1. Electric Aircraft Symposium Westin Hotel, Millbrae, California
Automotive Hybrid Experience Applied to Electric Aircraft Design by Marc W. Wiseman, Ph.D., Divisional Product Group Director, Advanced Technology and James C. Paul, P.E., Senior Engineer and Business Development Manager Ricardo, Inc.
NASA PAV Concept
Shadow 200 UAV
Electric Aircraft Symposium
Westin Hotel, Millbrae, California
23 May 2007

2. The auto industry has evaluated a wide range of hybrid schemes
Automotive Hybrid Experience Applied to Electric Aircraft Design
The auto industry has evaluated a wide range of hybrid schemes
Electrical Machines
Power Transmission
Energy Storage
Thesis 
The automotive industry has made significant progress in the area of electric vehicle (EV) and hybrid-electric vehicle (HEV) drive systems.
This experience can be leveraged to support development of electric and hybrid-electric PAVs and UAVs.
Energy storage, on-board power generation, vehicle modeling and integration, electric machines, and controls/power electronics will be discussed.
Possible integration of these technologies into future aircraft designs will be explored. 
NASA PAV Concept
Shadow 200 UAV  

3. Automotive Hybrid Experience Applied to Electric Aircraft Design
Company Overview

4. Ricardo has been involved in hybrid vehicle development since 1999:. 1
Ricardo has been involved in hybrid vehicle development since 1999: Proprietary programs for OEMs, component suppliers, government agencies, military Ricardo internal R&D programs
Selected Projects
GVWs have ranged from 3.5 to 25 tons.
HyTrans
i-MoGen
Ford Escape HEV
Efficient-C
Micro Hybrid
Mild Hybrid
Full Hybrid
Optimum Efficiency
US Government Advanced Hybrid Vehicles
Hybrid Refuse Truck
Military/Off-road

5. Projects have spanned the full range of hybridization, from “micro” to “full”
Mild
Full
Commercial

6. Ricardo’s hybrid experience includes over 120 dedicated development engineers & consultants
Program management
Capabilities
Current technology analysis
Market characteristic assessment
Opportunities assessment
Technical trend assessment
Program planning business case development
Program support & guidance
Powertrain and Vehicle
Production design and release
Vehicle engineering & system simulation
Engine and transmission design and development for hybrids
Prototype and pre-production build
Controls and Electronics
System simulation
Control strategy development
Embedded software development
Software tools
Hardware-in-the-loop application
Electric Machines,
Power Electronics and
Energy Storage
Motor development
Electronic hardware (including power electronics) development and validation
Energy storage modelling, test and validation
Ricardo is experienced in developing corporate strategies for hybrid vehicles

7. Ricardo has been actively engaged in advanced energy storage systems and integration into hybrids for over 6 years.
Requirements definition and cost/benefit analyses for EVs, HEVs and PHEVs
Mechanical design for vibration, shock and crash
Pack design for cost, assembly and manufacture (DFx)
Thermal design, analysis, development and validation
Simulation and test, validation of battery system
Control algorithm and software development for SOC/SOH
Battery Management System (BMS) hardware design and validation
Safety system integration, FMEA, and Hazard Analysis
Supply chain management of subsystems
Prototype manufacturing, validation and launch support
Ricardo currently studying market potential for establishing a Center of Excellence for Energy Storage development in Michigan

8. Status of Automotive Hybrid Technology
Toyota Prius
Honda Civic
Ford Escape
Saturn Vue
Nissan Altima
Five OEMs have hybrid products on the market. Many offer more than 1 vehicle and most are working on at least their second generation of hybrid technology.
Hybrids vehicles are low volume – key focus is on production quality of hybrid components to avoid warranty costs. Production targets include:
Design for less than 100 ppm failures in vehicle (i.e zero failure).
Design for 150k miles / 10 year life (equates to over 7500 hrs of operation time)
Robust to significant vibration and shock forces.
Robust to thermal temperature extremes.
NiMH batteries are proving to have good cycle life and good calendar life.
Lithium ion technology is being actively developed for next generation hybrid batteries.
Good understanding is being gained of potential operating failure modes for hybrid systems and mitigation strategies.

