Method for compensating for varying network time delay in external feedback and inner loop network paths of network cascade control system

Abstract

The invention provides a method for compensating for varying network time delay in external feedback and inner loop network paths of a network cascade control system and belongs to the technical field of network control systems. Real network data transmission processes between external feedback network path nodes and between inner loop network path nodes are adopted to substitute for a network time delay compensation model between the nodes; the measurement, the observation, the estimation or the identification of a network data transmission unknown varying time delay between the nodes are eliminated; and the requirement on the synchronization of a node clock signal is eliminated. By the method, the influence of the varying network varying network time delay on the stability of the system can be reduced and the control performance quality of the system is improved. The method is applied to the dynamic compensation and control of the varying network time delay only existing in the external feedback and inner loop network paths of the network cascade control system, in which the main controlled target mathematical model is known or unknown, the secondary controlled target mathematical model is known, and the network has a certain amount of packets.

Description

technical field [0001] The invention relates to a compensation method for time-varying 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 real-time distributed control system whose feedback loop is connected through the network is called networked control system (Networked Control Systems, NCS). and other fields are or will be applied. [0003] NCS can achieve resource sharing and remote operation and control, has high diagnostic capabilities, is easy to install and maintain, can effectively reduce the weight and volume of the system, and improve the flexibility and reliability of the system. However, NCS provides While the control system brings various conveniences, it also brings new challenges to the research of the system and control theory. The problems of network delay, packet loss and multi-packet transmission make t...

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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 time-varying 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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