Clamping Points Research Articles

RESEARCH ON THE RESPONSE MECHANISM OF CLAMPING POINT POSITION TO THE VIBRATION PROPAGATION CHARACTERISTICS OF WOODEN MATERIALS

Vibratory harvesting is to dislodge fruits by applying excitation force to fruit trees, so the vibration response characteristics of fruit trees are of great significance for vibratory forest and fruit harvesting machinery to realize efficient harvesting. The effects of different clamping points and vibration frequencies on vibration responsiveness and energy transfer in Broussonetia papyrifera branches are investigated in this study. The results show that the effects of different clamping point positions and vibration frequencies on the branch vibration response are mutual. The ideal distance between the clamping point position and the base of the main branch should be between 48% and 73% of the branch length, and the distance between the clamping point position and the base of the main branch increased with the increase of vibration frequency. This is because, when the clamping point is close to the base of the main branch, a higher excitation frequency increases the energy consumption at the base of the main branch, and the amount of ineffective vibration energy transferred to the base of the main branch also increases. Therefore, when the location of the clamping point is close to the base of the main branch, the suppression of high-frequency vibration at the base of the main branch is stronger than the suppression of low-frequency vibration. When the clamping point is located in the center of the branch, the overall response of the branch to vibration is better.

Relaxing free boundary conditions in resonant ultrasound spectroscopy for extreme environments

Elastic constants are thermodynamic susceptibilities, which provide symmetry-resolved insight into phase transitions and material anisotropy. Therefore, their importance spans basic to applied science and engineering. Resonant ultrasound spectroscopy (RUS) is a powerful method to determine elastic constants, because RUS simultaneously measures all elastic constants in small, low symmetry samples with high precision and accuracy. Conventionally, elastic constants in RUS are obtained from resonant frequencies assuming the sample freely resonates. However, achieving free resonance is often incompatible with experimental situations, because such configurations are inherently unstable. This limitation has hindered utilizing RUS to study phases arising in extreme environments like strong magnetic fields. To overcome these obstacles, we introduce a variation of RUS in which small, finite-area contact is maintained between the sample and ultrasonic transducers using an adhesive. First, we establish the conditions under which this clamped point contact can be treated as a small perturbation to free resonance. After comparing predictions from this modelling with experiment, we then experimentally demonstrate the ability to extract elastic constants, and their temperature dependence, with comparable accuracy and precision to conventional RUS. Finally, we show we can reproducibly map phase boundaries in temperature and magnetic fields using our new approach.

A Vision Based Approach to Localize Waste Objects and Geometric Features Exaction for Robotic Manipulation

The quantity of waste generated is increasing daily, demanding an intelligent waste management system for effective and timely solutions. Pollution induced by garbage has been one of the major problems globally for a long time. The unawareness among people about waste disposal causes a threat to living things and creates a major risk for sanitation workers during waste collection, sorting, and recycling. A method is proposed for real-time automatic waste material detection and segregation for easier recycling. The proposed approach uses the State-of-art deep learning architecture Mask RCNN to locate and classify waste objects from the natural environment. Further, the geometric features like centroid, orientation, and the clamping points of the objects are extracted to aid the robotic arm in grasping the waste object. Methods are investigated for ordering the objects in the scene for the energy-efficient automated system. The technique can be adapted into robotic machines for waste management to sort the waste on the road pavements and streets, providing safety, productivity, and reducing the risk on the sanitation workers.

Sliding nanomechanical resonators

The motion of a vibrating object is determined by the way it is held. This simple observation has long inspired string instrument makers to create new sounds by devising elegant string clamping mechanisms, whereby the distance between the clamping points is modulated as the string vibrates. At the nanoscale, the simplest way to emulate this principle would be to controllably make nanoresonators slide across their clamping points, which would effectively modulate their vibrating length. Here, we report measurements of flexural vibrations in nanomechanical resonators that reveal such a sliding motion. Surprisingly, the resonant frequency of vibrations draws a loop as a tuning gate voltage is cycled. This behavior indicates that sliding is accompanied by a delayed frequency response of the resonators, making their dynamics richer than that of resonators with fixed clamping points. Our work elucidates the dynamics of nanomechanical resonators with unconventional boundary conditions, and offers opportunities for studying friction at the nanoscale from resonant frequency measurements.

