Clamping Points Research Articles

New design for inertial piezoelectric motors

We have designed, implemented, and tested a novel inertial piezoelectric motor (IPM) that is the first IPM to have controllable total friction force, which means that it sticks with large total friction forces and slips with severely reduced total friction forces. This allows the IPM to work with greater robustness and produce a larger output force at a lower threshold voltage while also providing higher rigidity. This is a new IPM design that means that the total friction force can be dramatically reduced or even canceled where necessary by pushing the clamping points at the ends of a piezoelectric tube that contains the sliding shaft inside it in the opposite directions during piezoelectric deformation. Therefore, when the shaft is propelled forward by another exterior piezoelectric tube, the inner piezoelectric tube can deform to reduce the total friction force acting on the shaft instantly and cause more effective stepping movement of the shaft. While our new IPM requires the addition of another piezoelectric tube, which leads to an increase in volume of 120% when compared with traditional IPMs, the average step size has increased by more than 400% and the threshold voltage has decreased by more than 50 V. The improvement in performance is far more significant than the increase in volume. This enhanced performance will allow the proposed IPM to work under large load conditions where a simple and powerful piezoelectric motor is needed.

A boundary integral equation method for mode elimination and vibration confinement in thin plates with clamped points

We consider the bi-Laplacian eigenvalue problem for the modes of vibration of a thin elastic plate with a discrete set of clamped points. A high-order boundary integral equation method is developed for efficient numerical determination of these modes in the presence of multiple localized defects for a wide range of two-dimensional geometries. The defects result in eigenfunctions with a weak singularity that is resolved by decomposing the solution as a superposition of Green’s functions plus a smooth regular part. This method is applied to a variety of regular and irregular domains and two key phenomena are observed. First, careful placement of clamping points can entirely eliminate particular eigenvalues and suggests a strategy for manipulating the vibrational characteristics of rigid bodies so that undesirable frequencies are removed. Second, clamping of the plate can result in partitioning of the domain so that vibrational modes are largely confined to certain spatial regions. This numerical method gives a precision tool for tuning the vibrational characteristics of thin elastic plates.

Virtual grid and BPNN based collision avoidance control of automatic fixture system

In order to solve the motion collision between the cutter and clamping points, a multi-point fixture system is proposed, which is designed for the aircraft beams frame parts. This system is developed in modularization and the control is independent of the CNC system for practical universality in different situations. A simple, real-time and accurate detection method of cutter position is proposed by three laser sensors and special detection planes. The potential clamping modules that may collide with the cutter are found out fast by the virtual grid net method. Then the clamping modules are judged and controlled by the proposed collision model and BPNN methods. The validity of the proposed control method and fixture system is verified by the machining experiments, and the machining efficiency is improved by about 38.8% compared to the manual fixture.

Strong 4-mode coupling of nanomechanical string resonators

We investigate mechanical mode coupling between the four fundamental flexural modes of two doubly clamped, high-Q silicon-nitride nanomechanical string resonators. Strong mechanical coupling between the strings is induced by the strain mediated via a shared clamping point, engineered to increase the exchange of oscillatory energy. One of the resonators is controlled dielectrically, which results in strong coupling between its out-of-plane and in-plane flexural modes. We show both inter-string out-of-plane-in-plane and 3-mode resonances of the four coupled fundamental vibrational modes of a resonator pair, giving rise to a simple and a multimode avoided crossing, respectively.

A method to minimize the workpiece deformation using a concept of intelligent fixture

