METHOD FOR DIAGNOSIS AND/OR MAINTENANCE OF A BRAKE OF A TRANSPORTATION SYSTEM, SOFTWARE PROGRAM, AND BRAKE APPARATUS

Abstract

A method for diagnosis and/or maintenance of a brake configured to apply braking force to a hoisting machine of a transportation system includes controlling the brake to start a brake control action, e.g. an opening and/or a closing action of the brake; monitoring the brake to detect a response of the brake to the brake control action, wherein in case of the response the response is detected in a predefined manner; measuring a brake operating time interval from a first point in time of starting of the brake control action until a second point in time of monitoring the brake to detect the response; and, if either the response has not been detected until the brake operating time interval reaches and/or exceeds a predetermined threshold or the response has been detected after the brake operating time interval reaches and/or exceeds the predetermined threshold, establishing an information indicating that an operation of the brake should be modified. A computer program realizing the method and a brake apparatus configured to execute the method are also disclosed.

Claims

1. A method for diagnosis and/or maintenance of a brake configured to apply a braking force to a hoisting machine of a transportation system, wherein said method comprises: controlling the brake to start a brake control action; monitoring the brake to detect a response of the brake to the brake control action, wherein in case of the response the response is detected in a predefined manner; measuring a brake operating time interval from a first point in time of starting of the brake control action until a second point in time of monitoring the brake to detect the response; and if either the response has not been detected until the brake operating time interval reaches and/or exceeds a predetermined threshold or the response has been detected after the brake operating time interval reaches and/or exceeds the predetermined threshold, establishing an information indicating that an operation of the brake should be modified, wherein the information indicating that an operation of the brake should be modified is established by comprising a corrective action which may be one or more of the following: controlling the brake to lower an operating current of an electromagnet of the brake to reduce the brake operating time interval for detecting the response; and if an increase of the brake operating time interval for detecting the response or derivative of the increase of the brake operating time interval reaches and/or exceeds another threshold, the transportation system is taken out of service because of safety reasons.

2. The method of claim 1, wherein it is provided a brake control unit for controlling the brake, a sensor device for monitoring the brake to detect the response of the brake, and a timer device for measuring the brake operating time interval, wherein the timer device and/or the sensor device are/is provided as a device separate from the brake control unit or integrated into this unit.

3. The method of claim 1, wherein the information is established to further indicate a certain kind and/or severity of failure or problem of the brake or the transportation system such that a request for modifying the operation of the brake or the transportation system is signaled to the brake control unit, the transportation system control unit or another unit outside of the transportation system.

4. The method of claim 1, wherein the information indicating that an operation of the brake should be modified is established by comprising a corrective action which may be the following: requesting maintenance of the brake from a service center via a remote communication link.

5. The method of claim 1, wherein the transportation system is kept in continuous operation while a maintenance visit is pending by controlling the brake to lower the operating current of the electromagnet of the brake while requesting maintenance of the brake from the service center.

6. The method of claim 1, wherein the operating current of the electromagnet of the brake is controlled such that the brake operating time interval for detecting the response stays below or at the predetermined threshold and the controlled operating current of the electromagnet of the brake is monitored to determine a wear of a friction lining of a rope or belt of the transportation system and/or a misalignment of the friction lining.

7. The method of claim 5, wherein the brake operating time interval for detecting the response is measured by measuring a brake pick time and/or a brake drop time, wherein the brake pick time is less than 500 ms and/or the brake drop time ranges between 50 and 100 ms.

8. The method of claim 7, wherein a brake magnet iron saturation and magnet force are set to meet locking and/or picking force requirements by measuring the brake pick time and/or the brake drop time.

9. The method of claim 7, wherein the brake pick time is measured by one of the following: measuring from a point in time of feeding voltage to the electromagnet of the brake until a point in time when a proximity switch changes its state; measuring from the point in time of feeding voltage to the electromagnet of the brake until a point in time when a limit switch changes its state; and measuring from the point in time of feeding voltage to the electromagnet of the brake until a point in time when a peak of the operating current of the electromagnet of the brake can be detected.

10. The method of claim 7, wherein the brake drop time is measured by one of the following: measuring from a point in time of cutting off a feeding voltage to the electromagnet of the brake until a point in time when a proximity switch changes it state; measuring from the point in time of cutting off the feeding voltage to the electromagnet of the brake until a point in time when a limit switch changes it state; and measuring from the point in time of cutting off the feeding voltage to the electromagnet of the brake until a point in time when a peak of the operating current or an operating voltage of the electromagnet of the brake can be detected.

