A precision machining device and machining process for brake screw nuts

Abstract

This invention relates to the field of nut machining technology, specifically to a precision machining device and process for brake screw nuts. The process includes: acquiring grinding state data, machine tool parameter data, and the hardness value of the brake screw nut during grinding; analyzing the differences in grinding force; the difference between the helix angle of the brake screw nut and the maximum swing angle of the machine tool spindle; and the difference between the feed rate of the precision grinding wheel and the maximum feed rate. Furthermore, by combining the hardness value and utilizing the difference between the wear amount of the grinding wheel and the initial radius of the grinding wheel, the current moment's grinding force adaptive factor, helix angle compensation factor, and grinding wheel wear compensation factor are obtained. All factors are then used to adjust the feed rate of the precision grinding wheel. This invention achieves dynamic control of the precision grinding wheel through feed rate adjustment, improving the precision machining effect of brake screw nuts.

Description

Technical Field

[0001] This invention relates to the field of nut processing technology, specifically to a precision machining device and processing technology for brake screw nuts. Background Technology

[0002] Against the backdrop of the global manufacturing industry's transformation towards intelligent and high-end manufacturing, my country's intelligent manufacturing equipment industry is ushering in a period of rapid development, with the upgrading of high-precision key component processing technology becoming an important direction for industrial breakthroughs. As a core transmission component of the braking system, the machining accuracy and surface quality of the brake screw nut directly affect the stability and safety of the equipment, especially in high-end fields such as new energy vehicles and aerospace, where stringent requirements are placed on its precision and reliability.

[0003] Existing patent CN117862884A discloses a precision machining equipment and process for brake screw nuts. The equipment includes a machine tool body, a workpiece spindle movable along the Z-axis, and an X-axis slide plate movable along the X-axis. The X-axis slide plate is equipped with an internal thread rough milling spindle (equipped with an internal thread milling cutter) and an internal thread fine grinding spindle (equipped with a fine grinding wheel). It can also include components such as an external end face grinding wheel spindle. This equipment is designed for screw nut parts with deep thread raceways, enabling rough machining followed by fine grinding. Specialized grinding wheels and grinding parameters improve machining accuracy and efficiency, reduce grinding wheel wear and lower costs. Furthermore, the entire process is completed in a single workpiece clamping, enhancing machining accuracy.

[0004] However, the processing technology in this patent uses fixed grinding parameters when finishing the workpiece, without considering that the workpiece after rough milling may experience fluctuations in allowance due to uneven material hardness and heat treatment deformation. Fixed finishing grinding parameters may cause sudden changes in grinding force and vibration when different allowances are applied, resulting in overload wear of the grinding wheel and deviation in trajectory accuracy, thus reducing the machining accuracy. Therefore, how to collect data through sensors during the finishing process of brake screw nuts and adaptively control the feed speed of the finishing grinding wheel to avoid the reduction in accuracy caused by the fluctuation of allowance after rough milling is the key issue to improve the grinding effect. Summary of the Invention

[0005] This invention provides a precision machining device and machining process for brake lead screw nuts to solve existing problems.

[0006] The present invention provides a precision machining device and machining process for a brake screw nut, which adopts the following technical solution:

[0007] One embodiment of the present invention provides a machining process for a brake screw nut, the machining process comprising the following steps:

[0008] The grinding state data, machine tool parameter data, and hardness value of the brake screw nut are obtained during the grinding process of the brake screw nut. The grinding state data includes grinding force, grinding wheel wear, and helix angle of the brake screw nut. The machine tool parameter data includes the maximum swing angle capability of the machine tool spindle, the feed rate and maximum feed rate of the fine grinding wheel, and the initial radius of the grinding wheel.

[0009] The coefficients of the preset PID algorithm are combined with the difference between the grinding force and the preset target grinding force to obtain the grinding force adaptive factor at the current moment.

[0010] By combining the helix angle of the brake screw nut, the difference between the helix angle of the brake screw nut and the maximum swing angle of the machine tool spindle, and the difference between the feed rate of the fine grinding wheel and the maximum feed rate, the helix angle compensation factor at the current moment is obtained.

[0011] The wear degree of the grinding wheel is analyzed by combining the hardness value and the difference between the wear amount and the initial radius of the grinding wheel, and the grinding stage is determined based on the current moment, thereby obtaining the grinding wheel wear compensation factor at the current moment;

[0012] The feed rate of the fine grinding wheel is adjusted by using the grinding force adaptive factor, helix angle compensation factor, and grinding wheel wear compensation factor.

[0013] Furthermore, the coefficients of the preset PID algorithm, combined with the difference between the grinding force and the preset target grinding force, are used to obtain the grinding force adaptive factor at the current moment. The specific method includes:

[0014] The proportional coefficient, integral coefficient, and derivative coefficient of the preset PID algorithm are used to weight and fuse the difference between the grinding force and the target grinding force, thereby obtaining the grinding force adaptive factor at the current moment.

[0015] Furthermore, the specific method for weighted fusion of the difference between the grinding force and the target grinding force is as follows:

[0016] Based on the difference between the grinding force and the target grinding force, the proportional difference, integral difference, and differential difference of the grinding force at the current moment are obtained respectively. The proportional difference, integral difference, and differential difference are weighted using the proportional coefficient, integral coefficient, and differential coefficient respectively to obtain the proportional term, integral term, and differential term. The proportional term, integral term, and differential term are summed to obtain the grinding force adaptive factor at the current moment.

