JPH05211792A - Method and device for controlling ac servo motor - Google Patents

Abstract

PURPOSE:To enable a CPU to output a control signal composed of a fine sine wave even when a rotor is rotated at a high speed so as to prevent the occurrence of uneven rotation and vibrations and, at the same time, make the processing time of a system monitoring routine shorter by detecting the rotational angle of the rotor and making the actual value of the rotational angle to follow a position and speed commands inputted from the outside. CONSTITUTION:When the rotating speed of an AC servo motor is slower than a prescribed speed N0, the arithmetic operation of a system monitoring routine is preferentially executed and the routine is interrupted for a position control routine at every prescribed time interval T2 and, when the rotating speed is larger than the prescribe speed N0, the arithmetic operation of the position control routine is preferentially executed and the routine is interrupted for the system monitoring routine.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control method and a control device using a position control routine and a system monitoring routine in an AC servomotor.

[0002]

2. Description of the Related Art In an AC servomotor using a microcomputer (hereinafter referred to as CPU), control software can be roughly classified into a system monitoring routine and a position control routine. The system monitoring routine monitors the entire system and checks the system for abnormalities and sets the operation mode. The position control routine issues commands such as reading of a feedback counter (deviation counter), position control, and speed control.

FIG. 4 is a diagram showing the basic structure of a conventional apparatus. Reference numeral 1 is a servo motor, 2 is a rotation angle detector for detecting the rotation angle of its rotor, 3 is a microcomputer (CPU) for controlling, and 4 is a rotation angle detector. Is a power conversion circuit. CPU3
Performs feedback control so that the actual value detected by the detector 2 follows the position (rotation angle) command or speed command of the servo motor input from the outside, and outputs a sine wave current command signal b.

That is, the output pulse of the detector 2 is converted into a digital input signal a by the input side interface 5, and the CPU
Input to 3. This input signal a is counted by the feedback counter 3a of the CPU 3, and the torque command value c is calculated by the position / speed calculator 3b based on the difference between the position / speed command.
Is required. On the other hand, the rotor position counter 3c determines the rotor position based on the count value of the feedback counter 3a. The CPU 3 reads the sine wave corresponding to this rotor position from the sine wave table stored in the memory 3d. The multiplier 3e multiplies the torque command value c by this sine wave and outputs a sine wave current command signal b.

The power conversion circuit 4 converts the power supplied from the power supply into the power to be supplied to the servomotor based on the current command signal b. In the case of the AC servomotor, a PWM inverter is usually used.

Reference numeral 5 is an input side interface (IF) of the CPU 3, and 6 is an output side interface (IF).
Is. The interface 5 has an A / D converter,
When the encoder is used for the rotation angle detector 2, a digital speed calculation circuit for calculating the rotation speed from the output signal of the encoder is included.

In the case of a 4-pole motor, the CPU 3 outputs two cycles of a sine wave for one rotation of the rotor. CPU3 when the sampling interval of CPU3 is 1 msec
The current command signal b, which is the output of, is as shown in FIG. In this figure, (A) shows the time when the rotational speed is N = 3 RPM, and (B) shows the time when N = 3000 RPM.

That is, when N = 3, the CPU 3 outputs one sine wave having a cycle of 10 seconds because it makes one rotation in 20 seconds. The number of samples per cycle of this sine wave is 1 cycle / sampling cycle = 10 seconds / 1 msec. = 10,000. However, when N = 3000 RPM, 0.02se
Since the CPU makes one rotation in c, the CPU 3 outputs a sine wave with a period of 0.01 sec. Therefore, sine wave 1 in this case
The sampling number per cycle is 0.01 sec / 1 msec = 10.

[0009]

As described above, in the conventional apparatus, since the sampling cycle is always constant, the number of samplings of the rotation angle per cycle is remarkably reduced especially at high speed rotation. For this reason, there is a problem that the control signal b output from the CPU 3 cannot command a clean sine wave especially at high speed, which causes uneven rotation and vibration.

Further, the calculation processing time T ₁ of the position control routine
Is constant, and this routine is processed by interrupting the system monitoring routine at regular intervals (sampling period) T ₂₀ (see FIG. 1). However, as described above, in order to secure a sufficient number of samplings at high speed, the fixed time T ₂₀ needs to be sufficiently short.
_20- T ₁ ) is also shortened.

Since the system monitoring routine is divided into processing times (T ₂₀ -T ₁ ) at regular intervals, the routine takes a long time to complete one cycle, and when a system abnormality occurs, for example. There is a problem that anomaly detection is delayed.

