The entry vehicle for the Tianwen-1 mission successfully landed on the surface of Mars at 7:18 AM BJT on May 15,*** successful landing made China the first country to orbit,land,and release a rover in their first atte...
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The entry vehicle for the Tianwen-1 mission successfully landed on the surface of Mars at 7:18 AM BJT on May 15,*** successful landing made China the first country to orbit,land,and release a rover in their first attempt at the Mars *** guidance,navigation,and control(GNC)system plays a crucial role in the entry,descent,and landing(EDL)*** study focused on the attitude control component of the GNC system *** EDL phase can be divided into several sub-phases,namely the angle of attack control phase,lift control phase,parachute descent phase,and powered descent *** sub-phase has unique attitude control requirements and *** paper introduces the key aspects of designing attitude controllers for each ***,flight results are presented and analyzed.
To meet the requirements of the Tianwen-1 mission,adaptive entry guidance for entry vehicles,with low lift-to-drag ratios,limited control authority,and large initial state bias,was ***,the entry guidance law is divide...
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To meet the requirements of the Tianwen-1 mission,adaptive entry guidance for entry vehicles,with low lift-to-drag ratios,limited control authority,and large initial state bias,was ***,the entry guidance law is divided into four distinct phases:trim angle-of-attack phase,range control phase,heading alignment phase,and trim-wing deployment *** the range control phase,the predictor–corrector guidance algorithm is improved by planning an on-board trajectory based on the Mars sciencelaboratory(MSL)entry guidance *** nominal trajectory was designed and described using a combination of the downrange value and other states,such as drag acceleration and altitude *** a large initial state bias,the nominal downrange value was modified onboard by weighing the landing accuracy,control authority,and parachute deployment *** biggest advantage of this approach is that it allows the successful correction of altitude errors and the avoidance of control *** overview of the optimal trajectory design process,including a discussion of the design of the initial flight path angle,relevant event trigger,and transition conditions between the four phases,was also ***,telemetry data analysis and post-flight assessment results were used to illustrate the adaptive guidance law,create good conditions for subsequent parachute reduction and power reduction processes,and gauge the success of the mission.
Wavefront control is the fundamental requirement in optical *** optics have drawn intensive attention due to the merits of compactness and light ***,it remains a challenge to freely manipulate the dispersion,hindering...
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Wavefront control is the fundamental requirement in optical *** optics have drawn intensive attention due to the merits of compactness and light ***,it remains a challenge to freely manipulate the dispersion,hindering practical applications,especially in ***,we propose the concept of frequencysynthesized phase engineering to solve this problem.A phasefront-frequency matrix is properly designed to encode different spatial phases to separate frequencies,thus makes arbitrary dispersion tailoring and even frequency-separated functionalization *** periodically rotated director endows cholesteric liquid crystal with a spin and frequency selective ***,via presetting the local initial orientation of liquid crystal,geometric phase is encoded to the reflected *** verify the proposed strategy by cascading the chiral anisotropic optical media of specifically designed helical pitches and initial director *** this means,planar lenses with RGB achromatic,enhanced chromatic aberration and color routing properties are ***-sized and high-efficient lenses are fabricated with low crosstalk among *** releases the freedom of dispersion control of planar optics,and even enables frequency decoupled phase *** work brings new insights to functional planar optics and may upgrade the performance of existing optical apparatuses.
The powered-descent landing(PDL)phase of the Tianwen-1 mission began with composite backshell–parachute(CBP)separation and ended with landing-rover *** main tasks of this phase were to reduce the velocity of the land...
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The powered-descent landing(PDL)phase of the Tianwen-1 mission began with composite backshell–parachute(CBP)separation and ended with landing-rover *** main tasks of this phase were to reduce the velocity of the lander,perform the avoidance maneuver,and guarantee a soft *** PDL phase overcame many challenges:performing the divert maneuver to avoid collision with the CBP while simultaneously avoiding large-scale hazards;slowing the descent from approximately 95 to 0 m/s;performing the precise hazard-avoidance maneuver;and placing the lander gently and safely on the surface of *** architecture and algorithms of the guidance,navigation,and control system for the PDL phase were designed;its execution resulted in Tianwen-1’s successful touchdown in the morning of 15 May ***,the Tianwen-1 mission achieved a historic autonomous landing with simultaneous hazard and CBP avoidance.
