Method, elevator control unit, and elevator system for elevator car speed monitoring

Abstract

The invention relates to a system, control unit and a method for elevator car speed monitoring, which elevator car speed monitoring comprises multiple target speed levels for the elevator car (110) and corresponding target speed positions in an elevator hoistway (112) for each target speed level. The method comprises determining maximum allowed elevator car speed at each position of the elevator hoistway (112) or part of the elevator hoistway (112) based at least in part on a specified deceleration rate of an elevator car (110), the multiple target speed levels and the corresponding target speed positions (408, 410, 412), monitoring or receiving information related to the current elevator car position and elevator car speed, and monitoring that the elevator car speed is kept under the determined maximum allowed elevator car speed at current position of the elevator car (110) in the elevator hoistway (112) or part of the elevator hoistway (112).

Description

[0001] METHOD, ELEVATOR CONTROL UNIT, AND ELEVATOR SYSTEM FOR ELEVATOR CAR SPEED MONITORING

[0002] Technical Field

[0003] The invention concerns in general the technical field of elevator technology. Especially the invention concerns enhancing the safety of the elevators.

[0004] Background

[0005] Typically, an elevator comprises an elevator car and a hoisting machine configured to drive the elevator car in an elevator shaft between landings. The elevator further comprises hoisting machinery brakes, which may be opened or closed to brake the movement of the elevator hoisting machine and thus also the movement of the elevator car. Further, the elevator comprises an overspeed governor, which actuates electrically hoisting machinery brakes to stop the elevator car if the speed of the elevator car exceeds the speed limit, for example 1 15 percent of the maximum rated speed of the elevator car.

[0006] The elevator can comprise further safety equipment, such as a safety buffer, arranged in a pit of a hoistway. The safety buffer is dimensioned to absorb kinetic energy of an elevator car, which moves at the maximum rated speed. Further, a separate buffer may be provided in the pit to absorb kinetic energy of the counterweight.

[0007] When the elevator car is arriving to a landing, the elevator car is instructed to decelerate and finally to stop to the landing. To avoid dangerous situations when approaching a destination floor, the elevator speed is supervised by safety systems of the elevator. One of these systems can be a speed supervising system, e.g. normal terminal slowdown and stopping, which purpose is to supervise that the normal stopping means of the elevator are able to achieve a safe stop to the terminal floors. These speed supervising means can for example prevent hazardous situations in which a failed normal stopping means of the elevator would cause the elevator car to hit the buffers. The prior art elevator car speed supervising systems are able to monitor the speed only by a non-variable speed curve which is able to monitor that the elevator is able to stop at the desired point, e.g. a floor, with its nominal deceleration rate. If the speed of the elevator car exceeds the maximum speed allowed by the speed curve of the elevator car speed supervising system at certain location of the elevator hoistway, the elevator car is stopped and / or decelerated to next landing.

[0008] There can be some situations in which the speed of the elevator car should be reduced before the stopping e.g. in a nonlinear way and for example by reducing elevator speed in steps. Reasons for this kind of more advanced speed monitoring requirement can be safety related matters, e.g. the buffers are shortened and lower speeds should therefore be used, shaft requirements, e.g. the air pressure should be lowered at the terminal areas, or quality related matters, e.g. noise should be reduced in certain areas of the shaft.

[0009] The prior art speed supervising systems are not able to supervise these kinds of more complex situations in which at a first distance from the desired floor the speed of the elevator car is reduced to a certain speed level and at a second distance (closer to the desired floor) the speed of the elevator car is reduced further to a lower speed level. For these situations there would be a need for a speed supervision system which is able to supervise that also a variable speed level curve can be followed by the elevator car so that it is able to achieve the multiple desired speed levels safely at the desired locations.

[0010] Hence, there is a need to develop further solutions in order to mitigate the described drawbacks.

[0011] Summary

[0012] An objective of the invention is to present a method, an elevator control unit, and an elevator system for elevator car speed monitoring which can improve at least partly the safety of an elevator solution.

