JP4281167B2 - Positioning control device and positioning control method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a servo motor positioning control device and a positioning control method thereof.
[0002]
[Prior art]
Conventionally, in order to shorten the positioning time of the servo motor, a method of feeding forward to the position control loop has been taken. FIG. 5 is a block diagram showing an example of the control system.
[0003]
The control system 21 is a servo system that rotates the motor 4 so as to follow the target position signal r output from the computing unit 2 and moves the machine movable unit 6 composed of a ball screw and a nut to a desired position. is there. The motor 4 includes an encoder 8 for detecting the rotational position. The detection result is fed back, subtracted from the target position signal r by the adder 10, and output to the servo amplifier 12 as a speed command.
[0004]
Since the positioning cannot be expected with this alone, the target position signal r is differentiated by the differentiator 14 to generate a speed command, which is fed forward and added by the speed command output from the adder 10 and the adder 16. To do. In this way, the speed command signal is raised to achieve quick positioning.
[0005]
[Problems to be solved by the invention]
However, according to the above prior art, since there is no target position signal r at the time of the in-position check at the end of positioning (check whether the rotational position of the motor 4 is correct), feedforward is not substantially applied. For this reason, it takes time for positioning.
[0006]
This is shown in FIG. FIG. 6A shows a speed command (output waveform of the differentiator 14) by a solid line, and a graph superimposed with a one-dot chain line showing a signal (speed feedback) obtained by differentiating the position feedback signal from the encoder 8 for comparison. It is.
[0007]
Thus, even after the speed command becomes zero at time t ₁ (generally, the target position signal r no longer changes), since the control system 21 includes the position loop, the actual speed is the speed. The form is delayed with respect to the command. FIG. 6B is a graph showing the speed command to the servo amplifier 12. When the speed command becomes zero at time t ₁ , feedforward does not substantially work and the in-position check time cannot be shortened effectively.
[0008]
The present invention has been made in view of the above problems, and the positioning control device according to claims 1 and 2 and the positioning control method according to claims 6 and 7 reduce the in-position check time , and the original speed command. It is an object to reduce the in-position check time without affecting the signal and to effectively reduce the in-position check time . The positioning control device according to claim 3 and the positioning control method according to claim 8 are intended to shorten the in-position check time according to various speeds.
[0009]
[0010]
The positioning control device according to claim 4 and the positioning control method according to claim 9 are intended to prevent control failure such as overshoot from occurring. Positioning control method according to the positioning control device and claim 1 0 of Claim 5 is intended to prevent the excessive increase in the input signal to the servo amplifier.
[0011]
[Means for Solving the Problems and Effects of the Invention]
The positioning control device according to claim 1 of the present invention made to achieve such an object includes speed command generation means for generating a speed command signal from at least a position signal of a servo motor and a target position signal. In the positioning control device that performs positioning control of the servo motor by inputting the speed command signal output from the speed command generating means to the servo amplifier, the equivalent signal set in advance as a value corresponding to the speed command signal The equivalent signal generation means for generating the signal and the equivalent signal generated by the equivalent signal generation means are fed forward and input to the servo amplifier when there is no change in the target position signal, and the feed forward of the equivalent signal is started. Fidofu the predetermined time from the stop the feedforward after a lapse Characterized by comprising a word control means.
[0012]
In such a positioning control device, even when the target position signal is not changed, the equivalent signal is instead fed forward by the feedforward control means, so that the time required for positioning is shortened. Further, the feedforward control means stops the feedforward after a predetermined time has elapsed after starting the feedforward of the corresponding signal after the target position signal has ceased to change. There is no deviation in the rotational position of the servo motor.
[0013]
Therefore, according to the positioning control apparatus of the first aspect, the in-position check time can be shortened. In this claim, feedforward of the speed command generated by the differentiator 14 (see FIG. 5) is not an essential requirement, but the equivalent signal generation means and the feedforward control means are applied to a control system that does not have this feedforward. Even so, instead of the speed command, the equivalent signal is fed forward and stopped after the change of the target position signal is eliminated, so that the in-position check time can be shortened.
