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  • MDPI AG  (12)
  • 1
    Online Resource
    Online Resource
    Design and Performance Research of a Precision Micro-Drive Reduction System without Additional Motion
    MDPI AG ; 2022
    In:  Micromachines Vol. 13, No. 10 ( 2022-09-29), p. 1636-
    Details
    In: Micromachines, MDPI AG, Vol. 13, No. 10 ( 2022-09-29), p. 1636-
    Abstract: A micro-drive system is a key part of macro-micro-drive technology and precision positioning technology in which a micro-drive reduction system can provide more precise motion and suitable small space motion. Therefore, it is necessary to study precision micro-drive reduction systems. In this paper, based on the design of a micro-drive reduction mechanism without force and displacement in non-motion direction, a precision micro-drive reduction system driven by a piezoelectric ceramic actuator (PZT) was designed, and the strength, dynamic and motion performance of the system was analyzed. First, based on the principle of a flexure hinge lever and the principle of balanced additional force, a type of precision micro-drive reduction mechanism with an adjustable reduction ratio was designed. Second, the strength performance of the system was analyzed by finite element analysis, and the dynamic performance of the system was analyzed by finite element analysis and experiments. Finally, the kinematic performance of the system was analyzed by theoretical analysis, the finite element method and experiment, and the motion linear equation was calculated based on the linear fitting equations of three methods. The study results showed that the system had good strength and dynamic performances, and the system’s motion had the advantages of high precision and good linearity. This research has certain reference value for the design and performance research of micro-drive mechanisms.
    Type of Medium: Online Resource
    ISSN: 2072-666X
    URL: Article
    DOI: 10.3390/mi13101636
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
    detail.hit.zdb_id: 2620864-7
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  • 2
    Online Resource
    Online Resource
    Study of Bearing Characteristics and Damage Law of Grouting-Reinforced Bodies
    MDPI AG ; 2023
    In:  Minerals Vol. 13, No. 5 ( 2023-04-24), p. 591-
    Details
    In: Minerals, MDPI AG, Vol. 13, No. 5 ( 2023-04-24), p. 591-
    Abstract: To explore solutions for reinforcement problems of broken rock masses in deep roadways, it is necessary to study the performance of cement-based grout and its reinforcement effect. In this study, grouting-reinforced specimens with different particle sizes of broken coal were made, which revealed the reinforcement effect of grouting on the bearing capacity of broken coal and the mechanism for secondary bearing damage and the instability of the reinforced specimens. First, it was determined that the appropriate water–cement ratio (W/C) to meet the field grouting conditions is 0.45. Second, the uniaxial compression of the grouting-reinforced specimens with 0.45 W/C was carried out, and acoustic emission equipment was used to detect it. Finally, through indoor experiments, this study investigated the differences in failure modes, stress–strain curves, and acoustic emission signal characteristics among intact coal samples, grouting-reinforced bodies with different particle sizes, and grouting-reinforced bodies after anchoring. The deformation and failure patterns of grouting-reinforced bodies were revealed, and the failure mechanisms of grouting-reinforced bodies with different particle sizes were elucidated.
    Type of Medium: Online Resource
    ISSN: 2075-163X
    URL: Article
    DOI: 10.3390/min13050591
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2655947-X
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  • 3
    Online Resource
    Online Resource
    Positioning Performance of a Sub-Arc-Second Micro-Drive Rotary System
    MDPI AG ; 2021
    In:  Micromachines Vol. 12, No. 9 ( 2021-08-31), p. 1063-
    Details
    In: Micromachines, MDPI AG, Vol. 12, No. 9 ( 2021-08-31), p. 1063-
    Abstract: In the macro/micro dual-drive rotary system, the micro-drive system compensates for the position error of the macro-drive system. To realize the sub-arc-second (i.e., level of 1″–0.1″) positioning of the macro/micro dual-drive rotary system, it is necessary to study the positioning performance of the sub-arc-second micro-drive rotary system. In this paper, we designed a sub-arc-second micro-drive rotary system consisting of a PZT (piezoelectric actuator) and a micro rotary mechanism, and used simulation and experimental methods to study the positioning performance of the system. First, the micro-drive rotary system was developed to provide ultra-precise rotary motion. In this system, the PZT has ultrahigh resolution at a level of 0.1 nanometers in linear motion; a micro rotating mechanism was designed according to the composite motion principle of the flexible hinge, which could transform the linear motion of piezoelectric ceramics into rotating motion accurately. Second, the drive performance was analyzed based on the drive performance experiment. Third, kinematics, simulation, and experiments were carried out to analyze the transformation performance of the system. Finally, the positioning performance equation of the system was established based on the two performance equations, and the maximum rotary displacements and positioning error of the system were calculated. The study results showed that the system can provide precision motion at the sub-arc-second and good linearity of motion. This study has a certain reference value in ultra-precision positioning and micromachining for research on rotary motion systems at the sub-arc-second level.
