Multi-objective optimization of stacked radial passive magnetic bearing

2017 ◽  
Vol 232 (9) ◽  
pp. 1140-1159 ◽  
Author(s):  
KP Lijesh ◽  
Mrityunjay Doddamani ◽  
SI Bekinal ◽  
SM Muzakkir
Keyword(s):  
Carrying Capacity ◽  
Three Dimensional ◽  
Single Layer ◽  
Maximum Load ◽  
Magnetic Bearing ◽  
Load Carrying Capacity ◽  
Multi Objective Optimization ◽  
Design And Optimization ◽  
Multi Objective ◽  
Load Carrying

Modeling, design, and optimization for performances of passive magnetic bearings (PMBs) are indispensable, as they deliver lubrication free, friction less, zero wear, and maintenance-free operations. However, single-layer PMBs has lower load-carrying capacity and stiffness necessitating development of stacked structure PMBs for maximum load and stiffness. Present work is focused on multi-objective optimization of radial PMBs to achieve maximum load-carrying capacity and stiffness in a given volume. Three-dimensional Coulombian equations are utilized for estimating load and stiffness of stacked radial PMBs. Constraints, constants, and bounds for the optimization are extracted from the available literature. Optimization is performed for force and stiffness maximization in the obtained bounds with three PMB configurations, namely (i) mono-layer, (ii) conventional (back to back), and (iii) rotational magnetized direction. The optimum dimensions required for achieving maximum load without compromising stiffness for all three configurations is investigated. For designers ease, equations to estimate the optimized values of load, stiffness, and stacked PMB variables in terms of single-layer PMB are proposed. Finally, the effectiveness of the proposed method is demonstrated by considering the PMB dimensions from the available literature.

Design methodology for monolithic layer radial passive magnetic bearing

2018 ◽  
Vol 233 (6) ◽  
pp. 992-1000
Author(s):  
Lijesh K Parambil
Keyword(s):  
Carrying Capacity ◽  
Design Methodology ◽  
Design Procedure ◽  
Single Layer ◽  
Maximum Load ◽  
Magnetic Bearing ◽  
Computational Time ◽  
Load Carrying Capacity ◽  
Straightforward Method ◽  
Load Carrying

Passive magnetic bearings (PMBs) are considered to be one of the economical and effective methods for levitating two surfaces in relative motion. This obviates the use of lubrication, provides zero wear, and negligible friction, thereby making the operation maintenance free. Due to these advantages, the modeling and design of the PMBs were given substantial importance in many studies. However, a well-defined designing procedure to achieve desired load carrying capacity for the given space constraints for the intended PMB application is yet to be established. Prior studies were performed on PMBs for achieving maximum load carrying capacity, but no design methodology was proposed that could facilitate easier design of a PMB in lesser computational time. In the present work, a very effective and a straightforward method is proposed to design a PMB for its paramount output. For this, dimensions of PMBs from the literature are considered for analysis and a set of equations are proposed for the determination of mean radius, axial length, and clearance for a given inner and outer radii of single layer PMBs. Finally, an equation is provided for estimating the load carrying capacity for the determined dimensions of PMB from the proposed design procedure. The effectiveness of the proposed methodology is demonstrated by considering the dimensions of PMBs from 10 literature.

A Hybrid Framework of Efficient Multi-Objective Optimization of Stiffened Shells with Imperfection

2019 ◽  
Vol 17 (04) ◽  
pp. 1850145 ◽  
Author(s):  
Hanshu Chen ◽  
Zeng Meng ◽  
Huanlin Zhou
Keyword(s):  
Carrying Capacity ◽  
Light Weight ◽  
Load Carrying Capacity ◽  
Weight Optimization ◽  
Multi Objective Optimization ◽  
Stiffened Shell ◽  
Multi Objective ◽  
Stiffened Shells ◽  
Load Carrying ◽  
Hybrid Framework

