JPH09196658A - Decision method for alignment in coordinate measuring machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a decision method in which many parts of an alignment process are automated and in which measuring efficiency is enhanced. SOLUTION: The reference axis of an object to be measured is made to agree approximately with the reference axis of a coordinate measuring machine in advance. While one point regarding the object to be measured is used as a temporary reference point, the coordinates of the temporary reference point are measured for the number of portions of dimensions to be measured. The coordinate system of the object to be measured is converted (203) into the coordinate system of the measuring machine on the basis of a coordinate value (201), and a measuring path for alignment is created (202). Coordinates used to decide the alignment of the object to be measured are measured (204) by using the measuring path for alignment. A conversion table used to convert the coordinate system of the object to be measured into the coordinate system of the measuring machine is created (205) on the basis of the measured coordinate value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coordinate measuring apparatus for automatically measuring three-dimensional or two-dimensional coordinates of an object, and more specifically, when performing shape measurement of an object to be measured by the coordinate measuring apparatus, automatic measurement is performed. The present invention relates to an alignment determining method for determining a relative positional relationship between a coordinate system of a measuring object and a coordinate system of a measuring device for starting.

[0002]

2. Description of the Related Art Today, various measuring machines are used for measuring and inspecting manufactured products in the manufacturing process. That is, the manufactured product is used as an object to be measured, and whether or not the manufactured product is designed is determined using a measuring machine. Particularly in recent years, measurement using a coordinate measuring machine typified by a coordinate measuring machine has been remarkably popular because of its high accuracy, versatility, and ease of automation.

In this coordinate measuring machine, an object to be measured is divided into shape elements such as a straight line, a circle, a cylinder, a plane, a cone and a sphere,
The measuring element measures each element. As the measuring element, there are a contact type sensor using a contact element or a non-contact type sensor using light as a medium. This coordinate measuring machine measures the coordinates as spatial shape data for each shape element, and inputs the coordinate data to an electronic computer connected to the measuring machine for data processing for inspection. Is going.

That is, the electronic computer substitutes the data measured by the measuring machine into the corresponding shape element and calculates the shape parameter such as the position, posture, dimension, geometric deviation of the shape element. By comparing the shape parameters thus obtained with the numerical values described in the design document or the drawing, it is determined whether or not the measurement object is correctly manufactured. In a measuring device such as a coordinate measuring machine using a three-dimensional coordinate system, the position of the reference point on the XY plane and the vector from the reference point, the position of the reference point on the YZ plane and the vector from the reference point, and , The position of the reference point on the ZX plane and the vector from the reference point determine the coordinates of the measurement point.

Further, in order to perform coordinate measurement using a coordinate measuring machine or the like, the measuring object is fixed to the measuring device so that the coordinate system of the measuring object and the coordinate system of the coordinate measuring device are exactly matched. Alternatively, before the measurement of the shape is started, it is necessary to clarify a relative positional relationship such as a deviation between the coordinate system of the measuring object and the coordinate system of the coordinate measuring device. When the coordinate system of the measuring object is made to match the coordinate system of the coordinate measuring device, the coordinate system of the measuring object and the coordinate system of the coordinate measuring device are accurately matched within an allowable range. It is necessary to perform positioning. In order to perform this positioning efficiently, it is necessary to correctly detect the deviation of the measuring object with respect to the coordinate system of the coordinate measuring device with a small number of trials. For this purpose, it is preferable to previously align the position of the measuring object with the XY axes of the measuring device. It should be noted that it has been devised to simplify these operations while not relying on the intuition and experience of a skilled person (for example, JP-A-5-209743).
issue).

When the measuring object is fixed with the coordinate system of the measuring object and the coordinate system of the coordinate measuring device deviated from each other,
It is necessary to create a conversion matrix, which is a coordinate conversion formula as a relative positional relationship between the coordinate system of the measuring object and the coordinate system of the measuring device, as a conversion table. For this reason, first, after fixing the measuring object to the measuring device, at least six independent points of three points that determine the plane of the measuring object, two points that determine the axis, and one point as a reference point are measured at a minimum. doing. Then, the coordinate system of the measurement target is specified using the shape data of the measurement target and the coordinate values of the measured points, and a conversion matrix that is a coordinate conversion formula is created as a conversion table. Then, using this conversion table, the numerical value of the measuring object calculated from the coordinates measured by the coordinate measuring machine and the numerical value of the shape parameter stored in the CAD data or the like are compared.

