All-directional self-locking structure applied to a turning and milling combined electric spindle and method thereof

Abstract

This invention relates to the field of precision CNC machine tools and intelligent manufacturing equipment technology, specifically to an omnidirectional self-locking structure and method for a milling-turning composite electric spindle; it includes a stator housing, an elastic diaphragm chuck, an annular hydraulic cylinder, and a sensing feedback component; the system establishes a cold-state reference, and uses a stiffness mapping algorithm combined with real-time pressure peak value to calculate the rotor's thermal radial expansion and actual locking force; its core is to adaptively adjust the slope of the hydraulic control signal when the locking force exceeds the limit, actively correcting the control signal from a step to a ramp signal to reduce piston acceleration; this invention uses flexible, progressive thrust to offset high-energy rebound impact, effectively preventing diaphragm fatigue fracture caused by thermal stress superposition, and significantly improving the system robustness under extreme thermal conditions.

Description

Technical Field

[0001] This invention relates to the field of precision CNC machine tools and intelligent manufacturing equipment technology, specifically to an omnidirectional self-locking structure and method for use in milling-turning composite electric spindles. Background Technology

[0002] In the high-precision manufacturing environment of milling and turning, the electric spindle, as a core power component, needs to frequently switch between high-speed rotating milling mode and stationary positioning milling mode. Due to prolonged high-speed operation and the accumulation of cutting heat, the spindle rotor will experience significant radial thermal expansion. Existing spindle locking solutions typically employ hydraulic drives with preset pressure or mechanical interference structures, and their control logic is mostly an open-loop step response. When the spindle rotor undergoes micron-level thermal expansion, the elastic locking element will be forced to produce additional passive deformation, resulting in excessive elastic potential energy accumulation inside. At this time, if conventional rapid oil injection and unlocking are directly performed, the fluid inertial impact of the hydraulic system and the high-energy release of the material will superimpose, easily forming severe stress concentration at the root of the locking mechanism, inducing fatigue crack propagation or even brittle fracture. In addition, existing technologies cannot accurately isolate and quantify the actual mechanical deformation caused by thermal expansion under dynamic fluid interference, and often ignore the weakening effect of the material's elastic modulus at high temperatures on the locking stiffness, resulting in distorted locking force monitoring.

[0003] Therefore, how to ensure high rigidity and positioning accuracy while accurately sensing the thermal deformation state of the spindle and adaptively managing stress, and eliminating the risk of thermomechanical shock during the unlocking process, has become an urgent technical problem to be solved. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this invention is to provide an omnidirectional self-locking structure and method for a milling and turning composite electric spindle, which can solve the technical problems existing in the prior art. Specifically, the technical solution of this invention is as follows: An omnidirectional self-locking method for use in milling-turning composite electric spindles includes: S1. A hardware execution system for clamping a turning spindle is provided: the hardware execution system includes a stator housing, a spindle rotor, an elastic diaphragm chuck, an annular hydraulic cylinder, an annular piston and a sensing feedback assembly, and a hydraulic system that provides power to the annular hydraulic cylinder. The diaphragm chuck is a thin-walled circular ring with multiple independent elastic clamping flaps. Its outer edge is fixed to the stator housing, and its inner edge covers the main shaft rotor. In its natural state, the chuck contracts into a bowl shape to clamp the main shaft rotor. Under the pressure of the piston, it is forced to flip and tend to flatten, thereby releasing the main shaft rotor. S2. Establish chuck cold unlocking benchmark: When the spindle rotor is cold and stationary, increase the oil pressure to drive the annular piston to push the elastic diaphragm chuck. When the inner edge of the independent elastic clamping flap disengages from the rotor surface and the turning clamping state is released, record the hydraulic pressure value as the cold unlocking threshold. S3. Perform turning brake clamping: In the milling mode of turning-milling composite machining, the hydraulic system is unloaded, and the elastic diaphragm chuck returns to a bowl shape that contracts towards the axis. Relying on the elastic restoring force of the plurality of independent elastic clamping petals, it hugs the spindle rotor radially and omnidirectionally, directly resisting the cutting torque applied by the tool during turning and providing the spindle torsional stiffness required for turning. S4. Unlocking and Status Assessment after Turning: After turning is completed, unlocking is initiated: the annular hydraulic cylinder is driven to inject oil and push the chuck to rotate, and pressure data is collected simultaneously. The peak pressure generated at the moment of unlocking due to overcoming the additional resistance of thermal expansion of the spindle during the turning process caused by cutting heat is captured. The difference between the peak pressure and the cold unlocking threshold is calculated and converted into the thermal radial expansion of the spindle rotor and the actual locking force generated during the turning process based on the stiffness mapping algorithm. S5. Adaptive Flexible Control for Chuck Unlocking: If the actual locking force exceeds the warning value, adjust the slope of the hydraulic control signal to reduce the acceleration of the annular piston to perform flexible unlocking; if the pressure peak is lower than the safety limit, trigger a chuck failure shutdown alarm; if the actual locking force does not exceed the warning value and the pressure peak is not lower than the safety limit, maintain the current oil injection parameters.

[0005] Preferably, in step S1: the sensing feedback component includes a pressure transmitter connected in series in the oil inlet circuit of the annular hydraulic cylinder, and a non-contact displacement sensor installed at the end of the stroke of the annular piston.

[0006] Preferably, step S2 includes: Control the hydraulic system to output linearly increasing pressure oil; The position of the annular piston is monitored by the non-contact displacement sensor. When a sudden displacement of the annular piston is detected, it is determined that the inner edge of the elastic diaphragm chuck has disengaged from the main shaft rotor, and the current pressure value is recorded by the pressure transmitter as the cold unlocking threshold.

[0007] Preferably, in step S5: When the actual locking force is detected to exceed the fatigue limit warning value of the elastic diaphragm chuck material, the hydraulic proportional valve configured in the hydraulic system is controlled to change its control signal from a step signal to a ramp signal, the oil injection time is extended, and a flexible, progressive thrust is used to flip the chuck to counteract the elastic rebound impact.

[0008] Preferably, in step S3: when the elastic diaphragm chuck clamps the spindle rotor, the inner edges of the plurality of independent elastic clips form an omnidirectionally uniformly distributed interference fit locking interface with the outer cylindrical surface of the spindle rotor, so that the spindle rotor remains circumferentially stationary when subjected to the main cutting force during turning.

[0009] Preferably, in step S1: a high-hardness wear-resistant coating is processed on the outer surface of the spindle rotor in the area in contact with the elastic diaphragm chuck, and the surface roughness of the wear-resistant coating is controlled within Ra0.2.

[0010] Preferably, in step S4: the sampling frequency of the pressure transmitter is set to 1000Hz to accurately capture the millisecond-level pressure transients when the chuck is unlocked after turning.

