External feedback and inner loop nondeterministic network time delay compensation method of network cascade control system

Abstract

The invention provides an external feedback and inner loop nondeterministic network time delay compensation method of a network cascade control system, belonging to the technical field of network control systems. In the invention, network data transmission process between external feedback network path nodes and inner loop network path nodes of a true network cascade control system are adopted toreplace a network time delay compensation model therebetween, thereby avoiding measurement, observation, estimation or identification of network data transmission nondeterministic time delay among the nodes and the requirements on node clock signal synchronism. By adopting the method, the influence of nondeterministic network time delay on system stability can be lowered, and the control performance quality of the system can be improved. The method provided by the invention is suitable for known mathematical models of main and auxiliary controlled objects, the network time delay can be largerthan a plurality of and even dozens of sampling periods, a network only exists in dynamic compensation and control of nondeterministic network time delay in an external feedback and inner loop network path of the network cascade control system.

Description

technical field [0001] The invention relates to a method for compensating the non-deterministic network time delay of external feedback and internal loop network paths in a network cascade control system, belonging to the technical field of network control systems. Background technique [0002] The control loop is closed through a real-time network, which is called Networked Control Systems (NCS). Networked control systems can greatly reduce system wiring, reduce system costs, improve system reliability and flexibility, and facilitate system diagnosis and Maintenance has been widely used in aircraft, spacecraft, chemical plants, power systems and other fields. [0003] An important feature of the network control system is that the sensing information and control information in the closed-loop control loop are transmitted through the real-time network. Since the real-time network is inserted into the control loop, it will inevitably bring about network-induced delay and packe...

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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 , 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.

[0014] The key to reducing the impact of delay on system stability is whether the non-deterministic network delay τ 1 , τ 2 and τ 3 index term of and 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 , 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 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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