JPS59123908A - Function generator - Google Patents

Abstract

PURPOSE:To set acceleration to an arbitrary value and to complete setting quickly by generating a comparative positional function using the first speed information of constant acceleration characteristics and the second speed information that approaches a target and follows deceleration characteristics independently. CONSTITUTION:In a period from time T0 to T1, a start of movement at an indicated speed Vc1 designated by a computer is commanded, and an output (a) of a counter 3 changes against the position of movement at a fixed acceleration alphac1. When the output (a) arrives at the indicated speed at time T1, the state is continued until time T2. When the indicated speed is commanded to Vc2 which is lower than Vc1, a comparator 5 switches a switch 7 to the down side, and a counter 3 starts counting. When the output (a) arrives at the speed Vc2, that condition is maintained until time T4. From the time T4, the speed is reduced from the speed Vc2 to the constant acceleration alphac1, and when arrived at a target position Xc, the speed becomes zero and stops.

Description

Detailed Description of the Invention (1) Technical Field of the Invention The present invention relates to a computer that creates a motion plan for a servo mechanism based on instructions from an operator, various information about the work environment, etc., and a computer that actually operates an object. The present invention relates to a function generator or servo control device that is located between a servo motor and manages the operation of the servo motor while performing low-level judgment and processing in a predetermined range based on instructions from a computer.

(2) Background of the technology In various machine tools, semiconductor machines, industrial robots, etc. that use servo mechanisms, low-level noise around the servo motors has recently become more important as the servo mechanisms have become faster and more multi-axis. For example, it is not possible to perform position control, speed control, etc. using a dedicated control device independent of a computer.

This type of control device outputs position information that instructs the servo motor to move as a continuous function that changes over time (referred to as a comparative position function), so in this sense it is also called a function generator. Call out.

In the positional relationship generated by this function generator, due to the physical constraint that the force generated by the motor (proportional to the acceleration component of the position function) is finite, it is required that the velocity function, which is its derivative, is also continuous. be done. In addition, the basic requirements when generating these functions are that the position function accurately leads to the desired target position, and that the speed is decelerated to zero when the target position is reached. 4 Ru. Furthermore, the magnitude of acceleration during acceleration and deceleration.

There is an upper limit value due to restrictions on the force generated by the motor, and if this value is exceeded, the motor will be unable to follow the motion.On the other hand, in order to perform high-speed operation, the acceleration must be as large as possible.

In order to meet these requirements, when approaching the target position and decelerating, the system is equipped with a mechanism that generates a deceleration function (deceleration curve) as a function of the difference between the current position and the target position. This is necessary as a function generator.

(3) Prior art and problems Recently, such function generators have been developed to provide real-time (
Not only can it generate a position function in real time (real time), but it can also generate a speed function that has a finite constant acceleration relative to the commanded speed that is arbitrarily commanded during movement, and follow the needle to reach the target position. There are also advanced models that shift to deceleration operation while satisfying the above-mentioned speed function and continuity conditions when approaching. (For an example, see Japanese Patent Application Laid-open No. 56-22106.) By the way, in order to control the servo motor more precisely, there has been a demand to create a function generator that can also command acceleration from a measuring device. One came. However, in the function generator mentioned above,
The mechanism that determines the speed function consists of two systems: one that follows the speed instructed by the computer, and the other that approaches the target position and creates a deceleration curve, so it is quite difficult to make the acceleration of both parts the same. Ta.

Furthermore, in order to increase the acceleration while keeping the same configuration, there are methods such as calculating and setting circuit constants that will provide the necessary acceleration for both the part that follows the commanded speed and the part that decelerates independently according to the deceleration curve. In that case, the problem was that it required a lot of time.

(4) Purpose of the Invention The purpose of the present invention is, in order to improve such problems, to provide a system for both the part that follows a series of commands even if a completely arbitrary acceleration is specified, and the part that decelerates autonomously according to the deceleration curve. The object of the present invention is to provide a function generator that always provides the same acceleration. In other words, the objective is to provide a function generator that can be set up in a circuit configuration that instantaneously obtains the required acceleration when only one parameter is given.