[0017] Furthermore, obtaining the grinding force adaptive factor at the current moment also includes: using the grinding force adaptive factor as input to a saturation function, processing the value range of the grinding force adaptive factor using the saturation function, and limiting the value range of the grinding force adaptive factor to the range of [q1, q2], where q1 and q2 are preset first and second parameters.

[0018] Furthermore, the method for obtaining the helix angle compensation factor at the current moment by combining the helix angle of the brake screw nut, the difference between the helix angle of the brake screw nut and the maximum swing angle of the machine tool spindle, and the difference between the feed rate of the fine grinding wheel and the maximum feed rate includes:

[0019] Obtain the square of the cosine of the helix angle of the brake screw nut at the current moment, and denote it as the helix angle parameter; combine the difference between the helix angle of the brake screw nut and the maximum swing angle of the machine tool spindle, as well as the difference between the feed speed of the fine grinding wheel and the maximum feed speed of the fine grinding wheel, to obtain the difference parameter;

[0020] By combining the helix angle parameter and the difference parameter, the helix angle compensation factor at the current moment is obtained, wherein both the helix angle parameter and the difference parameter are positively correlated with the helix angle compensation factor.

[0021] Furthermore, the specific method for obtaining the difference parameter is as follows:

[0022] The ratio of the helix angle of the brake screw nut to the maximum swing angle of the machine tool spindle is obtained as the difference between the helix angle of the brake screw nut and the maximum swing angle of the machine tool spindle, and is recorded as the first difference; the ratio between the feed rate of the fine grinding wheel and the maximum feed rate of the fine grinding wheel is obtained as the difference between the feed rate of the fine grinding wheel and the maximum feed rate of the fine grinding wheel, and is recorded as the second difference; based on the first difference and the second difference, a difference parameter is obtained, wherein the first difference is negatively correlated with the difference parameter, and the second difference is positively correlated with the difference parameter.

[0023] Furthermore, the specific method for analyzing the wear degree of the grinding wheel by combining the hardness value and utilizing the difference between the grinding wheel wear amount and the initial radius of the grinding wheel includes:

[0024] The wear factor is obtained by obtaining the difference between the wear amount of the grinding wheel and the initial radius of the grinding wheel. The reciprocal of the hardness value of the brake screw nut is used as the weight of the wear factor to obtain the wear degree of the fine grinding wheel. Both the wear factor and the reciprocal of the hardness value of the brake screw nut are negatively correlated with the wear degree.

[0025] Furthermore, the specific method for determining the grinding stage based on the current moment includes:

[0026] A critical time for the wear stabilization stage and a stable wear rate constant are preset. The difference between the current moment and the critical time for the wear stabilization stage is obtained and denoted as the stage factor. The stable wear rate constant is used as the weight of the stage factor to obtain the grinding stage parameters. Both the stable wear rate constant and the stage factor are negatively correlated with the grinding stage parameters.

[0027] Furthermore, the specific method for adjusting the feed rate of the fine grinding wheel using the grinding force adaptive factor, helix angle compensation factor, and grinding wheel wear compensation factor includes:

[0028] The grinding force adaptive factor, helix angle compensation factor, and grinding wheel wear compensation factor at the current moment are summed to obtain the adjustment factor. The feed rate corresponding to the fine grinding wheel at the previous moment is adjusted using the adjustment factor to obtain the adjusted feed rate of the fine grinding wheel at the current moment. The adjustment factor and the feed rate corresponding to the fine grinding wheel at the previous moment are both positively correlated with the adjusted feed rate.

[0029] A precision machining apparatus for a brake screw nut includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the steps of the machining process for a brake screw nut as described in any one of the above.

[0030] The beneficial effects of the technical solution of this invention are as follows: By simultaneously collecting dynamic parameters such as grinding force, helix angle, and grinding wheel wear, and combining them with machine tool performance boundary values ​​(such as maximum swing angle and feed rate), a multi-dimensional compensation system is constructed. Each compensation factor (grinding force / helix angle / wear compensation) corresponds to the three core contradictions of cutting stability, thread accuracy consistency, and tool life, respectively, thereby achieving closed-loop optimization of the machining system. The use of a PID algorithm to compare the difference between the target grinding force and the actual value in real time enables the system to resist interference. In particular, the helix angle compensation factor is calculated through dual differences (the difference between the workpiece parameters and the machine tool limits, and the difference between the current speed and the limit speed). To prevent thread deformation caused by machine tool physical limitations, the wear rate is linked to the initial radius and material hardness. The compensation intensity is dynamically adjusted through a stage identification model, which avoids efficiency loss caused by over-compensation and quality defects caused by under-compensation. This nonlinear compensation logic based on wear rate improves the utilization rate of the grinding wheel. Finally, although the three compensation factors are calculated independently, they act uniformly on the feed rate. This maintains the specificity of each parameter adjustment (such as grinding force focusing on cutting stability and helix angle focusing on geometric accuracy), and achieves dynamic control of the fine grinding wheel through the final feed rate adjustment, thereby improving the finishing effect of the brake screw nut. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention 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 some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a flowchart illustrating the processing steps of a brake screw nut according to the present invention. Detailed Implementation

[0033] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation, structure, features, and effects of a precision machining device and machining process for a brake screw nut according to the present invention. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0035] The following description, in conjunction with the accompanying drawings, details the specific solution of the precision machining device and machining process for a brake screw nut provided by the present invention.