[0011] Preferably, in step S4: the stiffness mapping algorithm is based on a nonlinear stiffness mapping model, and the difference between the pressure peak and the cold unlocking threshold is used as the force required to overcome the additional stiffness of the diaphragm, which is converted into the additional radial displacement of the inner edge of the elastic diaphragm chuck, and the additional radial displacement is equivalent to the thermal radial expansion of the main shaft rotor.

[0012] An omnidirectional self-locking structure for use in a milling and turning composite electric spindle includes: The stator housing has an annular mounting groove machined on its inner wall; The main spindle rotor is coaxially inserted inside the stator housing and serves as the lathe spindle. The annular hydraulic cylinder body is fixed in the annular mounting groove by an interference fit. An annular piston is slidably mounted inside the annular hydraulic cylinder to form a hydraulic drive assembly. The elastic diaphragm chuck is a turning locking chuck with radial contraction clamping characteristics. It has a ring-shaped thin-walled structure and multiple independent elastic clamping petals on the inner diameter edge. Its outer edge is fixedly connected to the stator housing, and its inner edge covers the spindle rotor to provide an omnidirectional locking force to resist cutting torque during turning. The elastic diaphragm chuck is located on the thrust path of the annular piston and is controlled to generate a flipping deformation to release the clamping. Sensing feedback components, including pressure monitoring elements and displacement monitoring elements; The control system includes a memory and a processor. The memory stores a computer program that, when executed by the processor, implements the steps of the method described above. The computer program is configured to connect to the sensing feedback component and calculate the thermal radial expansion of the spindle rotor during turning based on monitoring data and to regulate the hydraulic drive component to perform adaptive control.

[0013] Preferably, the thrust end face of the annular piston is designed as a circular arc protrusion, which forms a line contact with the side surface of the elastic diaphragm chuck, and the line contact position is located between the root and the end of the elastic flap of the elastic diaphragm chuck.

[0014] Compared with the prior art, the present invention has the following improvements and advantages: 1. This invention calculates the actual locking force and thermal radial expansion in real time. When the actual locking force exceeds the warning value, it actively corrects the control signal of the hydraulic proportional valve from a step signal to a ramp signal. This control strategy prolongs the oil injection time and uses a flexible, progressive thrust to offset the violent rebound impact when the elastic diaphragm chuck is released. This effectively prevents stress concentration and fatigue crack propagation at the diaphragm root caused by the superposition of thermal stress and fluid inertia, and significantly improves the robustness of the omnidirectional self-locking structure under extreme thermal conditions. 2. This invention employs a method combining a cold-state benchmark model with a stiffness mapping algorithm. By capturing the pressure peak at the moment of unlocking and calculating the difference between it and the cold-state unlocking threshold, the internal microscopic mechanical deformation, which is difficult to measure directly, is transformed into a macroscopically measurable hydraulic pressure signal. Based on the nonlinear stiffness lookup table method, the system can accurately convert this pressure difference into the additional radial displacement of the inner edge of the elastic diaphragm chuck and the thermal radial expansion of the spindle rotor. Thus, without adding an additional temperature sensor, it achieves accurate perception of the thermal deformation state of the spindle, avoiding the distortion of locking force monitoring caused by ignoring material thermal softening or fluid interference. 3. This invention constructs a hard-on-hard wear-resistant contact interface by processing a high-hardness wear-resistant coating on the surface of the main shaft rotor and controlling the surface roughness. This reduces the frictional resistance during the unlocking process and ensures a long-term constant friction coefficient, thereby reducing the error of the calculation model. At the same time, the arc protrusion designed on the thrust end face of the annular piston forms a line contact with the side surface of the elastic diaphragm chuck, so that the diaphragm generates a small amount of rolling friction during the flipping deformation process, avoiding surface scratches and mechanical seizing caused by sharp corner contact. Combined with the radial non-penetrating slit structure of the elastic diaphragm chuck, it ensures uniform clamping of the main shaft rotor in the entire circumference and the structural integrity of long-term operation. 4. When executing the unlocking procedure, this invention sets a safe lower limit for the pressure peak value. If the collected pressure peak value is lower than this lower limit, the system can quickly identify fatal faults such as rupture of the elastic diaphragm chuck or severe pressure loss in the hydraulic circuit, and immediately trigger a shutdown alarm. This logic effectively fills the gap in traditional open-loop control that cannot detect physical failures of the actuator, prevents the electric spindle from performing milling operations when it loses locking force, and eliminates safety accidents caused by workpiece loosening or spindle movement. Attached Figure Description

