JPH04335411A - Position controller - Google Patents

Abstract

PURPOSE:To eliminate the uncontrollable area and to improve the positioning precision without decreasing a control speed and without making rigidity of a control system higher than necessary by providing a specific variable gain arithmetic means. CONSTITUTION:A target position signal (b) from a position command means 1 is supplied to a subtracter 3, and also, a position feedback signal (a) for showing the present position of an object 2 to be controlled, obtained in a position detector 4 is supplied to the subtracter 5, and in the subtracter 3, a position deviation amount (e) is derived on its output side. Subsequently, this position deviation amount (e) is converted to a speed command amount (v) and the position of the object 2 to be controlled is controlled. In such a state, a variable gain computing element 8 for varying hyperbolically the position gain against this position deviation amount (e) is provided. That is, in this variable gain computing element 8, whether the position deviation amount (e) is (e)>0, or (e)=0, or (e)<0 is judged and a prescribed operation is executed, but the position deviation amount (e) becomes smaller as it approaches a target position, and becomes a gain curve of a hyperbolic type.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position control device suitable for use in controlling the position of tools, workpieces, etc. of equipment such as machine tools that require precise and high-speed control.

0002

2. Description of the Related Art Previously, a closed-loop control type position control device using a numerical control device as shown in FIG. 5 has been proposed for controlling the position of controlled objects such as tools and workpieces of machine tools. That is, in FIG. 5, 1 indicates a position command means that generates a target position signal b indicating the target position of the controlled object 2, and the target position signal b from the position command means 1 is subtracted to obtain the position deviation amount e. Supply to vessel 3. Reference numeral 4 denotes a position detector for detecting the current position of the controlled object 2, and a position feedback signal a indicating the current position of the controlled object 2 obtained by the position detector 4 is supplied to the subtracter 3. This subtracter 3 is designed to obtain the positional deviation amount ee=ba.

[0003] This positional deviation amount e signal is supplied to an NC amplifier 5. In this NC amplifier 5, this positional deviation amount e
(μm), position gain g (1/sec) and control constant (
Speed command amount per unit speed of controlled object 2) k (sec/
Speed command amount v multiplied by μm)

0004

[Math. 1] v=e×g×k

0005 is obtained. Here, the position gain g is a control speed per unit position deviation amount, and is a gain that is set according to the rigidity (response characteristics) of the control system. This position gain g is kept constant, and a speed command amount v proportional to the positional deviation amount e is obtained from this NC amplifier 5. This speed command amount v signal obtained at the output side of this NC amplifier 5 is supplied to a drive amplifier 6. Here, the speed command amount v is a manipulated variable to be supplied to the drive amplifier 6, which is matched to the input specifications of the drive amplifier 6, and is an arbitrary unit determined in advance and is an anonymous number. The output signal of this drive amplifier 6 is supplied to a drive device 7 that drives the controlled object 2 . In this example, it is assumed that the linear position is controlled by a rotary drive device. In the example in FIG. 5, the control speed V is

[0006]

[Formula 2] V=v×(1/k)=eg

[0007] Here, 1/k is the speed of the controlled object 2 per unit speed command amount. Also

[0008]

[Math. 3] k=1/(r×d)

[0009] Here, r is the rotational speed of the drive device per unit speed command amount, and d is the amount of movement of the controlled object 2 per one rotation of the drive device. In the example shown in FIG. 5, the controlled object 2 can be moved to the target position specified by the position command means 1.

0010

However, in the example shown in FIG. 5, if the current position obtained from the position detector 4 is a discrete value, the position deviation amount e and the speed command amount v also become discrete values, so that Position detector 4 for precise positioning
If the detection resolution is increased, the speed command amount v corresponding to the minute positional deviation amount e will not be output, and as a result, position control will become impossible.

A specific example of this will be explained below. r=0.05 (rev/sec), d=2000 (μm
/rev), g = 25 (1/sec), substituting this into Equation 3 and Equation 1 gives k = 1/(r x d) = 0.01 (sec/μm) v = e
×g×k=0.25e. Since the positional gain g is constant, the relationship between the positional deviation amount e and the positional gain g is always constant (g=25) regardless of the change in the positional deviation amount e, as shown in FIG. On the other hand, the relationship between the position deviation amount e and the speed command amount v is as shown in FIG.
), the speed command amount v is zero, and this range is an area where position control is impossible. In this way, in conventional control where the position gain g is constant, when trying to improve positioning accuracy (the higher the resolution of the position detector 4 and the target position), such a position uncontrollable region is likely to occur, and this There was an inconvenience that led to deterioration of positioning accuracy.

In order to eliminate such a positional uncontrollable region, it is conceivable to increase the position gain g and to increase the speed command amount k per unit speed of the controlled object 2. In Equation 1, g is 100 (1/s
c) With the above, this position-uncontrollable area can be eliminated. However, as described above, the position gain g is set in accordance with the rigidity of the control system, so it is necessary to improve the rigidity of this mechanical system. If the position gain g exceeds a value corresponding to the rigidity of the machine, etc., the control system becomes unstable and exceeds the response characteristics of the control system, causing vibration and becoming uncontrollable. In general, improving the rigidity of machines requires a lot of effort and cost, and there are limits.

[0013] Also, in order to increase k by 4 times or more, from equation 3, r
×d may be set to 1/4. Here, if r is set to 1/4 using a 1/4 speed reducer, and r = 0.0125 in the above specific example, then k = 1/(r x d) = 0.04 (sec/μm) ∴v =
e, which eliminates the positional uncontrollable region, but there is a disadvantage that the maximum control speed is reduced to 1/4. In view of these points, it is an object of the present invention to enable more precise positioning without reducing the control speed or increasing the rigidity of the control system more than necessary.

