JP2757269B2 - Rotary axis synchronous repetition control method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to control of a servomotor used in a machine tool or the like, and more particularly to control in which the same pattern is repeatedly commanded at a predetermined cycle.

[0002]

2. Description of the Related Art In a servo motor control for controlling a machine tool or the like, in a machine tool such as a lathe having a rotary shaft and a linear shaft as shown in FIG. A servomotor 2 for driving and rotating a workpiece 30 while driving a linear axis on which a blade 31 is attached;
In 4 there is a case where the cutting tool 31 is repeatedly moved in the same pattern to perform processing. For example, as shown in FIG.
In some cases, the rotation is repeated at a period L and the linear axis is repeated at one period, and the processing is performed by linearly moving. When such an operation of repeating the same pattern is performed, a repetition control method is already known as a method of converging the position deviation to zero to obtain high-precision machining. For example, Japanese Patent Application Laid-Open
See JP-A-07104, Japanese Patent Application No. 2-124254, Japanese Patent Application No. 1-314154, and the like.

FIG. 9 is a block diagram of a main part in control of a servomotor to which the above-described repetitive control method is applied.
In FIG. 9, r (t) is a position command, ε (t) is a position deviation which is a difference between the position command r (t) and the actual position y (t), and 2 is a transfer function of a position loop and a velocity loop. And PI (proportional / integral) control. A repetition controller 10 is added to perform repetition control. The repetition controller 10 includes a band limiting filter 6, a delay element 7 for storing data for one cycle corresponding to a command repeated at a predetermined cycle L,
And a dynamic characteristic compensating element 8 for compensating for a phase delay and a decrease in gain of the controlled object.

[0004] The repetition controller 10 adds the data x at the time of sampling one cycle L before output from the delay element 7 to the position deviation ε every predetermined sampling cycle T,
The data of the band limiting filter 6 is stored in the delay element 7. The delay element 7 has n (= L / T) memories and can store each sampling data for one period L, and outputs the oldest data at each sampling. . That is, the input data is stored in the memory at address 1 by shifting the address by 1 for each sampling, and the data at address n is output. As a result, as the output of the delay element 7, sampling data delayed by one cycle L is output. Therefore, since the position command r (t) of the same pattern is given in the period L, the position deviation ε added by the adder 26 and the output of the delay element 7 become the same position on the pattern of the position command r (t). The data will be added.

The output of the delay element 7 is compensated by the dynamic characteristic compensating element 8 for the phase delay and gain below the controlled object, and the output of the repetitive controller 10, ie, the correction amount d
(T), the correction amount (t) is added to the position deviation ε, and a position / velocity loop process is executed based on the added data.

As a result, the treatment of the same pattern is repeated in a predetermined cycle L. If the positional deviation ε (t) at the time of a certain sampling is large in the preceding cycle, the sampling is performed in the current cycle. Is a large correction amount d (t) from the repetition controller 10.
Is output and added to the position deviation, the position deviation input to the position loop processing changes greatly, and the actual position y (t) also changes with respect to it.
(T) is corrected so that its value converges to zero, and high-precision motor control becomes possible.

[0007]

The accuracy of the workpiece 30 is determined by the rotation accuracy of the rotation axis and the linear axis. Although high position and speed accuracy can be obtained with respect to a linear axis, it is difficult to control the rotation axis with high accuracy due to a heavy rotating mechanism, a mechanical structure using gears, belts, and the like. It is also desirable to be able to use a spindle motor that controls the rotation axis with speed rather than position.

As shown in FIGS. 7 and 8, when one rotation of the rotating shaft is defined as one cycle L and the linear axis is repeated in the same pattern, the position of the linear axis is also changed at the same time without the one cycle. It is desirable that the position of the rotation axis be the same in any period. In other words, it is desirable that the position of the rotation axis and the position of the linear axis be in the same correspondence synchronously without each cycle L. If this correspondence deviates, even if a command is issued to the linear axis in the same pattern, the processed workpiece 30
Will be different for each period, and it will not be possible to always obtain the same constant shape.

