JP7567114B2 - Method for controlling lifting and lowering of a double rope bucket crane - Google Patents

Description

The present invention relates to a method for controlling the support motor and opening/closing motor to perform the hoisting and lowering operations of a crane equipped with a double rope bucket (hereinafter sometimes simply referred to as a "bucket") whose hoisting device is driven to hoist and lower by two independent motors of equal capacity, a support motor and an opening/closing motor, and which is moved by two types of rope, a support rope and an opening/closing rope, suspended from each of the independent support devices and opening/closing devices.

The operation of the double rope bucket is achieved by manipulating the movement of two types of ropes: the support rope and the opening and closing rope.
In the past, this operation was achieved using a differential reducer or a clutch, but due to issues with the manufacturability and maintainability of the mechanical system, the currently more common method is to electrically control two winding devices that are independent for support and opening and closing.
However, in double rope buckets, where the load balance between support and opening and closing changes depending on the state of the bucket, it is difficult to balance the support and opening and closing ropes, and there was a demand for technology to accurately control the support motor and opening and closing motor to balance the ropes.

To address this issue, various methods for controlling the bucket support motor and the opening and closing motor have been proposed (see, for example, Patent Documents 1 to 4).

JP 2002-128466 A Japanese Patent Application Publication No. 4-358696 Japanese Patent Application Publication No. 1-203194 Japanese Patent Application Publication No. 1-172198

In a conventional double rope bucket crane, for example, when the bucket is open, the support motor bears most of the load of the bucket, and the opening and closing motor bears almost no load of the bucket. For this reason, when an induction motor is used, motor slippage has an effect, and the support motor speed is slower than the opening and closing motor when hoisting, and conversely, the support motor speed is faster than the opening and closing motor when lowering. This speed difference between the support motor and the opening and closing motor is in the direction in which the bucket closes both when hoisting and lowering, and the bucket closes on its own when hoisting and lowering the bucket. For this reason, when the bucket is fully opened to grip loose cargo and lowered, the bucket is almost closed before it lands on the floor, so it is necessary to open the bucket again before the bucket lands on the floor and then grip it.

In addition, when the bucket is closed and gripped, if the support motor speed becomes faster than the opening/closing motor during hoisting, the bucket will open and the gripped bulk cargo will be dropped. Conversely, if the support motor speed becomes slower than the opening/closing motor, the support rope will slacken and the opening/closing device will become overloaded, causing heat generation and damage to the opening/closing motor and opening/closing speed control device.
Conversely, during lowering, if the support motor speed was slower than the opening/closing motor, the bucket would open and drop the bulk cargo it was holding. Conversely, if the support motor speed was faster than the opening/closing motor, the support rope would slacken and the opening/closing device would become overloaded, causing the opening/closing motor and opening/closing speed control device to overheat and break.

In consideration of the problems with the conventional cranes with double rope buckets, the present invention aims to provide an easy-to-use and efficient control of the lifting and lowering of a crane with a double rope bucket by controlling the support motor and opening and closing motor of the double rope bucket according to the condition of the bucket.

In order to achieve the above object, the present invention provides a method for controlling the hoisting and lowering of a crane with a double rope bucket, which controls the hoisting and lowering of a double rope bucket using two independent hoisting devices with equal capacity, a support motor and an opening/closing motor, and includes the following steps:
When the bucket is in a closed state from near the bucket closing deceleration position (a position slightly open from the closed end position) to the closing side (the bucket is judged to be closed and gripping the load, and the speed control characteristics of the support motor and the opening/closing motor when hoisting or lowering in this bucket open/closed state are proportional characteristics that vary the torque proportionally to the amount of speed deviation), the output speeds of the support motor and the opening/closing motor are controlled to slow down in proportion to the load size as the load increases during hoisting, and to speed up in proportion to the load size as the load increases during lowering (at this time, the speed ratio to the load is controlled to be the same for both the support motor and the opening/closing motor, so that the load sharing between the support motor and the opening/closing motor is the same, and hoisting and lowering can be performed while maintaining the load gripped).
When the bucket is in the vicinity of the bucket closing deceleration position (a position slightly open from the closed end position) to the opening side (a position where the load cannot be gripped), control is performed so that the speed deviation is small regardless of the size of the load when hoisting up or lowering (the speed control characteristics of the support motor and opening/closing motor when hoisting up or lowering are set to proportional-integral torque characteristics with respect to the speed deviation amount, thereby reducing the speed deviation amount with respect to the load fluctuation and reducing the speed fluctuation of the support motor and opening/closing motor with respect to the load), and when hoisting down, the speed control range of the opening/closing motor is expanded to a range exceeding the rated speed, and the opening/closing motor is made faster than the support motor. (Because the load factor of the opening/closing motor is low, it is possible to increase the opening/closing speed beyond the rated speed by the amount of spare power of the opening/closing motor, and when the bucket is not in the open end position and the opening/closing position is lowered, the opening/closing motor's lowering speed is made faster than the support motor's lowering speed, exceeding the rated speed, so that the bucket is moved toward the open end position while being lowered.) When the bucket is in the open end position, the speeds of the support motor and the opening/closing motor are made equal, so that the bucket is lowered while maintaining the open end position (when the open end position is reached, the open end position is actively maintained by lowering the bucket while keeping the support motor and the opening/closing motor at the same speed).
It is characterized by:

