control system

Abstract

This invention provides a technology that allows for the addition or removal of control devices in a control system that controls an object using multiple control devices. [Solution] The control system of the present disclosure comprises a plurality of control devices, at least one controlled object controlled by the plurality of control devices, and a computer connected to the plurality of control devices and the controlled object via a control network, wherein the computer is configured to perform the following: a process of receiving an application from an additional control device to join the control system; a process of acquiring information regarding the status of the plurality of control devices and transmitting it to the additional control device; and a process of managing transmission and reception within the control network.

Description

Technical Field

[0001] The present disclosure relates to a control system.

Background Art

[0002] A control system that performs feedback control of a control target from a control device is known. Patent Document 1 describes "In a control method of a state feedback control system in which a feedback coefficient is changed during operation, a predetermined state quantity periodically detected is differentiated or differenced from the previous state quantity, and the feedback coefficient is multiplied by the differential value or difference value, and the multiplication result is integrated or integrated with the previous control command value to obtain the current control command value."

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] [[ID=�4]] For example, there is a need to control one control target from a plurality of control devices for the purpose of constructing a redundant system. In this case, although the number of control devices may increase or decrease, it is difficult to increase the control devices midway when performing feedback control such as PID control.

[0005] Therefore, the present disclosure provides a technique that enables an increase or decrease in control devices in a control system that controls a control target from a plurality of control devices.

Means for Solving the Problems

[0006] To solve the above problems, the control system disclosed herein is a control system comprising a plurality of control devices, at least one controlled object controlled by the plurality of control devices, and a computer connected to the plurality of control devices and the controlled object via a control network, wherein the computer is configured to perform the following: a process of receiving an application from an additional control device to join the control system; a process of acquiring information regarding the status of the plurality of control devices and transmitting it to the additional control device; and a process of managing transmission and reception within the control network.

[0007] Further features relating to this disclosure will become apparent from the description herein and the accompanying drawings. Furthermore, aspects of this disclosure are achieved and realized through elements and various combinations of elements and the modes of the claims described herein and the accompanying claims. The descriptions herein are merely illustrative and do not limit in any way the claims or applications of this disclosure. [Effects of the Invention]

[0008] According to the technology disclosed herein, in a control system that controls a controlled object using multiple control devices, it becomes possible to increase or decrease the number of control devices. Other issues, configurations, and effects will be clarified by the following description of embodiments. [Brief explanation of the drawing]

[0009] [Figure 1] This block diagram shows an example of a control system that uses a single control device to control a single target. [Figure 2] This block diagram shows an example of a control system that uses two control devices to control a single target object. [Figure 3] This is a functional block diagram showing the configuration of the control system according to the first embodiment. [Figure 4] This is a hardware configuration diagram of the control unit. [Figure 5] This is a hardware configuration diagram for the control system management unit. [Figure 6]This is a functional block diagram showing the configuration of the control system according to the second embodiment. [Figure 7] This is a functional block diagram showing the configuration of the control system according to the third embodiment. [Modes for carrying out the invention]

[0010] [Regarding the control of the controlled object] Figure 1 is a block diagram showing an example of a control system 100 that controls a single control target 102 using a single control device 101. Here, for example, the control device 101 is a PLC, and the control target 102 is a motor. The PLC has a ladder program implemented that performs PID control for controlling the motor's rotation speed. The control device 101 sends the current value for motor rotation as a command value to the control target 102. The control target 102 sends the current motor rotation speed, obtained from a sensor, to the control device 101. Control is continued by using the current rotation speed in feedback control.

[0011] In some cases, a redundant system is configured to account for the event of a control unit failure. There are several ways to configure a redundant system. For example, a method called a dual system involves operating two control units simultaneously and comparing their outputs. If the outputs differ, the system is safely shut down. While this method significantly reduces malfunctions due to control unit failure, it is unavoidable that control will cease in such cases. If the likelihood of a failure is that command values ​​will not be output rather than abnormal values ​​being displayed, then a method of controlling the target system simultaneously from two control units can be considered instead of a dual system.

[0012] Figure 2 is a block diagram showing an example of a control system 200 that controls a single control target 203 using two control devices 201 and 202. The two control devices 201 and 202 transmit command values ​​to the control target 203. Sensor values ​​are then sent from the control target 203 to each control device 201 and 202, and feedback control is performed. Control devices 201 and 202 operate alternately with a timing difference. In this configuration, even if one control device fails and can no longer transmit command values, the other control device can continue to control the object. However, in this configuration, even if the failed control device is restored, it is not possible to return to a control state from both devices while continuing control. This is because, in the case of feedback control, especially integral control such as PID control, control cannot be executed without the previous control information.

