Force Sensor Research Articles

Simulation of a control method for active kinesiotherapy with an upper extremity rehabilitation exoskeleton without force sensor

Exoskeleton-aided active rehabilitation is a process that requires sensing and acting upon the motion intentions of the user. Typically, force sensors are used for this. However, they increase the weight and cost of these wearable devices. This paper presents the methodology for detecting users’ intentions only with encoders integrated with the drives. It is unique compared to other algorithms, as enables active kinesiotherapy while adding no sensory systems. The method is based on comparing the measured motion with the one computed with the idealised model of the multibody system. The investigation assesses the method’s performance and its robustness to model and measurement inaccuracies, as well as patients’ unintended motions. Moreover, the PID parameters are selected to provide the optimal regulation based on the dynamics requirements. The research proves the presented concept of the control approach. For all the tests with the final settings, the system reacts to a change in the user’s intention below one second and minimises the changes in proportion between the system’s acceleration and the generated user’s joint torque. The results are comparable to those obtained by EMG-based systems and significantly better than low-cost force sensors.

Quantitative evaluation of embedding resins for volume electron microscopy.

Optimal epoxy resin embedding is crucial for obtaining consistent serial sections from large tissue samples, especially for block faces spanning >1 mm2. We report a method to quantify non-uniformity in resin curing using block hardness measurements from block faces. We identify conditions that lead to non-uniform curing as well as a procedure to monitor the hardness of blocks for a wide range of common epoxy resins used for volume electron microscopy. We also assess cutting repeatability and uniformity by quantifying the transverse and sectional cutting forces during ultrathin sectioning using a sample-mounted force sensor. Our findings indicate that screening and optimizing resin formulations is required to achieve the best repeatability in terms of section thickness. Finally, we explore the encapsulation of irregularly shaped tissue samples in a gelatin matrix prior to epoxy resin embedding to yield more uniform sections.

Hybrid 3D printed three-axis force sensor aided by machine learning decoupling

ABSTRACT Identification of magnitude and orientation for spatially applied loading is highly desired in the fields of not only the machinery components but also human-machine interaction. Despite the fact that the 3-axis force sensor with different structures has been proposed to measure the spatial force, there are still some common limitations including the multi-step manufacturing-assembly processes and complicated testing of decoupling calibration. Here, we propose a rapid fabrication strategy with low-cost to achieve high-precision 3-axis force sensors. The sensor is designed to compose of structural Maltese cross base and sensing units. It is directly fabricated within one step by a hybrid 3D printing technology combining deposition modeling (FDM) with direct-ink-writing (DIW). In particular, a machine learning (ML) model is used to convert the strain signal to the force components. Instead of a mount of calibration tests, this ML model is trained by sufficient simulation data based on programmed batch finite element modeling. This sensor is capable of continuously identifying a spatial force with varying magnitude and orientation, which successfully quantify the applied force of traditional Chinese medicine physiotherapy including Gua Sha and massage. This work provides insight for design and rapid fabrication of multi-axis force sensors, as well as potential applications.

Bionic octopus-like flexible three-dimensional force sensor for meticulous handwriting recognition in human-computer interactions

With the advantages of high flexibility, multifunctional integration, and wearing comfort, flexible tactile sensors hold great potential for application in the field of intelligent sensing system and human-computer interaction. However, the high sensitivity acquisition and the issue of decoupling of complex tactile signals, and improving compatibility of flexible tactile sensors in human-computer interfaces are still serious challenges in current research. In this study, drawing inspiration from the body structure of an octopus, we developed a flexible three-dimensional (3D) force sensor in which a CNT/Ecoflex conductive elastomer as the body of the bionic octopus-like sensor could capture the normal component of 3D spatial force, meanwhile a laser-induced graphene sensing film transferred to Ecoflex (LIG/Ecoflex) as the tactile wrists of the bionic octopus sensor could discern the magnitude and direction of the tangential component of the 3D spatial force. The bionic sensor offered excellent sensing and wearable characteristics, including fast and efficient response, cyclic stability, and flexible skin-fit performance. The unique structural design of the sensor enabled spatial force sensing capability and precise decoupling and output of 3D forces through the use of a multilayer perceptron (MLP) for mapping and calibration. The octopus-inspired flexible 3D force sensors were further attached to the fingertips of human fingers for successful extraction of handwriting minutia of wearer, showcasing their promising potential in areas such as smart wearables, handwriting recognition, and interactive human-computer interfaces.

