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Títol: Hierarchy control architechture design for the MELiSSA Pilot Plant

Director/a: GÒDIA CASABLANCAS, FRANCESC

Departament: ALTRES

Títol: Hierarchy control architechture design for the MELiSSA Pilot Plant

Data inici oferta: 01-09-2020     Data finalització oferta: 01-04-2021


Estudis d'assignació del projecte:
    MU AEROSPACE S&T 15
Tipus: Individual
 
Lloc de realització: EETAC
 
Paraules clau:
Life Support, MELiSSA, Carbon Capture, Predictive control
 
Descripció del contingut i pla d'activitats:
The objective of this Master Thesis is the study, development of a
Hierarchy
Control Structure (HCS) to control first, the closed gas loop of
the current
MPP integration phase (C3 – C4a – C5), and then, to extend it to
the Higher
Plant Chamber(C5).

MELISSA Pilot Plant is a regenerative life support system
development that is
able to produce food, oxygen and water from space mission wastes.
It is
composed by compartments, where each of them has their own purpose.
Technologies as those studied in MELiSSA, will contribute to make
possible
the presence of humans on a planet like Mars. In the first part of
the MT,
work will focuss on the compartment C5 and C4A. C5 is the
compartment of the crew, in this case, the crew will be rats. The
input of the
C5 is oxygen while the output CO2. On the other side, C4 A will
produce
oxygen thanks to a photobioreactor. The connection between these
two
compartments is named as closed gas loop. The objective of the MT
is the
development of a control system able to control the production of
oxygen
provided by C4A in order to maintain a certain threshold of O2 in
the C5
compartment.

This control system is made by 4 levels and are based on Predictive
Control
approaches. These 4 layers use PFC (Predictive Functional Control),
MPC
(Model-based Predictive Control) and Mathematical Programming
techniques
coordinated to operate the process. The work will be focused on
Level 3 and
Level 4. The 3rd level aims to run model-based predictions of the
process to
optimally assign resources through a rolling horizon approach. The
criteria to
assign resources and to operate the plant is determined by Level 4,
which
should have a dynamic behaviour according to both the state of the
process
and management decisions.
 
Overview (resum en anglès):
MELiSSA (Micro Ecological Life Support System Alternative) is concieved as a loop of compartments to support the main functions of life support to humans in long-term exploration missions in Space. The system works in continuous mode with specific functions in each one of the compartments, to provide food production, water reuse, air regneration and waste treatment in an integrated mode.

The complexity of the system makes paramount to develop a control system, based on mathematical models encompassing both the individual compartments of the loop and the overall loop as such. The MELiSSA Pilot Plant (MPP) is the laboratory where all these technologies are integrated and demosntrated.

In the MELiSSA architecture domain, the exchange between CO$_2$ producing units, such as the crew compartment, and O$_2$ producing and CO$_2$ consuming units, such as the protosynthetic compartments, is complex and needs a fine tuning system to control the exchange of these two compounds between the different compartments. For this purpose, To this end, intermediate units allowing to concentrate O$_2$ and CO$_2$ should provide additional flexibility to the operation and control of the whole loop.

In this sense, this study presents a technology based on the one used to reduce carbon levels of the greenhouse gases in order to control the CO$_2$ of the MPP.

It is composed of a set of hollow fibers membranes that together with an amine enables to absorb CO$_2$ at high percentages. This makes it possible to lower the carbon concentration in the MELiSSA crew cabin to the required levels. Furthermore, this technology is also capable of desorbing CO$_2$, which facilitates the availability of a concentrated CO$_2$ tank to store and use the carbon according to the demand in the loop.

Subsequently, the current control structure in charge of controlling the O$_2$ is adapted to take into account the incorporation of Carbon Capture and the storage tank. This control structure has different levels and uses predictive algorithms such as the "model predictive controllers" (MPC).

Each level of the structure has specific functions. The level in charge of controlling the flows of the plant is level 2, here the control of the tank will be defined. The discharge or discharge of the tank will depend on the needs of compartments 4 of the plant, the only one that consumes CO$_2$ in MELiSSA's loop.

Finally, these changes are translated to the MATLAB environment. There, the entire pilot plant and the control structure are simulated. In the analysis of the results it is shown a decrease of the CO$_2$ as well as a correct control of it by the redefined level 2.

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