JPH06250713A - Feed controller - Google Patents

Abstract

PURPOSE:To perform correction so that the start position of next operation is securely kept by commanding feeding operation in two stages wherein a feed speed is switched from high to low so that a return to the start position of following operation is made after reverse fast forwarding. CONSTITUTION:A feed mechanism D is forwarded fast by a reverse fast forwarding means E to a 1st command position P1 in the opposite direction from next operation before the next operation when it is confirmed that current operation reaches a target position X1. Then a return correcting means F returns the feed mechanism D at an intermediate speed from the 1st command position P1 to a 2nd command position P2 in the same direction as the feed direction of the next operation and then sends it at a low speed to the start position of the next operation matching the target position X1 of the current position. Namely, a uniaxial feed mechanism D, for example, is overfed to beyond the start position X2 of the next operation to the position P1 which deviates by a feed quantity x1 larger than a backlash error DELTAL, and then makes an approach at the intermediate speed in the next feed direction and further approaches the start position P2 of the next operation at the low speed, so the feed mechanism D can be stopped accurately at the target position.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a feed control device for controlling the feed speed and feed amount of a feed mechanism in a numerically controlled machine tool, and more particularly, to accurately perform backlash correction.

[0002]

2. Description of the Related Art Generally, in a numerically controlled machine tool, a headstock for supporting a workpiece and a tool stand on which a tool is mounted are configured to be relatively movable by a feed mechanism including a combination of ball screws and nuts. A motor that drives the ball screw,
An absolute position detector that detects the absolute position from the rotation amount of the motor is provided, and the deviation amount between the current position signal output from the absolute position detector and the target position and the feed speed are calculated by a microcomputer or the like. It is designed to be instructed by a numerical control device composed of an integrated circuit. The numerical control for instructing the feed amount and the feed speed of the feed mechanism has a backlash correction function for correcting an error (backlash, lost motion, steady deviation, etc.) due to mechanical loss of the feed mechanism.

The backlash compensation function is a backlash amount ΔL, which is the amount of feed stagnation due to backlash of the ball screw (backlash) or elastic deformation of each element when the direction of advance of feed is reversed. By setting, each time the advancing direction of the feed is reversed, it is moved by ΔL. More specifically, in this type of feed control device, the reference pulse from the pulse generator synchronized with the rotation of the main shaft is distributed to each feed shaft.
As shown in (A) and (B), during distribution in which the feed direction is reversed (time t ₀ ), the pulse number N corresponding to ΔL is added to the first period. The horizontal axes of FIGS. 7A and 7B represent time, the vertical axis of FIG. 7B represents speed (positive and negative are feed directions), and the vertical axis of FIG. 7A is distribution pulse. Represents a number. When backlash correction is not performed,
As shown by the dotted line in (A), no correction pulse is added.

The conventional backlash correction is as described above.
The number of distributed pulses is added when the feed direction is reversed.

[0005]

However, in the above-mentioned conventional backlash correction, since the number of pulses is added, the feed speed due to the correction is increased, and an error may occur in the feed amount after reverse rotation. Further, the conventional backlash correction is performed only when the feed is reversed. However, even if only a single feed with a constant direction is used and the feed speed is high, as shown in FIG. Even if the ball screw itself stops, the tool base or the headstock does not stop at the target position X, and there is a risk that the ball screw excessively moves by the backlash and a feed error occurs. In FIG. 8, the horizontal axis represents time and the vertical axis represents tool displacement.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a feed control device for performing correction for surely keeping the starting position of the next operation.

[0007]

In order to solve the above problems, the feed control device of the present invention, as shown in FIG. 1, includes a servo unit B for controlling the operation of the feed mechanism D, and a servo unit B for controlling the operation of the feed mechanism D. The absolute position detecting means C for detecting the absolute position of the feed controlled feed mechanism D and the target position and speed for each feed operation of the feed mechanism D to the servo unit B are used for the next operation. Prior to commanding the target position and speed, the backward fast-forwarding means E for issuing a feed command at a fast-forward speed in a direction opposite to the feed direction of the next operation from the start position of the next operation which coincides with the target position of the current operation, After execution of the backward fast-forwarding means E, a numerical control means A having a return correcting means F for performing a two-step feed command for switching the feeding speed from high to low so as to return to the starting position of the next operation. To have. The present invention can be applied not only to the single feed mode in which the direction is stopped at the target position but the feed direction in which the feed direction is reversed.

