JPH02114109A - Method for detecting sudden change of shape - Google Patents

Abstract

PURPOSE:To establish a detection method capable of detecting in advance a sudden change in the shape of a model by allowing the optical axis of a distance measuring probe capable of measuring a distance in a non-contact state to be eccentric from a center-of-rotation axis. CONSTITUTION:The optical axis of a distance measuring probe 1 capable of measuring a distance in a non-contact state is made eccentric from a center-of- rotation axis and the distance measuring probe 1 is moved in a predetermined direction while the optical axis 1a is rotated around a center-of-rotation axis 2a and the position data of the point on the surface of a model are measured at a plurality of set angle-of-rotation positions. When the measurement of a distance becomes impossible at either one of a plurality of the measuring positions per one rotation, it is confirmed that a shape sudden change part is present. By this method, when the measurement of a distance becomes impossible at either one of a plurality of the measuring positions per one rotation, it can be previously confirmed that the shape sudden change part is present and, for example, digitizing can be accurately performed to a position to this side of the shape sudden change part by changing over a probe feed speed to a low speed.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a method for detecting sudden changes in shape, and in particular, detects a model surface by tracing the model surface with a distance measuring probe that can measure distance without contact using a laser beam. This invention relates to a method for detecting sudden changes in shape in non-contact digitizing for determining the coordinate values of points above.

<Prior Art> There is a non-contact decimating method in which model surface data is digitized by tracing a model surface with a probe sensor (distance measuring probe) capable of non-contact distance measurement such as a laser 4111 long probe.

In addition, the distance measurement probe used in non-contact digitizing generally has a reference distance. The difference between the actual measured distance and the reference distance L0 can be output as the error amount ΔL.

FIG. 7 is an explanatory diagram of non-contact copying. When model MDL is copied and points A, B, and C are appropriately selected sample points, first, distance L at point A, (=L , +ΔL
Measure 1) and this is the standard distance.

When there is an error by ΔL1 compared to , the correction operation is applied in the measurement axis direction (optical axis direction) by the amount of error while moving toward the next sampling point B. Then, the error amount ΔL at point B
2 and similarly correct the error by pointing to the 0 point, and thereafter performing the same process to trace the model surface without contact.

By the way, distance i! The li constant probe PB has a range in which it can accurately measure distances, and in Figure 8, the reference distance is set to L.
o and tori. The range of ±1 becomes the measurable range MSR.

For this reason, as shown in Fig. 9, there is a sudden shape change part WA in the model.
When L exists, the distance measuring probe PB is A
-*B, the distance cannot be measured at the corner P. When distance measurement becomes impossible, conventionally, the distance ft1lllll constant probe PB is returned in the opposite direction, the speed is extremely reduced, and the distance ivi:6FI constant probe PB is moved again in the A→B direction, and the distance is 81 When I reach retirement age, I will leave! The 1i1B fixed probe PB is lowered or raised to search for a measurable position, and when a measurable position is found, normal non-contact decimating is resumed from that position.

<Problem to be Solved by the Invention> However, in such a conventional non-contact decisizing method, when an all-distance decoupling error occurs in a part where the shape suddenly changes, and furthermore, it becomes impossible to measure the distance, the constant-distance probe is returned and sent at low speed. Therefore, there is a problem in that it takes a considerable amount of time until normal non-contact decimating is resumed.

From the above, it is an object of the present invention to provide a sudden shape change detection method that can detect sudden changes in model shape in advance.

Another object of the present invention is to provide a sudden shape change detection method that can detect sudden changes in model shape in advance, can accurately digitize up to just before the sudden shape change, and does not require returning the distance measuring probe.

Means for Solving the Problem> In the present invention, the above problem is solved by the distance i! ! Means for eccentrically centering the optical axis of the measuring probe from the central axis of rotation, moving the distance measuring probe in a predetermined direction, and rotating the optical axis around the central axis of rotation; This problem is solved by a means for determining the position data of a point on a surface, and a means for recognizing that a sudden change in shape exists when distance measurement becomes impossible at any one of the plurality of measurement positions per rotation. Ru.

Effect> The optical axis 1a of the distance measuring probe 1 (see Fig. 1) that can measure distance without contact is eccentric from the rotation center axis 2a, and the distance measuring probe 1 is moved in a predetermined direction and the optical axis is rotated. Rotate around the central axis and measure position data of points on the model surface at multiple preset rotation angle positions (0°90°180°, 270” positions), and measure multiple measurement positions per rotation. When it becomes impossible to measure the distance at any one of these points, it is recognized that a sudden shape change part WAL exists.

