Displacement sensor, galvanometer motor system, assembly method and signal processing method

Abstract

The invention discloses a displacement sensor, a galvanometer motor system, an assembling method and a signal processing method, the displacement sensor is connected with a motor shaft and adopts a transmission-type grating sandwich structure, and the transmission-type grating sandwich structure comprises a light source module which is arranged on the upper layer and comprises an aspheric collimating lens capable of generating uniform parallel light beams; the grating code disc is arranged on the middle layer and made of an optical glass substrate, and the grating code disc is fixed on the motor shaft through a code disc tray; the photoelectric receiving module is arranged on the lower layer, the photoelectric receiving module comprises a plurality of groups of orthogonally arranged photodiodes and photoelectric converters, the photodiodes are used for receiving light and shade changes of light stripes and forming optical signals, and the photoelectric converters are used for receiving the optical signals and converting the optical signals into electric signals. According to the invention, the size of the structure can be reduced, the position subdivision precision is improved, the signal processing speed and the anti-interference capability are improved, and thus the use effect of the galvanometer motor system is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of laser processing, and particularly to a displacement sensor, a galvanometer motor system, an assembly method, and a signal processing method. Background Art

[0002] A galvanometer motor system is a precision swing actuator based on electromagnetic drive. It realizes the nanoscale positioning of a laser beam through the high-speed periodic deflection of a lens, and is widely used in fields such as laser precision processing (such as wafer cutting, 3D printing), optical detection (such as surface profile scanning), and biomedical imaging. The core function of the galvanometer motor system is essentially dynamic angle-space position decoupling control, which needs to reproduce the preset trajectory to the actual deflection angle of the lens under microsecond-level response. During this process, the position feedback system, as a key link in closed-loop control, plays the following core roles: (1) Real-time deviation correction: During high-speed scanning, the instantaneous deviation of the galvanometer rotor due to inertial torque and external load disturbance needs to be compensated by the closed-loop of position data. (2) Jitter suppression: The resolution and delay of position feedback are directly related to the positioning jitter of the laser focal spot. For example, the line width error in semiconductor cutting is ≯0.1 μm. (3) The boundary restricting the system bandwidth: The upper limit of the closed-loop bandwidth is determined by the total delay of the feedback link (sensing + processing + transmission). The mechanical resonance frequency of the galvanometer motor system often reaches 5 - 20 kHz. However, when the feedback delay > 2 μs, the available bandwidth of the system is compressed to ≤2 kHz, resulting in a significant deterioration of the laser scanning rate and processing efficiency.

[0003] Currently, the general high-precision displacement detection devices on the market are mainly manufactured based on the principle of optical signal modulation and reception. Its core function is to convert the mechanical rotation amount into an electrical pulse signal through the on-off change of light. Its working principle can be decomposed into the following three core physical processes: (1) Optical path modulation: The core component of the encoder is a transparent disc (code disc), with equally spaced opaque grating grids engraved on its surface. The grating density determines the resolution (for example, for a 100-line / turn code disc, each grid corresponds to a 3.6° rotation angle). The light source (usually an LED) emits parallel light from one side of the code disc; when the code disc rotates, the opaque grating grids periodically block the light beam, causing the photodetector on the other side to receive light and dark alternating light signals. (2) Photoelectric conversion: The photodiode / phototransistor receives the light signal transmitted through the code disc and converts it into a current signal with varying strength. Through signal conditioning and amplification, a voltage signal that can be collected is formed to complete the simulation of the displacement signal. (3) Signal processing: Some products directly output the analog signal as the only signal, and some products will further convert the electrical signal into a pulse or a digital signal encoded in a fixed format and then output it.

[0004] The problems existing in the application of existing products in the galvanometer motor system are specifically as follows: (1) Conflict between physical configuration and system integration: Industrial-grade high-precision grating encoders generally adopt a general-purpose packaging structure (outer diameter > Φ25 mm), which seriously conflicts with the ultra-thin cavity space of the galvanometer motor (typical requirement ≤ Φ15 mm), resulting in physical interference.

[0005] (2) Simple electrical signal processing system: ① In the basic signal conditioning stage, the primary solution is to directly amplify the original Sin / Cos signals only using low-end operational amplifiers (typical gain error ±5%), without a filtering / shaping circuit, resulting in a low signal-to-noise ratio and inability to perform fine subdivision; the improved solution is to add an RC filtering network (cut-off frequency ~10 kHz), but it cannot eliminate the differential noise spikes during the acceleration stage of the galvanometer and has a phase lag; ② Lack of signal shaping function. Due to uneven stripes generated during the grating engraving process, as well as signal attenuation caused by dust, oil, and light sources during operation, the accuracy of position subdivision will be affected. Therefore, traditional encoders cannot achieve high accuracy without a signal shaping function.

