Elevator – industrial lift truck – or stationary lift for vehicle – Having specific load support drive-means or its control – Includes control for power source of drive-means
Reexamination Certificate
1999-12-21
2001-10-23
Salata, Jonathan (Department: 2837)
Elevator, industrial lift truck, or stationary lift for vehicle
Having specific load support drive-means or its control
Includes control for power source of drive-means
C182S069400
Reexamination Certificate
active
06305502
ABSTRACT:
TECHNICAL FIELD
The present invention relates to elevator systems and, more particularly, to an elevator passenger car active-acceleration control system that controls the acceleration of the elevator car floor.
BACKGROUND OF THE INVENTION
To enhance passenger comfort, elevator systems require acceleration control systems to suppress accelerations, e.g., vibrations, transmitted from various components of the elevator system to the elevator car. Most elevator systems provide one or more means for absorbing or dampening forces applied to an elevator car by surrounding structures. For example, friction dampers may be applied to roller guides. Such solutions add to the cost and space requirements of the overall system, and are subject to high levels of wear. Active-guidance control systems have been employed to reduce or eliminate certain types of vibrations associated with elevator car movement.
One factor that greatly affects elevator car ride quality is lateral vibration of the elevator car with respect to the hoistway or elevator guide rails. Lateral vibrations can be caused by aerodynamic forces acting directly on the elevator car during movement. Lateral vibrations may also be attributable to suspension forces resulting from imperfections in the manufacture and installation of the hoistway guide rails, or due to misalignment of the rails caused by building settlement.
Certain known systems stabilize the elevator car frame with respect to the hoistway guide rails. Systems of this type require a suspension-centering subsystem that adds weight, cost, and complexity to the overall elevator system. These types of systems are often subject to reliability problems. In addition, they typically consume large amounts of electrical power which requires additional cost and which presents thermal concerns. By stabilizing only the elevator car frame with respect to the hoistway guide rails, there still remains relative movement or vibration between the elevator car frame and the cab floor, on which the passengers stand.
At least one known system described in a publication, “Improving Control of Super-High-Speed Elevators”, Japan Society of Mechanical Engineers International Journal, Series C, Vol. 40, No. 1 1997 (the JSME Article), attempts to control lateral vibration in an elevator car by using an actuator attached between the elevator car frame and the elevator cabin. The intent is to isolate the elevator cabin from vibrations to which the elevator car frame is subject. The results are somewhat mediocre, however, as described in FIGS. 18 and 19 of the JSME Article, because the ballscrew actuator used in the system introduces high frequency vibrations. In addition, the ballscrews will undergo mechanical wear, limiting life, increasing noise and decreasing maintainability. Moreover, the prior art system described in the JSME Article is subject to controllability problems due to stiction, friction and backlash of its mechanically contacting components.
OBJECT AND SUMMARY OF THE INVENTION
It is an object of the present invention to provide a system for controlling lateral elevator cab floor vibration for improving ride quality using an active-guidance system. It is a further object of the present invention to provide such a system that provides superior and efficient performance over known, prior systems and that overcomes the shortcomings of such prior systems. These objects and others are achieved by the present invention described herein.
The present invention elevator cab acceleration control system directly minimizes the lateral vibration of an elevator cab floor, e.g., an elevator platform, by implementing electromagnets between the cab floor and the car frame in a novel fashion. The electromagnets are controlled in a closed-loop feedback manner by signals from accelerometers. The present invention system eliminates the cost, complexity and structural requirements of the prior art systems described above. In contrast to the prior art systems, the present invention system provides direct vibration control to the cab floor. Because the present invention system directly controls the vibration of the cab floor rather than the relatively heavy elevator car frame, the active vibration actuators employed have a much lower force requirement and thus a lower power supply requirement. The present invention system is of simple construction and can be easily retrofit on existing equipment.
The present invention elevator cab acceleration control system generally comprises three axes of vibration feedback utilizing accelerometers, a control system, vibration-suppressing actuators in the form of electromagnets, and an accompanying power supply. For each axis, an arrangement of an accelerometer and a reaction plate are attached to brackets that are fixed to a rigid member of the elevator cab floor, e.g., the platform structure. The rigid member may be, for example, a centrally-located platform-stiffening member. Electromagnets are mounted to a rigid member of the car frame structure, such as a safety plank. The electromagnets are arranged to cooperate with the reaction plates to control acceleration of the elevator platform. Power supply and control modules for the electromagnets and the accelerometers can be located in a variety of locations depending on such factors as safety and convenience for service personnel.
As the elevator cab platform vibrates in a given axis (postwise axis, front-to-back axis on left side of car, and front-to-back axis on right side of car), the vibration is detected by the accelerometer and an electrical signal proportional to the vibration level is fed to the control system. The control system varies current to the electromagnet to control the force required to nullify the vibration (i.e., acceleration) of the platform. The force is a function of the cab mass transfer function and vibration level. Closed-loop feedback of the cab vibration to the control system ensures that the electromagnetic force level signaled by the control system is continuously adjusted to provide the proper amount of vibration-attenuating force.
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patent: 5749444 (1998-05-01), Skalski
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patent: 5929399 (1999-07-01), Jamieson et al.
patent: 10245178-A (1998-09-01), None
Yoshiaki Yamazaki, Masao Tomisawa, Kouji Okada, and Yoshiki Sugiyama, “Vibration Control of Super-High-Speed Elevators”, Japanese Society of Mechanical Engineers International Journal, Series C, vol. 40, No. 1, 1997.
He Thomas
Malone, Jr. Thomas Francis
Otis Elevator Company
Salata Jonathan
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