Resistive Moment Research Articles

Impact of plantar flexion resistive moment of dynamic ankle foot orthosis on measures of center of pressure and clinical gait outcomes in individuals with post-stroke hemiparesis

BackgroundAn ankle-foot orthosis (AFO) with plantar flexion resistance (PFR) can improve the first rocker function during gait, but the incremental changes in the resistive moment on balance and gait have not been well identified. ObjectivesTo investigate the effect of changing the PFR moment of dynamic AFO (DAFO) on measures of the center of pressure (COP) and clinical gait outcomes in individuals with post-stroke hemiparesis. MethodIn this randomized repeated measure study of 36 stroke individuals, the customized DAFO using foot drop ankle units set in three PFR situations (low, medium, and high) was evaluated. The balance parameters for COP measures were investigated by HUMAC® Balance & Tilt System. Gait parameters and ankle kinematics were recorded using the 3D motion analysis through force platform and optoelectronic system. The comparison was made using a parametric ANOVA test and the P value was set at 0.05 for statistical significance. ResultsSignificant differences were observed for COP average velocity (1.30 ± 0.64, 1.10 ± 0.05, and 1.37 ± 0.43), COP path length (43.3 ± 4.6, 33.4 ± 4.3, and 36.3 ± 5.4), walking velocity (11.0 ± 3.1, 13.2 ± 4.4, and 9.9 ± 3.5), and cadence (31.5 ± 2.0, 33.0 ± 3.1, and 29.0 ± 1.6) respectively for low, medium and high PFR settings (P < 0.05). Except for the COP path length and cadence, posthoc multiple comparisons revealed significant differences between low and medium (P < 0.05) and medium and high (P < 0.05) PFR grades. PFR with medium resistance demonstrated near-normal maximal peak ankle dorsiflexion (mean deviation of 8 degrees, P < 0.05). ConclusionMedium PFR grade should be encouraged since it can enhance balance parameters like path length and average velocity of COP, increase cadence and average velocity during gait, and improve maximal peak ankle dorsiflexion.

A six degrees-of-freedom cable-driven robotic platform for head-neck movement.

This paper introduces a novel cable-driven robotic platform that enables six degrees-of-freedom (DoF) natural head-neck movements. Poor postural control of the head-neck can be a debilitating symptom of neurological disorders such as amyotrophic lateral sclerosis and cerebral palsy. Current treatments using static neck collars are inadequate, and there is a need to develop new devices to empower movements and facilitate physical rehabilitation of the head-neck. State-of-the-art neck exoskeletons using lower DoF mechanisms with rigid linkages are limited by their hard motion constraints imposed on head-neck movements. By contrast, the cable-driven robot presented in this paper does not constrain motion and enables wide-range, 6-DoF control of the head-neck. We present the mechatronic design, validation, and control implementations of this robot, as well as a human experiment to demonstrate a potential use case of this versatile robot for rehabilitation. Participants were engaged in a target reaching task while the robot applied both assistive and resistive moments on the head during the task. Our results show that neck muscle activation increased by 19% when moving the head against resistance and decreased by 28-43% when assisted by the robot. Overall, these results provide a scientific justification for further research in enabling movement and identifying personalized rehabilitation for motor training. Beyond rehabilitation, other applications such as applying force perturbations on the head to study sensory integration and applying traction to achieve pain relief may benefit from the innovation of this robotic platform which is capable of applying controlled 6-DoF forces/moments on the head.

Simulation of the hydraulic steering device, for a nose landing gear

The hydraulic steering simulation is done with SIMULINK, part of the MathWorks MATLAB® application. All parts, subassemblies, and assemblies that define the nose landing gear (NLG) and nose wheel steering are fully defined in 3D, with CATIA V5 - a computer-aided design software used for modeling, it is possible to carry out simulations that allow preliminary evaluation, theoretically and experimentally. The purpose of this simulation is to confirm the correctness of the steering gear kinematics, that the two hydraulic cylinders have been sized correctly and can overcome the resistive steering moment, and that the steering time complies with design specifications for the nose landing gear of a military training aircraft.

