Numerically controlled machine tool screw heat error active compensation device and method

Abstract

The application discloses a numerical control machine tool screw thermal error active compensation device and method, and relates to the technical field of precision machinery manufacturing. The numerical control machine tool screw thermal error active compensation device comprises a screw, a fixed support assembly, a pre-tensioning mechanism and a control system. The fixed support assembly is rigidly fixed with one end of the screw. The pre-tensioning mechanism comprises a floating support assembly, a reverse piezoelectric ceramic actuator and a force sensor. The reverse piezoelectric ceramic actuator is connected with the other end of the screw through the force sensor. The reverse piezoelectric ceramic actuator is connected with the floating support assembly through a connecting shaft. The control system is electrically connected with the reverse piezoelectric ceramic actuator and the sensor. The numerical control machine tool screw thermal error active compensation device and method can actively and accurately offset the thermal elongation of the screw in real time.

Description

Technical Field

[0001] This application relates to the field of precision machinery manufacturing technology, and in particular to a device and method for active compensation of thermal error of CNC machine tool lead screw. Background Technology

[0002] As a core transmission component of precision equipment such as CNC machine tools, the positioning accuracy of ball screws directly determines the machining accuracy of the equipment. During high-speed operation, the ball screw undergoes significant thermal expansion due to friction and temperature rise, leading to errors in the lead and a decrease in positioning accuracy, known as "thermal error." This is one of the key bottlenecks restricting the performance improvement of high-precision machining equipment.

[0003] In existing technologies, common methods for addressing thermal errors in lead screws include: 1. Forced cooling, which cools the lead screw using oil or air cooling. However, this method is complex, energy-intensive, and can only slow down the rate of temperature rise, not eliminate existing thermal expansion. Furthermore, the thermal inertia of the cooling medium causes a delay in temperature control, resulting in limited compensation. 2. Fixed pre-tensioning, which applies a fixed pre-tensioning force during lead screw installation to induce an initial negative elastic deformation, partially offsetting thermal expansion within the expected range. The compensation amount is based on an estimated, fixed maximum temperature rise (…). The design is a passive compensation method with a fixed compensation amount. In actual working conditions, the temperature rise of the lead screw is dynamic, causing it to be in an "undercompensated" or "overcompensated" state for most of the working time. Therefore, it cannot adapt to the dynamic thermal expansion under varying working conditions, resulting in inaccurate compensation. In addition, excessive pre-tension force will increase friction and wear. 3. Software error compensation, which establishes a thermal error model and performs backlash compensation in the CNC system. This method is affected by model accuracy and detection delay, resulting in lag, and cannot compensate for changes in lead screw rigidity. 4. Improving the lead screw structure or materials to reduce thermal error, such as using materials with low thermal expansion coefficients to manufacture the lead screw, or designing special structures to enhance the thermal stability of the lead screw. However, these methods face the problem of high cost. Materials with low thermal expansion coefficients, such as ceramic matrix composites, are several times or even tens of times more expensive than ordinary steel, which greatly increases the manufacturing cost of machine tools and limits their widespread application. Moreover, structural improvements (such as hollow cooling channels) often increase the complexity and manufacturing difficulty of the lead screw, requiring higher processing technology and further increasing costs. Summary of the Invention

[0004] The purpose of this application is to provide a device and method for active compensation of thermal error of CNC machine tool lead screw, which can actively and accurately compensate for thermal expansion of lead screw in real time.

[0005] To achieve the above objectives, this application provides an active thermal error compensation device for CNC machine tool lead screws, comprising: a lead screw, a fixed support assembly, a pre-tensioning mechanism, and a control system;

[0006] The fixed support assembly is rigidly fixed to one end of the lead screw;

[0007] The pre-tensioning mechanism includes a floating support assembly, a reverse piezoelectric ceramic actuator, and a force sensor. The reverse piezoelectric ceramic actuator is connected to the other end of the lead screw through the force sensor, and the reverse piezoelectric ceramic actuator is connected to the floating support assembly through a connecting shaft.

[0008] The control system is electrically connected to the inverted piezoelectric ceramic actuator and the force sensor.

[0009] In some embodiments, the fixed support assembly includes a fixed support base, a fixed bearing, a fixed pressure cap, and a locking nut. The bearing is mounted on the fixed support base, the lead screw is rotatably engaged with the fixed bearing, and the locking nut is sleeved on the lead screw and abuts against the fixed bearing.

