Vertical Reaction Force Research Articles

Feasibility of Stationary Cycling with Pedal Force Visual Feedback Post-Total Knee Arthroplasty: Implications for Inter-Limb Deficits in Knee Joint Biomechanics

The purpose of this study was to assess the biomechanical adaptations prompted by stationary cycling paired with visual feedback of vertical pedal reaction forces during both stationary cycling and overground walking for patients who underwent a total knee arthroplasty (TKA). Specifically, an emphasis on the inter-limb deficits in knee joint biomechanics were examined. Ten patients who underwent a TKA took part in an acute intervention with pre- and post-testing measurements of kinematics (240 Hz) and kinetics (1200 Hz) during stationary cycling and overground walking. The intervention phase consisted of six cycling sessions during which participants were provided with visual feedback of their bilateral peak vertical pedal reaction force, with instructions to maintain a symmetrical loading between limbs. A 2 × 2 (work rate/speed × time) repeated measures ANOVA (α = 0.05) was conducted on key outcome variables. Peak knee extension moment asymmetry during stationary cycling significantly improved (p = 0.038, η2p = 0.610) following the acute intervention. Walking velocities for both preferred (p = 0.001, d = 0.583) and fast (p = 0.002, d = 0.613) walking speeds displayed improvements from pre- to post-testing. Significant improvements in the total score (p = 0.009, d = 0.492) and ADL subscale score (p = 0.041, d = 0.270) for the Knee Injury and Osteoarthritis Outcome Score were present following the acute intervention. Stationary cycling with visual feedback may be beneficial post-TKA; however, further investigation is merited.

Interaction of SPI pellets with plasma on JET and associated disruptions

The presented data refer to the Shattered Pellet Injector (SPI) experiments carried out at JET in 2019–2020. This paper is a full journal version of the data originally presented as posters at TMPDM_2020 and EPS_2021. This paper presents various aspects of the interaction of pellets with plasma and associated disruptions. The experiment was performed with I p = (1.1–3.1) MA plasmas and mainly with Ne + D2 pellet composition, but also with Ar pellets. The Current Quench (CQ) time, τ 80−20, is the key characteristic of mitigation effectiveness. A pellet with a high content of Ne or Ar can reduce the CQ duration below the upper required JET threshold. Plasmas with high (thermal + internal poloidal magnetic) pre-disruptive plasma energy require a high content of Ne pellets to obtain a short CQ duration. Pellets with a small amount of Ne (and accordingly large amount of D), instead of causing a mitigated CQ, create the conditions for a ‘cold’ Vertical Displacement Events (VDE). The SPI was applied to plasma with different status: mainly to normal (‘healthy’) plasma, i.e. not prone to disruption, post-disruptive and VDE plasma. This study shows that SPI effectiveness in terms of CQ duration and, accordingly, EM loads does not depend on the state of the plasma, whether it is ‘healthy’ or post-disruptive plasma. SPI has been shown to reduce the axisymmetric vertical vessel reaction forces by about (30–40) % compared to unmitigated disruptions. On JET, the VDE, whether ‘hot’ or ‘cold’, always creates the conditions for a toroidal asymmetry in the plasma, so the VDE on the JET is referred to as Asymmetric VDE (AVDE). The interrupting of VDE and prevention of AVDE with SPI has been demonstrated. Thus, the effectiveness of disruption mitigation using SPI has been confirmed.

Failure Analysis for Overall Overturning of Concrete Single-Column Pier Bridges Induced by Temperature and Overloaded Vehicles.

Several overloaded-induced overturning incidents of girder bridges with single-column piers have occurred in recent years, resulting in significant casualties and economic losses. Temperature, in addition to overloading, may also play a role in exacerbating bridge overturning. To investigate the association between temperature and bridge overturning, an explicit finite element model (EFEM) of a three-span concrete curved continuous bridge considering nonlinearities was developed to simulate overall collapse. The effects of uniform and gradient temperatures on the overall overturning stability of curved and straight bridges were evaluated based on the EFEMs. Furthermore, the temperature-bridge coupling model and temperature-vehicle-bridge coupling model were utilized to examine how gradient temperature influences bridge overturning. The results show that the overall overturning collapse of a bridge follows four stages: stabilization, transition, risk and overturning. Variations in uniform temperature from -30 °C to 60 °C had a negligible effect on the ultimate vehicle weight for bridge overturning, with a variation of less than 1%. As the gradient temperature ranged from -30 °C to 60 °C, curved bridges show less than a 2% variation in ultimate vehicle weights, compared to a range of -6.1% to 11.7% for straight bridges. The torsion caused by positive gradient temperature in curved bridges can exacerbate bridge overturning, while negative gradient temperature in straight bridges can lead the girder to 'upward warping', facilitating girder separation from bearings. Monitoring the girder rotation angle and vertical reaction force of bearings can serve as important indicators for comparing the stability of bridges.

