JPH0145858B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a weighing method for a clay crane, and more particularly to a weighing method for a crane using a power conversion type.

In the weighing method using the power conversion method, the weight of the object to be measured, which is grabbed by a bucket in a crane, is measured based on the original power consumption, which is proportional to the power consumption of the motor, when the crane's electric motor is hoisting the object. It's heavy. In such a weighing device, the prior art detects only the power consumption of the electric motor during hoisting drive, and therefore cannot compensate for changes in the electric motor's power consumption due to temperature rises in the electric motor, changes in friction in the mechanical structure of the crane, etc. There are drawbacks. Therefore, in such prior art, it is not possible to accurately measure the weight.

An object of the present invention is to provide a weighing method for a crane that can solve the above-mentioned technical problems and perform accurate weighing.

In the present invention, the transported object storage device 3 that stores the transported object 4 is driven upward and downward by the electric motor 5, and the electric motor 5 is driven when the empty transported object storage device 3 is driven downward.
The difference ΔP, ΔP between the measured value PD′ and the pre-measured reference value PD of the power consumption of the electric motor 5 when the empty cargo storage device 3 is lowered is measured. =PD′−PD, calculate and find the weight ΔW to be corrected corresponding to the difference ΔP in power consumption, and calculate the weight ΔW to be corrected in accordance with the increase or decrease in the difference ΔP in power consumption. The polarity of is set as + and -, respectively, and the power consumption PL of the electric motor 5 when storing the transported object 4 in the transported object storage device 3 and driving it upward is measured, and E and Pφ are set as predetermined constants. and when,
This is a weighing method for a crane, which is characterized by calculating the weight W of the object 4 to be transported, W=E・(PL−Pφ)±ΔW.

In preferred embodiments, examples of the present invention will be described below with reference to the drawings. FIG. 1 is a system diagram of one embodiment of the present invention, and FIG. 2 is a flowchart showing the transportation process of the bucket crane 1 shown in FIG.
The weighing device 2 using the power conversion method according to the present invention includes:
This is to measure the weight of the object 4 being transported by the bucket 3, which is a storage device for the object in the crane 1. When the crane 1 is used to load an object 4 onto a truck (not shown), for example, the loaded weight can be calculated by integrating the weight W.

During the transportation operation of the crane 1, first, in step S1, the electric motor 5 is driven and the bucket cart 3 is lowered. Next, the bucket cart 3 is lowered to a position where it can grasp the object 4 to be transported, and in step S2, the driving of the electric motor 5 is stopped and the lowering of the bucket cart 3 is stopped.
In the next step S3, the bucket 3 is opened and closed by another electric motor (not shown) and the transported object 4 is opened and closed.
grab. In step S4, the electric motor 5 is driven again to wind up the bucket cart 3 that has grabbed the object 4 to be transported. In the next step S5,
The bucket cart 3 that has grabbed the object 4 is moved to the position where it is to be transported, and in step S6, the bucket cart 3 is opened by the electric motor (not shown), and the object 4 is dropped at the position. Transported object 4
is transported according to the transport process of the crane 1 shown in steps S1 to S6. In steps S1 and S4 in each of these transportation steps, the power consumption of the electric motor 5 is proportional to the weight of the object 4 held by the bucket 3.

The electric motor 5 in the crane 1 is connected to, for example, three-phase AC power lines 6a to 6c. These power lines 6a to 6c are provided with current transformers 7a and 7b for detecting the load current of the electric motor 5, and a transformer 8 for detecting the load voltage of the electric motor 5. These current transformers 7a, 7b and transformer 8 are provided, for example, in connection with a switch in a switchboard (not shown) provided in connection with the power lines 6a to 6c. The outputs from these current transformers 7a, 7b and transformer 8 are given to the power converter 9 of the weighing device 4, and the power converter 9 can thereby detect the power consumption of the electric motor 5.

In the weighing device 2, the power consumption of the electric motor 5 detected by the power converter 9 is calculated by the analog computing unit 1.
0 is converted into an analog signal and applied to the analog-to-digital converter AD. Electric motor 5 converted into digital signal by analog-to-digital converter AD
A signal representing the power consumption of is input to the processing unit CPU. The processing unit CPU is thereby connected to the electric motor 5.
The weight of the transported object 4 corresponding to the power consumption is calculated as described later, and the calculation result is displayed on the display 11.

FIG. 3 is a graph showing the relationship between the weight W of the object 4 caught by the bucket cart 3 and the power consumption P of the electric motor 5 when hoisting the bucket cart 3 that has caught the object 4. A solid line A shown in FIG. 3 shows a case where the relationship between the weight W and the power consumption P is ideal. This solid line A is the bucket 3 that grabbed the load with the rated weight WM.
The power consumption PM of the electric motor 5 when winding up the
This can be obtained by measuring in advance the power consumption Pφ of the electric motor 5 when hoisting up an empty bucket with a weight Wφ. Therefore, the electric motor 5 in this relationship
The relationship between the power consumption P and the weight W is shown by the first equation. In this first equation, W=WM/PM-Pφ can be considered a constant, and Pφ can be considered a constant.

W=(WM/PM-Pφ)×(P-Pφ)...(1) The broken line B indicates that the power consumption of the electric motor 5 increases compared to that shown by the solid line A due to a change in friction in the mechanical configuration of the crane 1, for example. The relationship between power consumption P and weight W when (increase amount + ΔP) is shown. The broken line C shows the relationship between the power consumption P and the weight W when the power consumption P of the electric motor 5 decreases (decreased amount - ΔP) from that shown by the solid line A due to the reasons explained in connection with the broken line B. show. Therefore, if the amount of weight change that changes depending on the increase/decrease ΔP in power consumption P in the electric motor 5 shown by broken lines B and C is ΔW, then the first equation is corrected as shown in the second equation.

