Kinematics of pantograph masts

This paper deals with the kinematics of pantograph masts. Pantograph masts have widespread use in space application as deployable structures. They are over constrained mechanisms with degree-of-freedom, evaluated by the Grübler–Kutzback formula, as less than one. In this paper, a numerical algorithm is used to evaluate the degree-of-freedom of pantograph masts by obtaining the null space of a constraint Jacobian matrix. In the process redundant joints in the masts are obtained. A method based on symbolic computation, to obtain the closed-form kinematics equations of triangular and box shaped pantograph masts, is presented. In the process, the various configurations such masts can attain during deployment, are obtained. The closed-form solution also helps in identifying the redundant joints in the masts. The symbolic computations involving the Jacobian matrix also leads to a method to evaluate the global degree-of-freedom for these masts.

A discrete state perspective of manipulator workspaces Vorstellungen von diskreten zuständen von manipulator-arbeitsräumen

The finite resolution of joint drives or sensors imparts a discrete nature to the joints of a manipulator. Because of this an arbitrary point in the workspace cannot be reached without error even in ideal mechanical environment. This paper investigates the effect of this discrete nature of the joints on the accuracy of performance of a manipulator and develops a method to select the joint states to reach a point with least error. It is shown that the configuration leading to least error cannot, in general, be found from configuration space, especially when there is large variation in the link lengths or joint resolutions or both. The anomaly becomes severe when the gross motion of the end-effector approaches the local resolution of the workspace. The paper also shows how to distinguish two workspaces which may be identical so far as the boundary points are concerned, taking the joint resolutions into account. Finally, the concepts have been extended to define continuous space global and local performance indices for general multi degree of freedom manipulators.

FE analysis of piezo-laminate composites under thermal loads

A shear flexible 4-noded finite element formulation, having five mechanical degrees of freedom per node, is presented for modeling the dynamic as well as the static thermal response of laminated composites containing distributed piezoelectric layers. This element has been developed to have one electrical degree of freedom per piezoelectric layer. The mass, stiffness and thermo-electro-mechanical coupling effects on the actuator and sensor layers have been considered. Numerical studies have been conducted to investigate both the sensory and active responses on piezoelectric composite beam and plate structures. It is. concluded that both the thermal and pyroelectric effects are important and need to be considered in the precision distributed control of intelligent structures.

Assessing Degree of Novelty of Products to Ascertain Innovative Products

Substantial increase in competition compels design firms to develop new products at an increasingly rapid pace. This situation pressurizes engineering teams to develop better products and at the same time develop products faster [1]. Continuous innovation is a key factor to enable a company to generate profit on a continued basis, through the introduction of new products in the market – a prime intention for Product Lifecycle Management. Creativity, affecting a wide spectrum of business portfolios, is regarded as the crucial factor for designing products. A central goal of product development is to create products that are sufficiently novel and useful. This research focuses on the determination of novelty of engineering products. Determination of novelty is important for ascertaining the newness of a product, to decide on the patentability of the design, to compare designers' capability of solving problems and to ascertain the potential market of a product. Few attempts at measuring novelty is available in literature [2, 3, 4], but more in-depth research is required for assessing degree of novelty of products. This research aims to determine the novelty of a product by enabling a person to determine the degree of novelty in a product. A measure of novelty has been developed by which the degree of ''novelty'' of products can be ascertained. An empirical study has been conducted to determine the validity of this method for determining the 'novelty' of the products.

Comparison of the degree of creativity in the design outcomes using different design methods

This work analyses the influence of several design methods on the degree of creativity of the design outcome. A design experiment has been carried out in which the participants were divided into four teams of three members, and each team was asked to work applying different design methods. The selected methods were Brainstorming, Functional Analysis, and SCAMPER method. The `degree of creativity' of each design outcome is assessed by means of a questionnaire offered to a number of experts and by means of three different metrics: the metric of Moss, the metric of Sarkar and Chakrabarti, and the evaluation of innovative potential. The three metrics share the property of measuring the creativity as a combination of the degree of novelty and the degree of usefulness. The results show that Brainstorming provides more creative outcomes than when no method is applied, while this is not proved for SCAMPER and Functional Analysis.

Analysis of the degrees-of-freedom of spatial parallel manipulators in regular and singular configurations

This paper presents a study of the nature of the degrees-of-freedom of spatial manipulators based on the concept of partition of degrees-of-freedom. In particular, the partitioning of degrees-of-freedom is studied in five lower-mobility spatial parallel manipulators possessing different combinations of degrees-of-freedom. An extension of the existing theory is introduced so as to analyse the nature of the gained degree(s)-of-freedom at a gain-type singularity. The gain of one- and two-degrees-of-freedom is analysed in several well-studied, as well as newly developed manipulators. The formulations also present a basis for the analysis of the velocity kinematics of manipulators of any architecture. (C) 2013 Elsevier Ltd. All rights reserved.

Influence of initial degree of saturation on swell pressures of compacted Barmer bentonite specimens

Densely compacted bentonite or bentonite-sand mixture has been identified as suitable buffer in deep geological repositories as its exceptionally high swelling capacity enables tight contact between the waste canister and surrounding rock. The degree of saturation of the compacted bentonite buffer can increase upon ingress of groundwater from the surrounding rock mass or decrease from evaporation due to high temperature (50-210 degrees C) derived from the waste canister. Available studies indicate that the influence of initial moisture content or degree of saturation on the swell pressure or swell potential of compacted bentonites is unclear. Some studies suggest that initial degree of saturation has an influence, while others suggest that it does not have bearing on the swell pressure of compacted bentonites. This paper examines the influence of initial degree of saturation in montmorillonite voids (termed,S-r,S-MF) on swell pressure of compacted Barmer bentonite-sand mixtures (dry density range: 1.4-2 Mg/m(3)) from micro-structural considerations. The experimental results bring out that, constant dry density specimens that developed similar number of hydration layers upon wetting developed comparable swell pressures and were unaffected by variations in initial S-r,S-MF values. Comparatively, constant dry density specimens that developed dis-similar number of hydration layers upon wetting established different swell pressures and were responsive to variations in initial S-r,S-MF. (C) 2015 Elsevier Ltd. All rights reserved.

