A coordinate measuring system and method for high-steep or deep-recess complex surfaces

Abstract

The application discloses a kind of high steepness or deep concave complex surface coordinate measuring system and method, system is equipped with inductive probe on the B axis of machine tool, inductive probe is connected data acquisition unit by signal amplification unit, data acquisition unit is also connected machine tool and control unit, can carry out the synchronization of the displacement signal of X axis and Z axis of machine tool and inductive probe indication signal, control unit is when inductive probe indication is zero, corresponding X axis and Z axis displacement signal is collected.The method comprises: aligning the C axis rotation center line of inductive probe and first main shaft;From current sampling point, inductive probe is moved to the vicinity of next sampling point along Z axis direction at first speed, then inductive probe is moved along X axis direction close to next sampling point at second speed until inductive probe indication is zero, and the displacement signal of X axis and Z axis at this time is collected.The inductive probe of the application is combined with ultra-precision machine tool, and the accuracy of complex surface coordinate measurement is effectively improved.

Description

Technical Field

[0001] This invention relates to the field of precision and ultra-precision machining technology, and in particular to a coordinate measurement system and method for highly steep or deeply concave complex curved surfaces. Background Technology

[0002] With the development of precision and ultra-precision machining technologies, high-precision complex surfaces are widely used in core components of industries such as aerospace, high-performance optical systems, automobiles, and shipbuilding. For example, highly steep conformal optics play a crucial role in supersonic / hypersonic aircraft windows, thermal imager lenses, and dome systems. They can significantly improve the aerodynamic performance of aircraft while ensuring their optical performance. Optical freeform surfaces are also increasingly widely used in various optoelectronic products due to their excellent performance in improving image quality and expanding the field of view. They have become a research hotspot in today's technological development. With the widespread application of these high-precision complex surfaces, the problems of adaptive processing and surface measurement arise. Although optical detection methods, such as holographic optical interferometry, have high measurement accuracy, their dynamic measurement range is low, making them unsuitable for measuring complex surfaces with large slopes. Measurements of different surfaces require different null-position optics, resulting in high costs.

[0003] Coordinate measuring machines (CMMs) and profilometers offer greater flexibility for measuring various types of complex surfaces. They are widely used in surface treatment to guide calibration patterns. Typical examples include Luphoscan, developed by Taylor Hobson, and Nanometer-Precision Non-Contact Measurement of Freeform Optical Surfaces (NANOMEFOS) from Eindhoven University of Technology. Both employ cylindrical coordinate systems with independent structure and measurement loops, achieving measurement uncertainties of 30 nm (2σ) and 100 nm respectively through online error compensation. However, for complex surfaces with large slopes, significant longitudinal elevation differences often exceed the probe's scanning stroke. Large deviations from aspherical surfaces and variations in surface slope can also exceed the probe's dynamic range and tolerance slope, making it difficult to guarantee measurement accuracy. The measurement uncertainty of CMMs is typically on the order of micrometers or submicrometers. For steep, large aspherical surfaces that wavefront interferometers cannot measure, coordinate measurement, besides its high flexibility, is the most economical and effective method. However, large surface slopes also limit the measurement accuracy of CMMs. Highly steep surfaces are more sensitive to motion and probe errors. In addition, there may be some “blind spots” or local features that the CMM probe can only access before the surface is repositioned or tilted into the accessible space of the CMM.

[0004] Patent CN101957182A discloses an online measurement system for large-aperture, high-steepness optical mirrors. Light emitted from a numerical aperture fiber optic source passes through a measurement grating, generating a set of shadow fringes. These fringes are then projected onto the large-aperture, high-steepness optical mirror after passing through a converging beam splitting system and a high-precision plane mirror. The light is then reflected back along the original path by the large-aperture, high-steepness optical mirror, and upon passing through the high-precision plane mirror and converging beam splitting system again, another beam is generated, producing a common image of the light source. This image is acquired by a digital CCD and transmitted to a computer for analysis. The computer information processing system calculates the surface shape error of the large-aperture, high-steepness optical mirror by comparing the deviation between the reflected image and the ideal image. This method requires very high surface quality of the measured surface; the roughness must be almost mirror-like for measurement. The entire system is large, making integration into machine tools inconvenient, and prone to spatial interference with machining systems on machine tools.

