Open stepped multi-stage extrusion friction peeling device and method for asparagus potato

Abstract

The present application relates to a kind of open step multi-stage extrusion friction peeling device and method of asparagus potato, belong to traditional Chinese medicinal material processing machinery technical field, mainly solve the problem of high flesh damage rate caused by incomplete peeling of epidermis due to single-stage extrusion of traditional peeling equipment.The device uses back plate and two side plates to form a processing space with open top and one side, multiple layers of roller groups are arranged inside, the shortest length of the uppermost layer of rollers increases layer by layer to form a stepped extrusion channel, an extrusion friction gap is formed between adjacent rollers and covered with a flexible elastic layer, and the surface is provided with a protruding structure.After the first stage of pretreatment, asparagus potato is fed from the top into the present application, and falls layer by layer along the stepped channel, and the flexible layer is extruded and rubbed by forward and reverse rotating rollers to achieve epidermal peeling.The present application can efficiently complete the peeling process of asparagus potatoes of different sizes, and is suitable for asparagus skin processing in the field of traditional Chinese medicinal materials and food processing, with high processing efficiency and good flesh integrity.

Description

Technical Field

[0001] This invention relates to the field of equipment technology for processing Chinese medicinal materials, and more specifically, to an open-type stepped multi-stage extrusion friction peeling device and method for Asparagus cochinchinensis. Background Technology

[0002] Asparagus cochinchinensis (Lour.) Merr, also known as Tianmendong, is a traditional Chinese medicine. Its tuberous roots require peeling to meet medicinal standards. For example, the Chinese patent CN112890230B discloses a flexible simulation multi-stage extrusion friction peeling equipment and process method for asparagus. The mechanical peeling equipment is based on a closed cavity design, such as roller extrusion. However, such equipment has the following problems in practical applications: Material blockage and cleaning are difficult due to the limited internal space of the enclosed processing chamber. Asparagus root and shed skin easily accumulate in the narrow channels, especially during continuous operation, where peeling residue is difficult to remove in time, leading to channel blockage. This not only requires frequent shutdowns for cleaning but also increases equipment maintenance costs. The root cause of this problem lies in the lack of an effective material flow path in the enclosed structure and the inability to automatically remove debris during operation.

[0003] Asparagus potatoes have a high breakage rate. Due to their high elasticity and fibrous skin, hard compression easily causes both the skin and flesh to deform simultaneously, rather than effectively separating them. Especially in roller designs with fixed spacing, insufficient initial compression may result in skin residue, while excessive pressure later can damage the flesh. Furthermore, the lack of cushioning when a hard surface is in direct contact with the asparagus potato leads to concentrated local pressure, further exacerbating breakage.

[0004] Solving the above problems faces the following challenges: First, the open structure design needs to maintain an effective extrusion path while avoiding material splashing, which places higher demands on the roller layout and guiding mechanism; second, the selection of materials and texture design of the flexible extrusion surface need to take into account both friction and durability in order to avoid increased costs caused by frequent replacements. Summary of the Invention

[0005] To address the aforementioned problems, another objective of this invention is to provide an open-type, multi-stage extrusion friction peeling device and method for asparagus potatoes, which solves the technical problems of limited internal space in traditional closed processing chambers, where asparagus potatoes and peeled skins tend to accumulate in narrow channels, especially during continuous operation, making it difficult to discharge peeling residues in real time, leading to channel blockage, and high asparagus potato breakage rate.

[0006] To achieve these objectives and other advantages of the present invention, the present invention provides an open-type stepped multi-stage extrusion friction peeling device for asparagus potatoes, comprising: The processing space is formed by the back panel and the two side panels, with the top and one side open. Several layers of roller groups are arranged within the processing space, each layer of roller group including multiple parallel rollers, wherein: The uppermost roller group has the shortest roller length, and along the material travel direction, the roller length of the adjacent lower roller groups increases step by step, forming a stepped extrusion channel that descends step by step toward the open side; Extrusion friction gaps are formed between adjacent rollers in each roller group, and the roller surface is covered with a flexible elastic layer; After being fed into the processing space from the top, the asparagus potatoes fall layer by layer along the stepped extrusion channel. The outer skin is peeled off through the progressive extrusion and friction of the asparagus potatoes by the flexible elastic layer. The open structure and stepped channel design avoid material blockage and reduce the breakage rate of the asparagus potatoes.

[0007] Preferably, the plurality of roller groups arranged within the processing space satisfy the following conditions: Each roller assembly contains 3 to 50 rollers arranged in parallel. The length of a single roller in an adjacent lower roller group is 80 mm to 250 mm longer than that of the upper roller; The vertical height difference between adjacent roller groups is 1.2 to 1.8 times the roller diameter; The spacing between adjacent rollers in the same roller group is 0.8 to 1.2 times the roller diameter; The inclination angle of the stepped extrusion channel is 0 degrees to 12 degrees; The thickness of the flexible elastic layer covering the roller surface of each roller assembly is 5 mm to 8 mm; The diameter of the rollers is between 80 mm and 120 mm, and all rollers in the same processing space have the same diameter.

[0008] Preferably, adjacent rollers in the same roller group rotate in opposite directions and can rotate in both directions; The flexible elastic layer has a uniformly distributed raised structure on its surface, and the axis of the raised structure forms an angle of 25 to 50 degrees with the axis of the roller. The raised structures of adjacent rollers in the same layer of roller group are staggered, and the minimum distance between the top of the raised structures of adjacent rollers is 3 mm to 5 mm. The cross-section of the protruding structure is trapezoidal, with the base length of the trapezoid being 6 mm to 10 mm and the height being 2 mm to 3 mm; The Shore hardness of the flexible elastic layer is 60A to 70A, and the Shore hardness of the flexible elastic layer of the adjacent roller group increases by 5A to 8A in each step. The width of the extrusion friction gap is 0.2 to 0.3 times the diameter of the roller, and the width of the extrusion friction gap between adjacent roller groups decreases by 10% to 15% at each level.

[0009] Preferably, the minimum distance between the top of the protrusion structure on the surface of the flexible elastic layer and the surface of the adjacent roller is 0.4 to 0.6 times the maximum diameter of the asparagus potato; The protrusions are distributed in a spiral pattern on the surface of the drum, and the lead of the spiral is 1.5 to 2 times the circumference of the drum. In the same layer of roller assembly, the roller end located on the open side is equipped with an elastic baffle, and the distance between the elastic baffle and the roller end face is 0.1 to 0.15 times the roller diameter; The material of the elastic baffle has a Shore hardness 10A to 15A lower than that of the flexible elastic layer of the same roller, and the thickness of the elastic baffle is 8 mm to 12 mm. When unpeeled sweet potatoes enter the extrusion friction gap, the spiral distribution of the protruding structure forces the sweet potatoes to move along the roller axis. If the diameter of the sweet potato is greater than the gap width, the sweet potato moves forward and contacts the elastic baffle, which is then compressed and deformed. The baffle rebounds, giving the sweet potato lateral acceleration, which causes it to shift to the open side and slide into the extrusion friction channel of the next roller group.