[0036] Please see Figure 1 The diagram illustrates a process flow chart of a brake screw nut manufacturing process according to an embodiment of the present invention, which includes the following steps:

[0037] Step S001: Obtain grinding status data, machine tool parameter data, and hardness value of the brake screw nut during the grinding process.

[0038] Specifically, in order to realize the machining process of the brake lead screw nut proposed in this embodiment, it is first necessary to collect grinding status data and machine tool parameter data. The specific process is as follows:

[0039] First, during the grinding process of the brake screw nut by the precision grinding wheel, multiple sensors are used to acquire grinding status data in real time. The grinding status data includes grinding force, grinding wheel wear, and helix angle of the brake screw nut.

[0040] The specific method for obtaining grinding condition data is as follows:

[0041] Employing a piezoelectric sensor, the grinding force (the resultant force of normal and tangential forces) is converted into an electrical charge signal based on the piezoelectric effect. This signal is then amplified by a charge amplifier and converted into a voltage signal. Mechanical vibration noise is filtered out using a Fourier transform (cutoff frequency 500Hz). Integrated into the torque transmission path between the internal thread grinding spindle and the grinding wheel (e.g., at the connection between the spindle end and the grinding wheel flange), it ensures direct sensing of the dynamic load on the grinding force transmission chain. The sampling frequency is 100Hz, and it outputs real-time grinding force values.

[0042] Based on laser triangulation, a semiconductor laser beam illuminates the surface of the grinding wheel to form a light spot. A CMOS detector at the receiving end calculates the distance change by tracking the light spot displacement, and then uses trigonometric relationships to determine the wear amount of the grinding wheel radius. The device is fixed to the front end of the X-axis slide plate using an L-shaped bracket. The transmitter and receiver are aligned with the side of the grinding wheel, maintaining a distance of 5–10 mm to avoid the cutting fluid spray area and prevent contamination. The sampling frequency is 0.1 Hz, and the output is the grinding wheel wear measurement.

[0043] An absolute photoelectric encoder is used, which outputs binary angle codes through a combination of light-transmitting and opaque areas on the code disk to obtain absolute angle values. An integrated tilting angle device drives the spindle of the internal thread grinding spindle, monitoring the spindle tilting angle in real time. The spindle tilting angle is the inclination angle of the grinding wheel spindle relative to the workpiece axis, while the helix angle is the angle between the tangent to the helix of the thread's pitch diameter cylindrical surface and a plane perpendicular to the thread axis. To ensure the grinding wheel grinds along the helix trajectory, both angles are equal. The sampling frequency is 10Hz, and the output helix angle has the same value as the spindle tilting angle.

[0044] The control module uses the 100Hz main clock of the grinding force sensor. In each calculation cycle (10ms), it first reads the latest grinding force data. For the data of the angle encoder, a zero-order hold is used to maintain the previous valid data until the update. For the data of the laser ranging module, the wear amount is recorded after each update and filled by linear interpolation to realize the signal synchronization of multiple sensors.

[0045] Then, the machine tool parameter data is obtained, including: the maximum swing angle capability of the machine tool spindle, the feed rate and maximum feed rate of the fine grinding wheel, and the initial radius of the grinding wheel.

[0046] Finally, obtain the hardness value of the brake screw nut.

[0047] Thus, the grinding status data, machine tool parameter data, and hardness value of the brake screw nut during the grinding process were obtained through the above method.

[0048] Step S002: Preset the coefficients of the PID algorithm and combine them with the difference between the grinding force and the preset target grinding force to obtain the grinding force adaptive factor at the current moment.

[0049] It should be noted that in the deep raceway fine grinding of brake screw nuts, factors such as uneven material hardness, residual deformation from heat treatment, or wear of the grinding wheel can cause fluctuations in the allowance, resulting in real-time fluctuations in the grinding force. Traditional fixed feed rate control methods cannot dynamically respond to such changes. When the grinding force suddenly increases (e.g., when encountering hard points in the material), it can easily lead to grinding wheel breakage or spindle damage. Conversely, if the grinding force is too low (e.g., due to insufficient allowance or decreased grinding wheel sharpness), failure to adjust the feed rate in time will result in wasted processing efficiency.

[0050] Specifically, as a preferred embodiment, the method for obtaining the grinding force adaptive factor includes:

[0051] The proportional coefficient, integral coefficient, and derivative coefficient of the PID algorithm are preset, and the difference between the grinding force and the target grinding force is weighted and fused using the proportional coefficient, integral coefficient, and derivative coefficient respectively, so as to obtain the grinding force adaptive factor at the current moment.

[0052] As an optional embodiment, the specific method for weighted fusion of the difference between the grinding force and the target grinding force using proportional coefficients, integral coefficients, and differential coefficients is as follows:

[0053] Based on the difference between the grinding force and the target grinding force, the proportional difference, integral difference, and differential difference of the grinding force at the current moment are obtained respectively. The proportional difference, integral difference, and differential difference are weighted using the proportional coefficient, integral coefficient, and differential coefficient respectively to obtain the proportional term, integral term, and differential term. The proportional term, integral term, and differential term are summed to obtain the grinding force adaptive factor at the current moment.

[0054] As an optional embodiment, the specific method for obtaining the grinding force adaptive factor is as follows:

[0055] First, calculate the grinding force adaptive factor. The calculation expression is as follows:

[0056]

[0057] Where, λF t The grinding force adaptive factor at time t is represented by Kp, KI, and KD, which represent the preset proportional coefficient, integral coefficient, and derivative coefficient in the PID algorithm, respectively. set denoted as the preset target grinding force; ∈ indicates the minimum value to prevent the denominator from being zero; F(τ) represents the grinding force at time τ; F(t) represents the grinding force at time t.

