JPH07314294A - Tracer control method - Google Patents

Abstract

PURPOSE:To obtain the correct digitizing data even in case of the model surface shape having the large change, by installing a feed direction determining means for determining the feed speed direction in the shift division at this time, on the basis of the angular difference between the shift vector in the shift division in the preceding time and the shift vector in the shift division in the forepreceding time. CONSTITUTION:A position increment calculating means 6 reads out the position and the displacement quantity on each axis of a copying plane in each prescribed cycle, and the increment from the value of the position detected in the preceding time is corrected by the increment from the value of the displacement quantity detected in the preceding time, and calculated as the position increment in the shift division in the preceding time. Then, a shift vector calculating means 7 calculates the shift vector in the shift division in the preceding time, on the basis of the position increment. On the basis of the angular difference of the shift vector in the shift division between in the preceding time and the forepreceding time, a feed direction detecting means 8 determines the feed speed direction in the shift division at this time, and a shaft shift control means 9 controls the shaft shift of a tracer head, in order to carry out the copying on the basis of the determined feed speed direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tracing control method for tracing and measuring a model surface shape, and more particularly to a tracing control method for tracing a model surface shape with a stylus.

[0002]

2. Description of the Related Art FIG. 7 is a diagram showing a conventional contouring control method in which a stylus is brought into contact with a model surface to follow the model surface shape. Here, the case where the tracing plane is the XZ plane is shown. In the conventional contour control method, when tracing the surface of the model 72 with the tip of the stylus 71, the stylus 7
Combined displacement amount ε of displacement amounts εx, εy, εz
Is calculated, and the direction perpendicular to the direction vector component εxz obtained by projecting the direction vector of the combined displacement amount ε onto the profile plane is calculated as the profile feed direction. Then, the following feed velocity component Vt and the correction velocity component Vn which is the correction value thereof are calculated to determine the feed velocity Vs. This feed velocity Vs is distributed to velocity components V1 and V2 on the respective contour plane axes X and Z represented by the following equations (11) and (12).

V1 = Vt.sin.theta.-Vn.cos.theta. (11) V2 = -Vt.cos.theta.-Vn.sin.theta. (12) where θ is the X of the direction vector component εxz of the combined displacement ε. It is the angle to the axis. When the feed direction is positive, Vt
> 0 and the stylus displacement ε is larger than the reference displacement amount ε0, Vn> 0.

In this way, the velocity components V1 and V2 are always obtained during the profile control, and the stylus 71 is accordingly obtained.
Is controlled to move. However, with such a control method,
A correction velocity component Vn is generated every time the direction vector component εxz of the combined displacement amount ε deviates from the line L11 of the model 72 surface, and the velocity Vs is calculated by correcting the feed velocity component Vt. Since this correction is continuously performed during the follow-up control, waves may be generated on the trajectory of the stylus 71, and the digitizing data may be inaccurate.

Therefore, the applicant of the present application detects the position and the displacement amount for each axis of the tracing plane in every predetermined period, corrects the increment amount from the previously read value by the displacement amount, and calculates it as the position increment amount. Then, by calculating the movement vector of the previous movement section based on the calculated position increment amount, and by controlling the axial movement of the tracer head by using the calculated movement vector as the tracing direction in the current movement section, An application has been filed for reducing the minute fluctuations in the profile feed direction due to the generation of the corrected velocity component (Japanese Patent Application No. 6-76948).

[0006]

However, in this technique, the movement vector of the previous movement section is used as it is as the movement vector of the present movement section. Therefore, when the change of the model surface shape is large, the movement section is changed. Accurate digitizing data could not be obtained unless it was set small.

The present invention has been made in view of the above points, and an object thereof is to provide a profile control method capable of obtaining accurate digitizing data even for a model surface shape having a large change. And

[0008]

In order to solve the above problems, the present invention provides a position control means for detecting the position of a tracer head and a tracer head in a tracing control system for tracing a model surface shape. Displacement amount detection means for detecting the displacement amount of the stylus provided, profile data storage means for storing the detected position and displacement amount in a predetermined cycle, and the position and the position for each axis of the profile plane in the predetermined cycle. Position increment calculation that reads the displacement amount and corrects the increment amount from the previously detected value of the position with the increment amount from the previously detected value of the displacement amount and calculates it as the position increment amount of the previous movement section Means, a movement vector calculation means for calculating a movement vector of a previous movement section based on the calculated position increment amount, and a movement vector of the previous movement section. And a tracer for performing tracing based on the determined feed speed direction, and a feed direction determining means for determining a feed speed direction in the current movement section based on an angular difference between the movement vector of the second and last movement section. An axial movement control means for controlling the axial movement of the head is provided.

