JP2010271880A - Machining force monitoring system and machine tool using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a machining force monitoring system that ensures robustness of the system without using an external sensor and detects machining force with high accuracy, and to provide a machine tool using the same. <P>SOLUTION: The machining force monitoring system includes: a work support means supporting a work; a drive means moving the work support means; a machining means machining the work; a disturbance observer estimating disturbance to the drive means based on a reference signal input to the drive means and an output signal output from the drive means, and performing feedback to the reference signal; and machining force estimation observer subtracting frictional force obtained in advance from the disturbance to the drive means estimated based on the reference signal input to the drive means and the output signal output from the drive means to estimate the machining force of the machining means. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a machining force monitoring system for monitoring a machining force of a machine tool or the like without using an external sensor, and a machine tool using the same.

  From the viewpoint of making machine tools that perform cutting and grinding intelligent, research on processing process monitoring technology has attracted attention. In particular, the development of technology for monitoring the machining process by monitoring the cutting force is regarded as important. Conventionally, as a technique for monitoring cutting force, there are a technique for attaching an external sensor between a machine tool table and a workpiece and monitoring a machining force, and a technique for measuring a driving current with an ammeter and estimating a machining force (non-) Patent Document 1).

"Sensor-Less Monitoring of Cutting Force During Ultraprecision Machining", H. Shinno, H. Hashizume, H. Yoshioka, Annals of the CIRP Vol.52 / 1/2003

  By using a piezoelectric force sensor as an external sensor, the machining force can be measured with high accuracy. However, at the site where an actual product is processed, processing with an external sensor attached to a machine tool is not used because it causes an increase in the setup process and a decrease in rigidity. In addition, an external sensor for measuring cutting force with high accuracy is very expensive, and it is almost impossible to mount this on all machines on the production site.

  The present invention is for solving the above-described problems, and does not use an external sensor, ensures a robust system, and detects a machining force with high accuracy, and a machine using the machining force monitoring system. The purpose is to provide a machine.

  Therefore, the machining force monitoring system of the present invention includes a workpiece support means for supporting a workpiece, a drive means for moving the workpiece support means, a machining means for machining the workpiece, a reference signal input to the drive means, and the drive. Based on the output signal output from the means, the disturbance to the driving means is estimated, the disturbance observer that feeds back to the reference signal, the reference signal input to the driving means, and the output signal output from the driving means And a machining force estimation observer for estimating a machining force of the machining means by subtracting a friction force obtained in advance from the estimated disturbance to the driving means.

  The processing force estimation observer includes a first processing force estimation observer having a filter that passes a predetermined frequency, and a filter that passes a frequency that is different from the frequency that the first processing force estimation observer passes. And 2 machining force estimation observers.

  Furthermore, the machine tool of the present invention includes the machining force monitoring system, the maximum machining force input means for inputting the maximum machining force that the tool can withstand, the machining force monitored by the machining force monitoring system, and the maximum machining force input means. A calculation means for comparing the input machining force and calculating the rotation speed and the optimum feed speed so that the machining force monitored by the machining force monitoring system does not exceed the machining force input to the maximum machining force input means; It is characterized by having.

  Further, the calculation means calculates the rotation speed and the optimum feed speed so that the machining force monitored by the machining force monitoring system is constant.

  Accordingly, the present invention can provide a machining force monitoring system that secures the robustness of the system and detects the machining force with high accuracy without using an external sensor, and a machine tool using the same. .

It is a figure which shows a processing force monitoring system. It is a figure which shows a disturbance observer. It is a figure which shows the processing force estimation observer. It is a figure which shows the machining force monitoring system provided with the some machining force estimation observer. It is a figure which shows a linear motor table. It is a system configuration diagram. 1 is a block diagram of a system. It is a figure which shows the method of the experiment 1. FIG. It is a figure which shows the result of Experiment 1. It is a figure which shows the method of Experiment 2. It is a figure which shows the result of the robustness of Experiment 2. It is a figure which shows the cutting force estimation of Experiment 2. FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  First, an embodiment of the processing force monitoring system will be described. FIG. 1 is a diagram showing a machining force monitoring system, FIG. 2 is a diagram showing a disturbance observer, and FIG. 3 is a diagram showing a machining force estimation observer. 1, 2, and 3, 1 is a machining force monitoring system, 2 is a motor as drive means, 3 is a disturbance observer, and 4 is a machining force estimation observer.

  The machining force monitoring system 1 includes a motor 2 that moves the workpiece W, a disturbance observer 3 that compensates the disturbance by estimating and feeding back the disturbance, and a machining force estimation observer 4 that estimates the machining force.

  In the processing force monitoring system 1, first, when a reference current Iref for driving the motor 2 is input as an input signal, the compensation current Icmp output from the disturbance observer 3 is added, and an addition signal of the reference current Iref and the compensation current Icmp. Is input to the motor 2. Further, the motor 2 is affected by disturbance due to the processing force Fcut and the frictional force Ffric. The disturbance F0dis is estimated by the disturbance observer 3, converted to a compensation current value Icmp, and compensated by feedback. The motor 2 compensates for the disturbance F0dis and outputs the position of the workpiece W.

