Multi-axis Force Research Articles

Direct measurement of three-dimensional forces at the medial meniscal root: A validation study

The posterior medial meniscal root (PMMR) experiences variable and multiaxial forces during loading. Current methods to measure these forces are limited and fail to adequately characterize the loads in all three dimensions at the root. Our novel technique resolved these limitations with the installation of a 3-axis sensing construct that we hypothesized would not affect contact mechanics, would not impart extraneous loads onto the PMMR, would accurately measure forces, and would not deflect under joint loads. Six cadaveric specimens were dissected to the joint capsule and a sagittal-plane, femoral condyle osteotomy was performed to gain access to the root. The load sensor was placed below the PMMR and was validated across four tests. The contact mechanics test demonstrated a contact area precision of 44 mm2 and a contact pressure precision of 5.0 MPa between the pre-installation and post-installation states. The tibial displacement test indicated an average bone plug displacement of < 1 mm in all directions. The load validation test exhibited average precision values of 0.7 N in compression, 0.5 N in tension, 0.3 N in anterior-posterior shear, and 0.3 N in medial–lateral shear load. The bone plug deflection test confirmed < 2 mm of displacement in any direction when placed under a load. This is the first study to successfully validate a technique for measuring both magnitude and direction of forces experienced at the PMMR. This validated method has applications for improving surgical repair techniques and developing safer rehabilitation and postoperative protocols that decrease root loads.

Patient-specific Ti-6Al-4V lattice implants for critical-sized load-bearing bone defects reconstruction

The advancement in additive manufacturing in recent years opened a new era for bone reconstruction methods, allowing for the design of customized implants that perfectly match clinical needs. This challenge is even more prominent in critical-sized bone defects, where the bone cannot heal independently. Here we present a novel workflow for such cases. First, a multidisciplinary team conducted the surgical plan, including the design of an intraoperative patient-specific instrument. Then, a Ti-6Al-4V implant was created to exactly fit the resected tumor's bone gap. An ambitious bone regenerative approach was taken in designing the implants with a porous-lattice body acting as a scaffold for new bone formation, reinforced with standard orthopedic instruments for adequate mechanical support. To prevent future failure of the implant, a finite element analysis was used to evaluate stress distribution simulation according to the multi-axis forces and moments applied on the bone during walking. Our results demonstrate the potential for Ti-6Al-4V implants to become the best practice for reconstructing significant bone defects. This proof-of-concept may enhance clinical care and catalyze new frontiers in patient-specific medicine. To the best of our knowledge, this is the first study to describe in detail the design and fabrication of this method.

A Multiaxis Force Sensor Based on Pre-Strained Piezoresistive Film Strips

A Multiaxis Force Sensor Based on Pre-Strained Piezoresistive Film Strips

BaroTac: Barometric Three-Axis Tactile Sensor with Slip Detection Capability.

Tactile sensors for robotic applications enhance the performance of robotic end-effectors as they ca n provide tactile information to operate various tasks. In particular, tactile sensors can measure multi-axial force and detect slip can aid the end-effectors in grasping diverse objects in an unstructured environment. We propose BaroTac, which measures three-axial forces and detects slip with a barometric pressure sensor chip (BPSC) for robotic applications. A BPSC is an off-the-shelf commercial sensor that is inexpensive, easy to customize, robust, and simple to use. While a single BPSC-based tactile sensor can measure pressure, an array of BPSC-based tactile sensors can measure multi-axial force through the reactivity of each sensor and detect slip by observing high frequency due to slip vibration. We first experiment with defining the fundamental characteristics of a single-cell BPSC-based sensor to set the design parameters of our proposed sensor. Thereafter, we suggest the sensing method of BaroTac: calibration matrix for three-axis force measurement and discrete wavelet transform (DWT) for slip detection. Subsequently, we validate the three-axis force measuring ability and slip detectability of the fabricated multi-cell BPSC-based tactile sensor. The sensor measures three-axis force with low error (0.14, 0.18, and 0.3% in the X-, Y- and Z-axis, respectively) and discriminates slip in the high-frequency range (75-150 Hz). We finally show the practical applicability of BaroTac by installing them on the commercial robotic gripper and controlling the gripper to grasp common objects based on our sensor feedback.

