Method for compensating unknown external feedback and inner loop network time delay of network cascade control system

Abstract

The invention provides a method for compensating unknown external feedback and inner loop network time delay of a network cascade control system, which belongs to the technical field of network control systems. A network data transmission process between an external feedback network path node and an inner loop network path node of a true network cascade control system is used instead of a networktime delay compensating model, so that the measurement, observation, estimation or identification of unknown network data transmission time delay between the nodes is eliminated and the requirement on the synchronization of a node clock signal is eliminated. The method can reduce the influence of unknown network time delay on the system stability and improves the system control performance and quality. The invention is suitable for dynamically compensating and controlling unknown network time delay when a network only exists in the external feedback and inner loop paths of the network cascadecontrol system, the mathematical models of main and auxiliary controlled objects are known or uncertain, unknown interference exists in the system and a certain quantity of packet losses exist in thenetwork.

Description

Technical field [0001] The present invention relates to a compensation method for external feedback and internal loop unknown network delay of a network cascade control system, and belongs to the technical field of network control systems. Background technique [0002] The control system that forms a closed loop through the network is called the networked control system (networked control system, NCS). On the one hand, the networked control system disperses the closed loop control loop on the real-time serial network, breaking through the limitations of the traditional control system in the physical location of space As well as the closedness and limitation of information, it has the incomparable advantages of traditional control systems. For example, it can realize resource sharing and remote operation and control, has high diagnostic capabilities, is easy to install and maintain, and can effectively reduce the weight and volume of the system. Improve the flexibility and reliabi...

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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 , τ 2 and τ 3 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 unknown network delay τ 1 , τ 2 and τ 3 index term of and Removed from the denominator of equation (1), that is, to realize that the closed-loop characteristic equation of the system does not contain all the exponential terms of network delay, and then realize the compensation of network delay. However, to realize the compensation of network delay, first must 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 , τ 2 and τ 3 measurement to compensate for the time delay τ 1 , τ 2 and τ 3 The impact on system stability. However, due to the network delay τ 1 , τ 2 and τ 3 Accurate measurement needs to meet the synchronization requirements of node clock signals. If hardware is used to realize the complete synchronization of node clock signals, a large economic investment will be required; if software is used to correct clock signals, it 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 However, due to the fact that 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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