Limit Of Motion Research Articles

Boosting the HP filter for trending time series with long-range dependence

This article extends recent asymptotic theory developed for the Hodrick Prescott (HP) filter and boosted HP (bHP) filter to long-range dependent time series that have fractional Brownian motion (fBM) limit processes after suitable standardization. Under general conditions, it is shown that the asymptotic form of the HP filter is a smooth curve, analogous to the finding in Phillips and Jin for integrated time series and series with deterministic drifts. Boosting the filter using the iterative procedure suggested in Phillips and Shi leads under well-defined rate conditions to a consistent estimate of the fBM limit process or the fBM limit process with an accompanying deterministic drift when that is present. A stopping criterion is used to automate the boosting algorithm, giving a data-determined method for practical implementation. The theory is illustrated in simulations and two real data examples that highlight the differences between simple HP filtering and the use of boosting. The analysis is assisted by employing a uniformly and almost surely convergent trigonometric series representation of fBM.

Diurnal cycles of rain storms over South China during the presummer rainy season

The variation characteristics of rain storms (RSs) are closely related to complex internal physical processes and external dynamic and thermodynamic conditions. Using a 17-year observational rainfall dataset from the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR), the diurnal cycles of various RS characteristics and their responses to the South China Sea Summer Monsoon (SCSSM) are investigated in South China (SC) during the presummer rainy season (PSRS). Before SCSSM outbreaks, the RSs in the western inland region of SC (WSC) have stronger precipitation intensities and convective features due to orographic lifting, especially at night, while those in the eastern inland region of SC (ESC) have higher RS occurrence frequencies with higher moisture transport, especially in the afternoon. The onset of the SCSSM leads to abundant moisture and sufficient convective available potential energy over the entire SC area, resulting in significant increases in the occurrence frequency, convective fraction, and precipitation top height of RSs. In the WSC, the weakened upward motion and smaller convective inhibition limit RS development, resulting in weaker rainfall intensity. In the ESC, a particularly unstable atmosphere and enhanced low-level moisture transport in the afternoon lead to a larger three-dimensional size, more active convection, and greater precipitation intensity in the RSs. These results offer fresh insight into the diurnal variation in rainfall during the PSRS and can be effectively used to evaluate numerical model simulations.

Swimming in viscoplastic fluids

Abstract Locomotion at small scales in the absence of inertia is a classical and enduring research topic. Here, recent developments in the theory of such locomotion through a viscoplastic ambient fluid are reviewed and explored. The specific focus here applies to motion of cylindrical filamentary bodies that are long and thin, for which an asymptotic slender-body theory can be exploited. Details of this theory are summarised and then applied to describe different swimming waveforms: undulation, peristalsis, and helical motion. It is shown that, in general, strong force anisotropy close to the limit of axial cylindrical motion has a significant effect on locomotion in viscoplastic media, allowing for highly efficient motion in which the swimmer is able to ‘cut’ through the material following very closely the path of its own axis. Some qualitative comparison with experiments is presented, and future extensions and research directions are reviewed. Graphical abstract Deformation fields around cylinders moving at different angles to their axis through a yield stress fluid, showing (a) a low yield stress and (b) a high yield stress

