Lab02 - Reactive-based Autonomous Robot Behavior

Motivations and Goals
Become familiar with reactive-based robot control
Become familiar with collision-avoidance and be aware of robot sensors
Be able to implement reactive based control of mobile robot
Tasks (teacher)
Implement “Tangent Bug algorithm” for autonomous reactive-based navigation of hexapod walking robot (2 Points)
The robot has to pass through the environment using the implemented algorithm
Lab resources
Lab scripts: lab02 resource files
V-REP scenes: simple_distance.ttt, obstacles.ttt
V-REP remoteAPI: hexapod_vrep

Bug algorithm

Reactive algorithm for obstacle avoidance ¹⁾ assuming only a local knowledge about the environment.
Uses only two motion primitives:

Follow a wall (left or right)
Move in straight line towards the goal

Different types of bug algorithm

Tangent bug algorithm

Head towards the goal
Follow obstacles until you can head to the goal again
Repeat

https://www.youtube.com/watch?v=SKelVC02S-U

Bug algorithm 1

Head towards the goal
Circumnavigate obstacles and remember how close you get to the goal
Return to the point which was closest to the goal and head to the goal
Repeat

https://www.youtube.com/watch?v=Vm37TRRJAjc

Bug algorithm 2

Head towards the goal along the straight line $m$ connecting start and goal
Circumnavigate obstacles until you encounter the $m$ line again
Continue towards the goal along the $m$ line
Repeat

https://www.youtube.com/watch?v=5MdKaZuXdfY

Task 1
Think of the pitfalls for individual versions of the bug algorithm. What are upper/lower bounds on the path length that the robot takes?

Task 2 (2 Points)
Implement the tangent bug algorithm and test its performance in obstacles.ttt scene. Set the goal position of the robot to be [-1.6, 1.6].

Support files

Support files for lab2

¹⁾

Carnegie Mellon University - School of Computer Science slides on bug algorithm

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