**7. References**


Williamson, C.H.K. & Roshko, A. (1988) *Vortex formation in the wake of an oscillating cylinder*, Journal of Fluids and Structures 2, pp.355-381 **28** 

**Application of Wavelets Transform in** 

Lei Dai1,2, Juntong Qi1, Chong Wu1,2 and Jianda Han1

*Shenyang Institute of Automation, Chinese Academy of Sciences* 

*2Graduate School of Chinese Academy of Sciences* 

*1State Key Laboratory of Robotics,* 

*People's Republic of China* 

**Rotorcraft UAV's Integrated Navigation System** 

Rotorcraft UAV (RUAV) has similar mechanical structure with helicopter. It can be operated in different flight modes which the fixed-wing UAV is unable to achieve, such as vertical take-off/landing, hovering, lateral flight, pirouette, and bank-to-turn. For these advantages, RUAV can be used in many fields where human intervention is considered difficult or dangerous (Napolitano et al., 1998). So it can perform the tasks such as regional surveillance, aerial mapping, communications relay, power-line inspection, aerial photography and precision load dropping, etc. RUAV has many advantages, such as small in size, low cost, simple operation and convenient transportation. Therefore, RUAV has broad application prospects, high demands, and advantages that the fixed-wing unmanned aircrafts and

Integrated navigation system can give the movement information of the carrier, thus every UAV has an integrated navigation system. Because of the limitations of weight, volume, power supply and cost, there is no redundant navigation system in RUAV. RUAV does not have the emergency landing properties of fixed-wing aircrafts or airships in case of failures. Therefore, a failure in any part of a RUAV can be catastrophic. If the failure is not detected, identified and accommodated, the RUAV may crash. The use of wavelet transforms the situation of accurately localizing the characteristics of a signal both in the time and frequency domains, the occurring instants of abnormal status of a sensor in the output signal can be identified by the multi-scale representation of the signal (Dabechies, 1988; Isermann, 1984; Zhang, 2000). Once the instants are detected, the distribution differences of the signal energy on all decomposed wavelet scales of the signal before and after the

In low cost and small size integrated navigation system, MEMS (Micro Electronic Mechanical System) inertial sensors are used widely. But MEMS inertial sensors, especially MEMS gyroscopes have large noise. It affects the calculation accuracy of angle rotation matrix, and will further affect calculation accuracy of other navigation data such as position, velocity, and angular velocity. In order to improve the calculation precision of position and angle, digital filter is required to reduce the noise of gyroscope. Commonly, we used

**1. Introduction** 

unmanned airship can not replace.

instants are used to claim and classify the sensor faults.
