Metering device

Abstract

To provide a metering device for increasing metering precision of an article.SOLUTION: A control CPU 62 acquires a time waveform of a weighing signal outputted when a PID control section 52 is operated in a state in which a weighing belt conveyor 3 is driven and respective parameters Kp, Ki, Kd of P, I, and D are set to initial values. The control CPU 62 adjusts at least one of the respective parameters Kp, Ki, Kd of P, I, and D on the basis of the acquired time waveform of a weighing signal. The control CPU 62 conveys an article 10 to the weighing belt conveyor 3, and measures the weight of the article 10 on the basis of a weighing signal outputted when the PID control section 52 is operated in a state in which the respective adjusted parameters Kp, Ki, Kd of P, I, and D are set.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a weighing device. [Background technology]

[0002] An electromagnetic compensation scale has been proposed as a weighing device as described above, as disclosed in Patent Document 1. With this electromagnetic compensation scale, while an object (article) is being transported, the displacement of the weighing platform due to the weight of the object is offset by the force of an electromagnetic coil, and the weight of the object is measured based on the current flowing through this electromagnetic coil. The current flowing through the electromagnetic coil is PID controlled so that the displacement of the weighing platform remains at a constant position.

[0003] In the PID control, the P, I, and D parameters are optimally set for the expected usage conditions, ensuring responsiveness and stability. However, if the actual usage conditions differ significantly from the expected usage conditions, the P, I, and D parameters may not be optimally set, resulting in poor weighing accuracy. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 2706825 Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a weighing device that improves the accuracy of weighing items. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, the weighing device according to the present invention is characterized by the following [1] to [5]. [1] a weighing conveyor (3) for conveying an article (10) to be weighed; a weighing table (511) that is displaced by a load applied to the weighing conveyor; a displacement sensor (512) for detecting the displacement of the weighing platform; an electromagnetic coil (513) that applies a force to the weighing platform against the load; a PID control unit (52) that performs PID calculation on a displacement signal output from the displacement sensor and controls a current flowing through the electromagnetic coil in accordance with the calculation result; a signal output unit (53) that outputs a weighing signal according to the current flowing through the electromagnetic coil; a waveform acquisition unit (62) that acquires a time waveform of the weighing signal output when the PID control unit is operated in a state where the weighing conveyor is driven and each of the P, I, and D parameters is set to an initial value; an adjustment unit (62) that adjusts at least one of the P, I, and D parameters based on the time waveform of the weighing signal acquired by the waveform acquisition unit; a weighing unit (62) that conveys the article on the weighing conveyor and weighs the article based on the weighing signal output when the PID control unit is operated with the P, I, and D parameters adjusted by the adjustment unit set, It is a measuring device (1). [2] [1] The weighing device according to [1], The adjustment unit is configured from a learning model in which the time waveform of the weighing signal acquired by the waveform acquisition unit is input and the adjusted P, I, and D parameters are learned as outputs. It is a measuring device. [3] [1] The weighing device according to [1], the waveform acquisition unit acquires a time waveform of the weighing signal output when the PID control unit is operated while the article is being transported by the weighing conveyor; the adjustment unit adjusts at least one of the P, I, and D parameters based on a rising waveform when the weighing signal rises after the article is transferred onto the weighing conveyor. It is a measuring device. [4] [1] The weighing device according to [1], the waveform acquisition unit acquires a time waveform of the weighing signal output when the PID control unit is operated while the article is being transported by the weighing conveyor; the adjustment unit adjusts at least one of the P, I, and D parameters based on a steady waveform that is vibrating steadily after the item is transferred onto the weighing conveyor and the weighing signal rises. It is a measuring device. [5] [1] The weighing device according to [1], the waveform acquisition unit acquires a time waveform of the weighing signal output when the PID control unit is operated in a state where the articles are not being transported by the weighing conveyor. It is a measuring device.

[0007] According to the configuration [1] above, the adjustment unit adjusts at least one of the P, I, and D parameters based on the time waveform of the weighing signal. This allows the parameters that provide the best weighing accuracy to be set for the product characteristics (weight, center of gravity position, instability of contents, hardness of the conveyor contact surface, etc.) and transport conditions, thereby improving the weighing accuracy of the product. According to the configuration of [2] above, by using a learning model, it may be possible to set more appropriate parameters. According to the configuration [3] above, parameters can be set to improve the response of the weighing signal. According to the configuration [4] above, parameters can be set that improve the stability of the weighing signal. According to the configuration [5] above, parameters can be set even when no article is being transported. [Effects of the Invention]

[0008] The weighing device according to the present invention has the effect of improving the accuracy of weighing items.

