Elastic Joints Research Articles

Force feedback reduces test time and interaction forces in telemanipulated palpation using a robotic endoscope with series elastic actuated joints.

Abstract Force feedback is currently missing in most surgical robot systems, even though it would be essential for many surgical tasks, such as palpating tissue. In this study, we used a previously developed robotic endoscope based on series elastic actuation and tested the feasibility of using it for force feedback with a pilot study. The participants had a lower test time (−27%) and lower applied forces (−23%) with force feedback enabled. While further studies are needed for validation in realistic surgical scenarios, these results suggest improved safety and efficiency in telemanipulated surgeries.

Measurement of safety state of cross-jointed segmental lining based on system performance index

The correlation between convergence deformation and the safety state of a cross-jointed segmental lining is investigated and clarified. The limitations of convergence deformation as a measuring scale is explored also. Firstly, an analytical algorithm (known as the relative stiffness method, RSM) is developed and verified for tracing the mechanical response of a cross-jointed segmental lining in failure history. Then, an explicit mapping relationship between convergence deformation and the causal factors is established using the RSM. Finally, the root causes of the limitations in using convergence deformation as a scale to evaluate tunnel safety state are discussed, and an alternative quantity, the system performance index (SPI), is proposed. It shows that: (1) The convergence deformation consists of three components induced by segment bending, elastic joint rotation, and joint stiffness attenuating, respectively. The deformation induced by attenuating joint stiffness is dependent on the failure index of segment joints and provides crucial information about the load-bearing state of the segment joints; (2) The components of elastic joint rotation and joint stiffness attenuating are significantly affected by the contact stiffness of the segment joint interface, including the physical and mechanical properties of the packing material. The magnitudes of convergence deformation and its components are not suitable for use as a quantitative scale to evaluate the safety state of the lining due to their inherent drawbacks; (3) The proposed dimensionless variable SPI can eliminate the influence of packing material on the safety state of the segment lining and reflect the comprehensive influence of the failure indexes of the segment joints.

ELEVATING ATHLETIC PERFORMANCE: THE BODY TECHNIQUE PROTOCOL'S EFFECT ON VITALITY AND RESPIRATORY WELLNESS

Engaging in regular exercise and sports can inadvertently lead to habitual movement patterns, restricting specific body parts' range of motion and diminishing joint elasticity. This decline in muscle flexibility impacts energy levels during physical activities, thus affecting overall vitality. Subjective Vitality State (SVS) captures the essence of feeling alive, reflecting an individual's energy reserves. The study involved 36 healthy young athletes aged 22.48±3.54 years, categorized into control and treatment groups. The treatment group followed a novel Body Technique exercise protocol (BT), while the control group adhered to a familiar conditioning protocol. Both protocols included five exercises targeting various muscle groups. The study focused on subjective vitality, perceived intensity load, and chest girth differences during breathing. Analysis of subjective vitality change within groups showed no significant difference for the control group before and after treatment (p=0.44), while the treatment group exhibited significantly higher subjective vitality after BT exercises (p=0.00). Significant differences were found in the "exhale-inhale" variable for the treatment group before and after treatment (p=0.00), but not for the control group (p=0.15). BT protocol demonstrated superior effects on SVS and chest girth, highlighting the significance of innovative, unconventional exercise in sports. By addressing concerns such as fatigue and injury, BT protocol may offer the prospect of better results in forthcoming training sessions. The study encourages a paradigm shift in exercise approaches, emphasizing conscious intervention to address novel movement patterns and enhance well-being in athletes.

