JP5351068B2 - CMM - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a three-dimensional measuring machine capable of quickly determining whether a probe or a movement mechanism collides with a measurement object with simple processing. <P>SOLUTION: The three-dimensional measuring machine 1 includes: a probe 21 for measuring a measurement object; a movement mechanism 22 for moving the probe 21; and a motion controller 3. The motion controller 3 includes: a current value detecting unit 33 that detects a current value for moving the probe 21 by the movement mechanism 22; a mode identification unit 34 that identifies a measurement mode measuring the measurement object by the probe 21 and a movement mode moving the probe 21 without measuring the measurement object; and a load determination unit 35 determining a status of a load applied on the movement mechanism 22 based on a current value detected by the current value detecting unit 33 and a threshold that is set in response to the identification result by the mode identification unit 34. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a coordinate measuring machine.

  2. Description of the Related Art Conventionally, a coordinate measuring machine including a probe for measuring an object to be measured, a moving mechanism that moves the probe, and a control device that controls the moving mechanism is known (for example, see Patent Document 1). In such a coordinate measuring machine, when the probe is moved by the moving mechanism, the probe or the moving mechanism may collide with the object to be measured due to, for example, a user's operation error. In such a case, it has a function of executing processing such as stopping movement of the probe.

Here, when the probe or the moving mechanism collides with the object to be measured, the load applied to the moving mechanism increases, and the current value for moving the probe by the moving mechanism increases. Therefore, in order to determine the collision between the probe or the moving mechanism and the object to be measured, when the current value is larger than a predetermined threshold, the third order is determined to determine that the probe or the moving mechanism and the object to be measured have collided. It is conceivable to construct an original measuring machine.
However, when the acceleration for moving the probe by the moving mechanism is small (the speed is slow), the current value is small, and when the acceleration is large (the speed is fast), the current value is large. If the threshold for determining the collision with the object to be measured is a constant value and the moving speed of the probe by the moving mechanism is slow, the probe or moving mechanism and the object to be measured collide. There is a problem that it takes time until it is determined that a collision has occurred in the CMM.

  The coordinate measuring machine (coordinate measuring machine) described in Patent Document 1 detects the value of current flowing in an electric motor for driving a moving mechanism composed of a column, a horizontal support, a horizontal feed base, and a coordinate measuring device. The detected current value is compared with the target speed at which the probe head (probe) is moved by the moving mechanism and the threshold value that is set stepwise according to the acceleration. It is determined whether or not the measurement object has collided. According to this, the coordinate measuring machine can quickly determine whether or not the probe, the moving mechanism, and the object to be measured collide with each other as compared with the case where the threshold value is constant.

Special table 2009-524032 gazette

  However, the coordinate measuring machine described in Patent Document 1 has a problem that complicated processing must be performed because the threshold is set stepwise according to the target speed and acceleration.

  An object of the present invention is to provide a three-dimensional measuring machine capable of quickly determining whether or not a probe or a moving mechanism and an object to be measured have collided with a simple process.

  The CMM of the present invention is a CMM comprising a probe for measuring an object to be measured, a moving mechanism for moving the probe, and a control device for controlling the moving mechanism, wherein the control The apparatus includes a current value detection unit for detecting a current value for moving the probe by the moving mechanism, a measurement mode for measuring the object to be measured by the probe, and without measuring the object to be measured. The movement based on a mode identification unit for identifying a movement mode for moving the probe, a current value detected by the current value detection unit, and a threshold set according to an identification result by the mode identification unit. And a load determination unit that determines a state of a load applied to the mechanism.

Here, when the speed at which the probe is moved by the moving mechanism is compared between the measurement mode and the movement mode, since the object to be measured is measured in the measurement mode, the speed in the measurement mode is higher than the speed in the movement mode. Will also be late.
According to the present invention, the load determination unit determines the state of the load applied to the moving mechanism based on the current value detected by the current value detection unit and the threshold value set according to the identification result by the mode identification unit. As a result of the determination, the probe or the moving mechanism and the object to be measured collide with each other by setting the threshold value small when the identification result by the mode identifying unit is the measurement mode and setting the threshold value large when the mode is the movement mode. It is possible to quickly determine whether or not. Therefore, the coordinate measuring machine can quickly determine whether or not the probe or the moving mechanism and the object to be measured have collided with a simple process.

  In the present invention, the load determination unit is configured to determine a state of a load applied to the moving mechanism based on a length of time during which a state where the current value detected by the current value detection unit is greater than the threshold value is maintained. Is preferably determined.

