Dynamic Force Measurement Research Articles

Hydrodynamic force characterization and experiments of underwater piezoelectric flexible structure

The unsteady hydrodynamics of underwater flexible structures internally actuated by smart materials are drawing growing attention. In this study, the dynamic measurement and characterization of hydrodynamic forces acting on flexible structures actuated by macro fiber composites (MFC) are performed. A measurement system composed of a cantilevered transducer and a laser sensor is proposed for dynamically acquiring the induced hydrodynamic force. The parameter indexes of the measurement system are carefully determined to achieve the requirements of high resolution, high sensitivity and good anti-interference of the designed measurement system. Calibration experiments demonstrate the good measuring performances. Then, the relationship between the hydrodynamic force and the actuation frequency is explored using the data obtained from the designed measurement system. Moreover, by decomposing the measured hydrodynamic force, it is found that the added mass component shares similar behaviors with the hydrodynamic force, whereas the hydrodynamic damping component initially increases and then decreases across the explored ranges. Finally, manageable formulas for these components in the forms of hydrodynamic function are developed, and explicit expressions for the Morison’s formula are obtained. These findings are meaningful for the realization of flexible structures with the actuation of smart materials in marine applications.

Результаты оценки силового воздействия тяжеловесных и длинносоставных грузовых поездов на железнодорожный путь различными методами измерений

Objective: to assess the force effect of heavy and long-component freight trains on the railway track by various measurement methods: Schlumpf, influence matrices and the two-section method (PGUPS). Methods: measurements of the assessment of the force effect of heavy and long-component freight trains on the railway track were carried out using the Schlumpf methods, influence matrices and the two-section method (PGUPS). Results: it was found that measurements of vertical dynamic forces by three methods are well correlated with each other, and the Schlumpf method gives overestimated results when measuring horizontal transverse force. Practical importance: the two-section method can be recommended for measuring the force effect of both new and upgraded rolling stock on the railway track, as well as for operated rolling stock in order to identify defects and deviations on the rolling surface of the wheels

Steel-ball-type six-dimensional dynamic force measurement platform with fault-tolerant performance

To satisfy the requirement of dynamic vibration testing of aerospace equipment on the ground prior to orbiting in space to guarantee the stable functioning of precision components, a steel-ball-type dynamic force measuring platform is suggested. First, based on two traditional platforms, a novel dynamic force measuring platform with fault-tolerant function, higher load capacity, and higher fundamental frequency is proposed, with its fault-tolerant measurement method theoretically deduced. Next, the study focuses on improving the measuring performance of redundant platforms by transforming conventional hard-connected branches into steel-ball branches. The structural parameters of these branches are examined theoretically, and simulations are used to confirm the theory's accuracy. Ultimately, the prototypes of the redundant steel-ball and hard-connected platforms are fabricated. Comparative experiments demonstrate that the steel-ball platform has superior performance, with static and dynamic measuring errors of 1.2% and 2.3%, respectively, and static and dynamic average coupling errors of 0.3% and 1.5%, respectively. The fault-tolerance function's validity is also confirmed.

Prediction Technique and Measuring Device for Coupled Disturbance Forces from Large Equipment in the Spacecraft.

To guarantee the accuracy of sophisticated equipment in spacecraft, it is essential to evaluate the dynamic forces of vibration sources. In contrast to conventional rigid-based measuring approaches, a method for predicting the interference of dynamic forces from large sources on spacecraft considering vibration coupling is proposed. In addition, a flexible-based dynamic force measuring platform capable of withstanding large masses and mounting large-volume vibration sources is designed. After that, the experiments for calibrating the platform and acquiring unknown terms in the derived theoretical models are detailed. The principle prototype is then manufactured for feasibility verification. It is demonstrated that despite the low fundamental frequency of the measuring platform of 242.8 Hz, the measurement error of the flexible measuring platform is less than 8% when the coupling is taken into account, which is 29% lower than that without coupling. Additionally, the prediction error of disturbance forces is within 17%. As a result, the accuracy of the proposed dynamic force measurement and prediction of large vibration sources considering coupling is substantially improved, providing a good reference for aerospace applications.