Abstract Manufacturing processes are commonly affected by the low stiffness of the components limiting the quality and precision of the final product. Precision is one of the most important issues in the machining process, and the main cause for rejection is the part static deformation and the dynamic vibrations. The static deformation is mainly affected by two factors: deformation due to clamping and process forces, and geometrical distortions due to material removal and residual stress relieving during processing. The deformations caused by the clamping in the fixture are normally associated to existing distortion in the raw workpiece due to previous manufacturing processes and to the clamping forces. These problems lead to uncertainties in the set-up process, hindering the fixture functions, the achievement of a right positioning of the workpiece and the avoidance of deformations due to clamping forces. This paper presents an analysis to identify the causes of the static deformations during clamping and a method to correct the geometrical distortion and deformation of a clamped workpiece by the evaluation of the reaction forces in the selected relevant clamping points. It covers the design and validation of an active clamping unit to minimize the deformation produced by the fixture that could affect the machining process. The developed clamping unit presents an alternative to combine the locator and the clamper in a single component that controls the reaction force and the deformation of the workpiece in the clamping point, and it performs the positioning of that point to minimize the distortion of the workpiece. The clamping unit was verified in laboratory conditions and then tested in an industrial application, evaluating the capabilities related to positioning and reaction force control.

Incorporating nuclear vibrational energies into the "atom in molecules" analysis: An analytical study.

The quantum theory of atoms in molecules (QTAIM) is based on the clamped nucleus paradigm and solely working with the electronic wavefunctions, so does not include nuclear vibrations in the AIM analysis. On the other hand, the recently extended version of the QTAIM, called the multi-component QTAIM (MC-QTAIM), incorporates both electrons and quantum nuclei, i.e., those nuclei treated as quantum waves instead of clamped point charges, into the AIM analysis using non-adiabatic wavefunctions. Thus, the MC-QTAIM is the natural framework to incorporate the role of nuclear vibrations into the AIM analysis. In this study, within the context of the MC-QTAIM, the formalism of including nuclear vibrational energy in the atomic basin energy is developed in detail and its contribution is derived analytically using the recently proposed non-adiabatic Hartree product nuclear wavefunction. It is demonstrated that within the context of this wavefunction, the quantum nuclei may be conceived pseudo-adiabatically as quantum oscillators and both isotropic harmonic and anisotropic anharmonic oscillator models are used to compute the zero-point nuclear vibrational energy contribution to the basin energies explicitly. Inspired by the results gained within the context of the MC-QTAIM analysis, a heuristic approach is proposed within the context of the QTAIM to include nuclear vibrational energy in the basin energy from the vibrational wavefunction derived adiabatically. The explicit calculation of the basin contribution of the zero-point vibrational energy using the uncoupled harmonic oscillator model leads to results consistent with those derived from the MC-QTAIM.

A methodology to enable automatic 3D routing of aircraft Electrical Wiring Interconnection System

Harness 3D routing is one of the most challenging steps in the design of aircraft Electrical Wiring Interconnection System (EWIS). This is due not only to the intrinsic complexity of the EWIS, but also to the increasing number of applying design constraints and its dependency on any change in the design of the airframe and installed systems. The current routing process employed by EWISdesign is largely based on the manual work of expert engineers, partially supported by conventional CAD systems. As a result, the routing process is quite inefficient, error prone and unable to deliver optimal solutions. Although many harness components are selected from catalogues and the design process is largely repetitive and rule based, it has been found that none or very limited automation solutions, which can significantly decrease the workload of engineers and increase their efficiency, are currently available. In this paper, an innovative approach is proposed to solve the 3D routing automation as an optimization problem. Knowledge Based Engineering (KBE) and optimization methods are proposed to achieve minimum cost routing solutions that satisfy all relevant design rules and constraints. The proposed solution is scalable in terms of constraints, can be deployed on any type of routing environment, and, thanks to the achieved level of automation, able to reduce the process lead time drastically. The basic idea is to achieve optimal EWIS routing solutions by optimizing the position of the harnesses clamping points, which are used as way-points to route the harnesses inside the aircraft digital mock-up. The challenge to solve this optimization problem is that the number and initial value of design variables, namely the number and position of clamping points, are not known a priori. To handle this challenge, a two-step, hybrid optimization strategy has been devised. The first step, called Initialization, uses a road map based path finding method to generate a preliminary harness definition, including the required number and preliminary position of its clamping points. The second step, called Refinement, uses a conventional optimization method to move the position of the clamps and refine the preliminary harness definition aiming for the minimum cost and the satisfaction of all the design constraints. This approach has been implemented into a KBE application connected with a commercial optimization package and tested on several routing cases. The results demonstrate that the proposed method is capable of handling cases of representative geometric complexity and design constraints and delivering proper 3D harness models in full automation.

