Self-powered fruit roller conveyor temperature and humidity monitoring system

Abstract

This invention belongs to the field of agricultural post-harvest processing and sensing technology, and provides a self-powered temperature and humidity monitoring system for a fruit roller conveyor. The system includes a roller conveyor unit, a triboelectric nano-power generation unit, an energy management circuit unit, and a sensing and signal processing unit. The roller conveyor unit includes conductive rollers; the triboelectric nano-power generation unit includes a polydimethylsiloxane film coated on the outer surface of the conductive rollers as a positive electrode friction pair, and the conveyed fruit as a negative electrode friction pair. It also includes a positive electrode collection electrode electrically connected to each conductive roller and a negative electrode collection electrode capable of sliding contact with the fruit surface; the energy management circuit unit is used for rectification, storage, and voltage stabilization; the sensing and signal processing unit is powered by the circuit and monitors temperature and humidity. This invention converts conveying mechanical energy into electrical energy by using the fruit as a negative electrode friction pair and setting a sliding contact negative electrode collection electrode, achieving self-powered monitoring system, which helps solve the problems of difficult wiring and high maintenance costs.

Description

Technical Field

[0001] This invention belongs to the field of agricultural post-harvest processing and sensing technology, and in particular relates to a temperature and humidity monitoring system for a self-powered fruit roller conveyor. Background Technology

[0002] In modern agricultural post-harvest processing and logistics transportation, real-time monitoring of ambient temperature and humidity is crucial for ensuring fruit quality and reducing losses. Currently, online temperature and humidity monitoring systems applied to fruit conveyor lines mainly rely on wired or battery power. However, wired power supply involves complex wiring, is difficult to implement on large, mobile, or modified conveyor lines, and poses safety hazards; battery power supply requires periodic shutdowns for replacement, resulting in high maintenance workload and costs, and the disposal of batteries is environmentally unfriendly.

[0003] Meanwhile, during automated fruit transport, the continuous rolling, contact, and separation of fruit and conveyor rollers generates a large amount of low-frequency, random mechanical energy that can be collected. Current technologies neglect this energy source, failing to convert it into usable electrical energy, resulting in energy waste. Traditional power supply methods make deploying distributed sensor networks at multiple key nodes of the conveyor line extremely complex and expensive, hindering the widespread adoption of intelligent, data-driven monitoring systems for the entire post-harvest fruit processing process. Summary of the Invention

[0004] In view of this, the present invention aims to propose a self-powered temperature and humidity monitoring system for fruit roller conveyors, in order to solve the problems of existing fruit conveying temperature and humidity monitoring equipment relying on external power sources or batteries, resulting in complex wiring, high maintenance costs, and waste of mechanical energy during the conveying process.

[0005] To achieve the above objectives, the technical solution of the present invention is implemented as follows: A self-powered temperature and humidity monitoring system for a fruit roller conveyor includes a roller conveyor unit, a triboelectric nanogenerator unit, an energy management circuit unit, and a sensing and signal processing unit. The roller conveyor unit comprises multiple parallel conductive rollers capable of rotating around their own axes. The triboelectric nanogenerator unit includes a polydimethylsiloxane film coated on the outer surface of the conductive rollers, and fruit that periodically contacts and separates from the polydimethylsiloxane film during conveying. The polydimethylsiloxane film serves as a positive electrode friction pair, and the fruit serves as a negative electrode friction pair. The triboelectric nanogenerator unit also includes a positive collecting electrode and a negative collecting electrode capable of sliding contact with the fruit surface. Each conductive roller is electrically connected to the positive collecting electrode. The two input terminals of the energy management circuit unit are electrically connected to the positive collecting electrode and the negative collecting electrode, respectively. The energy management circuit unit rectifies, stores, and stabilizes the generated electrical energy, and outputs a stable direct current. The sensing and signal processing unit is powered by the energy management circuit unit and includes a temperature and humidity sensor for monitoring and outputting ambient temperature and humidity data.

