JPH0695299B2 - Positioning servo system control method - Google Patents

Description

The present invention relates to a positioning servo system such as a robot using a head of a magnetic storage device, a DC motor, a direct-acting servo valve directly driven by a voice coil motor, and the like. Control method.

[Prior Art] Positioning servo systems driven by DC motors, linear motors, voice coil motors, etc. are used for positioning the head of a magnetic storage device, position control of an arm of an articulated robot, direct-acting electric / fluid pressure. It is used for controlling the opening of the spool of a servo valve, and as a drive unit for many other information equipment and industrial equipment.
FIG. 15 shows an example of the spool 3 by a permanent magnet 6 fixed to the valve body 1 and a movable coil 5 fixed to the spool 3 (this is called a voice coil motor).
It is an example of a direct-acting type electric / fluid pressure servo valve that directly drives the actuator. A spool 3 is slidably accommodated in a sleeve 2 fitted in a valve body 1, and a bobbin 4 around which a movable coil 5 is wound is fixed to one end thereof. Further, a permanent magnet 6 is attached to the valve body 1 so as to form a magnetic circuit with respect to the movable coil 5, and when the movable coil 5 is energized, the magnetic field generated by the permanent magnet 6 and the movable magnet are moved. The spool 3 is driven by the relationship with the magnetic field generated in the die coil 5 so that the fluid path provided in the valve body 1 is communicated with a desired state.

Further, in order to position the spool 3 with respect to the sleeve 2, a displacement gauge 7 for detecting the position of the spool 3 is provided at the other end of the spool 3, and a position signal 8 from the displacement gauge 7 is provided.
Is negatively fed back to the input side of the servo amplifier 9 that supplies a drive current to the movable coil 5, and a feedback control system is configured to maintain the localization of the spool 3. In addition to the position signal 8, the speed meter 10 is provided and the speed signal 11 is also negatively fed back to the servo amplifier 9 for the purpose of damping the controlled object (here, the spool 3), as described later.
In the figure, 12 is a set value, 13 is a command signal, P _S is a supply port, P _T is a return port, and P _A and P _B are control ports.

Such a voice coil motor is also used in a drive unit of a magnetic disk head.

A model of the apparatus shown in FIG. 15 is shown in FIG. 16, and the spool 3, which is a movable portion, is moved by the driving force F of the voice coil motor and the spring 14 positions it. When there is a deviation from the balance position, the restoring force of the spring 14 acts in the balance direction, and its magnitude is proportional to the amount of deviation. In the direct-acting type electro-hydraulic servo valve of FIG. 15, displacement is measured by a displacement detector 7 instead of a spring, and it is electrically converted into force.

By the way, in order to improve the responsiveness of positioning of the controlled object, that is, the spool 3, and the positioning accuracy, the following is important.

 Reduce the weight of moving parts.

 Increase the feedback gain.

, Means increasing the natural frequency of the controlled object.

 Appropriate braking works.

That is, if the weight is reduced, the target can be moved faster with the same motor, and if the position feedback gain is increased, the restoring force of the spring described above increases, and even if it deviates from the target value, it can be quickly returned to the original value. it can. Also, if you apply braking,
It is possible to prevent the vibration from continuing and to quickly settle the position of the spool 3 to the target value.

In order to meet the above-mentioned requirements, the following is required.

′ Lighten the weight of the controlled object (for example, spool 3 or magnetic disk head in FIG. 15) that is driven,
Do not reduce the rigidity.

′ Minimize the response delay in the forward loop of the control system, specifically, reduce the inductance of the drive motor.

′ Actively provide a damping mechanism such as a damper.

However, with regard to ″, even if the maximum effort is made through careful examination at the planning and design stages, it often happens that the rigidity and the performance limit of the motor do not make it to the point, and regarding ″, it is necessary to secure a mounting space. There were problems such as difficult things and cost increase.

