A spectral confocal sensor in-machine space pose calibration compensation method

Abstract

The present application provides a kind of spectral confocal sensor in-machine space pose calibration compensation method, this method includes: according to the target plane of spectral confocal sensor is moved ranging, determine the pitch angle offset of spectral confocal sensor;According to the confocal data of the optical axis of spectral confocal sensor and the C-axis of three-axis horizontal centering vehicle when centring, determine the eccentric offset of spectral confocal sensor and the geometric relationship between probe coordinate system, reference coordinate system, workpiece coordinate system;When spectral confocal sensor is scanned and measured to the measured surface of the measured workpiece, the measuring point coordinates of spectral confocal sensor in probe coordinate system are converted into target coordinates in workpiece coordinate system, on the premise of guaranteeing measurement accuracy, system structure and calibration process are greatly simplified, improve the implementability, stability and measurement consistency in machine environment.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of precision measurement, in particular to a method for calibrating and compensating the space pose of a spectral confocal sensor in a machine. BACKGROUND

[0002] With the rapid development of optical technology, high-performance optical systems have been widely used in fields such as space remote sensing, space exploration, infrared guidance, star sensors, and high-end imaging equipment. These applications have put forward very high requirements for the imaging quality, stability, and reliability of optical systems. Among them, the alignment accuracy of optical elements, especially the lens centering accuracy, is directly related to the imaging performance and overall index achievement of the system. Therefore, the centering machining and alignment technology of high-precision optical systems has become one of the key bottlenecks restricting the independent research and development and engineering application of optical equipment.

[0003] Compared with traditional vertical centering machines, horizontal centering machines have more advantages in the integration of machining and detection. First, the horizontal structure is conducive to the stable clamping and rotation of large-diameter and heavy optical elements, effectively reducing the deformation and deviation caused by gravity, thereby improving the overall machining precision and stability. Second, the horizontal layout facilitates the integration of multi-axis motion and detection modules, especially in realizing full-process automation and unmanned detection and alignment. However, traditional horizontal centering machines usually rely on autocollimators or contact probes for detection, which are mainly used to measure the spatial position of the ball center corresponding to the surface of the optical element in the near-axis region, and cannot obtain the geometric information of the surface in the edge region of the optical element. They have poor adaptability to high-steepness aspheric surfaces, free-form surfaces, and high-numerical-aperture lenses, and are prone to insufficient detection accuracy due to unstable surface reflection or signal loss, making it difficult to measure the spatial pose of the optical axis of aspheric lenses and other optical elements. This seriously limits their application in high-precision scenarios.

[0004] Spectral confocal sensors have been widely used in precision measurement and in-machine detection in recent years due to their non-contact measurement, high resolution, and strong adaptability to multiple materials. The sensor realizes single-point distance measurement through dispersion principle and can achieve complex surface profile acquisition at sub-micron level. However, the measurement result output by the spectral confocal sensor is only the distance signal along its own optical axis direction. If this signal is to be accurately converted into a three-dimensional point position in the workpiece coordinate system, the spatial pose (including direction and origin offset) of the sensor optical axis in the machine tool coordinate system must be accurately calibrated. The accuracy of pose calibration directly determines the geometric restoration accuracy of in-machine measurement point cloud and the reliability of optical axis fitting results.

[0005] Currently, there are various research and application approaches for the spatial pose calibration of spectral confocal sensors. Some studies are conducted in a coordinate measuring machine (CMM) environment, using planar and spherical geometric constraints to establish mathematical equations, and then iteratively solving for the optical axis direction and the sensor origin position using least squares or Levenberg-Marquardt (LM) algorithms. This method achieves high accuracy in offline environments, but relies on contact-type reference components and complex fitting, making it difficult to reflect the true error field of the machine tool in operation.

[0006] Another type of research, conducted on multi-axis ultra-precision lathes or in-machine measurement systems, establishes a mapping relationship between the beam vector model and the machine tool coordinate system to calibrate the beam direction and origin offset, and combines path planning or error compensation strategies to suppress cosine errors. This type of approach achieves the integration of in-machine calibration and measurement, but generally requires multiple scans to establish an overdetermined system of equations, and obtains the solution through iterative optimization. The process is complex and sensitive to initial values.

[0007] Meanwhile, most calibration methods rely on standard spherical reference parts, but spherical calibration presents numerous difficulties and uncertainties. First, standard spherical parts require extremely high machining accuracy and clamping posture; even slight deviations can introduce systematic errors. Second, variations in spherical curvature cause instability in the reflection signal of the spectral confocal sensor, with signal loss or reflection shift easily occurring in edge regions. Third, the distribution of measurement points is limited and requires multiple scans, making the calibration process complex and inefficient. Fourth, repeated clamping and repositioning are difficult to maintain consistency, easily causing fluctuations in calibration results.

[0008] Currently, most ultra-precision machine tools that have achieved integrated in-situ confocal spectral measurement systems are four-axis or five-axis structures. In addition to the basic X, Z, and C axes of the machine tool, four-axis ultra-precision machine tools usually add a B axis that rotates around the Y axis at the tool post position, while five-axis machine tools further add a linear motion axis of the Y axis. Therefore, this system is more complex, occupies more space, and has a higher cost. Summary of the Invention

[0009] To address the aforementioned technical problems, the technical solution adopted by this invention is as follows:

[0010] According to one aspect of this application, a method for on-machine spatial pose calibration and compensation of a spectral confocal sensor is provided, which is applied to a three-axis horizontal centering machine. The C-axis of the three-axis horizontal centering machine is a rotation axis. The workpiece to be measured is mounted on the C-axis of the three-axis horizontal centering machine. An inclined guide rail is mounted on the inclined slide of the Z-axis of the three-axis horizontal centering machine, and a spectral confocal sensor is mounted on the platform of the inclined guide rail.

