# Quadcopters Testing Platform for Educational Environments

^{*}

## Abstract

**:**

## 1. Introduction

## 2. System Overview

- Three degrees of freedom gyroscopic structure: mechanical structure that enables pitch, roll and yaw motions in a quadcopter, while at the same time constraining translational movements.
- Quadcopter: aerial vehicle with specifications for control law experimentation inside a laboratory.
- External power supply: element responsible for supplying electric current to the quadcopter.
- Computer: auxiliary tool for communication between user and platform in implementation of control algorithms using Matlab-Simulink.Some technical specifications of the test platform are presented below.
- Dimensional specificationsMaximum volume: $0.1235$ m
^{3}; base diameter: $0.38$ m ; total weight: $2.93$ kg ; maximum height: $0.56$ m - Motion specificationsAllowed ranges of motion: 360 degrees for roll, 360 degrees for pitch and 0 degrees for yaw.
- Power specificationsPropellers used: $10.14$ cm length, $11.43$ cm pitch, three blades. Motor revolution constant: 2300 kv; maximum power supply rating: $+12$ V; $12.5$ A.

**Possible control systems laboratory assignments**

- Design of a controller for angular stabilization
- Design of a controller for angular velocity
- Design of a controller for disturbance rejection
- Design of an uncertainty tolerant controller
- Design of a fault tolerant controller
- Verification of mathematical models

**Possible robotics lab assignments**

- Identification of multirotor system elements
- Understanding of basic multirotor maneuvers
- Control and operation of brushless motors
- Application of inertial sensors
- Signal processing and tuning of noise filters

## 3. Background and System Approach

- The power supply does not depend on the discharge time of a conventional UAV battery as in PT-3.
- It has full rotation range in its three axes unlike PT-4.
- It has a protection system that increases its safety level with respect to PT-2 and PT-3.
- The incorporation of MATLAB-Simulink for control algorithm programming promotes its adaptation to educational environments.
- It can adapt different quadcopter vehicles with similar geometrical dimensions, since they can be mounted on the gyroscopic structure without any difficulty. PT-2, PT-3 and PT-4 platforms do not have this feature since their design are more rigid.
- Due to the method for algorithm implementation that is proposed (external mode) and described later in Section 6.2, it is possible to define tuning parameters in the control algorithm that can be regulated during experimentation. This adds extra flexibility in the development phase of a control system.
- Since it is composed mostly of elements manufactured by 3D printing, its construction has a low level of complexity, which makes it feasible to replicate for laboratories and at lower cost compared with the market price of PT-3 and PT-4 platforms.

## 4. System Dynamics and Kinematics

#### 4.1. Quadcopter Dynamics

#### 4.2. Kinematic Description of the Gyroscopic Structure

## 5. Methods, Materials and Components

#### 5.1. Quadcopter Structural Design

**Center plate:**Element that joins the four quadcopter arms. It is made of PLA material by 3D printing. Its geometry comes from an elliptical segment and has a thickness of 5 mm.**Arms:**Components responsible for supporting the motors. Made of carbon fibre with a thickness of 3 mm and length of 250 mm.**Propeller protectors:**Made of PLA material by 3D printing. They have a thickness of 2 mm, height of 50 mm and diameter of 160 mm.

#### 5.2. Gyroscopic Platform Structural Design

#### 5.3. Quadcopter Electronic Design

#### 5.4. Gyroscopic Platform Electronic Design

## 6. Hardware and Software

^{®}Cortex

^{®}-M microprocessors, which drive the vehicle’s motors through PWM outputs. The main purpose for employing PX4 hardware in this prototype is to use MathWorks Build Tool Integration (BTI) to enable MATLAB software to invoke the ARM-GCC compiler in building applications based on Simulink block models. The system target file is ert.tlc (Embedded Real-Time) and is available with Embedded Coder.

#### 6.1. Capabilities and Features

^{®}autopilots, it is possible to generate C++ code from Simulink

^{®}models designed for Pixhawk FMUs (Flight Management Units). In this context, the PX4 toolchain is used to compile algorithms designed for this flight management unit, in which data from integrated sensors are incorporated [30].

