maximum channel signal MAX_CH(t-3) to check if the difference is greater than the step rate. If the differences in any of the incremental signal channels are greater than the step rate value, then procedure 300 proceeds to step 310 to set the rate flag before ending at step 312. If any of the differences in the incremental signal channels are not greater than the step rate value, routine 300 ends at step 312.Once the rate flag is set, the monitoring routine can activate a sensor output. Setting the rate flag reduces or eliminates false activations that may be due to condensation effects.

[0066] Routine 300 includes a decision step 308, which is implemented when the Δ-sensor count difference exceeds the valid activation rate. Decision step 308 compares the difference between the maximum channel signal MAX_CH(t) and the previous channel signal MAX_CH(t-1) with a valid fast activation rate. If the difference exceeds the valid fast activation rate, procedure 300 proceeds to step 310, setting the rate flag. Decision step 308 allows for a rapidly increasing difference in the Δ-sensor count for the current signal sample from the previous signal sample to enable activation, ignoring the previous sampling history. Therefore, the rate flag is set when the difference between the two most recent Δ-sensor counts indicates a very fast rate.

[0067] In one embodiment, the valid activation rate can be set to a value of 50 counts, the step rate can be set to a value of 1 count, and the valid fast activation rate can be set to a value of 100 counts. Consequently, according to one embodiment, the valid fast activation rate is twice as high as the valid activation rate. It is understood, however, that the valid activation rate, the valid fast activation rate, and the step rate can be set to other values ​​according to other embodiments.

[0068] The rate monitoring routine 300 monitors the maximum signal channel value and sets or resets the rate flag for the maximum signal channel according to the illustrated embodiment. By monitoring the maximum signal channel, the signal most likely to exhibit activation is continuously monitored and used to activate the rate flag to minimize condensation effects. It is understood that according to other embodiments, any signal channel other than the maximum signal channel can be monitored. The rate monitoring routine 300 sets and resets the rate flag for the maximum signal channel, but according to further embodiments, the rate monitoring routine 300 can also set and reset the rate flag for other signal channels besides the maximum signal channel. It is further understood that the sampling rate for acquiring the Δ-count signal sample values ​​can vary.A faster sampling rate provides faster speed for determining activation and identifying the presence of condensation. Signal monitoring can be continuous, and noise filtering can be used to eliminate noise.

[0069] Accordingly, the rate monitoring routine 300 advantageously monitors the rate of change of the Δ-sensor count and enables the activation of a switch, provided that the rate is of a sufficient value. This prevents false activations due to condensation and other potential effects. The proximity switch arrangement is thus able to generate an output signal indicating switch activation based on the rate flag being set, and to prevent activation when the rate flag is not set.

[0070] The proximity switch arrangement 20 further includes a common-mode drift suppression routine for handling the presence of electrical drift, such as a rise or fall in the sensor signals, that is not due to user interaction with the sensors. Various factors can disturb the capacitive electric field, such as environmental changes, including electromagnetic interference and interactions of internal components, with components of the capacitive interface electronics potentially interfering with the sensing of the capacitive field. Electromagnetic interference and other internal drift generally occur rapidly, and the magnitude of the drift can depend on the circuit design and the intensity and frequency of the interfering radiation.The common-mode drift suppression routine monitors the amplitude of a signal generated in response to each of the activation fields to detect the smallest signal and subtracts this smallest signal from each of the other signals before determining the activation of one of the plurality of proximity sensors or proximity switches based on the subtracted signals. The proximity switch arrangement preferably comprises a plurality of proximity switches such that the one proximity switch with the lowest signal value is assumed to have a value resulting from noise rather than being caused by a user connected to the sensors via an interface. The lowest signal is then assumed to be the common-mode signal that is subtracted from the other signals to suppress common-mode noise that may be caused by electromagnetic radiation or other internal drift.

[0071] Common-mode drift suppression can be used to determine the activation of one of a plurality of proximity switches by subtracting the smallest signal from each of the other signals generated by the proximity sensors. In the embodiment of the proximity switch arrangement, a plurality of proximity switches are included, each comprising a proximity sensor for providing a detection activation field, and a control circuit arrangement that processes the activation field of each proximity switch to detect activation. The control circuit arrangement implements a method for activating the proximity switch arrangement. The method includes generating activation fields with the plurality of proximity sensors associated with the plurality of proximity switches and monitoring the amplitude of a signal generated in response to each of the activation fields.The procedure also includes the steps of subtracting the smallest signal from each of the other signals and determining the activation of one of the plurality of proximity switches based on the subtracted signals. The plurality of proximity sensors can comprise at least three proximity sensors associated with at least three corresponding proximity switches. The activation of one of the proximity switches is determined by processing the largest signal based on one or more threshold values ​​once the smallest signal has been subtracted from the largest signal.

