JPS60201408A - Industrial robot - Google Patents

Abstract

PURPOSE:To reduce a shock at the time of acceleration and deceleration, and to position a high inertia load with high accuracy by approximating a moving speed by a trigonometrical function of time and outputting a position command, at the time of start and stop. CONSTITUTION:An accelerating time Ta<i> of each axis is calculated in accordance with Ta<i>=(pi¦V<i>¦)/2a<i>, subsequently, a distance d<i> to a point for shifting to a uniform speed from a start position P0<i> of each axis is calculated, based on d<i>= V<i>/2).{(-sinomegaTa/omega)+Ta}, and next, a moving distance L<i> is calculated in accordance with L<i>=P3<i>-P0<i>. Subsequently, a uniform speed time Tc is calculated from Tc=(L-2d)/V. In this case, L, (d), and V denote a distance between a start position and a stop position, a start distance, and a speed common to each axis set by a speed setting switch, namely, a composite speed. Subsequently, time t=0 is set as an initial state, a target position P<i> is calculated at every minute time DELTAt, and it is commanded as position information to each servo-circuit from a control device.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) This invention relates to industrial robots. More specifically,
The present invention relates to an industrial robot that controls the movement of a high inertia load.

(Description of Prior Art) An industrial robot having a plurality of control axes, each of which is started and stopped at the same time, is well known, for example, as disclosed in Japanese Patent Laid-Open No. 57-139810.

In such industrial robots, for example, when the weight of the controlled part such as the end effector is large and the movement speed is fast, the inertia becomes large. If this is necessary, it is usually necessary to increase the servo gain of the servo system for each control axis. However, increasing the servo gain increases the impact during acceleration and deceleration, and the In order to obtain sufficient strength, the rigidity of each part must be increased.Increasing the rigidity will increase the weight and inertia.
In the end, the problem cannot be resolved. That is, with conventional industrial robots, it is extremely difficult to position a high inertia load with high precision.

(Objective of the Invention) Therefore, an object of the present invention is to provide an industrial robot that can position a high inertia load with high precision by reducing impact during acceleration and deceleration.

(Summary of the Invention) To put it simply, the present invention is an industrial robot that issues a position command by approximating the moving speed by a trigonometric function of time when starting and stopping.

The above objects and other objects and features of the invention will become more apparent from the following detailed description with reference to the drawings.

(Description of Embodiments) FIG. 1 is an illustrative view showing an example of an industrial robot that forms the background of the present invention and in which the present invention can be advantageously implemented.

Although the industrial robot 10 shown in this example is a composite robot, the present invention is not limited to such a composite robot.
It should be pointed out in advance that the invention can be applied to industrial robots of any configuration.

The robot 10 includes a base 12 extending in the Y-axis direction (direction perpendicular to the plane of paper in FIG. 1).

A movable base I4 is placed on the base 12, and this movable base 14
is guided by the base 12 and is configured to be movable in the Y-axis direction. The position of the movable table 14 is controlled in the Y-axis direction by a power source 16. Although the power source 16 is not shown,
For example, it includes a motor and a pole shaft rotated by the motor.

A sliding arm 18 is supported on the movable table 14 so as to be movable in the X-axis direction, and the position of the sliding arm 18 is controlled in the X-axis direction by a power source 20 . A vertical arm 22 is supported at the tip of the sliding arm 18 so as to be rotatable around a vertical axis and can be raised and lowered. This vertical arm 22 is controlled to move in the X-axis direction by a power source 24, and its rotation angle β3 is controlled by a power source 26.
is controlled. The lower end of the vertical arm 22 has a horizontal axis 2
8, the end effector 30 is rotatably attached. In this example, the end effector 30 is configured as a gripping claw that can be opened and closed in the vertical direction. The rotation angle β4 of the end effector 30 about the shaft 28 is controlled by a power source (not shown). Therefore, the end effector 30 can take any angle β4 between the vertical attitude shown by the solid line in FIG. 1 and the horizontal attitude shown by the two-dot chain line.

The vertical arm 22 is provided with a rotating body 32 that can rotate coaxially with the vertical arm 22, and the rotating angle α1 of the rotating body 32 is controlled by a power source 34. A first arm 36 is supported by the rotary body 32 so as to be able to be raised and raised freely around a horizontal axis, and the elevation angle α2 of the first arm 36 is controlled by a power source 38 . A second arm 40 is further attached to such the 1115ii 36 so as to be able to move up and down about the horizontal axis. This second arm 40 is controlled by a power source 42 at an elevation angle α3
is controlled. A wrist 42 is supported at the tip of the second arm 40 so as to be rotatable or tiltable around a horizontal axis.
The elevation angle α4 is controlled by the power source 44.

