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Enhanced AHS Safety Through the Integration of Vehicle Control and Communication. October 2002 J. K. Hedrick, R. Sengupta, Q. Xu, C. Lee, Y. Kang. Communication architecture. Goal = wireless network useful for: 1) Cooperative friction estimation 2) Cooperative Emergency Maneuver

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enhanced ahs safety through the integration of vehicle control and communication

Enhanced AHS Safety Through the Integration of Vehicle Control and Communication

October 2002

J. K. Hedrick, R. Sengupta,

Q. Xu, C. Lee, Y. Kang

research areas
Communication architecture

Goal = wireless network useful for:

1) Cooperative friction estimation

2) Cooperative Emergency Maneuver

3) AHS and cooperative

adaptive cruise control

Emergency Braking Maneuvers

Tire/road friction estimation

Goal: Develop a safe control strategy for the emergency braking maneuver of platoons.

Goal: Real time estimation of maximum tire-road friction

Research Areas
project goals
Communication architecture

Tire/road friction estimation

Road

Condition & Maximum

Friction Coeff.

Information from other vehicles and road side infra structure.

Emergency Braking Maneuvers

“ SAFETY ”

Project Goals
overview and benefits of the research
Overview andBenefits of the Research
  • Overview
    • Empirical approach
    • Effect-based method
    • Real Time work
  • Benefits
    • Estimation of max. acceleration limit of the vehicle.
    • Emergency Braking Control for the Platoon.
    • Road Condition vs. Position Map.
slip friction coefficient calculation
Slip/Friction Coefficient Calculation
  • Friction Coefficient
  • Slip
  • Max Acceleration

Maximum friction coefficients determines

maximum acceleration or deceleration

slip slope vs
Slip Slope Vs

Affecting Factors

  • Road Condition
  • Tire Type
  • Tread Pattern
  • Tread Depth
  • Velocity

Focus on Linear Region

Slip Slope, k

static normal force observer
Static Normal Force Observer

Normal Force friction coefficient calculation

effective tire radius estimation

Static normal force observer assumes a static model for vehicle3% error comparing to dynamic vehicle model

Static Normal Force Model

effective tire radius observer
Effective Tire Radius Observer
  • Tire radius is required for Slip Calculation

Tire Radius Change is a Function of

  • Normal Force
  • Tire Pressure
  • Velocity
brake gain estimator
Brake Gain Estimator
  • Brake Gain Change
    • Heat
    • Water
    • Wear of Brake Pad, etc.

sometimes changes more than 50%

  • Model : Front Wheel Dynamics
  • Method : Recursive Least Square Method Using Bounded Forgetting
slip slope vs13
Slip Slope Vs

Each vehicle has its own slip slope under same road

Dry road condition set as Reference slip slope

Maximum friction coefficient change rate / Slip slope change rate based on reference slip slope

Linear Assumption

slip slope and estimation
Slip Slope and Estimation
  • Example : Wet  Dry

Slip Slope Estimation

Using RLS method

Estimation

Based on slip slope

emergency braking controller longitudinal control
Emergency Braking Controller(Longitudinal Control)
  • Requirements for emergency braking control
    • Control robustness against the high slip condition between road and tire.
    • Friction coefficients estimation algorithm.
  • Control method : Dynamic Surface Control
experimental set up
Experimental Set-up
  • Experimental Vehicle used

: Ford red Lincoln town car

  • Sensors and actuators

: wheel speed sensors

brake pressure sensors

5th wheel speed sensor

brake and throttle actuators

  • Computers with real-time OS

: QNX operating system

simulation results
Simulation Results
  • Simulation with Dynamic Surface Control (6 m/s2 deceleration)
experimental results
Experimental Results
  • Experiments in same situation

( 6 m/s2 deceleration)

analysis of the result
Analysis of the Result
  • The performance of the Dynamic Surface Controller is reasonable(1~2m error with –6 m/s2) in an emergency braking situation.
  • Control performance depends on friction coefficients.

 “Friction coefficient estimation” is

important.

emergency braking control strategies for platoons
((((Emergency Braking Control Strategies for Platoons
  • Emergency braking for the Platoons

: Difference of max. deceleration limit between vehicles can result in collision.

  • Cooperative Emergency Control.

))))

Vehicle with Worst Braking Capacity transmits its info.

simulation results22
Simulation Results
  • Space & velocity tracking

[m/s]

[m]

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