TW201344383A - A trajectory optimization method for machine tools - Google Patents

Abstract

A trajectory optimization method based on tension splines is designed for machine tools. Trajectories interpolated/generated with this method can pass all control points smoothly. By changing the tension values of each tension spline, the smoothness of each tension spline can be assigned freely. Online trajectory interpolation/generation can also be achieved by combining each new trajectory to the current one if we set the start boundary condition of the new one to be the same as the end boundary condition of the current one.

Description

Process path optimization method for machine tools

The invention relates to a method for optimizing a machining path for a machine tool, in particular to a method for generating and interpolating a machining path of a machine tool, which can be used for a numerical control device of a mechanical device, for example : Numerical control device for CNC lathe, numerical control device for CNC milling machine, numerical control device for tapping machine, or numerical control device for drilling machine.

With the advancement of computer numerical control (CNC) machine tool equipment, the traditional processing method of line segment interpolation can not meet the requirements of high speed and high precision, and more advanced interpolation methods are needed to describe the complexity. Surfaces or curves, the most widely used interpolation methods are B-Spline, Cubic Spline, polynomial curve or direct linear interpolation. These methods have shortcomings.

However, the most common interpolator using B-Spline as the interpolation curve is NURBS (Non-uniform rational B-Spline). The biggest trouble of NURBS in application is that the generated trajectory does not necessarily pass the control point. That is to go through the specified trajectory, you must reverse the corresponding control points to let the machine tool track.

In addition, the shape of Cubic Spline and the polynomial curve is difficult to control freely. Although Cubic Spline is smooth, it is difficult to generate a hard and straight curve. The polynomial curve is very prone to excessive amplitude and jitter.

However, the trajectory generated by the direct linear interpolation method is discontinuous in the speed (one-time differential), and it is easy to cause damage and vibration to the machine tool, so it is rarely used.

Therefore, the present invention proposes that the use of Tension Spline as an interpolation curve algorithm can achieve the advantages of convenient control through all control points, smooth track and track shape, and is more advantageous than the aforementioned interpolation method, and has different characteristics. .

In order to solve the above problems, one of the main objects of the present invention is to provide a processing path optimization method for a machine tool, which adjusts the curve between the control points on the processing path by the tension value in the trajectory interpolation algorithm of Tension Spline. The degree of sleekness can be used to solve the problem that the general interpolation curve often occurs. For example, the generated machining path trajectory does not necessarily pass through all the control points or the generated trajectory is prone to excessive amplitude and jitter.

In accordance with the above objects, the present invention provides a method for optimizing a processing path for a machine tool, comprising the steps of: providing a processing program and interpreting a processing program; providing a path planning unit that receives the interpreted processing program, And according to a numerical control parameter, a processing path is planned; an interpolator of the trajectory interpolation algorithm of the force cloud line is provided to smooth the processing path; and a motion planning unit is provided, which is based on the numerical control parameter and the tension cloud shape. The interpolator of the line trajectory interpolation algorithm gives the motion characteristics of the smoothing processing path; provides an interpolation unit, which is an interpolator of the interpolation algorithm based on the numerical control parameters and the tension cloud line. Completing the information of the machining path with motion characteristics of the motion planning, performing interpolation operation and generating an interpolation command; providing a driver to send the interpolation command to the driver; and using the driver to send a control signal to drive and control an axial motor; And providing a position sensing component that returns information on the position of the axial motor to the driver.

Through the optimization of the processing path for the machine tool provided by the present invention, the tension value of the tension cloud line (Tension Spline) can be adjusted to achieve the passing of all control points, track smoothing and track shape. Easy to control the advantages.

The present invention mainly discloses a processing path optimization method for a machine tool, wherein the construction and function of the numerical control device of the mechanical device mentioned and the principle of the interpolation curve B-Spline, Cubic Spline and polynomial curve, It will be apparent to those skilled in the relevant art, and the description below will be described in detail only with respect to the features of the processing path optimization method used in the machine tool of the present invention. In addition, the drawings in the following texts are not completely drawn in accordance with actual relevant dimensions, and their function is only to show a schematic diagram relating to the features of the present invention.

First, please refer to FIG. 1 , which is a flow chart of a method for optimizing a processing path used in a machine tool according to the present invention. As shown in Figure 1, the machining path optimization method used in the machine tool is as follows:

Step 100: Provide a processing program and interpret the processing program, and then proceed to step 101.

Step 101: Providing a path planning unit, which receives the processed program and processes a processing path according to a numerical control parameter; in detail, after the machine tool receives the processing program, the user machine compiles the completed program. The processing program is interpreted into a plurality of processing instructions, and a processing path including one of the plurality of control points is planned through the provided path planning unit, and then proceeds to step 102.

