Computer method and apparatus for constraining a non-linear approximator of an empirical process
First Claim
1. A computer readable memory medium that stores computer executable instructions that when executed by a processor perform model predictive control and optimization of a nonlinear process by implementing:
- a parametric universal nonlinear dynamic approximator for predictive control and optimization of a nonlinear process, comprising;
a parameterized dynamic model, configured to model the nonlinear process, wherein the parameterized dynamic model comprises one or more parameters that are not inputs or outputs of the nonlinear process; and
a nonlinear approximator, configured to model dependencies of the one or more parameters of the parameterized dynamic model upon operating conditions of the nonlinear process;
wherein the parametric universal nonlinear dynamic approximator is configured to predict process outputs necessary for predictive control and optimization of the nonlinear process by;
operating the nonlinear approximator to;
receive one or more process operating conditions, including one or more process inputs; and
generate values for the one or more parameters of the parameterized dynamic model based on the process operating conditions; and
operating the parameterized dynamic model to;
receive the values of the one or more parameters;
receive the one or more process inputs;
generate one or more predicted process outputs based on the received values of the one or more parameters and the received one or more process inputs, wherein the one or more predicted process outputs are dependent on the one or more process inputs, the values of the one or more parameters, and past values of the process inputs and outputs; and
store the one or more predicted process outputs;
wherein the parametric universal nonlinear dynamic approximator is configured to be coupled to the nonlinear process or a representation of the nonlinear process and the nonlinear process is configured to receive the one or more process inputs and produce the one or more process outputs;
wherein the nonlinear approximator and the parameterized dynamic model of the parametric universal nonlinear dynamic approximator are configured to be trained in an integrated manner by an optimization process that is configured to (i) determine model errors based on the one or more process outputs and the one or more predicted process outputs; and
(ii) adaptively train the parametric universal nonlinear dynamic approximator in an iterative manner using the model errors and the optimization process; and
wherein, in training the parametric universal nonlinear dynamic approximator in an iterative manner using the model errors and the optimization process, the optimization process is configured to;
identify process inputs and outputs (I/O);
determine an order of the parameterized dynamic model, wherein the order specifies a number of parameters comprised in the parameterized dynamic model;
collect data representing process operating conditions;
determine constraints on behavior of the parametric universal nonlinear dynamic approximator from prior knowledge, including one or more constraints for the nonlinear approximator for modeling dependencies of the one or more parameters of the parameterized dynamic model;
formulate an optimization problem;
execute an optimization algorithm to determine the dependencies of the parameters of the parameterized dynamic model upon operating conditions of the nonlinear process subject to the determined constraints by solving the optimization problem, thereby training the nonlinear approximator; and
verify compliance of the parametric universal nonlinear dynamic approximator with the determined constraints.
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Abstract
A constrained non-linear approximator for empirical process control is disclosed. The approximator constrains the behavior of the derivative of a subject empirical model without adversely affecting the ability of the model to represent generic non-linear relationships. There are three stages to developing the constrained non-linear approximator. The first stage is the specification of the general shape of the gain trajectory or base non-linear function which is specified graphically, algebraically or generically and is used as the basis for transfer functions used in the second stage. The second stage of the invention is the interconnection of the transfer functions to allow non-linear approximation. The final stage of the invention is the constrained optimization of the model coefficients such that the general shape of the input/output mappings (and their corresponding derivatives) are conserved.
