Operation detection device

Abstract

Provided is an operation detection device that reduces the influence of noise and has a high detection accuracy.　This operation detection device comprises an electrostatic sensor, a drive circuit that outputs a drive signal to the electrostatic sensor for the purpose of detecting an operation on the electrostatic sensor by an operator, and a control unit for determining whether there has been such an operation on the basis of electrostatic sensor output values and controlling the drive waveform of the drive signal. The control unit controls the drive waveform at a period that is a prescribed period including a detection period in which operation detection occurs and a non-detection period in which operation detection does not occur. The drive waveform has a shape based on a periodic function that repeats a constant pattern across the entire period. The control unit changes the phase of the drive signal during the detection period by controlling the drive waveform characteristic during the non-detection period.

Description

[Technical field]

[0001] The present invention relates to an operation detection device. [Background technology]

[0002] Conventionally, there has been a control device that controls a display device having a plurality of gate lines and a plurality of common electrodes shared for image display and touch detection, characterized in that the control device comprises a first acquisition unit that acquires a specific frequency to be avoided, a second acquisition unit that acquires a drive frequency of a gate signal supplied to the plurality of gate lines, and a change unit that changes the drive frequency when the acquired specific frequency and the drive frequency satisfy a change condition (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2020-158524 Summary of the Invention [Problem to be solved by the invention]

[0004] However, there is no description of the period during which the drive frequency is changed for the conventional control device. If the drive frequency is changed during a period in which the presence or absence of an operation is detected based on electrostatic capacitance, such as touch detection, the characteristics of the detection circuit may change, resulting in a decrease in detection accuracy.

[0005] In addition, in a device that detects the presence or absence of an operation based on electrostatic capacitance, if there is noise of a frequency that should be avoided and is relatively close to the drive frequency, and in order to realize the detection of the frequency to be avoided using the detection device in the same way as the judgment of the presence or absence of an operation, it is necessary to reduce the influence of such noise. However, if the detection value based on the noise and the detection value based on the touch are similar, the detection device may erroneously determine that a touch has been performed when it picks up the noise.

[0006] Therefore, an object of the present invention is to provide an operation detection device that reduces the influence of noise and has high detection accuracy. [Means for solving the problem]

[0007] An operation detection device according to an embodiment of the present invention includes an electrostatic sensor, a drive circuit that outputs a drive signal to the electrostatic sensor to detect an operator's operation of the electrostatic sensor, and a control unit that determines whether or not the operation is performed based on an output value of the electrostatic sensor and controls the drive waveform of the drive signal, wherein the control unit controls the drive waveform with a period of a predetermined period including a detection period in which the operation is detected and a non-detection period in which the operation is not detected, and the drive waveform has a shape based on a periodic function that repeats a certain pattern throughout the entire period, and the control unit changes the phase of the drive signal in the detection period by controlling the characteristics of the drive waveform in the non-detection period. Effect of the Invention

[0008] It is possible to provide an operation detection device that reduces the influence of noise and has high detection accuracy. [Brief description of the drawings]

[0009] [Figure 1] 1 is a diagram illustrating an example of an operation detection device 100 according to an embodiment. [Diagram 2] 1 is a diagram illustrating an example of a configuration of an operation detection device 100. FIG. [Diagram 3] FIG. 4 is a diagram illustrating an example of a sensing period. [Figure 4] 11 is a diagram showing an example of an output waveform of a detection circuit 121 and a detection value of a control unit 130 during a sensing period. FIG. [Diagram 5] FIG. 13 is a diagram showing an example of a time change in a change ΔAD of a detection value in a state where an operator is not performing an operation and there is noise. [Figure 6] 1 is a diagram showing an example of a composite wave in which a drive signal of an electrostatic sensor is superimposed on noise having a frequency close to the frequency of the drive signal; [Figure 7] 7 is a diagram showing an example of a detection value obtained from the composite wave shown in FIG. 6. FIG. [Figure 8] 10A and 10B are diagrams illustrating an example of a method for distinguishing noise having a frequency close to the drive frequency of a drive signal. [Figure 9] 11 is a diagram showing an example of a detection value obtained from a composite wave of a drive signal and noise; FIG. [Figure 10] 5A and 5B are diagrams illustrating an example of a relationship between a phase difference between a drive signal and noise and a composite wave. [Figure 11] 11A and 11B are diagrams illustrating an example of a method for shifting the phase difference of noise. [Figure 12] 10 is a diagram illustrating an example of a period (frequency change period) in which frequency hopping is performed in a sensing cycle. FIG. [Figure 13] 11A and 11B are diagrams illustrating an example of the effect of randomly changing the phase difference between a drive signal and noise by frequency hopping. [Figure 14] 13A and 13B are diagrams illustrating an example of a method for adjusting a phase difference according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment to which the operation detection device of the present invention is applied will be described.

