CN112809037B - Method for drilling on curved surface structure - Google Patents
Method for drilling on curved surface structure Download PDFInfo
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Abstract
The invention relates to a method for drilling a curved surface structure, which is characterized in that drilling equipment is utilized to drill a hole on the curved surface structure of an object to be drilled, the drilling equipment comprises a moving platform with multiple degrees of freedom and a drilling assembly connected with the moving platform, and the drilling assembly comprises a base unit arranged on the moving platform; the visual detection unit is aligned to a drilling area of an object to be drilled, and a normal direction of a position to be drilled in the drilling area is calculated; adjusting the position of the drilling unit, and enabling the axis of a drilling main shaft arranged on the drilling unit to coincide with the normal direction; and step three, driving the drilling main shaft to rotate at a high speed and move forwards, and obtaining the target hole after drilling is completed. The invention can improve the direction accuracy of the drilling of the curved surface structure by adopting the visual detection technology to obtain the normal direction of the drilling position and coinciding the normal direction with the axis of the drilling unit.
Description
Technical Field
The invention relates to the field of machining equipment, in particular to a method for drilling a curved surface structure.
Background
When drilling holes in curved surface structures, the included angle between the axis of the hole and the curved surface needs to be strictly controlled. Therefore, the normal direction of the curved surface structure at the drilling position must be accurately measured first, and on the basis of the normal direction, the position and the direction of the drilling tool are accurately adjusted, so that the direction of the hole can be well controlled. It follows that accurate measurement of the normal direction at the drilling location of a curved surface structure is a prerequisite. At present, it is common to measure the normal direction of a curved surface structure by using an indirect measurement method, where a plurality of distance measuring sensors (e.g., laser distance measuring sensors, etc.) or displacement sensors (e.g., length gauges, etc.) are arranged on a device, several points (at least 3) around a drilled hole area on the curved surface structure are measured by using the plurality of sensors, and coordinates of the several points are calculated based on the measured length values. For the geometric characteristics of the curved surface structure, assuming the form of a curved surface equation of the drilling area (for example, a spherical surface, a cylindrical surface, a saddle surface, a plane surface and the like can be assumed), deriving the curved surface equation of the drilling area by using the known coordinate values of several measuring points, and obtaining the normal direction of the drilling position by using the curved surface equation.
The method needs a user to make the assumption of the shape of the hole making region according to the geometric characteristics of the hole making region of the curved surface structure by experience, namely, the assumption that a plurality of measuring points all conform to a curved surface equation of a certain form, so as to deduce the equation and then solve the normal direction of a certain point in the curved surface equation. The equation form of the assumed curved surface is the key for solving, and because the curved surface structure is often not an ideal curved surface (many are irregular curved surfaces, even if the curved surface structure is designed into an ideal curved surface, the curved surface structure becomes a non-ideal curved surface due to factors such as processing errors and assembly errors), the assumed curved surface has errors, and in some cases, the errors are still large, thereby influencing the solving precision of the normal direction.
To reduce the errors caused by the assumptions, a more complex form of surface equations can be constructed, meaning that more parameters need to be solved and more measurement points are needed. There are two ways to add measurement points: more sensors are added for one-time measurement; and measuring for multiple times without adding a sensor. More sensors are added, so that the layout of the sensors needs to be planned, the installation space of the sensors is increased, the structure of the drilling device is enlarged, and the application range of the drilling device is influenced. In addition, the addition of sensors increases the cost of the measuring equipment, and the calibration and the precision maintenance of each sensor are also problems which cannot be ignored. If the sensor is not added, the measurement is realized for multiple times through multiple movements of the drilling device, the movement error of the drilling device can be counted into the measurement result, and the movement error is far larger than the measurement error of the sensor, so the movement error is required to be eliminated.
According to the analysis, the indirect measurement method adopting multiple sensors often has theoretical errors, the measurement precision is limited by a plurality of factors, and the measurement process is complicated. The direct measurement method represented by the binocular vision technology does not have the problems, the binocular vision detection system is adopted to replace a plurality of displacement sensors or distance sensors, the normal direction of the drilling position of the curved surface structure can be directly measured, the measurement precision of the position and the posture is improved theoretically, and on-machine detection of the drilling quality can be realized. The binocular vision detection system is used for guiding and positioning, and the relative position posture relation between the binocular vision detection system and the drilling unit must be accurately mastered.
