Continuous Force Research Articles

Automated continuous distraction osteogenesis system for limb lengthening and reconstruction

Distraction osteogenesis (DO) is a classical surgical technique for limb lengthening and reconstruction (LLR). Most existing DO devices for LLR are operated manually, and the accurate DO process is user dependant, which could affect new bone formation. Recently, automated devices have been introduced for continuous DO processes to aid in tissue healing. To the best of our knowledge, few automated continuous distraction osteogenesis (ACDO) devices have focused on DO surgery for the long bones of the extremities and monitoring of their status during the surgical process. This study presents a novel ACDO device, which is driven by a deceleration stepper motor for further reduction in total mass and amplification in distraction force, including a precise and programmable man–machine-interaction system to allow surgeons to control and monitor the treatment remotely. The mechanical device was verified to be capable of generating a continuous and controllable distraction force and rate. The proposed man–machine-interaction system possesses the functions of customizing and following up on treatment plan by clinicians, including setting the DO process, measuring and displaying parameters, and uploading DO information to the data cloud. During electromechanical system simulation and prototype experiments, the performance of the proposed system was consistent with the setting DO parameters and treatment plan.

Programming metastable transition sequences in digital mechanical materials

The realization of unconventional computing methods in soft matter has inspired the creation of mechanological systems capable of processing information. These systems often utilize bistable mechanisms that serve as mechanically abstracted bits to perform digital logic operations. Yet, the input of such operations often requires manual control of complex cyclic loading to reach a desired configuration. This research presents a method to design digital mechanical materials that can enter a programmable sequence of metastable configurations through simple displacement-controlled inputs. Interactions between serially connected bistable units enable the transition and reset behavior of mechanical bits. An analytical model using the principle of minimum total potential energy of a single bit is presented to articulate systematic ways to tune the critical force thresholds and displacements of metastable transition sequences. This work elucidates how the application of a prescribed displacement allows for novel resetting behavior that enables simultaneous transitions of multiple bits. By combining the principles of deterministic transition sequences and mechanical computing, a mechanical analog to digital conversion (ADC) material system is introduced that digitizes a continuous force stimulus into binary configurations that perform computations within the mechanical material based on the applied load. The mechanical ADC establishes a foundation for the integration of environmental sensing, information processing, and response in a soft material system.

Comparison of the Effect of Dressage Rider Skill Level on Physical Fitness Parameters and Posture on an Equestrian Simulator.

In dressage riding, rider posture plays an important role in the performance of the exercises. The purpose of this study was to compare physical fitness and posture on an equestrian simulator between different competitive dressage rider skill levels. Participants (ten expert and twelve novice competitive dressage riders) performed a physiotherapeutic screening test and an equestrian simulator test. The expert rider group (G2) had less variability in both left (P=.002) and right (P=.021) rein force during medium canter on the simulator compared to the novice rider group (G1). The shoulder angle of the expert riders was larger in all gaits. These findings indicate that the ability to maintain a constant force on the reins and a dynamically stable hand position during riding on a simulator are important indicators for good rider performance. Expert riders presented a trend toward a more stable posture on the simulator as indicated by the reduced trunk variability (P=.034 vs. CV=0.011) and smaller trunk ROM (P=.012 vs. CV=0.011) and knee ROM (P=.033 vs. CV=0.011) in the collected canter and collected walk respectively. These kinematic differences underscore their capability of maintaining a continued and constant force on the reins, but these findings require further research. No significant differences were found between groups in the physiotherapeutic screening. This underlines the difficulty in identifying the physical factors contributing to better rider performance. In conclusion, the current study shows that "stable rein contact" is the main difference between novice and expert competitive dressage riders on the simulator.

Phosphorescent extensophores expose elastic nonuniformity in polymer networks

Networks and gels are soft elastic solids of tremendous technological importance that consist of cross-linked polymers whose structure and connectivity at the molecular level are fundamentally nonuniform. Pre-failure local mechanical responses are not understood at the level of individual crosslinks, despite the enormous attention given to their macroscopic mechanical responses and to developing optical probes to detect their loci of mechanical failure. Here, introducing the extensophore concept to measure nondestructive forces using an optical probe with continuous force readout proportional to deformation, we show that the crosslinks in an elastic polymer network extend, fluctuate, and deform with a wide range of molecular individuality. Requiring little specialized equipment, this foundational single-molecule phosphorescence approach, applied here to polymer science and engineering, can be useful to a broad science and engineering community.

