Autonomous Drone Flight Control

Table of contents

• Project Overview
• Roadmap
• Hardware
• Electronic Schematics
• Software
• Control System

Project Overview

...

Drone Configuration

          Front
     cw  (1) (2)  ccw      x
           \ /           z ↑
            X             \|
           / \             +----→ y
    ccw  (4) (3)  cw
    

Channel	Command
1	yaw
2	pitch
3	throttle
4	roll
5	vra

Roadmap

1. Non-autonomous Drone

• Define basic data structures and workflow
• pcb design
• Implement Tx --> Rx communication using interrups
• Map commands <Throttle, Roll, Pitch, Yaw> into motor signals <m1, m2, m3, m4>
• Signal smoothening
• Implement a safe arm/disarm routine
• Testing

2. Hovering

• Implement an IMU class for MPU9250
• Implement a PID class and algorithm
• Implement a gyro-based hovering maneuver
• Testing
• Implement a real time Kalman Filter Algorithm
• Implement a full hovering maneuver
• Testing

3. Other Autonomous Maneuver

• Autonomous take-off and landing

Hardware

• Frame: S500 glass fiber 480mm
• Motors: Emax 2216 810kv
• Propellers: Emax 1045
• ESC: HAKRC 35A
• MCU: ATmega 328 (Arduino Nano)
• IMU: mpu9250 + barometer (10dof sensor)
• Lipo battery: 3S 5000mAh
• Radio Tx: Flysky FS-i6X
• Radio Rx: Flysky X6B

Electronic schematics

Pin Mapping

Board Pin	Port Pin	Signal	Hardware
A4	PC4	SDA	IMU
A5	PC5	SCL	IMU
D3	PD3	M4	Motor 4
D4	PD4	Ch4	Radio Rx
D5	PD5	Ch3	Radio Rx
D6	PD6	Ch2	Radio Rx
D7	PD7	Ch1	Radio Rx
D9	PB1	M3	Motor 3
D10	PB2	M2	Motor 2
D11	PB3	M1	Motor 1
D12	PB4	Ch5	Radio Rx

                       ATmega328
                    +--------------+           
                    | D13      D12 |<-------------|Ch5| (Radio Rx)
                    | 3.3v     D11 |----> (M1)
                    | Ref      D10 |----> (M2)
                    | A0        D9 |----> (M3)
                    | A1        D8 |
                    | A2        D7 |<-------------|Ch1| (Radio Rx)
                    | A3        D6 |<-------------|Ch2| (Radio Rx)
(MPU9250) |SDA|---->| A4        D5 |<-------------|Ch3| (Radio Rx)
(MPU9250) |SCL|---->| A5        D4 |<-------------|Ch4| (Radio Rx)
                    | A6        D3 |----> (M4)
                    | A7        D2 |
                    | 5v       GND |
                    | RST      RST |
           GND -----| GND       Rx |
          3.3v -----| VIN       Tx |
                    +--------------+

Power Busses

                                 +---------+        +-----------+
                                 | MPU9250 |        | Brushless |
                                 +---+--+--+        |  Motors   |
                                     |  |           +---+--+----+
+======+                             |  |               |  |
|      |-------------- GND ----------+--|----+----------+  |
| LIPO |----(buck)---- 3.3v ------------+    |             |
|  3S  |----(buck)---- 7.3v -----------------|--+          |
|      |------------ 11.1/12.6v -------------|--|----------+
+======+                                     |  |  
                                             |  |   
                                         +---+--+---+ 
                                         | Radio Rx | 
                                         +----------+     

Software

• Language: C/C++, Matlab
• IDE: Visual Studio Code w\ PlatformIO
• Additional libs: Arduino.h, Servo.h

Repository structure

.
├── include
│   ├── atmega328_pin_mapping.h
│   └── README
├── lib
│   ├── drone
│   │   ├── drone.cpp
│   │   └── drone.h
│   ├── MPU9250
│   │   ├── MPU9250.cpp
│   │   └── MPU9250.h
│   ├── PID
│   │   ├── PID.cpp
│   │   └── PID.h
│   └── README
├── platformio.ini
├── README.md
├── src
│   └── main.cpp
└── test
    └── README

Data Structures

Drone:

typedef struct drone{
    uint8_t state;

    int16_t av_throttle;
    int16_t av_roll;
    int16_t av_pitch;
    int16_t av_yaw;

    int16_t throttle[N];
    int16_t roll[N];
    int16_t pitch[N];
    int16_t yaw[N];
    int16_t ch5;

    float roll_coeff;
    float pitch_coeff;
    float yaw_coeff;

    uint16_t m1;
    uint16_t m2;
    uint16_t m3;
    uint16_t m4;

    IMU* imu;   // imu data for control
    PID* pid_x; // pid control on gyro_x
    PID* pid_y; // pid control on gyro_y
} drone;

PID controller:

typedef struct PID{
    float setpoint;
    float Kp, Ki, Kd;
    float dt;
    float err[2];
    float output[2];
    float P, I, D;
    float integral;
    float min, max;
}PID;

Control System

Sketch of control system for full hovering maneuver: