Inverse Kinematics Based on Fuzzy Logic and Neural Networks for the WAM-Titan II Teleoperation System

The inverse kinematic problem is crucial for robotics. In this paper, a solution algorithm is presented using artificial intelligence to improve the pseudo-inverse Jacobian calculation for the 7-DOF Whole Arm Manipulator (WAM) and 6-DOF Titan II teleoperation system. An investigation of the inverse kinematics based on fuzzy logic and artificial neural networks for the teleoperation system was undertaken. Various methods such as Adaptive Neural-Fuzzy Inference System (ANFIS), Genetic Algorithms (GA), Multilayer Perceptrons (MLP) Feedforward Networks, Radial Basis Function Networks (RBF) and Generalized Regression Neural Networks (GRNN) were tested and simulated using MATLAB. Each method for identification of the pseudo-inverse problem was tested, and the best method was selected from the simulation results and the error analysis. From the results, the Multilayer Perceptrons with Levenberg-Marquardt (MLP-LM) method had the smallest error and the fastest computation among the other methods. For the WAM-Titan II teleoperation system, the new inverse kinematics calculations for the Titan II were simulated and analyzed using MATLAB. Finally, extensive C code for the alternative algorithm was developed, and the inverse kinematics based on the artificial neural network with LM method is implemented in the real system. The maximum error of Cartesian position was 1.3 inches, and from several trajectories, 75 % of time implementation was achieved compared to the conventional method. Because fast performance of a real time system in the teleoperation is vital, these results show that the new inverse kinematics method based on the MLP-LM is very successful with the acceptable error

Determinants of Knowledge Sharing: The Roles of Learning Organization Culture, Empowering Leadership, and Learning Goal Orientation

This study examined how knowledge sharing attitudes (KSAs) and knowledge sharing intentions (KSIs) are affected by perceived learning organization culture (LOC), empowering leadership (EL), and learning goal orientation (LGO). From the data collected, we discovered that KSA was a significant partial mediator between KSI and LGO. Furthermore, LOC and EL had moderating roles on the LGO and KSA relationship. Such moderation effects were insignificant for KSI, however. This study incorporated the knowledge sharing research fields of motivation research, leadership, and organizational culture. We comment that this study was centered on relatively highly educated management consultants, as human resource management and information management practitioners can support employees and their managers to enhance organizational knowledge sharing by offering relevant practices and services

Simulation based approach to predict vertical axis wind turbine faults using computational fluid dynamics.

Use of on-line fault detection techniques is integral to successful operation and maintenance of a wind turbine installation. The deployment of condition monitoring systems needs to be structured and sensitive to likely faults that may occur. In this work effects of blade faults have been simulated to understand sensitivity of blade faults on torque output. It is expected that this will help in developing a blade related condition monitoring strategy for a wind turbine system. It has been seen that instantaneous torque is a strong function of any blade imbalance and the torque output can be used successfully to identify initiation of blade imbalance related effects

A study of static and dynamic robustness of hydro/omniphobic surfaces

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010.Cataloged from PDF version of thesis.Includes bibliographical references (p. 107-110).Liquid droplets in the Cassie-Baxter state form liquid-air interfaces that are not flat but distorted due to pressure differences across the interfaces between the asperities. These distorted interfaces play an essential role in the transition from the composite Cassie-Baxter state to the fully-wetted Wenzel state and in the determination of the robustness of the composite state. As well as the static pressure difference due to the Laplace pressure, dynamic pressure difference due to various configurations including drop impact is also a source that causes the transition with the distorted interfaces. However, there are few experimental and numerical studies that consider the details of the distorted interfaces for a wide range of liquids and there is a lack of an apriori method to evaluate the robustness of three-dimensionally complicated textures. In addition, previous studies on drop impact pressure did not cover the maximum pressure at impact in the range of low velocities (< 2 m/s). We have first investigated the shape of distorted liquid-air interfaces and their transition conditions experimentally by using droplets of various low surface tension liquids on millimeter-sized re-entrant surface topography. For the dynamic pressure difference, we proposed a modified water hammer pressure formula and compared with the experiment using a high speed camera. The static experimental results by using three dimensionally printed millimetric structures are in good agreement with our newly-developed finite element simulations. I These three-dimensional simulations of the interfacial shape provide a predictive tool for the robustness of a wide range of proposed micro-texture in terms of the breakthrough pressure at which the distorted liquid-air interface infiltrate into the space between asperities and the droplet transitions to the Wenzel state. The dynamic experimental results open a broad avenue to a novel approach to delve into the dynamic breakthrough pressure of droplets of a variety of liquids.by Kyoo Chul Park.S.M

