Input device using membrane force sensor and load detection method therefor

Abstract

Provided are an input device using a membrane-type force sensor and a load detection method therefor, whereby it is possible to obtain an updated baseline value at an appropriate timing, thereby enabling accurate load detection. This input device is provided with a film-type force sensor and a control circuit. The control circuit includes a measurement data acquisition unit, a moving average data calculation unit, a load data calculation unit, a load data correction unit, a standard deviation value calculation unit, a determination unit, a baseline update unit, and a storage unit. The determination unit determines that there is no load on the membrane-type force sensor when the standard deviation value is equal to or less than a threshold value. The baseline update unit updates the baseline value by replacing the baseline value with a value of the load data at the time of no-load determination.

Description

Technical Field

[0001] The present invention relates to an input device using a membrane type force sensor capable of accurately detecting a load and a load detection method thereof. Background Art

[0002] In recent years, a membrane-type three-axis force sensor has been known as a sensor that provides new concepts that cannot be realized with a joystick, a cross key, a mouse, or a touch panel to the development field of a user interface (UI).

[0003] The membrane-type three-axis force sensor can detect the force (pressure) of pressing, the state of sliding, the state of sliding, etc. by measuring the force in the three-axis (XYZ axis) direction at the contact point, and can input twisting, rotation, offset and other operations that cannot be controlled by existing controllers with a single finger. Since it is possible to measure the force (volume) not limited to on / off judgment, it can also correspond to the control of speed, movement amount, etc. Compared with a joystick or a cross key, it is possible to input the direction and movement amount at the same time through small movements of the finger. In addition, since it is a thin and light membrane-type sensor, it can also be installed on a curved surface. In addition, it is not necessary to measure all three-axis forces. For example, there may be a sensor that only measures the force in the XY axis direction.

[0004] As a membrane-type force sensor as described above, there can be cited an electrostatic capacitance force sensor, which is configured in a form in which an upper electrode and a lower electrode are opposite to each other with an air layer or an elastic layer sandwiched in between, and calculates the value of the applied load by utilizing the change in electrostatic capacitance value caused by the change in the distance between the electrodes when a force (hereinafter collectively referred to as load) is applied (see patent documents 1 and 2).

[0005] However, when performing load detection using the film type force sensor 2 using the electrostatic capacitance method, it is necessary to use the load estimation value (in Figure 6 In the example shown, the estimated value K for the Z-axis direction is z F z ave ) by subtracting the baseline value (in Figure 6 In the example shown, as F z BL The part drawn with thick dotted lines) is corrected (refer to Figure 5 ). Here, the baseline value refers to load data calculated in a state where no load is applied to the film type force sensor.

[0006] However, the load detection of the membrane type force sensor 2 using the electrostatic capacitance method has a problem of being affected by the resilience. That is, after the membrane type force sensor 2 is deformed by the application of a load (see Figure 7) When the load is released, the membrane force sensor will not immediately return to its shape before the load was applied until it is deformed, and the capacitance change will increase compared to the original value even in the no-load state. As a result, the load estimate calculated based on the capacitance change will not completely return to the baseline value in the no-load state ( Figure 6 The black arrow on the right side of the image).

[0007] Therefore, the amount of change in electrostatic capacitance in the no-load state often changes due to the influence of the restorative property, and therefore the baseline value needs to be updated in accordance with the change.

[0008] Prior art literature

[0009] Patent Literature

[0010] Patent Document 1: International Publication No. 2020 / 059766

[0011] Patent Document 2: Japanese Patent Application Publication No. 2017-156126 Summary of the invention

[0012] However, the baseline value to be updated is obtained based on the load estimate value calculated when no load is applied to the membrane type force sensor (in Figure 8 In the example shown, the estimated value K for the Z-axis direction is z F z ave ) data, but it is difficult to correctly judge the part where the load estimate value decreases sharply again based on the load data ( Figure 8 The load data of the portion surrounded by the dotted line shown in FIG. 1 is affected by the resilience of the film-type force sensor. In other words, it is not easy to update the baseline value.

[0013] Therefore, an object of the present invention is to achieve the above-mentioned problem and to provide an input device using a film-type force sensor and a load detection method thereof, which can acquire an updated baseline value at an appropriate timing and thereby perform accurate load detection.

[0014] Hereinafter, a plurality of methods will be described as means for solving the problems. These methods can be arbitrarily combined as needed.

[0015] An input device according to one aspect of the present invention includes a membrane type force sensor and a control circuit. The membrane type force sensor is disposed on the surface of a frame and is a sensor that detects a capacitance value that changes according to a load applied by a finger. The control circuit is electrically connected to the membrane type force sensor and is housed inside the frame.

[0016] The control circuit of such an input device includes a measurement data acquisition unit, a moving average data calculation unit, a load data calculation unit, a load data correction unit, a standard deviation value calculation unit, a determination unit, a baseline update unit, and a storage unit.

