JPH0852644A - Profile control method - Google Patents

Abstract

(57) [Summary] [Purpose] Perform stable movement of the tracer head and enable more accurate tracing control even at a sudden change in the model surface. [Structure] The position detecting means 3 detects the position of the tracer head 1 that follows the surface of the model 2, and the displacement amount detecting means 4 detects the amount of displacement of the stylus 1a provided on the tracer head 1. The correction position calculation means 5 calculates a correction position by correcting the position of the tracer head 1 with the displacement amount of the stylus 1a. The storage unit 6 stores the displacement-corrected position.
The movement vector calculation means 7 sets the first predetermined interval ds,
A second predetermined interval ΔS longer than the first predetermined interval ds
The previous position of the tracer head 1 is read from the first storage means 6, and the movement vector of the section between the read position and the current position is calculated. The profile speed calculation means 8 calculates the profile speed with the calculated movement vector as the feed direction, and the axis movement control means 9 controls the axis movement of the tracer head 1 based on the profile speed.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Conventionally, in a profile control method for measuring a model surface shape with a stylus, a direction vector of a combined displacement amount of a stylus is projected on a profile plane, and a direction perpendicular to the projected direction is set as a feed direction. Further, the velocity component in the feeding direction and the corrected velocity component are calculated according to the magnitude of the combined displacement amount, and the tracer head is axially moved according to these.

However, during actual tracing control, the displacement direction of the stylus often does not coincide with the normal direction of the model due to friction with the model surface. However, in conventional contour control, the amount of displacement due to friction could not be taken into account, so the correction velocity component was applied more than necessary, and the stylus moved too far away from the model surface or cut into it too much, causing waves in the digitizing data. There was a problem that it could be done.

Therefore, the applicant of the present application detects the position and the amount of displacement for each axis of the tracing plane for each predetermined period, corrects the increment amount of the position from the previously read value by the displacement amount, and calculates it as the position increment amount. However, the invention has applied for an invention in which the movement vector of the previous movement section is calculated based on the calculated position increment amount, and the calculated movement vector is set as the tracing direction in the present movement section (Japanese Patent Application No. 6-7694
No. 8).

[0005]

However, in this technique, since the moving section is relatively long, about 1 mm, when the change in the model surface shape is large, the moving vector having a constant value is used as the tracing direction in the moving section. It was inappropriate to do. On the other hand, if the movement section is set to be small, the data can be obtained finely, but the movement vector is greatly affected by the displacement amount of the stylus, which causes a problem that the tracing operation vibrates.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a profile control method capable of performing accurate profile control even when the model surface shape changes greatly.

[0007]

In order to solve the above problems, the present invention provides a position detecting means for detecting the position of a tracer head and a tracer head provided in the tracer head in a tracing control system for measuring a model surface shape. Amount detecting means for detecting the amount of displacement of the stylus, correction position calculating means for calculating a corrected position by correcting the position of the tracer head with the amount of displacement of the stylus, and storage for storing the displacement corrected position Means, and the position of the tracer head, which is before the first predetermined interval by a second predetermined interval longer than the first predetermined interval, is read from the storage means, and the section between the read position and the current position A moving vector calculating means for calculating the moving vector, and a following speed calculating means for calculating a following speed with the calculated moving vector as a feed direction, Is If There control method characterized is provided to have a, a shaft movement control means for controlling the axial movement of the tracer head based on the serial scanning velocity.

[0008]

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 corrected position calculation means calculates a corrected position by correcting the position of the tracer head with the displacement amount of the stylus. Then, the storage means stores the position whose displacement has been corrected. The movement vector calculation means reads the position of the tracer head that is a second predetermined interval longer than the first predetermined interval from the storage means for each first predetermined interval, and the read position and the current position are read. The movement vector of the section is calculated. The profile speed calculation means calculates the profile speed using the calculated movement vector as the feed direction, and the axis movement control means controls the axis movement of the tracer head based on the profile speed.

