JPH055627B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a position setting device for positioning a moving object such as an NC machine tool, and in particular a position setting device for reproducing and setting the current position of a moving object when the power is restored. This invention relates to a device for setting the current position of a machine tool.

[Conventional technology]

Generally, in position setting devices such as machine tools, the sixth
As shown in the figure, 10 is a moving object 12 such as a table that reciprocates on a sliding surface 11 and is to be positioned.
Numerals a and 12b are transmission mechanisms such as a ball nut 12a and a ball screw 12b that connect the moving object 10 and the servo motor 14 which is the drive source of the moving object 10, and 16 is a numerical control device. A rotational position signal of the output shaft of the servo motor 14 detected via the first detector 18 is fed back to the numerical control device 16 as a feedback signal. Further, the servo motor 14 is supplied with a movement signal based on a command signal supplied from a tape reader (not shown) or the like from the numerical control device 16 via an output circuit and a servo amplifier 34.
On the other hand, from the second detector 20, the servo motor 14
As a result of the rotation of the first detector 18, a finely divided pulse signal for counting is supplied to the numerical control device 16 in synchronization with the rotational position signal of the first detector 18. This numerical control device 16 calculates the rotational position signal from the first detector 18 and the counting pulse signal from the second detector 20 as movement command data, and sends a movement signal for positioning the moving object 10 to the servo. It is supplied to the motor 14.

In such a semi-closed loop control system position setting device, if the power is cut off due to an emergency or the like during workpiece machining, the moving object 1
The stopping position of 0 is unknown. Therefore, when the power is restored, unless a limit switch or the like (not shown) is installed at the original point of this apparatus and the moving object is returned to the original position, the work cannot be started. This is because the position setting device uses a relative position detection method in which the rotation of the servo motor 14 is counted and calculated using a position signal from the origin position and a counting pulse signal, and is controlled by replacing it with the position of the moving object 10. Therefore, when the power is cut off, the current position of the moving object 10 becomes unknown.

Therefore, as described above, the position of the moving object 10 by the position setting device is set by, for example, providing a limit switch at the origin specific to the position setting device, returning the moving object 10 to this origin (origin return), and pressing the limit switch. The point where the later rotational position signal from the first detector 18 is generated is defined as the reference point (origin). Therefore, the position setting device starts machining the workpiece again from this reference point, so if the distance from the point where the moving object 10 stops due to power cutoff to the origin is large, returning to the origin becomes cumbersome.
This restoration requires a lot of time for the work, which is uneconomical.

In addition, in the case of system-oriented line machines with a large number of numerically controlled machine tools such as machining centers, when the power is cut off due to a power outage, all of these machine tools must be returned to their origin, so it takes a lot of effort to return to their origin. The problem was that it took a lot of time and interfered with the work.

[Problem that the invention seeks to solve]

The present invention was made in view of the above problems, and
When the power is cut off in an emergency, a moving object such as a table moves at low speed in any direction from its current position, which is now unknown.
An object of the present invention is to provide a current position setting device for a machine tool that can restart machining work by determining the current position using a point of a nearby rotational position signal outputted by the rotation of a servo motor as a reference point.

[Means for solving problems and their effects]