[0005] Patent CN110500969A discloses an in-situ measurement planning method for highly steep and complex curved surfaces. First, it generates non-equidistant transverse cross-sectional contour lines of the complex curved surface using the iso-illuminance angle as a constraint. Combined with the longitudinal cross-sectional contour lines, it obtains a full-surface grid-like scanning measurement path. Then, it extracts surface concave-convex features based on the average curvature changes in the two parameter directions, generating locally refined scanning contour lines. Next, based on the iso-illuminance angle and the obtained scanning path, it performs multi-segment splicing measurement motion planning to obtain the motion trajectory of the sensor reference point. Finally, it verifies the measurement angle of the optical probe, completing the in-situ measurement planning for the complex curved surface. This method achieves in-situ scanning path generation and measurement motion planning for highly steep and complex curved surfaces, ensuring measurement accuracy in characteristic areas. This method uses an optical point displacement non-contact sensor, requiring the angle between the probe and the surface normal to be within a certain range during measurement, i.e., using the "iso-illuminance angle as a constraint." For measuring highly steep curved surfaces, the probe's posture needs continuous adjustment, necessitating the introduction of three or more axes of motion for contour scanning, which reduces measurement accuracy. Summary of the Invention

[0006] The technical problem to be solved by this invention is to achieve contact contour measurement of high-steep or deep-recessed parts with various surface qualities, and to improve trigger repeatability compared with existing commercial three-coordinate contact trigger probes (Zeiss, Renishaw).

[0007] To address the technical problems existing in the prior art, this invention provides a coordinate measurement system and method for highly steep or deeply concave complex curved surfaces. An inductive probe is added to an ultra-precision machine tool. Based on the repeatability accuracy of the inductive probe and the positioning accuracy of the ultra-precision machine tool, the sampling accuracy is greater than that of existing commercial coordinate measuring machines (Zeiss and Renishaw), and the single-point trigger sampling repeatability reaches 0.04μm.

[0008] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows:

[0009] A coordinate measurement system for steep or deeply concave complex curved surfaces includes a machine tool. A first spindle of the machine tool is equipped with a workpiece to be measured. A second spindle of the machine tool is equipped with an inductive probe. The first spindle moves linearly along the X-axis of the machine tool coordinate system and rotates along the C-axis of the machine tool coordinate system. The second spindle moves along the Z-axis of the machine tool coordinate system and rotates along the B-axis of the machine tool coordinate system. The inductive probe is mounted on the B-axis of the second spindle. The system also includes a signal amplification unit, a data acquisition unit, and a control unit. The inductive probe is connected to the data acquisition unit via the signal amplification unit, and the data acquisition unit is connected to the machine tool. The control unit is connected to the data acquisition unit.

[0010] The data acquisition unit is used to synchronize the displacement signals of the X-axis and Z-axis of the machine tool with the reading signals of the inductive probe;

[0011] The control unit is used to acquire the corresponding X-axis and Z-axis displacement signals when the inductive probe reading is zero.

[0012] Furthermore, the inductive probe is mounted on the B-axis of the second spindle via a height adjustment table, which moves linearly along the Y-axis of the machine tool coordinate system.

[0013] This invention also proposes a coordinate measurement method for steep or deeply concave complex surfaces, applied to the coordinate measurement system for such surfaces, comprising the following steps:

[0014] S1) Align the inductive probe with the C-axis rotation center line of the first spindle;

[0015] S2) Select at least two sampling points on the target arc of the workpiece to be measured. For each sampling point, start from the current sampling point and move the inductive probe along the Z-axis at the first speed to the vicinity of the next sampling point. Then move the inductive probe along the X-axis at the second speed to the vicinity of the next sampling point until the reading of the inductive probe is zero. Collect the displacement signals of the X-axis and Z-axis at this time.

[0016] S3) Use the displacement signals of the X-axis and Z-axis corresponding to each sampling point as the sampling point coordinate measurement value, and return to step S1) until the sampling points of all arcs on the surface of the workpiece to be measured are measured.

[0017] Furthermore, step S1) specifically includes the following steps:

[0018] S11) Install the inclined block with an inclination angle of γ on the first spindle, and adjust the inductive probe along the Y-axis direction of the machine tool coordinate system to align it with the C-axis rotation center line of the first spindle in the Y-axis direction.

