JPH04169914A - Speed controller for servo motor - Google Patents

Abstract

PURPOSE:To always stably control the speed by checking the friction of a driving system by the test operation at the time of starting a motor to determine the current value which corresponds to the actual friction and drives a servo motor and controlling the speed. CONSTITUTION:A test driving means 16 supplies a preliminarily determined reference current IR to a servo motor 14 for a certain time TR at the time of starting a motor. A speed detecting means 18 detects speed information V dependent upon the mechanical friction of a motor driving system obtained by motor driving of the means 16. A current value determining means 22 determines a current value corresponding to speed information of the detecting means 18 in accordance with a current table 20 where correspondence relations between speed information V dependent upon the friction of the motor driving system and a driving current I are preliminarily set. That is, the table is retrieved by detected speed information to determine the proper current value for speed control adapted to the friction, and this current value is used to control the speed in each of stages of acceleration, deceleration, and pressing. Thus, the speed of the servo motor 14 is stably controlled in consideration of the friction of the driving part.

Description

[Detailed Description of the Invention] [Summary] The drive current of the servo motor is determined based on the target position from the host device, the motor detection position, and the detection speed obtained from the speed detection means, and accelerates, constant speed, decelerates, and pushes. Regarding speed control devices for servo motors that control the speed of is determined, and a current value to be used for speed control is determined by referring to a current table in which current values corresponding to speed information indicating dependence on friction are stored in advance.

[Industrial Application Field] The present invention relates to a servo motor speed control device that controls the speed of a drive system using a servo motor.

Speed control of a drive system using a servo motor, such as a magnetic tape device, is performed by passing an accelerating current in response to an instruction from a host device to accelerate the drive system to a target speed, and upon completion of acceleration, detects the speed deviation between the target speed and the speed detected by the speed detection means. Turn on the accelerating current based on,
It is turned off to maintain the target speed, and when the deceleration start point is reached before the target position, the deceleration current is applied to the deceleration end point to decelerate.
The motor is controlled to a pushing target speed that ultimately becomes a low speed, and the motor is stopped when the target position is reached.

The friction of a drive system whose speed is controlled by a servo motor as described above varies considerably due to assembly, temperature changes, etc.

Therefore, for stable speed control, it is necessary to perform speed control that takes into consideration the friction of the drive system.

[Prior Art] FIG. 7 is a block diagram of a conventional servo motor speed control device.

In FIG. 7, 10 is an upper MPU, 12 is an encoder that detects the motor rotation angle, 14 is a servo motor, 24 is a lower MPU, 26 is Ilo, 28 is a DA converter, 3
0 is a constant current amplifier, and 32 is a counter for determining the motor position.

The speed control by the conventional device shown in FIG. 7 will be explained as follows with reference to the operation explanatory diagram showing the target speed curve and drive current shown in FIG. 8, and the flowcharts shown in FIGS. 9A and 9B.

First, the upper MPU10 sets the distance (counter value) from the current position to the target stop position in the counter 32 in step SL (hereinafter "step" is omitted). Next, in step 82, the upper MPU 10 issues a command to the lower MPU 24 to start operation. Upon receiving the operation start command, the lower MPU 24 takes in the moving distance from the counter 32 via l1026 and starts the operation.

First, in S3, the lower MPU 24 sets the acceleration current (2) to the DA converter 28. The output of the DA converter 28 is amplified by a constant current amplifier 30, and an accelerating current In is passed through the servo motor 14 to operate the drive section. When the servo motor 14 starts rotating, a pulse is output from the encoder 12, and the counter value (movement distance) of the counter 32 whose movement distance is set at Sl is counted down.

The motor speed is detected by reading the counter 32 at a constant sampling period and finding the difference between the previously read counter value and the currently read counter value. Further, the current position is the value read from the counter 32 at the current moment.

Target speed at which the motor speed reaches the top speed in S4■□
35. When it is determined that the target speed vR has been reached (point A), the speed of the drive unit is kept constant based on the target speed vR until the deceleration start point B. The acceleration current 1. turn on and off.

