Time filter

Source Type

Seifried R.,University of Stuttgart | Blajer W.,Technical University of Radom
Mechanical Sciences | Year: 2013

Underactuated multibody systems have fewer control inputs than degrees of freedom. In trajectory tracking control of such systems an accurate and efficient feedforward control is often necessary. For multibody systems feedforward control by model inversion can be designed using servo-constraints. So far servo-constraints have been mostly applied to differentially flat underactuated mechanical systems. Differentially flat systems can be inverted purely by algebraic manipulations and using a finite number of differentiations of the desired output trajectory. However, such algebraic solutions are often hard to find and therefore the servo-constraint approach provides an efficient and practical solution method. Recently first results on servo-constraint problems of non-flat underactuated multibody systems have been reported. Hereby additional dynamics arise, so-called internal dynamics, yielding a dynamical system as inverse model. In this paper the servo-constraint problem is analyzed for both, differentially flat and non-flat systems. Different arising important phenomena are demonstrated using two illustrative examples. Also strategies for the numerical solution of servo-constraint problems are discussed. © 2013 Author(s).

Wilczek A.,Technical University of Radom
Journal of Tribology | Year: 2011

This paper presents a model study of inductive, capacitive, and piezoelectric effects on the accuracy of pressure measurements in an EHD contact. Circuit and mathematical models of a thin-layer sensor and a measurement system were developed. It has been assumed that isolation layers of the sensor, deposited as SiOx (1 ≤ x ≤ 2) layers, have piezoelectric properties. The circuit model of the sensor contains a resistance, an electric capacitance, an inductance of a sensor's circuit, and an ideal current source representing piezoelectric properties of isolating layers of the sensor. The circuit model of the measurement system forms a full measuring bridge with the thin-layer sensor in one of its branches. A derived equation for output voltage of the measurement bridge was used as a mathematical model of the measurement system. The investigations show that at inappropriate electric parameters of the measurement system, inappropriate shape of the sensor's transducer and short transition time of the sensor through the contact zone, the capacitive, and piezoelectric effects have a significant impact on the accuracy of pressure measurement in the EHD contact. The transducer with an active part located along its connection edges (asymmetric transducer) and a transducer with the active part located in the middle of connections width (symmetric transducer) was tested. It was shown that in the case of the symmetric transducer, the pressure measurement signal change caused by the capacitive and piezoelectric effects, is much smaller than in the case of the asymmetric transducer. © 2011 American Society of Mechanical Engineers.

Blajer W.,Technical University of Radom
Computer Methods in Applied Mechanics and Engineering | Year: 2011

Multibody systems are frequently modeled as constrained systems, and the arising governing equations incorporate the closing constraint equations at the acceleration level. One consequence of accumulation of integration truncation errors is the phenomenon of violation of the lower-order constraint equations by the numerical solutions to the governing equations. The constraint drift usually tends to increase in time and may spoil reliability of the simulation results. In this paper a comparative study of three methods for constraint violation suppression is presented: the popular Baumgarte's constraint violation stabilization method, a projective scheme for constraint violation elimination, and a novel scheme patterned after that proposed recently by Braun and Goldfarb [D.J. Braun, M. Goldfarb, Eliminating constraint drift in the numerical simulation of constrained dynamical systems, Comput. Meth. Appl. Mech. Engrg., 198 (2009) 3151-3160]. The methods are confronted with respect to simplicity in applications, numerical effectiveness and influence on accuracy of the constraint-consistent motion. © 2011 Elsevier B.V.

Pawlak G.,Technical University of Radom
SAE International Journal of Fuels and Lubricants | Year: 2010

The paper presents some results of an examination of a dual fuel compression ignition engine fuelled with natural gas and diesel oil and a new concept of a dual fuel highly efficient internal combustion engine. For the examined dual fuel engine the homogeneous air-natural gas mixture was formed outside the engine cylinder and was ignited by a dose of diesel oil directly injected to the cylinder. The analysis of the combustion of a dual fuel mixture is based on cylinder pressure diagrams. The diagrams show some problems connected with self-ignition and control of the combustion of the mixture that should be solved to obtain a better engine performance and lower emissions. Particularly important is the control of the combustion process that causes many problems such as knock combustion or engine overheating. For the above-mentioned solution it is also difficult to reduce the engine emissions of hydrocarbons and nitrogen oxides. As a result of the analysis of the theoretical engine cycle and the dual fuel engine performance as well as some phenomena connected with dual fuelling of compression ignition engines a new idea of fuelling and combustion control was created. Generally, the idea combines Otto and Sabathè theoretical processes in one engine. The Otto process, which is more efficient, would be applied for lower engine load but the Sabathè process with changing share of heat supplied at constant volume is to be applied for higher engine loads. The concept of a dual fuel highly efficient internal combustion engine foresees the application of ethanol and diesel oil and two separate direct injection systems for these fuels as well as spark ignition system which would enable the ignition of stratified ethanol-air mixture. The engine can run in two modes - spark ignition mode (the engine fuelled with ethanol) for lower loads and compression ignition mode (the engine fuelled with ethanol and diesel oil) for higher and full loads. The ethanol-air mixture is lean for both modes. It could also contribute to higher engine efficiency as well as a relatively high maximum cylinder pressure for all range of loads. The tests of the new concept that are to be carried out will focus on the optimization of the engine control parameters. The parameters of the injection of both fuels and amount of air (controlled by throttle) would be changed in a very high range that could give a higher efficiency and lower emissions. It is also possible to apply natural gas instead of ethanol for the new concept of fuelling of IC engine. The concept could be described as dual fuel mixed ignition (DFMI) engine. © 2010 SAE International.