[0015] The present invention will be further explained below with reference to the accompanying drawings and embodiments: Figure 1This is a schematic diagram of the overall disassembled structure of the device; Figure 2 This is a schematic diagram of the main shaft rotor and its connection structure; Figure 3 This is a schematic diagram of the cross-sectional structure of an annular hydraulic cylinder. Figure 4 This is a flowchart of the method of the present invention; In the diagram: 1. Stator housing; 101. Annular mounting groove; 102. Stator housing end cover; 2. Main shaft rotor; 201. High-hardness wear-resistant coating; 3. Elastic diaphragm chuck; 301. Elastic clamping flap; 302. Radial non-penetrating slit; 303. Inner edge; 304. Outer edge; 4. Annular hydraulic cylinder body; 401. Oil inlet; 5. Annular piston; 502. Arc protrusion; 6. Sensing feedback assembly; 601. Pressure transmitter; 602. Non-contact displacement sensor. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0017] Example 1: Please see Figures 1-4 An omnidirectional self-locking method for use in milling and turning composite electric spindles, comprising: S1. A hardware execution system for clamping a spindle in turning operations is provided: the hardware execution system includes a stator housing 1, a spindle rotor 2, an elastic diaphragm chuck 3, an annular hydraulic cylinder 4, an annular piston 5, a sensing feedback component 6, and a hydraulic system that provides power to the annular hydraulic cylinder. The diaphragm chuck 3 is a thin-walled ring with elastic clamping flaps 301. Its outer edge 304 is fixed to the stator housing 1, and its inner edge 303 covers the main shaft rotor 2. In its natural state, the chuck 3 is cup-shaped and contracts to clamp the main shaft rotor 2. Under the pressure of the piston 5, it is forced to flip and tend to be flat, thereby releasing the main shaft rotor 2. S2. Establish the chuck cold unlocking benchmark: When the spindle rotor 2 is cold and stationary, increase the hydraulic pressure to drive the annular piston 5 to push the elastic diaphragm chuck 3. When the inner edge 303 of the independent elastic clamping petal 301 is separated from the rotor surface and the turning clamping state is released, record the hydraulic value as the cold unlocking threshold. S3, Perform turning brake clamping: In the milling mode of turning-milling composite machining, the hydraulic system is unloaded, the elastic diaphragm chuck 3 returns to the bowl shape that contracts towards the axis, and relies on the elastic restoring force of multiple independent elastic clamping petals 301 to hold the spindle rotor 2 radially and omnidirectionally, directly resisting the cutting torque applied by the tool during turning, and providing the spindle torsional stiffness required for turning. S4. Unlocking and Status Assessment after Turning: After turning is completed, unlocking is initiated, driving the annular hydraulic cylinder 4 to inject oil and push the chuck to rotate, and simultaneously collecting pressure data. The peak pressure generated at the moment of unlocking due to overcoming the additional resistance of thermal expansion of the spindle during the turning process caused by cutting heat is captured. The difference between the peak pressure and the cold unlocking threshold is calculated, and the thermal radial expansion of the spindle rotor 2 and the actual locking force generated during the turning process are converted based on the stiffness mapping algorithm. S5. Adaptive Flexible Control for Chuck Unlocking: If the actual locking force exceeds the warning value, adjust the slope of the hydraulic control signal to reduce the acceleration of the ring piston 5 to perform flexible unlocking; if the pressure peak is lower than the safety limit, trigger a chuck failure shutdown alarm; if the actual locking force does not exceed the warning value and the pressure peak is not lower than the safety limit, maintain the current oil injection parameters. This embodiment constructs a physical constraint system based on intrinsic elastic potential energy, aiming to solve the problem of locking force fluctuation caused by spindle thermal deformation in mill-turn machining. The stator housing 1 in the hardware execution system serves as a stationary base, with its inner hole machined with a high-precision positioning stop, a tolerance grade set to H6, and cylindricity controlled within... Within this range, it is used to bear the static reaction force of the entire locking mechanism; The annular hydraulic cylinder body 4 is made of high-strength aluminum alloy (7075-T6) and is embedded into the stator housing 1 through a hot-fit interference fit. This rigid connection ensures accurate transmission of hydraulic force under high-frequency vibration cutting conditions. The inner diameter of the annular hydraulic cylinder body 4 is set as follows: The outer diameter is The effective working area of ​​the annular piston 5 Calibrated as The maximum travel distance is ; The elastic diaphragm chuck 3, as the core actuator, is made of 65Mn spring steel, and its hardness is controlled after quenching and tempering. Its physical dimensions are precisely defined: wall thickness The cone angle is Its physical form is designed as a bistable structure, that is, in its natural state, it presents a bowl shape that contracts towards the axis. It uses the elastic modulus of the material itself to generate a huge radial clamping force. This normally closed logic ensures that the main shaft rotor 2 can still be reliably locked under extreme working conditions such as power failure or hydraulic pressure loss, eliminating safety hazards. When establishing the cold baseline model in step S2, the system is in a standard room temperature environment. By applying hydraulic loading, the minimum hydraulic work required to overcome the initial elastic potential energy of the diaphragm was accurately measured. This cold-state unlocking threshold became the zero-point benchmark for subsequent thermal compensation calculations. After entering the S3 milling mode, the hydraulic system is completely unloaded, eliminating the thermal interference of oil heating on the spindle accuracy. When the S4 unlocking program is executed, the spindle rotor 2 generates micron-level thermal radial expansion after high-speed rotation, causing the elastic diaphragm chuck 3 to be further expanded, storing additional elastic potential energy. At this time, the driving annular hydraulic cylinder 4 is injected with oil, and the hydraulic oil must overcome this additional potential energy to push the diaphragm to flip. By capturing this instantaneous pressure peak, the system uses the coupling relationship between fluid pressure and mechanical deformation to reverse-analyze the thermal expansion state of the spindle rotor 2. It is worth noting that this embodiment introduces dynamic-static decoupling logic when calculating the difference between the peak pressure and the cold unlocking threshold; the system recognizes that the unlocking process of S4 is a highly dynamic transient process with millisecond-level oil injection, and its pressure reading must contain fluid friction resistance and inertial pressure components that S2 does not have. ; Therefore, the computational logic removes this additional hydrodynamic interference, retaining only the effective static pressure increment used to overcome mechanical deformation. Simultaneously, for the step of converting the difference into thermal expansion based on the stiffness mapping algorithm, the system further considers the thermal accumulation effect caused by the S3 milling mode and performs thermal softening compensation on the material properties of the elastic diaphragm chuck 3. That is, the system does not simply attribute the pressure difference to geometric expansion, but simultaneously calculates the material's elastic modulus due to temperature increase. Attenuation avoids underestimating the actual thermal expansion due to material softening, thus realizing the transformation of internal microscopic deformation, which is difficult to measure directly, into a macroscopically measurable and physically accurate pressure signal. In S5, the control system uses an iterative learning control strategy to correct the slope of the hydraulic control signal for the next working cycle based on the analyzed thermal expansion and locking force state. Specifically, for the control action of reducing the acceleration of the ring piston 5, the system does not intervene in real time at the current millisecond-level unlocking moment, when the action has already been completed. Instead, it uses the currently captured over-limit locking force data as feedback input to update the feedforward parameters in the control algorithm. This allows the hydraulic system to output a smoothed flow waveform when the unlocking action is executed next time, thereby offsetting excessive stress impact with flexible action and preventing fatigue fracture of the diaphragm root due to long-term overload operation. This ensures locking reliability while extending the service life of key components. The safety lower limit set in step S5 is the critical pressure value at which the system confirms that the elastic diaphragm chuck 3 has basic structural integrity and hydraulic circuit sealing. This safety lower limit is set to 80% of the cold unlocking threshold. The setting of this proportional coefficient is based on a comprehensive consideration of the safety margin of the yield strength of the elastic diaphragm material and the allowable pressure fluctuation range of the hydraulic system, in order to prevent the shutdown logic from being accidentally triggered due to system noise. If the pressure peak captured during the oil injection process is lower than this lower limit, it indicates that the elastic diaphragm chuck 3 may have broken or the hydraulic system may have suffered severe pressure loss. At this time, a shutdown alarm is triggered to prevent the spindle from running without locking force. In step S1: the sensing feedback component 6 includes a pressure transmitter 601 connected in series in the oil inlet circuit of the annular hydraulic cylinder 4, and a non-contact displacement sensor 602 installed at the end of the stroke of the annular piston 5. This embodiment specifies the physical layout of the sensing feedback component 6, aiming to build a high-frequency