Eniko T Enikov

Abstract:

A novel stress-insensitive piezoresistor in the shape of an annulus has been developed to be used in conjunction with a piezoresistive bridge for temperature-compensated force measurements. Under uniform stress conditions, the annular resistor shows near-zero stress sensitivity and a linear response to temperature excitation within test conditions of 24-34 °C. Annular resistors were placed in close proximity to stress-sensitive elements in order to detect local temperature fluctuations. Experiments evaluating the performance of the temperature compensator while testing force sensitivity showed a thermal rejection ratio of 37.2 dB and near elimination of low-frequency noise (drift) below 0.07 Hz. Potential applications of this annular resistor include use in multi-axis force sensors for force feedback microassembly, improvements in the simplicity and robustness of high precision microgram sensitive balances, higher accuracy for silicon diaphragm-based pressure sensors and simple temperature compensation for AFM cantilevers. © 2011 IOP Publishing Ltd.

Abstract:

Combined thermionic emission and tunneling of hot elec- Trons (thermo-tunneling) has emerged as a potential new solid- state cooling technology. Practical implementation of thermo- Tunneling, however, requires the formation of a nanometer-sized gap spanning macroscopically significant surfaces. Thermo- Tunneling is a term used to describe combined emission of hot electrons (thermionic emission) and tunneling of electrons through a narrow potential barrier between two surfaces (field emission). Thermo-tunneling of hot electrons across a few- nanometer gap has application to vacuum electronics, flat panel displays, and holds great potential in thermo-electric cooling and energy generation. Development of new thermo-tunneling applications requires creation of a stable nanometer gap be- Tween two surfaces. This presentation is focused on our effort to investigate the stability of the the thin flexible structure under electrostatic and lorenz forces opposing each other. In this pre- sentation, we report the result of numerical simulation with some mathematical simplifications. The mathematical model used for the numerical simulation is well studied in the literature. Us- ing forth-order partial differential beam equation, we studied the steady state solutions of the thermo-tunneling beam model using Galerkin method.Essential output parameters of the model in- clude a central contact area measured by its length (delta) and the thermo-tunneling current. Both parameters are determined as a function of the externally applied external potential and magnetic field. Numerical solutions of the model show two possi- ble operating modes: (1) symmetric deformation with negligibly small current; and (2) asymmetric mode where the B-field con- Trols the current and contact area. Under practical values for the externally applied magnetic and electric fields, it has been shown that the second mode is only possible for electrode with very low work functions, e.g. below 0.5 eV. Therefore, novel materials such as Diamond-like carbon films are likely to be essential in thermo-tunneling applications. Copyright © 2012 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 [1-3]. 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. A simple to use, low cost system has been designed that provides a platform for experimentation in areas from basic open loop control, to frequency domain and digital control systems. This paper presents the design of the system, and demonstrates the ability of MAT-LAB tools such as Simulink Real Time Windows Target to illustrate implementation of various aspects of control design. The system setup 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, whos H-bridge allows the motor rotate in either forward or reverse directions. Attached to the micro-motor is a small propeller, providing thrust force to rotate the pendulum about its potentiometer. The circuit board communicates to the host computer using the USB protocol, utilizing usbser.sys to create a virtual COM port. MATLAB uses the serial port object to read and write from the control board. The control board is powered through two USB ports, requiring no external power adaptor or extra cabling. This paper shows the use of feedback linearization to arrive at a system where classical linear control design methods can be used. 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 is also presented. Copyright © 2011 by ASME.

Abstract:

The design and analysis of a miniature electromagnetic actuator for use in a novel virtual tactile display is described. The actuator operates in repulsive mode so that it can be used for vibro-tactile stimulation of a human fingertip. Pulsed current and permanent magnet based approaches are investigated and compared. Four frequencies (10, 50, 100, and 150 Hz) were used to test the perception limit of three human subjects. The results indicated that the perception is not strongly dependent on frequency in the test range. The required stimulation energy of individual pulses was estimated to be below 57 micro-Joules, while the average peak-force needed for reliable stimulation was 59 milli-Newtons. The perception of simple test shapes was also tested by attaching the actuator onto the fingertip of the human subjects and turning it on and off as a function of its position. © 2010 Elsevier Ltd. All rights reserved.

Abstract:

Traditional MEMS actuators have limited stroke and force characteristics. This paper describes the development of a novel hybrid actuation solution, which utilizes a micromachined actuator array to provide switching of mechanical motion of a larger meso-scale piezo-electric actuator. One motivating application of this technology is the development of a tactile display, where discrete mechanical actuators apply vibratory excitation at discrete locations on the skin. Specifically, this paper describes the development fabrication and characterization of a 4 × 5 micro-actuator array of individual vibrating pixels for fingertip tactile communication. The individual pixels are turned ON and OFF by pairs of microscopic thermal actuators, while the main vibration is generated by a vibrating piezo-electric plate. A thermo-electric and non-linear thermo-elastic models have been developed to account for the temperature dependence of the electrical resistance and the lateral buckling of the hot, respectively. Comparison between analytical and finite element models indicated very good agreement, confirming that the buckling of the hot arm has most significant impact in the overall actuator performance. The fabrication sequence and the actuation performance of the array are also presented. Copyright © 2004 by ASME.