Walking Cycle Research Articles

Automatic Assist Level Adjustment Function of a Gait Exercise Rehabilitation Robot with Functional Electrical Stimulation for Spinal Cord Injury: Insights from Clinical Trials.

This study aimed to identify whether the combined use of functional electrical stimulation (FES) reduces the motor torque of a gait exercise rehabilitation robot in spinal cord injury (SCI) and to verify the effectiveness of the developed automatic assist level adjustment in people with paraplegia. Acute and chronic SCI patients (1 case each) performed 10 min of gait exercises with and without FES using a rehabilitation robot. Reinforcement learning was used to adjust the assist level automatically. The maximum torque values and assist levels for each of the ten walking cycles when walking became steady were averaged and compared with and without FES. The motor's output torque and the assist level were measured as outcomes. The assist level adjustment allowed both the motor torque and assist level to decrease gradually to a steady state. The motor torque and the assist levels were significantly lower with the FES than without the FES under steady conditions in both cases. No adverse events were reported. The combined use of FES attenuated the motor torque of a gait exercise rehabilitation robot for SCI. Automatic assistive level adjustment is also useful for spinal cord injuries.

Simulation Analysis of a Passive Biped Robot

To more accurately understand the fundamental characteristics of the motion of a passive biped robot and to enhance the guidance provided by model research for the design of practical prototypes, we analyze the characteristics of this passive model and establish the corresponding dynamic model using the Lagrange method. Based on the characteristic that the stable walking cycle gait of the robot manifests as a limit cycle in the phase plane, we study the passive biped model with knee joints through co-simulation using Adams and Matlab. The process of simulating steady-state walking of the ideal model is demonstrated in detail, including the initial conditions required for the robot to achieve periodic steady-state walking, the motion characteristics, and the distribution, variation, and interconversion of kinetic and potential energy during the motion.

The role of limb alignment on natural tibiofemoral kinematics and kinetics.

This study aimed to analyze kinematics and kinetics of the tibiofemoral joint in healthy subjects with valgus, neutral, and varus limb alignment throughout multiple gait activities using dynamic videofluoroscopy. Five subjects with valgus, 12 with neutral, and ten with varus limb alignment were assessed during multiple complete cycles of level walking, downhill walking, and stair descent using a combination of dynamic videofluoroscopy, ground reaction force plates, and optical motion capture. Following 2D/3D registration, tibiofemoral kinematics and kinetics were compared between the three limb alignment groups. No significant differences for the rotational or translational patterns between the different limb alignment groups were found for level walking, downhill walking, or stair descent. Neutral and varus aligned subjects showed a mean centre of rotation located on the medial condyle for the loaded stance phase of all three gait activities. Valgus alignment, however, resulted in a centrally located centre of rotation for level and downhill walking, but a more medial centre of rotation during stair descent. Knee adduction/abduction moments were significantly influenced by limb alignment, with an increasing knee adduction moment from valgus through neutral to varus. Limb alignment was not reflected in the condylar kinematics, but did significantly affect the knee adduction moment. Variations in frontal plane limb alignment seem not to be a main modulator of condylar kinematics. The presented data provide insights into the influence of anatomical parameters on tibiofemoral kinematics and kinetics towards enhancing clinical decision-making and surgical restoration of natural knee joint motion and loading.

Open-source Software as an Alternative Means of Biomechanical Assessment

In an attempt to gain more and more resources for dynamic assessment of movement, and especially more accessible ones, we tried to utilize open-source software like kinovea for data extraction and Python for automatization. By using these we can show the ease of creating patterns of investigation, after which further data is simply collected and manipulated on the system created. The best part about having these resources as means for biomechanical assessment is that they are cost free. We broke down the walking cycle into four main stages and extracted the data from those, after which we made it more comprehensible even for the trained naked eye. Video footage was taken from 10 healthy subjects. The hypothesis of this work was thus: If we modify the walking speed we can check out from low intensity to high intensity, we won’t see bigger amounts of deviation at ankle level. After analyzing the data collected, we couldn’t say that by increasing the walking we also increase the amount of deviation in the ankle Keywords: Assessment; Kinovea; open-source; Biomechanics; Python

