Vertical Reaction Force Research Articles

Strict Stealth Walking of Legged Robot Formed by Four Parallelogram Links and Equipped with Wobbling Mass and Reaction Wheel

This paper proposes a novel legged locomotion robot model formed by four parallelogram links and equipped with a wobbling mass and a reaction wheel, and investigates the method for generating a strict stealth walking gait on the frictionless road surface. First, we describe the robot equation of motion, and design an output-following control system for generating a walking motion by ignoring the condition of the vertical ground reaction forces. Second, we redesign the control system taking into consideration the distribution of the vertical reaction forces or the zero-moment point. Furthermore, we discuss the improvement of energy efficiency using elastic elements in terms of specific resistance.

Dynamic analysis of a translating five-bar linkage mechanism

In this paper, the dynamic analysis of a translating five-bar linkage mechanism is presented. The dynamic model of the mechanism is developed with the applied force to the crank arm resolved into the two principal planes, that is, x- and y- directions and the resulting reaction forces and moments at the pin joints determined at various translating acceleration of 0, 10, 20, 30 and 40 m/s2 in the direction as well as in the opposite direction of the crank rotation. It was observed that the horizontal reaction forces at the pin joints were decreasing as the translating acceleration increases in the direction of crank rotation while it increases when the acceleration increases in the opposite direction to the crank rotation. It was also observed that the pin joint moments at point A decreases as the translation velocities increases in the crank arm rotation direction while it increases as the acceleration increases in the opposite direction. The converse is the case for pin joint B, while there were no significant differences for pin joint moments at pin joints C and D in all the considered acceleration in both directions. Also, the vertical reaction forces at the pin joints did not change in magnitude as the magnitude and directions of the acceleration were altered. The analysis brings to the fore the importance of the consideration of translating acceleration in the design, development and utilization of five – bar linkage to avoid failure at any of the joints.

External loading of common training drills: Ranking drills to design progressive return-to-run programs

Return-to-run protocols following lower extremity injuries commonly include a gradual training and loading progression to allow positive adaptation of musculoskeletal tissue. Before full return to running, training drills designed to provide a low to high external loading progression (i.e., vertical forces) may therefore minimize the risks of re-injury. However, the magnitude of external loading among various training drills has not yet been quantified. ObjectivesThe purpose of this study was to quantify peak vertical forces of multiple common training drills and rank each of them in order from lowest to highest peak vertical force. Design/Participants: 11 experienced runners completed five trials of 46 training drills while in-shoe vertical reaction force (vRF) was measured with wireless force insoles. Main outcome measuresAverage peak vRF was calculated for each drill across all participants. Drills were also grouped by vRF into four categories intended for use by clinicians as stages of rehabilitation. Results46 training drills were ranked in order from least to greatest vRF. The drill with the highest average peak vRF was “Ladder Single Leg Hop Forward”, at 2.80 BW. The drill with the lowest average peak vRF was “Squat Mini Jump”, at 1.02 BW. ConclusionsThese data provide valuable information for clinicians, coaches and pelvic floor practitioners when programming rehabilitation and return-to-run training progressions for runners coming back from lower extremity or pelvic injuries.

An experimental study of the stiffness and strength of cross-laminated timber wall-to-floor connections under compression perpendicular to the grain

In platform-type multi-story cross-laminated timber (CLT) buildings, gravity loads from upper floors, and vertical reaction forces from horizontal actions, like wind loads, cause substantial compressive forces in the CLT-floor elements. The combination of these high forces with a comparable low compression stiffness and strength perpendicular to the grain of timber, makes the compression perpendicular to the grain (CPG) verification of CLT an important design criterion. In this experimental study, CPG of CLT was investigated by means of typical wall-to-floor connections in CLT platform-type structures. CLT-wall elements were used for load application to transmit forces through the CLT-floor element by CPG. Compared to load application by steel elements, as it commonly is done in experiments, lower stiffness but similar strength were found for CLT walls. The study of different connection types showed the highest stiffness and strength for connections assembled with screws, followed by pure wood-to-wood contact, while connections with acoustic layers between the floor and wall elements showed the lowest stiffness and strength. In addition, these connections were tested for center and edge load position on the CLT-floor element. The strength for center and edge position compared to full surface loaded specimens increased linearly with the activated material volume, as determined by earlier proposed stress dispersion models. The stress dispersion effect was visualized by surface strain measurements using digital image correlation technique. Also, the stiffness increased with the activated material volume. Stress dispersion in the CLT-floor allowed to explain the increase in stiffness and strength with decreasing CLT-wall thickness. Strength values at different strain levels, and stiffness and strength increase factors suitable for the engineering design of CLT structures are provided.