As described above, in the conventional repetitive control method, at a certain point in the above-mentioned predetermined period, the position of the rotary axis and the position of the linear axis are repeatedly controlled assuming that they are at the predetermined corresponding positions. It is carried out. However, since it is difficult to control the rotation axis with high precision, the correspondence between the rotation axis and the linear axis may shift,
It is difficult to always obtain the same workpiece shape.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method of synchronously controlling a rotating shaft in which a rotating shaft and a linear shaft are synchronized with each other via a position to prevent a deviation of a corresponding positional relationship between the rotating shaft and the linear shaft.
And a device .

[0011]

SUMMARY OF THE INVENTION The present invention relates to a method for controlling the rotational position of a rotating shaft.
Memory that stores a position command that is repeated every predetermined cycle
Detects the rotational position of the rotating shaft each time the stage and sampling
Means, a section in which the read rotational position exists,
From the step, to the rotational position at both ends of the section, to the servomotor
Command for the rotational position detected by interpolation from the command position of
Means for obtaining position, position from this commanded position and actual position
Means for calculating deviation, rotational position and position at the time of previous sampling
Deviation and the rotational position and position deviation at the time of sampling.
And the position deviation for each rotational position stored in the storage means
Interpolated and found and repeatedly processed by the controller
Of the section where the rotational position at the time of sampling
The amount of correction for the rotational position at both ends stored in the storage means is calculated.
Means, and interpolate based on the two obtained correction amounts.
Means for determining the amount of correction at the time of
And a means for correcting the above positional deviation.
The rotation angle of the rotation axis and the position of the linear axis are synchronized and repeatedly controlled.
I did it .

[0012]

[Function] The rotational position of the rotating shaft is read and stored in the storage means.
The position of the servo motor with respect to the
Calculated as a position command for the servo motor. This position
Subtract current position of servo motor from command to calculate position deviation
Therefore, repeat the controller processing up to the rotation position.
To calculate the correction amount for the rotational position and calculate the correction amount.
Position error, and the position is corrected by the corrected position error.
Control the servo motor by performing the positioning and speed loop processing.
I will.

[0013]

FIG. 2 is a block diagram of a main part of a servo motor control of a machine tool according to an embodiment of the present invention. In FIG. 2, reference numeral 20 denotes a numerical control device for controlling a machine tool, and reference numeral 21 denotes a numerical control device. Is a shared memory for receiving various commands to the servomotor output from the CPU and passing it to the processor of the digital servo circuit 22; 22 is a digital servo circuit;
The processor is composed of a processor, a ROM, a RAM, and the like. The processor controls the position, speed, current, and the like of the servomotor 24 that drives the linear axis, and also performs processing such as repetitive control. Reference numeral 23 denotes a servo amplifier composed of a transistor inverter or the like, reference numeral 24 denotes a servomotor that drives a linear axis, and reference numeral 25 denotes a pulse coder as a position detector that detects the rotational position of the servomotor 24 and feeds it back to the digital servo circuit 22. Reference numeral 26 denotes a motor for driving the rotating shaft, and reference numeral 27 denotes a pulse coder serving as a position detector for detecting the rotating position of the rotating shaft.

The above configuration is the same as the configuration of a known digital servo circuit for controlling a servomotor of a machine tool or the like. However, the difference from the conventional configuration is that the digital circuit 22 uses a pulse coder for the rotating shaft and the digital circuit 22 for the rotating shaft. The difference is that the rotation position is received. In the conventional digital servo control, the position command to the servo motor 24 which is a linear axis motor is transmitted from the numerical controller 20 via the shared memory 21 to the digital servo. The point that the signal is sent to the circuit 22 is different from the present invention in that the processor of the digital servo circuit 22 generates a position command based on the rotation position of the rotation axis sent from the pulse coder 27 of the rotation axis.