    Type of Medium: Online Resource
    ISSN: 2072-666X
    URL: Article
    DOI: 10.3390/mi12091063
    Language: English
    Publisher: MDPI AG
    Publication Date: 2021
    detail.hit.zdb_id: 2620864-7
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  • 4
    Online Resource
    Online Resource
    Research on Continuous Error Compensation of a Sub-Arc-Second Macro/Micro Dual-Drive Rotary System
    MDPI AG ; 2022
    In:  Micromachines Vol. 13, No. 10 ( 2022-10-02), p. 1662-
    Details
    In: Micromachines, MDPI AG, Vol. 13, No. 10 ( 2022-10-02), p. 1662-
    Abstract: In this paper, a sub-arc-second macro/micro dual-drive rotary system is designed, and the continuous compensation of the system error and its experimental research are completed. First, the macro-drive system is driven by a direct-drive motor, and the micro-drive system uses a piezoelectric ceramic to drive the micro-drive rotary mechanism; the system uses a micro-drive system to compensate the motion error of the macro-drive system, and uses circular grating to feedback the displacement of the macro/micro total output turntable to form a macro/micro dual-drive closed-loop control system. Second, based on the establishment of the system error model, the design of the system’s continuous error compensation scheme is completed. Finally, the positioning accuracy testing of the system, direct error compensation of the macro-drive, manual error compensation of the macro-drive, error compensation performance of the micro-drive part and macro/micro compensation of the system are carried out in the study. The results show that the repeated positioning error and the positioning error of the system are reduced by 78.8% and 95.2%, respectively, after macro/micro compensation. The correctness and effectiveness of the designed system design, error compensation and control method are verified through performance tests, and its positioning accuracy is verified to the sub-arc-second (0.1 arcsecond) level. The research in this paper has important reference value for the development of ultra-precision macro/micro dual-drive technology.
    Type of Medium: Online Resource
    ISSN: 2072-666X
    URL: Article
    DOI: 10.3390/mi13101662
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
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  • 5
    Online Resource
    Online Resource
    Solution of Spatial Transformation Relationship of Similar Ruled Surfaces Based on Registration of Divided Regions
    MDPI AG ; 2022
    In:  Machines Vol. 10, No. 10 ( 2022-10-19), p. 956-
    Details
    In: Machines, MDPI AG, Vol. 10, No. 10 ( 2022-10-19), p. 956-
    Abstract: Since the geometric transformation relationship of similar surfaces with complex features, such as local deformation and curvature changes, is hard to be solved through global registration, this paper proposes a method for solving the spatial transformation relationship of similar ruled surfaces based on registration of divided regions. First, an adaptive region division algorithm is proposed to divide similar surfaces, and then, an improved registration algorithm is proposed by adding two constraints which are the curvature feature and differential geometric features of point clouds. Through this improved registration algorithm, the geometric transformation relationship of each sub-region can be solved, and then the spatial geometric transformation relationship of the overall similar surface can be established. Moreover, the improved registration algorithm can ensure that the differential geometric properties of corresponding points are similar after registration, which may provide a basis for mapping and reuse of process knowledge between corresponding points on similar surfaces. Finally, two similar ruled surface blades are taken as examples for simulation verification, the results show that the maximum registration error of each sub-region is 0.025 mm, which is within the allowable error range, and the registration speed of the proposed algorithm is better than the S-ICP algorithm. This proves that the method in this paper is feasible and effective.
