Rigid Shaft Research Articles

Comparative study of creep in a disk of rubber/copper fitted with rigid shaft

The article deals with the comparative study of creep analysis in a rotating disk made of rubber/copper material and fitted with rigid shaft. The effects of different pertinent parameters (i.e., angular speed and density) are considered for the rotating disk of rubber/steel material. The behaviour of creep stress/strain rate distribution, and density rise are investigated. From the obtained results, it is noticed that the radial stress requires a maximum value at the inner surface of the disk fitted with rigid shaft made of rubber material in comparison to the disk made of copper material. The strain rates must be decreased with increasing density parameter. Results have been discussed numerically and graphically.

A novel cytoprotective organ perfusion platform for reconstructing homeostasis of DCD liver while alleviating IRI injury

AbstractPump is a vital component for expelling the perfusate in small animal isolated organ normothermic machine perfusion (NMP) systems whose flexible structure and rhythmic contraction play a crucial role in maintaining perfusion system homeostasis. However, the continuous extrusion forming with the rigid stationary shaft of the peristaltic pumps can damage cells, leading to metabolic disorders and eventual dysfunction of transplanted organs. Here, we developed a novel biomimetic blood‐gas system (BBGs) for preventing cell damage. This system mimics the cardiac cycle and features an adjustable inspiratory‐to‐expiratory (IE) ratio to mitigate acidosis caused by continuous oxygen inhalation. In our study, adipose stem cells (ADSCs) were cultured within the circulatory system for 10 min, 2, and 4 h. Compared to the peristaltic pump, the BBGs significantly reduced cell apoptosis and morphological injury while enhancing cell proliferation and adhesion. Additionally, when the supernatant from ADSCs was introduced to LPS‐induced macrophages for 24 h, the BBGs group demonstrated a more pronounced anti‐inflammatory effect, characterized by reduced M1 macrophage expression. Besides, with isolated rat livers from donation after circulatory death (DCD) perfusion with ADSCs for 6 h by the BBGs, we detected fewer apoptotic cells and a reduced inflammatory response, evidenced by down‐regulated TNF‐α expression. The development of BBGs demonstrates the feasibility of recreating physiological liquid–gas circulation in vitro, offering an alternative platform for isolated organ perfusion, especially for applications involving cell therapy.

Interaction of a bush with a complex internal profile and a coated viscoelastic pipe worn on a rigid cylinder

Abstract The present study is devoted to obtaining an analytical solution to the contact problem for a rigid bush and a viscoelastic aging cylindrical coated tube mounted on a rigid shaft or cylinder. A feature of the formulation is the fact that the inner profile of the bush is described by a complex function, which introduces certain difficulties in numerical calculations. The article demonstrates how it is possible to simultaneously take into account both the rheological properties of the layers and the geometric features of the contacting bodies, so that the obtained analytical solution turns out to be effective in real numerical calculations. In the resulting analytical solution, the function describing the inner profile of the bush is included in a separate term. This makes it possible to use a small number of terms of an infinite functional series and at the same time obtain results with high accuracy.

An MRI-Conditional Flexible Endoscopic Robot with a Hydraulic Tendon-Driven Actuation System

This paper presents the conceptualization, mathematical modeling, and experimental validation of a magnetic resonance imaging (MRI)-conditional, flexible endoscopic robot for MRI-guided neurosurgery. The robotic assembly encompasses a straight rigid shaft, a tendon-driven steerable tip with two degrees of freedom, and a compact hybrid actuation system made of nonmagnetic modules. The robot’s small diameter, approximately 3 mm, allows for robot navigation through narrow cavities, such as nasal passages and the densely packed anatomy of the skull base. By filling the robot with deionized water, the MRI contrast of the robot can be improved, therefore enabling intra-operative tracking of the robot’s movement. In this paper, we present the design and fabrication process of the robotic system, kinematic analysis of the robot, and experimental studies to validate our model, characterize the robot, and test the feedback robot control. Furthermore, we demonstrate the MRI compatibility of the robot, along with the intra-operative tracking capability.