[0017] The measurement data acquisition unit is a component that acquires measurement data consisting of a time series of electrostatic capacitance changes detected by the membrane type force sensor. The moving average data calculation unit is a component that calculates moving average data by smoothing small changes in the measurement data with an arbitrary number of items. The load data calculation unit is a component that calculates load data by multiplying each value of the moving average data by an arbitrary coefficient representing the sensitivity of the membrane type force sensor. The load data correction unit is a component that corrects the load data by subtracting the baseline value from each value of the load data. The standard deviation value calculation unit is a component that calculates the standard deviation value within an arbitrary range of time from each moment of the load data. The judgment unit is a component that judges that there is a load on the membrane type force sensor when the standard deviation value is greater than an arbitrary threshold value, and judges that there is no load on the membrane type force sensor when the standard deviation value is less than the threshold value. The baseline update unit is a component that updates the baseline value by replacing the baseline value with the value at the time of the no-load judgment of the load data when it is judged that there is no load. The storage unit is a component that stores each value acquired, calculated, updated, and corrected.

[0018] In the above input device, the baseline updating unit may update the baseline value every time in the no-load state from when it is determined that there is no load to when it is determined that there is load again.

[0019] In the above-mentioned input device, the baseline updating unit may update the baseline value to the latest value at the time of no-load determination of the load data at regular intervals after the acquisition of the measurement data starts.

[0020] In the above input device, the film type force sensor may be a film type three-axis force sensor that detects electrostatic capacitance values ​​that change in accordance with loads applied in three axes of X, Y, and Z.

[0021] A load detection method for an input device according to one aspect of the present invention is a load detection method for an input device having a membrane type force sensor and a control circuit. The membrane type force sensor is arranged on the surface of a frame and is a sensor that detects a capacitance value that changes according to a load applied by a finger. The control circuit is electrically connected to the membrane type force sensor and is housed inside the frame.

[0022] Such a load detection method for an input device includes a measurement data acquisition step, a moving average data calculation step, a load data calculation step, a load data correction step, a standard deviation value calculation step, a determination step, a baseline update step, and a storage step.

[0023] In the measurement data acquisition step, measurement data consisting of a time series of changes in electrostatic capacitance detected by the membrane type force sensor is acquired. In the moving average data calculation step, the moving average data is calculated by smoothing small changes in the measurement data with an arbitrary number of items. In the load data calculation step, the load data is calculated by multiplying each value of the moving average data by an arbitrary coefficient representing the sensitivity of the membrane type force sensor. In the load data correction step, the load data is corrected by subtracting the baseline value from each value of the load data. In the standard deviation value calculation step, for each moment of the load data, the standard deviation value within an arbitrary range of time from the moment is calculated. In the determination step, when the standard deviation value is greater than an arbitrary threshold value, it is determined that there is a load on the membrane type force sensor, and when the standard deviation value is less than the threshold value, it is determined that there is no load on the membrane type force sensor. In the baseline update step, when it is determined that there is no load, the baseline value is updated by replacing the baseline value with the value of the load data at the time of the no-load determination. The storage step stores each value when each value is acquired, calculated, updated, and corrected.

[0024] In the load detection method for an input device, in the baseline updating step, the baseline value may be updated every time in the no-load state from when it is determined that there is no load until when it is determined that there is load again.

[0025] In the load detection method for an input device, in the baseline updating step, the baseline value may be updated to the latest value at the time of no-load determination of the load data at regular intervals after the acquisition of the measurement data is started.

[0026] In the load detection method of the input device, the film type force sensor may be a film type three-axis force sensor that detects electrostatic capacitance values ​​that change according to loads applied in three axes of X, Y, and Z.

[0027] According to the input device using the film-type force sensor and the load detection method thereof of the present invention, it is possible to acquire an updated baseline value at an appropriate timing, thereby enabling accurate load detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of a controller as an example of an input device using the film type force sensor according to the present invention.

[0029] Figure 2 It is a structural diagram of an input device using the film type force sensor according to the present invention.

[0030] Figure 3 is a calculated value (K) of the load on the Z axis when the baseline value is updated in the load detection method of the input device using the film type force sensor according to the present invention. z Fz ave ) time series with the baseline value (F z BL ) (the same applies to the X-axis and Y-axis).

[0031] Figure 4 This is a flowchart showing an example of a load detection process of an input device using the film type force sensor according to the present invention.

[0032] Figure 5 is the corrected load F x 、F y 、F z Calculation formula.

[0033] Figure 6 is the calculated value of the Z-axis load when the baseline value is not updated (K z F z ave ) time series with the baseline (F z BL ) (the same applies to the X-axis and Y-axis).

[0034] Figure 7 This is a schematic diagram showing the principle of a capacitive membrane force sensor.

[0035] Figure 8 This is a schematic diagram for explaining the problem of the timing of updating the baseline value (the same applies to the X-axis and the Y-axis).