That is, R of the digital servo circuit 22
In the AM (or ROM), as shown in FIG. 3, the rotational axis position θi within one repetition period L and the linear axis position ri corresponding to this rotational position θi are divided into n (i = 1 to n), and is created and stored as a table TB. When the rotational position θ (t) of the rotational axis is input from the pulse coder 27 of the rotational axis, the position r (θt) of the linear axis is obtained by interpolation from this table, and this position r (θt) is calculated. This is a command position of a linear axis servomotor.

FIG. 1 is a block diagram of servo control with repetition control performed by a digital servo circuit 22 for driving and controlling a linear axis servo motor. The difference from the conventional repetition control shown in FIG. , B, and C, and the position command r
The difference is that (θt) is generated by interpolation A and is not a command from the numerical controller. The delay element 7 of the repetition controller 3 includes one of the above repetition periods.
As many as n memories obtained by dividing the period L are provided as delay elements.

The rotational position θ (t) of the rotary shaft is read at each sampling period (position / speed control period of the linear axis) T, and the position r () of the linear axis with respect to the rotational position θ (t) is read from the table TB. θt) is obtained by performing interpolation A. Assuming that the interpolation A is performed, for example, by linear interpolation, as shown in FIG. 4, for example, assuming that the rotational position θ (t) is between θm and θm + 1 stored in the table TB, The positions rm and rm + 1 of the linear axis corresponding to the rotational positions θm and θm + 1 are read from the TB, and the following formula 1 is operated to calculate the position r (θ) of the linear axis corresponding to the rotational position θ (t).
Find t). r (θt) = rm + (θ (t) −θm) · (rm + 1−rm) / (θm + 1−θm) (1) Then, the position r (θt) obtained by this calculation is obtained.
Is a position command, and the position y (t) of the linear axis, which is a feedback signal from the pulse coder 25, is
(Θt) to obtain the position deviation ε (θt).

Next, the position θ (t) and the position deviation ε (θt) of the rotating shaft at the time of the sampling and the position θ (t−T) and the position deviation ε (θ (t−
T)), each divided rotational position θi (θi is the position θ (t
A position deviation εi corresponding to a rotation position from the next rotation position where −T) exists to the rotation position where the rotation position θ (t) at the time of the sampling exists) is obtained by interpolation B.

FIG. 5 is an explanatory diagram of the interpolation B process, in which the rotational position θ (t) at the time of the sampling is between θm and θm + 1 stored in the table TB, and the immediately preceding sampling time (t−t) Assuming that the rotation position θ (t−T) at the time T) is between θk and θk + 1, the position deviation ε (θ corresponding to the rotation positions θi (i = k + 1 to m) from the rotation positions θk + 1 to θm.
i) is obtained by linear interpolation using, for example, the following second equation. ε (θi) = ε (θ (tT)) + (θi−θ (tT)) · {ε (θt) −ε (θ (tT))} / (θ (t) −θ (tT))… ( 2) Then, the data x one cycle before the repetition cycle L stored in the delay element is added to the obtained position deviation ε (θi), and a filtering process (processing of the element 6) is performed. 7 is shifted by one and the filtered data is stored in the first memory of the delay element 7. Hereinafter, the position deviation ε (θ (k + 1) to ε until i becomes from k + 1 to m)
(Θm) is sequentially obtained and the above-described processing is performed.

In the interpolation C of the element 5, the following third correction values d (θm) and d (θm + 1) corresponding to θm and θm + 1 are obtained.
The correction value d (θt) is obtained by calculating the equation. d (θt) = d (θm) + (θ (t) −θm) · {d (θm + 1) −d (θm)} / (θm + 1−θm) (3) The correction thus obtained The value d (θt) is calculated as the position deviation ε
(Θt), and repeatedly calculates the position deviation corrected by the controller 3, performs a position / velocity loop process, and drives the servomotor 24. As a result, the position of the linear axis corresponding to the position of the rotation axis is input as a position command, and the controller 3 and the position
Since the speed loop processing is performed and the servo motor is driven and controlled, the rotation axis and the linear axis are synchronized according to the position, and even if the speed of the rotation axis fluctuates, the positional relationship may shift. High-precision machining.

