Graduate Capstone: simple 2 joint arm for serial chain manipulator education

See link below for full report.

In the completion of my graduate degree I chose to complete a capstone instead of a thesis in the interest of time. This project was made under the supervision of Dr. Christopher Kitts, the head of the Robotic System Laboratory at Santa Clara University. Dr. Kitts teaches several courses on mechatronics and robotics including a class focused on serial chain manipulators. He wanted a platform on which he could demonstrate properties of these robots and have students interface with the robot as well such that they could be assigned experiments adding a practical element to his course.

I developed this simple two link robot based on the requirements set forth by Dr. Kitts. The arm is driven by two Robotis Dynamixel servo motors, that also contain sensors. All of the software for the project is written in Python, and all of the computation is done on a raspberry pi. The pi handles serial communication with the dynamixel motors, does all of the kinematics and controls calculations, hosts a webserver with basic UI over which commands can be sent and telemetry viewed, and provides a livestream from a camera so that operations can be sent remotely.

The system includes a number of preprogrammed demonstrations enumerated below.
1. The "Controls refresher" performs go to joint position commands with different gains and one
DoF to show the affect of different gains on linear controller.
2. The "Jacobian demo" moves at a slow but constant ̇θ1 and accepts θ2 position as an argument
to demonstrate the relationship of joint speed and end effector speed in the base frame.
3. The "Workspace demo" shows the full functional workspace of the arm.
4. The "Dynamics, coupling demo" disables the second joint and moves the first joint in a jerky
motion, letting the second link flop back and forth.
5. The "Dynamics, time varying demo" performs an iterative experiment where θ2 is set to one
of several positions, and then θ1 is give a torque impulse.
6. Trajectories in the joint space and Cartesian space are possible with any of the controllers,
the only exception being joint trajectories when a Cartesian space controller is active. Time
is accepted as an argument,.

The system has a range of different control systems that can be used as detailed in the report, including: joint PID, feed forward velocity, resolved rate, Cartesian torque control, joint torque control, trajectory generation in both Cartesian and joint spaces, and more.