Electric vice self-adaptive clamping control method and system

Abstract

This invention belongs to the field of fixture processing technology and relates to an adaptive clamping control method for an electric vise. The electric vise includes a first jaw with a flat clamping surface and a second jaw with an array of distributed ejector pins. The method includes: acquiring workpiece surface contour data; driving the ejector pins to extend and form a contoured clamping surface and locking them; driving the second jaw to move as a whole towards the first jaw, so that the workpiece is in contact with the flat clamping surface to a reference position; detecting the contact pressure of each ejector pin, unlocking ejector pins that have not reached the pressure threshold and compensating for their extension until the threshold is reached; and driving the second jaw to continue moving to apply a final clamping force. This invention can achieve large-area uniform surface contact and a defined repeatable positioning reference during the clamping process of irregularly shaped workpieces.

Description

Technical Field

[0001] This invention relates to the field of clamping and machining technology, and in particular to an adaptive clamping control method and system for electric vises. Background Technology

[0002] Electric vises are used to clamp workpieces in machining. When the workpiece has a curved or irregular surface, the flat jaws and the workpiece can only form limited point or line contact, making slippage or even disengagement from the vise easy during machining. To address this, some manufacturers use an array-type floating pin structure, which arranges multiple independently retractable pins on the jaws. Each pin has a spring or magnetic drive element at its rear end. During clamping, the workpiece surface presses against the pin ends, and each pin passively retracts according to the local shape of the workpiece surface, forming a conformal contact pattern that roughly matches the workpiece surface. This expands the traditional point or line contact of the vise jaws into multi-point contact, increasing the number of contact points to a certain extent.

[0003] While this passive adaptation scheme achieves multi-point contact, the extension of each ejector pin is determined by the workpiece's squeezing action. The contact force of the ejector pins is affected by factors such as differences in spring stiffness and frictional dispersion, resulting in extremely uneven force distribution on the workpiece surface. Localized unloaded or overloaded conditions may occur. More importantly, when both jaws employ a floating ejector pin structure, the spatial position of the workpiece during clamping is determined by the force balance state of the ejector pins on both sides. This means that the actual position of the workpiece will drift uncontrollably after each clamping, making it impossible to guarantee repeatability and positioning accuracy. Summary of the Invention

[0004] Therefore, the purpose of this invention is to solve the defects of electric vises with arrayed floating pin jaws, such as uneven contact force distribution and lack of a definite positioning reference for the workpiece, and to provide an adaptive clamping control method and system for electric vises, so as to achieve large-area uniform surface contact and a definite repeatable positioning reference during the clamping process of irregular workpieces.

[0005] In a first aspect, to solve the above-mentioned technical problems, the present invention provides an adaptive clamping control method for an electric vise. The electric vise includes a first jaw and a second jaw. The first jaw has a flat clamping surface, and the second jaw is provided with an array of pins, each of which can be independently extended and retracted. The method includes: Acquire the surface contour data of the workpiece facing the second jaw; Based on the surface contour data, the ejector pins are driven to extend to contact the workpiece, so that the distal end face of the ejector pin array forms a contoured clamping surface that matches the shape of the workpiece surface, and each ejector pin is locked. Keeping all ejector pins locked, drive the second jaw as a whole to move towards the first jaw for the first time, so that the workpiece moves to the reference position that is in contact with the flat clamping surface under the pushing action of the flat clamping surface; Keep the workpiece in the reference position, detect the contact pressure between the ejector pin and the workpiece surface. If the contact pressure is less than the pressure threshold, unlock the ejector pin and drive the ejector pin to extend for compensation until the contact pressure between each ejector pin and the workpiece surface meets the condition. The second jaw is driven to move towards the first jaw a second time, applying the final clamping force.

[0006] Preferably, a differential strain gauge is provided at the root of each ejector pin to collect the time-domain strain signal of each ejector pin; the contact pressure between the ejector pin and the workpiece surface is determined based on the time-domain strain signal.

[0007] Preferably, the contact pressure between each ejector pin and the workpiece surface is determined one by one to obtain ejector pins whose contact pressure is less than the pressure threshold; each ejector pin to be compensated is unlocked one by one, and the currently unlocked ejector pin to be compensated is driven to extend towards the workpiece to compensate until the current contact pressure reaches the pressure threshold, and the ejector pin to be compensated is locked.

