Mitsubishi Electric: Technology of passive control of amplitude of fluctuation of ropes of elevators

2019: Development and testing of the device of passive control of fluctuations of a rope

On February 18, 2019 the Mitsubishi Electric corporation announced development of the device which passively controls amplitude and frequency of fluctuation of a rope in case of rocking of the high rise building at strong wind or long earthquakes. This device ensures stable functioning of elevators in difficult conditions for bigger convenience of passengers, claim in Mitsubishi Electric.

According to the developer, the operation principle of the device of passive control of fluctuations of a rope is based on impact of magnets (the principle of "negative rigidity") on the lower part of a rope. The negative rigidity is understood as application of force in the direction opposite to action of elastic force of the spring.

Key characteristics of the solution mentioned by the developer:

1. Stability augmentation of operation of the elevator thanks to significant reduction of vibration amplitude of a rope when rocking the building.
   • Sil of action of permanent magnets it is used for increase in vibration amplitude of a rope at a fastening point in an upper part of a cabin of the elevator.
   • Lowering of resonance frequency, or natural frequency, fluctuations of a rope complicates rocking of the building and a rope in this connection amplitude of fluctuation of a rope sharply decreases.
   • the Device allows to stabilize operation of the elevator, reducing time of operational idle time. The negative rigidity is reached using placement of the permanent magnets which are on different sides of a rope and turned to each other. The formed force works in the direction of fluctuation of a rope, increasing amplitude on the lower section as though it was loose (the rope with one free end has lower resonance frequency, than a rope with two fixed ends). As a result of the frequency of fluctuation of the building and a rope are different, the resonance does not arise that leads to reduction of amplitude of fluctuation of a rope. Use of magnets with a permanent field allows to stabilize operation of the elevator without use of the electric power.

2. Positive results of tests on decrease in effect of vibration of the lift systems in actual practice. During the testing imitating rocking of the building at a long earthquake it was established that when using the device of passive control amplitude of fluctuation of a rope can be reduced at least by 55% (fluctuation amplitude in the center of a rope on which the similar device is not used is taken for 1).

At tests, in specially built test elevator shaft of SOLAÉ Mitsubishi Electric (height 173 meters) at the Inazawa plant in Japan, an upper part of a rope fluctuated with a frequency imitating rocking of the building in case of a long earthquake. For lack of the monitoring device amplitude of fluctuation of a rope exceeded the threshold recommended by the company at which there is an elevator stop. While when using the monitoring device amplitude of fluctuation of a rope fell below this value, noted in Mitsubishi Electric.

High rise buildings owing to the construction are shaken both in case of earthquakes, and at strong wind gusts that leads also to rocking of a lift rope. If the oscillation frequency of the building and a rope are close to each other, they enter a resonance, the rope is shaken even stronger and faces the elevator shaft equipment. At emergence of similar conditions for the purpose of security the elevator can be stopped. In order to avoid such situations, it is necessary to reduce the frequency of fluctuation of a rope. As the rope fastens to an upper part of a cabin of the elevator where it is easy to set quenchers of vibrations, it is difficult to reduce amplitude of fluctuation of a rope at the specified configuration.

As reported in Mitsubishi Electric, the corporation intends to market the provided device by March 31, 2022.