In this case, when the opening and closing state of the bucket is on the closing side from near the bucket closing deceleration position and the speed or torque of the support motor and the opening and closing motor after acceleration has ended become equal during hoisting and lowering, if there is spare capacity in the motor torque, the speeds can be increased up to the maximum speed that each motor can output for the size of the load at that time.
In particular, when the bucket is closed and gripping the load, and the load sharing after the support motor and the opening/closing motor finish accelerating becomes the same during hoisting, the speed command is increased by the amount that the speed decreased during hoisting due to the proportional characteristic, to make up for the speed decrease, and if the support motor and the opening/closing motor have spare capacity relative to the size of the load, the speeds of the support motor and the opening/closing motor are further increased by the amount of that spare capacity, thereby improving the transport efficiency.

The method for controlling the lifting and lowering of a double rope bucket crane of the present invention appropriately controls the support motor and opening/closing motor according to the state of the bucket, reducing slack in the support rope or opening/closing rope, and enabling effective high-speed operation, providing a double rope bucket crane with stable operation, easy operation, and good transport efficiency.

FIG. 2 is a plan view of a winding device of a crane that controls a double-rope bucket. FIG. 2 is a structural explanatory diagram of a double rope bucket. FIG. 2 is an explanatory diagram of the opening and closing ropes of the double rope bucket. FIG. 4 is an explanatory diagram of the arrangement of open/close position detectors for a double rope type bucket. FIG. 13 is an explanatory diagram of the load sharing between the support motor and the opening/closing motor of the double rope type bucket. FIG. 13 is a torque characteristic diagram of the support motor and the opening/closing motor when the double rope type bucket is not gripped. FIG. 13 is a torque characteristic diagram of the support motor and the opening/closing motor when the double rope type bucket is gripped. FIG. 4 is a control block diagram of a speed control system that generates torque characteristics of a support motor and an opening/closing motor. FIG. 13 is an explanatory diagram of the operation under control when lowering a double rope type bucket. FIG. 13 is an explanatory diagram of a bridge state of the hopper.

The following describes the method for controlling the lifting and lowering of the double rope bucket crane of the present invention with reference to the drawings.

FIG. 1 shows a plan view of a winding device of a crane that operates a double rope bucket.
A support motor HM equipped with a speed detector PG is connected to a support drum HD via a brake BR and a reducer GR, and a support rope HW is wound around the support drum HD.
A load cell LC is attached to a portion that detects the load applied to the support rope HW (for example, the bearing portion of the support tram HD), and a support position detector HP is attached to the shaft of the support drum.
The opening and closing devices are also arranged independently for support and opening and closing, with an opening and closing motor GM with a speed detector PG connected to an opening and closing drum GD via a brake BR and a reducer GR, and an opening and closing rope GW is wound around the opening and closing drum GD. A load cell LC and an opening and closing position detector GP are also attached.

FIG. 2 shows the structure of the double rope bucket, and FIG. 3 shows the opening and closing ropes of the double rope bucket.
The support ropes HW are fixed to the upper sheave box HB and support the entire bucket.
The upper sheave box HB is connected to a connecting rod LL through a pin link structure, and is then connected to the shell CL. The shells CL are linked together by the lower sheave box BB. The claws TA are attached to the ends of the shells CL.
Here, the opening/closing rope GW is hung multiple times (four-way hanging in the example shown in Figure 3) through a sheave SH attached to a lower sheave pin BS in a lower sheave box BB and a sheave SH attached to an upper sheave pin HS in an upper sheave box HB, and the end of the opening/closing rope GW is fixed to the upper sheave pin HS by a cotter sheave CS.

The bucket GB performs five operations, opening, closing, gripping, hoisting, and lowering, by the movement of the support ropes HW and the opening/closing ropes GW.
The opening operation is performed by winding down the opening/closing rope GW while the support rope HW is stopped.
The closing operation is performed by winding up the opening/closing rope GW while the support rope HW is stopped.
The gripping operation is performed by slackening the support ropes HW and allowing the bucket GB to sink under its own weight while the opening/closing ropes GW are lifted up and the bucket is moved in the closing direction, thereby controlling the removal of slack in the support ropes HW.
The winding operation is performed by winding up both the support rope HW and the opening/closing rope GW at a uniform speed, and the winding down operation is performed by winding down both the support rope HW and the opening/closing rope GW at a uniform speed.
If the speeds of the support ropes HW and the opening/closing ropes GW are not uniform, the bucket may close or open during winding up or down, or one of the ropes may slacken.
In order to prevent this, the support ropes HW and the opening/closing ropes GW are controlled when hoisting or lowering as described below.