[0006] Compared with existing technologies, the self-powered temperature and humidity monitoring system for fruit roller conveyors described in this invention has the following advantages: (1) The self-powered fruit roller conveyor temperature and humidity monitoring system of the present invention integrates triboelectric nano-power generation technology into the fruit conveyor line. The conductive roller, the core execution component of the conveyor line, is used as the fixed electrode carrier, and the fruit itself is used as the moving triboelectric electrode. This achieves a high degree of integration between the power generation unit and the production equipment in terms of physical structure and function. There is no need to add a complicated power generation mechanism. The monitoring system is fully self-powered by directly utilizing the mechanical energy of the conveying process itself. This helps to solve the problems of difficult wiring and high battery maintenance costs of traditional monitoring equipment.

[0007] (2) The temperature and humidity monitoring system for the self-powered fruit roller conveyor described in this invention is designed with a multi-roller parallel positive electrode electrical connection network to ensure the continuity and stability of charge collection; at the same time, by adopting a negative electrode that can slide in contact with the surface of the fruit, it is beneficial to solve the problem of reliable electrical contact of the fruit as a moving and irregular electrode, thus ensuring the power generation efficiency.

[0008] (3) The temperature and humidity monitoring system for the self-powered fruit roller conveyor described in this invention increases the contact area and triboelectric effect by microstructuring the surface of the polydimethylsiloxane film, thereby improving the output performance; by setting up distributed sensor nodes and an independent power supply network, it realizes the coordination of multi-point monitoring and charge collection, thereby improving the overall power supply stability and monitoring accuracy of the system. Attached Figure Description

[0009] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a schematic diagram of the structure of the self-powered fruit roller conveyor temperature and humidity monitoring system according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the triboelectric nano-power generation unit in the temperature and humidity monitoring system of the self-powered fruit roller conveyor according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the energy management circuit unit in the temperature and humidity monitoring system of the self-powered fruit roller conveyor according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the sensing and signal processing unit in the temperature and humidity monitoring system of the self-powered fruit roller conveyor according to an embodiment of the present invention.

[0010] Explanation of reference numerals in the attached figures: 1. Conductive roller; 2. Polydimethylsiloxane film; 3. Positive collecting electrode; 4. Negative collecting electrode; 5. Fruit. Detailed Implementation

[0011] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0012] This invention provides a temperature and humidity monitoring system for a self-powered fruit roller conveyor, such as... Figures 1 to 4 As shown, it includes a roller conveyor unit, a triboelectric nanogenerator unit, an energy management circuit unit, and a sensing and signal processing unit.

[0013] Specifically, the roller conveyor unit includes multiple parallel conductive rollers 1 that can rotate around their own axes. In traditional conveyors, rollers are often coated with rubber or made of non-metallic materials to protect the fruit 5 from bumps. However, in this embodiment, conductive rollers 1 are used to achieve the electrostatic induction mechanism of triboelectric nano-generation. These conductive rollers 1 can be stainless steel rollers or aluminum alloy rollers. The two ends of the conductive rollers 1 are mounted on the conveyor frame via bearings. To prevent charge from being lost to the ground through the bearings, insulating gaskets or insulating bearings are used between the mounting ends of the conductive rollers 1 and the conveyor frame to ensure that the conductive rollers 1 are insulated from the ground.

[0014] The triboelectric nanogenerator unit includes a polydimethylsiloxane film 2 coated on the outer surface of a conductive roller 1, and fruit 5 that periodically contacts and separates from the polydimethylsiloxane film 2 during transport. The polydimethylsiloxane film 2 serves as the positive electrode triboelectric pair, and the fruit 5 serves as the negative electrode triboelectric pair. Specifically, the polydimethylsiloxane is located at the positive end in the triboelectric series, easily losing electrons and becoming positively charged; while the peel of the fruit 5, rich in water, pectin, and organic matter, is located at the negative end in the triboelectric series, easily gaining electrons and becoming negatively charged.

