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 A high-resolution and large force-range load cell by means of nonlinear cantilever beams

2016 ◽  
Vol 43 ◽  
pp. 241-256 ◽  
Author(s):  
Jocelyn M. Kluger ◽  
Themistoklis P. Sapsis ◽  
Alexander H. Slocum
Keyword(s):  
High Resolution ◽  
Load Cell ◽  
Cantilever Beams ◽  
Large Force ◽  
Force Range

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 Open Source Digitally Replicable Lab-Grade Scales

2020 ◽  
Author(s):  
Benjamin R. Hubbard ◽  
Joshua M. Pearce
Keyword(s):  
Open Source ◽  
Low Cost ◽  
Cost Savings ◽  
Load Cell ◽  
Significant Cost ◽  
Load Cells ◽  
The Cost ◽  
Cell Data ◽  
Precision Balance ◽  
Multiple Load

This study provides designs for a low-cost, easily replicable open source lab-grade digital scale that can be used as a precision balance. The design is such that it can be manufactured for use in most labs throughout the world with open source RepRap-class material extrusion-based 3-D printers for the mechanical components and readily available open source electronics including the Arduino Nano. Several versions of the design were fabricated and tested for precision and accuracy for a range of load cells. The results showed the open source scale was found to be repeatable within 0.1g with multiple load cells, with even better precision (0.01g) depending on load cell range and style. The scale tracks linearly with proprietary lab-grade scales, meeting the performance specified in the load cell data sheets, indicating that it is accurate across the range of the load cell installed. The smallest loadcell tested(100g) offers precision on the order of a commercial digital mass balance. The scale can be produced at significant cost savings compared to scales of comparable range and precision when serial capability is present. The cost savings increase significantly as the range of the scale increases and are particularly well-suited for resource-constrained medical and scientific facilities.

A Load Cell System in Foot Pressure Analysis

1982 ◽  
Vol 11 (3) ◽  
pp. 121-122 ◽  
Author(s):  
W V James ◽  
J F Orr ◽  
T Huddleston
Keyword(s):  
Low Cost ◽  
Cell System ◽  
Load Cell ◽  
Foot Pressure ◽  
Cost System ◽  
Pressure Sensitive ◽  
Low Profile ◽  
Load Cells ◽  
Pressure Analysis

A method of displaying discrete areas of pressure beneath the foot has been produced. The device employs a pressure sensitive elastomer which gives quantitative readings of the pressure developed. The 512 load cells are enclosed in a low profile platform only one inch in depth which provides a low-cost system that can be employed in clinical situations.

scholarly journals Contact-free unconstraint respiratory measurements with load cells under the bed in awake healthy volunteers: breath-by-breath comparison with pneumotachography

2019 ◽  
Vol 126 (5) ◽  
pp. 1432-1441 ◽  
Author(s):  
Shiroh Isono ◽  
Natsuko Nozaki-Taguchi ◽  
Makoto Hasegawa ◽  
Shinichiro Kato ◽  
Shinsuke Todoroki ◽  
...  
Keyword(s):  
Respiratory Rate ◽  
Human Subjects ◽  
Load Cell ◽  
The Body ◽  
Phase Changes ◽  
Body Postures ◽  
Load Cells ◽  
Centroid Shift ◽  
Lower Load ◽  
Contact Free

