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This paper aims at discussing the use of dissimilar hardware architecture to mitigate DESIGN ERRORS in a flight control system application, as one of the possible design techniques that, combined with the usage of development processes, will satisfy the safety objectives for airborne systems. To accomplish its purpose, the paper starts by understanding the origins of DESIGN ERRORS in micro-coded devices and the concerns of airworthiness certification authorities (or simply certification authorities from now on). After that, an overview of the aeronautical industry efforts in terms of development processes and certification requirements to mitigate DESIGN ERRORS will be presented. At this point, the dissimilar architecture is proposed as an effective mean to mitigate the problem of DESIGN ERRORS. Finally, a Flight Control System application using dissimilar architecture is proposed as a case study.

Current systems such as satellites, aircrafts, automobiles, turbines, wind power generators and traffic controls are becoming increasingly complex and/or highly integrated as prescribed by the SAE-ARP-4754 Standard. Such systems frequently require accurate generation, distribution and time or phase synchronization of signals with different frequencies that may be based on one reference signal and frequency. But the environment fluctuations or the non-linear dynamics of these operations cause uncertainties (skew and jitter) in the phase or time of the reference signal and its derived signals. So, techniques to reduce those causes or their effects are becoming important aspects to consider in the design of such systems. The PLL techniques are useful for establishing coherent phase or time references, jitter reduction, skew suppression, frequency synthesis, and clock recovery in numerous systems such as communication, wireless systems, digital circuits, rotors, and others.

Systems such as satellites, airplanes, cars and air traffic controls are becoming more and more complex and/or highly integrated. These systems integrate several technologies inside themselves, and must be able to work in very demanding environments, sometimes with few, or none, maintenance services, because of their severe conditions of work. To survive to such severe work conditions, the systems must present high levels of reliability, which are achieved through different approaches and processes. Therefore, it is necessary that the processes of decision analysis and making are progressively improved, taking into account experiences collected before by several technological communities, and then propose efficient modifications in the local processes. These experiences influence the proposition and improvement of several Reliability Standards Series taken by four different approaches and several technological communities.

In this work we discuss the fault avoidance and the fault tolerance approaches for increasing the reliability of aerospace and automotive systems. This includes: the basic definitions/concepts (reliability, maintainability, availability, redundancy, etc.), and characteristics (a priori analysis, a posteriori analysis, physical/hardware redundancy, analytical/software redundancy, etc.) of both approaches, their mathematical background and models (exponential, Weilbull, etc.), their basic theory, their methods and techniques (fault trees, dependence diagrams, Markov chains, etc.), some of their standards (SAE-ARP4761, AC 25.1309, etc.) and simulation environments (Cafta, etc.), and their applications to the reliability analysis and reliability improvement of aerospace and automotive vehicles. This is illustrated by some examples driven from the aerospace and automotive industries.

This paper presents the preliminary results of an "a posteriori" exercise of application of a Requirements Traceability Automation Tool (RT tool) to a set of documents. The documents have been prepared according to established Space System Engineering methodologies and with attention to text quality, but without attention to requirements traceability because the processes and methodologies used during their preparation predates the emergence of the processes and methodologies developed by Requirements Engineering (RE). This study is intended to determine some of the benefits of using a RT tool when compared with the previously used processes and methodologies. The set of documents under scrutiny have been prepared in the frame of the development of the CBERS-3 satellite (China-Brazil Earth Resources Satellite) and is composed of system, subsystem and equipment specification and covering documents related to the Electrical Power Subsystem (EPS) of the satellite.

This paper presents some techniques for fault diagnosis in aerospace and automotive systems. A diagnosis technique is an algorithm to detect and isolate fault components in a dynamic process, such as sensor biases, actuator malfunctions, leaks and equipment deterioration. Fault diagnosis is the first step to achieve fault tolerance, but the redundancy has to be included in the system. This redundancy can be either by hardware or software. In situations in which it is not possible to use hardware redundancy only the analytical redundancy approach can be used to design fault diagnosis systems. Methods based on analytical redundancy need no extra hardware, since they are based on mathematical models of the system.

On several engineering applications high Reliability is one of the most wanted features. The aspects of Reliability play a key role in design projects of aircraft, spacecraft, automotive, medical, bank systems, and so, avoiding loss of life, property, or costly recalls. The highly reliable systems are designed to work continuously, even upon external threats and internal Failures. Very convenient is the fact that the term 'Failure' may have its meaning tailored to the context of interesting, as its general definition refers to it as "any deviation from the specified behavior of a system". The above-mentioned 'deviation' may refer to: performance degradation, operational misbehavior, deviation of environmental qualification levels, Safety hazards, etc. Nevertheless, Reliability is not the only requirement for a modern system. Other features as Availability, Integrity, Security and Safety are always part of the same technical specification, in a same level of importance.