[0011] <Embodiment> Fig. 1 is a diagram showing an example of an operation detection device 100 according to an embodiment. As shown in Fig. 1, the operation detection device 100 is mounted on a vehicle, for example, and has an electrostatic sensor 110 mounted therein. The operation detection device 100 detects, for example, whether a driver's hand H is touching the electrostatic sensor 110. Determining whether the driver's hand H is touching the electrostatic sensor 110 is equivalent to determining whether the driver is operating the operation detection device 100.

[0012] For the sake of generalization, hereinafter, the driver of the vehicle will be referred to as the operator of the operation detection device 100. The operation detection device 100 is not limited to use in a vehicle. In the following, an operation detection device 100 capable of determining whether or not an operator is touching an object on which an electrostatic sensor 110 is provided will be described. The operator's touching an object on which an electrostatic sensor 110 is provided will be referred to as an operation by the operator.

[0013] 2 is a diagram showing an example of the configuration of the operation detection device 100. The operation detection device 100 includes an electrostatic sensor 110, a circuit unit 120, and a control unit .

[0014] The electrostatic sensor 110 has a capacitor Cs between the sensor electrode and a GND potential. In order to show a state in which an operator is performing an operation with a hand H, a capacitor C1 corresponding to the hand H is connected to the electrostatic sensor 110. The electrostatic sensor 110 is connected to a detection circuit 121 of the circuit section 120.

[0015] The circuit section 120 has a detection circuit 121 and a drive circuit 122. The detection circuit 121 detects the capacitance of the electrostatic sensor 110, filters and amplifies the detected capacitance, and outputs the detected capacitance to the control section 130. The drive circuit 122 outputs a drive waveform having a shape based on a periodic function that repeats a certain pattern over the entire period of a sine wave, square wave, or the like, in a section having a predetermined period as a cycle, to the electrostatic sensor 110. As an example, a sine wave-shaped AC waveform is output, and the detection circuit 121 performs filtering and amplification on the electric signal obtained via the electrostatic sensor 110.

[0016] The control unit 130 is realized, for example, by a microcomputer. The microcomputer is realized by a computer including a central processing unit (CPU), a random access memory (RAM), a read only memory (ROM), an input / output interface, an internal bus, and the like.

[0017] The control unit 130 has an AD (Analog to Digital) conversion unit 131 and a counter 132. The AD conversion unit 131 and the counter 132 are functional blocks showing the functions of a program executed by the control unit 130.

[0018] The AD conversion unit 131 converts the output of the detection circuit 121 into a digital value. The output of the AD conversion unit 131 is a detection value of the capacitance of the electrostatic sensor 110. The counter 132 counts a change ΔAD in the output of the AD conversion unit 131, and outputs it as a change ΔAD in the detection value. Note that the circuit unit 120 and the control unit 130 are realized, for example, by an IC (Integrated Circuit) chip.

[0019] 3 is a diagram showing an example of a sensing period. The sensing period is a period in which the operation detection device 100 detects the capacitance of the electrostatic sensor 110, and is composed of a non-sensing period and a sensing period. The non-sensing period is an example of a non-detection period, and the sensing period is an example of a detection period. The period of one sensing period is an example of a predetermined period including a detection period and a non-detection period. The non-sensing period is, for example, a period in which the detection value detected during the sensing period is processed.

[0020] As an example, one sensing cycle is 10 milliseconds (msec), the non-sensing period is a predetermined period from the start of the cycle, and the sensing period is the remaining period after the non-sensing period ends. The operation detection device 100 detects the capacitance of the electrostatic sensor 110 during the sensing period, and does not detect the capacitance during the non-sensing period.

