JPH0797916B2 - 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.

The present invention has been made in view of the above problems, and an object thereof is to prevent hunting operation of a shaft,
It is to provide a synchronous control device that operates stably.

[Means for Solving the Problems] In order to achieve the above object, in the present invention, as shown in FIG. 1, two servomotors 20 and 21 for respectively driving two mechanically independent axes, and Two position detectors 22 and 23 for respectively detecting the positions of the two axes, and the servo motors 2
0,21 drive circuits 42,44, respectively, by inputting to the drive circuits 42,44 the deviation between the command signal given to the servomotors 20,21 and the position signals from the position detectors 22,23. It has two feedback systems 5 and 6 for controlling the two servo motors 20 and 21 to predetermined rotations, respectively.
In a synchronous control device for synchronously rotating the two servo motors 20 and 21 in a state in which the shafts are coupled by a workpiece W, the synchronous control device according to the deviation amount of the position signals from the two position detectors 22 and 23. Correction value calculation means 2 for calculating a correction value to be added to the command signal given to the slave axis of the two axes;
Of the two axes, the correction means 1 uses a command signal given to the drive circuit of the master axis and the correction value as the command signal given to the drive circuit of the slave axis, and the feedback system 6 of the slave axis is unstable. Cycle time setting means 3 for setting a cycle time longer than time, and whether or not the cycle time set by the cycle time setting means 3 has elapsed from the time when the correction value was calculated by the correction value calculation means 2. And a cycle time counting means 4 for executing the correction value calculation means 2 only when the cycle time has elapsed.

[Operation] In the synchronous control device configured as described above, after the correction value is calculated, there is a quiescent period of a predetermined cycle time, and after the unstable state of the axis feedback system caused by the correction is converged, The next correction value is calculated and output. Therefore, when the axis feedback system is in an unstable state, a new correction value is not superimposed, and the axis feedback system is quickly stabilized.

Also, the predetermined cycle time for giving the correction pause time can be set according to the inertia value of the axis and the like.

[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 circuit 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 this embodiment, the correction means 1 for correcting the command signal to the drive circuit 44 of the slave axis (right spindle) 19, the correction value calculation means 2 for calculating and updating the correction value, and the correction value calculation means 2 are predetermined. The cycle time counting means 4 to be executed for each cycle time is realized as a process of the drive CPU 56. Further, a predetermined cycle time that determines the correction interval time is set from the keyboard 63, and is set and stored in the RAM 57 for the drive CPU 56 by the main CPU 51. Here, the keyboard 63 constitutes the cycle time setting means 3.

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

This synchronization control 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 102). 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
105).

In step 106, the correction value calculated as described above is added to the command value to make a correction to the command value to be given to the drive circuit 44. The processing of step 106 constitutes the correction means 1. And
In step 107, the original command 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 output to the right spindle motor 21.
Output to the (slave axis) drive circuit 44 via the D / A converter 58. 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 the correction value calculation process 105, the correction value is calculated and updated at predetermined time intervals. That is, in step 201, it is judged whether or not it is the timing of the cycle time for executing the correction calculation by checking the contents of the output cycle counter. The output cycle counter is a counter which is initialized by a value corresponding to a predetermined cycle time set in advance from the keyboard 63 and stored in the RAM 57 in the subsequent step 206. If the timing is not the timing of the cycle time, the process proceeds to step 210, the value of the output cycle counter is decremented by 1, and no other processing is performed. Waiting for the arrival of timing while executing step 210 one after another, and when the value of the output cycle counter becomes 0 and it is time to execute the correction calculation, the process proceeds from step 201 to step 203.
The processing of steps 201, 206 and 210 constitutes the cycle time counting means 4.

In the following, the amount of synchronization deviation between the left spindle 18 and the right spindle 19 is calculated from the position signals from the position detectors (rotary encoders) 22 and 23 read in step 102 (step 203). next,
A correction value is calculated and stored based on the synchronization deviation amount, and the previous correction value is updated (steps 204 and 205). The stored correction value is used in the correction processing in step 106. Then, since the calculation and update of the correction value have been completed, the value of the output cycle counter is initialized to leave a time interval until the next correction calculation (step 206). The values to be initialized are RAM from the keyboard 63 by the main CPU 51 in advance.
It is a value corresponding to the predetermined cycle time set to 57. The processing of steps 203 to 205 constitutes the correction value calculation means 2.