<Example> FIG. 2 is a block diagram of a system in which distance measurement is not possible according to the present invention.

1 is a distance measuring probe, 1a is an optical axis, 2 is a rotating part (including a motor) for rotating the distance measuring probe 1, 2
a is the center axis of rotation. Distance! The t1ilII constant probe 1 is attached to the rotating part 2 so that the optical axis 1a is eccentric by an amount R from the rotation center axis 2a.

As the distance measurement probe 1, for example, there is a probe that employs an optical triangulation method. A part of the light beam diffusely reflected by the lens creates a spot on the position detection element through the light receiving lens, and the distance is measured by changing the spot position according to the distance to the model surface. When distance measurement becomes impossible, a distance measurement impossible signal MIM is generated.

Reference numeral 3 denotes a rotational direction position detector, which is attached to the rotating shaft and is composed of a rotary encoder 3a that generates N pulses Pr per one rotation of the distance measuring probe 1, and a counter 3b with a capacity of N that counts the pulses. ing.

4 is a determination unit, which determines the optical axis rotation position (0
setting units 4a, 4b, . . . , 4cl that preset the rotational position of the optical axis (positions of 180°, 90', 180°, 270°), and comparison sections 4e, 4f, . . . that determine that the rotational position of the optical axis matches the set position.
, 4h, switch parts 4i and 4j that pass the distance No. 48 SL measured by the distance measuring probe 1 when they match.
..., 4m. For example, the rotation direction angle O of the optical axis.

90°, 180°, 270” (7) Positions of 4 points p,
.

In P2..., P4 (see Figure 3), the model MDr,
If the distance up to 411 is set, a numerical value O is set in the setting part 4a, a numerical value N/4 is set in the setting part 4b, a numerical value N/2 is set in the setting part 4c, and Part 4d
is set to the numerical value 3N/4.

When the count value of the counter 3b reaches 0, the comparator 4e outputs a high-level signal Sa and closes the switch 41, and when the count value of the counter 3b reaches N/4, the comparator 4f outputs a high-level signal Sa. sb and closes the switch 4j, and in the same manner, high-level signals Sc and Sd are outputted, and the distance signal SL to the model surface at that time is passed. - is moved in a predetermined direction according to non-contact tracing and rotated around the rotation center axis 2a. Therefore, 0゛90
' , 180°, 270' position distance & III Assuming that the optical axis trajectory I) 1゛l shown in Fig. 1(a) is
The distances at the upper points P□, 1], . . . +P4 are measured and output.

Returning to FIG. 2, 5 is a synthesis section that synthesizes and outputs the switch outputs, and 6 is a sampling and hold section.

7 is an A/D converter that converts the distance signal SL into digital distance data L and outputs it, and 8 is an A/D converter that converts the distance signal SL into digital distance data L and outputs it, and 8 indicates that the optical axis 1a has arrived at one of the set positions (0°, 90' 180°, 270° position). This is an OR gate that sometimes generates a high-level enable signal PES.

Hereinafter, a method for detecting a sudden change in shape according to the present invention in the case of non-contact digitizing will be explained.

FIG. 4 is a block diagram of the non-contact decitizing device, and the description will be made assuming that the scanning plane is the X-7 axis and the big feed direction is the Y axis. The same parts as in Fig. 2 are given the same symbols. 1 is the distance measuring probe, 2 is the rotating part (including the motor),
3a is a rotary encoder, 9 is an optical axis rotation position monitoring unit (
(corresponds to the parts indicated by numerals 3b to 8 in FIG. 2),
10 is a non-contact distance measurement si. This distance rnq determining device 10 outputs a distance IL and an enable signal P every time the distance fIf measuring probe 1 arrives at any set position.
Generates ES. Accordingly, during digitizing, the distances from four points P on the trajectory PTR of the tip of the optical axis shown in FIG. 1(a) to P2 . . . j P 4 are periodically output. Note that ATR in FIG. 1(a) is the locus of the intersection of the rotation center axis 2a and the model MDL.

11 is a non-contact decimating device; 122 and 12X are D/A converters that D/A convert the digital axis velocity signals Vx and Vz generated from the non-contact deciticing device 11;
132 and 13X are servo circuits for each axis, 14Z and 14X are Z-axis and 16Z, 16X, and 16Y reversibly count the pulses generated from the corresponding pulse coders according to the moving direction, and calculate the current position at the rotation center axis/model intersection Q (
This is a current position register that monitors Xn+, l, Yn+I, Zn+1).

