JPS5837562B2 - position control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a position control device, and more particularly to a position control device that can easily adjust the origin position when controlling the position of a controlled object in an incremental manner.

FIG. 1 is an overall perspective view showing an automatic welding apparatus that forms the background of this invention and in which this invention is implemented.

This automatic welding device will be briefly explained below in order to facilitate understanding of the present invention.

The length direction (X
In the axial direction) horizontal guides 2, 2 are fixedly provided above the table 1.

On these horizontal guides 2, 2, there are rails 3, 3, respectively.
will be placed.

Moreover, on the horizontal guides 2, 2, the rails 3, 3
A traveling beam 4 is mounted thereon, which is movable in the X-axis direction and is driven to travel by a motor 5.

This traveling beam 4 is arranged in the width direction (Y
It supports a moving body 6 which is movable in the axial direction) and which is driven to move by a motor 7.

Further, a column 8 is provided which is supported by the movable body 6 and movable in the vertical direction (Z-axis direction) and is driven up and down by a motor 9.

A torch mount 10 is provided at the lower end of the column 8 so as to be rotatable around a vertical axis.

This torch fixture 10 holds a tote T and a motor 1.
1 to adjust the orientation angle of the toner T with respect to the workpiece.

In this embodiment, l additional sets of similar devices are provided in similar combinations.

It is well known that the rotational speed of each motor 5, 7, 9, 11, the welding current applied to the toner T, and the toner position are controlled by a (positioning) control device (not shown).

In such an automatic welding apparatus, the position of the toner T is controlled to a preprogrammed point position with respect to the X, Y, and Z axes, for example, by an FTP method.

As a servo system for position control in such automatic welding equipment, so-called incremental
mental) method may be used.

When performing position control using the incremental method, once the power to the device is turned off, the value in the feedback buffer (counter) that represents the current position of the controlled object also disappears, and even if the device is restarted, the value in the feedback buffer (counter) will not reappear. Not done.

For this reason, it is well known that upon restart, it is necessary to adjust the controlled object to the original position and restart position control from there.

Conventionally, in order to adjust the home position, it is necessary to directly manually return the controlled object to the home position or manually operate a position control device to return the controlled body to the home position.

However, the former is troublesome to operate, and the latter is difficult to stop accurately at the origin position.

Therefore, the present inventors, for example,
As shown in this issue, we proposed an improved origin positioning method.

This is provided with an origin return means for moving the controlled object in the direction of the origin, and the controlled object is made to pass the origin by manually operating this origin return means, and the feedback buffer is cleared at this overrun position. This is an automatic position control device that automatically positions a controlled object at an appropriate commanded position after that.

Even with this improved device, there still remains the problem of requiring an open servo system for manual operation as a home return means for overrunning the controlled object. be.

In order to solve this problem, that is, to eliminate the need for a special servo system, a fairly large appropriate value is loaded into the position feedback buffer (counter) when the power is turned on again. It is possible to move it.

However, this requires a register with a correspondingly large capacity and is expensive.

Also, if you try to perform normal position control using only the required number of digits, you may not be able to overrun, or the encoder output may exceed the origin and the controlled object may go out of control. There is a problem with this.

SUMMARY OF THE INVENTION Therefore, the main object of the present invention is to solve the above-mentioned particular problems and to provide a position control device using an incremental method that is capable of simply and reliably regulating the origin position and is less expensive.

In summary, when the power is turned on again, this invention gives an appropriately determined numerical value as a position command for the controlled object, repeats position control based on this numerical value, and thereby moves the controlled object beyond the origin position. overrun, then return from this overrun position and issue a position command to cross the origin again,
This position control device responds to the fact that the controlled object has passed the origin position during position control based on the position command, and sets that position as the origin.

The above objects and other objects and features of the invention will become more apparent from the following detailed description with reference to the drawings.

FIG. 2 is a block diagram schematically showing a position control device according to an embodiment of the present invention.

