Search Results (50)

This work aimed to develop both a real implementation and a digital twin for a small CNC machining center. The X-, Y-, and Z-axes feed systems were realized as closed-loop motion loops with DC servo motors and encoders. Motion control was provided by Arduino boards and Pololu motor drivers. A simulation study of the step response parameters was carried out, and then the positioning regime was studied, followed by the two-axis simultaneous motion regime (circular interpolation). This study, based on a hybrid simulation diagram realized in Simulink–Simscape, allowed a preliminary tuning of the PID (proportional integral derivative) controllers. Next, the CAE (computer-aided engineering) simulation diagram was complemented with the CAM (computer-aided manufacturing) simulation interface, the two together forming an integrated digital twin system. To validate the contouring performance of the proposed CNC system, a circular groove with an outer diameter of 31 mm and an inner diameter of 29 mm was machined using a 1 mm cylindrical end mill. The trajectory followed the simulated 30 mm circular path. Two sets of controller parameters were applied. Dimensional accuracy was verified using a GOM Atos Core 200 optical scanner and evaluated in GOM Inspect Suite 2020. The results demonstrated good agreement between simulation and physical execution, validating the PID tuning and system accuracy. Full article

With the rapid development of Computerized Numerical Control (CNC) systems, traditional industrial communication protocols fail to meet the requirements for high real-time performance and reliability. To address these challenges, an open five-axis CNC system is designed and implemented based on the gLink-II bus protocol. This system features a layered architecture that integrates the Windows operating system with a Real-Time Operating System (RTOS) kernel, along with a multithreaded data interaction structure based on a circular buffer to enhance real-time data transmission performance and improve system responsiveness. In the direct linear interpolation control for five-axis machining, an acceleration and deceleration planning method is introduced, taking into account the kinematic constraints of the rotary axes. This method optimizes velocity and acceleration control. The experimental results show that the system achieves a maximum response error of less than 0.2 milliseconds and an interpolation period of less than 0.5 milliseconds in five-axis coordinated control. The system is capable of efficiently performing data processing and task scheduling, ensuring the stability of the CNC machining process. Full article

This study presents a novel localization framework that leverages the unique properties of chirp signals combined with a time division multiple access (TDMA)-based tactical data link to achieve high-precision positioning. Chirp signals, with their wide bandwidth and high temporal resolution, enable an oversampling-like effect, significantly enhancing distance estimation accuracy without the need for additional sampling rates. The proposed framework integrates chirp-based ranging and localization algorithms, incorporating raised cosine interpolation and circular shift techniques to improve temporal resolution and ensure precise peak detection. By utilizing the time differential of arrival (TDoA) and Fang’s algorithm, the system demonstrates robust performance, effectively mitigating challenges posed by multipath interference and jamming. The TDMA system provides synchronized time slots, allowing the seamless integration of communication and localization functionalities while ensuring stable and efficient operation. Experimental evaluations under various environmental conditions, including dense multipath and high-jamming scenarios, confirm the framework’s superiority over conventional localization methods in terms of accuracy, reliability, and resilience. These results highlight the framework’s potential applications in diverse fields, such as Internet of Things (IoT) networks, smart city infrastructure, and tactical communication systems, where high precision and robust localization are critical. Full article

This study aims to explore the influence of random pore characteristics inside rock mass on the fracture mechanical properties of rock under tensile stress. By means of numerical simulation based on the improved smoothed particle hydrodynamics (SPH) method, a specific kernel function approximate integral interpolation form and discrete particle superposition expression form are constructed to handle physical processes. The maximum tensile stress criterion and fracture marker ω are introduced to improve the traditional smooth kernel function for dealing with crack propagation. Meanwhile, the center and radius information of circular pores are generated using random numbers to create a rock model with random pores. The research results show that in terms of crack propagation morphology, as the pore percentage increases, the crack gradually changes from a straight propagation slightly disturbed by pores to an overall fragmentation propagation with frequent branching and coalescence; when the pore size increases, the crack propagation changes from a complex network-like shape frequently disturbed by small pores to a relatively simple through fracture controlled by key nodes of large pores. In terms of the stress–strain law, the increase in pore percentage leads to a decrease in the elastic modulus and peak strength of the rock and a weakened post-peak ductility; when the pore size increases, the elastic modulus first decreases and then increases, the peak strength changes similarly, and the post-peak characteristics change from complex fluctuations to a stable transition. The conclusion indicates that the pore percentage and size have a significant and complex influence on the mechanical properties of the rock. Full article

