Analog quantity output smooth switching method for PLC distributed redundancy control

Abstract

The invention discloses an analog quantity output smooth switching method for PLC (Programmable Logic Controller) distributed redundancy control, which relates to the technical field of industrial automation IO (Input / Output) redundancy control and comprises the steps of working architecture design, normal redundancy control, fault detection and judgment, fault redundancy control and system configuration. In a normal state, a dynamic output distribution strategy is adopted to equally divide a total output target value, and redundant modules are synchronously hot-standby; during operation, state data such as module power supply voltage and output current are collected, and faults are judged through multi-parameter joint detection; after a fault occurs, a fault module is isolated, the remaining normal modules dynamically redistribute output components, and continuous and stable analog quantity output is improved through non-hardware interruption switching; according to the invention, the switching time and the output deviation are reduced, the resource utilization rate and the system reliability are improved, a precise control scene is adapted, and the redundancy cost and the maintenance difficulty are reduced.

Description

Technical Field

[0001] This invention relates to the field of industrial automation I / O redundancy control technology, specifically to a method for smooth switching of analog outputs in PLC distributed redundancy control. Background Technology

[0002] In industrial automation control systems, I / O redundancy design is a core means to ensure reliable system operation. Analog output modules are widely used in the control of actuators such as valve positioners and frequency converters. The continuity and stability of their output signals directly determine the safety of the production process and product quality. Therefore, a smooth switching method for analog outputs in PLC distributed redundancy control is needed.

[0003] Existing technologies largely revolve around fault detection and rapid switching between primary and backup modules. For example, redundancy control schemes only focus on the rapid identification of faulty modules without addressing the optimization of output allocation mechanisms. Traditional redundancy products are also based on full-switching logic designs, failing to solve the signal continuity problem during the switching process. In precision control scenarios where analog outputs need to be dynamically adjusted in real time, such as chemical reaction control and precision positioning, these technologies struggle to meet the stringent signal stability requirements.

[0004] The existing technology has the following technical problems: 1. Output jump problem: When the module switches, the output signal will suddenly drop from the set value to 0 and then jump back to the set value, which will cause the controlled actuator to be impacted, oscillated or even malfunctioned, seriously affecting the service life and operational safety of the equipment.

[0005] 2. Insufficient system stability: For precision control processes, signal jumps can cause control loop oscillations, disrupting the stability of the production process and leading to fluctuations in product quality. This defect is particularly prominent in scenarios with extremely high requirements for signal continuity, such as chemical reactions and precision speed regulation.

[0006] 3. Response delay and safety risks: Signal interruption or abrupt change during the switching process can cause the controlled equipment to lose control temporarily, increasing the risk of process safety. In addition, the millisecond-level interruption of traditional mechanical switching cannot meet the real-time requirements of high-precision control.

[0007] 4. Low resource utilization: In the traditional master-slave mode, only some modules participate in normal operation, resulting in serious resource idleness; while the redundancy scheme with multiple redundant modules improves reliability, the module cost is too high and the economy is poor. Summary of the Invention

[0008] To address the aforementioned technical shortcomings, the present invention aims to provide a method for smooth switching of analog outputs in PLC distributed redundant control.

[0009] To solve the above technical problems, the present invention adopts the following technical solution: The present invention provides a method for smooth switching of analog output in PLC distributed redundant control, including the following steps: Step 1, working architecture design: constructing a working device system.

[0010] Step 2, Normal Redundancy Control: Based on the working device system, tasks are assigned to each physical module of the working device system, and the redundant modules of the working device system are hot-standby synchronized to run the working device system.

[0011] Step 3: Fault Detection and Judgment: During the operation of the working device system, the built-in status data of the device system is collected, and the built-in status data of the device system is analyzed to determine whether the working device system is faulty.

[0012] Step 4, Fault Redundancy Control: After the working device system detects a fault, it switches to redundant output.

[0013] Step 5: System configuration: Based on the redundancy control of the working device system, construct the redundancy control of the overall working device system.

[0014] Preferably, the analysis of the built-in status data of the device system is carried out in the following specific process: obtaining the standard range of power supply voltage, the standard range of actual output current value, and the standard range of communication response time from the database.

[0015] If the power supply voltage of a module is not within the standard power supply voltage range, the voltage status flag of that module is marked as abnormal and the output value is 1. If the power supply voltage of a module is within the standard power supply voltage range, the voltage status flag of that module is marked as normal and the output value is 0. The voltage status flags of each module are obtained in this way. Based on the method of obtaining the voltage status flags of each module, the current status flag and response status flag of each module are obtained.