The control device CNT includes a central processing unit CPU, which is an example of a command data generation means, and a command circuit ODx for each axis X, Y, and Z.
, ODy, ODz.

In the following, the X-axis command circuit ODx will be described as a representative example, but it should be pointed out in advance that the command circuits ODx, ODy, and ODz all have the same circuit configuration.

The X-axis command circuit ODx loads a position feedback counter FCx that counts pulse signals from an incremental encoder (described later) and indicates the current position information of the controlled object, and command position information regarding the X-axis from the processing unit CPU. and a command position buffer OBx, which is an example of command data storage means.

The position feedback counter FCx is processed by a processing device C.
It can load the commanded position from the PU and provides the current position to the processing unit CPU.

Both the position feedback counter FCx and the command position buffer OBx are connected to two terminals of the subtracter SBx.

The output of the subtracter SBx is given to the command limiter circuit OIx.

This command limiter circuit OLx receives minute speed information in the X-axis direction from the processing device CPU, and limits the moving speed.

In addition, the CLock t Nu 11 signal (described later in FIG. 7) detection circuit DEx receives the output from the X-axis servo system (not shown), detects that the controlled object has entered the CLock width or the Null region, and outputs the signal. occurs.

CLock or Nu l from this signal detection circuit DEx
Both signals are given to the processing device CPU, requesting the next position command, and giving a positioning command to the X-axis servo system.

Note that the subtracter SBx constitutes an example of displacement driving means in cooperation with an X-axis servo system (including, for example, the motor 5 in FIG. 1).

Here, the above CLock t Nu 11 will be explained.

In the saturation characteristics of a servo system using a limiter as in this embodiment (as clearly shown in FIG. 7), the non-saturation region corresponds to the CLock width, and a signal indicating that the servo system has entered this non-saturation region. is the Clock signal (non-saturation region signal).

Such a CLock signal is obtained, for example, by adding the commanded position and the current position, and then distinguishing the speed at that time from the commanded speed.

It should be noted in advance that the saturation characteristics described above are well known in the field of nonlinear automatic control.

On the other hand, the Null signal is a zero signal obtained from a servo amplifier included in the servo system as described above, and is derived in a region very close to the target position.

Therefore, the Null area is an area very close to the target position.

It should be noted in advance that the above-mentioned zero signal is well known.

Therefore, the X-axis servo system controls the movement of the controlled object OBJ on the X-axis, as shown in FIG.

This X-axis servo system is an incremental encoder EN
x, and provides a pulse signal to the position feedback counter \\ in the X-axis command circuit ODx of the control device CNT in accordance with its movement.

At the origin position XO on the X axis, there is an origin sensor OSx, which is an example of a controlled object detection means, for detecting whether the controlled object OBJ has reached (or exists in) the origin position.
will be placed.

This origin sensor OSx consists of, for example, a photoelectric switch, a proximity switch, or other mechanical switch,
When the controlled object OBJ is on the sensor position, it is turned on and the signal is given to the processing device CPU in the control device CNT.

The control device CNT is also provided with an operation panel OP for manual operation.

This operation panel OP is provided with a toggle switch (not shown) for manually giving position commands for each axis X, Y, and Z, and a toggle switch that is an example of a home return command means for commanding home return. A SW is provided.

Each axis toggle switch moves in the direction of the origin XO when pushed down, moves in the opposite direction when pushed up, and can be moved by a length related to the time it is pushed down.

Manual control is then stopped at the neutral position.

Note that the origin switch SW described above may be provided on the control device CNT side.

4 and 5 are flow diagrams for explaining the operation of the processing device CPU shown in FIG. 2, in particular, FIG. 4 shows the main flow, and FIG. 5 is a flow diagram of FIG. 4. shows the count lunan in.

Here, step numbers S401 to S417 are assigned to each operation step in the flowchart of FIG. 4, and the correspondence with the claims of the present invention will be explained.

First, operation steps 8407 to S410 constitute an example of origin direction displacement means.

Further, operation steps 8411 to S413 constitute an example of displacement stopping means.