Dynamic test of the continuously variable weak force by a torsion pendulum with pre-applied stress

High-precision, continuously variable weak force testing is required for high-precision drag-free control with micro-thrust of spacecrafts, which is a key technology for space gravitational wave detection programs, such as TianQin, LISA, and Taiji. The continuously variable micro-thrust range is 0.1∼100μN, and the noise is below 0.1 μNHz−1/2 from 10−4Hz to 1 Hz. The torsion pendulum is considered as the most classical weak force measurement tool. However, the large response of non-sensitive modes makes it unsuitable for dynamic weak force measurements. In this study, a dynamic test system is developed for continuously varying weak forces using a torsion pendulum. We pre-applied a stress to the torsion pendulum using a double wire structure, which can effectively reduce the interference of other modes, and used feedback control to improve the stability. The evaluation results obtained using the external continuously variable electrostatic force indicate that the measurement range of the system covers 100 μN, the response time is approximately 1.6 s, and the noise is below 0.1 μNHz−1/2 from 0.9×10−4Hz to 1.4 Hz, which can meet the requirements of the micro-thrust test in space gravitational wave detection missions.

SIGLEC-5/14 Inhibits CD11b/CD18 Integrin Activation and Neutrophil-Mediated Tumor Cell Cytotoxicity.

Since the successful introduction of checkpoint inhibitors targeting the adaptive immune system, monoclonal antibodies inhibiting CD47-SIRPα interaction have shown promise in enhancing anti-tumor treatment efficacy. Apart from SIRPα, neutrophils express a broad repertoire of inhibitory receptors, including several members of the sialic acid-binding receptor (SIGLEC) family. Here, we demonstrate that interaction between tumor cell-expressed sialic acids and SIGLEC-5/14 on neutrophils inhibits antibody-dependent cellular cytotoxicity (ADCC). We observed that conjugate formation and trogocytosis, both essential processes for neutrophil ADCC, were limited by the sialic acid-SIGLEC-5/14 interaction. During neutrophil-tumor cell conjugate formation, we found that inhibition of the interaction between tumor-expressed sialic acids and SIGLEC-5/14 on neutrophils increased the CD11b/CD18 high affinity conformation. By dynamic acoustic force measurement, the binding between tumor cells and neutrophils was assessed. The interaction between SIGLEC-5/14 and the sialic acids was shown to inhibit the CD11b/CD18-regulated binding between neutrophils and antibody-opsonized tumor cells. Moreover, the interaction between sialic acids and SIGLEC-5/14-consequently hindered trogocytosis and tumor cell killing. In summary, our results provide evidence that the sialic acid-SIGLEC-5/14 interaction is an additional target for innate checkpoint blockade in the tumor microenvironment.

Structural optimization and dynamic calibration for load sharing dynamic force measurement platform based on MIGA and SVR

In order to quantify dynamic forces/moments on the ground, a high-performance platform is necessary. This article improves the performance of the measurement platform from both structure and calibration. The platform’s loading capacity and base frequency have been significantly increased by the introduction of an innovative load sharing ring, which also allows the platform to have other important and practical characteristics. Further improvements in platform performance are then achieved by optimizing the platform parameters using a multi-island genetic algorithm (MIGA). In addition, the calibration method is improved. The maximum relative error and cross-coupling error for the novel non-linear support-vector-regression-based (SVR) method are 3.42% and 6.54%, respectively, which are much superior than the 9.98% and 15.39% for the traditional linear least-squares-based (LS) calibration method, indicating better accuracy and decoupling performance of the SVR-based dynamic calibration. This has important implications for measuring dynamic forces and improving the stability of equipment in spacecraft.

Density and Viscosity of Linear Siloxanes and Their Mixtures

Density and viscosity measurements are performed for ethanol, water, hexamethyldisiloxane (MM), octamethyltrisiloxane (MDM), decamethyltetrasiloxane (MD2M), and their mixtures (ethanol/water, MM/MDM, MM/MD2M, MDM/MD2M) at 100 kPa at different temperatures (293–423 K) and mixture compositions. To measure the density and viscosity, an IMETER measuring system with a combined dynamic and static force measurement method, a density meter with an oscillating U-tube measuring method, and a rheometer with a double-gap measuring system were used. The experimentally determined data for the pure substances show a very good agreement with literature data. However, there is a strong deviation of the mixture viscosity between max 7% for MM/MDM and 31% for MM/MD2M compared to Refprop v.10.0. In order to enable an improvement in the calculation of the density and viscosity for the mixtures, specific parameters for the Jouyban–Acree model are developed for all mixtures and thereby, a better description of the density and viscosity for the mixtures could be achieved.

