JP2014178852A - Control system and control program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To continuously perform control, accepting a packet loss within a range which does not cause problem in the process, even when the packet loss occurs in a network in a feedback control by using a shared line.SOLUTION: A control system has a drive device 20, measuring device 30, and a control device 10. The control device connected to the drive device and the measuring device via a network has a receiving part 112, a determination part 13, a calculation part 14, and a transmission part 15. The receiving part receives a second packet including a measurement result from the measuring device and calculates a sampling period based on a reception interval of the second packet. The determination part determines whether the sampling period exceeds a maximum allowable sampling period. When the period exceeds the maximum allowable sampling period, the calculation part generates a control signal to the drive device on the basis of the measurement result and a control target for the drive device. When the period does not exceed the maximum period, the calculation part suppresses generation of a control signal. The transmission part converts the control signal into a first packet to output it to the drive device.

Description

  Embodiments described herein relate generally to a control system that feedback-controls a drive device used in a process to be controlled via a network, and a control program used in the control system.

  In a recent control system, the role played by communication is increasing. For example, networking control that controls devices via a network, such as controlling a drive device from a remote location in real time via the Internet, or controlling many embedded devices connected by a shared line in a large-scale plant (NCSs: Networked Control Systems) is becoming a reality.

  Conventionally, the control theory in a control system assumes an infinite communication throughput (bps) for signal transmission in the feedback system. When communication within the control system is performed using a dedicated line, no particular problem arises even if the control device is mounted assuming an infinite communication throughput. On the other hand, when communication in the control system is performed using a shared line such as the Internet, there is a restriction on communication throughput. If the control system is designed ignoring the restrictions on the communication throughput, the control system performance and stability may be hindered.

  For example, the UDP communication protocol is used when a communication speed and / or real-time property is required. However, unlike TCP / IP, there are no functions such as 3-way handshake (connection establishment), retransmission control, and window control. There is no guarantee that the data packet will arrive. Therefore, so-called packet loss may occur in communication using the UDP communication protocol.

  By the way, in the conventional control system, there is a problem that when packet loss occurs on the network and data is not reached for a certain period of time, an alarm is issued or feedback control is stopped abnormally.

JP-A-8-305416 Japanese Patent Laid-Open No. 9-160851

  As described above, in the conventional control system, when trying to feedback control the drive device using a shared line, if a packet loss occurs on the network, an alarm is issued or the feedback control is abnormally stopped. There is a problem that it must be done.

  Therefore, the purpose is to perform control by allowing packet loss within a range that does not hinder the process even when packet loss occurs on the network when feedback control of the drive device is performed using a shared line. It is an object of the present invention to provide a control system capable of continuing and a control program used in the control system.

  According to the embodiment, the control system includes a drive device, a measurement device, and a control device. The driving device receives the control signal supplied as the first packet via the network, and executes a predetermined operation in the process to be controlled according to the received control signal. The measuring device measures the state of the process to be controlled, converts the measurement result into a second packet, and outputs the second packet to the network. The control device is connected to the drive device and the measurement device via the network, and includes a reception unit, a determination unit, a calculation unit, and a transmission unit. The receiving unit receives the second packet via the network, and calculates a sampling period based on a reception interval of the second packet. The determination unit determines whether or not the sampling period exceeds a preset maximum allowable sampling period, and if it exceeds, determines that an abnormality has occurred. When it is not determined that the abnormality has occurred, the arithmetic unit generates the control signal based on a measurement result included in the second packet and a control target set for the driving device, and the abnormality When it is determined that the occurrence of the control signal is generated, the generation of the control signal is suppressed. The transmission unit converts the generated control signal into the first packet and outputs the first packet to the network.

It is a schematic diagram which shows the structure of the control system which concerns on 1st Embodiment. It is a block diagram which shows the function structure of the control system shown in FIG. It is a figure explaining operation | movement of the control apparatus shown in FIG. It is a block diagram which shows the other example of a function structure of the control system shown in FIG. It is a block diagram which shows the other example of a function structure of the control system shown in FIG. It is a figure at the time of the sampling period calculation part shown in FIG. 5 calculating a 2nd maximum permissible sampling period. It is a block diagram which shows the other example of a function structure of the control system shown in FIG. It is a block diagram which shows the other example of a function structure of the control system shown in FIG. It is a block diagram which shows the function structure of the control system which concerns on 2nd Embodiment. It is a block diagram which shows the other example of a function structure of the control system shown in FIG. It is a block diagram which shows the other example of a function structure of the control system shown in FIG. It is a block diagram which shows the other example of a function structure of the control system shown in FIG.

  Hereinafter, embodiments will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a schematic diagram illustrating a configuration of a control system according to the first embodiment. The control system shown in FIG. 1 includes control devices 10-1 and 10-2, actuators 20-1 and 20-2, and measurement devices 30-1 and 30-2. The network between the control devices 10-1 and 10-2 and the actuators 20-1 and 20-2 and between the measurement devices 30-1 and 30-2 and the control devices 10-1 and 10-2 is a network. Connected. This network is an inexpensive shared line compared to leased line communication, and the communication throughput is likely to vary depending on noise and / or other communication conditions.

  The control devices 10-1 and 10-2 transmit the operation amount to the actuators 20-1 and 20-2 based on the target value. The actuators 20-1 and 20-2 are drive devices for executing a predetermined operation in the process to be controlled, and are, for example, a pump, a valve, an air conditioner, or the like. The actuators 20-1 and 20-2 are not limited to these. The measuring devices 30-1 and 30-2 measure the state of the process to be controlled, and are, for example, a thermometer, a hygrometer, a pH meter, or the like. Note that the measuring devices 30-1 and 30-2 are not limited to these.

  A control object process represents the process controlled via a network in various control object plants, such as a steel plant, a power system plant, a power generation plant, or a water and sewage plant, for example. The process to be controlled is, for example, a pond water level, piping pressure, room temperature, or the like. However, the process to be controlled is not limited to these.