[0010] Preferably, a spray assembly is provided directly above the extrusion friction gap of each roller group within the processing space; The spray assembly includes 2 to 4 fan-shaped nozzles distributed along the axial direction of the roller. The spray angle of the fan-shaped nozzles is 60 to 90 degrees, and the spray coverage includes the flexible elastic layer surface of the adjacent rollers and the extrusion friction gap. The installation height of the fan-shaped nozzle is 0.5 to 0.8 times the diameter of the drum, and the horizontal distance between the nozzle outlet and the center line of the extrusion friction gap is 20 mm to 30 mm. The fan-shaped nozzle is connected to an external water tank through a diversion pipeline. A pressure regulating valve is installed in the diversion pipeline, and the outlet pressure of the pressure regulating valve is 0.2MPa to 0.4MPa. The pressure regulating valve is electrically connected to the controller. Pressure sensors are installed at both ends of the roller to sense the squeezing force of adjacent rollers. The controller dynamically adjusts the opening of the pressure regulating valve based on the real-time squeezing force feedback signal of the adjacent rollers.

[0011] Preferably, the pressure sensor is installed on the inner wall of the bearing seat of the adjacent roller, and the detection range of the pressure sensor is 0N to 200N, and the detection accuracy is ±2N; The pressure sensor and the controller are connected via RS485 communication protocol, and the signal sampling interval of the controller is 100ms to 200ms; The valve core stroke of the pressure regulating valve is 0mm to 15mm, and the linear relationship between the valve core stroke and the jet water pressure is that for every 1mm increase in stroke, the water pressure increases by 0.02MPa to 0.025MPa. When the pressure sensor detects the real-time extrusion pressure of the adjacent rollers, the controller controls the pressure regulating valve according to the following logic: If the real-time extrusion pressure is 50N to 80N, the controller will adjust the valve core stroke of the pressure regulating valve from 5mm to 8mm, so that the jet water pressure increases from 0.25MPa to 0.3MPa; If the real-time extrusion pressure is 80N to 120N, the controller will adjust the valve core stroke from 8mm to 12mm, thereby increasing the jet water pressure from 0.3MPa to 0.4MPa. If the real-time extrusion pressure exceeds 120N, the controller will lock the valve core stroke to 15mm, so that the water jet pressure reaches 0.45MPa, and trigger the overload protection program of the drum drive motor. The valve core stroke adjustment response time of the pressure regulating valve is 0.5 seconds to 1 second after the pressure signal is triggered; The overload protection procedure includes reducing the drive motor speed by 20% to 30% from the current value, and the speed reduction operation lasts for 10 to 15 seconds after the extrusion pressure exceeds 120N; The linkage control parameters between the pressure sensor and the pressure regulating valve are set according to the hierarchical differences of the roller assembly, specifically as follows: The linkage control range of the uppermost roller assembly is 50N to 80N; The linkage control range of the intermediate layer roller assembly is 80N to 100N; The linkage control range of the lowest roller assembly is 100N to 120N; When the extrusion pressure of a certain roller group exceeds the upper limit of the corresponding linkage control range for 5 consecutive sampling values, the controller automatically increases the upper limit of the linkage control range of that roller group by 10N to 15N.

[0012] Preferably, a filter unit is provided upstream of the diversion pipeline, and the filter unit has a built-in stainless steel filter screen with a pore size of 0.5 mm to 1 mm; The bottom guide channel of the processing space has multiple drainage holes on its side wall. The diameter of the drainage holes is 5 mm to 8 mm, and the longitudinal spacing between adjacent drainage holes is 1 / 2 to 2 / 3 of the width of the guide channel. The end of the guide channel is connected to a spiral dewatering machine, which rotates at a speed of 20 rpm to 30 rpm, and the gap between the spiral blades and the dewatering machine housing is 3 mm to 5 mm.

[0013] This invention provides a step-by-step extrusion peeling process for asparagus potatoes, comprising the following steps: The asparagus potatoes were pre-treated by rolling and cutting. The height of the rolling and cutting blade was set to 1.1 to 1.3 times the thickness of the asparagus potato skin. After rolling and cutting, axial cuts with a depth of 0.8 mm to 1.2 mm were formed. Place the rolled and chopped asparagus into a pot, add water at a ratio of 3:1 (water to asparagus by weight), and steam at a constant temperature of 95°C to 100°C for 15 to 20 minutes. Add a peeling agent to the cooking pot. The peeling agent is a solution of sodium bicarbonate and citric acid mixed in a mass ratio of 2.4:1, with a final concentration of sodium bicarbonate of 0.6 wt% and a final concentration of citric acid of 0.25 wt%. Stir for 5 to 8 minutes. The processed asparagus potatoes are transferred to an open-type stepped peeling device, which includes multiple roller groups. The distance between adjacent rollers in each roller group is 0.8 to 1.2 times the diameter of the roller. The surface of the roller is covered with a polyurethane layer with a Shore hardness of 60A to 70A. The surface of the polyurethane layer is provided with trapezoidal protrusions with a protrusion height of 2 mm to 3 mm. The rotation speed of the top roller group is controlled at 30 rpm to 40 rpm, and the extrusion pressure of the adjacent rollers is 50 N to 80 N. The asparagus potatoes fall layer by layer through the stepped channel. With each layer, the rotation speed of the rollers increases by 5 rpm to 10 rpm and the extrusion pressure increases by 20 N to 30 N. During the peeling process, water mist with a pressure of 0.3MPa to 0.5MPa is sprayed into the extrusion friction gap of each roller group, with a water mist flow rate of 10L / min to 15L / min per meter of roller length, and the water temperature is maintained at 40℃ to 50℃.

[0014] Preferably, the fresh asparagus potatoes are first washed, graded and screened in sequence, and individuals with a diameter greater than 50 mm or less than 20 mm are removed after screening; then they are rolled and cut.

[0015] Preferably, the peeled asparagus potatoes are collected in a guide channel to a vibrating screen. The screen has an amplitude of 2 to 3 mm, a vibration frequency of 20 Hz to 25 Hz, and a screen mesh size of 5 to 8 mm. The sieved whole asparagus potato flesh is transferred to a hot air dryer, where the drying temperature is 55℃ to 60℃ and the air velocity is 2m / s to 3m / s, until the moisture content is less than 12wt%.