[0013] The objectives of the invention are reached by a method, an elevator control unit, and an elevator system as defined by the respective independent claims. According to a first aspect, the invention relates to a method for elevator car speed monitoring, which elevator car speed monitoring comprises multiple target speed levels for the elevator car and corresponding target speed positions in an elevator hoistway for each target speed level. The method comprises determining maximum allowed elevator car speed at each position of the elevator hoistway or part of the elevator hoistway based at least in part on a specified deceleration rate of an elevator car, such as an elevator nominal deceleration rate, the multiple target speed levels and the corresponding target speed positions. The method further comprises monitoring or receiving information related to the current elevator car position and elevator car speed and monitoring that the elevator car speed is kept under the determined maximum allowed elevator car speed at current position of the elevator car in the elevator hoistway or part of the elevator hoistway.

[0014] In one embodiment of the invention the method further comprises determining the maximum allowed elevator car speed at each position of the elevator hoistway or a part of the elevator hoistway so that the elevator car is able to achieve next target speed level at next target speed position corresponding the target speed level at the specified deceleration rate of an elevator car, such as nominal deceleration rate of the elevator car, and / or the elevator system.

[0015] In one embodiment of the invention the elevator car speed is controlled so that the elevator car speed is kept under the defined maximum allowed speed value at each position of the elevator hoistway or part of the elevator hoistway.

[0016] In one embodiment of the invention the elevator car speed monitoring is carried out when approaching a target floor, e.g. the elevator car speed monitoring starting at a certain predefined distance from the target floor.

[0017] In one embodiment of the invention the elevator car speed monitoring is carried out on at least one terminal zone of the elevator hoistway or at a part of the elevator hoistway being within a certain predefined distance from the terminal zone of the elevator hoistway.

[0018] In one embodiment of the invention the method further comprises stopping the elevator car and / or slowing down the elevator car to nearest landing if the monitored speed of the elevator car is above the determined maximum allowed speed at current position of the elevator car or if the received information related to the speed of the elevator car indicates speed above the determined maximum allowed speed at current position of the elevator car.

[0019] In one embodiment of the invention a control means for carrying out the speed monitoring is an independent function block, such as an independent software module, of e.g. an elevator control unit.

[0020] In one embodiment of the invention a control means for carrying out the speed monitoring is an independent processing unit, e.g. a control unit separate from other elevator control units.

[0021] In one embodiment of the invention the control means for carrying out the speed monitoring comprises inputs relating to at least elevator car position and elevator car speed, the inputs being independent input sources from other control systems of the elevator, such as a normal stopping means of the elevator, or common input sources with other control systems of the elevator, such as the normal stopping means of the elevator.

[0022] In one embodiment of the invention the elevator car speed is monitored in essentially the whole length of the elevator hoistway or at certain part(s) of the elevator hoistway, e.g. in an area with a predefined distance from end buffers of the elevator hoistway.

[0023] In one embodiment of the invention the current elevator car position and / or elevator car speed is obtained from at least one of the following: a position sensor, a drive, an acceleration sensor, a magnetic sensor of door zone sensor unit.

[0024] In one embodiment of the invention the elevator car position is determined by a position sensing element arranged in connection with the elevator car and / or arranged in connection with the motor or traction sheave.

[0025] According to a second aspect, the invention relates to an elevator control unit for elevator car speed monitoring, which elevator car speed monitoring comprises multiple target speed levels for the elevator car and corresponding target speed positions in an elevator hoistway for each target speed level. The elevator control unit comprises at least one processor and at least one memory storing at least one portion of computer program code. The at least one processor is configured to cause the elevator control unit at least to perform determining maximum allowed elevator car speed at each position of the elevator hoistway or part of the elevator hoistway based at least in part on a specified deceleration rate of an elevator car, such as an elevator nominal deceleration rate, the multiple target speed levels and the corresponding target speed positions. The at least one processor is further configured to cause the elevator control unit at least to perform monitoring or receiving information related to the current elevator car position and elevator car speed, and monitoring that the elevator car speed is kept under the determined maximum allowed elevator car speed at current position of the elevator car in the elevator hoistway or part of the elevator hoistway.

[0026] In one embodiment of the invention the at least one processor is configured to cause the elevator control unit at least to implement a method according to any embodiment of the invention.

[0027] In one embodiment of the invention the elevator control unit comprises an independent function block, such as an independent software module, for carrying out the speed monitoring.

