Forward channel random network time-delay compensation method for network cascade control system

Abstract

The invention provides a forward channel random network time-delay compensation method for a network cascade control system, and belongs to the technical field of network control systems. The real network data transmission process between forward network channel nodes is adopted to replace a network time-delay compensation model therebetween, the measurement, the observation, estimation or identification of network data transmission random time delay between the forward network channel nodes is avoided, and the requirement on node clock signal synchronization is avoided. The method can reduce the influence of the random network time delay on the system stability and improve the dynamic performance quality of the system. The compensation method is applied to dynamic compensation and control of the random network time delay in a forward channel of the network cascade control system in a network with certain data packet loss and known mathematical models of master / slave controlled objects.

Description

technical field [0001] The invention relates to a method for compensating the random network time delay of the forward path of a network cascade control system, and belongs to the technical field of network control systems. Background technique [0002] In the distributed control system, the closed-loop feedback control system composed of sensors and controllers, controllers and actuators through a real-time communication network is called networked control systems (NCS). Networked control systems and traditional point-to-point structures Compared with the traditional control system, it has the advantages of low cost, easy information sharing, easy expansion and maintenance, and great flexibility. Therefore, it has been widely used in industrial control processes in recent years. However, due to the limited carrying capacity of network communication bandwidth, network data There is inevitably network delay in transmission. The existence of delay will reduce the control perfo...

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Problems solved by technology

[0007] (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.

[0012] 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.

[0013] 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 auxiliary transmitter (controller) node can be realized. 1 index term of and the network delay τ between the secondary transmitter (controller) node and the actuator 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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