[0016] Preferably, the following dynamic control steps are performed during the peeling process: Real-time data on the residual thickness of the asparagus skin at the exit of each roller group was collected. A laser thickness gauge was used to scan the surface of the asparagus at a sampling frequency of 20Hz to 30Hz. The measurement accuracy of the thickness gauge was ±0.1mm. When the residual thickness of the skin is detected to be greater than 0.5mm, the controller executes the first adjustment strategy: increase the rotation speed of the current layer of rollers by 5rpm to 8rpm, and increase the extrusion pressure threshold of the next layer of rollers by 10N to 15N; When the residual thickness of the peel is less than 0.2 mm and the pulp damage rate exceeds 3%, the controller executes the second adjustment strategy: reduce the rotation speed of the current layer of rollers by 3 rpm to 5 rpm, and lower the extrusion pressure threshold of the next layer of rollers by 8 N to 12 N. The response delay time for the first adjustment strategy and the second adjustment strategy is 2 to 3 seconds after the detection signal is triggered; The pulp breakage rate is calculated in real time by the image processing module. The specific method is as follows: an industrial camera is set at the exit of each layer of roller group to capture images of the surface of the sweet potato at a frame rate of 60fps. The percentage of the intact area of ​​the skin is counted by the edge detection algorithm. When the percentage is less than 97%, it is judged as broken. The dynamic control process continues until the residual thickness of the peel in all layers of rollers stabilizes within the range of 0.2 mm to 0.5 mm and the pulp breakage rate is less than 3%.

[0017] The present invention has at least the following beneficial effects: Compared to the Chinese patent CN112890230B, which uses a closed rotary drum module (combination of main and sub-rotary drums) to form a multi-level processing space through primary and secondary extrusion friction modules, this invention designs an open stepped structure. It consists of multiple layers of rollers forming a progressively descending extrusion channel. The length of each roller in the roller group increases progressively, forming a stepped open space that allows the asparagus potatoes to fall naturally and be peeled through progressive extrusion friction, reducing the risk of material blockage. It also reduces the risk of asparagus potatoes being blocked and crushed. Furthermore, the use of a progressive structure for peeling further reduces the breakage rate.

[0018] Other advantages, objectives and features of the present invention will be apparent in part from the following description, and in part from the understanding of those skilled in the art through study and practice of the invention. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of the open-type stepped multi-stage extrusion friction peeling device for asparagus potatoes according to the present invention; Figure 2 This is a schematic diagram of the structure of the roller described in this invention; Figure 3 This is a schematic diagram of the front structure of a single-layer roller assembly of the present invention; Figure 4 This is a schematic diagram of the power transmission structure on the back of the single-layer roller assembly of the present invention.

[0020] The components include: processing space 10, side plate 101, back plate 102, open side 103, roller group 20, roller 201, mounting bracket 202, extrusion friction gap 203, flexible elastic layer 204, protruding structure 205, bearing seat 206, elastic baffle 207, adjusting hole 208, drive mechanism 30, motor 301, tensioning wheel 302, and belt 303. Detailed Implementation

[0021] The present invention will be further described in detail below with reference to embodiments, so that those skilled in the art can implement it based on the description.

[0022] like Figures 1-4 As shown, the present invention provides an open-type stepped multi-stage extrusion friction peeling device for asparagus potatoes, comprising: The processing space is formed by the back panel and the two side panels, with the top and one side open. Several layers of roller groups are arranged within the processing space, each layer of roller group including multiple parallel rollers, wherein: The uppermost roller group has the shortest roller length, and along the material travel direction, the roller length of the adjacent lower roller groups increases step by step, forming a stepped extrusion channel that descends step by step toward the open side; Extrusion friction gaps are formed between adjacent rollers in each roller group, and the roller surface is covered with a flexible friction elastic layer; After the pre-treated asparagus potatoes are fed into the processing space from the top, they fall layer by layer along the stepped extrusion channel. Through the flexible friction elastic layer, the asparagus potatoes are subjected to multiple progressive extrusions and frictions to peel off the outer skin.

[0023] Specifically, the processing space can be formed by welding 304 stainless steel plates, with a back plate thickness of 8mm and a side plate height of 1200mm. The distance between the two side plates can be adjusted to 600-800mm to accommodate different processing volumes. A guide funnel can be installed in the top open section, with the funnel tilt angle set to 45 degrees.

[0024] The roller assembly can be made of seamless 45# steel tubing, with a polyurethane elastic layer covering the surface. The polyurethane layer thickness can be 6mm, and the Shore hardness can be controlled at 65A±3. The spacing between adjacent rollers can be set to 100mm, adjustable via bearing seats at both ends. A 1.5kW variable frequency motor can be used as the drive motor, with roller rotation achieved through a transmission mechanism. The length of the top roller can be set to 500mm, increasing by 80mm for each subsequent layer.

[0025] like Figure 1 and 3As shown, the open side 103 is the discharge direction; the processing space is provided with mounting brackets 202, which are respectively fitted to one end of each layer of roller group. The rollers are installed and fitted with the mounting brackets through bearing seats, and adjustment holes can be provided on the mounting brackets, including spacing adjustment holes and height adjustment holes, to facilitate setting the spacing between adjacent rollers or the inclination of each layer of roller group.

[0026] During the process, the asparagus potatoes are fed into the processing space from the top, and the motor is started, causing the asparagus potatoes to fall layer by layer along the stepped extrusion channel. The outer skin is peeled off through the gradual extrusion and friction of the asparagus potatoes by the flexible elastic layer.

[0027] The stepped extrusion channel of this embodiment uses progressively increasing roller length and progressively decreasing gap width to peel the skin of the asparagus potato layer by layer under progressive pressure. Tests have shown that the peeling integrity rate can be increased to over 95%, while the flesh damage rate is controlled to within 3%.

[0028] Furthermore, in another embodiment, the plurality of roller groups arranged within the processing space satisfy the following conditions: Each roller assembly contains 3 to 30 rollers arranged in parallel. The length of a single roller in an adjacent lower roller group is 80 mm to 250 mm longer than that of the upper roller; The vertical height difference between adjacent roller groups is 1.2 to 1.8 times the roller diameter; The spacing between adjacent rollers in the same roller group is 0.8 to 1.2 times the roller diameter; The inclination angle of the stepped extrusion channel is from 0 to 12 degrees; the inclination angle of the stepped extrusion channel can be achieved by adjusting the installation height of the roller assembly. Specifically, each layer of roller assembly can be equipped with a height adjustment hole on its mounting bracket, with the adjustment interval set in 50mm increments.

[0029] The thickness of the flexible elastic layer covering the roller surface of each roller assembly is 5 mm to 8 mm; The diameter of the rollers is between 80 mm and 120 mm, and all rollers in the same processing space have the same diameter.

[0030] Specifically, the rollers in the roller assembly can be made of seamless 45# steel tubing with a hard chrome plating finish. The tube wall thickness can be set to 5mm, and 6206 deep groove ball bearings can be installed at both ends. The roller diameter can be 100mm, and all rollers in the same unit are set with the same diameter. The length difference between adjacent layers of rollers can be set to 80mm, for example, a progressive structure of 600mm for the first layer, 680mm for the second layer, and 760mm for the third layer.

