JP7291912B2 - control system and crane - Google Patents

Description

TECHNICAL FIELD The present invention relates to a control system and a crane, and more particularly to a control system and a crane that keep the drive shaft of an electric motor stopped.

A crane control device has been proposed in which a mechanical brake device mechanically brakes the rotation of the drive shaft of the electric motor to keep the drive shaft of the electric motor stopped (see, for example, Patent Document 1). When a problem occurs in the circuit that supplies current to the mechanical braking device, this control device forcibly stops the supply of current to the mechanical braking device, thereby activating the mechanical braking device and stopping the drive shaft. holds the state.

JP 2017-143648 A

However, the device described in Patent Literature 1 does not take any countermeasure against mechanical failure of the mechanical brake device. Therefore, a mechanical failure occurs in the mechanical brake device, and the mechanical brake device does not operate and the rotation of the drive shaft of the electric motor cannot be braked. It is not possible to respond to situations where rotation cannot be braked.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a control system and a crane in which the drive shaft of the electric motor is kept stopped even if a mechanical failure occurs in the mechanical braking device.

A control system according to the present invention for achieving the above objects includes a control device connected to an inverter for controlling the driving of an electric motor and a mechanical braking device for mechanically braking the rotation of the drive shaft of the electric motor. A system comprising a drive parameter acquisition device for acquiring a drive parameter relating to the drive of the electric motor , and a brake operation acquisition device for acquiring the operating state of the mechanical brake device, wherein the electric motor controlled by the inverter by the control device. The drive state includes a stop state in which the drive shaft stops rotating without generating torque, a power running state in which the drive shaft is driven to rotate and outputs driving force, and a driving state in which the drive shaft is driven to rotate and outputs braking force. and a pre-excitation state in which torque based on the drive parameter acquired by the drive parameter acquisition device is generated to stop the rotation of the drive shaft , and the control device responds to a stop command. and a control for issuing a command to operate the mechanical brake device based on the When a pre-brake operation condition indicating that no braking force is applied to stop the rotation of the drive shaft is established, the control for causing the inverter to bring the electric motor into the pre-excited state is stopped . It is characterized in that the operation is performed after the command is issued and before the rotational speed of the drive shaft becomes zero .

A crane according to the present invention for achieving the above object is characterized in that it comprises the above-described control system, and is configured such that the electric motor rotates a drum around which a cord-like body is wound.

According to the present invention, by controlling the electric motor to be in the pre-excited state as a backup for the mechanical brake device, even if a mechanical failure occurs in the mechanical brake device, the electric motor is in the pre-excited state and the drive shaft rotates. can be electrically braked to keep the drive shaft stopped.

1 is a combination of a configuration diagram illustrating an embodiment of a crane and a block diagram illustrating an embodiment of a control system included in the crane; FIG. FIG. 4 is a flow diagram illustrating a method of controlling a crane by a control system; FIG. 3 is a flow diagram following I in FIG. 2; FIG. 4 is a flowchart following II in FIG. 3; FIG. 5 is a flow diagram illustrating a control method performed in parallel with the control method shown in FIGS. 2 to 4; FIG.

Embodiments of the control system and crane of the present disclosure are described below. In the drawings, electrical connections are indicated by dashed-dotted lines, and include wired connections via signal lines and wireless connections via wireless communication equipment.

As illustrated in FIG. 1, the crane 1 of this embodiment includes a control system 10 and performs cargo handling work at a container terminal. The crane 1 includes a drum 4 around which a cord-like body 3 with a suspended body 2 is wound, an electric motor 6 that rotates the drum 4 via a transmission 5, and an inverter 7 that controls the driving of the electric motor 6. and a mechanical braking device 9 for mechanically braking the rotation of the drive shaft 8 of the electric motor 6 .

The crane 1 is limited in its type as long as it can lift and lower the suspended body 2 by winding and unreeling the rope 3 with a drum 4 that is rotationally driven by an electric motor 6 controlled by an inverter 7. isn't it. Examples of the crane 1 include a gantry crane, a wharf crane, and an unloader, each of which has a girder supported above a leg structure and a trolley that moves along the direction in which the girder extends. A gantry crane is a crane configured so that a girder straddles a storage lane for storing containers and performs cargo handling work between the storage lane and a transport vehicle. A quayside crane is a crane configured to have a girder protruding to the sea side and performs cargo handling work between a ship and a truck. An unloader is a crane whose girder protrudes toward the sea, and which handles bulk cargo such as iron ore and coal between a ship and a hopper. Examples of the crane 1 include a jib crane without a girder or a trolley and an overhead crane without a leg structure.

