Fruit and vegetable transportation system with fresh-keeping function

Abstract

The invention provides a fruit and vegetable transportation system with a fresh-keeping function, which belongs to the technical field of fruit and vegetable fresh-keeping and comprises a main transportation box placed in a transportation vehicle in a sealed manner and branch transportation boxes arranged in the main transportation box at equal intervals through vibration damper plates. A heat preservation layer and a temperature and humidity sensor are arranged on the inner surface of a shell of the main transport box, a bottom-layer buffering cushion is fixed in the shell, and a moisturizing connector communicated with the interior of the main transport box is formed in the front side face of the bottom of the shell and used for being connected with a transport vehicle temperature and humidity control system. Each branch transport box comprises an outer box body, an inner box body and a box cover, fruits and vegetables are placed in the inner box body, and the box cover is provided with a ventilation opening communicated with the interior of the inner box body. The temperature and humidity control system comprises a temperature and humidity environment automatic monitoring system and a temperature and humidity regulation and control decision system. The temperature and humidity sensors are respectively used for receiving temperature and humidity data transmitted by the temperature and humidity sensors, processing the data and adopting a gas feedback regulation algorithm and a PID closed-loop control algorithm to be matched with the heat preservation layer and the moisture preservation interface to achieve accurate control over the temperature and the humidity in the total transportation box.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of fruit and vegetable preservation, and particularly relates to a fruit and vegetable transportation system with a preservation function. BACKGROUND

[0002] For the transportation of fruits and vegetables, because of the diversity of fruits and vegetables, various transportation methods have been developed, and currently, the mainstream way is to use refrigerated vehicles for the transportation of fruits and vegetables.

[0003] However, the existing refrigerated vehicles for transporting fruits and vegetables only focus on a single preservation factor, such as only heat preservation, without considering the reduction of fruit and vegetable quality caused by humidity imbalance and vibration factors, and lack the ability to monitor fruits and vegetables in real time and adjust in real time according to environmental conditions during transportation.

[0004] Therefore, there is a need for a fruit and vegetable transportation device with self-adjusting ability and preservation function that can ensure that fruits and vegetables remain in good condition during transportation SUMMARY

[0005] The purpose of the present application is to provide a fruit and vegetable transportation box with a preservation function, characterized by comprising a total transportation box placed inside a closed transportation vehicle and a plurality of sub-transportation boxes, a plurality of fixed slots are separated in the total transportation box by a plurality of equally spaced shock-absorbing plates, and each fixed slot is fixed with a sub-transportation box;

[0006] The inner surface of the shell of the total transportation box is fixed with a heat preservation layer, the bottom of the shell is provided with a humidity interface, the humidity interface is connected with the fixed slot, and the connection is fixed with the transportation vehicle through a joint;

[0007] The inner surface of the shell of the total transportation box is also provided with a temperature and humidity sensor, and the transportation vehicle is provided with a temperature and humidity control system, including a temperature and humidity environment automatic monitoring system and a temperature and humidity control decision system;

[0008] The temperature and humidity environment automatic monitoring system receives the temperature and humidity data collected by the temperature and humidity sensor, the temperature and humidity control decision system processes the temperature and humidity data, and adopts a gas feedback adjustment algorithm and a PID closed-loop control algorithm to cooperate with the heat preservation layer and the humidity interface to realize accurate control of the temperature and humidity in the total transportation box.

[0009] Further, the operation of the temperature and humidity control decision system includes the following steps:

[0010] S1: Taking real-time temperature and humidity sensor readings as the key input, combined with optional feedback, to provide accurate data basis for subsequent control decisions;

[0011] S2: By comparing the preset target humidity value with the actual detected humidity value, accurately positioning the temperature and humidity deviation, and providing key parameters for the PID controller operation;

[0012] S3: According to the temperature and humidity deviation, calculate the total output for the PID controller, control the operation of the heating device, refrigeration device, humidification device and dehumidification device;

[0013] S4: Result feedback, that is, detect and return the new temperature and humidity value, repeat S1-S4 until the actual temperature and humidity value is the same as the preset temperature and humidity value, complete the operation of the temperature and humidity control decision system, and form a closed loop.

[0014] Further, S3 specifically includes the following steps:

[0015] S31: Proportional P link: using differential amplifier method, compare the preset temperature and humidity value with the detected actual temperature and humidity value, ensure the accuracy of error calculation, avoid calculation error leading to control deviation, the calculation formula is represented as:

[0016] u p (k)=K p e(k)K conv

[0017] Wherein, K p is the proportional gain, e(k) is the error at the current time in the proportional P link;

[0018] S32: Integral I link, used to eliminate steady-state error, the formula is represented as:

[0019]

[0020] Wherein, K i is the integral gain; e(j) is the error at the current time in the integral I link;

[0021] S33: Differential D link: according to the error rate to produce control effect, control in advance, suppress overshoot, represented as:

[0022] u d (k)=K d (e(k)-e(k-1))

[0023] Wherein, K d is the differential gain; e(k) is the error at the current time in the differential D link;

[0024] S34: The total output calculation formula of the PID controller is represented as:

[0025] u(k)=u p (k)+u i (k)+ u d(k)

[0026] The temperature and humidity control decision system precisely adjusts the power and frequency of the heating device, the refrigeration device, the humidifying device and the dehumidifying device according to the control instruction output by the PID controller, so that the temperature and humidity in the total transport box approach and maintain at the preset suitable temperature and humidity value.