The interplay between social environment and opportunities for physical activity within the built environment: a scoping review

BackgroundThe association between social and built environments plays a crucial role in influencing physical activity levels. However, a thorough understanding of their combined impact remains unclear. This scoping review seeks to clarify the interplay between social environments and opportunities for physical activity within different built environments, with a particular focus on the implications of socioeconomic status and urban planning on physical activity participation.MethodsWe conducted a systematic literature search across several databases to identify studies exploring the associations between social factors, built environment characteristics, and physical activity levels. The inclusion criteria were studies published in English between 2000 and 2022, encompassing urban, suburban, and rural contexts. Thematic analysis was employed to categorise studies based on the specific aspects of the built environment they investigated (walking infrastructure, cycling infrastructure, parks and open spaces, and sports facilities) and the social determinants they examined.ResultsA total of 72 studies were included in the review, illustrating a multifaceted relationship between access to physical activity opportunities and social determinants such as socioeconomic status, community engagement, and urban design. The findings highlight the significant role of socioeconomic factors and the quality of PA infrastructure in promoting or hindering PA across communities. Effective urban planning was identified as crucial in providing expanded physical activity opportunities, notably through more pedestrian-friendly environments, comprehensive cycling infrastructure, and accessible green spaces and sports facilities.ConclusionsThis review emphasises the significant impact of socioeconomic status and urban planning on access to physical activity opportunities. This underscores the necessity for urban planning policies to adopt an inclusive approach, considering the varied needs of different population groups to ensure equitable access to physical activity resources. Such strategies are crucial for public health initiatives aimed at enhancing physical activity levels across diverse community sectors, offering a potential avenue to alleviate health disparities associated with inactivity.

Behavior of the Coefficient of Friction of Textured Tibial Inserts of Total Knee Replacements under the Conditions Prescribed by ISO 14243-3:2014

This work investigates the effect of surface texturing on the coefficient of friction (COF) of tibial inserts (TIs), of total knee replacements (TKRs), using a servomechanical knee simulator operating under the conditions prescribed by ISO 14243-3:2014, which requires strict control of flexion/extension (FE), anterior/posterior displacement (AP), inward/outward rotation (IOR) movements, and load variation. Tests were carried out lubricating with fetal bovine serum solution with a protein concentration of 20 g/L at 37 ± 2 °C. TIs were manufactured by fused deposition modeling (FDM) using polylactic acid (PLA) because of the advantages associated with rapid prototyping and customization. The acquired COF data were analyzed using statistical parametric mapping (SPM) to determine how the surface of the TIs affects the COF, identifying ranges where significant differences occurred. Textured surfaces led to significant reductions in COF during the swing phase of the walking cycle.

Interactive Design of Stylized Walking Gaits for Robotic Characters

Procedural animation has seen widespread use in the design of expressive walking gaits for virtual characters. While similar tools could breathe life into robotic characters, existing techniques are largely unaware of the kinematic and dynamic constraints imposed by physical robots. In this paper, we propose a system for the artist-directed authoring of stylized bipedal walking gaits, tailored for execution on robotic characters. The artist interfaces with an interactive editing tool that generates the desired character motion in realtime, either on the physical or simulated robot, using a model-based control stack. Each walking style is encoded as a set of sample parameters which are translated into whole-body reference trajectories using the proposed procedural animation technique. In order to generalize the stylized gait over a continuous range of input velocities, we employ a phase-space blending strategy that interpolates a set of example walk cycles authored by the animator while preserving contact constraints. To demonstrate the utility of our approach, we animate gaits for a custom, free-walking robotic character, and show, with two additional in-simulation examples, how our procedural animation technique generalizes to bipeds with different degrees of freedom, proportions, and mass distributions.

Investigating spatiotemporal and kinematic gait parameters in individuals with Parkinson's disease with a history of freezing of gait and exploring the effects of dopaminergic therapy on freezing of gait subtypes.

