A position detection device and method

Abstract

The application discloses a position detection device and method, which comprises a light source, a servo motor containing a motor rotating shaft, a first grating engraved on the motor rotating shaft, the first grating being provided with first stripes with light and dark alternation, a light beam passing through the first stripes with light and dark alternation to generate a stripe pattern with light and dark alternation, a second grating provided on a propagation path of the light beam, the second grating being provided with second stripes with light and dark alternation for amplification modulation of the light beam, a photoelectric receiving unit for receiving the light beam passing through the first grating and the second grating and converting the light beam into an electric signal, and a signal processing unit connected with the photoelectric receiving unit for receiving the electric signal and performing position detection according to the electric signal. The grating is engraved on the motor rotating shaft to cancel the glass grating bearing structure of the traditional grating encoder, so that the rotating inertia of the motor can be reduced, the response performance of the motor is improved, and the position detection precision can be ensured.

Description

Technical Field

[0001] This invention relates to the field of grating displacement detection technology, and in particular to a position detection device and method. Background Technology

[0002] In the field of grating displacement detection, a common encoder structure consists of three parts: a light source, a grating disk, and a photodetector. The grating disk contains alternating light and dark grating stripes that are both transparent and opaque. When light emitted from the light source passes through the grating disk, alternating light and dark stripes are generated behind the disk. The photodetector receives the light transmitted from the disk and converts it into an electrical signal. When the disk rotates, the stripes also rotate, and the corresponding electrical signal changes accordingly, allowing the measurement of displacement. Alternatively, the grating disk can be made reflective, with the photodetector and light source placed on the same side. The principle remains the same: measuring the alternating light and dark stripes reflected from the grating disk to indirectly obtain position information. This approach is characterized by its simplicity and ease of production, and is widely used in the design of grating encoders.

[0003] However, in high-speed, high-precision laser scanning galvanometer servo motor applications, the motor needs to operate at extremely high accelerations, thus placing extremely stringent requirements on its load inertia—meaning the load inertia must be extremely low. As is well known, an object's inertia is directly proportional to its mass; the greater the weight, the greater the inertia. In grating displacement measurement systems, the grating scale disk accounts for a significant proportion of the motor's total load inertia. For some motors with relatively small lenses, the grating disk's inertia can even approach 50% of the total load inertia. Therefore, to further improve the motor's dynamic response capability, it is essential to reduce the load inertia, making weight reduction of the grating scale an urgent priority.

[0004] On the other hand, with a fixed grating pitch, improving the accuracy of a traditional encoder grating scale requires adding more scribe lines within the circular grating scale. However, since the grating pitch is fixed, adding more scribe lines means needing a larger radius grating scale, which in turn means a greater load inertia. Therefore, the negative impact of improving accuracy by increasing the grating scale radius is that it further reduces the response speed of the galvanometer, thereby further reducing the galvanometer speed. This presents a difficult trade-off for high-speed, high-precision galvanometer motors.

[0005] Therefore, how to ensure the accuracy of position measurement while avoiding increasing the load inertia of the motor, or even reducing the load inertia, is a problem that needs to be solved by those skilled in the art. Summary of the Invention

[0006] This invention provides a position detection device and method, which aims to improve position detection accuracy and reduce the load inertia of motors.

[0007] This invention provides a position detection device, comprising:

[0008] A light source, used to emit light beams;

[0009] A servo motor, including a motor shaft, wherein the light beam can be incident on the motor shaft;

[0010] The first grating is etched on the motor shaft. The first grating is provided with alternating light and dark stripes. The light beam can generate an alternating light and dark stripe pattern by passing through the alternating light and dark stripes.

[0011] A second grating is disposed on the propagation path of the light beam. The second grating has alternating bright and dark stripes for amplifying and modulating the light beam.

[0012] A photoelectric receiving unit is used to receive the light beam passing through the first grating and the second grating, and convert the light beam into an electrical signal;

[0013] A signal processing unit, connected to the photoelectric receiving unit, is used to receive the electrical signal and perform position detection based on the electrical signal.