In-situ synthesized poly(vinyl butyral)/MMT-clay nanocomposites: The role of degree of acetalization and clay content on thermal, mechanical and permeability properties of PVB matrix

Poly(vinyl butyral) - MMT clay nanocomposites were synthesized in situ with three different degrees of acetalization and with varying clay content for each vinyl butyral polymer ratio. The clay nano-platelet galleries were expanded, as determined by X-ray diffraction and TEM analysis. The glass transition temperature of the polymer nanocomposites were found to be similar to 56 degrees C and similar to 52 degrees C for the neat polymer and the 4% clay loaded samples, respectively. The 4 wt% clay loaded film showed higher strength and low strain to failure. The dynamic mechanical analysis also confirmed the improved stability of the matrix. The matrix with 0.5 butyral to alcohol ratio for 4 wt% clay exhibited good water vapor transmission compared to all other compositions. The encapsulated devices with 2.5 and 4 wt% clay loaded films increases the device life time and the efficiencies of these films were 50% higher than their encapsulated pristine polymer films. (C) 2015 Elsevier Ltd. All rights reserved.

Inverse Sensitivity Analysis of Singular Solutions of FRF matrix in Structural System Identification

The problem of structural damage detection based on measured frequency response functions of the structure in its damaged and undamaged states is considered. A novel procedure that is based on inverse sensitivity of the singular solutions of the system FRF matrix is proposed. The treatment of possibly ill-conditioned set of equations via regularization scheme and questions on spatial incompleteness of measurements are considered. The application of the method in dealing with systems with repeated natural frequencies and (or) packets of closely spaced modes is demonstrated. The relationship between the proposed method and the methods based on inverse sensitivity of eigensolutions and frequency response functions is noted. The numerical examples on a 5-degree of freedom system, a one span free-free beam and a spatially periodic multi-span beam demonstrate the efficacy of the proposed method and its superior performance vis-a-vis methods based on inverse eigensensitivity.

A computerized methodology for structural synthesis of kinematic chains: Part 1- Formulation

In an effort to develop a fully computerized approach for structural synthesis of kinematic chains the steps involved in the method of structural synthesis based on transformation of binary chains [38] have been recast in a format suitable for implementation on a digital computer. The methodology thus evolved has been combined with the algebraic procedures for structural analysis [44] to develop a unified computer program for structural synthesis and analysis of simple jointed kinematic chains with a degree of freedom 0. Applications of this program are presented in the succeeding parts of the paper.

Analysis of two degrees of freedom systems through weighted mean square linearization approach

In this paper a study of the free, forced and self-excited vibrations of non-linear, two degrees of freedom systems is reported. The responses are obtained by linearizing the nonlinear equations using the weighted mean square linearization approach. The scope of this approach, in terms of the type of non-linearities the method can tackle, is also discussed.

Analysis of two degrees of freedom systems through weighted mean square linearization approach

In this paper a study of the free, forced and self-excited vibrations of non-linear, two degrees of freedom systems is reported. The responses are obtained by linearizing the nonlinear equations using the weighted mean square linearization approach. The scope of this approach, in terms of the type of non-linearities the method can tackle, is also discussed.

Partial Integrated Guidance and Control of Surface-to-Air Interceptors for High Speed Targets

An important limitation of the existing IGC algorithms, is that they do not explicitly exploit the inherent time scale separation that exist in aerospace vehicles between rotational and translational motions and hence can be ineffective. To address this issue, a two-loop partial integrated guidance and control (PIGC) scheme has been proposed in this paper. In this design, the outer loop uses a recently developed, computationally efficient, optimal control formulation named as model predictive static programming. It gives the commanded pitch and yaw rates whereas necessary roll-rate command is generated from a roll-stabilization loop. The inner loop tracks the outer loop commands using the Dynamic inversion philosophy. Uncommonly, Six-Degree of freedom (Six-DOF) model is used directly in both the loops. This intelligent manipulation preserves the inherent time scale separation property between the translational and rotational dynamics, and hence overcomes the deficiency of current IGC designs, while preserving its benefits. Comparative studies of PIGC with one loop IGC and conventional three loop design were carried out for engaging incoming high speed target. Simulation studies demonstrate the usefulness of this method.

Decoupling in non-linear systems with two degrees of freedom

The problem of decoupling a class of non-linear two degrees of freedom systems is studied. The coupled non-linear differential equations of motion of the system are shown to be equivalent to a pair of uncoupled equations. This equivalence is established through transformation techniques involving the transformation of both the dependent and independent variables. The sufficient conditions on the form of the non-linearity, for the case wherein the transformed equations are linear, are presented. Several particular cases of interest are also illustrated.

Simplified theory of optical nonlinearities in spin-polarized semiconductors

The spin degree of freedom is largely disregarded in existing theories of the density-dependent optical properties of an interacting electron-hole plasma in quasiequilibrium. Here, we extended the pair equation, which is applicable to a bulk semiconductor at elevated temperatures, to calculate optical nonlinearities due to a spin-polarized plasma. We obtained agreement with recent circular dichroism data in laser-excited GaAs by using the plasma density alone as the fitting parameter. The simplicity of our theory, based on the analytical pair-equation formula, makes it ideal for conveniently modelling absorption in a carrier spin-polarized semiconductor.