On the Countering of Free Vibrations by Forcing: Part II—Damped Oscillations and Decaying Forcing

The present two-part paper concerns the active vibration suppression for the simplest damped continuous system, namely the transverse oscillations of an elastic string, with constant tension and mass density per unit length and friction force proportional to the velocity, described by the telegraph or wave-diffusion equation, in two complementary parts. The initial part I considers non-resonant and resonant forcing, by concentrated point forces or continuous force distributions independent of time, with phase shift between the forced and free oscillations, in the absence of damping, in which case the forced telegraph equation reduces to the forced classical wave equation. The present and final part II uses the forced wave-diffusion equation to model the effect of damping, both as amplitude decay and phase shift in time, for non-resonant and resonant forcing by a single point force, with constant magnitude or magnitude decaying exponentially in time at an arbitrary rate. Assuming a finite elastic string fixed at both ends, the free oscillations are (i) sinusoidal modes in space-time with exponential decay in time due to damping. The non-resonant forced oscillations at an applied frequency distinct from a natural frequency are also (ii) sinusoidal in space-time, with constant amplitude and a phase shift such that the work of the applied force balances the dissipation. For resonant forcing at an applied frequency equal to a natural frequency, the sinusoidal oscillations in space-time have (iii) a constant amplitude and a phase shift of π/2. In both cases, the (ii) non-resonant or (iii) resonant forcing dominates the decaying free oscillations after some time. Even by optimizing the forcing to minimize the total energy of oscillation, it remains below the energy of the free oscillation alone, but only for a short time—generally a fraction of the period. A more effective method of countering the damped free oscillations is to use forcing with amplitude decaying exponentially in time; by suitable choice of the forcing decay relative to the free damping, the total energy of oscillation over all time can be reduced to no more than 1/16th of the energy of the free oscillation.

Finite Element Study to Evaluate the Stress Around Mini-implant during Canine Retraction using Continuous and Interrupted Orthodontic Forces

Abstract:
 Objectives: This work aimed to determine the stress distribution around a mini-implant during dynamic canine retraction utilizing continuous and intermittent orthodontic forces and a three-dimensional finite element model.
 Materials and Methods: Establishing a three-dimensional finite element model of canine retraction. The model incorporates a mini-implant, alveolar bone, maxillary teeth, a closed coil spring, and an elastic chain. They were described as being homogeneous, isotropic, and linear elastic. Continuous and interrupted forces were approximated by a NiTi coil spring and an elastic chain, respectively. To retract the canine, a simulated orthodontic force of 1.5N, 2N, and 2.5N were loaded. ANSYS evaluated the value of the stress distribution around the mini-implant, canine, and bone interface (workbench 19).
 Results indicated that there was no significant difference between the values of maximum stress around the miniscrew, canine, and bone under different orthodontic loads when a closed coil spring and an elastic chain were evaluated.

Continuous deformation analysis and contact force estimation for pneumatic bending actuators interacting with environment

Soft bending actuators show high adaptability for applications such as rehabilitation or grasping. Although constant curvature assumption has been extensively used for free motion modeling, these actuators do not bend circularly when interacting with the environment. In such situation, conventional bending sensors cannot provide useful information on their shape. In this paper, the Finite Rigid Elements approach is utilized to model the behavior of a soft pneumatic bending actuator in free motion and contact. With this method, the variable curvature configuration under different external loads can be modeled. Then, the contact force between the actuator and an object located in a specific position is estimated utilizing the Gradient Descent optimization method. Experimental results verified the combinatorial proposed approach for both force estimation and structure deformation.