When it is determined in S7 that the deceleration start point B has been reached, the deceleration current -■ is set in S8, and the deceleration drive is performed in S9 until the motor speed falls from the target speed vIl to the pushing target speed VL as a low speed. continue.

When it is determined in S9 that the motor speed has become below the target speed VL (0 point), the current is switched from the deceleration current -■ to the pushing current IL in S10, and the target speed Vt is kept constant in S12.313. Turn the drive current on and off to operate. Subsequently, when the counter value of the counter 32 becomes zero, it is determined in S14 that the target stop position (point D) has been reached, and in S15, the upper MPU10 is notified of the end of the operation, and the series of processing is completed.

Note that the position of the deceleration starting point B is set based on the weight of the drive system and the control speed.

[Problems to be Solved by the Invention] However, in such conventional speed control methods for servo motors, speed control is performed assuming that the mechanical friction of the drive system is within a certain range. Although the magnitude of the current value is fixed, the friction in the drive system can vary considerably due to assembly, temperature changes, etc.

For this reason, speed control that considers friction in the drive system as a fixed consideration tends to cause servo loop oscillations and abnormal operations due to the influence of friction, and also causes the drive torque to be too much or too little relative to the actual friction, resulting in poor operation. There was a problem with instability.

The present invention was made in view of these conventional problems, and an object of the present invention is to provide a speed control device for a servo motor that can perform stable speed control even if there are variations in the frictional resistance of the motor drive system. shall be.

[Means to solve the problem] FIG. 1 is a diagram explaining the principle of the present invention.

First, the present invention is directed to a servo motor speed control device that determines and controls the drive current of the servo motor 14 based on the target position set from the host device 10 and the motor position detected by the position detection means 12. do.

In the present invention, such a speed control device for a servo motor includes: a test drive means 16 that supplies a predetermined reference current I to the servo motor for a certain period of time TR+ when the motor is started; A speed detection means 18 that detects speed information V that depends on the mechanical friction of the motor drive system obtained by driving the motor, and speed information V that depends on the friction of the motor drive system and drive current I.
The present invention is characterized in that it includes a current value determining means 22 that determines a current value corresponding to the speed information of the detecting means 18 from a current table 20 in which a correspondence relationship of the above is set in advance.

Here, the current value determining means 22 refers to the current table 20 and determines the acceleration current In used for controlling the target speed VII from startup to the deceleration start point before the target position, and the acceleration current In used for controlling the target speed VII from the start to the deceleration start point before the target position. Deceleration current used for speed control -I
The pressing current IL used to control the pressing target speed vL used during the period from the deceleration end point to the stop at the target position is determined.

[Function] According to the servo motor speed control device of the present invention having such a configuration, by supplying the reference current ■ to the servo motor for a certain period of time TR in a test operation at the time of starting the motor, The friction-dependent movement of the drive system at that time, that is, the amount of movement per unit time (speed information) is investigated. For example, if the friction is large, the distance traveled is short and the detected speed information is small.

Also, if the friction is small, the distance traveled will be large, and the speed information will also be large. The current value for speed control corresponding to the speed information obtained in such a test drive is prepared in advance as table information, and by searching the table based on the detected speed information, the appropriate current value for speed control that matches the friction at that time can be determined. is determined, and this current value is used to control the speed at each stage of acceleration, deceleration, and pushing.

As a result, stable speed control of the servo motor can be performed taking into consideration the friction of the drive section.

Embodiment FIG. 2 is a block diagram showing an embodiment of the present invention.

In FIG. 2, reference numeral 10 denotes a higher-level MPU, which issues a target movement position setting and startup command to a lower-level MPU 24 that constitutes a control section on the motor speed control device side.

The lower MPU 24 connects to the DA converter 2 via l1026.
Set the motor drive current for 8, and set the motor drive current to DA converter 2.
The output of 8 is amplified by a constant current amplifier 30 and then supplied to the servo motor 14. The servo motor 14 is provided with an encoder 12 as a position detecting means, and pulses from the encoder 12 are input to a counter 32 for detecting the moving position. The counter 32 receives the setting of a count value (movement distance) indicating the target movement position from the upper MPU l0 at the time of startup, subtracts this set count value with a pulse from the encoder 12, and sends the count value to the target position via l1026 to the lower MPU 24. You can give the remaining distance. Further, by reading the count value of the counter 32 at regular intervals, the speed of the servo motor 14 can be detected from the difference between the previous count value and the current count value.

