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Technical Paper

A Discussion on Fault Detection, Isolation, Identification and Reconfiguration in Networked Control Systems of Aerospace Vehicles

2011-10-04
2011-36-0088
In this work, the problem of fault detection, isolation, and reconfiguration (FDIR) for Networked-Control Systems (NCS) of aerospace vehicles is discussed. The concept of fault-tolerance is introduced from a generic structure, and a review on quantitative and qualitative methods (state estimation, parameter estimation, parity space, statistic testing, neural networks, etc.) for FDIR is then performed. Afterwards, the use of networks as loop-closing elements is introduced, followed by a discussion on advantages (flexibility, energy demand, etc.) and challenges (networks effects on performance, closed-loop fault-effects on safety, etc.) represented thereby. Finally, examples of applications on aerospace vehicles illustrate the importance of the discussion herein exposed.
Technical Paper

Influences of Data Bus Protocols on an Aircraft Fly-By-Wire Networked Control System

2008-10-07
2008-36-0008
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.
Technical Paper

A Worst Case Formula for a Communication and Computation Delay in NCS.

2010-10-06
2010-36-0358
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 that must be considered at the design time of a control system. This work, still in development, focuses on a worst case formula for a communication (TDMA) plus computation (RMS) on a NCS. This formula, in a first instance, agrees with the simulated cases under the hypotheses and conditions when the NCS is composed by 1 actuator - 1 sensor and when is composed by 2 actuators - 2 sensors. In the future, we intend to generalize this formula and extend this study to NCS that uses other communication protocols or others computer schedulers.
Technical Paper

Analysis, Design and Simulation of the Reconfigurable Control Architecture for the Contingency mode of the Multimission Platform

2010-10-06
2010-36-0333
This work presents the analysis, design and simulation of the reconfigurable control architecture for the contingency mode of the MultiMission Platform (MMP). The MMP is a generic service module currently under design at INPE. Its control system can be switched among nine main Modes of Operation and other Sub-Modes, according to ground command or information coming from the control system, mainly alarms. The implementation followed the specifications when they were found, otherwise it was designed. They cover operations from detumbling after launcher separation and solar acquisition, to achieving payload nominal attitude and orbital corrections maneuvers. The manager block of the control system was implemented as a finite state machine. The tests are based in simulations with the MatriX/SystemBuild software. They focused mainly on the worst cases that the satellite is supposed to endure in its mission, be it during modes or transitions between modes and submodes.
Technical Paper

Study on a Fault-Tolerant System Applied to an Aerospace Control System

2010-10-06
2010-36-0330
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.
Technical Paper

Current Trends Driving the Aerospace and Automotive Systems Architectures

2011-10-04
2011-36-0387
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.
Technical Paper

A Requirements Based Approach to Future Aeronautical Navigation Systems Based on Global Navigation Satellite Systems

2011-10-04
2011-36-0216
The increasing use of Global Navigation Satellite Systems-GNSS in future Aeronautical Navigation Systems-ANS is a current trend in the aeronautical operation and regulation communities. This trend implies the adoption of elements and interactions of a degree of complexity that is still being discussed around the world. Faced with that, we believe that a requirements based approach is an effective tool to deal with such highly complex and integrated systems. In this work we discuss a requirements based approach to future Aeronautical Navigation Systems based on Global Navigation Satellite Systems. To do that, we first briefly present the concept of Communication, Navigation, Surveillance/Air Traffic Management - CNS/ATM, and the current and potential benefits of the adoption of its paradigms.
Technical Paper

The Use of PLL Techniques for Accurate Time or Phase Synchronization in Aerospace and Automotive Systems

2011-10-04
2011-36-0179
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.
Technical Paper

Bump Reduction for the Reconfigurable Control Architecture of the MultiMission Platform

2011-10-04
2011-36-0187
Many control systems switch between control modes according to necessity. That is often simpler than designing a full control to all situations. However, this creates new problems, as determining the composed system stability and the transient during switching. The latter, while temporary, may introduce overshooting that degrade performance and damage the plant. This is particularly true for the MultiMission Platform (MMP), a generic service module currently under design at INPE. Its control system can be switched among nine main Modes of Operation and other submodes, according to ground command or information coming from the control system, mainly alarms. It can acquire one and three axis stabilization in generic attitudes, with actuators including magnetotorquers, thrusters and reaction wheels.
Technical Paper

Distributed Simulation of the Longitudinal Mode of an Aircraft by Using the DoD High Level Architecture (HLA)

2008-10-07
2008-36-0299
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.
Technical Paper

Stability degradation due to delays in a networked control systems

2008-10-07
2008-36-0286
In this work, still under development, we study the stability degradation due to delays in a networked control system. Our networked system is composed by: 1) a computer with Rate Monotonic Scheduler policy and, 2) a communication network based on TDMA access. Under this scenario, we analyze an integrated communication-computing delay and define the worst delay. The simulations shows that the presence of a worst delay can be determined only with an extensive analysis. The simulations were done in Matlab/Simulink with the help of Truetime toolbox.
Technical Paper

SURVEY AND ANALYSIS OF DETERMINISM IN NETWORK COMMUNICATIONS IN EMBEDDED COMPUTER SYSTEMS OF AEROSPACE VEHICLES

2008-10-07
2008-36-0282
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.
Technical Paper

Simulation Architechtures and Standards: Their Characteristics and Applications to the Simulation and Control of Aerospace Vehicles

2008-10-07
2008-36-0271
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
Technical Paper

