Fine module gear installation-free high-precision measurement method combining industrial camera and line structure light sensor

Abstract

The invention discloses a small module gear installation-free high-precision measurement method combining an industrial camera and a line structure light sensor. The measurement method comprises calibration of a measurement system and algorithm fitting. According to the measuring method, a calibration part is rotationally scanned through a line structure light sensor, the pose relation between the line structure light sensor and a rotating shaft is established, the pose relation between a measured gear and the line structure light sensor is established through an industrial camera, and six-degree-of-freedom parameters of the line structure light sensor are fitted through nonlinear least square. According to the invention, the installation-free high-precision measurement of the small-module gear can be realized, and the development of a small-module gear non-contact measurement technology is promoted.

Description

Technical Field

[0001] The invention relates to a high-precision measurement method for small-module gears that combines an industrial camera and a linear structured light sensor and belongs to the field of precision measurement technology. Background Art

[0002] Small modulus gears (usually refers to gears with a modulus less than 1mm) are an important part of the gear industry. With the advent of the intelligent era, gear transmission systems will inevitably develop in the direction of miniaturization and intelligence, and small modulus gears are in great demand. Due to the low stiffness, small intervals, and difficulty in adjustment and alignment of small modulus gears, it is difficult to position and clamp them during traditional measurement, making their measurement much more difficult than that of medium modulus gears.

[0003] Traditional gear measurement mostly uses contact measurement, mainly based on gear measurement centers, which have slow measurement speed and low measurement point density, and can only obtain partial point and line information on the tooth surface. When using a gear measurement center to measure small modulus gears, it is necessary to use a specific probe and high-precision positioning clamping, which has high requirements on measurement conditions and low measurement efficiency.

[0004] In recent years, in order to quickly obtain the complete three-dimensional tooth surface morphology, optical measurement technology has gradually developed in the field of gear measurement. The present invention studies a small-module gear installation-free high-precision measurement method that combines an industrial camera and a linear structured light sensor. This method belongs to non-contact gear measurement. While improving the measurement efficiency, it avoids the problem of difficult positioning and clamping of small-module gears, while taking into account the full information of the tooth surface, providing more complete and richer geometric surface information for gear quality evaluation. Summary of the invention

[0005] The invention discloses a method for realizing installation-free high-precision measurement of small-module gears by combining a line structured light sensor with an industrial camera, and provides a calibration and measurement method.

[0006] To achieve the above object, the method adopted by the present invention comprises the following steps:

[0007] S1. Calibration system coordinate system establishment

[0008] like Figure 1 As shown, a calibration measurement system is established, which includes: line structured light measurement line coordinate system δ l :O l -X l Y l , sensor coordinate system δ s :O s -X s Y s Z s , industrial camera coordinate system δ c :O c -Xc Y c , measuring turntable coordinate system δ t :O t -X t Y t Z t , calibration part coordinate system δ m :O m -X m Y m Z m ; Among them, the calibration coordinate system δ m The rotating motion around the rotary table axis is the moving coordinate system; the other coordinate systems are fixed coordinate systems. l Located in the plane where the sensor emits laser light, the coordinate origin is O l Centered at the nominal distance from the sensor, axis Y l From the coordinate origin O l Point to the origin O of the sensor coordinate system s , coordinate origin O m Located at the geometric center of the calibration piece, translate the two vertical sides of the calibration piece to the origin O m , as the axis X of the calibration coordinate system m , Y m . Coordinate origin O t Located at the center of the measuring turntable, before the measuring turntable makes a rotational motion, the translation axis X m , Y m To the coordinate origin O t Axis X as the coordinate system of the measuring turntable t , Y t .

[0009] The line structured light sensor is arranged around the calibration object, and the origin of the sensor coordinate system is O s Relative to the origin O of the turntable coordinate system t On the three coordinate axes X t Y t Z t The offsets in the directions are a, b, and c respectively; the three coordinate axes X of the sensor coordinate system s Y s Z s Relative to the three coordinate axes X of the turntable coordinate system t Y t X t The deflection angles are α, β, and γ respectively; therefore, a, b, c, α, β, and γ constitute the six degrees of freedom parameters of the position relationship between the sensor and the center of the turntable. Calibration of the spatial position of the line structured light sensor is to calibrate these six degrees of freedom parameters.