11. The method of claim 9, wherein the peak of the operating current of the electromagnet of the brake is verified when a brake pad of the brake contacts a surface whereon the braking force is to be applied, and the peaks verified at different points in time are used to determine a wear and/or misalignment of the brake pad.

12. The method of claim 1, wherein, after the information is established, it is transferred or made accessible to a remote maintenance center or a mobile service unit or the local transportation system control unit depending on a content of the information.

13. The method of claim 1, wherein the transportation system is selected from one of an elevator, an escalator, a moving walkway, a cablecar, a railway locomotive, a railcar, a roller coaster, a conveyor, a crane, a positioning unit, and combined systems of a plurality of single units of the same.

14. A software program realizing the method according to claim 1 when executed on a computer, wherein the computer is a distributed computing system, part of the distributed computing system being located in a cloud computing system.

15. A brake apparatus for application of a braking force to a hoisting machine of a transportation system, wherein the brake apparatus comprises: a brake control unit for controlling the brake; a sensor device for monitoring the brake to detect the response of the brake; and a timer device for measuring the brake operating time interval, wherein the timer device and/or the sensor device are/is provided as a device separate from the brake control unit or integrated into the brake control unit, and is configured to execute the method according to claim 1.

16. The method of claim 2, wherein the information is established to further indicate a certain kind and/or severity of failure or problem of the brake or the transportation system such that a request for modifying the operation of the brake or the transportation system is signaled to the brake control unit, the transportation system control unit or another unit outside of the transportation system such as a maintenance unit.

17. The method of claim 2, wherein the information indicating that an operation of the brake should be modified is established by comprising a corrective action which may be the following: requesting maintenance of the brake from a service center via a remote communication link.

18. The method of claim 3, wherein the information indicating that an operation of the brake should be modified is established by comprising a corrective action which may be the following: requesting maintenance of the brake from a service center via a remote communication link.

19. The method of claim 2, wherein the transportation system is kept in continuous operation while a maintenance visit is pending by controlling the brake to lower the operating current of the electromagnet of the brake while requesting maintenance of the brake from the service center.

20. The method of claim 3, wherein the transportation system is kept in continuous operation while a maintenance visit is pending by controlling the brake to lower the operating current of the electromagnet of the brake while requesting maintenance of the brake from the service center.

Description

[0060] Other aspects, features and advantages of the invention will become apparent by the below description of exemplary embodiments alone or in cooperation with the appended drawings.

[0061] FIG. 1 is a diagram showing over time a family of curves of magnetic forces of a brake and a family of corresponding curves in position of that brake according to exemplary embodiments of the invention,

[0062] FIG. 2 is a diagram showing curves of magnetic forces of a brake as a function of airgaps for different currents flowing in a coil of an electromagnet of the brake according to exemplary embodiments of the invention,

[0063] FIGS. 3, 4 is a schematic diagram showing magnetic flux densities of a brake with a current of 1 A (FIG. 3) and a current of 8 A (FIG. 4) flowing in a coil of an electromagnet of the brake according to two other exemplary embodiments of the invention, and

[0064] FIG. 5 is a cross-sectional view of a brake and the air gap between an electromagnet of the brake and an armature of the brake whereon braking force is to be applied according to another exemplary embodiment of the invention.

[0065] Now, exemplary embodiments of the invention will be described in further detail.

[0066] FIG. 1 shows the results of a transient FEM analysis on the operation of a brake according to the invention. It is shown over a time scale of 4 seconds a family of curves of magnetic forces from zero to 175 kN of a brake and a family of corresponding curves in position between zero and approximately 600 m of that brake when applying ten voltages between 80 and 230 Volt. The time scale is represented by x, the position is indicated by y1 on the left side of the diagram, and the magnetic force is indicated by y2 on the right side of the diagram.

[0067] A family of ten curves 1 each representing a magnetic force over time is shown where the upper curve with a peak at 1.5 seconds and 175 kN is excited by applying a transient voltage of 230 V. The lower curve of the family of curves 1 revealing at 2 seconds a peak at 72.5 kN is excited by applying a transient voltage of 80 V. The eight consecutive curves between the lower and upper curves are excited with a transient voltage of 96.7 V, 113.3 V, 130 V, 146.7 V, 163.3 V, 180 V, 196.7V, and 213.3 V, respectively. Each voltage is applied as a DC voltage to a coil of an electromagnet of a brake according to the invention starting at zero seconds (see reference sign 5) until 1.5 seconds indicated by the dot dashed line 6. Alternatively to a DC voltage an alternating voltage or a combination of a DC and an alternating voltage can be applied to increase the magnetic force and the magnetic energy of the braking system.

