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Design and Development of Different Regenerative Braking Systems for a Commercial Electric Bus

Delhi Technological University-Lalit Kumar Choudhary, Kunal Mathur, Aditya Natu
  • Technical Paper
  • 2019-24-0208
To be published on 2019-08-15 by SAE International in United States
In today’s world, energy saving has become a crucial need for day to day operations. It is because of this need for development and enhancement of energy efficient technology, various industries and organizations are researching on ways to improve the energy savings, which would not only be holistic but also increase their own brand value in the market. A similar such method that can have an immense positive impact on conservation of energy is “Regenerative Braking”, which is now being implemented by various OEMs. With the help of this concept, a decelerating vehicle’s kinetic energy is harvested and stored for utilization at a later stage; instead of dissipating this useful energy as heat such as in the conventional braking system. Such a concept of extracting and storing energy can be utilized by the emerging electric vehicles to generate electric current that can be used for recharging the battery, powering the onboard appliances and increasing the range of these vehicles. The following paper describes the detailed study of a unique flywheel based regenerative braking system (f-RBS)…

Advanced Driver-Assistance Systems for City Bus Applications

Kowloon Motor Bus Co-Chun Yi Lo
Queen's Univ of Belfast-Roy Douglas
  • Technical Paper
  • 2019-24-0067
To be published on 2019-08-15 by SAE International in United States
In 2017 there were over 1,700 fatalities on Great Britain roads, with almost 25,000 people seriously injured. With vehicle miles increasing each year it is important that there is improved on-road safety, both for passenger cars and for public transport. Nowadays, advanced driver-assistance systems (ADAS) are widely utilised, with the EU Commission mandating ADAS such as autonomous emergency braking (AEB), lane-keeping assistance and reversing cameras on all new cars from 2021. Transport for London have introduced the Bus Safety Standard, within which is the requirement for ADAS systems, many of which are due to become mandatory from 2021. Bus operators such as KMB in Hong Kong have also put an additional focus on bus safety due to concerns with casualty rates. This study uses statistical analysis of bus accidents that have occurred across Great Britain in order to determine which ADAS technologies will result in the largest reduction of potential bus accidents. It discusses the technologies available for bus applications and compares those that are appropriate with those utilised on cars. Police reported traffic accident…

Analyzing Field Environments to Understand Product Failure Causes

Vibration Research-Jade Vande Kamp
Published 2019-06-05 by SAE International in United States
Product failures often require expensive repairs or replacements. Over-engineering adds to recurring costs and its success is uncertain if the failure’s cause is not understood. Engineers need in-depth knowledge before attempting a re-design. This case study focuses on bus seat failures that occasionally occur in the field but are not predicted by current industry standard tests in the lab. The goal was to collect comprehensive field vibration data and analyze that data to understand the failure’s causes. The study used accelerometers placed at various points in multiple seating configurations and across multiple field environments. Analysis identified transmissibility issues between axes of motion, as well as a seat configuration with higher reliability.
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Service Brake Structural Integrity Requirements—Truck and Bus

Truck and Bus Foundation Brake Committee
  • Ground Vehicle Standard
  • J1404_201904
  • Current
Published 2019-04-24 by SAE International in United States
This SAE Recommended Practice presents requirements for the structural integrity of the brake system of all new trucks, buses, and combinations of vehicles designed for roadway use and falling into the following classifications: a Truck and Bus—Over 4500 kg (10 000 lb) GVWR b Combination Vehicles—Towing vehicle over 4500 kg (10 000 lb) GVWR The requirements are based on data obtained from SAE J294.
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Acceleration Testing of 2000 Van Hool 45 Foot Motor Coach

Collision Engineering Associates Inc.-Wesley Grimes, Jonathan Balasa
Wilcoxson Consulting LLC-Greg Wilcoxson
Published 2019-04-02 by SAE International in United States
The time/distance relationship for a motor coach accelerating from a stop is often needed to accurately assess the events leading up to a collision. Several series of tests were conducted to document the low speed acceleration performance of a 45 foot long 2000 Van Hool motor coach equipped with a Cummins ISM engine and an Allison B500 6-speed automatic transmission. These tests included three load configurations and two different acceleration rates, normal and rapid. Data were gathered with a Racelogic VBOX IIIi.
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Pure Electric Vehicles Simulation Using Powertrain Energy Estimator Tool

IAV Automotive Engineering Inc.-Salem Al-Assadi, Jason McConnell
  • Technical Paper
  • 2019-01-0367
Published 2019-04-02 by SAE International in United States
This paper describes first, the use of Powertrain Energy Estimator (PEE) tool to simulate and analyze the performance of the Pure Electric Vehicles (PEV’s) with all the powertrain components. The PEE uses basic physics calculations and measured components performance with the available vehicle parameters to model and simulate any conceptual PEV. The tool calculates the predicted torques, speeds, voltages, efficiency and power passed from one component to another then saves all the simulation results in a database for further user’s analysis. Secondly, we present a methodology to estimate the maximum power capacity required for PEV driving electric machine (E-Motor). The estimation approach is based on creating a power map, which combines the contour lines for all power levels over vehicle speeds/road climbing grades required for the PEV powertrain driving component (E-Motor) to meet all the vehicle’s performance requirements. The evaluation of the power map uses the vehicle’s specifications and performance requirements. The performance requirements are mainly cover the maximum vehicle speed, acceleration time and road climbing grade.Two types of PEV platform applications are considered in…
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Noise Source Identification of the Electric Bus Powertrain Using a Wavelet Transform and EEMD-RobustICA

