# Patent

## Title
Proximity switch assembly and activation method

## Abstract

A proximity switch assembly and method for detecting activation of a proximity switch assembly is provided. The assembly includes a plurality of proximity switches each having a proximity sensor providing a sense activation field and control circuitry processing the activation field of each proximity switch to sense activation. The control circuitry monitors the signal responsive to the activation field and determines a differential change in generated signal, and further generates an activation output when the differential signal exceeds a threshold. The control circuitry further distinguishes an activation from an exploration of the plurality of switches and may determine activation upon detection of a stable signal.

## Background
FIELD OF THE INVENTION
The present invention generally relates to switches, and more particularly relates to proximity switches having an enhanced determination of switch activation.
BACKGROUND OF THE INVENTION
Automotive vehicles are typically equipped with various user actuatable switches, such as switches for operating devices including powered windows, headlights, windshield wipers, moonroofs or sunroofs, interior lighting, radio and infotainment devices, and various other devices. Generally, these types of switches need to be actuated by a user in order to activate or deactivate a device or perform some type of control function. Proximity switches, such as capacitive switches, employ one or more proximity sensors to generate a sense activation field and sense changes to the activation field indicative of user actuation of the switch, typically caused by a user's finger in close proximity or contact with the sensor. Capacitive switches are typically configured to detect user actuation of the switch based on comparison of the sense activation field to a threshold.
Switch assemblies often employ a plurality of capacitive switches in close proximity to one another and generally require that a user select a single desired capacitive switch to perform the intended operation. In some applications, such as use in an automobile, the driver of the vehicle has limited ability to view the switches due to driver distraction. In such applications, it is desirable to allow the user to explore the switch assembly for a specific button while avoiding a premature determination of switch activation. Thus, it is desirable to discriminate whether the user intends to activate a switch, or is simply exploring for a specific switch button while focusing on a higher priority task, such as driving, or has no intent to activate a switch. Accordingly, it is desirable to provide for a proximity switch arrangement which enhances the use of proximity switches by a person, such as a driver of a vehicle.
SUMMARY OF THE INVENTION
According to one aspect of the present invention, a method of activating a proximity switch is provided. The method includes the steps of generating an activation field with a proximity sensor and monitoring amplitude of a signal generated in response to the activation field. The method also includes the step of determining a differential change in the generated signal and generating an activation output when the differential signal exceeds a threshold.
According to another aspect of the present invention, a proximity switch assembly is provided. The proximity switch assembly includes a plurality of proximity switches each providing a sense activation field. The proximity switch assembly also includes control circuitry processing the activation field of each proximity switch to sense activation, said control circuitry monitoring a signal responsive to the activation field, determining a differential change in the generated signal, and generating an activation output when the differential signal exceeds a threshold.
These and other aspects, objects, and features of the present invention will be understood and appreciated by those skilled in the art upon studying the following specification, claims, and appended drawings.



BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
FIG. 1 is a perspective view of a passenger compartment of an automotive vehicle having an overhead console employing a proximity switch assembly, according to one embodiment;
FIG. 2 is an enlarged view of the overhead console and proximity switch assembly shown in FIG. 1;
FIG. 3 is an enlarged cross-sectional view taken through line III-III in FIG. 2 showing an array of proximity switches in relation to a user's finger;
FIG. 4 is a schematic diagram of a capacitive sensor employed in each of the capacitive switches shown in FIG. 3;
FIG. 5 is a block diagram illustrating the proximity switch assembly, according to one embodiment;
FIG. 6 is a graph illustrating the signal count for one channel associated with a capacitive sensor showing an activation motion profile;
FIG. 7 is a graph illustrating the signal count for two channels associated with the capacitive sensors showing a sliding exploration/hunting motion profile;
FIG. 8 is a graph illustrating the signal count for a signal channel associated with the capacitive sensors showing a slow activation motion profile;
FIG. 9 is a graph illustrating the signal count for two channels associated with the capacitive sensors showing a fast sliding exploration/hunting motion profile;
FIG. 10 is a graph illustrating the signal count for three channels associated with the capacitive sensors in an exploration/hunting mode illustrating a stable press activation at the peak, according to one embodiment;
FIG. 11 is a graph illustrating the signal count for three channels associated with the capacitive sensors in an exploration/hunting mode illustrating stable press activation on signal descent below the peak, according to another embodiment;
FIG. 12 is a graph illustrating the signal count for three channels associated with the capacitive sensors in an exploration/hunting mode illustrating increased stable pressure on a pad to activate a switch, according to a further embodiment;
FIG. 13 is a graph illustrating the signal count for three channels associated with the capacitive sensors in an exploration mode and selection of a pad based on increased stable pressure, according to a further embodiment;
FIG. 14 is a state diagram illustrating five states of the capacitive switch assembly implemented with a state machine, according to one embodiment;
FIG. 15 is a flow diagram illustrating a routine for executing a method of activating a switch of the switch assembly, according to one embodiment;
FIG. 16 is a flow diagram illustrating the processing of the switch activation and switch release;
FIG. 17 is a flow diagram illustrating logic for switching between the switch none and switch active states;
FIG. 18 is a flow diagram illustrating logic for switching from the active switch state to the switch none or switch threshold state;
FIG. 19 is a flow diagram illustrating a routine for switching between the switch threshold and switch hunting states; and
FIG. 20 is a flow diagram illustrating a virtual button method implementing the switch hunting state.



DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to a detailed design; some schematics may be exaggerated or minimized to show function overview. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.
Referring to FIGS. 1 and 2, the interior of an automotive vehicle 10 is generally illustrated having a passenger compartment and a switch assembly 20 employing a plurality of proximity switches 22 having switch activation monitoring and determination, according to one embodiment. The vehicle 10 generally includes an overhead console 12 assembled to the headliner on the underside of the roof or ceiling at the top of the vehicle passenger compartment, generally above the front passenger seating area. The switch assembly 20 has a plurality of proximity switches 22 arranged close to one another in the overhead console 12, according to one embodiment. The various proximity switches 22 may control any of a number of vehicle devices and functions, such as controlling movement of a sunroof or moonroof 16, controlling movement of a moonroof shade 18, controlling activation of one or more lighting devices such as interior map/reading and dome lights 30, and various other devices and functions. However, it should be appreciated that the proximity switches 22 may be located elsewhere on the vehicle 10, such as in the dash panel, on other consoles such as a center console, integrated into a touch screen display 14 for a radio or infotainment system such as a navigation and/or audio display, or located elsewhere onboard the vehicle 10 according to various vehicle applications.
The proximity switches 22 are shown and described herein as capacitive switches, according to one embodiment. Each proximity switch 22 includes at least one proximity sensor that provides a sense activation field to sense contact or close proximity (e.g., within one millimeter) of a user in relation to the one or more proximity sensors, such as a swiping motion by a user's finger. Thus, the sense activation field of each proximity switch 22 is a capacitive field in the exemplary embodiment and the user's finger has electrical conductivity and dielectric properties that cause a change or disturbance in the sense activation field as should be evident to those skilled in the art. However, it should also be appreciated by those skilled in the art that additional or alternative types of proximity sensors can be used, such as, but not limited to, inductive sensors, optical sensors, temperatures sensors, resistive sensors, the like, or a combination thereof. Exemplary proximity sensors are described in the Apr. 9, 2009, ATMEL® Touch Sensors Design Guide, 10620 D-AT42-04/09, the entire reference hereby being incorporated herein by reference.
The proximity switches 22 shown in FIGS. 1 and 2 each provide control of a vehicle component or device or provide a designated control function. One or more of the proximity switches 22 may be dedicated to controlling movement of a sunroof or moonroof 16 so as to cause the moonroof 16 to move in an open or closed direction, tilt the moonroof, or stop movement of the moonroof based upon a control algorithm. One or more other proximity switches 22 may be dedicated to controlling movement of a moonroof shade 18 between open and closed positions. Each of the moonroof 16 and shade 18 may be actuated by an electric motor in response to actuation of the corresponding proximity switch 22. Other proximity switches 22 may be dedicated to controlling other devices, such as turning an interior map/reading light 30 on, turning an interior map/reading light 30 off, turning a dome lamp on or off, unlocking a trunk, opening a rear hatch, or defeating a door light switch. Additional controls via the proximity switches 22 may include actuating door power windows up and down. Various other vehicle controls may be controlled by way of the proximity switches 22 described herein.
Referring to FIG. 3, a portion of the proximity switch assembly 20 is illustrated having an array of three serially arranged proximity switches 22 in close relation to one another in relation to a user's finger 34 during use of the switch assembly 20. Each proximity switch 22 includes one or more proximity sensors 24 for generating a sense activation field. According to one embodiment, each of the proximity sensors 24 may be formed by printing conductive ink onto the top surface of the polymeric overhead console 12. One example of a printed ink proximity sensor 24 is shown in FIG. 4 generally having a drive electrode 26 and a receive electrode 28 each having interdigitated fingers for generating a capacitive field 32. It should be appreciated that each of the proximity sensors 24 may be otherwise formed such as by assembling a preformed conductive circuit trace onto a substrate according to other embodiments. The drive electrode 26 receives square wave drive pulses applied at voltage VI. The receive electrode 28 has an output for generating an output voltage VO. It should be appreciated that the electrodes 26 and 28 may be arranged in various other configurations for generating the capacitive field as the activation field 32.
In the embodiment shown and described herein, the drive electrode 26 of each proximity sensor 24 is applied with voltage input VI as square wave pulses having a charge pulse cycle sufficient to charge the receive electrode 28 to a desired voltage. The receive electrode 28 thereby serve as a measurement electrode. In the embodiment shown, adjacent sense activation fields 32 generated by adjacent proximity switches 22 overlap slightly, however, overlap may not exist according to other embodiments. When a user or operator, such as the user's finger 34, enters an activation field 32, the proximity switch assembly 20 detects the disturbance caused by the finger 34 to 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 charge pulse signal associated with the corresponding signal channel. When the user's finger 34 contacts two activation fields 32, the proximity switch assembly 20 detects the disturbance of both contacted activation fields 32 via separate signal channels. Each proximity switch 22 has its own dedicated signal channel generating charge pulse counts which is processed as discussed herein.
Referring to FIG. 5, the proximity switch assembly 20 is illustrated according to one embodiment. A plurality of proximity sensors 24 are shown providing inputs to a controller 40, such as a microcontroller. The controller 40 may include control circuitry, such as a microprocessor 42 and memory 48. The control circuitry may include sense control circuitry processing the activation field of each sensor 22 to sense user activation of the corresponding switch by comparing the activation field signal to one or more thresholds pursuant to one or more control routines. It should be appreciated that other analog and/or digital control circuitry may be employed to process each activation field, determine user activation, and initiate an action. The controller 40 may employ a QMatrix acquisition method available by ATMEL®, according to one embodiment. The ATMEL acquisition method employs a WINDOWS® host C/C++ compiler and debugger WinAVR to simplify development and testing the utility Hawkeye that allows monitoring in real-time the internal state of critical variables in the software as well as collecting logs of data for post-processing.
The controller 40 provides an output signal to one or more devices that are configured to perform dedicated actions responsive to correct activation of a proximity switch. For example, the one or more devices may include a moonroof 16 having a motor to move the moonroof panel between open and closed and tilt positions, a moonroof shade 18 that moves between open and closed positions, and lighting devices 30 that may be turned on and off. Other devices may be controlled such as a radio for performing on and off functions, volume control, scanning, and other types of devices for performing other dedicated functions. One of the proximity switches 22 may be dedicated to actuating the moonroof closed, another proximity switch 22 may be dedicated to actuating the moonroof open, and a further switch 22 may be dedicated to actuating the moonroof to a tilt position, all of which would cause a motor to move the moonroof to a desired position. The moonroof shade 18 may be opened in response to one proximity switch 22 and may be closed responsive to another proximity switch 22.