[0010] In some embodiments, the floating support assembly includes a floating bearing housing, a floating bearing, a butterfly spring, a preload cover, a retaining ring, and an adjusting screw. The preload cover and the floating bearing housing form a mating cavity. The adjusting screw is used to fix the preload cover to the floating bearing housing. The floating bearing is slidably fitted in the mating cavity and is movable relative to the floating bearing housing along its axial direction. The connecting shaft is rotatably fitted with the floating bearing. The butterfly spring is disposed on both sides of the floating bearing, and the retaining ring is disposed between the floating bearing and the connecting shaft.

[0011] In some embodiments, a temperature sensor is also provided, which is mounted on the lead screw via a nut connector and a nut, the temperature sensor abutting against the lead screw, and the temperature sensor being electrically connected to the control system.

[0012] In some embodiments, the control system includes a signal processing unit, a control algorithm unit, and a high-voltage drive circuit. The signal processing unit is used to receive signals from the force sensor and the temperature sensor. The control algorithm unit is used to calculate the required control voltage based on the signals received by the signal processing unit. The high-voltage drive circuit is used to input a high-voltage control signal to the brake based on the output signal of the control algorithm unit, so as to drive the inverse piezoelectric ceramic actuator to move.

[0013] In some embodiments, the signal processing unit has a built-in thermal expansion model and an inverse piezoelectric ceramic actuator control model. The thermal expansion model can calculate the thermal expansion and contraction of the lead screw based on the temperature change measured by the temperature sensor, and the inverse piezoelectric ceramic actuator control model can calculate the required control voltage.

[0014] In some embodiments, the inverse piezoelectric ceramic actuator employs a stacked structure.

[0015] In some embodiments, the reverse piezoelectric ceramic actuator is provided with heat dissipation fins on its exterior.

[0016] In some embodiments, an insulating pad is also provided, which is disposed between the reverse piezoelectric ceramic actuator and the force sensor, as well as between the reverse piezoelectric ceramic actuator and the floating support assembly.

[0017] A method for compensating the thermal error of a CNC machine tool lead screw in an active compensation device according to any one of the above claims, comprising:

[0018] When the lead screw is cold, the control system applies an initial voltage to the inverted piezoelectric ceramic actuator, causing the inverted piezoelectric ceramic actuator to apply an initial pre-tension force to the lead screw;

[0019] During the operation of the lead screw, temperature and preload changes are detected by temperature and force sensors.

[0020] Based on the monitored changes, the voltage applied to the reverse piezoelectric ceramic actuator is dynamically adjusted by the control system to drive the corresponding displacement of the reverse piezoelectric ceramic actuator, so as to maintain the pre-tension force constant or directly offset the calculated thermal elongation.

[0021] Compared to the background technology described above, the active thermal error compensation device for CNC machine tool lead screws provided in this application includes a lead screw, a fixed support assembly, a pre-tensioning mechanism, and a control system. The fixed support assembly is rigidly fixed to one end of the lead screw. The pre-tensioning mechanism includes a floating support assembly, a reverse piezoelectric ceramic actuator, and a force sensor. The reverse piezoelectric ceramic actuator is connected to the other end of the lead screw through the force sensor. The reverse piezoelectric ceramic actuator is connected to the floating support assembly through a connecting shaft. The control system is electrically connected to the reverse piezoelectric ceramic actuator and the sensor. A fixed support assembly and a pre-tensioning mechanism support the two ends of the lead screw, respectively. One end of the lead screw is fixed to the fixed support assembly. An inverse piezoelectric ceramic actuator applies an initial pre-tensioning force to the lead screw. When the lead screw expands due to temperature rise, a force sensor detects the change in the measured preload and transmits the data to the control system. The control system adjusts the voltage applied to the inverse piezoelectric ceramic actuator accordingly and moves the actuator so that the preload measured by the force sensor equals the pre-tensioning force. This achieves real-time compensation of the thermal expansion force of the lead screw caused by temperature rise, thus keeping the lead screw at a constant effective length and eliminating positioning errors caused by thermal elongation. The CNC machine tool lead screw thermal error active compensation device and method of this application utilizes the inverse piezoelectric effect of inverse piezoelectric ceramics to achieve nanometer-level precision, millisecond-level response, and dynamic adaptive lead screw thermal error suppression. This improves the stability and accuracy retention of high-precision machine tools under long-term, variable operating conditions; reduces the scrap rate caused by thermal errors; and improves production efficiency. It provides a compact and easy-to-modify solution for upgrading the precision of existing machine tools. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the active thermal error compensation device for CNC machine tool lead screws according to an embodiment of this application;

