JPS63306854A - Tool control system for machine tool device - Google Patents

Abstract

PURPOSE:To permit NC machining to be performed in high accuracy of the order of submicron or less by forming a control system by a feedback system, which compensates the displacement when this displacement of a tool cut driving piezo-electric actuator reaches no target value, and by a memory which instantaneously stores a compensated value of that displacement in memory. CONSTITUTION:Before cutting work, a device uses a route of a feedback system circulating the actual NC data. The device, whose control in this time is a closed loop control, compensates hysteresis of the dynamic displacement. Simultaneously the device applies a voltage value to an actuator, compensating the hysteresis, to be left as fetched into a memory 2. Next the device switches the route to a route, in which the piezo-electric actuator 8 is directly controlled by a data output from the memory 2, by a switch 4 performing a perfect open loop control by the data compensating the hysteresis in the time of the cutting work. This control system enables the dynamic displacement hysteresis of the piezoelectric actuator 8 to be compensated even by using the open loop control, and machining in the order of submicron or less can be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a machine tool device that uses a piezoelectric actuator to drive the cut of a cutting tool for sample machining, and is particularly suitable for controlling the cutting of the cutting tool using NC data.

[Conventional technology]

FIG. 4 shows the principle of a conventional control system for a fly-cutting device that uses a piezoelectric actuator to drive the cut of a cutting tool for machining.

The conventional device uses a DC servo motor 12. A tool rotating section consisting of an air spindle 14, etc., a feed screw-driven specimen moving section using a slider 16 for full guide, and a tool cutting amount control section consisting of an NC data signal generation circuit 1, a high voltage amplifier 5, etc. It was composed of and controlled as follows.

That is, the rotary encoder 1o detects the rotational angular position of a cutting tool rotationally driven by the DC servo motor 12, and the NC data signal generation circuit 1 generates a tool cutting signal. The tool cutting signal is amplified by the high voltage amplifier 5 to a high voltage signal necessary for driving the piezoelectric actuator 8, and is transmitted to the rotating piezoelectric actuator 8 via the slip ring 13. The piezoelectric actuator 8 is expanded or contracted in response to the above transmission signal, and as a result, the depth of cut of the diamond bit 18 fixed to the actuator is changed during cutting.

[Problem that the invention seeks to solve]

However, in conventional devices, the depth of cut control for the piezoelectric actuator in the tool depth of cut control section is open-loop control, so the depth of cut cannot be adequately compensated for the dynamic displacement hysteresis of the actuator shown in Figure 5. Ta. In other words, in the past, hysteresis compensation was not performed at all, or mathematical calculations or
Control was performed by creating NC data that compensated for the displacement hysteresis of the actuator using the hysteresis characteristic diagram shown in the figure. However, since the minor loop displacement characteristic 20 shown in FIG. 5 exists, it is difficult to compensate for hysteresis for all voltage changes.

On the other hand, even if feedback control is used to control the displacement of the processing tool, it is not easy to measure the amount of displacement during cutting because the tool is a processing tool. Moreover, even if the actual displacement amount can be measured after cutting, it is meaningless.

An object of the present invention is to compensate for the displacement hysteresis of a piezoelectric actuator in response to a dynamically changing applied voltage, which has not been taken into consideration in the prior art, by immediately responding to changes in cutting data in real time. As a result, in a fly force taking device that has a function to control the depth of cut of the tool in synchronization with the tool rotation angle, it is possible to achieve a higher precision NG machine of sub-micron order or less, which was difficult to achieve with conventional control. Processing becomes possible.

[Means for solving problems]

In order to achieve the above objective, we have developed a feedback system that monitors the actual displacement of the actuator induced by the applied voltage to the piezoelectric actuator for driving cutting tools, and compensates for the deviation if it does not reach the target value. A control system is composed of a memory system that stores deviation compensation values.

Note that there are two routes for applying voltage to the piezoelectric actuator: a route from the feedback system and a direct route from the memory system, and it is possible to switch between these routes.

[Effect]

The control operation will be explained using the control block diagram shown in FIG.

First, before the cutting process, actual NC data is sent using the feedback system route described in the above means. Since the control at this time is closed loop control, dynamic displacement hysteresis is compensated for. At the same time, the voltage value applied to the actuator with hysteresis compensated for is stored in the memory 2.

Next, the piezoelectric actuator 8 is switched to a route in which it is directly controlled by the data output from the memory 2, and complete open loop control is performed using data with hysteresis compensated for during cutting.

