RTG crane, RTG crane system, and RTG crane control method

Abstract

An RTG crane according to the present invention can operate automatically and comprises a drive unit that is involved with the conveyance of a load. The RTG crane also comprises a battery that supplies power to the drive unit, a generator that charges the battery, and a crane control unit that controls the drive unit. The crane control unit estimates the state of charge of the battery and, on the basis of the state of charge, controls at least one of the speed and the acceleration of operations brought about by the drive unit.

Description

RTG Crane, RTG Crane System, and RTG Crane Control Method

[0001] The present invention relates to an RTG crane, an RTG crane system, and an RTG crane control method.

[0002] Conventionally, a crane device for lifting and transporting loads such as containers has been known. In the crane device described in Patent Document 1, power generation by a generator, charging and discharging by a charging device, and control of regenerative power are performed. In this device, a crane drive device rotates a motor using the generated power from the generator and the discharge power from the charging device as drive power. The control device controls the discharge power based on the remaining amount of the charging device so that the discharge power can be continuously supplied from the charging device to the motor until the winding winding is completed. When lowering, the charging device is charged by the regenerative power from the motor.

[0003] Japanese Patent Application Laid-Open No. 2018-27833

[0004] In the above-described conventional device, a situation where the load on the generator suddenly increases due to a shortage of the remaining amount of the charging device before the end of winding is prevented. However, since the discharge power is controlled based on the remaining amount of the charging device, the operability such as the responsiveness of the crane device to the operation of the operator may decrease.

[0005] An object of the present invention is to provide an RTG crane, an RTG crane system, and an RTG crane control method that can suppress a decrease in the operability while reducing the possibility of operation stop by suppressing a decrease in the charge amount of the battery and ensuring the charge amount.

[0006] One aspect of the present invention is an RTG crane capable of automatic operation, including a drive unit related to the transportation of a load, and includes a battery that supplies power to the drive unit, a generator that charges the battery, and a crane control unit that controls the drive unit. The crane control unit estimates the charge amount of the battery and controls at least one of the speed and acceleration of the operation by the drive unit based on the charge amount.

[0007] This RTG crane allows for the suppression of battery charge degradation and ensures sufficient charge. As a result, the possibility of operational shutdowns due to insufficient charge is reduced. Furthermore, since the RTG crane is capable of automatic operation, no operator is required during automatic operation. Therefore, the impact on the operability of the RTG crane from controlling at least one of the speed and acceleration of the drive unit's movement based on the charge level is not a problem. In other words, the above-mentioned RTG crane can suppress a decline in operability while reducing the possibility of operational shutdowns.

[0008] In the above-described RTG crane, when regenerative power is generated from the drive unit, the battery may be charged by both the regenerative power and the power generated by the generator. With this configuration, when regenerative power is generated from the drive unit (during regenerative operation), the battery can be charged not only by the regenerative power but also by the power generated by the generator. Therefore, compared to conventional crane devices that charge the battery only by regenerative power, the decrease in the battery charge can be further suppressed. As a result, the possibility of operational shutdown due to insufficient charge can be reduced. More specifically, by suppressing the decrease in the battery charge, the operating time of the crane is extended, and the regenerative timing during operation increases. Therefore, by increasing the timing at which the battery can be charged by both regenerative power and the power generated by the generator, the decrease in the battery charge can be further suppressed.

[0009] In the above-described RTG crane, the crane control unit may estimate the battery charge level and, based on the charge level, determine the ratio of battery-supplied power to generated power in the drive unit's drive power. For example, it is possible to control the system by increasing the ratio of battery-supplied power when the battery charge level is high, and increasing the ratio of generated power when the battery charge level is low. This allows for effective utilization of the battery while suppressing the decrease in the battery charge level.

[0010] In the above-described RTG crane, the crane control unit estimates the battery charge level and, if the charge level is above a predetermined reference value, charges the battery using only regenerative power. If the charge level is below the reference value, it may charge the battery using both regenerative power and power generated by the generator. This control prevents regenerative power from being wasted and allows for its full and effective utilization. When a larger charge level is required, the crane can receive supplementary power from the generator, thereby increasing the battery charge level.

[0011] The above-mentioned RTG crane comprises a pair of legs with a traveling section at their lower end, a crane girder connecting the upper ends of the pair of legs, and a trolley capable of traversing along the crane girder. The crane control unit may stagger the timing of the trolley's traversal and the legs' travel based on the charge level. This control suppresses the decrease in battery charge due to combined operation and increases the charging time from the generator.

[0012] In another aspect of the present invention, an RTG crane system comprising a plurality of the above-described RTG cranes may be provided. The RTG crane system includes a system control unit that controls the RTG cranes, and the system control unit may estimate the current battery charge level of each RTG crane and select the RTG crane to perform the transport work based on the estimated current battery charge level. According to this RTG crane system, the current battery charge level is taken into consideration when selecting the RTG crane. Even if there is an RTG crane with an insufficient battery charge among the plurality of RTG cranes, it is possible to select an RTG crane with a sufficiently charged battery instead of such an RTG crane. As a result, cargo handling can be performed reliably.