[0027] Further, the thermal insulation layer uses polyurethane foam as the thermal insulation material, and the thermal insulation layer and various parameters are calculated according to a self-developed multi-layer medium heat conduction mathematical model, which is expressed as:

[0028]

[0029] Wherein, t is the water temperature in the pipe; tT is the soil temperature; h is the buried depth; λT is the soil thermal conductivity; and the thickness of the thermal insulation layer is determined according to the above parameters.

[0030] Further, the outer surface of the thermal insulation layer is uniformly coated with acrylic or polyurethane waterproof paint to prolong the service life of the thermal insulation layer and prevent the thermal insulation performance from being reduced due to moisture.

[0031] Further, the shell of the thermal insulation box is provided with a dismounting opening for facilitating replacement of the thermal insulation layer, and the edge of the dismounting opening is reinforced to avoid damage caused by frequent dismounting.

[0032] Further, a plurality of insertion slots are arranged in the total transport box, and the opposite sides of the shock-absorbing plate are inserted into the total transport box through the insertion slots, and a fixing groove is formed between adjacent two shock-absorbing plates.

[0033] The opposite sides of the shock-absorbing plate away from the total transport box extend outward to form limiting ears which are convenient to dismount and abut against the surface of the total transport box.

[0034] Further, a bottom buffer pad is arranged at the bottom and the two side shells of the total transport box, and the bottom buffer pad and the shock-absorbing plate are both rubber pads with a thickness of 5 cm.

[0035] Further, the sub-transport box comprises a box body and a box cover, the box body is provided with a lock catch for opening the box cover, and the box cover is provided with a ventilation opening for connecting the inside of the sub-transport box, and fruits and vegetables are placed in the box body.

[0036] Further, the box body comprises an outer box body and an inner box body, the outer box body is hollow inside, and a stepped surface is recessed in the upper surface of the outer box body, and the upper surface of the inner box body extends outward to form a flange around the inner box body, and the inner box body is fixed in the outer box body by the flange and the stepped surface.

[0037] The inner surface of the inner box body is provided with at least one recessed groove for fixing fruits and vegetables.

[0038] The bottom surface of the inner box body is covered with a buffer layer, and the buffer layer is a rubber pad which abuts against the inner bottom of the outer box body.

[0039] Compared with the prior art, the beneficial effects of the present application mainly include:

[0040] 1、 The present application has the advantages of effectively solving the preservation problem of melons, fruits and vegetables during transportation, by reasonably designing the heat preservation layer, buffer layer and temperature and humidity control system, the capacity of real-time adjustment of the temperature and humidity in the transport vehicle is provided, a stable and suitable transportation environment is provided for melons and fruits, the deterioration loss of melons, fruits and vegetables is significantly reduced, and the preservation period is prolonged.

[0041] 2、 The design of the heat preservation layer, shock absorbing plate, buffer layer and buffer pad comprehensively considers the thermal performance and economic performance, the selected material has excellent performance and reasonable structure, which can meet the preservation function requirements, and is convenient to maintain and operate, thereby improving the practicability and reliability of the total (partial) transport box.

[0042] 3、 The temperature and humidity control system can real-time monitor and accurately adjust the temperature and humidity in the transport box, individualized setting is carried out according to the fruit and vegetable types and transportation conditions, different schemes are set for different types of melons, fruits and vegetables, and the preservation effect is further improved, and the quality of melons and fruits is guaranteed. BRIEF DESCRIPTION OF DRAWINGS

[0043] Figure 1 It is a schematic view of the assembly of the total (partial) transport box of the present application.

[0044] Figure 2 It is an external structure view of the partial transport box in the present application.

[0045] Figure 3 It is a schematic view of the internal structure of the partial transport box in the present application.

[0046] Among them, 1, total transport box; 2, partial transport box; 21, outer box body; 22, box cover; 23, inner box body; 24, ventilation port; 25, lock catch; 26, groove; 27, lap plate; 3, shock absorbing plate; 4, moisture retaining interface. DETAILED DESCRIPTION

[0047] The present application will be described in more detail below with reference to the schematic view, wherein the preferred embodiment of the present application is shown, it should be understood that the present application described herein can be modified by those skilled in the art, and the advantageous effects of the present application can still be achieved, therefore, the following description should be understood as extensive knowledge for those skilled in the art, and not as a limitation of the present application.

[0048] A fruit and vegetable transport box with preservation function, comprising a total transport box 1 and a partial transport box 2, the number of the partial transport box 2 is multiple, in the embodiment, two groups are set, four in each group, and are respectively placed on both sides of the total transport box 1, and the total transport box 1 is placed in a sealed transport vehicle with refrigeration function.

[0049] I. Structural Design of the Transport Container

[0050] like Figure 1 As shown, the main transport box 1 includes a box body with recessed spaces on the front and rear sides. Multiple interconnected slots are provided on the upper and lower bottom surfaces and the inner bottom surface of these spaces. These slots are evenly spaced, and their width is adapted to the thickness of the shock-absorbing plate 3. The main transport box 1 is divided into fixing slots by inserting multiple shock-absorbing plates 33 into these slots. Each fixing slot holds a sub-transport box 2. Lugs extend from the front end of the shock-absorbing plate 3 to both sides. By abutting the lugs against the front (rear) sides of the main transport box 1, the shock-absorbing plate 3 can be easily disassembled.