An investigation of the ankle contact forces in a foot with hammer toe deformity. A comparison of patient-specific approaches using finite element modeling and musculoskeletal simulation.

The internal forces and stresses in the tissue are important as they are linked to the risk of mechanical trauma and injuries. Despite their value, the internal stresses and forces cannot be directly measured in-vivo. A previously validated 3D finite element model (FEM) was constructed using Magnetic Resonance Imaging (MRI) of a person with diabetes and hammer toe deformity. The foot model simulated at five different instances during the stance phase of gait. The internal stress distribution on the talus that was obtained using the FEM simulation, was used to calculate the joint reaction force at the ankle joint. In addition, the musculoskeletal model (MSM) of the participant with hammer toe foot was developed based on the gait analysis and was used to determine the muscle forces and joint reactions. The result showed that the vertical reaction forces obtained from the FEM and MSM follow a similar trend through the stance phase of gait cycle and are significantly correlated ( R=0.99). The joint reaction forces obtained through the two methods do not differ for the first 25% of the gait cycle, while the maximum difference was ∼0.7 Body weight that was observed at 50% of the stance phase. Clinical Relevance: Finite element modeling and musculoskeletal simulation can shed light on the internal forces at the ankle in pathological conditions such as hammer toe. The similarities and differences observed in the joint reaction forces calculated from the two methods can have implications in assessing the effect of clinical interventions.

Vertical Extension of a Multi-Storey Reinforced Concrete Building

The global population is increasing annually; thus, there is a need for more housing and buildings worldwide. As cities grow outward and buildable lands become scarce, it is necessary to increase the height of existing buildings in cities, especially where the height of the buildings is low. For crowded cities, the storey extension is an increasingly popular measure that can meet market demand for centrally located houses. This paper examines the possibility of the vertical extension of an existing (reference) reinforced concrete building in Gävle in Sweden. The StruSoft FEM-Design program is employed to carry out the research. The building is firstly modelled, analysed and designed completely. Thereafter, a storey extension is conducted vertically. The stresses and utilisation ratios of the load-bearing elements of the reference and extended buildings are assessed. It is found that some of the load-bearing elements of the building after the extension need strengthening. Different practical strengthening solutions are proposed. It is concluded that the building can successfully withstand the vertical extension after applying these proposed solutions. The maximum vertical reaction forces of the reference and extended buildings are obtained and compared. A comparison of the deflections of the buildings is made. The structural stability of the buildings is evaluated as well.

Biomechanical investigation of load differences on the upper extremities in dynamic hand strikes and isometric hand pushes during assembly tasks

AbstractThis study determines the effects of increasing forces on different musculoskeletal load parameters, such as muscle activity and joint movement, during assembly task‐related dynamic hand strikes and isometric push forces. Fifteen subjects (12 men and 3 women) were instructed to strike and push on a force plate in two selected conditions. In the first condition, the palmar surface of the dominant hand is oriented horizontal to the measuring surface; in the second condition, the body position is maintained, but the hand is turned 90° to allow the use of the ulnar side of the hand (fist strike position). The subjects accomplished four force levels in ascending order (i.e., 150, 250, 350, and 400 N) within the corresponding striking and pushing conditions. The extracted kinematic variables of interest were strike velocity, recoil velocity, force plate contact time, peak vertical reaction force component (force plate), force impulse, muscle activity, and maximum joint ranges of motion during the push or strike process. Differences in the results between pushes and strikes and, under certain circumstances, between fist and palm strikes were identified. Increasing push forces correlate with the muscle activity in the pectoralis and lower arm extensor muscles. The fact that, at push forces > 250 N, the subjects modify and adapt their upper body and arm posture to achieve the required force could reveal an obvious feasibility limit and explain why assembly workers tend to use their hands as a hammer.

