JPH07210221A - Numerical controller with torque ripple analyzing function - Google Patents

Abstract

PURPOSE:To provide the numerical controller for measuring, analyzing and recording torque ripple without separately preparing any measuring instrument. CONSTITUTION:This device is provided with a measured data buffer 21 for storing measured torque ripple data and an analystic part 22 for analyzing the torque ripple data, and an axial ball screw revolving frequency, the detected pitch frequency of a full closed detector and a motor turning frequency are displayed on a data display part 23 together with a torque ripple frequency component. Additionally, the torque ripple data are graphically displayed with a rod ball screw pitch, the detected pitch of the full closed detector and one turn of a rod motor as one cycle respectively, and one numerical controller 10 measures/specifies the generation factor of axial torque ripple without preparing any special measuring instrument such as an oscilloscope or an FET analyzer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a numerical controller for controlling a servomotor, and more particularly to a numerical controller having a torque ripple analysis function.

[0002]

2. Description of the Related Art FIG. 7 shows a block diagram of an example in which a numerical control device according to the prior art is applied to a drive mechanism of a machine tool. In FIG. 7, the numerical controller 1 is connected to a power amplifier 2 that supplies electric power to the servo motor 3 and a position detector 4S that detects the rotational position of the servo motor 3. Further, the numerical control device 1 includes the position error calculation unit 11
And the position control unit 12 that generates the speed command Vr based on the position error Pe, and the speed error V based on the speed command Vr and the like.
e, a speed error calculation unit 13, a speed control unit 14 that generates a torque command Tr based on the speed error Ve, a current control unit 15 that generates a current command value based on the torque command Tr, and a servo motor 3 The full-closed position and the semi-closed position of the drive load are detected from the current detection unit 16 that detects the current flowing in each phase of the above and the position detector 4S that detects the rotational positions of the induct sync 4F and the servomotor 3 and Current position Pa from position data
And a speed detection unit 18 that detects a speed from the current position Pa generated by the position detection unit 17.
And have. The operation of the conventional technique will be described below with reference to FIG. In the figure, based on the NC program read and interpreted by an NC program reading unit (not shown) and an NC program interpreting unit (not shown) in the numerical controller 1, a function generator (not shown) displays load movement information (target position, speed, etc.). And the position error calculation unit 11 receives the position command P
forward r. The position error calculation unit 11 obtains the difference between the position command value Pr and the current position Pa generated by the position detection unit 17 by a known method based on the detection value of the position detector 4S or the inductocin 4F. The position error Pe is calculated and sent to the position control unit 12. The position control unit 12 generates the speed command Vr based on the position error Pe by a known method. The speed error calculation unit 13 calculates the speed error Ve by taking the difference between the speed command value Vr and the speed detection value Va sent from the speed detection unit 18, and sends this to the speed control unit 14. The speed control unit 14 generates the torque command value Tr based on the speed error Ve by a known method such as proportional-integral operation feedback control. The current control unit 1 is based on this torque command value Tr.
In 5, the current feedback control finally generates a voltage command value and transfers the voltage command value to the power amplifier 2. In the power amplifier 2, the voltage command value (PWM
Voltage command), PWM processing is performed by a known technique,
Each phase voltage to be applied to the servo motor 3 is generated. A drive torque is generated in the servo motor 3 by applying this voltage, and the drive load including the ball screw 6, the table 8 and the bed 7 is driven at a desired position and speed via the timing belt 5 which is a speed change mechanism.

When a driving load as shown in FIG. 7 is driven by the numerical controller, so-called torque ripple may occur, which may cause a problem in driving control of the shaft. There are several possible causes of this torque ripple. now,
The servo motor 3 is an AC brushless servo motor (synchronous motor), and the relationship between the current flowing through the servo motor 3 and the generated torque in this case will be described. Servo motor 3
If the maximum magnetic flux density of the permanent magnets mounted on the rotor is B and the maximum value of the current flowing in each phase of the three-phase winding of the stator is I, the torque generated in each phase of U, V, W Are as in Equation 1, Equation 2, and Equation 3, respectively.

[Equation 1]

[Equation 2]

[Equation 3] When such a torque is generated in each phase, the combined output torque T of the three phases as a whole becomes irrelevant to the position θ of the servomotor rotor and the number P of poles, as shown in Formula 4.

[Equation 4] However, for example, when the servo motor 3 is energized by the three-phase three-wire method, the U-phase current has a current offset amount of α
However, when the W-phase current has a current offset amount of −α, the combined output torque T becomes as shown in Formula 5, and the torque ripple half the number of poles P is generated during one rotation of the servo motor 3. It appears in the combined output torque T.