[0013] Here, control information includes the control history of the control device. The control history includes the history of target values, the history of command values, the history of feedbacked sensor values, etc. In this specification, control information may also be referred to as information regarding the state of the control device. When the control device is restored, it is necessary to obtain this information regarding the state of the control device again.

[0014] [First Embodiment] <Example of a control system configuration> Disconnection and recovery due to control device failure can be generalized in the form of increasing or decreasing the number of control devices. In the first embodiment, a control system configuration is described in which it is possible to increase or decrease the number of control devices while continuing control when controlling a single control object from multiple control devices.

[0015] FIG. 3 is a functional block diagram showing the configuration of a control system 300 according to the first embodiment. The control system 300 is a system that controls a single control target 307 from a plurality of control devices. The control system 300 includes control devices 301 and 302, a control system management unit 303, a control target 307, a command value input unit 308, a sensor value acquisition unit 309, and a target value setting unit 310. Here, for example, the control devices 301 and 302 are PLCs, and the control target 307 is a motor. The control system management unit 303 has a control system reception unit 304, a control state recording unit 305, and a control network management unit 306.

[0016] The control devices 301 and 302 transmit command values to the control target 307. The command values pass through the control network management unit 306 in the control system management unit 303. The control network management unit 306 is configured to manage communications within the control system 300. Such a control network is realized by, for example, a Publish / Subscribe type (referred to as "Pub / Sub") network such as MQTT. The control network management unit 306 has a function corresponding to an MQTT broker. Alternatively, the control network may be a ring network.

[0017] The command value input unit 308 transmits the command value received from the control network management unit 306 to the control target 307. The sensor value acquisition unit 309 acquires the state of the control target 307 by a sensor. The sensor value acquisition unit 309 transmits the sensor value to each of the control devices 301 and 302 via the control network management unit 306, similar to the command value. At this time, the control system management unit 303 calculates (integrates or sums the history) the control state based on the command value and records it in the control state recording unit 305. This control state is, for example, an integrated value of the difference between the target value and the sensor value for use in integral control in PID control. The target value setting unit 310 determines the target value of the control and transmits it to the control devices 301 and 302 via the control network management unit 306.

[0018] The timing for each control device to perform control is arbitrary. The control cycle and control timing are determined by the performance of each control device itself or the requirements from the control system, without depending on other control devices. The sensor values transmitted from the sensor value acquisition unit 309 are updated in each control device, and the latest sensor values are retained. The control device performs control using the retained latest sensor values at the timing when it performs control. The same applies to the target values.

[0019] Figure 4 is a hardware configuration diagram of the control device 301. The control device 301 can be an arbitrary computer device such as a PLC or a general-purpose computer, for example. The control device 301 includes a processor 11, a memory 12, a storage 13, and a communication device 14. The memory 12 stores the programs necessary for feedback control. The processor 11 controls the control target 307 by executing the programs stored in the memory 12. The memory 12 or the storage 13 stores the sensor values and target values received via the control system management unit 303. The communication device 14 is configured to transmit and receive information with the control system management unit 303.

[0020] The control devices 302 and 311 can also have the same configuration as the control device 301, so the description thereof is omitted. Some of the control devices 301, 302, and 311 may be arranged on the cloud. Thus, the control target 307 can be controlled simultaneously by the physical control device and the control device on the cloud.

[0021] Figure 5 is a hardware configuration diagram of the control system management unit 303. The control system management unit 303 can be configured using computer equipment such as a general-purpose computer or a server device. The control system management unit 303 includes a processor 31, memory 32, storage 33, and communication device 34. The processor 31 realizes the functions of the control system reception unit 304, control network management unit 306, command value input unit 308, sensor value acquisition unit 309, and target value setting unit 310 by loading programs stored in the storage unit 33 into the memory 32 and executing them. The storage unit 33 functions as a control state recording unit 305. The communication device 34 is configured to send and receive information with the command value input unit 308 and the sensor value acquisition unit.

[0022] The control system management unit 303, command value input unit 308, sensor value acquisition unit 309, and target value setting unit 310 may be configured by one computer device or by multiple computer devices. However, the command value input unit 308 and sensor value acquisition unit 309 are physically located near the controlled object 307. The control system reception unit 304, control state recording unit 305, control network management unit 306, and target value setting unit 310 do not necessarily have to be physically located near the controlled object 307. Some or all of these functional units may be connected to the controlled object 307 via the internet, such as on the cloud, enabling communication. In this way, the hardware configuration can be constructed arbitrarily.