[0006] (3) Subdivision algorithm and accuracy bottleneck: ① No subdivision / direct analog output. Some low-end solutions directly output the original analog signals (such as ±5 V differential), forcing the controller to perform all interpolation operations, which will cause a large amount of interference to the signal before it is transmitted to the controller, ultimately resulting in a reduction in the effective subdivision accuracy; ② Insufficient simple digital subdivision ability. For example, a fixed coefficient hardware subdivider (such as 4× - 16×) is used, but due to volume limitations, large-scale processing circuits usually cannot be accommodated inside the encoder. Therefore, a simple analog comparator circuit is used for subdivision. Due to the low subdivision, it cannot meet the high-precision working requirements of the galvanometer motor system. The single grating pitch subdivision requirement of the galvanometer motor system reaches 8192x (calculated with a grating pitch of 40um, the position resolution after subdivision of 8192 can reach 4.88nm).

[0007] (4) Inherent defects in the signal transmission mode: ① Analog transmission (such as ±1 V differential) has the defects of weak common-mode interference resistance and large signal attenuation rate during long-distance transmission; ② Pulse counting transmission (such as A / B quadrature pulses) has the defects of relying on a high-frequency carrier (typical 10 MHz) and being vulnerable to electromagnetic interference (bit error rate > 10 -4 ) and being unable to be compatible with absolute position feedback, requiring an additional initialization process; ③ Low-speed digital buses (such as RS485, 2.5 Mbps) have uncontrollable transmission delays (single-frame data delay ≥ 4 μs), resulting in a 30% decrease in the phase margin of the galvanometer, and the need for polling communication in multi-axis coordination, exacerbating jitter (measured multi-axis synchronization error > 25 μrad).

[0008] In summary, the existing solutions face the following irreconcilable conflicts in the galvanometer motor system: (1) Physical adaptability: The geometric contradiction between the standard encoder size and the galvanometer cavity; (2) Signal chain completeness: There are cascading errors in the entire link from filtering and shaping, high-magnification subdivision to high-speed transmission; (3) Dynamic performance matching: The delay and noise level of the encoder limit the galvanometer control bandwidth to < 2 kHz (far lower than the theoretical mechanical bandwidth ≥ 5 kHz).

[0009] The root cause of the above contradiction system is that the design concept of traditional encoders focuses on general servo scenarios. Therefore, how to overcome the above contradiction defects and improve the use effect of the galvanometer motor system is a problem that those skilled in the art need to solve. Summary of the Invention

[0010] Embodiments of the present invention provide a displacement sensor, a galvanometer motor system, an assembly method, and a signal processing method, aiming to improve the use effect of the galvanometer motor system.

[0011] In the first aspect, embodiments of the present invention provide a displacement sensor connected to the motor shaft. The displacement sensor adopts a transmissive grating sandwich structure, and the transmissive grating sandwich structure includes: A light source module, arranged on the upper layer, and the light source module includes an aspheric collimating lens capable of generating a uniform parallel light beam; A grating code disk, arranged on the middle layer. The grating code disk is made of an optical glass substrate and is fixed on the motor shaft through a code disk tray; A photoelectric receiving module, arranged on the lower layer. The photoelectric receiving module includes multiple groups of orthogonally arranged photodiodes and a photoelectric converter, and the photoelectric converter is fixed on the motor stator. The photodiodes are used to receive the light and dark changes of the light stripes and form optical signals, and the photoelectric converter is used to receive the optical signals and convert them into electrical signals.

[0012] In the second aspect, embodiments of the present invention provide an assembly method of a displacement sensor, which is applied to the displacement sensor as described in the first aspect. The assembly method includes: Fix the code disk tray on the motor shaft and place the grating code disk on the disk surface of the code disk tray; Control the motor shaft to rotate at a constant speed, and detect whether the rotation center of the grating disk is concentric with the rotation center of the motor shaft; When the rotation center of the grating disk is not concentric with the rotation center of the motor shaft, monitor the beating condition of the grating disk from the edge of the grating disk; Correct the grating disk based on the beating condition of the grating disk so that the rotation center of the grating disk is concentric with the rotation center of the motor shaft.

[0013] In a third aspect, an embodiment of the present invention provides a galvanometer motor system, including the displacement sensor as described in the first aspect.

[0014] In a fourth aspect, an embodiment of the present invention provides a signal processing method for a galvanometer motor system, which is applied to the galvanometer motor system as described in the third aspect. The signal processing method includes: Obtain the optical signal of the target object and convert the optical signal into a digital signal; Perform offset conditioning and amplitude conditioning on the digital signal to obtain a target signal; Use a subdivision algorithm to perform position calculation on the target signal to obtain corresponding position information; Pack and output the position information in a set format.

[0015] Further, the obtaining the optical signal of the target object and converting the optical signal into a digital signal includes: Use a photoelectric converter to convert the optical signal into an electrical signal; Amplify the electrical signal through an analog amplification circuit to obtain an analog signal; Perform digital conversion on the analog information to obtain the digital signal.

[0016] Further, the performing offset conditioning and amplitude conditioning on the digital signal to obtain a target signal includes: Obtain the voltage sine period of the digital signal; Sample the maximum voltage and the minimum voltage in the sine period; According to the following formula, calculate the offset voltage in combination with the set voltage, and use the offset voltage to perform offset conditioning on the digital signal; COMPEN = RAW-(TAR_CEN-((MAX-MIN) / 2+MIN)); Where, COMPEN represents the voltage after offset conditioning, RAW represents the input original voltage, TAR_CEN represents the set voltage, MAX represents the maximum voltage, MIN represents the minimum voltage, and TAR_CEN-((MAX-MIN) / 2+MIN) represents the offset voltage.

