Cylindricity measurement method based on closed-loop turn-back path

Abstract

The invention relates to a cylindricity measurement method based on a closed loop turn-back path, and belongs to the field of cylindricity measurement. During measurement, the measured piece rotates relative to the sensor, meanwhile, the z-direction guide rail drives the sensor to do up-and-down reciprocating motion, and the rotation and the reciprocating motion are carried out synchronously. In the measuring process, the sensor can conduct data collection according to angles, heights and time, angle, height and radial data of sampling points can be synchronously obtained, then the full-cylinder surface profile with the data points evenly distributed is constructed, the measuring starting point and the measuring ending point are closed, and the drifting situation of the sensor can be conveniently observed. Compared with an existing circumference method, a generatrix method and a birdcage method, the method has the remarkable advantages that the measurement process is continuous and uninterrupted, and data points are evenly distributed, the cylindrical contour features of the rotary parts can be more comprehensively and accurately presented, and the cylindricity measurement accuracy and reliability are effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of precision geometric measurement, and in particular to a dynamic measurement method for cylindricity, in particular to a cylindricity measurement method based on a closed-loop return path. Background Art

[0002] In modern industrial manufacturing, cylindricity is a key indicator of the geometric accuracy of cylindrical parts. Its accurate measurement is crucial for ensuring the assembly precision, operational performance, and service life of mechanical products. Currently, high-precision cylindricity measurement mainly uses the circumference method, the generatrix method, the birdcage method, and the point distribution method. However, these methods all have significant limitations and are unable to meet the growing demand for industrial measurement.

[0003] 1. Circular method: This method evaluates cylindricity error by sampling different discrete cross-sections of the test piece and fitting a circular profile based on polar coordinate data. Its main drawbacks are: measurement is limited to discrete cross-sections, resulting in measurement gaps in the axial regions between cross-sections, making it impossible to fully capture the overall shape errors of the cylindrical surface, such as taper and curvature; data closure is only guaranteed for a single cross-section, and a spatial closed loop cannot be established for the entire cylindrical surface; and real-time monitoring of sensor runout and long-term drift during axial movement is impossible, directly affecting the comparability and overall accuracy of measurement results across different cross-sections.

[0004] 2. Busbar Method: This method indirectly assesses cylindricity by measuring the straightness of a limited number of busbars and their relative positions. Its main drawbacks are that the measurement results are highly dependent on the number and position of the selected busbars, making them insufficiently representative and unable to accurately reflect the true shape errors of the cylindrical cross section, such as ovality and roundness. Significant measurement gaps also exist between busbars. Similar to the circumference method, this method lacks the ability to monitor sensor status in real time.

[0005] 3. Birdcage Method: This method combines the circumference method with the busbar method, aiming to construct a "birdcage"-like measurement framework. Typically, the cross-section circumference is measured first, followed by the busbar measurement, and the data are finally fused. Its main drawback is that circumference and busbar measurements are typically performed independently and in separate timeframes. Sensor states may differ between measurements, making data fusion difficult and introducing additional errors. Furthermore, it fails to address the measurement gaps inherent in the circumference and busbar methods.

[0006] 4. Point distribution method: Commonly used in coordinate measuring machines (CMMs), this method controls the probe to perform contact measurement on a cylindrical surface according to a preset array of points by planning a path. Its main drawbacks are: low efficiency in point-by-point acquisition, which is particularly time-consuming for high-density sampling; discrete point measurement makes it difficult to describe complete and continuous contour information; the probe must repeatedly contact and release the measured surface, and changes in contact force and slight deviations in contact position can easily introduce random errors, affecting the accuracy and repeatability of the measurement results; measurement gaps also exist between points, and the contact measurement process cannot effectively monitor microscopic probe jitter or system drift; and it is still impossible to monitor sensor state changes during continuous measurement.

[0007] The common core defects of existing methods are:

[0008] Spatial sampling discontinuities and gaps: Whether it is discrete sections, discrete generatrixes or discrete points, there are areas on the cylindrical surface that are not directly measured, making it impossible to obtain truly continuous contour information;

[0009] Non-closed / open-loop measurement paths: Existing methods cannot form a spatially closed-loop measurement path that covers the entire cylindrical surface being measured. Local closed loops on a single section or generatrix cannot verify the consistency of the overall data and the global stability of the sensor.