A torch mount 46 is supported on the wrist 42 so as to be rotatable about a shaft 43 perpendicular to the vertical axis of the wrist 42 . This torch mount 46 is rotated through its rotation angle α by a power source 48.
5 is controlled. A welding torch 48 is then installed at the tip of this fixture 46. At this time, the operating point at the tip of the welding torch 48, that is, the welding point, is configured to be on the above-mentioned axis 43.

In this way, the robot 10 is controlled along the control axis X.

The parent robot has four degrees of freedom: y, z, β3, and β4. α2. α3. α4 and α5
It is configured as a composite robot with a child robot having five degrees of freedom. The control axes X, Y, Z, β3 and β4 of the parent robot are fixed on the fixed base 1.
The control axes α1 to α5 of the child robot are determined based on
It should be understood that it is provided with the tip of the arm 18 as a reference.

FIG. 2 is a block diagram showing an example of a control circuit for controlling the robot shown in FIG. 1. Power sources 16, 20 shown in FIG.
．． . . . are controlled by the corresponding servo circuits 50 to 68, respectively.

As is well known, these servo circuits 50 to 68 have the numbers -
A home motor M and an encoder E are provided. Encoder E
is for outputting rotation angle information for the amount of movement in each axis. And these servo circuits 50 to 68
are connected to the control device 7 by the pass line 70, respectively.
2. The control device 72 includes, for example, the CPU 7
4 and a memory 76 coupled to the CPU 74. Control device 72 is typically constituted by a microcomputer or microprocessor. Furthermore, an operation panel 78 is connected to the lotus line 70.

This operation panel 78 includes a speed setting switch 80. Mode selection switch 82 and manual operation switch group 8
4 is provided. The manual operation switch group 84 includes a selection switch 86 for selecting whether to operate the parent robot system or the child robot system.
Its function can be switched. The manual operation switch group 84 and the selection switch 86 are comprised of known three-position toggle switches. The operation panel 78 further includes a circular interpolation command switch 88 for the child robot system. A linear interpolation command switch 90 is provided.

A start switch 92 provides a start command in automatic mode and also provides a teaching command in teaching mode.

Next, an example of the operation of the above-mentioned robot will be explained. The operator energizes the robot 10, the control device 72, etc. to activate them. Then, the switch 82 is used to set the manual mode (M). As an example of the work performed by a robot, regarding a workpiece in which two steel channel materials W2 are placed facing each other on a steel plate W1 shown in FIG.
Assume that tack welding is performed on 1. In this case, the channel material W2 and the steel plate W1 are not directly attached to each other,
While holding the short channel material W3 by the end effector 30, as shown in FIG. 1, the short channel material W3 is placed over the channel material W2 and pressed against the steel plate W1, and the short channel material W3, the channel material W2, and the short channel material W3 are
and steel plate W1 are temporarily attached using a welding torch 48, respectively. In such a case, the parent robot must be controlled in order for the end effector 30 to grip and move the short channel material W3. In this way, since the child robot is further incorporated into the parent robot, large inertia occurs when the end effector 30 moves. The present invention is characterized by how to control a robot having such a high inertial load.

Figure 3 is a graph explaining the basic idea of this invention, Figure 3 (A) shows the relationship between speed (vertical axis) and time (horizontal axis), and Figure 3 (B) shows the relationship between time (horizontal axis) and speed (vertical axis). It is a graph showing acceleration with respect to the horizontal axis).

As can be seen from FIG. 3, in the present invention, during startup (time O to tl; T in FIG. 3) and stop (time t2 to tl;
3; The moving speed of T> is approximated by a trigonometric function of time, and the target position is commanded according to the moving speed. The target speed Vt at startup is given by the following equation (1), and the sequential target positions pt at that time are given by the following equation (2).

vt= (V/2) ・ (-cosωt+1)...
(1) P -(V/2) ・ ((=sinωt/ω)+t
)+Po... (2) Here, ■ is the speed set by the switch 80 on the operation panel 78, PO is the starting point as shown in FIG. 4, and P2 is the stop transition point. However, ω=π/T (0≦
t≦T), where T is the startup (or shutdown) time.