Data-driven depth calibration for distributed acoustic sensing

Distributed acoustic sensing (DAS) can make use of an ordinary telecom fiber as a continuous array of acoustic sensors to acquire, for example, downhole seismic. One challenge when using DAS is assigning correct depth to a given part of the DAS data record. Usually, depth is assigned by linear interpolation between reference points in the record for which the depth is known. We present a case where this approach did not work satisfactorily due to a fiber accumulation of unknown length between the reference points in the top and bottom of the well. The data we discuss were acquired using Silixa's iDAS technology retrofitted to previously installed fiber-optic cables. During installation, the cables were clamped to the tubing at each coupling between tubing sections. We found a pattern in the iDAS data that could be related to the clamping points. The pattern is particularly clear for frequencies in the 100–200 Hz band and may be caused by eigenmode vibrations set up by the clamping points. Based on this observation, a method for data-driven depth calibration was developed by matching the observed pattern to the clamp positions known from the tubing-tally information. An algorithm was designed to do the optimization. With regularly spaced clamps, several solutions are output, and some knowledge of the approximate depth is needed to pick the appropriate one. Our data-driven depth calibration was successfully applied to iDAS data from six wells.

A comparative analysis between conventional and new twelve sectors direct torque control strategies of induction machine using a multi level inverter

ABSTRACTthis paper presents a comparative analysis between conventional twelve sectors direct torque control (12_DTC) and a new twelve sectors direct torque control (12_DTC_3L) using a neutral clamped point (NPC) three level inverter. Those different strategies are compared by simulation in term of torque, flux and stator current performances. Finally, a summary of the comparative analysis is presented.

Large deflection of a cantilever beam with multiple geometric and/or material discontinuities under a concentrated end-point load

In this paper, large deflection problem of a discontinuous cantilever beam with multiple step changes in material and/or geometry is analyzed using elliptic integral method. The main objective is to solve the problem without using direct integration methods such as Runge–Kutta that is available to solve ordinary differential equations. The considered beam is assumed to be made of a linear elastic material with an external vertical load at the free end. At first, differential equations governing the behavior of a cantilever beam with one step change are presented. Then, considering the boundary conditions at the free end, the clamped point and the discontinuity point, two relations which represent the horizontal and vertical coordinates of any point along the neutral axis of the beam are obtained. The presented formulations are extended for the cantilever beams with arbitrary numbers of step changes in geometry and/or material. The accuracy of the obtained results for beams with one and two step changes in the material and geometry are verified using finite element results. The presented formulations can be used for modeling and optimization of structures that consist of step change beams.

A Closed Loop Current Control of PV-Wind Hybrid Source Fed Grid Connected Transformerless Diode Clamped-Multi Level Inverter

This paper presents a closed loop grid current control of Solar PV-Wind hybrid source fed split inductor based DC-MLI. Renewable energy sources generate significant proportion of global energy demand and will be the focal point of power generation by the turn of a few decades. Hybrid systems integrate the standalone efficiencies of PV and Wind generation to complement and reinforce individual output. A Diode Clamped or Neutral Point Clamped three level inverter reduces switching stresses and is apt for medium voltage high power applications. Space Vector PWM control of inverter reduces harmonic distortion besides eliminating neutral point fluctuation, capacitor balancing problem and common mode voltage reduction. It provides switching states for the inverter based on location of a space vector using reference voltage from grid. Using closed loop control the total harmonic distortion in grid current was reduced. The simulation and experimental results of the proposed renewable hybrid system were verified using Matlab/Simulink and FPGA.