[0023] <How to add a control device> This section describes the process when an additional control device (additional control device 311) joins the control system 300. The additional control device 311 is, for example, a control device that has been stopped due to some abnormality and then restored. First, the additional control device 311 sends a request to join the control to the control system reception unit 304 (e.g., an MQTT broker) within the control system management unit 303. The request to join includes communication information for the additional control device 311. Communication information is, for example, an IP address. The control system management unit 303 sends the control state information held by the control state recording unit 305 to the additional control device 311 that submitted the request to join. By receiving the control state information, the additional control device 311 becomes able to participate in feedback control. Furthermore, the control system reception unit 304 notifies the control network management unit 306 of the additional control device 311's participation and starts sending sensor values ​​and target values ​​to the additional control device 311. This process is, for example, a subscription in a Publish / Subscribe type network.

[0024] No special processing is required when a control device leaves the control system 300. The control system management unit 303 does not retain information on individual control devices, and participation and departure from the control network are free. In the control system 300 of this disclosure, there may be multiple control devices, and there is no particular limit to the number.

[0025] <Technical Effects> As described above, the control system 300 according to the first embodiment includes control devices 301 and 302 (multiple control devices), a controlled object 307 (at least one controlled object) controlled by the multiple control devices, and a control system management unit 303, a command value input unit 308, a sensor value acquisition unit 309, and a target value setting unit 310 connected to the multiple control devices and the controlled object via a control network. The control system management unit 303 (computer) is configured to perform the following: a process in the control system reception unit 304 to receive an application from an additional control device 311 to join the control system 300; a process to acquire information regarding the status of the multiple control devices recorded in the control state recording unit 305 and transmit it to the additional control device 311; and a process in the control network management unit 306 to manage transmission and reception within the control network.

[0026] According to the control system 300 of the first embodiment, in a control system that controls a single control object using multiple control devices, it becomes possible to increase or decrease the number of control devices.

[0027] [Second Embodiment] In the second embodiment, an example is shown in which the number of control devices can be increased or decreased without a control state recording unit by using speed-type control. In this embodiment, the control is PID control. Speed-type control is a type of control that generates the difference between the current command value and the command value, rather than directly generating the command value.

[0028] Figure 6 is a functional block diagram showing the configuration of the control system 400 according to the second embodiment. The control system 400 is a system that controls a single control target 407 from multiple speed-type control devices. The control system 400 comprises speed-type control devices 401 and 402, a control network management unit 403, a command value integrator 404, an error value differentiator 405, a control target 407, a command value input unit 408, a sensor value acquisition unit 409, and a target value setting unit 410. Here, for example, the speed-type control devices 401 and 402 are PLCs, and the control target 407 is a motor.

[0029] The speed control devices 401 and 402 transmit the command value difference to the controlled object 407. The command value integrator 404 integrates the command value difference and transmits it to the command value input unit 408. The command value input unit 408 transmits the integrated command value difference to the controlled object 407 as the actual command value. The sensor value acquisition unit 409 acquires the state of the controlled object 407 using a sensor and inputs it to the error value differentiator 405. Unlike the first embodiment, the target value setting unit 410 inputs the set target value to the error value differentiator. The error value differentiator 405 transmits the error value, which is the difference between the target value and the sensor value, along with the previously transmitted error value, to the speed control devices 401 and 402. The speed control devices 401 and 402 generate the next command value difference using the received error value and the previous error value.

[0030] The transmission and reception of command value differences and error values ​​are conducted via the control network management unit 403, as in the first embodiment. The control network management unit 403 has the same functions as the control system reception unit 304 and the control network management unit 306 of the first embodiment.

[0031] <How to add a control device> The process when an additional control device (additional control device 411) joins the control system 400 will be described. The additional control device 411 requests the control network management unit 403 to send an error value as a participation request. When the control network management unit 403 receives the participation request (request to send an error value) from the additional control device 411, it sends the error value (control information) received from the error value differentiator 405 to the additional control device 411. In speed-type control, control is possible using only the transmitted error value, so unlike the first embodiment, the additional control device 411 does not need to acquire control state information.

[0032] <Technical Effects> As described above, in the control system 400 according to the second embodiment, the plurality of control devices are speed control devices 401 and 402. In the control system 400, the command value integrator 404 performs the process of integrating the command value difference transmitted from the speed control devices 401 and 402. The error value differentiator 405 performs the process of transmitting the error value, which is the difference between the feedback value from the controlled object 407 and the target value, and the previous error value to the speed control devices 401 and 402. The control network management unit 403 manages the transmission and reception of the command value difference from the speed control devices 401 and 402, the error value from the error value differentiator 405, and the target value.

[0033] According to the control system 400 of the second embodiment, the control network management unit 403 does not need to transmit control status information in response to participation requests received from additional control devices 411, and the number of control devices can be increased or decreased even without the control status recording unit 305. Thus, the control system 400 has a simple process with no processing load on the control history.

