JP2942615B2 - NC control method for press-fit robot - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control method of a press-fitting robot, and more particularly, to move a current position of a press-fitting head to follow a target position.
It relates to the improvement of the NC control method.

Prior art Detecting the current position of a movable part driven by a servomotor, and operating the servomotor at a speed corresponding to the deviation between the target position and the current position while sequentially updating the target position, NC control for causing the movable portion to follow the sequentially updated target position is frequently used in various industrial robots. In such NC control, if the movable part stops or a significant following delay occurs due to interference with an obstacle or mechanical failure, the above-mentioned deviation increases, and a command is issued in accordance with the deviation. If the speed becomes excessive and the cause of interference or mechanical failure is eliminated, the movable part suddenly starts to move at the excessive speed.To prevent this, if the deviation becomes more than a certain value, make an abnormality judgment. Usually, the operation of the robot is urgently stopped or returned to the original position.

Problems to be Solved by the Invention However, such NC control in which an abnormality is determined according to the magnitude of the deviation cannot be applied to a robot in which a follow-up delay tends to occur and a deviation tends to be excessive, such as a press-fit robot. There was a problem. It should be noted that it is applicable if the abnormality determination is not performed, but it is troublesome to change the program and the like, and as described above, the movable part may suddenly start moving at an excessive speed.

The present invention has been made in view of the above circumstances, and its purpose is to apply NC control in which an abnormality is determined according to the magnitude of a deviation, to a press-fit robot in which a tracking delay is likely to occur. Is to do so.

Means for Solving the Problems In order to achieve such an object, the present invention detects a current position of a press-fit head linearly moved by a servomotor, and performs a constant control cycle time based on a predetermined moving speed. NC control of a press-fitting robot that sequentially updates a target position while operating the servomotor at a speed corresponding to a deviation between the target position and the current position to cause the press-fit head to follow the sequentially updated target position. In the method, when the deviation between the target position and the current position is equal to or more than a predetermined value, updating of the target position is stopped, and the deviation from the current position is obtained while the previous target position is maintained, and the servo motor is operated. It is characterized by the following.

In the NC control method for such a press-fit robot, when the deviation between the target position and the current position exceeds a certain value, the update of the target position is stopped, and the current position is maintained with the previous target position. The deviation between the target position and the current position does not become excessive even if the follow-up delay of the press-fit head becomes excessive, thus eliminating the cause of the follow-up delay. In such a case, there is no possibility that the press-fit head suddenly starts to move at an excessive speed.

In addition, since the deviation does not become excessive even if the tracking delay occurs, the tracking delay is likely to occur using the normal NC control program that performs the abnormality determination based on the magnitude of the deviation as it is. Even if the press-fit robot is NC controlled,
There is no need to develop a new control program that does not stop operation due to abnormality determination and does not perform abnormality determination based on deviation.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a configuration diagram illustrating an example of a press-fit robot controlled according to the method of the present invention. When a Z-axis servomotor 10 drives a ball screw 12 to rotate in both forward and reverse directions, the ball screw 12 is screwed. Slide unit combined
14 is reciprocated vertically while being guided by a guide (not shown). The press-fit head is attached to the slide unit 14, and is configured to perform a work of assembling fitting parts when the slide unit 14 is linearly moved downward.

The Z-axis servomotor 10 is operated in accordance with a drive pulse signal DM supplied from a control computer 16 to a servo amplifier 18, and the Z-axis servomotor 10 is provided with an encoder 20 and a position indicating the position of the slide unit 14. Signal SX is controlled by computer via servo amplifier 18
Supplied to 16. The control computer 16 is also set in advance with data on the moving speed V and the moving amount D of the slide unit 14 from the setting device 22.
The moving speed V and the moving amount D are determined by the user according to the work performed by the press-fitting robot, such as the work of assembling fitting parts.