The hoisting body 2 is a hoisting tool and a hoisted load (for example, a container) when the hoisting tool suspended on the rope-like body 3 is joined to the hoisted load, and when the hoisting tool is not joined to the hoisted load It is a hanging tool. A spreader for containers is exemplified as a lifting device, but it is not particularly limited, and a grab bucket, a hook, or a coil lifter may be used.

The electric motor 6 is composed of a servomotor capable of controlling the rotational speed Vx of the drive shaft 8 as well as the position θx of the drive shaft 8 . The electric motor 6 of this embodiment is constituted by an induction motor among servo motors. The driving state of the electric motor 6 is controlled via an inverter 7, and the driving states controlled by the inverter 7 include a stopped state, a power running state, a braking driving state, and a pre-excitation state.

The stopped state is a state in which the electric motor 6 does not generate torque and the rotation of the drive shaft 8 is stopped. The stopped state is a state in which power is not supplied from the inverter 7 to the electric motor 6 . The power driving state is a state in which the drive shaft 8 rotates and outputs a driving force for rotating the drum 4 in the direction in which the cord-like body 3 is wound up. The power running state is a state in which power is supplied from the inverter 7 to the electric motor 6 . The braking drive state is a state in which the drum 4 rotates in the direction in which the cord-like body 3 is drawn out, and the drive shaft 8 rotates along with the rotation to apply a braking force. An example of the braking drive state is regenerative braking in which the drive shaft 8 is rotationally driven to generate regenerative power. When the braking drive state is regenerative braking, the electric power generated by the electric motor 6 is supplied to the inverter 7 and stored in a battery (not shown) mounted on the crane 1, and the resistance of the braking resistor mounted on the crane 1. or is stored in a battery installed outside the crane 1 via a busbar or a power supply cable. In addition, reverse phase braking (also referred to as plucking) and single phase braking are also exemplified as the braking drive state.

The pre-excitation state is obtained by the electric motor 6 based on the driving parameters (the position θx of the drive shaft 8 and the rotation speed Vx) regarding the driving of the electric motor 6 acquired by the driving parameter acquisition device (the position acquisition device 13 and the rotation speed acquisition device 14) to be described later. This is a state in which the rotation of the drive shaft 8 is stopped while torque is being generated. In the pre-excitation state, electric power is supplied from the inverter 7 to the electric motor 6 . Examples of the pre-excitation state include a state of speed control (also referred to as zero speed control) and a state of position control (also referred to as servo lock control). The speed control in the pre-excitation state is control in which the rotation speed Vx of the drive shaft 8 is used as a driving parameter and the rotation speed Vx is held at zero by the inverter 7 . The position control is to use the position (more specifically, the angular position) of the drive shaft 8 as a drive parameter and cause the inverter 7 to hold the position of the drive shaft 8 . The pre-excitation state may be a state in which the rotation of the drive shaft 8 is stopped, and may be a state in which the speed is controlled or a state in which the position is controlled.

The mechanical brake device 9 is a brake that brakes the rotation of the drive shaft 8 of the electric motor 6 by frictional force. The mechanical braking device 9 of this embodiment is composed of an electrohydraulic thruster disk braking device. In the electro-hydraulic type thruster disk brake device, when the power supply is stopped, the hydraulic pressure is released and the thruster is driven, and the brake lining is pressed against the disk fixed directly to the drive shaft 8 . When electric power is supplied, the thruster is driven by hydraulic pressure to move the brake lining away from the disk and the rotation of the drive shaft 8 is released from the brake. The mechanical brake device 9 may be any device as long as it brakes the rotation of the drive shaft 8 by frictional force when the supply of electric power is stopped, and releases the braking of the rotation of the drive shaft 8 when the electric power is supplied. It is not limited to electrohydraulic thruster disc brakes.

The control system 10 of the present embodiment is provided in the crane 1, and controls the inverter 7 and the mechanical brake device 9 to control the winding and unreeling of the cord-like body 3 from which the suspended body 2 is suspended by the drum 4. be. It should be noted that the control system 10 is not limited to the one applied to the drum 4 for winding and unreeling the rope-like body 3 for suspending the suspended body 2 in the crane 1, but is applied to the drum for raising and lowering the girder and the drum for traversing the trolley. may be applied. In addition, the control system 10 is not limited to the drum as the object to be rotationally driven by the electric motor 6 and is not limited to the crane 1 .

