Identification approach for internal combustion engine mean value models
View Patent ↗A system or approach for identifying mean value models with a set of equations and appropriate constraints which define the model validity. A model may be used to design an algorithm for an engine system, collecting sensed data, optimizing control parameters based on the models and data, and providing control of the engine system. These processed may be reiterated for updating control of the engine system.
1. A mechanism for controlling an engine system, comprising:
an engine control module (ECM) connected to an engine system; and
a model representing the engine system; and
wherein:
the engine system comprises:
an engine;
actuators and sensors of the engine connected to the ECM;
a turbocharger having an output connected to an input of the engine; and
an aftertreatment device having an input connected to an output of the engine;
the model representing the engine system is situated in the ECM;
the model representing the engine system is a mean value model that uses equations and constraints;
the model representing the engine in a steady state comprises one or more equations consisting of terms {circumflex over (x)}, u, ŷ and θ representing internal state variables, exogenous variables, model outputs and model parameters, respectfully;
the one or more equations comprise
0= f ( {circumflex over (x)} ( t ), u ( t ),θ)
ŷ ( t )= g ( {circumflex over (x)} ( t ), u ( t ),θ);
the constraints ensure model validity in that equations of the model are prevented from evaluation with values outside of ranges allowed for the engine system being represented; and
the ECM receives data from the sensors of the engine system, which are processed in view of the model; and
the ECM sends signals, which are configured based on the model, to the actuators of the engine system.
2. The mechanism of claim 1 , wherein:
an identification of the model is cast in as a least squares optimization for observed input and output values {u k , y k , k=1 . . . K} as
min θ,x k Σ k=1 K ∥g( {circumflex over (x)} k ,u k ,θ)− y k ∥ 2 2 ;
and
the least squares optimization is constrained by f({circumflex over (x)} k ,u k ,θ)=0,∀k,
where ∀ indicates that f is for a sequence of k.
3. The mechanism of claim 1 , wherein
the signals from the ECM to the actuators are optimized in view of the model.
4. The mechanism of claim 1 , wherein the ECM provides real time control of the engine system.
5. A method for controlling an engine system based on an approximation of a cost function relative to nonlinear identification for a mean value model for the engine system, comprising:
selecting initial model parameters for an engine system; and
optimizing state model vectors for steady state operating points determining active constraints on states, that is, determining a first logical matrix of elements;
receiving data from sensors of the engine system, which are processed in view of the optimized state model vectors;
sending signals, which are configured based on the optimized state model vectors, to the actuators of the engine system; and
wherein the first logical matrix has as many rows as a number of state model vector constraints and as many columns as a number of individual operating points in data.
6. The method of claim 5 , further comprising:
initializing a second logical matrix of elements to virtually all true; and
wherein the second logical matrix has as many rows as a number of state model vector constraints and as many columns as a number of individual operating points in the data.
7. The method of claim 6 , further comprising:
iterating over steady state operating points with a true element in a column of the second logical matrix; and
wherein for a steady state operating point, an active set in a column in the first logical matrix is transformed to corresponding constraints on parameters.
8. The method of claim 5 , further comprising:
expressing a contribution to a cost function at the steady state operating point as a function of parameters only; and
optimizing model parameters with respect to a sum of constraints on parameters; and
wherein active constraints define elements of the second logical matrix.
9. The method of claim 8 , wherein if any element of the second logical matrix is false, then a solution is found.
10. The method of claim 8 , wherein:
if any element of the second logical matrix is true, then elements of the first logical matrix corresponding to true values in the second logical matrix are inverted; and
further comprising repeating the method recited in claim 6 .
11. A turbocharged engine model system comprising:
an engine model of an engine of an engine system;
a mixing point model having an output connected to an inflow port of the engine model;
a turbocharger model having an inflow turbine port connected to an outflow port of the engine model, an outflow compressor port connected to an input of the mixing point model, and having an outflow turbine port and an inflow compressor port; and
a processor incorporating a plurality of the models, including the engine model, mixing point model and the turbocharger model, and being connected to the engine; and
wherein:
the models are mean value models that use equations and constraints;
the engine model, when representing the engine in a steady state, comprises one or more equations consisting of terms {circumflex over (x)}, u, ŷ and θ representing internal state variables, exogenous variables, model outputs and model parameters, respectfully;
the one or more equations comprise
0= f ( {circumflex over (x)} ( t ), u ( t ),θ)
ŷ ( t )= g ( {circumflex over (x)} ( t ), u ( t ),θ),
the constraints ensure model validity in that the equations are prevented from evaluation with values outside allowed ranges; and
the processor receives data from sensors of the engine system and, in accordance with the models and calculated equations and constraints, provides optimized signals to actuators of the engine system.
12. The system of claim 11 , wherein the plurality of models further comprises:
an exhaust gas recirculation valve model having an input connected to the outflow port of the engine model; and
an exhaust gas recirculation cooler model having an input connected to an output of the exhaust gas recirculation valve model and an output to a second input of the mixing point model.
13. The system of claim 12 , wherein the plurality of models further comprises a charge air cooler model having an input connected to the outflow compressor port and an output connected to an input of the mixing point model.
14. The system of claim 13 , wherein the plurality of models further comprises a flow splitter model having an input connected to the outflow port of the engine model, a first output connected to the inflow turbine port of the turbocharger model and a second output connected to an inflow port of the exhaust gas recirculation valve model.