[0009]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing the concept of the function of this embodiment.
Tracer head 1 in which the position detecting means 3 follows the surface of the model 2
The displacement amount detecting means 4 detects the displacement amount of the stylus 1a provided on the tracer head 1. The correction position calculation means 5 calculates a correction position by correcting the position of the tracer head 1 with the displacement amount of the stylus 1a. The storage unit 6 stores the displacement-corrected position. The movement vector calculation means 7 reads from the first storage means 6 the position of the tracer head 1 that is a second predetermined distance ΔS longer than the first predetermined distance ds for each first predetermined distance ds. The movement vector of the section between the read position and the current position is calculated. The profile speed calculation means 8 calculates the profile speed with the calculated movement vector as the feed direction, and the axis movement control means 9 controls the axis movement of the tracer head 1 based on the profile speed.

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 overall operation of the profile control device 10 in accordance with this 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 on the tracing machine tool 20 calculates displacement amounts εx, εy, and εz in the X-axis, Y-axis, and Z-axis directions generated by the stylus 27 at its tip contacting the model 28. Detects and interfaces analog signal according to its displacement (INT)
Send to 18. The interface 18 converts each analog signal into a digital signal 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 axis moving speed, the processor 11 determines the X-axis speed command Vx, the Y-axis speed command Vy, and the Z-axis speed command. Speed command Vz is generated.
These speed commands are servo amplifiers 16x and 1x, respectively.
Servo motors 22x, 22y and 22 of the machine tool 20 which are input to 6y and 16z and which are output by the outputs
z is driven.

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 the keys on the panel (not shown) to input commands for the profile mode, profile plane, profile command speed, and the like. This input command is the following mode,
The profile plane, profile command speed, etc. can be determined by the interface 32.
Read on the bus 19 via the non-volatile memory 14
Stored in.

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.

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 has displacement amounts ε in the X-axis, Y-axis, and Z-axis directions generated by the stylus 27 at the tip contacting the model.
x, εy and εz are detected and sent to the axis control function unit 40 which is a software function of the profile control device 10 described above. Each displacement amount εx, εy input to the axis control function unit 40
And εz are input to the combining circuit 41 and the switching circuit 42.

In the synthesizing circuit 41, each displacement amount εx, εy and
And εz, the combined displacement amount ε = (εx ²+ Εy²+ Ε
z²)^1/2Is input to the arithmetic unit 43. Calculator 43
Between the combined displacement amount ε and the preset reference displacement amount ε0.
The difference Δε = ε−ε0 is calculated to calculate the velocity component generation circuit 44 and
And 45. The velocity component generation circuit 44 calculates the difference Δ
Based on ε, transmission in the direction perpendicular to the stylus displacement direction
Generate a velocity component (tangential velocity component) Vt and distribute
Send to road 46. In addition, the speed component generation circuit 45 determines the difference Δ
Corrected velocity component in the stylus displacement direction in proportion to ε
(Velocity component in normal direction) Vn is generated and sent to distribution circuit 46.
It

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 a contour plane, which are preliminarily input by the CRT / MDI unit 31, are selected and input to the indexing circuit 47. In this embodiment, the X axis and the Z axis are selected as the two axes.

The indexing circuit 47 samples the position data of the model surface at a minute predetermined interval ds, for example, 0.25 mm, from the start of the tracing operation and stores it in the non-volatile memory 14. Note that this position data is used for the tracer head 26.
Is a value corrected by the displacement amount of the stylus 27.
Then, the indexing circuit 47 has a predetermined interval ΔS from the start of the tracing operation, for example, 1 m which is four times the minute interval 0.25 mm.
Until moving by m, the index signals Ec and Es are obtained based on the following equations (1) and (2) using the displacement amounts ε1 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 component εxz obtained by projecting the combined displacement amount ε on the XZ plane is an angle formed with the X axis. In this case ε
1 corresponds to εx and ε2 corresponds to εz. The Ec and Es thus obtained are sent to the distribution circuit 46.

The indexing circuit 47 has a position detecting means 4
The data of the current position of each motor 22x, 22y, 22z detected in 9 is sent. The indexing circuit 47 reads the data of the sent position, and every time the tracer head 26 moves by a predetermined distance ds, the tracer head 2 at that time is read.
The position of 6 and the displacement of the stylus 27 are stored in the non-volatile memory 14.

FIG. 4 shows the operation timing of the indexing circuit 47.
It is a figure. In addition, each position Q₀, Q ₁, Q₂, Q₃etc
Is the position data of the tracer head 26
The displacement amount of the lath 27 is added and corrected. Model
Q for the start position of tracing the shape of Le 28₀Then, indexing
Each time the path 47 is moved by a predetermined distance ds in the X-axis direction,
Q of position data₁, Q₂, Q₃, Q_Four...
Sampled and stored in the non-volatile memory 14
It The indexing circuit 47 has a start position Q.₀4th position from Q
_FourUp to, based on equations (1) and (2) as described above
The index signals Ec and Es are obtained.

