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In the current research work, in-house developed and fabricated multi-axis near-dry Electrical Discharge Machine (near-dry EDM) has been used having different tool positions, i.e. tool electrodes in horizontal position (Case-I) and vertical positions (Case-II) as a novel machining techniques in hard-to-reach places and also to improve the process performance. Design of Experiment tool has been used with three process parameters: voltage, discharge current, and pulse-on-time for experimentation purposes. In order to maximize Material Removal Rate (MRR), it was necessary to compare and enhance these parameters in both cases, i.e. Case-I, and Case-II. The machining process is significantly influenced by the vertical tool positions, as indicated by the largest percentage contribution in the Analysis of Variance results. The voltage has the least influence, while the pulse-on time is relatively less. In contrast, for the horizontal tool position, the voltage proved the most prominent factor in terms of influence, while the current ranked second in significance. Conversely, the pulse-on time exhibited the least impact among the three factors. The highest MRR 2.45 mm3/min was achieved in the vertical tool position while in horizontal machining, the highest MRR 0.144 mm3/min was observed. These findings provide valuable insights into the multi-axis near-dry EDM with proposed methodology. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive methodology for developing a vibration measurement system, with a primary focus on monitoring rolling element bearings, widely recognised as pivotal components in generic machine vibration monitoring. Through the utilisation of sensors to capture vibration data signals, the system aims to meticulously analyse these signals to discern any indications of bearing health deterioration, thus facilitating the early identification of potential pre-breakdown conditions. The proposed system initiates the process by internally decomposing the three-axis vibration signal, enabling subsequent transmission of processed data to a remote location for the identification of specific faults in the roller element bearings. Installation of a three-axis accelerometer on the bearing housing, positioned radially, facilitates the capture of raw vibration data along one axial and two radial directions. Moreover, efforts to enhance computational efficiency involve cascading multiple identical modules in a serial pipeline structure, allowing for iterative loop computation of intrinsic mode functions within Empirical Mode Decomposition (EMD). Real-time computation is achieved through this serial pipeline structure, necessitating two distinct clock frequencies: one at 12.5 MHz for sampling and storing 3-axis vibration data in ping pong buffers, and another at 40 MHz for reading and processing the data signal retrieved from these buffers. Validation of the proposed method is demonstrated through simulation results obtained via synthesised Verilog code on Xilinx Artix-7 FPGA (XC7A35T-1CPG236C), affirming its efficacy in real-time applications. [ABSTRACT FROM AUTHOR]

Actuator control takes a pivotal role in achieving stability and accuracy, particularly in the context of multi-axial real-time hybrid simulation (maRTHS). In maRTHS, multiple hydraulic actuators are necessitated to apply precise motions to experimental substructures thus necessitating the application of multiple-input multiple-output (MIMO)control strategies. This study evaluates the data-driven nonlinear autoregressive with external input (NARX) based compensation for the servo-hydraulic dynamics within the maRTHS benchmark model. Different from previous study, nonlinear terms are incorporated into the NARX model. Online least square and ridge regression techniques are utilized to estimate the model coefficients to achieve optimal compensation. The influence of various model order and window length is assessed for the NARX model-based compensation. The findings of this research demonstrate that NARX-based compensation has significant potential not only in facilitating precise actuator control for maRTHS but also in enabling robust control in the presence of unknown uncertainties inherent to the servo-hydraulic system. [ABSTRACT FROM AUTHOR]

Angle measurement is an essential component of precision measurement and serves as a crucial prerequisite for high-end manufacturing. It guides the implementation of precision manufacturing and assembly. The current angle measurement methods mainly focus on multiple axes, high precision, and large measurement ranges. This article introduces the technology of angle measurement from the perspectives of single-axis and multi-axis measurement schemes. Firstly, the single-axis measurement scheme is primarily achieved through optical methods, such as encoder discs that measure energy changes and interferometric phase changes, as well as mechanical, electromagnetic, and inertial angle measurement methods, among which interferometric methods offer the highest accuracy, with high cost, and encoder discs provide the largest measurement range with an ordinary price. Secondly, in the multi-axis measurement scheme, autocollimation instruments, including plane mirrors, gratings, and self-designed targets, are the main options. Although grating encoders can achieve three degrees of freedom in angle measurement with an ordinary price, they are limited in terms of measurement range and sensitivity compared to self-designed targets. Lastly, artificial intelligence assistance precision measurement is increasingly being embraced due to significant advancements in computer performance, making it more convenient to identify the relationship between measured values and detection values. In conclusion, angle measurement plays a crucial role in precision manufacturing, and the evolving and improving technologies provide the manufacturing industry with greater choices. The purpose of this review is to help readers quickly find more suitable technical solutions according to current application requirements, such as single/multiple axes, accuracy level, measuring range, budget, etc. [ABSTRACT FROM AUTHOR]

