HCI Student Project

14 December 2011 1

Electric Vehicle Research:

The ChargeCar Project

Ben Brown hbb@cs.cmu.eduChris Bartley bartley@cmu.edu

CREATE Lab, The Robotics Institute

Carnegie Mellon University

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CREATE LABIllah Nourbakhsh

Community

Robotics

Education

And

Technology

Empowerment

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EV History

At the start of the 20th century, electric vehicles were on equal footing, or slightly ahead of, gasoline powered vehicles. They were quiet, clean and reliable, easy to start. An EV was the first car to break 60 mph. Then around 1910 the superior specific energy of fossil fuels became important as trips got longer. And, ironically, the electric starter made ICE vehicles much more convenient. Since then, $ billions have been funneled into the development and refinement of the internal combustion engine.

1913 Bailey Electric Roadster at the Autoneers Horseless Carriage Club's recent tour to AmesburyS.R. Bailey and CO, Amesbury, MA1898-1915Bart Bailey drivinghttp://www.earlyamericanautomobiles.com/

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EV MythsPerception TruthMust replace today's carsEV must be a 1:1 replacement for present ICE vehicle, with same range, acceleration, speed and features.

Perfect commuter vehicleEVs fill a niche as short-range commuter vehicles. Future technology will improve range and performance.

Range too shortEV won't serve all transportation needs

Typical commute <40 miles77% of US daily commutes are less than 40 miles (US DoT), well within the range of most EVs. Some EV s have range >200 miles per charge.

Poor performanceEvs don't have the power I want.

Good acceleration, highway speeds Typical EV can travel at highway speeds. Some very high-performance EV s have been built (e.g. Tesla Roadster).

Battery technology not readyWe need to wait until better batteries are developed.

Technology ready 10 years agoNiMH batteries used reliably in EV s such as RAV-4 EV >10 years. Newer LiFePO4 batteries have better specific energy, and promise life >2000 full charge cycles.

UnreliableWe need to wait until better batteries are developed.

Simple and reliableEVs have very few moving parts, minimal fluid systems, utilize regenerative braking to save brake wear

Overload electric gridThe grid cannot handle the extra load of charging millions of Evs.

Off-peak charging idealOvernight/off-peak charging can be done with existing capacity. Off-peak charging can provide load-leveling on a Smart Grid.

Charging infrastructure neededA massive network of charging stations will be needed to make Evs practical.

Existing infrastructure adequateFor short-range commuting, EV s can be charged on existing 120VAC outlets.

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ChargeCar Project

Community conversions• Recipes for conversion to EVs• Collaboration with local industry and garages• Practical, visible electric vehicles for the community

Research• Compound energy w/supercapacitor• Management of heterogeneous energy storage• Battery energy estimation

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Community Conversion Platform

7th generation Honda Civic sedan• Lightweight (~2600#)• Family size (seats 5)• Readily available at reasonable price w/manual trans.

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The Swap

115HP, 1.7L engine out 40HP, 3-phase induction motor in

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Modular system for quick, efficient conversion

Motor/transmission

assembly

Control/electronics module with electric heater and pumps

Battery pack

Computer/display unit

Using standard EV components, we have designed four basic modules required for the conversion. These modules will be fabricated and assembled by a local fabricator. The complete conversion—tear-out of ICE and related equipment, installation of electric power system—will require less than 3 days total at an automotive garage without special tools or expertise.

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Honda Civic EV Prototype

2005 Honda Civic LX

Range: >40 miles

Speed: >70mph

Battery: 106V, 10.5kWh LFP

Charge time: ~10 hrs. 120VAC

Efficiency: ~4 miles/kWh

Electricity cost: ~$0.03/mile

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Current Operator Interface

• LCD 4x20 Characters• 6-button menu selector• Interface Accessory Buttons

– A/C– Power Steering– Interior Heater

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Available from Current Display

• Battery voltage, current, temperature(s)• Motor and controller temperatures• Instantaneous power to motor• Total energy and charge consumed• Energy regenerated• Operating efficiency (e.g. miles/kWh) for trip and/or

instantaneous• GPS location

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Inputs

• BMS RS-232 Feed:– http://

lithiumate.elithion.com/php/rs232_specs.php

• GPS– NMEA Sentences

• Other:– motor temperature– controller temperature– car rpm– charging or running

• Interface Buttons– Direction Pad (4)– Select– Cancel– Accessory Buttons (3)

• AC Motor Controller

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Problems w/Current Display

• Long boot-up time (~60 seconds)

• Unreliable start-up

• Difficult to navigate menus

• Difficult to read display

• Spontaneous data resets

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• State of charge of battery pack, and estimated driving range

• Alerts for high/low temperatures (motor, controller, battery cells, etc.)

• Alerts for high/low voltages, currents

• Operating efficiency (e.g. miles/kWh) for trip and/or instantaneous

• Tips to improve efficiency

• GPS map/navigation system

• Map of reachable destinations on available charge

• Charging station locations and availability, features, etc.