The Influence of Mechanical Deformation Consideration on the Results of the Calculation of the Vacuum Circuit Breaker Drive Shaft

One of the important directions of theoretical, computational and experimental research related to the improvement and development of new design elements of modern electrical devices, primarily medium voltage circuit breakers and contactors, is the study of not only electromagnetic, but also mechanical processes in these electrical devices. The paper is devoted to the creation and use of computational models for calculating mechanical forces and deformations of an absolutely rigid and real drive shaft of a medium voltage vacuum circuit breaker in static mode with the aim of quantitative comparison of the obtained numerical results. Calculation studies are performed using the finite element method. A comparative analysis of the calculation of mechanical stresses in the drive shaft of a vacuum circuit breaker in a static mode for an absolutely rigid and real shafts is carried out in this paper on the basis of the developed models. The obtained results of computer modeling are given in detail in tabular and graphic forms, including the shape of the deflection of the medium voltage vacuum circuit breaker shaft at the maximum stroke of the actuator of the electrical device under study. It has been demonstrated that the mechanical deformation of the shaft causes a decrease in contact drop and contact pressure forces, but with a correctly selected cross-section, these values are not critical and have little effect on the circuit breaker operation (about 20% and 7%, respectively). It is shown that as a result of shaft bending, additional axial forces appear in the supports, which significantly affect the choice of bearings according to the equivalent static load.

Calculations of static and dynamic processes in the synchronizing shaft of a medium-voltage vacuum switch during the turn-on process

An important direction of theoretical research of modern electrical devices, medium voltage switches and contactors is the study of mechanical processes that occur during their operation. First of all, this is due to sufficiently large forces and accelerations acting on the structural elements and the synchronizing shaft of such devices in the process of switching on. In the article, on the basis of developed mathematical models, calculations of mechanical processes in the synchronizing shaft of a vacuum switch in static and dynamic mode for an absolutely rigid and real shaft are performed and their comparative analysis is carried out. The results of computer modeling are obtained in tabular and graphical forms, which include data on static and dynamic deformations of the shaft, as well as mechanical forces in its supports. It is shown that the mechanical deformation of the shaft causes a decrease in contact drop and contact pressure forces, but with a correctly selected cross-section of the synchronizing shaft, these values slightly affect the operation of the switch itself (the decrease is about 20% and 7%, respectively). It is also shown that as a result of the bending of the shaft, additional axial forces appear in the supports compared to the simplified calculation, which significantly affect the choice of bearings according to the equivalent static load. The calculated dynamic forces, taking into account the masses of contacts and contact rods, exceed similar static forces by 1.3 times, which must also be taken into account when choosing bearings in which the synchronizing shaft is held.

Development of a new T-bar for the geotechnical centrifuge at TU Delft

An accurate estimation of undrained shear strength of clay seabed is important for interpreting lateral pile-soil interaction response. The cylindrical T-bar is a widely used site investigation tool for profiling the undrained strength (su) of soft soils. As such, a new miniature T-bar penetrometer is designed and fabricated at TU Delft for characterization of the undrained shear strength profile of clay layer in centrifuge models, and OCR profile can be then derived from undrained shear strength profile with known pre-consolidation stress level. The miniature T-bar penetrometer head is a cylinder of 5 mm in diameter and 20 mm in length and the miniature T-bar penetrometer head is connected with a rigid shaft (Figure 1(a)). The T-bar penetration resistance along the depth of clay sample can be obtained and further interpreted into the undrained shear strength profile.
 Rate of penetration is one of the key parameters that govern the drainage behaviour of soil response around the T-bar and the resulting penetration resistance. A very low rate of penetration leads to partial pore water dissipation and thus partial drainage condition. When a very large rate of penetration is applied, the fully undrained condition is achieved. However, the effect of T-bar penetration rate has not previously been fully examined for normally consolidated and over consolicated clay in the centrifuge. In this paper, the tip resistance profile of T-bar penetration tests under different rates of penetration is analyzed to obtain undrained shear strength profile of clay soils.
 A series of T-bar tests are conducted in both normally consolidated and slightly over consolidated clay samples at 100 g. The sample drainage state is tested by varying the rate of penetration from 0.01 mm/s to 5 mm/s. The results are interpreted by two methods: (i) the conventional method by converting the measured penetration resistance to soil strength using a single bearing factor, indicating a full-flow mechanism at failure [1]; and (ii) an approach considering soil buoyancy and a reduced bearing factor arising from the shallow failure mechanism, indicating the shallow correction procedure has a significant influence on the soil strength profile inferred from a T-bar penetrometer test [2]. The interpreted undrained shear strength profile provides soil property and OCR information for further monopile tests in the centrifuge, allowing a comprehensive study of the soil-structure interaction on soft soils.

