JP3130426B2 - Motor control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor control device to which a position or speed command of a motor is input by communication.

[0002]

2. Description of the Related Art FIG. 4 is a block diagram showing an example of a motor control device using the prior art. FIG. 5 is a processing diagram of a communication control unit 10, a command switching unit 12, and an acceleration / deceleration calculation unit 14 in FIG. It is a figure showing a procedure.

An upper control circuit (not shown) has a predetermined period Tc
This is a circuit that outputs a command signal of the position or speed of the motor to the motor control device every time. A command signal (hereinafter, described as a position command) from the host control circuit is
It is input to the communication control unit 10 via the communication line at every command cycle Tc (S21).

The communication control unit 10 is a circuit that receives a position command from a higher-level control circuit and supplies it to the acceleration / deceleration calculation unit 14 and the memory 30. If a communication error has occurred, it is detected and a predetermined alarm signal ALARM is output to the command switching unit 12. In the k-th command cycle, if the position command received by the communication control unit 10 is PCMD (k), if the reception is normal (S22), the position command PCMD
(k) becomes the input command PC (k) of the acceleration / deceleration calculation unit 14 through the command switching unit 12 (S23).

The acceleration / deceleration calculation section 14 is a circuit for performing a moving average process described later as acceleration / deceleration calculation. The moving average processing suppresses the acceleration component of the input command PC (k) (S25, S26).
A target position command PREF (k) as the control target command of No. 6 is output (S26). Position command sent from host control circuit
If the acceleration component of PCMD (k) has an acceleration that the motor 20 cannot actually output, the control model of the motor becomes non-linear and stable motor control becomes difficult. Therefore, the acceleration / deceleration calculation unit 14 receives the input command PC (k)
, The acceleration component is suppressed, and stable motor control is always possible.

The position control calculation unit 16 reads the position P (k) of the motor from a position sensor 22 attached to the motor 20 and generally adjusts the position P (k) of the motor to the target position command PREF (k). A current command value CREF (k) required for the motor 20 is calculated using a well-known position control method. Then, the obtained current command value CREF (k) is supplied to the inverter 18.

The inverter 18 supplies a motor drive current corresponding to the current command value CREF (k) to the motor 20, and the position of the motor 20 is controlled so as to match the target position command PREF (k).

On the other hand, if a communication error occurs during reception and the communication control unit 10 cannot receive the position command PCMD (k) (S22), the communication control unit 10 outputs a predetermined alarm signal.
ALARM is output to the command switching unit 12. Command switching unit 1
2 is input to memory 3 by this alarm signal ALARM.
Switch to output from 0.

The memory 30 stores the position command PCMD (k-1) in the previous command cycle. If a communication error occurs, the position command PCMD (k-1) is transmitted via the command switching unit 12.
MD (k-1) is supplied to the acceleration / deceleration calculation unit 14 as an input command PC (k). As a result, the input command PC (k) becomes the input command PC (k
This is the same value as -1). Once a communication error occurs, the position command PCMD (k-1) is read from the memory 30 during the deceleration period until the speed component of the position command becomes 0 and the motor stops.
Is continuously output in a fixed manner (S24).

Next, the acceleration / deceleration processing performed by the acceleration / deceleration calculation section 14 will be described.

The acceleration / deceleration calculation unit 14 performs an acceleration / deceleration calculation using a mathematical method called a moving average. In this moving averaging process, the average of the past n times of the input command PC (k) is calculated by the following equation (1), so that the acceleration / deceleration time constant Tc × n
The target position command PREF (k) is output as the acceleration / deceleration result in.

[0012]

PREF (k) = {PC (k) + PC (k-1) + PC (k-2) +... + PC (k-n + 1)} / n (1) BUF1 that is updated every command cycle as a buffer for acceleration / deceleration processing that stores n input command values
Use BUF1 (n) from (1). The buffer for acceleration / deceleration processing stores the input command PC (k) when the communication control unit 10 or the memory 30
, The contents of BUF1 (1) to BUF1 (n) are updated (S25). Note that S25 in FIG.
In this document, this buffer content is updated such that data is moved in all buffers, but a ring buffer is used in which physical data does not move.

