JP2000152693A - Control method and system of servo motor, machine tool, and friction-compressing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform more accurate and stable, optimum control by achieving compound control where position, speed, and torque of two servo motors are correlated without adding separate control mechanisms. SOLUTION: First and second servo motor control devices 3 and 4 for supplying power suited for each servo motor according to a command to control each of first and second axis servo motors 1 and 2 are provided with current detectors 11 and 21 for performing feedback control, by detecting the actual values of the position, speed, and current of each servo motor with each encoder, encoder pulse counters 12 and 22, and torque/position/speed detection means 13-15 and 23-25. The position, speed, and output torque of the first servo motor which is detected by the first servo motor control device are inputted to a computing element 27 of the second servo motor control device, thus controlling the position, speed, and torque of the second servo motor based on a result calculated with a preset, prescribed relationship.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position, speed and / or position of each axis servomotor in a machine tool, an industrial robot and other industrial machines using two axis servomotors.
Also, the present invention relates to a method for controlling torque in a correlated manner, and a servo motor control system using the method. In particular, the present invention relates to a method and apparatus for controlling the position of a workpiece or a tool and the output torque at that position and the speed of the workpiece or a tool in a constant relationship in machining such as friction welding.

[0002]

2. Description of the Related Art Generally, a machine tool or the like using a servo motor for driving each axis has sensors for detecting a current flowing through the motor and a speed and a position of a motor output shaft. Drive control of each axis servomotor is performed using a control device that supplies electric power based on the information. Conventionally, in the control of such a mechanical system, the position control system or the speed control system of each axis servomotor is mostly executed individually, and it is rare to perform complex control for correlating the position and the speed range. There is. In a servo system of digital control, a position and a speed are detected by an output pulse from an encoder, and the position and the speed are controlled by performing an arithmetic process.

[0003]

However, in a mechanical system using two axis servomotors, it may be difficult to obtain higher and stable machining accuracy by the above-described conventional control based on position and speed. . In such a case, it is necessary to control by correlating the position, the speed, and the torque.For that purpose, for example, an encoder is directly connected to each servomotor or provided externally to detect the position and the speed, Conventional servo motor control, such as providing a torque detector or the like externally to detect the torque value, correcting the command of the servo motor control device based on these, or mechanically controlling by a braking means such as a powder brake Separate controls must be added in addition to the device.

[0004] Therefore, there is a possibility that the whole control system becomes complicated and the reliability is lowered, and further, there arises a problem that the whole apparatus becomes large and expensive. In particular, in the case of mechanical control, there is a possibility that stability may be impaired or accuracy may be reduced due to mechanical backlash, wear, or a problem of torque accuracy in braking means such as a powder brake. Furthermore, there is a problem that the relationship between the position, the speed and the torque cannot be easily and freely changed in response to a change in the processing conditions and the like, which leads to a reduction in work efficiency and productivity.

Further, in order to perform more accurate and stable control, the detected position, speed and torque values are calculated with a predetermined fixed relationship, and the servo motor control is performed based on the calculated result. Even in the case where commands of the device are corrected or mechanically controlled, there is a problem that the control system becomes further complicated if a separate control unit is added in addition to the conventional servo motor control device.

Accordingly, the present invention has been made in view of the above-mentioned conventional problems, and has as its object to provide a machine tool using two axis-driven servomotors,
In other industrial machines, each axis servomotor can be used without adding a separate control unit or control mechanism using a simple configuration consisting only of a servomotor control device provided for each axis servomotor as in the past. It is an object of the present invention to provide a servomotor control method and control system that enables highly accurate control of a mechanical system by controlling the position, speed, and / or torque of the servomotor in a correlated manner.

It is a further object of the present invention to have two axis servomotors each for driving a workpiece or tool, and to position one of the workpiece or tool and the corresponding axis servomotor at that location. The output torque and the position, speed and / or torque of the axis servomotor corresponding to the other workpiece or tool can be controlled in a correlated manner with a certain relationship, whereby the mechanical system and the control system can be controlled. It is an object of the present invention to provide a machine tool, in particular, a friction welding device, which can simultaneously realize simplification of machining and improvement of machining accuracy.

[0008]

According to the present invention, there is provided a method for controlling a servomotor, comprising: a servomotor for driving two shafts; In the method using two servo motor control devices for supplying electric power suitable for the servo motor and detecting the actual values of the position, speed and current of the servo motor and performing feedback control, the position of one of the detected servo motors The position, speed or torque of the other servomotor is controlled in accordance with a predetermined relationship set in advance based on at least two of speed, speed and output torque.

As described above, according to the present invention, the position, speed and torque of the two shaft servomotors are correlated by using only the same servomotor control device as in the prior art without adding a separate control mechanism. Combined control can be realized,
More accurate and stable control can be optimally performed.

