Papers by Keyword: Modal Control

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Authors: Wu Zhao, Dan Huang
Abstract: For suppressing torsional vibration on main driving system of the rolling mill, the paper studied modal control and control model of torsional vibration. Dynamic disturbance of the rolling mill main driving system were induced by small perturbation from torque fluctuation. Modal control analysis were investigated on include amplitude and phase response on reference change or load change, bode diagrams, and time domain simulations. Torque fluctuation reflects non-steady cyclical or quasi-cyclical characteristics on the torsional vibration system. Control model had been reconstructed from inversion of dynamic topology theory. The result of simulation showed that the established control model for suppressing torsional vibration was effectiveness. Feedback control experiment of nipping and throwing steel on the rolling mill’s main driving system using reaction control tactic was proved it could be easy input and output for controling to suppressing vibration.
509
Authors: Reinhard Bardenheier, Graham Rogers
Abstract: Fatigue damage plays an increasingly important role in the design of various safety critical components that are exposed simultaneously to thermal and mechanical loads. Non-isothermal conditions, as these are to be found in turbine components, rocket engines, but also in high-speed machining tools makes the understanding even more complex. As the nature of those loading histories is mostly multiaxial, design engineers are interested in material models, which take into account the complexity of stress state and temperature history as well. The experimental validations of those models require specially designed test set-ups. The basic concepts of experimental techniques to perform non-isothermal, uniaxial fatigue tests will be described in general. Test systems, capable to simulate non-isothermal multiaxial stress states are presented. A new miniaturised electrothermalmechanical test rig, which allows testing of small specimens under complex thermomechanical loading conditions, will be discussed.
1019
Authors: Wei Lin, Shang Hong Chen, Li Qiong Deng
Abstract: In recent years, the magnetorheological (MR) fluid damper-based semiactive control systems have received considerable attention for protecting structures against natural hazards such as strong earthquakes and high winds. In this paper, an improved modal controller integrated with a Kalman-filter observer is proposed for vibration control of spatial structures. The proposed modal controller can reduce the dimension of the control equation and thus can relieve the calculation burden greatly. In the proposed control system, a Kalman-filter observer, which estimates the full controlled modal states from local accelerometer outputs, is designed for rendering the controller to be more applicable to real spatial structures with a large number of degrees of freedom (DOFs). A numerical example of a lattice roof structure installed with MR dampers is presented. The effectiveness of the controller is evaluated under both Tianjin and El Centro earthquake excitations. The simulation results demonstrate not only its effectiveness of reducing vibration of spatial structure, but also its adaptability for versatile loading conditions.
2451
Authors: Stefan Chwastek
Abstract: Mobile heavy machines as unsprung vehicles exhibit low dissipation ability, hence the ride even at low speeds may give rise to intensive vibration, or even to the galloping effect due to enhanced vertical and angular vibration causing the road wheels to break away from the roadway. As these are mostly low-frequency vibrations, energy dissipation in wheel tires will reduce the vibration intensity in a minor degree only. As a result, the speed of a travel has to be reduced, which adversely affects the cost-efficiency of those machines. Observations of an unsprung machine during its forward ride lead us to formulate the hypothesis of reduced machines stability while it moves in the vertical plane of symmetry. The work [2] confirms the view that the vertical motion of an unsprung heavy machine while it moves forward is implemented under the condition of stability limit, mostly due to stiffness of the dynamic system in the horizontal direction. Mobile machines are dynamic systems, governed by nonlinear and often non-stationary differential equations of motion. Their stability is also dependent on the intensity of acting excitations.
69
Authors: Wei Yuan Wang, Kai Xue, Dong Yan Shi
Abstract: The purpose of this paper is to investigate the optimal placement of piezoelectric actuator for active vibration control of smart structure. The structures can be described in the modal space based on the independent modal space control method and dynamic equations derived from finite element model. The modal damping ratios are derived from modal equations and an optimal target is given by maximizing the modal damping ratios. Accumulation method is adopted to the optimization calculation. Simulations are carried out for active vibration control of a conical shell with distributed piezoelectric actuators. Control effects proved the validity of the optimal method above by compared with the non-optimal results. The optimal method in this paper gives a useful guide for quantity optimization of actuators to piezoelectric structures.
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