[0010] Lack of sensor status monitoring: The sensor's own status cannot be monitored in real time during continuous measurement, making it difficult to detect and compensate for system errors in real time. This seriously restricts the long-term stability, reliability and absolute accuracy of the measurement, and the problem is particularly prominent in high-precision and long-term measurement scenarios.

[0011] With the continuous improvement of precision requirements for industrial products and the emergence of complex working conditions, existing methods can no longer meet the needs in terms of measurement efficiency, data integrity, and accuracy stability. It is urgent to develop new cylindricity measurement technologies to break through the above bottlenecks. Summary of the Invention

[0012] In order to address the shortcomings of the existing technology, the present invention discloses a cylindricity measurement method based on a closed-loop return path. The technical solution of this method is more reasonable and flexible, the measurement process is continuous, and the cylindrical surface profile information extraction is more comprehensive, providing reliable technical support for high-precision cylindricity assessment.

[0013] The object of the present invention is achieved like this:

[0014] A cylindricity measurement method based on a closed-loop return path comprises the following steps:

[0015] Step a: Setting measurement parameters, including the first return height h1, the second return height h2, the number of return points p and the starting measurement height h0;

[0016] Step b: Distribute p turning points at heights h1 and h2 respectively according to the number of turning points p;

[0017] Step c: Select a sampling strategy, including sampling by angle, sampling by height, or sampling by time;

[0018] Step d: Control the z-guide rail to drive the sensor or the measured object to move along the z-axis at a speed v(t). When the sensor moves to the first return height h1 or the second return height h2, the z-guide rail changes its movement direction and controls the rotary axis to drive the measured object or the sensor to rotate at an angular velocity ω(t).

[0019] Step e: When the z-direction rail motion velocity v(t) and the rotational angular velocity ω(t) of the measured object relative to the sensor reach preset values ​​and enter a stable state, the sensor moves to the starting measurement height h0 and starts measurement; the sensor cooperates with the angle encoder and z-direction grating ruler to collect cylindrical surface profile data according to the sampling strategy selected in step c;

[0020] Step f: After the measurement period T, the sensor returns to the starting measurement height h0, and the sampling points form a spatial closed measurement loop to complete the measurement. The measurement period T is the time required for a complete measurement.

[0021] Further:

[0022] Define the turning point, which is the point where the sensor changes its movement direction at the first turning height h1 or the second turning height h2;

[0023] Define the return period t1, the time interval between two consecutive passes through the return point at the same height, then

[0024] Define the rotation period t2, the measured object rotates relative to the sensor at an angular velocity ω(t),

[0025] The angle increment of the turning point is defined as Δ, and the angle interval corresponding to adjacent turning points at the same height is defined as the time t when the sensor passes the current turning point. b After a return cycle t1, the measured object rotates relative to the sensor by an angle of The sensor passes the next turning point, and the turning step length is (np+i), where n is a positive integer and i and p are relatively prime, to ensure that all p turning points at the same height are traversed within p turning cycles, forming the basis of a closed-loop path;

[0026] Furthermore, the first return height h1 and the second return height h2 are constant values ​​or piecewise functions.

[0027] Furthermore, the relationship between the return period and the rotation period is pt1 = mt2 = T, where m is a positive integer.

[0028] Further, the turn-around period t1 includes a constant period and a non-constant period.

[0029] Further, the z-direction guide rail drives the sensor or the measured object to move along the z-axis direction, and the movement speed v(t) includes uniform speed and variable speed.

[0030] Further, the measured object rotates relative to the sensor at an angular speed ω(t), and the angular speed ω(t) includes uniform speed and variable speed.

[0031] Further, within the time T required for one complete measurement, the sensor path traverses all 2p turn-around points.

[0032] Further, the sampling trigger depends on the sensor hardware:

[0033] Angle sampling: angle encoder trigger, fixed interval Δθ;

[0034] Height sampling: z-direction grating ruler trigger, fixed interval Δh;

[0035] Time sampling: internal clock trigger, fixed time Δt.