Fault Detection and Diagnosis (FDD) on a Knock Sensor

2008-10-07
2008-36-0369
The purpose of this work is Fault Detection and Diagnosis (FDD) on a Knock Sensor because some of the modern petrol engines operate on the efficient four-stroke cycle, where each cylinder of the engine contains an intake and exhaust poppet valve that is operated at the appropriate time. The ECM (Engine Control Module) uses the Knock Sensor signal to control timing. The Knock Sensor detects engine knock and sends voltage signal to the ECM. These signals can be sufficient to detect abnormal combustion, like ‘spark knock’ and ‘surface ignition’. Engine knock occurs within a specified range. The Knock Sensor, located in the engine block, cylinder head, or intake manifold is tuned to detect that frequency, which motivates the use of signal models for detection. But this sensor is a wide-band accelerometer of the piezoelectric type too. Analogy with a general seismic mass system is possible since it is a general damped second order vibrating system which is forced into oscillatory motion.
Technical Paper

Automatic Code Generation of an Attitude Control System for the Multi-Mission Platform

2008-10-07
2008-36-0362
This paper presents the automatic code generation process of the academic design of an Attitude Control System (ACS) for the Multi-Mission Platform (MMP). The MMP is a three axis stabilized artificial satellite now under development at the National Institute for Space Research (INPE). Such design applied some software engineering concepts as: 1)visual modeling; 2)automatic code generation; 3)automatic code migration; 4)soft real time simulation; and 5)hard real time simulation. A block diagram based modeling and a virtual time simulation of the MMP ACS in its nominal operational mode were built in the MatrixX 7.1 environment satisfying the three axis pointing and stabilization requirements. After that, its AutoCode module was used to generate C ANSI code representing the block diagram model. Four operating systems were used for code migration: 1)Windows 2000; 2)Mandrake Linux 10.1; 3)RedHawk Linux 2.1; and 4)RTEMS 4.6.2.
Technical Paper

Analysis, Design and Simulation of the Transition from Pre-Nominal to Nominal Mode of the Reconfigurable Control Architecture for the Multi-Mission Platform

2008-10-07
2008-36-0343
This work presents the first part of the analysis, design and simulation of the reconfigurable control architecture for the Multi-Mission Platform (MMP), a generic service module currently under design at INPE. Its control system can be switched among nine main Modes of Operation. The implementation followed the specifications when they were found, otherwise it was designed. The manager block of the control system was implemented as a finite state machine. The tests were based in simulations with the MatriX/SystemBuild software. They focused mainly on the worst cases that the satellite is supposed to endure in its mission.
Technical Paper

Automatic Generation, Migration, and Tests of a Real Time Code to an Embedded Controller

2008-10-07
2008-36-0342
A constant challenge for the mobility engineering is to build correctly, the right product at the right time, cost and quality. This challenge gives opportunities to adopt new paradigms in system development, especially in generation, migration and tests of controller codes. This work presents the automatic generation, migration, and tests of real time code to an embedded controller. This is part of the Attitude and Orbit Control System (AOCS) for the Multi-Mission Platform (MMP) of the National Institute for Space Research (INPE). The modeling and simulation paradigm associated with automatic code generation makes possible the migration of a real time embedded controller code to a wide variety of target processors and/or Real Time Operating Systems (RTOS) using the same controller model. The MATRIXx (XMath/SystemBuild/AutoCode/DocumentIt) modeling and simulation environment was used to analyze and design the controller and generate its real time code.
Technical Paper

A Discussion on Methods Used in the Verification and Validation of Control Systems Architectures of Cyber-Physical Systems Based on Models and Systems Metrics

2012-10-02
2012-36-0458
The architecture is a concept very broad and important that is directly connected to the realization of a system. It defines what the system is capable of doing, how it accomplishes its mission and how the system is. Currently, the development of system architectures is considered a domain of knowledge where science meets art. In some specific areas, the methods on the development of system architectures are already well formalized. However, when analyzing the evaluation of system architectures such as those for multi-domain control systems, it is clear that there is still much room for rationalization. In these cases, the search for new methods for the evaluation of system architectures is currently in the state of art. In this work we discuss methods used in the verification and validation of control systems architectures of cyber-physical systems based on models and systems metrics.
Technical Paper

An Investigation on Techniques for Accurate Phase or Time Synchronization in Reconfigurable Control Systems

2012-10-02
2012-36-0398
Current systems such as: satellites, aircrafts, automobiles, turbines, power controls and traffic controls are becoming increasingly complex and/or highly integrated as prescribed by the SAE-ARP-4754 Standard. Such systems and their control systems use many modes of operation and many forms of redundancy to achieve high levels of performance and high levels of reliability under changing environments and phases of their lifecycle. The environment disturbances, environment variability, plant non-linear dynamics, plant wear, plant faults, or the non-symmetric plant operation may cause de-synchronization in phase or time among: 1) simultaneous units in the same normal mode of operation; 2) successive units in successive normal modes of operation; 3) main and spare units from normal to faulty modes of operation. So, techniques to reduce those causes or their effects are becoming important aspects to consider in the design of such systems.
Technical Paper

A Scheduler with a Dynamic Priority and its Influence on a Control System

2012-10-02
2012-36-0367
In critical real-time computer systems, whether aircraft, automotive and industrial products it is very common the use of a fixed priority scheduler. The fixed priority scheduler has shown a good performance in control applications even in different applications where it was adopted. But nowadays, to go forward with the technology, be it in hardware and software, schedulers with dynamic priority can be a better alternative in certain situations. The present work aims to show that a variable priority scheduler can improve the performance of a control system obtained with a fixed priority scheduler, even when it was bad conditioned. This study is based on a four motor position control system. For this, the study will make use of a specialized simulation tool. In the future, we intend to extend this study to schedulers that use random and sporadic tasks.
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