A high-resolution and low-cost mesoscale tactile force sensor based on mode-localization effect and fabricated using rapid prototyping

This paper presents a novel design of a high resolution and low-cost tactile force sensor, based on the concept of mode-localization in two weakly coupled resonators (WCRs). The sensor is fabricated at mesoscale by utilizing rapid prototyping techniques. The two WCRs in the sensor are operated at resonance by using an electrostatic actuation. Change in the oscillation amplitude ratios and resonant frequency shift, corresponding to an input force is utilized as an output metric for the measurement of force. The application of an applied force on the WCRs induced electrostatic strain, which acted as a negative stiffness perturbation. The outer body of sensor is manufactured using a soft silicone elastomer and shaped using molds based on laser cutting technique. The proposed tactile force sensor is analyzed numerically through finite-element-method (FEM) based simulations. For the testing of tactile force sensor, an actuation and sensing electronics scheme is developed. The experimental results revealed that the sensor is capable of measuring input force up to 20 mN with a relative amplitude ratio (AR) and resonant frequency shift based sensitivity of 27040 ppm/mN and 3553 ppm/mN respectively. The experimentally evaluated resolution for the sensor is 7.3 µN. The sensor shows the stability in response to the thermal variations and low-frequency vibrational environments.

Digital Twin Virtual Welding Approach of Robotic Friction Stir Welding Based on Co-Simulation of FEA Model and Robotic Model

Robotic friction stir welding has become an important research direction in friction stir welding technology. However, the low stiffness of serial industrial robots leads to substantial, difficult-to-measure end-effector deviations under the welding forces during the friction stir welding process, impacting the welding quality. To more effectively measure the deviations in the end-effector, this study introduces a digital twin model based on the five-dimensional digital twin theory. The model obtains the current data of the robot and six-axis force sensor and calculates the real-time end deviations using the robot model. Based on this, a virtual welding model was realized by integrating the FEA model with the digital twin model using a co-simulation approach. This model achieves pre-process simulation by iteratively cycling through the simulated force from the FEA model and the end displacement from the robot model. The virtual welding model effectively predicts the welding outcomes with a mere 6.9% error in lateral deviation compared to actual welding, demonstrating its potential in optimizing welding parameters and enhancing accuracy and quality. Employing digital twin models to monitor, simulate, and optimize the welding process can reduce risks, save costs, and improve efficiency, providing new perspectives for optimizing robotic friction stir welding processes.

Effect of Kinesio taping on wrist proprioception in healthy subjects: A randomized clinical trial

BackgroundAlthough the use of KT has increased considerably in the clinical practice in the last years, there is limited evidence about the effects of its application in proprioception. PurposeThe aim of this study was to determine the effect of KT on joint position sense and force sense on the wrist of healthy subjects. MethodsFifty-four subjects were analyzed in a randomized, crossover, single-blind study design. To determine the force sense, the subjects had to reach 50% of their maximum grip force. Wrist joint position sense was assessed during active repositioning tests at the target angles of 30° flexion and extension of wrist. A digital dynamometer was used to determine the sense of force and a digital goniometer was used to determine the joint position sense. Subjects were evaluated with KT (I- strip on ventral aspect of forearms from origin to insertion) and placebo (an inelastic tape was applied following the same procedure as KT). ResultsNo significant differences have been found in the force sense, neither in the comparisons between control and interventions (p=0.286), nor between pre and post-intervention (p=0.111). For wrist joint position sense, a statistically significant effect (p< 0.05) was found at 30º of extension between the control and experimental group in favor of the control group. ConclusionsThe application of KT did not produce changes in FS and only caused a significant improvement in JPS in extension (30º). The results appear to indicate that the application of KT to improve proprioception in healthy subjects should be reconsidered.

