Power Optimization of Electro-Thermal Systems Dr. Andrew G. Alleyne
How can modern control techniques and preview be used to improve energy management in constrained systems?
Optimization & Control Methodology
Main Results
• Modern vehicles are a heterogeneous mix of complex interconnected systems of various energy domains
• Electrification of many systems is resulting in increased power loads and thermal waste heat • Enhanced optimization of power generation, distribution, storage, and utilization can be achieved
using dynamic model-based control to improve performance and efficiency while preventing thermal runaway
Vision: With intelligent decision making the power density of existing electro-thermal systems can be improved by a factor of 2
• Event-based control updates • Top-down information flow allows for
effective planning of system states • Bottom-up information flow allows for
effective disturbance estimation • Controllers use robust Model Predictive
Control (MPC) or Genetic Algorithms
• Higher-level controllers - Plan an efficient path using large prediction
horizons - Select mode of operation for lower-level
controllers • Lower-level controllers employ fast
optimization (i.e. Explicit MPC)
Candidate Architecture Aircraft electrical, thermal, and engine systems
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Thermal PowerPneumatic PowerElectrical PowerChemical PowerMechanical Power
Source/SinkFast DynamicsMedium DynamicsSlow DynamicsAlgebraicSink
Qengine
Fuel Tank #1
BusBatt
MC 2
Generator
Fan Comp Turb
Sink
MC 1
FC 1
Fuel Tank #2
Qgenerator
Load
FuelAirLiquid Coolant #1Liquid Coolant #2ElectricalMechanical
HX1
HX2 ACM
ENGINE
Applying a graph based modeling approach
Electrical Control System
Thermal Control System
Information Flow
Vehicle Level
System Level
Subsystem Level
Component Level
Physical Level
Plant
60 sec
10 sec
1 sec
0.1 sec
0.001 sec
continuous
1C
2,1C 2,2C
3,1C 3,2C 3,3C
4,1C 4,2C 4,3C 4,4C 4,5C 4,6C
5,4C5,3C5,2C5,1C
Inputs/Outputs
• Overall vehicle and mission state
• Coordinate systems
• State of system, present and future loads and constraints
• Choose best mode
• Optimize operation of subsystems
• Identify constraints
• Determine setpoints for each control actuator
• Deliver servo-level inputs to change physical system
5-Level Control Hierarchy • Matches the natural hierarchy of many mobile systems • Handles temporal and functional separation of systems, subsystems, and components
Key Features
System Disturbances Electrical Loads & Thermal Sink Temperatures
Large electrical loads resulting in significant heat loads
Poor thermal sink availability means heat cannot be easily
removed from the system 0 20 40 60 80 100 120
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60
80
100
Tem
pera
ture
[°C
]
Time [min.]
0 20 40 60 80 100 120
20
40
60
80
100
Tem
pera
ture
[°C
]
Time [min.]
Cent. Hier.MC2FCMC1
Gen. Tank 1 Eng. Tank 2Cent. Hier.
System States Electrical & Aircraft System Temperatures
Hierarchical control performs better than centralized during
stressful events
Hierarchical control can take anticipatory action well before
centralized control, while utilizing similar amounts of computational resources
System: Tracks vehicle level commands and determines state trajectories for medium time scale dynamics which are passed to subsystem level controllers.
Subsystem: Tracks system level commands and determines state trajectories for fast time scale dynamics. Also measures plant states and communicates that information up through the hierarchy.
Vehicle: Determines state trajectories for slow time scale dynamics and sends those commands to system level controllers. Has some knowledge of disturbances.
State MeasurementsDisturbancesInformation CommunicationActuator Inputs
Vehicle
Thermal Engine Electrical
ElectricalCoolant LoopACM
Plant
Control Hierarchy Vehicle, System, & Subsystem Levels
F/A-18F cutaway graphic by Giuseppe Picarella & Tim Brown
F-35C cutaway graphic by Lockheed Martin
Graph Model of Candidate Architecture Edges capture power flow, vertices represent system states
Controller Development • Select candidate architecture • Represent the architecture as a directed
graph by analyzing how power flows through the system
• Partition graph based upon time constants • Partition graph into various systems &
subsystems based upon functional purposes • Develop individual controllers and determine
information flow
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24 Vehicle
Engine Sys
Thermal Sys Electrical Sys
Thermal Sub 1
Thermal Sub 2
Electrical Sub
Graph partitioning
Developing controllers within the hierarchy
Preliminary Results