[0058] Then, the grinding force adaptive factor is used as the input of the saturation function. The saturation function is used to process the value range of the grinding force adaptive factor, and the value range of the grinding force adaptive factor is limited to the range of [q1,q2], where q1 and q2 are the preset first and second parameters.

[0059] It should be noted that, in this embodiment of the invention, the proportional coefficient, integral coefficient, and derivative coefficient of the PID algorithm are preset to be 0.5, 0.01, and 0.001 respectively based on experience. In other embodiments, these values ​​can be adjusted according to actual conditions. This embodiment of the invention does not impose specific limitations. The adjustment ranges of each coefficient are typically as follows: the proportional coefficient ranges from [0.5 to 2.0], the integral coefficient ranges from [0.01 to 0.1], and the derivative coefficient ranges from [0.001 to 0.01]. In addition, the target grinding force is preset to be 100 (unit: Newtons (N)) based on experience. In other embodiments, these values ​​can be adjusted according to actual conditions. The target grinding force range is typically [80 to 150]. Furthermore, in this embodiment of the invention, the minimum value is 0.1, which can be adjusted according to actual conditions. This embodiment of the invention does not impose specific limitations.

[0060] It should be noted that the proportional term responds to the current error in real time and quickly adjusts the feed rate to suppress force fluctuations; the integral term represents the cumulative relative error of the grinding force deviating from the target value from the start time of the current workpiece to the current moment. The integral term eliminates static deviations by accumulating historical errors, and solves the problem of continuous overload or underload caused by uneven material hardness; the derivative term predicts the force change trend and compensates for acceleration impacts in advance by differential adjustment, thus suppressing vibration.

[0061] It should be further noted that, unlike traditional PID controllers, the proportional term in this embodiment of the invention uses proportional error. Instead of the traditional absolute error, it reflects the relative severity of force fluctuations and is more sensitive to fluctuations in grinding force; the integral term uses relative error accumulation instead of absolute error accumulation, the integral term has a larger weight and a faster convergence speed; the differential term uses the relative rate of force change instead of the traditional absolute error rate of change, it is more sensitive to the impact of hard particles in the material, and will output a stronger suppression signal, curbing the force fluctuation trend in advance and effectively curbing the sudden increase in force caused by the impact of hard particles.

[0062] It should also be noted that since the feed rate directly determines the amount of material removed per unit time, and the grinding force is approximately proportional to the material removal rate, when the grinding force deviates from the target value, the feed rate can be directly adjusted through a linearly positively correlated factor to keep the product of the grinding force and the speed constant. Therefore, in this embodiment of the invention, the range of the grinding force adaptive factor is limited to the range of [q1, q2] using a saturation function. Based on experience, the preset range [q1, q2] is [0.5, 1.5] to prevent excessive fluctuations in the feed rate and ensure a smooth machining process. The specific range can be adjusted according to the actual situation, and this embodiment of the invention does not impose a specific limitation.

[0063] The grinding force adaptive factor describes the degree to which the feed rate of the fine grinding wheel should be adjusted at a given time. The larger the value, the smaller the grinding force, and the more the feed rate of the fine grinding wheel should be increased to improve the material removal rate and increase efficiency. Conversely, the smaller the value, the larger the grinding force, and the more the feed rate should be reduced to decrease the depth of cut per unit time and reduce the grinding force to avoid overload.

[0064] Thus, the adaptive grinding force factor of the fine grinding wheel is obtained through the above method.

[0065] Step S003: Combine the helix angle of the brake screw nut, the difference between the helix angle of the brake screw nut and the maximum swing angle of the machine tool spindle, and the difference between the feed speed of the fine grinding wheel and the maximum feed speed to obtain the helix angle compensation factor at the current moment.

[0066] It should be noted that the grinding force adaptive factor is used to suppress force fluctuations during the machining process, thereby improving accuracy. However, it cannot solve the inherent trajectory accuracy problem caused by the geometric characteristics of the thread. The grinding wheel needs to move along the helical trajectory. If the adjusted feed rate does not match the helix angle, it will lead to thread lead error or deterioration of surface roughness. Therefore, the helix angle must also be considered.

[0067] As a preferred embodiment, the method for obtaining the helix angle compensation factor includes:

[0068] First, obtain the square of the cosine of the helix angle of the brake screw nut at the current moment, and denote it as the helix angle parameter. Then, by combining the difference between the helix angle of the brake screw nut and the maximum swing angle of the machine tool spindle, as well as the difference between the feed speed of the fine grinding wheel and the maximum feed speed of the fine grinding wheel, the difference parameter is obtained.

[0069] As an optional embodiment, the specific method for obtaining the difference parameter is as follows: The ratio of the helix angle of the brake screw nut to the maximum swing angle of the machine tool spindle is obtained as the difference between the helix angle of the brake screw nut and the maximum swing angle of the machine tool spindle, and is recorded as the first difference; the ratio between the feed rate of the fine grinding wheel and the maximum feed rate of the fine grinding wheel is obtained as the difference between the feed rates of the fine grinding wheel and the maximum feed rate of the fine grinding wheel, and is recorded as the second difference; based on the first difference and the second difference, the difference parameter is obtained, wherein the first difference is negatively correlated with the difference parameter, and the second difference is positively correlated with the difference parameter.