[0008]

According to the present feed control device, the feed mechanism D is configured as shown in FIG.
As shown in (4), when it is confirmed that the current operation reaches the target position X ₁ (however, the arrival at the target position x ₁ includes the backlash error ΔL), the next operation is performed before the next operation. The reverse fast-forwarding means E fast-forwards in the opposite direction to the first command position P ₁ . Then, by the return correcting means F, the feed mechanism D is returned from the first command position P ₁ to the second command position P ₂ at a medium speed in the same direction as the feed direction of the next operation, and then, At a low speed, it is sent to the starting position X ₂ of the next operation that logically matches the target position X ₁ of the current operation. That is, for example, in the case of the uniaxial feed mechanism D, the backlash error ΔL is exceeded by exceeding the starting position X ₂ of the next operation that should be originally stopped.
Larger predetermined feed amount x ₁ Deviated first command position P ₁
It is over-fed to reach the starting position P ₂ of the next operation from the same position P _{1 in the} same direction as the feeding direction of the next feeding operation at a medium speed as an approach. Such feed control does not add pulses for backlash, but stops slightly before the starting position X ₂ of the next operation, and at a low speed up to the starting position X ₂ without overshooting or swinging back. Since they are extremely close to each other, the feed mechanism D can be accurately stopped at the target position. The amount of movement from the final second command position to the target position is several times the steady deviation (several + pulses) in consideration of the steady deviation that is the difference between the feed command amount and the actual displacement. is there.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the feed control device according to the present invention will be described in detail below with reference to FIGS. In FIG. 3, the same elements as those of the configuration described in FIG. The feed mechanism D is a combination of a ball screw 11a and a ball nut 11b. The ball nut 11b is attached with a moving base 10 for moving a tool or a work piece on one axis, and the ball screw 11a is rotated by a drive motor 9. It is designed to be driven.

A speed detector 12 is connected to the drive motor 9 to detect the rotation speed. The speed detection signal 12a of the speed detector 12 is fed back to the drive circuit 8 of the servo unit B. It is fed back as a signal. The drive circuit 8 includes the microprocessor 1
The feed command speed S1 from the numerical control means A mainly composed of is supplied via the register 5 and the D / A converter 7 which constitute the servo unit B.

Further, the drive motor 9 is connected to a two-stage coupled first stage resolver 13 which constitutes an absolute position detecting means C, and the first stage resolver 13 is coupled to a rear stage resolver 15 via a speed reducer 14. Has been done. Each resolver 1
The outputs of 3 and 15 are phase-compared with the excitation signals from the resolver excitation circuit 16 by the first and second phase comparison circuits 17 and 18, respectively, and the phase output from each resolver 13 and 15 indicates the rotation angle of the drive motor 9. The digital signals are output from the first and second phase comparison circuits 17 and 18. These first and second phase comparison circuits 1
The outputs of 7 and 18 are input to the absolute position calculation circuit 19. The absolute position calculation circuit 19 converts the outputs from the first and second phase comparison circuits 17 and 18 into a signal 19a indicating the absolute position with reference to the mechanical origin of the feed mechanism D,
This absolute position signal 19a is interrupt signal S in real time.
It is adapted to be sent to the numerical control means A in synchronization with 2.

The numerical control means A comprises a microprocessor 1, a data input device 3 connected to the microprocessor 1, a program ROM 2 and a work RAM 4. The data input device 3 is, for example, an operation keyboard, and can change the contents of the RAM 4 or the like. A program for controlling the operation of the servo unit B, particularly the feed operation, is written in the program ROM 2. R
The AM4 has a register for setting an auxiliary function flag M for instructing the exchange of tools and workpieces, a flag setting register for performing backlash correction during the feed operation according to the present invention, a target position for the feed operation, and a command. A register for writing speed and a register for writing current position are included.

The microprocessor 1 of the numerical control means A is bidirectionally connected to the sequence controller 6. The sequence controller 6 has a memory means 6a such as a tape and performs sequential control of the feeding mechanism D. In the above configuration, the ROM 2 of the numerical control means A
The program shown in the flow charts of FIGS. 4 to 6 is written in. The operation of the present feed control device will be described below based on the above flow chart.

