JPS61122709A - Function generator - Google Patents

Abstract

PURPOSE:To improve the control accuracy of a DC motor or the like by increasing an objective acceleration when an objective speed is smaller than a prescribed value, and when the objective speed exceeds the prescribed value, reducing the objective acceleration. CONSTITUTION:When a switch S1 is closed, the acceleration a1 is stored in a register 22, the objective speed v(k+1)=v(k)+a(k) is successively calculated by an adder 23 and the objective position r(k+1)=r(k)+v(k)+(1/2)a(k) is successively calculated by an adder 25. A comparator 21a compares a previously specified prescribed speed v2 with a speed (v) stored in a register 24, and if v(k+1)>=v2, closes a switch S2. A comparator 21b compares a previously specified other prescribed speed v1(v1>v2) with the speed 24 stored in the register 24, and if v(k+1)<v1, stores an acceleration a2(a1>a2) in the register 22 through the switch S2. When v(k+1)>=1 is formed, the comparator 21b closes a switch S3 and stores the acceleration '0' in the register 22.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a function generator for generating a continuously changing target position of a controlled object in a servo control device.

[Conventional technology]

When servo-controlling a controlled object such as a DC motor, a servo control device (feedback system) shown in FIG. 4 has conventionally been used. In Figure 4, the controlled object (DC motor)
The actual position y of (2) is set by the compensator 3 to set the manipulated variable U to the controlled object 1 so that it follows the target position r generated by the function generator 2, that is, so that the error e'ar-y becomes zero.
is added.

By changing the target position r, the actual position y also changes accordingly. In this case, even if the controlled object l is at the current position ``.'', and when it is moved to the next position rl, the controlled object will not change instantaneously (stepwise) from r to r. Generally, the function generator 2 smoothly changes the target value r from ro to rl.At this time, the target position is changed from ro to r as shown in Fig. 5 1al. If the velocity V is changed linearly as shown in FIG. 5 (bl), the error e becomes large immediately after the velocity V changes, and the controlled object l vibrates unnecessarily.

Therefore, the conventional function generator 2 changes the target position r more smoothly as shown in FIG. 6(a), so that the target speed V draws a trapezoidal curve as shown in FIG. It was changed to. The slope of this trapezoidal curve corresponds to the target acceleration a, and is shown in FIG. 6 (C1).

FIG. 7 is a block diagram showing details of the conventional function generator 2. As shown in FIG. In FIG. 7, when the target speed v is smaller than the predetermined value v1, the switch Sl is closed and the acceleration a,
is stored in the register 22. Target speed V is predetermined value v1
When the value is reached, the switch S2 is closed and zero is stored in the register 22.

The adder 23 calculates the speed v (
The acceleration afkl output from the register 22 is added to kl and stored in the register 24 as a new velocity v(kl1). The adder 25 calculates the target position "(k)" stored in the register 26, the target velocity V(g) stored in the register 24, and the acceleration a output from the register 22.
(The sum of the value obtained by dividing kl by 2 in the divider 27, r (k
l + v (k) + -a (kl is stored in the register 26 as a new target position r(kl1).

In FIG. 6, the maximum value of speed V and the maximum value of acceleration a are determined from the maximum allowable speed and maximum allowable acceleration of the DC motor to be controlled, respectively.

To explain the above in more detail, the voltage E between the terminals of the motor is: E = Ri + K ++W ----- (1, R: Winding resistance i: Current 3: Back electromotive force constant W: It can be approximated by the rotational speed, and the angular acceleration a of the motor is expressed as K, 2 Torque constant J: Inertia of the load applied to the motor If you erase K.

becomes. Since the maximum voltage that can be applied to the motor is determined by the power amplifier's ability, the voltage between the terminals is limited by the maximum Emax. Therefore, the formula (3) is
・It becomes T. From this formula, the larger the speed W is, the more the acceleration change is,
It will no longer increase.

In an actual motor, the maximum speed and maximum acceleration are further reduced due to the effects of friction and the like.

In any case, this shows that when the speed is small, the acceleration that can be produced becomes impossible when the speed becomes large.

When the target speed generated by the function generator 2 is changed in a trapezoidal manner as shown in FIG. 6 fbl, the acceleration is constant during acceleration. Therefore, there is a problem that the acceleration that can be generated when the speed is small is no longer possible when the speed becomes large.

With conventional function generators, you can either suppress the acceleration so that the motor can generate it even if the speed increases, or suppress the maximum speed V so that it can generate a large acceleration. Crab was fixed.

That is, from equation (4), the speed W and the maximum speed ax that can be achieved at that speed are as shown in FIG. 8, and the acceleration a1 and maximum speed vl specified by the function generator are the straight line shown in FIG. must be below.

[Problem that the invention seeks to solve]

Therefore, in order to increase the acceleration, it may be set, for example, at the position of point A, but in this case, there is a problem that the maximum speed is suppressed to a small value of V.

Further, in order to increase the maximum speed, it is possible to set it to, for example, a point, but in this case there is a problem that the maximum acceleration is kept small to a.

