Adaptive Designs in Vibration Control

This paper aims to introduce two new adaptive designs of vibration control systems. First is an absorber and the second is an isolator. Absorbers are used for suppressing unwanted vibrations, while isolators isolating them. Structural parameter changes and excitation directions significantly affect the behavior of the conventional passive controllers. A Tuned Stiffness Damper (TSD), stepper motor moving on an elastic element, is used as a tuneable vibration damper of a wide frequency range controller. It can track and suppress only one target frequency of the vibrating system within its frequency range. While the second design of vibration controller uses a double layer ball bearings as a vibration isolator. Modelling, simulation and tests are used to check the proposed designs under different excitation methods. Normalized nodal acceleration, modal participation factors, modal damping and time response were all obtained during the simulation process. Impact, sinusoidal and step relation excitation methods were used in the experimental study of the proposed designs. Moreover, the results from impact tests were used in the experimental modal analyses. Numerical simulations and experimental results illustrate the success of these controllers. The results indicated that the proposed TSD is a good design of recycling tuned mass dampers, while the double layer ball bearings isolators are good way of recycling the single layer ball bearings isolators and conventional isolators. In addition, the measurement of the damper force and torques is not required in these designs. It is also highly possible to maintain the sliding modes and achieve a high robustness against model uncertainties and disturbances along with an ability to control biaxial excitation. NOMONCLATURE E :elastic modulus. I :moment of inertia. L :beam Length. l :stepper motor position. m k c , , :damping, stiffness, mass. r :ball radius. f :force. t :time. x x x & & &, , :vibration nodal displacement, velocity and acceleration. q q q & & &, . :modal coordinates. [ ] [ ] M K , , :stiffness, mass and foundation motion influence coefficients matrices. [ ] R [ ] Φ :modal shape matrix of the structure model. α :proportional damping. τ :time step. ω :natural frequency. Subscript: F :foundation. 0 :initial condition. S :structure. a :assembled system, (the structure plus the isolator). b :beam. bnc :ball in cone. d :damper. ex :external. i :(mode# in TSD). n :node. r :isolator. sm :stepper motor. Superscript: T :transpose. ̃ :modal.