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Citations
30 Claims
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1. A computer readable memory medium that stores computer executable instructions that when executed by a processor perform model predictive control and optimization of a nonlinear process by implementing:
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a parametric universal nonlinear dynamic approximator for predictive control and optimization of a nonlinear process, comprising; a parameterized dynamic model, configured to model the nonlinear process, wherein the parameterized dynamic model comprises one or more parameters that are not inputs or outputs of the nonlinear process; and a nonlinear approximator, configured to model dependencies of the one or more parameters of the parameterized dynamic model upon operating conditions of the nonlinear process; wherein the parametric universal nonlinear dynamic approximator is configured to predict process outputs necessary for predictive control and optimization of the nonlinear process by; operating the nonlinear approximator to; receive one or more process operating conditions, including one or more process inputs; and generate values for the one or more parameters of the parameterized dynamic model based on the process operating conditions; and operating the parameterized dynamic model to; receive the values of the one or more parameters; receive the one or more process inputs; generate one or more predicted process outputs based on the received values of the one or more parameters and the received one or more process inputs, wherein the one or more predicted process outputs are dependent on the one or more process inputs, the values of the one or more parameters, and past values of the process inputs and outputs; and store the one or more predicted process outputs; wherein the parametric universal nonlinear dynamic approximator is configured to be coupled to the nonlinear process or a representation of the nonlinear process and the nonlinear process is configured to receive the one or more process inputs and produce the one or more process outputs; wherein the nonlinear approximator and the parameterized dynamic model of the parametric universal nonlinear dynamic approximator are configured to be trained in an integrated manner by an optimization process that is configured to (i) determine model errors based on the one or more process outputs and the one or more predicted process outputs; and
(ii) adaptively train the parametric universal nonlinear dynamic approximator in an iterative manner using the model errors and the optimization process; andwherein, in training the parametric universal nonlinear dynamic approximator in an iterative manner using the model errors and the optimization process, the optimization process is configured to; identify process inputs and outputs (I/O); determine an order of the parameterized dynamic model, wherein the order specifies a number of parameters comprised in the parameterized dynamic model; collect data representing process operating conditions; determine constraints on behavior of the parametric universal nonlinear dynamic approximator from prior knowledge, including one or more constraints for the nonlinear approximator for modeling dependencies of the one or more parameters of the parameterized dynamic model; formulate an optimization problem; execute an optimization algorithm to determine the dependencies of the parameters of the parameterized dynamic model upon operating conditions of the nonlinear process subject to the determined constraints by solving the optimization problem, thereby training the nonlinear approximator; and verify compliance of the parametric universal nonlinear dynamic approximator with the determined constraints. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A computer implemented method for training a parametric universal nonlinear dynamic approximator of a nonlinear process, the method comprising:
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identifying process inputs and outputs (I/O); determining, using a computer, an order for a parameterized dynamic model comprised in the parametric universal nonlinear dynamic approximator, wherein the order specifies a number of parameters for the parameterized dynamic model, and wherein the parameters of the parameterized dynamic model are not inputs or outputs of the nonlinear process; determining, using the computer, a structure for a nonlinear approximator comprised in the parametric universal nonlinear dynamic approximator for modeling dependencies of the parameters of the parameterized dynamic model upon operating conditions of the nonlinear process; collecting, using the computer, data for the identified process I/O; determining, using the computer, constraints on behavior of the parametric universal nonlinear dynamic approximator from prior knowledge, including one or more constraints for the nonlinear approximator for modeling dependencies of the one or more parameters of the parameterized dynamic model; formulating, using the computer, an optimization problem for training the nonlinear approximator; executing, using the computer, an optimization algorithm to train the nonlinear approximator subject to the determined constraints by solving the optimization problem, thereby determining the dependencies of the parameters of the parameterized dynamic model upon operating conditions of the process, wherein outputs of the nonlinear approximator are not outputs of the nonlinear process; verifying, using the computer, compliance of the parametric universal nonlinear dynamic approximator with the determined constraints; storing, using the computer, the trained nonlinear approximator and the parameterized dynamic model, wherein the stored nonlinear approximator and the parameterized dynamic model compose a trained parametric universal nonlinear dynamic approximator; and wherein the trained parametric universal nonlinear dynamic approximator is usable to optimize and control the nonlinear process. - View Dependent Claims (17, 18, 19, 20)
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21. A system for training a parametric universal nonlinear dynamic approximator of a nonlinear process, the system comprising:
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means for identifying process inputs and outputs (I/O); means for determining an order for a parameterized dynamic model comprised in the parametric universal nonlinear dynamic approximator, wherein the order specifies a number of parameters for the parameterized dynamic model, and wherein the parameters of the parameterized dynamic model are not inputs or outputs of the nonlinear process; means for determining a structure for a nonlinear approximator comprised in the parametric universal nonlinear dynamic approximator for modeling dependencies of the parameters of the parameterized dynamic model upon operating conditions of the nonlinear process; means for collecting data for the identified process I/O; means for determining constraints on behavior of the parametric universal nonlinear dynamic approximator from prior knowledge, including one or more constraints for the nonlinear approximator for modeling dependencies of the one or more parameters of the parameterized dynamic model; means for formulating an optimization problem for training the nonlinear approximator; means for executing an optimization algorithm to train the nonlinear approximator subject to the determined constraints by solving the optimization problem, thereby determining the dependencies of the parameters of the parameterized dynamic model upon operating conditions of the process, wherein outputs of the nonlinear approximator are not outputs of the nonlinear process; means for verifying compliance of the parametric universal nonlinear dynamic approximator with the determined constraints; and means for storing the trained nonlinear approximator and the parameterized dynamic model, wherein the stored nonlinear approximator and the parameterized dynamic model compose a trained parametric universal dynamic approximator; wherein the parametric universal nonlinear dynamic approximator is usable to optimize and control the nonlinear process.
