JPH04273303A - Position sensor control method using servo mechanism - Google Patents

Abstract

PURPOSE:To improve the position detecting precision and also to effectively prevent the damage of a position sensor by stopping the movement of the sensor when it detects a subject. CONSTITUTION:When a touch probe 1 touches a work, a touch signal is supplied to a CPU 3, a command position rewriting part 5, and a control part respectively. The CPU 3 stops the output of a command position, the part 7 stops instantaneously the control of an actuator 2, and the part 5 rewrites the command position given from the CPU 3 at that time point into the present position of the probe 1 that is read when the touch signal is produced, i.e., a touching time point position. Then a comparison part 6 compares the command position rewritten into the touching time point position with the present position defined based on the information fed back from the actuator 2. When the coincidence is obtained between both positions, the movement of the actuator 2 is stopped. Then the movement of the probe 1 is also stopped.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a method for controlling a position detection sensor used in, for example, pre-teaching the cutting position of a plasma cutting machine, and particularly when the position detection sensor is controlled by a servo mechanism. Concerning a control method.

0002

[Prior Art] Recently, cutting and welding of metal plates has been performed by robots, but these robots move an end effector such as a cutting torch along a trajectory connecting pre-taught positions. cutting and welding. The teaching position described above can be obtained by installing a position detection sensor in place of the end effector on the same robot, and sequentially bringing this position detection sensor into contact with the cutting position of the workpiece, which is the target object, so that the CPU of this robot is memorized.

By the way, the above-mentioned position detection sensor is moved by a servo mechanism as shown in FIG. FIG. 5 shows a servo mechanism when a touch probe 51 is used as a position detection sensor. Touch probe 51 is driven by actuator 52 . The servo mechanism is C
A comparison unit 54 compares the commanded position issued from the PU 53 and the current position fed back from the actuator 52, and if there is a difference between the commanded position and the current position, a signal corresponding to the difference is transmitted to the control unit 55. . The control unit 55 controls the actuator 52 based on the signal transmitted from the comparison unit 54 so that the touch probe 51 moves to the position commanded by the CPU 53 .

In the conventional control of the position detection sensor using a servo mechanism, when the touch probe 51 detects an object, the touch probe 51 is stopped at the command position at that time, and the sensor stop position is used as the detection position. I tried to remember it.

[0005]

However, as in the prior art, when the touch probe 51 detects an object, it is difficult to stop the touch probe 51 at the commanded position at that time and to store the stopped position as the detected position. If you do so, the following problems will occur.

[0006] That is, as is clear from the above explanation,
When the touch probe 51 is moving in the servo mechanism described above, there is always a difference between the command position sent from the CPU 53 and the current position of the touch probe 51. Therefore, if the sensor stop position, which is the same as the commanded position of the CPU 53, is stored as the detection position, a problem arises in that the difference between this commanded position and the current position of the touch probe 51 directly becomes a detection error.

Further, the touch probe 51 as described above has its tip 51a touching the sensor body 5 within the range of stroke a.
It is configured to appear inside 1b. Therefore, when such a touch probe 51 is used as a position detection sensor, the current position A (x1, y
1, z1) and the command position B (x2, y2, z2)
is larger than the stroke a, the sensor body 5
1b collides with the object W, which causes the touch probe 5 to
There was a risk of damaging 1. In this way, in a situation where distance b becomes larger than stroke a,
This is particularly likely to occur when the touch probe 51 is moved at high speed. Further, even if the distance b is not larger than the stroke a, if the distance b is close to the stroke a, the load on the sensor becomes large, which may lead to a decrease in the performance of the touch probe 51.

The present invention has been made in view of the above-mentioned circumstances, and its first object is to provide a method of controlling a position detection sensor using a servo mechanism that causes almost no detection error.

A second object of the invention is to provide a method for controlling a position detection sensor using a servo mechanism, which prevents problems such as damage to the position detection sensor.

0010

[Means for Solving the Problems] In order to achieve the above object, a method for controlling a position detection sensor using a servo mechanism according to claim 1 is such that when the position detection sensor detects an object, the detected position is transferred to the servo mechanism. The feature is that the position detection sensor is stopped at the detection position by setting the command position.

A method of controlling a position detection sensor using a servo mechanism according to a second aspect of the present invention is, in the first aspect, when the position detection sensor detects an object, before the position detection sensor reaches the command position at the detection time. It is characterized in that its movement is stopped and then it is retreated to the detection position.

0012

According to claim 1, the position detection sensor stops at the position where the object is detected, even though it is controlled by the servo mechanism.