[0011] The on-machine space pose calibration and compensation methods for spectral confocal sensors include:

[0012] Step S100, according to the preset target plane corresponding to the optical confocal sensor, the direction vector of the optical axis of the optical confocal sensor is determined by moving ranging;

[0013] Step S200, according to the projection angle of the axis of the optical confocal sensor in the probe coordinate system corresponding to the optical confocal sensor, the pitch angle offset of the optical confocal sensor is determined;

[0014] Step S300, according to the confocal data of the optical axis of the optical confocal sensor and the C-axis of the three-axis horizontal centering machine when the centering, the eccentric offset of the optical confocal sensor is determined;

[0015] Step S400, according to the pitch angle offset and the eccentric offset of the optical confocal sensor, the geometric relationship between the probe coordinate system, the reference coordinate system corresponding to the machining tool of the three-axis horizontal centering machine, and the workpiece coordinate system corresponding to the measured workpiece is determined;

[0016] Step S500, when the optical confocal sensor scans and measures the measured surface of the measured workpiece, according to the geometric relationship between the probe coordinate system, the reference coordinate system and the workpiece coordinate system, the measurement point coordinates of the optical confocal sensor in the probe coordinate system are converted into the target coordinates in the workpiece coordinate system.

[0017] In an exemplary embodiment of the present application, step S100 comprises:

[0018] Step S110, according to the optical axis of the optical confocal sensor, a target plane is preset;

[0019] Step S120, the intersection of the optical axis of the optical confocal sensor when the target plane is in the initial position is determined as the first intersection point;

[0020] Step S130, taking the first intersection point as the origin, the probe coordinate system corresponding to the optical confocal sensor is established, so that the XOY plane of the probe coordinate system and the target plane are located in the same horizontal plane; the XOY plane of the probe coordinate system is the plane composed of the X-axis, the Y-axis and the origin of the probe coordinate system;

[0021] Step S140, the target plane is moved along the X-axis of the probe coordinate system by a preset first distance, the intercept of the optical axis of the optical confocal sensor on the moved target plane is determined as the first intercept, and the position of the target plane is restored;

[0022] Step S150, the target plane is moved along the X-axis of the probe coordinate system by a preset second distance, the intercept of the optical axis of the optical confocal sensor on the moved target plane is determined as the second intercept, and the position of the target plane is restored;

[0023] Step S160, moving the target plane along the Y axis of the probe coordinate system by a preset third distance, determining a first longitudinal intercept of the optical axis of the spectral confocal sensor on the moved target plane, and restoring the position of the target plane;

[0024] Step S170, moving the target plane along the Y axis of the probe coordinate system by a preset fourth distance, determining a second longitudinal intercept of the optical axis of the spectral confocal sensor on the moved target plane, and restoring the position of the target plane;

[0025] Step S180, moving the target plane along the Z axis of the probe coordinate system by a preset fifth distance, determining a first vertical intercept of the optical axis of the spectral confocal sensor on the moved target plane, and restoring the position of the target plane;

[0026] Step S190, moving the target plane along the Z axis of the probe coordinate system by a preset sixth distance, determining a second vertical intercept of the optical axis of the spectral confocal sensor on the moved target plane, and restoring the position of the target plane;

[0027] Step S191, determining the direction vector of the optical axis of the spectral confocal sensor according to the first distance, the first horizontal intercept, the second distance, the second horizontal intercept, the third distance, the first longitudinal intercept, the fourth distance, the second longitudinal intercept, the fifth distance, the first vertical intercept, the sixth distance, and the second vertical intercept.

[0028] In an exemplary embodiment of the present application, step S191 includes:

[0029] Step S1911, determining a first horizontal distance ratio according to the first distance and the first horizontal intercept ; wherein, the first horizontal intercept is the first distance;

[0030] Step S1912, determining a second horizontal distance ratio according to the second distance and the second horizontal intercept ; wherein, the second horizontal intercept is the second distance;

[0031] Step S1913, determining a first longitudinal distance ratio according to the third distance and the first longitudinal intercept ; wherein, the first longitudinal intercept is the third distance;

[0032] Step S1914, determining a second longitudinal distance ratio according to the fourth distance and the second longitudinal intercept ; wherein, the second longitudinal intercept is is the fourth distance;

[0033] Step S1915, determining a first vertical distance ratio according to the fifth distance and the first vertical intercept ; wherein, is the first vertical intercept, is the fifth distance;

[0034] Step S1916, determining a second vertical distance ratio according to the sixth distance and the second vertical intercept ; wherein, is the second vertical intercept, is the sixth distance;

[0035] Step S1917, determining a direction vector (l, m, n) of an axis of an optical axis of the spectral confocal sensor according to the following equation group:

[0036] .

