A method and system for speed look-ahead of a fracture path

Abstract

The application discloses a kind of broken path speed look-ahead method and system, method includes the following steps: complete processing path is parsed into multiple micro-path;Determine one or more broken paths from multiple micro-path;Combining the preset processing speed of complete processing path, determine the start feed speed V1 and end feed speed V2 of current broken path;According to V1, V2 and the length of current broken path, complete the interpolation of current broken path.The application calculates the speed of broken start point and broken end point according to inflection point speed, adjusts the feed speed of broken path under the premise of not changing the speed of broken start point and broken end point, thereby interpolates broken path, completes the speed look-ahead of broken path, avoids the frequent start and stop of motor in processing process encountered broken path, causes the wear and tear of machine tool and the low of processing efficiency, and the application can interpolate multiple broken paths simultaneously, and the calculation efficiency is high.

Description

Technical Field

[0001] This invention belongs to the field of motion control technology in CNC systems, specifically relating to a speed prediction method and system for fracture paths. Background Technology

[0002] With the rapid development of modern industry, competition in advanced manufacturing technologies commonly used in automobiles, aerospace, and various other industries is becoming increasingly fierce. This not only demands higher product quality but also increasingly higher production speeds. High-speed, high-precision manufacturing has become a crucial goal for modern manufacturing enterprises.

[0003] When machining special parts with complex curves and surfaces, such as molds, automotive, and aerospace components, high-speed machining requires a significant increase in the feed rate of the tool along the workpiece contour surface. The tool needs to traverse numerous tiny path segments in a short time. If conventional speed control methods are used, employing acceleration, constant speed, and deceleration phases for each path segment, the extremely short path segments fitting the complex curve result in extremely frequent acceleration and deceleration during machining, leading to an uneven speed curve and low machining efficiency. An effective solution to these problems is look-ahead control, which involves identifying inflection points in the machining path in advance and effectively controlling the feed rate. The idea is to approximate the workpiece contour with numerous continuous tiny line segments, pre-read multiple inflection points on these segments, and uniformly plan the speed at these inflection points. This achieves a smooth transition in feed rate, reducing the impact of abrupt speed changes on the machine tool and improving machining efficiency and quality.

[0004] However, current speed forecasting only applies to continuous, small paths. When a break occurs in the machining path, it is often necessary to reduce the feed rate to zero at the end of the machining path before the break, and the machining rate of the path after the break must also start from zero. When a machining path has multiple breaks, it is often necessary to frequently start and stop the machine tool's control motors, resulting in low machining efficiency. Summary of the Invention

[0005] To address the above problems, this invention discloses a velocity prediction method and system for fracture paths.

[0006] This invention discloses a velocity look-ahead method for fracture paths, comprising the following steps:

[0007] Step 1: parse the complete processing path into multiple smaller paths;

[0008] Step 2: Determine one or more break paths from the multiple micro-paths;

[0009] Step 3: Based on the preset processing speed of the complete processing path, determine the starting feed speed V1 and the ending feed speed V2 of the current fracture path;

[0010] Step 4: Based on V1, V2 and the length of the current fracture path, perform interpolation on the current fracture path.

[0011] Step 2 specifically includes:

[0012] Step 2.1: Determine whether the position of the end point of the current micro-path segment coincides with the position of the start point of the next micro-path segment. If not, record the path between the end point of the current micro-path segment and the start point of the next micro-path segment as a broken path.

[0013] Step 2.2: Record the next micro-path segment as the current micro-path segment, and repeat steps 2.1 and 2.2 until the last micro-path segment.

[0014] Step 3 specifically includes:

[0015] Based on the preset processing speed of the complete processing path, determine the feed rate of the inflection point between each group of adjacent micro-paths in the multiple micro-paths;

[0016] The feed rate of the inflection point corresponding to the tiny path connected to the starting point is denoted as V1;

[0017] The feed rate of the inflection point corresponding to the tiny path connected to the endpoint is denoted as V2.