[0051] An insulation layer, made of polyurethane foam, is installed on the outer shell of the container. It is fixed and tightly adhered to the outer surface of the transport box 2 using double-sided tape or specialized insulation nails. Before applying the double-sided tape, the surface treatment process is strictly followed to ensure the container surface is clean and dry, guaranteeing a good fit. The insulation nails are strategically placed to avoid stress concentration and material damage, preventing damage to the insulation layer structure and ensuring a stable, integrated structure between the insulation layer and the container. Leveraging the low thermal conductivity of the insulation material, it effectively blocks external temperature changes from affecting the fruits and vegetables inside the box. The insulation layer and its parameters are calculated using a self-developed multi-layered medium thermal conductivity mathematical model, which is expressed as follows:

[0052]

[0053] Where t is the water temperature inside the pipe; tT is the soil temperature; h is the burial depth; and λT is the soil thermal conductivity. The thickness of the insulation layer is determined using this calculation formula and the above parameters. The outer surface of the insulation layer is uniformly coated with an environmentally friendly, weather-resistant acrylic or polyurethane waterproof coating. Based on the principle of film-forming waterproofing, the polymer coating dries to form a dense and continuous film layer, blocking external moisture erosion, extending the service life of the insulation layer, and preventing a decrease in insulation performance due to moisture. Furthermore, based on the principle of balancing daily maintenance convenience with structural stability, the insulation layer design incorporates a pre-reserved disassembly port at the shell. Following structural reinforcement technical specifications, the edges of the opening are reinforced to avoid damage caused by frequent disassembly.

[0054] A temperature and humidity sensor is fixed to the inner surface of the main transport container 1, within a confined space. The sensor's built-in sensing element collects temperature and humidity data. It connects to the automatic temperature and humidity monitoring system within the temperature and humidity control system, transmitting the data. The temperature and humidity control decision system processes this data and employs a gas regulation feedback algorithm and a PID closed-loop control algorithm to precisely control the temperature and humidity within the main transport container 1.

[0055] The bottom layer cushion pad and the shock absorbing plate 3 are of the same structure, and according to the shock absorbing and buffering principle, a 5cm thick rubber pad is selected, which is made of high-performance rubber material mixed by natural rubber and synthetic rubber in a specific ratio. Based on the energy absorption and conversion principle, the material can effectively absorb the vibration impact from the bottom of the transport box and provide stable support for the upper structure due to its good elastic recovery performance, wear resistance and aging resistance. The thickness calculation formula is:

[0056] Fmax = 1.765 EN R1.5 Q H Fmax = 1.765 EM R1.5 Q H

[0057] Wherein, Fmax is the maximum impact force (kN), EM is the elastic modulus of the buffer layer (kpa), R is the equivalent radius of the rockfall, Q is the weight of the rockfall, and H is the falling height of the rockfall (m).

[0058] Due to the environmental protection and non-toxic characteristics of the water-based polyurethane adhesive and the high-strength bonding performance, the water-based polyurethane adhesive is selected to fix the plate body and rubber pad of the shock absorbing plate 3, the bottom layer cushion pad and the shell inside the total transport box 1. The amount of adhesive used is strictly controlled during application to prevent the adhesive from spilling and contaminating fruits and vegetables, and to ensure that the bottom layer cushion pad and the shock absorbing plate 3 remain stable without displacement and looseness in the long-term transport vibration environment.

[0059] The bottom shell of the total transport box 1 is also provided with a moisturizing interface 4 connected to the inside of each fixed groove. The moisturizing interface 4 is connected to the temperature and humidity control system of the transport vehicle through a connector. The moisturizing agent can be sprayed into the total transport box 1 through the moisturizing interface 4 by controlling the temperature and humidity control system, reducing the evaporation of fruit and vegetable moisture, and keeping the humidity inside the total transport box 1 and the sub-transport box 2 close to and maintaining the appropriate humidity for transporting fruit trees.

[0060] The shell surface of the total transport box 1 is also provided with support feet. The support feet are made of high-strength engineering plastic (such as nylon injection molding) or metal (such as stainless steel), and the height is determined according to the stability mechanics analysis. The surface is treated with special process (such as sanding, spraying anti-slip coating, etc.) to have anti-slip performance. The structural design fully considers the compatibility with transport tools such as pallets and shelves, and ensures the stability of the transport box according to the stable placement principle, and the transport box is not easy to fall during handling and stacking. The bottom of the support feet is designed with a cushion pad made of rubber or polyurethane to further absorb the vibration impact during placement and handling.

[0061] As Figures 2-3As shown, the structures of the plurality of sub-transport boxes 2 are the same, including a box cover 22, an outer box body 21 and an inner box body 23. The box cover 22 is designed to be connected by a hinge and fixed by a buckle, which takes into account the principles of convenient operation and reliable fastening, facilitates the loading and unloading of fruits and vegetables, and ensures that the box cover 22 is tightly closed during transportation. The hinge is made of stainless steel material, and the specification and model are determined according to the strength calculation based on the mechanical bearing principle, to ensure that it will not be damaged after long-term frequent opening and closing. The buckle is made of high-strength plastic or metal material, and is designed with an anti-misopening structure to ensure transportation safety.