FIG. 5 is a waveform diagram showing a change in the amount of synchronization deviation by the above-mentioned processing. The correction value for correcting the amount of synchronization deviation is updated at the timing of each predetermined cycle time T ₀ set from the keyboard 63.
It is performed at t ₁ , t ₂ and t ₃ . When the correction value is updated, the time T _{1 in} a transiently unstable state occurs until the right spindle motor 21 that has been rotating at a constant speed settles to the amount of synchronization deviation corresponding to the new correction value. The unstable state of the feedback system of this axis does not occur only in the right spindle motor 21 on the slave axis side where the correction value is added to the command value. Left and right spindle 1
Since 8, 19 are mechanically coupled by the workpiece W, they interfere with each other and the left spindle motor 20 on the master axis side also vibrates. This transient vibration state is damped in a short time,
The axis feedback system shifts to a stable state.

In this embodiment, since the correction value is updated at every predetermined cycle time T ₀ longer than the time T ₁ during which the axis feedback system is unstable, the amount of synchronization deviation when the feedback system of the right spindle motor 21 is stable A correction value is calculated based on the following, and the next correction value is added. Therefore, the correction value is calculated by the amount of synchronization deviation within the time T ₁ when the feedback system of the right spindle motor 21 is unstable, or the left and right spindles are unstable within the unstable time T ₁ .
When 18, 19 is oscillatory and the feedback system is in an unstable state, no further correction value is added, hunting of the left and right spindles 18, 19 is prevented, and the time until it stabilizes is shortened. be able to.

As the predetermined cycle time T ₀ , for example, a time of 100 to 200 ms is selected. Since the command value is output from the drive CPU 56 to the D / A converter 58 (steps 107 and 108) every 10 ms, the correction value is updated once every 10 to 20 times D / A output. Become.

The time T ₁ during which the axis feedback system is unstable after the correction is applied until the transient vibration state is attenuated depends on the weight of the workpiece W mounted on the left and right spindles 18 and 19 and GD ^2. Change. Therefore, according to the workpiece W, the predetermined cycle time
By setting T ₀ from the keyboard 63, better synchronization control becomes possible.

"Effects of the Invention" The present invention has the above-mentioned configuration, and since the correction value is added to the command signal at intervals of a predetermined cycle time longer than the time when the axis feedback system is unstable, There is an effect that the stability of synchronous control is improved in an apparatus in which the synchronously controlled axes are mechanically coupled by a workpiece and interference between the synchronous control axes is expected.

[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 flowcharts showing the processing in the drive CPU, and FIG. 1 ... correction means, 2 ... 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 converter , 63 ...
… Keyboard (cycle time setting means).

Claims (1)

[Claims] 1. A servo motor for driving two mechanically independent axes, two position detectors for detecting the positions of the two axes, and a drive circuit for driving each of the servo motors. And a feedback system for inputting a deviation between a command signal given to the servo motor and a position signal from the position detector to the drive circuit to control the two servo motors to predetermined rotations, respectively.
In a synchronous control device for synchronously rotating the two servo motors in a state in which the two axes are connected by a workpiece,
A correction value calculation means for calculating a correction value to be added to a command signal given to a slave axis of the two axes according to a deviation amount of the position signals from the two position detectors, and a master axis of the two axes. Correction means for giving a command signal given to the drive circuit of the slave axis to the command signal given to the drive circuit, and a cycle time for setting a cycle time longer than the unstable time of the feedback system of the slave axis It is determined whether or not the cycle time set by the cycle time setting means has elapsed from the time when the correction value was calculated by the setting means and the correction value calculating means, and only when the cycle time has elapsed A synchronous control device, comprising: cycle time counting means for executing the correction value computing means.