S14: Quadcopter

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Quadcopter

Abstract

A Quadcopter (Quad-rotor helicopter) is a multi-rotor aerial vehicle that is lifted and propelled by four rotors. The thrust generated by the propellers lifts the Quadcopter while the flight controller system govern the rotor speed for attitude control. A wireless remote control is used to interact with the flight controller system for changing the flight path. Our objective is to assemble the Quadcopter, then design and build a flight controller system that stabilizes the flight and accept commands from a hobbyist remote control during its flight.

Objectives

The scope of our project can be divided into three parts:

Design and build interfaces to all the on-board electronic sensor such as IMU, barometer and distance sensors
Design and build interfaces to telemetry and radio modules to communicate with remote control and the computer
Process the various sensor inputs and control the brushless motors on board using an electronic speed control system to stabilize the aircraft

Team Members & Responsibilities

Sree Harsha
- PWM Design, Remote Control Input, Quadcopter assembly
Balaji
- Sensor Data Processing, Quadcopter Assembly
Divya Kamath
- Flight Controller Design, Code Integration

Introduction

Quadcopter is one of the successful aerial vehicles which support vertical take-off and landing.It has 4 rotors - 2 run clockwise(CW) and 2 counter-clockwise(CCW). This is to cancel out the torque generated by a set of rotors running in any one direction.

File:Propeller direction.JPG

Fig 1. Propeller rotating direction

File:Propeller direction.JPG

Fig 1. Propeller rotating direction

Schedule

Sl. No	Start Date	End Date	Task	Status	Actual Completion Date
1	2/28	2/28	Order Components and Make a schedule	Component Ordering Partially Completed (critical components done), Motors pending. (Update 4/14 - All components ordered)	3/7/2014
2	3/1	3/30	Components Procurement.	Motors arrived but don't fit into the frame. Got motor mounts from Century Heli shop, drilled holes to fit the motors, backup IMU arrived.(Update 4/14 - All components ordered)	3/21/2014.
3	2/20	3/15	Establish communication with all sensors and validate data	IMU done.	3/14/2014
4	2/28	3/5	Establish communication with radio module of remote control	Coding complete. Testing in progress with Radio remote and receiver.
5	2/28	3/5	Speed control of motors	Flashed SimonKK firmware to ESC. One of the ESC went kaput and 2 others have problem running at slower speeds. Tested with another set and motors work fine. Ordered Afro ESC with pre SimonKK firmware flashed. Another frame, radio and few other components ordered as backup.	3/29/2014
6	2/28	3/25	Flight Controller Algorithm (PID Controller)	Coding. Playing with the coefficients. (Update 4/14 - Coding Completed, testing pending)
7	3/15	3/30	Create tasks and integrate complete code	In progress. (Update 4/14 - PID completed, Flight Controller tasks completed. Device driver for RC input ready. Pending - PWM (motors), Math calculation for motor speed from Raw RC data and sensor angles, UART communication and parser for IMU data)
8	4/10	4/10	Assemble quadcopter	Complete. Initial flight test with reference flight controller shows jitters with radio PWM input. Magnetometer goes crazy because of motor magnetic field. Control system and sensors will now be placed on an elevated platform.	3/29/2014
9	4/10	4/18	Initial testing and tweaks	In progress
10	4/15	- End	Final Testing

Parts List & Cost

Qty	Description	Manufacturer	Part Number	Total Cost
4	4x Electric Speed Controller (ESC)	Turnigy	Plush 25	$50.00
4	Turnigy Multistar 4822-690Kv 22Pole Multi-Rotor Outrunner	Turnigy	9392000004	$180.00
1	Inertial measurement unit (IMU) MPU-9150	Sparkfun	SEN-11486	$40.00
1	SJOne Board	Preet	LPC1758 SJSU CmpE Board	$80.00
1	DX6i 6 Channel 2.4Ghz Tx/Rx Remote Control	Spektrum	DX6i	$140.00
1	Turnigy nano-tech 6000mah Lipo battery	Turnigy	-	$15.97
1	Quadcopter frame	HJ MWC	-	$21.26
2	Motor mounts	Century Heli	-	$25.94
2	10x4.5MR, 10x4.5MRP Propellers, Prop Adapter Ring Set	APC		$26.94
2	6000mAH 4S LIPO battery	HJ MWC	-	$21.26
	Total Cost			increasing !

Backup Parts & cost

Qty	Description	Manufacturer	Part Number	Total Cost
1	6000mAH 4S LIPO battery hardcase	Turnigy		$50.00
2	Invensence 9150 IMU Breakout board	ebay		$17.00

Design & Implementation

The design section can go over your hardware and software design. Organize this section using sub-sections that go over your design and implementation.

Hardware Design

Discuss your hardware design here. Show detailed schematics, and the interface here.

Pin Connections

Sl. No	Port and Pin Number	Pin Type	Purpose
1	P0.0 and P0.1	UART 3	IMU Communication (Arduino)
2	P2.4, P2.5, P2.6, P2.7, P0.29, P0.30	GPIO Input	Remote Control Receiver Input
3	P2.0, P2.1, P2. 2, P2.3	PWM	PWM output to motors
4	P2.8, P2.9	UART2	ZigBee telemetry

Hardware Interface

In this section, you can describe how your hardware communicates, such as which BUSes used. You can discuss your driver implementation here, such that the Software Design section is isolated to talk about high level workings rather than inner working of your project.

Current Design UART for reading sensor data PWM for motor control UART for telemetry

Software Design

MPU-9150

The MPU-9150 consists of a 3-axis accelerometer, 3axis Gyroscope and a 3 axis magnetometer. its a one chip IMU solution with onboard Motion processor for sensor fusion.Though it inherently supports on board Sensor Fusion, the IP is undisclosed. Therefore we used the library for arduino by Pansenti. (https://github.com/Pansenti) The 6 axis sensor fusion (accel+gyro) is done on the MPU and sent to an arduino where the magnetometer data is used for YAW correction. The arduino transmits the orientation data over UART which is recieved by the SJONE for further processing.

For testing, we coded a GUI in python. The code parses the serial data from the arduino and displays the orientation of the IMU in real-time using Vpython.(video and code to be linked).

PID Controller

For our flight controller algorithm, we are using a PID controller. PID (proportional, integral, derivative) controller is a feedback control system which attempts to minimize the error in the output using three constant values: P, I and D i.e. the proportional, integral and derivative values.

Converting Remote Control Data to Motor Speed

The following steps are involved in converting raw RC (remote control) data to motor speed

Get the RC data. Usually a PWM signal
Scale up/down this value using a pre-decided curve. (Linear/Exponential)
Apply PID on Roll/Pitch/Yaw data.
Convert the output of PID into angles.
Adjust the PID output with the angles calculated by IMU (Inertial Measurement Unit)
Use these angles to adjust motor speeds and direction (Add/Subract to Throttle Command)

Implementation

This section includes implementation, but again, not the details, just the high level. For example, you can list the steps it takes to communicate over a sensor, or the steps needed to write a page of memory onto SPI Flash. You can include sub-sections for each of your component implementation.

Mechanical Design

Testing & Technical Challenges

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Include sub-sections that list out a problem and solution, such as:

My Issue #1

Discuss the issue and resolution.

Conclusion

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Project Video

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Project Source Code

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References

Acknowledgement

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References Used

Appendix

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