JP3077145B2 - Multi-axis machine where each axis is composed of servo mechanism - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a multi-axis machine such as an NC or a robot having two or more axes, and each axis is constituted by a servo mechanism. The present invention relates to a method of generating an orbit control command.

[Background Art] Generation of a free curve as a space curve in a multi-axis configuration machine such as an NC machine tool or a robot is performed by a broken line approximation in which a given curve is approximated by a straight line for each minute space. This straight line is given to the servo mechanism of each axis as a time function type command.

We strive to match the servo characteristics of each axis as much as possible to achieve an accurate shape. However, it is impossible to exactly match the characteristics, which causes a shape error.

In order to solve such problems, one reference axis is determined, and for the other axes, the reference axis command multiplied by a value and a constant calculated in advance, and the response characteristics of the reference axis and the axis are determined. A method has been proposed in which the sum of the difference multiplied by another constant is given as a command (Japanese Patent Application No. 62-183563).

[Problem to be Solved by the Invention] In the sample value control system, it is desirable to make the sampling cycle as short as possible. For that purpose, the amount of calculation to be performed for each sample must be reduced as much as possible.

However, this method has a disadvantage that the above-described calculation must be performed for each sample in the sample value control system, and the calculation time increases as the number of axes increases.

An object of the present invention is to realize high-accuracy trajectory control without increasing the calculation time for each sampling cycle. An object of the present invention is to provide a multi-axis machine in which each axis is constituted by a servo mechanism.

[Means for Solving the Problems] A multi-axis machine according to the present invention, in which each axis is formed by a servo mechanism, uses a certain axis as a reference when realizing an arbitrarily given space curve as its movement by broken-line approximation. and, the servo mechanism of the shaft, gives a polygonal line approximation as a command function f _l (t) is a function of time can be realized on figure (t), the servo mechanism of the other axes, K _i f _l (t) + f _i (t)
(Where, i = 2,3, ..., and N, f _i (t) is f _l (1 linear low function relates than t t), K _i is a constant) the position command calculating means for applying to generate a command function Having.

[Operation] As described above, since all the generating functions are obtained at the time of determining the polygonal line approximation, the amount of calculation for each sample has no effect even if the number of axes increases. In addition, differences in response characteristics between multiple axes can be completely compensated, and highly accurate trajectory control can be performed.

Example Next, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic configuration diagram of a servo system including two axes of an X axis and a Y axis showing an embodiment of the present invention, and FIG. 2 is a diagram showing a point (x ₀ , y ₀ ) to a point (x ₁ , y ₁ ). It is a figure showing signs that it moves in a straight line.

Here, a machine having a multi-axis configuration will be described using two axes as an example. In the case of more axes, the relationship between the first and second axes may be considered as the first, third, first and fourth axes.

(1) In the case of linearly interpolating by giving a speed command in a step-like manner The linear interpolation command shown in FIG. 2 is obtained by setting each of the X and Y axes to x _i (t), y _i (t), X, Y when the respective mobile shaft speed V _x, and V _y, (1), it is given by equation (2).

x _i (t) = V _X t (1) y _i (t) = V _Y t = KV _X t (2) Becomes In this, K _x the gain K of each axis, when K _y, stationary solutions of each axis by the following equation (3) and (4).

Than this Therefore, unless Kx = Ky, the actual straight line is shifted from the straight line to be drawn in parallel. In order to correct this deviation, m is added to the command. That is, when x _i of _{(t) = V X t ...} (5), and _{y i (t) = V Y} t + m ... (6) At this time, each steady solution is given by the following equations (7) and (8).

here, After all, Becomes When m is selected in this way, y (t) / x (t) = K becomes
Satisfied regardless of the values of K _Y and K _X.

Now, if x _i (t) = f _l (t) = V _x t, y _i (t) = K
f ₁ (t) + m. Here, m is given by equation (10).

Figure 3 shows the space curve FIG. 4 is a flowchart showing a process of calculating a position command by the position command calculation unit 1 in the case of FIG.