  FIG. 2 is a block diagram showing a functional configuration of the control system shown in FIG. In FIG. 2, the control device 10-1, the actuator 20-1, and the measurement device 30-1 will be described for the sake of brevity and will be referred to as the control device 10, the actuator 20, and the measurement device 30, respectively. .

  The control device 10 includes a measurement amount reception unit 11, a time measurement unit 12, a determination unit 13, a calculation unit 14, and an operation amount transmission unit 15. Note that the measurement amount reception unit 11, the determination unit 13, the calculation unit 14, and the operation amount transmission unit 15 may be realized, for example, by causing a computer included in the control device 10 to execute a control program.

  The measurement amount receiving unit 11 includes a reception time giving unit 111 and a reception processing unit 112.

  When the reception processing unit 112 receives the measurement amount, the reception time giving unit 111 outputs the time information supplied from the time measuring unit 12 to the reception processing unit 112.

  The reception processing unit 112 receives the measurement amount transmitted from the measurement device 30 via the network. When receiving the measurement amount, the reception processing unit 112 adds the time information output from the reception time adding unit 111 to the received measurement amount and stores it. In addition, when receiving the measurement amount, the reception processing unit 112 compares the time information output from the reception time giving unit 111 with the time information given to the measurement amount received last time, and calculates a sampling period. The reception processing unit 112 outputs the received measurement amount to the calculation unit 14 and outputs the calculated sampling period to the determination unit 13.

  The determination unit 13 stores in advance a maximum allowable sampling period set for each process to be controlled. The determination method of the maximum allowable sampling period is not limited, but is determined as follows, for example.

When packet loss occurs stochastically, a discrete-time linear system including a controlled process is given by the following equation of state.

Here, A _d and B _d are

A and B are expressed in discrete time. At this time, the controller F _d is designed so that the absolute values of the eigenvalues of A _d −B _d F _d are all less than 1.

If the network state is normal, the signal arrives at every predetermined control period ΔT, but when packet loss occurs σ (i) times continuously for one or more times, σ (i) with respect to the normal control period ΔT • The control cycle is delayed by ΔT. That is, in the discrete time system, when σ (i) packet loss occurs, the change in discrete time, _Ad and _Bd, are expressed by the following equations.

Here, τ (i) represents the time of the discrete time i.

Using the equation (1), σ (i) until the absolute value of the eigenvalue of A _d −B _d F _d becomes 1 with respect to the control law F _d designed assuming σ (i) = 0. Ask for. In this way, by obtaining σ (i), it is understood how much packet loss can be tolerated. The maximum allowable sampling period is determined based on the grasped allowable number of times.

Note that σ (i) until a positive definite matrix P such that P = A _d ^T PA _d + Q exists for any positive definite (or semi-definite) matrix Q from the Lyapunov stability condition for the discrete time system. May be adopted, and the maximum allowable sampling period may be determined. Further, according to the sampling theorem, the maximum allowable sampling period may be determined so as to allow up to 1/2 of the time constant of the process to be controlled. According to the sampling theorem, if measurement is performed at a frequency higher than 2f with respect to the maximum frequency f of the control target process, the measurement signal of the control target process can be completely restored on the receiving side.

  The determination unit 13 determines whether the sampling period output from the measurement amount reception unit 11 deviates from the maximum allowable sampling period stored in advance. When the determination unit 13 determines that the sampling period deviates from the maximum allowable sampling period, the determination unit 13 issues an alarm and outputs a stop signal to the calculation unit 14.

  The calculation unit 14 receives a control target value (SV) supplied from the outside and a measurement amount (PV) supplied from the measurement amount reception unit 11. The calculation unit 14 calculates an operation amount (MV) for driving the actuator 20 based on the measured amount and the control target value according to a preset control cycle. There are various algorithms for calculating the manipulated variable, such as PID control, model prediction control, and H-infinity control. However, in the present embodiment, feedback control may be used without adopting any of the above calculation methods. The calculating unit 14 outputs the obtained operation amount to the operation amount transmitting unit 15.

  In addition, when a stop signal is output from the determination unit 13, the calculation unit 14 stops the calculation process.

  The operation amount transmission unit 15 converts the operation amount output from the calculation unit 14 into a data packet of a protocol corresponding to the network. The operation amount transmission unit 15 specifies the actuator 20 and transmits the converted data packet to the network.

  The actuator 20 includes an operation amount receiving unit 21 and a driving unit 22. The operation amount receiving unit 21 operates the drive unit 22 based on the operation amount transmitted from the operation amount transmission unit 15 of the control device 10 via the network. When the actuator 20 is a pump, the operation amount is the pump rotation speed, and the drive unit 22 is a mechanism that rotates the impeller according to the pump rotation speed.

  The measurement device 30 includes a measurement unit 31 and a measurement amount transmission unit 32. The measurement unit 31 measures the state of the control target process at a preset cycle. The measurement amount transmission unit 32 converts the measurement amount measured by the measurement unit 31 into a data packet of a protocol corresponding to the network. The measured amount transmission unit 32 designates the control device 10 and transmits the converted data packet to the network.

  FIG. 3 is a schematic diagram for explaining the operation of the control device 10 according to the present embodiment. FIG. 3A shows the operation of the control device 10 when the network is normal. FIGS. 3B and 3C show the operation of the control device 10 in a state where the network is congested and packet loss occurs. FIG. 3D shows the operation of the conventional control apparatus in a state where the network is congested and packet loss occurs. In the following description, a case where the maximum allowable sampling period is 3.5Δt will be described. Further, in the conventional control device, if the next data packet does not arrive within 2Δt as a communication system restriction, an alarm is issued as a communication error and / or the actuator is stopped urgently.

  In FIG. 3A, the control device 10 receives data packets transmitted from the measurement device 30 via the network at ΔT intervals. When receiving the data packet at T = t + 3Δt, the reception processing unit 112 calculates Δt as a sampling period from the difference between the reception time T = t + 2Δt of the previously received data packet and T = t + 3Δt.