In the practical engineering applications of stiffened shell, the initial imperfection is inevitable and it could cause significant reduction in the load-carrying capacity of stiffened shell. The light-weight optimization of stiffened shell is generally performed under the constraint of fixed maximum load-carrying capacity. However, the load-carrying capacity of stiffened shell has been improved continuously as the promotion of manufacturing technology, which causes the previous strategies of light-weight optimization become conservative and outdated. Therefore, an improved hybrid framework of multi-objective optimization of stiffened shell with imperfection is necessary and presented in this paper, which focus on developing a general posterior design method to determine the optimal weight according to the different collapse loads. A new adaptive update criterion based on the Kriging model is developed to improve the efficiency and accuracy of the hybrid framework. The present optimal results provide a set of the Pareto optimal points and form a Pareto front, from which new posterior design can be achieved.

scholarly journals OPTIMIZATION OF GEOMETRICALLY NONLINEAR LATTICE GIRDERS. PART I: CONSIDERING MEMBER STRENGTHS

2015 ◽  
Vol 21 (4) ◽  
pp. 423-443 ◽  
Author(s):  
Tugrul Talaslioglu
Keyword(s):  
Optimization Algorithm ◽  
Carrying Capacity ◽  
Optimization Approach ◽  
Geometrically Nonlinear ◽  
Load Carrying Capacity ◽  
Multi Objective Optimization ◽  
Multi Objective ◽  
Load Carrying ◽  
Lattice Girder ◽  
Tubular Lattice

In this study, the entire weight, joint displacements and load-carrying capacity of tubular lattice girders are simultaneously optimized by a multi-objective optimization algorithm, named Non-dominated Sorting Genetic Algorithm II (NSGAII). Thus, the structural responses of tubular lattice girders are obtained by use of arc-length method as a geometrically nonlinear analysis approach and utilized to check their member strengths at each load step according to the provisions of the American Petroleum Institute specification (API RP2A-LRFD 1993). In order to improve the computing capacity of proposed optimization approach, while the optimization algorithm is hybridized with a radial basis neural network approach, an automatic lattice girder generator is included into the design stage. The improved optimization algorithm, called ImpNSGAII, is applied to both a benchmark lattice girder with 17 members and a lattice girder with varying span lengths and loading conditions. Consequently, it is demonstrated: 1) the optimal lattice girder configuration generated has a higher load-carrying capacity ensuring lower weight and joint displacement values; 2) the use of a multi-objective optimization approach increases the correctness degree in evaluation of optimality quality due to the possibility of performing a trade-off analysis for optimal designations; 3) the computing performance of ImpNSGAII is higher than NSGAII’s.

Magnetic Bearing Using Rotation Magnetized Direction Configuration

2015 ◽  
Vol 137 (4) ◽  
Author(s):  
K. P. Lijesh ◽  
Harish Hirani
Keyword(s):  
Rare Earth ◽  
Carrying Capacity ◽  
Permanent Magnets ◽  
Load Capacity ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Magnetic Bearing ◽  
Load Carrying Capacity ◽  
Load Carrying ◽  
Ring Magnet

Passive magnetic bearing (PMB), made of high remanence rare earth permanent magnets, is brittle in nature; therefore, precautions must be taken to reduce the chances of vibration transmitting to the permanent magnets. In the present work, a rotation magnetized direction (RMD) structure made of aluminum ring and square shaped magnetic pieces has been proposed. A comparative study of load carrying capacities of sector magnets and square magnets has been presented. Three-dimensional (3D) Coulombian model was solved to estimate the load carrying capacity. Theoretical and experimental studies on the load carrying capacities of full ring magnet (more prone to cracking) and the proposed structure have been presented to prove the superiority of the proposed structure. In addition to load capacity, comparison between amplitudes of vibration at different frequencies, orbit plots, and time taken for breakage of the magnets at the resonance frequency has been presented.