[0036] Fig. 9 This is another structural diagram of an input device using the film type force sensor according to the present invention.

[0037] Fig.10 This is a flowchart showing another example of the load detection process of the input device using the film type force sensor according to the present invention.

[0038] Fig.11 This is a schematic diagram showing a structural example of a capacitive film-type triaxial force sensor. DETAILED DESCRIPTION

[0039] [First embodiment]

[0040] Hereinafter, a first embodiment of the present invention will be described based on the drawings.

[0041] (1) Overall structure of the input device

[0042] First, use Figure 1 as well as Figure 2, the overall structure of an input device 1 according to an embodiment of the present invention will be described. Figure 1 It is a schematic diagram of a controller as an example of an input device using the film type force sensor according to the present invention. Figure 2 It is a structural diagram of an input device using the film type force sensor according to the present invention.

[0043] The input device 1 includes a housing 10, a film-type force sensor 2, a control circuit 3, a communication unit 4, and a battery 5 (see Figure 1 as well as Figure 2 ).

[0044] The film type force sensor 2 is a sensor that is disposed on the surface of the housing 10 and detects a capacitance value that changes according to a load applied by the finger 11 .

[0045] The control circuit 3 is electrically connected to the film type force sensor 2 and is accommodated in the housing 10. The control circuit 3 controls the film type force sensor 2 and acquires, calculates, updates, and corrects various data for the detection signal from the film type force sensor 2.

[0046] The communication unit 4 is accommodated in the housing 10 , is electrically connected to the control circuit 3 , and communicates with an external electronic device (not shown).

[0047] The battery 5 is housed in the housing 10 and supplies power to the control circuit 3 .

[0048] Hereinafter, the functions of each of the above-mentioned structures will be described in further detail.

[0049] (2) Frame

[0050] As the material of the frame 10, for example, general-purpose resins such as polystyrene resins, polyolefin resins, ABS resins, AS resins, and AN resins can be cited. In addition, general-purpose engineering resins such as polyphenylene ether-polystyrene resins, polycarbonate resins, polyacetal resins, polyacrylic acid resins, polycarbonate-modified polyphenylene ether resins, polybutylene terephthalate resins, polybutylene terephthalate resins, and ultra-high molecular weight polyethylene resins, or super engineering resins such as polysulfone resins, polyphenylene sulfide resins, polyphenylene ether resins, polyarylate resins, polyetherimide resins, polyimide resins, liquid crystal polyester resins, and polyallyl heat-resistant resins can also be used.

[0051] (3) Membrane-type force sensor

[0052] As the film type force sensor 2, there are generally known electrostatic capacitance type, piezoelectric type, strain gauge type, etc. Figure 7In the embodiment shown, the sensor detects the capacitance value that changes according to the load applied by the user's finger 11 in the obliquely downward direction defined by the X-axis direction and the Z-axis direction.

[0053] The film-type force sensor 2 comprises: an upper electrode member 24 having an upper electrode 23, the upper electrode 23 being composed of a plurality of electrodes 23a, 23b, ... arranged along the X-axis direction in a linear pattern extending in the Y-axis direction on an upper support 22; a lower electrode member 27 having a lower electrode 26, the lower electrode 26 being arranged in a manner opposite to the upper electrode member 24, and being composed of a plurality of electrodes 26a, 26b, ... arranged along the X-axis direction in a linear pattern extending in the Y-axis direction on a lower support 25; and an air layer or elastic layer 21 sandwiched between the upper electrode member 24 and the lower electrode member 27. In addition, Figure 7 In the example shown, the surface of the upper electrode member 24 on which the upper electrode 23 is formed faces the surface of the lower electrode member 27 on which the lower electrode 26 is formed, and the upper support 22 of the upper electrode member 24 also serves as a protective layer for protecting the upper electrode 23 .

[0054] The membrane type force sensor 2 of such a structure uses the following method to apply a load (the components of force in the X-axis direction and the Z-axis direction are F x 、F z ) is used to calculate the applied load F by changing the capacitance value due to the change in the distance between the electrodes. x 、F z The value of .

[0055] That is, when a load is applied obliquely downward to the surface of the film-type force sensor 2 by the finger 11, the elastic layer 21 is deformed, and one electrode 23a of the upper electrode 23 of the upper electrode member 24 moves in the horizontal direction (X-axis direction) and the vertical direction (Z-axis direction) according to the strength of the load, and not only the distance between the one electrode 26a of the lower electrode 26 located obliquely below it changes, but also the distance between the adjacent electrode 26b changes. Therefore, by measuring the change in the electrostatic capacitance value between the upper electrode 23a and the lower electrode 26a and the change in the electrostatic capacitance value between the upper electrode 23a and the lower electrode 26b, it is possible to measure not only the load (pressure) in the vertical direction (Z-axis direction) but also the strength of the load (also called shear force) in the horizontal direction (X-axis direction).