With this control method, the dynamic hysteresis of the piezoelectric actuator 8 can be compensated for even if open-loop control is used, so high-speed response and high-precision NG machining on the order of submicrons or less becomes possible.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

This device is a fly-cutting device that creates an aspherical surface on a sample using NC data control.

This device consists of a tool rotating section consisting of a DC servo motor 12 and an air spindle 14 connected to a tacho generator 11 and a rotary encoder 10, a moving table 15 for moving a sample 19, a drive device 17 for driving the moving table, and other parts. Sample moving section and NC data generation circuit 1. Length meter 7
．． Deviation detection circuit 3. It is composed of a tool cutting control section consisting of a high voltage amplifier 5, a cutting piezoelectric actuator 8 with a diamond cutting tool 18, and the like.

Corresponding to FIG. 1, the operation is first performed as follows.

That is, the rotational angular position of the cutting tool 8.18 that is rotationally driven by the DC servo motor 12 is determined by the rotary encoder 1.
0 is detected, and the NG data generating circuit 1 generates the tool cutting signal VO.

The tool cutting signal Vo is a value that is feedback-controlled so that the measurement value Nf of the length measuring meter 7 that detects the actual amount of change in the piezoelectric actuator for cutting becomes the set value Nr. Therefore, since the tool cutting signal Vo at this time is a signal that compensates for the dynamic hysteresis of the piezoelectric actuator, it has a value that corresponds one-to-one to the set value.

This signal Vo is generated using actual NG data before the cutting process, and at the same time, the value of Vo is stored in the memory 2.

Next, the voltage application route to the piezoelectric actuator is switched as shown in FIG. 2, and the actual cutting operation begins.

In this case, the data output from the memory during cutting is a value that compensates for the dynamic hysteresis of the actuator 8, and open-loop control is performed in which this value is simply transmitted to the high-voltage amplifier 5. Therefore, the response speed of the control system is also fast.

In the above embodiment described using FIGS. 1 and 2, the method of storing the deviation compensation value in the deviation compensation storage memory 2 in correspondence with all NC data was shown. However, before machining, a change compensation value is stored corresponding to the difference between the current data and the previous data of the NC setting data, and during machining, the change compensation value is added or subtracted from the NC setting data to obtain the actual deviation compensated data. Needless to say, a method with additional devices can also be implemented easily.

〔Effect of the invention〕

According to the present invention, there are the following effects.

(1) The dynamic hysteresis of the piezoelectric actuator that drives the cutting tool is completely compensated.

(2) The compensation accuracy of dynamic hysteresis can be expected to improve in proportion to the increase in measurement resolution of the length measuring needle.

(3) Dynamic hysteresis is compensated for by open-loop control that allows for high-speed response.

(4) Replacement of any type of piezoelectric actuator.

Easy to maintain.

(5) Due to (1) and (2) above, high-precision NC machining on the submicron order or less, which was difficult to achieve with conventional methods, becomes possible.

[Brief explanation of drawings]

Figure 1 is a block diagram showing the control configuration before sample processing in an embodiment of the present invention, Figure 2 is a block diagram showing the control configuration during sample processing in Figure 1, and Figure 3 is the control configuration in Figure 1. FIG. 4 is a block diagram of the circuit section, FIG. 4 is a block diagram showing the control configuration of the conventional device, and FIG. 5 is a characteristic diagram of dynamic displacement hysteresis of the voltage actuator. DESCRIPTION OF SYMBOLS 1... NO data generation circuit, 2... Storage memory for deviation compensated data, 3... Deviation compensation circuit, 4... Control data generation route switch, 5... High voltage amplifier, 6...
・Counter, 7... Length meter, 8... Piezoelectric actuator, 9... Displacement detection plate, 10... Rotary encoder, 11... Tacho generator, 12... D
C servo motor, 13... slip ring, 14...
- Air spindle, 15... Moving table, 16... Slider, 17... Drive device, 18... Diamond bite, 19... Sample, ;11; ノ]! ] Summary 2 National Government 3 Figure 4, No. 5! ! ] /l? Mr. ff)

Claims (1)

[Claims] 1. In a machine tool device that uses a piezoelectric actuator to drive cutting tools, the actual displacement of the piezoelectric actuator induced by the voltage applied to the piezoelectric actuator is monitored, and if it does not reach the target value, the deviation is The control system consists of a feedback system that compensates for the deviation, and a memory that can immediately store the deviation compensation value, and a closed loop from the feedback system and direct data output from the memory as a loop for applying voltage to the piezoelectric actuator. A tool control method for a machine tool device, which is characterized by the existence of an open loop due to the following, and which enables switching of the loop.