Large Force Research Articles

POF helical structure: a non-contact approach for wide-range force measurements based on the coupling method

Abstract This study proposes a non-contacting force measuring sensor design by utilizing the polymer optical fiber. The sensor design uses two separate fibers (i.e. sensor input and sensor output fibers). Sensor input fiber is used to helically wound on the supportive circular pipe, aiming to create the bend losses at every bend loop. The sensor output fiber is getting advantages by coupling the variable optical power from different bend loops of the sensor input fiber. The variable amount of the optical power coupling is directly associated with the applying force value on the spring. Where, the spring is intermediate in transferring force value to the sensor. Further, for variable ranges of the forces, the three different springs (i.e. Spring-A, B, and C) are used, which sustain variable force ranges (0 to 20 N, 0 to 40 N, and 0 to 60 N), respectively. The proposed sensor design addresses the critical need for force sensors capable of effectively measuring force across a wide dynamic range. The results of the present study support the sensor design, which has a wide range of force measuring capabilities from low, medium, and high range with a close repetitive response. The low range force measuring (0 to 20 N) indicates the sensor’s high sensitivity of 0.567 µW/N. Further, the sensor is also capable for a large force measuring range (0 to 60 N) with a sensitivity of 0.189 µW/N.

Large volume torsion (LVT) apparatuses for rock deformation at high pressure and temperature.

Laboratory studies of rock rheology rely on purpose-built devices that can apply planetarily relevant pressures, temperatures, and non-hydrostatic stresses. Generating these pressures and stresses requires the application of large forces over small specimen areas. However, because rocks are generally polymineralic and deformation microstructures form across many length scales, it is advantageous to study relatively large (millimetric) specimens. In addition, many microstructures continue to evolve with progressive strain, so it is vital that some apparatus are able to generate enough shear strain to study these deformation phenomena. This contribution describes two new rock deformation apparatus-the Large Volume Torsion apparatus-at Washington University in St. Louis, which are capable of deforming geological specimens at high pressure and temperature (P = 3GPa; T = 1800K). Deformation is imposed in a torsional geometry, which enables the generation of extremely large shear strains (γ > 100) relevant to Earth's plate boundaries and convecting mantle. A large specimen (diameter up to 4.2mm) permits detailed postmortem microstructural analysis. Apparatus design, calibration, experimental procedures, and some examples of applications are reviewed.

Wear and Plasticity in Railway Turnout Crossings: A Fast Semi-Physical Model to Replace FE Simulations

Severe changes in the profiles of the crossing nose are caused by large dynamic contact forces. To predict these forces as well as the profile evolution, the Whole System Model (WSM) was developed. However, it uses computationally expensive FE simulations. As a replacement, the semi-physical plasticity and wear model (SPPW) has been developed, thus majorly enhancing the overall performance of the WSM. The SPPW considers the influence of wear, plasticity, and wheel-profile-related effects. Its results have shown an overall good correlation with FE results, laboratory data for different materials, and field data from a real crossing. Due to the semi-physical nature of the model, the required computational time for the predictions was significantly reduced compared to FE simulations: minutes instead of weeks. The SPPW will be useful for time-efficient rail damage prediction, like wear and plastic deformation, and, as part of the WSM, contribute to a fast holistic track damage prognosis.

Design of Dielectric Elastomer Actuator and Its Application in Flexible Gripper.

Dielectric elastomer actuators (DEAs) are difficult to apply to flexible grippers due to their small deformation range and low output force. Hence, a DEA with a large bending deformation range and output force was designed, and a corresponding flexible gripper was developed to realize the function of grasping objects of different shapes. The relationship between the pre-stretch ratio and DEA deformation degree was tested by experiments. Based on the performance test results of the dielectric elastomer (DE), the bending deformation process of DEAs with different shapes was simulated by Finite Element Method (FEM) simulation. DEAs with different shapes were prepared through laser cutting and the relationship between the voltage and the bending angle, and the output force of the DEAs was measured. The result shows that under uniaxial stretching, the deformation of the DEA in the stretching direction gradually increases and decreases in the unstretched direction with the increase in the pre-stretch ratio. Under biaxial stretching, DEA deformation increases with the increase in the pre-stretch ratio. The shape of the DEA has a certain influence on the bending deformation range under the same conditions, and the elliptical DEA has a larger bending deformation range and higher output force compared with the rectangular DEA and the trapezium DEA. The elliptical DEA can produce a bending deformation of 40° and an output force of 37.2 mN at a voltage of 24 kV. The three-finger flexible gripper composed of an elliptical DEA can realize the grasping of a paper cup.