[0013] In the above-described RTG crane system, the system control unit may estimate the battery charge level at the end of the transport operation based on the current battery charge level and the content of the transport operation, and select the RTG crane to perform the transport operation based on the estimated battery charge level at the end of the transport operation. This control prevents the battery charge from running out in the middle of the transport operation, allowing for more reliable cargo handling.

[0014] The system control unit may acquire the weight of the load and, based on that weight, select an RTG crane to perform the transport operation. The heavier the load, the greater the expected decrease in charge level. This control prevents the charge level of battery B from decreasing too much.

[0015] In the above-described RTG crane system, the system control unit may estimate the degree of battery degradation in each RTG crane and preferentially assign transport work to the RTG crane with the highest estimated degree of degradation. According to this control, transport work is preferentially assigned to the RTG crane with the highest degree of battery degradation. Therefore, when viewed as a whole system, the replacement time for specific batteries is brought forward, resulting in improved overall maintainability (maintenance efficiency).

[0016] In yet another aspect of the present invention, an RTG crane control method is provided that controls an RTG crane capable of automatic operation, comprising a drive unit involved in the transport of cargo, a battery that supplies power to the drive unit, and a generator that charges the battery. In this RTG crane control method, the charge level of the battery is estimated, and based on the charge level, at least one of the speed and acceleration of the operation by the drive unit is controlled.

[0017] This RTG crane control method suppresses the decrease in battery charge and ensures sufficient charge. As a result, the possibility of operational shutdown due to insufficient charge is reduced. Furthermore, since the RTG crane is capable of automatic operation, no operator is required during automatic operation. Therefore, the impact on the operability of the RTG crane from controlling at least one of the speed and acceleration of the drive unit's movement based on the charge level is not a problem. In other words, the above RTG crane makes it possible to suppress a decline in operability while reducing the possibility of operational shutdown.

[0018] According to the present invention, by suppressing the decrease in battery charge and ensuring sufficient charge, it is possible to reduce the possibility of operational shutdowns while suppressing a decline in operability.

[0019] This is a plan view showing an exemplary container terminal to which an RTG crane system according to an embodiment of the present invention is applied. This is a schematic perspective view showing an RTG crane arranged in a container yard. This is a perspective view showing an RTG crane. This is a block diagram showing a control system that oversees the RTG crane system. This is a flowchart showing the contents of the automatic operation of the RTG crane. This is a block diagram showing the configuration related to power control in the RTG crane. This is a flowchart showing an example of a series of RTG crane selection controls in response to a transport instruction. This is a flowchart showing an example of the optimal RTG crane selection control in Figure 7. This is an example of a condition table that can be applied to the optimal RTG crane selection control. This is a flowchart showing another example of RTG crane selection control (automatic operation overall management process). This is a flowchart showing an example of control when transport work is performed by a single RTG crane. This is a table showing an example of hoisting acceleration and hoisting speed according to the charge amount in the transport control of Figure 11. This is a diagram showing the power supply form during power operation in the RTG crane. This is a table showing an example of the ratio of generated power according to the charge amount during power operation. This is a diagram showing the power supply form during regenerative operation in the RTG crane.

[0020] Embodiments of the present invention will be described below with reference to the drawings. In the description of the drawings, the same elements will be denoted by the same reference numerals, and redundant descriptions will be omitted.

[0021] First, with reference to Figures 1 to 3, an RTG crane system 100 equipped with multiple RTG cranes 10 will be described. As shown in Figure 1, the container terminal 1 is provided with a container yard 2 where multiple containers 3 (see Figure 2) are arranged, multiple gantry cranes 4 for transferring the containers 3 to docked ships, multiple RTG cranes 10 located in the container yard 2 for handling the containers 3, and a remote control room 5 that allows for the remote operation of the multiple RTG cranes 10.

[0022] For example, a travel path for transport vehicles such as freight cars, trucks, trailers, or AGVs (Automated Guide Vehicles) is laid out in the container yard 2. The RTG crane 10 acquires the container 3 being transported by the transport vehicle and places the container 3 at a predetermined location in the container yard 2. For example, multiple RTG cranes 10 are each located in a separate container yard 2. The RTG crane 10 acquires the container 3 placed in the container yard 2, transfers the container 3 to the transport vehicle, and then uses the transport vehicle to transport the container 3 to the outside.

[0023] Figure 2 is a schematic perspective view showing an RTG crane 10 located in container yard 2. As shown in Figure 2, the RTG crane 10 is a container handling crane for loading and unloading containers 3, and is a rubber-tired gantry crane (RTG). The RTG crane 10 automatically loads and unloads containers 3 located in container yard 2 at container terminal 1. Containers 3 are an example of cargo to be transported. The RTG crane 10 may transport items other than containers 3.

[0024] As shown in Figures 2 and 3, the RTG crane 10 comprises, for example, a crane body 11, a trolley 18 that can traverse on the crane girder 17 of the crane body 11, and a spreader 12 for loading and unloading containers 3. The crane body 11 has a gantry shape comprising a pair of legs 16 and a crane girder 17 connecting the upper ends of the pair of legs 16. A traveling section 15 is provided at the lower end of each of the pair of legs 16. The traveling section 15 rotates, for example, by the drive of a traveling motor 15a, and moves the pair of legs 16. The trolley 18 traverses, for example, by the drive of a traverse motor 27. The trolley 18, as an example, is equipped with a drum 19 that rotates in forward and reverse directions by a drum drive motor 29 (see Figure 6), and suspends the spreader 12 via a suspension member 30 such as a wire.