[0015] In practical applications, when fruit 5 is placed on conductive roller 1 and rotates with it, the weight of fruit 5 provides good contact pressure, allowing sufficient rolling friction and periodic contact and separation between the fruit 5's skin and the PDMS film. At the moment of contact, due to the significant difference in electron affinity, electrons transfer from the PDMS film to the fruit 5's skin, resulting in a positive charge on the PDMS film surface and a negative charge on the fruit 5's surface. When fruit 5 rotates away from the contact point with conductive roller 1, the two separate, and the centers of positive and negative charges are misaligned, generating a large potential difference. Because the inner side of the PDMS film is in close contact with conductive roller 1, electrostatic induction induces a negative charge inside conductive roller 1. Furthermore, to extract the generated electrical energy, the triboelectric nanogenerator unit also includes a positive collecting electrode 3 and a negative collecting electrode 4 that can slide in contact with the surface of fruit 5. Each conductive roller 1 is electrically connected to the positive collecting electrode 3.

[0016] Since fruit 5 is constantly moving and has an irregular shape with large variations in surface curvature, the key breakthrough of this invention is how to collect negative charges from fruit 5. In this embodiment, a sliding contact method is adopted between the negative electrode collecting electrode 4 and the surface of fruit 5. When the negatively charged fruit 5 passes by the negative electrode collecting electrode 4, the negative electrode collecting electrode 4 conducts the negative charges accumulated on the surface of fruit 5 through sliding contact with the fruit 5's skin, forming a negative output terminal.

[0017] In one embodiment of this invention, the negative electrode collecting electrode 4 is a flexible conductive brush or a flexible conductive curtain. Specifically, the flexible conductive brush is composed of multiple bundles of conductive fibers, such as carbon fiber bundles, metal-plated nylon filament bundles, or stainless steel microfilament bundles. The brush head composed of multiple bundles of conductive fibers has excellent flexibility and conformity. When the fruit 5 passes by, the conductive fibers can slide and brush along the curved surface of the fruit 5, which not only ensures the reliability of electrical contact but also avoids mechanical damage to the surface of the fruit 5.

[0018] Accordingly, the flexible conductive curtain is either a conductive rubber curtain or a conductive fabric curtain. For example, the conductive rubber curtain is made of silicone rubber mixed with carbon black or silver powder and vulcanized, possessing both the elasticity and conductivity of rubber; the conductive fabric curtain is made of silver-plated nylon cloth or a blend of stainless steel fibers. The flexible conductive curtain hangs on the side of the fruit 5's conveying path. When the fruit 5 passes by, the curtain naturally adheres to the surface of the fruit 5 and slides, achieving seamless discharge of charge.

[0019] In this embodiment, to ensure that the charge collected by the negative electrode collecting electrode 4 is not lost, the negative electrode collecting electrode 4 is installed insulated from the conveyor frame of the roller conveyor unit. Specifically, a polytetrafluoroethylene or nylon bracket can be used to fix the negative electrode collecting electrode 4 to the conveyor frame, and it is arranged below or to the side of the fruit 5 conveying path of the roller conveyor unit, so that the negative electrode collecting electrode 4 slides in contact with the skin of the passing fruit 5.

[0020] Specifically, the flexible conductive brush is installed upside down in the gap below the conveyor line of the roller conveyor unit. When the fruit 5 rolls on the conductive roller 1, the area below that is not in contact with the conductive roller 1 comes into contact with the flexible conductive brush. Alternatively, the flexible conductive curtain is suspended in the transition area between the two rows of conductive rollers 1. When the fruit 5 falls through the transition area, it will inevitably pass through the flexible conductive curtain, thus completing the charge transfer.