In the non-contact digitizing device 11, 11a is a tracing direction calculation unit that determines the tracing direction oni1.

1 l b C 2 points P,, P, (7) i%alILI
I L:+ite formula (L, +L,)/2 → L,' (1)
This is a distance correction unit that calculates the distance L1' between the rotation center axis and the model intersection point Q□. In addition, due to the sudden change in shape, point P3
If the distance cannot be measured at then, the distance measured at the next point P□' rotated by 180 degrees is used as L3. For this reason, the feed speed V of the distance measuring probe 1 is determined so that distance measurement will not become impossible at point P□. The method for determining this feed rate V will be described later.

11c is the distance L□' and the reference distance. 11d is a speed signal generation section that generates a normal velocity signal n, lie is a speed signal generation section that generates a tangential velocity signal Vt, and 11f is a velocity signal generation section that generates a tangential velocity signal Vt. Each axis direction velocity signal Vx, Vz using the copying direction on+1
The speed signal generator l1g generates the axis component from point P to point P on the trajectory PTR (ΔX, Δy, Δ2),
The axis components from point P2 to point P are (Δx', ΔY'+Δ
Z'), the normal vector calculation unit calculates the normal vector at the rotation center axis/model intersection point Q using the axis component, and llh calculates the coordinate value and normal vector of each point on the model surface. This is a memory that stores data in pairs.

Various data necessary for copying control, such as copying speed, copying range, copying method (surface copying), etc., are input from an operation panel (not shown). However, the eccentric radius is R1, and the rotational speed of the optical axis is ω
When , the feed rate is set to satisfy the relational expression % (2). The reason why the feed rate V must be determined according to equation (2) is as follows. In other words, if distance measurement becomes impossible at point P (see Figure 1), distance data and position data at that point P will not be captured, and the optical axis 1a will be rotated by a further 180 degrees f.
Take in the distance data and position data at point f1P□', and use the distance data and position data of the four points P, PtI, PI3, pt (regarded as 3 points) to calculate the coordinate values and method of the rotation center axis and model intersection point. I am trying to calculate line vectors. However, if equation (2) does not hold, point P1'
, it becomes impossible to measure the distance, and digitizing data no longer exists in a wide range from P□ to P. on the other hand,(
2) If the formula holds, decimation between P□ and P1' is possible, and the range where no decimating data exists becomes narrow from P□' to P, and decimation immediately before the sudden shape change part is possible. becomes possible. In particular, the lower the feed speed ■, the lower the range P in which digitizing cannot be performed.

~P becomes smaller. Therefore, when distance measurement becomes impossible, the feed speed V can be switched to a low speed.

After inputting the above data, when non-contact decitizing is activated, the non-contact decitizing device 11 rotates the distance measuring probe 1 around the rotation center axis 2a at a constant speed and starts a non-contact tracing operation.

Now, the optical axis rotation position monitoring unit 9 has an optical axis 1a of 0°90°,
Each time it reaches the four points 180' and 270', it outputs the distance and generates an enable signal PES.

The distance correction section 11b and the scanning direction calculation section ILa each read distance data and position data of the rotation center axis/model intersection (contents of the current position registers 16X to 162) each time the enable signal PES is generated. That is, the distance correction unit 11b corrects the point p□ on the optical axis trajectory PTR (FIG. 1(a)).
, distance to p3 #IL2. L, are sequentially read, and the scanning direction calculation unit 11a calculates rotation center axis/model intersection points Q, , Q2 . Q
3. Sequentially read the coordinate values at Q.4However, points P,
If the distance measurable signal MIM is generated at , it is recognized that there is a sudden change in shape, and even if the enable signal PES is generated, no distance data or position data is captured, and the optical axis is further rotated by 180 degrees. The distance measured at P is read as position data.

The distance correction unit 11b calculates the distance at the rotation center axis/model intersection Q by calculating equation (1), calculates ', and inputs it to the adder lie. When the distance ML' is input, the adder 11c calculates the error amount ΔL between the reference distance MLo and the measured distance RLx' and inputs it to the speed signal generators lid and lie.

The speed signal generators lid and lie generate a normal speed signal Vn and a tangential speed signal Vt according to the ΔL-Vn characteristics and ΔL-Vt characteristics shown in FIGS. 5 and 6.

