JP3255487B2 - Control method of grinder work robot - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a grinder working robot, in which a grinder is attached to a hand of a robot and grinder work is performed on a work surface while controlling a pressing force of the grinder.

[0002]

2. Description of the Related Art There has been known a grinder working robot in which a grinding tool such as a grinder is attached to a hand of a robot and a grinding operation is performed while pressing the grinder against a work having an arbitrary shape with a predetermined force.

As a control method of a grinder working robot, for example, a method described in Japanese Patent Application Laid-Open No. 4-164585 is known. In such a grinder working robot, the 6-axis force sensor attached to the tip of the arm detects the pressing force of the grinder, and compares the detected pressing force with the target pressing force to sequentially correct the target position / posture of the grinder. The control is performed so as to maintain the target pressing force.

By using such a known method, a grinding operation or the like is performed while reciprocating the grinder 11 a plurality of times with respect to a grinder grinding region 12 in a work 20 as shown in FIG. The inside can be made smooth. Here, the turning position of the grinder is given as follows. First, on the Y = 0 side, it is given as follows.

[0005]

(Equation 1) On the side of Y = Ya, it is given as follows.

[0006]

(Equation 2)

Note that Ya is a stroke in the Y direction, and Xp
Is a feed pitch amount in the X direction. (I-1) means the number of round trips. Note that force control is performed in the Z direction. Conventionally, assuming that Ya is a constant value (that is, the reciprocating distance of work is always controlled to be constant),
Grinding of a rectangular area of × (Xp × N) is performed.

[0008]

However, it is not preferable to perform a reciprocating grinder operation as shown in FIG. 9 when the work has a severe unevenness or when the work is relatively soft. In other words, there is no major problem when moving (retreating) the grinder 11 in the B direction.
When the wheel 11 is moved (advanced) in the direction A, the grindstone is in a posture that is easily caught by the work. If the burrs or irregularities on the work are severe, the grindstone (or the work or the robot itself) will be damaged, and if the work is relatively soft, the grindstone will bite into the work. Was not performed smoothly.

Therefore, in order to avoid such a problem, the grinder is pressed to perform grinding only when the grinder is retracted in the B direction, and when the grinder is advanced in the A direction, the space on the work is removed without grinding. A method of moving to the side of = 0 has been adopted.

However, in the method of moving the space on the work, it has been difficult to accurately return the grinder to the position where the grinder work is started again. This is because force control cannot be performed when the grinder is guided and returned.

For example, even if the grinder is guided to a point on the boundary of the work area (Z> 0) using the equation (1), usually, there is an error in the fixed position of the work, so that the grinder is too far from the work. Otherwise, the grinder may come into contact with the work, and the work may be cut too much and damaged. However, it is preferable to guide the grinder as close to the work as possible for efficient work.

On the other hand, in the method shown in FIG. 9, that is, when the grinder is moved at a constant speed and the force is controlled in the direction of the normal line (thickness) of the work, thereby performing grinding such as welding bead or plug welding. Will scrape the periphery of the weld bead. That is, according to the conventional method, it has been difficult to efficiently grind only the convex portion such as a weld bead or a plug weld.

In the case of grinding a weld bead, it is possible to grind along the ridge line of the weld bead. In this case, however, the number of grindings is specified in advance according to the height of the weld bead. I have to put it. Further, when the weld bead is not formed uniformly, there is a possibility that the bead is partially cut away more than necessary. As a result, it has been difficult to efficiently grind only the protrusions by the conventional method.

Therefore, the present invention provides a method of grinding a work in an arbitrary area of a work having an arbitrary shape, even when the burr or unevenness on the work is severe or when the work is relatively soft. It is an object of the present invention to provide a control method for a grinder working robot that can perform an efficient grinder work without being caught or penetrating into a work.

Another object of the present invention is to provide a method of controlling a grinder working robot capable of efficiently grinding only a convex portion when grinding a weld bead, a plug weld, or the like.