[0008] Preferably, the method further includes determining whether the workpiece is in contact with the flat clamping surface, which includes: calculating the total pressure P based on the contact pressure between each of the ejector pins and the workpiece surface; obtaining the displacement D of the first overall movement of the second jaw; calculating the pressure change rate k based on the total pressure P and the displacement D: k = ΔP / ΔD; if k ≥ k1, then the workpiece is determined to be in contact with the flat clamping surface; if k ≥ k2, then the workpiece is determined to be in contact with the flat clamping surface; ΔP and ΔD are the total pressure increment and displacement increment within the same unit time, respectively; k1 and k2 are threshold one and threshold two, respectively, and k2 > k1.

[0009] Preferably, the determination of threshold one and threshold two includes: driving the second jaw as a whole to move towards the first jaw under no-load conditions, so that each of the ejector pins contacts and presses against the flat clamping surface, and obtaining the no-load displacement D0 of the second jaw as a whole at this time; calculating the total no-load pressure P0 based on the contact pressure between each ejector pin and the flat clamping surface; calculating the no-load pressure change rate k0 based on the total no-load pressure P0 and the no-load displacement D0: k0=ΔP0 / ΔD0; counting the maximum value of k0 over the entire stroke, and recording it as the no-load reference k*; and determining threshold one and threshold two based on the no-load reference k*.

[0010] Preferably, the threshold k1 is set to (2~4)×k*; and the threshold k2 is set to (7~9)×k*.

[0011] Preferably, the unloaded state is as follows: each of the ejector pins extends and locks, the far end face of the ejector pin array forms a contoured clamping surface, and no workpiece is placed between the first jaw and the second jaw.

[0012] Preferably, the method for determining the pressure threshold includes: obtaining the contact pressure between each ejector pin and the workpiece surface at the instant the workpiece is in contact with the flat clamping surface, and calculating the average value Pt of each contact pressure. N is the number of ejector pins; i is the ejector pin number; select the material correction coefficient β according to the workpiece material, β takes the value of 0.7~1.3; calculate the pressure threshold P0 as: P0=β×Pt.

[0013] Preferably, the method for obtaining surface contour data includes: driving each of the ejector pins to extend individually or in groups to contact the workpiece surface and then retracting them, collecting the extension amount of each ejector pin, and generating the surface contour data based on the extension amount of each ejector pin.

[0014] Secondly, to solve the above-mentioned technical problems, the present invention also provides an adaptive clamping control system for an electric vise, used to execute the aforementioned adaptive clamping control method for an electric vise, the system comprising: The strain sensing unit includes differential strain gauges disposed at the root of each ejector pin to acquire the corresponding time-domain strain signal; The self-locking drive unit includes an electric lead screw that independently drives the extension and retraction of each ejector pin and locks itself in place; A clamping drive unit is used to drive the second jaw to move as a whole to clamp the workpiece to be processed; The control unit acquires the time-domain strain signal and controls the operation of the drive self-locking unit and the clamping drive unit according to the time-domain strain signal to perform adaptive clamping of the workpiece by the electric vise.

[0015] Compared with the prior art, the above-described technical solution of the present invention has the following advantages: The adaptive clamping control method and system for electric vises described in this invention, on the one hand, uses the flat clamping surface of the first jaw as a rigid reference to determine the final position of the workpiece, ensuring consistent spatial positioning for each clamping operation; on the other hand, each ejector pin re-establishes a tight fit with the workpiece surface through independent compensation extension, ensuring the integrity of the contour clamping surface and the uniformity of contact pressure. Finally, after the contact pressure of all ejector pins reaches the target, the second jaw is driven to advance towards the first jaw, applying the final clamping force. At this point, the contact pressure of each ejector pin has become uniform, and the final clamping force can be evenly distributed on various stress-bearing parts of the workpiece surface in a large-area surface contact manner, eliminating the problems of local overload and insufficient clamping force caused by point contact, and ensuring the stability of the workpiece during processing. Attached Figure Description

[0016] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0017] Figure 1 This is a schematic diagram of the structure of the electric vise in a preferred embodiment of the present invention; Figure 2 This is a flowchart of the adaptive clamping control method for an electric vise in a preferred embodiment of the present invention; Figure 3 This is a structural block diagram of the adaptive clamping control system of the electric vise in a preferred embodiment of the present invention.

[0018] Explanation of reference numerals in the attached diagram: 1. Workpiece; 2. First jaw; 21. Flat clamping surface; 4. Second jaw; 41. Ejector pin; 10. Strain sensing unit; 20. Drive self-locking unit; 30. Clamping drive unit; 40. Control unit. Detailed Implementation

[0019] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0020] Reference Figure 1 As shown, the electric vise includes a first jaw 2 and a second jaw 4 arranged opposite to each other. The first jaw 2 has a flat clamping surface 21, which serves as the absolute reference for workpiece positioning. This flat clamping surface 21 is perpendicular to the machine tool spindle direction, and its flatness is better than 0.03mm. The second jaw 4 is a movable jaw and is provided with an array of ejector pins 41, each of which can extend and retract independently.

