Radial Disturbance Research Articles

Visual depiction and numerical characterization of intricate flow in triply periodic minimal surface foams

Benefiting from the structural specificity and programmability, the bioinspired triply periodic minimal surfaces (TPMSs) bring excellent physicochemical properties that are distinct from conventional topologies. Especially with the rapid development of additive manufacturing and high-performance computing capacities, function-oriented design and synthesis of smart TPMS materials or devices have become feasible. Therefore, understanding the flow characterizations induced by TPMS foams is of remarkable importance to the successful design and practical operation. However, the in-depth studies and theoretical guidance on the relationship between structure and flow characterizations of TPMS foams are still limited. In this study, an Eulerian and Lagrangian coupled model is developed to investigate the internal flow behaviors and flow regime transition mechanism from creeping to inertial flow in four representative TPMS foams. The simulation accuracy is then validated by a high-resolution pore-scale flow field observation. Results show that the flow morphology and pressure drop characteristics are highly influenced by TPMS geometry and Re. Among which, Schwarz Diamond (D), Schoen Gyroid (G), and Fischer-Koch S (S) foams are more susceptible to radial flow disturbance, while Schoen inverted Weissenberg periodic foam to axial flow disturbance. In addition, higher porosities delay the transition to transitional regime of the flow. This work establishes firm theoretical and methodological foundations for the customization and intelligent development of bioinspired TPMS foam materials in broad fluidic applications.

Backstepping control based on adaptive neural network and disturbance observer for reconfigurable variable stiffness actuator

Reconfigurable variable stiffness actuator (RVSA) has attracted increasing attention in robotics due to its safety, compliance, and robustness. However, the control of the RVSA is challenging due to nonlinear factors such as high-order nonlinear dynamic, model uncertainties, time-varying model parameters, and disturbances. In this paper, firstly, a lightweight RVSA structure with both passive and active nonlinear variable stiffness characteristic is developed. Secondly, a dynamic surface backstepping control method based on a radial basis neural network and disturbance observer (DSBC-RBFNN-DOB) is proposed to achieve position control of the lightweight RVSA with matched and unmatched uncertainties. To address solve the “complexity explosion” and noise problems in traditional backstepping control, the dynamic surface backstepping control (DSBC) method is used to design the controller. Then, a method based on radial basis neural network (RBFNN) and disturbance observer (DOB) are used to compensate for the matched and unmatched uncertainties in the link and motor. In this method, the matched uncertainties are compensated using RBFNN, and the DOB is integrated to compensate RBFNN approximation errors and unmatched uncertainties. Through Lyapunov stability analysis, the semi-global boundedness of the controller is proven. Finally, the proposed method is simulated and actually implemented, verifying the effectiveness of the method. Simulation and experimental results show that the root mean square error (RMSE) of the proposed method is only 0.97277° and 0.6418°, respectively. Compared with PID, DSBC, and DSBC-RBFNN, the error reduction percentages in simulation (experiment) are 85.6 % (88.9 %), 49.4 % (88.4 %) and 36.1 % (80.0 %) respectively.

Accurate Modeling and Control System Simulation of Bearingless Brushless DC Motor

Background: Precise modeling and control system design are the basis of highperformance control of dual-winding bearingless brushless DC motors (BL-BLDCM), and the existing research is relatively few. Objective: This paper takes 12-slot/tooth 4-pole BL-BLDCM as the research object, establishes a set of a detailed mathematical model, and designs the control system of BL-BLDCM. Methods: Firstly, the structure of BL-BLDCM and the radial suspension force generation principle were introduced. Secondly, a set of an accurate mathematical model of BL-BLDCM was established which was finally verified by static and dynamic finite element method (FEM), the motor body model and control system were built by Matlab/Simulink software, and the simulation analysis of control performance was completed. Results: The established mathematical model is correct. The BL-BLDCM can generate stable electromagnetic torque and radial magnetic suspension force, and the control system has strong ability of resisting load torque disturbance and radial force load disturbance. Conclusion: It has certain reference significance for the accurate modeling and control system design of later BL-BLDCM.

