Improved tone control device for digital piano

Abstract

The present invention relates to a tone control device for a digital piano, and provides the tone control device comprising: a support body forming a keyboard or the bottom surface of the keyboard; and a moving part connected to the bottom of the support body, wherein the moving part includes: a base forming a background; and a plurality of openings formed in the base, the openings being provided in a color or as an opening differing from that of the base, so as to be distinguished from the base in terms of shading, wherein sensors for sensing the openings when the moving part moves downward are provided to face the openings, and the sensors count the number of openings passing through the sensors when the moving part moves downward.

Description

Improved digital piano pitch control device

[0001] The present invention relates to a tone control device for a digital piano.

[0002]

[0003] A digital piano is a type of keyboard designed to provide an alternative to the traditional piano in terms of playing style and sound. It offers an accurate simulation of an acoustic (analog) piano. Digital pianos are designed to resemble traditional pianos, such as upright or grand pianos. Digital piano sounds are produced by matching stored sounds with the positions of the keys played, using synthetic emulation or actual piano samples, and then playing the stored sounds through speakers. Digital piano keyboards come in three sizes: 88, 76, and 61 keys, but 88 keys are the most commonly used.

[0004] Digital pianos have the advantages of lower maintenance costs compared to acoustic pianos, sound is implemented using MIDI, built-in features to aid learning and composition, no microphone is required, and they are easy to carry. The keys of a digital piano are designed to feel similar to an acoustic piano and are velocity-responsive, meaning that the volume and timbre of the sound played depend on the speed at which the keys are struck. Digital pianos have hammers to simulate the touch of a real piano. They have analog sensors to detect key presses, which is what sets them apart from conventional electronic keyboards or synthesizers. Some digital pianos have built-in pedals, but those that have the function of adjusting the dampers by pressing the pedal to achieve resonance, like acoustic pianos, are very expensive.

[0005] Currently, the sound control of a digital piano is performed by, as illustrated in Fig. 9, placing a first rubber dome (102') inserted into a long column and a second rubber dome (104') arranged in a relatively short column on the lower surface of a rubber dome (100'), and placing a first contact portion (102a') and a second contact portion (104a') on a PCB substrate (106') facing them. Even if the lower surface of the key (100k') remains parallel and the rubber dome (100') is pressed, the first rubber dome (102') comes into contact with the first contact portion (102a') first due to the height difference, and the second rubber dome (104') comes into contact with the second contact portion (104a') later.

[0006] Here, when the player presses the key (100k'), as illustrated in Fig. 10, the time difference (T) between the first rubber dome (102') and the first contact portion (102a') and the second rubber dome (104') and the second contact portion (104a') is adjusted so that a small time difference (T) produces a large volume, and a large time difference (T) produces a small volume. In other words, the faster the player presses the key, the larger the volume, and the slower the player presses the key, the smaller the volume, which is a speed-response equation.

[0007] However, this method cannot replicate the acoustic piano effect, where pressing the keys hard (i.e., deeply) produces a louder sound, while pressing them lightly (i.e., slightly) produces a quieter sound. While the depth of the key press can affect not only the volume but also the timbre, dynamics, and softness, current digital pianos are limited in their ability to reflect this feature.

[0008] In order to solve this problem, the applicant disclosed in patent No. 10-2423603 registered on July 18, 2022 a sound control device (1') including a support (100a) at the top and a substrate (200') installed at the bottom facing the support (100a), as shown in FIG. 11.

[0009] On the lower surface of the support (100a), a first moving part (104a), a second moving part (106a) installed at a predetermined distance from the first moving part (104a), and a counter moving part (108a) installed at a predetermined distance from the second moving part (106a) are formed. The counter moving part (108a) is composed of a light-shielding part (108a', ..., 108a') and a light-transmitting part (108b', ..., 108b') in the shape of a horizontal bar. A slot (202a) is formed on the substrate (200a) for the first moving part (104a), the second moving part (106a), and the counter moving part (108a) to pass through, and a first sensor (304a), a second sensor (306a), and a counter sensor (308a) are installed on the side adjacent to the slot (202a), respectively.

[0010] The time difference (Td') is calculated based on the time it takes for the second moving part (106a) to pass through the second sensor (306a) and the time it takes for the first moving part (104a) to pass through the first sensor (304a), and the depth of the key press is measured using the counter moving part (108a) and the counter sensor (308a), thereby finally measuring the speed of the key.

