Lateral and Longitudinal Control

323 Pages·1996·4.53 MB·English

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Precursor Systems Analyses of
Automated Highway
Systems
R E S O U R C E M A T E R I A L S
Lateral and Longitudinal Control
U.S. Department of Transportation
Federal Highway Administration
Publication No. FHWA-RD-95-095
October 1994
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FOREWORD
This report was a product of the Federal Highway Administration’s Automated Highway System
(AHS) Precursor Systems Analyses (PSA) studies. The AHS Program is part of the larger
Department of Transportation (DOT) Intelligent Transportation Systems (ITS) Program and is a
multi-year, multi-phase effort to develop the next major upgrade of our nation’s vehicle-
highway system.
The PSA studies were part of an initial Analysis Phase of the AHS Program and were initiated to
identify the high level issues and risks associated with automated highway systems. Fifteen
interdisciplinary contractor teams were selected to conduct these studies. The studies were
structured around the following 16 activity areas:
(A) Urban and Rural AHS Comparison, (B) Automated Check-In, (C) Automated Check-
Out, (D) Lateral and Longitudinal Control Analysis, (E) Malfunction Management and
Analysis, (F) Commercial and Transit AHS Analysis, (G) Comparable Systems Analysis,
(H) AHS Roadway Deployment Analysis, (I) Impact of AHS on Surrounding Non-AHS
Roadways, (J) AHS Entry/Exit Implementation, (K) AHS Roadway Operational
Analysis, (L) Vehicle Operational Analysis, (M) Alternative Propulsion Systems Impact,
(N) AHS Safety Issues, (O) Institutional and Societal Aspects, and (P) Preliminary
Cost/Benefit Factors Analysis.
To provide diverse perspectives, each of these 16 activity areas was studied by at least three of
the contractor teams. Also, two of the contractor teams studied all 16 activity areas to provide a
synergistic approach to their analyses. The combination of the individual activity studies and
additional study topics resulted in a total of 69 studies. Individual reports, such as this one, have
been prepared for each of these studies. In addition, each of the eight contractor teams that
studied more than one activity area produced a report that summarized all their findings.
Lyle Saxton
Director, Office of Safety and Traffic Operations Research
and Development
NOTICE
This document is disseminated under the sponsorship of the Department of Transportation in the
interest of information exchange. The United States Government assumes no liability for its
contents or use thereof. This report does not constitute a standard, specification, or regulation.
The United States Government does not endorse products or manufacturers. Trade and manu-
facturers’ names appear in this report only because they are considered essential to the object of
the document.
ii
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1. Report No. 2. Government Accession No. 3. Recipients Catalog No.
4. Title and Subtitle 5. Report Date
Precursor Systems Analysis for Automated Highway Systems: October 1994
Volume II-Lateral and Longitudinal Control
Final Report 6. Performing Organization Code
7. Author(s) 8. Performing Organization Report No
Dickerson, J.A. Damos, D.*
Lai, M.C. Smith, D.*
† 10. Work Unit No. (TRAIS)
Ioannou, P.A. Shulman, M.
†
Chien, C.C. Eckert, S.
Kanaris, A.
9. Performing Organization Name and Address 11. Contract or Grant No.
University of Southern California
Center for Advanced Transportation Technology DTFH61-93-C-00196
EE–Systems Department
Los Angeles, California, 90089-2562 13. Type of Report and Period Covered
Final Report
* Human Factors Department, University of Southern California October 1993-September 1994
† Ford Motor Company, Electronics Division, 19540 Allen Road, Melvindale,
Michigan, 48122
12. Sponsoring Agency Name and Address 14. Sponsoring Agency Code
Federal Highway Administration
400 Seventh Street, SW
Washington D.C., 20590
15. Supplementary Notes
16. Abstract
This report analyzes the requirements, issues, and risks associated with lateral and longitudinal control of vehicles operating on the
AHS. This report presents a possible evolutionary path for the automation of lateral and longitudinal control. This evolutionary
path is characterized by five evolutionary representative system configurations (ERSCs). This analysis looks at the development of
longitudinal, lateral and finally combined lateral and longitudinal systems in terms of the performance and reliability requirements
and deployment scenarios. The performance requirement analysis covers driver comfort and acceptance issues during automatic
control and transitions between automatic and manual control in addition to investigating the sensor, actuator and controller
requirements for the control systems. Roadway traffic controllers may improve traffic flow through traffic networks in terms of
travel time reduction and congestion avoidance. The reliability requirements analysis uses NHTSA’s accident rates data to quantify
the reliability requirements in various levels of vehicle automation. This report derives the reliability functional requirements for
the automatic systems used in lateral and longitudinal control. The reliability functional requirements allows us to assess the
required redundancy and structural complexity in implementing these automatic systems. This information can be used to estimate
the cost and difficulty to build the automated highway systems.