[0021] For example, the shape of the ejector pin array is not limited to a specific geometry and can be designed according to the actual shape of the second jaw and the contour of the workpiece being clamped. Common methods include rectangular arrays, circular or annular arrays, contour-following arrays, etc. In this embodiment, the second jaw 4 is a rectangular structure with ejector pins distributed in a rectangular array, and each ejector pin 41 is arranged at equal intervals along the length and width directions of the second jaw 4. The ejector pin array covers the entire clamping area of ​​the second jaw. During the specific clamping process, the active area of ​​the ejector pin array is automatically determined according to the workpiece size, so that only the ejector pins located within the workpiece contour projection area participate in the contour acquisition and clamping operation, while the remaining ejector pins remain in a retracted state, thereby shortening the clamping cycle and reducing energy consumption.

[0022] For example, the tip of the ejector pin needs to contact workpieces of various materials (including soft aluminum alloys and hard stainless steel), preferably made of tungsten steel. The high hardness and good polishing properties of tungsten steel can maintain the stability of the end face shape when clamping hard workpieces and reduce the risk of surface damage when clamping soft workpieces. Furthermore, the ejector pin body is a cylindrical rod, facilitating sliding fit within the array of holes. The end of the ejector pin facing the workpiece is the end contact surface, which can be spherical, planar, or tapered. A planar end is suitable for soft or thin-walled workpieces, avoiding indentation; for hard workpieces, a spherical end is preferred, allowing for stable point contact in the initial contact phase, and multi-point clamping through the even distribution of the ejector pins during final clamping. The other end of the ejector pin is connected to the drive unit and can be machined into a square column structure to prevent rotation, facilitating positioning in the lead screw and nut assembly or push rod.

[0023] Each ejector pin 41 is equipped with an independent drive unit and a locking mechanism. The drive unit is used to drive the ejector pin 41 to extend or retract, and the locking mechanism is used to lock the ejector pin 41 in the current extended position. For example, a micro servo motor and a lead screw transmission mechanism can be used, utilizing the self-locking characteristic of the lead screw as the locking mechanism.

[0024] Each ejector pin 41 is also equipped with a pressure sensing element and a displacement sensing element. The pressure sensing element is used to detect the contact pressure between the ejector pin and the workpiece or the flat clamping surface, and the displacement sensing element is used to detect the extension of the ejector pin. For example, the pressure sensing element on each ejector pin is a differential strain gauge located at the root of the ejector pin 41. The differential strain gauges are connected to form a Wheatstone bridge. When the end of the ejector pin 41 is subjected to contact pressure, the elastic support structure undergoes a slight deformation. The differential strain gauge converts this deformation into a differential voltage signal output. This differential voltage signal is amplified and converted from analog to digital as a characterization signal of the contact pressure value.

[0025] For example, the displacement sensing element on each ejector pin is an optical grating ruler or a magnetic grating ruler, used to accurately measure the axial displacement of each ejector pin.

[0026] Example 1: Refer to Figure 2 As shown, the present invention provides an adaptive clamping control method for an electric vise, comprising the following steps: S100: Obtain the surface contour data of the workpiece facing the second jaw 4; S200. Based on the surface contour data, drive the ejector pin 41 to extend to contact the workpiece 1, so that the far end face of the ejector pin array forms a contour clamping surface that matches the shape of the workpiece surface, and lock each ejector pin. S300. Keep each ejector pin locked and drive the second jaw 4 to move towards the first jaw 2, so that the workpiece 1 moves to the reference position that is in contact with the flat clamping surface 21 under the pushing action of the flat clamping surface 21. S400. Keep workpiece 1 in the reference position, detect the contact pressure between ejector pin 41 and the surface of workpiece 1. If the contact pressure is less than the pressure threshold, unlock ejector pin 41 and drive ejector pin to extend for compensation until the contact pressure between each ejector pin and the surface of the workpiece meets the conditions. S500, drive the second jaw 4 to continue moving toward the first jaw 2, and apply the final clamping force.

[0027] The technical solution of this application will be described in detail below with reference to specific embodiments.

