Kinematic Compatibility Research Articles

Design and Optimization Analysis of an Adaptive Knee Exoskeleton

To solve the problem of undesired relative motion of human-machine interaction positions caused by misalignment of the human-machine joints rotation axis of the knee exoskeleton, this study designed an adaptive knee exoskeleton based on a gear-link mechanism (GLM) by considering the human body as a component of the exoskeleton mechanism. Simultaneously, the concept of the wearable area (WA) was proposed, which transformed the operation of aligning the exoskeleton rotation axis with the human knee joint rotation axis into a "face alignment point" in the sagittal plane, reducing the difficulty of aligning the human-machine joint rotation axis. In the kinematic analysis of GLM, the phenomenon of instantaneous movement of the central axis of the human knee joint was considered. Based on the kinematic model, the WA, velocity transfer ratio, and initial position static stiffness of GLM were analyzed. The NSGA-II optimization algorithm was used to optimize the size parameters of GLM, which increased the WA by 18.4%, the average velocity transfer ratio by 4.98%, and the average initial position static stiffness by 6.01%. Finally, the ability of the exoskeleton to absorb movement displacement (MD) was verified through simulation, and the good human-machine kinematic compatibility of the exoskeleton was verified through wearable tests conducted on the initial mechanism principle prototype.

A Kresling origami metamaterial with reprogrammable shock stiffness

Using origami folding concepts to design novel mechanical metamaterials has recently become a prevalent framework. Inspired by the Kresling origami structure, this study proposes a double-layer Kresling origami metamaterial with reprogrammable shock stiffness. Two combination strategies are constructed, each with different geometric constraints and kinematic compatibility. They are identified as assigned with same torsion direction (ASTD) and assigned with opposite torsion direction (AOTD), respectively. The shock stiffness of two double-layer Kresling origami metamaterials is analyzed using the finite element method, and results indicate that the AOTD metamaterial has superior impact resistance. Furthermore, the programmability of shock stiffness of the metamaterial is carried out comprehensively, and the influence of each design parameter is exhibited in detail. Finally, two prototypes of ASTD and AOTD metamaterials are fabricated, and experimental tests verify the analysis outcomes. This study provides a new approach to constructing mechanical metamaterials with reprogrammable shock stiffness for applications in energy absorption and vibration isolation engineering.

Evaluating the residual stresses and fracture behavior of glass-ceramics by numerical modeling

Residual stresses often arise after glass crystallization due to the residual glass and crystal phases' thermal and elastic properties mismatch. Using the Positional Finite Element Method, we developed a computational tool for nonlinear 2D geometric analysis to simulate residual stresses from crystal growth in a glass matrix. We implemented a damage model in which interface elements are introduced into the mesh. These elements' elastic modules were penalized after reaching a tensile stress limit to simulate crack propagation. The crystal mesh was generated separately and included in the glass mesh via kinematic compatibility without introducing degrees of freedom nor requiring mesh conformity. Results were consistent with analytical calculations using Selsing's model. The fracture mode in crystal-glass composite microstructures with different signs of thermal expansion mismatch is closely in accordance with the microstructure pictures in the literature. The adapted damage model showed excellent potential in evaluating and predicting crack patterns due to residual stresses in glass-ceramics.

A Simulation-Based Framework to Determine the Kinematic Compatibility of an Augmentative Exoskeleton during Walking

