System Modeling and Innovation for OffRoad vehicles Georgia Institute of Technology | Milwaukee School of Engineering | North Carolina A&T State University | Purdue University University of Illinois, Urbana-Champaign | University of Minnesota | Vanderbilt University
Zongxuan Sun May 25, 2016
Off-Road Vehicle Research Program
Agriculture
Construction
Mining and Quarrying
Military
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Background – Off Road Vehicle Market •
Off-road vehicles are used in agriculture, construction, mining and quarrying, forestry and by the military, among other end uses.
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Off-road vehicles and equipment and the associated supply chains provide significant economic activities in the US. The manufacturing segment alone accounted for more than $100B in shipments and direct employment of more than 250,000 in the U.S. in 2011.1
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The energy consumed by off-road vehicles in the U.S. by the agriculture, construction and mining industries etc. totaled 2.4 quads.2
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Energy efficiency and productivity are key drivers for global competition in the off-road vehicles market.
Off-road market consumes about 8% of the total transportation energy, 17% of the Non-LDV energy use, and is larger than either marine or aviation markets.
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Needs and Opportunities for Mobile Applications Significant opportunities exist for both on-road and off-road mobile applications. •
The new CAFE standard of 54.5 mpg by 2025 and the adoption of Tier 3 emissions standard in 2017 for light duty vehicles requires revolutionary technological development.
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EPA and NHTSA are setting the phase II of fuel efficiency standards for medium and heavy duty trucks, requiring 1624% further reduction of fuel consumption.
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Similar trends are impacting the off-road market segment. The recent implementation of Tier 4 emissions standard requires further reduction of PM and NOx by about 90%.
Regulations on improved fuel efficiency and reduced emissions share similar trend in Europe and Asia. 4
Why do Off-Road vehicles require different technologies than On-Road Vehicles •
Off-road vehicles use the internal combustion engine as the prime mover and fluid power and or mechanical transmission as the power transfer method.
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Unlike on-road vehicles which typically have a one input (ICE) and one output (wheels of the vehicle) system, off-road vehicles are one input (ICE) and multiple output (drivetrain and work functions) systems. Their duty cycles are also diversified and different from onroad vehicles. – Improved integration of these power systems for off-road vehicles represents a significant opportunity for improved energy efficiency.
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Off-Road Vehicles Currently Using Some Form of Fluid Power Subsector of off-road vehicles
Equipment types
Agricultural
Agricultural tractors Other agricultural equipment
Construction
Off-road trucks and tractors Other construction equipment
Mining, forestry, and oil field
Underground and surface mining equipment Forestry equipment Oil field equipment
Air
Airport ground service equipment
Rail
Rail maintenance equipment
Industrial
Forklifts Other industrial equipment
Lawn and garden
Commercial lawn and garden equipment Residential lawn and garden equipment
Personal and recreational
Snowmobiles Golf carts All-terrain vehicles Off-road motorcycles Specialty vehicle carts
Recreational watercrafts
Recreational boats Personal watercrafts
Fluid power market share
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Fluid Power Efficiency •
A recent DOE report (ORNL/TM-2011/14) indicates that, across all industries, fluid power system efficiencies range from less than 9% to as high as 60% (depending upon the application), with an average efficiency of 22%.
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A review of case studies shows that there are many opportunities to impact energy savings in both the manufacturing and transportation sectors by the development and deployment of energy efficient fluid power components and systems.
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An important reason for the relatively low efficiency is the lack of deep and synergistic integration of the fluid power system with the prime mover and the vehicles.
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Opportunities for Improving Off-Road Vehicles •
Some engine technologies from on-road vehicles can be transferred to the off-road segment. However, powertrain system integration and controls will be different from on-road vehicles due to the different hardware architecture and duty cycles.
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Fluid power efficiency can be significantly improved by more efficient components and removing the throttling loss of the fluid.
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Research in both engine and fluid power are required to significantly improve fuel efficiency and performance, but the integration of the engine and fluid power is especially critical. Successful examples include the CAT hydraulic hybrid excavator.
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Advanced manufacturing offers a new degree of freedom for novel fluid power components and systems.
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Streamlined Process for Innovation in Off-Road Vehicles •
How do we quantify the capabilities and constraints of advanced manufacturing methods when designing new fluid power components?
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How do we evaluate the performance and efficiency of the new fluid power components enabled by advanced manufacturing?
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How do we evaluate the overall system performance and efficiency and quantify the contributions from each component?
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How to we connect system simulation and experiments efficiently?
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Case Study: Hydraulic Hybrid Wheel Loader Lift cylinder
LA
Tilt cylinder
LB
TA
TB
LA – Lift chamber A LB – Lift chamber B TA – Tilt chamber A TB – Tilt chamber B
LS compensator PM1–Pump/motor1 PM2–Pump/motor2
Pressure limiter Working hydraulic system S ICE
PM1
C Loadingsensing pump
Final drive
R Planetary gear set
Drivetrain Power split hydraulic drivetrain: planetary gear set + hydrostatic transmission; Two power transfer paths: mechanical and hydraulic path; Hydraulic accumulator: second power source for regenerative braking and large acceleration; Hydraulic CVT: decouple the engine speed from wheel speed.
PM2
Hydraulic power split drivetrain
Power split hydraulic hybrid wheel loader (with only drivetrain and working function)
Working function Load-sensing hydraulic system: for both lift and tilt functions; Efficient operation: pump pressure always adapts to highest load pressure.
Wang, F., Mohd Zulkefli, A., Sun, Z. and Stelson, K., “Energy Management Strategy for a Power Split Hydraulic Hybrid Wheel Loader”, 10 Proceedings of the IMechE, Part D, Journal of Automobile Engineering, 2016.
System Modeling
Power split hydraulic hybrid drivetrain
Engine
Load-sensing working functions
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System Control Hierarchy High-level control (energy management system - EMS) Generate desired engine operation points (engine torque and speed) Middle-level control Engine speed control Vehicle speed control Bucket control (lift and tilt function) Low-level control Implementation in hydrostatic dyno
Hardware-in-the-loop control hierarchy of hydraulic hybrid wheel loader in a hydrostatic dyno (hardware in red)
Hydrostatic dynamometer at the U of MN 12
Case Study for On-Road Vehicles •
Autonomie was developed through collaborations of DOE and the automotive industry.
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The objective of Autonomie is “to accelerate the development and introduction of advanced technologies through a Plug&Play architecture that will be adopted by the entire industry and research community”.
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Evaluate component, architecture, system and control.
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Argonne National Lab is the technical lead for Autonomie.
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Needs for Off-Road Vehicles’ Modeling and Analysis •
Off-road vehicles needs similar functions including modeling, simulation and evaluation of components, architectures, systems and controls.
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It is more challenging for off-road vehicles due to the diversified architectures and driving cycles.
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The multi-disciplinary nature of the off-road vehicles including mechanical, fluid power, electrical and thermal systems need to be included.
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The manufacturing aspect needs to be included to connect the new manufacturing technologies with model based design and analysis.
Manufact uring
Design
Modeling
Analysis
Control
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Challenges for Off-Road Vehicles’ Modeling and Analysis •
How to integrate advanced manufacturing with model based design and analysis?
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How to obtain the component model in an efficient manner?
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How to decide the standard driving cycles for different off-road vehicles?
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How to develop system control efficiently?
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How to bring together experts for off-road vehicles, fluid power, manufacturing, system modeling and control to develop such a platform?
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