Offshore wind power main shaft finishing clamp

Abstract

This invention provides a precision machining fixture for offshore wind turbine spindles, belonging to the field of machine tool processing technology. It includes a clamping mechanism for clamping the spindle to be machined; a clamping force adjustment mechanism connected to the clamping mechanism for adjusting the clamping force; an acoustic emission sensor installed near the spindle clamping area for detecting acoustic emission signals generated by the release of residual stress inside the spindle; a vibration sensor installed near the clamping area for detecting vibration signals of the spindle relative to the clamping mechanism; a displacement sensor installed on a support base outside the clamping mechanism, with its detection direction facing the outer cylindrical surface of the spindle, for detecting radial displacement signals of the spindle relative to the clamping mechanism; a machining status identification module for acquiring current machining status information; and a controller connected to the clamping force adjustment mechanism, acoustic emission sensor, vibration sensor, displacement sensor, and machining status identification module.

Description

Technical Field

[0001] This invention relates to the field of machine tool processing technology, and in particular to a precision machining fixture for offshore wind turbine main shafts. Background Technology

[0002] Offshore wind turbine main shafts are long, heavy, and have complex internal residual stress distributions. During the finishing process, the removal of material can easily cause the residual stress to be released again. Current finishing methods for offshore wind turbine main shafts typically use hydraulic chucks, collets, or other clamping devices to hold the main shaft in place. The clamping force is set according to the workpiece specifications before machining begins, and the fixed clamping state is maintained during machining.

[0003] However, during finishing, as cutting continues, residual stress inside the spindle may gradually release, causing local deformation of the spindle or changes in the stress state of the clamping area. Simultaneously, cutting vibrations accumulate and are transmitted to the clamping area, causing workpiece displacement relative to the clamping mechanism. When these changes occur, traditional fixtures, lacking real-time sensing of the workpiece's state, continue to clamp according to a preset clamping force, unable to adjust based on the actual spindle condition. While existing technologies utilize vibration or displacement detection to monitor the machining state, most rely solely on a single detection signal for clamping adjustments. This makes it difficult to accurately distinguish between changes in clamping stability caused by different factors such as residual stress release, insufficient clamping, and excessive clamping, leading to potential misadjustments that affect machining accuracy and surface quality. Summary of the Invention

[0004] The present invention aims to solve the above-mentioned technical problems by providing a precision machining fixture for offshore wind turbine main shafts.

[0005] The technical solution of this invention is a precision machining fixture for offshore wind turbine main shafts, comprising: Clamping mechanism, used to clamp the spindle to be machined; A clamping force adjustment mechanism, connected to the clamping mechanism, is used to adjust the clamping force of the clamping mechanism; An acoustic emission sensor, installed near the spindle clamping area, is used to detect acoustic emission signals generated by the release of residual stress inside the spindle. A vibration sensor, installed near the clamping area, is used to detect vibration signals of the spindle relative to the clamping mechanism; A displacement sensor is mounted on a support base on the outside of the clamping mechanism, with its detection direction facing the outer circular surface of the spindle, and is used to detect the radial displacement signal of the spindle relative to the clamping mechanism. The processing status recognition module is used to obtain the current processing status information; The controller is connected to the clamping force adjustment mechanism, the acoustic emission sensor, the vibration sensor, the displacement sensor, and the machining state recognition module, respectively. The controller is configured to: construct the current clamping state based on the acoustic emission signal, the vibration signal, the radial displacement signal, and the machining state information; determine whether a state transition has occurred based on the clamping state; and determine the corresponding clamping control mode based on the state transition result, and control the clamping force adjustment mechanism to adjust the clamping force according to the determined clamping control mode to maintain clamping stability during the spindle finishing process.

[0006] In one implementation, the controller performs hierarchical dynamic clamping control based on the acoustic emission signal, the vibration signal, the radial displacement signal, and the processing status information. The hierarchical dynamic clamping control includes at least stress monitoring control, vibration suppression control, and adaptive trial control. The controller switches between stress monitoring control, vibration suppression control and adaptive trial control according to the current clamping state, and controls the clamping force adjustment mechanism to execute the clamping force adjustment strategy corresponding to the current control mode. The stress release state corresponds to the stress monitoring and control, the vibration accumulation state corresponds to the vibration suppression control, and the clamping instability state corresponds to the adaptive trial control.

