CN-122018426-A - Quick cutter shaft motion control method, medium and device based on dynamic unbalance

CN122018426ACN 122018426 ACN122018426 ACN 122018426ACN-122018426-A

Abstract

The invention relates to the technical field of precision machining tool control, in particular to a dynamic unbalance-based fast cutter shaft motion control method, medium and equipment. The method is applied to a dynamic rotary cutter cutting system. The method comprises the steps of obtaining processing track characteristics in real time, predicting tracking errors through a dynamic unbalance disturbance prediction model, superposing the errors on an original track to generate a compensation track, and taking the compensation track as a control input. The prediction model is obtained by applying sweep frequency signal acquisition data to the U-axis when the B-axis rotates and adopting Gaussian process regression to learn the mapping relation between the reference track and the error. The invention predicts and counteracts disturbance through a feedforward compensation mechanism, avoids phase lag, improves track tracking precision, solves the problem of dynamic centroid shift caused by U-axis displacement, and improves the processing quality of the micro lens array.

Inventors

ZHU LIMIN
WU HAO
ZHANG XINQUAN
REN MINGJUN
Jia Zelong
WU JINCHI
Tan Lingwen

Assignees

上海交通大学

Dates

Publication Date: 20260512
Application Date: 20251121

Claims (10)

1. A method for controlling movement of a fast cutter shaft based on dynamic unbalance, which is applied to a dynamic rotary cutter cutting system, wherein the system comprises a machine tool B shaft and a fast cutter device fixedly installed at the rotary end part of the machine tool B shaft, the fast cutter device comprises a fast cutter U shaft arranged along the radial direction of a workpiece and a fast cutter V shaft arranged along the cutting depth direction, and the method comprises the following steps: acquiring reference signal characteristics of a current processing track in real time; Predicting corresponding tracking errors through a pre-trained dynamic unbalance disturbance prediction model; superposing the predicted tracking error to the original reference track to generate a compensated reference track signal; taking the compensated reference track signal as an initial control input of a fast cutter U shaft; wherein the dynamic unbalance disturbance prediction model is obtained by the following method: Under the working condition that a machine tool B shaft rotates at a preset rotating speed, applying a frequency sweep signal to a fast cutter U shaft, and collecting a reference track and a corresponding actual output track of the fast cutter U shaft to construct a training data set, wherein the frequency range of the frequency sweep signal covers the frequency spectrum characteristics required by a processing track; based on the training data set, a Gaussian process regression model is adopted to learn a nonlinear mapping relation between the reference track characteristics and the tracking errors, and the dynamic unbalance disturbance prediction model is obtained.
2. The method according to claim 1, wherein the method further comprises: Obtaining a residual error between the actual output position of the fast cutter U shaft and the initial control input; The residual error is subjected to feedback adjustment by adopting a proportional-integral controller, and a feedback control signal is generated; and superposing the feedback control signal and the feedforward compensation signal to jointly control the motion of the fast cutter U-axis, thereby forming a feedforward and feedback double closed-loop control structure.
3. The method of claim 1, wherein the reference signal characteristics include at least a position, a velocity, an acceleration, a frequency characteristic of the reference trajectory.
4. The method of claim 4 wherein the reference signal characteristics further comprise a current position of a fast cutter U-axis, a machine B-axis rotational speed, and a machine B-axis phase angle.
5. The method according to claim 1, wherein the preset rotation speed is consistent with the rotation speed of the machine tool B-axis during actual machining, so that the dynamic unbalance disturbance prediction model obtained through training is suitable for compensation control under specific rotation speed working conditions.
6. The method of claim 1, wherein the fast knife device is a double-piezoelectric ceramic driven fast knife device and comprises a fast knife U shaft and a fast knife V shaft, wherein the fast knife U shaft is arranged along the radial direction of a workpiece, and the fast knife V shaft is orthogonally arranged on an actuator of the fast knife U shaft along the depth cutting direction; and the rotating motion of the machine tool B shaft is linked with the micro-displacement motions of the fast cutter U shaft and the fast cutter V shaft to form a real spiral cutter path for processing the free-form surface micro lens array.
7. The method of claim 6, wherein the knife V-axis is fully embedded within the actuator of the knife U-axis, forming an orthogonal tandem nested configuration.
8. The method of claim 6, wherein the dynamic rotary cutter cutting system further comprises: The mass balance block is arranged at the rotating end part of the machine tool B shaft, is positioned at two opposite sides of the machine tool B shaft with the double-piezoelectric ceramic driving fast knife device, and is used for compensating the weight of the double-piezoelectric ceramic driving fast knife device and realizing the static balance of the knife cutting system.
9.A non-transitory computer readable storage medium storing a computer program, wherein the computer program when executed by a processor implements a fast arbor motion control method based on dynamic unbalance according to any of claims 1-8.
10. An electronic device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, wherein the processor implements a fast arbor motion control method based on dynamic unbalance according to any of claims 1-8 when executing the computer program.