(5) Structure of the Invention In order to achieve this object, the function generator of the present invention has a constant acceleration characteristic for acceleration at startup or to follow a newly commanded command speed during movement. a first speed information generating means for generating speed information; and a first speed information generating means for generating a deceleration curve having constant acceleration characteristics as a function of the difference between a preset target position of the target object and a comparative position function at each instant during movement. It has two speed information generating means, and during the commanded speed following operation in which the movement follows the commanded speed from the start of movement, the first speed information generated by the first speed generating means is used to approach the target and autonomously move. a function generator that generates the comparison position function using second speed/reaction information generated by a second speed information generating means during autonomous deceleration to perform deceleration, the pulse train signal being supplied as one input; A first converting means and a second converting means output a pulse train with a frequency proportional to the product of the binary value supplied as the input of means for inputting a binary value proportional to the square root of the instructed acceleration;
a first counter means for outputting speed information of the second counter means;
The output pulse of the first converting means is supplied as one input of the converting means, and the first speed information from the first counter means is supplied as the other input during the instruction speed follow-up operation, and the independent means for supplying the second speed information during a target deceleration operation, and a second counter means for generating the comparative position function using a pulse train indicating each speed information from the second converting means as a clock source, First speed information with a constant acceleration specified in advance and second speed information.
It is characterized by generating speed information.

(6) Embodiment of the Invention An embodiment of the invention will be explained with reference to FIGS. 1 and 2. FIG. 1 shows a block diagram of the function generator of the invention, and FIG. It is an operation explanatory diagram.

In FIG. 1, the dotted line portion 20 is the function generation,
Similarly, 30 is a servo mechanism.

First, in the function generator 20, numerals 1 and 2 are binary rate multipliers (hereinafter referred to as BRM), which have a function of outputting a pulse train of a frequency corresponding to the product of the frequency of the input pulse train and a binary value.

3.4 is an up-down type counter, which counts up when a pulse is input to the up side and counts down when a pulse is input to the down side. 5 and 6 compare the size of the binary values, 〉.

A comparator that outputs the determination results of the three magnitude relationships of = and <; 7 is a changeover switch that switches the flow of the pulse train to the counter 3 according to the determination of comparator 5; %8 selects the binary value to BRJI2 according to the determination of comparator 6. 9 is a changeover switch that changes the flow of the pulse train to the counter 4 depending on the direction of movement; 10 is an absolute value calculation circuit that calculates the absolute value of the difference between the target position and the comparison position function Xr; 11.12 is a A square root ROM consisting of a read-only memory that stores a numerical table of input square roots.
%13 is an oscillator that oscillates a constant frequency pulse train, 1
4 is a D/A converter, and 15 is a sign selection circuit that gives negative, 7', and positive signs to the absolute value of acceleration.

The servo mechanism 30 has the same configuration as a known servo mechanism, including subtracters 31 and 32, an amplifier 33, a servo motor 34, an encoder 35, a counter 36 indicating the current position,
It consists of a closed loop controller 37.

Next, the operation shown in FIG. 1 will be explained together with the graph and waveform diagram shown in FIG. 2.

A computer (not shown) detects the position and speed of the object and
A target position Xc and a commanded speed Vc are given as decimal values.

Further, an instruction acceleration αC is given as a binary value based on the tracking characteristics of the object, the force generated by the servo motor, and the like.

Fig. 2 is a graph showing changes in the instruction contents of the instruction speed Vc and instruction acceleration αC.
C is αC1 (Fig. 2 (published), and the indicated speed Vc is T.

~T, Vc between , T, ~T5 is Vc (Fig. 2 (Al)), and between T6 and T81, the indicated acceleration αC is α et al. (Fig. 2 (Dl), the indicated The speed Vc is 1
■c3's between ゛6 and T6 Vc between T@ and Tto
4.T. ~stomach.

In the case where the gap is Vc (FIG. 2 (C1) is shown).

