The onboard avionics are compatible with the advanced Ground Control System and powered by an Analog Devices Blackfin at 500MHz processor. The capsule can be nose-loaded with the help of a bayonet fitting to the UAV fuselage or belly-fitted in the case of larger crafts. The Attitude Heading Reference System (AHRS) is made up primarily by two modules a GPS module and a 3-axis IMU. The inertial measurement unit (IMU) contains 3 orthogonally mounted gyro-scopes, accelerometers and magnetometers, the signals from which are combined in a compensation algorithm to stabilize the outputs. Fine altimetry measurement is performed by a laser proximity module in the range 0-1.00 meter and by a MEMS barometric pressure sensor in the range .50m-3,000 meters. The standard camera we are mounting on our micro-UAV initially is an Omnivision OV9655 1.3 Megapixel Sensor fitted with a 6.5mm lens F3.2. The GCS programming environment is Linux UBUNTU 7.10 and the whole application is written in small C and C++, compiled using gcc.
Ours is a second generation avionics system for unmanned vehicles offering on-board sophisticated programming capabilities, rather than the limited servo-control, sensor-recording and telemetry formerly associated with these units. Communication with the GCS is performed via a WiFi link for testing purposes and can be changed to a VHF link or other system as specified by the client. Currently, we offer an optional radio link aided by a directional antenna able to communicate at a maximum of 60 Km in line-of-sight as standard.
Main on-board processor
All modules are housed in a cylindrical water-proof container, housing the GPS antenna and provided with the camera on one of its round sides and power and other sensor connectors on the other. The main board’s specifications are:
- 500MHz Analog Devices Blackfin BF537 Processor (1000 integer MIPS)
- 32MB SDRAM, 4MB SPI Flash
- JTAG
- SPI Flash and UART boot mode select
- External I/O Header (32-pin - 16 x 2 x 0.1") :
- o 3.3V Input - 145mA total draw at 500MHz, including camera
- o Board dimensions - 50 mm x 60 mm (2.0" x 2.6"), 36g (1.25 oz) including camera module
- o 2 UARTS - tested at up to 2.5Mbps with CTS/RTS flow control
- o 4 Timers (2 share pins with UART1)
- o SPI - 2 slave select, 1 master select
- o I2C
- o 16 GPIO
- o S-32 expansion bus header will support stacking of expansion boards
- o RoHS compliant
- The default Firmware currently being tested includes the following specification:
- Full-speed frame capture direct to SDRAM at 1280x1024, 640x480, 320x256 or 160x128 pixel resolutions
- JPEG (Motion JPEG) compression
- Basic image processing - histogram, pixel sampling, mean, frame difference, blob, scan, count, find
- Motor control for PWM (H-bridge) and PPM (servo) interfaces
- Built-in interpreters for Small C
- Real-Time-Clock (milliseconds since reset), internal timer resolution to 10 nanoseconds
- Direct control of I2C and SPI devices
- In-Application-Programming (IAP) of flash memory
- XMODEM protocol for reliable file transfer
- Direct support for up to 4 Maxbotics ultrasound rangers
- Compiled with GNU Blackfin Toolchain
- Can be replaced by u-boot
- Radio/Motor Control Module
- WiFi communication via Lantronix Matchport WLAN 802.11g radio
- u.fl connector to external antenna
- On-board 3.3V high efficiency switching regulator (Recom R-783.3-1.0) for battery input (4.75 - 18.0 VDC)
- Dual H-bridge motor driver (Fairchild FAN8200) with 1000mA capacity per motor
- 2 switching transistor drivers with 100mA capacity for laser range pointers
- Board dimensions - 50 mm x 65 mm (2.0" x 2.6"), 10g (0.4 oz)
- Mounts to main board via 32-pin external S-32 expansion bus
- RoHS compliant
Camera module
The camera module has two pan-and-tilt servo motors mounted on the front of the avionics stack to provide a general purpose vision capability, with the following capabilities:
Omnivision OV9655 1.3 Megapixel Sensor (1280x1024 pixels max)
- Pan: 360 o & Tilt: 180o
- AA Format Module (32-pin header - 16 x 2 x 0.1")
- Interchangeable Lens - M12 P=0.5 format (12mm diameter, 0.5mm thread pitch). Standard lens is 3.6mm f2.0 (90-deg), optional 2.2mm f2.5 (120-deg)
- Camera header on production board is 90-degree female
- RoHS compliant
Sensors board
We currently offer an extensible sensor board from which vehicles such as blimps, helicopters and fixed-wing aircraft can be controlled. The common sensors found in all UAVs are housed in this board and include:
16-bit dsPIC33 digital signal controller core for rapid first-stage processing and efficient communication over SPI to the main processor.
- u-blox LEA-5 GPS with active antenna featuring excellent weak signal performance, "KickStart" rapid startup acquisition, WAAS support (~1 meter accuracy in North America, ~3 meter elsewhere). GPS provides good quality heading information making it valuable even in applications where the position error is too great to be of direct use.
- 3-axis accelerometer - ADXL330 MEMS inertial sensor measures accelerations up to 3.6g in any direction. Ideal for tilt sensing, UAV autopilot or IMU Kalman filter applications.
- 3-axis gyroscope - IDG300 and LISY300AL MEMS rate gyroscopes measure rate of turn up to 300 degrees per second in all axes. Suitable for UAV artificial horizon or strapdown INS applications.
- Magnetic compass - Honeywell 2-axis magnetometer gives magnetic heading information, essential as a steady reference for a Kalman filter-based IMU, as well as for general navigation orientation. Accurate approx. 1 degree with motors off, but quite strongly affected by motors - correction may be applied in software, or stop the motors to take a compass measurement.
- 31 general purpose I/O pins, compatible with 3.3V and 5V logic, brought out to 0.1" headers for easy connection to your own circuits and sensors.
- 9 of the GPIO pins may be reconfigured as up to 9 analog inputs with 12-bit resolution reading from 0 to 3 volts.
- 16 of the GPIO pins may be reconfigured as up to 16 servo outputs or radio-control inputs.
- 1 SCP1000 altimeter for precision barometric pressure and temperature measurements.
- 1 MicroSD socket, supporting cards up to 1GB, providing bulk storage such as 1 hour of high-quality recorded video.