JPH01133114A - Speed control system for polar coordinate interpolation - Google Patents

Abstract

PURPOSE:To execute cutting at a speed less than a max. speed by comparing a distance obtained by rotating a work from a current position in the C axis direction by DELTAthetaMAX and a distance obtained by moving the work in the R axis direction by RMAX with a moving distance of a program command, executing prescribed interpolating arithmetic the converting obtained data into polar coordinates. CONSTITUTION:Data for specifying the max. rotational variable DELTAthetaMAX per prescribed time in the rotational axis direction and the max. moving distance DELTARMAX in the straight axis direction are set up and a distance DC obtained by moving the work from a position Po on a program command passage and rotating the work by DELTAthetaMAX up to a position Pn is found out. A distance DR obtained by moving the work from the position Po in the straight axis direction by DELTARMAX up to a position Pm is found out. The moving distance DP per prescribed time based upon the program command is compared with the distances DC, DR, applying interpolating arithmetic to the rectangular coordinate system at a moving speed corresponding to the min. moving distance, and the obtained data are converted into polar coordinates, so that cutting work can be executed at a speed lens than the max. cutting speed.

Description

[Detailed Description of the Invention] <Industrial Application> The present invention relates to a speed control method for polar coordinate interpolation that is effective for cam grinding, etc., and in particular, the speed in the polar coordinate rotation axis direction and the polar coordinate linear axis direction does not become excessive. This paper relates to an improved speed control method for polar coordinate interpolation.

<Prior art> In a cam grinding machine, the workpiece WK is
is rotated around a predetermined point P8, and the tool (
The workpiece is machined into a desired cam shape by moving the grindstone TL back and forth in the direction of point 1-P, which is the center of rotation, according to the rotation of the workpiece and the cam shape. That is, according to the rotation of the workpiece WK, the tool TL is machined according to the commanded cam shape by controlling the central position of the tool so that it follows the contour of the commanded cam shape.

In addition, Figure 3 (al shows the initial state, Figure 3 (bl) shows the state where the workpiece has been rotated 90 degrees, and from now on, the direction of rotation is the direction of the polar coordinate rotation axis (C axis), and the direction of the rotation center is the direction of rotation. This will be referred to as the polar coordinate linear axis (R-axis) direction.

In such polar coordinate axes (C, R axis) control for cam grinding, since the cam shape is expressed in the design drawing using an orthogonal coordinate system, the NG machining program is created using the orthogonal coordinate system. Interpolation calculations are performed based on the received commands (NC machining program), and the interpolation results are converted into a polar coordinate system to control each polar coordinate axis.

That is, referring to FIG. 4, if the amount of movement per unit time in the orthogonal coordinate system determined from the feed rate command (F command) is Δf, interpolation in the orthogonal coordinate system is performed so that the tool moves by Δf per unit time. (linear interpolation or circular interpolation) is performed and the current position P, (X, , Y, ,) is updated. Then, the orthogonal coordinate value of this current position is converted to a polar coordinate value (θ., R,), and the increase or decrease in radius is calculated compared to the polar coordinate value (θr+-1' Rr+-1) of the current position Pn-1 a unit time ago. The minute ΔR,, is the amount of actual tool movement in the R-axis direction per unit time, and the angle increase/decrease Δθ. is the amount of rotation in the C-axis direction. Once ΔR0 and Δθ are determined, pulse interpolation calculations are performed on each axis of the polar coordinates to rotate each axis servo motor to rotate the workpiece (C axis) and move the tool (R axis).
control.

<Problem to be solved by the invention> However, in the conventional speed control method of polar coordinate interpolation, the origin P of polar coordinates
1. When a straight line, arc, etc. (which make up the cam contour) that passes near l is commanded, the distance (radius) from the origin becomes shorter, so even if the speed in the orthogonal coordinate system is not fast, it is converted to polar coordinates. As a result, the rotational speed of the polar coordinate rotation axis (C-axis) becomes extremely high, and may exceed the maximum cutting speed.