Augmentative exoskeletons (AEs) are wearable orthotic devices that, when coupled with a healthy individual, can significantly enhance endurance, speed, and strength. Exoskeletons are function-specific and individual-specific, with a multitude of possible configurations and joint mechanisms. This complexity presents a challenging scenario to quantitatively determine the optimal choice of the kinematic configuration of the exoskeleton for the intended activity. A comprehensive simulation-based framework for obtaining an optimal configuration of a passive augmentative exoskeleton for backpack load carriage during walking is the theme of this research paper. A musculoskeletal-based simulation approach on 16 possible kinematic configurations with different Degrees of Freedom (DoF) at the exoskeleton structure’s hip, knee, and ankle joints was performed, and a configuration with three DoF at the hip, one DoF at the knee, three DoF at the ankle was quantitatively chosen. The Root Mean Square of Deviations (RMSD) and Maximum Deviations (MaxDev) between the kinematically coupled human–exoskeleton system were used as criteria along with the Cumulative Weight Score (CWS). The chosen configuration from the simulation was designed, realised, and experimentally validated. The error of the joint angles between the simulation and experiments with the chosen configuration was less than 3° at the hip and ankle joints and less than 6° at the knee joints.

The effect of intense and distributed exercise in teaching the disease and controlling the compatibility of some body movements in sports walking among young women in Basmaya Sports Academy

This research dealt with the effect of intensive and distributed exercise on teaching to perform and control the compatibility of movements of body parts in athletic walking at the Basmaya Sports Academy for young women. The objective of the research focus on preparing special exercises with both intensive and distributed styles and identifying their effects in teaching , performing and control the compatibility of movements of body parts in athletic walking at the Basmaya Sports Academy For Young Women..The hypotheses included that there were statistically significant differences between the results of the pre and posttests of the two experimental research groups in teaching performance and controlling the motor compatibility of body parts in athletic walking. The research community was determined by the budding of the Basmaya Academy for the academic year 2019-2020, as the sample included (12) players ( female ) who were intentionally chosen from the beginners in teaching performance , controlling and matching the movements of body parts ..After the researcher made sure of the homogeneity of the sample, they were randomly distributed in two equal groups and performed parity in testing and evaluating the performance and kinetic compatibility of body parts in athletic walking. One of the groups represented the experimental group which is its teaching was according to intensive method ,while the other group used distributed method in teaching sport walking movements .The implementation of the main experiment took 5 weeks, with three teaching units per week. After the specified period, the tests and evaluations of the motions under study were re-examined. Statistical treatments were performed using the (spss) program by adopting the two tests (T) for the independent and interrelated samples. Conclusions showed excellence of 2nd group ( with distributed exercise ) and preference over first experimental group ( with intensive exercise ) in terms of teaching and controlling the kinematic compatibility of the movements of the parts of the body walking, and accordingly the recommendations came in the necessities of adopting exercises for the distributed method in teaching young beginners to the movements of athletic walking and controlling their compatibility

Development and Validation of a Self-Aligning Knee Exoskeleton With Hip Rotation Capability.

The self-aligning capability of an exoskeleton is important to ensure wearing comfort, and the delicate motion ability of the exoskeleton is essential for motion assistance. Designing a self-aligning exoskeleton that offers improved wearing comfort and enhanced motion-assistance functions remains a challenge. This paper proposes a novel spatial self-aligning mechanism for a knee exoskeleton to enable simultaneous assistance in the flexion and extension (FE) of the knee joint and the internal and external rotation (IER) of the hip joint. Additionally, considering the misalignment of the human-robot joint axes, a kinematic model of the knee exoskeleton is established and analyzed to demonstrate the kinematic compatibility of the exoskeleton. Furthermore, a global torque manipulability (GTM) index is proposed to evaluate the effects of dimensional parameters on the exoskeleton's performance, and then the knee exoskeleton is optimized according to the GTM index. Finally, experiments are conducted to validate the performance of the proposed exoskeleton. The experimental results show that during knee FE and hip IER, the proposed exoskeleton exhibits lower interaction forces and torques than existing exoskeletons.