The existing normal measuring system for the drilling position of the curved surface structure adopts an indirect measuring technology, and a curved surface equation is derived by detecting the coordinates of a plurality of points around the drilling area. There are four problems:
(1) not adapted to the region near the edge of the part
The existing detection technology needs to detect the coordinates of several points around the drilling area, and the several points must be located near the drilling position and belong to the same part, so that the curved surface equation of the drilling area of the part can be effectively established. Near the edge of the part, the measurement points of some sensors are likely to exceed the edge of the part, and the actual measurement points do not belong to the part, but it is impossible to judge whether the measurement points belong to the same part, thereby generating a large deviation.
(2) The theoretical error may be brought by assuming the equation form of the curved surface
The surface of some parts (for example, some parts meeting the requirement of the aerodynamic appearance of the airplane) belongs to a free-form surface and cannot be expressed by an equation, even if a curved surface equation with a more complex structure is constructed, the equation can only be expressed approximately, and the simplified approximate expression brings theoretical errors.
(3) The complicated surface equation is constructed, and more problems are introduced
In order to reduce the errors caused by the assumptions, a complex surface equation form needs to be constructed, which means that more parameters need to be solved, and more measurement points are needed. There are two methods of adding measurement points:
1) more sensors are added to measure multiple points at one time
More sensors are additionally arranged, more mounting spaces of the sensors need to be reserved on the drilling device, and the layout of the sensors is reasonably planned. On one hand, the number of the sensors is increased, the cost is improved, and the workload of calibration and precision maintenance of each sensor is increased; on the other hand, more sensors are installed, the structural size of the drilling device is increased, the drilling device cannot be used for machining parts with limited openness, and the application range of the drilling device is influenced.
2) Without adding sensor, measuring a few points for many times, and accumulating to obtain measured data of multiple points
The structure of the drilling device is not changed, the sensor is not added, multiple times of measurement is realized through multiple times of movement of the drilling device, the movement error of the drilling device can be measured, and under the common condition, the movement error of the drilling device is far larger than the measurement error of the sensor, so that the movement error must be eliminated. The difficulty of effectively identifying and eliminating motion errors is high, and the problem is not effectively solved so far.
(4) Can only be used for estimating the normal direction of the point position of the drilling hole, can not detect the diameter, the position and the direction of the hole, does not have the on-machine detection function, and the function of a detection instrument is not fully utilized
By adopting the existing multipoint detection method, the curved surface normal direction at the drilling position is estimated by detecting a plurality of points around the drilling area, and the positions of the points around the drilling area are obtained, so that the method can not be mastered no matter what operation is carried out in the area. Even if the position of the surrounding measuring points is changed due to operations such as drilling, the direction of the hole still cannot be accurately known, and the diameter and the position of the hole cannot be mastered. Therefore, the conventional method does not have an on-machine detection function of the hole position and direction. Generally, after batch drilling, measurement equipment or measurement tools are uniformly adopted to measure the positions and the directions of holes, so that quality problems in the drilling process cannot be found in time, machining process parameters cannot be adjusted in time according to the quality change trend, and once the position or the direction of one hole is out of tolerance in the subsequent drilling process, the whole part becomes waste, so that the previous work is abandoned, and great waste is caused. For small parts which can be disassembled and are convenient to measure, the position and the direction of the hole can be measured by adopting detection equipment such as a three-coordinate measuring machine, but the measurement link is added, so that the working process is interrupted, the links of disassembling, re-assembling and positioning are added, the processing period is prolonged, and the processing efficiency is reduced; for parts which are not allowed to be disassembled or large parts, detection equipment such as a three-coordinate measuring machine cannot be applied, manual measurement is carried out by adopting a measuring instrument, the measuring result is influenced by factors such as worker experience, working state and the like, misjudgment is easily caused, the potential hazards caused by out-of-tolerance are released, qualified products are abandoned, and waste is generated.
Accordingly, the inventors provide a drilling method applied to a curved structure.