[0010] S2. Calibration data acquisition and coordinate transformation

[0011] According to the coordinate system and coordinate relationship established by S1, the calibration part is installed on the spindle of the measuring turntable so that it rotates at the given speed of the spindle.

[0012] (1) Establishing the survey line coordinate system δ l To the sensor coordinate system δ s The coordinate transformation relationship matrix M ls :

[0013]

[0014] Where h is the nominal distance of the line structured light sensor.

[0015] (2) Establish the sensor coordinate system δ s To the calibration coordinate system δ m The coordinate transformation relationship matrix M sm :

[0016]

[0017] (3) Obtain the turntable angle ω at time i through the circular grating i (ω0,ω1,ω2,…ω i ), the line structured light sensor obtains the surface point cloud data of the calibration part (The upper right subscript l indicates that the coordinate point set D is defined in the coordinate system δ, and the lower subscript b indicates that D is the point set of the calibration part). Establish the calibration part coordinate system δ m To the measuring turntable coordinate system δ t The coordinate transformation relationship matrix M mt :

[0018]

[0019] (4) Figure 2 As shown, the industrial camera is installed on the top of the turntable, with the coordinate origin O c It is the origin of the image output by the industrial camera (located in the upper left corner of the image). The image of the calibration part is obtained before the turntable rotates. Through image processing, the slopes of the two vertical sides of the calibration part are fitted, and finally the axis X is obtained. t With axis X c The included angle θ is obtained by processing the contour of the calibration part to obtain the coordinates of the geometric center of the calibration part and the center of the measuring turntable in the industrial camera coordinate system (x t ,y t ).

[0020] (5) The survey line coordinate system δ is obtained through the above relationship l To the measuring turntable coordinate system δ t The coordinate transformation matrix M lt :

[0021] M lt =M ls ×M sm ×M mt (4)

[0022] According to the pose transformation matrix (1)-(5), the calibration object in the turntable coordinate system δ t Point cloud data

[0023]

[0024] S3. Geometric feature extraction of calibration parts

[0025] According to the calibration point cloud information obtained by S2 According to the geometric characteristics of the data, the calibration part information is divided into cylindrical point cloud information Plane point cloud information and It contains six degrees of freedom parameters a, b, c, α, β, and γ of the spatial posture of the wired structured light sensor.

[0026] S4. Pose parameter fitting calculation

[0027] According to the cylindrical and plane feature information of the calibration part extracted by S3, formula (6) and formula (7) can be obtained:

[0028]

[0029]

[0030] Among them, r ref is the theoretical value of the cylindrical radius of the calibration piece; [A, B, C, D] T is the coefficient of the calibration plane equation

[0031]

[0032] The nonlinear least square method is used to optimize the formula (8), and finally the six degrees of freedom parameters a, b, c, α, β, and γ of the spatial posture of the line structured light sensor are obtained. At this point, the calibration of the line structured light sensor relative to the turntable coordinate system is completed.

[0033] S5. Measure the gear under test

[0034] like Figure 3 As shown, the gear coordinate system δ is established based on S1 g :O g -X g Y g Z g , coordinate origin Og is the geometric center point of the gear, axis X g , Y g Parallel to axis X t , Y t The gear is placed on the measuring turntable, and the gear follows the speed given by the spindle around the measuring state origin O t Perform eccentric rotation and use the circular grating to trigger the sensor to sample data and obtain the gear tooth profile point cloud data

[0035] (2) Figures 4 to 7 As shown, in the industrial camera coordinate system δ c Next, click G(x g ,y g ) is the origin of the gear coordinate system, point T(x t ,y t ) is the origin of the turntable coordinate system, point G and axis X c , Y c The feet of the perpendicular are E and P respectively; point T and axis X c , Y c The feet of the perpendiculars are F and Q, the intersection of PG and TF is A, and the point T is perpendicular to the axis Y. g The foot of the perpendicular is B, TA and GB are on the Y axis g The intersection point is N. According to the geometric relationship, we can get BT and GB:

[0036] GA=y t -y g (9)

[0037] TA=x g -x t (10)

[0038] AN=tanθ·GA (11)

[0039] TN=TA+AN (12)

[0040]

[0041] BN=sinθ·TN (14)

[0042] GB=GN-BN (15)

[0043] BT=-cosθ·TN (16)

[0044] According to the six degrees of freedom parameters a, b, c, α, β, and γ obtained by S4 calibration, the point cloud data of the gear tooth profile in the turntable coordinate system can be calculated.

[0045]

[0046] According to the S2 geometric calculation results, BT and GB can be obtained, and the turntable coordinate system δ t To the gear coordinate system δ g The coordinate transformation matrix M tg :

[0047]

[0048] Point cloud data Substitute the transformation matrix M tg In the gear coordinate system δ g Point cloud data of the gear tooth profile under test

[0049] BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 This is the overall schematic diagram of the calibration system coordinate system.

[0051] Figure 2 This is a schematic diagram of the calibration system coordinate system.

[0052] Figure 3 It is a plane diagram of the measurement system coordinate system.

[0053] Figure 4 A geometric diagram for establishing the transformation relationship from the gear coordinate system to the turntable coordinate system.

[0054] Figure 5 A geometric diagram for establishing the transformation relationship from the gear coordinate system to the turntable coordinate system.

[0055] Figure 6 A geometric diagram for establishing the transformation relationship from the gear coordinate system to the turntable coordinate system.

[0056] Figure 7 A geometric diagram for establishing the transformation relationship from the gear coordinate system to the turntable coordinate system. DETAILED DESCRIPTION

[0057] The present invention is further described below with reference to the accompanying drawings and measurement examples.

[0058] S1. Calibration system coordinate system establishment

[0059] like Figure 1 As shown, a calibration measurement system is established, which includes: line structured light measurement line coordinate system δ l :O l -X l Y l , sensor coordinate system δ s :O s -X s Ys Z s , industrial camera coordinate system δ c :O c -X c Y c , measuring turntable coordinate system δ t :O t -X t Y t Z t , calibration part coordinate system δ m :O m -X m Y m Z m ; Among them, the calibration coordinate system δ m The rotating motion around the rotary table axis is the moving coordinate system; the other coordinate systems are fixed coordinate systems. l Located in the plane where the sensor emits laser light, the coordinate origin is O l Centered at the nominal distance from the sensor, axis Y l From the coordinate origin O l Point to the origin O of the sensor coordinate system s , coordinate origin O m Located at the geometric center of the calibration piece, translate the two vertical sides of the calibration piece to the origin O m , as the axis X of the calibration coordinate system m , Y m . Coordinate origin O t Located at the center of the measuring turntable, before the measuring turntable makes a rotational motion, the translation axis X m , Y m To the coordinate origin O t Axis X as the coordinate system of the measuring turntable t , Y t .

[0060] The line structured light sensor is arranged around the calibration object, and the origin of the sensor coordinate system is O s Relative to the origin O of the turntable coordinate system t On the three coordinate axes X t Y t Z t The offsets in the directions are a, b, and c respectively; the three coordinate axes X of the sensor coordinate system s Y s Z s Relative to the three coordinate axes X of the turntable coordinate system t Y t X tThe deflection angles are α, β, and γ respectively; therefore, a, b, c, α, β, and γ constitute the six degrees of freedom parameters of the position relationship between the sensor and the center of the turntable. Calibration of the spatial position of the line structured light sensor is to calibrate these six degrees of freedom parameters.

[0061] S2. Calibration data acquisition and coordinate transformation

[0062] According to the coordinate system and coordinate relationship established by S1, the calibration part is installed on the spindle of the measuring turntable so that it rotates at the given speed of the spindle.

