JPH0361201B2 - - Google Patents

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 manages the operation of a 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 bonding equipment, 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. Processing such as position control,
Speed control and the like are performed by a dedicated control device independent from a computer.

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

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. Ru. Furthermore, the magnitude of acceleration during acceleration and deceleration has an upper limit due to constraints on the force generated by the motor, and if this is exceeded, the motor will no longer be able to follow.
On the other hand, in order to perform high-speed operation, the acceleration is required to be as large as possible.

In order to meet these requirements, it must be equipped with a mechanism that generates at least a deceleration function (deceleration curve) as a function of the difference between the current position and the target position when decelerating as it approaches the target position. is required as a function generator.

(3) Prior art and problems Recently, such function generators can not only generate position functions in real time while satisfying the above constraints for arbitrary movement commands, but also generate position functions during movement. The system generates a speed function with a finite constant acceleration for the specified speed that is arbitrarily commanded, and follows this, and when it approaches the target position, the speed function starts decelerating while satisfying the continuity condition. Some fairly advanced methods such as migration have also appeared. (For example, see Japanese Patent Application Laid-open No. 56-22106.) By the way, in order to control servo motors more precisely, there has been a demand for creating a function generator that can also command acceleration from a computer. Ta. However, in the above-mentioned function generator, the mechanism that determines the speed function has two systems: one that follows the speed instructed by the computer, and the other that follows the deceleration curve as it approaches the target position, so the acceleration of both is the same. It was quite difficult just to do so.

Furthermore, in order to change the acceleration while keeping the same configuration, circuit constants must be calculated and set to provide the necessary acceleration for both the part that follows the commanded speed and the part that decelerates independently according to the deceleration curve. However, this method had the drawback of requiring a large amount of time.

(4) Purpose of the Invention The purpose of the present invention is to improve such problems by providing a part that follows the designated speed even if an arbitrary acceleration is specified, and a part that decelerates autonomously according to the deceleration curve. The purpose of the present invention is to provide a function generator that always provides the same acceleration for both. In other words, the object is to provide a function generator that can be set up into 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 uses constant acceleration specialization for acceleration at startup or to follow a newly commanded command speed during movement. a first speed information generating means for generating speed information having a constant acceleration characteristic as a function of a difference between a preset target position of the target object and a comparison position function at each instant during movement; It has a second speed information generating means, and during a 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 become independent. a function generator that generates the comparison position function using second speed information generated by a second speed information generating means during self-sustaining 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 commanded acceleration; and first counter means for outputting the first speed information that follows the commanded speed using the output pulse train of the first converting means as a clock pulse source. The output pulse of the first converting means is supplied as one input of the second converting means, and the output pulse of the first converting means is supplied as the other input during the instruction speed following operation.
and means for supplying the second speed information during the self-sustaining deceleration operation;
a second pulse train that generates the comparative position function using a pulse train indicating each speed information from the converting means as a clock source;
The present invention is characterized in that it has a counter means and generates first speed information and second speed information having a constant acceleration specified in advance.

(6) Embodiment of the Invention An embodiment of the present invention will be explained with reference to FIGS. 1 and 2.

FIG. 1 shows a block diagram of the function generator of the present invention, and FIG. 2 is an explanatory diagram of its operation.

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

First, in the function generator 20, reference numerals 1 and 2 are binary rate multibliers (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 and 4 are up-down type counters,
When a pulse is input to the UP side, it counts up, and when a pulse is input to the DOWN side, it counts down. 5 and 6 are comparators that compare the sizes of binary values and output the results of three magnitude relationship determinations >, =, and <; 7 is a switch that switches the flow of the pulse train to the counter 3 based on the determination of comparator 5; Switch, 8 is determined by comparator 6.
A data selector selects a binary value to be sent to BRM2, 9 is a changeover switch that changes the flow of the pulse train to counter 4 depending on the direction of movement, and 10 is an absolute value calculation that calculates the absolute value of the difference between target position Xc and comparison position function Xr. 11 and 12 are square root ROMs consisting of read-only memories in which a numerical table of input square roots is stored; 13 is an oscillator that oscillates a constant frequency pulse train; 14 is a D/A converter;
5 is a sign selection circuit that gives negative, zero, and positive signs to the absolute value of acceleration.