response closed-loop monitoring network; the pressure transmitter 601 is directly integrated into the oil inlet 401 of the annular hydraulic cylinder 4, shortening the length of the pressure guiding pipeline as much as possible to reduce the smoothing effect of fluid viscosity damping on pressure fluctuations and ensure that millisecond-level pressure transient signals can be sensitively captured. The non-contact displacement sensor 602 uses an oil-resistant, high-pressure type high-frequency eddy current sensor, and its range is set to... Linearity is better than The dynamic response frequency is not lower than The resolution reached The probe is installed in the through hole of the stator housing end cover 102. To ensure that the detection path is unobstructed, the bottom of the annular hydraulic cylinder 4 has a detection through hole at the corresponding sensor installation position, so that the probe end face directly contacts the hydraulic oil chamber and faces the back metal surface of the annular piston 5. This non-contact measurement method avoids mechanical wear and can work stably for a long time in oily environments. By synchronously acquiring pressure and displacement data, the control system can construct a pressure-displacement hysteresis curve. The slope of this curve directly reflects the evolution of the stiffness characteristics of the elastic diaphragm chuck 3, providing a multi-dimensional physical basis for subsequent fault diagnosis and thermal compensation. Specifically, for the fault diagnosis and handling process based on the pressure-displacement hysteresis curve, the controller internally performs the following logical operation: extracting the linear regression slope of the loading segment of the hysteresis curve as the real-time stiffness feature value. ; will The reference stiffness established during the system initialization phase Perform a comparison; if the calculated deviation If the value exceeds the set threshold by 15% and is accompanied by an increase in the displacement hysteresis loop area, it is determined that fatigue microcracks have appeared at the root of the elastic diaphragm chuck or the hydraulic transmission efficiency is abnormal, thereby triggering a system maintenance alarm. The steps of S2 include: controlling the hydraulic system to output linearly increasing pressure oil; monitoring the position of the annular piston 5 through the non-contact displacement sensor 602; when a sudden displacement change of the annular piston 5 is detected, determining that the inner edge 303 of the elastic diaphragm chuck 3 is disengaged from the main shaft rotor 2, and recording the current pressure value as the cold unlocking threshold through the pressure transmitter 601. This embodiment details the process of establishing the benchmark model, which is essentially a quasi-static mechanical calibration test. The control system drives the hydraulic pump to output pressure oil rising in a ramp shape, causing the annular piston 5 to slowly contact the elastic diaphragm chuck 3 at an extremely low speed. During this process, the reading of the non-contact displacement sensor 602 remains relatively static or changes by a small linear amount, caused only by material compression. When the oil pressure reaches a certain critical point, sufficient to overcome the static friction force of the diaphragm chuck on the main shaft rotor 2 and its own elastic restoring force, the diaphragm instantly flips, causing a step change in the displacement reading of the annular piston 5. The system captures the moment corresponding to the extreme point of this displacement derivative and locks the value of the pressure transmitter 601 at that moment. This value accurately characterizes the inherent structural stiffness and resistance of the system under the condition of no thermal deformation interference, eliminates the interference of system errors such as hydraulic pipeline pressure loss, and provides a high-confidence comparison benchmark for subsequent calculation of thermal expansion. In step S5: when the actual locking force exceeds the material fatigue limit warning value of the elastic diaphragm chuck 3, the hydraulic proportional valve in the hydraulic system is controlled to change its control signal from a step signal to a ramp signal, the oil injection time is extended, and a flexible progressive thrust is used to make the chuck flip to counteract the elastic rebound impact. This embodiment proposes a stress management strategy based on waveform shaping for overload locking conditions caused by spindle thermal expansion. When the thermal expansion of the spindle rotor 2 increases significantly, the elastic diaphragm chuck 3 is in a high tension limit state. If a traditional step signal is used for rapid oil injection and unlocking at this time, the severe hydraulic shock combined with the high energy release of the diaphragm itself will easily form stress concentration at the root of the diaphragm, inducing the propagation of microcracks. The control system predicts this risk through monitoring algorithms and actively intervenes in the drive logic of the hydraulic proportional valve to correct the originally vertically rising voltage command into a gently rising ramp curve. This control strategy allows the oil flow rate entering the annular hydraulic cylinder 4 to increase gradually, and the annular piston 5 to slowly push the diaphragm with controlled acceleration, giving the material lattice structure sufficient time for stress redistribution, thereby effectively suppressing transient impact loads, preventing brittle fracture failure caused by thermal stress superimposed on mechanical impact, and significantly improving the robustness of the locking mechanism under extreme thermal conditions. Regarding the fatigue limit warning value of the elastic diaphragm chuck 3 material, the system presets a physical model based on cantilever beam bending theory to correct the original simplified calculation logic. Although the elastic diaphragm chuck exhibits nonlinear jump characteristics during the flipping process, in micro-deformation fatigue analysis, its root is treated as a cantilever beam structure for equivalent calculation, which can obtain a conservative stress estimate, thus ensuring the reliability of the warning value. Specifically, this warning value... Determined by the following formula: in, The bending fatigue limit stress of the elastic diaphragm material, in units of ; The total flexural section modulus of the root of all 301 elastic flaps of the elastic diaphragm chuck, in units of ; The length of the locking lever arm from the fixed end at the root of the diaphragm to the clamping point at the inner edge 303, in units of ; For safety reasons, this embodiment takes... ; The formula incorporates the leverage ratio. Its definition is: in, The lever arm length is the distance from the fulcrum to the piston contact point; Here Defined as the equivalent hydraulic thrust warning value corresponding to the fatigue limit of the elastic diaphragm material; by introducing the lever ratio This formula maps the bending stress limit at the root of the diaphragm to the thrust threshold on the hydraulic cylinder side, thus allowing the control system to directly input the real-time collected hydraulic locking force. A direct comparison with this warning value should be made; it should be noted that, after dimensional calculation, the above formula... The calculation result is in units of It is consistent with the physical dimensions of the actual locking force; By clearly defining geometric parameters and introducing leverage ratio correction, the model accurately reflects the stress distribution gradient of the diaphragm under bending conditions; it ensures the consistency between the warning value used for comparison and the actual locking force in the physical dimension, and avoids threshold setting errors caused by ignoring the leverage effect. Furthermore, it should be noted that, regarding the adaptive control logic in step S5, considering the physical delay and causal logic of the hydraulic system response, this control strategy is essentially an iterative learning control based on historical data; that is, when the system detects that the actual locking force exceeds the warning value in the current working cycle N, the specific correction logic follows the iterative learning law: setting the first... The slope of the hydraulic proportional valve voltage ramp in the next unlocking cycle is... If maximum locking force is detected Then the first The slope of the next cycle is updated as follows: This formula represents an incremental correction based on the slope of the previous period to balance the physical dimensions; where, The preset learning gain coefficient includes a unit conversion factor, and its physical units are set to [value missing]. value range To ensure that the physical dimensions at both ends of the formula are consistent, until ; The controller records the abnormal event and actively calls the corrected ramp signal oil injection parameters in the unlocking procedure of the next working cycle N+1. This cross-cycle feedback mechanism avoids the physical time delay defect of trying to correct the impact in real time during the millisecond transient process, ensures the physical feasibility of the protection action, and effectively curbs the cumulative fatigue damage. In step S3: when the elastic diaphragm chuck 3 clamps the spindle rotor 2, the inner edges 303 of the plurality of independent elastic clips 301 form an omnidirectionally uniformly distributed interference fit locking interface with the outer cylindrical surface of the spindle rotor 2, so that the spindle rotor 2 remains circumferentially stationary during the turning process. In this embodiment, the topology of the elastic diaphragm chuck 3 is optimized to resolve the contradiction between circumferential stiffness and radial flexibility. The elastic diaphragm chuck 3 is processed with laser precision cutting technology to create 16 radial non-penetrating slits 302 on the inner diameter edge, dividing the continuous ring into 16 independent elastic clips 301. This segmented structure cuts off the circumferential stress transmission path of the inner edge 303, allowing each clip to independently adapt to the micro-morphology of the main shaft rotor 2 surface, greatly improving the tolerance to rotor roundness error.