Disclosure of Invention
(1) Technical problem to be solved
The embodiment of the invention provides a method for drilling a hole in a curved surface structure, wherein the normal direction of the position to be drilled is obtained by adopting a visual detection technology and is superposed with the axis of a drilling main shaft of a drilling unit, so that the directional precision of the drilling of the curved surface structure can be improved, and the efficiency and the quality of the drilling can be improved by utilizing the synchronous rotary motion and linear motion of the drilling main shaft.
(2) Technical scheme
In a first aspect, an embodiment of the present invention provides a method for drilling a hole in a curved structure, where a hole is drilled in the curved structure of an object to be drilled by using a drilling apparatus, the drilling apparatus includes a moving platform with multiple degrees of freedom and a drilling assembly connected to the moving platform, and the drilling assembly includes a base unit mounted on the moving platform; locate in a sliding way drilling unit on the frame unit and fixed connection in visual detection unit on the frame unit includes the following steps:
aligning the visual detection unit to a drilling area of the object to be drilled, measuring a curved surface in the drilling area, and calculating a normal direction of a position to be drilled in the drilling area;
step two: adjusting the position and the posture of the drilling unit, and enabling the axis of a drilling main shaft arranged on the drilling unit to coincide with the normal direction;
step three: and driving the drilling main shaft to rotate at a high speed and move forwards, and obtaining the target hole after drilling is completed.
Further, before the first step, the method further comprises determining the relative position and posture of the visual detection unit and the drilling unit, and comprises the following specific steps:
step 1: drilling a test hole on the object to be drilled;
step 2: adjusting the vision detection unit to measure the test holes at different positions and postures, and acquiring parameter information of all the positions and postures of the vision detection unit;
and step 3: and calculating the parameter information of the position and the posture of the visual detection unit determined relative to the drilling unit according to the parameter information.
Further, in the step of obtaining all the position and posture parameter information of the visual detection unit, the method further comprises the step of simultaneously obtaining the position and posture parameter information of the motion platform, and a first mathematical conversion relation is formed between the position and posture parameter information of the motion platform and the position and posture parameter information of the visual detection unit.
Further, the position and posture parameter information of the vision detection unit comprises parameter information of the vision detection unit at a first origin, the position and posture parameter information of the moving platform comprises parameter information of the moving platform at a second origin, and the parameter information of the first origin and the parameter information of the second origin have the first mathematical conversion relation.
Further, the position and posture parameter information of the vision detection unit includes parameter information of the first measurement point adjusted by the vision detection unit, and the parameter information of the first measurement point and the parameter information of the first origin have a second mathematical transformation relationship.
Further, the drilling assembly has parameter information of a third measurement point after the adjustment of the visual detection unit, the parameter information of the third measurement point has a third mathematical transformation relation with the parameter information of the second origin, and the parameter information of the first measurement point has a fourth mathematical transformation relation with the parameter information of the third measurement point.
Further, the parameter information of the first measuring point and the parameter information of the second origin point have two mathematical conversion relations, and the conversion results of the two mathematical conversion relations are the same.
Furthermore, the drilling assembly and the motion platform have the same parameter information of a second origin, the parameter information of the first origin and the origin parameter information of the drilling assembly have a fifth mathematical transformation relation, the fifth mathematical transformation relation and the fourth mathematical transformation relation are fixed, and the fifth mathematical transformation relation can be solved according to the first mathematical transformation relation, the second mathematical transformation relation, the third mathematical transformation relation and the fourth mathematical transformation relation.
Further, the method further comprises the following steps after the third step:
step 31: withdrawing the drilling spindle;
step 32: the visual detection unit detects the edge of the target hole to obtain circle center parameters of planes where all points on the edge are located, and the circle center parameters of the target hole are obtained by using a fitting method;
step 33: and calculating the diameter of the target hole according to the circle center parameter.
Further, the visual detection unit detects the edge of the target hole to obtain the position information of a plurality of points on the edge, and the axis direction of the target hole is obtained by using a fitting plane method.
(3) Advantageous effects
In conclusion, the invention can improve the direction precision of the drilling of the curved surface structure by adopting the visual detection technology to obtain the normal direction of the position to be drilled and coinciding the normal direction with the axis of the drilling main shaft of the drilling unit, and can improve the efficiency and the quality of the drilling by utilizing the synchronous rotary motion and the linear motion of the drilling main shaft.
