JPH01239609A - System for controlling position of shaft by motor - Google Patents

Abstract

PURPOSE:To always perform position control at high speed and accurately for the micro travel command of a shaft by attaching a prescribed positioning range on a position command, and controlling a servo system so as to be set at a large value outside the positioning range and a small value within the range. CONSTITUTION:An area discrimination part 15 compares the value ¦Xe¦ of the difference Xe of a targeted position of the shaft represented by the position command Xc and the present position X with a reference quantity E1 representing the positioning range, and discriminates whether the relative position relation of the Xe and the X exists in an area A or an area B. The discrimination signal SA is inputted to an amplification factor selection part 16, and a signal SG to select the amplification factors K1 and K2 of the area A and the area B is outputted to a PI amplifier 4A in a state representing the stoppage of the generation of a function by the function generation stopping signal SS of a command Xc, and a speed error signal Ve is amplified by the amplification factors K1 (K1<<K2) and K2, respectively, corresponding to the areas A and B, and the torque command Tc of a motor 6 is supplied to the motor 6 via a power amplifier 5. A table 10 on a sliding plane 13 can be propelled by torque generated in the motor 6.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention is applicable to electrical equipment used in NG (numerical control) machine tools, etc. l
The present invention relates to a shaft position control method using a J machine, and in particular to a glaze position control method capable of performing high-speed and accurate position control in response to minute movement commands of the shaft regardless of the characteristics of the sliding surface.

(Prior Art) Conventionally, position control devices used in applications such as NG machine tools that require highly accurate position control have been equipped with a position detector attached to a controlled object or connected to an electric motor that drives the controlled object. A highly accurate position control system is realized by directly or indirectly detecting the position of the axis to be controlled using a position detector, and by using this detection signal to form a position feedback loop.

FIG. 7 shows an example of a block configuration of a table drive system employing a position control device having a position feedback loop. In this example, the current position of table IO is
1 and 12, and this position detection signal is used as the position feedback signal X. Therefore, if the loop gain of the control system is high to some extent, the position command will eventually be x.

It is possible to perform positioning that approximately corresponds to . The subtracter 1 subtracts the position feedback signal X from the device command xc configured from the higher order command device, and calculates the position error X@.

The position feedback signal X is the table l to be controlled.
This is a position signal obtained by directly detecting the position of O by the inductosins 11 and 12. The position error x6 is amplified by the amplifier 2 and becomes the speed command VC. Further, the speed detection signal of the speed detector 7 mechanically connected to the electric motor 6 becomes the speed feedback signal V, and the subtractor 3 outputs the speed command VC.
Subtracting the speed feedback signal V from the speed error V,
Calculate. The speed error v8 is amplified by the PI amplifier 4 and becomes a torque command Tc for the electric motor 6. Torque command Te
is power amplified by the power amplifier 5, and its output becomes a current IC for causing the electric motor 6 to generate a torque corresponding to the torque command Tc. The torque generated in the electric motor 6 by the current IC is transmitted to the ball screw 9 via the coupling 8.
transmitted to. The ball screw 9 converts this transmitted torque into a propulsive force for the table 1O moving on the sliding surface 13 via the nut member 10A.

FIG. 8 shows a detailed circuit of the PI amplifier 4.
has an operational amplifier 14, which performs proportional-integral amplification (PI amplification) and then inverts the sign of its output -Tc to obtain a torque command Tc. Here, the operation of the operational amplifier 14 will be explained. Ro, R+, Rkl in Figure 8
are all resistances that determine the amplification factor of the operational amplifier 14.

