scispace - formally typeset
Search or ask a question
Author

O. P. Gandhi

Bio: O. P. Gandhi is an academic researcher from Indian Institute of Technology Delhi. The author has contributed to research in topics: Markov chain & System model. The author has an hindex of 9, co-authored 17 publications receiving 151 citations.

Papers
More filters
Journal ArticleDOI
TL;DR: The suggested approach guides how to diagnose root causes of a fault and is not only helpful to maintenance personnel in effective diagnosis but also in guiding designers in development of reliable automobile systems, accident investigations of automobiles, etc.
Abstract: Fault diagnosis of automobile systems is critical, as it adds-up to repair and maintenance time. It is, therefore, desired to make it efficient and effective. One of the conventional approaches is to use the fault tree diagram. But this approach is inadequate with its implicit system structure. Structure of the system means system elements and their interrelations. To alleviate this limitation, a new approach is suggested wherein the structure is in-built, i.e. incorporated explicitly, through digraph modeling that employs a systems approach of graph theory. A system digraph is developed, considering relationships among input and output parameters of subsystems/components of the automobile system in normal and failed conditions. Fault tree of a failure symptom that represents abnormality or a breakdown of the automobile system is obtained from the system digraph. The novelty is extension of the structural approach to automobile systems using digraph model, which has been successfully applied to chemical and process systems. Step-by-step methodology of the structural approach is presented. Its two main two steps are Steps 1 and 2, i.e. ‘Development of Fault tree diagram’ and ‘Diagnosis of fault using the tree diagram’, respectively. The suggested approach is illustrated for hydraulic power steering, an automobile system that is fitted on all current automobiles and particularly, in special purpose vehicles like heavy-duty trucks, earthmovers, dumpers, etc. The suggested approach guides how to diagnose root causes of a fault. The approach is not only helpful to maintenance personnel in effective diagnosis but also in guiding designers in development of reliable automobile systems, accident investigations of automobiles, etc.

28 citations

Journal ArticleDOI
TL;DR: In this paper, the authors developed a semi-Markov process-based analytical approach that is faster and more accurate than the simulation approaches used in the existing software programs such as RAPTOR (ARNIC, Annapolis, MD), BlockSim (Reliasoft, Tucson, AZ), etc., for system availability analysis.
Abstract: The focus of this article is to develop a semi-Markov process-based analytical approach that is faster and more accurate than the simulation approaches used in the existing software programs such as RAPTOR (ARNIC, Annapolis, MD), BlockSim (Reliasoft, Tucson, AZ), etc., for system availability analysis. The steady-state solution of the semi-Markov process (SMP) model provides system availability. For mechanical systems and their components, the degradation rate increases with the aging process. A Weibull distribution for the time to failure is appropriate for such systems. The semi-Markov model does capture dependencies of the repairable system. A steady-state solution was obtained by a two-stage analytical approach, which was validated by Monte Carlo simulation.

28 citations

Journal ArticleDOI
TL;DR: This paper proposes an optimal PM interval for maintenance cost minimization of manufacturing systems under reliability constraint, which will minimize maintenance cost, while maintaining their lower bound reliability.
Abstract: Profit is a main objective of production units, and minimization of its maintenance cost will help to achieve it. But with no compromise with plant machinery reliability constraints. Manufacturing systems do require maintenance, but deferring it due to production constraints may increase its requirements, resulting in the increased cost. The experience shows that carrying out of the preventive maintenance (PM) helps in avoidance of catastrophic failures, but this needs to be optimized. An optimal PM interval will minimize maintenance cost, while maintaining their lower bound reliability. Most existing optimization models do not address this issue especially in the context of real life industries. Particle swarm optimization is an effective meta-heuristic technique and is extensively applied to find optimal solution for various engineering problems. In this paper, this is proposed for maintenance cost minimization of manufacturing systems under reliability constraint. An example is illustrated to demonstrate it.

27 citations

Journal ArticleDOI
TL;DR: This paper suggests a methodology for availability evaluation of manufacturing systems using Semi-Markov model, which considers variable failure or repair rates, and does assume Weibull distribution for variable failure times and lognormal for variable repair times.
Abstract: Availability is a key measure of performance of systems in general and manufacturing systems are no exception. The elements of complex manufacturing systems such as Computer Integrated Manufacturing CIM follow variable, i.e., decreasing or increasing failure and repair rates. This creates difficulty in their availability evaluation. Conventional methods, which predict availability based on past experience, are inadequate for such systems. Existing analytical or simulation methods provide inaccurate availability estimate as these assume constant failure and repair rates, which follow exponential distribution. To address this concern, this paper suggests a methodology for availability evaluation of manufacturing systems using Semi-Markov model, which considers variable failure or repair rates. This is carried out by first understanding the system structure by identifying its elements; subsystem, assembly and component at its hierarchical levels and subsequently identifying their states; failed, operating, etc. Based on this, Semi-Markov models are developed for each element at various hierarchical levels of the system. The unique feature of this approach is that it does assume Weibull distribution for variable failure times and lognormal for variable repair times. The developed models are solved using an analytical solution method to obtain steady-state probabilities of their states and hence, the system steady-state availability. The methodology is illustrated by means of a case study conducted on a Vertical Machining Center VMC that is used in an automotive production plant.

