Browse Topic: Bus systems
This bus doesn’t use wheels to move around, but a CubeSat can’t get anywhere without it. In the world of these small, standardized, inexpensive satellites, a “bus” refers to the hardware foundation that provides it with power, communications, thermal stability, and other “services” a payload needs to function. Whether enabling data transfer for internet-enabled appliances, such as thermostats and refrigerators or tracking weather conditions, CubeSats continue to mature and support everyday services
The bus sector is currently lagging behind when it comes to implementing autonomous systems for improved vehicle safety. However, in cities such as London, public transport strategies are changing, with requirements being made for advanced driver-assistance systems (ADAS) on buses. This study discusses the adoption of ADAS systems within the bus sector. A review of the on-road ADAS bus trials shows that passive forward collision warning (FCW) and intelligent speed assistance (ISA) systems have been successful in reducing the number of imminent pedestrian/vehicle collision events and improving speed limit compliance, respectively. Bus accident statistics for Great Britain have shown that pedestrians account for 82% of all fatalities, with three quarters occurring with frontal bus impacts. These statistics suggest that the bus forward collision warning system is a priority for inclusion in future vehicles to enhance the driver’s direct vision, and to increase reaction time for earlier
Growing environmental concerns and stringent vehicle emissions regulations has created an urge in the automotive industry to move towards electrified propulsion systems. Reducing and eliminating the emission from public transportation vehicles plays a major role in contributing towards lowering the emission level. Battery electric buses are regarded as a type of promising green mass transportation as they provide the advantage of less greenhouse gas emissions per passenger. However, the electric bus faces a problem of limited range and is not able to drive throughout the day without being recharged. This research studies a public bus transit system example which servicing the city of Ann Arbor in Michigan and investigates the impact of different electrification levels on the final CO2 reduction. Utilizing models of a conventional diesel, hybrid electric, and battery electric bus, the CO2 emission for each type of transportation bus is estimated. Vehicle speed data collected from
This document defines requirements for digital, command/ response time division multiplexing (data bus) techniques for fiber optic implementation. The concept of operation and information flow on the multiplex data bus and the functional formats to be employed are also defined
The scope of this SAE Aerospace Information Report (AIR) is to present a guide for the determination of probable power output and the effect on the aircraft system that will be experienced when operating three-phase motors with one phase open. Unfortunately, the above subject cannot be resolved by specific rules. Modern aircraft or missile electrical systems are composed of a wide variety of electrical and electronic components. These components react differently under identical impetus due to the latitude of their design. This latitude of design must be allowed wherever possible to the accessory designer due to the various specification requirements. Therefore, it cannot be over-emphasized that the effect on the airplane or missile system, as well as motor operation, of three-phase motors on two-phase power must be thoroughly investigated
This test plan consists of two major sections for testing of MIL-STD-1553B data bus systems: Bus Network and System Integration Tests
In-vehicle networks (IVN) have been standardized from the beginning. The story of IVN standardization started at the beginning of the 90s. Today, several IVN technologies have been internationally standardized by ISO (International Organization for Standardization) including the related conformance test plans. But as all electronic technologies, IVNs are a matter of improvement and change due to new requirements and gained experiences. This makes it difficult to always keep the standard backwards compatible, in particular if immature approaches are submitted. Furthermore, new communication protocols are knocking on the door of international standardization bodies. The automotive industry itself is conservative and adapts new IVNs slowly. There are also concerns regarding too many different bus systems and networks in one vehicle. This paper discusses the benefits and challenges of the standardization of IVNs
This SAE Aerospace Standard (AS) contains requirements for a digital time division command/response multiplex data bus, for use in systems integration, that is functionally equivalent to MIL-STD-1553B with Notice 2. Even with the use of this document, differences may exist between multiplex data buses in different system applications due to particular application requirements and the options allowed in this document. The system designer must recognize this fact and design the multiplex bus controller (BC) hardware and software to accommodate such differences. These designer selected options must exist to allow the necessary flexibility in the design of specific multiplex systems in order to provide for the control mechanism, architectural redundancy, degradation concept, and traffic patterns peculiar to the specific application requirements