The control computer 16 includes a CPU 24, a ROM 26, and a RAM 28.
The CPU 24 performs signal processing according to a program stored in the ROM 26 in advance while utilizing the temporary storage function of the RAM 28, and for example, as shown in the flowchart of FIG. NC control of operation. The NC control shown in FIG. 2 is executed at a predetermined constant control cycle time T, for example, every 0.4 ms. The control computer 16 is provided with a clocking clock signal source (not shown). Provided.

Hereinafter, the operation of this embodiment will be described with reference to the flowchart of FIG.

First, in step S1, the current position of the slide unit 14 obtained by integrating the pulses of the position signal SX is input.
In S2, it is determined whether or not the command speed V ^* in the previous control cycle is higher than the constant value 1.5V, that is, 1.5 times the moving speed V set by the setting unit 22. If the previous command speed V ^* is less than the fixed value 1.5V,
After the Δ value is added to the target position in S3, step S4
Is executed, but if the previous command speed V ^* is larger than the fixed value 1.5V, step S4 is immediately executed without executing step S3.

The Δ value in step S3 represents the amount of movement for each control cycle time T in the case of moving the slide unit 14 at the moving speed V set by the setting device 22 in terms of the number of pulses. Required in advance. That is,
This step S3 is a step of updating the target position every control cycle time T, and the previous command speed V ^* is set to a constant value 1.
When it is larger than 5V, step S4 is executed without updating the target position.

Δ value = V · T (1) In step S4, a deviation is obtained by subtracting the current position from the target position. In the subsequent step S5, the deviation is multiplied by a gain K to obtain the command speed V. ^* Is calculated. Then, a drive pulse signal DM for operating the Z-axis servomotor 10 so that the slide unit 14 is moved at the command speed V ^* is output in the next step S6.

Therefore, in such NC control, when the movement of the slide unit 14 is slow, the deviation increases and the command speed V ^* is increased ^.
And the Z-axis servomotor 10 is operated so as to speed up the movement of the slide unit 14. On the other hand, when the movement of the slide unit 14 is fastened, the deviation decreases and the command speed V ^* is decreased, and the speed of the slide unit 14 is reduced. The Z-axis servomotor 10 is operated so as to slow down the movement. And
Change in deviation, ie, set moving speed V and slide unit
When the movement speed of 14 is balanced, slide unit 14
Is made to follow the target position with a certain deviation from the target position. This constant deviation is determined in step S5.
Is determined by the value of the gain K.

Also, in the operation of assembling the fitting parts, even if the movement of the slide unit 14 is hindered by press-fit resistance or the like, and the deviation between the target position and the current position increases and the command speed V ^* is increased, the slide unit 14 does not move. Cannot be moved at the command speed V ^* , the deviation further increases and the command speed V ^*
In the present embodiment, when the command speed V ^* exceeds the fixed value 1.5V, the determination in step S2 becomes YES, and step S4 is executed without updating the target position in step S3, and the previous The deviation from the current position is calculated while keeping the target position in the control cycle. For this reason, the deviation between the target position and the current position and the command speed V ^* do not increase any more, and for example, when the fitting failure at the time of press-fitting is eliminated, the slide unit 14 may suddenly start moving at an excessive speed. Absent.

Note that the command speed V ^* is obtained by multiplying the deviation by the gain K as is apparent from step S5, and is proportional to the deviation. In step S2, the deviation between the target position and the current position is equal to or more than a certain value. It is substantially the same as judging whether or not. Also, when the command speed V ^* becomes a fixed value of 1.5 V or less,
Update of the target position in step S3 is resumed, and the normal
NC control is performed.

On the other hand, since the deviation does not become excessive even if the following delay of the slide unit 14 occurs as described above, a normal NC control program that performs an abnormality determination based on the magnitude of the deviation is used. Even if the press-fit robot, which tends to cause a tracking delay, is used as it is, the operation is not stopped by the abnormality determination, and there is no need to newly develop a control program that does not perform the abnormality determination based on the deviation.
The fixed value of 1.5 V in step S2 is determined so that an abnormality determination based on at least the deviation is not made.