[0025] The spreader 12 is a lifting device for suspending the container 3. The spreader 12 can lock the container 3 from above, and by locking and lifting the container 3, it performs cargo handling of the container 3. The spreader 12 has a shape that extends in the direction of travel and is suspended from the lifting members 30 at two points in the direction of travel. A cargo handling lane, which is the travel path of transport trolleys such as trailers 80 on which the container 3 is transferred, is laid out in the container yard 2. The RTG crane 10 automatically transfers the container 3 to, for example, a trailer 80 that has stopped on the cargo handling lane. In other words, the RTG crane 10 is capable of automatic operation. The RTG crane 10 retrieves the container 3 that is being brought in by the trailer 80 from the trailer 80 and places the container 3 in a predetermined position in the container yard 2. Furthermore, the RTG crane 10 retrieves the container 3 located in the container yard 2, places the container 3 on the trailer 80, and uses the trailer 80 to transport the container 3 to the outside. In the following description, the "RTG crane system 100" will be simply referred to as the "crane system 100," and the "RTG crane 10" will be simply referred to as the "crane 10."

[0026] Next, with reference to Figure 4, the control system in the crane system 100 will be described. The crane system 100 comprises a plurality of cranes 10 and a system control device (system control unit) 90 that controls the plurality of cranes 10. The system control device 90 is a controller that comprehensively controls the plurality of cranes 10. The system control device 90 is an electronic control unit composed of a processor such as a CPU (Central Processing Unit), ROM (Read Only Memory), and RAM (Random Access Memory). For example, the system control device 90 receives a transport command generated by the higher-level operating system 200 and selects one of the cranes 10 that is suitable for executing the transport command. The system control device 90 assigns the transport work to the selected crane 10. A transport command is a command to transport a specific container 3 from the source (from location) to the destination (to location). While the crane system 100 is in operation, multiple transport commands are generated sequentially. Note that the higher-level operating system 200 is an external component of the RTG crane system 100 and is not included in the crane system 100.

[0027] The system control device 90 includes a communication unit 91, an information acquisition unit 92, a calculation unit 93, and a work assignment unit 94. The communication unit 91 communicates with the higher-level operating system 200 and each crane 10. The information acquisition unit 92 acquires information about the status of each crane 10, including an estimated value of the charge level of the battery B (details to be described later) in each crane 10. The calculation unit 93 performs various calculations related to the control of each crane 10. For example, the calculation unit 93 calculates the charge level at the end of transport in each crane 10 based on the transport command and information about the status of each crane 10. The calculation unit 93 selects one crane 10 suitable for executing the transport command. The work assignment unit 94 assigns the transport work to the selected crane 10. In other words, the work assignment unit 94 transmits a transport instruction to the crane 10 via the communication unit 91.

[0028] Here, the basic operation of the crane control device 60 when it automatically operates the crane 10 will be explained with reference to Figure 5. Figure 5 is a flowchart showing the contents of the automatic operation of the crane 10. When the process in Figure 5 is executed, it is assumed that the trailer 80 has arrived at the handover location CP (see Figure 3) and is waiting. In the following explanation, "automatically" means that each part of the crane 10 operates autonomously without any operation by the operator at the control panel. As shown in Figure 5, the crane control device 60 receives an instruction from the control panel to transport the container 3 (step S10). Next, the crane control device 60 automatically moves the spreader 12 and grasps the container 3 in the container yard 2 with the spreader 12 (step S20). Next, the crane control device 60 automatically transports the container 3 to the handover location CP via the spreader 12 (step S30). At this time, the container 3 and the spreader 12 are positioned above the loading platform of the trailer 80. Next, the crane control device 60 automatically loads the container 3 onto the trailer 80 by lowering the spreader 12 downwards (step S40). From the position where the container 3 is loaded onto the trailer 80, the crane control device 60 releases the fixing of the spreader 12 and automatically hoists it up (step S50). Next, the crane control device 60 automatically moves the spreader 12 to the home position, or if there is a next job item, it operates according to the next job item (step S60). With this, the process shown in Figure 5 is completed.

[0029] Furthermore, some steps, such as loading container 3 onto trailer 80, may be performed remotely from the remote control room 5.

[0030] In this description of the embodiment, the "estimated charge amount" will be simply referred to as "charge amount" below. While the charge amount in battery B can normally be measured by connecting a power meter to each battery B, the control system, including the system control device 90 and the crane control device 60, does not directly measure the charge amount. Instead, it estimates the charge amount based on the output from the components shown in Figure 6. Furthermore, the terms "charge rate" and "degree of degradation" may be used in relation to battery B. "Charge rate" and "degree of degradation" are also estimated values. Since the "charge amount" is calculated by multiplying the rated capacity of each battery B by the "charge rate," for control purposes, if the rated capacity is fixed, the "charge rate" has the same meaning as the "charge amount." The "degree of degradation" is calculated from the internal resistance of each battery B.

