Electromagnetic Resonance Sensing of Elevator Position Technical Field This invention relates to an elevator absolute position sensor that utilizes a plurality of sets of sine and cosine coils which become coupled to corresponding excitation coils by means of resonating coils or other short circuits, the relative phase of a set of sine and cosine sensing coils being indicative of the position at which the coupling occurred and the position of the coupling between the sets of sine and cosine coils being indicative of the absolute position of the sets of sine and cosine coils.

Background Art Knowledge of the position of an elevator is necessary in order to determine the floor being approached by an elevator, as well as the detailed position of the elevator with respect to the landing when the elevator slows down. One very typical floor-indicating position sensor uses N and N + 1 rotating code disks, driven by a long loop attached to the elevator, to unambiguously determine the floor position of the elevator. The problem with this sort of position sensor is that there is a large degree of wear in the driving loop, and always the possibility of getting out of synchronization.

Other types of sensors include optical encoders, optical strips and tapes and the like. However, these are all subject to mechanical wear, smoke and dirt causing errors or interrupting the sensing of indicia. Vibration of the elevator car and spacing between portions of the sensor system can render other types of encoders less than useful.

Disclosure of Invention Objects of the invention include : determining elevator position with relatively simple, durable apparatus which requires no calibration and little maintenance; elevator position determination in a manner not affected by the hoistway environment; provision of an elevator position sensor capable of

providing floor position as well as exact landing position; and improved elevator position sensing.

According to the present invention, elongated sine and cosine coils are coupled to an excitation coil by means of a resonating coil, the position of which is unambiguously defined with respect to the sine and cosine coils by the quadrature voltages induced therein. According further to the invention, pairs of elongated sine and cosine coils are utilized with resonating coils, the relative distance between which is utilized to identify the particular floor being monitored by the apparatus at any given time. Thus, the phase relationship in one elongated sensing strip determines the exact position of the elevator with respect to a particular landing, and the relationship between those signals and the signals in another elongated sensing coil strip are indicative of the elevator car floor position.

The invention is easily installed, not affected much by car vibration, insensitive to dirt and smoke, requires no correction runs and is useful in high rise as well as low rise buildings. There is less installation cost, no mechanical wear and lower maintenance costs. High accuracy is obtainable anywhere in the hoistway. A position sensor according to the invention has a very high position update rate, e. g. , microseconds.

Other objects, features and advantages of the present invention will become more apparent in the light of the following detailed description of exemplary embodiments thereof, as illustrated in the accompanying drawing.

Brief Description of the Drawings Fig. 1 is a plan view of an elongated sine/cosine sensing coil assembly with a corresponding resonating coupler.

Fig. 2 is a dual view perspective of an elevator car and a pair of elevator landings, incorporating the present invention.

Mode (s) for Carrying Out the Invention Referring to Fig. 1, a position sensor coil set 9 includes a printed circuit board 10 having an excitation coil 14, a sine sensing coil 15, and a cosine sensing coil 16. A resonating coupling coil 20 couples the excitation voltage, such as that illustrated by the sine wave 22, to the sine and cosine sensing coils 15,16. The coils are typically printed on printed circuit boards, but may be mounted on any suitable substrate. The sine and cosine coils are electrically isolated by being printed on opposite surfaces of the printed circuit board; the excitation coil 14 is spaced apart from whichever coil is on the same surface with it. The exact nature of operation of these devices and other manners in which they can be implemented are disclosed in U. S. Patent No. 6,124, 708, and to a certain degree, in other references therein.

Referring to Fig. 2, the sensing apparatus is arranged to have sensors 9 with boards 10 which are slightly longer than the distance between landings 26, 27 of the building 28. In order to determine the exact position of the elevator car 29 with respect to the nearest landing, a pair of coil sets 9a, 9b interact with a corresponding series of primary resonating coils 20a, 20b (and similar resonating coils for other landings in the building, not shown). In order to determine, unambiguously, the floor position of the elevator, another pair of coil sets 9c, 9d interact with a series of additional resonating coils 20c, 20d (as well as additional resonating coils at each landing of the building, not shown). Utilizing a pair of boards on each side of the elevator, such as coil sets 9a, 9b, ensures that there is one of the resonating coils interacting with one of the boards at all times. Having the coil sets 9a, 9b separated from the coil sets 9c, 9d by a large distance avoids any magnetic coupling between them. The coil sets 9a and 9b are sensed, simultaneously, and the coil sets 9c and 9d are sensed simultaneously, the sensing occurring in circuitry 32 that provides the excitation voltage to the coil 14, which may be disposed on the elevator car 29 within a housing 33 and connected to the boards by conductors (not shown). Alternatively, the signal processing apparatus could be located at some other part of the elevator system, in any implementation of the invention in which that would be preferable.

In order to derive floor information, the relationship of the signals sensed in the coil set 9a as a consequence of the position of the resonating coil 20a, compared with the relative phases of the signals in the coil set 9c sensed as a consequence of the position of the resonating coil 20c is compared with the relative difference between the sine and cosine signals sensed in the coil set 9b compared with those sensed in the coil set 9d. By positioning the resonating coils 20c, 20d at different vertical distances 35,36 from the corresponding resonating coils 20a, 20b, a difference in the phase will be apparent, so comparison of the signals on the coil sets 9a or 9c with those on the coil sets 9b or 9d will indicate the floor position of the elevator car.

The coil sets 9a and 9c are vertically spaced and longitudinally aligned with the coil sets 9b, 9d. If there is any electromagnetic interference between the upper and lower coil sets in either case, then electromagnetic shielding may be provided between the coil sets, as may be necessary in any given embodiment of the present invention.

The coil sets 9a, 9b are electromagnetically isolated from the coil sets 9c, 9d by the space across the face of the elevator. If these are desired to be disposed on the same side of the elevator (with the resonating coils similarly on the same side of the landings 26,27 in a straightforward manner), then suitable electromagnetic isolation between coil sets 9a, 9b'and coil sets 9c, 9d should be provided. One method of electromagnetic isolation is to operate the coils at different frequencies and employ well known filtering techniques to separate the signals.

The excitation voltage provided to the excitation coils 14 may be in the range of 100 KHz to 10MHz, as may suit any individual implementation of the present invention. The selected frequency determines the minimum separation distance between the resonant coil and the excitation coil.