Decentralized fault-tolerant control of modular robot manipulators with actuator saturation: neural adaptive integral terminal sliding mode-based control approach

A novel neural adaptive integral terminal sliding mode control for decentralized fault-tolerant control strategy, including the integral terminal sliding mode surface, the nonlinear disturbance observer, the radial basis neural network and robust controller, is presented in this paper to achieve fault-tolerant control of modular robot manipulators. First, the integral terminal sliding mode is designed for the fault-tolerant controller. Then, to boost the performance of the controlled system, the radial basis neural network and disturbance observer are introduced to approximate the nonlinear terms and disturbances. The reconstructed approximate uncertainty term is applied as compensation. Next, the super-twisting technique is employed to compensate for estimation errors to ensure stability. In addition, for the actuator saturation problem, the radial basis function neural network-based compensation control is proposed. Finally, the stability of the closed-loop robotic system is demonstrated based on Lyapunov theory. Computer simulations verified the efficiency and advantages of the presented approach.

The superficial branch of the radial nerve and sensory disturbance in the radial forearm flap donor-site

IntroductionSensory disturbance due to injury of the superficial branch of the radial nerve (SBRN) is a donor-site morbidity of the radial forearm (RF) flap. The relationship between the SBRN preservation method and the post-operative sensation at the flap donor-site was retrospectively investigated. MethodsWe included 39 patients who underwent head and neck reconstruction with a free RF flap at Hyogo Cancer Center between April 2014 and March 2018. The patients were classified into the following three groups according to the SBRN preservation method: group 1, zero preservation, excision of the entire SBRN; group 2, main trunk preservation, excision of all branches except the main trunk of the SBRN; and group 3, complete preservation, preservation of the entire SBRN. Objective sensations and subjective symptoms at the flap donor-site were analyzed. ResultsThe mean objective sensory scores were 3.18, 2.97, and 1.78 in groups 1, 2, and 3, respectively. Differences between groups 1 and 3 and between groups 2 and 3 were significant (p = 0.0035 and p = 0.037, respectively). The mean subjective symptom scores were 2.40, 1.33, and 1.40 in groups 1, 2, and 3, respectively. Differences between groups 1 and 2, and between groups 1 and 3 were significant (p = 0.032 and p = 0.019, respectively). ConclusionsZero preservation method had a higher risk of subjective symptoms and objective hypoesthesia development at the flap donor-site than the complete preservation method. Despite inevitable objective hypoesthesia, the main trunk preservation prevented the development of subjective symptoms. Complete preservation is optimal for RF flap harvest; however, in case of perforator crossing, main trunk preservation is another option.

The Types and Equations of Diesel Spray Angle Curve under Cloud Cavitation and Hydraulic Flip

For the five types of angle profile curve and possible low spray angles in the unsteady state of diesel spray, all the possible corresponding conditions are given and their curve regression equations can be established by experiments and deep learning methods proposed in this paper. The initial pressure rises sharply with the axial velocity difference significant so that we can infer the relatively large radial disturbance is also as an important reason for cloud cavitation formation. At the moment it is difficult to form wall-adherent cavitation and further develop into supercavitation and hydraulic flip and the too large spray angle is formed in the non-steady phase. And the closer to the maximum position the needle valve is, the slower the velocity increases. So there is a significant decline in the later period, which is caused by gradual cloud cavitation weakening. Especially after entering the steady phase, both angle and its variation range are much smaller, indicating that it is mainly affected by the disturbed flow due to the in-nozzle gas under hydraulic flip developing from wall-adherent cavitation. Besides, the experiment the results of cross-sectional, spatial, and three-dimensional detailed distribution under cloud cavitation should also be further developed through X-ray.

