Lucian Bogatu

Influence of technological parameters on the dynamic behavior of a MEMS accelerometer

The paper deals with studying the mechanical structure of a bulk-micromachined silicon piezoresistive accelerometer by using FEM (Finite Element Method). The vibration modes (resonant frequencies) and sensitivity were predicted. The results of numerical simulation, validated experimentally have pointed out the influence of manufacturing process parameters on the accelerometer performance.

Construction of a Vertical Displacement Service Robot with Vacuum Cups

Based on the results of interdisciplinary fields like mechanics, electronics and informatics the autonomous mobile robots are gaining more and more attention. The methods used for movement, actuation and none the last the ability to operate in unknown and dynamic environments give them a great complexity and a certain level of intelligence. The human model is still a challenge for mobility and robot movement. Robot mobility is satisfactorily achieved, in some cases even better with other types of locomotion means, but technical solutions that rigorously reproduce human walking are not yet identified. Feasible solutions can be found in the situation when human mobility reaches its limits (movement on planes with high inclination angles, including 90° – vertical and 180° – parallel to the horizontal plane – ceiling type). Autonomous robot mobility on planes characterized by high inclinations is less tackled in specialty literature, some encountered solutions being objects of patents. The research in this field has a tremendous potential especially in providing new ideas and/or knowledge development. The field of professional and domestic services, especially the wall cleaning of high buildings, is one of the areas that are expected to obtain a strong benefit from the use of robotic systems able to displace on vertical surfaces. The advantages of the technologies that use climbing and walking robots consist mainly of two aspects: • automatic cleaning of high buildings, improvement of technological level and of productivity of service industry in the field of building maintenance; • cleaning robots can be used on various types of building, avoiding thus high costs involved by permanent gondola-type systems (open platform-car or baskets) for individual buildings. The most common attachment principle is the vacuum adhesion (Cepolina et al., 2003), (Miyake et al., 2007), (Novotny&Horak, 2009), where the robot carries an onboard pump to create a vacuum inside the cups, which are pressed against the wall. This system enables the robots to adhere on any type of material, with low energy consumption. Vacuum adhesion is suitable for usage on smooth surfaces, because the roughness can influence a leakage loss in the vacuum chamber.

Manufacturing and testing technology for a silicon piezoresistive microaccelerometer

This paper deals with, the manufacturing technology by silicon bulk micromachining for a MEMS accelerometer with piezoresistive detection as well as the vibration testing of the acce-lerometer structure by using the MSA-500 Micro System Analyzer, a measurement instrument for analysis and visualization of structural vibrations and surface topography in microstructures such as MEMS devices. The technological results, in correlation with the dynamic behavior of the analyzed microstructure, are discussed. These results will be taken into account for design optimization of the device.

Design and Analysis for Motors Control of a 4-DOF Parallel Robot

In this paper, the complex robotic structure of a new 4-DOF parallel robot is designed in a mechatronic concept that integrates mechanical and control aspects. The kinematic and dynamic analysis for the control of motors that act the robot’s arms are presented. Delphi, LabView and SolidWorks softwares are used. The adopted constructive solution of the robot, designed in SolidWorks, has been presented. Then, the transposition of equations which describe the forward and inverse kinematic model of the robot has been performed using the LabView programming environment, a program that allows calling the servomotors’ control board - NI 7344 acquisition board. The angles for the actuated arms of robot have been calculated based on a program developed in the Delphi environment that contains both models - the forward and the inverse one. In order to determine the motor load, a dynamic computation and a simulation have been achieved in ComosMotion from the SolidWorks programming environment. Different results were extracted in the form of diagrams: the torque for the three servomotors acting the arms, the most loaded servomotor – the one that drives arm 1 and the variation of the angular velocity for the arm 1. Finally, the robot prototype has been achieved and interesting conclusions regarding the analyzed robotic structures have been inferred.

Innovative Solutions for Pneumatic Positioning Systems

A pneumatic system represents a safe and “clean” actuation mechanism. The paper presents several innovative solutions for such kind of systems. The aim is to increase the precision of positioning and especially its preservation, as it is known that, in the case of pneumatic positioning systems, these problems have not yet been solved. The proposed units provide an accurate positioning only on certain work areas, set by manual adjustment. At this moment, the presented solutions are in the prototype stage in the tests.

A New Method for Establishing the Performances of an Optoelectronic Sensor

The paper presents a method and a mechanical system able to generate imposed/standard trajectories (circle, ellipse, parabola, line or combinations of them) which, tracked by an optoelectronic sensor based on the triangulation principle, allowing evaluation of its accuracy performances. The maximum of the absolute values of the differences between the points of the standard curve and the curves obtained through data acquisition from the optoelectronic sensor represents the comparison value that allows the ranking of performances of various types of sensors, optical as well as based on other functional principles: ultrasounds, radio etc. The optoelectronic sensor presented in the paper is the base component of a system that controls mini robots having a sole mark/point placed on their body as displacement reference. Such a system is tackled in the frame of a complex scientific research performed by the authors.

Design and programming of a new 4-DOF

The paper presents an original solution of a 4-DOF parallel robot. Aspects of designing of the robot are described, as well as its programming and experimentation in order to manipulate objects of determined dimensions and to overlap them in form of tower. The robot is able to detect new objects in the workspace; object orientation can be achieved regardless of the angle at which the object is. A good timing between the functions of positioning and orientation has been demonstrated.

3D CAD, CAM and Rapid Prototyping Applied for Cam Fabrication

In this paper, a comparison between CNC manufacturing and Rapid Prototyping technology (FDM – Fused Deposition Modeling process), applied for a cam fabrication, is presented. In the products development area, a substantial support is offered by models, as intermediate between product configuration and technology design. The CAD/CAM/CNC technology is a widely used technique for creating prototypes, as well as production parts, using a subtractive type material-removal procedure from a semi-manufactured article. The rapid prototyping (RP) technologies are additive processes, where the part is built up layer by layer until done, directly from the 3D CAD model, within the precision limits of the chosen process. Similarities and differences between these two coexisting computer driven prototyping processes, the subtractive CNC 3 – axes milled part production and the additive RP/ FDM technique, are pointed out for a disk cam manufacturing as sample part.

A comparative study of computation models for dynamic behaviour of MEMS structures

A comparative study of computation models for predicting the vibration modes of some MEMS structures of cantilever type — as suspension arms of the inertial mass of a bulk-micromachined silicon accelerometer, reported to the experimentally measured values of resonance (natural) frequencies, is presented in this paper. The most appropriate values of silicon Youngs modulus depending on the crystal orientation of the structure and the type of model, including also the dynamic Youngs modulus determined by the authors, have been inferred.

New experimental setup for studying the influence of surface material and topography on tribological behavior

The paper presents the results of a scientific research using an original experimental setup dedicated for studying the influence of surface material and topography on tribological behavior. The experimental setup is provided with a safety clutch with two steel disks. On the frictional disk, permanently maintained, a ferodo ring is bonded. The other disk, with the material to be tested, was changed each time. Silicon microtextured wafers and chromium (non)textured thin layers deposited on silicon wafers were tested. The size and shape of the depressions were varied and their influence on the friction coefficient was studied. The angular speed of driver and driven shaft was measured with two non contact tachometers.