9. Ricardo’s Current Aerospace Activities
Focus on Unmanned Aerial Vehicles
Aviation Week & Space Technology April 2, 2007
Wide range of applications, 1hp to 1000hp
“Backpack” engine for suit cooling/local power
“Powerpack” handheld genset engine
Several UAV engine concepts, including High Altitude
UAV heavy fuel engine demonstrator
Helicopter powerplant concept for extended range

10. Ricardo’s Current Aerospace Activities
UAVs span a wide size range, including sizes appropriate for PAVs
Military applications are a primary driver for the UAV industry.
Current goals are:
Increased Endurance
Reduced Noise
Operate on Available Fuels
Increased Payload Capacity
Reduced Maintenance
Improved Durability

11. Approach to Electric/Hybrid Aircraft Design
Full-Throttle Power Available
MSC.EASY5
Perform mission requirement/energy requirements trade-off studies using:
Classical analysis (spreadsheets)
Computer simulation 
MSC.EASY5
Ricardo Powertrain Library
Ricardo Engine Library
Ricardo Fuel Cell Library
Ricardo Electric Drive Library 
Available libraries allow simulation of a wide range of power system designs to facilitate selection and sizing of components.

12. Approach to Electric/Hybrid Aircraft Design
Backside of power curve: if speed is decreased, power must be added to hold altitude
Design Propulsion System Based on Minimum Energy Mission Approach (takeoff, dash, cruise)
Power Required Curve 
Best Endurance Speed = Speed at Minimum Power (maximum time in air)
Best Range Speed = Speed at Which the Ratio HP/V is a Minimum (the speed giving the greatest ratio of velocity to horsepower required).
Assumes the thrust specific fuel consumption (lb/THP-hr) is essentially constant over the low HP range.  
Speeds for Best Range and Endurance for Propeller-Driven Aircraft
From: Dommasch Airplane Aerodynamics, Fourth Edition, Page 302

13. Approach to Electric/Hybrid Aircraft Design
TOOLS
Matlab Simulink, EASY5
Ricardo Powertrain Library for Simulink
V-SIM (IPT)
Ricardo Engine Simulation Libraries
CAPABILITIES
Duty Cycle Simulation (fuel consumption and emissions)
Performance Simulation (Climb, Dash, Top Speed)
Co-simulation with WAVE, FLOWMASTER, etc.
Drive Cycle Simulation of a Light commercial Truck
Motor-generator mechanical power
Engine torque
Set point versus actual speed
Average fuel economy
Battery state of charge
Battery power
Vehicle Control System Development

14. One challenge for Electric aircraft is the weight of the energy storage system.
For the following example, Lithium-Ion Batteries were Selected as Being Representative of the
Best Currently-Available Technologies for Energy and Power Density
Example Operating Characteristics for UAV
Target Weight
300 lbs [136 kg]
Typical cruise power
6 HP [4.5 kW]
Typical take off power
24 HP [18 kW]
Estimated take off energy
3 kWh
Estimated cruise energy
4.5kWh per hour of flight time.
Estimated Automotive Li-ion Battery Characteristics
Li –ion energy density
80 – 120 Wh / kg
Li-ion max power density
1300 – 1600 W / kg
Li-ion cont power density
800 – 1000 W / kg
Current estimated battery life
5000 flights

15. Battery weight remains a challenge which limits flight time
Calculations based on
a 300 lb UAV
The battery pack alone would be 300 lbs for a 3 hr flight time !!
UAV weight !!!
Example
A holistic approach is needed to improve flight time by finding ways to reduce takeoff and cruise power, take weight out of all components.

16. AeroVironment Helios Aircraft with Solar Panels on Wings
How can performance be improved if energy storage remains a limiting factor?
Reduce drag, CD
Reduce weight, W
Improve efficiency, CL/CD
Change mission profile (e.g. HP vs time history, improved take-off profiles)
On-board power generation (e.g. solar cells)
Improved energy storage systems 
Traditional aircraft design approaches have included trade-offs between efficiency and performance with focus on performance.
Electric aircraft will include similar trade-off studies, but the focus will be on minimizing energy use. 
AeroVironment Helios Aircraft with Solar Panels on Wings

17. To meet goal of 8hr+ flight time, efficiency improvements and alternative power sources are needed.
Solar cells alone are not optimum solution
Effort is required to reduce cruise power

18. Conclusions
Automotive engineering practice is providing high quality, robust and long life electric motors, electronics and battery systems.
Hybrid road vehicle technology is developing at a rapid pace with particular progress being made in the areas of 1) equipment costs (including manufacturing methods and economies of scale), 2) operational failure modes are well understood and mitigation strategies can be deployed, and 3) weight optimization methods.
Current battery technology presents a challenge for achieving weight targets.
Detailed analysis and a holistic approach to UAV/PAV design is required to meet mission requirements. Modeling tools are available to assist in configuration assessment and component sizing.
Note possible technology development opportunity: DARPA-sponsored Vulture Program (5 year-aloft, 1000 lb solar/battery/fuel-cell powered aircraft).