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Chain type system with wave excitation
Get PDFVarious systems based on waves and vibrations are used for displacing, grouping, classification of multidimensional media and bodies. This paper deals with such wave operation based systems augmented by self-stopping elements which ensure one-directional motion of the driven sub-systems. Such enhancements can improve some dynamical characteristics of the analysed systems. The objective of this paper is to develop models of systems and methods of analysis which would help to reveal nonlinear dynamical properties and phenomena of those systems. The conditions of solutions' existence and stability, basin boundaries are determined. Simpler cases are analysed analytically. The obtained relationships provide insight into nonlinear dynamics of complex systems which are analysed numerically
Analysis of vibrations of paper in a printing device
Get PDFThe model for the analysis of vibrations of paper in a printing device is presented. It is assumed that paper performs transverse vibrations as a membrane having stiffness due to static tension in its plane. The first eigenmodes are determined. It is shown that the eigenfrequencies of transverse vibrations of the analyzed paper can be controlled by the static tension in the plane of the paper. The model for the analysis of stability of paper in a printing device is presented. It is assumed that paper moves with constant velocity in a given direction. The analysis is performed using a plate-bending element with the contribution of the forces of inertia from the convective accelerations. This results in the eigenproblem determining the critical velocities and stability eigenmodes. The stand was made for obtaining the experimental investigations. Using it the nodal lines of the standing waves were determined and using projection moiré the eigenmodes were determined. The obtained results are used in the process of design of the elements of the printing device
Dynamic stability of a flexible rod under parametric excitation
Get PDFA homogeneous rod with a constant cross section, vertically mounted and cantilevered, is considered. At the unstrained state, the rod’s axis is straight. It is supposed lateral stiffness is that the rod buckles in static conditions only under gravity and its axis bends. Flexural oscillations of the rod when its base vibrates vertically are investigated. Stabilization circumstances of the rod axis rectilinearity depending on excitation parameters, internal and external damping, and rod flexibility are determined
Investigation of vibrations of a sheet of paper in the printing machine
Get PDFIt is assumed that a sheet of paper performs transverse vibrations as a plate having additional stiffness due to static tension in its plane. The first eigenmodes are determined. The setup for experimental investigation of the nodal lines of the standing waves and for the determination of eigenmodes using projection moire is created for the analysis of unsymmetric loading of the paper. The comparison of the theoretical and experimental results of investigations is performed. The obtained results could be used in the process of design of the elements of the printing devic
Vibration dampers for transmission of mechatronic systems
Get PDFThe paper reviews original torsional vibration dampers retaining their efficiency in a wide disturbing frequency band. Some potential design alternatives are considered. The basic structural element of the damper is a rotary flexible ring. The mathematical model of the system estimates inertia, flexible and gyroscopic terms. The equations to calculate the system motion are derived and stability conditions for the system dynamic balance are formulated, proper consideration is given to other possible stability loss forms and regions of the flexible ring. The analysis of the system natural frequencies is made. Efficiency estimation of the damper versus various parameters is effected following the expression of the equivalent inertia moment and its limit value
Calculation of vibrations of a single degree of freedom system
Get PDFThe three node numerical integration scheme with the displacement and velocity as the nodal variables for integration of the second order differential equation using finite elements in time on the basis of the method of least squares is proposed. The precision of integration is investigated and compared with the corresponding procedure based on the method of Galerkin. The error measure is introduced which shows the higher precision of the least squares techniqu
Dynamic photoplantography examination for tibial torsion measurement
Get PDFIn our work we used glass pedograph with digital camera under pedograph, computer and ultrasonograph. For tibial torsion measurement a patient was standing on the glass pedograph. A luminodiods was settled directly under tips of malleoli. Ankle joint axis passes through tips of malleoli and it was distal reference line. Rectangular ultrasound scanner probe was placed in parallel with posterior margin of the proximal articular surface of the tibia, it was proximal reference line. To avoid optic distortion we placed crus axis in line with optical system axis. Photoplantogramm was captured and estimated. We estimated angle between two reference lines (direct method of tibial torsion measurement). We measured tibial torsion with our method and MRI (5 patients, 10 legs). Tibial torsion measurement by MRI was performed by Schneider method (1997). Mean value of tibial torsion was 290 (our method) and 400 (Schneider method). Pearson correlation coefficient was 0.9. Dynamic photoplantography is cheap, informative, easy method in early pathology revelation. It can be used as screening method among large collectives. Functional photoplantograms help us to estimate foot arch function. Treatment control is very easy to perform with dynamic photoplantograph
Vibrations of a double wall plane adaptive to electrorheological materials
Get PDFAn analytical study of vibrations response and control capabilities of an Electrorheological (ER) material-filled double wall plate to random excitation pressure is presented. The governing equations of motion are developed by incorporating the ER material constitutive relations to thin face plate equations. A three-parameter viscoelastic model is used to characterize ER material behaviour in pre-yield regime. The effect of electric field strength on the response of the double wall sandwich plate with ER material is investigated. Numerical results include response spectral densities and modal frequencies for several ER material core thicknesses and different electric field level
Research of microstructure and steadfastness of bioceramic coatings formed by magnetronic method
Get PDFPaper presents the research of microstructure and steadfastness of polyethylene medical implants coated with ceramic and other materials. After 2500 loading cycles it was noticed that the strongest implant ceramic coatings are Co+TiO2 and Co-Cr-Mo. However the roughness of Co-Cr-Mo surface is far larger than Co+TiO2. The largest and the highest collections of granules are formed in the Co-Cr-Mo coating, and the medium -- in Co+TiO2 coating. Consequently, more durable implant coating is Co+TiO2
A distributed control for a grasping function of a hyperredundant arm
Get PDFThe paper focuses on the control problem of a tentacle robot that performs the coil function of grasping. First, the dynamic model of a hyperredundant arm with continuum elements produced by flexible composite materials in conjunction with active-controllable electro-rheological fluids is analyzed. Secondly, both problems, i.e. the position control and the force control are approached. The difficulties determined by the complexity of the non-linear integraldifferential equations are avoided by using a basic energy relationship of this system. Energy-based control laws are introduced for the position control problem. A force control method is proposed, namely the DSMC method in which the evolution of the system on the switching line by the ER fluid viscosity is controlled. Numerical simulations are also presente