[0036] Further, the sampling strategy also supports mixed sampling mode, which realizes dynamic sampling by parallel monitoring of at least two trigger conditions:

[0037] When angle-height mixed sampling is enabled, the angle encoder signal (interval Δθ) and the z-direction grating ruler signal (interval Δh) are synchronously monitored, and any condition that meets the trigger sampling;

[0038] When angle-time mixed sampling is enabled, the angle encoder signal (interval Δθ) and the system clock signal (interval Δt) are synchronously monitored, and any condition that meets the trigger sampling;

[0039] When height-time mixed sampling is enabled, the z-direction grating ruler signal (interval Δh) and the system clock signal (interval Δt) are synchronously monitored, and any condition that meets the trigger sampling;

[0040] When full mixed sampling is enabled, the three trigger conditions Δθ, Δh, and Δt are synchronously monitored, and any condition that meets the trigger sampling.

[0041] Advantages:

[0042] (1) The continuous scanning measurement mode using closed-loop turn-around path planning eliminates the data discontinuity and sampling blind area of traditional cylindricality measurement, improves data integrity, and constructs a more comprehensive cylindrical surface profile.

[0043] (2) The turn-back measurement path has a closed-end characteristic, and the redundancy check of the start-end point data and the iterative compensation lay a foundation for further constructing a sensor error self-calibration closed-loop system, and effectively suppresses systematic errors such as temperature drift and time drift of the sensor in a long-time measurement process;

[0044] (3) Based on the dynamic speed regulation mechanism of the two motion control units of rotary motion and z-direction guide rail linear motion, the gradient distribution of the sampling density is realized, the data acquisition amount of the key area cross section / cylinder surface can be increased according to the accuracy requirement of the key area of the measured cylinder, and the resolution and measurement reliability of the local feature are enhanced;

[0045] (4) Breakthrough the limitation of traditional single index measurement, can synchronously output the cylindricality error data, cross section roundness error data and generatrix straightness data, provide multi-dimensional evaluation result, provide comprehensive quantitative basis for quality evaluation of mechanical parts;

[0046] (5) Flexible measurement parameter configuration mode, can customize measurement path, sampling density and error compensation strategy according to actual working condition, improve adaptability in complex shape workpiece measurement scene, effectively meet the diversified needs of modern manufacturing industry for high precision and high efficiency geometric measurement. BRIEF DESCRIPTION OF DRAWINGS

[0047] Figure 1 is a cylindricality measurement method based on a closed-loop turn-back path of the application;

[0048] Figure 2 is a cross section straightness diagram of the cylindricality measurement method based on a closed-loop turn-back path of the application;

[0049] Figure 3 is a cross section roundness diagram of the cylindricality measurement method based on a closed-loop turn-back path of the application;

[0050] Figure 4 is a cylindricality measurement method based on a closed-loop turn-back path of the application;

[0051] Figure 5 is a straightness diagram of the cylindricality measurement method based on a closed-loop turn-back path of the application;

[0052] Figure 6 is a cylindricality measurement method based on a closed-loop turn-back path of the application;

[0053] Figure 7 is a roundness diagram of the cylindricality measurement method based on a closed-loop turn-back path of the application;

[0054] Figure 8 is a cylindricality measurement method based on a closed-loop turn-back path of the application;

[0055] Figure 9 It is a schematic diagram of a cylindricity measurement method of the present invention including a closed-loop return path in a sampling window area. DETAILED DESCRIPTION

[0056] In order to enable people in this technical field to better understand the solution of this application, the technical solution in the specific implementation mode of this application will be clearly and completely described below in combination with the drawings in the specific implementation mode of this application. Obviously, the specific implementation mode described is only a part of this application, not all of it.

[0057] The present invention will be described in detail below with reference to the accompanying drawings: Specific implementation method 1

[0059] A cylindricity measurement method based on a closed-loop return path comprises the following steps:

[0060] Step a: Set the first folding height h1 = 0 mm, the second folding height h2 = 100 mm, the number of folding points p = 12, and the starting measurement height h0 = 50 mm;

[0061] Step b: Distribute p = 12 turning points at heights h1 and h2, respectively, with the turning points evenly distributed on the circumference;

[0062] Step c: Sampling by angle, sampling interval

[0063] Step d: The z-guide rail drives the sensor at a uniform speed. When the sensor moves up and down along the z direction and reaches the first return height h1 = 0mm or the second return height h2 = 100mm, the z-direction rail changes its direction of movement and the return cycle The angular velocity of the measured object relative to the sensor Perform rotational motion, with a rotation period of t2 = 10s; the angular interval between adjacent turning points at the same height is The reentry step length is 11;

[0064] Step e: When the z-axis guide rail drives the sensor to reach the speed and the rotational speed of the measured object relative to the sensor reaches After that, the sensor moves to the starting measurement height h0 = 50mm and starts measuring. The sensor cooperates with the angle encoder and the z-axis grating ruler to perform equal angle sampling.

