Method of moving load with a crane and system for detecting abnormal situation of load

Abstract

A method for moving a load (200) using a crane, the method comprising: moving the load using at least two ropes (210, 215); receiving sensor data from two measuring units (230, 235) measuring acceleration, the first measuring unit (230) being located at a first location corresponding to a first end of the load and the second measuring unit (235) being located at a second location corresponding to a second end of the load, which is opposite to the first end of the load, detecting a first acceleration value based on the data from the first sensor and a second acceleration value based on the data from the second sensor, comparing the first and second acceleration values with each other, and if the difference between the first and second acceleration values is found to be greater than a threshold value, the movement of the load is stopped.

Description

[0001] METHOD OF MOVING LOAD WITH A CRANE AND SYSTEM FOR DETECTING ABNORMAL SITUATION OF LOAD

[0002] TECHNICAL FIELD

[0003] The application relates to monitoring crane operation and loads moved by cranes.

[0004] BACKGROUND

[0005] Cranes, such as container cranes, can be found in many different environments, such as ports. A crane may be capable of lifting a load, such as a container, using two or more ropes. For example, the crane may attach to the container using a container spreader. Efficient and smooth handling of loads is desirable in environments where large numbers of loads are handled, such as ports. If, for example, containers cannot be loaded and unloaded smoothly in a port area, port operations are slowed down, resulting in significant economic losses. For this reason, it is desirable to keep crane operations predictable, for example by preventing damage that could require repairs and thus slow down unloading and loading.

[0006] BRIEF DESCRIPTION

[0007] According one aspect is to provide a method to move the load using a crane, which comprises: moving the load using at least two ropes, receiving sensor data from two acceleration measuring units, the first measuring unit being located at a first position corresponding to the first end of the load and the second measuring unit being located at a second position corresponding to the second end of the load, which is opposite to the first end of the load, detecting a first acceleration value based on the data from the first sensor and a second acceleration value based on the data from the second sensor, comparing the first and second acceleration values with each other, and if the difference between the first and second acceleration values is found to be greater than a threshold value, the movement of the load is stopped.According to another aspect is to provide a system for detecting an abnormal condition of a load, wherein the system comprises a computer control unit and the system is configured: to receive sensor data from two acceleration measuring units, the first measuring unit being located at a first location corresponding to the first end of the load and the second measuring unit being located at a second location corresponding to the second end of the load, which is opposite to the first end of the load, to detect a first acceleration value based on the first sensor data and a second acceleration value based on the second sensor data, to compare the first and second acceleration values with each other, and if the difference between the first and second acceleration values is found to be greater than a threshold value, causing the movement of the load to be stopped.

[0008] BRIEF DESCRIPTION OF THE FIGURES

[0009] Figure 1 shows an example illustrating the accelerations at different points on the container in a situation where the container gets jammed during lifting.

[0010] Figure 2 illustrates the difference between measuring acceleration from the center of the container and measuring acceleration from the end of the container.

[0011] Figure 3 shows an example of a system that enables the detection of container jamming.

[0012] Figure 4 shows another example of a system that can be used in a crane to detect container jamming.

[0013] Figures 5 and 6 illustrate other abnormal load situations.

[0014] DETAILED DESCRIPTION

[0015] Container cranes can be used to move containers using a container spreader that attaches to the container and whose height is adjusted using the crane's ropes. In order for the lifting to be smooth, the container should move evenly. However, if an abnormal situation occurs, for example, if part of the container gets stuck during lifting, at least one rope may be subjected to overload stress, which can causepremature and unexpected damage to the rope. The container may get stuck, for example, if it is being lifted from a ship and one corner of the container is still attached to another container. Another example is if the container is being lifted in a confined space, such as between stacks of containers on a ship, where the space around the container is very limited. In such a confined space, the container can easily stick to the wall that limits the space, again causing an unbalanced situation for moving the container. A third example is when a container is lifted from a truck, one corner of the container may still be locked to the truck, preventing the container from being lifted evenly. When the container does not lift as smoothly as expected and one or more ropes are damaged, such as breaking, the damage causes a situation where load handling with the container crane cannot be safely continued until the ropes have been replaced.