Material Extrusion is a remarkably diverse and adaptable additive manufacturing technology that can print a range of geometries from a wide range of materials. To further expand the technology's capabilities, a pneumatic extruder was integrated onto a six degree of freedom robotic arm to enable conformal, multi-axis deposition of material on a range of geometries. In conjunction, a novel, printable cyanate-ester ink with minimal density and excellent thermomechanical properties was developed. The rheology of the ink was modified to allow the ink to be successfully extruded and then retain its shape during both conformal deposition and post-print thermal curing. The combination of the novel multi-axis printing modality and novel material enables a successful demonstration of conformal printing with a high-performance lightweight polymeric material. We demonstrate deposition on near vertical surfaces and produce final parts possessing a glass transition temperature above 400 °C and a strength of over 20 MPa.

This paper proposes a new scheme of pendulum accelerometer with sandwich structure. In this scheme, the electrical signal on the mass is connected to the wafer surface through glass isolated through-silicon-via (TSV), so that the basic characteristics of the accelerometer can be obtained by wafer-level testing. Compared with the current commercial device process scheme, the packaging and testing cost of the device can be greatly reduced. The glass-in-silicon (GIS) encapsulation caps on both sides of the device are prepared by glass isolated TSV and GIS reflow process. By designing the shape and size of the silicon electrode area and glass area of the GIS caps, the parasitic capacitance between the pendulum structure and the fixed electrode is reduced. Another advantage of using TSV to extract the electrical signal of the mass is that the Z -axis inertial force can be detected when the pendulum structure is placed perpendicular to the direction of gravity acceleration. In addition, electrodes are grown on the side of the split device, and when the pendulum structure is placed parallel to the direction of gravity acceleration, the inertial force of the XY -axis can be detected. The test shows that when the range of the pendulum accelerometer based on this scheme is ±2 g, the noise density of the accelerometer is 42 μ g √Hz−1 (X -axis), 40 μ g √Hz−1 (Y -axis) and 27 μ g √Hz−1 (Z -axis), and the bias instability is 6.6 μ g (X -axis), 7.1 μ g (Y -axis) and 6.8 μ g (Z -axis), reaching the level of commercial devices. [ABSTRACT FROM AUTHOR]

Precise prediction of milling force is a crucial issue in multi-axis milling, which is important for evaluating the tool life and surface quality. In this paper, an improved force model for ball-end milling is proposed based on a novel uncut chip thickness (UCT) model as well as the consideration of edge effect and size effect. The computational model of UCT takes into account the influence of lead and tilt angles in ball-end milling. In addition, it utilizes a new discretization method of the uncut chip area that ensures the local cutting edge is perpendicular to the length of the elemental uncut chip area, making it more compatible with the classical oblique cutting model. For each elemental cutting edge, the force components are calculated through a purely analytical approach, considering the shear force, edge force, and size effect caused by cutting edge geometry in milling process. The proposed model is comprehensively validated with both FEM and multi-axis milling experiments for aluminum and titanium. The results indicate that the proposed model can predict the dynamic milling force under various cutting conditions in a good manner. Moreover, considering edge and size effects can further improve the prediction accuracy. [ABSTRACT FROM AUTHOR]

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Angle measurement is an essential component of precision measurement and serves as a crucial prerequisite for high-end manufacturing. It guides the implementation of precision manufacturing and assembly. The current angle measurement methods mainly focus on multiple axes, high precision, and large measurement ranges. This article introduces the technology of angle measurement from the perspectives of single-axis and multi-axis measurement schemes. Firstly, the single-axis measurement scheme is primarily achieved through optical methods, such as encoder discs that measure energy changes and interferometric phase changes, as well as mechanical, electromagnetic, and inertial angle measurement methods, among which interferometric methods offer the highest accuracy, with high cost, and encoder discs provide the largest measurement range with an ordinary price. Secondly, in the multi-axis measurement scheme, autocollimation instruments, including plane mirrors, gratings, and self-designed targets, are the main options. Although grating encoders can achieve three degrees of freedom in angle measurement with an ordinary price, they are limited in terms of measurement range and sensitivity compared to self-designed targets. Lastly, artificial intelligence assistance precision measurement is increasingly being embraced due to significant advancements in computer performance, making it more convenient to identify the relationship between measured values and detection values. In conclusion, angle measurement plays a crucial role in precision manufacturing, and the evolving and improving technologies provide the manufacturing industry with greater choices. The purpose of this review is to help readers quickly find more suitable technical solutions according to current application requirements, such as single/multiple axes, accuracy level, measuring range, budget, etc.