Gear skiving is a highly productive method for manufacturing gears, especially internal gears. Circular arc internal gears are important parts of Rotary Vector (RV) reducers and harmonic reducers. This study presents the implementation of the gear skiving technique using a cylindrical tool to enhance the precision and efficiency of machining circular arc internal gears. By establishing the mathematical model for skiving a circular arc internal gear based on the conjugation theory of two surfaces, the barrel-shaped conjugate surface was solved by deducing gear meshing equations. A design method is proposed for a cylindrical skiving tool by utilizing the barrel-shaped conjugate surface with an off-center tool position along the axis. The cutting edge of the tool rake face was then obtained through cubic spline interpolation from the conjugate surface. The influence of the tool rake face offsets on the cutting rake angle and clearance angle is also discussed by defining the normal cutting plane of the tool. The correctness of the proposed cylindrical skiving tool was validated through simulation and actual skiving experiments. The experimental results demonstrated that the tooth profile error of the gear fell within ±0.004 mm, thereby satisfying the accuracy requirement for pin wheel housing gears. These research findings can contribute to advancements in novel cylindrical skiving tools. Full article

This study advances the state of the art by computing the macroscopic elastic properties of 2D periodic functionally graded microcellular materials, incorporating both isotropic and orthotropic solid phases, as seen in additively manufactured components. This is achieved through numerical homogenization and several novel MATLAB implementations (known in this study as Cellular_Solid, Homogenize_test, homogenize_ortho, and Homogenize_test_ortho_principal). The developed codes in the current work treat each cell as a material point, compute the corresponding cell elasticity tensor using numerical homogenization, and assign it to that specific point. This is conducted based on the principle of scale separation, which is a fundamental concept in homogenization theory. Then, by deriving a fit function that maps the entire material domain, the homogenized material properties are predicted at any desired point. It is shown that this method is very capable of capturing the effects of orthotropy during the solid phase of the material and that it effectively accounts for the influence of void geometry on the macroscopic anisotropies, since the obtained elasticity tensor has different $E_1$ and $E_2$ values. Also, it is revealed that the complexity of the void patterns and the intensity of the void size changes from one cell to another can significantly affect the overall error in terms of the predicted material properties. As the stochasticity in the void sizes increases, the error also tends to increase, since it becomes more challenging to interpolate the data accurately. Therefore, utilizing advanced computational techniques, such as more sophisticated fitting methods like the Fourier series, and implementing machine learning algorithms can significantly improve the overall accuracy of the results. Furthermore, the developed codes can easily be extended to accommodate the homogenization of composite materials incorporating multiple orthotropic phases. This implementation is limited to periodic void distributions and currently supports circular, rectangular, square, and hexagonal void shapes. Full article

The EtherCAT fieldbus system is widely applied in different types of computerized numerical control (CNC) machine tools due to its outstanding communication performance. In the field of ultra-precision CNC, some machine tools employ controllers that integrate EtherCAT master functionality to achieve real-time communication with other devices; however, the open-source IgH EtherCAT master has rarely been applied to the CNC systems of ultra-precision machine tools. The feasibility of using the IgH EtherCAT master to meet the communication performance requirements of ultra-precision machine tools remains uncertain; therefore, it is necessary to validate the control effect on precision axes under the application of the IgH EtherCAT master. In this work, EtherCAT applications were developed on a personal computer (PC) to alter it to a bus-type controller with the IgH EtherCAT master function. To provide the EtherCAT master with real-time and accurate motion data of the axes, an interpolation algorithm tailored for control experiments was designed, and a G-code data processing method was proposed. Moreover, precision aerostatic linear axes and servo drivers were chosen as EtherCAT slaves for single-axis motion and dual-axis linkage control experiments. The experimental results showed that the motion controller based on IgH can effectively control the precision axes to execute ultra-precision linear and circular interpolation motion. Full article