Effect of nonlinear terms in piston theory on characteristics of panel flutter

Currently, there is no systematic summary of the influence of the nonlinear terms in piston theory on the panel flutter. The two-dimensional nonlinear panel flutter equations under supersonic airflow based on the first, second, and third-order piston theories is established. The stability of the heated panel is analyzed by using the Lyapunov's indirect method, and the panel flutter equations are numerically solved based on the numerical analysis method to investigate the influence of the nonlinear terms in piston theory on the panel flutter. The results show that: ①Under a small temperature rise ratio, the panel response under the first-order piston theory only exhibits the convergent motion and single-period limit cycle flutter. While under higher-order piston theories, the panel response is more complex, exhibiting more complex nonlinear dynamic phenomena such as multi-period limit cycle flutter and chaotic motion in addition to the aforementioned characteristics. ②As the Mach number increases, the required dynamic pressure and temperature rise ratio decrease gradually when the dynamic response of the panel under the first-order piston theory and higher-order piston theories exhibit significant differences. ③The significant differences in the computational results of the second-order and third-order piston theory appear under the high Mach numbers and relatively high dynamic pressures, and the same phenomenon occurs underthe high temperature rise ratios. ④When the dynamic response characteristics of the panel are basically consistent, the displacement response peak calculated by using the higher-order piston theory is usually smaller than the result calculated by using the first-order piston theory, and the maximum error can reach about 16.66%. The present results have certain reference value for selecting the appropriate analysis method for the panel flutter under different conditions in practical applications.

KPZ equation limit of sticky Brownian motion

We consider the motion of a particle under a continuum random environment whose distribution is given by the Howitt-Warren flow. In the moderate deviation regime, we establish that the quenched density of the motion of the particle (after appropriate centering and scaling) converges weakly to the (1+1) dimensional stochastic heat equation driven by multiplicative space-time white noise. Our result confirms physics predictions and computations in [66,7] and is the first rigorous instance of such weak convergence in the moderate deviation regime. Our proof relies on a certain Girsanov transform and works for all Howitt-Warren flows with finite and nonzero characteristic measures. Our results capture universality in the sense that the limiting distribution depends on the flow only via the total mass of the characteristic measure. As a corollary of our results, we prove that the fluctuations of the maximum of an N-point sticky Brownian motion are given by the KPZ equation plus an independent Gumbel on timescales of order (log⁡N)2.

Poster 208: Predicting Patient-Specific Hip Motion During Functional Activities After Periacetabular Osteotomy

Objectives: Developmental dysplasia of the hip (DDH) is a condition in which the hypoplastic acetabulum provides inadequate coverage of the femoral head. This abnormal coverage, while pathological, may be advantageous in some sporting and recreational activities needing significant hip range of motion (ROM), including dance, ballet, and performing arts. Although DDH allows patients to perform activities requiring supraphysiologic hip motion, subluxation of the hip joint generates excessive articular stresses, leading ultimately to pain, osteoarthritis (OA), and total joint arthroplasty. In some DDH patients, this degenerative pathway can be interrupted by performing a periacetabular osteotomy (PAO) to reorient the acetabular fragment, which increases femoral head coverage and reduces intra-articular stresses. This improved coverage is believed to come at the sacrifice of range of motion, particularly noticed while performing high-demand activities requiring supraphysiologic end-range motion. This study addresses the questions: 1. Does a PAO reduce the range of motion of the hip enough to reduce a patient’s ability to perform daily living, recreational and sporting activities? 2. If so, what activities are most impacted by these changes? Methods: We created an inventory of daily living, recreational and sporting activities commonly performed by patients with hip dysplasia. A systematic review of the literature provided the maximum hip range of motion required (required ROM) to perform eight activities of daily living (ADL) and thirteen sporting movements. The concurrent peak value for each anatomic component of hip motion, (i.e flexion/extension; adduction/abduction; internal/external rotation) was classified for every activity in terms of physiologic demand relative to the average ROM of the adult hip. Based on these values, we created a 7-level ordinal scale according to the peak kinematic demand required to perform each activity (Table 1), ranging from low to extreme difficulty. To examine the impact of a PAO on the limits of hip motion, we selected, with IRB approval, a cohort of 24 dysplastic hips (12 left and 12 right). Patient-specific 3D models of each pelvis and hip joint were created from preoperative CT scans, and each activity in our hip inventory was simulated using a custom Matlab hip simulation routine. For each activity, the ROM of the hip was recorded as the point at which either bony impingement was detected, or the specified movement was successfully completed. The percentage of the required motion successfully completed (percent function) was then calculated (100*measured ROM/required ROM) for each movement. This procedure was repeated on the same hips after completion of a computer-simulated PAO according to the technique described by Ganz and colleagues in which the LCEA was increased to 35° and reoriented anteriorly to appropriately restore head coverage. Wilcoxon Signed Rank tests were performed to compare preoperative and postoperative percent function for each movement. Results: When all activities were combined, there was no significant difference (p > 0.05) between preoperative function (99.2 ± 0.6%) and postoperative function (98.0 ± 1.1%). The flexion portions of the right and left grand écart latéral, commonly used ballet movements, were the only activities where percent function was significantly decreased after PAO. Before surgery, the left hips performed 96.8 ± 1.8% of the motion required for the left grand écart latéral whereas after surgery hip function decreased to 82.5 ± 7.6% (p < 0.05). Preoperatively, the right hips performed the right grand écart latéral at 96.7 ± 3.3% compared to 77.4 ± 8.3% postoperatively (p < 0.05). There were no significant differences between preoperative and postoperative function for any other activities within the hip inventory. Conclusions: After testing a broad range of movements found in both daily life and sporting and recreational activities, just two of the twenty-one activities were significantly impaired after a computer-simulated PAO. A lack of significant change in percent function for most movements between preoperative and postoperative hips indicates that even high performing patients who undergo a PAO can expect little to no change in their ability to perform many of the activities they enjoyed before surgery. A significant change, however, was seen in the ballet positions right and left grand écart latéral and patients requiring performance of these activities after PAO should be counseled preoperatively regarding the demands of their sporting and recreational activities and their postoperative expectations. [Figure: see text]