Spherical Joint Actuator with Backstepping Sliding Mode Control for Robotic Manipulator Rigid-Flexible Coupling System

At present, the output shaft of a permanent magnet spherical actuator (PMSA) is a rigid structure, which has the problems of small load weight ratio and high energy consumption. It is difficult to meet the application requirements of lightweight, high speed, and low energy consumption. In this paper, a PMSA is proposed as the driving motor for the rigid-flexible coupling system (R-FCS) of the robotic manipulator, and a flexible mechanical arm is used to replace the rigid output shaft of the PMSA to connect the hand claw to form a spherical joint. Firstly, the partial differential dynamics model of the robotic manipulator in the coordinate system is established based on the Hamilton method, and the R-FCS is constructed according to the momentum conservation equation combined with the rigid axis dynamics model of the PMSA. Then, a backstepping sliding mode controller (BSMC) is designed to form a closed-loop control system by selecting an appropriate nonlinear gain function to estimate the unknown disturbances of the system, and the stability of the controller is guaranteed by the Lyapunov theory. Finally, the simulation and experimental results verify that the R-FCS can achieve better trajectory tracking and provide an effective driving method for robotic manipulator spherical joint.

Modeling and Disturbance Compensation Sliding Mode Control for Solar Array Drive Assembly System

In this study, a dynamic model of a solar array drive system that includes a pair of flexible solar arrays with a central rigid shaft and a permanent-magnet synchronous motor (PMSM) was developed, and a disturbance compensation sliding mode control (DCSMC) strategy was proposed to realize the speed smoothing and vibration suppression control of the system. The continuous nonlinear dynamic equation of the system was derived from Hamilton’s principle, and its linearized form was combined with the boundary conditions to obtain its natural frequency and global mode. The design of the DCSMC strategy was based on the solar array drive assembly (SADA) electromechanical dynamics model of the PMSM direct drive. An extended state observer (ESO) was used to estimate any system disturbances, and the signal was fed forward to sliding mode control (SMC) based on the varying gain saturation reaching law (VGSRL). To verify the validity of the model, its results were compared with those obtained using commercial finite element software. The numerical results showed that the SADA system with the DCSMC strategy outperformed the traditional proportional–integral (PI) control and SMC systems.

Safety Analysis in a Thermo–Mechanical Loaded Disk Made of Polymer Fitted with Rigid Shaft and Having Variable Thickness

Safety Analysis in a Thermo–Mechanical Loaded Disk Made of Polymer Fitted with Rigid Shaft and Having Variable Thickness

Development and validation of a flexible fetoscope for fetoscopic laser coagulation.

Fetoscopic laser coagulation for twin-to-twin transfusion syndrome is challenging for anterior placenta due to the rigidity of current tools. The capacity to keep entry port forces minimal is critical for this procedure, as is optimal coagulation distance and orientation. This work introduces technological tools to this end. A novel fetoscope is presented with a rigid shaft and a flexible steerable segment at the distal end. The steerable segment can bend up to 90[Formula: see text] even when loaded with a laser fiber. An artificial pneumatic muscle makes such acute bending possible while allowing for a low-weight and disposable device. The flexible fetoscope was validated in a custom-made phantom model to measure visual range and coagulation efficacy. The flexible fetoscope shows promising results when compared to a clinical rigid curved fetoscope to reach anterior targets. The new fetoscope was then evaluated in vivo (pregnant ewe) where it successfully coagulated placental vasculature. The flexible fetoscope improved the ability to achieve optimal coagulation angle and distance on anteriorly located targets. The fetoscope also showed the potential to lead fetoscopic laser coagulation and other fetal surgical procedures toward safer and more effective interventions.