[Equation 5] Alternatively, when the U-phase current has a gain error amount = β and the W-phase current has a gain error amount = −βISIN (Pθ / 2), the combined output torque T is as shown in Formula 6, and the servo motor 3 is 1 During the rotation, torque ripples corresponding to the number of poles P appear in the combined output torque T.

[Equation 6] It should be noted that there are other possible causes of torque ripple generation, and FIG. 10 is a table summarizing these factors.

When the torque ripple is a control problem, it is necessary to identify the cause of the problem. Since the numerical controller itself used in the prior art shown in FIG. 7 is not provided with the torque ripple analysis function, the torque waveform in the time domain is usually measured first with a measuring instrument such as the FFT analyzer 9. In FIG. 7, instead of directly measuring the combined output torque T of the servo motor 3, the torque command value Tr, which is the output of the speed control unit 14 in a constant speed operation, is FF.
It is measured by the T analyzer 9. FIGS. 8A and 8B show examples of the time domain torque waveform measured at this time. Further, FIGS. 9A and 9B show examples in which the frequency components of these time domain torque signals are measured by the FFT analyzer 9. In order to identify the cause of the occurrence from the measured torque ripple, it is necessary to check the presence or absence of its periodicity. Specifically, when the torque ripple is measured under the driving condition of a constant speed command, the speed detecting unit 1
From the actual feed speed generated in 8 and the pitch of the ball screw 6 (hereinafter referred to as the shaft ball screw pitch), one rotation cycle of the shaft ball screw at the feed speed, the feed speed and the gear ratio. The one rotation cycle of the axis servo motor at the calculated feed rate, the feed rate, and the detection pitch cycle of the induct thin 4F that is the axis full-closed detector are obtained in advance, and these three types of cycle and torque are calculated. The relationship with the ripple period will be investigated, and the cause will be estimated according to FIG. Alternatively, the frequencies that are the reciprocals of the respective periods are obtained, and the relationship between these frequencies and the torque ripple frequency component is investigated,
The cause will be estimated according to. Here, the detected pitch cycle of the induct thin 4F is the induct thin 4
It is defined as the time required to pass the absolute value detection stroke of F (for example, 2 mm) at the feed speed.

As described above, in the conventional numerical control apparatus, in order to investigate the periodicity of the torque ripple and estimate the factor of its occurrence, a measuring instrument such as an oscilloscope or an FFT analyzer 9 is used as the measuring means. However, since they are large and heavy, they have to be carried to the place where the survey target such as NC machine tool is installed each time. Therefore, it took a lot of time to set up the survey work. In addition, each measuring device is expensive. In addition, it is necessary to know in advance the so-called skeleton (coupling information) such as the gear ratio of the shaft for the calculation of each cycle, and since it is basically calculated manually, there is a possibility that calculation errors may occur. There is probably a problem. Further, in the numerical controller shown in FIG. 7, recording / storing of measurement data is not particularly considered, so that it is necessary to prepare a measuring instrument or the like having a data recording function in order to confirm the data later. At this time, the control target machine specifications (model, speed change mechanism, detector, power amplifier, motor specifications, etc.), manufacturing information (user name, manufacturing month, manufacturing number, etc.),
Measurement conditions (servo parameter settings, etc.) and file creation information (measurement / file creation date / time, measurement / file creator name, etc.) must be recorded. There is a problem that it is necessary to record the data, and there is a problem such as an error in associating the measurement data with the information because the data is not integrated with the measurement data itself, such as a transcription error during recording.

The present invention has been made to solve the above problems, and the purpose thereof is to generate the drive load without preparing a special measuring instrument such as an oscilloscope or an FFT analyzer. An object of the present invention is to provide a numerical control device capable of executing torque ripple analysis. Another object of the present invention is to provide a numerical control device capable of recording and storing servo characteristic data measured in combination with machine specifications of a control target, manufacturing information, and measurement conditions.