• Remote applications for information display (e.g. iPhone)

• Remote control (start/stop charging, turn on/off cabin heater or AC…)

• Portable unit used in vehicle or remotely

• Voice recognition, audio outputs

• Easily viewable display scheme

• Head-up display

Desirable Additions/Features

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Issues• What hardware platform• What information to display• Where to mount it for ease of viewing• How to select displayed views• Voice activation• Commercially available displays/interfaces• Existing apps we can use• Remote communication method• Cost to manufacture• User safety!

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User Types

• Near Future:– Commuters – drive to work everyday– Occasional Drivers – go shopping once a week, etc.– Technophiles – interested in how the system works– Company Cars – transport employees & positive press

• Further Ahead:– Community Vehicle Share– Rental Cars

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Should we design different interfaces for different user types?

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High Level Design Considerations

– Vehicle Well-Being

• Is there a problem?

• Is there avoidable damage being done?

– Driver Safety

• Interface must not be distracting while driving

– Ease of Use

• Intuitive for first time user

• Use should not require memorization

– Efficiency

• Power management to accessories

– Driver Education

• Educational information for aiding and encouraging self- improvement

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Driving ModeNormal View

– Speed (from dash speedometer)– State of Charge

• Representation: graphical, percentage or both?– Range Estimation– Sliding Scale Power Flow

• Full Regen. to Full Power (graphical?)– Fault and Error Indicator

• Do we also want to indicate when there are no errors?

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Review ModeNormal View

– This mode would provide information about the past to the driver when the vehicle is parked.

– Driving Efficiency• Resettable trip average (mile/kWh)• Convert to a “Driver Rating”

– (an easily remembered value from 1 to 10 stars)– Energy Odometer

• Convert to price– Time/Distance/Energy since Last Charge

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Charging ModeNormal View

• Time until Complete Charge– Alternatively, time when the charge will be complete– (Time until 80% Charge – optional)

• Estimated Range from Current Charge Level• State of Charge• Batteries Require Leveling Indication

– Either scheduled to happen once a month or based on cell voltages

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Early Display Window Design

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Another Display Concept

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Similar InterfacesTesla Roadster

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SpeedTempTime

State of ChargeEstimated Range

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Similar InterfacesChevy Volt

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• Power Flow• Time until full

charge• Electric/Gas %• MPG• Speed• Odometer• State of Charge• Temp• Time

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Similar InterfacesNissan Leaf

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State of ChargeSpeedPower FlowEstimated RangeTime ElapsedDistance DrivenTempTime

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Links to Other User InterfacesSearch on “electric vehicle user interface”

• http://novia.co.il/

• http://www.zemotoring.com/news/2011/01/ford-focus-electric-user-interface-myford-touch

• http://8020.com/#better-place

• http://www.auto-ui.org/11/docs/26_stromberg.pdf

• http://www.auto-ui.org/11/docs/30_loumidi.pdf

• http://www.auto-ui.org/11/docs/16_tractinsky.pdf

• http://ecars-now.wikidot.com/ecars-now:what:egui

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ChargeCar website: chargecar.org

This presentation: chargecar.org/hci/

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SPARE SLIDES FOLLOW

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Driving ModeExpert View

• Current (to/from motor)• Pack Voltage

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Review ModeExpert View

– Battery Information• Min/Avg/Max Cell Voltages• Number of Cells with Min/Max Voltage (& which ones)• Min/Avg/Max Cell Internal Resistances• Number of Cells with Min/Max Int. Res. (& which ones)

– Read-out of Complete BMS Data– Resettable Peak Current (for both regen. and discharge)– Look-up of any fault codes– Pack Information

• Capacity• Internal Resistance

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Charging ModeExpert View

• Charging Current• Range Charging Rate

– How many additional miles are gained each hour of charging?

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Research Purpose:Establish a method for estimating remaining available

battery energy for ChargeCar EVs from battery management system sensor data.

Available battery energy is most similar to a standard “fuel gauge”, where quantities of fuel provide a specific

amount of energy.

Overview

ChargeCar Battery Energy Estimation

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OverviewFor example, below is a record of a test drive where the goal is to estimate the available battery energy (shown in red) from vehicle sensor data (i.e. Instantaneous Power Consumption shown in black)*

ChargeCar Battery Energy Estimation

*A common estimation solution know as “Coulomb Counting” uses simple discrete time integration of Instantaneous Power, which accumulates error over time.

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Many other data features available (or possible to compute) from battery management system, including:

ChargeCar Battery Data

ChargeCar Battery Energy Estimation

•Average Cell Temperature•Total Pack Voltage•Load Current•Instantaneous Power•Open Circuit Voltage Estimate•First and Second Derivative of Voltage and Current•Sliding Window Average Voltage and Current

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Preliminary results

ChargeCar Battery Energy Estimation

Preliminary results from this computational system are shown below, the estimate (shown blue) does a reasonable job* of tracking the desired value (shown red).

*Deviations between the estimate and desired value are the result of the test data demonstrating, at certain times, input combinations not covered by the limited training data.

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http://chargecar.org/

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ChargeCar Team

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