[0009] The present invention has been briefly described above. The details of the present invention will become clearer by reading the following detailed description of the invention (hereinafter referred to as "embodiments") with reference to the accompanying drawings. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram showing an embodiment of a weighing machine incorporating a weighing device of the present invention. [Figure 2] FIG. 2 is a block diagram showing details of the scale unit and the indicator shown in FIG. [Figure 3] FIG. 3 is a flowchart showing a parameter setting process executed by the control CPU shown in FIG. [Figure 4] FIG. 4 is an explanatory diagram for explaining the adjustment shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0011] Specific embodiments of the present invention will be described below with reference to the accompanying drawings.

[0012] Fig. 1 is a schematic diagram showing one embodiment of a checkweigher incorporating a weighing device of this embodiment. The checkweigher 1 shown in Fig. 1 is an apparatus that weighs the weight of an item 10 and sorts the item 10 based on the weighing result. As shown in the figure, the checkweigher 1 includes an approach belt conveyor 2 that transports the item 10, a weighing belt conveyor 3 as a weighing conveyor, a sorting belt conveyor 4, a scale unit 5 that outputs a weighing signal obtained by weighing the item 10 transported by the weighing belt conveyor 3, and an instruction unit 6 that controls the scale unit 5.

[0013] In this embodiment, the belt conveyors 2 to 4 transport the articles 10 from left to right in the drawing. The approach belt conveyor 2 is disposed upstream in the transport direction of the weighing belt conveyor 3. The approach belt conveyor 2 separates the articles 10 to the interval required for weighing and transports the articles 10 to the weighing belt conveyor 3.

[0014] The weighing belt conveyor 3 transports the items 10 to the sorting belt conveyor 4. The scale unit 5 weighs the items 10 while they are being transported on the weighing belt conveyor 3. Any items 10 that are determined to be defective based on the weighing results from the scale unit 5 are rejected as defective items while being transported on the sorting belt conveyor 4.

[0015] Next, the weighing unit 5 and the instruction unit 6 will be described in detail with reference to Fig. 2. The weighing unit 5 includes a weighing unit 51, a PID control unit 52, a signal output unit 53, and a unit control unit 54. The weighing unit 51 includes a weighing platform 511 that is displaced by a load applied to the weighing belt conveyor 3, a displacement sensor 512 that detects the displacement of the weighing platform 511, and an electromagnetic coil 513 that applies a force to the weighing platform 511 that resists the load.

[0016] The PID control unit 52 performs PID calculations on the displacement signal output from the displacement sensor, and controls the current flowing through the electromagnetic coil 513 in accordance with the calculation results. Specifically, the PID control unit 52 calculates the error between the displacement signal and a target value. The PID control unit 52 calculates a proportional value P by multiplying the error by a P (proportional) parameter Kp, an integral value I by multiplying an integrated value of the error by an I (integral) parameter Ki, and a differential value D by multiplying a differentiated value of the error by a D (differential) parameter Kd, and controls the current flowing through the electromagnetic coil 513 based on the calculated proportional value P, integral value I, and differential value D. The PID control unit 52 controls the current flowing through the electromagnetic coil 513 so that the weighing platform 511 maintains a position corresponding to the target value, and the current flowing through the electromagnetic coil 513 has a value corresponding to the load applied to the weighing belt conveyor 3.

[0017] The signal output unit 53 outputs a weighing signal according to the current flowing through the electromagnetic coil 513. The unit control unit 54 is composed of a microcomputer, and controls the entire weighing unit 5. The unit control unit 54 communicates with a control CPU 62 of the instruction unit 6, which will be described later, and sets the P, I, and D parameters Kp, Ki, and Kd of the PID control unit 52 according to instructions from the control CPU 62.

[0018] The instruction unit 6 has an operation unit 61 and a control CPU 62. The operation unit 61 can be operated by a user to input required performance such as processing capacity (e.g., how many items to weigh per second) and the conveying speed of the items 10. The control CPU 62 is made up of a computer that processes according to a program, and sets the above-mentioned parameters Kp, Ki, and Kd and weighs the weight of the items 10 based on the weighing signal.