[0016]

In order to achieve the above object, according to the present invention, a grinder is attached to a hand of a robot, and a plurality of grinders are applied to a predetermined area of a work while controlling a pressing force of the grinder. In the control method of a grinder working robot performing work, a grinder guide line is calculated from a contact point by contacting the grinder with the work, and the grinder work on the work is started from the grinder guide line. And a control method for the grinder work robot.

A grinder is attached to the hand of the robot,
In a control method of a grinder working robot for performing a plurality of grinder work on a predetermined area of a work while controlling a pressing force of the grinder, a grinder guiding point is provided from a contact point of the grinder by bringing the grinder into contact with the work. And controlling the grinder work on the work to be started from the grinder guide point, and calculating a guide point related to the next and subsequent grinder work using the grinder guide point or the contact point. And a control method of the grinder work robot.

Further, when starting the grinder work from the grinder guide line, force control is performed in the normal direction of the work, and when performing the grinder work toward the grinder guide line, the force is controlled in the feed direction of the grinder. A control method for a grinder working robot, characterized by performing control so as to perform control.

Further, when starting the grinder work from the grinder guide line or the grinder guide point, force control is performed in the normal direction of the work, and the grinder work is performed toward the grinder guide line or the grinder guide point. The present invention provides a method for controlling a grinder working robot, wherein force control is performed in a feed direction of the grinder.

[0020]

In the present invention, a grinder guide line is calculated from a straight line or a curve from these contact points by making the grinder contact the workpiece at a plurality of points or continuously, and an arbitrary point on the grinder guide line is determined. Or the position to guide the grinder. Therefore, even when the grinder can be fed only in the retreating direction, if the space on the work is moved to this grinder guide line, the grindstone will not be damaged or cut into the work, and the grinder will be accurately positioned. It is possible to efficiently guide the user to the work start position.

Further, when starting the grinder work from the grinder guide line, force control is performed in the normal direction of the work, and when performing the grinder work toward the grinder guide line, force control is performed in the feed direction of the grinder. With such control, even when grinding a convex part such as a weld bead or a plug welding part, it is not necessary to cut off the periphery of the convex part more than necessary, so that only the convex part can be shaved and finished flat. become.

[0022]

Embodiments of the present invention will be described below in detail with reference to the drawings. First, FIG. 1 shows a control configuration of a grinder work robot used in the present invention. The features of this embodiment are as follows.
The point is that the work start position of the grinder is determined by actually touching the work a plurality of times. Therefore, information on the work start position is stored and held as a target value of the position and orientation, and this value is read out for each work and used for calculating the target trajectory. Alternatively, the work position / posture is calculated for each work from the point of the first contact, and thereby the target trajectory calculation is performed.

A target position of each axis is inversely transformed from the target trajectory calculation value, and a position feedback loop, a speed feedback loop, and the like are configured to follow the target position of each axis.

On the other hand, when performing force control, an actual pressing force is calculated from the output of a six-axis force sensor fixed near the grinder, and a force control calculation is performed based on the target pressing force and the calculated actual pressing force. The target trajectory calculation value is corrected based on the result. Thereby, force control can be performed so as to obtain a predetermined pressing force.

The target values of the position and orientation, the target values of the force and the moment, and the designation of the shape of the work and the boundary position of the work grinding area can be input via a computer. In practicing the present invention, the structure and basic control method of the robot are the same as those described in Japanese Patent Application Laid-Open No. 4-164585, and a detailed description thereof will be omitted.

Next, a description will be given of a first embodiment of a method for controlling a grinder working robot according to the present invention. This embodiment is particularly effective when the burrs and irregularities on the work are severe or when the work is relatively soft. Of course, the present embodiment is also effective under other conditions.

For example, in a work 20 as shown in FIG. 2, a rectangular grinding area 12 surrounded by Y = 0, Y = Ya, X = 0, X = Xa is reciprocated in the Y direction to perform a grinder work. The case will be described. FIG. 3 shows the flow of the grinder work.

