Mitsubishi Electric Develops Passive Rope-sway Control Device for Elevators in High-rise Buildings
Mitsubishi Electric has developed a device that passively controls rope sway when high-rise building elevator sway due to strong winds or long-period earthquakes. Negative stiffness is achieved by placing permanent magnets facing each other so as to sandwich the rope. The negative stiffness force acts in the same direction as the rope sway; increasing the sway amplitude at the rope terminal as if the terminal’s position were unfixed (a rope with one free end has a lower resonance frequency than a rope with two fixed ends). As a result, the building and rope sway at different frequencies, so they do not resonate and rope sway is greatly suppressed. The use of permanent magnets enables elevator operation to be stabilized without using electrical energy.
A test that simulated a building swaying due to a long-period earthquake demonstrated that, compared to a rope without a passive rope-sway control device, rope sway could be reduced by at least 55% . By enabling elevators to continue operating under such conditions, the new device will help to stabilize elevator operations and contribute to greater user convenience.