JP3722549B2 - Probe drive control method for coordinate measuring machine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a coordinate measuring machine, and more particularly to drive control for causing a probe to approach from a direction perpendicular to an object to be measured.
[0002]
[Background]
As a device for measuring the dimensions of an object to be measured placed on a surface plate, a coordinate measuring machine capable of computer drive control with respect to a probe moving mechanism is well known. Usually, a coordinate measuring machine has X, Y, and Z drive shafts that are orthogonal to each other, a probe for measurement is attached to the tip of the Z drive shaft, and a probe is attached to the tip of the probe. The coordinate measuring machine measures the center coordinate value of the measuring element by an encoder disposed on each of the X, Y, and Z drive shafts.
[0003]
Many of the objects to be measured with coordinate measuring machines are machined metal parts, and their geometric shapes are composed of combinations of geometric elements such as planes, circles, ellipses, spheres, cylinders, cones, etc. There are many. The coordinate measuring machine can measure the geometric element as a set of geometric element units to obtain the dimension of the geometric shape. In other words, measure the coordinate values of any point on this geometric shape, and calculate the parameters that identify the geometric shape using a method such as least squares to apply geometric elements such as circles and planes to these points. To do. For example, in the case of a plane, a coordinate value of an arbitrary point on the plane and a unit normal vector perpendicular to the plane are parameters for specifying the plane.
[0004]
In the measurement work, the operator can use the joystick to operate the X, Y, Z drive shafts of the coordinate measuring machine and move the measuring element to measure the object to be measured. When there are a plurality of measurement results, it is not efficient if the operator uses the joystick to measure each time, and there is a possibility that the position where the probe is brought into contact with each other may be shifted every time.
[0005]
Therefore, in order to solve the above-described problems, first, the operator performs a measurement operation on one object to be measured only once using a joystick and creates a part program file in which the contents of the operation are recorded. The measurement of other objects of the same shape can be automatically performed by causing the drive control device of the coordinate measuring machine to sequentially execute the procedure contents written in the part program file. Therefore, the measurement operation using the joystick is performed only once, and then automatic measurement can be performed by computer control.
[0006]
[Problems to be solved by the invention]
Since the movement path of the probe recorded in the part program file is the same as the path operated by the operator using the joystick, the probe must always approach from the direction perpendicular to the surface of the object to be measured. It is not always in contact with the object to be measured. For example, ideally, as shown in FIG. 3B, it is desirable that the measuring element approach the surface S of the object to be measured as a vector V2 perpendicularly to the surface S to obtain the measuring point P2. However, actually, as shown in FIG. 3A, the measurement direction vector V1 may be set slightly oblique to the surface S depending on the operation of the joystick. In this case, after the probe contacts the surface S, the probe may slightly slide in the direction of the vector VS and a measurement error may occur. If this operation content is recorded in the part program file as it is and this part program file is executed in the subsequent automatic measurement, a similar measurement error may occur.
[0007]
The present invention has been made in view of such circumstances, and its purpose is to change the measurement direction vector recorded in the part program file that automatically controls the coordinate measuring machine to a direction perpendicular to the surface of the object to be measured. Thus, a probe drive control device and a probe drive control method for a coordinate measuring machine that enable automatic measurement with higher reliability are provided.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a coordinate measuring machine comprising a probe for measuring an object to be measured, a drive control device for driving the probe, and an encoder for detecting the amount of movement of the probe. In a probe drive control method of a coordinate measuring machine that performs automatic measurement by executing a part program stored in a computer, an operator specifies a geometric shape to be manually measured, and drives the probe to measure the object Manually measuring the surface of the object and temporarily storing point coordinate values and measurement direction vectors; applying the geometric shape to the point coordinate values; calculating parameters for specifying the geometric shape; and the specifying determining a vector normal to the surface of the object to be measured at said point coordinate values based on the parameters of the geometry that is, the measurement And recording the part program in conjunction with the point coordinate value is replaced with the direction vector in the vertical vector, and further comprising a.
[0009]
According to the present invention , in the step of calculating the parameter for specifying the geometric shape, when the object to be measured has a reference plane, the point coordinate value is projected onto the reference plane, and based on the projected point. It is preferable to calculate a parameter for specifying the geometric shape.
[0010]
A predetermined geometric model is applied to the measurement points constituting the predetermined geometric shape measured during the teaching operation. A vector perpendicular to the predetermined geometric model and passing through each measurement point can be calculated. Next, the obtained vector is used as a measurement direction vector, and the measurement point is recorded as a target measurement point coordinate in a part program file. Next, the target measurement point coordinates and the measurement direction vector are read from the part program file and input to the drive control device, and the coordinate measuring machine is automatically operated, so that the direction from the direction substantially perpendicular to the surface of the object to be measured can be obtained. The coordinates of each measurement point can be obtained by approaching the probe.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments using the present invention will be described with reference to the drawings. In addition, what attached | subjected the same code | symbol in all the figures represents the same component.