Robot-Assisted Eye Surgery: A Systematic Review of Effectiveness, Safety, and Practicality in Clinical Settings.

Surgical innovation in ophthalmology is impeded by the physiological limits of human motion, and robotic assistance may facilitate an expansion of the surgical repertoire. We conducted a systematic review to identify ophthalmic procedures in which robotic systems have been trialled, evaluate their performance, and explore future directions for research and development of robotic techniques. The Cochrane Library, Embase, MEDLINE, Scopus, and Web of Science were searched. Screening adhered to five criteria: (1) English language; (2) primary research article; (3) human patients; (4) ophthalmological surgery; and (5) robot-assisted surgery. Quality assessment was conducted with Joanna Briggs Institute Tools for Critical Appraisal. The study protocol was registered prospectively (PROSPERO ID CRD42023449793). Twelve studies were included. In comparative studies, there was no difference in the occurrence of ocular harms in robot-assisted procedures and conventional surgery. However, robotic assistance did not demonstrate consistent benefits over manual surgery in terms of effectiveness or practicality, likely reflecting the learning curve associated with these systems. Single studies indicated the potential of robotic assistance to improve the consistency of subretinal drug infusion and efficiency of instrument manipulation in vitreoretinal surgery. Proof-of-concept studies have demonstrated the potential of robotic assistance to facilitate procedures otherwise infeasible or impractical, and may broaden access to surgery. However, robot-assisted surgery has not yet demonstrated any significant benefits over standard surgical practice. Improving the speed and reducing perioperative requirements of robot-assisted surgery are particular priorities for research and innovation to improve the practicality of these novel techniques. This systematic review summarizes the potential and limitations of robotic systems for assisting eye surgery and outlines what is required for these systems to benefit patients and surgeons.

Using Virtual Reality in a Rehabilitation Program for Patients With Breast Cancer: Phenomenological Study.

