Sweet potato sorting device

Abstract

To provide a sweet potato sorting device for stably sorting irregularly shaped sweet potatoes into normal sweet potatoes and defective sweet potatoes with high accuracy. [Solution] The sorting device is composed of a conveying unit 1, an information processing unit 2, and a sorting unit 3. The conveying unit 1 is equipped with a conveying means 11, an illumination means 12, and an imaging means 13. The information processing unit 2 calculates the normal or defective reliability of images based on a trained model that has learned to distinguish between normal and defective sweet potatoes, using images captured multiple times by the imaging means 13 while tracking sweet potatoes irradiated with illumination light by the illumination means 12 and moved by the conveying means 11. Sweet potatoes whose cumulative number of images whose normal or defective reliability exceeds a predetermined threshold value exceeds a predetermined number are classified as normal or defective. The sorting unit 3 is located downstream of the conveying unit 1, and switches the sweet potato discharge path based on the judgment of the information processing unit 2 to sort the sweet potatoes into normal and defective sweet potatoes.

Description

[Technical Field]

[0001] Sweet potatoes are agricultural products in which nutrients, primarily starch, accumulate in the roots that grow from the stem. The present invention relates to a sweet potato sorting device that uses image recognition to automatically sort irregularly shaped sweet potatoes into normal and defective sweet potatoes. In particular, the present invention relates to a sorting device that is effective when using sweet potato varieties with high starch content, such as "Koganesengan," "Shiroyutaka," and "Michishizuku," to separate normal sweet potatoes from defective sweet potatoes that require removal of defective parts when using them as raw materials for sweet potato shochu. [Background technology]

[0002] In potato shochu production facilities, the raw material sweet potatoes undergo washing and sorting during the raw material processing process to maintain the quality of the resulting shochu. When sweet potatoes are fed into the raw material processing process, they are first washed to remove any dirt or other impurities from their surface. The washed sweet potatoes then go to the sorting process, where they are separated into two types: normal and defective. Normal sweet potatoes are moved to downstream equipment, such as a potato steamer. Defective sweet potatoes, which have defects that make them unsuitable for shochu production, such as disease, damage, or damaged or discolored areas, are removed from the conveyance line. Once the defects are removed, they are returned to the conveyance line and moved to downstream equipment. In other words, defective sweet potatoes are still used in the production of potato shochu, but careful removal of the defects prevents the development of a spoiled potato odor, resulting in a shochu with a soft, refined sweetness.

[0003] Although the manufacturing facilities for sweet potato shochu are becoming increasingly mechanized, the sorting process in the raw material processing is still performed manually. To maintain the high quality of sweet potato shochu, it is desirable to inspect each and every sweet potato by hand (full inspection) and remove all defects. However, full inspection and removal of all defects requires many workers to work long hours. In large-scale factories, instead of full inspection, sweet potatoes flowing down the conveyor line are visually inspected, allowing good sweet potatoes to flow through while picking out defective sweet potatoes for sorting. When visually sorting sweet potatoes flowing continuously down the conveyor line, defective sweet potatoes can sometimes be overlooked. Furthermore, the judgment criteria become unclear depending on the skill level and individual ability of the workers, resulting in variations in the accuracy of sorting between good and defective sweet potatoes.

[0004] Although not for the sorting of sweet potatoes, Patent Document 1 discloses a technique for sorting transported edamame soybeans. In the example of Patent Document 1, edamame soybeans 60 are supplied in an aligned state from a carry-in device 10 onto a transparent endless belt 21 of an inspection and sorting device 20. In the inspection and sorting device 20, the edamame soybeans 60 are transported on the endless belt 21, and images of the edamame soybeans 60 are taken using image capture devices 24 and 25 positioned to capture the area through which the edamame soybeans 60 pass on the front and back of the endless belt 21. The image captured by the image capture devices 24 and 25 using reflected and transmitted light is then processed to identify defective edamame soybeans 60 based on their shape, color, and internal condition, thereby improving sorting accuracy. Furthermore, when edamame soybeans 60 determined to be defective arrive at a predetermined position, compressed air is sprayed toward a defective product collection box 29 for removal. Furthermore, Patent Document 1 states that the sorting device of the present invention can be applied to sorting any kind of product, including agricultural products and marine products, as an industrial applicability. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-80661 Summary of the Invention [Problem to be solved by the invention]

