JP3881882B2 - Servo controller - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a servo controller that controls the speed and position of a servo motor using a pulse train signal, and more particularly to a servo controller suitable for a servo control system including a plurality of servo motors.
[0002]
[Prior art]
Servo control systems (servo mechanisms) are often used to drive moving parts of machines that require precise position control and speed control, such as machine tools and motion simulation game systems. A servo controller is used for controlling the servo. In this case, the servo control system is configured as shown in FIG. 6, for example.
[0003]
FIG. 6 shows an example of a servo control system including a plurality of servo motors, for example, four servo motors 7 to 10. The plurality of servo motors 7 to 10 are controlled under the control of the servo controller 2. The servo amplifiers 3 to 6 are driven.
[0004]
At this time, the servo controller 2 supplies pulse train outputs (signals composed of pulse trains) to the servo amplifiers 3 to 6 via the transmission lines 11 to 14 in order to control the servo motors 7 to 10. Therefore, in the case of such a positioning system using a pulse train output for speed control and position control of the servo motor, it is called a pulse train output method.
[0005]
The servo controller 2 itself is composed mainly of a computer. At this time, data and programs necessary for controlling the servo motors 7 to 10 are programmed by the personal computer 1 and necessary for the control. It is stored in the servo controller 2 together with various data.
[0006]
By the way, in the case of such a pulse train output type servo system, if an abnormality such as disconnection occurs in the pulse train output transmission lines 11 to 14, the movement of the object to be driven by the servo motor becomes abnormal, and a correct servo operation is obtained. Not only will it disappear, but there will also be problems in maintaining safety.
[0007]
Therefore, for example, a feedback signal from the servo motor side such as an encoder signal for detecting the movement of the drive target is monitored, and the soundness of the entire pulse train output transmission system including the transmission lines 11 to 14 is confirmed. A method for detecting the occurrence of a transmission abnormality such as is conventionally known.
[0008]
However, this method cannot be applied because there is no feedback signal in the case of an open loop control type servo control system, but here, in the positioning system based on the pulse train output method, the open loop control method is often used.
[0009]
Therefore, in the case of the open loop control method, as shown in FIG. 7, a method for detecting the occurrence of transmission abnormality such as line disconnection by incorporating a detection circuit separately in each transmission line 11 to 14 is known as the prior art. It was done. In this figure, 16 is a driver, 17 is a receiver, 18 is a terminating resistor, 19 is a photocoupler, 20 is a bypass diode, and 21 is a disconnection detection circuit.
[0010]
In this case, if the transmission lines 11 to 14 are healthy, a current flows through the terminating resistor 18 as indicated by an arrow, so that a signal is taken out by the photocoupler 19, but when the line is disconnected, the photocoupler 19 No signal is output from the.
[0011]
Therefore, if the output of the photocoupler 19 is monitored by the disconnection detection circuit 21, the line disconnection can be detected and the soundness of the transmission lines 11 to 14 can be confirmed by the servo controller 2.
[0012]
[Problems to be solved by the invention]
The above prior art has not been taken into account that a separate detection circuit is required for detection of a transmission abnormality due to line disconnection or the like, and there has been a problem of cost increase.
[0013]
In the prior art, a new circuit for detecting disconnection is required in the middle of wiring or in the servo controller or servo amplifier, so this is not easy.In particular, when controlling multiple axes, it is necessary to detect disconnection for each axis. Therefore, the circuit and the man-hour are enormous, and therefore the cost is increased.
[0014]
An object of the present invention is to provide a servo controller capable of reliably detecting a transmission abnormality with a small cost increase.
[0015]
[Means for Solving the Problems]
The above-mentioned purpose is to control the speed and position of the servo motor by the pulse train signal, to detect the transmission abnormality of the pulse train signal, the change of the RUN bit of the servo controller indicating the output of the pulse train signal, and the positioning completion signal outputted from the servo amplifier. In a servo controller of a method for detecting from a temporal combination of changes in the above, there are provided means for calculating the current speed of the servo motor and means for comparing the calculated current speed with a preset monitoring speed, after said RUN bit has changed, said transmission error on the condition that the current velocity exceeds the monitored velocity is achieved in so that the detected.