By establishing the relative position and posture relation among the visual detection unit, the motion platform and the drilling unit, the calibration can be completed quickly and accurately without additional special parts or precise measuring instruments, the calibration principle is simple, and the process is easy to realize.
After drilling, the visual detection unit can be used for directly measuring the diameter and the position of the hole, measuring and calculating the axis direction of the target hole, and realizing online detection and judgment of the diameter, the circle center and the axis direction of the hole. And the position and the attitude parameters of the drilling unit are adjusted according to the measurement result, the processing potential of the drilling unit is excavated and exerted, and the processing efficiency is improved.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments of the present invention will be briefly described below, and it is obvious that the drawings described below are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
Fig. 1 is a schematic diagram of a movement trajectory of a drilling apparatus according to an embodiment of the present invention.
Fig. 2 is a schematic structural view of the drilling apparatus.
In the figure:
1-a base unit; 2-a drilling unit; 21-a drilling spindle; 22-a drill bit; 3-a visual detection unit; 41-an object to be drilled; 42-test wells; 43-a first origin; 44-a third measurement point; 45-a first measurement point; 46-coordinate system of the drilling assembly at the jth measurement; 47-coordinate system of the visual detection unit at j-th measurement; 48-second origin.
Detailed Description
The embodiments of the present invention will be described in further detail with reference to the drawings and examples. The following detailed description of the embodiments and the accompanying drawings are provided to illustrate the principles of the invention and are not intended to limit the scope of the invention, i.e., the invention is not limited to the embodiments described, but covers any modifications, alterations, and improvements in the parts, components, and connections without departing from the spirit of the invention.
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present application will be described in detail below with reference to the embodiments with reference to the attached drawings.
Fig. 2 is a schematic structural view of the drilling apparatus of the present invention, as shown in fig. 2, which includes a moving platform (not shown) having multiple degrees of freedom and a drilling assembly connected to the moving platform, the drilling assembly including a base unit 1 mounted on the moving platform; the drilling unit 2 is arranged on the base unit 1 in a sliding mode, and the visual detection unit 3 is fixedly connected to the base unit 1, the multi-freedom-degree motion platform is a robot or a mechanical arm with six degrees of freedom in the prior art or a three-dimensional motion device with vertical lifting, understanding, transverse translation or/and longitudinal translation and rotation around a vertical lifting shaft, the drilling unit 2 is arranged on the base unit 1 in a sliding mode, specifically, a sliding block or a pulley is arranged on the drilling unit 2, a sliding rail is arranged on the base unit 1, the drilling unit 2 can be provided with two motion paths in the mutually perpendicular direction or only one motion path in one direction, but the motion path in one direction can only be used for drilling.
Fig. 1 is a schematic diagram of a motion trajectory of a drilling apparatus according to an embodiment of the present invention, and as shown in fig. 1 and fig. 2, the present invention provides a method for drilling a hole on a curved structure, where the drilling apparatus is used to drill a hole on a curved structure of an object 4 to be drilled, and the method includes the following steps: the method comprises the following steps: aligning the visual detection unit 3 to a drilling area of the object 41 to be drilled and measuring a curved surface in the drilling area, and calculating a normal direction at the position of the object to be drilled in the drilling area; step two: adjusting the position and the posture of the drilling unit 2, and enabling the axis of a drilling main shaft arranged on the drilling unit 2 to coincide with the normal direction obtained by the calculation; step three: and driving the drilling main shaft to rotate and move forwards at a high speed to obtain the target hole after drilling is finished.