  The determination unit 13 determines whether the sampling period Δt deviates from the maximum allowable sampling period 3.5Δt. Here, since 3.5Δt> Δt and the sampling period does not deviate from the maximum allowable sampling period, the calculation unit 14 continues the feedback control for the actuator 20.

  In FIG. 3B, the data packet transmitted from the measuring device 30 via the network is lost at T = t + Δt and T = t + 2Δt. When receiving the data packet at T = t + 3Δt, the reception processing unit 112 calculates 3Δt as a sampling period from the difference between the reception time T = t of the previously received data packet and T = t + 3Δt.

  The determination unit 13 determines whether the sampling period 3Δt deviates from the maximum allowable sampling period 3.5Δt. Here, since 3.5Δt> 3Δt and the sampling period does not deviate from the maximum allowable sampling period, the calculation unit 14 continues the feedback control for the actuator 20.

  In FIG. 3C, the data packet transmitted from the measuring device 30 via the network is lost at T = t + Δt, T = t + 2Δt, and T = t + 3Δt. When receiving the data packet at T = t + 4Δt, the reception processing unit 112 calculates 4Δt as a sampling period from the difference between the reception time T = t of the previously received data packet and T = t + 4Δt.

  The determination unit 13 determines whether the sampling period 4Δt deviates from the maximum allowable sampling period 3.5Δt. Here, since 4Δt> 3.5Δt and the sampling period deviates from the maximum allowable sampling period, the determination unit 13 outputs a stop signal to the calculation unit 14. When the calculation unit 14 receives the stop signal, the calculation unit 14 stops the feedback control for the actuator 20.

  In FIG. 3D, when the data packet does not arrive at T = t + 2Δt, the conventional control apparatus does not reach the data packet exceeding 2Δt, which is a restriction of the communication system. Even if not, it is determined that a communication error has occurred, and feedback control for the actuator is stopped.

  As described above, in the first embodiment, the reception processing unit 112 calculates the sampling period for receiving the measurement amount. The determination unit 13 compares the sampling period with a preset maximum allowable sampling period, and determines whether the sampling period does not deviate from the maximum allowable sampling period. When the sampling period deviates from the maximum allowable sampling period, the determination unit 13 causes the calculation unit 14 to stop feedback control of the actuator 20. Accordingly, it is possible to determine whether to continue or stop the feedback control based on the maximum allowable sampling period that is not a restriction from the communication system but a restriction from the control system.

  Therefore, according to the control system according to the first embodiment, in the case where the drive device is feedback-controlled using a shared line, even if a packet loss occurs on the network, there is no problem in the process. The control can be continued while allowing packet loss.

  In the control system according to the first embodiment, the case where feedback control to the actuator 20 is stopped according to the determination result of the determination unit 13 has been described as an example. However, the present invention is not limited to this. For example, the control system may include a control device 40 shown in FIG. That is, the control device 40 includes a measurement amount receiving unit 11, a time measuring unit 12, a determination unit 41, a calculation unit 42, an operation amount transmission unit 15, and a steady state determination unit 43.

  The determination unit 41 determines whether the sampling period output from the measurement amount reception unit 11 deviates from the maximum allowable sampling period stored in advance. If the determination unit 41 determines that the sampling period deviates from the maximum allowable sampling period, the determination unit 41 outputs an error signal to the steady state determination unit 43.

  When the steady state determination unit 43 receives the error signal output from the determination unit 41, the steady state determination unit 43 determines whether the process to be controlled is in a steady state based on the measurement amount output from the measurement amount reception unit 11. The method for determining whether the process to be controlled is in a steady state is not limited. For example, the determination is performed as follows.

When the measurement amount x (k) at time k cannot be received, the measurement amounts x (k−1), x (k−2),..., X (k−i), i = 1, 2,. , N, consider the following average μ and variance σ.

The steady state determination unit 43 determines that the process to be controlled is in a steady state when the average μ and the variance σ are within a preset threshold range.

  When the steady state determination unit 43 determines that the process to be controlled is in a steady state, the steady state determination unit 43 continues the feedback control of the actuator 20 by the calculation unit 42. Further, when it is determined that the process to be controlled is not in the steady state, the steady state determination unit 41 issues an alarm and outputs a stop signal to the calculation unit 42.

  The calculation unit 42 receives a control target value supplied from the outside and a measurement amount supplied from the measurement amount reception unit 11. The computing unit 42 computes an operation amount for driving the actuator 20 based on the measured amount and the control target value according to a preset control cycle. The calculating unit 42 outputs the obtained operation amount to the operation amount transmitting unit 15. When the stop signal is output from the steady state determination unit 41, the calculation unit 42 stops the calculation process.

  Thereby, when the process to be controlled is in a steady state, the control device 40 can continue the feedback control of the actuator 20 even if the sampling period deviating from the maximum allowable sampling period is measured.

  The control system according to the first embodiment is an example in which the determination unit 13 stores the maximum allowable sampling period in advance and compares the sampling period supplied from the measurement amount receiving unit 11 with the maximum allowable sampling period. Explained. However, the present invention is not limited to this. For example, the control system may include a control device 50 shown in FIG. That is, the control device 50 includes a measurement amount receiving unit 11, a time measuring unit 12, a sampling period calculation unit 51, a determination unit 52, a calculation unit 14, and an operation amount transmission unit 15.

The sampling period calculation unit 51 stores in advance upper and lower limit values that are allowable as a measurement amount. The sampling period calculation unit 51 refers to the measurement amount received during a preset period and calculates an extrapolated value as a value indicating the trend of the measurement amount. As a method of calculating the extrapolated value, for example, a method of calculating using an AR model is conceivable. The extrapolated value is

Is required. Here, φ _i represents a model parameter, and c represents a constant. Further, when the measured quantity includes disturbance, that is, when y (k) = Cx (k) + v, there is a method of calculating an extrapolated value using a Kalman filter. Note that v represents noise. The extrapolated value is

Is required. Here, K indicates Kalman gain. Note that the method of calculating the extrapolation value is not limited to these.