[0016]
At this time, even if the process for detecting the transmission abnormality is repeated, and the transmission abnormality is detected at least twice, the above object can be achieved, and a plurality of servo motors are provided. The above object can be achieved even if the transmission abnormality of the pulse train signal is detected for each servo motor.
[0017]
According to the present invention, the positioning completion signal originally used for positioning is used.
[0018]
In the servo amplifier, there is a deviation between the position command received from the host and the current motor value during actual operation due to a delay in tracking, etc., and this position deviation (deviation between the position command value and the position detection value) is specified. When the value is smaller than the set value, a positioning completion signal is output.
[0019]
In a servo control system, this signal is generally output from a servo amplifier. Therefore, according to the present invention, a new signal or circuit is not required, and a transmission abnormality due to disconnection is detected. Will be obtained.
[0020]
Further, by inputting this signal and monitoring the input state by the servo controller, it is possible to stop only the axes of the servo motors that are synchronized when disconnection is detected.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a servo controller according to the present invention will be described in detail with reference to embodiments shown in the drawings.
Here, also in the servo controller according to the embodiment of the present invention, in the case of a servo mechanism to which the servo controller is applied, the block configuration is the same as that in the prior art described in FIG. Only the processing by the servo controller 2 is performed.
[0022]
Therefore, the operation of the servo controller 2 according to this embodiment will be described below. First, there is no particular mention in the description of the prior art, but it is well known in the case of a pulse train output type servo controller. As described above, the pulse period (1 / pulse frequency) in the pulse train output represents the speed command value of the servo motor, and the number of pulses is the position command value.
[0023]
Next, although this was not particularly mentioned, in the case of a general servo controller, a rotation operation period commanded to the servo motor in a series of operations of the servo motor consisting of repetition of a rotation period and a stop period. In order to display the operation stop period, the RUN bit 27 is usually set as shown in FIG. 1, and the servo controller 2 in this embodiment is the same.
[0024]
In FIG. 1, time t ₀ represents a disclosed time point in one of several rotation operation periods in a series of operations of the servo motor, and time t ₂ represents an end time point thereof. Here, the waveform 28 is a pulse train output, and the waveform 29 is a pulse train output at the servo amplifier input.
[0025]
Accordingly, in FIG. 1, the RUN bit 27 changes from low level to high level at time t ₀ , and a pulse train output 28 is generated from this point in time, which is input as a pulse train output 29 to the servo amplifier, and thereafter at time t _2. As a result, the RUN bit 27 falls to the low level, and the pulse train outputs 28 and 29 disappear accordingly.
[0026]
Furthermore, although this was not particularly mentioned, in the case of a general servo controller, the servo amplifier is positioned within a predetermined deviation from the commanded position after the pulse train output 28 is input. When this is done, it is usual that the positioning completion signal is generated and output to the servo controller side, and the servo amplifiers 3 to 6 in this embodiment are the same.
[0027]
Here, in FIG. 1, a waveform 30 is a positioning completion signal, and here, a high level indicates a positioning completion state, and a low level indicates a positioning incomplete state.
[0028]
Therefore, if the pulse train output 29 is input to the servo amplifier and the servo motor normally rotates, the positioning completion signal 30 is first set to the predetermined value after the RUN bit 27 rises at time t ₀ as shown in the figure. After the elapse of the delay time τ _D , the high level falls to the low level at time t ₁ .
[0029]
After this time t ₁ , while the pulse train output 29 is being input to the servo amplifier, the positioning completion signal 30 is kept at the low level. Thereafter, when the RUN bit 27 falls to the low level at time t ₂ , this time. Rises to a high level after a predetermined delay time τ _U elapses.
