Department of Mechanical Engineering

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IIT Jodhpur

Coaxial rotor helicopters at the Micro Air Vehicle scale are becoming widely accepted as an easy to fly and stable configuration. This study models the heave and yaw modes of the vehicles dynamics, based on the aerodynamic interaction of the two rotors. The linearized model is represented in state space with a closed form solution. It is then evaluated for its stability and control response. The coupling between the height and heading transient response is evaluated. Based on these characteristics, a technique for control mixing is proposed for the ease of pilot control and also closed loop design. The steady state values of the model are validated using typical parameters of a commercially available vehicle. The predicted thrust sharing between the rotors is found to match with that reported in experiments. The effect of the interaction between the two coaxial rotors on the system performance and stability is analyzed.

World University root node

AIAA Guidance, Navigation, and Control Conference

Analytical formulation of heave-yaw modes for a coaxial rotor micro aerial vehicle

International Journal of Thermal \& Environmental Engineering

Development of a Simulation Program to Optimise Process Parameters of Steam Power Cycles

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Journal of Micro/Nanolithography, MEMS, and MOEMS

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

Due to the high surface area and good bio-compatibility of nano structured ZnO, it finds good utility in biosensor applications. In this work we have fabricated highly dense ZnO nano bundles with the assistance of self assembled poly methylsilisesquoxane (PMSSQ) matrix which has been realized in a carpet like configuration with implanted ZnO nano-seeds. Such high aspect ratio structures (∼50) with carpet like layout have been realized for the first time using solution chemistry. Nanoparticles of PMMSQ are mixed with a nano-assembler Poly-propylene glycol (PPG) and Zinc Oxide nanoseeds (5-15 nm). The PPG acts by assembling the PMSSQ nanoparticles and evaporates from this film thus creating the highly porous nano-assembly of PMMSQ nanoparticles with implanted Zinc Oxide seeds. Nano-wire bundles with a high overall surface roughness are grown over this template by a daylong incubation of an aqueous solution of hexamethylene tetra amine and Zinc nitrate. Characterization of the fabricated structures has been extensively performed using FESEM, EDAX, and XRD. We envision these films to have potential of highly dense immobilization platforms for antibodies in immunosensors. The principle advantage in our case is a high aspect ratio of the nano-bundles and a high level of roughness in overall surface topology of the carpet outgrowing the zinc-oxide nanowire bundles. Antibody immobilization has been performed by modifying the surface with protein-G followed by Goat anti salmonella antibody. Antibody activity has been characterized by using 3D profiler. Bio-Rad Protein assay and UV-Visible spectrophotometer. © 2014 Materials Research Society.

Materials Research Society Symposium Proceedings

Antibody immobilization for ZnO nanowire based biosensor application

Soft lithography in 2-dimensional (2-D) was developed for polymer MEMS applications about two decades back. The technique was highly useful for replication of microstructure molds using a soft polymeric material called PDMS (polydimethylsiloxane). From its inception the process has been widely applied to microfluidics, biochips, hybrid biomedical microdevices etc. However, it was limited to only surface microstructures and 3-Dimensional (3-D) soft lithography although performed by some research groups involved some very precise and expensive techniques like stereolithography etc. The exploration of soft lithography in three dimensions by using a replication technique with copper wires with micron size diameters was performed by our group relatively recently (Singh et al. in International conference on MEMS, IIT Madras, Chennai, 2009). In this work we have used the 3-D replication and molding technique to develop concentric solenoid patterns around micro-channels in the bulk of PDMS. The solenoidal paths of various pitches ranging from 0.4 to 1.2 mm have been replicated in PDMS using an innovatively designed fixture. The solenoids have been structurally characterized using an inverted fluorescence microscope (Nikon 80i) for dimensional parameters like pitch, length etc. Further, the solenoidal path designs have been simulated, optimized and fabricated around a central channel of 80 μ diameter and we have observed the repeatability of this fabrication process multiple times. The purpose of this architecture is to initiate valving action wherein fluid movement in the central channel can be restricted by filling the surrounding solenoidal track with compressed air at high pressure so that it can squeeze the centrally located micro-channel carrying the liquid. This valving structure may find a lot of applications in lab on chip devices, PCR biochips, biomedical micro-devices etc. © 2013 Springer-Verlag Berlin Heidelberg.

