Flight measurement method and system for machine tool space precision detection

Abstract

The invention provides a flight measurement method and system for machine tool space precision detection, and the method comprises the steps: 1, installing a laser tracking interferometer on a stable plane near a machine tool, and installing a reflector on an x-axis of the machine tool for laser interference; 2, aligning a light beam of the laser tracking interferometer with the x axis of the machine tool, moving a reflector along the x axis of the machine tool at different speeds, and synchronously measuring a signal of the x axis position of the machine tool and a length signal of the laser tracking interferometer; 3, digital pulses are sent out through a trigger, the current position of the machine tool is stored, and after the machine tool is started to move, position information of all axes of the machine tool is synchronously collected at a preset sampling rate through a laser tracking interferometer and a machine tool grating ruler and transmitted to an upper computer; and 4, performing error evaluation on the synchronously acquired data to generate machine tool space error data. The laser tracking interferometer and the grating ruler are utilized, synchronous high-precision data acquisition and calibration are carried out in the movement process of the machine tool, and the time required for calibration of the machine tool is shortened.

Description

Technical Field

[0001] This invention relates to the field of precision testing technology, and more specifically, to a flight measurement method and system for spatial precision testing of machine tools. Background Technology

[0002] The existing method for calibrating machine tool spatial accuracy using a tracking interferometer involves stopping the machine tool at various measurement points and using the tracking interferometer to statically acquire the spatial position of these points. Measurements often last for several or even more than ten hours, which not only increases costs during non-production time but also, in a factory environment, the measured spatial accuracy is affected by time-varying factors such as temperature and humidity, impacting the measurement results.

[0003] Patent application CN109773585A discloses a spatial error detection method for five-axis CNC machine tools based on RTCP. This patent proposes using the RTCP function of a five-axis CNC machine tool to measure the error of the rotary axes and then inversely solve for all error terms. However, the patent mentions using dial indicators or micrometers for error measurement, which is less accurate than laser tracking interferometers, and the operation introduces installation errors. Furthermore, the patent's technical implementation requires the machine tool's RTCP function, resulting in limited versatility of the overall measurement system and potentially hindering its widespread application in industrial environments.

[0004] Patent application CN110666590A discloses a method for measuring the body diagonal error of a machine tool based on a multi-beam laser interferometer, including the following steps: (1) setting up an auxiliary light-adjusting mechanism for light adjustment, the auxiliary light-adjusting mechanism including mechanism A and mechanism B, mechanism A can realize adjustment of four degrees of freedom; mechanism B can realize adjustment of two degrees of freedom; mechanism A is installed on the worktable, and mechanism B is installed on the spindle end of the machine tool; (2) installing the transmitter of the XM60 multi-beam laser interferometer on mechanism A, and the laser receiver on mechanism B; (3) adjusting the angle and displacement of mechanism A and mechanism B, and measuring the body diagonal error of the machine tool; (4) establishing a mapping model between the 21 geometric errors of the CNC machine tool and the measurement results of step (3); (5) establishing a mapping model between the 21 geometric errors of the CNC machine tool and the end pose error of the machine tool in the machine tool coordinate system; (6) obtaining the mapping model between the end pose error of the machine tool in the machine tool coordinate system and the measurement results. However, this patent cannot completely solve the existing technical problems, nor can it meet the needs of the present invention. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the purpose of this invention is to provide a flight measurement method and system for detecting the spatial accuracy of machine tools.

[0006] The flight measurement method for machine tool spatial accuracy detection provided by the present invention includes:

[0007] Step 1: Install a laser tracking interferometer on a stable plane near the machine tool, and install a reflector on the x-axis of the machine tool for laser interferometry;

[0008] Step 2: Align the laser tracking interferometer beam with the machine tool's x-axis, move the reflector along the machine tool's x-axis at different speeds, and simultaneously measure the machine tool's x-axis position signal and the laser tracking interferometer length signal;

[0009] Step 3: A digital pulse is emitted through a trigger to store the current position of the machine tool. After the machine tool starts moving, the position information of each axis of the machine tool is synchronously collected by a laser tracking interferometer and the machine tool grating ruler at a preset sampling rate and transmitted to the host computer.