Further, the operation step S414 constitutes an example of origin direction redisplacement means.

Furthermore, operation steps 8415 to S417 constitute an example of a reset means.

The operation will be described below with reference to the flowcharts of FIGS. 4 and 5.

As for the operation, only the X-axis direction will be representatively explained, and the explanation about the Y-axis and Z-axis directions will be omitted.

In operation, the count flag CX in the processing unit CPU is set to "0" in response to some signal generated when the power is turned on again.

At the same time, the processing device CPU sends an arbitrary value X in the X-axis direction.
Command a.

That is, a value Xa approximately in the middle of the X axis shown in FIG. 6 is loaded into the command position buffer OBx and the position feedback counter FCx ('OB
=Xa).

Subsequently, the processing device CPU reads the X-axis manual toggle switch (not shown) on the operation panel OP.

Then, it is determined whether the X-axis manual toggle switch is turned up (up) or down (down).

If IYESJ, that is, if it is manual position control mode, the count flag CX is changed to "1" when it is up and to r-IJ when it is down.

Then, the process moves to the counting routine shown in FIG.

In the manual mode, the processing device CPU first determines whether the count flag CX is "-1", that is, whether it is down (movement toward the origin).

If l-NOJ, then it is determined whether cx=i, that is, whether it is up (movement toward the far end).

In this way, before turning on the home return switch SW to return the controlled object to the home position, the movement direction of the controlled object is manually controlled in two directions, positive and negative, by operating the toggle switch. This is because the state of the device (servo system) and therefore the position of the controlled object are uncertain, and if it is moved to the origin position as it is, it may interfere with other controlled objects or workpieces.

Therefore, when there is no risk that the controlled object will interfere with other controlled objects or workpieces, it is sufficient to turn on the home return switcher SW immediately.

Then, in the judgment step of “Is CX=-1?”
If rYEsJ, the processing device CP[J obtains the next commanded position Xn.

This is obtained by subtracting a certain predetermined count number (pitch) DX from the current position X (Xn=OBx-DX).

Next, in the processing device CPU, the discriminant D-Xn-X
Calculate min (Figure 6).

In this case, Xmin is determined to be smaller than an appropriate value Xa.

Therefore, it is determined whether this discriminant D is negative (D<0).

Here, in the initial state, Pituna DX is extremely small, and this discriminant D is positive, that is, rNOJ.

Therefore, the processing device CPU uses the position command buffer OBx
The command position Xn obtained above is loaded.

Accordingly, the X-axis servo system (positioning device)
Move BJ to the position Xn.

Then, the signal detection circuit D Ex determines whether or not the movement has entered the CLock width (non-saturation region of the servo system) shown in FIG.

FIG. 7 shows the speed state of the servo system, and the CLoc
FIG. 2 is an illustrative diagram for explaining a k signal (non-saturation region signal) or a Null signal (zero signal).

Here, the horizontal axis indicates position or timing, and the vertical axis indicates speed.

As can be understood from FIG. 7, the Clock
The signal is generated when the positioning device enters the servo area of the servo system.
This is the signal at which the speed begins to decrease.

Further, the Null signal is a zero signal obtained from the servo amplifier when the position is controlled by the servo system,
Area very close to the target position (timing to almost stop)
It is derived as

In other words, the Nu 11 signal is derived at a substantially constant position regardless of the speed, and the timing of the CLock signal's derivation changes depending on the speed (dashed line).

Therefore, in this embodiment, this CLock signal or Null signal is detected.

In the above case, the CLock signal is detected in order to ensure that the next position command precedes the current position.

If this CLock signal is obtained, the processing device CPU will:
Set the count flag CX=O.

Thereafter, the processing device CPU returns to the main routine shown in FIG. 4 again and reads whether or not the manual toggle switch is operated.

That is, as long as the manual toggle switch is operated,
This sub runn of FIG. 5 is repeated.

After several repetitions, the controlled object OBJ reaches the position Xmin shown in FIG. 6, and the next position Xn exceeds this point Xmin.