[0011] Although the first moving part (104a) and the second moving part (106a) are essential in the above patent, the inventor has confirmed that the piano's tone can be adjusted more precisely by employing only the configuration of the counter moving part (108a). This improved structure will not only improve the sound quality of digital pianos, but will also provide a digital piano tone control device that is simpler and more convenient to install and maintain.

[0012]

[0013] Therefore, the present invention aims to provide an improved digital piano sound control device that can control the sound according to the amount of pressing of the digital piano's keys, i.e., the moving distance, using only one moving part by further improving the inventor's prior patent.

[0014]

[0015] In order to achieve the above-described object, the present invention provides a sound control device for a digital piano, the device including a support forming a keyboard or a lower surface of the keyboard, and a moving part connected to a lower portion of the support, the moving part including a base forming a background, and a plurality of openings formed in the base, the openings being provided as a plurality of openings so as to distinguish between a base and a shade, and a sensor for detecting light or shade when the moving part moves downward is installed to face the sensor, the sensor counting the number of light or shade passing through the sensor when the moving part moves downward.

[0016] The above sensor may be either a sensor using a light source or an infrared sensor.

[0017] The above openings can be arranged in multiple columns horizontally and multiple rows vertically.

[0018] The above openings can be arranged in a straight line or diagonally so that a set of multiple rows rises upward at a predetermined interval from one side to the other side.

[0019] The above sensors can be installed to correspond to the number of rows of openings.

[0020] The above sensors can be installed to correspond to the number of the lowest row of the opening and the row above it.

[0021] The above moving part may be a plate shape that extends downward.

[0022] The left and right sides of the above moving part can be formed as inclined straight lines or inclined curved surfaces.

[0023] The above sensor may include a first sensor facing one side of the opening and a second sensor facing the other side of the opening.

[0024] In addition, the present invention provides a sound control device for a digital piano, the device including a support forming a keyboard or a lower surface of the keyboard, and a moving part connected to a lower portion of the support, the moving part including a connecting part connected to one lower surface of the support and extending at a steep incline, a guide extending from the connecting part at a gentle downward incline, and a slide part extending from the guide, and a line image sensor installed to face the slide part and detecting an initial position of the slide part and a final position to which the slide part has moved after a key is pressed.

[0025] A base forming a background in a sliding section of a moving part, and a plurality of openings formed in the base, the openings being provided with a different color or opening from the base so that the shade is distinguished from the base, and an additional image sensor that counts the number of passages through the openings when the sliding part moves can be placed.

[0026] The above slide portion can extend vertically from the above guide.

[0027] In addition, the present invention is a sound control device for a digital piano, the device including a support forming a keyboard or a lower surface of the keyboard, and a moving part connected to the lower portion of the support, the moving part extending downward in a plate shape and installed facing the lower portion of the moving part, and a line image sensor that detects the initial position of the moving part and the final position to which the moving part has moved after the key is pressed can be installed.

[0028] The above moving part may have a base forming a background and a plurality of openings formed in the base, and the sound control device may further include an image sensor that detects the number of times the openings pass when a key is pressed.

[0029] In addition, the present invention provides a sound control device for a digital piano, which includes a keyboard and a mechanism installed at a lower portion of the keyboard, and the mechanism includes a plate-shaped frame extending parallel to a lower surface of the keyboard and a bracket formed at a front portion of the frame, and a protrusion having a narrow width and extending downwards is formed at a rear lower portion of the bracket, and a sensor is installed at a position facing the protrusion or the protrusion at a predetermined distance therefrom.

[0030] A downwardly extending depression is formed on the lower surface of the keypad, the depression surrounds the bracket, and the lower surface of the bracket is secured and placed on the lower jaw of the depression, and the sensor can measure the vertical movement distance based on the lowest surface of the depression of the keyboard.

[0031]

[0032] The present invention controls the sound, including the increase or decrease in volume, according to the distance traveled by the digital piano keys, i.e., the degree of pressing, so that it produces the same effect as when pressing an analog piano key, and allows the player to play realistic music by making the most of his or her skills.

[0033] The sound control device of the present invention detects the pressing speed of a key through a single moving part, so it is simple, easy, and economical to manufacture.