[0016] The voltage status flag, current status flag, response status flag, and chip status flag of each module are merged into various flags of each module.

[0017] The system reports to the PLC main controller once every preset time interval via the internal bus. If a certain module outputs 1 for three consecutive times, the module is determined to be faulty. When a module is determined to be faulty, the working device system is determined to be faulty.

[0018] Preferably, the redundant output switching is performed as follows: S1. Confirmation of the number of remaining modules: The number of currently faulty modules t is obtained. If the faulty module is a working module, the number of normal modules is N-t+1. If the faulty module is a redundant module, the number of normal modules is N. When t is N, the value of t is recorded as n-1.

[0019] S2. Dynamic reallocation: Each normal module recalculates its output components, and the total analog output target value is divided by the number of normal modules to obtain the switching target value.

[0020] S3, No hardware interrupt switching: Each normal module directly adjusts its output current to the switching target value through its internal DAC.

[0021] Preferably, the redundant control of the overall working device system is implemented as follows: P1. Controller settings: In the host computer configuration software, add an IO substation to the PLC main controller, configure the type and quantity of N working modules and 1 redundant module, and download the configuration to the PLC main controller via programming cable or network.

[0022] P2. Status Data Acquisition: After establishing communication between the PLC main controller and the IO substation, the module status data of each module is periodically read.

[0023] P3. Normal Module Statistics: The host computer analyzes the status data of the modules through the built-in diagnostic logic. When an anomaly is detected, an alarm is triggered and the number of normal modules is counted.

[0024] P4. Allocation rule settings: Recalculate the output value of each module according to the S2 allocation rule during redundant output switching. When the number of normal modules is 0, trigger a high-level alarm and execute the safety policy.

[0025] P5, Module Switching Settings: The host computer sends a new output value to the PLC main controller, which then sends it to the normal module in the next scan cycle. The module outputs an electrical signal to the field actuator.

[0026] P6. Cyclic detection setting: The system continuously performs status monitoring and fault diagnosis in a cyclic manner. P2 to P3 is implemented at preset intervals, and P4 to P5 is implemented immediately when the number of normal modules changes.

[0027] The beneficial effects of this invention are as follows: 1. Under normal conditions, this invention adopts a dynamic output allocation strategy to evenly distribute the total output target value, and redundant modules are synchronously hot-standby; during operation, it collects status data such as module power supply voltage and output current, and determines faults through multi-parameter joint detection; after a fault, the faulty module is isolated, and the remaining normal modules dynamically redistribute the output components, improving the continuous stability of analog output through hardware interruption switching; and through configuration and cyclic monitoring to form closed-loop control, this invention reduces switching time and output deviation, improves resource utilization and system reliability, is suitable for precision control scenarios, and reduces redundancy costs and maintenance difficulty.

[0028] 2. This invention adopts a dynamic output allocation strategy, which allows all modules to share the output task under normal conditions. In case of failure, the remaining modules automatically adjust the load allocation, which improves the rationality of resource utilization and reduces the probability of module idleness or overload.

[0029] 3. This invention achieves fault switching through software parameter reconfiguration without hardware interruption. Combined with real-time hot standby synchronization of redundant modules, it improves the continuous stability of analog output signals during module failure or recovery, reduces the probability of signal jumps or interruptions, and improves the stability of the controlled actuator.

[0030] 4. The system architecture design of this invention is optimized, reducing the investment cost of redundant modules; it supports hot-swappable replacement of faulty modules, greatly shortening maintenance downtime; and it has online calibration and automatic parameter synchronization functions, reducing the workload and operational difficulty of manual maintenance.

[0031] 5. The present invention adopts a multi-parameter joint fault detection mechanism, which can accurately identify module faults, reduce false alarms, and enable the system to maintain stable output performance, effectively reducing the accumulation of output deviations caused by factors such as module aging. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 This is a schematic diagram of the implementation steps of the method of the present invention. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] according to Figure 1 As shown, the present invention provides a method for smooth switching of analog output in PLC distributed redundant control, including the following steps: Step 1, working architecture design: constructing the working device system.

[0036] In one specific embodiment, the construction process of the working device system is as follows: an N+1 redundant system is constructed, consisting of N PLC analog current-type working modules and 1 analog current-type redundant module, and each PLC analog current-type working module and the 1 analog current-type redundant module are referred to as each module.

[0037] Each module communicates with the PLC main controller via an internal high-speed synchronous bus and is physically integrated in the same redundant module box. The analog current type working module of each PLC is numbered a, a=1, 2...n, where n is a positive integer greater than 2.

[0038] It should be noted that the modules can also be physically integrated into a distributed installation in the control cabinet.