[0028] In one embodiment of the invention the control unit is an independent processing unit, e.g. separate unit from other elevator control units.

[0029] According to a third aspect, the invention relates to an elevator system for elevator car speed monitoring. The elevator system comprises at least one elevator shaft along which at least one elevator car is configured to travel between a plurality of floors, a means for determining speed of the at least one elevator car and a means for determining position of the at least one elevator car, and an elevator control unit according to any embodiment of the invention.

[0030] One advantage of the method, the elevator control unit, and the elevator system according to the invention is that the speed monitoring system of the present invention is able to monitor or supervise the speed of the elevator car also when the target speed curve for example for a desired stopping location, such as a floor, is a variable speed level curve, e.g. having multiple target speed levels (which may not be exceeded by the elevator car) with different distances from the desired stopping location, e.g. floor where the elevator car stops. For this reason, also more complex situations can be monitored with the solution of the invention and for example multiple speed level monitoring for safety related matters (e.g. the buffers are shortened), shaft requirements (e.g. lowering the air pressure at the terminal areas) or quality related matters (e.g. reducing the noise in certain areas of the shaft) can be achieved.

[0031] Based on at least the above-mentioned advantages, the method according to the invention improves at least partly the safety of the elevator system.

[0032] The exemplary embodiments of the invention presented in this patent application are not to be interpreted to pose limitations to the applicability of the appended claims. The verb "to comprise" is used in this patent application as an open limitation that does not exclude the existence of also un-recited features. The features recited in dependent claims are mutually freely combinable unless otherwise explicitly stated.

[0033] The expression "a number of” may herein refer to any positive integer starting from one (1 ). The expression "a plurality of” may refer to any positive integer starting from two (2), respectively.

[0034] The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objectives and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

[0035] Brief descriptions of the drawings

[0036] The embodiments of the invention are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings.

[0037] Figure 1 illustrates schematically an elevator system according to an example embodiment of the invention. Figure 2 illustrates schematically principles of a prior art elevator car speed monitoring solution.

[0038] Figure 3 illustrates schematically an example elevator car speed monitoring solution according to one example embodiment of the invention.

[0039] Figure 4 illustrates an example of an elevator car speed monitoring method with multiple target speed levels according to one example embodiment of the invention.

[0040] Figure 5 illustrates one example method according to one example embodiment of the invention.

[0041] Description of some embodiments

[0042] Figure 1 illustrates schematically an example elevator in which solution of the invention for monitoring the speed of the elevator car can be used. The elevator 100 according to an example embodiment may comprise an elevator car 1 10 arranged to be moved in an elevator shaft or hoistway 1 12. The moving of the elevator car 1 10 may be implemented by a hoisting rope or belt 1 13 in connection with a traction sheave 1 14 or the like. Furthermore, the elevator 100 comprises an elevator motor arranged to operate, such as rotate by the rotor thereof, the traction sheave 114 for moving the elevator car 1 10, if not essentially directly coupled to the hoisting rope 1 13. The traction sheave 1 14 may be connected, via a mechanical connection, directly or indirectly via a gear to a shaft of the motor. The elevator 100 may comprise a machine room or be machine roomless, such as have the motor in the elevator shaft or hoistway 1 12.

[0043] The elevator 100 may comprise at least one, or at least two, hoisting machinery brake(s) 1 16 configured for resisting or, preferably, preventing the movement of the motor, that is the rotor thereof, directly or via the traction sheave 114 or components thereof and / or therebetween. Furthermore, the elevator 100 may comprise a brake controller 125 configured to operate at least one of the at least one hoisting machinery brake 1 16. The brake controller 125 may further be in connection with other elements of the elevator 100, such as an elevator control unit and / or a safety system. The brake controller 125 may comprise an actuator (not shown) for operating the brake 1 16 or at least be in connection with such an actuating device.

[0044] There may additionally be, at least in some embodiments, a counterweight 1 18 arranged in connection with the elevator car 1 10 such as is known to a person skilled in the art of elevators. Still further, the elevator 100 may additionally comprise a guide rail 1 17 or rails 1 17 arranged into the elevator shaft or hoistway 1 12 for guiding the movement of the elevator car 1 10.

