Applied Mechanics and Materials Vols. 110-116

Abstract: A trajectory optimization method for hypersonic vehicle in glide phase satisfying maneuvering penetration is proposed. Divide the dangerous zones that the hypersonic vehicle may encounter during glide phase into avoidable no-fly zones and avoidless no-fly zones. Take the avoidable no-fly zones as path constraints to join the trajectory optimization. To penetrate the avoidless no-fly zones, trajectory is programmed by some maneuvering policy. Direct shooting method is used to discretize the control variable to piecewise constant functions. So the optimal control problem is transferred to a nonlinear programming (NLP) problem, and solved by the serial quadratic program (SQP) method.

Abstract: The paper presents a gauss pseudospectral solution for the trajectory optimization problem of a hypersonic vehicle. Determination of optimal trajectory of a hypersonic vehicle is of great interest due to the different path and boundary conditions that need to be met for high accuracy. Recent researches show that pseudospectral methods are capable of providing high accuracy in computationally efficient manner. The hypersonic vehicle optimized here is accelerated through solid rocket propulsion to mach 3.5 and after ejection of the rocket motor it is accelerated to mach 6 where it starts cruise for reaching target. The flight profile which is divided into boost, ascent, cruise and dive phase is optimized using multi-phase implementation programme of gauss pseudospectral method GPOPS. The optimization is carried out in 2D assuming non-rotating flat earth assumption and considering propulsion, dynamic and atmospheric constraints. The results are then analyzed for max range and max final velocity and hit angle. The results are found to be feasible.

Abstract: Typical seismic analysis using response spectrum method involves several steps from the initial step of extracting the modes. At the initial stage Eigen values are extracted corresponding to the modes of vibration. These give us Eigen vectors which are a series of relative displacement shapes; however these do not correspond to real displacements or stresses. Participation factors asses these Eigen vectors and grades them according to contribution they will have to the overall solution. Based on the spectral seismic acceleration, participation factor is used to calculate the mode coefficient, which is more of a scaling factor to give physical meaning to the values. Once the modes are extracted, the key issue is of combining these modes to obtain the seismic response. The modes cannot be added algebraically in reality as all the modes do not occur at the same time. Hence we employ methods which can add the modes in a more realistic manner. The objective of this paper is to do a comparative study of various mode combination methods with a focus on tank structures and study the effect of various geometrical parameters on the combination methods

Abstract: A new type of guidance law is developed for intercepting high maneuvering target. The law takes angular acceleration of line-of-sight as a primary input in place of the acceleration of target. As the significant required input quantity of the angular acceleration guidance (AAG), the angular acceleration of line-of-sight is estimated by a developed estimation approach based on sliding mode observer (SMO). Simulation results demonstrates advantages of this AAG guidance with the estimation approach based on SMO by comparing with the conventional guidance techniques and extended Kalman filter.

Abstract: The paper deals with possibilities of maintenance optimisation of k-out-of-n systems. The first part of the paper briefly analyses influence of preventive maintenance concept on reliability of k-out-of-n system and presents possibilities of preventive maintenance optimisation with respect to maintenance costs. The second part of the paper presents a suggested method of maintenance optimisation in the case of a processing machine for dosing tiny loose material and smaller piece goods. The method takes into account not only maintenance costs but also production losses caused by a prospective failure of the system. The proposed method facilitates decisions on maintenance intervals modification and the range of maintenance from the economic point of view.

Abstract: Micro hydro is that form of alternative source which refers to hydro power systems with a power rating of 100Kw. A 100kW system will produce 100 standard units of electricity in one hour. Micro hydro systems differ from large hydro power since the flows of water required are much smaller. This paper will give the details of our research on micro-hydro turbine. It also includes designing, fabricating and testing of a model for the prototype. The whole project has been done at the Pimpri Chinchwad municipal corporation’s water treatment plant. A complete model analysis report, with CAD design will be illustrated in the report. The details of model like its specifications, significance, figures, advantages and various forms of application will be documented. The flow in between various processes is utilised to generate electricity. The plus point of our project is that we design according to available conditions, not recondition according to available design

Abstract: A numerical simulation procedure for studying deposition of aerosol particles in a laminar convection flow of radiating gas over a backward-facing step including the effect of thermal force is developed. In the gas flow, all of the heat transfer mechanisms consisting of conduction, convection and radiation take place simultaneously. Behavior of solid particles is studied numerically based on an Eulerian–Lagrangian method. Two dimensional Navier-Stokes and energy equations are solved using CFD techniques, while the radiating transfer equation (RTE) is solved by discrete ordinate method (DOM) for calculating radiative heat flux distribution. The objective of this research is to study the effect of Reynolds number variation and also radiation on thermophoretic deposition of particles. Numerical results show a decrease in deposition percent by increasing in Reynolds number and the radiation effect is negligible. The results are compared with the existing experimental and numerical data and good agreement is found.

Abstract: This investigation is concerned with the non-linear multi-in-multi-out tracking control of a spacecraft with Double-gimbaled control moment gyros as actuators. An attitude dynamic model of rigid spacecraft with DGCMG and a kinematics model in terms of Modified Rodriguez parameters are given for the controller development. Then the control objective and system uncertainties in tracking problem are analyzed considering the major elements which work on the control performance such as moment of inertia change, wheel speed drift and external torque. A adaptive sliding mode controller is designed and is proved stable later in which the sliding mode control are used to compensate external torque and un-modeled dynamics while the adaptive parameters are used to estimate inertia and wheel speed on line. And a steering law of parallel mounted DGCMG is illuminated. Finally Monte Carlo simulation is carried out to prove the effectiveness of the controller.

Abstract: Spaceborn optical payload consists of optical elements supported by mechanical structure in desired orientation. Mechanical structure made up of various dissimilar materials like aluminum & invar possess dissimilar thermo-elastic behavior. Opto-mechanical assembly subjected to temperature change will results to change in optical element orientation which ultimately leads to change in optical parameters like registration. This is mainly due to dissimilar materials subjected to temperature variation will result to structural distortion. Use of dissimilar materials in an Opto- mechanical payload affects the angular stability of optical element due to temperature variation and results to change in optical element orientation. Flexure is required to be introduced within the opto-mechanical system having dissimilar materials to accommodate differential thermal expansion due to temperature variation and to maintain the registration. This paper explains, stability in dichroic element orientation of an opto-mechanical payload having dissimilar material & flexure design to maintain the orientation in opto-mechanical payload subjected to temperature variation without deterioration of fundamental frequency. It also explains theoretical thermo-elastic analysis and experimental test for validation of design, static and dynamic structural analysis like frequency response analysis to check the flexure survivability for vibration load.

Abstract: Supersonic chemical oxygen iodine laser (SCOIL) hasrecently proved itscapabilities against projectile targets such as missiles and rockets in the tests performed with ABL system. It is primarily a chemical based gas laser system involving extensive gas dynamics for achieving lasing action. COIL (l= 1.315 mm) is conducive for both defenseand industrial applications and the beam is optical fibre compatible. One of the chief components of a SCOIL device is the supersonic nozzle system which not only produces the desired cavity conditions in terms of Mach number and cavity pressure but is also responsible for efficient mixing of lasing [I2 + N2] and pumping media [O2 (1Dg) + N2]. The supersonic nozzle to a large extent controls the pressure recovery potential of the laser system and thereby the system volume. The present study discusses the performance of three nozzle configurations viz, slit, advanced/ ejector and winglet nozzle. The comparisons have been made in terms.