Aircraft Engine Control Research Articles

Multi-modal LSTM network for anomaly prediction in piston engine aircraft

An aircraft is a highly intricate system that features numerous subsystems, assemblies, and individual components for which regular maintenance is inevitable. The operational efficiency of an aircraft can be maximised, and its maintenance needs can be reduced using an effective yet automatic AI-based health monitoring systems which are more efficient as compared to designing and constructing expensive and harder to operate engine testbeds. It has been observed that aircraft engine anomalies such as undergoing flameouts can occur due to the rapid change in the temperature of the engine. Engine oil temperature and cylinder head temperature, two measures connected to this issue, might be affected differently depending on flight modes and operational conditions which in turn hamper AI-based algorithms to yield accurate prediction on engine failures. In general, previous studies lack comprehensive analysis on anomaly prediction in piston engine aircraft using modern machine learning solutions. Furthermore, abrupt variation in aircraft sensors' data and noise result in either overfitting or unfavourable performance by such techniques. This work aims at studying conventional machine learning and deep learning models to foretell the possibility of engine flameout using engine oil and cylinder head temperatures of a widely used Textron Lycoming IO-540 six-cylinder piston engine. This is achieved through pre-processing the data extracted from the aircraft's real-time flight data recorder followed by prediction using specially designed multi-modal regularised Long Short-Term Memory network to enhance generalisation and avoid overfitting on highly variable data. The proposed architecture yields improved results with root mean square error of 0.55 and 3.20 on cylinder head and engine oil temperatures respectively averaged over three case studies of five different flights. These scores are significantly better i.e., up to 84% as compared to other popular machine learning predictive approaches including Random Forest, Decision Tree Regression, Artificial Neural Networks and vanilla Long Short-Term Memory networks. Through performance evaluation, it can be established that the proposed system is capable of predicting engine flameout 2 minutes ahead and is suitable for integration with the software system of aircraft's engine control unit.

Research on integrated aircraft-engine control method of hypersonic vehicle based on dynamic inversion control

In order to reduce the influence of the coupling characteristics between the aircraft and engine of hypersonic vehicle, an integrated aircraft-engine control method of hypersonic vehicle is studied in this paper. Firstly, the control-oriented aircraft-engine integrated mathematical model of the hypersonic vehicle is established. Then, by using the nonlinear dynamic inversion (NDI) and the incremental nonlinear dynamic inversion (INDI), the outer loop control algorithm with slow attitude change and the inner loop control algorithm with fast angular rate change are respectively designed. Moreover, based on the online ontology model including aircraft-engine coupling characteristics of the hypersonic vehicle, the coupling control scheme of flight posture and engine of the hypersonic vehicle is designed in the form of control linkage. Finally, the reference model, error control, online estimation and other modules are introduced into the NDI controller to ensure the flight quality and robustness requirements of the hypersonic vehicle. The simulation results show that the aircraft-engine coupling control scheme based on the NDI achieves the expected control performance.

Застосування методу парирування відмов датчиків при управлінні роботою малорозмірного авіадвигуна

The subject of the research is the application of the method of parrying sensor failures - one of the modern progressive approaches to ensuring the smooth and efficient operation of complex automatic control systems. This article is devoted to the application of this method in the control of a small-sized aircraft engine, which is an actual solution for the development of the aviation industry. The purpose of this study is to choose the optimal method for parrying sensor failures of a small-sized aircraft engine by analyzing existing methods and choosing engine parameters that should be used for parrying. Tasks. Consider the main methods of countering sensor failure and justify the choice of the most effective one. To state the main principles of the method of replacing the parameter value at all stages of the development of the control unit for the operation of a small-sized aircraft engine and to carry out an analysis of the disadvantages and advantages of such an approach. Consider algorithms for identifying and countering sensor failures for the engine management system. Analyze the simulation of individual parameters of a small-sized aircraft engine and propose parameters that should be replaced in the event of sensor failure. Research methods. Comparative analysis of methods of parrying sensor failures and models for simulating the parameters of small-sized aircraft engines with adjacent ones. The results. The method for replacing the parameter value with an adjacent one, switching to a backup value, redundancy, and the use of backup data sources are analyzed. Among the parrying methods, the two most optimal ones are selected (the method of replacing the value of the failed sensor parameter with an adjacent parameter and the method of switching to a backup value) and their work algorithms are described. The advantages are increased reliability and efficiency of engine operation, prevention of information loss, adaptability, and improved diagnostics. Among the shortcomings, the existence of risks of erroneous measurements, complex settings, accuracy limitations, dependence on other parameters, cost and complexity of the system are highlighted. Using the example of the ECU-35 unit developed by JSC "Element", the model of replacing the engine rotor speed parameter using the current temperature of the gases behind the turbine, taking into account the calibration of the measurement channel, was described. Conclusions (scientific and practical novelty). It was found that the application of the method of identification and parrying of sensor failures ensured the smooth operation of the control system when individual sensors failed. Thanks to the method for parrying sensor failures, it was possible to achieve a significant improvement in the performance of a small-sized aircraft engine.