In addition to the direct-acting electric / fluid pressure servo valve shown in FIG. 15, the magnetic disk, printer, etc. for positioning by DC motor, linear motor, voice coil motor, etc.
This is generally true for information equipment such as XY blotters, and positioning servo systems for industrial machines such as NC machine tools and industrial robots. For this reason, some control solutions have been proposed in the past.

In order to explain such a control solution, first, a general configuration of the positioning servo system is shown in FIG. This is common to the above-mentioned information equipment such as a magnetic disk and general industrial machines such as a direct-acting electric / fluid pressure servo valve.

In Fig. 17, the target value Vr for positioning the controlled object is the displacement gauge.
The displacement signal Vx indicating the actual position of the controlled object measured by 15 is compared and subtracted by the comparison calculator 16, and the deviation signal Ve = Vr
−Vx is created. This deviation signal Ve is appropriately amplified by the operational amplifier 17 to become V _A ′, and is compared and subtracted by the comparison operation unit 19 with the speed detection signal Vc from the speedometer 18 to become the signal V _A ,
Further, it becomes a command current i that is amplified by the power amplifier 20 and drives the motor 21. The motor 21 generates a driving force F proportional to this command current i, and the controlled object of the mass m starts to move. The displacement x of the controlled object at that time is expressed as a value obtained by integrating the acceleration twice, as shown in the figure, detected by the displacement meter 15 and compared with the target value Vr as described above.
When the target value Vr and the displacement signal Vx of the controlled object 22 match, the deviation
Since Ve becomes zero and the command current i of the motor 21 becomes zero, the controlled object stops and positioning is completed.

Further, the reason that the speed of the controlled object is detected by the speedometer 18 and the negative feedback is performed is to apply the braking. In addition, 23 in FIG. 17 represents a specially manufactured control target.

However, it is known that when such a controlled object 23 is moved at high speed, there is a limit due to the natural vibration of the mechanical system, and residual vibration is likely to occur as shown in FIG. On the other hand, the commonly used method of detecting the speed and damping the controlled object has a limit due to the response delay of the motor, and a simpler solution is desired.

Considering the case where the controlled object follows the stepped target value, a simpler method is shown in FIG. 19 (a) (b).
As shown in (c), the step input, which is the target value, is divided into two, and after the first step input is applied, the second is delayed by the half cycle of the natural vibration cycle of the servo system to be controlled. In addition, it is already known to generate opposite phase vibrations and cancel each other with the original vibrations.

In FIGS. 19 (a), (b), and (c), a step input r ₁ smaller than the target value r is first applied as the target value Vr (see FIG. 17), and a step input r ₂ is further added after T time. Do (No.
Figure 19 (a)). Here, r = r ₁ + r ₂ . Then,
The individual responses due to r ₁ and r ₂ are oscillating as shown in Fig. 19 (b), but the point of time when step inputs r ₁ and r ₂ are applied is the time T corresponding to a half cycle of the natural vibration cycle. Since they are out of phase, their vibrations have opposite phases, and as a result, Fig. 19 (c)
The step response vibration disappears.

By the way, according to the study of the present inventors, such a method is as follows.
It is difficult to determine the ratio of step input amounts r ₁ and r ₂ and T at the time of application, and it is ideal except when the control target is a linear secondary vibration system (mass, spring system) such as the model in Fig. 16. The anti-vibration effect cannot be obtained. It turns out that there is a problem such as. In an actual positioning servo system, as shown in FIG. 17, the characteristics of the transmission delay due to the motor 21 overlap with the movement of the machine, and the solid friction that is a non-linear element in the sliding parts such as the disk head and the spool of the servo valve. Due to the existence of the above, the method shown in FIGS. 19 (a), (b), and (c) is less effective than expected.

[Problems to be Solved by the Invention] In view of the above situation, the present invention uses a signal in a control loop to prevent a continuous vibration from occurring more easily and reliably,
The objective is to realize a servo system with high response and high accuracy, and to do this easily and inexpensively.