[0072] Common-mode drift suppression can also be used to determine the activation of one of a plurality of proximity sensors. A proximity sensor array comprises a plurality of proximity sensors, each providing a detection activation field, and a control circuit arrangement for processing the activation field of each proximity sensor to detect activation. The control circuit arrangement implements a noise suppression method for the plurality of proximity sensors. The method includes generating activation fields with the plurality of proximity sensors and monitoring the amplitude of a signal generated in response to each of the activation fields. The method further includes subtracting the smallest signal from each of the other signals and determining the activation of one of the plurality of proximity sensors based on the subtracted signals.

[0073] The application of the common-mode drift suppression routine is illustrated by several examples, which are presented in Fig. 24A to 26B are shown. The ones in Fig. Signals 24A to 26B generated by 50A to 50C can be generated, according to an example, by the proximity sensors associated with the proximity switches 22 of group 22A, which are in Fig. Figure 2 shows that each of the signals 50A to 50C is generated by one of the three proximity sensors associated with the corresponding proximity switches 22 of group 22A. Fig. 24. A user's finger causes the signal 50A, generated by the first proximity sensor associated with the first proximity switch 22, to rise to a peak value of 56. The second signal 50B is generated by the second proximity sensor, also associated with the second proximity switch 22, which may be adjacent to the first proximity switch. It is shown to produce an amplitude smaller than that of the first signal 50A, which may be partly due to the user's finger being in close proximity to the second proximity sensor. A third signal 50C is generated by a third proximity sensor, also associated with the third proximity switch, which may be adjacent to the second proximity sensor. The third signal 50C is the lowest and smallest signal, shown to rise rapidly in an approximately step-like manner and remain at a substantially constant amplitude.In this example, it is assumed that this baseline rise of the smallest signal is caused by electrical drift, which can occur in a step-like manner and may be caused by electromagnetic radiation, for example, due to the switching on of one or more circuit components. The common-mode drift suppression routine determines the smallest signal, which in this example is the third signal 50C and is represented as min_CH, and uses this value to compensate for the electrical drift. Specifically, the routine subtracts the smallest signal min_CH from each of the other signals 50A and 50B, as shown in the diagram. Fig. Figure 24B illustrates this. Accordingly, the amplitude of the largest signal, 50A, is reduced by the amount min_CH to decrease or suppress electrical common-mode drift. In this example, drift suppression prevents noise-induced activation of the first proximity switch because the adjusted maximum amplitude is lower than the threshold active value.

[0074] In Fig. 25A and Fig. 25B are the first, second and third signals 50A, 50B and 50C, which are associated with first, second and third proximity sensors, which are associated with corresponding first, second and third proximity switches, without the common-mode drift suppression in Fig. 25A and according to another example with common-mode drift suppression in Fig. Figure 25B illustrates this. The common-mode drift suppression routine detects the smallest signal associated with one of the proximity sensors, represented as signal 50C labeled min_CH, and subtracts the value of min_CH from each of the other signals 50A and 50B, as shown in Figure 25B. Fig. 25B is shown. When this occurs, the ratio of the largest signal 50A to an accumulation of the other signals 50B and 50C is high enough to allow the intended activation of the first proximity switch using common-mode drift suppression, as shown in Fig. 25B shown.

[0075] In Fig. 26A and Fig. In 26B, the first, second, and third signals 50A, 50B, and 50C are represented according to another example such that they are generated by first, second, and third proximity sensors associated with corresponding first, second, and third proximity switches. In this example, the smallest signal that appears in Fig. 26A, represented as signal 50C, displays a value of min_CH that is high enough and greater than the threshold active, as in Fig. Figure 26A is shown. Applying the common-mode drift suppression routine, the smallest signal min_CH is subtracted from each of the other signals 50A and 50B to provide the signals as shown in Figure 26B. When this is done, only the largest signal is shown above the threshold active signal, which allows activation of the proximity switch associated with the largest signal, 50A.