[0031] The vertical height difference between adjacent layers can be achieved by adjusting the mounting brackets. When the roller diameter is 100mm, the layer height difference can be set to 140mm. This value corresponds to 1.4 times the roller diameter, which can create a material drop angle of 30-35 degrees. The spacing between adjacent rollers in the same layer can be set to 100mm, corresponding to a spacing equal to 1 times the roller diameter. At this distance, the extrusion friction gap width is 40mm. With this spacing, the asparagus can achieve 3-5 effective extrusion rolling cycles.

[0032] The flexible elastic layer can be made of polyurethane material by casting, with a thickness of 6.5mm ± 0.5mm. The polyurethane raw material can be Bayer's Desmopan® 385 series, with a Shore hardness controlled at 65A ± 3.

[0033] The inclined angle of the stepped channel can be set to 8°, which is achieved by adjusting the installation height of each roller assembly. At this angle, the average material residence time is approximately 35 seconds per layer, which can complete more than 90% of the skin peeling.

[0034] In this embodiment, the lengths of adjacent rollers increase by 50-100mm, creating a continuous rolling trajectory for the material within the stepped channel and reducing collision damage. Setting the vertical height difference to 1.2-1.8 times the roller diameter achieves the optimal parabolic trajectory. Setting the roller spacing to a ratio of 0.8-1.2 times the diameter achieves a spacing range of 96-144mm on a 120mm diameter roller, resulting in optimal compression deformation (12-15%) for 30-50mm diameter sweet potatoes, achieving a skin peeling rate of approximately 94% while controlling the flesh breakage rate to within 2.5%.

[0035] Furthermore, the traditional asparagus peeling device suffers from several drawbacks. The rotating drum in the same direction causes the material to be subjected to force in one direction, resulting in incomplete removal of the skin. The smooth drum surface has an insufficient coefficient of friction, resulting in a high proportion of residual skin. The fixed hardness friction layer cannot adapt to the physical characteristics of asparagus potatoes at different maturity levels. In another embodiment of the present invention, adjacent rollers in the same layer of roller assembly rotate in opposite directions and can rotate in both directions; the surface of the flexible elastic layer is uniformly distributed with raised structures, the axis of the raised structures forming an angle of 30 to 45 degrees with the roller axis; the raised structures of adjacent rollers in the same layer of roller assembly are staggered, and the minimum distance between the tops of the raised structures of adjacent rollers is 3 to 5 millimeters; the cross-section of the raised structure is trapezoidal, the length of the base of the trapezoid is 6 to 10 millimeters, and the height is 2 to 3 millimeters; the Shore hardness of the flexible elastic layer is 60A to 70A, and the Shore hardness of the flexible elastic layer of adjacent roller assemblies increases by 5A to 8A in each step; the width of the extrusion friction gap is 0.2 to 0.3 times the roller diameter, and the width of the extrusion friction gap of adjacent roller assemblies decreases by 10% to 15% in each step.

[0036] Specifically, the rotation direction of adjacent rollers can be achieved by staggering the drive motors. Two 1.1kW Y2-90L-4 type motors can be used to drive adjacent rollers respectively, with the motor speed set to 35rpm. Reverse gear sets can be installed on the roller bearing housings, with a gear module of 3mm and a transmission ratio set to 1:1. Preferably, as... Figure 4 As shown, the roller drive mechanism of this invention uses a single motor to achieve the opposite rotation of adjacent rollers on the same layer. It includes a motor 301, a tensioning pulley 302, and a belt 303. The belt is arranged in a figure-eight shape to engage with the adjacent rollers. The tensioning pulley is tensioned in conjunction with the belt. The motor drives the belt to rotate, thereby causing the adjacent rollers to rotate in opposite directions. This design of adjacent rollers rotating in opposite directions provides the material with bidirectional friction, promoting peeling.

[0037] The raised structure can be integrally molded from polyurethane material, with a trapezoidal base of 8mm, a top edge of 4mm, and a height of 2.5mm. The axial spacing between adjacent raised sections can be set to 15mm, and the helix angle can be set to 35 degrees. Under these parameters, the material achieves 3 effective friction cycles per revolution, and video recording shows that the skin peeling process takes 8-12 seconds. The distance between the tops of the raised sections can be controlled to 4mm ± 0.2mm with precision mold processing. The 30-45 degree inclination angle of the raised structure forms a friction trajectory with a helix angle of 25-35 degrees on a 100mm diameter roller, stabilizing the axial movement speed of the material at 0.2-0.3m / s and preventing localized overheating.

[0038] The flexible elastic layer can be a three-layer composite structure: a base layer of 65A hardness polyurethane, a middle layer of 70A hardness nitrile rubber, and a top layer of 73A hardness silicone rubber. The thickness of each layer can be set to 2mm, 3mm, and 1.5mm respectively. The initial width of the extrusion gap can be set to 22mm, decreasing by 2.6mm with each layer, for a total of 5 gap levels. Pressure sensor testing shows that the pressure in the final gap can reach 2.3 times that of the first gap, consistent with the mechanical properties of asparagus root. The extrusion gap width decreases by 12% in each level, creating a gradual gap of 20-17.6mm on a 100mm diameter roller, ensuring that materials of different sizes receive appropriate deformation space.

[0039] Furthermore, in another embodiment, the minimum distance between the top of the protruding structure on the surface of the flexible elastic layer and the surface of the adjacent roller is 0.4 to 0.6 times the maximum diameter of the asparagus potato. The protrusions are distributed in a spiral pattern on the surface of the drum, and the lead of the spiral is 1.5 to 2 times the circumference of the drum. In the same layer of roller assembly, the roller end located on the open side is equipped with an elastic baffle, and the distance between the elastic baffle and the roller end face is 0.1 to 0.15 times the roller diameter; The material of the elastic baffle has a Shore hardness 10A to 15A lower than that of the flexible elastic layer of the same roller, and the thickness of the elastic baffle is 8 mm to 12 mm. When unpeeled sweet potatoes enter the extrusion friction gap, the spiral distribution of the protruding structure forces the sweet potatoes to move along the roller axis. If the diameter of the sweet potato is greater than the gap width, the elastic baffle is deformed by the extrusion, causing the sweet potato to shift to the open side and slide into the extrusion friction channel of the next layer of rollers.

[0040] Specifically, the spacing between the protruding tips can be set to 0.5 times the maximum diameter of the asparagus potato to achieve effective extrusion deformation. For raw materials with a maximum diameter of 50mm, the spacing can be set to 25mm ± 2mm. This spacing is achieved by adjusting the roller installation position, using M12 precision adjusting bolts with an adjustment accuracy of up to 0.5mm. The spiral lead can be set to 1.8 times the roller circumference, corresponding to a 565mm lead on a 100mm diameter roller, with a spiral angle of 22 degrees, ensuring the material completes 3.2 axial movement cycles per minute, guaranteeing uniform force distribution across the entire circumference of the surface.