A Numerical Study on the Influences of Non-Pneumatic Tyre Shape on the Wheel Aerodynamics

Abstract: In the present work, the aerodynamic characteristics of two different tyre shapes, Slick Tyre (ST) and Non-Pneumatic Tyre (NPT), fitted to a rotating wheel, has been investigated using a CFD approach. The ST wheel has been primarily utilized to examine the adopted numerical model's validity. The ST wheel pressure coefficient (Cp) profile at its central plane (XY) has directly compared with the robust experimental data experienced from the literature. Further assessments on the computationally obtained outcomes such as drag coefficient, separation and stagnation angular locations are performed. Both wheel cases are compared concerning their aerodynamic coefficients and the flow characteristics around the wheel. Besides, for the NPT wheel case, a shape-optimization study changes the wheel side profile's spokes angle (α) is conducted. The dynamic action of wheel rotation is modelled using the Moving Reference Frame (MRF) technique, and the RNG k- ࢿ is utilized as the adopted turbulence model for Averaged Reynolds Navier Stokes equations (RANS). All cases run at 30 m/s upstream velocity to be within the fully developed flow regime (supercritical regime). That is equivalent to 6.8 ×105 Reynolds number based on the wheel diameter as the characteristic length. In general, the overall obtained results give a satisfactory agreement to those measured experimentally. In conclusion, The NPT wheel, compared to the ST wheel, has a dramatic increase in drag force by approximately 31%, while a slightly raised lift force is obtained. The minimized spoke angle came with a beneficial drag reduction, while the applied resistive moment remained relatively high. Keywords: automotive aerodynamics; wheel aerodynamics, tyre CFD; rotating wheel dynamics; MRF wheel simulation; airless tyre aerodynamics, non-pneumatic tyre aerodynamics.

Dynamic Modeling of Bucket-Soil Interactions Using Koopman-DFL Lifting Linearization for Model Predictive Contouring Control of Autonomous Excavators

A lifting-linearization method based on the Koopman operator and Dual Faceted Linearization is applied to the control of a robotic excavator. In excavation, a bucket interacts with the surrounding soil in a highly nonlinear and complex manner. Here, we propose to represent the nonlinear bucket-soil dynamics with a set of linear state equations in a higher-dimensional space. The space of independent state variables is augmented by adding variables associated with nonlinear elements involved in the bucket-soil dynamics. These include nonlinear resistive forces and moment acting on the bucket from the soil, and the effective inertia of the bucket that varies as the soil is captured into the bucket. Variables associated with these nonlinear resistive and inertia elements are treated as additional state variables, and their time evolution is represented as another set of linear differential equations. The lifted linear dynamic model is then applied to Model Predictive Contouring Control, where a cost functional is minimized as a convex optimization problem thanks to the linear dynamics in the lifted space. The lifted linear model is tuned based on a data-driven method by using a soil dynamics simulator. Simulation experiments on homogeneous soil verify the effectiveness of the proposed lifting linearization compared to its counterpart.

Effect of intraoperative treatment options on hip joint stability following total hip arthroplasty

Dislocation remains the leading indication for revision of total hip arthroplasty (THA). The objective of this study was to use a computational model to compare the overall resistance to both anterior and posterior dislocation for the available THA constructs commonly considered by surgeons attempting to produce a stable joint. Patient-specific musculoskeletal models of THA patients performing activities consistent with anterior and posterior dislocation were developed to calculate joint contact forces and joint positions used for simulations of dislocation in a finite element model of the implanted hip that included an experimentally calibrated hip capsule representation. Dislocations were then performed with consideration of offset using +5 and +9 offset, iteratively with three lipped liner variations in jump distance (10°, 15°, and 20° lips), a size 40 head, and a dual-mobility construct. Dislocation resistance was quantified as the moment required to dislocate the hip and the integral of the moment-flexion angle (dislocation energy). Increasing head diameter increased resistive moment on average for anterior and posterior dislocation by 22% relative to a neutral configuration. A lipped liner resulted in increases in the resistive moment to posterior dislocation of 9%, 19%, and 47% for 10°, 15°, and 20° lips, a sensitivity of approximately 2.8 Nm/mm of additional jump distance. A dual-mobility acetabular design resulted in an average 38% increase in resistive moment and 92% increase in dislocation energy for anterior and posterior dislocation. A quantitative understanding of tradeoffs in the dislocation risk inherent to THA construct options is valuable in supporting surgical decision making.