The following will explain each time segment.

(11 hours 'r='ro, that is, the value of the counter 3 at rest indicates zero, and the value of the counter 4 contains the value of the target position given during the previous movement, and the servo motor 34 is It is positioned in position.

Next, when a new target position χC is input from the machine, the absolute value calculation circuit 10 outputs the absolute value of the difference between the target position Xr (this value changes from moment to moment) and the target position Xc. And the square root ROMII is the square root f "π~Xr l
Output. Output a (zero) of counter 3 square root ROM
Since this is the output of the counter II, the comparator 6 switches the data selector 8 and guides the output of the counter 3 to the BRM2.

Next, when commanded acceleration αC=αC1 is given, αc.

A pulse train with a frequency proportional to the square root of is output from the HRMI.

(2) Directed speed following operation The commanded speed following operation is an operation in which the commanded speed Vc, , Vc, instructed by the computer is followed at a constant acceleration αc from the start of the operation.

(21) When "o < T <" + commanded speed Vc = Vc is given and movement start is commanded, the changeover switch 9 is operated and (Vc) Q
When , it is up side, Vc (when it is 0, it is down 1llI),
Counter 4 starts counting. Vc, =C) is the output a of the counter 3, so when the comparator 5 switches the changeover switch to the up side, the counter 3 counts the output pulses of the BRMI. Since the output pulse of the BRMI is proportional to F, the output a of the counter 3 indicates first velocity information that changes at a constant acceleration αC with respect to the moving position.

Since the output a of the counter 3 is further guided to the BRM 2, the rate of change of the value of the counter 4 increases or decreases depending on the value of the counter 3, and the comparison position Xr of the object is output.

Further, the commanded acceleration αc, which is a binary value, is converted into an analog quantity by the D/A converter 14 and supplied to the code selection circuit 15. On the other hand, the converter 5 is C) a as described above.
In this case, the selector switch 7 is switched to the up side, but at the same time, the sign selection circuit 15 is operated to make the sign positive. Therefore, the comparison acceleration αr output from the sign selection circuit 15 has a positive sign and a magnitude αC8 between To and T, as shown in FIG. 2B.

The servo mechanism 30 accelerates the foot (+αC,
) drives the servo motor 34 to move the object to the target position Xc.
Move towards.

This operating state continues until the output of the counter 3, that is, the first speed information a reaches the command speed Vc.

(2-2) 'r, ≦T (T.

At time T1, the output a of the counter 3 is the indicated speed Vc
When , a=C, the comparator 5 switches the selector switch 7 to the center terminal to stop the counting operation of the counter 3, and at the same time sets the sign of the sign selection circuit 15 to zero.

Therefore, between T and T2, the output a of the counter 3 indicates Vc as shown in FIG. 2A, and the sign selection circuit 15
The output αr becomes zero as shown in FIG. 2B.

The other parts continue the same operation as (2-1), so
The servo motor 34 continues to move the object toward the target position Xc while rotating at a foot speed Vc.

In this operating state, the computer sets a new commanded speed Vc at T,
Continues until commanded.

(23) Tt≦T(T3 When the instructed speed Vc is at time T, Vc is lower than Vc,
When the command is given to a) c, the comparator 5 switches the selector switch 7 to the down side to cause the counter 3 to start counting down, and at the same time, the sign selection circuit 15
The sign of the output αr of is made negative. Therefore, T, ~T3
In the meantime, the counter 3 generates first speed information that decelerates from the commanded speed Vc1 at a constant acceleration αC1 as shown in FIG. αc with negative sign as
A comparison acceleration αr having a magnitude of , is generated.

Since the other parts continue the same operations as in (2-1) and (2-2), the servo motor 34 has a constant acceleration (-αC
While decelerating and rotating with I), continue to move the object to the target position
Move it toward c.

In this operating state, the output a of the counter 3 is Vc.

The process continues until the new commanded speed ■ct is reached.