FIG. 4 shows a main routine executed by the numerical control means A for one sequence command, FIG. 5 shows a feed control routine in the main routine, and FIG. 6 shows a backlash correction routine in the feed control routine. Show. In FIG. 4, when the I-th data block is read by steps 100 and 110 [data block read], step 120 [data end? ], It is judged whether or not the code of the data indicates G9 (data end), and then step 130 [preparation processing of feed mechanism? ] To determine whether the code is G0 or G1. Code G
0 and G1 are processes for bringing the feed mechanism D into a ready state (for example, positioning to a reference position for machining) before actual machining, and for other codes, other processes 200 (for example, spindle control). ) To jump to. The code G0 is a preparation code when the backlash correction according to the present embodiment is not performed, and the code G1 is a preparation code for performing the backlash correction. The reason for providing the mode that does this backlash correction and the mode that does not do even with the same preparation code is
As will be described later, this backlash correction involves retrograde movement,
This is because the backward movement cannot be performed while the tool is in contact with the workpiece. Further, the feed by the code G1 has a low feed speed for machining the workpiece,
There is no need to worry about backlash.

Subsequent step 140 [code G1? ], It is determined whether or not it is a preparation code for performing this backlash correction, and if it is determined to be a G1 code in step 140, a BR flag indicating that backlash correction according to the present embodiment is performed in step 210 [BR flag ON]. Is set and the process proceeds to step 150 [forwarding command]. If the code G0 or other preparation code is used in step 140, the BR flag is not set and the process proceeds to step 150.

In step 150, the target position X and the command speed V for its feed are set. The target position and the feed command speed V are previously input to the RAM 4 by the data input device. After the feed command in step 150, step 160 [feed control] shown in FIG. 5 is performed. Step 160
Is a process of feeding the feed mechanism D to the target position X, as will be described in detail later, and the present invention performs the backlash correction shown in FIG. 6 when stopping at the target position X. After step 160, step 180 [BR flag check] is performed. If the BR flag is set, the flag is turned off (step 220). If the BR flag is not set, the next data block is read as it is. The same main routine is repeated after the processing (step 190) of issuing. One operation of the feeding mechanism is executed for each main routine.

In step 160 [feed control], the feed mechanism D is fed from the starting position to the target position X by calculation by the routine of steps 161-164, 168.
Step 164 in the routine [Are the target position reached? ] From step 169 to step 171, the backlash correction according to the present embodiment is performed. That is, in the feed control step 160, first, steps 161-1
63 [actual remaining movement amount RL calculation], the remaining movement amount to the target position X at the present time is obtained. Step 161
Then, the current position R is read from the absolute position calculating means C, the target position X set in step 150 is read in step 162, and R is subtracted from X in step 163 to obtain the actual remaining movement amount RL.

After the calculation in step 163, the next step 1
If it is determined at 64 that the actual remaining movement amount RL is a finite value (NO), the feed mechanism D is feed controlled at the feed speed V stored in the speed register of the RAM 4. Step 164 above
During the loop of 168, if it is determined in step 164 that the target position X and the current position R match and the actual remaining movement amount RL is zero, the process jumps to step 169 [feed command speed zero setting] and the feed command speed is set to zero. To do.

When the feed command speed Vc is set to zero, the rotation of the motor 9 is stopped, the feeding by the ball screw 11a is completed, and the moving table 10 is moved to the absolute position detecting means C connected to the motor 9. It means that it has been positioned at the target position x ₁ . However, the actual position of the movable table 10 is the position (x ₁ +) including the backlash error ΔL due to the feed command speed V.
It stopped at ΔL). Then, in step 170 [B
R flag check] is executed to determine whether or not the BR flag is set. Then, if the BR flag is set, the actual backlash correction as described with reference to FIG. 2 is executed in step 171, and if the flag is not set, the process returns to step 110.

In the backlash correction of this embodiment, the arrival of the current feed operation at the target position X ₁ is confirmed in step 164 (however, confirmation on the absolute position detecting means C), and step 1
When the feed command speed V is set to zero in 69, step 1
72, 173 [reverse fast feed], the feed mechanism D is fast forwarded to the first command position P ₁ in the direction opposite to the direction of the next feed operation until the first command position P ₁ at the command speed Vc obtained in step 172 before the next feed operation. To do. In the calculation of step 172, x
₁ a first command position P ₁ from the target position X ₁ of the current feeding operation
Represents the distance to, and in this case, it is in the opposite direction to the direction of the next feeding operation, and is therefore given a minus sign. Also, this x ₁
Is an amount that can be sufficiently compensated by moving x ₂ and Δx even when the backlash ΔL is maximum.