[0019] Next, the operation of the weight checker 1 configured as described above will be described with reference to Fig. 3. By operating the operation unit 61, the user can select a parameter setting mode for setting the parameters Kp, Ki, and Kd, or a weighing mode for weighing the article 10.

[0020] When the parameter setting mode is selected, the control CPU 62 executes the parameter setting process shown in Fig. 3. In the parameter setting process, the control CPU 62 displays a request input screen on a display unit (not shown) (S1). When the required performance described above is input from the operation unit 61, the control CPU 62 instructs the unit control unit 54 to set initial values ​​of the parameters Kp, Ki, and Kd according to the input required performance (S2).

[0021] A table showing required performance and the corresponding initial values ​​of the parameters Kp, Ki, and Kd is stored in advance in the storage unit of the control CPU 62. In S3, the control CPU 62 reads the initial values ​​of the parameters Kp, Ki, and Kd corresponding to the input required performance from the table. The unit control unit 54 sets the parameters Kp, Ki, and Kd to their initial values ​​in accordance with instructions from the control CPU 62.

[0022] Next, the control CPU 62 drives the belt conveyors 2 to 4 to transport the articles 10 (S3). The control CPU 62 also instructs the unit control unit 54 to operate the PID control unit 52 (S4). The unit control unit 54 operates the PID control unit 52 in accordance with the instructions from the control CPU 62. The PID control unit 52 performs PID control with the parameters Kp, Ki, and Kd set to their initial values.

[0023] Next, the control CPU 62 functions as a waveform acquisition unit, captures the weighing signal output from the signal output unit 53 while the item 10 is placed on the weighing belt conveyor 3 and then transported by the weighing belt conveyor 3, and acquires the time waveform of the weighing signal (S5).

[0024] Next, the control CPU 62 functions as an adjustment unit, adjusts the parameters Kp, Ki, Kd based on the time waveform of the acquired weighing signal, and instructs the unit control unit 54 to set the adjusted parameters Kp, Ki, Kd (S6), thereby ending the processing. The unit control unit 54 sets the parameters Kp, Ki, Kd to the adjusted values ​​in accordance with the instruction from the control CPU 62.

[0025] Next, the adjustment in S6 will be described with reference to Fig. 4. In Fig. 4(A) to Fig. 4(C), the solid lines show the time waveforms of the weighing signals acquired in S5, and the dotted lines show the time waveforms of ideal weighing signals. In the figures, Kp0, Ki0, and Kd0 are the initial values ​​of the parameters Kp, Ki, and Kd.

[0026] When an item 10 transfers from the approach belt conveyor 2 to the weighing belt conveyor 3, the weighing signal rises and repeatedly overshoots and undershoots a value corresponding to the weight of the item 10. The overshoot and undershoot gradually decrease over time. The weighing signal gradually converges to a value corresponding to the weight of the item 10 and becomes a steady vibration that oscillates with an almost constant amplitude.

[0027] For example, if the item 10 is harder than expected, as shown by the solid line in Figure 4(A), the overshoot and undershoot of the weighing signal when the item 10 is transferred to the weighing belt conveyor 3 will be larger than ideal, and it will take time for steady vibration to occur. As described below, the control CPU 62 measures the weight of the item 10 based on the weighing signal during steady vibration, so if it takes time for steady vibration to occur, the weighing accuracy of the item 10 will deteriorate. In such a case, the control CPU 62 adjusts the parameters Kp and Kd to values ​​Kp1 and Kd1 smaller than the initial values ​​Kp0 and Kd0. This causes the waveform of the weighing signal to approach the waveform shown by the dotted line.

[0028] As shown in Figure 4(B), even if the weighing signal does not overshoot and rises slowly, it takes time for the weighing signal to reach steady vibration. In such a case, the control CPU 62 adjusts the parameter Kp to a value Kp0 greater than the initial value Kp0. This causes the waveform of the weighing signal to approach the waveform shown by the dotted line.

[0029] For example, if the vibration caused by driving the weighing belt conveyor 3 is larger than expected, the amplitude of the weighing signal during steady vibration will be larger, as shown in Figure 4(C). In such a case, the control CPU 62 adjusts the parameter Kd to a value smaller than the initial value Kd0. This causes the waveform of the weighing signal to approach the waveform shown by the dotted line.