[0039] Step 2, Normal Redundancy Control: Based on the working device system, tasks are assigned to each physical module of the working device system, and the redundant modules of the working device system are hot-standby synchronized to run the working device system.

[0040] In one specific embodiment, the task allocation for each entity module of the working device system is carried out as follows: the PLC main controller sets the total analog output target value according to the process requirements.

[0041] When N+1 is even, the total analog output target value is divided by N+1 to obtain the output components evenly distributed among the modules. Each module calculates and executes the output components, and the redundant module outputs to the internal virtual load resistor. The resistance value of the internal virtual load resistor is consistent with that of the external load.

[0042] When N+1 is odd, the total analog output target value is divided by N+1 to obtain the module's preset evenly distributed output component. The PLC analog current type working modules and redundant modules numbered n-1 all execute the module's preset evenly distributed output component. The module's preset evenly distributed output component is multiplied by N to obtain the module's preset total output component. The total analog output target value is subtracted from the module's preset total output component to obtain the module's preset excess output component. The PLC analog current type working module numbered n executes the module's preset excess output component.

[0043] In one specific embodiment, the hot standby synchronization of the redundant modules of the working device system is performed as follows: the PLC analog current type redundant module receives the output parameter update of each PLC analog current type working module once every preset time interval through the internal high-speed synchronization bus.

[0044] The PLC analog current-type redundant module operates with the exact same output components as the working module, and the output signal is loaded onto an internally preset virtual load.

[0045] In one specific embodiment, the output parameters include the target value of the output component, the DAC calibration coefficient, and the temperature compensation parameter.

[0046] Step 3: Fault Detection and Judgment: During the operation of the working device system, the built-in status data of the device system is collected, and the built-in status data of the device system is analyzed to determine whether the working device system is faulty.

[0047] In one specific embodiment, the acquisition device system has built-in status data, and the specific acquisition process is as follows: the built-in status data of the device system includes the power supply voltage, actual value of output current, communication response time and internal DAC / ADC chip status of each module.

[0048] The actual values ​​of the power supply voltage and output current are acquired by a current sensor.

[0049] The round-trip time from sending a query command to the module's response command is collected by a timer and recorded as the communication response time.

[0050] The status of the internal DAC / ADC chip is read through the status register. When the internal DAC / ADC chip is in normal condition, the chip status flag is marked as normal and the output value is 0. When the internal DAC / ADC chip is in abnormal condition, the chip status flag is marked as abnormal and the output value is 1.

[0051] In one specific embodiment, the analysis of the built-in state data of the device system is carried out as follows: the standard range of power supply voltage, the standard range of actual output current value, and the standard range of communication response time are obtained from the database.

[0052] It should be noted that the standard ranges for power supply voltage, actual output current, and communication response time are all set by the staff.

[0053] If the power supply voltage of a module is not within the standard power supply voltage range, the voltage status flag of that module is marked as abnormal and the output value is 1. If the power supply voltage of a module is within the standard power supply voltage range, the voltage status flag of that module is marked as normal and the output value is 0. The voltage status flags of each module are obtained in this way. Based on the method of obtaining the voltage status flags of each module, the current status flag and response status flag of each module are obtained.

[0054] The voltage status flag, current status flag, response status flag, and chip status flag of each module are merged into various flags of each module.

[0055] The system reports to the PLC main controller once every preset time interval via the internal bus. If a certain module outputs 1 for three consecutive times, the module is determined to be faulty. When a module is determined to be faulty, the working device system is determined to be faulty.

[0056] Step 4, Fault Redundancy Control: After the working device system detects a fault, it switches to redundant output.

[0057] In a specific embodiment, the redundant output switching is performed as follows: S1. Confirmation of the number of remaining modules: The number of currently faulty modules t is obtained. If the faulty module is a working module, the number of normal modules is N-t+1. If the faulty module is a redundant module, the number of normal modules is N. When t is N, the value of t is recorded as n-1.

[0058] S2. Dynamic reallocation: Each normal module recalculates its output components, and the total analog output target value is divided by the number of normal modules to obtain the switching target value.

[0059] S3, No hardware interrupt switching: Each normal module directly adjusts its output current to the switching target value through its internal DAC.

[0060] It should be noted that analog current output modules always have a module with normal output, thus reducing output fluctuations caused by redundant switching after a failure in traditional architectures, thereby achieving smooth current output.

[0061] Step 5: System configuration: Based on the redundancy control of the working device system, construct the redundancy control of the overall working device system.