[0068] A compression spring is comprised by the brake such that, when the magnetic force reaches a level of 40 kN, a brake armature of the brake moves away from a surface of the brake whereon braking force is to be applied. Consequently, there is a family of curves 2 shown in FIG. 1 each of which indicating an opening of the brake by moving the brake armature away from the surface of the brake whereon braking force is to be applied within a fraction of a second by changing its position by approximately 600 m. The opening of the brake occurs depending on the transient voltage applied to the coil in a time interval 3 between approximately 0.4 and 1.3 seconds. As the driving voltage is lowered, the pick time of the brake is lengthened from ca. 0.4 seconds at 230 V to ca. 1.3 seconds at 80 V of voltage driving the coil of the electromagnet of the brake. As the pick time means the time from applying the DC voltage signal to the coil of brake electromagnet, such that coil current starts to gradually increase due to high inductance of the coil, to the time when brake has opens, such that the brake armature has moved so much that opening can be detected with opening detection means, the pick time tends to become longer when the applied voltage is smalleras shown in the time interval 3 of FIG. 1.

[0069] In the time interval between 1.5 and 2 seconds, the DC voltage for all curves of the family of curves 1 is set equal to 113.3 V (see dot dashed lines 6 and 7) leading to an increase for the three lower curves and a decrease in magnetic force for the other curves.

[0070] At 2 seconds as indicated by the dot dashed line 7, a counter-voltage is applied to the coil in the electromagnetic operation of the brake to decrease the magnetic force in the braking system as fast as possible. The drop time means the time from interrupting the voltage signal of brake coil to the time that the coil current has gradually decreased due to the inductance of the coil so much that the brake armature has moved back to closing position such that this movement can be detected. The dropping of the brake, i.e. closing of the brake, occurs depending on the transient voltage applied to the coil in the time interval 4 between approximately 2.2 and 3.3 seconds. As the driving voltage is lowered, the drop time of the brake is shortened from ca. 3.3 seconds at 230 V in the time interval between zero and 1.5 seconds to ca. 2.2 seconds at 80 V of voltage initially driving the coil of the electromagnet of the brake. Therefore, with decreasing voltage, the resultant magnetic force, and as a result thereof the stored magnetic energy of the braking system is also decreased, allowing for faster closing operation of the brake, as the counter-voltage of the electromagnetic operation is sufficient for diminishing the magnetic energy of the braking system low enough to let the compression spring release the brake to apply the braking force onto the surface whereon braking force is to be applied.

[0071] By determining the pick time and/or the drop time, it is possible to adjust the driving voltage to meet the required pick times and/or drop times from FIG. 1 without the transportation system having to go out of service for maintenance.

[0072] The diagram of FIG. 2 shows curves of static magnetic forces of a brake as a function of airgaps for different currents flowing in a coil of an electromagnet of the brake according to the invention. The air gap ranges between zero and 1.21 mm as indicated by the scale x. The magnetic force ranges between 15 and 175 kN depending upon which of the ten curves is monitored. The lower curve represents a brake comprising a coil through which a current of 1 A is flowing. The upper curve represents a coil which is driven with a current of 8 A. the curves between the lower and upper curves indicate coils whereto currents of 2 A, 3 A, 3.3 A, 4 A, 5 A, 5.6 A, 6 A, and 7 A, respectively, are applied. These currents are DC currents. However, alternatively to a DC current, an alternating current or a combination of a DC and an alternating current can be applied to increase the magnetic force and the magnetic energy of the braking system. While at 8 A of current the increase in magnetic force is almost linear with decreasing air gap (from left to right in x), there is a steady increase of the derivative in force when the air gap is decreased at a current of 1 A.

