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Due to the long-range data communication and complex Mars environment, the Mars lander needs to promote the ability to autonomously adapt uncertain situations ensuring high precision landing in future Mars missions. Based on the analysis of multiple disturbances, this study demonstrates an enhanced predictor–corrector guidance method to deal with the effect of atmospheric uncertainties during the entry phase of the Mars landing. In the proposed method, the predictor–corrector guidance algorithm is designed to autonomously drive the Mars lander to the parachute deployment. Meanwhile, the disturbance observer is designed to onboard estimate the effect of fiercely varying atmospheric uncertainties resulting from rapidly height decreasing. Then, with the estimation of atmospheric uncertainties compensated in the feed-forward channel, the composite guidance method is put forward such that both anti-disturbance and autonomous performance of the Mars lander guidance system are improved. Convergence of the proposed composite method is analysed. Simulations for a Mars lander entry guidance system demonstrates that the proposed method outperforms the baseline method in consideration of the atmospheric uncertainties.

This paper studies the control problem of approaching and docking autonomous system including an on-orbit servicing spacecraft with flexible appendages and an out-of-control target considering the coupled relative position and attitude dynamics. Choosing relative position and relative attitude quaternion as the system state and considering relative position and attitude coupled which is produced by propulsion installation, relative position and attitude coupled dynamics model of servicing spacecraft with respect to the out-of-control target is established. While considering the flexible appendages of servicing spacecraft such as robotic arm and solar panel etc., vibration from flexible appendages is modeled as a derivative-bounded disturbance to the position and attitude control system of rigid body. Aiming at attenuating the modeled disturbance, a disturbance-observer-based control (DOBC) is formulated for feeding forward compensation of elastic vibration. Then we designed a composite controller with a hierarchical architecture by combining DOBC and TSM control, where DOBC is used for rejecting the vibration effect from the flexible appendages. Numerical simulations are performed to demonstrate that by using the composite hierarchical control law, disturbances can be effectively attenuated and the TSM control law is robust with perfect tracking performance.

At present, deep learning has been applied more and more in monocular image depth estimation and has shown promising results. The current more ideal method for monocular depth estimation is the supervised learning based on ground truth depth, but this method requires an abundance of expensive ground truth depth as the supervised labels. Therefore, researchers began to work on unsupervised depth estimation methods. Although the accuracy of unsupervised depth estimation method is still lower than that of supervised method, it is a promising research direction. In this paper, Based on the experimental results that the stereo matching models outperforms monocular depth estimation models under the same unsupervised depth estimation model, we proposed an unsupervised monocular vision stereo matching method. In order to achieve the monocular stereo matching, we constructed two unsupervised deep convolution network models, one was to reconstruct the right view from the left view, and the other was to estimate the depth map using the reconstructed right view and the original left view. The two network models are piped together during the test phase. The output results of this method outperforms the current mainstream unsupervised depth estimation method in the challenging KITTI dataset.

An anti-disturbance controller which considers the reaction wheel friction dynamic is proposed for spacecraft attitude control system to overcome the deterioration of performance under reaction wheel friction. The dynamic model of the system, including the reaction wheel dynamic and the spacecraft dynamic, is given beforehand. Then in order to counteract the effect of the reaction wheel friction, a sliding mode observer is designed to obtain the friction estimation. Finally a H ∞ controller is adopted to attenuate the estimate error and other bounded disturbances, such as the environment disturbance. The simulation on the microsatellite attitude control system demonstrates the correctness and effectiveness of the proposed method.

Gravity gradient measurement satellite is a kind of drag-free satellite and suffers from multiple disturbances in the low earth orbit. So the disturbances estimation and compensation for the drag-free satellite is very important to improve measurement precision. In this paper, the characteristics of multiple disturbances are analyzed. Then, the frequency domain disturbance observer is designed for disturbance estimation and compensation. Next, a composite controller combining the frequency domain disturbance observer with PID controller is presented to reject and attenuate the multiple disturbances. At last, the simulation verification is carried out to verify the effectiveness of the proposed method.

Human pose estimation in monocular still image is a hotspot and difficult issue in the computer vision field, and it has important applicable to many novel area. However, the detecting rate is still poor due to many factors as variety of pose and clothing, occlusion, clustering background etc. A pose estimation approach combining deformable part model and full body model is presented to solve the problem of mistaking part orientation caused by the detecting error for body location. We use full body model to augment the spatial position of full body with head-shoulder detector. We find that the whole body location is benefit to capture human body parts. The experimental results on PARSE dataset show that our approach outperforms many past studies for several body parts.

For a comprehensive and objective understanding of the dynamic overload of armor-piercing bullet penetrating steel target, it must be processed of nonsteady penetrating acceleration signals. In this article, acceleration signals, which are obtained by the embedded high-overload electronic solid recorder at the test of armor-piercing bullet penetrating steel target, is done of wave filtering and integral analysis and so on in time domain, frequency-domain analysis through FFT, as well as Wigner-Ville time-frequency analysis and wavelet analysis. It is obtained of the characteristic signal when armor-piercing bullet penetrates steel target under certain conditions. Through signal processing and comprehensive analysis, the trait of armor-piercing bullet penetrating steel target is obtained, also a kind of data processing method is provided to engineers, by which concerned parameters can be got.

Complex event detection in stream is an important problem in event stream processing field. In this paper, we propose a new complex event detection algorithm in probabilistic stream, Instance Pruning and Filter-Detection Algorithm (IPF-DA). This algorithm is based on a kind of data structure called Chain Instance Queues (CIQ), to detect complex events satisfying query requirements with single-scanning probabilistic stream. In the process of complex event detection, IPF-DA prunes unnecessary event instances with query requirements and achieves filter for complex events with the given threshold. And it further improves the efficiency by setting proper tolerance, while insuring high recall. In addition, we construct Bayesian network to express and infer the probability distribution of uncertain events. Conditional Probability Indexing-Tree (CPI-Tree) is defined to store conditional probabilities of Bayesian network, saving query time compared with traditional Conditional Probability Table (CPT). Experimental results show that a series of strategies proposed by this paper are effective for complex event detection in probabilistic stream.

Last decade has proven a drastic change in information technology. Service Oriented Architecture (SOA), as a new generation of software technique, comes into being to face the challenge of the soaring business varieties and complexities. This paper offers a discussion of service properties and appoints 6 key service properties for SOA. Then, the paper puts forward a role-based reference model for SOA to detail how SOA ensure these properties by service roles and elements. The model is divided into static part and dynamic part: static model describes elements of service roles and files; dynamic model illustrates 6 kinds of interactions between service roles. At last, the paper summarizes the static model, dynamic model and their relationships.