Description 

This is a presentation on testing of safety critical control systems updated with DO178C, DO331 and DO 333 parts. I have added a few slides on ISO 26262 comparing it with DO178. I have added a dormant error which was found after 12 years in a flight control system. I have now added a section on formal methods. This section has been updated with addition of two errors found using formal methods. I have added a few modeling guidelines just to show the importance of these rules. 

You will gain 

An insight into the fascinating field of Model Based testing of Safety Critical Control Systems 

An insight into the mistakes we make – again and again 

A set of Best Practices in this field gleaned from the use of this type of testing on Aircraft Programs in India 

Outline 

• Safety Critical Control Systems – A brief overview 

• What are the mistakes we normally make? – a look at the errors made in the various programs since 1988 

• DO178B, DO178C and DO331 standard overview. How are other standards related. 

• What are these Models? – a look at how they function 

– Algorithms for implementing them 

• How do we test these blocks? – a block by block approach 

• What are functional coverage metrics? 

• Formal Methods in Flight Controls – An experimental approach 

• Modeling guidelines 

• Best Practices

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This is set of slides that tries to demystify Formal Methods. This I feel is a good stating point for the novice to know more about formal methods. The slides provide links for further reading and exploration. The slides walk you through safety critical errors, a need for formal methods, what are formal methods. It provides an example solved by using Theorem Proving, Model Checking and Abstract Interpretation.

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This is a set of slides that provide the essentials of Matlab and Simulink. In Matlab a list of commands that I have been using quite often in the work is described. The exercises in Matlab help you understand the concepts. These matlab commands can then be used for Simulink simulation. Simulink covers a set of blocks that models a differential equation. The discretization and the discrete set of models are described that can be used to model a control system.

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How do we implement an integrator, rate limiter, filter for control system. What is the algorithm? The slides and Simulink files provide the template to make a Matlab function. The Matlab function helps program these algorithm and test them.

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PID control has been in the industry for quite some time now. However, at a undergraduate level (at least in India) this is not being taught. These set of slides help the novice get a grasp of the concept. The Simulink models help one design the PID control laws. Optimization is used to tune the PID gains. This is demonstrated in the slides and models. The same Matlab optimization is used to model a plant from experimental data.

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Environmental control system in an aircraft is used to maintain the cabin pressure and temperature at a comfortable level. The set of Simulink models and slides models an aircraft cabin from first principles. A set of PID control are developed as a template to design cabin control laws and their implementation. The models describe the cabin, the mixer, valve, the heat sources and the atmosphere.

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Over the years I have contributed many Simulink models, Matlab code in the MathWorks file exchange. I plan to continue this. Have a look at this webpage for the various contributions.

I gave two talks using this presentation on MBSE. It is still work in progress. I would like your inputs on what I shoud add and delete from this.

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I had a long chat with ChatGPT on Bach Flower Remedies. This is a remedy that cures our bad emotions. I have a book on Amazon which is commerical. This book called Chatting on Bach Remedies is on the same lines but available as creative commons.

This is our notes developed during the study of Bach Flower Remedies. We have found it very useful and would like to share it with others. It contains bulleted information about, Dr Edward Bach, his remedies, details of the flowers, detailed remedies, combination of remedies, remedies for children, a note on emotions, selection process for the remedies and a section on Chakras. We have extended the first edition correcting for a few errors and added a repertory of ailments and chakras and the Bach Remedy for each ailment. This is again taken from different sources. We have been able to conclusively connect the Chakras and the seven divisions of Bach Remedies. We have provided a story at the end of the book to better remember the remedies.

I have uploaded the second edition of the Bach Flower book here. This is under creative commons.

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This is a presentation from INCOSE India Chapter on systems engineering steps. These are my views on this topic. I presented this at the first Medical Summit hosted by INCOSE India Chapter in Bengaluru. This is available under creative commons.

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This volume is the outcome of deliberations on formal methods in aerospace. The book specially delves into the use of formal methods for verification, validation, and optimization of software in safety critical and time critical applications, such as those in aerospace engineering. The chapters in this book are authored by leading corporate and government R&D scientists. The contents of this book will be useful to researchers and professionals alike.

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This is our notes developed during the study of Bach Flower Remedies. We have found it very useful and would like to share it with others. It contains bulleted information about, Dr Edward Bach, his remedies, details of the flowers, detailed remedies, combination of remedies, remedies for children, a note on emotions, selection process for the remedies and a section on Chakras. We have extended the first edition correcting for a few errors and added a repertory of ailments and chakras and the Bach Remedy for each ailment. This is again taken from different sources. We have been able to conclusively connect the Chakras and the seven divisions of Bach Remedies. We have provided a story at the end of the book to better remember the remedies.

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Demystifying Model Based Testing walks you through the various methods of software/system testing and dwells on Model Based Testing. The talk is based on the experiences of testing Aerospace systems. The topics that will be touched up are equivalence testing, robust testing, combinatorial testing, random testing and non-real time testing. How do you automate testing, how do you optimize testing, how do you test to satisfy certification? These are some of the topics covered as part of this talk.

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This is a talk recorded by UPES University. I had given talk on Flight Controls to the students. With the Nation in a lockdown it was good to interact with the students and share my knowledge online. I am posting this here to enable more students to benefit from the talk.

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Talk on Safety at ESSS 2022

- Safety is important but it is a human perception.

- Traditional safety analysis relies on the human mind.

- We need simulations and formal methods to find corner cases that the human mind cannot fathom.

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This talk was one of my first talks on safety critical systems. In the year 2014. The challenges are still valid today. This was a keynote at the launch of the LDRA Academic Alliance Program.

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There have been many failures in safety-critical systems. When developers design and develop these systems, they do not look at the whole picture and therefore the emergent behavior of the system Is not captured. Small faults in design percolate down to the system of system boundary and these lead to failures, sometimes fatal. The talk describes some of these failures and advocates measures to be taken that could perhaps help improve the safety of the system being developed. It is very difficult to predict Nature but developing systems in this manner may improve the situation.

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A TechGig presentation. Safety critical control systems are found in aerospace, medicine, nuclear and automobiles today. Software drives these control systems and often fails due to errors. Lives and millions of dollars is lost due to these failures. Automation is the need of the day. Model based testing is extensively used to design and test these systems. This webinar takes the audience through the safety critical controls systems in various domains, a brief view of the standards used, the concept of model based testing, coverage metrics and test automation with randomization, orthogonal arrays, design of experiments, simulated annealing or genetic algorithms. The audience will get glimpse of what these topics are and what are the tips and tricks to be used in case they want to take up this activity in their organization or for personal growth.

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