[0009]

When the position detecting means detects the position of the tracer head and the displacement amount detecting means detects the displacement amount of the stylus provided on the tracer head, the data storing means which traces the detected position and displacement amount has a predetermined cycle. Store with. The position increment amount calculating means reads the position and the displacement amount for each axis of the tracing plane for each predetermined cycle, and corrects the increment amount from the previously detected value of the position with the increment amount from the previously detected value of the displacement amount. Then, it is calculated as the position increment amount of the previous movement section. The movement vector calculation means calculates the movement vector of the previous movement section based on the calculated position increment amount. Then, the feed direction determination means determines the feed speed direction in the current movement section based on the angular difference between the movement vector of the previous movement section and the movement vector of the previous two movement sections, and based on the determined feed speed direction. The axis movement control means controls the axis movement of the tracer head to execute the tracing.

As a result, even on a model surface having a large change, it is possible to reduce minute fluctuations in the profile feed direction due to the generation of the correction velocity component, and accurate digitizing data can be obtained.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the concept of the function of the profile control method of this embodiment. Tracer head 1 is model 2
When the surface is flattened, the position detecting means 3 detects the position of the tracer head, and the displacement amount detecting means 4 detects the displacement amount of the stylus 1a provided on the tracer head 1. The data storage means 5 stores these detected positions and displacement amounts in a predetermined cycle. The position increment amount calculation means 6 reads the position and the displacement amount for each axis of the tracing plane for each predetermined cycle, and uses the increment amount from the previously detected value of the position as the increment amount from the previously detected value of the displacement amount. It is corrected and calculated as the position increment amount of the previous movement section.

The movement vector calculation means 7 calculates the movement vector of the previous movement section based on the calculated position increment amount. Then, the feed direction determining means 8 determines the feed speed direction in the current movement section based on the angular difference between the movement vector in the previous movement section and the movement vector in the previous two movement sections, and based on the determined feed speed direction. The axis movement control means 9 controls the axis movement of the tracer head in order to execute the taming.

FIG. 2 is a block diagram showing the configuration of a tracing / processing system according to an embodiment of the present invention. The profile / machining system is mainly composed of a profile control device 10 and a profile machine tool 20. The processor 11 of the profile control device 10 reads the system program stored in the ROM 12 via the bus 19 and controls the operation of the profile control device 10 as a whole according to the system program.
Temporary data is stored in the RAM 13. The non-volatile memory 14 is backed up by a battery (not shown) and stores various parameters such as a profile mode, profile plane, and profile speed input by a key on a panel (not shown) of the CRT / MDI unit 31. To be done. The non-volatile memory 14 also stores digitizing data of the model surface shape measured by the tracer head 26 of the tracing machine tool 20.

The tracer head 26 provided in the tracing machine tool 20 calculates displacement amounts εx, εy and εz in the X-axis, Y-axis and Z-axis directions, which are produced by the stylus 27 at the tip of the tracer head 26 coming into contact with the model 28. Detect and interface analog signal according to its size (INT)
Send to 18. The interface 18 converts each displacement amount εx, εy, and εz of the sent analog signal into a digital signal, digitally converts it, and sends it to the processor 11 side.

Based on the displacement amounts εx, εy and εz, the commanded tracing mode, the tracing plane, and the tracing speed, the processor 11 performs the X-axis speed instruction Vx and the Y-axis speed instruction Vy by the procedure described later. , And Z-axis speed command Vz are generated. These speed commands are D
The A / A converters 16x, 16y, and 16z perform analog conversion, input to the servo amplifiers 16x, 16y, and 16z, and the outputs thereof drive the servomotors 22x, 22y, and 22z of the model machine tool 20.