[0019] S12) Adjust the inclined plane of the inclined block to be parallel to the X-axis of the machine tool coordinate system, rotate the inclined block by 180°, calculate the distance difference Δz between the inductive probe and the inclined plane before and after the rotation, move the inductive probe along the Z-axis and repeat this step until the distance difference Δz is less than the preset first threshold.

[0020] S13) Adjust the inductive probe along the X-axis of the machine tool coordinate system and align it with the C-axis rotation center line of the first spindle in the X-axis direction;

[0021] S14) Adjust the inclined plane of the inclined block to be parallel to the Y-axis of the machine tool coordinate system, rotate the inclined block by 180°, calculate the distance difference Δz between the inductive probe and the inclined plane before and after the rotation, move the inductive probe along the Z-axis and repeat this step until the distance difference Δz is less than the preset second threshold.

[0022] Furthermore, in step S12), the parallelism of the inclined plane of the inclined block to the X-axis of the machine tool coordinate system is adjusted, and in step S14), the parallelism of the inclined plane of the inclined block to the Y-axis of the machine tool coordinate system is adjusted, both of which are less than 1 μm / 50 mm.

[0023] Furthermore, both the first threshold and the second threshold are 0.1 μm.

[0024] Furthermore, step S2) specifically includes the following steps:

[0025] S21) Calculate the Z-axis coordinate of each sampling point;

[0026] S22) Starting from position 1' corresponding to the current sampling point, move the second main axis along the Z-axis direction at the first speed, so that the inductive probe reaches position 2' corresponding to the Z-axis coordinate of the next sampling point;

[0027] S23) Fix the second main shaft and move the first main shaft along the X-axis at a first speed, so that the inductive probe is close to the next sampling point, until the inductive probe moves a preset distance relative to the next sampling point to position point 3';

[0028] S24) Move the first main axis along the X-axis at the second speed, so that the inductive probe continues to approach the next sampling point until the reading returned by the inductive probe is zero. Collect the Z-axis displacement of the second main axis and the X-axis displacement of the first main axis corresponding to the position point 4' of the inductive probe at the next sampling point.

[0029] S25) Move the first main shaft along the X-axis at a first speed, so that the inductive probe moves away from the next sampling point and reaches position point 5';

[0030] (S26) Return to step S22 until the Z-axis displacement of the second principal axis corresponding to the position point 4' of each sampling point and the X-axis displacement of the first principal axis have been collected.

[0031] Furthermore, the current sampling point position 1' coincides with the previous sampling point positions 3' and 5'.

[0032] Furthermore, in step S24), the trigger delay corresponding to the second speed is less than the preset third threshold.

[0033] Furthermore, the third threshold is 0.03 μm.

[0034] Compared with the prior art, the advantages of the present invention are as follows:

[0035] 1. This invention features an inductive probe mounted on the B-axis of a machine tool. Based on the excellent detection performance of the inductive probe, it can detect the contours of steep, deeply concave surfaces via lateral triggering, and the surface shape can be acquired simply by moving the X, Z, and C axes of the machine tool. This reduces errors from multi-axis motion; that is, the probe's orientation does not need to be changed even when the steepness varies over a wide range, and the acquired coordinate values ​​are directly in the machine tool's XZC coordinate system.

[0036] 2. This invention aligns the inductive probe with the C-axis of the machine tool, and then measures the sampling points by controlling the movement of the machine tool in the X and Z axes. By utilizing the repeatability of the zero position of the inductive probe, the trigger acquisition accuracy of the measurement system is within 0.04μm, which is higher than that of traditional common coordinate measuring machines (Zeiss and Renishaw). Attached Figure Description

[0037] Figure 1 This is an XZ plan view of the system according to an embodiment of the present invention.

[0038] Figure 2 This is a flowchart of a method according to an embodiment of the present invention.

[0039] Figure 3 This is a schematic diagram of the operation of method step S1 in an embodiment of the present invention.

[0040] Figure 4 This is a schematic diagram of the operation of method step S2 in an embodiment of the present invention.

[0041] Legend: 1-Machine tool, 2-Signal amplification unit, 3-Data acquisition unit, 4-Control unit, 11-First spindle, 12-Second spindle, 13-Height adjustment table. Detailed Implementation

[0042] The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but this does not limit the scope of protection of the present invention.

