Adaptive Space Expansion for Fast Motion Planning

The sampling process is very inefficient for sam-pling-based motion planning algorithms that excess random sam-ples are generated in the planning space.In this paper,we pro-pose an adaptive space expansion(ASE)approach which belongs to the informed sampling category to improve the sampling effi-ciency for quickly finding a feasible path.The ASE method enlarges the search space gradually and restrains the sampling process in a sequence of small hyper-ellipsoid ring subsets to avoid exploring the unnecessary space.Specifically,for a con-structed small hyper-ellipsoid ring subset,if the algorithm cannot find a feasible path in it,then the subset is expanded.Thus,the ASE method successively does space exploring and space expan-sion until the final path has been found.Besides,we present a particular construction method of the hyper-ellipsoid ring that uniform random samples can be directly generated in it.At last,we present a feasible motion planner BiASE and an asymptoti-cally optimal motion planner BiASE*using the bidirectional exploring method and the ASE strategy.Simulations demon-strate that the computation speed is much faster than that of the state-of-the-art algorithms.The source codes are available at https://github.com/shshlei/ompl.

An efficient adaptive space partitioning algorithm for electromagnetic scattering calculation of complex 3D models

The space partitioning algorithm based on the rounding and addressing operations has been proved to be an efficient space partitioning algorithm with the potential for real-time calculation.An improvement on this kind of space partitioning algorithms for solving complex 3D models is presented.Numerical examples show that the efficiency of the improved algorithm is better than that of the original method.When the size of most target elements is smaller than the size of spatial grids,the efficiency of the improved method can be more than four times of that of the original method.An adaptive method of space partitioning based on the improved algorithm is developed by taking the surface element density or the curvature as the threshold for deep partitioning and conducting the deep partitioning using the octree method.A computer program implementation for applying the method in some typical applications is discussed,and the performance in terms of the efficiency,reliability,and resource use is evaluated.Application testing shows that the results of the adaptive spacing partitioning are more convenient for the follow-up use than that of the basic uniform space partitioning.Furthermore,when it is used to calculate the electromagnetic scattering of complex targets by the ray tracing(RT)method,the adaptive space partitioning algorithm can reduce the calculation time of the RT process by more than 40%compared with the uniform space segmentation algorithm.

Traffic Accident Detection Based on Deformable Frustum Proposal and Adaptive Space Segmentation

Road accident detection plays an important role in abnormal scene reconstruction for Intelligent Transportation Systems and abnormal events warning for autonomous driving.This paper presents a novel 3D object detector and adaptive space partitioning algorithm to infer traffic accidents quantitatively.Using 2D region proposals in an RGB image,this method generates deformable frustums based on point cloud for each 2D region proposal and then frustum-wisely extracts features based on the farthest point sampling network(FPS-Net)and feature extraction network(FE-Net).Subsequently,the encoder-decoder network(ED-Net)implements 3D-oriented bounding box(OBB)regression.Meanwhile,the adaptive least square regression(ALSR)method is proposed to split 3D OBB.Finally,the reduced OBB intersection test is carried out to detect traffic accidents via separating surface theorem(SST).In the experiments of KITTI benchmark,our proposed 3D object detector outperforms other state-of-theartmethods.Meanwhile,collision detection algorithm achieves the satisfactory performance of 91.8%accuracy on our SHTA dataset.

Research on the Walkability Potential of Wangjing East Metro Station from the Perspective of Young Female

This paper mainly evaluates the road space adaptability of the streets around Wangjing East Metro Station(hereinafter referred to as“Wangjing East Station”),and studies the impact of the road space adaptability of Wangjing East Street on the walking activities of young female residents.Through literature survey,POI data analysis and street view photo scoring,the street characteristics that young female residents are suitable for walking and like walking are analyzed.The paper includes 3 parts:determination of functional types of streets around Wangjing East Station;the characteristics of young women’s group walkability activities and the establishment of evaluation system;spatial adaptability assessment of the existing roads around Wangjing East Station.

Hybrid force control of astronaut rehabilitative training robot under active loading mode

In order to mitigate the effects of space adaptation syndrome(SAS) and improve the training efficiency of the astronauts, a novel astronaut rehabilitative training robot(ART) was proposed. ART can help the astronauts to carry out the bench press training in the microgravity environment. Firstly, a dynamic model of cable driven unit(CDU) was established whose accuracy was verified through the model identification. Secondly, to improve the accuracy and the speed of the active loading, an active loading hybrid force controller was proposed on the basis of the dynamic model of the CDU. Finally, the actual effect of the hybrid force controller was tested by simulations and experiments. The results suggest that the hybrid force controller can significantly improve the precision and the dynamic performance of the active loading with the maximum phase lag of the active loading being 9° and the maximum amplitude error being 2% at the frequency range of 10 Hz. The controller can meet the design requirements.

