Adaptive Cruise Control Adaptive Cruise Control (ACC)(ACC)

.. Sushant S Sushant S VharakatVharakat

B.E. MechanicalB.E. Mechanical

ReferenceReference[1] [1] A Safe Longitudinal Control for Adaptive Cruise Control and A Safe Longitudinal Control for Adaptive Cruise Control and

Stop-and-Go ScenariosStop-and-Go ScenariosMartinez, J.-J.; Canudas-de-Wit, C.; Volume 15,  Issue 2,  March 2007 Martinez, J.-J.; Canudas-de-Wit, C.; Volume 15,  Issue 2,  March 2007 Page(s):246 – 258Page(s):246 – 258

[2] [2] Modeling a Cruise ControlModeling a Cruise Control http://www.library.cmu.edu/ctms/ctms/examples/cruise/cc.htmhttp://www.library.cmu.edu/ctms/ctms/examples/cruise/cc.htm

[3] [3] Highway Speed ControllerHighway Speed Controllerhttp://www.site.uottawa.ca/~misbah/elg4392/HC12CodeWarriorC/http://www.site.uottawa.ca/~misbah/elg4392/HC12CodeWarriorC/HighwaySpeedController/project.cHighwaySpeedController/project.c

[4] W. Jones, “Keeping cars from crashing,” IEEE Spectrum, vol. 38, no.9, pp. 40–45, Sep. 2001.

[5] M. A. Goodrich and E. R. Boer, “Designing human-centered automation:Tradeoffs in collision avoidance system design,” IEEE Trans. Intell.Transp. Syst., vol. 1, no. 1, pp. 40–54, Mar. 2000.

Problem StatementProblem Statement The main problem regarding the The main problem regarding the

normal Cruise Control technology is normal Cruise Control technology is that it is not aware of other vehicles’s that it is not aware of other vehicles’s movementmovement

The driver must be always aware. The driver must be always aware. Hence, possibility of mistakesHence, possibility of mistakes

Possibility of collision with the leading Possibility of collision with the leading car if not manually slowed downcar if not manually slowed down

Proposed SolutionProposed Solution Introduce Adaptive Cruise Control Introduce Adaptive Cruise Control

for longitudinal control of the for longitudinal control of the vehiclevehicle

Speed would be automatically Speed would be automatically adjusted for safe inter-distanceadjusted for safe inter-distance

Once safe inter-distance is reached, Once safe inter-distance is reached, the speed would return to the the speed would return to the desired speed set by the driverdesired speed set by the driver

Technical ObjectivesTechnical Objectives To design a control system for ACC.To design a control system for ACC. No overshootNo overshoot Settling Time of about 4-7 seconds.Settling Time of about 4-7 seconds. No oscillation (because no No oscillation (because no

overshoot)overshoot) A steady-state error of 0A steady-state error of 0

Vehicle CharacteristicsVehicle Characteristics If the inertia of the wheels is If the inertia of the wheels is

neglected, and it is assumed that neglected, and it is assumed that friction (which is proportional to the friction (which is proportional to the car's speed) is what is opposing the car's speed) is what is opposing the motion of the car, then the problem motion of the car, then the problem is reduced to the simple mass and is reduced to the simple mass and damper system shown in the next damper system shown in the next slide.slide.

Vehicle CharacteristicsVehicle Characteristics

System Block Diagram System Block Diagram [2][2]

Controller SelectionController Selection

Which kind of Controller is the best?Which kind of Controller is the best? No controller.No controller. P controller.P controller. PI controller.PI controller. PID controller.PID controller. PD controller.PD controller.

Controller SelectionController SelectionP ControllerP ControllerNo ControllerNo Controller

Step Response

Time (sec)

Ampl

itude

0 20 40 60 80 100 1200

0.002

0.004

0.006

0.008

0.01

0.012

0.014

0.016

0.018

0.02

System: untitled1Settling Time (sec): 76.7

Settling time = 76.7 sSteady state error > 98%

Kp = 10000Settling Time = 0.389sSteady state error = 2%

Step Response

Time (sec)

Ampl

itude

0 0.1 0.2 0.3 0.4 0.5 0.60

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

System: untitled1Settling Time (sec): 0.389

Controller SelectionController Selection

Kp=800, Ki=40Settling time = 4.89 sSteady state error = 0

Step Response

Time (sec)

Ampl

itude

0 1 2 3 4 5 6 70

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

System: untitled1Settling Time (sec): 4.89

PI ControllerPI Controller

*Final choice is PI Controller*

Distance Checking [1]Distance Checking [1]

Three scenarios:Three scenarios: ddr > r > dd00, cruises at desired speed, ACC inactive, cruises at desired speed, ACC inactive ddrr < d < dcc, danger zone, ACC enables to slow down, danger zone, ACC enables to slow down dd00 < d < drr < d < d00, ACC is enable to reach safe inter-, ACC is enable to reach safe inter-

distance distance

Implementation of Distance Implementation of Distance Checking [3]Checking [3]

The distance checking algorithm only requires a The distance checking algorithm only requires a minimum distance and a range.minimum distance and a range.

The algorithm calculates the actual minimum distance The algorithm calculates the actual minimum distance (> provided distance) and maximum distance and then (> provided distance) and maximum distance and then outputs the new speed of the vehicle. outputs the new speed of the vehicle.

The user can also provide a maximum and minimum The user can also provide a maximum and minimum speed for the vehicle.speed for the vehicle.

Implementation of Distance Implementation of Distance CheckingChecking

temp=(300*(speedmax-speedmin))/(12*range)

minimum_Distance=(minimum_Distance*32)/10

max_Distance = minimum_Distance + (3*range) if (distance > (max_Distance)) speed = speedmax; if (distance < minimum_Distance) speed = 0; if ((distance < max_Distance) and (distance>minimum_Distance)) if leader_speed > 0 speed = ((100*speedmin-(kvit*(minimum_distance))) + temp * distance)/100; else speed = ((100*speedmin+(kvit*(max_Distance))) + temp * distance)/100;

SimulationSimulation

Maximum follower vehicle speed = 100 m/sMaximum follower vehicle speed = 100 m/s Minimum follower vehicle speed = 0 m/sMinimum follower vehicle speed = 0 m/s Minimum distance = 40 mMinimum distance = 40 m Range = 20 mRange = 20 m Initial distance = 80 mInitial distance = 80 m Kp = 800Kp = 800 Ki = 40Ki = 40 b = 50b = 50 m = 1000m = 1000

The following parameters were used for the simulation:The following parameters were used for the simulation:

Final Model (simplified)Final Model (simplified)

SimulationSimulationYellow: Distance between two vehiclesBlue: Speed of the leader vehiclePurple: Speed of the follower vehicle

Limitations/ConclusionLimitations/Conclusion Not a complete transfer function of Not a complete transfer function of

the vehicle and environment.the vehicle and environment. Linear distance-checking model.Linear distance-checking model. No limitations on the acceleration No limitations on the acceleration

and jerk.and jerk. Our model is simplified compared to Our model is simplified compared to

real-time models, but can be used to real-time models, but can be used to implement a practical ACC.implement a practical ACC.