[0013]

In a motor control device which inputs a position or speed command of a motor by communication, a situation occurs where a normal command signal cannot be received transiently due to the occurrence of a communication error.

The higher-level control circuit outputs to the respective motor control devices a command in which the position coordinates of the respective position commands are synchronized with the plurality of motor control devices so as to move on the target composite contour trajectory. . In this case, if a communication error occurs in one motor control device, the previous position command PCMD (k-1) stored in the memory 30 is fixedly output as described above, and the motor is started after a predetermined period. Stop.

However, since the other motor that does not cause a communication error does not stop immediately, there is a problem that the trajectory obtained by synthesizing the position coordinates of each motor greatly deviates from the target trajectory due to the occurrence of the communication error.

To prevent this, there is a method for improving the reliability of communication. However, measures such as adding a data correction function to the physical layer itself of the communication means increase the cost of the device and further reduce the transfer speed of command signals and the like, so that the effect of improving the reliability of communication is diminished. I will.

On the other hand, the method of giving command data lost due to an error by a retransmission procedure is excellent in cost, transfer speed and reliability. However, in order to synchronously operate a plurality of motors, it is necessary to provide a time for retransmission between a regular communication time and a data use start time for acceleration / deceleration calculation and position control calculation. . Therefore, unless the data transfer speed is further improved, the dead time of the command response increases. However, the transfer speed that satisfies this is also limited by other processing speeds, so that the response time of the command signal cannot be shortened, and efficient motor drive cannot be performed.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem, and it is possible to eliminate the lack of command data due to a communication error by re-transmitting the command data without increasing the wasteful time of the response to the command signal and interpolating the command data. It is another object of the present invention to provide a motor control device capable of reducing a locus error between a locus of actual motor position coordinates and a target position coordinate.

[0019]

According to the present invention, there is provided a motor control device for supplying a position or speed command signal at a predetermined cycle via communication means and controlling a motor current so that the motor position or speed corresponds to the command signal. A communication control unit that receives a command signal at predetermined intervals, detects a communication error, and requests retransmission of the command signal, and replaces the command signal that could not be received when a communication error occurs. An alternative command calculation unit that generates a replacement command signal, an acceleration / deceleration calculation unit that calculates and outputs a control target signal based on the received command signal or the replacement command signal, and a past command signal that has already been received, When a retransmitted command signal is received, the past command signal in the acceleration / deceleration calculation unit is calculated based on a difference between the substitute command signal and the retransmitted command signal. In the next cycle in which a communication error has occurred, a control target signal in the next cycle is calculated based on the command signal in the next cycle and the corrected previous command signal. It is characterized by that.

The acceleration / deceleration calculation section stores a plurality of the past command signals supplied to the acceleration / deceleration calculation section, and stores the stored past command signal, the present command signal or the substitute command signal. And outputs the control target signal by performing a moving average calculation based on the above.

[0021] The command correction unit is configured to convert the command signal, in which the substitute command signal is substituted, out of the plurality of past command signals stored in the acceleration / deceleration calculation unit into the retransmitted command signal. It is characterized in that the difference between the retransmitted command signal and the substitute command signal is added to the oldest command signal.

[0022] The substitute command calculating section is characterized in that, when a communication error occurs in the k-th cycle, the substitute command signal is calculated by the following equation. (K-th substitute command signal) = 2 × (k−1-th command signal) − (k−2th command signal) The command correction unit converts the re-transmitted command signal and the substitute command signal. A trajectory error of an actual control trajectory with respect to a control target trajectory of the motor is obtained based on the trajectory, and it is determined whether the trajectory error exceeds a predetermined value.

When the trajectory error exceeds a predetermined value,
The motor is decelerated and stopped.

[0024]

The motor control device according to the present invention has a command correction function, and when a transient communication error occurs and a regular command signal cannot be received, the substitute command calculation unit substitutes the command signal. The signal is calculated and supplied. Therefore, accurate motor control can be continued by the substitute command signal without stopping the motor, and the trajectory error from the target position command can be minimized.

