JPH083739B2 - Robot speed program determination method - Google Patents

Description

The present invention relates to a motion control method for an industrial robot, and more particularly to a speed program determination method for reducing cycle time by devising a method of omitting acceleration / deceleration motion. .

[Conventional technology]

Generally, when performing acceleration / deceleration control of a robot, a position command signal that represents the amount of movement per unit time calculated based on the selected speed program is processed by a software filter and then used as a position command signal for the position control loop. Input to the servo control section of each axis of the robot arm.

Therefore, even if there is a sudden change in the speed in the speed program, the vibration of the robot during acceleration / deceleration is moderated by the action of the software filter. Therefore, when the speed is low to a certain extent, vibrations that would hinder practical use do not occur without using a speed program with acceleration / deceleration.

Therefore, when the specified speed set by the operator is lower than a predetermined speed set in advance, a program with a constant speed is selected and acceleration / deceleration is omitted to shorten the cycle time. That is, when the designated speed is lower than a reference speed (hereinafter simply referred to as a reference speed) preset as an allowable maximum speed in the constant speed program, the constant speed program in which the designated speed is used as the speed command is selected, and vice versa. If the specified speed is higher than the reference speed, a speed program with acceleration / deceleration with the specified speed as the upper limit of the speed was selected.

[Problems to be solved by the invention]

As described above, in the conventional technique, the constant speed program or the speed program with acceleration / deceleration is selected only based on the magnitude comparison with the reference speed of the designated speed.

That is, the magnitude of the designated speed with respect to the reference speed and the amount of movement between the two points at which the robot is to move have not been considered at all.

For example, when the designated speed set by the operator is higher than the reference speed but close to the reference speed, the moving time becomes longer than that of the constant speed program based on the reference speed because acceleration / deceleration is performed. Further, when the designated speed is sufficiently higher than the reference speed, there is a problem that the movement time becomes longer rather than the movement at the designated speed in the section where the movement amount between the two moving points is small.

The former problem is understood because the speed program with acceleration / deceleration takes longer than the constant speed program with the reference speed by the deceleration period, considering the case where the specified speed is close to the reference speed. The latter problem will be described in more detail with reference to FIGS. 3 and 4.

FIG. 3 is a diagram showing the relationship between the moving time T and the distance L between the two points where the tip of the robot arm moves. The straight line A and the curved line B show the case of the constant speed program and the speed program with acceleration / deceleration, respectively. It represents.

In this figure, a point Q ₃ is a point where the moving time of the constant speed program and the moving time of the speed program with acceleration / deceleration are equal to T ₃ when the distance is L ₂ . Also, at distance L ₃ , points Q ₄ and Q ₅
The moving time of the speed program with acceleration / deceleration is shorter as shown by the times T ₄ and T ₅ corresponding to. However, the distance is L ₂
In a shorter case, for example, at the distance L ₁ , the moving time of the speed program with acceleration / deceleration is longer as represented by the times T ₁ and T ₂ corresponding to the points Q ₁ and Q ₂ .

FIG. 4 illustrates the above relationship with respect to time and speed. V _s is a reference speed, V _c is a designated speed, a is acceleration, and b is deceleration. FIG. 4 (a) shows a case where the constant speed program and the speed program with acceleration / deceleration have the same moving time.
This corresponds to the distance L ₂ in FIG. FIG. 4 (b) shows a case where the moving time of the speed program with acceleration / deceleration becomes shorter, and corresponds to the distance L ₃ in FIG. On the contrary, FIG. 4 (c) shows the case where the moving time of the speed program with acceleration / deceleration becomes longer, and corresponds to the distance L ₁ in FIG.

Taking spot welding with a short distance between work points of the robot as an example of FIG. 4 (c), the designated speed V _c is set to a high speed because it is desired to move the work points between work points in the shortest possible time. Contrary to the aim, there were cases where the cycle time became longer.

For example, as shown in FIG. 5, the tip of the robot arm is sequentially programmed from the programmed point (program point) P ₁ to P ₂ P.
₃ ... Consider the case of performing spot welding work while moving each point of P ₇ P ₁ .

Since the case where the distance between points P ₁ to P ₄ is long is the case of FIG. 4 (b), there is no problem in setting the designated speed V _c higher than the reference speed V _s, but P ₄ to P ₇ In the section where the distance between the points is short, as described above, if the designated speed V _c is increased, the case shown in FIG. 4 (c) occurs, and the travel time is not shortened as intended.

Therefore, according to the present invention, if the operator sets the designated speed to a value higher than the reference speed, even if the designated speed is a value close to the reference speed, or if the amount of movement between program points is short,
It is to provide a method for determining the speed program of a robot that always realizes the shortest movement time.

[Means for solving problems]

In order to solve the above problems, the present invention uses a speed program determination method having the following features.