[0030]
This is because, in such a servo drive system, while the servo motor starts to rotate and rotates, it only follows the commanded position and is positioned close to the commanded position. This is because the pulse train output 29 is lost (details will be described later).
[0031]
The length of the delay times τ _D and τ _U at this time is determined by the torque of the servo motor, the moment of inertia (GD ² ), the inertia of the drive portion, and the like, and is therefore a specific constant for each servo motor.
[0032]
Here, because the transmission line (for example, one of the transmission lines 11 to 14 in FIG. 6) is disconnected, an abnormality occurs in the transmission system of the pulse train output, and the pulse train output 28 is output from the servo controller 2. It is assumed that the pulse train output 29 is not input to the servo amplifier from the beginning despite being output, or the servo motor is interrupted during the rotation operation.
[0033]
First, when the pulse train output 29 is not input to the servo amplifier from the beginning, as shown in FIG. 2, after the RUN bit 27 rises at time t ₀ , at time t ₁ after elapse of a predetermined delay time τ _D. Even in such a case, the positioning completion signal 30 remains high and does not change.
[0034]
This is because in this case, since the pulse train output 29 is not input to the servo amplifier from the beginning, the servo motor also does not start rotating, but is stopped at the previously commanded position, and the positioning is completed. is there.
[0035]
Next, when the pulse train output 29 is interrupted, it becomes as shown in FIG. Here, the time t _E is a transmission abnormality occurrence time. Therefore, after this time, the pulse train output 29 disappears from the input of the servo amplifier, and as a result, the positioning completion signal 30 at the time t ₃ after the delay time τ _U elapses. Changes from low to high.
[0036]
This is because the pulse train output 29 is interrupted after time t _E , so that the command position is also given by time t _E , and the servo motor is given by time t ₃ at time t _E. This is because it stops at the position and the positioning is completed.
[0037]
Here, when the relationship between the RUN bit 27 and the positioning completion signal 30 in FIGS.
First, in FIG. 1, when the RUN bit 27 changes, the positioning completion signal 30 always changes after the predetermined delay times τ _D and τ _{U have} elapsed. That is, when no abnormality occurs in the pulse train output transmission system, the change of the RUN bit 27 and the change of the positioning completion signal 30 appear as a set with the delay times τ _D and τ _U.
[0038]
On the other hand, in FIG. 2 and FIG. 3, such a change in which the RUN bit 27 and the positioning completion signal 30 are set is not seen.
First, in the case of FIG. 2, the positioning completion signal 30 remains unchanged even after the lapse of the delay time τ _U since the RUN bit 27 changes (in this case, from the low level to the high level) at the time t _0. If it remains high level) it has not changed.
[0039]
Next, in the case of FIG. 3, the delay time τ _D elapses from this time even though the positioning completion signal 30 has changed at this time t ₃ (in this case, from the low level to the high level). However, the RUN bit 27 remains unchanged (in this case, remains at high level).
[0040]
2 and 3 are cases where an abnormality has occurred in the pulse train output transmission system. Accordingly, when there is no abnormality in the pulse train output transmission system, the RUN bit is used. 27 and a change in the positioning completion signal 30 appear as a set. However, when an abnormality occurs in the pulse train output transmission system, the change in the set of the RUN bit 27 and the positioning completion signal 30 is not seen. You can see that.
[0041]
In other words, this means that it is possible to determine whether the pulse train output transmission system is in a normal state or whether an abnormality has occurred by merely looking at the state of the RUN bit 27 and the state of the positioning completion signal 30. .
[0042]
Therefore, the servo controller 2 according to this embodiment takes in the state of the RUN bit 27 and the state of the positioning completion signal 30, and when these are in the relationship shown below, a transmission abnormality has occurred in the transmission line disconnection or the like. To do.