FIG. 4 illustrates the detection positions of the open/close position detector of the double rope type bucket.
Fig. 4 (1) shows the open end position GO of the bucket GB when the opening operation is stopped by the open end stop limit switch, and the shell CL is completely open, and the opening/closing rope GW is set just before it starts to slacken slightly. Fig. 4 (2) shows the state of the open deceleration position GOD, which is set just before the open end position GO to slow down the speed just before the open end position GO during the opening operation of the bucket GB. Fig. 4 (4) shows the state of the closed end position GC of the bucket GB when the closing operation is stopped by the closed end stop limit switch, and the shell CL is perfectly aligned in an unladen state, and the support rope is set at a position where it does not slacken. Fig. 4 (3) shows the state of the closed deceleration position GCD, which is set just before the closed end position GC to slow down the speed just before the closed end position GC during the closing operation of the bucket GB.
Since the relative difference between the support rope movement amount and the opening/closing rope movement amount determines the opening/closing action, the rotation difference between the two detectors, the support position detector HP that detects the rotation of the support drum HD and the opening/closing position detector GP that detects the rotation of the opening/closing drum GD, determines the degree of opening/closing. There are several detection methods, such as a method of electrically detecting the rotation difference, and a method of inputting the rotations of both the support drum HD and the opening/closing drum GD to a differential reducer to mechanically detect the rotation difference and detect the degree of opening/closing from the rotation difference.

(5) in Fig. 4 is a state where a large amount of bulk cargo HO is caught between the shells CL and a gripping force is exerted. This state of gripping position GG is not a state detected by a position detector, but a state where the movement of the opening and closing rope GW in the closing direction is restricted by the bulk cargo HO being caught between the shells CL, and the opening and closing rope GW exerts a tension force to support the load, and both the support rope HW and the opening and closing rope GW support the load evenly as shown in (3) in Fig. 5. If the opening and closing rope GW is loosened a little from this gripping position GG, the bulk cargo HO will drop, and if the opening and closing rope GW is closed a little too much, the support rope HW will slacken as shown in (4) in Fig. 5. In this way, the gripping position GG is in a delicate positional relationship, and exists in a position where both the support rope HW and the opening and closing rope GW share the load, and it is ideal that the load sharing ratio of the support rope HW and the opening and closing rope GW is equally shared at 50:50.
This gripping position GG changes slightly depending on the state of the gripped bulk cargo HO, and is always located between the closing deceleration position GCD and the closing end position GC.
When the bucket GB is empty, the closed end position GC becomes the gripping position GG.
The opening/closing position of the closed deceleration position GCD, which is always located on the opening side from the gripping position GG, is a state in which the bucket GB alone is empty and no loose cargo HO can be held within the bucket GB.

In the structure of the opening and closing rope GW shown in FIG. 3, when the stroke of the lower sheave box BB moving while the bucket GB is moving from the open end position GO to the closed end position GC is 1.25 m, and the number of sheaves SH is four, the length of the opening and closing rope GW while the bucket GB is moving from the open end position GO to the closed end position GC is 5 m (1.25 m x 4). The open deceleration position GOD at this time is set to a position about 1.2 m in front of the position of the opening and closing rope GW at the open end position GO. The closed deceleration position GCD is set to a position about 0.6 m in front of the position of the opening and closing rope GW at the closed end position GC. At this time, the deceleration distance is different between the open side in the direction in which the load hinders deceleration and the closed side in the direction in which the load helps deceleration, so the deceleration distances of the open deceleration position GOD and the closed deceleration position GCD are set differently.

FIG. 5 shows the distribution of loads applied to the support ropes HW and the opening/closing ropes GW in each state of the bucket GB.
In the state of Fig. 5 (2) where the bucket GB is not gripped, the load of the bucket GB supported by the opening/closing ropes GW is the weight of the shell CL and the lower sheave box BB minus the load supported by the connecting rod LL, and the load applied to the opening/closing ropes GW is the load obtained by dividing the load by the number of loops of the opening/closing ropes GW (4 in the case of Fig. 3 because 4 ropes are looped), and the opening/closing ropes GW only support a small load of less than 15% of the load of the bucket GB, and the remaining load of 85% or more is supported by the support ropes. Furthermore, in the state of Fig. 5 (1) where the bucket GB is fully opened and the opening/closing ropes GW are slack, the support ropes HW share the entire load of the bucket GB, and the opening/closing ropes GW side does not share any load at all.

