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CN-122018436-A - Multi-spindle concurrent processing obstacle avoidance system and method based on digital twin and CBF

CN122018436ACN 122018436 ACN122018436 ACN 122018436ACN-122018436-A

Abstract

The invention belongs to the technical field of large multi-axis linkage numerical control machining, and particularly relates to a multi-spindle concurrent machining obstacle avoidance system and method based on digital twinning and CBF, which solve the problem that dynamic obstacle avoidance behaviors of multiple spindles cannot be intelligently coordinated. The system comprises a digital twin mapping unit, a layering state observation unit and a safety barrier control unit, wherein the digital twin mapping unit is used for simulating a material removal process in real time and updating a workpiece dynamic geometric model, the layering state observation unit is used for calculating the minimum directional distance and gradient among each main shaft, the workpiece, the main shaft and the like in real time by adopting algorithms such as octree, GJK and the like, the safety barrier control unit is embedded in an interpolation period of a numerical control system, utilizes the distance information to construct higher-order control barrier function constraint with relative order of two, and generates a correction control instruction which is safe and is close to an original instruction as much as possible on the premise of fully considering the dynamics limit of a machine tool shafting by solving a quadratic programming problem. The real-time, dynamic and collision-free processing effect of the multi-spindle in the cooperative operation in a narrow space is realized.

Inventors

  • ZHANG JINQIAO
  • HU HANXI

Assignees

  • 汉霸智能科技(台州)有限公司

Dates

Publication Date
20260512
Application Date
20251231

Claims (10)

  1. 1. Digital twinning and CBF-based multi-spindle concurrent processing obstacle avoidance system is characterized by comprising: The digital twin mapping unit is used for acquiring real-time joint state data of the physical machine tool, and executing Boolean subtraction operation of voxel level or grid level based on preset cutting parameters and a cutter geometric model so as to update dynamic geometric representation of a workpiece in real time; The hierarchical state observation unit is configured to roughly divide a machine tool working space by utilizing an octree structure, and calculate the minimum directional distance h (x) between each processing main shaft and the dynamic workpiece and between the main shafts and the gradient ∇ h (x) of the main shafts relative to state variables by combining a GJK algorithm and an expansion polyhedral algorithm; the safety barrier control unit is embedded in an interpolation period of the numerical control system and is used for solving a quadratic programming optimization problem with a relaxation variable; The digital twin mapping unit comprises predictive material removal logic that pre-calculates a tool sweep volume over N control cycles in the future based on current numerical control code instructions and logically removes the volume from the current workpiece model prior to performing a collision detection calculation, thereby excluding the expected cut contact area in the collision detection; The safety barrier control unit utilizes the minimum directional distance h (x) to construct higher-order control barrier function constraint with a relative order of 2, wherein the constraint comprises a first derivative and a second derivative term of a distance function so as to account for the inertia dynamics limit of each axis of the machine tool; the quadratic programming solver minimizes the deviation between an actual output instruction and a nominal processing instruction on the premise of meeting the constraint of the high-order control barrier function, and generates a corrected safety control instruction u; the objective function of the quadratic programming solver is Wherein For the nominal instruction that the G code resolves to, For the relaxation variables, Q and p are weight matrices.
  2. 2. The obstacle avoidance system of claim 1 wherein the higher order control barrier function constraint satisfies the form of a differential inequality: Wherein x is a machine tool joint state vector, delta is a non-negative relaxation variable for guaranteeing the feasibility of solution, k 1 and k 2 are gain coefficients which are adaptively adjusted based on the maximum braking capacity of a servo shaft, and the value of k 1 、k 2 is in a direct proportion relation with the maximum acceleration a max and the maximum jerk j max of each shaft.
  3. 3. The obstacle avoidance system of claim 1 wherein the higher order control barrier function constraint satisfies the following cascade form: the inequality of the following is satisfied, Wherein L f ,L g is Li Daoshu.
  4. 4. The obstacle avoidance system of claim 1 further comprising a zero-space redundancy analysis module that is activated when the kinematic chain in which the processing spindles are located has redundant degrees of freedom, and that calculates a zero-space projection matrix of the jacobian matrix of each spindle kinematic chain when a collision risk is detected, and generates a pose reconstruction velocity vector within the zero space that is superimposed into the safety control command such that the spindles change their own spatial occupancy poses while maintaining the knife point trajectories and knife axis vectors unchanged.
  5. 5. The obstacle avoidance system of claim 4 wherein a jacobian matrix J is constructed, and a zero-space projection matrix N = I-J † J is calculated; Joint velocity vector generated by obstacle avoidance task Additional control laws are generated by projection matrix mapping into the null space.
  6. 6. The obstacle avoidance system of claim 1 wherein the digital twin mapping unit performs boolean subtraction operations using a GPU parallel computing architecture.
  7. 7. The obstacle avoidance system of claim 1 wherein the hierarchical state observation unit updates voxel states and calculates gradients only within a local region of interest centered at the knife-tip and having a radius R.
  8. 8. A multi-spindle concurrent processing obstacle avoidance method based on digital twinning and CBF, adapted for use in an obstacle avoidance system as claimed in any one of claims 1 to 7, wherein when a potential risk of interference is detected, the following steps are performed: s1, posture negotiation and redundancy elimination, judging whether a system has redundancy degrees of freedom, and if so, avoiding physical interference by rotating a non-key chain shaft or a redundancy shaft under the condition of keeping a cutter point contact point and a cutter vector unchanged; s2, priority dynamic scheduling, namely distributing a master priority and a slave priority according to the cutting load or the precision grade of the current processing task; and S3, executing early warning avoidance, if the redundancy degree of freedom or gesture negotiation is not limited, reducing the feeding speed of the slave processing head according to the task priority W i , and executing forced avoidance along the direction of the escape vector generated by the expansion polyhedron algorithm.
  9. 9. The obstacle avoidance method of claim 8 wherein the redundancy resolution utilizes jacobian zero-space projection characteristics for systems having three axes of rotation or redundant linear axes to adjust the spatial footprint of the spindle head cantilever arm without interrupting the processing path.
  10. 10. The obstacle avoidance method of claim 8 wherein the priority schedule sets the high precision required machining head to a high priority during the finishing stage, the trajectory not fluctuating due to obstacle avoidance, but is assumed to be primarily evasive by the other machining head in rough or idle state.