[0006]

In order to achieve the above object, the invention according to claim 1 drives a drive load system to generate a torque based on a speed error to control a machine to be controlled. In the numerical controller, storage means for storing measurement data regarding torque ripple, analysis means for calculating / analyzing frequency component of torque ripple from measurement data recorded in the storage means, and analysis result by the analysis means are displayed. And a display means for measuring and displaying a torque ripple generated in the drive load system. According to a second aspect of the present invention, in the numerical controller with torque ripple analysis function according to the first aspect, the drive load system detects a ball screw, a motor for driving the ball screw, and a detection unit for detecting a rotational position of the motor. And the display means displays the ball screw rotation frequency, the detection pitch frequency of the detection means, and the motor rotation frequency together with the analysis result. According to a third aspect of the present invention, in a numerical controller that controls a machine to be controlled by driving a drive load system by generating torque based on a speed error, a frequency component of torque ripple is calculated from measurement data regarding torque ripple. Analysis means for analyzing, control target machine data storage means for storing information about the control target machine included in the drive load system, information stored in the control target machine data storage means, and the analysis result And a file creating means for creating a data file.

Therefore, according to the present invention, the calculation / analysis means is
The frequency component of the torque ripple is analyzed from the measurement data stored in the storage means. Since the display means can display the analysis result obtained by the calculation / analysis means, it is possible to identify the cause of the torque ripple without separately preparing a measuring instrument. Further, since the file generation means generates a data file by combining the information stored in the controlled machine data storage means and the analysis result, the controlled machine and the measurement data can be integrated.

[0007]

1 is a block diagram showing a configuration of an embodiment of a numerical control device adopting a torque ripple analysis function according to the present invention, and FIG. 2 illustrates an operation of torque ripple analysis in the embodiment of the present invention. It is a flow chart. In FIGS. 1 and 2, the functions and processing contents of the constituent elements indicated by the same numbers as those of FIG. 7 showing the conventional technique are the same as those of the conventional technique, and therefore the description thereof is omitted, and the essential part of the present invention. Only will be described below. In FIG. 1, the numerical controller 10 includes a measurement data buffer 2 for storing measurement data on torque ripple at a specified sampling interval.
1, an analysis unit 22 for calculating / analyzing the measurement data stored in the measurement data buffer 21, a data display unit 23 for outputting the analysis result as a graphic or character to a display device (not shown) in the numerical control device 10, A detector data storage unit 25 that holds the specifications and manufacturing information of the controlled machine such as the position detector 4S and the power amplifier 2 as data, and the measurement data calculated and analyzed by the analysis unit 22 to machine specification data, File generation unit 2 that generates one data file by adding manufacturing information, measurement conditions, and file creation information
Have four.

The operation in the torque ripple analysis mode of the numerical controller with torque ripple analysis function according to the present embodiment shown in FIG. 1 will be described below with reference to the flow chart of FIG. During normal operation of the numerical control device 10, the numerical control device 10 periodically reads a mode switching signal by a mode switching unit (not shown) (step S1), and either the torque ripple analysis mode or the normal NC operation mode is designated. It is determined (step S2). When the normal NC operation mode is designated in FIG. 2, a desired NC operation process is executed by a known technique (step S3). When the torque ripple analysis mode is designated, the operator first interactively inputs the axis designation data, the constant feed rate operation start position of the axis, and the feed rate by an interactive input means (not shown) (step S21). At this time, the shaft ball screw rotation frequency and the induct synch detection pitch frequency are calculated from the given feed speed, the shaft ball screw pitch data, and the induct sync absolute value detection stroke, and the shaft speed ratio and the feed speed are calculated. The motor rotation frequency is obtained, and it is confirmed that the predetermined torque ripple sampling frequency is within a certain high range with respect to the maximum frequency of these three types of frequencies. This range is due to the accuracy of frequency analysis and the limitation of the number of measurement data points that can be stored in the measurement data buffer 21, and in this embodiment, the sampling frequency is set to about 5 to 20 times the maximum frequency. If the sampling frequency is out of this range, guidance is displayed again on the operation panel or the like of the numerical controller 10 so that the operator can input a proper feed speed again.
When the torque ripple measurement condition is established, an operation command for each predetermined position control cycle, that is, a position command Pr is generated according to this condition (step S22). The torque command value Tr, which is the output of the speed control unit 14, is regarded as the torque ripple data after a predetermined acceleration / deceleration time has passed since the first position command Pr became valid, that is, at the time of reaching a constant speed. The data is sampled and stored in the measurement data buffer 21 as time series data (step S23). In the present embodiment, the data writing is the longest one of the measurement data buffer 21 being full, the ball screw pitch of the shaft, the absolute value absolute value detection stroke of the shaft, and the longest distance traveled when the shaft motor makes one rotation. It shall end when the drive load moves by a double distance. The frequency component of the measured torque ripple data is obtained by the analysis unit 22 by a known technique (step S24). This analysis result is calculated from the shaft ball screw rotation frequency calculated from the feed rate at the time of the torque ripple measurement and the detection pitch frequency of the fully closed detector, the shaft speed ratio and the feed rate at the time of the torque ripple measurement. The data is output from the data display unit 23 to the display device (not shown) in the numerical controller 10 together with the motor rotation frequency (step S25). FIG. 4A shows an example in which these data are displayed on the CRT. The operator can specify the torque ripple generation factor from these data based on FIG. 10. After displaying the processing result (step S25), the numerical controller 10 checks whether or not the operator has designated the creation of the data file (step S26), and if there is no data file creation instruction, the process proceeds to step S28 described later. When there is a data file creation instruction, the measured / analyzed torque ripple data is added to the data on the specifications of the controlled machine, manufacturing information, and measurement conditions stored in the data storage unit 25 such as the detector, as shown in FIG. 1 as shown
A data file of a book is generated (step S27). Then, it is determined whether or not there is an instruction to re-execute the torque ripple analysis by the operator (step S28), and when re-execution is designated, step S21 and subsequent steps are repeated, and when the measurement is to be ended, the process returns to step S1. In this way, the torque ripple analysis can be repeated without a measuring instrument such as an oscilloscope or FFT analyzer, and a measurement data file can be created as necessary.