[0014] Furthermore, the first grating and the second grating are arranged in parallel, and the period of the first stripe is the same as or different from the period of the second stripe.

[0015] Furthermore, the first grating and the second grating have a certain angle between them, and the period of the first stripe may be the same as or different from the period of the second stripe.

[0016] Furthermore, the first grating is engraved with oblique parallel lines that form a certain angle with the axial direction of the motor shaft.

[0017] Furthermore, the second grating is disposed between the first grating and the light source, or the second grating is disposed between the first grating and the photoelectric receiving unit.

[0018] Furthermore, the second grating can move relative to the first grating.

[0019] Furthermore, the first grating is made of a reflective material, and the second grating is made of a transmissive material.

[0020] Furthermore, the second grating is provided in multiple forms.

[0021] Furthermore, the alternating light and dark stripe pattern includes a first alternating light and dark stripe pattern with a single period and a second alternating light and dark stripe pattern with a mixed period; wherein, the second stripe pattern includes parallel stripe patterns and diamond-shaped stripe patterns with included angles.

[0022] This invention also provides a position detection method applicable to the position detection device described in any of the preceding claims, the method comprising:

[0023] A light source is used to emit a beam of light to the servo motor;

[0024] The servo motor shaft is controlled to rotate, and the light beam is modulated using a first grating engraved on the motor shaft to generate a striped pattern of alternating light and dark stripes; and the light beam is amplified and modulated using a second grating.

[0025] The photoelectric receiving unit receives the light beams passing through the first and second gratings and generates corresponding electrical signals.

[0026] The electrical signal is processed by a signal processing unit to achieve position detection.

[0027] This invention provides a position detection device and method. The device includes: a light source for emitting a light beam; a servo motor including a motor shaft, onto which the light beam can be incident; a first grating etched on the motor shaft, the first grating having alternating bright and dark stripes, the light beam passing through the alternating bright and dark stripes generating an alternating bright and dark stripe pattern; a second grating disposed on the propagation path of the light beam, the second grating having alternating bright and dark stripes, for amplifying and modulating the light beam; a photoelectric receiving unit for receiving the light beam passing through the first and second gratings and converting the light beam into an electrical signal; and a signal processing unit connected to the photoelectric receiving unit for receiving the electrical signal and performing position detection based on the electrical signal. This invention eliminates the glass grating support structure of traditional grating encoders by etching a grating on the motor shaft. This not only reduces the rotational inertia of the motor and improves its response performance but also ensures position detection accuracy. Furthermore, by adjusting parameters, the position detection accuracy can be further improved. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a schematic diagram of the structure of a position detection device provided in an embodiment of the present invention;

[0030] Figure 2 This is a schematic diagram of grating modulation in a position detection device provided by an embodiment of the present invention;

[0031] Figure 3 This is a schematic diagram of a first grating structure in a position detection device provided in an embodiment of the present invention;

[0032] Figure 4 This is a schematic diagram of a second grating structure in a position detection device provided in an embodiment of the present invention;

[0033] Figure 5 This is a schematic diagram of beam propagation in a position detection device provided in an embodiment of the present invention;

[0034] Figure 6 This is a schematic diagram of a striped image of a light beam in a position detection device provided in an embodiment of the present invention;

[0035] Figure 7 This is a schematic diagram of position detection in a position detection device provided in an embodiment of the present invention;

[0036] Figure 8 This is a schematic diagram of another grating modulation in a position detection device provided in an embodiment of the present invention;

[0037] Figure 9 This is another schematic diagram of grating modulation in a position detection device provided by an embodiment of the present invention;

[0038] Figure 10 This is a schematic diagram of the grating period in a position detection device provided in an embodiment of the present invention;

[0039] Figure 11 This is a schematic diagram of a grating arrangement in a position detection device provided by an embodiment of the present invention;

[0040] Figure 12 This is a schematic diagram of beam modulation in a position detection device provided in an embodiment of the present invention;