The speed Vt and position information pt at the time of stopping are given by the following equations (3) and (4), respectively.

vt-(V/2) ・ (cosωt+1)... (
3) Pt= (V/2) ・((sinωt/ω) 10t) 10P2... (4) And the maximum acceleration a (may) at the time of starting and stopping shown in Fig. 3(B) is , is given by the following equation (5).

a (max) − (d / d t) (V t),
jt-p-Vω/2 ・ ・ ・ (5) As mentioned above, by approximating the speed at startup and stop to a trigonometric function, as shown in FIG. 3(A),
The speed will change smoothly when starting and stopping. Therefore, even if a high-inertia load is controlled to move at high speed, vibrations and shocks are less likely to occur. Furthermore, approximation using trigonometric functions has the advantage that even high-order differentials are continuous, it is easy to obtain velocity integrals, and it is easy to synchronize each axis.

During constant movement, that is, from time tl to t2 in FIG. 3, that is, time Tc, it goes without saying that the target speed Vt
and target position pt are the following equations (6) and (
7) is given by

Vt=V ・ ・ ・ (6) pt=vt・Δt+PI ・・・ (7) Here, Pl
is the constant velocity transition point shown in FIG.

FIGS. 5A and 5B are flow diagrams illustrating the operation of an embodiment of the present invention. first step S
1, the initial state is shown. That is, the maximum acceleration a' (max) is stored in the memory 76 shown in FIG.
, set speed y+, starting position POI and stopping position P3
Stars are preset and stored. Here, the maximum acceleration a' (in ma) of the robot 10 with respect to each axis is
(Figure 1) This is a value required for design based on the weight, structure, etc.

Note that i is the number of degrees of freedom of the parent robot of the robot 10, that is, the number of axes in the rectangular coordinate system. The set speed or target speed (1) is speed data that is divided for each cuff with respect to the speed (V) set by the speed setting switch 80 on the operation panel 78.

The starting position PO1 is obtained by taking in the information on the orthogonal coordinates of that point as information for each axis through teaching, and corresponds to the point po shown in FIG. Further, the stop position P31 is obtained by taking in information on the orthogonal coordinates of that point by teaching as information for each axis, and corresponds to the point P3 in FIG. 4. It is assumed that the memory 76 (FIG. 2) also stores tables for trigonometric functions, ie, sine (sin) and cosine (cos), which will be described later.

In step S2, the CPU 74 (FIG. 2)
The acceleration time Ta' is calculated according to the following equation (8>).

Ta i = (πl V'l) /2a' (
max)... (8) Here, Ta' represents the acceleration time for each axis. and,
In the following step S3, the acceleration time (Ta'
) is judged or selected.

In step S4, the distance d at startup, that is, the distance d from the startup position po+ of each axis to the point P11 where the speed shifts to constant speed.
i is calculated based on the following equation (9).

2 d'-(V'/2) ・((-5ina+Ta/ω
) 10'l' a ) ... (9) Note that the trigonometric function sinωTa here is
6 (FIG. 2). The reason why the starting distance d1 is set in this way is that if the stop position P3i falls within the starting distance, it is necessary to perform another control. For the same reason, in step s5, the moving distance 11Li is calculated according to the following equation (10).

Li=P3i−POi ---(10) In addition, LI is
The distance between the starting position Pot and the stopping position P3I is divided proportionally to each axis.

If the starting distance di is less than half of the distance between the starting position po+ and the stopping position P3, the constant velocity movement time must be calculated using a special method.
6, rd l<L l/2? ", CPU74
(Figure 2) makes the judgment.

If the determination in step S6 is dl<LI/2, this means that the moving distance 1ilItL1 is short, and in this case, the coefficient C is calculated in the subsequent step S7. As this coefficient C, the largest one among L'/2Di is selected. Such a coefficient C is used to compress the velocity. In other words, if the speed ■1 increases, the time t decreases, and if VI decreases, the time t increases, but L
Using the fact that '/2 remains unchanged, the speed is made slower than in the normal case. In step S8, the new target speed vI is determined by the following equation (11), and the corresponding start button @di is determined by the following equation (12).

V + = CV + ... (11) d'-(V'/2) ・((-sinωTa/ω)
(12) In step S9, the constant velocity time, that is, the period Tc of time t1-t2 in FIG. 3 is calculated from the following equation (13).

Tc-(L-2d)/■ ... (13) Here, L
is the distance between the starting position and the stop position expressed in rectangular coordinates, d is the starting distance expressed in rectangular coordinates, and V is the speed setting switch 80 of the operation panel 78.
This is the speed common to each axis, that is, the composite speed manually set by . In an extreme example, that is, when the moving distance is very short, this constant velocity time Tc is
It may be 〇.

In the next step SIO, time t is set as an initial state.
=Q. Then, every minute time Δ, the target position P1
is calculated and commanded from the control device 72 to each servo circuit 50 to 68 as position information.

