JP2638467B2 - Robot controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a robot used in an assembling / machining process.

[0002]

2. Description of the Related Art In a robot controller, acceleration / deceleration processing is performed in order to generate a movement command that matches the physical movement ability of each joint. In the acceleration / deceleration process, a so-called interpolation process that determines the trajectory of the robot tip between adjacent passing point target values for a plurality of passing point target values specified so that the robot tip passes sequentially is necessary. Become. In the ordinary robot control device, the pass point target value is often specified on rectangular coordinates as shown in FIG. 7, but this is converted into the pass point target value of each robot joint by the pass point coordinate conversion unit, and added. The interpolation processing is performed on the joint coordinates according to the result of the deceleration processing. In the conventional apparatus, since the input data for the interpolation processing is only the pass point target value on the joint coordinates, the trajectory between the pass point target values is simply calculated as a straight line on the joint coordinates. At this time, as shown in FIG. 8, the joint angle command value calculated between two adjacent passing point target values is on a straight line connecting the two passing point target values. (Eg Aoki, etc.,
"High-accuracy trajectory control by input smoothing and coordination among multiple axes", Proceedings of the 35th Joint Conference on Automatic Control, October 1992, pp. 353-356).

[0003]

Generally, the coordinate transformation from the orthogonal coordinates to the joint coordinates is non-linear. For this reason, when performing interpolation on a plurality of passing point target values specified as target values of the robot tip on the orthogonal coordinates after converting them to joint coordinates, interpolation of adjacent passing point target values is performed. The trajectory specified by the orthogonal coordinates cannot be faithfully reproduced simply by connecting the lines with a straight line on the joint coordinates. For this reason, in the conventional apparatus, an error has occurred during interpolation processing at joint coordinates, such as acceleration / deceleration processing.

[0004] This will be described with reference to the drawings. As shown in FIG. 9, a plurality of passing point target values are designated at positions on a side of a polygon on rectangular coordinates, and these are coordinate-transformed into joint coordinates and then subjected to interpolation by linear approximation. A joint angle command value as shown by 10 is obtained. When the joint angle command value is again transformed into orthogonal coordinates, the actual trajectory of the robot tip is obtained as shown in FIG. Generally, since the coordinate transformation between the orthogonal coordinates and the joint coordinates is nonlinear, a point on the orthogonal coordinates corresponding to the joint angle command value that was on a straight line on the joint coordinates is not necessarily on a straight line. Therefore, an error occurs between the designated robot tip trajectory and the actual robot tip trajectory.

An object of the present invention is to solve the above-mentioned drawbacks of the prior art and to realize a robot control device which realizes more accurate interpolation processing.

[0006]

According to the present invention, there is provided a rectangular coordinate passing point target value designating section for designating a passing point target value on rectangular coordinates, and an output of the rectangular coordinate passing point target value designating section. A rectangular coordinate passing speed target value specifying unit that specifies a passing speed target value on rectangular coordinates at each position of the passing point target value, and the passing point target value specified by the rectangular coordinate passing point target value specifying unit. A passing point coordinate conversion unit that converts and calculates a passing point target value on joint coordinates; and a passing speed on joint coordinates by performing coordinate conversion on the passing speed target value designated by the orthogonal coordinate passing speed target value designating unit. A passing speed coordinate conversion unit that calculates a target value; an acceleration / deceleration processing unit that performs acceleration / deceleration processing on the output of the passing point coordinate conversion unit and the output of the passing speed coordinate conversion unit; Output and output of the passing speed coordinate conversion unit An interpolation processing unit that calculates a command value after the acceleration / deceleration processing based on the output of the acceleration / deceleration processing unit; and a servo processing unit that controls each joint motor of the robot arm based on the output of the interpolation processing unit. And the robot arm driven by the output of the servo processing unit.

[0007]

According to the present invention, when interpolation processing is performed on joint coordinates between a plurality of designated passing point target values of a robot tip on rectangular coordinates, the speed at which the passing point target value is passed on rectangular coordinates is determined. The specified passing speed target value is coordinate-transformed, and both the passing point target value and the passing speed target value specified on the joint coordinates are used. Rather than simply connecting the passing point target values with a straight line on the joint coordinates, select a trajectory whose speed at the passing point target value is also as specified, and adopt a point on the same trajectory as a joint angle command value Therefore, the actual movement of the robot tip not only passes the designated passing point target value, but also the movement speed there is as specified, and it is possible to draw a trajectory closer to the original robot tip trajectory.