Freezing of Gait (FOG) is a prevalent and debilitating symptom in idiopathic Parkinson's disease (PD). This study evaluated spatiotemporal and kinematic gait parameters in individuals with PD with a history of FOG and explored the effects of dopaminergic therapy on FOG subtypes. One hundred and nine individuals with PD underwent clinical assessments and quantitative biomechanical measures during walking cycles before and after dopaminergic therapy. Individuals with FOG were classified into levodopa-responsive and levodopa-unresponsive groups. Individuals with FOG displayed longer disease duration and higher Unified Parkinson's Disease Rating Scale (UPDRS) II, III, IV scores, and total scores and levodopa equivalent dose, than those without FOG (all p < 0.0001). Following propensity score matching of 15 pairs based on UPDRS total score and disease duration during the off-medication state, the analysis comparing the FOG and non-FOG groups revealed no significant differences in spatiotemporal and kinematic parameters. In 39 cases of FOG, dopaminergic therapy improved gait performance in individuals with PD, enhancing spatiotemporal parameters (speed, stride length, step length, step variability) and kinematic parameters (shoulder and elbow flexion/extension range of motion (ROM), pelvic rotation, and hip abduction/adduction ROM) regardless of FOG responsiveness to dopaminergic therapy. A significant difference in trunk sway ROM (p = 0.029) remained before and after dopaminergic therapy, even after adjusting for disease duration and clinical severity. Dopaminergic therapy had varying effects on PD with FOG, improving several spatiotemporal and kinematic gait parameters but being less effective in levodopa-unresponsive cases. Quantitative biomechanical measures offer detailed insights into gait performance, aiding personalized fall risk assessment and guiding individualized rehabilitation programs.

A Finite Element Analysis Study of Influence of Femoral Stem Material in Stress Shielding in a Model of Uncemented Total Hip Arthroplasty: Ti-6Al-4V versus Carbon Fibre-Reinforced PEEK Composite

Total hip arthroplasty is one of the most common and successful orthopaedic operations. Occasionally, periprosthetic osteolysis associated with stress shielding occurs, resulting in a reduction of bone density where the femur is not properly loaded and the formation of denser bone where stresses are confined. To enhance proximal load transfer and reduce stress shielding, approaches, including decreasing the stiffness of femoral stems, such as carbon fibre-reinforced polymer composites (CFRPCs), have been explored through novel modular prostheses. The purpose of the present study was to analyse, by the finite element analysis (FEA) method, the effect that the variation of material for the distal part of the femoral stem has on stress transmission between a modulable prosthesis and the adjacent bone. Methods: Through three-dimensional modelling and the use of commercially available FEA software Ansys R2023, the mechanical behaviour of the distal part of the femoral stem made of CFRPC or Ti-6Al-4V was obtained. A load was applied to the head of the femoral stem that simulates a complete walking cycle. Results: The results showed that the use of a material with mechanical characteristics close to the bone, like CFRPC, allowed for optimisation of the transmitted loads, promoting a better distribution of stress from the proximal to the distal part of the femur. This observation was also found in some clinical studies in literature, which reported not only an improved load transfer with the use of CFRPC but also a higher cell attachment than Ti-6Al-4V. Conclusions: The use of a material that has mechanical properties that are close to bone promotes load transfer from the proximal to the distal area. In particular, the use of CFRPC allows the material to be designed based on the patient’s actual bone characteristics. This provides a customised design with a lower risk of prosthesis loss due to stress shielding.

