JPS5913044B2 - High frequency positioning control device - Google Patents

Description

[Detailed description of the invention] 15 The present invention is a positioning control device for numerical control.

In particular, it relates to a high-frequency positioning control device. Generally, in order to perform high-frequency positioning control, it is necessary to control the workpiece, tool, etc. quickly without causing vibration, and to suppress overheating of the servo motor.

Regarding the event promptly, the present applicant has already applied for Japanese Patent Application Laid-Open No. 4
9-85478 ``Servo system to reduce tracking error''. This will be explained with reference to FIG. 1, but this method did not fully take into account the ability of the servo motor. 25 The present invention generates a parabolic velocity function so as to make maximum use of the servo motor's ability, thereby reducing the heat generation of the servo motor.In other words, by making the most of the servo motor's ability, the present invention further improves positioning. There are 30 things that can save time.

FIG. 1 is a block diagram of a conventional positioning device, which will be briefly explained in relation to the present invention.

In the figure, 1 is the arithmetic unit in the DDA system, and its output is the command value X () and the speed of the command value X () 35d.
X()N= is extracted.

2 is a subtracter that subtracts a detected value Y of the current position of the position detector 9, which will be described later, from the command value X.

That is, X(0-Y becomes the tracking error D. 3 is a DA converter which converts the tracking error D into σ.

4 is also a D-A converter, and the output N of the calculator Dx(t) is
=? Convert to N''.

5 is an adder/subtractor Dt unit which converts the DA converter outputs D", N" of 3 and 4 and the feedback voltage V of the tacho generator 8, which will be described later, into N'I-D'-V.
Addition and subtraction are performed as follows: =D''.

Reference numeral 6 denotes a servo amplifier which drives the servo motor 7 by inputting D''.

Reference numeral 8 denotes a tachogenerator directly connected to the servo motor, and its output is fed back to the input of the servo amplifier 6 in order to compensate for load fluctuations.

Reference numeral 9 denotes a position detector that detects the position of a table or the like driven by the servo motor 7, which feeds back a detected value Y of the current position and subtracts the value Y from the command value X (0).

In the above explanation, the command value x(
By using the velocity component Dx(t)N=---1 of t), the tracking error Dt is reduced.

Therefore, in positioning control, there is no delay in the primary system, so the positioning time can be shortened by a considerable amount. Figure 2 is a block diagram showing Figure 1 in more detail.
12 is an input means such as an input tape; 12 is a decoder for decoding the contents of the input means; 13 is a speed function generator 614 that generates a speed function based on the output of the decoder 12; This is a counting means that counts and outputs a position-related command.

In the figure, elements 2 to 9 are exactly the same as the elements with the same numbers in FIG. FIG. 3 is a block diagram that is substantially the same as FIG. 2, and an adder 15 is newly added to the line D that makes the D-A converter 4 in FIG. 2 unnecessary. That is, in the adder 15, the position-related command X(t) and the speed Dx(
t) Directive regarding degrees? are added in advance, and the addition result of Dt is used as the command output.

In the prior art shown in FIGS. 1 to 3 above, a uniform acceleration/deceleration velocity function as shown in FIG. 4 was used for short distance positioning, but in the present invention, a parabola as shown in FIG. It uses the velocity function of

By using this parabolic function, the heat generated by the servo motor can be reduced by about 30% compared to when using a constant acceleration/deceleration speed function, provided that conditions such as travel distance and travel time are the same.l). This will be explained below. Figure 4 shows the speed function of uniform acceleration/deceleration, with time t on the horizontal axis and speed f'' on the vertical axis.
(Indicates 0.

In this case, it means positioning a moving distance of t in a time of Δt. Therefore, the area of the triangle represents the moving distance t by 2t, and the height is calculated as -.

Δt If the motor load is an inertial load only, and K is a proportional constant, the armature current 1a has a relationship of 1a=K−f″(t).

Therefore, the square of the effective current 1 rms is as shown in the following equation.
Figure 5 shows a parabolic velocity function, where the horizontal axis shows time T.
The vertical axis shows the speed f'(t).

In this case, as in Fig. 4, it means positioning a moving distance of 1 fCt in a time of Δt, and the area surrounded by the parabola and the horizontal axis represents the moving distance t, and the height is calculated as the speed function f ''(t) is F5(t)=-At(t-Δt)
It is expressed as (2). Integrating fl(t) yields the following equation.

(However, a is a constant) tΔL. 5L Therefore, the height is f''(-)=-.1.

22Δt When the motor load is only an inertial load and K is a proportionality constant, the armature current 1a has the relationship 1a=K−f″(t).

Therefore, the square of the effective current 1rms is expressed as follows.

The ratio of heat output of the servo motor is equal to the ratio of 12rms (1)
164 Therefore, from equations (1) and (4), the relationship 1 = 1 = - is obtained (4) 123.