FIG. 1 shows a block diagram of a preferred embodiment of the present invention. The X axis drive motor 12A, the Y axis drive motor 12B, the Z axis drive motor 12C, and the amount of movement of each drive axis are controlled by signals from the drive control device 20 on the orthogonal X, Y, Z drive axes. The coordinate measuring machine 10 includes an X-axis encoder 13A, a Y-axis encoder 13B, and a Z-axis encoder 13C that detect and output the values to the drive control device 20. In addition, a probe 14 is provided that generates a touch signal when a probe is attached to the tip and the probe contacts the object to be measured.
[0012]
A CPU 21 to which signals from the X-axis encoder 13A, Y-axis encoder 13B, Z-axis encoder 13C, and probe 14 are input, a signal from the CPU 21, and a signal from the joystick operation panel 40 are input to the drive control device 20. An X-axis motor drive circuit 22A, a Y-axis motor drive circuit 22B, and a Z-axis motor drive circuit 22C are provided. The read values of the X-axis encoder 13A, Y-axis encoder 13B, and Z-axis encoder 13C are constantly taken into the CPU 21. Further, when the probe attached to the tip of the probe 14 comes into contact with the object to be measured from the probe 14, a rectangular wave touch signal is output and input to the CPU 21. When the operator tilts the joysticks 41A, 41B, 41C in the joystick operation panel 40, a voltage signal proportional to the tilt angle is output. This voltage signal is input to the X-axis motor drive circuit 22A, Y-axis motor drive circuit 22B, and Z-axis motor drive circuit 22C in the drive control device 20, and further drives the drive motor of each drive axis of the coordinate measuring machine 10. Thus, the probe can be moved.
[0013]
The host computer system 30 includes a host computer 31 that transmits / receives data to / from the CPU 21, a monitor 32 that displays a video signal from the host computer 31, and a keyboard 33 for inputting data and the like to the host computer 31. And a printer 34 for printing measurement results and the like. A command related to the movement of the probe output from the host computer 31 can be input to the CPU 21, and conversely, the measurement coordinate value data output from the CPU 21 can be input to the host computer 31. It is possible to automatically read out a drive command from a part program file describing a probe movement path and the like stored in the host computer 31 and input it to the CPU 21 to automatically operate the coordinate measuring machine. In addition, a series of operations measured by operating the joysticks 41A, 41B, and 41C can be recorded in the host computer 31 as part program files. For example, an operator can move a probe of a coordinate measuring machine using a joystick to measure a master work only once and create a part program file. Thereafter, with respect to an object to be measured having the same shape as the master work, the drive command can be sequentially read from the part program file and input to the CPU 21 to automatically operate and measure the coordinate measuring machine. Teaching this measurement operation to create a part program is called teaching.
[0014]
Next, a preferred embodiment of the present invention will be described with reference to FIG.
The operator inputs a command to the host computer 31 so as to start teaching from the keyboard 33 and designates the name of the part program file for recording the contents of teaching. When this input is completed, teaching is started in S50.
[0015]
After S51, recording of the movement path of the probe 14, a measurement command instructed by the operator from the keyboard 33, etc. is started in the part program file.
[0016]
In step S52, the operator designates the geometric shape to be measured from the keyboard 33 and records it in the part program file. For example, a plane is specified when measuring a plane on the object to be measured, and a circle is specified when measuring a hole. The host computer 31 can perform fitting calculation of the designated geometric shape for a plurality of point coordinate values measured immediately thereafter, and can calculate parameters for specifying the geometric shape.
[0017]
Next, in S53, the operator operates the joysticks 41A, 41B, 41C to move the probe, and measures the point coordinate value on the plane of the object to be measured.
[0018]
Next, in S54, the point coordinate value measured in S53 and the direction vector in which the probe has moved immediately before this measurement are temporarily stored as a measurement direction vector.
[0019]
Next, in S55, it is checked whether or not the number of points necessary for specifying the specified geometric shape has been measured. If the number of points is still insufficient, the process returns to S53. If the necessary score is satisfied, the process proceeds to S56. In order to specify the geometric shape, for example, data of two or more point coordinate values for a straight line, three or more points for a circle and a plane, and four or more point coordinate values for a sphere are necessary.