[0037] In an exemplary embodiment of the present application, step S200 comprises:

[0038] Step S210, determining an included angle between a projection of an axis of an optical axis of the spectral confocal sensor in an XOZ plane of a probe coordinate system and a Z axis of the probe coordinate system according to the direction vector (l, m, n) of the axis of the optical axis of the spectral confocal sensor ; wherein, the XOZ plane of the probe coordinate system is a plane composed of an X axis, a Z axis and an origin of the probe coordinate system; tan() is a preset tangent function;

[0039] Step S220, determining an included angle between a projection of an axis of an optical axis of the spectral confocal sensor in a YOZ plane of a probe coordinate system and a Z axis of the probe coordinate system according to the direction vector (l, m, n) of the axis of the optical axis of the spectral confocal sensor ; wherein, the YOZ plane of the probe coordinate system is a plane composed of a Y axis, a Z axis and an origin of the probe coordinate system;

[0040] Step S230, determining a pitch angle offset of an X axis of the probe coordinate system ; wherein, cos() is a preset cosine function;

[0041] Step S240, determining a pitch angle offset of a Y axis of the probe coordinate system .

[0042] In an exemplary embodiment of the present application, step S300 comprises:

[0043] Step S310, moving an X axis of a three-axis horizontal centering vehicle by a preset first moving distance at an initial centering position of an optical axis of the spectral confocal sensor and a C axis of the three-axis horizontal centering vehicle , and rotating the C-axis of the three-axis horizontal centering machine for one round to obtain a corresponding first eccentricity value ;

[0044] Step S320, moving the X-axis of the three-axis horizontal centering machine by a preset second moving distance at the initial centering position of the optical axis of the spectral confocal sensor and the C-axis of the three-axis horizontal centering machine , and rotating the C-axis of the three-axis horizontal centering machine for one round to obtain a corresponding second eccentricity value ;

[0045] Step S330, determining the eccentric offset of the X-axis of the probe coordinate system ;

[0046] Step S340, determining the eccentric offset of the Y-axis of the probe coordinate system .

[0047] In an exemplary embodiment of the present application, step S400 comprises:

[0048] Step S410, establishing a corresponding reference coordinate system of the machining tool of the three-axis horizontal centering machine, taking the intersection point of the C-axis of the machining tool of the three-axis horizontal centering machine and the upper surface of the measured workpiece as the origin, taking the movement direction of the X-axis of the machining tool of the three-axis horizontal centering machine as the positive direction of the horizontal coordinate axis, taking the movement direction of the Z-axis of the machining tool of the three-axis horizontal centering machine as the positive direction of the vertical coordinate axis, and determining the positive direction of the longitudinal coordinate axis according to a preset right-hand rule;

[0049] Step S420, translating the reference coordinate system along the positive direction of the X-axis of the reference coordinate system , translating the reference coordinate system along the positive direction of the Y-axis of the reference coordinate system , translating the reference coordinate system along the positive direction of the Z-axis of the reference coordinate system , rotating the reference coordinate system counterclockwise around the X-axis of the reference coordinate system , rotating the reference coordinate system counterclockwise around the Y-axis of the reference coordinate system , to obtain the probe coordinate system; wherein, is the vertical coordinate value of the origin of the probe coordinate system in the reference coordinate system;

[0050] Step S430, obtaining a workpiece coordinate system corresponding to the measured workpiece by rotating the reference coordinate system clockwise around the Z-axis of the machining tool of the three-axis horizontal centering machine by a preset adjustment angle and displacing the reference coordinate system by an adjustment distance along the positive direction of the X-axis of the machining tool of the three-axis horizontal centering machine; wherein, the adjustment distance is the distance that the optical axis of the spectral confocal sensor and the C-axis of the three-axis horizontal centering machine move along the positive direction of the X-axis of the machining tool of the three-axis horizontal centering machine after centering calibration.

[0051] In an exemplary embodiment of the present application, step S500 comprises:

[0052] In step S510, when the spectral confocal sensor scans and measures the measured curved surface of the measured workpiece, the measurement point coordinates of the detection point of the spectral confocal sensor in the probe coordinate system are obtained as follows:

[0053] ;

[0054] Wherein, m is the data measured by the spectral confocal sensor at the detection point;

[0055] In step S520, the measurement point coordinates of the detection point of the spectral confocal sensor in the probe coordinate system are converted to obtain the target coordinates of the detection point in the workpiece coordinate system as follows:

[0056] ;

[0057] Wherein, is the adjustment angle; sin() is a preset sine function; is the adjustment distance; z is the position coordinate value of the Z-axis of the machining tool of the three-axis horizontal centering machine in the reference coordinate system.

[0058] In an exemplary embodiment of the present application, the X-axis and the Z-axis of the three-axis horizontal centering machine are in a T-shaped layout, the X-axis and the Z-axis of the three-axis horizontal centering machine are straight axes, and the C-axis of the three-axis horizontal centering machine is mounted on the slide plate of the X-axis.

[0059] In an exemplary embodiment of the present application, the measured workpiece is a high-precision aspheric surface.

[0060] In an exemplary embodiment of the present application, the surface of the inclined guide rail and the horizontal plane form a preset angle.

[0061] The present application has at least the following beneficial effects:

[0062] The spectral confocal sensor in-machine space pose calibration compensation method of the present application determines the direction vector of the axis of the optical axis of the spectral confocal sensor according to the moving ranging of the preset target plane corresponding to the spectral confocal sensor, and determines the pitch angle offset of the spectral confocal sensor according to the projection angle of the axis of the spectral confocal sensor in the probe coordinate system corresponding to the spectral confocal sensor, so as to realize pitch calibration, determines the eccentric offset of the spectral confocal sensor according to the confocal data of the optical axis of the spectral confocal sensor and the C-axis of the three-axis horizontal centering machine when the centering is performed, so as to realize eccentric calibration, and then determines the geometric relationship among the probe coordinate system, the reference coordinate system corresponding to the machining machine of the three-axis horizontal centering machine, and the workpiece coordinate system corresponding to the measured workpiece according to the pitch angle offset and the eccentric offset of the spectral confocal sensor, so that when the spectral confocal sensor scans and measures the measured surface of the measured workpiece, the point coordinates of the spectral confocal sensor in the probe coordinate system are converted into target coordinates in the workpiece coordinate system according to the geometric relationship among the probe coordinate system, the reference coordinate system and the workpiece coordinate system, thereby greatly simplifying the system structure and the calibration process under the premise of ensuring the measurement accuracy, and improving the implementability, stability and measurement consistency in the in-machine environment. BRIEF DESCRIPTION OF DRAWINGS

[0063] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiment description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without any creative effort.