[0034]

[0035] FIG. 1 is a drawing of a sound control device of a digital piano according to one embodiment of the present invention, wherein FIG. 1a is a side view, FIG. 1b is a front view, and FIG. 1c is a perspective view.

[0036] Figure 2 is a drawing showing calculating the pressing speed of a keyboard based on the moving part of the present invention.

[0037] Figure 3 is a drawing showing an example of a CCD line image sensor.

[0038] FIG. 4 is a drawing illustrating an embodiment of a sound control device of the present invention using a line image sensor.

[0039] Figure 5 is a drawing showing an example of how a sound control device can be installed using an actual keyboard and mechanism in the present invention.

[0040] Fig. 6 is a configuration diagram of a sound control unit that controls keyboard sounds in relation to a sound control device in a digital piano of the present invention.

[0041] FIG. 7 is a drawing showing various embodiments of the moving part of the present invention related to FIG. 1.

[0042] FIG. 8 is a drawing showing various embodiments of the moving part of the present invention related to FIG. 4.

[0043] Figures 9 to 11 are drawings disclosing a key sound control device of a digital piano of the prior art.

[0044]

[0045] Each embodiment of the present invention is merely an example to aid understanding of the present invention, and the present invention is not limited to these embodiments. The present invention may be configured by a combination of at least one of the individual components and individual functions included in each embodiment.

[0046] FIG. 1 is a drawing of a sound control device (1) of a digital piano according to one embodiment of the present invention, wherein FIG. 1a is a side view, FIG. 1b is a front view, and FIG. 1c is a perspective view.

[0047] Referring to these drawings together, the sound control device (1) of the present invention includes an upper support (4) and a moving part (2) extending vertically downward from the lower surface of one side of the support (4).

[0048] The support (4) may be the keyboard itself or a part of the keyboard. Alternatively, it may be implemented as a mechanical part separately attached to the underside of the keyboard. The support (4) has a rectangular keyboard shape, but is not limited thereto. The support (4) reflects the depth of the keyboard press and the movement trajectory of the keyboard depending on the keyboard press.

[0049] The moving part (2) is installed along the longitudinal center line of the lower surface on one side of the support (4). The moving part (2) is illustrated as a rectangular plate shape with a narrow width and a tall height, but can be implemented in various shapes, such as a circular column. In addition, the moving part can be manufactured from various materials, such as rubber, plastic, and metal.

[0050] The moving part (2) includes a base (8) forming a background and a plurality of openings (6) formed in the base (8). Light or shadow passing through the openings is detected by a sensor (S). It is sufficient for the base (8) and the openings (6) to be distinguished by shadows.

[0051] In the present invention, the sensor (S) includes a first sensor (20) and a second sensor (30). The sensor (S) is installed facing the lower portion of the moving part (2). It is preferable that the sensor (S) be installed at a position facing at least one lowermost opening (6) in the position of the moving part (2) before the key is pressed. The first sensor (20) may be a light-receiving sensor, and the second sensor (30) may be a light-emitting sensor. Although a pair of sensors (S) is shown as an example, one may be installed as long as it can detect the opening (6). The sensor (S) may be fixed to a bracket or housing (not shown) as long as it faces the moving part (2) at an appropriate position, or may be installed on a substrate as in Patent No. 10-2423603, and the installation position is not restricted.

[0052] The sensor (S) can use all light source sensors (photodiode, PIN photodiode, photoavalanche diode, phototransistor, solar battery, CDS (Photoresistor), selenium, CCD (Charge Coupled Device), laser sensor, distance sensor, CIS (CMOS Image Sensor), CPD (Contact Potential Difference), CID (charge-injection device), phototube, photomultiplier, PSD (Position Sensitive Device). In addition, an infrared sensor can be used. Infrared rays are invisible to the human eye, but have a longer wavelength and lower energy than visible light, so they do not cause chemical or biological reactions easily and are mainly used to transfer heat. Infrared sensors can distinguish between sound and zero of objects, so they have a wider range of applications than sensors that use visible light.