An object of the present invention is to solve the above-mentioned problems in which the acceleration is set small in order to increase the maximum speed, or the maximum speed is set small in order to increase the acceleration.
To provide a function generator capable of increasing acceleration and maximum speed close to the limit of a motor's ability.

[Means for solving problems]

What is provided by the present invention to constitute the above object is to control the controlled object! In a servo control device that continuously moves to a final target position, means for calculating a target speed and a target position of the controlled object based on a target acceleration of the controlled object, and when the target speed exceeds a predetermined value. If so, the function generating device is characterized by comprising means for switching the target acceleration from a first value to a second value smaller than the first value.

[For production]

When the target speed is smaller than the predetermined value, the target acceleration is increased, and when the target speed exceeds the predetermined value, the target acceleration is decreased, thereby increasing the target acceleration and maximum target speed to near the limit of the ability of the controlled object such as a DC motor. can take a large amount.

(Example) Examples of the present invention will be described below based on FIGS. 1 to 3.

FIG. 1 is a block diagram showing a function generating device according to an embodiment of the present invention, and FIG. 2 is a flowchart showing the operation of the device shown in FIG. 1 implemented by a microprocessor. 1 and 2, first the switch S is closed, the acceleration a1 is stored in the register 22 (step s1), and the adder 2 is
3, the target speed v (k + 1) = v fk
l + a (kl is calculated one after another, and the adder 25 calculates the target position r (kl1) = r (kl + v (k
l + −a (kl is calculated one after another (stapper S
t).

The comparator 21a compares the predetermined speed vz and the register 2.
4. Compare the speed V stored in step S3).
If v(kll)≧vz, close switch s2. Further, the comparator 21b compares the speed V of the register 24 with another predetermined speed V+ (where vl>vt) specified in advance (step S4), and if v(kll)<■, switch S2
The acceleration a, (where a, > a,) is transferred to register 2 via
2 (step 5s) −v(kl1)≧V,
When the comparator 21b closes the switch S, the acceleration 0 is stored in the register 22 (step S6).
). In step St, K is incremented, and steps 82 to S7 are then repeated to output the target position during acceleration.

In FIG. 1 and FIG. 2, the flowchart of the function generator and its operation during deceleration is omitted because it can be easily inferred from the time of acceleration.

In the flowchart of FIG. 2, it should be noted that the velocity and acceleration are expressed in units of sampling time. That is, the meaning of velocity indicates how much r advances per sampling time, and the acceleration indicates how much the velocity advances per sampling time. V
, A is the velocity and acceleration in seconds, the sampling time is T seconds, and V is the unit of sampling time,
3, it can be converted to -VT a"AT".

FIG. 3 is a graph showing temporal changes in the target position, target velocity V, and target acceleration a obtained by the embodiment shown in FIGS. 1 and 2. As can be seen from FIG. The acceleration is al until time t, and from time t to L2, the acceleration becomes small as a2, and in the constant speed state after time t2, the acceleration is zero. It can be set close to the limit of the motor's maximum capacity.Also, since the acceleration is small between times t1 and t2,
Let the speed v be close to the limit of the motor's maximum capacity.

In the embodiment described above, only two types of acceleration are switched, but by adding more comparators and switches, it is possible to change the acceleration to three or more types one after another.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, in a servo control device, by switching the target acceleration according to the target speed of the controlled object, the maximum acceleration and maximum It becomes possible to set the speed, and a controlled object such as a DC motor can be quickly moved to the final target position.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a function generator according to an embodiment of the present invention, FIG. 2 is a flowchart showing the operation of the device shown in FIG. 1, and FIG. 3 is a block diagram showing the operation of the device shown in FIG. and a graph showing the relationship between target acceleration and time, FIG. 4 is a block diagram showing an example of a conventional servo wiWJ device,
Fig. 5 is a graph showing temporal changes in target position and target speed in the conventional device shown in Fig. 4, and Fig. 6 is a graph showing changes in target position and target velocity over time in the conventional device shown in Fig. 4, when the target acceleration is kept constant. Graph showing temporal changes in target position, target velocity, and target acceleration; FIG. 7 is a block diagram showing a conventional function generator in the conventional device of FIG. 4; FIG.
It is a graph showing the relationship between the speed of a motor and the acceleration that can be generated at that speed. 2a...Function generator, 21a, 21b...Comparator, 22...Register, 23...Adder, 24...Register, 25...Adder, 2
6...Register, 27...Divider.

Claims (1)

[Claims] 1. In a servo control device that continuously moves a controlled object to a final target position, a means for calculating a target speed and a target position of the controlled object based on a target acceleration of the controlled object, and a means for calculating a target speed and a target position of the controlled object based on a target acceleration of the controlled object, and a means for calculating a target speed and a target position of the controlled object based on a target acceleration of the controlled object, 1. A function generating device comprising means for switching the target acceleration from a first value to a second value smaller than the first value when the target acceleration exceeds a predetermined value.