Full-field strain investigation of twinned martensite in a thermally activated Cu–Al–Ni single crystal using Localized Spectrum Analysis

The paper presents a full-field strain analysis of the appearance/disappearance of twinned martensite in a Cu–Al–Ni single crystal subjected to thermal cycles. Localized Spectrum Analysis (LSA) was employed to process images of a checkerboard pattern preprinted on the sample’s surface, enabling us to obtain strain maps with a suitable trade-off between strain resolution (2×10−4) and spatial resolution (0.26 mm). During the cooling of the initially austenitic sample, habit plane variants (HPVs) were identified from the in-plane components of their mean right strain tensor. The match between measured data and theoretical expectations enabled us to measure the stretch parameters associated with the cubic-to-orthorhombic transformation occurring in the material. Various deformation mechanisms were revealed by an analysis in the strain space. In particular, the process of martensite appearance during cooling appeared to be based on the coordinated activation of HPVs pairs whose strain levels globally compensate each other. Elastic strain gradients were also evidenced, highlighting the need for additional deformation to achieve kinematic compatibility at microstructure interfaces. Lastly, several thermal cycles were applied to the previously-trained sample, enabling us to quantify the level of spatio-temporal repeatability of the phase transformation.

A Review on Ergonomics Factors Determining Working in Harmony with Exoskeletons

Exoskeletons are wearable devices that can enhance human strength and are used in various fields, such as healthcare and the manufacturing industry. However, poorly designed exoskeletons can strain the muscles and cause injuries to users. The objectives of this review paper are to review the ergonomics factors that contribute to a harmonious user-exoskeleton interaction and to explore the current trends, challenges, and future directions for developing ergonomically designed exoskeletons. In this review, 102 relevant papers published from 2015 to 2023 were retrieved from Web of Science, Scopus, and Google Scholar. These papers were considered in the analysis for gathering relevant information on the topic. The authors identified six ergonomics factors, namely kinematic compatibility, contact pressure, postural control, metabolic cost, cognitive workload, as well as task demands and workplace conditions, that can influence the interaction between users and exoskeletons. By understanding and addressing these ergonomics factors during the design and development process, exoskeleton designers can enhance the user experience and adoption of the devices in daily living activities and industrial applications.

Histology-informed multiscale modeling of human brain white matter

In this study, we propose a novel micromechanical model for the brain white matter, which is described as a heterogeneous material with a complex network of axon fibers embedded in a soft ground matrix. We developed this model in the framework of RVE-based multiscale theories in combination with the finite element method and the embedded element technique for embedding the fibers. Microstructural features such as axon diameter, orientation and tortuosity are incorporated into the model through distributions derived from histological data. The constitutive law of both the fibers and the matrix is described by isotropic one-term Ogden functions. The hyperelastic response of the tissue is derived by homogenizing the microscopic stress fields with multiscale boundary conditions to ensure kinematic compatibility. The macroscale homogenized stress is employed in an inverse parameter identification procedure to determine the hyperelastic constants of axons and ground matrix, based on experiments on human corpus callosum. Our results demonstrate the fundamental effect of axon tortuosity on the mechanical behavior of the brain’s white matter. By combining histological information with the multiscale theory, the proposed framework can substantially contribute to the understanding of mechanotransduction phenomena, shed light on the biomechanics of a healthy brain, and potentially provide insights into neurodegenerative processes.

Structural geology of the Mount Meager Volcanic Complex, BC, Canada: implications for geothermal energy and geohazards

The Mount Meager Volcanic Complex ( Qwe̓ lqwe̓ lústen or Mt. Meager) coincides tectonically with the intra-arc to back-arc transition zone and exhibits the loci of strain partitioning in response to a rapid change in orientation of the Pemberton and Garibaldi Arc segments that are coeval with a shift in Pacific plate motion after 5 Ma. This strain partition is manifested through development of a transpressional deformation from 5 to 1.9 Ma at the latitude of Mt. Meager. Mt. Meager is an active volcanic system with at least two explosive eruptions in the last 25 000 years, the most recent occurring around 2360 BP. Additionally, it is the site of the largest landslide in Canadian history, which occurred during the summer of 2010, originating from the southeastern side the massif. During early exploration at Mt. Meager, geothermal boreholes drilled to 3 km reached 270 °C but did not find sufficient permeability to sustain self-flowing conditions. To understand the geological challenges in Mt. Meager’s geothermal exploration, we analyzed outcrop-scale faults and folds, incorporating structural mapping, volcanic rock paleomagnetism, and radiometric dating to establish kinematic history and kinematic compatibility of structural geology features, including faults and folds. Our findings suggest that stress partitioning during the last 5 Ma resulted in the formation of a transpressional structure exhibited as an elongate and rhomboidal structure at Mt. Meager with anomalously high topographic elevations which led to east northeast–west southwest crustal shortening and exhumation of crystalline basement. This new structural geology model improves our understanding of the geothermal reservoir and potentially significant geohazards.