(2-4) Ts ≦T (T4 When the output a of the counter 3 slows down to the indicated speed v- at time T3, a = c, so the comparator 5 switches the changeover switch 7 to the center terminal and starts counting of the counter 3. The operation is stopped, and at the same time, the code of the code selection circuit 15 is set to zero.

Therefore, between 13 and 74, the output a of the counter 3 instructs ① as shown in FIG. 2A, and the code selection circuit 15
The output αr of will show zero.

Since the other parts continue the same operations as in (2-1) to (2-3), the servo motor 34 rotates at a constant speed ■4 and continues to move the object toward the target position Xc. .

This operating state is defined by the rate at which the square root R,OMx+ occurs,
That is, it continues until time T4 when the second speed information reaches 4. After time 1su 'T' 4, the next independent deceleration operation is started.

(3) Independent tracking operation (T4≦T≦Ts) The speed of the object when it reaches the target position Xc is zero, that is, the constant acceleration αC.

It is required that the speed decreases to zero and stops when the target position Xc is reached, while decelerating at the same time.

In order to satisfy this requirement, if the position of the object at time T4 is Xr4, then "21αC1°Xc, Xr
, (between 0, Vc, : 2 ac, lXc
-Xr, it is necessary that the following relationship holds true.

By the way, since the output value of the square root ROIVIII is proportional to the F value, the output value indicates the second velocity information of constant acceleration. Since the position of the object is far away from the target position Xc, this output is larger than the output a of the counter 3 before R4 as shown in FIG. 2A. Therefore, since a (b, comparator 6
switches the selector switch 8 to the upper side and supplies the output a of the counter 3 to the BRM 2.

T': 'l', when the second speed information from the square root ROM II reaches the output 8 of the counter 3, that is, Vc, a≧b, so the comparator 6 switches the changeover switch 8 to the lower side. BRM the output of square root ROMII
At the same time, the sign of the output αr of the sign selection (b) path 15 is made negative.

Therefore, between 1゛4 and T3, the square root box 11 outputs second speed information that decelerates at a constant acceleration αC0 as shown in FIG. 2A, and the sign selection circuit 15 outputs second speed information as shown in FIG. 2B. , generates a comparison acceleration αr having a negative sign and a magnitude of αC1.

T: At 'T', the object is at the target position Xc
When reaching Xc = Xr, the speed becomes zero and stops, and a series of operations for moving the object to the target position Xc with a constant acceleration αC1 is completed.

In FIG. 1, since the frequency of the pulse train at the position C actually moves the counter 4 up/down L''C, it is always proportional to the magnitude of the velocity of the counter 4, regardless of the change in the commanded acceleration αC.

On the other hand, the speed information in "c1, B, Vc" means that when the value of the commanded acceleration αC changes, the magnitude of the motor speed that is meant for the same binary value changes. In other words, the scale changes.This is due to the input pulse frequency and A, B in BRM2.
This is because the product of the binary data of , Vc becomes the pulse frequency of C. Once, the correspondence (conversion) between the binary values of A, B, and Vc and the actual speed (rod/s) is (binary values of A, B, and Vc) = --(actual speed rod/5)K -Tπ. At this time, the three speed information A, B, and Vc are connected by COMP5 and COMP6, so they have the same scale. Further, 4-1 is the magnitude of the actual velocity (rod/s) for 1 bit of the binary value, which is the velocity resolution, and is proportional to Lπ. K is the product of the position resolution (of the counter 4) and the oscillation frequency of the oscillator 13, and is a constant value.

In the present invention, the value of αC cannot be changed during movement (the actual speed is directly proportional to 17 J, so the speed becomes discontinuous at that point), so the value of αC is small (at least one time). A while moving.

B, Vc is l which is proportional to the speed, so in this sense A
*B, Vc was called velocity. Furthermore, in many cases, the present invention is used to output αC only once in an initial setting. Particularly in the case of an articulated robot, the function generator sets αC to a value that is close to the acceleration limit in order to quickly follow the commanded speed Vc. Acceleration control of the entire robot.