Alignment is a task of obtaining a conversion table which is a coordinate conversion formula, and fixing the measuring object to the measuring device so that the coordinate system of the measuring object matches the coordinate system of the coordinate measuring device. I'm calling. Before the alignment is determined, the relative relationship between the coordinate system of the measuring object and the coordinate system of the measuring device is unknown. Therefore, the operation of moving the tracing stylus to a predetermined measurement position of the measurement object has to be performed manually, and the determination of the alignment requires time and labor for the operation. In addition, skill and experience are naturally required for determining this alignment, which requires time and labor.

[0008]

Nowadays, demands for products are increasing, and high precision is required for inspection. For this reason, it has become extremely difficult to accurately fix the object to be measured to the measuring machine as an allowable range of error. Further, in the conventional alignment determining method for producing the conversion table, the measurement target can be fixed relatively easily. However, after fixing the measuring object to the measuring table, at least six specific points of the measuring object must be measured by manual operation. Therefore, it is necessary for a skilled worker to operate the measuring machine. Therefore, the burden on the operator is large and the alignment requires a long time.

Further, it is preferable that the measurement points on the measurement object necessary for alignment be easily grasped as a shape and that the subsequent coordinate conversion calculation be simplified. For this reason, for example, in three-dimensional measurement, it is preferable that the three-dimensional measurement includes three points on a plane, two points on a straight line, and one other point. Therefore, it was necessary to measure at least 6 points. However, for a measurement object that does not have a linear shape, such as a cylinder, a straight line on the measurement object cannot be directly measured. For this reason,
An indirect measurement has been performed in which the object to be measured is once fixed to a jig and the jig is fixed to a measuring machine for measurement. However,
In this method, there is an error in mounting the measuring object on the jig. Therefore, in order to improve the measurement accuracy, it is necessary for a skilled person to perform the work.

An object of the present invention is to solve the above-mentioned problems, and to provide a method of determining an alignment which can improve the measurement efficiency.

[0011]

The present invention is characterized in that the alignment process is divided into two stages. That is, the reference axis of the object to be measured is made substantially coincident with the reference axis of the coordinate measuring machine in advance, and a first step for manually measuring the number of measurement dimensions by using one point on the object to be measured as a temporary reference point is provided. Then, in the second step, the coordinate system of the measuring object is converted into the coordinate system of the measuring machine on the basis of the coordinate values manually measured to create the alignment measurement path. Further, coordinate measurement for determining the alignment of the measurement object is performed by this alignment measurement path. Also, a conversion table for converting the measuring object coordinate system to the measuring machine coordinate system based on the measured coordinate values is created. In this way, the first stage and the second
It will be divided into stages, and in these series of steps,
The second step after measuring the provisional reference points by the number of measurement dimensions is a method for determining alignment that can be automatically performed using an electronic computer.

As described above, according to the present invention, the alignment process is divided into the first stage which is the pre-process which requires the manual operation of the operator and the second stage which is the automatable post-process. In other words, the coordinate measurement for the minimum number of degrees of freedom is not performed every time the measurement object is exchanged, unlike the conventional case. That is, the first process as a pre-process including coordinate measurement by manual operation
At the stage, the provisional reference points are measured by the number of measurement dimensions, and it is not necessary to perform coordinate measurement for the number of measurement degrees of freedom. For example, in three-dimensional measurement, the number of times of manual coordinate measurement can be reduced from 6 points to 3 points by half. Furthermore, in the first step, which is a pre-process, it is sufficient to roughly align the reference axis of the measuring object with the reference axis of the measuring machine. Therefore, the skill of the operator does not influence the alignment accuracy as in the conventional method. Therefore, even if the measurement target has a shape such as a cylinder whose measurement position for alignment cannot be easily determined, the alignment can be easily performed using a guide or the like. In addition, the second stage
It can be automatically performed by the alignment measurement path. Therefore, once the alignment is completed, by recalling the stored alignment data, the shape measurement of the measurement object having the same shape can be automated thereafter.