[0056] As materials constituting the upper support 22 and the lower support 25, in addition to thermoplastic or thermosetting resin sheets such as acrylic, polyurethane, fluorine, polyester, polycarbonate, polyacetal, polyamide, olefin, etc., ultraviolet curing resin sheets such as cyanoacrylate, etc. can be cited, but there is no particular limitation. Since the film type force sensor 2 composed of such an upper support 22 and a lower support 25 can be arranged along the shape of the frame 10, it can also be mounted on a cylindrical surface, etc.

[0057] The upper electrode 23 and the lower electrode 26 can be made of a conductive material. As a conductive material, in addition to metal films such as gold, silver, copper, platinum, palladium, aluminum, and rhodium, conductive paste films in which conductive materials such as these metal particles or metal nanofibers and carbon nanotubes are dispersed in a resin binder can also be cited, but there is no particular limitation. As for the formation method, in the case of a metal film, a method of patterning by etching after forming a conductive film on the whole by electroplating, sputtering, vacuum evaporation, ion plating, etc. can be cited. In the case of a conductive paste film, a method of directly forming a pattern by printing methods such as screen, gravure, and offset can be cited.

[0058] As the elastic layer 21, for example, a synthetic resin sheet having elasticity such as silicone, fluorine, polyurethane, epoxy resin, ethylene vinyl acetate copolymer, polyethylene, polypropylene, polystyrene, butadiene rubber, or a non-woven fabric sheet having stretchability can be cited. In particular, an elastic sheet of a silicone resin such as silicone gel and silicone elastomer is more preferred because it has excellent durability in a wide temperature range from low to high temperatures and excellent elasticity. In addition, the elastic layer 21 is not limited to an elastic layer formed into a sheet by a general sheet forming method such as extrusion forming, and may also be a coating formed by printing or a coating machine.

[0059] When a resin such as polyethylene, polypropylene, or polystyrene is selected as the material of the elastic layer 21, since these synthetic resins have low elasticity alone, it is preferable to finely disperse gas in the synthetic resin to form a foamed state.

[0060] (4) Control circuit

[0061] Although not shown in the figure, the control unit 3 includes, for example, a substrate and a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and other electronic components mounted on the substrate. The control unit 3 is a device for controlling other devices based on hardware and software composed of a CPU (Central Processing Unit) and a memory.

[0062] In order to realize accurate load detection which is a feature of the present invention, the control circuit 3 includes at least a measurement data acquisition unit 31, a moving average data calculation unit 32, a load data calculation unit 33, a load data correction unit 34, a standard deviation value calculation unit 35, a determination unit 36, a baseline update unit 37, and a storage unit 38 (see Figure 2 ).

[0063] The measurement data acquisition unit 31 acquires measurement data consisting of a time series of electrostatic capacitance changes detected by the film type force sensor 2. This acquisition includes driving control of the film type force sensor 2. The acquired electrostatic capacitance changes (for example, as a time series of the load F applied in the Z direction) are z The capacitance change F z meas The measured data is sent to the storage unit 38 and stored, and is also sent to the moving average data calculation unit 32. The number of measurement data acquired is, for example, one per 10 milliseconds.

[0064] The moving average data calculation unit 32 is a component that calculates moving average data by smoothing minute changes in the measurement data with an arbitrary number of items (for example, the capacitance change amount F of the measurement data). z meas Calculated as the smoothed moving average F z ave ). By smoothing, a slow trend change can be obtained from the measurement data, and the influence of noise can be suppressed. The calculated moving average data is sent to the storage unit 38 and stored, and is also sent to the load data calculation unit 33. The number of items that become the average object of the measurement data is, for example, ten.

[0065] The load data calculation unit 33 multiplies each value of the moving average data by an arbitrary coefficient indicating the sensitivity of the film type force sensor 2 (for example, the smoothed moving average value F z ave is the coefficient K z ) to calculate the load data (for example, calculated as the load value K z F z ave ) components (refer to Figure 5 ). The calculated load data is sent to the storage unit 38 and stored, and is also sent to the standard deviation value calculation unit 35. The coefficient representing the sensitivity of the sensor is, for example, 1000 to 6000.

[0066] The load data correction unit 34 is a load data correction unit that corrects the load data from the load values ​​(for example, the load value K z F z ave ) minus the baseline value (e.g., baseline value F zBL ) to correct the load data. The baseline value refers to the load data calculated when no load is applied to the membrane type force sensor, so this amount needs to be removed from the load data. The corrected load data is sent to the storage unit 38 and stored.

[0067] However, as described above, the load detection of the membrane type force sensor 2 using the electrostatic capacitance method has a problem of being affected by the resilience. That is, after the membrane type force sensor 2 is deformed by the application of a load (see Figure 7 ) When the load is released, the membrane force sensor 2 remains deformed and does not immediately return to its shape before the load was applied. Even in the no-load state, the electrostatic capacitance value increases compared to the original value. As a result, the load estimation value calculated based on the electrostatic capacitance value does not completely return to the baseline value in the no-load state (see Figure 6 ). Therefore, due to the influence of the recovery property, the electrostatic capacitance value in the no-load state often shifts, and therefore the baseline value needs to be updated in accordance with the shift.