Direct torque control based on second order sliding mode controller for three-level inverter-fed permanent magnet synchronous motor: comparative study

Introduction. The permanent magnet synchronous motor (PMSM) has occupied a large area in the industry because of various benefits such as its simple structure, reduced moment of inertia, and quick dynamic response. Several control techniques have been introduced for the control of the PMSM. The direct torque control strategy associated to three-level clamped neutral point inverter has been proven its effectiveness to solve problems of ripples in both electromagnetic torque and stator flux with regard to its significant advantages in terms of fast torque response. Purpose. The use of a proportional integral speed controller in the direct torque control model results in a loss of decoupling with regard to parameter fluctuations (such as a change in stator resistance value induced by an increase in motor temperature), which is a significant drawback for this method at high running speeds. Methods. That is way a second order sliding mode controller based on the super twisting algorithm (STA) was implemented instead of PI controller to achieve a decoupled control with higher performance and to insure stability while dealing with parameter changes and external disturbances. Results. The simulation results carried out using MATLAB/Simulink software show that the model of direct torque control based on a three-level inverter-fed permanent magnet synchronous motor drive has better performance with second order sliding mode speed controller than the proportional integral controller. Through the response characteristics we see greater performance in terms of response time and reference tracking without overshoots. Decoupling, stability, and convergence toward equilibrium are all guaranteed.

DESIGN AND IMPLIMENTATION OF A MECHATRONIC SYSTEM NAMELY SEAT CHECK MODULE WITH APPLICATION TO CNC SYSTEM: A REVIEW

In this study an effective method has been developed to automate a process implemented in manufacturing industry "CNC system", it details the research and development of a mechatronic system to overcome one of the most difficult tasks in today's manufacturing industry which is to reduce number of rejected parts of NG parts. This problem mainly occurs when the metal workpiece is disturbed or not properly attached to the fixture and due to that small change in location, it gets improperly machined, which leads to part getting rejected. A gap inspection sensor is included in the design to confirm that the workpiece is properly seated on the fixture and all the components needed for module assembly are designed and tested on a VMC machine. As the gap check sensor uses the principle of back pressure sensing to monitor the gap or distance, the sensor is supplied with pneumatic pressure through a regulator to ensure stabilized input, and outlet of sensor is connected to the orifices on the fixture plate under clamping points, so when the job is placed properly there is no air leakage and the change in pressure will respond to sensor. The developed module gets linked to PLC and needed changes were also made in ladder logic program to incorporate the new module in machine running cycle. This developed architecture is flexible and can be used on many other machines and applications. Doing so automates the machine and prevents potential tool damage and material wastage. Keywords - Mechatronic System, Sensor, Automation, Back pressure Sensing, CNC Programming, PLC program (Ladder Logic), Precision manufacturing

CNN-GRU network-based force prediction approach for variable working condition milling clamping points of deformable parts

Improper clamping is one of the major causes of part deformation. Improving the fixture arrangement through force analysis of clamping points is an effective means to suppress or improve machining deformation. However, the existing research focuses on the monitoring and off-line optimization of the clamping point force, which has a certain lag on the machining deformation control, and it is difficult to predict the clamping point force due to the time-varying coupling effect of multiple factors such as process parameters, cutting force, and clamping point force in the machining process. Inspired by the excellent performance of convolutional neural networks and gated recurrent networks in feature extraction and learning of temporal association laws, this paper proposes a CNN-GRU-based method for predicting the force state of clamping points under variable working conditions. Firstly, a force prediction model of clamping point during milling process with variable working conditions is established. Secondly, a convolutional neural network is designed to extract the features of dynamic coupled machining conditions. Then, a network of gated recurrent units is constructed to learn the temporal correlation law between the machining conditions and the forces on the clamping points to achieve force prediction of the clamping points during machining. Finally, it was verified by the milling process of the piston skirt. The results show that CNN-GRU can effectively predict the clamping force. In addition, CNN-GRU has higher computational efficiency and accuracy compared with CNN-LSTM, CNN-RNN and CNN-BP.