[0018] The preset processing speed of the complete processing path includes the maximum feed acceleration;

[0019] Based on the preset processing speed of the complete processing path, the feed rate of the inflection point between each group of adjacent micro-paths in the multiple micro-paths is determined, specifically including:

[0020] Based on the maximum feed acceleration, calculate the approximate velocity of the inflection point between each group of adjacent micropaths;

[0021] Each of the coarse speeds is compared with the maximum feed speed, and the smaller value is taken as the feed speed for the corresponding inflection point.

[0022] Preferably, the coarse velocity of the inflection point is calculated according to a first formula, which is:

[0023]

[0024] In the formula: v t The approximate velocity at the inflection point; a max The maximum feed acceleration is a preset value; α is the angle between the two small paths corresponding to the inflection point; Ts The interpolation period is the preset value.

[0025] The present invention also discloses a velocity look-ahead system for fracture paths, comprising:

[0026] A processing path parsing module, which is used to parse a complete processing path into multiple micro-paths;

[0027] A fracture path determination module is used to determine one or more fracture paths from the multiple micro-paths.

[0028] A fracture speed determination module is used to determine the starting feed speed V1 and the ending feed speed V2 of the current fracture path by combining the preset processing speed of the complete processing path.

[0029] A fracture path interpolation module is used to interpolate the current fracture path based on V1, V2 and the length of the current fracture path.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] This invention calculates the velocities of the fracture initiation and fracture endpoint based on the inflection point velocity. Without changing the velocities of the fracture initiation and fracture endpoint, it adjusts the feed speed of the fracture path to interpolate the fracture path and complete the velocity prediction of the fracture path. This avoids the frequent start-stop of the motor when encountering the fracture path during the processing, which causes wear on the machine tool and low processing efficiency.

[0032] The method of the present invention can simultaneously calculate the velocities of multiple inflection points to obtain the velocities of multiple fracture initiation points and fracture termination points, and can simultaneously perform velocity look-ahead calculations on multiple fracture paths, thereby improving the computational efficiency of the system.

[0033] This invention calculates the velocity at the break point by combining the angle corresponding to the inflection point, the maximum feed acceleration, and the initial cycle with the maximum feed speed. The calculation is simple and requires little computation. Attached Figure Description

[0034] Figure 1 This is a flowchart of the fracture path look-ahead method of the present invention;

[0035] Figure 2 This is a structural diagram of the fracture path prediction system of the present invention;

[0036] Figure 3 This is a schematic diagram of the software framework structure of the control system of the present invention;

[0037] Figure 4 This is a schematic diagram of the interpolation algorithm in this invention;

[0038] Figure 5 This is a speed variation diagram of interpolation performed on different fracture paths in the embodiments of the present invention;

[0039] Figure 6 This is a schematic diagram of the hardware connection of the CNC motor in this invention;

[0040] Figure 7 This is a schematic diagram illustrating the simultaneous use of forward and backward methods to meticulously calculate the inflection point velocity within the current processing block in this invention.

[0041] Figure 8 This is a speed prospect flowchart of a complete processing path including a fracture path, according to an embodiment of the present invention.

[0042] In the diagram, 101 is the processing path analysis module; 102 is the fracture path determination module; 103 is the fracture velocity determination module; and 104 is the fracture path interpolation module. Detailed Implementation

[0043] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of the invention. However, those skilled in the art will understand that the invention can be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods are omitted so as not to obscure the description of the invention with unnecessary detail.

[0044] like Figure 1 The present invention discloses a velocity look-ahead method for fracture paths, comprising the following steps:

[0045] Step 1: parse the complete processing path into multiple smaller paths;

[0046] like Figure 3 As shown, in this invention, the host computer converts the pre-set motion trajectory of the machine tool into corresponding G-commands, and then transmits the commands to the multi-axis motion controller via a CAN bus or a 485 bus. After receiving and parsing the commands, the controller controls the machine tool's motors to move simultaneously according to their respective target motion trajectories. To ensure the accuracy of the machine tool's movement trajectory, an interpolation algorithm is used to discretize the continuous motion trajectory into a large number of interconnected micro-paths. After discretization, the length of each micro-path is known.

