JPH0217311B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling a robotic device.

Conventionally, robotic devices have been equipped with the ability to memorize the operating process at that time when a heteronomous or forced movement is applied, for example, manually or by a copying device, and then repeat that operating process at any time. These robot devices are now being used not only in factories but also in a wide range of fields as robots capable of performing tasks similar to those performed by humans.

Currently, the functions of this type of robotic equipment are significantly improved compared to conventional equipment, but on the other hand, control circuits, etc. are becoming increasingly sophisticated, and larger capacity and higher speeds are required. There is.

In addition, with this type of robotic equipment, the program is automatically set by operating the equipment with input, so there is a problem that the actual operation is not necessarily carried out in the most rational and smooth manner. It was hot.

The present invention has been made based on the above-mentioned viewpoints, and its purpose is to develop a robot device in which an operation program is automatically set by moving it by human power or the like. The object of the present invention is to provide a new control method that requires a control device that is not very large in capacity and high speed, and that can guarantee smooth operation at all times.

The gist of this is to replace and simplify the complicated motion path of a specific point of this type of robot device with a straight line and a circular arc through each process described below, and to move along this simplified path. The purpose is to move the specific point.

Hereinafter, the details of the present invention will be specifically explained with reference to the drawings.

Fig. 1 is a perspective view showing an embodiment in which the method of the present invention is applied to control a welding robot device, and Fig. 2 shows the relationship between the locus of a manually set specific point and the movement path set by the method of the present invention. FIG. 3 is an explanatory diagram showing a specific procedure for carrying out the method of the present invention.

In the figure, 1 is a robot equipped with a welding head 2, 3 is a welding rod, 4 and 5 are steel shells to be welded, and 6 is a welding line. 1b, 1c, 1d, 1e, universal joints 1f, 1g and 1i, welding head 2
is equipped with a welding rod feeding device 2a and an arc watch 2b.

The robot 1 includes actuators and servo control devices that operate each part, various sensors,
The welding head 2 is equipped with an automatic welding rod feeder, a weaving mechanism, a welding current control circuit, etc., and the present invention has a special relationship with these. Since this is not the case, the explanation will be omitted here.

In FIG. 1, shells 4 and 5 are fixed by a jig and a mounting base (not shown), and are welded along a welding line 6 by a robot 1 and a welding head 2.

Therefore, first, prior to welding, a specified dummy 3' is attached in place of the welding rod 3, and the arms 1b, 1c, 1d, and 1e are manually moved to point A (welding) at the tip of the dummy 3'. The rod 3 (corresponding to the arc point) is brought into contact with the welding line 6, and is moved from the starting point Po to the ending point Pz.

In such a case, the operating status of the robot 1, that is, the rotation angle change rate of the universal joints 1f, 1g, and 1i, is recorded in a storage device (not shown), so that the same process can be repeated at any time thereafter. become.

Therefore, the dummy 3' is removed and the welding rod 3
By supplying the welding head 2 and operating the welding head 2, the shells 4 and 5 can be welded.

Although the actual welding line 6 is a three-dimensional curve having curvature and torsion, here, to simplify the explanation,
It is assumed that the welding line 6 is a two-dimensional curve on the xz plane, as shown in FIGS. 1 and 2.

When three-dimensional Cartesian coordinates are used, the movement of the welding head 2 is performed simultaneously by one-, two-, or three-axis movement in the setting units (usually 10 μm to 10 mm) in each coordinate axis direction depending on the configuration of the device. It is carried out with This setting unit may be set to be large or small depending on the arm portion or the like.

In addition, since the attitude of the welding head 2 must actually be controlled, the trajectory of the point A corresponding to the center point of the arc shown in FIG.
The locus 7 of the reference point B set on the welding head 2 is also recorded.
We need to control the point A.
Only the control will be explained.

A dummy 3' is attached in place of the welding rod 3, and the point A at the tip thereof is manually moved along the welding line 6.

During the movement, the angles of the universal joints 1f, 1g, 1i are read by an encoder (not shown) at appropriate time intervals or for each moving distance, and are sequentially recorded.

Conventionally, when performing actual welding work, the angular changes of the universal joints 1f, 1g, 1i are tracked and reproduced, and the tip of the welding rod 3 is moved along the welding line 6.

Of course, in reality, the welding rod 3 wears out quickly, so
What is directly controlled by this method is the intersection of the center line of the welding rod feeding device 2a and the optical axis of the arc watch 2b, and the welding rod feeding device 2a always keeps the tip arc of the welding rod 3 within the field of view of the arc watch 2b. This is to feed out the welding rod 3 so that it is in the correct position, and to replenish the wear.

Therefore, in this method, each universal joint 1f, 1
In order to record the angles g and 1i in detail, an extremely large capacity storage device is required.

