On-line adaptive model predictive control in a process control system
First Claim
1. A process controller for controlling a process, the process controller comprising:
- a dynamic matrix control controller having a controller algorithm that uses a gain vector to produce a control signal based on an input signal, the control signal being developed for controlling a process variable;
a process model estimation unit coupled to the process to collect process data during the on-line operation of the process and that determines a process model representing the operation of the process from the collected process data, the process model including multiple model parameters including a process dead time parameter; and
a controller adaptation unit that uses the process model including the process dead time parameter to calculate a new gain vector for use in the dynamic matrix controller algorithm and that adapts the controller algorithm of the dynamic matrix controller to use the new gain vector, wherein the controller adaptation unit adapts the controller to use the new gain vector while the controller is operating on-line to control the process.
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Abstract
A method of creating and using an adaptive DMC type or other MPC controller includes using a model switching technique to periodically determine a process model, such as a parameterized process model, for a process loop on-line during operation of the process. The method then uses the process model to generate an MPC control model and creates and downloads an MPC controller algorithm to an MPC controller based on the new control model while the MPC controller is operating on-line. This technique, which is generally applicable to single-loop MPC controllers and is particularly useful in MPC controllers with a control horizon of one or two, enables an MPC controller to be adapted during the normal operation of the process, so as to change the process model on which the MPC controller is based to thereby account for process changes. The adaptive MPC controller is not computationally expensive and can therefore be easily implemented within a distributed controller of a process control system, while providing the same or in some cases better control than a PID controller, especially in dead time dominant process loops, and in process loops that are subject to process model mismatch within the process time to steady state.
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Citations
25 Claims
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1. A process controller for controlling a process, the process controller comprising:
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a dynamic matrix control controller having a controller algorithm that uses a gain vector to produce a control signal based on an input signal, the control signal being developed for controlling a process variable; a process model estimation unit coupled to the process to collect process data during the on-line operation of the process and that determines a process model representing the operation of the process from the collected process data, the process model including multiple model parameters including a process dead time parameter; and a controller adaptation unit that uses the process model including the process dead time parameter to calculate a new gain vector for use in the dynamic matrix controller algorithm and that adapts the controller algorithm of the dynamic matrix controller to use the new gain vector, wherein the controller adaptation unit adapts the controller to use the new gain vector while the controller is operating on-line to control the process. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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25. A process controller for controlling a process, the process controller comprising:
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a dynamic matrix control controller having a controller algorithm that uses a gain vector to produce a control signal based on an input signal, the control signal being developed for controlling a process variable; a process model estimation unit coupled to the process to collect process data during the on-line operation of the process and that determines a process model representing the operation of the process from the collected process data; and a controller adaptation unit that uses the process model to calculate a new gain vector for use in the dynamic matrix controller algorithm and that adapts the controller algorithm of the dynamic matrix controller to use the new gain vector, wherein the controller adaptation unit adapts the controller to use the new gain vector while the controller is operating on-line to control the process; wherein the dynamic matrix control controller is a single-loop, model predictive control (MPC) controller that includes one or more feedback paths and one or more feedforward paths and wherein the control algorithm uses a control horizon at least ten times shorter than a prediction horizon.
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Specification