This Recommended Practice covers air braked trucks, truck-tractors, trailers and buses. It enumerates the identification and installation of the air brake components not covered in other SAE recommended practices and standards
Public transport has been considered the preferred strategy to reduce congestion and pollution from urban road traffic. For low to medium capacity, bus systems are considered the most affordable and flexible mode. Currently, diesel based systems still dominate transit bus market, due to their high productivity, low deployment costs, technological maturity, operational reliability and flexibility (high daily ranges, fast refuelling and no infrastructure requirement along the routes). However, although some important improvements in engine technology and aftertreatment devices, enforced by emission standards improvements (Euro VI, US 2010 and those related), have been achieved, it is well known that there is a limit to cleaning exhaust diesel buses exhaust. In this context, transit authorities and operators have been under pressure to shift for more environmental friendly technologies. Electric traction meet deserved operational and environmental features, with its high motor efficiency
This document contains guidance for using SAE publications, AS4112 through AS4117 (MIL-STD-1553 related Test Plans). Included herein are the referenced test plan paragraphs numbers and titles, the purpose of the test, the associated MIL-STD-1553 paragraph, commentary concerning test methods and rationale, and instrumentation requirements
The way to autonomous driving is closely connected to the capability of verifying and validating Advanced Driver Assistance Systems (ADAS), as it is one of the main challenges to achieve secure, reliable and thereby socially accepted self-driving cars. Hardware-in-the-Loop (HiL) based testing methods offer the great advantage of validating components and systems in an early stage of the development cycle, and they are established in automotive industry. When validating ADAS using HiL test benches, engineers face different barriers and conceptual difficulties: How to pipe simulated signals into multiple sensors including radar, ultrasonic, video, or lidar? How to combine classical physical simulations, e.g. vehicle dynamics, with sophisticated three-dimensional, GPU-based environmental simulations? In this article, we present current approaches of how to master these challenges and provide guidance by showing the advantages and drawbacks of each approach. Therefore, we discuss different
Urban Mobility is one of the most critical issues at the present. Public transport in connection with feeder bus system is proposed to be one of the main solution. Chulalongkorn University has a fleet of electric feeder bus in operation for a few years now. The fleet service is, however, to be improved because of current limitations in battery energy capacity and long battery charging time. This paper aims to examine the total cost of ownership (TCO) of the electric feeder buses using various types of energy storage. The results on the sensitivity analysis highlight the major parameters that exert strong influence in the TCOs. The fast charging system using supercapacitor battery bus shows the lowest TCO for the present bus fleet. The travel distance (km/year) and operational years were illustrated to be the top two parameters that exert major influence towards the TCO
Current massive urbanization process concentrates high amount of population and impose an increased demand on transport systems. In this context, transit bus system plays an important role, as the most dynamic and less capital intensive transit option available. At the same time, it is strongly dependant on fossil fuels, predominantly diesel fuel, with its intrinsic polluting and greenhouse (climate change) effects. This has boosted research and investments for alternative and renewable fuels. One solution currently receiving widespread recognition is biogas use in transit bus fleets, as it allows the use of a renewable fuel, made from substrates derived basically from waste and sewage that otherwise would produce methane released to the atmosphere. Biogas contains basically methane, carbon dioxide, trace amounts of hydrogen sulfides and water, and to be used as engine fuel need to be upgraded, which means increasing the methane content up to 97% and removing water and other gases
The growing concentration of population in world metropolis caused by increasing urbanization rates has pushed the demand for high capacity and efficient public transport systems. At the same time, environmental concerns have led to increasingly stricter emission standards. In this context, transit authorities have become strongly focused on making their bus fleets more efficient and cleaner, by incorporating new alternative fuels and clean propulsion technologies. This has led to increased interest in electric driven technologies, with their intrinsic efficient, quiet and environment friendly features. Trolleybuses, a well proven mature electric technology already adopted in some cities, although efficient and clean, are burdened by high infrastructure costs and operational inflexibility. Hydrogen fuel cell buses, an infant technology, currently on a precommercial status, still presents some hurdles on hardware durability and hydrogen supply, which need to be surpassed before reach
