Optimal Design of Underwater Shells With Active Stiffeners

2001 ◽  
Author(s):  
W. Akl ◽  
M. Ruzzene ◽  
A. Baz
Keyword(s):  
Optimal Design ◽  
Low Cost ◽  
Element Model ◽  
Design Parameters ◽  
Optimization Approach ◽  
Noise Radiation ◽  
Stiffened Shells ◽  
Shell Vibration ◽  
The Cost ◽  
Controllability And Observability

Abstract The optimal design parameters of fluid-loaded shells, provided with actively controlled stiffeners, are determined using a rational multi-criteria optimization approach. The adopted approach aims at simultaneously minimizing the shell vibration, associated sound radiation, weight of the stiffening rings, the control energy, and the cost of the shell/stiffeners assembly while maximizing the controllability and observability indices. A finite element model is presented to predict the vibration and noise radiation from cylindrical shells, with active stiffeners, into the surrounding fluid domain. The production cost as well as the life cycle and maintenance costs of the stiffened shells are computed using the Parametric Review of Information for Costing and Evaluation (PRICE) model. A Pareto/min-max multi-criteria optimization approach is then utilized to select the optimal locations and dimensions of the active stiffeners. Numerical examples are presented to compare the vibration and noise radiation characteristics of me optimally designed/controlled stiffened shells with the corresponding characteristics of plain un-stiffened and uncontrolled shells. The obtained results emphasize me importance of the adopted multi-criteria optimization approach in the design of quiet, low weight and low cost underwater shells which are suitable for various critical applications.

Kinetostatic backflip strategy for self-recovery of quadruped robots with the selected rotation axis

Robotica ◽  
2021 ◽  
pp. 1-19
Author(s):  
Shengjie Wang ◽  
Kun Wang ◽  
Chunsong Zhang ◽  
Jian S Dai
Keyword(s):  
Optimal Design ◽  
Energy Analysis ◽  
Rotation Axis ◽  
Low Cost ◽  
Minimum Energy ◽  
Design Parameters ◽  
Quadruped Robots ◽  
Design Idea ◽  
The Relationship

Abstract A kinetostatic approach applied to the design of a backflip strategy for quadruped robots is proposed in this paper. Inspired by legged animals and taking the advantage of the leg workspace, this strategy provides an optimal design idea for the low-cost quadruped robots to achieve self-recovery after overturning. Through kinetostatic and energy analysis, a four-stepped backflip strategy based on the selected rotation axis with minimum energy is proposed, with a process of selection, lifting, rotating, and protection. The kinematic factors that affect the backflip are investigated, along with the relationship between the design parameters of the leg and trunk being analyzed. At the end of this paper, the strategy is validated by a simulation and experiments with a prototype called DRbot, demonstrating that the strategy endows the robot a strong self-recovery ability in various terrains.

A vibration-based identification of elastic properties of stitched sandwich panels

2018 ◽  
Vol 53 (5) ◽  
pp. 579-592 ◽  
Author(s):  
Nan Li ◽  
Mabrouk Ben Tahar ◽  
Zoheir Aboura ◽  
Kamel Khellil
Keyword(s):  
Elastic Properties ◽  
Transverse Direction ◽  
Sandwich Panel ◽  
Low Cost ◽  
Element Model ◽  
Vibration Test ◽  
Structural Application ◽  
Sensibility Analysis ◽  
The Cost ◽  
Non Destructive

Stitched sandwich becomes popular in structural application owing to its better performance in the transverse direction with respect to classical sandwich structure and relatively low-cost additional stitching process. The identification of its elastic properties is essential for offering a tailored structure for specific applications. A non-destructive identification method based on vibration test is proposed to obtain these parameters. The number of parameters is firstly reduced by a sensibility analysis. The retained parameters are identified by minimizing the cost function which indicates the gap between measured frequencies from vibration test and calculated frequencies from a finite element model. This method is applied to a stitched sandwich panel and its elastic properties are successfully identified.

scholarly journals Optimal Design of Rated Wind Speed and Rotor Radius to Minimizing the Cost of Energy for Offshore Wind Turbines

