The high-quality grinding of the aviation blade components with the industry robot presents tremendous challenges because of the complexity of blade surface. The hybrid force/position ...anti-disturbance control strategy is developed base on fuzzy PID control to improve the quality of grinding aviation blades. Firstly, according to gravity compensation technology, the perception of contact force is discussed to solve the contact force between the blades and abrasive belt machine. Then, the hybrid force/position anti-disturbance control strategy is designed to ensure the stability of robot automatic grinding system. The speed gain loop and the dual fuzzy PID control are introduced to enhance the anti-disturbance ability of the control system. Meanwhile, the analysis of stability and steady-state error for force control loop are performed to prove the validation of the feasibility of control system. Eventually, the simulation and experiments are carried out on the robot automatic grinding system. The experimental results reveal that the proposed control strategy can achieve better control effect and grinding quality compared with the traditional PID control.
Due to the compute-intensiveness and the lack of robustness of the algorithms for reconstruction of meshes and spline surfaces from point clouds, there is a need for further research in the topic of ...direct tool-path planning based on point clouds. In this paper, a novel approach for planning iso-parametric tool-path from a point cloud is presented. Since such planning falls into the iso-parametric category, it intrinsically depends on the parameterization of point clouds. Accordingly, a point-based conformal map is employed to build the parameterization. Based on it, formulas of computing path parameters are derived, which are much simpler than the conventional ones. By regularizing parameter domain and on the basis of the previous formulas, boundary conformed tool-path can be generated with forward and side step calculated against specified chord deviation and scallop height, respectively. Experimental results are given to illustrate the effectiveness of the proposed methods.
•A point-based iso-parametric tool-path planning method was proposed.•The formulas for computing forward and side step were simplified significantly.•Boundary conformed tool-path was generated for point clouds.
The selection of machining parameters in milling thin-walled plates affects deformation, quality, and productivity of the machined parts. This paper presents an optimization procedure to determine ...and validate the optimum machining parameters in milling thin-walled plates. The regression models for cutting force and surface roughness are developed as objective functions according to experimental results. Besides, the influences of machining parameters on cutting force and surface roughness are also investigated. The objectives under investigation in this study are cutting force, surface roughness, and material removal rate subjected to constraints conditions. As the effects of milling parameters on optimization objectives are conflicting in nature, the multi-objective optimization problem in thin-walled plates milling is proposed. A non-dominated sorting genetic algorithm (NSGA-II) is then adopted to solve this multi-objective optimization problem. The optimized combinations of machining parameters are achieved by the Pareto optimal solutions, and these solutions are verified by the chatter stability.
With the rapid development of the information age, electronic components are developing toward miniaturization, which makes the manufacturing of chips more and more difficult. Water jet-guided laser ...processing technology (WJGL) is a composite processing technology that combines pulsed laser and water jet, which can ensure the accuracy and efficiency of processing while small size parts machining. This paper is based on the “element birth and death” technique in the finite element method and the three-dimensional transient temperature field and subsequent material removal model of 6061 aluminum alloy are established. The effects of laser average power, pulse repetition frequency, and pulse action time on the transient thermal distribution, aperture, taper, and other forming qualities with the two technologies of fixed-point drilling and spiral drilling, respectively, are studied. Combining the experimental process, the general rule of morphology change of the micro-hole is obtained. The results show that WJGL of micro-hole is based on the combined effect of thermal ablation and real-time cooling. Spiral drilling can maintain a better hole shape but fixed-point drilling can achieve a smaller hole taper. With the increase of laser power, the hole taper increases, reaching saturation at 8 W. The repetition frequency is between 50 and 70 kHz to obtain better hole morphology while maintaining better processing efficiency, and the minimum hole taper is 8.21°.
The hybrid force/position control base on fuzzy proportional-integral-derivative (PID) is proposed to improve the quality of robotic automatic grinding aviation blades. First, the perception for the ...contact force/torque is discussed. A multi-source parameters gravity compensation matrix is established to identify the parameters through matrix reorganization. The contact force/torque is perceived according to the gravity compensation result. Then, the hybrid force/position control base on fuzzy PID is designed to realize active force control. Nevertheless, the sharp edge phenomenon occurs although the force control algorithm, which seriously affects the grinding quality of blades. Finally, the fusion control of force and torque is proposed to weaken the sharp edge phenomenon. The experiment proves that the introduction of torque control avoids effectively the sharp edge phenomenon. Meanwhile, comparing the proposed control algorithm with the traditional PID control, the results show that the proposed hybrid force/position control based on fuzzy PID can ensure the stability of the contact force and improve the quality of the aviation blades.