[0068] Furthermore, the baseline value to be updated is obtained based on the load estimation value calculated when no load is applied to the film type force sensor 2 (in Figure 6 In the example shown, the estimated value K for the Z-axis direction is z F z ave ) data, but it is difficult to correctly judge whether the load is applied to the film type force sensor 2 or affected by the resilience based on the load data (refer to Figure 8 ). That is, it is not easy to update the baseline value.

[0069] Therefore, in the present invention, by providing the control unit 3 with the standard deviation value calculation unit 35 and the determination unit 36 ​​, it is possible to acquire the updated baseline value at an appropriate timing.

[0070] The standard deviation value calculation unit 35 is a component that calculates the standard deviation value within an arbitrary range of time from each time point of the load data. The calculated standard deviation value is sent to the storage unit 38 and stored, and is also sent to the determination unit 36. The range of time that becomes the calculation object of the standard deviation value is, for example, 1000 msec.

[0071] The standard deviation value is an indicator of the magnitude of the deviation of the data. If the data is concentrated near the average value, the standard deviation becomes smaller, and conversely, if it spreads from the average value, the standard deviation becomes larger. When a load is applied to the surface of the membrane type force sensor 2 by the user's finger 11, the deviation of the load application method becomes larger because the surface of the human body performs subtle movements that are invisible to the naked eye due to breathing, blood flow, etc. In other words, the difference in whether the user's finger 11 touches the surface of the membrane type force sensor 2 is expressed as the degree of deviation of the load data.

[0072] In addition, as for the data used as the object when calculating the standard deviation value, for each time point of the above-mentioned load data, the time point may be set as any one of the start time point, the middle time point, or the end time point.

[0073] The determination unit 36 ​​determines that the film type force sensor is loaded when the standard deviation value is greater than an arbitrary threshold value, and determines that the film type force sensor is not loaded when the standard deviation value is less than the threshold value. The threshold value corresponds to 0.1N, for example.

[0074] The baseline update unit 37 is a component that updates the baseline value by replacing the baseline value with the value of the load data at the time of the no-load determination when the load is determined to be no-load. The updated baseline value is sent to the storage unit 38 and stored. In this specification, "update" is defined as the designation of a new baseline value, and is separated from "storage" of the updated value.

[0075] In the present embodiment, the baseline updating unit 37 updates the baseline value once every time the load state is in the period from when the load is determined to when the load is determined again. Here, updating of the baseline value also includes the case where the updated value is the same as the value before the update.

[0076] (5) Ministry of Communications

[0077] The communication unit 4 communicates with the external electronic device via a wireless LAN (local area network) such as WI-FI (wireless LAN communication technology) (registered trademark), BLUETOOTH (Bluetooth) (registered trademark), NFC (Near Field Communication). The communication unit 4 can communicate in one direction or two directions. In addition, the controller of the input device 1 of this embodiment can also control multiple external electronic devices simultaneously or individually.

[0078] As an external electronic device for communicating, in addition to the head-mounted display or smart glasses used in xR, it can also be a smart TV, a laptop computer, a desktop computer, a tablet computer, a car audio system, an automatic control device for home, work, or environment, or any other such device or system, but is not limited to these.

[0079] (6) Battery

[0080] As the battery 5, a rechargeable battery such as a lithium battery can be used. In the case of a rechargeable battery, the user can charge it simply by USB or by placing the input device 1 on a charging pad. In addition, a non-rechargeable battery can also be used as the battery 9, and it can be taken out from the inside of the housing 10 for replacement.

[0081] (7) Load detection method

[0082] The input device 1 using the film type force sensor having the above structure is used. Figure 4 , a load detection method based on the control unit 3 is explained. Figure 4 FIG. 1 is a flowchart showing an example of a load detection process of an input device using a film-type force sensor according to the present invention. Figure 4 Steps S1 to S7 in the flowchart shown will be described.

[0083] Initially, in Figure 4 In step S1, the measurement data acquisition unit 31 of the control unit 3 acquires measurement data consisting of a time series of electrostatic capacitance changes detected by the film type force sensor 2. The acquired electrostatic capacitance changes (for example, as a load F applied in the Z-axis direction) are z The capacitance change F z meas The measured data is sent to the storage unit 38 and stored (not shown as a step in the flowchart), and the process moves to step S2.

[0084] In step S2, the moving average data calculation unit 32 of the control unit 3 calculates moving average data by smoothing the small changes of the measurement data called from the storage unit 38 with an arbitrary number of items. The calculated moving average data is sent to the storage unit 38 and stored (not shown as a step in the flowchart), and the process transfers to step S3.