[0024] Figure 2 This is a cross-sectional view of the active thermal error compensation device for the CNC machine tool lead screw according to an embodiment of this application;

[0025] Figure 3 for Figure 2 Enlarged view of point A in the middle;

[0026] Figure 4 This is a schematic diagram of the pre-tensioning mechanism according to an embodiment of this application;

[0027] Figure 5This is a schematic diagram of the installation of the temperature sensor according to an embodiment of this application;

[0028] Figure 6 This is a cross-sectional view of the inverse piezoelectric ceramic actuator according to an embodiment of this application;

[0029] Figure 7 This is a flowchart illustrating the lead screw thermal error compensation method of the active compensation device for lead screw thermal error in CNC machine tools, as described in this application.

[0030] in:

[0031] 1. Lead screw; 2. Fixed support assembly; 21. Fixed bearing housing; 22. Fixed bearing; 23. Fixed gland; 24. Locking nut; 3. Pre-tensioning mechanism; 31. Reverse piezoelectric ceramic actuator; 311. Heat sink fins; 32. Force sensor; 33. Floating support assembly; 331. Floating bearing housing; 332. Floating bearing; 333. Disc spring; 334. Pre-tightening gland; 335. Snap ring; 336. Adjusting screw; 34. Connecting shaft; 4. Temperature sensor; 5. Nut connector; 6. Nut; 7. Insulating gasket; 8. Conductive slip ring. Detailed Implementation

[0032] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0033] To enable those skilled in the art to better understand the present application, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0034] It should be noted that the directional terms such as "upper end," "lower end," "left side," and "right side" mentioned below are defined based on the accompanying drawings in the instruction manual.

[0035] like Figures 1 to 6 As shown in the embodiment of this application, the active thermal error compensation device for CNC machine tool lead screws includes a lead screw 1, a fixed support assembly 2, a pre-tensioning mechanism 3, and a control system. The fixed support assembly 2 is rigidly fixed to one end of the lead screw 1. The pre-tensioning mechanism 3 includes a floating support assembly 33, a reverse piezoelectric ceramic actuator 31, and a force sensor 32. The reverse piezoelectric ceramic actuator 31 is connected to the other end of the lead screw 1 through the force sensor 32. The reverse piezoelectric ceramic actuator 31 is connected to the floating support assembly 33 through a connecting shaft 34. The control system is electrically connected to the reverse piezoelectric ceramic actuator 31 and the sensor.

[0036] Understandably, the force sensor 32 can be a high-precision strain gauge force sensor connected in series in the force flow path to directly measure the actual preload force acting on the lead screw 1 in real time. The fixed support assembly 2 and the pretensioning mechanism 3 support the two ends of the lead screw 1 respectively. One end of the lead screw 1 is fixed to the fixed support assembly 2. The reverse piezoelectric ceramic actuator 31 applies an initial pretension force to the lead screw 1. When the lead screw 1 expands due to temperature rise, the force sensor 32 can detect the change in the measured preload force and transmit the data to the control system. The control system adjusts the voltage applied to the reverse piezoelectric ceramic actuator 31 accordingly and moves the reverse piezoelectric ceramic actuator 31 so that the preload force measured by the force sensor 32 is equal to the pretension force, thereby achieving real-time cancellation of the thermal expansion force generated by the temperature rise of the lead screw 1, so that the lead screw 1 always maintains a constant effective length and eliminates the positioning error caused by the thermal elongation of the lead screw 1.

[0037] In some embodiments, such as Figures 1 to 3 As shown, the fixed support assembly 2 includes a fixed support base, a fixed bearing 22, a fixed pressure cover 23, and a locking nut 24. The bearing is installed on the fixed support base, the lead screw 1 is rotatably engaged with the fixed bearing 22, and the locking nut 24 is sleeved on the lead screw 1 and abuts against the fixed bearing 22.

