China Mechanical Engineering

A Review of Force Sensing Technology in Robot-assisted Laparoscopic Surgery

ZHANG Jianxun, YAO Bin, DAI Yu, XIA Guangming,

2021, 32(21): 2521-2531. DOI: 10.3969/j.issn.1004-132X.2021.21.001

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In order to promote the further research and clinical applications of force sensing technology in robot-assisted laparoscopic surgery， the research progresses were reviewed. Sensor force sensing was divided into two categories：electrical signal-based sensing and optical signal-based sensing. Some key indicators were analyzed， such as sensor position distribution on surgical instruments， mechanical structure， measurement range， measurement accuracy and electromagnetic compatibility. Sensors advantages and disadvantages were discussed. Sensorless force sensing was divided into two categories：vision-based sensing and dynamic model-based sensing. And the realization method， technical obstacle and error sources were analyzed. Finally， the development trend of force sensing technology in robot-assisted laparoscopic surgery was prospected.

Model-driven Software-physical Parallel Conceptual Design for Complex Mechatronics Systems

CAO Yue, WU Lingjiu, QIN Xujia, CHEN Jiazhou, LIU Yusheng

2021, 32(21): 2532-2541. DOI: 10.3969/j.issn.1004-132X.2021.21.002

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Parallel design was an important trend in the conceptual design of mechatronics systems. However, as an indispensable constituent of complex mechatronics systems, software was normally designed after that the design of physical subsystems was frozen. Such sequential design approached restrict the design space of software subsystems and might cause severe design defects in early design. In order to realize the parallel design of software and physical subsystems in the conceptual design stages of complex electromechanical systems, a model-driven software-physical parallel conceptual design approach was proposed based on SysML. A hybrid functional model was defined by combining the physical-oriented flow-based functional representation and the data/control flow diagram for software functional representation. From this model, two subsystems might be designed in parallel. For the physical design, working principles might be retrieved and filtered considering implicit temporal constraints by leveraging the functional effectiveness matching techniques and a temporal rule template. For the software design, an algorithm for automatically generating the software components and their behavior models was proposed based on the distributed control application design pattern. A mobile robot system was used as a case study to illustrate the parallel conceptual design processes.

Experimental Study of Wear Resistance of Bionic Striped Middle Trough for Scraper Conveyors

LI Juanli, LIU Zhaoyang, LI Bo, MA Haozhou, ZHAO Baolin,

2021, 32(21): 2542-2551，2561. DOI: 10.3969/j.issn.1004-132X.2021.21.003

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To improve wear resistance of middle trough of scraper conveyors， a bionic middle plate was designed as bionic prototype with scallop shell and pangolin scales non-smooth stripe structure. Based on single factor method and response surface method， wear analyses were performed to explore the optimal parameters of wear-resistant bionics while taking wear depth as response value. Results show that the significant effects from large to small are sorted as follows， width， ratio of width to height and pitch. And the interactions between ratio of width to height and width of stripe are the most obvious. Under certain working conditions（coal particle size of 6~8 mm， load of 20 N， scraper chain speed of 0.65 m/s）， an optimal combination of wear resistance parameters of striped structure is width to height ratio of 4.94 mm， width of 1.81 mm， and a pitch of 6.33 mm. The wear resistance of striped middle plate under the optimal parameter combination was compared with the smooth middle plate through simulations and experiments. Results show that the striped middle plate under the optimal combination of wear-resistant parameters has good anti-wear performance， and the wear mass may decrease 78.54% in comparison with the smooth middle plate. The wear resistance mechanism was analyzed， and it is found that the striped convex body has a diversion and guiding effect on the flow of bulk coal， which relieves the stress on the middle plate surface and reduces the wear depth.

