Autonomous Helicopter: James Lyden Harris Okazaki EE 496 A project to create a system that would allow a remote- controlled helicopter to fly without user interaction.

Project Design: Initial Goals Create a system to allow computer control of a remote-controlled helicopter. Utilize sensors and wireless communications Replace existing on-board control system Create software to allow hybrid control Stabilization controlled by software User input used to determine expected flight path User override to shut down helicopter

Project Design: Approach Hardware: Bottom-up Approach Determined what sensors we would need Selected a means of wireless communication Selected a microcontroller that would be able to interface with other devices Tested each piece of hardware individually Assembled and integrated components Used microcontroller to pull it all together

Project Design: Approach Software: Top-down Approach First characterized the entire helicopter as a class Spun off complex parts into separate classes Continued refinement until sufficiently modular Exported all relevant functionality to helicopter class Wrote an example driver for the helicopter class

Project Design: Structure User: input flight plan 3 Axis Accel Gyro Servos PC w/BT: calculates control signals Master μ C BT transc eiver Slave μ C OFFBOAR D ONBOARD

Project Design: Hardware Secondary μ C Software Flow Initialize: Open Serial Port Initialize PWMs Get Correction Data: Wait For UART Ready Read 4-Byte Word Set Control Signals: Parse First 2 Bytes Set PWM Duty Cycles Primary μ C Software Flow Initialize: Open Serial Ports Initialize Sensors Initialize PWMs Get Sensor Data: Send Commands Read/Save Responses Format Sensor Data: Use 8 MSbs Cast To Chars Send Sensor Data: fprintf Each Byte Wrap Word With Tags Get Correction Data: Wait For UART Ready Read 4-Byte Word Set Control Signals: Parse First 2 Bytes Set PWM Duty Cycles

Project Design: Hardware Schematic

Project Design: Hardware Acceleromet er Angular Rate Sensor Secondary PIC Primary PIC BluetoothModule Voltage Regulator Master Power Switch Headers UART TX UART RX PWM0+ PWM0- PWM1+ PWM1- PWM2+ PWM2- PWM3+ PWM3- NC GND VDD BAT+ BAT-

Project Design: Software PC Software Flow Initialize: Open Serial Port Test Serial Port Get Data: Listen for Packet Parse Packet Store Data: Update Pos/Vel/Acc Update Error Values PID Calculations: Read Error Values Compute Corrections Flight Planning: Check Flight Mode Add Desired Offsets Format Output: Combine Offsets+PID Put Data Into Buffer Send Data: Write Buffer to Serial Port Class Diagram

Project Design: Design Choices Guidance system Fully on-board the helicopter vs. separate Microcontroller-based PC-based Sensor arrangement and type Off-center accelerometer vs. angular rate sensor Three single-axis devices vs. one three axis device Relative location vs. absolute location

Project Design: Design Changes Sensor interfaces (from analog to digital)‏ Analog was simpler to implement Digital updates faster, uses sensors' ADCs Power supply (from separate to helicopter's)‏ The helicopter battery is rechargeable, longer life Separate power supply took more space and weight Correction algorithm (from proportional to PID)‏ Proportional was simpler to implement PID is better at smooth corrections

Final Status PC software complete Tested with simulations Communications complete Microcontroller can talk to PC via bluetooth Servo control complete PWM outputs can drive helicopter control surfaces Sensors problematic Data received is garbled and often static Perhaps sensors are broken, or high noise on data lines

Remaining Issues Sensors not giving reliable data Accelerometer readings are unintelligible Intermittent error codes from both devices The implementation of I²C and/or SPI may be faulty Not getting full range from servos PWM swing is from 0-5V Original swing was from 0-7.8V Darlington pairs can be used to step up the voltage

Future Work Data logging Record both sensor readings and corrections Save in a format that can be used by MATLAB Load information from files A configuration file that can initialize PID constants Get flight plan information from user-specified file Real-time user control Computer performs stabilization User specifies flight patterns on the fly Printed circuit board

Demonstration