The Study On The Model-Based Control Systems

Networked Control Systems (NCS) belongs to distributed control systems which the sensors, controllers and actuators are connected by a shared communication networked. This class of feedback control systems, which use a data network as medium for the feedback path, have the advantages of low-cost, easy maintenance, and flexibility over the traditional control systems. And it is widely applied in industrial plants, unmanned aerial vehicles (UAVs) , etc. Because there are many nodes in the network and the medium of control network is time sharing multiplexing, when transmitting the information in the bandwidth limited communication network, inevitably presents the information dashing and retransmission. Given this point, the network-induced delay is introduced into the networked control systems inevitably, which will result in the degradation of system performance, even leads to instability. This makes it hard to design and analyze the Networked Control Systems. This dissertation will focus on bandwidth constraints and network-induced delay problem, by reducing the node package transmission rate to solve the problem of bandwidth constraints. The primary coverage is as follows:In this paper a class of networked control systems called Model- Based Networked Control Systems (MB-NCS) is investigated. This control architecture uses an explicit model of the plant in order to reduce the network traffic while attempting to prevent excessive performance degradation. The model is used to simulate plant conditions between transmission instants when no information about the plant is available. It is assumed throughout the work that the plant model dynamics are a non-exact approximation of the real plant dynamics. Several control problems are formulated starting with the stability analysis of linear continuous and discrete systems. Necessary and sufficient conditions for stability are derived for different network and control scenarios such as state feedback, output feedback, and presence of networked-induced delays. The results obtained relate the stability of each of the MB-NCS considered to the eigenvalues of a matrix M. The matrix M contains information about the plant dynamics and the error between the plant and model dynamics. As for the network with bandwidth constraints, a new transmission rule which is called based on error threshold communication logic, is introduced and applied to the MB-NCS. A new type of smart sensor determining when the data should be transmitted is designed. When all the plant states of the NCS are available directly, the state feedback is adapted; when the state is not directly measurable, output feedback control is adapted. Also the model with transmission rule is constructed. The simulation indicates that the new rule can reduce the usage of network bandwidth, meanwhile assure the stability and performance for the Networked Control Systems.