[0041] The elastic stop strip can be made of silicone rubber sheet with a Shore hardness of 55A and a thickness of 10mm. The stop strip can be installed 5mm from the outer side of the roller end and fixed with a stainless steel pressure plate. The pressure plate can be made of 1.5mm thick 304 stainless steel, and the mounting hole spacing can be set to 80mm. The 12mm gap between the stop strip and the roller end face can be finely adjusted by ±2mm using adjusting bolts.

[0042] When a 55mm diameter asparagus potato enters a 22mm gap, it moves axially to the baffle area under the drive of the spiral protrusion. Upon contact with the baffle, a lateral force is applied, causing the baffle to undergo a 4mm elastic deformation. The rebound force generated by this deformation pushes the material away from the contact surface, resulting in a 15-degree offset angle, making it easier for the material to slide to the next layer. After adjusting the lower layer gap to 19mm, further peeling is performed.

[0043] The asparagus potato peeling device is prone to jamming when processing large-sized materials, and the existing guide structure is too rigid and easily damages the flesh. This embodiment solves this problem through the combined design of elastic baffles and spiral protrusions.

[0044] Furthermore, in another embodiment, a spray assembly is provided directly above the extrusion friction gap of each roller group within the processing space; The spray assembly includes 2 to 4 fan-shaped nozzles distributed along the axial direction of the roller. The spray angle of the fan-shaped nozzles is 60 to 90 degrees, and the spray coverage includes the flexible elastic layer surface of the adjacent rollers and the extrusion friction gap. The installation height of the fan-shaped nozzle is 0.5 to 0.8 times the diameter of the drum, and the horizontal distance between the nozzle outlet and the center line of the extrusion friction gap is 20 mm to 30 mm. The fan-shaped nozzle is connected to an external water tank through a diversion pipeline. A pressure regulating valve is installed in the diversion pipeline, and the outlet pressure of the pressure regulating valve is 0.2MPa to 0.4MPa. The pressure regulating valve is electrically connected to the controller, which dynamically adjusts the opening of the pressure regulating valve based on the real-time extrusion pressure feedback signal from the adjacent rollers.

[0045] Specifically, such as Figure 1 As shown, the processing space is equipped with a transverse mounting rod 401 for mounting spray components 402. Each spray component 402 includes 2 to 4 fan-shaped nozzles distributed along the roller axis. Preferably, Lechler 460.848 type fan-shaped nozzles are used, with 3 nozzles equidistantly installed along the roller axis. The nozzle mounting bracket is fixed at a height of 80mm above the roller assembly, and the bracket is made of aluminum alloy profile (section 20×40mm). The horizontal distance between the nozzle outlet centerline and the extrusion gap centerline is set to 25mm, and the spray angle is locked at 75 degrees using an angle adjuster. The axially distributed 3 fan-shaped nozzles (spaced 200mm apart) at a 75-degree spray angle form a continuous coverage band on a 100mm diameter roller. Actual measurements show that the water mist coverage rate increased from 68% to 95%, and the amount of residual surface debris decreased by 82%. When the nozzle height is set to 60mm (0.6 times the diameter), the droplet size is controlled at 150-300μm, and the wetting depth reaches 1.2mm of the epidermis to prevent the pulp from absorbing water and swelling.

[0046] The branch line can be configured with an SMC VQD2121-5G pressure regulating valve, with the inlet connected to a 1.5kW centrifugal water pump (flow rate 12m³ / h). A Honeywell 26PC series pressure sensor can be selected and installed 1.2m from the nozzle on the pipeline. The controller is programmable to set the pressure-water pressure curve (e.g., for every 10N increase in pressure, the water pressure increases by 0.05MPa).

[0047] Furthermore, in another embodiment, the pressure sensor is installed on the inner wall of the bearing seat of the adjacent roller, and the detection range of the pressure sensor is 0N to 200N, with a detection accuracy of ±2N. The pressure sensor and the controller are connected via RS485 communication protocol, and the signal sampling interval of the controller is 100ms to 200ms; The valve core stroke of the pressure regulating valve is 0mm to 15mm, and the linear relationship between the valve core stroke and the jet water pressure is that for every 1mm increase in stroke, the water pressure increases by 0.02MPa to 0.025MPa. When the pressure sensor detects the real-time extrusion pressure of the adjacent rollers, the controller controls the pressure regulating valve according to the following logic: If the real-time extrusion pressure is 50N to 80N, the controller will adjust the valve core stroke of the pressure regulating valve from 5mm to 8mm, so that the jet water pressure increases from 0.25MPa to 0.3MPa; If the real-time extrusion pressure is 80N to 120N, the controller will adjust the valve core stroke from 8mm to 12mm, thereby increasing the jet water pressure from 0.3MPa to 0.4MPa. If the real-time extrusion pressure exceeds 120N, the controller will lock the valve core stroke to 15mm, so that the water jet pressure reaches 0.45MPa, and trigger the overload protection program of the drum drive motor. The valve core stroke adjustment response time of the pressure regulating valve is 0.5 seconds to 1 second after the pressure signal is triggered; The overload protection procedure includes reducing the drive motor speed by 20% to 30% from the current value, and the speed reduction operation lasts for 10 to 15 seconds after the extrusion pressure exceeds 120N; The linkage control parameters between the pressure sensor and the pressure regulating valve are set according to the hierarchical differences of the roller assembly, specifically as follows: The linkage control range of the uppermost roller assembly is 50N to 80N; The linkage control range of the intermediate layer roller assembly is 80N to 100N; The linkage control range of the lowest roller assembly is 100N to 120N; When the extrusion pressure of a certain roller group exceeds the upper limit of the corresponding linkage control range for 5 consecutive sampling values, the controller automatically increases the upper limit of the linkage control range of that roller group by 10N to 15N.

[0048] Specifically, the pressure sensor can be installed in the M8 threaded hole on the inner wall of the roller bearing housing. The distance between the sensor detection surface and the outer ring of the bearing can be set to 2mm ± 0.5mm. The signal line is led out through the Φ6mm wire hole on the side of the bearing housing. The detection range can be set to 0-200N, and the zero-point drift compensation can be set to automatically calibrate once every 24 hours.

[0049] The controller can be a Siemens S7-1200 PLC, with an RS485 communication baud rate set to 9600bps. The signal sampling interval can be set to 150ms, and the AD conversion accuracy to 12-bit. The linear relationship between valve core stroke and water pressure can be achieved through the positioning accuracy of the servo motor; each 1mm stroke corresponds to a water pressure increase of 0.023MPa. The motor speed reduction operation in the overload protection program can be achieved by switching the preset parameter group of the frequency converter.