[0085] In step S3, the load data calculation unit 33 of the control unit 3 calculates the load data by multiplying each value of the moving average data retrieved from the storage unit 38 by an arbitrary coefficient indicating the sensitivity of the film-type force sensor. The calculated load data is sent to the storage unit 38 and stored (not shown as a step in the flowchart), and the process moves to step S4.

[0086] In step S4, the standard deviation value calculation unit 35 of the control unit 3 calculates the standard deviation value within an arbitrary range of time from each time point of the load data retrieved from the storage unit 38. The calculated standard deviation value is sent to the storage unit 38 and stored (not shown as a step in the flowchart), and the process transfers to step S5.

[0087] In step S5, the determination unit 36 ​​of the control unit 3 determines that there is a load on the film type force sensor when the standard deviation value retrieved from the storage unit 38 is greater than an arbitrary threshold value (the condition of "the deviation is within the range?" in step S5 is No), and determines that there is no load on the film type force sensor when the standard deviation value is less than the threshold value (the condition of "the deviation is within the range?" in step S5 is Yes). If it is determined that there is a load, the process transfers to step S7 without updating the baseline value. On the other hand, if it is determined that there is no load, the process transfers to step S6.

[0088] In step S6, the baseline update unit 37 updates the baseline value by replacing the baseline value with the value of the load data at the time of no-load determination. The updated baseline value is sent to the storage unit 38 and stored (not shown as a step in the flowchart), and the process proceeds to step S7.

[0089] Figure 3 is a calculated value (K) of the load on the Z axis when the baseline value is updated in the load detection method of the input device using the film type force sensor according to the present invention. z F z ave ) time series with the baseline value (F z BL ) (the same applies to the X-axis and Y-axis).

[0090] In the present embodiment, step S6 updates the baseline value once every time the no-load state is in the period from when it is determined that there is no load to when it is determined that there is a load again.

[0091] In step S7, the load data correction unit 34 corrects each value of the load data (for example, the load value K z F z ave ) minus the baseline value (e.g. baseline value F z BL ) to correct the load data. At this time, when the process goes from step S5 to step S7 without going through step S6, the baseline value retrieved from the storage unit 38 is an unupdated value. Also, at this time, when the process goes from step S5 to step S7 via step S6, the baseline value retrieved from the storage unit 38 is an updated value. The corrected load data is sent to the storage unit 38 and stored (not shown as a step in the flowchart).

[0092] As described above, the load detection method of the input device 1 using the film type force sensor 2 of the present invention determines whether the user's finger 11 is in contact with the surface of the film type force sensor 2 by calculating the degree of deviation (standard deviation value) of the load data and comparing it with the threshold value, and can obtain the updated baseline value at an appropriate timing (refer to Figure 3 ). This enables accurate load detection.

[0093] [Second embodiment]

[0094] Hereinafter, a second embodiment of the present invention will be described based on the drawings.

[0095] Fig. 9 This is another structural diagram of an input device using the film type force sensor according to the present invention.

[0096] Fig.10 This is a flowchart showing another example of the load detection process of the input device using the film type force sensor according to the present invention.

[0097] In the first embodiment, the baseline updating unit 37 of the control unit 3 updates the baseline value once each time in the no-load state from the time when the load is determined to be no-load until the load is determined to be present again, but the input device and the load detection method thereof of the present invention are not limited thereto. For example, the baseline updating unit 37 may update the baseline value to the latest value at the time of no-load determination of the load data at regular intervals from the start of acquisition of the measurement data (see Fig.10 ).

[0098] Specifically, the control circuit 3 includes a base line updating unit 37 as a part of the base line updating unit 37 or separately from the base line updating unit 37 (see Fig. 9 ), a timer unit 39 that counts the elapsed time after the start of acquisition of the measurement data, and when the elapsed time after the acquisition of the measurement data counted by the timer unit 39 reaches a predetermined time, the baseline updating unit 37 updates the baseline value.

[0099] This configuration has the advantage of improving the efficiency of receiving and processing data compared to each update.

[0100] In this case, the flowchart showing the load detection process of the input device is similar to the first embodiment (see Figure 4 ) are different, such as Fig.10 As shown, step S8 exists between step S5 and step S6.

[0101] In step S8, if the time elapsed after the acquisition of measurement data measured by the timer unit 39 of the control unit 3 has not passed the update time at regular intervals (the condition of "has the update time passed?" in step S8 is No), the process moves to step S7 while the baseline value is not updated. If the time elapsed after the acquisition of measurement data has passed the update time at regular intervals (the condition of "has the update time passed?" in step S8 is Yes), the process moves to step S6.

[0102] Since the other structures are the same as those of the first embodiment, the description thereof will be omitted.

[0103] [Third Embodiment]

[0104] Hereinafter, a third embodiment of the present invention will be described based on the drawings.

[0105] Fig.11 This is a schematic diagram showing a structural example of a capacitive film-type triaxial force sensor.