[0043] Example 1

[0044] Based on the type of sensor used, surface profile measurement methods are currently mainly divided into contact methods and optical non-contact methods.

[0045] Optical non-contact sensors can acquire the position of a point or surface on a workpiece with high resolution and efficiency. However, accuracy is often sensitive to environmental conditions and surface roughness.

[0046] Wavefront interferometers are susceptible to interference from vibrations and air turbulence. Furthermore, the cost of commercial wavefront interferometers is typically too high for factory use.

[0047] Another type of optical non-contact sensor is the point displacement sensor. Examples include diffuse laser triangulation sensors and color confocal sensors, which can adapt to a relatively large angular incidence range, but their angular adaptability is still insufficient.

[0048] Contact probes are robust to surface characteristics such as roughness and shape. Furthermore, airflow and temperature fluctuations have no effect on test results. As a representative of contact probes, the 3D trigger probe commonly used in coordinate measuring machines (CMMs) can adapt to steep or deeply concave surfaces. However, commercially available 3D trigger probes can only achieve a trigger repeatability accuracy of approximately 0.25 μm.

[0049] To achieve contact-based contour measurement of high-slope or deeply recessed parts with various surface qualities, and to improve trigger repeatability compared to existing commercially available coordinate measuring machine (CMM) contact trigger probes (Zeiss, Renishaw), we consider integrating inductively coupled horizontal ...

[0050] like Figure 1 As shown, the coordinate measurement system for steep or deeply concave complex curved surfaces in this embodiment includes a machine tool 1. In this embodiment, the machine tool 1 is an XZCB four-axis ultra-precision machine tool, including a first spindle 11 on which the workpiece to be measured is mounted, and a second spindle 12 on which an inductive probe is mounted. The first spindle 11 includes a first motor and a first turntable. The first motor drives the first turntable to move linearly along the X-axis of the machine tool coordinate system, and the first turntable rotates along the C-axis of the machine tool coordinate system. The second spindle 12 includes a second motor and a second turntable. The second motor drives the second turntable to move along the Z-axis of the machine tool coordinate system, and the second turntable rotates along the B-axis of the machine tool coordinate system. The workpiece to be measured is mounted on the center part of the first turntable by a three-jaw chuck, and the inductive probe is mounted on the B-axis of the second spindle 12, that is, on the edge part of the second turntable. With the above structure, utilizing the extremely high positioning and motion accuracy of ultra-precision machine tools, the radial and axial rotation accuracy of the first spindle 11 is less than 50nm, the straightness of the two feed axes Z and X in each direction is less than 50nm / 25mm, and the positioning resolution is less than 1nm.

[0051] In this embodiment, the inductive probe is a lever-type inductive probe with a repeatability accuracy of 0.03μm. It is mounted on the edge of the second turntable via a height adjustment platform 13, which can drive the lever-type inductive probe to move linearly along the Y-axis of the machine tool coordinate system.

[0052] like Figure 1 As shown, the coordinate measurement system for steep or deeply concave complex curved surfaces in this embodiment further includes a signal amplification unit 2, a data acquisition unit 3, and a control unit 4. The inductive probe is connected to the data acquisition unit 3 through the signal amplification unit 2, and the data acquisition unit 3 is connected to the machine tool 1. The control unit 4 connects the data acquisition unit 3 and the machine tool 1, wherein:

[0053] Signal amplification unit 2 uses a signal amplifier with an indication resolution of 0.01μm. The reading signal of the inductive probe is amplified by the signal amplifier and output in real time.

[0054] The data acquisition unit 3 uses a Dewesoft data acquisition card to synchronize the displacement signals of the X-axis and Z-axis of the machine tool 1 with the reading signals of the inductive probe.

[0055] The control unit 4 is a PC, used to control the movement and rotation of the first spindle 11 and the second spindle 12 of the machine tool 1 through NC (digital control) program, and to set the trigger acquisition conditions to acquire the corresponding X-axis and Z-axis displacement signals when the inductive probe reading is zero.

