Design Of Force Sensor Research Articles

Waterproof Design of Soft Multi-Directional Force Sensor for Underwater Robotic Applications

Directional force sensing is an intrinsic feature of tactile sensing. As technologies of exploratory robots evolve, with special emphasis on the emergence of soft robotics, it is crucial to equip robotic end-effectors with effective means of characterizing trends in force detection and grasping phenomena, while these trends are largely derived from networks of tactile sensors working together, individual sensors must be built to meet an intended function and maintain functionality with respect to environmental operating conditions. The harshness of underwater exploration imposes a unique set of circumstances onto the design of tactile sensors. When exposed to underwater conditions a tactile sensor must be able to withstand the effects of increased pressure paired with water intrusion while maintaining computational and mechanical integrity. Robotic systems designed for the underwater environment often become expensive and cumbersome. This paper presents the design, fabrication, and performance of a low-cost, soft-material sensor capable of multi-directional force detection. The fundamental design consists of four piezo-resistive flex elements offset at 90∘ increments and encased inside of a hemispherical silicone membrane filled with a non-compressive and non-conductive fluid. The sensor is simulated numerically to characterize soft-material deformation and is experimentally interrogated with indentation equipment to investigate sensor-data patterns when subject to different contact forces. Furthermore, the sensor is subject to a cyclic loading test to analyze the effects of hysteresis in the silicone and is submerged underwater for a 7-day period to investigate any effect of water intrusion at a shallow depth. The outcome of this paper is the proposed design of a waterproofed, soft-material tactile sensor capable of directional force detection and contact force localization. The overall goal is to widen the scope of tactile sensor concepts outfitted for the underwater environment.

The behaviour of different design of flexible force sensor based velostat during implementation of static load with different contact area

Great attention has been given to flexible force sensors and the materials that have been used as a sensing material by studying their properties and evaluate their behaviours with different types of loads. Velostat is one of the most promising sensing materials that has been widely studied and evaluated for different applications due to their distinct traits of flexibility, suitable cost as well as their ability to cover the wearable applications. This work makes focus on the behaviour of Velostat flexible force sensor by measuring the resistivity of the sensor while applying loads with different contact area. Two different designs of sensor have been studied, which are the single output flexible force sensor and multioutput matrix flexible force sensor, by applying loads starting from 0.98 (N) to 9.8 (N) with four compression disc having different diameters. It has been found that the two design behave in opposite manner. The resistance of the single output design decreased as the contact area increased, while the matrix design showed an increasing in the resistance as the contact area increased.

Design and development of a multi-axis force sensor based on the hall effect with decouple structure

This paper investigates the design and development of a novel 3-axis force sensor for human–robot interaction purposes. Based on the characteristics of the sensing technologies proposed in the literature, the Hall effect sensor is chosen according to its linearity, low-cost and appropriate range for voltage output. Then, by properly positioning the hall effect sensors, an asymmetric structure for the force sensor is presented. The proposed structure is inspired by an gyroscope’s architecture which provides an independent output on the sensor’s axes. As a result, each axis of the sensor, independently, creates a relationship between force and displacement which is covered by a silicon structure. Therefore, the Jacobian matrix of the proposed structure becomes an identity matrix for which the least-squares estimation is used to identify the force/displacement relationship. The developed force sensor has the ability to measure the force along the three cartesian axes Xˆ, Yˆ, Zˆ with the resolution of 2 mN, 1.5 mN, and 0.2 N, respectively. In order to illustrate the performance of the proposed multi-axis force sensor, an interactive simple control is carried out which is performed by attaching the sensor to the end-effector of a parallel robot, the so-called Tripteron robot, and enable to have a safe reaction in the case of occurring a collision in an environment.