Force Perception for Rigid-Soft Finger Without Force Sensors: Theoretical Analysis, and Model Transfer

Force Perception for Rigid-Soft Finger Without Force Sensors: Theoretical Analysis, and Model Transfer

A fully textile-based, tunable, force and strain sensing resistor for e-textile applications

This work presents a novel approach towards integrating electronic components with textiles, by successfully creating a fully textile-based element that is capable of detecting applied forces by variation in its resistance value. The fabrication of the device consists of a specialized siliconized conductive fabric, which is placed above and below a layer of switch fabric, which acts as a force sensor. In this paper, the effects of three different geometries are observed, as well as the washability of the device, along with tension testing. Μoreover, the device behavior is simulated as well as applied in a real-life scenario. The proposed element demonstrates a good dynamic range, high repeatability and stability, and minimal impact of washing, creating a great candidate for integration in e-textiles.

In vivo force measurements on formin Cdc12p using new coiled-coil force sensors

In vivo force measurements on formin Cdc12p using new coiled-coil force sensors

Multiparameter Remote Contact Force Sensor With Embedded Bend Sensing for Tendon-Driven Hand Robots

Integrating multiple sensors without increasing the structural complexity and their original form factor is a major concern in robotic applications, particularly in tendon-driven systems. This study proposes a multiparameter contact force sensor with bend sensing by utilizing an improved Bowden cable design. The proposed sensor consists of an end tip with an elastomer membrane, a Bowden cable consisting of a sheath and dual inner wires, and a remotely separated sensing component. The electrical wirings are decoupled from the mechanical Bowden cable system. The displacement difference between the force-sensing and bend-sensing wires is transmitted through the sheath, indicating the contact force on the end tip. The modeling and experiments verify that the contact force applied on the end tip is linearly related to the sensor output signal and is reliable after repeated measurements. The proposed sensor, utilizing the flexible Bowden cable as its sensing modality, can be integrated into a diverse range of tendon-driven robotic applications. These applications include a robotic hand with tactile and angle sensing capabilities, as well as a soft wearable robot for the hand (Exo-glove Poly II). The compact form factor of the proposed sensor enables geometric sensing without increasing structural complexity for multiparameter sensing in robotic applications.

In silico analyses of molecular force sensors for mechanical characterization of biological systems

In silico analyses of molecular force sensors for mechanical characterization of biological systems

Bite Force Measurement in Children with Primary Dentition

BACKGROUND&#x0D; This study intended to compute the maximum bite force in the primary dentition of the young children (3-6 years old) and examine the possible influences of caries, malocclusions (such as crossbite and bruxism), and other factors on maximum bite force. We wanted to ascertain the extent of biting forces in young children's primary dentition, aged three to six, and examine the impact of several factors, including the subjects' gender, caries, crossbite, and bruxism, on the maximum bite force in this study.&#x0D; METHODS&#x0D; Children within the age group of 3-6 years were selected from nearby schools. A dental examination was done for caries and malocclusion. The subjects were asked to bite on the unit consisting of a force sensor wedged between wooden sticks wrapped in a polyethylene sheet, 3 times on each side (posteriors) and on anterior teeth with maximum bite force and then the mean value was taken.&#x0D; RESULTS&#x0D; 502 subjects between the age group of 3-6 years were included in the study. The levels of bite force recorded showed that there was a significant difference in all three teeth standardized for the bite force measurement in the four groups included (p&lt;0.001). The maximum bite force of the posterior teeth was 351.5N seen in the control group, in the caries group (281.7N), crossbite (181.1N), and bruxism (250.2N).&#x0D; CONCLUSIONS&#x0D; Bite forces in primary dentition showed comparatively wide intra- and inter-individual variation. For both boys and girls, there was no discernible variation in the maximal bite force, however maximum bite force in children with caries and bruxism had significant differences compared to the control group. No significant difference in bite forces was seen in children having crossbite and non-crossbite sides.