According to the second aspect of the present invention, the position detection sensor temporarily stops before reaching the command position issued at the time when the object is detected, and then retreats to the position where the object is detected.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of a servo mechanism for implementing the method of the present invention, and FIG. 2 is a schematic perspective view of a robot equipped with a position detection sensor whose movement is controlled by the method of the present invention.

A touch probe 1, which is a position detection sensor, is driven by an actuator 2. The touch probe 1 outputs a contact signal when it contacts a workpiece.

The actuator 2 is constructed in a robot RB as shown in FIG. This robot RB is a rectangular coordinate type laser cutting robot, and has a movable table 12 on a base 11 that can be moved in the X direction (horizontal direction) by a motor M1 (not shown). A workpiece (not shown) is placed on. A beam 14 is installed at the top of the column 13 vertically erected on both sides of the base 11, and the beam 14 extends in the Z direction (vertical direction) in the figure and is moved in the Y direction by a motor M2. A possible moving column 15 is provided. Moving column 1
5 is provided with a motor M4 that moves up and down in the Z direction by a motor M3. With this motor M4,
An arm 16 provided eccentrically from the central axis of the moving column 15 rotates in the ω direction in the figure. Further, a motor M5 is provided on the side of the lower end of this arm 16,
The touch probe 1 is connected to this motor M5. The motor M5 rotates the touch probe 1 in the ψ direction in the figure. As is clear from the above, the actuator 2 is shown in FIG.
It is composed of motors M1 to M5. Each of these actuators 2 is equipped with a rotation speed detection section such as an encoder, and the rotation speed of the actuator detected by each rotation speed detection section is constantly fed back to the command position rewriting section 5 and comparison section 6 of the servo system 4, which will be described later. has been done.

The position of the actuator 2 is controlled by a servo system 4 that operates in response to commands issued from the CPU 3.

The CPU 3 outputs a command position in response to an operator's instruction when the operator controls the actuator 2 so that the touch probe 1 comes into contact with a score line drawn in advance on a workpiece, for example. Also, this C
The PU 3 can input a contact signal that is output when the touch probe 1 contacts a target part such as a workpiece,
When this is input, it is determined that this is an interrupt and the output of the command position based on the operator's instruction is stopped.

The servo system 4 includes a command position rewriting section 5, a comparison section 6, and a control section 7.

The command position rewriting unit 5 inputs the command position from the CPU 3, and at the same time, like the CPU 3,
A contact signal from the touch probe 1 is input. The command position rewriting unit 5 outputs the command position input from the CPU 3 as is to the comparison unit 6 when the contact signal is not input. However, when the command position rewriting unit 5 receives the contact signal, it reads the contact point position of the touch probe 1 obtained based on the information fed back from the actuator 2 at that time, and changes the command position to the comparison unit 6 from this position. Rewrite to the position at the time of contact. As described above, the CPU 3 stops outputting a new command position at the time the contact signal is output. Therefore, in this command position rewriting section 5, there is no need to select one command position from the two command positions, but simply the CP that has appeared up to that point.
The command position from U3 is simply rewritten to the position at the time of contact. The command position rewriting unit 5 feeds back the position at the time of contact to the CPU 3 as the stop position of the touch probe 1.

The comparison unit 6 compares the current position calculated based on the initial position of the touch probe 1 and the detection value of the rotation speed detection unit of the actuator 2 with the command position commanded from the CPU 3, and calculates the current position according to the difference. The comparison signal obtained is output to the control section 7. After the touch probe 1 generates a contact signal, the command position rewriting unit 5 compares the contact point position rewritten to the command position with the current position calculated from the newly fed-back detection value. Outputs a signal according to the difference. The current location can be known.

The control unit 7 controls the actuator 2 based on the signal received from the comparison unit 6 so that the touch probe 1 moves to the command position sent via the command position rewriting unit 5. Actuator 2 is touch probe 1
The touch probe 1 is moved until the current position of is the same as the commanded position, and when the commanded position and the current position match, the touch probe 1 is stopped at that position.

The above servo mechanism moves the touch probe 1 to the robot RB by repeating the above control.
The target position is detected by sequentially contacting desired positions on the workpiece mounted on the workpiece.

FIG. 3 shows a flowchart of a method for controlling a touch probe according to the method described above.

First, a command position is issued from the CPU 3 (step S1), and then the command position issued from the CPU 3 is compared with the current position based on the information fed back from the actuator 2 in the comparison section 6 (step S2). ). Here, if there is a difference between the commanded position and the current position, a comparison signal corresponding to the difference is output from the comparison section 6 to the control section 7 (step S3). The control unit 7 controls the actuator 2 to move the touch probe 1 to the commanded position (step S4).