[0076] In Fig. Figure 28 shows a simplified main routine 400 for processing activations of the proximity sensor or proximity switch. It is understood that routine 400 is a simplified version of an activation routine, such as routine 100, which is described in Fig. Figure 15 shows the addition of common-mode rejection. The basic steps of routine 400 are simplified and illustrate a main loop 402, followed by step 404 of acquiring the signals for each of the signal channels CH[i]. Routine 400 includes step 406 of performing common-mode rejection before step 408 of detecting activations using the signal channel CH_CH[i] and subsequently processing the activations in step 410. Each of the steps of acquiring the signals in step 404, detecting the activations in step 408, and processing the activations in step 410 can be performed, as shown, by routine 100 in Figure 100. Fig. 15 will be implemented.

[0077] In Fig. Figure 28 illustrates the common-mode drift suppression routine 420 according to one embodiment. The common-mode drift suppression routine 420 begins at step 422 and proceeds to step 424 to find the smallest signal associated with one of the proximity sensors, which is associated with one of the proximity switches. In this embodiment, the signals generated by all of a plurality of proximity sensors are monitored, and the smallest associated signal is selected. Next, at step 426, the routine 420 subtracts the smallest signal channel from all of the other signal channels. Accordingly, the smallest signal has been treated as a common-mode signal, which is subtracted from, or reduced in value by, each of the other signals. The routine 420 then terminates at step 428.

[0078] With reference to Fig.Figure 29 shows a common-mode drift suppression routine 430 according to another embodiment. In this embodiment, the common-mode drift suppression is applied to selected groupings of proximity sensors and proximity switches. For example, if a plurality of groups of proximity sensors are provided with the proximity switch arrangement, each group can only subtract the common-mode signal associated with that group. Routine 430 starts at step 432 and proceeds to step 434 to normalize all proximity sensors. This can involve weighting certain proximity sensors based on contact point or interface configurations, including size and shape. Accordingly, a sensor with a larger interaction area can be weighted differently than a sensor with a smaller interaction area.Next, at decision step 436, routine 430 determines whether common-mode rejection is active for the current sensor group i and skips to decision step 442 if it is not. If common-mode rejection is active for the current sensor group i, routine 430 proceeds to step 438 to find the smallest signal in the current sensor group i. Next, at step 440, routine 430 subtracts the smallest signal channel from all other signal channels within the current group i before proceeding to decision step 442. At decision step 442, routine 430 determines whether all sensor groups have been processed and terminates at step 444 if so. If not all sensor groups have been processed, routine 430 returns to step 436 to process the next sensor group.Accordingly, in this embodiment, each of the groups is processed separately to determine the smallest signal and to subtract the smallest signal from all of the other signal channels associated with that group.

[0079] Accordingly, the common-mode drift suppression routine advantageously monitors the activation signals and determines the smallest signal associated with the proximity array or grouping of proximity sensors. It then subtracts this smallest signal from each of the other signals and determines the activation of one of the multiple proximity sensors or switches based on the subtracted signals. This enables the suppression of interference, such as electromagnetic interference and other internal drift, that disrupts the capacitive electric field, which can occur relatively quickly and without being caused by user interaction with the proximity array.

[0080] It is understood that changes and modifications to the aforementioned structure may be made without deviating from the concepts of the present invention, and it is further understood that such concepts are intended to be covered by the following claims, unless expressly stated otherwise by the wording of these claims.

Claims

[1] Method for activating a proximity circuit arrangement (20) comprising a common-mode drift suppression routine (430) for dealing with the presence of electrical drift, the method comprising: Generating activation fields (32) with a plurality of proximity sensors (24) associated with a plurality of proximity switches (22); wherein the common-mode drift suppression routine (430) monitors the amplitude of a signal (50A, 50B, 50C) generated in response to each of the activation fields (32), to detect a common-mode signal, which is the signal (50A, 50B, 50C) with the lowest amplitude, associated with the proximity sensors (24) to compensate for drift that may be caused by electromagnetic interference or other internal drift, and to subtract the common-mode signal from each of the other signals (50A, 50B, 50C) before determining activation of one of the plurality of proximity switches (22) based on the subtracted signals; wherein the proximity switch arrangement (20) provides a plurality of groups (22A, 22B, 22C) of proximity sensors (22), wherein each of the groups (22A, 22B, 22C) subtracts only the common-mode signal associated with that group (22A, 22B, 22C). [2] Method according to claim 1, wherein the common-mode rejection routine (430) subtracts the common-mode signal from all other signals within the current group (22A, 22B, 22C) when common-mode rejection is active at the current group (22A, 22B, 22C), and wherein the common-mode rejection routine (430) determines whether all groups (22A, 22B, 22C) have been processed, and if not all groups (22A, 22B, 22C) have been processed, processes the next group (22A, 22B, 22C), and terminates when all groups (22A, 22B, 22C) have been processed.

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