Description

Multi-spindle concurrent processing obstacle avoidance system and method based on digital twin and CBF Technical Field The invention belongs to the technical field of large five-axis linkage numerical control machining, and particularly relates to a multi-spindle concurrent machining obstacle avoidance system and method based on digital twin and CBF. Background Along with the development of intelligent manufacturing, the multi-spindle numerical control machine tool is widely applied because the multi-spindle numerical control machine tool can process a plurality of surfaces of a workpiece at the same time, and the processing efficiency is remarkably improved. However, the concurrent movement of multiple spindles within a limited working space is very prone to risk of collision interference between spindles and dynamically changing workpieces, which severely restricts the exertion of equipment potential and the safety of the machining process. The traditional obstacle avoidance method is mainly divided into two types, namely 1, offline pre-planning, and collision detection and track adjustment are carried out through simulation software before a numerical control code is generated. The method cannot cope with real-time changes caused by sudden situations, cutter abrasion or workpiece clamping errors in the machining process, and has poor flexibility. 2. Based on the real-time control of the low-order barrier function, the obstacle avoidance problem is converted into real-time control constraint. However, the traditional (first-order) control barrier function only considers the position and the speed, but does not fully consider the dynamic characteristics of acceleration, inertia and the like of a servo shaft of a machine tool, and in a high-speed and high-dynamic scene, obstacle avoidance response lag can be caused by system inertia, so that collision is caused or severe shaking is generated, and the machining precision and the service life of equipment are influenced. In addition, the prior art lacks accurate and real-time sensing capability on dynamically changing workpiece geometry, and also fails to effectively utilize kinematic redundancy existing in multi-axis machine tools, in particular compound machine tools and robot milling systems, and disturbance-free obstacle avoidance is realized through gesture self-adjustment. Therefore, a dynamic obstacle avoidance control system and method that can deeply integrate real-time environmental awareness, consider system dynamics, and intelligently coordinate multi-spindle behaviors is needed. Disclosure of Invention The invention aims to solve the problems in the prior art and provides a multi-spindle concurrent processing obstacle avoidance system based on digital twinning and CBF. The aim of the invention can be achieved by the following technical scheme: A digital twinning and CBF based multi-spindle concurrent processing obstacle avoidance system, comprising: The digital twin mapping unit is used for acquiring real-time joint state data of the physical machine tool, and executing Boolean subtraction operation of voxel level or grid level based on preset cutting parameters and a cutter geometric model so as to update dynamic geometric representation of a workpiece in real time; The hierarchical state observation unit is configured to roughly divide a machine tool working space by utilizing an octree structure, and calculate the minimum directional distance h (x) between each processing main shaft and the dynamic workpiece and between the main shafts and the gradient ∇ h (x) of the main shafts relative to state variables by combining a GJK algorithm and an expansion polyhedral algorithm; the safety barrier control unit is embedded in an interpolation period of the numerical control system and is used for solving a quadratic programming optimization problem with a relaxation variable; The digital twin mapping unit comprises predictive material removal logic that pre-calculates a tool sweep volume over N control cycles in the future based on current numerical control code instructions and logically removes the volume from the current workpiece model prior to performing a collision detection calculation, thereby excluding the expected cut contact area in the collision detection; The safety barrier control unit utilizes the minimum directional distance h (x) to construct a higher-order Control Barrier Function (CBF) constraint with a relative order of 2, wherein the constraint comprises a first derivative and a second derivative term of a distance function so as to account for the inertia kinetic limitation of each axis of the machine tool; the quadratic programming solver minimizes the deviation between an actual output instruction and a nominal processing instruction on the premise of meeting the constraint of the high-order control barrier function, and generates a corrected safety control instruction u; the objective function of the quadratic programming sol