[Means for Solving the Problem] In order to achieve the above object, in the first means, a deviation is calculated by performing a comparison operation between an input signal that is a target value and a displacement signal that is an output signal of a control target, and the deviation is calculated. In the positioning servo system that feedback-controls the output of the motor and the moving direction so as to be smaller, it is in the same direction as the changing direction of the input signal, and the natural vibration cycle of the positioning servo system with respect to the change of the input signal. A correction signal that occurs with a time delay corresponding to a half cycle of the above, and is configured to be added to the input signal in a relatively short time thereafter, and the speed signal of the control target is used as the correction signal. A signal delayed by a time corresponding to a half cycle of the natural vibration cycle is used. In the second means, the same direction as the changing direction of the input signal is used in the positioning servo system. And a correction signal that is generated with a time delay corresponding to a half cycle of the natural vibration cycle of the positioning servo system with respect to the change of the input signal, and that becomes zero in a relatively short time thereafter. And a signal obtained by sample-holding the speed signal of the controlled object at a predetermined sampling cycle is used as the correction signal. A correction that is in the same direction as the signal change direction, occurs with a time delay corresponding to a half cycle of the natural vibration cycle of the positioning servo system with respect to the change of the input signal, and becomes zero in a relatively short time thereafter. A signal is added to the input signal, and a differential signal of the displacement of the controlled object for each predetermined time interval is used as the correction signal. According to the fourth means, in the positioning servo system, the direction is the same as the changing direction of the input signal, and the change of the input signal corresponds to a half cycle of the natural vibration cycle of the positioning servo system. A correction signal that occurs with a time delay and becomes zero in a relatively short time thereafter is configured to be added to the input signal, and the deviation signal is used as the correction signal, which corresponds to a half cycle of the natural vibration cycle. The signal delayed by the time is used.

[Operation] In any of the first to fourth means, the input signal for correction, which is formed by positively feeding back to the input section, is a target value delayed by a time corresponding to a half cycle of the natural vibration cycle of the controlled object. Since it is added to the input signal and decreases to zero in a relatively short time after being applied, continuous vibration of the mechanical system to be controlled is prevented easily and reliably, and the machine reaches the target value stably and at high speed. To do.

[Examples] Examples of the present invention will be described below with reference to the accompanying drawings.

First, the principle on which the present invention is based will be described with reference to FIG. 1. A target value r is given and a small step input for correction of r ₃ is given after a certain time T ₀ . By doing so, it is possible to determine the timing T ₀ at which the step input r ₃ is entered after observing the movement of the displacement X of the wrapper roll with respect to the target value r. This point is almost the same as the conventional method shown in (a) to (c) of FIG. Also, T ₀ is selected with reference to the time corresponding to a half cycle of the natural vibration cycle of the controlled object, and is adjusted by observing the actual movement. Furthermore, it has been confirmed that there is no problem in practice even if r ₃ is a substantially fixed value for various target values r, but in order to obtain high results, r ₃ = 0.3r to 0.5r The applied amount may be changed automatically. Incidentally, since the displacement x of the controlled object is r + r ₃ if it is left as it is, the step input r ₃ for correction is set to zero after an appropriate time has elapsed.

As described above, since the actual controlled object includes the non-linear element as described above (the state of the response changes depending on the size of the input), r ₁ smaller than r as in the conventional example is not given, but the true controlled If the target value r is given and the movement of the controlled object is observed and then the correction input is given, as shown by the movement of the displacement of the controlled object of the actual machine in FIG. Can be prevented.