[0064] Figure 1 The flow chart of the spectral confocal sensor in-machine space pose calibration compensation method provided by the embodiment of the present application;

[0065] Figure 2 The structure diagram of the three-axis horizontal centering machine provided by the embodiment of the present application;

[0066] Figure 3 The calibration diagram of the standard inclined plane where the inclined guide rail is located, provided by the embodiment of the present application;

[0067] Figure 4 The initial position schematic diagram of the target plane, provided by the embodiment of the present application;

[0068] Figure 5 The schematic diagram of the target plane moving along the X-axis of the probe coordinate system, provided by the embodiment of the present application;

[0069] Figure 6 The eccentric value measurement schematic diagram, provided by the embodiment of the present application;

[0070] Figure 7A schematic diagram illustrating the geometric relationship between the probe coordinate system, the reference coordinate system, and the workpiece coordinate system provided in an embodiment of the present invention;

[0071] Figure 8 This is a schematic diagram illustrating the transformation relationship between the probe coordinate system, the reference coordinate system, and the workpiece coordinate system provided in an embodiment of the present invention. Detailed Implementation

[0072] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0073] This application proposes an on-board spatial pose calibration and compensation method for a spectral confocal sensor. This method is applied to a three-axis horizontal centering car, such as... Figure 2 As shown, the three-axis horizontal centering car consists of a horizontal centering car body, a main spindle unit, an XZC three-axis motion system, a slant platform-type Y-axis fine-tuning device based on linear motor drive, a spectral confocal sensor, a control and acquisition system, and a data processing module.

[0074] The three-axis horizontal centering lathe features linear axes for its X and Z axes, with the Z axis responsible for vertical movement. The X and Z axes are arranged in a T-shape, a design that helps reduce error coupling and improve the machine tool's accuracy. The C-axis is a rotary spindle with angle servo functionality. It is mounted on the slide of the X-axis. The workpiece is mounted on the C-axis and can be rotated and its angle adjusted; the workpiece is a high-precision aspherical surface. An inclined guide rail is mounted on the inclined slide of the Z-axis. Figure 3 As shown, the standard inclined plane of the inclined guide rail is at a preset angle (e.g., 2°) to the horizontal plane to allow the inclined guide rail to move in the inclined direction. A clamp is installed on the platform of the inclined guide rail to hold the spectral confocal sensor.

[0075] The spectral confocal sensor is a high-precision measurement system for detecting and measuring the surface features of a workpiece. In the process of in-situ measurement, the optical axis of the spectral confocal sensor needs to complete the following operations: the optical axis of the spectral confocal sensor is kept in the same horizontal plane as the rotating shaft of the three-axis horizontal centering machine and determines the fixed position of the probe coordinate system (the coordinate system corresponding to the spectral confocal sensor), which can ensure that the entire surface of the workpiece can be completely measured and the surface reconstruction is completed. Unlike the tool which can be adjusted by adjusting the bolts, the existing in-situ measurement platform does not have an adjustment tool to adjust the direction of the Y-axis of the optical axis. Therefore, the Y-axis adjustment platform is introduced to realize the centering of the optical axis. Specifically, as shown in Figure 2 , a linear motor is used as the driving device of the motor. In order to avoid the weight of the measurement platform being completely concentrated on the linear motor, a slide rail is introduced as a load-bearing device. The slide rail and the linear motor are connected through a driving platform. Therefore, the overall platform of the three-axis horizontal centering machine has two basically symmetrical parts. The left side is used for the installation of the Renishaw probe, and the right side is used for the installation of the spectral confocal sensor.

[0076] The model of the Renishaw probe used in this application can be TP200. The micro-strain sensor technology is adopted, which has high measurement accuracy and good repeatability. It has six-direction measurement capability, and the measurement distance of the probe can reach 100 mm. The sensor has a rich secondary development package of measurement interface, which can meet the development needs of the in-situ measurement system.

[0077] Since the measurement centers of the Renishaw probe and the spectral confocal sensor are both at the rotation center of the spectral confocal sensor, if the installation meets the theoretical conditions, the measurement axes of the Renishaw probe and the spectral confocal sensor do not need to be adjusted repeatedly. The Y-axis position can be completed by positioning the linear motor to the same position.

[0078] As shown in Figure 1 , the in-machine space pose calibration compensation method of the spectral confocal sensor proposed in this application includes:

[0079] Step S100, according to the movement and distance measurement of the preset target plane corresponding to the spectral confocal sensor, the direction vector of the axis of the optical axis of the spectral confocal sensor is determined;

[0080] Further, step S100 includes step S110-step S191:

[0081] Step S110, according to the optical axis of the spectral confocal sensor, a target plane is preset;

[0082] Step S120, the intersection of the target plane when in the initial position and the axis of the optical axis of the spectral confocal sensor is determined as the first intersection point;

[0083] As shown in Figure 4 , the first intersection point is P point.