Solving a multi-dimensional matching problem for grouping clamping points on car body parts

Modern car body production is faced by an increasing number of car models as well as individualizing options, which leads to the need for more adaptable assembly equipment, e.g. grippers and fixtures that can switch between models in a matter of seconds. Based on known clamping positions, automated jigs consisting of several clamps can already adapt to different part geometries.To enable an efficient flexible jig, exactly one clamp must be assigned to each clamping point of each model taking into account different optimization criteria. Therefore, clamping points need to be grouped across all different models in the planning phase. Grouping of clamping points e.g. in order to minimize adaptation time or tooling costs is usually performed manually.In this paper, the grouping optimization problem is formalized, and a mathematical algorithm is introduced to solve this multi-dimensional matching. The envisaged approach uses a greedy algorithm to get an initial solution, which is optimised to a technically feasible solution considering economical aspects. To conclude, a short evaluation of the achieved results - especially in comparison with expert based grouping - is given.

Influence of the gasket materials on the clamping pressure distribution in a PEM water electrolyzer: Bolt torques and operation mode in pre-conditioning

To keep optimally connected, all electrolysis cell elements is one of the most important design criteria. The optimal distribution of the clamping points is crucial to increasing cell performance. In this work, the compression pressure distribution inside of a 25 cm2 PEM electrolysis cell was evaluated, using different materials: Teflon®, Viton®, ethylene propylene diene monomer rubber (EPDM), and nitrile rubber. Sealing material evaluation was performed taking as performance indicators: total compressed area (%) and compression pressure, for different torques applied. Pressure distribution was obtained by using pressure-sensitive films, analyzing the distribution of pressure points from three-dimensional plots (3D), and quantifying intensities of the images obtained. Results showed that pressure points distribution depends on the stiffness and thickness of the gasket materials. For a tightening torque of 3.70 N m, a pressure of 2.23 MPa is obtained with 85% of the membrane area compressed using nitrile rubber-EPDM gaskets.

Energy-dispersive X-ray micro Laue diffraction on a bent gold nanowire.

This article reports on energy-dispersive micro Laue (µLaue) diffraction of an individual gold nanowire that was mechanically deformed in three-point bending geometry using an atomic force microscope. The nanowire deformation was investigated by scanning the focused polychromatic X-ray beam along the nanowire and recording µLaue diffraction patterns using an energy-sensitive pnCCD detector that permits measurement of the angular positions of the Laue spots and the energies of the diffracted X-rays simultaneously. The plastic deformation of the nanowire was shown by a bending of up to 3.0 ± 0.1°, a torsion of up to 0.3 ± 0.1° and a maximum deformation depth of 80 ± 5 nm close to the position where the mechanical load was applied. In addition, extended Laue spots in the vicinity of one of the clamping points indicated the storage of geometrically necessary dislocations with a density of 7.5 × 1013 m-2. While µLaue diffraction with a non-energy-sensitive detector only gives access to the deviatoric strain, the energy sensitivity of the employed pnCCD offers absolute strain measurements with a resolution of 1%. Here, the residual strain after complete unloading of the nanowire amounted to maximum tensile and compressive strains of the order of +1.2 and -3%, which is comparable to the actual resolution limit. The combination of white-beam µLaue diffraction using an energy-sensitive pixel detector with nano-mechanical testing opens up new possibilities for the study of mechanical behavior at the nanoscale.

Software assisted clamping point classification and position optimization for the efficient flexibilization of carbody fixtures using mathematical geometry-based search algorithms

The Fraunhofer IWU has been developed specialized clamping robots for production of different car-models on one fixture. One of the challenges with universal clamping of different components is the contact point between part and clamping device. For the optimization of the clamping contours, a software was developed with which the geometries of the clamping points can be automatically analyzed and classified. With target search criteria, the clamping position on the component can be changed so that the clamping contours are geometrically simplified. Thus, a huge reduction in the complexity of the flexible clamping device is possible.