[0062] In one specific embodiment, the redundancy control of the overall working device system is implemented as follows: P1, Controller settings: In the host computer configuration software, add an IO substation to the PLC main controller, configure the type and quantity of N working modules and 1 redundant module, and download the configuration to the PLC main controller via programming cable or network.

[0063] P2. Status Data Acquisition: After establishing communication between the PLC main controller and the IO substation, the module status data of each module is periodically read.

[0064] P3. Normal Module Statistics: The host computer analyzes the status data of the modules through the built-in diagnostic logic. When an anomaly is detected, an alarm is triggered and the number of normal modules is counted.

[0065] P4. Allocation rule settings: Recalculate the output value of each module according to the S2 allocation rule during redundant output switching. When the number of normal modules is 0, trigger a high-level alarm and execute the safety policy.

[0066] P5, Module Switching Settings: The host computer sends a new output value to the PLC main controller, which then sends it to the normal module in the next scan cycle. The module outputs an electrical signal to the field actuator.

[0067] P6. Cyclic detection setting: The system continuously performs status monitoring and fault diagnosis in a cyclic manner. P2 to P3 is implemented at preset intervals, and P4 to P5 is implemented immediately when the number of normal modules changes.

[0068] In one specific embodiment, the execution of the safety strategy is carried out as follows: the PLC main controller immediately outputs a preset safety value to all modules. This safety value is associated with the safety action of the actuator, and the output signal is forcibly output through the module's built-in hardware protection circuit.

[0069] It should be noted that the preset safety value is a fixed analog output parameter pre-configured in the system based on the safety requirements of specific industrial control scenarios, the operating characteristics of the actuator, and process safety specifications. This value is compatible with the output specifications of analog current-type modules and is a key benchmark value to ensure the safety of equipment and processes under extreme fault conditions. This value is forcibly output through the module's built-in hardware protection circuit and is not affected by software-level faults. It ensures that even if the core control logic of the system is abnormal, it can still reliably trigger safety actions, thus ensuring operational safety under extreme fault scenarios from a hardware perspective and avoiding the risk of actuator loss of control due to the lack of control signals. Preset safety values ​​include specific current safety values ​​and clamping force preset safety values, and the specific values ​​are set by the operator.

[0070] The examples described in this invention are not limited to the specific embodiments listed above. The examples are merely illustrative to facilitate understanding of the invention and do not constitute a limitation on the scope of protection of this invention. Any modifications, equivalent substitutions, etc., made within the spirit and principles of this invention should be included within the scope of protection.

[0071] The above description is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the concept of the invention or exceed the scope defined in this specification, they should all fall within the protection scope of the present invention.

Claims

1. A method for smooth switching of analog output in PLC distributed redundant control, characterized in that, Includes the following steps: Step 1: Work Architecture Design: Construct the working device system; Step 2, Normal Redundancy Control: Based on the working device system, tasks are assigned to each physical module of the working device system, and the redundant modules of the working device system are hot-standby synchronized to run the working device system. Step 3: Fault Detection and Judgment: During the operation of the working device system, the built-in status data of the device system is collected, and the built-in status data of the device system is analyzed to determine whether the working device system is faulty. Step 4, Fault Redundancy Control: After the working device system detects a fault, it switches to redundant outputs. Step 5: System configuration: Based on the redundancy control of the working device system, construct the redundancy control of the overall working device system.

2. The method for smooth switching of analog output in PLC distributed redundant control according to claim 1, characterized in that, The specific construction process of the construction device system is as follows: Construct an N+1 redundant system consisting of N PLC analog current-type working modules and 1 analog current-type redundant module. Each PLC analog current-type working module and the 1 analog current-type redundant module are denoted as a module. Each module communicates with the PLC main controller via an internal high-speed synchronous bus and is physically integrated in the same redundant module box. The analog current type working module of each PLC is numbered a, a=1, 2...n, where n is a positive integer greater than 2.

3. The method for smooth switching of analog output in PLC distributed redundant control according to claim 2, characterized in that, The task allocation process for each entity module of the working device system is as follows: The PLC main controller sets the target value for the total analog output according to process requirements; When N+1 is even, the total analog output target value is divided by N+1 to obtain the output components evenly distributed among the modules. Each module calculates and executes the output components, and the redundant module outputs to the internal virtual load resistor. The resistance value of the internal virtual load resistor is consistent with that of the external load. When N+1 is odd, the total analog output target value is divided by N+1 to obtain the module's preset evenly distributed output component. The PLC analog current type working modules and redundant modules numbered n-1 all execute the module's preset evenly distributed output component. The module's preset evenly distributed output component is multiplied by N to obtain the module's preset total output component. The total analog output target value is subtracted from the module's preset total output component to obtain the module's preset excess output component. The PLC analog current type working module numbered n executes the module's preset excess output component.