Flexible six-dimensional force sensor inspired by the tenon-and-mortise structure of ancient Chinese architecture for orthodontics

Precise multi-axis operation is essentially required in orthodontics for tooth movement. Despite the development of flexible multi-dimensional force sensors that have effectively perceived multi-dimensional forces, they still face the challenge of simultaneously 3D force and moment in a single flexible force sensor. Six-dimensional force perception can successfully operate objects that critically rely on directional tracking and accurate monitoring of complex multi-axis stimuli. To realize the integration of sensing units with the perception of six-dimensional force under even a soft touch, we design a flexible six-dimensional force sensor with tenon-and-mortise interlocking structures inspired by traditional Chinese ancient architecture. This unique structure enables conjunction of deformation, which can be studied and decoded by Deep Neural Networks (DNN) with six-dimensional force, including forces and rotating moments in the x, y, and z directions. This soft sensor with minimal size (7 × 7 × 7 mm3) and high detection accuracy (the DNN error is below 10−4) can be used in orthodontic treatment for precise correction with a full collection of orthodontic force. This unique flexible six-dimensional force sensor provides a new strategy for the design of multi-dimensional force sensors, paving the way for the development of intelligent robotics, interactive human-machine interfacing, and advanced prosthetics.

Design of fiber force sensors for surgical probes

Design of fiber force sensors for surgical probes

一种新型三维力传感器结构设计与优化

一种新型三维力传感器结构设计与优化

A low cost 3-DOF force sensing unit design for wrist rehabilitation robots

In this study, a low cost and modular three degree-of-freedom force sensor design is developed for the purposes of wrist rehabilitation. The proposed sensor in this study and the existing sensors in the literature are compared to each other considering nine main topics namely, measurement capability, design purpose, measurement approach, force limits, dimensions, producing & assembly complexity, producing cost, modularity and electronics. The comparison results are given as a table. Considering the sensors developed especially for the purpose of wrist rehabilitation in the literature, the proposed sensor has some advantages as follows: The proposed sensor has i) modular structure, ii) less producing & assembly complexity, iii) low cost and iv) integrated electronic and mechanical structures. A specific experimental setup is also developed for both performing force measurements and control of flexion/extension movements. Linearity, hysteresis and repeatability errors of proposed multi-axis force sensor unit are given as table. A set of force measurements is carried out using this experimental setup. Measurements are illustrated as figures. It can be concluded that the proposed force sensor can be used for human-robot interaction in wrist rehabilitation.

Design and Experimental Validation of a Fiber Bragg Grating-Enabled Force Sensor With an Ortho-Planar Spring-Based Flexure for Surgical Needle Insertion

This paper presents the development of a novel and high-precision Fiber Bragg Grating (FBG)-based sensor for the measurement of insertion forces during the needle puncture procedure. The proposed sensor mainly comprises two compact orthogonal planar springs connected in a parallel arrangement, one suspended FBG optical fiber and a hand-held sensor frame. Two orthogonal planar springs with curved limbs have been utilized to design the force-sensitive flexure with an excellent linear force-displacement relationship along the axial direction. The employed optical fiber has been arranged along the flexure’s central line, and it is tightly suspended under a pre-tension force with its two ends glued. This two-point pasting configuration can attain improved sensitivity and resolution and avoid the drawbacks of chirping and low repeatability. Finite element modeling (FEM)-enabled simulation has been implemented for design optimization to further advance the sensor sensitivity and performance investigation. The sensor’s axial sensitivity has been increased in the condition when the radial crosstalk decreased. The proposed sensor has been prototyped and calibrated to achieve a high resolution of 1.5mN within [0, 6N] and an excellent linearity with a small linearity error of 0.5%. This design can be conveniently customized to achieve adjustable measurement range and force sensitivity, which has been validated by the further simulation sensor version with a resolution of 4.9mN within [0, 20N]. In-vitro puncture experiments on silicone phantoms, artificial venipuncture simulation module and eggshell membrane, and ex-vivo puncture experiments on porcine liver and porcine aorta have been implemented to validate the effectiveness of the presented sensor design.