Comparison of Isolated Bidirectional DC/DC Converters Using WBG Devices for More Electric Aircraft

With the aim towards lighter and more efficient electrical systems in future aircraft, design of DC/DC converters with high efficiency, power density and improved thermal management becomes necessary. This paper investigates the detailed design of isolated bidirectional DC/DC converters for more electric aircraft (MEA). Use of wide bandgap (WBG) devices to enhance system efficiency is considered. A transformer optimization technique based on switching frequency for different converter topologies is investigated. The control strategy of the discussed configurations are verified in the PLECS simulation environment. Dual active bridge (DAB), input-series output-parallel (ISOP), neutral point clamped (NPC) and active neutral point clamped (ANPC) converters are considered to exploit benefits offered by WBG devices for MEA. A comparison is performed in terms of efficiency, thermal management, power density and electromagnetic interference (EMI). The results indicate that the ANPC converter is better for efficiency, thermal management and power density. The DAB converter showed similar results to the ISOP with the DAB yielding higher efficiency. The NPC and ANPC configurations resulted in the best EMI performance. The NPC converter proved to be the least effective solution with regard to efficiency, thermal management and power density.

Effect of the Anti-Yaw Damper on Carbody Vertical Vibration and Ride Comfort of Railway Vehicle

The theoretical research on means to reduce the vertical vibrations and improve the ride comfort of the railway vehicle relies on a mechanical model obtained from the simplified representation of the vehicle, while considering the important factors and elements affecting the vibration behaviour of the carbody. One of these elements is the anti-yaw damper, mounted longitudinally, between the bogie and the vehicle carbody. The anti-yaw damper reduces the lateral vibrations and inhibits the yaw motion of the vehicle, a reason for which this element is not usually introduced in the vehicle model when studying the vertical vibrations. Nevertheless, due to the position of the clamping points of the anti-yaw damper onto the carbody and the bogie, the damping force is generated not only in the yawing direction but also in the vertical and longitudinal directions. These forces act upon the vehicle carbody, impacting its vertical vibration behaviour. The paper analyzes the effect of the anti-winding damper on the vertical vibrations of the railway vehicle carbody and the ride comfort, based on the results derived from the numerical simulations. They highlight the influence of the damping, stiffness and the damper mounting angle on the power spectral density of the carbody vertical acceleration and the ride comfort index.

A performance comparison of transformer-less grid tied PV system using diode clamped and neutral point shorted inverters

Grid tied photovoltaic (PV) system is an operation mode of PV system working together with utility power supply to provide power to the power load. Conventionally, transformer is used together with the power inverter. The power transformer works as galvanic insolation amongst PV system and power grid. It works also to raise the voltage of power inverter. However, use of transformer will add system complexity, price, weight and size of the entire system. Transformer-less system is an alternative to make the system simpler and more practical in use. The paper discusses performance of transformer-less grid tied PV systems using diode clamped and neutral point shorted inverters. Effects of transformer elimination to the feat of the grid tied PV system especially harmonics content and leakage current of PV system were examined and analyzed. The performance was also compared with the traditional system using H-bridge inverter. The leakage currents did not flow in the system applying diode clamped inverter, and neutral point shorted inverter. In case of harmonics content, the diode clamped inverter injected less harmonics components than the neutral point shorted inverter. The neutral point shorted provides a simpler inverter circuit in the transformerless systems. Normal 0 false false false MS X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman",serif;}

Investigate on computer-aided fixture design and evaluation algorithm for near-net-shaped jet engine blade

This study proposes a computerized framework for computer-aided fixture design and evaluation for near-net-shaped jet engine blades. First, the manufacturing process of near-net-shaped jet engine blades and requirements for the fixture design and evaluation were analyzed. Second, a numerical model of the positioning error and the corresponding experimental platform were established. Third, a mechanical model of the blade under cutting conditions was analyzed, a finite element model (FEM) was established. Fourth, a mathematical model of the machining fixture layout optimization was established, and the positioning clamping points of the machining fixture were optimized by the combination of finite element analysis (FEA) and genetic algorithm. Finally, the corresponding algorithm verification was carried out by positioning error and cutting experiments. The results showed that the proposed computerized framework could evaluate and optimize the fixture of the same type blade to obtain the positioning and mechanical behavior of the fixture, and can realize high-precision manufacturing of near-net-shaped jet engine blades.