[0070] Then, by combining the helix angle parameter and the difference parameter, the helix angle compensation factor at the current moment is obtained, wherein the helix angle parameter and the difference parameter are both positively correlated with the helix angle compensation factor.

[0071] As an optional embodiment, the specific calculation method for the helix angle compensation factor is as follows:

[0072]

[0073] Where, λα t α represents the helix angle compensation factor at time t; t α represents the helix angle of the brake screw nut. max This represents the maximum swing angle of the machine tool spindle, v. t v represents the feed rate of the grinding wheel at time t; max This represents the maximum feed rate of the fine grinding wheel; cos() represents the cosine function.

[0074] In some specific embodiments of the present invention, the maximum swing angle of the machine tool spindle is typically in the range of [30°, 45°], and in this embodiment, the maximum swing angle of the machine tool spindle is 35°; in addition, the feed rate (unit: mm / r) of the fine grinding wheel is typically in the range of [0.1, 0.2], and in this embodiment, the value is 0.15 mm / r.

[0075] It should be noted that the maximum swing angle of the machine tool spindle and the feed rate and maximum feed rate of the fine grinding wheel are fixed parameters of the corresponding components in the machine tool, which are obtained through actual measurement. Therefore, no specific limitations are made in this embodiment of the invention.

[0076] It should be noted that the larger the helix angle, the higher the required thread trajectory accuracy. Therefore, the feed rate needs to be reduced for matching. The attenuation effect of the angle on the feed rate is quantified using a cosine square function to obtain the helix angle parameter cos. 2 (α tThe larger the angle, the smaller the speed correction factor. Simultaneously, the maximum swing angle of the equipment is introduced as a safety boundary. When the actual swing angle approaches the limit, the speed is forcibly reduced to avoid overloading the swing angle device. Furthermore, by combining the ratio between the real-time feed speed and the maximum feed speed of the equipment, difference parameters are obtained. This is to reduce attenuation at higher speeds, balance accuracy and processing efficiency, and ensure a balance between the accuracy of the helical trajectory and the operation of the equipment during deep raceway thread processing.

[0077] It should be noted that the value of the helix angle compensation factor is between [0,1]. The larger the value, the higher the allowable feed speed of the fine grinding wheel, which is suitable for scenarios with a small helix angle or sufficient equipment swing angle capability. In this case, the trajectory forming difficulty is low, and processing efficiency can be taken into account. Conversely, the feed speed is forcibly reduced, which is suitable for scenarios with a large helix angle or swing angle close to the limit of the equipment. By sacrificing speed, the coaxiality of the helical axis and the outer circle axis is ensured, and the swing angle device is avoided from being overloaded.

[0078] Thus, the helix angle compensation factor is obtained through the above method.

[0079] Step S004: Combine the hardness value with the difference between the wear amount and the initial radius of the grinding wheel to analyze the wear degree of the grinding wheel, and determine the grinding stage based on the current moment, thereby obtaining the grinding wheel wear compensation factor at the current moment.

[0080] It should be noted that the helix angle, as an inherent geometric parameter of the thread, is uniquely determined by the thread lead and pitch diameter and remains unchanged during the machining of a workpiece. However, when the grinding wheel wears down due to long-term use, its outer radius decreases and its profile accuracy declines. At this time, although the set angle of the spindle tilting device remains unchanged, the contact position between the actual grinding surface of the grinding wheel and the internal thread of the workpiece shifts, causing a radial deviation between the grinding wheel's central axis and its ideal position. This deviation causes the angle between the grinding wheel's tangent direction and the thread helix direction to deviate from the theoretical helix angle, resulting in an equivalent angular error. Furthermore, uneven wear of the grinding wheel will further disrupt its relative motion trajectory with the workpiece, leading to dynamic drift of the actual helix angle. Therefore, when matching the feed rate with the helix angle, it is necessary to monitor not only the helix angle but also the grinding wheel wear.

[0081] Specifically, as a preferred embodiment, the method for obtaining the grinding wheel wear compensation factor includes:

[0082] First, the difference between the wear amount of the grinding wheel and the initial radius of the grinding wheel is obtained to obtain the wear factor. The reciprocal of the hardness value of the brake screw nut is used as the weight of the wear factor to obtain the wear degree of the fine grinding wheel. Both the wear factor and the reciprocal of the hardness value of the brake screw nut are negatively correlated with the wear degree.

[0083] Then, the critical time of the wear stabilization stage and the stable wear rate constant are preset, and the difference between the current time and the critical time of the wear stabilization stage is obtained and recorded as the stage factor. The stable wear rate constant is used as the weight of the stage factor to obtain the grinding stage parameters. Both the stable wear rate constant and the stage factor are negatively correlated with the grinding stage parameters.

[0084] Finally, by combining the wear degree and grinding stage parameters, the grinding wheel wear compensation factor is obtained. The wear degree and grinding stage parameters are both positively correlated with the grinding wheel wear compensation factor.

[0085] As an optional embodiment, the specific calculation method for the grinding wheel wear compensation factor is as follows:

[0086]

[0087] Where, λW t denoted as the grinding wheel wear compensation factor at time t; ΔR(t) represents the amount of grinding wheel wear collected at time t; R0 represents the initial radius of the grinding wheel; k represents the preset hardness correlation coefficient; a represents the stable wear rate constant; t0 represents the critical time of the stable wear stage; exp[] represents the exponential function with the natural constant as the base; e represents the natural constant.