[0028] In specific implementation step S100, firstly, all ejector pins 41 are driven to retract to their initial zero position, which is the position where each ejector pin 41 is retracted to the position furthest from the first jaw 2. Then, each ejector pin 41 is controlled to extend sequentially from the edge of the array towards the center or from the center towards the edge, with only one ejector pin extending at a time. When the end of the ejector pin 41 contacts the workpiece surface, the contact pressure detected by its pressure sensing element changes abruptly, rising from zero to a preset small contact force value, set between 0.5N and 2N, just enough to determine contact without damaging the workpiece surface. At this time, the extension amount of the ejector pin in the current state is recorded, and this extension amount is read by the displacement sensing element. After recording, the ejector pin is driven to retract to its initial zero position. The above operation is repeated, sequentially allowing each ejector pin 41 to complete one extension contact and record the extension amount, until the extension amount data of all ejector pins has been recorded. Based on the recorded extension amount data of each ejector pin, surface contour data of the workpiece facing the second jaw is generated.

[0029] It should be noted that in the above-described step-by-step scanning method, only one ejector pin contacts the workpiece at a time, thus not generating a force sufficient to move the workpiece and ensuring that the workpiece position remains unchanged during the scanning process. In another embodiment, a group extension method can also be used, where a group of adjacent ejector pins extends for scanning at a time to improve scanning efficiency.

[0030] In this embodiment of the invention, the workpiece surface contour data is acquired by scanning the ejector pins one by one. Compared with external contour scanning equipment, the core advantage lies in the simplification of structure, cost reduction, and improved accuracy brought about by functional reuse. Specifically, external equipment (such as a vision profiler or laser scanner) acquires the three-dimensional point cloud data of the workpiece in the measurement coordinate system. To use this data to drive the vise ejector pins, a coordinate transformation process is required. Any transformation error will cause a deviation between the ejector pin extension position and the actual surface of the workpiece. In this solution, the ejector pins directly contact the workpiece surface in the clamping coordinate system of the vise and record the displacement. The measurement data and the execution data are naturally consistent, fundamentally eliminating the coordinate transformation error.

[0031] Furthermore, non-contact optical measurement methods are easily affected by factors such as workpiece surface color, gloss, roughness, ambient light, and cutting fluid splashes, leading to distorted measurement data. This solution employs contact measurement, where the results of physical contact are unaffected by these environmental or surface characteristic changes, making it more stable and reliable in the machining workshop environment.

[0032] In specific implementation step S200, based on the workpiece surface contour data obtained above, the target extension amount of each ejector pin is determined. This target extension amount is the extension amount of the ejector pin recorded above. Subsequently, all ejector pins are driven to extend simultaneously to their respective target extension amounts, so that the distal end faces of each ejector pin together form a contoured clamping surface adapted to the shape of the workpiece surface. After all ejector pins are extended to their positions, each ejector pin is locked in its current extension position by a locking mechanism. In this embodiment, the driving unit of each ejector pin is a lead screw and nut pair driven by a micro servo motor. The helix angle of the lead screw is smaller than its friction angle, forming a self-locking thread pair. When the micro servo motor stops supplying power, the lead screw and nut pair relies on the self-locking action of the thread pair to keep the ejector pin in its current extension position, achieving locking without continuous power supply. The advantage of this locking method is that the extension amount of each ejector pin in the locked state is not affected by external forces, and the shape of the contoured clamping surface can be stably maintained. At this point, although the distal end face of each ejector pin forms a contoured clamping surface that matches the shape of the workpiece surface, no substantial clamping force has yet been generated between the contoured clamping surface and the workpiece surface. Its function is to lock the shape rather than apply force.

[0033] In specific implementation step S300, after the contoured clamping surface of the ejector pin array is formed and locked, the second jaw 4 is driven to move as a whole towards the first jaw 2. At this time, each ejector pin 41 moves together with the second jaw 4 as a whole, and the relative positional relationship between each ejector pin 41 remains unchanged. Therefore, the shape of the contoured clamping surface formed by the entire ejector pin array remains unchanged during the movement.

[0034] As the second jaw 4 advances, the distal end faces of each ejector pin 41 simultaneously contact the workpiece surface and push the workpiece towards the first jaw 2. Since each ejector pin end face has been pre-formed to fit the workpiece surface, this overall advancement allows each ejector pin end face to synchronously conform to different parts of the workpiece surface.