The present invention is a current position setting device for a machine tool that sets the current position of a moving object whose movement and positioning is controlled by a drive motor with respect to a base, wherein when moving the moving object, one rotation of the drive motor is performed. a first detector that outputs a rotational position signal of one pulse at a time; a second detector that outputs a counting pulse signal for each minimum movement unit when the moving object moves; and a second detector that outputs a counting pulse signal for each minimum movement unit when the moving object moves; a rotational position signal reference point counter that counts the rotational position signal output position of the detector as a reference point; a third detector that outputs an absolute value signal representing the output position of the rotational position signal of the first detector as an absolute value; a position data conversion unit that converts an absolute value signal into position data of the moving object; and a current position that calculates the current position of the moving object by calculating this position data and a pulse count value for counting of the rotational position signal base point counter. When the power is restored from a power-off state, the moving object is moved to the rotational position signal output position of the first detector, and the calculation unit calculates the counting pulse count value of the rotational position signal reference point counter and the Current position setting of a machine tool, characterized in that the current position of the moving object is set by calculating position data of the moving object near the rotational position signal output position obtained from the absolute value signal when the rotational position signal is output. It is a device.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to the drawings. 1 to 5 are diagrams according to embodiments of the present invention. As shown in FIG. 1, a worm gear 24 is connected to the output shaft of the servo motor 14.
A detection member 26 is meshed with the worm gear 24, and rotation is transmitted to the detection member 26 by the driving force of the servo motor 14. The detection member 26 includes a regular hole 2 of a binary code that passes light through an opaque disk, as shown in FIG.
6a and grooves 26b are opened, for example, openings by holes and grooves are opened at every predetermined angle in the radial direction.
By providing columns, it is possible to distinguish and set the movement range of a moving object in 1024 (2 to the 10th power) ways. Also,
The detection member 26 is rotatably supported by a shaft 25, and a third detector 27 is integrally supported coaxially with the detection member 26. This third detector 27 is
The absolute position signal from the sensing member 26 (that is, the interval absolute movement position of the moving object 10) is supplied to the numerical control device 28. This numerical control device 28 includes the first detector 18 and the second detector 2 described above.
0 is connected.

As shown in FIG. 3, the first detector 18 is
The servo motor 14 is set so that, for example, a rotational position signal of one pulse per rotation is output (FIG. 3A). The second detector 20 outputs a counting pulse signal obtained by further dividing one rotation of the ball screw 12b into 1/n (a number determined by the accuracy of the machine tool), which is the minimum movement unit. Further, the third detector outputs an absolute position signal that represents the output position of the rotational position signal of the first detector in absolute position, and is configured to output an absolute position signal to approximately the center between the pulses of the first detector 18. (Figure 3 C).

Note that the absolute position signal of the third detector 27 is
Although there is an error range (error area) due to backlash of the decelerator, etc., the absolute value within the other range (setting area) of the current position can be accurately known. That is, the rotational position signal of the first detector 18 may be set near the center between the absolute position signals of the third detector 27, and may be set within a range in which this absolute value is expected to be obtained without fail.

Further, the other constituent parts are the same as those of the conventional example shown in FIG. 6, so the explanation will be omitted.

FIG. 4 is a block diagram in which the numerical control device 28 is connected to an input circuit 30 to which command signals from a table reader 29 are input, a keyboard 31 for inputting information, and a display device 33 for displaying information on this keyboard 31. The input/output device 32, the servo motor 14 which is rotated by amplifying the control signal from the output circuit 36 via the servo amplifier 34, and the absolute position of the third detector 27 corresponding to the rotational position signal of the first detector 18. A data reading unit 38 into which signals are read via the discriminator 37, a current position calculation unit (calculation unit) 40 that calculates the current position based on input data, and a central processing unit (hereinafter referred to as CPU) to which these are connected. 4
It is composed of 2.

The CPU 42 includes a first detector 1 that outputs a rotational position signal according to the rotation of the servo motor 14.
8 and a second detector 20 that outputs a pulse signal that counts the 1/n angular change between the rotational position signals (for example, one rotation) of the first detector 18, and the pulse signal gives the amount of position change with sufficient accuracy for machining.

The CPU 42 includes a position data conversion unit (shift data in FIG. 4) 44 that converts the absolute value signal given to the rotational position signal into position data of the machine tool.
and a third detection data extractor (third detection data in FIG. 4) that extracts the absolute value signal from the third detector 27, and a counting pulse signal of the second detector 20 that extracts the absolute value signal from the first detector 27. A rotational position signal reference point counter (counter in FIG. 4) 48 that counts the rotational position signal output position of the detector 18 as a reference point is connected to each of them. Note that the calculation unit 40 calculates the current position of the moving object 10 by calculating the position data converted by the shift data 44 and the counting pulse count value of the counter 48. Next, the effect will be explained. As shown in FIG. 5, when the power is cut off in an emergency and the moving object 10 is stopped, the stopping point of the moving object 10 becomes unknown (step 52). Therefore, the axis of the servo motor 34 is slightly moved in an arbitrary direction by manual operation or the like (step 53). Then, a rotational position signal corresponding to the rotational position of the servo motor 14 is output from the first detector 18 (step 54).