[0043]
(1) When the positioning completion signal 30 does not change after the predetermined determination time τ _ED has elapsed after the RUN bit 27 has changed (in the case of FIG. 2).
(2) When the RUN bit 27 does not change even after a predetermined determination time τ _ED has elapsed after the positioning completion signal 30 has changed (in the case of FIG. 3).
[0044]
Here, the determination time τ _ED is provided to set a waiting time necessary for determining the abnormality, and in order to reliably determine that the abnormality has occurred, the delay time τ _D and τ _U are anticipated. As shown in the figure, τ _ED > τ _D and τ _ED > τ _U are set.
[0045]
The servo controller 2 generates a command for coping with signal monitoring and abnormality detection at this time. In this embodiment, a ladder program is used for this purpose.
[0046]
Here, as described above, the RUN bit 27 and the positioning completion signal 30 are obtained by a function that is generally provided even in the case of the servo mechanism according to the prior art, and therefore, according to this embodiment. For example, it is possible to easily and reliably detect the occurrence of a transmission abnormality due to a transmission line disconnection or the like without separately providing a detection circuit or the like.
[0047]
By the way, the positioning completion signal 30 described here is generated by each of the servo amplifiers 3 to 6. At this time, as described above, after the pulse train output 28 is input, the predetermined position is instructed for the position commanded at this time. This occurs (changes) when the servo motor is positioned within the deviation. Therefore, the details of the generation operation at this time will be described below.
[0048]
In each of the servo amplifiers 3 to 6, as described above, the pulse cycle (1 / pulse frequency) in the pulse train output 28 supplied from the host device, that is, the servo controller 2 represents the speed command value of the servo motor. The number is the position command value.
[0049]
Therefore, if the speed command based on the pulse period of the pulse train output 28 is, for example, as shown in the speed command 22 of FIG. 4A, each of the servo motors 7 to 10 has a rotational speed characteristic 23. Follow as shown in.
[0050]
In this case, the position command based on the number of pulses of the pulse train output 28 is as indicated by the position command 24 in FIG. 4B, whereas each servo motor 7 to 10 has a position characteristic 25 as shown in FIG. It follows with a predetermined positional deviation ΔP, stops when the positional deviation ΔP becomes 0, and positioning is completed.
[0051]
Therefore, the servo amplifiers 3 to 6 may generate the positioning completion signal 30 when the position deviation ΔP is 0. In practice, however, there is a limit to the accuracy of position detection. Even if the servo motor is stopped, the position deviation ΔP may not converge to zero.
[0052]
Therefore, as described above, each of the servo amplifiers 3 to 6 performs positioning when the positional deviation Δ is equal to or smaller than a preset positioning width ΔP _MIN as shown in FIGS. 4 (b) and 4 (c). The completion signal 30 is generated (changed).
[0053]
By the way, at this time, when the command speed becomes slow, the followability of each of the servo motors 7 to 10 becomes relatively good, and follows the position command with a small position deviation ΔP. As a result, the servo motor Even during rotation, there is a possibility that the position deviation ΔP becomes equal to or less than the positioning width ΔP _MIN and the positioning completion signal 30 is always positioned completely.
[0054]
Therefore, in this embodiment, the transmission abnormality occurrence due to disconnection or the like is determined by the process shown in FIG. 5, and the transmission abnormality occurrence detection process will be described below with reference to this flowchart.
[0055]
The process shown in FIG. 5 is executed by the programmable servo controller 2 and is started when the servo controller 2 starts operation. First, in processing step S1, generation of the RUN bit 27 is monitored to determine whether or not a pulse is output to the servo amplifiers 3 to 6.
[0056]
Accordingly, when the RUN bit 27 is not generated, that is, while it is at the low level, it remains in the processing step S1, and when the RUN bit 27 is changed to the high level (High), the process proceeds to the next processing step S2.
[0057]
In processing step S2, the speed commanded from the servo controller 2 to the servo amplifiers 3, that is, the current speed is calculated. This current speed is stored by storing the current position managed by the servo controller 2 every fixed period ΔTS.