[0021] In one embodiment of this invention, for the collection of the positive electrode, the end shafts of each conductive roller 1 are connected in parallel to a busbar via wires, and the busbar constitutes the collection of the positive electrode 3. Since there are multiple conductive rollers 1 on the conveyor line, connecting them in parallel can increase the charge collection area, so that no matter which conductive roller 1 the fruit 5 is on, the induced charge generated can be collected on the busbar in real time, ensuring the continuity and stability of the output current.

[0022] For example, the busbar is typically made of copper and is electrically connected to the end shafts of each conductive roller 1 via conductive slip rings through wires. It should be understood that those skilled in the art can also choose other electrical connection methods according to actual needs, which will not be elaborated here.

[0023] In one embodiment of this invention, the two input terminals of the energy management circuit unit are electrically connected to the positive collection electrode 3 and the negative collection electrode 4, respectively. The energy management circuit unit is used to rectify, store and regulate the generated electrical energy, and output a stable DC power.

[0024] Since the triboelectric nanogenerator outputs high-voltage, low-current AC pulses, it cannot directly power electronic components. Therefore, the energy management circuit unit includes a rectifier bridge, an energy storage device, and a DC-DC regulator module connected in sequence. The rectifier bridge, composed of low-junction-capacitance Schottky diodes, converts AC pulses into DC; the energy storage device smooths the voltage and stores energy; and the DC-DC regulator module boosts or bucks the fluctuating DC voltage to a standard logic level such as 3.3V or 5V.

[0025] In one embodiment of this invention, the energy storage device is a supercapacitor or a rechargeable lithium battery. Supercapacitors have extremely high power density and near-infinite charge-discharge life, making them suitable for high-frequency pulse charging scenarios such as triboelectric nanogenerators; while rechargeable lithium batteries have higher energy density, providing longer-lasting power to the system during the fruit conveyor's operation. In practical applications, those skilled in the art can select a suitable energy storage device based on the operating frequency of the conveyor line.

[0026] In one embodiment of this invention, the sensing and signal processing unit is powered by the energy management circuit unit and includes a temperature and humidity sensor for monitoring and outputting ambient temperature and humidity data.

[0027] For example, the temperature and humidity sensor is preferably an SHT3x series digital temperature and humidity sensor, which has extremely low power consumption and is suitable for the power output capability of this self-powered system. In practical applications, the sensing and signal processing unit can be placed in a protective housing, which is installed beside the conveyor line to avoid moisture and mechanical damage.

[0028] In one embodiment of this invention, to achieve unmanned monitoring, the sensing and signal processing unit further includes a low-power microprocessor and a wireless communication module. The temperature and humidity sensor is electrically connected to the wireless communication module via the low-power microprocessor. The low-power microprocessor wakes up periodically, reads the data from the temperature and humidity sensor, and transmits the data to the remote monitoring platform via the wireless communication module.

[0029] In one embodiment of this invention, to further improve the output performance of the triboelectric nanogenerator, the surface of the polydimethylsiloxane film 2 has a microstructured layer, which is a nanowire array or a micropyramid array. During the PDMS curing process, a silicon mold hot pressing method or a plasma etching method can be used to form a micro-nano-scale structure on the PDMS surface. This microstructured layer greatly increases the effective contact area between the friction pairs and generates more air breakdown micro-discharge channels during contact separation. According to the physical mechanism of triboelectric charging, this will cause the transferred charge density to increase exponentially, thereby improving the power generation. This allows sufficient electrical energy to drive the sensor even when the fruit 5 is transported at a slow speed or is lightweight.

[0030] In one embodiment of this invention, in a large-scale fruit post-harvest processing center, the conveyor line is often tens of meters long, and monitoring a single node cannot reflect the environmental status of the entire line. Therefore, the system includes multiple sensing and signal processing units distributed along the conveyor line. Each sensing and signal processing unit is independently powered by at least one conductive roller 1 in the corresponding section and an associated triboelectric nanogenerator unit and energy management circuit unit.

[0031] Specifically, this distributed self-powered network architecture eliminates the hassle of long-distance cabling, and the failure of any node will not affect the operation of other nodes, thus improving the robustness and scalability of the system.