Viscoplastic Flow in the Material of a Cylindrical Layer Suspended on a Rigid Shaft under the Conditions of Its Variable Rotation

Viscoplastic Flow in the Material of a Cylindrical Layer Suspended on a Rigid Shaft under the Conditions of Its Variable Rotation

Viscoplastic Flow in the Material of a Cylindrical Layer Suspended on a Rigid Shaft under the Conditions of Its Variable Rotation

The development of viscoplastic flow in the material of a cylindrical layer placed on a rigid cylindrical shaft and rotating with it around their common axis is calculated. Depending on the increasing speed of rotation up to the maximum, the place and time points of the beginning of the viscoplastic flow, the patterns of propagation of the flow area, the changing strains and stresses in the deformable material are determined. As a condition for viscoplastic flow, the corresponding generalization of the condition for maximum octahedral stresses is taken. For the purposes of testing the calculation programs, an exact solution of the problem of a steady viscoplastic flow of a material during rotation of a compound cylinder at a constant speed has been obtained.

Scope actuation system for articulated laparoscopes

BackgroundAn articulated laparoscope comprises a rigid shaft with an articulated distal end to change the viewing direction. The articulation provides improved navigation of the operating field in confined spaces. Furthermore, incorporation of an actuation system tends to enhance the control of an articulated laparoscope.MethodsA preliminary prototype of a scope actuation system to maneuver an off-the-shelf articulated laparoscope (EndoCAMaleon by Karl Storz, Germany) was developed. A user study was conducted to evaluate this prototype for the surgical paradigm of video-assisted thoracic surgery. In the study, the subjects maneuvered an articulated scope under two modes of operation: (a) actuated mode where an operating surgeon maneuvers the scope using the developed prototype and (b) manual mode where a surgical assistant directly maneuvers the scope. The actuated mode was further assessed for multiple configurations based on the orientation of the articulated scope at the incision.ResultsThe data show the actuated mode scored better than the manual mode on all the measured performance parameters including (a) total duration to visualize a marked region, (a) duration for which scope focus shifts outside a predefined visualization region, and (c) number of times for which scope focus shifts outside a predefined visualization region. Among the different configurations tested using the actuated mode, no significant difference was observed.ConclusionsThe proposed articulated scope actuation system facilitates better navigation of an operative field as compared to a human assistant. Secondly, irrespective of the orientation in which an articulated scope’s shaft is inserted through an incision, the proposed actuation system can navigate and visualize the operative field.

Follow-The-Leader Mechanisms in Medical Devices: A Review on Scientific and Patent Literature.

Conventional medical instruments are not capable of passing through tortuous anatomy as required for natural orifice transluminal endoscopic surgery due to their rigid shaft designs. Nevertheless, developments in minimally invasive surgery are pushing medical devices to become more dexterous. Amongst devices with controllable flexibility, so-called Follow-The-Leader (FTL) devices possess motion capabilities to pass through confined spaces without interacting with anatomical structures. The goal of this literature study is to provide a comprehensive overview of medical devices with FTL motion. A scientific and patent literature search was performed in five databases (Scopus, PubMed, Web of Science, IEEExplore, Espacenet). Keywords were used to isolate FTL behavior in devices with medical applications. Ultimately, 35 unique devices were reviewed and categorized. Devices were allocated according to their design strategies to obtain the three fundamental sub-functions of FTL motion: steering, (controlling the leader/end-effector orientation), propagation, (advancing the device along a specific path), and conservation (memorizing the shape of the path taken by the device). A comparative analysis of the devices was carried out, showing the commonly used design choices for each sub-function and the different combinations. The advantages and disadvantages of the design aspects and an overview of their performance were provided. Devices that were initially assessed as ineligible were considered in a possible medical context or presented with FTL potential, broadening the classification. This review could aid in the development of a new generation of FTL devices by providing a comprehensive overview of the current solutions and stimulating the search for new ones.