[0016] If the container crane has to be taken out of service, even for a short period of time, the financial consequences are significant. For example, if one or more ropes on a container crane have to be replaced due to a container getting stuck, the cost can run into thousands of dollars, even if replacing the rope or ropes only takes an hour. If the rope has to be replaced twice a month due to jamming, for example, this can easily cost tens of thousands of dollars a year, even if the container crane can be repaired in an hour. However, it often takes several hours to repair a container crane. It is therefore advisable to prevent damage caused by jamming.

[0017] In order to prevent the container from jamming, it is important to detect when jamming is about to occur. Jamming can cause a situation where lifting a jammed load causes a jerk that overloads at least one rope, exceeding the load capacity of that rope. The crane's general overload protection can be used to detect such a jamming situation. The purpose of this protection is to prevent a situation where the load is too heavy for the ropes. Overload situations can be detected, for example, based on sensor data obtained from axle sensors attached to the ends of the lifting ropes. There may be two or four lifting ropes for lifting a single load. The lifting mechanism uses ropes to lift the lifting frame, under which there is a container spreader. Theremay be, for example, one lifting mechanism per rope, and they may have separate controls. However, such protection may be too slow to react if the container is at least partially attached to, for example, the ship's structures. This may be due to the fact that in such a jammed situation, the rope stretches, making it impossible to measure the forces acting on it quickly enough, for example, using the strain gauge at the end of the rope.

[0018] In situations where the container becomes stuck, mechanical or hydraulic damping can also be used to protect the rope. When a container jams, causing at least one rope to suddenly become overloaded, a hydraulic system, for example, can act like a spring and prevent damage to the rope before the lift can be stopped. Mechanical protection works in a similar way, allowing time for lifting to be stopped by protecting the rope for the time required to stop when the load jams. In addition, it is possible to use tilt and / or acceleration sensors in the lifting frame, which produce sensor data that can be used to detect load jamming. However, such systems can be expensive and complex and may require maintenance.

[0019] Figure 1 shows an example illustrating the accelerations at different points of the container in a situation where the container jams during lifting. In this example, there is a container 100 being lifted by a container crane with two ropes, ropes 110 and 115, for lifting. In situation 120, the lifting is performed as planned and both ends of the container 100 rise at the same speed 102, for example at a speed of 90 m / min. In this case, the speed of the first end of container 100 is the same as the speed of the second end of the load. If the container spreader has at least one acceleration sensor at the point corresponding to the first end of container 100, i.e., the first acceleration sensor, and there is at least one acceleration sensor at the point corresponding to the second end of container 100, i.e., the second acceleration sensor, the acceleration sensors will report equal acceleration values. It is also possible that the acceleration sensors also provide the direction of the accelerations, and in situation 120, the directions of the accelerations substantially correspond to each other.Figure 1, situation 130, illustrates a situation in which the container being lifted suddenly becomes stuck. In this example, the first end of container 100 hits obstacle 105, which prevents the first end of the load from being lifted in the same way as the second end of the load. In this example, the force caused by obstacle 105 is opposite to the lifting force and thus either slows down the lifting or prevents it altogether. In this example, obstacle 105 prevents the first end of container 100 from continuing to be lifted, and thus the speed 104 of the first end of container 100 in this example becomes 0 m / min. However, the speed of the second end of container 100 is still speed 102, i.e., 90 m / min, for example. Due to these differences, the first acceleration sensor and the second acceleration sensor indicate different accelerations, the direction of which may also be different. Since the first end of container 100 is stuck, if the lifting of the first end is continued, a jerk will occur, which will strain the rope 110, causing an overload that will damage the rope 110.