Robust Control Based on Adaptive Neural Network for the Process of Steady Formation of Continuous Contact Force in Unmanned Aerial Manipulator

Contact force control for Unmanned Aerial Manipulators (UAMs) is a challenging issue today. This paper designs a new method to stabilize the UAM system during the formation of contact force with the target. Firstly, the dynamic model of the contact process between the UAM and the target is derived. Then, a non-singular global fast terminal sliding mode controller (NGFTSMC) is proposed to guarantee that the contact process is completed within a finite time. Moreover, to compensate for system uncertainties and external disturbances, the equivalent part of the controller is estimated by an adaptive radial basis function neural network (RBFNN). Finally, the Lyapunov theory is applied to validate the global stability of the closed-loop system and derive the adaptive law for the neural network weight matrix online updating. Simulation and experimental results demonstrate that the proposed method can stably form a continuous contact force and reduce the chattering with good robustness.

Continuous Grasping Force Estimation With Surface EMG Based on Huxley-Type Musculoskeletal Model.

Continuous grasping force estimation based on electromyography (EMG) signals, is very useful in practical applications including prosthetic control and human force observation. However, implementing the practical grasping force estimation usually considers a trade-off between the computational precision and resources. Specifically, the estimation based on the Huxley-type muscle model reaches detailed approximation of physiological process at a cost of larger computational resources for solving nonlinear partial differential equations while the counterpart with a traditional Hill-type muscle model. In this article, we achieve the grasping force estimation based on a reduced Huxley-type musculoskeletal model with high accuracy yet low time delay. Leveraging on a balanced truncation method, we further reduce the dimensionality of the spectral method solution in the Huxley-type musculoskeletal model for the model simplification. In addition, we introduce the Kalman filter method to process the EMG signals obtained by an armband, yielding better real-time performances and accuracy compared to the signal treatment using the traditional EMG filter method. Moreover, we also implement an effective identification of the model parameters using a particle swarm method. Finally, we trained the model on the first day and made grasping force estimation experiments involved with three participants over the course of a month. We envision that this effective and practical method would further improve the practical applications in the field of grasping force estimation.

The Myth of Men's Stable, Continuous Labor Force Attachment: Multitrajectories of U.S. Baby Boomer Men's Employment.

Over the past several decades, U.S. men's paid work has transformed from a state of high stability and continuity to a state of increased instability and precarity. Despite this, full-time employment throughout adulthood remains the presumed standard for modern American men. The authors investigated the diversity of men's workforce experiences using the National Longitudinal Survey of Youth "National Longitudinal Survey of Youth - 1979 cohort" and identified six multitrajectories of men's time spent employed, unemployed, and out of the labor force from ages 27 to 49. The authors identified one multitrajectory of steady work, three of increasing unemployment or time out of work, one of increasing steady work, and one of intermittent work. Contrary to conventional assumptions, only 41 percent of men followed a trajectory of continuous, high employment over the duration of their prime earning years. This suggests that most men do not achieve the "ideal worker norm," raising implications for how research and policy conceptualize men's work experiences.

Optimized Model Selection for Concurrent Decoding of Finger Kinetics and Kinematics

Myoelectric-based motor intent detection is typically used to interface with assistive devices. However, the intent detection performance is sensitive to interference of electromyogram (EMG) signals. Recently, EMG signals are decomposed into motor units (MU) firing activities, and neuron binary firing activities can be used to predict motor output in a continuous manner. Different functions that map MU firings to motor output have been implemented, and both composite MU firing frequency and individual MU firing frequency have been used. It is unclear whether one mapping function outperform others. Accordingly, we evaluated three MU-based finger kinetic and kinematic prediction models, by varying the number of MUs and the method of including MU firings into the regression model. We also compared the performance of three EMG amplitude-based models with varying number of channels. We performed MU decomposition in advance for real-time implementations. Our results showed that individual firing frequency of five MUs provided the lowest estimation error (force: 4.66±0.36 %MVC; joint angle: 4.81±0.49°) and highest correlation (force: 0.86±0.01; joint angle: 0.93±0.01) with the measured motor outputs, when compared with mapping method using the populational firing frequency of all MUs or the populational firing frequency of a group of MUs with similar firing activities. The results indicated that firing information at the population level may mask critical information of individual MU firings. These findings allowed us to identify the optimal models for concurrent and continuous finger force and joint angle estimation. A combination of the minimal level of complexity and high accuracy make these models suitable for real-time control of assistive robotic devices.