[0035] Next, the second jaw 4 continues to move towards the first jaw 2 until the side of the workpiece facing the first jaw 2 is completely in contact with the flat clamping surface 21 of the first jaw 2. At this point, the workpiece reaches the reference position. During this process, the flat clamping surface 21 of the first jaw 2 serves as a defined mechanical reference surface, pushing the workpiece to a known and fixed spatial position. Since the position of the flat clamping surface 21 of the first jaw 2 in the machine tool coordinate system is fixed and known, the side of the workpiece facing the first jaw is always in the same position each time it is clamped, thus establishing a defined spatial positioning reference for the workpiece.

[0036] In specific implementation step S400, after the workpiece reaches the reference position, the contact pressure between each ejector pin and the workpiece surface is detected by the pressure sensing element on each ejector pin. At this time, because the workpiece moves from the initial placement position to the reference position, its spatial position changes, and the original contact state between the end face of each ejector pin and the workpiece surface may change. Some ejector pins experience a decrease in contact pressure or even disengagement due to slight translation of the workpiece. The current contact pressure value of each ejector pin is compared with a preset pressure threshold. If the contact pressure of a certain ejector pin is less than the pressure threshold, the ejector pin is marked as an ejector pin to be compensated.

[0037] In this embodiment, the pressure threshold can be predetermined through theoretical calculation, based on the minimum clamping force required to prevent workpiece slippage during processing, and then comprehensively determined according to factors such as workpiece material, number of ejector pins, and contact area. Alternatively, the pressure threshold can be determined after the workpiece reaches the reference position by multiplying the average actual contact pressure of each ejector pin by a material correction coefficient. The material correction coefficient ranges from 0.7 to 1.3, with lower values ​​for soft materials and higher values ​​for hard materials, thereby avoiding damage to soft workpieces due to overpressure during subsequent compensation.

[0038] Subsequently, the compensation extension operation is performed on all the ejector pins to be compensated one by one. Specifically, first, all ejector pins except the one currently to be compensated are kept in a locked state. Then, the locking mechanism of the ejector pin to be compensated is unlocked, allowing it to move independently relative to the second jaw. The ejector pin is driven to extend towards the workpiece for compensation. During the compensation extension process, the pressure sensing element continuously detects the contact pressure of the ejector pin until the contact pressure reaches a preset pressure threshold. At this point, the control module immediately stops driving the ejector pin to extend and relocks it. The same operation is then performed on the next ejector pin to be compensated until all ejector pins marked as to be compensated have completed their compensation extension and been relocked.

[0039] In this embodiment, the operation method of unlocking one ejector pin at a time while keeping the others locked ensures that when compensating a certain ejector pin, the remaining ejector pins maintain their original contact state and contoured clamping surface shape, avoiding interference with the ejector pins that have already met the standards. After all ejector pins to be compensated have completed their compensation, the contact pressure of all ejector pins reaches or exceeds the preset pressure threshold, and the contact pressure distribution between the ejector pin array and the workpiece surface tends to be uniform.

[0040] In specific implementation step S500, after the contact pressure of all ejector pins reaches the target, the second jaw 4 is driven to continue moving towards the first jaw, applying the final clamping force. During the application of the final clamping force, since the extension of each ejector pin is locked, a large area of ​​surface contact is maintained between the distal end face of each ejector pin and the workpiece surface, and the final clamping force can be evenly transmitted to the workpiece surface through each ejector pin. At this point, the workpiece is firmly clamped between the flat clamping surface of the first jaw and the ejector pin array of the second jaw.

[0041] The adaptive clamping control method and system for electric vises described in this invention, on the one hand, uses the flat clamping surface of the first jaw as a rigid reference to determine the final position of the workpiece, ensuring consistent spatial positioning for each clamping operation; on the other hand, each ejector pin re-establishes a tight fit with the workpiece surface through independent compensation extension, ensuring the integrity of the contour clamping surface and the uniformity of contact pressure. Finally, after the contact pressure of all ejector pins reaches the target, the second jaw is driven to advance towards the first jaw, applying the final clamping force. At this point, the contact pressure of each ejector pin has become uniform, and the final clamping force can be evenly distributed on various stress-bearing parts of the workpiece surface in a large-area surface contact manner, eliminating the problems of local overload and insufficient clamping force caused by point contact, and ensuring the stability of the workpiece during processing.