As a result, the tracer head 26 moves, and the table 21 moves in the X axis direction and the Y axis direction perpendicular to the paper surface. At this time, the relative positional relationship between the tracer head 26 and the model 28 is controlled so as to be kept constant. Then, the workpiece 24 is processed in the same shape as the model 28 by the cutter 24 which is Z-axis controlled similarly to the tracer head 26.

Further, the servo motors 22x, 22y and 22z are provided with pulse coders 23x, 23y and 23z which generate detection pulses FPx, FPy and FPz, respectively, each time they rotate a predetermined amount. Current position registers 17x and 17y in the profile control device 10
And 17z are the detection pulses FPx, FPy and FP
The current position data Xa, Ya, and Za of the tracer head 26 are obtained by counting up / down each z according to the rotation direction, and these position data are read by the processor 11.

The processor 11 sends an image display signal or the like showing the state during the profile processing through the bus 19 to the CRT / MDI.
Send to unit 31. In the CRT / MDI unit 31, the built-in graphic control device converts the sent image display signal into image data and displays it on a display device (not shown). On this display device, an input operation screen for the conditions of the profile processing is displayed at the start of the profile processing. The operator uses keys on the panel (not shown) to input commands for the profile mode, profile plane, profile speed, and the like. The input commanded profile mode, profile plane, profile speed, etc. are read onto the bus 19 via the interface 32 and stored in the non-volatile memory 14.

An operation panel 30 is connected to the bus 19 via the interface 15. On the operation panel 30,
A profile machining start command and a stop command are issued. Each of these command signals is sent to the processor 11 via the interface 15 and the bus 19.

Next, a specific procedure of the profile control method of this embodiment will be described. FIG. 3 is a block diagram showing a specific configuration of the function of the profile control method of this embodiment. The tracer head 26 detects the displacement amounts εx, εy and εz in the X-axis, Y-axis and Z-axis directions caused by the stylus 27 at the tip contacting the model, and uses the software function of the tracing control device 10 described above. It is sent to a certain axis control function unit 40. The displacement amounts εx, ε input to the axis control function unit 40
y and εz are input to the combining circuit 41 and the switching circuit 42.

In the synthesizing circuit 41, the synthetic displacement ε (ε = (εx ² + εy ² + ε) is calculated from the respective displacements εx, εy and εz.
z ² ) ^1/2 ) is calculated and input to the calculator 43. Arithmetic unit 4
3 calculates a difference Δε (Δε = ε−ε0) between the combined displacement amount ε and a preset reference displacement amount ε0 and inputs it to the velocity component generation circuits 44 and 45. Speed component generation circuit 44
Generates a feed velocity component (tangential velocity component) Vt in the direction perpendicular to the stylus displacement direction based on the difference Δε and sends it to the distribution circuit 46. In addition, the speed component generation circuit 45
Is a correction speed component Vn which is a feed speed component (normal direction speed component) in the stylus displacement direction in proportion to the difference Δε.
Is generated and sent to the distribution circuit 46.

On the other hand, in the switching circuit 42, each displacement amount ε
From x, εy, and εz, biaxial displacement amounts ε1 and ε2 forming the contour plane TS, which have been preliminarily input by the CRT / MDI unit 31, are selected and input to the indexing circuit 47. From the start of the tracing operation until the tracer head 26 exceeds the first movement section, the indexing circuit 47 has a displacement amount ε1.
The index signals Ec and Es are obtained based on the following equations (1) and (2) using ε2 and ε2.

Ec = ε1 / (ε1 ² + ε2 ² ) ^1/2 = cos θ (1) Es = ε2 / (ε1 ² + ε2 ² ) ^1/2 = sin θ (2) where θ is The above-mentioned εxz in FIG. 7 is the same as the angle θ formed with the X axis. In this case, ε1 corresponds to εx and ε2 corresponds to εz. The Ec and Es thus obtained are sent to the distribution circuit 46.