[0062] The outer box body 21 is also provided with support feet around the periphery, which are integrally arranged with the outer box body 21 and made of high-strength material according to the structural mechanics principle, for supporting the entire transport box and ensuring its stability during transportation to prevent the sub-transport box 2 from falling over. The front side of the outer box body 21 is provided with a lock 25 for locking the opening and closing state between the box cover 22 and the outer box body 21. The connection relationship between the box cover 22 and the outer box body 21 is controlled by screwing the lock 25, so as to realize the opening and closing and locking of the box cover 22, and prevent the box cover 22 from being accidentally opened during transportation. The front side of the outer box body 21 is also provided with a ventilation opening 24 communicating with the inner box body 23. The ventilation opening 24 serves to ensure the circulation of air inside and outside the box, and helps the temperature and humidity control system to control the temperature and humidity in the sub-transport box 2, preventing fruits and vegetables from deteriorating due to poor ventilation. The inner box body 21 is hollow inside, and its upper surface is recessed with a step layer, which is used to cooperate with the inner box body 23 to realize the positioning and fixing of the inner box body 23.

[0063] The inner box body 23 is recessed with a placing groove for placing fruits and vegetables, and its inner bottom surface and opposite side surface are provided with two grooves 26 for fixing fruits and vegetables. The top of the inner box body 23 extends outwardly with a lap plate 27, which cooperates with the step layer to realize the positioning of the inner box body 23. The bottom outer surface of the inner box body 23 is fixed with a buffer layer, specifically a rubber pad, which is arranged in abutment with the inner bottom surface of the outer box body 21 when the inner box body 23 is placed inside the outer box body 21.

[0064] It is worth mentioning that 10cm thick EPE (foamed polyethylene) foam plastic can also be used between fruits and vegetables, which is cut and shaped according to the morphological characteristics of fruits and vegetables, and its light weight, high elasticity, heat and sound insulation characteristics are used to buffer the collision of fruits and vegetables and reduce physical damage. The top is equipped with a 3mm thick EPS (foamed polystyrene) foam plastic partition, which can further separate the space and reduce the risk of displacement of fruits and vegetables in the vertical direction by virtue of its rigid barrier to the extrusion of the upper layer of heavy objects on the lower layer of fruits and vegetables. At the inner box 23, the inner part of the placing groove is separated into several relatively independent areas according to the type, size and packing plan of fruits and vegetables by using hard plastic or paperboard partitions, based on the principle of reducing friction and collision, to reduce direct contact and friction between fruits and vegetables. Sedimentation can also be increased, and foam plastic or sponge is used as a liner and laid on the contact part of the partition and fruits and vegetables and the contact part of the inner wall of the inner box 23, which protects fruits and vegetables in all directions according to the principle of enhancing buffer protection.

[0065] II. Setting of the temperature and humidity control system of the transport box

[0066] The temperature and humidity control system includes a temperature and humidity environment automatic monitoring system and a temperature and humidity control decision system, wherein the temperature and humidity environment automatic monitoring system is used to collect temperature and humidity data, and the temperature and humidity control decision system includes data processing, control decision, temperature regulation execution, humidity regulation execution, and monitoring and remote control implementation methods, etc. The parts work together to ensure that the temperature and humidity in the box is suitable for the preservation and transportation of fruits and vegetables.

[0067] The process of temperature and humidity data collection includes: relying on high-precision temperature and humidity sensors (integrated temperature and humidity sensitive elements), and based on the principle of accurate positioning of heat conduction and water vapor diffusion balance of the sensor and the box wall, the sensor is accurately embedded or pasted in the inner wall of the total transport box 1 shell. The installation position of the sensor is optimized through thermal simulation and humidity field simulation to ensure that the collected data accurately and accurately reflect the average temperature and humidity of the microenvironment of fruits and vegetables in the box.

[0068] According to the differences in physiological characteristics of fruits and vegetables and the estimated transportation time, different types of fruits and vegetables are preset with different data collection frequencies: for perishable fruits and vegetables (such as strawberries and leafy vegetables) in long-distance transportation (more than 2 days), the temperature is collected every 5-10 minutes and the humidity is collected every 10-15 minutes; for storage-resistant fruits and vegetables (such as apples and potatoes), the temperature is collected every 15-30 minutes and the humidity is collected every 30-60 minutes. For perishable fruits and vegetables in short-distance transportation (1-2 days), the temperature is collected every 10-15 minutes and the humidity is collected every 15-30 minutes; for storage-resistant fruits and vegetables, the temperature is collected every 30-60 minutes and the humidity is collected every 60-120 minutes. The temperature and humidity environment automatic monitoring system automatically wakes up the sensor to collect data at the preset frequency and transmits the data in real time. The transmission process uses an encrypted communication protocol to ensure data security, accuracy and no loss.

[0069] The data processing and decision-making process includes: the built-in temperature and humidity control system for different fruits and vegetables has a temperature and humidity threshold database (such as strawberry suitable temperature 0-2℃, humidity 90%-95%, etc. The threshold of each fruit and vegetable is determined based on a large amount of experimental data, industry standards and expert experience). After collecting data, the temperature and humidity change curve is drawn in real time, the change rate is calculated, and the operation of the air supply equipment, dehumidification equipment, refrigeration equipment and heating equipment in the transport vehicle is controlled, so as to realize the control of temperature and humidity.