[0018] Furthermore, in the actual machining environment, the spindle rotor 2 is equipped with an independent cooling system and is combined with an external ring spray cooling tool. The overall heat source management mechanism is perfect, and the cold and hot state changes of the spindle rotor 2 are minimal, avoiding the superposition of severe thermal stress. At the same time, the spindle rotor 2 assembly adopts dynamic balancing technology and is calibrated at the factory using professional testing equipment and adjustment methods, resulting in minimal vibration amplitude during actual cutting operations. Under the excellent operating boundary conditions of low thermal fluctuation and low amplitude, the peak stress borne by the elastic diaphragm chuck 3 under alternating loads is significantly reduced, far below the fatigue limit of the material. The machine tool's comprehensive environmental protection eliminates the risk of instability, deformation, and fatigue fracture of the elastic clamping flap 301 under high-frequency thermal cycling and high-frequency vibration, ensuring the long-term stability of the omnidirectional self-locking effect.

[0019] In its natural state, the diaphragm is pre-formed into a truncated cone-shaped bowl structure, which gives it a huge initial elastic potential energy. When the annular piston 5 applies axial thrust, it forces the diaphragm to cross the dead point and flip into a near-planar disc shape. This nonlinear geometric deformation efficiently converts the axial thrust into radial expansion displacement, realizing rapid unlocking under short stroke drive. At the same time, it ensures uniform clamping of the main shaft rotor 2 in the entire circumference under the locked state, avoiding rotor deformation caused by excessive local stress. In step S1: a high-hardness wear-resistant coating 201 is processed on the outer surface of the main spindle rotor 2 in the contact area with the elastic diaphragm chuck 3, and the surface roughness of the wear-resistant coating is controlled within Ra0.2; In this embodiment, targeted reinforcement was carried out on the microstructure of the friction pair interface. Considering that the elastic diaphragm chuck 3 is made of high-hardness spring steel, direct contact with the main spindle rotor 2 substrate is prone to fretting wear, which will affect the locking accuracy. Therefore, a tungsten carbide coating is deposited in the contact area of ​​the main spindle rotor 2 using a supersonic flame spraying process, so that its surface hardness reaches HV1200 or higher, thus constructing a wear-resistant barrier for hard-hard contact. Meanwhile, the surface roughness of the coating is strictly controlled within Ra0.2 through precision grinding. This mirror-like surface quality not only reduces frictional resistance during the unlocking process and reduces piston drive power consumption, but more importantly, it ensures the long-term constancy of the friction coefficient. A constant friction coefficient is a prerequisite for the system to accurately invert the mathematical relationship between locking force and thermal expansion, eliminating the distortion of the calculation model caused by surface wear and roughening. Although the low roughness surface of Ra0.2 reduces the friction coefficient, the inherent elastic modulus generated by the bistable structure of the elastic diaphragm chuck 3 in Example 1 is still maintained. Despite the enormous radial clamping force, the system can still generate a static friction torque sufficient to resist the cutting torque by increasing the normal force. This achieves a performance balance between low-wear unlocking and high-reliability locking; In step S4: the sampling frequency of pressure transmitter 601 is set to 1000Hz to accurately capture the millisecond-level pressure transients when the chuck is unlocked after turning. This embodiment clarifies the time resolution requirement for data acquisition, which is the key to achieving high dynamic feature extraction. Because the pressure wave of hydraulic oil in the pipeline propagates extremely fast, and the sudden change in the mechanical state at the moment of diaphragm unlocking often occurs within milliseconds, conventional low-frequency sensors are prone to aliasing or missed sampling, resulting in peak clipping. Setting the sampling frequency of the pressure transmitter 601 to 1000Hz, that is, acquiring one data point every 1 millisecond, can completely depict the fine waveform of the pressure rise edge. This high-density data stream enables the control system to accurately capture the inflection points and instantaneous peaks on the pressure curve, which are characteristic points for overcoming static friction and maximum elastic potential energy. More importantly, this high-frequency sampling rate is a prerequisite for the fluid dynamics compensation in Example 7. This is necessary to accurately calculate and eliminate the superimposed fluid dynamics pressure increment under condition S4. The algorithm needs to calculate the rate of change of pressure over time. And the second derivative; the 1000Hz sampling rate provides sufficient time resolution to construct a high-fidelity pressure differential curve, enabling the system to quantify fluid inertia and damping effects, thereby accurately identifying the static elastic force increment hidden under the dynamic pressure peak, which is caused only by the micron-level thermal expansion change. This embodiment fully considers the fluid inertia and damping characteristics of the hydraulic system. Although the theoretical acoustic pressure wave transmission speed is extremely fast, due to the volume effect of the annular hydraulic cylinder 4, the friction resistance of the pressure guiding pipeline, and the physical limitation of the throttle orifice, the actual pressure rise and fall time at the pressure transmitter 601 is physically broadened to more than 20ms, that is, the main frequency component of the effective bandwidth of the signal is much lower than 500Hz. According to the Nyquist sampling theorem, a sampling rate of 1000Hz provides at least 20 times the oversampling factor for capturing transient processes with a duration greater than 20ms. This not only fully meets the requirements for signal reconstruction, which is sufficient to construct a high-fidelity stress curve and capture the real peak data, but also avoids data redundancy and processing delay caused by excessively high sampling rates, and there is no phenomenon of missed sampling or peak clipping distortion due to insufficient sampling rate. In step S4: the stiffness mapping algorithm is based on the nonlinear stiffness lookup table method, that is, the segmented application of Hooke's law in a variable stiffness system. The difference between the pressure peak and the cold unlocking threshold is used as the force required to overcome the additional stiffness of the diaphragm, which is converted into the additional radial displacement of the inner edge 303 of the elastic diaphragm chuck 3. The additional radial displacement is equivalent to the thermal radial expansion of the main shaft rotor 2. This embodiment reveals the physical conversion logic from hydraulic signals to geometric deformation; the core algorithm is based on a discretized Hooke's law model, treating the elastic diaphragm chuck 3 as a variable stiffness spring system; and a correction factor is introduced. Location-dependent stiffness function On the classics The formula performs nonlinear compensation; When the main spindle rotor 2 undergoes thermal expansion, it is equivalent to applying an additional pre-compression to the spring system, causing its operating point to move towards the high potential energy region along the force-displacement curve; the increment of the unlocking pressure is physically the force required to overcome this additional pre-compression stroke; the control system stores the mechanical constitutive equation of the diaphragm or generates a lookup table through finite element analysis, directly mapping the collected pressure difference value to the passive radial displacement of the inner edge 303 of the diaphragm; since the diaphragm is in close contact with the rotor surface, this displacement is numerically strictly equivalent to the thermal radial expansion of the main spindle rotor 2; To address the model distortion issues caused by dynamic characteristic mismatch and thermal decay of materials, this embodiment performs multiphysics correction on the stiffness mapping algorithm; a fluid dynamics compensation term is introduced to remove the inelastic pressure component introduced by the S4 high-speed oil injection; considering the nonlinear relationship between pressure build-up rate and actuator speed in hydraulic drive, the algorithm no longer directly equates the pressure derivative with speed, but instead adopts a transformation model based on the hydraulic cavity effect: in, Fluid viscosity damping coefficient, unit: ; Fluid inertia coefficient, unit: Both were obtained through offline system identification; the specific identification process was as follows: with the main spindle rotor 2 not installed, the hydraulic system was controlled to perform an unloaded step response test, at which time the mechanical deformation force Record the pressure at different flow rates With speed The data is used to construct the objective function using the least squares method: By solving and Coefficient of determination and The value of ; considering that the annular piston has not yet produced macroscopic displacement at the moment of unlocking, here Defined as the equivalent virtual velocity generated by the fluid compression effect within the hydraulic cavity, its calculation formula is as follows: Here The rate of change of pressure over time is collected in real time. The effective working area of ​​the aforementioned annular piston ; The equivalent volume of the hydraulic control circuit includes the cylinder cavity and conduit volume; in this embodiment, it is set to... ; The bulk modulus of hydraulic oil is taken as a typical value. ,Right now This accurately quantifies the inertia and damping effects caused by fluid compressibility, and introduces a material thermal softening correction factor: considering the elastic modulus of the diaphragm material 65Mn. The temperature decreases as the temperature increases; the algorithm integrates a thermal-stiffness coupling model. Lacking a direct temperature sensor, the system uses a thermal-mechanical observer to estimate the diaphragm's thermal state based on the duration and rotational speed of step S3, and generates a stiffness attenuation coefficient. ( Specifically, the thermal observer performs the following discretized energy integration algorithm: in, To accumulate heat energy, For real-time rotational speed, The convective heat transfer coefficient is... The coefficient of heat generation is the viscosity. The effective surface area for convective heat transfer between the elastic diaphragm chuck 3 and air, in units of: ; The diaphragm temperature estimated at the previous moment. Ambient temperature; The time step is for discrete calculations; where the viscous heat generation coefficient is... Defined as: In the formula, The dynamic viscosity of the hydraulic oil is taken as... , The rotor diameter is Contact length; To accommodate the oil film gap between the stator and rotor, in this embodiment, the typical value of this gap is controlled within a certain range. to between; It is particularly important to note that when applying the above formula for calculations, all length-related parameters must be converted to international standard units (SI units). To ensure that the calculated heat generation power is in units of To prevent the calculation model from failing due to dimensional confusion, in this embodiment, based on the physical fact of shear heat generation of fluid in rotating annular gaps, and considering the double-sided boundary layer shear effect and laminar flow assumption of the narrow gap flow field in this embodiment, the denominator of the power consumption coefficient is experimentally calibrated and corrected to 4, instead of 2 in the traditional Petrov law. convective heat transfer coefficient Set as a function of rotational speed: Here The hydraulic diameter is taken as the rotor outer diameter. ; The thermal conductivity of air; The calculation formula is: Among them, the rotating Reynolds number Defined as: In the formula, For standard air density, take ; For aerodynamic viscosity, take ; Let be the Prandtl number for air, and take the value of a constant. This formula adopts a convective heat transfer correlation applicable to a rotating cylinder in still air, replacing the original formula for internal flow in a pipe, in order to accurately describe the heat dissipation characteristics of the rotating spindle surface. It should be noted that the values ​​of the above thermodynamic parameters are only for standard atmospheric pressure and... Typical values ​​under different environments; In practical engineering applications, in order to improve the robustness of the model at different altitudes and temperatures, the above parameters can be preset as lookup functions of temperature and pressure, or corrected in real time through environmental sensor data integrated into the system. To complete the closed-loop iteration of the temperature state, the system performs temperature update calculations according to the first law of thermodynamics: in, For the effective thermal mass of the diaphragm, For specific heat capacity; calculate ,in, Let be the elastic modulus and temperature decay coefficient of the 65Mn material for the elastic diaphragm chuck 3, which is a constant; the final displacement conversion formula is corrected as follows: in, It is the inverse function of the pre-calibrated pressure-displacement nonlinear characteristic curve.

