SU370588A1 - METHOD OF PROGRAM MANAGEMENT OF METAL THREADING MACHINES12 - Google Patents

Description

A known method of software control of machine tools, in which information about the contour approximation area and the contour speed is converted by the number of coordinates into interconnected pulse sequences. The number of pulses at a given coordinate determines the displacement, and their frequency, the feed rate.

Such pulse sequences are fed to the inputs of coordinate following systems. In the combined servo systems, the pulse frequency is converted into an analog signal, which is fed to the summing amplifier of the drive, and the number of pulses from the position sensor is subtracted from the number of pulses of the input sequence, which leads to the formation of an error signal in position.

However, with this method, significant dynamic errors occur on the contour of the workpiece, since there is no relationship between the individual coordinate tracking systems. Particularly large dynamic errors when processing roundings of small radius at a high feed rate. The value of the dynamic error in this case may exceed the value of discreteness (price of impulse) several times and, thus, significantly worsen the accuracy of machining the part.

The purpose of the invention is to reduce the contour dynamic errors of machining. It is achieved by calculating the components of the contour error vector based on the initial information about the contour approximation area and on the actual position of the machine working elements and sending signals proportional to these components on the corresponding coordinate drives.

FIG. 1 and 2 illustrate the proposed method.

The given region of contour approximation is described by equation (X). According to the contour speed Vk and

the type of function (X) at each point (X, Y) (see Fig. 1) is used to calculate the components Vx and the contour speed n signals, proportional to these components, are fed to the inputs of the feed drives, respectively, Vx - to

drives X, V, j - to drive U. These signals give an approximate direction of movement, since absolutely exact setting of the speeds Vx and Vy is not possible due to known reasons. Therefore, the complex joint movement of two

The machine's working elements, controlled by drives A and U, will occur along a different path, described by equation (X). The positions of the working bodies of the machine according to the coordinates X and Y are measured by the position sensors of these coordinates. We define the contour error vector as the distance in the norms from the point (Xd, Yd) by the actual trajectory of movement (X) to a given approximation area (a given surface in general) or to its continuation at the junction of two approximation areas. In the process of moving along a given trajectory, the components of the contour error vector 8hx and 8ky are continuously calculated. Signals proportional to b and 8ky are fed to the inputs of the X and Y actuators respectively. It is knowledge of the contour error calculated from the initial information and information about the actual position of the machine working parts at each point of the trajectory makes it possible to correct the complex movement of the tool 15 to a given approximation area (normal to the contour). In this case, the total vector () is always directed toward the contour and always contributes to the reduction of dynamic errors. In the general case, there is no exit to the end point of a given area of approximation, i.e. the curves (X) and (X) at the end point / do not intersect. In connection with 25, the end of the real segment of the approximation is determined by the last match of the real and given coordinates (point / in Fig. 1). Moreover, the magnitudes of displacements received from the moment of their coincidence (point 2) until the last match for other coordinates are remembered and when going to a new section of approximation, the coordinates of its beginning are corrected by adding these displacement values to the corresponding coordinates of the beginning (segment 3 -7) This is due to the fact that the coordinates of the points of the approximation sites are given in the local coordinate system. Thus, in the local coordinate system of the new approximation area, the coordinates of a point are obtained, starting with which the calculation of the components of the contour error vector is already performed relative to the new approximation area. The implementation of the method will be considered on the example of a two-coordinate digital control system with the possibility of approximating the contour with linear sections. The coordinates of the plot approximation set in the local Cartesian coordinate system (see Fig. 2). Century-50

the velocity torus Vk coincides with the direction of the linear region, and its components Al and Vy depend, respectively, on the displacements Xn and Yk.

The components Vx and Vy are calculated, for example, on an analog computing device using the formulas:

X,

.y, and 1 / --- 4

Vu,

 Vx -I- to Y and + k

no contour speed Vh specified in the program. The signals Vx and Vy are fed to the inputs of the respective drives.

Subject invention

The method of software control of machine tools based on the introduction

high-speed signals for controlling the feed axis drives, characterized in that, in order to reduce the contour dynamic machining error, the components of the contour vector are calculated

errors based on the initial information about the contour approximation area and information on the actual position of the machine working elements and give a signal proportional to these components to the corresponding coordinates

natny drives. The magnitude of the contour error module can be determined as follows: b, / + G.sin arctg - arctg 1 After the corresponding transformations, we get: g kXe - XitYQ The error vector components are: and - and. T {Y, X, -X, Y,) - + yl - (Y, -X, Y,) X ky ki + Y Xl + Yl Since the expression Y Xd-XkY is a formula for the evaluation function for the linear interpolator, used in conventional software control systems, this expression is calculated on a linear interpolator, the control circuit and the current coordinate meters of which are fed by displacement pulses from position sensors along the X and Y axes. Further calculation of the components of the contour error vector 8hx and 8hy produced on an analog computing device, and signals proportional to and byyu, under are the inputs drives the respective coordinates X n Y, where these signals are summed with the speed signal V and Vy motion and fed working machine bodies precisely on a predetermined straight line. The end of the approximation section is produced in the linear interpolator, as usual, according to the coincidence of the values of Hy and Usg in the counters of the current coordinates with the given values of Xh and Ud. The difference is that after a match, for example, Jd ft, the number of pulses AX before the match is fixed in the additional counter and when the next value Xk is entered, is added to it.

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