Further, even when there is a difference between the command signal retransmitted as a command signal at the time of occurrence of a communication error and the substitute command signal, based on the command signal retransmitted in the next command cycle, An internal variable of the acceleration / deceleration processing unit, that is, a past command signal is corrected. Therefore, it is possible to suppress the trajectory error between the trajectory of the position coordinates of the motor control device and the target position coordinates from accumulating, and to minimize the error.

Further, based on the retransmitted command signal and the substitute command signal, a trajectory error (a trajectory error of the actual position coordinates of the motor with respect to the trajectory of the target position coordinates of the motor)
When the trajectory error exceeds a predetermined value, the motor is decelerated and stopped. Thus, it is possible to prevent the motor control from continuing in a state where the trajectory error between the trajectory of the motor position coordinates and the trajectory of the target position coordinates exceeds the allowable value. Therefore, it is possible to reliably cope with machining conditions that require extremely high motor position accuracy.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a motor control device having a command correction function according to the present invention.
The same parts as those in the drawings already described are denoted by the same reference numerals and description thereof will be omitted.

In this embodiment, an alternative command operation unit 24 and a command correction unit 26 are provided. When a communication error occurs, a predetermined alarm signal ALARM is sent from the communication control unit 10 to the alternative command calculation unit 24, the command correction unit 26,
And the command switching unit 12.

Here, when a communication error occurs and the alarm signal ALARM is output from the communication control unit 10, the substitute command computing unit 24 computes a substitute command signal that replaces the command signal that could not be received due to the error. Circuit. For example, when a communication error occurs in the k-th command cycle, the substitute command signal is obtained from the position command PCMD (k-1) received in the past by the communication control unit 10 by a method described below. Then, the command switching unit 12 and the command correction unit 26
Supplied to

The command correction unit 26 is supplied with the position command PCMD (k) from the communication control unit 10, the communication alarm signal AALLM, and the substitute command TMPCMD (k) of the substitute command calculation unit 24.
Then, when the retransmitted command signal PCMD (k) is received, the substitute command signal TMPCMD (k) and the retransmitted command signal PCM (k) are received.
Based on the difference from D (k), the contents of the second stage BUF1 (2) and the final stage BUF1 (n) of the acceleration / deceleration processing buffer of the acceleration / deceleration calculation unit 14 are corrected.

Next, the command correction process of the motor control device of this embodiment shown in FIG. 1 will be described with reference to FIG.

First, the position command PCMD from the host control circuit
Is input to the communication control unit 10 via the communication line every command cycle Tc as in the conventional case (S1).

Assuming that the position command received in the k-th command cycle is PCMD (k), if no communication error has occurred and reception is normal (S2), the command switching unit 12
, The position command PCMD (k) becomes the input command PC (k) of the acceleration / deceleration calculation unit 14 (S3).

Next, a case where a communication error occurs in the k-th command cycle will be described. In the k-th command cycle in which a communication error has occurred, the communication control unit 10 detects this error and outputs an alarm signal ALARM, and the communication error signal becomes valid. On the other hand, the substitute command calculating unit 24 stores the past position commands PCMD (k-1) and PCMD (k-2) and calculates the substitute command TMPCMD (k) according to the following equation (2) (S).
4).

[0036]

[Expression 2] TMPCMD (k) = 2 · PCMD (k−1) −PCMD (k−2) (2) If a communication error signal is generated, the command switching unit 12 substitutes the substitute command TMPCMD (k). Is connected to the output side. Then, the substitute command TMPCMD (k) is supplied to the acceleration / deceleration calculation unit 14 as an input command PC (k) (S5). As described above, the position command PCMD is obtained by obtaining the substitute command signal by the equation (2).
Assuming that the velocity component of (k) is F (k), if F (k) = F (k-1) holds, the substitute command TMPCMD (k) is obtained from the equation (2) by the position command PCMD (k). And no trajectory error occurs. Therefore,
Even if a communication error occurs transiently, it is possible to continue control of the motor with high positional accuracy.