[0032] In one embodiment of this invention, the system is also well adaptable to different types of fruit 5, namely apples, citrus fruits, pears, or peaches. The skins of apples and pears are relatively hard and smooth, resulting in a large contact area with the PDMS film when rolling on the roller, leading to a significant triboelectric effect. The skins of citrus fruits and peaches contain an oil layer or fuzz, and although their coefficients of friction are different, they are also at the negative end of the triboelectric series, effectively carrying away electrons.

[0033] It should be noted that for fruits with sensitive skin (5), the hardness of the flexible conductive brush bristles or the assembly angle of the flexible conductive curtain can be adjusted to ensure electrical contact while avoiding damage to the skin.

[0034] By utilizing the above setup, this system helps break away from the traditional mindset of relying on external power for monitoring equipment. It introduces an independent layer mode of triboelectric nanogenerator (TENG) by leveraging the inevitable rolling contact process of the fruit 5 on the roller conveyor. The conductive roller 1 is coated with polydimethylsiloxane as the positive electrode friction pair and charge sensing carrier, while the fruit 5 itself serves as the negative electrode friction pair, thus converting the previously wasted mechanical contact energy into electrical energy. By setting a negative electrode collection electrode 4 that can slide in contact with the surface of the fruit 5, and connecting each conductive roller 1 in parallel to form a combined positive electrode 3, a complete closed loop of power generation and charge collection is constructed. After rectification, storage, and voltage regulation by the energy management circuit, a self-sufficient and continuous power supply is ultimately provided to the temperature and humidity sensor.

[0035] In the actual operation scenario of post-harvest processing of fruit, the system operation process is as follows: Scenario 1: Continuous Self-Powered Monitoring in an Apple Sorting Line. Apples move forward on conductive roller 1, their weight ensuring close contact with the PDMS film-coated roller. As the roller rotates, the apples rotate and move forward, undergoing a continuous contact-separation cycle with the PDMS film, generating a large amount of charge. When a negatively charged apple passes a flexible conductive brush inverted below the roller, the carbon fiber bundles of the brush gently sweep across the apple's equatorial surface, drawing out the negative charge. Simultaneously, the positive charge induced on conductive roller 1 flows to the busbar via end-shaft wires. The energy management circuit unit continuously collects and stores the generated pulsed electrical energy in a supercapacitor, stabilizing it to power a low-power microprocessor and temperature and humidity sensors. The microprocessor wakes up every second to read the ambient temperature and humidity data and transmits it to the control room via a LoRa module, achieving passive monitoring of temperature and humidity in key areas of the sorting line throughout the entire process, avoiding production interruptions caused by battery replacements.

[0036] Scenario 2: Distributed Network Monitoring of a Citrus Packaging Line. Along the long-distance citrus packaging line, a sensing and signal processing unit is installed every meter. Each unit is powered by an independent triboelectric nanogenerator composed of conductive rollers above it. Because citrus peels contain citrus oil, the triboelectric effect is more pronounced. A flexible conductive curtain is suspended at the seam between two rollers. As the citrus fruit crosses the seam, it inevitably passes through the conductive curtain, which slides against the surface of the fruit, efficiently collecting negative charges. Each sensing node is independently powered and collects data. Environmental parameters from multiple points are aggregated and uploaded uniformly via a ZigBee self-organizing network, providing data support for the refined control of the cold chain environment in the packaging workshop.

[0037] It should be understood that although this embodiment describes the specific form of the flexible conductive brush and the flexible conductive curtain, in other embodiments, the negative electrode collecting electrode 4 may also adopt a structure that can slide in contact with the surface of the fruit 5, such as a roller-type conductive sponge or an elastic conductive finger, as long as it meets the functional requirement of collecting negative charges from the moving surface of the fruit 5.

