Elevator – industrial lift truck – or stationary lift for vehicle – With barrier for regulating access to load support – Includes motor or motor driven linkage for shifting barrier
Patent
1994-04-06
1996-03-05
Wong, Peter S.
Elevator, industrial lift truck, or stationary lift for vehicle
With barrier for regulating access to load support
Includes motor or motor driven linkage for shifting barrier
318807, 49118, 187289, B66B 1306, E05F 104
Patent
active
054959187
ABSTRACT:
An elevator car door is moved by a variable voltage, variable frequency linear induction motor which is driven open current loop to achieve a desired velocity profile indicated by an incremental linear encoder, with washed out proportional and integral gain. A magnetizing current insufficient to overcome the weight of the door is added in quadrature with the linear force current, and frequency is determined open loop in a predetermined fashion. Pulse width modulation voltage control signals are utilized to apply fixed voltages of correct polarity through a low pass three phase filter to the windings of the motor for correct intervals of time so as to synthesize desired sinusoidal winding currents. A boost of current is provided following each zero crossing of the sinusoidal winding currents to overcome lags therein. A ramp down of voltage avoids dropping the door at the end of door opening and door closing.
REFERENCES:
patent: 4698876 (1987-10-01), Karita
patent: 4876765 (1989-10-01), Karita
patent: 5134324 (1992-07-01), Sakagami et al.
patent: 5172518 (1992-01-01), Yoshino
patent: 5373120 (1994-12-01), Barrett et al.
Ahigian Edward E.
Barrett David W.
He Thomas
Jaminet Jerome F.
Kowalczyk Thomas M.
Nappi Robert E.
Otis Elevator Company
Wong Peter S.
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