Rate of respiration is a fundamental vital sign. Accuracy and precision of respiratory rate measurements with contact-free load cell sensors under the bed legs were assessed by breath-by-breath comparison with the pneumotachography technique during two different dynamic breathing tasks in 16 awake human adults resting on the bed. The subject voluntarily increased and decreased the respiratory rate between 4 and 16 breaths/min ( n = 8) and 10 and 40 breaths/min ( n = 8) at every 2 breaths in 6 different lying postures such as supine, left lateral, right lateral, and 30, 45, and 60° sitting postures. Reciprocal phase changes of the upper and lower load cell signals accorded with the respiratory phases indicating respiratory-related shifts of the centroid along the long axis of the bed. Bland-Altman analyses revealed 0.66 and 1.59 breaths/min standard deviation differences between the techniques (limits of agreement: −1.22 to 1.36 and −2.96 to 3.30) and 0.07 and 0.17 breaths/min fixed bias differences (accuracy) (confidence interval: 0.04 to 0.10 and 0.12 to 0.22) for the mean respiratory rates of 10.5 ± 3.7 and 24.6 ± 8.9 breaths/min, respectively, regardless of the body postures on the bed. Proportional underestimation by this technique was evident for respiratory rates >40 breaths/min. Sample breath increase up to 10 breaths improved the precision from 1.59 to 0.26 breaths/min. Abnormally faster and slower respirations were accurately detected. We conclude that contact-free unconstraint respiratory rate measurements with load cells under the bed legs are accurate and may serve as a new clinical and investigational tool. NEW & NOTEWORTHY Four load cells placed under the bed legs successfully captured a centroid shift during respiration in human subjects lying on a bed. Breath-by-breath comparison of the breaths covering a wide respiratory rate range by pneumotachography confirmed reliability of the contact-free unconstraint respiratory rate measurements by small standard deviations and biases regardless of body postures. Abnormally faster and slower respirations were accurately detected. This technique should be an asset as a new clinical and investigational tool.

An integrated MEMS three-dimensional tactile sensor with large force range

2000 ◽  
Vol 80 (2) ◽  
pp. 155-162 ◽  
Author(s):  
Tao Mei ◽  
Wen J. Li ◽  
Yu Ge ◽  
Yong Chen ◽  
Lin Ni ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Tactile Sensor ◽  
Large Force ◽  
Force Range

scholarly journals A Soft Wearable and Full Textile Piezoresistive Sensor for Plantar Pressure Capturing

2020 ◽  
Author(s):  
Yongsong Tan ◽  
Kamen Ivanov ◽  
Zhanyong Mei ◽  
Hui Li ◽  
Ludwig Lubich ◽  
...  
Keyword(s):  
Plantar Pressure ◽  
Printed Circuit Board ◽  
High Sensitivity ◽  
Fast Response ◽  
Circuit Board ◽  
Plantar Pressure Distribution ◽  
Piezoresistive Sensor ◽  
Flexible Printed Circuit ◽  
Circuit Electrode ◽  
Force Range

Abstract The trends of health wearable monitoring system have led to growing demands for gait capturing device. The comfortability and durability under repeated stress in the existing sensor-enabled footwear are still problems. Herein, a flexible textile piezoresistive sensor (TPRS) consisting of rG-cotton fabric electrode and Ag fabric circuit electrode is prepared. Based on the mechanical and electrical properties of two fabric electrodes, the TPRS exhibits superior sensing performance, which includes high sensitivity of 3.96kPa-1 in the lower pressure range of 0-36kPa, wide force range (0-800 kPa), fast response time (170 ms), remarkable durability stability (1000 cycles) and dection ability in differrent pressures. For practical application of capturing plantar pressure, six TPRSs are mounted on a flexible printed circuit board and integrated into an insole. The dynamic plantar pressure distribution is displayed through drawing the pressure maps during walking. The proposed full textile piezoresistive sensor is a strong candidate for next-generation plantar pressure wearables monitoring device.

scholarly journals Criterion and Construct Validity of Prosthesis-Integrated Measurement of Joint Moment Data in Persons With Transtibial Amputation

2014 ◽  
Vol 30 (3) ◽  
pp. 431-438 ◽  
Author(s):  
Goeran Fiedler ◽  
Brooke Slavens ◽  
Roger O. Smith ◽  
Douglas Briggs ◽  
Brian J. Hafner
Keyword(s):  
Construct Validity ◽  
Gait Analysis ◽  
Pearson Correlation ◽  
Measurement Methods ◽  
Load Cell ◽  
Joint Moments ◽  
Transtibial Amputation ◽  
Study Results ◽  
Flexion Extension ◽  
Load Cells

