scholarly journals Logarithmic Strain Model for Nonlinear Load Cell

Sensors ◽  
2019 ◽  
Vol 19 (16) ◽  
pp. 3486
Author(s):  
Young-Dae Hong ◽  
Bumjoo Lee
Keyword(s):  
Force Measurement ◽  
Contact Point ◽  
Surface Profile ◽  
Strain Curve ◽  
Measurement Range ◽  
Load Cell ◽  
Measurement Unit ◽  
Design Parameters ◽  
Nonlinear Load ◽  
Force Range

General load cells have typically constant sensitivity throughout the measurement range, which is acceptable for common force measurement systems. However, it is not adequate for high-performance control and high-stroke applications such as robotic systems. It is required to have a higher sensitivity in a small force range than that in a large force range. In contrast, for large loading force, it is more important to increase the measurement range than the sensitivity. To cope with these characteristics, the strain curve versus the force measurement should be derived as a logarithmic graph. To implement this nonlinear nature, the proposed load cell is composed of two mechanical components: an activator, which has a curved surface profile to translocate the contact point, and a linear torque measurement unit with a moment lever to measure the loading force. To approximate the logarithmic deformation, the curvature of the activator was designed by an exponential function. Subsequent design parameters were optimized by an evolutionary computation.

scholarly journals Ring-Based Stiffening Flexure Applied as a Load Cell With High Resolution and Large Force Range

2017 ◽  
Vol 139 (10) ◽  
Author(s):  
Jocelyn M. Kluger ◽  
Alexander H. Slocum ◽  
Themistoklis P. Sapsis
Keyword(s):  
High Sensitivity ◽  
Load Cell ◽  
Nonlinear Load ◽  
Cell Functions ◽  
Force Magnitude ◽  
Large Force ◽  
Load Cells ◽  
Nonlinear Flexure ◽  
Force Range ◽  
Rigid Surfaces

This paper applies linear elastic theory and Castigliano's first theorem to design nonlinear (stiffening) flexures used as load cells with both large force range and large resolution. Low stiffness at small forces causes high sensitivity, while high stiffness at large forces prevents over-straining. With a standard 0.1 μm deflection sensor, the nonlinear load cell may detect 1% changes in force over five orders of force magnitude. In comparison, a traditional linear load cell functions over only three orders of magnitude. We physically implement the nonlinear flexure as a ring that increasingly contacts rigid surfaces with carefully chosen curvatures as more force is applied. We analytically describe the load cell performance as a function of its geometry. We describe methods for manufacturing the flexure from a monolithic part or multiple parts. We experimentally verify the theory for two load cells with different parameters.

scholarly journals Improving the Detection of the Contact Point in Active Sensing Antennae by Processing Combined Static and Dynamic Information

Sensors ◽  
2021 ◽  
Vol 21 (5) ◽  
pp. 1808
Author(s):  
Luis Mérida-Calvo ◽  
Daniel Feliu-Talegón ◽  
Vicente Feliu-Batlle
Keyword(s):  
Contact Point ◽  
Load Cell ◽  
Robotic Systems ◽  
Accurate Estimation ◽  
Flexible Beam ◽  
Dynamic Information ◽  
New Developments ◽  
Static Information ◽  
Insect Antennae ◽  
Flexible Antenna

The design and application of sensing antenna devices that mimic insect antennae or mammal whiskers is an active field of research. However, these devices still require new developments if they are to become efficient and reliable components of robotic systems. We, therefore, develop and build a prototype composed of a flexible beam, two servomotors that drive the beam and a load cell sensor that measures the forces and torques at the base of the flexible beam. This work reports new results in the area of the signal processing of these devices. These results will make it possible to estimate the point at which the flexible antenna comes into contact with an object (or obstacle) more accurately than has occurred with previous algorithms. Previous research reported that the estimation of the fundamental natural frequency of vibration of the antenna using dynamic information is not sufficient as regards determining the contact point and that the estimation of the contact point using static information provided by the forces and torques measured by the load cell sensor is not very accurate. We consequently propose an algorithm based on the fusion of the information provided by the two aforementioned strategies that enhances the separate benefits of each one. We demonstrate that the adequate combination of these two pieces of information yields an accurate estimation of the contacted point of the antenna link. This will enhance the precision of the estimation of points on the surface of the object that is being recognized by the antenna. Thorough experimentation is carried out in order to show the features of the proposed algorithm and establish its range of application.

