Compensation method for external feedback and internal loop randomness network time delay of network cascade control system

Abstract

The invention provides a compensation method for external feedback and internal loop randomness network time delay of a network cascade control system, belonging to the technical field of network control systems. In the invention, a network time delay compensation model is replaced by utilizing an actual network data transmission process between an external feedback network path node and an internal loop network path node of the network cascade control system, measurement, observation, estimation or identification of network data transmission randomness time delay between the nodes is avoided, and the requirement on the clock signal synchronism of the nodes is eliminated. By utilizing the method, the influence of a randomness network time delay on the system stability can be reduced, and the control performance quality of the system is improved. The compensation method is suitable for the dynamic compensation and control of the randomness network time delay of the network only existing in the external feedback and internal loop network paths of the network cascade control system when a main controlled object mathematical model and an auxiliary controlled object mathematical model are known.

Description

technical field [0001] The invention relates to a method for compensating the random network time delay of external feedback and internal loop network paths in a network cascade control system, belonging to the technical field of network control systems. Background technique [0002] The closed-loop feedback control system composed of nodes such as transmitters, controllers and actuators through a real-time communication network is called a networked control system (Networked Control Systems, NCS). Networked control systems first appeared in 1998 in the treatise of Walsh, University of Maryland, USA At that time, the structure of the networked control system was only illustrated by means of diagrams. Compared with the traditional point-to-point structure system, the networked control system has the advantages of low cost, easy information sharing, easy expansion and maintenance, and great flexibility. It has been widely used in industrial control over the years. However, due...

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Problems solved by technology

[0008] (2) The network delay that occurs in the process of transmitting network data from the previous node to the next node, no matter what prediction or estimation method is used in the previous node, it is impossible to know in advance the subsequent network delay Accurate value. Time delay leads to system performance degradation and even system instability, and also brings difficulties to the analysis and design of the control system.

[0013] Since the denominator of the closed-loop transfer function shown in equation (1) includes the network delay τ 1 , τ 2 and τ 3 index term of and The existence of time delay will deteriorate the control performance quality of the system, and even cause the system to lose stability, and in severe cases, the system may fail.

[0014] The key to reducing the impact of delay on system stability is whether the random network delay τ 1 , τ 2 and τ 3 index term of and It is removed from the denominator of equation (1), that is, the exponential term of all network delays is not included in the closed-loop characteristic equation of the system, and then the compensation of network delay is realized. However, to realize the compensation of network delay, first, Know the size of the network delay. At present, the method commonly used at home and abroad is to measure the network delay τ 1 , τ 2 and τ 3 measurement to compensate for the time delay τ 1 , τ 2 and τ 3 The impact on system stability. However, due to the network delay τ 1 , τ 2 and τ 3 The accurate measurement of the node needs to meet the synchronization requirements of the node clock signal. If hardware is used to realize the complete synchronization of the node clock signal, a large economic investment is required; if the software is used to correct the clock signal, the correction signal may encounter Due to the influence of network delay, it is difficult to achieve complete synchronization of node clocks. If the method of estimating, observing, identifying or predicting network delay is used to obtain the size of network delay, the accurate probability distribution of network delay must first be known, or An accurate mathematical model, but because the network delay is related to factors such as specific network protocols, network load, and network topology, there may be deviations in the estimation, observation, identification or prediction of network delay.

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