Specifically, the drilling unit 2 moves along a guide rail on the housing unit 1, and the drill bit 22 of the drilling unit 2 can advance along the guide rail to complete drilling. In this embodiment, the drilling unit 2 has only one degree of freedom, that is, only has a movement of moving forward or backward along the drilling direction, and cannot adjust the position and the posture, so that the drilling unit needs to be mounted on the moving platform to have a movement function in the other degree of freedom, and only has a function of adjusting the position and the posture. The visual detection unit 3 is an image acquisition device common in the prior art, such as a camera or a camera, and displays acquired image data or information on an additional display screen through a self-contained control system, and the visual detection unit 3 of the embodiment adopts two cameras to acquire an image of a drilling area of an object to be drilled, so that no dead angle is guaranteed during shooting, and the accuracy of image acquisition is improved. The edge image of the curved surface structure of the drilling area is detected by the visual detection unit 3, the control system in the visual detection unit 3 processes the detected edge image information, an equation of a fitting plane is constructed to be ax + by + cz + d as 0, and coefficients a, b and c are normal directions of the plane. The normal at the location to be drilled is obtained by least squares fitting, i.e. assuming that the sum of the squares of the distances of the points from the plane is minimal (meaning that the sum of the squares of the distances of the points from the plane of the fit is minimal).
The position and the posture of the drilling unit 2 are adjusted through a plurality of freedom functions of the motion platform, wherein the position refers to coordinate values of any point in a three-dimensional coordinate x, y and z space, and the posture refers to a three-dimensional angle and is an angle of an object rotating around any coordinate axis in the three-dimensional coordinate x, y and z. The axial direction and the normal direction of the drilling spindle 21 on the drilling unit 2 are coincided, the coordinate system of the drilling unit 2 is adjusted according to the normal direction conversion result obtained by calculating the drilling area detected by the visual detection unit 3 by establishing the conversion relation of the position and the posture between the visual detection unit 3 and the drilling unit 2, so that the axial line of the drilling spindle 21 on the drilling unit 2 is coincided with the normal direction of the drilling position, the conversion relation is the prior art, and the description is omitted here. When the controller of the visual inspection unit 3 determines that the axis of the drilling spindle 21 coincides with the normal direction of the drilling position, the external driving source is controlled to drive the drilling spindle 21 to drive the drill bit 21 to rotate at a high speed and move forward (i.e., move along the normal direction of the drilling position) to the drilling position to be drilled in the drilling area with the drilling object 41, so as to complete drilling and obtain a target hole.
The invention can improve the direction precision of the drilling of the curved surface structure by adopting the visual detection technology to obtain the normal direction of the position to be drilled and coinciding the normal direction with the axis of the drilling main shaft of the drilling unit, and can improve the efficiency and the quality of the drilling by utilizing the synchronous rotary motion and the linear motion of the drilling main shaft.
As a preferred embodiment, as shown in fig. 1 and 2, before the first step, i.e. before the visual inspection unit is aligned with the drilling area of the object to be drilled, it is required to determine the relative position and posture of the visual inspection unit 3 and the drilling unit 2, and the method comprises the following specific steps: step 1: drilling a test hole in the object 41 to be drilled; step 2: adjusting the vision detection unit 3 to measure the test holes 42 at different positions and postures, and acquiring parameter information of all the positions and postures of the vision detection unit 3; and step 3: the parameter information of the position and orientation of the visual detection unit 3 determined with respect to the drilling unit 2 is calculated from the parameter information in step 2.
According to the invention, by establishing the relative position and posture relation among the visual detection unit, the motion platform and the drilling unit, calibration can be completed quickly and accurately without additional special parts or precise measuring instruments, the calibration principle is simple, and the process is easy to realize.
As other alternative embodiments.