Switching Anti-windup Control for Aircraft Engines

In this article, we propose a switching anti-windup scheme for the aircraft engine control. The linear engine model with asymmetric saturation is first transformed into a switched system, each subsystem of which is subject to symmetric saturation. A state-dependent switching logic is presented to orchestrate the switching among multiple anti-windup compensators. We then establish the sufficient condition to guarantee the regional stability and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mathcal {L}_{2}$</tex-math></inline-formula> performance of the resulting closed-loop system. This condition is less conservative since the non-symmetric nature of the saturation nonlinearity can be fully exploited in the control design. Optimization algorithms are further developed for the anti-windup gain design. The theoretical aspect of the proposed method is analyzed rigorously, and the effectiveness is validated through experiments performed on a semi-physical test bed.

Anti-Windup Synthesis for Linear Systems With Asymmetric Input Saturation: Application to Aircraft Engine Control

This brief proposes a novel anti-windup scheme for linear systems subject to asymmetric input saturation. The asymmetrically saturated system is converted into an equivalent one with symmetric saturation through coordinate transformation. Based on the transformed model, we establish the set invariance condition of the resulting closed-loop system. This condition is less conservative since the non-symmetric nature of the saturation nonlinearity can be fully exploited in the control design. An optimization algorithm to maximize the invariant set is further developed for anti-windup gain design. The theoretical aspect of this method is analyzed rigorously, and the effectiveness is verified through an application to the aircraft engine control with experiments performed on a semi-physical test bed.

Удаленное сопровождение и модернизация программно-технических комплексов для испытаний авиационных двигателей

The introductory part of the article provides information that JSC "Element" is one of the leading enterprises of Ukraine in the scientific and technical direction "Electronic systems for measuring, monitoring parameters and aircraft engine control". As a result of cooperation between the team of Element JSC and a number of divisions of Motor Sich JSC, software and hardware complexes (SHC) were developed to automate the technological processes of bench tests of aircraft engines. For 15 years, about 20 such SHCs have been supplied to Motor Sich JSC and other enterprises. An important task of Element JSC was to provide support for its hardware and software complexes, to promptly resolve issues related to their performance and modernization as new requirements and technological processes emerge. The SHC Polygon became the main tool in solving these problems. The description of the SHC Polygon is given, which is a functionally standard SHC, but with a reduced composition of measuring modules. The SHC polygon consists of two hierarchical levels: lower and upper. The upper level of the PTK Polygon is a device for communication with the object, the main tasks of which are the transformation of parameters coming from the sensors and the primary processing of information, control of technological operations, and emergency protection of the engine. The upper level is two workstations that display information and provide interaction between the operator and the system. The Polygon SHC includes a software product (SP) operating in the environment of the QNX 4.25 real-time operating system. The main feature of the SHC Polygon is the ability to launch the SP of any of the developed SHC, adapted to work with the existing set of measuring modules. A list of the most frequently performed works in the course of post-warranty maintenance of the hardware and software complex, including the introduction of new technological operations and algorithms, is given. It is noted that the SHC Polygon turned out to be a successful solution for remote support of aircraft engine tests at the stands of Motor Sich JSC. It allows you to solve most of the problems identified in the operation of the equipment of test stands and hardware and software systems, and also provides modernization and refinement of algorithms without specialists visiting the site. The possibility of remote maintenance of the SHC is especially important in the context of the Covid-19 pandemic and quarantine restrictions in Ukraine.