In one embodiment, at least two of the detected position, speed and output torque of one servomotor are calculated with a predetermined relationship, and the position and speed of the other servomotor are calculated based on the calculation result. Alternatively, the torque can be controlled. The predetermined relationship can be set and changed easily and freely according to the control conditions.

According to another aspect of the present invention, a first shaft drive is provided.
And for driving and controlling the second servo motor, supplying electric power suitable for the corresponding servo motor,
And a control system including first and second servomotor control devices for detecting and feedback-controlling the actual values of the position, speed, and current of the servomotor, wherein the second servomotor control device includes the second servomotor control device. The position of the second servomotor based on at least any two of the position, speed, and output torque of the first servomotor detected by the first servomotor control device; A control system for a servomotor, which controls speed or torque, is provided.

In one embodiment, the second servo motor control device has a calculator for calculating at least any two of the detected position, speed and output torque of the first servo motor in a predetermined relationship. Then, the position, speed or torque of the second servomotor can be controlled based on the calculation result. The setting of the predetermined relation in such an arithmetic unit can be performed relatively easily and freely according to the control conditions, and can be changed.

According to the present invention, the first and second servomotors for driving the shafts and the electric power suitable for the respective servomotors are supplied, and the position, speed and current of the servomotors are adjusted. A machine tool including first and second servo motor controllers for detecting an actual value and performing feedback control, wherein the second servo motor controller is detected by the first servo motor controller. Controlling the position, speed or torque of the second servomotor with a predetermined relationship based on at least two of the position, speed and output torque of the first servomotor. Machine tool to be provided.

Thus, the position of the two axis servomotors
By the speed / torque correlation control, it is possible to stably and optimally control the machining with higher accuracy and improve machining accuracy.

Further, according to the present invention, an axis-driven first servomotor for driving a feed table for holding a fixed-side work,
The second axis drive that drives the headstock that holds the rotating workpiece
Servo motors and first and second servo motor control devices for supplying electric power suitable for the corresponding servo motors, and detecting and feedback-controlling the actual values of the position, speed and current of the servo motors Wherein the second servomotor control device is set in advance based on the position and output torque of the first servomotor detected by the first servomotor control device. A position, speed, or torque of the second servomotor is controlled with a predetermined relationship.

Since the position, speed or torque of the second servomotor can be optimally set in correlation with the position and output torque of the first servomotor, the fixed work and the rotary work can be optimally set. And the positional accuracy at the time of completion of the pressure welding can be ensured.

[0017]

FIG. 1 schematically shows a preferred embodiment of a control system for realizing a servo motor control method according to the present invention. First and second embodiments each include a known encoder mounted thereon. Axis servomotors 1 and 2 and the corresponding first and second servomotor controllers 3 and 4
And Each of the servomotor control devices 3 and 4 has substantially the same configuration as that of the conventional control device, and supplies a power from an external power supply to the axis servomotors 1 and 2 and controls the driving thereof. , 20. Each of the servo control units has known current detectors 11 and 21 connected to the corresponding axis servomotors 1 and 2, and encoder pulse counters 12 and 22 connected to the respective encoders.

Each of the current detectors 11 and 21 includes a torque detecting means 13 for detecting an output torque of each of the axis servomotors.
23, and the encoder pulse counters 12 and 22 are connected to position detecting means 14 and 24 and speed detecting means 15 and 25 for detecting the position and speed of each axis servomotor, respectively. The output of each detecting means is connected to output means 16 and 26, and the output is connected to computing units 17 and 27. Each of the arithmetic units outputs a position, speed or torque command to the corresponding axis servo motor to the servo control unit, and performs feedback control of the axis servo motor based on information input from each of the detection units. The servo motor control device may be either an analog control system or a digital control system.

In this embodiment, the output means 16 of the first servomotor control device 3 is connected to the calculator 27 of the second servomotor control device 4. Next, a procedure for controlling the driving of the second axis servomotor 2 based on the operating state of the first axis servomotor 1, ie, the position, speed, and torque, will be described.

First, the encoder pulse counter 12
A pulse signal output from the encoder of the first axis servomotor 1 is detected, and for example, an output pulse train is counted by an up / down counter and output to the position detecting means 14 and the speed detecting means 15. The position detecting means detects the position of the first axis servomotor 1 based on the input count value. The speed detecting means detects the speed by, for example, subtracting the detected position based on the input count value. In this case, the position detecting means can also serve as speed detecting means. At the same time, the torque detecting means 13 detects the torque of the first shaft servomotor based on the current flowing from the current detector 11 and flowing through the first shaft servomotor 1, as is well known.