Fatigue Analysis of Prosthetic Osseointegration with a Novel Protection System

Recent advancements in osseointegration technology offer a promising alternative to traditional prosthetic limbs, leading to improved comfort and functionality for amputees. However, the primary concern lies in the risk of catastrophic failure and falling due to fractures within the osseointegration system. To address this challenge, a protective system has been designed. The new design includes an internally rod part with a notch at the bottom to ensure failure at that point, made of ductile cast iron. A cover made of Ti6Al4V alloy is placed to ensure fracture isolation within the protection nail during sudden loading, preventing unexpected falls. After conducting tensile tests for the mentioned alloys and materials, and then relying on the ground reaction force in the numerical analysis using SolidWorks software, Finite Element Analysis (FEA) simulations confirmed the effectiveness of this design, with the expected fracture point occurring in the protection nail after exceeding 54973 walking cycles, surpassing the expected maintenance lifespan of the prosthetic limb. This design represents a significant step forward in enhancing the safety and reliability of integrated prosthetic limbs, ultimately leading to improved mobility and peace of mind for amputees.Recent advancements in osseointegration technology offer a promising alternative to traditional prosthetic limbs, leading to improved comfort and functionality for amputees. However, the primary concern lies in the risk of catastrophic failure and falling due to fractures within the osseointegration system. To address this challenge, a protective system has been designed. The new design includes an internally rod part with a notch at the bottom to ensure failure at that point, made of ductile cast iron. A cover made of Ti6Al4V alloy is placed to ensure fracture isolation within the protection nail during sudden loading, preventing unexpected falls. After conducting tensile tests for the mentioned alloys and materials, and then relying on the ground reaction force in the numerical analysis using SolidWorks software, Finite Element Analysis (FEA) simulations confirmed the effectiveness of this design, with the expected fracture point occurring in the protection nail after exceeding 54973 walking cycles, surpassing the expected maintenance lifespan of the prosthetic limb. This design represents a significant step forward in enhancing the safety and reliability of integrated prosthetic limbs, ultimately leading to improved mobility and peace of mind for amputees.

Examination time-distance characteristics of gait and pelvic kinematics in individuals with Diabetic polyneuropathy: a case-control study

ABSTRACT Background Diabetic Peripheral Neuropathy (DPN) disrupts body and movement biomechanics, increases mechanical stress during walking, and predisposes individuals to injuries owing to the repetitive effects of these stresses. Aims This study aimed to assess and compare the impact of neuropathy on gait and pelvic kinematics in individuals with DPN. Methods This case-control study included two groups: 23 individuals diagnosed with DPN aged between 35–70 and 23 healthy individuals aged–35–70. The BTS-G, a wireless motion sensor, was used to assess the time-distance characteristics of walking in all participants. The system analyzed data pertaining to walking speed, cadence, percentages of stance and swing phases, durations of walking cycles, double-step lengths, pelvic tilt, obliquity, and rotation symmetries. Results There were no statistically significant differences between the groups in cadence, left and right stance phase percentages, or left and right swing phase percentages (p > 0.05). However, significant differences were observed between the groups in terms of speed, left and right walking cycle durations, and left and right double-step lengths (p < 0.05). Additionally, no statistically significant difference was found between the groups in pelvic tilt symmetry and left and right pelvic tilt range of motion values (p > 0.05). Nevertheless, significant differences were identified between the groups in pelvic obliquity symmetry, pelvic rotation symmetry, left and right pelvic obliquity range of motion, and left and right pelvic rotation range of motion values (p < 0.05). Conclusions The findings of this study suggest that individuals with DPN exhibit decreased walking speed, prolonged gait cycle duration, increased double step length, and reduced pelvic obliquity and rotation range of motion.

Design of an SMA-Based Actuator for Replicating Normal Gait Patterns in Pediatric Patients with Cerebral Palsy.

Cerebral Palsy refers to a group of incurable motor disorders affecting 0.22% of the global population. Symptoms are managed by physiotherapists, often using rehabilitation robotics. Exoskeletons, offering advantages over conventional therapies, are evolving to be more wearable and biomimetic, requiring new flexible actuators that mimic human tissue. The main objective behind this article is the design of a flexible exosuit based on shape-memory-alloy-based artificial muscles for pediatric patients that replicate the walking cycle pattern in the ankle joint. Thus, four shape-memory-alloy-based actuators were sewn to an exosuit at the desired actuation points and controlled by a two-level controller. The loop is closed through six inertial sensors that estimate the real angular position of both ankles. Different frequencies of actuation have been tested, along with the response of the actuators to different walking cycle patterns. These tests have been performed over long periods of time, comparing the reference created by a reference generator based on pediatric walking patterns and the response measured by the inertial sensors. The results provide important measurements concerning errors, working frequencies and cooling times, proving that this technology could be used in this and similar applications and highlighting its limitations.