Next, it is determined whether or not the tip of the touch probe 1 has come into contact with the workpiece due to the movement in step 4 (
Step S5). If the touch probe 1 does not come into contact with the workpiece, the process returns to step S1 and the above flow is repeated.

When the touch probe 1 comes into contact with the workpiece during the movement in step S4, the touch probe 1 generates a contact signal (step 6). This contact signal is input to the CPU 3, the command position rewriting section 5, and the control section 7. CPU3
Then, the output of the command position is stopped (step S7), and the control section 7 immediately stops controlling the actuator 2 (
Step S8), the command position rewriting unit 5 at that point
The command position given from the PU 3 is rewritten to the current position of the touch probe 1 read at the time when the contact signal was generated, that is, the position at the time of contact (step S9). Also,
The CPU 3 receives data on the position at the time of contact from the command position rewriting unit 5, sets this as the stop position of the touch probe 1, stops the program, and prepares for the next instruction from the operator (step 10).

Next, returning to step 2, the comparator 6 compares the command position rewritten to the position at the time of contact in step S8 with the current position based on the information fed back from the actuator 2. If the command position and the current position match, the movement of the actuator 2 is stopped,
The touch probe 1 also stops (step S10).

As is clear from the above explanation, when the movement of the touch probe 1 is controlled in the above manner, the touch probe 1 is moved to a position where it is in contact with an object such as a workpiece, even though the movement is controlled by a servo mechanism. can be stopped. That is, the position of the touch probe 1 can be detected with an accuracy commensurate with the rotation speed detection accuracy of the actuator 2. Further, in the above embodiment, when the touch probe 1 contacts the target object, the command from the CPU 3 is stopped, control of the actuator 2 by the control unit 7 is stopped, and the command position rewriting unit 5 rewrites the command. The actuator is controlled using the position at the time of contact as a command position. Therefore, touch probe 1
The movement of the touch probe 1 can be stopped before the tip reaches the commanded position from the CPU 3, and a situation where the touch probe 1 collides with an object such as a workpiece and is damaged can be prevented. .

In the above embodiment, the command position rewriting unit 5 is provided in the servo system 4 to rewrite the command position issued by the CPU 3, but as shown in FIG.
The contact signal generated by the touch probe 1 is input to the CPU 3A and the control unit 7, and the feedback signal from the actuator 2 is input to the CPU 3A and the comparison unit 6. The rewriting may be performed in the CPU 3A. In this case, the command signal is always sent directly from the CPU 3A to the comparator 6.

Furthermore, it goes without saying that the position detection sensor used in the present invention is not necessarily limited to the above-mentioned touch probe.

[0032]

According to the invention of claim 1, since the position detection sensor can be stopped at the position where the position detection sensor detects the object, the position can be detected with high accuracy by using this stopping position as the detection position. It can be performed.

According to the invention of claim 2, it is possible to effectively prevent the inconvenience that the position detection sensor is damaged due to the position detection sensor reaching the command position issued at the time when the object is detected. can be resolved.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of an apparatus for performing a method of controlling a position detection sensor using a servo mechanism.

FIG. 2 is a schematic perspective view of the external appearance.

FIG. 3 is a flowchart of a method for controlling a position detection sensor using a servo mechanism.

FIG. 4 is a schematic configuration diagram showing a modification of an apparatus for performing a method of controlling a position detection sensor using a servo mechanism.

FIG. 5 is a schematic configuration diagram of an apparatus for performing a conventional method of controlling a position detection sensor using a servo mechanism.

FIG. 6 is an explanatory diagram showing the moving state of the touch probe.

[Explanation of symbols]

1 Touch probe (position detection sensor) 3
CPU 4 Servo system 5 Command position rewriting section 6 Comparison section 7 Control section

Claims (2)

[Claims] 1. A method for controlling a position detection sensor moved by a servo mechanism, wherein when the position detection sensor detects an object, the detected position is set as a command position of the servo mechanism, so that the position detection sensor is moved. A method of controlling a position detection sensor using a servo mechanism, characterized by stopping the sensor at a detection position. 2. In the method of controlling a position detection sensor using a servo mechanism according to claim 1, when the position detection sensor detects an object, the movement of the object is stopped before the position detection sensor reaches the commanded position at the time of said detection. A method of controlling a position detection sensor using a servo mechanism, comprising stopping the sensor and then retreating to the detection position.