[0021] Fig. 4 is a diagram showing an example of the output waveform of the detection circuit 121 during the sensing period and the detection value of the control unit 130. The output waveform and detection value shown in Fig. 4 are in a state where the operator is not performing an operation (a state where the operation detection device 100 is not detecting the operator's hand H, etc.) and where there is no noise.

[0022] 4, the output waveform of the detection circuit 121 during a series of sensing periods is the same, and the detection value generated by the control unit 130 through AD conversion is also constant. In a noise-free state, a constant detection value is obtained like this. When the operator performs an operation, the output waveform of the electrostatic IC 120 changes, and the detection value also changes.

[0023] Fig. 5 is a diagram showing an example of a change over time in the change ΔAD of the detection value when the operator is not performing an operation and there is noise. In Fig. 5, the horizontal axis is time (seconds), and the characteristics over a period of 4 seconds are shown as an example. The vertical axis showing the change ΔAD indicates a threshold value used by the control unit 130 to determine whether or not an operation is being performed. When the change ΔAD becomes equal to or greater than the threshold value, it is determined that an operation is being performed. The characteristics shown in Fig. 5 will be described as being obtained not in the operation detection device 100 but in a comparative operation detection device. The comparative operation detection device has an electrostatic sensor 110 and a circuit unit 120, similar to the operation detection device 100.

[0024] Here, there is a noise source near the comparative operation detection device, and the drive frequency of the drive signal of the drive circuit 122 and the noise frequency are so close that they affect the detection of the capacitance in the electrostatic sensor 110 and the detection circuit 121.

[0025] When there is noise even if the operator is not performing an operation, the electrostatic sensor 110 picks up the noise, and the change ΔAD in the detection value fluctuates. When the operator is not performing an operation and there is no noise, the change ΔAD in the detection value becomes zero. Furthermore, when the frequency of the noise is close to the drive frequency of the drive signal, the change ΔAD in the detection value changes slowly at a pace of about 2 to 3 times per second, as shown in FIG. 5. In this way, when there are changes of about 2 to 3 times per second, the characteristics become similar to a state in which the operator performs an operation in a noise-free environment, and there is a risk of erroneously detecting that an operation has been performed.

[0026] Fig. 6 is a diagram showing a composite wave in which a drive signal and noise are superimposed. When the drive signal shown in Fig. 6(A) and the noise shown in Fig. 6(B) are superimposed, it becomes as shown in Fig. 6(C), and the composite wave becomes a waveform like that which has been modulated by AM (Amplitude Modulation) as shown in Fig. 6(D).

[0027] FIG. 7 is a diagram showing an example of a detection value obtained by the composite wave shown in FIG. 6. The composite wave is obtained as an output waveform of the detection circuit 121. As shown in FIG. 7, the detection value obtained from the composite wave of the drive signal and noise changes in a sinusoidal shape over time. If there is noise even when the operator is not performing an operation, the noise is picked up by the electrostatic sensor 110, and the change ΔAD in the detection value fluctuates, for example, as shown in FIG. 7. In this way, if the change ΔAD in the detection value fluctuates at a relatively large time interval, there is a risk of erroneously detecting that an operation has been performed.

[0028] It would be ideal if the drive signal and noise could be distinguished inside circuit section 120 and removed using a filter or the like, but if there is noise with a frequency close to the drive frequency of the drive signal of drive circuit 122, it is difficult to remove the noise.

[0029] Therefore, in the embodiment of the operation detection device 100, when noise having a frequency close to the drive frequency of the drive signal occurs, the detection value obtained during the sensing period of the sensing cycle changes in a pattern that cannot occur due to human operation, making it possible to distinguish between the detection value based only on human operation and a composite wave including noise having a frequency close to the drive frequency of the drive signal.

[0030] Fig. 8 is a diagram for explaining an example of a method for distinguishing noise having a frequency close to the drive frequency of the drive signal. Fig. 8(A) shows the same waveform as the time change of the change amount ΔAD of the detection value shown in Fig. 7. The time change of the change amount ΔAD of the detection value shown in Fig. 8(A) is obtained when there is noise having a frequency very close to the drive frequency of the drive signal when the operator is not performing an operation.

