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CN-121973225-A - Control method and system for mechanical arm for high-precision machining

CN121973225ACN 121973225 ACN121973225 ACN 121973225ACN-121973225-A

Abstract

The invention discloses a control method and a control system of a mechanical arm for high-precision machining, and relates to the technical field of machining control, wherein the method comprises the steps of constructing an operation data set, calculating a screw displacement error Wx (t), acquiring an angle error vector epsilon (phi) through a mapping relation between time and angle established by a screw transmission ratio, and carrying out superposition averaging on the angle error vector by adopting a periodic signal superposition technology to obtain a screw angle error value Es (phi); the method comprises the steps of obtaining fitting parameter groups through a least square fitting algorithm, constructing a screw pitch error index Wwc (phi), carrying out dynamic error compensation on a screw rotation angle variable phi to generate a corrected path track Xc, calculating a periodic residual error ratio Rre of errors before and after correction through extracting actual displacement and theoretical displacement data, and evaluating a compensation state. According to the method, dynamic correction and precise control of the motion error of the mechanical arm screw rod are realized through time and angle domain collaborative modeling and periodic residual error closed-loop evaluation.

Inventors

  • XU SONGQING
  • XU XIUFENG
  • XU HUAFENG

Assignees

  • 深圳市松青锌镁铝精密压铸有限公司

Dates

Publication Date
20260505
Application Date
20260311

Claims (10)