[0041] Figure 13 This is a schematic diagram of another beam modulation in a position detection device provided in an embodiment of the present invention;

[0042] Figure 14 This is a schematic diagram of another grating arrangement in a position detection device provided in an embodiment of the present invention;

[0043] Figure 15 This is another schematic diagram of beam modulation in a position detection device provided by an embodiment of the present invention;

[0044] Figure 16 This is a flowchart illustrating a position detection method provided in an embodiment of the present invention. Detailed Implementation

[0045] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0046] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0047] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0048] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0049] Please see below. Figure 1 and Figure 2 This invention provides a position detection device, comprising:

[0050] Light source 1, used to emit a beam of light;

[0051] The servo motor 2 includes a motor shaft 21, and the light beam can be incident on the motor shaft 21;

[0052] The first grating 3 is etched on the motor shaft 21. The first grating 3 is provided with alternating light and dark stripes. The light beam can generate an alternating light and dark stripe pattern by passing through the alternating light and dark stripes.

[0053] The second grating 4 is disposed on the propagation path of the light beam. The second grating 4 is provided with alternating bright and dark second stripes for amplifying and modulating the light beam.

[0054] The photoelectric receiving unit 5 is used to receive the light beam passing through the first grating 3 and the second grating 4, and convert the light beam into an electrical signal;

[0055] The signal processing unit, connected to the photoelectric receiving unit 5, is used to receive the electrical signal and perform position detection based on the electrical signal.

[0056] In this embodiment, the position detection device includes a light source 1, a servo motor 2, a first grating 3, a second grating 4, a photoelectric receiving unit 5, and a signal processing unit. Both the first grating 3 and the second grating 4 are provided with alternating bright and dark stripes. When the light beam emitted by the light source 1 is incident on the servo motor 2, the servo motor 2 drives the motor shaft 21 to rotate. The first grating 3 rotates with the rotation of the motor shaft 21, and the modulated light reflected by the first grating 3 also changes with the change in the bright and dark stripes, thereby generating an alternating bright and dark stripe pattern. Simultaneously, the alternating bright and dark stripes of the second grating 4 further amplify the light beam. Subsequently, the photoelectric receiving unit 5 converts the light beam modulated by the first grating 3 and the second grating 4 into a periodically changing electrical signal and sends it to the signal processing unit, which then performs signal detection based on the electrical signal.

[0057] In this embodiment, a grating is engraved on the motor shaft 21, thereby eliminating the glass grating support structure of the traditional grating encoder. This not only reduces the rotational inertia of the motor and improves the motor response performance, but also ensures the position detection accuracy. Furthermore, the position detection accuracy can be further improved by adjusting the parameters.

[0058] Here, combined Figure 3 and Figure 4 The alternating bright and dark stripes of the first grating 3 and the second grating 4 both refer to stripes arranged in alternating black and white patterns. The black stripes are light-absorbing areas, where light is absorbed by specially designed structures, surfaces, or materials, or diffusely reflected to reduce its intensity in a specific direction. The white stripes are highly reflective areas, reflecting all or most of the incident light along the normal direction of the incident surface. It should be noted that the first grating 3 and the second grating 4 described in this embodiment include, but are not limited to, alternating bright and dark binary gratings and other types of gratings, as long as they can satisfy the optical structure required to produce the alternating bright and dark stripe pattern.

[0059] The photoelectric receiving unit 5 generates periodically changing electrical signals, which may include sine waves, triangular waves, square waves, and other signals with specific periodic patterns. These periodically changing signals can be decoded into position information by relevant circuits. When the first grating 3 rotates by an angle of one brightness cycle, the photoelectric receiving unit 5 also generates a periodic electrical signal with a specific pattern, which is usually a 360° periodic image of a sine or cosine curve. The photoelectric receiving unit 5 includes, but is not limited to, devices that can convert optical changes into electrical signal changes, such as CMOS cameras, CCD cameras, and photodiode arrays.

