JPS60172443A - Synchronous control with high accuracy - Google Patents

Abstract

PURPOSE:To improve control accuracy in a large-sized machine tool and permit the machining with superhigh accuracy in a small or medium-sized machine by controlling the shafts to be synchronously revolved, on the basis of the feedback signals of the shaft of the partner. CONSTITUTION:In an NC controller 9, the input information supplied from a tachogenerator 3 and a resolver 4 on a cutter shaft is incorporated into a work- shaft system and used for controlling a work-shaft driving motor 6, while the feedback signal of the work shaft is input from a tachogenerator 7 and a resolver 8 and incorporated into a cutter-shaft system and used for controlling a cutter-shaft driving motor. In the conventional NC driving motor, the response performance, namely the recovery force and trailing force are proportional to the magnitude of the error from instruction. In other words, the deflection from the instruction value is larger, a larger motor torque is generated. The control depends only upon the instruction value of the NC controller 9 in the conventional method, while in this method the control permits the direct followng to the movement of an object, having the motor speed of the partner which is to be synchronized, as instruction value, and the control accuracy can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control method for improving the precision of synchronous control in machine tools with two axes that require synchronous control, such as gear shaping machines and hobbing machines, and multi-axis NC machine tools. .

For example, in gear shapers (hereinafter referred to as gear shapers), numerical control (hereinafter referred to as NC) has recently been implemented for the purpose of facilitating setup and improving gear cutting accuracy. This NC gear shaper employs the control method shown in FIG.

That is, the cutter shaft drive motor 2 that drives the pinion cutter 1 is equipped with a tacho generator 3 for rotation speed detection and a resolver 4 for phase detection, and the work shaft drive motor 6 that drives the workpiece 5 is also equipped with a tacho generator 7 and a resolver. 8 is provided. The NC control device 9 takes in the detection outputs of the respective tacho generators 3 or 7 and resolvers 4 or 8 and compares them with the target values, and if there is a difference (deviation), sends a control signal to the corresponding drive motor 2 or t or 6. It is something. This type of control method usually controls the cutter axis and workpiece axis to improve the accuracy of the indexing system, and it has already been shown that sufficient gear cutting accuracy can be obtained for practical use. There is.

However, this method of simultaneously controlling synchronously rotating axes is
On the cutter axis side, the system on that side is controlled individually, and on the workpiece axis side, the system on that side is controlled individually, and the relationship between the cutter axis and workpiece axis is not directly related, and the NC control system ft9 This is a semi-closed control system in which the drive motors 2 and 6 follow only the NC commands. In such cases, if the machine is enlarged or the purpose is ultra-high precision machining, the workpiece system and cutter system are separate, and the N
The above method, which achieves tracking accuracy only by the C command, naturally has a limit.

In view of the above-mentioned drawbacks, one object of the present invention is to provide a high-precision synchronous control method that increases control precision even in large-sized machines and enables ultra-high-precision machining with small and medium-sized machines.

The present invention, which achieves this object, is characterized in that, in a machine tool configured to numerically control a plurality of axes, each of the axes to be rotated synchronously is controlled based on feedback signals from the other axes. shall be.

The present invention will now be described in detail with reference to FIGS. 2, 3, and 6. In FIG. 2, the same parts as in FIG. 1 are given the same reference numerals. Cutter axis control information (feedback signal) is input from the tacho generator 3 and resolver 4 to the NC control device 9 . In this NC control device 9, the feedback signal of the cutter shaft is taken into the work shaft system to control the work shaft drive motor 6.

On the other hand, a feedback signal of the work axis is manually inputted from the tachometer generator 7 and resolver 8 to the NC control device 9. In this case, this feedback signal is taken into the cutter shaft system to control the cutter shaft drive motor 2.

A block diagram of such a control system centered on the NC control device 9 is shown in FIG. The inside of the NC control device f9 is the cutter shaft system (
It is divided into two parts: the Y-axis system) and the workpiece axis (referred to as the C-axis system).
Each system is equipped with stages consisting of command value acquisition, registers, pulse distribution, smoothing, phase modulation, position control, and amplification. Each system receives commands from an external memory, such as a magnetic tape, via a command buffer. The amplification stage of each group is driven by a drive motor according to its system, that is, the Y-axis system is driven by a Y-axis (cutter axis) drive motor, and the C
The shaft systems are each connected to a C-axis (workpiece M) drive motor, and motor control is performed. On the other hand, each tacho generator 3.7 and resolver 4, 8 is connected to the final stage of the other system as shown in FIG. As a result, the workpiece axis feedback signal is taken into the cutter axis system, and the cutter axis feedback signal is taken into the workpiece axis system.

The responsiveness of a conventional NC drive motor, that is, the recovery force and follow-up force, is proportional to the magnitude of the error from the command.For example, the magnitude of the torque generated in the drive motor is expressed as F=K・
Approximately indicated by △. Here, F is torque, K is gain (constant), and Δ is the difference (deviation) from the command value. In other words, the greater the deviation from the command value, the greater the motor torque generated in proportion to the magnitude. Furthermore, as shown in Fig. 5, in the past, the respective rotation angles of the Y-axis motor and the C motor were lowered by the droop amount + error amount Dy, Da relative to the command values Ys, Cs to follow the command values. go. Ms and Me are tracking values. In FIG. 5, Dy > Do. In this way, in the past, it depended only on the command value of the NC control device 90, but in the present invention, there is a value equivalent to the droop amount as shown in FIG. It can be regarded as a value and tracked. In Fig. 6, Ms indicates the actual movement of the Y-axis motor and Me indicates the actual movement of the C-axis motor.

As explained above, according to the present invention, indirect N
It is now possible to directly follow the movement of the other party rather than using C commands, increasing control accuracy with large machine tools.
In addition, small and medium-sized machines can perform ultra-high precision machining.

[Brief explanation of drawings]

Figures 1, 4, and 5 show the control method of a conventional NC gear shaper. Figure 1 is a configuration diagram of the device, Figure 4 is a graph showing the relationship between command value and motor torque, and Figure 5 is a graph showing the relationship between command value and motor torque. Follow-up schematic diagram of Y-axis motor and C-axis motor, Fig. 2, Fig. 3, Fig. 6
The figures show an embodiment according to the present invention, Fig. 2 is a block diagram of the control device of the NC gear shaper, Fig. 3 is a block diagram of the NC control device, and Fig. 6 is a schematic diagram of the tracking of the Y-axis motor and the C-axis motor. . In the figure, 2 is a cutter axis (Y-axis) drive motor, 3.7 is a tacho generator, and 4.8 is a resolver. 6 is a work axis (C-axis) drive motor, and 9 is an NC control device. Patent Applicant: Mitsubishi Heavy Industries, Ltd. Nippon Automotive Engineering Co., Ltd. Patent Attorney: Shibu Mitsuishi (and 1 other person) Mine hAi value standard II @v-s 5' star register register 02% 1 o"+L2' order We ・ now-e , -9 s4-+-゛shi@Wr 0 钒l set value 碍 11 1 day No. 3 0 Kure...] ■ 7 6% Change 1 Fig. 4 F (Kg-cm) Fig. 5 0 4□=.

Claims (1)

[Claims] A high-precision synchronous control method in a machine tool configured to numerically control a plurality of axes, characterized in that each of the axes to be rotated synchronously is controlled based on feedback signals from the other axes.