Cruise ControlCruise Control

OutlineOutline► Introduction to Cruise Control Introduction to Cruise Control ►CC ModelingCC Modeling►CC SimulationCC Simulation

► Introduction to Adaptive ControlIntroduction to Adaptive Control►ACC ModelingACC Modeling►ACC SimulationACC Simulation

Cruise Control SystemCruise Control System

► Input: buttons on Input: buttons on the steering wheel, the steering wheel, brake, clutch, gas brake, clutch, gas pedal and feedback pedal and feedback signalsignal

► ProcessorProcessor► SensorSensor►Output: the throttle Output: the throttle

positionposition

ModelingModeling

m s V s( ) b V s( ) U s( )

Newton’s Second Law: m

dvdt

b v t( ) u t( )

Laplace Transform:

Transfer FunctionTransfer FunctionY s( )U s( )

1m s b

Design SpecificationDesign Specification►Rise time < 5 secRise time < 5 sec►Overshoot < 10%Overshoot < 10%►Steady-State Error < 2%Steady-State Error < 2%

Open-Looped SystemOpen-Looped System

Closed-Loop w/ PI ControlClosed-Loop w/ PI Control

Kp = 100 Kp = 800 and Ki = 40

weight of the carweight of the car

m = 500 kg

PI Control: Kp = 800 and Ki = 40

m = 2000 kg

Adaptive Cruise ControlAdaptive Cruise Control►So-called Active Cruise Control (ACC)So-called Active Cruise Control (ACC)►Traffic flow characteristicsTraffic flow characteristics►Collision-avoidance systemCollision-avoidance system►Not to be considered as a safety Not to be considered as a safety

feature by automakersfeature by automakers

BackgroundBackground►First laser-based system – Toyota’s First laser-based system – Toyota’s

Progress, a compact luxury sedan, in Progress, a compact luxury sedan, in 19981998

►First radar-based system – Nissan’s First radar-based system – Nissan’s Cima 41LV-2, a luxury sedanCima 41LV-2, a luxury sedan

►First American ACC model – Lexus’ LS First American ACC model – Lexus’ LS 430, in 2000430, in 2000

FunctionFunction► Preset and maintain the car speedPreset and maintain the car speed►Measure the distance to the preceding car Measure the distance to the preceding car

and the relative speedand the relative speed► Adjust the car speed accordinglyAdjust the car speed accordingly►Maximum deceleration = 3.5m/s^2Maximum deceleration = 3.5m/s^2

Adaptive Cruise ControlAdaptive Cruise Control►Change gear automaticallyChange gear automatically►Function properly in poor weather conditionFunction properly in poor weather condition►Cannot pick up non-moving objectsCannot pick up non-moving objects►Effective in the speed between 30km-Effective in the speed between 30km-

180km/h180km/h

Two types of ACC Two types of ACC ►Radar-Based System Radar-Based System – – Three overlapping radar-beams (76-Three overlapping radar-beams (76-

77kHz)77kHz)-- Detects moving object up to 120 m -- Detects moving object up to 120 m – – work in poor weather conditionswork in poor weather conditions►Laser-Based System (lidar) Laser-Based System (lidar) – – less expensive and easier to package less expensive and easier to package – – light beams are narrower than water light beams are narrower than water

droplet and snowflakesdroplet and snowflakes

Radar-based Adaptive Cruise Radar-based Adaptive Cruise ControlControl

Modeling in Highway Merging Modeling in Highway Merging

rd t( ) 6.33v0.48 2

By R. Sengupta and Q. Xu

ades t( ) kv tr t( )d

d kp r t( ) rd t( )

ACC Controller

Desired Range

Highway Merge-In ScenarioHighway Merge-In Scenario►1. At 0 sec, the preceding vehicle is 1. At 0 sec, the preceding vehicle is

traveling 12.5 m/straveling 12.5 m/s►2. The follower vehicle w/ACC is 150 2. The follower vehicle w/ACC is 150

m behind the preceding vehicle and is m behind the preceding vehicle and is traveling at 25 m/straveling at 25 m/s

►3. At 10 sec, the third vehicle cut in in 3. At 10 sec, the third vehicle cut in in between the two vehiclesbetween the two vehicles

Simulation in Highway Simulation in Highway MergingMerging

By R. Sengupta and Q. Xu

AccelerationAcceleration

Dotted Line = Desired AccelerationSolid Line = Actual Acceleration

By R. Sengupta and Q. Xu

ImplementationImplementation

Distance Source Distance Source

ACC Response CC Response (for comparison)