ここで、Ｋt[N/A]はモータ２の推力定数、Ｉref[A]は参照電流である。 Next, the disturbance observer 3 will be described. As shown in FIG. 2, the disturbance observer 3 receives an input signal to the motor 2 and an output signal from the motor 2, and estimates the disturbance F0dis. For example, in the case of a linear motor drive table, the table mass is M [kg], the speed is x '[m / s], the generated thrust of the motor is Fm [N], the cutting force is Fcut [N], and the friction force of the guide surface When Fkric [N] is used to describe the equation of motion, the following equation (1) is obtained.

Here, Kt [N / A] is a thrust constant of the motor 2 and Iref [A] is a reference current.

In practice, the mass M and the thrust constant Kt vary by ΔM and ΔKt from their nominal values Mn and Ktn. The sum of the fluctuation thrust due to these parameter fluctuations, the cutting force Fcut, and the friction force Ffric is the disturbance F0dis, and is expressed by the following equation (2). At this time, Expression (1) is converted into Expression (3).

  Since the disturbance Fdis calculated by the disturbance observer 3 includes high-frequency noise, the noise is removed through the low-pass filter LPFa, converted to the disturbance F0dis, and then converted into a compensation current Icmp and fed back to compensate for the disturbance Fdis. Thus, the robustness of the system can be improved. In addition, although the output signal from a motor is converted into a position signal and input as a signal input to the disturbance observer 3, it may be input as a speed signal.

  Next, the processing force estimation observer 4 will be described. As shown in FIG. 3, the machining force estimation observer 4 has substantially the same structure as the disturbance observer 3. The machining force estimation observer 4 estimates the machining force F0cut by subtracting the frictional force F0fric estimated in advance from the disturbance F0dis estimated and output in the same manner as the disturbance observer 3. Since the frictional force F0fric is the same as the disturbance F0dis when the motor 2 is driven in a no-load state, the value may be obtained and stored in a database in advance in a table or function.

  The machining force monitoring system 1 applies such a disturbance observer 3 and a machining force estimation observer 4. The variation in thrust is removed by appropriately adjusting the nominal mass value Mn and the thrust constant nominal value Ktn, which are parameters of the machining force estimation observer 4.

  As described above, the machining force monitoring system 1 of the present embodiment improves the control system used in a machine tool or the like without using an external force sensor, thereby ensuring the robustness of the system and processing. The force can be estimated at high speed and with high accuracy. Further, the machining force can be controlled at high speed by feeding back the machining force estimated by the machining force estimation observer 4.

  Further, since the path or cutoff frequency of the low-pass filter LPFa incorporated in the disturbance observer 3 and the low-pass filter LPFb incorporated in the machining force estimation observer 4 can be determined independently, the path or cutoff frequency of the disturbance observer 3 to be fed back is not changed. In addition, it is possible to estimate the machining force by freely changing the path or cutoff frequency of the machining force estimation observer 4 while maintaining the robustness of the system.

  Therefore, as shown in FIG. 4, the machining force monitoring system 1 includes a first machining force estimation observer 4a having a filter that passes a predetermined frequency, and a first machining force estimation observer 4a as the machining force estimation observer 4. With the second machining force estimation observer 4b having a filter that passes a frequency different from the frequency that passes, machining forces in different frequency bands due to the rotation period, tool deflection, etc. can be estimated simultaneously. . Thereby, for example, it becomes possible to simultaneously measure the machining force of the DC component and the AC component in end milling or the like. Note that the number of processing force estimation observers 4 is not limited to two and any number may be provided.

  Next, an embodiment in which the machining force monitoring system 1 is used for controlling the linear motor table will be described. FIG. 5 is a diagram showing a linear motor table, FIG. 6 is a system configuration diagram, and FIG. 7 is a block diagram of the system. In the figure, 51 is a table as a work supporting means, 52 is a guide, 53 is a scale, and 54 is a linear encoder.

  The table 51 is movable along the guide 52 by driving the linear motor 2. As shown in FIG. 6, the position information of the table 51 is fed back to the machining force processing system 1 by the linear encoder 54 reading the scale 53. Then, the processing force processing system 1 gives a command value to the linear motor 2 based on the position information of the table 51.

  As shown in FIG. 7, a command signal xcmd for instructing the position of the table from an input means (not shown) is differentiated into an acceleration signal x ″ cmd by a proportional differential controller, converted to a reference current Iref by a signal converter, and processed with a machining force process. The processing force processing system 1 executes the processing described with reference to Fig. 1 to Fig. 3. The output position x is added to the command signal xcmd by a proportional differential controller.

  Next, a performance experiment in the embodiment in which the machining force monitoring system 1 is used for controlling the linear motor table will be described.

  First, Experiment 1 will be described. FIG. 8 is a diagram illustrating the method of Experiment 1, and FIG. 9 is a diagram illustrating the result of Experiment 1.