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22. A computer implemented method for controlling a nonlinear process, the method comprising:
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a) initializing, using a computer, a parametric universal nonlinear dynamic approximator to a current status of the nonlinear process, comprising process inputs and outputs, said initializing comprising; a1) initializing, using the computer, inputs to a nonlinear approximator comprised in the parametric universal nonlinear dynamic approximator, wherein the nonlinear approximator is trained to model dependencies of one or more parameters of a parameterized dynamic model of the nonlinear process comprised in the parametric universal nonlinear dynamic approximator upon operating conditions of the nonlinear process by; identifying process inputs and outputs (I/O); determining an order of the parameterized dynamic model, wherein the order specifies a number of parameters comprised in the parameterized dynamic model; collecting data representing process operating conditions; determining constraints on behavior of the parametric universal nonlinear dynamic approximator from prior knowledge, including one or more constraints for the nonlinear approximator for modeling dependencies of the one or more parameters of the parameterized dynamic model; formulating an optimization problem; executing an optimization algorithm to determine the dependencies of the parameters of the parameterized dynamic model upon operating conditions of the nonlinear process subject to the determined constraints by solving the optimization problem, thereby training the nonlinear approximator; and verifying compliance of the parametric universal nonlinear dynamic approximator with the determined constraints; a2) executing, using the computer, the trained nonlinear approximator to determine initial values for the one or more parameters of the parameterized dynamic model based on the current status of the nonlinear process; and a3) initializing, using the computer, the parameterized dynamic model with the determined initial values for the one or more parameters; b) formulating, using the computer, an optimization problem, including specifying an objective function for optimization of the nonlinear process; c) generating, using the computer, a profile of manipulated variables for the nonlinear process over a control horizon in accordance with the specified objective function for optimization of the nonlinear process; d) operating, using the computer, the parametric universal nonlinear dynamic approximator in accordance with the generated profile of manipulated variables, thereby generating predicted outputs for the nonlinear process; e) determining, using the computer, a deviation of the predicted outputs from a desired behavior of the nonlinear process; f) repeating b)-e) one or more times to determine an optimal profile of manipulated variables in accordance with the specified objective function for optimization of the nonlinear process; g) operating, using the computer, the nonlinear process in accordance with the optimal profile of manipulated variables, thereby generating process output; and repeating a)-g) one or more times to dynamically control the nonlinear process. - View Dependent Claims (23, 24)
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25. A system for controlling a nonlinear process, the system comprising:
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means for a) initializing a parametric universal nonlinear dynamic approximator to a current status of the nonlinear process, comprising process inputs and outputs, comprising; means for a
1) initializing inputs to a nonlinear approximator comprised in the parametric universal nonlinear dynamic approximator, wherein the nonlinear approximator is trained to model dependencies of one or more parameters of a parameterized dynamic model of the nonlinear process comprised in the parametric universal nonlinear dynamic approximator upon operating conditions of the nonlinear process by;identifying process inputs and outputs (I/O); determining an order of the parameterized dynamic model, wherein the order specifies a number of parameters comprised in the parameterized dynamic model; collecting data representing process operating conditions; determining constraints on behavior of the parametric universal nonlinear dynamic approximator from prior knowledge, including one or more constraints for the nonlinear approximator for modeling dependencies of the one or more parameters of the parameterized dynamic model; formulating an optimization problem; executing an optimization algorithm to determine the dependencies of the parameters of the parameterized dynamic model upon operating conditions of the nonlinear process subject to the determined constraints by solving the optimization problem, thereby training the nonlinear approximator; and verifying compliance of the parametric universal nonlinear dynamic approximator with the determined constraints means for a2) executing the trained nonlinear approximator to determine initial values for the one or more parameters of the parameterized dynamic model based on the current status of the nonlinear process; means for a3) initializing the parameterized dynamic model with the determined initial values for one or more parameters; means for b) formulating an optimization problem, including specifying an objective function for optimization of the nonlinear process; means for c) generating a profile of manipulated variables for the nonlinear process over a control horizon in accordance with the specified objective function for optimization of the nonlinear process; means for d) operating the parametric universal nonlinear dynamic approximator in accordance with the generated profile of manipulated variables, thereby generating predicted outputs for the nonlinear process; means for e) determining a deviation of the predicted outputs from a desired behavior of the nonlinear process; means for f) repeating b)-e) one or more times to determine an optimal profile of manipulated variables in accordance with the specified objective function for optimization of the nonlinear process; means for g) operating the nonlinear processing accordance with the optimal profile of manipulated variables, thereby generating process output; and means for repeating a)-g) one or more times to dynamically control the nonlinear process.