Improved nonlinear MPC for aircraft gas turbine engine based on semi-alternative optimization strategy

The development of advanced control systems is motivated to achieve the complicated aircraft engine control, so a novel semi-alternative optimization strategy based model predictive control is proposed. In this proposed controller, a nonlinear state-space model is generated as the predictive model on the basis of a baseline engine model that estimates the current operating state of engine with an extended Kalman filter every sampling instant, and a quadratic constrained problem rather than a higher order nonlinear problem is constructed based on this model. Moreover, a novel control sequence to be optimized based on semi-alternative optimization strategy is proposed, which includes two parts. The first part represents that all the control variables of the engine are optimized for the current sampling instant while the second part represents that different control variables are optimized alternatively for different future sampling instants over the control horizon. The proposed model predictive control method is implemented to a twin-spool turbofan engine. Simulation results demonstrate not only that the proposed method can achieve a smaller control error than the standard model predictive control algorithm does, but also that the proposed controller is more time-saving than the standard model predictive control, which can save up to about 61% optimization time when control horizon increases to nine.

Assessment of organizational agility in response to disruptive innovation: a case of an engineering services firm

PurposeThe purpose of this paper is to develop a framework to manage the strategy to counter disruptive innovation by identifying stronger attributes and key strategic areas for improvements in an engineering services context with less freedom to orchestrate product innovation. The authors also validate the combined use of multi-grade fuzzy, Importance-Performance Analysis (IPA) and gap analysis in developing the strategy to mitigate turbulence.Design/methodology/approachThe paper presents a framework using a combination of Dynamic Capabilities and Organizational Agility to develop the strategy. The study uses data gathered from a 60-member engineering project team working on an Aircraft Engine Controller design to identify 50 attributes and the related importance and performance ratings. The research study is designed using a three-tier approach. First, multi-grade fuzzy is utilized to measure the overall firm response agility index. In the second step, the IPA is used to analyze the strength and weaknesses of the firm and to identify the attributes where the firm needs to focus. In the past step, gap analysis is used to prioritize the identified attributes. The findings are validated by panel discussions with a different group of experts from the project team and action points were arrived at.FindingsThis research work finds that the firms’ response agility index of 6.97 is comparable to that of the Original Equipment Manufacturers (OEMs) from previous literature, but still needs a better agility score to effectively counter turbulence from disruptive innovations. It also identifies seven key areas for improvement and their relative priority to effectively improve the response agility by utilizing the least number of resources, the reasons for the gap and the mitigation strategy to close the gap. The findings highlight a few key differences between an engineering services firm in comparison to OEMs and Software Services firms.Practical implicationsThe findings help the practitioners with a comparative agility score of an engineering services firm, and an effective way of measuring agility, identify key focus areas and prioritize the actions using a simple set of data that could be collected regularly to keep track of the improvements. The provided strategic framework to improve the agility score can be used for continuous improvement.Originality/valueThis paper contributes to the existing literature by developing a framework for outsourcing services companies to cope with the turbulence by using dynamic capabilities and organizational agility. It also adds to the literature by extending the validity of IPA and gap analysis in making strategic decisions in an industrial set-up.

Information flows of parallel computing of the distributed control systems of aviation engines

The ongoing work on scientific and technical suggestions for 6th generation engines has been considered and the necessity for developing methods for constructing adaptive control of aircraft engines has been substantiated, which will allow, due to the flexible structure of the control system, to determine the number of adjustable parameters and the number of adjustable factors for the formation of engine control programs. The information flows of aircraft engine control systems have been analyzed using an example of a system with full responsibility of the FADEC type and a method for their parallel calculations is proposed, for the implementation of which it is necessary to develop a virtual channel model, a background stream generator, and a data parallelization method.

NEURAL NETWORK COMPUTER FOR RECOVERING LOST INFORMATION FROM STANDARD SENSORS OF THE ON-BOARD SYSTEM FOR CONTROL AND DIAGNOSTICS OF TV3-117 AIRCRAFT ENGINE