Design and optimization of a quadrupedal dynamic disturbance force measurement platform using strain gauges

A novel quadrupedal dynamic disturbance force measurement platform is described for the measurement of the disturbance forces of low-frequency sources in large optical facilities on the ground. The support of four strain monopodia makes the measuring platform more rigid. The optimal structural parameters of the strain monopodia are obtained adopting response surface methodology, which allows the sensitivity and stiffness of the platform to be balanced. D optimization is adopted to obtain a more accurate calibration matrix from the redundant outputs and thus improve the measurement accuracy of the platform. Model simulation results show that the load capacity of the measurement platform is more than 1000 kg. Using the results of theoretical analysis, a prototype system was fabricated and tested. The experimental results show that the fundamental frequency of the platform is 749.5 Hz, the dynamic relative error is less than 5.6 % in the frequency range of 3–300 Hz, and the static relative error is less than 5 %. The linearity of the generalized force is within 1.5 %FS, and the repeatability is within 1.1 %FS.

Micro-vibration modeling and analysis of single-gimbal control moment gyros

Micro-vibration modeling and analysis of single-gimbal control moment gyros (SGCMGs) are conducted in this study. Considering the rotation and support effect of the low-speed gimbal, a nonlinear time-varying dynamic model for micro-vibration analysis of an SGCMG is established using the energy theorem. By considering the Hertzian contact, elastohydrodynamic lubrication, and surface waviness, the nonlinear supporting forces and moments of the angular contact ball bearings on the high-speed rotor and low-speed gimbal are derived, and accordingly, an iterative solution method is proposed. Based on a three-axis dynamic force measurement platform, the dynamic characteristics of a real SGCMG are tested to verify the rationality of the proposed micro-vibration model. Subsequently, the effects of unbalance mass, surface waviness amplitude, gimbal lock angle, and rotation angular speed of the gimbal on the three-axis gimbal bearing transmission forces are discussed. The findings of this study provide insights for clarifying the micro-vibration characteristics and provide a theoretical basis for the working state design and structural optimization of SGCMGs.

Dynamic Measurement of Patellofemoral Compression Forces: A Novel Method for Patient-Specific Patella Resurfacing in Total Knee Replacement

Functional dissatisfaction following total knee replacement (TKR) is recorded as high as 20%. The majority of these patients report anterior knee pain (AKP) as the main source of dissatisfaction. Elevated patellofemoral compression forces and soft tissue extensor hood strain have been implicated in the generation of significant AKP. A novel method of assessing and measuring patellofemoral compression forces dynamically in the native and resurfaced patella for TKR in four different quadrants of the patella is described. Results are reported from an in vitro model and cadaveric studies in the native and resurfaced knee. Patellofemoral compression forces are shown to be characteristic and consistent over repeated assessments in the native knee. Placement of a TKR significantly alters this pattern. Furthermore, over-stuffing or under-stuffing the resurfaced patella also significantly alters the nature and magnitude of patellofemoral compression forces. These studies may lead to an improved understanding of the nature of AKP following TKR, and using this assessment tool presents an opportunity to more effectively balance the third space, reproduce the native patellofemoral forces, and subsequently reduce AKP following TKR.

Experimental Investigation on Jet Vector Deflection Jumping Phenomenon of Coanda Effect Nozzle

The Coanda effect nozzle is a fluid thrust vectoring technology that uses the Coanda effect to control jet vector deflection. The jumping phenomenon often occurs in the process of controlling jet vector deflection. This phenomenon leads to the nonlinearity of thrust vector control. It destroys the control performance of the aircraft and brings potential dangers to the safety of the aircraft. The jumping phenomenon occurs in an unsteady flow field different from the traditional flow phenomenon. The flow structure in an unsteady flow field changes with time, so it is not easy to control by the traditional active flow control method. This paper explains the reasons for the jumping phenomenon from two aspects: flow field stability and flow structure. Secondly, the unsteady flow field with the jumping phenomenon is studied and analyzed by a flow visualization experiment and dynamic force measurement. Furthermore, the dynamic modal decomposition (DMD) method is used to extract the characteristic frequencies of the critical vortices causing jets to jump in unsteady flow fields. Finally, a pulsed jet with the same characteristic frequency is used to control the varying vortices in the unsteady flow field. The experimental results show that the active flow control method, which extracts the characteristic frequency of the critical flow field structure by DMD, effectively suppresses the jumping phenomenon in the unsteady flow field. It also linearizes the process of jet nonlinear vector deflection.

