JPH01188913A - Servo control system - Google Patents

Abstract

PURPOSE:To realize the smooth control of revolutions for a servomotor without increasing the mechanical resolution of a position detector attached to a servo drive source of the servomotor, etc., by setting the shift value data at a reciprocal of the product obtained between the speed resolution and the sampling time. CONSTITUTION:The pulses are produced from a pulse generator serving as a position detector attached to a servomotor 12 in a unit of the resolution RS (pulse number/rotational frequency) in accordance with the revolutions of the servomotor 12. The output position detecting pulses PP=NXRS (N: rotational speed, i.e., rps of the servomotor 12) are counted by a feedback counter 28. The output signal C0 of the counter 28 is multiplied as prescribed by a 2nd multiplier 30 and stored in a 2nd accumulator 32 for feedback pulses in the form of the feedback pulse data FP. This data FP is supplied to a subtraction input terminal of a deviation counter 16 for each sampling clock T as a feedback subtraction signal S2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a servo control system, and more particularly to a servo drive such as a servo motor or a servo valve that is substantially driven by an output signal from a deviation counter. The present invention relates to a smooth servo control system that is suitably employed when feeding a source, particularly at very low speed.

[Background of the Invention] For example, the cutting shaft moving means of a polishing machine that polishes a shaft member such as a crank pin, or the cutting shaft moving means of a gear grinding machine that processes gear grinding processes at an ultra-low speed and smoothly. Since it is necessary to feed the parts, it is conceivable to adopt a so-called servo control system that uses a servo motor that has a large torque and can perform synchronous machining.

However, when conventional servo control systems are used for cutting feed in polishing machines, etc., ultra-low speed feed is required, so the workpiece feed table has the disadvantage of index movement every pulse. , there is an inherent drawback that smooth servo with a predetermined accuracy cannot be achieved as it is.

In order to improve this drawback, it is necessary to set the positioning resolution to high precision, so select a feedback encoder itself such as a shaft encoder that is attached to the servo motor that has high resolution, that is, high precision. However, this type of feedback encoder is extremely expensive and has physical limitations due to its mechanical configuration. It has not yet been improved enough.

[Purpose of the Invention] The present invention has been made to overcome the above-mentioned disadvantages, and includes integral control of command values or feedback pulses using software when rotating or moving a servo drive source at extremely low speeds. To provide a servo control system that can obtain a smooth rotational state or moving state that exceeds the resolution without increasing the resolution of the feedback encoder itself, thereby making it possible to process an abrasive object or an object to be ground with high precision. The purpose is to

[Means for achieving the object] In order to achieve the above object, the present invention includes a first multiplier that multiplies the movement amount command data of the servo drive source by a predetermined value, and an output signal from the first multiplier. a first accumulator for temporary storage; a counter for counting pulses from a position accumulator connected to the servo drive source; a second multiplier for multiplying the output signal from the counter by a predetermined value; and the second multiplier. a second accumulator that temporarily stores an output signal from the accumulator, and a deviation counter that performs a deviation calculation to which the output signals from the first and second accumulators are sequentially inputted in synchronization with the sampling signal. The servo drive source is characterized in that the servo drive source is smoothly moved by substantially introducing an output signal into the servo drive source.

Furthermore, the present invention is characterized in that the predetermined multipliers of the first and second multipliers are the number of samplings per unit time.

[Embodiments] Next, preferred embodiments of the servo control system according to the present invention will be described in detail with reference to the accompanying drawings.

In FIG. 1, reference numeral 10 indicates a control device, and a rotation command signal S is sent from the control device 10. is output. This rotation command signal S. are the rotational speed data AS of the servo motor 12 and the movement amount data AR of the ball screw 13 which is attached to the servo motor 12 and rotationally driven by the servo motor 12. Output rotation command signal S. Among them, the movement amount data AR is multiplied by a predetermined value using the first multiplier 15, as will be described later, and introduced into one input terminal of the first accumulator 14 as the movement amount data ARE. It is stored in the dimulator 14. on the other hand,
Rotation command signal S. Among them, the rotational speed data AS is the first
It is introduced into the other input terminal of the achinimulator 14. The rotation command signal Sl from the first accumulator 14 is introduced into the addition input terminal of the deviation counter 16 every sampling clock T. The digital deviation output signal from the deviation counter 16 is input to the servo amplifier 20 via the D/A converter 18 as an analog deviation output signal, and the servo amplifier 20 outputs the analog deviation output signal to the servo motor. The voltage is amplified to a voltage sufficient to drive the servo motor 12 and is sent to the servo motor 12. In this case, a ball screw 13 is pivotally attached to the servo motor 12, a traverse table 24 is integrally fixed to the nut portion 22 of the ball screw 13, and by rotating the servo motor 12, the traverse table 24 is moved in the direction of the arrow. The traverse table 24 moves forward and backward to perform crowning of a work fixed on the traverse table 24, such as a gear (not shown).