Body CoM Acceleration for Rapid Analysis of Gait Variability and Pedestrian Effects on Structures

Knowledge of body motion features and walk-induced effects is of primary importance for the vibration analysis of structures, especially low-frequency slabs and lightweight and/or slender systems, as well as for clinical applications. Structurally speaking, consolidated literature procedures are available for a wide set of constructional solutions and typologies. A basic assumption consists in the description of walking humans’ effects on structures through equivalent deterministic loads, in which the ground vertical reaction force due to pedestrians depends on their mass and motion frequency. However, a multitude of additional parameters should be taken into account and properly confirmed by dedicated laboratory studies. In this paper, the focus is on the assessment of a rapid analysis protocol in which attention is given to pedestrian input, based on a minimized sensor setup. The study of gait variability and related effects for structural purposes is based on the elaboration of single Wi-Fi sensor, body centre of mass (CoM) accelerations. A total of 50 walking configurations was experimentally investigated in laboratory or in field conditions (for more than 500 recorded gaits), with the support of an adult volunteer. Parametric gait analysis is presented considering different substructure conditions and motion configurations. Body CoM acceleration records are then used for the analysis of a concrete slab, where the attention is focused on the effects of (i) rough experimental body CoM input, or (ii) experimentally derived synthetized gait input. The effects on the structural side of rough experimental walk time histories or synthetized experimental stride signals are discussed.

Optimal Relationship between Vertical Velocity and Movement Time to Reduce Vertical Bar Reaction Force during the Arm Support Phase of Kicking Pullovers

Optimal Relationship between Vertical Velocity and Movement Time to Reduce Vertical Bar Reaction Force during the Arm Support Phase of Kicking Pullovers

Spatial failure mechanism of coastal bridges under extreme waves using high-efficient pseudo-fluid-structure interaction solution scheme

Coastal bridges serve as lifelines in evacuation and rescue after coastal natural hazards. It is thus vital to reveal the spatial failure mechanism for coastal bridges under extreme waves. In this study, a high-efficient pseudo-fluid-structure interaction (PFSI) solution scheme is proposed to investigate the spatial failure mechanism of coastal bridges under extreme waves. A series of laboratory experiments and numerical simulations are conducted to verify the proposed solution scheme. The results solved by the proposed solution scheme are acceptable and reliable under the small rotation of the deck, which could be used to efficiently assess the deck failure, and the calculation process is high-efficient. The spatial failure mechanism of the typical coastal bridge is investigated by using the proposed solution scheme in this study. The properties of wave forces on the deck are discussed based on numerous experimental measurements considering various wave parameter combinations and inundation conditions firstly. Subsequently, the failure thresholds of bearing vertical and horizontal reaction forces are obtained by parametric analysis considering various wave parameter combinations using the proposed solution scheme. Additionally, two typical failure modes (i.e., fall-beam failure and overturning failure) are analyzed by considering time-varying restraining stiffnesses in vertical and horizontal directions. The obtained results can be served as a robust reference for the design and management of coastal bridges under extreme waves.

Characterization of loading profiles via handrails and harness during body weight supported treadmill training

Abstract Body weight supported treadmill training is used for patients who are severely limited in their movements. During walking therapy handrails and harnesses ensure the patient’s stability and safety. Although, locomotion training is a common rehabilitation technique, data of forces applied to handrails or overhead lifts are limited. Therefore, the primary objective of this study was to measure the vertical reaction force during treadmill therapy. An additional purpose was the characterization of the loading profiles by defining suitable parameters. To measure the patient’s needs for support during treadmill training, the handrails were instrumented with strain gauges and a force sensor was placed between the harness and the ceiling lift. In order to provide gait phase detection, an inertial sensor was attached to each foot. The results confirm that the combined measuring systems are appropriate to record the total vertical weight relief. Although all patients show different loading profiles, a recurring pattern can be recognized for each patient, which allows the derivation of various parameters to characterize the single profiles. The additional information of the measurements can help the supervising physiotherapist to better understand the specific level of support the patient needs. A subsequent response and the providing of corresponding instructions by the therapist can lead to an even more individualized therapy.

A simulation based large bus side slip and rollover threshold study in slope-curve section under adverse weathers.