[0106] In the first embodiment, the film type force sensor 2 is a so-called two-axis force sensor that detects the electrostatic capacitance values ​​that change according to the load applied by the user's finger 11 in the oblique downward direction consisting of the X-axis direction and the Z-axis direction, but the input device of the present invention is not limited to this. For example, the film type force sensor 2 may also be a film type three-axis force sensor that detects the electrostatic capacitance values ​​that change according to the load applied in the three axes of XYZ.

[0107] As a film-type three-axis force sensor, for example, the following pattern can be used: the lower electrode 26 of the lower electrode member 27 is composed of an island pattern, and the upper electrode 23 of the upper electrode member 24 is composed of two layers of a surface side upper electrode 231 and a back side upper electrode 232 formed separately on both sides of the upper support body 22 (see Fig.11 (a)), and is composed of a plurality of stripe-shaped patterns that intersect the front-side upper electrode 231 and the back-side upper electrode 232 in a plan view (see Fig.11 (b)), a portion of the island pattern of the lower electrode 26 overlaps with a portion of the pattern of the upper electrode 231 on the front side and a portion of the pattern of the upper electrode 232 on the back side in a plan view. In this case, as Fig.11 As shown in (a), in order to protect the upper electrode 231 on the surface side of the upper electrode member 24 , it is preferable to provide a protective layer 28 on the surface of the upper electrode member 24 on the side opposite to the elastic layer 21 .

[0108] exist Fig.11In the example shown in (b), the angle at which the front-side upper electrode 231 and the back-side upper electrode 232 intersect is 90° (i.e., orthogonal) in such a manner that the linear pattern of the front-side upper electrode 231 extends in the X-axis direction and is arranged in the Y-axis direction, and the linear pattern of the back-side upper electrode 232 extends in the Y-axis direction and is arranged in the X-axis direction, but the present invention is not limited thereto. When the intersecting angles are orthogonal, the pattern of the lower electrode 26 becomes a rectangular checkerboard, and when the intersecting angles are not orthogonal, the pattern of the lower electrode 26 becomes a parallelogram checkerboard.

[0109] The membrane type force sensor 2 of such a structure utilizes the following method to apply a load (the components of force in the X-axis direction, the Y-axis direction, and the Z-axis direction are F x 、F y 、F z ) is used to calculate the applied load F by changing the capacitance value due to the change in the distance between the electrodes. x 、F y 、F z The value of .

[0110] That is, if the upper electrode 23 applies a load obliquely downward to the surface of the membrane type force sensor 2 through the finger 11, the elastic layer 21 is deformed, and the upper electrode 231 on the surface side and the upper electrode 232 on the back side of the upper electrode member 24 move in the horizontal direction (XY axis direction) and the vertical direction (Z axis direction) according to the strength of the load, and the distance and overlapping area between the lower electrode 26 of the island pattern and the upper electrode 231 on the surface side, and between the lower electrode 26 of the island pattern and the upper electrode 232 on the back side change, resulting in the electrostatic capacitance values ​​between the electrodes changing respectively. Therefore, if the changes in the respective electrostatic capacitance values ​​are measured, it is possible to measure not only the load in the vertical direction (the component force F in the Z axis direction) but also the load in the vertical direction (the component force F in the Z axis direction). z ), and also the horizontal load (the Y-axis component force F of the linear pattern arrangement of the upper electrode 231 on the surface side) can be measured. y , the component force F in the X-axis direction of the linear pattern arrangement of the back-side upper electrode 232 x )’s strength.

[0111] The material of the front-side upper electrode 231 and the back-side upper electrode 232 can be the same as the material constituting the upper electrode 23 and the lower electrode 26 of the first embodiment.

[0112] The same material as that constituting the upper support 22 and the lower support 25 of the first embodiment can be used as the material of the protective layer 28. The protective layer 28 can also be provided with design properties by conceiving a sheet material, leather, rubber, cloth, or the like.

[0113] Since the other structures are the same as those of the first embodiment, the description thereof will be omitted.

[0114] The film type force sensor 2 used in the present invention is not limited to the first embodiment and the present embodiment, and a known electrostatic capacitance type film type force sensor 2 can be used. For example, the embodiments or modifications described in Patent Documents 1 and 2 can be applied.

[0115] [Example of variation]

[0116] Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the gist of the invention. In particular, the multiple embodiments and modifications described in this specification can be arbitrarily combined as needed.

[0117] (a) In each of the above embodiments, the input device 1 receives the final calculated and corrected load (e.g., F x 、F y 、F z ) is directly sent to an external electronic device, but the input device 1 of the present invention is not limited thereto. For example, the control unit 3 may also include an event detection unit that detects events based on the value of the load and sends the detected event information to the external electronic device.