17. Key Words 18. Distribution Statement
vehicle lateral and longitudinal control, evolutionary No Restrictions.
representative system configurations, reliability
requirements, redundancy, performance requirements,
human factors, capacity benefits, autonomous vehicles
19. Security Classif. 20. Security Classif. 21. No. of Pages 22. Price
(of this report) (of this page) 299
Unclassified Unclassified
Form DoT F17007 (8-72) Reproduction of Completed Page Authorized
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Table of Contents
Section 1: Introduction.............................................................................1
Section 2. Evolutionary Representative System Configuratio.n...s.......5
ERSC 1............................................................................................................7
ERSC 2............................................................................................................8
ERSC 3............................................................................................................10
ERSC 4............................................................................................................11
ERSC 5............................................................................................................12
Section 3: Headway Selection And Capacit.y.........................................13
Stopping Scenario for Vehicle Followin..g...................................................13
Minimum Headway For Collision-Free Vehicle Follow.i.n..g........................
.........................................................................................................................17
Accident Severity And Headway Selectio..n.................................................20
Steady State Highway Capacit.y...................................................................25
Section 4: Reliability.................................................................................27
Reliability Indices...........................................................................................27
Longitudinal Reliability of Human Drive.r.s..................................................28
Lateral Reliability of Human Driver.s............................................................28
Section 5: ERSC 1 Analysis......................................................................31
Description of ERSC 1...................................................................................31
Performance Requirements..........................................................................33
Reliability Requirement Analys.i.s.................................................................56
ERSC 1 Driver Tasks and Workloa.d............................................................74
Key Results.....................................................................................................81
Section 6: ERSC 2 Analysis......................................................................95
Description of ERSC 2...................................................................................95
Performance Requirements..........................................................................97
Reliability Requirement Analys.i.s.................................................................123
ERSC 2 Driver Tasks and Workloa.d............................................................138
Key Results.....................................................................................................143
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Table of Contents
(continued)
Section 7: ERSC 3 Analysis......................................................................151
Description of ERSC 3...................................................................................151
Performance Requirements..........................................................................153
Reliability Requirement Analys.i.s.................................................................169
Driver Tasks and Workload...........................................................................183
Key Results.....................................................................................................189
Section 8: ERSC 4 Analysis......................................................................191
Description of ERSC 4...................................................................................191
Performance Requirements..........................................................................193
Reliability Requirement Analys.i.s.................................................................207
Driver Tasks and Workload...........................................................................220
Key Results.....................................................................................................224
Section 9. ERSC 5 Analysis......................................................................225
Description of ERSC 5. .................................................................................225
Performance Requirements..........................................................................226
Reliability Requirement Analys.i.s.................................................................235
Driver Tasks and Workload...........................................................................239
Key Results.....................................................................................................241
Section 10 Conclusions.............................................................................243
Appendix A: Communication System.s.................................................253
Appendix B: Roadway Traffic Controlle.r..............................................263
References ..................................................................................................273
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List of Figures
1. Main automatic vehicle functions for each ERSC. The arrow indicates the introduction of a new
fully automated vehicle function.............................................................................................2
2. Acceleration profile for the leading vehicle in the worst case...................................................14
3. Longitudinal forces on the leading vehicle..............................................................................14
4. Acceleration profile of the trailing vehicle...............................................................................15