The nuclear reactor coolant pump (NRCP) is the heart of the nuclear power plant. This paper focuses on robot automation grinding processing for NRCP, which includes scanning, point cloud processing, ...grinding trajectory generation, and quality evaluation system based on reverse engineering. In this work, firstly, the point cloud of NRCP is obtained by robotic scanner system of hand-eye calibration. Secondly, the research proposes a novel method for point cloud simplification, denoising, and boundary extraction base on
k
neighborhood octree structure. More important, the efficient trajectory generation of grinding relies on transforming point cloud into adaptive triangular mesh. Lastly, quality evaluation system can calculate the deviation between point cloud and qualified workpiece. And the further path is generated according to the deviation. Experiments show that the accuracy of “246” hand-eye calibration method is less than 0.02 mm. The method of point cloud processing has obvious efficiency advantages over other researchers’ algorithms. The final results indicate that the error of grinding is less than 3 mm and efficiency can be improved by 2.5 times compared with manual grinding.
Computer-aided manufacturing (CAM) software outputs machining data by encoding a tool-path into a series of G-codes which are composed of various lengths of line segments. The discontinuities of ...these line segments may cause inefficiency for computer numerical control (CNC) system. To achieve high-speed continuous motions, corner smoothing algorithms based on look-ahead methods are widely used. However, it is difficult to meet smoothing trajectories in real-time requirements. Based on machine learning method, in this paper, a support vector machine (SVM) system is presented for directly outputting classification results of the various geometric continuities at the transition corners. The feature values used for generating continuity classification model are extracted from sampling paths of the previous publication work: the machining parameters, length, fairness criteria, the root mean square (RMS) contour errors, and dominant stage type of movement of each sampling path are calculated. The acceleration/deceleration (ACC/DEC) feedrate planning scheme is used to determine the feedrate at the transition corners. Simulations and experiments show that the proposed algorithm can realize accurately and efficiently continuity classification in real-time requirements under the conditions of machining accuracy.
At present, the use of microstructure to change the optical properties and wetting properties of the material itself has become the main means to improve the utilization rate of materials in the ...manufacturing industry. Due to the hydrophilicity of the material surface can achieve underwater self-cleaning, directional transportation function, it becomes an indispensable part of surface modification. Water jet-guide laser processing can significantly reduce the formation of the heat-affected zone and crack, and can clearly ablate the material, with higher precision and resolution. In this experiment, the effects of scan spacing, laser output power and channel aspect ratio are examined and processing conditions for achieving near superhydrophilicity are provided. Owing to the anaerobic processing environment, the surface chemical composition of the material does not change, and the hydrophilicity is increased by 8% to 43% compared with that before. Increasing the aspect ratio can increase the wettability, when the aspect ratio is more than 1.63, the wettability begins to rebound, and the wettability becomes worse. Using small laser power and multiple scanning processing scheme can make the surface covered with tiny small pillars of micro-nano particles layer beneficial to increase the droplet adhesion, and the minimum contact angle can reach 37.2°.
Laser shock processing (LSP) is an advanced material surface hardening technology that can significantly improve mechanical properties and extend service life by using the stress effect generated by ...laser-induced plasma shock waves, which has been increasingly applied in the processing fields of metallic materials and alloys. With the rapidly development of modern industry, many new technologies developed from LSP have emerged, which broadens the application of LSP and enriches its technical theory. In this work, the technical theory of LSP was summarized, which consists of the fundamental principle of LSP and the laser-induced plasma shock wave. The new technologies, developed from LSP, are introduced in detail from the aspect of laser shock forming (LSF), warm laser shock processing (WLSP), laser shock marking (LSM) and laser shock imprinting (LSI). The common feature of LSP and these new technologies developed from LSP is the utilization of the laser-generated stress effects rather than the laser thermal effect. LSF is utilized to modify the curvature of metal sheet through the laser-induced high dynamic loading. The material strength and the stability of residual stress and micro-structures by WLSP treatment are higher than that by LSP treatment, due to WLSP combining the advantages of LSP, dynamic strain aging (DSA) and dynamic precipitation (DP). LSM is an effective method to obtain the visualized marks on the surface of metallic materials or alloys, and its critical aspect is the preparation of the absorbing layer with a designed shape and suitable thickness. At the high strain rates induced by LSP, LSI has the ability to complete the direct imprinting over the large-scale ultrasmooth complex 3D nanostructures arrays on the surface of crystalline metals. This work has important reference value and guiding significance for researchers to further understand the LSP theory and the new technologies developed from LSP.
Waterjet-guided laser processing is a novel machining technique for metallic materials. To investigate and analyse the effects of processing parameters on surface topography change, micro-texturing ...evolution, and hydrophobicity, micromorphology machining experiments were conducted on stainless steel using self-developed waterjet-guided laser processing equipment. Nd:DPSS laser system with repetition frequency of 20–120 kHz and maximum power of 50W is used in the equipment. A scanning electron microscope (SEM) is used to measure surface topography. Energy-dispersive spectrometer (EDS) is used to evaluate the material composition of processing zone and no processing zone. The effects of grid spacing and laser power coupled into the jet are examined and processing conditions for hydrophobicity are provided. There was oxidation and no crack on the kerf edge. The surface contact angle dramatically increases from 92.94 to 138.41° with the decreasing of the grid size. It has been shown that waterjet-guided laser processing yields textures with a hydrophobic surface and is suit for micro-texture micro-machining.
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