[0073] The inductance is inversely proportional to the air gap or air gap length such that, when the air gap lengthens, inductance diminishes. When the air gap increases, for example because of wearing of a brake pad, the magnetic force decreases and the thrust force of the compression spring relative to the magnetic force tends to increase. When the air gap widens, a higher brake current is needed to open the brake. Drop time includes also the travel time of the brake armature from open to close which increases when the air gap is widened. Additionally, if the brake current is high then the brake iron of the magnet core electromagnet is highly saturated. This also increases the drop time. It takes time before the brake current has dimished so much that the brake armature starts to move. The travel time is short, but the hold time before the brake current has diminished and the brake armature starts to move is the dominating time for the drop time. On the other hand, when the air gap between the brake armature and the magnet core of the electromagnet of the brake increases, more brake current is needed to pick the brake.

[0074] Each of FIG. 3 and FIG. 4 show a schematic diagram of the same brake B in cross sectional view X and Y with magnetic flux densities of the brake with a current of 1 A and 8 A, respectively, flowing in a coil of an electromagnet of the brake (see reference signs 30 in FIGS. 3 and 40 in FIG. 4). Comparing both figures, at the corners the distributions of magnetic flux become more inhomogeneous with increasing current. There are three flux regimes e.g. in area 31 in FIG. 3 and in the corresponding area 41, there are four flux regimes in FIG. 4. In particular, the current of 8 A results in a highly saturated material in FIG. 4 indicated by the region 42. Also, inductance is not linear, but the brake coil current is so high that it leads to saturation of the iron around the brake coil. This saturation tends to make the brake slower (see increasing pick time and drop time in FIG. 1 with increasing voltage leading at given resistance to an increasing current in the coil). This means that extra thrust force of the compression spring has been needed to meet the pick and drop time requirements.

[0075] However, by controlling the operating current of the electromagnet of the brake, i.e. the driving current of the coil, such that the brake operating time interval stays below or at the predetermined threshold, the pick time and/or drop time can be controlled with the least possible current avoiding a saturation as shown in FIG. 4.

[0076] In FIG. 5, a cross-sectional view of a brake B and an air gap 57 is shown between an electromagnet of the brake B and a brake armature 52 of the brake B. The electromagnet comprises a magnet core 51 and a coil 53. The cross-sectional view of the brake B is shown in the X-Y plane. A spring 54 is arranged between the armature 52 and the magnet core 51 which is compressed as long as a current is flowing through the coil 53 to generate an attractive force between the electromagnet and the armature 52 which is larger than the thrust force of the spring 54 to keep the brake B open. Instead of a single spring 43, several springs may be used. If the attractive force between the armature 52 and the electromagnet diminishes by reducing the current through the coil 53 and becomes smaller than the thrust force of the spring 54, the brake B drops. Therefore, in case of a power outage, the brake B is dropped automatically by the spring 54 spreading the armature 52 and the magnet core 51 from each other. Between the spring 54 and the magnet core 51, there is arranged a spacer 55, also called LM. The height 56 of the spacer 55 is selected to adjust a value of the air gap 57. The value of the air gap 57 is thus determined by the shape and dimensions of the magnet core 51, a height of the spring 54 and the height 56 of the spacer 55. The bigger the dimension of the air gap 57 becomes, the smaller the thrust force of the compression spring 54 and the magnetic force/brake torque of the electromagnet of the brake B must be.

[0077] The invention provides a method for allowing a bigger brake torque and spring force window or range from current brakes, still ensuring the required brake reaction times for UCMP and ETSL braking. It is therefore not necessary anymore that a given brake control module is providing one preset current value only which must provide fast enough reaction times with full spring force. The method according to the invention allows to control and/or reduce and/or avoid excessive brake torque which has not been addressed with conventional rope elevators with conventional single wrap roping where rope slip has limited maximum deceleration. In case of an over saturation of the magnet iron due to an excessive current (force) compared to the spring force that the magnet force must overcome, a counter voltage peak can reduce the brake magnet force to a state in which a set spring force can create initial air gap between magnet and armature. This way, the initial air gap will be created by the counter voltage such that the applied spring force reaction time of the brake will not exceed reaction time limits. Friction lining wear and misalignment detection in the prior art is based on preventive maintenance visits by service personnel.

[0078] By adjusting the brakes according to method described above, it is possible to use a friction lining which has a bigger fluctuation in the coefficient of friction than the fluctuation able to be used previously.

[0079] A technical feature or several technical features which has/have been disclosed with respect to a single or several embodiments discussed herein before, e.g. the embodiment of condition based maintenance with respect to an elevator, may be present also in another embodiment, e. g. with respect to an escalator or crane, except it is/they are specified not to be present or it is impossible for it/them to be present for technical reasons.