FR2737713A1 - METHOD AND SYSTEM FOR CORRECTING THE STOP PRECISION OF AN ELEVATOR CABIN - Google Patents

Abstract

This system comprises: - a device (18, 20, 22) capable of giving stop information, - a control logic (26) in which the information given by said device is processed and which consequently issues an order of 'stop, - a device (28, 30, 32) for measuring the speed of movement of the cabin, - a microprocessor (38) provided with a stop management program and a memory, - a calculation unit (36) in which is calculated a time delay T, - and a programmable time module (40).

Description

Method and system for accuracy correction

stopping an elevator car.

  The present invention relates to a method for correcting the stopping accuracy of an elevator car at different levels. It is recalled that the stopping accuracy is the difference between the threshold level of the cabin and that of the threshold of the landing when the cabin is stopped. It is known that the stop descent and uphill information are given respectively at each level at the moment of the meeting of a magnetic sensor fixed on the cabin with a magnet fixed in the hopper at this level. The stop information is sent to a stop control logic which is fitted to the elevator installation and which sends a stop command to the drive motor means of the car. In the context of the invention, these drive means may be constituted by a two-speed motor with drum brake (called AC2 motor). This engine drives the cab at a first speed over most of its stroke between stages, and at a lower speed (of the order of a quarter of the first speed) over a short distance before

the stopping of the cabin.

  Currently, the stop accuracy at the bearings of an elevator equipped with an AC2 motor is within a range of + 20 mm. Such unevenness can lead to serious material inconvenience. For example, users may stumble, or the loading of a pallet truck may be shaken and deteriorated. This poor performance represents the limits of the technique

current with this motorization.

  The reason for the poor performance of the AC2 engine is mainly because the braking force of the engine is not locked to the load carried by the cab, but is set once and for all to have a comfortable deceleration. It follows that with this engine, it does not control the braking distance according to the load for the same stop information. It is considered that, in the case of a high speed brake stop with the unladen cab, the setting of the braking force should result in a stopping of the cab for a distance greater than or equal to 80% of the distance. traveled by the cabin in 1 second at rated speed. For example, if the rated speed is 1 m / s, the cab must stop

  after traveling a minimum distance of 0.80 m.

  Another reason for poor performance is to be found in the fact that the speed before stopping is still relatively high, even if the car is moving at a slow speed. As a result, the inertia of the mobile system constituted by the cab and the counterweight is important and the brake must dissipate a great deal of energy. Moreover, this energy evolves so

  significant with the load in the cabin.

  The solutions that are currently used to solve this problem all have the purpose of reducing the speed of movement before stopping in order to reduce the energy to be dissipated by the brake. Indeed, it avoids modifying the braking device because it must comply with the standards in force (EN81). To reduce the speed of movement before stopping one can: - either perform an electronic control of the speed, for example by means of a motorization of the type of variation of frequency (VF), which is perfect from this point of view, because it makes it possible to obtain the stopping information at the moment when the speed is almost zero, the brake then having a simple role of parking brake; - Or increase the number of poles of the low speed winding AC2 motor to obtain a very low speed;

  - or finally use a mechanical variator.

  Unfortunately, all these solutions and mainly the first are too expensive to be applied to a two-speed motor AC2. The additional cost of these solutions would make the selling price of the installation too high compared to that practiced by the competition. The present invention aims to remedy these drawbacks and therefore relates to a method for correcting the stop accuracy of AC2 motor lifts while keeping the cheap side of this engine. The idea of the invention came from two observations made by the Applicant: 1. The curves of variation of the stopping accuracy of the cabin as a function of its load PA = f (C), both uphill and downhill, are comparable to two straight lines and are therefore reproducible. It can be concluded that if a device was set when it was put into service, with the cabin empty, by correctly adjusting the position of the magnets with respect to the magnetic sensors, so as to obtain a zero stop accuracy, and if in addition, we know the evolution of the stop accuracy as a function of the load, we can estimate the stop accuracy for

each charge.

  2. The curves of variations of the speed of displacement of the cabin according to its load V = g (C), as well in rise as in descending, are comparable to lines. From these two families of curves, one can deduce the curves of variations of the stop accuracy as a function of the speed PA = h (V) up and down, which are

  they can also be assimilated to straight lines.

  The advantage of taking speed as a parameter to estimate the stopping accuracy to be corrected, rather than the load, is that it is easy to measure speed. The measurement can be carried out for example by means of the optical fork device which is the subject of the patent application No. 95 08428 filed in the name of the Applicant, which

  has the advantage of being simple and cheap.

  It follows from the foregoing that it is possible to estimate from the measurement of the speed before stopping the car at each level, the stopping accuracy, that is to say at which

  distance the cabin threshold will stop above or below

below the threshold of the landing.