[0031] Referring to Figure 6, the configuration related to power control in the crane 10 will be described. As shown in Figure 6, the crane 10 includes, for example, a small engine-type generator 41, a battery unit 50 having, for example, three batteries B, a drum drive motor 29 that drives the drum 19 (see Figure 3) powered by the generator 41 and batteries B, and an auxiliary machine 25 powered by the generator 41. The crane 10 further includes a travel motor 15a that drives the travel section 15 powered by the generator 41 and batteries B, and a traverse motor 27 that traverses the trolley 18 powered by the generator 41 and batteries B. As shown in Figure 3, the battery unit 50 is attached, for example, near the bottom of one leg 16. The type of each battery B is not particularly limited, but for example, lithium-ion batteries are used. Lithium-ion batteries are superior from the viewpoint of environmental protection. The generator 41 is attached, for example, near the bottom of the other leg 16. The drum drive motor 29 is a drive unit involved in the transport of the container 3. The crane 10 is further equipped with a crane control device (crane control unit) 60 that controls each part of the crane 10. The crane control device 60 is an electronic control unit composed of a processor such as a CPU, ROM and RAM, etc. The crane control device 60 is installed, for example, near the battery unit 50.

[0032] The crane 10 includes, for example, one engine converter 42. An AC / DC converter 46 is provided between the generator 41 and the engine converter 42. The engine converter 42 is controlled by the power control unit 65 of the crane control device 60 to perform boost control. The crane 10 includes, for example, one inverter drive 43 and two or three battery converters 44 connected in parallel (in the figure, multiple battery converters 44 are shown together). The inverter drive 43 converts the power from the engine converter 42 and the power from the battery converters 44 to AC and supplies AC power to the drum drive motor 29, the travel motor 15a, and the traverse motor 27. The inverter drive 43 converts the regenerative power from the drum drive motor 29 to DC and supplies DC power to the battery converters 44. In the crane 10, a DC voltage (DC current) flows between the AC / DC converter 46 (or engine converter 42), the inverter drive 43, and the battery B.

[0033] A DC link 47 is provided between the engine converter 42 and the inverter drive 43 and battery converter 44. The DC link 47 is a device that inputs DC power from the engine converter 42 to the inverter drive 43 and battery converter 44. A reference voltage is set for the DC link 47. When the voltage of the DC link 47 rises above the reference voltage, current flows from the DC link 47 to the battery converter 44 to maintain the voltage of the DC link 47 at the reference voltage, and the battery unit 50 is charged. When the voltage of the DC link 47 falls below the reference voltage, current flows from the battery unit 50 to the DC link 47 to maintain the voltage of the DC link 47 at the reference voltage, and the battery unit 50 is discharged.

[0034] The generator 41 can supply generated power to the drum drive motor 29 via the engine converter 42 and inverter drive 43. The generator 41 can also supply generated power to each battery B of the battery unit 50 via the engine converter 42 and battery converter 44. In other words, the generator 41 charges each battery B.

[0035] Each battery B in the battery unit 50 can supply power to the drum drive motor 29 via the battery converter 44 and the inverter drive 43. That is, each battery B supplies power to the drum drive motor 29. Power is supplied to the drum drive motor 29 from at least one of the batteries B and the generator 41 (i.e., either one or both) during the hoisting operation of the trolley 18. Hoisting operation will also be referred to as power operation below.

[0036] Meanwhile, the drum drive motor 29 generates regenerative power during the lowering operation of the trolley 18. The drum drive motor 29 can supply regenerative power to each battery B of the battery unit 50 via the inverter drive 43 and the battery converter 44. The supply of regenerative power to the batteries B and the supply of generated power to the batteries B as described above are compatible (can be supplied simultaneously). Lowering operation will hereafter also be called regenerative operation.

[0037] The power control components shown in Figure 6 may be any known devices as appropriate. For example, the generator 41 is not limited to an engine-type generator, but may be a fuel cell generator that generates electricity using another fuel. The number of batteries B may be four or more, or it may be two or one. The engine converter 42 may be omitted. Multiple inverter drives 43 may be provided independently to correspond to each motor.

[0038] One feature of the crane 10 in this embodiment is that the generator 41 is miniaturized. The power ratio between the power from three batteries B (battery output) and the rated power generation of the generator 41 (rated output) is preferably 5:5 to 8:2. More specifically, it is preferable to set the rated power generation of the generator to 100 kW or less, more preferably 60 kW or less, in terms of reducing fuel consumption and exhaust gas emissions.

[0039] The crane control device 60 includes a communication unit 61, a battery information acquisition unit 62, a storage unit 63, a calculation unit 64, a power control unit 65, and a drive control unit 66. The communication unit 61 communicates with the communication unit 91 of the system control device 90. The battery information acquisition unit 62 acquires information about the state of each battery B, such as the charge amount and degree of deterioration of each battery B. The storage unit 63 stores the past charge amount of the batteries B. In particular, the storage unit 63 stores the past charge amount of the batteries B along with time information. The calculation unit 64 calculates the hoisting speed and hoisting acceleration of the drum drive motor 29 by a predetermined calculation (calculation based on the state of the batteries B) which will be described later.