In addition, the indexing circuit 47 includes the position detecting means 4
The data of the current position of each motor 22x, 22y, 22z detected in 9 is sent. Further, the indexing circuit 47 is supplied with a switching signal CS which indicates in which movement section the tracer head 26 is located. The indexing circuit 47 is
The data of the sent position is read and the tracer head 26
Every time the movement of the movement section set to a predetermined distance (for example, 1 mm) is completed, the position of the tracer head 26 at that time and the displacement amount ε projected onto the tracing plane of the stylus 27
1 and ε2 are stored. When the movement of the tracer head 26 enters the second movement section beyond the first movement section, the indexing circuit 47 calculates the movement vector of the tracer head 26 in the first movement section, and this movement vector Is the feed direction in the second movement section, and the index signals Ec and Es are calculated and output based on the feed direction. For the movement vector of the tracer head 26, the difference between the current and previous detection values of the position of the tracer head 26 and the difference between the current and previous detection values of the displacement amount of the stylus 27 are calculated separately, and each calculated value is added. To obtain.

Further, the indexing circuit 47 obtains the indexing signals Ec and Es by the following procedure after the tracer head 26 reaches the steady state beyond the second movement section from the start of the tracing operation.

FIG. 4 shows the index signals Ec and E in the steady state.
It is a figure which shows how to obtain | require s. Here, the position of the tracer head 26 at the time of this detection is Pn, the previous position is Pn-1, and the position two times before is Pn-2. The positional relationship between the positions Pn, Pn-1 and Pn-2 is corrected by adding the displacement amount of the stylus 27 at each detection. Further, here, an example of the XZ plane is shown as the profile plane.

When the tracer head 26 reaches the position Pn, the indexing circuit 47 calculates the movement vector Bn2 from the position Pn-2 to Pn-1. In addition, the indexing circuit 47
A movement vector Bn1 from the position Pn-1 to Pn is calculated. Since the movement vector Bn2 has already been calculated in the previous movement section, the movement vector Bn2 may be stored in the RAM 13 or the like and read out without recalculation.

The indexing circuit 47 uses these movement vectors Bn2.
And the movement vector Bn1 are calculated, the angles θn-2 and θn-1 with respect to the respective X-axis are calculated, and Δθ =
Calculate θn-1 − θn-2. Then, Δθ is added to the angle θn-1 of the movement vector Bn1 of the previous movement section, and this is set as the movement vector of the feed speed component Vt of the present movement section. That is, if the angle of the vector of the feed speed component Vt with respect to the X axis is θn, then θn = θn-1 + Δθ.
However, in FIG. 4, apparently | θn | = | θn-1
| − | Δθ |.

When the vector of the feed speed component Vt is determined, the corrected speed component Vn is determined in the direction perpendicular to the feed speed component Vt as shown in the figure. When the feed axis is the X axis, the angle of the correction speed component Vn with respect to the X axis is θa.
Then, the index signals Ec and Es are given by the following equations (3) and (4), respectively. Ec = cos θa = -sin θn = -sin (θn-1 + Δθ) = -sin θn-1 ・ cos Δθ -cos θn-1 ・ sin Δθ = -sin θn-1 ・ cos (θn-1 -θn-2) -cos θn-1 ・ sin (Θn-1 -θn-2) = -sinθn-1 (cosθn-2 · cosθn-1 + sinθn-2 · sinθn-1) −cosθn-1 (sinθn-2 · cosθn-1 − cosθn-2 · sinθn-1) ) (3) Es = sin θa = cos θn = cos (θn-1 + Δθ) = cos θn-1 ・ cos Δθ -sin θn-1 ・ sin Δθ = cos θn-1 ・ cos (θn-1 -θn-2) -sin θn- 1 * sin ((theta) n-1 (theta) n-2) = cos (theta) n-1 (cos (theta) n-2 * cos (theta) n-1 + sin (theta) n-2 * sin (theta) n-1) -sin (theta) n-1 (sin (theta) n-2 * cos (theta) n-1-cos (theta) n-2 * sin (theta) n) -1) (4) The indexing circuit 47 determines the index calculated by these equations (3) and (4). It sends a signal Ec and Es the distribution circuit 46.

