Eniko T Enikov

Abstract:

The design and fabrication of a novel multi-degree-of-freedom force sensor is described. The three-dimensional structure of the sensor is a result of combining several microfabrication techniques: wet bulk micromachining, fusion bonding, chemical mechanical polishing, deep RIE, LPCVD, PECVD and thermally evaporated thin films. The sensor is designed to operate in the 0-500 μN force range and the 0-10 μNm torque range. The flexibility of the process to create overhanging structures with arbitrary lengths and heights is illustrated by the integration of micro-tweezers directly onto the force sensor. Among other advantages of the developed process is a dicing-free self-release of wafer structures. This allows very fragile structures, such as micromirrors and other optical components, to be individually packaged.

Abstract:

Teaching classical controls systems design to mechanical engineering students presents unique challenges. While most mechanical engineering programs prepare students to be wellversed in the application of physical principles and modeling aspects of physical systems, implementation of closed loop control and system-level analysis is lagging. It is not uncommon that students report difficulty in conceptualizing even common controls systems terms such as steady-state error and disturbance rejection. Typically, most courses focus on the theoretical analysis and modeling, but students are left asking the questions... How do I implement a phase-lead compensator? ...What is a non-minimum phase system? This paper presents an innovative approach in teaching control systems design course based on the use of a low-cost apparatus that has the ability to directly communicate with MATLAB and its Simulink toolbox, allowing students to drag-and-drop controllers and immediately test their effect on the response of the physical plant. The setup consists of a DC micro-motor driving a propeller attached to a carbon-fiber rod. The angular displacement of the rod is measured with an analog potentiometer, which acts as the pivot point for the carbon fiber rod. The miniature circuit board is powered by the USB port of a laptop and communicates to the host computer using the a virtual COM port. MATLAB/Simulink communicates to the board using its serial port read/write blocks to command the motor and detect the deflection angle. This presentation describes a typical semester-long experimental protocol facilitated by the low-cost kit. The kit allows demonstration of classical PID, phase lead and lag controllers, as well as non-linear feedback linearization techniques. Comparison between student gains before and after the introduction of the mechatronic kits are also provided. Copyright © 2012 by ASME.

Abstract:

In the field of nanotechnology and applied engineering, an area that has received a great deal of attention is that of nanoassembly. The objective of this study was to demonstrate nanoassembly of type-I collagen on specified surfaces in response to an electric field. Two, otherwise identical, collagen solutions were prepared and adjusted to pHs of 5.5 and 8. The isoelectric fosusing point of collagen occurs at pH=6.7 which implies that the suspended collagen fibers in the aforementioned solutions possessed a net positive or negative charge, respectively. In each collagen solution, one volt was applied through a set of submerged electrodes for one minute. Atomic force microscopy was used to detect if and where assembly had occurred on the electrodes. The positively charged fibrils (pH=5.5) assembled on the negative electrode, but not on the positive electrode. The negatively charged fibrils (pH=8) assembled only on the positive electrode, but not on the negative electrode. In both cases, assembly occurred on the electrode of opposite charge of the suspended collagen fibrils, which was anticipated. The assembly of the positively charged fibrils (pH=5.5) on the cathode produced larger fibers than the fibers that were produced by the negatively charged fibrils (pH=8) on the anode. This indicated the more favorable environment for nanoassembly was the positively charged fibril solution (pH=5.5). Copyright © 2005 by ASME.

Abstract:

Engineering education has the objective of not only presenting the scientific principles, i.e., engineering science, but also of teaching students how to apply these to real problems. Therefore, hands-on laboratories have been an integral part of the engineering curriculum since its inception. This presentation will demonstrate the use of a novel low-cost experimental apparatus for use in a typical undergraduate course in control systems taught to mechanical engineering students, i.e. students with limited exposure to electrical engineering. The system demonstrates the use of MATLAB tools such as Simulink Real Time Windows Target and Control Systems toolboxes to illustrate all stages of design of a closed-loop control systems including: system modeling, parameter identification, analysis of stability of a closed-loop system, design of dynamic compensator in the continuous space and implementation of an equivalent digital controller using the Simulink Real Time Windows Target environment. The hardware apparatus consists of a DC micro-motor attached to a carbon fiber rod. The angular displacement is measured with an analog potentiometer, which acts as the pivot point for the carbon fiber rod. The DC micro-motor is powered by a low cost, custom circuit board, which is USB-powered requiring no external power adaptor or extra cabling. Attached to the micro-motor is a small propeller which provides thrust force needed to rotate the pendulum to a desired angle. The experiment is designed to operate from student's laptops, therefore no special laboratory space is required. The project was tested in a classical control systems design class offered to senior-level mechanical engineering students. Student feedback and survey data on the effectiveness of the module are presented along with examples of student assignments illustrating the use of hardware. © 2012 American Society for Engineering Education.

Abstract:

This paper describes the assembly experiments conducted with a novel miniature assembly cell for microelectro-mechanical systems. The cell utilizes a novel transparent electro-static gripper and uses several disparate sensing modalities for position control: computer vision for part alignment with respect to the gripper, a fiber-coupled laser, and a position-sensitive detector for part to assembly alignment. The assembly experiments performed indicate that the gripping force and stage positioning accuracy of the gripper are sufficient for insertion of micromachined parts into slots etched in silicon substrates. Details of the cell operation, the control algorithm used, and their limitations are also provided. Potential applications of the developed assembly cell are assembly of miniature optical systems, integration of optoelectronics, such as laser diodes with CMOS, and epitaxial lift-off of thin films used in optoelectronic devices. © 2005 IEEE.