Defect related vortex dynamics behaviors in ‘1144’-type iron-based superconductors

Abstract We have synthesized ‘1144’- type (Ca1–x Pr x KFe4As4 and CaKFe4As4) and ‘122’-type (Ba0.6K0.4Fe2As2 and Ba0.6Rb0.4Fe2As2) iron-based superconductors. Based on these crystals, we have investigated the vortex dynamics of the ‘1144’- and ‘122’-type iron-based superconductors. The results indicate that the novel flux dynamics behaviors of the ‘1144’-type iron-based superconductors are closely related to their defect structures. First, the intergrowths in ‘1144’-type superconductors can function as columnar defects under an applied magnetic field H∥ab-plane, which results in a dip structure in the magnetization hysteresis loops (MHLs) near zero field due to the self-field effect. Second, the intergrowths, as strong pinning sites, provide a large pulling force on the flux lines and cause a small magnetization peak at temperatures below 10 K under magnetic fields from about 3–7 T in MHLs for the ‘1144’-type superconductors. Third, there may be vortex entanglement due to the presence of strong pinning centers, which impedes the elastic-to-plastic motion of vortices (E–P phase transition) resulting in a weak second magnetization peak (SMP) effect in the bulk ‘1144’-type superconductors. Fourth, the intergrowths introduce disorder into the superconductors and accelerate the magnetic 3D-to-2D transition, which causes the thickness-dependent J c and SMP effects due to the rigidity of flux lines with decreasing sample thickness. The current results are significant for our understanding of the relationship between the flux pinning behaviors and the defect structures for a superconductor.

Dynamics of post-impact merged droplets under different droplet–droplet interaction modes upon successive impingement on the substrate of different wettabilities

Successive impingement of multiple droplets onto a substrate is common in applications. However, the effects of the substrate properties and droplet–droplet interaction modes on the dynamics of the post-impact merged droplet remain unclear. In this study, we simulate the successive impingement of two droplets and the dynamics of the merged droplet on a superhydrophobic surface and a hydrophilic–hydrophobic patterned surface under different droplet–droplet interaction modes, based on a two-dimensional single-component pseudopotential multiphase lattice Boltzmann model. On the superhydrophobic surface, if the leading droplet is at spreading stages upon successive impingement, the merged droplet's maximum spreading factor, rebounding height, and merged droplet–substrate contact time decrease with the spreading of the leading droplet. Conversely, if the leading droplet is at recoiling stages upon successive impingement, the merged droplet's maximum spreading factor and rebounding height remain a small constant, while the merged droplet–substrate contact time increases with recoiling of the leading droplet. The dynamics of the merged droplet on a superhydrophobic surface under different droplet–droplet interaction modes are attributed to amplifying or suppressing the leading droplet kinetic energy upon successive impingement. However, on the hydrophilic–hydrophobic patterned surface, it is found that the hydrophilic stripes enhance the merged droplet spreading. The relatively large viscous force of the hydrophilic stripes and the energy barrier at the boundary of the pattern stripes significantly dissipate the kinetic energy of the merged droplet. The merged droplet does not rebound on the hydrophilic–hydrophobic patterned surface and has a small oscillation amplitude and fast energy decay rate.

Neural network adaptive admittance control for improving position/force tracking accuracy of fracture reduction robot

The accuracy of fracture reduction robot is critical factor for clinical application. In this study, a neural network adaptive admittance control (NNAAC) system is proposed to improve the position/force tracking accuracy of the robot under large variable reduction forces and uncertain robot dynamic models. The NNAAC consists of an inner loop and an outer loop. The inner loop combines inverse dynamics control (IDC) and radial basis function neural network (RBFNN) to compensate for inaccuracies in the dynamic model, and an admittance parameter adaptive controller based on the RBFNN in the outer loop improves force tracking accuracy and stability. The performance of the NNAAC is evaluated by fracture model reduction experiments, comparing it with the inverse dynamics control and constant admittance control. The experimental results show that the NNAAC achieves better control effectiveness and high accuracy with a maximum reduction force of 190 N. Specifically, the proposed controller exhibits a maximum position error of less than 1 mm and a maximum orientation error of less than 0.5°.