Preferably, as shown in fig. 1, in the step of acquiring all the parameter information of the position and orientation of the vision detecting unit 3, the method further includes acquiring the parameter information of the position and orientation of the moving platform at the same time, and the parameter information of the position and orientation of the moving platform and the parameter information of the position and orientation of the vision detecting unit 3 have a first mathematical conversion relationship therebetween. The position and posture parameter information of the vision detecting unit 3 comprises parameter information of the vision detecting unit 3 at a first origin 43, the position and posture parameter information of the moving platform comprises parameter information of the moving platform at a second origin 48, and the parameter information of the first origin 43 and the parameter information of the second origin 48 have a first mathematical conversion relation. The position and posture parameter information of the vision detecting unit 3 includes parameter information of the first measuring point 45 adjusted by the vision detecting unit 3, and the parameter information of the first measuring point 45 has a second mathematical transformation relation with the parameter information of the first origin 43. After the adjustment of the vision inspection unit 3, the drilling assembly has the parameter information of the third measurement point 44, the parameter information of the third measurement point 44 has a third mathematical transformation relation with the parameter information of the second origin 48, and the parameter information of the first measuring point 45 has a fourth mathematical transformation relation with the parameter information of the third measuring point 44, the parameter information of the first measuring point 45 has two mathematical transformation relations with the parameter information of the second origin 48, and the conversion results of the two mathematical conversion relationships are the same, the drilling assembly and the motion platform have the same parameter information of the second origin 48, and the parameter information of the first origin 43 has a fifth mathematical transformation relationship with the origin parameter information of the drilling assembly, and the fifth mathematical transformation relationship and the fourth mathematical transformation relationship are fixed, a fifth mathematical transformation relationship may be solved from the first mathematical transformation relationship, the second mathematical transformation relationship, the third mathematical transformation relationship, and the fourth mathematical transformation relationship.
Specifically, a test hole 42 is drilled in an object 41 to be drilled by using the drilling unit 2, the position of the vision detecting unit 3 in a three-dimensional coordinate x, y, z space and an angle of rotation around any axis of the three-dimensional coordinate x, y, z, that is, a posture are adjusted by the motion platform to measure the test hole, the coordinate where any point in the three-dimensional coordinate x, y, z space is located and which has a pose change is referred to as a coordinate system described below, that is, the motion platform is fixedly mounted on the table and has parameter information (i.e., position and orientation information) of the second origin 48 which is the base coordinate system 48, and the vision inspection unit 3 has parameter information (i.e., position and orientation information) of the first origin 43 which is the base coordinate system 43, and is a fixed, unknown coordinate system, and R is used for the conversion relationship between the base coordinate system 43 of the vision inspection unit 3 and the base coordinate system 48 of the motion platform.cb-rbRepresenting a first mathematical transformation relation, Rcb-rbIs a fixed value, the drilling assembly (comprising the vision detection unit 3 and the drilling unit 2) moves under the adjustment of the moving platform at the ith measurement time and has a coordinate system 44, namely parameter information (namely position and attitude information) of a third measurement point 44, and the conversion relation between the coordinate system 44 and a basic coordinate system 48 of the moving platform is Rirt-rbThe coordinate system 45 of the vision inspection unit 3 at the time of the i-th measurement, i.e., the parameter information (i.e., the position and orientation information) of the first measurement point 45 under the adjustment of the motion platform, and the conversion relation R for the coordinate system 45 of the vision inspection unit 3 at the time of the i-th measurement and the basic coordinate system 43 of the vision inspection unit 3 is expressed as a third mathematical conversion relationicm-cbRepresenting a second mathematical transformation R for the transformation between the coordinate system 45 of the vision inspection unit 3 at the i-th measurement and the coordinate system 44 of the drilling assembly at the i-th measurementicm-irtRepresenting a fourth mathematical transformation relationship.
For the ith measurement as an example, there are two ways to convert the coordinate system 45 of the vision inspection unit 3 and the base coordinate system 48 of the motion platform in the ith measurement, as shown in fig. 1, which are: 45-43-48, 45-44-48, the effect of the two paths is the same (i.e. the parameter information of the first measuring point 45 has two mathematical transformation relations with the parameter information of the second origin 48, and the transformation results of the two mathematical transformation relations are the same), so that there are
Ricm-cb·Rcb-rb＝Ricm-irt·Rirt-rb (1)
Since the vision inspection unit 3 and the drilling assembly are adjusted synchronously, the transformation between the base coordinate system 43 of the vision inspection unit 3 and the base coordinate system of the drilling assembly is fixed, i.e. the transformation between the coordinate system 45 of the vision inspection unit 3 at the ith measurement and the coordinate system 44 of the drilling assembly at the ith measurement is fixed, and thus, there are
Ricm-irt＝Rcm-rt (2)
Therefore, for the ith measurement, the following relationship exists
Ricm-cb·Rcb-rb＝Rcm-rt·Rirt-rb (3)
Wherein R iscm-rt(i.e., a fifth mathematical transformation relation) is a transformation relation between the basic coordinate system 43 of the vision inspection unit 3 and the basic coordinate system of the drill assembly to be obtained, i.e., a relation to the coordinate system (i.e., parameter information of the relative position and posture), and equation (3) is written as
Similarly, the coordinate system 46 of the drilling assembly at the jth measurement and the coordinate system 47 of the vision inspection unit 3 at the jth measurement have similar transformation relationships, and the data of the ith and jth measurements have the following relationship
Can be converted into
The formula (6) is abbreviated
RM·Rcm-rt·RT＝Rcm-rt (7)
In the formula (I), the compound is shown in the specification,
are all known quantities.