Static and impact performance of engineered cementitious composites with hybrid graphite nano platelets modified PVA and shape memory alloy fibres

Polyvinyl alcohol (PVA) fibre has been widely adopted to produce engineered cementitious composites (ECC), the overall performance of which is highly dependent on the fibre surface characteristics. The traditional approach to improve PVA fibre bridging ability is to tailor the surrounding matrix properties. However, this common practice need to do a lot of laborious experimental works, and thus it has limited efficiency and practicality. Therefore, special surface treatments on PVA fibres are required to create synergistic interactions between fibre and surrounding matrix to retain excellent tensile ductility and better mechanical performance. This paper proposes a novel treatment method for PVA fibres using nano graphite platelets to modify the PVA fibre surface and improve the mechanical properties of PVA fibre reinforced ECC. To evaluate the effectiveness of such treatment, a systematic experimental study was performed. Firstly, static contact angle measurements, scanning electron microscopy and atomic force microscopy were employed to monitor the wettability and physical changes on the fibre surface. Then, the static and dynamic mechanical properties as well as microstructural characteristics of ECC with hybrid modified PVA fibres (2 vol%) and shape memory alloy (SMA) fibres (0.25 vol%, 0.50 vol% and 1 vol%) were examined. The results indicate that the graphite nanoplatelets treated PVA fibres (GPVA) exhibit high hydrophobicity and surface roughness providing steady-state crack propagation, which is a necessary condition to ensure multiple cracking and improving the higher fibre bridging complementary energy. This is evidenced by significantly densified the transition zone between the graphite treated PVA fibres and the matrix, and improved the flexural tensile strength and the toughness. The calculated surface roughness of 28.86 μm and lots of peaks and valleys on the 3D topographical micrographs of the cracking faces confirmed that 1 SMA-2 GPVA specimen efficiently participated in transferring stress through the composite, leading to a greater vertical impact reaction force. Finally, the structure-property relation for flexural versus fracture behaviour and the effectiveness of SMA fibres on the crack-healing feature of the composites were studied by using digitized fractal analysis and through the heat treatment. The disseminated fracture energy (Ws/Gf) value reached 130 and the crack sizes the crack size decreased by 34 %, which were much better than that of the reference composites. The nano treatment of PVA fibres in ECC provides an innovative and sustainable solution for engineering structures with requirement of high tensile ductility and high impact resistance, e.g., military infrastructure and industrial floors.

About the Use of Gearless Electric Motors in the Construction of an Exoskeleton Walking on an Uneven Surface

The regular walking (up or down) on a ladder (or an inclined plane) of a human operator with an exoskeleton of the lower extremities, carrying an additional load, is considered. It is assumed that the exoskeleton is equipped with high— torque electric motors without gearboxes — in the knee and, perhaps, in other joints. The modes of flat, single-support quasi-comfortable walking are considered, in the implementation of which both electric motors and a human operator with experience working with this mechanism participate. The nominal pattern of movement associated, in particular, with the circumvention of obstacles (steps) with a portable foot and placing it in the support position at the next step is set and supported by a person. The task of the algorithm controlling electric motors is to partially reduce the load that falls on the operator. From the point of view of minimizing human energy consumption, the supporting leg and especially its knee joint are the most important. In the knee joint of the supporting leg, an algorithm for controlling the corresponding electric motor is proposed, based on measuring the vertical reaction force of the support in combination, perhaps, with the angle in the knee and angular velocity. Feedback is constructed, the "successful" values of the coefficients of which can be predicted using a kind of least squares method along the nominal mode. The task of this feedback is actually the distribution of the load that falls to the share of the operator and the system of electric motors. It is shown by using numerical research methods to what benefits in terms of energy consumption in one regular step this can, in principle, lead. This principle of feedback construction extends further to the hip and ankle moments of the supporting leg. It is assumed that the portable leg is controlled everywhere only by the human operator’s own efforts, the absence of gearboxes allows this to be done without much friction loss, which in turn affects the smallness of energy costs and for the operator.