  1. 1. A control method of a mechanical arm for high-precision machining is characterized by comprising the following steps: S1, acquiring signal data when a mechanical arm executes machining path movement in real time through a monitoring technology and a servo control system, acquiring an operation data set after data preprocessing, and calculating a screw displacement error Wx (t); s2, establishing a corresponding relation between time and angle, carrying out phase normalization and period resampling, establishing an angle error vector epsilon (phi) through linear interpolation, and carrying out superposition average calculation to obtain a lead screw angle error quantity Es (phi); S3, carrying out matching solving on the angle error quantity Es (phi) of the screw rod by adopting a least square fitting algorithm to obtain a fitting parameter set, and then carrying out pitch error analysis on the screw rod according to the fitting parameter set; s4, carrying out dynamic error compensation on a screw rod rotation angle variable phi according to a screw pitch error analysis result, superposing the screw rod rotation angle variable phi on the basis of a theoretical path track Xt to form a corrected path track Xc, generating a corrected servo control signal, synchronously acquiring actual displacement Xa1 in a correction process, differentiating the actual displacement Xa1 with the corrected path Xc (t) to obtain a displacement error Wx (t), and transmitting the displacement error Wx (t) back to S1 in real time; s5, after each lead screw period is finished, extracting an actual displacement Xa1 and a pitch error analysis result in the current lead screw period, and calculating a periodic residual ratio Rre of errors before and after correction to carry out compensation state evaluation.
  2. 2. The method for controlling a high-precision machining robot arm according to claim 1, wherein S1 comprises S11; S11, acquiring signal data of the mechanical arm during executing the machining path movement in real time through a monitoring technology and a servo control system; The monitoring technology comprises an angle coding technology and a laser displacement measuring means; When the mechanical arm executes the machining path movement through an angle coding technology and a laser displacement measuring means, a rotation angle variable signal and an actual displacement signal of the lead screw are collected in real time, and a theoretical displacement instruction corresponding to each time point output by the servo control system is called.
  3. 3. The method for controlling a mechanical arm for high-precision machining according to claim 2, wherein S1 further comprises S12 and S13; s12, performing signal synchronization, sliding filtering and outlier rejection on the acquired signal data to acquire an operation data set; The signal synchronization is processed by time reference unification and phase alignment through a time synchronization control algorithm and a time stamp comparison algorithm, data offset caused by signal sampling delay, bus transmission and servo response difference is eliminated, and sliding filtering and outlier rejection are used for inhibiting high-frequency disturbance signals caused by environmental vibration, electromagnetic interference and optical reflection noise; the operation data set comprises a rotation angle variable phi, an actual displacement Xa and a theoretical displacement Xt; S13, calculating according to the operation data set through a time synchronization algorithm to obtain a screw displacement error Wx (t), wherein the screw displacement error Wx (t) =Xa (t) -Xt (t), and storing the screw displacement error Wx (t) =Xa (t) -Xt (t) into a time sequence database according to a time index.
  4. 4. The method for controlling a high-precision machining robot arm according to claim 3, wherein S2 comprises S21 and S22; S21, synchronously recording pulse count N of a servo encoder and a corresponding lead screw displacement error Wx (t) in a sampling period delta t, establishing a corresponding relation phi=N×rs between time and angle according to a lead screw transmission ratio rs, synchronously mapping an error signal from a time domain to an angle domain, acquiring an angle sequence epsilon (phi), carrying out phase normalization and period resampling processing, discretizing an angle interval [0, ts ] into m equidistant sampling points phi i (i=1, 2, the number of m), and reassigning original error points to standard angles through linear interpolation to form angle error vectors epsilon (phi) = { epsilon (phi 1), epsilon (phi 2), epsilon (phi m) of uniform sampling density; s22, carrying out superposition average calculation on an angle error vector epsilon (phi) in a lead screw period by using a periodic signal superposition technology and an angle period Ts corresponding to the lead screw pitch as a sliding window, and obtaining a lead screw angle error quantity Es (phi), wherein the angle error quantity Es (phi) represents a repeated error rule of the lead screw in a complete lead screw period, describes an error change trend of the lead screw in a complete screw pitch rotation, and is used for identifying the error rule, and specifically comprises the following steps: where n represents the number of statistical cycles and k represents the variable of the number of statistical cycles.
  5. 5. The method for controlling a high-precision machining robot arm according to claim 4, wherein S3 comprises S31 and S32; S31, matching and solving a lead screw angle error waveform and an ideal periodic waveform by adopting a least square fitting algorithm for the lead screw angle error quantity Es (phi), wherein the standard form of the least square fitting algorithm in a periodic function fitting scene is as follows The fitting error energy Q, the sine component amplitude As and the cosine component amplitude Bs are biased to zero to form a two-element linear equation set And obtaining a fitting parameter set comprising a sine component amplitude As and a cosine component amplitude Bs, wherein sin represents a sine function, cos represents a cosine function, pi represents a circumference ratio, and the value is two bits after decimal point.
  6. 6. The method for controlling a mechanical arm for high-precision machining according to claim 5, wherein: the step S3 further comprises the step S32; S32, carrying out pitch error analysis on the lead screw by adopting a nonlinear sine and cosine function modeling technology on the fitting parameter set, and constructing a lead screw pitch error index Wwc (phi) for describing the dimensional position error change of the lead screw under any rotation angle variable phi, wherein the method specifically comprises the following steps: And converting the identified error result into a compensation model for control, wherein sin represents a sine function, cos represents a cosine function, pi represents a circumference rate, and the value is two bits after decimal point.
  7. 7. The method for controlling a high-precision machining robot arm according to claim 6, wherein S4 comprises S41; S41, loading a screw pitch error index Wwc (phi) to a control module in real time through a servo control logic interface calling mechanism when the mechanical arm executes a machining path instruction, performing dynamic error compensation on a screw rotation angle variable phi in the motion process of the mechanical arm, and superposing the dynamic error compensation on a theoretical path track Xt to form a corrected path track Xc, wherein the method specifically comprises the following steps of: wherein Xt (t) is a theoretical track signal of a processing task at the moment t, wwc (phi (t)) is a screw pitch error index output by a screw rotation angle variable at the moment t, and Xc (t) is a corrected path track signal generated at the moment t; S42, the mechanical arm controller corrects the pulse output frequency and the phase according to the screw rotation angle variable phi and the screw pitch error index Wwc (phi) in each servo period, so that the output quantity of the driving signal and the corrected path track Xc are kept synchronous, and a corrected servo control signal is generated; In the process of correcting the servo control system according to the corrected servo control signal, synchronously acquiring the actual displacement Xa1 in the current lead screw period, carrying out differential ratio pair with the current corrected path track signal Xc (t) to acquire a lead screw displacement error Wx (t), and transmitting the acquired lead screw displacement error Wx (t) back to S1 in real time.
  8. 8. The method for controlling a high-precision machining robot arm according to claim 7, wherein S5 comprises S51; S51, after each lead screw period is finished, automatically extracting an actual displacement Xa1 and a lead screw pitch error index Wwc (phi) in the current lead screw period through a time sequence database retrieval technology, calculating a corrected lead screw displacement error Wx1 (t) with a theoretical displacement Xt, and then calculating a periodic residual error ratio Rre of errors before and after correction, wherein the periodic residual error ratio Rre is used for quantifying the periodic error correction degree of a compensation model in the current period, and specifically comprises the following steps: 。
  9. 9. The method for controlling a high-precision machining robot arm according to claim 8, wherein S5 further comprises S52; S52, according to the precision die processing neighborhood, the position error is kept within 20% of the tolerance range, and compensation state evaluation is carried out on the position error and the periodic residual error ratio Rre, wherein the specific evaluation scheme is as follows; when the periodic residual ratio Rre is smaller than 0.2, the compensation effect is stable, and the current compensation instruction is kept; When the periodic residual ratio Rre is more than or equal to 0.2, indicating that the deviation still exists after compensation, automatically marking the current lead screw period as a compensation offset period, recording the rotation angle variable phi 1 after compensation and the actual displacement Xa1, and performing iterative compensation through S2.
  10. 10. The mechanical arm control system for high-precision machining comprises the mechanical arm control method for high-precision machining, which is characterized by comprising a data acquisition module, an error trend analysis module, an error compensation module, a track correction module and a dynamic evaluation module; the data acquisition module is used for acquiring signal data when the mechanical arm executes machining path movement in real time through a monitoring technology and a servo control system, acquiring an operation data set after data preprocessing, and calculating a screw displacement error Wx (t); The error trend analysis module is used for establishing a corresponding relation between time and angle, carrying out phase normalization and period resampling, establishing an angle error vector epsilon (phi) through linear interpolation, and carrying out superposition average calculation to obtain a lead screw angle error quantity Es (phi); The error compensation module is used for carrying out matching solution on the angle error quantity Es (phi) of the screw rod by adopting a least square fitting algorithm to obtain a fitting parameter set, and then carrying out pitch error analysis on the screw rod according to the fitting parameter set; The track correction module is used for carrying out dynamic error compensation on a screw rod rotation angle variable phi according to a screw pitch error analysis result, superposing the screw rod rotation angle variable phi on the basis of a theoretical path track Xt to form a corrected path track Xc, generating a corrected servo control signal, synchronously acquiring actual displacement Xa1 in the correction process, differentiating the actual displacement Xa1 with the corrected path Xc (t) to obtain a displacement error Wx (t), and transmitting the displacement error Wx (t) back to the data acquisition module in real time; The dynamic evaluation module is used for extracting the actual displacement Xa1 and the pitch error analysis result in the current lead screw period after each lead screw period is finished, and calculating the periodic residual error ratio Rre of the errors before and after correction to evaluate the compensation state.