The lower MPU 24 includes a test drive section 16 and a detection section 1 in order to perform speed control taking into account friction in the drive system of the servo motor 14.
8. Each function of the current table 2o and the current value determining section 22 is realized by program control.

When the test drive unit 16 receives a start command from the host MPU10, it supplies a predetermined reference current IR to the servo motor 14.
is supplied for a certain period of time TR to perform a test operation to detect friction in the drive system. The detection unit 18 reads the amount of movement of the servo motor 14 obtained by the test operation of the test drive unit 16 from the change in the count value of the counter 32, and since this change in the amount of movement is the amount of movement for a certain period of time TR, it is used as speed information. V
Detected as.

A current table 20 is provided for the current value determination unit 22, and the current table 20 is used to control the servo motor 1 using speed information (■) corresponding to changes in frictional resistance obtained experimentally as an address.
4, the current value used for speed control, i.e. acceleration current I, 11
The values of deceleration current -IN and pushing current IL are stored.

FIG. 3 is an explanatory diagram of the current table 20 in FIG. 2. For example, for each of table numbers θ to n, prescribed current values experimentally determined as accelerating current, pushing current, and decelerating current are shown. Data is stored. The table numbers of the current table 20 in FIG. It is determined based on Vn. The characteristics of acceleration, pressing, and deceleration currents for speed information thresholds v1 to Vn are as shown in the current table characteristic diagram of FIG. 4.

In Fig. 4, the relationship between the speed information V shown on the horizontal axis and the friction of the drive system is such that the larger the friction, the smaller the speed information ■, so the smallest speed information threshold V1 is the maximum friction of the drive system. , and the largest speed information threshold Vn corresponds to the minimum friction of the drive system. For example, acceleration current 1. For example,
The largest acceleration current l at the speed information v1 with the largest friction
Yo. , and conversely, set the smallest acceleration current ■□ at the speed information sail Vn with the smallest friction.

The same holds true for the pushing current I.

Furthermore, the deceleration current -IN has completely opposite characteristics in the negative direction.

Next, the speed control according to the embodiment shown in FIG. 2 will be explained with reference to the processing flow diagram shown in FIG.

In FIG. 5, first, at 51oo, the upper MPU10 sets a counter value indicating the moving distance to the target position in the counter 32, and at the next 5IOI, the upper MPU10 issues a start command to the lower MPU 24.

Lower M that received a start command from upper MPU10
In step 5102, the PU 24 sets a value for causing the reference current IR to flow through the test drive unit 16 in the DA converter 28;
A reference current I is supplied to the servo motor 14 by the constant current amplifier 30.
Flow R and perform a test drive. As the reference current IR to be passed through the servo motor 14 in step 5102, a desired current value is used that can sufficiently drive the motor against the expected maximum friction of the drive system.

Subsequently, in 5103, the test drive section 16 operates for a certain period of time T.
It checks whether R has elapsed or not, and when the TR time has elapsed, the reference current IA is stopped and the process proceeds to 5104, where the count value of the counter 32 at that time is read as the current count value, and at 5100 it is set by the upper MPU10. Friction-dependent speed information V is obtained by subtracting the current counter value from the initial counter value.

Next, the process advances to 5105, and the speed information V obtained in 5104 is compared with the maximum value Vn of the speed information threshold corresponding to the minimum friction.
If it is equal to or greater than the threshold value Vn, the process proceeds to 8106, and the acceleration current I□ and the pushing current IL are determined with reference to the n-th table in FIG. and deceleration current −I,. Determine.

If the speed information V is smaller than the threshold value Vn, it is compared with a threshold value v n-1 (not shown).

Here, in FIG. 5, the threshold value Vn
, VR and vl are shown.