Further, in the present invention, when the reference axis of the measurement object in the first step is made to substantially coincide with the reference axis of the coordinate measuring machine,
A guide member having three orthogonal planes as reference planes may be used to bring the measurement object into contact with the guide member. In this case, the posture of the measurement target can be easily determined. That is, the guide member is
Since it has three planes as orthogonal reference planes, it is easy to make each of these reference planes coincide with each measurement axis direction of the coordinate measuring machine. Since the attitude of the measurement target is determined by this guide member, it is extremely easy to make the reference axis of the measurement target substantially coincide with the reference axis of the coordinate measuring machine.

Further, in the present invention, the position of the reference surface of the guide member may be measured when measuring the provisional reference points by the number of measurement dimensions. In this case, the intersection of the three reference planes of the guide member is used as the temporary reference point. Therefore, the coordinate value of the temporary reference point in the measuring machine coordinate system can be easily measured. That is, the measurement of the reference surface of the guide member is relatively easy. Further, the guide member and the measurement object to be brought into contact with the guide member in a fixed posture are always related in a fixed position and posture. Therefore, a part of the guide member is regarded as a part of the measuring object, and the temporary reference point for the measuring object is measured by measuring the reference surface.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The embodiment of the present invention uses an apparatus for reading shape data such as CAD data using a CAD system 11 as shown in FIG.
This apparatus has a shape data storage means 13 which edits the read shape data into shape data for an inspection drawing and stores it. Further, this apparatus has a measurement path information storage means that stores various measurement paths for measuring the elements of the measuring object 35.
With 15. The apparatus also has a measurement data storage means 23 for storing the measurement result. Also, a measurement command is transmitted to the coordinate measuring machine 30 through the measurement path, and measurement data is formed from the coordinate data from the coordinate measuring machine 30 and stored in the measurement data storage means 23. It has an arithmetic processing means 21 for sending to a result output means 25 such as a printer. Then, it has a measurement instruction input means 17 for editing and correcting the shape data, creating a measurement path, and determining parameters of the measurement path.

According to the present invention, this device forms a measurement path which is a movement path of the probe of the coordinate measuring machine 30. This measurement path is created based on the shape data stored in the shape data storage means 13 and the measurement path information stored in the measurement path information storage means 15. Further, according to the present invention, when measuring the shape of the measuring object 35 by the coordinate measuring machine 30, the alignment adjustment is determined by using the guide member 40.

The guide member 40 enables the object 35 to be measured to be placed on the measuring table 31 of the coordinate measuring machine 30 in a fixed posture. That is, as shown in FIG. 1, the guide member 40 has, for example, an L shape and has a first reference surface 41 and a second reference surface 42 which are orthogonal to each other. The upper surface of the guide member 40 is a third reference surface 43 parallel to the inspection table.

In the alignment, as shown in the procedure of FIG. 2, the guide member 40 is first fixed to the measuring table 31 in the first stage (101). At the time of this fixing, the first reference surface 41 of the guide member 40 is fixed to the coordinate measuring machine.
It is fixed within the moving inspection range of the contact point so that it almost coincides with the X axis of 30. Then, the measuring object 35 is brought into contact with the guide member 40 to position the measuring object 35 (10
2) It is.

The shape data storage means 13 stores the shape data of the guide member 40 together with the shape data of the measuring object 35 (103). Then, using the shape data of the measurement object 35 and the shape data of the guide member 40, the shape data of the guide member 40 and the shape data of the measurement object 35 are changed by changing the position and orientation of the measurement object 35. Combine (104). That is, the composite shape data of the guide member 40 and the measurement object 35 representing the state in which the posture of the measurement object 35 is determined on the measurement table 31 by the guide member 40 fixed to the measurement table 31 is created. Further, only one provisional reference point for the measurement object 35 is determined, and the coordinates of this provisional reference point in the coordinate measuring machine 30 are measured (105).

As the temporary reference point, the first reference surface 41 of the guide member 40 that supports the measuring object 35 in a fixed posture.
The intersection of the second reference plane 42 and the third reference plane 43 was used as the temporary reference point. Therefore, when performing three-dimensional measurement as the measurement of the temporary reference point, Y of the first reference surface 41 of the guide member 40 is measured.
The coordinates, the X coordinate of the second reference plane 42, and the Z coordinate of the third reference plane 43 are manually measured. In this measurement, the coordinates of the temporary reference point are measured on the coordinate measuring machine 30 only three times which is the measurement order.