[0020] Figure 1, situation 140, shows the situation during lifting after the first end of container 100 has become stuck due to obstacle 105. Since the lifting of the first end is prevented by obstacle 105, but the lifting of the second end continues at speed 102, container 100 undergoes a rotational movement 106 around the center of container 100. This rotational movement also has its own rotational speed, which also causes additional acceleration at the other end of the element, increasing the difference between the accelerations measured by the first acceleration sensor and the second acceleration sensor. When this difference in the accelerations of the first and second ends of container 100 is greater than the previously defined threshold value, this difference can be interpreted as the load lifting getting stuck, i.e., a jammed situation that may endanger at least the integrity of the structure of the second rope if the jamming results in a jerk that is too strong for the rope 110. Based on such an observation, the lifting of container 100 can be slowed down or stopped and damage to rope 110 can be prevented.

[0021] Even if accelerations in different directions can be measured at both ends of the container 100, when an abnormally high acceleration is detected in an abnormaldirection relative to the opposite end, it can be interpreted that the container 100 is stuck and the lifting can be slowed down or stopped. If acceleration is measured at corresponding points at both ends of the container 100, the distance between the acceleration sensors amplifies the difference in the accelerations they measure, as the acceleration at the ends is greater than in the middle of the load due to the rotational movement in a jammed situation. This difference, amplified by the lever arms, causes the detection of jamming to be faster, as the situation becomes clearer and is detected earlier due to the amplification of the difference caused by the lever arms.

[0022] Figure 2 illustrates the difference when acceleration is measured from the center of the container or from the end of the container. Situation 240 describes a situation where sensor data is obtained from the center of the container during lifting. In this example, there is a container 200 and a container crane grips it using a container spreader 205. In this example, the container spreader 205 is moved using two ropes, namely ropes 210 and 215. In the middle of the container spreader is a measuring unit 220, which comprises at least one acceleration sensor. Optionally, it may also comprise an inclinometer and / or other sensors that produce sensor data. When the container is lifted, sensor data is obtained from the measuring unit, which can be processed by a computer unit. The computer unit can be any unit capable of processing data based on computer commands. The computer unit may also comprise, for example, programmable logic circuits, or it may comprise at least one processor and at least one memory unit, which work together so that data can be processed in accordance with a computer program. The computer program comprises computer commands. The computer unit can compare the sensor data obtained with predetermined values, and if a certain predetermined threshold value is exceeded, the lifting of container 200 can be slowed down or stopped. For example, when a container spreader has one measuring unit located at a point corresponding to the center of the container 200, it is possible to detect when rope 215 slackens and rope 210 tightens due to the end of the container 200 lifted by rope 210 jamming during lifting. This situation can cause, for example, a load corresponding to a mass of100 g to increase on rope 210, while the load on rope 215 is reduced by an amount corresponding to a mass of 100 g.

[0023] Figure 2, situation 245, shows a similar situation where container 200 gets stuck during lifting, but in this case, container spreader 205 has two measuring units 230 and 235, each of which contains at least one acceleration sensor and possibly also at least one tilt sensor. The measuring units 230 and 235 may be similar to the measuring unit 220. The measuring unit 230 is positioned so that it is located at a point corresponding to the first end of the container 200, and the measuring unit 235 is positioned so that it is located at a point corresponding to the second end of the container 200. This makes it possible to compare the sensor data obtained from measurement units 230, which describes the acceleration or deceleration of the first end of container 200, with the sensor data obtained from the other end of container 200, which describes the acceleration or deceleration of the opposite end of container 200. For example, if the first end of container 200 jams, measurement unit 230 detects a greater change in acceleration than if it were located at a point corresponding to the middle of container 200. This jamming may cause, for example, the load on rope 210 to increase by an amount corresponding to a mass of 150 g and the load on rope 215 to decrease by an amount corresponding to a mass of 50 g. Since measuring unit 235 is located at the other end of container spreader 205, this measuring unit detects greater acceleration at this point than in the middle of container spreader 205. Thus, both measuring units 230 and 235 detect stronger acceleration values than the measuring unit 220 located in the middle of the container spreader 205, and the difference between them helps to detect jamming faster than the detection based on the data produced by the measuring unit 220. Graph 250 illustrates this difference in speed. In this graph, the x-axis represents time t and the y-axis represents the force F applied to the rope. Point 252 represents the moment when the container 200 jams and at least one of the ropes 210 and 215 is damaged as a result of the jerk caused by the jamming, if the lifting is not stopped. Point 254 depicts the stage at which the jamming is detected in situation 240 based on the data from measurement unit 220, and point 256 depicts the stage at which thejamming is detected in situation 245 based on the data from measurement units 230 and 235. As can be seen in Figure 250, measurement units 230 and 235 enable jamming to be detected earlier than measurement unit 220 and, therefore, measurement units 230 and 235 allow the most time to stop the lifting of container 200.