Therefore, in the present invention, these universal joints 1
The angles f, 1g, and 1i are only partially and temporarily recorded, not all of them are recorded for a long time, and the partially and temporarily recorded data allows the welding rod 3
The trajectory of the tip A of is calculated, and it is determined whether or not there is a part of the trajectory that can be approximated by a straight line.The part that can be approximated by a straight line is determined by that straight line, and the part where it is not possible is approximated by an arc. Obtain a continuous circular arc/straight line composite curve from the start point to the end point of the above trajectory, record the specifications of these straight lines and arcs in place of the angle data of the above universal joints 1f, 1g, 1i, and calculate the actual When performing the welding work, the robot 1 is controlled by applying linear interpolation and circular interpolation techniques known in the field of numerical control to achieve the desired purpose.

Now, in FIG. 2, it is assumed that point A is moved along welding line 6 from starting point Po to ending point Pz.

First, the points following the starting point Po are Pa, Pb, Pc, Pd,...
The angle data of the universal joints 1f, 1g, and 1i corresponding to are recorded sequentially. All of these data are integral multiples of the set unit angle, and based on these data, the xz coordinate values of points Pa, Pb, Pc, Pd, . . . are sequentially calculated.

At this time, adjust the density of the initial angle data as appropriate so that the xz coordinate values of each point calculated above are separated by an appropriate set unit length in the direction of each coordinate axis, or the distance between each point It is recommended to keep it approximately constant.

The next task is to test whether the section following point Po can be approximated by a straight line.

Therefore, when this section can be approximated by a straight line, a straight line that can cover as long a section as possible within a predetermined tolerance range is found.

Specific examples of these calculations will be explained later using FIG. 3.

In FIG. 2, the line segment connecting points Po and Pg is the longest line segment that can be substituted for the locus of point A in this section, so this line segment PoPg is adopted.

In the next section, the end point Pg of the previous section is newly set as the starting point Qo, and it is tested whether the following sections can be approximated by a straight line. In this case, since linear approximation is impossible, an approximate circular arc QoQm that can approximate the longest section within a predetermined tolerance range is determined, and thereafter approximate circular arcs RoRe and SoSg are determined in the same manner.

Here, these points will be explained in more detail with reference to FIG.

A part of the welding line 6 is shown in FIG. 3, and on the welding line 6 there are many passing points Pa, Pb, Pc, ..., Qo, Qa, Qb, ... along with the starting point Po. ,
Ro, Ra, Rb, ..., So, Sa, ... are shown.

It is assumed that the state of the robot 1 is measured and recorded at each passing point. However, in order to simplify the diagram, only a small number of passing points are shown here, but in reality, a large number of passing points are set at very fine pitches.

One recommended method for testing a straight line is to
Find a straight line PoPc that connects a passing point appropriately distant from Po, for example, the third passing point Pc from Po, and the starting point Po, and connect the passing points Pa, Pb between the above two points and the above straight line.
Calculate the distance to PoPc, check whether this distance, that is, the deviation from the straight line PoPc, is within a predetermined tolerance range, and calculate the distance Lca,
When both Lcb are less than the allowable tolerance E, it is assumed that a straight line approximation is possible; otherwise, a straight line approximation is not possible and an arc approximation is adopted.

This tolerance range is usually ±E, but in some cases, a positive or negative sign is introduced for L, and
This tolerance may be defined as +E to 0, +Ea to -Eb, etc.

Therefore, when linear approximation is possible, the longest line segment that can be replaced is found.

For this reason, the passing points Pd, Pe, ... beyond the passing point Pc
For the straight line connecting each of Pi... and the starting point Po,
Similarly to the above, the distance Lij to each intermediate passing point Pj is calculated.

For all intermediate passing points Pi, the longest one among the line segments PoPi for which E≧Lij holds is the solution to be sought, and in Figure 3, i=h, that is, the line segment
PoPh is indicated as its equivalent,
In this section, the line segment PoPh is adopted as the route along which point A should actually be moved.

Thus, the passing point Ph is set as the starting point Qo of the next section, and thereafter the line segment QoQc is adopted in the same manner as above, and the point Qc is further set as the starting point Ro of the next section.

In the section starting from the starting point Ro (Qc), the points Ro and Rc
Distances Lca, Lcb between the line segment connecting and the intermediate points Ra, Rb
It is assumed that linear approximation is impossible because either one exceeds the tolerance E.

In this case, first, find one of the points Ro to Rc and their intermediate passing points, for example, a circle passing through Ra (circle 8 with center Oc in the figure), and this arc RoRc
Calculate the distance Lcb between and the remaining passing point Rb, and if E≧Lcb, the travel route in this section is this arc RoRc
This makes it possible to replace it with

Therefore, the number of passing points between points Ro and Rc is
If the selection is made appropriately according to the curvature of the curve, this arc will always be obtained.

