Indirect Force Measurement Research Articles

Evaluation of Temperature-Dependent Boundary Lubrication Behavior of Stearic Acid Using a Force-Controlled Tribometer.

A quick evaluation of the effectiveness of additives is important in lubricant formulation. In this study, we employed a friction-force measurement approach using a newly designed lateral force-controlled tribometer. This tribometer evaluates the lubricant properties under boundary lubrication. In this lateral force-controlled tribometer, the absence of a stiffness-altering sensor enables the modeling of the actual contact conditions without altering the contact stiffness. Indirect friction force measurement ensures precise measurements of friction properties while avoiding common measurement errors encountered in conventional tribometers, such as sensor misalignment and changes in the stiffness of the machine due to the sensor. The tribometer designed and built consists of a pendulum that measures the rate of dissipation of the oscillation amplitude as a function of time. The unique characteristics of the machine are the possibility of changing the energy input into the tribosystem without altering the tribo-contact conditions and the capability to do experiments at higher temperatures. To evaluate the capabilities of this tribometer, the impact of temperature on the frictional properties of a base oil and a blend of base oil and stearic acid (SA) (a prominent Organic Friction Modifier) is investigated. The test result shows that frictional energy dissipation decreases when stearic acid is present in the lubricant. And, as the temperature of the oil increases, the energy dissipation increases for pure base oil but reduces for the blend. The observed frictional trends are attributed to the decrease in the viscosity of the base oil with an increase in the temperature. The decrease in friction for the SA blend is attributed to tribofilm formation. Fourier transform infrared (FTIR) and X-ray Photoelectron Spectroscopy (XPS) analyses confirm the presence of the SA tribofilm on the surface. XPS indicates an increase in tribofilm quantity with rising temperatures. The kinetics of film formation and thickness increase with temperature, consequently reducing the friction in the SA blend.

Indirect Force Measurement via Hamiltonian Monte Carlo-Based Probabilistic Model of FSR Sensor

Indirect Force Measurement via Hamiltonian Monte Carlo-Based Probabilistic Model of FSR Sensor

Analysis of Rowing Force of the Water Strider Middle Leg by Direct Measurement Using a Bio-Appropriating Probe and by Indirect Measurement Using Image Analysis.

Rowing force of the middle leg of a water strider is one of the important factors affecting water repellency and applications in biomimetics, biomechanics, and biology. However, many previous studies have been based on estimated leg rowing force and lack some credibility. Therefore, we tried to measure leg rowing force directly by a force transducer. In this article, we report the rowing force of water striders obtained by direct and indirect measurements. In the direct measurement, water striders were set onto a sensor system and the rowing force of a middle leg of the set water striders was directly measured using a bio-appropriating probe (BAP), a kind of hook. In the indirect measurement, water striders were not fixed and the rowing force of locomoting water striders was evaluated by image analysis using a high-speed camera. As a result, we determined the rowing force by the direct measurement to be 955 μN, while the rowing force by the indirect measurement was 493 μN. We considered that the indirect measurement might lack some credibility because half the propellant energy was lost in the indirect force measurement due to various other factors.

Indirect force measurement system in a mechanical microgripper

Sensing the grasping force is crucial in microassembly processes. In contrast to commonly used expensive and fragile laser-based or piezoelectric sensors the authors present a diverse methodology based on an indirect force measurement without sensors while exploiting the present camera equipment. Therefore, a unique compliant 2D microgripper with a carefully developed amplification and pointing mechanism was designed and manufactured. The detection of the pointer via a camera allows the authors to differentiate between the free movement of the gripper and the contact with the object, and to determine the grasping force. The behavior of the gripper was first simulated numerically for the grasping of different sized pins and eventually investigated experimentally. The recorded video was being processed in real time by an object detection software. To eliminate distortion and parallax errors the visual system was subjected to a standard calibration. The simulated and the experimental results displayed satisfying coherence.

Investigation on aerodynamic characteristics for steel tubular cross-arms of transmission tower under skew wind

A study of the aerodynamic characteristics of steel tubular butterfly-shaped cross-arms in a transmission tower head under skew wind is presented. A wind tunnel test was conducted under skew wind by using a scaling model, and a numerical simulation was performed with a high-precision three-dimensional tower head model. The drag coefficient, skew wind load factor, and wind load distribution factor of the cross-arms obtained from the experiment and numerical simulation were identified and compared with those acquired from different codes. It is concluded that the indirect force measurement method was found to underestimate aerodynamic forces acting on windward cross-arms. For single cross-arm, the horizontal cross-arm showed stronger shielding effect than the inclined cross-arm. A fitting formula for the skew wind load factor of the cross-arm is proposed, and values obtained from it matched experimental and simulation data well. A comparison between calculated and measured wind load distribution factors showed that although longitudinal load distribution factors calculated with the Chinese standard (2018) were consistent with measured data, calculated transverse load distribution factors did not match measurements well. It is suggested that the effect of the transverse lift wind force should be considered in the calculation of wind load distribution factors.