[0006] The edamame described in Patent Document 1 are relatively thin, with clearly distinguishable surfaces and almost identical shapes. However, sweet potatoes, while roughly cylindrical, are irregular in shape, and even the same variety can vary in thickness and length, and their size also varies depending on the farm and harvest time. Unlike edamame, sweet potatoes can also rotate irregularly during transportation. Furthermore, defective areas on sweet potatoes do not occupy a fixed surface area, nor do they appear in specific locations on the surface. Therefore, it is difficult to adequately detect defective areas simply by photographing them from above and below while they are being transported. Therefore, even if the technology in Patent Document 1 is applied to sorting sweet potatoes in the raw material processing process, it is impossible to properly sort normal and defective sweet potatoes.

[0007] The present invention aims to provide a sweet potato sorting device that can appropriately detect defective parts of sweet potatoes and can sort normal sweet potatoes from defective sweet potatoes with high accuracy and stability. [Means for solving the problem]

[0008] The sweet potato sorting device of the present invention is a sweet potato sorting device that sorts irregularly shaped sweet potatoes into normal and defective sweet potatoes, and the sorting device is composed of a conveying unit, an information processing unit, and a sorting unit, and the conveying unit is equipped with a conveying means, an illumination means, and an imaging means, and the information processing unit calculates the normal reliability or defective reliability based on a trained model that has learned to distinguish normal or defective sweet potatoes for images taken multiple times by the imaging means while tracking the sweet potatoes that are irradiated with illumination light by the illumination means and moved by the conveying means, and distinguishes sweet potatoes as normal or defective sweet potatoes when the cumulative number of images whose normal reliability or defective reliability exceeds a predetermined threshold exceeds a predetermined number, and the sorting unit is located downstream of the conveying unit and switches the sweet potato discharge path based on the determination of the information processing unit to sort the sweet potatoes into normal and defective sweet potatoes.

[0009] The conveying means in the sweet potato sorting device of the present invention is preferably composed of multiple belt conveyors connected in series, with the belt height at the outlet of the upstream belt conveyor being higher than the belt height at the entrance of the downstream belt conveyor so that the sweet potatoes rotate at the transfer point between the belt conveyors, and multiple different sides of the sweet potatoes are photographed by the photographing means. The photographing means photographs the sweet potatoes moving by the conveying means from above, but defective parts of the sweet potatoes are not necessarily located on the top surface and photographed. Therefore, by rotating the sweet potatoes and photographing multiple different sides, it is possible to prevent defective sweet potatoes from being overlooked and improve sorting accuracy. Furthermore, the conveying means may be composed of two belt conveyors, but may also be composed of three or more belt conveyors to further increase the frequency of rotation.

[0010] The sorting section of the sweet potato sorting device of the present invention preferably has a plurality of plates arranged in a width direction perpendicular to the flow direction in which the sweet potatoes are moved by the conveying means, the angle of which can be changed, and the width position of the sweet potato is recognized from an end image photographed by the photographing means of the sweet potato at the end position of the conveying means, and the discharge path for the sweet potato is switched by changing the angle of a single plate or multiple plates connected in the width direction corresponding to the width position. If the width position of the sweet potato is within the range of a single plate, the angle of the corresponding single plate is changed, and if the width position of the sweet potato for which the discharge path is switched exceeds the range of a single plate, the angle of the multiple plates connected in the width direction corresponding to the width position of the sweet potato is changed to switch the discharge path.

[0011] The change holding time for changing the angle of the plate may be set to the time required for the largest sweet potato to pass through, but it is preferable to measure the flow direction length of the sweet potato from the end image and change the angle of the plate to a change holding time corresponding to the flow direction length. For example, if small sweet potatoes in the same position in the width direction are relatively close to each other and are alternately classified as normal sweet potatoes and defective sweet potatoes, adopting a change holding time corresponding to the flow direction length can prevent the sweet potatoes from flowing into the wrong discharge path and being sorted.