First, after moving the grinder above the origin O (0, 0) (Z> 0), the grinder is lowered and brought into contact with the vicinity of the origin O. Since a six-axis force sensor is attached to the tip of the arm, the presence or absence of contact can be easily determined based on the output of this sensor.

Then, a point P0 which is slightly separated from this point with respect to the contact point is stored. The method of selecting the point P0 is arbitrary. For example, a point about 1 mm in the Z direction from the contact point can be considered, but a point separated not only in the Z direction but also in the Y direction may be used.

If the contact point is stored, the contact point may be calculated as being within the work surface depending on the deflection of the arm or grindstone or the response of the force sensor. For this reason, it is preferable for safety to store the point P0 separated from the contact point. In order to perform the work more efficiently, it is desirable to set P0 as close to the work as possible as long as there is no risk of contact with or collision with the work.

Although the point P0 may be calculated from the contact point by calculation, the position may be stored by slightly moving the grinder in a direction away from the work. Next, after moving the grinder above another point (Xa, 0) of the grinding area boundary, the vicinity of the point (Xa, 0) is brought into contact. And points
As in the case of P0, the point PN slightly separated from the point (Xa, 0) is stored.

After the points P0 and PN are obtained in this way, a straight line L1 including the points P0 and PN is calculated.
(Hereinafter, a line such as the calculated straight line L1 is referred to as a "grinder guide line", and the points P0 and P1 are referred to as "grinder guide points.") Then, to the grinder guide point P0 on the grinder guide line L1. Guide the grinder.

Then, while performing force control in the work normal direction (Z direction) from the same position, the grinder is moved backward to perform the grinder work up to a point P0 'on the straight line L2 (Y = Ya).
Here, the plane to be ground is a plane including the point 0 and the point P0 ′, and the grinder guide point P0 does not exist on this plane. However, by starting the force control from the grinder guide point P0 and moving the grinder in the Y direction, the grinder moves obliquely so as to contact the work. Therefore, as a result, it is possible to grind from point 0 to point P0 '. By setting the grinder guide line L1 closer to the work, it is possible to further reduce the dead time in which the grinder moves obliquely until it contacts the work, and it is possible to accurately specify the grinding area.

When the grinding to the point P0 'is completed, the grinder is separated from the work 20. And the grinder works 20
The space on the work 20 is moved so as not to contact or collide with the object (while maintaining a non-contact state), and the space is guided to a new grinder guide point P1 on the grinder guide line L1.
Here, the grinder guidance point at which the grinder is newly guided is represented by the following equation.

[0035]

(Equation 3)

Note that i is a grinder guidance point at the time of the i-th guidance. N is the number of reciprocations of the grinder, and if the lateral feed pitch is Xp, N = Xa / Xp (where N
Is a natural number). Equation (3) is a vector representation.

The path of the grinder thus ground and guided is indicated by a dotted line in FIG. The trajectory of the grinder is shown obliquely from the grinder guidance point (for example, point P0 or point P1) on the grinder guidance line L1, as described above, when the grinder starts force control from a non-contact state and Y This is because they are moved in the direction. Then, such an operation is performed at the other end PN ′ of the grinding area 12.
By repeating the above, the grinder work of the work area 12 can be performed.

In this embodiment, since the grinder guide point Pi is determined in advance on the grinder guide line L1, even if there is an error in the fixed position of the work, the grinder does not contact or collide with the work. Therefore, when moving in a space, it can be moved at a high speed, and can be guided to the vicinity of the grinding start position in a short time. Thereby, the entire operation can be efficiently performed. In addition, there is no problem that the grinder is too far from the work or, conversely, comes into contact with the work and the work is excessively shaved.

The grinding operation may be started from the point PN. In this case, the moving time from the point PN to the point P0 can be reduced. Although the above embodiment is an example in which the present invention is applied to a planar grinding region, it is needless to say that the present invention can be applied to a grinding region having another shape.

