Multi-rotor drone control system

The goal of the project is to develop and test a control system for multi-rotor unmanned air systems. It is continuing from the conclusion of the Advanced Multi-rotor Drone project. The project deliverables include an electronic control system to balance the aircraft (a drone modeled as a seesaw with propellers mounted on each arm), and a (shaker) table designed to have test aircraft (model) mounted to it and (stimulate the model) create vibrations in order to test the response of the control systems.

=Problem Definition=

Background
This project originated with the Advanced Multi-rotor Drone project from Fall 2018 - Spring 2019. That project culminated with several test stands, and the hardware necessary to operate both a quad-copter drone, and a single axis Seesaw.

Deliverables
The purpose of this project is to design and create both a control system for the Seesaw and equipment to test the response of the controls in the form of a (shaker) vibrating table. The (seesaw) control system will be written to operate on an Arduino-like micro-controller, and will control the two motors at the ends of the seesaw arm to balance the arm at a given angle and respond to disturbances (created by the shaker table). This system will also be generalized to the quad-copter drone in the future.

In order to test the response of any control system it is necessary to be able to give it defined disturbances. We will be doing this in the form of a table that performs user-defined vibrations. The seesaw, and later the quad-copter, will be attached to the table and shaken in order to measure the response of their control systems.

Specifications
The major specifications for the 2 project deliverables are below. This does not include minor requirements such as power and environmental specifications.

The Table

 * Will create vibrations up to a frequency of 10 Hz.
 * Will create vibrations up to a displacement of 1 inch.
 * Can withstand a minimum of 150,000 cycles.

The Seesaw

 * Will remain stable with disturbances up to 10 Hz and 1 inch displacement.

Shared Requirements

 * Both will remain within a $2500 shared budget.
 * Both will be easy to use and operate without significant training.

=Project Learning= Our project learning has occurred in two main phases, research and design, followed by prototyping.

The Table
The Design

Two main designs were looked into:
 * The Stewart Platform
 * The Crank-Slider

We decided on the crank slider because it is simpler to add axes one at a time, and the cost was much significantly lower than the other options

Motor Selection

We looked into a selection of motors, including:
 * Voice Coil Motors
 * DC Induction Motors
 * Stepper Motors

We are currently using stepper motors due to cost (high force voice coils are thousands of dollars) and the ease of controlling speed. The trade-off is a loss of torque at high speeds.

The Seesaw
The Design

Work on the control system can be found on Github

Reading

Design elements we are looking to implement include:
 * Sensor Fusion
 * PID control
 * Ziegler-Nichols Loop Tuning.

The Table
In our early prototypes the table saw a much larger high frequency vibration environment than expected due to the stepper motors. This will be fixed with adding damping inside the linkage connections. Several parts of the linkage will also be machined out of aluminum to lengthen the usability of the table.

The stepper controllers are still in development and are currently running into heat issues caused by the current demand at high speeds.

The Seesaw
Early testing has ruled out proportional control methods, as the inertia of the system is large relative to the response of the motors. This has led us to the Ziegler-Nichols Method of tuning a PI control loop.

=Final Design=

=Validation=

=Team Members=

=Additional Documentation=

Project Schedule



Meeting Minutes



Client Interview