A fruit sugar content spectral detection device

Abstract

This utility model relates to a fruit sugar content spectral detection device, belonging to the field of non-destructive testing technology for fruit quality. It aims to solve the problems of vibration interference, affecting the stability of spectral acquisition and the accuracy of sugar content measurement, caused by the rigid connection between the conveyor mechanism and the detection chamber in existing equipment. The device includes a conveyor belt mechanism, a chamber, and an image acquisition device. The chamber has a transversely penetrating detection channel, and an internally mounted, liftable support is located above the detection channel and driven by a screw-driven lifting mechanism. The image acquisition device is installed under a pan-tilt unit at the bottom of the support. The conveyor belt mechanism horizontally penetrates the detection channel and is not in contact with the chamber, forming a vibration isolation gap between them. A fruit loading box is placed on the bearing surface. This device is mainly used for efficient, stable, and non-destructive testing of the sugar content of fruits such as durian.

Description

Technical Field

[0001] This utility model relates to the field of fruit quality testing technology, and in particular to a fruit sugar content spectral testing device. Background Technology

[0002] In the field of post-harvest quality inspection of fruit, non-destructive testing equipment based on spectral technology has become an important research direction and application. These devices typically use a conveyor mechanism to feed the fruit into the testing chamber, where an internal optical system acquires and analyzes images. However, in practical applications, the overall structure and working mechanism of such equipment still have some inherent problems that affect the accuracy and stability of the testing.

[0003] First, vibration interference from the equipment is a major factor contributing to measurement errors. In common equipment designs, the conveyor belt mechanism and the housing structure used for spectral acquisition are usually rigidly connected. During start-up, shutdown, and constant-speed operation, the conveyor belt inevitably generates mechanical vibrations. These vibrations are directly transmitted through the connecting structure to the precision optical acquisition unit inside the housing, causing camera blurring or image shift, ultimately reducing the signal-to-noise ratio of the acquired spectral data and compromising the accuracy of the sugar content prediction model. Attempts to reinforce the structure or install simple vibration damping pads often fail to effectively isolate broadband vibrations while maintaining the overall rigidity of the equipment.

[0004] Secondly, the stability and accuracy of the focusing mechanism in the optical system need improvement. To accommodate the detection of fruits of different sizes, the camera height needs to be adjustable. Existing equipment either uses manual adjustment, which is inefficient and relies heavily on operator experience; or it uses a simple motor-driven lifting mechanism, but the structural design often neglects the constraint of off-center load torque. A single lead screw or guide rail is prone to jamming, wobbling, or even slight torsion when bearing asymmetrical loads such as those from the camera gimbal, causing the camera's optical axis to fail to remain perpendicular and resulting in poor repeatability of posture after each lifting and lowering. This leads to random errors in object distance and field of view in the acquired spectral images, severely affecting the consistency and comparability of data from different batches of tests.

[0005] Furthermore, the lack of effective guidance in the feeding process means that when fruit loading boxes enter the narrow inspection channel, they are prone to collisions and jamming at the entrance due to placement deviations or conveyor belt misalignment, leading to production interruptions and affecting the automation and continuity of inspection efficiency.

[0006] In summary, existing technologies suffer from problems such as vibration transmission, insufficient stability of the focusing mechanism, and inadequate material feeding guidance, which hinder the development of fruit sugar content spectral detection equipment towards higher precision, higher efficiency, and greater stability. Utility Model Content

[0007] The purpose of this invention is to solve the following problems: In existing fruit sugar content spectral detection equipment, vibrations generated by the conveyor mechanism are easily transmitted to the image acquisition unit, leading to blurred images and unstable spectral data, ultimately affecting the accuracy of the sugar content prediction model. The root cause lies in the fact that the conveyor mechanism and the detection chamber are mostly rigidly connected, lacking effective vibration isolation design.

[0008] Existing lifting mechanisms suffer from unstable operation, jamming, and failure to self-lock after power failure when used to adjust camera height. Single-screw drives lack sufficient rigidity when bearing the eccentric torque of the gimbal and camera, easily leading to frame torsion and affecting camera posture and image repeatability.

[0009] When detecting spherical or irregularly shaped fruits, unidirectional light source illumination can easily create strong reflective spots or heavy shadows on the fruit surface, obscuring the true spectral information and resulting in uneven reflectance data, which introduces errors into subsequent modeling.

[0010] The lack of effective guidance during the material feeding process means that when fruit loading boxes enter the narrow inspection channel, they are prone to collisions and jamming at the entrance due to placement deviations or conveyor belt misalignment, leading to production interruptions and affecting the automation and continuity of inspection efficiency.

[0011] The inability to accurately and reliably detect the moment each fruit loading box enters the detection channel makes it difficult to trigger the control system to perform synchronous image acquisition. Common causes include improper sensor installation location or poor sensor type selection, which can easily lead to missed detections, false triggers, or unstable signals.

[0012] The system cannot automatically and non-contactly acquire the height and dimensions of the fruit before it enters the detection area. This prevents the system from proactively and adaptively adjusting the camera to the optimal focus height. Relying on a fixed height or manual prediction leads to unstable image quality and affects detection accuracy.

[0013] The fixed, rigid feeding channel places extremely stringent requirements on the dimensional tolerances of the fruit loading box. If the size is slightly too large, it will jam; if the size is slightly too small, it will wobble. It has poor fault tolerance and is prone to jamming due to minor dimensional deviations or improper placement in actual production.

[0014] Ordinary flat or curved guide plates often have point or line contact with the side walls of loading boxes of specific shapes. The constraint force is concentrated and unstable, which can easily cause the box to tilt, shake or wear during the guiding process, affecting the consistency of its posture when entering the detection channel.

[0015] Using simple flat plates or trays to hold fruit can easily cause the fruit to roll and shift during transport and testing, resulting in inconsistent target areas for each spectral acquisition and severely reducing the repeatability and accuracy of the test data.

[0016] To achieve the above objectives, this utility model provides a fruit sugar content spectral detection device, comprising a conveyor belt mechanism, a housing, and an image acquisition device. The housing has a transversely penetrating detection channel. Inside the housing, a liftable support is installed above the detection channel, including a screw lifting mechanism, a frame driven by the screw lifting mechanism, and a pan-tilt unit installed at the bottom of the frame. The conveyor belt mechanism horizontally penetrates the detection channel, with its frame and housing connected without contact, forming a vibration isolation gap between them. A fruit loading box is placed on the bearing surface of the conveyor belt mechanism. The image acquisition device, fixed below the pan-tilt unit, includes a multispectral camera for acquiring images of the fruit below.

[0017] Preferably, the screw lifting mechanism of this utility model includes a vertically arranged screw and a nut seat fixed to the frame, the screw passing through the nut seat and forming a self-locking thread engagement with it; an auxiliary guide assembly including two guide shafts parallel to the screw, the two ends of the guide shafts being fixed to the internal frame of the housing; linear bearings fixed to both ends of the frame, the linear bearings being sleeved on the guide shafts; and a servo motor driving the screw to rotate, the servo motor being fixed to the housing through a flange.

[0018] Preferably, the bottom of the frame of this utility model is provided with multiple evenly distributed light source modules, and the light emission direction of the light source modules is directed towards the fruit carrying area below their center.

[0019] Preferably, the detection channel entrance of this utility model is provided with a detachable feeding rack, which includes: a base that is engaged with the frame of the conveyor belt mechanism, the base having a positioning protrusion, and the frame having a positioning groove matching the protrusion; a plurality of parallel feeding channels parallel to the conveying direction, the width of each feeding channel being matched with the gap of the fruit loading box; and an end plate of the feeding rack near the detection channel, the end plate having guide doors corresponding to the feeding channels one by one, the width of the guide doors being greater than the width of the loading box.

[0020] Preferably, the end plate of this utility model has a first mounting hole, and the photoelectric sensor is fixed in the first mounting hole; the transmitting end and the receiving end of the photoelectric sensor are symmetrically arranged on the two side walls of the guide door, and its optical path direction is perpendicular to the conveying direction and horizontally penetrates the guide door, for sensing the fruit loading box passing through the guide door, and is connected to the control unit through a cable.

[0021] Preferably, the feed rack of this utility model has a second mounting hole, and the distance sensor is fixed in the second mounting hole; the probe of the distance sensor is vertically downward facing the bearing surface under the feed channel, and its signal output terminal is connected to the control unit through a cable.

[0022] Preferably, the output of the control unit of this invention is connected to the servo motor via a cable for adjusting the distance between the image acquisition device and the bearing plane.

[0023] Preferably, each side wall of the feed channel of this utility model is provided with a guiding mechanism; the guiding mechanism includes: a guide plate, which extends toward the guide door, with one end near the guide door being a free end, and the other end being connected to the side wall of the feed channel through a hinge shaft, so that the guide plate can swing around the hinge shaft in a vertical plane; a compression spring, installed on the side wall of the feed channel, elastically supporting the guide plate; the guide plates on both sides of the feed channel together form a tapered guiding channel under the elastic support of the compression spring.

[0024] Preferably, the side of the guide plate of this invention is an irregular shape, which is adapted to the shape of the side wall of the fruit loading box.

[0025] Preferably, the bottom of the fruit loading box of this utility model is provided with a limiting groove for accommodating and limiting the fruit, and the top is an open structure.

[0026] This utility model has at least the following beneficial effects: 1. By setting a vibration isolation gap, mechanical decoupling between the conveyor belt mechanism and the detection box was achieved, effectively blocking the transmission of vibrations generated by the conveyor belt operation to the image acquisition device. This provides a stable working environment for the multispectral camera, fundamentally ensuring that the acquired fruit images are clear and stable, significantly reducing spectral data noise, and laying a solid foundation for the accuracy of subsequent sugar content analysis.

[0027] 2. The lead screw and nut transmission pair provides reliable self-locking performance, ensuring that the frame can stably remain in any position after the motor is powered off, thus enhancing equipment safety. The combination of dual guide optical axes and linear bearings greatly enhances the rigidity and stability of the lifting motion, effectively suppressing possible torsion and swaying of the frame during movement, ensuring that the gimbal and camera always maintain a precise horizontal posture, thereby ensuring a high degree of repeatability in imaging field of view and focal length.

[0028] 3. Multiple light source modules, evenly illuminating from different angles, together form a uniform shadowless illumination field. This multi-angle collaborative illumination scheme can effectively eliminate specular reflection highlights and deep shadows on the surface of spherical fruits caused by a single light source, ensuring that spectral information from all parts of the fruit surface can be collected fully and consistently. This greatly reduces measurement errors caused by uneven illumination, improves the quality of spectral data, and enhances the robustness of the sugar content prediction model.

[0029] 4. The detachable snap-fit ​​design facilitates cleaning and maintenance of this area. The combination of parallel feed troughs and guide doors forms a guiding mechanism that effectively corrects the posture and positional deviations of the fruit loading boxes before entering the detection channel, ensuring that they enter the detection area with a stable and consistent trajectory. This significantly reduces the risk of jamming and improves the continuity and efficiency of equipment operation.

[0030] 5. U-shaped photoelectric sensors are directly integrated into both sides of the guide gate, forming a precise detection light curtain. This arrangement ensures that every loading box entering the detection channel is detected without exception, achieving strict synchronization between the detection event and the spatial position of the loading box. This installation method is compact in structure, provides stable and reliable signals, and offers a precise timing trigger reference for the control system, guaranteeing a high degree of matching between image acquisition and fruit position.

[0031] 6. Online, non-contact measurement of fruit height during the feeding stage provides the system with pre-processing time. This allows the control system to adjust the camera to the preset optimal imaging height based on real-time measured fruit height data, before the fruit arrives at the inspection station. This achieves automated and adaptive adjustment of the inspection height, ensuring that fruits of different sizes can be imaged under optimal conditions and improving the consistency of inspection accuracy.

[0032] 7. The control unit performs closed-loop control of the servo motor based on sensor signals, achieving fully automated, intelligent, and high-precision camera height adjustment. This electronic control method offers rapid response and accurate positioning, completely replacing inefficient and error-prone manual adjustments. It is seamlessly integrated into the automated detection process, ensuring a high degree of uniformity in spectral acquisition conditions for different batches of fruit, and greatly improving the automation level and detection efficiency of the equipment.

[0033] 8. The swing-type elastic guide mechanism provides self-adaptive capability for the feeding process. The guide plate can swing passively under the action of a compression spring, which can accommodate the dimensional tolerances of the fruit loading boxes and continuously provide flexible lateral correction force. This tapered elastic channel structure reduces the precision requirements for the processing and placement of the loading boxes, significantly improves the smoothness and reliability of feeding, and reduces downtime caused by box jamming.

[0034] 9. The irregularly shaped surface design, matching the sidewall shape of the loading box, optimizes traditional point-line contact into large-area surface contact. This contact method results in a more uniform distribution of guiding force and more stable and reliable constraint, greatly reducing the shaking, rotation, and wear of the loading box during travel. This ensures that the loading box enters the detection area in the correct and stable posture, providing precise positional assurance for subsequent spectral acquisition.

[0035] 10. The limiting groove effectively holds the fruit in place, preventing it from rolling or shifting during transport and inspection, stabilizing it in a preset, fixed position and posture. The open top structure ensures unobstructed optical detection field of view and light path. Together, these features guarantee a high degree of consistency in the spectral image acquisition area for each measurement, fundamentally improving the repeatability and accuracy of the detection data.

[0036] Other advantages, objectives and features of this invention will be partly apparent from the following description, and partly understood by those skilled in the art through study and practice of this invention. Attached Figure Description

[0037] Figure 1 This is a three-dimensional structural diagram of the fruit sugar content spectral detection device of this utility model; Figure 2 This is a side view of the fruit sugar content spectral detection device of this utility model; Figure 3 This is a three-dimensional structural diagram of the box body of this utility model; Figure 4 This is a three-dimensional structural diagram showing the cooperation of the frame, screw lifting mechanism, and auxiliary guide components of this utility model. Figure 5 This is a side view of the frame, screw lifting mechanism, and auxiliary guide components of this utility model. Figure 6 This is a partial structural diagram of the feeding rack of this utility model; Figure 7 This is a schematic diagram of the feed channel of this utility model.

[0038] The components include: box body 10, conveyor belt mechanism 20, feeding rack 30, fruit loading box 40, durian pulp 50, image acquisition device 60, light source module 70, detection channel 101, heat dissipation hole 102, lead screw 103, frame 104, guide optical axis 105, linear bearing 106, gimbal 107, transmission gear 1031, servo motor 1032, nut seat 1041, frame 201, belt 202, feeding trough 301, partition 302, guide door 303, positioning protrusion 304, guide plate 305, hinge shaft 306, compression spring 307, and end plate 308. Detailed Implementation

[0039] The present invention will be further described in detail below with reference to the embodiments, so that those skilled in the art can implement it based on the description.

[0040] As shown in Figures 1-7, a fruit sugar content spectral detection device includes a conveyor belt mechanism 20, a housing 10, and an image acquisition device 60. The housing 10 has a transversely penetrating detection channel 101 with a rectangular cross-section; its width can be set to 600 mm and its height to 400 mm. The interior of the housing 10 is constructed of welded profiles to form a frame, and a liftable support is mounted on this frame and positioned directly above the detection channel 101. The liftable support includes a screw lifting mechanism 501, a frame 104 driven by the screw lifting mechanism, and a gimbal 107 threadedly connected to the bottom of the frame 104. The frame 104 can be made of aluminum alloy, and the gimbal 107 can be a standard universal gimbal. The conveyor belt mechanism 20 horizontally penetrates the detection channel 101, and its frame 201 is independently fixed to the ground by anchor bolts, without contact with the housing 10, forming a vibration isolation gap with a width of 20 mm to 50 mm between them. A fruit loading box 40, which is injection molded, is placed on the bearing plane 101 of the conveyor belt mechanism 20. An image acquisition device 60 is fixed to the bottom of the pan-tilt head 107 by screws. Its multispectral camera can be a model with a wavelength range between 900 nm and 1700 nm, and the camera lens faces vertically downwards to acquire images of the fruit directly below it. Preferably, the outer wall of the box is provided with heat dissipation holes 102.

[0041] The conveyor belt mechanism 20 is driven by a motor-driven roller that moves the belt. The belt linear speed can be set to 100 mm per second. The fruit loading box 40 is placed on the conveyor belt bearing plane 101 by a person or a robot and passes through the detection channel 101 of the box 10 at a uniform speed. During the passage, the image acquisition device 60, located on a liftable bracket, takes images of the fruit inside the box. The lifting function of the liftable bracket is used to adapt to the detection needs of fruits of different sizes. By adjusting, the multispectral camera lens maintains a fixed optimal imaging distance with the fruit surface. This distance can typically be set between 300 mm and 500 mm. Throughout the operation, because the conveyor belt mechanism 20 and the box 10 are independent of each other and there is a vibration isolation gap, the vibration generated by the conveyor belt during operation is effectively isolated, preventing the vibration from being transmitted to the image acquisition device 60, thereby ensuring the clarity and stability of the image acquisition.

[0042] Compared to the closest existing technology, existing equipment typically rigidly connects the conveyor belt mechanism 20 to the detection chamber 10, leading to mutual vibration interference and affecting measurement accuracy. The distinguishing technical feature of this embodiment is the inclusion of a vibration isolation gap, achieving mechanical decoupling and thus solving the problem of vibration interference, ensuring the accuracy of the sugar content spectral data. This equipment structure is easy to assemble and implement, enabling efficient, stable, and non-destructive detection of fruit sugar content.

[0043] In another embodiment, the lead screw lifting mechanism 501 of the fruit sugar content spectral detection device includes a vertically arranged lead screw 103 and a nut seat 1041 fixed to the frame 104 by screws. The lead screw can be single or two; when two are used, a motor drives synchronous rotation. The lead screw 103 is a trapezoidal threaded lead screw with a nominal diameter of 20 mm and a lead of 5 mm. It passes through the nut seat 1041 and forms a self-locking thread engagement with its internal trapezoidal threaded hole. This engagement ensures that the frame 104 can reliably remain in any position without slipping when the motor is powered off. The auxiliary guiding assembly includes at least two guide shafts 105 parallel to the lead screw 103. The diameter of the guide shafts can be 16 mm, and preferably, the surface is hard chrome plated to enhance wear resistance. The two ends of the guide shafts 105 are fixed to the internal frame of the housing 10 by flange bearing seats, and their parallelism error after installation is less than 0.05 mm. Correspondingly, a linear bearing 106 is fixedly connected to each side of the frame 104 and the guide optical shaft 105 via a connecting block. The linear bearing 106 can be a standard LM type linear bearing, with its inner hole fitted onto the corresponding guide optical shaft 105, providing precise guidance for the lifting and lowering movement of the frame 104 and withstanding possible bending moments. The servo motor 1032 that drives the lead screw 103 to rotate is fixedly mounted on the top of the housing 10 via its own flange and bolts. The output shaft of the servo motor 1032 is connected to the lead screw 103 via a common mechanism such as a transmission gear 1031, a transmission screw, a helical gear, a bevel gear, or a rigid coupling.

[0044] During operation, the control unit sends pulse signals to the servo motor 1032, driving it to rotate precisely. The motor's rotation drives the lead screw 103 to rotate synchronously. Since the nut seat 1041 is constrained by the frame 104 and the guide mechanism and cannot rotate, the rotational motion of the lead screw is converted into linear lifting motion of the frame 104, along with the pan-tilt head 107 and the image acquisition device 60 below it. The linear bearing 106 slides along the guide optical axis 105, effectively preventing the frame 104 from rotating or jamming during lifting, ensuring the smoothness and accuracy of the movement. The lifting stroke can be set according to the size of the fruit, with a maximum stroke of 300 mm and a positioning accuracy of ±0.1 mm, thus enabling the multispectral camera to be precisely adjusted to the preset shooting height.

[0045] Compared to common chain or wire rope lifting methods, this implementation uses a lead screw and nut system supplemented by optical axis guidance. Its distinguishing technical features and advantages lie in combining the self-locking characteristics of lead screw drive with the high rigidity of optical axis guidance. The self-locking characteristic of the lead screw and nut eliminates the need for an additional braking device, simplifying the structure and improving safety. Meanwhile, the dual optical axis guidance structure overcomes the drawback of a single lead screw easily jamming under eccentric loads, ensuring that the gimbal 107 and camera maintain a horizontal posture throughout the lifting process. This provides crucial positional stability for obtaining clear and consistent spectral images, ultimately improving the accuracy and repeatability of sugar content detection results.

[0046] In another embodiment, the bottom of the frame 104 of the fruit sugar content spectral detection device is provided with multiple evenly distributed light source modules 70. The light source modules 70 can be high-power LED integrated light sources, whose emission spectrum range can cover the visible to near-infrared region, for example, models with wavelengths in the range of 400 nanometers to 1000 nanometers. Each light source module 70 is fixedly installed in a pre-drilled mounting hole at the bottom of the frame 104 by screws, with its light emission direction all facing the fruit-bearing area below the center of the frame 104, i.e., the detection station through which the fruit loading box 40 passes on the conveyor belt. The number of light source modules 70 can be determined according to the size of the irradiation area; for example, four or six can be set, and they are evenly distributed in a centrally symmetrical manner to ensure a uniform and shadowless illumination field. The installation tilt angle of each light source module 70 can be set between 30 degrees and 90 degrees. This angle helps to concentrate the light onto the surface of the fruit sample, facilitating accurate image acquisition.

[0047] In one operation, when the conveyor belt transports the fruit loading box 40 containing fruit directly below the image acquisition device 60, all light source modules 70 are simultaneously illuminated by the control unit (or can be set to constant illumination), providing stable and uniform lighting for the fruit sample below. The light shines on the fruit surface, and the reflected light is captured by the multispectral camera lens directly above. This multi-angle, uniform lighting method effectively reduces interference from stray ambient light and suppresses light spots and shadows caused by the unevenness of the fruit surface, allowing for more complete and consistent acquisition of the spectral information of the fruit surface.

[0048] Compared to common single top light source or ring light source illumination schemes, this implementation uses multiple evenly distributed light source modules 70 arranged at specific angles. Its distinguishing technical feature and advantage lies in providing illumination collaboratively from multiple directions. This design effectively overcomes the drawbacks of single-direction illumination, which easily produces strong reflections or heavy shadows on the surface of spherical fruits. This allows the multispectral camera to acquire more uniform spectral reflectance data across the entire fruit surface, significantly reducing measurement errors caused by uneven illumination. This provides a crucial high-quality raw data foundation for establishing a stable and accurate sugar content prediction model, thereby improving the reliability and accuracy of the entire detection system.

[0049] In another embodiment, the fruit sugar content spectral detection device has a detachable feed rack 30 at the entrance of its detection channel 101. The main structure of the feed rack 30 can be made of aluminum alloy profiles or carbon steel plates and assembled by bolt connection. The feed rack 30 includes a base with a downwardly protruding positioning protrusion 304. The cross-sectional shape of the positioning protrusion 304 can be designed as rectangular, with dimensions of 20 mm long, 10 mm wide, and 5 mm high. The frame 201 of the conveyor belt mechanism 20 has a positioning groove at a corresponding position that matches the shape and size of the positioning protrusion 304. The depth of the positioning groove can be slightly greater than the height of the positioning protrusion 304, for example, 6 mm. By embedding the positioning protrusion 304 into the positioning groove, the feed rack 30 and the frame 201 can be quickly aligned and locked together, facilitating subsequent disassembly and maintenance.

[0050] The upper part of the feeding rack 30 is provided with several parallel feeding channels 301 parallel to the conveying direction. The number of feeding channels 301 can be set according to the detection throughput requirements, such as 4 or 6 channels. The channels are formed by partitions 302, and their width is in a gap fit with the width of the fruit loading box 40. The gap on one side can be set between 1 mm and 3 mm, which can ensure that the loading box passes through smoothly and effectively prevent it from twisting during movement. The end of the feeding rack 30 near the detection channel 101 is provided with a vertical end plate 308. The end plate 308 has guide doors 303 that correspond one-to-one with each feeding channel 301. The width of the guide door 303 is greater than the width of the fruit loading box 40. The extra width can be set between 5 mm and 10 mm to form a loose entrance to compensate for possible slight deviation of the conveyor belt or installation alignment errors, ensuring that the loading box can smoothly enter the narrow detection channel 101.

[0051] During operation, the operator places the fruit loading boxes 40 containing fruit into the designated feeding troughs 301 one by one. Driven by the conveyor belt mechanism 20, the fruit loading boxes 40 move forward along the feeding troughs 301, reach the end plate 308, and enter the detection channel 101 of the housing 10 through the guide door 303. The width margin of the guide door 303 allows the loading boxes to pass smoothly even with slight deviation, avoiding jamming. The entire feeding rack 30 is fixed by a snap-fit ​​method, ensuring accurate and quick installation and positioning, and can be easily removed as a whole when cleaning or replacement is required.

[0052] Compared to existing technologies that fix the feeding structure to the housing or frame, this embodiment employs a detachable snap-fit ​​feeding rack 30 structure, whose distinguishing technical features and advantages lie in its modular and precise guiding design. The detachable connection facilitates cleaning and maintenance of this area, preventing sugar residue from attracting pests or breeding bacteria. The parallel feeding channel 301 with a clearance fit and the precisely calculated guide door 303 work together to form two guiding measures, ensuring that the fruit loading box 40 can be accurately delivered into the detection area in a stable and consistent posture and position. This provides a prerequisite for the repeatability and accuracy of subsequent spectral acquisition, while reducing the risk of downtime due to box jamming and improving equipment operating efficiency.

[0053] In another embodiment, the fruit sugar content spectral detection device has a first mounting hole on the end plate 308 of the feed rack 30. This first mounting hole can be designed as a through hole, located on one side wall of the guide door 303. A completely coaxial first mounting hole is also provided on the opposite side wall, symmetrically opposite to the first mounting hole. The diameter of both holes can be set to 8 mm for fixing a photoelectric sensor. The photoelectric sensor can be a U-shaped (groove-type) photoelectric sensor, with its transmitting and receiving ends embedded and fixed in the pair of first mounting holes on the side walls of the guide door 303, and secured by nuts from the back of the end plate 308. The sensor's optical path is strictly perpendicular to the conveyor belt's running direction and horizontally penetrates the entire width of the guide door 303, thus forming an invisible detection light curtain. The photoelectric sensor is connected to the device's control unit via its built-in cable. The cable can be a shielded cable to enhance anti-interference capability, and the connector can be an M8 or M12 standard industrial connector.

[0054] During operation, as the fruit loading box 40 moves forward with the conveyor belt and passes through the guide gate 303, it momentarily blocks the infrared beam emitted from the transmitter of the U-shaped photoelectric sensor to the receiver. This blocking action is detected by the sensor in real time, and its internal output circuit immediately generates a transitional electrical signal (e.g., from high level to low level). This signal change is transmitted to the control unit via a cable. The control unit can be programmed to set a short delay time (e.g., 50 milliseconds) to eliminate jitter interference, and then determine this signal as a valid trigger event. This event indicates that a loading box has entered the detection channel, and the control unit can use this signal to start subsequent processes, such as activating the light source module 70 and multispectral camera to take pictures, or for counting.

[0055] Compared to existing technologies that install detection sensors at other locations on the conveyor belt or employ other triggering methods, this implementation method, which directly integrates photoelectric sensors on both sides of the guide gate 303, offers distinct technical features and advantages in terms of the accuracy and reliability of the detection point. By directly placing the detection light curtain at the entrance throat of the loading box entering the sealed detection channel, every entering loading box is detected without exception, achieving strict synchronization between the detection event and the spatial position of the loading box. This installation method is compact, avoiding the hassle of installing additional brackets in narrow channels. The integrated slot-type photoelectric sensor eliminates the need for complex optical path alignment adjustments between the transmitter and receiver after installation. It exhibits strong resistance to ambient light interference, and its output signal is stable and reliable, providing the control unit with a precise timing control reference. This ensures a high degree of matching between image acquisition and fruit position, fundamentally preventing detection failures or data corruption caused by false or missed triggers.

[0056] In another embodiment, the fruit sugar content spectral detection device has a second mounting hole on its feed rack 30. This second mounting hole is typically located directly above the feed channel 301 and can be a blind hole with internal threads. The hole diameter can be set to M6 or M8 standard threads, and the mandrel is perpendicular to the lower bearing surface. The distance sensor can be an ultrasonic rangefinder or a laser rangefinder. Its probe is screwed into the second mounting hole 607 via its own external threads or fixed by a matching mounting bracket, ensuring that its sensing surface is vertically downward, directly facing the bearing surface of the feed channel 301 (i.e., the conveyor belt surface). The mounting height of the distance sensor can be adjusted to cover a measurement range of 0 to 100 mm to accommodate fruit loading boxes 40 and fruits of different heights. The sensor's signal output is connected to the device's control unit via a shielded cable. The cable length can be determined according to the actual wiring path, for example, 1.5 meters, and the connector type matches the control unit interface.

[0057] In one operation, when a fruit loading box 40 is placed into a feeding chute 301 and moves directly below a distance sensor, the distance sensor continuously measures the vertical distance from its probe to the top surface of the top layer of fruit inside the loading box (or, in the case of an empty box, to the bottom). This analog or digital signal is transmitted to the control unit in real time. The control unit has a pre-stored reference height value, which can be the distance from the sensor to the surface of the empty conveyor belt. The control unit compares the measured value with the reference value and calculates the approximate height of the fruit. Based on this height value, the control unit can determine the size category of the fruit, or more importantly, generate corresponding control commands.

[0058] Compared to existing technologies that rely on fixed heights for detection or require manual prediction of fruit size to set the camera height, the integrated online distance detection solution employed in this implementation method distinguishes itself by achieving automated preprocessing and adaptive adjustment of the detection height. By measuring the fruit height in real-time and non-contact during the feeding stage and transmitting this information to the control system in advance, the system has sufficient time to drive the lifting mechanism to adjust the multispectral camera to the optimal focus height preset for that type of fruit before it arrives at the detection station. This process requires no manual intervention, significantly improving the automation level and production efficiency of the equipment. More importantly, it ensures that fruits of different sizes and batches can be spectrally acquired at a consistent and optimal imaging distance, minimizing errors in imaging clarity and spectral data caused by variations in object distance. This provides a crucial guarantee for the accuracy and consistency of subsequent sugar content analysis.

[0059] In another embodiment, the output of the control unit of the fruit sugar content spectral detection device is connected to the servo motor 1032 via a cable. The control unit can be a standard programmable logic controller (PLC) or an industrial computer (IPC), and its digital output module or dedicated pulse output port is connected to the driver control signal input of the servo motor 1032 via a shielded cable. The cable can be a multi-core shielded twisted pair cable, such as RVVP 4×0.75mm² cable, where two cores are used to transmit pulse and direction signals, and the other two cores serve as the common terminal and ground for the shielding layer. An aviation connector can be used to ensure reliable connection. The driver parameters of the servo motor 1032, such as the electronic gear ratio and the number of pulses per revolution, need to be set according to the lead of the lead screw 103 and the required control accuracy; for example, it can be set to 1000 pulses per millimeter of movement.

[0060] During operation, the control unit performs logical calculations based on received external signals (such as fruit height measurements from a distance sensor, position signals from a photoelectric sensor, or recipe instructions preset by the operator via a human-machine interface (HMI). After the calculations are completed, the control unit sends out corresponding pulse sequences and directional level signals from its output port. These electrical signals are transmitted to the servo driver via cables, where the driver decodes and amplifies them into three-phase current to drive the servo motor 1032 to rotate precisely. The number and direction of the motor's rotation directly determine the linear displacement and direction of motion of the lead screw lifting mechanism 501, thereby ultimately achieving automatic adjustment of the distance between the image acquisition device 60 and the supporting plane. For example, when a large fruit is detected, the control unit calculates that the camera needs to be raised by 20 millimeters and sends out a corresponding number of pulses to drive the motor to rotate forward.

[0061] Compared to existing technologies that use manual cranks to adjust height or simple limit switches for coarse positioning, this implementation employs a closed-loop control scheme where the control unit directly drives the servo motor 1032 via cable. Its distinguishing technical feature and advantage lies in achieving intelligent, high-precision automatic focusing height adjustment. This direct electrical signal control method offers fast response speed, positioning accuracy far exceeding manual operation, and seamless integration into automated inspection processes. It enables the image acquisition device 60 to automatically adjust to the optimal working distance in real time based on the actual conditions of each box of fruit, completely avoiding inefficiency and operational errors caused by manual intervention. This fundamentally ensures the consistency of spectral acquisition conditions for different batches and sizes of fruit, laying a solid foundation for the accuracy and repeatability of the final sugar content assessment model.

[0062] In another embodiment, the fruit sugar content spectral detection device has a guide mechanism on each side wall of the feed channel 301. The guide mechanism includes a guide plate 305, which can be made of a wear-resistant material with a low coefficient of friction, such as polyoxymethylene (POM) or nylon (PA66). Its length can be set to 150 mm, and its width is approximately equal to the height of the side wall of the feed channel 301. The guide plate 305 extends towards the guide door 303, with one end near the guide door 303 being a free end, and the other end connected to the side wall of the feed channel 301 via a hinge shaft 306. The hinge shaft 306 can be a stainless steel optical shaft with a diameter of 5 mm. It passes through a shaft hole at the base of the guide plate 305 and is fixed to a mounting base on the side wall of the channel via snap rings or bushings at both ends, allowing the guide plate 305 to swing at a certain angle in the vertical plane around the hinge shaft 306. A compression spring 307 is installed between the side wall of the feed channel 301 and the back of the guide plate 305. This compression spring can be made of spring steel wire with a diameter of 0.8 mm and its free length can be set to 30 mm. It continuously provides an upward elastic support force to the free end of the guide plate 305. Under the elastic support of their respective compression springs 307, the free ends of the guide plates 305 on both sides of the feed channel 301 are usually kept at a position slightly narrower than the inherent width of the channel, together forming a V-shaped or U-shaped guide channel with a wide inlet and a gradually narrowing outlet.

[0063] During operation, when the operator places the fruit loading box 40 into the feed trough 301, the fruit loading box 40 is driven forward by the conveyor belt mechanism 20. As the box moves forward, whether tilted or uneven, the sides of the box press against the free ends of the guide plates 305, causing it to overcome the elastic force of the compression springs 307 and swing slightly downwards. This swinging process helps to straighten the loading box and avoids rigid collisions. As the conveyor belt moves the loading box towards the guide gate 303, the guide plates 305 on both sides, under the action of spring force, straighten the loading box, continuously correcting and guiding its direction of movement, ensuring that it approaches and passes through the guide gate 303 in the correct posture, effectively preventing jamming caused by placement deviations or belt misalignment.

[0064] Compared to existing technologies that use fixed-width rigid channels for guidance, the swing-type elastic guiding mechanism employed in this embodiment differs in its self-adjusting capability. Rigid channels impose extremely stringent dimensional tolerances on the loading boxes, easily leading to jamming or excessive looseness. In contrast, the guide plate 305 in this solution can swing adaptively under the action of the compression spring 307, accommodating dimensional deviations within a certain range while continuously providing flexible lateral restraint during operation. This tapered, elastic guiding channel structure significantly reduces the requirements for the machining and placement accuracy of the loading boxes, greatly improving the smoothness and reliability of the feeding process, reducing downtime caused by box jamming, and thus enhancing the overall production efficiency and automation level of the testing equipment.

[0065] In another embodiment, the guide plate 305 of the fruit sugar content spectral detection device has an irregularly shaped side surface. This irregular surface can be designed according to the common side wall shape of the fruit loading box 40. For example, if the side wall of the loading box 40 is a vertical plane, the working surface of the guide plate 305 in contact with it can be machined into a matching vertical plane; if the side wall of the loading box 40 has a certain angle or curvature, the working surface of the guide plate 305 should also be designed accordingly as a matching inclined plane or concave arc surface. This irregularly shaped surface can be manufactured by machining or injection molding to ensure its shape accuracy. The material of the guide plate 305 can be selected from engineering plastics with self-lubricating properties that meet food safety requirements, such as polyoxymethylene (POM), to reduce the coefficient of friction between it and the side wall of the loading box 40. The surface roughness of the irregularly shaped surface can be controlled within Ra 3.2μm to ensure smooth contact.

[0066] During operation, when the fruit loading box 40 is placed into the feeding trough 301, the irregularly shaped surface of the guide plate 305 will closely abut against the side wall of the loading box 40 under the elastic force of the compression spring 307. Because the irregularly shaped surface is highly compatible with the shape of the loading box side wall, the contact area between them is maximized. This large-area surface contact significantly improves the stability and accuracy of guidance compared to point or line contact. When the conveyor belt drives the loading box 40 forward, the guide plates 305 on both sides apply a uniform lateral restraint force to the loading box through their irregularly shaped surfaces, effectively preventing it from rotating or shifting laterally, ensuring that it always runs smoothly along the predetermined straight trajectory until it accurately passes through the guide gate 303.

[0067] Compared to existing technologies that use simple planar or curved surfaces for guidance, this implementation employs a uniquely shaped surface design adapted to the side wall shape of the fruit loading box 40. Its distinguishing technical features and advantages lie in achieving precise shape matching and optimized force transmission. A guide plate with a general shape often forms unstable point-to-line contact with a loading box of a specific shape, easily leading to uneven constraint forces, box wobbling, and even wear. This solution, through customized irregularly shaped surface contact, evenly distributes the constraint force over a larger area of ​​the loading box's side wall, greatly enhancing stability during the guidance process, reducing unnecessary friction and wear, and ensuring a high degree of consistency in the loading box's posture before entering the precision detection area, providing a reliable positional guarantee for subsequent spectral image acquisition.

[0068] In another embodiment, the fruit sugar content spectral detection device uses a fruit loading box 40 with a limiting groove at the bottom for accommodating and restraining the fruit. The shape of the limiting groove can be designed according to the common shape of the fruit to be tested. For example, for apples and citrus fruits that are nearly spherical, the groove can be designed as a hemispherical shape; for elliptical fruits such as durian pulp, mango, and kiwi, the groove can be designed as an ellipsoidal shape to fit them. The depth of the groove can be set between 30% and 40% of the average diameter of the fruit, for example, 30 mm. Its opening diameter is slightly smaller than the average diameter of the fruit it accommodates. For example, for a fruit with a diameter of about 80 mm, the diameter of the groove opening can be set to 75 mm, thereby using its constricting structure to achieve preliminary clamping and restraint of the fruit. The top of the loading box 40 is an open structure without any obstructions. This design ensures that the multispectral camera and the light source module 70 have an unobstructed field of view and light path, and can directly act on the exposed upper surface of the fruit. The loading box 40 can be molded in one piece using a one-time injection molding process. The material can be food-grade polypropylene (PP) or high-density polyethylene (HDPE), and the color should preferably be white or black, or other colors that have little interference with the detection spectrum.

[0069] During operation, operators manually or with the aid of tools place individual fruits into the limiting grooves of the loading box 40. Due to the constricted design of the grooves, the fruits are stably supported and constrained in the center of the box, preventing them from rolling or shifting due to vibrations during transport. The loading box is then placed on the bearing surface of the conveyor belt mechanism 20 and enters the detection channel 101. At the detection station, a light source shines downwards, allowing unobstructed light to reach the fruit surface; simultaneously, a multispectral camera located directly above can capture complete spectral image information of the fruit's surface through the open top. Throughout the process, the fruit is stably constrained in a known, fixed position and posture, ensuring consistency in the image area captured each time.

[0070] Compared to using flat trays to directly hold fruit or simple containers without specific positioning structures, this implementation method employs a loading box design with specifically shaped positioning grooves and an open top. Its distinguishing technical features and advantages lie in achieving a unified approach of precise fruit positioning and unobstructed detection. Fruit on flat trays is prone to rolling during transport, leading to random sampling locations and severely impacting data consistency. This solution effectively prevents fruit movement through the positioning grooves 401, stabilizing it in a preset position and ensuring the spatial repeatability of the sample. Simultaneously, the open top structure completely avoids interference from the container itself with optical detection, creating the necessary conditions for obtaining high-quality spectral data. This design significantly improves the repeatability and accuracy of spectral acquisition, serving as a fundamental and crucial element for achieving reliable non-destructive sugar content detection.

[0071] Although the embodiments of this utility model have been disclosed above, they are not limited to the applications listed in the specification and embodiments. It can be applied to various fields suitable for this utility model. Other modifications can be easily made by those skilled in the art.

Claims

1. A fruit sugar content spectral detection device, comprising a conveyor belt mechanism, a housing, and an image acquisition device, characterized in that: The enclosure has a horizontally penetrating detection channel; inside the enclosure is a liftable support frame located above the detection channel, which includes a screw lifting mechanism, a frame driven by the screw lifting mechanism, and a gimbal installed at the bottom of the frame. The conveyor belt mechanism runs horizontally through the inspection channel, and its frame is not in contact with the box, forming a vibration isolation gap between them; the fruit loading box is placed on the bearing plane of the conveyor belt mechanism. The image acquisition device is fixed below the gimbal and includes a multispectral camera for acquiring images of the fruit below.

2. The fruit brix spectral detection apparatus of claim 1, wherein, The screw lifting mechanism includes a vertically arranged screw and a nut seat fixed to the frame. The screw passes through the nut seat and forms a self-locking thread engagement with it. The auxiliary guide assembly includes two guide optical shafts parallel to the lead screw, with both ends of the guide optical shafts fixed to the internal frame of the housing (2); linear bearings are fixed to both ends of the frame, and the linear bearings are sleeved on the guide optical shafts; A servo motor drives the lead screw to rotate, and the servo motor is fixed to the housing via a flange.

3. The fruit sugar content spectral detection apparatus according to claim 2, wherein The bottom of the frame is provided with multiple evenly distributed light source modules, and the light emission direction of the light source modules is directed towards the fruit-bearing area below their center.

4. The fruit sugar content spectral detection apparatus according to claim 3, wherein A detachable feed rack is provided at the entrance of the inspection channel. The feed rack includes: A base that engages with the frame of the conveyor belt mechanism, the base having a positioning protrusion, and the frame having a positioning groove that matches the protrusion; Several parallel feeding channels in the parallel conveying direction, the width of each feeding channel is matched with the gap of the fruit loading box; The end plate of the feeding rack is close to the detection channel. The end plate has guide doors that correspond one-to-one with the feeding channel. The width of the guide doors is greater than the width of the loading box.

5. The fruit sugar content spectral detection apparatus according to claim 4, wherein The end plate has a first mounting hole, and the photoelectric sensor is fixed in the first mounting hole. The transmitting end and receiving end of the photoelectric sensor are symmetrically arranged on the two side walls of the guide door. Its light path direction is perpendicular to the conveying direction and horizontally penetrates the guide door. It is used to sense the fruit loading box passing through the guide door and is connected to the control unit through a cable.

6. The fruit sugar content spectral detection apparatus according to claim 5, wherein The feed rack has a second mounting hole, and the distance sensor is fixed in the second mounting hole; the probe of the distance sensor is vertically downward facing the bearing surface under the feed channel, and its signal output terminal is connected to the control unit through a cable.

7. The fruit sugar content spectral detection apparatus according to claim 6, wherein The output of the control unit is connected to the servo motor via a cable, and is used to adjust the distance between the image acquisition device and the bearing plane.

8. The fruit sugar content spectral detection apparatus according to claim 4, wherein Each side wall of the feed channel is equipped with a guiding mechanism; the guiding mechanism includes: The guide plate extends toward the guide door, with one end near the guide door being a free end and the other end being connected to the side wall of the feed channel via a hinge shaft, allowing the guide plate to swing around the hinge shaft in a vertical plane. A compression spring is installed on the side wall of the feed channel to elastically support the guide plate; The guide plates on both sides of the feed channel form a tapered guide channel under the elastic support of the compression spring.

9. The fruit sugar content spectral detection apparatus according to claim 8, wherein The side of the guide plate is irregularly shaped to match the shape of the side wall of the fruit loading box.

10. The fruit brix spectral detection apparatus of claim 1, wherein, The bottom of the fruit loading box is provided with a limiting groove for accommodating and limiting the fruit, and the top is an open structure.

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