Physico-chemical hydrodynamics of droplets on textured surfaces with engineered micro/nanostructures

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2013.Cataloged from PDF version of thesis.Includes bibliographical references.Understanding physico-chemical hydrodynamics of droplets on textured surfaces is of fundamental and practical significance for designing a diverse range of engineered surfaces such as low-reflective, self-cleaning or anti-fogging glass, easy-cleaning robust inkjet printer heads, or efficient fog-harvesting surfaces. Developing such functional surfaces requires interdisciplinary considerations that have not been broadly explored and which integrate principles from capillarity, optics, nanofabrication, hydrodynamics of complex fluids, and even aerodynamics. The primary contribution of this thesis is to integrate consideration of wetting phenomena coupled with reflection of light, mechanical failure of slender structures, energy dissipation in non-Newtonian fluids, and aerodynamics of airborne droplets impacting onto permeable structures. Based on this integrative understanding, we construct design frameworks for both quantifying the performance of the desired functionalities for each application and for developing optimal functional surfaces. The first part of this thesis is focused on the development of superhydrophobic and superphotophilic surfaces that can be used for improving light-harvesting efficiency of photovoltaic cells. A design framework that combines wetting phenomena and adiabatic refractive index-matching together with a novel nanofabrication method is introduced to select slender tapered nanostructures that fulfill the multiple functionalities. The resulting nanoconetextured glass substrate exhibits highly robust superhydrophobicity and omnidirectional broadband anti-reflectivity as well as self-cleaning or anti-fogging property when conformally coated with a suitable chemical layer. Extending the nonwettability of textured surfaces to low surface tension oils is more difficult because oleophobic surfaces require a re-entrant topography. Deep reactive ion etching is used to fabricate square arrays of silicon nanopillars with wavy sidewalls that help support the superoleophobic state. The effect of the re-entrant nanotexture on the apparent contact angle, contact angle hysteresis, and sliding angle of water and hexadecane droplets is studied. We discuss numerical predictions for the critical pressure differences that cause failure of the Cassie- Baxter state that characterizes the super-repellent state for water and hexadecane droplets on the textured surfaces. In addition, dimensionless design parameters for quantifying the resistance to bending or buckling of the slender nanostructures are derived to design robust superoleophobic inkjet printer heads. Because of the natural repellency of many leaf surfaces to water, non-Newtonian fluids such as dilute polymer solutions are widely used to maximize the deposition rate of aqueous droplets sprayed onto textured liquid-repellent target surfaces. The drop impact dynamics of complex liquids on such surfaces is studied to develop a systematic understanding of the coupled effects of fluid viscoelasticity and the resulting dynamic wetting characteristics. We use hydrophobically-coated flat glass substrates, microtextured pillar surfaces, and nanocone surfaces as well as natural lotus leaves in conjunction with impacting droplets of dilute polyethylene oxide solutions to construct a drop impact dynamics diagram that can be used for understanding deposition of complex fluids on a wide range of hydrophobic textured surfaces. Lastly, the fundamental principles underlying the collection of fog droplets impacting permeable and textured structures such as woven meshes are studied. A design map predicting the theoretical collection efficiency is constructed based on two important dimensionless ratios that characterize the mesh geometry and the impacting droplet stream. Two physical limitations associated with clogging and re-entrainment are identified and potential solutions utilizing surface wettability are discussed. We use a family of physico-chemically patterned meshes with a directed stream of fog droplets to simulate a natural foggy environment and demonstrate a fivefold enhancement in the fog-collecting efficiency of a conventional polyolefin mesh. The design rules developed in this thesis can be applied to select a mesh surface with optimal topography and wetting characteristics to harvest enhanced water fluxes over a wide range of natural convected fog environments. In summary, by developing an integrative understanding of the physico-chemical hydrodynamics of droplets on textured substrates, we have been able to realize a number of novel functionalities using textured surfaces and have constructed design frameworks that can be applied for optimizing the performance of each multi-functional surface. For future work, initial steps for commercializing several of these multi-functional surfaces developed in this thesis are briefly discussed.by Kyoo Chul Park.Ph.D