[0031] In the operation detection device 100 of the embodiment, when noise having a frequency close to the drive frequency of the drive signal occurs, the change amount ΔAD of the detection value changes randomly as shown in Fig. 8(B) as an example. In Fig. 8(B), the horizontal axis represents time (milliseconds), and the change amount ΔAD changes randomly every 10 milliseconds.

[0032] In this way, the change amount ΔAD that changes randomly every 10 milliseconds cannot be realized by human operation. Even if a human moves their hand quickly, they can only move it a few times per second. For this reason, the operation detection device 100 of the embodiment distinguishes the change in the change amount ΔAD due to noise from the change in the change amount ΔAD due to human operation by determining whether the change in the change amount ΔAD is a possible change due to human operation.

[0033] Fig. 9 is a diagram showing an example of a detection value obtained from a composite wave of a drive signal and noise. The composite wave is obtained as an output waveform of the detection circuit 121. The detection value is equal to Fig. 8(B). When the detection value obtained from the composite wave of a drive signal and noise changes over time as shown in Fig. 9, the change ΔAD in the detection value fluctuates randomly. Since the change ΔAD that fluctuates randomly in a period of several tens of milliseconds or less cannot be realized by human operation in this way, it is possible to distinguish that the change in the change ΔAD is due to noise.

[0034] Fig. 10 is a diagram for explaining an example of the relationship between the phase difference between the drive signal and noise and the composite wave. The composite wave shown in Fig. 10 is equal to the composite wave shown in Fig. 9. In Fig. 10, the upper side shows the composite wave, and the lower side shows the waveforms and phase difference of the drive signal and noise.

[0035] As an example, the phase difference of the noise with respect to the drive signal is 135 degrees, -160 degrees, -15 degrees, -180 degrees, -160 degrees, 120 degrees, -180 degrees, 15 degrees, 135 degrees, -160 degrees, and 20 degrees every 10 milliseconds. In this way, if the phase difference of the noise with respect to the drive signal can be shifted randomly, the composite wave of the drive signal and noise can be made randomly different for each sensing period, and the change amount ΔAD can be changed randomly.

[0036] Fig. 11 is a diagram for explaining an example of a method for shifting the phase difference of noise with respect to a drive signal. Fig. 11 shows an example of waveforms of the drive signal and noise output by the circuit unit 120 of the operation detection device 100. Here, the drive frequency of the drive signal is temporarily changed by frequency hopping.

[0037] The drive frequency of the drive signal is temporarily changed to a different frequency by frequency hopping. For ease of understanding, it is assumed that the phases of the drive signal and noise are aligned at time t1, just before frequency hopping. From time t1 over period T1, the drive frequency of the drive signal is changed to a different frequency by frequency hopping. The noise frequency does not change. At time t2, when period T1 ends, the phases of the drive signal and noise are shifted. After time t2, the drive frequency of the drive signal is returned to the original frequency.

[0038] By controlling the driving circuit 122, it is possible to change the driving frequency of the driving signal in this way. Since the driving circuit 122 can change only the frequency without changing the amplitude, distortion is unlikely to occur, and the impact of worsening radiation noise when changing the frequency is minor. At times t1 and t2, the frequency can be changed while maintaining the continuity of the waveform of the driving signal.

[0039] It should be noted that the same effect can be obtained regardless of the frequency, as long as the frequency is hopped to a frequency different from the drive frequency of the drive signal before frequency hopping and from the frequency of the noise.

[0040] 12 is a diagram for explaining an example of a period (frequency change period) during which frequency hopping is performed in a sensing cycle. The control unit 130 performs AD conversion on the output of the detection circuit 121 during the sensing period of the sensing cycle, and calculates the change ΔAD of the detection value. For this reason, it is only necessary to shift the phase difference between the drive signal and noise during the sensing period. Since the sensing period is a period during which the change ΔAD is calculated, it is not preferable to perform frequency hopping during the sensing period.

[0041] For this reason, frequency hopping is performed during the non-sensing period, as shown in Fig. 12. In this way, the phase difference between the drive signal and noise during the sensing period can be shifted, and since there is no change in the waveform of the drive signal during the sensing period, changing the drive frequency does not affect the change in the detection value ΔAD.

