Problem

The is no open source tool that calculates thrust for DC rotors of drones for a variety of inputs.

Requirements

Handle various inputs and calculate the thrust for n DC rotors.

Code Documentation

Code documentation

Dependencies

These dependencies are not specified in the requirements because they needed to be installed on the system itselfs. - For displaying the uml diagrams in the documentation install graphviz and asciidoctor-diagram.

For Linux:

apt install graphviz
gem install asciidoctor-diagram

Design

Architecture

This describes the architecture of the project with it’s different layers, but unlike convention it will also describe the interface due to simplicity of the project.

Architecture Type

This will be implemented as layer architecture. This is useful as we’ll have a well defined input and a even more defined output.

class diagram
Important
 This is not a formal uml diagram but a visualization of the structure.

Layers

Input Layer

The input will be different dictionaries which contains observation key value sets from sensors and dictionaries of the target state of the drone.

Calculation Layer

This will do the actual calculation to satisfy the requested drone state.

Output Layer

This will return a dictionary containing n key value pairs of rotor thrusts. How ever the first RC will aim to control four rotors. The thrusts are values from 0 to 1. Depending of the type of request it could vary from python dictionary to json object. This could be useful if this services runs on a different machine than the requester.

Layer Components

Input Layer
RequestHandler

It expects a dictionary of either a user input, this could be keyboard, game pad or a RC controller, or a computer generated dictionary of a short term expected state of the drone.

User Input (Keyboard):

Key Value Type

Rotation Forward

bool

Rotation Right

bool

Rotation Backward

bool

Rotation Left

bool

Acceleration

float in [-1,1]

The input can actually be a DroneState already.

DroneStateMapper

Maps the input from RequestHandler to expected DroneState for the calculation layer. Is has currently one method called keyboard that calculates an future DroneState from keyboard input. It expects the current DroneState and a dictionary of the user input (s. RequestHandler above).

DronePhysics

This is a wrapper class, that contains the physical properties of the drone.

Key Value

mass

float of the mass of the drone in kg

thrust_per_rotor

float the maximal thrust one rotor of the drone can produce in Newton

rotor_count

the drone’s rotor amount

radius

the horizontal distance of each rotor to the center of mass
DroneState

A wrapper for a dictionary containing the target state of the drone.

Key Value

position

three dimensional vector of floats (optional)

rotation

three dimensional vector of floats

translation velocity

three dimensional vector of floats

angular velocity

three dimensional vector of floats (optional)

translation acceleration

three dimensional vector of floats

angular acceleration

three dimensional vector of floats
Calculation Layer
ThrustCalculator

This expects the momentary DroneState and the expected DroneState. It will try to calculate the rotors thrusts to minimize the differences.

There are multiple thrust calculators for different aircrafts. Currently implemented are:

Name Parameter

ThrustCalculatorQuadroCopter

- mass

- max. thrust per rotor

- radius to the center of mass

- scalar factor of the inertia torque (optional)
Output Layer
JSON Wrapper

Wraps the n rotor thrusts in a json object and returns it to redirect url.

Dict Wrapper

Wraps the n rotor thrusts in a dictionary and returns it to the python caller.

Dependency Graph

Dependency