The controller 40 is further shown having an analog to digital (A/D) comparator 44 coupled to the microprocessor 42. The A/D comparator 44 receives the voltage output VO from each of the proximity switches 22, converts the analog signal to a digital signal, and provides the digital signal to the microprocessor 42. Additionally, controller 40 includes a pulse counter 46 coupled to the microprocessor 42. The pulse counter 46 counts the charge signal pulses that are applied to each drive electrode of each proximity sensor, performs a count of the pulses needed to charge the capacitor until the voltage output VO reaches a predetermined voltage, and provides the count to the microprocessor 42. The pulse count is indicative of 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 provides a pulse width modulated signal to the pulse width modulated drive buffer 15 to generate a square wave pulse train VI which is applied to each drive electrode of each proximity sensor/switch 22. The controller 40 processes a control routine 100 stored in memory to monitor and make a determination as to activation of one of the proximity switches.
In FIGS. 6-13, the change in sensor charge pulse counts shown as Δ Sensor Count for a plurality of signal channels associated with a plurality of proximity switches 22, such as the three switches 22 shown in FIG. 3, is illustrated according to various examples. The change in sensor charge pulse count is the difference between an initialized referenced count value without any finger or other object 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 three proximity switches 22, generally one sense activation field at a time with overlap between adjacent activation fields 32 as the user's finger moves across the array of switches. Channel 1 is the change (Δ) in sensor charge pulse count associated with a first capacitive sensor 24, channel 2 is the change in sensor charge pulse count associated with the adjacent second capacitive sensor 24, and channel 3 is the change in 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 close proximity of a sensor 24, the finger alters the capacitance measured at the corresponding sensor 24. The capacitance is in parallel to the untouched sensor pad parasitic capacitance, and as such, measures as an offset. The user or operator induced capacitance is proportional to the user's finger or other body part dielectric constant, the surface exposed to the capacitive pad, and is inversely proportional to the distance of the user's limb to the switch button. According to one embodiment, each sensor is excited with a train of voltage pulses via pulse width modulation (PWM) electronics until the sensor is charged up to a set voltage potential. Such an acquisition method charges the receive electrode 28 to a known voltage potential. The cycle is repeated until the voltage across the measurement capacitor reaches a predetermined voltage. Placing a user's finger on the touch surface of the switch 24 introduces external capacitance that increases the amount of charge transferred each cycle, thereby reducing the total number of cycles required for the measurement capacitance to reach the predetermined voltage. The user's finger causes the change in sensor charge pulse count to increase since this value is based on the initialized reference count minus the sensor reading.
The proximity switch assembly 20 is able to recognize the user's hand motion when the hand, particularly a finger, is in close proximity to the proximity switches 22, to discriminate whether the intent of the user is to activate a switch 22, explore for a specific switch button while focusing on higher priority tasks, such as driving, or is the result of a task such as adjusting the rearview mirror that has nothing to do with actuation of a proximity switch 22. The proximity switch assembly 20 may operate in an exploration or hunting mode which enables the user to explore the keypads or buttons by passing or sliding a finger in close proximity to the switches without triggering an activation of a switch until the user's intent is determined. The proximity switch assembly 20 monitors 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, exploration of the proximity switch assembly 20 is allowed, such that users are free to explore the switch interface pad with their fingers without inadvertently triggering an event, the interface response time is fast, activation happens when the finger contacts a surface panel, and inadvertent activation of the switch is prevented or reduced.
Referring to FIG. 6, as the user's finger 34 approaches a switch 22 associated with signal channel 1, the finger 34 enters the activation field 32 associated with the sensor 24 which causes disruption to the capacitance, thereby resulting in a sensor count increase as shown by signal 50A having a typical activation motion profile. An entry ramp slope method may be used to determine whether the operator intends to press a button or explore the interface based on the slope of the entry ramp in signal 50A of the channel 1 signal rising from point 52 where signal 50A crosses the level active (LVL_ACTIVE) count up to point 54 where signal 50A crosses the level threshold (LVL_THRESHOLD) count, according to one embodiment. The slope of the entry ramp is the differential change in the generated signal between points 52 and 54 which occurred during the time period between times tth and tac. Because the numerator level threshold-level active generally changes only as the presence of gloves is detected, but is otherwise a constant, the slope can be calculated as just the time expired to cross from level active to level threshold referred to as tactive2thresold which is the difference between time tth and tac. A direct push on a switch pad typically may occur in a time period referred to tdirectpush in the range of about 40 to 60 milliseconds. If the time tactive2thresold is less than or equal to the direct push time tdirectpush, then activation of the switch is determined to occur. Otherwise, the switch is determined to be in an exploration mode.
According to another embodiment, the slope of the entry ramp may be computed as the difference in time from the time tac at point 52 to time tpk to reach the peak count value at point 56, referred to as time tactive2peak. The time tactive2peak. may be compared to a direct push peak, referred to as tdirect_push_pk which may have a value of 100 milliseconds according to one embodiment. If time tactive2peak is less than or equal to the tdirect_push_pk activation of the switch is determined to occur. Otherwise, the switch assembly operates in an exploration mode.
In the example shown in FIG. 6, the channel 1 signal is shown increasing as the capacitance disturbance increases rising quickly from point 52 to peak value at point 56. The proximity switch assembly 20 determines the slope of the entry ramp as either time period tactive2threshold or tactive2peak for the signal to increase from the first threshold point 52 to either the second threshold at point 54 or the peak threshold at point 56. The slope or differential change in the generated signal is then used for comparison with a representative direct push threshold tdirect_push or tdirect_push_pk to determine activation of the proximity switch. Specifically, when time tactive2peak is less than the tdirect_push or tactive2threshold is less than tdirect_push, activation of the switch is determined. Otherwise, the switch assembly remains in the exploration mode.
Referring to FIG. 7, one example of a sliding/exploration motion across two switches is illustrated as the finger passes or slides through the activation field of two adjacent proximity sensors shown 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 change in sensor count on signal 50A to increase at a slower rate such that a lessened differential change in the generated signal is determined. In this example, the profile of signal channel 1 experiences a change in time tactive2peak that is not less than or equal to tdirect_push, thereby resulting in entering the hunting or exploration mode. Because the tactive2threshold is indicative of a slow differential change in the generated signal, no activation of the switch button is initiated, according to one embodiment. According to another embodiment, because the time tactive2peak is not less than or equal to tdirect_push_pk, indicative of a slow differential change in a generated signal, no activation is initiated, according to another embodiment. The second signal channel labeled 50B is shown as becoming the maximum signal at transition point 58 and has a rising change in Δ sensor count with a differential change in the signal similar to that of signal 50A. As a result, the first and second channels 50A and 50B reflect a sliding motion of the finger across two capacitive sensors in the exploration mode resulting in no activation of either switch. Using the time period tactive2threshold or tactive2peak, a decision can be made to activate or not a proximity switch as its capacitance level reaches the signal peak.