That is, the speed program determining method according to the present invention is such that the rotation speed of each axis of the multi-axis robot or the movement speed of the arm tip for moving the tip of the arm to a preset program point consisting of a plurality of point sequences. Is a device for controlling the speed program, wherein a maximum speed allowed as a constant speed program is preset as a reference speed, and the constant speed is determined based on the magnitude judgment between the designated speed set as the moving speed and the reference speed. In a case where a program or a speed program with acceleration / deceleration is selected, if the specified speed is higher than the reference speed, the specified speed is set as an upper limit of the speed and the acceleration / deceleration is set in advance.
The division number N _A (moving later) when moving between two program points and the division number N _NA (moving later) when moving between the two program points at the reference speed without performing acceleration / deceleration are set in advance. Calculate and compare, and if the division number N _NA is small, move between the two program points using the reference speed as a command value,
When the number of divisions N _A is small, the program is characterized by moving between the two program points by a speed program with acceleration / deceleration in which the specified speed is the upper limit of the speed.

[Action]

By means of the above means, if the operator sets the specified speed to a value higher than the judgment reference speed, the speed that is always the shortest time even if the specified speed is close to the reference speed or the amount of movement between program points is small. Since the program is automatically selected, the movement time of the robot is shortened and the cycle time is shortened without violating the intention of the operator.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to specific examples.

FIG. 1 is a block diagram of a control system showing a concrete embodiment of a method for determining a speed program of a robot according to the present invention, and only one robot axis is shown as a representative. FIG. 2 is a processing flow of the speed program determination unit.

In FIG. 1, 1 is a servo motor for driving a robot axis, 2 is a servo control unit for controlling the servo motor according to a position command as an input signal, 3 is a robot controller, and 4 to 10 are inside the controller. It represents some of the software functions of. 4 is a user program storage unit for storing preprogrammed position data, 5 is an interpreter unit, 6 is an operation control calculation unit, 7 is a speed program determination unit, 8 is an interpolation calculation unit, 9 is a position command calculation unit, and 10 is It is a software filter unit. Reference numerals 11 and 12 are position command signals that represent the amount of movement during the control clock (for example, 12 ms clock) cycle of the robot controller.

In the robot controller having the above-mentioned configuration, when moving the tip of the arm from the program points P ₁ to P ₂ shown in FIG. 5, the arithmetic processing performed by the speed program determination unit of FIG. FIGS. 6 (a) and 6 (b), FIG. 7 (a),
A description will be given with reference to (b) and (c). The following description is the same for the movement after P ₂ .

Here, the prerequisites will be given before the description of each step of the arithmetic processing.

Although only one axis is shown in FIG. 1 as a representative axis of the robot, a six-axis robot is used as an example in the following description.

In the “Problems to be solved by the invention”, the movement speed program of the tip when the tip of the arm moves by linearly interpolating between two points has been described. Therefore, the movement amount is the distance L and the movement speed is the velocity V. Expressed as In the following embodiment, a rotation speed program for each axis in joint operation will be described.

The linear interpolation operation is an operation that restricts the movement of the tip of the arm, whereas the joint operation is an operation that restricts the movement of each axis of the robot.

Therefore, in the joint operation, the movement amount between two points is represented by the rotation amount of each axis, and the movement speed is represented by the rotation speed (for example, angular velocity). Velocity is simply expressed as movement amount, velocity, acceleration, and deceleration. That is, assuming that the positions of the points P ₁ and P ₂ are rotation angles θ ₁ i (i = 1 to 6) and θ ₂ i (i = 1 to 6) from the reference angle of each axis of the robot arm, respectively, 2 The amount of movement between the points is θ ₂ i−θ ₁ i (i = 1 to 6), which is represented by dθi, and the reference speed, the designated speed, the acceleration, and the deceleration are W _s , W _c , α, and β, respectively. I will represent it.

Further, the time is represented by the number of control clocks (hereinafter referred to as the number of divisions) based on the control clock of the robot controller,
The unit of the movement amount dθi is the number of pulses, the unit of the speed is the number of pulses per control clock, and the unit of the acceleration is the number of pulses of speed change per one control clock.

The calculation processing in the speed program determination unit is performed according to the following step numbers (1) to (3.6). Step numbers (1) to (3.6) correspond to step numbers (1) to (3.6) in the flowchart of FIG.

(1) Movement amount (rotation amount) dθi of each axis between two points P ₁ and P ₂
(I = 1 to 6) is calculated.

dθi = θ ₂ i−θ ₁ i (i = 1 to 6) (2) Number of divisions between two points P ₁ and P ₂ when moving at reference speed W _s without performing acceleration / deceleration N _NA (maximum value ).

N _NA = max [d.theta.i / Ws] (i = 1~6) (3) designated speed W dividing number between the two points P _1, P _{2 when c} is a move deceleration operation as the upper limit of the speed N _A Is calculated by the following steps (3.1) to (3.3).

(3.1) Find the division number N _N (maximum value) between two points P ₁ and P ₂ when moving at the specified speed W _c without performing acceleration / deceleration operation.

N _N = max [dθi / W _c ] (i = 1 to 6) (3.2) In the case of a speed program with only acceleration / deceleration and no constant speed section, peak speed W _P , number of divisions of acceleration section and deceleration section N ₁ , N ₃ is calculated.

