Model Based Control of Refrigeration Containers

							Model Based Control of
Refrigeration Containers


   Kresten Kjær Sørensen
  Lodam electronics a/s and
     Aalborg University
                                               Outline
• Developmental, commercial and scientific
  objectives
• System overview
• Project status
• Issues that should be addressed
• Research


   Lodam electronics a/s · Kærvej 77 · DK-6400 Sønderborg · Tlf. +45 73 42 37 37 · Fax +45 73 42 37 30 · www.lodam.com
         Developmental Objectives

“A set of methods that enable optimal,
 adaptive, constrained control of a
 refrigeration container that is also
 applicable to other thermodynamical
 systems”


 Lodam electronics a/s · Kærvej 77 · DK-6400 Sønderborg · Tlf. +45 73 42 37 37 · Fax +45 73 42 37 30 · www.lodam.com
                 Commercial Objectives

• Better competitiveness through:
  – Reduced energy consumption
  – Reduced mechanical wear and tear
  – Improved adaptiveness of the controller




   Lodam electronics a/s · Kærvej 77 · DK-6400 Sønderborg · Tlf. +45 73 42 37 37 · Fax +45 73 42 37 30 · www.lodam.com
                      Scientific Objectives

• To use MPC for refrigeration by:
  – Finding a suitable method for modeling
    nonlinear dynamics of the refrigeration system
    that may be used by an MPC.
  – Finding a method to cope with changes in
    system dynamics in the event of failure.


   Lodam electronics a/s · Kærvej 77 · DK-6400 Sønderborg · Tlf. +45 73 42 37 37 · Fax +45 73 42 37 30 · www.lodam.com
                         System overview

                                                                                   •     Known refrigeration
                                                                                         system dynamics
                                                                                   •     Unknown cargo
                                                                                         dynamics
                                                                                   •     Known constraints on
                                                                                         cargo temperature
                                                                                   •     Economizer gives an
                                                                                         additional degree of
                                                                                         freedom




Lodam electronics a/s · Kærvej 77 · DK-6400 Sønderborg · Tlf. +45 73 42 37 37 · Fax +45 73 42 37 30 · www.lodam.com
                        Log(p)-h Diagram




Lodam electronics a/s · Kærvej 77 · DK-6400 Sønderborg · Tlf. +45 73 42 37 37 · Fax +45 73 42 37 30 · www.lodam.com
                                  Project Status

• A library of nonlinear refrigeration
  component models has been developed.
• A composite simulation model has been
  developed.
• A framework that allows to test a
  controller, working within Matlab, with real
  hardware is ready.
   Lodam electronics a/s · Kærvej 77 · DK-6400 Sønderborg · Tlf. +45 73 42 37 37 · Fax +45 73 42 37 30 · www.lodam.com
                     Simulation Model 1/2

• Nonlinear simulation model of the
  refrigeration system.
• Composed of smaller component models
  from a library.
• Simulation is done in Matlab by a set of
  custom functions.

   Lodam electronics a/s · Kærvej 77 · DK-6400 Sønderborg · Tlf. +45 73 42 37 37 · Fax +45 73 42 37 30 · www.lodam.com
                    Simulation Model 2/2
            Simulation Model.xml
                                                                 •     The simulation model is
                                                                       described by a number of files
Component1.xml                     Component2.xml
                                                                 •     Each component are simulated
Component1.m                       Component2.m                        separately for a short time step
                                                                 •     All outputs at the end of the
                                                                       simulation is propagated to the
                                                                       relevant inputs
                                                                 •     Simulation run again for another
                                                                       time step
Component3.xml                     Component4.xml
Component3.m                       Component4.m                  •     Equivalent of simulating a large,
                                                                       combined function with ZOH’s
                                                                       inserted between components


   Lodam electronics a/s · Kærvej 77 · DK-6400 Sønderborg · Tlf. +45 73 42 37 37 · Fax +45 73 42 37 30 · www.lodam.com
   Issues that must be addressed
• The system is nonlinear and has a large
  area of operation for both hot and cold
  temperatures.
• There are discrete actuators with strong
  influence on the dynamics that cannot be
  neglected.
• In case of partial system malfunction it is
  very important to continue cooling.
   Lodam electronics a/s · Kærvej 77 · DK-6400 Sønderborg · Tlf. +45 73 42 37 37 · Fax +45 73 42 37 30 · www.lodam.com
                                          Research

• Adaptive MPC for increased robustness in
  the event of failure.
• Auto-generation of a model usable with
  MPC, based on the simulation model.



   Lodam electronics a/s · Kærvej 77 · DK-6400 Sønderborg · Tlf. +45 73 42 37 37 · Fax +45 73 42 37 30 · www.lodam.com