Input the system clock ΔT, servo gains K _X and K _Y (step 11), and input the speed V and the total number of points M (step 11).
12). The position j of the point is set to 1 (step 13). Point j, j +
An X-axis direction of the velocity V _X between 1 calculates the interpolation number N (step 14), to calculate the value of m in (10). It is assumed that the initial value of the number of interpolations i = 1, the initial value of the position command δx _o = 0, δy _o = 0 (step 16), and N position commands δx _i , δy _i between points j and j + 1
Is calculated and output to the X-axis servo mechanism 2 and the Y-axis servo mechanism 3 (steps 17 to 20). Step 14-20 are repeated for each polyline to the point P _M (step 21).

(2) When a speed command is given in the form of a ramp and linear interpolation is performed, x _i (t) = αt ² (11) y _i (t) = Kαt ² + mt + n (12) I do. The steady-state solution of the response for each axis is given by the following equations (13) and (14).

Therefore, Becomes The following equation is obtained from equations (15) and (16).

Again, when x _i (t) = f ₁ (t) = αt ² , y _i (t) = Kf ₁ (t) + f ₂ (t) where f ₂ (t) = mt + nm, n is ( 17) and (18).

When the following functions are generated and commands are issued to the servo mechanisms 2 and 3 for each of the X and Y axes, the response is an ideal straight line regardless of the difference between the gains K _X and K _Y.

(3) When the acceleration is changed in a straight line Since the case where the speed is a step or a ramp has already been described, the case where the speed is accelerated by a square curve will be described.

When the speed is a square curve, the position command is x _i (t) = a _x t ³ (19).

At this time, this method means that y _i (t) = Ka _x t ³ + mt ₂ + nt + p (20).

Here, x _i (t) and y _i (t) are represented by respective servo mechanisms.
When a command is given to a few, the response is Therefore, Is led. From these three equations Is obtained.

This means that when x _i (t) = f ₁ (t), a function of y _i (t) = Kaf ₁ (t) + mt ² + nt + p is generated, and the servo systems 2 and 3 of the X and Y axes are respectively provided. This shows that the command gives an ideal straight line.

The operations shown above (Equations (5), (6), (11), (1
2), (19), and (20)) need not be performed for each sample, but may be performed at each break point of the broken line approximation.

[Effects of the Invention] As described above, the present invention makes it possible to modify a command to another axis in advance in consideration of the characteristics of a servo system based on a command of one axis that has been linearly approximated, By using this as a command for each axis, there is an effect that high-accuracy trajectory control of a multi-axis machine is realized without increasing the calculation time for each sampling cycle.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a servo system including two axes of an X axis and a Y axis showing an embodiment of the present invention, and FIG. 2 is a diagram showing a point (x ₀ , y ₀ ) to a point (x ₁ , y ₁ ). Fig. 3 shows the state of linear movement to FIG. 4 is a flowchart showing a process of calculating a position command by the position command calculation unit 1 in the case of FIG. 1. Position command calculator 2. X-axis servo mechanism 3. Y-axis servo mechanism 11 to 22 steps.

Continuation of the front page (56) References JP-A-64-28705 (JP, A) JP-A-60-105012 (JP, A) JP-A-62-252610 (JP, A) JP-A-1-177108 (JP) , A) Jpn. Sho 56-22601 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G05B 19/404 G05B 19/4103

Claims (1)

(57) [Claims] 1. In a multi-axis machine having two or more axes and each axis being constituted by a servo mechanism, V _X and V _Y are respectively represented by X-axis and Y-axis movement speeds, K _X and K _Y. Where x is the gain of the X-axis and Y is the time, and t is the time, and the command functions x _i and y _i of the X-axis and Y-axis are: 1) When a speed command is given in a step-like manner and linear interpolation is performed, x _i (t) = V _X · t, y _i (t) = K · V _X · t + m where 2) In the case of linearly interpolating by giving a speed command in a ramp shape, x _i (t) = αt ² , y _i = K · αt ² + mt + n where α is a constant. 3) When the acceleration is changed in a straight line, x _i (t) = a _x t ³ , y _i = K _{× a} t ³ + mt ² + nt + p where a _x is given as a constant. In the case of three or more axes, there is provided position command calculating means for giving a command function of another axis so that the relation between the other axis and the X axis becomes the above-mentioned relation between the X axis and the Y axis. A multi-axis mechanism in which each axis is constituted by a servo mechanism.