Now, assuming that no charge is stored in the capacitor C, when a step-like manual force is commanded as the speed error v6, the output -Te of the operational amplifier 14 immediately after that is -Te--'Ve...・(1) O. After this, output. gradually increases as the charge is gradually stored in the capacitor C, and finally converges to 6° Next, the table movement when a minute movement command of △X is input to the drive system in Fig. 7. This will be explained using FIG. 9 and FIG. 1O. FIG. 9 shows that the initial state is table position x1, and a minute movement command ΔX is manually applied in the P direction at time t0.
After that, each time to passes (time 'l, t2,'
3 +...) shows the relationship between the position command xc and the actual table position X when a minute movement command ΔX is manually input each time. FIG. 1O shows the friction torque when the table IO moves on the sliding surface 13, isometrically converted into a torque command Tc which is the output of the pi amplifier 4. Time t. When X is manually applied to the minute movement command, a position error of x8 and a speed command Δvc are generated. As a result, a human power △Ve is generated in the PI amplifier 4, and the output of the amplifier 4 is Te 7 (R1/RO
) XΔV occurs. Thereafter, the torque command Tc gradually increases, and when it exceeds the static friction torque TFS of the sliding surface 13, the table IO starts operating φ. table lO
When the amplifier 4 starts operating, the human power Ve of the amplifier 4 starts to decrease, so that the torque command Tc also decreases. After this, when the table position reaches (XI+ΔX), the table operation stops and the sliding surface 13 to be positioned is moved to the first position.
If the table has negative resistance characteristics as shown in Figure 0, even if the table position reaches (XI+ΔX), the output will be T at that point.

Since the relationship is lJ<Tc>>Tp, the table movement does not stop and continues to move in the P direction, resulting in the characteristic (a) shown in Figure 9.
), a position jump phenomenon occurs. In order to prevent this jump phenomenon, the resistance RKI that determines the maximum amplification factor of the operational amplifier 14 is made small, and the output Tc of the PI amplifier 4 is reduced after the table operation starts, so that the table position is (XI"ΔX ) is set as the Tc valve Tp-, and the table operation is stopped at the hollow position.However, if the negative resistance characteristic of the sliding surface 13 is large, the jump phenomenon can be prevented. The resistance RKI that can be used is Tc-((n+, RKI)/RO) ・
ΔVll<Trs, and table movement becomes impossible in response to the minute movement command ΔX. As shown in FIG. 9, after the next minute movement command ΔX is added at time t1, Te - ((R'
Table operation becomes possible only when the relationship: l, RKI)/no)・2・ΔV, > T, s is established. In other words, a so-called feed motion as shown by characteristic (b) in FIG. 9 occurs.

As explained above, it is difficult to realize stable axis movement with a movement amount corresponding to a minute movement command with an axis of a machine tool whose sliding surface has a large negative resistance characteristic.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to always perform high-speed and accurate position control in response to minute movement commands of the axis, regardless of the characteristics of the sliding surface. The object of the present invention is to provide a shaft position control method using an electric motor.

(Means for Solving the Problems) The present invention amplifies a position error signal between an axis position command value generated by a function from a higher order command device and a position feedback signal which is the shaft position detection output using an amplifying means, The present invention relates to a shaft position control method using an electric motor that controls the position of the shaft by driving the electric motor according to this amplified output. , the amplification of the amplification means, which is set in advance for each divided region, is performed using a region determination signal obtained by performing region determination for dividing the relative relationship of the shaft position with respect to the position command value into multiple stages from the position error signal. This is achieved by switching the rate.

(Function) In the present invention, a certain reference range is set based on the axis position command value, and the amplification factor of the proportional-integral amplifier is set high outside this reference range, and set low within the reference range. The amplification factor switching control is performed as follows. This results in
In response to minute movement commands, when starting an axis that operates outside the standard range, the speed is increased by a high amplification factor, and when positioning an axis that operates within the standard range, the integral component rapidly decreases due to the low amplification factor. However, the response delay of the proportional-integral amplifier, which is the direct cause of the jump phenomenon, can be improved. According to the present invention, even a shaft having a large negative resistance characteristic on its sliding surface can be positioned quickly and accurately in response to a minute movement command.

(Example) Embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows the block configuration of the shaft drive system according to the present invention in correspondence with FIG.
Difference X between the current position X and the target position of the glaze indicated by c. I
It is determined whether the state is I<El or lX, l≧E1.

