From Chapter 12, answer the following questions: 1, 2, 3, 4, and 24.Describe each of the following:FMECAFTAFrom Chapter 13, answer the following questions: 1, 2, 3, 4 & 21.1212.1 define reliability wh
CS672 – System Engineering and Analysis
Discussion 6 - 11/9/2018
Samson Kamal Victor
Chapter 12, Question 1:
Reliability:
Reliability is an ability of software to run with minimum number of failure rate in the given period of time. The software failure may be some errors, uncertainty, and misinterpretation of initial system requirement. Software faults are the design faults of the system (Jiantao, 1999)
Characteristics:
Design faults cause
Errors may occur without warnings
Restart in certain time period will reduce the failure
Reliability of prediction is depend on the human design
Software interfaces are not visual or physical it is only conceptual
Software reliability is not operational time dependence but depend on number of successful operations
Based on the number of failure rate to predict the future system
Proper well designed framework can lead more reliable software
Chapter 12, Question 2:
System design:
The reliability in system design is very important to predict of failure, quantitative and qualitative reliability requirement of mean time between failure (MTBF) and meantime between maintenance (MTBM)
The reliability need to be checked in each stage of the lifecycle. In the conceptual design stage, preliminary design, detail design and development, production, operation and support. Complete weaved in development cycle
To extend the reliability in the system design then in the conceptual design stage must be done in detailed with the reliability requirements. If the reliability is analyzed properly then it would product may work for extend period of life time. The reliability analyses, evaluation prediction and the formal design review and approval
Chapter 12, Question 3:
Quantitative measure of reliability:
Understanding the nature of system thoroughly and the product metric help to measure the quantitative measure of software reliability. The size of the product can be measured using the line of code (LOC), also using the source line of code (SLOC) and thousand source line of code (KSLOC) with no comments, allows to understand the functionality and complexity of the code, the flow chart diagram will show simplified representation of code, testing of the code functionality and estimate the fault will make the product more reliable (Jiantao, 1999)
The quantitative measure of personal reliability can be measured based on the three factors over time (test-retest reliability) the intelligence of the personal in consistent across time. Internal consistency is represents the self esteem or good qualities of the personal and interact reliability of social skills and how they interaction with others (ReliabilityMeasurement, 2015)
The hardware system is physical device like sensor, controllers and actuators. The hardware reliability is required of time related model to check the physical device fail over time to avoid the physical faults
The quantitative measure of data reliability supported by the positivist or scientific paradigm that up of observable, measurable facts
Chapter 12, Question 4:
Failure rate:
The failure rate is necessary to be identified in the systems engineering to define the products usability duration. It is a mean value and probability of number of failure and total number of hours
Failure rate (λ) = number of failures / total operating hours
The mean time between failure (MTBF) provide the guidance for the system to minimize failures in the high quality system 1/ λ (David, n.d.)
Chapter 12, Question 24:
Sequential reliability testing:
Advantage: allow very low failure rates and doesn’t not allow very high failure rates in shorter time. Less testing time (GoogleBooks, n.d. Page. 301)
Disadvantage: The total test duration is undetermined and for the maximum duration must be planned before (GoogleBooks, n.d. Page. 301)
Failure mode effect and critical analysis (FMECA):
It is a bottom up approach to find the top level failure in the system. The top events cannot be identified by externally. The FMECA primary goal is to determine all the possible failure modes. It requires the intervention of both human and software (Murray, 2009)
Fault tree analysis (FTA):
It is a top down approach to find the lowest level failure in the system. FTA is a easiest and faster way of identifying the failure modes in the system and provide more focus on the engineering minds. It uses the graphical block diagram to visualize the failures (Murray, 2009)
Chapter 13, Question 1:
Maintainability:
Maintainability is a measure done at the stage of designing the system with the fact of down time required for the product, software development lifecycle cost, and support cost. Maintenance is the process of doing the action to solve the issue or problem occurred to maintain the system to run properly in regular basics for example: fault tree, optimize reliability allocation, cluster storage (Davood, 2016)
Chapter 13, Question 2:
System design for maintainability:
The importance of maintainability in system design is to reduce the costs involved in the building system design, safety, accuracy, maintenance within the system to improve the effectiveness and efficiency of maintenance. To design the maintainability the knowledge of operation and maintenance is must
The maintainability is done throughout system lifecycle like conceptual design phase to define all the necessary need for the system to run smooth and less maintenance cost, acquisition phase of well planned in requirement stage, operation and maintenance phase to monitoring and provide the system support and disposal phase logistics to ship the products (Davood, 2016)
Chapter 13, Question 3:
Quantitative measure of maintainability:
The measure of the maintainability must ensure that all the needs mentioned in the design phase are satisfied and all done by the quantitative measure. All the system need to consider the required parameter to measure. These parameters include mean time to repair (MTR), mean time between failures (MTBF), and scheduled maintenance frequencies factor (MFF), Maintenance labor hour (MLH) maintenance man-hours per operating hour and fault detection and isolation, and Maintenance elapsed time factor (METF)
Chapter 13, Question 4:
Mean time between failures (MTBF) represents the reliability measure of system and average failure of the system to operate in the total uptime (Adman, 2017)
MTBF = 1 / (number of failures / total operating hours)
Mean time between maintenance (MTBM) represents the maintenance hours between the another maintenance time to analyze the only the maintenance activity, maintenance can be scheduled or unscheduled
MTBM = 1 / (1/MTBM + 1/MTBM)
Mean tie between repairs (MTBR) represents the total repair time in hours. To understand the number of hour of failure in the system only for repair
MTBR = Total repair time / number of repair
Chapter 13, Question 21:
FMECA and RCM analysis:
Reliability centered maintenance (RCM) is systematic process the involved to develop the effectiveness, economy, focused and maintenance and other plans for the system. The main technique is the system check for the previous system process used for design, development and implementation and risk involved. The same would be carried out for evaluation of preventive maintenance in new system
The FMECA is the part of RCM process after adding the step five failure consequences then step one to four makes up the FMECA. The FMECA take the preventive measure from the RCM to justify the information of the system is reliable further or not, thus the RCM is integrate in the FMECA tools
References:
Adman K, (Jan 30 2017), “MTBF, MTTR & MTBM, Reliability metrics” https://www.linkedin.com/pulse/mtbf-mttr-mtbm-reliablility-metrics-mohamed-izzaldin-ahmed
David, (n.d.), “How to Calculate Failure Rates.”, https://sciencing.com/calculate-failure-rates-6403358.html
Davood M, (Jan 27 2016), “Maintainability Engineering”,
https://www.linkedin.com/pulse/maintainability-engineering-davood-mosaddar
Davood M, (Jan 27 2016), “Reliability and Maintainability Management Tasks in System Life Cycle”, https://www.linkedin.com/pulse/reliability-maintainability-management-tasks-system-life-mosaddar
GoogleBooks, (n.d.), “Reliability of Software Intensive Systems.”, https://books.google.com/books/about/Reliability_of_Software_Intensive_System.html?id=BONKLjwV7AoC
Jiantao P, (1999), “Software Reliability”, https://users.ece.cmu.edu/~koopman/des_s99/sw_reliability/
Murray S, (Sep 1 2009), “FMECA or FTA?” https://opsalacarte.com/fmeca-or-fta/
ReliabilityMeasurement, (Oct 13 2015), “Reliability and Validity of Measurement” https://opentextbc.ca/researchmethods/chapter/reliability-and-validity-of-measurement/