[0020]
Next, in S56, the specified geometric shape is applied to the measured point coordinate values, and parameters for specifying the geometric shape are calculated. For example, when three points on the inner wall surface of the hole are measured, a calculation is performed by fitting a circle to a point obtained by projecting the three points on the reference plane using the plane measured at the upper end of the hole measured in advance as the reference plane. By this calculation, the center coordinate value and the radius value of the circle are obtained, and data obtained by adding the data of the unit normal vector of the reference plane to this is recorded as a parameter for specifying the circle.
[0021]
In step S57, a vector that passes through each measurement point and is perpendicular to the surface of the object to be measured is obtained based on the parameters that specify the geometric shape. For example, in the case of the above hole, as shown in FIG. 6, a vector passing through the central axis of the hole and directed to each measurement point is calculated and used as a measurement direction vector.
[0022]
Next, in S58, instead of the measurement direction vector temporarily stored in S54, the vector newly obtained in S57 is used as the measurement direction vector, and the measurement point coordinate value and this measurement direction vector are recorded in the part program file.
[0023]
Next, in S59, it is confirmed whether or not teaching is to be ended. If it is to be ended, the process proceeds to S60, and if teaching is to be continued, the process returns to S52 .
[0024]
If the coordinate measuring machine is automatically driven using this part program file after the teaching work is completed, the point coordinate value on the measured object measured during teaching is aimed at the surface of the measured object. Then, the probe of the coordinate measuring machine is driven and controlled to approach the probe based on the vertical measurement direction vector.
[0025]
In the above description, only the measurement of the hole shown in FIG. 6 has been described. However, the present invention can be applied to geometric shapes other than the hole. For example, the straight line or end face shown in FIG. 4, the plane shown in FIG. 5, the ellipse shown in FIG. 7, the cylinder shown in FIG. 8, the cone shown in FIG. 9, the circular tube shown in FIG. It is done. Therefore, the present invention can coordinate the probe so that the probe approaches the object to be measured as long as the geometric model is fitted and a vertical vector can be calculated for the geometric model. The probe of the measuring machine can be driven and controlled.
[0026]
【The invention's effect】
As described above, according to the present invention, the measurement direction vector in the part program file for automatically controlling the coordinate measuring machine can be corrected, and the probe can be measured from the direction perpendicular to the surface of the object to be measured. Is possible. Therefore, the probe does not slide on the surface of the object to be measured, causing a measurement error, and automatic measurement with higher reliability is possible.
[Brief description of the drawings]
FIG. 1 is a block diagram of a coordinate measuring machine system according to an embodiment of the present invention.
FIG. 2 is a flowchart showing an operation procedure of the system.
FIG. 3 is a diagram illustrating a relationship between measurement direction vectors and measurement points.
FIG. 4 is a diagram illustrating a measurement direction vector in measurement of a straight line or an end face.
FIG. 5 is a diagram showing measurement direction vectors in plane measurement.
FIG. 6 is a diagram showing measurement direction vectors in hole measurement.
FIG. 7 is a diagram showing measurement direction vectors in the measurement of an ellipse.
FIG. 8 is a diagram showing a measurement direction vector in measurement of a cylinder.
FIG. 9 is a diagram showing measurement direction vectors in cone measurement.
FIG. 10 is a diagram showing a measurement direction vector in measurement of a circular pipe.
FIG. 11 is a diagram showing measurement direction vectors in the measurement of an elliptic tube.
[Explanation of symbols]
10 Coordinate measuring machine
14 Probe
20 Drive controller
30 Host computer system
31 Host computer
40 Joystick control panel

Claims (2)

A part program stored in a computer is executed by a coordinate measuring machine having a probe for measuring an object to be measured, a drive control device for driving the probe, and an encoder for detecting a movement amount of the probe. In a probe drive control method of a coordinate measuring machine that performs automatic measurement,
Specifying the geometry that the operator wishes to measure manually;
Driving the probe to manually measure the surface of the object to be measured and temporarily storing a point coordinate value and a measurement direction vector;
Applying the geometric shape to the point coordinate value to calculate a parameter for specifying the geometric shape;
Obtaining a vector perpendicular to the surface of the object to be measured at the point coordinate value based on the specified geometric parameter;
Replacing the measurement direction vector with the vertical vector and recording it in the part program together with the point coordinate values;
A probe driving control method for a coordinate measuring machine. In the probe drive control method of the coordinate measuring machine according to claim 1,
In the step of calculating a parameter for specifying the geometric shape, when the object to be measured has a reference surface, the point coordinate value is projected onto the reference surface, and the geometric shape is specified based on the projected point. Calculate the parameters to
A probe drive control method for a coordinate measuring machine.

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