Rirt-rbIs a transformation matrix of the coordinate system of the drilling assembly relative to the basic coordinate system of the moving platform during the ith measurement, and the attitude transformation sequence is that the drilling assembly rotates around the Z axis, then rotates around the Y axis and finally rotates around the X axis, therefore, the attitude transformation matrix is
Considering the translation vector of the coordinate system, then
Ricm-cbIs a transformation matrix of the actual coordinate system (after adjusting the position) of the visual detection unit 3 relative to the basic coordinate system (built on the product) of the visual detection unit 3 during the ith measurement of the camera, and the posture transformation sequence is firstly rotating around the X axis, then rotating around the Y axis, and finally rotating around the Z axis, so that the posture transformation matrix is
R can be obtained from the formulas (8) to (14)MAnd RTFor ease of derivation, let RMAnd RTAre respectively abbreviated as
Let R becm-rtHas the following forms
Unfolding the formula (7) by
Then there is
The system of equations has 12 equations and 12 unknowns, which can be solved.
As another preferred embodiment, as shown in fig. 1 and 2, the drilling method further includes the following steps after completing the drilling to obtain the target hole in step three: step 31: retracting the drilling spindle 21; step 32: the vision detection unit 3 detects the edge of the target hole to obtain the circle center parameters of the plane where all points on the edge are located, and the circle center parameters of the target hole are obtained by using a fitting method; step 33: and calculating the diameter of the target hole according to the circle center parameter of the target hole. After drilling, the visual detection unit can be used for directly measuring the diameter and the position of the hole, measuring and calculating the axis direction of the target hole, and realizing online detection and judgment of the diameter, the circle center and the axis direction of the hole. And the position and the attitude parameters of the drilling unit are adjusted according to the measurement result, the processing potential of the drilling unit is excavated and exerted, and the processing efficiency is improved.
Preferably, as shown in fig. 1 and 2, the vision detecting unit 3 detects an edge of the target hole to acquire position information of a plurality of points on the edge, and obtains the axis direction of the target hole by using a fitting plane method. By the mode, after drilling, the diameter, the circle center and the axial direction of the drilled hole can be measured on line and in place without removing a drilling device or disassembling a product.
Specifically, the fitting method is a conventional method in the prior art, such as an average value method, a weighted average method, a least square method, and the like, taking the average value method as an example, theoretically, the coordinates of the center of the target hole should be the average value of the coordinate values of the center of the circle where each point on the edge of the target hole is located, actually measured points may not be exactly and uniformly distributed on the circle, even some points are not yet on the circle, but as long as the points on the edge are distributed uniformly, the average value of the coordinate values of each measured point can be used as the coordinates of the center of the circle, and the average value of the distances from the center of the circle to the points on the edge can be used as the approximate value of the radius of the circle. The circle center parameter refers to the circle center coordinate. The fitting plane method is to use a plane as a fitting plane according to the edge shape of the target hole, and by setting the equation ax + by + cz + d to 0, the coefficients a, b, and c are normal directions of the plane. The axial direction of the target hole can be obtained by using least square fitting, namely, assuming that the square sum of the distances between each point on the edge and the plane is minimum (meaning that the square sum of the distances between each point and the fitted plane is minimum).
It should be clear that the embodiments in this specification are described in a progressive manner, and the same or similar parts in the embodiments are referred to each other, and each embodiment focuses on the differences from the other embodiments. The present invention is not limited to the specific steps and structures described above and shown in the drawings. Also, a detailed description of known process techniques is omitted herein for the sake of brevity.