FIG. 2 is an example of the input section for giving the target value of the positioning servo system of FIG. 15 which embodies the principle of FIG. 1, in which 31 is a switch, 32 is a delay circuit, 33 is a function circuit, 34, Reference numeral 35 is an adder / subtractor. In FIG. 2, when the switch 31 is turned on,
The target value r is input to the servo amplifier 9, and the correction step input r ₃ is a time corresponding to a half cycle of the natural vibration cycle of the control target.
It is delayed by T ₀ and sent from the delay circuit 32 to the adder / subtractor 34,
At the same time, from the function circuit 33, a function rt having a maximum value of r ₃ as shown in any one of (a), (b) and (c) of FIG. ₃ is added / subtracted.
Sent to 34 and subtracted from the step input r ₃ , the signal is
It is sent to the adder / subtractor 35 as r ₃ −rt, added by the adder / subtractor 35, and r + r ₃ −rt is sent to the servo amplifier 9 as the target value 12. When the function of the function circuit 33 is as shown in FIG. 3A, the correction input r ₃ is attenuated as shown in FIG. 1, and even when the function is as shown in FIGS. The input decays to zero at the end.

A command signal is given from the servo amplifier 9 to the servo valve shown in FIG. 15, the servo valve 11 is controlled by the signal of r + r ₃ -rt, and the spool 3 to be controlled is as shown in FIG. Controlled by.

The shape of the correction input added to the step input r in FIG. 1 after a certain time T _{0 is} shown in FIGS. 4 (a), (b) and (c). Third
Depending on how to select the function rt shown in Figures (a), (b) and (c),
The shape of the correction input is determined as shown in FIGS. 4 (a), (b), and (c) (in addition to the functions shown in FIGS. 3 (a) to 3 (c), any function that decays to zero after a certain period of time can be used. Needless to say, other signals may be used. By the way, any signal having a shape as shown in FIGS. 4 (a) to 4 (c) can be used as a correction input. The present inventor has noticed and confirmed that all of the following four methods are effective by computer simulation and application to an actual machine. In each of these methods, the positioning servo system uses a signal derived as a result of the step input r, which is a target value, starting to move, so that the magnitude r of the correction input is automatically adjusted according to the magnitude of the step input r. ₃ (Fig. 4 (a) to (c)) has changed and has the characteristic that it can be applied to actual machines more easily than the examples shown in Fig. 1 to Fig. 3 (a) to (c). ing.

Hereinafter, they will be sequentially described.

The displacement x of the spool 3 in FIG. 15 is as shown in FIG. 5 (a), and the corresponding speed has a waveform as shown in FIG. 5 (b). Since this is similar in shape to the correction input shown in FIGS. 4 (a) to (c), this is used as the first method for making the correction input, and as shown in claim 1. Can be corrected to. FIG. 6 is a configuration example of the input unit when the speed of the spool 3 is used as a step input for correction, and is an example of a device for embodying the first method of the present invention. In the figure, 36 is a speedometer and 37 is an operational amplifier.

The speed signal detected by the speedometer 36 is appropriately amplified by the operational amplifier 37 and sent to the delay circuit 32. After the target value r is input to the servo amplifier 9, a half cycle of the natural vibration cycle of the controlled object is obtained. The speed signal delayed by the time T ₀ is sent to the adder / subtractor 35, the signal is added to the target value r by the adder / subtractor 35, and the signal is sent to the servo amplifier 9. Subsequent operations are the same as those described with reference to FIG.

FIG. 7 shows a second method for making a correction input, which corresponds to the second claim. The speed of the controlled object has a shape as shown in Fig. 4 (b), but when this is delayed by a time corresponding to a half cycle of the natural vibration cycle of the controlled object, its output is used as a vibration isolation correction signal. When sampling is performed with the sampling period Δts determined to have a sufficiently effective value, a sample-held signal 38 as shown in FIG. 7 is obtained. Here, as the sampling cycle Δts, a value corresponding to a half cycle of the natural vibration cycle of the controlled object may be selected. Thus, this can be used as a step input signal for correction. FIG. 8 shows an example of the configuration of the input section when the sampled and held signal 38 of FIG. 7 is used as a step input for correction, and is an example of an apparatus for embodying the second method of the present invention. In the figure, 39 is a sampling and holding circuit.