[0017] Further, the step of performing bias conditioning and amplitude conditioning on the digital signal to obtain a target signal further includes: Calculating a gain ratio according to the following formula in combination with a preset standard signal peak-to-peak value, and performing amplitude conditioning on the digital signal according to the gain ratio; OUT = ((MAX - MIN) / STAD)*RAW; where OUT represents the voltage after amplitude conditioning, STAD represents the standard signal peak-to-peak value, and (MAX - MIN) / STAD represents the gain ratio.

[0018] Further, the step of performing position calculation on the target signal by using a subdivision algorithm to obtain corresponding position information includes: Obtaining a sine period of the target signal, and extracting a first sine signal and a second sine signal with a 90° phase difference from the sine period of the target signal; Performing polar coordinate conversion on the first sine signal and the second sine signal, and forming a Lissajous figure based on the fluctuation periods of the first sine signal and the second sine signal; According to the following formula, calculating corresponding angle information for any point on the Lissajous figure: α = atan (Y / X) = atan (B / A); where α represents the angle information, atan represents the arctangent trigonometric function, A represents the first sine signal, B represents the second sine signal, and X and Y represent the coordinates of any point on the Lissajous figure; According to the following formula, calculating the position information in combination with the angle information: P = (N*M) + α / 360*N; where P represents the position information, N represents the subdivision ratio, and M represents the number of sine periods.

[0019] Further, the step of obtaining an optical signal of a target object and converting the optical signal into a digital signal further includes: Comparing the optical signal with a preset first signal amplitude and a preset second signal amplitude respectively; wherein the first signal amplitude is higher than the second signal amplitude; When the optical signal exceeds the first signal amplitude, performing step-by-step cutting on the base of the optical receiver to expand the gap between the grating disk and the optical converter; When the optical signal is lower than the second signal amplitude, inserting a gasket between the grating disk and the optical converter to reduce the gap between the grating disk and the optical converter.

[0020] Further, after the step of performing position calculation on the target signal by using the subdivision algorithm to obtain the corresponding position information, the following steps are included: Perform filtering processing on the position information.

[0021] The embodiments of the present invention provide a displacement sensor, a galvanometer motor system, an assembly method, and a signal processing method. Through optimized design and the adoption of advanced manufacturing processes, the overall size of the encoder is significantly reduced, making it more compact, thereby better adapting to the limited space of the galvanometer motor. Also, by using high-resolution sensors and refined signal processing algorithms, the position subdivision accuracy is significantly improved, ensuring high-precision positioning and motion control of the galvanometer motor. And by improving signal transmission technology and enhancing electromagnetic compatibility design, the transmission speed of the encoder is significantly increased, and at the same time, it has stronger anti-interference ability, ensuring stable operation even in a complex electromagnetic environment. Thus, the overall usage effect of the galvanometer motor system is improved. Description of the Drawings

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0023] Figure 1 It is a schematic structural diagram of a displacement sensor provided by an embodiment of the present invention; Figure 2 It is a schematic structural diagram of another perspective of a displacement sensor provided by an embodiment of the present invention; Figure 3 It is a schematic flow diagram of an assembly method of a displacement sensor provided by an embodiment of the present invention; Figure 4 It is a schematic flow diagram of a signal processing method of a galvanometer motor system provided by an embodiment of the present invention; Figure 5 It is a first example diagram of a signal processing method of a galvanometer motor system provided by an embodiment of the present invention; Figure 6 It is a second example diagram of a signal processing method of a galvanometer motor system provided by an embodiment of the present invention; Figure 7 It is a third example diagram of a signal processing method of a galvanometer motor system provided by an embodiment of the present invention. Detailed Embodiments

[0024] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0025] 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, wholes, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components, and / or their combinations.

[0026] It should also be understood that the terms used in this specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in this specification of the present invention and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an", and "the" are intended to include the plural forms.

[0027] It should be further understood that the term "and / or" used in this specification of the present invention and the appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0028] Please refer to the following Figure 1 and Figure 2 , the embodiment of the present invention provides a displacement sensor connected to the motor shaft 1. The displacement sensor adopts a transmissive grating sandwich structure, and the transmissive grating sandwich structure includes: A light source module 2 is arranged on the upper layer. The light source module 2 includes an aspherical collimating lens that can generate a uniform parallel light beam. A grating code disk 3 is arranged on the middle layer. The grating code disk 3 is made of an optical glass substrate, and the grating code disk is fixed on the motor shaft 1 through a code disk tray 4. A photoelectric receiving module 5 is arranged on the lower layer. The photoelectric receiving module 5 includes multiple groups of orthogonally arranged photodiodes and a photoelectric converter. The photoelectric converter is fixed on the motor stator 6. The photodiodes are used to receive the brightness change of the light stripe and form an optical signal, and the photoelectric converter is used to receive the optical signal and convert it into an electrical signal.

