High-precision continuous laser displacement height measurement detection method and application

Abstract

The invention relates to the field of dispensing, and particularly discloses a high-precision continuous laser displacement height measurement detection method which comprises the following steps: S1, constructing a detection system; s2, in the continuous motion process of the motion platform, a high-speed data acquisition card synchronously acquires pulse signals of an X-axis encoder and a Y-axis encoder and analog quantity signals of a laser displacement sensor at a preset sampling frequency to obtain a synchronous position-height original data stream; s3, the upper computer PC unit screens out a height value corresponding to the target position from the original data stream according to a preset sampling strategy; the sampling strategy comprises a point mode, a line mode or a continuous acquisition mode; and S4, performing position compensation on the screened height value according to the response hysteresis characteristic of the laser displacement sensor to obtain a compensated actual height value.

Description

Technical Field

[0001] This invention belongs to the field of measuring the height or thickness of products, and in particular relates to a high-precision continuous laser displacement height measurement method and its application. Background Technology

[0002] In the processing, assembly, and placement of modern intelligent equipment in the manufacturing industry, the selection of measurement tools is a crucial step, directly impacting product quality. Measurement accuracy affects the error of the equipment's measurements, thus influencing the final product quality. The measurement method also affects the efficiency of the entire production process. Laser displacement sensors can accurately measure the position and height of the object being measured, featuring good linearity, high response time, and non-contact measurement, making them widely used in the precision manufacturing of electronic products.

[0003] Laser displacement sensors can acquire signals via serial port, Ethernet communication, and analog signals. When using these communication methods, the height of the measured object is affected by the transmission rate. Furthermore, with the increasing demands for efficiency in automated production, the response time of laser displacement sensors limits the real-time signal acquisition of the measured object. When the measured object is moving at high speed or the sensor is following its movement, acquiring the position coordinates and height signals of each measurement point on the object during its motion is challenging with single communication methods and single-point position signal acquisition methods.

[0004] Some controllers integrating laser displacement sensors also include corresponding encoder pulse acquisition channels. While these are useful for position coordinate feedback in a single dimension of the motion trajectory, their positioning accuracy is poor when interpolation is used. Furthermore, the programmable position options of these controllers are limited, failing to meet the requirements for on-demand signal acquisition, storage, and processing. Summary of the Invention

[0005] This invention provides a high-precision continuous laser displacement height measurement method. The purpose of this invention is to address the shortcomings of existing laser displacement detection schemes by providing a method for synchronous signal acquisition and processing based on motion control. This method can simultaneously receive analog signals and two-dimensional encoder pulse signals, accurately acquiring position and height information during motion in real time. Furthermore, it proposes a control scheme for point-to-point, on-demand, and continuous acquisition, thereby meeting the needs of high-efficiency and high-precision detection applications of the measured object.

[0006] To address the aforementioned technical problems and achieve a high-precision, dynamic, and continuous laser displacement detection method, the feasibility of this invention is fully described. The specific technical solution is as follows. To better understand this technical solution, a detailed system description of the invention is provided in conjunction with illustrations. The corresponding experimental methods and data analysis methods are also described. The experimental procedures and methods based on this technology, including parameter settings, testing procedures, data analysis, and compensation algorithms, all fall within the protection scope of this invention.

[0007] The technical solution provided by this invention is as follows: First technical solution: A high-precision continuous laser displacement height measurement method, comprising the following steps: S1. Construct a detection system; S2. During the continuous motion of the motion platform, the high-speed data acquisition card synchronously acquires the pulse signals of the X-axis and Y-axis encoders and the analog signals of the laser displacement sensor at a preset sampling frequency to obtain a synchronous position-height raw data stream. S3. The host computer PC unit filters out the height value corresponding to the target position from the raw data stream according to the preset sampling strategy; the sampling strategy includes point mode, line mode or continuous acquisition mode; S4. Based on the response hysteresis characteristics of the laser displacement sensor, position compensation is performed on the selected height values ​​to obtain the compensated actual height value. The position compensation can be achieved using any of the following methods: Fixed offset compensation: based on sensor hysteresis time Given the motion platform's running speed s and running direction angle Θ, calculate the position offset. x= t × s × sinΘ, y= t × s × cosΘ, and shift the measurement position in the opposite direction of the motion. x and After y, obtain the corresponding height value as the actual height value; Sampling number compensation: based on sensor hysteresis time Given t and the sampling frequency f of the high-speed data acquisition card, calculate the offset sampling number δ = t × f, and offset the height data array by δ sampling points in the opposite direction of time to align the original height data with its theoretical position.

[0008] Preferably, the motor drive unit in the detection system drives the motion platform to move the object under test or the laser displacement sensor, and simultaneously sends the position feedback signals of the X-axis and Y-axis encoders to the motion control unit and the high-speed data acquisition card; the laser displacement sensor sends the measured height analog signal to the high-speed data acquisition card.