Energies ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2728 ◽  
Author(s):  
Longfu Luo ◽  
Xiaofeng Zhang ◽  
Dongran Song ◽  
Weiyi Tang ◽  
Jian Yang ◽  
...  
Keyword(s):  
Wind Speed ◽  
Optimal Design ◽  
Wind Energy ◽  
Wind Turbines ◽  
Offshore Wind ◽  
Design Parameters ◽  
Offshore Wind Energy ◽  
Offshore Wind Turbines ◽  
Cost Of Energy ◽  
The Cost

As onshore wind energy has depleted, the utilization of offshore wind energy has gradually played an important role in globally meeting growing green energy demands. However, the cost of energy (COE) for offshore wind energy is very high compared to the onshore one. To minimize the COE, implementing optimal design of offshore turbines is an effective way, but the relevant studies are lacking. This study proposes a method to minimize the COE of offshore wind turbines, in which two design parameters, including the rated wind speed and rotor radius are optimally designed. Through this study, the relation among the COE and the two design parameters is explored. To this end, based on the power-coefficient power curve model, the annual energy production (AEP) model is designed as a function of the rated wind speed and the Weibull distribution parameters. On the other hand, the detailed cost model of offshore turbines developed by the National Renewable Energy Laboratory is formulated as a function of the rated wind speed and the rotor radius. Then, the COE is formulated as the ratio of the total cost and the AEP. Following that, an iterative method is proposed to search the minimal COE which corresponds to the optimal rated wind speed and rotor radius. Finally, the proposed method has been applied to the wind classes of USA, and some useful findings have been obtained.

Mission architecture for Mars exploration based on small satellites and planetary drones

2016 ◽  
Vol 4 (3) ◽  
pp. 142-162 ◽  
Author(s):  
Pierpaolo Pergola ◽  
Vittorio Cipolla
Keyword(s):  
Electric Propulsion ◽  
Low Cost ◽  
Scientific Data ◽  
Reference Points ◽  
Design Parameters ◽  
Optimization Approach ◽  
Low Thrust ◽  
Content Type ◽  
Mars Atmosphere ◽  
Small Satellites

Purpose The purpose of this paper is to deal with the study of an innovative unmanned mission to Mars, which is aimed at acquiring a great amount of detailed data related to both Mars’ atmosphere and surface. Design/methodology/approach The Mars surface exploration is conceived by means of a fleet of drones flying among a set of reference points (acting also as entry capsules and charging stations) on the surface. The three key enabling technologies of the proposed mission are the use of small satellites (used in constellation with a minimum of three), the use of electric propulsion systems for the interplanetary transfer (to reduce the propellant mass fraction) and lightweight, efficient, drones designed to operate in the harsh Mars environment and with its tiny atmosphere. Findings The low-thrust Earth-Mars transfer is designed by means of an optimization approach resulting in a duration of slightly more than 27 months with a propellant amount of about 125 kg, which is compatible with the choice of considering a 500 kg-class spacecraft. Four candidate drone configurations have been selected as the result of a sensitivity analysis. Flight endurance, weight and drone size have been considered as the driving design parameters for the selection of the final configuration, which is characterized by six rotors, a total mass of about 6.5 kg and a flight endurance of 28 minutes. In the mission scenario proposed, the drone is assumed to be delivered on the Mars surface by means of a passive entry capsule, which acts also as a docking station and charging base. Such a capsule has been sized both in terms of mass (68 kg) and power (80 W), showing to be compatible with 500 kg-class spacecraft. Research limitations/implications As a general conclusion, the study shows the mission concept feasibility. Practical implications The concept would return incomparable scientific data and can be also be potentially implemented with a relatively low budget exploiting of the shelf components to the larger extent, small identical spacecraft buses and modular low-cost drones. Originality/value The innovative mission architecture proposed in this study aims at providing a complete coverage of the surface and lowest atmospheric layers. The main innovation factor of the proposed mission consists in the adoption of small multi-copter UAVs, also called “drones,” as remote-sensing platforms.

scholarly journals ASPECTS REGARDING OPTIMAL DESIGN FOR THE WORM-GEAR DRIVE

2021 ◽  
Vol 13 (3) ◽  
pp. 59-65
Author(s):  
Daniela Ghelase ◽  
◽  
Luiza Daschievici ◽  
Keyword(s):  
Optimal Design ◽  
Machine Tools ◽  
Worm Gear ◽  
Design Parameters ◽  
Support Vector ◽  
Optimization Approach ◽  
Design Algorithm ◽  
Transmission Errors ◽  
Gear Drive ◽  
Gear Drives