If induction motors are used for the support motor HM and the opening/closing motor GM and they are operated without speed control, when hoisting is performed with the load distribution of (1) or (2) in Figure 5, the support motor HM is pulled by the load and its speed slows down by the amount of motor slippage, and the opening/closing motor, which has a light load and less motor slippage, runs faster than the support motor. This speed difference between the support motor HM and the opening/closing motor GM causes the bucket GB to move in the closing direction. Then, when lowering is performed, the support motor HM is pulled by the load and its speed becomes faster than the opening/closing motor GM by the amount of motor slippage, so the bucket GB also moves in the closing direction.
Therefore, when the opening/closing state of the bucket GB is on the opening side of the closing deceleration position GCD, it is not gripping the bulk cargo HO, so by adding speed control so that the motor characteristics of both the support motor HM and the opening/closing motor GM become the characteristics shown in Figure 6, the speed is kept constant regardless of the size of the load, and the closing phenomenon when hoisting or lowering is minimized.
However, even with the characteristics shown in FIG. 6, in reality, there is a slight steady-state deviation, and when an acceleration torque during acceleration is applied to a load torque of 85% or more of the support motor HM, the torque limiter LM (150% in this embodiment) may be slightly applied, and a phenomenon in which it closes slightly during acceleration may occur.
In order to eliminate this slight closing phenomenon, when the bucket GB is on the opening side of the closing deceleration position GCD, the load share of the opening/closing motor GM is small, and the opening/closing motor GM is accelerated beyond the rated speed by the amount of its remaining power, and the speed of the opening/closing motor GM is made faster than the support motor HM, thereby performing an opening operation while winding down as shown in FIG. 9, and by performing position control so as to move toward the open end position GO, the slight closing phenomenon is eliminated.

In the characteristic diagram of FIG. 6, the horizontal axis represents speed ω and the vertical axis represents torque T, with the positive side of torque T being the winding-up side and the negative side of torque T being the winding-down side.
As shown in the characteristic curve of FIG. 6, the speed ω with respect to the torque change is a curve that rises straight above the speed target value ω ^* without any speed change.
However, in reality, there is a slight steady-state error.
The curve that rises straight above the speed target value ω ^* reaches the torque limiter LM (150% in this embodiment) where the output torque reaches the limit of its capacity, and the speed becomes slow when winding up and fast when winding down.
The direction in which this steady-state deviation and the torque limiter LM occur is the direction in which the bucket GB closes both during hoisting and lowering.
When the speed ω exceeds 100% of the rated speed, the torque T that can be output decreases as the speed ω increases due to a problem of the motor characteristics.

When the bucket GB is on the closing side of the closing deceleration position GCD, it is determined that the bucket is gripping a bulk cargo, and by setting the control characteristics of the support motor HM and the opening/closing motor GM to the characteristics of Fig. 7, it is possible to create and maintain the load sharing state of Fig. 5 (3) at the gripping position GG shown in Fig. 4 (5). At this time, the load sharing state of the support motor HM and the opening/closing motor GM is 50:50 by giving the same speed target value with the same slope of Fig. 7 to both the support motor HM and the opening/closing motor GM. The characteristics of Fig. 7 are such that when a load is applied to the hoisting side, the speed slows down in proportion to the magnitude of the load, and conversely, the speed of the lowering side (negative torque side) increases as the load increases, and the characteristics of the embodiment of Fig. 7 are such that a speed deviation of 8% occurs at a load torque of 100% in the embodiment.
The slope of the control characteristic in Figure 7 resembles the slip characteristics when an induction motor is operated without speed control, but while the slip of an induction motor is about 2%, the corresponding slope of the characteristic in Figure 7 is 8% in order to more actively converge the load sharing of the support motor HM and the opening/closing motor GM to a 50:50 equal and balanced state more quickly and to maintain that 50:50 equal and balanced state more stably.
In other words, the phenomenon in which the bucket GB closes by itself during winding or lowering due to induction motor slippage is prevented by performing speed control when the bucket GB is on the closed side of the closing deceleration position GCD, thereby more proactively creating this condition.
In this case, if the slope of the characteristics of the support motor HM in FIG. 7 is left at 8%, and the slope of only the opening/closing motor GM is set to, for example, 7%, the load sharing of the opening/closing motor GM can be increased, but in terms of the characteristics of the bucket GB, there is no need to change the load sharing, and the ideal load sharing is 50:50, and it is also ideal for the support motor and the opening/closing motor to have equal characteristics.

When the support motor HM and the opening/closing motor GM are actually operated according to the control characteristics shown in Fig. 7, when the support motor HM and the opening/closing motor GM have the same characteristics as shown in Fig. 7 and the same speed target value ω ^* is set, for example, when the support share ratio increases during winding, the support speed slows down, and the opening/closing speed, which reduces the burden ratio, increases, and the support becomes loose and the opening/closing becomes tense, so the load share tries to return to the opening/closing side, and the load share tries to converge to 50:50. The converged position is the gripping position GG.
During lowering, for example, if the share of the support motor HM increases, the support speed increases, the speed of the opening/closing side, which has a lighter share of the load, decreases, and the support rope HW slackens and the opening/closing rope GW becomes taut, so the load share tries to return to the opening/closing side, and the load share tries to converge to 50:50. Again, the converged position is the gripping position GG.
In this way, by adopting the characteristics of FIG. 7, the gripping position GG of FIG. 5(3) is actively attempted to converge, so that the gripped object does not spill out as in FIG. 5(2), and the opening/closing motor GM does not become overloaded as in FIG. 5(4), and the gripping end position is maintained.

In the case of ores with a high specific gravity, the weight ratio between the bucket GB and the bulk cargo HO is often designed so that the bucket GB's own weight is the same as the weight of the bulk cargo HO when it is full (rated capacity); however, in the case of bulk cargo HO with a light specific gravity such as wood chips, grains, and combustible waste, the weight of the bulk cargo HO is generally about 60% to 30% of the bucket GB's weight.
When heavy ore or the like is grabbed with a lightweight bucket, the weight of the rated capacity of the bulk cargo HO may be heavier than the weight of the bucket GB, but this is a rare case.

