JPH0763226B2 - Synchronous control device - Google Patents

Description

Description: “Industrial field of use” The present invention relates to a synchronous control device for controlling the rotational positions of two shafts by electrically synchronizing them. INDUSTRIAL APPLICABILITY The present device is applied to, for example, a pin grinder that grinds a crankshaft of an engine, for synchronous control of two main shafts that respectively support and rotate both shaft ends of a crankshaft that is a workpiece.

"Prior Art" Conventionally, in this type of pin grinder, the left and right main shafts that support the workpiece are mechanically connected by a synchronous shaft to rotate synchronously.

Further, there is a device in which two axes that are mechanically separated are driven by a servo motor equipped with a position detector, and are electrically synchronized by using a servo technique. In principle, the same command signal should be given to the servo motor drive circuits for the two axes,
The command signal for one axis (slave axis) is corrected in accordance with the amount of deviation between the two axes. A conventional synchronous control device of this type calculates a correction value corresponding to the amount of synchronization deviation at that time every time a command signal is given to the drive circuit, and gives a correction to the command signal.

[Problems to be Solved by the Invention] However, the mechanical connection causes transmission loss of the gear system and the like, the driving force of the two shafts does not occur similarly, and the gear system backlash and the like occur. As a result, complete synchronization control could not be performed. For this reason, there is a problem that there is a limit in the accuracy of processing dimensions, surface orientation, etc. when used for the left and right spindles of a pin grinder. Further, since the mechanical connection mechanism must be built in, there is a problem that the rigidity of the table of the machine body cannot be sufficiently high.

Further, the electrically synchronized type has a problem that two servo motors may interfere with each other and become unstable when they are used for the left and right main spindles of the pin grinder.
This is because by fixing the workpiece to the main spindle, the left and right main spindles are connected and the two servo motors are connected to each other, so that the driving force of one servo motor is applied to the other and they interfere with one another There is a problem in that the hunting phenomenon of the axis fluctuates and the hunting phenomenon of the axis continues for a relatively long time.

Further, when the correction value for correcting the command signal to the servo motor drive circuit is a correction value calculated based only on the synchronization deviation amount of the two axes detected each time, the synchronization deviation amount is completely zero. There was a problem that it was difficult.
It is considered that this is due to a subtle difference in rigidity of the biaxial servo motor.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a synchronization control device that enables highly accurate synchronization control with a small amount of synchronization deviation and that operates stably. Especially.

[Means for Solving the Problems] In order to achieve the above object, in the present invention, as shown in FIG. 1, servomotors 20 and 21 respectively driving mechanically independent two axes, and the two axes are provided. Position detectors 22 and 23 for respectively detecting the positions of the servomotors, drive circuits 42 and 44 for driving the servomotors 20 and 21 in accordance with the respective command signals, and 2
And a correction means 1 for making a command signal given to a drive circuit 42 for one axis (master axis) of one axis a correction value as a command signal for a drive circuit for the other axis (slave axis). In the above, a correction addition value calculation means 2 for calculating a correction addition value to be added to the command value based on the deviation amount of the position signals from the two position detectors 22 and 23, and the calculated correction addition value and a predetermined value A correction addition limiting means 3 that compares the allowable value with the smaller absolute value to obtain the final correction addition value, and a correction value calculation means 4 that adds the final correction addition value to the previous correction value to obtain the current correction value. And a tolerance value setting means 5 for setting the predetermined tolerance value, and a synchronization control device is provided.

[Operation] In the synchronization control device configured as described above, the correction value for correcting the synchronization deviation is a value obtained by accumulating the correction addition values. The first correction value is the correction addition value itself calculated from the shift amount of the position signal. If the synchronization deviation amount does not become 0 by the first correction and the synchronization deviation remains, the correction addition value calculated from the remaining synchronization deviation amount is added to the previous correction value and the next correction value. To be done. There are various factors such as machine stiffness and servo rigidity that may cause the synchronization deviation to remain without being corrected by one correction. The correction values are successively accumulated, and the synchronization deviation tends to converge to zero regardless of the cause. It should be noted that the correction addition value can take either positive or negative values, and depending on its sign, it also acts to reduce the excessive correction value.