Prosthesis-integrated sensors are appealing for use in clinical settings where gait analysis equipment is unavailable, but accurate knowledge of patients’ performance is desired. Data obtained from load cells (inferring joint moments) may aid clinicians in the prescription, alignment, and gait rehabilitation of persons with limb loss. The purpose of this study was to assess the accuracy of prosthesis-integrated load cells for routine use in clinical practice. Level ground walking of persons with transtibial amputation was concurrently measured with a commercially available prosthesis-integrated load cell, a 10-camera motion analysis system, and piezoelectric force plates. Ankle and knee flexion/extension moments were derived and measurement methods were compared via correlation analysis. Pearson correlation coefficients ranged from 0.661 for ankle pronation/supination moments to 0.915 for ankle flexion/extension moments (P < .001). Root mean squared errors between measurement methods were in the magnitude of 10% of the measured range and were explainable. Differences in results depicted differences between systems in definition and computation of measurement variables. They may not limit clinical use of the load cell, but should be considered when data are compared directly to conventional gait analysis data. Construct validity of the load cell (ie, ability to measure joint moments in-situ) is supported by the study results.

Contact Forces Acting on Large Femoral Osteochondral Allografts During Forced Knee Extension

2017 ◽  
Vol 45 (12) ◽  
pp. 2804-2811 ◽  
Author(s):  
Peter Z. Du ◽  
Keith L. Markolf ◽  
Christopher J. Lama ◽  
David R. McAllister ◽  
Kristofer J. Jones
Keyword(s):  
Clinical Relevance ◽  
Knee Extension ◽  
Load Cell ◽  
Contact Forces ◽  
Osteochondral Allograft ◽  
Human Knee ◽  
Native Bone ◽  
Load Cells ◽  
The Mean ◽  
Femoral Condyles

Background: A single cylindrical graft plug is commonly used for large focal femoral defects during osteochondral allograft (OCA) transplantation. Excessive contact force (CF) on a proud plug could compromise initial healing. CFs during forced knee extension are of particular interest because this maneuver is used by therapists to restore early postoperative range of motion. Hypothesis: A proud OCA plug will significantly increase the CF and significantly decrease the knee extension angle (KEA). Study Design: Controlled laboratory study. Methods: Eleven human knee specimens had miniature load cells installed in both femoral condyles at standardized locations representative of clinical defects. Each load cell had a 20-mm–diameter cylinder of native bone/cartilage attached at its precise anatomic location. Four spacers, 0.5 mm in thickness, were inserted sequentially between each load cell and its mounting bracket to create proud plug conditions of 0.5 to 2 mm. Measurements of the CF and KEA were recorded at extension moment levels up to 8 N·m. Results: At 8 N·m, the mean CFs for flush plugs were 149 ± 18 N (lateral) and 34 ± 13 N (medial). The mean increases in the medial CF (compared with flush) for 0.5-mm, 1-mm, 1.5-mm, and 2-mm proud conditions were 31 N (+91%), 64 N (+188%), 111 N (+325%), and 154 N (+451%), respectively. Corresponding increases for lateral proud plugs were 55 N (+37%), 120 N (+81%), 162 N (+109%), and 210 N (+141%), respectively. The CFs (and CF increases) for lateral grafts were significantly ( P < .05) higher than corresponding values for medial grafts at each proudness condition. Medial plug proudness had no consistent effect on the KEA. A 1-mm proud lateral plug significantly reduced the KEA by −1.6° (0 N·m) and −0.9° (2 N·m). Conclusion: Graft proudness of only 0.5 mm significantly increased CFs during forced knee extension, emphasizing the surgical precision necessary to achieve normal CF levels. Clinical Relevance: It is believed that some amount of CF is beneficial in the early stages of graft healing, and our findings suggest that forced knee extension may be well suited for this purpose. However, the surgeon should be aware that large extension moments can also generate relatively high CFs, especially if the plug is proud.

A prototype high sensitivity load cell using single walled carbon nanotube strain gauges

2012 ◽  
Vol 180 ◽  
pp. 120-126 ◽  
Author(s):  
Dongil Lee ◽  
Hyun Pyo Hong ◽  
Myung Jin Lee ◽  
Chan Won Park ◽  
Nam Ki Min
Keyword(s):  
Carbon Nanotube ◽  
High Sensitivity ◽  
Load Cell ◽  
Strain Gauges ◽  
Single Walled Carbon Nanotube ◽  
Single Walled Carbon
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