[0047] Step 2: Identify one or more break paths from multiple small paths;

[0048] Step 2 specifically includes:

[0049] Step 2.1: Determine whether the position of the end point of the current micro-path coincides with the position of the start point of the next micro-path. If not, record the path between the end point of the current micro-path and the start point of the next micro-path as a broken path.

[0050] Step 2.2: Record the next micro-path segment as the current micro-path segment, and repeat steps 2.1 and 2.2 until the last micro-path segment.

[0051] In other embodiments of the invention, the fracture path may also be a point where the velocities of the fracture initiation point and fracture endpoint change abruptly and the acceleration directions are opposite.

[0052] Step 3: Combine the preset processing speed of the complete processing path to determine the starting feed speed V1 and ending feed speed V2 of the current fracture path;

[0053] Step 3 specifically includes:

[0054] Based on the preset processing speed of the complete processing path, determine the feed rate of the inflection point between each group of adjacent micro-paths in multiple micro-paths;

[0055] In one embodiment of the invention, the speed connection between the broken paths can also be: there is no connection between the broken paths, the speed is decelerated to zero, and then the next segment restarts.

[0056] In another embodiment of the invention, speed transitions between broken paths can also be achieved without deceleration.

[0057] In this invention, the feed rate of the inflection point corresponding to the tiny path connected to the starting point is denoted as V1;

[0058] The feed rate at the inflection point of the tiny path connecting to the endpoint is denoted as V2.

[0059] Preferably, the preset processing speed of the complete processing path includes the maximum feed acceleration;

[0060] Based on the preset processing speed of the complete processing path, the feed rate of the inflection point between each group of adjacent micro-paths in the multiple micro-path segments is determined, specifically including:

[0061] Based on the maximum feed acceleration, calculate the approximate velocity of the inflection point between each group of adjacent micropaths;

[0062] Preferably, the coarse velocity at the inflection point is calculated according to the first formula, which is:

[0063]

[0064] In the formula: v t The approximate velocity at the inflection point; a maxThe maximum feed acceleration is a preset value; α is the angle between the two small paths corresponding to the inflection point; T s The interpolation period is the preset value.

[0065] Each coarse feed rate is compared with the maximum feed rate, and the smaller value is taken as the feed rate at the corresponding inflection point.

[0066] This invention calculates the velocity at the break point by combining the angle corresponding to the inflection point, the maximum feed acceleration, and the initial cycle with the maximum feed speed. The calculation is simple and requires little computation.

[0067] Step 4: Based on V1, V2 and the length of the current fracture path, complete the interpolation of the current fracture path.

[0068] In this invention, step 4 specifically involves keeping V1 and V2 unchanged, and adjusting the maximum speed and feed acceleration according to the length of the fracture path, combined with an acceleration / deceleration algorithm, to achieve interpolation of the fracture path.

[0069] Figure 5 This is a speed variation diagram of interpolation performed on different fracture paths in an embodiment of the present invention.

[0070] The method of this invention can simultaneously calculate the velocities of multiple inflection points to obtain the velocities of multiple fracture initiation points and fracture termination points, and the calculation can simultaneously perform velocity look-ahead for multiple fracture paths, thereby improving the computational efficiency of the system.

[0071] like Figure 2 As shown, the present invention also discloses a velocity look-ahead system for fracture paths, comprising:

[0072] The processing path parsing module 101 is used to parse a complete processing path into multiple micro-paths.

[0073] The fracture path determination module 102 is used to determine one or more fracture paths from multiple micro-paths.

[0074] The fracture speed determination module 103 is used to determine the starting feed speed V1 and the ending feed speed V2 of the current fracture path by combining the preset processing speed of the complete processing path.

[0075] The fracture path interpolation module 104 is used to interpolate the current fracture path based on V1, V2 and the length of the current fracture path.

[0076] This invention calculates the velocities of the fracture initiation and termination points based on the inflection point velocity. Without changing the velocities of the fracture initiation and termination points, it adjusts the feed speed of the fracture path to interpolate the fracture path, thereby completing the velocity prediction of the fracture path. This avoids the frequent start-stop of the motor when encountering the fracture path during processing, which causes wear on the machine tool and low processing efficiency.

