Force Measurement System Research Articles

Design, calibration and validation of a wheel-rail contact force measurement system in V-Track

An innovative downscale test rig called V-Track has been constructed for wheel-rail contact experiments under impact loading conditions. In this paper, a force measurement system termed a dynamometer was developed in V-Track to measure the wheel-rail contact forces. The dynamometer consists of four 3-component piezoelectric force sensors and was mounted between the wheel assembly and the steel frame of V-Track, enabling it to measure the forces transmitted from the wheel-rail interface to the frame. Static tests were first carried out to calibrate the dynamometer in three directions. Then, several tests were performed in V-Track to examine the reliability and validity of the dynamometer for measuring the wheel-rail contact forces under running conditions. Experimental results show that the dynamometer is capable of reliably and accurately measuring these forces. Utilizing the measurement results from the dynamometer, the control of the wheel-rail contact forces in V-Track has also been achieved.

Experimental Investigation on Frost Heaving Force (FHF) Evolution in Preflawed Rocks Exposed to Cyclic Freeze-Thaw Conditions

This work is aimed at investigating the structural deterioration and the frost heaving force evolution characteristics of flawed rocks using a self-developed frost heaving force (FHF) measurement system. Three kinds of preflawed rocks with different flaw geometry parameters were used to conduct the FHF measurement tests. The testing results reveal five distinguished stages from the frost heaving force evolution curve; they are the inoculation stage, explosive stage, decline to steady stage, recovery stage, and sudden drop stage. In addition, a secondary frost heaving phenomenon is found, and the secondary peak value is lower than the initial peak value. Moreover, the FHF decreases with increasing the F-T cycle number, and its decreasing rate becomes faster at a high F-T cycle. The frost heaving force is affected not only by flaw geometry but also by the lithology. For low-pore hard rock, damage propagates quickly after the occurrence of freeze-thaw damage. It is suggested that the mesoscopic structure of rock affects the water migration and water-ice phase transformation, and rock can be fractured by FHF in the preexisting flaws.

Assessment of the possibility of using GPR to determine the working resistance force of tools for subsoil reclamation

The article presents a study on the determination of working resistance force of a tool that reclaims the topsoil based on GPR research. The experiment used a strain gauge force measurement system in a three-point linkage suspension system of the tool on a tractor with automatic registration of other operating parameters of the unit at a frequency of 10H. For the research with the use of GPR, a shielded antenna with a frequency of 800 MHz was used, allowing to obtain a wavelength of 0.12 m and a resolution of 0.03 m. The tests were carried out for several combinations of soil compaction, which was initially measured with the Eijkelkamp cone penetrometer. A large convergence of the results of the working resistance forces was found with the indications of the states of excessive compaction identified in the space of the echogram. It should be noted that the convergence of the measurement results increases with the degree of soil compaction. Therefore, it is possible to estimate the energy consumption of cultivation treatments on the basis of non-invasive GPR surveys and selective soil reclamation treatment with degraded subsoil.

Cantilever-based micro thrust measurement and pressure field distribution of biomimetic robot fish actuated by macro fiber composites (MFCs) actuators

Underwater autonomous vehicles (UAVs) actuated by smart actuators have attracted increasing attention. A miniature macro fiber composite (MFC)-actuated robot fish inspired by koi fish is developed. A cantilever mechanism is designed to transfer the dynamic micro thrust of the robot fish. Three design indexes, namely the bending stiffness, the ratio of the bending stiffness to the torsional stiffness, and the natural frequency of the cantilever transducer are proposed. Thus, a simple and effective method to determine the structural parameters of the cantilever-based micro thrust force measurement system is presented. Calibration results demonstrated that the parameters of the proposed cantilever transducer match well with the designed indexes. Dynamic variation mechanisms of the micro thrust force associated with the swimming behaviors of the robot fish are well captured using the proposed measurement system. Experimental results show that the MFC-actuated robot fish obtains the biggest mean thrust of 1.73 mN in the case of the largest oscillating velocity. The maximum instant thrust grows with the increment of the oscillating frequency, and achieves its maximum of 7.35 mN in the case of 10 Hz. While the maximum instant drag first decreases then increases as the actuation frequency increases, and obtains its minimum of −2.62 mN in the case of the maximum oscillating velocity. On the contrary, variations of the thrust pattern/oscillating period are reversed to those of the maximum instant drag. Computational fluid dynamics results demonstrate that variations of the instant thrust are fully determined by the distribution and intensity of the concentrated pressure regions induced by the oscillating caudal fin. The cycle-averaged velocity fields are closely related to the mean thrust generated by the MFC-actuated robot fish. As a result, the fluid–structure interaction mechanisms associated with the thrust variations of the MFC-actuated robot fish are revealed. This study may be useful for the design and realization of UAVs actuated by smart actuators.