Surgery is an essential treatment for early-stage breast cancer. However, various side effects of breast cancer surgery, such as arm dysfunction and lymphedema, remain causes for concern. Rehabilitation exercises to prevent such side effects should be initiated within 24 hours after surgery. Virtual reality (VR) can assist the process of rehabilitation; however, the feasibility of applying VR for rehabilitation must be explored, in addition to experiences of this application. This study explored patients' attitudes toward and experiences of using VR for their rehabilitation to determine the feasibility of such VR use and to identify potential barriers. A phenomenological qualitative study was conducted from September to December 2021. A total of 18 patients with breast cancer who had undergone surgical treatment were interviewed using open-ended questions. The Colaizzi 7-step procedure for phenomenological analysis was used for data analysis. To ensure high study reliability, this study followed previously reported quality criteria for trustworthiness. Three themes were identified: (1) VR was powerful in facilitating rehabilitation, (2) early and repetitive upper limb movements were an advantage of VR rehabilitation, and (3) extensive VR use had challenges to be overcome. Most of the interviewed patients reported positive experiences of using VR for rehabilitation. Specifically, VR helped these patients identify appropriate motion and angle limits while exercising; in other words, knowledge gained through VR can play a key role in the rehabilitation process. In addition, the patients reported that the use of VR provided them company, similar to when a physiotherapist is present. Finally, the gamified nature of the VR system seemed to make VR-based rehabilitation more engaging than traditional rehabilitation, particularly with respect to early rehabilitation; however, the high cost of VR equipment made VR-based rehabilitation difficult to implement at home. The interviewed patients with breast cancer had positive experiences in using VR for rehabilitation. The high cost of both VR equipment and software development presents a challenge for applying VR-based rehabilitation.

Powering an autonomous clock with quantum electromechanics

We theoretically analyse an autonomous clock comprising a nanoelectromechanical system, which undergoes self-oscillations driven by electron tunnelling. The periodic mechanical motion behaves as the clockwork, similar to the swinging of a pendulum, while induced oscillations in the electrical current can be used to read out the ticks. We simulate the dynamics of the system in the quasi-adiabatic limit of slow mechanical motion, allowing us to infer statistical properties of the clock’s ticks from the current auto-correlation function. The distribution of individual ticks exhibits a tradeoff between accuracy, resolution, and dissipation, as expected from previous literature. Going beyond the distribution of individual ticks, we investigate how clock accuracy varies over different integration times by computing the Allan variance. We observe non-monotonic features in the Allan variance as a function of time and applied voltage, which can be explained by the presence of temporal correlations between ticks. These correlations are shown to yield a precision advantage for timekeeping over the timescales that the correlations persist. Our results illustrate the non-trivial features of the tick series produced by nanoscale clocks, and pave the way for experimental investigation of clock thermodynamics using nanoelectromechanical systems.

MPMC-frame: Multiplatform migration control framework for manipulator control

Existing robot control models suffer from poor generalization performance due to varied tasks between manipulators, configuration differences, and physical limits of motion. To address this problem, a multiplatform migration control framework (MPMC-frame) based on a constrained dynamics model is proposed in this paper. First, a model of the robotic manipulator dynamics with configuration adjustment (CA) is constructed based on a neural network to unify the physical joint data of different manipulators. Second, the model-based controller that can be integrated into the framework is designed, and the constraint on the upper bound on the error of uncertain parameters in the control law to guarantee the control robustness and accuracy of the controller for different manipulator platforms. Final, the generic potential function is designed based on multiplatform task requirements, and a task parameter table is constructed to improve the joint motion control performance of MPMC-frame. The feasibility of the method proposed in this paper are verified through simulations and experiments based on the ABB_irb120 and AUBO_i5 robotic manipulators.

Rayleigh–Bénard convection with an immersed floating body

The paper presents the results of an experimental and numerical study of turbulent thermal convection in a rectangular box containing an extended immersed free-floating plate. Varying the values of control parameters, such as Rayleigh number, aspect ratio and vertical position of the plate, provides a wide range of possible modes, from immobile and purely periodic to stochastic. We have shown that stable periodic motions occur when the plate floats close to one of the heat exchangers. An increase in the distance between the plate and the heat exchanger breaks the periodic motion and (at moderate Rayleigh numbers) leads to a pronounced asymmetry, when the plate stays close to one of the walls most of the time, makes rare excursions to the opposite wall and immediately returns. As the Rayleigh number increases, the plate motions from one edge of the box to the other reappear, but always have an irregular character. Regarding the dependence of the system behaviour on the geometry of the box, both lower and upper limits of periodic plate motions were found in the experiments. In the numerical simulations, the upper limit was not achieved – the plate moves quasi-periodically through the chain of vortices of different signs even at the largest aspect ratio being considered. The heat-insulating floating plate provides the spatial and temporal variation of the heat flux and reduces the integral heat flux, but the reduction in heat flux depends significantly on the vertical position of the plate.