Comprehensive accuracy analysis for large closed-loop deployable structures based on matrix structure analysis and linear-complementarity-based contact analysis of spatial joint clearances

The surface accuracy of the deployable structure is crucial in determining the electromagnetic performance of the large satellite antenna. This paper proposes a comprehensive accuracy analysis framework for deployable structures considering clearances of spatial joints, geometric deviations, elastic deformations, external loads, and preloads, all of which can affect surface accuracy during the assembly process. Surface accuracy is calculated by combining the global equilibrium analysis of the deployable structure with the local equilibrium analysis of clearance-affected joints. First, a global elastostatic equilibrium analysis of the deployable structure is performed based on a unified mathematical formulation that describes the elasticity of beams and joints. Then, the local equilibrium analysis for the clearance-affected joints is transformed into a quadratic optimization problem through a linear-complementarity-based method. This method avoids the necessity for a combinatorial search for several traditional discontinuous contact configurations. Considering both global and local equilibrium in iterative analysis, the surface accuracy of the antenna is calculated. This integration avoids prior artificial assumptions about contact configurations of the joints. Finally, the proposed method is validated by comparing it with simulations and experimental results.

On the stability of rotation in an environment with resistance of a suspended Lagrange gyroscope taking into account the elasticity of spherical joints

On the stability of rotation in an environment with resistance of a suspended Lagrange gyroscope taking into account the elasticity of spherical joints

On the stability of rotation in an environment with resistance of a free system of two rigid bodies connected by an elastic Hook joint

On the stability of rotation in an environment with resistance of a free system of two rigid bodies connected by an elastic Hook joint

Vibration responses of vertical coupling plates considering elastic boundary and flexible joint connection using traveling wave approach

Complex structures are usually assembled by basic structure components, such as beams, plates, with different boundaries. It is necessary to study the vibration responses of coupling structures considering the connection effects between plates, which is the basis for structural vibration suppression and high-precision control of complex structures. In this work, the vibration responses of vertical coupling finite-length plates considering elastic boundary and flexible joint connection are investigated using numerical methodology. First, the theoretical model of the vertical coupling plates is established using the traveling wave method, in which the plate boundary is considered as elastic support, and the connection between vertical coupling plates is considered as flexible connection joint. The mathematical model of flexible connection between vertical coupling plates as well as the elastic boundary is introduced by using equivalent spring-damper model. Then, the influence of boundary conditions, connection conditions and excitation on the vibration responses are investigated by different case studies. The numerical simulation results indicate that boundary conditions, connection conditions and excitation have significant effects on the vibration responses of the vertical coupling plates. This investigation provides a theoretical basis for vibration response predication and vibration suppression and high-precision control of complex structures, which plays important theoretical significance and engineering application prospect.

Model free sliding mode control for serial robot manipulator: rigid and elastic joint robot

Model free sliding mode control for serial robot manipulator: rigid and elastic joint robot

Yoga, a mindfulness therapy to prevent PTSD as to encompass athletes' performance.

Yoga is one of the physical and mental activities used in elite sports training for risk prevention and medical rehabilitation in case of injuries caused by overtraining or accidents. This study examined the opinions of Romanian elite athletes and coaches on the feasibility of incorporating yoga practice into training regimens for purposes of injury prevention and medical recovery. This study surveyed a group of 500 athletes, coaches, and medical personnel from three universities in Romania, all of which are part of the Faculty of Physical Education and Sport (PES). An online survey was administered which evaluates athletes' experience of yoga integration in pre/post training and its positive effects on reducing posttraumatic stress disorder (PTSD). The data were then analyzed with a structural equation model utilizing SmartPLS software. According to the survey, Romanian athletes use yoga both before and after competitions to improve their focus, balance, muscle, and joint elasticity, foster a winning mindset, control their emotions and PTSD, visualize their competition performance, and see themselves as winners. The survey also found that yoga is seen as useful for cardiac rehabilitation, neuropathic pain, pulmonary disease, orthopedic illness, muscle strain, and managing symptoms of Posttraumatic Stress Disorder (PTSD). This study contributes to enhancing athletes' mindfulness and health, offering valuable insights to trainers and athletes interested in incorporating yoga into professional sports activity. The results support the notion that yoga integration in training activity promises to positively influence athletes' performance and reduce collateral side effects of competitions. The results are also in line with the objectives of the Global Action Plan on Physical Activity 2018-2030 (GAPPPA) - with the theme of "being more efficient to prevent than to treat" - which places special emphasis on the demands for certain programs and services, sports coverage, and healthy workplace initiatives. The study further indicates that Romanian elite athletes and coaches support the use of yoga is an effective method for enhancing athletic training and medical therapy for post-traumatic illnesses and stress disorders.