Here, the current value detected by the current value detector is not limited to when the probe or moving mechanism collides with the object to be measured, for example, when accelerating the speed at which the probe is moved by the moving mechanism. , May be larger than the threshold value.
According to the present invention, the load determination unit determines the state of the load applied to the moving mechanism based on the length of time that the current value detected by the current value detection unit is greater than the threshold value. Therefore, it is possible to prevent erroneous determination of the state of the load applied to the moving mechanism when accelerating the speed at which the probe is moved by the moving mechanism.

The whole schematic diagram which shows the three-dimensional measuring machine which concerns on one Embodiment of this invention. The block diagram which shows schematic structure of the coordinate measuring machine in the said embodiment. The flowchart which shows the load determination process of the coordinate measuring machine in the said embodiment. The graph which shows the relationship between the speed which moves a probe with the moving mechanism in the said embodiment, and the electric current value detected by an electric current value detection part. The graph which shows the state of the electric current value when moving a probe with the movement mechanism in the measurement mode in the said embodiment, and a movement mode. The figure which shows the relationship between the threshold value of the movement mode in the said embodiment, acceleration time, and duration.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
[Schematic configuration of CMM]
FIG. 1 is an overall schematic diagram showing a coordinate measuring machine 1 according to an embodiment of the present invention. FIG. 2 is a block diagram illustrating a schematic configuration of the coordinate measuring machine 1. In FIG. 1, the upper direction is defined as the + Z-axis direction, and two axes orthogonal to the Z-axis are described as an X-axis and a Y-axis, respectively.

  As shown in FIG. 1, the coordinate measuring machine 1 instructs the motion controller 3 via a coordinate measuring machine body 2, a motion controller 3 that executes drive control of the coordinate measuring machine body 2, an operation lever, and the like. And giving a predetermined command to the operation means 4 for manually operating the CMM main body 2 and the motion controller 3, and a workpiece 10 (object to be measured) installed on the CMM main body 2 A host computer 5 that executes arithmetic processing such as shape analysis, input means 61 connected to the host computer 5, and output means 62. The input means 61 is for inputting measurement conditions and the like in the coordinate measuring machine 1 to the host computer 5, and the output means 62 is for outputting the measurement results obtained by the coordinate measuring machine 1.

The three-dimensional measuring machine main body 2 has a probe 211 for contacting the surface of the workpiece 10 on the distal end side (−Z-axis direction side), a probe 21 for measuring the workpiece 10, and a proximal end of the probe 21 While holding the side (+ Z-axis direction side), a moving mechanism 22 for moving the probe 21 and a surface plate 23 on which the moving mechanism 22 is erected are provided.
The moving mechanism 22 includes a slide mechanism 24 that holds the proximal end side of the probe 21 and allows the probe 21 to slide, and a drive mechanism 25 that moves the probe 21 by driving the slide mechanism 24.

  The slide mechanism 24 extends from both ends of the surface plate 23 in the X-axis direction in the + Z-axis direction and is supported by the two columns 241 provided to be slidable along the Y-axis direction. A beam 242 extending along the direction, a slider 243 formed in a cylindrical shape extending along the Z-axis direction and slidably movable along the X-axis direction on the beam 242, and the inside of the slider 243 And a ram 244 provided to be slidable along the Z-axis direction inside the slider 243.

  As shown in FIGS. 1 and 2, the drive mechanism 25 supports a column 241 on the + X-axis direction side of each column 241, and slides along the Y-axis direction. An X-axis drive unit 25X (not shown in FIG. 1) that slides on the beam 242 to move the slider 243 along the X-axis direction, and a ram 244 that moves along the Z-axis direction by sliding the inside of the slider 243 A Z-axis drive unit 25Z (not shown in FIG. 1). Although not shown, the drive mechanism 25 is provided with sensors for detecting the amount of movement of the slide mechanism 24 in each axial direction, and each sensor outputs a signal corresponding to the amount of movement of the slide mechanism 24. Output.

As shown in FIG. 2, the motion controller 3 as a control device includes a drive control unit 31 that controls the drive mechanism 25 in response to a command from the operation unit 4 or the host computer 5, and a sensor provided in the drive mechanism 25. The signal detection part 32 which detects the signal output from is provided.
The signal detection unit 32 detects the amount of movement of the slide mechanism 24 by detecting a signal output from each sensor. Then, the movement amount of the slide mechanism 24 detected by the signal detection unit 32 is output to the host computer 5. Note that the amount of movement of the slide mechanism 24 is adjusted to indicate the position of the center of gravity of the probe 211.