Tuning the nonlinear dispersive coupling of nanomechanical string resonators

We investigate nonlinear dispersive mode coupling between the flexural in- and out-of-plane modes of two doubly clamped, nanomechanical silicon nitride string resonators. As the amplitude of one mode transitions from the linear response regime into the nonlinear regime, we find a frequency shift of two other modes. The resonators are strongly elastically coupled via a shared clamping point and can be tuned in and out of resonance dielectrically, giving rise to multimode avoided crossings. When the modes start hybridizing, their polarization changes. This affects the nonlinear dispersive coupling in a nontrivial way. We propose a theoretical model to describe the dependence of the dispersive coupling on the mode hybridization.

Improving Clamping Accuracy of Thin-walled Workpiece in Turning Operation

This study presents theoretical and experimental error analysis and avoidance which results from the fixation of a thin-walled metal disk workpiece on a duplex turning machine. The distance between the rotating workpiece surface and a fixed datum point is measured using a laser displacement sensor (LDS). The measured data are analyzed numerically to get the error in the fixation system in terms of Euler angles. Then the workpiece clamping points are axially adjusted according to the calculated angles. Moreover, the problem formulation and the solution procedures are presented in details. Finally, a case study has been used to verify the proposed approach. The results indicate that the proposed technique can be used to decrease the fixation error to a reasonable range.

Research on Machining Fixture Layout Optimization for Near-Net-Shaped Jet Engine Blade

The design of machining fixture layout optimization for near-net-shaped jet engine blade is a major problem in the blade processing and manufacturing process. In this paper, the mathematical model of machining fixture layout optimization is established, and the influence of the clamping point position on the machining deformation of the blade-fixture system is analysed. Firstly, the mathematical model of machining fixture layout optimization is established according to the process requirements and clamping characteristics. Secondly, the positioning clamp points of machining fixture is optimized by the combination of finite element analysis (FEA) and genetic algorithm under the optimization target of the minimum value of the maximum deformation of the blade. Finally, cutting experiments are carried out to verify the reliability of the optimal layout fixtures, and the feasibility of the algorithm is verified by comparing with the minimum value obtained by the traditional Monte Carlo statistical method.

Use of a Safety Clamp When Performing Arthroscopic Knot Tying Preserves the Suture When It Is Placed Under Excessive Tension.

The purpose of this study was to compare the location of the suture breakage between tying by hand vs with a safety clamp, needle driver. FiberWire No. 2 and 2-0 (Arthrex, Naples, Florida) were fastened onto the hook attachment of the digital force gauge. Sutures were placed under excessive strain using a hand tying technique vs a safety clamp, or instrument tying. Peak forces at which the sutures failed under tension along with locations of the suture breakage, measured from the site of the knot, were recorded. For FiberWire No. 2, the mean load to failure was 142.60±2.33 N for hand tying and 78.79±1.97 N for the safety clamp (P<.0001). For FiberWire 2-0, the mean load to failure was 62.98±4.90 N for hand tying and 34.43±2.46 N for the safety clamp (P<.0001). For FiberWire No. 2, the mean location of suture breakage was 0 cm, at the site of the knot, for hand tying and at the clamping point (10.45±0.34 cm from the knot) for the safety clamp (P<.0001). For FiberWire 2-0, the mean location of suture breakage was 0 cm, at the site of the knot, for hand tying and at the clamping point (10.47±0.22 cm from the knot) for the safety clamp (P<.0001). Use of a safety clamp while mastering arthroscopic suture technique preserves the suture knot when placed under excessive tension. [Orthopedics. 2019; 42(1):e25-e28.].

A Switched-Capacitor-Based Multilevel Inverter Topology With Reduced Components

This letter presents an improved sensorless nine-level inverter topology with reduced number of components. It is formed by cascading a three-level T-type neutral clamped point inverter with a floating capacitor (FC) fed two-level converter unit. Additionally, two line-frequency switches are appended across the dc-link. A simple logic-form equations-based pulse width modulator is designed which is in-charge of maintaining the FC voltage at its reference value without any aid of voltage and current sensor. Thus, the complexity in control of the proposed topology is very minimal. The working principle of the proposed inverter and formulation of logic-form equations is deliberated in detail. Furthermore, experimental results obtained from the developed prototype are presented to validate feasibility and operability of the proposed topology. Finally, a comprehensive comparison with some of the recently reported inverter topologies proving the merits of the proposed topology is included.