[0007] In one implementation, the controller pre-stores multiple reference parameter sets corresponding to processing stages. The reference parameter sets include a reference parameter set for determining stress release state, a reference parameter set for determining vibration accumulation state, and a reference parameter set for determining clamping instability state. The controller calls the corresponding reference parameter set according to the processing stage identified by the processing state identification module, and performs clamping state determination based on the called reference parameter set.

[0008] As one implementation, the stress release state corresponds to the stress monitoring and control mode. When the controller detects that the acoustic emission signal meets the stress release judgment condition corresponding to the current processing stage, it determines the current clamping state as a stress release state. The controller controls the clamping force adjustment mechanism to perform an adjustment operation to maintain the current clamping force or increase the clamping force based on the comparison result between the radial displacement signal and the corresponding displacement reference parameter.

[0009] As one implementation, the vibration accumulation state corresponds to the vibration suppression control mode. When the controller detects that the vibration signal meets the vibration accumulation judgment condition and the radial displacement signal shows periodic change characteristics, it determines the current clamping state as the vibration accumulation state. The controller controls the clamping force adjustment mechanism to perform periodic clamping force disturbances, including a pressure boosting phase, a pressure holding phase, and a recovery phase, in order to suppress the trend of continuous increase in vibration during the processing.

[0010] As one implementation, the clamping instability state corresponds to an adaptive trial control mode. When the controller detects that the acoustic emission signal, vibration signal and radial displacement signal simultaneously meet the clamping instability judgment conditions, it determines the current clamping state as a clamping instability state. The controller controls the clamping force adjustment mechanism to apply a trial adjustment to the current clamping force, and at the same time acquires the response change information of the acoustic emission signal, vibration signal and radial displacement signal after the trial adjustment. The controller determines the clamping influencing factors corresponding to the change in clamping stability based on the response change information, and generates a corresponding clamping force adjustment strategy accordingly.

[0011] As one implementation, the tentative adjustment is a single transient active disturbance operation that reduces the current clamping force. After completing the active disturbance operation, the controller acquires the response change information of the acoustic emission signal, the vibration signal, and the radial displacement signal within a preset time window.

[0012] As one implementation, when the response change information indicates that the acoustic emission signal, vibration signal, and radial displacement signal are all decreasing, the controller determines that the current change in clamping stability is caused by excessive clamping force and generates an adjustment strategy to reduce the clamping force.

[0013] As one implementation, when the response change information does not indicate that the acoustic emission signal, vibration signal, and radial displacement signal are all decreasing in a common way, the controller determines that the current change in clamping stability is caused by insufficient clamping force and generates an adjustment strategy to increase the clamping force.

[0014] In one implementation, the controller controls the clamping force adjustment mechanism to adjust the clamping force to a new target clamping force according to the generated clamping force adjustment strategy, and continuously corrects the target clamping force based on subsequently acquired acoustic emission signals, vibration signals, and radial displacement signals.

[0015] The advantages of this invention compared to the prior art are that it acquires various processing state information through acoustic emission sensors, vibration sensors, displacement sensors, and processing state recognition modules, and constructs the current clamping state based on the acquired information, enabling the controller to comprehensively determine the clamping state during the spindle processing process and improve the accuracy of clamping state recognition.

[0016] This invention determines the corresponding clamping control mode based on whether a state transition occurs during clamping, and switches between stress monitoring control, vibration suppression control, and adaptive trial control. This allows the clamping force adjustment to match the actual state changes during spindle machining, thereby improving clamping stability. Specifically, in the stress release state, judgment is made by combining acoustic emission signals and radial displacement signals. In the vibration accumulation state, the trend of continuous vibration enhancement is suppressed by periodic clamping force perturbation, which helps to reduce unnecessary clamping force adjustments and reduce the impact of vibration on the machining process.