Further, since the maximum absolute value of the correction addition value is limited to within the predetermined allowable value, abrupt fluctuation of the correction value is suppressed and the stability of the synchronization control is enhanced.

[Examples] Examples of the present invention will be described with reference to the drawings.

FIG. 2 is a configuration diagram showing a cylindrical grinding machine provided with a synchronous control device according to the present invention. This cylindrical grinder is a pin grinder for machining the crankshaft of an engine, and is used for grinding and finishing the pin portion of the crankshaft.

In front of the bed 10 of the grinder, there is a table 11 in the left-right direction (Z
It is slidable in the axial direction) and is moved via a feed screw 13 by a servomotor 12 attached to the side surface of the bed 10. On the table 11, a pair of left and right headstocks 14, 15 are arranged. Spindles 18 and 19 equipped with eccentric chuck devices 16 and 17 are mounted on the respective spindle stocks 14 and 15, and are rotatably driven by spindle motors 20 and 21, which are servo motors, respectively. Rotation encoders 22 and 23 are attached to the respective spindle motors 20 and 21 to detect the rotational positions of the spindles 18 and 19. The crankshaft of the engine, which is the workpiece W, is held by the eccentric chucks 16 and 17 of the left and right main shafts 18 and 19 at the journal end of the shaft end, and is rotationally driven about the pin portion to be ground. The left main shaft 18 serves as a master shaft, the right main shaft 19 serves as a slave shaft, and the right main shaft motor 21 follows the rotation of the left main shaft motor 20 and is rotationally driven as if it were one shaft.

On the other hand, behind the bed 10, a grindstone 25 is guided so as to be movable in a direction (X-axis direction) orthogonal to the rotation axis of the main shaft 18, and a servo motor 26 fixed to the rear surface of the bed 10 feeds it through a feed screw 27. It is supposed to be moved. Whetstone stand
A grinding wheel G is mounted on 25 in parallel with the axis of the main shaft 18, and is rotationally driven by a grinding wheel driving motor 28.

A rest device 30 is provided in front of the bed 10 at a position facing the grinding wheel G. Contact 31 of rest device 30
Is movable in the direction toward the grinding wheel G (I-axis direction), and is moved forward and backward by the servomotor 32. The contact 31 of the rest device 30 is pressed against the grinding surface of the workpiece W to stop the swing of the workpiece W.

Servomotors 12, 26, 32 for each axis and left and right spindle motors 20, 21
Is connected to each servo motor drive rotation 41-45,
It is rotated according to a command signal from the numerical control device (NC device) 50.

The numerical controller 50 is a main CPU 5 for controlling the grinder.
1, ROM 52 for storing control programs, RAM 53 for storing NC data, etc. are provided, and signals from tape reader 61, CRT display 62, keyboard 63, operation panel 64 are interface 54
Be entered via. The numerical controller 50 includes a drive CPU 56 for servo control in addition to the main CPU 51, and the drive C
It is connected to the main CPU 51 via the RAM 57 of the PU 56. Further, the drive CPU 56 receives signals from the rotary encoders 22 and 23 for detecting the rotational positions of the spindles 18 and 19 as an interface 55.
Be entered via. The drive CPU 56 outputs a command signal to each of the servo motor drive circuits 41 to 45 via the D / A conversion circuit 58.

In the present embodiment, the correction means 1 for correcting the command signal given to the drive circuit 44 of the slave axis (right spindle) 19, the correction addition calculation means 2 for calculating the correction addition value from the deviation amount of the position signal,
The correction addition value limiting means 3 for limiting the maximum correction addition value and the correction value calculating means 4 for calculating the current correction value from the correction addition value are realized as the processing of the drive CPU 56. Also, the predetermined allowable value that determines the maximum value of the correction addition value is set from the keyboard 63, and the main CPU 51 drives the drive CPU 56
It is set and stored in the RAM 57 for use. Here the keyboard 63
Constitutes the allowable value setting means 5.