[0024] It should be noted that although in the previous examples the container is lifted using two ropes, there may also be more ropes, for example four, so that there is one rope for each corner of the container. This enables the container to be controlled in such a way that even movement of the container can be ensured, even when the container is tilted, as each corner can be controlled. The corners of the container can be controlled by means of so-called micro-movements, which refer to small lateral movements. These movements can advantageously have their own rope mechanisms. According to one embodiment, the container can be lifted with two or four ropes, and in addition, the micro-movements can be controlled with four ropes.

[0025] Since jamming can occur quickly during lifting, and the resulting jerk can damage at least one rope, causing it to break, for example, preventing damage to the rope requires quick observation of the jamming and a response to it so the jerk that causes damage to at least one rope can be prevented. In order for observation to be quick, the data transferred from the measuring units must be able to be quickly transferred to the computer control unit for processing. The computer control unit must also be able to process the data quickly enough and issue a command to slow down or stop the lifting before jamming occurs and causes damage. The container crane brakes must also be fast so that the container can be stopped before damage occurs to one or more ropes.

[0026] Figure 3 shows a computer control unit that receives sensor data from two measuring units and is thus able to detect a jamming-induced jerk in advance. In this example, the computer control unit 320 is part of the lifting frame 300, which is attached to the container crane by ropes, or alternatively, the computer control unit320 can be attached to a container spreader supported by ropes. However, it should be noted that the computer control unit 320 may also be a separate unit from the lifting frame 300, or alternatively from the container spreader, in such a way that the computer control unit 320 is connected to the lifting frame 300 or the container spreader. The computer control unit 320 is also connected to the container crane control unit. In this example, the lifting frame 300 is configured to control the container spreader and to control the movement of the container. In this example, the lifting frame 300 is an integral part of the lifting machinery. The container spreader, on the other hand, can be detached from the lifting frame 300. The container spreader may comprise actuators, and since the container spreader can be detached from the lifting frame 300, if one of the actuators fails, the container spreader can be replaced and the faulty container spreader can be taken for repair without having to completely shut down the container crane for a long period of time.

[0027] In this example, there are two measuring units, measuring units 310 and 315. It should be noted that there may also be a different number of measuring units. In this example, measuring units 310 and 315 each comprise at least one acceleration sensor. The acceleration sensor can be any suitable acceleration sensor, such as a triaxial acceleration sensor, a capacitive MEMS acceleration sensor, a piezoelectric acceleration sensor, or a piezoresistive acceleration sensor. Measurement units 310 and 315 may each comprise, in addition to one or more acceleration sensors, other sensors that provide sensor data to computer control unit 320. Such other sensors may include, for example, one or more inclinometers, known in English as inclinometers, and / or gyroscope sensors.

[0028] In this example, the measuring units 310 and 315 are positioned so that they are located at both ends of the longitudinal side of the movable load. In this way, the distance from the center of the load to the end of the load forms a lever arm that amplifies the phenomena that measurement units 310 and 315 can measure. This makes observation based on sensor data easier. It should also be noted that, since measuring units 310 and 315 are on opposite sides of the longitudinal direction, thelever arms can amplify any observable phenomena, such as acceleration, in opposite directions, and thus the difference observable in the sensor data produced by measurement units 310 and 315 is clearly highlighted compared to when measurement units 310 and 315 are located closer to the center of the load. This enables a faster response, which can prevent jamming-induced jerking that could damage at least one rope.