[0084] Step S130, establishing a probe coordinate system corresponding to the spectral confocal sensor with the first intersection point as the origin, so that the XOY plane of the probe coordinate system and the target plane are located in the same horizontal plane;

[0085] The XOY plane of the probe coordinate system is a plane composed of the X axis, the Y axis and the origin of the probe coordinate system.

[0086] Step S140, moving the target plane along the X axis of the probe coordinate system by a preset first distance, determining the intercept of the optical axis of the spectral confocal sensor on the target plane after moving as the first intercept, and restoring the position of the target plane;

[0087] The first distance is as shown in Figure 5 . The first distance is as shown in

[0088] Step S150, moving the target plane along the X axis of the probe coordinate system by a preset second distance, determining the intercept of the optical axis of the spectral confocal sensor on the target plane after moving as the second intercept, and restoring the position of the target plane;

[0089] Step S160, moving the target plane along the Y axis of the probe coordinate system by a preset third distance, determining the intercept of the optical axis of the spectral confocal sensor on the target plane after moving as the first vertical intercept, and restoring the position of the target plane;

[0090] Step S170, moving the target plane along the Y axis of the probe coordinate system by a preset fourth distance, determining the intercept of the optical axis of the spectral confocal sensor on the target plane after moving as the second vertical intercept, and restoring the position of the target plane;

[0091] Step S180, moving the target plane along the Z axis of the probe coordinate system by a preset fifth distance, determining the intercept of the optical axis of the spectral confocal sensor on the target plane after moving as the first vertical intercept, and restoring the position of the target plane;

[0092] Step S190, moving the target plane along the Z axis of the probe coordinate system by a preset sixth distance, determining the intercept of the optical axis of the spectral confocal sensor on the target plane after moving as the second vertical intercept, and restoring the position of the target plane;

[0093] Step S191, determining the direction vector of the optical axis of the spectral confocal sensor according to the first distance, the first intercept, the second distance, the second intercept, the third distance, the first vertical intercept, the fourth distance, the second vertical intercept, the fifth distance, the first vertical intercept, the sixth distance and the second vertical intercept.

[0094] The step S191 comprises steps S1911-S1917:

[0095] The step S1911 comprises determining a first horizontal distance ratio according to the first distance and the first horizontal intercept. ; wherein, is the first horizontal intercept, is the first distance.

[0096] The step S1912 comprises determining a second horizontal distance ratio according to the second distance and the second horizontal intercept. ; wherein, is the second horizontal intercept, is the second distance.

[0097] The step S1913 comprises determining a first vertical distance ratio according to the third distance and the first vertical intercept. ; wherein, is the first vertical intercept, is the third distance.

[0098] The step S1914 comprises determining a second vertical distance ratio according to the fourth distance and the second vertical intercept. ; wherein, is the second vertical intercept, is the fourth distance.

[0099] The step S1915 comprises determining a first longitudinal distance ratio according to the fifth distance and the first longitudinal intercept. ; wherein, is the first longitudinal intercept, is the fifth distance.

[0100] The step S1916 comprises determining a second longitudinal distance ratio according to the sixth distance and the second longitudinal intercept. ; wherein, is the second longitudinal intercept, is the sixth distance.

[0101] The step S1917 comprises determining a direction vector (l, m, n) of an optical axis of the spectral confocal sensor according to the following equation group:

[0102] .

[0103] The step S200 comprises determining an elevation angle offset of the spectral confocal sensor according to a projection angle of an axis of the spectral confocal sensor in a probe coordinate system corresponding to the spectral confocal sensor.

[0104] Further, the step S200 comprises steps S210-S240:

[0105] Step S210: Based on the direction vector (l,m,n) of the optical axis of the spectral confocal sensor, determine the angle between the projection of the optical axis of the spectral confocal sensor onto the XOZ plane of the probe coordinate system and the Z-axis of the probe coordinate system. ;

[0106] The XOZ plane of the probe coordinate system is the plane formed by the X-axis, Z-axis and origin of the probe coordinate system; tan() is the preset tangent function.

[0107] Step S220: Based on the direction vector (l,m,n) of the optical axis of the spectral confocal sensor, determine the angle between the projection of the optical axis of the spectral confocal sensor onto the YOZ plane of the probe coordinate system and the Z-axis of the probe coordinate system. ;

[0108] The YOZ plane of the probe coordinate system is the plane formed by the Y-axis, Z-axis and origin of the probe coordinate system.

[0109] Step S230: Determine the pitch angle offset of the X-axis of the probe coordinate system. ;

[0110] Here, cos() is the preset cosine function.

[0111] Step S240: Determine the pitch angle offset of the Y-axis of the probe coordinate system. .

[0112] Step S300: Determine the eccentricity offset of the spectral confocal sensor based on the confocal data of the optical axis of the spectral confocal sensor and the C-axis of the triaxial horizontal centering carriage when they are aligned.

[0113] Furthermore, step S300 includes steps S310-S340:

[0114] Step S310: At the initial alignment position between the optical axis of the spectral confocal sensor and the C-axis of the triaxial horizontal centering carriage, move the X-axis of the triaxial horizontal centering carriage by a preset first moving distance. The C-axis of the three-axis horizontal centering machine is rotated one revolution to obtain the corresponding first eccentricity value. ;

[0115] Step S320: At the initial alignment position between the optical axis of the spectral confocal sensor and the C-axis of the triaxial horizontal centering carriage, move the X-axis of the triaxial horizontal centering carriage by a preset second moving distance. The C-axis of the three-axis horizontal centering machine is rotated one revolution to obtain the corresponding second eccentricity value. ;

[0116] like Figure 6 In and i.e. the first and second movement distances.