In this work we study the stability of digital controls of flexible/Vibratory aerospace/automobile systems by the graph norm technique, occurring in sampled-data control systems due to sampling period variations. To do so, this work tries to establish regions (graphs) of stability and instability in a Banach Space, the distances (norms) between them and a given design to detect analytically and/or numerically its margins of stability or conditions of instability. Based on that, we sketch the first steps for a design methodology of stable digital controllers of flexible/vibratory systems embedded in a sampled-data system with adjustable sampling periods of A/D and D/A converters. A short tutorial about the graph norm technique is also given and some theoretical results as well numerical results are shown. This work was done in two folds to unmask the stability secrets hidden in a general sampled-data control system, until today not revelated.

In this work we discuss some types of simulators and simulations, their characteristics and applications to the simulation and control of aerospace vehicles. This includes: the basic definitions, types and characteristics of simulators and simulations (physical, computational, hybrid, etc.; discrete events, discrete time, continuous time, etc; deterministic, stochastic, etc.) their basic compromise (simplicity × fidelity), their man-machine interfaces and interactions (virtual, constructive, live, etc.), their evolution law (time, events, mixed, etc.), their architectures (“standalone”, PIL, HIL, MIL, DIS, HLA, etc.), their environments (discrete, continuous, hybrid, etc.) and their applications to the simulation and control of aerospace vehicles. This is illustrated by some examples driven from the aerospace industry

In this work we discuss some types of simulation environments and laboratories, their characteristics and applications to the simulation and control of aerospace vehicles. This includes: the basic definitions, types and characteristics of simulators and simulations (physical, computational, hybrid, etc.; discrete events, discrete time, continuous time, etc; deterministic, stochastic, etc.) their basic compromise (simplicity × fidelity), their man-machine interfaces and interactions (virtual, constructive, live, etc.), their evolution law (time, events, mixed, etc.), their architectures (“stand-alone”, PIL, HIL, MIL, DIS, HLA, etc.), and especially, their environments (discrete, continuous, hybrid, etc.) and laboratories (physical, computational, hybrid, etc.), and their applications to the simulation and control of aerospace vehicles. This is illustrated by some examples driven from the aerospace industry.

In this work we discuss some types of simulation architectures and standards, their characteristics and applications to the simulation and control of aerospace vehicles. This includes: the basic definitions, types and characteristics of simulators and simulations (physical, computational, hybrid, etc.; discrete events, discrete time, continuous time, etc; deterministic, stochastic, etc.) their basic compromise (simplicity x fidelity), their man-machine interfaces and interactions (virtual, constructive, live, etc.), their evolution law (time, events, mixed, etc.), their architectures (“stand-alone”, PIL, HIL, MIL, DIS, HLA, etc.), their standards (OMBA, SIMNET, ALSP, DIS, HLA 1.3, HLA 1516, ASIA, AP2633, etc.) and their applications to the simulation and control of aerospace vehicles. This is illustrated by some examples driven from the aerospace industry

Computer systems aboard aerospace vehicles have become more and more distributed in an attempt to solve “real-life” problems such as commonality and longevity of components and subsystems. On the other hand, distributed systems pose a much bigger challenge in system design than traditional, “monolithic” systems, whereby functions are performed by a single component combining hardware and software. “Determinism” (predictability in the occurrence of events), “causality” (temporal ordination of occurrence of events) and “synchronism” (simultaneousness in the occurrence of events) can be pointed out as major challenges in system design. This paper shall survey methods of analyzing determinism in network communications in distributed computer systems aboard aerospace vehicles in different network topologies using a representative model.

The realization of modern systems subjected to automatic control, such as aircraft, automobiles, satellites, rocket launchers, cargo and military ships, and so forth; increasingly assume, within its very set of requirements, the task of providing better dependability, i.e.: safety, reliability, and availability altogether. Towards this demand, fault-tolerant control greatly meets such growing demand of dependability, by its ability of recognizing the occurrence of potentially hazardous/hazardous faults within the overall (closed-loop) system, and by taking remedial action whenever necessary/mandatory. The process of fault tolerance can be segregated into two fundamental steps: (1) that of fault diagnosis, comprising fault detection-isolation-identification, and, (2) control adjustment/reconfiguration. This paper focuses on the second step, of control adjustment/reconfiguration.

