Stabilization System for UAV Landing on Rough Ground by Adaptive 3D Sensing and High-Speed Landing Gear Adjustment

2021 ◽  
Vol 33 (1) ◽  
pp. 108-118
Author(s):  
Mikihiro Ikura ◽  
◽  
Leo Miyashita ◽  
Masatoshi Ishikawa
Keyword(s):  
Unmanned Aerial Vehicles ◽  
High Speed ◽  
Landing Gear ◽  
Detailed Measurement ◽  
Contact Points ◽  
Measurement Results ◽  
3D Sensing ◽  
Landing Gears ◽  
Spatio Temporal ◽  
Measurement Area

This paper proposes a real-time landing gear control system based on adaptive and high-speed 3D sensing to enable the safe landing of unmanned aerial vehicles (UAVs) on rough ground. The proposed system controls the measurement area on the ground according to the position and attitude of the UAV and enables high-speed 3D sensing of the focused areas in which the landing gears are expected to contact the ground. Furthermore, the spatio-temporal resolution of the measurement can be improved by focusing a measurement area and the proposed system can recognize the detailed shape of the ground and the dynamics. These detailed measurement results are used to control the lengths of the landing gears at high speed, and it is ensured that all the landing gears contact the ground simultaneously to reduce the instability at touchdown. In the experiment setup, the proposed system realized high-speed sensing for heights of contact points of two landing gears at a rate of 100 Hz and almost simultaneous contact on ground within 36 ms.

scholarly journals AdjustSense: Adaptive 3D Sensing System with Adjustable Spatio-Temporal Resolution and Measurement Range Using High-Speed Omnidirectional Camera and Direct Drive Motor

Sensors ◽  
2021 ◽  
Vol 21 (21) ◽  
pp. 6975
Author(s):  
Mikihiro Ikura ◽  
Sarthak Pathak ◽  
Jun Younes Louhi Kasahara ◽  
Atsushi Yamashita ◽  
Hajime Asama
Keyword(s):  
Temporal Resolution ◽  
High Speed ◽  
Measurement Range ◽  
Direct Drive ◽  
Multiple Measurement ◽  
Sensing System ◽  
Drive Motor ◽  
3D Sensing ◽  
Spatio Temporal ◽  
Conventional Systems

Many types of 3D sensing devices are commercially available and were utilized in various technical fields. In most conventional systems with a 3D sensing device, the spatio-temporal resolution and the measurement range are constant during operation. Consequently, it is necessary to select an appropriate sensing system according to the measurement task. Moreover, such conventional systems have difficulties dealing with several measurement targets simultaneously due to the aforementioned constants. This issue can hardly be solved by integrating several individual sensing systems into one. Here, we propose a single 3D sensing system that adaptively adjusts the spatio-temporal resolution and the measurement range to switch between multiple measurement tasks. We named the proposed adaptive 3D sensing system “AdjustSense.” In AdjustSense, as a means for the adaptive adjustment of the spatio-temporal resolution and measurement range, we aimed to achieve low-latency visual feedback for the adjustment by integrating not only a high-speed camera, which is a high-speed sensor, but also a direct drive motor, which is a high-speed actuator. This low-latency visual feedback can enable a large range of 3D sensing tasks simultaneously. We demonstrated the behavior of AdjustSense when the positions of the measured targets in the surroundings were changed. Furthermore, we quantitatively evaluated the spatio-temporal resolution and measurement range from the 3D points obtained. Through two experiments, we showed that AdjustSense could realize multiple measurement tasks: 360∘ 3D sensing, 3D sensing at a high spatial resolution around multiple targets, and local 3D sensing at a high spatio-temporal resolution around a single object.