Modeling and Validation of a Passenger Car Tire Using Finite Element Analysis

This paper focuses on the modeling and analysis of a four-groove passenger car tire, size 235/55R19, using finite element analysis. The Mooney–Rivlin material model is employed to define the hyperelastic behavior of the tire rubber compounds for all solid elements. The tire rim is modeled as a rigid body using aluminum alloy material, and the beads are modeled as beam elements using steel material. The tire model is validated in both static and dynamic domains through several simulations and is compared to published measured data. The tire is validated using footprint and vertical stiffness tests in the static domain. In the static footprint test, a steady-state vertical load is applied, and the tire–road contact area is computed. In the vertical stiffness test, a ramp vertical load is applied, and the tire’s vertical displacement is measured to calculate the tire’s vertical stiffness. In the dynamic domain, the tire is validated using drum-cleat and cornering tests. In the drum-cleat test, a drum with a 2.5 m diameter and a cleat with a 15 mm radius is used to excite the tire structure and obtain the frequency of the vertical and longitudinal first modes of vibration, that is, by applying the fast Fourier transformation (FFT) of the vertical and longitudinal reaction forces at the tire center. In addition to this test, the tire model is pre-steered on a flat surface with a two-degree slip angle and subjected to a steady state linear speed of 10 km/h to predict the cornering force and compute the cornering stiffness. In addition, the effect of tire longitudinal speed on the rolling resistance coefficient is then predicted at zero slip angle using the ISO 28580 rolling resistance test. The findings of this research work provide insights into passenger car tire–road interaction analysis and will be further used to perform tire rubber compound material model sensitivity analysis.

Comparing three generic musculoskeletal models to estimate the tibiofemoral reaction forces during gait and sit-to-stand tasks

The choice of musculoskeletal (MSK) model is crucial for performing MSK estimations to evaluate muscle demands and joint forces. This study compared two previously published generic MSK models and a modified model to estimate tibiofemoral reaction forces (TFRF) during gait, sit-to-stand, and stand-to-sit. The estimated tibiofemoral reaction forces were compared with an in vivo dataset from six patients using an instrumented knee prosthesis. A correlation and root mean square error (RMSE) in the time-series analysis and relative peak error (RPE) were evaluated. The results showed that the three MSK models were similar in estimating the vertical forces, with a large correlation, and RPE was found around 20 % during gait. The RMSE and the RPE indicated that the modified model had lower total and lateral compartment forces errors for sit-to-stand and stand-to-sit, showing the best performance. The shear forces for all tasks and models showed significant errors. Future MSK studies should consider these findings when researching functional tasks. The modified model was found to be more effective in estimating the vertical tibiofemoral joint reaction forces in tasks that impose greater demands on muscle forces and require high knee and hip flexion.

Differences in the Rotation Axis Between Professional and Experienced Amateur Ballet Dancers During pirouette en dehour in Classical Ballet With Wearing Pointe Shoes: A Pilot Study.

Introduction: En pointe, in which weight is placed on the tiptoes, is a fundamental practice for female ballet dancers with pointe shoes. The center of mass (COM) is maintained over the base of support and the relative position of COM to the center of pressure (COP) is especially important when conducting a pirouette in ballet. A pirouette is a fundamental turn in classical ballet with flat shoes and pointe shoes. The investigation of the turn with pointe shoes would be favorable for understanding the movement with limited base of support. Herein, we aimed to determine the differences in the ability to perform pirouettes with pointe shoes between professional and amateur ballet dancers. Methods: This study included 8 professional and 9 amateur ballet dancers. The dancers performed a single pirouette, and the movement was captured and analyzed in 3 phases: turning with double-leg support (TDS), turning with single-leg support in pre-swing (TSSp), and turning with single-leg support in mid-swing (TSSm). The analysis focused on the inclination between the vertical angle and the COP-COM line, the vertical maximum reaction force, and the jump-up time in each phase. Results: The results showed no significant differences between the TDS and TSSp. However, professional ballet dancers exhibited significantly lesser posterior inclinations (professional; 2.05° ± 0.90°, amateur; 3.88° ± 1.67°) and jump-up time (professional; 0%, amateur; 1.4% ± 1.3%) than amateur dancers during TSSm. Conclusion: Overall, the findings suggest that professional dancers exhibit superior control skills regarding the COP-COM line than amateur dancers during TSSm. These results may be attributed to the fact that professional dancers can maintain the COM as close to the upright as on the COP without jumping during TSSm. This enables professional dancers to conduct the movements esthetically and continue on to the other movements in the dance phase.

