A Simulink Pathway for Model-Based Control of Vapor Compression Cycles

2015 ◽  
Author(s):  
Anhtuan D. Ngo ◽  
Joshua R. Cory ◽  
Brandon M. Hencey ◽  
Soumya S. Patnaik
Keyword(s):  
Control Design ◽  
Control Synthesis ◽  
Vapor Compression ◽  
Linear Quadratic ◽  
Model Based Control ◽  
Model Based ◽  
Cycle System ◽  
Vapor Compression Cycle ◽  
Compression Cycle ◽  
Transient Thermal

Current and next generation tactical aircraft face daunting thermal challenges that involve reliably maintaining thermal constraints despite large transient loads. Model-based control synthesis has the potential to improve the performance of a vapor compression cycle system during its transient operating condition, driven by intermittent and dynamic thermal loads, when compared to the current heuristic control design technique. However, the excessive labor and expertise necessary to develop models amenable to model-based control design techniques has been an impediment to widespread deployment. This paper demonstrates a Simulink pathway for model-based design via the AFRL Transient Thermal Modeling and Optimization (ATTMO) toolbox. An effective, simple linear quadratic gaussian control design is demonstrated and opens the door for widespread deployment of many advanced control techniques.

scholarly journals A Model-Based Control Design Approach for Linear Free-Piston Engines

2017 ◽  
Vol 139 (11) ◽  
Author(s):  
T. N. Kigezi ◽  
J. F. Dunne
Keyword(s):  
Control Design ◽  
Linear Quadratic Regulator ◽  
Design Approach ◽  
Linear Quadratic ◽  
Free Piston ◽  
Model Based Control ◽  
Model Based ◽  
Bottom Dead Center ◽  
Free Piston Engine ◽  
Advanced Control

A general design approach is presented for model-based control of piston position in a free-piston engine (FPE). The proposed approach controls either “bottom-dead-center” (BDC) or “top-dead-center” (TDC) position. The key advantage of the approach is that it facilitates controller parameter selection, by the way of deriving parameter combinations that yield both stable BDC and stable TDC. Driving the piston motion toward a target compression ratio is, therefore, achieved with sound engineering insight, consequently allowing repeatable engine cycles for steady power output. The adopted control design approach is based on linear control-oriented models derived from exploitation of energy conservation principles in a two-stroke engine cycle. Two controllers are developed: A proportional integral (PI) controller with an associated stability condition expressed in terms of controller parameters, and a linear quadratic regulator (LQR) to demonstrate a framework for advanced control design where needed. A detailed analysis is undertaken on two FPE case studies differing only by rebound device type, reporting simulation results for both PI and LQR control. The applicability of the proposed methodology to other common FPE configurations is examined to demonstrate its generality.

Decentralized Feedback Structures of a Vapor Compression Cycle System

2008 ◽  
Author(s):  
Brandon Hencey ◽  
Neera Jain ◽  
Bin Li ◽  
Andrew Alleyne
Keyword(s):  
Multiple Input Multiple Output ◽  
Thermodynamic Cycle ◽  
Coefficient Of Performance ◽  
Vapor Compression ◽  
Input Output ◽  
Single Input Single Output ◽  
Loop Design ◽  
Cycle System ◽  
Vapor Compression Cycle ◽  
Compression Cycle

In vapor compression cycle (VCC) systems, it is desirable to effectively control the thermodynamic cycle. By controlling the thermodynamic states of the refrigerant with an inner-loop, supervisory algorithms can manage critical objectives such as maintaining superheat and maximizing the coefficient of performance, etc. In the HVAC industry, it is generally preferred to tune multiple single-input-single-output (SISO) control inner-loops rather than a single multiple-input-multiple-output (MIMO) control inner-loop. This paper presents a process by which a simplified feedback control structure amenable to a decoupled SISO control loop design may be identified. In particular, the many possible candidate input-output pairs for decentralized control are sorted via a decoupling metric, the relative gain array number. From a reduced set of promising candidate input-output pairs, engineering insight is applied to arrive at the final pairings successfully verified on a refrigeration test stand.

Thermodynamics-Based Optimization and Control of Vapor-Compression Cycle Operation: Control Synthesis

2011 ◽  
Author(s):  
Neera Jain ◽  
Andrew G. Alleyne
Keyword(s):  
Fluid Dynamic ◽  
Control Synthesis ◽  
Vapor Compression ◽  
Vapor Compression Cycle ◽  
Compression Cycle ◽  
Optimization And Control ◽  
Operation Control ◽  
Thermodynamic Variables ◽  
And Control ◽  
Control Methodology

This paper considers the implementation of an exergy-based multiple degree of freedom (MDOF) optimization and control methodology for the operation of VCC systems. The optimization problem for the standard VCC is characterized in terms of 4 thermodynamic variables and 1 fluid-dynamic variable. The resulting control problem is then analyzed, and a design variable, Λ, is introduced which allows the user to choose how the optimization variables are projected onto a control space of lower dimension. The potential of this approach to improve operational efficiency, with respect to both first and second law efficiency metrics, is demonstrated on an experimental VCC system through implementation of the proposed optimization using a feedforward plus feedback control architecture.

Decentralized Feedback Structures of a Vapor Compression Cycle System

2010 ◽  
Vol 18 (1) ◽  
pp. 185-193 ◽  
Author(s):  
Neera Jain ◽  
Bin Li ◽  
Michael Keir ◽  
Brandon Hencey ◽  
Andrew Alleyne
Keyword(s):  
Vapor Compression ◽  
Cycle System ◽  
Vapor Compression Cycle ◽  
Compression Cycle
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