[0060] The light source 1 includes, but is not limited to, various forms of energy sources that generate photoelectron radiation, such as point light sources 1, surface light sources 1, parallel light sources 1, and Gaussian light sources 1. The methods of generating photoelectron radiation include, but are not limited to, various forms of photoelectron radiation devices such as LEDs, LDs (laser diodes), VECSELs (Vertical External Cavity Surface Emitting Lasers), and other lasers. The light source 1 may also include certain DOEs (diffraction optical elements), lenses, and other components. Figure 5 and Figure 6 As shown, the light beam emitted by light source 1, after being modulated by the first grating 3 and the second grating 4, can produce a corresponding alternating bright and dark stripe pattern, such as... Figure 7 As shown, after the stripe pattern is received and converted by the photoelectric receiving unit 5, an electrical signal containing displacement information can be obtained.

[0061] In addition, the servo motor 2 includes a motor stator 22, which can be a magnet or a coil.

[0062] This embodiment uses the principle of stripe imaging for position measurement. Unlike traditional transmissive methods, which require light to pass through a etched code disk and then the photoelectric receiving unit 5 to receive the stripes of varying brightness caused by the code disk's etched lines, this embodiment eliminates the transparent code disk design and instead employs a specially designed imaging method using two gratings: the first grating 3 and the second grating 4. When light from the light source 1 passes through the first grating 3 and the second grating 4, it produces stripes of varying brightness. Furthermore, when the light beam illuminates the surface of the motor shaft 21, the first grating 3 of the motor shaft 21 reflects the incident light, generating information containing displacement and rotation in the outgoing light. The photoelectric receiving unit 5 receives the pattern generated by the light beam reflected from the motor shaft 21. As the motor shaft 21 rotates, the resulting alternating bright and dark stripe pattern moves with the rotation of the motor shaft 21, thus obtaining corresponding position feedback information.

[0063] It should also be noted that this embodiment eliminates the traditional glass code disk, thus significantly reducing the rotational inertia of the motor shaft 21. Furthermore, it eliminates the traditional sandwich structure where the light source 1, code disk, and receiver are located at the top, middle, and bottom respectively, instead placing the receiver and transmitter on the same side. This reduces assembly and debugging difficulty. Moreover, unlike traditional encoders that receive stripes of light and dark variations caused by the shadows cast by a single grating disk, this embodiment uses a composite grating pair structure composed of two gratings. The resulting stripes have a magnification effect, producing a clearer image and better signal quality.

[0064] In one embodiment, combined with Figure 8 and Figure 9 The first grating 3 and the second grating 4 are arranged in parallel, combined with Figure 10 The period of the first stripe may be the same as or different from the period of the second stripe.

[0065] In another embodiment, combined Figure 11 The first grating 3 and the second grating 4 have a certain angle between them, and the period of the first stripe is the same as or different from the period of the second stripe.

[0066] In this embodiment, the first grating 3 can be placed parallel to the second grating 4, such as... Figure 12 As shown, after modulation, the waveform period of the beam can be amplified, which significantly improves the detectability of the stripes and the final detection accuracy. Of course, in this embodiment, the first grating 3 and the second grating 4 can also be set at a certain angle, for example, the second grating 4 can be tilted relative to the first grating 3, meaning the stripes on the second grating 4 are not parallel to the stripes on the first grating 3, but rather at a certain angle. This will improve the amplification effect of the second grating 4, thereby producing stripe patterns that are easier to detect and have a longer period, such as... Figure 13 As shown, this improves the final position detection accuracy.

[0067] In addition, the fringe periods of the first grating 3 and the second grating 4 can be the same or different. For example, one fringe may have a larger period of brightness variation, while the other fringe may have a smaller period of brightness variation.

[0068] In one embodiment, the first grating 3 is engraved with oblique parallel lines that have a certain angle with the axial direction of the motor shaft 21.

