Nondeterministic time delay compensation method of external forward path and internal feedback path of network cascade control system

Abstract

The invention provides a nondeterministic time delay compensation method of an external forward path and an internal feedback path of a network cascade control system, which belongs to the technical filed of network control systems. In the method, the network data transmitting process between a node of the external forward path of a real network cascade control system and a node of the internal feedback path is adopted to replace a network time delay compensation model between the nodes, therefore, the measurement, observation, estimation or identification of nondeterministic time delay of the network data transmission between the nodes is avoided, and the requirement for synchronization of clock signals of the nodes is avoided. By adopting the method, the influence of the nondeterministic network time delay on system stability can be reduced; and the control performance quality of a system is enhanced. The method is suitable for dynamic compensation and control of nondeterministic network time delay under the conditions that mathematic models of a primary and an assistant controlled objects are known, certain interference signals exist in the system, certain data packet loss exists in the network, and the network is only in the external forward path and the internal feedback path of the network cascade control system.

Description

technical field [0001] The invention relates to a compensation method for the non-deterministic network time delay of the external forward and internal feedback paths of a network cascade control system, belonging to the technical field of network control systems. Background technique [0002] Networked control system (Networked control systems, NCS) is a fully distributed, networked real-time feedback control system, which is used to provide data transmission between devices, so that users in different locations in the region can share resources and coordinate operations. [0003] The research on network control system was developed in the middle and late 1990s, and it has become one of the hot spots in the development of automatic control and network communication technology. Network control system has the advantages of less system connection, convenient expansion, simple diagnosis and maintenance, and flexible With the advantages of high performance, resource sharing and ...

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Problems solved by technology

[0009] (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.

[0014] Since the denominator of the closed-loop transfer function shown in equation (1) includes the network delay τ 1 and τ 2 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.

[0015] The key to reducing the impact of delay on system stability is whether the network delay τ between the main transmitter (controller) node and the execution (secondary controller) node can be realized. 1 index term of and the network delay τ between the secondary transmitter and the executive (secondary controller) node 2 index term of 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 and τ 2 measurement to compensate for the time delay τ 1 and τ 2 The impact on system stability. However, due to the network delay τ 1 and τ 2 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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