Simulation of low-energy impacts on the human hand for prediction of peak reaction forces and bone fracture

Hands of workers in extractive and heavy-duty industries are susceptible to suffering injuries of varying severity. Improved safety procedures and new technologies for production and maintenance tasks have contributed to reducing the severity of injuries. However, manual tasks with high-risk factors can still lead to hand injuries. Hand bone fractures and dislocations can be caused by relatively small objects impacting a region of the hand at velocities in the range of 1.3 to 1.6 m per second. This impact can produce significant functional, physical, and psychological consequences in those affected and result in high costs derived from medical care. This study presents the results of a finite element simulation study conducted to reproduce impacts with energies in the range of 7 to 10 Joules of an object on the dorsal region of the hand. Simulation results are compared to previous experimental results obtained from controlled impact tests performed using cadaveric hand specimens. The vertical peak reaction force (PRF) as a function of the impact position was used as a primary outcome for comparisons. Simulation results for all impact positions were within the standard deviation measured experimentally, with differences in the PRF values in the range of −5.3% to 4.9%. Bone stress analyses at the position of impacts showed the locations where the maximum principal stress exceeded the bone strength, as well as the variability in the correspondence between the stress distribution predicted by the FE models and the fracture rate distribution observed experimentally.

Vertical Reaction Force And Protein Intake Influences On Muscle Soreness Following High-intensity Interval Training

Vertical Reaction Force And Protein Intake Influences On Muscle Soreness Following High-intensity Interval Training

Load capacity of penstock manifolds subjected to increasing settlements at the vertical supports

AbstractHydroelectric power plants usually have penstock manifolds near the powerhouse, including individual bifurcations to provide several turbines. These steel constructions have numerous vertical supports and are designed based on linear elastic behaviour, leading to very small allowable settlements at the supports.For a representative built manifold, with five bifurcations (six branch pipes), the elastic‐plastic load capacity was studied in detail, assuming dead load, internal pressure and increasing settlements at the supports. Different settlement patterns were studied. The development of plastic zones was analyzed, depending on the rate of settlement. Due to the high bending stiffness of the penstock manifold, the penstock detaches from the single supports due to the settlement, leading to a significant redistribution of the vertical reaction forces at the supports.The comprehensive calculations show adequate robustness of the penstock manifolds, even though in case of very high settlements at the supports. Due to the significant redistribution of the reaction forces at the supports, these vertical supports must have an increased bearing capacity, in comparison to the reaction forces due to dead load and internal pressure based on linear elastic analyses.

Finite element optimization of Pratt trusses using trial and error

Steel production is considered one of the most material and energy-consuming industries, and using less energy is considered vital to promote environmental sustainability. Steel is used as the main building material in the construction of factories, hangars, and workshops in the form of trusses. A truss system is a set of structural elements connected at pin joints, with different types, shapes, and weights. Optimizing truss systems for max strength and minimum weight is a sustainable approach to reducing steel production and promoting environmental sustainability. In this paper 27 Pratt trusses were optimized by trial and error using finite element analysis (FEM) to predict the optimum topology for various cross-sections. Correlations between the span length, cross-sectional area, and height of the trusses were developed to conclude the ideal topology of the Pratt truss that gives minimum compression and tension stresses. The effect of topology on the reaction forces was also addressed. Results showed that the optimum horizontal span length between joints ranged between 3.4 and 3.6 m for minimal compressive stresses and minimum horizontal and vertical reaction forces at supports, and from 3.0 to 3.6 m for minimal tensile stresses.

Single body sensor for calibration of Spring-Mass-Damper parameters in biodynamic pedestrian modelling

For structural design and vibration monitoring purposes, several simplified equivalent-force models or more complex computational strategies are available to describe Human-Structure Interaction (HSI) phenomena on pedestrian systems, and in particular the vertical reaction forces induced by walking occupants. Among others, various Spring-Mass-Damper (SMD), Single Degree of Freedom (SDOF) biodynamic models of literature can be used to mechanically describe a single pedestrian in the form of equivalent body mass m, spring stiffness k and viscous damping coefficient c. Basically, existing SMD formulations are characterized by specific theoretical assumptions and (often complex) experimental methods for the calibration of m, k, c. Usually, SMD parameters can be optimally quantified when multiple sensors (on pedestrian’s body and on the structure) are used to capture motion features and the corresponding reaction force. In this paper, body accelerations of a pedestrian are tracked by means of a single Centre of Mass (CoM) sensor and are elaborated to derive basic input parameters for an alternative, newly optimized SMD model. Experimental registrations from a total of 30 random walks and more than 300 gaits (on rigid floor) are taken into account, and fitting expressions for m, k, c are proposed. The present SMD formulation (SMD-0) is validated towards a selection of literature proposals (SMD-1 to SMD-4), based on parametric numerical dynamic analyses (100 in total), which are carried out by taking into account various pacing frequencies (fp = 1.5–2 Hz the explored range) and four different pedestrian structures / floors (F#1 to F#4). The comparison of classical performance indicators for human-induced structural vibrations proves the efficiency and potential of current SMD-0 approach, and suggests further investigations in support of optimized protocols.