Two-to-three times increase in natural hip and lumbar non-sagittal plane kinematics can lead to anterior cruciate ligament injury and cartilage failure scenarios during single-leg landings

BackgroundAnalyzing sports injuries is essential to mitigate risk for injury, but inherently challenging using in vivo approaches. Computational modeling is a powerful engineering tool used to access biomechanical information on tissue failure that cannot be obtained otherwise using traditional motion capture techniques. MethodsWe extrapolated high-risk kinematics associated with ACL strain and cartilage load and stress from a previous motion analysis of 14 uninjured participants. Computational simulations were used to induce ACL failure strain and cartilage failure load, stress, and contact pressure in two age- and BMI-matched participants, one of each biological sex, during single-leg cross drop and single-leg drop tasks. The high-risk kinematics were exaggerated in 20% intervals, within their physiological range of motion, to determine if injury occurred in the models. Where injury occurred, we reported the kinematic profiles that led to tissue failure. FindingsOur findings revealed ACL strains up to 9.99%, consistent with reported failure values in existing literature. Cartilage failure was observed in all eight analyzed conditions when increasing each high-risk kinematic parameter by 2.61 ± 0.67 times the participants' natural landing values. The kinematics associated with tissue failure included peak hip internal rotation of 22.48 ± 19.04°, peak hip abduction of 22.51 ± 9.09°, and peak lumbar rotation away from the stance limb of 11.56 ± 9.78°. InterpretationOur results support the ability of previously reported high-risk kinematics in the literature to induce injury and add to the literature by reporting extreme motion limits leading to injurious cases. Therefore, training programs able to modify these motions during single-leg landings may reduce the risk of ACL injury and cartilage trauma.

The geometry of the Rindler black hole

Using Einstein's equations for gravity for a spherically symmetric field in a static state and the mass function method, a general form of the metric for Schwarzschild-type black holes is proposed. A qualitative analysis of Schwarzschild, Reissner–Nordström and Rindler geometries is performed. In the paper, it is found that Rindler black hole geometry is structurally inverse to Reissner–Nordström geometry, i.e. it has two T-regions and one R-region. In this regard Rindler geometry is like geometry of the Kottler black hole, which does not have flat asymptotics. Potential curves in the gravitational field of the Rindler black hole are constructed, which makes it possible to calculate the limits of finite motion for a test particle in this field. In addition, a qualitative comparison with the known Schwarzschild field metric is performed. Their similarity in behavior at small distances and absolutely different behavior at large scales are shown. Using the known accelerations of the Pioneer spacecraft, limits are numerically found for the T- and R-regions of their motion in the gravitational field of the Solar System.

Analytical and numerical stability analysis of a toroidal wheel with nonholonomic constraints

In this paper, a detailed and comprehensive linear stability analysis of a rolling toroidal wheel is performed. The wheel is modeled as a rigid toroid-shaped body rolling without slipping on a horizontal surface. The nonlinear equations of motion constitute a Differential-Algebraic Equations system, given by the dynamic equilibrium equations augmented with the nonholonomic constraints, which arise from the no-slip condition. The circular steady motion and the linearized equations of motion along this relative equilibrium are obtained, for both the solid and hollow tori. The expressions of the linearized equations and the corresponding eigenvalues are derived analytically as a function of the torus aspect ratio. The variation of the stability boundary with the torus aspect ratio is shown. A comparison of the results obtained in the solid and hollow scenarios is included, and all the results are validated with the rolling hoop, which corresponds to a degenerate torus with zero aspect ratio. In the particular case of the steady straight-line rolling and spinning about a vertical diameter, which constitute limit motions of the circular steady motion, the critical rotational and angular speeds required for stabilization are obtained.