[0045] The elevator 100 of Fig. 1 can further comprise a converter unit. The converter unit may comprise, or substantially be, an inverter or a frequency converter for connecting to and controlling the operation of the motor, and a controller in connection with the converter unit, wherein the controller is configured to operate the converter unit to provide electrical power (signals), such as having variable voltage and variable frequency, to the windings of the motor. The controller may be a separate controller device or be comprised in the converter unit, for instance.

[0046] Still further, the converter unit may be arranged to be fed by an electrical power source, such as of the elevator 100, for example from an external electrical power grid or mains power supply, or another power source, for example, a battery system. Additionally, the electrical power source may intake electrical power from the converter unit.

[0047] There may be one or several devices arranged between the electrical power source and the converter unit, such as input filter(s), circuit breaker(s), and / or contactor(s) or relay(s), and / or a device for charging the energy storage element(s) of the converter unit.

[0048] The elevator 100 preferably comprises landings 119 or landing floors 1 19 and, for example, landing floor doors and / or openings, between which the elevator car 1 10 is arranged to be moved during the normal operation of the elevator 100, such as to move persons and / or items between said floors 1 19.

[0049] The elevator may comprise at least one a control unit 120 unit for controlling the operation of the elevator and / or the safety system of the elevator. The control unit 120 may be a separate device or may be comprised in the other components of the elevator such as in or as a part of the electrical drive. The control unit may also be implemented in a distributed manner so that, e.g., one portion of the conveyor control unit may be comprised in the electrical drive and another portion in the elevator car. The control unit may also be arranged in distributed manner at more than two locations or in more than two devices. In one embodiment of the invention the control unit is configured to control the power units supplying power to the conveyor system. The elevator control unit can also be configured to collect status information of an elevator car and fault information when an elevator fails.

[0050] The movement of the elevator car can be at least partly controlled by an elevator control unit. When the elevator car is configured to arrive to a desired landing, the speed of the elevator car is instructed to be decelerated so that the elevator car may be stopped at the landing. Deceleration is an operation of reducing the speed of the elevator car from normal operating speed to a lower speed and / or to a stop. Deceleration may also be referred to as slowdown.

[0051] The elevator car speed monitoring solution of the invention can be used for example with an elevator as described in connection with Figure 1 . The speed monitoring solution of the invention can monitor and supervise the speed of the elevator car. The elevator car speed monitoring can comprise multiple target speed levels for the elevator car and corresponding target speed positions in an elevator hoistway for each target speed level. The solution comprises determining maximum allowed elevator car speed at each position of the elevator hoistway or part of the elevator hoistway based at least in part on a specified elevator deceleration rate, such as an elevator nominal deceleration rate, multiple target speed levels and target speed positions for each target speed level. In the solution of the invention the current elevator car position and elevator car speed is monitored, or information related to the current elevator car position and elevator car speed is received, and it is monitored that the elevator car speed is kept under the determined maximum allowed elevator car speed at current position of the elevator car in the elevator hoistway or part of the elevator hoistway. Determination of the maximum allowed speed can be done so the maximum allowed speed at each position of the elevator hoistway or a part of the elevator hoistway is the speed from which the elevator car is able to achieve next target speed level at next target speed position with a specified deceleration rate of the elevator car, e.g. with nominal deceleration rate of the elevator car and / or the elevator system.

[0052] The elevator car speed is controlled so that the elevator car speed is kept under the defined maximum allowed speed value at each position of the elevator hoistway or part of the elevator hoistway. If the monitored speed of the elevator car is above the determined maximum allowed speed at current position of the elevator car or if the received information related to the speed of the elevator car indicates speed above the determined maximum allowed speed at current position of the elevator car, the elevator car can be stopped and / or slowed down to a nearest landing.

[0053] The elevator car speed can be monitored with the monitoring solution of the invention in essentially the whole length of the elevator hoistway or at certain part(s) of the elevator hoistway, e.g. in an area with a predefined distance from end buffers of the elevator hoistway.