Today, the Controller Area Network (CAN) is a widely used in-vehicle network. However, due to the constraint of the theoretical upper bound speed of CAN, we proposed Scalable-CAN (SCAN), which employs round-robin scheduling to improve upper bound speed while keeping the compatibility with traditional CAN. Moreover, we proposed the worst-case response time (WCRT) analysis for a single SCAN bus system and showed the real-time performance. In this paper, to apply SCAN to a next-generation in-vehicle network composed of a SCAN bus and a CAN bus, we first propose a schedulability analysis method for the integrated network system. Second, we show its real-time performance and highlight the effects of the bandwidth extension and throughput performance of the SCAN integrated system. Finally, we conclude that SCAN achieves lower latency, high schedulability, and high integrity toward a next-generation in-vehicle network
This paper describes a study on electrical power management for the More Electric Aircraft (or MEA) and the More Electric Engine (or MEE). This study explored power management solutions based on an integrated engine/power control system and a permanent magnet motor. In recent years, electrical power management has emerged as a key aspect of aircraft system design. In cases in which the Electromechanical Actuator (or EMA) systems are used for flight control, the power bus systems must also be designed to dissipate the power regenerated from flight control systems. In their study, the authors focused on achieving an optimal balance between aircraft power management and operational requirements of the aero-engines. The study results suggest an effective and novel power control concept based on integrated engine control technologies that ensure stable power systems
This document is intended to explain, in detail, the rationale behind the features and functions of the AS4074, Linear, Token-passing, Bus (LTPB). The discussions also address the considerations which a system designer should take into account when designing a system using this bus. Other information can be found in these related documents: AIR4271 - Handbook of System Data Communication AS4290 - Validation Test Plan for AS4074
The increasing number of electronic control units (ECUs) in vehicles leads to more and more complex systems with a steadily growing demand for data exchange. This growth includes the number of bus participants, the amount of data and hence the data transfer rates. In addition, the trend towards car-to-x connectivity reinforces the need for new in-vehicle communication solutions. Since the early 1990s Controller Area Network (CAN) is the most widely used powertrain bus system. Since 2000 FlexRay is used in addition to CAN in the premium segment. For classic powertrain applications, the data transfer rates of these bus systems are sufficient; however the utilization is sometimes difficult and gateways are often required. For new applications like hybrid and electric vehicles and the next generation of external communication applications (e.g. telematics services) new concepts based on the existing bus systems or completely new solutions are needed. Looking outside of automotive business
This test plan consists of two major sections for testing of MIL-STD-1553B data bus systems: Bus Network and System Integration Tests
This SAE Aerospace Standard (AS) contains requirements for a digital time division command/response multiplex data bus, for use in systems integration, that is functionally equivalent to MIL-STD-1553B with Notice 2. Even with the use of this document, differences may exist between multiplex data buses in different system applications due to particular application requirements and the options allowed in this document. The system designer must recognize this fact and design the multiplex bus controller (BC) hardware and software to accommodate such differences. These designer selected options must exist to allow the necessary flexibility in the design of specific multiplex systems in order to provide for the control mechanism, architectural redundancy, degradation concept, and traffic patterns peculiar to the specific application requirements
The increasing demand for urban mobility, combined with the constriction of investment capacity of transit authorities and private companies make bus based systems a great option for public transport systems, since they allow the provision of high quality services at a fraction of the costs of rail based systems. In this scenario, Bus Transit System - BTS and Bus Rapid Transit - BRT allow the implementation of transport networks at considerably lower costs than their rail system counterparts. This is specially true to developing-nation cities, that have infrastructure costs as a pre-eminent decision-making factor in technology selection. From an environmental perspective, traction technology and fuel option are decisive to define systems' performance. Unlike rail based systems, that are generally electrified, bus based systems allow the use of a variety of traction options, like Diesel and Otto engines, Trolleybus, Hybrid (Diesel-Electric) and Fuel Cell Engine as well as fuels, like
This Recommended Practice covers air braked trucks, truck-tractors, trailers and buses. It enumerates the identification and installation of the air brake components not covered in other SAE recommended practices and standards
