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Technical Paper

A Discussion on the Process of Eliciting and Validating Requirements to Handle Single Event Upsets in Avionic Systems

2012-10-02
2012-36-0519
Avionics Systems are increasingly used to perform safety-critical functions at high altitudes. But their increasing capacity and concentration of memory and logics leads to more frequent occurrences of single event upsets, especially in high altitudes. In this work we discuss the process of eliciting and validating requirements to handle single events upsets in avionic systems. To do that we initially summarize and update the concepts of radiation environment of the atmosphere, radiation induced errors, single event upsets, etc. presented in a previous paper. Then, we discuss some of their effects on avionic systems and ways of mitigation, reported in the literature. Finally, we discuss provisions to demand the adoption of such mitigation measures, and their sufficiency by transforming them into requirements, according to recommendations of compliance described in standards as SAE ARP 4754A and RTCA DO-254.
Technical Paper

Refinements of the GPS Kalman Estimates for the Position and Velocity of a Vehicle during High Acceleration Transients Using IMU Measurements

2012-10-02
2012-36-0513
Currently, the use of Global Navigation Satellite Systems-GNSS has been widely disseminated for the most different applications, from the aeronautical navigation to the car traffic system, being the Global Positioning System-GPS the most used system for such objectives. New applications of such systems have presented more demanding requirements in terms of precision for the position and velocity provided by these systems. Some solutions, as the precision augmentation systems based on satellite or ground improve the precision of the position and velocity estimates. However, the sampling rate of these systems is not substantially improved. Therefore, it constitutes a major limitation of such systems for the position and velocity estimates during high acceleration transients. On other hand, Inertial Navigation Systems- INSs present superior performance under these circumstances.
Technical Paper

A Discussion on the Causes and Effects of Thermal Avalanche in Artificial Satellite Battery Charging and Discharging Systems

2012-10-02
2012-36-0558
The supply of electrical power is one of the most important functions required by the diverse payloads of satellites. A fault in the corresponding subsystem might lead to mission or even vehicle loss. Among the causes of such faults, we highlight the phenomenon of thermal avalanche in batteries. It can be explained as an energetic unbalance where the rate of heat generated in the interior of the system exceeds its capacity to dissipate it. This occurred to the OAO1 of NASA just after its launch on April 8, 1966; and with the CBERS2 of CAST and INPE already in orbit in 2007 and 2009. This work presents a discussion on the causes and effects of thermal avalanches in artificial satellite battery charging and discharging systems.
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

Application of Methods to Smooth the Transition Between Control Submodes in the Nominal Mode of the Multimission Platform

2012-10-02
2012-36-0378
The Multimission Platform (MMP) is a generic service module currently in Project at INPE. In the 2001 version, its control system can be switched between nine main Operation Modes and other submodes, according to information from satellite sensors and ground commands. The Nominal Mode stabilizes the MMP in three axes and takes it to a nominal attitude, using three reaction wheels. Each wheel has coarse and fine acquisition submodes. The use of multiple modes of control for specific situations frequently is simpler than projecting a single controller for all cases. However, besides being harder to warrant its general stability, the mere switching between these submodes generates bumps, which can reduce the performance and even damage the actuator or plant. In this work, we present an application of diverse methods to smooth the transition between control submodes of the Nominal Mode of the MMP.
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.
Technical Paper

An Overview of an Assurance Process of Immunity of Embedded Electronic Systems to Single Event Upsets Caused by Ionizing Particles

2013-10-07
2013-36-0535
The aerospace and automotive electronic systems are getting more complex and/or highly integrated, as defined by ARP 4754A, making extensive use of microelectronics and digital memories which, in turn, operates in higher frequencies and lower voltages. In addition, the aircraft are flying in higher altitudes, and polar routes are getting more frequent. These factors raise the probability of occurrence of hazardous effects like the Single Event Upsets in their embedded electronic systems. These must be designed in a way to tolerate and assure the immunity to the Single Event Upsets, based upon criteria such as reliability, availability and criticality. This paper proposes an overview of an assurance process of immunity of embedded electronic systems to Single Event Upsets caused by ionizing particles by means of a review of literature and an analysis of standards as ECSS-E-ST-10-1, NASA Single Event Effects Criticality Analysis and IEC TS 62396-1.
Technical Paper

An Overview of Models, Methods and Tools for Verification, Validation and Accreditation of Real Time Critical Software

2013-10-07
2013-36-0530
Real-time critical systems are those whose failures may cause loss of transactions/data, missions/batches, vehicles/properties, or even people/human life. Accordingly, some regulations prescribe their maximum acceptable probability of failures to range from about 10−4 to 10−10 failures per hour. Examples of such systems are the ones involving nuclear plants, aircrafts, satellites, automobiles, or traffic controls. They are becoming increasingly complex and/or highly integrated as prescribed by the SAE-ARP-4754A Standard. Those systems include, most of the time, real time critical software that must be specified, designed, implemented, validated, verified and accredited (VVA). To do that, models, specially the V-Model, are frequently adopted, together with methods and tools which perform software VVA to ensure compliance (of correctness, reliability, robustness, etc.) of software to several specific standards such as DO178-B/DO-178C (aviation) or IEC 26262 (automotive) among others.
Technical Paper