A Pragmatic Optimization of Axial Stack-Radial Passive Magnetic Bearings

2017 ◽  
Vol 140 (2) ◽  
Author(s):  
K. P. Lijesh ◽  
Mrityunjay Doddamani ◽  
S. I. Bekinal
Keyword(s):  
Carrying Capacity ◽  
Performance Optimization ◽  
Optimization Technique ◽  
Three Dimensional ◽  
Maximum Load ◽  
Outer Radius ◽  
Optimization Techniques ◽  
Load Carrying Capacity ◽  
Load Carrying ◽  
Optimum Solution

Passive magnetic bearing's (PMB) adaptability for both lower and higher speed applications demands detailed and critical analysis of design, performance optimization, and manufacturability. Optimization techniques for stacked PMB published in recent past are less accurate with respect to complete optimum solution. In this context, the present work deals with a pragmatic optimization of axially stacked PMBs for the maximum radial load using three-dimensional (3D) equations. Optimization for three different PMB configurations, monolithic, conventional, and rotational magnetized direction (RMD), is presented based on the constraints, constants, and bounds of the dimensions obtained from published literature. Further, to assist the designers, equations to estimate the mean radius and clearance being crucial parameters are provided for the given axial length and outer radius of the stator with the objective of achieving maximum load-carrying capacity. A comparison of the load-carrying capacity of conventional stacked PMB using the proposed equation with the equation provided in literature is compared. Finally, effectiveness of the proposed pragmatic optimization technique is demonstrated by analyzing three examples with reference to available literature.

Pavement Damage Due to Conventional and New Generation of Wide-Base Super Single Tires

2005 ◽  
Vol 33 (4) ◽  
pp. 210-226 ◽  
Author(s):  
I. L. Al-Qadi ◽  
M. A. Elseifi ◽  
P. J. Yoo ◽  
I. Janajreh
Keyword(s):  
Carrying Capacity ◽  
Material Properties ◽  
Three Dimensional ◽  
Fe Analysis ◽  
Load Carrying Capacity ◽  
Inflation Pressure ◽  
3D Finite Element ◽  
Load Carrying ◽  
Pavement Damage ◽  
New Generation

Abstract The objective of this study was to quantify pavement damage due to a conventional (385/65R22.5) and a new generation of wide-base (445/50R22.5) tires using three-dimensional (3D) finite element (FE) analysis. The investigated new generation of wide-base tires has wider treads and greater load-carrying capacity than the conventional wide-base tire. In addition, the contact patch is less sensitive to loading and is especially designed to operate at 690kPa inflation pressure at 121km/hr speed for full load of 151kN tandem axle. The developed FE models simulated the tread sizes and applicable contact pressure for each tread and utilized laboratory-measured pavement material properties. In addition, the models were calibrated and properly validated using field-measured stresses and strains. Comparison was established between the two wide-base tire types and the dual-tire assembly. Results indicated that the 445/50R22.5 wide-base tire would cause more fatigue damage, approximately the same rutting damage and less surface-initiated top-down cracking than the conventional dual-tire assembly. On the other hand, the conventional 385/65R22.5 wide-base tire, which was introduced more than two decades ago, caused the most damage.

Maximum load carrying capacity of mobile manipulators: optimal control approach

Robotica ◽  
2009 ◽  
Vol 27 (1) ◽  
pp. 147-159 ◽  
Author(s):  
M. H. Korayem ◽  
A. Nikoobin ◽  
V. Azimirad
Keyword(s):  
Optimal Control ◽  
Optimal Control Problem ◽  
Control Problem ◽  
Carrying Capacity ◽  
Nonholonomic Constraints ◽  
Maximum Load ◽  
Mobile Manipulators ◽  
Load Carrying Capacity ◽  
Maximum Payload ◽  
Load Carrying