For a slow direct push motion such as shown in FIG. 8, additional processing may be employed to make sure that no activation is intended. As seen in FIG. 8, the signal channel 1 identified as signal 50A is shown more slowly rising during either time period tactive2threshold or tactive2peak which would result in the entering of the exploration mode. When such a sliding/exploration condition is detected, with the time tactive2threshold greater than tdirect_push if the channel failing the condition was the first signal channel entering the exploration mode and it is still the maximum channel (channel with the highest intensity) as its capacitance drops below LVL_KEYUP_Threshold at point 60, then activation of the switch is initiated.
Referring to FIG. 9, a fast motion of a user's finger across the proximity switch assembly is illustrated with no activation of the switches. In this example, the relatively large differential change in the generated signal for channels 1 and 2 are detected, for both channels 1 and 2 shown by lines 50A and 50B, respectively. The switch assembly employs a delayed time period to delay activation of a decision until the transition point 58 at which the second signal channel 50B rises above the first signal channel 50A. The time delay could be set equal to time threshold tdirect_push_pk according to one embodiment. Thus, by employing a delay time period before determining activation of a switch, the very fast exploration of the proximity keypads prevents an unintended activation of a switch. The introduction of the time delay in the response may make the interface less responsive and may work better when the operator's finger motion is substantially uniform.
If a previous threshold event that did not result in activation was recently detected, the exploration mode may be entered automatically, according to one embodiment. As a result, once an inadvertent actuation is detected and rejected, more caution may be applied for a period of time in the exploration mode.
Another way to allow an operator to enter the exploration mode is to use one or more properly marked and/or textured areas or pads on the switch panel surface associated with the dedicated proximity switches with the function of signaling the proximity switch assembly of the intent of the operator to blindly explore. The one or more exploration engagement pads may be located in an easy to reach location not likely to generate activity with other signal channels. According to another embodiment, an unmarked, larger exploration engagement pad may be employed surrounding the entire switch interface. Such an exploration pad would likely be encountered first as the operator's hand slides across the trim in the overhead console looking for a landmark from which to start blind exploration of the proximity switch assembly.
Once the proximity sensor assembly determines whether an increase in the change in sensor count is a switch activation or the result of an exploration motion, the assembly proceeds to determine whether and how the exploration motion should terminate or not in an activation of proximity switch. According to one embodiment, the proximity switch assembly looks for a stable press on a switch button for at least a predetermined amount of time. In one specific embodiment, the predetermined amount of time is equal to or greater than 50 milliseconds, and more preferably about 80 milliseconds. Examples of the switch assembly operation employing a stable time methodology is illustrated in FIGS. 10-13.
Referring to FIG. 10, the exploration of three proximity switches corresponding to signal channels 1-3 labeled as signals 50A-50C, respectively, is illustrated while a finger slides across first and second switches in the exploration mode and then activates the third switch associated with signal channel 3. As the finger explores the first and second switches associated with channels 1 and 2, no activation is determined due to no stable signal on lines 50A and 50B. The signal on line 50A for channel 1 begins as the maximum signal value until channel 2 on line 50B becomes the maximum value and finally channel 3 becomes a maximum value. Signal channel 3 is shown having a stable change in sensor count near the peak value for a sufficient time period tstable such as 80 milliseconds which is sufficient to initiate activation of the corresponding proximity switch. When the level threshold trigger condition has been met and a peak has been reached, the stable level method activates the switch after the level on the switch is bound in a tight range for at least the time period tstable. This allows the operator to explore the various proximity switches and to activate a desired switch once it is found by maintaining position of the user's finger in proximity to the switch for a stable period of time tstable.
Referring to FIG. 11, another embodiment of the stable level method is illustrated in which the third signal channel on line 50C has a change in sensor count that has a stable condition on the descent of the signal. In this example, the change in sensor count for the third channel exceeds the level threshold and has a stable press detected for the time period tstable such that activation of the third switch is determined.
According to another embodiment, the proximity switch assembly may employ a virtual button method which looks for an initial peak value of change in sensor count while in the exploration mode followed by an additional sustained increase in the change in sensor count to make a determination to activate the switch as shown in FIGS. 12 and 13. In FIG. 12, the third signal channel on line 50C rises up to an initial peak value and then further increases by a change in sensor count Cvb. This is equivalent to a user's finger gently brushing the surface of the switch assembly as it slides across the switch assembly, reaching the desired button, and then pressing down on the virtual mechanical switch such that the user's finger presses on the switch contact surface and increases the amount of volume of the finger closer to the switch. The increase in capacitance is caused by the increased surface of the fingertip as it is compressed on the pad surface. The increased capacitance may occur immediately following detection of a peak value shown in FIG. 12 or may occur following a decline in the change in sensor count as shown in FIG. 13. The proximity switch assembly detects an initial peak value followed by a further increased change in sensor count indicated by capacitance Cvb at a stable level or a stable time period tstable. A stable level of detection generally means no change in sensor count value absent noise or a small change in sensor count value absent noise which can be predetermined during calibration.
It should be appreciated that a shorter time period tstable may result in accidental activations, especially following a reversal in the direction of the finger motion and that a longer time period tstable may result in a less responsive interface.
It should also be appreciated that both the stable value method and the virtual button method can be active at the same time. In doing so, the stable time tstable can be relaxed to be longer, such as one second, since the operator can always trigger the button using the virtual button method without waiting for the stable press time-out.
The proximity switch assembly may further employ robust noise rejection to prevent annoying inadvertent actuations. For example, with an overhead console, accidental opening and closing of the moonroof should be avoided. Too much noise rejection may end up rejecting intended activations, which should be avoided. One approach to rejecting noise is to look at whether multiple adjacent channels are reporting simultaneous triggering events and, if so, selecting the signal channel with the highest signal and activating it, thereby ignoring all other signal channels until the release of the select signal channel.
The proximity switch assembly 20 may include a signature noise rejection method based on two parameters, namely a signature parameter that is the ratio between the channel between the highest intensity (max_channel) and the overall cumulative level (sum_channel), and the dac parameter which is the number of channels that are at least a certain ratio of the max_channel. In one embodiment, the dac αdac=0.5. The signature parameter may be defined by the following equation:




  signature
  =
  
    
      max_channel
      sum_channel
    
    =
    
      
        
          
            max
            
              
                i
                =
                0
              
              ,
              n
            
          
          ⁢
          
            channel
            i
          
        
        
          
            ∑
            
              
                i
                =
                0
              
              ,
              n
            
          
          ⁢
          
            
          
          ⁢
          
            channel
            i
          
        
      
      .
    
  




The dac parameter may be defined by the following equation:

dac=∀channelsi>αdac max_channel.

Depending on dac, for a recognized activation not to be rejected, the channel generally must be clean, i.e., the signature must be higher than a predefined threshold. In one embodiment, αdac=1=0.4, and αdac=2=0.67. If the dac is greater than 2, the activation is rejected according to one embodiment.
When a decision to activate a switch or not is made on the descending phase of the profile, then instead of max_channel and sum_channel their peak values peak_max_channel and peak_sum_channel may be used to calculate the signature. The signature may have the following equation:




  signature
  =
  
    
      
        peak_max
        ⁢
        _channel
      
      
        peak_sum
        ⁢
        _channel
      
    
    =
    
      
        
          max
          ⁡
          
            (
            
              max_channel
              ⁢
              
                (
                t
                )
              
            
            )
          
        
        
          max
          ⁡
          
            (
            
              sum_channel
              ⁢
              
                (
                t
                )
              
            
            )
          
        
      
      .
    
  




