Liquid level system PI control method based on virtual unmodeled dynamics compensation

Abstract

A liquid level system PI control method based on virtual unmodeled dynamics compensation comprises the steps that a liquid level target value is set, a water pump is started, the water pump starts to rotate and pumps water from a reservoir, and water flow enters a sealed container or an open container after passing through a flow detection device; the liquid level height is detected in real time through a liquid level sensor in the sealed container or the open container; a PI control model based on virtual unmodeled dynamics compensation is built, the input of the model is a deviation signal formed by a liquid level target value and a liquid level height measurement value, and the output of the model is a pulse width modulation duty ratio used for driving the water pump of an execution mechanism. The liquid level system PI control method based on virtual unmodeled dynamics compensation uses the features that a PI controller is simple in principle structure, low in order and high in robustness, uses a data driving control method and makes full use of the features of historical input and output data and historical data information of unmodeled dynamics, thereby better extracting the dynamic features of the system, carrying out effective estimation and compensation of the virtual unmodeled dynamics at a former time point, and obviously improving stability and the control effect.

Description

technical field [0001] The invention belongs to the technical field of automatic design, in particular to a PI control method of a liquid level system based on virtual unmodeled dynamic compensation. Background technique [0002] In the liquid level control system of the process industry, due to the influence of variable measurement, material and signal transmission and other factors, the phenomenon of time lag generally exists, so that the control signal output by the water pump is delayed to act on the liquid level output of the system, which will cause more obvious problems. Overshoot and long adjustment time; at the same time, due to the complex structure of the liquid level control system in the industrial process, the system often has high-order characteristics, it is difficult to obtain the ideal low-order PI or PID controller widely used in industrial processes Control effect. Based on the above analysis, the control of high-order time-delay liquid level systems is e...

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Problems solved by technology

[0002] In the liquid level control system of the process industry, due to the influence of variable measurement, material and signal transmission and other factors, the phenomenon of time lag generally exists, so that the control signal output by the water pump is delayed to act on the liquid level output of the system, which will cause more obvious problems. Overshoot and long adjustment time; at the same time, due to the complex structure of the liquid level control system in the industrial process, the system often has high-order characteristics, it is difficult to obtain the ideal low-order PI or PID controller widely used in industrial processes Control effect. Based on the above analysis, the control of high-order time-delay liquid level systems is extremely challenging, both in theory and in engineering practice. How to achieve precise and stable control of such systems has always been a research hotspot.

[0003] Although methods such as Smith Prediction (SP) and Internal Model Control (IMC) can deal with system time delays, they are only applicable to low-order systems and are sensitive to model errors and disturbances; H in modern control theory 2 and H ∞ The optimal control method has achieved some research results in the control of time-delay systems, but the optimal controller obtained by the above method is often of higher order, which is generally equal to or greater than the order of the high-order controlled object, which makes the controller’s The implementation cost is high, and it is difficult to apply to industrial sites

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