Public transportation system and specifically transit bus systems are key element of the national transportation network in United States. Buses are one of the safest forms of transportation. Nonetheless, bus crashes resulting in operator injuries and fatalities do occur. According to National Transportation Statistics from 1990-2002, the number of transit motor buses in the U.S. has increased by 30% [1]. The majority of fatal crashes involving transit buses result from frontal crashes which could be fatal for bus operators. Therefore, crashworthiness research is a continuing effort. Research has been performed to analyze and improve the safety of transit bus operators. This paper describes the design, analysis and testing of an inflatable restraint system for a bus operator. At present a three point restraint is the only safety feature implemented on transit buses. The primary objective was to study the level of safety provided by the present safety system. To do this a physical
The scope of this SAE Aerospace Information Report (AIR) is to present a guide for the determination of probable power output and the effect on the aircraft system that will be experienced when operating three-phase motors with one phase open. Unfortunately, the above subject cannot be resolved by specific rules. Modern aircraft or missile electrical systems are composed of a wide variety of electrical and electronic components. These components react differently under identical impetus due to the latitude of their design. This latitude of design must be allowed wherever possible to the accessory designer due to the various specification requirements. Therefore, it cannot be over-emphasized that the effect on the airplane or missile system, as well as motor operation, of three-phase motors on two-phase power must be thoroughly investigated
This document defines requirements for digital, command/ response time division multiplexing (data bus) techniques for fiber optic implementation. The concept of operation and information flow on the multiplex data bus and the functional formats to be employed are also defined
The task-specific nature of an embedded system application typically defines a narrow scope of performance requirements. But the range of options for achieving those requirements are broad — from multicore processors and rugged single board computers (SBCs) to I/O devices and the bus systems that tie everything together. And the choices to be made are critical in their impact on cost, on performance efficiency in compute-intensive operations, and on the ability to function reliably in hot, cold, dusty or wet environments
Bus systems like CAN or FlexRay allowed great advances in automotive electronics over the last 20 years. In order to function in an environment which requires the communication medium to tolerate one safety-relevant fault, these bus systems require a second, redundant bus to act as a backup for the original unit. With the network approach presented in this paper (SafeNet) it is possible to use the network intrinsic redundancy to keep the network fail-safe after at least one safety relevant fault in the network. To ensure this, messages are relayed to every node in the network. Even though the message delivery times in the network are not deterministic, it is shown that it is suitable for safety-relevant applications like drive-by-wire. Due to the simple point-to-point connections used to connect the nodes, high speeds can be achieved. The network approach is compared to both CAN and FlexRay under different aspects
This paper presents model-based predictions of the performance of diesel, compressed natural gas (CNG), and hybrid buses on bus routes in the City of San Francisco. The bus route details were obtained by recording time-series measurements of speed and grade during actual runs of buses on the city streets under different traffic conditions. The transit buses' physical and mechanical characteristics were obtained from manufacturers' data and chassis dynamometer testing of the buses on different city cycles. Both the bus routes and the bus performance characteristics were put into the simulation package ADVISOR from the National Renewal Energy Laboratory (NREL). The most extreme results were for the San Francisco routes that have high grades. The high grades cause performance and emissions problems for both the diesel and CNG buses relative to the hybrid bus. A large portion of the performance and emissions problems can be directly related to the hydraulic torque converter that is
SAE 100 Future look: In the early 1970s the foundations of what is now MTS Sensors began with the development of magnetostrictive technology and its application in industrial position-sensing applications. Much has been written about the adoption and benefits of electrohydraulic systems in off-highway vehicles, and an equal amount of attention has been given to the sensor technologies needed to effectively complete those systems. In many cases, these sensors are inherently “behind the scenes,” both technologically and economically. All the same, the advancements in both technology and economics are helping to transform off-highway vehicles-and the pace of change is accelerating. In the early 1970s the foundations of what is now MTS Sensors began with the development of magnetostrictive technology and its application in industrial position-sensing applications. These sensors are still known as Temposonics, and although the fundamental principle of the sensing technology has not changed
This document is intended to explain, in detail, the rationale behind the features and functions of the AS4074, Linear, Token-passing, Bus (LTPB). The discussions also address the considerations which a system designer should take into account when designing a system using this bus. Other information can be found in these related documents
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