JPS62143104A - Method for controlling position of robot - Google Patents

Abstract

PURPOSE:To increase the rate of acceleration/deceleration when a load is small to execute positioning within a short period by driving only any one of plural motion axes at its maximum output only for a fixed period immedately after the start of operation to measure an angular acceleration. CONSTITUTION:The angles DELTAtheta1, DELTAtheta2 of rotation of the 1st and 2nd motors 3, 2 are calculated from the teaching data of the start and end points of PTP operation. If ¦DELTAtheta1¦>¦DELTAtheta2¦ is formed, the speed command omegar1 of the 1st motor 3 is set up to the maximum angular speed omega1max and the speed command omegar of the 2nd motor 2 is set up to '0'. When an operation time is t<DELTAt, the 1st motor 3 is accelerated at the maximum output by receiving the step-like speed command values and the angular acceleration of the 1st motor 3 at that time is measured. When the operation time becomes t>=DELTAt, the load W of the tip of the robot is calculated, decelerations beta1, beta2 are calculated based on a corresponding table between the load and deceleration to supply the speed commands omegar1, omegar2. When the load is small, the operation can be attained at a large acceleration/deceleration, so that positioning control can be attained within a short period.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for controlling the position of a robot having a multi-degree-of-freedom motion mechanism, which has a plurality of motion axes and each motion axis is driven by an individual axis servo system. It is something.

Conventional technology Conventionally, position control (hereinafter FT
The P motion) is performed at a constant acceleration/deceleration rate predetermined for each motion axis, and is controlled at an acceleration/deceleration rate that allows each motion axis to follow when the load at the tip of the robot is maximum.

In other words, in order to control robots with different load conditions, it is necessary to adjust to the one that is difficult to accelerate or decelerate, that is, the one that takes time to accelerate or decelerate, and there is a problem that it is not possible to stop and position in the shortest time. Ta.

On the other hand, as an attempt to stop the motor in the shortest possible time depending on the load condition, there is an attempt to stop the motor in the shortest possible time, as disclosed in Japanese Patent Laid-Open No. 57-160378. In this disclosed technology, the minimum position θ is determined from the angular acceleration αM determined from the motor torque TM and the moment of inertia JM, and the maximum speed command ω1. (=ω27(2
αM)) and position command θ. Compare θ. ≧θ. If so, by measuring the predetermined maximum speed command ω1 and the angular acceleration at the time of acceleration, which is the beginning of the position control operation, calculate the position θd at which deceleration should start and the speed command ωNk from that position to the operation end point. and decelerates according to the command. Also, θ. 〈θ. If so, deceleration is performed using predetermined θd and ωN or θd and ωN calculated during the previous position control.

That is, the angular acceleration measured during acceleration is used as a deceleration rate that can follow the external load during the operation.

Based on this deceleration rate, the position θd at which deceleration should start and the speed command ωNt from that position to the operation end point are calculated.

Problems to be Solved by the Invention However, when this disclosed technology is applied to an articulated robot, the moment of inertia around each axis of motion changes depending on the posture of the articulated robot, and the drive torque of a certain axis of motion changes. Since it may affect the motion of other motion axes, it is difficult to grasp the external load state directly from the angular acceleration measured near the start of motion, and it is not possible to use the measured angular acceleration as a total deceleration rate for position control. could not. Therefore, it has been impossible to completely change the acceleration/deceleration rate in accordance with the external load of the robot and to increase the acceleration/deceleration rate when the load is small to perform positioning in a short time.

In view of the above-mentioned problems, the present invention uses a relatively simple method to grasp the external load on the robot, change the acceleration/deceleration rate according to the external load, and increase the acceleration/deceleration rate when the load is small. The present invention provides a position control method for a robot that performs positioning.

Means for Solving the Problems In order to solve the above-mentioned problems, the robot position control method of the present invention is such that during FTP operation of the robot, only for a certain period of time Δt immediately after the start of the operation, the plurality of motion axes of the robot are controlled. Operate only one of the axes at the maximum output, measure the angular acceleration α, calculate the moment of inertia I = T/α around this axis with respect to the torque T of this axis, and further calculate the robot's moment of inertia from The tip load W is calculated, and the deceleration rate β of each axis is determined according to the calculated tip load W.

Effect The present invention uses the method described above to provide a fixed period of time J immediately after the start of operation.
Only during the period t, only one of the multiple operating axes is operated at maximum output.