With the prevalence of international trade protectionism and transformation and the upgrading of the domestic market structure, the contradiction between the demand for and the competitive development of the port market in the Yangtze River Delta in China has become increasingly prominent. The 19 major ports of the Yangtze River Delta in China were selected for this study, and using the methods of index evaluation, gravitational model, and spatial interpolation, the spatial effects in the hinterland were calculated from three dimensions, central potential, spatial gravity and distribution convenience, and the regional coordination of port services. The results show that the potential of the Shanghai Port and Ningbo Zhoushan Port in China is stronger, and the difference in the distribution of the ports is quite clear. The spatial gravity of each port city can be superimposed over one another to form a clear dense semi-circular zone, and the ability of the marginal ports to participate in this zone is weak. The convenience of their distribution in the hinterland changes from being location-dependent to traffic-dependent. The service gap in the hinterland of the port system is more significant, but the expansion of spatial effects makes the sustainability of regional coordination gradually improve. Finally, several policy suggestions are proposed to ensure ecological responsibility among resource-oriented enterprises. Full article

The failure of 3D-printed Polylactide (PLA) specimens with circular holes was studied under tensile and cyclic loading, respectively, by an inserted pin. Experiments were conducted for the perforated PLA specimens with various print angles from 0° to 90°, as well as [0°/90°]s and [0°/±45°/90°]s. The hole locations varied along the specimens. The PLA specimens showed two different failure modes: one through the print lines and the other between the print lines. Different print angles resulted in different tensile failure stresses under pin loading. The cyclic tests of different print angles showed very similar S-N data as the applied stresses were normalized to their tensile failure stresses if the failure mode was through the print lines. On the other hand, cyclic failure between print lines showed distinctly separated S-N data, even with the normalized applied stresses. The tensile failure stresses, failure locations, and orientations were successfully predicted using the failure criterion that is based on both stress and stress gradient conditions. A proposed mathematical interpolation equation provided good estimations of the tensile failure stresses and S-N curves of specimens with different print angles once the failure stresses were known for the 0° to 90° specimens. Full article

In this study, a moving single-station direct position determination (DPD) algorithm based on virtual interpolated arrays is proposed. Existing moving single-station algorithms face challenges such as the incomplete utilization of sparse array apertures and insufficient consideration of mixed circular and non-circular signals. To address these issues, we propose an enhanced gridless DPD algorithm, suitable for multiple mixed circular and non-circular sources. Through constructing a non-zero unconjugated covariance matrix from the non-circular components of the mixed signals, the data dimensionality is expanded, and the gridless method is used to fill the voids in the coarray, significantly improving localization performance. Additionally, a unitary transformation method is applied to reduce computational complexity. This method transforms complex operations into real operations by applying unitary transformations to steering vectors and subspaces. Simulation results demonstrate that the proposed algorithm offers significant advantages in terms of array degrees of freedom and localization accuracy. Full article

This work investigates the mechanical behaviour of sandwich beams with cellular cores using a multiscale approach combined with a meshless method, the Natural Neighbour Radial Point Interpolation Method (NNRPIM). The analysis is divided into two steps, aiming to analyse the efficiency of NNRPIM formulation when combined with homogenisation techniques for a multiscale computational framework of large-scale sandwich beam problems. In the first step, the cellular core material undergoes a controlled modification process in which circular holes are introduced into bulk polyurethane foam (PUF) to create materials with varying volume fractions. Subsequently, a homogenisation technique is combined with NNRPIM to determine the homogenised mechanical properties of these PUF materials with different porosities. In this step, NNRPIM solutions are compared with high-order FEM simulations. While the results demonstrate that RPIM can approximate high-order FEM solutions, it is observed that the computational cost increases significantly when aiming for comparable smoothness in the approximations. The second step applies the homogenised mechanical properties obtained in the first step to analyse large-scale sandwich beam problems with both homogeneous and functionally graded cores. The results reveal the capability of NNRPIM to closely replicate the solutions obtained from FEM analyses. Furthermore, an analysis of stress distributions along the beam thickness highlights a tendency for some NNRPIM formulations to yield slightly lower stress values near the domain boundaries. However, convergence towards agreement among different formulations is observed with mesh refinement. The findings of this study show that NNRPIM can be used as an alternative numerical method to FEM for analysing sandwich structures. Full article