Returning to FIG. 3, the distribution circuit 46 outputs the index signals Ec, Es, the feed speed component Vt and the correction speed component V.
The following equations (5) and (6) are calculated using n. V1 = Vt × Es + Vn × Ec (5) V2 = −Vt × Ec + Vn × Es (6) The output axis selection circuit 48 has the CRT / MDI unit 31 in advance among the X-axis, Y-axis and Z-axis. Of these velocity components V1 and V on the two axes forming the tracing plane TS
2 are made to correspond and output as speed signals Vx, Vy and Vz. In FIG. 4, velocity components V1 and V2 are
Each corresponds to the X axis and the Z axis. The output speed signals Vx, Vy and Vz are output to the servo amplifiers 16x, 16
Amplified by y and 16z.

Then, the servo amplifiers 16x and 16y
The servo motors 22x and 22y are driven by the output of, and the table 21 shown in FIG. 2 moves. Further, the servo motor 22z is driven by the output of the servo amplifier 16z, and the tracer head 26 and the cutter 24 move in the Z-axis direction. As a result, the stylus 26 moves relative to the model 28 in the following velocity direction, which is the combined velocity of the velocity components V1 and V2.

FIG. 5 is a flow chart showing the basic processing procedure in the functional portion of the indexing circuit 47. [S1] It is determined whether or not the tracer head 26 is within the first movement section from the start of the tracing operation, and if so, the process proceeds to step S2, and if not, the process proceeds to step S3. [S2] Tracing control is performed in which the feed velocity component Vt is in the direction perpendicular to the displacement direction of the stylus 26. [S3] It is determined whether the stylus 26 is in the second movement section, and if so, the process proceeds to step S4, and if not, the process proceeds to step S5. [S4] A vector of the moving direction of the tracer head 26 in the first moving section is calculated, and the extension direction of this vector is set to 2
The following control is executed as the feed speed component Vt in the th movement section. [S5] Every time the stylus 26 moves for a predetermined distance, the vector of the moving direction of the previous moving section and the vector of the moving direction of the previous moving section are calculated, and the feed speed component Vt is calculated based on these moving vectors. Perform profile control.

FIG. 6 is a flow chart showing the specific processing of step S5 of FIG. [S11] The movement vector Bn1 of the previous movement section of the stylus 26 is calculated. [S12] The movement vector Bn2 of the movement section of the stylus 26 two times before is calculated. [S13] Angle difference Δ between vector Bn1 and vector Bn2
Calculate θ. [S14] The angle θn = θn-1 + Δθ of the vector of the feed velocity component Vt in the current movement section with respect to the X axis is calculated. [S15] Ec and E based on the calculated vector
Calculate s. [S16] The axis control of the current movement section is performed by the speed components V1 and V2 calculated based on Ec and Es.

As described above, in the present embodiment, in the steady state, the angular difference Δθ between the movement vector Bn1 of the previous movement section of the stylus 26 and the movement vector Bn2 of the movement section two times before the stylus 26 is calculated, and the movement this time is further performed. Angle of vector of feed rate component Vt of section with respect to X axis θn = θn-1 + Δθ
Since the velocity components V1 and V2 are calculated by calculating, it is possible to sufficiently follow the change in the shape of the model 28 surface and obtain accurate digitizing data.

Further, in this embodiment, the tracer head 26
In the first movement section, since the feed velocity component Vt is set in the direction perpendicular to the displacement direction of the stylus 26 as in the conventional case, accurate tracing control can be performed without sampling data. This is because there is no kinetic friction or static friction between the stylus 27 and the model 28 before the tracing operation is started, and it is considered that the tracer head 27 moves substantially parallel to the model surface.

Further, in this embodiment, the tracer head 26
If you are in the second movement section from the start of tracing,
Since the vector in the moving direction of the tracer head 26 in the first moving section is calculated and this vector is used as the feed velocity component Vt in the second moving section, accurate tracing is possible even in the moving section in which there is no previous data. It can be controlled.

In this embodiment, the tracer head 26
Although the predetermined period for detecting the position and the displacement amount is set to the time when the movement distance of the tracer head 26 moves by a predetermined distance, this may be set to a predetermined time. Further, in determining the movement of the predetermined distance, the tracer head 26 may be a three-dimensional composite movement distance or a movement distance in a specific axial direction.