Lateral dynamics of a monopile partially embedded in layered saturated soil with radial disturbance

A bidirectional transfer matrix method is presented to investigate the impedances of a laterally loaded monopile partially embedded in layered saturated soil with radial disturbance. To characterize the radial variation of soil properties induced by construction excitations or cyclic lateral excitations, the radial transfer matrix of the saturated soil is developed to determine the horizontal resistance of soil to the pile shaft based on Biot's theory. Lateral, rocking and lateral-rocking coupled impedances at the head of the monopile are obtained by solving the differential equations for transverse vibration of the pile shaft based on the Timoshenko beam theory, combined with an axial transfer matrix to treat the layered property of soil along the partially embedded monopile. The proposed model is validated by comparing it with some existing results. The theoretical rigour and broad engineering applicability of the present model are highlighted by a series of parametric analyses for the influences of soil and pile properties on the impedances of the laterally loaded monopile.

Active Disturbance Rejection and Ripple Suppression Control Strategy With Model Compensation of Single-Winding Bearingless Flux-Switching Permanent Magnet Motor

The speed and radial displacement of the rotor have the obvious ripples due to the strong coupling between torque and suspension force of a single-winding bearingless flux-switching permanent magnet motor, and the traditional PID/PI controller is difficult to suppress the disturbance of the unbalanced magnetic force. A linear active disturbance rejection control method based on model compensation is proposed in this article. First, the topology and operation principle of the motor are described, and then the dynamic model of the rotor and flux linkage model of the motor are analyzed. Accordingly, the integral-series standard mathematical models of the displacement and speed are deduced, and then the mathematical expressions of the controller gain and radial disturbance are obtained. Second, the linear extended state observer with known model perturbation information and the linear feedback control law are designed, and the parameters tuning method is given. Finally, the simulation and experimental results verified that the proposed method can significantly reduce the rotor displacement and torque ripples, and it has better disturbance rejection performance than the traditional PID/PI control method in the same stability margin.

Generation of streamwise helical vortex loops via successive reconnections in early pipe transition

We extend the vortex-surface field (VSF), a Lagrangian-based structure identification method, to investigate the vortex reconnection in temporally evolving transitional pipe flows. In the direct numerical simulation (DNS) of round pipe flows, a radial wave-like velocity disturbance is imposed on the inlet region to trigger the transition. The VSF isosurfaces are vortex surfaces composed of vortex lines, and they are concentric tubes with different wall distances at the initial time. The VSF evolution is calculated by the two-time method based on the DNS velocity field, and it is effective to identify the vortex reconnection. In the early stage of transition, the vortex surfaces are first corrugated with streamwise elongated bulges. The escalation and descent of vortex surfaces characterize the generation of high- and low-speed streaks and streamwise vortex pairs, along with the surge of the wall-friction coefficient. The resultant highly coiled and stretched vortex loops then reconnect with each other under the viscous cancelation mechanism. Subsequently, successive vortex reconnections occur via a “greedy snake” mechanism. The streamwise vortex loops consecutively capture the secondary vortex rings pinched off with self-reconnection, forming long helical vortex loops spanning over ten pipe radii in the streamwise direction. Finally, the Kelvin–Helmholtz instability of the shear layer at the trailing edge breaks down the streamwise helical vortex loops into turbulent spots.

Radial disturbance compensation device of cylindrical cantilever beam using embedded piezoelectric ceramics with bending mode

To eliminate the disturbance in all-radial directions of the circular cross-section cantilever beam, this study proposes an embedded piezo-compensator (EPC). Different from cantilever beams with rectangular cross-sections, cantilever beams with circular cross-sections have isotropic stiffness in all-radial directions. This feature makes cylindrical cantilever beams have been widely used in various mechanical structures. However, the current trend towards more compact and more lightweight design in machinery poses a huge challenge to its anti-disturbance ability. Most of the current studies are based on rectangular cantilevers and eliminate the disturbances in one direction. Research on eliminating the disturbances in whole radial direction is rarely reported. Therefore, based on the characteristics of the circular cross-section and piezoelectric materials, an EPC is proposed. The structure and output model of the proposed device are presented and established. Experimental results show that the proposed device can reduce the disturbance by more than 90% in the frequency range from 0 Hz to 600 Hz. At 1000 Hz, it can still reduce disturbance by 69%. With this method, disturbance compensation device can be deployed on the cylindrical cantilever without significant modifications to the original structure, which expands the application in size-sensitive scenarios.

