DS-SLAM: A Semantic Visual SLAM towards Dynamic Environments

Simultaneous Localization and Mapping (SLAM) is considered to be a fundamental capability for intelligent mobile robots. Over the past decades, many impressed SLAM systems have been developed and achieved good performance under certain circumstances. However, some problems are still not well solved, for example, how to tackle the moving objects in the dynamic environments, how to make the robots truly understand the surroundings and accomplish advanced tasks. In this paper, a robust semantic visual SLAM towards dynamic environments named DS-SLAM is proposed. Five threads run in parallel in DS-SLAM: tracking, semantic segmentation, local mapping, loop closing, and dense semantic map creation. DS-SLAM combines semantic segmentation network with moving consistency check method to reduce the impact of dynamic objects, and thus the localization accuracy is highly improved in dynamic environments. Meanwhile, a dense semantic octo-tree map is produced, which could be employed for high-level tasks. We conduct experiments both on TUM RGB-D dataset and in the real-world environment. The results demonstrate the absolute trajectory accuracy in DS-SLAM can be improved by one order of magnitude compared with ORB-SLAM2. It is one of the state-of-the-art SLAM systems in high-dynamic environments. Now the code is available at our github: https://github.com/ivipsourcecode/DS-SLAMComment: 7 pages, accepted at the 2018 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS 2018). Now the code is available at our github: https://github.com/ivipsourcecode/DS-SLA

Growth inhibition of mouse embryonic stem (ES) cells on the feeders from domestic animals

Mouse embryonic stem cells (mESCs) can be propagated in vitro on the feeders of mouse embryonic fibroblasts. In this study, we found growth inhibition of mESCs cultured on embryonic fibroblast feeders derived from different livestock animals. Under the same condition, mESCs derived from mouse embryonic fibroblast feeders were seen on the mass-like colonies and round or oval images, and more significant growth in the total number of colonies (p<0.05) and viable cells in the colonies (p<0.01) than that from goat embryonic fibroblast feeders, and viable cells in the colonies (p<0.05) than that from porcine embryonic fibroblast feeders. The feeders from bovine embryonic fibroblasts also reduced viable cells in the colonies, but were not significantly different in the total number of colonies and viable cells in the colonies with mouse embryonic fibroblast feeders. mESCs on the different embryonic fibroblast feeders were expressed as stem cell-specific markers Oct 4 and stage-specific embryonic antigen 1 (SSEA 1). Here, our results indicate that the feeders from goat, porcine and bovine embryonic fibroblasts inhibit the proliferation of mESCs.Key words: Domestic animals, feeders, mouse embryonic stem cells (mESCs), growth

A Comparison Study on the Orientation Capability and Parasitic Motions of Two Novel Articulated Tool Heads with Parallel Kinematics

This paper proposes two novel articulated tool heads based on three degree-of-freedom (DoF) parallel kinematic mechanisms (PKMs). They can realize one translation and the A/B-axis (rotations about the x - and y -axes) linkage movements. Both of the proposed tool heads can be used as modular machining units in five-axis machine centers. Based on the proposed configurations, the performance comparison on orientation capability and parasitic motions is carried out to provide theoretical foundation for the design of a five-axis hybrid machine. In this process, the motion/force transmissibility is taken into consideration and the orientation capability is investigated by using local transmission index (LTI) as the evaluation criterion. To get better orientation performance of the selected configuration, kinematic optimization is carried out and a geometric deviation parameter is brought into the already established configuration. Consequently, the orientation capability of more than fifty degrees is achieved. The proposition of the tool heads and the corresponding comparison and optimization are very helpful for the development of the new hybrid machine tool

Performance Evaluation of Redundant Parallel Manipulators Assimilating Motion/Force Transmissibility

Performance evaluation is one of the most important issues in the field of parallel kinematic manipulators (PKMs). As a very important class of PKMs, the redundant PKMs have been studied intensively. However, the performance evaluation of this type of PKMs is still unresolved and a challenging endeavor. In this paper, indices that assimilate motion/force transmissibility are proposed to evaluate the performance of redundant PKMs. To illustrate the application of these indices, three PKMs with different kinds of redundancies are taken as examples, and performance atlases are plotted based on the definitions of the indices. Transmissibility comparisons between redundant PKMs and the corresponding non-redundant ones are carried out. To determine the inverse solutions of the PKMs with kinematic redundancy, an optimization strategy is presented, and the rationality of this method is demonstrated. The indices introduced here can be applied to the performance evaluation of redundant parallel manipulators

Kinematic optimization of a five degrees-of-freedom spatial parallel mechanism with large orientational workspace

This paper deals with the kinematic optimization of a five degrees-of-freedom (DoFs) spatial parallel mechanism with three kinematic chains. Inspired by the structure of the icosahedron, the base of the discussed mechanism has been designed into a compact and light-weight frame. Due to the potential advantages, this mechanism is used as a movable plug-in module in a multi-axis machine center to process large-scale parts with rotary contour surfaces. To derive its optimal parameters, kinematic optimization based on the motion/force transmissibility is carried out. The parameter design space (PDS) is generated first. Then, the performance evaluation index (i.e., local transmission index (LTI)) is derived sequentially. On this basis, the good transmission positioning workspace (GTPW) for a given orientation is defined by constraining the value of LTI with a certain metric. Thereafter, the atlases of the GTPW and the optimal region satisfying the workspace constraint are derived in the PDS. Within this region, a set of optimal parameters without dimension are selected. Consequently, the cuboid workspaces within GTPWs are identified in detail. By using the ratio between required workspace in application and the derived cuboid workspaces, optimal geometric parameters with dimension are derived. Workspace analysis results show that, for an arbitrary orientation between the vertical and horizontal directions, there is always a cuboid workspace within GTPW larger than required workspace. In addition, the orientational capability of the mechanism can reach more than 90 deg, and the flexible 2DoFs rotations can also be realized. The work in this paper is very helpful to the development of a mobile machining module

Functionalization of α-In2Se3 Monolayer via Adsorption of Small Molecule for Gas Sensing

Based on first-principles calculations, the adsorption of NO and NO2 gas molecules on the α-In2Se3 monolayer have been studied. The adsorption configuration, adsorption energy, electronic structure and charge transfer properties are investigated. It is found that the charge transfer processes of NO and NO2 adsorbed on the surface of α-In2Se3 monolayer exhibit electron donor and acceptor characteristics, respectively. After the adsorption of the molecules, the α-In2Se3 monolayers have new states near the Fermi level induced by NO and NO2, which can trigger some new effects on the conducting and optical properties of the materials, with potential benefits to gas selectivity. The present work provides new valuable results and theoretical foundation for potential applications of the In2Se3-based gas sensor

Optimal Design and Development of a Decoupled A/B-Axis Tool Head with Parallel Kinematics

This paper is an attempt to design a decoupled A/B-axis tool head with parallel kinematics, due to the increasing demand for A/B-axis tool heads in industry, particularly in thin wall machining applications for structural aluminium aerospace components. In order to carry out further analysis, the method of orientation description based on the azimuth and tilt angles is introduced, which is a convenient method describing kinematics, parasitic motions, and orientation workspace. For the purpose of optimal design, three indices are defined to evaluate the force transmission performance of the tool head. They have obvious physical significance and are dependent of any coordinate system. Based on the indices and their performance atlases, the optimization process is presented in detail. The parasitic motions and orientation capability of the designed tool head are analyzed finally. The results show that the designed device is far from singularity, has good force transmissibility, and has very high tilting angle. The indices and analysis and design method used here should be said to be extended to other parallel robots