Dynamic response of a semi-submersible floating wind turbine-point absorption wave energy hybrid energy system under rated and extreme conditions

In this paper, the response of a semi-submersible offshore wind turbine, combined with an absorbing wave energy converter (WEC), is analyzed within the FAST to AQWA coupling framework after single mooring line (ML) failure, under rated and extreme (1 in 10 years wind and wave) conditions. Comparisons are made among the six-degree of motions of the platform, power output, and tensions of the unbroken MLs. With upwind mooring line, the hybrid system suffers the most: surge up to 3.3 times the rotor diameter (D) due to the large hub forces and turbine power reduction by 80%, owing to the pitch response of the platform in both rated and extreme conditions; more likelihood of fatigue in unbroken ML under extreme conditions. Regardless of the failure line condition, the mean tension of the unbroken MLs reduces at the expense of larger motions, compared to a non-faulty line condition. The shutdown measures can reduce significantly the tensions in the MLs at rated conditions, owing to turbine larger influence on the platform than WEC, higher motion response and damping processes. The effect of the WEC on the platform is mainly reflected in heave and roll, providing more stability than in a stand-alone floating turbine case. During extreme conditions, the turbine shuts down, and thus, the response is more attributed to the drift of the platform rather than turbine or WEC operation. On a wider level, research is also needed to determine the response in simultaneously ML failures and misaligned operating flows.

Stabilizing complex-Langevin field-theoretic simulations for block copolymer melts.

Complex-Langevin field-theoretic simulations (CL-FTSs) provide an approximation-free method of calculating fluctuation corrections to the self-consistent field theory (SCFT) of block copolymer melts. However, the complex fields are prone to the formation of hot spots, which causes the method to fail. This problem has been attributed to an invariance under complex translations, which allows the system to drift away from the real-valued saddle-point of SCFT. Here, we apply dynamical stabilization to CL-FTSs of diblock copolymer melts, whereby the drift is suppressed by a small imaginary force on the composition field. The force needs to be sufficient to hold the system near the real saddle-point but also small enough not to significantly bias the statistics. Although larger forces are required as the fluctuations become more intense, we are able to lower the invariant polymerization indices of the CL-FTSs by several orders of magnitude before this becomes a problem. The new CL-FTS results are then used to test conventional Langevin simulations (L-FTSs), in which the instability is removed by a partial saddle-point approximation to the pressure field. As found previously, the L-FTSs agree accurately with the CL-FTSs, provided that the comparison is performed using a Morse calibration.

Full scale test on reinforced concrete elements of an existing bridge: on-site investigation and laboratory testing design

The evaluation of mechanical characteristics and degradation level of existing bridges is a highly relevant topic today. This paper presents the initial phases of an integrated experimental-numerical research project focused on a pre-scheduled demolition of an existing reinforced concrete bridge. The controlled demolition of existing bridges represents an invaluable opportunity, allowing to deepen our comprehension on their behavior, especially when degradation analysis is concerned. Both on-site tests and subsequent laboratory experiments design are carried out on full-scale elements extracted from the bridge. These tests are complemented by Finite Element analyses conducted at various levels of detail. Specifically, after the description of the knowledge phases of the bridge performed on-site, the paper illustrates the preliminary numerical analyses carried out to support the customized design of the experimental setup, where mean values of all material parameters are assumed to acquire the essential information on the expected test results. Additionally, Monte Carlo analysis has been performed to evaluate the impact of statistical variability of material parameters on structural response. This aspect is particularly relevant for the design of the experimental test setup, due to the large forces involved and large displacements expected in order to reach the full collapse of the beams.

Energy Efficient Excavator Implement by Electro-Hydraulic/Mechanical Drive Network