Non-Invasive Force Measurement Based on Magneto-Elastic Effect for Steel Wire Ropes

Force measurement on steel wire rope (SWR) is significant to ensure the safety of people and property. Previous methods propose the electro-magnetic sensor, which measures the force applied on the SWR non-invasively and does not damage the structure of the SWR. Based on the magneto-elastic effect and integration of induction voltage as the indicator, electro-magnetic sensors perform well in many situations. However, in practice, the integration of induction voltage method is noise-sensitive, because the noise is easily accumulated by integration in the practical environment. In this case, we propose an improved method based on a novel indicator, maximal induction voltage. The maximal induction voltage method is influenced less by noise, as no integration of noise term is involved, so the maximal induction voltage method has better performance on noise reduction. Moreover, the paper builds a force measurement system by deriving the analytical linear relation between force and maximal induction voltage, and this linear relation can be estimated by prior experimental data. The experimental results show that the proposed method has higher linearity and sensitivity than the integration of induction voltage method.

Design and Calibration of a Tri-Directional Contact Force Measurement System

In low pressure turbine stages, adjacent blades are coupled to each other at their tip by covers, called shrouds. Three-dimensional periodic contact forces at shrouds strongly affect the blade vibration level as energy is dissipated by friction. To validate contact models developed for the prediction of nonlinear forced response of shrouded blades, direct contact force measurement during dynamic tests is mandatory. In case of shrouded blades, the existing unidirectional and bi-directional contact force measurement methods need to be improved and extended to a tri-directional measurement of shroud contact forces for a comprehensive and more reliable validation of the shroud contact models. This demands an accurate and robust measurement solution that is compatible with the nature and orientation of the contact forces at blade shrouds. This study presents a cost effective and adaptable tri-directional force measurement system to measure static and dynamic contact forces simultaneously in three directions at blade shrouds during forced response tests. The system is based on three orthogonal force transducers connected to a reference block that will eventually be put in contact with the blade shroud in the test rig. A calibration process is outlined to define a decoupling matrix and its subsequent validation is demonstrated in order to evaluate the effectiveness of the measurement system to measure the actual contact forces acting on the contact.

Measurement and Modeling of Contact Forces during Robot-guided Drag Finishing

Robot-guided drag finishing is a free abrasive grinding operation that is used for polishing and deburring of workpieces with complex shaped geometries. The workpiece is attached to a robot and moved through a bulk of abrasive particles. The motion of abrasive particles during contact with the workpiece is the basis of the material removal mechanisms. To investigate the motion of abrasive particles during contact, a force measurement system was used to determine contact forces. The experimental setup was replicated in a numerical simulation based on the discrete element method (DEM). Based on the comparison of experimental and simulative results the qualitative validity of the DEM model was concluded. With the presented DEM model, the characteristic particle behavior during contact with the workpiece can be modeled which allows the prediction of resulting processing marks. Consequently, the DEM model can be used to design free abrasive grinding operations without using the time and cost intensive trial and error approach.

Setting up the braking force measurement system of the tractor semi-trailer

The braking force of the tractor semi-trailer depends on many random factors and road parameters. Therefore, determining the braking force based on theoretical calculation or simulation is not accurate. This paper presents the method of setting up the braking force measurement system of the tractor semi-trailer on the road and constructing the braking dynamics model of the tractor semi-trailer to investigate the braking force using Matlab-Simulink software. The study results show that the average error between the simulation and experimental results of the tractor semi-trailer braking force is 9,81%.

Evaluation of the Wearable Ground Reaction Force Measurement System for the Rehabilitations of the Lower Limb Fractured Patients

Evaluation of the Wearable Ground Reaction Force Measurement System for the Rehabilitations of the Lower Limb Fractured Patients

Pressure conditions during the immersed tumbling process

An approach to improve the tool wear behaviour of milling tools made of cemented carbide is a defined cutting edge preparation usingthe immersed tumbling process. One significant factor that influences cutting edge preparation is the effective pressure generated by the relative movement of the cutting tools and the abrasive particles. However, the development and influence of the process pressure has been discussed almost exclusively based on machining and preparation results. For a profound process understanding a wireless force measurement system was designed and the pressure forces of two media were examined. The influences of the used lapping media, the velocityas well as the depth of immersion using a simplified linear movement were analysed. The results provide information about the pressure conditions that change in the real process.