The control system 10 includes a control device 11 , an operation device 12 , a position acquisition device 13 , a rotation speed acquisition device 14 , a brake operation acquisition device 15 and a warning device 16 . The control device 11 is electrically connected to each of the inverter 7, the mechanical brake device 9, the operation device 12, the braking operation acquisition device 15, and the warning device 16, and is connected to the electric motor 6 and the position acquisition device 13 via the inverter 7. and the rotational speed acquisition device 14, respectively. Note that each of the position acquisition device 13 and the rotation speed acquisition device 14 may be electrically connected directly to the control device 11 without the inverter 7 .

The control device 11 is hardware composed of a central processing unit (CPU) that performs various types of information processing, an internal storage device capable of reading and writing programs and information processing results used for performing the various types of information processing, and various interfaces. is. When the control device 11 is installed on the crane 1, it is installed in a machine room or a trolley (not shown). Note that the control device 11 is not limited to being installed on the crane 1 and may be installed at a remote location away from the crane 1 .

The operation device 12 is used by the driver to operate the console 12b based on the information displayed on the display device 12a, and to transmit the drive command C1 and the stop command C2 to the control device 11 as the operation signals. The drive command C1 is an operation signal that brings the electric motor 6 into a power running state or a braking drive state, and is an operation signal that rotationally drives the drive shaft 8 . It is assumed that the drive command C1 includes an acceleration command and a deceleration command. The stop command C2 is an operation signal that actuates the mechanical brake device 9 and stops the electric motor 6, and is an operation signal that stops the rotation of the drive shaft 8 and maintains the stopped state of the drive shaft 8. The stop command C2 in this embodiment is also an operation signal for bringing the electric motor 6 into the pre-excitation state. Like the control device 11 , the operating device 12 may be installed in a machine room or a trolley (not shown) when installed in the crane 1 and may be installed in a remote location away from the crane 1 . In addition, instead of the operation device 12 operated by the driver, a host control device for automatically controlling the crane 1 may be provided, and the drive command C1 and the stop command C2 may be transmitted from the host control device to the control device 11. good.

The position acquisition device 13 functions as a drive parameter acquisition device and is a device that acquires the position (more specifically, the angular position) θx of the drive shaft 8 . A rotary encoder and a potentiometer are exemplified as the position acquisition device 13 . The rotation speed acquisition device 14 functions as a drive parameter acquisition device and also functions as a brake parameter acquisition device that acquires a brake parameter relating to the effectiveness of the mechanical brake device 9 , and is a device that acquires the rotation speed Vx of the drive shaft 8 . A rotary encoder and a potentiometer are exemplified as the rotational speed acquisition device 14 . The drive parameter acquisition device may be configured by a single device having the function of the position acquisition device 13 and the function of the rotation speed acquisition device 14 . Further, in the crane 1, the drive parameter acquisition device calculates the position θx and the rotation speed Vx of the drive shaft 8 based on the winding amount and the extension amount of the cord-like body 3, or the position and rotation speed of the drum 4. may be configured.

In the present embodiment, the effectiveness of the mechanical brake device 9 indicates a state in which the mechanical brake device 9 operates and braking force is actually applied to the drive shaft 8 . Examples of brake parameters include the change in deceleration of the drive shaft 8 before and after the mechanical brake device 9 is activated, and the braking force applied to the drive shaft 8 . In this embodiment, the change in deceleration of the drive shaft 8 according to the rotation speed Vx of the drive shaft 8 is used as the brake parameter. A load cell is exemplified as a brake parameter device when the braking force applied to the drive shaft 8 is used as the brake parameter.

The brake operation acquisition device 15 is a device that acquires the operating state of the mechanical brake device 9, and is preferably a device that acquires that the mechanical brake device 9 has been operated to apply a braking force to the drive shaft 8. . A limit switch and a laser rangefinder are exemplified as the braking operation acquiring device 15 . For example, a limit switch may be installed in the drive mechanism of the mechanical brake device 9 to detect the operating state of the drive mechanism when the brake linings are actuated to contact the disc. A laser rangefinder is installed to detect the distance between the brake lining and the disc. In this embodiment, the actuation of the mechanical brake device 9 indicates that the drive mechanism of the mechanical brake device 9 has been driven. In other words, it is assumed that the operation of the mechanical brake device 9 is not synonymous with the effect of the mechanical brake device 9 . The brake operation acquiring device 15 outputs ON as the operation signal C3 when detecting that the mechanical braking device 9 is operated, and outputs OFF as the operating signal C3 when detecting that the mechanical braking device 9 is not operated. As the brake actuation acquisition device 15, a device that acquires the state in which the braking of the drive shaft 8 is released without the mechanical brake device 9 being operated may be used. It may be acquired that the mechanical braking device 9 has been activated when it is not acquired.

