Cascaded model predictive control with abstracting constraint boundaries

A method of cascaded model predictive control (MPC), comprising:

• providing an upper tier controller and at least one lower tier controller, wherein the at least one lower tier controller is configured to store a plurality of numerical operating constraints that define an operating space for controlling a process and a plurality of variables that comprise:
• manipulated variables (MVs), controlled variables (CVs), and at least one conjoint manipulated variable (CMV);
• passing, by the upper tier controller, a target value for the at least one CMV to the at least one lower tier controller when the at least one lower tier controller is operating at a current operating point;
• calculating, by the at least one lower tier controller, a local optimal operating point for the at least one CMV, wherein the local optimal operating point is indicative of a steady state operating point for the at least one CMV;
• moving, by the at least one lower tier controller, the at least one CMV towards the target value starting at the local optimal operating point for the at least one CMV;
• identifying, by the at least one lower tier controller, at least one of the numerical operating constraints as a limiting constraint, wherein the limiting constraint limits the movement of the local optimal operating point towards the target value;
• passing, by the at least one lower tier controller, the limiting constraint to the upper tier controller;
• performing, by the upper tier controller, an optimization for the process using the limiting constraint to generate an optimal value for the at least one CMV, and
• passing, by the upper tier controller, the optimal value for the at least one CMV to the lower tier controller as a new target value for the at least one CMV;
• using, by the lower tier controller, the new target value to generate updated operating points for at least one of the MVs and CVs;
• and
• controlling, by the at least one lower tier controller, the process utilizing the updated operating points.