Patent Application
20130081909
The subject matter disclosed herein relates to determining elevator car position. More particularly, the subject matter disclosed herein relates to determining elevator car position using bi-stable sensors.
It is known in the elevator art to define terminal zones at both ends of the elevator hoistway. The top landing of the building will normally be located within the top terminal zone as will the lower landing be located within the bottom terminal zone. It is desired that the elevator car stop normally at a top or bottom landing of the hoistway in such a terminal zone. As a safety measure, it is necessary to provide a number of backup means to ensure the elevator car does not collide with the mechanical hard-limits. Three levels of protection are usually provided when the elevator enters a terminal zone: the Normal Stopping Device, the Normal Terminal Stopping Device (or NTSD), and the Emergency Terminal Speed Limiting Device (or ETSLD). Embodiments of the invention may be used with NTSD which will take over from the Normal Stopping Device should the normal speed control signals fail to stop the car at the designated positions at the upper and lower ends of the hoistway. Two similar NTSDs are usually provided in the two terminal zones. One NTSD is installed at the bottom of the hoistway and one NTSD at the top of the hoistway. The NTSD system is designed to override the normal speed command signals and bring the car to stop at the terminal. It is also designed such that the NTSD terminal speed profile causes the slowdown pattern to be relatively smooth.
In order to implement the NTSDs, the position of the elevator car needs to be known by a control system. One existing method of determining elevator car position employs three sensors for detecting car position and a fourth sensor as a latching or clock input. The clock input indicates when the three sensors should be read to determine car position. As system noise can cause false clocking signals, improvements to such systems would be well received in the art. In addition, positions identified through the use of a simple binary code is sub-optimal in the required number of sense elements.
According to one aspect of the invention, a system for monitoring elevator car travel includes a plurality of bi-stable sensors traveling with an elevator car; a plurality of sense elements positioned along a path of the sensors; the sense elements causing the sensors to assume one of a first state and a second state; wherein states of the sensors define a zone code identifying a zone corresponding to the elevator car position, the zone code being a gray code.
According to one aspect of the invention a method for monitoring elevator car travel includes positioning a plurality of bi-stable sensors to travel with an elevator car; positioning a plurality of sense elements along a path of the sensors; the sense elements causing the sensors to assume one of a first state and a second state; obtaining states of the sensors, wherein the states of the sensors define a zone code identifying a zone corresponding to the elevator car position, the zone code being a gray code.
These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.
The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings.
Sensors 12 travel with car 10, and may be mounted directly to the car 10 or on a support 14 extending from the car 10. Sensors 12 are positioned and spaced to correspond to sense elements 20. As described in further detail herein, sensors 12 are bi-stable sensors, meaning sensors 12 maintain a first state until being toggled to a second state, and vice versa. To change state, the sensors 12 need to be exposed to energy initiating the change in state; mere absence of a sensed element 20 will not cause the state of sensor 12 to change. In an exemplary embodiment, sensors 12 are bi-stable reed switches sensitive to magnetic energy. It is understood that other types of bi-stable sensors may be used (e.g., optical).
Sense elements 20 are positioned along a path of travel of the sensors 12. The sense elements 20 are positioned and spaced to correspond to the positions and spacing of the sensors 12. Sense elements 20 may be mounted in the hoistway, if sensors 12 travel within the hoistway. As long as the sensors 12 pass close enough to the sense elements 20 to detect the sense elements 20, the exact mounting location in the elevator system is not critical.
The sense elements 20 are mounted on vanes 22, with each vane positioned at a transition between zones. As described in further detail herein, as the group of sensors 12 passes each zone boundary, one of the sensors 12 changes states in response to a sense element 20 positioned at the boundary between the zones. As only one sensor 12 changes state at each zone transition, the zone code 30 generated by the sensors 12 follows a gray code. As known in the art, a gray code is a series of binary numbers in which only a single bit changes from one element in the series to the next.
The direction of travel of the car 10 also affects the state of the sensor 12. For example, when the car 10 (and sensors 12) is traveling upwards, the first sense element 201 causes the sensor 12 to assume a first value (e.g., a logic 1) and the second sense element 202 causes the sensor 12 to assume a second value (e.g., logic 0). Alternatively, when the car 10 (and sensors 12) is traveling downwards, the first sense element 201 causes the sensor 12 to assume the second value (e.g., a logic 0) and the second sense element 202 causes the sensor 12 to assume a first value (e.g., logic 1).
In the example of an upwardly moving car 10, the zone code is initially 000 when the car 10 is between the top zones and the bottom zones (shown in
As the car moves downward through the top zone, the states of sensor 121, 122, 123 are altered by the sensors 12 passing the sense elements 20. When the car 10 is moving downwards, the sense elements 20 have the opposite effect on the states of sensors 12 (as compared to an upwardly moving car) and the zone code 30 is the same for each zone, regardless of whether the car is moving up or down.
A controller 106 receives the zone code 30 and issues control signals, as needed. The controller 106 may be implemented with one or more processors executing computer program code, memory adapted to store software programs and data structures, input-output devices, etc. The controller 106 may also receive other inputs, such as elevator car speed. In an exemplary embodiment, the controller determines when the car 10 is entering a terminal zone (e.g., top or bottom) and determines if the car speed is acceptable. If not, a control signal is generated to initiate the NTSD to reduce car speed in the terminal zones. As the zone code 30 for the top zone and bottom zone follows the same pattern (from entry to the terminal zone), controller 106 can be simplified to detect when the terminal zone is approaching.
In alternate embodiments, the top zone codes 30 and the bottom zone codes 30 are different and follow a different pattern. This can be useful in determining whether the car is in the top zone or bottom zone. Processor 106 can determine which zone the car is in by analyzing the zone code 30.
Technical effects of exemplary embodiments include providing a mechanism for accurately determining the zone of an elevator car. The determination of the zone of the elevator car may then be used to determine whether certain safety initiatives are warranted.
While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US2010/038798 | 6/16/2010 | WO | 00 | 12/13/2012 |