[0077] like Figure 8 As shown, in another embodiment, the process of implementing the present invention for a complete processing path including continuous and broken paths is as follows:

[0078] Step 1: Enter the preset value into the system;

[0079] Enter the following preset values ​​into the system: the starting speed of the first micro-path segment is Vstart, the ending speed of the last micro-path segment is Vend, the feed jerk during acceleration is J1, the feed jerk during deceleration is J2, and the interpolation period is T. S The maximum feed rate is V M .

[0080] Step 2: Calculate the feed rate at the inflection point (the connection point between tiny paths) using the forward push method;

[0081] The machine tool controller pre-reads j paths after the starting point, starting from the feed rate Vstart of the first path, and combining the length of each small path segment with the maximum feed rate V. M The approximate velocity V at the current path inflection point can be calculated. t1 In V M and V t1 The minimum value between the two points is taken as the feed speed v of the current inflection point. Since the inflection point is the starting point and the ending point of the next micro-path, the feed speed of the currently calculated inflection point can be used as the starting speed of the next micro-path, and thus the speed of each inflection point can be calculated in turn.

[0082] Step 3: Calculate the inflection point feed rate using the backtracking method;

[0083] The machine tool controller pre-reads the j paths before the starting point, based on the starting speed Vend of the last path, and the length of each small path combined with the maximum feed rate V. M The approximate velocity V at the current path inflection point can be calculated. t2 In V M and V t2 The minimum value between the two points is taken as the feed speed v′ of the current inflection point. Since the inflection point is the end point of the current micro-path and the starting point of the next micro-path, the feed speed of the currently calculated inflection point can be used as the starting speed of the next micro-path, and thus the speed of each inflection point can be calculated in turn.

[0084] Step 4: Calculate the inflection point feed rate by combining the forward push method and the backtracking method;

[0085] like Figure 7 As shown in this embodiment of the invention, the processing path is planned into multiple processing areas. The division principle is that all paths on every two adjacent break paths are divided into one block.

[0086] Let V be the feed rate at the starting point of the block containing the current machining path. h The end-point feed rate of the block is V. s+1 Because the feed rate at the starting point of the current block is the feed rate at the end point of the previous broken path. The feed rate at the end point of the block is the feed rate at the starting point of the subsequent broken path. Break point V h and V s+1 The speed can be obtained from the calculation method described above, and will not be repeated here;

[0087] Check and record the longest tiny continuous path L of the current processing block. r Without changing the starting point velocity V of the block where the current processing path is located, the fracture initiation velocity is... h and the final feed rate V s+1 In this case, the velocity Vg (g = h+1, h+2, h+3, ..., r-1, r) of each inflection point within the current processing path block is calculated from front to back using a look-ahead method, while the velocity Vw (w = s+1, s, ..., r+1) of each inflection point within the current processing path block is calculated from back to front using a backtracking method, until the starting point V of the longest infinitesimal continuous path in this processing block is calculated. r and the endpoint V r+1 At this point, without changing V... r and V r+1 In this case, the longest path can be interpolated by readjusting the feed jerk J1 and J2;

[0088] Step 5: Verify the calculated inflection point velocity three times to obtain the final inflection point velocity;

[0089] Regression fitting was performed on the inflection point velocities calculated three times, combined with the preset maximum feed rate V. M The minimum value is selected as the final inflection point velocity to be calculated.

[0090] Step 6: Interpolate the complete machining path based on the final inflection point speed;

[0091] Since the speeds of adjacent inflection points are not necessarily the same, acceleration / deceleration can be determined based on their magnitudes. When the speed of the current inflection point is less than the speed of the next inflection point, the feed rate needs to be increased, provided it does not exceed the maximum feed rate V. MIn the case of a given situation, the required number of acceleration steps can be calculated; correspondingly, if the current inflection point speed is greater than the next inflection point speed, the required number of deceleration steps can be calculated.

[0092] Take the interpolation algorithm from the first inflection point to the second inflection point as an example;

[0093] If acceleration is required, the number of acceleration steps can be calculated using the second formula:

[0094]

[0095] In the formula, na is the number of acceleration steps, and k is a constant, which is a preset value;

[0096] If deceleration is required, the number of deceleration steps can be calculated using the second formula:

[0097] The number of steps required for the deceleration phase can be derived from this formula:

[0098]

[0099] In the formula, n b The deceleration step is k, which is a constant and a preset value.