The subject matter of the article is TV3-117 aircraft engine and methods for control and diagnostics its technical condition. The goal of the work is the development of a neural network computer for recovering lost information from standard sensors of the on-board control and diagnostics system of TV3-117 aircraft engine technical state in real time. The following tasks were solved in the article: recovering of lost information by an auto-associative neural network in case of a single sensor failure, recovering of lost information by an «optimal» auto-associative neural network in case of single sensor failures of the on-board control and diagnostic system, recovering the lost information by an auto-associative neural network and an on-board control and diagnostic system from the gas temperature registration sensor before the turbine compressor in case of its failure. The following methods were used: methods of probability theory and mathematical statistics, methods of neuroinformatics, methods of the theory of information systems and data processing. The following results were obtained: The urgent task of recovering lost information from standard sensors in real time has been solved. Various computer architectures and recovery algorithms were investigated. An engineering technique for recovering lost information using a neurocomputer is proposed. As a result of the use of the neurocomputer, effective and high-quality information recovery from standard sensors was ensured under the conditions of the on-board control and diagnostics system of TV3-117 aircraft engine. Conclusions: The use of an auto-associative neural network in the on-board control and diagnostics system for information recovery makes it possible to ensure fault tolerance of the measuring channels of control systems, in particular, the TV3-117 aircraft engine. The main advantage of using neural networks as part of an on-board control and diagnostics system is the possibility of training and learning in real time, taking into account the individual characteristics of a particular engine. Information recovery in case of sensor failure using an auto-associative neural network provides data recovery error of no more than 0.45 % for single failures and not more than 0.6 % for double failures. At the same time, the time of one data recovery cycle is 1589.544 ns for the Raspberry Pi NanoPi M1 Plus calculator and 196.246 ns for the specialized Intel Neural Compute Stick 2 neuroprocessor, which meets the requirements of onboard implementation as part of an onboard control and diagnostic system.

Robust Output Constrained Control for Uncertain Nonlinear Systems Subject to Magnitude and Rate Saturation: Application to Aircraft Engine

In this article, we investigate the output constrained control problem of uncertain nonlinear systems subject to magnitude and rate saturation. First, a novel output constrained controller is proposed based on the antiwindup approach and the active disturbance rejection control technique. Second, the stability is analyzed for the closed-loop system incorporating the proposed controller. Third, we establish the admissible set of initial states, which the initial state belongs to such that the output limit violation is prevented. An optimization algorithm is then presented for the antiwindup gain computation. The computed antiwindup gain guarantees a maximized admissible set of initial states and local asymptotic stability. Finally, the proposed method is applied to the aircraft engine control based on a semiphysical platform. The experimental results validate the effectiveness of the proposed method.

A scientometric analysis and critical review of gas turbine aero-engines control: From Whittle engine to more-electric propulsion

The gas turbine aero-engine control systems over the past eight decades have been thoroughly investigated. This review purposes are to present a comprehensive reference for aero-engine control design and development based on a systematic scientometric analysis and to categorize different methods, algorithms, and approaches taken into account to improve the performance and operability of aircraft engines from the first days to present to enable this challenging technology to be adopted by aero-engine manufacturers. Initially, the benefits of the control systems are restated in terms of improved engine efficiency, reduced carbon dioxide emissions, and improved fuel economy. This is followed by a historical coverage of the proposed concepts dating back to 1936. A comprehensive scientometric analysis is then presented to introduce the main milestones in aero-engines control. Possible control strategies and concepts are classified into four distinct phases, including Single input- single output control algorithms, MIN-MAX or Cascade control algorithms, advanced control algorithms, More-electric and electronic control algorithms and critically reviewed. The advantages and disadvantages of milestones are discussed to cover all practical aspects of the review to enable the researchers to identify the current challenges in aircraft engine control systems.

БАЗОВОЕ ИСПОЛНЕНИЕ РЕГУЛЯТОРА АВИАДВИГАТЕЛЯ И ЕГО МОДИФИКАЦИИ

It is shown that the creation of a unified electronic control and control equipment for aircraft gas turbine engines is one of the determining trends in the experimental design work of enterprises developing components of aircraft equipment. The results of the creation of some helicopter and aircraft engine controllers (turboshaft and turboprops) in JSC Element are presented. The basic model for them was the regulator RDC-450М (category A component product according to AP-21 classification), which was developed for the AI-450M family of turboshaft engines of Мi-2M and Mi-2MSB and in 2014 received the APPLIANCE DESIGN APPROVAL. There is given information concerning the mass-produced regulator RDTs-450M rework to meet the new requirements specified by the engine designer as the results of certification tests of the AI-450M engine and state tests of the Mi-2M and Mi-2MSB helicopters. It is shown that the rework was carried out taking into account the maximum possible “modifiability” of the regulator, which is the maximum ease of its adaptation in the future to new requirements, including requirements for working with other types of engines, including turboprops. The modular principle of constructing the functional structure and design of the regulator is described; its structural scheme is given. Data are given on the results of equivalent cyclic tests of the regulator RDTs-450M, which was modified to meet the new requirements, and on subsequent work on its adaptation to monitor and regulate the modes of turboprop aircraft engines AI-450C (including its modifications) and MS-500V-02S. Information is given on the newly developed regulators RDTs-450M-S, RDTs-450M-S-1, RDTs-450M-S-T-P, RDTs-450S-500, among which there is an engine regulator designed for an unmanned aerial vehicle. It is noted that the modular design assumes the presence of a significant number of board-to-board connections, and the prospects of increasing the reliability of regulator having a modular design by using the technology of flexible-rigid boards are described.