  On the basis of this result, the Applicant has devised a method for correcting the stop accuracy of the invention. The subject of the invention is a method for correcting the stopping accuracy of an elevator car provided with a device giving a stopping information when the car is in the vicinity of a level, and a stop control logic which gives the stop command to the cab drive means, said method being characterized in that it consists of: - constructing the variation curves V = f (C) of the speed of movement of the car uphill and downhill, depending on the load carried by the car, by measuring the speed before stopping the car at a given level, at least in the case where the car is empty and in the case where it carries its nominal load, - to construct the curves of variations PA = g (C) of the stopping precision of the cabin, in ascent and descent, according to the load by measuring the precision of stopping of the cabin uphill and downhill in the two cases mentioned above, - to the curves of variations PA = h (V) of the stop accuracy as a function of the speed of displacement, the calculation of the correction of the stop accuracy in the particular case where the cabin reaches a certain level, with a given direction of movement and a given load being carried out by the following operations which consist in: - measuring the displacement speed V of the cabin at the level and in the direction of displacement considered, - calculating a specific delay T, by the formula T = PA / V, where PA is the value of the stop precision recorded on said curve PA = h (V), for said measured value of the speed, and to include this delay between the stop information and

the stop order.

  The present invention also relates to a system for correcting the stop accuracy for the implementation of this method, characterized in that it comprises: a device capable of giving stop information each time the cabin of elevator arrives in the vicinity of a level, a control logic in which the information given by said device is processed and which consequently issues a stop command, - a device for measuring the speed of movement of the cabin before stopping at each level, - a microprocessor provided with a stop management program and a memory in which the variation curves, PA = h (V), are stored in ascending and descending, - a calculation unit in which a delay time T is computed by the formula T = PA / V, in which PA is the particular value of the stop accuracy for a specific speed measured at a level, said value being recorded in said mth and a programmable timing module for including said delay in the stop information given by the device. The invention will now be explained with reference to the accompanying drawings in which: FIG. 1 is a schematic view of an elevator installation equipped with the stop accuracy correction system; Fig. 2 is a graph showing the variation in stop accuracy as a function of load, ascent and descent; FIG. 3 is a graph showing the variation of the speed of movement of the elevator car as a function of load, up and down; FIG. 4 is a graph derived from those of FIGS. 2 and 3 and showing the variation of the stop accuracy as a function of the speed of displacement, and FIG. 5 is a flowchart which details the operations performed by the correction system of FIG. the invention. In FIG. 1, an elevator car 10 is shown in a hopper 12, at a level of a bearing 14. The installation is equipped with a position reference system known per se for providing information of stop when the cab is slightly ahead of the stop position. This system comprises a magnet 18 fixed in the hopper at each level, and two magnetic sensors 20, 22 fixed on the cabin one above the other. The upper magnetic sensor 20 transmits a stop information when it encounters the magnet when the car is lowered, while the lower magnetic sensor 22 emits

  stopping information when the car is climbing.

  This information transmitted at each level is sent to an input 24 of a control unit which can advantageously be integrated into the control logic 26 which is provided with any elevator installation. The control logic 26 gives a stop command to the drive motor

  of the cab and controls the release of the engine brake.

  Engine and brake are not shown for clarity

of the figure.

  The elevator installation is also equipped with a device for measuring the speed of the car. This may be of any known type, but it will be advantageous to use an optical fork device because of

  its simplicity and its low cost.

  It is recalled that this speed measuring device comprises an optical fork 28 fixed on the elevator car and a plurality of flags 30, 32 fixed in the hopper. The optical fork comprises two hollow arms in which are respectively housed a transmitter and an infrared ray receiver. The arms are arranged in a horizontal plane, so that the infrared beam 34 passes horizontally through the gap between the arms. The flags are constituted by vertical plates, opaque to infrared rays and they are arranged to cut the infrared beam 34 each time the optical fork reaches their level. In Figure 1 there is shown the two flags associated with a level. The upper flag 30 serves to measure the downhill speed and the lower flag 32 serves to measure the

climbing speed.

  The infrared radiation receiver transmits signals having a first logic state when the infrared beam passes and a second logic state when the beam is turned off. These signals are transmitted to a computing unit 36 which, advantageously, can be integrated into the logic of

control 26.

  From these signals, the unit 36 calculates the duration At of interruption of the infrared beam by a flag, then the speed of displacement V of the cabin by the formula

  V = h / At, h being the height of the flag.

  Having explained how the stop information is detected and the speed is measured, the method of correcting the stopping accuracy of the car can now be explained. For this purpose, the two important observations mentioned above are exploited, namely that the stopping accuracy varies linearly as a function of the load transported by the car and that the speed of movement of the car before stopping also varies linearly as a function of the load. .

  The first observation is illustrated in Figure 2.

  In this figure, the load C is plotted on the abscissa and the stop accuracy PA on the ordinate, in millimeters. The negative values of PA mean that the threshold of the stalled cabin is above the threshold of the landing. Before making the measurements, the brake and the stopping accuracy were set, with the cab empty. The variation curves were obtained by measuring only four values of the stopping accuracy: - stopping accuracy with empty cab (CV) uphill

(PA CVM),

  - stop accuracy with empty cab down (PA CVD), the stop accuracy in these two cases being equal to 0 (point O in figure 2), if the installation is well adjusted, - stop accuracy with loaded cab (CC) at its rated climb load (PA CCM), and stopping accuracy with downhill loaded cab

(CCD PA).

  The second observation is illustrated in Figure 3.

