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January 1998 - present
Publications
Publications (50)
This paper presents a screw theory based method for determining the set of possible second-order relative motions between two 3D rigid objects which are initially in a finite number of unilateral point contacts. Using adjoint transformation for twist and twist-derivative, the motion space allowed by each contact is referred to a common coordinate s...
A computational method for estimating the functional reach envelopes for standing postures using Digital Human Model (DHM) is presented. A DHM that embodies a static-stability model based on Functional Stability Region (FSR), a biomechanics based postural effort model, and uses non-linear programming for predicting reach is first described. The mod...
This paper studies the instantaneous second-order total freedom of two smooth objects initially in contact at a single point. The analytical determination of the set of physically allowed second-order motions is formulated in the Euclidean space using the screw theoretic concepts of twist and twist-derivative. Mathematical expression that character...
In this paper, the proposed formulation of the single contact motion space analysis using screws and differential screws, shows that only the geometric kinematical properties affect the second-order motion space characteristics w.r.t. a contact. The classical Eulery-Savary equation derived through the present approach established its necessity and...
This paper presents a study on restraining the motion of planar mechanisms using point contacts between the links of the mechanisms. First-order form-closure (FFC) and second-order form-closure (SFC) of 1- and 2-degrees-of-freedom (d.o.f.) smooth planar motions are studied. It is shown geometrically that two and three point contacts are sufficient...
An ergonomic assembly process is safer for operators and is more efficient in quality, time, cost and productivity. An assembly process is carried out in a series of distinct events. Ergonomic assessment of an assembly process therefore involves identification of the distinct events within the process and assessment of difficulty in carrying out ea...
For real-time ergonomic applications, it is essential to track body data and perform real-time data analysis, for detecting postural deviations and possible ergonomic difficulties. This paper presents a setup that uses a body tracking system for automated, real-time postural data collection during an assembly task, for use in ergonomic studies. An...
BACKGROUND: In 2013 alone, 5000 new cases of Upper limb (UL) loss in India were reported. This segment has been poorly understood, with limited or no access to quality prosthetic rehabilitative care. Furthermore, very few studies have been carried out to capture their needs and concerns. OBJECTIVE: To understand demographics and needs of UL prosthe...
This paper revisits the classical envelope theory in plane, which deals with two planar curves in a point contact moving in relative roll-slide motion. The well known result about the centers of curvature of the generating curve and the envelope curve behaving as coordinated centers, is shown to be valid even if the instantaneous relative angular v...
Digital Human Modelling (DHM) is rapidly emerging as one of the most cost-effective tool for generation computer based human- in-the-loop simulations for a better understanding of human behaviour under complex systems. In this paper we present a functional vision based human simulation framework (visDHM). It incorporates human visual acuity based c...
Digital Human Models (DHM) are used in digital mockups to identify human factor problems in design and assembly. Present applications are mostly limited to the posture, biomechanics, reach and simple visibility analysis and they are mostly developed for independent simulations that are mostly hand crafted by designers. Our aim is to develop natural...
Identification of distinct events in an assembly process plays a vital role in assigning difficulty of assembly to specific events within the process. Literature addresses identification of events in assembly by analyzing videos, which is a manual process. We propose an approach to identify these events automatically using a method based on trackin...
Assemblability is defined as the ease of assembling parts in a product. It is important to address the factors that affect assemblability, so as to generate knowledge with which to take targeted measures to reduce the difficulty of humans involved in assembly tasks and increase productivity. Existing literature addresses few factors that affect ass...
In this paper we have presented a pilot study done on seven subjects for analyzing the variation of human task performance on precision manual tasks by changing the visual distance. A trivial screw fastening task was performed at sitting and standing posture. It was observed that as long as components remained properly visible and within hand reach...
This paper investigates the instantaneous spatial higher pair to lower pair substitute-connection which is kinematically equivalent up to acceleration analysis for two smooth surfaces in point contact. The existing first-order equivalent substitute-connection consisting of a Hooke's joint (U-joint) and a spherical joint (S-joint) connected by an ad...