A noise rejection triggers hunting mode may be employed. When a detected activation is rejected because of a dirty signature, the hunting or exploration mode should be automatically engaged. Thus, when blindly exploring, a user may reach with all fingers extended looking to establish a reference frame from which to start hunting. This may trigger multiple channels at the same time, thereby resulting in a poor signature.
Referring to FIG. 14, a state diagram is shown for the proximity switch assembly 20 in a state machine implementation, according to one embodiment. The state machine implementation is shown having five states including SW_NONE state 70, SW_ACTIVE state 72, SW_THRESHOLD state 74, SW_HUNTING state 76 and SWITCH_ACTIVATED state 78. The SW_NONE state 70 is the state in which there is no sensor activity 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 point in time. The SW_THRESHOLD state is the state in which activity as determined by the sensor is high enough to warrant activation, hunting/exploration, or casual motion of the switch assembly. The SW_HUNTING state 76 is entered when the activity pattern as determined by the switch assembly is compatible with the exploration/hunting interaction. The SWITCH_ACTIVATED state 78 is the state in which activation of a switch has been identified. In the SWITCH_ACTIVATED state 78, the switch button will remain active and no other selection will be possible until the corresponding switch is released.
The state of the proximity switch assembly 20 changes depending upon the detection and processing of the sensed signals. When in the SW_NONE state 70, the system 20 may advance to the SW_ACTIVE state 72 when some activity detected by one or more sensors. If enough activity to warrant either activation, hunting or casual motion is detected, the system 20 may proceed directly to the SW_THRESHOLD state 74. When in the SW_THRESHOLD state 74, the system 20 may proceed to the SW_HUNTING state 76 when a pattern indicative of exploration is detected or may proceed directly to switch activated state 78. When a switch activation is in the SW_HUNTING state, an activation of the switch may be detected to change to the SWITCH_ACTIVATED state 78. If the signal is rejected and inadvertent action is detected, the system 20 may return to the SW_NONE state 70.
Referring to FIG. 15, the main method 100 of monitoring and determining when to generate an activation output with the proximity switch arrangement is shown, according to one embodiment. Method 100 begins at step 102 and proceeds to step 104 to perform an initial calibration which may be performed once. The calibrated signal channel values are computed from raw channel data and calibrated reference values by subtracting the reference value from the raw data in step 106. Next, at step 108, from all signal channel sensor readings, the highest count value referenced as max_channel and the sum of all channel sensor readings referred to as sum_channel are calculated. In addition, the number of active channels is determined. At step 110, method 100 calculates the recent range of the max_channel and the sum_channel to determine later whether motion is in progress or not.
Following step 110, method 100 proceeds to decision step 112 to determine if any of the switches are active. If no switch is active, method 100 proceeds to step 114 to perform an online real-time calibration. Otherwise, method 116 processes the switch release at step 116. Accordingly, if a switch was already active, then method 100 proceeds to a module where it waits and locks all activity until its release.
Following the real-time calibration, method 100 proceeds to decision step 118 to determine if there is any channel lockout indicative of recent activation and, if so, proceeds to step 120 to decrease the channel lockout timer. If there are no channel lockouts detected, method 100 proceeds to decision step 122 to look for a new max_channel. If the current max_channel has changed such that there is a new max_channel, method 100 proceeds to step 124 to reset the max_channel, sum the ranges, and set the threshold levels. Thus, if a new max_channel is identified, the method resets the recent signal ranges, and updates, if needed, the hunting/exploration parameters. If the switch status is less than SW_ACTIVE, then the hunting/exploration flag is set equal to true and the switch status is set equal to SW_NONE. If the current max_channel has not changed, method 100 proceeds to step 126 to process the max_channel naked (no glove) finger status. This may include processing the logic between the various states as shown in the state diagram of FIG. 14.
Following step 126, method 100 proceeds to decision step 128 to determine if any switch is active. If no switch activation is detected, method 100 proceeds to step 130 to detect a possible glove presence on the user's hand. The presence of a glove may be detected based on a reduced change in capacitance count value. Method 100 then proceeds to step 132 to update the past history of the 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 ending at step 136.
When a switch is active, a process switch release routine is activated which is shown in FIG. 16. The process switch release routine 116 begins at step 140 and proceeds to decision step 142 to determine if the active channel is less than LVL_RELEASE and, if so, ends at step 152. If the active channel is less than the LVL_RELEASE then routine 116 proceeds to decision step 144 to determine if the LVL_DELTA_THRESHOLD is greater than 0 and, if not, proceeds to step 146 to raise the threshold level if the signal is stronger. This may be achieved by decreasing LVL_DELTA_THRESHOLD. Step 146 also sets the threshold, release and active levels. Routine 116 then proceeds to step 148 to reset the channel max and sum history timer for long stable signal hunting/exploration parameters. The switch status is set equal to SW_NONE at step 150 before ending at step 152. To exit the process switch release module, the signal on the active channel has to drop below LVL_RELEASE, which is an adaptive threshold that will change as glove interaction is detected. As the switch button is released, all internal parameters are reset and a lockout timer is started to prevent further activations before a certain waiting time has elapsed, such as 100 milliseconds. Additionally, the threshold levels are adapted in function of the presence of gloves or not.