This paper presents a multi-axis low-cost soft magnetic tactile sensor with a high force range for force feedback in robotic surgical systems. The proposed sensor is designed to fully decouple the output response for normal, shear and angular forces. The proposed sensor is fabricated using rapid prototyping techniques and utilizes Neodymium magnets embedded in an elastomer over Hall sensors such that their displacement produces a voltage change that can be used to calculate the applied force. The initial spacing between the magnets and the Hall sensors is optimized to achieve a large displacement range using finite element method (FEM) simulations. The experimental characterization of the proposed sensor is performed for applied force in normal, shear and 45° angular direction. The force sensitivity of the proposed sensor in normal, shear and angular directions is 16 mV/N, 30 mV/N and 81 mV/N, respectively, with minimum mechanical crosstalk. The force range for the normal, shear and angular direction is obtained as 0–20 N, 0–3.5 N and 0–1.5 N, respectively. The proposed sensor shows a perfectly linear behavior and a low hysteresis error of 8.3%, making it suitable for tactile sensing and biomedical applications. The effect of the material properties of the elastomer on force ranges and sensitivity values of the proposed sensor is also discussed. [ABSTRACT FROM AUTHOR]

The purpose of this study is to determine impact of several multi-axis 3D printing strategies on buildability, surface quality, accuracy, and strength of large scale single-walled object (printed in a so called vase mode). To achieve this goal, test objects were printed using four different printing strategies by an industrial robotic arm and a pellet-fed screw extruder. The strategies tested in this study are regular 3-axis deposition with planar layers, 5-axis deposition with planar layers, 3-axis deposition with nonplanar layers, and 5-axis deposition with nonplanar layers. Custom scripts for nonplanar slicing and for tilt control during multiaxis printing were developed to achieve these prints and are explained in this study. The results were evaluated using 3D scanning and mechanical testing, and surface accuracy, surface roughness, and layer adhesion strength were compared. The most important findings are (1) 5-axis motion alone does not improve the results of the printing; (2) while nonplanar printing can improve surface quality, its usability is geometry dependent; and (3) multi-axis nonplanar printing, even with partial tilt (30°) can expand printability with enhanced quality to at least 75° overhang angle. The future potential of these methods and the requirements to achieve them are discussed. [ABSTRACT FROM AUTHOR]

Aerosol extinction profiles at 550 nm were retrieved by applying multi-axis differential optical absorption spectroscopy (MAX-DOAS) and lookup table. Then the tropospheric NO2 and HCHO vertical column densities were retrieved using a two-step method from 28 July to 5 August of 2015 in Shanghai. The retrieved results were compared with the satellite products, and then their diurnal variation was observed. A consistency check was performed before the inversion to obtain a correction factor. Based on the sensitivity of geometric angles to oxygen dimer air mass factor (O4 AMF, AMF is the ratio of the slanted column density to the vertical column density), the parameterization scheme of geometric angles in the lookup table is optimized. The results show that the aerosol increased significantly in the afternoon. The diurnal variation of tropospheric NO2 and HCHO vertical column densities (VCDs) are bimodal and unimodal patterns respectively, and their values are higher than those of GOME-2 and OMI satellite products. A process of aerosol reduction and recovery are related to ground particulates and meteorological elements. The chemical sensitivity of local ozone production also has a clear diurnal variation. [ABSTRACT FROM AUTHOR]