[0053] In the present invention, the openings (6) are arranged in 4 columns horizontally and 9 rows vertically, and each column is a set of 9 rows of openings. In addition, the sets of 9 rows are arranged so that they go up by a predetermined interval from the first column on the left to the right column. The first and second sensors (20, 30) are arranged in a parallel row of 4 each according to the number of columns of the openings (6) and face each other. In the initial state, the sensors (S) are installed so as to face each other with at least a part of the opening (6) at the lowest opening (6), that is, the openings (6) in the first column and the ninth row interposed therebetween. For convenience, the openings (6) are exemplified as long squares, but various shapes such as circles, ovals, triangles, or continuous lines can be used.

[0054] When a key is pressed, the moving part (2) moves downwards through the gap provided by the first sensor (20) and the second sensor (30). At this time, the openings (6) detected by the sensor (S) are in the order of 1st row, 9th column, 2nd row, 9th column, 4th row, 8th column, …, and finally, the opening (6) of 4th row, 9th column is detected. That is, 36 openings (6) are sequentially detected by the sensor (S) at regular intervals and time differences. Therefore, the inclined or diagonal opening (6) matrix arrangement of the present invention is particularly advantageous in detecting the slight pressing of the key. In addition, the diagonal arrangement structure is reasonable in that the moving part (2) rotates slightly to the left in the drawing and moves downward when the key is pressed, and therefore the opening (6) passing through the sensor (S) passes through the sensor (S) in a straight line.

[0055] Those skilled in the art will understand that the opening (6) in the present invention can be arranged in various ways.

[0056] A method for calculating the pressing speed of the keyboard of the present invention is described based on Fig. 2. The sensor (S) is illustrated as the first sensor (20).

[0057] Before the key is pressed, at the initial position (P1), the first sensor (20) detects the opening at the bottom, that is, the opening (6) in the 1st row and 9th column. After the key is pressed, at the final position (P2), the first sensor (20) detects the opening (6) in the 3rd row and 4th column. During this process, the total number of openings (6) detected by the first sensor (20) is counted. In the example of Fig. 2, it can be seen that a total of 23 black openings (6) were counted. In the present invention, based on the time (T) taken from the initial position (P1) to the final position (P2), the counter is subtracted from the time (T) to adjust the strength of the sound according to the pressing speed of the key.

[0058] In the above embodiment of the present invention, the number of openings (6) is counted, so that the keyboard speed can be precisely measured. However, as the number of columns and rows increases and the number of openings is increased, the number of sensor elements must also be placed.

[0059] In consideration of this, another embodiment of the present invention describes a configuration for detecting the degree of pressing of a keyboard using a line image sensor (10). There are various types of CCD line image sensors (Charge coupled device Line Image Sensors) among image sensors, but they basically have a structure such as, for example, FIG. 3, and when a detected member (D') moves linearly above the line image sensor (10), if the frontmost line of the detected member (D') is used as a detection reference, the movement distance and movement time from the sensing start position (P1') to the sensing end position (P2') can be measured to calculate the "velocity" of the detected member (D').

[0060] Fig. 4 illustrates an embodiment of a sound control device (1) of the present invention using a line image sensor (10).

[0061] A long plate-shaped moving part (12) is connected from one side of the lower surface of the support (14) and extends toward the line image sensor (10). The support (14) may be the keyboard itself or a part of the keyboard. The moving part (12) includes a connecting part (120) that is connected to one side of the lower surface of the support (14) and extends downward at a steep incline, a guide (122) that extends downward at a gentle incline from the connecting part (120), and a slide part (124) that preferably extends parallel to the lower surface of the support (14) from the guide (122). The line image sensor (10) may be installed on a substrate (not shown).

[0062] In this state, when the key is pressed, the support (14) moves downward, and accordingly, the moving part (12) moves to the left side of the drawing, and the sliding part (124) moves linearly over the line image sensor (10). When the detection standard is the tip (1240), the tip (1240) is at the first position (P1) in the initial state, and when the key is pressed, it moves to the second position (P2). The speed of the key can be calculated using the time (T) between the first position (P1) and the second position (P2) and the distance between the first position (P1) and the second position (P2).

[0063] The measured speed in Fig. 4 may have a slight difference in quantitative terms compared to the speed based on the aperture counter measured in Fig. 2, but is substantially the same. One of the advantages of using a line image sensor (10) is that it is simple to install and easy to maintain since only one sensor is required.

[0064] Next, a preferred embodiment of installing the sound control device (1) of the present invention on an actual keyboard will be described with reference to FIG. 5.