Audience perceptions of Foley footsteps and 3D realism designed to convey walker characteristics

AbstractFoley artistry is an essential part of the audio post-production process for film, television, games, and animation. By extension, it is as crucial in emergent media such as virtual, mixed, and augmented reality. Footsteps are a core activity that a Foley artist must undertake and convey information about the characters and environment presented on-screen. This study sought to identify if characteristics of age, gender, weight, health, and confidence could be conveyed, using sounds created by a professional Foley artist, in three different 3D humanoid models, following a single walk cycle. An experiment was conducted with human participants (n=100) and found that Foley manipulations could convey all the intended characteristics with varying degrees of contextual success. It was shown that the abstract 3D models were capable of communicating characteristics of age, gender, and weight. A discussion of the literature and inspection of related audio features with the Foley clips suggest signal parameters of frequency, envelope, and novelty may be a subset of markers of those perceived characteristics. The findings are relevant to researchers and practitioners in linear and interactive media and demonstrate mechanisms by which Foley can contribute useful information and concepts about on-screen characters.

Ventricular arrhythmia burden during different physical activities in patients with arrhythmogenic right ventricular cardiomyopathy: preliminary analysis

Abstract Background Patients suffering from arrhythmogenic right ventricular cardiomyopathy (ARVC) should avoid intense endurance exercise to reduce the risk of adverse cardiac events and disease progression. While an active lifestyle would be preferable to a sedentary one, evidence for safe levels of physical activity in ARVC, however, is scarce. Purpose This study aimed to describe the ventricular arrhythmia burden experienced during exercise and immediate recovery - estimated as the prevalence of premature ventricular contractions (PVC) - of different exercise modalities and intensities on ARVC patients. Methods This preliminary analysis includes four (1F, 33±12 yrs, BMI 24±4 kg/m2) ARVC patients harboring a pathogenic plakophilin-2 variant and carrying an implantable cardioverter-defibrillator that performed different exercises while monitored via 12-lead ECG. The order of modalities was randomized and participants instructed to stop when surpassing perceived exertion of 15 on the Borg 6-20 scale. Resistance exercises included two-legged squats and single arm biceps curls (20 repetitions and 2 min duration). Endurance exercise included 5 min of treadmill walking and 3-min cycling bouts at heart rates (HR) of 80, 100 and 120 bpm, as well as cycling at 120 bpm with 2 additional min of active cool down. Blood lactate concentration was assessed after each cycling bout. Results No adverse cardiac event or early termination for medical reasons occurred. Figure 1 summarizes the relationship between HR, perceived exertion and PVC burden. During walking (HR 76 ± 8 bpm), PVC burden was 11 ± 6% (range 4 – 18%). Cycling at 82 ± 4 bpm induced a PVC burden of 7 ± 5% (range 3 – 14%), which increased to 13 ± 8% (range 3 – 21%) at 93 ± 2 bpm and increased further to 16 ± 16% (range 7 – 37%) at 105 ± 3 bpm. In all three intensities the PVC burden was higher in the first 3 min of recovery than during the activity itself. Adding a 2-min active cool down increased the PVC burden to 25 ± 16% (range 6 – 45%). 2-legged squats (HR 101 ± 15 bpm) had a PVC burden of 9 ± 12%, which increased to 19 ± 14% at recovery. One arm biceps curls (HR 75 ± 13 bpm) had a PVC burden of 4 ± 3% during the activity and 9 ± 5% during recovery. Perception of effort varied widely when cycling at 80 bpm (range 6 – 12) or 100 bpm (range 8 – 14), but less so at 120 bpm (range 13 – 15). Blood lactate concentration when cycling at 120 bpm ranged between 2.2 and 3.5 mmol/L, typically associated with exercise in the "heavy" intensity domain. Conclusions PVC burden was high and seemingly intensity-dependent during exercise and immediate recovery. The wide range of PVC burden for physiological or subjective markers of effort call for personalized recommendations on physical activity. Exercises with small muscle mass such as biceps curls seem to minimize the PVC burden, thus, training the different muscles separately could be an interesting avenue to maintain physical fitness in ARVC patients.

Biomechanical gait analysis in sheep: kinematic parameters.