The layer-by-layer deposition process used in material extrusion (ME) additive manufacturing results in inter- and intra-layer bonds that reduce the mechanical performance of printed parts. Multi-axis (MA) ME techniques have shown potential for mitigating this issue by enabling tailored deposition directions based on loading conditions in three dimensions (3D). Planning deposition paths leveraging this capability remains a challenge, as an intelligent method for assigning these directions does not exist. Existing literature has introduced topology optimization (TO) methods that assign material orientations to discrete regions of a part by simultaneously optimizing material distribution and orientation. These methods are insufficient for MA-ME, as the process offers additional freedom in varying material orientation that is not accounted for in the orientation parameterizations used in those methods. Additionally, optimizing orientation design spaces is challenging due to their non-convexity, and this issue is amplified with increased flexibility; the chosen orientation parameterization heavily impacts the algorithm's performance. Therefore, the authors (i) present a TO method to simultaneously optimize material distribution and orientation with considerations for 3D material orientation variation and (ii) establish a suitable parameterization of the orientation design space. Three parameterizations are explored in this work: Euler angles, explicit quaternions, and natural quaternions. The parameterizations are compared using two benchmark minimum compliance problems, a 2.5D Messerschmitt-Bölkow-Blohm beam and a 3D Wheel, and a multi-loaded structure undergoing (i) pure tension and (ii) three-point bending. For the Wheel, the presented algorithm demonstrated a 38% improvement in compliance over an algorithm that only allowed planar orientation variation. Additionally, natural quaternions maintain the well-shaped design space of explicit quaternions without the need for unit length constraints, which lowers computational costs. Finally, the authors present a path toward integrating optimized geometries and material orientation fields resulting from the presented algorithm with MA-ME processes. [ABSTRACT FROM AUTHOR]

Multi-axis fused deposition modelling (FDM) 3D printing technology has been paid attention to by more and more people. However, existing FDM extruders are usually short and fat, which significantly restricts the popularization of multi-axis FDM 3D printing technology because one significant trend of additive manufacturing is the use of long and thin extruders to avoid collisions between extruders and workpieces in the printing process. This paper presents the design of a throat-extended FDM extruder to print complex-shaped workpieces with details. The main contributions in this paper include: (i) presenting a novel extruder structure including an extended-throat, a smaller heater block, and a cooling mini-fan; (ii) designing an optimized heater block using the shapes of its components and the milling tool as constraints to make its volume as little small as possible; (iii) Construct experimental and simulation methods to examine the temperature distribution of the throat to optimize the shapes of the heat dams of nozzle throats and the wind speed of the heat-dissipation fan. Based on the throat-extended FDM extruder, a five-axis FDM 3D printer has been developed, and various complex-shaped workpieces have been printed without any support. [ABSTRACT FROM AUTHOR]

This paper presents a multi-axis low-cost soft magnetic tactile sensor with a high force range for force feedback in robotic surgical systems. The proposed sensor is designed to fully decouple the output response for normal, shear and angular forces. The proposed sensor is fabricated using rapid prototyping techniques and utilizes Neodymium magnets embedded in an elastomer over Hall sensors such that their displacement produces a voltage change that can be used to calculate the applied force. The initial spacing between the magnets and the Hall sensors is optimized to achieve a large displacement range using finite element method (FEM) simulations. The experimental characterization of the proposed sensor is performed for applied force in normal, shear and 45° angular direction. The force sensitivity of the proposed sensor in normal, shear and angular directions is 16 mV/N, 30 mV/N and 81 mV/N, respectively, with minimum mechanical crosstalk. The force range for the normal, shear and angular direction is obtained as 0–20 N, 0–3.5 N and 0–1.5 N, respectively. The proposed sensor shows a perfectly linear behavior and a low hysteresis error of 8.3%, making it suitable for tactile sensing and biomedical applications. The effect of the material properties of the elastomer on force ranges and sensitivity values of the proposed sensor is also discussed.

Aerosol extinction profiles at 550 nm were retrieved by applying multi-axis differential optical absorption spectroscopy (MAX-DOAS) and lookup table. Then the tropospheric NO2 and HCHO vertical column densities were retrieved using a two-step method from 28 July to 5 August of 2015 in Shanghai. The retrieved results were compared with the satellite products, and then their diurnal variation was observed. A consistency check was performed before the inversion to obtain a correction factor. Based on the sensitivity of geometric angles to oxygen dimer air mass factor (O4 AMF, AMF is the ratio of the slanted column density to the vertical column density), the parameterization scheme of geometric angles in the lookup table is optimized. The results show that the aerosol increased significantly in the afternoon. The diurnal variation of tropospheric NO2 and HCHO vertical column densities (VCDs) are bimodal and unimodal patterns respectively, and their values are higher than those of GOME-2 and OMI satellite products. A process of aerosol reduction and recovery are related to ground particulates and meteorological elements. The chemical sensitivity of local ozone production also has a clear diurnal variation.