Microsystem Technologies

Design and fabrication of 3-dimensional helical structures in polydimethylsiloxane for flow control applications

We report a novel pH-sensitive hydrogel based micro-valve for metered flow that has applications in a laboratory made "Intelligent valving system". The hydrogel solution was prepared through Chitosan and poly vinyl alcohol in acetic acid and crystallized using gluteraldehyde as the crosslinking agent in the form of thin wafers and it was found to be very sensitive to pH changes. The pore structure of hydrogel was investigated through Field Emission Scanning Electron Microscopy and thin wafers of the gel were physically placed inside PDMS microchannels. Flow metering in these channels was observed by controlled expansion of the hydrogel plug till complete valving was realized. This valving device was further precisely characterized with micro Particle Image Velocimetry using a solution containing fluorescent polymeric micro beads. The principle advantage of this hydrogel device is the smaller range of pH (varying between pH 3 and 7) over which the valving response is observed. © 2014 Springer-Verlag Berlin Heidelberg.

A novel microfluidic switch for pH control using Chitosan based hydrogels

SAKSHAR: An Image-projective Desktop Varnamala Trainer (IDVT) for Interactive Learning of Alphabets

A novel compliant robot is proposed for traversing on unstructured terrains. The robot consists of modules, each containing a link and an active wheel-pair, and neighboring modules are connected using a passive joint. This type of robots are lighter and provide high durability due to the absence of link-actuators. However, they have limited climbing ability due to tendency of tipping over while climbing big obstacles. To overcome this disadvantage, the use of compliant joints is proposed in this work. Stiffness of each compliant joint is estimated by formulating an optimization problem with an objective to minimize link joint moments while maintaining static-equilibrium. This is one of the key novelties of the proposed work. A design methodology is also proposed for developing an n-module compliant robot for climbing a given height on a known surface. The efficacy of the proposed formulation is illustrated using numerical simulations of the three and five module robots. The robot is successfully able to climb maximum heights upto three times and six times the wheel diameter using three and five modules, respectively. A working prototype was developed and the simulation results were successfully validated on it. © 2014 IEEE.

Proceedings - IEEE International Conference on Robotics and Automation

A compliant multi-module robot for climbing big step-like obstacles

Traditionally, High Dynamic Range (HDR) images are created by combining photographs taken at different exposure times. This technique has the overhead to capture more than single image of the scene while changing the exposure value. The proposed approach, InternetHDR, aims at creating an HDR image without the need of explicitly taking differently exposed images. This novel approach uses a single Low Dynamic Range (LDR) image as input to create an HDR image by combining information from visually similar images mined from the internet sites using Google image search. The results show that visually pleasing HDR images can be created using a single LDR image and additional information from the visually similar images mined from the internet. © 2014 IEEE.

2014 20th National Conference on Communications, NCC 2014

InternetHDR: Enhancing an LDR image using visually similar Internet images

This paper presents a novel visual servoing controller for a satellite mounted dual-arm space robot. The controller is designed to complete the task of servoing the robot's endeffectors to the desired pose, while regulating orientation of the base-satellite. Task redundancy approach is utilized to coordinate the servoing process and attitude of the base satellite. The visual task is defined as a primary task, while regulating attitude of the base satellite to zero is defined as a secondary task. The secondary task is formulated as an optimization problem in such a way that it does not affect the primary task, and simultaneously minimizes its cost function. A set of numerical experiments are carried out on a dual-arm space robot showing efficacy of the proposed control methodology. © 2014 IEEE.