Next, another operation in the torque ripple analysis mode of the numerical controller with torque ripple analysis function according to this embodiment shown in FIG. 1 will be described with reference to the flow chart of FIG.
The description of the operation steps not shown in FIG. 3 is exactly the same as the case of FIG. When the torque ripple analysis mode is specified,
First, the operator interactively inputs the axis designation data, the constant feed rate operation start position of the axis, and the feed rate by an interactive input means (not shown) (step S210). Except for the distance required for acceleration / deceleration, the measured operation distance in this embodiment is 5 which is the longest of the shaft ball screw pitch, the induct sync absolute value detection stroke, and the shaft moving distance corresponding to one rotation of the shaft motor. Doubled. When the torque ripple measurement condition is determined, an operation command for every predetermined position control cycle, that is, a position command Pr is generated according to this condition (step S220). The torque command value Tr, which is the output of the speed control unit 14, is regarded as the torque ripple data after a predetermined acceleration / deceleration time has passed since the first position command Pr became valid, that is, at the time of reaching a constant speed. While sampling, the current position Pa at the time of sampling
And the torque command value Tr are paired and written as time series data in the order of sampling in the measurement data buffer 21 (step S230). The measured torque ripple data is analyzed by the analysis unit 22 for each pitch (distance) of the shaft ball screw pitch, the induct sync absolute value detection stroke, and the shaft movement distance corresponding to one rotation of the shaft motor within one cycle. The position to which the torque ripple data corresponds is specified (step S240). This will be referred to as a phase analysis process at a predetermined pitch (three pitches above) for convenience. Specifically, the phase is determined as follows. For example, the phase angle θm of the torque ripple data having the current position Pa at the time of sampling at the shaft movement distance (abbreviated as Pm) corresponding to one rotation of the shaft motor.
Is calculated by Equation 7.

[Equation 7] When the phase angle of each torque ripple data at the relevant pitch is obtained, the range of 360 degrees in one cycle is divided into sections of 1 degree, and the respective torque ripple data is aggregated for each of the corresponding sections and each of these sections is divided. A noise reduction process is performed on the measurement data by taking an arithmetic mean (step S250). Next, the average value of the torque in the one cycle of the pitch is calculated (step S260), and the graphic data of the circle having the size corresponding to the average value in the polar coordinates in which the one cycle of the pitch is 360 degrees of each torque ripple data is calculated. The numerical control device 1 that generates and uses the data display unit 23
It is output to a graphic display device (not shown) within 0 (steps S270 and S280). Figure 4 (b)
Shows an example of displaying these graphic data on a CRT. The operator can specify the torque ripple generation factor from these graphic display data based on FIG. 10. That is, as shown in FIG. 4B, if the beginning and end of one cycle are continuous as a figure, it is understood that the torque ripple is synchronized with the pitch. FIG. 5 shows the torque ripple of the same measurement data as (a) the distance traveled when the shaft motor makes one revolution,
The display when the coordinates are calculated with (b) the absolute value detection stroke of the induct cin and (c) the ball screw pitch of the shaft as one cycle is shown. Also in this case, the fact that the torque ripple is synchronized with the distance traveled when the shaft motor makes one rotation is not synchronized with the induct cin absolute value detection stroke and the ball screw pitch of the shaft due to the connection of the torque ripple pattern. You can visually understand that it is not.