Therefore, the above-mentioned discriminant D becomes negative.

In this way, if the discriminant D is negative, that is, IYES
J, the processing unit CPU loads FCx+(Xa - Xmin) into the position feedback counter FCx, and loads Xa into the command position buffer OBx.

This is because the same operation is repeated several times as long as the manual toggle switch is operated without changing the relative relationship between the current position Xmin of the controlled object OBJ and the command position.

Further, in this subroutine (count routine), if "NO" to "CX=-1?j", it is then determined whether this count flag CX is "1".

If "NO", this routine ends and returns to the main routine.

Then, in the judgment step “Is CX=1?”, r
If YESj, the processing device CPU selects the next command position Xn
seek.

This is obtained by adding a certain predetermined count number (bits) DX to the current position X (Xn=OBx+DX).

Next, in the processing unit CPU, the discriminant D = X n
- Calculate Xmax (Figure 6).

In this case, Xmax is determined to be larger than the appropriate value Xa.

Therefore, it is determined whether this discriminant D is positive (D>O).

Here, in the initial state, bituna DX is extremely small, and this discriminant D is negative, that is, lNOj.

Therefore, the processing device CP[J is the position command buffer OB
The command position Xn obtained above is loaded to x.

Accordingly, the X-axis servo system (positioning device)
Move BJ to the position Xn.

During this movement, a CLock signal is detected in order to ensure that the next position command precedes the current position.

If this CLock signal is obtained, the processing device CPU will:
Set the count flag CX=O.

Thereafter, the processing device CPU returns to the main routine shown in FIG. 4 again and reads whether or not the manual toggle switch is operated.

That is, as long as the manual toggle switch is operated,
This sub runn of FIG. 5 is repeated.

After repeating the rounds, the controlled object OBJ reaches the position Xmax shown in FIG. 6, and the next position xn exceeds this point Xmax.

Therefore, the above-mentioned discriminant D becomes positive.

In this way, if the discriminant D is positive, that is, rYEs
J, the processing unit CPU loads FCx-(Xmax-Xa) into the position feedback counter FCx, and loads Xa into the commanded position buffer OBx.

This is because the same operation is repeated several times as long as the manual toggle switch is operated without changing the relative relationship between the current position Xmax of the controlled object OBJ and the command position.

At the end of the above-mentioned counting routine, ie, at the end of the manual operation, the manual toggle switcher is returned to the neutral position.

Therefore, in the judgment step "Up or down?", the answer is "NO".

Next, the return-to-home switch SW is turned on, and the return-to-home operation, which is of particular interest to this embodiment, is started.

First, the processing device CPU reads whether or not the origin return switch SW of the operation panel OP has been operated.

In this case, the purpose is to regulate the origin position, and naturally the origin return switch SW is on.

If the home return switch SW is on, the processing unit CPU will
Since movement in the direction of the origin (down direction) must be performed, the count flag is set as CX--1.

Then, it enters the subrunan shown in Figure 5. In this counting routine, is the above-mentioned icX--1? '', the process according to rYEsJ is executed one by one.

Thereafter, the processing device CPU reads the state of the origin sensor OSx as shown in FIG.

Here, if "NO" in the determination step "Is the origin sensor on?", the processing unit CPU sets the count flag CX to "-1" again and repeats the above-mentioned subroutine.

At this time, when approaching the origin XO and the origin sensor OSx
In the next step where remains OFF, the position command is issued in response to the CLock signal, so the next position command is issued before the current position reaches the command position, and it is guaranteed that, for example, The position is controlled (overrun) beyond the origin Xo shown in FIG.

When the origin sensor OSx is turned on, the processing device CP[J determines whether a Null signal is obtained in the position control described above.

If YESJ, the controlled object OBJ is stopped by the action of a well-known servo system, and is moved beyond the origin position Xo in FIG. 6 to, for example, position Xo' in FIG. .