A warning device 16 is provided together with the operating device 12 . A device that emits a warning sound is exemplified as the warning device 16, but the display device 12a or a display device different from the display device 12a may be configured by a device that displays a warning on a screen or a device that vibrates the driver. good too. Also, the warning device 16 may be composed of a device that gives a warning by blinking light.

The control device 11 has a brake control section 17, an electric motor control section 18, and a warning control section 19 as functional elements for maintaining a state in which the drive shaft 8 of the electric motor 6 is stopped. Each functional element is stored as a program in the internal storage device of the control device 11, read out by the central processing unit, and executed as appropriate. In addition to the program, each functional element may also be an electric circuit that functions independently. Alternatively, each functional element may be configured with a programmable logic controller (PLC), and the control device 11 may be an aggregate of a plurality of PLCs.

The brake control unit 17 is a functional element that receives a stop command C2 and performs control to operate the mechanical brake device 9 based on the stop command C2. Specifically, when the stop command C2 is input, the brake control unit 17 stops supplying electric power to the mechanical brake device 9 and operates the mechanical brake device 9 to brake the rotation of the drive shaft 8. . Further, when the drive command C1 is input and the stop command C2 is canceled, the brake control unit 17 supplies electric power to the mechanical brake device 9 to release the mechanical brake device 9 from braking the rotation of the drive shaft 8. operate as

The brake control unit 17 is configured to operate the mechanical brake device 9 when the rotation speed Vx of the drive shaft 8 becomes slower than a preset first set speed Va when the stop command C2 is input. It is desirable that Specifically, the brake control unit 17 receives the rotation speed Vx of the drive shaft 8 acquired by the rotation speed acquiring device 14 in addition to the stop command C2. When the stop command C2 is input to the brake control unit 17, the motor control unit 18 causes the inverter 7 to power the electric motor 6 when the input rotation speed Vx of the drive shaft 8 is equal to or higher than the first set speed Va. Control is performed to reduce the rotational speed Vx of the drive shaft 8 by reducing the driving force output in the driving state or increasing the braking force applied in the braking driving state. Next, the brake control unit 17 stops supplying electric power to the mechanical brake device 9 to operate the mechanical brake device 9 when the rotation speed Vx of the drive shaft 8 becomes slower than the first set speed Va.

The first set speed Va is a value set in advance through experiments and tests, and is stored in the internal storage device of the control device 11 . The first set speed Va is set to a value that allows determination of the state immediately before the rotational speed Vx of the drive shaft 8 is reduced by the electric motor 6 and the rotation of the drive shaft 8 is stopped. The first set speed Va is desirably set based on the rated speed of the electric motor 6, and has a positive correlation with the rated speed. Note that the rated speed is a speed preset according to the types of the electric motor 6 and the inverter 7 . If the first set speed Va is set to zero, the operation of the mechanical brake device 9 is slowed down, and there is a possibility that the drive shaft 8 cannot be stopped at the desired timing. Further, if the first set speed Va is set to a speed higher than 10% of the rated speed, when the mechanical braking device 9 is actuated, the braking will be abrupt, reducing the durability of the mechanical braking device 9 and causing suspension. There is a risk that the body 2 will shake greatly. Therefore, the first set speed Va is preferably set to a speed higher than zero and slower than 10% of the rated speed, more preferably set to a speed of 4% to 6% of the rated speed. . If the first set speed Va is set to a speed that is 4% to 6% of the rated speed, it is more advantageous for avoiding delayed operation of the mechanical brake device 9 and sudden braking.

The motor control unit 18 is a functional element that receives the driving command C1 and controls the driving state of the motor 6 via the inverter 7 based on the driving command C1. When the stop command C2 is input, the electric motor control unit 18 controls the inverter 7 to pre-excite the electric motor 6 as a backup for the mechanical brake device 9 based on the pre-brake operation condition, and at the same time, according to the pre-brake release condition. It is a functional element that controls the inverter 7 to cancel the pre-excitation state of the electric motor 6 based on the above. In addition, while the electric motor control unit 18 causes the inverter 7 to pre-excite the electric motor 6, even if a command other than the drive command C1 for the electric motor 6 is input, the electric motor 6 does not rotate the drum 4. It is a functional element that controls to prohibit Acquired values acquired by the position acquisition device 13 , the rotation speed acquisition device 14 , and the brake operation acquisition device 15 are input to the electric motor control unit 18 . The motor controller 18 has a timer 18a.