[0042] As a preferred embodiment of the above, the method further includes determining whether the workpiece is in contact with the flat clamping surface. Specifically, after the contoured clamping surface of the ejector pin array is formed and locked, the second jaw is driven to move towards the first jaw for the first time. During the first movement, the contact pressure between each ejector pin and the workpiece surface is acquired in real time, and the total pressure P is calculated. At the same time, the displacement D of the second jaw is acquired, and k = ΔP / ΔD is calculated, where ΔP and ΔD are the increment of the total pressure and the increment of the displacement, respectively, within the same unit time. When k ≥ k1 is detected, it is determined that the workpiece has begun to contact the flat clamping surface of the first jaw. At this time, the moving speed of the second jaw can be switched from the first speed to a lower second speed (e.g., from 10 mm / min to 2 mm / min) to more accurately control the subsequent advancing process. The second jaw continues to be driven to move towards the first jaw. When k ≥ k2 is detected, it is determined that the workpiece is completely in contact with the flat clamping surface. At this time, the movement of the second jaw is stopped, and the current position of the second jaw is recorded as the reference position.

[0043] It should be noted that the total pressure P represents the sum of the contact pressures between each ejector pin and the workpiece surface, and the displacement D represents the distance the second jaw moves from its initial position towards the first jaw. When the workpiece has not yet contacted the flat clamping surface, the advancement of the second jaw only needs to overcome frictional resistance, and P increases gradually with D, resulting in a small k value. When the workpiece begins to contact the flat clamping surface, due to the intervention of workpiece rigidity, the rate at which P increases with D increases significantly, and the k value changes abruptly. Therefore, k ≥ k1 is used as the basis for determining contact. When the workpiece is fully in contact with the flat clamping surface, the flat clamping surface forms a rigid limit on the workpiece, and the rate at which P increases with D further increases to its maximum value. K ≥ k2 is used as the basis for determining fit. This method eliminates the need to place any sensors on the flat clamping surface, fully maintaining its integrity and accuracy as a positioning reference.

[0044] It should be noted that this solution addresses the issue of workpiece positioning consistency in the second jaw's feeding direction (i.e., the direction perpendicular to the flat clamping surface of the first jaw). However, for other degrees of freedom of the workpiece (such as translation along the surface of the first jaw and rotation about the feeding direction), this solution relies on: Positioning features of the workpiece itself: such as positioning bosses and reference edges of castings; External positioning elements: used in conjunction with auxiliary positioning devices such as stops, positioning pins, and V-blocks; Overall constraint of the ejector pin array: Each ejector pin forms multi-point contour contact with the workpiece surface, constraining the workpiece posture from multiple directions.

[0045] In batch processing, to ensure the consistency of workpieces in all degrees of freedom, auxiliary positioning elements can be set in the first jaw or on the machine tool table according to the specific shape of the workpiece, and used in conjunction with the positioning features of the workpiece.

[0046] In the above, k1 and k2 represent threshold one and threshold two, respectively, and are predetermined before actual clamping. Since different electric vises have different mechanical structure stiffness, number of ejector pins, and driving methods, this embodiment of the invention provides a no-load calibration method to determine k1 and k2. Specifically, before starting no-load calibration, each ejector pin is first extended and locked, so that the distal end face of the ejector pin array forms a contoured clamping surface. It should be noted that in the no-load state, no workpiece is placed between the first jaw 2 and the second jaw 4; therefore, after the ejector pin extends, its end directly faces the flat clamping surface of the first jaw.

[0047] Subsequently, the second jaw is driven to move uniformly towards the first jaw. During this movement, the distal ends of the pins on the second jaw sequentially or simultaneously contact and press against the flat clamping surface of the first jaw. Throughout the entire movement, the unloaded contact pressure P0 between each pin and the flat clamping surface and the unloaded pushing displacement D0 of the second jaw as a whole are synchronously acquired at a preset sampling frequency at each sampling moment. Based on the sum of the unloaded contact pressure values ​​P0 and the unloaded pushing displacement D0 acquired at each sampling moment, the unloaded normalized pressure change rate k0 = ΔP0 / ΔD0 corresponding to each sampling moment is calculated. The maximum value of k0 during the entire movement process is recorded as the unloaded reference k. This unloaded reference k reflects the maximum equivalent stiffness of the vise system itself and is not affected by the difference in the distribution of the protrusion of each pin. Subsequently, threshold k1 is set to 2 to 4 times the unloaded reference k, and threshold k2 is set to 7 to 9 times the unloaded reference k, where k2 > k1.

[0048] The physical basis of this ratio relationship is as follows: Under load, when the workpiece begins to contact the flat clamping surface, the equivalent stiffness of the electric vise increases from the unloaded reference, at which point k reaches 2 to 4 times the unloaded reference. When the workpiece is fully in contact with the flat clamping surface, the workpiece stiffness fully participates in the total system stiffness, and k reaches 7 to 9 times the unloaded reference. This ratio range is determined by both theoretical analysis and experiments, and the specific value can be adjusted after calibration based on the actual system stiffness.