Analysis of Force Sensor Using Polymer Optical Fiber Based on Twisting Structure

This article highlights an intensity variation-based force sensor for polymer optical fiber (POF) that relies on the twisting structure. The sensing phenomena of the sensor rely on cladding mode frustrated total internal reflection (CMFTIR). A portion of two POFs is twisted in the middle where the light source is connected with illuminating fiber, and the power meter is connected with the forward end of the second fiber. Thus, the force measurement is taken from the second fiber by observing the variation of coupled intensity in which the applied force is up to 0–20 N. The sensor is analyzed on straight fiber, twisted fiber with bend, and without bend (considering the sensor’s sensitivity). The experimental results show that the sensor has higher sensitivity in the twisted with-bend structure, and the bending radius also affects the sensor sensitivity. Moreover, a multipoint and multiaxis force sensor is also presented. The POF is twisted up to 100 cm for multipoint sensing, and force is applied at five different points, whereas the cascading scheme is adopted for multiaxis to achieve the individual response of each axis. This study provides an alternative way to measure force based on intensity changes and has an additional advantage of being cheaper than fiber Bragg gratings and other systems.

Easy-to-Deploy Combined Nasal/Throat Swab Robot With Sampling Dexterity and Resistance to External Interference

Robots have been used extensively in the battle against the COVID-19 pandemic since its outbreak. One prominent direction is the use of robots for swab sampling, which not only solves the shortage of medical staffs, but also prevents them from being infected during face-to-face sampling. However, a massive deployment of sampling robots is still not achievable due to their high costs, safety concerns, deployment complexity, and so on. In this letter, we propose a flexible, safe, and easy-to-deploy swab robot in a compact bench-top system. The robot can perform nasal/throat swab sampling tasks as dexterous as a human manual operation. The bio-mimetic rigid interior and soft exterior design guarantee the sampling robot with both flexibility and safety. Furthermore, the integration of 3-D fiber Bragg grating (FBG) based shape sensor and multi-axis force sensor may enhance the control performance. A dedicated constrained compliance control (CCC) algorithm was developed to tackle the unexpected interactions during sampling, which ensures the validity and safety of the sampling under disturbance. Various experiments are conducted to validate our system and prove its feasibility, flexibility, high safety, and efficiency for both nasal/throat swab sampling tasks. The proposed system is promising to be massive duplicated for robotic swab sampling.

Optimal design of loading device based on a redundantly actuated parallel manipulator

Reliability of machine tools has attracted much attention both in academia and industry. The loading device is very important for the reliability study of CNC machine tools as it can apply multi-axis dynamic forces to the spindle to replace cutting tests. A loading device based on the redundantly actuated parallel manipulator (R5LD) with strong loading capability is proposed in this paper. Firstly, to evaluate the loading capability, this paper proposes new transmission indices for redundantly actuated parallel manipulators (PMs). Besides, the prescribed flexible orientation workspace and regular workspace are defined for the loading device. Then, the corresponding performance atlases are represented graphically in the design space. The structure parameters of the R5LD are achieved in the optimum region of performance atlases. Finally, the R5LD with the optimum parameters is compared with the loading device based on the corresponding non-redundant PM. The R5LD has a larger regular workspace and better transmission performance. The additional UPS chain of the R5LD makes the configuration more symmetrical, balances forces distribution among chains, and strengthens the loading capability of the loading device.

Redundant Parallel Beam Multiaxis Force Sensor—Accuracy Space

The principle of the redundant parallel beam multi-axis force sensor is a transformation from displacement domain to force domain. This paper proposed a general force error model of a distributed force measurement system with redundant multi-axis force sensors based on the measurement <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$/$ </tex-math></inline-formula> surveying adjustment method to transform displacement sensor errors to force errors. The optimum accuracy space is defined according to the error model. According to the accuracy space, the torque error increase sharply when the measuring point is far away from the optimum accuracy space, but the force error remains constant. A long-distance arrangement of displacement sensors can increase the size of the optimum accuracy space and a high-precision displacement sensor can increase the measurement accuracy in the whole space. A deformation filter can minimize the affection of the loading platform deformation on the measurement accuracy. A dual-measurement system is recommended to increase both the force accuracy and the torque accuracy when the measuring point is far from the optimum accuracy space of the main multi-axis force sensing system. The error point cloud is used to verify the proposed error model.

A Miniature Soft Sensor with Origami-Inspired Self-Folding Parallel Mechanism.