  When the extrapolation value is calculated, the sampling period calculation unit 51 calculates the time until the extrapolation value reaches the upper and lower limit values as shown in FIG. The sampling period calculation unit 51 sets the calculated time as the second maximum allowable sampling period. The sampling period calculation unit 51 outputs the calculated second maximum allowable sampling period to the determination unit 52.

  The determination unit 52 determines whether or not the second maximum allowable sampling period calculated by the sampling period calculation unit 51 is equal to or greater than the maximum allowable sampling period stored in advance, and if so, is output from the measurement amount reception unit 11. It is determined whether the sampling period is not the maximum allowable sampling period but deviates from the second maximum allowable sampling period. When it is determined that the sampling period deviates from the second maximum allowable sampling period, the determination unit 52 issues an alarm and outputs a stop signal to the calculation unit 14.

  When the second maximum allowable sampling period is less than the maximum allowable sampling period, the determination unit 52 determines whether the sampling period output from the measurement amount receiving unit 11 does not deviate from the maximum allowable sampling period. If the determination unit 52 determines that the sampling period deviates from the maximum allowable sampling period, the determination unit 52 issues an alarm and outputs a stop signal to the calculation unit 14.

  As a result, the control device 50 can continue the feedback control of the actuator 20 even when a sampling period that deviates from the maximum allowable sampling period is measured, when the timing at which the measured amount exceeds the upper limit value can be acquired. It becomes possible.

  Moreover, in 1st Embodiment, the calculating part 14 demonstrated as an example the case where the operation amount was calculated according to the preset control period. However, the present invention is not limited to this. For example, the control system may include a control device 60 shown in FIG. That is, the control device 60 includes a measurement amount receiving unit 61, a time measuring unit 12, a determination unit 13, a calculation unit 62, and an operation amount transmission unit 15.

  The measurement amount receiving unit 61 includes a reception time giving unit 111 and a reception processing unit 611. When receiving the measurement amount, the reception processing unit 611 calculates a sampling period. The reception processing unit 611 outputs the received measurement amount to the calculation unit 62 and outputs the calculated sampling period to the determination unit 13 and the calculation unit 62.

  The calculation unit 62 includes a period correction unit 621 and an operation amount calculation unit 622.

  When receiving the sampling period output from the measurement amount receiving unit, the period correcting unit 621 synchronizes the control period with the received sampling period. The period correction unit 621 outputs a control period synchronized with the sampling period to the operation amount calculation unit 622.

The operation amount calculator 622 receives a control target value supplied from the outside and a measured amount supplied from the measured amount receiver 61. The operation amount calculation unit 622 calculates an operation amount for driving the actuator 20-1 based on the measurement amount and the control target value according to the control cycle output from the cycle correction unit 621. When calculating the operation amount by PID control, the operation amount is calculated based on the following equation.

Here, MV (k) indicates an operation amount to be transmitted at time k, ΔMV (k) indicates a differential operation amount at which the operation amount is changed at time k, and e (k) is a control target value and measurement at time k. A deviation of the quantity is indicated, Kp indicates a preset proportional gain, Ti indicates a preset integration time, and ΔT indicates a control period corrected by the period correcting unit 621. The operation amount calculator 622 outputs the calculated operation amount to the operation amount transmitter 15.

  The packet loss rate that occurs on the network is defined by the amount of received data [bit] and the amount of transmitted data [bit], as shown in equation (4). Here, the packet loss that occurs in the router on the network depends on the router processing capability B [bps], the transmission cycle T [sec], and the transmission data amount M [bit], as shown in equation (5). The transmission data amount M is obtained from the number of data n [pieces] × data size S [bits].

Packet loss rate [%] = 1- (received data amount [bit] / transmitted data amount [bit]) (4)
Received data amount [bit] = transmitted data amount [bit] −Σ ((M / T) [bps] −B [bps]) (5)
(However, when M / T ≦ B, received data amount = transmitted data amount)
That is, the packet loss rate is reduced by lengthening the transmission cycle and reducing the amount of transmission data.

  When packet loss occurs (particularly in a burst manner), the control device 60 cannot receive the measurement amount necessary for the operation amount calculation for a long time. Therefore, the control device 60 cannot create an operation amount based on the measured amount of the process to be controlled and the desired control target value. Thereby, the packet loss can be a factor causing a system abnormality as a communication abnormality in the control system.

  The calculation unit 62 changes the control cycle based on the sampling cycle calculated by the measurement amount reception unit 61 by the cycle correction unit 621, and calculates the operation amount according to the changed control cycle by the operation amount calculation unit 622. Thereby, when the sampling period is long, the control device 60 can reduce the amount of data packets to be transmitted. Although the packet loss rate depends on the communication specifications and / or the surrounding environment such as a router, the control device 60 according to the present embodiment suppresses the packet loss rate by adjusting the data packet transmission cycle. I do. Thereby, when the network is congested, it is possible to minimize the influence of packet loss.

  Moreover, in the control system which concerns on 1st Embodiment, the case where time information was not included in the measured quantity transmitted from the measuring device 30 demonstrated as an example. However, the present invention is not limited to this. For example, the control system may include a control device 70, actuators 20-1 and 20-2, and a measurement device 80 shown in FIG. The measurement device 80 includes a measurement unit 31, a measurement amount transmission unit 81, and a time measurement unit 82.

  The measured amount transmission unit 81 includes a transmission time giving unit 811 and a transmission processing unit 812. The transmission time giving unit 811 outputs the time information supplied from the time measuring unit 82 to the transmission processing unit 812 when the measurement amount is measured by the transmission unit 31.

  When the measurement amount is measured, the transmission processing unit 812 adds the time information output from the transmission time adding unit 811 to the measured measurement amount. The transmission processing unit 812 converts the measurement amount given the time information into a data packet of a protocol corresponding to the network. The transmission processing unit 812 specifies the control device 70 and transmits the converted data packet to the network.

  The control device 70 includes a measurement amount receiving unit 71, a time measuring unit 12, a determination unit 13, a calculation unit 72, and an operation amount transmission unit 15.

  The measurement amount receiving unit 71 includes a reception time giving unit 111 and a reception processing unit 711.