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26. A computer readable memory medium that stores computer executable instructions that when executed by a processor perform model predictive control and optimization of a nonlinear process by implementing:
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a state space model for predictive control and optimization of a nonlinear process, comprising; a state space dynamic model, configured to model the nonlinear process, wherein the state space dynamic model comprises one or more coefficients that are not inputs or outputs of the nonlinear process; and a nonlinear approximator, configured to model dependencies of the one or more coefficients of the state space dynamic model upon operating conditions of the nonlinear process; wherein the state space model is configured to predict process outputs necessary for predictive control and optimization of the nonlinear process by; operating the nonlinear approximator to; receive one or more process operating conditions, including one or more process inputs; and generate values for the one or more coefficients of the state space dynamic model based on the process operating conditions; and operating the state space dynamic model to; receive the values of the one or more coefficients; receive the one or more process inputs; generate one or more predicted process outputs based on the received values of the one or more coefficients and the received one or more process inputs, wherein the one or more predicted process outputs are dependent on the one or more process inputs, the values of the one or more coefficients, and past values of the process inputs and outputs; and store the one or more predicted process outputs; wherein the state space model is configured to be coupled to the nonlinear process or a representation of the nonlinear process and the nonlinear process is configured to receive the one or more process inputs and produce the one or more process outputs; wherein the nonlinear approximator and the state space dynamic model of the state space model are configured to be trained in an integrated manner by an optimization process that is configured to (i) determine model errors based on the one or more process outputs and the one or more predicted process outputs; and
(ii) adaptively train the state space model in an iterative manner using the model errors and the optimization process; andwherein, in training the state space model in an iterative manner using the model errors and the optimization process, the optimization process is configured to; identify process inputs and outputs (I/O); determine an order of the state space dynamic model, wherein the order specifies a number of coefficients comprised in the state space dynamic model; collect data representing process operating conditions; determine constraints on behavior of the state space model from prior knowledge, including one or more constraints for the nonlinear approximator for modeling dependencies of the one or more coefficients of the state space dynamic model; formulate an optimization problem; execute an optimization algorithm to determine the dependencies of the coefficients of the state space dynamic model upon operating conditions of the nonlinear process subject to the determined constraints by solving the optimization problem, thereby training the nonlinear approximator; and verify compliance of the state space model with the determined constraints.
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27. A computer implemented method for training a state space model of a nonlinear process, the method comprising:
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identifying, using a computer, process inputs and outputs (I/O); determining, using the computer, an order for a state space dynamic model comprised in the state space model, wherein the order specifies a number of coefficients for the state space dynamic model, and wherein the coefficients of the state space dynamic model are not inputs or outputs of the nonlinear process; determining, using the computer, a structure for a nonlinear approximator comprised in the state space model for modeling dependencies of the coefficients of the state space dynamic model upon operating conditions of the nonlinear process; collecting, using the computer, data for the identified process I/O; determining, using the computer, constraints on behavior of the state space model from prior knowledge, including one or more constraints for the nonlinear approximator for modeling dependencies of the one or more coefficients of the state space dynamic model; formulating, using the computer, an optimization problem for training the nonlinear approximator; executing, using the computer, an optimization algorithm to train the nonlinear approximator subject to the determined constraints by solving the optimization problem, thereby determining the dependencies of the coefficients of the state space dynamic model upon operating conditions of the process, wherein outputs of the nonlinear approximator are not outputs of the nonlinear process; verifying, using the computer, compliance of the state space model with the determined constraints; and storing, using the computer, the trained nonlinear approximator and the state space dynamic model, wherein the stored nonlinear approximator and the state space dynamic model compose a trained state space model; wherein the trained state space model is usable to optimize and control the nonlinear process.
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28. A system for training a state space model of a nonlinear process, the system comprising:
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means for identifying process inputs and outputs (I/O); means for determining an order for a state space dynamic model comprised in the state space model, wherein the order specifies a number of coefficients for the state space dynamic model, and wherein the coefficients of the state space dynamic model are not inputs or outputs of the nonlinear process; means for determining a structure for a nonlinear approximator comprised in the state space model for modeling dependencies of the coefficients of the state space dynamic model upon operating conditions of the nonlinear process; means for collecting data for the identified process I/O; means for determining constraints on behavior of the state space model from prior knowledge, including one or more constraints for the nonlinear approximator for modeling dependencies of the one or more coefficients of the state space dynamic model; means for formulating an optimization problem for training the nonlinear approximator; means for executing an optimization algorithm to train the nonlinear approximator subject to the determined constraints by solving the optimization problem, thereby determining the dependencies of the coefficients of the state space dynamic model upon operating conditions of the process, wherein outputs of the nonlinear approximator are not outputs of the nonlinear process; means for verifying compliance of the state space model with the determined constraints; and means for storing the trained nonlinear approximator and the state space dynamic model, wherein the stored nonlinear approximator and the state space dynamic model compose a trained state space model; and wherein the state space model is usable to optimize and control the nonlinear process.