5. The effect of trailing vehicle reaction time..............................................................................18
6. The effect of deceleration difference between the leading and trailing vehicles........................19
7. The effect of road-tire friction coefficient under constant Æ Am..............................................19
8. The effect of initial velocity difference....................................................................................20
2
9. (h, Æ V ) curves for different values of thr..............................................................................22
2
10. (h, Æ V ) curves for Alm = 0.8g, Afm varies from 0.4 to 0.7g. As Afm decreases the collision
damage increases....................................................................................................................23
11. Block diagram of the speed and headway maintenance function. The sensors measure the relative
speed and spacing of the vehicles, then the controller sends commands to the brake and throttle
actuators so that the vehicle maintains the selected speed and/or headway...............................33
12. Sensor requirements for range and closing rate detection for the speed and headway maintenance
system.....................................................................................................................................34
13. The maximum sensor range with respect to the maximum deceleration of the vehicles for two
different velocities. These values come from the “brick wall” scenario when the lead vehicle or
debris is stopped on the highway.............................................................................................35
14. Minimum safe time headway with respect to differences in the maximum deceleration between
vehicles ÆAm= Alm–Afm. A negative acceleration value means that the follower car can brake
faster than the lead car. T1 is the time that the following vehicle detects the lead vehicle
deceleration and initiates soft braking......................................................................................38
15. Minimum safe distance between vehicles for different human reaction times. The human
reaction time is measured from the time that the vehicle ahead begins braking. The solid line
shows the headway for a communications system. The dashed line shows the headway for a
sensor-based system................................................................................................................39
16. Block diagram for the rear-end collision warning system. The system senses the distance and
closing rate of the target vehicle. Then the warning algorithm computes the headway between
the vehicles and warns the driver if necessary..........................................................................41
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List of Figures
(continued)
17. Changes in the detection time for lane change/merge collisions have a small effect on the
accident severity. T1=0.1s shows the case for the ideal sensor. T1=0.4s shows the case for the
single beam sensor..................................................................................................................42
18. Changes in the human reaction time for lane change/merge collisions have a large effect on the
accident severity. Thr=0.7s shows the best case for human reaction time to an unexpected
hazard. Thr=2.0s shows the worst case for human reaction time to an unexpected hazard........43
19. The probability of correctly deciding that the vehicle ahead is decelerating depends on the space
between the two signals d. As d increases the detection-false alarm trade-off improves..........45
20. The deceleration difference between the vehicles ÆAm=Afm-Alm has a large effect on accident
severity. As ÆAm increases the potential accident severity increases......................................46
21. Block diagram for the blind spot warning system....................................................................48
22. The shaded area shows the region of coverage for a blind spot sensor on the left side of the
vehicle....................................................................................................................................49
23. As the road-tire friction coefficient decreases (the road gets more slippery), the minimum safe
time headway increases. ÆAm = Alm – Afm is the deceleration difference between the vehicles.
A positive value means that the lead car has a larger deceleration than the follower vehicle.....54
24. The functional block diagram of the SHM system...................................................................57
25. The reliability functional block diagram of the SHM-driver system.........................................58
26. The required SHM system failure rates very as the driver’s reliability degrades.......................60
27. The functional block diagram of the RECW system................................................................64
28. The RECW system framework for reliability design................................................................66
29. The functional block diagram of the BSW system...................................................................68
30. The BSW system framework for reliability design.................................................................69
31. A block diagram of the roadway to vehicle speed/highway command function.......................71
32. A freeway system subdivided into sections.............................................................................82
33. Traffic flow entering section 1 during case with a low input traffic flow..................................84
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List of Figures
(continued)
34. (a) Evolution of traffic density when no roadway controller is present. The disturbance
propagates back down the roadway after the accident is removed from section 8. (b) Evolution
of traffic density when the roadway controller is present. The disturbance quickly dies out after
the accident is removed from section 8. ..................................................................................85
35. (a) Evolution of traffic velocity when no roadway controller is present. The disturbance
propagates back down the roadway after the accident is removed from section 8 causing changes
of speed back to section 1. (b) Evolution of traffic velocity when the roadway controller is
