JPS6244814A - Grating point positioning system for digital servo - Google Patents

Abstract

PURPOSE:To remove the dispersion of positioning due to a non-sensitive band of a position detector by setting up the offset corresponding to 1/2 pulse to be a position detecting unit as a positional deviation. CONSTITUTION:A digital servo positioning system is constituted of a control element 4 for outputting a practical position signal (x) at a positional deviation value DELTAP and a position detector 5. An offset value setter 7 for outputting the offset value corresponding to 1/2 pulse to be the position detecting unit and a comparator/adder 8 for outputting the positional deviation value DELTAP are added. The comparator/adder 8 outputs the positional deviation value DELTAP obtained by adding the offset value corresponding to 1/2 pulse to a difference between a positional command pulse Pc and a position feedback pulse Pf and the control element 4 executes control operation on the basis of the output DELTAP to position the digital servo so that the positional deviation value DELTAP is zero.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a digital servo positioning method using digital feedback.

[Conventional technology]

FIG. 3 is a block diagram showing a conventional digital servo positioning system. In the same figure, 1 is the position command pulse P
2 is a signal gland to which the position feedback pulse Pf is sent, and 3 is the position command pulse P. A comparator consisting of a deviation value counter or a subtracter which calculates the difference between the position deviation amount ΔP and the position feedback pulse Pf and outputs the position deviation amount ΔP=PC−P (4) performs a control operation depending on the position deviation amount ΔP input as an operation signal. , a control element that outputs the actual position signal The actual position Xμm of the 1μm/A las position detector and the position feedback pulse P
It is a diagram showing the relationship with f, where the * mark is included in the dead zone PL, and the ○ mark is not included in the dead zone FL.

Next, the operation of the digital servo positioning method with the above configuration will be explained. First, the comparator 3 takes the difference between the position command pulse P0 and the position feedback pulse P (and outputs the position deviation amount ΔP to the control element 4. Therefore, the control element 4 receives the input of this position error amount ΔP. Through multiple control operations, the feedback loop including the two-position detector 5 operates until the position where the positional deviation amount ΔP becomes zero (ΔP−0) is operated, and the position is determined.

[Problem that the invention seeks to solve]

In the conventional digital servo positioning method described above, positioning is performed such that the position deviation amount ΔP is zero (ΔP = 0), but the position feedback pulse Pf is
On the other hand, as shown in FIG. 4, in the interval N≦x(N+1, Pf=N, which is constant), so there is a problem that the actual positioning position expressed as ΔP-0 varies within this dead zone PL.

[Means for solving problems]

The digital servo lattice point positioning method according to the present invention gives an offset amount of 1/2 pulse of the position detection unit to the amount of position deviation.

[Effect]

This invention can eliminate positioning variations due to the dead zone of the position detector.

〔Example〕

FIG. 1 is a block diagram showing an embodiment of a digital servo grid point positioning method according to the present invention. In the figure, 7 is an offset amount setter that outputs an offset amount of 1/2 pulse of the position detection unit, and 8 is a position command pulse P.

The position deviation amount Δp-Po-p(
This is a comparison adder that outputs +1/2.

Next, the operation of the digital servo grid point positioning method described above will be explained. First, the comparison adder 8 receives the position command pulse P. The positional deviation amount Δp is the difference between the position feedback pulse Pf and the offset amount of 1/2 pulse.
= Po-Pf+1/2 is output.

Therefore, the control element 4 performs a control operation based on the input of this positional deviation amount ΔP, and a feedback loop operates until the position where the positional deviation amount ΔP increases (ΔP==O), and the positioning is performed. At this time, considering positioning using the position command pulse Po-N pulses, even if the feedback pulse P( returns by N pulses, the position deviation amount ΔP is ΔP=N-N+1/2=1/2
Therefore, Δp=o, and even if the feedback pulse returns by one pulse, ΔP=N−(N+1)+
Since 1/2=-1/2, Δp=o does not hold, and a reverse operation is started this time, the image is taken centering on the point where the feedback pulse of Pf=N+1 pulse returns.

The point where this feedback pulse is generated is called a lattice point, and if the control system is such that the vibration width converges to a sufficiently small value, positioning can be performed on the lattice point as shown in Figure 2. . In FIG. 2, points where feedback pulses are generated, lattice point arrays Xk, are lined up on the actual position X on the horizontal axis.

The vertical axis is the position command P. It shows the position deviation amount ΔP pulse at the time of −N pulses, where k=N+1st grid point xN+t2
Since the sign of the positional deviation amount ΔP is reversed at the boundary, the point of convergence from the positional deviation amount ΔP to 0 is the lattice point XN+1.

〔Effect of the invention〕

As explained in detail above, according to the digital servo grid point positioning method according to the present invention, by providing the position deviation with an offset amount of 1/2 pulse of the position detection unit, positioning due to the dead zone of the position detector is prevented. There is an effect that variations can be eliminated by positioning at grid points where feedback pulses are generated.

−5−〇〇

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the digital servo grid point positioning method according to the present invention, and FIG. 2 is a diagram showing the relationship between the actual position X and the positional deviation amount ΔP in FIG.
FIG. 3 is a block diagram showing a conventional digital servo positioning system, and FIG. 4 is a diagram showing the relationship between the actual position X and the position deviation amount ΔP in FIG. 1--Input terminal, 2--Signal line, 4--Control element, 5--Position detector, 6--Output terminal, γ
...Offset amount setter, 8...Comparison adder.

Claims (1)

[Claims] A digital servo mechanism having a digital position detector, characterized in that positioning is performed at a grid point where a position feedback pulse is generated by making the position deviation amount equal to the offset amount of 1/2 pulse of the position detection unit. grid point positioning method.