This repository contains code for the robot controller, it should be added as a submodule to the main Webots project repository. Documentation can be found at https://idp-l211.github.io/controllers/.
The robot chooses the closest accessible target to drive to, or perform a scan if no such target is available. When the robot reaches a target, it will check the colour using two LDRs. If the colour is wrong, the robot will send the confirmed position to the other robot.
Custom classes for devices are created by inheriting from classes in Webots C
interface, which are then composed together in a robot class. Various
subroutines are also handle by child classes (e.g. TargetingHandler). The
class diagram is shown below
DBSCAN clustering algorithm is used in the scanning subroutine to calculate block positions from filtered data from IR sensor and GPS. This means the effect of noise is minimised, and the target positions are relatively accurate.
The targeting algorithm picks the closest block of a valid class that has a clear path to it. A clear path is determined by creating a rectangle from the robot to the target and checking no other object is inside it. It will start the check from the closest potential target and continue until a valid target is found. When driving to the selected target, an active collision avoidance algorithm (with a similar working principle) diverts the robot to a different target if necessary.
A passive collision avoidance algorithm is used when the robot is not moving towards a block. It calculates the distance to each known object and then does a weighted sum of the current target angle and the angles to avoid each object (i.e. right angle away from it). A recursive component is added to combine small obstructions into larger ones to avoid clusters of blocks.
When the robot is far from the target, proportional combined with open loop control is used to achieve a velocity. When nearby, a proportional distance controller is used. A non-linear controller which uses both error and derivative are used to control the angle. The two controllers produced forward and rotational velocities respectively, which were combined to give the overall motor velocities.
It is useful to set up a proper development environment with the provided
controller module (a C interface) included in your linter/IDE and set the
robot controller to <extern> in Webots for debugging. More information at
https://cyberbotics.com/doc/guide/using-your-ide?tab-language=python. The main
steps for PyCharm are:
- Configure the virtual environment in Project Interpreter
- Add the correct Webots
controllerdirectory (depending on your system and Python configuration,controller/_controller.sois slightly different) as Content Root under Project Structure - Create a Run/Debug Configuration, setting the relevant environment variables
If you prefer to run controller directly from Webots, have a look at
https://cyberbotics.com/doc/guide/using-python. This is especially important
for people using macOS and Homebrew, you may need to set the full path to your
Python interpreter (get it by which python3).