Then, in 5107, if the speed information V is equal to or higher than the threshold value V7, 5
At step 108, the acceleration current I□ and the pressing current ILR% deceleration current -INll shown in FIG. 3 are determined with reference to the R-th table.

In addition, if the speed information V is smaller than the minimum threshold value ■1 for maximum friction shown in FIG.
Go to step 3, refer to table number 0 in Figure 3, and find the largest accelerating current ■□. , pushing current■,. and deceleration current −INo
Determine.

In 5105 to 5110, if the accelerating current, pushing current, and decelerating current are determined by referring to the table, 51
Proceeding to step 11, each speed control of acceleration, constant speed, deceleration, and pressing is performed based on the determined current value. The speed control in this 5ill is the same as the processing in S3 to S15 in FIGS. 9A and 9B.

FIG. 6 is a control explanatory diagram showing a speed curve in speed control in consideration of friction of the drive system of the present invention and differences in each current with respect to the magnitude of friction.

In Fig. 6, (a) is the speed curve; acceleration control is performed up to point A, and when the target speed v, l is reached at point A, the current flowing through the servo motor 14 is turned on and off to reach the target value. When the deceleration start point B is reached, deceleration control is performed, and when the low-speed pushing target speed VL is reached, the deceleration is stopped and the current is turned on and off to maintain the pushing target speed VL. It performs control and stops when it reaches the target position.

For such a speed curve, Fig. 6(b)(c)(d)
shows the current when the friction is medium, small, and large. This is based on the relationship between friction (velocity information V) and current value shown in FIG.

Due to speed control that takes such friction into account, even if variations in drive system friction occur during assembly or due to temperature changes, the actual friction at that time is measured during test operation immediately after startup, and the current is adjusted by referring to the table. The value is determined and speed control is performed, and stable speed control is performed without causing excess or deficiency in the drive torque of the servo motor 14 in response to changes in friction.

In the above embodiment, the current is determined by referring to the current table 20 based on the speed information detected in the test operation, but it goes without saying that an appropriate calculation formula may be used instead of the table. It is.

[Effects of the Invention] As explained above, according to the present invention, the friction of the drive system is investigated through a test operation when the motor is started, and the current value for driving the servo motor corresponding to the actual friction is determined to control the speed. Therefore, stable speed control can always be performed even if the friction of the drive system changes due to assembly, temperature changes, etc.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the principle of the present invention; Fig. 2 is an exemplary configuration diagram of the present invention; Fig. 3 is an explanatory diagram of the current value table of the present invention; Fig. 4 is an explanatory diagram of the current value table of the present invention; Figure 5 is a processing flow diagram of the present invention; Figure 6 is an explanatory diagram of control of the present invention with respect to the magnitude of friction; Figure 7
FIG. 8 is an explanatory diagram of conventional speed control operation; FIGS. 9A and 9B are flowcharts of conventional speed control processing. In the figure, 10: Upper device (upper MPU) 12: Position detection means (encoder) 14: Servo motor 16: Test driving means (part) 18: Speed detection means (part) 20: Current value table 22: Current value determining means (Part) 24: Lower MPU 26: l10 28: DA converter 30: Constant current amplifier 32: Counter

Claims (2)

[Claims] (1) Control the motor speed by determining the drive current (1) of the servo motor (14) based on the target position set from the host device (10) and the motor position detected by the position detection means (12). A speed control device for a servo motor includes: a test drive means (16) that supplies a predetermined reference current (I_R) to the servo motor for a certain period of time (T_R) when the motor is started; ) for detecting speed information (V) dependent on mechanical friction of the motor drive system obtained by motor drive; and speed information (V) dependent on friction of the motor drive system and drive. The present invention is characterized by comprising a current value determining means (22) for determining a current value corresponding to the speed information of the detecting means (18) from a current table (20) in which a correspondence relationship of currents (I) is set in advance. Servo motor speed control method. (2) In the servo motor speed control system according to claim 1, the current value determining means (22) includes a current table (20).
With reference to A speed control device for a servo motor, characterized in that it determines a pushing current (I_L) used to control a low target speed from a deceleration end point to a stop at a target position.