[0017] Furthermore, in the case of clamping instability, this invention tentatively adjusts the current clamping force and obtains information on the changes in the adjusted response to determine the clamping influencing factors corresponding to changes in clamping stability, and then generates a corresponding clamping force adjustment strategy. Compared to directly adjusting based on detection results, the control method adopted by this invention can improve the targeting and rationality of clamping force adjustment, thereby improving clamping stability, machining accuracy, and machining quality during the precision machining process of offshore wind turbine main shafts. Attached Figure Description

[0018] Figure 1 A first view of a precision machining fixture for offshore wind turbine main shafts provided in an embodiment of the present invention; Figure 2 A second view of the offshore wind turbine main shaft finishing fixture provided in an embodiment of the present invention; Figure 3 A hardware connection block diagram of the offshore wind turbine main shaft precision machining fixture provided for an embodiment of the present invention; In the diagram: 1. Support base; 2. Clamping mechanism; 3. Clamping force adjustment mechanism; 4. Acoustic emission sensor; 5. Vibration sensor; 6. Displacement sensor; 7. Processing status recognition module; 8. Controller. Detailed Implementation

[0019] The above and other embodiments and advantages of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0020] like Figures 1 to 3As shown, a precision machining fixture for offshore wind turbine main shafts includes a clamping mechanism 2, a clamping force adjustment mechanism 3, an acoustic emission sensor 4, a vibration sensor 5, a displacement sensor 6, a controller 8, and a machining status identification module 7. The clamping mechanism 2 is used to clamp the offshore wind turbine main shaft to be machined. In this embodiment, the clamping mechanism 2 can be a hydraulic chuck, a hydraulic collet, or other clamping device capable of providing radial clamping force. The clamping force adjustment mechanism 3 is connected to the clamping mechanism 2 and is used to adjust the clamping force generated by the clamping mechanism 2. The clamping force adjustment mechanism 3 preferably includes a hydraulic power unit, an electro-hydraulic proportional regulating valve, and a pressure actuation component, and the clamping force is changed by adjusting the hydraulic output pressure. The acoustic emission sensor 4 is installed near the clamping area to detect the acoustic emission signal generated during the release of residual stress inside the main shaft in real time. The vibration sensor 5 is installed near the clamping area to detect the vibration changes between the main shaft and the clamping mechanism 2 during machining. Displacement sensor 6 is mounted on the outer support 1 of clamping mechanism 2, with its detection direction facing the outer cylindrical surface of the spindle, and is used to detect the radial displacement change of the spindle relative to clamping mechanism 2. Machining state identification module 7 is communicatively connected to the machine tool control system to acquire information about the current machining stage. Preferably, machining state identification module 7 acquires the machine tool speed, feed rate, and current tool position, and identifies the current machining stage (roughing, semi-finishing, or finishing) based on the acquired information. Controller 8 is connected to clamping force adjustment mechanism 3, acoustic emission sensor 4, vibration sensor 5, displacement sensor 6, and machining state identification module 7. Controller 8 receives data collected by the aforementioned sensors and constructs the current clamping state based on the received data.

[0021] In this embodiment, the controller 8 divides the clamping state into a stable state, a stress-relief state, a vibration accumulation state, and a clamping instability state. The controller 8 calls the corresponding reference parameter set based on the processing stage identified by the processing state identification module 7. Different processing stages correspond to different reference parameter sets.

[0022] For example, in the roughing stage, a larger cutting volume allows for a wider range of vibration variations; in the finishing stage, due to the higher machining accuracy requirements, the vibration reference parameters and displacement reference parameters are correspondingly reduced. After calling the corresponding reference parameter group according to the current machining stage, controller 8 performs a comprehensive analysis of the acoustic emission signal, vibration signal, and radial displacement signal to determine the clamping state.

[0023] When the controller 8 detects that the acoustic emission signal meets the stress release judgment condition, it indicates that the residual stress inside the spindle has begun to be released. At this time, the controller 8 switches from the current clamping state to the stress release state and enters the stress monitoring and control mode. In the stress monitoring and control mode, if the radial displacement signal does not reach the corresponding displacement reference parameter, it indicates that the residual stress release has not yet caused significant deformation, and the controller 8 maintains the current clamping force unchanged. If the radial displacement signal reaches the corresponding displacement reference parameter, it indicates that the residual stress release has caused the spindle to produce an actual displacement change, and the controller 8 controls the clamping force adjustment mechanism 3 to increase the clamping force to compensate for the decrease in clamping stability.