Biomimetic Design of a Tendon-Driven Myoelectric Soft Hand Exoskeleton for Upper-Limb Rehabilitation.

Degenerative diseases and injuries that compromise hand movement reduce individual autonomy and tend to cause financial and psychological problems to their family nucleus. To mitigate these limitations, over the past decade, hand exoskeletons have been designed to rehabilitate or enhance impaired hand movements. Although promising, these devices still have limitations, such as weight and cost. Moreover, the movements performed are not kinematically compatible with the joints, thereby reducing the achievements of the rehabilitation process. This article presents the biomimetic design of a soft hand exoskeleton actuated using artificial tendons designed to achieve low weight, volume, and cost, and to improve kinematic compatibility with the joints, comfort, and the sensitivity of the hand by allowing direct contact between the hand palm and objects. We employed two twisted string actuators and Bowden cables to move the artificial tendons and perform the grasping and opening of the hand. With this configuration, the heavy part of the system was reallocated to a test bench, allowing for a lightweight set of just 232 g attached to the arm. The system was triggered by the myoelectric signals of the biceps captured from the user's skin to encourage the active participation of the user in the process. The device was evaluated by five healthy subjects who were asked to simulate a paralyzed hand, and manipulate different types of objects and perform grip strength. The results showed that the system was able to identify the intention of movement of the user with an accuracy of 90%, and the orthosis was able to enhance the ability of handling objects with gripping force up to 1.86 kgf.

Kinematic and Kinetic Assessment of a Novel Polycentric Knee Joint for Powered Walking Assist Exoskeletons

Loss of mobility and independence directly affects the quality of life of many vulnerable individuals. In order to address this, researchers have been developing wearable walking assist exoskeletons to aid users with their daily activities. While this technology has advanced tremendously in the past decade, current exoskeletons are yet to be ergonomic, causing discomfort and injuries to the user, leading to early device rejection. This research intends to assess the kinematic and kinetic compatibility of a novel knee joint suitable for exoskeletons. The proposed knee design can be adapted to accommodate a kinematic offset and optimize force delivery. This is achieved by ensuring that the mechanical and biological joint rotation axes are aligned and that the moment arm can be varied to mimic the mechanical characteristics of a biological knee. Model simulations and mechanical testing of fabricated prototypes were achieved to analyze and validate the design. Results confirmed the compatibility of the design, which demonstrated kinematic absolute error values of 1.68 and 0.32 mm for the offset and aligned joints, respectively. It was shown that the moment arm can be varied throughout flexion, allowing future iterations to achieve optimal and effective moment transfer.

Transmission and actuation systems in cable-driven, walking-assistance exosuits based on postural and dynamic synergies