Step 102: Providing an interpolator of the trajectory interpolation algorithm of the Tension Spline, and smoothing the processing path; the step is mainly performed by the trajectory interpolation algorithm of the tension cloud line The interpolator, and set the boundary conditions of the position, velocity and acceleration between the control points on the machining path to smooth the interpolation curve between the control points on the machining path, and the calculus equation of the trajectory interpolation algorithm of the tension cloud line is as follows (1) shown:

Where q _j,i (t) represents the interpolation trajectory of the j-th axis in the i-segment, and σ _j,i represents the tension value of the i-th segment of the j-th axis, thereby adjusting the curve between the control points on the processing path smooth degree (shown in FIG. 2), the obtained interpolation curve is more stiff when the tension value σ _{j, i} larger, conversely, when the tension value σ _{j, i} is smaller the more smooth the interpolation curve can be obtained, and h _i represents the length of the i-th period, ie h _i = t _{i + 1} - t _i , where t _i represents the time point at which the i- th control point is reached, thereby adjusting the control path from one control point to another The time required for the point; and equations (2) to (4) represent the boundary condition equations for the position, velocity and acceleration of the trajectory interpolation algorithm of the tension cloud line:

Step 103: Providing a motion planning unit, which is based on a numerical control parameter and an interpolator of the trajectory interpolation algorithm of the tension cloud line, and imparts motion characteristics of the processing path of the smoothing process; in detail, the provided motion The process planning unit assigns the motion characteristics of the machining path according to a numerical control parameter, including its velocity and acceleration.

Step 104: Providing an interpolation unit according to a numerical control parameter and an interpolator of the trajectory interpolation algorithm of the tension cloud line, and performing interpolation operation on the data of the processing path having the motion characteristic of the completed motion planning An interpolation command is generated; in detail, the interpolation unit provided performs the path interpolation operation of the tension cloud line on the machining path data that completes the motion planning and has the motion characteristic, and then proceeds to step 105.

Step 105: Provide a driver to send an interpolation command to the driver; in detail, one of the interpolation commands obtained after the interpolation operation is transmitted to the driver, and then proceeds to step 106.

Step 106: Using a driver to send a control signal to drive and control the axial motor of the machine tool; in detail, the driver sends a control signal to drive the axial motor action after receiving the interpolation command, and finally proceeds to step 107.

Step 107: Provide a position sensing component that returns information on the position of the axial motor of the machine tool to the driver.

Next, please refer to FIG. 2 , which is a graph showing the curvature of the tension cloud line under different tension values of the present invention. As shown in FIG. 2, the curvature expression of the tension cloud line is compared with the tension values=100, 4, 1, and 0.01. When the tension value is larger, for example, the tension value=100, a harder straight curve is generated; The smaller the tension value is, for example, the tension value = 0.01, a smoother curve is obtained. Therefore, by adjusting the tension value, the smoothness of the curve between the control points on the machining path can be adjusted, thereby achieving different processing requirements.

An embodiment of a machining path optimization method for a machine tool is described. Referring to FIG. 3, it is a block diagram of a numerical controller of a CNC mechanical device. As shown in FIG. 3, first, a processing program 32 is used to interpret the processing program 32, and is input to the digital control module 30 to generate a control signal for driving an axial motor 44, wherein the digital control mode The group 30 is composed of a path planning unit 34, a motion planning unit 36, an interpolation unit 38, and a numerical control parameter 40. The path planning unit 34 receives the interpreted processing program 32 and plans according to the numerical control parameter 40. A processing path including one of a plurality of control points, and then an interpolator of the trajectory interpolation algorithm of the tension cloud line smoothing the processing path to smooth the interpolation curve between the processing path control points; The planning unit 36 assigns motion characteristics of the processing path of the smoothing process according to the numerical control parameter 40 and the interpolating algorithm of the trajectory interpolation algorithm of the tension cloud line, for example, speed and acceleration; after that, the interpolation unit 38 controls the parameters according to the numerical value. 40. Interpolator of the trajectory interpolation algorithm of the tension cloud line, inserting the data of the processing path with motion characteristics of the completed motion planning Computing and generating an interpolation command, and then transmitting the interpolation command to a driver 42; then, after receiving the interpolation command, the driver 42 sends a control signal to drive and control one of the machine tool axial motor 44; Each axial position sensing element 46, such as a motor encoder or optical scale, will feedback the positional information of the axial motor 44 back to the driver 42 for closed loop control. Therefore, the present invention applies an interpolator of the trajectory interpolation algorithm of the tension cloud line to the path planning unit 34, the motion planning unit 36, and the interpolation unit 38 for smoothing the processing path to obtain smoothing interpolation. curve.

Next, please refer to FIG. 4, which is a schematic diagram of a processing program of the present invention. As shown in Fig. 4, G01 represents the linear cutting command, Z derivative represents the end point coordinate of the set block, F2000 represents the cutting feed rate, and G5.1 Q1 E0.02 represents the path interpolation of the open tension cloud line. Algorithm, where E is a parameter that the user can adjust by itself, that is, an error tolerance value. Although the present invention takes the tolerance of 0.02 mm as an example, it is not limited to use 0.02 mm, and then G01 X0. Y10. and X30. Y20. The smoothing planning and interpolation will start in a single section until the G5.1 Q0 will end the trajectory interpolation of the interpolation algorithm of the tension cloud line. Therefore, by using the numerical control parameter 40 set on the numerical controller of the CNC mechanical device and the error tolerance value E of the user, the tension value σ in the equation (1) can be adjusted to achieve a smooth machining path effect. .