    Type of Medium: Online Resource
    ISSN: 2075-1702
    URL: Article
    DOI: 10.3390/machines10100956
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
    detail.hit.zdb_id: 2704328-9
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  • 6
    Online Resource
    Online Resource
    Improving the Corrosion Resistance of Aluminum Alloy by Creating a Superhydrophobic Surface Structure through a Two-Step Process of Etching Followed by Polymer Modification
    MDPI AG ; 2022
    In:  Polymers Vol. 14, No. 21 ( 2022-10-25), p. 4509-
    Details
    In: Polymers, MDPI AG, Vol. 14, No. 21 ( 2022-10-25), p. 4509-
    Abstract: A multifunctional aviation aluminum alloy with good superhydrophobicity and corrosion resistance was prepared by a two-step process of etching followed by polymer modification. Meanwhile, micro- and nanostructures formed on the processed sample. Compared with bare sample, the static liquid contact angle on the as-prepared sample was increased by 100.8°. Further polarization tests showed that the corrosion potential of such a sample increased, and the corrosion current density decreased obviously, thus suggesting that the corrosion resistance of the modified sample was significantly improved. The same conclusion was confirmed by subsequent impedance testing. The work is of great economic value and practical significance to enhance the corrosion resistance of aviation actuator materials and also lays a foundation for future hydrophobic application research in aeronautical engineering.
    Type of Medium: Online Resource
    ISSN: 2073-4360
    URL: Article
    DOI: 10.3390/polym14214509
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
    detail.hit.zdb_id: 2527146-5
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  • 7
    Online Resource
    Online Resource
    A Tightly Coupled LiDAR-Inertial SLAM for Perceptually Degraded Scenes
    MDPI AG ; 2022
    In:  Sensors Vol. 22, No. 8 ( 2022-04-15), p. 3063-
    Details
    In: Sensors, MDPI AG, Vol. 22, No. 8 ( 2022-04-15), p. 3063-
    Abstract: Realizing robust six degrees of freedom (6DOF) state estimation and high-performance simultaneous localization and mapping (SLAM) for perceptually degraded scenes (such as underground tunnels, corridors, and roadways) is a challenge in robotics. To solve these problems, we propose a SLAM algorithm based on tightly coupled LiDAR-IMU fusion, which consists of two parts: front end iterative Kalman filtering and back end pose graph optimization. Firstly, on the front end, an iterative Kalman filter is established to construct a tightly coupled LiDAR-Inertial Odometry (LIO). The state propagation process for the a priori position and attitude of a robot, which uses predictions and observations, increases the accuracy of the attitude and enhances the system robustness. Second, on the back end, we deploy a keyframe selection strategy to meet the real-time requirements of large-scale scenes. Moreover, loop detection and ground constraints are added to the tightly coupled framework, thereby further improving the overall accuracy of the 6DOF state estimation. Finally, the performance of the algorithm is verified using a public dataset and the dataset we collected. The experimental results show that for perceptually degraded scenes, compared with existing LiDAR-SLAM algorithms, our proposed algorithm grants the robot higher accuracy, real-time performance and robustness, effectively reducing the cumulative error of the system and ensuring the global consistency of the constructed maps.
    Type of Medium: Online Resource
    ISSN: 1424-8220
    URL: Article
    DOI: 10.3390/s22083063
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
    detail.hit.zdb_id: 2052857-7
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  • 8
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    Online Resource
    Two-Dimensional Mechanical Behavior Analysis of Multilayered Solids Subjected to Surface Contact Loading Based on a Semi-Analytical Method
    MDPI AG ; 2020
    In:  Coatings Vol. 10, No. 5 ( 2020-04-26), p. 429-
    Details
    In: Coatings, MDPI AG, Vol. 10, No. 5 ( 2020-04-26), p. 429-
    Abstract: In this paper, a two-dimensional semi-analytical method is developed for the mechanical behavior analysis of multilayered solids subjected to surface contact loading, which is indispensable for realizing an optimized tribological performance from the mechanical behavior point of view. Firstly, the explicit analytical frequency response functions of the multilayered solid are derived in a recursive form by analytically solving a system of linear equations established according to the boundary conditions and the interface continuous conditions. Then, the two-dimensional elastic field solution in the subsurface of multilayered solids in the space domain is converted from its corresponding frequency response functions by employing a numerical conversion method based on the inverse fast Fourier transformation. The present method is validated by comparing with the solution given by other methods. Lastly, the stress analysis of multilayered coatings with various structure layouts and various layer number of the multilayers were performed with the present method.