[0029] In this embodiment, the displacement sensor adopts a transmissive grating sandwich architecture in terms of structure, which is divided into three layers: The light source module 2 on the upper layer uses a high-power LED, and is paired with an aspherical collimating lens to generate a uniform parallel light beam, and the spot uniformity can exceed 95%. The grating code disk 3 in the middle layer uses an ultra-thin optical glass substrate, and other light-transmitting materials can also be used for production. Further, a hard anti-reflection coating is applied to the surface of the code disk, including but not limited to anti-reflection coatings, and anti-reflection coatings, polarization coatings, and coatings that can limit the wavelength bandwidth can also be used. The grating is designed to include but not limited to incremental tracks, such as Figure 2 the grating track 9 in

[0030] The photoelectric receiving module 5 in the lower layer includes four groups of orthogonally arranged photodiodes, which are used to receive the brightness changes of the light stripes, convert them into electrical signals, and finally output them in the form of differential signals. The photoelectric converter is fixed on the motor stator 6.

[0031] Although the principle of the sensor is similar to that of an ordinary encoder, the displacement sensor provided in this embodiment can greatly reduce the structural volume through a more compact structural layout, and cleverly integrates the entire optoelectronic structure with the galvanometer motor. For example, structures such as the separate housing, bearings, and oil seals of the encoder are cancelled, and they are directly encapsulated at the rear of the motor, as shown in Figure 1 and Figure 2 shown, the displacement sensor is integrated in the motor housing 7 and connected to the circuit board 8 on the galvanometer motor. At the same time, the photoelectric converter is directly fixed on the motor stator, which can greatly reduce the volume occupied by the sensor.

[0032] Figure 3 It is a schematic flow chart of an assembly method of a displacement sensor provided by an embodiment of the present invention. The assembly method is applied to the displacement sensor described above. The assembly method includes: steps S101 to S104.

[0033] Step S101: Fix the code disk tray on the motor shaft and place the grating code disk on the disk surface of the code disk tray; Step S102: Control the motor shaft to rotate at a constant speed and detect whether the rotation center of the grating code disk is concentric with the rotation center of the motor shaft; Step S103: When the rotation center of the grating code disk is not concentric with the rotation center of the motor shaft, monitor the jumping condition of the grating code disk from the edge of the grating code disk; Step S104: Correct the grating code disk based on the jumping condition of the grating code disk so that the rotation center of the grating code disk is concentric with the rotation center of the motor shaft.

[0034] In this embodiment, through a special assembly process, the concentricity between the grating code disk and the motor shaft is improved, thereby enhancing the overall structural accuracy. The concentricity between the grating code disk of the structural sensor and the motor shaft is an important factor affecting the displacement measurement accuracy. Considering that the traditional direct connection method easily causes the rotation centers of the motor shaft and the encoder code disk to be non-concentric, resulting in a large position error and accuracy loss. Therefore, this embodiment sets a corresponding assembly process based on the described structural sensor to ensure the concentricity between the grating code disk and the motor shaft.

[0035] Specifically, first, fix the code disk tray on the motor shaft, apply glue on its tray surface, and then place the grating code disk. Next, make the motor shaft rotate at a constant speed. At this time, observe whether the rotation centers of the motor shaft and the grating code disk are concentric. Here, if the rotation center of the grating code disk is not concentric with the rotation center of the motor shaft, then when looking down at the edge of the grating code disk, it will be observed that the edge of the grating code disk does not stay in the same position but bounces up and down as it rotates. Therefore, in practical applications, devices such as a CCD camera or a laser displacement sensor can be used to align with the edge of the grating code disk, monitor its bounce, and perform correction and adjustment on the bounce to make it significantly reduced until the camera can no longer observe the bounce. For the corrected structure, it can be fixed by means such as glue curing to form a perfectly concentric mechanism.

[0036] The embodiment of the present invention also provides a galvanometer motor system, including the displacement sensor as described above.

[0037] Furthermore, as Figure 4 shown, the embodiment of the present invention also provides a signal processing method for a galvanometer motor system. This signal processing method is applied to the galvanometer motor system as described above, and the signal processing method includes: steps S201 - S204.

[0038] Step S201, obtain the optical signal of the target object and convert the optical signal into a digital signal; Step S202, perform offset conditioning and amplitude conditioning on the digital signal to obtain a target signal; Step S203, use a subdivision algorithm to perform position calculation on the target signal to obtain corresponding position information; Step S204, pack and output the position information in a set format.

[0039] In this embodiment, first, an optical signal is acquired and converted into a digital signal. Then, the digital signal is compensated and conditioned through two methods: bias conditioning and amplitude conditioning to obtain a target signal. Next, the target signal is subdivided to obtain the position information corresponding to the optical signal. Then, the position information is packed into encoded information in a specific format to enhance its anti-interference performance. Finally, the position information is output externally. Through the above signal processing flow, the signal processing efficiency, accuracy, and anti-interference ability of the galvanometer motor system can be significantly improved.

[0040] In a specific embodiment, the acquiring of the optical signal of the target object and the conversion of the optical signal into a digital signal include: Converting the optical signal into an electrical signal by using an optoelectronic converter; Amplifying the electrical signal through an analog amplification circuit to obtain an analog signal; Performing digital conversion on the analog information to obtain the digital signal.