The motion controller 3 executes a predetermined process such as stopping the movement of the probe 21 when the probe 21 or the slide mechanism 24 collides with the work 10 due to a user's operation error or the like. It has a function of executing a load determination process for this purpose.
Specifically, the motion controller 3 includes a current value detection unit 33, a mode identification unit 34, and a load determination unit 35.
The current value detection unit 33 detects a current value for moving the probe 21 by the moving mechanism 22.
The mode identifying unit 34 identifies a measurement mode in which the workpiece 21 is measured by the probe 21 and a movement mode in which the probe 21 is moved without measuring the workpiece 10.
The load determination unit 35 determines the state of the load applied to the moving mechanism 22 based on the current value detected by the current value detection unit 33 and the threshold value set according to the identification result by the mode identification unit 34. .

  The host computer 5 includes a CPU (Central Processing Unit), a memory, and the like. The host computer 5 controls the coordinate measuring machine main body 2 by giving a predetermined command to the motion controller 3, and the moving mechanism 22 uses the probe 211. Is moved along the surface of the workpiece 10 to measure the shape of the workpiece 10.

[Load determination processing of CMM]
FIG. 3 is a flowchart showing the load determination process of the coordinate measuring machine 1.
As shown in FIG. 3, when the load determination process is executed, the motion controller 3 executes the following steps S <b> 1 to S <b> 35. Note that the load determination process is repeatedly executed at predetermined intervals.
First, the current value detection unit 33 detects a current value for moving the probe 21 by the moving mechanism 22 (S1: current value detection step).

FIG. 4 is a graph showing the relationship between the speed V at which the probe 21 is moved by the moving mechanism 22 and the current value I detected by the current value detection unit 33. In FIG. 4, the speed V and the current value I are on the vertical axis, and the time t is on the horizontal axis. In FIG. 4, the change in the speed V that accelerates from the speed V = 0 to the speed V = Va is shown by a graph G1 (hereinafter, the time taken to accelerate the speed V is referred to as an acceleration time Ta). The accompanying change in the current value I is shown by a graph G2.
As shown in FIG. 4, the current value I increases when the change in the speed V is large, that is, when the acceleration increases, and decreases when the change in the speed V is small, that is, when the acceleration decreases. The current value I becomes constant when the change in the speed V is eliminated (hereinafter referred to as a steady state).

When the current value I is detected in the current value detection step S1, the mode identification unit 34 identifies the measurement mode and the movement mode (S2: mode identification step).
In the present embodiment, the mode identifying unit 34 identifies the measurement mode and the movement mode based on information transmitted from the operation unit 4 or the host computer 5.

FIG. 5 is a graph showing the state of the current value I when the probe 21 is moved by the movement mechanism 22 in the measurement mode and the movement mode. In FIG. 5, the current value I is on the vertical axis and the time t is on the horizontal axis. In FIG. 5, similarly to FIG. 4, changes in the current value I accompanying changes in the speed V are shown by graphs G21 and G22. Specifically, the graph G21 is a graph showing a change in the current value I in the measurement mode, and the graph G22 is a graph showing a change in the current value I in the movement mode. The graph G22 is the same graph as the graph G2 in FIG.
Here, when the speed V is compared between the measurement mode and the movement mode, since the workpiece 10 is measured in the measurement mode, the speed V in the measurement mode is slower than the speed V in the movement mode.
Therefore, as shown in FIG. 5, the change in the current value I in the measurement mode is smaller than the change in the current value I in the movement mode.

When the measurement mode and the movement mode are identified in the mode identification step S2, the load determination unit 35 executes the following steps S31 to S35, and the current value I detected in the current value detection step S1 and the mode Based on the threshold set according to the identification result in the identification step S2, the state of the load applied to the moving mechanism 22 is determined (S3: load determination step).
In the load determination step S3, first, the load determination unit 35 sets a threshold according to the identification result in the mode identification step S2 (S31: threshold setting step).
In the present embodiment, when the load determination unit 35 is identified as the measurement mode in the mode identification step S2, the load determination unit 35 sets a threshold value Imes that is about 120% with respect to the steady-state current value I in the measurement mode. When the movement mode is identified, a threshold value Imov that is about 120% of the steady-state current value I in the movement mode is set (see FIG. 5).