[0088] It should be noted that the hardness correlation coefficient is used to characterize the influence factor of the hardness of the workpiece on the wear rate of the grinding wheel. The greater the hardness of the workpiece, the smaller the value. In the specific embodiment, it is preset according to the hardness value of the brake screw nut, and the preset value range is [3,5]. In addition, the stable wear rate constant is used to describe the wear rate after the grinding wheel enters the stable wear stage, and the value range is 0.1 to 0.5 / h. In this embodiment, the value is 0.2. The critical time of the wear stabilization stage represents the time from the start of processing to the wear entering the stable period, and the range is 0.3 to 0.6h. In this embodiment, the value is 0.4h.

[0089] It should be noted that this scheme dynamically compensates for the impact of grinding wheel wear on machining accuracy through a two-stage model. In the initial stage, the wear is small, the grinding wheel is sharp, and a higher feed rate is allowed. As the wear increases, an exponential decay is used to characterize the wear sensitivity when the grinding wheel sharpness is high in the initial stage of machining, suppressing the increase in depth of cut caused by grinding wheel dulling. In the stable period, the wear accumulates linearly, and a(t-t0) is smoothly decayed using a Logistic function to obtain... To avoid processing fluctuations caused by sudden compensation; finally and The grinding wheel wear compensation factor is obtained by multiplying the two parts.

[0090] Further, it should be noted that the grinding wheel wear compensation factor is used to describe the wear state of the grinding wheel, and its value is between (0, 1). The larger the value, the smaller the wear amount of the grinding wheel or the initial sharp state, and a higher feed rate is allowed to improve the processing efficiency; the smaller the value, the more serious the wear of the grinding wheel or the stable wear stage is entered. It is necessary to compensate for the increase in the actual cutting depth caused by the reduction of the grinding wheel radius by reducing the feed rate to avoid the decrease in processing accuracy or the overload of the grinding wheel caused by wear accumulation; among them By combining the change in the wear amount of the grinding wheel at the corresponding moment compared to its initial radius, and using the hardness correlation coefficient of the grinding wheel as the weight of the initial radius of the grinding wheel, so that reflects the wear amount characteristics of the fine grinding wheel. When ΔR(t) increases, it indicates that the fine grinding wheel is severely worn, while reflects the wear stage of the grinding wheel. In the initial stage of grinding (t < t0), the value of the grinding wheel wear compensation factor is close to 1, indicating that the grinding wheel is in the initial sharp state, with a high wear rate but a small actual wear amount; when the grinding time approaches or exceeds the critical time t0 (t ≥ t0), the value of the grinding wheel wear compensation factor approaches 0, indicating that the grinding wheel enters the stable wear stage, with a gentle wear rate but significant cumulative wear.

[0091] Thus, the grinding wheel wear compensation factor is obtained through the above method.

[0092] Step S005: Adjust the feed rate of the fine grinding wheel by using the grinding force adaptive factor, the helix angle compensation factor, and the grinding wheel wear compensation factor.

[0093] Sum up the grinding force adaptive factor, the helix angle compensation factor, and the grinding wheel wear compensation factor at the current moment to obtain an adjustment factor, and use the adjustment factor to adjust the feed rate corresponding to the fine grinding wheel at the previous moment of the current moment to obtain the adjusted feed rate of the fine grinding wheel at the current moment. Both the adjustment factor and the feed rate corresponding to the fine grinding wheel at the previous moment of the current moment are positively correlated with the adjusted feed rate.

[0094] As an optional embodiment, the specific calculation method of the adjusted feed rate of the fine grinding wheel is as follows:

[0095] v t =v t-1 ×(λF t +λα t +λW t )

[0096] Among them, v(t) represents the feed rate at the adjusted t-th moment, and v t-1 represents the feed rate at the (t - 1)-th moment; λF t represents the grinding force adaptive factor at the t-th moment; λα<λW represents the helix angle compensation factor at time t. t This represents the grinding wheel wear compensation factor at time t.

[0097] It should be noted that the initial velocity range is 0.02–0.1 mm / r, and the value used in this scheme is 0.05 mm / r. To avoid the feed rate being too high or too low, its output is limited to 0.8v0–1.2v0 using a saturation function.

[0098] The control module converts the calculated dynamic feed speed into servo motor control commands, driving the X-axis slide to adjust the feed amount of the fine grinding wheel in real time.

[0099] To verify the effectiveness of the embodiments of the present invention, in another embodiment of the present invention, a plurality of comparative examples are set, specifically including:

[0100] Example 1: The initial feed rate was set to 0.05 mm / r and dynamically adjusted during the finishing process.

[0101] Comparative Example 1: The feed rate is set to 0.02 mm / r, and no dynamic adjustment is made during the finishing process.

[0102] Comparative Example 2: The feed rate was set to 0.05 mm / r, and no dynamic adjustment was made during the finishing process.

[0103] Comparative Example 3: The feed rate was set to 0.08 mm / r and was not dynamically adjusted during the finishing process.

[0104] It should be noted that, in order to ensure the comparative effect, the parameters were controlled by the controlled variable method. That is, except for the above-mentioned limitation on whether the feed parameters and the fine grinding process were adjusted, the process flow and parameters of comparative examples 1, 2 and 3 were consistent with those of example 1.

[0105] By performing precision machining on the same type of brake screw nut in Example 1 and Comparative Examples 1, 2, and 3 respectively, the machining time, surface roughness, grinding wheel wear, and scrap rate were obtained, thus forming a corresponding comparison table of machining effects, as shown in Table 1.