[0029] Measuring units 310 and 315 can be connected to computer control unit 320 via any suitable connection. The connection may be, for example, via a bus, provided that the bus allows sufficiently fast data transfer. The bus may be, for example, Ethercat, CAN bus, or Profinet. It should also be noted that, instead of or in addition to a digital bus, the measuring unit can produce sensor data that is transmitted as an analog measurement signal, and this analog signal can then be read by an analog input card, after which it can be processed in the computer control unit 320.

[0030] The measuring units 310 and 315 may be attached, for example, to one or more of the following: the crane's container spreader, the crane's lifting frame, or the ends of mounting arms that are spaced apart from each other. The measuring units 310 and 315 may be attached, for example, by means of magnets, or they may be permanently integrated. Since the measuring units 310 and 315 can be attached separately, as well as the computer control unit 320, their ability to detect the jerk caused by jamming before it occurs means that a system based on them can also be installed on existing cranes, such as container cranes.

[0031] The example shown in Figure 3 illustrates a system that enables the measurement of rapid changes in load position. This is a system that enables the detection of container jamming. It should be noted that this works both when lifting and lowering the load; these rapid changes in load position can be detected and, if necessary, responded to, for example, by slowing down or stopping the movement of the load. Although jamming during lowering is unlikely to damage the rope, it may still be undesirable as it may damage other structures involved in moving the container, suchas those in the vicinity of the container. It should be noted that the sensor data produced by the measuring units also enables the detection of jamming when it is caused by something other than an obstacle, such as obstacle 105, or a situation where the container tilts in such a way that the stress it causes is distributed unevenly on the ropes.

[0032] In this example, the computer control unit compares the acceleration value obtained from measurement unit 310 with the acceleration value obtained from measurement unit 315. As explained earlier, if the difference between these acceleration values is greater than a predetermined threshold value, the computer control unit 320 can conclude that a jam has been detected. The acceleration values may also include the directions of the accelerations, in which case both the magnitudes and directions of the accelerations can be compared. Thus, when the difference between the values exceeds a predetermined threshold value, the computer control unit 320 may send an indication of the detected jamming to the crane control unit. However, it is also possible that the conclusion is not made solely on the basis of the difference in acceleration values. For example, the computer control unit 320 may also receive information from at least one tilt measurement sensor, which is slower than the acceleration sensor but can help to confirm the conclusion made based on the acceleration sensor. If the sensor data obtained from at least one tilt measurement sensor supports the conclusion that a jam has been detected, an indication of the jam can then be transmitted to the crane control unit. Alternatively, or in addition, a gyroscope can also be used to verify the conclusion based on the acceleration sensors. On the other hand, if the sensor data obtained from the tilt sensor and / or gyroscope does not support the conclusion based on the acceleration sensors, the conclusion can be interpreted as incorrect and ignored without sending an indication of jamming to the crane control unit. It is also possible that, in order to avoid sending an indication of jamming when the conclusion is incorrect, measurements from different measurement units can be taken at different time intervals, after which the measurements obtained can be averaged and filtered. Other suitable processingmethods can also be applied to the processing of measurement results in order to prevent false interpretations of jamming.

[0033] In one example, when comparing the signals from two acceleration sensors, if jamming has occurred, the end in question and its acceleration signal reading increase in the direction of negative acceleration. When the signal is found to deviate from the normal noise level, the deviation typically increases in a monotonic growth curve. The free, i.e., non-jammed end continues to lift normally, i.e., there is no significant change in its acceleration, because the lifting speed remains substantially constant at this end after the start of movement, or the change is significantly different, i.e., the acceleration of the free end differs significantly from the acceleration of the jammed end.