[0049] In the above embodiment, the determination of whether to independently compensate for the extension of the ejector pin is made by comparing whether the contact pressure between the ejector pin and the workpiece surface reaches a pressure threshold. The embodiment of this invention determines the pressure threshold in the following way: at the instant the workpiece is determined to be in contact with the flat clamping surface (i.e., when k≥k2), the real-time contact pressure values ​​between each ejector pin and the workpiece surface are simultaneously collected, i.e., P1, P2, P3…PN, where N is the total number of ejector pins. The average value Pt of each contact pressure is calculated according to Pt = (P1+P2+P3+…+PN) / N. Subsequently, a material correction coefficient β is selected based on the workpiece material, with β ranging from 0.7 to 1.3. Specifically, when the workpiece material is a soft material such as aluminum alloy, copper alloy, or plastic, β is taken as 0.7~0.85 to prevent the compensated pressure from exceeding the material's yield strength and causing surface indentation; when the workpiece material is a medium-hardness material such as carbon steel or alloy steel, β is taken as 0.85~1.0; when the workpiece material is a high-hardness material such as stainless steel or titanium alloy, β is taken as 1.0~1.3 to ensure sufficient clamping force. The pressure threshold P0 is calculated according to P0=β×Pt. The physical meaning of this pressure threshold P0 is: the target contact pressure value that each ejector pin needs to achieve in the subsequent compensation stage.

[0050] After the pressure threshold is determined, the current contact pressure value between each ejector pin and the workpiece surface is detected by the pressure sensing element on each ejector pin, and each current contact pressure value is compared with the pressure threshold P0 one by one. If the current contact pressure value of a certain ejector pin is less than the pressure threshold P0, the ejector pin is marked as an ejector pin to be compensated. Compensation extension operation is performed on all ejector pins to be compensated one by one.

[0051] Specifically, firstly, all ejector pins except the one currently being compensated are kept locked. Then, the locking mechanism of the ejector pin to be compensated is unlocked, allowing it to move independently relative to the second jaw. The ejector pin is then driven to extend towards the workpiece for compensation. During this extension, a pressure sensor continuously monitors the contact pressure of the ejector pin until it reaches the pressure threshold P0. At this point, the extension is stopped and the pin is relocked. The same operation is then performed on the next ejector pin to be compensated, until all pins marked as being compensated have completed their extension and are relocked. After all ejector pins have completed compensation, the contact pressure of all pins reaches or exceeds the pressure threshold P0, and the contact pressure distribution between the ejector pin array and the workpiece surface becomes more uniform.

[0052] Example 2: Refer to Figure 3 As shown, an embodiment of the present invention provides an adaptive clamping control system for an electric vise, used to execute the aforementioned adaptive clamping control method for an electric vise. The system includes: The strain sensing unit 10 includes differential strain gauges disposed at the root of each ejector pin to acquire the corresponding time-domain strain signal. The self-locking drive unit 20 includes an electric lead screw that independently drives the extension and retraction of each ejector pin and locks it in place; The clamping drive unit 30 is used to drive the second jaw to move as a whole to clamp the workpiece to be processed; The control unit 40 acquires the time-domain strain signal and controls the operation of the drive self-locking unit and the clamping drive unit according to the time-domain strain signal to perform adaptive clamping of the workpiece by the electric vise.

[0053] This system, through the coordinated operation of the strain sensing unit 10, the self-locking drive unit 20, the clamping drive unit 30, and the control unit 40, achieves the three-order control of active contour locking, overall alignment to the reference, and single-point compensation to restore contact in the aforementioned method embodiment. A closed control loop is formed between the units: the strain sensing unit provides pressure feedback signals, the self-locking drive unit performs position adjustment and locking of the ejector pin, the clamping drive unit performs overall advancement and clamping, and the control unit makes real-time decisions based on the feedback signals and drives the execution unit to act. The entire clamping process can adapt to workpieces of different shapes and materials, achieving consistency and reliability in each clamping operation.

[0054] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. An adaptive clamping control method for an electric vise, the electric vise comprising a first jaw and a second jaw, the first jaw having a flat clamping surface, and the second jaw having arrayed pins, each pin being independently extendable and retractable, characterized in that... The method includes: Acquire the surface contour data of the workpiece facing the second jaw; Based on the surface contour data, the ejector pins are driven to extend to contact the workpiece, so that the distal end face of the ejector pin array forms a contoured clamping surface that matches the shape of the workpiece surface, and each ejector pin is locked. Keeping all ejector pins locked, drive the second jaw as a whole to move towards the first jaw for the first time, so that the workpiece moves to the reference position that is in contact with the flat clamping surface under the pushing action of the flat clamping surface; Keep the workpiece in the reference position, detect the contact pressure between the ejector pin and the workpiece surface. If the contact pressure is less than the pressure threshold, unlock the ejector pin and drive the ejector pin to extend for compensation until the contact pressure between each ejector pin and the workpiece surface meets the condition. The second jaw is driven to move towards the first jaw a second time, applying the final clamping force.