A New Cam-follower Safety Joint Mechanism Design based on Variable-length Four-bar Linkage for Robot Safety

2021 ◽  
pp. 1-24
Author(s):  
Seung Guk Baek ◽  
Hyungpil Moon ◽  
Hyouk Ryeol Choi ◽  
Ja Choon Koo
Keyword(s):  
Load Transfer ◽  
Impact Damage ◽  
Surface Profile ◽  
Length Change ◽  
Variable Length ◽  
Core Element ◽  
Nonlinear Load ◽  
Cam Follower ◽  
Joint Mechanism ◽  
The Impact

Abstract Humans come into physical contacts with various machines such as robots in daily life. This leads to the underlying issue of guaranteeing safety during such human-robot interactions. Thus, many devices and methods have been studied for impact damage reduction. A safety joint mechanism (SJM) using four-bar linkages has been highlighted as an impact cutoff device owing to its capabilities of nonlinear load transfer. This paper focuses on a new design and testing for a kinematic element of an SJM based on four-bar linkages to improve the impact cutoff performances. In the present work, a set of variable-length floating link designs is proposed, and the mechanism is implemented by mechanical contact surface profile shaping between the cams and followers. The performance of the cam-follower mechanism is evaluated depending on the variable length of the floating link, by using equivalent stiffness method, which successfully quantifies the performance of the proposed mechanism. Based on this design and analysis, two SJMs having symmetrical arrangements for four numbers of cam-follower mechanisms are fabricated: one SJM has fixed-length floating links and the other has variable-length floating links. The effect of the new kinematic elements on the performance improvement is verified by comparing the absorbed impact rates of the two SJMs by impact hammer-like drop tests. Consequently, it is confirmed that the rapid length change of the floating link is the core element for improving the performance of the safety mechanism.

A Two-Dimensional Surface Profile Imaging Technique Based on Heterodyne Interferometer

2005 ◽  
Vol 295-296 ◽  
pp. 477-482
Author(s):  
K.W. Wang ◽  
Z.J. Cai ◽  
Li Jiang Zeng
Keyword(s):  
High Speed ◽  
Imaging Technique ◽  
Surface Profile ◽  
Ccd Camera ◽  
Measurement Range ◽  
Interference Signal ◽  
Two Dimensional ◽  
Step Method ◽  
Heterodyne Interferometer ◽  
Dimensional Surface

A two-dimensional surface profile imaging technique based on heterodyne interferometer is proposed. A piezo translator vibrated grating is used to generate a heterodyne signal. A high speed CCD camera is used to extract the interference signal using a five step method. The uncertainty in the displacement measurement is approximately 0.035 µm within a measurement range of 1.7 µm, confirming the two dimensional heterodyne interferometer is valid for measuring the surface profile. The method is also available for low coherence heterodyne interferometer due to the optical frequency shifts caused by the vibration of grating independent on the wavelength.

scholarly journals Back loading estimation during team handling: Is the use of only motion data sufficient?