Performed in a rectangular coordinate system (x-y-z) that integrates all axes,
This is because the fourth method is often transmitted to the function generator of each axis in the form of a change in the indicated speed. (If the acceleration on each axis is too limited, the trajectory will be incorrect.) Of course, αC may be changed for each movement.

In this case, the computer refers to the conversion table to binary value data (K. It is a good idea to rewrite the value of this conversion table at the same time as setting the command acceleration αC, and it will not cause any trouble.

Fig. 2 (Q, (DJ instructs the commanded acceleration αC to a new α value, and further changes the commanded speed Vc to Vc → Vc4 → Vc
, the commanded speed follow-up operation (between T1 and 1゛) when a command is given to move the object to the target position by increasing and decreasing,
It shows the independent deceleration operation (between T11 and 1 and 2) and the change in the comparative acceleration αr. The operation is the same as in the case of FIG.

Note that the servo motor mechanism 3o can output the comparison acceleration function αr as a feedforward signal in order to improve the response of the closed loop control system. Further, if the servo motor is a pulse motor, it can be driven in the same way by guiding up pulses and down pulses, which are the inputs of the counter 4, to it.

(7) Effects of the Invention According to the present invention, the acceleration can be set to an arbitrary value for the function generator, and the setting can be completed almost instantaneously. Furthermore, it is possible to easily realize a function generator that constantly generates the same heavy acceleration both during the instructed speed follow-up operation and during the independent deceleration operation.

Because of these characteristics, the present invention can be applied to a function generator that operates at a limit acceleration specific to each servo mechanism, such as when servo mechanisms with different characteristics are connected to the same function generator. It can be used when setting up the acceleration from a computer using the initial setting values, or when using the same servo mechanism, and when you want to freely select the acceleration according to the nine work steps.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the function generator of the present invention, and FIG. 2 is a block diagram of the function generator of the present invention.
Generation of the function generator of the present invention. It is a graph and a waveform diagram of a moving speed relationship and a comparative acceleration function. 1.2 is Binary Rate Multiplier (BRM)
%3 and 4 are up/down type counters. 5.6 is a comparator, 7 is a changeover switch, 8 is a data selector, 9 is a changeover switch, 10 is an absolute value calculation circuit,
11.12 is a square root ROM that outputs the square root of the input, 1
3 is an oscillator, 14 is a D/A converter, 15 is a code selection circuit, 2o is a function generator, 30 is a servo mechanism, 31
, 32 is a subtraction chair, 33 is an amplifier, 34 is a servo motor,
35 is an encoder, 36 is a counter, and 37 is a closed loop controller. Patent applicant Fujitsu Ltd. Representative Patent Attorney Akira Yamatani

Claims (1)

[Claims] A first speed information generation means that generates speed information having constant acceleration characteristics for acceleration at startup or to follow a newly commanded command speed during movement; It has a second speed information generating means that generates a deceleration curve having constant acceleration characteristics as a function of the difference between the target position and the comparison position function at each instant during movement, and performs an operation that follows the commanded speed from the start of movement. During the instructed speed following operation, the first speed information generated by the first speed generation means is used, and during autonomous deceleration when approaching the target and autonomously decelerated, the second speed information generation means generates the second speed information. A function generator that generates the comparison position function using velocity information, and outputs a pulse train with a frequency proportional to the product of a pulse train signal supplied as one input and a binary value supplied as the other input. a first conversion means, a second conversion means, a means for inputting a constant frequency pulse train and a binary value proportional to the square root of the commanded acceleration commanded from a computer to the first conversion means; a first counter means for outputting the first speed information that follows the commanded speed using the output pulse train of the conversion means as a clock pulse source; means for supplying an output pulse, and supplying, as the other input, first speed information from the first counter means during the instructed speed following operation, and supplying the second speed information during the self-sustaining deceleration operation; , a second counter means for generating the comparison position function using a pulse train indicating each velocity information from the second conversion means as a clock source, the first velocity information having a predetermined constant acceleration; A function generator characterized in that it generates second velocity information.