Feature Line Extraction for Point Cloud Based on Normal Vector Region Clustering Segmentation

SHI Hongxia, WANG Jianmin

2021, 32(21): 2552-2561. DOI: 10.3969/j.issn.1004-132X.2021.21.004

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In oder to solve the problems of incomplete extraction of transition lines and detail feature lines of scattered point cloud models in reverse engineering, a method of extracting feature lines was proposed based on normal vector region clustering. Principal component analysis of adaptive neighborhood was used to estimate the normal vector of the model, and the FA optimized FCM clustering algorithm was introduced to cluster the normal vectors for realizing the effective segmentation of the model. The candidate feature points were extracted from the boundary points of each block by constructing the rule of eliminating and merging point sets, and then the feature points were extracted based on the principal axis direction of local neighborhood. Experimental results show that the feature lines of simple models may be extracted accurately and completely, and the extraction rate of the number and the length of feature lines of some complex models may reach 90% and 85%, respectively. The algorithm has good adaptability and accuracy, and may extract sharp features and detail features from the point cloud model, meanwhile getting transition features as much as possible.

Research on Instantaneous Hobbing Force Model for Chip Forming Processes

DING Guolong, YE Mengchuan, XIANG Hua, YANG Chunlan

2021, 32(21): 2562-2570. DOI: 10.3969/j.issn.1004-132X.2021.21.005

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The establishment of time-varying hobbing force model in hobbing processes was the premise of optimizing hobbing process parameters， reducing hobbing force fluctuation and improving machining accuracy， where the model for hobbing chip forming processes was the most direct physical method to improve modeling accuracy. For the chip forming processes of dry gear hobbing， a model of hob rake face motion was established， and the dynamic link library of hob tooth motion track was generated by MATLAB. After that， three-dimensional Boolean operation was performed to extract geometric features of undistorted chips and to develop dynamic link library of chip geometric model based on SolidWorks. In addition， C# was used to call the dynamic link library of MATLAB and SolidWorks to realize three-dimensional motion simulation for building multi-tooth instantaneous hobbing force model. Indirected measurement of instantaneous hobbing forces was performed through prototype hobbing on YK3216CNC gear hobbing machine and full stroke current detection was carried out combined with HNC-SSTT software. The instantaneous hobbing forces of simulation machining are basically in accordance with the change trend of measured hobbing forces， which indicates that the instantaneous hobbing force model is reasonable and effective.

Optimization of Posture Adjustment Trajectory of a Redundant and Hybrid ADRM

PAN Guowei, CHEN Wenliang

2021, 32(21): 2571-2576，2589. DOI: 10.3969/j.issn.1004-132X.2021.21.006

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Aiming at the diversification of fastening postures caused by redundant DOF of the hybrid ADRM， a method of posture adjustment trajectory optimizationwas proposed based on dynamic programming. Through discretizing the feasible solution spaces of each riveting point， the full connection layer model of the fastening task was constructed. The dynamic programming was adopted to obtain the optimal trajectory of fastening posture adjustments. Firstly， the redundant DOF of the ADRM was analyzed and the inverse solution that was obtained based on screw method. Then， the optimization principle was explained by considering the characteristics of the assembly tasks. Taking the energy consumption as the optimization objective， the optimal posture adjustment trajectory of Cartesian space was obtained， which was mapped to the joint space for joint trajectory smoothing. Finally， the above method was verified by examples and experiments. The results show that the method is more time-efficient for the fastening of aircraft panels.

Sine Cosine Algorithm Based on Honey Gathering Mechanism and Its Applications in Mechanical Optimal Designs