In this study, we introduce an adaptive model-free coupling controller while using recurrent fuzzy neural network (RFNN) for multi-axis system to minimize the contour error. The proposed method can be applied to linear or nonlinear multi-axis motion control systems following desired paths. By the concept of cross-coupling control (CCC), multi-axis system is transferred into a nonlinear time-varying system due to the time-dependent coordinate transformation; tangential, normal, and bi-normal components of desired contour. Herein, we propose a model-free adaptive coupling controller design approach for multi-axis linear motor system with uncertainty and nonlinear phenomena. RFNN establishes the corresponding adaptive coupling controller to treat the uncertain system with nonlinear phenomenon. The stability of closed-loop system is guaranteed by the Lyapunov method and the adaptation of RFNN is also obtained. Simulation results are introduced in order to illustrate the effectiveness. [ABSTRACT FROM AUTHOR]

Aiming at the shortcomings of low efficiency and poor accuracy of the existing pressure sensor pre-tightening parameter measurement system, an automatic multi-axis wrist force sensor pre-tightening parameter measurement system is designed. The multi-axis wrist force sensor module is used to collect real-time tension signal from the loaded hand wheel. After amplification, the signal is transmitted to the multi-channel gating module through RS485 communication module to realize the tested sensing. After fast switching and constant current source power supply control function, the data collector collects the pull signal obtained by multi-axis wrist force pressure sensor and transmits it to the upper computer of the system designed by LabVIEW through RS485 bus. The upper computer controls and collects the pressure sensor according to the pull signal feedback from the data collector, and the pre-tightening displacement of multi-axis wrist force sensor is determined by parameters such as axial displacement and friction resistance moment. The experimental results show that the designed system can fully measure the pre-tightening parameters of the sensor, and the starting moment measurement error is only 0.102%. The system can meet the requirements of batch measurement and calibration of multi-axis wrist force sensor with accuracy of 1%-0.1%. [ABSTRACT FROM AUTHOR]

Lifestyle heavily influences intervertebral disc (IVD) loads, but measuring in vivo loads requires invasive methods, and the ability to apply these loads in vitro is limited. In vivo load data from instrumented vertebral body replacements is limited to patients that have had spinal fusion surgery, potentially resulting in different kinematics and loading patterns compared to a healthy population. Therefore, this study aimed to develop a pipeline for the non-invasive estimation of in vivo IVD loading, and the application of these loads in vitro. A full-body Opensim model was developed by adapting and combining two existing models. Kinetic data from healthy participants performing activities of daily living were used as inputs for simulations using static optimisation. After evaluating simulation results using in vivo data, the estimated six-axis physiological loads were applied to bovine tail specimens. The pipeline was then used to compare the kinematics resulting from the physiological load profiles (flexion, lateral bending, axial rotation) with a simplified pure moment protocol commonly used for in vitro studies. Comparing kinematics revealed that the in vitro physiological load protocol followed the same trends as the in silico and in vivo data. Furthermore, the physiological loads resulted in substantially different kinematics when compared to pure moment testing, particularly in flexion. Therefore, the use of the presented pipeline to estimate the complex loads of daily activities in different populations, and the application of those loads in vitro provides a novel capability to deepen our knowledge of spine biomechanics, IVD mechanobiology, and improve pre-clinical test methods. [ABSTRACT FROM AUTHOR]

Force sensing has always been an important necessity in making decisions for manipulation. It becomes more appealing in the micro-scale context, especially where the surface forces become predominant. In addition, the deformations happening at the very local level are often coupled, and therefore providing multi-axis force sensing capabilities to microgripper becomes an important necessity. The manufacturing of a multi-axis instrumented microgripper comprises several levels of complexity, especially when it comes to the single wafer fabrication of a sensing and actuation mechanism. To address these requirements, in this work, an instrumented two-axis force sensing tool is proposed, which can then be integrated with the appropriate actuators for microgripping. Indeed, based on the task, the gripper design and shape requirements may differ. To cover wide needs, a versatile manufacturing strategy comprising of the separate fabrication of the passive and sensing parts was especially investigated. At the microscale, signal processing brings additional challenges, especially when we are dealing with multi-axis sensing. Therefore, a proper device, with efficient and appropriate systems and signal processing integration, is highly important. To keep these requirements in consideration, a dedicated clean-room based micro-fabrication of the devices and corresponding electronics to effectively process the signals are presented in this work. The fabricated sensing part can be assembled with wide varieties of passive parts to have different sensing tools as well as grippers. This force sensing tool is based upon the piezoresistive principle, and is experimentally demonstrated with a sensing capability up to 9 mN along the two axes with a resolution of 20 μN. The experimental results validate the measurement error within 1%. This work explains the system design, its working principle, FEM analysis, its fabrication and assembly, followed by the experimental validation of its performance. Moreover, the use of the proposed sensing tool for an instrumented gripper was also discussed and demonstrated with a micrograsping and release task.