When the threshold value is set in the threshold value setting step S31, the load determination unit 35 compares the current value I detected in the current value detection step S1 with the threshold value set in the threshold value setting step S31 (S32). : Current value determination step).
The load determination unit 35 increments the duration when the current value I is larger than the threshold (S331: duration increment step), and resets the duration when the current value I is smaller (S332: duration reset). Step). The duration indicates the length of time during which the state where the current value I is larger than the threshold value is maintained, and is a variable of the initial value 0 stored in the memory of the motion controller 3.

  When the duration is updated in the duration increment step S331 or duration reset step S332, the load determination unit 35 compares the updated duration with the predetermined time Tb (S34: duration determination step). . Then, the load determination unit 35 outputs an error when the duration is longer than the predetermined time Tb (S35: error output step), and ends the load determination process without outputting an error when the duration is shorter. . That is, the load determination unit 35 determines the state of the load applied to the moving mechanism 22 based on the duration time.

FIG. 6 is a diagram illustrating the relationship among the threshold value Imov of the movement mode, the acceleration time Ta, and the predetermined time Tb. In FIG. 6, changes in the current value I when the probe 21 and the workpiece 10 collide are illustrated by dashed-dotted lines graphs G <b> 31 and G <b> 32.
As shown in graphs G31 and G32 in FIG. 6, the load determination unit 35 collides with the probe 21, the slide mechanism 24, and the workpiece 10, the current value I becomes larger than the threshold value Imov, and the duration is predetermined. If it becomes longer than time Tb, an error is output in error output step S35.
Then, when an error is output in the error output step S35, the motion controller 3 executes a predetermined process such as stopping the movement of the probe 21.

  In the present embodiment, the predetermined time Tb is set to substantially the same length as the acceleration time Ta. Therefore, since the duration when accelerating the speed V at which the moving mechanism 22 moves the probe 21 is shorter than the predetermined time Tb, the load determination unit 35 resets the duration in the duration reset step S332. That is, the load determining unit 35 does not output an error when accelerating the speed V at which the probe 21 is moved by the moving mechanism 22.

According to this embodiment, there are the following effects.
(1) The load determination unit 35 determines the load applied to the moving mechanism 22 based on the current value I detected by the current value detection unit 33 and the threshold value set according to the identification result by the mode identification unit 34. Since the state is determined, it is possible to quickly determine whether or not the probe 21 or the slide mechanism 24 has collided with the workpiece 10. Therefore, the coordinate measuring machine 1 can quickly determine whether the probe 21 and the slide mechanism 24 have collided with the workpiece 10 with a simple process.
(2) Since the load determination unit 35 determines the state of the load applied to the moving mechanism 22 based on the length of the duration, when accelerating the speed V at which the probe 21 is moved by the moving mechanism 22, It is possible to prevent erroneous determination of the state of the load applied to the moving mechanism 22.

[Modification of Embodiment]
It should be noted that the present invention is not limited to the above-described embodiment, and modifications, improvements, etc. within a scope that can achieve the object of the present invention are included in the present invention.
For example, in the above embodiment, the predetermined time Tb is set to be substantially the same as the acceleration time Ta, but the predetermined time Tb may be set to a length other than this.
In the embodiment, the load determination unit 35 determines the state of the load applied to the moving mechanism 22 based on the length of the duration, but the load applied to the moving mechanism 22 based on the length of the duration. It is not necessary to determine the state. In short, the load determination unit may determine the state of the load applied to the moving mechanism based on the current value detected by the current value detection unit and the threshold value set according to the identification result by the mode identification unit. .

  The present invention can be suitably used for a coordinate measuring machine.

1 ... coordinate measuring machine 3 ... motion controller (control device)
10 ... Workpiece (object to be measured)
DESCRIPTION OF SYMBOLS 21 ... Probe 22 ... Moving mechanism 51 ... Current value detection part 52 ... Mode identification part 53 ... Load determination part

Claims (2)

A coordinate measuring machine comprising a probe for measuring an object to be measured, a moving mechanism for moving the probe, and a control device for controlling the moving mechanism,
The control device includes:
A current value detection unit for detecting a current value for moving the probe by the moving mechanism;
A mode identifying unit for identifying a measurement mode for measuring the object to be measured by the probe and a movement mode for moving the probe without measuring the object to be measured;
A load determination unit that determines a state of a load applied to the moving mechanism based on a current value detected by the current value detection unit and a threshold value set according to an identification result by the mode identification unit. A coordinate measuring machine. The three-dimensional measuring machine according to claim 1,
The load determination unit determines a state of a load applied to the moving mechanism based on a length of time during which a state where the current value detected by the current value detection unit is larger than the threshold value is maintained. A coordinate measuring machine.

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