45119386 Adaptive Cruise Control

Published on May 2016 | Categories: Documents | Downloads: 47 | Comments: 0 | Views: 554
of 43
Download PDF   Embed   Report

Comments

Content

Adaptive Cruise Control
Gurulingesh R. KReSIT, IIT Bombay

Advisor(s): Prof. Krithi Ramamritham Prof. S. Ramesh Prof. Kavi Arya

Overview
• • • • • • • • Introduction Components Design Implementation Results and Observations Further Work References Demo/Video

Goals of the Project
• Study the ACC application and to identify
– Components – Algorithms – Real-Time Issues

• Real-Time approach to Design • Setup a basic platform

Introduction to ACC

• Extension of Cruise Control. • Operates either in • Distance Control state

• Speed Control state

Des_Dist = Host_Vel * Timegap + ∆
Host_Vel TimeGap ∆

where

is Host Vehicle velocity is set by the driver for additional safety

Requirements
• Functional:
– – – – Detect leading vehicle. Maintain desired speed. Maintain desired timegap. Communicate actions to User Interface

• Non-Functional (timing constraints):
– Response Time – Data update rate and so on…

• ISO Limitations:
– mean dec ≤ 3.0 m/s2 (over 2 s), – acceleration ≤ 2 m/s2

Overview
• • • • • • • Introduction Components Design Implementation Results and Observations Further Work References

Components of ACC
USER INTERFACE SENSOR SENSOR FUSION TAC TA

Sensors: Four Wheel Sensors, Brake Pedal Sensor, Throttle Pedal Senor, Radar … Actuators: Brake Actuator, Throttle Actuator. Controllers: High level & Low level controller. Communication Medium

CONTROL UNIT
TARGET DETECTION TARGET TRACKING

BAC

BA

RADAR

Overview
• • • • • • • Introduction Components Design Implementation Results and Observations Further Work References

Functionality and Data Flow

Controller State Diagram
State Variables
1. Current speed 2. Cruise Status

3. Brake
4. Throttle 5. Leading Vehicle 6. Driver Intervention

Possible Events:
Curr-speed > 25 km/h

Radar contact found
Driver intervention Lead-distance > safe-dist and so on.

State Switching Issue
• When to switch state?
S-to-D: Curr_Dist < TimeGap * Host_Vel + ∆ D-to-S: (Host_Vel > Des_Vel) || (Curr_Dist ≥ TimeGap * Host_Vel + ∆)

• Chattering
S-to-D: Curr_Dist < TimeGap * Host_Vel + ∆ - hyst && RoD ≤ 0 D-to-S: (Host_Vel > Des_Vel) || (Curr_Dist ≥ TimeGap * Host_Vel + ∆ + hyst && RoD ≥0)

where RoD

is Rate of change of Distance

Task and Data Items
• Tasks:
WheelTi(1≤i≤4), SpeedT, RadarT, DriverT, SwitchT, ExceptionT, AdjLaneT, FrictionT, AdaptT, ModeSwT.

• Data Items:
WheelSpeed[wi], HostVel, LeadVel, LeadDist, RoadType, LeftLane[vi, di], RightLane[vi, di], DesAcc, DesSpeed.

Issues
1. Dynamically varying data
Dist






Time

Prepare for the Worst Over-Sampling

Issues (cont…)
2. When to Update

Unnecessary Updates

Issues (cont…)
3. All Tasks and Data throughout the system operation??
•AdaptT when lead car is near

•AdjLaneT, TimeLeftT when car is far

Poor CPU utilization Scheduling Overhead Not modular

Approach
• Mode-Change System
– Exclusive modes of operation – Mode change leads to:
• Addition of a task • Change in frequency of execution • Deletion of a task

• Data Repository

(Neera Sharma)

– updates in response to changes in the data items (on-demand update).

Approach (cont…)
• Mode-Change System
– Dynamically varying data – All Tasks and Data throughout the system operation

• Data Repository
– Dynamically varying data – Derived Data Items

Issues
• With mode-changes:
– How many modes – What triggers mode change – When to switch mode – Chattering – Mode-change delay – Schedulability

• With Data Repository
– How many levels – When to update

Solution to mode-change
• How many?
– Two: Safety-Critical(SC), Non-Safety Critical(NC)

• When to switch?
– Finish task execution.

• Mode-change delay
– Bounded by longest periodicity task.

• Schedulability
– Static checking.