In this paper, a new design technique is presented to estimate and reduce the cross-axis sensitivity (CAS) in a single-drive multi-axis microelectromechanical systems (MEMS) gyroscope. A simplified single-drive multi-axis MEMS gyroscope, based on a mode-split approach, was analyzed for cross-axis sensitivity using COMSOL Multiphysics. A design technique named the “ratio-matching method” of drive displacement amplitudes and sense frequency differences ratios was proposed to reduce the cross-axis sensitivity. Initially, the cross-axis sensitivities in the designed gyroscope for x and y-axis were calculated to be 0.482% and 0.120%, respectively, having an average CAS of 0.301%. Using the proposed ratio-matching method and design technique, the individual cross-axis sensitivities in the designed gyroscope for x and y-axis were reduced to 0.018% and 0.073%, respectively. While the average CAS was reduced to 0.045%, showing a reduction rate of 85.1%. Moreover, the proposed ratio-matching method for cross-axis sensitivity reduction was successfully validated through simulations by varying the coupling spring position and sense frequency difference variation analyses. Furthermore, the proposed methodology was verified experimentally using fabricated single-drive multi-axis gyroscope.

Miniaturized multi-axis (force & torque) tactile sensors are paramount for the robot system to interact safely with the external environment, especially for the controlled adhesive robots. However, there exists a drawback——measurement anisotropy, which prevents sensors from performing equally well in all the directions and the high degree of integration. Based on the plate capacitive mechanism, this paper introduces a miniaturized 5-axis tactile sensing method with a novel double-layer sensitive structure. Practically, shear force is detected by measuring the change of overlap area in the upper-layer-sensing cell, while the normal force and moment can be obtained by the variable space between two plates arranged in a ${2} \times {2}$ -grid in the lower-layer-sensing cell. Moreover, in order to achieve the measurement isotropy, the relationship between the force/torque and the capacitance is clarified to facilitate the independent adjustment of the sensitivity of each axis. Based on the methodology, a miniature 5-axis flat tactile sensor is manufactured. The experimental results show that the shear sensitivity of the prepared sensor is over 0.2557pF/N within 7 N, reaching the same magnitude as normal force (0.2859pF/N over 3N range). The sensitivities of torque are over 1.8406 $({N}\cdot {m})^{-{1}}$ with a full-scale range of $0.04~{N}\cdot {m}$. The results demonstrate that the miniaturized tactile sensor is capable of isotropic measurement among 5-axis for robotic manipulation. [ABSTRACT FROM AUTHOR]

Long-duration blasts are typically defined by positive pressure durations exceeding 100 ms. Such blasts can generate dynamic pressures (blast winds) capable of exerting damaging drag loads on comparatively slender structural components such as columns. With limited drag coefficient availability for specific structural geometries, Computational Fluid Dynamics (CFD) can be the only satisfactory approach for analysing blast loading on user-specified, finite geometries. The ability to analyse long-duration blasts with commercially available CFD programmes is still not confidently offered, with no prior studies examining the accuracy of modelling interaction with relatively much smaller, finite geometries. This paper presents a comparative investigation between numerical and experimental results to assess the predictive capacity of inviscid Eulerian CFD as a method for calculating long-duration blast drag loading on finite cross-sectional geometries. Full-scale long-duration blast experiments successfully measured surface pressure–time histories on a steel I-section column aligned at four orientations. Calculated pressure–time histories on exposed geometry surfaces demonstrated good agreement although reduced accuracy and under-prediction occurred on shielded surfaces manifesting as overestimated net loading. This study provides new understanding and awareness of the numerical capability and limitations of using CFD to calculate long-duration blast loads on intricate geometries. [ABSTRACT FROM AUTHOR]

There has been considerable research in recent years on the additive manufacturing (AM) of continuous-fibre-reinforced thermoplastic composite parts (CFRTPs) based on fused-deposition modelling (FDM). Most current AM processes are achieved by sandwiching long fibres between the matrix material, which confines the specimens to a single fixed building direction and leads to inferior interfacial performance. Herein, we present a new strategy for printing CFRTPs in three-dimensional space using a novel self-designed multi-axis AM machine. Two head systems are introduced to deposit the thermoplastic and long fibres. Moreover, the multi-axis movement approach advantageously enables the fibre to be deposited on any programmed surface, or wound around the parts. Three types of wound material specimens are manufactured, tested, and compared with specimens produced by a traditional flat layer stacking process. The results show that the tensile and flexural strengths of the composites are significantly enhanced by the continuous fibre, and the interlaminar shear performance of the wound fibre parts were also improved. Additionally, the proposed process makes the manufacturing of complicated composites more convenient, and exhibits significant potential for practical applications. [ABSTRACT FROM AUTHOR]