[0070] For temperature and humidity control, the following scheme can be used:

[0071] When the temperature in the box is higher than the upper limit of the suitable temperature for fruits and vegetables, for small transport vehicles or high-precision requirements (±0.5℃ precision requirement) scenarios, semiconductor refrigeration technology is used. Based on the semiconductor thermoelectric effect, through the combination of high-precision current controller and temperature sensor feedback, the cooling current size is accurately controlled to change the cooling intensity; the heat dissipation end is combined with high-efficiency cooling fins and small fans to accelerate heat dissipation according to the principle of heat convection, and maintain the stability of cooling. Large transport vehicles use a refrigeration system with a scroll compressor as the core, using environmentally friendly refrigerants (such as R410A) to circulate, based on the principle of phase change heat absorption and release of refrigerants, the compressor drives the refrigerant to absorb heat in the evaporator and release heat to the outside of the box in the condenser, and the control system adjusts the compressor power and operation time in real time according to the temperature deviation.

[0072] When the temperature is lower than the lower limit of the suitable temperature for fruits and vegetables, electric heating wire heating is used. The electric heating wire is made of nickel-chromium alloy material, which has high resistivity and strong oxidation resistance. It is installed at the bottom or side of the transport vehicle where the air flow is good. In some large transport vehicles, a tube-and-shell heat exchanger is used for heating. The heat medium (such as hot water or hot air) flows in the tube and exchanges heat with the air in the vehicle through the tube wall. The temperature and humidity control system accurately controls the flow and temperature of the heat medium according to the temperature sensor data, such as by adjusting the flow of the hot water pump or the wind speed of the hot air fan, to accurately adjust the temperature in the vehicle and ensure that the fruits and vegetables are transported in a suitable temperature environment.

[0073] The process of humidity adjustment includes:

[0074] When the humidity is lower than the threshold, a humidification interface 4 installed in the total transport box 1 is used. The device uses ultrasonic atomization technology, and the nozzle is made of stainless steel, which is designed based on the principle of corrosion resistance and not easy to block. It can atomize pure water or finely filtered water into small particles and spray them evenly in the total transport box 1. The temperature and humidity control system controls the amount of spray of the spray device through PWM technology according to the humidity deviation, such as when the humidity is within a certain percentage below the lower limit of the threshold, the amount of spray is appropriate to humidify; if the humidity is more than a certain percentage below the lower limit of the threshold, the amount of spray is increased to ensure rapid humidity increase, while avoiding excessive humidity causing fruit and vegetable diseases.

[0075] A wet pad can also be provided in the inner box body 23 of the sub-transport box 2, which is made of linen or cheesecloth with good water absorption and hygiene. The area of the wet pad is designed to be 80% of the area of the bottom of the box according to the space in the box and the requirement of uniform humidity increase. When the humidity is insufficient, the wet pad is kept at a certain humidity through a micro water pump and a water flow control system. The water pump flow is dynamically adjusted according to the feedback of the humidity sensor, so that the moisture slowly evaporates on the wet pad, uniformly increases the humidity in the box, and ensures environmental protection without polluting fruits and vegetables.

[0076] The refrigerant circulation refrigeration principle in the dehumidifier in the transport vehicle is used. When air flows through the evaporator, moisture condenses into water on the surface of the evaporator due to cold, and is discharged outside the vehicle through a drainage system to achieve dehumidification effect. The refrigerating capacity of the dehumidifier is selected according to the volume of the sub-transport box 2 and the moisture production of fruits and vegetables. When the humidity is within a certain percentage above the upper limit of the threshold value, the dehumidifier operates at a low wind speed and a low refrigeration power according to the humidity sensor data. When the humidity is more than a certain percentage above the upper limit of the threshold value, the wind speed and the refrigeration power are increased to a certain percentage of the rated power to quickly dehumidify.

[0077] A proper amount of silica gel desiccant, molecular sieve or other desiccants can also be placed in the inner box body 23 of the sub-transport box 2. The amount of desiccant is determined according to the volume of the inner box body 23, the type of fruits and vegetables and the estimated transport time. The desiccant is packed in a cloth bag or a mesh bag with good air permeability and is evenly distributed in the corners and under the partitions of the inner box body 23 according to the distribution law of water vapor accumulation. When the humidity is high, the desiccant absorbs excess water vapor. When the absorption is close to saturation (which can be judged by weight change or color indication), the desiccant is replaced in time to ensure continuous and effective dehumidification effect.

[0078] Further, a monitoring and remote control implementation method is provided, which includes the following steps:

[0079] An LCD liquid crystal display screen is installed on the surface of the main transport box 1. According to the display principle, the current temperature, humidity value, collection time and equipment running state and other information in the box can be clearly displayed. At the same time, through the built-in Internet of Things module, the temperature and humidity data are transmitted to the remote monitoring terminal such as mobile phone APP or cloud platform in real time. The mobile phone APP interface is designed to be simple and intuitive, showing the real-time temperature and humidity data of the main transport box 1 in the form of charts, numbers, etc., so that the transport personnel or management personnel can check at any time and find abnormal temperature and humidity in time.

[0080] The manager uses the remote monitoring system to remotely control the operation of the refrigeration or heating, humidification or dehumidification equipment through the mobile phone APP or network platform according to the real-time temperature and humidity data. During transportation, if the temperature is found to be too high, the manager can start the refrigeration equipment on the mobile phone APP, and remotely adjust the power of the refrigeration equipment according to the temperature deviation, such as adjusting the compressor frequency or current size through the sliding bar; if the humidity is low, the humidification equipment can be remotely started, and the spray amount of the spray device can be adjusted, such as clicking the “humidification +” button to gradually increase the spray amount according to the preset increment, so that the fruits and vegetables are always in a suitable temperature and humidity environment, and intelligent and fine management is realized.

