Liquid level monitoring method and device, tail gas aftertreatment system and motor vehicle

Abstract

The invention relates to a liquid level monitoring method and device, a tail gas aftertreatment system and a motor vehicle. The liquid level change rate A of a set time period and the liquid level change rate B of a next time period are obtained; when the ultrasonic signal for measuring the liquid level has no echo and the sensor for measuring the concentration has no signal, a signal indicating that the liquid level is empty is sent out; when the ultrasonic signal for measuring the liquid level has no echo, meanwhile, the sensor for measuring the concentration has a signal, and the liquid level change rate A is greater than the liquid level change rate B, the output liquid level signal is subjected to first-order low-pass filtering delayed for C seconds, and the filtered signal is used as the actually monitored urea liquid level signal. When a sensor for measuring the concentration at the same time in an abnormal state has a signal, it is considered that a certain amount of urea solution is still contained in the urea box at the moment, and whether the urea box still contains a certain amount of urea solution or not is further determined according to the change rate of the liquid level.

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