Description

Control method and system for mechanical arm for high-precision machining Technical Field The invention relates to the technical field of machining control, in particular to a method and a system for controlling a mechanical arm for high-precision machining. Background In the field of modern high-precision machining, a mechanical arm is used as an important actuating mechanism of automatic equipment and is used for carrying out operations such as positioning, cutting, carrying, clamping and the like of a precise workpiece. With the increase of the requirements of complex curved surface machining and microstructure manufacturing, the track precision of the mechanical arm when executing the machining path motion directly determines the quality and the size consistency of the machined surface. The core motion component of the mechanical arm is usually composed of a servo system, a transmission mechanism and a screw rod execution unit, wherein the screw rod is used as a key component for converting rotary motion into linear motion, and the transmission precision of the screw rod has a decisive influence on the pose precision of the end execution point of the mechanical arm. Therefore, the dynamic control and compensation are performed on the error accumulation and nonlinear response of the screw transmission system in long-term operation, and the method becomes a key research direction in the field of high-precision machining mechanical arm control. Screw pitch errors and angle errors caused by factors such as manufacturing errors, assembly deviations, thermal expansion, abrasion and the like commonly exist in the existing screw transmission system, and the errors can cause deviation between the tail end displacement of the mechanical arm and a theoretical track in the machining process. The existing compensation method mostly adopts a static correction mode, obtains a lead screw error curve through offline measurement, and performs fixed compensation in a control system. However, static compensation is difficult to reflect dynamic error changes of the screw in the actual running process, and particularly under the working conditions of high-frequency motion and temperature gradient change, the screw error presents nonlinear and time-varying characteristics, and the traditional compensation model is not easy to accurately correct the real-time error. In addition, the partial correction method only performs closed-loop control through position feedback, and fails to analyze the dynamic coupling relation between the screw rotation angle variable and the actual displacement, so that the phenomenon of compensation lag or excessive correction is caused. Disclosure of Invention Aiming at the defects of the prior art, the invention provides a control method and a control system for a mechanical arm for high-precision machining, which solve the problems in the prior art. In order to achieve the purpose, the invention is realized by the following technical scheme that the mechanical arm control method for high-precision machining comprises the following steps: S1, acquiring signal data when a mechanical arm executes machining path movement in real time through a monitoring technology and a servo control system, acquiring an operation data set after data preprocessing, and calculating a screw displacement error Wx (t); s2, establishing a corresponding relation between time and angle, carrying out phase normalization and period resampling, establishing an angle error vector epsilon (phi) through linear interpolation, and carrying out superposition average calculation to obtain a lead screw angle error quantity Es (phi); S3, carrying out matching solving on the angle error quantity Es (phi) of the screw rod by adopting a least square fitting algorithm to obtain a fitting parameter set, and then carrying out pitch error analysis on the screw rod according to the fitting parameter set; s4, carrying out dynamic error compensation on a screw rod rotation angle variable phi according to a screw pitch error analysis result, superposing the screw rod rotation angle variable phi on the basis of a theoretical path track Xt to form a corrected path track Xc, generating a corrected servo control signal, synchronously acquiring actual displacement Xa1 in a correction process, differentiating the actual displacement Xa1 with the corrected path Xc (t) to obtain a displacement error Wx (t), and transmitting the displacement error Wx (t) back to S1 in real time; s5, after each lead screw period is finished, extracting an actual displacement Xa1 and a pitch error analysis result in the current lead screw period, and calculating a periodic residual ratio Rre of errors before and after correction to carry out compensation state evaluation. Preferably, the S1 includes S11; S11, acquiring signal data of the mechanical arm during executing the machining path movement in real time through a monitoring technology and a servo control system; The m