Dynamic compliance of energy-saving legged elastic parallel joints for quadruped robots: design and realization

Dynamic compliance of energy-saving legged elastic parallel joints for quadruped robots: design and realization

Optimal gaits for inertia-dominated swimmers with passive elastic joints.

Animals and some robots locomote by interacting with the environment through cyclic shape changes, or gaits. Many animals make significant use of passive dynamics with flexible tails or pendulum action to reduce the effort required to execute these gaits. Although geometric tools have been developed to study optimal passive gaits for swimmers in drag-dominated physics regimes, they have not yet been used to study larger-scale swimmers whose physics are dominated by inertial effects. In this paper, we leverage previous work in the geometric mechanics field to examine passive-elastic inertial swimmers and show that geometric mechanics can be used to rapidly determine many classes of optimal gaits for such systems. We also discuss how considering swimmer metabolic costs in addition to the mechanical costs of driving actuation is useful for discussing swimmer efficiency. In particular, we focus on two models of active-passive swimming inertial systems: the perfect-fluid three-link swimmer, and a swimmer with a passively flexible tail.

Development of a Novel Tendon-Sheath-Driven Upper Limb Exoskeleton With Elastic Joints for Assisting Surgeon-Performing Microlaryngoscopic Surgery

Abstract When performing microlaryngoscopic surgery, surgeons must maintain their arm positions for a long time, which can cause arm soreness and affect the success rate of surgery. In this study, a novel tendon-sheath-driven upper limb exoskeleton with elastic joints (TULEE) is proposed and developed to support the arms of doctors wearing the TULEE. The functional requirements of the TULEE were proposed according to the needs of microlaryngoscopic surgery, and the overall structure of the TULEE was designed. Then, the positive kinematics of the TULEE were derived based on the D–H transformation matrices, and the accuracy of the positive kinematic control was verified experimentally. The reachable workspace of the wrist joint of the TULEE was analyzed, and the dexterous workspace of the wrist was analyzed by using the condition number of the Jacobian matrix. The control strategy of the TULEE was proposed based on the principle of admittance control. Finally, an experimental prototype of the TULEE was built, and the feasibility of the control strategy was verified by a servo control experiment testing a single joint and a combined control experiment testing multiple joints. Through simulated surgical experiments, it was verified that TULEE can follow the wearer's arm movement, provide assistance for the wearer's arm movement in the following control mode, and lock the joint rotation angle in the steady-state control mode to reduce external disturbances and reduce the risk of unsuccessful surgery.

Design and Control of the Rehab-Exos, a Joint Torque-Controlled Upper Limb Exoskeleton

This work presents the design of the Rehab-Exos, a novel upper limb exoskeleton designed for rehabilitation purposes. It is equipped with high-reduction-ratio actuators and compact elastic joints to obtain torque sensors based on strain gauges. In this study, we address the torque sensor performances and the design aspects that could cause unwanted non-axial moment load crosstalk. Moreover, a new full-state feedback torque controller is designed by modeling the multi-DOF, non-linear system dynamics and providing compensation for non-linear effects such as friction and gravity. To assess the proposed upper limb exoskeleton in terms of both control system performances and mechanical structure validation, the full-state feedback controller was compared with two other benchmark-state feedback controllers in both a transparency test—ten subjects, two reference speeds—and a haptic rendering evaluation. Both of the experiments were representative of the intended purpose of the device, i.e., physical interaction with patients affected by limited motion skills. In all experimental conditions, our proposed joint torque controller achieved higher performances, providing transparency to the joints and asserting the feasibility of the exoskeleton for assistive applications.