W=(WM/PM-Pφ)×(P-Pφ)±ΔW...(2) Therefore, by calculating using the second formula, it is possible to accurately measure the weight W of the transported object 4. can. For reference, the power conversion type weighing device in the prior art calculates using only the first equation. The weight change amount ΔW in the second equation is calculated using the third equation.

ΔW=K×ΔP (3) Here, K is a proportionality constant of the amount of change in weight ΔW with respect to the amount of change ΔP in power consumption. This constant of proportionality K
In the present invention, the amount of change ΔP in power consumption is detected in connection with step S1 shown in the second diagram. Therefore, the proportionality constant K is the power consumption of the electric motor 5 when lowering the bucket 3 holding the rated weight WM.
This can be obtained by measuring in advance the PDM and the power consumption PD of the electric motor 5 when the empty bucket 3 (weight Wφ) is lowered. This proportionality constant K is expressed by the fourth equation.

K=WM/PDM-PD (4) The amount of change in power consumption △P is detected in connection with step S1 shown in the second diagram as described above. If the power consumption P when input to
The amount of change ΔP is determined by the formula.

ΔP=PD′−PD (5) As described above, the weight of the object 4 to be carried by the bucket 3 can be calculated accurately using equations (2) to (5). . In the weighing device 2, the weighing operation can be accomplished by reading each power consumption value required for calculation of these second to fifth equations.

Figure 4 shows the transported object 4 explained in relation to Figure 3.
It is a flowchart which shows the concrete processing procedure of the weighing device 2 according to the weighing method. In step n1, the processing device
It is determined whether the signal representing the power consumption of the electric motor 5 input to the CPU is a signal representing the power consumption PD' when lowering the empty bucket 3.
In step n2, it is determined whether the power consumption PD' is the highest value at the time of output, that is, the power consumption when the motor 5 is in the top notch state. In steps n3 to n4, power consumption is reduced for a certain period of time.
A time wait is performed until PD' reaches a stable value. In step n5, the stable power consumption
PD′ is read. The power consumption PD′ read in this way is calculated at step S1 in the second diagram.
is read in the processing unit CPU during the operation of the crane 1.

In the next step n6, from the previously measured power consumption PD when lowering the empty bucket 3 and the read power consumption PD',
The amount of change ΔP in power consumption of the electric motor 5 is calculated. In step n7, the amount of change ΔP in power consumption obtained in step n6 is calculated from the third equation to the weight ΔW to be corrected. In steps n8 to n10,
Weight ΔW that should be corrected by determining the polarity of the amount of change in power consumption ΔP, that is, whether ΔP is an increase or decrease
Determine the polarity of

In the next steps n11 to n14, steps n1 to n14
Similar to step n5, processing is performed to read the power consumption PL of the electric motor 5 when hoisting the bucket 3 holding the object 4 to be transported. step n12
Then, the weight of the object to be transported 4 is calculated using the second equation from this power consumption PL and the weight change amount ΔW to be corrected obtained in steps n1 to n8. In this way, the weighing device 2 performs the transportation work (steps S1 to S6) on the crane 1 shown in the second diagram.
Corresponding to the arithmetic processing shown in the fourth figure (step n1
~n14) is performed.

In the embodiment of the present invention, it has been explained that the weighing device 2 is provided in conjunction with the bucket type crane 1, but it does not have to be a bucket type, and can be used to raise and lower the transported object 4. It can be widely implemented with respect to cranes equipped with an electric motor 5 for lowering and driving. Further, when provided in conjunction with the bucket cart type crane 1, the opening/closing method of the bucket cart 3 may be either a cable type or a hydraulic type.

As described above, according to the present invention, a change in the power consumption of the electric motor due to a rise in the temperature of the electric motor, a change in friction in the mechanical structure of the crane, etc. is detected, and the amount of weight change is corrected in accordance with the amount of change in power consumption. This allows for accurate weighing.

[Brief explanation of drawings]

FIG. 1 is a system diagram of an embodiment of the present invention, FIG. 2 is a flowchart showing the transportation process of the bucket crane 1 shown in FIG. 1, and FIG. A graph showing the relationship between W and the power consumption P of the electric motor 5 when hoisting the bucket 3 that has caught the object 4, and FIG. 4 shows a specific example of the weighing device 2 related to the explanation of FIG. It is a flow chart showing a processing means. DESCRIPTION OF SYMBOLS 1... Crane, 2... Weighing device, 4... Transported object, 5... Electric motor, 9... Power converter, 10...
...Analog computing unit, 11...Display unit, P, PD,
PD', PL, PM, Pφ...power consumption, ΔP...change in power consumption, W, WM, Wφ...weight, ΔW...
...Amount of weight change.

Claims (1)

[Claims] 1. A transported object storage device 3 for storing a transported object 4,
The electric motor 5 drives the electric motor 5 upward and downward, and the electric motor 5 when driving the empty cargo storage device 3 downward.
The difference ΔP, ΔP between the measured value PD′ and the pre-measured reference value PD of the power consumption of the electric motor 5 when the empty cargo storage device 3 is lowered is measured. = PD′−PD, calculate and find the weight ΔW to be corrected corresponding to the difference ΔP in power consumption, and calculate the weight ΔW to be corrected in accordance with the increase and decrease in the difference ΔP in power consumption. The polarity is determined as + and -, respectively, and the power consumption PL of the electric motor 5 is measured when the transported object 4 is stored in the transported object storage device 3 and driven upward, and E and Pφ are predetermined constants. A weighing method for a crane, characterized in that the weight W of the transported object 4 is calculated as follows: W=E・(PL−Pφ)±ΔW.