PLoS ONE ◽  
2020 ◽  
Vol 15 (12) ◽  
pp. e0244405
Author(s):  
Antoine Muller ◽  
Philippe Corbeil
Keyword(s):  
Team Member ◽  
Force Measurement ◽  
Accurate Estimate ◽  
Measurement Unit ◽  
Prediction Methods ◽  
Compression Force ◽  
Joint Moments ◽  
Team Members ◽  
Motion Data ◽  
Manual Handling

Analyzing back loading during team manual handling tasks requires the measurement of external contacts and is thus limited to standardized tasks. This paper evaluates the possibility of estimating L5/S1 joint moments based solely on motion data. Ten subjects constituted five two-person teams and handling tasks were analyzed with four different box configurations. Three prediction methods for estimating L5/S1 joint moments were evaluated by comparing them to a gold standard using force platforms: one used only motion data, another used motion data and the traction/compression force applied to the box and one used motion data and the ground reaction forces of one team member. The three prediction methods were based on a contact model with an optimization-based method. Using only motion data did not allow an accurate estimate due to the traction/compression force applied by each team member, which affected L5/S1 joint moments. Back loading can be estimated using motion data and the measurement of the traction/compression force with relatively small errors, comparable to the uncertainty levels reported in other studies. The traction/compression force can be obtained directly with a force measurement unit built into the object to be moved or indirectly by using force platforms on which one of the two handlers stands during the handling task. The use of the proposed prediction methods allows team manual handling tasks to be analyzed in various realistic contexts, with team members who have different anthropometric measurements and with different box characteristics.

Geometrical consideration for mechanical contact between rolling circle and surface roughness as an improvement to the surface profile

2021 ◽  
Vol 15 (1) ◽  
pp. 7846-7859
Author(s):  
Tsuyoshi Shimizu ◽  
Yasutake Hramiishi ◽  
Takaaki Ishii ◽  
Yuzairi Abdul Rahim ◽  
Mohd Fadzil Ali Ahmad ◽  
...  
Keyword(s):  
Contact Point ◽  
Surface Profile ◽  
Displacement Sensor ◽  
Nose Radius ◽  
Rolling Circle ◽  
Actual Surface ◽  
Contact Type ◽  
Measurement Surface ◽  
Surface Profiles ◽  
Tip Radius

This paper describes measurement methods of surface profiles that improve contact-type displacement sensor outputs by focusing on the contact point between the sphere tip of the sensor and the rough surface. We examined the geometry of a surface profile model and compared measurements using various methods with the measurement using a roughness meter. The spherical tip of the contact type displacement sensor touches the measurement surface and detects the displacement. The sphere tip radius of a typical contact-type displacement sensor ranges from 1–3 mm, causing the roughness curve to be “filtered” by the radius of the sphere.  Three methods for estimating the valley portion of the surface profile are evaluated in this study: a) linear approximation of the concave portion of the surface profile, b) function approximation of the concave portion, and c) using the known nose radius of the machining tool. The following sphere tip radii were used to measure actual surface profiles: 0.25 mm, 0.5 mm, 1.0 mm and 1.5 mm. Given the conditions of the experimental model, we found that surface profiles with a roughness that approximates a predictable curve can be measured with a high degree of accuracy.

Profile Measurement by Using a Femtosecond Laser Chromatic Confocal Probe

2020 ◽  
Author(s):  
Ryo Sato ◽  
Yuki Shimizu ◽  
Hiraku Matsukuma ◽  
Wei Gao
Keyword(s):  
Thermal Stability ◽  
Femtosecond Laser ◽  
Surface Profile ◽  
Sample Surface ◽  
Measurement Range ◽  
Laser Source ◽  
Profile Measurement ◽  
Experimental Setup ◽  
Chromatic Confocal Probe ◽  
Surface Profile Measurement

Abstract Confocal probes are widely employed in many industrial fields due to the depth-sectioning effect. The author’s group has also proposed a chromatic confocal probe employing a mode-locked femtosecond laser source which can realize an axial resolution of 30 nm and a measurement range of 40 μm Efforts have also been made to improve the thermal stability of the developed femtosecond laser chromatic confocal probe so that the probe can be applied for long-term displacement measurement or surface profile measurement. Meanwhile, surface profile measurement has not been carried out by using the developed femtosecond laser chromatic confocal probe. For the verification of the performance of developed probe in profile measurement, in this paper, an experimental setup is built and a basic experiment is carried out. By using the probe with further improved thermal stability, the measurement of a sample surface profile is carried out. In this paper, the development of the experimental setup with the femtosecond laser chromatic confocal probe, as well as the results of the surface profile measurements, is presented.