[0065] Step f: After sampling T = 110 s, the sensor returns to the starting measurement height h0 = 50 mm, and the sampling points form a closed loop, completing the measurement.

[0066] Sensor path such as Figure 1As shown, the dotted line represents the first folding height h1 = 0 mm and the second folding height h2 = 100 mm, and the starting point is represented by “●”.

[0067] Reference Figure 2 In this embodiment, the angles are sampled at equal intervals. Except for the 11 angle straightness data at the turning point (the intersection of the turning line has 2 data), which are represented by "●", the remaining angle straightness data are 12, which are represented by "o". Specific implementation method 2

[0069] A cylindricity measurement method based on a closed-loop return path comprises the following steps:

[0070] Step a: Set the first folding height h1 = 0 mm, the second folding height h2 = 100 mm, the number of folding points p = 12, and the starting measurement height h0 = 50 mm;

[0071] Step b: Distribute p = 12 turning points at heights h1 and h2, respectively, with the turning points evenly distributed around the circumference.

[0072] Step c: Sampling by height, with a sampling interval of Δh = 1 mm;

[0073] Step d: The z-guide rail drives the sensor at a uniform speed When the sensor moves up and down along the z direction and reaches the first return height h1 = 0mm or the second return height h2 = 100mm, the z-direction rail changes its direction of movement and the return cycle The angular velocity of the measured object relative to the sensor Perform rotational motion, with a rotation period of t2 = 10s; the angular interval between adjacent turning points at the same height is The reentry step length is 11;

[0074] Step e: When the z-axis guide rail drives the sensor to reach the speed and the rotational speed of the measured object relative to the sensor reaches After that, the sensor moves to the starting measurement height h0 = 50mm and starts measuring. The sensor cooperates with the angle encoder and the z-axis grating ruler to sample according to the height;

[0075] Step f: After sampling T = 110 s, the sensor returns to the starting measurement height h0 = 50 mm, and the sampling points form a closed loop, completing the measurement.

[0076] Sensor path such as Figure 1 As shown, the dotted line represents the first folding height h1 = 0 mm and the second folding height h2 = 100 mm, and the starting point is represented by “●”.

[0077] Reference Figure 3In this embodiment, sampling is performed at equal intervals according to height. Except for collecting 12 circular data at the first return height h1=0mm and the second return height h2=100mm, which are represented by "o", 24 circular data are collected at the remaining heights, which are represented by "+".

[0078] Combining the specific implementation mode 1 and the specific implementation mode 2, the sensor simultaneously performs equal angle sampling (sampling interval ) and equal height sampling (sampling interval h = 1mm), the cylindrical error data, cross-section roundness error data and busbar straightness data can be output synchronously. Specific implementation method three

[0080] A cylindricity measurement method based on a closed-loop return path comprises the following steps:

[0081] Step a: Set the first return height h1 = 0 mm, the second return height h2 = 100 mm, the number of return points p = 12, and the starting measurement height h0 = 0 mm;

[0082] Step b: Distribute p = 12 turning points at heights h1 and h2, respectively, with the turning points evenly distributed around the circumference.

[0083] Step c: Sampling by angle, sampling interval

[0084] Step d: The z-guide rail drives the sensor at a uniform speed at the z-coordinates [0,40] mm and [60,100] mm. Move up and down along the z direction, at a uniform speed at the z coordinate [40,60] mm When the sensor moves up and down along the z direction and reaches the first return height h1 = 0mm or the second return height h2 = 100mm, the z-direction rail changes its direction of movement and the return cycle The angular velocity of the measured object relative to the sensor Perform rotational motion, with a rotation period of t2 = 10s; the angular interval between adjacent turning points at the first turning height and the second turning height is The reentry step length is 17;

[0085] Step e: When the z-guide rail drives the sensor to reach speed v and the rotation speed of the measured object relative to the sensor reaches After that, the sensor moves to the starting measurement height h0 = 0mm and starts measuring. The sensor cooperates with the angle encoder and the z-axis grating ruler to sample according to the preset angle;

[0086] Step f: After sampling T = 170s, the sensor returns to the starting measurement height h0 = 0mm, and the sampling points form a closed loop, completing the measurement.