[0069] like Figure 14 As shown, the first grating 3 can depict oblique parallel lines with a certain angle to the axis of rotation, and it also has a modulation function. At the same time, the modulated waveform may have an amplification effect.

[0070] In one embodiment, the second grating 4 is disposed between the first grating 3 and the light source 1, or the second grating 4 is disposed between the first grating 3 and the photoelectric receiving unit 5.

[0071] In this embodiment, the second grating 4 can be placed at the incident direction of the first grating 3. That is, the light beam from the light source 1 first passes through the second grating 4 and then illuminates the first grating 3 on the motor shaft 21. The reflected light then reaches the photoelectric receiving unit 5, thereby generating the same modulation pattern for position detection. Of course, the second grating 4 can also be placed at the exit direction of the first grating. That is, the light beam from the light source 1 first illuminates the first grating 3 on the motor shaft 21, and the reflected light can then pass through the second grating 4 and reach the photoelectric receiving unit 5, thus still generating the same modulation pattern for position detection.

[0072] In one embodiment, the second grating 4 may move relative to the first grating 3. For example... Figure 15 As shown, when the first grating 3 and the second grating 4 are relatively displaced, the bright and dark fringes of the modulated beam will also change with the movement of the moving grating.

[0073] In one embodiment, the first grating 3 is made of a reflective material, and the second grating 4 is made of a transmissive material.

[0074] Here, the first grating 3 is etched on the motor shaft 21 and will rotate with the movement of the motor shaft 21, so it is a reflective grating. The second grating 4 is used to transmit light beams to achieve amplification and modulation, so it is set as a transmission grating.

[0075] In one embodiment, the second grating 4 is provided in multiple forms.

[0076] In this embodiment, multiple second gratings 4 can be set according to actual needs, that is, multiple second gratings 4 can be connected in series for application. This allows for further modulation of the pattern to further improve the magnification effect, and also produces stripes with a wider period. For example, three or more second gratings 4 can be used for position detection.

[0077] In one embodiment, the alternating light and dark stripe pattern includes a first alternating light and dark stripe pattern with a single period and a second alternating light and dark stripe pattern with a mixed period; wherein the second stripe pattern includes parallel stripe patterns and diamond-shaped stripe patterns with included angles.

[0078] In this embodiment, after modulation by the first grating 3 and the second grating 4, the resulting alternating light and dark stripe pattern includes, but is not limited to, alternating light and dark stripes of a single period, and alternating light and dark stripes of two different periods forming a mixed period stripe. The mixed period stripes can be parallel to each other, or they can be diamond-shaped stripes with a certain angle, or other different mixed patterns composed of two stripes.

[0079] like Figure 16 As shown, this embodiment of the invention also provides a position detection method applicable to the position detection device described above, the method comprising: steps S101 to S104.

[0080] Step S101: Use light source 1 to emit a beam of light to servo motor 2;

[0081] Step S102: Control the motor shaft 21 of the servo motor 2 to rotate, and use the first grating 3 engraved on the motor shaft 21 to modulate the light beam to generate a striped pattern of alternating light and dark; and use the second grating 4 to amplify and modulate the light beam.

[0082] Step S103: The photoelectric receiving unit 5 receives the light beam passing through the first grating 3 and the second grating 4, and generates the corresponding electrical signal.

[0083] Step S104: The electrical signal is processed by the signal processing unit to achieve position detection.

[0084] In this embodiment, when performing position detection based on the position detection device, the light source 1 is first turned on to emit a stable beam of light to the servo motor 2. At this time, the servo motor 2 starts running under control commands, and the motor shaft 21 rotates accordingly. Since the first grating 3 is etched on the motor shaft 21, it rotates synchronously with the motor shaft 21. When the beam of light is incident on the first grating 3, the alternating bright and dark stripes on the first grating 3 modulate the beam of light, generating a pattern of alternating bright and dark stripes with a specific pattern. Simultaneously, since a second grating 4 is also provided in the beam's propagation path, the second grating 4 amplifies and modulates the passing beam of light. The doubly modulated beam of light is then received by the photoelectric receiving unit 5, which converts the optical signal into an electrical signal. This electrical signal may contain information due to changes in the grating stripes and the rotation of the shaft. Finally, the signal processing unit receives the electrical signal from the photoelectric receiving unit 5 and extracts position-related information through analysis and processing of the electrical signal, thereby achieving accurate position detection.