The equation of motion between Δ of this motion axis is generally (J(θ)
It can be expressed in a simple form as +W(l(θ))α=T. If we assume that the angular change of the operating axis between Δ is minute, then I(θ
) and l(θ) can be calculated in advance using each joint angle θ before the start of motion, so the tip load can be easily calculated from the moment of inertia I=7(θ)+W(l(θ))2=work α. can be calculated. For the tip load W,
If the maximum possible deceleration rate β of the robot is determined in advance, the deceleration rate can be changed according to the external load, and when the load is small, the deceleration rate can be increased to perform positioning in a short time.

EXAMPLE Hereinafter, an example of the present invention will be described based on the accompanying drawings.

Figure 2 shows a direct drive type robot to which the robot position control method of the present invention is applied. A first prime mover 3 installed with a meticulous and independently drivable means, a support 4 for holding the second prime mover 2 and the first prime mover 3, and a direct connection to the output shaft of the second prime mover 2. a second arm rotatably coupled to the other end of the first arm 6; and a third arm 7 rotatably coupled to the other end of the second arm 6. , is rotatably coupled to a rotating shaft 8 located at a third arm 7± separated from the coupling point of the second arm 6 and the third arm 7 by the same distance as the length of the first arm 5, and the other end thereof is A 47th arm 9 which is directly connected to the output shaft of the first prime mover 3 and has the same length as the 27th arm 6, and the third arm 7 and the 47th arm 9.
A hand 10 having vertical and rotational movement axes is provided on the third arm on the opposite side of the connection point between the second arm 6 and the 37th arm 7, and this hand 10 is driven. For this purpose, a rotary drive, a town motor 11 and a vertical drive motor are arranged between the connection point between the third arm 7 and the fourth arm 9 and the connection point between the second arm 6 and the third arm 7. It has 12 points. Further, the rotational movement of the hand 1o is performed by transmitting the output of the rotary drive prime mover 11 by a toothed belt (not shown), and the vertical movement of the hand 1o is performed by transmitting the output of the rotational drive prime mover 11 by the toothed belt and the output direction of the vertical drive prime mover 12. This is done by transmission using a ball screw (not shown).

In this embodiment, the robot is moved in a horizontal plane (
Since the robot position control method of the present invention is applied only to position control in the I-y plane (assumed to be the x-y plane), we will first consider the motion system that is the basis of the movement in the I-y plane. The basic configuration of the robot is shown in Figure 3, and the equation of motion is as follows.

(■11+Wlj) Tei (112-M2 (Js-Jl))
cos(θ1-θ2"2+('12-"2(13-41
)) sin(θ1-θ2) '2=”l ”” ””■
(IZ'+W"3-11)2)'OL!"012-W1
2C13-11)) CO3 (θ, 4゜) 驇-(112-
W12(t3-61/5・ko(114°so'I=T2・
......■. Here ■, 1: 1st: Effective moment of inertia around the motive, 2
: Mutual moment of inertia between the first prime mover and second prime mover 12 □: Effective moment of inertia around the second prime mover W: Robot tip end load mass 11: Length e2 of first arm 5: lX2 arm 6 and fourth arm 9 Length 13:
Length T1 of the third arm 7: Output torque T2 of the first prime mover 3: Output torque of the second prime mover 2. According to equations (1) and (2), the output torque T1 of the first prime mover is generated, and the angle θ1. Angular velocity d1.
It can be seen that when the angular acceleration °θ'1 occurs, the interference inertial force and centrifugal force shown by the second and third terms on the left side of equation (2) occur, and this influence affects the rotation angle θ2 of the first arm. However, as mentioned above as a means to solve the problem, FTP
Since only either the first prime mover or the second prime mover is operated for a period of Δt after the start of operation, consider the equation of motion for the first axis of motion. If it works]......(J22+W(13-11)2)'0°2="2 [
When only the second prime mover operates]...■. At the start of PTP operation, the prime mover reaches a maximum torque of 1m.
ae A is controlled to output 2 maz, and Δ
If the angular acceleration)° or 72 is measured between

Once the robot tip load W is determined, it is only necessary to determine a deceleration rate β that can be followed according to the load.

Next, for the robot shown in FIG. 2, a deceleration rate β that can follow the robot tip load W is determined. Figure 4 shows the maximum positive torque T applied to the first prime mover 3 and the second prime mover 2 at the same time.
1! na = 100N-m, T2ma = 1100N-
occurs, the angular acceleration of the first prime mover -°1 (the fourth
Figure (a)) and the angular acceleration of the second prime mover 1°2 (Figure 4 (b)
)). On the horizontal axis,
The distance r from the first prime mover and second prime mover to the robot tip load W is taken as an expression of the robot's posture (see FIG. 3).