Solution to mode-change…
• What triggers mode change?
LeadDist RoD OR OR
LeadDist FAR RoD DECR-FAST Mode SC

FAR
FAR FAR CLOSE

INCR-FAST
DECR-SLOW INCR-SLOW ----

NC
NC NC SC

LeadDist & RoD

FOLLOW

----

RETAIN

Solution to mode-change…
• Chattering
– In SC Mode:
(Safe_Dist+ < Curr_Dist ≤ Follow_Dist-) || (Follow_Dist+ < Curr_Dist ≤ Radar_Dist && RoD = DECR-FAST) (Follow_Dist- < Curr_Dist ≤ Follow_Dist+ && Curr_Mode = SC) ||

– In NC Mode:
(Follow_Dist+ < Curr_Dist ≤ Radar_Dist && RoD ≠ DECR-FAST) (Follow_Dist- < Curr_Dist ≤ Follow_Dist+ && Curr_Mode = NC) ||

Solution to Data Repository
• How many levels

Example:
First-Level: Raw data from radar, wheel sensor, etc… Second-Level: Host Velocity, Lead Distance, etc…

Solution to Data Repository…
• When to update

First-Level: Continous Second-Level: On-Demand based on R(d)

Scheduling
• Mode-Change approach
– All Tasks are identified in advance. – All tasks are periodic. – RMS

• Data Repository approach
– Aperiodic tasks. – Guarantee to aperiodic tasks. – CBS

Overview
• • • • • • • Introduction Components Design Implementation Results and Observations Further Work References

Implementation
• Hardware
– Ultra-sonic Distance Meter (UDM)
• Purpose: leading vehicle distance • Range: 1.3m • Accuracy: ± 2.5cm • Sampling Rate: 1 per sec

– Shaft Encoder (ENC)
• Purpose: Host Velocity • Resolution: 1 cm per step

– Communication (PC
• Printer Port

Robot)

Ver – 1: Leader and Follower

Hardware Expert: Sachitanand Malewar

Follower Version-2

Front view • UDM • Shaft Encoder

Side View

• Range: 2m, Accuracy: ± 1cm, Sampling Rate: 10 per sec

• Resolution: 0.4cm

Software Implementation
• Two-Level Repository Approach

• CBS Scheduling

Software Implementation …
• Mode-Change Approach
– Same task structure with:
• dummy tasks in each mode. • Mode-switch task.

– All Tasks are periodic.
– RMS Scheduling

– Mode change after the completion of least priority task.
• Delay bounded by its periodicity.

Software Implementation …
• Mode-Change Approach (cont…)
– Task Periodicity (in seconds):
• • • • • UDM_WR: 0.2 ENC_WR: 0.3 UDM_RD, UDM_VEL: 0.4 ENC_RD: 0.6 CTRL_TASK: 0.7 MODE_SW: 0.4 ( = UDM_RD)

Software Implementation …
• Data Logging:
– RT-FIFO

RTLinux Architecture

Overview
• • • • • • • Introduction Components Design Implementation Results and Observations Further Work References

Results & Observations
• Cruise Control Operation • Set speed = 35 m/s2

• Open-loop lower controller •Shaft encoder error

Results & Observations…
• Constant Leading Distance • LeadDist = 63 cm • Timegap = 1.8 s

Results & Observations…
• Linear Increase-Decrease • Timegap = 1.5 s

Results & Observations…
• Two-Level Repository • Tested for UDM_RD Task

•Lead Dist = 69 cm

Overview
• • • • • • • Introduction Components Design Implementation Results and Observations Further Work References

More Experiments…
• Effect of mode-change delay

• Improve in CPU utilization
• LeadDist, RoD values • Periodicity of tasks, data update rate

• Chattering b/w SC-NC Mode Switching
BETTER VEHICLE

Further Work
• More experiments to evaluate the design.

• Implementing two-level repository on RealTime Data Base.
• Is printer port good enough or need for RTCommunication (TTP/TTCAN/CAN). • Merging with Lane Changing.

• Inter-Vehicle communication.
• Formal modeling using UPPAAL/KRONOS.

Goals Revisited
• Study the ACC application and to identify
– Components – Algorithms – Real-Time Issues

• Real-Time approach to Design • Setup a basic platform

References
• Petros Ioannou; Cheng-Chih Chien. “Autonomous Intelligent Cruise Control”. IEEE Trans. On Vehicular Technology, 42(4):657-672, 1993. • Thomas Gustafsson; Jörgen Hansson. “Dynamic on-demand updating of data in real-time database systems”. In Proceedings of ACM SAC 2004. • Gerhard Fohler; “Flexibility in Statically Scheduling Real-Time Systems”. PhD Thesis, Technischen Universitat Wien Austria, Apr. 1994. • L. Sha; R. Rajkumar; J. Lehoczky; K. Ramamritham. “Mode Change Protocols for Priority-Driven Preemptive Scheduling”. Technical Report: UM-CS-1989-060, University of Massachusetts Amherst, MA, USA.

Video Clip

THANK YOU

Sponsor Documents

Or use your account on DocShare.tips

Hide

Forgot your password?

Or register your new account on DocShare.tips

Hide

Lost your password? Please enter your email address. You will receive a link to create a new password.

Back to log-in

Close