In the present embodiment, the difference between the current and previous detection values of the position of the tracer head 26 and the difference between the current and previous detection values of the displacement amount of the stylus 27 are separately calculated in the indexing circuit 47. It was calculated and the accurate increment amount of the position in the movement section was calculated by adding each calculated value, but the value obtained by adding each detected value of the position and the displacement amount this time,
It is also possible to separately calculate the value obtained by adding the previous detection values of the position and the displacement amount, and subtract the previous addition value from the present addition value.

[0039]

As described above, according to the present invention, the position of the tracer head and the displacement amount of the stylus are stored at a predetermined cycle, while the position and the displacement amount are read for each axis of the tracing plane every predetermined cycle, and the previous position The increment amount from the detected value is corrected by the increment amount from the previously detected value of the displacement amount to calculate as the position increment amount of the previous movement section, and the previous movement section is calculated based on the calculated position increment amount. Is calculated, and the feed direction determining means determines the feed velocity direction in the current movement section based on the angular difference between the movement vector in the previous movement section and the movement vector in the previous two movement sections. It is possible to sufficiently follow even a model surface having a shape with large changes, and it is possible to reduce minute fluctuations in the profile feed direction due to generation of a correction speed component. Therefore, accurate digitizing data can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing the concept of the function of a profile control method according to the present embodiment.

FIG. 2 is a block diagram showing the configuration of a tracing / processing system according to an embodiment of the present invention.

FIG. 3 is a block diagram showing a specific configuration of the function of the profile control method of the present embodiment.

FIG. 4 is a diagram showing how to obtain an index signal in a steady state.

FIG. 5 is a flowchart showing a basic processing procedure in a functional portion of an indexing circuit.

FIG. 6 is a flowchart showing a specific process of step S3 of FIG.

FIG. 7 is a diagram showing a conventional contouring control method in which a stylus is brought into contact with a model surface to follow the model surface shape.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tracer head 1a Stylus 2 Model 3 Position detecting means 4 Variable detecting means 5 Profile data storing means 6 Position increment calculating means 7 Movement vector calculating means 8 Profile direction determining means 9 Axis movement control means 10 Profile control device 20 Profile machine tool 11 Processor 26 Tracer Head 27 Stylus 28 Model

Claims (7)

[Claims] 1. A tracing control method for tracing a model surface shape, comprising position detecting means for detecting a position of a tracer head, and displacement amount detecting means for detecting a displacement amount of a stylus provided on the tracer head. , A profile data storage means for storing the detected position and displacement amount in a predetermined cycle, and reading the position and displacement amount for each axis of the profile plane in each of the predetermined period, from the previously detected value of the position. Position increment amount calculating means for correcting the increment amount with the increment amount from the previously detected value of the displacement amount and calculating it as the position increment amount of the previous movement section, and the position increment amount of the previous time based on the calculated position increment amount. A movement vector calculating means for calculating a movement vector of the movement section; and an angle difference between the movement vector of the previous movement section and the movement vector of the movement section two times before. A feed direction determining means for determining the feed speed direction in the current movement section based on the feed direction; and an axis movement control means for controlling the axial movement of the tracer head for performing tracing based on the determined feed direction. Tracing control method characterized by the following. 2. The feed direction determining means is configured to set an angle direction obtained by adding the angle difference to an angle of a movement vector in the previous movement section as a tracing direction in the current movement section. The profile control method according to claim 1, wherein: 3. The profile control method according to claim 1, wherein the predetermined period is set in correspondence with a moving distance of the tracer head. 4. The profile control method according to claim 1, wherein the predetermined cycle is set in correspondence with a moving time of the tracer head. 5. The feed direction determining means is configured such that, at least in the initial state of the tracing operation, a direction perpendicular to a projection displacement direction of the stylus on a tracing plane is the tracing direction. The profile control system according to claim 1. 6. The position increment amount calculation means separately calculates the difference between the current and previous detection values of the position and the difference between the current and previous detection values of the displacement amount, and adds the calculated values. The tracing control method according to claim 1, wherein the tracing control method is configured to: 7. The position increment amount calculation means separates a value obtained by adding the current detected values of the position and the displacement amount and a value obtained by adding the previous detected values of the position and the displacement amount separately. 2. The profile control method according to claim 1, wherein the profile control method is configured to be calculated as described above, and the previous addition value is subtracted from the current addition value.