[0041] After the optical signal is acquired, first, the optical signal is converted into a weak electrical signal by an optoelectronic converter, then the weak electrical signal is converted into a measurable signal by an analog amplifier, and then through analog-to-digital conversion, the analog signal is converted into a digital signal, that is, the digital signal.

[0042] In another specific embodiment, after the step of performing position calculation on the target signal by using a subdivision algorithm to obtain the corresponding position information, it includes: Performing filtering processing on the position information.

[0043] After the position information is obtained, a filter can be used to perform filtering processing on it to filter out the interference information generated by the optical path and the circuit, thereby smoothing the position. Thereafter, the filtered position information can be packed.

[0044] In an embodiment, the performing of bias conditioning and amplitude conditioning on the digital signal to obtain a target signal includes: Obtaining the voltage sine period of the digital signal; Sampling the maximum voltage and the minimum voltage in the sine period; According to the following formula, calculating the bias voltage in combination with the set voltage, and using the bias voltage to perform bias conditioning on the digital signal; COMPEN = RAW-(TAR_CEN-((MAX-MIN) / 2+MIN)); Among them, COMPEN represents the voltage after offset conditioning, RAW represents the original input voltage, TAR_CEN represents the set voltage, MAX represents the maximum voltage, MIN represents the minimum voltage, and TAR_CEN - ((MAX - MIN) / 2 + MIN) represents the offset voltage.

[0045] Further, the offset conditioning and amplitude conditioning of the digital signal to obtain a target signal further includes: Calculating a gain ratio according to the following formula in combination with a preset standard signal peak-to-peak value, and performing amplitude conditioning on the digital signal according to the gain ratio; OUT = ((MAX - MIN) / STAD)*RAW; Among them, OUT represents the voltage after amplitude conditioning, STAD represents the standard signal peak-to-peak value, and (MAX - MIN) / STAD represents the gain ratio.

[0046] Due to the influence of factors such as dust, oil stains, and LED light intensity attenuation, the quality of the electrical signal changes slightly with the change of the operating environment, thus affecting its positioning accuracy. Therefore, in order to compensate for the attenuation and offset of the signal, this embodiment uses two methods of offset conditioning and amplitude conditioning to compensate for it.

[0047] Among them, when performing offset compensation, for the converted digital signal, sample the maximum and minimum values of each sine period, and obtain the center voltage (MAX - MIN) / 2 + MIN based on the maximum and minimum values. Then, by taking the difference from the set voltage, obtain the offset amount, and subtract this part of the value from the original signal, thereby realizing the compensation for the offset voltage.

[0048] When performing amplitude compensation, the voltage peak-to-peak value MAX - MIN can be calculated based on the maximum and minimum values, and then divided by the standard voltage amplitude to obtain its gain ratio. Combining with the original voltage can obtain the voltage after gain compensation.

[0049] Through the above two compensation methods, the quality and consistency of the signal can be greatly improved, thereby providing a reliable guarantee for the subsequent positioning accuracy and ensuring the stable operation of the system in different environments.

[0050] The set voltage can be adaptively adjusted according to environmental changes, thereby further optimizing the working performance of the displacement sensor. This adaptive adjustment mechanism can monitor the working state of the system in real time and dynamically adjust the set voltage as needed to adapt to different working environments and conditions. For example, in the presence of pollutants such as dust or oil, the system can automatically increase the set voltage to compensate for signal attenuation and ensure the accuracy and stability of the signal. In addition, this mechanism can also automatically adjust the gain ratio according to the attenuation of the LED light intensity, thereby maintaining high-quality signal transmission. This adaptive adjustment function not only improves the robustness and reliability of the system, but also reduces the maintenance cost, enabling the system to operate stably in various complex environments.

[0051] In some alternative embodiments, the set voltage is obtained by an adaptive dichotomy voltage regulation algorithm. Specifically, it includes: First, preset a target voltage V target , and define the allowable error range Δe, such as ±0.1%. Then continuously collect multiple sets of output voltages V output of the galvanometer motor system and the corresponding adjustment step sizes D, and then calculate the current error e = V target - V output . At the same time, fit the V−D characteristic curve by the least squares method and establish a linear relationship model between the output voltage and the adjustment amount: V output = k1*D + b; where k1 is the slope and b is the intercept, which can be understood as the adjustment sensitivity; through this linear relationship model, the corresponding adjustment step size D can be calculated after obtaining V output subsequently; Dynamically adjust the step size ΔD according to the current error e: ΔD = k2*|e| + k3*de / dt; where k2 is the proportional coefficient and k3 is the differential coefficient, which gives priority to fast response to large errors and focuses on stable convergence for small errors. Here, if the adjustment directions are the same for two consecutive times, the step size is reduced to 50% of the original value.

[0052] Subsequently, update the adjustment amount according to the error direction: If e > 0, increase the adjustment compensation, that is, D new = D current + ΔD; where D current is the most recent adjustment step size; If e < 0, decrease the adjustment compensation, that is, D new = D current + ΔD.

