"An Xilinx Microblaze-based UAV Flight Control System"

Robert H. Klenke, Quan Cheng, Jefferson McBride, Hoan Nguyen, and William Sleeman
Virginia Commonwealth University

Abstract

The UAV research group at the Virginia Commonwealth University (VCU) previously presented their unmanned aerial vehicle (UAV) control system based on the Atmel FPSLIC device. The FPSLIC includes an 8-bit AVR microcontroller, 32K bytes of memory, and a 40K gate equivalent FPGA. The authors have recently completed the implementation and testing of a much-improved system on two more sophisticated Xilinx field programmable devices. The first implementation utilizes the Xilinx Microblaze soft-core processor implemented in a Spartan III FPGA. A commercial implementation of a Spartan-III based board, called the Suzaku, was used for development. The Suzaku board contains either a 400k- or 1000k-gate Spartan III FPGA, 16 MB of SRAM and 4 MB of Flash memory, 10/100Base-T Ethernet and RS-232 ports, and 84 general-purpose I/O pins. The Spartan III FPGA comes pre-loaded with the 32-bit Microblaze core running at 14.7 MHz, and the Flash memory contains a pre-loaded version of the Linux core called uCLinux. Users can develop additional hardware for the Spartan III on the Suzaku using Xilinx’s Embedded Developers Kit (EDK) and software applications for Linux on the Microblaze using a version of the GNU compiler. 

The second implementation of the flight control system utilizes the Xilinx Virtex-II Pro device which contains a 270 MHz PowerPC 405 core along with an approximately 40K gate equivalent FPGA. This device is also available on a commercial board called the Suzaku-V. The Suzaku-V contains the Virtex-II Pro device, 32 MB of SRAM and 8 MB of Flash memory, 10/100Base-T Ethernet and RS-232 ports, and 70 general-purpose I/O pins. The PowerPC also runs a version of the Linux operating system and utilizes the same development tool chain as the Microblaze-based Suzaku. 

This presentation will describe the authors’ experiences in developing a complete UAV control system on the Suzaku boards described above. This includes the development of custom hardware implemented in the FPGA portion of the devices to interface the respective processors to the flight control system sensors. It also includes the development of the flight control system software for the Linux operating system on the respective processors. This software must not only execute complex functions such as the Proportional, Integral, Derivative (PID) controllers for altitude and heading control, but must also interface to the built-in and custom hardware used to communicate with the sensors and outside devices like the Ublox GPS receiver and the radio modem link to the ground station. The flight control system is currently undergoing testing in low-cost UAV’s based on the FQM-117B “MIG-27” Army target drone as well as a high-speed jet turbine powered UAV and a rotary-winged UAV.

 

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