After the reverse fast forward, steps 174, 1
75, 176 [medium speed return feed] is executed. The steps 174, 175 and 176 are processing for returning the feed mechanism D in the direction of the next feed operation at a medium speed from the _first command position P ₁ to the second command position P ₂ . In this case, step 174
While the process does not proceed to [computation of command speed Vc for reverse feed], the reverse feed command speed is output in step 173, and the feed mechanism D is in the reverse feed state. Then, in step 175, the command speed Vc for the backward feed is calculated, and when the command speed Vc is output in step 176, the feed mechanism D
Is fed back to the second command position P ₂ at medium speed.

In the next step 177, the feeding mechanism D is moved to the second
If it is determined that the movement has been completed to the command position P ₂ and the completion of the movement is determined, the minimum feed command speed V _min is output in step 178. As a result, the feeding mechanism D is fed at a low speed at which the backlash error ΔL does not occur at the starting position X ₂ of the next feeding operation that logically matches the target position X ₁ of the current feeding operation. In step 179, it is determined whether or not the starting position X ₂ of the next feeding operation has been reached. If it is determined that the starting position X ₂ has been reached, the process returns to step 110 and execution of the next feeding operation is performed.

As described above, this backlash correction is over-fed to the _first command position P ₁ deviating from the predetermined feed amount x ₁ beyond the starting position X ₂ of the next feed operation which should be originally stopped,
From the same position P _1, it approaches at the medium speed in the same direction as the feeding direction of the next feeding operation, and finally at the low speed, it extremely approaches the starting position X ₂ of the next feeding operation. Therefore, the backlash correction is stopped at a speed lower than the backward feed over position (first command position P ₁ ) and before the start position X ₂ of the next feed operation, and does not cause overshoot or swing back. Since the pulse is added very close to the starting position X ₂ and the pulse for backlash due to mechanical loss of the ball screw 11a and the ball nut 11b is not added, an error may be caused by increasing the feed rate by adding such a pulse. There is no.

In the above embodiment, the backlash correction is described in the case where the current command and the next command are in the opposite moving directions, but the backlash correction is also performed when the current command and the next command are in the same direction. Is performed, and in this case, the movement for backlash correction is performed in the direction opposite to the current command.

[0025]

As described above in detail, the feed control device of the present invention is designed to overrun the target position of the current feed operation before commanding the target position and speed for the feed of the next feed operation. Fast-forwards in the direction opposite to the direction of the next feed operation, feeds halfway at a medium speed to return to the target position of the current feed operation, and finally reaches the target position of the current operation at a low speed that does not cause overshoot or swing back. Since it is returned, no pulse is added when the direction is reversed and there is no cause of error, and it is possible to keep an accurate position at the starting position of the next feed operation.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing the present invention.

FIG. 2 is an operation explanatory diagram illustrating an operation of the present invention.

FIG. 3 is a configuration diagram showing a specific embodiment of the present invention.

FIG. 4 is a flowchart showing a main routine in which backlash correction of the present invention is performed.

FIG. 5 is a flowchart showing a feed control program according to the present invention.

FIG. 6 is a flowchart showing a program for backlash correction according to the present invention.

FIG. 7 is an explanatory diagram illustrating a conventional backlash correction.

FIG. 8 is an explanatory diagram illustrating backlash in a single-direction feed mode.

[Explanation of symbols]

A ... Numerical control means, B ... Servo unit, C ... Absolute position detection means, D ... Feed mechanism, 150 ... Feed command, 173 ...
Feed command at rapid feed speed, 176 ... Feed command at medium speed,
178 ... Feed command at low speed.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoichi Ito 1-1 Asahi-cho, Kariya city, Aichi Toyota Koki Co., Ltd. (72) Inventor Koji Tsuchiya 1-1-1 Asahi-cho, Kariya city, Aichi Toyota Koki Within the corporation

Claims (1)

[Claims] 1. A servo unit for controlling an operation of a grinding mechanism, an absolute position detecting means for detecting an absolute position of the feed mechanism feed-controlled by the servo unit, and a servo unit for each operation of the feed mechanism. And a numerical control means for instructing the target position and speed of the feed, the numerical control means prior to commanding the target position and speed for the next operation, the next operation that matches the target position of the current operation. From the starting position, the reverse fast-forwarding means for issuing a feed command at a fast-forwarding speed in the direction opposite to the feeding direction for the next operation, and the feed speed from the high speed for returning to the starting position for the next operation after the execution of this backward fast-forwarding means. A feed control device comprising return correction means for issuing a feed command for switching to a low level.