  Here, the load is plotted on the abscissa and the speed of movement of the cabin is plotted on the ordinate. To plot the curves only four speed values were measured: speed with empty cabin uphill (VCVM) speed with empty cab downhill (VCVD) speed with uphill cab (VCCM)

  speed with cabin loaded downhill (VCCD).

  From these curves, it is easy to deduce the curves of variations of the stop accuracy as a function of the speed. It suffices to report on a coordinate system PA = h (V) the values of the pairs (PA, V) recorded in FIGS. 2 and 3 for the zero load and for the full load. We obtain the two linear segments

shown in Figure 4.

  Thanks to these curves, it is possible to estimate in advance the stopping accuracy that will be obtained at a given level, if only the real speed of movement of the cabin is known before stopping at said level, and it will then be possible to correct the stop accuracy to make it substantially zero. For this, according to the invention, a delay T is introduced between the stop information given by the magnetic sensors 20 or 22 and the stop command given to the control logic of the installation. This delay is calculated by the formula T = PA / V, in which PA is equal to the stop precision which is read on one of the curves of FIG. 4 for the case of load considered, that is to say say in fact for the speed V measured just before stopping and in the direction of travel considered. In practice, the control logic 26 is provided with a microprocessor 38 provided with a stop management program and a memory in which the eight values PACVM, PACVD, PACCM, PACCD, VCMD, VCVD, VCCM are stored. and VCCD and a timing module 40 which delays the stop information of said delay T before transmitting it to the output 42

control logic 26.

  The operations performed by the system according to the invention are explained by the flowchart of FIG. 5. In phase 50, the magnetic sensors 20, 22 detect whether the cabin has reached a stop level and a check is made if the speed of movement of the

  cab became equal to the low speed before stopping.

  If this is not the case, the program is not initiated. If yes, in step 52 the computing unit 36 calculates, from the information At which it receives, the actual speed of the

  cabin. This value is kept in memory.

  Once the actual speed has been calculated, the microprocessor 38 calculates the particular stop precision PA which corresponds to said speed, from the curve PA = h (V) which corresponds to the direction of movement considered and which is stored in the memory. This value of PA as well as the measured speed v kept in memory are loaded into the calculation unit 36 which calculates the delay T. This result is stored and loaded into the timing module 40 placed between the stop information given by the sensor and the stop command. In step 56, the system checks whether the detection of the stop information has occurred. If so, the module

  timer 40 is started at step 58.

  In step 60, the system checks whether the delay time T has elapsed. If so, the stop information is transferred to the stop management program at

step 62.

  To test the system according to the invention, the Applicant has used an automaton grafted on the control logic of the installation to perform the program for calculating the speed and delays on stops. The setting of the drive motor brake has been set to a deliberately comfortable value for very poor stopping accuracy. Yet the stop accuracy obtained is + 10 mm for the entire load range in

  both directions of movement and on all levels.

  This result is excellent, because the same elevator not equipped with the correction system of the invention, has a stopping accuracy in climb of between - 60 mm and 0 mm and in descent between - 48 mm and 0 mm. In addition, the PLC used had a time base of 4ms, which is too long and degrades the accuracy of the calculations of speed and delay time. By improving the time base, we can

  obtain a stop accuracy of + 5 mm.

Claims (2)

  1. A method of correcting the stopping accuracy of an elevator car provided with a device (18, 20, 22) giving stopping information when the car (10) is in the vicinity of a level , and stop control logic (26) which gives the stop command to the cab drive means, said method being characterized in that it consists of: - constructing the variation curves V = f (C) the speed of movement of the car uphill and downhill, as a function of load, by measuring the speed before stopping the car at a given level, at least in the case where the car is empty and in the case where it carries its nominal load, - to construct the curves of variations PA = g (C) of the stopping accuracy of the cabin, in ascent and descent according to the load, by measuring the accuracy of stopping of the car uphill and downhill in the two cases mentioned above, - to deduce the curves of variations PA = h (V) of the stop accuracy as a function of the displacement speed, the calculation of the correction of the stop accuracy in the particular case where the cabin reaches a certain level, with a direction of movement and a given load being carried out by the following operations which consist: - in measuring the speed of displacement V of the cabin at said level and with said direction of displacement, - in calculating a specific delay T, by the formula T = PA / V, o PA is the value of the stop precision recorded on said curve PA = h (V), for said measured value of the speed, and to include this delay between the stop information and the stop order.   2. system for correcting the stop accuracy for implementing the method of claim 1, characterized in that it comprises: a device (18, 20, 22) capable of giving stop information to whenever the elevator car arrives near a level, - a control logic (26) in which the information given by said device is processed and which accordingly issues a stop command, - a device ( 28, 30, 32) for measuring the speed of movement of the car before stopping at each level, - a microprocessor (38) provided with a stop management program and a memory in which are stored the variation curves PA = h (V), in rise and fall, - a calculation unit (36) in which a delay time T is calculated by the formula T = PA / V, in which PA is the value particular of the stop accuracy corresponding to a specific speed V measured at a level, the value being read from said memory; and a programmable timing module (40) for including said delay in the stop information   given by the device (18, 20, 22).