[0056] We refer to the set trigger acquisition conditions as the "zero-point trigger mode," which means acquiring the XZC coordinates of the probe in the machine tool coordinate system when it deflects to a fixed zero position (reading is zero) while measuring a certain point. When moving only along the X and Z axes, the position of the probe coordinate system relative to the machine tool coordinate system does not change, and the linearity error of the probe is not introduced. Because the repeatability positioning accuracy of the ultra-precision machine tool's moving axes is much higher than that of the inductive probe, theoretically, ignoring the ball-sensing error, the accuracy of the probe's acquisition value at a certain measurement point depends on the probe's zero-point repeatability—0.03 μm in this embodiment. The detection method involves a fixed Z-axis feed, approaching the workpiece surface along the X-axis and contacting the probe's fixed zero position, at which point the X-axis and Z-axis displacement signals are triggered and acquired.

[0057] In summary, the coordinate measurement system for steep or deeply concave complex surfaces in this embodiment is equipped with an inductive probe on the B-axis of an ultra-precision machine tool. Based on the excellent detection performance of the inductive probe, it can detect the contours of steep and deeply concave surfaces via lateral triggering, and only requires moving the X, Z, and C axes of the machine tool to complete the surface shape acquisition. This reduces the error of multi-axis motion; that is, the probe's attitude does not need to be changed even when the steepness varies over a wide range, and the acquired coordinate values ​​are directly in the machine tool's XZC coordinate system.

[0058] Example 2

[0059] This embodiment proposes a coordinate measurement method for steep or deeply concave complex surfaces, applied to the coordinate measurement system for steep or deeply concave complex surfaces described in Embodiment 1, such as... Figure 2 As shown, it includes the following steps:

[0060] S1) Align the inductive probe with the C-axis rotation center line of the first spindle 11;

[0061] S2) Select at least two sampling points on the target arc of the workpiece to be measured. The target arc of the workpiece to be measured is the outline of the workpiece to be measured in the XZ plane. For each sampling point, start from the current sampling point and move the inductive probe along the Z-axis at the first speed to the vicinity of the next sampling point. Then move the inductive probe along the X-axis at the second speed to the vicinity of the next sampling point until the reading of the inductive probe is zero. Collect the displacement signals of the X-axis and Z-axis at this time.

[0062] S3) Use the displacement signals of the X-axis and Z-axis corresponding to each sampling point as the sampling point coordinate measurement value, control the first spindle 11 to drive the workpiece to be measured to rotate along the C-axis by a certain angle, and take the outline of the workpiece to be measured under the XZ plane as the new target arc, and return to step S1) until the sampling points of all arcs on the surface of the workpiece to be measured are measured.

[0063] In this embodiment, the repeatability of the measurement system is determined by the repeatability of the probe. Equally important is the positioning accuracy of the measurement system, i.e., the accuracy of the probe's measured values. Since the coordinates of the point to be measured are in the machine tool coordinate system, the alignment of the probe center with the machine tool's C-axis is crucial for positioning accuracy. We align the probe center with the machine tool's C-axis sequentially along the Y-axis and X-axis of the machine tool coordinate system. Therefore, step S1) specifically includes the following steps:

[0064] S11) as Figure 3 As shown, a wedge block with an inclination angle of γ is installed on the first spindle 11. In this embodiment, γ = 20°. The height adjustment table 13 is adjusted along the Y-axis direction of the machine tool coordinate system to drive the inductive probe to rise and fall, and to align it with the C-axis rotation center line of the first spindle 11 in the Y-axis direction, that is, to be located in the same XZ plane.

[0065] S12) Adjust the inclined plane of the inclined block to be parallel to the X-axis of the machine tool coordinate system, with a parallelism within 1μm / 50mm. Measure the coordinates of the inductive probe at the contact point on the inclined plane. Then, control the first spindle 11 to rotate the inclined block 180° and measure the coordinates of the inductive probe at the contact point on the inclined plane again. Calculate the distance difference Δz between the inductive probe and the inclined plane before and after rotation based on the coordinates of the two contact points. This is the difference in the X-axis coordinates of the two contact points. The relationship between the distance difference Δz and the height difference Δh of the probe relative to the C-axis rotation center line in the X-axis direction is as follows:

[0066]

[0067] In this embodiment, the height difference Δh needs to be controlled within 0.2μm. Therefore, the distance difference Δz needs to be less than the preset first threshold of 0.1μm. If the distance difference Δz does not meet this condition, the second spindle 12 is controlled to move the inductive probe along the Z-axis and this step is repeated until the distance difference Δz is less than the first threshold. At this time, the measurement error of the outer circle radius introduced by the height difference Δh is theoretically less than 0.01μm.