In this paper, a novel toolpath generation approach is proposed for concentric laser metal deposition (LMD) technology, which is an additive manufacturing (AM) process. The toolpaths define the movements to be carried out by the deposition head to manufacture the part through a layer-by-layer construction process. In this way, the characteristics of the generated deposition strategy directly affect the quality of the construction, that could lead to geometric distortions and irreparable defects. This work introduces a toolpath generator that provides several capacities with respect to the previous works: (1) an optimized hybrid deposition strategy that combines contour curves and zigzag filling patterns and ensure a uniform Z growth for each layer by a constant overlap parameter, (2) a multi-axis movement strategy that guarantees the deposition on the previous layer in overhang walls, and (3) a non-planar slicing strategy that adapts the layers to the variable vertical growth in single-bead wall structures with variable inclinations and multi-axis deposition strategy. The effectiveness of the generated toolpaths was proved through the implementation and validation on LMD technologies by the construction of different three-dimensional geometries. [ABSTRACT FROM AUTHOR]

Highlights • Column orientation greatly influences total blast drag loading exerted. • Drag loading is influenced by column section projected area and aerodynamics. • Column structural response varied for different blast angles of incidence. • Blast drag loading at different angles requires accurate characterisation. Abstract This paper reports experimental results pertaining to the effects of planar long-duration blast waves interacting with steel I-section column elements about different angles of incidence. Long-duration blast waves are typically defined by a positive pressure phase duration in excess of 100 ms, characteristic of very large explosion events such as industrial accidents. Blasts of this magnitude result in large impulses and dynamic pressures with the potential to exert high drag forces on column elements within an open frame structure. Due to relatively small dimensions in comparison to the blast wavelength, individual column elements are predominantly subjected to translational drag loading. Blast drag loading is complex to characterise, generally requiring approximation using drag coefficients, although proposed values in literature display inconsistency and typically lack provision for multi-axis interaction with I-shape geometries. Four full-scale long-duration experiments investigated blast interaction and elastic structural response of two steel I-section columns as a function of orientation to the incident shock wave. Drag coefficients were calculated as a function of I-section orientation using experimental pressure data and compared to values proposed in literature. It was found that drag coefficients proposed in literature have the potential to under-predict drag loading for certain oblique I-section orientations examined in these experiments. Importantly, intermediate oblique I-section orientations recorded higher loading and exhibited higher drag coefficients compared to orthogonal orientations, resulting in larger structural elastic response. Results from this experimental work have confirmed that I-section columns are axis-sensitive to blast wave direction giving rise to varying magnitudes of drag loading and structural response. [ABSTRACT FROM AUTHOR]

Abstract In contrast to standard layer based additive manufacturing methodologies, multi-axis material deposition can print structures without the need for support material. However, this method is jeopardized by potential collisions between a depositing unit (nozzle, wire, power and powder sources, etc.) and the already deposited material. The goal of this research is to initiate development of a methodology to check manufacturing feasibility of geometries and generate subsequent process planning strategies. The paper describes a geometry-based concept to decompose the product geometry into discrete volumes by using space partitioning with infinite planes and considering advantages and constraints of multi-axis additive manufacturing. The discrete volumes are used to generate process planning variants and to compute and generate boundary conditions for such process planning strategies. The algorithm generates multi-axis slices that require no support structures because of relative nozzle/workpiece orientation. In addition, the planning tackles more complex scenarios, in which overhangs, nozzle orientation, and gravity can be considered. [ABSTRACT FROM AUTHOR]

In this study, we introduce an adaptive model-free coupling controller while using recurrent fuzzy neural network (RFNN) for multi-axis system to minimize the contour error. The proposed method can be applied to linear or nonlinear multi-axis motion control systems following desired paths. By the concept of cross-coupling control (CCC), multi-axis system is transferred into a nonlinear time-varying system due to the time-dependent coordinate transformation; tangential, normal, and bi-normal components of desired contour. Herein, we propose a model-free adaptive coupling controller design approach for multi-axis linear motor system with uncertainty and nonlinear phenomena. RFNN establishes the corresponding adaptive coupling controller to treat the uncertain system with nonlinear phenomenon. The stability of closed-loop system is guaranteed by the Lyapunov method and the adaptation of RFNN is also obtained. Simulation results are introduced in order to illustrate the effectiveness.