A new elastic T-shape joint of longitudinally connected slab ballastless track structure for releasing thermal stress caused by non-uniform temperature loads

In a longitudinally connected slab ballastless track structure (LCSBTS), the T-shape joint is the critical section where severe damage is often found due to the extremely high-temperature effect, mainly concerned with routine high-speed railway maintenance. This paper proposes a new elastic T-shape joint that replaces a section of the original C55 concrete joint with elastic material. A numerical model of LCSBTS with a new elastic T-shape joint is established to simulate the development of the interfacial bond failure and joint compressive damage under temporally and spatially non-uniform temperature loads. The influence of the size, material properties and replacement position of the elastic material with the new elastic T-shape joint on the damage, deformation, and stress of LCSBTS subjected to the temperature loads is investigated. Results show that, by adopting the new elastic T-shape joint, the joint compressive damage and the longitudinal thermal stress of LCSBTS are reduced significantly. The lower the elastic modulus of the elastic material, the greater the longitudinal thermal stress release of the track structure. As the elastic modulus of the elastic material decreases, the vertical displacement of the track slab, interfacial damage of LCSBTS and joint compressive damage increase while the vertical displacement of the joint improves. The best new elastic T-shape joint is to replace the middle of the wide joint made of C55 concrete with 50 mm-width elastic material, where the elastic modulus is 17324 MPa. Compared to the original designation of C55 concrete joint, LCSBTS with a new elastic T-shape joint achieves 11.2% maximum thermal stress reduction ratio and reduces the joint compressive damage by 23.5% and interfacial damage by 4.2%.

Chirality effects in panto-cylindrical structures

In this paper, we apply a numerical integration strategy recently developed for determining the deformation shapes of structures constituted by Cosserat rods, to predict the behavior of panto-cylinders. Panto-cylinders have, as microstructure, a set of two families of helicoidal beams interconnected by perfect or elastic joints. The pivot’s free rotation axis is, in the reference configuration, orthogonal to the cylindrical surfaces spanned by the beams. We perform a series of numerical simulations looking for the mechanical parameters which exalt the chirality effects in the structure. For the performed compression, extensions, shear, and torsion tests, we find chiral deformation patterns with a dependence on the type of joint and its length.

On the stability of rotation in an environment with resistance of a free system of two elastically connected rigid bodies

The equations of rotation in a medium with resistance of a free system of two rigid bodies connected by an elastic spherical joint or Hooke's joint are obtained. Under the assumption that the center of mass of solid bodies is located on the third axis of inertia, equations of perturbed motion are obtained. These equations are represented as eight ordinary differential equations with periodic coefficients. For two Lagrange gyroscopes, a fourth-order characteristic equation is obtained. Based on the Liénard-Schipart criterion, written in the form of innors, conditions for the asymptotic stability of uniform rotations of Lagrange gyroscopes are obtained. These conditions are presented in the form of three inequalities. Analytical studies of stability conditions were carried out. It has been proven that the first inequality is always satisfied. From the third inequality it follows that if the gyroscopes have equal axial moments of inertia and rotate with the same angular velocities in different directions or there is no elasticity in the hinge, then the characteristic equation has a multiple root. In this case, the issue of sustainability requires additional research. The conditions for stability in terms of kinetic moments are written out and it is shown that the leading inequality coefficients are positive, from which it follows that stability will always be possible for sufficiently large values of one or two kinetic moments. Similar conclusions were obtained with the Hooke's hinge, and it was also shown that with identical gyroscopes the characteristic equation splits into two equations. In the absence of elasticity, a multiple zero root appears in the hinge and stability requires additional study.

Identification of Deformable Linear Object Dynamics from Input-output Measurements in 3D Space

Controlling deformable linear objects requires reliable models that capture their complex and high-dimensional dynamics. This paper aims to obtain accurate state-space models of such objects from input-output measurements only, tailored for the use in a model predictive control setting. The proposed identification approach is initialized by a physics-inspired baseline model which approximates a deformable linear object by a serial chain of rigid bodies connected via elastic joints. The nonlinear residual dynamics of the baseline model are then modeled by an artificial neural network, where a key element is the so-called guided residual search that first infers the latent residual and state trajectories in the time domain, in this way facilitating supervised learning of the neural network. The efficacy of the modeling approach is demonstrated on experimental data of the 3D end-point motion of a flexible aluminum rod, excited by a 7-axis Franka Panda robot arm. Compared to a physics-inspired baseline model, the proposed method achieves a 14% prediction performance increase, and compared to a fully neural network-based approach with a similar number of parameters, it achieves a 58% improvement, while also reporting a training time that is more than 5 times faster.