[0024] When the controller 8 detects that the vibration signal meets the vibration accumulation judgment condition and the radial displacement signal exhibits periodic variation characteristics, the controller 8 transitions the current clamping state to the vibration accumulation state and enters the vibration suppression control mode. In the vibration suppression control mode, the controller 8 controls the clamping force adjustment mechanism 3 to perform periodic clamping force disturbances. These periodic clamping force disturbances include a pressure increase phase, a pressure holding phase, and a recovery phase. By periodically changing the clamping force, the inherent response of the clamping system changes, thereby weakening the trend of continuous vibration enhancement and suppressing the further development of machining chatter.

[0025] When the controller 8 detects that the acoustic emission signal, vibration signal, and radial displacement signal simultaneously meet the clamping instability judgment condition, the controller 8 transitions the current clamping state to the clamping instability state and enters the adaptive trial control mode. In the adaptive trial control mode, the controller 8 first controls the clamping force adjustment mechanism 3 to perform a trial adjustment of the current clamping force. In this embodiment, the trial adjustment adopts a single transient reduction of the current clamping force as an active disturbance. The controller 8 sends a decompression command to the clamping force adjustment mechanism 3 to reduce the clamping force by a preset amplitude. After the decompression is completed, the controller 8 continuously collects the acoustic emission signal, vibration signal, and radial displacement signal within a preset time window and obtains the corresponding response change information. If the controller 8 detects that the acoustic emission signal, vibration signal, and radial displacement signal all show a downward trend, it determines that the current clamping stability change is mainly caused by excessive clamping force. At this time, the controller 8 generates an adjustment strategy to reduce the clamping force and controls the clamping force adjustment mechanism 3 to adjust the clamping force to a level lower than the target clamping force before the disturbance. If the controller 8 detects that the above signals do not show a common decreasing trend, it determines that the current change in clamping stability is mainly caused by insufficient clamping force. At this time, the controller 8 generates an adjustment strategy to increase the clamping force and controls the clamping force adjustment mechanism 3 to adjust the clamping force to a level higher than the target clamping force before the disturbance. After completing the clamping force adjustment, the controller 8 continues to collect acoustic emission signals, vibration signals, and radial displacement signals, and continuously corrects the target clamping force based on the subsequent collection results, so that the clamping force is always kept within a range suitable for the current processing state.

[0026] Through the above scheme, the present invention can not only detect the release of residual stress, vibration accumulation and displacement changes during the spindle machining process, but also identify the root cause of the decrease in clamping stability through active disturbance, and generate a targeted clamping force adjustment strategy accordingly, thereby achieving adaptive control of clamping force and improving clamping stability, dimensional accuracy and surface finish during the precision machining of offshore wind turbine spindles.

[0027] The specific embodiments described above further illustrate the inventive purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. In particular, it should be noted that any modifications, equivalent substitutions, or improvements made by those skilled in the art within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A precision machining fixture for offshore wind turbine main shafts, characterized in that, include Clamping mechanism, used to clamp the spindle to be machined; A clamping force adjustment mechanism, connected to the clamping mechanism, is used to adjust the clamping force of the clamping mechanism; An acoustic emission sensor, installed near the spindle clamping area, is used to detect acoustic emission signals generated by the release of residual stress inside the spindle. A vibration sensor, installed near the clamping area, is used to detect vibration signals of the spindle relative to the clamping mechanism; A displacement sensor is mounted on a support base on the outside of the clamping mechanism, with its detection direction facing the outer circular surface of the spindle, and is used to detect the radial displacement signal of the spindle relative to the clamping mechanism. The processing status recognition module is used to obtain the current processing status information; The controller is connected to the clamping force adjustment mechanism, the acoustic emission sensor, the vibration sensor, the displacement sensor, and the processing state recognition module, respectively. The controller is configured to: construct the current clamping state based on the acoustic emission signal, the vibration signal, the radial displacement signal, and the processing state information; and determine whether a state transition has occurred in the current clamping state based on the clamping state. Based on the state transition results, the corresponding clamping control mode is determined, and the clamping force adjustment mechanism is controlled to adjust the clamping force according to the determined clamping control mode in order to maintain the clamping stability during the spindle finishing process.