[0054] In one embodiment of the invention the elevator car speed monitoring according to the solution of the invention is carried out when approaching a target floor, e.g. the elevator car speed monitoring starting at a certain predefined distance from the target floor. In one embodiment of the invention the elevator car speed monitoring is carried out according to the solution of the invention on at least one terminal zone of the elevator hoistway or at a part of the elevator hoistway being within a certain predefined distance from the terminal zone of the elevator hoistway. In one embodiment of the invention elevator car speed monitoring is not carried out for every target floor but only on the at least one terminal zone of the elevator hoistway or at a part of the elevator hoistway being within a certain predefined distance from the terminal zone of the elevator hoistway. In these embodiments, the steps of determining maximum allowed elevator car speed at different positions of the elevator hoistway and monitoring that the elevator car speed is kept under the determined maximum allowed elevator car speed at current position of the elevator car are carried out in those areas where elevator car speed monitoring is carried out.

[0055] The control means for carrying out the speed monitoring can comprise inputs relating to at least elevator car position and elevator car speed. The inputs can be independent input sources from other control systems of the elevator, such as a normal stopping means of the elevator, or common input sources with other control systems of the elevator, such as the normal stopping means of the elevator.

[0056] In one embodiment of the invention the speed monitoring is a software based multilevel speed supervision, e.g. integrated to elevator drive software. In one embodiment of the invention the drive software and safety device software can be separate software components from each other. In one embodiment of the invention the speed monitoring unit or element can be designed as an independent function block e.g. an independent software module. It can be for example an independent software module an elevator control unit.

[0057] In one embodiment of the invention the speed monitoring unit can be an entirely independent processing unit with common or independent input sources from other elevator units, e.g. the normal stopping means of the elevator. In one embodiment of the invention the speed monitoring is a separate (e.g. physically separate) safety device which is supervising the safety of terminals, e.g. normal terminal slowdown and stopping and / or emergency terminal speed limiting. The advantage of separate device (e.g. a hardware module separate from other elevator modules) is that it is easier to change the software of the other elevator components, e.g. drive, as the changes would not cause PESSRAL (SIL-rated) software changes and the heavy process involved to PESSRAL (SIL-rated) software approvals.

[0058] Figure 2 illustrates schematically a prior art elevator car speed monitoring solution. On the x-axis of the Figure 2 is distance from a specified location, e.g. an end of an elevator shaft, and on the y-axis is speed. The line 202 of the figure presents the maximum allowed speed of the elevator car at a certain location of the elevator shaft. This line 202 can be considered to present the maximum allowed speed curve of the elevator car. It is the speed from which the elevator car can be taken to target location, e.g. a floor, given the specified deceleration rate of the elevator car, e.g. nominal deceleration of the elevator car. Line 204 of the figure presents the elevator car speed which is first constant at certain speed level when the elevator is moving in the elevator hoistway and then when the elevator car is approaching the floor where it is supposed to stop, the elevator car is decelerated so that its speed is kept under the determined maximum allowed speed. If the elevator car speed intercepts the maximum allowed speed 202, an immediate slow down to nearest landing can be triggered. This example presents a prior art solution in which there is only one speed level requirement for the elevator and that can be monitored with the prior art solutions. If further maximum allowed speed levels are introduced, these can’t be monitored with the maximum allowed speed curve of the prior art solutions.

[0059] Figure 3 illustrates schematically an example elevator car speed monitoring solution according to one embodiment of the invention. The elevator system can comprise normal stopping means, normal terminal slowdown and stopping, and speed supervision module to ensure that the elevator is operating safely. The normal stopping means is used to stop the elevator car when desired and e.g. at certain floor. Normal terminal slowdown and stopping is used to supervise that the normal stopping means operate correctly and will stop the elevator car safely to the terminal floors. Normal terminal slowdown and stopping can’t be used to detect a variable maximum speed allowed by the elevator car and thus, in addition or instead of normal terminal slowdown and stopping, the solution of the invention, i.e. speed monitoring or supervision, is used which is able to monitor multiple speed levels of the elevator car. If some of these systems indicate abnormal situations, e.g. malfunctions or overspeed of the elevator car, safety output control of the elevator will indicate about this situation and necessary steps can be taken, e.g. the elevator car can be stopped immediately or decelerated to the next floor.

[0060] The monitoring of the speed of the elevator car with the speed monitoring solution can be performed in the whole elevator hoistway or at certain parts of the elevator hoistway, e.g. at certain distance from the end of the elevator hoistway.