[0050] The linkage range of the upper roller assembly can be set to 50-80N, corresponding to a valve core stroke of 5-8mm. The middle layer range can be set to 80-100N, corresponding to a stroke of 8-11mm. The lower layer range can be set to 100-120N, corresponding to a stroke of 11-14mm. When the extrusion pressure of a certain layer exceeds the limit five times consecutively (e.g., 105N is detected in the middle layer), the controller can increase the upper limit of that layer to 110N, with an increase step size of 10N. The parameter adaptive adjustment cycle can be set to learn once every 30 minutes.

[0051] In this embodiment, when the pressure is 50-80N, the water pressure linearly increases from 0.25MPa to 0.3MPa, ensuring the synergistic effect of surface wetting and mechanical extrusion. The linear relationship between 1mm valve core stroke and 0.023MPa water pressure ensures an adjustment accuracy error ≤ ±0.005MPa. The graded settings of the upper zone (50-80N), middle zone (80-100N), and lower zone (100-120N) match the gradual characteristics of stepped extrusion, improving water pressure utilization.

[0052] Furthermore, in another embodiment, a filter unit is provided upstream of the diversion pipeline, and the filter unit has a built-in stainless steel filter screen with a pore size of 0.5 mm to 1 mm. The bottom guide channel of the processing space has multiple drainage holes on its side wall. The diameter of the drainage holes is 5 mm to 8 mm, and the longitudinal spacing between adjacent drainage holes is 1 / 2 to 2 / 3 of the width of the guide channel. The end of the guide channel is connected to a spiral dewatering machine, which rotates at a speed of 20 rpm to 30 rpm, and the gap between the spiral blades and the dewatering machine housing is 3 mm to 5 mm.

[0053] The present invention provides a step-by-step extrusion peeling process for asparagus potatoes, comprising the following steps: The asparagus potato was pre-treated by rolling and cutting using existing equipment (such as announcement number CN112890230B). The height of the rolling and cutting blade was set to 1.1 to 1.3 times the thickness of the asparagus potato skin. After rolling and cutting, axial cuts with a depth of 0.8 mm to 1.2 mm were formed.

[0054] Place the rolled and chopped asparagus potatoes into a pot, add water at a ratio of 3:1 (by weight of asparagus potatoes), and steam at a constant temperature of 95℃ to 100℃ for 15 to 20 minutes. (Alternative methods, such as those in Publication No. CN112890230B, can also be used.) Add a peeling agent to the cooking pot. The peeling agent is a solution of sodium bicarbonate and citric acid mixed in a mass ratio of 2.4:1, with a final concentration of sodium bicarbonate of 0.6 wt% and a final concentration of citric acid of 0.25 wt%. Stir for 5 to 8 minutes. (Alternatively, existing methods can be used, such as washing, grading, rolling, adding enzymes, boiling, and treating with chemicals to soften and loosen the skin and flesh of the asparagus, as described in announcement number CN112890230B.) The processed asparagus potatoes are transferred to the open-type stepped peeling device of the present invention. The device includes a multi-layer roller group, in which the distance between adjacent rollers in each roller group is 0.8 to 1.2 times the diameter of the roller. The surface of the roller is covered with a polyurethane layer with a Shore hardness of 60A to 70A. The surface of the polyurethane layer is provided with a trapezoidal protrusion structure with a protrusion height of 2 mm to 3 mm. The rotation speed of the top roller group is controlled at 30 rpm to 40 rpm, and the extrusion pressure of the adjacent rollers is 50 N to 80 N. Asparagus falls down layer by layer through the stepped channel. With each layer, the rotation speed of the rollers increases by 5 rpm to 10 rpm and the extrusion pressure increases by 20 N to 30 N. During the peeling process, water mist with a pressure of 0.3MPa to 0.5MPa is sprayed into the extrusion friction gap of each roller group, with a water mist flow rate of 10L / min to 15L / min per meter of roller length, and the water temperature is maintained at 40℃ to 50℃.

[0055] Specifically, in this embodiment, the first-layer roller is set with a diameter of 100mm, a rotation speed of 35rpm, and an extrusion pressure of 65N. The polyurethane layer can be Bayer Desmopan® 385 series, with a Shore hardness of 65A±3. The trapezoidal protrusion design has a bottom edge of 8mm, a top edge of 4mm, and a height of 2.5mm. The water mist system can be configured with fan-shaped nozzles, with 3 nozzles installed per meter of roller length and an inclination angle of 60°. Water temperature control can be achieved through a plate heat exchanger, with temperature fluctuations ≤±1℃. The processing capacity is stable at 320kg / h, the peeling integrity rate is 95.3%, the pulp breakage rate is 2.0%, and the temperature rise of the roller assembly after 8 hours of continuous operation is ≤6℃.

[0056] Preferably, in traditional asparagus pretreatment processes, direct peeling of ungraded raw materials leads to over-compression and damage of small-sized materials, while large-sized materials are not thoroughly peeled. This invention first washes and grades fresh asparagus potatoes sequentially, removing individuals with a diameter greater than 50 mm or less than 20 mm after grading; then it rolls and cuts them. By grading and removing materials exceeding the diameter limit, the problem of peeling quality fluctuations caused by size differences is solved, while also preventing equipment jamming due to abnormal material sizes.

[0057] After peeling, the asparagus potatoes are collected in a guide channel and fed into a vibrating screen. The screen has an amplitude of 2-3 mm, a vibration frequency of 20-25 Hz, and a screen aperture of 5-8 mm. The separated whole asparagus potato flesh is then transferred to a hot air dryer. The drying temperature is 55-60℃, the air velocity is 2-3 m / s, and the drying time is reduced to a moisture content of less than 12 wt%. The vibrating screen with an amplitude of 2.5 mm and a frequency of 22 Hz achieves a 98.3% separation efficiency between the flesh and the skin. The 5 mm aperture screen can intercept 99% of the flesh fragments (>3 mm), and the skin residue rate is ≤0.8%. When the hot air drying is performed at 58℃ and 2.5 m / s, the drying rate is stable at 1.2% / min, which shortens the drying time by 35% compared to traditional processes, and the surface cracking rate is ≤1%.

[0058] Furthermore, in another embodiment, during the peeling process, the residual thickness of the asparagus skin at the outlet of each roller group can be collected in real time. Specifically, a laser thickness gauge is used for measurement. The sampling frequency of this device can be set to 20Hz to 30Hz, and the measurement accuracy is ±0.1mm. The laser thickness gauge can be installed in the outlet guide channel of each roller group (e.g., Figure 1 The vertical distance between the laser beam and the falling trajectory of the asparagus (located directly above the end of the central guide channel) is 50mm to 80mm. During measurement, the laser beam scans the surface of the asparagus perpendicular to the material's direction of travel, generating thickness distribution data in real time and transmitting it to the controller. When the residual thickness of the skin at a certain exit point is detected to be greater than 0.5mm, the controller triggers the first adjustment strategy.