The _{W c · N N = α ·} N 1 2/2 + β · N 3 2/2 Wp = α · N 1 α · N 1 = β · N 3 or more N ₃ = α · N ₁ / β W _P = α · N ₁ .

(3.3) Compare the specified speed W _c with the peak speed W _P. If W _c is larger, the total number of divisions when moving between two points while performing acceleration / deceleration operation with the specified speed W _c as the upper limit of the speed. N
_A is N _A = N ₁ + N ₃ .

FIG. 6 (a) shows the relationship between the speed and the number of divisions in the steps (3.1) and (3.2).

(3.4) Compare the specified speed W _c and the peak speed W _P , and if W _c is smaller, set the number of divisions N ₁ , N ₂ and N ₃ for the acceleration section, constant speed section and deceleration section as follows. Then, the total number of divisions N _A is obtained from the result.

_{α · N 1 = W c ∴N} 1 = W c / α β · N 3 = W c ∴N 3 = W c / β W c · N N = α · N 1 2/2 + β · N 3 2/2 + W _{c · N 2 ∴N 2 = {} W c · N N - (α · N 1 2 + β · N 3 2) / 2} / W c N A = N 1 + N 2 + N 3 FIG. 6 (b) is The relationship of the step (3.4) is illustrated.

(3.5) _{Comparing the} division number _NA and the division number N _A , if N _A is larger, the operation without acceleration / deceleration is performed at the reference speed W _s .

(3.6) Comparing the number of divisions _NA with the number of divisions N _A , if N _A is smaller, execute a speed program with acceleration / deceleration operation with the specified speed W _c as the upper limit.

FIG. 7 shows a concrete example of the steps (3.5) and (3.6).

In FIG. 7, (a), (b), and (c) all show the case where the designated speed W _c is higher than the reference speed W _s .
(A) is a case where the movement amount between two points is large, and the number of divisions is smaller when the acceleration / deceleration operation is performed than when the operation is performed at the constant speed W _s . (B) shows a case where the movement amount between the two points is small, and (c) shows a case where the designated speed W _c and the reference speed W _s are close to each other. In either case, the acceleration / deceleration operation is performed, and the number of divisions is large. It has become.

Although the embodiment has been described with reference to the joint operation, the same applies to the linear interpolation operation if the speed program for each axis is replaced with the speed program for the tip of the arm.

〔The invention's effect〕

As described above, in the robot speed program determination method of the present invention, the designated speed set by the operator as the moving speed of the robot arm tip or the rotation speed of each axis is set as the maximum allowable speed in the constant speed program. Even if the speed is greater than the reference speed, the number of divisions N _A when moving between two points is calculated by the speed program with acceleration / deceleration with the specified speed as the upper limit before the start of movement, and the two points are calculated by this and the constant speed program based on the reference speed. Is compared with the number of divisions N _N in the case of moving, and the speed program with the smaller number of divisions is selected.

Thus, conventionally, the designated speed is simply compared with the reference speed, and if the designated speed is larger than the reference speed, even if the speed program with acceleration / deceleration is mechanically selected, it is possible to change the speed as shown in FIGS. By selecting the constant speed program based on the reference speed without taking the speed program with acceleration / deceleration as shown in (), it is possible to shorten the moving time by the time corresponding to the number of divisions of N _A -N _NA .

As described above, according to the present invention, if the operator sets a high-speed designated speed in order to move the work points of the robot in the shortest possible time, the movement time is always the shortest, and therefore the cycle time should be shortened. You can Especially,
This is effective in applications with many work points with short point-to-point distances (such as spot welding in automobile body assembly).

[Brief description of drawings]

FIG. 1 is a block diagram of a control system showing an embodiment of the present invention, FIG. 2 is a processing flow of a speed program determining section in the embodiment, and FIG.
FIG. 4 is a diagram showing that the relationship with the distance between points is different, FIG. 4 is a diagram showing a concrete example of FIG. 3, FIG. 5 is a motion path diagram of the robot, FIG. 6 is a division number explanatory diagram, and FIG. FIG. 4 is a diagram showing an effect of the invention in the embodiment.

Claims (1)

[Claims] 1. A method for controlling a speed program relating to the rotational speed of each axis or the moving speed of an arm tip of a multi-axis robot that performs work by moving the tip of an arm to a preset program point consisting of a plurality of point sequences. The maximum speed allowed as a constant speed program is preset as a reference speed, and whether it is a constant speed program or a speed program with acceleration / deceleration based on the magnitude comparison between the designated speed set as the moving speed and the reference speed. In the method for determining a speed program for a robot, the specified speed is higher than the reference speed, and the specified speed is used as an upper limit of the speed to move between the two program points at a preset acceleration / deceleration. Time division number N _A ,
The number of divisions N _NA when moving between the two program points at the reference speed without acceleration / deceleration is calculated in advance and compared, and when the number of divisions N _NA is small, the reference speed is used as the command value and the Number of divisions N _A by moving between two program points
Is smaller, the speed program determination method for a robot is characterized in that the speed program with acceleration / deceleration having the designated speed as an upper limit of the speed is used to move between the two program points.