JPS5835828B2 - Corner control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling part of a corner in copying machining.

When the stylus of the tracer head is applied to a model and the feed of the tracer bed and tool is controlled by a displacement signal to process a workpiece along the contour of the model, digging occurs in some of the corners of the model.

This point will be explained with reference to FIG. 1. In this figure, 1 is the tip of the stylus, 2 is a model, and 2a is a part of its right angle corner.

When the stylus tip touches model 2, it moves from position ■ in the direction of arrow F1 to position ■, which is part of the corner, and then moves in the direction of arrow F2 until it reaches position ■. At position (2), a displacement measuring device such as a differential transformer built into the tracer head outputs displacement ε1 in the y-axis (arrow F2) direction.

This displacement ε1 is a value ε suitable for operating the subsequent servo mechanism etc. in a normal position such as position 0.

selected. Next, when the stylus tip 1 hits the corner part 2a, the displacement ε1 is still output at the moment of the collision, but the displacement vector rapidly rotates clockwise with the collision, and εi
After taking an intermediate state such as, the displacement ε2 has a direction opposite to Fl.

Focusing on the speed ■ of the stylus tip 1, the moment of collision is equal to the speed ■1 just before that, and when the displacement changes to εi due to the collision, a driving force in the F2 direction is applied to the stylus tip 1, and the speed vector changes to rotate. At first, the speed gradually becomes 2 in only the F2 direction, and the stylus tip leaves the corner part 2a.

During this time, the case portion of the tracer head and the tool that moves integrally with the case portion draw a trajectory as shown by the thick line, and bite occurs at the corner portion 2a.

This biting depth will be explained with reference to Fig. 2.
Figure 1 shows the displacement deviation △ε−ε−ε.

This is a graph showing changes in the tangential velocity vT and normal velocity VN with the horizontal axis being taken as the horizontal axis.As shown in this figure, in tracing control, when the deviation Δε is O, only the tangential velocity vT is given to the tracer head. A deviation △ε occurs (this is △
(This means that the stylus tip tends to move away from the model surface or try to bite into the model surface depending on the sign of ε), the tangential velocity VT decreases and the normal velocity VN appears instead, and its resultant Make sure the speed points in the correct tangential direction.

As long as the tangential velocity VT of the tracer head has a finite value,
It penetrates into the model and ends only when VT=0 at destination point A, and thereafter continues to move in the F2 direction as it returns.

In this way, the amount of bite changes depending on the characteristics of the deviation Δεε cutting linear velocity T, and as shown in FIG. 2, if the speed VT is set to decrease as the deviation increases, the amount of bite can be reduced.

However, in a portion where the direction changes rapidly, such as a part of a right-angled corner, considerable biting still occurs with the Δε-VT characteristic as shown in FIG.

The present invention aims to improve these points and reduce the amount of bite by speeding up the rotation of the resultant velocity vector in areas where the deviation Δε is extremely large.

The present invention is based on the displacement ε of the stylus detected by the tracer head.
and the reference displacement ε.

The feed rate vT in the tangential direction is determined by the deviation signal Aε obtained from
and a displacement direction component εX of the stylus which generates a command signal for the feed speed vN in the normal direction and which is detected by the tracer head.

A correction signal εxJε' obtained from εy and a correction amount Aε' that gradually increases or decreases and is generated when the displacement direction component and the deflection signal exceed a certain positive or negative value.

Displacement direction signal COSθ with respect to the reference axis from εyJε′
, sin θ, and these signals □□□θ, sin
θ.

In a tracing control method in which the stylus of the tracer head follows the model surface with a constant displacement amount using VN and VT, when the deviation signal Aε is greater than a certain value, the correction amount Aε' is set to dog and the direction of the stylus at a part of the corner is changed. The invention is characterized by speeding up the conversion, which will now be described in detail with reference to examples.

