Department of Mechanical Engineering

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Pose estimation of cylindrical pellet using a single camera-in-hand configuration of a robot is discussed in this paper. Approaches to estimate pose in both isolated and an occluded environment is discussed. The pellet contour from the segmented image of the scene was compared with contours in the database to ascertain the matching orientation. For occluded pellets, a multiple-view based pose recognition system is proposed. Later, the estimated pose was communicated to the robot to enable it to pick-up the pellet. This has been experimentally implemented for cylindrical pellets and the performance is discussed. The algorithm enables online pellet pose determination and pick-up using KUKA KR5 robot. © 2013 ACM.

World University root node

Department of Computer Science & Engineering

ACM International Conference Proceeding Series

Cylindrical pellet pose estimation in clutter using a single robot mounted camera

A method is presented in this paper to predict cascade flutter under subsonic stalled flow condition in a quasi-steady manner. The ability to predict the occurrence of aeroelastic flutter is highly important from the compressor design point of view. In the present work, the well known Moore-Greitzer compression system model is used to evaluate the flow under rotating stall and the linearized aerodynamic theory of Whitehead is used to estimate the blade loading. The cascade stability is then predicted by solving the structural model, which is posed as a complex eigenvalue problem. The possibility of occurrence of flutter in both bending and torsional modes is considered and the latter is found to be the dominant one, under subsonic stalled flow, for a large range of frequency ratios examined. It is also shown that the design of compressor blades at frequency ratios close to unity may result in rapid initiation of torsional flutter in the presence of stalled flow. A frequency ratio of 0.9 is primarily emphasized for most part of the study as many interesting features are revealed and the results are physically interpreted. Roughly a pitchfork pattern of energy distribution appears to occur between bending mode and torsional mode which ensures that only one flutter mode is possible at any instant in time. A bifurcation from bending flutter to torsional flutter is shown to occur during which the frequency of the two vibrating modes appear to coalesce for a very short period of time. © 2013 Elsevier Ltd.

Journal of Fluids and Structures

Quasi-steady prediction of coupled bending-torsion flutter under rotating stall

Experimental studies have been performed on elastomeric layered composites to characterize the nonlinearity in dynamic stiffness and specific damping energy, so that their performance can be enhanced as isolators. The present study is divided into two parts: (a) analytical modeling of isolator samples, and (b) formulation for glue characteristics. Several samples of layered arrangement of elastomer and metal strips were used in the experiments. Dynamic and static loading experiments were performed. All these experimental results were used in developing nonlinear empirical models for the elastomer characteristics. Furthermore creep-fatigue test was performed to explain certain observed behavior in the elastomer characteristics. Concluding part of the paper discusses empirical formulation of the layered sample considering elastomer and adhesive layers as basic elements, thus evolving a method to calculate adhesive properties. © 2013 Elsevier Ltd.

Journal of Sound and Vibration

Analytical and empirical modeling of multilayered elastomeric isolators from damping experiments

The extremely low limit of detection (LOD) posed by global food and water safety standards necessitates the need to perform a rapid process of integrated detection with high specificity, sensitivity and repeatability. The work reported in this article shows a microchip platform which carries out an ensemble of protocols which are otherwise carried in a molecular biology laboratory to achieve the global safety standards. The various steps in the microchip include pre-concentration of specific microorganisms from samples and a highly specific real time molecular identification utilizing a q-PCR process. The microchip process utilizes a high sensitivity antibody based recognition and an electric field mediated capture enabling an overall low LOD. The whole process of counting, sorting and molecular identification is performed in less than 4 hours for highly dilute samples.

Fulltext

Scientific Reports

Integrated sorting, concentration and real time PCR based detection system for sensitive detection of microorganisms

Conventional photolithography normally utilizes a photomask for patterning light onto a chemical resist film. Therefore, the accuracy of microfabrication is highly dependent on the accuracy of the photomasks. Fabrication of hard masks involves the use of expensive laser pattern generators and other sophisticated machines using very highprecision stages and the necessary control instrumentation; therefore, an inexpensive strategy is highly necessary for laboratory-level fabrication. As this technology is primarily based on raster scanning of a laser beam, the mask making as such becomes a low-throughput process. A strategy of high-throughput manufacturing of hard masks with laser micromachining using a one-step exposure process of a chromated glass slide through a micromachined aluminum shadow mask is proposed. The features that are finally embedded in the mask are highly demagnified and well focused. Optimization of the laser machining process is carried out by considering all processing parameters. The features are characterized using an optical microscope, a scanning electron microscope, and a self-developed image analysis code. Geometrical methods are used to estimate the average edge roughness and feature size. We have also validated the usage of these masks by performing microfabrication on films made of photoresist. © 2013 Society of Photo-Optical Instrumentation Engineers.