[0061] The embodiments of the invention may be implemented in an elevator system as described. The elevator system can comprise an elevator car, a hoisting machine, an elevator control unit, and at least one of the following: position sensor, drive, acceleration sensor, door zone sensor unit. The hoisting machine is configured to drive the elevator car in an elevator shaft between a plurality of landings. The speed of the elevator car may be obtained directly. Alternatively or in addition, the speed of the elevator car may also be obtained indirectly by obtaining, for example, the position of the elevator car as a value for indicating the speed of the elevator car. Alternatively or in addition, the speed of the elevator car may be determined and thus also speed monitoring of the elevator car may be carried out based on a combination of a plurality of the obtained values for indicating the speed of the elevator car.

[0062] In one embodiment elevator car speed and position can be determined by at least one of the following: a drive, a position sensor, an acceleration sensor, a magnetic sensor, a magnetic sensor of door zone sensor unit. The position can be obtained as a function of time. If a position sensor is used, it can be fixed to the elevator car.

[0063] The speed of the elevator car may be determined on a basis of acceleration of the elevator car obtained by means of at least one acceleration sensor. The at least one acceleration sensor may be arranged in the door zone sensor unit, for example.

[0064] The speed of the elevator car may be determined in a drive by obtaining a signal from at least one encoder mounted in a hoisting motor and communicatively coupled to the drive.

[0065] The means for determining position and / or speed of the elevator car which can be used in the solution of the invention may comprise an encoder. The encoder may be arranged to the elevator car, in association with elevator car pulley(s) or at least one guide roller, i.e. guide shoe, interposed between the elevator car and a guide rail to provide continuous position information of the elevator car. In one embodiment the encoder may be in association with the governor pulley of the mechanical overspeed governor to provide continuous position information of the elevator car. In one embodiment the encoder may be arranged to the counterweight in association with counterweight pulleys or at least one second guide roller interposed between the counterweight and the second guide rail to provide continuous position information of the counterweight.

[0066] In some embodiments, like in the example of Figure 3, elevator car speed and position related information can be determined at least in part based on a position sensing element 308 arranged in connection with the elevator car 306 and / or a position sensing element 302 arranged in connection with the motor or traction sheave 304.

[0067] Figure 4 illustrates an example of an elevator car monitoring method with multiple target speed levels according to one example embodiment of the invention. Figure 4 illustrates, in the same way as Figure 2, on the x-axis distance from a specified location, e.g. from an end of an elevator shaft, and on the y-axis speed of the elevator car. The line 402 of the figure presents the maximum allowed speed of the elevator car at each location of the elevator shaft as would be monitored by a single speed level supervision solution like normal terminal slowdown and stopping (as in the Figure 2). In this example multiple speed levels for the elevator are used at different parts of the elevator hoistway and single speed level solution 402 can’t monitor these multiple speed levels. Line 404 of the figure presents the elevator car speed which is first constant at certain speed level (a first speed level) and then the elevator is decelerated to a lower speed (a second speed level). This second speed level is used for a certain amount of travel and then the elevator car is further decelerated to a lower speed (a third speed level) which is used before the elevator car is decelerated to a stop, e.g. at the desired floor.

[0068] The line 406 of Figure 4 presents the maximum allowable elevator car speed determined with one example embodiment of the speed monitoring solution of the invention. In the maximum allowed speed curve 406 there are speed target points or positions 408, 410 and 412 in which maximum allowed speed of the elevator car is specified for that location. In these locations the elevator car may not exceed the determined values. The maximum allowed speed curve 406 of this example is specified so that the elevator car is able to achieve always the next specified target speed as specified, i.e. the maximum allowed speed at each point or position of the elevator hoistway is the speed from which the elevator car can be taken to next target speed point or position given the nominal deceleration or desired or specified deceleration rate of the elevator car. This principle can also be utilized for other embodiments and examples of the invention.