FIG. 6 is a flowchart of the above-described processing performed by the processor of the digital servo circuit at every predetermined sampling period. First, initialization is performed at the time of a machining start command, and the processor repeatedly stores memories M1 to Mn corresponding to delay elements of the controller 3, and a rotation position θ (t), a position deviation ε (θt), and a rotation position ε (θt) before one sampling. Registers Rθ, Rε, Rm storing the value of m indicating the position on the table TB where
The process shown in FIG. 6 is performed for each sampling cycle.

First, the processor includes the pulse coder 25, 2
7 is the position feedback θ (t) of the rotating shaft output from
And the position feedback y (t) of the linear axis is read (step S1). Next, the position θ of the read rotation axis is
The rotational position stored in the table corresponding to (t) is obtained. Staple T satisfying θm ≦ θ (t) <θm + 1
The pointer m of B is searched (step S2). When the pointer m is detected, the rotational positions θm, θm + 1 and the linear axis positions rm,
rm + 1 is read from the table TB, and the first formula operation is performed to obtain a command position r (θt) (process of interpolation A) (step S3).

Next, the position deviation ε (θt) is obtained by subtracting the position y (t) of the linear axis read in step S1 from the command position r (θt) (step S5), and the value stored in the register Rm (step S5). "0" at the first sampling of the processing start
Is set to the index i (step S5), and the data one sample before (stored at the start of machining, "0" at the start of machining) stored in the registers Rθ and Rε. The second equation is calculated from the rotational position θ (t) and the position deviation ε (θt) obtained in steps S1 and S4, and the position corresponding to the rotational position θi indicated by the index i between the previous sampling and the sampling is performed. The deviation ε (θi) is obtained (step S6).

Next, the data stored in the memory Mn one cycle before L is multiplied by the coefficient Gx of the dynamic characteristic compensating element 8 to obtain a correction amount d.
(Θm) is stored in the register (step S
7). Then, the data in the memory Mn is added to the position deviation ε (θi) obtained in step S6 to perform a filter process (element 6).
Is performed, and the memories M1 to Mn are shifted (Mn
← Mn−1,..., M2 ← M1), and stores the filtered data in the memory M1 (step S8). Next, it is determined whether or not the index i is equal to the pointer m (step S).
9) If not equal, the index i is incremented by "1" (step S10), and steps S6 to S10 are repeated. If the index i becomes equal to the pointer m, step S11 is performed.
Move to

As a result, the correction amount stored in the register in the processing of step S7 is the correction amount d corresponding to the rotational position θm.
(Θm). In step S11, the data stored in the memory Mn is multiplied by the coefficient Gx of the dynamic characteristic compensating element 8 to obtain a correction amount d (θm + 1) corresponding to the rotational position θm + 1.
Rotation position θm, θm + 1, correction amount d (θm), d (θm + 1
) To calculate the correction amount d
(Θt) is obtained (step S12), and the rotational position θ (t), position deviation ε (θt) and pointer value m at the time of the sampling are stored in registers Rθ, Rε, Rm (step S13). Then, the position deviation ε (θt) obtained in step S3 is added to the correction amount d (θ
t) is added, a position deviation corrected by the correction amount by the processing of the controller 3 is repeatedly obtained, and a position / velocity loop process is performed based on the position deviation (step S1).
4, S15), and the processing at the time of the sampling ends.