The values of the position, speed and / or torque detected by the respective detecting means are output from the output means 16 to the computing unit 27 of the second servomotor control device 4. A predetermined relationship between position, speed, and torque is set in the arithmetic unit 27 in advance. The arithmetic unit 27 performs an arithmetic operation on the input position, speed, and / or torque based on the predetermined relationship, and outputs the result to the servo control unit 20. The servo control unit 20 outputs this as a speed or torque command to the second axis servomotor 2 based on the calculation result,
The drive is optimally controlled. The predetermined relationship can be set and changed easily and freely according to the operating conditions of the industrial machine or the like to which the control system of the present embodiment is applied.

In one embodiment, the calculator 27 of the second servomotor control device 4 calculates the second axis necessary at that time from the current position of the first axis servomotor 1 and the current torque value. The speed of the servomotor 2 is calculated, and the result is output to the servo control unit 20 as a speed command, whereby the speed of the second axis servomotor 2 can be controlled. As described above, according to the present invention, the combined control in which the positions, speeds, and torques of the two axis servomotors are correlated can be performed by using only two servomotor controllers as in the related art without providing a separate control mechanism. Can be realized by:

Further, in another embodiment, the actual speed and / or torque of the second axis servomotor 2 are respectively detected by the speed detecting means 2 in the same manner as in the case of the first axis servomotor 1.
5. It can be detected by the torque detecting means 23 and output to the calculator 27 via the output means 26. Arithmetic unit 27
Is the actual speed of the input second axis servomotor 2 /
Alternatively, the torque is compared with the calculation result, and a correction command is output to the servo control unit 20 to perform feedback control so that they match with each other.
Can be more optimally controlled.

FIG. 2 schematically shows the structure of a friction welding apparatus to which the present invention is applied. Friction welding device 3 of this embodiment
0 is for friction welding the two works 31 and 32
A feed device 34 and a headstock 35 are provided on a base 33. The feed device 34 has a feed base 37 for holding the fixed-side work 31 so as not to rotate by the chuck 36. The feed base is provided with a power transmission mechanism suitable for the first shaft servomotor 1 and the output shaft of the motor. Is moved on the guide table 39 in a direction approaching or moving away from the headstock 35 by the rotating shaft 38 connected via the.

Headstock 3 fixed on fixed table 40
5 has a chuck 41 for holding the rotating side work 32, and this chuck is rotatably connected to the output shaft of the second shaft servomotor 2 via an appropriate power transmission mechanism. The first and second axis servomotors 1 and 2 have corresponding first and second servomotor controllers 3 and 4 respectively.
Is connected, and its driving is performed as shown in FIG.
The composite control is performed in the same manner as described in relation to.

The rotating work 32 is rotated by the second shaft servomotor 2, and the feed base 37 is driven by the first shaft servomotor 1 so that the fixed work 31 approaches the rotating work 32 in a predetermined direction. To the position. When the fixed-side work 31 is further fed while being in contact with the rotating work 32, the contact surface is heated and melted by the friction, and when the fixed-side work reaches the predetermined position, the work 32 rotates. Are stopped, and both are pressed and welded by the upset thrust. At this time, the fixed work 3
1 is the first servo motor control device 3
Is determined corresponding to the position of the first axis servomotor 1 controlled by

The first servomotor control device 3 detects an output torque generated in the first axis servomotor 1 by the contact between the two works 31 and 32, and outputs a signal proportional to the torque value to the second servomotor. Output to the control device 4. Also,
The position information of the first axis servomotor 1 is continuously supplied to the second servomotor controller 4. The second servo motor control device 4 calculates the input information based on a predetermined relationship among position, speed, and torque, and controls the speed of the second axis servo motor 2 using the calculation result as a speed command. The predetermined relationship among the position, the speed, and the torque is set in advance in an arithmetic unit of the second servomotor control device 4.

FIG. 3 shows the position x (mm) and torque T (Kgf · m) of the first axis servomotor 1 in this case.
And the speed of the second axis servomotor 2 (= rotation speed n (rp
m)). As shown in the figure, by setting the rotation speed of the second axis servomotor 2 optimally in correlation with the change of the output torque accompanying the position control of the first axis servomotor 1, And the rotating side work 32 can be joined in an optimal state, and the processing accuracy is improved. In addition, the position of FIG.
The relationship between the speed and the torque can be set and changed easily and freely according to the type and characteristics of the work to be used.

Further, by positioning the first axis servomotor 3 by the first servomotor control device 3 as described above, the positional accuracy of the fixed workpiece 31 in the feed direction is ensured, and A second servo motor controller 4 based on the position / output torque information of the axis servo motor
The rotation angle of the second axis servomotor 2 is determined, the positioning is performed, and the rotation is stopped, so that the relative position accuracy at the time of completion of the pressure contact between the fixed work 31 and the rotation work 32 is ensured. Can be. Therefore, product quality and productivity can be improved.

