Research On Technology Of Pan-Tilt System Of UAV Mission Payloads

Recent years, the stimulation of military needs and promotion of civilian using hasbeen to promote the continuous growth of the UAV market. Countries around theworld have increased investment in research and development of this area. At present,the ability of UAV is mainly decided by various types of mission payloads; In order tofully perform mission payloads’ function, they mostly need to be installed on Pan-Tilt inorder to achieve rotation in the horizontal and vertical directions.With the development of the UAV and kinds of mission payloads, as an importantpart of the UAV system, the airborne Pan-Tilt impacts the ability of UAV to performtasks directly. Mission payloads that have been put into use in all countries are generallyequipped with dedicated Pan-Tilt, but with the development of a variety of small andmodular mission payload, it is very necessary to design a kind of universal and smallPan-Tilt system.This paper designed a universal Pan-Tilt system, including the four functional mo-dules: drive and control module of the motors of Pan-Tilt, remote control commandprocessing module, the aerial image acquisition andtransmission modules, target detect-ion and tracking module.The Pan-Tilt uses two two-phase hybrid stepper motors as the executing agency, toachieve rotation in the horizontal and vertical directions. Two L298n chips and a PSoCchip named CY8C27443-24PXI which is a production of Cypress Company are used asmotor drive and the main chip to make up the Motor Drive and Control Module. TheSPWM technique is used to control current vector of the stepper motor rotate equallyand evenly, which makes eight segments subdivided driver of stepper motor realized; Sothat the resolution and running-performance of the motor are improved, the noise andmechanical vibration are restrained when the stepper motor runs; And the host computercan send control commands to control the motor rotation through the serial port, whichensure the stability and flexible control of rotation of the stepper motor.The Several other functional modules are realized in linux2.6operating systemplatform which is running on ARM11core processor named S3C6410producted bySamsung Company. The several open source libraries: jRTPlib, Xvid, OpenCV, whichcan be ported to the Linux OS, provide a powerful support for the implementation of thefunctional models. The ARM processor uses a USB camera which has1.2million pixelsto obtain aerial images which are clear from low altitude space in which small UAV flying. The aerial video or pictures can be transmitted to the ground station usingstreaming media technology through the data link system with Ethernet interface. Theground station use TCP datagram to transmit command through the data system tothe command processing module for parsing and processing, to achieve control of thePan-Tilt system.The target detection and tracking module can track the interested target in theimage obtained by the camera automatically for a long time stable using severaltracking algorithm such as color model, frame subtracting method, opical flow method.This module also can control the motors to drive the rotation of the camera, to make thetarget been always in the camera range, by sending command to the PSoC processorthrough the serial port. Using this function, UAV can realize automatic navigation andseeker landing.