The preliminary brake activation condition is established when the mechanical brake device 9 is not activated, or when the mechanical brake device 9 is activated but the mechanical brake device 9 does not apply a braking force to stop the rotation of the drive shaft 8. do. In this embodiment, the electric motor control unit 18 determines that the mechanical brake device 9 is not operating when the actuation signal C3 output from the brake actuation acquisition device 15 is OFF. Further, the electric motor control unit 18 sets the rotation speed Vx acquired by the rotation speed acquisition device 14 functioning as a brake parameter acquisition device when the mechanical brake device 9 is operated to a speed lower than the first set speed Va in advance. If the vehicle does not decelerate to the second set speed Vb, it is determined that the braking force is not applied. Note that when the brake parameter acquisition device is composed of a load cell, the electric motor control unit 18 may determine that the braking force is not applied when the braking force detected by the load cell is lower than a preset threshold value. . Further, the electric motor control unit 18 controls the braking force when the deceleration of the drive shaft 8 after the mechanical brake device 9 is activated does not become larger than the deceleration of the drive shaft 8 before the mechanical brake device 9 is activated. It may be determined that is not given. In this embodiment, the mechanical brake device 9 is configured to operate when the rotational speed Vx of the drive shaft 8 becomes equal to or lower than the first set speed Va. Therefore, it is possible to determine that the braking force is not applied when the rotational speed Vx of the drive shaft 8 does not decrease to the second set speed Vb when the mechanical brake device 9 is actuated.

The second set speed Vb is set in advance by experiments and tests, is a value set to a speed slower than the first set speed Va, and is stored in the internal storage device of the control device 11 . The second set speed Vb is used for judging whether or not the pre-brake operation condition is established, and is also used for timing the electric motor 6 to be pre-excited. The second set speed Vb is a value at which it can be determined that the rotation speed Vx of the drive shaft 8 is decelerated so that the rotation of the drive shaft 8 is stopped by the operation of the mechanical brake device 9, that is, the mechanical brake device 9 is set to a value that can determine that the deceleration of the drive shaft 8 has increased due to the operation of . The second set speed Vb is a value that allows determination of the state immediately before the rotational speed Vx of the drive shaft 8 is reduced by the electric motor 6 and the rotation of the drive shaft 8 is stopped. The value is set to a value that allows determination of a state in which the inverter 7 is not overloaded when it is turned on. Like the first set speed Va, the second set speed Vb is desirably set based on the rated speed of the electric motor 6, and has a positive correlation with the rated speed. If the second set speed Vb is set to zero, the response delay in the control system slows down the operation of the backup brake, and there is a possibility that the drive shaft 8 cannot be stopped at the desired timing. Further, if the second set speed Vb is set to a speed of 5% or more of the rated speed, the inverter 7 may be overloaded when the backup brake is operated, and the backup brake may stop operating. Therefore, the second set speed Vb is a speed faster than zero, preferably set to a speed slower than 5% of the rated speed, and more preferably set to a speed of 1% to 3% of the rated speed. . If the second set speed Vb is set to a speed that is 1% to 3% of the rated speed, it is more advantageous for avoiding a delay in the actuation of the backup brake and overloading the inverter 7 .

The pre-brake release condition is when it is determined that the drive command C1 is input by the operating device 12 while the electric motor 6 is being controlled to the pre-excited state, or after the electric motor 6 enters the pre-excited state counted by the timer 18a. Established when it is determined that the elapsed time tx has reached the preset release period ta.

The cancellation period ta is a value set in advance by experiments and tests, and is stored in the internal storage device of the control device 11 . The release period ta is set to a value that allows determination of overload of the inverter 7 when the electric motor 6 is driven in the pre-excitation state. It is desirable to set the cancellation period ta based on the capacity of the inverter 7 and has a positive correlation with the capacity of the inverter 7 .

When the electric motor control unit 18 pre-excites the electric motor 6, the warning control unit 19 causes the warning device 16 to warn the driver. It is a functional element that controls the

As illustrated in FIGS. 2 to 5, the control method of the crane 1 of this embodiment will be described as a function of the control system 10. FIG. This control method is started when the operation device 12 is operated to issue a stop command C2. The position acquisition device 13, the rotation speed acquisition device 14, and the braking operation acquisition device 15 each acquire an acquired value each time a preset cycle elapses. Assume that one cycle elapses when the order returns to the upper step in the control flow and when those devices acquire acquired values. At the start of the control flow, it is assumed that the speed of vertical movement of the suspended body 2 is decelerated at a constant deceleration. The state in which the speed of the vertical movement of the suspended body 2 is decelerated at a constant deceleration is the speed at which the drum 4 winds up the cord-like body 3 by controlling the electric motor 6 to the power driving state when the suspended body 2 is raised. may be decelerated, or the speed at which the drum 4 lets out the cord-like body 3 may be decelerated by controlling the electric motor 6 to be in a braking drive state when the suspended body 2 is lowered. It is also assumed that the control method illustrated in FIGS. 2 to 4 and the control method illustrated in FIG. 5 are processed in parallel.