An Orthotic Joint Design for Enhancing Ankle Mobility With Ankle Foot Orthoses Use

Abstract Articulated ankle foot orthoses (AFOs) are prescribed to treat drop-foot, a common neuromuscular weakness observed after a stroke. These assistive devices prevent the toe from dragging during swing (drop-foot) by providing a resistive moment at the ankle. However, existing ankle joint designs for articulated AFOs introduce additional gait pathologies as they also constrain ankle mobility during stance. A novel ankle joint for AFOs to prevent drop-foot during swing and improve ankle mobility during stance was developed, thereby reducing compensatory knee motion during stance. The design intent was to mimic the unconstrained kinematic response of a nonpathologic ankle at initial contact while preventing drop-foot during swing. The design incorporated two modes of operation: locked during swing for support and unlocked during stance for enhanced range of motion. Proof of concept testing with able-bodied subjects was conducted to test walking ability over level ground based on kinetic and kinematic parameters. The comparative tests confirmed the ability of the novel design to prevent drop-foot and its potential for enhanced ankle mobility during stance. Preliminary results indicate that the novel ankle joint should be refined to facilitate smooth and consistent unlocking but can be safely used in its current form with mobility impaired individuals.

A novel concept for adaptive friction damper based on electrostatic adhesion

This work presents a novel concept for an adaptive friction damper based on electrostatic adhesion for medium to small industrial applications and investigates the effects of electrostatic tuning on the energy dissipated by the damper under quasi-static as well as dynamic conditions. The novel damper has a low mechanical complexity. The amount of energy dissipated can be controlled through an electric voltage and be easily adapted to different working conditions. The concept is based on a stack of electrostatic clutches hinged around a common axis, which can dissipate energy through Coulomb friction. An electric field is used to vary the maximum shear stress transferred by the clutches and, consequently, to control the damping level. A prototype of the damper was manufactured and tested. The experimental results demonstrate the increase in the resistive moment of the clutches with increasing electric field and display the capability of the concept to adapt the damping level of a single-degree-of-freedom resonating system. The presented concept might replace linear dampers in rotating machines operating at different regimes, in road vehicles as well as in aircrafts.

Do Tangential Finger Forces Utilize Mechanical Advantage During Moment of Force production?

This study investigated the beneficial effects of the utilization of mechanical advantage (MA) of finger tangential forces during the moment production. Subjects produced the resistive moment of force against the external torque while the moment arms of the tangential forces were systematically changed. We observed a relatively large contribution to the net moment by the tangential forces with the increased moment arms, whereas the vector sum of normal and tangential forces decreased. The indices of multi-finger coordination for the stabilization of the moment of forces and force direction increased with the moment arms. The current results provide evidence that the utilization of MA is associated with both the efficiency of force production and the stabilization of performance variables.

Impact of alignment and kinematic variation on resistive moment and dislocation propensity for THA with lipped and neutral liners.

Instability and dislocation remain leading indications for revision of total hip arthroplasty (THA). Many studies have addressed the links between implant design and dislocation; however, an understanding of the impact of alignment and kinematic variability on constraint of modern THA constructs to provide joint stability is needed. The objective of this study is to provide objective data to be considered in the treatment algorithm to protect against joint instability. Joint contact and muscle forces were evaluated using musculoskeletal models of THA patients performing activities consistent with posterior and anterior dislocation. Position and joint loads were transferred to a finite element simulation with an experimentally calibrated hip capsule representation, where they were kinematically extrapolated until impingement and eventual dislocation. Cup anteversion and inclination were varied according to clinical measurements, and variation in imposed kinematics was included. The resistive moment provided by the contact force and joint capsule, and overall dislocation rate (dislocations/total simulations) were determined with neutral and lipped acetabular liners. Use of a lipped liner did increase the resistive moment in posterior dislocation, by an average of 5.2 Nm, and the flexion angle at dislocation by 1.4° compared to a neutral liner. There was a reduction in similar magnitude in resistance to anterior dislocation. Increased cup anteversion and inclination, hip abduction and internal rotation all reduced the occurrence of posterior dislocation but increased anterior dislocation. A quantitative understanding of tradeoffs in the dislocation risk inherent to THA construct options is valuable in supporting surgical decision making.