2. The adaptive clamping control method for an electric vise according to claim 1, characterized in that: Differential strain gauges are installed at the root of each ejector pin to collect the time-domain strain signal of each ejector pin; the contact pressure between the ejector pin and the workpiece surface is determined based on the time-domain strain signal.

3. The adaptive clamping control method for an electric vise according to claim 2, characterized in that: The contact pressure between each ejector pin and the workpiece surface is determined one by one to obtain ejector pins whose contact pressure is less than the pressure threshold; each ejector pin to be compensated is unlocked one by one, and the currently unlocked ejector pin is driven to extend towards the workpiece to compensate until the current contact pressure reaches the pressure threshold and then the ejector pin to be compensated is locked.

4. The adaptive clamping control method for an electric vise according to claim 2, characterized in that: It also includes determining whether the workpiece is in contact with the flat clamping surface, which includes: Calculate the total pressure P based on the contact pressure between each ejector pin and the workpiece surface; Obtain the displacement D of the first overall movement of the second jaw; Calculate the pressure change rate k based on the total pressure P and displacement D: k = ΔP / ΔD; If k≥k1, then it is determined that the workpiece is in contact with the flat clamping surface; If k≥k2, then the workpiece is determined to be in contact with the flat clamping surface; ΔP and ΔD are the total pressure increment and displacement increment, respectively, within the same unit time; k1 and k2 are threshold one and threshold two, respectively, and k2>k1.

5. The adaptive clamping control method for an electric vise according to claim 4, characterized in that: The methods for determining the threshold one and threshold two include: In an unloaded state, drive the second jaw as a whole to move toward the first jaw, so that each of the pins contacts and presses the flat clamping surface, and obtain the unloaded displacement D0 of the second jaw as a whole at this time. Calculate the total no-load pressure P0 based on the contact pressure between each ejector pin and the flat clamping surface; Calculate the rate of change of no-load pressure k0 based on the total no-load pressure P0 and the no-load displacement D0: k0 = ΔP0 / ΔD0; The maximum value of k0 during the entire journey is recorded as the no-load reference k*. The threshold one and threshold two are determined based on the no-load reference k*.

6. The adaptive clamping control method for an electric vise according to claim 5, characterized in that: The threshold k1 is set to (2~4)×k*; the threshold k2 is set to (7~9)×k*.

7. The adaptive clamping control method for an electric vise according to claim 5, characterized in that: The unloaded state is as follows: each of the ejector pins extends and locks, the far end face of the ejector pin array forms a contoured clamping surface, and no workpiece is placed between the first jaw and the second jaw.

8. The adaptive clamping control method for an electric vise according to claim 4, characterized in that: The pressure threshold is determined in the following ways: Obtain the contact pressure between each ejector pin and the workpiece surface at the instant the workpiece is in contact with the flat clamping surface, and calculate the average value Pt of each contact pressure: N represents the number of ejector pins; i represents the ejector pin number. Select the material correction factor β according to the workpiece material, with β ranging from 0.7 to 1.3; The pressure threshold P0 is calculated as: P0 = β × Pt.

9. The adaptive clamping control method for an electric vise according to claim 1, characterized in that: The method for obtaining surface contour data includes: driving each of the ejector pins to extend individually or in groups to contact the workpiece surface and then retracting them, collecting the extension amount of each ejector pin, and generating the surface contour data based on the extension amount of each ejector pin.

10. An adaptive clamping control system for an electric vise, used to execute the adaptive clamping control method for an electric vise according to any one of claims 1-9, characterized in that: The system includes: The strain sensing unit includes differential strain gauges disposed at the root of each ejector pin to acquire the corresponding time-domain strain signal; The self-locking drive unit includes an electric lead screw that independently drives the extension and retraction of each ejector pin and locks itself in place; A clamping drive unit is used to drive the second jaw to move as a whole to clamp the workpiece to be processed; The control unit acquires the time-domain strain signal and controls the operation of the drive self-locking unit and the clamping drive unit according to the time-domain strain signal to perform adaptive clamping of the workpiece by the electric vise.

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