Current speed = (Current speed−Current position stored last time) / ΔT _S
Can be calculated as
[0058]
Next, the process proceeds to processing step S3, where the current speed thus calculated is compared with a preset monitoring speed, and it is determined whether or not the current speed is larger than the monitoring speed. When the determination result is N (No), the process proceeds to processing step S4, and the retry count value is cleared.
[0059]
The monitoring speed at this time is the speed of the servo motor when the position deviation ΔP during the following operation of the servo motor described in FIG. 4 is larger than the positioning width ΔP _MIN . That is,
Monitor speed → (position deviation ΔP> positioning width ΔP _MIN )
[0060]
This is because the positioning completion signal 30 is always in a positioning completion state (high level) as described with reference to FIG. 4 when the speed of the servo motor is slower than a certain level. This is because the servo motor is in a stopped state and cannot be distinguished.
[0061]
On the other hand, when the determination result in processing step S3 is Y (positive), the process proceeds to processing step S5, and it is determined whether or not the positioning completion signal 30 is at a high level (High). When the determination result is N (No), the process proceeds to processing step S4, and the retry count value is cleared in the same manner.
[0062]
Then, when the determination result in processing step S5 is Y, the processing proceeds to processing step S6, where the retry count UP, that is, the count value is increased by one, and then processing proceeds to processing step S7.
[0063]
In process step S7, the retry count value is checked to determine whether or not it is greater than or equal to the specified retry count value. When the result is N, the process returns to the processing step S1, and when it is Y, the transmission abnormality is detected.
[0064]
Here, as described above, if the RUN bit 27 is at the high level and the speed of the servo motor is equal to or higher than the monitoring speed, the positioning completion signal 30 is at the low level.
[0065]
Therefore, when the process proceeds from the process step S2 to the process step S6, it can be considered that a transmission abnormality such as disconnection has occurred. However, as described above, the possibility that the actual servo motor speed is lower than the monitoring speed due to a follow-up delay or the like cannot be denied.
[0066]
Therefore, in this embodiment, even when the RUN bit 27 is high, the servo motor speed is equal to or higher than the monitoring speed, and the positioning completion signal 30 is high level, that is, when the process proceeds from the process step S2 to the process step S6. However, when this state continues for a certain time T _m , the transmission abnormality is detected for the first time.
[0067]
Here, this time _Tm is the time required for the servo motor to reach the monitoring speed or higher, and this is defined by the specified retry count value in the processing step S7 of FIG. This is because the processing of FIG. 5 is programmed in the above-described constant period ΔT _S , and therefore, the time T _m is the product of the constant period ΔT _S and the specified retry count value, that is, T _m = ΔT _S. This is because it is set at x (specified retry count value).
[0068]
Thus, in FIG. 5, when satisfying the condition of processing steps S3, S5, in terms of the retry count UP in processing step S6, when the retry count value becomes equal to or greater than the specified retry count, and the within time T _m The condition, that is, the condition that the RUN bit 27 is at the high level, the servo motor speed is equal to or higher than the monitoring speed, and the positioning completion signal 30 is at the high level is satisfied, and the transmission abnormality can be accurately detected. .
[0069]
The time T _{m at} this time is the difference between the determination time τ _ED and the delay time τ _U in FIG. 3 (τ _ED −τ _U ), and the delay from the transmission abnormality occurrence time t _E to the transmission abnormality occurrence detection time t _ED. It will be time.
[0070]
Here, when the condition for executing the retry count UP is not satisfied, that is, when the speed of the servo motor is equal to or lower than the monitoring speed, or when the positioning completion signal is at the low level, the retry count is cleared in processing step S4. Therefore, this ensures that the retry count is increased only when the above conditions are continuously satisfied.
