Method for compensating uncertain network delay of forward passage of network cascade control system

Abstract

The invention provides a method for compensating uncertain network delay of a forward passage of a network cascade control system, belonging to the technical field of a network control system technology. A real network data transmission process among forward passage nodes is adopted instead of a network delay compensation model; the measurement, observation, estimation and identification of the uncertain delay of network data transmission among the forward passage nodes are omitted; and requirements on the clock signal synchronization of the nodes are eliminated. By adopting the method, the influence of uncertain network delay on the system stability can be reduced, and the control performance quality of the system is improved. The method provided by the invention is suitable for compensating and controlling the uncertain delay for which the mathematical models of the primary and secondary controlled objects are known, the network only exists in the forward passage of the network cascade control system, and the network delay is greater than several or even dozens of sampling periods.

Description

technical field [0001] The invention relates to a compensation method for the non-deterministic 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] A closed-loop feedback control system based on a real-time communication network is called a networked control system (Networked control systems, NCS). A networked control system is usually composed of nodes such as transmitters, controllers, and actuators. Compared with traditional point-to-point structure systems Compared with the network control system, the complex control system can be integrated horizontally and vertically, which enhances the flexibility of the system, improves the diagnosability and maintainability of the system, and reduces the installation cost. However, due to the constraints of communication bandwidth, Communication resources compete among nodes, and network delay will inevitably occur du...

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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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