Sediment mobility over a dispersive inner shelf from combined wave and tide bed shear stress

The sediment transfers that take place between the beach and the depth of closure on the inner continental shelf play a major role in the evolution of sandy shores at different time scales. The depth of closure of the foreshore sedimentary prism, which is generally dependent on wave conditions, remains poorly constrained in the context of an internal macrotidal platform. This work aims to define and evaluate this theoretical depth, which delimits the extension of sedimentary exchanges, in particular by including the constraints applied on the sea bottom by the tidal circulation, which are very strong on the inner continental shelf of western Brittany. The use of wave (WAVEWATCH III®), tidal (MARS3D), and bottom sediment (EMODnet) databases allows us to follow an original cartographic approach to study closure depths, based on the formulations of Hallermeier (1978 and 1981) and Soulsby (1997). This cartographic approach is adapted to a spatial analysis of sediment mobility on a regional scale. First, the depth of closure shows a regional spatialisation of the seaward extension of the sediment mobility zone according to exposure to different wave climates and tidal ranges. Secondly, the method for calculating the depth of closure with the combined shear stresses (wave and tide), applied at the scale of the internal platform of western Brittany, allows the identification of three areas of movement of sedimentary particles according to critical mobility thresholds: 1) Area of no motion; 2) Area of transport and deposition; 3) Area of transport without deposition. The main contribution of this work is to propose at distinction between 2 offshore sediment motion limits, the transition to the upper plane bed (DoTupb), and the incipient motion of particle (DoTmotion). In addition, this study confirms the potential of transport and deposition of sand particles at depths >100 m in the most hydrodynamically intense areas, which implies the possibility of interconnections between hydro-sedimentary cells, through bypassing of headlands and crossing over rocky outcrops.

Restudy of shoulder motion in the theropod dinosaur Mononykus olecranus (Alvarezsauridae)

Background Range of motion in the forelimb of the Upper Cretaceous theropod dinosaur Mononykus olecranus, a member of the family Alvarezsauridae, has previously been investigated. However, the method used to investigate range of motion at the shoulder in M. olecranus did not follow the standardized procedure used in subsequent studies. The latter procedure yields more reliable results, and its standardization provides that its results are directly comparable to the results of similar studies in other species. I therefore reinvestigated the range of motion at the shoulder in M. olecranus, using the latter procedure. Methods Casts of the left scapula and coracoid of M. olecranus were posed on a horizontal surface, supported from beneath with modeling clay, with the medial surface of the scapula facing toward the horizontal surface. A cast of the left humerus was posed at the limits of motion through the transverse and parasagittal planes. Photos of the poses in orthal views were superimposed and used to measure range of motion, which was measured as the angle between lines drawn down the long axis of the humerus in each position. Results Through the transverse plane, the humerus of M. olecranus could be elevated to a subhorizontal position and depressed to a subvertical position. It could move through the parasagittal plane from a subvertical position at full protraction to a position above the horizontal at full retraction. These results correct the previous mischaracterization of shoulder motion in M. olecranus as restricted to a small arc with the arms held in a permanent sprawl. The range of humeral motion in M. olecranus is much greater than that found by the previous method and allowed the animal to tuck its arms in at the sides, in addition to allowing them to sprawl so as to orient the palm downward. The wide range of humeral motion allowed M. olecranus to forage for insects by employing hook-and-pull digging at surfaces with a wider range of orientations than the previous study showed to be possible.

