Green driving strategies based on intervehicle communications: theoretical formulation and smartphone implementation

Transcription

1 Green driving strategies based on intervehicle communications: theoretical formulation and smartphone implementation ITS America Webinar October 31, 2012 Wenlong Jin University of California, Irvine 1

2 Contents Introduction Theoretical formulation Constant and dynamic strategies Simulations Smartphone implementation Inter-vehicle communication Green driving strategy 2

3 Introduction Motivation o In 2004, transportation sector responsible for one third of greenhouse gas emission. o 80% of emissions in transportation from passenger cars and freight trucks. Major causes (Barth and Boriboonsomsin, 2008) o Congestion: slow speeds o Excessive speed, i.e., speed over 65 mph. o Traffic oscillation, i.e., stop-and-go traffic 3

4 Introduction What is Green Driving? In addition to new vehicular technologies and traffic operation strategies, drivers behaviors in carfollowing, lane-changing, merging, diverging, route choice, and so on can be adjusted to improve fuel efficiency and reduce vehicle emissions. Strategies o Speed bump, police enforcement o Variable speed limits o Intelligent speed adaptation o Routing o... 4

5 Comparison Traditional methods Speed bumps, police enforcement, etc Usually focus on safety No clear environmental benefits Advanced methods Methods Variable speed sign Intelligent speed adaptation (ISA) Display Roadside changeable message signs In-car display Inter-vehicle communication In-car display Detectors Loop detectors Loop detectors In-car sensors Information Aggregate speed and Aggregate speed and Individual vehicles collected density density locations and speeds Communication Visual Cellular network Vehicle to vehicle method (DSRC) Delay NA ~ 1 s ~ 100 ms Coverage NA Cellular coverage Depends on the market penetration of equipped vehicles 5

6 Constant speed limit: An analysis The constant speed limit of the following vehicle n is U n = v n 1 + ε where ε is a constant term, and 0 U n v f. ε = 0 ε > 0 ε < 0 6

7 Dynamic green driving Goals o Follow the leader in the long run; o Works with just one green driving vehicle; o The more green driving vehicles, the better. Design principles o Speed limit should not be smaller than the average speed o Speed limit should be close to the average speed 7

8 Simulations Car-following model (Newell, 2002) CMEM (Barth et al., 1995) Feedback control with vehicle to vehicle communication 8

9 Impacts of market penetration rates 9

10 Impacts of communication delays 10

11 Smartphone implementation Why smartphones? Integrated GPS and communication components High market penetration rate The green driving strategy works for relatively high communication delays Characteristics? GPS accuracy Communication delay 11

12 Vehicle to vehicle communication 12

13 Findings location errors: 4 meters generally (about 25 meters during warm-up period of GPS devices) communication delays: 3G (1 s) > WiFi ( s) minimum location updating intervals of GPS devices: 1 s location updating frequency related to parameters in the Android apps and traveling speed 13

14 Implementation of green driving strategy 14

15 Field test HC (mg/km) CO (mg/km) NOx (mg/km) CO2 (mg/km) Fuel (liter/km) Mean speed (mph) std of speed (mph) Without GD App With GD App Leader Follower Diff Leader Follower Diff 2.29E E % 2.23E E % 5.55E E % 5.52E E % 4.07E E % 3.85E E % 2.03E E % 1.92E E % Test without GD App 9.17E E % 8.67E E % % % % % Tested Road Test with GD App 15

16 Conclusion and future work Conclusion o Inter-vehicle communication enables feedback control in green driving strategies. o Analysis of a constant speed limit strategy leads to design principles of dynamic green driving strategies; o Higher MPR => higher emission reduction; larger communication delay => lower reduction. Future work o More realistic traffic conditions; o More realistic vehicle to vehicle communications, such as package delivery ratio; o More field tests. 16