Research of features of oscillating process’ behavior in the nonlinear system of individual traction drive of an electrobus

BACKGROUND: When a vehicle is in motion, self-oscillations which properties are dependent on slip rate in a contact patch may occur in the area of tire interaction with ground surface. Oscillations frequency will vary in dependence with value of wheel slip relative to ground surface. Soft self-oscillations are excited by variable set of initial conditions at full slip in traction and driven wheel rolling modes as well as in mixed braking mode with partial slip. Hard mode of self-oscillations occurs at full wheel slip in braking mode. These processes have a negative impact on the processes in electric drive and mechanical drivetrain reducing their efficiency and may cause damage of components. Oscillations in the system are excited by interaction forces of an elastic tire with ground surface featuring vertical oscillations due to elastic behavior of its interaction with road unevenness. AIMS: Research of features of oscillating process behavior in the nonlinear system of individual traction drive of an electrobus. METHODS: Simulation of self-oscillation excitation processes in the area of contact interaction of a wheel and road was carried out in the MATLAB/Simulink software package. RESULTS: The article features the results of simulation and experimental studies of self-oscillation excitation processes of the KAMAZ 6282 electrobus moving on asphalt-concrete surface. It was found that vertical wheel displacement when moving through unevenness lead to oscillating behavior of vertical reaction forces in contact patches and, as a consequence, to oscillating behavior of longitudinal reaction forces, torque and rotation velocity of the shaft of the traction electric motor of the individual drive. It was defined that tire oscillation frequency is 67 Hz that coincides with electric motor shaft rotation oscillation frequency and this value is the same for both experiment and simulation. CONCLUSIONS: Practical value of the study lies in ability of using the study results at development of self-oscillation processes exclusion algorithms as a part of vehicle control system.

Review of Structural Strength in the Event of a One-Leg Punch through for a Wind Turbine Installation Vessel

As the demand for eco-friendly energy increases, the offshore wind power generation sector is showing rapid growth. As offshore wind turbines become larger, the need for specialized installation vessels is becoming a more crucial issue. Wind turbine installation vessels (WTIV) require a necessary pre-loading process where the legs and spudcans are penetrated into the seabed to secure stability during installation. Due to these operational characteristics, the installation work can be completed safely when safe pre-loading is finished. Analyzing previous structural collapse accidents investigated by HSE, 53% of them were punch-through problems related to the seabed, which occurred with a high frequency. Therefore, these lead to major accidents, which is a very high-risk problem. In this study, we investigated and analyzed the punch-through accident cases, and a WTIV model with six legs was applied to numerically examine the maximum vertical reaction force variation when punch through occurs for each leg. The maximum vertical reaction force takes place in leg number three when a punch through occurs in leg number five and maximum stress exceeds the allowable criteria in both hull and legs. This requires proper structural reinforcement such as an increase in the thickness and change in the high-yield stress. The key results of this investigation can be used to determine the basic specifications of wind turbine installation vessels, and the reaction force distribution pattern can be used as fundamental data for leg and hull structural design.

A simple model of human walking

Aim. We investigate Alexander’s inverted pendulum model, the simplest mathematical model of human walking. Although it successfully explains some kinematic features of human walking, such as the velocity of the body's centre of mass, it does not account for others, like the vertical reaction force and the maximum walking speed. This paper aims to minimally extend Alexander’s model in such a way as to make it a viable and quantitative model of human walking for clinical biomechanics.Material and methods. In order to compare the predictions of Alexander’s model with experimental data on walking, we incorporate in it a robust phenomenological relation between stride frequency and stride length derived in the literature, and we introduce a step-angle dependent muscle force along the pendulum. We then analytically solve the pendulum's motion equation and find the corresponding analytical expression for the average walking speed.Results. The values of the average walking speed for different heights predicted by our model are in excellent agreement with the ones obtained in treadmill experiments. Moreover, it successfully predicts the observed walking-running transition speed, which occurs when the stride length equals the height of an individual. Finally, our extended model satisfactorily reproduces the experimentally observed ground reaction forces in the midstance and terminal stance phases. Consequently, the predicted value of the (height-dependent) maximum walking speed is in reasonable agreement with the one obtained in more sophisticated models of human walking.Conclusions. Augmented with our minimal extensions, Alexander’s model becomes an effective and realistic model of human walking applicable in clinical investigations of the human gate.