[0030] When the weighing mode is selected, the control CPU 62 drives the belt conveyors 2 to 4 and operates the PID control unit 52. The PID control unit 52 performs PID control using the parameters Kp, Ki, and Kd adjusted in the parameter setting mode. After detecting that an item 10 has been transferred onto the weighing belt conveyor 3 using a sensor (not shown), the control CPU 62 waits for a predetermined time to elapse during which the weighing signal reaches steady vibration, and then captures the weighing signal. The control CPU 62 then functions as a weighing unit, and, for example, measures the weight of the item based on the average value of the captured weighing signal during steady vibration.

[0031] According to the above-described embodiment, the control CPU 62 adjusts the parameters Kp, Ki, and Kd based on the time waveform of the acquired weighing signal, thereby enabling the parameters Kp, Ki, and Kd to be set to provide the best weighing accuracy for the product characteristics (weight, center of gravity position, instability of contents, hardness of the conveyor contact surface, etc.) and transport conditions.

[0032] Furthermore, a single type of weighing platform 511 and weighing belt conveyor 3 can be used to accurately weigh a wide range of items 10, from light to heavy.

[0033] Furthermore, the influence of instrumental error of the scale unit 5 can be reduced, and the cost required for precise assembly and adjustment work during manufacturing can be reduced.

[0034] Furthermore, PID control can be performed in accordance with the deterioration of the scale unit 5 and the weighing belt conveyor 3 over time, thereby extending the operating time of the device.

[0035] The present invention is not limited to the above-described embodiments, and can be appropriately modified, improved, etc. Furthermore, the material, shape, size, number, location, etc. of each component in the above-described embodiments are arbitrary and not limited as long as they can achieve the present invention.

[0036] According to the above-described embodiment, the parameters Kp, Ki, and Kd are adjusted using an algorithm of the control CPU 62, but this is not limiting. The parameters Kp, Ki, and Kd may be adjusted using a learning model that uses the time waveform of the weighing signal acquired by the waveform acquisition unit and the parameters Kp, Ki, and Kd before adjustment as inputs and learns the adjusted parameters Kp, Ki, and Kd as outputs (i.e., parameters Kp, Ki, and Kd that result in the ideal waveforms shown by the dotted lines in FIG. 4). Using the learning model may enable more appropriate parameters Kp, Ki, and Kd to be set.

[0037] Furthermore, the adjustment of the parameters Kp, Ki, and Kd is not limited to the above-described embodiment. For example, the parameter Kp may be adjusted based on the rising waveform of the time waveform of the weighing signal, and the parameter Kd may be adjusted based on the stationary waveform of the weighing signal that is oscillating steadily after the rising waveform of the time waveform of the weighing signal. This allows the parameters Kp, Ki, and Kd to be adjusted so that the rising waveform of the weighing signal approaches the ideal waveform, thereby improving the responsiveness of the weighing signal. Furthermore, the parameters Kp, Ki, and Kd may be adjusted so that the stationary waveform of the weighing signal approaches the ideal waveform, thereby improving the stability of the weighing signal.

[0038] According to the above-described embodiment, the parameters Kp, Ki, and Kd are adjusted based on the time waveform of the weighing signal acquired while the article 10 is being conveyed, but this is not limited to this. The parameters Kp, Ki, and Kd may also be adjusted based on the time waveform of the weighing signal acquired when the weighing belt conveyor 3 is driven without conveying the article 10. In this case, a weighing signal similar to a steady waveform can be obtained.

[0039] Here, the features of the above-described embodiments of the weighing device according to the present invention will be briefly summarized and listed below in [1] to [5].