  As shown in FIG. 8, in Experiment 1, a load is applied while the table 51 is driven by the linear motor 2, and load measurement values are measured on the load cell 71 side as an external force sensor and on the table 51 side monitored by the machining force monitoring system 1. To compare. The experimental conditions were a feed rate of 0.6 mm / min.

  As shown in FIG. 9, the load measurement values of the output A on the load cell 71 side as an external sensor and the output B on the table 51 side monitored by the machining force monitoring system 1 are substantially the same.

  As described above, the machining force monitoring system 1 can estimate the machining force at high speed and with high accuracy, similar to the external sensor.

  Next, Experiment 2 will be described. FIG. 10 is a diagram illustrating the method of Experiment 2, FIG. 11 is a diagram illustrating the result of robustness of Experiment 2, and FIG. 12 is a diagram illustrating the cutting force estimation of Experiment 2.

  As shown in FIG. 10, in Experiment 2, the work W is placed on the table 51, groove processing is performed, the response position to the position command signal is detected, and the robustness improvement by the disturbance observer is confirmed, and the cutting is performed. It confirms the measurement of force.

Cutting conditions, the aluminum workpiece was placed in a 3 Jikutategata machining center, the end mill of 3mm diameter, rotational speed 1000min ^-1, fed at a feed rate 3mm / min, cutting depth of 1 mm.

  In FIG. 11, the horizontal axis represents time, and the vertical axis represents the position of the table. Further, xcmd is a position command signal, x is a position when a disturbance observer is used, and xa is a position when a disturbance observer is not used.

  As shown in FIG. 11, in the case of x using a disturbance observer, the table follows the position command signal xcmd. However, in the case of xa without using a disturbance observer, a deviation occurs and the followability is poor. It has become. Therefore, it can be confirmed that the robustness is improved by compensating the disturbance by the disturbance observer.

  Moreover, as shown in FIG. 12, the estimated value of the periodic cutting force corresponding to a rotational speed is output with high precision.

  As described above, the machining force monitoring system 1 can estimate the machining force at high speed and with high accuracy while maintaining the robustness of the system without using an external force sensor. Further, the machining force can be controlled at high speed by feeding back the machining force estimated by the machining force estimation observer 4. For example, by using it for the z-axis of grinding machines and polishing machines, a machine that performs constant pressure grinding and constant pressure polishing without a sensor, or a machining center that drills with a constant thrust force and processes with a constant DC component cutting force of the end mill. Can be developed.

  Further, in a machine tool equipped with a control function by the machining force monitoring system 1, it is possible to instantaneously derive an optimum feed speed corresponding to the rotational speed by only inputting the maximum cutting force that the tool can withstand to the command value.

  Furthermore, in a machine tool equipped with a control function by the processing force monitoring system 1, it is possible to process brittle materials and composite / laminated materials that are difficult to process materials under optimum conditions while adjusting the processing force. For example, a brittle material such as glass or ceramics can be processed in a ductile state by instructing processing with a force in an elastic region.

  That is, the machining force monitoring system 1, the maximum machining force input means for inputting the maximum machining force that the tool can withstand, the machining force monitored by the machining force monitoring system 1, and the machining force input to the maximum machining force input means And a calculation means for calculating the rotation speed and the optimum feed speed so that the machining force monitored by the machining force monitoring system 1 does not exceed the machining force input to the maximum machining force input means. It becomes possible.

  Further, it is preferable that the calculation means calculates the rotation speed and the optimum feed speed so that the machining force monitored by the machining force monitoring system is constant.

  DESCRIPTION OF SYMBOLS 1 ... Machining force monitoring system, 2 ... Motor (drive means), 3 ... Disturbance observer, 4 ... Machining force estimation observer, 51 ... Table (work support means), 52 is a guide, 53 is a scale, 54 is a linear encoder, W …work

Claims (4)

A work support means for supporting the work;
Drive means for moving the workpiece support means;
Processing means for processing the workpiece;
A disturbance observer for estimating a disturbance to the driving unit based on a reference signal input to the driving unit and an output signal output from the driving unit, and feeding back to the reference signal;
Machining that estimates the machining force of the machining means by subtracting the frictional force obtained in advance from the disturbance to the drive means estimated based on the reference signal input to the drive means and the output signal output from the drive means A force estimation observer;
A processing force monitoring system characterized by comprising: The processing force estimation observer is
A first machining force estimation observer having a filter that passes a predetermined frequency;
A second machining force estimation observer having a filter that passes a frequency different from a frequency that the first machining force estimation observer passes;
The processing force monitoring system according to claim 1, further comprising: The processing force monitoring system according to claim 1 or 2,
Maximum machining force input means for inputting the maximum machining force that the tool can withstand,
Compare the machining force monitored by the machining force monitoring system with the machining force input to the maximum machining force input means, and the machining force monitored by the machining force monitoring system exceeds the machining force input to the maximum machining force input means. Calculation means for calculating the rotation speed and the optimum feed speed so that there is no;
A machine tool characterized by comprising:   The machine tool according to claim 3, wherein the calculating means calculates the rotation speed and the optimum feed speed so that the machining force monitored by the machining force monitoring system is constant.

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