Measurement of energy gaps in superconductors by means of quantum interference devices

The effect of temperature on the form of discrete changes in the current in highly inductive (~10-6 H) doubly-connected superconductors with niobium-niobium clamped point contacts is determined experimentally. The magnitude and duration of the voltage pulse on a doubly-connected superconductor is measured at the time of the discrete change in its current state. The pulse magnitude is close to the energy gap 2D/e of the superconductor and its duration (~10-6 s) corresponds to the minimum possible time (~10-12 s) for a change in the state of the contact when the depairing current through it is reached. The measurement data are discussed in terms of models of the quantum interference of currents in a doubly-connected superconductor with clamped point contacts in the form of a quantum interferometer.

A high stability and repeatability electrochemical scanning tunneling microscope.

We present a home built electrochemical scanning tunneling microscope (ECSTM) with very high stability and repeatability. Its coarse approach is driven by a closely stacked piezo motor of GeckoDrive type with four rigid clamping points, which enhances the rigidity, compactness, and stability greatly. It can give high clarity atomic resolution images without sound and vibration isolations. Its drifting rates in XY and Z directions in solution are as low as 84 pm/min and 59 pm/min, respectively. In addition, repeatable coarse approaches in solution within 2 mm travel distance show a lateral deviation less than 50 nm. The gas environment can be well controlled to lower the evaporation rate of the cell, thus reducing the contamination and elongating the measurement time. Atomically resolved SO4(2-) image on Au (111) work electrode is demonstrated to show the performance of the ECSTM.

Influence of Clamping Systems during Milling of Carbon Fiber Reinforced Composites

Carbon fiber reinforced composites (CFRP) are mostly manufactured near net shape. Nevertheless, a final milling step at the edges of the cured components is still necessary. Damages which occur during milling or drilling of CFRP lower the durability of the components and increase the production costs. Requirements concerning the clamping system for milling or drilling CFRP are rising simultaneously with increasing complexity of the components. This stresses the need for complex clamping systems like linear clamping jaws around the whole workpiece. However such types of clamping systems induce poor accessibility to the component being worked on and hence longer machining time. As a result to the need for complex clamping systems, the production costs are increased. Therefore, several benefits can be achieved by increasing the distances between the clamping points of the clamping system to reduce machining time and production costs. This paper discusses investigations of milling tests with variable clamping conditions of the workpieces. In the experiments a linear milling operation the edge of the workpiece is examined. The clamping of the planar specimens was realized with a clamping system which enables the adjustment of different distances between the clamping points of the specimen. The process forces and the resulting damage at the workpiece surfaces were measured during the experiments. These results are compared with a linear clamping system to examine the influence of rising clamping distances. The results demonstrate that the distance of the clamping points while milling the edge of the workpiece has a significant influence on the process forces.

Mechanical Properties and Biological Interaction of Aortic Clamps: Are These All Minimally Invasive?

Although specifically designed aortic clamps are mainstay of minimally invasive cardiac surgery, so far, no comparative reports about their mechanical properties and interaction with the aortic wall have been reported. In this study, the generated force in the clamps' jaws and the biological response of the aorta after clamping are evaluated. The jaw force of five commercially available clamps [Geister, Cygnet, Cardiovision (CV) 195.10, CV 195.40, and CV 195.83] was assessed by clamping a 2.2-mm compression load cell with a dedicated computer universal serial bus interface at the proximal, the middle, and the distal site from the fulcrum. Biological response of the aortic wall was assessed in five minipigs (weight, 38-40 kg) that underwent thoracic aorta clamping and leakage point test. Immunohistochemistry and morphometric analysis were carried out for each aortic segment tested. Force generation pattern is peculiar of each clamp, being higher in the proximal and the middle portion and lower in the distal part. One clamp (Cygnet) exhibited homogeneous maximal force generation at all three sites. All clamps exhibited peculiar crushing artifacts. A variable degree of endothelial layer disruption occurred in all clamping tests; three clamps (CV 195.10, Cygnet, and Geister) had the lower amount of intact endothelium. The clamping force was not associated with the degree of endothelial disruption (P value was not significant). The choice of a clamp that is not only minimally invasive in design but also least traumatic will help avoid complications of aortic manipulation.