Animals have been used as models to help to better understand biological and anatomical systems, and pathologies in both humans and non-human species, and sheep are often used as an in vivo experimental model for orthopedic research. Gait analysis has been shown to be an important tool in biomechanics research with clinical applications. The purpose of this study was to perform a kinematic analysis using a tridimensional (3D) reconstruction of the sheep hindlimb. Seven healthy sheep were evaluated for natural overground walking, and motion capture of the right hindlimb was collected with an optoelectronic system while the animals walked in a track. The analysis addressed gait spatiotemporal variables, hip, knee and ankle angle and intralimb joint angle coordination measures during the entire walking cycle. This study is the first that describes the spatiotemporal parameters from the hip, knee and ankle joints in a tridimensional way: flexion/extension; abduction/adduction and inter/external rotation. The results of this assessment can be used as an outcome indicator to guide treatment and the efficacy of different therapies for orthopedic and neurological conditions involving the locomotor system of the sheep animal model.

Females Maintain Fluid Balance across Consecutive Workdays in Heat When Fluids are Readily Accessible

Workers should aim to fully replace fluid losses during work in the heat to maintain work productivity and minimize risk of heat illnesses, however, fluid balance of females working during consecutive days in the heat is unknown. The purpose of this study was to test the hypothesis that females would maintain fluid balance during work across two consecutive workdays. Eight healthy females (age: 29±5, body mass: 75.3±20.1, body fat: 23±8%) completed two consecutive days (Day 1, Day 2) of heavy intensity work in a hot environment (35.9±1.2°C, 24±6% relative humidity). Work consisted of repeated 45/15 work/rest cycles of treadmill walking or cycling at 398±7 W of metabolic heat production and seated rest for 4 h. Every 20 min, participants were provided 237 mL of a sport drink to consume ad libitum. Urine flow rate (UFR) was measured before work. Urine specific gravity (USG) and nude body mass were measured before and after work. Fluid volume consumed and thirst (9-point Likert scale, 1=not thirsty at all, 9=very, very thirsty) were measured during work. Two-way repeated measures analysis of variance and paired samples t-tests were used to compare differences. Significance was set at p≤0.05. Percent body mass loss was not different between Day 1 (0.69±0.82%) and Day 2 (0.96±2.25%, p=0.935). Similarly, sweat rate was not different between Day 1 (0.57±0.12 L/h) and Day 2 (0.65±0.21 L/h, p=0.312). Participants consumed less fluid on Day 1 (64±21%, 25±10 mL/kg) compared to Day 2 (74±20%, p=0.026; 29±10 mL/kg, p=0.025). Participants consumed 68±19% and 77±20% (p=0.040) of fluid offered during work and 55±27% and 66±22% (p=0.173) of fluid offered during rest on Day 1 and Day 2, respectively. Resting thirst (Day 1: 2.1±1.1, Day 2: 1.6±0.5, p=0.096), change in thirst (Day 1: -0.5±0.9, Day 2: +0.3±1.3, p=0.111) and maximum thirst (Day 1: 3.6±1.1, Day 2: 3.6±1.4, p=1.000) were not different between days. USG was not different (p=0.839) across days before (Day 1: 1.009±0.010, Day 2: 1.009±0.010) or after (Day 1: 1.012±1.010, Day 2: 1.012±0.010) work, respectively. UFR was not different between days (Day 1: 2.2±1.4 mL/min, Day 2: 2.0±1.2 mL/min, p=0.836). Females completing heavy intensity work in heat maintained fluid balance across two consecutive days when fluids were readily accessible. Ad libitum fluid consumption may be suffcient to adequately replace fluid losses in females across consecutive days of work in heat. This project was funded by the National Institute for Occupational Safety and Health (1K01OH012016-01A1). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Urban Physical Environments Promoting Active Leisure Travel: An Empirical Study Using Crowdsourced GPS Tracks and Geographic Big Data from Multiple Sources