[0010] Step 4: Perform error assessment on the synchronously acquired data to generate machine tool space error data.

[0011] Preferably, the machine tool x-axis position signal satisfies:

[0012] x MT =x0+v·τ±u MT

[0013] Where, x MT This is the signal for the machine tool's x-axis position, where x0 represents the initial x-axis position, v represents the machine tool's speed along the x-axis, τ represents the time the machine tool spends moving along the x-axis, and u... MT It is the uncertainty of machine tool position measurement.

[0014] Preferably, the length signal of the laser tracking interferometer satisfies:

[0015] x Taccr =x0+v·(τ+Δ τ,SYS 0+Δ MT,YSYS (x)±u Tracer

[0016] Where, x Tacer It is the length signal of the laser tracking interferometer, Δ τ,SYS It is the time synchronization error, Δ MT,YSYS (x) is the systematic error along the x-axis, u Tracer It is the uncertainty of the laser tracking interferometer measurement.

[0017] Preferably, the error evaluation expression is:

[0018] x Tracer -x MT =v·Δ τ,SYS +Δ MT,YSYS (x)±u MT,Tracer

[0019] Among them, u MT,Tracer =u MT +uTracer This represents the combined measurement uncertainty of the machine tool and the laser tracking interferometer.

[0020] Preferably, if the evaluated error is less than the preset error measurement threshold, the measurement data is determined to be valid and the measurement continues to the next position; otherwise, the measurement data is determined to be invalid, the error correction mechanism is triggered, the timestamps of the laser tracking interferometer and the counting card on the machine tool grating ruler are rematched, and the measurement is repeated.

[0021] The flight measurement system for machine tool spatial accuracy detection according to the present invention includes:

[0022] Module M1: Controls the reflector to move along the x-axis of the machine tool at different speeds, and synchronously measures the position signal of the machine tool x-axis and the length signal of the laser tracking interferometer. The laser tracking interferometer is mounted on a stable plane near the machine tool, and the laser tracking interferometer beam is aligned with the x-axis of the machine tool. The reflector is mounted on the x-axis of the machine tool for laser interferometry.

[0023] Module M2: It generates digital pulses through a trigger, stores the current position of the machine tool, and after the machine tool starts moving, it synchronously collects the position information of each axis of the machine tool through a laser tracking interferometer and the machine tool grating ruler at a preset sampling rate and transmits it to the host computer.

[0024] Module M3: Performs error assessment on synchronously acquired data and generates machine tool space error data.

[0025] Preferably, the machine tool x-axis position signal satisfies:

[0026] x MT =x0+v·τ±u MT

[0027] Where, x MT This is the signal for the machine tool's x-axis position, where x0 represents the initial x-axis position, v represents the machine tool's speed along the x-axis, τ represents the time the machine tool spends moving along the x-axis, and u... MT It is the uncertainty of machine tool position measurement.

[0028] Preferably, the length signal of the laser tracking interferometer satisfies:

[0029] x Taccr =x0+v·(τ+Δ τ,SYS )+Δ MT,YSYS (x)±u Tracer

[0030] Where, x Tacer It is the length signal of the laser tracking interferometer, Δ τ,SYS It is the time synchronization error, Δ MT,YSYS (x) is the systematic error along the x-axis, u Tracer It is the uncertainty of the laser tracking interferometer measurement.

[0031] Preferably, the error evaluation expression is:

[0032] x Tracer -x MT =v·Δ τ,SYS +Δ MT,YSYS (x)±u MT,Tracer

[0033] Among them, u MT,Tracer =u MT +u Tracer This represents the combined measurement uncertainty of the machine tool and the laser tracking interferometer.

