An RTOS-Based Run-Time Reconfigurable Avionics System for UAVs

Abstract

This paper overviews the design and implementation of a run-time reconfigurable avionics system. The system provides run-time reconfiguration and monitoring by employing a real-time operating system, a custom software layer, and a custom graphical user interface. Unlike typical embedded system designs, the proposed approach enables testing and devoplemnt by allowing manipulations on both the task and the parameter levels. The described avionics system was successfully used in the development of the avionics system of four rotor unmanned aerial system (UAV) at Oakland University. ypically embedded systems are configured and set during the design process. However, the ability to reconfigure at runtime can be beneficial. This paper overviews the design and implementation of a run-time reconfigurable avionics system. The proposed architecture has three main benefits: First, the monitoring and reconfiguration abilities at the task level can reduce system development and evaluation time by allowing the testing of alternative software designs, the testing of different modes of operation, and the evaluation of hardware module alternatives. Second, the monitoring and reconfiguration at the parameter level can help in system debugging, performance monitoring, and in robustness testing by simplifying fault injection. Finally, the approach can be used as a framework for adaptive avionics systems that can reconfigure in response to different mission profiles or in response to changes in the operating environment. The presented design is based on µC/OS-II TM , a real-time operating system, and a custom graphical user interface. A custom made quadrotor is used as a test-bed for the implementation and evaluation of the design. The focus in the tests was on the development and tuning of attitude control loops for the vehicle. The paper is organized as follows: The next section overviews the test-bed vehicle. Section III discusses the avionics system design and implementation. The run-time reconfiguration and monitoring system is overviewed in Section IV. Section V shows the results. Finally, the paper is concluded in Section VI. II. The Test-Bed The quadrotor 1 test-bed system, shown in Figure 1, consists of two subsystems. The first is a ground station that is responsible for flight control, data processing, reconfiguration control, and run-time monitoring. The other subsystem is the aerial vehicle which carries the avionics and payload systems. The two subsystems are connected by three wireless links: a 1.3 GHz link for video down-streaming, a 75 MHz traditional R/C radio for manual flight control, and a bidirectional 2.4 GHz ZigBee link for telemetry and reconfiguration control. The body of the quadrotor consists of a magnesium hub joining four carbon fiber arms. Mounted at the end of each arm is a magnesium motor mount that holds a brushless motor and propeller assembly. The avionics system’s hardware, shown in Figure 2, is a dual-processor design communicating through a CAN bus. Other hardware components include an IMU, altimeter, and a modular GPS unit for attitude, altitude, and position estimation, respectively. The ground station includes a navigation algorithm, target recognition software, and the graphical user interface (GUI) for parameter monitoring and reconfiguration purposes.