When the communication control unit 10 detects a communication error, it requests the upper control circuit to retransmit the position command PCMD (k) (S6). The retransmission request is issued at a timing such that the reception of the position command PCMD (k + 1) is completed before the transmission of the next position command PCMD (k + 1) starts. Therefore, although there is no particular stipulation on the context of the k-th other data processing (S4 to S11), it is preferable to make a retransmission request as soon as possible after the start of the data processing.

When the input command PC (k) is supplied from the communication control unit 10 or the substitute command calculation unit 24, the acceleration / deceleration calculation unit 14 changes the acceleration / deceleration processing buffers BUF1 (1) to BUF1
The content of (n) is updated (S7). Here, as an acceleration / deceleration processing buffer of the acceleration / deceleration calculation unit 14, a ring buffer in which physical data does not move is used.

When the acceleration / deceleration processing buffer is updated, it is next determined whether or not a communication error has occurred at the previous (k-1) th time (S8). The average value of all the buffers is obtained based on the past command signals stored in the buffers, and the position control calculation unit 1
Then, the position command PREF (k) is output to 6 (S11).

On the other hand, if a communication error has occurred in the previous (k-1) th command cycle, the previous command retransmitted by the retransmission request from the communication The signal PCMD (k-1) is output from the communication control unit 10 to the command correction unit 26 (S9). Here the last command
PCMD (k-1) sets the communication control unit 10 by the start of the k-th process.
Is retransmitted and received by the request of
Is stored inside the.

Next, the command correction unit 26 performs the second-stage BUF1 (2) of the acceleration / deceleration processing buffer, that is, the previous substitute command TM.
Command signal replaced by PCMD (k-1) (input command PC (k
-1)), the command signal of the last stage BUF1 (n), which is the oldest command signal, is corrected as follows (S10).

First, the second-stage BUF1 (2) is corrected to the previous command signal PCMD (k-1) retransmitted as shown in equation (3).

[0043]

[Equation 3] BUF1 (2) = PCMD (k-1) (3) Also, the last substitute command is given to the command signal of the last stage BUF1 (n).
The difference between TMPCMD (k-1) and the retransmitted previous command signal PCMD (k-1) is added and corrected as in equation (4).

[0044]

BUF1 (n) = BUF1 (n)-TMPCMD (k-1) + PCMD (k-1) (4) After the contents of the acceleration / deceleration processing buffer are corrected, the acceleration / deceleration calculation unit 1
4 calculates an average value of all buffers and outputs the average value to the position control calculation unit 16 as a target position command PREF (k) (S1).
1). Here, the calculation of the sum of the acceleration / deceleration processing buffer is
The processing time can be shortened by storing the previous total and adding only the present difference.

As described above, when a communication error occurs at the (k-1) th time, the second stage BU of the acceleration / deceleration processing buffer is used.
By correcting F1 (2) and the command signal of the last stage BUF1 (n) which is the oldest command signal, the target position command PREF (k) output from the acceleration / deceleration calculation unit 14 in the k-th process
Does not substantially change.

Further, by adding the difference between the previous substitute command TMPCMD (k-1) and the retransmitted previous command signal PCMD (k-1) to the oldest final stage BUF1 (n), k At the +1 time, this difference is deleted from the buffer. Therefore, the contents of the buffer after the k + 1-th processing are the same as when there is no communication error, and the trajectory error from the target position command can be minimized.

In the command correction unit 26, the substitute command TMPCMD (k-1) and the retransmitted position command are
Based on PCMD (k-1), estimated maximum value of trajectory error Δ
Calculate lmax.

When the maximum value Δlmax of the trajectory error exceeds a predetermined value, it is determined and transmitted to the host control circuit via the communication control unit 10.

When the target position command PREF (k) is obtained by calculation and output to the position control calculation unit 16, the position control calculation unit 16 reads the position sensor 2 attached to the motor 20.
Read the motor position P (k) from 2. Then, the current command value CREF (k) required for the motor is obtained by general position control so that the motor position P (k) matches the target position command PREF (k).
Is calculated, and the obtained current command value CREF (k) is
8

The inverter 18 supplies a motor drive current corresponding to the current command value CREF (k) to the motor 20, and the position of the motor 20 is controlled so as to match the target position command PREF (k).

