Estimation method for internal state of catalyst of diesel engine postprocessing device

Abstract

The invention discloses an estimation method for an internal state of a catalyst of a diesel engine postprocessing device. The estimation method comprises the following steps that a Urea-SCR postprocessing device catalyst internal state observer is designed; an observer gain is designed to guarantee that an observer error is asymptotically converged to zero; based on an NOX concentration value measured by a tail gas emission analysis meter, estimation of NOX concentration and NH3 concentration and ammonia coverage rate in a Urea-SCR catalyst is acquired through a Romberg nonlinearity observer;a positive definite lyapunov function is established, and a derivative of the lyapunov function is designed as a negative definite so that an error of estimation can be asymptotically converged to zero; designing is carried out to solve a coupling state not eliminated yet in a Urea-SCR model in an error dynamic equation; and a range condition met by the gain in the lyapunov function is derived. According to the estimation method for the internal state of the catalyst of the diesel engine postprocessing device, the nonlinear observer which can precisely estimate immeasurable states in the catalyst is provided.

Description

technical field [0001] The invention relates to the technical field of engine emission control, in particular to a method for estimating the internal state of a catalytic converter of a diesel engine post-processing device. Background technique [0002] Diesel engines have the characteristics of high power, wide power coverage, low fuel consumption and good durability, and are widely used in medium and heavy trucks, medium and large buses, construction machinery, agricultural machinery, ships and other fields; way, hydrocarbons (HC), carbon monoxide (CO) and other emissions are low, but particulate matter (PM) and nitrogen oxides (NO X ) emit more emissions. According to the statistics of "Annual Report on the Prevention and Control of Motor Vehicle Pollutants in China (2017)", in 2016 the national diesel vehicle NO X The emissions were 3.673 million tons, and the emissions of particulate matter were 512,000 tons, accounting for 68.7% and 99% of the total vehicle emissions....

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Problems solved by technology

[0003] Urea-SCR system as NO X One of the effective means of emission control is widely used in diesel engines; in order to meet the national V and above emission regulations, the Urea-SCR post-treatment system of diesel engines needs to adopt a closed-loop control strategy, and the state information of the Urea-SCR system needs to be obtained for feedback control , there are two ways to obtain state information, one is direct measurement through sensors, and the other is through soft testing (state estimation through algorithms); it is difficult to directly use sensors to obtain all the state information required by the controller, on the one hand The cost of sensors is high, on the other hand, some state quantities cannot be directly measured by sensors

[0004] NO X Sensors have been widely used in diesel engines after large-scale production in the 1990s, but ammonia sensors have not been widely used due to immature technology, few categories, and high cost; ammonia coverage is an important state quantity of Urea-SCR control system. But currently there are no sensors or devices to directly obtain measurements of ammonia coverage

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