For example, points A, B, and C on the cylindrical surface shown in FIG.
The case where the grinding area 12 surrounded by C and D is ground will be described. First, when the grinder grinding operation is performed in the direction of A → B, the point A and the point C
To find the grinder guidance points A 'and C',
The grinder guidance line A'C 'may be calculated. In the case of curved surface grinding, unlike the case of a flat surface, it is necessary to change the posture of the grinder, but usually, the posture of the grinder does not need to be strictly defined for the work. Therefore, there is no error that causes a problem. The posture at each position may be given in advance by calculation according to the shape of the work.

Next, when the grinder grinding operation is performed in the direction A → C, the grinder guide line becomes an arc.
In such a case, an arc-shaped grinder guide line A 'is obtained from the grinder guide lines A' and B 'and R obtained by contacting the points A and B with the radius R given in advance. B ′ can be easily calculated. Radius R
Is unknown, a point E between the point A and the point B is contacted, and the grinder guide line A'B 'can be calculated from the three points A, B, and E.

Further, when grinding a curved surface whose shape cannot be easily grasped, it is preferable to contact a large number of points with a grinder. The number of contact points may be such that the grinder guide line can approximate a straight line or an arc. Of course, in each of the above-described examples, the grinder guide line may be calculated by setting a plurality of contact points of the grinder. In particular, when there are many burrs and irregularities near the contact point, calculating the grinder guide line by contacting a plurality of points enables the grinding to be performed to the target surface shape more reliably.

Therefore, in this embodiment, if the grinder guide line can be calculated, the grinding area can be made to correspond to a plane, a quadratic surface, or a three-dimensional surface. Next, a method of calculating a grinder guide line by continuously contacting the work will be described.

In the work 20 as shown in FIG.
0, Y = Ya, X = 0, X = Xa
Will be described when a grinder operation is performed. Here, a coordinate system along the work 20 is employed. In this example, the grinder is continuously contacted from the origin O to the point (Xa, 0) (shown by a bold line in the figure), a grinder guide line is calculated from the contacted line, and each grinder guide point (point in the figure) Is shown). At this time, since the grinder can be moved laterally (that is, in the radial direction of the grindstone), the grindstone moves so as to roll on the surface of the work 20 in the X direction. Therefore, the contact is performed smoothly without applying a load to the grindstone.

The grinder guidance points may be stored, for example, at equal intervals as shown.
According to the present embodiment, there is no need to perform complicated calculations such as approximating a complicated grinder guide line to a straight line or an arc, and it is possible to easily deal with a complicated workpiece shape.

Next, a third embodiment will be described. First
Similarly to the embodiment of FIG.
In the following, a description will be given, with reference to FIG. 6, of a case where the grinding area 12 surrounded by Y = 0, Y = Ya, X = 0, and X = Xa is grindered.

FIG. 6 shows the trajectory of the grinder by a solid line in an enlarged manner near the grinder guide point Pi. The locus of this grinder corresponds to that shown by the dotted line in FIG.

The present embodiment is a method of determining a new grinder guidance point from the previous grinder guidance point or the previous contact point. Previous grinder contact position Zt
(i-1) is stored, and the grinder guide point Pi is determined based on the position. Therefore, the (Xi, Yi, Zi) component of the grinder guide point Pi can be expressed as follows, starting from X = 0.

[0049]

(Equation 4)

Here, Xp is the feed pitch of the grinder. Zt (i-1) represents the Z-direction component of the point that came into contact with the workpiece at the beginning of the previous cutting, and Za represents the separation distance from the workpiece in the Z-direction.

Here, since the grinding in the XY plane is considered, the positions in the X and Y directions are determined in advance in accordance with the grinding area. Further, assuming that the position in the Z direction is substantially the same as the previous position, the position is guided to a position Za away from the Z component Zt (i-1) of the previous contact point. By setting Za as small as possible, the grinder work can be performed more efficiently.