[0065] In Fig. 5a, the keyboard is a support (4). A mechanism (100) is installed at the bottom of the support (4). The mechanism installed at the bottom of a digital piano keyboard may be used as is, but the mechanism (100) of the present invention includes a plate-shaped frame (102) extending parallel to the lower surface of the keyboard, and a square frame-shaped bracket (104) formed at the front (right side of the drawing) of the frame (102). A narrow, downwardly extending protrusion (106) is formed at the rear lower portion of the bracket (104).

[0066] A long downward pressing portion (14a) is formed on the lower surface of the keypad on the right side of the keyboard. The pressing portion (14a) surrounds the bracket (104) as shown in the initial state, and the lower surface of the bracket (104) is secured and placed on the lower jaw of the pressing portion (14a).

[0067] Fig. 5b illustrates a drawing of a case where the keyboard, which is the support (4), is pressed in the initial state of Fig. 5a. The position of the mechanism (100) does not change. The support (4) is pressed and moves downwards by the key operation, and the vertical movement distance based on the lowest surface of the pressing portion (14a) of the keyboard is actually approximately 7 mm.

[0068] If the above structure is utilized, the sensor (S) of the present invention can be installed at a position facing the protrusion (106) at a predetermined distance, thereby measuring the movement distance of the pressing portion (14a). If the moving portion (2) is integrated or added at least to the lower portion of the pressing portion (140a), the embodiment of Fig. 1 can be implemented to measure the speed of the keyboard. Alternatively, the sensor (S) can be installed on the protrusion (106) capable of capturing the movement of the keyboard.

[0069] Also, from the drawings of FIGS. 5a and 5b, it can be seen that the embodiment of FIG. 1 or FIG. 5 can be implemented because the vertical movement distance (V) and the horizontal movement distance are distinguished when the key is pressed.

[0070] Fig. 6 is a configuration diagram of a sound control unit (200) that controls keyboard sounds in relation to a sound control device (1) in a digital piano of the present invention. The sound control unit (200) is electrically connected to a sensor (S) installed in relation to each keyboard.

[0071] The sound control unit (200) includes a main control unit (MCU; 202) which is a central controller. The MCU (202) includes a power supply unit (204), a counter unit (206), a time measurement unit (208), and a sound dynamics calculation unit (208). The power supply unit (204) is a power source that supplies power to the digital piano and starts the sound control unit (200). The counter unit (206) counts the number of openings (6) measured by the sensor (S) with a counter (C). The time measurement unit (208) measures the time (T) taken to reach the final position from the initial position. Finally, the sound dynamics calculation unit (208) subtracts the counter (C) from the time (T) to determine the sound to be transmitted based on the sound dynamics value according to the pressing speed of the keyboard.

[0072] The sound control unit (200) of the present invention may include an external terminal (210) such as a USB, an audio AMP circuit (212), and a speaker (214). A sound signal with controlled intensity is amplified by the AMP circuit (212) and radiated to the outside through the speaker (214).

[0073] Next, various other embodiments of the present invention will be described with reference to the attached drawings.

[0074] FIG. 7a shows that the openings (6) of the moving part (2) are arranged in multiple stages with one long slot on the left and right sides of a square as a unit, and one first sensor (20) and one second sensor (30) are installed on the opposite side facing the opening (6). FIG. 7b is the same as the embodiment of FIG. 1, but the openings (6) are arranged in a more inclined diagonal shape. FIG. 7c is the same as FIG. 7b, but the moving part (2) is arranged to be inclined in the longitudinal direction of the support (4), that is, to the left in the drawing. As shown in FIG. 7d, the front and rear sides of the moving part (2) can be formed into a curved surface. FIG. 7e is the same as FIG. 7d, but the openings (6) are arranged in multiple stages with one long slot on the left and right sides of a square as a unit, and one first sensor (20) and one second sensor (30) are installed on the opposite side facing the opening (6).

[0075] Figure 7f illustrates that the apertures (6) are arranged in parallel rows, with eight sensors (S) arranged in the lowest row and the next lowest row. In this case, as the number of sensors (S) increases, the resolution is increased, allowing for more precise detection of the movement speed of the keyboard. In the present invention, more sensors can be arranged in the horizontal or vertical direction to increase the resolution.

[0076] Figure 8 illustrates various modified examples of Figure 5 of the present invention.