[0085] In this embodiment, a grating is engraved on the motor shaft 21, thereby eliminating the glass grating support structure of the traditional grating encoder. This not only reduces the rotational inertia of the motor and improves the motor response performance, but also ensures the position detection accuracy. Furthermore, the position detection accuracy can be further improved by adjusting the parameters.

[0086] It should be noted that in this embodiment, when processing the electrical signal through the signal processing unit to achieve position detection, existing technical solutions can be used. For example, a Fast Fourier Transform (FFT) algorithm can be employed to perform spectral analysis on the electrical signal, extracting frequency components related to position changes, and then calculating accurate position information. Alternatively, digital signal processing (DSP) technology can be used to filter, amplify, and digitize the electrical signal to improve the signal-to-noise ratio and resolution, thereby further enhancing the accuracy of position detection. In practical applications, appropriate signal processing algorithms and techniques can be selected based on specific needs and scenario characteristics to achieve optimal position detection results.

[0087] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the systems disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple; relevant parts can be referred to in the method section. It should be noted that those skilled in the art can make various improvements and modifications to this application without departing from the principles of this application, and these improvements and modifications also fall within the protection scope of the claims of this application.

[0088] It should also be noted that, in this specification, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

Claims

1. A position detection device, characterized in that, include: A light source, used to emit light beams; A servo motor, including a motor shaft, wherein the light beam can be incident on the motor shaft; The first grating is etched on the motor shaft. The first grating has alternating light and dark stripes. The light beam can generate an alternating light and dark stripe pattern by passing through the alternating light and dark stripes. The first grating is etched with oblique parallel lines that have a certain angle with the axial direction of the motor shaft. A second grating is disposed on the propagation path of the light beam. The second grating has alternating bright and dark stripes for amplifying and modulating the light beam. The second grating is movable relative to the first grating. A photoelectric receiving unit is used to receive the light beam passing through the first grating and the second grating, and convert the light beam into an electrical signal; A signal processing unit, connected to the photoelectric receiving unit, is used to receive the electrical signal and perform position detection based on the electrical signal.

2. The position detection device according to claim 1, characterized in that, The first grating and the second grating are arranged in parallel, and the period of the first stripe is the same as or different from the period of the second stripe.

3. The position detection device according to claim 1, characterized in that, The first grating and the second grating are at a certain angle, and the period of the first fringe is the same as or different from the period of the second fringe.

4. The position detection device according to claim 1, characterized in that, The second grating is disposed between the first grating and the light source, or the second grating is disposed between the first grating and the photoelectric receiving unit.

5. The position detection device according to claim 1, characterized in that, The first grating is made of a reflective material, and the second grating is made of a transmissive material.

6. The position detection device according to claim 1, characterized in that, The second grating is provided in multiple ways.

7. The position detection device according to claim 1, characterized in that, The alternating light and dark stripe pattern includes a first alternating light and dark stripe pattern with a single cycle and a second alternating light and dark stripe pattern with a mixed cycle; wherein, the second stripe pattern includes parallel stripe patterns and diamond-shaped stripe patterns with included angles.

8. A position detection method, applicable to the position detection device as described in any one of claims 1-7, characterized in that, The method includes: A light source is used to emit a beam of light to the servo motor; The servo motor shaft is controlled to rotate, and the light beam is modulated using a first grating engraved on the motor shaft to generate a striped pattern of alternating light and dark stripes; and the light beam is amplified and modulated using a second grating. The photoelectric receiving unit receives the light beams passing through the first and second gratings and generates corresponding electrical signals. The electrical signal is processed by a signal processing unit to achieve position detection.

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