Search results for "VIBRATION"
showing 10 items of 823 documents
2014
A feedback control method based on an extended state observer (ESO) method is implemented to vibration reduction in a typical semiactive suspension (SAS) system using a magnetorheological (MR) damper as actuator. By considering the dynamic equations of the SAS system and the MR damper model, an active disturbance rejection control (ADRC) is designed based on the ESO. Numerical simulation and real-time experiments are carried out with similar vibration disturbances. Both the simulation and experimental results illustrate the effectiveness of the proposed controller in vibration suppression for a SAS system.
Effect of amorphous sequences on the longitudinal acoustic modes in partially crystalline polymers. I. Transfer matrix method
1983
A novel theoretical scheme is developed which enables the determination of the LAM-like vibrations of polymer chains made up of crystalline and amorphous parts as they occur in partially crystalline structures. The boundary conditions effective at the junction points are formulated in terms of the compliances of the associated amorphous sequences. These compliances can be derived from their eigenfrequencies and eigenvectors in a disconnected state. The treatment uses a matrix formalism which can be extended to include bending and torsional motions in a general state of vibration of the crystalline stem. A first numerical example demonstrates that the LA mode of a crystalline stem can be str…
Vibration control of vehicle engine-body systems with time delay: an LMI approach
2013
The objective of this chapter is to study the problem of vibration control analysis and synthesis in a vehicle engine-body vibration structure. It is assumed that the actuator is subject to a time-varying delay for control of bounce and pitch vibrations. Based on a Lyapunov-Krasovskii functional and using some free weighting matrices, delay-dependent sufficient conditions for designing desired state- and output-feedback controllers are given in terms of linear matrix inequalities (LMIs). The state- and output-feedback controllers, which guarantee asymptotic stability with a prescribed γ-level L2-gain (or H∞ performance), are then developed directly instead of coupling the second-order model…
The effect of 26 versus 29-inch wheel diameter in the transmission of vibrations in cross-country mountain biking.
2021
Vibrations experienced by cyclists can affect their performance and health. We analysed the vibrations transmitted by mountain bike (26 or 29-inch wheels), in a 2,110 m circuit with a sample of 55 cyclists. The results indicate that the 29"-wheel increases speed (
On Bifurcation Analysis of Implicitly Given Functionals in the Theory of Elastic Stability
2015
In this paper, we analyze the stability and bifurcation of elastic systems using a general scheme developed for problems with implicitly given functionals. An asymptotic property for the behaviour of the natural frequency curves in the small vicinity of each bifurcation point is obtained for the considered class of systems. Two examples are given. First is the stability analysis of an axially moving elastic panel, with no external applied tension, performing transverse vibrations. The second is the free vibration problem of a stationary compressed panel. The approach is applicable to a class of problems in mechanics, for example in elasticity, aeroelasticity and axially moving materials (su…
Rib-Roller Wear in Tapered Rolling Element Bearings: Analysis and Development of Test Rig for Condition Monitoring
2020
Rolling Element Bearings (REBs) are present in virtually all machines with moving or rotating parts, and are vital for proper performance and safe operation. Condition Monitoring (CM) of bearings often receive particular interest, as this component group rarely reach design lifetime and hence is responsible for unplanned machine downtime. Unplanned maintenance can represent a large cost which motivates development of improved CM methods for implementation of advanced maintenance regimes. Based on observations of a used bearing from an offshore drilling machine, wear on roller ends in the rib-roller contact area was identified as an area of interest for future research. A test rig for creati…
Integrated System for Monitoring the Tool State Using Temperature Measuring by Natural Thermocouple Method
2014
The intensive developments of intelligent manufacturing systems in the last decades open the large possibilities of more accurate monitoring of the metal cutting process. One of the most important factors of the process is the tool state given by the rate of the tool wear, which is the result of a lot of influences of almost all cutting parameters. The modern tool monitoring systems relieved that the accuracy of the results increases when using a combination of surveyed signals such as: vibrations, power consumption, acoustic emission, forces or tool temperature. Combining the output signals in a monitoring function using the neural network method gives the best results when using on-line m…
Actuators and sensors allocation for adjacent buildings vibration control
2012
This paper puts forward an actuators and sensors allocation approach to the design of the adjacent buildings vibration attenuation under seismic excitation. A full order model of an adjacent buildings system with the location information of actuators and sensors is considered and by retaining the modes which make the largest contributions to the model with the Modal Cost Analysis (MCA), a reduced order model is established so that the controller can be designed conveniently. In view of the fact that not all the states of the system can be measured by the sensors, a dynamic output feedback H ∞ controller is designed for the adjacent buildings system. By considering that the output powers of …
Nonlinear vibrations of elastic beams with external general visco-elastic devices
2011
Vibration damping for slender beams is achieved by applying devices at external points. The latter consist of general single visco-elastic springpot elements. An approximate nonlinear boundary value problem is found in frequency domain that holds for moderately large vibrations or for linear beams with external nonlinear devices, both in the vicinity of primary resonances. The interaction force of a so-called springpot element is expressed as a sum of two separate forces: the first develops due to the external loading function at the device location, and the second contribution arises due to an imposed time-harmonic support excitation with no other external forces acting on the structure. F…
Semiactive vibration control of offshore wind turbine towers with tuned liquid column dampers using H<inf>&#x221E;</inf> output feedb…
2010
This short paper addresses the problem of vibration in wind turbine towers. These structures are subject to winds and waves causing undesirable vibrations that affect the structure integrity and system performance. In order to mitigate the vibrations of the tower, a controllable tuned liquid column damper is placed on its top. We propose the use of H ∞ control techniques to formulate a control law. Furthermore, the controller uses output feedback to avoid the dependence on the knowledge of the states of the system. Simulation results illustrate the design procedure proposed in this paper.