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Viewing 1 to 30 of 4639
Technical Paper
2014-10-13
Chunshan Li, Guoying Chen, Changfu Zong
This paper presents a fault-tolerant control (FTC) approach for four-wheel independently driven and steered (4WID/4WIS) electric vehicles. An adaptive control-based passive fault-tolerant controller is designed to improve vehicle safety, performance and maneuverability when an actuator fault happens. The proposed fault tolerant control method consists of the following three parts: 1) a fault detection and diagnosis (FDD) module that monitors vehicle driving condition, detects and diagnoses actuator failures with the inequality constraints ; 2) a motion controller that computes the generalized forces/moments to track the desired vehicle motion using Model Predictive Control (MPC); 3) a reconfigurable control allocator that redistributes the generalized forces/moments to four wheels with equality constrained optimization. The FTC approach is based on the reconfigurable control allocation which reallocates the generalized forces/moments among healthy actuators once the actuator failures is detected.
Technical Paper
2014-09-30
Abhinav Tomar
The major emissions of diesel engines are oxides of nitrogen (NOx), particulate matter (PM), carbon dioxide (CO2), carbon monoxide (CO). Among these emissions, oxides of nitrogen (NOx) and the particulate matter are the reasons of serious concern. The usage of CNG in Dual fuel engine along with pilot diesel injection; the emissions have been decreased drastically. Homogeneous mixing of fuel and air leads to cleaner combustion and lower emissions. As peak temperatures are significantly lower than in typical CI engines, NOx levels are supposed to reduce significantly. The premixed lean mixture reduces soot particles. Dual fuel provides up to a 30% fuel saving, while meeting current emission standards along with higher efficiency and lower NVH levels compared to conventional CI engines within certain range of loads. A methodology using a small pilot quantity of diesel fuel injected during the compression stroke to improve the power density and operation control is carried out for an Dual fuel engine based on a stationary, water cooled truck engine.
Technical Paper
2014-09-30
Giorgio malaguti MD, Carlo Ferraresi, Luca Dariz, Massimiliano Ruggeri
Vehicle complexity is growing due to various factors: new functionalities, functional safety, hybridization, task management, etc. On the other hand both service centers need to up to date their competences and knowledge in newer vehicles, in order to efficiently repair and maintain new vehicles. Finally users of special machines, like military, agricultural, mining vehicles etc, need to be able to recover by faults or even repair the vehicles in critical conditions, in order to maintain the vehicle functionality, even in case of failure occurrence. Complex manuals don't provide the most efficient solution, while Augmented Reality represents a very promising technology both if applied to traditional smart-phones, and if applied to the newly glasses presented to the market. By now, this technology has been adopted mainly for games, and marketing purposes, such as tourist information. Instead, the paper deals with other ways in which AR can be extremely useful: AR has been used for two new topics, fast learning of simple procedures by low-skilled personnel and fault recovery or maintenance in hazardous environments or work places.
Technical Paper
2014-09-30
Mukunda Gopalakrishnan, Frederico Paulo Tischer
With growing concern about emissions of GHG (greenhouse gases) the use of natural gas as fuel has been seen as a very interesting alternative. Natural gas, whose main constituent is methane, due to its higher ratio of hydrogen / carbon and their higher content of energy generates about 22% less carbon dioxide (CO2) emissions compared to diesel considering the same combustion efficiency. To make use of this advantage in commercial vehicles there are many barriers to overcome: efficiency, drivability and legislation are some of them. According to tests conducted so far, the use of natural gas compression ignition (diesel cycle) allows the equivalent efficiency of a diesel engine maintaining the same torque and power curve. Controlling the torque in the dual fuel engine with diesel and CNG is an absolute necessity. This allows not only converting a required driver demand torque into actuator signal but also calculating if a change in operating point of any of the torque controlling factors is needed so that the driver demand can be immediately realized.
Technical Paper
2014-09-16
Marco Amrhein, Jason Wells, Eric Walters, Seana McNeal, Brett Jordan, Peter Lamm
Electrical power system components, such as electrical machines and power electronic converters, face many conditions that can have a detrimental impact on life and reliability [1] and are of a mechanical, electrical, and thermal nature. One specific aspect not discussed in detail in the literature concerning the reliability of such systems is the impact of changing electrical operating conditions (i.e., transient loading) on component life. Besides well-known power quality challenges, dynamic or transient loading in electrical power systems (EPS) can impact individual components connected to the EPS because of secondary effects associated with such transients [2]. Specifically, transient loads can cause additional loss in the electrical conduction path consisting of windings, power electronics devices, distribution wires, etc., particularly when loads introduce high peak vs. average power ratios. Additional loss contributes to heating of components and devices, which in turn decreases the life expectancy of power electronic devices, passive filtering components (capacitors and inductors), and wire and winding insulation systems.
