Current Issue : April - June Volume : 2014 Issue Number : 2 Articles : 6 Articles
A new algorithm was developed for the initial parameters optimization of guided projectiles with multiple constraints. Due to the\r\nrelationship between the analytic guidance logic and state variables of guided projectiles, the Radau pseudospectral method was\r\nused to discretize the differential equations including control variables and state variables with multiple constraints into series\r\nalgebraic equations that were expressed only by state variables. The initial parameter optimization problem was transformed\r\nto a nonlinear programming problem, and the sequential quadratic programming algorithm was used to obtain the optimal\r\ncombinations of initial height and range to target for the final velocity of guided projectiles maximum with constraints. Comparing\r\nwith the appropriate initial conditions solved by Monte Carlo method and the flight characteristics solved by integrating the\r\noriginal differential equations in the optimal initial parameters computed by the new algorithm, the feasibility of new algorithm\r\nwas validated...
A landing mechanism to an asteroid with soft surface is developed. It consists of three landing feet, landing legs, cardan element,\r\ndamping element, equipment base, anchoring system, and so on. Static structural analysis and modal analysis are carried out\r\nto check the strength and natural frequency of the landing mechanism with FEA. Testing platform for the anchoring system is\r\nintroduced, and then the penetrating and anchoring tests of the anchoring system are carried out in different media. It shows that\r\ncohesion of the media has large influence on the penetrating and anchoring performance of the anchoring system. Landing tests\r\nof the landing mechanism with different velocities under simulated microgravity environment are carried out on the air-floating\r\nplatform, and the impact accelerations are measured by the sensors on the landing mechanism. At the same time, these impact\r\naccelerations are processed by spectrum analysis to find the natural frequency of the landing mechanism....
A global (volume averaged) model pertaining to N2O discharges is used to design and to study electric propulsion applications,\r\nespecially helicon plasma thrusters fed with pure N2O and also with N2/O2 mixtures including air. Results obtained for N2O\r\nfeeding are discussed and compared to those pertaining to an air-like N2/O2 mixture feeding. An interesting similarity is observed.\r\nComparison of the N2O model results versus those of Ar shows lower ionization percentage with higher electron temperature for\r\nN2O propellant....
This paper presents the development of a small-scale unmanned aerial vehicle (UAV) helicopter system based on a Raptor 90 hobby\r\nhelicopter. Firstly, onboard avionics system and ground station are designed carefully. The onboard avionics system mainly consists\r\nof sensors, flight control board, RF modem, and power supply system. The ground station comprises a computer and a RF modem.\r\nThe main function of ground station is to monitor the status of onboard avionics. To avoid the effect of noises, some efficient\r\nsensor data processing and integrated navigation algorithms are designed and implemented on the onboard avionics. As a result,\r\nthe constructed system exhibits low weight, small size, antivibration, and low power consumption; the essential information for\r\nsystem identification and automatic control can be easily acquired. Several ground and flight tests have been performed to verify\r\nthe feasibility and reliability of the total system. The results show that it is sufficient for system identification and automatic control....
This paper deals with star tracker algorithms validation based on star field scene simulation and hardware-in-the-loop test\r\nconfiguration.Alaboratory facility for indoor tests, based on the simulation of star field scenes, is presented.Attainable performance\r\nis analyzed theoretically for both static and dynamic simulations. Also, a test campaign is presented, inwhich a star sensor prototype\r\nwith real-time, fully autonomous capability is exploited. Results that assess star field scene simulation performance and show the\r\nachievable validation for the sensor algorithms and performance in different operating modes (autonomous attitude acquisition,\r\nattitude tracking, and angular rate-only) and different aspects (coverage, reliability, and measurement performance) are discussed....
This study describes the start/unstart characteristics of a finite and rectangular supersonic biplane wing. Two wing models were\r\ntested in wind tunnels with aspect ratios of 0.75 (model A) and 2.5 (model B). The models were composed of a Busemann biplane\r\nsection. The tests were carried out using supersonic and transonic wind tunnels over a Mach number range of 0.3 = ??8 = 2.3\r\nwith angles of attack of 0�°, 2�°, and 4�°. The Schlieren system was used to observe the flow characteristics around the models. The\r\nexperimental results showed that these models had start/unstart characteristics that differed from those of the Busemann biplane\r\n(two dimensional) owing to three-dimensional effects.Models A and B started at lowerMach numbers than the Busemann biplane.\r\nThe characteristics also varied with aspect ratio: model A (1.3 < ??8 < 1.5) started at a lower Mach number than model B\r\n(1.6 < ??8 < 1.8) owing to the lower aspect ratio. Model B was located in the double solution domain for the start/unstart\r\ncharacteristics at??8 = 1.7, and model B was in either the start or unstart state at??8 = 1.7. Once the state was determined, either\r\nstate was stable....
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