Vytautas Turla

Overhead crane anti-swing system based on the Pontryagin’s maximum principle

Overhead cranes are widely used at industrial enterprises for transportation of materials and products. They are successfully adaptable to technological processes used at an enterprise and their exploitation is inexpensive; in addition, the price of cranes is relatively low. However, extension of requirements set for technological processes results in shortened time for transportation and stiffened requirements for accuracy of cargo delivery and cargo safety. In the attempts to satisfy the latter requirements, particular attention is paid to swings of the cargo-holding rope. There is a number of factors that cause increased requirements for the control system of the crane drive. The slewing movement affects the total system of the crane and aggravates the crane movement control. In modern overhead cranes, the abilities and qualification of an operator (who is assisted by a certain anti-swing system) predetermine the cargo swings and the accuracy of its positioning. The said circumstance latterly caused a particular attention to computerisation of overhead crane control. However, a nonlinearity of the mechanical system of a crane and complicated control of swings often cause undesirable swings, in particular in the beginning and the end of cargo transporting process, thus reducing the efficiency of usual crane control systems. In addition, it should be taken into account that the parameters of a crane, as a controlled mechanical system, depend on the cargo and the conditions of its transportation. Consequently, a development of an effective cargo swing reduction system is a currently topical engineering problem.

Dynamic Reaction Forces of an Overhead Crane on Lifting

Abstract In the recent period, girder bridge cranes are replaced with double-beam overhead cranes with a rectangular cross-section of the beams. In addition, new materials are used for producing them thus applying other values of allowable loads and deformations. The paper focuses on two overhead cranes working for JSC Vilniaus kranai (Vilnius Cranes). The presented mathematical model provides an opportunity to assess the structural peculiarities of the above introduced cranes. The calculated results of dynamic loads appearing in the beginning and the end of the lifting process and having an impact on the lifting mechanism and metal structure are provided in the article.

Vibrational analysis of angle measurement comparator

The comparators of angle measurement are designed for measurement of angle gauges (limbs) and angular movements (turning) for calibration measurement errors of measuring systems. The vibration isolation issue for angle comparators is particularly relevant. Vibration analysis became essential for angle comparators operating in dynamic mode and used for precise angular measurements. In this paper, an analysis of wavelet intensity distributions of angle comparators is carried out by applying the theory of covariance functions. Data from measurements of vibrational signals at fixed points were acquired in the form of data arrays (matrices). Estimates of covariance functions between the arrays of data and the estimates of covariance functions of single arrays were calculated upon changing the quantization interval on the time scale. For signal processing, MATLAB 7 software was applied.

Identification of the Prints Elastic Parameters Using Vibrational Methods

One of the indirect tensile identification methods is the measurement of the structure of the response to the vibration excitation. Then this response is simulated using digital methods. If the similarity to the response structure is achieved, the elasticity parameters can be determined. Using the methodology discussed in this work, the problem of the determination of the elasticity parameters of prints as a consisting of the paper and several layers of inks is solved. The determined parameters of prints will be used for the modeling of the printing process in web printing presses.

Paper and Prints as Composite Materials

Paper and prints on it are analyzed as composite materials. Printing, varnishing and lamination are described in terms of the formation of the composite material. The article discusses why and how the properties of a print should differ from the properties of paper.

An Investigation Into Fault Diagnosis in a Rotor-Bearing System with Dampers Used in Centrifugal Milk Separators

This paper deals with the problems encountered in the fault diagnosis in damped rotorbearing systems used in centrifugal milk separators. It is shown that direct bearing vibration measurements are more reliable than indirect (through rotor housing) vibration measurements. However, in most cases it is not possible to measure bearing vibrations directly. The factors causing large diagnostic measurement errors, such as the influence of the vibration damping system, step-up gear and electric motor noise are discussed in the paper. It is established that vibration measurements of the damping system are noninformative and cannot be used to diagnose faults in bearings. It is proposed to use the vibration spectra correlation to predict bearing failures in rotor-bearing systems of this type.

The Dynamic Errors of Mechatronically Controlled Lifting Equipment

Upon striving to ensure the cargo safety and precizity of its delivery, mechatronic control systems are more and more widely applied in lifting mechanisms. They get information from various sensors, including those involved in registering the rope’s deformations. The got information may be distorted because of the appearance of cargo swinging that’s level depends on the mode of operation of the lifting mechanism and the rope’s elasticity. The latter varies dependently on the length of the unwound rope and the way of deformation of rope’s wires. In the paper, a mathematical model of a lifting mechanism that describes its dynamics on lifting when both the cargo and the rope swing in respect of a vertical axis is provided. The model was examined by a special program developed upon using MATLAB and SIMULINK program packages. The obtained dependences of the swing parameters on the mode of operation of the lifting mechanism and the rope’s parameters enable assessing a possible application of the lifting mechanism.

The investigation of dynamics of misaligned units in vehicle transmission

Abstract In the article the problems related to the dynamics of a mechanic system on misalignment of shafts in radial direction are presented. The object of the investigation is a two-shaft system connected with an elastic centrifugal ring coupling. Using equations of static equilibrium it was found that an internal moment of resistance to rotation appears in the coupling connecting the radially misaligned shafts. Using Dalambers principle for the rotational movement the differential equation that describes the rotation of the second shaft has been developed. It was shown that after the perfonnance of the corresponding actions and the introduction of a new variable the said equation is transformed in to an equation which character virtually coincides with the equation describing free oscillations of a mathematical pendulum. Because the value of misalignment of shafts in the radial direction is small in comparison with other parameters, a small parameter method was used for the solution of this equation. ...

The Influence of Formulating a Damping Solution on Dot Gain

Difference in dot gain using various additives to the damping solution was investigated on two offset web presses. Dot gain was measured using a densitometer and calculated considering CIE L*a*b* coordinates. It was found that while using a non alcohol additive instead of the alcohol one, dot gain became smaller and printing stability was lower. Changes in dot gain depend on the ink that may vary in colours. The influence of changes in dot gain on the colour was determined. Besides, it was found that differences in colour were unacceptable in many cases.

Universal Coupling for Shaft of Actuators in Mechatronic Systems

The design of shaft coupling ensuring serviceability of an actuator under varying conditions is presented in this paper. The driving half coupling is an eccentric balanced over the axis of rotation. The torque of the coupling is determined by the parameters of the flexible ring and eccentricity. When the parameters of coupling are properly selected, the transfer coefficient of vibration can be reduced markedly.