JPH02308311A - Interpolation speed commanding method for multijoint robot - Google Patents

Abstract

PURPOSE:To smoothly operate a multishaft robot at a realizable maximum speed even in the vicinity of a peculiar point by setting the speed command value at each sampling time so that one joint is operated at an about maximum allowable angular speed and the other joints are operated more slowly. CONSTITUTION:Plural interpolation points which the front end of an arm passes are set between an operation start point and an operation target point, and the speed command value at each sampling time is so set that one joint is operated at an about maximum allowable angular speed and the front end of the arm passes the locus defined by interpolation points and the other joints are operated more slowly. The angular speed of each joint is lower than an allowable value and the movement speed of the front end of the arm is maximum in the range of the joint allowable angular speed while the front end of the arm in moved on the locus defined by interpolation points from the operation start point to the operation target point, and oscillation, runaway, and the reduction of the operation speed of the front end of the arm are prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an improvement in a method for creating linear motion command values for an articulated robot.

(Prior Art) When the tip of the arm of a conventional articulated robot is program-controlled, as shown in FIG. 14, a plurality of points ('ao, at...
・an) were taken as interpolation points at equal intervals, the tip of the arm passed through each interpolation point, and the movement of the arm between each interpolation point was arbitrary so that the robot could easily move.

(Problem to be Solved by the Invention) However, in the above method, the equal spacing in the Cartesian space in which the arm tip moves does not correspond to the equal spacing in the joint angle space of the robot, as shown in FIG. An angular velocity exceeding the maximum allowable angular velocity is required when the arm passes near a fixed singularity.

Naturally, the robot cannot follow such movement commands, which can cause vibrations and runaway behavior. In order to prevent such vibrations, the operating speed between interpolation points is considerably reduced.

In Fig. 15, A is the movement starting point, B is the movement target point, and 0
are the fixed points of the arm, and A2 and A2 are the first and second links of the arm.

An object of the present invention is to provide a method for creating motion command values for an articulated robot that prevents vibration and runaway of the robot and improves the operating speed between interpolation points.

(Means for Solving the Problems) A feature of the present invention is that in a command method for moving the tip of an arm of an articulated robot from a motion starting point to a motion target point according to a programmed axis track and speed, Set multiple interpolation points that the arm tip passes between, and any one joint moves at the maximum allowable angular velocity, and the arm tip passes through the axis trace defined by the interpolation point.
The present invention provides an interpolation speed command method for an articulated robot in which a speed command value at each sampling time is set so that other joints operate at a speed equal to or lower than the angular velocity.

(Operation) According to the present invention, one of the joints operates at the maximum allowable angular velocity, and the other joints operate at the angular velocity or less. The moving speed of the arm tip is determined by the maximum allowable angular velocity of the joint.

Therefore, when the arm tip moves along the trajectory defined by the interpolation point from the motion starting point to the motion target point, the angular velocity of each joint is below the allowable value, and the moving speed of the arm tip is within the range of the joint's allowable angular velocity. is the largest.

Therefore, vibration and runaway are prevented, and the operating speed of the arm tip is not significantly reduced, achieving the object of the present invention.

(Example) FIG. 1 is a flowchart for creating the fastest angular velocity command value for linear interpolation according to the present invention. A method for creating the fastest angular velocity command will be explained below in accordance with this flowchart.

Assuming an n-axis articulated robot, the displacement and angular velocity of each joint are (θ1.θ3..., On), (θ1.θ
2. ..., On). The maximum allowable angular velocity of the joint is ω
, 8.

(a) Create a linear interpolation angular velocity command (δ8, θ2, . . . ) from the given operation start point to the end point. The method is the coordinate transformation θ, = f between the joint coordinate system (θ1, θ2..., On) and the Cartesian system (x, y).
, Ω, θ1. θ2. ..., θ. )by. For example, in the case of a SCARA type robot, it is given by the following equation.

These angular velocity command values are calculated at each sampling time, for example, every 20 vasac, and are held as a table.

(b) Maximum angular velocity δ at each sampling time:. ax
Find (δ2.δ2.+@It, e, ). (c) Correct the speed command value of each axis θi (i・1, 2, . . . , n) using the following formula.

Margin below 1 θj1 The meaning of this equation is that the absolute value of the angular velocity command value of the maximum angular velocity axis is ω,X, and the angular velocities of the other axes are corrected without changing the angular velocity ratio between the axes.

(d) Once the corrections at all sampling times are completed, the creation is complete.

The sampling time interval is converted using the following equation.

Here, Δt is the original sampling interval, Δt is the new graduate Linear interpolation is executed using (on) as the command value.