Khronometric Theories of Modified Newtonian Dynamics

In 2011 Blanchet and Marsat suggested a fully relativistic version of Milgrom's modified Newtonian dynamics in which the dynamical degrees of freedom consist of the spacetime metric and a foliation of spacetime, the khronon field. This theory is simpler than the alternative relativistic formulations. We show that the theory has a consistent nonrelativistic or slow-motion limit. Blanchet and Marsat showed that in the slow motion limit, the theory reproduces stationary solutions of modified Newtonian dynamics. We show that these solutions are stable to khronon perturbations in the low acceleration regime, for the cases of spherical, cylindrical, and planar symmetry. For nonstationary systems in the low acceleration regime, we show that the khronon field generally gives an order unity correction to the modified Newtonian dynamics. In particular, there will be an order unity correction to the MOND version of Kepler's third law, potentially relevant to ongoing efforts to test MOND using GAIA observations of wide binaries.

Masses and Densities of Dwarf Planet Satellites Measured with ALMA

We have used the Atacama Large Millimeter/submillimeter Array to measure precise absolute astrometric positions and detect the astrometric wobble of dwarf planet Orcus and its satellite Vanth over a complete orbit. We also place upper limits to the astrometric wobble induced by Dysnomia on dwarf planet Eris around its orbit. From the Vanth–Orcus barycentric motion, we find a Vanth–Orcus mass ratio of 0.16 ± 0.02—the highest of any known planet or dwarf planet. This large ratio is consistent with the hypothesis that Vanth is a largely intact impactor from a giant collision in the system and that the system has likely evolved to a double synchronous state. We find only an upper limit of the barycenter motion of Eris, which implies a 1σ upper limit to the Dysnomia–Eris mass ratio of 0.0085, close to the modeled transition region between giant impact generated satellites, which are largely intact remnants of the original impactor and those which form out of reaccreted disk material left over postimpact. The low albedo of Dysnomia leads us to marginally favor the intact impactor scenario. We find that Dysnomia has a density of <1.2 g cm−3, significantly lower than the 2.4 g cm−3 of Eris.

Design and Additive Manufacturing of a Continuous Servo Pneumatic Actuator.

Despite an emerging interest in soft and rigid pneumatic lightweight robots, the pneumatic rotary actuators available to date either are unsuitable for servo pneumatic applications or provide a limited angular range. This study describes the functional principle, design, and manufacturing of a servo pneumatic rotary actuator that is suitable for continuous rotary motion and positioning. It contains nine radially arranged linear bellows actuators with rollers that push forward a cam profile. Proportional valves and a rotary encoder are used to control the bellows pressures in relation to the rotation angle. Introducing freely programmable servo pneumatic commutation increases versatility and allows the number of mechanical components to be reduced in comparison to state-of-the-art designs. The actuator presented is designed to be manufacturable using a combination of standard components, selective laser sintering, elastomer molding with novel multi-part cores and basic tools. Having a diameter of 110 mm and a width of 41 mm, our prototype weighs less than 500 g, produces a torque of 0.53 Nm at 1 bar pressure and a static positioning accuracy of 0.31° with no limit of angular motion. By providing a description of design, basic kinematic equations, manufacturing techniques, and a proof of concept, we enable the reader to envision and explore future applications.

Dynamic analysis of a 5 MW Barge-type FOWT with two-mooring failure of wind-wave misalignment scenarios

A floating offshore wind turbine (FOWT) experiencing two mooring failure can substantially escalate the risk of persistent damage to the remaining moorings. Industry standards mandate that FOWTs must demonstrate the capability of maintaining self-sustainability even in the occurrence of dual mooring failure. Therefore, it is importance to investigate the dynamic response of wind turbines in the case of two mooring line failure. In this study, a novel coupling method of FAST and AQWA was used to analyze the dynamic response of a 5 MW FOWT installed on a barge platform when two mooring lines fail at the same corner. The time-domain response processes of rated and extreme sea conditions were simulated for different failure time intervals (0s, 60s, and 1500s), and the dynamic response of the platform and the change of mooring line tension at each stage are regularly explored. The results indicate that a shorter interval between two mooring line failures results in a more unstable FOWT state. The center of gravity of the wind turbine presents an irregular spiral trajectory, and the platform response exhibits varying characteristics at each stage of the failure process. The transient effect is smaller as the wind turbine approaches the motion limit state.