Experimental study of a porous electrospray thruster with different number of emitterstrips

The electrospray thruster is becoming popular in space propulsion due to its low power and high specific impulse.Before this work,an electrospray thruster based on a porous emitter was developed.In order to achieve larger and more stable thrust,the thruster was redesigned,and the influence of the space between strips on thrust was studied.Four types of emitter were tested,and they had 1,3,4 and 14 emitter-strips on the emission surface of the same size respectively.According to the experimental results,the maximum extraction voltage and emission current of the four thrusters are different under stable operational conditions.The measured stable emission currents and extraction voltages were-500μA/-5000 V,-1570μA/-3800 V,-1200μA/-3800 V,and-650μA/-4500 V,respectively.Increasing the number of strips may not result in the emission current increasing,but changing the stable operational range of the emission current per strip and the extraction voltage.The maximum stable operational extraction voltages of 3 and 4 emitter-strips are lower than those of 1 and 14 emitter-strips,but the emission currents are higher than those of 1 and 14 emitter-strips.Time-of-flight mass spectrometry was used to analyze the mass distribution and obtain the performance of the thruster in the case of thrusters with 1 and 3 emitter-strips.Both of their plumes were composed of very small ion cluster(the pure-ion regime),and their thrusts were 80.1μN,219.2μN with specific impulses of 5774 s,5047 s,respectively.

Gain self-scheduled H_∞ control for morphing aircraft in the wing transition process based on an LPV model

This article investigates gain self-scheduled H 1 robust control system design for a tailless fold- ing-wing morphing aircraft in the wing shape varying process. During the wing morphing phase, the aircraft's dynamic response will be governed by time-varying aerodynamic forces and moments. Nonlinear dynamic equations of the morphing aircraft are linearized by using Jacobian linearization approach, and a linear parameter varying (LPV) model of the morphing aircraft in wing folding is obtained. A multi-loop controller for the morphing aircraft is formulated to guarantee stability for the wing shape transition process. The proposed controller uses a set of inner-loop gains to provide stability using classical techniques, whereas a gain self-scheduled H 1 outer-loop controller is devised to guarantee a specific level of robust stability and performance for the time-varying dynamics. The closed-loop simulations show that speed and altitude vary slightly during the whole wing folding process, and they converge rapidly after the process ends. This proves that the gain self-scheduled H 1 robust controller can guarantee a satisfactory dynamic performance for the morphing aircraft during the whole wing shape transition process. Finally, the flight control system's robustness for the wing folding process is verified according to uncertainties of the aerodynamic parameters in the nonlinear model.

EMMAE failure detection system and failure evaluation over flight performance

Purpose-The purpose of this paper is to present the research into fault detection and isolation(FDI)and evaluation of the reduction of performance after failures occurred in the flight control system(FCS)during its mission operation.Design/methodology/approach–The FDI is accomplished via using the multiple models scheme which is developed based on the Extend Kalman Filter(EKF)algorithm.Towards this objective,the healthy mode of the FCS under different type of failures,including the control surfaces and structural,should be considered.It developed a bank of extended multiple models adaptive estimation(EMMAE)to detect and isolate the above mentioned failures in the FCS.In addition,the performances including the flight envelope,the voyage and endurance in cruising are proposed to reference and evaluate the process of mission,especially for UAV under failure conditions.Findings-The contribution of this paper is to provide the information not only about the failures,but also considering whether the UAV can accomplish the task for the ground station.Originality/value-The main contribution of this paper is in the areas of the structural and control surface faults researching,which are occurred in the mission procedures and emphasized the identification of those failures’magnitudes.The FDI scheme includes the performance evaluation,while the evaluation obtained through the extensive numerical simulations and saved in the offline database.As a consequence,it is more accurate and less computationally demanding while evaluating the performance.