The relationship between the orthogonal coordinate system and the polar coordinate system will be explained with reference to FIG. Note that the origin of the orthogonal coordinate system and the origin of the tli coordinate system are made to coincide, and the X axis in the orthogonal coordinate system and the R axis in the polar coordinate system are made to coincide. Now, command 4 in the orthogonal coordinate system.
Even if and 12 are the same distance, the rotation angle θ of 12 with the smaller radius
2 is considerably larger than θ, 9. When trying to distribute pulses within a unit time, the rotation speed also becomes faster.

In such a case, machining cannot be performed normally or a servo alarm occurs. To prevent these phenomena,
When creating a program, find the point closest to the center of the polar coordinates for each block of the cam contour, and use Cartesian coordinates where the speed after converting to polar coordinates at that point does not exceed the maximum cutting speed in the C-axis and R-axis directions. It is conceivable to calculate the feed rate in the system and issue the command, but there is a problem in that programming is troublesome.

From the above, it is an object of the present invention to be able to control the maximum cutting speed in each axis direction of polar coordinates so as not to exceed it, to be able to program without considering the maximum cutting speed, and to be able to command the maximum cutting speed as long as the maximum cutting speed is not exceeded. An object of the present invention is to provide a speed control method for polar coordinate interpolation that allows cutting at a specified speed.

Means to solve problems〉 FIG. 1 is a schematic explanatory diagram of the present invention.

11 is a program command path, X, Y are orthogonal coordinate axes, C,
R is a polar coordinate axis, ΔθMAX'l is the maximum amount of rotation in the C-axis direction per predetermined time, ΔRr, A8 is the maximum amount of movement in the R-axis direction per predetermined time, and Po is the current position on the program command path.

Effect〉 Maximum rotation amount Δ in the direction of the polar coordinate rotation axis per predetermined time
Data specifying θMAX and the maximum movement amount ΔRMo in the polar coordinate linear axis direction are set in advance, and the data is set in advance to move from the current position P0 on the program command path 11 and move Δθ1. Point P when rotated by lAx, (
Travel distance D to FIG. 1(a). At the same time, calculate the moving distance DFI to the point P□ (Fig. 1 (b)) when moving from the current position P0 on the program command path 11 in the direction of the polar coordinate linear axis (R axis) by ΔR1,,Ax. , and calculate the movement amount 1IIDP per predetermined time instructed by the NC machining program and each movement distance D0. Compare the magnitude with D, perform interpolation calculation in the orthogonal coordinate system at a moving speed according to the minimum moving distance, and convert the interpolation calculation result into polar coordinates.

<Embodiment> FIG. 2 is a block diagram of a numerical control device according to the method of the present invention.

1 is an NG machining program programmed in a Cartesian coordinate system to move the tool along the cam contour shape,
The data is read by a tape league (not shown) and stored in the memory built into the NC device, and read one block at a time from the memory during processing.

A preprocessing means 2 extracts information necessary for interpolation calculations from the instructed NG machining program, performs offset processing, etc., and converts the information into a format that allows interpolation calculations. 3 is a command speed determining means, which determines the speed F commanded from the machining program.
. Multiply the ratio set by the override switch on the operation panel 4 to the command speed ΔF (=wa・FC).
Determine.

5 is a speed processing unit which inputs the maximum rotational speed ΔFC1, lAx in the polar coordinate rotation axis direction, the maximum movement speed ΔFIMAX in the polar coordinate linear axis direction, and the command speed ΔF, and performs the processing described later from these to obtain the actual movement speed. Determine and output F.

6 is an interpolation calculation unit that performs interpolation (linear interpolation or circular interpolation) in the orthogonal coordinate system so that the tool moves on the program path at the feed rate F determined by the speed clamp unit 5, and also calculates the current position P0 ( xo, Yo) are updated.