An Angle‐Sensitive Microcolumn‐Based Capacitive Shear Force Sensor for Robot Grasping

AbstractShear force sensors play an indispensable role in tactile perception for robot manipulation tasks. However, recent advancements in shear force sensors have been hindered by issues such as direction sensitivity and integration limitations. This paper proposes a microcolumn array dielectric layer produced using photolithography technology that enables tunability of sensor sensitivity and detection range by adjusting the aspect ratio and interval of the microstructures. Meanwhile, the impact of five constant normal force couplings on the sensitivity of shear force perception is investigated. The structure array with a 1:2 aspect ratio and 600 µm interval demonstrates an ultrahigh sensitivity of 6.189 N−1 and outstanding linearity (R2 = 0.9873) within the range up to 0.1 N. The sensor exhibits low hysteresis and robust stability over 3000 cycles. Additionally, it exhibits remarkable anisotropic direction sensitivity, enabling accurate positioning within a quarter‐circle angle. An intentionally designed orthogonal array is employed to extend the shear angle range up to 360°. Owing to the high performance of the sensor, it is further integrated onto a gripper to facilitate the grasping operation and effectively capture delicate movements. The experimental outcomes highlight that the designed sensor holds promise for applications in robotic applications and electronic skin domains.

Adaptive tactile interaction transfer via digitally embroidered smart gloves

Human-machine interfaces for capturing, conveying, and sharing tactile information across time and space hold immense potential for healthcare, augmented and virtual reality, human-robot collaboration, and skill development. To realize this potential, such interfaces should be wearable, unobtrusive, and scalable regarding both resolution and body coverage. Taking a step towards this vision, we present a textile-based wearable human-machine interface with integrated tactile sensors and vibrotactile haptic actuators that are digitally designed and rapidly fabricated. We leverage a digital embroidery machine to seamlessly embed piezoresistive force sensors and arrays of vibrotactile actuators into textiles in a customizable, scalable, and modular manner. We use this process to create gloves that can record, reproduce, and transfer tactile interactions. User studies investigate how people perceive the sensations reproduced by our gloves with integrated vibrotactile haptic actuators. To improve the effectiveness of tactile interaction transfer, we develop a machine-learning pipeline that adaptively models how each individual user reacts to haptic sensations and then optimizes haptic feedback parameters. Our interface showcases adaptive tactile interaction transfer through the implementation of three end-to-end systems: alleviating tactile occlusion, guiding people to perform physical skills, and enabling responsive robot teleoperation.

Wilhelmy balance—A simple and reliable method for determining immersion angles and surface energies even on non‐planar and complex geometries?

The growing significance of surface properties in modern materials, particularly in medical technology, drives the need for accurate characterization techniques. Traditional contact angle measurements face challenges when applied to intricate surfaces like dental implants. Here, tensiometry applying the Wilhelmy plate method has been described in the last decade to offer one solution for the evaluation of complex surface geometries by quantifying apparent contact angles based on wetting forces. This study evaluates a simple setup employing the Wilhelmy balance concept for immersion angle determination. Instead of using a force sensor as in tensiometers, the wetting force is determined via changes in mass signal by means of an analytical balance available in standard laboratories. The force is thus recorded inverse to conventional tensiometry. The approach was validated on diverse geometries and extended to intricate structures, including plasma‐treated dental implants. Results were compared to conventional contact angle analysis systems underlining the reliability of the method in characterizing non‐planar and complex surfaces. Additionally, the method was successfully extended to the evaluation of surface energies on planar and non‐planar surfaces using various solvent sets. However, results evidenced that specimen geometry can influence the measurements to such an extent that immersion contact angles can no longer be calculated due to capillary effects. An outlook suggests further exploration with a wider range of test liquids to enhance accuracy in surface energy determination.

