JP2747802B2 - Robot control method and control device - 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 and a device for controlling a robot. More specifically, the present invention relates to a robot control method and a control device that do not cause a sudden change in posture of the robot.

[0002]

2. Description of the Related Art Conventionally, in arc welding robots and painting robots, control is performed to move the tip of a robot arm on a predetermined path at a constant speed. In this case, since the teaching work is easy and the path is easily corrected, only the main points are taught at the time of teaching, and a command regarding the position between the teaching points is made by a method such as linear interpolation or circular interpolation. A value (interpolation command value) is calculated at predetermined time intervals, and the interpolation command value is input to the robot to control the robot. At this time, at the same time, an interpolation command value for the posture for equalizing the posture angle change between the two teaching points is output.

However, if the attitude angle is changed in this manner, the angular velocities of the axes of the robot rapidly change from the teaching point. For this reason, even though an interpolation command value is given to the robot so that the tip of the robot arm has a constant speed, each axis of the robot does not operate according to the interpolation command value. As a result, the movement of the tip of the robot arm lacks smoothness,
This means that its uniform velocity is also impaired.

To cope with such a problem of the prior art, Japanese Patent Laid-Open Publication No. Hei 4-282706 discloses a teaching data storage unit in which the position, posture and speed of a robot taught by teaching means of the robot are stored. The position creating unit obtains the position and orientation, and the robot operation command creating unit creates an operation command of the robot that controls the acceleration and deceleration of the attitude angular velocity based on the amount of the attitude movement, and outputs the same to the robot controller. Robot control methods have been proposed.

However, in the control method in the above-mentioned proposal, since the processing is to be performed only by the taught position, posture and speed (see FIG. 4), the acceleration / deceleration of the robot accompanying the amount of posture change between two teaching points is If the motion is within the maximum acceleration / deceleration of each axis of the robot, the operation can be smoothed. However, the acceleration / deceleration of the robot due to the posture change amount between two teaching points exceeds the maximum acceleration / deceleration of each axis of the robot. In that case, the operation will not be smooth.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and does not cause a sudden change in angular velocity on each axis of a robot, thereby allowing a robot arm to move along a path taught by a robot. It is an object of the present invention to provide a control method and a control device for a robot that can move at a specified speed along the robot.

[0007]

Means for Solving the Problems A control method of a robot the present invention is a control method of a robot controlled by interpolation command value the operation of the robot between teaching points, the interpolation command about the position and posture of operating a robot As the value, the average value of the required number of supplementary command values for the position and orientation calculated before that,
It is characterized in that they are calculated differently and the calculated average value is used.

Here, it is preferable that the sampling time zone of the smaller interpolation command value of the required number is included in the sampling time zone of the larger interpolation command value.

On the other hand, the robot control device of the present invention
What is claimed is: 1. A control device used in a control method of a robot for controlling an operation of a robot between teaching points by an interpolation command value, the control device comprising: an interpolation command value generation unit; an interpolation command value correction unit; And the position and shape generated by the interpolation command value generation unit by the interpolation command value correction unit.
The interpolation command value relating to the force is the required number of positions and orientations according to the condition given by the correction condition giving unit.
Average value, calculator made different in number of the interpolation command value
Then, the calculated average value regarding the position and orientation is input to the robot as an interpolation command value regarding the position and orientation . Here, the required number of
The sampling time zone of the smaller interpolation command value is
Included in the sampling time zone of the larger interpolation command value
Is preferred.

[0010]

According to the present invention, each axis of the robot is controlled using the average value of the interpolation command values generated earlier as the interpolation command value, so that rapid movement of each axis of the robot can be avoided. Thus, a smooth operation can be achieved. Further, in a preferred embodiment of the present invention, the number of samples is made different when averaging the interpolation command values relating to the position and the posture, so that the position and the posture can be changed with the required smoothness.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described based on embodiments with reference to the attached drawings, but the present invention is not limited to only such embodiments.

FIG. 1 shows a control device used in the robot control method of the present invention. The control device 1 includes a teaching data storage section 2 for storing teaching data, an interpolation command value generating section for generating an interpolation command value. 3, an interpolation command value correction unit 4 for correcting the interpolation command value generated by the interpolation command value generation unit 3 and a correction condition providing unit 5 for providing a correction condition to the interpolation command value correction unit 4 as main components. It is. In addition, the control device 1 having such a configuration is specifically realized by combining a ROM, a RAM, an input / output interface, and the like in which a control program corresponding to a process to be described later is stored, mainly using a CPU.

The interpolation command value correction unit 4 calculates an average of a required number of interpolation command values relating to a previously generated posture for an interpolation command value at a location where the posture changes rapidly, and calculates the average value. As an interpolation command value for a posture, and for an interpolation command value for a location where a position changes rapidly, an average of a required number of interpolation command values for a position generated in advance is calculated, and the average value is calculated for the position. It is output as an interpolation command value.

