Robotics Group 7

This repository allows to control a robotic arm with 4 AX-12A servos.

Units conventions

If not specified otherwise:

• All angles are in radians.
• All distances are in meters.

Frames

The robot is composed of 4 frames following the Denavit-Hartenberg convention.

The frames are defined as follows:

Frame	theta	d	a	alpha
1	theta_1	0.05	0	pi/2
2	theta_2	0	0.093	0
3	theta_3	0	0.093	0
4	theta_4	0	0.05	0

The end effector isn't represented in the current version.

Description of the files

• Servo.py: contains the class Servo which allows to control a servo motor.
• RobotDescription.py: contains the class RobotDescription which allows to describe the robot, especially the frames and the reverse kinematics.
• Robot.py: contains the class Robot which allows to control the robot. It uses the class Servo.
• Simulation.py: contains the class Simulation which allows to simulate the PacketHandler from the dynamixel library.
• Visualizer.py: contains the class Visualizer which allows to visualize the robot in 3D.
• Camera.py: contains the class Camera which allows to calibrate and control the camera.
• test_reverse_kinematics.py: contains the tests for the reverse kinematics. Use mpi to run the tests in parallel.

Camera frames

Camera frame

How to use

Installation

pip install -r requirements.txt

Note: tqdm and mpi4py are only required for the test of the reverse kinematics.

Start

Change the value of sim in main.py to False to use the real robot. The calibration of the camera requires a chessboard image.

python main.py

Then follow the instructions in the terminal.

Start the test of the reverse kinematics

mpiexec -n 8 python -m mpi4py test_reverse_kinematics.py