Guidance, Navigation and Control (GNC)

Development of Guidance, Navigation and Control Algorithms for unmanned aerial systems

Avionics and Unmanned Systems Department develops advanced GNC algorithms for unmanned rotatory and fixed-wing aircrafts. The whole development cycle is performed by the department from the design phases to the integration and field tests.

Model-based methodology with automatic code generation is used on the development of GNC algorithm. This framework provides an easy interaction between control and software engineers reducing development time. This methodology is based on the use of MathWorks© tools such as Simulink and Real-Time Workshop, as well SCADE© which generates DO-178B certifiable code.

Aircrafts modeling is done using commercial tools such as AVL and CIFER which model the aircraft in terms of its frequency responses. Navigation algorithms on their side are based on INS/GPS sensor fusion using extended Kalman filtering. Those algorithms provide a low cost and high performance solution that can be adapted to any type of vehicle including spacecraft, aircraft and ground vehicle.

The automated generated code generated using this framework is compiled ready to be used on real-time operating system running on an onboard embedded PC. Besides commercial autopilot hardware platforms, CATEC has its own autopilot hardware and ground control station which brings to the developer a high degree of flexibility for adapting to our clients needs. Before performing the first flight tests, the GNC algorithms are tested in the laboratory using a HIL (Hardware in the Loop) environment. This testing environment allows running the navigation and flight control software on the real hardware that will be onboard the aircraft. The hardware is connected to a set of systems that emulate the flight dynamic of the aircraft as well as the sensor data required by the navigation algorithm (both inertial and GPS data). Aircraft dynamic is simulated in real-time using a National Instruments PXI system. Positioning data is simulated employing a Spirent GPS emulation system by generating the same RF signal that a real GPS receiver would receive from the satellites including the errors such as those due to ionospheric effects. Spirent emulator is also capable of simulate the inertial sensor data including the errors that are common to these sensors.

Before performing the first flight tests, the algorithms are tested in the laboratory using a HIL (Hardware in the Loop) environment in which the navigacion and flight control software is run in the real hardware that will be onboard the aircraft. This hardware is connected to a set of systems that emulate the flight dynamic of the aircraft as well as the sensor data that will be employed by the navigation algorithm (both inertial and GPS data). The dynamic is simulated in real-time using a National Instruments PXI system. Positioning data are simulated employing a Spirent GPS emulation system that generates the same signal that a real GPS receiver would receive from the satellites including the errors such as those due to ionospheric effects. Spirent emulator is also capable of simulate the inertial sensor data including the errors that are common to these sensors.

The developed GNC systems have already been integrated and tested in several rotatory and fixed-wing aircrafts with weights between 12 and 100 kg performing real flight tests in different conditions. The department has also developed GNC systems that permit landing rotatory aircrafts on moving platforms and the relative guidance without GPS.

Finally other research lines are followed jointly with the multivehicle systems laboratory for efficient trajectory generation in presence of obstacles that can be integrated in detect and avoid anti-collision systems.

 


Model-based Design methodology

HIL (Hardware in the Loop) test environment
   

Sensor fusión scheme for navigation

CATEC’s rotatory-wing platforms

 

 

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