In this case, assuming that the average value of the interpolation command values related to the position is the interpolation command value, so-called inward development occurs around the inside of the designated path as shown in FIG. for that reason,
When it is necessary to faithfully move according to the designated route as in an arc welding robot, averaging is not performed on the position interpolation command value, but only on the posture interpolation command value. By doing so, each axis of the robot can be smoothly operated while maintaining a predetermined trajectory.

An instruction as to whether or not to perform averaging on the interpolation command value at this position, or an instruction as to the number of samples at the time of averaging, is provided by the correction condition providing unit 5.

[0016] Incidentally, the teaching data storage unit 2 is the same bets also been used to control apparatus for a robot conventionally for storing teaching data and interpolation command value generator 3
Is the same as also the <br/> are used in the robot controller conventionally to generate the interpolation command value by linear interpolation or circular interpolation. Therefore, the detailed description is omitted.

Next, the averaging of the interpolation command value in the interpolation command value correction section 4 will be described more specifically.

The interpolation command value H _i of the robot, can be expressed as equation 1 using 4 columns 4 rows of the matrix.

[0019]

(Equation 1)

Here, the vector P (P _x , P _y , P _z ) constituting this matrix represents the position of the tip of the robot arm, and is expressed by equation 2 constituting this matrix. 3
A matrix S of three rows and columns represents the posture of the robot arm.

[0021]

(Equation 2)

[0022] Now, interpolation command value H _t before averaging at time t, as described above, be expressed as equation 3 using the position vector P _t and the posture matrix S _t.

[0023]

(Equation 3)

However, the attitude matrix S can be replaced with Euler angles O, A, and T. Therefore, for averaging of the interpolation command value related to the posture, the one replaced with the Euler angles O, A, and T will be used for the convenience of the arithmetic processing. Note that the averaging process may be performed by replacing the attitude matrix S with RPY.

Then, after averaging using the position vector P and the Euler angles O, A, and T, the position interpolation command value _Pu and the posture interpolation command values O _u , A _u , and T at time _{u are obtained} . _u is represented by Equations 4, 5, 6, and 7, respectively. Note that n and m in the expressions 4, 5, 6, and 7 each represent the number of samples. Here, the sample numbers m and n may be equal or different. Further, the interpolation command value for performing sampling is not limited to the value between two teaching points, and sampling may be performed beyond the teaching point.

[0026] _{P u = (P t + P} t-1 + ... + P t- (n-1)) / n (4) O u = (O v + O v-1 + ... + O v- (m _-1) ) / m (5) A _u = (A _v + A _v-1 +... + A _{v- (m-1)} ) / m (6) _Tu = (T _v + T _v-1 + ... + T _{v- (m-1)} ) / m (7)

Next, the obtained interpolation command values P _u , O _u , A
_u and _Tu are inversely transformed to calculate an interpolation command value for each axis of the robot.

Here, when averaging the position and orientation interpolation command values, if the numbers of samples are different, the sampling time zone with the smaller number of samples is replaced by the sampling time zone with the larger number of samples. Sampling is performed as included. Hereinafter, the method will be described with reference to specific examples.

(1) Number of Samples at Position and Sample at Posture
When the number of pulls is both odd, the center time of the smaller sampling is made to coincide with the center time of the larger sampling, so that the smaller sampling time is included in the larger sampling time and the sampling is performed. Calculate the average of the interpolation command values. For example, when the number of position samples is three and the number of posture samples is five, the time: t
With respect to the position around -2, time: t-1, t
The average value of the interpolation command values at −2 and t−3 is used as the interpolation command value for the position.
The average value of the interpolation command values at t-2, t-3, and t-4 is used as the posture interpolation command value. Equations 8, 9, 10, and 11 indicate the position and orientation interpolation command values calculated in this manner.

_Pu = ( _Pt-1 + _Pt-2 + _Pt-3 ) / 3 (8) _Ou = ( _Ot + _Ot-1 + _Ot-2 + _Ot-3 + O _t-4 ) / 5 (9) A _u = (A _t + A _t-1 + A _t-2 + A _t-3 + A _t-4 ) / 5 (10) _Tu = (T _t + T _{t) -1} + T _t-2 + T _t-3 + T _t-4 ) / 5 (11)

In this case, regarding the position, the average value of the interpolation command values at times t, t-1, and t-2 may be used as the position interpolation command value.

(2) Number of Samples at Position and Sample at Posture
When the number of pulls is an even number For example, when the number of samples at the position is 2 and the number of samples at the posture is 4, the position is interpolated at time: t, t-1 or at time: t-1, t-2. The average value of the command values is used as the position interpolation command value.
The average value of the interpolation command values at t-1, t-2, and t-3 is set as the posture interpolation command value. Formulas 12, 13, 14, 15
Indicates the position and orientation interpolation command values calculated in this way.