Further, the servo mechanism 30 has the same configuration as a known servo mechanism, including subtracters 31 and 32, and an amplifier 3.
3, a servo motor 34, an encoder 35, a counter 36 that indicates the current position, and 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 calculator (not shown) detects the position and speed of the object and calculates the target position Xc and the indicated speed, which are binary values.
Give Vc. Further, a commanded acceleration αc consisting of a binary value is given from the following characteristics of the object, the force generated by the servo motor, etc.

Fig. 2 is a graph showing changes in the instruction contents of the instruction speed Vc and instruction acceleration αc. During the period T ₀ to T ₅ , the instruction acceleration αc is αc ₁ (Fig. 2B), and the instruction speed Vc is from T ₀ to T 5.
Vc ₁ between T ₂ and Vc ₁ between T ₂ and _{T 5} (second
(Fig. A), the commanded acceleration αc is αc ₂ between T ₆ and _{T 12} (Fig. 2 D), and the commanded speed Vc is Vc ₃ between T ₆ and _{T 8} ,
A case is shown in which the voltage is Vc ₄ between T ₈ and _{T 10} and Vc ₅ between T ₁₀ and T ₁₂ (FIG. 2C).

The following will explain each time segment.

(1) Time T = T ₀ , that is, at rest The value of counter 3 indicates zero, and the value of counter 4 contains the value of the target position given during the previous movement, and the servo motor 34 is moved to the previous position. is positioned.

Next, when a new target position Xc is input from the computer, 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 ROM 11 outputs its square root √|~|. Output a of counter 3
Since (zero)<output b of the square root ROM 11, the comparator 6 switches the data selector 8 and guides the output of the counter 3 to the BRM 2.

Next, given the commanded acceleration αc = αc ₁ , αc ₁
BRM1 is a pulse train with a frequency proportional to the square root of
is output from.

(2) Instruction speed following operation The instruction speed following operation is an operation that follows the instruction speeds Vc ₁ and Vc ₂ instructed by the computer from the start of operation at a constant acceleration αc ₁ .

(2-1) T ₀ < T < T ₁ When the commanded speed Vc=Vc ₁ is given and movement start is commanded, the changeover switch 9 operates (Vc>0
(up side when Vc<0, down side when Vc<0), counter 4 starts counting. Since Vc ₁ = C > output a of counter 3, when comparator 5 switches the changeover switch to the UP side, counter 3
Count the output pulses of BRM1. Since the output pulse of the BRM 1 is proportional to √ ₁ , the output a of the counter 3 indicates first velocity information that changes at a constant acceleration αc ₁ 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
Output.

In addition, the commanded acceleration αc ₁ consisting of a binary value is D/
The A converter 14 converts it into an analog quantity and supplies it to the code selection circuit 15. On the other hand, the comparator 5 switches the changeover switch 7 to the up side when c>a as described above, but at the same time operates the sign selection circuit 15 to make the sign positive. Therefore, the comparison acceleration αr output from the sign selection circuit 15 is
As shown in FIG. 2B, the period between T ₀ and T ₁ indicates an acceleration with a positive sign and a magnitude αc ₁ .

The servo mechanism 30 drives the servo motor 34 at constant acceleration (+αc ₁ ) according to a known operation, and moves the object toward the target position Xc.

This operating state corresponds to the output of counter 3, that is, the first
The speed information a continues until the speed information a reaches the command speed _Vc1 .

(2-2) T ₁ ≦ T < T ₂ At time T ₁ , when the output a of the counter 3 reaches the indicated speed Vc ₁ , a=c, so the comparator 5 switches the changeover switch 7 to the center terminal. The counting operation of the counter 3 is stopped, and at the same time, the code of the code selection circuit 15 is set to zero. Therefore, between _T1 and _T2 , the output a of the counter 3 indicates _Vc1 as shown in FIG.
The output αr will be zero as shown in FIG. 2B.

Since the other parts continue the same operation as in (2-1), the servo motor 34 continues to move the object toward the target position Xc while rotating at a constant speed _Vc1 .

