JP3339642B2 - How to determine the acceleration / deceleration time constant of the robot - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a robot teaching position,
The present invention relates to a method for determining an acceleration / deceleration time constant of a drive shaft affected by load inertia by a teaching posture.

[0002]

2. Description of the Related Art Generally, a robot performing a path operation performs acceleration / deceleration control to obtain a smooth motion when operating at a high speed. The acceleration / deceleration time constant for performing this acceleration / deceleration control is:
There are the following. 1) The acceleration / deceleration time constant at the minimum load inertia or the maximum load inertia is provided as a fixed parameter. 2) The distance from the drive shaft affected by the load inertia to the control point is calculated, and the approximate acceleration / deceleration time constant is determined from this distance using an equation. T = AL ² + D..., Where T: acceleration / deceleration time constant A: correction constant L: distance projected from the axis affected by load inertia to the control point on the ground D: minimum load inertia Acceleration / deceleration time constant at

[0003]

However, in the case of 1), it is difficult to determine the acceleration / deceleration time constant. For example, if the acceleration / deceleration time constant at the minimum inertia is used as a parameter, the acceleration / deceleration time is shortened, so that there is a problem of life. Conversely, if the acceleration / deceleration time constant at the maximum inertia is used as a parameter, the acceleration / deceleration time becomes longer, and thus the operation time becomes longer. Regarding 2), 1) is improved by considering the acceleration / deceleration time constant of the drive shaft affected by the load inertia. However, as can be seen by comparing FIGS. 5A and 5B, according to the equation, there is a case where there is a distance projected from the axis affected by the load inertia due to the position and orientation to the control point on the ground. In the case of b) where the distance is shorter, an acceleration / deceleration time constant with smaller load inertia is obtained. But in fact,
As can be seen by comparing the shaft lengths in FIG. 5, the load inertia is larger in b) than in a). in this way,
In the method 2), an inappropriate acceleration / deceleration time constant is determined depending on the form of the robot. Therefore, an object of the present invention is to simultaneously reduce the operating time at low load inertia and improve the life at high load inertia.

[0004]

SUMMARY OF THE INVENTION In order to solve the above problems, a method for determining the acceleration / deceleration time constant of a robot according to the present invention comprises a drive which is affected by load inertia depending on the position and attitude of a teaching point of the robot. For each axis, the mass and center of gravity of each axis of the robot are stored in advance as parameters, and the load
Determine the acceleration / deceleration time constant of the drive shaft from the value of inertia.
Equations are set in advance, and the robot operation start point and
And the load inertia of the drive shaft at the end point
Calculated using the above parameters, and the value of the load inertia
Then, the acceleration / deceleration time constant is determined using the above formula .

[0005]

According to the above-described method for determining the acceleration / deceleration time constant of the robot according to the present invention, when the taught point is interpolated in the path, each part of the parameter is set for the axis affected by the load inertia depending on the position and posture of the robot. The load inertia is determined from the mass, the position of the center of gravity, and the position of each axis at the operation start point, and the time constant during acceleration is determined. Further, the time constant at the time of deceleration is obtained by calculating the load inertia from the mass and the position of the center of gravity of each part of the parameters and the position of each axis at the operation end point. Then, the obtained acceleration / deceleration time constant acts to realize smooth and optimal acceleration / deceleration control during path interpolation.

In general, the relationship between life, acceleration, and inertia can be expressed by the following equation: τ = F (d ² θ / dt ² ) L _H = (τ _c / τ) ^X (C / N) Where τ is torque, F is load inertia, d ² θ / dt ² is acceleration, L _H is life, x is a constant that varies depending on the life target (for example, bearing), N is the rated rotation speed of the drive shaft, and C is the correction. Is a constant. From this equation, F and d ²
It can be seen that the life shortens as θ / dt ² increases. Further, it can be seen that the life becomes longer as F and d ² θ / dt ² become smaller. Therefore, in order to maintain a certain life, F
When d increases, d ² θ / dt ² needs to be reduced. When F is reduced, d ² θ / dt ² may be increased.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for determining a robot acceleration / deceleration time constant according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an example of a system for implementing the present method. In the figure, 11 is a position teaching unit, 12 is a position storage area, 13 is a parameter storage area, 14 is an acceleration / deceleration time constant calculation unit, Reference numeral 15 denotes an interpolation operation unit, and reference numeral 16 denotes a drive unit.
FIG. 2 is a skeleton diagram showing the teaching points and the form of the robot. The teaching point (S) is the operation start point, and the teaching point (E) is the end point of the operation. θ _2S is the position of the start point of the second axis, θ
_3S is the position of the start point of the third axis, θ _2E is the position of the end point of the second axis, and θ _3E is the position of the end point of the third axis.

FIG. 3 is an external view of a robot used in this embodiment, which is composed of three axes. (1) the first shaft having a degree of freedom in the vertical (z ₀ axis) direction with respect to the ground 1. (2) z provided at the tip of the first shaft 1 and perpendicular to the z ₀ axis
_A second axis 2 having a degree of freedom about _one axis. (3) provided at the distal end portion of the second shaft 2, z ₁ parallel to the axis z
Third axis 3 having degrees of freedom around _two axes. As described above, each axis of the robot shown in FIG. 3 has one degree of freedom, and the robot has a total of three degrees of freedom. And
The axis affected by the load inertia is the first axis 1.
The distance from the rotation center P ₂ of the second shaft 2 to the center of gravity P _2G of the arm of the second shaft 2 is R ₁ , and the distance from the rotation center P ₃ of the third shaft ₃ to the third
The distance between the center of gravity P _{3 G} of the arm of the shaft 3 is defined as R ₂ . The work is attached to the tip of the second shaft 2 and the distance from the center of rotation P ₃ of the third shaft ₃ to the center of gravity P _WG of the work is R ₃ ,
The mass of the arm of the shaft 2 is W ₂ , the mass of the arm of the third shaft 3 is W ₃ , and the mass of the work is W. These R ₁ , R ₂ , R
₃ , W ₂ , W ₃ , and W are preset as parameters in the parameter storage area 13 of FIG. Then, as a preparation before starting the operation, the acceleration / deceleration time constant calculation unit 14 determines the acceleration / deceleration time constant.