When the tracer head 26 reaches the first position Q ₄ where the steady state is reached, the indexing circuit 47 causes the tracer head 26 to move to the position before the predetermined interval ΔS, that is, to the position Q ₀ before 4 × ds. The 26 movement vectors B ₀ are calculated by the procedure described later. Then, up to the position Q ₅ at the next predetermined interval ds, the movement vector B ₀ is set as the tracing feed direction, and the index signals Ec and Es are obtained based on the movement vector B ₀ by the procedure described later. After that, similarly, every time the position Q ₅ , Q ₆ , Q ₇ , Q ₈ ...
Positions Q ₁ , Q ₂ , Q ₃ , Q ₄ ...
・ The movement vectors B ₁ and B ₂ between and are calculated, and the tracing feed direction is determined based on them.

FIG. 5 is a diagram showing how to obtain the movement vector in the steady state. Here, the position when the tracer head 26 is ahead by .DELTA.S is Pn-1 and the current position is Pn. The amount of movement in the X-axis direction between the positions Pn-1 and Pn is dx (= ΔS), and the amount of movement in the Z-axis direction is dz.

When the positions Pn-1 and Pn are obtained, the indexing circuit 4
7 calculates a movement vector value from the position Pn-1 toward the position Pn, and sets this as a vector indicating the direction of the feed velocity component Vt. When the direction of this feed speed component Vt is determined,
As shown in the figure, the correction speed component Vn is equal to the feed speed component Vt.
Determined in a direction perpendicular to. When the feed axis is the X axis, and the angle of the corrected speed component Vn with respect to the X axis is θa, the index signals Ec and Es are respectively Ec = cos θa = −dz / (dx ² + dz ² ) ^1/2 Es = sin θa = Dx / (dx ² + dz ² ) ^1/2 . Returning to FIG. 3, the indexing circuit 47 sends the indexing signals Ec and Es to the distribution circuit 46.

The distribution circuit 46 receives the index signals Ec, E.
The following equations (3) and (4) are calculated using s, the feed velocity signal Vt and the corrected velocity component Vn. V1 = Vt × Es + Vn × Ec (3) V2 = −Vt × Ec + Vn × Es (4) V1 and V2 are biaxial velocity components of the profile plane,
In FIG. 5, they correspond to the X axis and the Z axis, respectively. These velocity components V1 and V2 are output as velocity signals Vx, Vy, and Vz for the X-axis, Y-axis, and Z-axis via the output shaft selection circuit 48, and amplified by the servo amplifiers 16x, 16y, and 16z.

Then, the servo amplifiers 16x and 16z
The servo motors 22x and 22z are driven by the output of, and the table 21 shown in FIG. 2 moves. As a result, the stylus 26 moves with respect to the model 28 by the velocity component V.
Tracing speed Va, which is the composite speed of 1 and V2 (FIG. 5)
Is moved in the direction of. Further, the servo motor 22z is driven by the output of the servo amplifier 16z, and the cutter 24 shown in FIG. 2 moves in the Z-axis direction together with the tracer head 26.

FIG. 6 is a flow chart showing the main processing procedure of the tracing control device 10. It should be noted that this flowchart is started to be executed when the operation of the profile control is started. [S1] Profile control for calculating the feed direction based on the displacement of the stylus 27 is performed. [S2] It is determined whether or not it has moved by a predetermined distance ds, and if it has moved, the process proceeds to step S3, and if not, the process proceeds to step S5. [S3] The current position of the tracer head 26 is sampled and stored in the nonvolatile memory 14. [S4] It is determined whether or not a predetermined distance ΔS has been moved from the start of the profile control, and if it is moved, the process proceeds to step S6, and if not, the process proceeds to step S5.