Therefore, even in this case, it is desirable to use the longest possible arc.

Therefore, in the same way as above, a circle 9 with the center Od passing through the points Ro, Rb, and Rd, and a circle 9 with the center passing through the points Ro, Rc, and Re.
Circle 10 of Oe, circle 11 of center Of passing through points Ro, Rc, Rf, each passing point Rd, Re, Re, etc. after passing point Rc,
The distance LK1 between each of Rk and the remaining passing point R1 is calculated for each circle passing through the starting point Ro and any one passing point existing between these two points, and if they are within the tolerance range. The longest arc is chosen. In the example shown in FIG. 3, the arc RoRf corresponds to this.

Hereinafter, by repeating similar calculations, a moving path consisting of straight lines and circular arcs and continuous from the initial starting point Po to the ultimate ending point Pz shown in FIGS. 1 and 2 is obtained.

Although the movement locus of a specific point when the robot is actually operated manually is not necessarily smooth, the movement path obtained as described above becomes a substantially smooth continuous curve.

Furthermore, when the robot is actually operated manually, the motion state of each part of the robot is often unnatural and cannot necessarily be called ideal.

Therefore, in the present invention, the specifications of these straight lines and curves are recorded, and the most desirable points are recorded in order to move the corresponding specific points along these movement paths according to the form and degree of freedom of the robot. The method of operation is calculated.

What is usually recorded are the coordinates of the starting point and ending point for a straight line, and the coordinates of the starting point, ending point, and center of curvature for a circular arc.

Therefore, robot operations during actual work are performed using known linear interpolation,
By the method of circular interpolation, the arms 1b, 1c, 1d, 1
This is what activates e.

In the present invention, the universal joints 1f, 1g and 1i or the arms 1b, 1c, 1 at the time of initial manual setting
The states of d and 1e are only partially recorded temporarily and are not recorded during work. Therefore, the movement of the robot during actual work is not necessarily the same as the movement during manual setting, but the optimum movement is adopted to achieve the desired purpose.

In the above explanation, for the sake of simplicity, the explanation has been made on the assumption that two-dimensional motion is performed, but it will be easily understood that three-dimensional motion can also be processed in the same manner as described above.

The steps in this case can be summarized as follows.

(a) A specific point on the robot is moved along a desired path by the other hand, and the motion state of the robot at this time is sequentially recorded over time at predetermined intervals, and each of the recorded state records of the robot is recorded. Correspondingly, a step of calculating the position of the specific point, that is, a passing point, and temporarily recording it.

(b) The motion starting point (Xo, Yo, Zo) of the above specific point,
i-th passing points Xi, Yi, Zi from the movement starting point (Xo, Yo, Zo) [where i is assumed to be larger than a predetermined minimum value imin. ], and each passing point (Xj,
Yj, Zj) [However, j=1, 2, ......(i-
1). ] is a straight line verification process in which all of the distances Lij do not exceed the tolerance E and the value of i is the maximum.

(c) This step is performed when the solution i=n is obtained in the linear verification step in the previous section, and is performed when the starting point (Xo,
A straight line section setting process in which a line segment connecting points (Yo, Zo) and points (Xn, Yn, Zn) is set as a straight line section, and the specifications of the line segment are recorded as necessary.

(d) This is a process performed when a solution cannot be obtained in the b-term linear verification process, and is performed when the motion starting point (Xo,
Yo, Zo) and the k-th passing point (Xk, Yk, Zk) from the movement starting point (Xo, Yo, Zo) [However, k is assumed to be larger than a predetermined minimum value kmin. ] and any one passing point (Xs, Ys, Zs) that exists between the above two points, and each other passing point (X1, Y1, Z1) that exists between the above two points. [However, 1=1, 2,...
(k-1). ] Arc verification step (e) to find the arc whose distance Lk1 does not exceed the tolerance E and whose value of k is maximum Then, set the arc connecting the starting point (Xo, Yo, Zo) and the passing points (Xs, Ys, Zs) and (Xm, Ym, Zm) as the arc section, and adjust the specifications of the above arc as necessary. Arc section setting process to record.

(f) Straight line as described in paragraph b, with the section end point (Xn, Yn, Zn) or (Xm, Ym, Zm) obtained by the straight line section setting step described in paragraph c or the arc section setting step described in the previous paragraph as a new starting point The same calculations as in the verification step are performed, and the steps described in sections b to e are sequentially repeated until the final movement end point (Xz, Yz, Zz) is reached, and a continuous movement path is set over the entire interval. calculation process.

(g) A step of moving the specific point along the movement path set by the steps described in each section above.

