Unknown time delay compensation method for external forward and internal feedback paths of network cascade control system

Abstract

The invention provides an unknown time delay compensation method for external forward and internal feedback paths of a network cascade control system, and belongs to the technical field of network control systems. A real network data transmission process between an external forward path node and an internal feedback path node of the network cascade control system replaces a network time delay compensation model amid so as to avoid measurement, observation, estimation or identification of unknown network data transmission time delay between the nodes and avoid the requirement for node clock signal synchronization. The method can reduce the influence of the unknown network time delay on the stability of the system and improve the control performance quality of the system. The method is applied to dynamic compensation and control when mathematical models of primary and secondary controlled objects are known or unknown, the system has unknown interference, the network has a certain amount of data packet loss, the network time delay can be greater than several or dozens of sampling cycles and the network only has known network time delay in the external forward and internal feedback paths of the network cascade control system.

Description

Technical field [0001] The present invention relates to a method for compensating the unknown network delay of the external forward and internal feedback paths of a network cascade control system, and belongs to the technical field of network control systems. Background technique [0002] The closed-loop feedback control system based on the real-time communication network is called Networked control systems (Networked control systems, NCS). Networked control systems can realize complex large systems and remote network control, realize network resource sharing, increase system flexibility and reliability, and at the same time It can also make the analysis and design of the system extremely complicated. In recent years, network control systems have been widely used in electric power, high-speed railways, weapon systems, marine environment monitoring, robotics, industrial remote control, remote medical treatment, remote teaching, Building automation, home automation, agricultural au...

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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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