[0040] The power control unit 65 controls at least one of the generator 41, engine converter 42, inverter drive 43, and battery converter 44 in order to perform the following various controls. When regenerative power is generated from the drum drive motor 29, i.e., during regenerative operation, the power control unit 65 charges the battery B using both or either the regenerative power and the power generated by the generator 41. More specifically, the current charge level of each battery B is acquired by the battery information acquisition unit 62 of the crane control device 60. A predetermined reference value for the total charge level of the three batteries B is stored in the storage unit 63. During regenerative operation, when the charge level of the battery B is equal to or greater than the reference value, the power control unit 65 charges the battery B using only the regenerative power. When the charge level of the battery B is lower than the reference value, the power control unit 65 charges the battery B using both the regenerative power and the power generated by the generator 41.

[0041] Furthermore, during powered operation, the power control unit 65 determines the ratio of the power supplied by the battery B to the power generated by the generator 41 in the driving power of the drum drive motor 29, based on the charge level of the battery B. The power control unit 65 may include known components related to power control, but as an example, it may include a battery management system (such as a BMU if a lithium-ion battery is applied to the battery unit 50), a control board with an integrated program, and a programmable logic controller (PLC).

[0042] The drive control unit 66 controls at least one of the devices included in the drum drive motor 29, the traveling motor 15a, the traversing motor 27, and the auxiliary machine 25 in order to perform the following various controls. The drive control unit 66 controls the drum drive motor 29 based on the charge amount of the battery B, and controls at least one of the speed and acceleration of the winding-up operation by the drum drive motor 29. Further, the drive control unit 66 controls the traversing motor 27 and the traveling motor 15a based on the charge amount of the battery B, and shifts the timing of the traversing of the trolley 18 and the traveling of the pair of leg portions 16. Specific examples of the various controls in the crane control device 60 described above will be described later.

[0043] Next, referring to FIGS. 7 to 10, the overall control (overall control) of the plurality of cranes 10 executed by the system control device 90 of the crane system 100 will be described. FIG. 7 is a flowchart showing an example of a series of crane selection controls for a conveyance instruction. FIG. 8 is a flowchart showing an example of the optimal crane selection control in FIG. 7. As shown in FIG. 7, the communication unit 91 (see FIG. 4) receives a conveyance instruction from the upper operating system 200 and receives information regarding a plurality of cranes 10 that are candidates (step S01). The information acquisition unit 92 and the calculation unit 93 determine (select) any one crane 10 suitable for executing the conveyance command (step S02).

[0044] The process of this step S02 (optimal crane determination control) is shown in FIG. 8. The information acquisition unit 92 acquires information related to the conveyance work (step S11). The information acquisition unit 92 acquires, as information related to the conveyance work, the weight (or load) of the container 3 and information related to the work content of the conveyance work, for example, the conveyance direction (lifting, that is, upward, or lowering, that is, downward). Further, the information acquisition unit 92 acquires information related to the battery B (step S12). The information acquisition unit 92 acquires, as information related to the battery B, the current charge amount and the degree of deterioration of each battery B. The calculation unit 93 calculates (estimates) the charge amount of the battery B at the end of the conveyance work from the current charge amount of the battery B and the work content of the conveyance work for each crane 10 (step S13).

[0045] For example, the upward work amount (J) is calculated based on the following formula. Upward work amount (J): Wu = Mc × g × Lu. Here, Mc is the container weight, and Lu is the upward movement distance. Also, the downward work amount (J) is calculated based on the following formula. Downward work amount (J): Wd = Mc × g × Ld. Here, Ld is the downward movement distance. Also, the battery energy used is calculated based on the following formula. Used battery energy: Wu × Ku × Kb - (Wd × Kd). Here, Ku and Kd are mechanical losses, motor efficiency, etc., and Kb is the load sharing coefficient of battery B. Based on the above calculation formulas, the change in the charge amount (SOC) of battery B is calculated, and the charge amount after the movement is completed is calculated. Note that the energy required for horizontal movement is relatively small and can be ignored. Of course, based on the horizontal conveyance distance obtained from the From position and the To position, the energy required for horizontal movement may be taken into account.

[0046] The arithmetic unit 93 determines (selects) any one of the cranes 10 suitable for executing the conveyance command (step S14). Specifically, the arithmetic unit 93 determines the crane 10 with a positive charge amount of battery B at the end of the conveyance operation as the optimal crane. When there are a plurality of cranes 10 with a positive charge amount of battery B at the end of the conveyance operation, among them, the crane 10 with a higher degree of deterioration of battery B may be preferentially set as the optimal crane.

[0047] In the present embodiment, one crane 10 includes three batteries B, but the charge amount may be evaluated as the sum of the charge amounts of the three batteries B. The degree of deterioration may adopt the degree of deterioration of the most deteriorated (worst) battery B among the degrees of deterioration of the three batteries B as a representative value.

[0048] Subsequently, returning to FIG. 7, the arithmetic unit 93 reports the optimal crane to the upper operating system 200, and at the same time, reports the estimated conveyance time and the presence or absence of mid-course charging to the upper operating system 200 (step S03).

[0049] The work assignment unit 94 transmits a transport instruction to the target crane (the optimal crane determined in step S02) that will perform the transport operation (step S04). In other words, the work assignment unit 94 assigns the transport operation to the target crane. Subsequently, the transport operation is performed by the target crane. After the transport operation is completed, the communication unit 91 receives a transport completion report from the crane control device 60 of the target crane (step S05). The communication unit 91 and the information acquisition unit 92 also receive notification of the charge level of battery B at the time of transport completion (step S06).