The focus on electrification of mobile working machines is increasing in industry as well as in the academic community, and ways to realize both technically and commercially feasible solutions are continuously being pursued. At this point, solutions presented by industry has mainly focused on avoiding internal combustion engines by installing cable or battery fed electric motors powering the main pump(s) which supplies the working hydraulics. However, rotary functions are sought powered directly by electro-mechanical drives, not including hydraulics. In this endeavor a main challenge is the operation of linear actuators that remain controlled by hydraulic control valves. The associated throttle losses necessitates large batteries to be compensated or alternatively results in low machine uptimes, potentially rendering electrified machines commercially infeasible. An obvious approach to avoid throttle losses may be the replacement of valve-controlled linear actuators by electro-mechanical solutions in low to medium force applications, whereas heavy duty working machines subject to large forces such as medium/large excavators may benefit from standalone electro-hydraulic primary controlled/variable-speed drives. Utilization of such solutions will substantially increase the energy efficiency due to absent or at least limited throttle losses, and the electric power sharing and electric energy recuperation capabilities offered by common DC-bus’ and batteries. However, such standalone solutions/drives must be able to meet both the required maximum force and maximum speed, and even thought these maximum quantities seldom are required concurrently, these requirements may render the associated motors and inverters somewhat large. Hence, applying such solutions may lower the battery requirements, but require substantial levels of motor and inverter power to be installed, which again may compromise the commercial feasibility. This paper presents a potentially feasible alternative to these solutions for an excavator implement, in the form of an electro-hydraulic/mechanical drive network. This is applied for actuation of three linear implement functions as well as the rotary swing function. The realization of the electro-hydraulic/mechanical drive network involves chamber short-circuiting and electro-hydraulic variable-speed displacement machines enabling electro-hydraulic power sharing. The proposed drive network is compared to a highly efficient standalone dual motor electro-hydraulic drive solution as well as a separate metering valve drive supplied by a battery fed electro-hydraulic pump. Results demonstrate that, compared to the standalone dual motor electro-hydraulic drive solution, the proposed drive network is realizable with similar energy efficiency and hydraulic displacement but less installed motor power and likely less integration effort, rendering this a more sustainable and cost-efficient solution. Finally, besides being realizable with less installed motor power and hydraulic displacement, the proposed drive network shows substantially improved energy efficiency compared to the separate metering valve drive solution.

The psychophysical assessments of tactile, temperature and electrical perception for implants with metal prosthetic surfaces.

The tactile function and thermal perception are two primary functions of oral structures. Implants without periodontal ligament and pulp might fail to sense the tactile and temperature change. This study aimed to investigate implants' tactile, thermal, and electrical perception by detailed psychophysical assessments. A total of forty-eight patients with single implant restoration were recruited. Mechanical (5 intensities), cold (4 temperatures), and electrical stimulation were respectively applied to implants and natural teeth, and the psychophysical results were recorded with a visual analog scale (VAS) and compared between implants and natural teeth. For tactile perception, at low and medium forces, implants were significantly poorer than natural teeth (P<0.01), but at the largest force, there were no significant differences (P >0.05). Regarding thermal perception, thermal changes on implants could be detected, although the signals were weaker when compared to natural teeth (P<0.01). Implants were less sensitive to electrical stimulation than natural teeth (P<0.01). Even though there is no periodontium and pulp, dental implants could perceive the mechanical, thermal, and electrical stimulation weakly.

Manipulator Control of the Robotized TMS System with Incurved TMS Coil Case

This paper proposes the force/torque control strategy for the robotized transcranial magnetic stimulation (TMS) system, considering the shape of the TMS coil case. Hybrid position/force control is used to compensate for the error between the current and target position of the coil and to maintain the contact between the coil and the subject’s head. The desired force magnitude of the force control part of the hybrid controller is scheduled by the error between the current and target position of the TMS coil for fast error reduction and the comfort of the subject. Additionally, the torque proportional to the torque acting on the coil’s center is generated to stabilize the contact. Compliance control, which makes the robot adaptive to the environment, stabilizes the coil and head interaction during force/torque control. The experimental results showed that the force controller made the coil generate a relatively large force for a short time (less than 10 s) for the fast error reduction, and a relatively small interaction force was maintained for the contact. They showed that the torque controller made the contact area inside the coil. The experiment also showed that the proposed strategy could be used for tracking a new target point estimated by the neuronavigation system when the head moved slightly.

The Influence of Changing Belt Loading Conditions on the Operational Condition of the Belt Transmission

Given the fact that belt drives are used to transmit power to a fairly large extent, it is natural to devote scientific attention to their transmission with an effort to contribute to the constant technical and technological progress in the field of belt production and use. For testing and monitoring belt drives, a measuring system was designed and manufactured, which allowed the installation of various types of belt drives and, under a controlled load, to monitor selected parameters and the behavior of individual transmission elements. The presented contribution presents both the measuring system itself and experimental measurements on three V-belts of the same size manufactured by three different manufacturers. During the experimental measurements, parameters such as belt tension were changed by changing the axial distances of the pulley axes; by connecting electric motors through frequency converters, it was possible to control the change in the input speed of the transmission and, at the same time, the load on the output pulley. On the proposed specific design solution for testing belt drives, the actual speed of the input and output pulleys was measured by sensors to determine the belt slip, and the belt’s floating in one plane was monitored using high-precision distance measurement sensors. The analysis of the belt drives also included an assessment of their impact on other parts of the machine or equipment (for example, when transmitting large forces, this can have a negative impact on bearings and gearbox components) on which they are installed; therefore, vibration measurements were also performed. The results of the experimental measurements can contribute to designers choosing a belt drive, for example, even under boundary load parameters and extreme conditions.