[0081] Building of the temperature and humidity control decision system

[0082] The gas feedback regulation algorithm and the PID closed-loop control algorithm are adopted, which specifically includes the following steps:

[0083] Step 1: The temperature and humidity control system operates through the closed-loop control system. First, the input link, with the real-time humidity sensor reading as the key input, combines optional feedback to provide accurate data basis for subsequent control decisions. The sensor converts the physical quantities of temperature and humidity into analog signals and transmits them to the controller. The sensor accuracy is optimized through calibration to ensure accurate and reliable signal conversion, with conversion error controlled within a very small range (according to sensor technical indicators, such as ±0.1%).

[0084] Step 2: Comparison link: error (target value - measured value), by comparing the preset target humidity value with the actual measured humidity value, accurately positioning the humidity deviation, providing key parameters for PID controller operation. The comparison process uses a high-precision operational amplifier to ensure accurate error calculation and avoid regulation deviation caused by calculation error.

[0085] Step 3: PID controller link

[0086] Step 3.1: Proportional (P) link: the proportional link generates control action according to the difference between the current set value and the actual measured value.

[0087] The target value and the measured value are compared using a differential amplifier method. High-precision operational amplifiers are used in the comparison process to ensure accurate error calculation and avoid regulation deviation caused by calculation error. The formula is:

[0088] u p (k)=K p e(k)K conv

[0089] K p is the proportional gain, e(k) is the current time error of the proportional (P) link (for example: for temperature, e T (k)=T set -Tmeasured )。

[0090] In the said fruit and vegetable transport box, the proportional gain takes the empirical value K p = 4.

[0091] Step 3.2: integral (I) link: the integral link is used to eliminate the steady-state error. The formula is:

[0092]

[0093] K i is the integral gain, and e(j) is the error at the current time of the integral (I) link. In this embodiment, K i The integral gain takes the empirical value K i = 0.2.

[0094] Step 3.3: differential (D) link: the differential link generates control action according to the rate of change of error. Control is performed in advance to suppress overshoot. The formula is:

[0095] u d (k) = K d (e(k) - e(k-1))

[0096] K d is the differential gain, and e(k) is the error at the current time of the differential (D) link. In this embodiment, K d The differential gain takes the empirical value K d = 0.5.

[0097] Step 3.4: total output of the PID controller: the formula is:

[0098] u(k) = u p (k) + u i (k) + u d (k)

[0099] According to the output u(k) of the PID controller, the operation of the heating device, the refrigeration device, the humidifying device, and the dehumidifying device is controlled.

[0100] In the temperature and humidity precise regulation system based on PID control, the execution link precisely adjusts the power and frequency of the humidifying device or the dehumidifying device according to the control instruction output by the PID controller, so as to make the environmental humidity approach and maintain at the preset target humidity value.

[0101] In actual operation, it is still necessary to adjust the PID parameters by observing the response of the system (such as response speed, overshoot, and steady-state error). For the values of each gain in actual operation, the trial-and-error method, Ziegler-Nichols method, and other methods are used to adjust the empirical parameters to balance the response speed, overshoot, and steady-state error.

[0102] When the temperature and humidity control system determines that the current environmental humidity is lower than the preset target humidity, the PID controller generates a positive control signal after operation, and the execution module responds immediately. For ultrasonic humidifying equipment driven by PWM technology, its built-in circuit or external control module adjusts the PWM wave duty cycle accurately according to the control signal. The duty cycle increases, and the power-on time ratio of the humidifying equipment spray generating element in unit time rises, and the spray amount approximately linearly increases to achieve the purpose of humidification. For example, the preset target humidity is 90% RH, the current humidity is 80% RH, the PID controller calculates the humidification power required according to the system characteristics and environmental parameters, and the control signal drives the PWM module to increase the duty cycle from 30% to 60%, and the spray amount of the humidifying equipment increases significantly.

[0103] From the hardware architecture, the microcontroller is used as the core control unit, and its high-performance timer is used to generate accurate PWM signals. The selected TIM4 timer channel (such as channel 1) is connected to the humidifying equipment drive control pin, and the system is initialized. The pre-division coefficient, automatic reload value, and count mode of TIM4 are finely configured to determine the PWM signal frequency and resolution that adapt to the humidifying equipment. For example, set the pre-division coefficient to 84-1 (system clock 84MHz) and the automatic reload value to 1000-1 to build a 10kHz, 1000-level resolution PWM signal system. When executing the humidity regulation instruction, update the TIM4 channel 1 comparison register value in real time according to the PID output value to accurately control the humidifying equipment spray power.

[0104] For dehumidifying equipment based on condensation dehumidification principle, the compressor operating frequency is related to the dehumidification efficiency. When the temperature and humidity control system monitors that the environmental humidity is higher than the preset target humidity, the PID controller generates a negative control signal to indicate that the dehumidification intensity needs to be increased. At this time, by means of inverter technology, direct current is converted into variable frequency alternating current to drive the compressor to run at high frequency. The microcontroller establishes a data interaction link with the inverter through the built-in communication interface module, and transmits accurate frequency control instructions to the inverter.