Hereinafter, the above-described processing will be executed at each sampling time.
The values of the memories M1 to Mn of the delay element 7 and the registers R.theta., R.epsilon., And Rm for storing the data at the time of one sampling are "0" by default. Is no longer “0”, and the position of the linear axis is controlled in synchronization with the position of the rotation axis.

[0027]

According to the present invention, since the servomotor which repeats the operation of the same pattern is controlled in synchronization with the position of the rotating shaft, even if the rotating shaft has uneven rotation or a certain offset, the work piece can be controlled. Accuracy is improved.

Therefore, since it is not necessary to perform position control on the motor of the rotating shaft, it is possible to use a spindle motor that performs only speed control.

[Brief description of the drawings]

FIG. 1 is a block diagram of one embodiment of the present invention.

FIG. 2 is a block diagram of a main part of a machine tool for implementing the embodiment.

FIG. 3 is a diagram showing an example of a table for storing a relationship between a rotational position and a position of a linear axis stored in a storage device of a digital servo circuit in the embodiment.

FIG. 4 is an explanatory diagram for obtaining a position of a linear axis from a rotational position by linear interpolation in the embodiment.

FIG. 5 is an explanatory diagram for obtaining a position deviation corresponding to a rotation position stored in a table in the embodiment by linear interpolation.

FIG. 6 is a flowchart of a process performed by a processor of the digital servo circuit in the embodiment.

FIG. 7 is a block diagram showing an example of processing to which the present invention is applied.

FIG. 8 is an explanatory diagram of an operation of a rotation axis and a linear axis in the embodiment.

FIG. 9 is a block diagram of control by a conventional repetition controller.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Element of interpolation A 2 Element of transfer function of control object 3 Iterative controller 4 Element of interpolation B 5 Element of interpolation C 6 Band limiting filter 7 Delay element 8 Dynamic characteristic compensation element

 ────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-53-141990 (JP, A) JP-A-60-89201 (JP, A) JP-A-2-256417 (JP, A)

Claims (2)

(57) [Claims] 1. A servo motor control method comprising a repetitive controller for driving a rotating shaft and controlling the servo motor in synchronization with the rotating shaft by a position command repeated at a predetermined cycle. The position command of the predetermined cycle for the rotational position is stored, and the rotational position of the rotational shaft is read and read every time sampling is performed.
The section where the taken rotational position exists is detected from the storage unit
And the rotational position at both ends of the section and the command position to the servomotor.
Command position for the rotational position by interpolation from the
Calculate the position deviation from the command position and the actual position, and
Position and position deviation during sampling and sampling
Each rotation stored in the storage means from the rotation position and position deviation of
Interpolate the position deviation with respect to the position, and repeat control
The sampling time obtained by performing roller processing
Rotation of both ends stored in the storage means of the section where the shift position exists
From the correction amount for the position, the correction amount at the time of the sampling
Is obtained by interpolation, and this correction amount is compensated for the position deviation.
Rotating axis synchronous repetitive control method characterized by positive
Law . 2. A repetition controller having a rotating shaft.
Drive and a position command
Servo motor that controls the servo motor in synchronization with the rotation axis
In the data controller, the rotation position of the rotation shaft
Storage means for storing the position command of the predetermined cycle,
Means for detecting the rotational position of the rotating shaft each time the pulling is performed
And a section in which the read rotational position exists.
From the rotation positions at both ends of the section,
Command position for rotational position detected by interpolation from command position
Means for determining the position and the position from this command position and the actual position.
Means for calculating the deviation, and the rotational position and position during the previous sampling
Deviation and the rotational position and position deviation at the time of the sampling.
The position deviation for each rotational position stored in the storage means
And iteratively processes the controller.
Section in which the obtained rotational position at the time of sampling exists
The amount of correction for the rotational position at both ends stored in the storage means of
The means for obtaining and the interpolation based on the obtained two correction amounts
Means for determining a correction amount at the time of sampling;
Means for correcting the position deviation by the correction amount.
And a rotation axis synchronous repetition control device .