1. Autonomous vehicle navigation An Obstacle Avoidance Exercise
Luca Baglivo, Mariolino De Cecco

2. We’re using two-dimensional grids: maps represented as images!

3. Example from CAD to Image

4. Let’s consider the following simplified scenario:
Goal
Start

5. + ATTRACTIVE POTENTIAL REPULSIVE POTENTIAL
… AND IMAGINE ROBOT AS A BALL ROLLING DOWN HILLS

6. TOTAL POTENTIAL

7. POTENTIAL FIELDS METHOD FEATURES:
AUTOMATIC PATH PLANNING FOR OBSTACLE AVOIDANCE
IS BOTH A PLANNING & CONTROL STRATEGY ALL-IN-ONE
BEST FOR LOCAL PATH PLANNING->UNEXPECTED OBSTACLES
BE AWARE FROM LOCAL MINIMA! HARMONIC POTENTIAL FUNCTIONS HAS PROVEN ONLY GLOBAL MINIMA
NOT SUITABLE FOR HIGH PRECISION POSITIONING ON TARGET

8. A FORMULATION

9. A FORMULATION

10. A FORMULATION

11. A FORMULATION

12. A FORMULATION

13. THE RESULTING FORCE IS THE GRADIENT AND GIVES DIRECTION TO THE ROBOT
This example is in the Matlab script “OstacoliQuadrati.m”

14. ANOTHER, NAIVE FORMULATION
A VIRTUAL CORIDOR ALIGNMENT FOR LINE FOLLOWING
The attractive potential can be defined punctually as desired.
Build a vector field that point towards desired path.

15. ANOTHER, NAIVE FORMULATION
A VIRTUAL CORRIDOR ALIGNMENT FOR LINE FOLLOWING
How to define it yF
alphaK
angles (+) y K xF Lc

16. ANOTHER, NAIVE FORMULATION
A VIRTUAL CORIDOR ALIGNMENT FOR LINE FOLLOWING
How to compute steering angle input aK d y K
steering axis

17. ANOTHER, NAIVE FORMULATION
A VIRTUAL CORIDOR ALIGNMENT FOR LINE FOLLOWING
Now add the repulsive force vector Frep, and play …
Frep
Ftot
delta’ y K

18. ANOTHER, NAIVE FORMULATION
A VIRTUAL CORIDOR ALIGNMENT FOR LINE FOLLOWING
A control sketch y
Potential field gradient vector
velocity
Robot kinematic model
alphaK
steer angle -
delta +
Steer control
kcontrol

19. ANOTHER, NAIVE FORMULATION
A VIRTUAL CORIDOR ALIGNMENT FOR LINE FOLLOWING
Try with:
Tricycle robot forward velocity, point obstacle at (xF,yF) = (4,1.5) yR b D1

20. Bibliography
Siegwart R., Nourbakhsh I, Scaramuzza D., Introduction to Autonomous Mobile Robots