The normal vector calculation unit 11g obtains the distance data from the distance measuring probe 1 and the rotation center axis/model intersection point X from the current position register 16X every time the enable signal PES is generated.
Read the axial coordinate value.

That is, the normal vector calculation unit 11g reads the distance L~L4 from the point P to ~P4 on the optical axis trajectory PTR, and
Read the X-axis direction coordinate values Xi (i=1 to 4) at the rotation center axis/model intersection points Q4 to Q4.

Then, by the following formula % formula %, the axis component (Δx,
O, ΔZ1), and using the following formula 2% (where R is the radius from the rotation center axis to the optical axis), the axis component (0°Δy, Δ
Calculate za).

Next, the normal vector calculation unit 11g.

(Δx, 0.Δ2□) is the traveling direction vector, (0, Δy
, Δz2) is the cross-sectional direction vector perpendicular to the traveling direction,
A normal vector is obtained as the outer product of these two vectors and is output to memory llh.

The memory llh stores the contents of each axis current position register (rotation center axis/coordinate value of the model intersection Q□) and the normal vector at the intersection Q calculated by the normal vector calculation unit as a set. Thereafter, similar processing is performed, and the coordinate values of all points on the model surface are stored in pairs with the normal vector in the memory llh.

On the other hand, if it becomes impossible to measure the distance at point P, and also at point P□' where the optical axis has rotated 180 degrees, it is assumed that decimating is impossible, and the distance measuring probe is lowered or raised from then on. When it becomes possible to measure the distance, resume digitizing. If digitizing becomes impossible, sudden shape change processing may be performed, such as tilting the optical axis at a predetermined angle and then restarting non-contact copying (see Japanese Patent Application No. 62-312913).

Also, when it becomes impossible to measure distance, the probe feed speed is further slowed down to continue digitizing, when digitizing becomes impossible, the probe is moved up and down, and when distance measurement becomes possible, the feed speed is increased. Alternatively, the digitizing may be restarted.

<Effects of the Invention> According to the present invention, when it becomes impossible to measure distance at any one of a plurality of measurement positions per rotation, it is possible to recognize in advance that there is a sudden change in shape. By switching the feed speed to a low speed, it is possible to accurately digitize up to just before the sudden change in shape, and when decimating becomes impossible, there is no need to return the probe and feed at a low speed, and decimating can be restarted in a short time.

In addition, according to the present invention, since the distance measuring probe is configured to move at a feed rate V that satisfies the following formula (%), digitizing can be performed with high precision up to just before a sudden change in the model shape, and digitizing can be restarted. Time can also be reduced.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram of the present invention. Fig. 2 is a configuration diagram of the distance measurement position according to the present invention, Fig. 3 is an explanatory diagram of the distance measurement position, Fig. 4 is a block diagram of the non-contact decimating device, and Figs. 5 and 6 are non-contact profiling. FIGS. 7 to 9 are explanatory diagrams of conventional examples. 1...Distance measurement probe, 1a...Optical axis, 2...Rotating part, 2a...Rotation center axis Patent applicant Chiki Saito, agent, patent attorney, FANUC CORPORATION 3 Figure 5 Figure 6 Figure 7

Claims (2)

[Claims] (1) In a sudden shape change detection method in non-contact digitizing, in which a distance measuring probe that can measure distance without contact traces a model surface and the coordinate values of points on the model surface are obtained, the distance that can be measured without contact is The optical axis of the measurement probe is eccentric from the rotation center axis, the distance measurement probe is moved in a predetermined direction, and the optical axis is rotated around the rotation center axis, and the distance measurement probe is moved on the model surface at a plurality of preset rotation angle positions. A method for detecting a sudden shape change, characterized in that position data of a point is measured, and when distance measurement becomes impossible at any one of the plurality of measurement positions per rotation, it is recognized that a sudden shape change part exists. (2) Measure the position data of points on the model surface at multiple positions including the 0° position and 180° position of the optical axis based on the traveling direction of the distance measurement probe, and use the position data to is calculated and output as a pair with the position coordinate value, and the eccentric radius between the optical axis and the rotation center axis of the distance measurement probe is R, the rotation speed of the optical axis is ω, and the feed rate of the rotation center axis is v.
The sudden shape change detection method according to claim 1, wherein the distance measuring probe is moved at a feed rate v that satisfies the relational expression v<(ω/π)·R.