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PIC18 Microcontrollers for Record-Breaking 48-Hour Flight

CHANDLER, Ariz. - Microchip Technology Inc., announced that AC Propulsion utilized the high-density memory, high pin count PIC18 microcontrollers to control its SoLong Solar Electric-Powered Unmanned Aerial Vehicle (UAV) during its record-breaking 48-hour flight earlier this month. The SoLong’s creator and chief pilot, a self-proclaimed analog guy, selected Microchip because of its development tools.

“I consider myself a newcomer to microcontrollers –- I was strictly an analog guy until four years ago,” said Alan Cocconi, founder, chairman and chief engineer of AC Propulsion Inc. “With Microchip’s MPLAB® Integrated Development Environment (IDE), I only had to learn one set of development tools to use a wide variety of products, which gave me more time to concentrate on completing the SoLong.”

The SoLong UAV’s systems that are controlled by the 12 onboard PIC18 microcontrollers include:


A PIC18LF452 operating at 20 MHz clock speed decodes 13 Pulse-With Modulator (PWM) control inputs from the uplink receiver, serial data from the Ublox GPS module, and takes in analog sensor data from 23 channels. The assembly-language code calculates four PID loops for stability augmentation, as well as managing the GPS navigation and waypoints. The same PIC18LF452 microcontroller also generates the telemetry data stream and eight channels of command pulses for the flight controls.

Motor Drive

A PIC18F452 operating at 24 MHz clock speed is used in conjunction with a Flash memory lookup table to generate nine sine-modulated 38 kHz PWM outputs for the 800W sensorless Brushless DC (BLDC) motor drive.

Peak Power Tracker

A PIC18F452 operating at 40 MHz clock speed controls the 4 phase 38 kHz PWM of the 300W DC-DC converter, with a dynamic peak power tracking algorithm to match the solar array output to the Lithium-Ion (Li-Ion) battery.


Each of the six servo motors use a PIC18LF1320 operating at 20 MHz clock speed to calculate a 600 Hz PID loop, and output 78 kHz PWM to run the small DC motor. The PIC18LF1320 stores in-flight load and wear data to help ensure system reliability for the long flights.

Battery Monitor

Two PIC18F1220s using the internal clock, operating at 250 kHz, monitor the individual cell voltages with 20 mV resolution and protect the Li-Ion battery pack. A serial data-stream is available for diagnostics.

Tracking Downlink Antenna and Anemometer

A PIC18C452 operating at 20 MHz clock speed communicates with the telemetry decoding PC (which runs Labview) using the serial port, and controls two servos that aim the antenna at the airplane using the GPS data. Analog wind speed and direction data is acquired and sent to the PC through the same port for display.

Lunes, 27 Junio, 2005 - 04:47
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