An Overview of Clock Synchronization Algorithms and their Uses in Aerospace and Automotive Systems

2013-10-07
2013-36-0541
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-4754a Standard. Such systems operate in a real time distributed environment which frequently requires a common knowledge of time among different devices, levels and granularities. So, temporal correctness is mostly needed, besides logical correctness. It can be achieved by hardware clocks and devices, software clocks and algorithms, or both, to avoid or tolerate, within appropriate margins, the time faults or failures that may occur in aerospace and automotive systems. This paper presents an overview of clock synchronization algorithms and their uses in aerospace and automotive systems. It is based on a review of the literature, discussion and comparison of some clock synchronization algorithms with different policies.
Technical Paper

Reconfiguration of Control Systems as Means for Reaching Fault Tolerance: An Assessing Study on Methods Available

2013-10-07
2013-36-0639
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.
Technical Paper

Refinements of the Kalman Estimates for the Position and Velocity of a Vehicle Obtained with GPS Using Inertial Navigation System's Measurements: A Comparative Analysis

2013-10-07
2013-36-0650
Currently, the use of Global Navigation Satellite Systems-GNSS has been widely disseminated for the most different applications, from the aeronautical navigation to the car traffic, being the Global Positioning System-GPS the most used system for such objectives. New applications have presented challenges in terms of the main requirements associated to such systems, namely: precision, reliability, availability, continuity and integrity. It is because proposed solutions, such as satellite or ground-based augmentation systems, depend on signals provided by the GNSS satellite constellation. It constitutes a limitation for using such systems for position and velocity estimations. On other hand, Inertial Navigation Systems-INS, being independent of external signals, have a big potential to be applied on these circumstances; furthermore, they present characteristics that may be considered complementary to the GNSS.
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

Highly Accurate Measure of Time in PC Simulations of Control Systems with Sensors in the Loop

2000-12-01
2000-01-3296
The measure of time intervals with relatively high accuracy (of 1 milisecond, at least) in PC computers is a relatively hard task to solve. But this is essential for the digital simulation, with sensors in the loop, of fast control systems. This work allows the reading of the programmable internal timer 8253 present in a typical PC, reaching 1 ms resolution, at least, through a C high level language routine. The determination of the angular velocity of a 53M2-30H Contraves 3-axis dynamic simulator used in that simulation was improved by the use of this work, allowing the acquisition of consecutive measures of angles and angular velocities with a time interval smaller than 10 ms in some cases. Using this routine and other simulator control and monitoring softwares we estimated the angular velocity faster (100 ms × 210 ms)and better than the simulator Rate Readout Module, and used it in a fast real time control simulation.
Technical Paper

Stabilizing and Improving the Active Vibration Damping by a New S-Z Mapping for Digital Control

2000-12-01
2000-01-3297
This paper presents an analytical and simulation study of the stabilization and improvement of the active vibration damping of a system modeled by a simple analog harmonic oscillator driven by discrete time control. Initially, this control is the Bilinear (or Tustin) s-z mapping equivalent of a continuous-time asymptotically stable Proportional plus Derivative (PD) control. It is tested with high values of the sampling period. It is shown that all classical mappings (Tustin, Schneider, etc.) tested may instabilize the system. To circumvent this, we propose and use a new (ST1) mapping that behaves better than the classical ones tested under the same conditions. We also model an active discrete control of a suspension of a vehicle, and compare the performance between the PD controllers designed by Bilinear and by the new (ST1) S-Z mappings, for this example.
Technical Paper

Generation and Customization of Real Time Code for Embedded Controllers Using a Modeling and Simulation Environment

2007-11-28
2007-01-2924
This works presents the generation and customization of real time code for embedded controllers using a modeling and simulation environment. When the controller model is considered satisfactory, the developers can use a code generation tool to build a real time source code capable to be migrated to an embedded target processor. The code generation tool used is capable to generate real time code in ANSI C or ADA 95 languages. This process can be customized to adequate to a target processor and/or a Real Time Operating System (RTOS). The code customization can be achieved using a specific Template Programming Language (TPL) that specifies how the code will be generated. This technique makes it possible the instantiation of real time embedded controllers code using the same controller model to a wide variety of target processors and/or RTOSs.
Technical Paper

Influence of Sharing Bus on Real-Time Networked Control Systems Performance

2007-11-28
2007-01-2692
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 effect of sharing bus between the control system and the other devices connected to the bus foreigner to control. These last devices are called interferences. We intented to show, through simulations, the influence of sharing bus on real time control systems performance. To compare effects, we choose the CanBus protocol where the medium access control is event driven; and the TTP protocol where the medium access control is time driven.
Technical Paper

Design of an Attitude Control System for the Multi-Mission Platform and its Migration to a Real Time Operating System

2007-11-28
2007-01-2857
This paper presents the first of four parts of the academic design of an Attitude Control System (ACS) for the Multi-Mission Platform (MMP) and its migration to a Real Time Operating System. 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. Time characteristics were added to the ACS generated code to make it the real time control software of MMP nominal operational mode.
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

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.
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