[0100] In this embodiment of the invention, the feed speed is anticipated by using a method that does not decelerate when there is tangency between small line segments or when the change in direction angle is less than a certain value, or by setting a maximum speed limit when the motion path encounters a sharp turn. This method can ensure interpolation efficiency while meeting the accuracy of the interpolation trajectory.

[0101] Compared with the prior art, the present invention has the following beneficial effects:

[0102] (1) The present invention calculates the speed of the fracture start point and the fracture end point based on the inflection point speed. Without changing the speed of the fracture start point and the fracture end point, the feed speed of the fracture path is adjusted to interpolate the fracture path and complete the speed prediction of the fracture path. This avoids the need for the motor to start and stop frequently when encountering the fracture path during the processing, which causes wear on the machine tool and low processing efficiency.

[0103] (2) The method of the present invention can calculate multiple inflection point velocities simultaneously to obtain the velocities of multiple fracture initiation points and fracture endpoints, and can simultaneously perform velocity look-ahead calculations on multiple fracture paths, thereby improving the computational efficiency of the system.

[0104] (3) The present invention calculates the velocity of the fracture point by combining the angle of the inflection point, the maximum feed acceleration and the initial cycle with the maximum feed speed. The calculation is small and simple.

[0105] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A velocity look-ahead method for fracture paths, characterized in that, Includes the following steps: Step 1: parse the complete processing path into multiple smaller paths; Step 2: Determine one or more break paths from the multiple micro-paths; Step 3: Based on the preset processing speed of the complete processing path, determine the starting feed speed V1 and the ending feed speed V2 of the current fracture path; Step 4: Based on V1, V2 and the length of the current fracture path, perform interpolation on the current fracture path.

2. The velocity prediction method for fracture paths according to claim 1, characterized in that, Step 2 specifically includes: Step 2.1: Determine whether the position of the end point of the current micro-path segment coincides with the position of the start point of the next micro-path segment. If not, record the path between the end point of the current micro-path segment and the start point of the next micro-path segment as a broken path. Step 2.2: Record the next micro-path segment as the current micro-path segment, and repeat steps 2.1 and 2.2 until the last micro-path segment.

3. The velocity prediction method for fracture paths according to claim 1, characterized in that, Step 3 specifically includes: Based on the preset processing speed of the complete processing path, determine the feed rate of the inflection point between each group of adjacent micro-paths in the multiple micro-paths; The feed rate of the inflection point corresponding to the tiny path connected to the starting point is denoted as V1; The feed rate of the inflection point corresponding to the tiny path connected to the endpoint is denoted as V2.

4. The velocity prediction method for fracture paths according to claim 3, characterized in that, The preset processing speed of the complete processing path includes the maximum feed acceleration; Based on the preset processing speed of the complete processing path, the feed rate of the inflection point between each group of adjacent micro-paths in the multiple micro-paths is determined, specifically including: Based on the maximum feed acceleration, calculate the approximate velocity of the inflection point between each group of adjacent micropaths; Each of the aforementioned coarse speeds is compared with the maximum feed speed, and the smaller value is taken as the feed speed for the corresponding inflection point.

5. The velocity prediction method for fracture paths according to claim 4, characterized in that, The approximate velocity at the inflection point is calculated according to the first formula, which is: ， In the formula: The approximate velocity at the inflection point; This is the maximum feed acceleration, which is a preset value. The inflection point corresponds to the angle between two tiny paths. The interpolation period is the preset value.

6. A velocity look-ahead system for a fracture path, characterized in that, include: A processing path parsing module, which is used to parse a complete processing path into multiple micro-paths; A fracture path determination module is used to determine one or more fracture paths from the multiple micro-paths. A fracture speed determination module is used to determine the starting feed speed V1 and the ending feed speed V2 of the current fracture path by combining the preset processing speed of the complete processing path. A fracture path interpolation module is used to interpolate the current fracture path based on V1, V2 and the length of the current fracture path.

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