Technical Paper
2014-09-16
Janice Meraglia, Mitchell Miller
As part of a comprehensive counterfeit mitigation effort, the Defense Logistics Agency (DLA) has created a program of four initiatives including the requirement of SigNature DNA marking on microcircuits. The Agency’s efforts began prior to the National Defense Authorization Act of Fiscal Year 2012, Section 818. Also, in the April 26, 2013 memo from Under Secretary Frank Kendall, the Office of Secretary of Defense is clearly focused on “prevention and early warning,” as the “primary” defense against counterfeits. SigNature DNA marking is within the spirit and guidance set forth by both DLA and OSD. Section 818 compels government action and creates real liability for contractors. Among other provisions, Section 818 requires the government and contractors to establish “…policies and procedures to eliminate counterfeit electronic parts from the defense supply chain” and “…mechanisms to enable traceability of parts.” SigNature® DNA provides per part forensic traceability and can be implemented as part of a comprehensive inventory management system.
Technical Paper
2014-09-16
Karl Strauss
“Today’s electronic components rely on principles of physics and science with no manufacturing precedence and little data on long term stability and reliability.” [1] Yet many are counting on their reliable performance years if not decades into the future, sometimes after being literally abandoned in barns or stored neatly in tightly sealed bags. What makes sense? To toss everything away, or use it as is and hope for the best? Surely there must be a middle ground! This paper discusses a three-phase initiative ultimately leading to the issuance of guidelines on the use of devices that have been subjected to long term storage, including recommended and required re-examinations based on Physics of Failure rather than fear and conjecture that is so prevalent today
Technical Paper
2014-05-10
Robert E Smith, Edward Lumsdaine
Since transient vehicle HVAC computational fluids (CFD) simulations take too long to solve in a production environment, the goal of this project is to automatically create a lumped-parameter flow network from a steady-state CFD that solves nearly instantaneously. The data mining algorithm k-means is implemented to automatically discover flow features and form the network (a reduced order model). The lumped-parameter network is implemented in the commercial thermal solver MuSES to then run as a fully transient simulation. Using this network a “localized heat transfer coefficient” is shown to be an improvement over existing techniques. Also, it was found that the use of the clustering created a new flow visualization technique. Finally, fixing clusters near equipment newly demonstrates a capability to track localized temperatures near specific objects (such as equipment in vehicles).
Technical Paper
2014-05-09
John O. Manyala
The emergence of tougher environmental legislations and ever increasing demand for increased ride comfort, fuel efficiency, and low emissions have triggered exploration and advances towards more efficient vehicle gearbox technologies. The growing complexity and spatial distribution of such a mechatronic gearbox demands precise timing and coordination of the embedded electronics, integrated sensors and actuators as well as excellent overall reliability. The increased gearbox distributed systems have seen an increased dependence on sensors for feedback control, predominantly relying on hardware redundancy for faults diagnosis. However, the conventional hardware redundancy has disadvantages due to increased costs, weight, volume, power requirements and failure rates. This paper presents a virtual position sensor-based Fault Detection, Isolation and Accommodation (FDIA), which generates an analytical redundancy for comparison against the actual sensor output. The proposed FDIA scheme has been validated experimentally using an electro-hydraulic test rig and the gearshift simulation model, including the non-linear hydraulic actuator dynamics.
Technical Paper
2014-05-09
John O. Manyala, Todd W. Fritz
Electro-hydraulic actuated systems are widely used in industrial applications due to high torque density, higher speeds and wide bandwidth operation. However, the complexities and the parametric uncertainties of the hydraulic actuated systems pose challenges in establishing analytical mathematical models. Unlike electro-mechanical and pneumatic systems, the nonlinear dynamics due to dead band, hysteresis, nonlinear pressure flow relations, leakages and friction affects the pressure sensitivity and flow gain by altering the system's transient response, which can introduce asymmetric oscillatory behavior and a lag in the system response. The parametric uncertainties make it imperative to have condition monitoring with in-built diagnostics capability. Timely faults detection and isolation can help mitigate catastrophic failures. This paper presents a signal-based fault diagnostic scheme for a gearbox hydraulic actuator leakage detection using the wavelet transform. The novelty of the work is the development of a high fidelity leakage fault detection as low as 0.128 lit/min.