7 is a polar coordinate conversion processing unit, and the current position P. Convert the orthogonal coordinate values (xo, Yo) to polar coordinate values (θo, R0),
Compared to the current position a unit time ago, the increase/decrease in radius ΔR is the amount of movement of the actual tool in the R-axis direction per unit time, and the increase/decrease in angle Δθ is the amount of rotation in the C-axis direction.

8 is a servo control unit, which performs simultaneous two-axis pulse interpolation calculation on each axis (C, R axis) of polar coordinates using ΔR2Δθ, and uses the obtained distributed pulses to control the servo motor 9C for each axis.
, 9R to rotate the workpiece (C axis) and move the tool (
R axis).

FIG. 1 is an explanatory diagram of the speed determination process in the speed clamp processing section 5. In Figure 1 (al, (bl), 11 is one block shape (straight line) in the program command path (for example, cam contour), x, Y are Cartesian coordinate axes, C, R
i, is the polar coordinate axis, P6 is the origin of each coordinate system, Pe is the block start point, p is the block end point, ΔθMAX (Fig. 1 (a)
)) is the maximum rotation amount in the direction of the polar coordinate rotation axis (C axis) per predetermined time, ΔRMAX 'Figure 1 (b)) is the maximum amount of movement in the direction of the polar coordinate linear axis (R axis), and Po is the maximum amount of rotation in the direction of the polar coordinate rotation axis (R axis) per predetermined time. The current position, P, (Fig. 1(a)) is the point when moving from the current position P0 on the program command path 11 and rotating by ΔθMAX in the direction of the polar coordinate rotation axis, P, (
Fig. 1(b)) shows movement from the current position P0 on the program command path 11 to the direction of the polar coordinate linear axis (radial direction) ΔR.
This is the point when moving to MAX.

Now, every time the current position P0 (see FIG. 1) is updated in the interpolation calculation unit 6, the speed clamp processing unit 5 calculates the current position coordinate value and the maximum rotation speed in the direction of the polar coordinate rotation axis that has been input in advance. The actual moving speed is determined using ΔFoMAX, the maximum moving speed ΔFR, 1IAX in the direction of the polar coordinate linear axis, and the command speed ΔF determined by the command speed determination unit 3. That is, first, the maximum rotational speed ΔFCM□
, ΔFl'1. The maximum rotation amount ΔθMAX in the direction of the polar coordinate rotation axis per predetermined time using MAX (Fig. 1 f
(see at) and the maximum movement amount ΔRMAy in the polar coordinate linear axis direction
(Calculate Figure 1 (see bl).

Next, the current position P. Δθ in the direction of the polar coordinate rotation axis by moving on the program command path 11. □Calculate the moving distance DC to the point P when rotated (Figure 1 [a
(see l). In addition, this moving distance. is calculated as follows. In other words, the straight line connecting the origin P in Figure 1 (al) and the current position P can be expressed by the following formula (% formula % (1)), and the straight line connecting the origin P and point P can be expressed by the following formula (% formula % (2)). ), so the coordinate value of point P, (X,,.

Y, , ) can be obtained as the coordinate value of the intersection of these two straight lines, and therefore the distance #Do can be calculated from the following equation.

Once the distance D0 is determined, the current position P is determined. from the program command path 11 to the polar coordinate linear axis direction (radial direction)
Movement distance D to point P1 when moving by ΔR18 to
Find R (see Figure 1(b)). Furthermore, this moving distance D
R is determined as follows. In other words, the straight line connecting the origin P8 and the current position P0 in Fig. 1(b) can be expressed by the following formula (%); and the circle with radius R centered at the origin PPl can be expressed by the following formula (%). Coordinate values of point P (xl.

Y, ) can be obtained as the coordinate values of the intersections of these straight lines and circles, and therefore the distance MDo can be calculated from the following equation.

Thereafter, the speed clamp processing unit 5 calculates the moving distance DP per predetermined time based on the command speed ΔF input from the command speed determining unit 3, and calculates each moving distance 111Dp, Do.