[0020] The characteristic curve was obtained through offline finite element analysis (FEA): In the simulation settings, the boundary conditions were defined as: full degree of freedom constraint on the outer edge of the elastic diaphragm chuck, and an axially uniformly distributed displacement load was applied on the contact trajectory of the corresponding annular piston thrust circle, with the step size set to [value missing]. Considering contact nonlinearity, a series of pressure loads are applied to the diaphragm model, and the corresponding radial displacements are recorded. A lookup table is generated and implanted into the controller to replace simple linear stiffness division, thus more accurately describing the mechanical behavior of the bistable structure near the buckling point. In the simplified calculation model, it can be approximated as: in, This refers to the cold unlocking threshold recorded in step S2; this means that under the same pressure difference, considering the softening of the material, the actual amount of thermal expansion deduced is... The calculated value will be larger than that of the uncompensated model, thus eliminating the calculation error caused by ignoring material softening; at the same time, for the calculation of the actual locking force mentioned in step S4, the algorithm strictly follows the operation logic based entirely on the difference. Specifically, the system calculates the peak pressure at the moment of unlocking. With cold unlock threshold The difference, using the formula The hydraulic thrust increment is obtained; using the lever principle, this axial thrust is converted into an increase in radial clamping force acting on the rotor surface. : in, The cone angle of the elastic diaphragm chuck in its natural state is a truncated cone; this increment... The total actual locking force is obtained by superimposing it with the pre-stored cold-state reference locking force. And compare it with the previously calculated material fatigue limit warning value. Comparisons are made to perform adaptive control. Given the bistable nonlinear geometric large deformation characteristics, the formula in Defined as the equivalent hydraulic stiffness coefficient, with units of MPa / mm; it is not a single physical constant, but a dynamic variable that varies with the diaphragm flip angle; this embodiment constructs a nonlinear lever ratio dynamic compensation model for this purpose. Reconstructed for piston displacement Functions: in, The equivalent force-bearing area of ​​the elastic diaphragm chuck corresponding to the piston thrust is... For the inherent stiffness of the material, For displacement The changing instantaneous lever ratio function, i.e., the ratio of the lever arm length from the fulcrum to the piston contact point to the lever arm length from the fulcrum to the clamping point, is obtained through cubic polynomial fitting; the cubic polynomial fitting function is specifically expressed as: Among them, coefficient The method of obtaining it is: extracting it from finite element simulation software. to The N discrete displacement points within the range and their corresponding lever arm ratios are determined using regression analysis; under the specific geometric dimensions and material properties of this embodiment, such as the cylinder inner diameter... diaphragm wall thickness The typical fit coefficients obtained through finite element analysis regression are: The system collects displacement data in real time during calculation and substitutes it into the function to compensate for the nonlinear fluctuation of the lever ratio during large deformation. This algorithm, which is based on difference superposition and is dynamically compensated and thermally corrected, eliminates the zero-point drift error that may be introduced by directly using the absolute value of pressure, and accurately characterizes the instantaneous radial clamping force applied by the diaphragm chuck to the main shaft rotor 2 under the current thermal conditions.

