**2.2.3 Flight control system**

The fight control processor uses the same processor as the navigation system, so we can share the code of the operating system and reduce the debug time. The LPC3250 with an ARM926EJ-S CPU Core implementation uses Harvard architecture with a 5-stage pipeline and operates at CPU frequencies up to 266 Hz. The Vector Floating Point (VFP) coprocessor makes the micro controller suitable for advanced navigation and control algorithm, and processing speed and interface versatility is guaranteed. The industry standard operation

Application of Wavelets Transform in Rotorcraft UAV's Integrated Navigation System 621

To increase the control distance and reliability, the half duplex industry radios are installed in the ground station and the airborne system to exchange data. The data includes commands, operating status and possible damages, which is received and reported to the ground station. The flight data can be logged in SD card, we can analysis the data after flight

Without loss of generality, assume that the vehicle's sensor output *y*( )*t* is described as

Where *n t*( ) is a noise signal and the measured *x t*( ) changes with a *k*-degree polynomial function *f*[ ( )] *x t* which describes the measured process changes. Stone-Weierstrass Theorem states that any continuous function on a compact set can be approximated to any degree of accuracy by a polynomial function (Rudin, 1976). Therefore, using a polynomial function to

( , ) ( ) ( ) [ ( ) ( )] ( ) *WT s fs s*

*y t t*

( )*t* is said to have *m* vanishing moments if and only for all positive integers *k<m*, the

*y*( ) [ ( )] ( ) *t f xt nt* (1)

 

( )*t* by the scale factor *s*. The wavelet transform

*f xt nt t* (2)

represents the wavelet transform. A wavelet

( )*t* be a wavelet function

test. The architecture of the RUAV control system is presented in Figure 7.

Fig. 7. Architecture of the RUAV control system

represent any function *f*[ ( )] *x t* will not lose the generality. Let

be the dilation of

Where denotes the convolution and (, ) *WT s <sup>f</sup>*

**3. Wavelet-based fault detection** 

(Zhang & Yan, 2001):

and ( ) (1/ ) ( / ) *<sup>s</sup>*

of *y t*( ) can be written as:

 *t s ts* 

following equation is satisfied:

temperature from -40℃ to 80℃ extends the usage of RUAV in various environments. The LPC3250 includes a USB 2.0 Full Speed interface, seven UARTs, two I2C interfaces, two SPI/SSP ports, and two I2S interfaces; Such a great number interfaces of LPC3250 makes it very suitable for navigation and control system with a plenty of sensors in standard interface. We designed interface circuit to drive the actuator and log the flight data.

To decrease the developing work in programming, while increasing the system stability, a μC/OS-II embedded system is installed to organize the software development. This small sized embedded system is quite convenient to install; the hard-real-time architecture also makes it suitable for a time critical avionics system in RUAV. We divided the work of software into 5 parts. First, the OS Kernel is to maintain the whole system and arrange the task schedule. Second, the algorithms implements navigation and control theory. Third, the device interface process is to handle the task for sensor data acquire and drive the actuator. Fourth, the user interface carries out the job to display and receive necessary information to the user. Fifth, the log interface is to log the flight data for our experiment. To make sure that the algorithms can be calculated in time, a hardware timer is used instead of the software timer provided by operator system. With a proper design of the software architecture, the system's stability is maintained and the flexibility is also provided for other algorithm implementations.

Fig. 6. Implemented ServoHeli-40 RUAV

### **2.2.4 System realization**

The GPS receiver and magnetometer are in a separate part and the others are in the main navigation part. The flight control system and main navigation system are assembled in an anti-jamming aluminum box, and called flight control box. Such a separation is with the consideration that the GPS and magnetometers are susceptible to the install position because they may be influenced if it is covered by the airborne or near some magnetic material. The flight control box is mounted under fuselage of the RUAV. The separate part can be equipped in a proper place on the airframe. To avoid the disciplinary vibration about 20-22.5Hz caused by revolving of main rotor, ENIDINE aviation wire rope isolators are also used. They are comprised of stainless steel stranded cable, threaded through aluminum alloy retaining bars, crimped and mounted for effective vibration isolation. The assembled RUAV system with the necessary components is shown in Figure 6.

To increase the control distance and reliability, the half duplex industry radios are installed in the ground station and the airborne system to exchange data. The data includes commands, operating status and possible damages, which is received and reported to the ground station. The flight data can be logged in SD card, we can analysis the data after flight test. The architecture of the RUAV control system is presented in Figure 7.

Fig. 7. Architecture of the RUAV control system