Output characteristics and experimental study of a highly linear and large-range force sensor based on the Villari effect

Based on the principle of the Villari effect, a force sensor with a giant magnetostrictive material (GMM) as the sensitive element, high linearity, and a large range was studied. A Hall element integrated into the structure was used to detect the magnetic flux density and measure the external force. First, the finite element method was used to verify the validity of the intended magnetization process. Second, an equation for GMM magnetization was derived based on the Jiles–Atherton (J–A) model and the magneto-mechanical coupling effect. The relationships between magnetization and the biased magnetic field, and magnetization and the external force were analyzed under the dynamic coupling model of positive and negative effects. Finally, the influences of various biased magnetic fields and external forces on the sensor output characteristics were determined experimentally. The sensitivity of the designed force sensor was 0.337 mV/N when the bias current was 1.2 A and the preload was 120 N. When a force of 1000 N was applied, the linearity was 0.82%. The experimental results are consistent with the theoretical design values. These research results aid in the development of a highly linear, large-range force sensor. This study provides the theoretical and technical foundations for a high-performance force sensor that can be used in industrial testing.

Design and Characterization of a New Soft Fingertip Force Sensor for Precision Robotic Grasping Task

Nowadays, a new robotic field has emerged, called Soft Robotics, and it is a new field that involves new challenges, such as soft manipulation, considering external force measure or contact sensors. Thus, in this paper, a new soft fingertip force sensor is introduced. The methodology proposed consists in a quantitative applied research aiming to propose a device able to detect and measure external applied forces. In order to reach the above target, the following steps have been performed: i.) requirements identification, ii) transductor selection, ii) rigid structure design, iii.) soft structure design, iv.) definition of variables parameters for sensor characterization, v.) implementation of the experiments to quantify the relation between external forces and output voltage for different operation conditions, and vi.) proposition of the mathematical model. The mathematical model is defined to describe applied external force and sensor output voltage, demonstrating different mathematical models for two soft materials (polyaddition and polycondensation silicones). It has been found out that using a softer silicone increases the sensor sensitivity. However, the selection of silicone depends on the application requirements. Moreover, the use of soft materials gives a high compliance level with contact objects. On the other hand, a new sensor structure that could be implemented using a 3D print and a FSR traductor, easily implemented by a 3D Printer, has been proposed. Then the mathematical model presented could be used by researchers Moreover, researchers could modify the parameters explained in order to obtain different soft sensor performance. Thus, the soft sensor is endowed with versatility, compliance, and molding.

Optimal design of sensor structure based on virtual calibration test

The design of wheel six-component force sensor includes elastic body, strain gauges distribution scheme, signal acquisition and processing and so on. In this paper, the virtual calibration test is used to optimize the structure of the sensor elastic body. According to the structure and principle of the self-developed six component force sensor calibration test-bed, a set of calibration device is designed for the sensor. The stress distribution and strain output of the elastic body are obtained by finite element method. The optimization of elastic body is carried out from the requirements of material strength and coupling rate of output signal. Finally, the sensor elastic body structure which meets the strength requirements and has low coupling rate is obtained.

Development and Verification of a Tire Three-component Force Sensor for Increasing the Control Performance of the Chassis Electronic Control System

This paper presents a tire three-component force sensor which can be used to increase electronic control system performance. Firstly, the shape and strain gauges distribution scheme of the tire three-force sensor are designed. As a car-installed force sensor, it is in small size, and there is no crosstalk between forces according to simulation result. Secondly, the force sensor entity is calibrated by using self-developed calibration device. Finally, experiments on vehicle is carried out. This paper is an important guidance for the design of a car-installed tire three-component force sensor. By supplying real-time tire forces to electronic control system, it offers a new way of developing intelligent tire.

DESIGN AND CHARACTERIZATION OF A MINIATURE THREE-AXIAL MEMS FORCE SENSOR

This paper reports the design, fabrication and calibration results of a miniature cross-shaped three-axial piezoresistive force sensor, which can simultaneously detect three force components in orthogonal directions. MEMS technology was used to fabricate the sensor structure and deposit a phosphosilicate layer on the silicon wafer to form piezoresistive resistors. Using the finite element simulation, the developed sensor performance characteristics, such as linearity, repeatability, sensitivity, and hysteresis, are analyzed for different arrangements of eight piezoresistors on the silicon beam surface. The sensor performance was experimentally validated by monitoring the voltage variation of Wheatstone bridge when a load-bearing rigid rod was loaded in three different directions by a set of weights. Calibration results exhibited linear output responses with the maximum linearity of 0.98 and small crosstalk below 7%. The MEMS sensor repeatability was tested with a commercial stepper motor by measuring a step function-varying profile force was applied to the sensor. Further optimization of the sensor design for sensing six degrees of freedom movement is envisaged with its sensitivity enhancement by the silicon substrate reduction.