[0021] To overcome the dynamic interference of factors such as friction, oil temperature, material relaxation, and hydraulic hysteresis on the unlocking pressure under actual working conditions, this system re-executes the calibration program before each cold start of the machine tool to obtain the cold unlocking threshold, thereby eliminating the cumulative error caused by material stress relaxation and hydraulic circuit hysteresis from a physical and logical perspective. At the same time, the spindle's excellent heat source management ensures stable oil temperature, and the high-hardness wear-resistant coating 201 in the contact area ensures a long-term constant friction coefficient. Through the above-mentioned hardware boundary condition constraints and periodic calibration mechanism, the system eliminates uncontrolled interference variables and ensures a highly accurate and unique mapping relationship between pressure and actual thermal radial expansion, which is in line with technical common sense.

[0022] Example 2: Please see Figures 1-3 An omnidirectional self-locking structure for use in milling and turning composite electric spindles, comprising: The stator housing 1 has an annular mounting groove 101 machined on its inner wall; the main spindle rotor 2 is coaxially inserted inside the stator housing 1 and serves as the lathe spindle. The annular hydraulic cylinder body 4 is fixed in the annular mounting groove 101 with an interference fit. An annular piston 5 is slidably installed inside an annular hydraulic cylinder 4, forming a hydraulic drive assembly. The elastic diaphragm chuck 3 is a turning locking chuck with radial contraction clamping characteristics. It has a ring-shaped thin-walled structure and multiple independent elastic clamping petals 301 on the inner diameter edge. Its outer edge 304 is fixedly connected to the stator housing 1, and its inner edge 303 covers the spindle rotor 2 to provide an omnidirectional locking force to resist cutting torque during turning. The elastic diaphragm chuck 3 is located on the thrust path of the annular piston 5 and is controlled to generate flipping deformation to release the clamping. The sensing feedback component 6 includes a pressure monitoring element and a displacement monitoring element; The control system includes a memory and a processor. The memory stores a computer program. When the computer program is executed by the processor, it implements the above-mentioned method steps. It is configured to connect to the sensing feedback component 6 and calculate the thermal radial expansion of the spindle rotor 2 during turning based on the monitoring data and regulate the hydraulic drive component to perform adaptive control. The thrust end face of the annular piston 5 is designed as an arc protrusion 502. The arc protrusion 502 forms a line contact with the side surface of the elastic diaphragm chuck 3. The line contact position is located between the root and the end of the elastic clamping flap 301 of the elastic diaphragm chuck 3.

[0023] This embodiment provides an integrated mechanical architecture that integrates sensing and execution functions; the stator housing 1 serves as the main load-bearing body, and the annular mounting groove 101 on its inner wall provides embedded mounting space for the hydraulic power unit, making the entire locking mechanism compact and not occupying the effective machining stroke of the spindle; the interference fit design between the annular hydraulic cylinder 4 and the stator housing 1 not only enhances the overall rigidity, but also utilizes the large heat capacity of the housing to assist in the cooling of the hydraulic oil. Specifically, the thrust end face of the annular piston 5 is designed as an arc protrusion 502, forming a line contact mode with the planar sidewall of the elastic diaphragm chuck 3; this contact area is macroscopically a line contact, and microscopically a Hertzian contact elliptical narrow band under stress; this contact line is specially arranged at a specific lever point between the root and the end of the elastic clamp 301. This geometric design utilizes the lever principle to form a typical third-class lever system. Although, according to the law of conservation of energy and the lever balance condition, obtaining a large radial opening displacement at the end of the diaphragm in this type of structure is accompanied by an increase in driving force, i.e., a greater axial thrust is required, this characteristic is consistent with the output characteristics of hydraulic systems with large thrust and short stroke. The design aims to utilize the ample thrust reserve of the hydraulic cylinder to obtain a valuable radial opening stroke, thereby inducing a radial displacement at the end of the diaphragm sufficient to release the main shaft rotor 2 within a limited piston axial movement space, effectively solving the engineering problem of driving a large opening with a small stroke. Meanwhile, the line contact between the arc surface and the plane allows the diaphragm to undergo a small amount of rolling friction during the flipping process, avoiding surface scratches and stress concentration caused by sharp corner contact, and ensuring the long-term reliability of the mechanism under frequent start-stop operations; the control system, as the brain, transforms this mechanical structure into an intelligent component with self-sensing capabilities by connecting pressure and displacement monitoring elements.