Technical Paper
2014-04-28
Santosh Bhoomaraddi
Abstract The influence of embedded optical fibre on the strength and stiffness of flexurally loaded composite laminate is studied in this paper. In a given structure, different loads create a complex state of stresses in the structure. In-situ structural health monitoring of composite structures could be achieved by using embedded optical fiber as sensors. Modern OFS (Optical Fibre Sensors) are suitable for the measurement of temperature, pressure, strain, angular rotation, speed, acceleration, curvature, flow, refractive index, and many other parameters. The strength and fracture behaviour of the structure could be significantly affected by improper alignment and placement of optical fibres in the laminate. The utilization of embedded optical fibres for damage detection is accurate and reliable if the interaction between the optical fibre and the delamination is known. Despite their small size, compared to the typical diameter of the reinforcement fibres, the diameter of optical fibre is large enough to induce stress concentrations and geometric discontinuities in the structure.
Technical Paper
2014-04-01
Derek R. Braden, David M. Harvey
Abstract There is a continual growth of test and validation in high reliability product applications such as automotive, military and avionics. Principally this is driven by the increased use and complexity of electronic systems deployed in vehicles, in addition to end user reliability expectations. Higher reliability expectations consequently driving increased test durations. Furthermore product development cycles continue to reduce, resulting in less available time to perform accelerated life tests. The challenge for automotive electronic suppliers is performing life tests in a shorter period of time whilst reducing the overall associated costs of validation testing. In this paper, the application of prognostic and health monitoring techniques are examined and a novel approach to the validation and testing of automotive electronics proposed which it is suggested may be more cost effective and efficient than traditional testing. The holistic method explored in this paper fuses real time test data obtained during the monitoring of products throughout an environmental exposure with key factors from manufacturing and product design.
Technical Paper
2014-04-01
Antonino La Rocca, Gianluca Di Liberto, Paul Shayler, Christopher Parmenter, Mike Fay
The determination of size distribution of soot particles and agglomerates in oil samples using a Nanosight LM14 to perform Nanoparticle Tracking Analysis (NTA) is described. This is the first application of the technique to sizing soot-in-oil agglomerates and offers the advantages of relatively high rates of sample analysis and low cost compared to Transmission Electron Microscopy (TEM). Lubricating oil samples were drawn from the sump of automotive diesel engines run under a mix of light duty operating conditions. The oil samples were diluted with heptane before analysing. Results from NTA analysis were compared with the outputs of a more conventional analysis based on Dynamic Light Scattering (DLS). This work shows that soot-in-oil exists as agglomerates with average size of 115 nm. This is also in good agreement with TEM analysis carried out in a previous work. NTA can measure soot particles in polydisperse oil solutions and report the size distribution of soot-in-oil aggregates. NTA allows for an estimation of soot mass contained in the soot-laden oil samples.
Technical Paper
2014-04-01
Cosmin Emil Dumitrescu, Christopher Polonowski, Brian T. Fisher, A. S. (Ed) Cheng, Gregory K. Lilik, Charles J. Mueller
Natural luminosity (NL) and chemiluminescence (CL) imaging diagnostics are employed to investigate fuel-property effects on mixing-controlled combustion, using select research fuels-a #2 ultra-low sulfur emissions-certification diesel fuel (CF) and four of the Fuels for Advanced Combustion Engines (FACE) diesel fuels (F1, F2, F6, and F8)-that varied in cetane number (CN), distillation characteristics, and aromatic content. The experiments were performed in a single-cylinder heavy-duty optical compression-ignition (CI) engine at two injection pressures, three dilution levels, and constant start-of-combustion timing. If the experimental results are analyzed only in the context of the FACE fuel design parameters, CN had the largest effect on emissions and efficiency. Low-CN fuels had higher indicated specific nitrogen oxides (ISNOx) emissions, but up to 9 and 33 times lower smoke emissions, ∼ 0.01 filter smoke number (FSN), at 80 MPa and 180 MPa injection pressure, respectively, independent of intake oxygen concentration, relative to the high-CN fuels.