Journal of Micro/Nanolithography, MEMS, and MOEMS

Optimization of laser machining process for the preparation of photomasks, and its application to microsystems fabrication

Robotic systems studied in Chap. 6 have their bases fixed, however, in reality many robotic systems have their bases mobile or floating. In the case of a fixed-base robotic system, the base does not influence the dynamics, whereas it significantly influences the dynamics in the case of a floating-base robotic system. Space manipulators and legged robots are examples of floating-base robotic systems. Legged robots find applications in maintenance task of industrial plants, operations in dangerous and emergency environments, surveillance, maneuvering unknown terrains, human care, terrain adaptive vehicles and many more. In the case of legged robots they are either classified based on the number of legs, e.g., biped, quadruped, hexapod, etc., or the way it balances, e.g., statically or dynamically balanced. As reviewed in Chap. 2, legged robots (1) have variable topology, (2) move with high joint accelerations, (3) are dynamically not balanced if Center-of-Mass (COM) moves out of the polygon formed by the support feet, and (4) are under actuated. Hence, objective of achieving stable motion is difficult to decompose into actuator commands. Therefore, control of legged robots is intricate and dynamics plays vital role in achieving stable motion. © 2013, Springer Science+Business Media Dordrecht.

Intelligent Systems, Control and Automation: Science and Engineering

Recursive Dynamics for Floating-Base Systems

This paper presents a method to capture the orbiting objects using a robotic system mounted on a service satellite. The main objective is to manipulate the robot such that no reaction moment gets transferred to the base satellite. This will avoid use of any attitude controller resulting in fuel savings. Note that the constraints leading to zero reaction moment are nonholonomic, and this makes path planning a complex problem. In this work, first a method based on holonomic distribution of the nonholonomic constraints is discussed. As this method exploits constraints in terms of joint velocities, it does not always ensure successful capture. Next, a method based on task-level constraints, written in terms of end-effector's velocities, has been illustrated. It is shown that the path planned using this method has several singular points. In order to overcome disadvantages of the above two methods a novel approach is proposed which uses holonomic distribution to reach closer to the target and task-level constraints to finally capture the target. Efficacy of the method is shown using a 3-link robot mounted on a service satellite. © 2013 ACM.

Control strategies for reactionless capture of an orbiting object using a satellite mounted robot

This paper proposes a systematic method to optimize wheel torques in a compliant modular robot, which consists of 3 link-wheel modules connected by revolute joints. Conventionally, actuators are used at these joints for posture control while climbing. In this work, use of torsional springs at the joints is proposed for posture control. The compliance thus obtained is profitably used to manoeuvre on uneven terrains. It is also shown how the springs are designed to be stiff enough to restrict the link-wheel module from tipping over while climbing big step-like obstacles. The only actively controlled variables of the robot are wheel torques, which are optimized to minimize wheel slip. This helps in reducing odometric error and maximizing energy efficiency. The proposed optimization builds on the quasi-static analysis of the robot and forms one of the key novelties of this paper. The results show the advantages of modularity in climbing big steps without any slip. The proposed wheel-torque optimization lends utility in the design of an appropriate wheel velocity controller.

1st International and 16th National Conference on Machines and Mechanisms, iNaCoMM 2013

Wheel torque optimization for a compliant modular robot

This paper presents strategies for point-to-point reactionless manipulation of a satellite mounted dual-arm robotic system for capture of tumbling orbiting objects, such as out-of-commission satellites and space debris. Use of the dual-arm robot could be more effective than the single-arm when there is no provision for a grapple fixture or the object is tumbling. The dual arms can also provide dexterous manipulation. As the main objective in capture of orbital objects is to move the end-effector from initial position to the grapple point with desired velocity, the task-level reactionless constraints in terms of end-effector velocities are derived. The trajectory planned using these constraints, however, results in several singular points within the robot's workspace. In order to overcome this shortcoming, three point-to-point path planning strategies are presented, which improve the reactionless operation of the dual-arm robot. The strategies are illustrated by carrying out simulations for a 6-degree-of-freedom (DOF) dual-arm robotic system mounted on a satellite.

AIAA Guidance, Navigation, and Control (GNC) Conference

Reactionless path planning strategies for capture of tumbling objects in space using a dual-arm robotic system

The present paper analyzes the effects of plumes for heat transfer enhancement at solid-liquid interface taking both smooth and grooved surfaces. The experimental setup consists of a tank of dimensions 265×265×300 (height) containing water. The bottom surface was heated and free surface of the water was left open to the ambient. In the experiments, the bottom plate had either a smooth surface or a grooved surface. We used 90? V-grooved rough surfaces with two groove heights, 10mm and 3mm. The experiment was done with water layer depths of 90mm and 140mm, corresponding to values of aspect ratio(AR) equal to 2.9 and 1.8 respectively. Thymol blue, a pH sensitive dye, was used to visualize the flow near the heated plate. The measured heat transfer coefficients over the grooved surfaces were higher compared that over the smooth surface. The enhanced heat transport in the rough cavities cannot be ascribed to the increase in the contact area, rather it must be the local dynamics of the thermal boundary layer that changes the heat transport over the rough surface. Copyright © 2013 by ASME.