Miniature soft sensors are crucial for the perception of soft robots. Although centimeter-scale sensors have been well developed, very few works addressed millimeter-scale, three-dimensional-shaped soft sensors capable of measuring multi-axis forces. In this work, we developed a millimeter-scale (overall size of 6 mm × 11 mm × 11 mm) soft sensor based on liquid metal printing technology and self-folding origami parallel mechanism. The origami design of the sensor enables the soft sensor to be manufactured within the plane and then fold into a three-dimensional shape. Furthermore, the parallel mechanism allows the sensor to rotate along two orthogonal axes. We showed that the soft sensor can be self-folded (took 17 s) using a shape-memory polymer and magnets. The results also showed that the sensor prototype can reach a deformation of up to 20 mm at the tip. The sensor can realize a measurement of external loads in six directions. We also showed that the soft sensor enables underwater sensing with a minimum sensitivity of 20 mm/s water flow. This work may provide a new manufacturing method and insight into future millimeter-scale soft sensors for bio-inspired robots.

Effects of Different Stitch Types and Stitch Combinations on the Seam Bursting Strength and Seam Strength of Workwear

Workwears are produced to protect the wearer against occupational or environmental hazards. One of the shared properties of several workwear types is resisting external forces during occupation. As for workwear fabrics, the seams of the workwear should be strong enough to resist uniaxial or multiaxial forces to maintain the properties in the cut and sewn parts of the garment. Therefore, in this study, effects of different stitch types and their combinations on the workwear seam and bursting strengths were evaluated. According to results, a 2-step failure was observed at the seam strength tests of samples those contained stitch combinations. Here, the main function of the second stitch row was to form a safety stitch rather than increasing the overall performance. Contrarily, usage of stitch combinations obviously contributed to the seam bursting strengths. In this case, the stitch rows responded to the bursting forces together therefore the bursting failures occurred in 1-step.

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.

Tactile Sensing for Minimally Invasive Surgery: Conventional Methods and Potential Emerging Tactile Technologies.

As opposed to open surgery procedures, minimally invasive surgery (MIS) utilizes small skin incisions to insert a camera and surgical instruments. MIS has numerous advantages such as reduced postoperative pain, shorter hospital stay, faster recovery time, and reduced learning curve for surgical trainees. MIS comprises surgical approaches, including laparoscopic surgery, endoscopic surgery, and robotic-assisted surgery. Despite the advantages that MIS provides to patients and surgeons, it remains limited by the lost sense of touch due to the indirect contact with tissues under operation, especially in robotic-assisted surgery. Surgeons, without haptic feedback, could unintentionally apply excessive forces that may cause tissue damage. Therefore, incorporating tactile sensation into MIS tools has become an interesting research topic. Designing, fabricating, and integrating force sensors onto different locations on the surgical tools are currently under development by several companies and research groups. In this context, electrical force sensing modality, including piezoelectric, resistive, and capacitive sensors, is the most conventionally considered approach to measure the grasping force, manipulation force, torque, and tissue compliance. For instance, piezoelectric sensors exhibit high sensitivity and accuracy, but the drawbacks of thermal sensitivity and the inability to detect static loads constrain their adoption in MIS tools. Optical-based tactile sensing is another conventional approach that facilitates electrically passive force sensing compatible with magnetic resonance imaging. Estimations of applied loadings are calculated from the induced changes in the intensity, wavelength, or phase of light transmitted through optical fibers. Nonetheless, new emerging technologies are also evoking a high potential of contributions to the field of smart surgical tools. The recent development of flexible, highly sensitive tactile microfluidic-based sensors has become an emerging field in tactile sensing, which contributed to wearable electronics and smart-skin applications. Another emerging technology is imaging-based tactile sensing that achieved superior multi-axial force measurements by implementing image sensors with high pixel densities and frame rates to track visual changes on a sensing surface. This article aims to review the literature on MIS tactile sensing technologies in terms of working principles, design requirements, and specifications. Moreover, this work highlights and discusses the promising potential of a few emerging technologies towards establishing low-cost, high-performance MIS force sensing.

Multi-Axis Loading on Multiple Flanges of Intermediate Aero-Engine Case Based on Parallel Robotic Simulation

Applying multi-axis force to an intermediate aero-engine case to simulate its working force environment is critical to accurately evaluate its mechanical properties. This paper presents a multi-axis loading method based on parallel robots to simultaneously add complex forces on two mounting flanges of the aero-engine case. The multi-axis loading device (MLD) for each flange was developed based on a 6-UPS parallel robot. Its geometric structure was presented and kinematics was analyzed. The static mapping between the multi-axis force and linear actuating force was derived on each flange, and the influence of loading two flanges at the same time was discussed. A force control algorithm based on admittance control was designed and the multi-axis loading on two flanges of aero-engine case was validated by simulations. Results illustrate that the MLD could apply multi-axis force to each flange and using two MLDs could simultaneously load two flanges. This suggests that parallel robots could be implemented as a general system to produce complex force environments for a series of aero-engine cases with multiple mounting flanges, which could mimic their actual working loads by ground tests to improve the accuracy of the mechanical property tests.

