Tracking scheme of airborne star tracker based on event-triggered sliding mode control with known input delay.

The airborne star tracker is crucial in aircraft navigation systems, with its tracking performance directly impacting navigation accuracy. Under airborne conditions, the performance of its tracking control will be compromised by various disturbances. Moreover, the limitation in computational resources is another issue that must be addressed.

An Electromagnetic-Driven Microshutter Array in a Field-of-View Gated Image System for All-Time Star Sensors.

Aiming at the application requirements of a field of view (FOV) gated imaging system for all-time star sensors, a key device of a microshutter array with large unit size, high duty cycle, and fast response speed based on the electromagnetic actuation is designed. The proposed microshutter array adopts the principle that the current-carrying coil is subjected to the magnetic force in the magnetic field. The coil element is deflected by the loading current and acts as a light barrier in realizing the optical switch function.

ISSM-ELM - a guide star selection for a small-FOV star sensor based on the improved SSM and extreme learning machine.

The construction of a guide star catalog is crucial for a star sensor to achieve accurate star map recognition and attitude determination. At present, the methods of a guide star catalog for a large field of view (FOV) star sensor have been relatively mature. However, for a small-FOV star sensor, there are still certain problems, such as a large storage capacity of a guide star catalog, uneven distribution of stars, and easy occurrence of voids.

Optical imaging system for an all-time star sensor based on field of view gated technology.

The wide field of view (FOV) of traditional star sensor optical systems restricts the ability to suppress atmospheric background. An optical imaging system for an all-time star sensor based on FOV gated technology is proposed. In this system, a wide FOV telescope is used to observe a large sky area containing multiple stars.

Star Sensor Denoising Algorithm Based on Edge Protection.

Single-pixel noise commonly appearing in a star sensor can cause an unexpected error in centroid extraction. To overcome this problem, this paper proposes a star image denoising algorithm, named Improved Gaussian Side Window Filtering (IGSWF). Firstly, the IGSWF algorithm uses four special triangular Gaussian subtemplates for edge protection.

Heavy metal poisoning resistance of a Co-modified 3Mn10Fe/Ni low-temperature SCR deNOx catalyst.

Heavy metals have a great influence on the deNO efficiency of catalysts. The 3Mn10Fe/Ni catalyst that used nickel foam (Ni) as the carrier, Mn and Fe as the active components, and Co as a trace auxiliary was prepared using an impregnation method. The catalysts poisoned by Pb or Zn and Co-modified catalysts with Pb or Zn poisoning were studied.

Experimental Study of the Influences of Temperature on the Properties of Particles in a Gasifier during Coal-Water Slurry Gasification.

Studies were made on the influence of temperature and oxygen to carbon ratio (the O/C ratio) on the properties of particles during water coal slurry gasification by taking a new-type coal-water slurry gasifier as the thermal experiment platform, coal-water slurry as a gasification material, and oxygen as the oxidant. The results show that the higher the gasification temperature, the more spherical particles are generated, the higher the content of Na, Fe, and S on the particle surface, and the greater the mass percentage of fine particles. With increase in the O/C ratio, the production of fine particles also increases, while the carbon content of the particles decreases.

A Convenient Calibration Method for LRF-Camera Combination Systems Based on a Checkerboard.

In this paper, a simple and easy high-precision calibration method is proposed for the LRF-camera combined measurement system which is widely used at present. This method can be applied not only to mainstream 2D and 3D LRF-cameras, but also to calibrate newly developed 1D LRF-camera combined systems. It only needs a calibration board to record at least three sets of data.

Polarization-modulated three-dimensional imaging using a large-aperture electro-optic modulator.

To implement high-resolution and low-light sensitive three-dimensional (3D) imaging for long-range applications while simplifying data collection and reducing collection time, a polarization-modulated 3D imaging structure, using a large-aperture electro-optic modulator (EOM) and electron-multiplying CCD (EMCCD), is proposed in this paper. As the EMCCD camera itself has no ability of time resolution and high-speed gating due to the time integration mechanism, large-aperture EOMs are used to provide time resolution and high-speed shutter simultaneously for the EMCCD cameras to obtain the polarization-modulated images from which a 3D image can be reconstructed. A narrow field of view was designed to match the divergence of laser beam for long-range imaging, and therefore through the receiver, the incident angle on the EOM would still be limited to within a small angle, which would not degrade the modulation performance significantly during electro-optic modulation.

Efficient subpixel registration for polarization-modulated 3D imaging.

To implement real-time 3D reconstruction and displaying for polarization-modulated 3D imaging lidar system, an efficient subpixel registration based on maximum principal component analysis (MPCA) is proposed in this paper. With which only the maximum principal component is estimated to identify non-integer translations in spatial domain while other principal components affected by noise are ignored. Consequently, robustness and stability of the subpixel registration is implemented in presence of noise, while computational complexity is reduced and memory size is saved simultaneously, especially when the image size is large.

Scale Estimation and Correction of the Monocular Simultaneous Localization and Mapping (SLAM) Based on Fusion of 1D Laser Range Finder and Vision Data.

This article presents a new sensor fusion method for visual simultaneous localization and mapping (SLAM) through integration of a monocular camera and a 1D-laser range finder. Such as a fusion method provides the scale estimation and drift correction and it is not limited by volume, e.g.

Electro-optic modulation methods in range-gated active imaging.

A time-resolved imaging method based on electro-optic modulation is proposed in this paper. To implement range resolution, two kinds of polarization-modulated methods are designed, and high spatial and range resolution can be achieved by the active imaging system. In the system, with polarization beam splitting the incident light is split into two parts, one of which is modulated with cos(2) function and the other is modulated with sin(2) function.

Low-pass parabolic FFT filter for airborne and satellite lidar signal processing.

In order to reduce random errors of the lidar signal inversion, a low-pass parabolic fast Fourier transform filter (PFFTF) was introduced for noise elimination. A compact airborne Raman lidar system was studied, which applied PFFTF to process lidar signals. Mathematics and simulations of PFFTF along with low pass filters, sliding mean filter (SMF), median filter (MF), empirical mode decomposition (EMD) and wavelet transform (WT) were studied, and the practical engineering value of PFFTF for lidar signal processing has been verified.

Non-iterative method for camera calibration.

This paper presents a new and effective technique to calibrate a camera without nonlinear iteration optimization. To this end, the centre-of-distortion is accurately estimated firstly. Based on the radial distortion division model, point correspondences between model plane and its image were used to compute the homography and distortion coefficients afterwards.

Volcanic history of the Imbrium basin: A close-up view from the lunar rover Yutu.

We report the surface exploration by the lunar rover Yutu that landed on the young lava flow in the northeastern part of the Mare Imbrium, which is the largest basin on the nearside of the Moon and is filled with several basalt units estimated to date from 3.5 to 2.0 Ga.