In addition, since the feedforward of the corresponding signal is started when the change of the target position signal ceases, in the state where the change of the target position signal is present (for example, the period up to t ₁ in FIG. 6A ), the feed is performed. The equivalent signal output by the forward control means is not input to the servo amplifier at all. Then, when the target position signal no longer changes (time t ₁ in FIG. 6A), feed-forward of the corresponding signal is started.
Also, the feedforward control means starts feedforward of the corresponding signal when the target position signal no longer changes, that is, at the earliest time within the range that does not affect the original speed command signal. It is easy to secure a period during which the signal is fed forward.
Therefore, according to the positioning control apparatus of the first aspect, the in-position check time can be shortened without any influence of the corresponding signal on the original speed command signal.
In addition, since the feedforward control means stops the feedforward after a predetermined time has elapsed since the start of feedforward of the corresponding signal, the feedforward of the corresponding signal is ensured for a predetermined time. The in-position check time can be effectively shortened.
[0014]
The positioning control device according to claim 2 is clearly applied to a control system that performs feedforward of a speed command. That is, the present invention described in claim 2 is the positioning control device according to claim 1, wherein the speed command generation means includes a target position signal of the servo motor in addition to the position signal of the servo motor and the target position signal. The speed command signal is generated on the basis of a value proportional to the differential value.
[0015]
In the control system that performs feedforward of the speed command in this way, as described above, if the target position signal stops changing, feedforward does not work. Even in such a state, the equivalent signal generated by the equivalent signal generating means is fed. According to this positioning control apparatus provided with the feedforward control means for forwarding, the in-position check time can be shortened.
[0016]
According to a third aspect of the present invention, in the positioning control device according to the first or second aspect, the equivalent signal generating means generates the equivalent signal having a larger value as the change in the target position signal increases. It is characterized by being. This corresponds to increasing the size of the equivalent signal as the size of the speed command increases. On the other hand, if the size of the corresponding signal is kept constant regardless of the speed command, the feed forward of the corresponding signal does not work sufficiently when the speed signal is large, or the servo is triggered by the corresponding signal when the speed signal is small. There is a risk that the motor may overshoot. In addition, it may be difficult to set an optimal equivalent signal size that can support various speeds. Conversely, if the corresponding signal is made smaller as the speed command becomes larger, the possibility that these problems will occur increases.
[0017]
In this regard, according to the positioning control device of the third aspect, the in-position check time can be effectively reduced at various speeds .
[0018]
[0019]
[0020]
[0021]
According to a fourth aspect of the present invention, in the positioning control device according to any one of the first to third aspects, the feedforward control means is configured such that the target position signal does not change and the position deviation amount of the servo motor is The feedforward of the corresponding signal is stopped when the value becomes equal to or less than a predetermined value.
[0022]
On the other hand, if the feedforward of the corresponding signal is continued even though the positional deviation amount is sufficiently small, there is a possibility that control failure such as overshooting of the rotational position of the motor may occur. In this regard, according to the positioning control device of the fourth aspect, it is possible to prevent such a control failure from occurring.
[0023]
According to a fifth aspect of the present invention, in the positioning control device according to any one of the first to fourth aspects, the input of the equivalent signal and the speed command signal is received, and only the larger one of them is output. And comparing means for inputting to the servo amplifier.
[0024]
On the other hand, if the equivalent signal and the speed command signal are simply added to the servo amplifier and input, the input signal may become excessive. Therefore, in claim 5 , a comparison means is provided, and only the larger one of these signals is input to the servo amplifier. According to such a positioning control device, an excessive input signal to the servo amplifier can be prevented.
[0025]
The positioning control devices according to claims 1 to 5 are configured as positioning control methods according to the present invention according to claims 8 to 10 , respectively, and can achieve the same effects as the corresponding positioning control devices. .