That is, when positioning the same moving distance t with the same moving time Δt, the conventional constant acceleration/deceleration speed function generates about 30% more heat than the parabolic speed function of the present invention. Therefore, in the present invention, the speed function is given as a parabola, but in this case it is necessary to specify the travel distance and travel time.

There is no problem since the travel distance is given in the program, but
The travel time is calculated by inputting the travel distance, pause time, two servo motors, load conditions, etc. FIG. 6 is a block diagram of one embodiment of the positioning control device of the present invention.
A travel time calculation means 20 is provided. The other elements are exactly the same as those shown in FIGS. 1-3. FIG. 7 shows one embodiment of the travel time calculation means 20 shown in FIG. 6, and the principle that provides this FIG. 7 will be explained. First, when performing uniform acceleration/deceleration control as shown in Fig. 8 f″(t) 6
The current waveform of the motor is as shown in FIG. 8 1a. Considering that the servo motor is operated under the rated load condition, and assuming that the load is only the inertial load, there is a relationship between the motor current 1a during acceleration, the motor rated current IN, the moving time r, and the resting time c as shown in the following equation. . VrTl Ratio of motor current magnitude between constant acceleration/deceleration control and parabolic speed control K, = 7Tr and effective value of acceleration/deceleration current 1
Correlation between a, motor rated current 1N, travel time r, and rest time c÷t=,A]? We discussed 2nd 1st
Travel time R and rest time C during parabolic speed control shown in Figure 0
, and the movement distance b will be explained.

When the motor current and the motor generated torque are proportional 6 When performing the movements shown in Figures 4 and 5, the maximum value of acceleration 6 speed. The distance traveled is proportional to the amount of current allowed by the motor.

Therefore, during the parabolic speed control shown in Fig. 10, the moving distance b is the moving distance b = (area of the triangle with constant acceleration/deceleration shown in Fig. 8). Is the ratio of the amount of motor movement allowed during constant acceleration/deceleration control to the amount of motor movement allowed during constant acceleration/deceleration control? It is.

K2 is the acceleration when continuous rated current flows through the motor, and when expressed as the angular acceleration of the motor shaft, here is dω K2 = - = motor shaft angular acceleration under load Dt TN = = motor rated torque IN = motor rating Current = Total inertia converted to motor shaft Kr = Motor torque constant Therefore, if r is determined from the equation (5), it will be the desired travel time when using the servo motor's capacity to the maximum during parabolic speed control. It is.

A specific embodiment of the method of determination is shown in FIG. In Fig. 7, 21 inputs the moving distance b, and when K is a constant determined by the servo motor and load conditions, 6k=K
-B2 is a calculation means. 22 is the movement time of the servo motor to be determined. When the pause time is c, 6t=
This is a calculation means for obtaining R4+Cr3.

Here, if you want to maximize the servo motor's capacity, use formula (5), ie R4+Cr3=K. This means finding r that satisfies the relationship b2.

(However, K=K3) 23 compares the above T2:k, and t≧
It is a comparator that outputs "1"" when k. The comparator 624 is an inverter. Reference numeral 25 denotes an arithmetic unit necessary for calculating r of the calculating means 22. 96 calculates an initial value d, which is a provisional travel time, as 1, -, -, etc. at each calculation timing. To go.

Note that the output n of the one arithmetic unit 25 represents the calculation accuracy of the travel time at that time. 26 indicates that the output of the inverter 24 is ``1''.
'', that is, when t<k, this is an AND gate that passes the output n of the r calculator 25.

27 is 6 when the output m of the comparator 23 is "1"", that is, t
When ≧k, it is an AND gate that passes the output n of the 14 arithmetic unit 25.

28 adds the output n of the 14 arithmetic unit 25 that has passed through the AND gate 26, and subtracts the output n of the 14 arithmetic unit 25 that has passed through the AND gate 27. It is also a counting means that accumulates.

29 is the value of n indicating the calculation accuracy at that time and the allowable calculation error t
It is a comparator that compares the , and when n≦t, the output is 8ba1
make a comparison.

30 outputs the output r of the counting means 28 to the speed function generator 13 in FIG. 6 as the final desired travel time e when the output 8 of the comparator 29 emits "1"". And gate.

The operation example shown in FIG. 7 will be explained.