CATARC Co., Ltd.-Hanzhengnan Yu
Hebei University of Technology-Changyin Wei, Jingang Wang, Yong Chen, Hai Liu, Kunqi Ma
Published 2019-04-02 by SAE International in United States
Electric buses have been used widely as cities' short-range commuter vehicles, because of their excellent power, fuel economy and emission characteristics. However, the lack of a noise masking effect for the traditional internal combustion engine, the high-frequency noise becomes more prominent for the powertrain system. The high-frequency noise gives people an unpleasant feeling on psychological and physiological. To control electric vehicle powertrain noise, the identification of the main noise source of the powertrain is well needed. In this paper, Empirical Mode decomposition (EMD) combined with Independent component Analysis (ICA) and continuous Wavelet transform (CWT) was used to identify the main noise source of the electric bus powertrain. The contribution of each noise source to the overall noise level was calculated and compared. The results showed that there were four main noise sources of the electric bus powertrain: the engagement noise of the shifting gear and constant-mesh gear, cogging harmonic noise and switching frequency noise. The contribution of the shifting gear engagement noise was the greatest, followed by the constant-mesh gear engagement noise, and the contributions…
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Combined Sizing and EMS Optimization of Fuel-Cell Hybrid Powertrains for Commercial Vehicles

AVL Powertrain UK Ltd.-Tommi Jokela, Athanasios Iraklis, Bill Kim, Bo Gao
Published 2019-04-02 by SAE International in United States
During the last years, fuel-cell-based powertrains have been attracting a lot of attention from commercial vehicle manufacturers for reducing vehicle-related Greenhouse Gas (GHG) emissions. Compared to Battery-Electric Vehicles (BEV), fuel-cell-based powertrains has the strong advantage of dealing with range-anxiety, which is crucial for commercial vehicle with high duty-cycle energy requirements. Amongst the different fuel-cell types, Proton Exchange Membrane Fuel-Cells (PEMFC) have the greatest potential for utilization in automotive applications, due to their relatively high technical readiness, market availability and utilization of hydrogen (H2) fuel. In addition, Solid Oxide Fuel-Cells (SOFC) show good potential due to existing re-fueling infrastructure for light hydrocarbon fuels or heavier hydrocarbon fuels (e.g. diesel). This study focuses on the application of both PEMFCs and diesel-fueled SOFCs in Fuel-Cell Hybrid Electric Vehicle (FCHEV) architectures for commercial vehicles. Delivery vans in the 2.5 t-3.5 t weight range, coach buses and 3-axle tractor-type long-haul trucks are considered energy-driven types and highly suitable for fuel-cell systems, which offer high energy density values. Due to the high number of vehicle application types and system configurations, and…
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Modelling and Control of a Hybrid Urban Bus

Queen's University Belfast-Martin Murtagh, Juliana Early, Gary Stevens, Geoffrey Cunningham, Roy Douglas
Wrightbus-Robert Best
  • Technical Paper
  • 2019-01-0354
Published 2019-04-02 by SAE International in United States
This paper describes the development and on-vehicle validation testing of next generation parallel hybrid electric powertrain technology for use in urban buses. A forward-facing MATLAB/Simulink powertrain model was used to develop a rule-based deterministic control system for a post-transmission parallel hybrid urban bus. The control strategy targeted areas where conventional powertrains are typically less efficient, focused on improving fuel economy and emissions without boosting vehicle performance. Stored electrical energy is deployed to assist the IC engine system leading to an overall reduction in fuel consumption while maintaining vehicle performance at a level comparable with baseline conventional IC engine operation. Regenerative braking is integrated with the existing braking systems on the vehicle, and the control system tailored to maximise the amount of energy recuperated during deceleration events and accelerator pedal lift off without adversely impacting on the normal behaviour of the vehicle. The control system was implemented on both prototype single (Streetlite) and double-deck (Streetdeck) vehicle configurations for real vehicle testing with partner Wrightbus. The hybridisation has reduced equivalent CO2 emissions by 34% (single-deck)/ 35% (double-deck)…
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Numerical Analysis of Underbody Diffusers with Different Angles and Channels

CATARC-Xuelong Liu, Qinglu Chen
Jilin University-Jie Tian, Yingchao Zhang
Published 2019-04-02 by SAE International in United States
The underbody diffusers are used widely in race cars to improve the flow field structure at the bottom of the car and provide enough downforce. In recent years, passenger cars have begun to use bottom diffuser to improve aerodynamic characteristics, so as to reduce drag and increase downforce. In this paper, the aerodynamic characteristics of the bus with different underbody diffuser angles and channel numbers are studied by numerical simulation analysis. Firstly, the aerodynamics of the bus under different diffuser inlet and outlet angles are studied, and then an optimal inlet and outlet angle is determined based on the simulation results. Then, using this angle as a constant, the 2, 3, and 4 channel numbers were chosen as the diffuser channel variables to study the influence of the multiple-channel diffusers on the aerodynamic drag of the vehicle. The results of the study show that reasonable diffuser inlet and outlet angles can improve the bottom pressure distribution and wake structure of the bus, resulting in a maximum increase in downforce of 38.2%. In addition, under a…
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