[0034] When the monotonic change in the signal of the jammed end has continued after the signal has deviated from normal noise (time point 1) by a fraction of a second above a predetermined critical limit (time point 2), the signal continues to increase monotonically, in which case a jam is detected and the computer control unit can issue a command to stop the lifting motors. Thus, by waiting for the time between time points 1 and 2 and observing that the difference between the acceleration signals, or the first signal, continues to increase, a jam can be reliably detected, while at the same time avoiding unnecessary stop commands. By reacting at time point 2, a jam can be reliably detected, and this is done early enough to allow sufficient time to stop the lifting motor so that the ropes can be protected from damage.

[0035] Similarly, when the signal has been increasing at time point 1 and continues to increase for some time after that, but then returns to the normal noise level so that it does not continue to increase monotonically at time point 2, it can be determined that the situation was a minor, temporary disturbance in lifting. In this case, there is no need to issue a command to stop the lifting motors, thus avoiding unnecessary interruption.For each crane or for different lifting situations, a suitable time delay or a sufficient number of consecutive measurements can be set in advance in the crane control system or in the control system of the electric drives of the lifting motors between time points 1 and 2, on the basis of which the event can be determined. The length of the delay may be affected by factors such as the flexibility of the crane structure, the movement of the ship in waves, the lifting speed, the position of the container spreader, the properties of the ropes, the free length of the ropes, the cycle time of the control system processor, the delay between the crane control system and the electric drives, the properties of the electric drives, and the delay in the engagement of the brake connected to the motor. In addition to the signals from the described acceleration sensors, force measurement proportional to the mass of the load can also be used to detect and / or confirm jamming. Force measurement can be based on force sensors in the rope mechanisms or on information obtained from the electric drives of the lifting motors.

[0036] In addition to the data obtained from measurement units 310 and 315, the context of the container being moved, for example, can also be taken into account when determining whether jamming has been detected. This context can be determined by detecting the location of the container using any suitable method. The location of the container can be determined, for example, based on sensor data and / or image recognition. The context can be taken into account, for example, in such a way that it affects a predetermined threshold value, on the basis of which it can be concluded whether the load is stuck. The context can thus be determined based on the location of the container in such a way that it is, for example, one or more of the following: crane trolley tracking, container lifting height, speed at which the container is moved, container mass, container length, such as 20 or 40 feet, container contents, and / or container location. In addition to this, or alternatively, the container spreader can detect whether the container is attached to the container spreader, or whether the distance between the container spreader and the container is such that it can be interpreted as a small distance. Load sensors connected to rope mechanisms can also be used as additional data to determine whether a jam has been detected.Figure 4 illustrates another example of a system that can be used to detect container jamming in a crane. In this example, the object being lifted is container 400. In this example, there are four measuring units: measuring units 410, 415, 420, and 425. The measuring units are like measuring units 310 and 315. Measuring units 410, 415, 420, and 425 are positioned so that they are located at the corners of container 400.

[0037] In this example, there is a lifting frame 430 that comprises or is connected to a computer control unit 435. The computer control unit receives sensor data from measurement units 410, 415, 420, and 425. The computer control unit 435 corresponds to the computer control unit 320. The computer control unit 435 receives data from the crane control unit 450, to which it is connected by a connection 440, which may be any suitable fixed connection. Similarly, computer control unit 435 can send data, such as indications, to crane control unit 450, to which it is connected by fixed connection 445. Alternatively, or in addition, the computer control unit may transmit data to the crane control unit using a wireless connection 457. For this purpose, the computer control unit 435 may be connected to a transmitter 452 that transmits data wirelessly to a receiver 455. The receiver 455 is connected to the crane control unit 450 and transmits the data it receives to it.

