HAKUSAN Corporation

Our company, who is involved in earthquake observation, designed a translation mechanism considering the following reproduction performance goals for designing an earthquake experience device.

• ・The system must be able to accurately reproduce the waveforms of earthquakes with seismic intensities of five or greater that have actually been observed.
• ・The system must be able to reproduce long-period ground motion, which is supposed to be caused by an ocean-trench-type earthquake.
• ・The system should reproduce not only geological phenomena, such as seismic motions (observation data), but also the shaking caused by the deformation of the upper floors of buildings (response simulation data), thereby simulating various cases in which citizens are actually affected.

The development of the Vuton control unit also required unique innovations. In the design of electric automated guided vehicles (AGVs), which are often used in industrial applications, it is sufficient to select and arrange the power supply and motor drive circuits required for motor acceleration at the start of travel and during cruising, and deceleration is simply considered as acceleration in the opposite direction. However, the acceleration generated by an earthquake motion simulator is incomparable to that of an AGV, and intense acceleration and deceleration are repeated in 0.01 s without interruption. Consequently, with repeated acceleration and deceleration, the effect of the motor current flowing backward at the moment of deceleration causes the power supply unit to fail. If the Vuton were a running vehicle, it would be equipped with brakes; however, because acceleration (deceleration) must be accurately controlled during earthquake reproduction, servo control must be used. This problem was resolved using a shunt regulator circuit and regenerative resistor in the control unit to consume excess current in the form of heat.
We considered incorporating a bank of supercapacitors (large-capacity capacitors), which began to gain popularity at the time, into the control unit to store regenerative current and reuse it during acceleration, a method used in hybrid cars and elevators. However, the cycle of charging and discharging was excessively intense, and we judged that the life of the capacitor would not be sufficient. Thus, we abandoned this idea at the development stage. Capacitors have made significant progress in recent years owing to the widespread use of electric vehicles and may eventually gain utility in Jishin-The-Vuton.

The control unit, which includes additional functions such as video reproduction, was designed to operate with a 100 V commercial power supply. The driving motors of Jishin-The-Vuton are four units rated at 400 W, which are instantaneously driven at hundred percent of their rated output. However, Jishin-The-Vuton is operated in conference rooms in offices and lobbies of condominiums, where power supply capacity is limited; thus, the selection of a power supply has to be well considered.
Real observed seismic motion data (acceleration values) were filtered for translation control by speed servos, and the video content of indoor damage was edited to enable easy interpretation of the operation of an earthquake menu to select different types of experiences. Joint research was conducted with the Midorikawa Laboratory at the Tokyo Institute of Technology.
Improvements were made in response to the problems encountered when we took our prototype to various conferences and local government events before the product was commercialized. This is a good example of the following design thinking that we value: fabricate a product, deploy it in the field, and then continue improving it.