Observer-based incremental backstepping sliding-mode fault-tolerant control for blended-wing-body aircrafts

This paper presents an adaptive incremental nonlinear backstepping sliding-mode (INBSM) controller, for fault tolerant tracking control of a blended wing body (BWB) aircraft with unknown disturbances and actuator faults. The INBSM controller is based on a nonlinear dynamics model of the BWB aircraft. In addition, a radial basis function neural network disturbance observer (RBF-NNDO) is proposed to enhance the disturbance attenuation ability. A fault estimator is suggested to improve actuator fault tolerant control level. The closed-loop control system of the BWB aircraft is proved to be globally asymptotically stable using Lyapunov theory. Simulations of the combined NNDO-INBSM controller are presented and compared with both the INBSM design and an adaptive fuzzy controller. The results demonstrate an improved capability of the NNDO-INBSM control for the BWB aircraft to execute realistic attitude tracking missions, even in the presence of center of gravity movement, unknown disturbances, model uncertainties and actuator faults.

Anti‐disturbance adaptive sampled‐data observers for a class of nonlinear systems with unknown hysteresis

AbstractIn this article, based on radial basis function neural network (RBFNN) and disturbance estimator (DE), an adaptive sampled‐data observer design scheme is proposed for a class of nonlinear systems with unknown Prandtl–Ishlinskii (PI) hysteresis and unknown multiple disturbances. To begin with, we investigate a class of sampled‐data nonlinear systems and present corresponding sufficient conditions ensuring ultimate uniform boundedness (UUB). Subsequently, a sampled‐data observer and a DE are designed to estimate the unknown states and compounded disturbances, respectively. Additionally, the unknown hysteresis and the unknown unmatched disturbances are approximated by RBFNNs. Meanwhile, we also give the learning laws of the weights of RBFNNs. The estimation errors of the states and the weights are verified to be UUB in the light of the obtained sufficient conditions and a special constructing Lyapunov–Krasovskii function. Finally, the effectiveness of the proposed design method is verified by numerical simulations.

Synchronous Control with Heartbeat in a Magnetically Levitated Centrifugal Blood Pump by Estimating a Pump Flow Rate with a Radial Disturbance Observer–Validation in a Simple Mock Circulation Loop–

The purpose of this research was to propose synchronous control of the pump flow rate with the natural heart by estimating heartbeat and estimated a pump flow rate without using additional sensors. In this study, we have developed a disturbance observer to estimate heartbeat for estimating the radial thrust, which is the force generating on the impeller by the blood flow in the blood pump. The pump flow rate was also estimated from the radial thrust by experimentally determining the relationship between the pump flow rate and the radial thrust. The validation test was conducted using a simple mock circulation loop, and the heartbeat and the pump flow rate were successfully estimated by the proposed method. Our results concluded that using the heartbeat and pump flow rate estimation system proposed in this study enabled synchronous control with simulated natural heart in a simple mock circulation loop.

Variable Bandwidth Adaptive Course Keeping Control Strategy for Unmanned Surface Vehicle

This paper proposes a new and original course keeping control strategy for an unmanned surface vehicle in the presence of modeling error, external disturbance and input saturation. The trajectory linearization control method is used as the basic algorithm to design the course keeping strategy, and the radial basis function neural network and disturbance observer are used to compensate modeling error and external disturbance respectively to enhance the robustness of the control system. Moreover, a robust term is used to compensate various compensation errors to further improve the robustness of the system. In addition, hyperbolic tangent function and Nussbaum function are hired to deal with the potential input saturation problem, and the neural shunting model is adopted to avoid the computational explosion caused by the derivation of virtual control law. Taking the above facts into account will help to further realize engineering practice. Finally, the control strategy proposed in this paper is compared with the classical proportional–integral–derivative control strategy. The simulation results show that the course control results of the proposed control strategy are more robust than proportional–integral–derivative control, regardless of whether the external disturbance is weak or strong.