The initial conditions are: Pause time C=16 Travel distance b=7. Constant K = 54 determined by the servo motor and load conditions. Initial value of temporary travel time d=16. Let the allowable calculation error t=0.25. In the circuit shown in FIG. 7, calculations are repeated until a predetermined accuracy is obtained, and each value at that time is D in Table 1 below. During the first calculation, the calculation means 21 is used. k=K-B2=56.72=264
6 is calculated and keeps a constant value thereafter. In the calculation means 22, since the counting means 28 is initially set, r=
0 is entered. t-R4+Cr3-04+1・03=0
Therefore, the output m of the comparator 23 becomes 0''''. Therefore, the "05" output is inverted by the inverter 24 and opens the AND gate 26. Therefore, at this time, n=16 output from the 14 arithmetic unit 25 is inverted by the AND gate 2.
6 and is input to the addition side input of the counting means 28. At this time, the output n of the 14 arithmetic units 25 is 1
Since 6 is larger than the allowable calculation error t-0.25, the output S of the comparator 29 is not generated, and the AND gate 3
0 does not allow the output r of the counting means 28 to pass as the desired output. During the second calculation, r-16 is input to the calculation means 22, and t-R4+c-R3=164.
The output m of the D comparator 23 is +1·163−69632. Therefore, the "1" output is the AND gate 2
Open 7. Therefore, at this time, n=8 outputted from the I arithmetic unit 25 passes through the AND gate 27 and is input to the subtraction side input of the counting means 28, and 16-8=8 is calculated, resulting in r-8. Become. At this time as well, the output n of the arithmetic unit 25 is
Since 8 is larger than the allowable calculation error t-0.25, the comparator 29 does not output the output s and the AND gate 30 does not pass the output r of the counting means as the desired output.
In this way, the 3rd to 6th calculations are repeated, but at the start of the 7th calculation, the 14 calculation unit outputs V)n=0.25, and the tolerance t= 0.
25, the output S of the comparator 29 is
Therefore, the AND gate 30 is opened and the output r=6.5 of the counting means 28 is outputted as the desired output e=6.5. The value of the calculated value r changes as shown in FIG. 9, and can be determined with any precision depending on the value of the calculation error t. As explained above, according to the present invention, the speed function due to high-frequency positioning control is a parabolic function, so when trying to position the same travel distance in the same travel time, the heat generation of the servo motor is reduced by about 30%. I can do it.

Therefore, by making full use of the capabilities of the servo motor, it is possible to position the same moving distance in a shorter time.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a conventional positioning device, Fig. 2 is a block diagram showing Fig. 1 in more detail, Fig. 3 is a block diagram substantially the same as Fig. 2, and Fig. 4 is a block diagram of a conventional positioning device. Figure 5 is a diagram showing the speed function of uniform acceleration/deceleration, Figure 5 is a diagram showing the parabolic velocity function of the present invention, Figure 6 is a block diagram of the positioning control device of the present invention, and Figure 7 is the calculation of moving time in Figure 6. Means 20
A detailed block diagram of one embodiment of Fig. 6 Fig. 8 is a diagram showing the relationship between speed and acceleration current in the case of equal acceleration/deceleration to derive the principle for calculating travel time, and Fig. 9 shows the calculation based on Fig. 7. FIG. 10 is a diagram showing a state in which the value r is calculated to a desired value in sequence, and FIG. 10 is a diagram showing the relationship between speed and accelerating current in the case of a parabola, which introduces the principle for calculating travel time. 13... Speed function generator, 20... Travel time calculation means. 21...Calculation means 1622...Calculation means 2, 2
3... Comparator. 25... One arithmetic unit, 28... Counting means.

Claims (1)

[Scope of Claims] 1 Information input means, decoding means for decoding the contents of the information input means, speed function generation means for generating a velocity component during positioning based on the manual force of the decoding means, and a counting means for counting the speed component of the output of the speed function generating means and outputting it as a position-related command value; and a closed-loop numerical value for commanding the speed component of the output of the speed function generating means as well as the position-related command value of the output of the counting means. The control device is provided with a travel time calculation means for calculating the travel time required for positioning, and the speed function generator is calculated based on the travel time that is the output of the means and the travel distance specified by the information input means. A high-frequency positioning control device characterized in that a parabolic velocity function is generated at . 2 The moving time calculation means has the relationship r^4+c・r^3=K・b^2, where b is the moving distance, K is a constant determined by the servo motor and load conditions, etc., and c is the rest time. 2. A high-frequency positioning device as claimed in claim 1, including a circuit configured to determine the travel time r from an equation. 3. The travel time calculating means includes a counting means 1 that obtains k=K・b^2, a calculating means 2 that obtains l=r^4+c・r^3, and an output l of the calculating means 2 and the calculating means 1. A first comparator that compares the output k and outputs an output "1" when l≧k, and a certain initial value for calculating the travel time as input,
a 1/2 arithmetic unit that halves the value at each calculation timing; and a counting means that cumulatively adds or subtracts the output of the 1/2 arithmetic unit based on the output of the first comparator. , 1 above
/2 Compare the output n of the arithmetic unit with a certain allowable calculation error t, and calculate n
A second comparator that outputs an output "1" when ≦t, and an AND gate that passes the accumulated value of the counting means as a moving time when the second comparator outputs "1". A high-frequency positioning control device according to claim 1 or 2.