In the present embodiment, a normal NC control program including a program related to abnormality determination based on the deviation is employed. In the flowchart of FIG. 2 for NC controlling the operation of the Z-axis servo motor 10, step S2 is performed. It is only added. However, even if a predetermined period of time elapses after the start of the movement of the slide unit 14, the slide unit
If the target point 14 does not reach the target point moved by the set movement amount D, abnormality determination is made and emergency stop of the robot, abnormality display, and the like are performed.

As described above, the NC control robot of this embodiment has the command speed V
^{If *} exceeds a fixed value of 1.5 V, updating of the target position is stopped,
Since the deviation from the current position is calculated while keeping the target position in the previous control cycle, the deviation and the command speed V ^* are calculated ^.
Is no longer increased, and there is no danger that the slide unit 14 will suddenly start moving at an excessive speed.Furthermore, a follow-up delay will occur using the normal NC control program that performs abnormality determination based on deviation. This makes it possible to perform NC control on the press-fitting robot that is easy.

As mentioned above, although one Example of this invention was described in detail based on drawing, this invention can be implemented in another aspect.

For example, in the above embodiment, the moving speed V and the moving amount D of the slide unit 14 are set in advance, and the command speed V ^* is also the moving speed of the slide unit 14, but is set by the rotation speed and the rotation amount of the Z-axis servomotor 10. Alternatively, the command speed V ^* may be determined as the rotation speed of the Z-axis servo motor 10.

Further, in the above-described embodiment, a normal NC control program in which an abnormality is determined based on the deviation is employed, but a new control program or the like which does not perform the abnormality determination based on the deviation may be used.

In the above embodiment, the update of the target position is stopped when the command speed V ^* is larger than the fixed value 1.5V. However, the fixed value 1.5V of 1.5 can be changed as appropriate and the set moving speed V Irrespective of the threshold value, a constant value may be set in advance, and the determination in step S2 may be performed based on the deviation obtained in step S4.

Further, in the above-described embodiment, when the slide unit 14 does not reach the target point moved by the set movement amount D even after a predetermined period of time has elapsed after the start of the movement of the slide unit 14, the abnormality determination is performed. However, other abnormality determination methods are used, such as performing an abnormality determination when the stop state of the slide unit 14 continues for a certain period of time or more, or when the YES determination in step S2 is repeated a certain number of times. You can also.

Further, in the embodiment command speed V ^* is in the control computer 16 prompts, the driving pulse signal DM corresponding to the command speed V ^* is to be outputted to the servo amplifier 18, a part of It can also be performed by a servo mechanism composed of a hard logic circuit. For example, a drive pulse signal having the number of pulses corresponding to the Δ value is output from the control computer 16 to the servo mechanism every control cycle time T, and the number of pulses of the pulse signal and the number of pulses of the position signal SX in the servo mechanism. Alternatively, the Z-axis servomotor 10 may be operated at a speed corresponding to the difference. In this case, as shown in FIG. 3, for example, when the deviation obtained in step S4 is larger than a fixed value of 1.5 V / K, the output of the driving pulse signal of the number of pulses corresponding to the Δ value is output. It should be canceled.

Although not specifically exemplified, the present invention can be implemented in various modified and improved modes based on the knowledge of those skilled in the art.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating an example of a press-fitting robot in which the method of the present invention is suitably performed. FIG. 2 is a flowchart for explaining the operation of the press-fit robot of FIG. FIG. 3 is a flowchart for explaining another embodiment of the present invention. 10: Z-axis servo motor 14: Slide unit (press-fit head) 16: Control computer

Claims (1)

(57) [Claims] 1. A method for detecting a current position of a press-fit head linearly moved by a servomotor, and sequentially updating the target position with a predetermined control cycle time based on a predetermined moving speed, while simultaneously updating the target position and the current position. In the NC control method of the press-fitting robot that operates the servomotor at a speed corresponding to the deviation from the position to cause the press-fit head to follow the sequentially updated target position, the deviation between the target position and the current position is An NC control method for a press-fit robot, wherein the updating of the target position is stopped when the value is equal to or more than a certain value, and the servomotor is operated by obtaining a deviation from the current position while maintaining the previous target position.