Tomasz Szolc

Simulation of Dynamic Interaction between the Railway Bogie and the Track in the Medium Frequency Range

In the present paper, the dynamicinteraction between a bogie of a modern railwaypassenger car and a track is considered with the helpof a discrete-continuous mechanical model. This modelenables us to investigate the bending-torsional-axialvibrations of the wheelsets coupled with the verticaland lateral vibrations of the track through thewheel-rail contact forces. The numerical results areobtained in the form of frequency response functionsfor the linearized bogie-track system as well as bymeans of computer simulation of forced vibrationsperformed for the non-linear system. Particularlysevere interaction between the bogie and the track iscaused by kinematic and parametric excitation from thetrack and by kinematic excitation due to wheel treadpolygonalization.

An application of torsional wave analysis to turbogenerator rotor shaft response

In this paper transient torsional vibrations of a steam turbogenerator rotor shaft system due to high speed reclosing of the electric network are investigated. The analysis is performed using torsional elastic wave theory applied to a continuous model in the form of a stepped shaft. Wave solutions of the equations of motion are used in order to determine dynamic torsional elastic moments and vibratory angular velocities in cross-sections of the turbine shafts. The results are illustrated in the form of graphs.

Experimental and Numerical Investigations for the Controlled Rotary Damper Dynamically Interacting with the Electromechanical Rotating System

In the paper dynamic electromechanical coupling between the structural model of the rotating machine drive system and the circuit model of the asynchronous motor has been investigated. By means of the computer model of the rotating machine drive system the results of experimental testing have been confirmed. From the obtained results of computations and measurements it follows that the coupling between the considered rotating system and the installed rotary dampers with the magneto-rheological fluid (MRF) results in effective energy dissipation leading to significant reduction of undesired torsional vibrations.

Semi-Active Reduction of Vibrations of Periodically Oscillating System

Periodical vibrations are common phenomenon affecting a wide range of mechanical systems. Most frequently it affects machines designed to work in a steady-state conditions like: turbine, pump, rail vehicle, etc. In those kinds of machines it is always possible to decompose the system motion to basic average-speed constant component and oscillatory component. Usually the second term is treated as undesirable and various techniques are applied in order to minimize it as far as it is possible. These techniques refers to both the hardware selection – meaning the type of damping system (active, semi-active, passive) and the control method selection – meaning the damping system control method. Concerning the control methods, there are many algorithms available in literature devoted to transient systems. One of typical application is to use them in systems experiencing sudden, external force excitation. After destabilization of the system, caused by excitation, the role of the control algorithm is to restore the system stable position and additionally to reach the extreme of some additional criterion. Typical criterions are minimization of the time, of restoring the stable position, minimizing the consumed control energy, etc. On the other hand, considering the steady-state systems, especially based on semi-active damping elements, there are not so many control methods available.This paper focuses on developing the proper methodology for deriving the optimal control strategy of semi-active damping element, to be used in periodically vibrating mechanical system. The control strategy is developed on the basis of the Optimal Control Theory. Numerical computations are involved in order to solve the optimal control problem for the considered test system. Problem solution reveals the periodical nature of optimal control function.

Modeling and Dynamic Analysis of the Precise Electromechanical Systems Driven by the Stepping Motors

In the paper there is investigated electromechanical dynamic interaction between the driving stepping motor and the driven laboratory belt-transporter system imitating an operation of the robotic device in the form of working tool-carrier under translational motion. The considerations are performed by means of the circuit model of the electric motor and the discrete, non-linear model of the mechanical system. In the computational examples various scenarios of the working tool-carrier motion and positioning by the belt-transporter are simulated.

Influence of Various Control Strategies on Transient Torsional Vibrations of Rotor-Machines Driven by Asynchronous Motors

In the paper, a dynamic electromechanical interaction between the selected kind of rotating machines and their driving electric motors is investigated. These are the high-speed beater mills and crushers as well as blowers, pumps and compressors, all driven by the asynchronous motors through elastic couplings with linear and non-linear characteristics. In particular, there is considered an influence of negative electromagnetic damping generated by the motor on a possibility of excitation of resonant torsional vibrations. Moreover, for the asynchronous motor in transient and steady-state operating conditions, there are tested several control strategies which are based on the closed-loop vector and scalar principles. The theoretical calculations have been performed by means of the advanced structural mechanical models. Conclusions drawn from the computational results can be very useful during a design phase of these devices as well as helpful for their users during a regular maintenance.

Dynamic Analysis of the High-Speed Flexible Rotors Supported on the Electrodynamic Passive Magnetic Bearings

In the paper comparative rotor-dynamic analyses are carried out for various rotor-shaft systems supported on the classical journal-, rolling element- and on the passive magnetic bearings. The investigations are performed by means of the advanced 3D finite element model of the electrodynamic passive magnetic bearing and of the structural model of the rotor-shaft—bearing systems, using which proper Campbell diagrams, amplitude—frequency characteristics and complex eigenvalues have been determined as well as numerical simulations of rotor-shaft transient dynamic responses were carried out. The presented study is focused on the lateral vibration damping abilities realized by the mentioned above bearing types. In this way, advantages of the prospective passive magnetic bearing have been emphasized.