Coaxial Shafts Research Articles

The burden of cardiovascular disease in South Asia: the need for effective treatment

Dear Ma'am, Cardiovascular disease (CVD) is rapidly becoming the leading cause of death worldwide (1). According to global health projections, it will remain the number one cause of death in 2030. The Asian region has been shown to have a higher cardiovascular disease burden than Western countries, and most of this burden is borne by economically disadvantaged people mainly located in South Asian regions such as Pakistan. (1). A large-scale survey conducted in 53 cities in Punjab, Pakistan, found that 17.5% of the population suffered from cardiovascular disease (2). Mechanical thrombectomy is a minimally-invasive procedure where a specialized interventional radiologist utilizes specific equipment to remove a blood clot from an artery in a patient's body. This procedure treats arterial blockages caused by blood clots such as Deep Vein Thrombosis (DVT), Ischemic Stroke, etc (3). MegaVac, a part of mechanical thrombectomy, is the newest technique for the removal of blood clots from arteries. It is an invasive procedure that ensures the complete removal of clots from the occluded artery. The biggest advantage of this technique over typical clot removal is that it prevents embolus formation, which can occlude smaller arteries. The MegaVac Thrombectomy System is an intravascular mechanical thrombectomy and aspiration device with a single use that includes a thrombowire with an embolectomy component. A distal silicone-coated nitinol braid used in the SafeSealTM technology of the MegaVac Catheter swells to momentarily obstruct antegrade blood flow. The braid is expanded by the inner and outer coaxial shafts of the catheter body, briefly occluding the channel and enabling aspiration. SafeSeal funnel is activated by the assembly of the proximal handle. A nitinol embolectomy component that is part of the thrombowire can be used to draw material in the direction of the MegaVac catheter when it is inflated by the proximal actuation handle (4). Thrombectomy is a common and effective procedure for clot removal but in Pakistan thrombectomy is not as common compared to developed countries, primarily due to two reasons. First, Mechanical thrombectomy is exclusively available in four hospitals nationwide, with only one public hospital in Lahore providing this procedure (5). Second, it is an expensive procedure that ranges from 1700$ to 5000$ depending on the severity of the patient and the complexity of the procedure. Health Departments of Pakistan should provide this facility in more public hospitals so it becomes accessible to more people.

Motion Modeling of a 5-Axis Delta Robot with Telescopic Shafts

Abstract This paper deals with motion modeling of a 5-axis industrial Delta robot. The robot has extra rotational two degrees-of-freedom (DoF) realized with a wrist arm driven through two co-axial telescopic shafts as compared to the basic 3-DoF Delta robot. The kinematic model is derived with fully symbolic Jacobian matrices. Using the derived Jacobians, a novel simplified dynamic model is proposed based on the virtual work principle and the trajectory dependent artificial mass distribution. As compared to the existing literature, the proposed dynamic model does not require Lagrangian multiplier calculation or recursive and parallel computing so that it provides advantage for model-based control design. Also a linear regression model is provided to identify the dynamic parameters. The presented models are suitable to be employed for basic Delta and the extended Delta robots with parallel telescopic shafts as well. The derived models are verified through a Simulink model where the 3D CAD files of robot bodies having the information of real dimensions, masses and moments of inertia are used. The adequate agreement of the proposed dynamic model with the simulation results is illustrated via performing three different generated trajectory profiles. We also demonstrate the better accuracy of the proposed dynamic model as compared to a simplified and widely employed model for basic 3-DoF Delta robot. The simulation model is shared online to serve as a research and test platform for performing tasks such as motion planning, model prototyping, and control design.

Physical model test and parametric optimization of a hydroelectric generating system with a coaxial shaft surge tank

The novel structure of the surge tank is often designed in hydropower stations, for example, the Coaxial Shaft Surge Tank (CSST). Reasonable mathematical modeling and physical model verification are effective methods in dealing with novel structure tanks. This study aims to analyze the influence of geometric and hydraulic parameters on the hydraulic characteristics of the Hydroelectric Generating Systems (HGS) with CSST in the transient process. First, the mathematical model of CSST and the physical model of HGS with a geometric scale of 42.33 are established. The correctness of the mathematical model is verified by the physical model test. Second, an evaluation method is proposed to optimize the specific transient parameters of HGS. The results show that the sensitivity coefficient of the diversion tunnel diameter to the highest surge in CSST is 6.09, and the impedance hole coefficient φ of CSST to the maximum water hammer pressure of the spiral casing reaches 13.47. The results also indicate that changing the diameter of the penstock can adjust the maximum water hammer pressure while keeping the surge wave in CSST unchanged. This research provides design guidance and a theoretical basis to design HGS and improve its operational safety.