[S5] It is judged whether or not a command to stop the tracing operation has been issued. If it is done, this flow chart is terminated, and if not, the process returns to step S1. [S6] A movement vector between the current position and the position preceding by the predetermined interval ΔS is calculated. [S7] The feed direction is calculated based on the calculated movement vector, and the profile control is performed. [S8] It is determined whether or not the predetermined distance ds has been moved, and if the movement is made, the process proceeds to step S10, and if not, the process proceeds to step S9. [S9] It is determined whether or not a command to stop the conforming operation has been issued. If the command is issued, the present flowchart is terminated, and if not, the process returns to step S7. [S10] The current position of the tracer head 26 is sampled and stored in the nonvolatile memory 14. [S11] It is determined whether or not a command to stop the conforming operation has been issued. If the command is issued, this flowchart is ended, and if not, the process returns to step S6.

As described above, in this embodiment, the position of the tracer head 26 is sampled at a minute predetermined interval ds,
For each sampling position, a movement vector during a predetermined interval ΔS, which is sufficiently larger than the predetermined interval ds, is calculated, and this movement vector is used as the feed direction to perform speed control only during the next predetermined interval ds. The feed direction can be determined at finer intervals and without being greatly affected by changes in the stylus displacement amount. Therefore, stable tracing operation can be performed even in a sudden change portion, and accurate digitizing data can be obtained.

In this embodiment, the predetermined intervals ds and ΔS correspond to the moving distance of the X axis, but they may correspond to the moving distance along the plane of the model 28 or the moving distance of the Z axis.

Further, in the present embodiment, the predetermined intervals ds and ΔS correspond to the moving distance of the tracer head, but they may correspond to the moving time. Further, in the present embodiment, the ratio between the predetermined interval ds and ΔS is set to 1: 4, but the present invention is not limited to this, and another ratio may be used depending on the situation.

[0034]

As described above, according to the present invention, at every first predetermined interval, the section between the position of the tracer head and the current position which is a second predetermined interval longer than the first predetermined interval. Since the moving vector of is calculated and the calculated moving vector is used as the feed direction to calculate the speed,
The feed direction can be determined at a finer interval and without being greatly affected by the change in the stylus displacement amount. Therefore, stable tracing operation can be performed even in a sudden change portion, and accurate digitizing data can be obtained during digitizing.

[Brief description of drawings]

FIG. 1 is a diagram showing a concept of functions of 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 a calculation timing of an indexing circuit.

FIG. 5 is a diagram showing how to obtain a movement vector in a steady state.

FIG. 6 is a flowchart showing a main processing procedure of the tracing control device.

[Explanation of symbols]

 1 Tracer Head 1a Stylus 2 Model 3 Position Detecting Means 4 Displacement Detecting Means 5 Correcting Position Calculating Means 6 Storage Means 7 Moving Vector Calculating Means 8 Tracing Velocity Calculating Means 9 Axis Movement Controlling Means 10 Processor 12 ROM 13 RAM 14 Non-volatile memory 20 Tracing machine tool 26 Tracer head 27 Stylus 28 Model 47 Indexing circuit

Claims (6)

[Claims] 1. A tracing control method for measuring a model surface shape, comprising position detecting means for detecting a position of a tracer head, displacement amount detecting means for detecting a displacement amount of a stylus provided on the tracer head, A correction position calculation unit that calculates a correction position in which the position of the tracer head is corrected by the amount of displacement of the stylus, a storage unit that stores the position where the displacement is corrected, and the first predetermined interval for each first predetermined interval. Second longer than the interval
The position of the tracer head before a predetermined interval of, from the storage means, the movement vector calculation means for calculating the movement vector of the section between the read position and the current position, and the calculated movement vector as the feed direction A profile control method comprising: a profile speed calculating unit for calculating a profile speed; and an axis movement control unit for controlling the axial movement of the tracer head based on the profile speed. 2. The profile control method according to claim 1, wherein the second predetermined interval is an integral multiple of the first predetermined interval. 3. The tracing control method according to claim 1, wherein the storage means is a non-volatile memory. 4. The tracing speed calculation means, from the start of the tracing operation to the movement of the stylus by the second predetermined interval, a feed direction is a direction perpendicular to a projection displacement direction of the stylus onto a tracing plane. The tracing control method according to claim 1, wherein the tracing control method is configured to: 5. The profile control method according to claim 1, wherein the first predetermined interval and the second predetermined interval are set in correspondence with a moving distance of the tracer head. 6. The tracing control method according to claim 1, wherein the first predetermined interval and the second predetermined interval are set in correspondence with a moving time of the tracer head.