CN103513602B - The PLC waveform data of a kind of accurate timer shaft produces and storage method - Google Patents

Abstract

The invention discloses a precise time axis PLC waveform data generation and storage method, which can be used for PLC acquisition waveform data storage. The method adopts a waveform data acquisition method in which the generation and storage processes are separated to construct a precise time axis PLC waveform data. Data generation and storage methods. The separation of the generation and storage process refers to the process of generating data in the PLC and storing data in the host computer; the precise time axis refers to the accurate correspondence between time and amplitude. The implementation of the method includes: PLC controller 1, waveform data generation ladder diagram program 2, upper computer 3, human-computer interaction software 4 based on virtual instruments, and OPC C/S 5. The invention makes the correspondence between the waveform time axis and the vertical axis data accurate, the time deviation is within 1 ms, and is an ideal data storage method for experiments that require high correspondence between time and amplitude.

Description

A PLC waveform data generation and storage method with precise time axis

technical field

The invention relates to a method for generating and storing PLC waveform data with precise time axis.

Background technique

PLC has the functions of control and acquisition, and can be used as an experimental monitoring device. For the defect of its small memory card capacity, it usually stores the collected data by means of a host computer. However, there are still deficiencies in this solution: when the upper computer is used to read the data collected by the PLC and create the waveform, due to the delay in data communication, the time axis of the waveform curve does not correspond to the data on the vertical axis. This time deviation increases with the amount of transmitted data. Therefore, only the waveform curve can be obtained, and it is impossible to know whether there is delay in the waveform and how much delay, especially when it is necessary to compare the time difference between the control signal and the acquisition signal, this solution cannot be used. Taking the Ethernet communication with a faster transmission speed as an example, a 1.5-meter-long network cable connects the upper computer and the PLC Ethernet module. After testing, the data delay time caused by transmission is shown in the table below

In the case of a small amount of data, the transmission delay between the PLC and the host computer can reach more than 100ms. Obviously, for some experiments that require high accuracy in the correspondence between time and amplitude, the existing data storage methods are difficult to meet the requirements.

Contents of the invention

In order to solve the above problems, the present invention provides a method for generating and storing PLC waveform data with a precise time axis, so that the corresponding accuracy of time and amplitude of waveform data is significantly improved, and the time deviation is within 1 ms.

The technical scheme adopted by the present invention is: using the waveform data acquisition method with separate generation and storage processes, constructing a PLC waveform data generation and storage method with a precise time axis for PLC waveform data recording, the scheme includes PLC controller, waveform Data generation ladder diagram program, upper computer, human-computer interaction software based on virtual instrument, OPCC/S.

The separation of the generation and storage process refers to obtaining the time difference between the system time and the zero moment in each cycle of the main cycle of the PLC program, reading the collected data of each input channel, and storing all the data into the preset waveform In the data block; in the human-computer interaction software, read all the data of the waveform data block in a fixed cycle and store it in the file.

The precise time axis refers to the accurate correspondence between time and amplitude; the preset waveform data block is a shared data block, including time and data of each channel; the fixed cycle is determined according to the data refresh cycle set by OPCC/S; The zero time is the start time of data recording.

The ladder diagram program generated by the waveform data is stored in the MMC card of the PLC controller; the PLC controller is provided with an Ethernet communication interface module; the human-computer interaction software and OPCC/S based on virtual instruments run on the host computer.

The method flow is: PLC starts running, when the interrupt time is not up, execute the next judgment, when the interrupt time is up, enter the interrupt, obtain the time and the amplitude of each channel, send the data to the data block and update the data of the data block , and then send the content of the data block to the OPCServer; send the updated content of the data block to the OPCServer via Ethernet, and be read by the I/OClient; run the human-computer interaction software, and execute the next time when the data reading period is not up Judgment, when the data reading cycle is up, read the data in the OPCServer from the I/OClient to form waveform data, store it in the measurement file, and then judge whether to read the data next time.

The invention has the advantages that the waveform time axis and the vertical axis data correspond accurately, the time deviation is within 1 ms, and it is an ideal data storage method for experiments requiring high correspondence between time and amplitude.

Description of drawings:

Fig. 1 is a scheme implementation block diagram of a precise time axis PLC waveform data generation and storage method.

Fig. 2 is a flow chart of a method for generating and storing PLC waveform data with a precise time axis.

Figure 3 is a comparison diagram of experimental curves between this method and the method of generating waveforms by the host computer.

Figure 4 is the multi-channel waveform curve recorded by the experiment.

detailed description

The present invention will be described in detail below through embodiments and with reference to the accompanying drawings.