Research and application of an improved internal thrust force measurement system for rock and soil mass based on OFDR

Internal thrust force of unstable rock and soil mass is an essential parameter for prediction of many geological hazard. Currently, fiber bragg grating (FBG) and optical time-domain reflectometer (OTDR) are widely used to measure internal stress of unstable rock and soil mass. However, these methods have disadvantages such as low spatial resolution and the paucity of distributed measurements. This paper develops a quasi-distributed thrust measurement system based on an optical frequency domain reflectometer (OFDR). Firstly, we design an optical fiber stress sensor head using the characteristics of the optical fiber microbending effect. And then, the cubic spline interpolation method is used to compensate for the nonlinear effects of the OFDR. Finally, we implement a laboratory experiment of lateral stress to make error calibration. As a result, the OFDR sensing system achieved a spatial resolution of 20 cm by using a 500 m test fiber, maximum measurement pressure reached 1.059 MPa and relative error is 8.9%. We implemented OFDR in the Chenjiagou landslide located at the Three-Gorge of Chongqing in China. The results showed that this system can accurately locate six fiber stress sensors within the landslide over a range of 0 ∼ 420 m, obtaining the lateral thrusts as well.

Investigations on nonlinear deformation phenomena in a force calibration system

Previous investigations show, in force calibration and measurement systems that are based on electromagnetic force compensation (EMFC), deformations of the flexure hinges can cause significant contributions to the uncertainty of the system. A Simulink model of the Planck-Balance 2 (PB2) is established in MATLAB according to the CAD model. <br />The results are compared to simplified analytical models and the results obtained from measurement.

Practical investigation for the concept of a serial-type build-up force measurement system

This paper introduces a proposed design for the first Serial-type Build-Up System (S-BUS). The work includes the design and implementation of two S-BUS prototypes, the metrological characteristics of the prototypes were evaluated. The evaluation results prove the validity of the system practically. The paper also discusses the key differences between the Parallel Build-Up System (P-BUS) and the S-BUS, and what makes it important to study the S-BUS concept.

Levitation properties of pre-magnetized HTS tape stacks

This study presents new results on investigation of the levitation force between a permanent magnet and pre-magnetized HTS tape stacks containing from 20 to 100 tapes of 12 mm × 12 mm. Stacks were magnetized in superconducting magnet capable of creating a field of up to 8 T and placed in a levitation force measurement system. Experimental data on levitation force value and the effect of lateral displacement on it for stacks of tapes with different values of the captured flux and thickness have been obtained. Levitation force decay during the lateral displacements above a permanent magnet was observed for different stacks.

​The importance of occlusal force measurement in orthognathic surgery - A pilot study

Purpose: This pilot investigation was designed to apply several, newly developed and more sophisticated methods of measuring muscle structure and function in a situation where adaptation of muscle is pivotal to the success of a therapeutic approach. Materials and Methods: Patients attending the combined orthodontic/orthognathic surgery clinic at the Clitrofa – Centro Médico, Dentário e Cirúrgico, in Trofa - Portugal were tested according to the protocol of Bite force and occlusal contact area were simultaneously measured with Bite Training Machine and Occlusal Force Diagnostic System. An Experimental design used for the measurement of occlusal force. The study involved the contribution of two independent examiners that measured the bite pressure (psi) in five different FSS sensors at three different time moments. A combination of different parametric tests has been used to compare the different experimental variables. Results: Neither the variation of examiner, nor the variations of time have shown to influence the bite pressure (psi). In contrast, the occlusal force measurement system developed has shown a high level of sensitivity due to the distribution of the five FSS sensors in the horseshoe-shaped form. A three-pressure region model fits the experimental data shown in this study, comprising a low-pressure region located in the anterior part of the dental arch, a medium-pressure region in the medial part of the dental arch and an high-pressure region located in the posterior part of the dental arch. Conclusions: The piezoelectric sensors used in the present study have shown high reproducibility of measurement. Due to the recent miniaturization of FSS sensors, the authors are developing new occlusal force measurement systems comprising a higher number of piezoelectric sensors, with the objective of attaining even higher sensitivity of measurement throughout the different region of the dental arches.

Voltage- and Current-Measurement Based Force Estimation in Broaching Using Synchronous Motor Drive

Monitoring the cutting force in broaching provides valuable information about the tool condition as well as the effect of the process on the workpiece surface integrity. This study uses a synchronous-motor-drive broaching machine and deals with the motor-current based indirect-measurement of the cutting force, which is based on detecting the variation of the motor torque during cutting. Most current-based methods need to model the relationship between the motor current and the cutting force. However, when the feed drive mechanism is modeled to obtain this relationship, modeling errors occur. For accurate modeling, a calibration test using a force sensor is necessary before performing the indirect-force measurement. Therefore, this study focuses on the energy conversion from electrical power to mechanical power, and it identifies this relationship based on the voltage equation of the drive motor by using not only current measurement but also voltage measurement. Then, a developed model with the identified relationship calculates the cutting force, excluding electrical and mechanical losses that do not contribute to the process. By conducting a tool-wear test in broaching of Inconel 718, a possible application of the indirect force measurement system was demonstrated.