[0042] Based on this idea, the operation detection device 100 performs frequency hopping within a non-sensing period in each sensing cycle, for example, so that the phase difference between the drive signal and noise changes randomly within the sensing period in each sensing cycle.

[0043] In this way, when noise occurs at a frequency close to the drive frequency of the drive signal, the phase difference between the drive signal and the noise can be changed randomly, as shown in FIG. 10, and the detection value ΔAD can be changed quickly and randomly in a way that cannot be achieved by human operation.

[0044] By detecting such a change in the detection value ΔAD, it is possible to distinguish the change in the change ΔAD due to noise from the change in the change ΔAD due to human operation.

[0045] The frequency change period during which the frequency is changed in frequency hopping during the non-sensing period may be set as follows: The phase difference between the drive signal and noise at time t1 in Fig. 11 immediately before frequency hopping is performed may be adjusted within a range from 0 degrees to 360 degrees.

[0046] In addition, if there is a period between the end of the frequency change period and the start of the sensing period, the phase difference between the drive signal and noise at the end of the frequency change period is strictly different from the phase difference between the drive signal and noise at the start of the sensing period; however, the difference in frequency between the drive signal and the noise is so small that it can be ignored.

[0047] Fig. 13 is a diagram for explaining an example of the effect of randomly changing the phase difference between the drive signal and noise by frequency hopping. For comparison, Fig. 13(A) shows the change ΔAD in the detection value when frequency hopping of the drive signal is not performed. The change ΔAD is ±1500 in count value.

[0048] Figure 13(B) shows the change ΔAD in the detected value when frequency hopping of the drive signal is performed. It can be seen that the change ΔAD changes randomly and frequently. Since human operation cannot achieve such quick random changes, it is possible to determine that the change ΔAD has changed due to noise. The change ΔAD is ±1500 in count value.

[0049] As described above, by changing the driving frequency of the driving signal by frequency hopping during the non-sensing period, the phase difference between the driving signal and noise can be changed randomly at a pace of several tens of milliseconds or less during the sensing period following the non-sensing period. Such rapid random changes are not achievable by human operation. Furthermore, when the change in the detection value ΔAD changes due to human operation, the number of changes is at most several times per second, and the change in the change ΔAD does not become rapid and random. Therefore, based on the change in the detection value ΔAD, it is possible to distinguish and detect the change in the change ΔAD due to noise and the change in the change ΔAD due to human operation. As a result, when it is determined that the change ΔAD due to noise has occurred, it is possible to reduce the influence of noise by changing the driving frequency of the driving signal throughout the entire period (frequency hopping).

[0050] Therefore, it is possible to provide an operation detection device 100 that reduces the influence of noise and has high detection accuracy.

[0051] In addition, the control unit 130 changes the frequency of the drive waveform of the drive signal in the non-sensing period, so that it is possible to change the phase difference between the drive signal and noise in the sensing period. In addition, since frequency hopping that changes the frequency in the non-sensing period is performed, the frequency of the drive signal is constant in the sensing period and there is no change in the waveform of the drive signal in the sensing period, so there is no effect on the change ΔAD in the detection value.

[0052] In addition, the control unit 130 randomly changes the frequency of the drive signal during the non-sensing period for each sensing cycle, so that the change in the detection value ΔAD changes randomly, making it easier to distinguish the change in the detection value ΔAD caused by human operation. As a result, it is possible to provide the operation detection device 100 that reduces the influence of noise and has higher detection accuracy.

[0053] Furthermore, the control unit 130 changes the drive frequency of the drive signal during the non-sensing period so that the change in the detection value change ΔAD generated to determine the presence or absence of an operation based on the output value of the electrostatic sensor 110 during the sensing period is at a level that can be distinguished as a change due to noise, so that the change in the detection value change ΔAD due to noise can be reliably distinguished from the change in the detection value change ΔAD due to a human operation. As a result, it is possible to provide an operation detection device 100 that reduces the effects of noise and has even higher detection accuracy.

[0054] In addition, since the change in the detection value change amount ΔAD at a level that can be determined as a change due to noise is a change in the detection value change amount ΔAD at a speed that cannot be realized by human operation, the change in the detection value change amount ΔAD due to noise can be more reliably distinguished. As a result, it is possible to provide an operation detection device 100 that reduces the influence of noise and has extremely high detection accuracy.