[0050] Through the above series of controls, one transport operation is completed by one crane 10. However, the control method is not limited to calculating the battery B charge level at the end of the transport operation, as shown above. As illustrated in Figure 9, the calculation unit 93 may determine the optimal crane (target crane) based on the battery B charge level, the weight of the container 3, the transport direction, and the degree of battery B degradation, whichever crane meets the conditions. Regarding the weight of the container 3, the maximum weight determined by the size of the container 3 is set as 100%, and the weight of each container 3 is obtained. The heavier the container 3, the greater the expected decrease in charge level. The system control device 90 obtains the weight of the container 3 and, based on that weight, selects the RTG crane to perform the transport operation, thereby preventing the battery B charge level from decreasing too much. As shown in Figure 9, if the battery B charge level is 40% or higher, a heavy container 3 is not a problem (see conditions 1 and 2). When the charge level of battery B is less than 40%, the lower the charge level of battery B, the smaller (lighter) the corresponding weight of container 3 becomes under each condition.

[0051] In this embodiment, the system control device 90 selects the crane 10 to perform the transport operation, taking into account the charge level of the battery B and the content of the transport operation (load of the container 3). The system control device 90 also selects the crane 10 to perform the transport operation, taking into account the degree of degradation of the battery B. Efforts may be made to equalize the degree of degradation of the battery B. By the system control device 90 considering the degree of degradation of the battery B when selecting the crane 10, it is possible to prevent uneven replacement timing of the batteries B.

[0052] Alternatively, as shown in the modified example in Figure 10, the target crane may be predetermined by the higher-level operating system 200. The communication unit 91 receives a transport instruction and also receives information about one crane 10 designated as the target crane (step S21). The calculation unit 93 checks whether or not intermediate charging is required for the crane 10 based on the current charge level of the battery B and the content of the transport operation (step S22). If it is determined that intermediate charging is required (step S23; required), the calculation unit 93 reports this to the higher-level operating system 200 and receives designation of another target crane (step S24). If it is determined that intermediate charging is not required (step S23; not required), the work assignment unit 94 sends a transport instruction to the target crane that will perform the transport operation (the optimal crane determined in step S02) (step S25). In other words, the work assignment unit 94 assigns the transport operation to the target crane. The processes in steps S26 and S27 are the same as the processes in steps S05 and S06 described above (see Figure 7), so their explanation is omitted.

[0053] In addition, in the crane selection control described above, the system control device 90 may report to the higher-level operating system 200 if it detects that one or more cranes 10 are experiencing insufficient charge in battery B. Alternatively, the system control device 90 may request the higher-level operating system 200 to change the loading / unloading position.

[0054] Next, with reference to Figures 11 to 15, an example of transport control in a crane 10 performing transport work (particularly an example including hoisting control) will be described. Each of the following controls is performed by the crane control device 60 of the crane 10 (see Figure 6). The transport control shown in Figure 11 is performed by the crane 10 selected as the optimal crane between steps S04 and S05 in the overall control shown in Figure 7, or between steps S25 and S26 in the overall control shown in Figure 10. First, the battery information acquisition unit 62 detects the current charge level of battery B (step S31). Next, the calculation unit 64 calculates the difference between the current charge level of battery B and the charge level of battery B one hour ago stored in the memory unit (step S32). Next, the calculation unit 64 checks the current charge level of battery B (step S33). Here, the calculation unit 64 determines the hoisting speed and hoisting acceleration of the drum drive motor 29 according to the table illustrated in Figure 12. When the charge level is 40% or higher, both the winding speed and winding acceleration are set to the normal speed, i.e., 100%. On the other hand, when the charge level is between 20% and 40%, both the winding speed and winding acceleration are set to a value lower than the normal speed. The lower the charge level, the lower the values ​​set for both the winding speed and winding acceleration.

[0055] In actual control, in addition to the charge amount, the difference between the charge amount of battery B from a predetermined time in the past to the present (hereinafter simply referred to as the "charge amount difference") calculated in step S32 is taken into consideration. If the charge amount is 40% or more, or if the charge amount difference is a positive value, the winding speed is set to 100%, and the winding acceleration is also set to 100% (step S34A). In this way, if the current charge amount is greater than the past charge amount (i.e., the charge amount has increased), both the winding speed and winding acceleration are set to their maximum values. If the charge amount is 30% or more, or if the charge amount difference is -20% or more, the winding speed is set to 70%, and the winding acceleration is also set to 70% (step S34B). If the charge amount is 20% or more, or if the charge amount difference is -40% or more, the winding speed is set to 50%, and the winding acceleration is also set to 50% (step S34C). If the charge level is less than 20%, regardless of the charge level difference, operation of the crane 10 is stopped, and the power control unit 65 charges the battery B from the generator 41 (step S34D).

[0056] After the settings in steps S34A, S34B, and S34C are made, the drive control unit 66 controls the drum drive motor 29 to perform winding control (step S35). Also, after step S34D, when the charge level of battery B reaches 20% or more, the drive control unit 66 controls the drum drive motor 29 to perform winding control (step S35).