[0106] Table 1. Comparison of processing effects between Example 1 and Comparative Examples 1, 2, and 3

[0107]

[0108] It should be noted that, as shown in Table 1, the surface roughness of Example 1 is significantly better than that of the comparative examples. This is because Example 1 utilizes a PID algorithm to suppress force fluctuations in real time, avoiding surface defects caused by overload; it dynamically matches the feed rate and swing angle according to the thread geometry to ensure the accuracy of the helical trajectory; and it adjusts the feed rate by monitoring wear in real time to compensate for depth of cut errors. In contrast, the comparative examples use a fixed feed rate, which cannot cope with allowance fluctuations, leading to a deterioration in surface roughness. This verifies the significant advantage of dynamic adaptive control in improving machining accuracy.

[0109] By following the above steps, the feed speed of the fine grinding wheel is obtained and controlled after adjustment.

[0110] A precision machining apparatus for a brake screw nut includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the steps of the machining process for a brake screw nut as described in any one of the above.

[0111] In the above embodiments, implementation can be achieved, in whole or in part, through software, hardware, firmware, or any combination thereof. When implemented in software, it can be implemented, in whole or in part, as a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the processes or functions described in this application are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, digital subscriber line) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium accessible to a computer or a data storage device such as a server or data center that integrates one or more available media. The available medium can be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape), an optical medium (e.g., DVD), or a semiconductor medium (e.g., solid-state drive).

[0112] Furthermore, in an alternative embodiment, the memory described above may include read-only memory and random access memory, and provide instructions and data to the processor. The memory may also include non-volatile random access memory. For example, the memory may also store device type information.

[0113] The aforementioned processor can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. General-purpose processors can be microprocessors or any conventional processor. It is worth noting that the processor can be a processor supporting Advanced Reduced Instruction Set Machines (ARM) architecture.

[0114] This invention constructs a multi-dimensional compensation system by simultaneously collecting dynamic parameters such as grinding force, helix angle, and grinding wheel wear, combined with machine tool performance boundary values ​​(such as maximum swing angle and feed rate). Each compensation factor (grinding force / helix angle / wear compensation) corresponds to three core contradictions: cutting stability, thread accuracy consistency, and tool life, achieving closed-loop optimization of the machining system. A PID algorithm is used to compare the target grinding force with the actual value in real time, giving the system anti-interference capabilities. Specifically, the helix angle compensation factor is calculated using dual differences (the difference between workpiece parameters and machine tool limits, and the difference between the current speed and the limit speed) to prevent interference. The thread deformation is caused by the physical limitations of the machine tool. In addition, the wear of the grinding wheel is associated with the initial radius and the material hardness. The compensation intensity is dynamically adjusted through a stage identification model. This avoids efficiency loss caused by over-compensation and prevents quality defects caused by under-compensation. This nonlinear compensation logic based on wear rate improves the utilization rate of the grinding wheel. Finally, although the three compensation factors are calculated independently, they act uniformly on the feed rate. This maintains the specificity of each parameter adjustment (such as grinding force focusing on cutting stability and helix angle focusing on geometric accuracy). The dynamic control of the fine grinding wheel is achieved through the final feed rate adjustment, which improves the finishing effect of the brake screw nut.

[0115] It should be noted that the exp(-x) model used in this embodiment is only used to represent negative correlation and constrain the output of the model to be within the (0,1) interval. In specific implementation, it can be replaced by other models with the same purpose. This embodiment only uses the exp(-x) model as an example for description and does not make specific limitations on it, where x refers to the input of the model.

[0116] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A processing technology for a brake screw nut, characterized in that, The processing technology includes the following steps: The grinding state data, machine tool parameter data, and hardness value of the brake screw nut are obtained during the grinding process of the brake screw nut. The grinding state data includes grinding force, grinding wheel wear, and helix angle of the brake screw nut. The machine tool parameter data includes the maximum swing angle capability of the machine tool spindle, the feed rate and maximum feed rate of the fine grinding wheel, and the initial radius of the grinding wheel. The coefficients of the preset PID algorithm are combined with the difference between the grinding force and the preset target grinding force to obtain the grinding force adaptive factor at the current moment. By combining the helix angle of the brake screw nut, the difference between the helix angle of the brake screw nut and the maximum swing angle of the machine tool spindle, and the difference between the feed rate of the fine grinding wheel and the maximum feed rate, the helix angle compensation factor at the current moment is obtained. The wear degree of the grinding wheel is analyzed by combining the hardness value and the difference between the wear amount and the initial radius of the grinding wheel, and the grinding stage is determined based on the current moment, thereby obtaining the grinding wheel wear compensation factor at the current moment; The feed rate of the fine grinding wheel is adjusted by using the grinding force adaptive factor, the helix angle compensation factor, and the grinding wheel wear compensation factor; The specific calculation method for the grinding force adaptive factor is as follows: ； in, Indicates the first The grinding force adaptive factor at any given time; , and These represent the proportional coefficient, integral coefficient, and derivative coefficient preset in the PID algorithm, respectively. This indicates the preset target grinding force; This indicates a minimum value to prevent the denominator from being zero; Indicates the first The grinding force at all times; Indicates the first The grinding force at all times; The specific calculation method for the helix angle compensation factor is as follows: ； in, Indicates the first The helix angle compensation factor at any given time; This indicates the helix angle of the brake screw nut. Indicates the maximum swing angle of the machine tool spindle. Indicates the first The feed rate of the precision grinding wheel at all times; This indicates the maximum feed rate of the fine grinding wheel; Represents the cosine function; The specific calculation method for the grinding wheel wear compensation factor is as follows: ； in, Indicates the first The grinding wheel wear compensation factor at any given time; Indicates the first The amount of grinding wheel wear collected at all times. Indicates the initial radius of the grinding wheel. This represents the preset hardness correlation coefficient. This represents the stable wear rate constant. Indicates the critical time for the wear stabilization stage; Represents an exponential function with the natural constant as its base; Represents the natural constant.

