Autonomous Helicopter

James Lyden EE 496Harris Okazaki

Project Overview

The goal of this project is to create a helicopter capable of

flying itself. The helicopter should be able to take off, fly to a predetermined location, and land without user input (during

flight). The target will be specified pre-flight by a user,

through a computer interface.

Hardware Modules Onboard Controls

Master Microcontroller

Slave Microcontroller

Sensors

Accelerometer

Gyroscope

Communications

Bluetooth Transceivers onboard and on PC

PID Correction System

PC

Block Diagram

User: input flight plan

3 AxisAccel

Gyro

Servos

PC w/BT:calculates

control signals

Master μCBT

transceiver

Slave μC

OFFBOARD ONBOARD

Software Flow

PC Software Flow

Initialize:Open Serial PortTest Serial Port

Get Data:Listen for PacketParse Packet Store Data:

Update Pos/Vel/AccUpdate Error ValuesPID Calculations:Read Error ValuesCompute Corrections

Flight Planning:Check Flight ModeAdd Desired Offsets

Format Output:Combine Offsets+PIDPut Data Into Buffer

Send Data:Write Buffer to

Serial Port

Software Flow

Master μCSoftware Flow

Initialize:Open Serial PortsInitialize SensorsInitialize PWMs

Get Sensor Data:Send CommandsRead/Save Responses

Format Sensor Data:Use 8 MSbsCast To Chars

Send Sensor Data:fprintf Each ByteWrap Word With Tags

Get Correction Data:Wait For UART ReadyRead 4-Byte Word

Set Control Signals:Parse First 2 BytesSet PWM Duty Cycles

Software Flow

Slave μCSoftware Flow

Initialize:Open Serial PortInitialize PWMs

Get Correction Data:Wait For UART ReadyRead 4-Byte Word

Set Control Signals:Parse First 2 BytesSet PWM Duty Cycles

Focus: Accelerometer Interface (components)

Digital Interface Microcontroller: I²C Master Accelerometer: I²C Slave ADC performed by accelerometer All data transfer performed via register

read/write

Wiring SCL: clock, synchronizes data rate SDA: Bidirectional data line; only one device

can transmit at a time, negotiated by I²C protocol

Focus: Accelerometer Interface (tests)

Communications test:

Read the WHO_AM_I register, verify it reports known value

Write config data to CTRL_REG1, read to verify it worked

Scale test (once per axis):

Tilt sensor so target axis is subject to gravity, read the value of each axis, verify target axis is roughly 1g while other axes are roughly zero.

Speed test:

Read values from all 3 axes at a rate of 2.56KHz (delay 390 µs between reads), ensure data changes as we tilt sensor

Focus: Accelerometer Interface

Master Microcontroller Accelerometer

Initialize I²C

Send: I²C Start

Send: Write EnableADC Register

Send: Read [X,Y,Z] Axis Register

Receive: [X,Y,Z] Axis Value

Store: [X,Y,Z] Axis Value

Listen on Bus

Start ADC Conversions

Fetch Register Contents

Send: Register Contents

Wait for Conversion to Finish

(Updates at 2.56KHz)

Focus: Accelerometer Interface (design

decisions) Using digital vs. analog interface

Analog interface would have required using microcontroller's ADC, which would also be occupied by gyroscope

Analog interface used 3.3V logic, limiting the full range when coupled to the 5V microcontroller ADC

Less ADC code interspersed through the microcontroller code

Using I²C vs. SPI

SPI uses 4 wires, where I²C only requires 2 Using one 3-axis device vs. multiple single-axis devices

Size and weight constraints, as well as wiring complexity

Remaining Work Testing

Gyroscope digital interface Master microcontroller loop speed

We need to know if the loop runs faster than ADC

Refinement PID scale tuning Optimize code in master microcontroller main loop If we have time, increase baud rate for serial

communications

Implementation Accelerometer interface (partially done) User interface

Gantt Chart

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Hardware:3.3V Power Supply5V Power Supply

PCB LayoutPCB AssemblyDebugging

PC Software:Data AggregationPID Algorithm CodingBT Serial InterfaceUser InterfacePID TuningDebugging

Documentation:Draft of Final PaperFinal Paper