[0038] Similarly, the morphology of the microstructured processing layer is not limited to nanowires or micro pyramids, but can also be micro hemispherical arrays, trench structures or combinations thereof, all with the aim of increasing the effective contact area to improve power generation efficiency.

[0039] For the energy management circuit unit, the rectifier bridge can also use a synchronous rectifier chip to reduce the losses caused by diode voltage drop, or a maximum power point tracking adapter circuit can be added before the energy storage device to achieve impedance matching between the triboelectric nanogenerator and the energy storage element, thereby maximizing energy harvesting efficiency.

[0040] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.

Claims

1. A temperature and humidity monitoring system for a self-powered fruit roller conveyor, characterized in that: It includes a roller conveyor unit, a triboelectric nanogenerator unit, an energy management circuit unit, and a sensing and signal processing unit; The roller conveyor unit includes multiple parallel conductive rollers that can rotate around their own axis. The triboelectric nanogenerator unit includes a polydimethylsiloxane film coated on the outer surface of the conductive roller, and fruit that periodically contacts and separates from the polydimethylsiloxane film during the conveying process. The polydimethylsiloxane film serves as a positive electrode friction pair, and the fruit serves as a negative electrode friction pair. The triboelectric nanogenerator unit also includes a collecting positive electrode and a negative collecting electrode that can slide in contact with the surface of the fruit. Each of the conductive rollers is electrically connected to the collecting positive electrode. The two input terminals of the energy management circuit unit are electrically connected to the positive and negative collection electrodes, respectively. The energy management circuit unit is used to rectify, store, and regulate the generated electrical energy, and output a stable DC power. The sensing and signal processing unit is powered by the energy management circuit unit and includes a temperature and humidity sensor for monitoring and outputting ambient temperature and humidity data.

2. The temperature and humidity monitoring system for a self-powered fruit roller conveyor according to claim 1, characterized in that: The surface of the polydimethylsiloxane film has a microstructured treatment layer, which is a nanowire array or a micro pyramid array.

3. The temperature and humidity monitoring system for a self-powered fruit roller conveyor according to claim 1, characterized in that: The negative electrode collecting electrode is a flexible conductive brush or a flexible conductive curtain.

4. The temperature and humidity monitoring system for a self-powered fruit roller conveyor according to claim 3, characterized in that: The negative collecting electrode is insulated from the conveyor frame of the roller conveyor unit and is arranged below or to the side of the fruit conveying path of the roller conveyor unit, so that the negative collecting electrode slides in contact with the surface of the fruit passing by.

5. The temperature and humidity monitoring system for a self-powered fruit roller conveyor according to claim 1, characterized in that: The positive terminal of the assembly is the busbar, and the end shafts of each conductive roller are connected to the busbar in parallel via wires.

6. The temperature and humidity monitoring system for a self-powered fruit roller conveyor according to claim 1, characterized in that: The energy management circuit unit includes a rectifier bridge, an energy storage device, and a DC-DC voltage regulator module that are connected in sequence.

7. The temperature and humidity monitoring system for a self-powered fruit roller conveyor according to claim 6, characterized in that: The energy storage device is a supercapacitor or a rechargeable lithium battery.

8. The temperature and humidity monitoring system for a self-powered fruit roller conveyor according to claim 1, characterized in that: The sensing and signal processing unit further includes a low-power microprocessor and a wireless communication module, and the temperature and humidity sensor is electrically connected to the wireless communication module through the low-power microprocessor.

9. The temperature and humidity monitoring system for a self-powered fruit roller conveyor according to claim 1, characterized in that: The system includes a plurality of sensing and signal processing units distributed along the fruit conveying path of the roller conveyor unit. Each sensing and signal processing unit is independently powered by at least one conductive roller in the corresponding section and an associated triboelectric nanogenerator unit and energy management circuit unit.

10. The temperature and humidity monitoring system for a self-powered fruit roller conveyor according to claim 1, characterized in that: The fruit mentioned is an apple, citrus, pear, or peach.

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