Scaling‐up of an Insect Cell‐based Virus Production Process in a Novel Single‐use Bioreactor with Flexible Agitation

AbstractA novel single‐use bioreactor was recently introduced to the market that is agitated by impellers suspended on flexible ropes rather than a rigid shaft. Computational fluid dynamics (CFD) models were created and validated by particle image velocimetry (PIV) to predict the bioreactor's fluid flow and mixing. The data were then used to scale‐up a Spodoptera frugiperda, subclone 9 (Sf9) insect cell‐based production of recombinant adeno‐associated virus (AAV) from a benchtop glass bioreactor to the single‐use system with 30 L working volume. This viral vector is one of the most commonly used in gene therapies. The volumetric power input was kept constant while maintaining reasonable mixing times and shear stresses between the scales. Peak cell densities of up to 7.2 × 106 cells mL−1 and maximum virus titers of 1.7 × 1011 vg mL−1 were achieved. Similar cell growth and metabolite profiles further proved the successful process transfer between the two geometrically non‐similar bioreactor systems. The pilot bioreactor yielded between 3.3 and 4.8 × 1015 vg that, depending on the therapy, can be sufficient for the treatment of a single patient.

Modeling for transient and modal analysis of a flexible beam attached to a rigid shaft undergoing free rotational motion considering two-way inertia coupling

A novel linear dynamic model is proposed for the transient and modal analyses of a flexible beam attached to a rigid shaft undergoing free rotational motion. For the proposed modeling of the shaft-beam coupled system, the shaft angular speed is modeled as the sum of a reference angular speed and generalized speed instead of the time derivative of the shaft rotation angle which has traditionally been used for the shaft dynamic modeling. Thus, the shaft-beam coupled system is linearized around the reference angular speed for deriving the equations of motion. With the proposed modeling method, the two-way inertia coupling effect between the rigid shaft and flexible beam can be considered accurately. The transient responses obtained with the proposed model are in good agreement with those obtained with a nonlinear dynamic analysis program. Moreover, due to the linearity of the proposed dynamic model, modal characteristics of the shaft-beam coupled system can be also accurately identified.

Virtual Shaft Control of DFIG-Based Wind Turbines for Power Oscillation Suppression

The flexible shaft coupled to the synchronous generator (SG) is critical for the doubly-fed induction generators (DFIG) based wind turbines to improve the ability to suppress system power oscillations. The rigid shaft coupling relationship between the DFIG and SG is analyzed first under the current virtual synchronous generator (VSG) control. To give the power system a vibrational degree of freedom, a novel virtual shaft is added to the VSG emulated by the DFIG-based wind turbine. The power system's two-degree-of-freedom (TDOF) coupled motion model with VSG is then established. The virtual shaft coupling adapted to a DFIG is designed using anti-resonance theory, and the amplitude-frequency characteristic of the TDOF power system is analyzed. With the additional stiffness of the virtual shaft, the power support functions of the VSG, including inertia and damping, are integrated by optimizing the oscillation amplitude at two fixed points in the frequency domain. Finally, on a controller hardware-in-the-loop platform, a typical power system with a high penetration of wind power generation is simulated. The test results demonstrate that by employing virtual shaft coupling, it is possible to suppress system frequency variation and rotor angle oscillation during transient events, significantly improving the reliability of the power support provided by wind turbines.

Design and Simulation of the Controlled Failure of Custom-Built Rigid Shaft Coupling

Design and Simulation of the Controlled Failure of Custom-Built Rigid Shaft Coupling

Динамическая диагностическая 3D-модель шпинделя шлифовального станка. Гибридный способ моделирования

We use a grinding machine spindle as an example to consider a hybrid (numerical and analytical) method of simulating a rotor with a rigid shaft. The paper describes a spatial dynamic model of the rotor constructed via this method that takes into account support stiffness asymmetry. We show that introducing support stiffness asymmetry allows the spatial simulation to explain a number of physical phenomena, including spectrum frequency splitting, which are fundamentally impossible to explain when using flat axially symmetric models.