Sounds from products which carry information about its performance can be called as product sounds. Product sounds can aid visual display and controls if designed effectively. In this work, the authors collected 6,190 sound samples. Out of this, 670 sounds were coded, based on three categories of abstractions, namely index (on causality), icon (on...
Perineum pressure due to riding bicycle with conventional nosed-seats is a well-known problem documented in literature. The problem of perineum pressure due to seating arrangement in bicycle is investigated and detailed analysis is carried out to understand the problems associated. An ergonomic bicycle seat is then designed keeping in mind the spec...
This paper describes the use of liaison to better integrate product model and assembly process model so as to enable sharing of design and assembly process information in a common integrated form and reason about them. Liaison can be viewed as a set, usually a pair, of features in proximity with which process information can be associated. A liaiso...
This paper presents a simple second-order, curvature based mobility analysis of planar curves in contact. The underlying theory deals with penetration and separation of curves with multiple contacts, based on relative configuration of osculating circles at points of contact for a second-order rotation about each point of the plane. Geometric and an...
Toggle mechanisms are ubiquitous in electrical switches. However, literature for their mechanical design is scarce. This paper defines and classifies the toggle phenomena observed during switching. The concept of double toggle introduced in this paper enables a systematic screening of kinematic structure for the suitability in high performance swit...
The paper identified and characterized a special multi-degree of freedom toggle behavior, called double toggle, observed in a typical MCCB switching mechanism. For an idealized system, the condition of toggle sequence is derived geometrically. The existing tools available in a multi-body dynamics package are used for exploring the dynamic behavior...
In the product conceptualization phase of design, sketches are often used for exploration of diverse behaviour patterns of the components to achieve the required functionality. This paper presents a method to animate the sketch produced using a tablet interface to aid verification of the desired behaviour. A sketch is a spatial organization of stro...
Sketch is the primary mode of concept exploration and development in the early stages of design. In a global product development scenario, collaboration in the early fluidic stages could minimize design conflicts and enhance design understanding. In this work, the potential modalities of interactions among the collaborating designers in early stage...
Posture modeling for DHMs has significant effect on their usage in evaluation of product ergonomics. Direct manipulation schemes, such as joint level maneuvering for changing posture, are tedious and need more user intervention; complex scenarios are hardly simulated. This paper presents a high-level, relations based, description scheme for human p...
Digital human modeling (DHM) involves modeling of structure, form and functional capabilities of human users for ergonomics simulation. This paper presents application of geometric procedures for investigating the characteristics of human visual capabilities which are particularly important in the context mentioned above. Using the cone of unrestri...
This paper deals with mask shape design to ensure a statistical fit for a given population represented by tessellated 3D head scans. The mask rim curve should contact the face without gaps. This work identifies corresponding points on the mask and facial landmarks. The landmarks define a coordinate frame which helps extract rim contours (mask conto...
The paper introduces the concept of functional segmentation for segregating the strokes in a product concept sketch into functionally meaningful groups. Analysis of the distributions of starting points, time and mean pressure associated with the strokes in sketches revealed that shape defining and shape detailing strokes are separable through thres...
Understanding of the shape and size of different features of human body from the scanned data is necessary for automated design and evaluation of product ergonomics. In this paper, a computational framework is presented for automatic detection and recognition of several facial feature-regions from scanned head and shoulder polyhedral models. A nois...
This paper makes explicit the relation between relative part position and kinematic freedom of the parts which is implicitly available in the literature. An extensive set of representative papers in the areas of assembly and kinematic modelling is reviewed to specifically identify how the ideas in the two areas are related and influencing the devel...
This paper presents a geometric method for estimating the filed-of-view (FoV) for monocular and binocular vision using a 3D scanned human face. The traditional vision-cone approach offers simplicity but may lead to spurious inferences during ergonomic evaluations involving peripheral vision. FoV is asymmetric due to unrestricted zygomatic vision an...