Design Requirements for Personal Mobility Vehicle (PMV) with Inward Tilt Mechanism to Minimize Steering Disturbances Caused by Uneven Road Surface

The Personal Mobility Vehicle (PMV), which has an inward-tilting angle, turns with lateral force due to a large camber angle, so it is necessary to consider the lateral movement of the tire vertical load axis during turning. Although the steering torque mechanisms are very different from those of automobiles, there are not many studies of the steering torque mechanisms of PMVs. In this paper, based on the effects of the force of six components acting on the tires, a method for setting the steering axis specifications is derived, including the geometrical minimization of steering moment disturbance due to the vertical load reaction force during turning. Automobile tires have a significant ground camber angle when traveling on rutted roads, but they do not have it on slanted roads because the vehicle body tilts along the road surface. On the other hand, in PMVs, the vehicle body always keeps upright when traveling both on slanted roads and on rutted roads. Therefore, the tires have ground camber angles on both types of road surface. We study the straight running ability under such road surface disturbances based on the geometrical minimization of steering moment disturbance due to the vertical load reaction force during turning. This straight running ability can be a remarkable strong point of PMVs with an inward tilt mechanism. In this study, it was proved that the steering axis parameters can be derived uniquely by taking into consideration the requirement to zero the moment (disturbance) around the steering axis due to the reaction force against the vertical load at all internal tilt angles.

Learning Ergonomic Control in Human–Robot Symbiotic Walking

This article presents an imitation learning strategy for extracting ergonomically safe control policies in physical human–robot interaction scenarios. The presented approach seeks to proactively reduce the risk of injuries and musculoskeletal disorders by anticipating the ergonomic effects of a robot's actions on a human partner, e.g., how the ankle angle of a prosthesis affects future knee torques of the user. To this end, we extend ensemble Bayesian interaction primitives to enable the prediction of latent biomechanical variables. This methodology yields a reactive control strategy, which we evaluate in an assisted walking task with a robotic lower limb prosthesis. Building upon the learned interaction primitives, we also present a model-predictive control (MPC) strategy that actively steers the human–robot interaction toward ergonomic and safe movement regimes. We compare the introduced control strategies and highlight the framework's ability to generate ergonomic, biomechanically safe assistive prosthetic control. A rich analysis of constrained MPC shows a 20× reduction in the effects of large perturbations on prosthetic control system. We empirically demonstrate a 16% reduction in vertical knee reaction forces in real-world jumping experiments utilizing our control methodology and examine other optimal control strategies in simulated walking experiments.

Calculation model of concrete-filled steel tube arch bridges based on the “arch effect”

In view of the limitations of the current code based on the equivalent beam-column method with the “rod mode” instead of the “arch mode” for the calculation of concrete-filled steel tube arch bridges, this paper takes the real bearing mechanism of the arch as the starting point and analyzes the different bearing mechanisms of the arch and eccentric pressurized column. The concrete-filled steel tube arch model test was carried out to analyze the deformation state and damage mode, and the geometric non-linear bending moment of the measured arch was compared with the bending moment value calculated by the eccentricity increase coefficient of the “rod mode.” The results showed that the transfer of internal force is from the axial force to the arch axis, causing the vertical reaction force and horizontal thrust. However, the eccentric compression column only produced the vertical force at the bottom and combines with the lateral deformation indirectly generated by the eccentric distance. In addition, the deformation stage of the arch is basically the same as that of the eccentric compression column. The final failure mode of the arch is 4-hinge damage, and the final failure mode of the eccentric compression column is single-hinge damage. The preliminary geometric non-linear bending moment value obtained by the two modes accords well. Therefore, the main factors for the difference in the bearing mechanism between the two modes are different force structures, force transmission routes, and sources of deformation. Due to the difference in the bearing mechanism, the final failure mode is different, and the deformation ability of the arch is weakened by using the “rod mode” instead of the “arch mode.” The geometric non-linear bending moment of the control section calculated by the eccentricity increase coefficient is conservative, but the influence of the geometric non-linearity of other sections is not considered enough.

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.