The design of walking-assistance exosuits is becoming increasingly popular among those who aim at developing a light, affordable and wearable system. They are indeed an alternative to traditional exoskeletons, which tend to be bulkier and more expensive. The main advantages of exosuits, as opposed to exoskeletons, are their lower weight and price, as well as their increased wearability and kinematic compatibility with the user. Thus, it is key to optimize their design and, particularly, the number of actuators and the actuation scheme. One of the current, common ways to achieve better designs, is to conduct a Principal Component Analysis (PCA) on some of the involved variables to reduce their dimensionality and thus, simplify the actuation system. The goal of this paper is to analyze the different variables upon which PCA can be conducted and propose the resulting actuation schemes, comparing the results and determining the best design approach for the design of a synergy-based, gait-assistance exosuit. The study focuses on both postural and dynamic synergies to optimize their design. Here, both synergy types are reviewed from a design perspective, yielding different design criteria following a PCA-based study, each with their own set of advantages and disadvantages. Thus, the design of cable-driven exosuits is optimized via analysis of gait parameters related with its actuation, such as joint torque or cable extensions. Kinematics or postural synergies lead to a higher cumulative variance of the first principal component and the transmission system is simpler than the ones obtained through dynamic synergies.

Multiscale topology optimization of cellular structures using Nitsche-type isogeometric analysis

This paper proposes a multiscale topology optimization method using Nitsche-type isogeometric analysis (IGA) for design of structures described by multiple non-uniform rational B-spline (NURBS) patches. In this method, at macroscale, unknown structural responses are calculated by Nitsche-type IGA, which not only ensures the consistency between geometric and analytical models, but also offers an effective way to enforce kinematic compatibility and mechanical equilibrium on interfaces between adjacent NURBS patches. At microscale, mechanical properties of microstructures are predicted by a Kriging metamodel at a low computational cost, which is constructed via some sample lattice unit cells (LUCs). In addition, analytical computation of sensitivities for coupled elements is developed. Finally, the structures are infilled by graded LUCs according to the density distribution within the design space. Some 2D and 3D numerical examples with conforming and non-conforming NURBS patches are presented to test the proposed method. Results indicate that the proposed method is effective for design of structures described by multiple NURBS patches.

A multiscale framework for atomistic–continuum transition in nano-powder compaction process using a cap plasticity model

In this paper, a computational atomistic-continuum multiscale framework is presented for the simulation of the nano-powder compaction process using a cone-cap plasticity model. The atomistic representative volume element (RVE) comprises of nano-powder particles that is used to perform the molecular dynamics analysis in order to capture the mechanical behavior of nano-powder material. The periodic boundary condition is applied over the atomistic RVE to satisfy the inter-scale kinematic compatibility, and the stress tensor is derived according to the inter-scale energetic consistency principals from the nanoscale at each material point of the powder component. A multiscale framework is performed using the constitutive law of the coarse-scale domain enhanced by the molecular dynamics results of the fine-scale domain. The coarse-scale constitutive law is conformed to the cone-cap plasticity model as a robust and capable constitutive relation in modeling the powder compaction process, in which the cap plasticity parameters are determined using the data derived from the molecular dynamics simulations. The mechanical response of nano-powder particles within the RVE is obtained from the confining pressure test and true-triaxial test, where a sensitivity analysis is accomplished on the computed parameters of the cone-cap plasticity model. The enhanced cap plasticity model is then employed to simulate various industrial nano-powder components that illustrates the performance and efficiency of the proposed multiscale computational homogenization method.

A method to design stone structures based on origami

The equivalence between first order kinematic compatibility and equilibrium of forces that appears in studying origami is used as a starting point to propose a method for the design of structures made of stone blocks, possibly reinforced by steel bars. The equivalence is demonstrated under the assumption of small changes in the folding of an origami model. External forces that were not previously identified appear. Those forces are configuration dependent and are essential for the subject at issue. The role played by the choice of the reference configuration of the folding model is also put in a new light. The design method is set in the framework of limit analysis, with failures occurring possibly only at the interfaces between blocks. Its purpose is to help in defining a subdivision of a given volume into blocks that is safe under given loads. A set of propositions is put forward for the design of structures made of blocks, from fragmented slabs to fragmented shells, reinforced with rebars or not. Illustrative examples are provided.

Effects of stance control via hidden Markov model-based gait phase detection on healthy users of an active hip-knee exoskeleton.