WANG Lianguo, LIU Xiaojuan

2021, 32(21): 2577-2589. DOI: 10.3969/j.issn.1004-132X.2021.21.007

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Aiming at the shortcomings of poor local development ability， slow convergence rate and low solution accuracy in solving the function optimization problems of standard SCA， a sine cosine algorithm based on the honey gathering mechanism（SCAHGM） was proposed. To begin with， the positions of parameters r2， r3 and r4 were changed， so as to adopt the same parameters r1， r2， r3 and r4 for each individuals， meanwhile the parameters r1 and r3 were adjusted respectively by power decreasing function adaptively and in oneform dynamically， which reduced randomness and improved search efficiency of the algorithm. Then， the greedy selection strategy， the operators of employed bees and reconnaissance bees were utilized， which sped up the convergence rate， improved the optimization accuracy of the algorithm， increased diversity of the population and protected the algorithm from falling into local optimum. Besides， the sine cosine operator or employed bees’ operator was executed alternately with a certain probability in the iterative processes of the algorithm， which better balanced global exploration and local development capability of the algorithm. At last， simulation results with 23 standard benchmark functions illustrate that SCAHGM performs better optimization performance than that of basic SCA， improved algorithms for SCA and other meta-heuristic algorithms， and the feasibility and applicability were verified by optimizing two mechanical design examples.

Multi-scene Motion Planning of Manipulators Based on Improved RRT*FN Algorithm

FANG Lijin, WU Zhenghan, WANG Huaizhen

2021, 32(21): 2590-2597. DOI: 10.3969/j.issn.1004-132X.2021.21.008

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Aiming at the problems of low precision, poor environmental adaptability of RRT*FN algorithm, an improved RRT*FN motion planning algorithm for manipulators was proposed. Firstly, in the iteration processes, combining the advantages of target biased random sampling and ellipsoid subset sampling, a new heuristic method was constructed to constrain the sampling areas, so as to ensure better search paths. Then, in expanding node processes, the preset values of total number of nodes in the tree were configured, and the leaf nodes in the tree were deleted by weighting method, which avoided the infinite growth of tree sizes. Finally, under the dynamic environment, a heuristic replanning method of node pruning and connection was adopted to effectively improve the adaptability of dynamic environment. Experimental results show that the algorithm herein has faster convergence speed and higher efficiency in planning processes, and has strong environmental adaptability.

Automatic Inspection of Space Clearances between Welding Gun Head and Sheet Metal Parts

DONG Yude, WU Wenzhe, CHEN Jian, WU Haijiang, ZOU Wenjun

2021, 32(21): 2598-2605. DOI: 10.3969/j.issn.1004-132X.2021.21.009

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In order to solve the problems such as complicated inspection processes and inaccurate inspection results of space clearances of welding gun head and sheet metal parts near welding spot in 3D model of car body, an automatic inspection method for space clearances of welding gun head and sheet metal parts was proposed. Based on the feature recognition algorithm and bounding box technology, the analysis elements such as welding spot features, sheet metal features and nut features were obtained. Based on the projection algorithm and distance measurement algorithm of 3D model, the distance between topological surface of sheet metal parts and virtual welding gun was calculated. After compared with safety threshold, dangerous planes, holes and nuts that interfered with welding gun were screened out. The welding spots with insufficient welding space were marked and taken screenshot. The above algorithm was realized by using the function library provided by the secondary development environment. The feasibility of the automatic inspection system was verified by running examples and the actual uses of enterprises.

Multi-objective Restart Variable Neighborhood Search Algorithm for Assembly Line Balancing Considering Preventive Maintenance

ZHAO Lianpeng, TANG Qiuhua, ZHANG Zikai, MENG kai,

2021, 32(21): 2606-2616. DOI: 10.3969/j.issn.1004-132X.2021.21.010

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Aiming at the assembly line balancing problems considering preventive maintenance, a multi-objective variable neighborhood search algorithm with restart strategy was proposed to optimize task adjustments and cycle times under normal work and equipment maintenance scenarios. The proposed algorithm combined heuristics and stochastic methods to obtain a better initial solution. Four types of neighborhood operators with strong optimization ability as well as complementarity and their search strategy were designed, selected and effectively combined for better global exploration and local exploitation. In order to promote the advancement of Pareto front, a restart operator with adaptive capability was proposed to adjust the iteration threshold according to the scale of the problems and to expand the search space based on the optimization processes. The proposed algorithm is simple and has no fixed parameters. Experimental results show that the algorithm may obtain a set of non-dominated solutions with competing performance.