[0057] Next, with reference to Figures 13 and 14, the power supply configuration for the crane 10 during hoisting operation, i.e., power operation, will be explained. Figure 13 is a diagram showing the power supply configuration for the crane 10 during power operation. Figure 14 is a table showing an example of the ratio of generated power according to the charge amount during power operation. The following control is performed by the power control unit 65 of the crane control device 60. As shown in Figure 13, when the inverter drive 43 is started during power operation, the power from the DC link 47 is converted to AC, and power flows to the drum drive motor 29 (motor drive power P11). The current from the DC link 47 to the inverter drive 43 is detected (inverter inflow current P12), and the current from the generator 41 is calculated by multiplying the current value by the ratio shown in Figure 14. The calculated current is used as the current command for the engine converter 42, and the engine converter 42 performs boost control (engine converter current P13). At this time, the voltage of the DC link 47 drops below the reference voltage, so the battery converter 44 is controlled to maintain the reference voltage, and current flows from battery B to the DC link 47 (battery converter current P14). In other words, the battery converter 44 performs boost control, and battery B discharges. As described above, during hoisting operation, both the current from the generator 41 (engine converter current P13) and the current from battery B (battery converter current P14) are supplied to the drum drive motor 29.

[0058] As an example, the power control unit 65 determines the ratio of the power supplied by battery B to the power generated by generator 41 in the driving power of the drum drive motor 29 according to the table shown in Figure 14. In the example shown in Figure 14, if the charge level of battery B is 40% or less, no current is supplied from battery B to the drum drive motor 29 (the battery converter current P14 is zero). In addition, a control mode that operates using only battery B may be provided as an emergency response in the event of a generator 41 failure.

[0059] Next, with reference to Figure 15, the power supply configuration in the crane 10 during lowering operation, i.e., regenerative operation, will be explained. Figure 15 is a diagram showing the power supply configuration in the crane 10 during regenerative operation. The following control is performed by the power control unit 65 of the crane control device 60. As shown in Figure 15, when the inverter drive 43 is started during regenerative operation, the inverter drive 43 converts the regenerative power from the drum drive motor 29 to DC and sends it to the DC link 47 (motor regenerative power P21). The voltage of the DC link 47 rises (DC link voltage P22). When the voltage of the DC link rises above the reference voltage, the battery converter 44 is controlled to maintain the reference voltage and sends current from the DC link 47 to the battery B (battery converter current P23). At this time, the battery converter 44 performs step-down control and the battery B is charged. Also, if the charge level of the battery B is lower than the reference value at this time, the power control unit 65 gives a replenishment current command to the engine converter 42 and charges the battery B with the power generated by the generator 41 as well (engine converter current P24). In other words, when the charge level of battery B is above a reference value, the power control unit 65 charges battery B using only regenerative power (only the battery converter current P23 flows), and when the charge level of battery B is below a reference value, it charges battery B using both regenerative power and the power generated by the generator 41 (both the battery converter current P23 and the engine converter current P24 flow).

[0060] In the crane 10 and control method of this embodiment, the charge level of the battery B is estimated, and the speed and acceleration of the operation by the drum drive motor 29 are controlled based on the charge level. This control suppresses the decrease in the charge level of the battery B and increases the charging time from the generator 41. As a result, the possibility of operational shutdown due to insufficient charge level can be reduced. Furthermore, since the crane 10 is capable of automatic operation, no operator is required during automatic operation. Therefore, the impact on the operability of the crane 10 by controlling at least one of the speed and acceleration of the operation by the drum drive motor 29 based on the charge level is not a problem. In other words, the crane 10 can suppress a decrease in operability while reducing the possibility of operational shutdown.

[0061] Furthermore, the crane control device 60 may control either the speed or acceleration of the drum drive motor 29 based on the charge level of the battery B. By controlling these parameters, the operating time of the crane 10 is extended by suppressing the decrease in the charge level of the battery B, and the regenerative timing during operation is increased. Therefore, the timing at which the battery B can be charged by both regenerative power and the power generated by the generator 41 is increased, thereby further suppressing the decrease in the charge level of the battery B.

[0062] In the crane 10, during traction operation, power is supplied from the battery B to the drum drive motor 29. Furthermore, when regenerative power is generated from the drum drive motor 29 (during regenerative operation), the battery B can be charged not only by the regenerative power but also by the power generated by the generator 41. Therefore, compared to conventional crane systems that charge the battery B only with regenerative power, the decrease in the charge level of the battery B can be suppressed and the charge level can be maintained. As a result, the possibility of operational shutdown due to insufficient charge can be reduced. In other words, the total operating time can be extended compared to cases where the charging control of the battery B using the generator 41 as described above is not performed. In addition, by avoiding situations corresponding to step S34D above, operational shutdown due to insufficient charge can also be prevented.

[0063] The RTG crane described above can be controlled by the crane control device 60 to increase the proportion of power supplied by battery B when the charge level of battery B is high, and to increase the proportion of power generated when the charge level of battery B is low (see Figure 14). This makes it possible to effectively utilize battery B while suppressing the decrease in the charge level of battery B.

[0064] The power control unit 65 charges battery B using only regenerative power when the charge level of battery B is above a reference value, and charges battery B using both regenerative power and power generated by the generator 41 when the charge level of battery B is below the reference value. This control ensures that regenerative power is not wasted and can be fully utilized. When a larger charge is needed, the battery B can receive supplementary power from the generator 41, thereby increasing the charge level of battery B.