Development of methods to measure the forces at the rear suspension of a race car during racetrack driving

The forces generated by the tyres of a vehicle are responsible for the maximum achievable performance for a race car. In this work, a geometric matrix method combined with a sensitivity matrix method has been applied to a rear multi-link suspension of a rear-wheel-drive race car to estimate the tyre forces from the measurement of the loads acting on the suspension arms. The geometric matrix method calculates the wheel forces from the equilibrium of the wheel assembly, thus involving all reaction forces exchanged with the suspension arms. The reaction forces have been measured through the application of axial strain gauge bridges on the link arms; however, the lower arm has a complex geometry and exchanges multi-axial forces with the upright, therefore a sensitivity matrix method has been implemented. The strain gauges positions have been identified with FE analyses and after installing the sensors, the calibration of the entire suspension assembly has been performed in a dedicated test rig where known forces at the ideal contact point between the wheel and the ground can be applied. After the calibration and validation in the laboratory, the instrumented suspension has been installed in a race vehicle and multiple racetrack acquisitions have been successfully performed.

Resonant sensors for multi-axis force and torque estimation in collaborative robotics

This paper presents a complete design methodology for a multi-axis resonant force sensor. The proposed device has been designed to be useable in a context of physical interaction between robots and humans. The proposed solution allows the three force components and the three torque components to be measured simultaneously and can be inserted into an interface handle or a robot end-effector. The information on wrench can then be used to detect and control interactions for cooperative tasks between humans and robots. In the context of sensors for robotic co-manipulation, it is imperative to guarantee not only a certain level of performance (accuracy, dynamics, size) but also to guarantee certain non-functional specifications associated with safety, measurement redundancy or functional integration of the sensor into its environment. The consideration of all these design specifications, both functional and non-functional, led to the principles and technologies used to develop this sensor. Multi-axis resonant sensors have excellent performance and safety characteristics, two key elements for collaborative robotics, but the literature review did not reveal any significant previous work in this area. Thus, this paper proposes an original sensor based on a breakthrough technology in the crucial field of multi-axis force sensors. The performances obtained on our prototype are already close to the performances of the best existing 6-axis industrial sensors, which suggests very good prospects for this new technology. In addition, and compared to alternative technologies, resonance technology offers new possibilities in terms of sensor fault detection, thus improving the intrinsic safety of these devices.

Optimization of IC engine mounts for BAJA All-Terrain Vehicle

Vibration isolation has been a key area of focus in almost every mechanical component. The impact of vibrations on efficiency, longevity and performance of a machine component is tremendous. An automotive engine poses a very challenging vibration problem due to the multi-axial forces of varying amplitude. With the increasing supremacy of computational methods, the current work focuses on solving the vibration isolation in the time domain, using various computational techniques. The study focuses on the decoupling of the vibration modes, and work has been done to optimize the design in such a way that forces in all directions are transformed into a force along a single direction (Torque Roll Axis) parallel to the applied force about the crankshaft. The decoupling of the vibration ensures that the engine is robust to changes in the frequency of applied torque. The work also focuses on the implementation of multiple optimization methods on multi-objective functions using conventional and evolutionary algorithms and comparing their results. The engine used in a student Off-road Racing event (BAJA SAE) has been considered throughout this work.

BASF PETRONAS Chemicals to expand 2-EHA production capacity

Vibration isolation has been a key area of focus in almost every mechanical component. The impact of vibrations on efficiency, longevity and performance of a machine component is tremendous. An automotive engine poses a very challenging vibration problem due to the multi-axial forces of varying amplitude. With the increasing supremacy of computational methods, the current work focuses on solving the vibration isolation in the time domain, using various computational techniques. The study focuses on the decoupling of the vibration modes, and work has been done to optimize the design in such a way that forces in all directions are transformed into a force along a single direction (Torque Roll Axis) parallel to the applied force about the crankshaft. The decoupling of the vibration ensures that the engine is robust to changes in the frequency of applied torque. The work also focuses on the implementation of multiple optimization methods on multi-objective functions using conventional and evolutionary algorithms and comparing their results. The engine used in a student Off-road Racing event (BAJA SAE) has been considered throughout this work.

Evaluation of Applied Force During Nasopharyngeal Swab Sampling Using Handheld Sensorized Instrument.