Referring to FIG. 17, a routine 200 for determining the status change from SW_NONE state to SW_ACTIVE state is illustrated, 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 the max_channel is greater than LVL_ACTIVE. If the max_channel is greater than LVL_ACTIVE, then the proximity switch assembly changes state from SW_NONE state to SW_ACTIVE state and ends at step 210. If the max_channel is not greater than LVL_ACTIVE, the routine 200 checks for whether to reset the hunting flag at step 208 prior to ending at step 210. Thus, the status changes from SW_NONE state to SW_ACTIVE state when the max_channel triggers above LVL_ACTIVE. If the channels stays below this level, after a certain waiting period, the hunting flag, if set, gets reset to no hunting, which is one way of departing from the hunting mode.
Referring to FIG. 18, a method 220 for processing the state of the SW_ACTIVE state changing to either SW_THRESHOLD state or SW_NONE state is illustrated, 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 the max_channel is less than LVL_ACTIVE and, if so, proceeds to step 228 to change the switch status to SW_NONE. Accordingly, the status of the state machine moves from the SW_ACTIVE state to SW_NONE state when the max_channel signal drops below LVL_ACTIVE. A delta value may also be subtracted from LVL_ACTIVE to introduce some hysteresis. If the max_channel is greater than the LVL_THRESHOLD, then routine 220 proceeds to decision step 230 to determine if a recent threshold event or a glove has been detected and, if so, sets the hunting on flag equal to true at step 232. At step 234, method 220 switches the status to SW_THRESHOLD state before ending at step 236. Thus, if the max_channel triggers above the LVL_THRESHOLD, the status changes to SW_THRESHOLD state. If gloves are detected or a previous threshold event that did not result in activation was recently detected, then the hunting/exploration mode may be entered automatically.
Referring to FIG. 19, a method 240 of determining activation of a switch from the SW_THRESHOLD state is illustrated, according to one embodiment. Method 240 begins at step 242 to process the SW_THRESHOLD state and proceeds to decision block 244 to determine if the signal is stable or if the signal channel is at a peak and, if not, ends at step 256. If either the signal is stable or the signal channel is at a peak, then method 240 proceeds to decision step 246 to determine if the hunting or exploration mode is active and, if so, skips to step 250. If the hunting or exploration mode is not active, method 240 proceeds to decision step 248 to determine if the signal channel is clean and fast active is greater than a threshold and, if so, sets the switch active equal to the maximum channel at step 250. Method 240 proceeds to decision block 252 to determine if there is a switch active and, if so, ends at step 256. If there is no switch active, method 240 proceeds to step 254 to initialize the hunting variables SWITCH_STATUS set equal to SWITCH_HUNTING and PEAK_MAX_BASE equal to MAX_CHANNELS, prior to ending at step 256.
In the SW_THRESHOLD state, no decision is taken until a peak in MAX_CHANNEL is detected. Detection of the peak value is conditioned on either a reversal in the direction of the signal, or both the MAX_CHANNEL and SUM_CHANNEL remaining stable (bound in a range) for at least a certain interval, such as 60 milliseconds. Once the peak is detected, the hunting flag is checked. If the hunting mode is off, the entry ramp slope method is applied. If the SW_ACTIVE to SW_THRESHOLD was a less than a threshold such as 16 milliseconds, and the signature of noise rejection method indicates it as a valid triggering event, then the state is changed to SWITCH_ACTIVE and the process is transferred to the PROCESS_SWITCH_RELEASE module, otherwise the hunting flag is set equal to true. If the delayed activation method is employed instead of immediately activating the switch, the state is changed to SW_DELAYED_ACTIVATION where a delay is enforced at the end of which, if the current MAX_CHANNEL index has not changed, the button is activated.
Referring to FIG. 20, a virtual button method implementing the SW_HUNTING state is illustrated, according to one embodiment. The method 260 begins at step 262 to process the SW_HUNTING state and proceeds to decision step 264 to determine if the MAX_CHANNEL has dropped below the LVL_KEYUP_THRESHOLD and, if so, sets the MAX_PEAK_BASE equal to MIN (MAX_PEAK_BASE, MAX_CHANNEL) at step 272. If the MAX_CHANNEL has dropped below the LVL_KEYUP_THRESHOLD, then method 260 proceeds to step 266 to employ the first channel triggering hunting method to check whether the event should trigger the button activation. This is determined by determining if the first and only channel is traversed and the signal is clean. If so, method 260 sets the switch active equal to the maximum channel at step 270 before ending at step 282. If the first and only channel is not traversed or if the signal is not clean, method 260 proceeds to step 268 to give up and determine an inadvertent actuation and to set the SWITCH_STATUS equal to SW_NONE state before ending at step 282.
Following step 272, method 260 proceeds to decision step 274 to determine if the channel clicked. This can be determined by whether MAX_CHANNEL is greater than MAX_PEAK_BASE plus delta. If the channel has clicked, method 260 proceeds to decision step 276 to determine if the signal is stable and clean and, if so, sets the switch active state to the maximum channel at step 280 before ending at step 282. If the channel has not clicked, method 260 proceeds to decision step 278 to see if the signal is long, stable and clean, and if so, proceeds to step 280 to set the switch active equal to the maximum channel before ending at step 282.
Accordingly, the determination routine advantageously determines activation of the proximity switches. The routine advantageously allows for a user to explore the proximity switch pads which can be particularly useful in an automotive application where driver distraction can be avoided.
It is to be understood that variations and modifications can be made on the aforementioned structure without departing from the concepts of the present invention, and further it is to be understood that such concepts are intended to be covered by the following claims unless these claims by their language expressly state otherwise.