[0038] Specifically, the fixed bearing 22 can be a paired bearing to completely eliminate the clearance between the fixed bearing 22 and the fixed bearing housing 21. The fixed cover 23 can be installed on the fixed bearing housing 21 to prevent the fixed bearing 22 from detaching from the fixed bearing housing 21, and the lead screw 1 is completely fixed under the action of the locking nut 24.

[0039] It is understandable that by setting the fixed support component 2, the thermal elongation of the lead screw 1 after it heats up tends to be closer to one end of the pre-tensioning mechanism 3.

[0040] In some embodiments, such as Figure 1 , Figure 2 and Figure 4 As shown, the floating support assembly 33 includes a floating bearing seat 331, a floating bearing 332, a butterfly spring 333, a preload cover 334, a retaining ring 335, and an adjusting screw 336. The preload cover 334 and the floating bearing seat 331 form a mating cavity. The adjusting screw 336 is used to fix the preload cover 334 to the floating bearing seat 331. The floating bearing 332 is slidably fitted in the mating cavity and can move relative to the floating bearing seat 331 along its axial direction. The connecting shaft 34 is rotatably fitted with the floating bearing 332. The butterfly spring 333 is located on both sides of the floating bearing 332, and the retaining ring 335 is located between the floating bearing 332 and the connecting shaft 34.

[0041] It is understood that the connecting shaft 34 is coaxially distributed with the lead screw 1. The connecting shaft 34 is provided with a positioning groove. One end of the snap ring 335 is connected to the groove wall of the positioning groove, and the other end is connected to the floating bearing 332. The snap ring 335 is used to position the floating bearing 332 axially on the connecting shaft 34. The preload cover 334 is used to prevent the floating bearing 332 from falling out of the mating cavity. By adjusting the adjusting screw 336, the preload cover 334 can be adjusted to press the floating bearing 332. The floating bearing 332 is elastically preloaded by the butterfly springs 333 on both sides of the floating bearing 332, thereby eliminating the axial clearance of the floating bearing 332 in the initial state. The outer ring of the floating bearing 332 and the inner hole of the floating bearing seat 331 are H7 / g6 clearance fit, which allows the floating bearing 332 to move axially relative to the floating bearing seat 331 in the mating cavity, while preventing the floating bearing 332 from rotating relative to the floating bearing seat 331. During the initial pre-tension, the reverse piezoelectric ceramic actuator 31 contracts and applies a force to the lead screw 1 and the floating bearing 332 until the outer ring of the floating bearing 332 compresses the disc spring 333 and reaches equilibrium, thereby establishing the initial tension. .

[0042] In some embodiments, such as Figure 1 , Figure 2 and Figure 5 As shown, a temperature sensor 5 is also provided. The temperature sensor 5 is installed on the lead screw 1 through a nut connector 5 and a nut 6. The temperature sensor 5 abuts against the lead screw 1 and is electrically connected to the control system.

[0043] It is understandable that the temperature sensor 5 can be a PT100 platinum resistance thermometer or a thermocouple, and is installed on the nut 6 of the lead screw 1, which is most prone to heat generation, or on the surface of the lead screw 1. The temperature sensor 5 can monitor the temperature of the lead screw 1 in real time and reflect the temperature change of the lead screw 1 during its operation.

[0044] In some embodiments, the control system includes a signal processing unit, a control algorithm unit, and a high-voltage drive circuit. The signal processing unit is used to receive signals from the force sensor 32 and the temperature sensor 5. The control algorithm unit is used to calculate the required control voltage based on the signals received by the signal processing unit. The high-voltage drive circuit is used to input a high-voltage control signal to the brake based on the output signal of the control algorithm unit, so as to drive the inverse piezoelectric ceramic actuator 31 to move.

[0045] Understandably, the signal processing unit filters, amplifies, performs AD conversion, and improves the signal-to-noise ratio of the signals emitted by the force sensor 32 and the temperature sensor 5. The control algorithm unit controls the output of the high-voltage drive unit through an algorithm, thereby precisely driving the inverted piezoelectric ceramic actuator 31.

[0046] Based on the above embodiments, the signal processing unit has a built-in thermal expansion model and an inverse piezoelectric ceramic actuator control model. The thermal expansion model can calculate the thermal expansion and contraction of the lead screw 1 based on the temperature change measured by the temperature sensor 5, and calculate the required control voltage through the inverse piezoelectric ceramic actuator control model.