When the rotational position signal is output from the first detector 18, the counter 48 detects the second detector 2 by the movement of the axis caused by the rotation of the servo motor 34.
A counting pulse signal of 0 is added starting from 0, and the moving amount Y of the moving object 10 is counted with an accuracy of 1/n between the rotational position signals (step 55). Simultaneously with the output of the rotational position signal from the first detector 18, the CPU
From step 42, a command to stop the movement of the axis is issued to the servo motor 14 (step 56), and the third detection data 46 is
A data signal X representing the absolute value at the time of outputting the rotational position signal is read from the third detector 27,
Current position data X is determined from this data signal X and the known pitch dimension of the ball screw (step 57).

After checking whether the axis has stopped rotating (step
58), the addition of the movement amount Y of the counter 48,
This is performed until the shaft stops rotating, and at the same time as the shaft stops rotating, the addition of the movement amount Y also stops.

When it is confirmed that the rotation of this shaft has stopped, the calculation unit 40
The briset shift amount S, which is the conversion data of the absolute value before and after the stop position, the current position data Perform calculations (step 59). Note that the movement amount Y due to this counting pulse is, for example, the moving object 10 in FIG.
The setting is such that addition is performed for the amount of movement of the axis that moves the axis to the left, and subtraction is performed for the amount of movement of the axis that is moved to the right. The amount of movement Y is added or subtracted from the data X to calculate the current position of the object 10 (step 60).

〔Effect of the invention〕

As described above, when the power is restored from a power-off state, the moving object is moved to the rotational position signal output position of the first detector, and the pulse count value for counting of the rotational position signal reference point counter is The current position of the moving object is set by calculating the position data of the moving object in the vicinity of the rotational position signal output position obtained from the absolute value signal at the time of outputting the rotational position signal. In other words, by simply passing the rotational position signal output position of the first detector when the power is turned on, the current position of the moving object can be determined, the current position can be set, and the interrupted work can be continued from this current position. can do. Therefore, the reference point can be set extremely effectively and with high accuracy in a short period of time. Furthermore, as described above, it can be installed in a conventional semi-closed loop control system and has a simple structure, so it has advantages such as being able to be manufactured at low cost.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the position setting device of the present invention, and FIG.
The figure is a partially enlarged view of the encoder, and Figure 3 is a diagram showing the pulse signals of each detector, where A is the first detector, B is the second detector, C is the third detector.
5 is a block diagram, FIG. 5 is a flowchart, and FIG. 6 is a diagram showing a conventional position setting device. 10...Moving object, 18...First detector, 20
...Second detector, 26...Detection member, 27...Third detector.

Claims (1)

[Scope of Claims] 1. A current position setting device for a machine tool that sets the current position of a moving object whose movement and positioning is controlled by a drive motor with respect to a base, wherein when moving the moving object, the drive motor a first detector that outputs a rotational position signal of one pulse per rotation; a second detector that outputs a counting pulse signal for each minimum movement unit when the moving object moves; a rotational position signal base point counter that counts the rotational position signal output position of the first detector as a base point; and a third detector that outputs an absolute value signal representing the output position of the rotational position signal of the first detector as an absolute value. a position data conversion unit that converts the absolute value signal into position data of the moving object; and a position data converter that calculates the current position of the moving object by calculating the position data and a counting pulse count value of the rotational position signal reference point counter. and a current position calculation unit that calculates the current position, and when the power is restored from a power-off state, the moving object is moved to the rotational position signal output position of the first detector, and the pulse count value for counting of the rotational position signal base point counter is calculated. and position data of the moving object near the rotational position signal output position obtained from the absolute value signal at the time of outputting the rotational position signal to set the current position of the moving object. Current position setting device.