[0024] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. An omnidirectional self-locking method for a milling-turning composite electric spindle, characterized in that, include: S1. A hardware execution system for clamping a spindle in turning is provided: the hardware execution system includes a stator housing (1), a spindle rotor (2), an elastic diaphragm chuck (3), an annular hydraulic cylinder (4), an annular piston (5), a sensing feedback component (6), and a hydraulic system that provides power to the annular hydraulic cylinder; The diaphragm chuck (3) is a thin-walled ring with a plurality of independent elastic clamping flaps (301). Its outer edge (304) is fixed to the stator housing (1), and its inner edge (303) covers the main shaft rotor (2). In its natural state, the chuck (3) contracts into a bowl shape to clamp the main shaft rotor (2). Under the pressure of the piston (5), it is forced to flip and tend to straighten, thereby releasing the main shaft rotor (2). S2. Establish the chuck cold unlocking benchmark: When the spindle rotor (2) is cold and stationary, increase the oil pressure to drive the ring piston (5) to push the elastic diaphragm chuck (3). When the inner edge (303) of the independent elastic clamping flap (301) is separated from the rotor surface and the turning clamping state is released, record the hydraulic value as the cold unlocking threshold. S3, Perform turning brake clamping: In the milling mode of turning and milling compound machining, the hydraulic system is unloaded, and the elastic diaphragm chuck (3) returns to the bowl shape that contracts towards the axis. Relying on the elastic restoring force of multiple independent elastic clips (301), it hugs the spindle rotor (2) radially and omnidirectionally, directly resisting the cutting torque applied by the tool during turning and providing the spindle anti-torsional stiffness required for turning. S4. Unlocking and status assessment after turning: After turning is completed, start unlocking: drive the annular hydraulic cylinder (4) to inject oil and push the chuck to flip, and collect pressure data at the same time. Capture the pressure peak generated at the moment of unlocking due to overcoming the additional resistance of thermal expansion of the spindle during the turning process caused by cutting heat. Calculate the difference between it and the cold unlocking threshold, and convert it into the thermal radial expansion of the spindle rotor (2) and the actual locking force generated during the turning process based on the stiffness mapping algorithm. S5, Adaptive Flexible Control for Chuck Unlocking: If the actual locking force exceeds the warning value, adjust the slope of the hydraulic control signal to reduce the acceleration of the ring piston (5) to perform flexible unlocking; If the peak pressure is lower than the safety limit, a jamming failure shutdown alarm will be triggered; if the actual locking force does not exceed the warning value and the peak pressure is not lower than the safety limit, the current oil injection parameters will be maintained.

2. The omnidirectional self-locking method for a milling-turning composite electric spindle according to claim 1, characterized in that, In step S1: the sensing feedback component (6) includes a pressure transmitter (601) connected in series in the oil inlet circuit of the annular hydraulic cylinder (4), and a non-contact displacement sensor (602) installed at the end of the stroke of the annular piston (5).

3. The omnidirectional self-locking method for a milling-turning composite electric spindle according to claim 2, characterized in that, The steps of S2 include: controlling the hydraulic system to output linearly increasing pressure oil; monitoring the position of the annular piston (5) through the non-contact displacement sensor (602); when a sudden displacement change of the annular piston (5) is detected, determining that the inner edge (303) of the elastic diaphragm chuck (3) is disengaged from the main shaft rotor (2), and recording the current pressure value as the cold unlocking threshold through the pressure transmitter (601).

4. The omnidirectional self-locking method for a milling-turning composite electric spindle according to claim 1, characterized in that, In step S5: when the actual locking force is detected to exceed the fatigue limit warning value of the elastic diaphragm chuck (3) material, the hydraulic proportional valve configured in the hydraulic system is controlled to change its control signal from a step signal to a ramp signal, the oil injection time is extended, and a flexible progressive thrust is used to flip the chuck to offset the elastic rebound impact.

5. The omnidirectional self-locking method for a milling-turning composite electric spindle according to claim 1, characterized in that, In step S3: when the elastic diaphragm chuck (3) holds the spindle rotor (2), the inner edges (303) of the plurality of independent elastic clips (301) form an omnidirectionally uniformly distributed interference fit locking interface with the outer cylindrical surface of the spindle rotor (2), so that the spindle rotor (2) remains circumferentially stationary when subjected to the main cutting force of turning.

6. The omnidirectional self-locking method for a milling-turning composite electric spindle according to claim 1, characterized in that, In step S1: a high-hardness wear-resistant coating (201) is processed on the outer surface of the main shaft rotor (2) in the contact area with the elastic diaphragm chuck (3), and the surface roughness of the wear-resistant coating is controlled within Ra0.

2.

7. The omnidirectional self-locking method for a milling-turning composite electric spindle according to claim 2, characterized in that, In step S4: the sampling frequency of the pressure transmitter (601) is set to 1000Hz to accurately capture the millisecond-level pressure transients when the chuck is unlocked after turning.

8. The omnidirectional self-locking method for a milling-turning composite electric spindle according to claim 1, characterized in that, In step S4: the stiffness mapping algorithm is based on a nonlinear stiffness mapping model, and takes the difference between the pressure peak and the cold unlocking threshold as the force required to overcome the additional stiffness of the diaphragm, and converts it into the additional radial displacement of the inner edge (303) of the elastic diaphragm chuck (3), which is equivalent to the thermal radial expansion of the main shaft rotor (2).

9. An omnidirectional self-locking structure for use in a milling-turning composite electric spindle, characterized in that, A spindle chuck device for turning is provided, comprising: a stator housing (1) with an annular mounting groove (101) machined on its inner wall; a spindle rotor (2) coaxially inserted inside the stator housing (1) as a lathe spindle; and an annular hydraulic cylinder (4) interference-fitted and fixed in the annular mounting groove (101) to form a hydraulic drive assembly. The annular piston (5) is slidably installed in the annular hydraulic cylinder (4); the elastic diaphragm chuck (3) is a turning locking chuck with radial shrinkage clamping characteristics. It has a thin-walled annular structure and multiple independent elastic clips (301) on the inner diameter edge. Its outer edge (304) is fixedly connected to the stator housing (1), and its inner edge (303) covers the spindle rotor (2) to provide an omnidirectional locking force to resist cutting torque during turning. The elastic diaphragm chuck (3) is located on the thrust path of the annular piston (5) and is controlled to generate a flipping deformation to release the clamping. The sensing feedback component (6) includes a pressure monitoring element and a displacement monitoring element; The control system is configured to connect to the sensing feedback component (6) and calculate the thermal radial expansion of the spindle rotor (2) during turning based on the monitoring data and perform adaptive control.

10. The omnidirectional self-locking structure for a milling-turning composite electric spindle according to claim 9, characterized in that, The thrust end face of the annular piston (5) is designed as an arc protrusion (502). The arc protrusion (502) forms a line contact with the side surface of the elastic diaphragm chuck (3). The line contact position is located between the root and the end of the elastic flap (301) of the elastic diaphragm chuck (3).

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