FIG. 3 shows a tracing control device to which the present invention is applied, 11
~13 is a differential transformer built into the tracer head,
Excited by the excitation power source 14, the displacement of the stylus is
y, z components εX, ε9. Output ε2.

After this output is amplified by amplifiers 15, 16, and 17,
It is added to the synthesis circuit 18 and the switching circuit 19.

The synthesis circuit 18 outputs a displacement ε expressed as ε=e"+e"+e'yz, and the adder 20 outputs this displacement ε
and the reference displacement ε.

The deviation signal Δε is applied to the normal velocity generation circuit 21 and the tangential velocity generation circuit 22, and these circuits output the normal velocity vN and the tangential velocity vT and distribute them. Add to circuit 23.

The switching circuit 19 outputs the displacement components εX and εy depending on which plane, such as the XY plane or the YZ plane, the scanning is carried out (for example, if the scanning is carried out on the XY plane, the displacement components εX and εy are outputted).

The indexing circuit 25 receives these displacement direction signals ε8. ε and correction signals A and B from the indexing correction circuit 24 to output feeding direction signals C and D, which are applied to the distribution circuit 23.

The distribution circuit 23 uses these signals ■N, ■T, and C2D to adjust the X and Y transport speeds of the tracer head and tool V
+ V Y is calculated and output.

These points will be explained in more detail with reference to FIG.

As shown in Figure 4, the stylus tip 1 is attached to the model 2 at a point P.
If the center of the model curved surface at this point P is O, then when the stylus 1 is stationary and correctly pressed against the model 2, the displacement ε of the tracer head is ε as described above.

become. This displacement ε has X and y components ε8. ε, and output from the tracer head, and these ε8. The feed direction θ-jan'εX/ε is determined from ε, and this calculation is performed by the indexing circuit 25.

The tangential velocity ■To is determined as a vector making an angle of 90° with the displacement vector 2o, and if the stylus is sent at this velocity ■To, the desired tracing can be performed.

However, when the stylus is moving, the displacement vector is shifted backward by Δθ as shown in the figure, for example, due to friction or the like.

As a result, the tangential vector is found as VT, and since it deviates from the correct feeding direction, the contact pressure on the model also changes, and therefore the magnitude of the displacement ε is also ε.

It becomes something different. To avoid this, output a correction signal vN in the opposite direction to the displacement vector ε, and change vT to ■T
It is necessary to return to o.

The magnitude of this correction signal VN is the magnitude of the deviation Δεε−ε.

and the direction is perpendicular to VT. Circuit 21 in Figure 3
, 22 output the signal -VN+VT.

Correct truncation speed vT based on T1 normal speed vN
It is also possible to obtain o and perform copying based on this, but since this method is simply proportional control, errors will always remain.

To avoid this, it is desirable to correctly grasp the feed direction angle θ itself and to set the cutting line speed to vTo from the beginning.

The index correction circuit 24 is for the purpose of

FIG. 5 shows an example of the circuit.

As mentioned above, the angle of deviation △θ occurs due to friction, etc.
Therefore, it is constant.

Therefore, a fixed value may be prepared as the amount of correction, and this may be adjusted as appropriate according to the error.

In Fig. 5, 38 is an integrator that generates this correction amount △ε'.
The capacitor Ci is supplied with positive and negative constant current sources +Io and -I until the deviation △ε becomes zero.

is charged through the switching circuit 34 and switch 36, and outputs the correction amount Δε'.

This correction amount is determined by multipliers 39 and 40 as displacement direction components ε.

ε, multiplied by It is output as correction signals A and B represented by .

In Fig. 5, 31 is a discrimination circuit that produces a "1" output when △ε>0, and a switching circuit 34 and 35 when the output is "1".
to +■o, +11 side, -IOj when +101+ output
Switch to the It side.

32 has a predetermined width W1 or more centered on △ε−〇, that is, the sixth
As shown in the figure, this is a dead band circuit that produces an output of "1" when Δε1 or more, and the switch 36 is closed when the output is "1".

