Adaptive multivariable MPC controller
View Patent ↗A method is disclosed for developing and using a high-speed adaptive multivariable controller by removing the dynamics of the PID controllers from a Model Predictive Controller that was developed using identification testing of a process. The resulting multivariable controller, based on final control elements as the manipulated variables is then used in a novel control adaptation with all of the PID controllers switched to manual.
1. A method for controlling a process having a plurality of independently controllable, manipulated variables and at least one controlled variable dependent upon said independently controllable, manipulated variables comprising the steps of:
gathering data about said process by separately introducing test disturbances in each of said manipulated variables and measuring the effect of the disturbances on said controlled variable;
using said effects of the disturbances on said controlled variable to generate a first linearized dynamic model relating said at least one controlled variable to said independently controllable, manipulated variables;
interchanging selected final control element position controlled variables with their corresponding selected independently controllable, manipulated PID controller set point variables in said first linearized dynamic model using matrix row elimination mathematics to generate a second linearized dynamic model that has a new set of independently controllable, manipulated variables, said second linearized dynamic model having the dynamics of said selected independently controllable, manipulated PID controller set point variables removed from said second linearized dynamic model;
measuring the present value of said variables;
pre-setting operating limits for said at least one controlled variable;
pre-setting test limits for said at least one controlled variable that fall within said operating limits;
using the second linearized dynamic model to calculate a first set of prediction vectors for said at least one controllable variable;
placing said second linearized dynamic model in an adaptive test mode wherein all of the PID controllers are switched to manual;
perturbing the final control element manipulated variables with random excitation signals;
calculating for discrete intervals of time from said gathered data about said process, said measured present values and pre-selected operating constraints a set of moves for present and future times for at least said manipulated variables to obtain new values for said manipulated variables and to move said at least one dependent controllable variable towards at least one of said constraints; and
when the prediction vector is outside of test limits for said at least one controlled variable, changing said process by adjusting said manipulated variables for said set of moves for present and future times to cause said process to move said at least one dependent controllable variable towards at least one of said constraints.
2. The method of claim 1 , wherein said perturbing step additionally comprises perturbing said test limits for said at least one controlled variable with random excitation signals.
3. The method of claim 2 , wherein said process comprises at least one uncontrolled variable that is dependent on said manipulated variables and wherein said step of calculating said set of moves for present and future times further comprises calculating said set of moves such that said at least one uncontrolled variable is limited to a predetermined constraint.
4. The method of claim 3 , wherein said step of calculating said set of moves for present and future times further comprises calculating said set of moves such that at least one of said manipulated variables is limited to a predetermined constraint.
5. The method of claim 1 , wherein said process comprises at least one uncontrolled variable that is dependent on said manipulated variables and wherein said step of calculating said set of moves for present and future times further comprises calculating said set of moves such that said at least one uncontrolled variable is limited to a predetermined constraint.
6. The method of claim 5 , wherein said step of calculating said set of moves for present and future times further comprises calculating said set of moves such that at least one of said manipulated variables is limited to a predetermined constraint.
7. The method of claim 1 , wherein said step of calculating said set of moves for present and future times comprises calculating said set of moves employing quadratic programming techniques.
8. The method of claim 7 , wherein said step of calculating said set of moves for present and future times further comprises calculating said set of moves such that at least one of said manipulated variables is limited to a predetermined constraint.
9. The method of claim 7 , wherein said process comprises at least one uncontrolled variable that is dependent on said manipulated variables and wherein said step of calculating said set of moves for present and future times further comprises calculating said set of moves such that said uncontrolled variable is limited to a predetermined constraint.
10. The method of claim 1 , wherein said step of calculating said set of moves for present and future times comprises calculating said set of moves employing linear programming techniques.
11. The method of claim 10 , wherein said step of calculating said set of moves for present and future times further comprises calculating said set of moves such that at least one of said manipulated variables is limited to a predetermined constraint.
12. The method of claim 10 , wherein said process comprises at least one uncontrolled variable that is dependent on said manipulated variables and wherein said step of calculating said set of moves for present and future times further comprises calculating said set of moves such that said uncontrolled variable is limited to a predetermined constraint.
13. The method of claim 1 , wherein said step of calculating said set of moves further comprises calculating said set of moves such that at least one of said manipulated variables is limited to a predetermined constraint.
14. The method of claim 13 , wherein said process comprises at least one uncontrolled variable that is dependent on said manipulated variables and wherein said step of calculating said set of moves for present and future times further comprises calculating said set of moves such that said uncontrolled variable is limited to a predetermined constraint.