As described above, the Y coordinate of the first reference surface 41 substantially coincident with the X axis, the X coordinate of the second reference surface 42 substantially coincident with the Y axis, and the height Z of the third reference surface 43. After measuring the coordinates, based on this measurement value, the reference plane of the measurement object 35, the reference axis, and a temporary conversion matrix for calculating the coordinate value of the reference point in the measuring machine coordinate system is created. 106).

In the case of two-dimensional measurement, manual measurement is sufficient if the Y coordinate of the first reference plane 41 and the X coordinate of the second reference plane 42 are measured. Further, as a second step, a reference plane, a reference axis, and a reference point are selected and determined from the shape data (201). In addition, from the measurement path information storage means 15, an appropriately categorized measurement path is selected and a path for measuring the reference axis and the reference point is created (202). That is,
Create a path for measuring 3 points on the plane according to the position and orientation of the reference plane to be measured, and a path for measuring 2 points for measuring the axis coordinates according to the position of the reference axis. Then, a path for measuring the reference point is created. In other words, a path for automatically performing the alignment measurement, which is conventionally performed manually, that is, an alignment measurement path is created. Then, by using the combined shape data stored in the shape data storage means 13 and the coordinates of the temporary reference points, the positions of the reference plane, the reference axis, and the reference points to be measured are converted and converted into the coordinates of the measuring machine by the temporary conversion matrix. (203). Then, by the alignment measurement path based on the coordinate values converted into the coordinates of the measuring machine coordinate system, the probe of the coordinate measuring machine 30 is moved to automatically measure the six points of the coordinates determined on the measuring object 35. (204). Furthermore, based on the coordinates of 6 points in this measuring machine coordinate system, the measurement object 35
A conversion matrix, which is a conversion table from the coordinate system to the coordinate system of the measuring machine, is created (205).

In this way, the posture of the measuring object 35 is specified by using the guide member 40, and the reference plane of the guide member 40 is made to substantially coincide with the reference axial direction of the measuring machine, and at least 6 of the measuring object 35 is measured. Create an alignment measurement path that measures the coordinates of points, and use the shape data and the provisional conversion matrix to
The coordinates are calculated in the coordinate system of the measuring machine that moves the probe according to the path. Therefore, it is possible to automate the measurement of at least 6 points necessary for the alignment of the measuring object 35. Then, in the case of three-dimensional measurement in accordance with the number of measurement dimensions, if the three points of the guide member 40 are manually measured, the alignment can be automatically adjusted thereafter.

Further, in the present embodiment, the intersection of the first reference surface 41, the second reference surface 42 and the third reference surface 43 of the guide member 40 is used as the temporary reference point. Therefore, when manually measuring the three points of this guide member 40 to measure the coordinates of the temporary reference point,
Like the Y coordinate of the first reference plane 41 and the X coordinate of the second reference plane 42,
It is enough to measure the coordinates of the plane in the direction perpendicular to the plane. Therefore, the coordinates of the temporary reference point can be measured extremely easily.

The measurement of the temporary reference point is not limited to the case of measuring the reference surfaces such as the first reference surface 41 and the second reference surface 42 formed on the guide member 40. That is, when the shape of the measuring object 35 is simple, the plane of the measuring object 35 may be directly measured by the number of measurement dimensions. Also, the guide member 40
Is not limited to the L-shape, but may be a shape including irregularities that can determine the posture of the measurement object 35 in accordance with the shape of the measurement object 35. Also in this case, it is preferable to have a shape having three visually distinct planes that are orthogonal to each other.

That is, the guide member 40 has a concavo-convex shape conforming to the shape of the measuring object 35 and is orthogonal to each other.
The shape also has a plane. Therefore, the combined shape of the guide member 40 and the measurement object 35 can be easily made into a constant shape by the unevenness according to the shape of the measurement object 35. If the guide member 40 is formed with three planes orthogonal to each other, the three planes serving as the reference planes of the guide member 40 can be easily found. Therefore, when fixing each reference surface of the guide member 40 to the measurement table 31, it is possible to easily make the reference surfaces substantially coincide with each other.

Further, in the method of determining the posture and the position of the measuring object 35 using the guide member 40 as described above, when the measuring object 35 having the same shape is continuously measured, the guide member 40 is fixed. It is possible to easily replace only the measurement object 35 in the state. In this case, it is not necessary to change the temporary reference point. Therefore, the alignment can be determined by immediately performing the 6-point automatic measurement in the second stage.