[0047] Specifically, based on the feedback signals from temperature sensor 5 and force sensor 32, the control system calculates the control voltage to be applied to the inverted piezoelectric ceramic actuator 31 using a built-in thermal expansion model and an inverted piezoelectric ceramic actuator control model. This voltage drives the inverted piezoelectric ceramic actuator 31 to produce precise elongation or contraction, thereby increasing or decreasing the pre-tension force on the lead screw 1, ensuring that the effective length of the lead screw 1 remains constant under thermal deformation. The control strategy of the control system includes the following three strategies:

[0048] Feedforward control: Based on the temperature signal, predict the impending thermal error using a thermal expansion model, calculate the compensation voltage, and take action in advance;

[0049] Feedback control: Based on the force sensor 32 signal, the preload is kept constant through PID algorithm to eliminate the prediction error of the feedforward model and various unmodeled disturbances;

[0050] Composite control: It integrates temperature and force signals. Feedforward control is responsible for "coarse adjustment" to quickly offset most of the thermal expansion force, while feedback control is responsible for "fine adjustment" to precisely eliminate the remaining error. The combination of the two ensures both the speed of the system and the final accuracy and stability, thus improving the composite accuracy.

[0051] Taking composite control as an example, its specific implementation method is as follows:

[0052] Step 1: Determine if the system is in the cold initialization phase. If so, the control system applies a preset initial voltage to the inverting piezoelectric ceramic actuator 31. This establishes a precise initial preload. This force serves as the benchmark for all subsequent compensation operations. Once completed, the system enters a continuous running loop.

[0053] Step 2: In each control cycle, the system synchronously collects two key physical quantities:

[0054] Temperature sensor 5 reads the current temperature of lead screw 1 ;

[0055] The force sensor 32 reads the actual preload currently acting on the lead screw 1. .

[0056] Step 3, Feedforward control path (predictive compensation)

[0057] Calculate the temperature rise: ( (This refers to either the cold reference temperature or the dynamically updated reference temperature).

[0058] Predicting deformation: based on materials science formulas Calculate the theoretical thermal elongation of lead screw 1 (where α is the linear expansion coefficient of lead screw 1 material, and L is the effective length of lead screw 1);

[0059] Calculate the feedforward: Based on the displacement-voltage coefficient Kd of the inverse piezoelectric ceramic, calculate the amount needed to offset... Required feedforward voltage increment .

[0060] Step 3 is the feedforward control path, which has an extremely fast response and can proactively compensate for thermal errors in advance.

[0061] Step 4, Feedback control path (accuracy correction)

[0062] Calculation of force deviation: Ideally, this value should be zero.

[0063] PID calculation: The force deviation e is fed into the PID controller to calculate the feedback voltage correction. ;

[0064] Where Kp, Ki, and Kd are pre-tuned PID parameters.

[0065] Proportional term: Fast response deviation;

[0066] Integral term: Eliminates steady-state error;

[0067] Differential term: suppresses overshoot and improves stability;

[0068] Step 4 is the feedback control path. This path has extremely high precision and can eliminate the prediction error of the feedforward model, overcome unknown interference such as friction changes, and ensure that the preload is kept constant with high accuracy.

[0069] Step 5, synthesize the final control command: superimpose the feedforward and feedback quantities to obtain the total voltage applied to the inverse piezoelectric ceramic actuator 31. ;

[0070] High-voltage drive and execution: The high-voltage drive circuit will... The signal is converted into a high-voltage signal, which drives the inverting piezoelectric ceramic actuator 31 to produce precise micro-displacement. .

[0071] The micro-displacement of the inverse piezoelectric ceramic actuator 31 directly offsets the thermal expansion of the lead screw 1, keeping the effective length of the lead screw 1 constant and fundamentally eliminating positioning errors. After waiting for an extremely short sampling time, the system returns to step 2 and begins the next control cycle, thereby achieving uninterrupted real-time, dynamic, and high-precision compensation.

[0072] In some embodiments, the reverse piezoelectric ceramic actuator 31 employs a stacked structure.

[0073] Understandably, if the reverse piezoelectric ceramic actuator 31 adopts a stacked structure, ideal displacement can be obtained with a smaller voltage, increasing safety performance.

[0074] In some embodiments, such as Figure 6 As shown, the reverse piezoelectric ceramic actuator 31 has heat dissipation fins 311 on its exterior.