[0038] In this example, four measuring units 410, 415, 420, and 425 enable the tilt of the container 400 to be observed in all directions. In addition, the acceleration values obtained from the acceleration sensors of the measuring units 410, 415, 420, and 425 and their directions can be compared with each other. It should be noted that the sensor data of all measuring units can be compared with each other. If the difference between the acceleration values obtained from measurement units 410, 415, 420, and 425 exceeds a predefined threshold value, it can be concluded that container 400 is jammed and that the movement of container 400 should be stopped. If necessary, this conclusion can also be verified based on other sensor data, as described in the previous examples.Once it has been confirmed that the load is jammed, an indication can be sent to the crane control unit 450 via either a wired or wireless connection. The crane control unit 450 is connected to the brakes 460 and the motor 470 of the crane. This enables it to control the motor 470 and brakes 460. In addition, the crane control unit 450 controls the lifting speed and height of the container 400. It can also control the direction and acceleration of the lifting. The crane control unit also has information about the permissible speeds for moving the container 400. Thus, when it receives an indication from the computer control unit 435 that the movement of the container 400 should be stopped, it is able to verify the indication before stopping the movement of the container 400. Verification may be based, for example, on the crane control unit 450 knowing what speeds are permitted for moving the container 400, and if the current speed for one rope, for example, is not permitted, the crane control unit may cause the movement of the container 400 to be stopped. The movement and position of the container 400 can also be monitored by using load sensing in connection with the crane's rope mechanisms. Load sensing can be provided by separate load measuring devices or integrated into the electric drives. Stopping can be achieved, for example, by activating the brakes 460 using a separate brake stop circuit designed for rapid stopping. In conjunction with the activation of the brakes 460, the power to the motor 470 can also be cut off by using the frequency converter to cut off the power supply to the motor 470. Alternatively, a torque opposite to the direction of rotation of motor 470 can be applied to motor 470. Thus, once the indication has been verified, an emergency braking signal can be activated, which activates the brakes 460 and also causes motor 470 to stop.

[0039] As illustrated in Figure 1, at least one rope overload situation can occur when the container collides with an obstacle, such as obstacle 105. It should be noted that overload situations can also occur in other ways, and these other ways are not necessarily as simplified as the example in Figure 1. For example, the container may catch on the vertical surfaces of the ship's hatch when it is moved in a narrow vertical hatch, causing the container to jam and the ropes to become strained.The examples described above illustrate a jamming situation that can occur when lifting a container, in which case the lifting can be stopped before the jamming and continued lifting in that situation cause a jerk that damages at least one of the crane ropes.

[0040] Figures 5 and 6 illustrate other abnormal load situations. Instead of the jamming situation described above, the method and system according to the invention also apply to other abnormal load situations when the load is being moved. One example may relate to a collision situation involving container 500. In addition to the collision of container 500, the position of container 500 can be monitored, which must be within certain limits, almost horizontal in all directions. A snag situation, in which a part of the structure or equipment catches on container 500 as it moves (driving movement 520), may be one in which there are no large accelerations when container 500 gets caught on one of its corners or ends and container 500 is lowered or raised slowly. In this case, the acceleration sensors can be used to obtain, directly or indirectly, angle data on the position of container 500. This allows any abnormal tilt to be detected, in which case an alarm can be sent to the operator, who can slow down or stop the lifting or lowering movement of container 500 or its horizontal driving movement. The tilt angle can be longitudinal or transverse, because container 500 is suspended from at four corners, two of which may be load-bearing. Such a situation can also occur when container 500 is lowered onto obstacle 510 so that only one end remains supported and the other end descends.

[0041] Instead of the aforementioned jamming or collision situation, another example may relate to the rotation of container 600. The rotational movement of container 600 can be monitored so that an abnormal situation is detected when the container hits obstacle 610 in lateral movement 620 and starts to rotate around the vertical axis. The direction of rotation can be counterclockwise or clockwise. In this case, the acceleration sensors provide, directly or calculated, angular information about the position of container 600. An abnormal tilt can then be detected, and an alarm can besent to the operator, who slows down or stops the lifting or lowering movement of container 600 or its horizontal movement.

[0042] In accordance with the basic idea of the invention, any abnormal positioning of containers 100; 200; 400; 500; 600 can be detected effectively and with little delay thanks to the fact that measuring units 220; 230, 235; 310, 315; 410, 415, 420, 425 are located at a distance 1 to the side of the rope lines moving the container. For example, jamming of the container during lifting is caused by the lifting ropes 110, 115; 210, 215 and a new unknown force torque pair that tilts the container into an abnormal position. The tilt caused by the moment pair is quick to detect because the measuring units can be located far apart, in which case the longitudinal dimension of the container can be used as a reinforcing lever arm and the quantity describing the change in the space of motion, such as acceleration, increases with the contribution of the lever arms. The same applies to the detection of the container's width dimension. In this way, various tilts or rotations (tilt, list, skew) can be detected, regardless of the axis around which they occur.