scholarly journals Prediction of Stress–Strain Curves Based on Hydric Non-Destructive Tests on Sandstones

Materials ◽  
2019 ◽  
Vol 12 (20) ◽  
pp. 3366 ◽  
Author(s):  
Marco Ludovico-Marques ◽  
Carlos Chastre
Keyword(s):  
Physical Properties ◽  
Mechanical Behavior ◽  
Water Absorption ◽  
Analytical Model ◽  
Strain Curve ◽  
Low Pressure ◽  
Design Parameters ◽  
Compression Tests ◽  
Stress Strain ◽  
Non Destructive

The study of the mechanical behavior of building stones is traditionally supported by destructive compression tests carried out on representative specimens. However, in order to respect the monuments’ integrity, the study of the mechanical behavior of stones can be based mostly on physical properties obtained from non-destructive tests (NDT). For this study, a simple and cheap NDT—water absorption under low pressure—was used to carry out fast surveys and to predict the most important design parameters of loadbearing masonry, among which are the compressive strength, strain at failure, and even elastic modulus on monument blocks. The paper presents the results of the experimental work conducted to obtain the physical properties and stress–strain curves of the sandstones tested. Supported by these results, it was possible to correlate the various parameters and develop an analytical model that predicts the stress–strain curve of the sandstones based on water absorption under low pressure tests. A good agreement is observed between the analytical model and the experimental tests.

3D Coordinate Measurement System Using Single Camera and IMU

2011 ◽  
Vol 308-310 ◽  
pp. 351-355
Author(s):  
Syed Ghafoor Shah ◽  
Gui Li Xu ◽  
Wei Ji Ni ◽  
Yong Qiang Ye
Keyword(s):  
Inertial Measurement Unit ◽  
Vision System ◽  
Contact Point ◽  
Measurement Unit ◽  
Single Camera ◽  
Inertial Measurement ◽  
Coordinate Measurement ◽  
Improve Accuracy ◽  
Continuous Scanning ◽  
Feature Calculation

This paper proposes a new method for measuring 3D coordinates of a point using a single camera vision system. The contact point is determined by using 3D force sensors. In addition, the force limiting system has also been incorporated to improve accuracy of the results. 3D point is captured when the touching probe senses the force up to certain limit and subsequently recording of that point is initiated. The points being recorded are then processed for the required feature calculation such as distance between planes, angle, radius etc. The IMU (inertial measurement unit) initially estimates the target plane position which enables the whole system to perform the required task quickly. Hence, this system can be used for continuous scanning of any surface.

FORCE CALIBRATION OF NANO UNIVERSAL TESTING MACHINE USING MILLIGRAM WEIGHTS

2013 ◽  
Vol 24 ◽  
pp. 1360031
Author(s):  
CHUNG-LIN WU ◽  
CHING-FEN TUAN
Keyword(s):  
Force Measurement ◽  
Testing Machine ◽  
Calibration Method ◽  
Force Transducer ◽  
Force Measurements ◽  
Universal Testing Machine ◽  
Universal Testing ◽  
Small Force ◽  
Force Calibration ◽  
Force Range

This paper presents an approach for calibrating the force transducer on the nano universal testing machine using milligram weights. Previous research on force calibration of such a system focused on the range from 10 mN to 200 mN, ignoring forces below 10 mN. The main purpose of this study is to analyze and calculate the uncertainty of force measurements within the range from 0.2 mN to 10 mN. The ABA calibration method in accordance with OIML R111-1 is adopted to determine the uncertainty in force measurement. The results indicate that the maximum relative uncertainty of force measurement is 7.0 × 10−3 with a 95% confidence level. The investigation can be used as the basis for evaluating measurement uncertainty of the system in small force range.

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