[0117] Step S330, determine the eccentric offset of the X-axis of the probe coordinate system ;

[0118] Step S340, determine the eccentric offset of the Y-axis of the probe coordinate system .

[0119] Step S400, according to the pitch angle offset and the eccentric offset of the spectral confocal sensor, determine the geometric relationship between the probe coordinate system, the reference coordinate system corresponding to the machining tool of the three-axis horizontal centering machine, and the workpiece coordinate system corresponding to the measured workpiece;

[0120] Further, step S400 includes steps S410-S430:

[0121] Step S410, establish the reference coordinate system corresponding to the machining tool of the three-axis horizontal centering machine, with the intersection of the C-axis of the machining tool of the three-axis horizontal centering machine and the upper surface of the measured workpiece as the origin, with the movement direction of the X-axis of the machining tool of the three-axis horizontal centering machine as the positive direction of the horizontal coordinate axis, with the movement direction of the Z-axis of the machining tool of the three-axis horizontal centering machine as the positive direction of the vertical coordinate axis, and with the preset right-hand rule to determine the positive direction of the longitudinal coordinate axis;

[0122] Step S420, translate the reference coordinate system along the positive direction of the X-axis of the reference coordinate system , along the positive direction of the Y-axis of the reference coordinate system , along the positive direction of the Z-axis of the reference coordinate system , counterclockwise around the X-axis of the reference coordinate system , counterclockwise around the Y-axis of the reference coordinate system , to obtain the probe coordinate system;

[0123] wherein, is the vertical coordinate value of the origin of the probe coordinate system in the reference coordinate system;

[0124] Step S430, rotate the reference coordinate system clockwise around the Z-axis of the machining tool of the three-axis horizontal centering machine by a preset adjustment angle, and displace the reference coordinate system by an adjustment distance along the positive direction of the X-axis of the machining tool of the three-axis horizontal centering machine, to obtain the workpiece coordinate system corresponding to the measured workpiece;

[0125] wherein, the adjustment distance is the distance that the optical axis of the spectral confocal sensor moves along the positive direction of the X-axis of the machining tool of the three-axis horizontal centering machine after the centering calibration of the optical axis of the spectral confocal sensor and the C-axis of the three-axis horizontal centering machine.

[0126] Step S500, when the spectral confocal sensor scans and measures the measured curved surface of the measured workpiece, the measured point coordinates of the detection point of the spectral confocal sensor in the probe coordinate system are converted into target coordinates in the workpiece coordinate system according to the geometric relationship among the probe coordinate system, the reference coordinate system and the workpiece coordinate system.

[0127] In the in-situ measurement process, the spectral confocal sensor outputs the distance information between the zero reference point and the measured surface of the measured workpiece, and the machining tool system provides the real-time position information of each axis. Since the two types of data are located in different reference systems, the three-dimensional coordinates of the workpiece surface cannot be directly obtained. Therefore, in order to realize the conversion from one-dimensional distance value to complete spatial coordinates, coordinate transformation is required. As shown in Figure 7 and Figure 8 By uniformly modeling the spatial relationship among the probe coordinate system P, the reference coordinate system O and the workpiece coordinate system W, and establishing the corresponding transformation matrix, the distance data measured by the spectral confocal sensor and the displacement information of the machining tool can be fused, so as to accurately calculate the spatial position of each detection point on the workpiece surface.

[0128] Further, step S500 includes steps S510-S520:

[0129] Step S510, when the spectral confocal sensor scans and measures the measured curved surface of the measured workpiece, the measured point coordinates of the detection point of the spectral confocal sensor in the probe coordinate system are obtained as:

[0130] ;

[0131] Wherein, m is the data measured by the spectral confocal sensor at the detection point;

[0132] Step S520, the measured point coordinates of the detection point of the spectral confocal sensor in the probe coordinate system are converted to obtain the target coordinates of the detection point in the workpiece coordinate system as:

[0133] ;

[0134] Wherein, is the adjustment angle; sin() is a preset sine function; is the adjustment distance; z is the position coordinate value of the Z axis of the machining tool of the three-axis horizontal centering machine in the reference coordinate system.

[0135] The in-machine spatial pose calibration and compensation method of the spectral confocal sensor of the present application will be further described below in combination with the experimental results of calibrating the standard bevel constraint model and the standard sphere constraint model respectively. Table 1 is a calibration experimental result table of the two models, and Table 2 is a calibration residual table of the two models.

[0136] Table 1 Calibration results:

[0137]

[0138] Table 2 Calibration residual:

[0139]

[0140] Comprehensive analysis of the maximum residual and average residual indicators, in the two compared calibration models, the standard slope constraint model shows a more uniform and smaller amplitude residual distribution, indicating that it has a significant advantage in calibration accuracy. In comparison, the calibration accuracy of the standard sphere constraint model is slightly lower.

[0141] Overall, the sensor pose parameters obtained based on the standard slope constraint model calibration method for reconstructing the measured surface calculation, the maximum value of the measurement residual is 1.0042 μm, the average residual is 0.5190 μm, the overall measurement accuracy reaches microns, fully meets the application requirements of in-situ high-precision measurement.

