ANALYSIS FOR AIRCRAFT TAXIING AT VARIABLE VELOCITY ON UNEVENNESS RUNWAY BY THE POWER SPECTRAL DENSITY METHOD

In this paper a novel approach for the analysis of non stationary response of aircraft landing gear taxiing over an unevenness runway at variable velocity is explored, which is based on the power spectral density method. A concerned analytical landing gear model for simulating actual aircraft taxiing is formulated. The equivalent linearization results obtained by probabilistic method are inducted to treat landing gear non linear parameters such as shock absorber air spring force, hydraulic damping and Coulomb friction, tire stiffness and damping. The power spectral density for non stationary analysis is obtained via variable substitution and then Fourier transform. A representative response quantity, the overload of the aircraft gravity center, is analyzed. The frequency response function of the gravity overload is derived. The case study demonstrates that under the same reached velocity the root mean square of the gravity acceleration response from constant acceleration taxiing is smaller than that from constant velocity taxiing and the root mean square of the gravity acceleration response from lower acceleration taxiing is greater than that from higher acceleration.

DESIGN OF NEW PASSIVE ADAPTIVE SHOCK ABSORBER OF LANDING GEAR AND STUDY OF ITS LANDING PERFORMANCE

A new passive adaptive shock absorber of the landing gear with double-cavity and dual-damping is studied. Its mathematical model and the virtual prototype are established based on the dynamics simulation software ADAMS. The landing dynamic characteristics and the effect of the parameters on the proposed adaptive shock absorber are analyzed. The results show that the proposed adaptive shock absorber has the slightly better landing performance at the normal load case and much less overload at the crudely landing case than the shock absorber with single-cavity and variable orifice. It also can be concluded that the overload of the proposed adaptive shock absorber can be reduced through increasing the volumes of both cavities or decreasing the pressure of the high pressure cavity or increasing the pressure of the low pressure cavity.

Pre-locate net for object detection in high-resolution images

Small-object detection has long been a challenge.High-megapixel cameras are used to solve this problem in industries.However,current detectors are inefficient for high-resolution images.In this work,we propose a new module called Pre-Locate Net,which is a plug-and-play structure that can be combined with most popular detectors.We inspire the use of classification ideas to obtain candidate regions in images,greatly reducing the amount of calculation,and thus achieving rapid detection in high-resolution images.Pre-Locate Net mainly includes two parts,candidate region classification and behavior classification.Candidate region classification is used to obtain a candidate region,and behavior classification is used to estimate the scale of an object.Different follow-up processing is adopted according to different scales to balance the variance of the network input.Different from the popular candidate region generation method,we abandon the idea of regression of a bounding box and adopt the concept of classification,so as to realize the prediction of a candidate region in the shallow network.We build a high-resolution dataset of aircraft and landing gears covering complex scenes to verify the effectiveness of our method.Compared to state-of-the-art detectors(e.g.,Guided Anchoring,Libra-RCNN,and FASF),our method achieves the best m AP of 94.5 on 1920×1080 images at 16.7 FPS.