## Claims

1. A method of activating a proximity switch comprising:
generating an activation field for each of a plurality of proximity sensors;
monitoring with a controller amplitude of a signal generated in response to each of the activation fields;
providing an exploration mode;
determining a base level at a peak value or a substantially stable amplitude of one signal during a user touch interaction in the exploration mode; and
generating an activation output when the one signal subsequently is substantially stable and exceeds the base level by a differential change in the signal during the same user touch interaction.

2. The method of claim 1 further comprising determining a first value at the base level, determining a second value at a threshold, and determining the differential change in the generated one signal based on a difference between the first value and the second value.

3. The method of claim 2, wherein the threshold comprises a signal threshold for determining activation of the switch.

4. The method of claim 2, wherein the threshold comprises the peak value of the one signal during the user touch interaction.

5. The method of claim 2, wherein the first value comprises a first time and the second value comprises a second time, wherein the differential change in the generated signal comprises the difference in time between the first time and the second time.

6. The method of claim 5, wherein the differential change in generated signal is compared to a predetermined time period, and wherein an activation output is generated when the differential signal exceeds the difference in time.

7. The method of claim 1, wherein a plurality of activation fields are generated for the plurality of proximity sensors, and wherein the largest amplitude signal associated with the plurality of activation fields is processed to determine activation of one of the proximity sensors.

8. The method of claim 7, wherein the method further processes the plurality of activation fields to determine interaction with the plurality of sensors which enables a user to explore the plurality of proximity sensors in the exploration mode without activating the proximity switch.

9. The method of claim 1, wherein the proximity switch is installed on a vehicle for use by a passenger in the vehicle.

10. The method of claim 1, wherein the proximity switch comprises a capacitive switch comprising one or more capacitive sensors.

11. A proximity switch assembly comprising:
a plurality of proximity switches each comprising a proximity sensor providing a sense activation field; and
control circuitry processing the activation field of each proximity switch to sense activation, said control circuitry monitoring a signal responsive to the activation field, detecting a first peak value or a substantially stable amplitude of the largest signal during a user touch interaction while in an exploration mode, establishing a base level at the determined peak value or stable amplitude, and generating an activation output when the signal is substantially stable and is greater than the base level by a differential signal during the same user touch interaction.

12. The switch assembly of claim 11, wherein the control circuitry determines a first value at the base level, determines a second value at a threshold, and determines the differential change in the generated signal based on a difference between the first value and the second value.

13. The switch assembly of claim 12, wherein the threshold comprises a signal threshold for determining activation of the switch.

14. The switch assembly of claim 12, wherein the second threshold comprises the peak value of the signal during the user touch interaction.

15. The switch assembly of claim 12, wherein the first value comprises a first time and the second value comprises a second time, wherein the differential change in the generated signal comprises the difference in time between the first time and the second time.

16. The switch assembly of claim 15, wherein the differential change in generated signal is compared to a predetermined time period, and wherein an activation output is generated when the differential signal exceeds the difference in time.

17. The switch assembly of claim 11, wherein a plurality of activation fields are generated for a plurality of proximity sensors, and wherein a largest amplitude signal associated with the plurality of activation fields is processed to determine activation of one of the proximity sensors.

18. The switch assembly of claim 11, wherein the plurality of proximity switches are installed in a vehicle for use by a passenger of the vehicle.

19. The switch assembly of claim 11, wherein the plurality of proximity switches comprises a plurality of capacitive switches each comprising one or more capacitive sensors.

20. A method of activating a proximity switch comprising:
generating an activation field with a plurality of proximity sensors;
monitoring with a controller amplitude of a signal generated in response to each of the activation fields;
determining a base level at a peak value of one signal during a user touch interaction in an exploration mode; and
generating an activation output when the one signal subsequently exceeds the base level by a differential change in the signal during the same user touch interaction.