[0063] (1) Establishing the survey line coordinate system δ l To the sensor coordinate system δ s The coordinate transformation relationship matrix M ls :

[0064]

[0065] Where h is the nominal distance of the line structured light sensor.

[0066] (2) Establish the sensor coordinate system δ s To the calibration coordinate system δ m The coordinate transformation relationship matrix M sm :

[0067]

[0068] (3) Obtain the turntable angle ω at time i through the circular grating i (ω0,ω1,ω2,…ω i ), the line structured light sensor obtains the surface point cloud data of the calibration part (The upper right subscript l indicates that the coordinate point set D is defined in the coordinate system δ, and the lower subscript b indicates that D is the point set of the calibration part). Establish the calibration part coordinate system δ m To the measuring turntable coordinate system δ t The coordinate transformation relationship matrix M mt :

[0069]

[0070] (4) Figure 2 As shown, the industrial camera is installed on the top of the turntable, with the coordinate origin O c It is the origin of the image output by the industrial camera (located in the upper left corner of the image). The image of the calibration part is obtained before the turntable rotates. Through image processing, the slopes of the two vertical sides of the calibration part are fitted, and finally the axis X is obtained. t With axis X c The included angle θ is obtained by processing the contour of the calibration part to obtain the coordinates of the geometric center of the calibration part and the center of the measuring turntable in the industrial camera coordinate system (x t ,yt ).

[0071] (5) The survey line coordinate system δ is obtained through the above relationship l To the measuring turntable coordinate system δ t The coordinate transformation matrix M lt :

[0072] M lt =M ls ×M sm ×M mt (4)

[0073] According to the pose transformation matrix (1)-(5), the calibration object in the turntable coordinate system δ t Point cloud data

[0074]

[0075] S3. Geometric feature extraction of calibration parts

[0076] According to the calibration point cloud information obtained by S2 According to the geometric characteristics of the data, the calibration part information is divided into cylindrical point cloud information Plane point cloud information and It contains six degrees of freedom parameters a, b, c, α, β, and γ of the spatial posture of the wired structured light sensor.

[0077] S4. Pose parameter fitting calculation

[0078] According to the cylindrical and plane feature information of the calibration part extracted by S3, formula (6) and formula (7) can be obtained:

[0079]

[0080]

[0081] Among them, rr e f is the theoretical value of the cylindrical radius of the calibration piece; [A, B, C, D] T is the coefficient of the calibration plane equation

[0082]

[0083] The nonlinear least square method is used to optimize the formula (8), and finally the six degrees of freedom parameters a, b, c, α, β, and γ of the spatial posture of the line structured light sensor are obtained. At this point, the calibration of the line structured light sensor relative to the turntable coordinate system is completed.

[0084] S5. Measure the gear under test

[0085] like Figure 3 As shown, the gear coordinate system δ is established based on S1 g :O g -X g Y g Z g , coordinate origin O g is the geometric center point of the gear, axis X g , Y g Parallel to axis X t , Y t The gear is placed on the measuring turntable, and the gear follows the speed given by the spindle around the measuring state origin O t Perform eccentric rotation and use the circular grating to trigger the sensor to sample data and obtain the gear tooth profile point cloud data

[0086] (2) Figures 4 to 7 As shown, in the industrial camera coordinate system δ c Next, click G(x g ,y g ) is the origin of the gear coordinate system, point T(x t ,y t ) is the origin of the turntable coordinate system, point G and axis X c , Y c The feet of the perpendicular are E and P respectively; point T and axis X c , Y c The feet of the perpendiculars are F and Q, the intersection of PG and TF is A, and the point T is perpendicular to the axis Y. g The foot of the perpendicular is B, TA and GB are on the Y axis g The intersection point is N. According to the geometric relationship, we can get BT and GB:

[0087] GA=y t -y g (9)

[0088] TA=x g -x t (10)

[0089] AN=tanθ·GA (11)

[0090] TN=TA+AN (12)

[0091]

[0092] BN=sin θ·TN (14)

[0093] GB=GN-BN (15)

[0094] BT=-cosθ·TN (16)

[0095] According to the six degrees of freedom parameters a, b, c, α, β, and γ obtained by S4 calibration, the point cloud data of the gear tooth profile in the turntable coordinate system can be calculated.