[0105] In the dehumidification strategy execution branch process of the PID control algorithm, the compressor operating frequency is accurately set according to the PID output absolute value and the pre-calibrated frequency mapping relationship. For example, the preset target humidity is 85% RH, and the humidity rises to 92% RH. The PID controller calculates that the dehumidification needs to be strengthened, and the system instructs the inverter to increase the compressor frequency from 30Hz to 50Hz through the SetDehumidifierFrequency function to enhance the dehumidification capacity.

[0106] Step 4: Feedback loop, detect and return new humidity value, form a closed-loop humidification system. Choose high-precision, high-stability capacitive humidity sensor, which can capture subtle fluctuations in environmental humidity with high resolution, and convert it into precise changes in capacitance. The system integrates a compatible capacitive-digital converter (CDC) circuit module, which uses analog-to-digital conversion technology to quantize the capacitance value with high resolution into a digital value and transmit it to the core microcontroller.

[0107] In terms of PID control system software algorithm, humidity data acquisition and processing functions are used to drive the CDC circuit to complete data acquisition and calibration, and to accurately convert data based on sensor characteristics.

[0108] In the main program of the temperature and humidity control system, the above functions are called periodically according to the preset accurate sampling time interval (such as every 2 seconds, set according to the system's response to humidity and the time required for device adjustment) to obtain the latest humidity monitoring value and inject it into the PID control algorithm process.

[0109] The following is the PID algorithm pseudocode. The function implementation of the PID control algorithm mainly consists of three stages:

[0110] The first stage of the PID control algorithm, Algorithm 1, is used to obtain the input data for PID control, specifically the target temperature, current temperature, target humidity, and current humidity. These four key values are assigned and then returned as a dictionary. These data provide basic information for subsequent PID control decisions.

[0111] The second stage of the PID control algorithm, Algorithm 2, is based on the dictionary data containing target and current temperature and humidity values passed in (i.e., data obtained from the previous algorithm). It evaluates the current control situation by calculating the temperature and humidity errors and determines whether temperature or humidity needs to be adjusted. It returns a corresponding prompt string to indicate the current control state of the system. Calculate the temperature and humidity errors, then make conditional judgments based on the set error thresholds. If the temperature error is greater than 2, it means the current temperature is much higher than the target temperature, and a prompt to cool down is returned. If the temperature error is less than -2, it means the temperature is too low, and a prompt to heat up is returned. For humidity, if the humidity error is greater than 5, it means the humidity is too high, and a high humidity prompt is returned. If the humidity error is less than -5, it means the humidity is too low. If both the temperature and humidity errors are within their respective reasonable ranges, it means the current PID control is in an acceptable state and no additional adjustment is needed.

[0112] The third stage of the PID control algorithm, i.e., Algorithm 3, is the core part of the PID control algorithm, responsible for calculating specific output values for temperature and humidity adjustment according to the input temperature and humidity data, and then simulating the control of corresponding devices (heating, cooling, humidifying, and dehumidifying devices) based on these output values, and finally returning a dictionary containing temperature and humidity control output values for possible subsequent recording or further processing. First, the parameters of the PID control (proportional gain, integral gain, and derivative gain) and related variables used in the calculation process (such as the temperature and humidity error variables and the integral term) are initialized. Then, the temperature error and humidity error at the current time are recalculated, and then the core calculation of the PID control is performed for temperature and humidity respectively, including calculating the accumulation of the integral term, the derivative term (the difference between the current error and the last error), and then calculating the temperature output value and the humidity output value according to the basic PID formula (weighted sum of the three terms: proportion, integration, and differentiation). After that, the corresponding device control function is called according to these output values to adjust the operation state of the device, realizing the actual control of temperature and humidity. Finally, the last temperature error and humidity error values are updated to prepare for the next loop calculation, and the dictionary containing the temperature and humidity control output is returned, completing a complete PID control output adjustment process.

[0113] During the entire implementation process, various parts work closely together, and the heat preservation layer, shock absorbing plate 3, buffer layer, buffer pad, and temperature and humidity regulation system cooperate with each other to create a stable and suitable transportation environment for melons, fruits, and vegetables. Whether in a normal temperature environment, high temperature and hot summer, or low temperature and cold winter conditions, the transportation box can ensure the freshness of fruits and vegetables during transportation through precise temperature and humidity control and effective shock protection, reduce deterioration and loss, prolong the preservation period, and improve transportation quality and efficiency, providing strong technical support for the cold chain logistics link of the fruit and vegetable industry. At the same time, the design of the total (partial) transportation box fully considers practicality, reliability, and maintainability, facilitating large-scale application in various fruit and vegetable transportation scenarios to meet the needs of different users.

[0114] The above is only a preferred embodiment of the present application, and does not limit the present application in any way. Any person skilled in the art can make any form of equivalent replacement, modification or change to the technical solutions and technical content disclosed by the present application without departing from the scope of the technical solutions of the present application, and such changes still fall within the protection scope of the present application.