[0043] It is also clear to the skilled person in the art that, although some examples have been described above, the invention can be implemented in different ways and is therefore not limited to the examples described above.

Claims

CLAIMS1. A method for moving a load using a crane, the method comprising: moving the load using at least two ropes;receiving sensor data from two measuring units measuring acceleration, the first measuring unit being located at a first location corresponding to a first end of the load and the second measuring unit being located at a second location corresponding to a second end of the load, which is opposite to the first end of the load;detecting a first acceleration value based on the first sensor data and a second acceleration value based on the second sensor data;comparing the first and second acceleration values with each other; and if a difference between the first and second acceleration values is found to be greater than a threshold value, the movement of the load is stopped.

2. The method according to claim 1, wherein the first measuring unit comprises at least one acceleration sensor and the second measuring unit comprises at least one acceleration sensor.

3. The method according to claim 2, wherein the first measuring unit comprises at least two acceleration sensors at the first longitudinal end of the load and / or the second measuring unit comprises at least two acceleration sensors at the second longitudinal end of the load.

4. The method according to claim 3, wherein the first measuring unit comprises one acceleration sensor at a first corner of the first longitudinal end of the load and one acceleration sensor at a second corner of the first longitudinal end of the load; and / or wherein the second measuring unit comprises one acceleration sensor at a first corner of the second longitudinal end of the load and one acceleration sensor at a second corner of the second longitudinal end of the load.

5. The method according to any of the preceding claims, wherein the first measuring unit and the second measuring unit are attached to one of the following: thecrane's container spreader, the crane's lifting frame, or the ends of mounting arms spaced apart from each other.

6. The method according to any of the preceding claims, wherein detecting the difference in the acceleration values further comprises detecting a difference in a direction of the acceleration values, and detecting that the direction of the first acceleration value is different from the direction of the second acceleration value.

7. The method according to any of the preceding claims, further comprising: detecting location of the container;determining context of container movement based on the location; and taking the context into account in determining the threshold value.

8. The method according to claim 7, wherein the context comprises one or more of the following: crane trolley tracking, load lifting height, speed at which the load is moved, load mass, load length, load content, or load location.

9. The method according to any of the preceding claims, wherein one or more of the acceleration sensors are triaxial acceleration sensors.

10. The method according to any of the preceding claims, wherein one or more of the acceleration sensors is one of the following: a capacitive MEMS acceleration sensor, a piezoelectric acceleration sensor, or a piezoresistive acceleration sensor.

11. The method according to any of the preceding claims, wherein at least the first or second measurement unit further comprises a tilt measurement sensor and / or a gyroscope sensor.

12. The method according to any of the preceding claims, wherein the first and second measurement units are connected to a computer control unit configured tocompare the first and second acceleration values with each other and to cause the load movement to stop if the difference between the first and second acceleration values is detected to be greater than the threshold value.

13. The method according to claim 12, wherein the connection operates via Ethercat or CAN bus.

14. The method according to claim 12 or 13, wherein the computer control unit is located in the container spreader or lifting frame, and wherein the computer control unit is connected to the crane control system.

15. A system for detecting abnormal load condition, wherein the system comprises a computer control unit and the system is configured to:receive sensor data from two acceleration measuring units, the first measuring unit being located at a first location corresponding to a first end of the load and the second measuring unit being located at a second location corresponding to a second end of the load, which is opposite to the first end of the load;detect a first acceleration value based on the first sensor data and a second acceleration value based on the second sensor data;compare the first and second acceleration values with each other; and if the difference between the first and second acceleration values is found to be greater than a threshold value, causing the movement of the load to be stopped.

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