Specific environmental characteristics can encourage active leisure travel and increase physical activity. However, existing environment-travel studies tend to ignore the differences in environmental characteristics associated with route choice and travel distance, of which the latter could be more important for health benefits, since longer trips are associated with increased exercise. Additionally, the most recent studies focus on leisure walking and leisure cycling, and activities such as hiking, climbing, and running are examined less frequently. This study, therefore, compares the similarities and differences of the environmental factors associated with route selection and travel distance through non-parametric tests and Cox proportional hazard models. The results show that two intersecting sets of environmental elements relate to both the route chosen and the distance traveled. Land use diversity and varied topography are appealing for both leisure trips and trip length. In addition, the differences in environmental characteristics among specific leisure travels may be attributed to variations in physical activity requirements, preferences for landscape viewing, and/or sensitivity to crowding. Therefore, conclusions drawn without considering the different types of leisure travel could be skewed. Whether particular surroundings may effectively increase physical activity remains uncertain. A more holistic perspective could be beneficial when studying the connection between the environment, active travel, and health.

Porcine computational modeling to investigate developmental dysplasia of the hip.

While it is well-established that early detection and initiation of treatment of developmental dysplasia of the hip (DDH) is crucial to successful clinical outcomes, research on the mechanics of the hip joint during healthy and pathological hip development in infants is limited. Quantification of mechanical behavior in both the healthy and dysplastic developing joints may provide insight into the causes of DDHand facilitate innovation in treatment options. In this study, subject-specific three-dimensional finite element models of two pigs were developed: one healthy pig and one pig with induced dysplasia in the right hindlimb. The objectives of this study were: (1) to characterize mechanical behavior in the acetabular articular cartilage during a normal walking cycle by analyzing six metrics: contact pressure, contact area, strain energy density, von Mises stress, principal stress, and principal strain; and (2) to quantify the effect on joint mechanics of three anatomic abnormalities previously identified as related to DDH: variation in acetabular coverage, morphological changes in the femoral head, and changes in the articular cartilage. All metrics, except the contact area, were elevated in the dysplastic joint. Morphological changes in the femoral head were determined to be the most significant factors in elevating contact pressure in the articular cartilage, while the effects of acetabular coverage and changes in the articular cartilage were less significant. The quantification of the pathomechanics of DDH in this study can help identify key mechanical factors that restore normal hip development and can lead to mechanics-driven treatment options.

Controlling flat-foot limit cycle walkers with compliant joints based on local stability variation.

This study investigates local stability of a four-link limit cycle walking biped with flat feet and compliant ankle joints. Local stability represents the behavior along the solution trajectory between Poincare sections, which can provide detailed information about the evolution of disturbances. The effects of ankle stiffness and foot structure on local stability are studied. In addition, we apply a control strategy based on local stability analysis to the limit cycle walker. Control is applied only in the phases with poor local stability. Simulation results show that the energy consumption is reduced without sacrificing disturbance rejection ability. This study may be helpful in motion control of limit cycle bipedal walking robots with flat feet and ankle stiffness and understanding of human walking principles.

Enhancing speed recovery rapidity in bipedal walking with limited foot area using DCM predictions

The research on bipedal robots with limited foot area is gaining increasing attention. To tackle the challenge of dealing with unknown disturbances in the environment, the adjustment of footstep placement plays a vital role in maintaining stable motion during bipedal walking. This paper introduces an innovative approach based on the relationship between the Divergent Component of Motion (DCM) and footstep. It utilizes a DCM prediction model to optimize the optimal speed for recovering the foothold position. The goal is to enable quick and relevant footstep selection for bipedal robots, thereby facilitating the swift recovery of robot speed. The paper provides insights into the process of designing the desired DCM for achieving an optimal average walking speed without relying on predefined footstep sequences. By establishing a state equation between the DCM and footstep placement, this approach enables the prediction of multiple footstep positions within a fixed walking cycle, thereby facilitating the desired average motion speed. Extensive numerical simulations are conducted to compare the proposed method with various conventional footstep adjustment algorithms. The results emphasize our method’s ability to converge more rapidly to the target speed, even with minor step adjustments. To validate the feasibility and robustness of the algorithm, we conduct experiments on the bipedal robot BHR-B2. These experiments further confirm the algorithm’s effectiveness. Given its promising performance, this algorithm holds potential for applications in legged robots with point feet.