[0075] It is understandable that by adding heat dissipation fins 311, the heat dissipation performance of the reverse piezoelectric ceramic actuator 31 is increased, thereby improving its accuracy and reliability.

[0076] In some other embodiments, the inverse piezoelectric ceramic actuator 31 can be replaced with a closed-loop piezoelectric actuator with an internally integrated high-precision strain gauge or capacitive sensor to overcome the inherent hysteresis and creep nonlinearity of piezoelectric materials.

[0077] In some embodiments, an insulating pad 7 is also provided, which is disposed between the reverse piezoelectric ceramic actuator 31 and the force sensor 32, and between the reverse piezoelectric ceramic actuator 31 and the floating support assembly 33.

[0078] Understandably, since the reverse piezoelectric ceramic actuator 31 operates with high voltage, it must be electrically isolated from the machine tool body (grounded) by a high-strength ceramic or composite resin gasket to prevent high voltage from damaging components such as bearings, while ensuring the effective transmission of preload.

[0079] In some embodiments, such as Figure 4 As shown, a conductive slip ring 8 is also provided.

[0080] Specifically, the conductive slip ring 8 is sleeved on the connecting shaft 34 and is located between the reverse piezoelectric ceramic actuator 31 and the floating bearing 332.

[0081] Understandably, the conductive slip ring 8 is used for signal transmission of the reverse piezoelectric ceramic actuator 31.

[0082] like Figure 7 The lead screw thermal error compensation method of the active compensation device for lead screw thermal error of CNC machine tool shown in this application embodiment includes:

[0083] The first step is system initial state calibration. The system is started in a cold state, the control system reads the initial value of the force sensor 32, and applies an initial voltage to the inverse piezoelectric ceramic actuator 31. This causes a small initial contraction displacement, thereby applying a suitable preload to the lead screw 1 and stabilizing it at the preset optimal value. ( (Determined by the specifications and operating conditions of lead screw 1), at this time, the reading of force sensor 32 should be... The system records the reading of temperature sensor 5 at this time. As a reference temperature.

[0084] The second step involves temperature sensor 5 collecting temperature data in real time. Force sensor 32 collects the preload force in real time due to the thermal expansion of lead screw 1. .

[0085] The third step is to calculate the temperature feedforward compensation amount, with temperature sensor 5 collecting temperature data in real time. Calculate the temperature rise The control algorithm calculates the theoretical thermal elongation. Then, based on the actuator's displacement-voltage coefficient Calculate the amount of thermal expansion to offset the theoretical thermal expansion. Required theoretical feedforward voltage increment While calculating the temperature feedforward compensation, the force feedback compensation is also calculated. Force sensor 32 collects the preload force that increases due to the thermal expansion of lead screw 1 in real time. The force deviation 'e' is calculated and fed into a digital PID controller, where the PID algorithm is used to calculate... Control system integration and The total control voltage is obtained. High-voltage drive circuit receives The digital instructions are converted into analog high voltage and applied to the inverting piezoelectric ceramic actuator 31. The inverting piezoelectric ceramic actuator 31 operates under voltage... Precise axial expansion and contraction are produced under the action of [the agent / mechanism]. , The adjustment of the preload force of the lead screw 1 is achieved through the floating support component 33:

[0086] If the lead screw 1 expands thermally There is an increasing trend ( > If the piezoelectric ceramic actuator 31 extends, it pushes the floating bearing 332 away from the lead screw 1, thereby releasing the additional pressure generated by the thermal expansion of the lead screw 1 and restoring the net preload acting on the lead screw 1 to its normal value. ;

[0087] If the temperature drops, lead screw 1 will contract. There is a decreasing trend ( < The reverse piezoelectric ceramic actuator 31 contracts to maintain the tension. ;

[0088] Ultimately, this keeps the effective length L of the lead screw 1 macroscopically constant.

[0089] In particular, the system can periodically update the reference temperature. To adapt to changes in ambient temperature, upper and lower limit protections for voltage and force are set to prevent overload damage to the reverse piezoelectric ceramic actuator 31 and the lead screw 1.

