Active Mass Dampers

IHI applied its strong technical expertise to the development of active mass dampers. The adoption of active mechanisms to mass dampers adds a number of features.

Features

* Simple mechanisms with few components.
* Low height as no suspension mechanisms is used.
* Light moving mass controlled over long strokes, moving mass is controlled by displacement to achieve effective control to the stroke end. It also supports large accelerations.
* Two axis (X and Y directions) are adopted for effective control of building sway in the long and short axis directions.

* Installing two diametrically-opposed systems provides effective control of torsional sway of the building.
* Installing two diametrically-opposed systems also provides effective control of torsional sway of the building.

* Systems operate effectively until 200 Gal horizontal acceleration is reached at the floor where the systems are installed.
Operation stops when 200 Gal is exceeded and restarts when acceleration drops back below 200 Gal.
* Modern control theory is applied to achieve strong damping with respect to complex vibration modes.

Example of Mass Damping Effect

Movies

			Description of mechanism System behavior during earthquakes

Energy Recovery System

This system reuses the electrical energy discarded during driving of the Active Mass Damper (AMD). Re-using the energy generated during deceleration of the additional mass attached to the active mass damper reduces the power capacity needed to drive the AMD to between 1/3 and 1/5 the conventional requirement. The energy consumption is reduced to at least half the conventional value.

Features

* In this system, the inverter DC intermediate circuit capacitance in the AMD electrical circuit is a large electrical double layer capacitor (EDLC). This capacitor accumulates power during energy recovery and supplies power when the system is driven.

* The power system supply capacity needed to drive the AMD can be reduced to between 1/3 and 1/5 the conventional requirement.
* The system uses an environmentally friendly electrical double layer capacitor to store energy.

The system was designed for greater safety than a lead-acid battery system during disposal or in the event of destruction.

Hybrid Mass Damper System for Buildings (Pendulum Type)

Dual-axis pendulum type hybrid mass damper system Total system weight: 42 tons

Features

* Simple swinging mechanism reduces cost.
* Simple adjustment of natural period.
* Easier maintenance with fewer components.
* Small footprint.
* Long mass stroke even in low buildings with a short natural period.
* Rubber mount vibration isolator reduces vibrations to lower levels.
* Low acoustic noise level.

Hybrid Mass Damper System for Buildings (V-shaped)

Features

* Simple swinging mechanism reduces cost.
* Simple adjustment of natural period.
* Easier maintenance with fewer components.
* Small footprint.
* Permits installation under low eaves.
* Rubber mount vibration isolator reduces vibrations to lower levels.
* Low acoustic noise level.

Active-damping Bridge

Features

* Lighter and more compact than conventional AMD systems using weights, as no weight is required.
* Works against small wind vibrations that passive damper systems cannot handle.
* Can be located outside, resulting in small installation space.
* Smooth, backlash-free drive mechanism eliminates concerns about noise and vibrations.
* Can be used as a connecting bridge or emergency escape.

Tuned Mass Damper for Bridge Beam

Features

* Reduces vertical vibrations of bridge beams during strong winds, such as typhoons.
* Load parts through the diaphragm opening and assemble inside the box -- no opening is required in the floor.
* Compact design since parts of bridge beam can be used as frame for the system.
* Passive system requires no electrical power supply.
* Can be tuned on site.
* Simple and easy maintenance, only lubrication.

Hybrid Mass Damper System for Bridge Main Towers

Features

* Reduces swaying of main towers during construction.
* Roller system achieves compact mechanism design.
* Basic passive construction reduces control forces from actuators. Requires just 1/3 to 1/5 power supply capacity of an active mass damper.
* Operates as a passive mass damper and maintains damping capacity during a power failure.
* Rapid response to random external wind forces achieves stable mass damping.