Dynamic force measurement to assess NVH performance of electric motors

The electromagnetic (EM) force induced motor whine is a major noise source of hybrid and electric vehicles. Experimental quantification of dynamic EM force is highly desirable to assess the NVH performance of electric motors. However, it is difficult to measure EM forces directly on the stator teeth. This paper describes a new indirect method to measure the dynamic forces at stator mounting ear locations. First, high-precision tri-axial piezoelectric force ring sensors are selected and calibrated to measure dynamic forces under compressive mean loading. Next, special motor housings are designed and built to accommodate force sensors between the stator ears and the base mounting plate. Force sensors are then aligned with the stator circumferential directions to measure dynamic forces in radial, tangential and axial directions as a function of motor torque and speed. The new technology is successfully implemented for electric motors of GM's Spark and Bolt EVs. Measured dynamic forces correlate well with finite-element analytical results and show consistent trends with noise and vibration responses. This confirms the dynamic mounting force can be used as an effective and measurable indicator to optimize NVH designs for electric motors.

Aerodynamic Metrologists Guide to Dynamic Force Measurement

Static aerodynamic force measurement is generally of interest in both low- and high-speed ground test facilities, but dynamic force measurement is typically associated with higher-speed facilities. This work will show that dynamic force measurement is relevant to all aerodynamic metrologists because wind tunnel system dynamics can change the force transducer’s dynamic sensitivity resulting in differences between the static and dynamic sensitivity. In addition, the field of dynamic force measurement will be introduced using realistic wind tunnel scenarios, wherein the wind tunnel system dynamics contribute to increased uncertainty in what would otherwise be considered a static force measurement. A design approach focused on estimating the dynamic response is presented to achieve measurement objectives through the use of static force measurement techniques where possible. To that end, a reduced-order model is developed to characterize the dynamic response of the system, which can serve as a predictive tool in the design process. Then, strategies for characterizing wind tunnel system dynamics to determine acceptable bandwidths wherein the static measurements may be sufficient are discussed. In the event that systems have undesirable dynamic characteristics, which cannot be avoided in the design process, two dynamic compensation techniques to correct the measured signals are discussed.

Experimental investigation of flow control of a curved-surface jet at Mach 5 hypersonic flow

Jet flow-control technology is a promising area of fluid research. In this work, the flow-control effect of a curved-surface jet in an incoming flow of Mach = 5 and its underlying control mechanism are experimentally studied using high-speed photography and dynamic force measurement. From the establishment of complete stability of the flow field, the evolutionary process can be roughly divided into five stages: two equilibrium stages (short and long term), jet acceleration stage, bow shock formation stage, interference removal stage, and stable state. By defining the pressure ratio (PR) as an independent variable, it is found that the flow control of the jet occurs through different wave-system structures. The interaction between the jet and the incoming flow produces an oblique shockwave and expansion waves. The shockwave generates thrust and forms a virtual rudder surface; the expansion waves interact with the backflow region and the separated shear layer to generate lift. Moreover, PR has an optimal solution of PRopt. When PR < PRopt, the effect of flow control is related to α, Ve, and ρe, and the greater the PR, the stronger the flow-control effect. When PR > PRopt, the flow-control effect is related to α and ρe, and the larger the PR, the weaker the effect of the shockwave and the stronger the effect of the expansion waves but the slower the growth. In experiments, the thrust, pitching moment, and lift increased by 17.43%, 17.75%, and 9.45%, respectively, because of the appearance of wave-system structure when PRopt = 201.32.

A dynamic disturbance force measurement system based on array sensor for large moving device in spacecrafts

The control of micro-vibrations is an increasingly significant aspect of the research related to high-precision equipment in spacecraft. As the scale and mass of these vibration sources become larger, the control precision required also increases, and the requirements for the vibration source ground test equipment are thus becoming more demanding. This paper therefore proposes a generalized disturbance force measurement system for large device vibration sources. The use of a redundant array of piezoelectric sensors can significantly increase the size, load capacity and stiffness of the platform. In addition, the D-optimal designs used by the system overcomes the redundant measurement errors introduced by array-based measurements. Based on the above, a more accurate 3D force decoupling expression is obtained using the linear decoupling algorithm of the full regression method. A system prototype is then designed and tested based on the results of this approach. Experimental results show that the system guarantees high load capacity (416 kN) and stiffness, the dynamic relative error within the 8–800 Hz frequency range is less than 3% for a 3D generalized force in the force hammer test, and the relative error of the test system under sinusoidal excitation is within 5%; additionally, the linearity for generalized forces over the full range is within 0.1% full scale and the results are not affected by the characteristics of the measured object.