An Inductive Force Sensor for In-Shoe Plantar Normal and Shear Load Measurement

Diabetic foot ulcers (DFUs) are a severe global public health issue. Plantar normal and shear load are believed to play an important role in the development of foot ulcers and could be a valuable indicator to improve assessment of DFUs. However, despite their promise, plantar load measurements currently have limited clinical application, primarily due to the lack of reliable measurement techniques particularly for shear load measurements. In this paper we report on the design and evaluation of a novel tri-axis force sensor to measure both normal and shear load on the foot’s plantar surface simultaneously. The sensor consists of a group of inductive sensing coils above which a conductive target is placed on a hyperelastic elastomer. Movement of the target under load affects the coil inductances which are measured and digitized by an embedded system. Using a computational finite element model, we investigated the influence of sensing coil form and configuration on sensor performance. A sensor configured with four-square coils and maximal turns provided the best performance for plantar load measurements. A prototype was fabricated and calibrated using a neural network to map the non-linear relationship between the sensor output and the applied tri-axis load. Experimental evaluation indicates that the tri-axis sensor can effectively detect shear load of ±16 N and normal load up to 105 N (RMS errors: 1.05 N and 1.73 N respectively) with a high performance. Overall, this sensor provides a promising basis for plantar normal and shear load measurement which are crucial for improved assessment of DFU.

Electric Modulation on the Sensitivity and Sensing Range of CMOS-MEMS Tactile Sensor by Using the PDMS Elastomer Fill-In

This study presents the design and implementation of a MEMS capacitive tactile force sensor with polydimethylsiloxane (PDMS) filler for in-process and in-use modulation of the sensing range and sensitivity performance. The presented MEMS tactile force sensor consists of a loading unit with driving electrodes, PDMS filler, and a sensing unit. By varying input voltages on the driving electrodes (either in curing process or in-use), the stiffness of the PDMS filler as well as the loading unit can be modulated. Thus, the sensitivity and sensing range of the presented tactile force sensor was modulated accordingly. Since each sensor has its own driving electrodes and electrical routings, different input voltages can be applied to modulate the PDMS for each individual sensor. As a result, tactile sensors of different sensitivities and sensing ranges can be simultaneously fabricated and monolithically integrated on the same chip using the presented approach. The tactile sensors were implemented using TSMC 0.18 μm 1P6M standard CMOS process together with the in-house post-CMOS releasing and the polymer filling processes. Experiments demonstrate the capabilities of implementing various tactile sensors with different sensing ranges and sensitivities on a single chip by the in-process and in-use modulation techniques. Through the in-process and in-use modulation, the presented CMOS-MEMS tactile sensors show the sensing window: (1) for sensitivity modulation: 8.6 fF/N to 219.1 fF/N, and (2) for sensing range modulation: 30 mN to 270 mN.

Self‐adhesive plasticized regenerated silk on poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) for bio‐piezoelectric force sensor and microwave circuit design

AbstractThis study shows that regenerated silk (RS), a natural biodegradable and biocompatible polymer, can behave as a self‐adhesive thermoplastic material with multifunctional properties. In particular, Ca ions‐plasticized RS hybrids with gold nanorods have been produced. It has been found that at mild conditions of temperature and pressure, RS hybrids undergo to the loss of the β‐sheet content and forms a tough self‐adhesive material on poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) substrate. The structure‐dependent piezoelectricity of such RS adhesives on PHBV films was investigated and it was demonstrated that this forms a RS/PHBV piezoelectric sensor that can be used for the monitoring of force. The constitutive parameters (i.e., permittivity and loss tangent) of both PHBV and RS/PHBV were measured in view of their use as dielectric substrates in microwave circuit design. Being fully made of biodegradable and biocompatible materials, this self‐adhesive material can be used in tissue engineering for different applications.