It is known that, from the point of view of the accuracy of a machine-tool, at its design, the dynamic behaviour of each element of the kinematic chains prevails. Worm-gear drives are widely used in the different machine-tools and robots. Therefore, it is important that during meshing, as far as possible, there are no vibrations, shocks, power losses, noise and low durability. These requirements can be met if, for example, the gear ratio is constant during meshing, without transmission errors, which means that the worm-gear drive should have a high accuracy. The accuracy improvement of the worm-gear drive has long been a focus of attention for machine-tools designers. Thus, this paper presents various approaches to solving such problems, based on modelling and simulation, such as: estimating the load share of worm-gear drives and to calculate the instantaneous tooth meshing stiffness and loaded transmission errors; the desired worm-gear drive design configuration by altering the optimum set of worm-gear drive design parameters which are suitable for the required performance by associating it with SVM (Support Vector Machine); optimization approach for design of worm-gear drive based on Genetic Algorithm; design optimization of worm-gear drive with reduced power loss; etc. The optimization of the worm-gear design is an important problem for the research because the design variables are correlated to each other. An optimal design algorithm developed by the authors of this paper, for worm-gear drive, is also presented.

Optimal Design of Asymmetric Passive and Semi-Active Dampers

2007 ◽  
Author(s):  
N. Eslaminasab ◽  
S. Arzanpour ◽  
M. F. Golnaraghi
Keyword(s):  
Optimal Design ◽  
Low Cost ◽  
Relative Displacement ◽  
Industrial Applications ◽  
Active Systems ◽  
Vibration Isolators ◽  
Response Characteristics ◽  
Optimal Damping ◽  
Optimal Values ◽  
The Cost

Vibration isolators are essentially used to reduce the magnitude of motion or force transmitted from a vibrating source to vibration recipient bodies. Such recipients might be a foundation, a structure, or even a human’s body. Despite all the advancement in vibration control using active and semi-active systems, passive vibration isolators are still widely used in different industrial applications because of their simplicity and low cost. In this paper we investigate an asymmetric one-degree of freedom vibration isolator. This is very important in practice, because all hydraulic dampers are asymmetric in nature. Due to the non-linearity of this system as a result of asymmetric damping, analytical methods of averaging and numerical simulation are used to analyze its frequency and time response characteristics. Optimal damping and stiffness values for the isolator are obtained by minimizing the cost functions, which are the Root Mean Square (RMS) of the acceleration transmissibility and the relative displacement transmissibility. The effect of the asymmetric damping on the optimal values in passive systems are then analyzed and used to create a design chart for the isolator parameters. In addition, the effect of asymmetry on the conventional semi-active systems is studied and the method to the optimal design of asymmetric semi-active systems is discussed.

scholarly journals A Low Cost Potentiostat Device For Monitoring Aqueous Solution

2018 ◽  
Vol 217 ◽  
pp. 04001
Author(s):  
S. N. H. Umar ◽  
E. A. Bakar ◽  
N. M. Kamaruddin ◽  
N. Uchiyama
Keyword(s):  
Metal Ion ◽  
Control Algorithm ◽  
Low Cost ◽  
Environmental Water ◽  
Design Parameters ◽  
Potential Control ◽  
And Performance ◽  
Main Component ◽  
The Cost

This study developed a new design of a low cost potentiostat circuit device. This device is an alternative electrochemical instrument applied for monitoring heavy metal ion in environmental water. It was developed to alleviate the cost burden of equipment procurement and due to the requirement for in-situ application since the existing commercialize devices are bulky and expensive. the main component of the device consist of electronics configuration of operational amplifier. the device was first modelled and simulated to acquire the design parameters and performance. the potential control algorithm was developed on open-source microcontroller platform. A dummy cell was used to validate the capabilities of the device.