[0040] [1] a weighing conveyor (3) for conveying an article (10) to be weighed; a weighing table (511) that is displaced by a load applied to the weighing conveyor; a displacement sensor (512) for detecting the displacement of the weighing platform; an electromagnetic coil (513) that applies a force to the weighing platform against the load; a PID control unit (52) that performs PID calculation on a displacement signal output from the displacement sensor and controls a current flowing through the electromagnetic coil in accordance with the calculation result; a signal output unit (53) that outputs a weighing signal according to the current flowing through the electromagnetic coil; a waveform acquisition unit (62) that acquires a time waveform of the weighing signal output when the PID control unit is operated in a state where the weighing conveyor is driven and each of the P, I, and D parameters is set to an initial value; an adjustment unit (62) that adjusts at least one of the P, I, and D parameters based on the time waveform of the weighing signal acquired by the waveform acquisition unit; a weighing unit (62) that conveys the article on the weighing conveyor and weighs the article based on the weighing signal output when the PID control unit is operated with the P, I, and D parameters adjusted by the adjustment unit set, Weighing device (1). [2] [1] The weighing device according to [1], The adjustment unit is configured from a learning model in which the time waveform of the weighing signal acquired by the waveform acquisition unit is input and the adjusted P, I, and D parameters are learned as outputs. Weighing device. [3] [1] The weighing device according to [1], the waveform acquisition unit acquires a time waveform of the weighing signal output when the PID control unit is operated while the article is being transported by the weighing conveyor; the adjustment unit adjusts at least one of the P, I, and D parameters based on a rising waveform when the weighing signal rises after the article is transferred onto the weighing conveyor. Weighing device. [4] [1] The weighing device according to [1], the waveform acquisition unit acquires a time waveform of the weighing signal output when the PID control unit is operated while the article is being transported by the weighing conveyor; the adjustment unit adjusts at least one of the P, I, and D parameters based on a steady waveform that is vibrating steadily after the item is transferred onto the weighing conveyor and the weighing signal rises. Weighing device. [5] [1] The weighing device according to [1], the waveform acquisition unit acquires a time waveform of the weighing signal output when the PID control unit is operated in a state where the articles are not being transported by the weighing conveyor. Weighing device. [Explanation of symbols]

[0041] 1. Weight sorter (weighing device) 3 Weighing belt conveyor (weighing conveyor) 10 Goods 52 PID control unit 53 Signal output section 62 Control CPU (waveform acquisition section, adjustment section, measurement section) 511 Weighing Platform 512 Displacement Sensor 513 Electromagnetic Coil

Claims

1. a weighing conveyor (3) for conveying an article (10) to be weighed; A weighing platform (511) that is displaced by a load applied to the weighing conveyor; a displacement sensor (512) for detecting the displacement of the weighing platform; an electromagnetic coil (513) that applies a force to the weighing platform against the load; a PID control unit (52) that performs PID calculation on a displacement signal output from the displacement sensor and controls a current flowing through the electromagnetic coil in accordance with the calculation result; a signal output unit (53) that outputs a weighing signal according to the current flowing through the electromagnetic coil; a waveform acquisition unit (62) that acquires a time waveform of the weighing signal output when the PID control unit is operated in a state where the weighing conveyor is driven and each of the P, I, and D parameters is set to an initial value; an adjusting unit (62) that adjusts at least one of the P, I, and D parameters based on the time waveform of the weighing signal acquired by the waveform acquiring unit; a weighing unit (62) that conveys the article on the weighing conveyor and measures the weight of the article based on the weighing signal output when the PID control unit is operated with the P, I, and D parameters adjusted by the adjustment unit set, Weighing device (1).

2. 2. The weighing device according to claim 1, the adjustment unit is configured by a learning model in which the time waveform of the weighing signal acquired by the waveform acquisition unit is input and the adjusted P, I, and D parameters are learned as outputs. Weighing device.

3. 2. The weighing device according to claim 1, the waveform acquisition unit acquires a time waveform of the weighing signal output when the PID control unit is operated while the article is being transported by the weighing conveyor; the adjustment unit adjusts at least one of the P, I, and D parameters based on a rising waveform when the weighing signal rises after the article is transferred onto the weighing conveyor. Weighing device.

4. 2. The weighing device according to claim 1, the waveform acquisition unit acquires a time waveform of the weighing signal output when the PID control unit is operated while the article is being transported by the weighing conveyor; the adjustment unit adjusts at least one of the P, I, and D parameters based on a steady waveform that is vibrating steadily after the item is transferred onto the weighing conveyor and the weighing signal rises. Weighing device.

5. 2. The weighing device according to claim 1, the waveform acquisition unit acquires a time waveform of the weighing signal output when the PID control unit is operated in a state where the articles are not being transported by the weighing conveyor. Weighing device.

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