Indirect Force Measurement Using Spindle Currents for Grinding Processes in Aerospace Industry

Indirect Force Measurement Using Spindle Currents for Grinding Processes in Aerospace Industry

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.

A Study on Surface Force Measurement for Contacted Arbitral Two Surfaces —Effect of Surface Roughness, and Indirect Surface Force Measurement Method—

The present paper is intended to show effect of surface roughness on surface force measurement and to demonstrate a newly-proposed indirect surface force measurement using two probes. In the case of hydrogen-terminated and octadecyl-trichloro-silane-coated Si surfaces with micro-mounds, measured surface forces is strongly affected by micro-roughness. The surface force, which varies from 2 μN to 180 μN, is proportional to the logarithm of the curvature radius of the micro-mound. Meanwhile, in the proposed indirect measurement method of surface force, surface force of arbitrary two surface is calculated on the basis of modified JKR and Fowkes theories with surface forces measured by two kinds of probes. The authors prepared a specialized OTS-coated probe as well as a standard glass probe to verify validity of the indirect surface force measurement. For a case of surface force between Si and APTES surfaces, the indirectly measured value reasonably corresponds to the directly measured value. It is confirmed that the proposed method is effective for surface force evaluation for arbitrary two surfaces without probe coating.

Force calibration for an endovascular robotic system with proximal force measurement.

Surgeons, while performing manual endovascular procedures with conventional surgical tools (catheters and guidewires), experience forces on the tool outside the patient's body that are proximal to the point of actuation. Currently, most of the robotic systems for endovascular procedures use active catheters to navigate vasculature and to measure the contact forces at the distal end (tool tip). These tools are more expensive than the conventional surgical tools used in endovascular procedures. To avoid dependence on specialized devices like active catheters, we have developed a novel endovascular robotic system (ERS) that uses conventional surgical tools. Our robot can indirectly measure proximal forces and provide haptic feedback to surgeons. This paper discusses the theory, methodology, and calibration of indirect proximal force measurement. This new calibration technique is presented as a nested optimization problem that is solved using bi-level optimization. The results of experimental validation of the new force calibration methodology are also discussed. The results show that unbiasing of the indirect force measurement by means of force calibration will allow the use of conventional tools in robotic endovascular procedures.

Методические аспекты определения тяги безроторных воздушно-реактивных двигателей при стендовых и летных испытаниях

This article examines methodological aspects of the indirect calculation of thrust characteristics of irrotational air-breathing jet engines using telemetry data that can be obtained during high-speed aircraft flight tests. Specific features of determining thrust characteristics during bench and flight tests are described. Mathematical models are developed for data analysis and calculation of the thrust and the specific impulse of an irrotational air-breathing jet engine by internal parameters, as well as its effective thrust in integration with a high-speed aircraft. The proposed approaches are tested, and the developed mathematical models are validated according to the results of experimental bench tests of the thrust characteristics of irrotational air-breathing jet engines in integration with a model fuselage of a high-speed aircraft. Satisfactory convergence of the results of indirect and direct (experimental) force measurements is shown. The data obtained can be used for further development of the method and analysis of bench and flight tests of aircraft with irrotational air-breathing jet engines.

Adhesion force measurements on functionalized microbeads: An in-depth comparison of computer controlled micropipette and fluidic force microscopy

Characterization of the binding of functionalized microparticles to surfaces with a specific chemistry sheds light on molecular scale interactions. Polymer or protein adsorption are often monitored by colloid particle deposition. Force measurements on microbeads by atomic force microscopy (AFM) or optical tweezers are standard methods in molecular biophysics, but typically have low throughput. Washing and centrifuge assays with (bio)chemically decorated microbeads provide better statistics, but only qualitative results without a calibrated binding force or energy value. In the present work we demonstrate that a computer controlled micropipette (CCMP) is a straightforward and high-throughput alternative to quantify the surface adhesion of functionalized microparticles. However, being an indirect force measurement technique, its in-depth comparison with a direct force measurement is a prerequisite of applications requiring calibrated adhesion force values. To this end, we attached polystyrene microbeads to a solid support by the avidin-biotin linkage. We measured the adhesion strength of the microbeads with both a specialized robotic fluid force microscope (FluidFM BOT) and CCMP. Furthermore, the bead-support contact zone was directly characterized on an optical waveguide biosensor to determine the density of avidin molecules. Distribution of the detachment force recorded on ∼50 individual beads by FluidFM BOT was compared to the adhesion distribution obtained from CCMP measurements on hundreds of individual beads. We found that both methods provide unimodal histograms. We conclude that FluidFM BOT can directly measure the detachment force curve of 50 microbeads in 150 min. CCMP can provide calibrated binding/adhesion force values of 120 microbeads in an hour.

