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Autonomous Obstacle Avoidance Exercise in Vehicle Navigation

Explore obstacle avoidance using attractive and repulsive potentials in two-dimensional grids. Learn about potential fields method for automatic path planning and control strategy. Find out more with a virtual corridor alignment for line following.

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Autonomous Obstacle Avoidance Exercise in Vehicle Navigation

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  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) D1 yR b

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

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