The speed of the controlled object 3 is detected by the speedometer 36, and the operational amplifier
After being properly calculated and amplified in 37, it is sampled and held in the sample hold circuit 39 at every set sampling period Δts, and the signal is sent to the adder / subtractor 35 and added to the target value r. Since the signal sampled by the sample hold circuit 39 is zero in the first sampling period, the sample hold circuit 39 outputs a small step input sequence delayed by Δts. Therefore, the delay circuit 32 shown in FIG. 6 is determined by determining Δts so that its output becomes sufficiently effective as the image stabilization correction signal at the time when it is delayed by a time corresponding to a half cycle of the natural oscillation cycle of the controlled object as described above.
The same function as the above can be achieved.

FIGS. 9 (a) and 9 (b) show a third method of making a correction input, which corresponds to the third aspect of the claims and the tenth method.
The figure is an example of an apparatus for implementing the third method of the present invention. The displacement x of the spool 3 in response to the step input is the ninth
As shown in FIG. 7B, sampling is performed at a certain time interval Δt to obtain the variation Δx, and the variation Δx is divided by the time interval Δt, that is, Δx / Δt is obtained.
This represents the average speed during the time interval Δt. Now, since Δt is constant, the variation Δx becomes a signal proportional to the speed of the spool 3, and the variation Δx is illustrated in FIG. 9 (b).
The shape is as shown in. Therefore, it can be used as a step input signal for correction. FIG. 10 shows an embodiment of the input section when this variation Δx is used as a step input signal for correction. In the figure, 40 is a displacement meter, 41 is an arithmetic unit, and 42 is an operational amplifier.

The displacement of the controlled object detected by the displacement meter 40 is a time determined such that the output becomes a value that is sufficiently effective as a vibration isolation correction signal when delayed by a time corresponding to a half cycle of the natural vibration cycle of the controlled object. The variation Δx is calculated by the arithmetic unit 41 for each interval Δt, and the variation Δx is properly amplified by the operational amplifier 42, sent to the adder / subtractor 35, added with the target value r, and sent to the servo amplifier 9. As can be seen from the waveform of the displacement x shown in FIG. 9 (a), the variation Δx is zero for a certain period of time after the step input r is applied. Therefore, the calculator 41 outputs a signal with a certain period of delay. It Therefore, by determining the sampling time interval Δt so that the output becomes a value that is sufficiently effective as a vibration isolation correction signal at the time point delayed by a time corresponding to a half cycle of the natural vibration cycle of the controlled object, the delay circuit The same function as that provided can be performed. Here, as the time interval Δt, it is known from the experience in the computer simulation and the actual machine that the value of approximately 1/4 cycle of the natural vibration cycle of the controlled object may be selected. FIG. 11 shows that the step response is zero when the above-mentioned calculated speed signal is used as a step input for correction, and the vibration shown in FIG. 18 disappears.

FIGS. 12 (a) to 12 (c) show a fourth method for making a correction input, which corresponds to claim 4 of the claims, and FIG.
The figure is an example of an apparatus for implementing the method of the present invention.
In the positioning servo system shown in FIG. 17, the same applies to the deviation signal Ve between the target value Vr and the signal Vx indicating the actual position of the controlled object (or the output _VA of the comparison calculator 19 and the output i of the power amplifier 20). Yes) has the shape shown in FIG. Since this has a shape similar to that of the correction input shown in FIG. 4 (a), it can be used as the correction input. FIG. 13 shows an example of the configuration of the input section in this case.
Deviation signal output from the positioning servo system controller
Ve is properly amplified by the operational amplifier 37 and sent to the delay circuit 32, and after the target value r is input to the servo amplifier 9, it is delayed by a time T ₀ corresponding to a half cycle of the natural vibration cycle of the controlled object. The deviation signal Ve is sent to the adder / subtractor 35, and the signal is added to the adder / subtractor.
The target value r is added at 35, and the signal is output to the servo amplifier 9. The subsequent steps are as already described.