Experimental and Theoretical Study of the Cavity Growth of Spherical Fragment Penetrating Liquid-Filled Container

Abstract When high-velocity penetrator impacts and penetrates a liquid-filled container such as an aircraft fuel tank, the hydrodynamic ram (HRAM) event occurs. This process could be roughly divided into four phases, each of which could cause different degrees of damage to the liquid-filled container or the surrounding equipment. Spherical fragment impacting tests of different velocities were performed on two sizes of liquid-filled containers to investigate the effect of boundary constraints on cavity growth. The velocity range in the experiment was from 600 m/s to 1400 m/s. Through theoretical analysis and experimental results, it is found that the radial disturbance range of the cavity is not constant in different containers and under different impact velocities. An improved method is presented to modeling the cavity growth in the drag-cavity phases of HRAM events. The approach quantitatively describes the radial disturbance range of the cavity and is appropriate for the calculation of the cavity growth in HRAM. Moreover, the effect of liquid type on cavity growth is studied theoretically. When the fragment velocity is less than Mach 0.5, the length and radius of the cavity are mainly affected by the density of the liquid. When the fragment velocity exceeds Mach 0.5, the characteristics of cavity shape are mainly affected by the acoustic velocity in the liquid.

Dendroecological investigation of red-cockaded woodpecker cavity tree selection in endangered longleaf pine forests

Old-growth longleaf pine (Pinus palustris) is a keystone/foundation species for 29 threatened or endangered species in the Coastal Plain of the southeastern United States. The endangered red-cockaded woodpecker (Dryobates borealis; RCW) and endangered longleaf pine have an established ecological association. Here, we explore differences in climate/growth response and radial growth disturbance events in trees with RCW cavities compared to non-cavity trees in the Sandhills Gameland Reserve in North Carolina, USA. Using standard dendrochronological techniques, we collected and analyzed core samples from trees selected by RCW for their cavities (RCWC) and adjacent control trees (RCWCo) that had no visible cavity. We developed RCWC and RCWCo tree-ring chronologies that allowed us to examine if climate vulnerability is a component of the RCW selection process for their nests. Specifically, we investigated climate/growth responses, radial growth suppressions, and physical characteristics of both tree types through a comparison of tree age, latewood radial growth measurements, and number of resin ducts. For long-term climate response (1910–2018), we found no significant differences between RCWC and RCWCo trees. However, we identified temporal differences in climate/growth relationships between RCWC and RCWCo as well as significant differences in the number of suppression events and spatially-grouped suppression events. For tree physiology, we found more resin ducts during 1950–2018 in RCWC trees. Our dendroecological-based investigation examines multiple factors in addressing the question of why RCWs select specific longleaf pine trees for cavities, which may help improve conservation efforts for RCW and longleaf pine.

Radial Neck Fracture With 180° Rotational Displacement in Pediatrics: A Case Report of a 6-Year-Old Child

Introduction: Radial neck fracture is one of the rare traumas in the upper extremity among the children accounting for 5%-10% of the pediatric elbow injuries. The valgus strain-induced radial neck displacement often ranges from 10° to 90. Rotational displacement with 180° rotation is very rare. Case Presentation: In this case report, we present a 6-year-old child who had radial neck fracture with 180 rotation and joint surface tilt toward the distal direction after falling on her outstretched hand. The close reduction was conducted under the fluoroscopic guide and the radial neck-shaft was restored with 15 angulation. The elbow was immobilized by a long forearm cast for 3 weeks. Based on conventional radiography taken after 3 weeks, a complete union was achieved. Six-month follow-up showed no radial growth disturbance and radial head avascular necrosis. Conclusions: The radial head could be displaced in the form of 180° rotation during the radial neck fracture. In this regard, careful attention to the joint surface is important to minimize the lateral displacements or angulation and to avoid any misdiagnosis. The closed reduction was a successful treatment and caused no complications.