FIG. 3 is a flowchart showing the processing in the drive CPU 56 that realizes the synchronous control.

This synchronization process is repeatedly executed, for example, every 10 ms.
When the synchronous control process (step 100) is started, the command value is read (step 101) and the position signals from the position detectors (rotary encoders) 22 and 23 are read (step 1).
02). Then, the respective positional deviations of the left main spindle 18 forming the master axis and the right main spindle 19 forming the slave axis are calculated (steps 103 and 104). Next, a correction value for correcting the amount of synchronization deviation between the left spindle 18 and the right spindle 19 is calculated (step 10
Five).

In step 106, the correction value calculated above is added to the command value to correct the command value given to the drive circuit 44 that rotationally drives the right main shaft motor 21 (slave shaft). The processing of step 106 constitutes the correction means 1. Then, in step 107, the original command value (command value before adding the correction value) is output to the drive circuit 42 of the left spindle motor 20 (master axis) via the D / A converter 58, and in step 108. The corrected command value is applied to the drive circuit 44 of the right main spindle motor 21 (slave axis) by the D / A converter 58.
Output via. The process shown in FIG. 3 is generally performed in synchronous control, and is the same as the conventional process. The present embodiment is characterized by the correction value calculation processing in step 105.

FIG. 4 is a flow chart showing details of the correction value calculation processing 105. In this correction value calculation process, the current correction value is calculated by adding the correction addition value calculated from the synchronization deviation amount to the previous correction value. That is, step 10
From the position signals from the position detectors (rotary encoders) 22 and 23 read in 2, the amount of synchronization deviation between the left spindle 18 and the right spindle 19 is calculated (step 202). Then, the correction addition value is calculated according to the amount of synchronization deviation (step 203). The correction addition value is, for example, a value calculated by multiplying the synchronization deviation amount by a predetermined coefficient, and can take any positive or negative value. Step 202
The processing of 203 and 203 constitutes the corrected addition value calculating means 2.

In step 204, the magnitude of the absolute value between the calculated correction addition value and the predetermined allowable value is compared. The predetermined allowable value is a value preset in the RAM 57 by the main CPU 51 from the keyboard 63, and is a value indicating an allowable maximum value of fluctuation of the correction value. If the calculated correction addition value is larger than the allowable value, the limit is exceeded, so the process proceeds to step 205, and the value of the correction addition value is replaced with a predetermined allowable value instead of the calculated value, and the final correction addition is performed. The value. On the other hand, if the calculated correction addition value is smaller than the predetermined allowable value, nothing is executed and the process proceeds from step 204 to step 206, and the calculated correction addition value is set as the final correction addition value. I.e. step
The processing of 204 and 205 constitutes the correction addition value limiting means 3 for limiting the value of the final correction addition value.

In step 206, the final correction addition value is added to the previous correction value to obtain a new correction value. Step 206 constitutes the correction value calculation means 4. The correction value calculated in this way is used by the snap 106 shown in FIG. 3 to correct the command value given to the drive circuit 44, and the left and right spindles 18, 19 are synchronized.

5 (a) and 5 (b) are waveform charts showing changes in the synchronization deviation amount and the correction value due to the above-described processing. The correction value for correcting the amount of synchronization deviation is updated every predetermined period.

At first, it is assumed that the correction value is 0 and the amount of synchronization deviation is as large as A ₀ . The final correction value D ₀ calculated in step 203 from this synchronization deviation amount A ₀ becomes large. But step 20
By the processing of 4,205, the final correction addition value is limited to the allowable value L ₀ , and the final correction value C ₀ becomes the allowable value L ₀ . This correction value C ₀ reduces the amount of synchronization deviation from A ₀ to A ₁ . However, It should be noted that the correction added value is calculated from the synchronization deviation amount A ₁ B ₁
Is large and the allowable value L ₀ is adopted as the final correction addition value for the second time, and the value obtained by adding the allowable value L ₀ to the previous correction value C ₀ is set as the current correction value C ₁ . With this correction value C _{1, the} amount of synchronization deviation is
Further decrease from A ₁ to A ₂ .