In each of the above embodiments, the case where the step input is added as the target value has been described, but generally in information equipment and industrial robots, the triangular speed reference curve and the parabolic speed shown in FIG. Positioning is performed by giving a reference curve. In this case, it is equivalent to giving the curves of the shapes (c) and (d) instead of the step input as the target value of the position, but the present invention can also be applied in this way.

In the embodiment of the present invention, as the example of the positioning servo system, the case of the direct acting type electric / fluid pressure servo valve driven by the voice coil motor has been described, but the head of the magnetic disk or the NC machine tool is described. Applicable to all positioning control systems such as the control system with the configuration shown in Fig. 17,
The embodiment shown in FIGS. 5 to 13 can be applied to the input of the target value of any shape, and various modifications can be made without departing from the scope of the invention. is there.

[Advantages of the Invention] According to the control method of the positioning servo system of the present invention, it is possible to prevent continuous vibration from occurring in the mechanical system to be controlled without being affected by the characteristics of the mechanical system to be controlled, and to provide a high response and a high response. It is possible to realize a high-precision servo system, and moreover, it can be done by a simple method, so the price when it is implemented as a device becomes cheap, and compensation for preventing the vibration of the signal formed by returning from the controlled object. The input signal for correction automatically changes when the magnitude of the input signal, which is the target value, changes, so that the vibration can be prevented with higher accuracy and reliability. A variety of excellent effects can be achieved.

[Brief description of drawings]

FIG. 1 is a graph for explaining the principle on which the method of the present invention is based, FIG. 2 is an explanatory view of a control block when control is performed using the principle of FIG. 1, and FIG. ) (B)
(C) is an explanatory diagram of an example of a function set in the function circuit in the control block of FIG. 2, and FIG. 4 (A) (B) (C) is an explanatory diagram showing a shape that can be used as a correction input. Figure 5 (a)
Is a graph showing the displacement and time change of the mechanical system to which the first method of the present invention is applied, FIG. 5 (b) is a graph showing the relationship between the same speed and time, and FIG. 6 is FIG. 5 (b). Of the control block for carrying out the first method of the present invention when the speed of the present invention is used as an input for correction, and FIG. 7 shows the speed of a mechanical system to which the second method of the present invention is applied. FIG. 8 is a graph showing the relationship between sample-held speed and time when held, FIG. 8 shows the second method of the present invention when the sample-held speed shown in FIG. 7 is used as a step input for correction. Of the control block for
FIG. 9 (a) is a graph showing the relationship between displacement and time when the displacement difference of the mechanical system to which the third method of the present invention is applied is determined at predetermined time intervals, and FIG. 9 (b) is the same determination. FIG. 10 is a graph showing the relationship between the variation and the time, and FIG. 10 shows a control block for carrying out the third method of the present invention when the difference Δx in FIG. 9B is used as an input for correction. Explanatory drawing, No.
FIG. 11 is a graph showing the step response of the actual machine according to the third method of the present invention when the correction input is made by the additional amount by the calculated speed signal and the mechanical system is controlled, and FIG. 12 (a) (b)
(C) is an explanatory view showing the shape of the deviation signal Ve, and FIG. 13 is an explanatory view of a control block for carrying out the fourth method of the present invention when the deviation signal Ve is used as an input for correction, 14
Figures (a) and (b) are graphs of the speed reference curve given as target values, and Figures 14 (c) and (d) are the speed reference curves of Figure 14 (a) and (b) converted to target values for displacement. FIG. 15 is a graph, FIG. 15 is an explanatory view of a positioning servo system of a direct-acting type electric / fluid pressure servo valve, FIG. 16 is an explanatory view when the device of FIG. 15 is modeled, and FIG. 17 is a device of FIG. Diagram of the control block of the positioning servo system for controlling the spool position of the
Fig. 19 is a graph showing the change in displacement with time when the spool is controlled by the device shown in Fig. 15, and Fig. 19 (a) (b) (c)
Is a graph for explaining a conventional method in which a step input is divided into two with respect to a vibration waveform of a mechanical system and a second step input is delayed by a time corresponding to a half wavelength to prevent vibration. In the figure, 1 is a valve body, 2 is a sleeve, 3 is a spool, 4 is a bobbin, 5 is a movable coil, 6 is a permanent magnet, and 9 is a permanent magnet.
Is a servo amplifier, 7,15,40 are displacement gauges, 16 is a comparison calculator,
7 is an operational amplifier, 18 is a speedometer, 19 is a comparison calculator, 20 is a power amplifier, 21 is a motor, 23 is a characteristic of a controlled object, 31 is a switch, 32 is a delay circuit, 33 is a function circuit, and 34 and 35 are An adder / subtractor, 36 is a speedometer, 37 is an operational amplifier, 39 is a sample hold circuit, 40 is a displacement meter, 41 is an operational unit, and 42 is an operational amplifier.