[0068] Next, align the probe center with the machine tool's C-axis along the X-axis of the machine tool coordinate system. The alignment process is similar to that along the Y-axis of the machine tool coordinate system, and includes the following steps:

[0069] S13) Adjust the inductive probe along the X-axis direction of the machine tool coordinate system and align it with the C-axis rotation center line of the first spindle 11 in the X-axis direction, that is, control the first spindle 11 to move along the X-axis direction so that the inductive probe and the C-axis rotation center line of the first spindle 11 are located in the same YZ plane.

[0070] S14) Adjust the inclined plane of the inclined block to be parallel to the Y-axis of the machine tool coordinate system, with a parallelism within 1 / 50 mm. At this time, the inclined block has rotated 90° compared to when the inclined plane is parallel to the X-axis of the machine tool coordinate system. Measure the coordinates of the inductive probe at the contact point on the inclined plane at this time. Then control the first spindle 11 to rotate the inclined block 180°. Measure the coordinates of the inductive probe at the contact point on the inclined plane again. Calculate the distance difference Δz between the inductive probe and the inclined plane before and after rotation based on the coordinates of the two contact points. That is, the difference in the coordinates of the two contact points on the X-axis. Move the inductive probe along the Z-axis and repeat this step until the distance difference Δz is less than the preset second threshold of 0.01 μm.

[0071] To improve the theoretical triggering accuracy of the contact measurement system, we developed a zero-position triggering method for the probe, following the "zero-position triggering mode" in Example 1. This method involves acquiring the coordinates of the point where the probe reading becomes inherently zero. When moving only along the X and Z axes of the machine tool coordinate system, the position of the probe coordinate system relative to the machine tool coordinate system remains constant, eliminating the introduction of linear errors in the probe. Since the repeatability accuracy of the machine tool axes (0.015 μm) is higher than the repeatability accuracy of the probe (0.03 μm), theoretically, the accuracy of the acquired value at a given point is determined by the probe's repeatability accuracy, i.e., 0.03 μm (ignoring probe errors). The probe detection method involves fixing the Z-axis feed and moving the X-axis closer to the workpiece surface, triggering the acquisition of displacement signals along both the X and Z axes. The triggering condition is that the probe's voltage signal becomes zero, i.e., the probe reading is zero.

[0072] like Figure 4 As shown, step S2) of this embodiment specifically includes the following steps:

[0073] S21) Calculate the Z-axis coordinate of each sampling point. In this embodiment, the sampling points are manually sampled points on the arc of the workpiece to be measured. Multiple manually sampled points fit the approximate position of the arc. The number of sampling points is determined by the degrees of freedom of the theoretical shape of the arc. For example, for a specific meridional arc on a spherical shell, the position of the arc is determined by manually collecting three points, and then each sampling point P is determined by interpolation. i The position of each sampling point, and the Z-axis coordinate of each sampling point is determined by the sampling interval;

[0074] S22) From the current sampling point P i Starting from the corresponding position point 1', the second main axis 12 moves along the Z-axis at the first velocity, so that the inductive probe reaches the next sampling point P. i+1 The Z-axis coordinate corresponds to the position point 2';

[0075] S23) Fix the second spindle 12, i.e. fix the Z-axis feed, and move the first spindle 11 along the X-axis at a first speed, so that the inductive probe approaches the sampling point P. i+1 Until the inductive probe is relative to the sampling point P i+1 Move the preset distance to position 3'. The distance between position 3' and position 2' can be a preset fixed value.

[0076] S24) The first main shaft 11 moves along the X-axis at a second speed, which is less than the first speed, so that the inductive probe continues to approach the sampling point P. i+1 The sampling point P is reached when the reading returned by the inductive probe is zero. i+1 The sampling point is located at position 4', and the Z-axis displacement of the second spindle 12 and the X-axis displacement of the first spindle 11 corresponding to position 4' are triggered. In this step, considering the existence of machining errors, the sampling point P is...i+1 The actual surface of the workpiece being measured has a machining tolerance of ±T compared to the theoretical surface; that is, the estimated range of the actual machining point deviates from the nominal machining point. However, the value of T cannot exceed the sensing range of the inductive probe to prevent damage to the inductive probe. Furthermore, since it is impossible to perfectly synchronize the acquisition of the probe reaching zero position with the trigger signal for acquiring the XZ axis coordinates, the inductive probe relative to the sampling point P... i+1 The faster the forward speed, the greater the delay in triggering the acquisition of displacement coordinates. Therefore, in this step, the trigger delay is minimized by reducing the speed. The theoretical maximum trigger accuracy of the inductive probe is 0.03μm, so the trigger delay corresponding to the second speed is less than the preset third threshold trigger delay of 0.03μm.