As illustrated in FIG. 2, when a stop command C2 is generated by the operating device 12, the rotation speed acquisition device 14 acquires the rotation speed Vx of the drive shaft 8 (S110). Next, the brake control unit 17 determines whether or not the obtained rotation speed Vx is lower than the preset first set speed Va (S120). If it is determined that the rotation speed Vx is lower than the first set speed Va (S120: YES), the brake control unit 17 stops supplying electric power to the mechanical brake device 9 so as to brake the rotation of the drive shaft 8. A command to operate the mechanical brake device 9 is issued (S130). On the other hand, if it is determined that the rotation speed Vx is equal to or higher than the first set speed Va (S120: NO), the process returns to step S110.

As illustrated in FIG. 3, when a command to operate the mechanical brake device 9 is issued, the brake operation acquisition device 15 acquires that the mechanical brake device 9 has been operated and transmits an operation signal C3 (S210). In this step S210, the actuation signal C3 is turned on when the mechanical brake device 9 is activated, and the actuation signal C3 is turned off when the mechanical brake device 9 is not activated. Next, the electric motor control unit 18 determines whether or not the preliminary brake activation condition is satisfied.

Specifically, the motor control unit 18 determines whether or not the actuation signal C3 is on. (S220). When it is determined that the actuation signal C3 is ON (S220), the rotation speed acquisition device 14 acquires the rotation speed Vx of the drive shaft 8 (S230). Next, the electric motor control unit 18 determines whether or not the obtained rotational speed Vx has decreased to the preset second set speed Vb (S240). Note that steps S230 and S240 may be performed after a predetermined time (for example, 1 to 2 seconds) has elapsed since the mechanical braking device 9 was activated.

If it is determined that the actuation signal C3 is on (S220: YES) and if it is determined that the rotational speed Vx has decreased to the second set speed Vb (S240: YES), the preliminary brake actuation condition is not satisfied, and the electric motor control section 18 causes the inverter 7 to stop the electric motor 6 (S250), and this control flow ends. The state in which step S250 is completed is a state in which the drive shaft 8 of the electric motor 6 is stopped by the mechanical brake device 9 and maintained.

On the other hand, if it is determined that the actuation signal C3 is off (S220: NO), or if it is determined that the actuation signal C3 is on and the rotation speed Vx is not decelerated to the second set speed Vb (S220: YES, S240 : NO), the condition for operating the preliminary brake is established, and the motor control unit 18 controls the inverter 7 to bring the motor 6 into the preliminary excitation state.

Specifically, when the preliminary brake operation condition is satisfied, the rotation speed acquisition device 14 acquires the rotation speed Vx of the drive shaft 8 (S260). Next, the electric motor control unit 18 determines whether or not the obtained rotational speed Vx has decreased to the preset second set speed Vb (S270). If it is determined that the rotation speed Vx has not decreased to the second set speed Vb (S270: NO), the process returns to step S260. On the other hand, when it is determined that the rotation speed Vx has decreased to the second set speed Vb (S270: YES), the position acquisition device 13 acquires the position θx of the drive shaft 8 (S280). Next, the electric motor control unit 18 causes the inverter 7 to set the electric motor 6 to the position control (servo lock control) state of the pre-excitation state so as to hold the acquired position θx (S290), and the mechanical brake device 9 As a backup, an electric brake is operated by the pre-excited state of the electric motor 6 . It should be noted that the motor 6 of the inverter 7 may be placed in the speed control (zero speed control) state of the pre-excitation state when the pre-brake actuation condition is established.

It should be noted that the motor 6 is kept in the speed control state of the pre-excitation state by the inverter 7 until the rotational speed Vx of the drive shaft 8 becomes zero, and steps S280 and S290 are performed when the rotational speed Vx becomes zero. can be That is, when the preliminary brake operation condition is satisfied, the position θx of the drive shaft 8 may be held by the position control after the rotation speed Vx is reduced to zero by the speed control.