[0033] _{P u = (P t + P} t-1) / 2 or _{P u = (P t-1} + P t-2) / 2 (12) O u = (O t + O t-1 + O _{t-2 + O t-3} ) / 4 (13) A u = (A t + A t-1 + A t-2 + A t-3) / 4 (14) T u = (T t + T t _-1 + T _t-2 + T _t-3 ) / 4 (15)

(3) One of the samples is an even number and the other is
For example, when the number of samples is odd, for example, when the number of samples at the position is 3 and the number of samples at the posture is 4, with respect to the position, time: t, t−1, t−
2 or time: The average value of the interpolation command values at t-1, t-2, and t-3 is used as the position interpolation command value, and the attitude is calculated at times: t, t-1, t-2, and t-3. The average value of the interpolation command values at is taken as the posture interpolation command value. Equation 16, 1
Reference numerals 7, 18, and 19 indicate the position and orientation interpolation command values calculated in this manner.

[0035] _{P u = (P t + P} t-1 + P t-2) / 3 or _{P u = (P t-1} + P t-2 + P t-3) / 3 (1 6) O u = (O _t + O _t-1 + O _t-2 + O _t-3 ) / 4 ( 17 ) _Au = (A _t + A _t-1 + A _t-2 + A _t-3 ) / 4 ( 18 ) _Tu = ( _Tt + _Tt-1 + _Tt-2 + _Tt-3 ) / 4 ( 19 )

EXPERIMENTAL EXAMPLE AND COMPARATIVE EXPERIMENTAL EXAMPLE Next, a simulation of the motion of the robot arm when the control method of the present invention was applied was averaged only for the posture without averaging the position (average number: 50).
Under the condition that FIG. 3A shows the change in the angular velocity of the robot axis at that time (an experimental example). For comparison, a simulation using a conventional control method was also performed. FIG. 3B shows a change in the angular velocity of the robot shaft at that time (comparative experimental example). From FIGS. 3A and 3B, it can be seen that the change in the angular velocity in the experimental example is very smooth, whereas that in the comparative experimental example is sharp.

[0037]

As described in detail above, according to the present invention,
An excellent effect is obtained that the movement of each axis of the robot can be made smooth even if the posture changes greatly. In addition, since the movement of each axis of the robot can be made smooth, there is also obtained an effect that deviation of the tip of the robot arm from a predetermined trajectory and a change in speed due to rapid movement of each axis of the robot can be eliminated. Furthermore, since the number of samples at the time of averaging can be appropriately selected with respect to the position and the posture, it is possible to obtain an effect that control according to the use can be performed.

[Brief description of the drawings]

FIG. 1 is a block diagram of a control device used for a robot control method according to the present invention.

FIG. 2 is an explanatory diagram of inward development that occurs when a robot is controlled using an average value of position interpolation command values.

FIG. 3 is a graph of a change in angular velocity of a shaft of a robot,
2A shows the result obtained by the control method of the present invention, and FIG. 2B shows the result obtained by the conventional control method.

FIG. 4 is a graph showing a change in the angular velocity of the robot shaft by the control method proposed in Japanese Patent Application Laid-Open No. 4-282706.

[Explanation of symbols]

 Reference Signs List 1 control device 2 teaching data storage unit 3 interpolation command value generation unit 4 interpolation command value correction unit 5 correction condition giving unit

Claims (4)

(57) [Claims] 1. A robot control method for controlling an operation of a robot between teaching points by an interpolation command value, wherein the interpolation command value relating to a position and a posture at which the robot is operated includes a previously calculated position and posture.
Of the required number of interpolation command values to the position and orientation
The numbers are calculated differently and the calculated
A robot control method, characterized by using an average value obtained from the average value . Wherein said sampling time period required number interpolation command value with the smaller ones of, many people of claim 1 of the robot, characterized in that it is included in the sampling time period of the interpolation command value Control method. 3. A control device used in a control method of a robot for controlling an operation of a robot between teaching points by an interpolation command value, the control device comprising: an interpolation command value generation unit; an interpolation command value correction unit; A correction condition providing unit, wherein the interpolation command value correcting unit corrects the interpolation command value relating to the position and orientation generated by the interpolation command value generating unit in accordance with the condition provided by the correction condition providing unit . Yo
The average value of the required number of interpolation command values for fine attitude, the
The numbers are calculated differently, and the calculated position and
A control device for a robot, wherein an average value related to the position and the posture is input to the robot as an interpolation command value related to the position and the posture . 4. An interpolation command for a smaller one of the required numbers.
If the sampling time of the value
Claims that are included in the pulling time zone
Item 4. The control device for a robot according to Item 3.