Vibration Control

Tuned Mass Damper (TMD) pipe is a passive damper for the reduction of vibrations in piping systems and is composed of a mass, springs and dampers.

Working principle: The TMD tuned to the resonance of the piping system to increase the damping, thus reducing the resonant amplitudes. As a purely mechanical structure TMD Pipe does without electrical components so that it can easily be used in hazardous areas. Moreover, it requires no external power supply. This makes it more reliable, during earthquakes, for example, where full operation is required even during power failure.

Passive Dampers

TMD Pipe has been specifically developed for industrial use in facilities such as those within the chemical industry or in power plants. All components have increased corrosion protection. In addition, it operates reliably even under rough and changing environmental conditions.

Tuned mass damper pipe

Active Dampers

Active dampers are based on the principle that accelerating a suspended mass results in a reaction force on the supporting structure. An embedded sensor monitors the supporting structure vibration. The sensor readings are sent to an external feedback controller that drives the internal electromagnetic actuator of the active damping device.

As it does not rely on a model of the structure to be controlled, a rather simple control algorithm can be implemented. It will work theoretically on any type of structure and will damp any vibration mode that is observable in its open-loop transfer function. The only selectable parameters for the control system are the actuator/sensor location and the feedback gain.

ADD Drive & ADD 45N for Active vibration reduction

Anti-Noise

Anti-Noise consists in cancelling the vibration by generating a force opposite to the incoming perturbation

Whenever the sensitive area cannot be isolated from the vibration excitation forces and whenever the vibrations are not amplified by the mechanical structure but mainly transmitted, the only remaining method to reduce the vibration (without a complete re-design of the system) is the anti-noise where a force opposite to the vibration excitation (same frequency, same amplitude but opposite phase) is generated resulting in a destructive interference process at the location where the control force are applied. It is important to note that anti-noise is a local vibration reduction method that lower the modal shape; applying damping locally will only reduce the vibration at this point and may lead to a vibration amplification elsewhere.

Passive anti-noise systems are mainly based on the use of Tuned Mass Absorbers or TMA where an oscillating spring-mass system is mounted on the target structure, i.e. at the location where the vibration is to be cancelled. This TMA will absorb the vibration energy at the resonance frequency of the oscillating appendice. It is well suited for stationary harmonic excitations.

Active anti-noise systems are open-loop devices, relying on actuators, sensors and a feed forward control algorithm. Two sensors are necessary in this control scheme: a reference signal correlated to the incoming perturbation (e.g. the engine speed) and an error signal located where the vibration is to be attenuated. The control algorithm (usually a x-filtered LMS) will filter the reference signal and apply the resulting signal to the actuator; the filter parameters being continuously adapted in such a way that the error signal is minimized. Because of the computation and adaptation, this control scheme is well suited for slowly varying harmonic excitations.