On the other hand, as the servo motor 12 rotates, the servo motor 12
A pulse generator 26 which is a position detector pivoted on the
from resolution R, [:pulses/revolut i
on ), and the output position detection pulse Pp = NXR5C. However, the symbol N is the rotation speed (rps) of the servo motor 12)
Counted by 8.

The output signal Co of the feedback counter 28 is multiplied by a predetermined value using a second multiplier 30, as will be described later, and stored as feedback pulse data FP in a second accumulator 32, which is an accumulator for feedback pulses. Therefore, the feedback pulse data FP stored in the second accumulator 32 is introduced as a feedback subtraction signal S2 to the subtraction input terminal of the deviation counter 16 every sampling clock T, and a feedback operation is performed.

Note that the velocity resolution RV of the servo control system is l
p p s (pulse/5ec), and the positioning resolution R1, that is, the value obtained by dividing the amount of movement per one rotation of the ball screw 13 by the resolution R3 of the pulse generator 26, is 1 μm, and the sampling period Ts of the sampling clock T is assumed to be 1 ms.

The servo control system according to this embodiment is basically configured as described above, and its operation and effects will be explained next.

FIG. 2 is a flowchart applied to the servo control system according to the present embodiment shown in FIG. 1, and the operation will be explained below based on this flowchart.

First, the operation will be described when the rotation speed data AS is set to 5 pps and the movement amount data AR of the traverse table 24 due to the rotation of the ball screw 13 is set to 1 mark. In this case, the rotation speed data AS=
5pps is set in the first accumulator 14, and the movement amount data AR now indicates that the positioning resolution R1 is 1μ.
m, so 1000 times (in+m=1μmxlooO
) and fed to the first multiplier 15. First multiplier 15
The magnification α of is set to . Therefore, the movement amount data ARE is 1000
The data corresponding to 000 pulses is stored in the first accumulator 14 (STPI).

Next, in step 2, it is determined whether the movement amount data ARE stored in the first accumulator 14 is zero. In this case, since the movement amount data A RE is not zero, that is, the movement amount data A RE = 1000.
Since all 000 pieces are stored, this judgment is not satisfied and the process proceeds to step 3 (SrF2).

In step 3, the first sampling clock T
is applied to the first accumulator 14, the first accumulator 14 performs a predetermined calculation, that is, (movement amount data ARE - rotational speed data AS), subtracts 5, and calculates the rotational speed data AS, which is the subtracted value. =5 is the addition value of the deviation counter 16, that is, the rotation command signal S,
is introduced into the deviation counter 16 as (SrF2).

Now, the feedback subtraction signal S is introduced from the second accumulator 32 to the subtraction input terminal of the deviation counter 16.
Since 2 is a zero value, the digital deviation output signal Dd is set to 5, and the D/A converter 18 outputs an analog deviation output signal.
and is introduced into the servo amplifier 20. in this case,
The gain of servo amplifier 20 is 1/1000 (1/α)
Since the servo motor 12 is adjusted to 5/100
Start rotating at a speed of 0 (rps). At this time, the speed resolution R9 of the pulse generator 26 is 1 pps.

Therefore, no position detection pulse P is outputted yet, so no signal is introduced into the feedback counter 28, and the count value of the feedback counter 28 is zero. On the other hand, since the data stored in the second accumulator 32 is zero, the set value after the calculation in step 5 is set to zero, and the process moves to the next step 6 (SrF5).