[0034] Preferably, if the evaluated error is less than the preset error measurement threshold, the measurement data is determined to be valid and the measurement continues to the next position; otherwise, the measurement data is determined to be invalid, the error correction mechanism is triggered, the timestamps of the laser tracking interferometer and the counting card on the machine tool grating ruler are rematched, and the measurement is repeated.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] (1) By using continuous flight measurement, the problem of excessive time consumption for machine tool spatial accuracy detection using only a laser tracking interferometer was solved, and the time required for machine tool calibration was shortened;

[0037] (2) By adopting a method of synchronously acquiring signals from machine tools and laser tracking interferometers with a high sampling rate, the calibration speed can be significantly accelerated through continuous dynamic measurement. There is no need to accelerate / decelerate at each sampling point, which improves measurement efficiency and effect. This solves the problem of high uncertainty in continuous measurement caused by low sampling rate and provides high-precision data for the spatial accuracy error of flight measurement machine tools. Attached Figure Description

[0038] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0039] Figure 1 This is a flowchart of the flight measurement method for machine tool spatial accuracy detection according to the present invention;

[0040] Figure 2 This is a schematic diagram of the flight measurement system for machine tool spatial accuracy detection according to the present invention.

[0041] The figure shows: x MT It is the signal for the machine tool's x-axis position, x Tacer It is the length signal of the laser tracking interferometer. Detailed Implementation

[0042] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0043] Example 1

[0044] This invention proposes an on-the-fly measurement method based on a laser-tracking interferometer to achieve synchronous high-precision data acquisition and calibration during machine tool movement. As the machine tool moves along a specified path, signals from the machine tool position and the laser-tracking interferometer are simultaneously acquired at a high sampling rate. These signals are then transmitted to a host computer for calculation, thereby deriving data on the machine tool's spatial accuracy error mapping.

[0045] like Figure 2 The main hardware components of the flight measurement system are:

[0046] 1) Laser tracking interferometer (such as LaserTRACER-NG) supports uncertainty of 0.2μm+0.3μm / m and 32kHz high-frequency sampling. The tracking interferometer is connected to the host computer for measurement data transmission.

[0047] 2) The machine tool to be calibrated is equipped with a grating ruler. The sampling frequency of the grating ruler is greater than 32kHz. The grating ruler is connected to a multi-channel counting card, and the grating ruler data is collected through the counting card.

[0048] 3) The host computer is equipped with a real-time operating system and a multi-channel counter card. The multi-channel counter card is used to connect to the grating ruler to acquire data; the real-time operating system, together with the counter card software, is used for the digitization of machine tool analog signals and error data processing. The machine tool CNC system communicates with the host computer via Ethernet to receive motion commands.

[0049] like Figure 1 The workflow is as follows:

[0050] 1) Install a laser tracking interferometer on a stable plane near the machine tool, and install a reflector on the x-axis of the machine tool for laser interferometry;

[0051] 2) Perform time synchronization and evaluate the time synchronization of continuous measurements. Align the laser tracking interferometer beam with the machine tool's x-axis, move the machine tool's reflector along the x-axis at different speeds, and simultaneously measure the changes in the x-axis position and the length signal of the laser tracking interferometer. Figure 2 The signal indicating the machine tool's x-axis position. MT Uncertainty u of position measurement MT The effect of this is expressed by formula (1). The length signal x of the laser tracking interferometer. TacerIncluding the systematic error Δ on the x-axis MT,YSYS (x), time synchronization error Δ τ,SYS and the uncertainty u of the laser tracking interferometer Tracer The difference between the two signals is the position error of the x-axis, expressed by formula (2).

[0052] x MT =x0+v·τ±u MT #(1)

[0053] x Taccr =x0+v·(τ+Δ τ,SYS )+Δ MT,YSYS (x)±u Tracer #(2)

[0054] x Tracer -x MT =v·Δ τ,SYS +Δ MT,YSYS (x)±u MT,Tracer #(3)

[0055] Where x0 represents the initial position along the x-axis; v represents the speed of the machine tool along the x-axis; τ represents the time it takes for the machine tool to move along the x-axis; u MT,Tracer =u Tracer +u MT This represents the combined measurement uncertainty of the machine tool and the laser tracking interferometer.

[0056] 3) After time synchronization is completed, data acquisition is performed. After the trigger sends out digital pulses, the current position of the machine is stored and the machine starts to move. The laser tracking interferometer records the position information of each axis of the machine tool, and at the same time, the grating ruler records the position information of each axis of the machine tool. After a set of data acquisitions is completed, the measurement data is transmitted from the machine to the host computer for processing via Ethernet.