SUMMARYIn this paper, finding the maximum load carrying capacity of mobile manipulators for a given two-end-point task is formulated as an optimal control problem. The solution methods of this problem are broadly classified as indirect and direct. This work is based on the indirect solution which solves the optimization problem explicitly. In fixed-base manipulators, the maximum allowable load is limited mainly by their joint actuator capacity constraints. But when the manipulators are mounted on the mobile bases, the redundancy resolution and nonholonomic constraints are added to the problem. The concept of holonomic and nonholonomic constraints is described, and the extended Jacobian matrix and additional kinematic constraints are used to solve the extra DOFs of the system. Using the Pontryagin's minimum principle, optimality conditions for carrying the maximum payload in point-to-point motion are obtained which leads to the bang-bang control. There are some difficulties in satisfying the obtained optimality conditions, so an approach is presented to improve the formulation which leads to the two-point boundary value problem (TPBVP) solvable with available commands in different softwares. Then, an algorithm is developed to find the maximum payload and corresponding optimal path on the basis of the solution of TPBVP. One advantage of the proposed method is obtaining the maximum payload trajectory for every considered objective function. It means that other objectives can be achieved in addition to maximize the payload. For the sake of comparison with previous results in the literature, simulation tests are performed for a two-link wheeled mobile manipulator. The reasonable agreement is observed between the results, and the superiority of the method is illustrated. Then, simulations are performed for a PUMA arm mounted on a linear tracked base and the results are discussed. Finally, the effect of final time on the maximum payload is investigated, and it is shown that the approach presented is also able to solve the time-optimal control problem successfully.

Development of Z-Factor for Circumferential Part-Through Surface Cracks in Dissimilar Metal Welds

2008 ◽  
Author(s):  
D.-J. Shim ◽  
G. M. Wilkowski ◽  
D. L. Rudland ◽  
F. W. Brust ◽  
Kazuo Ogawa
Keyword(s):  
Correction Factor ◽  
Carrying Capacity ◽  
Limit Load ◽  
Maximum Load ◽  
Load Carrying Capacity ◽  
Surface Cracks ◽  
Crack Driving Force ◽  
Dissimilar Metal ◽  
Load Carrying ◽  
J Estimation

Section XI of the ASME Code allows the users to conduct flaw evaluation analyses by using limit-load equations with a simple correction factor to account elastic-plastic fracture conditions. This correction factor is called a Z-factor, and is simply the ratio of the limit-load to elastic-plastic fracture mechanics (EPFM) maximum-load predictions for a flaw in a pipe. The past ASME Section XI Z-factors were based on a circumferential through-wall crack in a pipe rather than a surface crack. Past analyses and pipe tests with circumferential through-wall cracks in monolithic welds showed that the simplified EPFM analyses (called J-estimation schemes) could give good predictions by using the toughness, i.e., J-R curve, of the weld metal and the strength of the base metal. The determination of the Z-factor for a dissimilar metal weld (DMW) is more complicated because of the different strength base metals on either side of the weld. This strength difference can affect the maximum load-carrying capacity of the flawed pipe by more than the weld toughness. Recent work by the authors for circumferential through-wall cracks in DMWs has shown that an equivalent stress-strain curve is needed in order for the typical J-estimation schemes to correctly predict the load carrying capacity in a cracked DMW. In this paper, the Z-factors for circumferential surface cracks in DMW were determined. For this purpose, a material property correction factor was determined by comparing the crack driving force calculated from the J-estimation schemes to detailed finite element (FE) analyses. The effect of crack size and pipe geometry on the material correction factor was investigated. Using the determined crack-driving force and the appropriate toughness of the weld metal, the Z-factors were calculated for various crack sizes and pipe geometries. In these calculations, a ‘reference’ limit-load was determined by using the lower strength base metal flow stress. Furthermore, the effect of J-R curve on the Z-factor was investigated. Finally, the Z-factors developed in the present work were compared to those developed earlier for through-wall cracks in DMWs.

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