NEURAL NETWORK INTERPOLATION PARAMETERS OF A MULTI-MODE DYNAMIC MODEL OF THE AIRCRAFT ENGINE

The foundations of the concept of creation of intelligent aircraft engine control systems based on the decomposition of control processes within the architecture of open information systems are considered. Unlike well-known approaches, the suggested approach allows achieving the management goal based on the principle of minimum entropy by redistributing system resources in conditions of their shortage, as well as adapting system characteristics when changing the management situation based on self-learning and self-organization of intelligent control systems. Based on an analysis of the development trends of aircraft engines, as well as development trends of production and technological systems, including the creation of new composite materials and new technologies for the manufacture and control of parts and components of aircraft engines, the intellectualization of their automatic control systems is discussed. Moreover, the development trends of aircraft engine control systems are considered from the development of their structures, functions, properties, and abilities for new qualitative changes. The article gives the general characteristics and the main directions of the design of intelligent control systems for aircraft engines as complex technical objects. The problem of designing nonlinear dynamic models of aircraft engines using artificial neural networks is discussed. The statement of this problem and possible approaches to its solution are being formed. The results of the neural network identification of an aircraft engine are compared using the least-squares method. Such a technique for designing a model of aircraft engines makes it possible to indirectly calculate engine coordinates inaccessible to measurement - traction, fuel consumption, etc. The suggested approach allows calculation of the design of neural networks simulating aircraft engines at each step using standard procedures, which makes it possible to automate the creation of neural networks. To reduce the computation time, it is suggested using the optimization algorithms taking into account changes in the state entropy. This simplifies the implementation of the neural network model of an aircraft engine in real time as part of an onboard computer complex.

Design of Linear Parameter-Varying Based Sliding Mode Regulator for Limit Protection of Aero-Engines

Abstract In aircraft engine control, replacing linear regulators by sliding mode control (SMC) regulators is considered as an effective approach to reducing the conservatism in the traditional treatment for limit protection. However, most of the relevant studies are based on linear descriptions, which cannot represent the nonlinear systems directly due to their limited valid range. Even if gain scheduling techniques are employed, the stability of the nonlinear systems cannot be theoretically guaranteed. In this paper, a sliding mode strategy for a class of uncertain linear parameter varying (LPV) systems is studied. LPV descriptions are applied to extend the valid range of the linear models covering the entire operation envelope with guaranteed performance and stability. The mismatch between LPV and the real systems is considered as uncertainties. With a sliding surface defined by the tracking errors, system properties on the surface are proved to be satisfactory. After that, a reaching law is designed to ensure global invariance of SMC. Based on a reliable model turbofan, simulation results show that the SMC method can fully exploit the limit margin and, compared to the traditional proportional-integral-derivative (PID) control, has a faster response. In addition, stability and effectiveness of the proposed method are verified in a temperature protection case.

Automatic Control of Aircraft Engine in Conditions of Stand Test

The general principles of automatic control of aircraft engines and functionally related systems in the conditions of their stand tests are suggested. These principles are prospectively reduced to six sequentially implemented procedures or steps. In accordance with these principles, the control of aircraft engine parameters is carried out by a computer-aided test equipment (CTE) based on a computer complex that implements algorithms based on Boolean algebra and the algebra of events and states. These algorithms allow control procedures to be carried out in dynamic mode in accordance with the schedule of testing an aircraft engine. With this control, the specified sequence of operating modes of the aircraft engine undergoing testing is observed without fixing them in time and with the possibility of skipping or repeating individual modes. Parameters are monitored at each of the next aircraft engine operating modes only after all parameters are checked in the previous mode and the value of the main determining parameter reaches the value determined for this mode. During the period of transient processes, parameters are controlled only at the points of extremum of the values of the main determining parameter with fixing the time of transient processes and determining that. "In the tolerance" or "not in the tolerance" is the checked parameter and the fixed time interval. Upon arrival of the signals from the monitoring object, the time of occurrence of which is unknown, and only the time interval during which they can appear is known, any of the CTE operation modes are terminated, tolerance control of the parameters provided by the program is performed, and the previously interrupted mode is restored. Simultaneously with the tolerance control of the parameters, the time of arrival of the above signals is recorded. The group of emergency parameters is monitored continuously throughout the entire period of stand test.