When the weight of the bucket GB is the same as the weight of the bulk cargo HO when it is full (rated capacity), the load of the support motor HM in FIG. 5(1) and the load of the support motor HM and the opening/closing motor GM in FIG. 5(3) are equal and are the maximum loads. Therefore, it is economical to set this load value as the rated output of the support motor HM and the opening/closing motor GM, and this is the general design. However, even in this case, it is rare to grab the bulk cargo, and usually only about 60 to 80% of the cargo is grabbed, so there is generally a surplus of power in the output of the support motor HM and the opening/closing motor GM in the state of FIG. 5(3).
In the case of a bucket that grabs loose cargo with a light specific gravity, the weight of the loose cargo HO when fully loaded is lighter than the load of the bucket GB, so the support motor HM in Fig. 5 (1) is at its maximum load, and this state is set as the rated output of the support motor HM, and the opening/closing motor GM is generally designed to match this. In this case, in the state of Fig. 5 (3), there is a surplus in the output of the support motor HM and the opening/closing motor GB. Furthermore, since the bucket cannot normally be fully loaded and only about 60 to 80 percent of the cargo can be grabbed, there is a surplus in the motor output in the state of Fig. 5 (3).
In the case of a lightweight bucket that grabs heavy items, when the bucket is in the state shown in Figure 5 (3) and is fully loaded with bulk cargo HO, the load on the support motor HM and the opening/closing motor GM reaches its maximum, and it is an economical and common design to set this state as the rated output of the support motor HM and the opening/closing motor GM.
When using such a lightweight bucket, due to the principle of a double rope bucket in which the gripping force is generated by the bucket GB's own weight, it is difficult to grip the entire bucket, and in many cases the weight of the bulk cargo HO that can be gripped is limited to about 50%, which results in a surplus of power in the output of the support motor HM and the opening/closing motor GM, in the state shown in Figure 5 (3).

The characteristic of Fig. 7 used in the gripping state of Fig. 5 (3) is such that the more the slope of the graph, which is the amount of variation of the speed ω with respect to the torque T, is inclined, the easier it becomes to balance the torque T of the support motor HM and the opening/closing motor GM. However, the characteristic of Fig. 7 makes the speed during hoisting slower than the rated speed. This causes the rated hoisting speed of the crane to be insufficient and the performance relative to the performance display value cannot be maintained. To compensate for this, after confirming that the output torques of the support motor HM and the opening/closing motor GM are in balance after the end of hoisting acceleration, the amount by which the actual speed ω lags behind the speed target value ω ^* is added to the speed target value ω ^* of the support motor HM and the opening/closing motor GM to compensate for the delay.

In addition, when the value of the torque T when the torque T of the support motor HM and the opening/closing motor GM is balanced has a margin for the rated torque of the support motor HM and the opening/closing motor GM, the speed target value ω ^* of the support motor HM and the opening/closing motor GM is increased up to the maximum speed that can be output for that margin, thereby increasing the winding speed and shortening the conveying time.

In the characteristics shown in FIG. 7 used in the state of gripping position GG in FIG. 5 (3), the speed on the lowering speed side (negative torque side) exceeds the rated output, but since the mechanical loss of the reducer helps the motor output during lowering, a slight increase in speed (8% in this embodiment) does not pose a problem in terms of motor capacity.
Furthermore, just as during hoisting, when the torque T of the support motor HM and the opening/closing motor GM are balanced during lowering, it is possible to increase the speed by the amount of the motor's spare power. However, due to the transport pattern of a bucket crane, there is almost no lowering operation in a gripping state, so there is almost no opportunity to utilize this capability.

Fig. 8 shows a control block diagram of a speed control system for realizing the characteristics shown in Fig. 6 when the bucket GB is not gripped (an opening/closing position on the more open side than the closed deceleration position GCD) and the characteristics shown in Fig. 7 when the bucket GB is gripped (an opening/closing position on the more closed side than the closed deceleration position GCD). In this control block diagram, the speed target value ω ^* is the value of ω when the torque T is zero in the characteristic diagram of Fig. 6 or Fig. 7. A speed deviation amount obtained by subtracting the value of the speed ω actually outputted by the speed detector PG from the speed target value ω ^* is inputted to the automatic speed setter ASR.
To realize the characteristics shown in Fig. 6, the automatic speed setting device ASR is set to a proportional-integral characteristic PIC, the speed deviation amount is accumulated in an integrator, and torque is controlled to be output until the integral is released, thereby realizing a characteristic in which there is no speed deviation for the torque T shown in Fig. 6. However, since the speed deviation amount is accumulated in the integrator only after it occurs, a slight steady-state deviation occurs. And since the torque target value T ^* is set by passing through the torque limiter LM after passing through the automatic speed setting device ASR, the amount applied to the torque limiter LM here occurs as a large speed deviation.
To realize the characteristics of Fig. 7, the automatic speed setter ASR to which the speed deviation amount is input is set as a proportional characteristic PC, and a torque proportional to the speed deviation amount is output by performing calculations using the slope of the proportional characteristic PC of the graph in Fig. 7, and a torque target value T ^* is generated after passing through the torque limiter LM. This results in the characteristics of Fig. 7, which slows down the output speed in proportion to the size of the load when hoisting, and speeds up in proportion to the size of the load when lowering.