MULTIDIMENSIONAL SIMULATIONS AND TEST FIRES OF A HYDROGEN-FUELED RAMJET WITH AN ANNULAR DETONATIVE COMBUSTOR AT APPROACHING AIR FLOW OF MACH 2 AND 1.5

2020 ◽  
Author(s):  
V. S. IVANOV ◽  
◽  
V. S. AKSENOV ◽  
S. M. FROLOV ◽  
P. A. GUSEV ◽  
...  
Keyword(s):  
Unmanned Aerial Vehicles ◽  
High Speed ◽  
Constant Pressure ◽  
Air Flow ◽  
Thermodynamic Cycle ◽  
Aerial Vehicles ◽  
Mach Numbers

Modern high-speed unmanned aerial vehicles are powered with small-size turbojets or ramjets. Existing ramjets operating on the thermodynamic cycle with de§agrative combustion of fuel at constant pressure are efficient at flight Mach numbers M ranging from about 2 to 6.

scholarly journals Cavitation between cylinder-liner and piston-ring in a new designed optical IC engine

2021 ◽  
pp. 146808742110080
Author(s):  
Jamshid Malekmohammadi Nouri ◽  
Ioannis Vasilakos ◽  
Youyou Yan
Keyword(s):  
High Speed ◽  
Contact Point ◽  
Cylinder Liner ◽  
Optical Methods ◽  
Engine Management System ◽  
Great Success ◽  
Ic Engine ◽  
Contact Points ◽  
Lubricant Flow ◽  
Cavitation Intensity

A new engine block with optical access has been designed and manufactured capable of running up to 3000 r/min with the same specification as the unmodified engine. The optical window allowed access to the full length of the liner over a width of 25 mm to investigate the lubricant flow and cavitation at contact point between the rings and cylinder-liner. In addition, it allowed good access into the combustion chamber to allow charged flow, spray and combustion visualisation and measurements using different optical methods. New custom engine management system with build in LabView allowed for the precise full control of the engine. The design of the new optical engine was a great success in producing high quality images of lubricant flow, cavitation formation and development at contact point at different engine speeds ranging from 208 to 3000 r/min and lubricant temperatures (30°C–70°C) using a high-speed camera. The results under motorised operation confirmed that there was no cavitation at contact points during the intake/exhaust strokes due to low in-cylinder presure, while during compression/expansion strokes, with high in-cylinder pressure, considerable cavities were observed, in particular, during the compression stroke. Lubricant temperatures had the effect of promoting cavities both in their intensity and covered ring area up to 50°C as expected. Beyond that, although the cavitation intensity increases further with temperature, its area reduces due to possible collapse of the cavitating bubbles at higher temperature. The change of engine speed from 208 to 800 r/min increased cavitating area considerably by 52% of the ring area and was further increased by 19% at 1000 r/min. After that, the results showed very small increase in cavitation area (1.3% at 2000 r/min) with similar intensity and distribution across the ring.

scholarly journals Experimental study of the dynamic behaviour of High Performance Concrete (HPC) under tensile loading

2018 ◽  
Vol 183 ◽  
pp. 02043 ◽  
Author(s):  
Bratislav Lukić ◽  
Dominique Saletti ◽  
Pascal Forquin
Keyword(s):  
High Speed ◽  
High Performance ◽  
High Performance Concrete ◽  
Imaging System ◽  
Spall Strength ◽  
High Speed Imaging ◽  
Dynamic Tensile Strength ◽  
Full Field ◽  
Local Point ◽  
Measurement Results

This paper presents the measurement results of the dynamic tensile strength of a High Performance Concrete (HPC) obtained using full-field identification method. An ultra-high speed imaging system and the virtual fields method were used to obtain this information. Furthermore the measurement results were compared with the local point-wise measurement to validate the data pressing. The obtained spall strength was found to be consistently 20% lower than the one obtained when the Novikov formula is used.

scholarly journals Research for Space Interception Simulation under Nonlinear Time-Varied Similarity

2020 ◽  
Vol 38 (4) ◽  
pp. 715-722
Author(s):  
Xiaodong Lu ◽  
Tao Cui ◽  
Jiayao Gu
Keyword(s):  
Dimensional Analysis ◽  
High Speed ◽  
Uniform Motion ◽  
Simulation Algorithm ◽  
Large Magnitude ◽  
Small Magnitude ◽  
Whole Process ◽  
Scale Factors ◽  
Reference Motion ◽  
Spatio Temporal