[0118] (b) In each of the above embodiments, an example in which the input device 1 is a controller for communicating and operating an external electronic device is described, but the input device 1 of the present invention is not limited to such a controller. For example, in addition to the head-mounted display or smart glasses used in the xR, the input device 1 can also be integrated with a smart TV, a laptop computer, a desktop computer, a tablet computer, a car audio system, an automatic control device for home, work, or environment, or any other such device. In this case, the communication unit 4 is not required. In addition, the battery 5 can also be omitted. Furthermore, a display device such as an LCD, a microphone, a speaker, etc. can also be provided.

[0119] In addition, the input device 1 may also be a controller for operating an external electronic device via a wired connection such as a USB cable.

[0120] Description of Reference Numerals

[0121] 1: Input device (controller); 2: Membrane type force sensor; 21: Elastic layer; 22: Upper support body; 23, 23a: Upper electrode; 231: Upper electrode on the surface side; 232: Upper electrode on the back side; 24: Upper electrode part; 25: Lower support body; 26, 26a, 26b: Lower electrode; 27: Lower electrode part; 28: Protective layer; 3: Control unit; 31: Measurement data acquisition unit; 32: Moving average data calculation unit; 33: Load data calculation unit; 34: Load data correction unit; 35: Standard deviation value calculation unit; 36: Determination unit; 37: Baseline update unit; 38: Storage unit; 39: Timer unit; 4: Communication unit; 5: Battery; 10: Frame; 11: Finger.

Claims

1. An input device using a membrane type force sensor, comprising: A film-type force sensor is disposed on the surface of the housing and detects an electrostatic capacitance value that changes according to a load applied by a finger; and a control circuit electrically connected to the film type force sensor and housed inside the frame; The control circuit comprises: a measurement data acquisition unit that acquires measurement data consisting of a time series of capacitance changes detected by the film type force sensor; a moving average data calculation unit that smoothes minute changes in the measurement data by an arbitrary number of items to calculate moving average data; a load data calculation unit that calculates load data by multiplying each value of the moving average data by an arbitrary coefficient representing the sensitivity of the film type force sensor; a load data correction unit that corrects the load data by subtracting a baseline value from each value of the load data; a standard deviation value calculation unit that calculates, for each time point of the load data, a standard deviation value within an arbitrary range of time from the time point; a determination unit that determines that a load is applied to the film type force sensor when the standard deviation value is greater than an arbitrary threshold value, and determines that no load is applied to the film type force sensor when the standard deviation value is less than the threshold value; a baseline updating unit that, when it is determined that there is no load, updates the baseline value by replacing the baseline value with a value of the load data at the time of the no-load determination; as well as The storage unit stores the acquired, calculated, updated, and corrected values.

2. The input device using a film type force sensor according to claim 1, wherein: The baseline updating unit updates the baseline value every time in the no-load state from when the no-load state is determined to when the load state is determined again.

3. The input device using a film type force sensor according to claim 1, wherein: The baseline updating unit updates the baseline value to a latest value of the load data at the time of the no-load determination at regular intervals after the acquisition of the measurement data is started.

4. The input device using a film type force sensor according to claim 1, wherein: The film type force sensor is a film type three-axis force sensor that detects electrostatic capacitance values ​​that change according to loads applied in three axes of X, Y, and Z.

5. A load detection method for an input device using a membrane type force sensor, the input device comprising: a membrane type force sensor disposed on a surface of a housing, and detecting an electrostatic capacitance value that changes according to a load applied by a finger; and a control circuit electrically connected to the film type force sensor and housed inside the frame, The load detection method of the input device comprises: a measurement data acquisition step of acquiring measurement data consisting of a time series of capacitance changes detected by the film type force sensor; a moving average data calculation step of smoothing small changes in the measured data by an arbitrary number of items to calculate the moving average data; a load data calculation step of calculating load data by multiplying each value of the moving average data by an arbitrary coefficient representing the sensitivity of the film type force sensor; a load data correction step of subtracting a baseline value from each value of the load data to correct the load data; A standard deviation value calculation step, for each moment of the load data, calculating a standard deviation value within any range of time from that moment; a determination step of determining that a load is applied to the film type force sensor when the standard deviation value is greater than an arbitrary threshold value, and determining that no load is applied to the film type force sensor when the standard deviation value is less than the threshold value; a baseline updating step of, when it is determined that there is no load, updating the baseline value by replacing the baseline value with a value of the load data at the time of the no-load determination; and The storing step stores the values ​​when the values ​​are acquired, calculated, updated, or corrected.

6. The load detection method of an input device using a film type force sensor according to claim 5, wherein: The baseline updating step updates the baseline value every time in the no-load state from when the no-load state is determined to when the load state is determined again.

7. The load detection method of an input device using a film type force sensor according to claim 5, wherein: The baseline updating step updates the baseline value to the latest value of the load data at the time of the no-load determination at regular intervals after the acquisition of the measurement data is started.

8. The load detection method of an input device using a film type force sensor according to claim 5, wherein: The film type force sensor is a film type three-axis force sensor that detects electrostatic capacitance values ​​that change according to loads applied in three axes of X, Y, and Z.

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