That is, in step S12, "t<Ta?J
to determine whether it is during startup time. If it is during the startup time, in the next step S13, the target position Pi(t) is determined based on the above-mentioned equation (2).
Calculate. At the same time, a point that will serve as a reference for the next calculation, that is, a constant velocity transition point Pli, is calculated in advance. Then, as time passes, in the judgment at step 314, t≦
Ta+Tc becomes Ta+Tc, and the movement shifts to constant velocity. During this uniform movement, the target position Pi(t) is successively calculated based on the formula (6) as shown in step S15. At the same time, in this step S15, a reference point for the next calculation, that is, a stop start point (corresponding to P2 in FIG. 4) P2+ is determined. As time passes thereafter, in the judgment in step S16, t≦2Ta+Tc, and the constant velocity movement ends and stopping begins. During such a standstill, in step S17, time t' is calculated according to the following equation (14).

t'-t-Ta-Tc (14) Next, successive target positions PI(t) are calculated based on the above-mentioned equation (4). At the same time, the starting position to be used as a reference point for controlling the next section is calculated.

As can be seen from the above explanation, during startup and floating, the successive position commands are approximated by trigonometric functions.
Therefore, starting and stopping operations are performed very smoothly.

6. In the above embodiment, step S13. In S15 and S17, reference points for the next calculation are calculated in advance.

However, this is only for convenience of calculation, and the target position P1 (t) may be calculated successively based on the time from the starting position POi in each step.

(Effects of the Invention) As described above, according to the present invention, each speed during acceleration and deceleration is made into a trigonometric function of time, and sequential position commands are performed based on the speed. In this case, the movement of the end effector or the controlled part becomes very smooth.

Therefore, even if a high inertia load is controlled to move, the influence of inertia is reduced, so positioning can be performed with relatively high precision. Furthermore, since vibration or impact during acceleration and deceleration can be prevented, there is no need to increase the rigidity of each part.

[Brief explanation of the drawing]

FIG. 1 is an illustrative diagram showing an example of an industrial robot that forms the background of the present invention and in which the present invention can be advantageously implemented. FIG. 2 is a block diagram showing an example of a control circuit for controlling the robot shown in FIG. 1. FIG. 3 is a graph for explaining the basic idea of this invention. FIG. 4 is an illustrative diagram showing the positions of each point. FIGS. 5A and 5B are flowcharts illustrating an example of operation or operation. In the figure, 10 is an industrial robot, 50 to 68 are servo circuits for each axis, 72 is a control device, and 7th is an operation panel. Patent Applicant ShinMaywa Industries Co., Ltd. Agent Patent Attorney Oka 1) Zen Kei (and 1 other person) 9 Procedural Amendment Stamp Commissioner of the Patent Office Kazuo Wakasugi 1, Indication of Case 1980 Patent Side No. 058645 2 , Name of the invention Industrial robot 3, Relationship to the case of the person making the amendment Patent applicant address 1-5-25 Kozone-cho, Nishinomiya-shi, Hyogo Name (235) ShinMaywa Industries Co., Ltd. Representative Tamagawa So
Next 4, agent e540 'm Osaka (06) 764
-5443 Address 5-30 Tanimachi, Higashi-ku, Osaka
Address 7, contents of amendment (1) "Sliding arm" in lines 15, 16, and 17 of page 4 of the specification is corrected to "sliding arm." (2) In the specification, page 5, line 15, line 17, line 18, line 20, page 6, line 2, line 3, 1 "downward" is corrected to "downward." (3) Formula (2) on page 10 of the specification is corrected as follows. Note P j" (V/2) ・((-sinωt/ω) 10t) 10po... (2) (4) [Starting point, P2
is the stop transition point. " is corrected to "It is a starting point." (5) [... is given] on page 10, line 17 of the specification. '', add the following sentence: ``P2 is the stop transition point.''that's all

Claims (1)

[Claims] 1. An industrial robot that moves an end-effector from a starting point to a stopping point, which approximates a set speed by a trigonometric function of time and issues a position command when starting and stopping. , Industrial Lojosoto. 2. When the distance from the starting point to the stopping point is less than or equal to twice the distance at the time of starting, another speed is determined and this other speed is approximated by a trigonometric function of time, according to claim 1. Industrial robot y'p. 3. The industrial robot according to claim 2, wherein the other speed is calculated based on the set speed and a constant coefficient. 4. The method according to Claims 1 to 3, wherein the positions are set sequentially based on the starting point, the first constant velocity transition point, and the constant velocity end point, respectively, during the first constant velocity movement at the time of starting and the time of stopping, respectively. The industrial robot described in any of the above.