Further, as an example of the coordinate measuring machine 30, any device such as a measuring machine, a processing machine, an assembling machine or the like can be used as long as it can measure the shape of the measuring object 35 as coordinate values on a plane or space. But it can be used.

[0029]

According to the present invention, the reference axis of the object to be measured is made substantially coincident with the reference axis of the coordinate measuring machine in advance, the coordinates of the temporary reference point relating to the object to be measured are measured, and the alignment measurement path is created. is there. Therefore, it is possible to automate many parts of the alignment process manually performed by an operator. Therefore, the alignment time can be shortened and the burden on the operator can be reduced.

Further, in the process manually performed by the operator, the skill of the operator does not influence the alignment accuracy as in the conventional method. That is, since the conversion table is created by performing coordinate measurement by automatic measurement using the alignment measurement path, it is possible to easily perform highly accurate alignment. Furthermore, even if the measurement target has a shape such as a cylinder whose coordinate measurement position for alignment is not easily determined, the alignment can be easily performed using the guide member or the like.

Due to these characteristics, it becomes easy to automatically attach and detach the object to be measured by a robot or the like, and it is possible to promote automation of the entire shape measurement. Then, when a large number of measurement objects having the same shape are measured, it is not necessary to perform the alignment each time the measurement objects are remounted on the measuring machine as in the conventional method. That is, it is sufficient to repeat only a part of the alignment. Therefore, the alignment time can be shortened and the burden on the operator can be reduced.

As described above, the practical effects of the present invention are extremely large. The invention described in claim 2 is a method of fixing a reference object of a guide member having three orthogonal planes as reference surfaces so that the reference surfaces are substantially aligned with the measurement axis direction and the measurement target is brought into contact with the guide member. Therefore, the posture of the measurement object can be easily determined, and it becomes extremely easy to make the reference axis of the measurement object substantially coincide with the reference axis of the coordinate measuring machine. Further, there are advantages that the alignment time can be shortened and the burden on the operator can be reduced.

The invention described in claim 3 is a method for measuring the position of the reference plane of the guide member. Therefore, it is possible to easily measure the coordinates of the provisional reference point of the measuring object in the measuring machine coordinate system. Further, since the accurate alignment determination can be automated, the manual alignment work can be simplified.

[Brief description of drawings]

FIG. 1 is a schematic block diagram of an apparatus used for an alignment determination method according to the present invention.

FIG. 2 is a flowchart showing an outline of an alignment determination method according to the present invention.

[Explanation of symbols]

11 CAD System 13 Shape Data Storage Means 15 Measurement Path Information Storage Means 17 Measurement Instruction Input Means 21 Arithmetic Processing Device 23 Measurement Data Storage Means 25 Result Output Means 30 Coordinate Measuring Machine 31 Measuring Stand 35 Measuring Object 40 Guide Member 41 First Criteria Surface 42 Second reference surface 43 Third reference surface

Claims (3)

[Claims] 1. A reference axis of a measuring object is made substantially coincident with a reference axis of a coordinate measuring machine in advance, one point relating to the measuring object is used as a temporary reference point, and the coordinates of the temporary reference point are measured by the number of measurement dimensions. The coordinate system of the measuring object is converted to the coordinate system of the coordinate measuring machine based on the coordinate value to create an alignment measuring path, and the alignment of the measuring object is determined using the alignment measuring path. Coordinate measurement is performed, and a conversion table for converting the coordinate system of the measuring object into the coordinate system of the measuring machine based on the measured coordinate values is used to perform alignment measurement in the coordinate measuring machine. How to decide. 2. A guide member having three planes orthogonal to each other as reference planes is used, and each reference plane of the guide member is fixed so as to be substantially aligned with each measurement axis direction of the coordinate measuring machine. The method for determining alignment in a coordinate measuring machine according to claim 1, wherein the measuring object is brought into contact with and the reference axis of the measuring object is made substantially coincident with the reference axis of the coordinate measuring machine in advance. 3. The coordinate measuring machine according to claim 2, wherein the position coordinates of the reference plane of the guide member are measured when measuring the coordinates of the temporary reference points of the measurement object by the number of measurement dimensions. Method for determining alignment in.