Please continue to refer to FIG. 5 , which is a schematic diagram of the influence of different tension values on the processing path. The invention can be used on the processing path of any object, and the tension value can be adjusted according to the given error tolerance value E to adjust the smoothness of the curve. The larger the tension value (σ), the harder the straight interpolation curve can be obtained. In this embodiment, the tension value (σ)=100 is taken as an example but is not limited to the use of the tension value (σ)=100; otherwise, when the tension value (σ) The smoother the interpolation curve is obtained, the smaller the hour, the tension value (σ) = 0.1 is taken as an example, but the tension value (σ) = 0.1 is not limited.

Next, please refer to FIG. 6, which is a schematic diagram of a curve generated by using the same interpolation points by different interpolation methods. As shown in Fig. 6, the interpolation method includes: a cubic cloud line (Cubic Spline), a straight line, a Tension Spline with a fixed tension value, and a Tension Spline with a varying tension value, wherein the linear interpolation is performed. The interpolation curve produced by the complementary method is not smooth enough, and is rarely used in practical applications. In addition, the cubic cloud line (Cubic Spline) is composed of multi-segment cubic polynomials, which are polynomial in basic properties, and the shape of the curve is difficult to control freely; Tension Spline, which changes the tension value, has many characteristics. When the tension is small, it can produce a curve similar to Cubic Spline. When the tension is moderate, the vibration can be obtained. The smooth curve, under large tension, will result in a harder straight curve, so the method proposed by the present invention can be applied to different processing needs.

Finally, see Figure 7, which is a comparison of the Tension Spline and the polynomial curve. Although both methods can pass all the control points completely, the Tension Spline can be smoother than the polynomial curve. Through the control points that need to pass and the oscillation is less, and all the control points to pass are at the apex of the transition, the curve will not easily exceed the control point, which means that the Tension Spline has better Controllability, as long as the control points are properly selected, the resulting curve will not exceed the selected control point.

While the present invention has been described above in terms of the preferred embodiments thereof, it is not intended to limit the invention, and the invention may be modified and modified without departing from the spirit and scope of the invention. The patent protection scope of the invention is subject to the definition of the scope of the patent application attached to the specification.

100, 101, 102, 103, 104, 105, 106, 107. . . step

30. . . Digital control module

32. . . Processing program

34. . . Path planning unit

36. . . Motion planning unit

38. . . Interpolation unit

40. . . Numerical control parameter

42. . . driver

44. . . Axial motor

46. . . Position sensing element

1 is a flow chart of a method for optimizing a processing path for a machine tool according to the present invention.

Figure 2 is a graph showing the curvature of a tension cloud line below the different tension values of the present invention.

3 is a block diagram showing the numerical controller of the CNC mechanical device of the present invention;

Figure 4 is a schematic view of a processing program of the present invention;

Figure 5 is a schematic view showing the influence of different tension values on the processing path of the present invention;

6 is a schematic diagram of a curve generated by the same control point by using different interpolation methods according to the present invention;

Figure 7 is a comparison of the tension cloud line and the polynomial curve of the present invention.

100, 101, 102, 103, 104, 105, 106, 107. . . step

Claims (7)

A processing path optimization method for a machine tool, comprising: providing a processing program and interpreting the processing program; providing a path planning unit that receives the interpreted processing program and controls parameter planning according to a numerical value a processing path is provided; an interpolator of the trajectory interpolation algorithm of the force cloud line is provided to smooth the processing path; and a motion planning unit is provided, according to the numerical control parameter and the trajectory of the tension cloud line An interpolator of the complement algorithm, which imparts motion characteristics of the processing path of the smoothing process; and an interpolation unit is provided, according to the numerical control parameter and the interpolator of the trajectory interpolation algorithm of the tension cloud line, Completing the data of the machining path with motion characteristics of the motion planning, performing an interpolation operation and generating an interpolation command; providing a driver to send the interpolation command to the driver; and using the driver to generate a control signal to drive and control An axial motor; and a position sensing element that provides feedback of the position information of the axial motor to the driver. The processing path optimization method for use in a machine tool according to claim 1, wherein the processing path includes a plurality of control points. The processing path optimization method for a machine tool according to claim 2, wherein the control points set a boundary condition by an interpolator of the trajectory interpolation algorithm of the tension cloud line. The processing path optimization method for use in a machine tool according to claim 3, wherein the boundary condition is the position, velocity, and acceleration of the control points. The method for optimizing a machining path for a machine tool according to claim 2, wherein the interpolator of the trajectory interpolation algorithm of the tension cloud line includes a force value for adjusting the machining path. These control the smoothness of the curve between points. The processing path optimization method for a machine tool according to claim 2, wherein the interpolator of the tension cloud line trajectory interpolation algorithm includes a time value for adjusting the processing path from one The time elapsed from the control point to another control point. The processing path optimization method for use in a machine tool according to the first aspect of the invention, wherein the step of imparting the motion characteristic of the processing path of the smoothing process comprises imparting the processing path speed and acceleration.