Apparatus and method for calculating proxy limits to support cascaded model predictive control (mpc)

Patent metadata

Field	Value
Publication number	US-2016018797-A1
Application number	US-201414523508-A
Country	US
Kind code	A1
Filing date	Oct 24, 2014
Priority date	Jul 21, 2014
Publication date	Jan 21, 2016
Grant date	—

Abstract

A method includes receiving, at a master model predictive control (MPC) controller from a slave MPC controller, information indicating to what extent the slave MPC controller is able to change multiple manipulated variables in each of multiple directions within a variable space without violating process variable constraints of the slave MPC controller. The method also includes estimating a feasibility region associated with the slave MPC controller using the information, where the feasibility region identifies a portion of the variable space in which combinations of manipulated variable values satisfy the process variable constraints. In addition, the method includes performing plantwide optimization at the master MPC controller using the feasibility region, where a solution generated during the plantwide optimization includes one of the combinations of manipulated variable values within the feasibility region.

First claim

What is claimed is:

1 . A method comprising:
receiving, at a master model predictive control (MPC) controller from a slave MPC controller, information indicating to what extent the slave MPC controller is able to change multiple manipulated variables in each of multiple directions within a variable space without violating process variable constraints of the slave MPC controller; estimating a feasibility region associated with the slave MPC controller using the information, the feasibility region identifying a portion of the variable space in which combinations of manipulated variable values satisfy the process variable constraints; and performing plantwide optimization at the master MPC controller using the feasibility region, wherein a solution generated during the plantwide optimization includes one of the combinations of manipulated variable values within the feasibility region.

2 . The method of claim 1 , further comprising:
sending multiple inquiry optimization calls from the master MPC controller to the slave MPC controller; wherein receiving the information comprises receiving proxy limit values from the slave MPC controller in response to the inquiry optimization calls.

3 . The method of claim 2 , wherein each proxy limit value identifies a maximum distance in one of the directions within the variable space that the slave MPC controller is able to change the manipulated variables without violating the process variable constraints.

4 . The method of claim 1 , wherein the multiple directions are defined with reference to a current operating point associated with the slave MPC controller, the current operating point defining a specified point in the variable space.

5 . The method of claim 4 , wherein the multiple directions are evenly spaced around the current operating point associated with the slave MPC controller.

6 . The method of claim 1 , further comprising:
identifying at least one of the multiple directions.

7 . The method of claim 6 , wherein at least one of the multiple directions comprises a direction substantially perpendicular to a linear variable limit associated with the slave MPC controller.

8 . The method of claim 1 , further comprising:
repeating the receiving and identifying steps for multiple slave MPC controllers; wherein the solution generated during the plantwide optimization honors all process variable constraints of all slave MPC controllers.

9 . An apparatus comprising:
a master model predictive control (MPC) controller comprising:
at least one network interface configured to receive, from a slave MPC controller, information indicating to what extent the slave MPC controller is able to change multiple manipulated variables in each of multiple directions within a variable space without violating process variable constraints of the slave MPC controller; and
at least one processing device configured to:
estimate a feasibility region associated with the slave MPC controller using the information, the feasibility region identifying a portion of the variable space in which combinations of manipulated variable values satisfy the process variable constraints; and
perform plantwide optimization using the feasibility region, wherein a solution generated during the plantwide optimization includes one of the combinations of manipulated variable values within the feasibility region.

10 . The apparatus of claim 9 , wherein:
the at least one processing device is further configured to initiate transmission of multiple inquiry optimization calls to the slave MPC controller; and the at least one processing device is configured to receive proxy limit values from the slave MPC controller in response to the inquiry optimization calls.

11 . The apparatus of claim 10 , wherein each proxy limit value identifies a maximum distance in one of the directions within the variable space that the slave MPC controller is able to change the manipulated variables without violating the process variable constraints.

12 . The apparatus of claim 9 , wherein the multiple directions are defined with reference to a current operating point associated with the slave MPC controller, the current operating point defining a specified point in the variable space.

13 . The apparatus of claim 12 , wherein the multiple directions are evenly spaced around the current operating point associated with the slave MPC controller.

14 . The apparatus of claim 9 , wherein the at least one processing device is further configured to identify at least one of the multiple directions.

15 . The apparatus of claim 14 , wherein at least one of the multiple directions comprises a direction substantially perpendicular to a linear variable limit associated with the slave MPC controller.

16 . The apparatus of claim 9 , wherein:
the at least one processing device is further configured to repeat the receiving and identifying operations for multiple slave MPC controllers; and the solution generated during the plantwide optimization honors all process variable constraints of all slave MPC controllers.

17 . A non-transitory computer readable medium embodying a computer program, the computer program comprising computer readable program code for:
receiving, at a master model predictive control (MPC) controller from a slave MPC controller, information indicating to what extent the slave MPC controller is able to change multiple manipulated variables in each of multiple directions within a variable space without violating process variable constraints of the slave MPC controller; estimating a feasibility region associated with the slave MPC controller using the information, the feasibility region identifying a portion of the variable space in which combinations of manipulated variable values satisfy the process variable constraints; and performing plantwide optimization at the master MPC controller using the feasibility region, wherein a solution generated during the plantwide optimization includes one of the combinations of manipulated variable values within the feasibility region.

18 . The computer readable medium of claim 17 , wherein:
the computer program further comprises computer readable program code for sending multiple inquiry optimization calls from the master MPC controller to the slave MPC controller, the information comprising proxy limit values from the slave MPC controller in response to the inquiry optimization calls; and each proxy limit value identifies a maximum distance in one of the directions within the variable space that the slave MPC controller is able to change the manipulated variables without violating the process variable constraints.

19 . The computer readable medium of claim 17 , wherein:
the multiple directions are defined with reference to a current operating point associated with the slave MPC controller, the current operating point defining a specified point in the variable space; and the computer program further comprises computer readable program code for identifying at least one of the multiple directions.

20 . The computer readable medium of claim 17 , wherein:
the computer program further comprises computer readable program code for repeating the receiving and identifying operations for multiple slave MPC controllers; and the solution generated during the plantwide optimization honors all process variable constraints of all slave MPC controllers.

Assignees

• Honeywell Int Inc

Inventors

• Lu Joseph Z

Classifications

• G05B13/048 Primary

  using a predictor · CPC title

• H04L67/10

  in which an application is distributed across nodes in the network (software deployment G06F8/60; multiprogramming arrangements G06F9/46) · CPC title

• H04L41/042

  comprising distributed management centres cooperatively managing the network · CPC title

• H04L41/0823

  characterised by the purposes of a change of settings, e.g. optimising configuration for enhancing reliability (for optimising operational conditions of wireless networks H04W24/02) · CPC title

• H04L41/145

  involving simulating, designing, planning or modelling of a network · CPC title