Estimation method of ammonia injection rate and state synchronization in diesel urea-scr system

Abstract

A method for synchronously estimating ammonia injection rate and state of a diesel engine Urea-SCR system is disclosed. The present disclosure first proposes a high-gain observer design method for general nonlinear systems, which can simultaneously obtain system state and unknown parameter estimation. The outputs are derived, assuming only that these input dynamics are bounded, and no assumptions are made about how these unknown inputs vary. According to the above method, a high-gain observer is designed for the Urea-SCR system, which can obtain the ammonia injection rate, NOx concentration, NH 3 Simultaneous estimation of states such as concentration, ammonia coverage, etc. The ETC test cycle simulation and error analysis results show that the high-gain observer designed in the present invention has high estimation accuracy, and these estimation information can be used for fault diagnosis of Urea‑SCR system, and can also be used for full-state feedback control strategy or adaptive control strategy , can save the cost of installing the sensor.

Description

technical field [0001] The disclosure relates to the field of engines, in particular to a method for synchronously estimating ammonia injection rate and state in a Urea-SCR system of a diesel engine. Background technique [0002] Selective catalytic reduction (SCR) technology is widely used in medium and heavy duty diesel vehicle NOx emission control due to its advantages of high efficiency, high selectivity, high economy and sulfur tolerance. To meet the latest National VI emission regulations, the diesel engine aftertreatment system needs to adopt a closed-loop feedback control strategy to reduce the calibration workload and improve transient control performance. [0003] The closed-loop feedback control strategy of the Urea-SCR system usually requires the feedback of the outlet state information of the catalytic converter to modify the control variables. On the other hand, the ammonia injection rate is an important parameter in the control of the Urea-SCR system, but as ...

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Problems solved by technology

[0005] The state observers designed in most studies are mainly used to obtain the ammonia coverage, NOx concentration, NH 3 The proposed observer cannot provide any information for unknown input. In these observers, the ammonia injection rate of the Urea-SCR system is usually taken as a known parameter, but the study found that with the Urea- As the service time of the SCR system increases, the actual ammonia injection rate may change with the aging of the system. This change may be slowly time-varying and uncertain, and it usually needs to be regarded as an unknown parameter. There is no research yet Situations involving simultaneous estimation of ammonia injection rate and catalytic converter internal state

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