EcoDrive: A Mobile Sensing and Control System for Fuel Efficient Driving

Lei Kang, Bozhao Qi, Dan Janecek and Suman Banerjee

University of Wisconsin-Madison

Motivation

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 savingsMore by sacrificing travel time

EcoDrive Overview

• 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

STOP

EcoDrive Architecture

•Sensing OBD parameters•Modeling vehicle forces•Controlling air/fuel injection rate

Sensing OBD Parameters

OBD Parameters and Power Transition

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

… … … … …

1 2 3 4

OBD Data Collection

• Urban: Madison and Chicago, 5000+ miles

• Highway: Local highways and cross-state highways, 5000+ miles

Modeling Vehicle Forces

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)

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

… …

Controlling Fuel Injection Rate

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

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

Implementation and Evaluation

Implementation

•Hardware• 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

In-vehicle Setup

Evaluation

• Real road test (over 100 miles)• Urban: Road segments with various lengths (50-1000m)• Highway: Various highway segments (2km each)

• Comparison• Theoretical value• Human drivers• Cruise control

Urban Road Segment

• Human drivers and EcoDrive: drive 10 times on the same road segment

Case Study: Cruise Control

• Cruise control: accelerate aggressively on upslope or human manipulation

• EcoDrive: gradually change air/fuel injection rate, adapt to road conditions

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

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

Highway Statistics

• Drivers drive much faster than best KPL speed (green line)

• Drivers drive at higher speeds than speed limits 55-70mph (90-110km/h)

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

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

Thanks

Q&A