What is cloud?
The term cloud refers to the way of operation and access to e-services remotely via the network, most often the Internet. The principle is based on the fact that the provider of a given cloud service runs a server, which is usually located on the Internet, and clients can connect to it from anywhere and use the service/feature. One of the examples of the cloud today is the widespread e-mail service of the
gmail.com type, where the client can work with e-mails remotely in the Web browser. Another example is
Google Docs, where the user can create various documents by means of a Web browser, share them with collaborators etc.
The Cloud can be operated as public, i.e. available to any user, or non-public, that is only available to a defined user group. Access to cloud services may be charged or can be provided free of charge.
Cloud technologies are also being used in automation and industry. Typical applications in this area are distributed applications, where the individual parts of the technology are spread over a wide area and the data needs to be processed in one place (on the server). In addition, it is often necessary to provide views of processed data to various clients at different locations (remotely). In such cases, it can be advantageous to address monitoring applications using cloud technologies.
In a cloud-based application, four basic segments need to be addressed:
1.
Data source - Each data origin point must be able to send the data (connectivity) into the Cloud in some way. From the communication point of view of, the data source is the one who controls the communication - it is the client/Master.
2.
Data server - must be able to receive data from individual data sources and write/archive it into the data warehouse (or the intermediate storage). As a data warehouse, some SQL database is used (e.g.
MS SQL,
Oracle,
MySQL). From the communication point of view, it waits for data from individual clients - it is a
server/Slave.
3.
Application server - reads and processes data from the central data server and offers them to clients in the form of Web pages usually. From the communication point of view, it waits for requests for reading data from individual clients - it is a
server/Slave.
4.
Clients - must be able to connect to the application server from anywhere and from any device (only by using a Web browser - a thin client). From the communication point of view, the client actively requests the server for data - it is a
client/Master.
The potential of the PROMOTIC system with Cloud technology
1. PROMOTIC as data source
An application created in the PROMOTIC system can read data from various PLCs and other devices within a single site. This data is then written to a cloud-based data server. The method of writing data to the server is dependent on server type (cloud). This can be done e.g. with XML communication,
OPC UA communication, or communication protocols used in automation (for example
Modbus).
With this architecture, it is appropriate for the data source to have a mechanism (a local data buffer) to store and add a certain amount of data in case of malfunction of the communication with Cloud.
2. PROMOTIC as data server
The PROMOTIC application can be used also as a data server under certain circumstances. However, it is necessary to ensure the reception of data from individual data sources. In the PROMOTIC system, a
PmaData object enabled to the Web to which the data source can write XML data in PROMOTIC format can be used for this purpose. This mode is especially suited for cases where individual data sources are also PROMOTIC applications. In other cases, it is necessary to ensure on the side of the individual data sources that the data is sent to the server in PROMOTIC XML format.
Continuous operation of the application as well as the running of computer data server can be ensured by using the
WatchDog subsystem. The accessibility of the computer of the data server type must be secured using a static public IP address. As a data repository the PROMOTIC allows to use virtually any database system (e.g.
MS SQL,
MySQL,
Oracle, etc.)
3. PROMOTIC as application server
The PROMOTIC system contains by default an integrated Web server and can therefore provide processed data from a data server to individual clients. For clients to access the application server, the server must be available through a static public IP address. According to the type of the application, the data access rights of individual clients sometimes have to be addressed as it is often necessary for one client to have access to his data, but has no access to the data of another client (access rights).
IoT, Cloud and PROMOTIC
In practice, there are increasingly emerging solutions with devices that have built-in direct support for some cloud communication technologies and can be used as data source. We can label such devices as part of the "Internet of Things" (
IoT). A typical example is the
Sigfox cloud technology.
Sigfox-enabled devices can write relatively small amounts of data to the
Sigfox cloud.
The PROMOTIC system can connect to the
Sigfox cloud and read data from individual device or a group of devices. In this case the PROMOTIC application may work as application server. PROMOTIC reads and processes data from individual devices connected to
Sigfox cloud and provides such data to its Web clients (SCADA visualization). In order to communicate with the
Sigfox cloud, the PROMOTIC system contains a preconfiguration:
Sigfox - Communication with cloud service backend.sigfox.com - Communication set with data and panel. This preconfiguration reads data in the
JSON format via the
REST API.
Sigfox is a very suitable technology for acquiring relatively small amounts of data from various devices geographically located in a large area (flow meters, gas meters, etc.).
Sigfox devices are often designed to be extremely energy-efficient for battery operation, it means that they can also be used in places where electricity is not available. The disadvantage is the very limited amount of data transferred.
Sigfox devices write data to the
Sigfox cloud, where it is temporarily available for later processing - from the PROMOTIC point of view, the
Sigfox cloud works as a temporary data repository.
Another example of PROMOTIC using the cloud of other manufacturers are the
eWON devices. Some
eWON devices (
Flexy) allow write its variables into the
eWON cloud (
Talk2M). The PROMOTIC system contains a preconfiguration for reading data from
eWON cloud:
eWON - Communication with eWON industrial routers - Communication set with data and panel,
eWON - Communication with cloud service Talk2M DataMailbox - Communication set with data and panel. From the PROMOTIC point of view, the
eWON cloud works as a temporary data repository.
As a conclusion it can be said that the PROMOTIC system is technically prepared to include various Cloud services that provide data in
XML,
JSON etc.