Then, the processing device CPU loads predetermined position information xi (FIG. 6) to the position feedback counter FCx, and loads predetermined position information X2 (FIG. 6) to the command position buffer OBx. Load.

For these positions X1 and X2, even if the controlled object OBJ causes the maximum overrun and stops, "X2-X1" is always the current position X.

' to origin position X.

It is determined that the length should be at least the length of .

Therefore, the X-axis positioning device returns the controlled object OBJ to the origin X based on the value IX2-X11 from the subtracter SBx.

This movement causes the controlled object OBJ to
is always driven to move beyond the origin position.

At this time, the processing device CPU is reading the state (on, off) of the origin sensor OSx.

Note that the controlled object OBJ has a certain width, and the origin sensor OSX remains on even when it exists at the current position Xo'.

When the origin sensor O S x is turned off, this means that the controlled object OBJ has been returned toward the origin and has reached the position shown by the two-dot chain line in FIG. 3.

That is, the controlled object OBJ is at the mechanical origin Xo on the X axis.
Indicates that the position has been adjusted.

In response, the processing device CPU clears the position feedback counter FCx to "0".

In this way, the origin position regulation of the controlled object OBJ is achieved.

Although the above-mentioned embodiment has been described using an automatic welding device as an example, it goes without saying that this can be similarly implemented in other similar position control devices or machine tools.

As described above, according to the present invention, in an incremental type position control device, the origin position of a controlled object can be easily and automatically corrected without requiring any special additional equipment.

[Brief explanation of drawings]

FIG. 1 is an overall perspective view showing an example of an automatic welding device that forms the background of the present invention and in which the present invention can be implemented. FIG. 2 is a block diagram schematically showing a position control device according to an embodiment of the present invention. FIG. 3 is an illustrative view showing the X-axis direction. FIG. 4 is a flow diagram for explaining the operation of the processing device CP[J. FIG. 5 is a flow diagram showing the counting routine. FIG. 6 is an illustrative diagram showing the positional relationship of each point on the X-axis. Figure 7 shows the speed status of the servo system (CLock, Null).
) is an illustrative diagram for explaining. In the figure, CNT is a control device, OP is an operation panel, SW is a return-to-origin switcher, CPU is a processing device, and ODx t O
Dy + ODz is a command circuit, and OBJ is a controlled object.

Claims (1)

[Claims] 1. Feedback pulse generating means ENx that generates incremental feedback pulses in accordance with the displacement of the controlled object. 1. A counter FCx that counts the feedback pulses and provides data representing the current position of the controlled object. , a command data generating means CPU1 for generating command data for displacing and controlling the controlled object; a command data storing means OB for storing the command data;
x, and displacement driving means for displacing and driving the controlled object along a displacement axis having a determined origin position by comparing data representing the current position of the counter with command data of the command data storage means; The position control device includes an SBx, and is provided in association with the origin position I of the displacement axis and an origin return command SW1 that provides a command signal for returning the controlled object to the origin position. , further comprising a controlled object detection means OSx for detecting that the controlled object exists at the origin position, and the command data generation means, in response to a command signal from the origin return command means, detects the presence of the controlled object at the origin position. Displacement data corresponding to a constant displacement of the body is generated and sequentially supplied to the command data storage means, and the displacement drive means 1 sequentially moves the controlled body by the constant displacement in the direction of the origin position. Displacement means 8407, 8408, 8409, 8410 for displacing the controlled object in the direction of the origin, and displacement stopping means 8 for stopping the displacement of the controlled object in the direction of the origin in response to the output of the controlled object detection means.
411, 8412, 8413, and in response to said stop,
Generate appropriate command data to cause the controlled object to exceed the origin position again, and apply it to the command data storage means, and cause the displacement drive means to displace and drive the controlled object again in the direction of the origin position. When the controlled object is being redisplaced toward the origin position by the displacement means S414 and the origin direction redisplacement means, the counter is reset to an initial state in response to the output of the controlled object detection means. Resetting means 8415, 8416, 8417
and a position control device.