[0090] In other embodiments, multiple temperature sensors 5 can be arranged on the lead screw 1 to form a sensor array, and temperature field distribution data can be collected in real time. Then, based on algorithms or heat transfer principles, a thermal imaging prediction model can be established, from the temperature of a few key measuring points to the overall temperature field and thermal elongation morphology of the lead screw 1. Based on this model, the control system can not only calculate the overall thermal elongation... It can also predict complex deformations such as minute bending caused by temperature gradients in the lead screw 1. This complex deformation is also used as a compensation target to correct the control voltage. More precise compensation is achieved through the inverse piezoelectric ceramic actuator 31, realizing the upgrade from "one-dimensional linear compensation" to "multi-dimensional morphology compensation", which solves the problem of non-pure axial elongation caused by uneven heating of the lead screw 1.

[0091] In some other embodiments, upon initial system operation, an excitation signal is automatically executed to identify the dynamic parameters of the current lead screw-bearing system, such as overall stiffness and damping, and the optimal PID parameters (Kp, Ki, Kd) are tuned accordingly. During subsequent operation, the control effect is continuously monitored (which could be the integral sum of squares of the force deviation). When the effect deteriorates, the PID parameters are automatically fine-tuned, or the system switches to another preset parameter set for different operating conditions (such as high speed or heavy load). Furthermore, the system periodically (e.g., every 100 hours of operation) uses historical operating data to automatically calibrate and update key parameters (such as the linear expansion coefficient α) in the built-in "lead screw 1 thermal expansion model" to adapt to long-term wear and performance changes in lead screw 1. In this embodiment, the system possesses "learning" and "evolution" capabilities, maintaining optimal compensation throughout its entire lifespan, demonstrating a high degree of intelligence.

[0092] In other embodiments, a typical thermodynamic curve (a curve showing temperature changes over time) is pre-stored in the machine tool CNC system. After the machine tool is powered on, the system enters a "preheating mode." During this stage, the reverse piezoelectric ceramic actuator 31 no longer aims to maintain a constant preload, but actively and programmatically changes the preload based on the thermodynamic curve and real-time temperature, guiding the lead screw 1 to quickly enter a thermal equilibrium state. When the system detects that the rate of temperature change tends to stabilize, it automatically switches to the standard "constant force / composite compensation mode." This mode significantly shortens the machine tool preheating waiting time, improves equipment utilization, and is particularly suitable for batch production scenarios sensitive to start-up time.

[0093] In other embodiments, during normal compensation, the system continuously records waveform data from the force sensor 32 and the drive voltage, and uses signal processing techniques (such as spectrum analysis) to monitor for abnormal frequency components in the signal that correspond to fault characteristics such as wear of the lead screw 1 or pitting of the ball bearings. Once a potential fault characteristic is detected, the system can issue an early warning message to prompt equipment maintenance. This embodiment endows the compensation device with predictive maintenance capabilities, upgrading it from a "precision guarantor" to a "health guardian," greatly enhancing the added value of the product.

[0094] In other embodiments, based on the existing main actuator integrated at the end of the lead screw 1, one or more small-stroke driven reverse piezoelectric ceramic actuators 31 are integrated inside the nut of the lead screw 1, combined with the nut's preload structure. The main actuator is responsible for coarse compensation for macroscopic, overall thermal expansion, while the driven actuator is responsible for compensating for lead error and backlash caused by local temperature rise in the nut. This embodiment achieves source compensation and global compensation for thermal errors in the lead screw 1 transmission system, while also compensating for errors in the lead screw 1 body and the nut pair, maintaining a constant and optimal nut preload, providing more comprehensive compensation, avoiding wear and heat generation of the lead screw 1, backlash, and transmission chain errors that may exist in end-compensation, resulting in higher accuracy.

[0095] It should be noted that in this specification, relational terms such as first and second are used only to distinguish one entity from several other entities, and do not necessarily require or imply any such actual relationship or order between these entities.

[0096] The above provides a detailed description of the active thermal error compensation device and method for CNC machine tool lead screws provided in this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the embodiments above are merely for the purpose of helping to understand the solution and core ideas of this application. It should be noted that those skilled in the art can make various improvements and modifications to this application without departing from its principles, and these improvements and modifications also fall within the protection scope of the claims of this application.