Investigation on wind loads on angle-steel cross-arms of lattice transmission towers via direct force measurement

Cross-arms are key structural components of transmission towers usually located horizontally on the upper part and therefore bear large wind loads that contribute a lot to the base bending moment. In wind tunnel tests of wind loads on cross-arms, indirect force measurement (IFM) method is usually applied, which obtains the wind loads on the cross-arms by subtracting the forces measured on tower-body models with and without the cross-arms. This method over-simplifies the interference of the flow field between the cross-arm and the tower-body and therefore cannot provide an accurate evaluation on the exact wind forces on the cross-arm. A novel wind tunnel test method – direct force measurement (DFM) method, which directly measures the wind loads on a cross-arm attached to a tower model, is proposed in this article. DFM method and IFM method are both employed to investigate wind loads on cross-arms of a lattice transmission tower. Drag coefficients and cross-wind force coefficients of cross-arms are then identified. Wind tunnel test results and standard-calculated values of skewed wind load factors are compared. Calculation methods of wind load distribution factors from various standards are derived and wind tunnel test results and standard calculations are compared. It is concluded that drag coefficients of cross-arms obtained with the DFM method is very close to the standard-calculated values and are larger than those obtained with IFM method. A fitting formula for the skewed wind load factors is proposed which well fits the test data. Comparison between wind load distribution methods illustrates that ASCE (2010) standard-calculated values match well with all wind tunnel test results which show significant differences from other standards. It is indicated from wind tunnel test results that the calculation formula for skewed wind factor proposed in this article is simple but effective.

A time-dependent parametric model order reduction technique for modelling indirect bearing force measurements

Model order reduction is frequently used to keep computational effort affordable at the expense of a minimal loss of accuracy. One particularly challenging problem that yet needs to be solved satisfactorily in this regard is the efficient treatment of time-varying multiple-input/multiple-output behaviour. Recent developments in the field of parametric model order reduction have led to a novel method that deals with moving loading or boundary conditions, but only a few of them are active at a certain time. This work extends the novel method, named static modes sliding, to deal with time-varying multiple-input/multiple-output behaviour for use in dynamic simulation of three-dimensional models. A parametric relationship which describes the location of externally applied loads on a linear tetrahedron mesh has been described to form a continuously time-varying reduction space. A mode tracking technique is inherently incorporated in this method by interpolating among the correct modes. The dynamic simulation of an indirect dynamic bearing load measurement setup serves as a technically relevant case-study. Moreover, the viability of the proposed strategy in an industrial environment with respect to conventional reduction techniques is discussed. The numerical results demonstrate the potential in the development of dedicated reduction schemes for bearings and gears.

Indirect Clamping Force Measurement Method Using Current Sensor for Electro-Mechanical Dual Acting Pulley Continuously Variable Transmission System

This paper introduces an electro-mechanical dual acting pulley continuously variable transmission (EMDAP CVT) system and presents a method of measuring belt-pulley clamping force indirectly using a DC motor current sensor. The EMDAP CVT mainly consists of two movable primary (input) and secondary (output) pulley sheaves connected by metal pushing V-belt. Two DC motor’s actuation systems adjust the CVT ratio. Additionally, the secondary actuation system controls belt-pulley clamping force by adjusting the flatness of the spring discs placed at the back of each secondary pulley sheave to keep the belt tight and prevent belt slip. Ideally, a force sensor is used to measure the belt-pulley clamping force however the use of force sensor inside transmission gearbox is not feasible due to high temperature and oily environment. A viable solution for indirectly measuring the clamping force using current sensor for DC motor is proposed. Since the DC motor actuates the movable pulleys to clamp the belt, the relationship between the DC motor current and belt-pulley clamping force can then be investigated experimentally. The results will give positive impact on precisely controlling belt-pulley clamping force of EMDAP CVT using current sensor which is relatively simpler and less expensive than force sensor.

Indirect boundary force measurements in beam-like structures using a derivative estimator

This paper proposes a new method for the identification of boundary forces (shear force or bending moment) in a beam, based on displacement measurements. The problem is considered in terms of the determination of the boundary spatial derivatives of transverse displacements. By assuming the displacement fields to be approximated by Taylor expansions in a domain close to the boundaries, the spatial derivatives can be estimated using specific point-wise derivative estimators. This approach makes it possible to extract the derivatives using a weighted spatial integration of the displacement field. Following the theoretical description, numerical simulations made with exact and noisy data are used to determine the relationship between the size of the integration domain and the wavelength of the vibrations. The simulations also highlight the self-regularization of the technique. Experimental measurements demonstrate the feasibility and accuracy of the proposed method.