  The reception processing unit 711 receives the measurement amount transmitted from the measurement device 80 via the network. When receiving the measurement amount, the reception processing unit 711 adds the time information output from the reception time adding unit 111 to the received measurement amount and stores it.

  In addition, when receiving the measurement amount, the reception processing unit 711 compares the time information output from the reception time giving unit 111 with the time information given to the measurement amount received last time, and calculates the sampling period. The reception processing unit 711 outputs the received measurement amount to the calculation unit 72 and outputs the calculated sampling period to the determination unit 13.

  In addition, when the reception processing unit 711 receives the measurement amount, the reception processing unit 711 compares the transmission time information given to the measurement amount with the time information output from the reception time addition unit 111, and transmits the measurement amount through the network. Calculate the time required to do this. The reception processing unit 711 determines whether the required time exceeds an allowable required time set in advance. When the required time exceeds the preset allowable required time, the reception processing unit 711 creates a flag assignment signal and outputs the created flag assignment signal to the calculation unit 72. The allowable required time set in advance is a packet arrival time for determining that the network is congested.

  The calculation unit 72 includes an operation amount calculation unit 721 and a flag assignment unit 722.

  The operation amount calculation unit 721 receives a control target value supplied from the outside and a measurement amount supplied from the measurement amount reception unit 71. The operation amount calculation unit 721 calculates an operation amount for driving the actuators 20-1 and 20-2 based on the measured amount and the control target value according to a preset control cycle. The operation amount calculation unit 721 outputs the calculated operation amount to the flag assignment unit 722.

  In addition, when the stop signal is output from the determination unit 13, the operation amount calculation unit 721 stops the arithmetic processing.

  The flag assigning unit 722 stores a priority set in advance for the actuators 20-1 and 20-2. When the flag assigning unit 722 receives the flag assigning signal output from the measured amount receiving unit 71, the priority is given to the operation amount in which the actuator having the higher priority is designated as the transmission destination among the actuators 20-1 and 20-2. Give a flag. The flag assigning unit 722 outputs the operation amount assigned with the priority flag and the operation amount not assigned to the operation amount transmitting unit 15.

  At this time, the network includes a protocol for preferentially transmitting the data packet to which the priority flag is assigned to the actuator.

  As described above, when the network is congested, the flag assigning unit 722 assigns a priority flag to the operation amount targeted for the actuator having a high priority so that the data packet reaches the actuator preferentially. ing. Although the packet loss rate depends on the communication environment that is the communication environment and / or the surrounding environment such as the router, the control device 70 according to the present embodiment attaches a priority flag to the data packet to be transmitted preferentially, The packet loss rate is suppressed. That is, with respect to the minimum necessary operation amount, it is possible to prevent packet loss on the network as much as possible.

  In the first embodiment, the determination units 13, 41, and 52 will be described by taking as an example the case where the sampling period deviates from the maximum allowable sampling period and an alarm is issued and a stop signal is output to the calculation unit. did. However, the present invention is not limited to this. For example, when the sampling period deviates from the maximum allowable sampling period, the determination units 13, 41, and 52 make “Emergency stop”, “Abnormal alarm”, “Standby”, “Continue with extrapolation of signal”, etc. Alternatively, an instruction signal for instructing may be output.

(Second Embodiment)
FIG. 9 is a block diagram illustrating a functional configuration of a control system according to the second embodiment. The control system shown in FIG. 9 includes a control device 90, an actuator 20, and a measurement device 30. The control device 90 and the actuator 20 and the measurement device 30 and the control device 90 are connected by a network.

  The control device 90 includes a measurement amount receiving unit 91, a time measuring unit 92, a calculation unit 93, and an operation amount transmission unit 94. Note that the measurement amount reception unit 91, the calculation unit 93, and the operation amount transmission unit 94 may be realized, for example, by causing a computer included in the control device 90 to execute a control program.

  The measurement amount receiving unit 91 includes a reception processing unit 911. The reception processing unit 911 receives the measurement amount transmitted from the measurement device 30 via the network. When receiving the measurement amount, the reception processing unit 911 outputs the received measurement amount to the calculation unit 93.

  The calculation unit 93 includes an operation amount calculation unit 931 and a determination unit 932.

  The operation amount calculation unit 931 receives a control target value (SV) supplied from the outside and a measurement amount (PV) supplied from the measurement amount reception unit 91. When receiving the measurement amount, the operation amount calculation unit 931 calculates an operation amount (MV) for driving the actuator 20 based on the received measurement amount and the control target value. There are various algorithms for calculating the manipulated variable, such as PID control, model prediction control, and H-infinity control. However, in the present embodiment, feedback control may be used without adopting any of the above calculation methods. The operation amount calculation unit 931 outputs the obtained operation amount to the determination unit 932 and the operation amount transmission unit 94.

  In addition, when the stop signal is output from the determination unit 932, the operation amount calculation unit 931 stops the arithmetic processing.

  The determination unit 932 is connected to the time measuring unit 92 and is supplied with time information. When the determination unit 932 receives the operation amount output from the operation amount calculation unit 931, the determination unit 932 adds and stores the time information supplied from the time measuring unit 92 to the received operation amount. In addition, when the operation amount is received, the determination unit 932 compares the time information supplied from the time measuring unit 92 with the time information given to the operation amount received last time, and calculates a control cycle.

  The determination unit 932 stores in advance a maximum allowable control period set for each process to be controlled. Although the determination method of the maximum allowable control period is not limited, for example, it is determined by the same method as the maximum allowable sampling period in the first embodiment.

  The determination unit 932 determines whether the calculated control cycle deviates from the maximum allowable control cycle stored in advance. When the determination unit 932 determines that the control cycle deviates from the maximum allowable control cycle, the determination unit 932 issues a warning and outputs a stop signal to the operation amount calculation unit 931.

  The operation amount transmission unit 94 converts the operation amount output from the calculation unit 93 into a data packet of a protocol corresponding to the network. The operation amount transmission unit 94 specifies the actuator 20 and transmits the converted data packet to the network.