Operational Modal Analyses of Brush Seals and Seating Load Simulations

Abstract Brush seals are one of the most effective sealing technologies in turbomachinery since they enable contact-type operation for close clearance control. Brush seal bristles must interact under turbine conditions, and the minimum pressure load to initiate proper contact between fibers is called seating load. Seating load evaluation is essential for the durability and stability assessment of bristles since unseated fibers may flutter and cause seal failure. Even with proper seating, brush seal critical modes may still be excited by flow-induced fluctuations or bucket tip excitations. In this study, a finite element-based methodology was developed to determine the seating load and identify the critical modes of brush seals. Under pressure load, brush seal nonlinear contact simulations are followed by frequency-based analysis to determine bristle and seal pack critical modes. To determine the seating load of the brush seal, the change in modal response is examined. In this paper, the modeling methodology, parameter correction procedures, geometric inspection of test seals, correlation of transient analyses with dynamic tip force measurements, operational modes of brush seals and seating load evaluation methods are detailed.

Theoretical study on the sensitivity of dynamic acoustic force measurement through monomodal and bimodal excitations of rectangular micro-cantilever

We present a detailed analysis on measurement sensitivity of dynamic acoustic forces via numerical simulation of the micro-cantilever responses. The rectangular micro-cantilever is regarded as a point mass in the dynamic model of forced and damped harmonic oscillator. We use single- and bimodal-frequency excitation schemes for actuation of the micro-cantilever in the presence of dynamic acoustic forces. In bimodal-frequency excitation scheme, the micro-cantilever is excited at its first two eigenmode frequencies simultaneously as opposed to single-frequency excitation. First, we numerically obtain micro-cantilever deflections by solving the equations of Motions (EOMs) constructed for the first two eigenmodes. Then, we determine oscillation amplitude and phase shift as a function of acoustic force strength within different frequency regions. Moreover, we relate amplitude and phase shift to virial and energy dissipation in order to explore the interaction between flexural modes in multifrequency excitation. The simulation results point out that bimodal-frequency excitation improves the measurement sensitivity of dynamic acoustic forces at particular frequencies. Herein, simultaneous application of driving forces enables higher sensitivities of observables and energy quantities as acoustic force frequencies become around the eigenmode frequencies. For our case, we obtain the highest phase shift (∼178°) for the acoustic force strength of 100 pN at the frequency of around 307.2 kHz. Therefore, this method can be easily adapted to improve measurement sensitivity of dynamic acoustic forces in a wider frequency window.

Development and implementation of a dynamic force measurement system for automatic tool changer system and drawbar mechanism in machining center

Automatic tool changer system (ATCS) and drawbar mechanism (DM) are two of key basic parts for realizing the automatic tool-changing cycle in machining centers. The dynamic force in a tool-changing cycle plays an essential role in condition monitoring, fault diagnosis, and failure warning for the ATCS and DM. However, existing force detection systems have limitations in practical application. In this paper, a novel dynamic force measurement system (DFMS) is developed, which is based on a force sensing element installed on the BT40 tool holder and operating through a wireless network. The force sensing element is used to convert the dynamic force into the electrical signal. Digital measurements are collected from the 24-bit sigma-delta analog-to-digital converter with a programmable gain array, which then are transmitted to the upper computer software via a wireless transceiver. Besides, a Teager energy operator based dual-threshold two sentences endpoint detection method is proposed to recognize the temporal onset and offset of each force event in the dynamic force recording. Experimental results show that the DFMS is reliable and suitable to measure the dynamic force in automatic tool-changing cycles.

Virial and Energy Dissipation in Measurement of Dynamic Acoustic Forces Using Bimodal-frequency Excitation of Micro-cantilever Array

Virial and energy dissipation, related to oscillation observable responses, possess complementary information regarding acoustic force measurements. In this paper, we introduce a mathematical framework describing the analytic relationship between oscillation observables and energy quantities at the second eigenmode in the measurement of dynamic acoustic forces. We utilize a bimodal-frequency excitation scheme for actuation of the micro-cantilever array to obtain high-sensitivity frequency bands. Herein, we analyze the virials of acoustic force interaction and the energy dissipation levels on the domain of acoustic force frequency. For our case, we obtain the high-frequency bands of around 200-270 kHz and 440-570 kHz for the force strengths in the range of 4.0-36.0 pN. In addition, results of virials and dissipated power with respect to acoustic force strengths are introduced for low- and high-sensitivity frequency regions. Therefore, the energy quantities can be robustly utilized to determine high-sensitivity frequency windows in the measurement of dynamic acoustic forces.