Optical Force Sensor With Enhanced Resolution for MRI Guided Biopsy

A novel fiber optic force sensor design with enhanced resolution through titanium coating is fabricated using Fabry-Perot Interferometry (FPI) method and integrated into an 18 gauge MRI compatible biopsy needle, to be used in MRI guided interventional biopsy operations. The force sensor range and resolution are defined, and also needle insertion detection, deflection detection, tissue characterization and differentiation capabilities are tested via benchtop experiments. Overall system performance is tested via in vitro experiments under MRI using a commercial prostate phantom with representative leisons and it was shown that high resolution force sensing can help user to make sure that biopsy specimens are taken from the correct location. The fabricated sensor can measure forces up to 20 N with 0.1 N resolution and Ti coating enhances the sensor resolution to 0.03 N. Using biopsy needles with force measurement capability can improve the accuracy and safety of MRI guided minimally invasive biopsy procedures such as prostate biopsy. Biopsy needles incorporating high resolution force sensor can be used as a promising tool for cancer diagnosis thru stiffness detection of benign and malignant tissues instead of collecting biopsy specimens.

Enhance the sensitivity of strain-gauge-based force sensors using moving morphable units method

This paper presents a new automatic optimal design formulation to achieve high sensitivities of the strain-gauge-based force sensors based on the method of moving morphable units (components or voids). We examine our design formulation through several examples, of which the results demonstrate the feasibility and efficiency of the proposed approach. In addition to the explicit boundaries that are finally derived, the current formulation has another superiority that the strain gauge locations can be easily treated as design variables by taking the sensing areas as additional components. Furthermore, the formulation is compatible with the shape optimization such that we can unite topology design and shape design of force sensors into one optimization framework.

Stiffness modeling and force mapping analysis of hybrid-limb six-axis force sensor

To meet the needs of large load and high reliability measurement under complex working conditions and downsize the outline of six-axis force sensor as much as possible, the design concept of hybrid limb is proposed to the design of parallel six-axis force sensor. A kind of heavy-load-bearing flexible integrated six-axis force sensor with hybrid limbs is proposed. The proposed force sensor adopts a hybrid-limb configuration integrating eight measuring redundant limbs and four load-bearing limbs. It is capable of measuring 5500 N vertical force, 3000 N horizontal force, 160 N·m moment about the vertical axis, and 130 N·m moment about the horizontal axis. Based on the superposition principle under small deformation, the whole stiffness matrix of force sensor and the analytical mapping relation are constructed, respectively. The accuracy of the theoretical modeling is verified by the stress analysis of the designed sensor using finite element method software ANSYS. Finally, the prototype is calibrated, and the results show that it has good linearity.

Shoe-Integrated, Force Sensor Design for Continuous Body Weight Monitoring.

Traditional pedobarography methods use direct force sensor placement in the shoe insole to record pressure patterns. One problem with such methods is that they tap only a few points on the flat sole under the foot and, therefore, do not account for the total ground reaction force. As a result, body weight tends to be under-estimated. This disadvantage has made it more difficult for pedobarography to be used to monitor many diseases, especially when their symptoms include body weight changes. In this paper, the problem of pedobarographic body weight measurement is addressed using a novel ergonomic shoe-integrated sensor array architecture based on concentrating the applied force via three-layered structures that we call Sandwiched Sensor Force Consolidators (SSFC). A shoe prototype is designed with the proposed sensors and shown to accurately measure body weight with an achievable relative accuracy greater than 99%, even in the presence of motion. The achieved relative accuracy is at least 4X better than the existing state of the art. The SSFC shoe prototype is built using readily available soccer shoes and piezoresistive FlexiForce sensors. To improve the wearability and comfort of the instrumented shoe, a semi-computational sensor design methodology is developed based on an equivalent-area concept that can accurately account for SSFC’s with arbitrary shapes. The search space of the optimal SSFC design is shown to be combinatorial, and a high-performance computing (HPC) framework based on OpenMP parallel programming is proposed to accelerate the design optimization process. An optimal sensor design speedup of up to 22X is shown to be achievable using the HPC implementation.