  As described above, in the second embodiment, the determination unit 932 calculates the control cycle for calculating the operation amount. The determination unit 932 compares the control cycle with a preset maximum allowable control cycle, and determines whether the control cycle does not deviate from the maximum allowable control cycle. When the control cycle deviates from the maximum allowable control cycle, the determination unit 932 causes the operation amount calculation unit 931 to stop feedback control. Accordingly, it is possible to determine whether to continue or stop the feedback control based on the maximum allowable control period that is not a restriction from the communication system but a restriction from the control system.

  Therefore, according to the control system according to the second embodiment, in the case where feedback control of the driving device is performed using the shared line, even when packet loss occurs on the network, there is no problem in the process. The control can be continued while allowing packet loss.

  In the control system according to the second embodiment, the case where feedback control to the actuator 20 is stopped according to the determination result of the determination unit 932 has been described as an example. However, the present invention is not limited to this. For example, the control system may include a control device 100 shown in FIG. That is, the control device 100 includes a measurement amount receiving unit 91, a time measuring unit 92, a calculation unit 101, and an operation amount transmission unit 94.

  The calculation unit 101 includes an operation amount calculation unit 1011, a determination unit 1012, and a steady state determination unit 1013.

  The determination unit 1012 determines whether the control cycle calculated based on the operation amount output from the operation amount calculation unit 1011 does not deviate from the maximum allowable control cycle stored in advance. If the determination unit 1012 determines that the control cycle deviates from the maximum allowable control cycle, the determination unit 1012 outputs an error signal to the steady state determination unit 1013.

  When the steady state determination unit 1013 receives the error signal output from the determination unit 1012, the steady state determination unit 1013 determines whether the process to be controlled is in a steady state based on the measurement amount output from the measurement amount reception unit 91. Although the method for determining whether the control target process is in a steady state is not limited, for example, the determination is performed using Expressions (2) and (3).

  When the steady state determination unit 1013 determines that the process to be controlled is in a steady state, the operation amount calculation unit 1011 continues the feedback control of the actuator 20. When the steady state determination unit 1013 determines that the process to be controlled is not in the steady state, the steady state determination unit 1013 issues an alarm and outputs a stop signal to the operation amount calculation unit 1011.

  The operation amount calculation unit 1011 receives a control target value supplied from the outside and a measurement amount supplied from the measurement amount reception unit 91. When receiving the measurement amount, the operation amount calculation unit 1011 calculates an operation amount for driving the actuator 20 based on the received measurement amount and the control target value. The operation amount calculation unit 1011 outputs the obtained operation amount to the determination unit 1012 and the operation amount transmission unit 94. Further, when a stop signal is output from the steady state determination unit 1013, the operation amount calculation unit 1011 stops the arithmetic processing.

  As a result, when the process to be controlled is in a steady state, the control device 100 can continue the feedback control of the actuator 20 even if a control cycle that deviates from the maximum allowable control cycle is measured.

  In the control system according to the second embodiment, the determination unit 932 stores a maximum allowable control period in advance, and compares the control period obtained from the calculated operation amount with the maximum allowable control period. explained. However, the present invention is not limited to this. For example, the control system may include the control device 110 illustrated in FIG. That is, the control device 110 includes a measurement amount receiving unit 91, a time measuring unit 92, a calculation unit 113, and an operation amount transmission unit 94.

  The calculation unit 113 includes an operation amount calculation unit 931, a control cycle calculation unit 1131, and a determination unit 1132.

  The control cycle calculation unit 1131 stores upper and lower limit values that are allowable as a measurement amount in advance. The control period calculation unit 1131 refers to the measurement amount output from the measurement amount reception unit 91 during a preset period, and calculates an extrapolated value as a value indicating the trend of the measurement amount. When calculating the extrapolation value, the control cycle calculation unit 1131 calculates the time until the extrapolation value reaches the upper and lower limit values. The control cycle calculation unit 1131 sets the calculated time as the second maximum allowable control cycle. The control cycle calculation unit 1131 outputs the calculated second maximum allowable control cycle to the determination unit 1132.

  When the determination unit 1132 receives the operation amount output from the operation amount calculation unit 931, the determination unit 1132 compares the time information supplied from the time measuring unit 92 with the time information given to the operation amount received last time, and controls the control cycle. Is calculated.

  In addition, the determination unit 1132 determines whether the second maximum allowable control cycle calculated by the control cycle calculation unit 1131 is greater than or equal to the maximum allowable control cycle stored in advance, and if so, from the operation amount calculation unit 931. It is determined whether the control cycle obtained from the output operation amount is not the maximum allowable control cycle but deviates from the second maximum allowable control cycle. When it is determined that the control cycle deviates from the second maximum allowable control cycle, the determination unit 1132 issues an alarm and outputs a stop signal to the operation amount calculation unit 931.

  When the second maximum allowable control cycle is less than the maximum allowable control cycle, the determination unit 1132 determines whether the calculated control cycle deviates from the maximum allowable control cycle. When it is determined that the control cycle deviates from the maximum allowable control cycle, the determination unit 1132 issues an alarm and outputs a stop signal to the operation amount calculation unit 931.

  As a result, the control device 110 performs feedback control of the actuator 20 without receiving the measurement amount due to the packet loss when the measurement amount may exceed the upper and lower limit values before deviating from the maximum allowable control cycle. It becomes possible to stop.

  In the control system according to the second embodiment, the case where the time information is not included in the measurement amount transmitted from the measurement device 30 has been described as an example. However, the present invention is not limited to this. For example, the control system may include the control device 120, the actuators 20-1, 20-2, and the measurement device 80 illustrated in FIG. The measuring device 80 operates in the same manner as the measuring device 80 shown in FIG.

  The control device 120 includes a measurement amount reception unit 121, a time measurement unit 92, a calculation unit 122, and an operation amount transmission unit 94.

  The measurement amount receiving unit 121 includes a reception time giving unit 1211 and a reception processing unit 1212.

  When the reception processing unit 1212 receives the measurement amount, the reception time giving unit 1211 outputs the time information supplied from the time measuring unit 92 to the reception processing unit 1212.

