Passive Damping Devices

We propose passive “Tuned Mass Damper (TMD)” and “Tuned Mass Absorber (TMA)”. Both are based   on a resonant mechanical device (spring + mass) to be appended on the “noisy” structure and reduce mechanical vibrations in a given frequency band.

Tuned Mass Damper

TMDs include a damping element and act on structural resonances. Adequately tuned, it will attenuate the high-peak at the structure resonance frequency, hence reducing the dynamic amplification at that frequency. With a TMD the vibration energy is dissipated in the device damping element. The device performances (e.g. main structure damping) are directly proportional to the mass ratio between the mass of the target structure and that of the TMD. Typically, a mass ratio of about 5-10% is recommended.



Tuned mass Absorber

TMAs exhibit as little damping as possible and absorb harmonic vibrations at a given point. Adequately tuned, it will absorb the vibration in a narrow frequency band at the location of the TMAs. The vibration is transferred to the TMA where it is less/not detrimental to the target application. The device performances (e.g. the absorption width) are directly proportional to the mass ratio between the mass of the target structure and that of the TMA. Typically, a mass ratio of about 5-10% is recommended.


Main Characteristics:


Vibration reduction with TMDs/TMAs is a non-intrusive process. No structural modification is needed. The TMD/TMA is just fixed on the apparatus and damps/kills vibrations. The device does not degrade the static strength or stiffness of the target structure.


TMAs and TMDs are fully passive and do not require any energy supply.

Additive Process

Performances with TMDs/TMAs is an additive process. In other words, the more devices you attach to the structure or machine, the more vibration reduction you get.

Frequency Band

TMAs and TMDs must be tuned to respective the target resonance/excitation frequency.

Custom Design:

While the TMD/TMA technology is well known for years and is conceptually a very simple device, each implementation requires specific attention (TMD/TMA weight, tuning frequency, available space & mechanical interfaces, manufacturing costs, thermal environment…).

Therefore, we provide support in:

  • The vibration diagnostic and requirement specifications (definition of spring, mass and damping Components, mechanical interfaces, available space…).
  • The design of dedicated TMD/TMA
  • The manufacturing and commissioning of the TMD/TMAs

Passive Damping devices implementation Roadmap

The usual TMD/TMA implementation roadmap is a 3-step process

  1. Simulation of expected performances based on the results from a quick vibration response test (Hammer test) and/or an existing FEM model of the structure.
  2. Custom design, prototype manufacturing and prototype testing.
  3. Serial manufacturing.

Example of devices

  • Scroll compressors are used in heat pumps. Their vibrations can be propagated to the building walls, hence generating acoustic noise. A Tuned Mass Absorber (TMA) is mounted close to the exit of the pump. It is tuned at the nominal operation speed of the pump (48Hz), at that frequency, the pump vibration energy is transferred to the TMA and no more to the building
  • Wind turbines experience tonalities which are sounds at discrete frequencies peaking above the broad- band noise, mainly originating from the gearbox vibrations then transmitted to sound emission areas, such as the tower or the blades. Tuned Mass Dampers (TMA) are mounted on the wind turbine gearbox torque arms in order to prevent these vibrations to reach the sound emission

Examples of existing application

  • Wind turbines: TMAs are located on the gearbox torque arms to avoid unwanted acoustic tonalities due to gearbox harmonic vibrations transmitted to the
  • Air compressors: TMAs are located either at the resilient supports, to avoid structure borne acoustics, or at the compressor output, to avoid transmission to the piping
  • Piping : TMDs are located at critical locations to avoid leaks and limit fatigue due to the fluid pulsations.
  • Water pumps : TMDs are located on pump motor support to limit vibration amplifications at critical pump velocities.
  • Semi-conductors: TMDs are used for the reduction of chatter in silicon wafer polishing


Active Damping Devices

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.


An Application of ADD in Machining Process

Example of Devices



  • Non-Intrusive: Generating damping within a structure or machine with ADDs is a non-intrusive process. No structural modification is needed. the ADD is just fixed on the apparatus and adds damping. If the control is turned off, the structure just behaves like originally. Once the control is turned on again, the structural behavior remains the same, but resonances are damped.
  • Control Robustness: Thanks to the selected configuration of collocated sensors and actuator pair, it can be demonstrated that a more robust and stable control scheme can be achieved, and hence that stability is less of an issue.
  • Additive Process: Damping with ADDs is an additive process. In other words, the more ADDs you attach to the structure or machine, the more damping you get.
  • Low previous knowledge of the structure is required: As the selected closed-loop damping strategy with DVF is quite universal, the ADD can be applied with no or no deep previous knowledge of the structural behavior of the structure or machine it is attached to. No in-depth preliminary modeling or structural analysis is required before being able to generate damping with ADDs.
  • No external mechanical connections: Being based on an inertial actuator there is no need for and external mechanical link like it would be the case with classical dampers as illustrated in figure. Unlike classical dampers that need a physical reference anchor, the ADD has a virtual reference pint: it is “hooked to the sky”. Hence, ADDs can be installed where structural parts connected to the ground are not present or not practicable, or even on moving parts.

Active Damping with an inertial Actuator

  • Wide operating bandwidth: The ADD damps all the modes of the structure it is attached to and that are “seen” by the collocated sensor. Unlike “Tuned Mass Dampers” that address one mode only, the ADD can damp several modes within its operating bandwidth (typically between 25 and 2000Hz). This allows maintaining efficiency even when there is structural variability – i.e. the locations of the structure modes changes for some reasons – or whenever an external perturbation source to the structure is varying (e.g. motor with a range of rotating speeds generating a changing vibration spectrum)
  • Compactness: The performances of the ADD are not driven by the mass ratio between the structure and the actuator such as with a tuned mass damper. The size of the actuator depends only on the required control force i.e. the amount of vibration energy to be extracted from the structure. Impressive damping ratio has been achieved on a 400kg structure with a 20ge actuator.

Active Damping Devices Implementation

  1. Computation based on an existing FEM model of the structure and/or on the results from a quick vibration response test allows evaluating the required force to implement in the actuator.
  2. A test involving existing actuators generating the computed force is performed to check performance and improvement of customers’ machine or process.
  3. If needed – custom actuators and/or controllers are designed to fit customers’ machine or process.



  • Pointing accuracy improvement for systems with vibrating base
  • Moving camera and optics stabilization time improvement by structural damping
  • Noise emission reduction of structural born noise
  • Chatter avoidance in machine tools (damping the machine structure prevents the chatter from appearing).