[0096]

[0097] According to the S2 geometric calculation results, BT and GB can be obtained, and the turntable coordinate system δ t To the gear coordinate system δ g The coordinate transformation matrix M tg :

[0098]

[0099] Point cloud data Substitute the transformation matrix M tg In the gear coordinate system δ g Point cloud data of the gear tooth profile under test

[0100]

[0101] Compared with the traditional small module gear measurement method, this method has the following advantages:

[0102] 1. This measurement method has a simple mechanical structure and requires low measurement conditions.

[0103] 2. This method is used to calibrate the measurement system with higher accuracy.

[0104] 3. Compared with contact measurement, this method has a faster measurement speed. For mass production of small-module gears, this method can meet the full inspection of gears.

[0105] 4. The measurement method avoids the problem of difficult positioning and clamping of small-module gears.

[0106] 5. Applying this method to measure gears can obtain complete tooth profile point cloud data of the measured gear, which provides more comprehensive information and greater room for subsequent data processing.

Claims

1. A high-precision measurement method for small modulus gears without installation by combining an industrial camera and a linear structured light sensor, characterized in that: The specific steps are as follows: Establishment of the coordinate system of the calibration system; Calibration data acquisition and coordinate transformation; Extraction of geometric features of calibration parts; Pose parameter fitting calculation; The spatial position relationship of the line structured light sensor is confirmed and the calibration is completed; Measure the gear under test; S1. Establishment of calibration system coordinate system; Establish a calibration measurement system, including: Line structured light measurement line coordinate system δ l :O l -X l Y l , sensor coordinate system δ s :O s -X s Y s Z s , industrial camera coordinate system δ c :O c -X c Y c , measuring turntable coordinate system δ t :O t -X t Y t Z t , calibration part coordinate system δ m :O m -X m Y m Z m ; Among them, the calibration coordinate system δ m The rotating motion around the rotary axis of the turntable is the moving coordinate system; the other coordinate systems are fixed coordinate systems; the measuring line coordinate system δ l Located in the plane where the sensor emits laser light, the coordinate origin is O l Centered at the nominal distance from the sensor, axis Y l From the coordinate origin O l Point to the origin O of the sensor coordinate system s , coordinate origin O m Located at the geometric center of the calibration piece, translate the two vertical sides of the calibration piece to the origin O m , as the axis X of the calibration coordinate system m , Y m ; Coordinate origin O t Located at the center of the measuring turntable, before the measuring turntable makes a rotational motion, the translation axis X m , Y m To the coordinate origin O t Axis X as the coordinate system of the measuring turntable t , Y t ; The line structured light sensor is arranged around the calibration object, and the origin of the sensor coordinate system is O s Relative to the origin O of the turntable coordinate system t On the three coordinate axes X t Y t Z t The offsets in the direction are a, b, and c respectively; the three coordinate axes X of the sensor coordinate system s Y s Z s Relative to the three coordinate axes X of the turntable coordinate system t Y t Z t The deflection angles are α, β, and γ respectively; therefore, a, b, c, α, β, and γ constitute the six degrees of freedom parameters of the position relationship between the sensor and the center of the turntable. Calibration of the spatial position of the line structured light sensor is to calibrate these six degrees of freedom parameters; S2. Calibration data acquisition and coordinate transformation; According to the coordinate system and coordinate relationship established by S1, the calibration part is installed on the spindle of the measuring turntable so that it rotates at the given speed of the spindle; (1) Establishing the survey line coordinate system δ l To the sensor coordinate system δ s The coordinate transformation relationship matrix M ls : Where h is the nominal distance of the line structured light sensor; (2) Establish the sensor coordinate system δ s To the calibration coordinate system δ m The coordinate transformation relationship matrix M sm : (3) Obtain the turntable angle ω at time i through the circular grating i (ω0,ω1,ω2,···ω i ), the line structured light sensor obtains the surface point cloud data of the calibration part The upper