The state of lX, l<El is I Xel・l X--XI
<El, so rewriting this equation as an inequality regarding the current position x becomes, and similarly for the state of lX, l≧E1, X≦
Xc-E, -・-(4)×≧xc+E1
...(5). In other words, l Xs
If it can be determined that + < El, the relative positional relationship between the target position xc and the current position
If it can be determined that X81≧E1, the relationship between the two can be seen in the area [
B].

The region discrimination signal S8 discriminated by the region discrimination section 15 in this manner is manually inputted to the amplification factor selection section 16. The amplification factor selection unit 16 sets the amplification factors of 1 to the regions [A] and [B].
2 is set in The amplification factor selection signal SG selected by the switch 17 shown in FIG. 3 in 4A is output. FIG. 3 shows the PI amplifier 4A in detail, in which a resistor I'KI+RK2 is connected in parallel to the capacitor C, and a switch 17 that is selectively turned on and off by the amplification factor selection signal SG is connected in series to the resistor RKl+RK2. There is.

Further, when the function generation stop signal SS indicates that the function is being generated, the amplification factor selection unit 16 sets the amplification factor to 2 regardless of the area discrimination signal.
An amplification factor selection signal SG corresponding to the amplification factor selection signal SG is output. This is because if the amplification factor is switched during the operation of the axis that is controlling the position trajectory, the motor output torque will suddenly change, so the operating speed of the axis will change regardless of the position command xc, and the position command trajectory will differ from the actual This is because the position locus of the axis is out of sync with the axis position locus. Here, in the present invention, the amplification factor for regions [A] and [B] is 1
The resistors RKI and RK2, which are selected according to the amplification factors of 1 and 2, have a relationship of RKI <<RK2 so that 1 and 2 are satisfied.

Next, table operation when a minute movement command ΔX is manually applied to the shaft drive system shown in FIG. 1 will be described with reference to FIG. 4.

In FIG. 4, as in FIG. 9, the table position X is set as the initial state. A minute movement command ΔX is manually given in the P direction at a time t. Every time (time tl, t2.t3
．． . . ) shows the relationship between the position command X and the actual table position X when the minute movement command ΔX is manually input every time. Here, since the function generation of the minute movement command ΔX is instantaneously performed, the function generation stop signal SS indicates a stopped state except for the moment when the minute movement command ΔX is generated. For this reason,
Switching of the amplification factor depends only on whether the table position X exists in the region [A] or [B] with respect to the position command X. If the reference amount E1 is set in advance so that when the minute movement command ΔX is input at time t0, E<<ΔX, then at this time t0 the table position ], and the resistor RK2 corresponding to the amplification factor of 2 is selected in the operational amplifier 14 in the amplifier 48. Here, since the resistance RK2 takes on a large value, the output Tc to the amplifier 4 increases rapidly, exceeding the static friction torque TF'S of the sliding surface 13, and the table IO starts moving in the P direction. After this, the table operation continues and the table position Xh)X -Xc -E+
-(X++ΔX) -E, the table position X exists in the region [A] with respect to the position command XC, and the operational amplifier 14 in the amplifier 4A
is switched to a resistor RXI corresponding to an amplification factor of 1 via . Since the resistance RKI has a sufficiently small value with respect to RK2, the output TC to the amplifier 4 decreases rapidly, and before the table position X reaches (X+ΔX), Tc<TP,
, and table operation stops. After that, t+
, h, and ts, even if the minute movement command ΔX is added to the position command XC, the table position can be positioned within the range of error E1 with respect to the target position each time. Further, even in the case where the table 10 is operated by an external force from outside the control device after positioning, the table position is ±El (area [A]
), a large restoring torque is generated and the range [
The control device operates to maintain positioning within A].

(Modification) In the above-described embodiment of the present invention, the positional relationship of the table IO with respect to the target position xc is defined as the area [A].

