Ernestas Šutinys

Research of Modified Mechanical Sensor of Atomic Force Microscope

Atomic force microscope (AFM) is a remarkable device for nanoscale surface scanning. Among several positive features, speed of a scanning limits implementation of AFM. This paper proposes method that enables to increase a speed of scanning by modifying some features of mechanical sensor by adding a nonlinear force to lever of a mechanical sensor of AFM. Proposed method is modeled theoretically, using Simulink features by realizing original algorithm, and researched experimentally, using original modification of AFM sensor. Original results are obtained after a research is performed. Finally, comparison of results of original and modified AFM scans is made and corresponding conclusions are drawn.

The Research of Wire Rope Defect Using Contactless Dynamic Method

This paper is intended to reveal possibilities of defects finding in the wire ropes using dynamic properties of the tensed wire rope using specially designed test rig. The subject of the research is the tensioned wire rope with broken wires, located on surface of the rope.Fragment of steel rope (4 mm diameter and 1.35 m length) was tested experimentally in order to find mentioned defects. A measurement of vibrations of the wire fragment on this test rig was performed using contactless vibration sensors. Fragment of the rope, installed in the test rig was excited with electrodynamics vibrator, which created sinusoidal excitement indirectly, i.e. through own frame. Research of vibrations of the rope was performed in wide ranges of frequencies and desired dynamic properties of the rope fragment as a dynamic system was obtained. Finally, results of the experimental research are presented and conclusions are drawn.

Modification of the AFM Sensor by a Precisely Regulated Air Stream to Increase Imaging Speed and Accuracy in the Contact Mode

Increasing the imaging rate of atomic force microscopy (AFM) without impairing of the imaging quality is a challenging task, since the increase in the scanning speed leads to a number of artifacts related to the limited mechanical bandwidth of the AFM components. One of these artifacts is the loss of contact between the probe tip and the sample. We propose to apply an additional nonlinear force on the upper surface of a cantilever, which will help to keep the tip and surface in contact. In practice, this force can be produced by the precisely regulated airflow. Such an improvement affects the AFM system dynamics, which were evaluated using a mathematical model that is presented in this paper. The model defines the relationships between the additional nonlinear force, the pressure of the applied air stream, and the initial air gap between the upper surface of the cantilever and the end of the air duct. It was found that the nonlinear force created by the stream of compressed air (aerodynamic force) prevents the contact loss caused by the high scanning speed or the higher surface roughness, thus maintaining stable contact between the probe and the surface. This improvement allows us to effectively increase the scanning speed by at least 10 times using a soft (spring constant of 0.2 N/m) cantilever by applying the air pressure of 40 Pa. If a stiff cantilever (spring constant of 40 N/m) is used, the potential of vertical deviation improvement is twice is large. This method is suitable for use with different types of AFM sensors and it can be implemented practically without essential changes in AFM sensor design.

Modification of the AFM Sensor by the Precisely Regulated Air Stream to Increase the Imaging Speed and Accuracy

Increasing of the imaging rate of conventional atomic force microscopy (AFM) is almost impossible without impairing of the imaging quality, since the probe tip tends to lose contact with the sample. We propose to apply the additional nonlinear force on the upper surface of a cantilever, which will help to keep the tip and surface in contact. In practice this force can be produced by the precisely regulated airflow. Such an improvement affects the AFM system dynamics, which were evaluated using a mathematical model presented in this paper. The model defines the relationships between the additional nonlinear force, the pressure of the applied air stream and the initial air gap between the upper surface of the cantilever and the end of the air duct. It was found that the nonlinear force created by the stream of compressed air (aerodynamic force) prevents the contact loss caused by the high scanning speed or higher surface roughness, and at the same time has minimal influence on the interaction force, thus maintaining stable contact between the probe and the surface. This improvement allows to effectively increase the scanning speed by at least 10 times using a soft (spring constant of 0.2 N/m) cantilever by applying the air pressure of 40 Pa. If a stiff cantilever (spring constant of 40 N/m) is used, the potential of accuracy improvement reaches 92 times. This method is suitable for use with different types of AFM sensors and can be implemented practically without essential changes in AFM sensor design.