Introduction: In the past years, robotic lower-limb exoskeletons have become a powerful tool to help clinicians improve the rehabilitation process of patients who have suffered from neurological disorders, such as stroke, by applying intensive and repetitive training. However, active subject participation is considered to be an important feature to promote neuroplasticity during gait training. To this end, the present study presents the performance assessment of the AGoRA exoskeleton, a stance-controlled wearable device designed to assist overground walking by unilaterally actuating the knee and hip joints. Methods: The exoskeleton's control approach relies on an admittance controller, that varies the system impedance according to the gait phase detected through an adaptive method based on a hidden Markov model. This strategy seeks to comply with the assistance-as-needed rationale, i.e., an assistive device should only intervene when the patient is in need by applying Human-Robot interaction (HRI). As a proof of concept of such a control strategy, a pilot study comparing three experimental conditions (i.e., unassisted, transparent mode, and stance control mode) was carried out to evaluate the exoskeleton's short-term effects on the overground gait pattern of healthy subjects. Gait spatiotemporal parameters and lower-limb kinematics were captured using a 3D-motion analysis system Vicon during the walking trials. Results and Discussion: By having found only significant differences between the actuated conditions and the unassisted condition in terms of gait velocity (ρ = 0.048) and knee flexion (ρ ≤ 0.001), the performance of the AGoRA exoskeleton seems to be comparable to those identified in previous studies found in the literature. This outcome also suggests that future efforts should focus on the improvement of the fastening system in pursuit of kinematic compatibility and enhanced compliance.

Model reduction for constrained mechanical systems via spectral submanifolds

Dynamical systems are often subject to algebraic constraints in conjunction with their governing ordinary differential equations. In particular, multibody systems are commonly subject to configuration constraints that define kinematic compatibility between the motion of different bodies. A full-scale numerical simulation of such constrained problems is challenging, making reduced-order models (ROMs) of paramount importance. In this work, we show how to use spectral submanifolds (SSMs) to construct rigorous ROMs for mechanical systems with configuration constraints. These SSM-based ROMs enable the direct extraction of backbone curves and forced response curves and facilitate efficient bifurcation analysis. We demonstrate the effectiveness of this SSM-based reduction procedure on several examples of varying complexity, including nonlinear finite-element models of multibody systems. We also provide an open-source implementation of the proposed method that also contains all details of our numerical examples.

Development and simulation of a device for upper limb rehabilitation

Robotics with exoskeletons has opened a new era of research in the field of modern rehabilitation and assistive technologies. The technology promises to improve the functionality of the upper limbs, which are necessary for daily operations. Exoskeleton technology is developing rapidly but requires interdisciplinary research to solve technical problems such as kinematic compatibility and the development of effective human-robot interaction. This article presents a new design of a device that helps to rehabilitate the upper extremities. The proposed design is characterized by a lightweight structure with an adaptable geometry for various users with low cost and easy to wear characteristics. The CAD model is developed for design details and for modeling, the results of which provide data on the feasibility of the proposed design and its characteristics in the main operational characteristics.

Design and Experimental Verification of a Hip Exoskeleton Based on Human–Machine Dynamics for Walking Assistance

High motion compatibility with the human body is essential for lower limb exoskeletons. However, in most exoskeletons, internal/external rotational degrees of freedom are not provided, which makes accurate alignment between the biological and mechanical joints difficult to achieve. To solve this problem, a novel hip exoskeleton with a parallel structure is developed in this article. The unique parallel structure eliminates the misalignment problem and enables walking free of restrictions. On the other hand, this requires a coordinated control among actuations within the parallel exoskeleton structure. In this light, a model-based controller is proposed in this article. The controller is based on a human–machine integrated dynamic model and can generate coordinated force control references that could increase the closed-loop system's sensitivity to its wearer's movements. The controller requires only kinematic information from the wearer, but not interaction force data that most existing exoskeletons require in their control design, which saves spaces and makes the system compact for use. Experiments were conducted to demonstrate the kinematic compatibility and assistive performance of the proposed hip exoskeleton.