[0026]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a control system 1 to which the present invention is applied. In addition, the same code | symbol is attached | subjected about the structure of the same name as the control system 21 shown in FIG.
[0027]
Similar to the control system 21, the control system 1 is a servo system that moves the machine movable unit 6 to a desired position by rotating the motor 4 so as to follow the target position signal r output from the computing unit 2. Also in this control system 1, the detection result by the encoder 8 provided in the motor 4 is fed back, subtracted from the target position signal r by the adder 10, and input to the servo amplifier 12 via the comparator 19 described later. It becomes a command. Then, the target position signal r is differentiated by the differentiator 14, feed-forwarded, and added by the adder 16 and the speed command signal output from the adder 10. Here, the adder 16 corresponds to the speed command generation means of the present invention.
[0028]
The computing unit 2 outputs not only the target position signal r but also a corresponding signal v set in advance as a value corresponding to the speed command signal. That is, the arithmetic unit 2 corresponds to the equivalent signal generation means of the present invention. In the control system 1, the equivalent signal v is a constant value regardless of the magnitude of the target position signal r and its differential value.
[0029]
The equivalent signal v is input to the comparator 19 via the feedforward control unit 20 that performs a switching operation. The feedforward control unit 20 performs ON / OFF control as to whether or not the equivalent signal v is output to the comparator 19. The condition for turning on is that the state where the target position signal r has changed has shifted to a state in which the change has disappeared. In the control system 1, by detecting that the output of the differentiator 14 has become zero, this equivalent signal v is turned on and input to the comparator 19.
[0030]
On the other hand, there are two OFF conditions, which are turned OFF when any of the following conditions is satisfied. That is, one is that a certain time has elapsed since the corresponding signal v is turned on, and the other is that the positional deviation amount is equal to or less than a certain amount. When one of these is established, the equivalent signal v is turned off.
[0031]
The comparator 19 receives the output signal x from the adder 16 and the equivalent signal v (when the feedforward control unit 20 is in the ON state), and the larger of them is output. Therefore, if the feedforward control unit 20 is in the OFF state, the output signal x from the adder 16 is output. That is, the comparator 19 corresponds to the comparison means of the present invention.
[0032]
For example, the control system 1 is configured as shown in FIG. When a floppy disk drive (denoted as FDD in this figure) 23 is read by a floppy disk in which an NC (numerical control) program for operating the machine movable unit 6 in a desired order is recorded in advance, the NC program causes the FDD controller 24 to operate. To the CPU 27. Based on a command for positioning the table 25 at the target position in the NC program, the CPU 27 calculates time-series data of the target speed from the target position (this corresponds to the speed command in FIG. 4A). Expand to. Based on this, in order to shorten the in-position check time of the control target composed of the motor 4 and the servo amplifier 12, the CPU 27 further calculates an appropriate control signal and inputs the interface (described as I / F in this figure) 31 to D / Output to the A converter 33. Software for performing such a series of processes is stored in the ROM 35 in advance. In the D / A converter 33, the digital signal received from the I / F 31 is converted into an analog signal and input to the servo amplifier 12. Then, the motor 4 is operated to rotate the ball screw 39, and the table 25 is moved together with the nut 41. Reference numeral 43 denotes a crystal oscillator that emits a processing signal of the control unit 45 including the CPU 27 and the like and a clock signal that serves as a reference of a timer described later.
[0033]
The computing unit 2, the adder 10, the differentiator 14, the adder 16, the feedforward control unit 20, and the comparator 19 are stored as software in the ROM 35, and are realized by the CPU 27 executing this software. Of the software executed by the CPU 27, a flowchart of processing as the feedforward control unit 20 is shown in FIG. This process is started every predetermined time (for example, 2 msec).