A linkage mechanism with high mechanical advantage for robotic grippers

Abstract In this paper, a compact linkage mechanism with high mechanical advantage and stroke is designed. The mechanism converts a small input force into a large output force using a toggle mechanism. Its feasibility for application in large gripping force manipulators has been verified. In the paper, the kinematic and static analyses of the mechanism are carried out. The effects of the mechanism parameters on its characteristics are investigated. Then, a dynamic mechanism simulation is carried out using ADAMS to obtain its mechanical gain and gripping force during motion. Finally, the processed double toggle mechanism is analyzed experimentally to verify its applicability. The simulation and experimental results show that the linkage mechanism performs better in the case of large gripping force demand. It can provide effective help for the design of mechanical grippers with large gripping force.

Modelling individual variation in human walking gait across populations and walking conditions via gait recognition.

Human walking gait is a personal story written by the body, a tool for understanding biological identity in healthcare and security. Gait analysis methods traditionally diverged between these domains but are now merging their complementary strengths to unlock new possibilities. Using large ground reaction force (GRF) datasets for gait recognition is a way to uncover subtle variations that define individual gait patterns. Previously, this was done by developing and evaluating machine learning models on the same individuals or the same dataset, potentially biasing findings towards population samples or walking conditions. This study introduces a new method for analysing gait variation across individuals, groups and datasets to explore how demographics and walking conditions shape individual gait patterns. Machine learning models were implemented using numerous configurations of four large walking GRF datasets from different countries (740 individuals, 7400 samples) and analysed using explainable artificial intelligence tools. Recognition accuracy ranged from 52 to 100%, with factors like footwear, walking speed and body mass playing interactive roles in defining gait. Models developed with individuals walking in personal footwear at multiple speeds effectively recognized novel individuals across populations and conditions (89-99% accuracy). Integrating force platform hardware and gait recognition software could be invaluable for reading the complex stories of human walking.

A ferrofluid microrobot for manipulation in multiple workspaces

Ferrofluid droplet has wide applications in bioanalysis manipulation. This study presents a ferrofluid microrobot for manipulation in different workspaces. Based on the deformation character of droplet, the ferrofluid microrobot has the capabilities of climbing the 3D (3-dimensional) surface, splitting in the channel, and transporting large particles. To manipulate in multiple workspaces with the capabilities, the size and magnetic force of ferrofluid are studied for suitable scenes. It shows that the diameter of 0.5 μl ferrofluid is around 980 μm. The manipulation force of different ferrofluid microrobots ranges from micronewton to millinewton. Subsequently, we have verified the manipulation of the ferrofluid microrobot on a 3D chip by permanent magnet. The ferrofluid microrobot can climb the stairs only when the height of the magnetic fluid is higher than twice the height of the stairs. Meanwhile, splitting of ferrofluid microrobot in the microfluidic chip has been successfully demonstrated. It indicates that the splitting influenced by the magnetic field and large magnetic force is easier to split the microrobot. Finally, the transportation of large polystyrene microparticles (150 μm) is confirmed by the ferrofluid microrobot. These capabilities show that the ferrofluid microrobot has the potential application advantage in biomedicine's micro-drug testing.

Research and discussion on traceability of force values for large force standard machines

Research and discussion on traceability of force values for large force standard machines

Tooth Design of Ophthalmic Microsurgical Forceps Based on Minimum Slip Force

This study proposed the use of the minimum slip force as an indicator to measure the clamping ability of microsurgical forceps. By analyzing the minimum slip forces of four typical tooth types of microsurgical forceps, the clamping capacity of each type was evaluated. Among the existing tooth forms, the staggered tooth type exhibited a relatively large minimum slip force. Consequently, a new tooth-shaped structure for microsurgical forceps - the hemispherical convex structure was proposed. Simulation and experimental studies demonstrated that this new dental structure could achieve stable and reliable clamping.

Perturbation analysis of internally constrained beams subjected to large longitudinal force

Perturbation analysis of internally constrained beams subjected to large longitudinal force