As described above, according to the present embodiment, control can be continued even when a transient communication error occurs.

In this embodiment, the absolute coordinates are used as the position command. However, even when a position increment command or a speed command is given, the function is similarly performed by replacing the integrated value with the position command of the present embodiment. realizable.

Next, in the motor control device of the present invention,
The trajectory error between the target position coordinates and the motor position coordinates generated when a communication error occurs is evaluated. Here, it is assumed that the positions of the two motor control devices are orthogonal to each other and can be taken as X and Y coordinates.

Now, the command position PCMD (k) moves on the straight line of the equation (5) shown in FIG. 3 at a constant speed F for a time longer than the acceleration / deceleration time constant Tc × n, and the motor position P (k) changes. Consider a case following this (however, the command period Tc and the number of moving average terms n).

[0055]

Y = X · tan θ (5) The position coordinates of both axes of the motor position P (k) at this time are represented by Px (k),
Py (k), and the length Δl (k) of the perpendicular drawn from P (k) to the straight line of equation (5) is defined as a trajectory error. Then, from FIG. 3, the trajectory error Δl (k) with respect to the trajectory of the target position coordinates is given by the following equation (6).
It is represented by

[0056]

Δl (k) = Py (k) cos θ−Px (k) sin θ (6) Assuming that the position control of both motor controllers is ideally performed, the position command PCMD (k) and the motor The position P (k) can be regarded as input / output of the moving average processing. Here, since the moving average processing is an integral operation, linearity is guaranteed between input and output. Therefore, the position command on equation (5) which is a linear function
Similarly to PCMD (k), the motor position P (k) also moves on the line of equation (5).

Assume now that a communication error has occurred only in the motor control device for the X-axis in the command cycle m, and the position command PCMDx (k) could not be received.

In the conventional motor control device, the position command of the X axis is fixed to PCMDx (m-1) when a communication error occurs.
On the other hand, the occurrence of the communication error on the X axis is transmitted to the host control circuit, and the output of the position command on the Y axis stops at least at the next m + 1 command cycle. Therefore, after the command cycle m, the command error ΔPCMDx (m) between PCMDx (m-1) and PCMDx (m) shown in Expression (7) is continuously generated on the X axis.

[0059]

ΔPCMDx (m) = PCMDx (m−1) −PCMDx (m) = F · cos θ · Tc (7) From the command cycle m + n after the acceleration / deceleration time has elapsed, the above equation (7) is used. The following equation (8) holds.

[0060]

Px (k) = Px (m) −F · cos θ · Tc, Py (k) = Py (m) (8) Here, Px (m) and Py (m) are expressed by the following equation (5). )
By substituting the relationship of equation (8) into equation (6) and rearranging, the following equation (9) is obtained.

[0061]

Δl (k) = F · cos θ · sin θ · Tc (9) Here, the trajectory error estimated by differentiating the equation (9) with respect to θ (the actual trajectory error relative to the trajectory of the target position coordinates of the motor) When the maximum value of the trajectory error of the trajectory of the position coordinates is obtained, the following equation (10) is obtained.
It becomes like.

[0062]

Δlmax = F · Tc / 2 (10) (k> m−1θ = π / 4 + p · π / 2p = 0, 1, 2,...) On the other hand, it has a command correction function. In the motor control device of the present invention, the result changes for the first time in the command period m at which a communication error has occurred, depending on whether the speed component of the command signal has changed from F to 0. That is, the velocity component of the position command PCMD (k) is
If F (m) = F (m-1) holds when F (k) holds, the substitute command TMPCMD (m) matches PCMD (m) from equation (2), so the trajectory error is Does not occur.

Considering the case where F (m-1) = F and F (m) = 0, the following is obtained.

First, the command signal PCMDx in the command cycle m
The command error included in (k) is expressed by equation (11).