Technical Paper
2014-04-01
Gopal Athani, Prasad Yerraguntla, Anand Gajaraj, Kapil Dongare
Abstract Micro Hybrid Systems are a premier approach for improving fuel efficiency and reducing emissions, by improving the efficiency of electrical energy generation, storage, distribution and consumption, yet with lower costs associated with development and implementation. However, significant efforts are required while implementing micro hybrid systems, arising out of components like Intelligent Battery Sensor (IBS). IBS provides battery measurements and battery status, and in addition mission critical diagnostic data on a communication line to micro hybrid controller. However, this set of data from IBS is not available instantly after its initialization, as it enters into a lengthy learning phase, where it learns the battery parameters, before it gives the required data on the communication line. This learning period spans from 3 to 8 hours, until the IBS is fully functional and is capable of supporting the system functionalities. This scenario poses a great challenge to conduct the system performance checks at End of Line testing stations in assembly lines, and also in after sales service stations, as the battery data is not available, without which the micro hybrid systems cannot perform their full set of functions.
Technical Paper
2014-04-01
Youji Hiraoka, Katsunari Yamamoto, Tamotsu Murakami, Yoshiyuki Furukawa, Hiroyuki Sawada
Abstract The authors propose computerized support for Fault Tree Analysis (FTA) based on new knowledge management in product design. FTA is a method of analyzing and visualizing the causes of a fault event by Fault Tree diagram (FT diagram) that has a tree structure with logical step. Many methods of support for FTA are studied, but they are not effective for our FTA. We have developed the system of Computer-Aided FTA (FTAid) for design engineers by the collaborative research group (JATCO Ltd, The University of Tokyo and National Institute of Advanced Industrial Science and Technology). We reported this system in SAE2012 World Congress. After that, the knowledge management for FTA and new functions of this system have been studied continuously. In this paper we report that FT diagrams used FTAid improved to be useful for design engineers are analyzed based on individual qualification and skill of FTA, we study improvement of FTAid and the FTA education system.
Technical Paper
2014-04-01
Rasoul Salehi, Aria Alasty, Gholam-Reza Vossoughi
Proper operation of an internal combustion engine is required by demands of a vehicle driver and governmental legislations. Therefore it is necessary to monitor, within an online technique, the engine and detect any fault which disrupts its normal operation. In this paper, the air-charge path, as a key element in a turbocharged engine, is monitored for an air leakage fault. At first, a robust algorithm to estimate unmeasured turbocharger rotational speed is presented. The sliding mode methodology is used to design the estimator which is shown to be robust to the compressor modeling uncertainties. The estimation error from the sliding mode observer (SMO) is then used to detect abnormal behavior of the turbocharger along with the engine due to a leakage fault in the air-charge path. Experimental results from a modern turbocharged SI engine indicate the designed monitoring technique is able to detect a leakage fault, of 7 mm or higher sizes, in the air-charge path.
Technical Paper
2014-04-01
Rui Chen, Xinlei Wang
Abstract In this paper, a model-based diagnostic system was developed to detect and isolate the dosing fault and the outlet NOx sensor fault for the SCR system. The dosing fault is treated as an actuator additive fault, while the outlet NOx sensor drift and/or offset fault is treated as a sensor additive fault. First, a 0-D SCR model was developed to facilitate the model-based approach. A parity equation residual generator was designed based on the linearized SCR model and the fault transfer function matrix. The diagnostic algorithm is then implemented in the Matlab/Simulink environment for validation. A high fidelity nonlinear 1-D SCR model is used to generate system outputs and to simulate the plant. The simulation results show that the model-based fault diagnosis system succeeds in detecting and isolating the outlet NOx sensor and dosing faults with good sensitivity and robustness
Technical Paper
2014-04-01
Peter Subke
Abstract In the past, the automotive industry has learned the lesson that competition on the level of bits and bytes, proprietary bus systems, data communication and diagnostic protocols is unrewarding. Too much time and money has been spent on the development of proprietary diagnostic tools. Vehicle manufacturers and suppliers realized that standardization would be the best way to overcome this situation. Furthermore, regulatory requirements in the US and the EU for such standardization have strengthened this lesson. As a result, the automotive industry has standardized the technology for the communication of external test equipment with electronic control units (ECUs) in road vehicles. Standardization serves the price, the quality and the maintainability via scale and training curve effects. This paper contains a technical introduction of internationally standardized diagnostic protocols (UDS on CAN, WWH-OBD, UDSonIP and DoIP), the D-Server (MVCI) with D-Server API and D-PDU API, the diagnostic data format (ODX) and the open test sequence exchange format (OTX).