Rolling Bearing Fault Diagnosis Method Based on Enhanced Deep Auto-encoder Network

TONG Jinyu, LUO Jin, ZHENG Jinde

2021, 32(21): 2617-2624. DOI: 10.3969/j.issn.1004-132X.2021.21.011

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To improve the feature mining capabilities of deep auto-encoder networks and select the network hyperparameters adaptively， an enhanced deep auto-encoder network was proposed for rolling bearing fault diagnosis. Maximum correlation entropy was used to replace mean square error as the loss function of auto-encoder. Sparse penalty term and contractive penalty term embedded with non-negative constraints were added to further reduce the reconstruction errors. Key parameters of the network were adaptively selected through gray wolf optimization algorithm. After experimental analyses， results show that compared with the existing methods， the proposed method has stronger feature extraction ability and stability. For bearing vibration data under variable operating conditions， the proposed method may also achieve high recognition accuracy.

Analysis and Experiments of Stable Rotation Conditions for Cylindrical Rollers in Double Disc Straight Groove Lapping

HE Qingshun, HE Chunlei, CHEN Guang, LIU Weifeng, DENG Xiaofan, REN Chengzu

2021, 32(21): 2625-2634. DOI: 10.3969/j.issn.1004-132X.2021.21.012

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To solve the stable rotation problems of cylindrical rollers in double disc straight groove lapping processes, theoretical analysis on rotating motions of cylindrical rollers in lapping state was carried out, and the stable rotation conditions were calculated. A kind of electromagnetic lapping disc was designed to increase frictional driving torques of rotation by applying electromagnetic forces. The stable rotation conditions were also improved. The parametric design, electromagnetic simulation and optimization were performed on the electromagnetic path of electromagnetic lapping disc. An electromagnetic lapping disc was fabricated. Both of simulation and experimental results show that the electromagnetic lapping disc may provide enough and uniform electromagnetic forces on cylindrical rollers. Lapping experiments were performed with 12 mm×18 mm cylindrical roller on the homemade experimental platform, and the correctness of the rotation conditions was verified. After 60 min lapping, the roundness errors of cylindrical rollers are obviously decreased from 2.55 μm to 0.63 μm. The shape accuracy is also improved obviously.

Investigation on End Circumferential Wrinkles of Large Deformation Pushing Diameter-reducing Tubes with Wall Thickness Deviation

LIU Heng, WANG Liandong, TAN Qiying, WANG Xiaodi, SONG Xiliang

2021, 32(21): 2635-2645. DOI: 10.3969/j.issn.1004-132X.2021.21.013

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Circumferential winkles in inner wall of tube end during pushing diameter-reducing production practice would seriously affect the quality of parts. The wall thickness of seamless steel tubes was measured， and the distribution law of wall thickness along circumferential direction was alternately thin and thick. A mechanics model of pushing diameter-reducing of tubes with wall thickness deviation was established. The stress and deformation in reducing， rounded corner and exit stage were analyzed， and the generation mechanism of circumferential winkles at the ends was obtained. Four times pushing diameter-reducing tests of tubes with different wall thickness deviation were carried out. Results show that the end unevenness is greater than the initial one, and the sizing area unevenness is less than the initial one， which are consistent with theoretical analyses. The influence laws of wall thickness deviation and reducing times on unevenness and relative unevenness were summarized， and the ranges of process parameters for producing circumferential wrinkles were given. A geometrical model of tubes with wall thickness deviation was established， where the inner surface shapes were periodic sinusoidal variation and the outer surface shapes were circle. The generation and development of circumferential winkle were simulated， the evolution laws of wall thickness and relative unevenness in each stages were obtained. Simulation results show that theoretical analyses are consistent with the tests. By means of pushing-pulling diameter-reducing， the end unevenness and warpage may be greatly reduced， and the forming quality may be effectively improved.

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