The objective of this work is to use the relational configuration schema to describe hand postures and to simulate the posture-evolution. First, a general scheme of vocabulary for describing relational configurations is developed. Translating the conventional way of describing relationships using this scheme it is found that it is possible to evolv...
The paper presents a novel slicing based method for computation of volume fractions in multi-material solids given as a B-rep whose faces are triangulated and shared by either one or two materials. Such objects occur naturally in geoscience applications and the said computation is necessary for property estimation problems and iterative forward mod...
This paper presents a novel method of representing rotation and its application to representing the ranges of motion of coupled joints in the human body, using planar maps. The present work focuses on the viability of this representation for situations that relied on maps on a unit sphere. Maps on a unit sphere have been used in diverse application...
The objective of this work is to develop a systematic methodology for describing hand postures and grasps which is independent of the kinematics and geometry of the hand model which in turn can be used for developing a universal referencing scheme. It is therefore necessary that the scheme be general enough to describe the continuum of hand poses....
In this paper a method to determine the internal and external boundaries of planar workspaces, represented with an ordered set of points, is presented. The sequence of points are grouped and can be interpreted to form a sequence of curves. Three successive curves are used for determining the instantaneous center of rotation for the second one of th...
Computer aided design of machines involves modeling and analysis of the articulated assemblies. An assembly model is created by relative positioning of parts, whereas a kine-matic model is created by specifying kinematic constraints between the parts. Over 100 papers are reviewed in the areas of relative part positioning and deriving kinematic info...
In this paper the influence of dimensional variability of the arm on the reach in a given operational space is studied. The arm is modeled as a two-linked planar manipulator using the upper and lower arm dimensions from a public domain anthropometric database. The probability of reach for different points is determined assuming independent distribu...
The paper presents a systematic non-iterative procedure for a priory design of link shapes for interference-free motion of a planar mechanism. We define the notions of unilayer and multi-layer links and show that generality of shapes that can be conceived depends upon the designer’s choice about the physical implementation of the joints. We propose...
The paper presents a systematic methodology for synthesis of link geometry for interference free planar mechanisms with a given set of kinematic dimensions. All links are assumed to be flat, of same thickness; all the joints are assumed to be of revolute type. For this class of physical systems, the procedure guarantees that the complete range of k...
In this paper a graph-based method is presented which not only characterizes topological classification of the tessellated surfaces but also simultaneously generates the substantial circles or generators on the surface. Canonical polygons cannot always be mapped back to the original surface in terms of the edges of the given triangles. Hence, inste...
This paper presents a general methodology for the synthesis of the external boundary of the workspaces of a planar manipulator with arbitrary topology. Both the desired workspace and the manipulator workspaces are identified by their boundaries and are treated as simple closed polygons. The paper introduces the concept of best match configuration a...
The paper presents a fast and reliable method of determination of the external boundary of workspaces of planar manipulators with arbitrary topology. In this method, first, enough number (not necessarily very large) of points are generated in the workspace and then techniques of computational geometry are applied to determine the boundary. The meth...
The paper presents a centro-based characterization of singularities in planar multi-DOF mechanisms with arbitrary kinematic structure. A multi-DOF mechanism is treated as an assembly of several single DOF link sets and hence the terms like affected link set, active link set and active centro have been defined. Criteria for end-effector dependent an...
A homogeneous planar kinematic chain (KC) is a KC having all its constituting smallest independent circuits (fundamental circuits) of the same size. Davies [J. Mech. 3, 87-100 (1968)] established, using graph theory, that a planar KC (homogeneous) of mobility M cannot have all fundamental circuits of size greater than M + 4. In the present paper ma...
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...
In this paper the capabilities of a proposed serial, multi-link, snake-like, planar manipulator with highly restricted joint motion (only three states per joint) have been studied. Two different types of problem namely reach-the-point and follow-the-path problems, have been solved for such a manipulator when the number of links is assumed unlimited...