Even when the grinding area is not a plane but a curved surface, if the curvature is relatively small, the grinder guide point can be determined by the above-described method. When the shape of the workpiece is known in advance, for example, when the curvature of the arc is known, the grinder guide point can be determined from the previous contact point of the grinder based on the curvature and the pitch of the lateral feed.

According to the present embodiment, it is not necessary to obtain a grinder guide line in advance before work, and a new grinder guide point can be determined as needed using the previous guide point or the previous contact point. it can. Then, as in the above embodiment, the grinder contacts the workpiece,
It is possible to move the space on the work so as not to collide (while maintaining a non-contact state), and to guide to the grinder guide point.

It is also possible to determine a new grinder guide point from the previous grinder guide point (ie, two or more round trips earlier). Next, a fourth embodiment of the present invention will be described. In each of the above-described embodiments, a method suitable for a case where the burr or unevenness of the work is severe or the work is relatively soft has been described. However, the fourth embodiment is suitable for a case where a weld bead or a plug weld portion is ground. Method will be described.

For example, a case where a weld bead as shown in FIG. 7 is ground will be described. In this embodiment, the first
This is a case where the grinder guide line or the grinder guide point of the third to third embodiments is applied to the grinder return position.

In this embodiment, as in the first embodiment, Y
= 0, Y = Ya, X = 0, X = Xa It is assumed that a rectangular grinding area 12 surrounded by a grinding operation is performed. And
The grinder guide line L1 is calculated by contacting the workpiece in the same manner as described above. Here, the grinder guide point and the grinder guide line may be set on the work surface, or they may be set at positions slightly separated from the work surface, as in the first embodiment.

Next, grinding is performed with a constant pressing force and a constant feed speed from the Y = 0 side to the Y = Ya side. At this time, it is preferable to perform grinding with a weaker pressing force than usual so as not to cut away portions other than the weld bead 15, that is, non-convex portions of the work 20 more than necessary.

After the grinding to the side of Y = Ya is performed in this manner, in the above-described embodiment, the grinder is moved in a non-contact manner using the space on the work 20. However, in the present embodiment, the movement is linearly returned to the grinder guide point on the grinder guide line L1. Then, at the time of this movement return, the convex portion of the weld bead 15 is cut off while performing force control in the feed direction of the grinder.

Then, the grinding of the weld bead 15 is completed while the work is advanced by reciprocating the grinder a plurality of times. That is, a point on the grinder guide line L1 is a turning point of the grinder grinding operation.

FIG. 8 shows a state of the grinder grinding operation when the work 20 is viewed from the X direction. When the grinder 11 is moved (advanced) in the direction A, if the feed speed is constant, the grindstone is caught on the convex portion of the weld bead 15, resulting in an overload, which is dangerous. Therefore, the grinder 11
Is detected by a six-axis force sensor (not shown), and the feed speed is determined so that the force F is always constant.
When the force F acting on the grinder is represented by using the value detected by the six-axis force sensor, the following expression is obtained.

[0061]

(Equation 5)

In order to move the grinder linearly to the grinder guide point Pi on the grinder guide line L1 while always keeping the force acting on the grinder constant, the target position of the grinder at each sampling is required. Pdn may be given by the following equation.

[0063]

(Equation 6)

Here, Pd (n-1) is a target position at the time of previous sampling, and K is a force control gain. Equation (6)
Is a vector display. According to this method, the weld bead
A portion other than 15, that is, a non-convex portion of the work 20 is not cut away more than necessary, and only the convex portion can be efficiently cut off regardless of the height of the weld bead 15.

In the present embodiment and the first embodiment, although the trajectory and the force control method when the grinder is advanced are different,
The point that the grinder guidance line and the grinder guidance point are adopted is the same. Therefore, the second and third
As shown in the embodiment, the application method when the grinding area is a curved surface or the method of determining a new grinder guide point from the previous grinder guide point can be used as it is.