It compares the magnitude with DFI, and outputs the moving speed corresponding to the minimum moving distance to the interpolation calculation unit 6 at the next stage as the actual moving speed F in the orthogonal coordinate system.

In addition, as described above, the speed F in the speed clamp processing section 5
is determined, the interpolation calculation unit 6 performs interpolation calculation using the speed to obtain the moving distances ΔX and ΔY of each axis per predetermined time, and updates the current position P0 (xo, Yo) using the following formula % formula % do. Then, the speed clamp processing unit 5 updates the new current position P0(xo
, Yo) to determine the next new speed.

On the other hand, the polar coordinate conversion processing unit 7 converts the polar coordinate value (
RO, θ. ) is calculated using the following formula % formula %, and compared with the polar coordinate value of the previous current position, the difference Δ
R2Δθ is input to the servo control unit 8 as an incremental amount for each axis of the polar coordinate system to control each axis of the polar coordinate system.

In addition, although the case where the present invention is applied to a cam grinder has been described above, the present invention is not limited to a cam grinder but can also be applied to X, Z, C
It can also be applied to a three-axis lathe or the like composed of axes.

Furthermore, although the case has been described in which the maximum speed in each axis direction of the polar coordinates is input to the speed clamp processing section, a moving distance of 1 m (equivalent to speed) per predetermined time may also be input.

<Effects of the Invention> According to the present invention, data specifying the maximum rotation amount Δθ0 in the polar coordinate rotation axis direction and the maximum movement amount ΔRMAx in the polar coordinate linear axis direction per predetermined time are set in advance, and the current position P . Point P when moving on the program command path and rotating ΔθrlAx in the direction of the polar coordinate rotation axis from
. In addition to finding the moving distance D0 from the current position wP0, the moving distance IaiD1. l is calculated, and the moving distance glDP per predetermined time instructed by the NC machining program and each of the moving distances DC2D1 . Since the configuration is configured to compare the magnitude with l, perform interpolation calculation in the orthogonal coordinate system at a movement speed according to the minimum movement distance, and convert the interpolation calculation result to polar coordinates, the maximum cutting speed in each axis direction of polar coordinates can be calculated. It is possible to control the speed so that it does not exceed the maximum cutting speed, and also to program without considering the maximum cutting speed, and furthermore, it is possible to cut at the commanded speed as long as the maximum cutting speed is not exceeded.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of the present invention, Fig. 2 is a block diagram of a numerical control device according to the present invention, Figs. 3 and 4 are explanatory diagrams of cam grinding, and Fig. 5 is an explanation of conventional problems. It is a diagram. 11...Program command path, ΔθM□...Maximum rotation amount in the C-axis direction per predetermined time, Δ
R.M. ...Maximum movement amount in the R-axis direction per predetermined time, Po
...Current position patent applicant on program command path
Agent for FANUC Co., Ltd.
Patent Attorney Chiki Saito Figure 1 (a) (b) Figure 3 Figure 4

Claims (1)

[Claims] In a speed control method for polar coordinate interpolation in which interpolation calculations are performed based on a machining program instructed in a Cartesian coordinate system, and the interpolation results are converted to a polar coordinate system to control polar coordinate axes, Maximum rotation amount Δ in the direction of the rotation axis
θ_M_A_X and maximum movement amount ΔR_ in polar coordinate linear axis direction
Data specifying M_A_X is set in advance, and the moving distance D_C when moving on the program command path from the current position and rotating Δθ_M_A_X in the direction of the polar coordinate rotation axis is calculated, and the movement distance D_C is calculated when moving on the program command path from the current position. Find the moving distance D_R when moving ΔR_M_A_X in the direction of the polar coordinate linear axis using A speed control method for polar coordinate interpolation characterized by performing interpolation calculations in a rectangular coordinate system at a moving speed according to the speed.