[0087] Sensor path such asFigure 4 As shown, the dotted line represents the first return height h1=0mm, the second return height h2=100mm, the lower limit of the critical section h3=40mm and the upper limit of the critical section h4=60mm, the collection starting point is represented by "●", and the critical section path density is increased.

[0088] Reference Figure 5 In this embodiment, the angles are sampled at equal intervals. Except for the 15 angle straightness data at the turning point (the intersection of the turning line has 2 data), which are represented by "●", the remaining angle straightness data are 17, which are represented by "o". This can better observe the changes in straightness in key areas. Specific implementation method four

[0090] A cylindricity measurement method based on a closed-loop return path comprises the following steps:

[0091] Step a: Set the first return height h1 = 0 mm, the second return height h2 = 100 mm, the number of return points p = 23, and the starting measurement height h0 = 0 mm;

[0092] Step b: Distribute p = 23 turning points at heights h1 and h2, respectively, 12 of which are evenly distributed on the circumference and the remaining 11 are evenly distributed between two adjacent turning points.

[0093] Step c: Sampling by height, with a sampling interval of Δh = 1 mm;

[0094] Step d: The z-guide rail drives the sensor at an angle of At a uniform speed Move up and down along the z direction and at a uniform speed at other angles Uniform speed When the sensor moves up and down along the z direction and reaches the first return height h1 = 0mm or the second return height h2 = 100mm, the z-direction rail changes its direction of movement and the return cycle The angular velocity of the measured object relative to the sensor Perform rotational motion, with a rotation period of t2 = 10s; the angular interval between adjacent turning points at the first turning height and the second turning height is The equivalent reentry step length is 11;

[0095] Step e: When the z-guide rail drives the sensor to reach speed v and the rotation speed of the measured object relative to the sensor reaches After that, the sensor moves to the starting measurement height h0 = 0mm and starts measuring. The sensor cooperates with the angle encoder and the z-axis grating ruler to sample according to the height;

[0096] Step f: After sampling T = 110 s, the sensor returns to the starting measurement height h0 = 0 mm, and the sampling points form a closed loop, completing the measurement.

[0097] Sensor path such as Figure 6 As shown, the dotted line represents the first folding height h1=0 mm and the second folding height h2=100 mm, and the starting point is represented by “●”.

[0098] Reference Figure 7 In this embodiment, sampling is performed at equal intervals according to height. Except for collecting 23 circular data at the first return height h1=0mm and the second return height h2=100mm, which are represented by "o", 46 circular data are collected at the remaining heights, which are represented by "+", so as to better observe the roundness changes in key areas. Specific implementation method five

[0100] A cylindricity measurement method based on a closed-loop return path comprises the following steps:

[0101] Step a: Set the first folding height h1 = 0 mm and the second folding height h2 120 mm at the top and 100 mm at other angles, the number of turning points p = 23 and the starting measurement height h0 = 0 mm;

[0102] Step b: Distribute p = 23 turning points at heights h1 and h2, respectively, 12 of which are evenly distributed on the circumference and the remaining 11 are evenly distributed between two adjacent turning points.

[0103] Step c: Sampling by height, with a sampling interval of Δh = 1 mm;

[0104] Step d: The z-guide rail drives the sensor at an angle of At a uniform speed Move up and down along the z direction and at a uniform speed at other angles When the sensor moves up and down along the z direction and reaches the first return height h1=0mm or the second return height h2, the z guide rail changes its direction of movement and the return cycle The angular velocity of the measured object relative to the sensor Perform rotary motion, with a rotation period of t2 = 10s;

[0105] Step e: When the z-guide rail drives the sensor to reach speed v and the rotation speed of the measured object relative to the sensor reaches After that, the sensor moves to the starting measurement height h0 = 0mm and starts measuring. The sensor cooperates with the angle encoder and the z-axis grating ruler to sample according to the height;

[0106] Step f: After sampling T = 110 s, the sensor returns to the starting measurement height h0 = 0 mm, and the sampling points form a closed loop, completing the measurement.