In step 6, the feedback subtraction signal S2, in this case zero data, is introduced from the second accumulator 32 to the subtraction input terminal of the deviation counter 16 every sampling clock T. Therefore, in the deviation counter 16, the feedback subtraction signal S2 applied to the subtraction input terminal of the deviation counter 16 is subtracted, but since it is currently at zero value, the digital deviation output output from the deviation counter 16 is The value of the signal remains unchanged (SrF2)
.

That is, the value of the digital deviation output signal RI of the deviation counter 16 is 5, and this digital deviation output signal RI is D.
After being converted into an analog deviation output signal by the /A converter 18, it is amplified by a predetermined amount by the servo amplifier 20, and the servo motor 12 is driven (SrF8).

In this way, the rotation command signal S1 is sequentially input to the addition input terminal of the deviation counter 16 every sampling clock T.
The pulse generator 26 outputs one position detection pulse P only when the value of the digital deviation output signal P of the deviation counter 16 becomes 5000 or more. This position detection pulse P is multiplied by the second multiplier 30 at the same magnification α as that of the first multiplier 15, that is, 1
000 and stored in the second accumulator 32 as feedback pulse data FP multiplied by 1000 (SrF2). Then, the feedback subtraction signal S2 is input to the subtraction input terminal of the deviation counter 16 in units of 5 when the next sampling clock T is generated (SrF2
), as a result, the digital deviation output signal from the deviation counter 16 is subtracted by 5 (SrF2), so that the digital deviation output signal from the deviation counter 16 is reduced by 5 (SrF2).

The value of is 5005 or 5000. At this time, since the gain of the servo amplifier 20 is adjusted to 1/1000, the smoothness, that is, the position resolution is improved by 1000 times, and the ball screw 1 which is attached to the servo motor 12 is
3 rotates. Therefore, gears, crank pins, etc. that are traverse-fed by the nut portion 22 that meshes with the ball screw 13 can be easily machined. In this way, the data stored in the first accumulator 14 becomes 5000.
When the value becomes less than 5, the value of the digital deviation output signal Dd from the deviation counter 16 is also subtracted by 5 from 5000, and the servo motor 12 is gradually decelerated. Then, after the value of the digital deviation output signal R from the deviation counter 16 becomes zero, that is, after 1000 position detection pulses P are generated from the pulse generator 26, the servo motor 12 stops. The positioning control ends.

[Effects of the Invention] As described above, according to the present invention, the movement amount data is set to the reciprocal of the product of velocity resolution and sampling time. Therefore, it is possible to smoothly control the rotation of the servo motor without increasing the mechanical resolution of the position detector mounted on the servo drive source such as the servo motor. Therefore, it can be employed in cases such as crowning of gears, where positioning accuracy is not so required, but smooth control is required. Moreover, since there is no need to use a high-precision, high-resolution position detector, the cost of the device itself can be reduced.

Although the present invention has been described above with reference to preferred embodiments, the present invention is not limited to these embodiments.
It goes without saying that various improvements and design changes can be made without departing from the spirit of the present invention, such as, for example, similar effects can be achieved by replacing the servo motor with a servo valve.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a servo control system according to the present invention, and FIG. 2 is a flowchart explaining the operation of the servo control system shown in FIG. 1. 10...Control device 12...Servo motor 1
3... Ball screw 14... First accumulator 15... First multiplier 16... Deviation counter 18... D/A converter 20... Servo amplifier 2
4...Traverse table 26...Pulse generator 28...Feedback counter 30...Second multiplier 32...Second Akicomulator patent applicant Honda Motor Co., Ltd., Dai.

Claims (2)

[Claims] (1) A first multiplier that multiplies the movement amount command data of the servo drive source by a predetermined value, a first accumulator that temporarily stores the output signal from the first multiplier, and a position detector connected to the servo drive source. a counter that counts pulses from the device;
a second multiplier that multiplies the output signal from the counter by a predetermined value; a second accumulator that temporarily stores the output signal from the second multiplier; and the output signals from the first and second accumulators are converted into sampling signals. It is characterized by comprising a deviation counter which is sequentially input in synchronization and performs deviation calculation, and by substantially introducing the output signal of the deviation counter into the servo drive source, the servo drive source can be smoothly moved. Servo control system. (2) The servo control system according to claim 1, wherein the predetermined multipliers of the first and second multipliers are the number of samplings per unit time.