Load shedding characteristics of an oscillating surge wave energy converter with variable geometry

This study investigates performance and load shedding capabilities of an oscillating surge wave energy converter (OSWEC) that utilizes adjustable geometry to control hydrodynamic coefficients. The body consists of a bottom-hinged rectangular paddle in which the frame holds five horizontal flaps spanning the interior of the frame. Each flap can rotate independently about its center of rotation to alter hydrodynamic coefficients. A 1:14 scale model was built for wave tank tests where the OSWEC's natural response to regular waves was measured. Tests with the paddle fixed vertically were conducted to measure the moment induced by incident waves. Results were compared to numerical simulations which determined that flap orientation significantly affected wave energy transmission past the device. Numerical simulations with the addition of a linear rotational damper power take-off (PTO) suggested that with flaps open, the resistive moment was reduced by up to 47%, the surge force on the foundation up to 55%, and the capture width up to 72% over a range of wave periods and PTO damping values. The experimental nondimensional excitation moments and reflection coefficients were reduced by up to 54%. Overall, the flaps provide mechanical means to reduce loads, thus improving the design life of a WEC system.

Modeling the mechanical and electrical characteristics of the synchronous motor

This paper presents the mechanical and electrical characteristics of the synchronous motor for variations of the required moment. It is presented the test configuration used to determine the mechanical and electrical characteristics of the synchronous motor. Engine torque modelling allows the shaft to be loaded with various resistive moments generated by an electromechanical brake. The presented characteristics highlight the mechanical characteristic of the synchronous motor, which does not depend on the resistant mechanical torque of the working machine during the technological process. There are presented the mechanical characteristics of the rotation speed depending on the variation of the resistant moment until the synchronism exit of the synchronous motor. The determination of these characteristics is dependent on the variation of the excitation current of the synchronous motor.

Hydraulic Experiments on a Small-Scale Wave Energy Converter with an Unconventional Dummy Pto

This paper investigates on a Wave Energy Converter (WEC) named Energy &amp; Protection, 4th generation (EP4). The WEC couples the energy harvesting function with the purpose of protecting the coast from erosion. It is formed by a flap rolling with a single degree of freedom around a lower hinge. Small-scale tests were carried out in the wave flume of the maritime group of Padua University, aiming at the evaluation of the device efficiency. The test peculiarity is represented by the system used to simulate the Power Take Off (PTO). Such dummy PTO permits a free rotation of two degrees before engaging the shaft, allowing the flap to gain some inertia, and then applying a constant resistive moment. The EP4 was observed to reach a 35% efficiency, under short regular waves. The effects, in terms of coastal protection, are small but not negligible, at least for the shortest waves.

Task space-based dynamic trajectory planning for digging process of a hydraulic excavator with the integration of soil–bucket interaction

In this paper, a task space-based methodology for dynamic trajectory planning for digging process of a hydraulic excavator is presented, with the integration of soil–bucket interaction. An extended soil–bucket interaction model, which adds the resistive moment compared to the previous models, is provided in this research. This improved model is validated by comparing with the measurement data taken from field experiments before integrating it into a dynamic model of an excavator. Further, Newton–Euler method is used for the derivation of the dynamics of each link of the excavator to determine the joint forces, which can cause the machine damage. The position and orientation trajectories of the bucket in the task space are parameterized by using the B-splines, so as to achieve the task-oriented operations and ensure the operation flexibility. The joint space motion characteristics are obtained by solving the inverse kinematics of the working mechanism of an excavator. Moreover, to avoid the operation uncertainty for a given bucket tip position trajectory and reduce the computational effort, the self-motion parameters are introduced when solving the inverse kinematics of the redundant working mechanism. All these self-motion parameters are taken as a set of design variables in the trajectory optimization problem. Also, the limits on the hydraulic driving forces, joint angles, angular velocities and accelerations, as well as bucket capacity are considered as the optimization constraints for the digging process. Finally, optimization examples of two typical digging categories (i.e. level digging work and slope digging work) are given to demonstrate and verify the capabilities of the new methodology proposed in this research. The results show that the proposed method can effectively generate the optimal trajectories satisfying the following criteria: time efficiency, energy efficiency, and least machine damage. This work lays a solid foundation for motion planning and autonomous control of an excavator.