[0012]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and the CPU can output the control signal b consisting of a beautiful sine wave even at the time of high speed rotation, thereby preventing the occurrence of uneven rotation and vibration. It is a first object of the present invention to provide a control method for an AC servomotor that is capable of achieving a high processing speed of the system monitoring routine. It is also a second object to provide an apparatus directly used for carrying out this method.
The purpose of.

[0013]

According to the present invention, a first object is to detect a rotation angle of a rotor, and to control a microcomputer so that a position / speed command inputted from the outside is followed by an actual value of the rotation angle. In the AC servo motor, when the rotation speed is lower than a predetermined speed (No), the operation of the system monitoring routine is prioritized and the position control routine is interrupted at predetermined time intervals (T ₂ ). This is achieved by a method for controlling an AC servomotor, characterized in that the system monitoring routine is interrupted at predetermined time intervals by giving priority to the routine calculation.

A second object is a rotation angle detector for detecting the rotation angle of the rotor, a microcomputer for performing feedback control so that the rotation angle follows an externally input position / speed command, and In an AC servomotor including a power conversion circuit that controls a field current based on a control signal output from a microcomputer, the microcomputer sets a priority flag below a predetermined rotation speed (No) and sets a predetermined rotation speed (No). ) A speed discriminating means (step 16) that clears the above is provided, and below the predetermined rotation speed (No), the system control routine is prioritized and the position control routine is interrupted at regular time intervals (T ₂ ), while Above the rotation speed, the position control routine is given priority and the system monitoring routine is divided at regular time intervals. It is achieved by the control apparatus of the AC servo motor, characterized in that the Maseru manner.

[0015]

1 is a conceptual diagram of an embodiment of the present invention, FIG. 2 is an operation flow chart of an execution program control routine, and FIG. 3 is an operation flow chart of a system monitoring routine. First, the principle of the present invention will be described with reference to FIG.

In FIG. 1, N is the rotational speed of the rotor (RP
M) and T ₂ indicate execution time intervals of the position control routine.
In the conventional device, this execution time interval T ₂₀ is constant as shown by p in FIG. 1, so it is necessary to reduce the execution time interval T ₂₀ in order to secure a large number of samplings at high speed. Then, as described above, the system monitoring routine takes a long time to process.

Therefore, in the present invention, this execution time interval T ₂
As shown by the solid line q in FIG. The relationship between T ₂ and N can be set by, for example, a linear equation, T ₂ = T ₀ −kN, as shown in the figure. Here, -k indicates the slope of the straight line q. In this case, since the interval T ₂ increases as the velocity N decreases,
Position control routine of processing time T ₁ difference between the (constant is) (T ₂ -T ₁₎ increases with decreasing speed. Therefore, the processing time (T ₂ −T ₁ ) of the system monitoring routine shown by hatching in FIG. 1 becomes longer as the speed becomes slower, and the processing speed becomes faster.

At a constant speed N ₀ or more, T ₂ becomes excessively small, and the processing time of the system monitoring routine (T ₂ −
It is possible that T ₁ ) becomes too small or negative. Therefore, at the speed N ₀ or higher, the position control routine is prioritized and the system monitoring routine is interrupted at a predetermined time interval. In FIG. 1, r indicates the processing time of this position control routine, and s indicates the processing time of the system monitoring routine. By doing so, the processing time of the system monitoring routine is secured, and the inconvenience of delaying the processing and delaying the system abnormality detection does not occur.

Next, an operation example will be described with reference to FIGS.
This embodiment has an execution program control routine for controlling the priority of two programs, a system monitoring routine and a position control routine. This routine is shown in Figure 2.
It is shown in.

First, in FIG. 2, when starting, the position control routine interrupt is enabled (step 10), and the system monitoring routine is disabled (step 1).
2). Then, the execution interval of the position control routine, that is, FIG.
The interval T _{2 in} is calculated based on the above-mentioned linear expression, that is, the straight line q (step 14).

Next, if the speed N is equal to or lower than the constant speed N ₀ (step 16), the priority flag is set (step 18). If the speed N is equal to or higher than N ₀ , the priority flag is cleared (step 20). That is, when this priority flag is set, the interrupt of the system monitoring routine is disabled and this routine is prioritized (step 2
2), the position control routine is called at every execution interval T ₂ and its calculation is performed (steps 24, 14).