Intelligent Force-Measurement System Use in Shock Tunnel.

The inertial vibration of the force measurement system (FMS) has a large influence on the force measuring result of aircraft, especially on some tests carried out in high-enthalpy impulse facilities, such as in a shock tunnel. When force tests are conducted in a shock tunnel, the low-frequency vibrations of the FMS and its motion cannot be addressed through digital filtering because of the inertial forces, which are caused by the impact flow during the starting process of the shock tunnel. Therefore, this paper focuses on the dynamic characteristics of the performance of the FMS. A new method—i.e., deep-learning-based single-vector dynamic self-calibration (DL-based SV-DSC) of an impulse FMS, is proposed to increase the accuracy of aerodynamic force measurements in a shock tunnel. A deep-learning technique is used to train the dynamic model of the FMS in this study. Convolutional neural networks with a simple structure are applied to describe the dynamic modeling so that the low-frequency vibration signals are eliminated from the test results of the shock tunnel. By validation of the force test results measured in a shock tunnel, the current trained model can realize intelligent processing of the balance signals of the FMS. Based on this new method of dynamic calibration, the reliability and accuracy of force data processing are well verified.

Direct Measurement of Contraction Force in Cardiac Tissue Construct in 2D-Plane Using Dual Axis Cantilever Sensor

In this work, we present a technique for a dual axis contraction force measurement of human cell based cardiac tissue constructs. The cardiac tissue constructs consist of a vascular-like network and induced pluripotent stem cell derived cardiomyocytes. Before the force measurements, the cardiac tissue constructs were detached from the culture substrate to allow less restricted contraction. The in-house prepared force sensors are composed of piezoelectric sensing elements and a metallic cantilever for contacting the cardiac tissue constructs. A dedicated measurement platform with embedded signal processing software is used for data acquisition from the sensors. Dual axis force sensor results are compared with our previously developed single axis force sensor technique. Additionally, the proposed dual axis force measurement system can measure two-dimensional displacement trajectories of the cantilever probe tip. We propose a pattern matching method for classification of the captured cardiac contraction cycle patterns and for extracting anomalies in the measured cycles. We demonstrate both single and dual axis peak cardiac construct contraction force measurement results in the ranges of 3.4 - $6.7~\mu \text{N}$ and 9.4 - $10.6~\mu \text{N}$ , respectively. The relative standard deviation of the peak contraction force results varied between 1.0 and 4.1% in eight captured 60 second measurement sequences.

Experimental Study on Bearing Capacity of Water Striders on Water Surface

The paper developed a measuring device which can measure bearing capacity of water striders on the water surface, the measuring range is 1-10000μN, the precision is 0.1μN. The device includes micro force measurement and feed movement control system, electronic balance and control system can communicate with upper computer through RS232C serial. Through testing determination, the smallest linear feed speed of the device is 1 mm/min, which can satisfy the measurement requirements. The experiment measured the maximum bearing capacity of 5 samples of water striders on the water surface, which is 23.6 times its body weight.

Impulse force-measurement system

Shock tunnels are important ground test facilities that can generate high-enthalpy flow. Flight velocity at a high Mach number can be simulated for aerodynamic testing of chemically reacting flows. However, the application of these tunnels is limited due to the only milliseconds-long test duration, especially for aerodynamic force measurement using traditional strain gauge balances. This study presents an impulse force-measurement system, which was used for a large-scale test model to measure its drag in a high-enthalpy shock tunnel with an approximately 3–7-ms test time. Force tests were conducted for a cone in the JF-10 high-enthalpy shock tunnel in the Institute of Mechanics, Chinese Academy of Sciences. An integrated design of the impulse force-measurement system was proposed for load measurement over a short duration, for which a recommended design criterion is that the measurement period be a minimum of twice the period corresponding to the lowest natural frequency of the measurement system. The current measurement technique breaks the limitations of the application of the conventional strain gauge balance. As an integrated measuring system, the impulse force-measurement system expands the structural design concept of strain gauge balances. The impulse force-measurement system performed well in the present tests. The test results show differences from the numerical simulations and some data obtained in a conventional wind tunnel. A preliminary analysis was performed on the real gas effects on the aerodynamic force.