Effects of Walkbot gait training on kinematics, kinetics, and clinical gait function in paraplegia and quadriplegia.

The robotic-assisted gait training (RAGT) system has gained recognition as an innovative, effective paradigm to improve functional ambulation and activities of daily living in spinal cord injury and stroke. However, the effects of the Walkbot robotic-assisted gait training system with a specialized hip-knee-ankle actuator have never been examined in the paraplegia and quadriplegia population. The aim of this study was to determine the long-term effects of Walkbot training on clinical for hips and knee stiffness in individuals with paraplegia or quadriplegia. Nine adults with subacute or chronic paraplegia resulting from spinal cord injury or quadriplegia resulting from cerebral vascular accident (CVA) and/or hypoxia underwent progressive conventional gait retraining combined with the Walkbot RAGT for 5 days/week over an average of 43 sessions for 8 weeks. Clinical outcomes were measured with the Functional Ambulation Category (FAC), Modified Rankin Scale (MRS), Korean version of the Modified Barthel Index (K-MBI), Modified Ashworth Scale (MAS). Kinetic and kinematic data were collected via a built-in Walkbot program. Wilcoxon signed-rank tests showed significant positive intervention effects on K-MBI, maximal hip flexion and extension, maximal knee flexion, active torque in the knee joint, resistive torque, and stiffness in the hip joint (P < 0.05). These findings suggest that the Walkbot RAGT was effective for improving knee and hip kinematics and the active knee joint moment while decreasing hip resistive force. These improvements were associated with functional recovery in gait, balance, mobility and daily activities. These findings suggest that the Walkbot RAGT was effective for improving knee and hip kinematics and the active knee joint moment while decreasing hip resistive force. This is the first clinical evidence for intensive, long-term effects of the Walkbot RAGT on active or resistive moments and stiffness associated with spasticity and functional mobility in individuals with subacute or chronic paraplegia or quadriplegia who had reached a plateau in motor recovery after conventional therapy.

Effects of Gait Modification on Lower Extremity Sagittal Plane Biomechanics

Gait modification (GM) via real-time biofeedback (RTB) is a conservative intervention that has shown positive outcomes in post stroke and diabetic patients. Results from a recent systematic review support the effectiveness of this approach for increasing peak internal knee extension moment (iPKEM). iPKEM is a resistive moment to peak external knee flexion moment (ePKFM), which is associated with altered joint loading. Scarce information exists on the comparative effectiveness of existing GM strategies. PURPOSE: To compare the effectiveness of trunk lean (TL), medial knee thrust (MKT), and foot progression (FP) on iPKEM. METHODS: 10 healthy individuals volunteered for this study (28.4±3.8 years, 1.73±0.1 m, 75.3±12.5 kg). Mean and standard deviation (SD) for iPKEM, trunk angle, knee angle (KA), and foot angle during stance were calculated from 10 baseline trials using a motion capture system (200Hz) and force plates (1000Hz). 10 trials completed for each strategy using RTB so that joint angles fell within a determined range (1-5 SD) relative to baseline. Visual 3D (V3D) was used to project visual RTB as a line graph displaying real-time joint angle during stance. V3D was used to calculate joint angles (°) and internal moments (Nm/kgm). Participants modified their gait based on strategy so the line fell within a highlighted bandwidth representing target ranges. Repeated measures ANOVA was used to assess differences in iPKEM between strategies. Dependent t-tests were conducted to compare joint angles between baseline and modification strategy (p<0.05). RESULTS: A significant difference between strategies was attained for iPKEM (p=0.001). MKT (.53±.24) had higher iPKEM than all other strategies (Baseline: .31±.2, FP: .34±.12, TL: .31±1.4). No other statistically significant difference was found (p>0.05). CONCLUSION: MKT gait increased iPKEM despite no significant differences in KA compared to baseline. The observed increase in iPKEM during MKT gait suggests that participants were successful at attenuating ePKFM during the absorption phase of stance. Lack of significant changes in joint angles across conditions suggests that overall gait kinematics were similar for all conditions. Future research employing greater values for kinematic change is needed to further understand the effect of GM on iPKEM.