The above will be described with reference to the drawings. As shown in FIG. 2, when a plurality of pass point target values and pass speed target values specified on orthogonal coordinates are converted to joint coordinates and interpolation processing is performed using the target values, as shown in FIG. A joint angle command value is obtained. Since the position and speed of the tip trajectory of the robot that moves in accordance with the joint angle command value at each passing point are as specified, a trajectory that is close to the specified trajectory on the orthogonal coordinates is drawn as shown in FIG.

[0009]

Next, the present invention will be described with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. According to this embodiment, first, the point at which the robot tip should pass through the rectangular coordinates is the rectangular coordinate passing point target value designating unit 1, and the speed at which the robot tip passes the passing point target value in the rectangular coordinates is the rectangular coordinate. The passing speed target value designation unit 2 designates each. Hereinafter, a point at which the robot tip should pass is defined as a passing point target value, and a designated value of the speed at which the robot tip passes the passing point target value is defined as a passing speed target value.

The passing point target value specified by the rectangular coordinate passing point target value specifying unit 1 is converted by the passing point coordinate conversion unit 3 from a value in rectangular coordinates to a value in joint coordinates. The passing speed target value specified by the rectangular coordinate passing speed target value specifying unit 2 is converted by the passing speed converting unit 4 from a value in the rectangular coordinates to a value in the joint coordinates.

The acceleration / deceleration processing unit 5 performs acceleration / deceleration processing based on the output of the passing point coordinate conversion unit 3 so that the operation of each joint of the robot falls within a preset maximum allowable speed and maximum allowable acceleration. , And calculates a parameter for correcting the joint angle command value.

Based on the output of the passing point coordinate conversion unit 3 and the output of the passing speed coordinate conversion unit 4, the interpolation processing unit 6 calculates a plurality of target values between the plurality of passing point target values in accordance with the acceleration / deceleration parameters calculated by the acceleration / deceleration processing unit 5. Is performed. The inputs of the interpolation processing unit 6 include an acceleration / deceleration parameter s (k) output from the acceleration / deceleration processing unit 5 and a joint coordinate passing point target value q (k) = [q ( k) _i ] = [q (k) ₁ ,
q (k) ₂ ,..., q (k) _n ] ^T , and the joint coordinate passing speed target value w output from the passing speed coordinate conversion unit 4.
(K) = [w (k) _i ] = [w (k) ₁ , w (k) ₂ ,
.., W (k) _n ]. Here, s (k) is a time axis parameter for the k-th joint angle command value, and q
(K) _i represents the angle of the joint i at the k-th joint coordinate passing point target value, and w (k) _i represents the angular velocity of the joint i at the k-th joint coordinate passing speed target value. The output of the interpolation processing unit 6 is a joint angle command value q ′ (k) = [q ′
(K) _i ] = [q ′ (k) ₁ , q ′ (k) ₂ ,.
q '(k) _n ] ^T. Here, q ′ (k) _i represents a command value to the joint i at the k-th joint angle command value.

The rotation angle pls = [pls] of the angular joint at that time measured by the interpolation processing unit 6 and the robot arm 8
_i ] = [pls ₁ , pls ₂ ,..., pls _n ], and the current command value ic = [ic _i ] = [ic ₁ , ic ₂ ,...・ 、
ic _n ] is calculated, and the robot arm 8 is driven based on the current command value. Here, pls _i represents the current angle of the joint i, and ic _i represents a current command value to the joint i.

FIG. 5 is a diagram for explaining the time axis parameters calculated by the acceleration / deceleration processing unit 5 in the present embodiment described with reference to FIG. In the figure, Δt is a sample time of the robot controller. Passing point target value coordinate conversion unit 3
Then, the k-th joint coordinate passing point target value q (k) is kΔt
At the point where the robot should pass. By interpolating the joint coordinate passing point target value, a joint coordinate passing point target value q ^* (t) at a general time t is obtained. It should be noted here that q ^* (t) is a curve obtained by interpolating the joint coordinate passing point target value q (k), that is, q ^* (t) is the joint coordinate passing point target value. Means passing the value q (k). This can be expressed by the following equation.

