Study And Application Of Model-free Adaptive Predictive Control For Networked Control Systems

With the development of network communication technology and computer technology,networked control systems(NCSs)have been applied in more and more fields gradually.However,the communication networks with limited bandwidths are used to transmit a large amount of real-time control information,which has brought many problems to the analysis and design for networked control systems.Network-induced delay and packet dropout are two main factors that affect the performance of networked control systems.The general idea for these two problems is to establish the mathematical models of networked control systems,and then the controllers are designed based on the mathematical models.But the mathematical models of networked control systems are difficult to establish in reality.Thus,these design methods based on the mathematical models of networked systems face many challenges.As a kind of data-driven control method,the model-free adaptive predictive control(MFAPC)provides a new idea for the research of networked control systems,which only uses the on-line or off-line I/O data of the plants to design controllers,does not rely on the mathematical models of the plants.The problem of modeling for networked control systems is avoided.Therefore,a kind of networked MFAPC method for the NCSs with network-induced time delay and packet dropouts is proposed and verified,which is important in theory and practice.The main work of this thesis is as follows:1)For the networked control systems with network-induced time delay and packet dropouts,an improved data-based networked predictive control(iDBNPC)method is proposed by adding the error rate-of-change information to the prototype control law.2)Aiming at the deficiency of MFAPC,an improved MFAPC(iMFAPC)is proposed.In order to improve the accuracy of the prediction model,the prediction model error correction mechanism is introduced to the prediction model.In addition,a new control law that makes full use of output error and error rate-of-change information can be obtained by modifying the control input criterion function.Then,a networked iMFAPC method is proposed for the networked control systems with network-induced time delay and packet dropouts.3)In MATLAB/Simulink environment,the simulation platform for the networked control systems is set up through TrueTime toolbox,and the proposed control methods are simulated and analyzed.Compared with the original methods,the iDBNPC method and the iMFAPC method can greatly improve the convergence speed of the control systems.The iDBNPC method and the iMFAPC method both have good compensation effect on network-induced time delay and packet dropouts,but the convergence speed of the networked iMFAPC method is faster than that of iDBNPC method.4)In order to further verify the effectiveness of the proposed method,a networked liquid level control system was set up in the laboratory,and the proposed methods was verified experimentally.The experimental results show that both the iDBNPC method and the networked iMFAPC method can compensate network-induced time delay and packet dropouts well,but the networked iMFAPC method has faster convergence speed than the iDBNPC method.