[0107] Sensor path such as Figure 8 As shown, the dotted line represents the first folding height h1 = 0 mm and the second folding height h2 = 100 mm and 120 mm, and the starting point is represented by “●”.

[0108] In this embodiment, the angle is When the sampling height is extended to 120mm, the part exceeding 100mm can still obtain data to participate in the evaluation of cylindricity, providing more comprehensive data for the cylindricity measurement of special-shaped workpieces. Specific implementation method six

[0110] Set the DUT at an angle of There is a convex or concave area at a height of [50,60] mm, which is not within the measurement sampling range. Expand the range and define the sampling window as [0.85π,1.4π] and a height of [48,62] mm. Then:

[0111] A cylindricity measurement method based on a closed-loop return path comprises the following steps:

[0112] Step a: Set the first turning height h1 = 0m, the second turning height h2 = 100mm, the number of turning points p = 12, and the starting measurement height h0 = 0mm;

[0113] Step b: Distribute p = 12 turning points at heights h1 and h2, respectively, with the turning points evenly distributed around the circumference.

[0114] Step c: Sampling by height, with a sampling interval of Δh = 1 mm;

[0115] Step d: The z-guide rail drives the sensor at a uniform speed Move up and down along the z direction, within the range of the cylinder's axial height z∈[48,62]mm, excluding the rest of the cylindrical area with angle θ∈[0.85π,1.4π] as the effective sampling area. At other angles, move at a uniform speed. When the sensor moves up and down along the z direction and reaches the first return height h1=0mm or the second return height h2, the z guide rail changes its direction of movement and the return cycle The angular velocity of the measured object relative to the sensor Perform rotary motion, with a rotation period of t2 = 10s;

[0116] In this specific embodiment, if the sensor moves to the left boundary of the sampling window and the z guide rail moves upward, the measured object and the sensor stop relative motion, the z guide rail drives the sensor to z = 62 mm (i.e., the upper boundary of the sampling window), the z guide rail speed becomes v = 0, the measured object resumes motion relative to the sensor, and when the sensor moves to the current return path point, the z guide rail resumes motion; if the sensor moves to the left boundary of the sampling window and the z guide rail moves downward, the measured object and the sensor stop relative motion, the z guide rail drives the sensor to z = 48 mm (i.e., the lower boundary of the sampling window), the z guide rail speed becomes v = 0, the measured object resumes motion relative to the sensor, and when the sensor moves to the current return path point, the z guide rail resumes motion; if the sensor moves to the upper or lower boundary of the sampling window, the z guide rail speed becomes v = 0, when the sensor moves to an angle θ = 1.4π (i.e., the right boundary of the sampling window), the measured object stops relative motion relative to the sensor, and when the z guide rail drives the sensor to the current return path point, the measured object resumes motion relative to the sensor.

[0117] Step e: When the z-guide rail drives the sensor to reach speed v and the rotation speed of the measured object relative to the sensor reaches After that, the sensor moves to the starting measurement height h0 = 0mm and starts measuring. The sensor cooperates with the angle encoder and the z-axis grating ruler to sample according to the height;

[0118] Step f: After sampling T = 110 s, the sensor returns to the starting measurement height h0 = 0 mm, and the sampling points form a closed loop, completing the measurement.

[0119] Reference Figure 9 , where the dotted line represents the first return height h1=0mm, the second return height h2=100mm, and the sampling window, and the starting point is represented by “●”.

[0120] In this embodiment, except for the area where the sensor is located at an angle of [0.85π, 1.4π] and a height of [48, 62] mm, the sampling data points in other areas are not affected, thereby providing a data basis for the maximum cylindricity evaluation of the cylindrical surface of the special-shaped part.

[0121] It should be noted that in the motion control and sampling processes described in the embodiments of the present invention, when the rotary axis rotates at a constant speed, the sampling point distribution characteristics obtained by time sampling and angle sampling are equivalent; similarly, when the z-guide rail moves at a constant speed, the sampling point distribution characteristics obtained by time sampling and height sampling are also equivalent. For the specific case of uniform motion described above, based on the equivalence of the sampling point distribution, the specific implementation details of time sampling will not be elaborated in this specification.