4. The method for smooth switching of analog output in PLC distributed redundant control according to claim 3, characterized in that, The hot standby synchronization of redundant modules in the working device system is performed as follows: The PLC analog current-type redundant module receives the output parameter updates of each PLC analog current-type working module once at a preset time interval via the internal high-speed synchronous bus. The PLC analog current-type redundant module operates with the exact same output components as the working module, and the output signal is loaded onto an internally preset virtual load.

5. The method for smooth switching of analog output in PLC distributed redundant control according to claim 4, characterized in that, The output parameters include the target value of the output component, the DAC calibration coefficient, and the temperature compensation parameter.

6. The method for smooth switching of analog output in PLC distributed redundant control according to claim 1, characterized in that, The data acquisition device system has built-in status data, and the specific acquisition process is as follows: The device system has built-in status data including the power supply voltage, actual output current, communication response time, and internal DAC / ADC chip status of each module. The actual values ​​of the power supply voltage and output current are acquired through a current sensor; The round-trip time from the PLC main controller sending a query command to the module returning a response command is collected by a timer and recorded as the communication response time. The status of the internal DAC / ADC chip is read through the status register. When the internal DAC / ADC chip is in normal condition, the chip status flag is marked as normal and the output value is 0. When the internal DAC / ADC chip is in abnormal condition, the chip status flag is marked as abnormal and the output value is 1.

7. The method for smooth switching of analog output in PLC distributed redundant control according to claim 5, characterized in that, The analysis of the device system's built-in status data is as follows: Retrieve the standard range of power supply voltage, the standard range of actual output current value, and the standard range of communication response time from the database; If the power supply voltage of a module is not within the standard range of power supply voltage, the voltage status flag of the module is marked as abnormal and the output value is 1. If the power supply voltage of a module is within the standard range of power supply voltage, the voltage status flag of the module is marked as normal and the output value is 0. The voltage status flag of each module is obtained in this way. Based on the method of obtaining the voltage status flag of each module, the current status flag and response status flag of each module are obtained. The voltage status flag, current status flag, response status flag, and chip status flag of each module are merged into various flags of each module; The system reports to the PLC main controller once every preset time interval via the internal bus. If a certain module outputs 1 for three consecutive times, the module is determined to be faulty. When a module is determined to be faulty, the working device system is determined to be faulty.

8. The method for smooth switching of analog output in PLC distributed redundant control according to claim 1, characterized in that, The redundant output switching process is as follows: S1. Confirmation of the number of remaining modules: Calculate the number of currently faulty modules t. If the faulty module is a working module, the number of normal modules is N-t+1. If the faulty module is a redundant module, the number of normal modules is N. When t is N, record the value of t as n-1. S2, Dynamic reallocation: Each normal module recalculates its output components, and the total analog output target value is divided by the number of normal modules to obtain the switching target value; S3, No hardware interrupt switching: Each normal module directly adjusts its output current to the switching target value through its internal DAC.

9. The method for smooth switching of analog output in PLC distributed redundant control according to claim 1, characterized in that, The redundancy control of the overall working device system is described in the following specific control process: P1. Controller settings: Add an IO substation to the PLC main controller in the host computer configuration software, configure the type and quantity of N working modules and 1 redundant module, and download the configuration to the PLC main controller via programming cable or network. P2. Status Data Acquisition: After establishing communication between the PLC main controller and the IO substation, the module status data of each module is periodically read. P3. Normal Module Statistics: The host computer analyzes the module status data through built-in diagnostic logic. When an abnormality is detected, an alarm is triggered and the number of normal modules is counted. P4. Allocation rule setting: Recalculate the output value of each module according to the S2 allocation rule in the redundant output switching. When the number of normal modules is 0, a high-level alarm is triggered and the safety policy is executed. P5, Module Switching Settings: The host computer sends a new output value to the PLC main controller, which then sends it to the normal module in the next scan cycle. The module outputs an electrical signal to the field actuator. P6. Cyclic detection setting: The system continuously performs status monitoring and fault diagnosis in a cyclic manner. P2 to P3 is implemented at preset intervals, and P4 to P5 is implemented immediately when the number of normal modules changes.

10. A method for smooth switching of analog output in PLC distributed redundant control according to claim 9, characterized in that, The specific execution process of the security policy is as follows: The PLC main controller immediately outputs a preset safety value to all modules. This safety value is associated with the safety action of the actuator, and the output signal is forced out through the module's built-in hardware protection circuit.

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