Research of the New Type of Compression Sensor

Measuring process of physical parameters for mechatronic system well developed and available sensors covers vast amount of interest area. Nevertheless, there are areas with some requests for sensors with special properties. Many applications require sensors, able to operate in harsh conditions.

Implementation of Different Gas Influence for Operation of Modified Atomic Force Microscope Sensor

This paper presents modelling of various gas application to modified atomic force microscope sensor in order to change its existing dynamic characteristics. This paper represents part of continuous research, which is focused on improvement of scanning speed of atomic force microscope (AFM) sensor. Subject of our research is enhancement of dynamic characteristics of Atomic force microscope sensor. Natural frequency of AFM sensor is the main factor influencing max scanning speed of atomic force microscope. In case of working range of frequencies approaches to the resonant frequency of cantilever, scanning results becoming inaccurate and unreliable. Improvement of properties of atomic force sensor made by adding additional nonlinear aerodynamic force to the AFM sensor. This force would act as additional controllable stiffness element, which allows shift resonant frequency to higher side. In this paper is presented research of additional nonlinear force behavior using different gasses as well as compressed air. Research covers factor of humidity of compressed air. Our research performed using 3D atomic microscope cantilever model in SolidWorks flow simulation software. Results of simulation delivered as dependencies of additional stiffness in the AFM sensor in all modelled cases. Finally, results presented in graphical form and conclusions are drawn.

Modelling of Double-Pendulum Based Energy Harvester for Railway Wagon

Powering various electronic devices using mechanic energy harvester became ordinary solution for remotely installed ones. Recent installation of harvesters on surfaces with steady-state harmonic vibrations is well known. Harvesters, utilizing chaotic vibration for energy gaining, require define design and its dynamic parameters. Implementation of energy harvester on railroad cargo wagon for signaling and diagnostic information transfer requires special characteristics of such harvester. In such case, mostly vibrating surface in the cargo wagon is bogy, therefore vibration data for the harvester taken from real measurements of the bogy vibration on real railroad. In order to solve problem of harvester parameters, modelling using Simulink software performed. Dynamic model of harvester contains horizontal pendulum and electrical elements, serving of mechanical damper – electric energy transfer. Excitation of this system applied as kinematic excitement of pendulum pins, connected with harvester body. This model build using II type of Lagrange equation, pendulums built using special supporting springs, limiting pendulum active angles. Simulation of this model performed for 1 km of drive using measurements of newly build railway. Results of the modelling presented graphically and amount of gained energy evaluated by integrating resulting vibration. On basis of the results, conclusions are drawn and recommendations given.

Experimental Research of Improved Sensor of Atomic Force Microscope

Atomic force microscope (AFM) – is device widely used in many scientific fields for nano-scale surface scanning. AFM also can be used to probe mechanical stiffness, electrical conductance, resistivity, magnetism and other properties. The main limitation of AFM implementation is relatively low scanning speed. This speed depends from dynamical characteristics of AFM sensor and from surface roughness of scanned sample. Our research is focused on increasing scanning speed of AFM microscope assuming AFM mechanical sensor as sensitive dynamic system. Our proposed method enables increase of scanning speed by modifying some features of mechanical sensor by adding non-linear force to the surface of cantilever of AFM sensor. Proposed method is modelled theoretically using Simulink features. This paper presents research of mechanical sensor of AFM. After performed research, obtained results are presented on graphical form. At the end of paper discussion presented and conclusions are drawn.

Experimental Definition of Compressive Stiffness of Cotton Flock

Definition of Young’s modulus for majority of materials is the routine operation. In case of materials with low stiffness this task requires special procedure and sophisticated machinery. Cotton flock is the case, where compressive stiffness of cotton flock is so small for direct measurement, so one of possible solution is proposed indirect method of its definition. Recently cotton processing industry uses dynamic methods of cotton cleaning, therefore it is required to know compressive stiffness of cotton flock in order to optimize vibration parameters of device and adjust them to current status of cleaning material. Real compression stiffness of cotton depends on many factors, so in this paper is made an attempt to create simple method of compressive stiffness definition, which can be applied in simple workshop. Paper contains initial assumptions, mathematical derivations of final formula, methodology of experimental research and results.