Here, the switching between the characteristics in Fig. 6 when the bucket GB is not gripped and the characteristics in Fig. 7 when the bucket GB is gripped is performed before the motor starts to move at the moment when a hoisting or lowering operation is performed, switching from the closed deceleration position GCD to the closed side or from the closed deceleration position GCD to the open side, and switching between the control characteristics in Fig. 6 and Fig. 7 is not performed while the motor is operating. This is in consideration of the occurrence of switching shock at the time of switching.
For example, even if the closed deceleration position GCD is switched after the state shown in FIG. 6 or FIG. 7 is reached at the very limit of the switching position of the closed deceleration position GCD and the motor starts to move, the previous control state is maintained.

The reason why the closed deceleration position GCD is used to switch the control characteristics between Figures 6 and 7 is that the gripping position GG is always located slightly to the closing side from the closed deceleration position GCD, and at the closed deceleration position GCD, the bulk cargo HO cannot be held in the bucket. From this position to the opening side, the load sharing for support and opening/closing with the bucket GB alone is in the position of (2) in Figure 5, and the closed deceleration position GCD and the control switching position are the same optimal position (in the embodiment, the opening/closing rope GW is 0.6 m to the opening side from the closed end position GC), so the closed deceleration position GCD is used as the control switching position.
At this time, when winding or lowering is performed from the closing deceleration position GCD according to the characteristics of FIG. 7, it quickly moves to the gripping position GG and the load sharing between the support motor HM and the opening/closing motor GM converges to 50:50.
Furthermore, if the bucket opens slightly from the gripping position GG, the gripping force for gripping the bulk cargo HO is lost, causing the bulk cargo HO to fall through the gap in the shell CL, and when the bucket GB is in the opening and closing position of the closed deceleration position GCD, the inside of the bucket GB is empty.

6 on the opening side of the closing deceleration position GCD, the characteristics in Fig. 6 maintain the state even if the loads on the support motor HM and the opening/closing motor GM are unbalanced, and if the loads are in an overload state, the state will be maintained. However, since only the load of the bucket GB alone is applied at the closing deceleration position GCD, the load supported by the support motor HM is less than 100%, and the load on the support motor HM does not exceed 100% and become overloaded.
Furthermore, in the position on the closing side from the closing deceleration position GCD, when the opening/closing rope GW is further tightened to the closed end position GC from the opening/closing position of gripping position GG where the bulk cargo is caught between the shells CL and the opening/closing is restricted, the support rope HW slackens as shown in Figure 5 (4), and the weight of the bucket GB and the weight of the bulk cargo HO are all placed on the opening/closing rope GW alone, resulting in an overloaded opening/closing state. However, since the control characteristics are as shown in Figure 7 on the closing side from the closing deceleration position GCD, when winding up or lowering is performed with the control characteristics of Figure 7, the load sharing between the support motor HM and the opening/closing motor GM is quickly converged to and maintained at the gripping position GG where it is 50:50, so the state of Figure 5 (4) does not occur, and the opening/closing motor GM and the opening/closing speed control device will not be damaged by overload, etc.

The transport pattern of a bucket crane CR is generally to grab a bulk object HO below a pit PT, etc., and open it above a hopper HOP, etc., as shown in the layout in Figure 9. However, a transport pattern in which the object is grabbed above and opened below is not common.
In operation examples other than those shown in Fig. 9, for example, an unloader grabs the cargo in the lower hold and opens it at the upper hopper HOP. A dredging bucket also grabs the cargo on the riverbed or seabed below the water surface and opens it on a barge or land above the water surface. Even in operation examples where the cargo is opened at the discharge truck, the discharge truck is located above the grab position.
In this way, the transport pattern of the bucket crane is such that when hoisting, the bulk cargo HO is gripped, and when lowering, the bucket GB is not gripped and goes to grab the cargo with the bucket in the open end position GO.

During the process of lowering the cargo while gripping it in the transport pattern of a bucket crane, the bucket GB may be gripped and lowered at a slow speed while being lowered above the hopper HOP or the discharge truck in order to reduce the shock of the bulk cargo HO scattering or falling onto the hopper HOP or the discharge truck, but the lowering distance is short and the impact on the overall transport process is small.
In the transport pattern with the bucket open, apart from the operation of grabbing loose cargo HO with the bucket GB in the fully open open end position GO, there is a process of transporting the bucket to a bucket storage area to rest the bucket. Even when the bucket GB is waiting to be rested, it is sufficient to ensure that the bucket is in the open end position GO state where it is most stable and where the claws TA are least damaged.
In this way, in a bucket crane, only the gripping position GG or the open end position GO are the two open/closed states necessary for transport, and the other intermediate positions between the open and closed positions are not necessary for transport and are merely transitory states, so there is no need to maintain the intermediate positions between the open and closed positions. Therefore, when not gripping, the open end position GO is actively created.