[0053] When the error e is within the allowable error range Δe, the iteration is stopped, and the adjustment step size at this time is set as the target step size, and the set voltage is obtained in combination with the target voltage: V = V target +D new . In this way, the set voltage can be made more in line with the actual working requirements, and the influence of voltage fluctuation on the accuracy of the displacement sensor can be avoided. At the same time, the adaptive dichotomy voltage regulation algorithm can also be dynamically adjusted according to the real-time working state of the galvanometer motor system to ensure that the system is always in the best working state.

[0054] In some alternative embodiments, the standard signal peak-to-peak value is set by the differential threshold detection method. Specifically, it includes: first collecting the optical signal and converting it into a digital signal (denoted as S(t) here, where t represents the time), then using mean filtering, median filtering or a low-pass filter to eliminate high-frequency noise (such as glitch interference), and eliminating the influence of baseline drift by subtracting the signal mean or moving average. Next, a first-order difference calculation is performed, that is, the forward difference sequence ΔS(t) = S(t - 1) - S(t) is calculated for S(t) to reflect the change in the signal slope. Then, extreme value candidate points are screened. Among them, the peak is the point where the difference value changes from positive to negative, that is, ΔS(t) > 0 and ΔS(t + 1) < 0, and the trough is the point where the difference value changes from negative to positive, that is, ΔS(t) < 0 and ΔS(t + 1) > 0. A dynamic threshold is set according to the signal characteristics. For example, the mean μ and standard deviation σ within the sliding window of the absolute value of the difference are taken, and the adaptive threshold is set accordingly: T = μ + k4σ, where k4 is an empirical coefficient. Here, if the absolute value of the difference on both sides of the extreme value candidate point is less than the threshold T, it is regarded as noise interference and eliminated. At the same time, the interference section is excluded by combining the symbolic approximation matching method. Then, the set of peak and trough points passing the threshold screening is retained, and the maximum value V max in the peaks and the minimum value V min in the troughs are selected from the set, and thus the standard signal peak-to-peak value V pp =V max -V min is obtained.

[0055] In one embodiment, the position operation is performed on the target signal by using the subdivision algorithm to obtain the corresponding position information, including: Obtaining the sine period of the target signal, and extracting a first sine signal and a second sine signal with a 90° phase difference from the sine period of the target signal; Performing polar coordinate conversion on the first sine signal and the second sine signal, and forming a Lissajous figure based on the fluctuation periods of the first sine signal and the second sine signal; According to the following formula, for any point on the Lissajous figure, the corresponding angle information is calculated: α = atan(Y / X) = atan(B / A); Wherein, α represents angle information, atan represents the arctangent trigonometric function, A represents the first sine signal, B represents the second sine information, and X and Y represent the coordinates of any point on the Lissajous circle; According to the following formula, the position information is calculated by combining the angle information: P = (N * M) + α / 360 * N; Wherein, P represents position information, N represents the subdivision magnification, and M represents the number of sine periods.

[0056] In the traditional scheme, even if the signal is subdivided, the subdivision magnification generally does not exceed 16 times. That is to say, usually only 16 pulses can be generated by one sine wave. However, due to the extremely high precision of the galvanometer, the required subdivision magnification must be above 8192, that is, 8192 position data or pulses need to be generated for each sine wave period. Therefore, a more refined scheme must be adopted to implement this function. Therefore, in this embodiment, a subdivision algorithm is used to perform position calculation on the target signal to meet the actual use requirements.

[0057] In this embodiment, first, an A-phase sine signal and a B-phase sine signal with a 90° phase difference are obtained from the target signal, that is, the aforementioned first sine signal and second sine signal. Since the waveforms of the ideal A-phase sine signal and B-phase sine signal are the same and the signals differ by 90°, after performing polar coordinate transformation on them, in the polar coordinate system, when the A-phase sine signal and B-phase sine signal fluctuate for a complete cycle, a complete circle can be formed, that is, the Lissajous circle. Further, through inverse trigonometric function operations, the corresponding angle information can be calculated based on the X and Y coordinates of any point on the circle, and this angle information is unique within each sine wave period. Then, by accumulating the angle information of multiple periods, the subdivided position information is generated.

[0058] The angle calculation formula is: α = atan(Y / X) = atan(B / A). Where α is the angle of a single sine period, B is the amplitude of the B-phase sine signal, A is the amplitude of the A-phase sine signal, and atan is the arctangent trigonometric function.

[0059] Correspondingly, the calculation formula for the position information is: position P = (8192 * number of sine periods) + α / 360 * 8192. That is, the corresponding position information can be obtained through the above angle calculation formula and position calculation formula.

[0060] In one embodiment, the obtaining of the optical signal of the target object and the conversion of the optical signal into a digital signal further include: Compare the optical signal with a preset first signal amplitude and a preset second signal amplitude respectively; wherein, the first signal amplitude is higher than the second signal amplitude. When the optical signal exceeds the first signal amplitude, stepwise cut the base of the optoelectronic receiver to expand the gap between the grating code disk and the optoelectronic converter. When the optical signal is lower than the second signal amplitude, insert a spacer between the grating code disk and the optoelectronic converter to reduce the gap between the grating code disk and the optoelectronic converter.