[0034] [Third Embodiment] In the second embodiment, a control system was described in which one control target 407 is controlled by a plurality of speed-type control devices 401, 402, and 411. In the third embodiment, a control system for controlling multiple control targets will be described in the same configuration as in the second embodiment.

[0035] Figure 7 is a functional block diagram showing the configuration of the control system 500 according to the third embodiment. Unlike the second embodiment, the control system 500 has two controlled objects 501 and 502. Each controlled object is provided with a command value integrator 404, an error value differentiator 405, a command value input unit 408, a sensor value acquisition unit 409, and a target value setting unit 410. There is one control network management unit 403, which sends and receives information with the command value integrator 404 and error value differentiator 405 of each controlled object.

[0036] Each speed control device 401 and 402 has a command value input and a sensor value output, similar to the second embodiment. The information for each command value and sensor value is distinguished for each controlled object 501 and 502, making it possible to determine which controlled object is being controlled when using the sensor value.

[0037] Furthermore, the control system 500 includes a control priority determination unit 503 capable of sending and receiving information with the control network management unit 403. The control priority determination unit 503 is configured to select which control target to prioritize. The control priority can be changed dynamically. Based on the received control command value and the pre-set control target information, the control priority determination unit 503 transmits control priority information to the control device via the control network management unit 403. For example, if the control targets are equivalent in the pre-set control target information, the priority of the control target to which the command value was sent is lowered, and the control of the control target to which the command value was not sent is prioritized. Alternatively, if, for example, the target control period of control target 501 is 100ms and the target control period of control target 502 is 200ms, and the elapsed time since the last control is 80ms and 120ms respectively, the priority of control target 501 is increased. The control priority determination unit 503 can adjust the control priority in this way. The adjustment of the control priority is not limited to the method described above, and any method can be used.

[0038] In this embodiment, the case where there are two controlled objects has been described, but there may be three or more. Even when there are three or more controlled objects, the control system 500 can be configured in the same manner as described above.

[0039] <Technical Effects> As described above, the control system 500 according to the third embodiment makes it possible to control multiple control targets in a speed-type control system similar to that of the second embodiment.

[0040] [Differentiation] This disclosure is not limited to the embodiments described above, but includes various modifications. For example, the embodiments described above are described in detail for the purpose of illustrating this disclosure, and do not necessarily have to include all the configurations described. Furthermore, parts of one embodiment can be replaced with the configurations of another embodiment. Furthermore, configurations of other embodiments can be added to the configuration of one embodiment. Furthermore, parts of the configuration of each embodiment can be added, deleted, or replaced with parts of the configurations of other embodiments. [Explanation of symbols]

[0041] 100, 200, 300, 400, 500... control systems 301, 302, 401, 402… Control devices 303...Control System Management Department 304...Control System Reception Department 305...Control status recording unit 306, 403…Control Network Management Department 307, 407, 501, 502… Controlled 308, 408... Command value input section 309, 409... Sensor value acquisition unit 310, 410... Target value setting section 311, 411… Additional control devices 503...Control priority determination unit

Claims

1. Multiple control devices, At least one controlled object controlled by the plurality of control devices, A control system comprising a computer connected to the plurality of control devices and the controlled object via a control network, The aforementioned computer, A process for receiving applications from additional control devices to participate in the control system, A process of acquiring information regarding the status of the plurality of control devices and transmitting it to the additional control device, A control system configured to perform processing for managing transmission and reception within the aforementioned control network.

2. In claim 1, The aforementioned computer, Further processing is performed to record information regarding the state of the aforementioned plurality of control devices in a storage device. A control system configured to transmit, in the transmission process, information regarding the status of the recorded plurality of control devices to the additional control device that transmitted the participation application.

3. In claim 1, The plurality of control devices transmit the command value difference to the computer. The aforementioned computer, A process of integrating the difference in the command values ​​transmitted from the control device, A control system configured to perform the following process: transmit to the multiple control devices an error value, which is the difference between a feedback value from the controlled object and a target value, and the previous error value, as information regarding the state of the multiple control devices.

4. In claim 3, The aforementioned at least one controlled object includes a plurality of controlled objects, The aforementioned computer, A control system configured to further perform a process to determine the control priority of the plurality of controlled objects based on command values ​​from the plurality of control devices, information regarding the status of the plurality of control devices, or information regarding each of the plurality of controlled objects.

5. In claim 1, A control system in which the aforementioned plurality of control devices are speed-type control devices.

6. In claim 1, A control system in which any of the aforementioned plurality of control devices is located on a cloud that can communicate with the computer via the internet.

7. In claim 1, The control network is of the Public / Subscribe type, and the control system is of this type.

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