[0065] Furthermore, according to the crane system 100, the current charge level of battery B is taken into consideration when selecting a crane 10. Even if one of the multiple cranes 10 has an undercharged battery B, a crane 10 with a sufficiently charged battery can be selected instead. As a result, cargo handling can be performed reliably.

[0066] According to the control system that selects the crane 10 to perform the transport operation based on the charge level of battery B at the end of the transport operation, the charge level of battery B will not run out during the transport operation, and cargo handling can be performed more reliably.

[0067] The system control device 90 acquires the weight of the container 3 and selects a crane 10 to perform the transport operation based on that weight. The heavier the container 3 is, the greater the expected decrease in the charge level of battery B. This control prevents the charge level of battery B from decreasing too much.

[0068] Furthermore, transport operations are preferentially assigned to crane 10 with a higher degree of battery B degradation. Therefore, when considering the system as a whole, the replacement time for specific batteries B is brought forward, resulting in superior overall maintainability (maintenance efficiency).

[0069] Although embodiments of the present invention have been described above, the present invention is not limited to the above embodiments. For example, the crane control device 60 may stagger the timing of the trolley 18's traverse and the leg portion 16's travel based on the charge level of the battery B. For example, if this control is performed when the charge level of the battery B is below a predetermined threshold, the decrease in the charge level of the battery B due to combined operation can be suppressed, and the charging time from the generator 41 can be increased.

[0070] The crane control device 60 may always charge the battery B using both the regenerative power generated by the drum drive motor 29 and the power generated by the generator 41 when regenerative power is generated from the drum drive motor 29.

[0071] Variable control of the speed and acceleration of the drive unit does not need to be performed.

[0072] The drive unit subject to power control according to the present invention may be a motor other than the drum drive motor 29. The present invention is applicable to any drive unit involved in the transport of cargo that is capable of generating regenerative power. For example, when regenerative power is generated from the travel motor 15a of the travel unit 15, the battery B may be charged by both the regenerative power and the power generated by the generator 41. When regenerative power is generated from the traverse motor 27 of the trolley 18, the battery B may be charged by both the regenerative power and the power generated by the generator 41.

[0073] The higher-level operating system 200 may be a component within the RTG crane system 100 and may be included in the crane system 100.

[0074] 3...Container (cargo), 10...RTG crane, 15...Traction unit, 16...Leg unit, 17...Crane girder, 18...Trolley, 25...Auxiliary equipment, 29...Drum drive motor (drive unit), 41...Generator, 42...Engine converter, 43...Inverter drive, 44...Battery converter, 50...Battery unit, 60...Crane control device (crane control unit), 65...Power control unit, 66...Drive control unit, 90...System control device (system control unit), 100...RTG crane system, B...Battery.

Claims

1. An RTG crane equipped with a drive unit for transporting cargo and capable of automatic operation, comprising: a battery for supplying power to the drive unit; a generator for charging the battery; and a crane control unit for controlling the drive unit, wherein the crane control unit estimates the charge level of the battery and controls at least one of the speed and acceleration of the operation by the drive unit based on the charge level.

2. The RTG crane according to claim 1, wherein when regenerative power is generated from the drive unit, the battery can be charged by both the regenerative power and the power generated by the generator.

3. The RTG crane according to claim 2, wherein the crane control unit estimates the charge level of the battery and determines the ratio of the power supplied by the battery to the power generated in the drive unit based on the charge level.

4. The RTG crane according to claim 2, wherein the crane control unit estimates the charge amount of the battery, charges the battery using only the regenerative power when the charge amount is equal to or greater than a predetermined reference value, and charges the battery using both the regenerative power and the power generated by the generator when the charge amount is lower than the reference value.

5. The RTG crane according to claim 1, comprising: a pair of legs having a running section at their lower end; a crane girder connecting the upper ends of the pair of legs; and a trolley capable of traversing along the crane girder, wherein the crane control unit staggers the timing of the trolley's traversal and the legs' movement based on the charge amount.

6. An RTG crane system comprising a plurality of RTG cranes according to any one of claims 1 to 5, the system comprising a system control unit for controlling the RTG cranes, wherein the system control unit estimates the current charge level of the battery in each of the RTG cranes, and selects an RTG crane to perform the transport operation based on the estimated current charge level of the battery.

7. The RTG crane system according to claim 6, wherein the system control unit estimates the battery charge level at the end of the transport operation from the current battery charge level and the work content of the transport operation, and selects an RTG crane to perform the transport operation based on the estimated battery charge level at the end of the transport operation.

8. The RTG crane system according to claim 6, wherein the system control unit obtains the weight of the load and selects an RTG crane to perform the transport operation based on the weight.

9. The RTG crane system according to claim 6, wherein the system control unit estimates the degree of battery degradation in each of the RTG cranes and preferentially assigns the transport work to the RTG crane with the highest estimated degree of degradation.

10. An RTG crane control method for controlling an RTG crane capable of automatic operation, comprising a drive unit for transporting cargo, a battery for supplying power to the drive unit, and a generator for charging the battery, wherein the method estimates the charge level of the battery and controls at least one of the speed and acceleration of the operation by the drive unit based on the charge level.

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