Description

Quick cutter shaft motion control method, medium and device based on dynamic unbalance Technical Field The invention relates to the technical field of precision machining tool control, in particular to a dynamic unbalance-based fast cutter shaft motion control method, medium and equipment. Background In the field of precision optical element manufacturing, the surface topography accuracy of microlens arrays is closely related to optical performance. In the prior art, a rotary Fast Tool Servo (FTS) system is widely used for precision machining of free-form surface microlens arrays. A typical system configuration comprises a machine B-axis as the primary axis of rotational motion, and a two-dimensional fast knife device integrated into the rotating end of the machine B-axis. The fast tool device is generally composed of a fast tool U-axis (workpiece radial direction) and a fast tool V-axis (depth of cut direction) arranged in quadrature, wherein the fast tool V-axis end is used for mounting a single crystal diamond cutting tool. In the processing process, the machine tool B shaft provides continuous main rotary motion, the fast cutter U shaft and the fast cutter V shaft perform micro-displacement adjustment according to the target surface shape, and the three parts cooperatively move to form a spiral cutter path corresponding to each micro lens unit in the large-scale micro lens array, so that the accurate forming of the free curved surface is realized. However, in the above system configuration, the trajectory tracking accuracy of the fast-knife U-axis is significantly affected by dynamic imbalance disturbance. Because the fast knife device is directly fixedly connected to the end part of the B shaft of the rotary machine tool, when the B shaft of the machine tool is in a high-speed rotation state, any non-uniformity of the mass distribution of the system can generate centrifugal force and moment, vibration is caused, and track deviation is caused. In the rotary fast knife servo cutter cutting system described above, such dynamic imbalance disturbances mainly result from two aspects: First, it is difficult for the system to reach an ideal static equilibrium state. Although balancing weights can be adopted for balancing adjustment in the assembly process, the system can only realize static balance with limited precision due to the comprehensive influence of machining tolerance, assembly error, uneven material density distribution and other factors. When the rotation speed of the B axis of the machine tool is increased, the centrifugal moment generated by the initial residual unbalance amount is increased in proportion to the square of the angular velocity, and the disturbance amplitude can reach hundreds of times of the magnitude of the working condition of low rotation speed (such as 80 rpm) under the working condition of high rotation speed (such as 800 rpm), so that the machining precision is seriously deteriorated. Secondly, in the micro lens array processing process, in order to ensure that the geometric center of each micro lens unit is accurately aligned with the movement track of the cutter, the U axis of the fast cutter needs to be subjected to position repositioning when different units are processed. This process characteristic results in the center of mass position of the fast knife device changing in real time with the fast knife U-axis displacement, creating a dynamic eccentric effect. It is noted that even if an ideal static balance is achieved during initial assembly, any displacement of the fast knife U-axis will disrupt the original balance and cause the knife to deviate from the axis of rotation. Such dynamic centroid shifts caused by active motion of the fast knife U-axis have time-varying characteristics, and the traditional one-time static balance technology cannot be effectively restrained. The two types of dynamic unbalance disturbance are mutually coupled under the working condition of high-speed rotation, and the track tracking performance of the fast cutter U-axis is severely restricted. Particularly, when processing special-shaped microlenses (such as triangles and quadrilaterals) with sharp corner features, the fast cutter U-axis needs to accurately track the track instruction of high-frequency change. However, periodic disturbances caused by dynamic imbalance can lead to system response delays, resulting in corner rounding and surface shape distortion, significantly degrading optical surface quality. The prior art generally adopts a proportional-integral (PI) controller to form a single closed-loop control system, and the method can only carry out feedback correction on the track error which occurs, and cannot predict the periodic disturbance related to the active rotation inhibition. Therefore, development of an advanced control method capable of effectively identifying and compensating dynamic unbalance disturbance is needed to improve the track tracking precision of the system