[0009] Preferably, the sampling frequency of the high-speed data acquisition card is not less than 100kHz, and the clock source used for acquiring encoder signals and analog signals is consistent.

[0010] Preferred method: In point mode, the host computer PC unit controls the motion platform to move to the target point and pause briefly, and collects the average value of all height data within ±0.1mm of the target point as the height value of the target point.

[0011] Preferred mode: In online mode, the host computer PC unit controls the motion platform to move at a constant speed along a preset trajectory, and collects the average value of all height data within a predetermined distance near each target point on the trajectory as the height value of that target point.

[0012] Preferred configuration: In continuous acquisition mode, the host computer PC unit controls the motion platform to move continuously along any preset trajectory, and the high-speed data acquisition card synchronously records the entire position-height raw data stream; after acquisition, the height value of any position is extracted from the raw data stream according to the analysis requirements, and position compensation is performed on the height value.

[0013] Preferably, the position information in the synchronized position-height raw data stream is two-dimensional coordinates (X, Y), provided by the X-axis and Y-axis encoders.

[0014] Preferably, the hysteresis time of the laser displacement sensor needs to be obtained through experimental calibration before position compensation is performed. t.

[0015] Preferably, the data acquisition card is also used to synchronously acquire other analog signals associated with the location information, including pressure signals, flow signals, or film thickness signals.

[0016] Second technical solution: The application of a high-precision continuous laser displacement height measurement method is described in a precision dispensing process. This method detects the height of the area to be dispensed in real time and feeds back the compensated actual height value to the dispensing control system to dynamically adjust the height of the dispensing needle.

[0017] The advantages over existing technologies are: 1. Perfect balance between efficiency and precision: Through continuous motion measurement, the inefficient aspects of the traditional "start-stop" mode are completely eliminated; Second: Hardware-level synchronization, zero data distortion: A dedicated data acquisition card is used to ensure strict synchronization of position and altitude signals at the hardware level, eliminating the uncertainty caused by software splicing and laying a solid data foundation for high-precision dynamic measurement.

[0018] Third: The compensation algorithm is accurate and effective: Whether it is the fixed offset method based on the physical model or the sampling number method based on data processing, it can effectively eliminate the system error caused by sensor hysteresis.

[0019] Fourth: Flexible and scalable system architecture: The open architecture of host computer + high-speed acquisition card makes the system easy to integrate into various automated equipment. At the same time, this synchronous acquisition framework has good versatility. It is not only suitable for laser displacement signals, but also for synchronous acquisition of other analog signals such as pressure, flow, and tension, so as to realize the synchronous detection of multiple physical quantities.

[0020] 5. Reduce the burden on the host computer: The high-speed data acquisition card undertakes the tasks of real-time data acquisition and preliminary processing, effectively reducing the computing load on the host computer's CPU and ensuring the stability and real-time performance of the entire system. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments or prior art, the accompanying drawings used in the description of the embodiments or prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the process of the present invention. Detailed Implementation

[0023] To facilitate understanding of the present invention, a more detailed description is provided below with reference to the accompanying drawings and specific embodiments. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0024] It should be noted that when a component is described as being "fixed to" another component, it can be directly attached to the other component or there may be an intervening component. When a component is described as being "connected to" another component, it can be directly connected to the other component or there may be an intervening component. The terms "fixed," "integral," "left," "right," and similar expressions used in this specification are for illustrative purposes only, and in the figures, structurally similar units are labeled with the same reference numerals.

[0025] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention.

[0026] like Figure 1 As shown, one embodiment of the present invention is: a high-precision continuous laser displacement height measurement method, comprising the following steps: S1. Construct a detection system; It should be noted that: the motor drive unit in the detection system drives the motion platform to move the object under test or the laser displacement sensor, and simultaneously sends the position feedback signals of the X-axis and Y-axis encoders to the motion control unit and the high-speed data acquisition card; the laser displacement sensor sends the analog signal of the height it measures to the high-speed data acquisition card; A high-speed PCIe data acquisition card with a sampling frequency of 100kHz was selected, featuring two quadrature encoder input channels and eight 16-bit analog input channels. The X-axis and Y-axis encoder signals from the XY linear motor platform were connected to the two encoder channels of the acquisition card, respectively. A high-precision laser displacement sensor with a spot diameter of 30μm was selected, and its analog output was connected to the AD0 channel of the acquisition card. The host industrial computer was connected to the acquisition card via Gigabit Ethernet and used the manufacturer's C++ DLL for development. The motion control unit employed a high-performance multi-axis motion controller, communicating with the host computer via an EtherCAT bus.

