Stanisław Wojciech

Dynamics of a Mobile Crane and Optimisation of the Slewing Motion of Its Upper Structure

In the paper the 3-D model of a telescopic mobile crane is presented. In the model flexibilities and damping have been taken into account and also the number of degrees of freedom can be chosen according to the complexity of an approach. The algorithm of optimisation of drive functions for the slewing upper structure is given. The main goal of optimisation was to ensure load positioning at the end point of a work cycle in the case when oscillations are minimal. In order to achieve appropriate numerical effectiveness, the optimisation problem was solved for the simple, fully rigid model of a mobile crane. The method of compensating neglected flexibilities of the base structure of the crane and inner disturbances connected with the feedback control system via digital PID controller is presented.

Rigid Finite Element Method in Analysis of Dynamics of Offshore Structures

This book describes new methods developed for modelling dynamics of machines commonly used in the offshore industry. These methods are based both on the rigid finite element method, used for the description of link deformations, and on homogeneous transformations and joint coordinates, which is applied to the modelling of multibody system dynamics. In this monograph, the bases of the rigid finite element method and homogeneous transformations are introduced. Selected models for modelling dynamics of offshore devices are then verified both by using commercial software, based on the finite element method, as well as by using additional methods. Examples of mathematical models of offshore machines, such as a gantry crane for Blowout-Preventer (BOP) valve block transportation, a pedestal crane with shock absorber, and pipe laying machinery are presented. Selected problems of control in offshore machinery as well as dynamic optimization in device control are also discussed. Additionally, numerical simulations of pipe-laying operations taking active reel drive into account are shown.

Application of rigid finite element method to dynamic analysis of spatial systems

This paper presents an application of the rigid finite element method to modeling of flexible links of spatial systems. It is assumed that the movement of the base, with which the flexible system is connected, is known. The model presented takes into account large deflections of the link and an influence of centrifugal forces on deflections and deformations. Methods applied in dynamic analysis of manipulators with rigid links are used to derive the equations of motion. The results of numerical calculations are compared with those obtained by other authors who used the finite element approach.

The Rigid Finite Element Method

Actual kinematic chains commonly contain links whose flexibility greatly exceeds that of other links. It may then be necessary to take that flexibility into account. Booms of cranes and certain links of manipulators count among those. A large number of approaches in analysis of multibody systems can be found in literature with with one and more flexible links [Zienkiewicz O. C., 1972], [Wittbrodt E., 1983], [Wojciech S., 1984], [Huston R. L., Wanga Y., 1994], [Arteaga M. A., 1998], [Zienkiewicz O. C., Taylor R. L., 2000], [Berzeri M., et al., 2001], [Adamiec-Wojcik I., 2003], [Wittbrodt E., et al., 2006]. Chapter 9 introduces models of offshore cranes (a column one and an A-frame) which enable taking into account the flexibility of the supporting structure.

Numerical Effectiveness of Models and Methods of Integration of the Equations of Motion of a Car

The paper presents models of car dynamics with varying complexity. Joint coordinates and homogenous transformations are used to model the motion of a car. Having formulated the models of the car, we discuss the influence of the complexity of the model on numerical efficiency of integrating the equations describing car dynamics. Methods with both constant and adaptive step size have been applied. The results of numerical calculations are presented and conclusions are formulated.

A New Approach to the Rigid Finite Element Method in Modeling Spatial Slender Systems

The static and dynamic analysis of slender systems, which in this paper comprise lines and flexible links of manipulators, requires large deformations to be taken into consideration. This paper presents a modification of the rigid finite element method which enables modeling of such systems to include bending, torsional and longitudinal flexibility. In the formulation used, the elements into which the link is divided have seven DOFs. These describe the position of a chosen point, the extension of the element, and its orientation by means of the Euler angles Z′Y′X′. Elements are connected by means of geometrical constraint equations. A compact algorithm for formulating and integrating the equations of motion is given. Models and programs are verified by comparing the results to those obtained by analytical solution and those from the finite element method. Finally, they are used to solve a benchmark problem encountered in nonlinear dynamic analysis of multibody systems.

The integrated computer system for modelling of air pollution based on the digital data

The paper presents the integrated computer system for modelling emission and dispersion of car exhaust pollutants in mesoscale. Whole data used in system, concerning information about topography and meteorological condition are gained from GIS. The model of traffic flow is based on well-known safe distance Krauss models. Calculation of pollutants concentration is based on Gaussian finite line source model (GFLSM). In computational system all results of simulation can be visualized and export in acceptable formats to geographical information system. This causes that proposed system has almost unlimited chances in analyses of car exhaust pollutants over space and time.

Application of the Rigid Finite Element Method to Static Analysis of Lattice-Boom Cranes

Abstract In the paper a nonlinear model of a lattice-boom crane with lifting capacity up to 700mT for static analysis is presented. The rigid finite element method is used for discretisation of the lattice-boom and the mast. Flexibility of rope systems for vertical movement and for lifting a load is also taken into account. The computer programme developed enables forces and stress as well as displacements of the boom to be calculated. The model is validated by comparison of the authors’ own results with those obtained using professional ROBOT software. Good compatibility of results has been obtained.

Identification of Impulse Force at Electrodes’ Cleaning Process in Electrostatic Precipitators (ESP)

In the studies related to simulation of vibrations in collecting electrodes of dry electrostatic precipitators, it is necessary to correctly determine the course of impact force of a beater on an anvil beam to which the plates with deposited particulate matter are attached. The courses of these forces have a direct impact on the effectiveness of rapping particulate matter, and therefore on accelerations causing the detachment of dust particles. The paper presents a procedure, which allows for an approximate determination of the course of impact force, based on the results of vibration measurements and computer simulation, in which a self-developed model of the system was used. The analysis covered repeated series of acceleration measurements at several tens points of the system of collecting electrodes. Acceleration measurements were performed using IPC 356A02 triaxial sensors. A computer model, based on the rigid finite element method (RFEM) allows for the determination of a course of accelerations for a strictly specific course of impact force. Comparing the results (of acceleration) obtained by measurements and calculations, a correct course of the impact force was found. Knowing the correct course of the impact force, it is possible, using only computer simulations, to conduct studies of the influence of geometrical and structural parameters of the system on the effectiveness of rapping particulate matter.

Numerical Effectiveness of Different Formulations of the Rigid Finite Element Method

Abstract The paper presents an application of different formulations of the rigid finite element method (RFEM) to dynamic analysis of flexible beams. We discuss numerical effectiveness of the classical RFEM and an alternative approach in which continuity of displacements is preserved by means of constraint equations. The analysis is carried out for a benchmark problem of the spin-up motion in planar and spatial cases. Torsion is omitted for numerical simulations and two cases of the new approach are considered. The results obtained by means of these methods are compared with the results obtained using a nonlinear two-node superelement