[0071]
Therefore, as described above, according to this embodiment, it is possible to easily and reliably detect the occurrence of a transmission abnormality due to a transmission line disconnection or the like without separately providing a detection circuit or the like.
[0072]
Further, according to this embodiment, even in an open loop servo control system in which there is no feedback signal from the servo amplifier, it is possible to easily and surely generate a transmission abnormality due to a transmission line disconnection or the like without separately providing a detection circuit or the like. Can be detected.
[0073]
Furthermore, according to this embodiment, when the occurrence of a transmission abnormality due to disconnection or the like is detected, a program that outputs a stop instruction or an error specifying an axis according to the operation content of the servo system at that time causes a problem. It is possible to stop only the necessary axes without stopping the operation of the shaft without any, and it is possible to stop both the synchronized axes together.
[0074]
In the case of synchronous operation with a servo system having a plurality of axes, if only one axis breaks the pulse and stops, the movement becomes close to runaway. However, according to the above-described embodiment, it is possible to detect the disconnection of each axis, stop all the axes that are synchronously operated by the pulse train output servo controller from the controller, and hinder the other axes that are operated asynchronously. There is no safe and efficient control.
[0075]
【The invention's effect】
According to the present invention, it is possible to easily detect the occurrence of a transmission abnormality such as disconnection without separately adding a detection circuit or wiring to the detection of the transmission abnormality.
In addition, according to the present invention, even in an open loop servo control system without a feedback signal from a servo amplifier, it is possible to easily and surely detect the occurrence of a transmission abnormality due to a disconnection of a transmission line without providing a separate detection circuit. can do.
[0076]
Furthermore, according to the present invention, since both the command side and the receiving side can be monitored by the servo controller, when a transmission abnormality such as disconnection is detected, the stop axis can be arbitrarily specified according to the operation content, error output, etc. You can also deal with it flexibly.
[Brief description of the drawings]
FIG. 1 is a timing chart for explaining the operation of a servo controller according to an embodiment of the present invention.
FIG. 2 is a timing diagram for explaining a transmission abnormality occurrence detection operation by a servo controller according to an embodiment of the present invention.
FIG. 3 is a timing chart for explaining a transmission abnormality occurrence detection operation by a servo controller according to an embodiment of the present invention.
FIG. 4 is a characteristic diagram for explaining operating characteristics of a servo motor in a servo control system.
FIG. 5 is a flowchart for explaining a transmission abnormality occurrence detection operation according to an embodiment of the present invention;
FIG. 6 is a block diagram showing an example of a servo control system to which the servo controller according to the present invention is applied.
FIG. 7 is a circuit diagram showing an example of a disconnection detection circuit according to the prior art.
[Explanation of symbols]
1 Programming device (PC)
2 Servo controllers 3 to 6 Servo amplifiers 7 to 10 Servo motors 11 to 14 Cable (including positioning complete signal line)
16 Transmitter 17 Receiver 20 Termination resistor 19 Photocoupler 20 Bypass diode 21 Disconnection detection circuit 27 RUN bit 28 Pulse train output 29 Servo amplifier input 30 Positioning completion signal

Claims (3)

The speed and position of the servo motor is controlled by the pulse train signal, transmission abnormality of the pulse train signal, the change of the RUN bit of the servo controller indicating the output of the pulse train signal, and the time of the change of the positioning completion signal output from the servo amplifier Servo controller that detects from a combination of
Means for calculating the current speed of the servo motor, and means for comparing the calculated current speed with a preset monitoring speed;
After it said RUN bit has changed, the servo controller, wherein the current speed is configured so that detected said transmission error on condition that exceeds the monitored velocity. In the invention of claim 1,
The servo controller is configured to repeat the process for detecting the transmission abnormality and determine that the transmission abnormality is detected at least twice . In the invention according to claim 1 or claim 2,
A plurality of the servo motors are provided,
A servo controller configured to detect a transmission abnormality of the pulse train signal for each servo motor.

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