Comparing IoT Control System and National Control System, we find that in essence, it collects the state information of physical system, transmits the information in a real-time and reliable manner through communication network, and sends control commands through network after analyzing data to control the physical system.
The IoT Control System emphasizes diversity and openness of the network, geographical distribution of sensing nodes, heterogeneity and mass of sensing information, diversity of controlled objects, and intelligence of control. Therefore, it is necessary to draw on a large number of existing research results of network control system to design the control system, and at the same time meet the characteristics of Internet of Things when building.
Based on the single-layer and double-layer design of network control system, IoT control system can also construct a single-layer and a double-layer respectively.
When the control system is relatively simple and there is no need for coordinated control among multiple controllers, the single-layer IoT control system architecture shown in the figure below is adopted. The features are:
When control strategy is relatively complex, two-layer IoT control system architecture shown in the figure below can be used. The difference between single-layer control system and two-layer control system is:
(1) The sensoring layer network, low-level network controllers, actuators, controlled objects, and sensors correspond to the sensoring layer in IoT system; High-level network controllers, other data sources and application services correspond to the application layer in IoT system.
(2)The low-level network controller can exist in the form of a control gateway or a PLC controller; The high-level controller exists in the form of a support platform, which is also a cloud in the general sense. When most of the information processing tasks and user service requests in the system are completed by support platform, the function of controller is mainly realized by high-level controller, and low-level controller can be weakened into a gateway. If most of information processing tasks and user service requests in the system are completed by low-level controller, then support platform where high-level controller is located can be weakened into a database management platform. If the control strategy is more complex, the relatively independent control strategy can be implemented by low-level controller, and system-level strategy or coordination between low-level controllers is completed by high-level controller.