Physical Model Test and Parametric Optimization of a Hydroelectric Generating System with a Coaxial Shaft Surge Tank

Physical Model Test and Parametric Optimization of a Hydroelectric Generating System with a Coaxial Shaft Surge Tank

Multi-Axis Electric Stepper Motor

Multi-axis stepper motors offer a compact solution to actuate multiple degrees of freedom in a mechanical system by a single device. This research presents an electric stepper motor with three coaxial shafts driven by a single stator. The motor dimensions are 42 × 42 × 44 mm$^3$ (excluding output shafts), its mass is 0.326 kg and it includes three rotors of height 7 mm and different number of teeth. The maximum torque for one rotor at low speed and 1 A current is 0.10 N m, which is comparable to that of a conventional stepper motor with similar rotor size. When multiple rotors are driven simultaneously, then the total power has to be distributed over the three rotors, resulting in 42% lower torque on average. The maximum no-load speed is 4000 revolutions per minute. The coaxial output shaft configuration poses significant challenges but also unique opportunities in actuating multiple joints of a robotic system. In many applications, the mechanical design can be redesigned to make effective use of the multi-motor design. An example of a three-DOF robot arm is demonstrated that can be efficiently driven by the proposed motor.

Active fault-tolerant control system for a swash mass helicopter using back-stepping approach

In this article, an active fault-tolerant control system is designed and analyzed for a new model structure of unmanned aerial vehicles, which is referred to a swash mass helicopter. It consists of a double-blade coaxial shaft rotor for generating the necessary thrust and four masses that are located on the main body structure to maneuver the helicopter. The translational and rotational subsystems of the helicopter are highly coupled. Therefore, change of coordinate and feedback linearization methodologies are applied to address the problem and achieve the canonical form of the model. Next, actuator fault as a loss of effectiveness and bias faults are modeled for the dynamic. The main contribution of this article is to design an active fault-tolerant control system based on back-stepping and T-S fuzzy estimation methods for the swash mass helicopter which has never been designed in the last decades. T-S fuzzy methodology is responsible for obtaining the estimated value of the actuator faults during the flight. The Lyapunov theory illustrates that the proposed control strategy can stabilize the system despite the actuator’s fault. The simulation results show the effectiveness of the proposed scheme compared with another method.

THE EFFECT OF BLADE PROFILE ON THE PERFORMANCE OF A SIDE CHANNEL PUMP

This article presents the results of a numerical modeling of a steady turbulent flow of an incompressible fluid in an open-type vortex pump with an open side channel, comparing the generalized simulation results with the existing experimental data. The mathematical model is based on the Reynolds-averaged Navier — Stokes and continuity equations, as well as on the equations of the two-layer Realizable k-ε turbulence model that accounts for the curvature of streamlines. The authors have estimated the grid independence of the solution and studied the influence of 14 blade profiles on the head and efficiency of the vortex pump. The solution of the model equations was achieved by the finite volume method using a sequential algorithm in three calculation areas (“feeder channel”, “blade wheel”, “open hull side channel and diverter channel”) with the evaluation of grid independence of the solution. The result of the solution between the calculated areas was transmitted at the corresponding points of the interface surfaces. The authors have studied the influence of 14 profiles of a blade on pressure and efficiency of the vortex pump: the initial profile of the blade with the installation in the wheel coaxial shaft of the ring plate of different width, the initial profile of the blade with a bevel on the discharge side, a profile in the form of an isosceles triangle, a profile in the form of a quadrangle, the initial profile with a rounded blade on the suction side, and a profile in the form of a rectangular triangle with a rounded blade on the suction side, among others. The simulation results have aided in proposing the blade profiles: in the form of a rectangle with a convex rounding of the blade on the suction side with a 10 mm radius and a right-angled triangle with a concave rounding of the blade on the suction side with a 52 mm radius and without rounding, giving a significant increase in pressure — more than 20%. Nevertheless, none of the considered cases have revealed any significant increase in the vortex pump hydraulic efficiency.

Radiation-resistant robotic manipulator controlled by 6-DoF haptic control device to perform technological tasks in hot cells

The paper describes the results of developing a radiation-hardened robotic complex including the following original constituting elements: a robotic manipulator with a 2-finger gripper, a 6-DoF control device with force feedback, control software. The implementation of rotational motion of joints of the robotic manipulator through coaxial gear shafts resulted in its high resistance to ionizing radiation of up to 107 Gy. The control device features high ergonomics similar to that of mechanical master-slave manipulators. The control software has a modular structure and contains both original and the state-of-the-art program components. A prototype of the robotic complex was built which demonstrated the capability of performing typical technological operations in a demo hot cell in both manual and automated modes.