[0057] 4) The host computer evaluates the synchronization data, assessing the positional error of each axis at a defined operating speed v. An error measurement threshold is set. If the error is less than the threshold, the time synchronization error is considered acceptable, the data is valid, and the measurement continues to the next position. Otherwise, the synchronization error is considered too large, triggering an error correction mechanism. The timestamps of the tracking interferometer and the machine tool's optical scale counter are re-matched, and the measurement is repeated. After completing the measurement process, the final machine tool spatial error data is generated.

[0058] Example 2

[0059] The present invention also provides a flight measurement system for machine tool spatial accuracy detection. The flight measurement system for machine tool spatial accuracy detection can be implemented by executing the process steps of the flight measurement method for machine tool spatial accuracy detection. That is, those skilled in the art can understand the flight measurement method for machine tool spatial accuracy detection as a preferred embodiment of the flight measurement system for machine tool spatial accuracy detection.

[0060] The system includes: Module M1: controls a reflector to move along the x-axis of the machine tool at different speeds, synchronously measuring the position signal of the machine tool's x-axis and the length signal of the laser tracking interferometer. The laser tracking interferometer is mounted on a stable plane near the machine tool, and the laser tracking interferometer beam is aligned with the x-axis of the machine tool. The reflector is mounted on the x-axis of the machine tool for laser interference. Module M2: emits digital pulses through a trigger to store the current position of the machine tool. After the machine tool starts moving, it synchronously collects the position information of each axis of the machine tool at a preset sampling rate through the laser tracking interferometer and the machine tool grating ruler, and transmits it to the host computer. Module M3: performs error evaluation on the synchronously collected data and generates machine tool spatial error data.

[0061] The machine tool x-axis position signal satisfies:

[0062] x MT =x0+v·τ±u MT

[0063] Where, x MT This is the signal for the machine tool's x-axis position, where x0 represents the initial x-axis position, v represents the machine tool's speed along the x-axis, τ represents the time the machine tool spends moving along the x-axis, and u... MT It is the uncertainty of machine tool position measurement.

[0064] The length signal of the laser tracking interferometer satisfies:

[0065] x Taccr =x0+v·(τ+Δ τ,SYS )+Δ MT,YSYS (x)±u Tracer

[0066] Where, x Tacer It is the length signal of the laser tracking interferometer, Δ τ,SYS It is the time synchronization error, Δ MT,YSYS (x) is the systematic error along the x-axis, u Tracer It is the uncertainty of the laser tracking interferometer measurement.

[0067] The error evaluation expression is:

[0068] x Tracer -x MT =v·Δ τ,SYS +Δ MT,YSYS (x)±uMT,Tracer

[0069] Among them, u MT,Tracer =u MT +u Tracer This represents the combined measurement uncertainty of the machine tool and the laser tracking interferometer.

[0070] If the assessed error is less than the preset error measurement threshold, the measurement data is deemed valid and the measurement continues to the next position. Otherwise, the measurement data is deemed invalid, triggering the error correction mechanism to rematch the timestamps of the laser tracking interferometer and the counting card on the machine tool grating ruler, and then the measurement is repeated.

[0071] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A flight measurement method for detecting the spatial accuracy of machine tools, characterized in that, include: Step 1: Install a laser tracking interferometer on a stable plane near the machine tool, and install a reflector on the x-axis of the machine tool for laser interferometry; Step 2: Align the laser tracking interferometer beam with the machine tool's x-axis, move the reflector along the machine tool's x-axis at different speeds, and simultaneously measure the machine tool's x-axis position signal and the laser tracking interferometer length signal; Step 3: A digital pulse is emitted through a trigger to store the current position of the machine tool. After the machine tool starts moving, the position information of each axis of the machine tool is synchronously collected by a laser tracking interferometer and the machine tool grating ruler at a preset sampling rate and transmitted to the host computer. Step 4: Perform error assessment on the synchronously acquired data to generate machine tool space error data.