[0055] In addition, since the control unit 130 adjusts the phase difference between the drive signal and noise at the start of the sensing period within a range of 0 degrees to 360 degrees, it is possible to reliably adjust the phase difference between the drive signal and noise at the start of the sensing period.

[0056] In addition, a condition (predetermined condition) for performing frequency hopping may be set for the output value of the electrostatic sensor 110. For example, in the case where noise is not always generated but a very large level of intermittent noise is generated before the generation of continuous noise, frequency hopping may be performed to prepare for the sensing period when the control unit 130 detects that the output value of the electrostatic sensor 110 represents a very large level of intermittent noise. When the output value of the electrostatic sensor 110 satisfies the predetermined condition for performing frequency hopping, the phase difference between the noise and the drive signal can be adjusted, and the change in the change in the detection value ΔAD due to noise and the change in the detection value ΔAD due to human operation can be more efficiently and reliably distinguished.

[0057] In the above, a configuration in which a drive signal is constantly applied to the electrostatic sensor 110 has been described, but the present invention is not limited to this configuration. The drive signal may be applied to the electrostatic sensor 110 intermittently, for example.

[0058] In the above, a form has been described in which the phase difference between the drive signal and noise in the sensing period is adjusted by performing frequency hopping in the non-sensing period, but the phase difference may be adjusted as shown in Fig. 14. Fig. 14 is a diagram for explaining an example of a method for adjusting the phase difference according to a modified example.

[0059] 14, as an example, the sensing cycle is 10 milliseconds, the non-sensing period is a predetermined period from the start of the cycle, and the sensing period is the remaining period after the non-sensing period ends. Here, the drive signal is activated only during the sensing period.

[0060] The driving signal starts to be driven after switching from the non-sensing period to the sensing period. By providing a timing adjustment period at the beginning of the sensing period and adjusting the timing at which the driving signal starts to be driven, the phase difference between noise and the driving signal can be adjusted. For example, by changing the length of the timing adjustment period for each sensing cycle, when noise is detected, the change in the detection value ΔAD can be changed quickly and randomly. This makes it possible to reliably distinguish between the change in the detection value ΔAD due to noise and the change in the detection value ΔAD due to human operation. As a result, it is possible to provide an operation detection device 100 that reduces the influence of noise and has high detection accuracy.

[0061] The above describes an exemplary embodiment of an operation detection device of the present invention. However, the present invention is not limited to the specifically disclosed embodiment, and various modifications and changes are possible without departing from the scope of the claims.

[0062] This international application claims priority to Japanese patent application No. 2021-063104, filed on April 1, 2021, the entire contents of which are incorporated herein by reference. [Explanation of symbols]

[0063] 100 Operation detection device 110 Electrostatic Sensor 120 Circuit section 121 Detection circuit 122 Drive circuit 130 Control section

Claims

1. An electrostatic sensor; a drive circuit that outputs a drive signal to the electrostatic sensor in order to detect an operation of the electrostatic sensor by an operator; a control unit that determines whether or not the operation is performed based on an output value of the electrostatic sensor and controls a drive waveform of the drive signal; Including, the control unit controls the drive waveform with a cycle of a predetermined period including a detection period in which the operation is detected and a non-detection period in which the operation is not detected; the drive waveform has a shape based on a periodic function that repeats a constant pattern over the entire period, The control unit controls the characteristics of the drive waveform during the non-detection period for each cycle to randomly change the frequency of the drive signal so that the change in the detection value generated based on the output value of the electrostatic sensor during the detection period is at a level that can be distinguished as a change due to noise, thereby randomly changing the phase of the drive signal during the detection period.

2. The operation detection device according to claim 1 , wherein the change in the detection value that can be determined to be caused by noise is a change in the detection value at a speed that cannot be achieved by human operation.

3. The operation detection device according to claim 1 , wherein the control unit changes a frequency of the drive signal in the non-detection period when an output value of the electrostatic sensor satisfies a predetermined condition.

4. The operation detection device according to claim 3 , wherein the control unit adjusts a period during which the frequency of the drive signal is changed in the non-detection period.

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