Method for controlling an injector for injecting a reductant into an exhaust system of an internal combustion engine

Patent metadata

Field	Value
Publication number	US-10196956-B2
Application number	US-201715496746-A
Country	US
Kind code	B2
Filing date	Apr 25, 2017
Priority date	Apr 25, 2016
Publication date	Feb 5, 2019
Grant date	Feb 5, 2019

Abstract

A method is disclosed for controlling an injector for injecting a reductant into a selective catalytic reduction system of an internal combustion engine. A value of a concentration of nitrogen-oxides in the exhaust gas aftertreatment system downstream of the selective catalytic reduction system is measured, and a first difference is calculated between the measured value of the nitrogen-oxides concentration and a predetermined reference value thereof. A value of a concentration of ammonia in the exhaust gas aftertreatment system downstream of the selective catalytic reduction system is measured, and a second difference is calculated between the measured value of the ammonia concentration and a predetermined reference value thereof. A quantity of reductant to be injected by the injector is calculated as a function of the calculated first difference and second difference, and the injector is operated to inject the calculated quantity of reductant.

First claim

What is claimed is:

1. A method of controlling a reductant injector for a selective catalytic reduction system in an exhaust gas aftertreatment system of an internal combustion engine comprising:
measuring a value of nitrogen-oxide concentration in an exhaust gas downstream of the selective catalytic reduction system;
calculating a first difference between the measured value of nitrogen-oxide concentration and a first predetermined reference value;
measuring a value of ammonia concentration in the exhaust gas downstream of the selective catalytic reduction system;
calculating a second difference between the measured value of the ammonia concentration and a second predetermined reference value;
calculating a quantity of reductant to be injected by the injector as a function of the first difference and second difference, including:
solving an optimization control function based on the first difference and second difference, the optimization control function subjecting the first difference and second differences and the quantity of reductant to respective predetermined constraint conditions; and
calculating a minimum value of a quadratic performance index subjected to predetermined constraint conditions, wherein the quantity of reductant is a manipulated variable of the quadratic performance index and the first difference and second difference are, respectively, a first and a second state quantity of the quadratic performance index; and

controlling the injector using the calculated quantity for injecting a reductant into the selective catalytic reduction system.

2. The method of claim 1 , wherein the quadratic performance index comprises a third state quantity determined by a variation of the quantity of reductant at each control cycle.

3. The method according to claim 2 , wherein the predetermined constraint conditions comprise the condition that the variation of the quantity of the reductant at each control cycle is within an interval ranging from a minimum negative threshold value to a maximum positive threshold value thereof.

4. The method of claim 2 , wherein the quadratic performance index is defined by the following equation:

J
=

(

∑

k
=
0

N
-
1

⁢

[

W

NO
x

⁡

(

NO

x
,
k

-

NO

x
,
ref

)

2

+

W

NH
3

⁡

(

NH

3
,
k

-

NH

3
,
ref

)

2

+

W
u

⁡

(

NH

3
⁢
in

,
k

)

2

+

W
du

⁡

(

Δ
⁢

⁢

RED

in
,
k

)

2

]

)

wherein NO x,k is the measured value of the nitrogen-oxides concentration, NO x,ref is the reference value of the nitrogen-oxides concentration, NH 3,k is the measured value of the ammonia concentration, NH 3,ref is the reference value of the ammonia concentration, W NO x is a first weight factor, W NH 3 is a second weight factor, NH 3in,k is the quantity of the reductant to be calculated, W u is a third weight factor, ΔRED in,k is the variation of the quantity of the reductant at each control cycle, W du is a fourth weight factor and N is a predetermined number of control cycles into a predetermined discrete-time prediction horizon.

5. The method of claim 4 , further comprising determining the first weight factor, the second weight factor, the third weight factor, and the fourth weight factor of the quadratic performance index

Assignees

• Gm Global Tech Operations Llc

Inventors

• Alfieri Vincenzo
• Mazzara Bologna Giuseppe
• Conte Giuseppe
• Bemporad Alberto
• Bernardini Daniele

Classifications

• F01N9/00

  Electrical control of exhaust gas treating apparatus (monitoring or diagnostic devices for exhaust-gas treatment apparatus F01N11/00; conjoint electrical control of two or more combustion engine functions F02D43/00) · CPC title

• F01N2560/021

  for measuring or detecting ammonia NH3 · CPC title

• F01N2900/1812

  Flow rate · CPC title

• F01N3/208 Primary

  Control of selective catalytic reduction [SCR], e.g. by adjusting the dosing of reducing agent · CPC title

• F01N9/005

  using models instead of sensors to determine operating characteristics of exhaust systems, e.g. calculating catalyst temperature instead of measuring it directly · CPC title