[B] The amplification factor of the control system is varied in two stages, but as shown in Figure 5, the region is divided into more stages and the amplification factor of the control system is varied. By appropriately controlling the table movement speed at each stage, it is possible to control the table movement speed when reaching the final area [A]. The distance the table moves until it actually stops becomes smaller. Therefore, as a result, the reference value E that determines the range of the area [A] can be set small, and the positioning points can be limited to a smaller range. In FIG. 6, the amplification factor of the control system is varied in three stages of regions [A], [B], and [C], and the gain is varied for a predetermined time t. This figure shows the relationship between the position command XC and the actual table position X when the minute movement command ΔX is manually applied at each time.

It is also possible to generalize this further, by setting the amplification factor to K, and 2. 3. ......, (Kl<K2
<K3<・<Ko), and when the upper command device is in a state where function generation is stopped, the magnitudes lX, l of the position error signal are set to the positive reference quantity group E, , E2 .・・・
・+En-1(E, <E2<, ..., <E.

-1), the amplification factor K may be selected and switched as follows.

Also, even in the case where a position feedback loop is formed using a detection signal from a position detector coupled to the electric motor 6 as a position feedback signal, is this position detection signal indirect?
If the table position is accurately detected, applying the present invention can achieve exactly the same effect as using a direct table position detector to form a position feedback loop. .

(Effects of the Invention) In a drive system position control device having a position feedback loop, if the sliding characteristics of the load to be controlled have negative resistance characteristics, jump phenomenon may occur during positioning in response to minute movement commands. Alternatively, a feed phenomenon occurs because the axis does not move unless the minute movement command is repeatedly issued.

The present invention has a certain positioning range for the position command value of the glaze, and controls the amplification factor of the servo system so that it is large outside the positioning range and small within the range, so that it can be adjusted according to the sliding characteristics of the load. First, we provide a position control method that realizes high-speed and accurate positioning without skipping or stopping in response to minute movement commands.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an example of a device to which the method of the present invention is applied, FIG. 2 is a diagram for explaining its operation, FIG. 3 is a circuit diagram showing a part of FIG. 1 in detail, and FIG. 6 to 6 are diagrams for explaining the present invention, FIG. 7 is a configuration diagram showing a conventional control device, FIG. 8 is a circuit diagram showing a part of it in detail, and FIGS. 9 and 10 are FIG. 3 is a diagram for explaining the operation. 1.3...Subtractor, 2.4...Amplifier, 6...Electric motor, 7...Speed detector, 9...Ball screw, lO
...Table, 11.12...Inductosyn, 1
5... Area determination section, 16... Amplification factor selection section. Applicant's agent Yasugata Mu IL 3rd 20th S/r Figure 3

Claims (1)

[Claims] 1. A position error signal between an axis position command value generated by a function from a higher order command device and a position feedback signal which is a position detection output of the axis is amplified by an amplifying means, and the position error signal is amplified according to the amplified output. In an axis position control method using an electric motor that controls the position of the axis by driving an electric motor, the axis position relative to the position command value is determined from a signal indicating the stoppage of function generation of the position command of the upper command device and the position error signal. The electric motor is characterized in that the amplification factor of the amplifying means, which is set in advance for each divided region, is switched based on a region determination signal obtained by performing region determination for dividing the relative relationship between the two into multiple stages. Axis position control method. 2. Let the amplification factor be K_1, K_2, K_3, ・
..., K_n(K_1<K_2<K_3<...
<K_n), and when the upper command device is in a function generation stop state, the magnitude |X_e| of the position error signal is set to a positive reference quantity group E_1, E_2.
,...,E_n_-_1(E_1<E_2<,...
..., <E_n_-_1), 0
≦｜X_e｜<E_1 then K=K_1 E_1≦｜X_e|<E_2 then K=K_2E_n_−
If _2≦|X_e|<E_n_-_1 then K=K_n_-
Claim 1 wherein the amplification factor K is selected and switched such that K=K_n if _1E_n_-_1≦|X_e|
Axis position control method using an electric motor as described in .