To study the side slip and rollover threshold of large bus in slope–curve section under adverse weather, factors that affect the safety of large buses that run in slope–curve section, such as rain, snow, cross-wind environmental factors, and road geometry, were analyzed to obtain the friction coefficient of the road surface under different rainfall and snowfall intensities through field measurements and to determine the six-component force coefficient of wind that acts on large buses through wind tunnel tests. The force analysis of large bus in slope-curve section was carried out, and the mechanical equations of large bus under the limit conditions of sideslip and rollover in slope-curve section were established. TruckSim simulation test platform was used to establish a three-dimensional road model and large bus mechanical model at a design speed of 100 km/h. Input parameters, such as cross-wind speed and road friction coefficient, simulate the impact of wind-rain/snow coupling. Under the combined action of wind-rain/snow, the operation test of large bus in slope-curve section was carried out, and the key parameters and indicators of the sideslip and rollover of large bus in slope-curve section were outputted and analyzed. The sudden change point of lateral acceleration is the judging condition for sideslip of large bus in slope-curve section under different road friction coefficient (0.2–0.7), changing from 0.15m/s2 and stabilizing to 0.52 m/s2, and a 0N vertical reaction force of the inner tire is the critical judging condition for rollover under road friction coefficient0.8, and the operating speed thresholds were proposed under different road friction coefficient. This study is expected to provide theoretical support for the speed limit of large bus in slope-curve section under adverse weather.

An Investigation of Differences in Lower Extremity Biomechanics During Single-Leg Landing From Height Using Bionic Shoes and Normal Shoes.

Bionic shoes utilizing an actual foot shape sole structure can alter lower limb’s biomechanics, which may help in the development of specific training or rehabilitation programs. The purpose of this study was to investigate the biomechanical differences in the lower limb during a single-leg landing task using bionic shoes (BS) and normal shoes (NS). Fifteen healthy male subjects participated in this study, sagittal, and frontal plane data were collected during the landing phase (drop landing from 35 cm platform). Our study showed that BS depicted a significantly greater minimum knee flexion angle at initial contact (p = 0.000), a significantly greater minimum (initial contact) hip flexion angle at initial contact (p = 0.009), a significantly smaller sagittal plane total energy dissipation (p = 0.028), a significantly smaller frontal plane total energy dissipation (p = 0.008), a significantly smaller lower limb total energy dissipation (p = 0.017) than NS during the landing phase. SPM analysis revealed that BS depicted a significantly smaller knee joint vertical reaction force during the 13.8–19.8% landing phase (p = 0.01), a significantly smaller anterior tibia shear force during the 14.2–17.5% landing phase (p = 0.024) than NS. BS appears to change lower limb kinematics at initial contact and then readjust the landing strategies for joint work and joint reaction force, thereby reducing the risk of lower limb skeletal muscle injury. BS have great potential for future development and application uses, which may help athletes to reduce lower limb injury risk.

Association of Machine Learning-Based Predictions of Medial Knee Contact Force With Cartilage Loss Over 2.5 Years in Knee Osteoarthritis.

The relationship between in vivo knee load predictions and longitudinal cartilage changes has not been investigated. We undertook this study to develop an equation to predict the medial tibiofemoral contact force (MCF) peak during walking in persons with instrumented knee implants, and to apply this equation to determine the relationship between the predicted MCF peak and cartilage loss in patients with knee osteoarthritis (OA). In adults with knee OA (39 women, 8 men; mean ± SD age 61.1 ± 6.8 years), baseline biomechanical gait analyses were performed, and annualized change in medial tibial cartilage volume (mm3 /year) over 2.5 years was determined using magnetic resonance imaging. In a separate sample of patients with force-measuring tibial prostheses (3 women, 6 men; mean ± SD age 70.3 ± 5.2 years), gait data plus in vivo knee loads were used to develop an equation to predict the MCF peak using machine learning. This equation was then applied to the knee OA group, and the relationship between the predicted MCF peak and annualized cartilage volume change was determined. The MCF peak was best predicted using gait speed, the knee adduction moment peak, and the vertical knee reaction force peak (root mean square error 132.88N; R2 = 0.81, P < 0.001). In participants with knee OA, the predicted MCF peak was related to cartilage volume change (R2 = 0.35, β = -0.119, P < 0.001). Machine learning was used to develop a novel equation for predicting the MCF peak from external biomechanical parameters. The predicted MCF peak was positively related to medial tibial cartilage volume loss in patients with knee OA.