[0061] The conditioning of the signal is divided into coarse tuning and fine tuning. The foregoing parts such as signal compensation and subdivision belong to fine tuning. In order to further improve the accuracy of signal conditioning in this embodiment, the signal is also coarsely tuned. Since the interference fringes of light are very sensitive to the change of position, when the displacement between the code disk and the optoelectronic converter changes slightly, it may bring obvious changes in the strength of the interference fringe signal, and then bring changes in the electrical signal and the influence of the subdivision accuracy. Therefore, by coarsely tuning the gap between the grating code disk and the optoelectronic converter, the amplitude deviation of the finally generated electrical signal can be within 0.1V.

[0062] For example, when the signal amplitude is too high, the base of the optoelectronic receiver can be stepwise cut with a file at an amplitude of 0.05 mm to expand the gap between the code disk and the optoelectronic converter, so as to reduce the light intensity and cut down the electrical signal amplitude. When the signal amplitude is too low, a spacer (the thickness grading includes 0.025 mm, 0.05 mm and 0.1 mm) can be inserted between the grating code disk and the optoelectronic converter to reduce the gap, so as to increase the light intensity signal and enhance the electrical signal amplitude.

[0063] In one embodiment, when outputting the packaged position information externally, a dedicated high-speed communication protocol can be used. The high-speed position transmission protocol dedicated to the galvanometer is mainly used to minimize the transmission delay, avoid interference and identify error codes, etc.

[0064] This embodiment uses digital differential mode transmission at the physical layer for anti-interference, especially for the suppression of common-mode interference, and the effect is obvious. Compared with the traditional analog quantity transmission mode, it has obvious advantages. During actual transmission, a clock rate greater than or equal to 10 MHz is used for data transmission. And full-duplex communication is adopted, that is, sending and receiving are carried out simultaneously. In this way, the signal processing device can simultaneously complete the request sending of the next frame of position information and the reception of the current position information. Compared with the common 2.5 MHz half-duplex communication on the market, not only the signal transmission frequency is increased by more than 4 times, but also the single-line communication mode of asking and answering is avoided, and the efficiency is at least doubled again. Therefore, the comprehensive efficiency is increased by more than 8 times.

[0065] In addition, a CRC check and packet sequence number check mechanism can also be adopted to ensure that each frame of data is trustworthy. At the same time, the distinction between different function frames is clearly made, which significantly reduces the bit error rate and cumulative error compared with the pulse transmission method that cannot distinguish the pulse source at all.

[0066] In an actual application scenario, performance test verification is carried out on the galvanometer motor system provided in this embodiment, as Figures 5 - 7 shown, where Figure 5 is the Lissajous figure without bias compensation, Figure 6 is the Lissajous figure without gain compensation, Figure 7 is the effect after compensation. It can be seen that Figure 7 the Lissajous figure shown reaches the best state for both the A-phase sine signal and the B-phase sine signal used for subdivision after bias and amplitude calibration. That is, the signal quality is significantly improved, and at the same time, the errors caused by each link in the product production process are uniformly corrected, which is very helpful for improving product consistency.

[0067] In addition, the parameter comparison between the galvanometer motor system provided in this embodiment and the general servo motor is shown in Table 1 as follows: Table 1

[0068] It can be seen from Table 1 above that the galvanometer motor system provided in this embodiment shows significant advantages in aspects such as single-turn resolution, signal calibration, volume, and single-frame position information communication rate. Especially in terms of single-turn resolution, this embodiment reaches 23 bits, that is, 8192 position data or pulses can be generated per sine wave cycle, which far exceeds the 11-bit resolution of the existing servo motors, thus achieving higher positioning accuracy and finer control effects.

[0069] Generally speaking, this embodiment has developed a unique structural sensor for the galvanometer motor system and successfully achieved the following technical effects: (1) Volume reduction: By optimizing the design and adopting advanced manufacturing processes, the overall size of the encoder is significantly reduced, making it more compact, so as to better adapt to the limited space of the galvanometer motor; (2) Improvement of position subdivision accuracy: By adopting high-resolution sensors and fine signal processing algorithms, the position subdivision accuracy is significantly improved, ensuring high-precision positioning and motion control of the galvanometer motor; (3) Enhancement of speed and anti-interference ability: By improving signal transmission technology and enhancing electromagnetic compatibility design, the transmission speed of the encoder is significantly increased, and at the same time, it has stronger anti-interference ability, ensuring stable operation in a complex electromagnetic environment.

[0070] In summary, the structural sensor provided in this embodiment not only meets the stringent requirements of the galvanometer motor system for volume, accuracy, speed, and anti-interference, but also provides strong technical support for the high-performance applications of the galvanometer motor system.

[0071] The various embodiments in the specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. For the same or similar parts among the various embodiments, reference can be made to each other. For the system disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple. For the relevant parts, reference can be made to the description in the method part. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the principle of this application, several improvements and modifications can be made to this application, and these improvements and modifications also fall within the protection scope of the claims of this application.

[0072] It should also be noted that in this specification, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "including one..." does not exclude the existence of another identical element in the process, method, article or device including the said element.

