1. EcoDrive: A Mobile Sensing and Control System for Fuel Efficient Driving
Lei Kang, Bozhao Qi, Dan Janecek and Suman Banerjee
University of Wisconsin-Madison

2. Motivation

3. More by sacrificing travel time
EcoDrive Overview
EcoDrive models fuel consumption rate of each acceleration at each speed
EcoDrive controls fuel injection rate to control acceleration (human driver controls brake)
20% ~ 30% fuel savings
More by sacrificing travel time

4. EcoDrive Overview
SPEED LIMIT
40km/h
STOP
Driver Conserver: Cruises at 1km/h (low efficiency speed)
Driver Aggressor: Accelerates to 40km/h in 1 second and cruise to the end (low efficiency acceleration)
EcoDrive: Calculates the fuel consumptions of various acceleration and cruising strategies

5. EcoDrive Architecture
Sensing OBD parameters
Modeling vehicle forces
Controlling air/fuel injection rate

6. Sensing OBD Parameters

7. OBD Parameters and Power Transition1 2 3 4
No.
OBD Parameters
Description 1
Gas Pedal Angel
Angel of the gas pedal, controlled by driver 2
Air/Fuel Flow Rate
Air/Fuel injection rate, controlled by gas pedal angle 3
Engine RPM
Engine rotation speed, transit power to wheel through transmission 4
Vehicular Speed
Speed of the vehicle …
… …

8. OBD Data Collection Urban: Madison and Chicago, 5000+ miles
Highway: Local highways and cross-state highways, miles

9. Modeling Vehicle Forces

10. Model Vehicles Forces Engine Propulsion
Function of air/fuel rate and gear ratio (estimated by vehicular speed and engine RPM)
Drivetrain loss and wind resistance
Function of propulsion when driving in constant speed
Grade resistance
Function of altitude changes (extracted from online elevation dataset)

11. Build AFR Profile (A Lookup Table)
AFR(v, a) : the air/fuel rate when accelerates at a (m/s/s) under speed v(km/h)
Example
Air/Fuel Rate
0.0 m/s/s
0.1 m/s/s
0.2 m/s/s
… …
1 km/h
2 km/h
AFR(2, 0.1)
3 km/h
4 km/h
5 km/h

12. Controlling Fuel Injection Rate

13. Computer Controlled Gas Pedal
Gas Pedal (drive-by-wire)
Human driver press the gas pedal
The position sensor senses gas pedal position
The gas pedal sends the position value to the Electronic Control Unit (ECU)
ECU controls the volumes of air/fuel injected into the engine
EcoDrive Controller (Emulate gas pedal)
It calculates the gas pedal position value
It sends the value to the ECU through an Arduino board

14. Driving from A to B by DP D: A-B road segment length V: speed limit
S(v, d): minimum fuel cost at distance d with speed v
Case 1: The car cruises to state (v + 1, d + 1)
S(v + 1, d + 1) = S(v + 1, d) + AFR(v + 1, 0) * time
Case 2: The car accelerates to state (v + 1, d + 1) at acceleration ax
S(v + 1, d + 1) = S(v, d - dx) + AFR(v, ax) * time

15. Implementation and Evaluation

16. Implementation Hardware Software OBD Scanner with ELM327 USB interface
Arduino board converts digital gas pedal position to voltage signals
Software
One thread writes commands to OBD interface through serial communication
One thread reads OBD parameters and write gas pedal position to Arduino board

17. In-vehicle Setup

18. Evaluation Real road test (over 100 miles) Comparison
Urban: Road segments with various lengths ( m)
Highway: Various highway segments (2km each)
Comparison
Theoretical value
Human drivers
Cruise control

19. Urban Road Segment
Human drivers and EcoDrive: drive 10 times on the same road segment

20. Case Study: Cruise Control
Cruise control: accelerate aggressively on upslope or human manipulation
EcoDrive: gradually change air/fuel injection rate, adapt to road conditions

21. Highway Segment
Method: EcoDrive drives 2km on various speeds and compare with history driving data on same highway segments
Result: EcoDrve achieves 30% higher fuel efficiency for same travel time

22. Travel Time vs. KPL
EcoDrive achieves higher KPL than human drivers in similar travel time
EcoDrive provides a trade-off between travel time and fuel consumption

23. Highway Statistics
Drivers drive much faster than best KPL speed (green line)
Drivers drive at higher speeds than speed limits 55-70mph ( km/h)

24. Summary
EcoDrive controls fuel injection rate and achieves 20%~30% improvement than human drivers
EcoDrive has higher gas mileages than human drivers in same travel time
EcoDrive provides trade-offs between travel time and gas mileage
Cruise control is not fuel efficient when accelerating or going upslopes

25. Take-Aways Gradually press gas pedal, avoid frequent press and release
Use cruise control, which generally performs better than human drivers
Drive under speed limit will have 20%~40% gas mileage improvements

26. Thanks Q&A