One challenge that the space, aeronautical and automotive industries are facing today is the fast growing number of vehicles versus the slowly growing number of useful orbits, routes, and speedways. Furthermore, the adoption of “free-flight”, “speed-drive”, etc. policies in the near future will only aggravate it. All these factors increase the risk of collisions and the frequency of deviation maneuvers to avoid them. But they also create the opportunity to devise policies to mitigate such problems, including algorithms to propagate the uncertainties in vehicle motions and to predict the risk of their collisions. This work discusses the development and simulation of an algorithm for the propagation of navigation uncertainties in the trajectory of aerospace vehicles, to minimize the risk of collisions. The scenario of Satellites Formation Flying shall be used for the simulations, with focus on the prediction of the collision probability.

Modeling and Simulation (M&S) of dynamic systems based on computers is a multidisciplinary field that involves several knowledge areas and tools, and is broadly used in all development areas of space industry such as rocket and satellite design and construction. Once space systems are divided into several subsystems for ease of engineering, their models are divided the same way for the same reason. Such models may be done using different computational tools that are based on either physical flows, informational flows, or hybrid flows, depending on the subsystem nature. This is specially true for a satellite propulsion subsystem, and its physical (volume, mass, energy, enthalpy, entropy, linear momentum, etc.) flows. This paper presents the modeling and simulation of a satellite propulsion subsystem by physical and signal flows. To accomplish this task, two different computational tools were used: AMESim and MatLab.

Control systems that can switch between control or plant modes have the advantage of being simpler to design than an equivalent system with a single mode. However, the transition between these modes can introduce steps or overshootings in the state variables, and this can degrade the performance or even damage the system. This is can be of extreme importance in fields such as aerospace and automobilistic, as the switching between manual and autopilot modes or the switching of gears In this work, we will use integral criteria in original ways, to determine a coefficient on the system which should optimize the trajectory of the control signal, during the switching between two modes. Effectively, each transition will be done by a subsystem specific for it, according to the selected criterion. The simulations will be made in MATRIXx, MatLab or both, using models chosen from aerospace or automobilistic fields.

A major trend in modern aerospace and automotive systems is to integrate computing, communication and control into different levels of the vehicle and/or its supervision. A well fitted architecture adopted by this trend is the Common Bus Network Architecture. A Networked Control System (NCS) is called when the control loop is closed through a communication network. The presence of this communication network introduces new characteristics (sharing bus, delays, jitter etc.) to be considered at design time of a control system. This work focuses on the influences of data bus protocols on an aircraft Fly-By-Wire (FBW) networked control system. We intent to show, through simulations, the influences of sharing bus on a real time control system. To compare effects, we choose the CAN Bus protocol where the medium access control is event driven; and the TTP protocol where the medium access control is time driven.

This work presents the identification of the longitudinal mode of an aircraft by using time and frequency response methods. To do this, the transfer function was identified based on the sampled response to a step input. The transfer function was validated comparing the model step response with the original system step response. The identification of the system transfer function was performed by using the Fast Fourier Transform (FFT) and Bode Graphs methods. The model validation quantification was performed by means of the mean quadratic-error method applied to the step response difference. Based on that, the identified model was considered to be quite representative, thus proving the suitability of the applied methods.

This work presents the distributed simulation of the longitudinal mode of an aircraft by using the DoD High Level Architecture (HLA). The HLA is a general-purpose architecture for simulation reuse and interoperability. This architecture was developed under the leadership of the Defense Modeling and Simulation Office (DMSO) to support reuse and interoperability across the large numbers of different types of simulations developed and maintained by the DoD. To do this, the transfer function of the longitudinal mode of a hypothetical aircraft was implemented by means of a SystemBuild/MATRIXx model. The output of this model was connected to a Run-Time Infrastructure (RTI) and monitored on a remote computer. The connection between the model and the RTI was implemented by using a wrapper which was developed in C++. The HLA RTI implementation used in this work was the poRTIco.

In this work we discuss current trends driving the aerospace and automotive systems architectures. This includes trends as: 1) pos-globalization and regionalization; 2) the formation of knowledge oligopolies; 3) commonality, standardization and even synergy (of components, tools, development process, certification agents, standards); 4) reuse and scalability; 5) synergy of knowledge and tools convergence; 6) time, cost and quality pressures and innovation speed; 7) environmental and safety issues; and 8) abundance of new technologies versus scarcity of skilled manpower to apply them.