Product category: Microprocessors, Microcontrollers and DSPs
News Release from: Microchip Technology | Subject: PIC18 microcontrollers
Edited by the Electronicstalk Editorial Team on 29 June 2005
MCUs take control
of unmanned aerial vehicle
AC Propulsion used a number of high-pin-count PIC18 microcontrollers to control its SoLong solar-powered unmanned aerial vehicle during its record-breaking 48h flight earlier this month
AC Propulsion used a number of high-memory-density high-pin-count PIC18 microcontrollers to control its SoLong solar-powered unmanned aerial vehicle (UAV) during its record-breaking 48h flight earlier this month. The SoLong's creator and chief pilot, a self-proclaimed 'analogue guy', selected Microchip because of its development tools.
This article was originally published on Electronicstalk on 29 June 2005 at 8.00am (UK)
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'I consider myself a newcomer to microcontrollers - I was strictly an analogue guy until four years ago', said Alan Cocconi, founder, Chairman and Chief Engineer of AC Propulsion.
'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 are controlled by 12 onboard PIC18 microcontrollers.
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A PIC18LF452 operating at 20MHz clock speed decodes 13 pulsewidth modulator (PWM) control inputs from the uplink receiver, serial data from the Ublox GPS module, and takes in analogue 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.
A PIC18F452 operating at 24MHz clock speed is used in conjunction with a Flash memory lookup table to generate nine sine-modulated 38kHz PWM outputs for the 800W sensorless brushless DC (BLDC) motor drive.
A PIC18F452 operating at 40MHz clock speed controls the four-phase 38kHz PWM of the 300W DC/DC convertor, with a dynamic peak power tracking algorithm to match the solar array output to the lithium-ion (Li-ion) battery.
Each of the six servomotors uses a PIC18LF1320 operating at 20MHz clock speed to calculate a 600Hz PID loop, and output 78kHz 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.
Two PIC18F1220s, using the internal clock operating at 250kHz, monitor the individual cell voltages with 20mV resolution and protect the Li-ion battery pack.
A serial data-stream is available for diagnostics.
A PIC18C452 operating at 20MHz 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 aeroplane using the GPS data.
Analogue wind speed and direction data are acquired and sent to the PC through the same port for display.
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