    Type of Medium: Online Resource
    ISSN: 2079-6412
    URL: Article
    DOI: 10.3390/coatings10050429
    Language: English
    Publisher: MDPI AG
    Publication Date: 2020
    detail.hit.zdb_id: 2662314-6
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  • 9
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    Online Resource
    Design and Ductile Behavior of Torsion Configurations in Material Extrusion to Enhance Plasticizing and Melting
    MDPI AG ; 2021
    In:  Polymers Vol. 13, No. 18 ( 2021-09-19), p. 3181-
    Details
    In: Polymers, MDPI AG, Vol. 13, No. 18 ( 2021-09-19), p. 3181-
    Abstract: In the present work, the ductile formation mechanism of a newly proposed torsion configuration has been investigated. One of the unique attributes of this paper is the first-time disclosure of the design and fabrication of a novel prototype screw with torsional flow character validating the orthogonal test model experimentally. The torsional spiral flow patterns that occurred in the torsion channel cause a ductile deformation of polymer in the form of a spiral, which in turn enhances the radial convection, achieving an effective mass transfer of material from the top region to the bottom region and vice versa. Furthermore, the characteristic parameters of torsion configuration have a significant influence on the plasticizing and melting capability of polymer. By range analysis and weight matrix analysis, the best factor and level combination was obtained. Results indicated that the aspect ratio of the torsion channel is almost equal to 1, and the plasticizing and melting capability of polymer is optimal. This novel design innovation offers a paradigm shift in the energy-efficient plasticization of polymer compounds.
    Type of Medium: Online Resource
    ISSN: 2073-4360
    URL: Article
    DOI: 10.3390/polym13183181
    Language: English
    Publisher: MDPI AG
    Publication Date: 2021
    detail.hit.zdb_id: 2527146-5
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  • 10
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    Online Resource
    3D LiDAR Point Cloud Registration Based on IMU Preintegration in Coal Mine Roadways
    MDPI AG ; 2023
    In:  Sensors Vol. 23, No. 7 ( 2023-03-26), p. 3473-
    Details
    In: Sensors, MDPI AG, Vol. 23, No. 7 ( 2023-03-26), p. 3473-
    Abstract: Point cloud registration is the basis of real-time environment perception for robots using 3D LiDAR and is also the key to robust simultaneous localization and mapping (SLAM) for robots. Because LiDAR point clouds are characterized by local sparseness and motion distortion, the point cloud features of coal mine roadway environments show a weak texture and degradation. Therefore, for these environments, the traditional point cloud registration method to register directly will lead to problems, such as a decline in registration accuracy, z-axis drift, and map ghosting. To solve the above problems, we propose a point cloud registration method based on IMU preintegration with the sensor characteristics of LiDAR and IMU. The system framework of this method mainly consists of four modules: IMU preintegration, point cloud preprocessing, point cloud frame matching and point cloud registration. First, IMU sensor data are introduced, and IMU linear interpolation is used to correct the motion distortion in LiDAR scanning, and the IMU preintegration error function is constructed. Second, the point cloud segmentation is performed using the ground segmentation method of RANSAC to provide additional ground constraints for the z-axis displacement and to remove the unstable flawed points from the point cloud. On this basis, the LiDAR point cloud registration error function is constructed by extracting the feature corner points and feature plane points. Finally, the Gaussian Newton solution is used to optimize the constraint relationship between the LiDAR odometry frames to minimize the error function, complete the LiDAR point cloud registration and better estimate the position and pose of the mobile robot. The experimental results show that compared with the traditional point cloud registration method, the proposed method has a higher point cloud registration accuracy, success rate and computational efficiency. The LiDAR odometry constructed using this method can better reflect the authenticity of the robot trajectory and has higher trajectory accuracy and smaller absolute position and pose error.
    Type of Medium: Online Resource
    ISSN: 1424-8220
    URL: Article
    DOI: 10.3390/s23073473
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2052857-7
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