Time-varying delay compensation method for external forward and internal feedback channel of network cascade control system

Abstract

The invention provides a time-varying delay compensation method for an external forward and internal feedback channel of a network cascade control system, which belongs to the technical field of network control systems. A network delay compensation model is replaced by a network data transmission process between an external forward channel node and an internal feedback channel node of a real network cascade control system, so that measurement, observation, estimation or identification of network data transmission time-varying delay between the nodes is avoided and the requirement on the synchronization of node clock signals is eliminated. Due to the adoption of the method, the influence of time-varying network delay on system stability can be reduced and the control performance quality ofthe system is improved. The method is suitable for dynamic compensation and control of time-varying network delay when a main controlled object mathematical model is known or unknown, an auxiliary controlled object mathematical model is known, a certain number of data packet losses can exist in a network and the network only exists in the external forward and internal feedback channel of the network cascade control system.

Description

technical field [0001] The invention relates to a compensation method for the time-varying network delay of the external forward and internal feedback paths of a network cascaded 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. The networked control system is another profound change in the field of automation. It complies with the gradual decentralization and networking of industrial control systems. , the trend of intelligent development, with many advantages such as low cost, low power consumption, easy maintenance, high reliability, etc., has been more and more widely used in industrial process control, energy transportation, aerospace and remote control and other fields. [0003] Due to the introduction of the network, there is a network delay in the process of information transmission in ...

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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 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.

[0014] 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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