In this embodiment, the torque ripple sampling and its analysis / data display are performed separately. That is, although the analysis and display are performed offline, online processing may be used if real-time processing capability is available. Further, at the time of the display of FIG. 4, the specifications and manufacturing information of the position detector 4S, the power amplifier 2, and the target machine, which are stored in the numerical control device 1 such as the ball screw pitch and are mounted in the target machine in advance, are analyzed. It may be displayed together with the result. Further, in step S21 of FIG. 2, the operator may only input the measurement operation start position, and the numerical control device 10 may automatically determine the measurement operation feed speed and the movement distance for measurement.

As described above, the present invention has storage means for storing measurement data relating to torque ripple and analysis means for analyzing the torque ripple data, and calculates from the feed rate at the time of torque ripple measurement. Displaying the shaft ball screw rotation frequency and the detection pitch frequency of the fully closed detector, and the motor rotation frequency calculated from the shaft speed ratio and the feed rate at the time of torque ripple measurement together with the frequency of the frequency component on the display means. Since this is done, there is an effect that the factor that causes the shaft torque ripple can be measured and specified by one numerical controller without preparing a special measuring instrument such as an oscilloscope or an FFT analyzer. In addition, the measured data on the measured and analyzed torque ripple is added to the specification data of the detector, the power amplifier and the target machine, the manufacturing information and the measurement conditions to generate a data file. -When saving, there is an effect that one data file can be created together with the specifications, manufacturing information, and measurement conditions of the controlled machine. Further, since the information about the controlled machine is stored in the controlled machine data storage means in advance, it is possible to prevent a transcription error by a person in charge of investigation.

[Brief description of drawings]

FIG. 1 is a block diagram of a numerical control device with a torque ripple analysis function according to an embodiment of the present invention.

FIG. 2 is a flow chart illustrating an operation of torque ripple analysis in the embodiment of the present invention.

FIG. 3 is a flowchart illustrating the operation of torque ripple analysis in the embodiment of the present invention.

FIG. 4 is a diagram showing a display example of a torque ripple analysis result in the embodiment of the present invention.

FIG. 5 is a diagram showing a display example of a torque ripple analysis result in the embodiment of the present invention.

FIG. 6 is a diagram showing an example of a structure of a servo characteristic data file generated in the numerical controller according to the present invention.

FIG. 7 is a block diagram of a numerical control device according to the prior art.

FIG. 8 is a diagram showing a torque ripple signal waveform.

FIG. 9 is a diagram showing frequency components of a torque ripple signal.

FIG. 10 is a diagram showing a torque ripple generation factor.

[Explanation of symbols]

 1, 10 Numerical Control Device 2 Power Amplifier 3 Servo Motor 4S Position Detector 4F Induct Thin 5 Timing Belt 6 Ball Screw 7 Bed 8 Table 11 Position Error Calculation Unit 12 Position Control Unit 13 Speed Error Calculation Unit 14 Speed Control Unit 15 Current Control Section 16 current detection section 17 position detection section 18 speed detection section 21 measurement data buffer 22 analysis section 23 data display section 24 file generation section 25 detector and other data storage section

Claims (3)

[Claims] 1. A numerical control device for controlling a machine to be controlled by driving a drive load system by generating a torque based on a speed error, and a storage means for storing measurement data on torque ripple, and the storage means. The torque ripple generated in the drive load system is measured and displayed, including an analyzing unit that calculates and analyzes the frequency component of the torque ripple from the stored measurement data, and a display unit that displays the analysis result by the analyzing unit. Numerical control device with torque ripple analysis function characterized by: 2. The numerical controller with torque ripple analysis function according to claim 1, wherein the drive load system includes a ball screw, a motor for driving the ball screw, and a detection unit for detecting a rotational position of the motor. A numerical control device with a torque ripple analysis function, wherein the display means displays the ball screw rotation frequency, the detection pitch frequency of the detection means, and the motor rotation frequency together with the analysis result. 3. A numerical controller for controlling a machine to be controlled by driving a drive load system by generating torque based on a speed error, to calculate and analyze a frequency component of torque ripple from measurement data on torque ripple. Analysis means, control target machine data storage means that stores information about the control target machine included in the drive load system, and information stored in the control target machine data storage means and the analysis result together. A numerical control device with a torque ripple analysis function, comprising: a file generating means for generating a data file.