Claims

1. A displacement sensor, characterized in that, The displacement sensor is connected to the motor shaft and adopts a transmissive grating sandwich structure, and the transmissive grating sandwich structure includes: A light source module, which is arranged on the upper layer. The light source module includes an aspheric collimating lens that can generate a uniform parallel light beam; A grating code disk, which is arranged on the middle layer. The grating code disk is made of an optical glass substrate, and the grating code disk is fixed on the motor shaft through a code disk tray; A photoelectric receiving module, which is arranged on the lower layer. The photoelectric receiving module includes multiple groups of orthogonally arranged photodiodes and a photoelectric converter, and the photoelectric converter is fixed on the motor stator. The photodiodes are used to receive the brightness change of the light stripe and form a light signal, and the photoelectric converter is used to receive the light signal and convert it into an electrical signal.

2. An assembly method of a displacement sensor, applied to the displacement sensor as described in claim 1, characterized in that, The assembly method includes: Fix the code disk tray on the motor shaft and place the grating code disk on the disk surface of the code disk tray; Control the motor shaft to rotate at a constant speed and detect whether the rotation center of the grating code disk is concentric with the rotation center of the motor shaft; When the rotation center of the grating code disk is not concentric with the rotation center of the motor shaft, monitor the jumping condition of the grating code disk from the edge of the grating code disk; Correct the grating code disk based on the jumping condition of the grating code disk so that the rotation center of the grating code disk is concentric with the rotation center of the motor shaft.

3. A galvanometer motor system, characterized in that, It includes the displacement sensor as described in claim 1.

4. A signal processing method for a galvanometer motor system, applied to the galvanometer motor system as described in claim 3, characterized in that, The signal processing method includes: Obtain the light signal of the target object and convert the light signal into a digital signal; Perform offset conditioning and amplitude conditioning on the digital signal to obtain a target signal; Use a subdivision algorithm to perform position calculation on the target signal to obtain corresponding position information; Pack and output the position information in a set format.

5. The signal processing method of the galvanometer motor system according to claim 4, characterized in that The obtaining the light signal of the target object and converting the light signal into a digital signal includes: Use a photoelectric converter to convert the light signal into an electrical signal; Amplify the electrical signal through an analog amplification circuit to obtain an analog signal; Perform digital conversion on the analog information to obtain the digital signal.

6. The signal processing method of the galvanometer motor system according to claim 4, characterized in that The performing offset conditioning and amplitude conditioning on the digital signal to obtain a target signal includes: Obtain the voltage sine period of the digital signal; Sample the maximum voltage and the minimum voltage in the sine period; According to the following formula, calculate the offset voltage in combination with the set voltage, and use the offset voltage to perform offset conditioning on the digital signal; COMPEN = RAW-(TAR_CEN-((MAX-MIN) / 2+MIN)); Where, COMPEN represents the voltage after offset conditioning, RAW represents the input original voltage, TAR_CEN represents the set voltage, MAX represents the maximum voltage, MIN represents the minimum voltage, and TAR_CEN-((MAX-MIN) / 2+MIN) represents the offset voltage.

7. The signal processing method of the galvanometer motor system according to claim 6, characterized in that The performing offset conditioning and amplitude conditioning on the digital signal to obtain a target signal further includes: According to the following formula, calculate the gain ratio in combination with the preset standard signal peak-to-peak value, and perform amplitude conditioning on the digital signal according to the gain ratio; OUT = ((MAX - MIN) / STAD)*RAW; Where, OUT represents the voltage after amplitude conditioning, STAD represents the peak-to-peak value of the standard signal, and (MAX - MIN) / STAD represents the gain ratio.

8. The signal processing method of the galvanometer motor system according to claim 4, characterized in that, The step of performing position calculation on the target signal by using the subdivision algorithm to obtain the corresponding position information includes: Obtaining the sine period of the target signal, and extracting a first sine signal and a second sine signal with a 90° phase difference from the sine period of the target signal; Performing polar coordinate conversion on the first sine signal and the second sine signal, and forming a Lissajous figure based on the fluctuation periods of the first sine signal and the second sine signal; According to the following formula, for any point on the Lissajous figure, calculating to obtain the corresponding angle information: α = atan (Y / X) = atan (B / A); Where, α represents the angle information, atan represents the arctangent trigonometric function, A represents the first sine signal, B represents the second sine information, and X and Y represent the coordinates of any point on the Lissajous figure; According to the following formula, combining the angle information to calculate the position information: P = (N*M) + α / 360*N; Where, P represents the position information, N represents the subdivision ratio, and M represents the number of sine periods.

9. The signal processing method of the galvanometer motor system according to claim 4, characterized in that The step of obtaining the optical signal of the target object and converting the optical signal into a digital signal further includes: Comparing the optical signal with a preset first signal amplitude and a second signal amplitude respectively; wherein, the first signal amplitude is higher than the second signal amplitude; When the optical signal exceeds the first signal amplitude, performing step-by-step cutting on the base of the optical receiver to expand the gap between the grating disk and the optical converter; When the optical signal is lower than the second signal amplitude, inserting a gasket between the grating disk and the optical converter to reduce the gap between the grating disk and the optical converter.

10. The signal processing method of the galvanometer motor system according to claim 4, characterized in that, After the step of performing position calculation on the target signal by using the subdivision algorithm to obtain the corresponding position information, it includes: Performing filtering processing on the position information.

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