In the third correction, since the correction addition value B ₂ calculated from the synchronization deviation amount A ₂ is smaller than the allowable value L ₀ , it is used as it is as the final correction addition value, and the previous correction value C _{1 is set} to the current correction value C ₁ . The value obtained by adding the correction addition value B ₂ is the correction value C _{2 of} this time. That is, C ₂ = C ₁ + B ₂ .

In this way, the correction addition value B ₂ is integrated and the correction value C _{2 at} that time is calculated. For example, the correction value C ₂ is C ₂ = D ₀
= (L ₀ + L ₀ + B ₂ ). Since the correction value C ₀ -C correction addition value is ₂ B _1, B ₂ are integrated successively until synchronization shift is 0, the correction value C ₀ -C ₂ converges to a value that the synchronization error to zero . If the correction values C _{0 to} C ₂ are excessive, they are adjusted by the negative correction addition value.

By enabling the correction value C ₂ as shown in this drawing, it becomes possible to eliminate the residual synchronization deviation due to various factors such as machine stiffness and servo rigidity, thereby improving the synchronization accuracy.

Further, in the present embodiment, since the maximum value of the fluctuation of the correction values C _{0 to} C ₂ is limited within the allowable value L ₀ , the correction is gradually performed even when a large synchronization deviation occurs, and the spindle Do not give excessive disturbance to the motor 21. Therefore, the stability of the synchronous control is enhanced, hunting of the spindle motors 20 and 21 is prevented, damage to the spindle motors 20 and 21 and damage to the work W are prevented.

In the embodiments described above, the synchronous control of the left and right spindles of the cylindrical grinder that performs pin grinding has been described as an example. However, the present invention allows the grindstone and the workpiece to rotate synchronously in a gear grinder, a cam grinder, or the like. It is obvious that it can also be applied to the synchronous control of a machine for machining, in which the synchronous control axes are not mechanically coupled to each other.

[Advantages of the Invention] Since the present invention has the above-mentioned configuration and uses the value obtained by integrating the correction addition value as the correction value for the cycle control, the existence of various factors such as servo rigidity that causes the residual synchronization deviation. However, there is an effect that the synchronization deviation amount can be made extremely small and the synchronization accuracy is improved. Further, since the correction addition value limiting unit suppresses a rapid change in the correction value, the stability of the synchronization control is improved.

[Brief description of drawings]

The drawings show an embodiment of the present invention, FIG. 1 is a block diagram showing the constitution of the present invention, FIG. 2 is a constitutional view showing a cylindrical grinder, and FIG.
FIG. 4 and FIG. 4 are flow charts showing processing in the drive CPU, and FIGS. 5 (a) and 5 (b) are waveform charts showing changes in synchronization deviation amount and correction value due to correction. 1 ... correction means, 2 ... correction addition value calculation means, 3 ... correction addition value limiting means, 4 ... correction value calculation means, 18 ... left spindle (master axis), 19 ... right spindle (slave axis) ), 20,21
...... Spindle motor (servo motor), 22,23 …… Rotary encoder (position detector), 42,44 …… Drive circuit, 50 …… Numerical control device, 56 …… Drive CPU, 58 …… D / A conversion Bowl, 63
…… Keyboard (allowable value setting means).

Claims (1)

[Claims] 1. A servomotor that drives mechanically independent two axes, a position detector that detects the position of each of the two axes, and a drive circuit that drives each servomotor according to a respective command signal. A command signal given to the drive circuit of one of the two axes (master axis) and a correction value is added to the other axis (slave axis)
And a correction unit that uses the drive circuit as a command signal, and a correction addition value calculation unit that calculates a correction addition value to be added to the command value from the deviation amount of the position signals from the two position detectors. And a correction addition value limiting unit that compares the calculated correction addition value with a predetermined allowable value and uses the smaller absolute value as the final correction addition value, and adds the final correction addition value to the previous correction value. A synchronization control device, comprising: a correction value calculation means for setting a current correction value, and an allowance value setting means for setting the predetermined allowance value.