[0077] S25) Move the first main shaft 11 along the X-axis at a first speed, so that the inductive probe moves away from the sampling point P. i+1 And reach location point 5', thus sampling point P i+1 The sampling has ended, and the sampling point P... i+2 Sampling begins; in this embodiment, sampling point P... i+2 Position 1' and sampling point P i+2 Positions 3' and 5' coincide, with position 5' indicating the end of this sampling and the beginning of the next sampling;

[0078] S26) Sample point P i+1 As the current sampling point, return to step S22 until the Z-axis displacement of the second spindle 12 corresponding to the position point 4' of each sampling point and the X-axis displacement of the first spindle 11 are collected, thereby obtaining the XZ plane coordinates of all sampling points on the current arc in the machine tool coordinate system.

[0079] According to step S3 of this embodiment, before each sampling point of the arc of the workpiece to be tested on the XZ plane, the workpiece to be tested is rotated by a certain angle so that the new target arc is in the XZ plane where the rotation axis of the C axis is located. Therefore, each sampling point on the same arc collected corresponds to the coordinates on the C axis, and the coordinates of all sampling points on the surface of the workpiece to be tested in the XZC coordinate system of the machine tool can be obtained.

[0080] In summary, the method described in this embodiment offers better stability and robustness to changes in workpiece surface quality and environmental conditions compared to optical measurements. It overcomes the limitation of optical non-contact probes requiring normal incidence on the workpiece surface for measurement. Furthermore, it achieves higher triggering accuracy than existing contact coordinate measuring machines, realizing a triggering and acquisition accuracy within 0.04 μm.

[0081] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Therefore, any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention should fall within the protection scope of the present invention.

Claims

1. A coordinate measurement system for steep or deeply concave complex curved surfaces, characterized in that, The system includes a machine tool (1), on which a workpiece to be measured is mounted on a first spindle (11) and an inductive probe is mounted on a second spindle (12). The first spindle (11) moves linearly along the X-axis of the machine tool coordinate system and rotates along the C-axis of the machine tool coordinate system. The second spindle (12) moves along the Z-axis of the machine tool coordinate system and rotates along the B-axis of the machine tool coordinate system. The inductive probe is mounted on the B-axis of the second spindle (12). The system also includes a signal amplification unit (2), a data acquisition unit (3), and a control unit (4). The inductive probe is connected to the data acquisition unit (3) through the signal amplification unit (2), and the data acquisition unit (3) is connected to the machine tool (1). The control unit (4) is connected to the data acquisition unit (3). The data acquisition unit (3) is used to synchronize the displacement signals of the X-axis and Z-axis of the machine tool (1) with the reading signals of the inductive probe; The control unit (4) is used to collect the corresponding X-axis and Z-axis displacement signals when the inductive probe reading is zero; The coordinate measurement system is used to perform the following steps: S1) Align the inductive probe with the C-axis rotation center line of the first spindle (11); S2) Select at least two sampling points on the target arc of the workpiece to be measured. For each sampling point, start from the current sampling point and move the inductive probe along the Z-axis at a first speed to the vicinity of the next sampling point. Then move the inductive probe along the X-axis at a second speed less than the first speed to the vicinity of the next sampling point until the reading of the inductive probe is zero. Collect the displacement signals of the X-axis and Z-axis at this time. S3) Use the displacement signals of the X-axis and Z-axis corresponding to each sampling point as the sampling point coordinate measurement value, and return to step S1) until the sampling points of all arcs on the surface of the workpiece to be measured are measured.

2. The coordinate measurement system for steep or deeply concave complex curved surfaces according to claim 1, characterized in that, The inductive probe is mounted on the B-axis of the second spindle (12) via a height adjustment table (13), and the height adjustment table (13) moves linearly along the Y-axis of the machine tool coordinate system.