2. The processing technology of a brake screw nut according to claim 1, characterized in that, The coefficients of the preset PID algorithm, combined with the difference between the grinding force and the preset target grinding force, are used to obtain the grinding force adaptive factor at the current moment. The specific method includes: The proportional coefficient, integral coefficient, and derivative coefficient of the preset PID algorithm are used to weight and fuse the difference between the grinding force and the target grinding force, thereby obtaining the grinding force adaptive factor at the current moment.

3. The processing technology of a brake screw nut according to claim 2, characterized in that, The specific method for weighted fusion of the difference between grinding force and target grinding force is as follows: Based on the difference between the grinding force and the target grinding force, the proportional difference, integral difference, and differential difference of the grinding force at the current moment are obtained respectively. The proportional difference, integral difference, and differential difference are weighted using the proportional coefficient, integral coefficient, and differential coefficient respectively to obtain the proportional term, integral term, and differential term. The proportional term, integral term, and differential term are summed to obtain the grinding force adaptive factor at the current moment.

4. The processing technology of a brake screw nut according to claim 3, characterized in that, The process of obtaining the grinding force adaptive factor at the current moment further includes: using the grinding force adaptive factor as input to a saturation function, processing the range of the grinding force adaptive factor using the saturation function, and limiting the range of the grinding force adaptive factor to within a certain range. Within the range, of which and These are the preset first and second parameters.

5. The processing technology of a brake screw nut according to claim 1, characterized in that, The method for obtaining the helix angle compensation factor at the current moment by combining the helix angle of the brake screw nut, the difference between the helix angle of the brake screw nut and the maximum swing angle of the machine tool spindle, and the difference between the feed rate of the fine grinding wheel and the maximum feed rate includes: Obtain the square of the cosine of the helix angle of the brake screw nut at the current moment, and denote it as the helix angle parameter; combine the difference between the helix angle of the brake screw nut and the maximum swing angle of the machine tool spindle, as well as the difference between the feed speed of the fine grinding wheel and the maximum feed speed of the fine grinding wheel, to obtain the difference parameter; By combining the helix angle parameter and the difference parameter, the helix angle compensation factor at the current moment is obtained, wherein both the helix angle parameter and the difference parameter are positively correlated with the helix angle compensation factor.

6. The processing technology of a brake screw nut according to claim 5, characterized in that, The specific method for obtaining the difference parameter is as follows: The ratio of the helix angle of the brake screw nut to the maximum swing angle of the machine tool spindle is obtained as the difference between the helix angle of the brake screw nut and the maximum swing angle of the machine tool spindle, and is recorded as the first difference; the ratio between the feed rate of the fine grinding wheel and the maximum feed rate of the fine grinding wheel is obtained as the difference between the feed rate of the fine grinding wheel and the maximum feed rate of the fine grinding wheel, and is recorded as the second difference; based on the first difference and the second difference, a difference parameter is obtained, wherein the first difference is negatively correlated with the difference parameter, and the second difference is positively correlated with the difference parameter.

7. The processing technology of a brake screw nut according to claim 1, characterized in that, The specific method for analyzing the wear degree of the grinding wheel by combining the hardness value and utilizing the difference between the grinding wheel wear amount and the initial radius of the grinding wheel includes: The wear factor is obtained by obtaining the difference between the wear amount of the grinding wheel and the initial radius of the grinding wheel. The reciprocal of the hardness value of the brake screw nut is used as the weight of the wear factor to obtain the wear degree of the fine grinding wheel. Both the wear factor and the reciprocal of the hardness value of the brake screw nut are negatively correlated with the wear degree.

8. The processing technology of a brake screw nut according to claim 1, characterized in that, The specific method for determining the grinding stage based on the current moment is as follows: A critical time for the wear stabilization stage and a stable wear rate constant are preset. The difference between the current moment and the critical time for the wear stabilization stage is obtained and denoted as the stage factor. The stable wear rate constant is used as the weight of the stage factor to obtain the grinding stage parameters. Both the stable wear rate constant and the stage factor are negatively correlated with the grinding stage parameters.

9. The processing technology of a brake screw nut according to claim 1, characterized in that, The specific method for adjusting the feed rate of the fine grinding wheel using the grinding force adaptive factor, helix angle compensation factor, and grinding wheel wear compensation factor is as follows: The grinding force adaptive factor, helix angle compensation factor, and grinding wheel wear compensation factor at the current moment are summed to obtain the adjustment factor. The feed rate corresponding to the fine grinding wheel at the previous moment is adjusted using the adjustment factor to obtain the adjusted feed rate of the fine grinding wheel at the current moment. The adjustment factor and the feed rate corresponding to the fine grinding wheel at the previous moment are both positively correlated with the adjusted feed rate.

10. A finishing apparatus for a brake screw nut, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the machining process of a brake screw nut as described in any one of claims 1 to 9.

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