Continuation of front page (56) Reference JP-A-48-61878 (JP, A) JP-A-54-98477 (JP, A) JP-A-56-27404 (JP, A) JP-A-58-46402 (JP , A) JP 58-60002 (JP, A) JP 59-146485 (JP, A) JP 58-144908 (JP, A) JP 58-169212 (JP, A) JP 37-12311 (JP, B1)

Claims (4)

[Claims] Claims: 1. Positioning in which an input signal, which is a target value, and a displacement signal, which is an output signal of a controlled object, are compared and calculated to find a deviation, and the output of the motor and the moving direction are feedback-controlled so that the deviation becomes small. In the servo system, it occurs in the same direction as the change direction of the input signal, and occurs with a time delay corresponding to a half cycle of the natural vibration cycle of the positioning servo system with respect to the change of the input signal. A correction signal that becomes zero in time is configured to be added to the input signal, and as the correction signal, a signal obtained by delaying the speed signal of the controlled object by a time corresponding to a half cycle of the natural vibration cycle is used. A method for controlling a positioning servo system, characterized by: 2. Positioning in which an input signal that is a target value and a displacement signal that is an output signal of a controlled object are compared and calculated to obtain a deviation, and the output of the motor and the moving direction are feedback-controlled so that the deviation becomes smaller. In the servo system, it occurs in the same direction as the change direction of the input signal, and occurs with a time delay corresponding to a half cycle of the natural vibration cycle of the positioning servo system with respect to the change of the input signal. Positioning characterized in that a correction signal which becomes zero in time is configured to be added to the input signal, and a signal obtained by sample-holding the speed signal of the controlled object at a predetermined sampling cycle is used as the correction signal. Servo system control method. 3. Positioning in which an input signal, which is a target value, and a displacement signal, which is an output signal of a controlled object, are compared and calculated to obtain a deviation, and the output of the motor and the moving direction are feedback-controlled so that the deviation becomes smaller. In the servo system, it occurs in the same direction as the change direction of the input signal, and occurs with a time delay corresponding to a half cycle of the natural vibration cycle of the positioning servo system with respect to the change of the input signal. A positioning servo system characterized in that a correction signal which becomes zero in time is configured to be added to the input signal, and as the correction signal, a differential signal of the displacement of the controlled object at predetermined time intervals is used. Control method. 4. A positioning method in which an input signal, which is a target value, and a displacement signal, which is an output signal of a control target, are compared and calculated to obtain a deviation, and the output of the motor and the moving direction are feedback-controlled so that the deviation becomes small. In the servo system, it occurs in the same direction as the change direction of the input signal, and occurs with a time delay corresponding to a half cycle of the natural vibration cycle of the positioning servo system with respect to the change of the input signal. A correction signal that becomes zero in time is configured to be added to the input signal, and a signal obtained by delaying the deviation signal by a time corresponding to a half cycle of the natural vibration cycle is used as the correction signal. Control method for positioning servo system.