[0077] FIG. 8a shows that a plurality of openings (6) are formed in the slide portion (124) of the moving portion (12), and the pressing speed of the keyboard is detected by the line image sensor (10) as well as the first sensor (20) and the second sensor (30). FIG. 8b shows that the downward movement speed of the moving portion (2) is detected by vertically arranging the line image sensor (10) to face the lower portion of the moving portion (2) as in FIG. 1. FIG. 8c shows that the slide portion (124) of the moving portion (12) is manufactured vertically, and the line image sensor (10) is vertically installed to face it. This structure can be applied when utilizing a structure around the keyboard.

[0078] Although the embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications and variations are possible for the present invention.

[0079] It is self-evident that the scope of the present invention extends to a scope identical or equivalent to the claims described below.

Claims

1. A sound control device for a digital piano, the device including a support forming a keyboard or the lower surface of the keyboard, and a moving part connected to the lower portion of the support, The above moving part includes a base forming a background, and a plurality of openings formed in the base, and the openings are provided as a plurality of openings so that the base and the shade are distinguished, and a sensor that detects light or shade when the moving part moves downward is installed to face the sensor, and the sensor passes through the sensor when the moving part moves downward. A tone control device that counts the number of lights or shades.

2. In paragraph 1, The above sensor is a sound control device that is either a sensor using a light source or an infrared sensor.

3. A sound control device in the second paragraph, wherein the openings are arranged in a plurality of horizontal columns and a plurality of vertical rows.

4. In paragraph 3, The above opening is a sound control device in which a set of multiple rows is arranged in a straight or diagonal manner so that the rows go up at a predetermined interval from one side to the other side.

5. In paragraph 3, The above sensor is a sound control device installed to correspond to the number of rows of openings.

6. In paragraph 5, The above sensor is a sound control device installed to correspond to the number of the lowest row of the opening and the row above it.

7. In paragraph 2, The above moving part is a sound control device having a plate shape that extends downward.

8. In paragraph 7, A sound control device in which the left and right sides of the above moving part are formed as inclined straight lines or inclined curved surfaces.

9. In paragraph 1, A sound control device, wherein the above sensor includes a first sensor facing one side of the opening and a second sensor facing the other side of the opening.

10. A sound control device for a digital piano, the device including a support forming a keyboard or the lower surface of the keyboard, and a moving part connected to the lower portion of the support, A sound control device in which the above moving part includes a connecting part that is connected to one side of the lower surface of the support and extends at a steep incline, a guide that extends from the connecting part at a gentle downward incline, and a slide part that extends from the guide, and is installed facing the slide part, and a line image sensor that detects the initial position of the slide part and the final position to which the slide part has moved after a key is pressed.

11. In paragraph 10, A sound control device comprising a base forming a background on a slide portion of a moving part, a plurality of openings formed in the base, the openings being provided with a different color or opening from the base so as to be shaded differently from the base, and an additional image sensor that counts the number of passages through the openings when the slide portion moves.

12. In paragraph 10, A sound control device in which the above slide portion extends vertically from the above guide.

13. A sound control device for a digital piano, the device including a support forming a keyboard or the lower surface of the keyboard, and a moving part connected to the lower portion of the support, the moving part extending downward in a plate shape, and installed facing the lower portion of the moving part, and a line image sensor installed to detect the initial position of the moving part and the final position to which the moving part has moved after the key is pressed.

14. In paragraph 13, A sound control device, wherein the moving part has a base forming a background and a plurality of openings formed in the base, and the sound control device further includes an image sensor that detects the number of times the openings pass when a key is pressed.

15. A tone control device for a digital piano, wherein the tone control device includes a keyboard and a mechanism installed at the bottom of the keyboard, the mechanism includes a plate-shaped frame extending parallel to the bottom surface of the keyboard, and a bracket formed at the front of the frame, and a protrusion having a narrow width and extending downward is formed at the rear bottom of the bracket. A sound control device in which the sensor of the first clause is installed at a position facing the protrusion or at a predetermined distance from the protrusion.

16. In paragraph 15, A downwardly extending depression is formed on the lower surface of the keypad, the depression surrounds the bracket, and the lower surface of the bracket is secured to the lower jaw of the depression. The above sensor is a sound control device that measures the vertical movement distance based on the lowest surface of the pressing part of the keyboard.

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