right corner subscript l indicates that the coordinate point set D is in the coordinate system δ l The following definition, subscript b indicates that D is the point set of the calibration part; establish the calibration part coordinate system δ m To the measuring turntable coordinate system δ t The coordinate transformation relationship matrix M mt : (4) Install the industrial camera on the top of the turntable, with the coordinate origin O c It is the origin of the image output by the industrial camera. The image of the calibration part is obtained before the turntable rotates. Through image processing, the slopes of the two vertical sides of the calibration part are fitted, and finally the axis X is obtained. t With axis X c The included angle θ is obtained by processing the contour of the calibration part to obtain the coordinates of the geometric center of the calibration part and the center of the measuring turntable in the industrial camera coordinate system (x t ,y t ); (5) The survey line coordinate system δ is obtained through the above relationship l To the measuring turntable coordinate system δ t The coordinate transformation matrix M lt : According to the pose transformation matrix (1)-(5), the calibration object in the turntable coordinate system δ t Point cloud data S3. Extraction of geometric features of calibration parts; According to the calibration point cloud information obtained by S2 According to the geometric characteristics of the data, the calibration part information is divided into cylindrical point cloud information Plane point cloud information and The six degree-of-freedom parameters a, b, c, α, β, and γ of the spatial position of the wired structured light sensor are included; S4. Pose parameter fitting calculation; According to the cylindrical and plane feature information of the calibration part extracted by S3, formula (6) and formula (7) are obtained: Among them, r ref is the theoretical value of the cylindrical radius of the calibration piece; [A, B, C, D] T is the coefficient of the calibration plane equation The nonlinear least square method is used to optimize the formula (8), and finally the six degrees of freedom parameters a, b, c, α, β, and γ of the spatial position of the line structured light sensor are obtained. Thus, the calibration of the line structured light sensor relative to the turntable coordinate system is completed. S5. Measure the gear under test; Establish the gear coordinate system δ based on S1 g :O g -X g Y g Z g , coordinate origin O g is the geometric center point of the gear, axis X g , Y g Parallel to axis X t , Y t ; Place the gear on the measuring turntable, and the gear will follow the speed given by the spindle around the measuring state origin O t Perform eccentric rotation and use the circular grating to trigger the sensor to sample data and obtain the gear tooth profile point cloud data (2) In the industrial camera coordinate system δ c Next, click G(x g ,y g ) is the origin of the gear coordinate system, point T(x t ,y t ) is the origin of the turntable coordinate system, point G and axis X c , Y c The feet of the perpendicular are E and P respectively; point T and axis X c , Y c The feet of the perpendiculars are F and Q, the intersection of PG and TF is A, and the point T is perpendicular to the axis Y. g The foot of the perpendicular is B, TA and GB are on the Y axis g The intersection point is N, and BT and GB are obtained according to the geometric relationship: GA=y t -and g (9) TA=x g -x t (10) AN=tanθ·GA (11) TN=TA+AN (12) BN=sinθ·TN (14) GB=GN-BN (15) BT=-cosθ·TN (16) According to the six degrees of freedom parameters a, b, c, α, β, and γ obtained by S4 calibration, the point cloud data of the gear tooth profile in the turntable coordinate system can be calculated. According to the S2 geometric calculation results, BT and GB are obtained, and the turntable coordinate system δ t To the gear coordinate system δ g The coordinate transformation matrix M tg : Point cloud data Substitute the transformation matrix M tg In the gear coordinate system δ g Point cloud data of the gear profile under test 2. The method for high-precision measurement of small modulus gears without installation by combining an industrial camera and a linear structured light sensor according to claim 1, characterized in that: Applicable to the rapid measurement of small module gears without high-precision positioning and clamping.

3. The method for high-precision measurement of small modulus gears without installation by combining an industrial camera and a linear structured light sensor according to claim 1, characterized in that: Applied to non-contact 3D high-precision measurement of small module gears.

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