Seismic Response Reduction of Cable-Stayed Bridge with Viscous Dampers

2011 ◽  
Vol 137 ◽  
pp. 154-158
Author(s):  
Wen Liang Qiu ◽  
Meng Jiang ◽  
Xing Bo Zhang
Keyword(s):  
Seismic Waves ◽  
Time History ◽  
Longitudinal Direction ◽  
Element Model ◽  
Design Parameters ◽  
Longitudinal Displacement ◽  
Cable Stayed Bridge ◽  
History Analysis ◽  
Floating System ◽  
The Cost

For floating system cable-stayed bridge, the longitudinal displacement of girder and moments of towers are very large when strong earthquake happens. The dampers installed between girder and towers in longitudinal direction can reduce efficiently displacement of the girder and moments of the towers induced by longitudinal seismic waves. Using spatial finite element model and time history analysis method, the influences of design parameters of viscous damper on seismic responses of cable-stayed bridge are studied in detail. The results of study show that, with the damping constant increasing, the longitudinal displacement of girder and moment of tower decrease, and the forces of damper increase. With velocity exponent increasing, the longitudinal displacement of girder and moment of tower increase, and the force of damper decrease. So, when determining the design parameters of damper, the cost of dampers, difficulty of construction and seismic reduction effects should be considered together.

Optimal Design of a Hip Joint Implant With Hollow Stem Using Finite Element Method

2006 ◽  
Author(s):  
Nasser Zakeri ◽  
Farzam Farahmand ◽  
Hamid Katoozian
Keyword(s):  
Finite Element ◽  
Optimal Design ◽  
Bone Cement ◽  
Hip Joint ◽  
Cylindrical Cavity ◽  
Hip Prosthesis ◽  
Element Model ◽  
Optimization Criterion ◽  
Design Parameters ◽  
Joint Implant

Complication of artificial joint replacement is often attributed to the distribution of mechanical stresses over the bone-cement, and cement-implant interfaces. This study represents the analysis and optimization of a hollow-stem hip prosthesis to reduce the micro-motion and maintain uniformity of stress distribution over the interface regions. A three-dimensional finite element model of the proximal femur was constructed in ANSYS, including the cortical bone, the cancellous bone, the bone cement and the femoral component of hip joint implant. Three design parameters were considered for the implant stem, including the length of the stem and the length and radius of the distal cylindrical cavity. The optimization criterion was defined as a linear combination of the standard deviations of the equivalent Von-Mises stresses and the total displacements at the cement-implant interface nodes. The Response Surface Method and sensitivity analysis indicated that the length of the stem has a major impact on the optimization criterion and the length and the radius of the cavity stand as the minor factors. The optimal design was obtained to have a 10.5 cm length stem with a cylindrical cavity of 23.4 mm length and 1.3 mm radius. The assumed optimization criterion reduced substantially from 3.1 in the initial design to 2.52 in the optimal deign.

scholarly journals Identification of Material Properties and Optimal Design of Magnetically Shielded Rooms

2021 ◽  
Vol 7 (2) ◽  
pp. 23
Author(s):  
Aldo Canova ◽  
Fabio Freschi ◽  
Luca Giaccone ◽  
Maurizio Repetto ◽  
Luigi Solimene
Keyword(s):  
Magnetic Field ◽  
Magnetic Material ◽  
Optimal Design ◽  
Design Procedure ◽  
Magnetic Characteristic ◽  
Design Parameters ◽  
Ferromagnetic Structure ◽  
Shielding Factor ◽  
The Cost ◽  
Low Magnetic Field

In this paper, we propose an optimal design procedure for magnetically shielded rooms. Focusing on multi-layer ferromagnetic structures, where inner layers operate at very low magnetic field, we propose an identification method of the magnetic material characteristic in the Rayleigh region. A numerical model to simulate the shielding efficiency of a multi-layer ferromagnetic structure is presented and experimentally tested on different geometries and layer configurations. The fixed point iterative method is adopted to handle the nonlinearity of the magnetic material. In conclusion, the optimization of the design parameters of a MSR is discussed, using the Vector Immune System algorithm to minimize the magnetic field inside the room and the cost of the structure. The results highlight that a linear magnetic characteristic for the material is sufficient to identify the suitable geometry of the shield, but the nonlinear model in the Rayleigh region is of fundamental importance to determine a realistic shielding factor.

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