#### 6.2. External Mode Execution

## 7. System Parameters Identification

^{2}, moment of inertia ${I}_{yy}=0.41$ kgm

^{2}and moment of inertia ${I}_{zz}=1.07$ kgm

^{2}. Other parameters obtained from physical measurements include: total vehicle mass $\left(m\right)=0.720$ kg, arm distance $\left(l\right)=0.129$ m, gravitational acceleration $\left(g\right)=9.81$ m/s

^{2}.

## 8. Model and Control Strategy

#### 8.1. Nonlinear State Space Model

#### 8.2. Linear State Space Model

#### 8.3. Linear State-Space Model for Pitch and Roll Motions

#### 8.4. Control Scheme for System Stabilization

## 9. Controller Development

#### 9.1. Basic Control Theory Student Lab Assignment: PID-Based Controller Design

**Subsystem for roll motion**

**Subsystem for pitch motion**

- Roll motion $\varphi $: ${T}_{ss}\approx 8s$, ${M}_{p}\approx 40\%$, $\varsigma \approx 0.28$ and ${\omega}_{n}\approx 1.32$.
- Pitch motion $\theta $: ${T}_{ss}\approx 4.s$, ${M}_{p}\approx 9\%$, $\varsigma \approx 0.6$ and ${\omega}_{n}\approx 1.22$.

#### 9.2. Advanced Control Theory Student Lab Assignment: Controller Design from a State Feedback

## 10. Implementation and Results

#### 10.1. State Feedback Control Experimentation

#### 10.2. PID Control Results

## 11. Conclusions and Future Work

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Acknowledgments

## Conflicts of Interest

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**Figure 1.**Experimental prototype of three degrees of freedom for validation of control algorithms in quadcopter systems.

**Figure 5.**(

**a**) CAD model of quadcopter structure assembly. (

**b**) Center plate. (

**c**) Propeller protector. (

**d**) Arm.

**Figure 16.**Block diagram in “Control algorithm” subsystem for state feedback controller implementation.

Background Knowledge | Level |
---|---|

C/C++ programming skills | Basic |

MATLAB/Simulink | Medium |

Signal processing | Basic |

Computer skills | Basic |

Control theory | Basic/Medium |

Quadcopter dynamics | Basic |

Electronics | Basic |

Design and assembly of multirotors | Basic |

Safety in robotic laboratories | Basic |

PT-1 | PT-2 | PT-3 | PT-4 | |
---|---|---|---|---|

Degrees of freedom | 3 | 3 | 3 | 3 |

System autonomy | Unlimited | Unlimited | Limited | Unlimited |

Software | Matlab | Matlab | Private | Private |

Cost | Low | Low | High | High |

Security Level | High | Medium | Medium | High |

Pitch range | 360° | 360° | 360° | 75° |

Roll range | 360° | 360° | 360° | 75° |

Yaw range | 360° | 360° | 360° | 360° |

Experimental flexibility | High | Low | Low | Low |

Replication level | High | High | Low | Low |

Component | Brand | Model |
---|---|---|

Brushless motors | Emax | RD2205-2300 |

Speed controls | ZTW | Beatles 30A BEC |

Energy Distribution Card | REALACC | XT60 |

Microcontroller | 3DR | Pixhawk 1 PX4 |

Power supply | Mean Well | RS-150-12 |

Moment of Inertia | Nominal | Upper Limit | Lower Limit |
---|---|---|---|

${I}_{xx}$ | 0.26 Kgm^{2} | 0.312 Kgm^{2} | 0.208 Kgm^{2} |

${I}_{yy}$ | 0.44 Kgm^{2} | 0.528 Kgm^{2} | 0.352 Kgm^{2} |

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## Share and Cite

**MDPI and ACS Style**

Veyna, U.; Garcia-Nieto, S.; Simarro, R.; Salcedo, J.V.
Quadcopters Testing Platform for Educational Environments. *Sensors* **2021**, *21*, 4134.
https://doi.org/10.3390/s21124134

**AMA Style**

Veyna U, Garcia-Nieto S, Simarro R, Salcedo JV.
Quadcopters Testing Platform for Educational Environments. *Sensors*. 2021; 21(12):4134.
https://doi.org/10.3390/s21124134

**Chicago/Turabian Style**

Veyna, Uriel, Sergio Garcia-Nieto, Raul Simarro, and Jose Vicente Salcedo.
2021. "Quadcopters Testing Platform for Educational Environments" *Sensors* 21, no. 12: 4134.
https://doi.org/10.3390/s21124134