[0142] In view of the requirements of complex curved surface in-machine high-precision and high-efficiency measurement, mainly aiming at the problems of relying on standard ball, multiple iterative fitting, sampling path sensitive, mechanical adjustment complex and the like in the process of traditional spectral confocal sensor space pose calibration, the application proposes a three-axis horizontal centering car spectral confocal sensor in-machine space pose calibration and compensation method based on inclined plane constraint. The method designs an inclined platform type Y fine adjustment mechanism based on linear motor drive on the basis of the original XZC three-axis, which can realize high-precision optical axis space positioning and attitude adjustment under the premise of keeping the overall structure of the machine tool compact. By establishing an eccentric-pitch combined model, the optical axis direction and sensor origin offset can be solved simultaneously by using a single inclined plane, avoiding complex iterative fitting process. At the same time, combined with the established homogeneous transformation coordinate model, the unification and automatic compensation of the probe coordinate system and the reference coordinate system are realized, and the self-consistent conversion of the probe coordinate system and the workpiece coordinate system is realized, which ensures that the ranging signal of the spectral confocal sensor can be accurately projected to the workpiece space, realizes non-contact high-precision point cloud reconstruction, thereby greatly simplifies the system structure and calibration process under the premise of ensuring the measurement accuracy, improves the implementability, stability and measurement consistency in the in-machine environment. After calibration, through the pose parameters under the workpiece coordinate system, the subsequent measurement data of any workpiece can be compensated and error corrected in real time, without the need to adjust the sensor attitude or mechanical structure, thereby significantly improving the measurement repeatability and system universality.

[0143] The above merely illustrates the specific embodiments of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of the changes or replacements within the technical range disclosed by the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for on-board spatial pose calibration and compensation of a spectral confocal sensor, characterized in that, It is applied to a three-axis horizontal centering lathe, wherein the C-axis of the three-axis horizontal centering lathe is a rotating axis, the workpiece to be measured is mounted on the C-axis of the three-axis horizontal centering lathe, and a slanted guide rail is mounted on the slanted slide of the Z-axis of the three-axis horizontal centering lathe, and a spectral confocal sensor is mounted on the platform of the slanted guide rail; The on-board spatial pose calibration and compensation method for the spectral confocal sensor includes: Step S100: Determine the direction vector of the optical axis of the spectral confocal sensor by moving and measuring the distance to the preset target plane corresponding to the spectral confocal sensor. Step S200: Determine the pitch angle offset of the spectral confocal sensor based on the angle between the projection of the axis of the spectral confocal sensor into the probe coordinate system corresponding to the spectral confocal sensor. Step S300: Determine the eccentricity offset of the spectral confocal sensor based on the confocal data of the optical axis of the spectral confocal sensor and the C-axis of the triaxial horizontal centering carriage when they are aligned. Step S400: Based on the pitch angle offset and eccentricity offset of the spectral confocal sensor, determine the geometric relationship between the probe coordinate system, the reference coordinate system corresponding to the machining tool of the three-axis horizontal centering lathe, and the workpiece coordinate system corresponding to the workpiece being measured. Step S500: When the spectral confocal sensor scans and measures the surface of the workpiece, the coordinates of the measuring point of the spectral confocal sensor in the probe coordinate system are transformed into the target coordinates in the workpiece coordinate system according to the geometric relationship between the probe coordinate system, the reference coordinate system and the workpiece coordinate system.

2. The method according to claim 1, characterized in that, Step S100 includes: Step S110: Based on the optical axis of the spectral confocal sensor, a target plane is preset; Step S120: Determine the first intersection point as the point where the target plane is in its initial position intersects with the optical axis of the spectral confocal sensor. Step S130: Establish the probe coordinate system corresponding to the spectral confocal sensor with the first intersection point as the origin, so that the XOY plane of the probe coordinate system and the target plane are located on the same horizontal plane; the XOY plane of the probe coordinate system is the plane composed of the X-axis, Y-axis and origin of the probe coordinate system; Step S140: Move the target plane along the X-axis of the probe coordinate system by a preset first distance, determine the first abscissa of the axis of the optical axis of the spectral confocal sensor on the moved target plane, and restore the position of the target plane. Step S150: Move the target plane along the X-axis of the probe coordinate system by a preset second distance, determine the second abscissa as the intercept of the optical axis of the spectral confocal sensor on the moved target plane, and restore the position of the target plane; Step S160: Move the target plane along the Y-axis of the probe coordinate system by a preset third distance, determine the first ordinate intercept of the optical axis of the spectral confocal sensor on the moved target plane, and restore the position of the target plane. Step S170: Move the target plane along the Y-axis of the probe coordinate system by a preset fourth distance, determine the intercept of the optical axis of the spectral confocal sensor on the moved target plane as the second ordinate intercept, and restore the position of the target plane. Step S180: Move the target plane along the Z-axis of the probe coordinate system by a preset fifth distance, determine the first vertical intercept of the optical axis of the spectral confocal sensor on the moved target plane, and restore the position of the target plane. Step S190: Move the target plane along the Z-axis of the probe coordinate system by a preset sixth distance, determine the intercept of the optical axis of the spectral confocal sensor on the moved target plane as the second vertical intercept, and restore the position of the target plane. Step S191: Determine the direction vector of the optical axis of the spectral confocal sensor based on the first distance, the first horizontal intercept, the second distance, the second horizontal intercept, the third distance, the first vertical intercept, the fourth distance, the second vertical intercept, the fifth distance, the first vertical intercept, the sixth distance, and the second vertical intercept.