  The reception processing unit 1212 receives the measurement amount transmitted from the measurement device 80 via the network. When the reception processing unit 1212 receives the measurement amount, the reception processing unit 1212 compares the transmission time information given to the measurement amount with the time information output from the reception time addition unit 1211, and transmits the measurement amount through the network. Calculate the required time. The reception processing unit 1212 determines whether or not the required time exceeds the preset allowable required time. When the required time exceeds the preset allowable required time, the reception processing unit 1212 creates a flag assignment signal and outputs the created flag assignment signal to the calculation unit 122.

  The calculation unit 122 includes an operation amount calculation unit 1221, a determination unit 932, and a flag assignment unit 1222.

  The operation amount calculation unit 1221 receives a control target value supplied from the outside and a measurement amount supplied from the measurement amount reception unit 121. When receiving the measurement amount, the operation amount calculation unit 1221 calculates an operation amount for driving the actuators 20-1 and 20-2 based on the received measurement amount and the control target value. The operation amount calculation unit 1221 outputs the calculated operation amount to the determination unit 932 and the flag assignment unit 1222.

  Further, when a stop signal is output from the determination unit 932, the operation amount calculation unit 1221 stops the arithmetic processing.

  The flag assigning unit 1222 stores priorities set in advance for the actuators 20-1 and 20-2. When the flag assigning unit 1222 receives the flag assigning signal output from the measurement amount receiving unit 121, the priority is given to the operation amount in which the actuator having the higher priority is designated as the transmission destination among the actuators 20-1 and 20-2. Give a flag. The flag assigning unit 1222 outputs the operation amount assigned with the priority flag and the operation amount not given to the operation amount transmitting unit 94.

  At this time, the network includes a protocol for preferentially transmitting the data packet to which the priority flag is assigned to the actuator.

  As described above, when the network is congested, the flag assigning unit 1222 assigns a priority flag to the operation amount targeted for the actuator with a high priority so that the data packet reaches the actuator preferentially. ing. Although the packet loss rate depends on the communication environment that is the communication environment and / or the surrounding environment such as the router, the control device 120 according to the present embodiment attaches a priority flag to the data packet to be transmitted preferentially, The packet loss rate is suppressed. That is, with respect to the minimum necessary operation amount, it is possible to prevent packet loss on the network as much as possible.

  In the second embodiment, the determination units 932, 1012 and 1132 issue an alarm when the control cycle deviates from the maximum allowable control cycle, and output a stop signal to the operation amount calculation unit. Explained. However, the present invention is not limited to this. For example, when the control period deviates from the maximum allowable control period, the determination units 932, 1012, and 1132 calculate an operation amount such as “emergency stop”, “abnormal alarm”, “standby”, or “continue by extrapolating a signal” An instruction signal for instructing the unit may be output.

(Other embodiments)
In the first and second embodiments described above, the operation amount transmitting units 15 and 94 have been described by taking as an example a case where a data packet to which no priority flag is assigned is transmitted to the network. However, the present invention is not limited to this. For example, the operation amount transmission units 15 and 94 may not transmit data packets to which no priority flag is assigned. Thereby, it becomes possible to reduce the communication load of the network and suppress packet loss.

  In the first and second embodiments, the operation amount transmitted to the actuator with low priority has been described as an example in which the operation amount is transmitted to the network without being assigned the priority flag. However, the present invention is not limited to this. For example, the control device may perform processing on the data packet so that the data packet with low priority reaches the actuator at a certain rate even a little. For example, the flag assigning units 722 and 1222 may assign a priority flag to a data packet having a low priority in a predetermined cycle. In addition, the operation amount transmission units 15 and 94 may weight the data packets to which the priority flag is not assigned at a predetermined cycle and transmit the data packets. As a result, the situation where only high-priority data packets flow in a congested network situation continues, so that low-priority data packets are not processed at all, and a situation where communication other than the controlled process cannot be performed is avoided. It becomes possible.

  Further, in the control systems according to the first and second embodiments, the case where one measuring device is targeted has been described as an example. However, the present invention is not limited to this. For example, in the determination unit 13, the priority order is set in advance for a plurality of measuring devices, and when the data packet has not reached for a time longer than the maximum allowable sampling period, the measuring device that has transmitted the measurement amount As the subsequent processing in descending order of priority, “emergency stop”, “abnormal alarm”, “standby”, “continue with extrapolation of signal” or the like may be selected. In the determination unit 932, priorities are set in advance for a plurality of measuring devices, and when the operation amount is not calculated for a time longer than the maximum allowable control cycle, the priority order of the measuring devices that have transmitted the measured amounts As the subsequent processing in descending order, “Emergency stop”, “Abnormality notification”, “Standby”, “Continue with extrapolation of signal”, or the like may be selected.

  The control program executed by the control systems according to the first and second embodiments may be recorded on a computer-readable recording medium.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

  10, 10-1, 10-2, 40, 50, 60, 70, 90, 100, 110, 120 ... control device, 11, 61, 71, 91, 121 ... measured quantity transmission unit, 111, 1211 ... reception time Giving unit, 112, 611, 711, 911, 1212 ... reception processing unit, 12, 82 ... timing unit, 13, 41, 52, 932, 1012, 1132 ... determination unit, 14, 42, 62, 72, 93, 101 , 113, 122 ... arithmetic unit, 15, 94 ... operation amount transmission unit, 20, 20-1, 20-2 ... actuator, 21 ... operation amount reception unit, 22 ... drive unit, 30-1, 30-2 ... measurement Device 31 ... Measurement unit 32 ... Measurement amount transmission unit 43, 1013 ... Steady state determination unit 51 ... Sampling cycle calculation unit 621 ... Period correction unit 622,721,931,1011,1221 ... Operation amount calculation unit , 22,1222 ... flag addition unit, 81 ... measurement amount transmission section, 811 ... transmission time assigning portion 812 ... transmission processing unit, 1131 ... control cycle calculator

Claims (11)