Modeling and simulation of ventilation and cooling of aircraft piston engine based on genetic algorithm

With the gradual orderly opening of low-altitude areas and the increasing number of private aircraft, the general aviation industry has ushered in new opportunities for development. Ventilation and cooling optimization of the piston aeroengine has become a very important field in general aviation enterprises. The traditional aircraft engine design method and control system do not consider the coupling between aircraft and engine, which can not meet the needs of development. Therefore, an optimization method for the ventilation and cooling of aircraft piston engines based on a genetic algorithm is proposed. Firstly, the engine cooling model is constructed, the ventilation and cooling principles of aircraft piston engines are analyzed, and then the genetic algorithm is used to optimize the ventilation and cooling program of the aircraft piston engine. The results show that the method can effectively optimize the ventilation and cooling scheme of the aero piston engine. During the optimization process, the average convergence value is always greater than 95.00%. Under different working conditions, the maximum failure rate of the optimized ventilation and cooling scheme is 0.03. The maximum failure rate is lower than that of similar methods.

An Output-Based Limit Protection Strategy for Turbofan Engine Propulsion Control with Output Constraints

To accomplish the limit protection task, the Min-Max selection structure is generally adopted in current aircraft engine control strategies. However, since no relationship between controller switching and limit violation is established, this structure is inherently conservative and may produce slower transient responses than the behavior by engine nature. This paper proposes an output-based limit management strategy, which consists of the safety margin module and the parameter prediction module to monitor system responses, plus the switching logic to govern switches between the main controller and limiters, and, in this way, a faster transient performance is achieved, and the limit protections in transient states become more effective. To realize smooth switching control, the linear-quadratic bumpless transfer method is developed. The design principle of the multi-loop switching control and bumpless compensator is detailed, and the effect—on limit protection control performance—of the design parameters in the safety margin and parameter prediction modules are also analyzed. The proposed approach is tested using simulations covering the whole flight envelope on the nonlinear component-level model of a turbofan engine, and the superiority over the Min-Max architecture is also validated.

Sliding mode control with system constraints for aircraft engines

This paper proposes a constraint-tolerant design with sliding mode strategy to improve the stability of aircraft engine control. To handle the difficulties associated with the high-frequency switching laws, merely attenuating the chattering is far from satisfactory. System constraints on input, output, and input rate should be addressed in the design process. For a sort of uncertain nonlinear systems subjected to the constraints, sliding mode regulators are designed using Lyapunov analysis. A turbofan engine is adopted for simulation, which shows that the methodology developed in this paper can handle the speed tracking and limit protection problem in a stable fashion, despite the negative influence posed by the system constraints.

A Product Line Systems Engineering Process for Variability Identification and Reduction

Software Product Line Engineering has attracted attention in the last two decades due to its promising capabilities to reduce costs and time to market through reuse of requirements and components. In practice, developing system level product lines in a large-scale company is not an easy task as there may be thousands of variants and multiple disciplines involved. The manual reuse of legacy system models at domain engineering to build reusable system libraries and configurations of variants to derive target products can be infeasible. To tackle this challenge, a Product Line Systems Engineering process is proposed. Specifically, the process extends research in the System Orthogonal Variability Model to support hierarchical variability modeling with formal definitions; utilizes Systems Engineering concepts and legacy system models to build the hierarchy for the variability model and to identify essential relations between variants; and finally, analyzes the identified relations to reduce the number of variation points. The process, which is automated by computational algorithms, is demonstrated through an illustrative example on generalized Rolls-Royce aircraft engine control systems. To evaluate the effectiveness of the process in the reduction of variation points, it is further applied to case studies in different engineering domains at different levels of complexity. Subject to system model availability, reduction of 14% to 40% in the number of variation points are demonstrated in the case studies.