Flux boundary measurements for the study of tree stability

The shear strength of soil is an important parameter that affects tree stability and can vary depending on the magnitude of the soil’s negative pore-water pressure (matric suction). The surface flux boundary condition affects the matric suction of soil, and therefore is important for tree stability. Field measurements were performed around a roadside tree for 2 years. The instrumentation results show that the matric suction in the soil fluctuated between 0 and 35 kPa. Matric suction changes in the soil could lead to a decrease in the tree resistive moment of up to 80 %.

Simulation and Measurement of the Adhesion Moment of a Particle‐Wall Contact on the Atomic Scale

AbstractIf a particle in contact with a wall gets stressed by an external force and the contact breaks, the particle will start an evasive movement. In many cases, the evasive movement with the smallest force to overcome is rolling. The resistive force – or better, resistive moment – that holds the particle in place was observed. To do so, a computer‐based simulation was developed to calculate this adhesion moment for two contact cases: a smooth spherical particle on a wall in a gaseous environment and another spherical particle with an also spherical roughness. These calculated values can now be compared to experimental data, since an apparatus to measure the adhesion moment was installed at an environmental scanning electron microscope.

Direct measurement of plantarflexion resistive moments and angular positions of an articulated ankle-foot orthosis while walking in individuals post stroke: A preliminary study.

The plantarflexion resistive moments of an articulated ankle–foot orthosis play an important role in improving gait in individuals post stroke. However, the evidence regarding their magnitude required from the articulated ankle–foot orthosis to improve walking is still limited. Therefore, the primary aim of this study was to directly measure the plantarflexion resistive moments and the joint angular positions while walking using a prototype instrumented articulated ankle–foot orthosis in five individuals post stroke. The secondary aim was to investigate their moment–angle relationship by changing its preset plantarflexion stiffness. Each subject was fitted with the instrumented articulated ankle–foot orthosis and walked on a treadmill under four different preset plantarflexion stiffness conditions (0.35 N·m/°, 0.51 N·m/°, 0.87 N·m/°, and 1.27 N·m/°). For each subject, the plantarflexion resistive moments and the joint angular positions of five continuous gait cycles were extracted and averaged for each condition. Data were plotted and presented as case series. Both plantarflexion resistive moments and joint angular positions of the ankle–foot orthosis changed according to the preset plantarflexion stiffness in all subjects. Using the instrumented articulated ankle–foot orthosis could potentially advance the understanding of the biomechanics of an ankle–foot orthosis, as well as contribute to more evidence-based orthotic care of patients.

The effect of changing plantarflexion resistive moment of an articulated ankle–foot orthosis on ankle and knee joint angles and moments while walking in patients post stroke

BackgroundThe adjustment of plantarflexion resistive moment of an articulated ankle–foot orthosis is considered important in patients post stroke, but the evidence is still limited. Therefore, the aim of this study was to investigate the effect of changing the plantarflexion resistive moment of an articulated ankle–foot orthosis on ankle and knee joint angles and moments in patients post stroke. MethodsGait analysis was performed on 10 subjects post stroke under four different plantarflexion resistive moment conditions using a newly designed articulated ankle–foot orthosis. Data were recorded using a Bertec split-belt instrumented treadmill in a 3-dimensional motion analysis laboratory. FindingsThe ankle and knee sagittal joint angles and moments were significantly affected by the amount of plantarflexion resistive moment of the ankle–foot orthosis. Increasing the plantarflexion resistive moment of the ankle–foot orthosis induced significant decreases both in the peak ankle plantarflexion angle (P<0.01) and the peak knee extension angle (P<0.05). Also, the increase induced significant increases in the internal dorsiflexion moment of the ankle joint (P<0.01) and significantly decreased the internal flexion moment of the knee joint (P<0.01). InterpretationThese results suggest an important link between the kinematic/kinetic parameters of the lower-limb joints and the plantarflexion resistive moment of an articulated ankle–foot orthosis. A future study should be performed to clarify their relationship further so that the practitioners may be able to use these parameters as objective data to determine an optimal plantarflexion resistive moment of an articulated ankle–foot orthosis for improved orthotic care in individual patients.