Blajer W.,Technical University of Radom | Kolodziejczyk K.,Technical University of Radom
Multibody System Dynamics | Year: 2011

Cranes are underactuated systems with less control inputs than degrees of freedom. Dynamics and control of such systems is a challenging task, and the existence of solution to the inverse dynamics simulation problem in which an r-degree-of-freedom system with m actuators, m

Walasek J.,Technical University of Radom
Macromolecular Theory and Simulations | Year: 2012

The theory presented starts from the model of gas of statistical segments with potential interactions between them. The fact that the system considered is an elastomer is incorporated into the model by constraints imposed on orientations of segments. Constraints are caused by the elastomer structure. The structure is determined by a connection of segments in linear chains, while chains are connected in the network structure. The statistical and thermodynamic description of the system is obtained by use of the conditional optimization of its free energy (Helmholtz function). The Lagrange multipliers for that optimization are calculated by use of cumulants and the multivariate method. In general, results of the theory presented are formulated for any type of potential interactions. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Komorska I.,Technical University of Radom
Mechanika | Year: 2013

An engine vibration and noise signal being applied for the engine combustion assessment contains also information on: a valve clearance, head gasket damage and wearing out of elements of a vehicle drive system. As the engine mileage increases the wearing out of driving system elements also increases, and in consequence the characteristics of vibration and noise generated by individual sub-assemblies are changing. Diagnosing of defects can be performed on the grounds of the model-based vibroacoustic signal by comparing the measured signal with this mod-el. However, this model should be adapted after each changes of driving system elements and after each engine overhaul. Thus, it should be easily and fast automatically identifiable. Methods of generating the base model and its identification were proposed. The model based diagnostic method was verified - in the paper - on the example of the engine exhaust valve defect.

Walasek J.,Technical University of Radom
Journal of Polymer Science, Part B: Polymer Physics | Year: 2010

The distribution function of orientations of a segment, which interacts with the orienting field and is within the chain with given the end-to-end distance-vector, Is calculated. The number of segments per chain is finite. The Lagrange method of conditional minimization of the chain free energy (the Helmholtz function) functional is used. Constraints for the segment orientations stem from fixed the chain end-to-end distance-vector. Hence, Lagrange multipliers, energy, free energy, and entropy, for the chain with given the end-to-end distancevector, are calculated. Then, the distribution function of values of that vector is obtained. Furthermore, an average free energy per chain inside the polymer network with given a topological structure, the system self-deformation, and modulus of elasticity are calculated and discussed in Gaussian limit, that is, for the number of segments per chain tending to infinity. © 2009 Wiley Periodicals, Inc.

Kotnarowska D.,Technical University of Radom
Progress in Organic Coatings | Year: 2010

Destruction of epoxy coatings was examined under the influence of ageing with sulphuric acid aqueous solutions (3, 10 and 20%). The ageing caused oxidation, blistering and porosity increase of examined coatings as well as their surface roughness increase. © 2009 Elsevier B.V. All rights reserved.

This paper presents the experimental study of the construction features of a thin-layer sensor on the accuracy of pressure measurements in an EHD contact. Two common types of transducer shapes and isolating layers of the sensor, made of SiO are considered. The measurements were carried out on a two-disc machine, with the use of two mating lubricated steel cylindrical disks. On the outside surface of one of the discs, a pressure sensor was deposited with two transducers of different shapes, symmetric and asymmetric, located close to each other. The pressure transducer has an active part in the form of a layer contraction, and two wider parts of the layer serves as electrical leads (connections). In the symmetric transducer, the active part is located in the middle of the connections width and in the asymmetric transducer the active part is located along the edge of connections. In case of no current supply for the measurement bridge, the measurement signals from the sensor were observed. The occurrence of these signals indicated piezoelectric properties of the insulation layers of the sensor. The investigations showed that the shape of the transducer has a significant influence on the accuracy of pressure measurements. In the case of the asymmetric transducer, the measurement signal distortions caused by the piezoelectric effects and changes in the electric capacitance of the sensor were much larger than in the case of the symmetric transducer. Measurement signal courses coming from the asymmetric transducer were significantly influenced by the transition velocity of the sensor trough the contact, by the value of the current supplying the measurement bridge and by the rotation direction of the disc with the sensor. © 2012 American Society of Mechanical Engineers.

Loading Technical University of Radom collaborators
Loading Technical University of Radom collaborators