When the present embodiment is applied to an arbitrary three-dimensional curved surface or the like, if the trajectory for advancing the grinder is not a straight line, the trajectory is appropriately changed according to the finished shape. You may.

In any of the methods, a portion other than the weld bead, that is, a non-convex portion of the workpiece is not cut more than necessary, and it is possible to efficiently cut off only the convex portion regardless of the height of the weld bead. become able to.

The present invention can be variously modified without departing from the spirit of the present invention. For example, a grinder working robot can employ any arbitrary shaft configuration and force control method.

[0069]

As described above, according to the present invention, a grinder guide line is calculated from a straight line or a curve from these contact points by bringing the grinder into contact with the work at a plurality of points or continuously. An arbitrary point on the guide line was defined as a position where the grinder was turned back or a position where the grinder was guided. Therefore, even when the grinder can be fed only in the retreating direction, if the space on the work is moved to this grinder guide line, the grindstone will not be damaged or cut into the work, and the grinder will be accurately positioned. It is possible to efficiently guide the user to the work start position.

When starting the grinder work from the grinder guide line, force control is performed in the normal direction of the work, and when performing the grinder work toward the grinder guide line, force control is performed in the feed direction of the grinder. With such control, even when grinding a convex part such as a weld bead or a plug welding part, it is not necessary to cut off the periphery of the convex part more than necessary, so that only the convex part can be shaved and finished flat. become.

[Brief description of the drawings]

FIG. 1 is a block diagram of a control configuration used in a grinder working robot of the present invention.

FIG. 2 is a perspective view showing an example of a work to be grinder-worked.

FIG. 3 is a flowchart showing a procedure of a grinder operation according to the present invention.

FIG. 4 is a perspective view showing another example of a work to be grinder-worked.

FIG. 5 is a perspective view showing another example of a work to be grinder-worked.

FIG. 6 is an enlarged explanatory view near a grinder guidance point.

FIG. 7 is a perspective view showing another example of a work to be grinder-worked.

FIG. 8 is a side view showing a state of a grinder work on the work shown in FIG. 7;

FIG. 9 is a diagram illustrating a grinder operation according to a conventional method.

[Explanation of symbols]

 11… Grinder 12… Grinding area 15… Weld bead 20… Work

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B23Q 15/00-15/28 G05B 19/18-19/46 B25J 3/00-3/04 B25J 9 / 10-9/22 B25J 13/00-13/08 B25J 19/02-19/06 B24B 27/00 B24B 41/00-51/00

Claims (4)

(57) [Claims] A grinder is attached to a hand of a robot,
A control method of a grinder work robot for performing a plurality of grinder work on a predetermined area of a work while controlling a pressing force of the grinder, wherein the grinder guide line is provided from a contact point of the work by bringing the grinder into contact with the work. Is calculated,
A method for controlling a grinder work robot, wherein the grinder work on the work is controlled to start from the grinder guide line. 2. A grinder is attached to a hand of the robot.
A control method of a grinder working robot for performing a plurality of grinder work on a predetermined area of a work while controlling a pressing force of the grinder, wherein the grinder is brought into contact with the work by a grinder guiding point from a contact point of the grinder. And controlling the grinder work on the work to be started from the grinder guide point, and calculating a guide point related to the next and subsequent grinder work using the grinder guide point or the contact point. Control method of grinder work robot. 3. When starting the grinder work from the grinder guide line or the grinder guide point, force control is performed in the normal direction of the work, and when returning to the grinder guide line or the grinder guide point, the grinder is used. The method according to claim 1 or 2, wherein the workpiece and the workpiece are kept in a non-contact state. 4. When starting the grinder work from the grinder guide line or the grinder guide point, force control is performed in the normal direction of the work, and the grinder work is performed toward the grinder guide line or the grinder guide point. the method of claim 1 or 2, wherein the grinder working robot and performing a force control in the feeding direction of the grinder to.