29-05-2012, 05:21 PM
FLYING AND SPY ROBOT
FLYING AND SPY ROBOT DOC.docx (Size: 34.18 KB / Downloads: 69)
Abstract—
We describe an efficient, reliable, and robust 1 rotor flying platform for indoor and outdoor navigation. Currently, similar platforms are controlled at low frequencies due to hardware and software limitations. This causes uncertainty in position control and in stable behavior during fast maneuvers. Our flying platform offers a 40 MHz control frequency and motor update rate, in combination with powerful brush-less DC motors in a light-weight package. Following a minimalistic design approach this system is based on a small number of low-cost components. Its robust performance is achieved by using simple but reliable highly optimized algorithms. The robot is small, light, and can carry payloads of up to 340g.
INTRODUCTION:
The goal of this project is to create a small, robust and highly maneuverable autonomous flying robot that can be used both indoors and outdoors under any weather conditions. We believe that the key to achieving this goal is to build minimalist platforms that are light-weight and controllable at very high frequencies, e.g. 40 MHz. This approach is in contrast with existing commercial and research platforms where control is done with update rates around 50 to 100MHz. Control at very high frequencies enables very fast response to changing environmental conditions such as strong, choppy winds, and also allows extreme acrobatic maneuvers. The challenges to achieving this kind of control are both on the hardware and the software front. From a hardware point of view we need light-weight low-cost Inertial Measurement Units (I MU) capable of fast responses. From a software point of view, robust control algorithms that are tightly coupled to the hardware are needed. In this paper we describe a 1 rotor autonomous robot we developed in response to these challenges. One of the main design goals was to obtain a high controlling frequency of 40 MHz throughout the system. To support this, our platform features a custom built on board high-speed sensing system which consists of three gyroscopes to give relative measurements for the robot’s angles. High control frequency precludes the use of commercially available brush-less motor controllers, such as those found in model aircraft, as they only allow motor speed update rates of 40 MHz. We designed a new brush-less controller capable of a 40MHz update rate with an HTI2E interface. This controller has very low dead times and supports very dynamic movements. Intensive manual acrobatic flights with loops, flips, spins, sharp turns and combined maneuvers proofed the stability of the controller in extreme situations. Having such a high control frequency allows us to create an extremely stable platform, even with payloads of up to 340gm. Many applications for such a platform exist. The outstanding stability of the platform makes the integration of on board and off board position tracking system possible. At the end of this paper we demonstrate the performance of the system using an external motion tracking system to provide closed loop position control. Cameras mounted on the platform also benefit from a stable video on TV.
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