[0122] In addition, for more general cases involving non-uniform motion, embodiments of the present application can employ, for example, a time-sampling approach in which sampling points are uniformly distributed based on a system clock. This approach does not change the sampling path itself, but only affects the density distribution of discrete points on the path. The effects of sampling point density distribution under non-uniform motion and optimization strategies for the same are within the purview of those skilled in the art, who can adjust them according to specific process requirements, and will not be discussed here.

Claims

1. A cylindricity measurement method based on a closed-loop return path, characterized in that: The following steps are involved: Step a: Setting measurement parameters, including the first return height h1, the second return height h2, the number of return points p and the starting measurement height h0; Step b: Distribute p turning points at heights h1 and h2 respectively according to the number of turning points p; Step c: Selecting a sampling strategy, wherein the sampling strategy includes sampling by angle, sampling by height, or sampling by time; Step d: Control the z-guide rail to drive the sensor or the measured object to move along the z-axis at a speed v(t). When the sensor moves to the first return height h1 or the second return height h2, the z-guide rail changes its movement direction and controls the rotary axis to drive the measured object or the sensor to rotate at an angular velocity ω(t). Step e: When the z-direction rail motion velocity v(t) and the rotational angular velocity ω(t) of the measured object relative to the sensor reach preset values ​​and enter a stable state, the sensor moves to the starting measurement height h0 and starts measurement; the sensor cooperates with the angle encoder and z-direction grating ruler to collect cylindrical surface profile data according to the sampling strategy selected in step c; Step f: After the measurement period T, the sensor returns to the starting measurement height h0, and the sampling points form a spatial closed measurement loop to complete the measurement. The measurement period T is the time required for a complete measurement.

2. The cylindricity measurement method according to claim 1, characterized in that: The point where the sensor changes its movement direction at the first return height h1 or the second return height h2 is the return point, and the time interval between two consecutive passes through the return point at the same height is defined as the return period t1. The measured object rotates relative to the sensor at an angular velocity ω(t), and the rotation period is t2. The angle increment of adjacent turning points at the same height is defined as Δ, and the time when the sensor passes the current turning point is t b After a return cycle t1, the measured object rotates relative to the sensor by an angle of The sensor passes through the next turning point, and the turning step length is (np+i), where n is a positive integer and i and p are relatively prime.

3. The cylindricity measurement method according to claim 1, characterized in that: The first return height h1 and the second return height h2 are fixed values ​​or piecewise functions.

4. The cylindricity measurement method according to claim 1, characterized in that: The relationship between the return period and the rotation period is pt1=mt2=T, where m is a positive integer.

5. The cylindricity measurement method according to claim 1, characterized in that: The return period t1 includes a fixed value period and a variable value period.

6. The cylindricity measurement method according to claim 1, characterized in that: The z-guide rail drives the sensor or the measured object to move along the z-axis direction, and the movement speed v(t) includes uniform speed movement and variable speed movement.

7. The cylindricity measurement method according to claim 1, characterized in that: The measured object rotates relative to the sensor at an angular velocity ω(t), and the angular velocity ω(t) includes uniform motion and variable speed motion.

8. The cylindricity measurement method according to claim 1, characterized in that: Within the time T required for one complete measurement, the sensor path traverses all 2p turning points.

9. The cylindricity measurement method according to any one of claims 1 to 8, characterized in that: The sampling trigger conditions of the sampling strategy include: when sampling by angle, triggering at a fixed angle interval Δθ; when sampling by height, triggering at a fixed height interval Δh; when sampling by time, triggering at a fixed time interval Δt.

10. The cylindricity measurement method according to claim 9, characterized in that: The sampling strategy supports mixed sampling mode, which implements dynamic sampling by monitoring at least two trigger conditions in parallel: (a) When angle-height mixed sampling is enabled, the angle encoder signal (interval Δθ) and the z-axis grating scale signal (interval Δh) are monitored synchronously. Sampling is triggered when either condition is met. (b) When angle-time mixed sampling is enabled, the angle encoder signal (interval Δθ) and the system clock signal (interval Δt) are monitored synchronously, and sampling is triggered when either condition is met; (c) When height-time mixed sampling is enabled, the z-axis grating scale signal (interval Δh) and the system clock signal (interval Δt) are monitored synchronously. Sampling is triggered when either condition is met. (d) When full mixed sampling is enabled, the three trigger conditions of Δθ, Δh, and Δt are monitored synchronously. Sampling is triggered when any of the conditions is met.

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