[0065]

ΔPCMDx (m) = (TMPCMD (m) −PCMDx (m)) / n = F · cos θ · Tc / n (11) Next, in the command cycle m + 1, equations (3) and (4) ), The contents of the acceleration / deceleration processing buffer are corrected, so that the command error ΔPCMDx (m + 1) is given by Expression (12).

[0066]

ΔPCMDx (m + 1) = − F · cos θ · Tc / n (12) After the command cycle m + 1, the contents of the acceleration / deceleration processing buffer all match the normal command signal. No error occurs. From the equations (11) and (12), the maximum value Δlmax of the trajectory error estimated in the same manner as in the related art is obtained by the following equation (1
It looks like 3).

[0067]

Δlmax = F · Tc / 2n (k = m, m + 1 θ = π / 4 + p · π / 2p = 0, 1, 2,...) (13) Equation (8) From Expression (10), the maximum value of the trajectory error amount estimated to occur in the motor control device according to the present invention is 1 /
It can be seen that it has been reduced to n. Since the value of n is generally about 10, the trajectory error is greatly reduced.

In the present invention, the command correction unit 26 determines the maximum value Δ of the trajectory error represented by the equation (13) based on the substitute command TMPCMD (m) and the retransmitted position command PCMD (m).
Calculate lmax. When the maximum value Δlmax of the trajectory error exceeds a predetermined value, it is determined and transmitted to the higher-level control circuit via the communication control unit 10.

The upper control circuit determines the maximum value Δ
When lmax exceeds a predetermined value, the motor operation can be stopped by holding the position command to the motor control device of each axis. Thus, it is possible to prevent the motor control from continuing in a state where the trajectory error between the trajectory of the motor position coordinates and the target position coordinates exceeds the allowable value. Therefore, it is possible to reliably cope with processing conditions that require extremely high motor position accuracy.

A trajectory error occurs only when a communication error occurs at the timing when the speed component of the command signal changes. In general, the acceleration / deceleration calculation unit 14
Is often connected in cascade, and the error that appears with a different sign in a continuous cycle due to the acceleration / deceleration calculation at the subsequent stage is further averaged and reduced, so that the trajectory error can be extremely small. It is clear that it has an effect.

In this embodiment, the moving average processing has been described as an example of the acceleration / deceleration calculation. However, the present invention is not limited to this, and may be an exponential acceleration / deceleration processing. The error correction processing when the exponential acceleration / deceleration processing is used will be described below.

In the exponential acceleration / deceleration processing, the target position command PREF (k) output to the position control calculation unit 16 is given by the following equation (1)
4). As is clear from the equation (14), according to the exponential acceleration / deceleration processing, the operation can be performed by storing only the previous PREF (k-1), and the operation amount is small.

[0073]

PREF (k) = PREF (k-1) + Ke ｛PC (k) -PREF (k-1)} (14) Here, ke is a coefficient which is a reciprocal of a time constant.

The target position command obtained by equation (14) is
As (k) ', it is assumed that a communication error occurs at the (k-1) th time. When a communication error occurs, the substitute command signal TMPCMD (K-1)
It is generated by equation (2) as in the moving average processing. In this case, the command correction unit 26 substitutes the target position command PREF (k-2) to the position control calculation unit 16 at the (k-2) th time and the retransmitted PCMD (k-1) into the equation (14). Then, the previous target position command PREF (k-1) is obtained by equation (15).

[0075]

PREF (k-1) = PREF (k-2) + Ke × ｛PC (k-1) -PREF (k-2)} (15) PREF (k-1) is output to the acceleration / deceleration calculation unit 14 and stored in the acceleration / deceleration calculation unit 14.
PREF (k-1) 'is corrected to this correct previous PREF (k-1). Further, at the time of the acceleration / deceleration calculation process in the k-th command cycle, the acceleration / deceleration calculation unit 14 executes the exponential acceleration / deceleration calculation shown in Expression (14) using the corrected value of PREF (k-1).

As described above, even with the exponential acceleration / deceleration processing, accurate control can be continued by the substitute command signal without stopping the motor, and the trajectory error from the target position command can be minimized.