present. The disturbance quickly dies out after the accident is removed from section 8 and the
vehicles resume a constant speed.............................................................................................86
36. (a) The traffic flow evolution with respect to time with no roadway control. It takes more than
30 minutes (2000 s) for the traffic flow disturbances to subside. (b) The traffic flow evolution
with respect to time for the roadway with roadway control. The traffic flow quickly smooths out
to the steady state velocity......................................................................................................87
37. The traffic flow evolution with respect to time for the roadway with roadway control. The traffic
flow quickly smooths out to the steady state velocity..............................................................89
38. (a) Evolution of traffic density when no roadway controller is present. The disturbance
propagates back down the roadway after the accident is removed from section 8. (b) Evolution of
traffic density when the roadway controller is present. The disturbance quickly dies out after the
accident is removed from section 8. .......................................................................................90
39. (a) Evolution of traffic velocity when no roadway controller is present. The disturbance
propagates back down the roadway after the accident is removed from section 8 causing changes
of speed back to section 1. (b) Evolution of traffic velocity when the roadway controller is
present. The disturbance quickly dies out after the accident is removed from section 8 and the
vehicles resume a constant speed.............................................................................................91
40. Block diagram of the speed and headway maintenance function. The sensors measure the relative
speed and spacing of the vehicles, then the controller sends commands to the brake and throttle
actuators so that the vehicle maintains the target speed or minimum headway.........................98
41 Sensor requirements for range and closing rate detection for the speed and headway maintenance
system.....................................................................................................................................99
42. The maximum distance sensor range versus the maximum vehicle deceleration for the “brick
wall” scenario at two different velocities. The maximum vehicle deceleration is the vehicle
capability on the roadway at a given time. It reflects the road-tire friction coefficient and
vehicle’s capabilities...............................................................................................................100
43. Minimum safe time headway with respect to differences in the maximum deceleration between
vehicles ÆAm= Alm–Afm. A negative acceleration value means that the follower car can brake
faster than the lead car. ERSC 1 is the headway when the driver is responsible for any
emergency braking situations. ERSC 2 shows the minimum headway when the vehicle has a
rear-end collision avoidance function......................................................................................102
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List of Figures
(continued)
44. Minimum safe time headway with respect to differences in the initial velocity of the vehicles
ÆVm= Vfm–Vlm. A negative velocity difference means that the follower car is going faster than
the lead car. ERSC 1 is the headway when the driver is responsible for any emergency braking
situations with a 1.5 second human reaction time. ERSC 2 shows the minimum headway when
the vehicle has a rear-end collision avoidance function............................................................103
45. As the road-tire friction coefficient decreases (the road gets more slippery), the minimum safe
time headway increases. ÆAm= Alm–Afm is the deceleration difference between the vehicles in
g. A positive value means that the lead car has a larger deceleration than the follower vehicle.104
46. Minimum safe distance between vehicles for different velocities . ERSC 1 is the headway
when the driver is responsible for any emergency braking situations. ERSC 2 shows the
minimum headway when the vehicle has a rear-end collision avoidance function....................105
47. Block diagram of the rear-end collision avoidance system. The sensor measures the distance to
obstacles. The controller assesses collision potential. This controller overrides the SHM
function if an emergency stop is required................................................................................107
48. Different collision avoidance scenarios for the rear-end collision avoidance function. (a) The
vehicle ahead begins an emergency stopping maneuver. (b) Another vehicle is stopped in the
lane ahead. (c) The preceding vehicle performs an evasive maneuver by steering out of the lane
to avoid a vehicle or debris ahead. (d) Another vehicle cuts-in ahead.....................................108
49. The maximum sensor range with respect to the maximum deceleration of the vehicle at 60 mph
for ERSCs 1 and 2 (SHM without and with rear-end collision avoidance) These values come
from the “brick wall” scenario when the lead vehicle is stationary or there is debris on the
highway..................................................................................................................................109
50. Changes in the detection time for lane change/merge collisions have a large effect on the
potential accident severity.......................................................................................................110
51. The probability of correctly deciding that the vehicle ahead is decelerating depends on the space
between the two signals d. As d increases the detection-false alarm trade-off improves..........112
52. The deceleration difference between the vehicles ÆAm= Alm–Afm has a large effect on accident
severity. As ÆAm increases the potential accident severity increases......................................113
53. Block diagram of the lane departure warning system.. The lane position sensors give the
vehicle’s position in the lane. The warning system calculates the time-to-lane-crossing and
warns the driver if necessary...................................................................................................115
54. Variables used in the calculation of the time to lane crossing..................................................116