Technical Paper
2014-04-01
Olof Lindgarde, Rune Prytz
Abstract This paper presents an approach to fault detection and isolation that is based on off-board 1D simulation tools such as GT-power or AVL Boost. The proposed method enables engineers to develop diagnostic functions early on in a development project. The proposed algorithm is evaluated based on measurements from the air path system of the new Volvo FH truck. The results are encouraging. The paper discusses pros and cons of the method and concludes that it has clear potential to be used for on-board diagnostics.
Technical Paper
2014-04-01
Alex Beresnev, Max Beresnev
The article provides the rationale for, and describes a new internal combustion engine (ICE) diagnosing method, which involves obtaining a signal within the audio frequency range and its examination together with engine performance through the use of algorithms of high resolution time-and-frequency analysis and techniques involving partial signal reconstruction in the phase space. Examples of how the method may be applied to reveal defects and faults of various units and systems are also described in the article. The paper shows that the method may also be used for other assemblies and units of cars (apart from engines) to analyze patterns for periodic wave structures.
Technical Paper
2014-04-01
Håkan Warnquist, Mattias Nyberg, Jonas Biteus
When a truck or bus suffers from a breakdown it is important that the vehicle comes back on the road as soon as possible. In this paper we present a prototype diagnostic decision support system capable of automatically identifying possible causes of a failure and propose recommended actions on how to get the vehicle back on the road as cost efficiently as possible. This troubleshooting system is novel in the way it integrates the remote diagnosis with the workshop diagnosis when providing recommendations. To achieve this integration, a novel planning algorithm has been developed that enables the troubleshooting system to guide the different users (driver, help-desk operator, and mechanic) through the entire troubleshooting process. In this paper we formulate the problem of integrated remote and workshop troubleshooting and present a working prototype that has been implemented to demonstrate all parts of the troubleshooting system.
Technical Paper
2014-04-01
Johan Hult, Simon Matlok, Stefan Mayer
A combination of optical and laser based methods have been employed for simultaneously studying fuel jet penetration and ignition behaviour of fuel jets inside the cylinder of a large marine two-stroke diesel engine during operation. Tests were performed on a four-cylinder Diesel engine with a bore diameter of 0.5 meter. Optical access was obtained through a custom designed engine cover. A double pulsed laser was employed for global illumination of the liquid fuel jet. For detection a dual camera set-up was employed, which allowed both simultaneous fuel jet and flame emission imaging, or dual frame fuel jet imaging for velocity measurements. From the data recorded the liquid penetration, jet cone angle, jet penetration velocity, ignition location, ignition time and flame lift-off could be extracted. Data was recorded for two different charge densities and temperatures, for two different atomizer designs, and for two different fuels. The fuel jet was observed to ignite at a position around 1/4 of the length downstream.
Technical Paper
2013-11-27
Rajesha Kundrukote
A vehicle electronic control unit consists of various high side power stages for driving different loads. Common faults such power stages experience are Short Circuit to Battery (SCB), Short Circuit to Ground (SCG) and Open Load (OL). These faults can occur during either on-state or off-state of power stage output. It is essential to diagnose a fault such as SCB during switch off-state, SCG during switch on-state and OL during both on and off-state of the switch in order to avoid system malfunction, power-stage damage etc. A high-side power-stage mainly consists of a switching power MOSFET and its driver section. Quite often the semiconductor manufacturers provide diagnostic information through a digital status (ST) output. A logic low level on the ST pin indicates a fault. The limitation the ST signal is its inability to distinguish faults SCG, SCB and OL. For high-side switches (HSS), to overcome these drawbacks, there is a need of proper diagnosing technique. The diagnosis technique should address i Detect a fault of power stage.ii Clearly distinguish the kind of fault.