Further, even if there is a difference between the retransmitted command signal at the time of occurrence of the communication error and the substitute command signal, the previous command signal is used in the next command cycle based on the retransmitted normal command signal. Is corrected and arithmetic processing is performed. Therefore, the trajectory error between the trajectory of the position coordinates of the motor control device and the trajectory of the target position coordinates does not accumulate, and it is possible to minimize the error.

[0078]

As described above, when a transient communication error occurs and a normal command signal cannot be received,
An alternative command operation unit calculates and supplies an alternative command signal that substitutes for the command signal. Therefore, accurate control can be continued without stopping the motor and by the substitute command signal, and the trajectory error from the target position can be minimized.

Further, even when there is a difference between the retransmitted command signal which is a command signal at the time of occurrence of a communication error and the substitute command signal, it is determined based on the normal command signal retransmitted in the next control cycle. The internal variable of the acceleration / deceleration processing unit, that is, the past command signal is corrected. Therefore, it is possible to suppress the trajectory error between the trajectory of the position coordinates of the motor control device and the trajectory of the commanded position coordinates from accumulating, and to minimize the error.

Further, a trajectory error based on the retransmitted command signal and the substitute command signal is determined, and when the trajectory error exceeds a predetermined value, the motor is decelerated and stopped.
Thus, it is possible to prevent the motor control from continuing in a state where the trajectory error between the trajectory of the position coordinates of the motor control device and the command position coordinates exceeds the allowable value. Therefore, it is possible to reliably cope with machining conditions that require extremely high motor position accuracy.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an example of a circuit of a motor control device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a correction processing procedure in the motor control device of FIG. 1;

FIG. 3 is a diagram illustrating a trajectory error amount.

FIG. 4 is a block diagram illustrating an example of a circuit of a conventional motor control device.

FIG. 5 is a diagram showing a data processing procedure in the motor control device of FIG. 4;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Communication control part 12 Command switching part 14 Acceleration / deceleration calculation part 16 Position control calculation part 18 Inverter 20 Motor 22 Position sensor 24 Alternative command calculation part 26 Command correction part

Claims (6)

(57) [Claims] 1. A motor control device for supplying a position or speed command signal at a predetermined cycle via communication means and controlling a motor current so that the motor position or speed corresponds to the command signal. A communication control unit that receives a command signal, detects a communication error, and requests retransmission of the command signal; and, when a communication error occurs, an alternative command signal that replaces the command signal that could not be received. An acceleration / deceleration operation unit that calculates and outputs a control target signal based on the received instruction signal or the alternative instruction signal and a previously received past instruction signal, A command for correcting the past command signal in the acceleration / deceleration calculation unit based on a difference between the substitute command signal and the retransmitted command signal. A correction unit, wherein in the next cycle in which a communication error has occurred, the control target signal in the next cycle is calculated based on the command signal in the next cycle and the corrected past command signal. Characteristic motor control device. 2. The motor control device according to claim 1, wherein the acceleration / deceleration calculation unit stores a plurality of the past command signals supplied to the acceleration / deceleration calculation unit, and stores the stored past command signal. And performing a moving average calculation based on the current command signal or the substitute command signal and outputting the control target signal. 3. The motor control device according to claim 2, wherein the command correction unit substitutes the substitute command signal among a plurality of past command signals stored in the acceleration / deceleration calculation unit. The motor control device, wherein the command signal is corrected to the retransmitted command signal, and a difference between the retransmitted command signal and the substitute command signal is added to the oldest command signal. 4. The motor control device according to claim 1, wherein the substitute command calculation unit is configured to execute k k when a communication error occurs in a k-th cycle. A motor control device wherein a second substitute command signal is obtained by the following equation. (K-th substitute command signal) = 2 × (k−1-th command signal) − (k−2-th command signal) 5. The motor control device according to claim 1, wherein the command correction unit is configured to perform the control based on the retransmitted command signal and the substitute command signal. And calculating a trajectory error of an actual control trajectory with respect to a control target trajectory of the motor, and determining whether the trajectory error exceeds a predetermined value. 6. The motor control device according to claim 5, wherein the motor is decelerated and stopped when the trajectory error exceeds a predetermined value.