[0034]
When this processing is started, first, at step (hereinafter referred to as S) 100, it is determined whether or not the command speed, that is, the output of the differentiator 14 is zero. If it is zero, it will progress to S110 and it will be determined whether the command speed when this process was started last time was not zero. If Yes, that is, if not zero, the process proceeds to S120, and the switch of the feedforward control unit 20 is turned on. Actually, since this switch is realized by software, it should be said that the equivalent signal v is a comparison target in the comparator 19. Then, a timer is started in S130, and the process proceeds to S140. If NO is determined in S100, or if NO is determined in S110, the process goes straight to S140.
[0035]
In S140, it is determined whether or not the switch of the feedforward control unit 20 is ON, that is, the equivalent signal v is a comparison target in the comparator 19. If it is to be compared, the process proceeds to S150, and whether or not the measured value of the timer is larger than a preset time, that is, the set time elapses after the equivalent signal v becomes the comparison target in the comparator 19. Determine if you did. If it has elapsed, the process proceeds to S160, the switch is turned off, that is, the corresponding signal v is not output to the comparator 19, and the measured value of the timer is returned to zero (denoted as reset in this figure) in S170, and this process is terminated. When it is determined NO in S150, the process proceeds to S180, and it is determined whether or not the position deviation amount is equal to or less than a preset deviation amount. If the result of this determination is Yes, the process proceeds to S160, and if the result is No, this process ends. If NO is determined in S140, the process is terminated as it is.
[0036]
In the control system 1 configured as shown in FIGS. 1 and 2 and performing processing including the processing shown in FIG. 3, speed feedback when the same command pattern as the speed command shown in FIG. FIGS. 2A and 2B show the output signal of the comparator 19 (corresponding to the speed command to the servo amplifier 12 in the control system 21).
[0037]
That is, when the same target position signal r generated by the calculator 2 in FIG. 6A is generated by the calculator 2, the speed command is naturally the same. The speed feedback is the same until the speed command becomes zero. When the speed command becomes zero at time t ₁ , the feedforward control unit 20 is turned on and the equivalent signal v is input to the comparator 19. As a result, a constant equivalent signal v is output from the comparator 19 as shown in FIG. As a result, the speed feedback exhibits a larger value than the speed feedback shown in FIG. 6A, as indicated by a one-dot chain line in FIG. As a result, the motor 4 reaches the correct rotational position at time t ₃ earlier than time t ₂ shown in FIG. 6, and the in-position check time is shortened. Here, it is assumed that the equivalent signal v is turned off because the positional deviation has become a certain amount or less. For this reason, a desirable control result is obtained that the in-position check time is shortened without the speed feedback also exhibiting overshoot or vibration. Here, the experiment was conducted such that the maximum speed was 50 m / min and the corresponding signal v was turned off when 50 msec had elapsed since the ON or when the positional deviation became 100 pulses or less.
[0038]
Depending on how the target position signal r is given, the equivalent signal v may be turned off because a certain time has elapsed since it was turned on. Even in such a case, since the equivalent signal v is fed forward for the predetermined time, the in-position check time can be shortened. Further, when the position deviation becomes small in the middle of this fixed time, the equivalent signal v is turned off, so that the ON period of the equivalent signal v is too long and a desired control result cannot be obtained.
[0039]
As described above, the control system 1 has been described as an embodiment of the present invention, but the present invention is not limited to this embodiment and can be implemented in various modes. For example, although the equivalent signal v is a constant value in the control system 1, it may be changed according to the target position signal r and its differential value. As an example, if the change of the target position signal r increases (that is, the speed command increases), the corresponding value v of a larger value is increased, so that the feedforward of the corresponding signal is sufficiently performed when the speed signal is large. It is possible to prevent such a situation that the servo motor does not work or the servo motor causes an overshoot by the corresponding signal when the speed signal is small.
[0040]
Further, the OFF condition of the equivalent signal v in the feedforward control unit 20 may be set only when the position deviation is equal to or smaller than a certain amount (that is, S150 is deleted), or the feedforward control unit 20 is turned on. It may be only that a certain time has passed (corresponding to deleting S180). On the other hand, the ON condition of the equivalent signal v may not be the time when the speed command becomes zero, but may be a time before that (for example, the time when the speed command starts to decrease). Even in this case, the comparator 19 inputs the larger one of the output signal x and the corresponding signal v to the servo amplifier 12, so that an appropriate speed command is input to the servo amplifier 12.