Claims

1. A CNC machine tool lead screw thermal error active compensation device, characterized in that, include: Lead screw (1); A fixed support assembly (2) is rigidly fixed to one end of the lead screw (1); The pre-tensioning mechanism (3) includes a floating support assembly (33), an inverse piezoelectric ceramic actuator (31), and a force sensor (32). The inverse piezoelectric ceramic actuator (31) is connected to the other end of the lead screw (1) through the force sensor (32), and the inverse piezoelectric ceramic actuator (31) is connected to the floating support assembly (33) through a connecting shaft (34). The control system is electrically connected to the reverse piezoelectric ceramic actuator (31) and the force sensor (32).

2. The active thermal error compensation device for CNC machine tool lead screws according to claim 1, characterized in that, The fixed support assembly (2) includes a fixed support base, a fixed bearing (22), a fixed pressure cap (23), and a locking nut (24). The bearing is installed on the fixed support base, the lead screw (1) is rotatably engaged with the fixed bearing (22), and the locking nut (24) is sleeved on the lead screw (1) and abuts against the fixed bearing (22).

3. The active thermal error compensation device for CNC machine tool lead screws according to claim 2, characterized in that, The floating support assembly (33) includes a floating bearing seat (331), a floating bearing (332), a butterfly spring (333), a preload cover (334), a retaining ring (335), and an adjusting screw (336). The preload cover (334) and the floating bearing seat (331) form a mating cavity. The adjusting screw (336) is used to fix the preload cover (334) to the floating bearing seat (331). The floating bearing (332) is slidably fitted in the mating cavity. The floating bearing (332) can move relative to the floating bearing seat (331) along its axial direction. The connecting shaft (34) is rotatably fitted with the floating bearing (332). The butterfly spring (333) is located on both sides of the floating bearing (332). The retaining ring (335) is located between the floating bearing (332) and the connecting shaft (34).

4. The active thermal error compensation device for CNC machine tool lead screws according to claim 3, characterized in that, A temperature sensor (4) is also provided. The temperature sensor (4) is installed on the lead screw (1) through a nut connector (5) and a nut (6). The temperature sensor (4) abuts against the lead screw (1) and is electrically connected to the control system.

5. The active thermal error compensation device for CNC machine tool lead screws according to claim 4, characterized in that, The control system includes a signal processing unit, a control algorithm unit, and a high-voltage drive circuit. The signal processing unit is used to receive signals from the force sensor (32) and the temperature sensor (4). The control algorithm unit is used to calculate the required control voltage based on the signals received by the signal processing unit. The high-voltage drive circuit is used to input a high-voltage control signal to the brake based on the output signal of the control algorithm unit, so as to drive the reverse piezoelectric ceramic actuator (31) to move.

6. The active thermal error compensation device for CNC machine tool lead screws according to claim 5, characterized in that, The signal processing unit has a built-in thermal expansion model and an inverse piezoelectric ceramic actuator control model. The thermal expansion model can calculate the thermal expansion and contraction of the lead screw (1) based on the temperature change measured by the temperature sensor (4), and calculate the required control voltage through the inverse piezoelectric ceramic actuator control model.

7. The active thermal error compensation device for CNC machine tool lead screws according to claim 1, characterized in that, The reverse piezoelectric ceramic actuator (31) adopts a stacked structure.

8. The active thermal error compensation device for CNC machine tool lead screws according to claim 7, characterized in that, The reverse piezoelectric ceramic actuator (31) is provided with heat dissipation fins (311) on its exterior.

9. The active thermal error compensation device for CNC machine tool lead screws according to claim 8, characterized in that, An insulating pad (7) is also provided, which is respectively disposed between the reverse piezoelectric ceramic actuator (31) and the force sensor (32), and between the reverse piezoelectric ceramic actuator (31) and the floating support assembly (33).

10. A method for compensating for thermal errors in lead screws, applied to the active thermal error compensation device for lead screws in CNC machine tools as described in any one of claims 1-9, characterized in that, The lead screw thermal error compensation method includes: When the lead screw (1) is cold, the control system applies an initial voltage to the reverse piezoelectric ceramic actuator (31) so that the reverse piezoelectric ceramic actuator (31) applies an initial pre-tension force to the lead screw (1); During the operation of the lead screw (1), the temperature and pre-tension force of the lead screw (1) are detected by temperature sensor (4) and force sensor (32); Based on the monitored changes, the voltage applied to the reverse piezoelectric ceramic actuator (31) is dynamically adjusted by the control system to drive the corresponding displacement of the reverse piezoelectric ceramic actuator (31) in order to maintain the pre-tension force constant or directly offset the calculated thermal elongation.

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