The correction signals A and B are added to the adders 26 and 27 in FIG.

The direction of displacement now sensed by the stylus includes a deviation of Δθ, thus ε, −ε, , COS (θ+Δθ).

εy=ε8. Assuming that sin (θ+△θ),
The above formula becomes.

The indexing circuit 25 receives the inputs A/ and B/ and indicates the correct displacement direction angle θ that does not include errors Δθ.

In the present invention, such an index correction is utilized to cause the speed vector to change rapidly at a portion of the corner described above.

Circuit elements 33, 35, and 37 in FIG. 5 are for the purpose of S.

This circuit 33 is a dead band circuit having a width W1 larger than that of the circuit 32, and as shown in FIG. 6, when the deviation Δε is greater than or equal to Δε2, a “1” output is generated and the switch 37 is closed.

Also, 35 is a switching circuit similar to 34, with positive and negative constant current sources +
Io.

-I.

Positive and negative constant current sources with larger current values +I, -I,
connected to.

Note that a voltage source may be used instead of the constant current source.

If a circuit for turning the signal is added to the integrating circuit 38, the deviation △ε becomes very large in places where there is a sudden change in direction, such as at a corner, and as a result, the circuit 33 in addition to the circuits 31 and 32 becomes very large. produces a ``1'' output, and the capacitor Ci of the integrator 38
is rapidly charged as shown by curve section cb in FIG.

As a result, the correction amount △ε' suddenly becomes a dog, and the correction signal A
, B, etc., the feeding direction is rapidly changed.

When the direction change progresses and the deviation Δε becomes equal to or less than Δε2, the dead band circuit 33 does not lose its output, the switch 37 opens, and the above-described rapid correction ends.

Thereafter, the correction amount Δε' is gradually adjusted by the constant current sources ±■o as shown by the curved portion Ca in FIG.

In order to rapidly rotate the speed vector, a constant current source 1, a dead band circuit 33 for controlling it, and a switch 37 are required.
It is also conceivable to simply set the output current value of the constant current source (2) to the same value without providing the constant current source, but in this method, the gain of the loop is always set to the same value, and undesirable effects such as oscillation are likely to occur.

As explained in detail above, in the present invention, the direction correction signal is suddenly increased in parts such as corners where the direction changes rapidly to speed up the rotation of the speed vector. can.

[Brief explanation of the drawing]

1 and 2 are diagrams explaining the operation of the stylus in a part of a corner, FIGS. 3 and 5 are block diagrams of the tracing control device according to the present invention, and FIG. An explanatory diagram showing the mutual relationship of signals, FIG. 6 is an explanatory diagram of dead band width,
FIG. 7 is a diagram showing charging characteristics. In the drawing, 1 is the stylus tip of the tracer head, ε is a displacement signal, vT is a tangential direction feed rate command, VN is a normal direction corrected feed rate command, ε8. ε is a displacement direction signal, Δε is a deviation signal, A and B are correction signals, 33 is a dead band circuit that outputs when Δε is a certain value or more, and ±■1 is a constant current source.

Claims (1)

[Claims] 1. Displacement ε of the stylus detected by the tracer head and reference displacement ε. The feed rate vT in the tangential direction is determined by the deviation signal Aε obtained from
and normal direction feed speed VN, and when the displacement direction components εX, εy of the stylus detected by the tracer head, the displacement direction components and the deviation signal are greater than a certain positive or negative value. The correction signals εXAε′, εyJε obtained from the “gradually increasing or decreasing correction amount”ε′
' and the displacement direction signal ωSθ with respect to the reference axis, sin
θ and these signals cos θ, sin θt V
N + VT In a tracing control method in which the stylus of the tracer head follows the model surface with a constant displacement amount, when the deviation signal ε is greater than a certain value, the correction amount Aε
A method for controlling a part of a corner, characterized in that the direction change of the stylus at the part of the corner is accelerated by making the stylus ' into a dog.