A dynamic measurement of a disc chipper cutting forces

Nowadays wood chips produced from raw material of inferior quality are mainly used to feed domestic and industrial boilers. For this use, a good chip size distribution and low manufacturing energy consumption are required. Cutting forces are still inaccurately measured during the wood chipping process, which implies the use of oversized chippers' motors. A test bench for chipping wood under reasonably realistic conditions of industrial production is improved by adding an indirect force measurement system with high bandwidth of 3 KHz. The dynamic experimentations give the data needed to compute the curve presenting the vertical component of the cutting force, which is composed of three sections; the first one presents the values of the impact force; the second one is relatively straight and it refers to shear stress in wood; the third section corresponds to the period between two crosscuts.

Impact Force Identification by Using Modal Transformation Method for Automobile Test Rig

In the automobile industry, impact force is the main cause for material fatigue in lightweight vehicles. Bump-excited impact force is the most common case, which causes damage to vehicles and reduces the quality of the ride. Force identification is important to reflect the structure's health so that action such as structure modification can be taken before material fatigue. However, direct measurement by using force transducer is not practical due to difficulty in force sensor configuration. A methodology utilizing Operating Deflection Shape (ODS) analysis, Frequency Response Function (FRF) measurement and Modal Transformation Method (MTM) to evaluate the dynamic force is proposed here. This method is called indirect force measurement by using inverse technique. The performance of this approach was demonstrated via experiment. From the measured responses and measured dynamic characteristics of an automobile test rig, a real time mathematical manipulation can generate the systems input force. The force location is known in priori for impact excitation and therefore the inverse problem is well-posed. This method was tested using different force location with unique input force. It shows that high quality of curve fitting to extract the modal parameters such as damped natural frequency, modal damping and residue mode shape is essential to obtain a high accuracy force determination result.

Indirect foot force measurement for obstacle detection in legged locomotion

Foot/ground detection is crucial in legged locomotion because it determines which leg can be swung to reach its new footprint in such a way that the robot moves properly while keeping stability. Generally, contact is detected with sensors located on the feet: however, they are likely to meet hazardous environments in legged locomotion. For this reason, another method to detect ground, or more generally obstacles, is desirable with the aim of improving the robot's robustness. This article assesses an indirect foot force measurement: on the one hand, a dynamic model computes in real-time the joint forces as if there were no obstacles. On the other hand, the real joint forces are measured through a motor current transducer. Comparison between real and estimated forces shows if an obstacle is present. The principle is developed for obstacle detection in 3D, and is implemented on the hexapod robot AMRU5 for ground detection. A discussion establishes the potential interests of the developed method.

High-Resolution Indirect Feet–Ground Interaction Measurement for Hydraulic-Legged Robots

Feet-ground interactions influence the legged robot's stability. In this paper, a high-resolution indirect force measurement for hydraulic-legged robots is presented. The use of pressure transducers placed at one or both chambers of the robot's double-effect hydraulic actuators is investigated, and conclusions are drawn regarding their capability for indirectly measuring the contact forces between the feet and the ground. Because of the nonlinear dynamic properties of hydraulic cylinders, friction modeling is essential to determine at all times the true forces of each foot against the soil. The test case is called ROBOCLIMBER, which is a bulky quadruped climbing and walking machine able to carry heavy-duty drilling equipment for landslide consolidation and monitoring works. Sensor calibration and signal filtering requirements are also taken into consideration. To end, the overall proposed approach to measure feet-ground interactions is experimentally evaluated.

Validity of Mechanical Power Output Measurement at Bench Press Exercise

Validity of Mechanical Power Output Measurement at Bench Press Exercise In sport training and rehabilitation practice, it is usual to use methods of mechanical muscle power output measurement, which are based mainly on indirect force measurement. The aim of this study was to verify the validity of indirect measurement for mechanical muscle power output with bench press exercise. As a criterion of validity, we selected a combination of kinematic and dynamic analyses. Ten men participated in this study. Average age of tested subjects was 28.0 ± 3.4 years. At mechanical power output measurement, these subjects lifted at maximum possible speed loads of 18, 26.5, 39.2 and 47.7 kg. Validity of mechanical power output measurement by means of a method using indirect force measurement was estimated using Spearmen's Correlation Coefficient. Factual significance of differences in average values of power output, force and velocity, measured by a method using indirect force measurement, in comparison to the selected criterion, was evaluated by means of effect of size. Power output measurement method using indirect force measurement showed lower values of force in relation to the criterion in the whole scope of selected loads. Velocity values in the whole scope of selected loads did not show any significant difference between the criterion and the verified method. The mechanical muscle power output measured by the method using indirect force measurement is lower in relation to the criterion, especially in the low scope of loads, where also validity rate was low (R = 0.5).