A piezo motor based on a new principle with high output force, rigidity and integrity: The Tuna Drive

We present a linear piezoelectric motor as simple as one piezoelectric scanner tube (PST) spring-clamping a central shaft at both ends with roughly equal clamping forces. The clamping points are aligned with ±X electrodes at one end and ±Y electrodes at the other end. Thus, the ±X (or ±Y) push-pull motions of the PST can cause the push-pull motions of the clamping points on the shaft (called push-pull rubbing), which reduces the total dynamic friction force at one (or the other) end of the PST. This new piezo motor advances one step by fast push-pull rubbing at one end while slowly retracting the PST followed by fast push-pull rubbing at the other end while slowly elongating the PST. Apart from the obvious advantages of simplicity, rigidity, integrity, etc., we will also show that this motor can produce a large output force, which we believe is because of the huge drop of the clamping friction force when the push-pull rubbing occurs.

Fabrication of tunable clamped–clamped microresonators in silicon (1 1 0)

We fabricated clamped–clamped resonators by anisotropic etching of silicon-on-insulator wafers with a (1 1 0)-oriented top layer. The geometry of the resonator and its clamping points is confined by silicon (1 1 1) planes. The slow etch rate of these planes yields low surface roughness and enables accurate control over the resonator dimensions, and thus over its resonance frequencies. Lateral resonators were fabricated and characterized, and the measured resonance frequencies match closely with the calculated values for stress-free silicon beams. The resonance frequency can be tuned by electrostatic forces exerted via gate electrodes. The described method enables the fabrication of high-aspect-ratio silicon resonators without the need for deep reactive ion etching.

Nanomachining and clamping point optimization of silicon carbon nitride resonators using low voltage electron beam lithography and cold development

The authors report the nanomachining of sub-20-nm wide doubly clamped silicon carbon nitride resonators using low keV electron beam lithography with polymethyl methacrylate resist and cold development. Methodologies are developed for precisely controlling the resonator widths in the ultranarrow regime of 11–20 nm. Resonators with lengths of 1–20 μm and widths of 16–280 nm are characterized at room temperature in vacuum using piezoelectric actuation and optical interferometry. Clamping and surface losses are identified as the dominant energy loss mechanisms for a range of resonator widths. The resonator clamping points are optimized using an original electron beam lithography simulator. Various alternative clamping point designs are also modeled and fabricated in order to reduce the clamping losses.

Automatic Planning Approach of Auxiliary Clamping Points of Rapid Fixture in Thin-Walled Parts

In order to solve the deformation of thin-walled parts when fixed by fixtures in the environment of examination, transport, welding, assembly and demonstration, the paper is based on automatic planning approach of main champing points in Rapid Fixture Design System and mainly focuses on auto-planning auxiliary clamping points of thin-walled parts in Rapid Fixture Design System and represents the layout of auxiliary clamping points to deal with the problem of easy deformation of thin-wall parts when under small stress environment, which establishes automatic planning approach of RP. Finally, the paper gives an example to verify the effectiveness of the approach. Achieve the goal of designing rapid fixture automatically, fast and efficiently and enhance the capacity of enterprises responding quickly to dynamic changes in the market.

Load Transfer and Recovery Length in Parallel Wires of Suspension Bridge Cables

A new simplified contact model aimed at capturing the load transfer and recovery length in parallel steel wires, commonly used in main cables of suspension bridges, is presented. The approach is based on placing elastic–perfectly plastic spring elements at the contact region between the objects. These springs have varying stiffness (Model I) or yielding (Model II) depending on their proximity to the clamping loads. Their stiffness or yielding is highest when they are closer to this force, and it decays when they are farther away from the clamp. This decayed behavior is assigned according to Boussinesq’s well-known solution to a point load (applied on a half space). Both models converge quickly compared with a full contact model and recover Coulomb friction law on a two-dimensional (2D) benchmark problem. Moreover, when the same properties are chosen for all springs (disregarding Boussinesq solutions), the models reduce to the classical shear-lag model, which for high clamping (point) loads gives inaccurat...