When opening the bucket GB on the hopper HOP, if the bucket GB is opened forcefully, the loose cargo HO put in may become in a bridge BRI state on the top surface of the hopper HOP as shown in Figure 10, and only the bottom may come out, and the loose cargo HO may become clogged in the hopper HOP, causing the hopper HOP to stop functioning. This phenomenon is caused by the nature of the loose cargo HO and the way the bucket GB is opened. In order to prevent this bridge BRI phenomenon, there is a method of opening the bucket GB a little at the edge of the hopper HOP as shown in (1) of Figure 9 to gradually drop the loose cargo HO that is being held. This method has the effect of preventing dust from scattering and, when loading onto a transport truck, also has the effect of mitigating the impact on the truck.
After the loose cargo HO inside the bucket GB is dropped by opening the bucket GB in this manner, the bucket GB enters an area above the pit PT where it can be unloaded while simultaneously performing the lateral or traveling operation TS and opening the bucket GB, but has not yet reached the open end position GO.
In the present invention, rather than waiting until the open end position is reached to perform the lowering operation, if the lowering operation is performed while the bucket is in the open opening/closing position on the opening side of the closing deceleration position GCD, even if the open end position GO has not been reached, the speed of the opening/closing motor GM is output at a speed exceeding the rated speed, and the speed of the opening/closing motor GM is made faster than the support motor HM to create a speed difference, thereby performing the opening operation while lowering in the flow from (1) to (4) in Figure 9, and improving the conveying efficiency.

The transport pattern for lowering when the bucket is in a bucket opening/closing position on the open side of the closing deceleration position GCD can only be a situation where it goes to grab or goes to the bucket maintenance position, either of which requires the open end position GO. In this case, the load shared by the support motor HM and the opening/closing motor GM is small as shown in (2) of Figure 5, so the opening/closing motor GM has the capacity to exceed the rated speed.
Then, the speed target value ω ^* of the opening/closing motor GM is increased more than that of the support motor HM to move toward the open end position GO and control is performed to maintain the open end position GO, so that the phenomenon in which the bucket GB closes due to the slight steady-state deviation present in the characteristics of FIG. 6 and the influence of the torque limiter LM can be completely eliminated.

Since the opening and closing load torque is less than 15%, it is possible to set the opening and closing motor GM to a speed of 200%, but if the opening and closing motor GM is set to a lowering speed twice that of the support motor HM and then the lowering operation is stopped, the deceleration distance of the opening and closing ropes GW (4.8 m in this embodiment) will be four times the deceleration distance of the support ropes HW (1.2 m in this embodiment), and the relative deceleration distance between support and opening and closing will be three times (3.6 m in this embodiment), and if the lowering is stopped in this state, the opening and closing ropes GW will be unwound by a large amount.
To prevent this, the speed of the opening/closing motor GM is limited to 2 ^1/2 times that of the support motor, and the deceleration distance of the opening/closing rope GW is set to twice that of the support rope HW, keeping the relative deceleration distance to 1.
When the speed of the opening/closing motor GM is increased more than that of the support motor HM during simultaneous operation of lowering and opening, and then both the support motor HM and the opening/closing motor GM are decelerated and stopped at the same time, the deceleration distance increases with the square of the speed difference, and the opening/closing rope GW is unwound significantly, so it is better not to increase the speed of the opening/closing motor GM too much and keep it at 2 ^1/2 . However, when the speed of the opening/closing motor GM is increased more than that of the support motor HM and the opening/closing motor GM is made equal from the state in which lowering and opening are simultaneously performed, the deceleration distance for opening and closing when only the opening operation is stopped and lowering is continued is the normal deceleration distance, so if the opening and closing speed is kept so as not to be too high, it will take time to open and close.

In the simultaneous operation of lowering and opening, the deceleration and stopping operation for opening only is performed as shown in FIG. 9, the speed of the opening/closing motor GM is set to 2 ^1/2 times the speed of the support motor HM to perform lowering, and when the opening deceleration position GOD is reached, the speed of the opening/closing motor GM is decelerated to a speed slightly faster than the support speed, and when the speed is maintained and the open end position GO is reached, the support speed and the opening/closing speed are made equal.
In this way, the speed difference between the support speed and the opening and closing speed is kept small, and the winding down is performed while opening slowly, but the opening time takes time because the speed difference has to be controlled by only detecting two points, the open deceleration position GOD and the open end position GO. At this time, instead of controlling only two points, the open deceleration position GOD and the open end position GO, the relative distance between the support and the opening and closing up to the open end position GO is captured numerically. If the speed difference is controlled linearly while calculating the maximum relative speed that can be output for that relative distance, it is possible to achieve a speed difference of 2 ^1/2 times or more, which makes it possible to speed up the opening time during winding down, and also improves the performance of maintaining the position of the open end position GO after it reaches the position of the open end position GO.