[0027] S2. During the continuous motion of the motion platform, the high-speed data acquisition card synchronously acquires the pulse signals of the X-axis and Y-axis encoders and the analog signals of the laser displacement sensor at a preset sampling frequency to obtain a synchronous position-height raw data stream. It should be noted that: The host computer software is started, the CAD drawing of the product under test is loaded, and the testing trajectory is planned. The operator selects "line mode" and sets the running speed to 100mm / s. The host computer sends motion commands to the motion controller. The motion platform begins to move continuously along the preset polygonal trajectory. During this process, the data acquisition card continuously records the X and Y encoder count values ​​(converted to physical coordinates) and the laser sensor voltage value (converted to height Z) at a frequency of 100kHz, and packages this synchronous data for real-time upload to the host computer's memory buffer via Ethernet.

[0028] S3. The host computer PC unit filters out the height value corresponding to the target position from the raw data stream according to the preset sampling strategy; the sampling strategy includes point mode, line mode or continuous acquisition mode; It should be noted that the host computer software allocates a separate thread to read the synchronous data stream from the buffer in real time. For each target point on the trajectory, the software calculates its theoretical coordinates (…). , Search the data stream for all expressions that satisfy |x - |<0.05mm and |y - Data points with heights less than 0.05 mm are collected, and the arithmetic mean of the heights Z of these points is calculated as the original height value of the target point.

[0029] S4. Based on the response hysteresis characteristics of the laser displacement sensor, position compensation is performed on the selected height values ​​to obtain the compensated actual height value. The position compensation can be achieved using any of the following methods: Fixed offset compensation: based on sensor hysteresis time Given the motion platform's running speed s and running direction angle Θ, calculate the position offset. x= t × s × sinΘ, y= t × s × cosΘ, and shift the measurement position in the opposite direction of the motion. x and After y, obtain the corresponding height value as the actual height value; Furthermore, fixed offset compensation can be replaced with dynamic offset compensation; the hysteresis time Δt of the laser displacement sensor is obtained through experimental calibration. During continuous measurement, the host computer PC unit or motion control unit calculates and outputs the instantaneous velocity vector (s, Θ) of the motion platform at each sampling moment in real time. This instantaneous velocity can be obtained by differentiating the encoder position data (i.e., differentiating over consecutive position sampling points) or directly read from the internal state register of the motion controller. Subsequently, based on physical formulas, the position offset corresponding to each sampling point is dynamically calculated: x[n] = t × s[n] × sinΘ[n]; y[n] = During compensation, the theoretical position (x[n], y[n]) of the original measurement point is shifted in the opposite direction of its instantaneous motion (t × s[n] × cosΘ[n]). x[n], y[n]), obtain the compensated position (x'[n], y'[n]), and then query the height value Z'[n] corresponding to the compensated position from the synchronous data stream through an interpolation algorithm (such as linear interpolation or spline interpolation).

[0030] Sampling number compensation: Based on the sensor hysteresis time ∆t and the sampling frequency f of the high-speed data acquisition card, calculate the offset sampling number δ = t × f, and offset the height data array by δ sampling points in the opposite direction of time to align the original height data with its theoretical position.

[0031] Further: The lag time Δt needs to be pre-calibrated. Since the sampling frequency f of the high-speed data acquisition card is known and constant, the fixed offset sampling number δ can be calculated. t × f. During compensation, the original height data array Z[n] is directly shifted by δ points in the opposite direction of time (or sampling point index) to obtain a new height array Z'[n] = Z[n+δ]. This method is naturally applicable to any motion state (uniform speed, acceleration, deceleration) because its compensation logic depends only on the time delay and is independent of the spatial motion trajectory.

[0032] It should be noted that before the formal measurement, a calibration experiment was first conducted to determine the sensor lag time Δt. Using a standard block with a known step height, the time required for the sensor output to rise from 10% to 90% was measured, and Δt was determined to be 0.8 ms.

[0033] Using the sample number compensation method: Given f = 100kHz, then δ = 0.8ms 100kHz = 80. The software shifts the original height data array Z[n] forward by 80 points to obtain the compensated array Z'[n].

[0034] Results Verification: Measurements were performed on the same product in both dot pattern (baseline) and compensated line pattern (100mm / s). The results showed that the mean deviation of each point in the compensated line pattern was less than 0.015mm, and the variance was less than 0.01, fully meeting the accuracy requirements of the dispensing process (usually ±0.05mm).

[0035] Closed-loop control: The compensated real-time height value is sent to the dispensing control system via a communication interface. Based on this height value, the dispensing controller dynamically adjusts the position of the Z-axis servo motor to ensure that the dispensing needle maintains a constant dispensing distance from the product surface, thereby guaranteeing the consistency of glue volume and shape.

[0036] The high-precision continuous laser displacement height measurement method also includes setting the detection resolution.

[0037] To meet the accuracy requirements of different application scenarios, laser displacement sensors of different specifications can be selected. Preferably, the spot diameter of the laser displacement sensor is less than 50 μm to achieve accurate detection of tiny feature areas.