2. The flight measurement method for machine tool spatial accuracy detection according to claim 1, characterized in that, The machine tool x-axis position signal satisfies: x MT =x0+v·τ±u MT Where, x MT This is the signal for the machine tool's x-axis position, where x0 represents the initial x-axis position, v represents the machine tool's speed along the x-axis, τ represents the time the machine tool spends moving along the x-axis, and u... MT It is the uncertainty of machine tool position measurement.

3. The flight measurement method for machine tool spatial accuracy detection according to claim 2, characterized in that, The length signal of the laser tracking interferometer satisfies: x Taccr =x0+v·(τ+Δ τ,SYS )+D MT,YSYS (x)±u Tracer Where, x Tacer It is the length signal of the laser tracking interferometer, Δ τ,SYS It is the time synchronization error, Δ MT,YSYS (x) is the systematic error along the x-axis, u Tracer It is the uncertainty of the laser tracking interferometer measurement.

4. The flight measurement method for machine tool spatial accuracy detection according to claim 3, characterized in that, The error evaluation expression is: x Tracer -x MT =v·Δ τ,SYS +D MT,YSYS (x)±u MT,Tracer Among them, u MT,Tracer =u MT +u Tracer This represents the combined measurement uncertainty of the machine tool and the laser tracking interferometer.

5. The flight measurement method for machine tool spatial accuracy detection according to claim 1, characterized in that, If the assessed error is less than the preset error measurement threshold, the measurement data is deemed valid and the measurement continues to the next position. Otherwise, the measurement data is deemed invalid, triggering the error correction mechanism to rematch the timestamps of the laser tracking interferometer and the counting card on the machine tool grating ruler, and then the measurement is repeated.

6. A flight measurement system for spatial accuracy detection of machine tools, characterized in that, include: Module M1: Controls the reflector to move along the x-axis of the machine tool at different speeds, and synchronously measures the position signal of the machine tool x-axis and the length signal of the laser tracking interferometer. The laser tracking interferometer is mounted on a stable plane near the machine tool, and the laser tracking interferometer beam is aligned with the x-axis of the machine tool. The reflector is mounted on the x-axis of the machine tool for laser interferometry. Module M2: It generates digital pulses through a trigger, stores the current position of the machine tool, and after the machine tool starts moving, it synchronously collects the position information of each axis of the machine tool through a laser tracking interferometer and the machine tool grating ruler at a preset sampling rate and transmits it to the host computer. Module M3: Performs error assessment on synchronously acquired data and generates machine tool space error data.

7. The flight measurement system for machine tool spatial accuracy detection according to claim 6, characterized in that, The machine tool x-axis position signal satisfies: x MT =x0+v·τ±u MT Where, x MT This is the signal for the machine tool's x-axis position, where x0 represents the initial x-axis position, v represents the machine tool's speed along the x-axis, τ represents the time the machine tool spends moving along the x-axis, and u... MT It is the uncertainty of machine tool position measurement.

8. The flight measurement system for machine tool spatial accuracy detection according to claim 7, characterized in that, The length signal of the laser tracking interferometer satisfies: x Taccr =x0+v·(τ+Δ τ,SYS 0+D MT,YSYS (x)±u Tracer Where, x Tacer It is the length signal of the laser tracking interferometer, Δ τ,SYS It is the time synchronization error, Δ MT,YSYS (x) is the systematic error along the x-axis, u Tracer It is the uncertainty of the laser tracking interferometer measurement.

9. The flight measurement system for machine tool spatial accuracy detection according to claim 8, characterized in that, The error evaluation expression is: x Tracer -x MT =v·Δ τ,SYS +D MT,YSYS (x)±u MT,Tracer Among them, u MT,Tracer =u MT +u Tracer This represents the combined measurement uncertainty of the machine tool and the laser tracking interferometer.

10. The flight measurement system for machine tool spatial accuracy detection according to claim 6, characterized in that, If the assessed error is less than the preset error measurement threshold, the measurement data is deemed valid and the measurement continues to the next position. Otherwise, the measurement data is deemed invalid, triggering the error correction mechanism to rematch the timestamps of the laser tracking interferometer and the counting card on the machine tool grating ruler, and then the measurement is repeated.

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