[0059] The first adjustment strategy involves increasing the drive motor speed of the current roller assembly by 5 rpm to 8 rpm, for example, from 35 rpm to 40 rpm. Simultaneously, the pressure threshold of the next roller assembly is increased by 10N to 15N, for example, from 80N to 95N. The adjustment is executed automatically through a preset program on the controller, with a response delay of 2 to 3 seconds after the detection signal is triggered. Speed ​​adjustment is achieved by controlling the motor via a frequency converter, while the pressure threshold adjustment is dynamically corrected based on feedback signals from pressure sensors.

[0060] Fruit pulp breakage rate detection is achieved using an industrial camera (such as a Basler ace acA2000-50gm). The camera can be installed on the exit side of each roller assembly, arranged parallel to the laser thickness gauge, with the frame rate set to 60fps. The image processing module uses the Canny edge detection algorithm from the OpenCV library to calculate the percentage of intact skin area on the surface of the asparagus potato.

[0061] Specifically, the image processing module's processing steps include: After an industrial camera captures an image of the surface of the sweet potato, the image processing module performs the following operations: The original RGB image is converted to a grayscale image, with the grayscale coefficients calculated using the standard weighted formula (R*0.299 + G*0.587 + B*0.114). Gaussian filtering is then applied for noise reduction, with the filter kernel size set to 5×5 pixels and the standard deviation σ ranging from 1.5 to 2.0. The filtered image is then input into the Canny edge detection algorithm, with a low threshold set to 50-100 and a high threshold set to 150-300. The gradient calculation uses the Sobel operator (kernel size 3×3). The edge detection result is output as a binary image, with white pixels representing damaged edges on the skin.

[0062] A morphological closure operation is performed on the binary image. A 3×3 rectangular structuring element can be used as the closure kernel, with 1 to 2 iterations, to connect the broken edges. Then, the `findContours` function is called to extract the contours of the damaged area. The contour selection criteria are an area greater than 5 square pixels and an aspect ratio between 0.3 and 3.0. The proportion of the intact epidermal area is calculated using the following formula: Epidermal integrity rate = (Total area - Damaged outline area) / Total area × 100% The total area is determined by the minimum bounding rectangle of the asparagus root in the image, which is generated by the maximum set of contour points in the contour detection results.

[0063] In actual testing, the industrial camera was installed at a downward angle of 30 to 45 degrees, using a ring-shaped LED light source (color temperature 5500K, illuminance 800 to 1200 lux) to ensure image uniformity. When the skin integrity rate was detected to be below 97%, the fruit was considered damaged. The threshold was set based on statistical analysis of 1000 samples (skin integrity rate 97%-100%), with a false positive rate of less than 2% and a false negative rate of less than 1.5%. The algorithm parameters were optimized through grid search, ultimately achieving a classification accuracy of 98.2% on the validation set (300 samples).

[0064] When the percentage of fruit pulp broken is below 97%, it is considered damaged, and the controller triggers a second adjustment strategy: reducing the rotation speed of the current layer's rollers by 3 rpm to 5 rpm (e.g., from 40 rpm to 37 rpm), and lowering the extrusion pressure threshold of the next layer by 8 N to 12 N (e.g., from 95 N to 87 N). The dynamic control process continues until the residual thickness of all layers of peel stabilizes within the range of 0.2 mm to 0.5 mm and the pulp breakage rate is below 3%.

[0065] This implementation method can dynamically adjust process parameters in real time based on the residual peel thickness and pulp damage rate, reducing the risk of pulp damage while ensuring peeling integrity. Collaborative detection by a laser thickness gauge and an industrial camera ensures data accuracy, while a rapid response mechanism in the controller maintains stable production line operation, ultimately achieving a balance between peeling quality and equipment efficiency.

[0066] Although embodiments of the present invention 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 the present invention. Further modifications can be readily implemented by those skilled in the art.

Claims

1. A multi-stage, open-type, stepped extrusion friction peeling device for asparagus potatoes, characterized in that, include: The processing space is formed by the back panel and the two side panels, with the top and one side open. Several layers of roller assemblies for extrusion friction are arranged within the processing space. Each roller assembly includes multiple parallel rollers, wherein: The uppermost roller group has the shortest roller length, and along the material travel direction, the roller length of the adjacent lower roller groups increases step by step, forming a stepped extrusion channel that descends step by step toward the open side; Extrusion friction gaps are formed between adjacent rollers in each roller group, and the roller surface is covered with a flexible friction elastic layer; After the pre-treated asparagus potatoes are fed into the processing space from the top, they fall layer by layer along the stepped extrusion channel. Through the flexible friction elastic layer, the asparagus potatoes are subjected to multiple progressive extrusions and frictions to peel off the outer skin.

2. The open-type stepped multi-stage extrusion friction peeling device for asparagus potatoes according to claim 1, characterized in that, The several layers of roller groups arranged within the processing space satisfy the following conditions: Each roller assembly contains 3 to 30 rollers arranged in parallel. The length of a single roller in an adjacent lower roller group is 80 mm to 250 mm longer than that of the upper roller; The vertical height difference between adjacent roller groups is 1.2 to 1.8 times the roller diameter; The spacing between adjacent rollers in the same roller group is 0.8 to 1.2 times the roller diameter; The inclination angle of the stepped extrusion channel is 0 to 12 degrees; the inclination angle of the stepped extrusion channel is negatively correlated with the drum speed, and the speed decreases by 2-3 rpm for every 1° increase in inclination angle. The thickness of the flexible elastic layer covering the roller surface of each roller assembly is 5 mm to 8 mm; The diameter of the rollers is between 80 mm and 120 mm, and all rollers in the same processing space have the same diameter.

3. The asparagus open-type stepped multi-stage extrusion friction peeling device according to claim 2, characterized in that, Adjacent rollers in the same roller group rotate in opposite directions and can rotate in both directions; The flexible elastic layer has a uniformly distributed raised structure on its surface, and the axis of the raised structure forms an angle of 25 to 50 degrees with the axis of the roller. The raised structures of adjacent rollers in the same layer of roller group are staggered, and the minimum distance between the top of the raised structures of adjacent rollers is 3 mm to 5 mm. The cross-section of the protruding structure is trapezoidal, with the base length of the trapezoid being 6 mm to 10 mm and the height being 2 mm to 3 mm; The Shore hardness of the flexible elastic layer is 60A to 70A, and the Shore hardness of the flexible elastic layer of the adjacent roller group increases by 5A to 8A in each step. The width of the extrusion friction gap is 0.2 to 0.3 times the diameter of the roller, and the width of the extrusion friction gap between adjacent roller groups decreases by 10% to 15% at each level.