What Fig. 1 shows is a scheme implementation block diagram of the PLC waveform data generation and storage method of a kind of precise time axis, as shown in the figure, a kind of PLC waveform data generation and storage method of precise time axis comprise: PLC controller 1, waveform Data generation ladder diagram program 2, upper computer 3 (industrial control computer), human-computer interaction software based on virtual instruments 4, OPCC/S5; Obtain the time difference between the system time and the zero time, and read the collected data of each input channel, and store all the data in the waveform data block; in the human-computer interaction software, read all the data of the waveform data in a fixed cycle, Deposit in file; Described waveform data generation ladder diagram program is stored in the MMC card of PLC controller, and described PLC controller is provided with Ethernet communication interface module, and described human-computer interaction software and OPCC/S operation based on virtual instrument On the host computer; the waveform data block is a shared data block, including time and each channel data; the fixed cycle is determined according to the data refresh rate set by OPCC/S; the zero moment is the data recording start time.

A network cable (such as an RJ-45 network cable) is used to transmit data between the PLC controller and the host computer.

FIG. 2 shows a flowchart of a method for generating and storing PLC waveform data with a precise time axis, as shown in the figure.

Step 1: The PLC is powered on, and the internal program of the PLC starts to run. When the interrupt time is not up, execute the next judgment. When the interrupt time is up, enter the interrupt, obtain the time and the amplitude of each channel, send the data to the data block and perform The data of the data block is updated, and then the content of the data block is sent to OPCServer. For example, in the process of pressure data acquisition, time acquisition and pressure data acquisition are executed within the interrupt, and they are used to update the time point in the data block and the pressure data of each channel. Time acquisition is the calculation of the current system time and the system time at the start of recording. The content of the data block includes the time and the amplitude of multiple channels, which is convenient for the data to be transmitted to the I/OClient of NI LabVIEW as a whole.

Step 2: Send the updated data block content to OPCServer via Ethernet, and read it by I/OClient. For example, to transmit the pressure waveform data of 8 channels to the host computer, first establish the communication connection between the PLC Ethernet communication module and the host computer, that is, configure the PC site on the STEP7 software of Siemens in the host computer, and create it in the OPCScout software 1 time variable and 1 REAL array of 8 elements; secondly, it is necessary to establish a data connection between OPCServer and I/OClient, that is, to establish a shared data type in the human-computer interaction software of the industrial control computer that is the same as that of OPC monitoring. variable, and bind it to the variable of OPCServer.

Step 3: Run the human-computer interaction software. When the data reading period is not up, execute the next judgment. When the data reading period is up, read the data in the OPCServer from the I/OClient to form waveform data and save it into the measurement file , and then judge whether to read data next time. Cycle judgment waveform data storage, the storage cycle needs to be determined according to the data refresh cycle set by OPCC/S, and the refresh rate depends on the respective CPU configurations of the host computer and PLC. For example, if the data refresh period set by OPC is 100ms, it is better to set the storage period as 100ms.

Taking valve adjustment as an experiment, the waveform curve was recorded by the method proposed in the present invention, and the waveform curve obtained by establishing the time axis in the host computer was recorded at the same time. The comparison between the two is shown in Figure 3, and the time difference is close to 100ms. According to the method proposed in the present invention, the multi-channel waveform curve is recorded as shown in FIG. 4 .

Claims (5)

1. A method for generating and storing PLC waveform data with an accurate time axis, characterized in that: data generation and storage adopt a method of process separation, that is, construct real-time PLC waveform data blocks, transmit data through Ethernet, and utilize upper computer storage Waveform data; separation of generation and storage processes refers to obtaining the time difference between the system time and zero time in each cycle of the main cycle of the PLC program, reading the collected data of each input channel, and storing all the data into the preset waveform In the data block; in the human-computer interaction software, read all the data of the waveform data block in a fixed cycle and save it in the file. 2. according to the PLC waveform data generation and storage method of the described accurate time axis of claim 1, it is characterized in that: the method implementation scheme comprises: PLC controller (1), waveform data generation ladder diagram program (2), upper computer ( 3), human-computer interaction software (4), OPCC/S (5) based on virtual instrument; Described waveform data generation ladder diagram program is stored in the MMC card of PLC controller, and described PLC controller is provided with Ethernet communication The interface module, the virtual instrument-based human-computer interaction software and OPCC/S run on the host computer. 3. according to the PLC waveform data generation and storage method of the described accurate time axis of claim 2, it is characterized in that: described accurate time axis refers to that time and amplitude correspond accurately; Described waveform data block is shared data block, comprises time and data of each channel. 4. according to the PLC waveform data generation and storage method of the described accurate time axis of claim 1, it is characterized in that: described fixed cycle is determined according to the data refresh cycle set by OPCC/S; Described zero moment is the data recording start time. 5. according to the PLC waveform data generation of the described accurate time axis of claim 1 and storage method, it is characterized in that: The method flow is: PLC starts to run, when the interrupt time is not up, execute the next judgment, when the interrupt time is up, enter the interrupt, obtain the time and the amplitude of each channel, send the data to the waveform data block and perform the waveform data block Update the data, and then send the content of the waveform data block to OPCServer; send the updated content of the waveform data block to OPCServer through Ethernet, and read it by I/OClient; run the human-computer interaction software, when the data reading period is not yet , execute the next judgment, when the data reading cycle is up, read the data in the OPCServer from the I/OClient, form the waveform data, store it in the measurement file, and then judge whether to read the data next time.