Beam-column joint modeling effects on the seismic response of a non-ductile reinforced concrete building

Seismic performance evaluation of existing reinforced concrete buildings requires numerical approaches that reflect the damage modes that may arise from deficiencies in beam-column joints. In this study, the seismic performance of an existing reinforced concrete building with four stories was investigated by applying elastic and deformable beam-column joint models. The deformable beam-column joint model was verified using an exterior non-ductile beam-column joint test. The model included a rotational spring located at the joint with two connected nodes in a zero-length with rigid elements in the vicinity of frame elements. Moment- rotation relationships represent the joint behavior, and they were defined based on shear stresses and strains. After effective modeling of beam-column joints, it was aimed to obtain the cyclic behavior of the building model using non-linear time history analysis. For this purpose, scaled earthquake records were applied to the three-dimensional numerical model, and the results were compared in terms of inter-storey drift ratios, column and beam chord rotations, and base shear. It was determined that the exterior beam-column joints reached their strength and deformation capacity, while the beam and columns remained below their section deformation limits according to the Turkish Earthquake Code.

3D hybrid modeling approach combining the finite and discrete element methods: Validation based on masonry shear wall tests

The masonry structures represent a remarkable portion of the world’s built heritage. The preservation of these buildings requires a multidisciplinary diagnostic approach that includes a structural assessment to estimate their stability. However, this task remains difficult because of the high nonlinearity behavior of the masonry material and the complexity of the geometries of this type of building. For this reason, several robust modeling strategies have been developed. Among these strategies, block-based models (BBM) based on the discrete element method and more specifically the NSCD “Non Smooth Contact Dynamics” allows to take into account the actual geometrical texture of masonry. However, in this type of approach, blocks are generally rigid or elastic and nonlinearity appears only at the interfaces between blocks governed by cohesive frictional laws. In this study, a new hybrid approach is proposed. It consists of integrating a model combining (i) a frictional cohesive zone model “FCZM” describing the block-mortar interface and (ii) a quasi-brittle damage model associated with the block while (iii) the elasticity of mortar joints is explicitly taken into account in the FCZM model by adding a linear spring in both normal and tangential directions. Thus, avoiding the use of extended blocks and corresponding homogeneous properties. The validation of this numerical approach is carried out on the basis of an experimental campaign on masonry shear wall test subjected to compression.

Про стійкість обертання вільної системи двох пружно зв’язаних твердих тіл

The equations of rotation of the free system of two rigid bodies connected by an elastic spherical joint or a Hook joint are derived. Assuming that the center of mass of the rigid bodies is located on the third main axis of inertia, the equations of the disturbed motion of the mechanical system under consideration are written in the form of eight ordinary differential equations with periodic coefficients. In the case of two Lagrangian gyroscopes, a characteristic equation of the fourth order is obtained. On the basis of the Lénar-Schipar criterion, written in innor form, the necessary conditions for the stability of uniform rotations of Lagrange gyroscopes in the form of a system of three inequalities are obtained. Analytical studies of these stability conditions were carried out. It is proved that the first inequality is always satisfied. It follows from the third inequality that when gyroscopes have equal axial moments of inertia and rotate with the same angular velocities in different directions or there is no elasticity in the hinge, then the characteristic equation has multiple roots and the question of stability requires additional research. The conditions of stability with respect to kinetic moments are written and it is shown that the older coefficients of these two inequalities are positive, from which it follows that stability will always be possible with sufficiently large values of one of the two kinetic moments. Similar conclusions were obtained in the case of Hook's hinge, and it was also shown that when the gyroscopes are the same, the characteristic equation breaks down into two equations. The first and second equations describe the steady free rotation of one gyroscope on which the restoring moment acts, only in one of the equations it is necessary to add the mass moment of the second gyroscope to the equatorial moment. In the absence of elasticity in the joint, multiple zero roots appear and the question of stability requires additional research.