Space Flight Validation of Design and Engineering of the ZDPS-1A Pico-satellite

The ZDPS-1A pico-satellites are the first satellites in China within the 1-10 kg mass range that are successfully operated on orbit. Unlike common pico-satellites, they are designed to be ＂larger but stronger＂ with more powerful platforms and unique payloads so as to bear a better promise for real applications. Through their space flight mission, the functionality and perform- ance of the two flight models are tested on orbit and validated to be mostly normal and in consistency with design and ground tests with only several inconforming occasions. Moreover, they have worked properly on orbit for one year so far, well exceed- ing their life expectancy of three months. Therefore, the space flight mission has reached all its goals, and verified that the design concept and the engineering process of the pico-satellites are sufficient in allowing them the desired functionality and perform- ance in, and the adaption to the launch procedure and the low-Earth orbit space environment. In the foreseeable future, the plat- form together with the design concept and the engineering process of the pico-satellites are expected to be applied to more com- plicated real space applications.

Fuzzy adaptive robust control for space robot considering the effect of the gravity

Space robot is assembled and tested in gravity environment, and completes on-orbit service（OOS） in microgravity environment. The kinematic and dynamic characteristic of the robot will change with the variations of gravity in different working condition. Fully considering the change of kinematic and dynamic models caused by the change of gravity environment, a fuzzy adaptive robust control（FARC） strategy which is adaptive to these model variations is put forward for trajectory tracking control of space robot. A fuzzy algorithm is employed to approximate the nonlinear uncertainties in the model, adaptive laws of the parameters are constructed, and the approximation error is compensated by using a robust control algorithm. The stability of the control system is guaranteed based on the Lyapunov theory and the trajectory tracking control simulation is performed. The simulation results are compared with the proportional plus derivative（PD） controller, and the effectiveness to achieve better trajectory tracking performance under different gravity environment without changing the control parameters and the advantage of the proposed controller are verified.

ICA Based Speckle Filtering for Target Extraction in SAR Images Using Adaptive Space Separation

A novel approach based on independent component analysis (ICA) for speckle filtering and target extraction of synthetic aperture radar (SAR) images is proposed using adaptive space separation with weighted information entropy (WIE) incorporated. First the basis and the independent components are respectively obtained by ICA technique, and WIE of the image is computed; then based on the threshold computed from function T-WIE (threshold versus weighted-information-entropy), independent components are adaptively separated and the bases are classified accordingly. Thus, the image space is separated into two subspaces: "clean" and "noise". Then, a proposed nonlinear operator ABO is applied on each component of the 'clean' subspace for further optimization. Finally, recovery image is obtained reconstructing this subspace and target is easily extracted with binarisation. Note that here T-WIE is an interpolated function based on several representative target SAR images using proposed space separation algorithm.

A novel repetition space-time coding scheme for mobile FSO systems

Considering the influence of more random atmospheric turbulence, worse pointing errors and highly dynamic link on the transmission performance of mobile multiple-input multiple-output （MIMO） free space optics （FSO） communica- tion systems, this paper establishes a channel model for the mobile platform. Based on the combination of Alamouti space-time code and time hopping ultra-wide band （TH-UWB） communications, a novel repetition space-time coding （RSTC） method for mobile 2x2 free-space optical communications with pulse position modulation （PPM） is devel- oped. In particular, two decoding methods of equal gain combining （EGC） maximum likelihood detection （MLD） and correlation matrix detection （CMD） are derived. When a quasi-static fading and weak turbulence channel model are considered, simulation results show that whether the channel state information （CSI） is known or not, the coding sys- tem demonstrates more significant performance of the symbol error rate （SER） than the uncoding. In other words, transmitting diversity can be achieved while conveying the information only through the time delays of the modulated signals transmitted from different antennas. CMD has almost the same effect of signal combining with maximal ratio combining （MRC）. However, when the channel correlation increases, SER performance of the coding 2×2 system de- grades significantly.

适配性重要吗?对乡村社会空间与乡村生活圈的特征与关系进行分析

The construction of rural life circle has an essential impact on the change of rural social space.Analyzing the adaptation relationship between the two can be a new content in the study of “physical-social” space.Using social behavior as a link,we construct a logical relationship framework between rural life circle and social space.Based on the survey data of Baijia village in the loess hilly region,this paper analyzes the characteristics and adaptability of the two and discusses preliminary ideas of life circle reorganization and social space reconstruction.The study results are as follows:(1) Based on the location of four types of service facilities and the travel mode of villagers,two life circles of 15 min and 25 min have been formed in Baijia village.The rural social spaces such as communicative behavior space,health seeking behavior space,leisure behavior space,and consumption behavior space show a specific concentric circle structure and unique hierarchical structure.(2) The analysis of the adaptation between them shows that the 15 min life circle in Baijia village has a high level of adaptation to communicative and leisure behavior spaces.It plays a positive feedback role in the construction of social space.However,it has a low level of adaptability to the space of health seeking and consumption behavior spaces and has a negative feedback effect on the construction of social space.The 25 min life circle is the opposite.(3) The reorganization of facility layout,hierarchical structure,and service functions in the village life circle will lead to changes in the range,frequency,and purpose of villagers’ behavioral activities,resulting in a new social spatial pattern.These findings are important for formulating village development and construction plans,improving the settlement habitat,and reconstructing the order of social life.