Q ^* (kΔt) = q (k) The joint angle command value q ′ (k) at time kΔt obtained as a result of acceleration / deceleration processing and interpolation processing for q ^* (t) is represented by time s
Target value q ^* (s (k)) of the joint coordinate passing point in (k)
Given as That is, the joint angle command value q '(k)
Is given by the following equation:

Q '(k) = q ^* (s (k)) FIG. 6 is a flowchart showing the processing of the interpolation processing section 6. According to the flowchart, the interpolation processing is realized using the time axis parameters described in FIG. According to this, the interpolation processing unit 6 first calculates a time LΔt that is smaller than and closest to the time axis parameter s (k) among the times specified to pass the passing point target value. The difference between the time axis parameter s (k) and the time LΔt is set to ds (k). Next, the increment of the joint coordinate passing point target value at time (L + 1) Δt with respect to the joint coordinate passing point target value at time LΔt is defined as dq (L). The increment of the joint coordinate passing speed target value at the time (L + 1) Δt with respect to the joint coordinate passing speed target value at the time LΔt is defined as dw (L). Based on the above, the joint angle command value q ′ (k) at the time kΔt is obtained according to the following equation.

[0018]

(Equation 1)

As described above, the robot control device according to the present invention is obtained.

In this embodiment, the acceleration / deceleration processing unit 5
The time axis parameter may be calculated so that the joint angular velocity and the joint angular acceleration do not exceed the preset maximum allowable speed and maximum allowable acceleration. It is also apparent that the effects of the present invention can be obtained by general acceleration / deceleration processing for calculating a time axis parameter according to an operating range, torque, and other appropriate criteria.

[0021]

As described above, in the robot controller according to the present invention, not only the position of each point but also the instantaneous moving speed of the passing point target value specified on the rectangular coordinates is specified. Thus, even if interpolation processing is performed between a plurality of passing point target values on the joint coordinates, the trajectory specified on the orthogonal coordinates is accurately reproduced at the robot tip. Therefore, it is possible to suppress errors that occur during interpolation processing such as acceleration / deceleration processing.

[Brief description of the drawings]

FIG. 1 shows an embodiment of a robot control device according to the present invention.

FIG. 2 shows a target value of a passing point and a target value of a passing speed specified by the robot controller of the present invention.

FIG. 3 is a joint angle command value obtained by interpolation processing by the robot control device of the present invention.

FIG. 4 is a robot tip trajectory obtained by a joint angle command value by the robot control device of the present invention.

FIG. 5 is an explanation of a time axis parameter.

FIG. 6 is a flowchart of an interpolation processing unit according to the present invention.

FIG. 7 is an embodiment of a conventional robot control device.

FIG. 8 shows a joint angle command value obtained by interpolation processing by a conventional robot controller.

FIG. 9 shows a passing point target value specified by a conventional robot controller.

FIG. 10 is a joint angle command value obtained by interpolation processing by a conventional robot controller.

FIG. 11 shows a robot tip trajectory obtained by a joint angle command value by a conventional robot controller.

[Description of Signs] 1 Cartesian coordinate passing point target value specifying unit 2 Cartesian coordinate passing speed target value specifying unit 3 Passing point target value coordinate converting unit 4 Passing speed target value coordinate converting unit 5 Acceleration / deceleration processing unit 6 Interpolation processing unit 7 Servo processing unit 8 Robot arm

Claims (1)

(57) [Claims] 1. A robot control apparatus, comprising: a rectangular coordinate passing point target value designating unit for designating a passing point target value on rectangular coordinates; and the passing point target value output from the rectangular coordinate passing point target value designating unit. A rectangular coordinate passing speed target value designating unit for designating a passing speed target value on rectangular coordinates at each position; and a coordinate conversion of the pass point target value designated by the rectangular coordinate passing point target value designating unit, and joint coordinates. A passing point coordinate conversion unit for calculating the above passing point target value; and a coordinate conversion of the passing speed target value specified by the orthogonal coordinate passing speed target value specifying unit to calculate a passing speed target value on joint coordinates. A passing speed coordinate conversion unit, an acceleration / deceleration processing unit that performs acceleration / deceleration processing on the output of the passing point coordinate conversion unit and the output of the passing speed coordinate conversion unit, and the output of the passing point coordinate conversion unit and the passing speed Output of coordinate transformation unit And an interpolation processing unit that calculates a command value after the acceleration / deceleration processing based on the output of the acceleration / deceleration processing unit; and a servo processing unit that controls each joint motor of the robot arm based on the output of the interpolation processing unit. And a robot arm driven by an output of the servo processing unit.