The Effect of Varus Deformity on Co-Activation of Abdominal and Lower Limb Muscles during Landing Task in Female Subjects

Objective: Genuvarum deformity experience knee instability. This deformity can lead the patient to sever osteoarthritis. The recovery of postural stability is very important to prevention of these patients. Strategies aimed at stabilizing the muscle can have a long-term effect on the joint. This study was performed to determine the relationship between muscle stabilization strategies and knee instability, in order to determine how people with knee Genuvarum, respond to rapid absorption and muscle co- contraction during landing task. Methods: Twenty female participants, (10 normal and 10 Genuvarum) in the present study. The subjects were land by preferred lower limb from a table (30 cm high) on a force plate. Vertical ground reaction force, time to peak of vertical reaction force, velocity of vertical ground reaction force to reach the maximum, time to stability in X and Y directions and resultant vector were calculated as postural control parameters. Also surface electromyography of transverse abdominal/int. oblique, vastus medialis, vastus lateralis, lateral gastrocnemius, and medial gastrocnemius muscles were recorded during landing. Motor control strategy were measured by similarity index and voluntary response index. Results: There are significant difference between Genuvarum and Healthy subjects in motor control strategy (P&lt;0.05).A significant difference are detected in postural control parameters between two groups (P&lt;0.05). Conclusion: Genuvarum deformity may be linked to altered quadriceps, abdominal and gastrocnemius muscles reciprocal co-activation patterns during landing task. In addition, may be affected voluntary motor control strategy in synergy concepts. Postural control is affected in these deformity and shock absorption may be reduced in parallel to increase of response vector and reduce of instability in landing task.

Flexural behavior analysis on RC simply supported girder strengthened by adding diagonal brace

Adding the diagonal bracing to strengthen RC simply supported beam bridge has certain engineering application space. In order to study the flexural performance of the strengthened members, the finite element model was established by Midas/Civil to calculate and analyze the load effect of 20m span RC simply-supported T beam under 12 flexural strengthening conditions. The results showed that the connection form of diagonal brace has little influence on the deformation behavior of the strengthened beam. After reinforcement, the positive moment and deflection of mid-span of the main beam can be reduced by more than 50%. At the same time, the main beam appears negative moment, horizontal reaction force, and vertical negative reaction force may occur. The reasonable arrangement of the brace position can ensure that the main beam does not have vertical negative reaction force, and the main beam negative moment and horizontal reaction force, the horizontal and vertical reaction force of the diagonal brace are controlled to obtain ideal load effect results.

Determination of Instability Critical Speed of Articulated Vehicle on Ramp Section Based on Response Surface Method

In order to improve the driving safety of vehicles on the ramp section, aiming at the lateral instability problems such as sideslip and rollover in the corner driving of semi-trailer trains, the six-axis articulated vehicle, which is the representative model of current highway freight transportation in China, is selected as the research object. The TruckSim simulation software is used to establish the vehicle dynamic model of nonlinear articulated vehicle, and the orthogonal simulation test of different loading quality and different road adhesion coefficient is designed. The vertical reaction force and lateral displacement of the wheel are taken as the evaluation indexes of vehicle sideslip and rollover, and the critical speed of instability under various road conditions is obtained. On the basis of surface function fitting, combined with the simulation experimental data, the response surface mathematical model of instability critical speed, road adhesion coefficient and loading quality is established. The comparison calculation shows that only 2.23% of the calculation error of the mathematical model reduces the error of the traditional model and improves the calculation accuracy of the model. The results show that the critical speed threshold of instability decreases with the increase of loading mass. With the increase of road adhesion coefficient, the threshold of instability critical speed increases. When the road adhesion coefficient reaches 0.6, the change of instability critical speed threshold tends to be steady. The research results can provide a reference for the evaluation of rollover and sideslip during the turning of articulated vehicle and the determination of anti-instability warning speed of articulated vehicle crossing the ramp section safely.