This operating state continues until the computer commands a new commanded speed Vc ₂ at T ₂ .

(2-3) T ₂ ≦T < T ₃ Indicated speed Vc is lower than Vc ₁ at time T ₂ Vc ₂
Since a>c holds, the comparator 5 switches the changeover switch 7 to the down side, causes the counter 3 to start counting down, and at the same time makes the sign of the output αr of the sign selection circuit 15 negative. Therefore, between T ₂ and T ₃ , the counter 3 generates first speed information that decelerates from the commanded speed Vc ₁ at a constant acceleration αc ₁ , as shown in FIG. 2, using the output pulse train of the square root ROM 11. and code selection circuit 1
5 generates a comparative acceleration αr having a negative sign and a magnitude αc ₁ as shown in FIG. 2B.

The other parts continue the same operations as in (2-1) and (2-2), so the servo motor 34 continues to move the object to the target position Xc while decelerating and rotating at a constant acceleration (-αc ₁ ). Move towards.

This operating state continues until the output a of the counter 3 reaches the new commanded speed Vc ₂ from Vc ₁ .

(2-4) T ₃ ≦ T < T ₄ When the output a of the counter 3 reaches the commanded speed Vc ₂ at time T ₃ , a=c, so the comparator 5 switches the changeover switch 7 to the center terminal and 3 is stopped, and at the same time, the code of the code selection circuit 15 is set to zero. Therefore, between T ₃ and T ₄ , the output a of the counter 3 is the second
Vc ₂ is specified as shown in Figure A, and the sign selection circuit 1
The output αr of 5 will show zero.

Since the other parts continue the same operations as in (2-1) to (2-3), the servo motor 34 continues to move the object toward the target position Xc while rotating at a constant speed _Vc2 .

This operating state continues until time _T4 when the speed generated by the square root ROM 11, ie, the second speed information, reaches _Vc2 . After time _T4 , the next independent deceleration operation is started.

(3) Independent tracking operation (T ₄ ≦T≦T ₅ ) The speed of the object when it reaches the target position Xc is _zero , that is, _the target position When reaching , the speed must reach zero and the vehicle must stop.

In order to satisfy this requirement, if the position of the object at time T ₄ is Xr ₄ , then Vc ₂ , αc ₁ , Xc,
It is necessary that the following relationship holds between Xr ₄ : Vc ₂ =√2 ₁ |− ₄ |.

By the way, the output b of the square root ROM 11 is √|
Since it is proportional to -Xr|, the output b indicates the second velocity information of constant acceleration. This output b is
Since the position of the object is far away from the target position Xc, the output a is larger than the output a of the counter ₃ before T4, as shown in FIG. 2A. Therefore, since a<b, the comparator 6 switches the changeover switch 8 to the upper side and outputs a from the counter 3.
is supplied to BRM2.

When the second speed information b from the square root ROM 11 reaches the output a of the counter 3, that is, Vc ₂ at T=T ₄ , since a≧b, the comparator 6 switches the changeover switch 8 to the lower side and outputs the square root ROM 11. is supplied to the BRM 2, and at the same time, the sign of the output αr of the sign selection circuit 15 is made negative.

Therefore, between T ₄ and _{T 5} , the square root ROM11
As shown in FIG. 2A, the second speed information decelerating at a constant acceleration _αc1 is output from
generates a comparative acceleration αr with a negative sign and a magnitude αc ₁ , as shown in FIG. 2B.

At T=T ₅ , when the object reaches _the target position
This completes the series of operations to move the image to .

In FIG. 1, the frequency of the pulse train at position C actually turns up/down the counter 4, so it is always proportional to the magnitude of the motor speed regardless of the change in the commanded acceleration αc.