A Vaporization Model for Continuous Surface Force Approaches and Subcooled Configurations

A Vaporization Model for Continuous Surface Force Approaches and Subcooled Configurations

A study of tension band wiring in patella, olecranon and malleolar fractures in adults

Background: Fractures of the eccentrically loaded bones like patella, olecranon, and medial malleolus are one of the most common fractures encountered by an orthopaedic surgeon. They continue to pose vexing problems as these being intra-articular are being subjected to continuous deforming forces from muscles.Objectives: To evaluate the clinical results of the tension band wiring in patella, olecranon and malleolar fractures in adults.Material & Methods: Study Design: A prospective hospital based observational study. Study area: Department of Orthopaedics, Government General Hospital, Mahbubnagar. Study Period: May 2022 – Jan 2023 [9 months]. Study population: Cases of fractures of Patella, Olecranon, Malleoli treated by tension band wiring. Sample size: study consisted of 30 subjects. Sampling Method: Purposive sampling technique. Study tools and Data collection procedure: As soon as the patient was admitted, a detailed history was taken and a meticulous examination of the patient was done. The required information was recorded and proforma was prepared. Radiographs were taken in approximate views and diagnosis was established by clinical and radiological means. Then splinting of fractures was done with above knee POP slab for patellar fractures above elbow POP slab for olecranon fractures and below knee POP slab for medial malleolar fracture. All patients were taken for elective surgery as soon as possible after necessary blood, urine and radiographic preoperative work-up.Results: In our study, best results were obtained in fracture of patella 60%, olecranon fracture 42.8%, and medial malleolus 46.15%. In total of 30 cases, 15 (50%) had excellent results, 8 (26.66%) had good results, 3 (10%) had fair and poor result is 4(13.33%).Conclusion: It was concluded from the present study that, Tension band wiring by principle overcomes the distractive force, achieves compression at the fracture site and maintains the alignment by minimum hardware. By achieving compression at fracture site, the fracture heals faster and the patient is back to work earlier.

Continuous Gesture Recognition and Force Estimation Using sEMG Signal

Continuous Gesture Recognition and Force Estimation Using sEMG Signal

On the conservative phase-field method with the N-component incompressible flows

This paper presents a conservative Allen–Cahn model coupled with the incompressible Navier–Stokes equation for tracking the interface with the N-component immiscible fluids system. The proposed conservative phase-field model can track the interface with large deformation in divergence-free velocity fields. The erroneous estimation of the normal vector is a challenging numerical issue for the interface capturing due to the appearance of spurious oscillations. The improved phase-field-based method combines the nonlinear preprocessing operation guided by the level-set method with local artificial viscosity stabilization to improve the computation of the discrete normal vector. The interfaces between different immiscible components are replaced by the transition region with finite thickness in the continuous phase field. The surface tension effects are represented with the continuous surface tension force in the system, which is not limited by the number of components. The third-order Runge-Kutta time discretization and second-order spatial discretization are applied for the multi-component system. To eliminate the spurious oscillations caused by discontinuous and steep gradient for capturing the shocks and sharp interfaces, we apply the third-order weighted essentially non-oscillatory method for the advection term. Several quantitative results of numerical tests, such as error estimation with the proposed method, comparative tests with different methods, and convergence rate for classical benchmark test, have been performed to illustrate that our method works well for the interface tracing issue with high numerical accuracy. In addition, various representative qualitative tests have been presented to demonstrate the applicability of our method.

Cellular and Structural Changes of the Pulp in Rats after Continuous Orthodontic Force Application: A Pilot Study

Cellular and Structural Changes of the Pulp in Rats after Continuous Orthodontic Force Application: A Pilot Study

A note on the modelling of lubrication forces in unresolved simulations

Lubrication forces play a major role in the behaviour of fluid-solid systems, where they affect the collisions between particles. Current implementations of lubrication forces in unresolved simulations often suffer from shortcomings, such as neglecting parts of the physics or relying on arbitrarily defined parameters. In this short communication, we propose a novel implementation, rigorously defined based on physical and numerical factors. Both particle roughness and deformation are considered, and the model accuracy is demonstrated through comparison with experimental results. • A rigorously-defined lubrication force model for unresolved simulations is proposed. • Surface roughness and particle deformation are considered. • Numerical stability is ensured by a continuous force formulation. • Good correspondence with experimental data is demonstrated.