[Brief description of the drawings]
FIG. 1 is a block diagram of a control system 1 according to an embodiment of the present invention.
FIG. 2 is an explanatory diagram showing an outline of a configuration of a control system 1;
FIG. 3 is a flowchart of processing corresponding to feedforward control means, which is executed by a CPU 27.
FIG. 4 is a graph showing speed feedback in the control system 1 and changes in a speed command signal to the servo amplifier 12;
FIG. 5 is a block diagram of a control system 21, which is an example of a conventional positioning control system.
6 is a graph showing speed feedback in the control system 21 and changes in a speed command signal to the servo amplifier 12. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Control system, 2 ... Operation unit, 4 ... Motor, 6 ... Machine movable part, 8 ... Encoder,
DESCRIPTION OF SYMBOLS 10, 16 ... Adder, 12 ... Servo amplifier, 14 ... Differentiator, 19 ... Comparator 20 ... Feedforward control part, 21 ... Conventional control system,
27 ... CPU, r ... target position signal, v ... equivalent signal, x ... output signal.

Claims (10)

At least a speed command generating means for generating a speed command signal from the position signal and the target position signal of the servo motor is provided, and at least the speed command signal output by the speed command generating means is input to a servo amplifier to control positioning of the servo motor. In the positioning control device for performing
Equivalent signal generation means for generating an equivalent signal set in advance as a value corresponding to the speed command signal;
The equivalent signal generated by the equivalent signal generating means is feed-forwarded when the change in the target position signal ceases to be input to the servo amplifier, and is determined in advance after starting feed-forward of the equivalent signal. Feedforward control means for stopping the feedforward after a lapse of a given time ;
A positioning control device comprising: The positioning control device according to claim 1,
The speed command generating means is
A positioning control device for generating the speed command signal based on a value proportional to a differential value of the target position signal of the servo motor in addition to the position signal of the servo motor and the target position signal. In the positioning control device according to claim 1 or 2,
The positioning control device characterized in that the equivalent signal generating means generates the equivalent signal having a larger value as the change in the target position signal becomes larger. The positioning control device according to any one of claims 1 to 3,
When the predetermined time has not elapsed since the start of feedforward, the feedforward control means performs feedforward of the corresponding signal when the position deviation amount of the servomotor becomes equal to or less than a predetermined value. A positioning control device that stops. In the positioning control device according to any one of claims 1 to 4 ,
A positioning control apparatus comprising: a comparison unit that receives the equivalent signal and the speed command signal, outputs only the larger one of these signals, and inputs it to the servo amplifier. In a positioning control method for performing positioning control of a servo motor by inputting a speed command signal generated from at least a position signal of a servo motor and a target position signal to a servo amplifier,
A corresponding signal preset as a value corresponding to the speed command signal is fed forward and input to the servo amplifier when the change in the target position signal ceases, and feed forward of the corresponding signal is started. A positioning control method , wherein the feedforward is stopped after a predetermined time has elapsed . The positioning control method according to claim 6 ,
The positioning control method, wherein the speed command signal is generated based on a value proportional to a differential value of the target position signal of the servo motor in addition to the position signal and the target position signal of the servo motor. In the positioning control method according to claim 6 or 7 ,
The positioning control method, wherein the value of the equivalent signal is increased as the change of the target position signal is increased. The positioning control method according to any one of claims 6 to 8 ,
When a predetermined time has not elapsed since the start of feedforward of the equivalent signal, the feedforward of the equivalent signal is stopped when the position deviation amount of the servo motor becomes equal to or less than a predetermined value. A positioning control method characterized by the above. The positioning control method according to any one of claims 6 to 9 ,
A positioning control method, wherein the larger one of the corresponding signal and the speed command signal is input to the servo amplifier.

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