Disc type piezoelectric motor with two coaxial rotors

• A new bimorph disc-type ultrasonic piezoelectric motor was developed for micro air vehicle. • The piezoelectric motor has a novel design and can rotate two coaxial rotors in different directions. • The motor operates at a low voltage and achieves the maximum rotational speed of 7100 rpm and torque of 0.0647 mNm under a driving voltage of 15 V. • Numerical and experimental investigation was performed, and the operating principle of the actuator was validated. A small disc type piezoelectric motor was developed that can be used for micro flying vehicles. The operating principle of the motor is based on radial-bending type hybrid vibrations. The stator of the motor is a bimorph disc with the special quadrilateral shaped waveguides in the inner circumference of the disc. Waveguides are aligned with the tangential direction of the contacting ring. Such configuration of the actuator allows transforming radial vibrations of the disc into rotational vibrations of the contacting ring. Elliptical motion of the contact points is obtained by superposition of radial and bending vibration modes. The motor has two truncated cone-shaped rotors. Although the actuator is asymmetrical, two coaxial shafts of the motor can be rotated in both directions depending on the phase of excitation signals. Moreover, the proposed piezoelectric motor allows controlling the rotation speed of the rotors in different directions depending on the amplitude of the applied voltage. Numerical and experimental investigation of the piezoelectric motor was performed to validate the operating principle and to analyze vibrations of the contact points. Electrical and mechanical output characteristics of the piezoelectric motor were measured. The motor achieved a maximum no load rotational speed of 7108 rpm at 15 V while maximum torque is 0.0647 mN m.

STRENGHT AND DYNAMIC ANALYSIS OF A STRUCTURAL NODE LIMITING THE MULTI-OUTPUT GEAR MECHANISM

The rapidly advancing technological development leads to designing and researching a new multi- output gear mechanism. The investigated new double-output gear mechanism has two output coaxial shafts located against the input shaft on the other side of the gearbox. The gear mechanism achieves high gear ratios. Its limiting structural node is the output stage, to which the gears belong. The problem is addressed through the analysis of the stress resistance of tooth flanks in contact and bending. The content of the paper is a comparison of analytical computations with the modal analysis on the model. We expect that new findings will be beneficial for further optimization of the gear mechanism.

Chaotic Vibration Analysis of a Coaxial Rotor System in Active Magnetic Bearings and Contact With Auxiliary Bearings

In many cases of rotating systems, such as jet engines, two or more coaxial shafts are used for power transmission between a high/low-pressure turbine and a compressor. The major purpose of this study is to predict the nonlinear dynamic behavior of a coaxial rotor system supported by two active magnetic bearings (AMBs) and contact with two auxiliary bearings. The model of the system is formulated by ten degrees-of-freedom in two different planes. This model includes gyroscopic moments of disks and geometric coupling of the magnetic actuators. The nonlinear equations of motion are developed by the Lagrange's equations and solved using the Runge–Kutta method. The effects of speed parameter, speed ratio of shafts, and gravity parameter on the dynamic behavior of the coaxial rotor–AMB system are investigated by the dynamic trajectories, power spectra analysis, Poincaré maps, bifurcation diagrams, and the maximum Lyapunov exponent. Also, the contact forces between the inner shaft and auxiliary bearings are studied. The results indicate that the speed parameter, speed ratio of shafts, and gravity parameter have significant effects on the dynamic responses and can be used as effective control parameters for the coaxial rotor–AMB system. Also, the results of analysis reveal a variety of nonlinear dynamical behaviors such as periodic, quasi-periodic, period-4, and chaotic vibrations, as well as jump phenomena. The obtained results of this research can give some insight to engineers and researchers in designing and studying the coaxial rotor–AMB systems or some turbomachinery in the future.

Percutaneous Management of Accidentally Retained Foreign Bodies During Image-Guided Non-vascular Procedures: Novel Technique Using a Large-Bore Biopsy System.