[0069] In this example of Figure 4 the elevator car travels at first speed as indicated by line 404 and then when approaching target speed point or position 408, the speed of the elevator car is reduced to the maximum allowed speed at that location (i.e. the second target speed). Then when the elevator car travels further, it uses second target speed which is same as the maximum allowed speed at target speed point or position 408. When approaching point or position 410, the speed of the elevator car is reduced to the maximum allowed elevator car speed at that location (i.e. the third target speed) and the elevator uses the third speed which is same as the maximum allowed speed at target speed point or position 410. When approaching the destination floor 412, the speed of the elevator car is decelerated towards zero so that the elevator is stopped at the desired location. If the speed of the elevator car is above the maximum allowed and determined speed, the elevator car should be decelerated to a safe speed level and / or decelerated to next possible landing or stopped.

[0070] As can be seen from figure 4, the elevator car can use previous maximum allowed speed (of a target speed point or position) as it travels further (and not accelerate) but the monitoring solution can determine the maximum allowed speed so that the next target speed can be reached, i.e. the maximum allowed speed can be raised after the speed target point or position so that elevator car can achieve the maximum allowed speed at the next speed target point or position.

[0071] In the above example three different target speed levels are used but the solution of the invention can be used with any number of target speed levels. Thus, determination of the maximum allowed speed can be done so the maximum allowed speed at each position of the elevator hoistway or a part of the elevator hoistway is the speed from which the elevator car is able to achieve next target speed level at next target speed position with a specified deceleration rate of the elevator car, e.g. with nominal deceleration rate of the elevator car and / or the elevator system. And with the solution of the invention the elevator car speed can be monitored so that it does not exceed the determined maximum allowed speed at each position of the elevator hoistway in which the monitoring is carried out.

[0072] Figure 5 illustrates one example method according to one example embodiment of the invention. The example method comprises determining maximum allowed elevator car speed at each position of the elevator hoistway or part of the elevator hoistway based at least in part on a specified deceleration rate of an elevator car, the multiple target speed levels, and the corresponding target speed positions, monitoring or receiving information related to the current elevator car position and elevator car speed, and monitoring that the elevator car speed is kept under the determined maximum allowed elevator car speed at current position of the elevator car in the elevator hoistway or part of the elevator hoistway.

[0073] An elevator unit, a control unit or a controller of the system (e.g. an elevator control unit, a control unit of a safety system, a speed monitoring unit) may comprise one or more processors, one or more memories being volatile or nonvolatile for storing portions of computer program code and any data values and possibly one or more user interface units. The mentioned elements may be communicatively coupled to each other with e.g. an internal bus. The one or more processors of the processing unit may be any suitable processor for processing information and control the operation of the unit, among other tasks. The memory unit may store portions of computer program code and any other data, and the processing unit may cause the unit to operate as described above by executing at least some portions of the computer program code stored in the memory unit. Furthermore, the one or more memories of the memory unit may be volatile or nonvolatile. Moreover, the one or more memories are not limited to a certain type of memory only, but any memory type suitable for storing the described pieces of information may be applied in the context of the invention. The communication unit may be based on at least one known communication technologies, either wired or wireless, in order to exchange pieces of information as described earlier. The communication unit can provide an interface for communication with any external unit, such as the brake control unit of the drive unit, positioning system, database and / or any external systems. The unit can also comprise a user interface comprising I / O devices, such as buttons, keyboard, touch screen, microphone, loudspeaker, display and so on, for receiving input and out-putting information.

[0074] The verb "meet" in context of a levelling speed limit is used in this patent application to mean that a predefined condition is fulfilled. For example, the predefined condition may be that the levelling speed limit value is reached and / or exceeded. The specific examples provided in the description given above should not be construed as limiting the applicability and / or the interpretation of the appended claims. Lists and groups of examples provided in the description given above are not exhaustive unless otherwise explicitly stated.

Claims

Claims1 . A method for elevator car speed monitoring, which elevator car speed monitoring comprises multiple target speed levels for the elevator car (1 10) and corresponding target speed positions in an elevator hoistway (1 12) for each target speed level, wherein the method comprises: determining maximum allowed elevator car speed at each position of the elevator hoistway or part of the elevator hoistway based at least in part on a specified deceleration rate of an elevator car (1 10), the multiple target speed levels, and the corresponding target speed positions (408, 410, 412), monitoring or receiving information related to the current elevator car position and elevator car speed, and monitoring that the elevator car speed is kept under the determined maximum allowed elevator car speed at current position of the elevator car (1 10) in the elevator hoistway (1 12) or part of the elevator hoistway (1 12).