[0014]

[Means for Solving the Problems] The position control device of the present invention converts the position deviation amount e of the difference between the target position and the current position of the controlled object 2 into the speed as shown in FIGS. 1, 2, 3, and 4. In a position control device that controls the position of the controlled object 2 by converting it into a command amount v, a variable gain calculation means 8 is provided that changes the position gain G in a hyperbolic manner with respect to the position deviation amount e. It is something that

[0015]

[Operation] According to the present invention, as shown in FIG. 3, the position gain G is made to change hyperbolically with respect to the position deviation amount e, so stable and good control can be performed, and the speed command amount As shown in FIG. 4, the relationship between v and the positional deviation amount e is such that there is no uncontrollable area, the positioning accuracy is improved, and N
High-speed positioning can be performed by effectively using the speed control ratio of the C amplifier, and there is no need to increase the rigidity of the controlled object 2 more than necessary, and there is no need for labor costs for this purpose.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the position control apparatus of the present invention will be described below with reference to FIGS. 1 to 4. In FIG. 1, parts corresponding to those in FIG. 5 are designated by the same reference numerals, and detailed explanation thereof will be omitted. In the example shown in FIG. 1, the target position signal b from the position command means 1 is supplied to the subtractor 3, and the position
Position feedback signal a indicating the current position of the controlled object 2 obtained in
is supplied to this subtracter 3. In this subtracter 3, the positional deviation amount ee=ba is obtained on its output side.

This positional deviation amount e signal is supplied to the NC amplifier 5. In this NC amplifier 5, an output signal v'v'=e is obtained by multiplying the positional deviation amount e by the position gain g and the control constant k (speed command amount per unit speed of the controlled object 2).
Obtain ×g×k. In this example, this output signal v' is supplied to the variable gain calculator 8, so that the speed command amount v signal is obtained at the output side of the variable gain calculator 8. The variable gain calculator 8 performs calculations as shown in FIG. 2 at predetermined timings. That is, the variable gain calculator 8 determines whether the positional deviation amount e is e>0, e=0, or e<0,

[
0018

[Math. 4] v=e×g×k+P

The following calculation is performed. In this case, when e>0, P
=C, when e=0, P=0, and when e<0, P=-C. Here, C is a gain constant, and the gain constant C set in the variable gain calculator 8 is set to an arbitrary value according to the control state. Here number 4
If we set P=kp in, then from equation 2, the control speed V is

00
20]

[Math 5] V=(e×g×k+kp)/k =e(g+p/e)

[0021] As is clear from comparing Equation 5 and Equation 2, the position gain G in this example is the conventional position gain g plus p/e, and the position deviation amount e becomes smaller as it approaches the target position, and p Since is a constant, this position gain G has a hyperbolic gain curve as shown in FIG.

The speed command amount v signal obtained at the output side of the variable gain calculator 8 is supplied to the drive amplifier 6. In this example, the other configuration is the same as that in FIG. 5.

In this example, as described above, the position gain G is made to vary hyperbolically with respect to the position deviation amount e as shown in FIG. 3, so the relationship between the position deviation amount e and the speed command amount v is as shown in FIG. As shown in the figure, there is no uncontrollable area.

[0024] To explain this using a specific example, r = 0.05 (rev/sec), d = 2000 (μm
/rev) If g=25 (1/sec), k=0.0
1 (sec/μm), and v=e×25×0.01+P=0.25e+P, so when the gain constant C=1, it becomes as shown in Figure 4, and there is no uncontrollable area, and positioning Improves accuracy. Further, in this example, since a reduction gear or the like is not used, the speed control ratio of the NC amplifier 5 can be used effectively and high-speed positioning can be performed. Furthermore, according to this example, there is no need to increase the rigidity of the controlled object 2 more than necessary, and no effort or expense is required for this purpose. Furthermore, according to this example, when the input sensitivity of the drive amplifier 6 is lower than the speed command unit of the NC amplifier 5, it is possible to output a speed command of the NC amplifier 5 that exceeds the input sensitivity. It goes without saying that the present invention is not limited to the above-described embodiments, and that various other configurations can be adopted without departing from the gist of the present invention.

[0025]

[Effects of the Invention] According to the present invention, the control system can be controlled without reducing the control speed or increasing the rigidity of the control system more than necessary.
There is an advantage that the uncontrollable area can be eliminated and positioning accuracy can be improved satisfactorily.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a position control device of the present invention.

FIG. 2 is a flowchart for explaining essential parts of the present invention.

FIG. 3 is a diagram for explaining a specific example of the present invention.

FIG. 4 is a diagram for explaining a specific example of the present invention.

FIG. 5 is a configuration diagram showing an example of a conventional position control device.

FIG. 6 is a diagram for explaining a conventional example.

FIG. 7 is a diagram for explaining a conventional example.

[Explanation of symbols]

1 Position command means 2. Controlled object 3. Subtractor 4 Position detector 5 NC amplifier 6 Drive amplifier 7 Drive device 8 Variable gain calculator

Claims (1)

[Claims] 1. A position control device that controls the position of the controlled object by converting a position deviation amount of the difference between a target position and the current position of the controlled object into a speed command amount, wherein the position deviation amount is 1. A position control device comprising variable gain calculation means for hyperbolically changing a position gain relative to the position.