First, the teaching position taught by the position teaching unit 11 is stored in a position storage area 12. From the position storage area 12, θ _2S and θ _{2 at the} operation start point are _read.
3S (see FIG. 2) is given to the acceleration / deceleration time constant calculator 14. The acceleration / deceleration time constant calculator 14 calculates this data as θ ₂ ,
The load inertia F _S is obtained by substituting into θ ₃ and performing calculation.
It is to be noted that parameters stored in the parameter storage area 13 are used in advance.

F _S = 4 gW ₂ (R ₁ cos θ ₂ ) ² +4 gW ₃ (R ₁ cos θ ₂ + R ₂ cos θ ₃ ) ² +4 gW (R ₁ cos θ ₂ + R ₂ cos θ ₃ + R ₃ cos θ ₃ ) ² - where g is the gravitational acceleration, the theta ₂ angle of the second shaft, the theta ₃ is the angle of the third shaft.

Next, the above F _S is substituted for F in the equation, and a time constant T _S during acceleration is calculated and determined. T = aF + b Here, T is a time constant, a is a correction value of the time constant, and b is an offset value of the time constant, and sets an acceleration / deceleration time constant at the time of minimum load inertia. From the above description, the equation for manipulating d ² θ / dt ² by F is an equation, and the relationship between T and d ² θ / dt ² is d ² θ / dt ² = V / T. Where V is the speed. Therefore, it is understood that d ² θ / dt ² decreases as T increases. Therefore, it is an equation to find T corresponding to F.

[0012] Next, given the theta _2E and theta _3E at the operation end point, when the time of substituting F _E deceleration F of Formula seeking load inertia F _E performs calculations substituted into theta _2, theta ₃ of formula Constant T
_Ask for _E. The acceleration / deceleration time constants T _S and T _E thus obtained
At the start of operation, acceleration is performed according to T _S , and at the end, T
Decelerate according to _E and end the operation. FIG. 4 is a graph showing the operation state of the first axis, in which the vertical axis represents speed and the horizontal axis represents time. From the end of acceleration to the start of deceleration, the robot is driven at the interpolation speed calculated by the interpolation calculation unit 15 in FIG. As described above, according to the present embodiment, the acceleration / deceleration time constant corresponding to the load inertia is obtained. If the load inertia is large, the acceleration / deceleration time constant is large, and if the load inertia is small, the acceleration / deceleration time constant is small. Is obtained, and the acceleration / deceleration control of the robot is performed with this acceleration / deceleration time constant, so that the life can be ensured at a high load and a speedy operation at a low load can be obtained.

Although the mass of the workpiece is a parameter in the above description, the maximum payload is generally set. However, the robot does not always operate at the maximum payload, so by setting the payload in the robot language, an accurate load inertia is obtained, and the acceleration / deceleration time constant based on it is obtained. Further, the operation performance is improved.

[0014]

As described above, according to the method for determining the acceleration / deceleration time constant of the robot according to the present invention, the mass and the center of gravity of each part are given as parameters, and the position of each drive shaft taught at each teaching point is given. By calculating the load inertia and determining the optimal acceleration / deceleration time constant based on the load inertia, it is possible to shorten the operation time at the low load inertia and to improve the service life at the high load inertia.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a skeleton diagram showing a teaching position and a form of a robot for explaining the embodiment.

FIG. 3 is a configuration diagram of a robot used in the present embodiment.

FIG. 4 is a velocity diagram of a first axis when operated in the present embodiment.

FIG. 5 is a diagram for explaining a problem of the conventional control;
FIG. 4B is a diagram of the robot when there is a distance projected from the axis affected by the load inertia due to the position and posture to the control point on the ground, and FIG.

[Explanation of symbols]

1 1st axis, 2nd axis, 3rd axis, 11 position teaching section, 12 position storage area, 13 parameter storage area, 14 acceleration / deceleration time constant calculation section, 15 interpolation calculation section, 1
6 Drive

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-335410 (JP, A) JP-A-4-30203 (JP, A) JP-A-2-12407 (JP, A) JP-A-62-162 126881 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G05B 19/18-19/46 B25J 3/00-3/04 B25J 9/10-9/22 B25J 13/00 -13/08 B25J 19/02-19/06 G05D 3/00-3/12

Claims (1)

(57) [Claims] For a drive axis which is affected by load inertia depending on the position and orientation of a teaching point of a robot, the mass and center of gravity of each axis of the robot are stored in advance as parameters, and the load inertia is calculated from the load inertia value. Deceleration time constant
Is set in advance and the operation of the robot is started.
Load inertia of the drive shaft at start and end points
Calculate the shear using the above parameters and calculate the load inertia.
Determine the acceleration / deceleration time constant from the value of shear using the above formula.
Deceleration time constant determination method of the robot, characterized in that that.