Mineral Tanning‐Inspired Metal Ions Coordination Hydrogels with Outstanding Mechanical Strength and Toughness for Flexible Force Sensors

AbstractBy virtue of reversible energy dissipation and good ionic conductivity, metal ions have been extensively introduced to construct hydrogels. However, the traditional soaking method to prepare metal ions coordination hydrogels (MI‐HG) faces the challenge of diffusion and combination of metal ions, leading to weak mechanical properties. Inspired by the leather mineral tanning mechanism, a strategy that controls the accessibility of hydrogels by pickling and basifying processes thus significantly improving the strength and toughness of MI‐HG is proposed. To achieve this, polyvinyl alcohol/poly(acrylamide‐co‐acrylic acid) (PVA/PAM‐co‐PAA) hydrogels‐bearing ligands similar to those of leather collagen are fabricated. Zr4+, Cr3+, Al3+, and Fe3+ commonly used for mineral tanning are chosen as the metal source. The results demonstrate that the mechanical properties of the products (MI‐HGTanning) are significantly promoted, especially for Cr3+ and Zr4+. For example, the tensile strength of Zr‐HGTanning and toughness of Cr‐HGTanning reach 7.79 ± 0.41 Mpa and 28.01 ± 3.1 MJ m−3, approximately three and seven times that of their soaking samples. From macro to micro characterization and by theoretical simulation, the mineral tanning mechanism of metal ions first permeating and then effectively combining with carboxylates, thus improving the mechanical performance of MI‐HGTanning is deciphered, the products of which are promised applications in flexible force sensors.

INVESTIGATION OF LOW-COST PIEZOELECTRIC FORCE SENSOR

The use of piezoelectric force sensors is well-established in industrial systems and devices, but their adoption in consumer products has been limited due to the high cost of implementation as well as complex peripheral electronics. This paper proposes an alternative approach to force sensing using commonly available piezoelectric buzzer elements, which could potentially reduce the cost of such sensors and promote their integration into consumer products. The paper represents experimental investigations of output characteristics of two different piezoelectric force sensors, which are based on disc-shaped buzzers. The goal of the investigation is to indicate and experimentally confirm electromechanical characteristics of proposed piezoelectric sensors under different sensing and signal management conditions. The results of the investigations showed that piezo buzzers have the potential to serve as cost-effective force sensors in consumer products as well as in different mechatronic systems.

Design and analysis of parallel six-dimensional force sensor based on near-singular characteristics

The high sensitivity six-dimensional force sensor is the core component of intelligent robot force feedback perception, which is related to the structure of the sensor. This paper proposes a new modeling method to chain the near singular eight-branch Stewart mechanism, which indicates the relationship between structural parameters and sensitivity. The new method gains 16 new configurations by innovating the traditional Stewart institution. A configuration with high sensitivity in Fz, Mx and My directions is selected for further study. The theoretical stiffness model and force mapping model show that the sensitivity of the new structure can be amplified by 4 times in specific degrees of freedom. The results show that the nonlinear error and coupling error are 2.77% and 2.26%, respectively. The proposed method can be widely applied in the field of parallel six-dimensional force sensors.

A BIOCOMPATIBLE GLASS-ENCAPSULATED TRIAXIAL FORCE SENSOR FOR IMPLANTABLE TACTILE SENSING APPLICATIONS.

This paper reports a microfabricated triaxial capacitive force sensor. The sensor is fully encapsulated with inert and biocompatible glass (fused silica) material. The sensor comprises two glass plates, on which four capacitors are located. The sensor is intended for subdermal implantation in fingertips and palms and providing tactile sensing capabilities for patients with paralyzed hands. Additional electronic components, such as passives and IC chips, can also be integrated with the sensor in a hermetic glass package to achieve an implantable tactile sensing system. Through attachment to a human palm, the sensor has been shown to respond appropriately to typical hand actions, such as squeezing or picking up a bottle.