Artificial neural network that modifies muscle activity in sit-to-stand motion using sensory input

Sit-to-stand motion is an important daily activity, and it is important to study the mechanism of the motion to improve the ability when it becomes weak. To study the mechanism, we hypothesized that muscle synergy generates muscle activity as a feedforward signal, which is modified by sensory input. This study focuses on determining the sensory input primarily used for modifying sit-to-stand motion. To obtain this, we built artificial neural network models that generate muscle activities based on sensory input and feedforward signals and analyzed the effect of each input on the output. The models were built for each motion phase. The input was information from vestibular and somatosensory input and averaged muscle synergy as feedforward signals, and the output was muscle synergy. As a result, it was revealed that humans may primarily use hip angle to bend forward, ankle and vertical foot reaction force to hip rise, ankle, knee, and lumber angles and vertical foot reaction force to extend body, and lumber angle to stabilize. This indicates the type of sensory input used to control each muscle synergy in each motion phase. The information should be used to modify the sit-to-stand motion in environmental conditions where the motion is performed.

The effect of eight-week elastic walking exercise on the pattern of plantar pressure distribution in women with chronic low back pain during walking

Background: Training of elastic walking is a new method for elasticity in gait and correction of the distribution pattern of plantar pressure in patients with low back pain during gait. This study aimed to investigate the distribution pattern of plantar pressure during gait in women with low back pain following 8 weeks-training of elastic walking. Methods: The present study was quasi-experimental. In this research, 20 women with low back pain were divided into control (n=11) and experimental (n=9) groups. Subjects from the experimental group performed elastic gait training for 3 sessions per week for 8 weeks while the control group didn’t have any exercise program. The plantar pressure variables included the peak of vertical ground reaction forces, the time to peak of ground reaction forces, loading rate, the peak of plantar pressure on the ten foot regions, the peak of ground reaction forces on the ten foot regions, and displacement of the pressure center in two internal-external (copx) and anterior-posterior (copy) lines. The distribution pattern of plantar pressure during gait was recorded by a foot scan system (Sampling rate 300 Hz) in pre-training and post-training. Two-way ANOVA was used to analyze the data. The significance level was set at P &lt; 0.05. Results: In the experimental group, the results of this study demonstrated lower peak vertical reaction force (FzMS component) during post-test compared with pre-test (P = 0.002). Moreover, findings showed that the main effect of group on peak pressure in the mid-foot region was significant (P = 0.011). The results showed no significant difference concerning the main effect of group, the main effect of time and effect, interaction time and group on peak vertical reaction force, displacement of pressure center, vertical loading rate, and walking stance time (P &gt; 0.05). Conclusion: The findings of this study showed that training of elastic walking does not have a significant effect on stance time. Also, training of elastic walking in the experimental group reduced the peak vertical ground reaction force (FzMS component) during the post-test compared with the pre-test that can correct the walking pattern and improve the chronic low back pain.

A Useful Combination of Quantitative Ultrashort Echo Time MR Imaging and a Probing Device for Biomechanical Evaluation of Articular Cartilage.

In this study, we combined quantitative ultrashort echo time (UTE) magnetic resonance (MR) imaging and an investigation by a probing device with tri-axial force sensor to seek correlations with mechanical properties of human patellar cartilage for in situ evaluation of biomechanical properties. Cartilage blocks (15 × 20 × 5 mm3) were dissected from the patella of six donors; 5 mm square regions of interest from the cartilage blocks were imaged using UTE-MR imaging sequences (T2* and magnetization transfer ratio (MTR)), and mechanical properties were measured using a micro indentation device. Then, the vertical reaction force on the cartilage surface was measured while push-probing forward 3 mm with the probing device at a 30° tilt to the horizontal plane. The results showed a positive correlation between stiffness/elastic modulus and each predictor variable (UTE-T2* (r = 0.240 and 0.255, respectively, UTE-MTR (r = 0.378 and 0.379, respectively), and probing device force (r = 0.426 and 0.423, respectively). Furthermore, multiple linear regression analysis showed the combination of the three predictors had stronger correlation (adjusted r2 = 0.314 (stiffness), 0.323 (elastic), respectively). Our results demonstrate the potential for these non- and less- invasive methods for in situ evaluation of the mechanical properties of cartilage tissue.