Claims

1. A fruit and vegetable transportation system with preservation function, characterized in that, It includes a main transport box and multiple sub-transport boxes placed inside a closed transport vehicle. The main transport box is divided into multiple fixed slots by multiple equally spaced and fixed shock-absorbing plates, and each fixed slot is fixed with one sub-transport box. The inner surface of the main transport box is fixed with an insulation layer, and the bottom of the box is provided with a moisture-retaining interface. The moisture-retaining interface is connected to the fixing groove and is fixed to the transport vehicle through a connector. The inner surface of the main transport container is also equipped with a temperature and humidity sensor, and the transport vehicle is equipped with a temperature and humidity control system, including an automatic temperature and humidity monitoring system and a temperature and humidity control decision system. The automatic temperature and humidity monitoring system receives temperature and humidity data collected by temperature and humidity sensors. The temperature and humidity control decision system processes the temperature and humidity data and uses a gas feedback regulation algorithm and a PID closed-loop control algorithm in conjunction with the insulation layer and the moisture-retaining interface to achieve precise control of the temperature and humidity inside the main transport box.

2. The fruit and vegetable transportation system with preservation function according to claim 1, characterized in that, The operation of the temperature and humidity control decision system includes the following steps: S1: Using real-time temperature and humidity sensor readings as key inputs, combined with optional feedback, it provides a precise data foundation for subsequent control decisions; S2: By comparing the preset target humidity value with the actual detected humidity value, the temperature and humidity deviation is accurately located, providing key parameters for the PID controller calculation; S3: Calculate the total output of the PID controller based on the temperature and humidity deviation, and control the operation of the heating equipment, cooling equipment, humidification equipment and dehumidification equipment; S4: Result feedback, that is, detecting and returning new temperature and humidity values, repeating S1-S4 until the actual temperature and humidity values ​​are the same as the preset temperature and humidity values, completing the operation of the temperature and humidity control decision system and forming a closed loop.

3. The fruit and vegetable transportation system with preservation function according to claim 2, characterized in that, S3 specifically includes the following steps: S31: Proportional P stage: A differential amplifier method is used to compare the preset temperature and humidity values ​​with the actual detected temperature and humidity values ​​to ensure accurate error calculation and avoid control deviations caused by calculation errors. The calculation formula is expressed as follows: you p (k)=K p e(k)K conv Among them, K p Here, e(k) represents the proportional gain, and e(k) represents the error at the current time in the proportional P element. S32: Integral I element, used to eliminate steady-state error, expressed by the formula: Among them, K i Let e(j) be the integral gain; e(j) is the error at the current moment in the integral I stage. S33: Differential D element: It generates control based on the rate of change of the error, providing early control and suppressing overshoot, expressed as: you d (k)=K d (e(k)-e(k-1)) Among them, K d e(k) represents the differential gain; e(k) represents the error at the current time in the differential D stage. S34: The formula for calculating the total output of the PID controller is expressed as follows: u(k)=u p (k)+u i (k)+u d (k) The temperature and humidity control decision system precisely adjusts the power and frequency of the heating, cooling, humidifying and dehumidifying equipment by controlling the output commands of the PID controller, so that the temperature and humidity inside the total transport box approach and are maintained at the preset suitable temperature and humidity values.

4. The fruit and vegetable transportation system with preservation function according to claim 1, characterized in that, The insulation layer uses polyurethane foam as the insulation material. The insulation layer and its parameters are calculated based on a self-developed multilayer dielectric thermal conductivity mathematical model, which is expressed as follows: Where t is the water temperature inside the pipe; tT is the soil temperature; h is the burial depth; λT is the thermal conductivity of the soil; and the thickness of the insulation layer is determined by the above parameters.

5. The fruit and vegetable transportation system with preservation function according to claim 1, characterized in that, The outer surface of the insulation layer is uniformly coated with acrylic or polyurethane waterproof coating to extend the service life of the insulation layer and prevent the insulation performance from being reduced due to moisture.

6. The fruit and vegetable transportation system with preservation function according to claim 1, characterized in that, The shell of the insulated box is provided with a disassembly port to facilitate the replacement of the insulation layer. The edges of the disassembly port are reinforced to avoid damage caused by frequent disassembly.

7. The fruit and vegetable transportation system with preservation function according to claim 1, characterized in that, The main transport box has multiple slots inside, and the opposite sides of the shock-absorbing plate are inserted into the main transport box through the slots, forming the fixing groove between two adjacent shock-absorbing plates; The shock-absorbing plate has outwardly extending lugs on both sides opposite to the end of the main transport box, which are limited and easy to disassemble. The lugs are arranged to abut against the surface of the main transport box.

8. The fruit and vegetable transportation system with preservation function according to claim 7, characterized in that, The bottom shell and the two side shells of the main transport box are also lined with a bottom buffer pad. The bottom buffer pad and the shock-absorbing plate are both rubber pads with a thickness of 5cm.

9. The fruit and vegetable transportation system with preservation function according to claim 1, characterized in that, The sub-transport box includes a box body and a box lid. The box body is equipped with a latch for opening the box lid, and the box lid has a ventilation opening that connects to the inside of the sub-transport box. Fruits and vegetables are placed inside the box body.

10. The fruit and vegetable transportation system with preservation function according to claim 9, characterized in that, The box includes an outer box and an inner box. The outer box is hollow inside and has a stepped surface recessed on its upper surface. The upper surface of the inner box has a ramp extending outward around its four sides, and the ramp is fixed inside the outer box by the cooperation of the ramp and the stepped surface. The inner surface of the inner box is provided with at least one recessed groove for fixing fruits and vegetables; The bottom surface of the inner box is covered with a buffer layer, which is a rubber pad, and the rubber pad is set to abut against the inner bottom of the outer box.

Images