A drive device that receives a control signal supplied as a first packet via a network, and executes a predetermined operation in a process to be controlled according to the received control signal;
A measurement device that measures the state of the process to be controlled, converts the measurement result into a second packet, and outputs the second packet to the network;
A control device connected to the drive device and the measurement device via the network,
A receiver that receives the second packet via the network and calculates a sampling period based on a reception interval of the second packet;
It is determined whether the sampling period exceeds a preset maximum allowable sampling period, and if it exceeds, a determination unit that determines that an abnormality has occurred,
When it is not determined that the abnormality has occurred, the control signal is generated based on a measurement result included in the second packet and a control target set for the driving device, and the abnormality has occurred. If determined, an arithmetic unit that suppresses generation of the control signal;
A control system comprising: the control device comprising: a transmission unit that converts the generated control signal into the first packet and outputs the first packet to the network. The controller is
A stationary state determination unit that refers to measurement results included in the plurality of second packets received immediately before and determines whether or not the state of the process to be controlled is a steady state;
The control system according to claim 1, wherein the calculation unit suppresses the generation of the control signal when it is determined that an abnormality has occurred in the determination unit and the steady state determination unit determines that the abnormality is not in a steady state. The controller is
Sampling period calculation that refers to the measurement results included in the plurality of second packets received immediately before, and calculates the time until the measurement results reach preset upper and lower limit values as the second maximum allowable sampling period Further comprising
The determination unit uses the second maximum allowable sampling period instead of the maximum allowable sampling period when the second maximum allowable sampling period is longer than the maximum allowable sampling period, and the sampling period is the first 3. The control system according to claim 1, wherein it is determined whether or not a maximum allowable sampling period of 2 is exceeded, and if it is exceeded, it is determined that an abnormality has occurred.   The control system according to claim 1, wherein the calculation unit generates the control signal according to the sampling period. A plurality of the drive devices,
The measuring device gives a transmission time for transmitting the second packet to the second packet,
The reception unit calculates a time required for transmitting the second packet through the network from a difference between a transmission time of the second packet and a reception time of the second packet, and the required time If it exceeds the preset allowable time, generate a flag assignment signal,
When the abnormality is not determined to have occurred and the flag assignment signal is generated, the arithmetic unit refers to the priority order of the plurality of drive devices, and sets the control signal for the drive device having a higher priority order. 5. A control system according to claim 1, wherein a priority flag for preferentially transmitting the control signal is added. A drive device that receives a control signal supplied as a first packet via a network, and executes a predetermined operation in a process to be controlled according to the received control signal;
A measurement device that measures the state of the process to be controlled, converts the measurement result into a second packet, and outputs the second packet to the network;
A control device connected to the drive device and the measurement device via the network,
A receiving unit for receiving the second packet via the network;
An operation amount calculating unit that generates the control signal based on a measurement result included in the second packet and a control target set for the driving device;
A control cycle is calculated based on an interval at which the control signal is generated, and it is determined whether or not the control cycle exceeds a preset maximum allowable control cycle. A determination unit for suppressing generation of the control signal in the calculation unit;
A control system comprising: the control device comprising: a transmission unit that converts the generated control signal into the first packet and outputs the first packet to the network. The controller is
A stationary state determination unit that refers to measurement results included in the plurality of second packets received immediately before and determines whether or not the state of the process to be controlled is a steady state;
The control according to claim 6, wherein the operation amount calculation unit suppresses generation of the control signal when the determination unit determines that an abnormality has occurred and the steady state determination unit determines that the abnormality is not a steady state. system. The controller is
Control cycle calculation that refers to the measurement results included in the plurality of second packets received immediately before and calculates the time until the measurement results reach preset upper and lower limit values as the second maximum allowable control cycle. Further comprising
When the second maximum allowable control cycle is longer than the maximum allowable control cycle, the determination unit uses the second maximum allowable control cycle instead of the maximum allowable control cycle, and the control cycle is the first 8. The control system according to claim 6, wherein it is determined whether or not a maximum allowable control period of 2 is exceeded, and if it exceeds, the generation of the control signal in the operation amount calculation unit is suppressed as an abnormality has occurred. A plurality of the drive devices,
The measuring device gives a transmission time for transmitting the second packet to the second packet,
The reception unit calculates a time required for transmitting the second packet through the network from a difference between a transmission time of the second packet and a reception time of the second packet, and the required time If it exceeds the preset allowable time, generate a flag assignment signal,
The controller is
When the flag assignment signal is generated, the priority order of the plurality of drive devices is referred to, and the control signal for the drive device having the higher priority order among the control signals generated by the operation amount calculation unit is controlled. The control system according to any one of claims 6 to 8, further comprising a flag assigning unit that assigns a priority flag for preferentially transmitting a signal. A control program used in a drive device that executes a predetermined operation in a process to be controlled, a measurement device that measures a state of the process to be controlled, and a control device connected via a network,
A process of receiving a first packet including a measurement result from the measurement device via the network and calculating a sampling period based on a reception interval of the first packet;
Determining whether the sampling period exceeds a preset maximum allowable sampling period, and if it exceeds, a process of determining that an abnormality has occurred;
When it is not determined that the abnormality has occurred, a process of generating a control signal based on the measurement result and a control target set for the drive device;
When it is determined that the abnormality has occurred, a process of suppressing generation of the control signal;
The control program which makes the computer of the said control apparatus perform the process which converts the produced | generated control signal into a 2nd packet, and outputs to the said drive device via the said network. A control program used in a drive device that executes a predetermined operation in a process to be controlled, a measurement device that measures a state of the process to be controlled, and a control device connected via a network,
Processing for receiving a first packet including a measurement result from the measurement device via the network;
Processing for generating a control signal based on the measurement result and a control target set for the driving device;
Processing for calculating a control period based on an interval for generating the control signal;
It is determined whether or not the control cycle exceeds a preset maximum allowable control cycle, and if it exceeds, a process of suppressing generation of the control signal;
The control program which makes the computer of the said control apparatus perform the process which converts the produced | generated control signal into a 2nd packet, and outputs to the said drive device via the said network.

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