To describe a novel percutaneous image-guided technique using a large-bore biopsy system to retrieve foreign bodies (FBs) accidentally retained during non-vascular interventional procedures. Between May 2013 and October 2015, five patients underwent percutaneous retrieval of five iatrogenic FBs, including a biopsy needle tip in the femoral head following osteoblastoma biopsy and radiofrequency ablation (RFA); a co-axial needle shaft within a giant desmoid tumour following cryoablation; and three post-vertebroplasty cement tails within paraspinal muscles. All FBs were retrieved immediately following original procedures under local or general anaesthesia, using combined computed tomography (CT) and fluoroscopic guidance. The basic technique involved positioning a 6G trocar sleeve around the FB long axis and co-axially advancing an 8G biopsy needle to retrieve the FB within the biopsy core. Retrospective chart review facilitated analysis of procedures, FBs, technical success, and complications. Mean FB size was 23mm (range 8-74mm). Four FBs were located within 10mm of non-vascular significant anatomic structures. The basic technique was successful in 3 cases; 2 cases required technical modifications including using a stiff guide-wire to facilitate retrieval in the case of the post-cryoablation FB; and using the central mandrin of the 6G trocar to push a cement tract back into an augmented vertebra when initial retrieval failed. Overall technical success (FB retrieval or removal to non-hazardous location) was 100%, with no complications. Percutaneous image-guided retrieval of iatrogenic FBs using a large-bore biopsy system is a feasible, safe, effective, and versatile technique, with potential advantages over existing methods.

Kinematics Analysis of a 3-RRR Spherical Parallel Mechanism with Coaxial Input Shafts

As an important mechanism with special and extensive application, the three degrees of freedom spherical parallel mechanism is always a research hot in the mechanical fields. In this paper, the feature of the 3-RRR spherical parallel mechanism with coaxial input shafts is introduced, and its motion feature is analyzed based on the screw theory. The mobility of the spherical parallel mechanism is calculated by using the Modified Kutzbach-Grübler criterion, and the inverse displacement problem of the mechanism is solved. Then the expression of the Jacobian matrix is deduced based on the kinematics equation and its inverse solution. The contents of this paper should be useful for the further application of the spherical parallel mechanism.

Effect of the axial scraping velocity on enhanced heat exchangers

Abstract The flow pattern within an enhanced tubular heat exchanger equipped with a reciprocating scraping device is experimentally analysed. The insert device, specially designed to avoid fouling and to enhance heat transfer, has also been used to produce ice slurry. It consists of several circular perforated scraping discs mounted on a coaxial shaft. The whole is moved alternatively along the axial direction by a hydraulic cylinder. The phase-averaged velocity fields of the turbulent flow have been obtained with PIV technique for both scraping semi-cycles. Special attention has been paid to the effect of the non-dimensional scraping velocity and the Reynolds number in the flow field. CFD simulations provide support for the identification of the flow patterns and the parameter assessment extension. The results show how the scraping parameters affect the turbulence level produced in the flow and therefore the desired heat transfer enhancement.

Analyzing the jamming of parts on the shaft in assembly processes

PurposeThe purpose of this paper is to investigate the process of jamming of the hollow parts on the shaft and to derive a mathematical model for jamming in an assembly process.Design/methodology/approachThe mathematical model for jamming of parts on the shaft in an assembly process is based on the sizes, geometry, angular declination of part and shaft axes, and the frictional factor.FindingsThe equation for angular positional tolerance of coaxial parts and shafts, based on their geometry and sizes and leading to jamming, was derived.Research limitations/implicationsA mathematical model of parts jamming on the shaft is developed for assembly mechanisms. This research does not consider flexible deformations of components in assembly mechanisms, which results in the axis concentricity of part and shaft in the assembly process.Practical implicationsThe results presented in the form of angular positional tolerance for coaxial parts and shafts based on their geometry and sizes make it possible to avoid the jamming of the parts. The results allow for formulating the angular positional tolerance of the assembly mechanisms that clamp the parts.Originality/valueThe proposed method for calculating the angular positional tolerance of coaxial parts and shafts for the assembly process should allow for increasing the reliability of the assembly process in the manufacturing industry.

Vehicle Inter-dependent Control Transmission Architectures - VICTA

This paper proposes a novel hybridized vehicle inter-dependent control transmission architecture (VICTA) that offers key advantages over existing systems. It embodies a compact torque generation system formed by two or more electric machines axially linked through a conventional mechanical differential gear assembly by means of a simple yet innovative pair of co-axial shafts. The resultant electric-mechanical hybridized drivetrain system allows a unique and automatic way of transmitting, differentially and inter-dependently, the electromagnetic torques generated by the motors at either side of differential gear. A realistic virtual prototype of the VICTA based on MATLAB/Simulink modules is developed to validate the concept. Comprehensive performance prediction tests, including steering maneuvering and variations of the road surface, are undertaken. Excellent simulation results from the VICTA virtual prototype demonstrate its stability and motility performance. The results also confirm the VICTA concept has key advantages such as reliability, modularity, high efficiency and simplicity, and yet does not inherit the undesirable features of high unsprung mass or complex software control that continue to challenge and even flaw the existing systems.