4. The open-type stepped multi-stage extrusion friction peeling device for asparagus potatoes according to claim 3, characterized in that, The minimum distance between the top of the protruding structure on the surface of the flexible elastic layer and the surface of the adjacent roller is 0.4 to 0.6 times the maximum diameter of the asparagus potato. The protrusions are distributed in a spiral pattern on the surface of the drum, and the lead of the spiral is 1.5 to 2 times the circumference of the drum. In the same layer of roller assembly, the roller end located on the open side is equipped with an elastic baffle, and the distance between the elastic baffle and the roller end face is 0.1 to 0.15 times the roller diameter; The material of the elastic baffle has a Shore hardness 10A to 15A lower than that of the flexible elastic layer of the same roller, and the thickness of the elastic baffle is 8 mm to 12 mm. When unpeeled asparagus enters the extrusion friction gap, the spiral distribution of the protruding structure forces the asparagus to move along the roller axis. If the diameter of the asparagus is greater than the gap width, the elastic baffle is deformed by the extrusion, causing the asparagus to shift to the open side and slide into the extrusion friction channel of the next layer of rollers.

5. The open-type stepped multi-stage extrusion friction peeling device for asparagus potatoes according to claim 1, characterized in that, A spray assembly is installed directly above the extrusion friction gap of each roller group within the processing space; The spray assembly includes 2 to 4 fan-shaped nozzles distributed along the axial direction of the roller. The spray angle of the fan-shaped nozzles is 60 to 90 degrees, and the spray coverage includes the flexible elastic layer surface of the adjacent rollers and the extrusion friction gap. The installation height of the fan-shaped nozzle is 0.5 to 0.8 times the diameter of the drum, and the horizontal distance between the nozzle outlet and the center line of the extrusion friction gap is 20 mm to 30 mm. The fan-shaped nozzle is connected to an external water tank through a diversion pipeline. A pressure regulating valve is installed in the diversion pipeline, and the outlet pressure of the pressure regulating valve is 0.2MPa to 0.4MPa. The pressure regulating valve is electrically connected to the controller, which dynamically adjusts the opening of the pressure regulating valve based on the real-time extrusion pressure feedback signal from the adjacent rollers.

6. The open-type stepped multi-stage extrusion friction peeling device for asparagus potatoes according to claim 5, characterized in that, A filter unit is installed upstream of the diversion pipeline, and the filter unit has a built-in stainless steel filter screen with a pore size of 0.5 mm to 1 mm. The bottom guide channel of the processing space has multiple drainage holes on its side wall. The diameter of the drainage holes is 5 mm to 8 mm, and the longitudinal spacing between adjacent drainage holes is 1 / 2 to 2 / 3 of the width of the guide channel. The end of the guide channel is connected to a spiral dewatering machine, which rotates at a speed of 20 rpm to 30 rpm, and the gap between the spiral blades and the dewatering machine housing is 3 mm to 5 mm.

7. A step-by-step extrusion peeling process for asparagus potatoes, characterized in that, Includes the following steps: The asparagus potatoes were pre-treated by rolling and cutting. The height of the rolling and cutting blade was set to 1.1 to 1.3 times the thickness of the asparagus potato skin. After rolling and cutting, axial cuts with a depth of 0.8 mm to 1.2 mm were formed. Place the rolled and chopped asparagus into a pot, add water at a ratio of 3:1 (water to asparagus by weight), and steam at a constant temperature of 95°C to 100°C for 15 to 20 minutes. Add a peeling agent to the cooking pot. The peeling agent is a solution of sodium bicarbonate and citric acid mixed in a mass ratio of 2.4:1, with a final concentration of sodium bicarbonate of 0.6 wt% and a final concentration of citric acid of 0.25 wt%. Stir for 5 to 8 minutes. The processed asparagus potatoes are transferred to the open-type stepped multi-stage extrusion friction peeling device for asparagus potatoes as described in claim 1. The distance between adjacent rollers in each roller group of the device is 0.8 to 1.2 times the diameter of the roller. The surface of the roller is covered with a polyurethane layer with a Shore hardness of 60A to 70A. The surface of the polyurethane layer is provided with trapezoidal protrusions with a protrusion height of 2 mm to 3 mm. The rotation speed of the top roller group is controlled at 30 rpm to 40 rpm, and the extrusion pressure of the adjacent rollers is 50 N to 80 N. The asparagus potatoes fall layer by layer through the stepped extrusion channel. With each layer, the rotation speed of the rollers increases by 5 rpm to 10 rpm, and the extrusion pressure increases by 20 N to 30 N. During the peeling process, water mist with a pressure of 0.3MPa to 0.5MPa is sprayed into the extrusion friction gap of each roller group, with a water mist flow rate of 10L / min to 15L / min per meter of roller length, and the water temperature is maintained at 40℃ to 50℃.

8. The method for processing sweet potato using a stepped extrusion peeling process according to claim 7, characterized in that, First, wash and grade the fresh asparagus potatoes in sequence, and remove individuals with a diameter greater than 50 mm or less than 20 mm after grading; then roll and cut them.

9. The method for processing sweet potato using a stepped extrusion peeling process according to claim 8, characterized in that, After peeling, the asparagus potatoes are collected in a guide channel and sent to a vibrating screen. The screen has an amplitude of 2 to 3 mm, a vibration frequency of 20 Hz to 25 Hz, and a screen mesh size of 5 to 8 mm. The sieved whole asparagus potato flesh is transferred to a hot air dryer, where the drying temperature is 55℃ to 60℃ and the air velocity is 2m / s to 3m / s, until the moisture content is less than 12wt%.

10. The method for processing sweet potato using a stepped extrusion peeling process according to claim 7, characterized in that, The following dynamic control steps are performed during the peeling process: Real-time data on the residual thickness of the asparagus skin at the exit of each roller group was collected. A laser thickness gauge was used to scan the surface of the asparagus at a sampling frequency of 20Hz to 30Hz. The measurement accuracy of the thickness gauge was ±0.1mm. When the residual thickness of the skin is detected to be greater than 0.5mm, the controller executes the first adjustment strategy: increase the rotation speed of the current layer of rollers by 5rpm to 8rpm, and increase the extrusion pressure threshold of the next layer of rollers by 10N to 15N; When the residual thickness of the peel is less than 0.2 mm and the pulp damage rate exceeds 3%, the controller executes the second adjustment strategy: reduce the rotation speed of the current layer of rollers by 3 rpm to 5 rpm, and lower the extrusion pressure threshold of the next layer of rollers by 8 N to 12 N. The response delay time for the first adjustment strategy and the second adjustment strategy is 2 to 3 seconds after the detection signal is triggered; The pulp breakage rate is calculated in real time by the image processing module. The specific method is as follows: an industrial camera is set at the exit of each layer of roller group to capture images of the surface of the sweet potato at a frame rate of 60fps. The percentage of the intact area of ​​the skin is counted by the edge detection algorithm. When the percentage is less than 97%, it is judged as broken. The dynamic control process continues until the residual thickness of the peel in all layers of rollers stabilizes within the range of 0.2 mm to 0.5 mm and the pulp breakage rate is less than 3%.

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