3. A coordinate measuring method of a high-steepness or deep-recess complex curved surface, applied to the coordinate measuring system of the high-steepness or deep-recess complex curved surface according to claim 1 or 2, characterized in that, Includes the following steps: S1) Align the inductive probe with the C-axis rotation center line of the first spindle (11); S2) Select at least two sampling points on the target arc of the workpiece to be measured. For each sampling point, start from the current sampling point and move the inductive probe along the Z-axis at the first speed to the vicinity of the next sampling point. Then move the inductive probe along the X-axis at the second speed to the vicinity of the next sampling point until the reading of the inductive probe is zero. Collect the displacement signals of the X-axis and Z-axis at this time. S3) Use the displacement signals of the X-axis and Z-axis corresponding to each sampling point as the sampling point coordinate measurement value, and return to step S1) until the sampling points of all arcs on the surface of the workpiece to be measured are measured.

4. The coordinate measuring method of high steepness or deep concave complex curved surface according to claim 3, characterized in that, Step S1) specifically includes the following steps: S11) install the inclined block with the inclination angle of to the first main shaft (11), adjust the inductive probe along the Y axis direction of the machine tool coordinate system and make it aligned with the C axis rotation center line of the first main shaft (11) in the Y axis direction; S12) Adjust the inclined plane of the inclined block to be parallel to the X-axis of the machine tool coordinate system, rotate the inclined block 180°, and calculate the distance difference between the inductive probe and the inclined plane before and after the rotation. Move the inductive probe along the Z-axis and repeat this step until the distance difference is reached. Less than the preset first threshold; S13) Adjust the inductive probe along the X-axis of the machine tool coordinate system and align it with the C-axis rotation center line of the first spindle (11) in the X-axis direction; S14) adjusting the slope of the inclined block to be parallel to the Y axis of the machine coordinate system, rotating the inclined block by 180°, and calculating the distance difference of the inductive probe relative to the slope before and after the rotation , moving the inductive probe along the Z axis direction and repeating the step until the distance difference is less than a preset second threshold value.

5. The coordinate measuring method of high steepness or deep concave complex curved surface according to claim 4, characterized in that, In step S12), the parallelism of the inclined plane of the inclined block to the X-axis of the machine tool coordinate system is adjusted, and in step S14), the parallelism of the inclined plane of the inclined block to the Y-axis of the machine tool coordinate system is adjusted, both of which are less than 1 μm / 50 mm.

6. The coordinate measuring method of high steepness or deep concave complex curved surface according to claim 4, characterized in that, Both the first threshold and the second threshold are 0.1 μm.

7. The coordinate measurement method for highly steep or deeply concave complex curved surfaces according to claim 3, characterized in that, Step S2) specifically includes the following steps: S21) Calculate the Z-axis coordinate of each sampling point; S22) Starting from position 1' corresponding to the current sampling point, move the second main axis (12) along the Z-axis direction at the first speed, so that the inductive probe reaches position 2' corresponding to the Z-axis coordinate of the next sampling point; S23) Fix the second main shaft (12) and move the first main shaft (11) along the X-axis at a first speed, so that the inductive probe is close to the next sampling point until the inductive probe moves a preset distance relative to the next sampling point to position point 3'; S24) Move the first main axis (11) along the X-axis at the second speed, so that the inductive probe continues to approach the next sampling point until the reading returned by the inductive probe is zero. Collect the Z-axis displacement of the second main axis (12) corresponding to the position point 4' of the inductive probe at the next sampling point, and the X-axis displacement of the first main axis (11). S25) Move the first main shaft (11) along the X-axis at a first speed, so that the inductive probe moves away from the next sampling point and reaches the position point 5'; S26) Return to step S22 until the Z-axis displacement of the second principal axis (12) corresponding to the position point 4' of each sampling point and the X-axis displacement of the first principal axis (11) are collected.

8. The coordinate measuring method of high steepness or deep concave complex curved surface according to claim 7, characterized in that, The current sampling point position 1' coincides with the previous sampling point positions 3' and 5'.

9. The coordinate measuring method of high steepness or deep concave complex curved surface according to claim 7, characterized in that, In step S24), the trigger delay corresponding to the second speed is less than the preset third threshold.

10. The coordinate measuring method of high steepness or deep concave complex curved surface according to claim 9, characterized in that, The third threshold is 0.03 μm.

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