[0012] In the sweet potato sorting device of the present invention, if the defective sweet potatoes exceed a predetermined flow rate during sweet potato sorting, it is preferable to lower the normal reliability threshold or raise the defective reliability threshold set in the information processing unit. The flow rate indicated here may be the weight of sweet potatoes per unit time or the number of sweet potatoes per unit time. Because sweet potatoes are an agricultural product, the proportion of defective sweet potatoes with defects is not constant. It is desirable to sort even sweet potatoes with minor defects as defective and remove the defective parts downstream of the sorting device. However, if the flow rate of defective sweet potatoes exceeds the processing capacity downstream of the sorting device, the sweet potato sorting speed must be reduced. This reduces work efficiency and requires an extended operation time. Therefore, if the flow rate of defective sweet potatoes becomes excessive, it is preferable to change the setting to within a threshold range that is deemed acceptable in terms of quality, limiting the flow rate of defective sweet potatoes, and continuing the sorting operation.

[0013] Furthermore, if the flow rate of defective sweet potatoes drops after exceeding a predetermined flow rate during sweet potato sorting and limiting the flow rate of defective sweet potatoes, the threshold value of normal reliability or defective reliability set by the information processing unit may be returned to its original value. Furthermore, the threshold value of normal reliability or defective reliability may be adjusted so that the flow rate of defective sweet potatoes remains constant within a threshold range that can be determined to be within an acceptable quality range. [Effects of the Invention]

[0014] According to the sweet potato sorting device of the present invention, by discriminating images of irregularly shaped sweet potatoes based on a trained model, it is possible to sort normal and defective sweet potatoes with high accuracy and stability, and the sorting work between normal and defective sweet potatoes can be automated. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a side cross-sectional view of a sweet potato sorting device according to one embodiment of the present invention. [Figure 2] Front cross-sectional view of the sweet potato sorting device shown in Figure 1 [Figure 3] A cross-sectional plan view of the sweet potato sorting device shown in Figure 1 [Figure 4] Enlarged view of part S in Figure 3 [Figure 5] 1 is a side cross-sectional view of a sweet potato sorting device according to another embodiment of the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0016] An embodiment of the present invention will be described with reference to Figures 1 to 5. Regarding the sweet potato sorting device of the present invention, Figure 1 is a side cross-sectional view, Figure 2 is a front cross-sectional view, Figure 3 is a plan cross-sectional view, and Figure 4 is an enlarged view of section S in Figure 3. Figure 5 is a side cross-sectional view of the sorting device to which a foreign object discharge path has been added. The numerical values ​​in this embodiment are merely examples and may be changed as appropriate. In this embodiment, a sorting device is described that sorts sweet potatoes transported from a cleaning device at a processing capacity of 11.5 t / h (approximately 1,000 potatoes per minute).

[0017] The sorting device of this embodiment is composed of a conveying unit 1 equipped with a conveying means, an illumination means, and an imaging means, an information processing unit 2, and a sorting unit 3. In this embodiment, a belt conveyor 11 is provided as the conveying means of the conveying unit 1. The belt conveyor 11 comprises an upstream belt conveyor 111 having a total length of 1850 mm and a width of 1500 mm, and a downstream belt conveyor 112 having a total length of 750 mm and a width of 1500 mm, which are installed in series. The belt speed of the upstream belt conveyor 111 is 10 m / min, and the belt speed of the downstream belt conveyor 112 is 20 m / min, so that when the sweet potatoes transfer to the downstream belt conveyor 112, the spacing between the sweet potatoes is wider than when they were being transported on the upstream belt conveyor 111. In addition, the belt height at the exit of the upstream belt conveyor 111 is made higher than the belt height at the entrance of the downstream belt conveyor 112 so that the sweet potatoes rotate at the transfer point between the upstream belt conveyor 111 and the downstream belt conveyor 112. The rotation of the sweet potatoes allows multiple different sides of the sweet potatoes to be photographed by the photographing means.

[0018] The width and speed of the belt conveyor 11 can be appropriately designed taking into account the degree of dispersion of the sweet potatoes in the sorting section 3 and the processing capacity of the sweet potatoes. In addition, the overall length of the belt conveyor 11 can be appropriately designed and modified depending on the time the sweet potatoes are to be retained on the belt conveyor 11, taking into account the number of times the images are taken in the transport section 1. Furthermore, in this embodiment, the belt conveyor 11 as a transport means is composed of two belt conveyors, the upstream belt conveyor 111 and the downstream belt conveyor 112, but the belt conveyor 11 can also be composed of three or more belt conveyors to increase the frequency of the rotational movement of the sweet potatoes at the transfer section.

[0019] In this embodiment, the conveying section 1 is provided with eight lights 12 above the belt conveyor 11 as illumination means: two in the sweet potato flow direction and four rows in the width direction perpendicular to the flow direction. The lights 12 illuminate the sweet potatoes at varying angles to reduce the shadows cast on the sweet potatoes, allowing for accurate imaging of damaged and discolored areas. Furthermore, if a case with a white interior is installed surrounding the belt conveyor 11, the shadows cast on the sweet potatoes can be reduced by the effect of light reflected from the interior of the case. The number of lights 12 can be adjusted appropriately, taking into account the performance of each light. Additionally, nine inspection cameras 13 are provided above the belt conveyor 11 as imaging means: three in the sweet potato flow direction and three rows in the width direction. The inspection cameras 13 track the sweet potatoes from the time they enter the conveying section 1 until they reach the sorting section 3, capturing 130 images per sweet potato. The information processing unit 2 identifies defective sweet potatoes based on the images taken by the inspection camera 13. The number of times images are taken can be changed as appropriate depending on the sweet potato processing capacity, the belt speed of the belt conveyor 11, and the performance of the inspection camera 13 and the information processing unit 2. The number of inspection cameras 13 can be changed as appropriate, taking into account the performance of each camera.

[0020] The information processing unit 2 has the function of recognizing sweet potatoes from images captured by the inspection camera 13 based on previously learned image data of sweet potatoes. When the information processing unit 2 recognizes a sweet potato, it surrounds the sweet potato with a rectangle along both ends of the width and length of the belt conveyor 11 (see Figure 4), and sets the width X, length Y, and center Z of the sweet potato (the intersection of the diagonals of the rectangle). Furthermore, it assigns an arbitrary tracking ID number (No. 1 to No. 3 in Figure 4) to each recognized sweet potato so that each sweet potato can be tracked. The shape surrounding the recognized sweet potato can be any shape that can surround the entire sweet potato, and can be a polygon other than a rectangle or an ellipse.

[0021] Next, the information processing unit 2 calculates the defect reliability of the recognized sweet potato based on a trained model that has learned about defective sweet potatoes, and determines the sweet potato as defective if the defect reliability exceeds a threshold. In this embodiment, the defect reliability ranges from 0 to 1, with larger values ​​indicating a higher probability of defect. Sweet potatoes with a defect reliability exceeding the threshold of 0.85 are determined to be defective. To avoid erroneous determinations, the number of times each sweet potato has been determined to be defective is passed from the upstream inspection camera 13 to the downstream inspection camera 13, and sweet potatoes with images determined to be defective two or more times are determined to be defective. The cumulative number of images determined to be defective is linked to each sweet potato's tracking ID number, so defective sweet potatoes can be tracked even if the sweet potato is rotated and the defective part is turned inside out and becomes invisible. The threshold value of the defective reliability set here and the cumulative number of images to determine a defective sweet potato can be set appropriately depending on the sweet potato to be sorted, etc.

[0022] The sorting section 3, located downstream of the conveying section 1, is equipped with 20 plates 31 arranged in the width direction. The plates 31 are installed with their upper surfaces inclined toward normal discharge path B so that normal sweet potatoes dropping from the end of the downstream belt conveyor 112 will fall into normal discharge path B. The angle of each plate 31 can be changed using an air cylinder 32 attached to it, allowing the plate 31 to be swung so that its upper surface is vertical (opening the plate 31). Opening the plate 31 allows defective sweet potatoes to fall into defective discharge path A. In the present invention, it is sufficient to allow normal and defective sweet potatoes to fall into different discharge paths, so the discharge paths may be reversed. In other words, the plate may be opened for normal sweet potatoes, and the plate may not be opened for defective sweet potatoes, allowing them to fall into their respective discharge paths.

[0023] Below, in this embodiment, the flow from when sweet potatoes are put into the sorting device to when they are sorted will be described.

[0024] Sweet potatoes that have been cleaned in advance using a cleaning device are placed into the sorting device. The placed sweet potatoes are photographed by an upstream inspection camera 13, and the photographed image is sent to the information processing unit 2. The information processing unit 2 recognizes sweet potatoes from the image based on pre-trained image data of sweet potatoes, calculates the defect reliability of the recognized sweet potatoes based on a trained model that has learned about defective sweet potatoes, and determines whether or not they are defective. Sweet potatoes that have been judged as defective two or more times are confirmed as defective.

[0025] The timing for opening and closing the plates 31 was determined by setting a virtual reference line L at the downstream end of the downstream belt conveyor 112. When the center Z of a sweet potato determined to be defective crossed the reference line L, the air cylinder 32 of the sorting unit 3 was activated to open one or more plates 31 that overlapped the width X of the sweet potato for a modified holding time corresponding to the length Y of the sweet potato, allowing the defective sweet potato to fall into the defective discharge path A. In this embodiment, the modified holding time for opening the plates 31 was 0.40 seconds for sweet potatoes 100 mm or longer and 0.35 seconds for sweet potatoes less than 100 mm. On the other hand, for normal sweet potatoes not determined to be defective, the air cylinder 32 of the sorting unit 3 was not activated, and the sweet potato was rolled along the slope of the plate 31 and dropped into the normal discharge path B. In this embodiment, the modified holding time was selected from two preset values, but it may also be a modified holding time proportional to the length Y of the sweet potato.

[0026] In this embodiment, after operating for approximately 3.5 hours and sorting 40 tons of sweet potatoes, the percentage of sweet potatoes sorted as defective was 6.67% of the total. This operation was able to sort defective sweet potatoes in the same way as conventional visual inspection by humans, and was able to maintain a consistent high level of precision from start to finish.

[0027] In the above embodiment, the information processing unit 2 uses a learning model that has learned about defective sweet potatoes to discriminate defective sweet potatoes and sort normal and defective sweet potatoes. However, a learning model that has learned about normal sweet potatoes may also be used to discriminate normal sweet potatoes and sort normal and defective sweet potatoes. Furthermore, the normal reliability or defective reliability may be calculated based on a trained model that has learned about both normal and defective sweet potatoes. Using a trained model that has learned about both normal and defective sweet potatoes is preferable because it increases the accuracy of the reliability.

[0028] Furthermore, while the stems of sweet potatoes are removed reliably during harvesting, some sweet potatoes have roots at the tips that are not removed. If these roots are transported as they are to downstream equipment such as a disintegrator or pump, they can become entangled in the rotating parts, causing the equipment to overload and stop. Therefore, it is preferable to calculate the normality or defect reliability based on a trained model that has learned that sweet potatoes with roots at the tips are defective sweet potatoes rather than normal sweet potatoes.

[0029] The threshold value of the defect reliability for distinguishing defective sweet potatoes set in the information processing unit 2 may be set to any value, but lowering the threshold reduces the risk of defective sweet potatoes being mixed into the normal discharge route, but increases the risk of normal sweet potatoes being sorted into the defective discharge route; therefore, an appropriate threshold value is set according to the learning accuracy of the information processing unit 2. Defective sweet potatoes may also be further classified into two or more types based on the type and degree of defect, and different threshold values ​​may be set for each. For example, defective sweet potatoes that are discolored may be separated from defective sweet potatoes that have cracked, or defective sweet potatoes with many discolored parts may be separated from defective sweet potatoes with few discolored parts.

[0030] Instead of the timing of opening and closing the plate material 31 in the above embodiment, the plate material 31 may be opened a certain time after the center Z of the sweet potato passes the reference line L. When the flow rate of sweet potatoes is high and the distance between sweet potatoes in the flow direction is short, sorting errors can be prevented by opening the plate material 31 only at the moment when the sweet potato falls from the outlet of the downstream belt conveyor 112 and passes by. Also, the plate material 31 may be opened after the end of the sweet potato passes the reference line L, rather than the center Z of the sweet potato.

[0031] Although it is possible to prevent sweet potato clogging due to the opening and closing operation of the plate 31 in the sorting section 3 by adjusting the opening and closing timing of the plate 31, if it is not possible to recognize that sweet potatoes have become clogged, the possibility of the device stopping or being damaged increases. Therefore, a monitoring camera separate from the inspection camera 13 may be installed above the sorting section 3 to monitor for sweet potato clogging in the sorting section 3 and sound an alarm if sweet potatoes become clogged. Alternatively, a monitoring camera may not be installed and the inspection camera 13 may also be used to monitor for clogging.

[0032] During harvesting, foreign objects such as stones may occasionally be mixed in with sweet potatoes. If the foreign object moves to a device downstream of the sweet potato sorting device, the downstream device will stop or be damaged, so the foreign object must be sorted out and removed. It is preferable to use a trained model that has been trained with the foreign object added as the trained model for the information processing unit 2, to sort out the foreign object as a defective sweet potato, and to remove the foreign object when sorting out the defective sweet potato sorted into the defective sweet potato side.

[0033] Furthermore, while defective sweet potatoes and normal sweet potatoes were sorted in the above embodiment, it is also possible to have the trained model of the information processing unit 2 learn foreign objects in addition to defective and normal sweet potatoes, so that the sweet potatoes can be sorted into three types: defective sweet potatoes, normal sweet potatoes, and foreign objects. In this case, as shown in Figure 5, additional plate 33 and air cylinder 34 can be installed below plate 31 and air cylinder 32 to sort defective sweet potatoes, normal sweet potatoes, and foreign objects into defective discharge path A, normal discharge path B, and foreign object discharge path C. In other words, if a foreign object is identified, opening both plate 31 and plate 33 will allow the foreign object to fall into foreign object discharge path C.

[0034] Furthermore, if the sweet potatoes flowing on the belt conveyor 11 become crowded together, it may become difficult to sort the sweet potatoes. To sort the sweet potatoes efficiently, multiple conveying lanes may be provided as a dispersion mechanism to forcibly disperse the sweet potatoes flowing on the belt conveyor 11. For example, multiple conveying lanes may be provided on the belt conveyor 11 by adding members along the flow direction on the belt conveyor 11, which is the conveying means. [Explanation of symbols]

[0035] 1. Conveyor 11 Belt conveyor (transport means) 111 Upstream belt conveyor 112 Downstream belt conveyor 12 Light (lighting means) 13 Inspection camera (photography means) 2. Information Processing Section 3. Sorting Department 31 Board material 32 Air cylinder 33 Board material 34 Air cylinder A. Defective discharge route B. Normal excretion pathway C. Foreign body excretion route

Claims

1. A sweet potato sorting device that sorts irregularly shaped sweet potatoes into normal sweet potatoes and defective sweet potatoes, The sorting device is composed of a conveying unit, an information processing unit, and a sorting unit, the transport unit includes a transport means, an illumination means, and an imaging means; The information processing unit calculates a normal reliability or a defective reliability for images captured multiple times by the photographing unit while tracking the sweet potato that is irradiated with illumination light by the lighting unit and moved by the conveying unit, based on a trained model that has learned about normal sweet potatoes and defective sweet potatoes, and determines as normal or defective sweet potatoes those sweet potatoes for which the cumulative number of images for which the normal reliability or the defective reliability exceeds a predetermined threshold exceeds a predetermined number, The sorting unit is located downstream of the conveying unit and switches the discharge path of the sweet potatoes based on the determination of the information processing unit to sort the sweet potatoes into normal sweet potatoes and defective sweet potatoes.

2. The conveying means is composed of a plurality of belt conveyors connected in series, The belt height at the outlet of the upstream belt conveyor is set higher than the belt height at the inlet of the downstream belt conveyor so that the sweet potatoes can rotate at the transfer section between the belt conveyors.

2. The sweet potato sorting device according to claim 1, wherein the photographing means photographs different surfaces of the sweet potato.

3. The sorting section has a plurality of plates arranged in a width direction perpendicular to the flow direction in which the sweet potatoes move by the conveying means, and the angle of the plates can be changed, The width direction position of the sweet potato is recognized from an end image of the sweet potato at the end position of the conveying means photographed by the photographing means, A sweet potato sorting device as described in claim 1, characterized in that the discharge path of the sweet potatoes is switched by changing the angle of a single plate member or multiple plates consecutive in the width direction corresponding to the width direction position.

4. Measure the flow direction length of the sweet potato from the end image; A sweet potato sorting device as described in claim 3, characterized in that the angle of the plate material is changed by a changed holding time corresponding to the flow direction length.

5. A sweet potato sorting device as described in claim 1, characterized in that if the number of defective sweet potatoes during the sweet potato sorting operation exceeds a predetermined flow rate, the normal reliability threshold set in the information processing unit is lowered or the defective reliability threshold is raised.

Images