Dynamic characterization of a mechanical coupling for a rotating shaft

This article concerns the dynamic characterization of a flexible coupling that connects two co-axial shafts. Four different lumped parameter coupling models from the literature are investigated to see which model could best predict the dynamic behaviour of the coupling. The finite-element method was used to model the rotor dynamic system incorporating the coupling. Frequency response functions from this model were compared with measured frequency response functions from the rotor test rig with the shaft and coupling rotating at a specific speed. Parameters from the model were adjusted to minimize an objective function involving the measured and predicted frequency response functions. It was found that the simplest model of the coupling that could reasonably represent the coupling involves rotational (bending) stiffness and damping.

Finite element modeling of the laminar and transition flow of the Superblend dual shaft coaxial mixer on parallel computers

Abstract The macro-mixing mechanisms of the Superblend coaxial mixer consisting of a Maxblend impeller and a double helical ribbon agitator mounted on two independent coaxial shafts rotating at different speeds are numerically investigated. The simulations are based on the resolution of the Navier–Stokes equations with help of a parallel three-dimensional finite element solver exploiting the capabilities of high performance computers. To model the rotation of agitators a hybrid approach based on a novel finite element sliding mesh and fictitious domain method is used. The power consumption, the flow patterns, the shear rate distribution, the pumping capacity and the mixing time of the Superblend mixer are calculated from the simulated hydrodynamics. The simulations allow observing the flow as it evolves from deep laminar (Re=0.1) to transition (Re=520) regime. As Reynolds number increases, several recirculation zones above and below the middle of the tank are formed. It is found that operating the agitators in co-rotation mode requires less power consumption and exhibits equal or shorter mixing time than counter-rotation mode. The larger power consumption in counter-rotating mode is caused by the presence of high shear vortices generated between the two coaxial agitators. Furthermore it is shown that the shear distribution throughout the Superblend coaxial mixer operating in co-rotation mode is almost homogenous, which is highly desirable for shear sensitive products. In view of the results obtained in this work, the Superblend coaxial mixer is found as a good alternative for tough mixing applications.

Experimental Investigation of Superblend Coaxial Mixer

®impeller and a helical ribbon mounted on two independently actuated coaxial shafts are experimentally investigated. The work focuses on the effect of the rotating modes (co- and counter-rotating) in the laminar, transition and turbulent flow regimes, and the performance is compared with previously studied dual shaft coaxial mixers. Power consumption and mixing time experiments using a discoloration technique have been conducted using Newtonian aqueous solutions of corn syrup. Based on mixing efficiency criteria, this study confirms that the co-rotating mode consistently yields the best results in the laminar and early transition regimes. Recent power correlations introduced by our group for coaxial mixers have been tested for their applicability and they are proven to be readily applicable for the Superblend. This work demonstrates the remarkable efficiency of the Superblend and its superiority when compared to standard coaxial mixers based on different mixing efficiency criteria.

Novel Microstrip Antenna With Rotatable Patch Fed by Coaxial Line for Personal Handy-Phone System Units

An enhanced microstrip antenna is proposed that incorporates a patch that rotates around the inner conductor of the coaxial line or dielectric shaft and a novel coaxial line feeding technique that offers constant electromagnetic coupling. This proposal addresses the disadvantages in our previous patch antenna in which the resonant frequency diverges from the center frequency of the personal handy-phone system (PHS) band and the bandwidth decreases as the patch rotates because of the changing electromagnetic coupling between the patch and microstrip line due to the patch rotation. We verify that this enhanced patch antenna achieves the antenna gain of approximately 0 dBd, which is the same as that of the previously proposed antenna, while suffering no significant gain degradation due to unit inclination over inclination angles from plusmn45deg compared to a conventional quarter-wavelength whip antenna, which experiences a degradation of approximately 2.7 dB. We show that the maximum resonant frequency separation from the center frequency of the PHS band is reduced to 15 MHz from 31.4 MHz of the previous antenna using the novel coaxial line feeding technique. The effective bandwidth needed for PHS is achieved over the inclination angles of -20deg to +40deg. Approximately 93% of the total bandwidth needed for PHS is achieved while the previous microstrip line type achieved only 58% coverage; accordingly, an adequate bandwidth for PHS use is obtained.