Below, we will show two examples of the fastest linear interpolation achieved by applying this method to a SCARA type (two-axis horizontal type) robot arm. The arm length of the robot is 200 mm for the first arm and 150 mm for the second arm.

The first example is point A (300°0
) to point B (50,200).

Figure 2 shows the posture of the arm every 0.1 seconds when linear interpolation is performed from A to B in 5 seconds.

FIG. 3 shows the temporal changes in X and y during the interpolation shown in FIG.

FIG. 4 shows 01.00 when interpolating FIG. 2. This is a change in θ2 over time.

This is an angular velocity command. It can be seen that the interpolation that took 5 seconds was completed in just over 1 second. However, the maximum angular velocity ω□8
= π/2.

FIG. 7 shows the movement of the arm when the fastest angular velocity command is used, the same as in FIG. 2, every <0.1 seconds. Since the number of lines is 11, the required time is about 1.1 seconds.

The second example is point A (50°-20
This is a case of linear interpolation from point B (0) to point B (50,200).

Figure 8 shows the posture of the arm when interpolating in 5 seconds, drawn every 0.1 seconds.

Fig. 9 shows the time change of X+V, and Fig. 10 shows θ1. It shows the change in θ2 over time.

It can be seen that the maximum angular velocity exceeds π/2 in seconds. In other words, a real robot cannot follow this command.

Figure 12 shows the fastest angular velocity command obtained by applying this method.
l\ θ□, θ2 are shown. Speed command value is maximum speed π/2
It can be seen that the operation is completed in about 2.5 seconds.

FIG. 13 depicts the movement of the arm when using the fastest angle command shown in FIG. 12 at intervals of <0.1 seconds, the same as in FIG. 8. As shown in Fig. 8, there is no place where the intervals are widened, and it can be confirmed that uniform movement is obtained.

(Effects of the Invention) As explained in detail above, according to the present invention, one axis always operates at the maximum allowable angular velocity during interpolation operation, and the remaining axis velocities do not exceed the maximum allowable angular velocity. It is possible to operate a multi-axis robot smoothly even in close proximity, and at the maximum achievable speed.

Although linear interpolation has been described in the embodiment, the idea of the present invention can also be applied to other interpolation methods.

[Brief explanation of drawings]

Fig. 1 is an operation flow for creating the fastest angular velocity command value according to the present invention, Fig. 2 is a diagram showing the movement of the arm during linear interpolation according to the present invention, and Fig. 3 is a diagram showing the time change of X+V in Fig. 2. The figure shown in FIG. 4 is θ1. FIG. 5 is a diagram showing the time change of θ2. FIG. 6 is a diagram showing the time change of the fastest angular velocity command value in FIG. 2. FIG. 7 is a diagram showing the movement of the arm at the time of the fastest angular velocity command. FIG. 9 is a diagram showing the movement of the arm in another example of operation. FIG. 9 is a diagram showing the time change of X+V in FIG. 8. FIG. 10 is a diagram showing the θ1. FIG. 11 is a diagram showing the time change of θ2. Figure 12 is a diagram showing the time change of θ2, Figure 12 is a diagram showing the time change of the fastest angular velocity command in Figure 8, Figure 13 is a diagram showing the movement of the arm at the time of the fastest angular velocity command in Figure 8, and Figure 14 is a diagram showing the time change of the fastest angular velocity command in Figure 8. FIG. 15 is a diagram showing a conventional linear interpolation operation, and is a diagram showing the movement of a conventional two-joint robot in the vicinity of a singular point. A: Operation starting point, B: Operation target point, AH, A2
;Arm, ao, at,...an;Interpolation point.

Claims (2)

[Claims] (1) In a command method for moving the tip of an arm of an articulated robot from a motion starting point to a motion target point according to a programmed axis track and speed, multiple interpolation points are used for the arm tip to pass between the motion origin and the motion target point. is set, and each sampling is performed so that one of the joints operates at approximately the maximum allowable angular velocity, the arm tip passes through the axis trace defined by the interpolation point, and the other joints operate at or below the angular velocity. An interpolation speed command method for an articulated robot, characterized by setting a speed command value at a time. (2) The angular velocity ■ of other joints is ■＿i=(■＿i/｜■＿j|)ω_m_a_x■＿i
is the i-axis interpolated angular velocity command value ■_j is the maximum angular velocity ω_m_a at the angular sampling time
2. The interpolation speed command method for an articulated robot according to claim 1, wherein _x is given by the absolute value of the angular velocity command value of the maximum angular velocity axis.