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29. A computer implemented method for controlling a nonlinear process, the method comprising:
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a) initializing, using a computer, a state space model to a current status of the nonlinear process, comprising process inputs and outputs, said initializing comprising; a1) initializing, using the computer, inputs to a nonlinear approximator comprised in the state space model, wherein the nonlinear approximator is trained to model dependencies of one or more coefficients of a state space dynamic model of the nonlinear process comprised in the state space model upon operating conditions of the nonlinear process by; identifying process inputs and outputs (I/O); determining an order of the state space dynamic model, wherein the order specifies a number of coefficients comprised in the state space dynamic model; collecting data representing process operating conditions; determining constraints on behavior of the state space model from prior knowledge, including one or more constraints for the nonlinear approximator for modeling dependencies of the one or more coefficients of the state space dynamic model; formulating an optimization problem; executing an optimization algorithm to determine the dependencies of the coefficients of the state space dynamic model upon operating conditions of the nonlinear process subject to the determined constraints by solving the optimization problem, thereby training the nonlinear approximator; and verifying compliance of the state space model with the determined constraints; a2) executing the trained nonlinear approximator to determine initial values for the one or more coefficients of the state space dynamic model based on the current status of the nonlinear process; and a3) initializing the state space dynamic model with the determined initial values for the one or more coefficients; b) formulating, using the computer, an optimization problem, including specifying an objective function for optimization of the nonlinear process; c) generating, using the computer, a profile of manipulated variables for the nonlinear process over a control horizon in accordance with the specified objective function for optimization of the nonlinear process; d) operating, using the computer, the state space model in accordance with the generated profile of manipulated variables, thereby generating predicted outputs for the nonlinear process; e) determining, using the computer, a deviation of the predicted outputs from a desired behavior of the nonlinear process; f) repeating b)-e) one or more times to determine an optimal profile of manipulated variables in accordance with the specified objective function for optimization of the nonlinear process; g) operating, using the computer, the nonlinear process in accordance with the optimal profile of manipulated variables, thereby generating process output; and repeating a)-g) one or more times to dynamically control the nonlinear process.
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30. A system for controlling a nonlinear process, the system comprising:
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means for a) initializing a state space model to a current status of the nonlinear process, comprising process inputs and outputs, comprising; a
1) means for initializing inputs to a nonlinear approximator comprised in the state space model, wherein the nonlinear approximator is trained to model dependencies of one or more coefficients of a state space dynamic model of the nonlinear process comprised in the state space model upon operating conditions of the nonlinear process by;identifying process inputs and outputs (I/O); determining an order of the state space dynamic model, wherein the order specifies a number of coefficients comprised in the state space dynamic model; collecting data representing process operating conditions; determining constraints on behavior of the state space model from prior knowledge, including one or more constraints for the nonlinear approximator for modeling dependencies of the one or more coefficients of the state space dynamic model; formulating an optimization problem; executing an optimization algorithm to determine the dependencies of the coefficients of the state space dynamic model upon operating conditions of the nonlinear process subject to the determined constraints by solving the optimization problem, thereby training the nonlinear approximator; and verifying compliance of the state space model with the determined constraints; a2) means for executing the trained nonlinear approximator to determine initial values for the one or more coefficients of the state space dynamic model based on the current status of the nonlinear process; a3) means for initializing the state space dynamic model with the determined initial values for one or more coefficients; means for b) formulating an optimization problem, including specifying an objective function for optimization of the nonlinear process; means for c) generating a profile of manipulated variables for the nonlinear process over a control horizon in accordance with the specified objective function for optimization of the nonlinear process; means for d) operating the state space model in accordance with the generated profile of manipulated variables, thereby generating predicted outputs for the nonlinear process; means for e) determining a deviation of the predicted outputs from a desired behavior of the nonlinear process; means for f) repeating b)-e) one or more times to determine an optimal profile of manipulated variables in accordance with the specified objective function for optimization of the nonlinear process; means for g) operating the nonlinear processing accordance with the optimal profile of manipulated variables, thereby generating process output; and means for repeating a)-g) one or more times to dynamically control the nonlinear process.
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Specification