Although the present invention has been described in detail with reference to preferred embodiments, the present invention can be implemented with various modifications and alterations to the above embodiments within the technical scope thereof. For example, as the encoder used for detecting the position and speed of the shaft servomotor, various types of conventionally known encoders can be used, and other detection means other than the encoder can be used.

[0031]

Since the present invention is configured as described above, it has the following effects. According to the servomotor control method of the present invention, the position, speed, and torque of two servomotors can be correlated without adding a separate control mechanism or control unit other than the control device normally used for the servomotors. Combined control can be realized,
Not only can the mechanical system and the control system be simplified, but also the problems of torque accuracy in the braking means such as mechanical system wear, wear, and powder brake can be solved.
Since the relationship among position, speed, and torque can be optimally controlled according to use conditions, control can be further stabilized and accuracy can be further improved.

Further, according to the servo motor control system of the present invention, since the conventional control system can be used as it is, it is possible to prevent an increase in the size of the apparatus, the complexity of the apparatus and control, and to reduce the cost. be able to.

According to the machine tool of the present invention, in addition to the various advantages described above, machining accuracy is improved, quality and productivity can be improved, and high performance can be realized at low cost. it can.

In particular, according to the friction welding apparatus of the present invention, the fixed side work and the rotating side work can be optimally joined and the relative positional accuracy at the time of completion of the pressure welding can be ensured, so that the quality and productivity of the product can be greatly improved. Can be done.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram showing the entire configuration of a servomotor control system according to the present invention.

FIG. 2 is a schematic diagram showing a configuration of a friction welding apparatus to which the present invention is applied.

FIG. 3 is a diagram showing an example of a correlation characteristic of a position, a speed, and a torque of a servo motor in the apparatus shown in FIG. 2;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st axis servomotor 2 2nd axis servomotor 3 1st servomotor control device 4 2nd servomotor control device 10, 20 servo control unit 11, 21 current detector 12, 22 encoder pulse counter 13, Reference Signs List 23 Torque detecting means 14, 24 Position detecting means 15, 25 Speed detecting means 16, 26 Output means 17, 27 Computing unit 30 Friction welding device 31 Fixed work 32 Rotating work 33 Base 34 Feeder 35 Headstock 36 Chuck 37 Feed Table 38 Rotating shaft 39 Guide table 40 Fixed table 41 Chuck

Claims (6)

[Claims] In order to drive and control two servomotors driven by two axes, electric power suitable for the respective servomotors is supplied, and actual values of the position, speed and current of the servomotor are detected. Feedback control 2
In the method using two servo motor control devices, based on at least any two of the detected position, speed, or output torque of one of the servo motors, the other servo motor has a predetermined relationship set in advance. A method for controlling a servomotor, comprising controlling position, speed or torque. 2. The position, speed, or output torque of the other servomotor is calculated based on a result of the calculation with respect to at least any two of the position, speed, and output torque detected by the one servomotor. The method according to claim 1, wherein the torque is controlled. 3. To drive and control the first and second axis-driven servomotors, supply electric power suitable for the corresponding servomotors, and calculate the actual position, speed and current of the servomotors. A control system comprising first and second servomotor control devices for detecting a value and performing feedback control, wherein the second servomotor control device detects the first servomotor control device. A servo for controlling the position, speed or torque of the second servomotor based on at least any two of the position, speed and output torque of the first servomotor with a predetermined relationship set in advance; Motor control system. 4. The computer system according to claim 1, wherein the second servo motor control device has a calculator for calculating at least any two of the detected position, speed and output torque of the first servo motor with the predetermined relationship. 4. The servomotor control system according to claim 3, wherein the position, speed or torque of the second servomotor is controlled based on the calculation result. 5. A method according to claim 1, further comprising: supplying first and second shaft-driven servo motors and electric power suitable for the corresponding servo motors, and detecting actual values of the position, speed, and current of the servo motors. A machine tool comprising first and second servomotor control devices for performing feedback control, wherein the second servomotor control device detects the first servomotor detected by the first servomotor control device. A machine tool for controlling the position, speed or torque of the second servomotor in a predetermined relationship based on at least two of the position, speed and output torque of the second servomotor. 6. An axis-driven first servomotor that drives a feed stand that holds a fixed-side work, a shaft-driven second servomotor that drives a headstock that holds a rotation-side work,
Friction welding including first and second servomotor control devices for supplying electric power suitable for the corresponding servomotors and detecting and feedback-controlling actual positions, speeds and currents of the servomotors. An apparatus, wherein the second servomotor control device has a predetermined relationship based on a position and an output torque of the first servomotor detected by the first servomotor control device. The position of the second servomotor,
A friction welding device for controlling speed or torque.