Design, Implement and Testing of a Rotorcraft UAV System

Unmanned aerial vehicles (UAV) are useful for many applications where human intervention is considered difficult or dangerous. Traditionally, the fixed-wing UAV has been served as the unit for these dangerous tasks because the control is easy. Rotorcraft UAV (RUAV), on the other hand, can operate in many different flight modes which the fixed-wing one is unable to achieve, such as vertical take-off/landing, hovering, lateral flight, pirouette, and bank-to-turn. Due to the versatility in maneuverability, helicopters are capable to fly in and out of restricted areas and hover efficiently for long periods of time. These characteristics make RUAV applicable for many military and civil applications. However, the control of RUAV is difficult. Although some control algorithms have been proposed (Sanders et al., 1998, Garratt et al., 2003, Enns et al., 2000, Bijnens et al., 2005, Koo et al., 1998, Jiang et al., 2006), most of them were verified by simulation instead of real experiments. One reason for this is due to the complicate, nonlinear and inherently unstable dynamics, which has cross coupling between main and tail rotor, and lots of time-varying aerodynamic parameters. Another reason is that the flight test is in high risk. If a RUAV lost its control, it would never be stabilized. Shenyang Institute of Automation, Chinese Academy of Sciences (SIA, CAS) as a national research institute focus its future research on RUAV 5 years ago. Until now, we have 3 types of experimental platforms for advanced control algorithm research demonstration. ServoHeli-20 (Fig.1) is a model class platform which has 20 kilograms takeoff weight. ServoHeli-40 (Fig.2) and ServoHeli-110 (Fig.3) are engineering class platforms for highway patrol, electrical line patrol and photography. They have 40 and 110 kilograms takeoff weight and have finished full autonomous flight control experimental demonstration. In SIA, the control algorithm research on RUAV involves in navigation, advanced flight control, 3D path planning and fault tolerant control. This paper details the development of an unmanned helicopter testbed – ServoHeli-20 (Qi et al., 2006) (Fig.3), and the experiments performed toward achieving full autonomous flight. The brief of this paper is as follow: the ServoHeli-20 platform is introduced in Section II. The introduction of sensor package is in Section III. The modeling of the RUAV system is presented in the Section IV. In Section V, we introduce an independent-channel control scheme as a baseline control of the platform. In Section VI, an overview of fault tolerant