Technical Paper
2013-10-14
Chao Liu, Changfu Zong, Lei He, Chunshan Li, Minghui Liu
A fault detection and diagnosis (FDD) algorithm of 4WID/4WIS Electric Vehicles has been proposed in this study aiming to find the actuator faults. The 4WID/4WIS EV is one of the promising architectures for electric vehicle designs which is driven independently by four in-wheel motors and steered independently by four steering motors. The 4WID/4WIS EVs have many potential abilities in advanced vehicle control technologies, but diagnosis and accommodation of the actuator faults becomes a significant issue. The proposed FDD approach is an important part of the active fault tolerant control (AFTC) algorithm. The main objective of the FDD approach is to monitor vehicle states, find the faulty driving motor and then feedback fault information to the controller which would adopt appropriate control laws to accommodate the post-fault vehicle control system. The unique character of the proposed FDD approach is that it is a system-level method, namely it tries to locate the faulty motor and motor driver systems, while it does not need to identify which part of the motor and motor driver systems has a failure.
Technical Paper
2013-10-07
Fernanda Meneses Kelly, Helaine Maria Braga Sbampato
On cab-over trucks to access the engine and others components it is necessary to tilt the cab. This is a regular procedure done several times during the vehicle life cycle. In order to make it easier and safer for mechanical tilting system, it was developed an articulated safety bar to sustain and maintain the cab on the open position. On the current bars available in the market, to close the cab it is necessary that the operator get under the cab to disengage the safety bar. This procedure puts the operator under risk because an accident can happen while the disengagement and the cab can close over him. Thinking on that and looking for a better ergonomic and safety situation, the objective of this work is to present a new articulated safety bar that the engagement and disengagement is done automatically with the natural tilting movement of the cab. This solution was developed at Iveco Latin America for adoption on the new Vertis HD and is under patent process.
Technical Paper
2013-10-07
Hélio Rocha Pegorer, João Vilan Júnior, Max Mauro Dias Santos
The increasing application of embedded electronic components in vehicles brings the need to use diagnostic systems for track and control of parameters. Development, manufacturing and after-sales are all fields that use diagnostic systems' help to execute their tasks. Applying communication protocols such as KWP2000, SAEJ1939/73 and UDS makes diagnostic device and automotive network communicate to each other according to standards. This work aims to present an overview about a few communication protocols for diagnostic and services, by showing their specific tools and applications.
Technical Paper
2013-09-24
Arnold Taube, Michael Mercier
Adoption of a new Electronic Systems Computer-Aided Design (ECAD) system for modeling electrical systems design by Product Engineering offers the promise of improved accuracy and productivity for Service Publication's authors to create wiring diagrams and to standardize their format; while improving the comprehension and functionality of those documents for service technicians. It is also potentially disruptive, requiring new workflows, processes, standards and lines of communication to be developed. This paper describes how to structure and organize a project for effectively and efficiently bringing a new ECAD system for modeling electrical system design into Service Publications. It also provides insight into some lessons learned.
Technical Paper
2013-09-24
Tomi Krogerus, Mika Hyvönen, Kalevi Huhtala
In this paper, the operating states of a wheel loader were studied for diagnostics purposes using a real time simulation model of an articulated-frame-steered wheel loader. Test drives were carried out to obtain measurement data, which were then analyzed. The measured time series data were analyzed to find the sequences of operating states using two different data sets, namely the variables of hydrostatic transmission and working hydraulics. A time series is defined as a collection of observations made sequentially in time. In our proposed method, the time series data were first segmented to find operating states. One or more segments build up an operating state. A state is defined as a combination of the patterns of the selected variables. The segments were then clustered and classified. The operating states were further analyzed using the quantization error method to detect anomalies. The recognized operating states define the operation of the machine so the analysis can be focused on specific sections and situations in time series and to identify which kinds of operating situations generate anomalies.
Technical Paper
2013-09-20
Shawki Abouel-Seoud, Mohamed Khalil, Sameh Metwalley, Essam Allam, Hany Assad
Reliability has always been an important aspect in the assessment of industrial products and/or equipments. Good product design is of course essential for products with high reliability. However, no matter how good the product design is, products deteriorate over time since they are operating under certain stress or load in the real environment, often involving randomness. Maintenance has, thus, been introduced as an efficient way to assure a satisfactory level of reliability during the useful life of a physical asset. The earliest maintenance technique is basically breakdown maintenance (also called unplanned maintenance, or run-to-failure maintenance), which takes place only at breakdowns. A later maintenance technique is time-based preventive maintenance (also called planned maintenance), which sets a periodic interval to perform preventive maintenance regardless of the health status of a physical asset. The vehicle component is judged to be safe depending on its reliability. Consequently, there is a general attention to establish approach by which the failure risk has to be known.
Viewing 1 to 30 of 4639