Previous studies have quantified the biodynamic responses to vibration in a laboratory set-up using mainly rigid seats and single axis excitation. This study investigates the effect of the backrest contact, headrest contact, backrest angle, arm angle and the extent of gripping the steering wheel on the acceleration of the head in a real life multi-axis vibration environment. Fifteen male subjects drove a car on a paved road at a speed of 40 km/h adopting one of eight seating conditions at a time. The acceleration of the head was measured in the x, y and z-directions during the exposure duration. The results were presented as r.m.s. values and PSDs of the accelerations of the head. The greatest effect on the acceleration of the head resulted from using the backrest and the headrest. The arm angle and the extent of gripping the steering wheel showed no or little effect on the acceleration of the head. The effect of the seating conditions was found generally different from that reported in studies conducted in the labs with single, dual, or tri-axial vibration exposure. [ABSTRACT FROM AUTHOR]

The complexity of multi-axis spine testing often makes it challenging to compare results from different studies. The aim of this work was to develop and implement a standardized testing protocol across three six-axis spine systems, compare them, and provide stiffness and phase angle limits against which other test systems can be compared. Standardized synthetic lumbar specimens (n = 5), comprising three springs embedded in polymer at each end, were tested on each system using pure moments in flexion–extension, lateral bending, and axial rotation. Tests were performed using sine and triangle waves with an amplitude of 8 Nm, a frequency of 0.1 Hz, and with axial preloads of 0 and 500 N. The stiffness, phase angle, and R 2 value of the moment against rotation in the principal axis were calculated at the center of each specimen. The tracking error was adopted as a measure of each test system to minimize non-principal loads, defined as the root mean squared difference between actual and target loads. All three test systems demonstrated similar stiffnesses, with small (<14%) but significant differences in 4 of 12 tests. More variability was observed in the phase angle between the principal axis moment and rotation, with significant differences in 10 of 12 tests. Stiffness and phase angle limits were calculated based on the 95% confidence intervals from all three systems. These recommendations can be used with the standard specimen and testing protocol by other research institutions to ensure equivalence of different spine systems, increasing the ability to compare in vitro spine studies. [ABSTRACT FROM AUTHOR]

Additive manufacturing is an emerging technology that enables new product design. However, major inhibitors are long building times and a fixed build direction of the workpieces. In this article, new optimization and path planning methods for multi-axis additive manufacturing are presented going beyond conventional three-axis systems. This includes an adaptation of the building direction and an algorithm for the special case of cylindrical axes. These methods can reduce the production time drastically by avoiding support structures and by using the integration of predefined building blocks to substitute the infill. We present both, the new manufacturing process and the necessary computation methods for optimal process and path planning. Decreasing the building time and the amount of support structures paves the way for new application domains of additive manufacturing in the future. [ABSTRACT FROM AUTHOR]

Multi-axis motion systems have been widely applied in industrial fields, and the contour error is an important indicator to measure the quality of the products. Contour error is defined as the orthogonal deviation of actual position from the desired tool path, and contouring control is a very useful method to reduce or eliminate it. In this study, by finding the reference point nearest to the current actual position, and then projecting the actual position onto the osculating plane at this reference point, a high-accuracy contour error estimation method is proposed. When the estimated contour error cannot be described as an analytic expression of tracking errors, the cross-coupling control (CCC) is not applicable. And, task coordinate frame approach (TCFA) has a relatively complex computation. In order to overcome these shortcomings, by compensating the axis component of contour error into each loop of the servo motor simultaneously, a simple and effective contouring compensation control method is proposed. Experiments are carried out on a real-time in-house-developed multi-axis motion system. The results show that the contour error estimated by using the proposed method is close to the true one, and the proposed contouring control method can achieve the proportional reduction of the contour error effectively. [ABSTRACT FROM AUTHOR]

This paper focuses on the application of a multi-axis automatic control system for the “two-in-hand” configuration ITER PF6 winding line for the PF6 coil. The automatic control system is based on a Siemens Simotion D platform, which houses 16 servo motors and 68 interlocks. Tests are performed after the establishment of the hardware and debugging of the program. High precision and reliability are achieved, which demonstrated that the automatic control system satisfied the requirements of the PF6 coil double pancake winding. [ABSTRACT FROM AUTHOR]