The configuration of spacecraft thrusters directly affects the realization of precise automatic control and propellant consumption. At present, the design of thruster configuration lacks of theoretical guidance. space...
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Consider a class of satellite with rotating payload that has high moment of inertia and high rotation speed. In general, the ideal condition of perfect symmetry cannot be satisfied for the rotating payload. It is reco...
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Satellite attitude determination is one of the key parts of control system design. Star sensor (STS) is one of the high-precision attitude measurement instruments. However, the STS fixed on the load platform rotate an...
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Partial Differential Equations(PDEs)are model candidates of soft sensing for aero-engine health management *** existing Physics-Informed Neural Networks(PINNs)have made ***,unmeasurable aero-engine driving sources lea...
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Partial Differential Equations(PDEs)are model candidates of soft sensing for aero-engine health management *** existing Physics-Informed Neural Networks(PINNs)have made ***,unmeasurable aero-engine driving sources lead to unknown PDE driving terms,which weaken PINNs *** this end,Physically Informed Hierarchical Learning followed by Recurrent-Prediction Term(PIHL-RPT)is ***,PIHL is proposed for learning nonhomogeneous PDE solutions,in which two networks NetU and NetG are *** is for learning solutions satisfying PDEs;NetG is for learning driving terms to regularize NetU ***,we propose a hierarchical learning strategy to optimize and couple NetU and NetG,which are integrated into a data-physics-hybrid loss ***,we prove PIHL-RPT can iteratively generate a series of networks converging to a function,which can approximate a solution to well-posed ***,RPT is proposed for prediction improvement of PIHL,in which network NetU-RP is constructed to compensate for information loss caused by data sampling and driving sources’***,artificial datasets and practical vibration process datasets from our wear experiment platform are used to verify the feasibility and effectiveness of PIHL-RPT based soft ***,comparisons with relevant methods,discussions,and PIHL-RPT based health monitoring example are given.
To solve the problem that external systematic errors of the optical camera cannot be fully estimated due to limited computing resources,a unified dimensionality reduction representation method for the external systema...
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To solve the problem that external systematic errors of the optical camera cannot be fully estimated due to limited computing resources,a unified dimensionality reduction representation method for the external systematic errors of the optical camera is proposed,and autonomous relative optical navigation is *** camera translational and misalignment errors are converted into a three-dimensional rotation error,whose differential model can be established through specific attitude control and appropriate ***,the rotation error and the relative motion state are jointly estimated in an augmented Kalman filter *** with the traditional method that estimates the camera translational and misalignment errors,the proposed method reduces the computational complexity in that the estimated state dimension is ***,as demonstrated by numerical simulation,the estimation accuracy is improved significantly.
Lightweight thin-walled structures with lattice infill are widely desired in satellite for their high stiffness-to-weight ratio and superior buckling strength resulting fromthe sandwich *** structures can be fabricate...
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Lightweight thin-walled structures with lattice infill are widely desired in satellite for their high stiffness-to-weight ratio and superior buckling strength resulting fromthe sandwich *** structures can be fabricated bymetallic additive manufacturing technique,such as selective laser melting(SLM).However,the maximum dimensions of actual structures are usually in a sub-meter scale,which results in restrictions on their appliance in aerospace and other *** this work,a meter-scale thin-walled structure with lattice infill is designed for the fuel tank supporting component of the satellite by integrating a self-supporting lattice into the thickness optimization of the *** designed structure is fabricated by SLM of AlSi10Mg and cold metal transfer welding ***-static mechanical tests and vibration tests are both conducted to verify the mechanical strength of the designed large-scale lattice thin-walled *** experimental results indicate that themeter-scale thin-walled structure with lattice infill could meet the dimension and lightweight requirements of most spacecrafts.
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