Note that although the coordinates have been explained above as being in the Cartesian coordinate system, this is only for the convenience of explanation. Of course, it includes

Furthermore, in the above explanation, only the position of a single specific point is controlled, but in reality, the welding rod feeding device 2
Since it is necessary to control the posture of point a, etc., at least two specific points are provided and their positions are controlled simultaneously. In that case, a tolerance is determined for each specific point, and control is performed while satisfying the constraint conditions between both specific points.

Furthermore, the present invention can be applied to the control of all kinds of robot equipment in addition to the welding robot described above, and furthermore, in addition to the method of calculating the setting of the straight line section and circular arc section, the method of least squares and other known statistics can be used. It is also possible to easily devise a higher-order interval setting by introducing a data processing method or a corrective calculation according to the purpose of use of the robot, and the present invention does not encompass all of them. be.

Since the present invention is configured as described above, when the present invention is used, the robot can record data sequentially over time at predetermined intervals when a specific point on the robot is moved along a desired path manually or the like. Based on the status record, it is automatically and appropriately verified whether each part of the movement path can be replaced with a straight line or whether it is more appropriate to replace it with a circular arc, and the specific points when actually operating the robot are automatically verified. The movement path is simplified by straight lines and circular arcs to a smoothly continuous movement path, and is set to a movement path that is most suitable for the purpose of work and approximates the desired path when moving manually etc. The operation program of a robot device whose operation program is automatically set by being moved by human power or the like can be easily and quickly set optimally, and the robot device can be easily and optimally set. It can be operated very smoothly with a large-capacity, low-speed control device.

[Brief explanation of drawings]

Fig. 1 is a perspective view showing an embodiment in which the method of the present invention is applied to control a welding robot device, and Fig. 2 is a relationship between the locus of a manually set specific point and the movement path set by the method of the present invention. FIG. 3 is an explanatory diagram showing a specific procedure for carrying out the method of the present invention. 1...Robot, 2...Welding head, 3...Welding rod, 3'...Dummy, 4, 5...Ciel, 6...
...Welding line, 7... Locus of point B, 8, 9, 10, 1
1... yen.

Claims (1)

[Scope of Claims] 1. A method for controlling a robot device, characterized by comprising the steps described in items a to g below. (a) A specific point on the robot is moved along a desired path by external force, and the state of motion of the robot at this time is sequentially recorded over time at predetermined intervals, and each recorded state of the robot is recorded. The process of calculating and temporarily recording the position of the specific point (hereinafter referred to as "passing point") in response to the above. (b) The movement starting point (Xo, Yo, Zo) and the i-th passing point sequentially arranged on the movement path from the movement starting point (Xo, Yo, Zo) to the ending point (Xz, Yz, Zz).
th passing point (Xi, Yi, Zi) [However, it is assumed that i is larger than a predetermined minimum limit value i min. ] and each passing point (Xj, Yj, Zj) between the above two points [where j=1,
2, ......(i-1). ] is a straight line verification process in which all of the distances Lij do not exceed the tolerance E and the value of i is the maximum. (c) This step is performed when the solution i=n is obtained in the linear verification step in the previous section, and is performed when the starting point (Xo,
A straight line section setting process in which a line segment connecting points (Yo, Zo) and points (Xn, Yn, Zn) is set as a straight line section, and the specifications of the line segment are recorded as necessary. (d) This is a process performed when a solution cannot be obtained in the b-term linear verification process, and is performed when the motion starting point (Xo,
Yo, Zo) and the K-th passing point (Xk, Yk, Zk) from the movement starting point (Xo, Yo, Zo) [where k is greater than a predetermined minimum value k min. ] and any one passing point (Xs, Ys, Zs) that exists between the above two points, and each other passing point (X1, Y1, Z1) that exists between the above two points. [However, 1=1, 2,......
(k-1). ] is an arc verification process for finding an arc whose distance Lk1 does not exceed the tolerance E and whose value of k is maximum. (e) When understanding k=m is obtained in the arc verification step in the previous section, the starting point (Xo, Yo, Zo), passing point (Xs, Ys, Zs) and (Xm, Ym, Zm) An arc section setting step in which an arc connecting the is set as an arc section, and the specifications of the arc are recorded as necessary. (f) Using the section end point (Xn, Yn, Zn) or (Xm, Ym, Zm) obtained by the straight line section setting step described in section c or the arc section setting step described in section e as a new starting point, perform the process described in section b. Perform the same calculation as the straight line verification step, and repeat the steps described in sections b to e in the same manner until the final movement end point (Xz, Yz, Zz) is reached, and set a continuous movement path over the entire section. Iterative calculation process. (g) A step of moving the specific point along the movement path set by the steps described in each section above. 2. The method of controlling a robot device according to claim 1, wherein a plurality of specific points are provided, and all calculations and operations are performed for all of the specific points while satisfying constraint conditions between the specific points.