When the priority flag is cleared, the execution time interval T ₃ of the system monitoring routine is set (step 26) and the interrupt priority of this monitoring routine is raised (step 28). That give priority to the position control routine, here to interrupt the monitoring routine at regular time intervals T _3.

The system monitoring routine performs the operation shown in FIG. First, when starting, 1 is added to the content n of the order counter (step 30). The system monitoring routine, for each execution time interval T ₂ (T ₂ -T
_Since it is processed for ₁ ) time, this routine ends up with n
It will be divided into processes and executed. The order counter stores which of the system monitoring routines divided into n is executed in order to continuously perform the processing n times.

If n = n, it means that the entire processing of this routine has been completed. Therefore, the processing is returned to n = 0 (step 32), and if the priority flag is set (step 34), the first processing, that is, n. = 0 is entered (step 36). If the flag is clear, N> N ₀ and the position control routine has priority, so the process corresponding to the value n of the order counter at that time is finally performed and the end is reached (step 38). That is, for example, if n = 1, the process 1 is performed last (step 39), and since the priority flag is clear (step 40), the process goes to the end.

In this embodiment, the time interval T ₃ of the system monitoring routine for interrupting N> N ₀ is a fixed value (fixed value).
However, this may be variable. Similarly, the interrupt time interval T of the position control routine for N <N _0
2 may be given by a hyperbolic function inversely proportional to N, in addition to the one given by a linear expression of the velocity N as in the above embodiment. Further, this time interval T ₂ may be a constant value.

[0026]

As described above, according to the invention of claim 1, N <N
_{When 0} , the system monitoring routine is prioritized, and the position control routine is interrupted at predetermined time intervals (T ₂ ), while when N> N ₀ , the position monitoring routine is prioritized and interrupted by the system monitoring routine. From
Even during high-speed rotation, the sampling cycle of the position data can be made sufficiently small so that the output control signal of the CPU can be brought close to a clean sine wave. Therefore, it is possible to reduce uneven rotation and vibration.

Further, since the processing time of the system monitoring routine can be sufficiently secured at the low speed, it is possible to shorten the time required for the processing to complete one cycle and speed up the detection of an abnormality. Here, it is desirable to decrease the time interval T ₂ for interrupting the position control routine with N <N ₀ with respect to the increase of the speed N (Claim 2). Especially, if it is a linear function of N, the calculation becomes simple ( Claim 3). According to claim 4, an apparatus is provided which is used directly for carrying out the method.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of the principle of an embodiment of the present invention.

FIG. 2 is an operation flow chart of an execution program control routine.

FIG. 3 is an operation flowchart of a system monitoring routine.

FIG. 4 is a conceptual diagram of a conventional device.

FIG. 5 is a waveform diagram of a CPU output control signal.

[Explanation of symbols]

 1 Servo Motor 2 Rotation Angle Detector 3 Microcomputer 12 Speed Discriminating Means Step

Claims (4)

[Claims] 1. An AC servomotor controlled by a microcomputer so as to detect a rotation angle of a rotor and cause a position / speed command inputted from the outside to follow an actual value of this rotation angle, a predetermined rotation speed (No). In the following, the calculation of the system monitoring routine is given priority and the predetermined time interval (T ₂ )
The AC servomotor is characterized in that the position control routine is interrupted every time, and when the rotational speed is equal to or higher than the predetermined rotation speed (No), the operation of the position control routine is prioritized and the system monitoring routine is interrupted at every predetermined time interval. Control method. 2. A predetermined time interval (T ₂ ) for interrupting a position control routine at a speed equal to or lower than a predetermined rotation speed is a rotation speed (N).
A according to claim 1, which is set to decrease with an increase in
C Servo motor control method. 3. The predetermined time interval (T ₂ ) is the rotational speed (N)
The method of controlling an AC servomotor according to claim 2, wherein the AC servomotor is set by a linear function. 4. A rotation angle detector for detecting a rotation angle of a rotor, a microcomputer for performing feedback control so that the rotation angle follows an externally input position / speed command, and this microcomputer outputs. In an AC servomotor including a power conversion circuit that controls a field current based on a control signal, the microcomputer sets a priority flag below a predetermined rotation speed (No) and clears above a predetermined rotation speed (No). A speed discriminating means (step 16) is provided and the predetermined rotation speed (N
o) In the following, the system monitoring routine is prioritized to interrupt the position control routine at constant time intervals (T ₂ ), while above the predetermined rotation speed, the position control routine is prioritized and the system monitoring routine is interrupted at constant time intervals. A control device for an AC servomotor, which is characterized in that