[0038] The application of a high-precision continuous laser displacement height measurement method is described in a precision dispensing process. This method detects the height of the area to be dispensed in real time and feeds back the compensated actual height value to the dispensing control system to dynamically adjust the height of the dispensing needle.

[0039] It should be noted that this invention is also applicable to other scenarios. For example, when detecting the thickness of flexible printed circuit boards (FPCs), the laser displacement sensor can be replaced with a non-contact film thickness measuring instrument. Its output analog signal can also be synchronously captured by a high-speed data acquisition card and correlated with position information to achieve online full inspection of FPC thickness. In pressure detection scenarios, the analog signal from the pressure sensor can be connected to the data acquisition card to achieve synchronous recording of pressure and position for analysis of pressure distribution, etc.

[0040] It should be noted that the above-mentioned technical features can be combined with each other to form various embodiments not listed above, all of which are considered to be within the scope of this invention specification; and, for those skilled in the art, improvements or modifications can be made based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A high-precision continuous laser displacement height measurement method, characterized in that: Includes the following steps: S1. Construct a detection system; S2. During the continuous motion of the motion platform, the high-speed data acquisition card synchronously acquires the pulse signals of the X-axis and Y-axis encoders and the analog signals of the laser displacement sensor at a preset sampling frequency to obtain a synchronous position-height raw data stream. S3. The host computer PC unit filters out the height value corresponding to the target position from the raw data stream according to the preset sampling strategy; the sampling strategy includes point mode, line mode or continuous acquisition mode; S4. Based on the response hysteresis characteristics of the laser displacement sensor, position compensation is performed on the selected height values ​​to obtain the compensated actual height value. The position compensation can be achieved using any of the following methods: Fixed offset compensation: based on sensor hysteresis time Given the motion platform's running speed s and running direction angle Θ, calculate the position offset. x= t × s × sinΘ, y= t × s × cosΘ, and shift the measurement position in the opposite direction of the motion. x and After y, obtain the corresponding height value as the actual height value; Sampling number compensation: based on sensor hysteresis time Given t and the sampling frequency f of the high-speed data acquisition card, calculate the offset sampling number δ = t × f, and offset the height data array by δ sampling points in the opposite direction of time to align the original height data with its theoretical position.

2. The high-precision continuous laser displacement height measurement method according to claim 1, characterized in that: The detection system consists of a PC unit, a motion control unit, a motor drive unit, a data acquisition card, and a laser displacement sensor. The motor drive unit drives the motion platform to move the object under test and the laser displacement sensor, and simultaneously sends the position feedback signals of the X-axis and Y-axis encoders to the motion control unit and the high-speed data acquisition card. The laser displacement sensor sends the analog height signal it measures to the high-speed data acquisition card.

3. The high-precision continuous laser displacement height measurement method according to claim 1, characterized in that: The high-speed data acquisition card has a sampling frequency of no less than 100kHz, and its internal clock source for acquiring encoder signals and analog signals is consistent.

4. The high-precision continuous laser displacement height measurement method according to claim 1, characterized in that: In point mode, the host computer PC unit controls the motion platform to move to the target point and pause briefly, collecting the average of all height data within ±0.1mm of the target point as the height value of the target point.

5. The high-precision continuous laser displacement height measurement method according to claim 1, characterized in that: In online mode, the host computer PC unit controls the motion platform to move at a constant speed along a preset trajectory, and collects the average value of all height data within a predetermined distance near each target point on the trajectory as the height value of that target point.

6. The high-precision continuous laser displacement height measurement method according to claim 1, characterized in that: In continuous acquisition mode, the host computer PC unit controls the motion platform to move continuously along any preset trajectory, and the high-speed data acquisition card synchronously records the entire position-height raw data stream; after acquisition, the height value of any position is extracted from the raw data stream according to the analysis requirements, and position compensation is performed on the height value.

7. The high-precision continuous laser displacement height measurement method according to claim 1, characterized in that: The position information in the synchronized position-height raw data stream is in two-dimensional coordinates (X, Y), provided by the X-axis and Y-axis encoders.

8. The high-precision continuous laser displacement height measurement method according to claim 1, characterized in that: Before performing position compensation, the hysteresis time of the laser displacement sensor needs to be obtained through experimental calibration. t.

9. The high-precision continuous laser displacement height measurement method according to claim 1, characterized in that: The data acquisition card is also used to synchronously acquire other analog signals associated with location information, including pressure signals, flow signals, or film thickness signals.

10. The application of a high-precision continuous laser displacement height measurement method, characterized in that: The method is applied in precision dispensing processes, which detects the height of the area to be dispensed in real time and feeds back the compensated actual height value to the dispensing control system to dynamically adjust the height of the dispensing needle.

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