A nonlinear time-varied similarity(NTVS) simulation algorithm is proposed to solve the problem that the process of space interception is intractable to simulate with high precision in limited platform under the linear constant similarity(LCS). Firstly, the similarity criterions based on the dimensional analysis are given in the simulation of the interception motion at high-speed, and the disadvantage of LCS is analyzed. Then, the reference motion is introduced to establish a time-varied spatio-temporal transform system which scale factors are self-adaptive with time, and the method is proved to satisfy the similarity consistency. Finally the way that linear separation and independent mapping solve the problem that the large magnitude uniform motion in approaching directions and small magnitude overload motion in lateral directions are simulated in a limited ground platform. The results show that the NTVS can simulate the whole process of interception and perform better in accuracy comparing with that via LCS.

Reduction of ground-borne vibrations from rail lines on viaducts by means of elastic anti-vibration mats

2018 ◽  
Vol 233 (5) ◽  
pp. 550-565
Author(s):  
Caiyou Zhao ◽  
Wang Ping ◽  
Mengting Xing ◽  
Qiang Yi ◽  
Liuchong Wang
Keyword(s):  
High Speed ◽  
Reaction Force ◽  
Field Tests ◽  
Ground Vibration ◽  
Coupling System ◽  
Step Procedure ◽  
Measurement Results ◽  
Track Bridge ◽  
Bridge Bearing ◽  
The Impact

In this paper, the effectiveness of elastic anti-vibration mats in reducing ground-borne vibrations from rail viaducts is investigated by means of theoretical analysis and is validated by the results of field tests. A two-step procedure is adopted for analyzing the vehicle-track-bridge-soil coupling system. In the first step, the train-track-bridge-pier subsystem is considered, and the bridge-bearing reaction force is solved. In the second step, the pier-pile-soil subsystem is considered, and the ground vibration solution is obtained by applying the negative bridge-bearing reaction force to the pier top on a pier-pile-soil model. The accuracy of the presented model is then verified in comparison with in-situ measurement results. On the basis of this comparison, a parametric study on the impact of anti-vibration mats on ground-borne vibrations was investigated theoretically, and the effectiveness of elastic anti-vibration mats with the suggested optimal parameters was further validated by field tests. The results show that when the stiffness of the elastic anti-vibration mats is 1.5 MPa/m, ground vibration decreases significantly and the vertical rail displacement agrees with high-speed railway regulations.

Design and flight-stability analysis of a closed fixed-wing unmanned aerial vehicle formation controller

2018 ◽  
Vol 233 (8) ◽  
pp. 1045-1054 ◽  
Author(s):  
Jialong Zhang ◽  
Bing Xiao ◽  
Maolong Lv ◽  
Qiang Zhang
Keyword(s):  
Unmanned Aerial Vehicles ◽  
Collision Avoidance ◽  
High Speed ◽  
Physical Simulation ◽  
Controller Design ◽  
Formation Flight ◽  
External Factors ◽  
Flight Stability ◽  
Aerial Vehicles ◽  
Closed Formation

This article addresses a flight-stability problem for the multiple unmanned aerial vehicles cooperative formation flight in the process of the closed and high-speed flight. The main objective is to design a cooperative formation controller with known external factors, and this controller can keep the consensus of attitude and position and reduce the communication delay between any two unmanned aerial vehicles and increase unmanned aerial vehicles formation cruise time under the known external factors. Known external factors are taken into consideration, and longitude maneuvers using nonlinear thrust vectors were employed with unsteady aerodynamic models, according to the attitude and position of unmanned aerial vehicles, which were employed as corresponding input signals for studying the dynamic characteristics of unmanned aerial vehicles formation flight. In addition, the relative distance between any two unmanned aerial vehicles was not allowed to exceed their safe distance so that the controller could perform collision avoidance. An analysis of formation flight distance error shows that it converged to a fixed value that well ensured unmanned aerial vehicles formation flight stability. The experimental results show that the controller can improve the speed of a closed formation effectively and maintain the stability of formation flight, which provides a method for closed formation flight controller design and collision avoidance for any two unmanned aerial vehicles. Meanwhile, the effectiveness of proposed controller is fully proved by semi-physical simulation platform.

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