Mechanically controlled robotic gripper with bistability for fast and adaptive grasping

This paper presents a novel bistable gripper inspired by the closure motion found in the jaw of a hummingbird. With a bistable characteristic, the robotic gripper can grasp objects rapidly without applying continuous external force. The bistable gripper comprises a linkage-driven mechanism and two bionic jaws consisting of thin elastic polyvinyl chloride sheets with two clamped ends connected by a hinge. The shape of the thin sheets was modeled and optimized using geometric analysis, and the morphing processes of the bionic jaw were analyzed using finite element simulations and experiments. Furthermore, we explored the motion characteristics of the clamps during the snap-through and snap-back processes and divided the motion into two phases: delay and snap. Force and response time tests show that the proposed bistable gripper can achieve fast bending within milliseconds under a low pull force during the snap phase. Grasping experiments demonstrated that the proposed robotic gripper is adaptable for grasping objects of various shapes and weights. After grasping, the bistable gripper can release the target by pulling the actuating rod and automatically return to the open state. This study reveals the unique bending mechanism of thin sheets that can be exploited for fast, versatile, and adaptive grasping. The bistable gripper exhibits the potential to reduce energy consumption and simplify control when performing tasks in unstructured environments such as space and underwater.

Fourier Series Approximation of Vertical Walking Force-Time History through Frequentist and Bayesian Inference

The increased ambition of architects coupled with advancements in structural materials, as well as the rapidly increasing pressure on civil engineering sector to reduce embodied carbon, have resulted in longer spans and more slender pedestrian structures. These structures often have one or more low natural frequencies in the range of human walking accompanied with low modal masses and damping ratios. Thus, they are prone to excessive and often resonant vibrations that may compromise the serviceability limit state. Principally the uncertainty in prediction of the vibration serviceability limit state mainly originates from unreliable estimates of pedestrian loading. The key rationale behind this situation is the limited mathematical characterisation featuring in current design codes and guidelines pertinent to pedestrian-induced loading. The Fourier approximation is typically used to describe individual walking forces. Historically, such models are based on limited experimental data and deterministic mathematical descriptions. Current industry used load models featured in design codes and guidelines have been shown to incorporate inherent bias through limited intra-subject variation and poor correlation with real walking loads. This paper presents an improved Fourier model of vertical walking force across multiple harmonics, presented in a Bayesian and Frequentist statistical parameterisation. They are derived using the most comprehensive dataset to date, comprising of over ten hours of continuous vertical walking force signals. Dissimilar to previous Fourier models, the proposed models attempt to encapsulate the surround energy leakage around harmonic integers with a singular value. The proposed models provide consistently lower force amplitudes than any previous model and is shown to be more representative of real walking. The proposed model provides a closer approximation of a structural acceleration than any other similar Fourier-based model. The proposed model provides further evidence to combine the so called high and low frequency load models.

Improvement of surface tension discrete model in the ISPH-FVM coupling method

In the simulation of two-phase incompressible fluid involving surface tension, the approximate calculation of surface tension plays an important role in the accuracy of phase interface tracking and reproduction. The ISPH-FVM coupling method was proposed to simulate two-phase incompressible flow, which combines the advantages of the incompressible smoothed particle hydrodynamics (ISPH) in interface tracking and the finite volume method (FVM) in the calculation of flow field. In the original ISPH-FVM coupling method, the continuous surface force model (CSF) is used to estimate the surface tension between phase interfaces, which is discretized by smoothed particle approximation (ISPH-FVM-S). In the calculation of ISPH-FVM-S, the accuracy of surface tension method will be decreased through the direct particle interpolation when the interface changes complex. To improve the simulation accuracy of the ISPH-FVM coupling method, this paper proposes two improved discrete models for surface tension calculation, one is inspired by VOF method (ISPH-FVM-V) and the other is inspired by Level Set method (ISPH-FVM-L). Several benchmark cases are tested to illustrate the effectiveness of two improved surface tension discrete models. The results show that ISPH-FVM-V model and ISPH-FVM-L model have better accuracy and stability than ISPH-FVM-S in two-phase flow problems with complex interface topology changes. The work of this paper can further expand the application of ISPH-FVM coupling method in simulation of complex two-phase flow involving surface tension.