On the other hand, if the speed information at symbols A, B, and Vc in Figure 1 changes the value of the indicated acceleration αc, the magnitude of the motor speed that is meant for the same binary value will change. . In other words, the scale changes. This means that in BRM2, the product of the input pulse frequency and the binary data of A, B, and Vc is C
This is because the pulse frequency becomes . Therefore,
Binary values of A, B, Vc and actual speed (rod/s)
The correspondence (conversion) is as follows (binary values of A, B, and Vc) = 1/K・√αc・(actual speed rod/s). At this time, the three speed information A, B, and Vc are connected by COMP5 and CRMP6, so they have the same scale. Also K・√
is the size of the actual speed (rod/s) for 1 bit of the binary value, which is the speed resolution, and is proportional to √. 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 the movement (actual speed is proportional to 1/√, so the speed becomes discontinuous at that point), so at least one movement is performed. The interval is A,
Since B and Vc are quantities proportional to velocity, in this sense A, B, and Vc are called velocity. Further, as a purpose of use of the present invention, αc is often outputted only once in an initial setting form. Particularly in the case of an articulated robot, the function generator sets αc to a value close to the acceleration limit in order to quickly follow the commanded speed Vc. Acceleration control of the entire robot is often performed using a rectangular coordinate system (x-y-z) that integrates all axes, and then transmits this in the form of a change in commanded speed to the function generator of each axis. It depends.
(If the acceleration is restricted too much on each axis, the trajectory will become inaccurate.) Of course, αc may be changed for each movement.
In this case, the computer refers to the conversion table (values of each axis of K and √) to binary value data for the commanded speed calculated by the actual speed rod/s, so the commanded acceleration αc All you have to do is rewrite the values in this conversion table at the same time as the resetting, and there will be no trouble.

Figures C and D show the case where the commanded acceleration αc is commanded to a new αc ₂ , and the commanded velocity Vc is increased/decreased from Vc ₃ → Vc ₄ → Vc ₅ to move the object to the target position. Directed speed following operation (T ₆ to _{T 11}
(between T11 and T12), autonomous deceleration operation (between _T11 and _T12 ), and changes in comparative acceleration αr. Since the operation is the same as that shown in FIGS. 2A and 2B, the explanation will be omitted.

Note that the servo motor mechanism 30 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 always provides constant acceleration of the same magnitude both during the instructed speed follow-up operation and during the autonomous deceleration operation.

Because of these characteristics, the present invention can be used to connect function generators and servomechanisms that operate at their own limit accelerations, such as when servo mechanisms with different characteristics are connected to the same function generator. It can be used when setting up initial settings from a computer, or when using the same servo mechanism, and when you want to freely select an acceleration depending on the work or work procedure.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the function generator of the present invention, and FIG. 2 is a graph and waveform diagram of the moving speed relationship and comparative acceleration function generated by the function generator of the present invention. 1 and 2 are binary rate multipliers (BRM), 3 and 4 are up-down counters, 5 and 6 are comparators, 7 is a changeover switch,
8 is a data selector, 9 is a changeover switch, 10 is an absolute value calculation circuit, 11 and 12 are square root ROMs that output the square root of the input, 13 is an oscillator, 14 is a D/A converter, 15 is a sign selection circuit, and 20 is a function generator, 30 is a servo mechanism, 31, 32 are subtracters, 33 is an amplifier, 34 is a servo motor, 35
is an encoder, 36 is a counter, and 37 is a closed loop controller.

Claims (1)

[Claims] 1 A first speed information generation means that generates speed information having constant acceleration characteristics for acceleration at startup or to follow a newly commanded speed while moving; The second speed information generating means 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 the second speed information generating means generates a deceleration curve having constant acceleration characteristics, and the second speed information generating means 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. The first speed generation means generates the first
A function generator that generates the comparative position function using the second speed information generated by the second speed information generating means during autonomous deceleration when approaching the target and decelerating autonomously. a first converting means and a second converting means for outputting a pulse train having a frequency proportional to the product of a pulse train signal supplied as one input and a binary value supplied as the other input; means for inputting a constant frequency pulse train and a binary value proportional to the square root of the commanded acceleration commanded by the computer into the converting means; The output pulse of the first converting means is supplied as an input to one of the first counter means outputting speed information of 1 and the second converting means, and the output pulse of the first converting means is supplied as the input of the other during the instructed speed following operation. 1 from the counter means of
and means for supplying the second speed information during the self-sustaining deceleration operation;
a second pulse train that generates the comparative position function using a pulse train indicating each speed information from the converting means as a clock source;
1. A function generator comprising a counter means for generating first velocity information and second velocity information having a predetermined constant acceleration.