As illustrated in FIG. 4, when the electric motor 6 is pre-excited as a backup for the mechanical brake device 9, the warning controller 19 issues a warning to the driver via the warning device 16 (S310). Next, the electric motor control unit 18 determines whether or not the preliminary brake release condition is satisfied. Specifically, the electric motor control unit 18 determines whether or not the drive command C1 has been issued by the operation device 12 (S320). In addition, the electric motor control unit 18 counts the time tx that has elapsed since the electric motor 6 entered the pre-excitation state, and determines whether or not the counted time tx has reached the preset cancellation period ta (S330, S340). .

When it is determined that the drive command C1 has been issued (S320: YES) and the warning device 16 stops warning (S350), the preliminary brake release condition is satisfied and the electric motor control unit 18 causes the inverter 7 to pre-excit the electric motor 6. The state is released, and the inverter 7 puts the electric motor 6 in the power running state or the braking state based on the drive command C1 (S360), and this control flow ends.

On the other hand, if it is determined that the drive command C1 will not be issued (S320: NO) before the counted time tx reaches the release period ta (S330: YES), the preliminary brake release condition is met without the warning being stopped. When established, the electric motor control unit 18 causes the inverter 7 to release the pre-excitation state of the electric motor 6, and causes the inverter 7 to put the electric motor 6 into a braking drive state so as to lower the suspended body 2 (S370). By this step S370, the suspended body 2 descends and lands at a predetermined position. Next, the motor controller 18 causes the inverter 7 to stop the motor 6 (S380). The warning device 16 then stops warning (S390) and the control flow ends.

As illustrated in FIG. 5, when the electric motor 6 is set to the pre-excited state as a backup for the mechanical brake device 9 (S410: YES), the electric motor control unit 18 controls the operation other than the vertical movement in the drive command C1 of the operation device 12. is prohibited (S420), and this control flow ends. The motion other than the vertical movement is exemplified by, for example, a traversing motion of a trolley (not shown), a traveling motion by a travel device of the crane 1, or a swinging motion of a jib (not shown). Therefore, in step S420, the electric motor control section 18 issues a control prohibition command to the control section that controls the traversing motion of the trolley, the traveling motion of the traveling device, the turning motion of the jib, and the like.

On the other hand, if the electric motor 6 is not in the preliminary example state (S410: NO), the electric motor control section 18 cancels prohibition of operations other than vertical movement (S430), and this control flow ends. In this step S430, the electric motor control section 18 issues a control permission command to the control section that controls the traversing motion of the trolley, the traveling motion of the traveling device, the turning motion of the jib, and the like.

As described above, the crane 1 equipped with the control system 10 is configured to control the inverter 7 to bring the electric motor 6 into the pre-excitation state as a backup for the mechanical brake device 9 . Therefore, according to the crane 1, even if a mechanical failure occurs in the mechanical brake device 9 and the mechanical brake device 9 does not operate normally, or even if the mechanical brake device 9 operates, the drive shaft 8 cannot be operated. Even if the rotation cannot be braked, the motor 6 is pre-excited and the electric brake is activated, so that the rotation of the drive shaft 8 can be maintained in a stopped state. That is, by having an electric brake as a backup function against mechanical failure of the mechanical brake device 9, safety in cargo handling work can be improved.

The speed control in the pre-excitation state of the electric motor 6 may deviate the position of the drive shaft 8 stopped for the speed control. On the other hand, the position control can suppress the displacement of the stopped drive shaft 8 for the control of position control. Therefore, it is desirable that the control system 10 performs position control so as to maintain the acquired position θx of the drive shaft 8 when the electric motor 6 is brought into the pre-excitation state. Using the position-controlled electric motor 6 as a spare for the mechanical brake device 9 in this way is advantageous in improving the accuracy of the stop position.

Control system 10 preferably accounts for response delays. In this embodiment, the response delay is the delay from when the controller 11 issues a command to the inverter 7 to bring the electric motor 6 into the pre-excited state until the electric motor 6 actually comes into the pre-excited state. It is indicated by the transfer characteristic indicated by the combination of elements and multi-order lag elements. Therefore, the control system 10 preferably controls the inverter 7 to pre-excite the electric motor 6 before the acquired rotation speed Vx of the drive shaft 8 becomes zero. In the present embodiment, the timing at which the electric motor 6 is brought into the pre-excitation state is the timing at which the rotation speed Vx of the drive shaft 8 becomes slower than the second set speed Vb set to a speed higher than zero. In this way, the second set speed Vb, which is set to a speed higher than zero, is used to control the timing of bringing the electric motor 6 into the pre-excited state, so that the electric motor 6 can be driven before the rotation speed Vx of the drive shaft 8 becomes zero. can be pre-excited. This is advantageous for avoiding delays in the activation of the electric brake due to response delays.