2. The offshore wind turbine main shaft precision machining fixture according to claim 1, characterized in that, The controller performs hierarchical dynamic clamping control based on the acoustic emission signal, the vibration signal, the radial displacement signal, and the processing status information. The hierarchical dynamic clamping control includes at least stress monitoring control, vibration suppression control, and adaptive trial control. The controller switches between stress monitoring control, vibration suppression control and adaptive trial control according to the current clamping state, and controls the clamping force adjustment mechanism to execute the clamping force adjustment strategy corresponding to the current control mode. The stress release state corresponds to the stress monitoring and control, the vibration accumulation state corresponds to the vibration suppression control, and the clamping instability state corresponds to the adaptive trial control.

3. The offshore wind turbine main shaft precision machining fixture according to claim 2, characterized in that, The controller has pre-stored multiple reference parameter sets corresponding to processing stages. The reference parameter sets include a reference parameter set for determining stress release state, a reference parameter set for determining vibration accumulation state, and a reference parameter set for determining clamping instability state. The controller calls the corresponding reference parameter set according to the processing stage identified by the processing state identification module, and performs clamping state determination based on the called reference parameter set.

4. The offshore wind turbine main shaft precision machining fixture according to claim 2 or 3, characterized in that, The stress release state corresponds to the stress monitoring and control mode. When the controller detects that the acoustic emission signal meets the stress release judgment condition corresponding to the current processing stage, it determines the current clamping state as a stress release state. The controller controls the clamping force adjustment mechanism to perform an adjustment operation to maintain the current clamping force or increase the clamping force based on the comparison result between the radial displacement signal and the corresponding displacement reference parameter.

5. The offshore wind turbine main shaft precision machining fixture according to claim 2 or 3, characterized in that, The vibration accumulation state corresponds to the vibration suppression control mode. When the controller detects that the vibration signal meets the vibration accumulation judgment condition and the radial displacement signal shows periodic change characteristics, it determines the current clamping state as the vibration accumulation state. The controller controls the clamping force adjustment mechanism to perform periodic clamping force disturbances, including a pressure boosting phase, a pressure holding phase, and a recovery phase, in order to suppress the trend of continuous increase in vibration during the processing.

6. The offshore wind turbine main shaft precision machining fixture according to claim 2, characterized in that, The clamping instability state corresponds to an adaptive trial control mode. When the controller detects that the acoustic emission signal, vibration signal and radial displacement signal simultaneously meet the clamping instability judgment conditions, it determines the current clamping state as a clamping instability state. The controller controls the clamping force adjustment mechanism to apply a trial adjustment to the current clamping force, and at the same time acquires the response change information of the acoustic emission signal, vibration signal and radial displacement signal after the trial adjustment. The controller determines the clamping influencing factors corresponding to the change in clamping stability based on the response change information, and generates a corresponding clamping force adjustment strategy accordingly.

7. The offshore wind turbine main shaft precision machining fixture according to claim 6, characterized in that, The tentative adjustment is a single transient active disturbance operation that reduces the current clamping force. After completing the active disturbance operation, the controller acquires the response change information of the acoustic emission signal, the vibration signal, and the radial displacement signal within a preset time window.

8. The offshore wind turbine main shaft precision machining fixture according to claim 7, characterized in that, When the response change information indicates that the acoustic emission signal, vibration signal, and radial displacement signal are all decreasing, the controller determines that the current change in clamping stability is caused by excessive clamping force and generates an adjustment strategy to reduce the clamping force.

9. The offshore wind turbine main shaft precision machining fixture according to claim 7, characterized in that, When the response change information does not indicate that the acoustic emission signal, vibration signal, and radial displacement signal are all decreasing in a common way, the controller determines that the current change in clamping stability is caused by insufficient clamping force and generates an adjustment strategy to increase the clamping force.

10. The offshore wind turbine main shaft precision machining fixture according to claim 8 or 9, characterized in that, The controller controls the clamping force adjustment mechanism to adjust the clamping force to a new target clamping force according to the generated clamping force adjustment strategy, and continuously corrects the target clamping force based on the subsequently acquired acoustic emission signal, vibration signal and radial displacement signal.

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