2. A method according to claim 1 , wherein the method further comprises determining the maximum allowed elevator car speed at each position of the elevator hoistway (1 12) or a part of the elevator hoistway (1 12) so that the elevator car is able to achieve next target speed level at next target speed position corresponding the target speed level at the specified deceleration rate of the elevator car (1 10) and / or the elevator system.

3. A method according to claim 1 or 2, wherein the elevator car speed is controlled so that the elevator car speed is kept under the defined maximum allowed speed value at each position of the elevator hoistway (112) or part of the elevator hoistway (1 12).

4. A method according to any previous claim, wherein the elevator car speed monitoring is carried out when approaching a target floor, e.g. the elevator car speed monitoring starting at a certain predefined distance from the target floor.

5. A method according to any previous claim, wherein the elevator car speed monitoring is carried out on at least one terminal zone of the elevator hoistway or at a part of the elevator hoistway being within a certain predefined distance from the terminal zone of the elevator hoistway.

6. A method according to any previous claim, wherein the method further comprises stopping the elevator car (1 10) and / or slowing down the elevator car (1 10) to nearest landing if the monitored speed of the elevator car (1 10) is above the determined maximum allowed speed at current position of the elevator car (1 10) or if the received information related to the speed of the elevator car (1 10) indicates speed above the determined maximum allowed speed at current position of the elevator car.

7. A method according to any previous claim, wherein a control means for carrying out the speed monitoring is an independent function block, such as an independent software module, of e.g. an elevator control unit.

8. A method according to any previous claim, wherein a control means for carrying out the speed monitoring is an independent processing unit, e.g. separate from other elevator control units.

9. A method according to any previous claim, wherein the control means for carrying out the speed monitoring comprises inputs relating to at least elevator car position and elevator car speed, the inputs being independent input sources from other control systems of the elevator, such as a normal stopping means of the elevator, or common input sources with other control systems of the elevator, such as the normal stopping means of the elevator.10 A method according to any previous claim, wherein the elevator car speed is monitored in essentially the whole length of the elevator hoistway (1 12) or at certain part(s) of the elevator hoistway (1 12), e.g. in an area with a predefined distance from end buffers of the elevator hoistway.1 1. A method according to any previous claim, wherein the current elevator car position and / or elevator car speed is obtained from at least one of the following: a position sensor, a drive, an acceleration sensor, a magnetic sensor of door zone sensor unit.

12. A method according to any previous claim, wherein the elevator car position is determined by a position sensing element arranged in connection with the elevator car and / or arranged in connection with the motor or traction sheave.

13. An elevator control unit for elevator car speed monitoring, which elevator car speed monitoring comprises multiple target speed levels for the elevator car (1 10) and corresponding target speed positions in an elevator hoistway for each target speed level, wherein the elevator control unit comprises:- at least one processor, and- at least one memory storing at least one portion of computer program code, wherein the at least one processor being configured to cause the elevator control unit at least to perform: determining maximum allowed elevator car speed at each position of the elevator hoistway (1 12) or part of the elevator hoistway (1 12) based at least in part on a specified deceleration rate of an elevator car (1 10), the multiple target speed levels, and the corresponding target speed positions (408, 410, 412), monitoring or receiving information related to the current elevator car position and elevator car speed, and monitoring that the elevator car speed is kept under the determined maximum allowed elevator car speed at current position of the elevator car (1 10) in the elevator hoistway (1 12) or part of the elevator hoistway (1 12).

14. An elevator control unit according to claim 13, wherein the at least one processor is configured to cause the elevator control unit at least to implement a method according to any claim 2 - 12.

15. An elevator control unit according to claim 13 or claim 14, wherein the elevator control unit comprises an independent function block, such as an independent software module, for carrying out the speed monitoring.

16. An elevator control unit according to any claim 13 - 15, wherein the control unit is an independent processing unit, e.g. separate unit from other elevator control units.

17. An elevator system for elevator car speed monitoring, wherein the elevator system comprises:at least one elevator shaft (1 12) along which at least one elevator car (1 10) is configured to travel between a plurality of floors, means for determining speed of the at least one elevator car and means for determining position of the at least one elevator car, and an elevator control unit according to any claim 13 - 16.

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