Angular acceleration 'e'1. 'e°2 decreases as the load W increases, and also decreases as the distance r increases. Figure 6 shows the maximum positive torque T = 100N- for the first prime mover 3.
m.

maw Maximum negative torque on the second prime mover 2 - 2max = -10
When 0N-m occurs, the angular acceleration of the first prime mover)°
1 (Fig. 6(a)) and the angular acceleration of the second prime mover)°2 (in Fig. 6). The horizontal axis represents the distance r from the first prime mover and second prime mover to the robot tip load W, as in FIG. 4.

Angular acceleration 'e'1. 'e'2 decreases as the load W increases, and increases as the distance r increases. From Fig. 4 and Fig. 6, the direction of the torque of the two prime movers and the distance I
The angular acceleration that can be generated in accordance with the load W is determined regardless of the load W. The correspondence table between this load and acceleration is shown in Table 1 below. In this embodiment, the external load is roughly detected in three types: 06#1121&, and the corresponding deceleration rate β is also set to 3.

Once the deceleration rate is determined, positioning can be achieved in a short time by decelerating the speed command value ω1 with respect to the angle θ from the operation end point by .

FIG. 1 shows a procedure for obtaining a speed command ω in the robot position control method of the present invention. First, the rotation angles Δθ1 and Δθ2 of the first prime mover and the second prime mover or the fourth arm and the first arm are determined from the teaching data of the start point and end point of the FTP operation.

If 1Δθ11>1Δθ21, the speed command ωr1 of the first prime mover is the maximum angular velocity ω determined from the characteristics of the first prime mover, and the speed command 1ml of the second prime mover! IX ω1°=0. While the operating time t is t<Δt, the first prime mover receives the step-like speed command value and accelerates at the maximum output, and the second prime mover does not operate. The angular acceleration 71 of the first prime mover at this time is measured and used for load calculation.
If Δθ,1<1Δθ21, the second prime mover is operated conversely and the angular acceleration)2 is measured.

Note that the reason for detecting angular acceleration by moving the axis with a larger operating angle first is that the axis with a larger operating angle often has a longer operating time. This is because the FTP operation time of is determined.

In other words, if an axis with a large operating angle and a long operating time is moved with a delay, the FTP operating time of the robot will become longer.

When the operating time t≧Δt, the measured r゛1 or 1°
Using the value of 2, the tip load W of the robot is determined from Equation 0 or Equation 0, and the deceleration rates β1 and β2 are determined from the correspondence table of load and deceleration rate shown in Table 1 below. Then, the speed command ωr1. ω, 2 as ωr1 = m'n("1 ma
X'u)ωr2"m"(ω2max, Ewa7
).

As described above, according to this embodiment, the rotation angle of the first prime mover and the second prime mover whose absolute value is larger is selected first.

Since the acceleration is determined by operating the robot by the amount of Δ, and the load W at the tip of the robot is determined, the load calculation formula can be simplified to 0 formula or 0 formula. In addition, the deceleration rate β corresponds to the load W (see 1 below).
(shown in the table), and when the load is small, operation can be performed at a large acceleration/deceleration rate, making it possible to control the position in a quasi-minimum time.

Table 1 Effects of the Invention As described above, the present invention measures the angular acceleration by moving only one axis among a plurality of operating axes during the Δ at the start of FTP operation,
The robot tip load is determined from this detected angular acceleration, and
Since the deceleration rate is changed in accordance with the load, operation can be performed at a large acceleration/deceleration rate when the load is small, making it possible to control the position in a short time.

[Brief explanation of drawings]

FIG. 1 is a basic configuration diagram of a robot in an embodiment of the robot according to an embodiment of the present invention, and FIGS.
The figure is a graph showing acceleration at maximum output. 2... Second prime mover, 3... First prime mover, 5... First arm, 6... Second arm, 7...・Third arm, 8...Rotation axis, 9...Fourth arm. Name of agent: Patent attorney Toshio Nakao and one other person θf
(z fo"rd/S' ) -bustling prisoner θ'l (X igt lie cold 1) 141 (x □trru175t)E,
cr' prisoner

Claims (2)

[Claims] (1) The tip position and posture of the robot, which is a multi-degree-of-freedom motion mechanism that has multiple motion axes and each motion axis is driven by an individual axis servo system, are taught at the motion start and end points; When controlled based on data, only one of the multiple operating axes is operated at maximum output for a certain period of time Δt immediately after the start of operation, and the angular acceleration α is measured. Find the moment of inertia I=T/α around this operating axis for the torque T, then calculate the tip load W of the robot from the moment of inertia I, and set the deceleration rate β of each axis according to the calculated tip load W. A robot position control method characterized by determining the position of a robot. (2) The robot according to claim 1, characterized in that the axis to be operated during a certain period of time Δt immediately after the start of the operation is the operation axis that has the maximum amount of movement with respect to the taught operation. position control method.