Scada web HMI system and HMI client
A web browser ( 5 ) makes a communication thread ( 7 ) and a DOM update thread ( 6 ) run in parallel. The communication thread ( 7 ) overwrites, when signal data having the same unique identifier as received signal data already exists in a buffer area, the signal data stored in the buffer area with the received signal data. When receiving a signal data request event from the DOM update thread ( 6 ), the communication thread ( 7 ) transmits all signal data stored in the buffer area to the DOM update thread ( 6 ). The DOM update thread ( 6 ) updates a DOM for all the signal data. The DOM update thread ( 6 ) transmits, after updating the DOM, the signal data request event to the communication thread and updates, according to the updated DOM, a display content of a display part displayed on the web browser ( 5 ).
1. A SCADA web HMI system, comprising:
a web HMI server that transmits signal data, a unique identifier and a signal value being associated with each other in the signal data, the unique identifier specifying a display part related to a monitoring target, the signal value being received from a programmable logic controller connected to the monitoring target; and
an HMI client that displays an HMI screen on a web browser, the display part being arranged on the HMI screen, receives the signal data from the web HMI server, and changes a display content of the display part corresponding to the received signal data;
wherein
the HMI client includes:
a memory that stores a program and temporarily stores the signal data in a buffer area;
a processor that is configured to make a communication thread and a DOM update thread run in parallel on the web browser by executing the program; and
a display that displays the web browser;
the communication thread executes:
reception processing of periodically receiving the signal data from the web HMI server;
buffer overwrite processing of overwriting signal data stored in the buffer area with the received signal data when a unique identifier included in the received signal data and a unique identifier included in the signal data stored in the buffer area are the same; and
buffer transmission processing of transmitting a DOM update request event to the DOM update thread when receiving a signal data request event from the DOM update thread, the DOM update request event including all signal data stored in the buffer area; and
the DOM update thread executes:
DOM update processing of updating a DOM for all the signal data included in the DOM update request event when receiving the DOM update request event; and
after updating the DOM, rendering processing of transmitting the signal data request event to the communication thread and updating, according to the updated DOM, a display content of the display part displayed on the web browser.
2. The SCADA web HMI system according to claim 1 , wherein
the communication thread executes:
transmission processing of transmitting the DOM update request event including the received signal data to the DOM update thread when processing in the DOM update thread is stopping; and
buffer processing of storing the received signal data in the buffer area when processing in the DOM update thread is running; and
the buffer overwrite processing is executed in the buffer processing.
3. An HMI client, wherein
the HMI client displays an HMI screen on a web browser, a display part related to a monitoring target being arranged on the HMI screen, receives signal data, a unique identifier and a signal value being associated with each other in the signal data, the unique identifier specifying the display part, the signal value being related to the monitoring target, and changes a display content of the display part corresponding to the received signal data; and
the HMI client comprises:
a memory that stores a program and temporarily stores the signal data in a buffer area;
a processor that is configured to make a communication thread and a DOM update thread run in parallel on the web browser by executing the program; and
a display that displays the web browser;
the communication thread executes:
reception processing of periodically receiving the signal data from the web HMI server;
buffer overwrite processing of overwriting signal data stored in the buffer area with the received signal data when a unique identifier included in the received signal data and a unique identifier included in the signal data stored in the buffer area are the same; and
buffer transmission processing of transmitting a DOM update request event to the DOM update thread when receiving a signal data request event from the DOM update thread, the DOM update request event including all signal data stored in the buffer area; and
the DOM update thread executes:
DOM update processing of updating a DOM for all the signal data included in the DOM update request event when receiving the DOM update request event; and
after updating the DOM, rendering processing of transmitting the signal data request event to the communication thread and updating, according to the updated DOM, a display content of the display part displayed on the web browser.
4. The HMI client according to claim 3 , wherein
the communication thread executes:
transmission processing of transmitting the DOM update request event including the received signal data to the DOM update thread when processing in the DOM update thread is stopping; and
buffer processing of storing the received signal data in the buffer area when processing in the DOM update thread is running; and
the buffer overwrite processing is executed in the buffer processing.