The above description is only an example of the present application and is not limited to the present application. Various modifications and alterations to this application will become apparent to those skilled in the art without departing from the scope of this invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.
Claims (3)
1. A method for drilling a hole in a curved structure, using a drilling apparatus for drilling a hole in a curved structure of an object (41) to be drilled, the drilling apparatus comprising a motion platform having multiple degrees of freedom and a drilling assembly connected to the motion platform, the drilling assembly comprising a housing unit (1) mounted on the motion platform; locate in a sliding way drilling unit (2) on frame unit (1) and fixed connection in visual detection unit (3) on frame unit (1), its characterized in that includes the following steps:
the method comprises the following steps: aligning the visual detection unit (3) to a drilling area of the object to be drilled (41) and measuring a curved surface within the drilling area, calculating a normal direction at a position to be drilled within the drilling area;
step two: adjusting the position and the posture of the drilling unit (2), and enabling the axis of a drilling main shaft (21) arranged on the drilling unit (2) to coincide with the normal direction;
step three: driving the drilling main shaft (21) to rotate and move forwards at a high speed, and obtaining a target hole after drilling is finished;
the method further comprises the steps of determining the relative position and the posture of the visual detection unit (3) and the drilling unit (2) before the step one, and specifically comprises the steps of drilling a test hole (42) on the object to be drilled (41); then adjusting the vision detection unit (3) to measure the test hole (42) at different positions and postures, and acquiring all positions of the vision detection unit (3)And attitude parameter information and simultaneously acquiring the position and attitude parameter information of the motion platform, wherein a first mathematical conversion relation R is formed between the position and attitude parameter information of the motion platform and the position and attitude parameter information of the visual detection unit (3)cb-rbThe position and posture parameter information of the visual detection unit (3) comprises parameter information of the visual detection unit (3) at a first origin (43) and parameter information of a first measurement point (45) adjusted by the visual detection unit (3), and the parameter information of the first measurement point (45) and the parameter information of the first origin (43) have a second mathematical transformation relation, namely Ricm-cbThe position and attitude parameter information of the motion platform comprises parameter information of the motion platform at a second origin (48), and the parameter information of the first origin (43) and the parameter information of the second origin (48) have the first mathematical transformation relation; the drilling assembly has parameter information of a third measuring point (44) after the visual detection unit (3) is adjusted, and the parameter information of the third measuring point (44) and the parameter information of the second origin (48) have a third mathematical transformation relation, namely Rirt-rbAnd the parameter information of the first measuring point (45) and the parameter information of the third measuring point (44) have a fourth mathematical conversion relation Ricm-irtThe parameter information of the first measuring point (45) and the parameter information of the second origin (48) have two mathematical conversion relations, and the conversion results of the two mathematical conversion relations are the same, namely Ricm-cb·Rcb-rb＝Ricm-irt·Rirt-rbThe drilling assembly and the motion platform have the same parameter information of a second origin (48), and the parameter information of the first origin (43) and the origin parameter information of the drilling assembly have a fifth mathematical transformation relation Rcm-rtAnd the fifth mathematical transformation relationship and the fourth mathematical transformation relationship are fixed, i.e. Ricm-irt＝Rcm-rtAnd the fifth mathematical transformation relation, namely R, can be solved according to the first mathematical transformation relation, the second mathematical transformation relation, the third mathematical transformation relation and the fourth mathematical transformation relationcm-rt＝Rjcm-cb·R-1 icm-cb·Rcm-rt·Rirt-rb·R-1 jrt-rbCalculating parameter information of the position and attitude of the visual detection unit (3) determined with respect to the drilling unit (2).
2. The method for drilling a hole in a curved structure according to claim 1, further comprising the following step after said step three:
step 31: retracting the drilling spindle (21);
step 32: the vision detection unit (3) detects the edge of the target hole to obtain circle center parameters of planes where all points on the edge are located, and the circle center parameters of the target hole are obtained by using a fitting method;
step 33: and calculating the diameter of the target hole according to the circle center parameter.
3. The method for drilling a hole in a curved surface structure according to claim 2, wherein the vision inspection unit (3) inspects the edge of the target hole to obtain the position information of a plurality of points on the edge, and the axis direction of the target hole is obtained by using a fitting plane method.
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