It is desirable that the control system 10 warns the driver that the electric motor 6 has been pre-excited by means of a warning device 16 when the electric motor 6 is pre-excited as a backup for the mechanical brake device 9 . When the time tx elapsed after the electric motor 6 is pre-excited as a backup for the mechanical brake device 9 reaches the release period ta, the inverter 7 becomes overloaded and the pre-excitation state of the electric motor 6 is released. Therefore, by warning that the electric motor 6 is in the pre-excitation state by means of the warning device 16, it is advantageous to encourage the driver to operate the operation device 12 and issue the drive command C1.

If the drive command C1 is not issued from the operation device 12 before the time tx reaches the release period ta, the motor control unit 18 automatically lowers the suspended body 2 to land on the floor. state is preferred.

In addition to determining the operation status of the mechanical brake device 9 acquired by the brake operation acquisition device 15, the control system 10 determines whether the mechanical brake device 9 has applied a braking force to stop the rotation of the drive shaft 8. It is desirable to determine whether or not This makes it possible to cope with a situation where the mechanical braking device 9 is activated by the stop command C2 but the rotation of the drive shaft 8 cannot be braked.

For example, when the electric motor 6 is in a pre-excited state and the trolley is caused to travel, the suspension body 2 may vibrate. If the electric motor 6 and the inverter 7 are overloaded due to this vibration, there is a possibility that the drive shaft 8 cannot be kept in a stopped state. Therefore, it is desirable that the control system 10 prohibits any operation other than the rotational driving of the drum 4 when the electric motor 6 is pre-excited. In this way, when the electric motor 6 is in the pre-excited state, prohibiting operations other than rotational driving of the drum 4 is advantageous in avoiding overloading of the electric motor 6 and the inverter 7. It is advantageous to keep the rotation stopped.

1 Crane 2 Suspended body 3 Cable body 4 Drum 6 Electric motor 7 Inverter 8 Drive shaft 9 Mechanical brake device 10 Control system 11 Control device 13 Position acquisition device 14 Rotation speed acquisition device 15 Braking operation acquisition device

Claims (6)

A control system comprising a control device connected to an inverter for controlling driving of an electric motor and a mechanical braking device for mechanically braking rotation of a drive shaft of the electric motor,
a driving parameter acquiring device for acquiring a driving parameter related to driving the electric motor; and a brake operation acquiring device for acquiring an operating state of the mechanical braking device,
The drive state of the electric motor controlled by the inverter by the control device includes a stop state in which the rotation of the drive shaft is stopped without generating torque, and a power running state in which the drive shaft is driven to rotate and output driving force. , a braking drive state in which the drive shaft is rotationally driven to apply a braking force, and a pre-excitation state in which torque based on the drive parameter acquired by the drive parameter acquisition device is generated and rotation of the drive shaft is stopped. , consisting of
The control device controls issuing a command to operate the mechanical braking device based on a stop command, and after issuing the command, the mechanical braking device does not operate or the mechanical braking device operates. a control for causing the inverter to bring the electric motor into the pre-excited state when a pre-brake operating condition indicating that braking force is not applied to stop the rotation of the drive shaft by the mechanical brake device is satisfied; and before the rotation speed of the drive shaft becomes zero after the stop command is issued. A rotation speed acquisition device for acquiring the rotation speed of the drive shaft as the drive parameter acquisition device,
The control for issuing a command to operate the mechanical brake device is a first set speed in which the rotation speed of the drive shaft acquired by the rotation speed acquisition device after the stop command is input is set to a speed higher than zero. is done later than
In the control for causing the pre-excitation state, the operating state of the mechanical braking device acquired by the braking operation acquisition device and the rotation speed of the drive shaft acquired by the rotation speed acquisition device are lower than the first set speed. and determining whether or not the vehicle has decelerated to a second set speed set to a speed higher than zero, wherein the control device determines whether or not the preliminary brake operating condition has been established. The control system described in . A position acquisition device that acquires the position of the drive shaft as the drive parameter acquisition device,
3. The control according to claim 1 or 2 , wherein the drive parameter is the position of the drive shaft, and the pre-excitation state is a state in which position control is performed to hold the position of the drive shaft acquired by the position acquisition device. system. 2. The control system according to claim 1, further comprising a warning device for warning a driver that said electric motor is in said pre-excited state as a backup for said mechanical brake device when said electric motor is in said pre-excited state. . A crane comprising the control system according to any one of claims 1 to 4, wherein the electric motor rotates a drum around which a cord-like body is wound. 6. The crane according to claim 5, wherein, while the electric motor is in the pre-excited state, the control device performs control to prohibit operations other than rotational driving of the drum.

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