A graphic tool is developed and validated for the verification and updating of large structure finite element models (FEM) for better correlation with modal test data. The elaborated Linear Quadratic optimization (LQO...
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Improvement of structural models by incorporating measured structural modal parameters is approached from a controls aspect. The approach is developed for linear structures that exhibit nonproportional damping. Residu...
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For a sampled data feedback system, the compensator consists of a prefilter F(s), a sampler with a sample period T, a digital computer D(z), and a hold device H(s). The objective of a feedback controller design is to ...
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For a sampled data feedback system, the compensator consists of a prefilter F(s), a sampler with a sample period T, a digital computer D(z), and a hold device H(s). The objective of a feedback controller design is to choose these elements to stabilize the plant G(s) and to meet various performance specifications. In this paper, an improvement to other methods is given by guaranteeing closed-loop stability, approximating a performance cost function, and improving the numerical condition of the problem. The general formulation will be stated. The work describes a solution that is suboptimal but computationally less expensive than the general approach stated. Examples for both approaches are presented,
A reanalysis technique is presented for obtaining changes in response variables due to changes in design parameters with the boundary-element method. The approach is considered for static response analysis and design ...
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Gliding descent in autorotation is used by helicopter pilots in case of engine failure. A successful landing following an autorotation descent requires considerable skill, and since it is seldom practiced, it is consi...
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Gliding descent in autorotation is used by helicopter pilots in case of engine failure. A successful landing following an autorotation descent requires considerable skill, and since it is seldom practiced, it is considered quite dangerous. Methods and devices have been proposed to improve helicopter autorotational landing characteristics. In this paper a point-mass model of an OH-58A helicopter is used to determine its autorotation profiles that minimize the impact velocity of the helicopter while staying within bounds on the rotor's collective pitch and angular speed. The optimal control strategies obtained are similar to those used by pilots in autorotational landings. The study indicates that there is a potential for reducing the H-V restriction zone of OH-58A helicopters using optimal energy management techniques.
In this paper, a ten-joint 3-D kinematic model has been developed by carefully *** the anatomy of the lower limb during bicycling for understandmg and analyzmg the complex motions of the joints. An optimization algori...
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In this paper, a ten-joint 3-D kinematic model has been developed by carefully *** the anatomy of the lower limb during bicycling for understandmg and analyzmg the complex motions of the joints. An optimization algorithm has also been developed and used to compute the Joint vanables and find the numerical solution. In order to simulate the indeterminate kinematic system, random vectors of multinormal distribution have been generated and statistical means and variances have been obtained from these random vector samples. The validity of the developed model has been checked by comparing the results with that of *** measurements. The model developed has good desirability to descnbe the hmb and IS more accurate than 2-D models to predict the motion of lower extremities.
The existing need to develop methods whereby the shape design efficiency can be improved through the use of high-quality approximation methods is addressed. An efficient approximation method for stress constraints in ...
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The present work is directed toward establishing an optimization capability for sizing wing structures that are subjected to a combination of deterministic and random flight loads. This includes the implementation of ...
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The present work is directed toward establishing an optimization capability for sizing wing structures that are subjected to a combination of deterministic and random flight loads. This includes the implementation of efficient methods for computing response sensitivity required by the optimization algorithm. The random loads are treated as a stationary, homogeneous process with a Gaussian distribution. A frequency-domain analysis has been selected for the solution of the dynamic response problem, wherein the gust loads are represented by a power spectral density spectrum of gust velocities. The combination of optimization algorithms with analysis tools such as EAL and ISAC makes available a tool for stress, displacement, frequency, flutter, and gust-response-constrained optimization. Furthermore, implementation of semi-analytical gradient calculations provides added computational efficiency to the programming system.
Considerable progress has been made in developing analytical methods for design sensitivity analysis of structural and mechanical systems. Numerical accuracy of sensitivity vectors effects the search direction and gra...
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Considerable progress has been made in developing analytical methods for design sensitivity analysis of structural and mechanical systems. Numerical accuracy of sensitivity vectors effects the search direction and gradient of the Lagrangian that are used in optimization algorithms. Most sensitivity expressions require numerical implementation of several steps before the final sensitivity vectors are obtained. This is particularly true for problems involving transient dynamic response and shape optimization. Therefore, it is important to verify numerical implementation and calculations based on the analytical sensitivity expressions before optimization of the problem is carried out. This paper describes three numerical procedures for verification of the sensitivity calculations. An example from optimal control literature is used to demonstrate the procedures and make recommendations for practical applications.
Computerized structural optimization is applied to designing space shuttle main engine (SSME) turbopump blades. optimization is implemented using a specially developed code, SSME/STAEBL. The capabilities of this code ...
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