Nasopharyngeal swab is the most widely used diagnostic test for COVID-19 detection. However, enormous tests have posed a high risk of infection to medical professionals due to close contact with patients and substantial health burden. While automation of the nasopharyngeal swab is regarded as a potential solution to address these problems, the quantitative study of force for safe and effective control has not been widely performed yet. Hence, this study presents applied force during the standard nasopharyngeal swab sampling procedure using a handheld sensorized instrument. The sensorized instrument can simultaneously measure multi-axis forces and 6-DOF hand motion while allowing natural hand motion as is used in the standard swab sampling. To accurately measure force from the handheld instrument, the compensation of gravity bias is accomplished online while estimating the orientation of the hand with an embedded IMU sensor. As a result, the instrument can measure all three-axes forces by an error below 5 mN. A simulated test on a phantom model using the sensorized instrument shows that how the forces vary during the sampling sequences.

Triaxis Static Force Sensing for Langevin-Type Ultrasonic Tools Using Lead-Zirconate-Titanate Ceramic Rings

A novel triaxis static force sensor that uses lead zirconate titanate (PZT) ceramic rings is proposed. The actuator ring is driven at the resonance frequency of the thickness vibration mode to generate ultrasonic waves in the detector rings. The electric potential between the top and bottom surfaces of the detector ring due to the direct piezoelectric effect is measured. The sensing mechanism is based on the variation of the compliance coefficient with the applied force. The bolt-clamped Langevin transducer is the most widely used ultrasonic actuator in ultrasonic machining. The proposed design composed of two PZT ceramic rings imparts triaxis static force sensing capability to the Langevin transducer without the use of external components. The statics model, relationship between stress and the compliance coefficient, and decoupling matrix were derived to estimate the forces on the tool tip based on the voltages at the electrodes on the detector ring. The mean differences between the calculated and experimental results in terms of ${F} _{\textbf {x}}$ , ${F} _{\textbf {y}}$ , and ${F} _{\textbf {z}}$ were 1.92%, 2.54%, and 4.26%, respectively, the full range of ±150 N. The experiments were conducted using different weights and a multiaxis force reference sensor.

Evaluation of the influence of platelet-rich plasma (PRP), platelet lysate (PL) and mechanical loading on chondrogenesis in vitro

The aim of this work is to investigate the capability of PRP as an adjuvant therapy to autologous chondrocyte implantation (ACI) in combination with multi-axial load with respect to cartilage regeneration. Articular cartilage shows poor repair capacity and therapies for cartilage defects are still lacking. Well-established operative treatments include ACI, and growing evidence shows the beneficial effects of PRP. Platelets contain numerous growth factors, among them transforming growth factor beta (TGF-β). Dynamic mechanical loading is known to be essential for tissue formation, improving extracellular matrix (ECM) production. For our ACI model monolayer expanded human chondrocytes were seeded into polyurethane scaffolds and embedded in fibrin (hChondro), in PRP-Gel (PRP), or in fibrin with platelet lysate (PL), which was added to the media once a week with a concentration of 50 vol%. The groups were either exposed to static conditions or multi-axial forces in a ball-joint bioreactor for 1 h per day over 2 weeks, mimicking ACI under physiological load. The culture medium was collected and analyzed for glycosaminoglycan (GAG), nitrite and transforming growth factor beta 1 (TGF-β1) content. The cell-scaffold constructs were collected for DNA and GAG quantification; the expression of chondrogenic genes, TGF-β and related receptors, as well as inflammatory genes, were analyzed using qPCR. Loading conditions showed superior chondrogenic differentiation (upregulation of COL2A1, ACAN, COMP and PRG4 expression) than static conditions. PRP and PL groups combined with mechanical loading showed upregulation of COL2A1, ACAN and COMP. The highest amount of total TGF-β1 was quantified in the PL group. Latent TGF-β1 was activated in all loaded groups, while the highest amount was found in the PL group. Load increased TGFBR1/TGFBR2 mRNA ratio, with further increases in response to supplements. In general, loading increased nitrite release into the media. However, over time, the media nitrite content was lower in the PL group compared to the control group. Based on these experiments, we conclude that chondrogenic differentiation is strongest when simulated ACI is performed in combination with dynamic mechanical loading and PRP-gel or PL supplementation. An inflammatory reaction was reduced by PRP and PL, which could be one of the major therapeutic effects. Loading presumably can enhance the action of TGF-β1, which was predominantly activated in loaded PL groups. The combination of load and PRP represents an effective and promising synergy concerning chondrocyte-based cartilage repair.