3. The method according to claim 2, characterized in that, Step S191 includes: Step S1911: Determine the first lateral distance ratio based on the first distance and the first lateral intercept. ;in, The first x-intercept, This is the first distance; Step S1912: Determine the second lateral distance ratio based on the second distance and the second lateral intercept. ;in, The second x-intercept, This is the second distance; Step S1913: Determine the first longitudinal distance ratio based on the third distance and the first longitudinal intercept. ;in, The first y-intercept. The third distance; Step S1914: Determine the second longitudinal distance ratio based on the fourth distance and the second longitudinal intercept. ;in, The second y-intercept, This is the fourth distance; Step S1915: Determine the first vertical distance ratio based on the fifth distance and the first vertical intercept. ;in, The first vertical intercept, The fifth distance; Step S1916: Determine the second vertical distance ratio based on the sixth distance and the second vertical intercept. ;in, This is the second vertical intercept. The sixth distance; Step S1917: Determine the direction vector (l,m,n) of the optical axis of the spectral confocal sensor according to the following set of equations: 。 4. The method according to claim 3, characterized in that, Step S200 includes: Step S210: Based on the direction vector (l,m,n) of the optical axis of the spectral confocal sensor, determine the angle between the projection of the optical axis of the spectral confocal sensor onto the XOZ plane of the probe coordinate system and the Z-axis of the probe coordinate system. Wherein, the XOZ plane of the probe coordinate system is the plane formed by the X-axis, Z-axis and origin of the probe coordinate system; tan() is a preset tangent function; Step S220: Based on the direction vector (l,m,n) of the optical axis of the spectral confocal sensor, determine the angle between the projection of the optical axis of the spectral confocal sensor onto the YOZ plane of the probe coordinate system and the Z-axis of the probe coordinate system. Wherein, the YOZ plane of the probe coordinate system is the plane formed by the Y-axis, Z-axis and origin of the probe coordinate system; Step S230: Determine the pitch angle offset of the X-axis of the probe coordinate system. Where cos() is the preset cosine function; Step S240: Determine the pitch angle offset of the Y-axis of the probe coordinate system. .

5. The method according to claim 4, characterized in that, Step S300 includes: Step S310: At the initial alignment position between the optical axis of the spectral confocal sensor and the C-axis of the triaxial horizontal centering carriage, move the X-axis of the triaxial horizontal centering carriage by a preset first moving distance. The C-axis of the three-axis horizontal centering machine is rotated one revolution to obtain the corresponding first eccentricity value. ; Step S320: At the initial alignment position between the optical axis of the spectral confocal sensor and the C-axis of the triaxial horizontal centering carriage, move the X-axis of the triaxial horizontal centering carriage by a preset second moving distance. The C-axis of the three-axis horizontal centering machine is rotated one revolution to obtain the corresponding second eccentricity value. ; Step S330: Determine the eccentricity offset of the X-axis of the probe coordinate system. ; Step S340: Determine the eccentricity offset of the Y-axis of the probe coordinate system. .

6. The method according to claim 5, characterized in that, Step S400 includes: Step S410: Taking the intersection of the C-axis of the three-axis horizontal centering lathe and the upper surface of the workpiece to be measured as the origin, the X-axis of the three-axis horizontal centering lathe as the positive direction of the horizontal coordinate axis, and the Z-axis of the three-axis horizontal centering lathe as the positive direction of the vertical coordinate axis, the positive direction of the vertical coordinate axis is determined by the preset right-hand rule, and a reference coordinate system corresponding to the three-axis horizontal centering lathe is established. Step S420: Translate the reference coordinate system sequentially along the positive direction of the X-axis of the reference coordinate system. Translate along the positive direction of the Y-axis of the reference coordinate system. Translate along the positive direction of the Z-axis of the reference coordinate system. Rotate counterclockwise around the X-axis of the reference coordinate system Rotate counterclockwise around the Y-axis of the reference coordinate system To obtain the probe coordinate system; wherein, The vertical coordinate value of the origin of the probe coordinate system on the reference coordinate system; Step S430: Rotate the reference coordinate system clockwise around the Z-axis of the three-axis horizontal centering lathe by a preset adjustment angle, and then move it along the positive X-axis of the three-axis horizontal centering lathe by an adjustment distance to obtain the workpiece coordinate system corresponding to the workpiece being measured; wherein, the adjustment distance is the distance that the optical axis of the spectral confocal sensor and the C-axis of the three-axis horizontal centering lathe move in the positive X-axis direction of the three-axis horizontal centering lathe after centering calibration.

7. The method according to claim 6, characterized in that, Step S500 includes: Step S510: When the spectral confocal sensor scans and measures the surface of the workpiece, the coordinates of the detection point of the spectral confocal sensor in the probe coordinate system are obtained as follows: ； Where m is the data measured by the spectral confocal sensor at the detection point; Step S520: Transform the coordinates of the detection point of the spectral confocal sensor in the probe coordinate system to obtain the target coordinates of the detection point in the workpiece coordinate system. ； in, The adjustment angle is given; sin() is a preset sine function; The adjustment distance is z; z is the position coordinate value of the Z-axis of the three-axis horizontal centering lathe in the reference coordinate system.

8. The method according to claim 1, characterized in that, The X-axis and Z-axis of the three-axis horizontal centering car are arranged in a T-shape. The X-axis and Z-axis of the three-axis horizontal centering car are linear axes. The C-axis of the three-axis horizontal centering car is mounted on the slide of the X-axis.

9. The method according to claim 1, characterized in that, The workpiece being tested is a high-precision aspherical surface.

10. The method according to claim 1, characterized in that, The surface of the inclined guide rail is at a preset angle to the horizontal plane.

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