In order to perform the hoisting and opening operations simultaneously, the speed of the support motor HM can be increased or the speed of the opening/closing motor GM can be decreased. However, as shown in the load distribution in Figure 5 (1), the support motor does not have the capacity to increase its speed beyond the rated speed, and the method of opening by decreasing the speed of the opening/closing motor GM does not contribute to shortening the transport time. Furthermore, since the situation in which the bucket GB needs to be opened by hoisting it upwards is a rare case in the transport pattern, the method of opening while hoisting is not a very important function.

The above describes the control method for hoisting and lowering a double rope bucket crane of the present invention based on its embodiment, but the present invention is not limited to the configuration described in the above embodiment, and the configuration can be changed as appropriate within the scope of the spirit of the invention.

The control method for hoisting and lowering a double rope bucket crane of the present invention optimizes the control of the support motor and the opening and closing motor according to the state of the bucket, and optimizes the load sharing between support and opening and closing to reduce failures due to motor overload, provides easy-to-use control without rope slack, and ensures efficient transportation by matching the movement to the transportation process, making it ideal for use with a double rope bucket crane.

CR Crane HD Support drum GD Open/close drum HM Support motor GM Open/close motor BR Brake GR Reducer LC Load cell HP Support position detector GP Open/close position detector PG Speed detector HW Support rope GW Open/close rope GB Bucket HB Upper sheave box LL Connecting rod CL Shell TA Claw BB Lower sheave box HS Upper sheave pin BS Lower sheave pin SH Sheave CS Cotter sheave GO Open end position GOD Open deceleration position GCD Closed deceleration position GC Closed end position GG Gripping position HT Support torque GT Open/close torque ω Speed T Torque ω ^* Speed target value T ^* Torque target value ASR Automatic speed setter PC/PIC Proportional characteristic/Proportional integral characteristic LM Torque limiter PT Pit HO Bulk cargo handling HOP Hopper BRI Bridge TS Traverse or travelling operation HR Support lowering operation GR Open/close lowering operation

Claims (3)

A method for controlling the hoisting and lowering of a crane with a double rope bucket, which controls the hoisting and lowering of a double rope bucket using two types of hoisting devices with equal capacity, which are independent of a support motor and an opening/closing motor, comprising:
When the open/closed state of the bucket is on the closing side from near the closing deceleration position slightly open from the closed end position of the bucket, it is determined that the bucket is closed and gripping the load, and the speed control characteristics of the automatic speed setters of the support motor and opening/closing motor when hoisting or lowering are set to proportional characteristics which vary the torque proportionally to the amount of speed deviation, and the output speeds of the support motor and opening/closing motor are controlled to slow down in proportion to the size of the load as the load increases when hoisting, and to speed up in proportion to the size of the load as the load increases when lowering, and the speed ratio to the load is controlled to be the same for both the support motor and the opening/closing motor, so that the load sharing of the support motor and the opening/closing motor is the same, thereby allowing hoisting or lowering to be performed while maintaining the load gripped state,
a speed control device for controlling the speed of the opening and closing motor when the bucket is opened from near a closed deceleration position slightly open from the closed end position of the bucket to the open side, the device determines that the load is not being gripped, and when hoisting or lowering, the speed control characteristics of the automatic speed setters of the support motor and the opening and closing motor are set to proportional and integral torque characteristics with respect to the speed deviation amount to reduce the speed deviation amount with respect to the load variation, and the speed fluctuation of the support motor and the opening and closing motor with respect to the load is reduced, and when hoisting or lowering, the device controls so that the speed deviation is small regardless of the size of the load, and when lowering, the speed control range of the opening and closing motor speed is expanded to a range exceeding the rated speed, and the opening and closing motor speed is made faster than the support motor to perform the opening operation while lowering, and when lowering when the bucket is not in the open end position, the lowering speed of the opening and closing motor is made faster than the support motor speed at a speed exceeding the rated speed so that the bucket is moved toward the open end position while being lowered, and when the bucket is in the open end position, the speed of the support motor and the opening and closing motor are made equal to each other to perform the lowering while maintaining the open end position. The automatic speed setting device of the support motor and the opening/closing motor is switched between the proportional characteristic and the proportional integral characteristic of the speed control characteristic when the motor starts to move at the moment when the winding-up or winding-down operation is performed, and the opening/closing state of the bucket is changed from the vicinity of the closing deceleration position slightly opened from the closed end position of the bucket to the closing side.
2. The method for controlling the hoisting and lowering of a double rope type bucket crane according to claim 1, wherein the hoisting and lowering is performed on the opening side. 3. A method for controlling the hoisting and lowering of a double rope type bucket crane as claimed in claim 1 or 2, characterized in that when the open/closed state of the bucket is from near a bucket closing deceleration position slightly open from the closed end position to the closing side and the bucket is closed to grip a load, when the speeds or torques of the support motor and the opening/closing motor after acceleration have ended become equal during hoisting and lowering, if there is spare capacity in the motor torque, the speeds are increased to the maximum speed that each motor can output for the size of the load at that time.

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