High-frequency disturbance force suppression mechanism of a flywheel equipped with a flexible dynamic vibration absorber

Flywheels generate speed-related disturbances and induce micro-vibrations that influence the performance of high-sensitivity instruments on board. This study addresses dynamic modeling and disturbance force suppression of the flywheels due to its inherent characteristic structural modes. The disturbance force transmission of a rotating flywheel due to a unit radial force applied at the rim of the wheel body is reported using the three-dimensional finite element method and frequency response function–based substructuring method. The characteristic structural modes for the radial and axial disturbance forces are identified. The axial deformation–dominated flapping mode and the radial deformation–dominated transverse mode will contribute most to the axial and radial disturbance forces, respectively. A flexible ring structure, which is rested on the arms of the wheel body through independent viscoelastic pads and simultaneously in contact with the inner rim of the wheel body by independent resilient cushion members, is proposed to function as a damped dynamic vibration absorber. The modes of the dynamic vibration absorber and the modes of the flywheel equipped with the dynamic vibration absorber are analyzed. It is shown that the dynamic vibration absorber is effective to suppress both the radial and axial disturbance forces at the characteristic structural modes under different rotational speeds, provided that the loss factor of the complex elastic modulus for the viscoelastic pads is larger than 0.2 and the proportional damping constant for the stiffness matrix is larger than 6 Ns/m. Experimental analyses are conducted on a flywheel with a well-designed dynamic vibration absorber to validate the theoretical findings. Modal tests and disturbance force measurements are carried out for the flywheel with/without the dynamic vibration absorber. It is shown that the identified characteristic structural modes will contribute remarkable peaks for the radial and axial disturbance forces. The proposed dynamic vibration absorber is capable to suppress the high-frequency disturbance forces efficiently under different rotational speeds.

Long-term Outcomes Following Vickers Ligament Release and Growth Modulation for the Treatment of Madelung Deformity.

Madelung deformity arises from a partial distal radial growth disturbance in combination with an abnormal hypertrophic ligament spanning the volar radius and carpus, termed, the Vickers ligament. The purpose of this study is to report long-term clinical and radiographic outcomes following Vickers ligament release and distal radial physiolysis in a population of skeletally immature patients with symptomatic Madelung deformity. Medical records were retrospectively reviewed of patients with Madelung deformity surgically treated between 1994 and 2005. All eligible patients who underwent a Vickers ligament release and distal radial physiolysis were contacted and invited to return to the clinic for follow-up. Six patients (8 wrists) with Madelung deformity underwent Vickers ligament release and distal radial physiolysis. All were white females with a mean age at initial presentation of 11.4 years (10 to 12.8 y). Mean age at the time of initial surgery was 12.0 years (10.0 to 14.5 y). The median follow-up time was 10.6 years (5.8 to 21.9 y) and the average age at last follow-up was 23.1 years (17.5 to 32.2 y). Pain alone or in combination with concerns for deformity was the chief complaint in 6 of 8 of the wrists. At 1 year of clinical follow-up, 7 of 8 wrists were reported to be pain-free, and 6 of the 8 were noted to be completely pain-free at last follow-up. Motion in flexion, extension, pronation, supination, radial, or ulnar deviation was similar between the preoperative status and long-term follow-up. The average preoperative ulnar tilt was 35.1 degrees (SD: 8.5 degrees), average preoperative lunate subsidence was 1.9 degrees (SD: 1.8 degrees), and average preoperative palmar carpal displacement was 21.9 degrees (SD: 2.9 degrees). At the final follow-up, there was a large progression in lunate subsidence, but minimal change in ulnar tilt and palmar carpal displacement. At last clinical follow-up, 2 of the 6 patients had undergone a subsequent procedure including 1 radial dome osteotomy and 1 ulnar shortening osteotomy. In the skeletally immature patient population with Madelung deformity with growth potential remaining, distal radial physiolysis and Vickers ligament release is associated with relief of pain, preservation of motion, and, a reasonable rate of reoperation. This was a therapeutic study. Level II.

GYMNAST’S WRIST: A RETROSPECTIVE ANALYSIS OF DESCRIPTIVE EPIDEMIOLOGY, CLINICAL & RADIOLOGIC FEATURES, TREATMENT & OUTCOMES

Background:Distal radial physeal stress syndrome, or ‘gymnast’s wrist’ (GW), refers to an overuse condition of the distal radial physis, resulting from repetitive compressive loading and shear forc...