The meshless displacement error-recovery parametric investigation in finite element method-based incompressible elastic analysis is presented in this study. It investigates key parameters such as interpolation schemes, patch configurations, dilation indexes, weight functions, and meshing patterns. The study evaluates error recovery effectiveness (local and global), convergence rates, and adaptive mesh improvement for triangular/quadrilateral discretization schemes. It uses meshless moving least squares (MLS) interpolation with rectangular and circular support regions and solves benchmark plate and cylinder problems. It is observed that a circular influence region, a cubic spline weight function, and regular mesh patterns yield a better performance of than an MLS-based error recovery method. The study also concludes that lower dilation index values with rectangular influence regions are preferable for regular meshes, while higher dilation index values with radial influence regions are suitable for preferable meshes to enhance MLS error recovery. Full article

This study presents a comprehensive multiscale analysis of sandwich beams with a polyurethane foam (PUF) core, delivering a numerical comparison between finite element methods (FEMs) and a meshless method: the radial point interpolation method (RPIM). This work aims to combine RPIM with homogenisation techniques for multiscale analysis, being divided in two phases. In the first phase, bulk PUF material was modified by incorporating circular holes to create PUFs with varying volume fractions. Then, using a homogenisation technique coupled with FEM and four versions of RPIM, the homogenised mechanical properties of distinct PUF with different volume fractions were determined. It was observed that RPIM formulations, with higher-order integration schemes, are capable of approximating the solution and field smoothness of high-order FEM formulations. However, seeking a comparable field smoothness represents prohibitive computational costs for RPIM formulations. In a second phase, the obtained homogenised mechanical properties were applied to large-scale sandwich beam problems with homogeneous and approximately functionally graded cores, showing RPIM’s capability to closely approximate FEM results. The analysis of stress distributions along the thickness of the beam highlighted RPIM’s tendency to yield lower stress values near domain edges, albeit with convergence towards agreement among different formulations. It was found that RPIM formulations with lower nodal connectivity are very efficient, balancing computational cost and accuracy. Overall, this study shows RPIM’s viability as an alternative to FEM for addressing practical elasticity applications. Full article

Under shear and non-uniform loads, the deformation of the section shape of a casing results in an irregular section, and the spatial continuity is poor. The change in the distance between the wall of the casing before and after stress is recorded to analyze the deformation of the casing, and the distance value is taken as the key characteristic of the casing. A large number of the key characteristic values of shale gas casing deformation can be obtained by using the circular traversal detection method. At the same time, this article focuses on the center deviation between the laser sensor axis and the pipe string axis, as well as on the disturbance problem during measurement. An eccentricity error correction algorithm is derived to correct the eccentricity error that occurs during the detection process, and then we use interpolation algorithms to draw cubic spline curves to improve detection accuracy. The test results show that the algorithm can effectively eliminate eccentricity errors in measurement and achieve the accurate measurement of deformation casing characteristic values, which can provide basic data for the study of a shale gas casing deformation mechanism. Full article

In this work, an artificial neural network (ANN)-based model is proposed to describe the input–output relationships in a Limaçon-To-Circular (L2C) gas expander with an inlet valve. The L2C gas expander is a type of energy converter that has great potential to be used in organic Rankine cycle (ORC)-based small-scale power plants. The proposed model predicts the different performance indices of a limaçon gas expander for different input pressures, rotor velocities, and valve cutoff angles. A network model is constructed and optimized for different model parameters to achieve the best prediction performance compared to the classic mathematical model of the system. An overall normalized mean square error of 0.0014, coefficient of determination ($R^2$) of 0.98, and mean average error of 0.0114 are reported. This implies that the surrogate model can effectively mimic the actual model with high precision. The model performance is also compared to a linear interpolation (LI) method. It is found that the proposed ANN model predictions are about 96.53% accurate for a given error threshold, compared to about 91.46% accuracy of the LI method. Thus the proposed model can effectively predict different output parameters of a limaçon gas expander such as energy, filling factor, isentropic efficiency, and mass flow for different operating conditions. Of note, the model is only trained by a set of input and target values; thus, the performance of the model is not affected by the internal complex mathematical models of the overall valved-expander system. This neural network-based approach is highly suitable for optimization, as the alternative iterative analysis of the complex analytical model is time-consuming and requires higher computational resources. A similar modeling approach with some modifications could also be utilized to design controllers for these types of systems that are difficult to model mathematically. Full article