19 citations

Journal ArticleDOI
TL;DR: The developed SMP model is solved using two-stage analytical approach for steady-state availability analysis of the system and CBM interval is decided for maximizing system availability using Genetic Algorithm approach.
Abstract: Maintenance helps to extend equipment life by improving its condition and avoiding catastrophic failures. Appropriate model or mechanism is, thus, needed to quantify system availability vis-a-vis a given maintenance strategy, which will assist in decision-making for optimal utilization of maintenance resources. This paper deals with semi-Markov process (SMP) modeling for steady state availability analysis of mechanical systems that follow condition-based maintenance (CBM) and evaluation of optimal condition monitoring interval. The developed SMP model is solved using two-stage analytical approach for steady-state availability analysis of the system. Also, CBM interval is decided for maximizing system availability using Genetic Algorithm approach. The main contribution of the paper is in the form of a predictive tool for system availability that will help in deciding the optimum CBM policy. The proposed methodology is demonstrated for a centrifugal pump.

18 citations


Cited by
More filters
01 Apr 1996
TL;DR: Clark College's Mechatronics Technology (MTX) classes emphasize current concepts and technology by providing practical, hands-on experiences with the latest, industry standard equipment, in addition to the technical knowhow needed to maintain and repair equipment, the certificate and degree programs will help prepare students to think critically, function as a successful team member and communicate clearly too internal and external customers.
Abstract: Mechatronics Technology is a growing career field that deals with the integration of mechanical and electronic components managed by control systems. Mechatronics technicians troubleshoot, maintain and repair mechanical equipment controlled by electrical, electronic and computer systems. These types of systems are increasingly used in a wide variety of manufacturing and industrial settings. Clark College's Mechatronics Technology (MTX) classes emphasize current concepts and technology by providing practical, hands-on experiences with the latest, industry standard equipment. In addition to the technical knowhow needed to maintain and repair equipment, the certificate and degree programs will help prepare students to think critically, function as a successful team member and communicate clearly too internal and external customers.

251 citations

Book ChapterDOI
01 Jan 1997
TL;DR: In this article, the performance of a system is given in terms of the probabilities of complete or partial failure and the resulting economic and other consequences may be estimated, based on the calculated probabilities.
Abstract: The estimation of the reliability of a system is an important branch of performance engineering. As in most cases of attempting to predict the future, we can do so only in probabilistic terms. Just as in teletraffic studies, the precise behaviour of the system is dependent upon the behaviour of the individual users, so in estimating the reliability performance we are at the mercy of more or less random failures of the individual components. However, even though we cannot predict the precise time of failure of each component, it is useful to know the probabilities and consequences of component failure. The performance of the system is then given in terms of the probabilities of complete or partial failure and the resulting economic and other consequences may be estimated. Managerial judgement is required to decide then whether or not the reliability of the system is acceptable but at least decisions can be made in the light of the calculated probabilities.

92 citations

Journal ArticleDOI
TL;DR: Fault Detection and Diagnosis (FDD) is a well-studied area of research as discussed by the authors, where malfunction monitoring capabilities are instilled in the system for detection of the incipient faults and anticipation of their impact on the future behavior of the system using fault diagnosis techniques.
Abstract: Safety and reliability are absolutely important for modern sophisticated systems and technologies. Therefore, malfunction monitoring capabilities are instilled in the system for detection of the incipient faults and anticipation of their impact on the future behavior of the system using fault diagnosis techniques. In particular, state-of-the-art applications rely on the quick and efficient treatment of malfunctions within the equipment/system, resulting in increased production and reduced downtimes. This paper presents developments within Fault Detection and Diagnosis (FDD) methods and reviews of research work in this area. The review presents both traditional model-based and relatively new signal processing-based FDD approaches, with a special consideration paid to artificial intelligence-based FDD methods. Typical steps involved in the design and development of automatic FDD system, including system knowledge representation, data-acquisition and signal processing, fault classification, and maintenance related decision actions, are systematically presented to outline the present status of FDD. Future research trends, challenges and prospective solutions are also highlighted.

77 citations

Journal ArticleDOI
TL;DR: A new method based on the combination of the stochastic process method and the universal generating function technique is suggested to evaluate the instantaneous availability and the mean instantaneous performance deficiency of the proposed repairable MSS.

63 citations