JPH09190211A - System for controlling route of numerically controlled device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a shock on a machine and to reduce work errors by inserting spline interpolation between work commands when the acceleration directions of the continuous work commands become discontinuous. SOLUTION: When an arc command is continuously given by following a linear command, acceleration vertical to the travel direction of a tool suddenly changes with the switch of the command. Then, the coordinate of a switch point A is set to be (0, 0) and spline interpolation is inserted in a period from the position of a start point B going up to the side of linear interpolation by d1 to the position of an end point C advanced to arc interpolation by d2. Generally, a spline curve is displayed by an n-th order polynomial. For continuously and smoothly changing acceleration among the continuous interpolation blocks, the spline curve passes through adjacent routes at the starting point and the end point. Then, a spline function is decided so that the primary and secondary differential vectors of the curve continue with the adjacent route at the starting point and the end point. Thus, work control is realized without the shock based on it.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a numerical controller, and more particularly to control of a machining path along which a tool moves.

[0002]

2. Description of the Related Art In path control in a numerical controller, an arc command and a linear command are continuously commanded, and there is no change in the tool advancing direction at the connection point, that is, a straight line is commanded to contact the arc. In this case, the acceleration in the direction perpendicular to the tool traveling direction suddenly changes. In such a case, the arc portion is applied in the direction perpendicular to the tool advancing direction, but the linear portion is not subjected to acceleration. FIG. 13 is a diagram for explaining the path error of the processing path. FIG. 13 shows a case where an arc command is issued subsequent to the straight line command, and is perpendicular to the traveling direction of the arc at the joint where the straight line (a in FIG. 13) changes to the arc (b in FIG. 13). The acceleration f is applied in any direction. As a result, the acceleration in the direction perpendicular to the tool advancing direction suddenly changes, so that a large shock is applied to the machine and a machining error (c in FIG. 13) occurs due to the deflection of the machine. Conventionally, as an effective means for reducing the shock to this machine, a method of post-interpolation acceleration / deceleration using a command or the like that has passed through a filter is known.

[0003]

However, when the shock to the machine is reduced by the acceleration / deceleration after the interpolation, since the acceleration / deceleration is performed for each axis, a path error may occur at a place where the tool advancing direction changes. become. Reference character d in FIG. 13 denotes a locus resulting from post-interpolation acceleration / deceleration, and its path passes inside the arc command. Further, since this error amount changes depending on the feed speed, when the feed speed is changed by the feed speed override or the like, a step occurs at the position where the feed speed is changed (e in FIG. 13).

In order to prevent such a path error or step due to post-interpolation acceleration / deceleration, deceleration is performed instead of post-interpolation acceleration / deceleration at a location where a shock occurs, or the time constant of post-interpolation acceleration / deceleration is set to be extremely small. Then, a method is adopted in which an error does not occur as much as possible. However, such a method has a problem that the processing time is extended although the shock is reduced.

Therefore, the present invention solves the above-mentioned conventional problems and provides a path control system capable of reducing the shock to the machine, reducing the machining error and not extending the machining time. With the goal.

[0006]

According to the present invention, in a path control system in a numerical controller, by inserting spline interpolation between two machining commands when the acceleration directions of successive machining commands are discontinuous, It is possible to reduce the shock to the machine, reduce the machining error, and perform the route control without extending the machining time.

In the spline interpolation according to the present invention, in a continuous machining command in which the acceleration direction is discontinuous, both ends of the spline interpolation pass through the route of the adjacent machining command, and the velocity and acceleration at both ends are continuous. It can be performed by using a spline curve that satisfies certain three conditions, and the spline curve can be realized by a function representing the spline curve or a minute linear block connected through points on the spline curve.

When machining is performed by the route control method in the numerical controller, a block for performing spline interpolation is automatically provided between the machining blocks when the acceleration direction due to the machining blocks in the machining program becomes discontinuous. This can be done by inserting and executing the processing block of this spline interpolation.

Further, when the machining program is generated by the path control method in the numerical controller, if the acceleration direction of the machining blocks continuous in the machining program is discontinuous, spline interpolation is performed between the machining blocks. This can be done by automatically inserting the block to be made.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a diagram for explaining the relationship between interpolation blocks in the route control method of the present invention.
The route example shown in FIG. 1 shows a case where an arc command is issued following the straight line command. As described above, when the circular-arc command is continuously issued following the linear command, the switching of the commands causes the acceleration in the direction perpendicular to the tool traveling direction to change suddenly. Therefore, in the path control method of the present invention, by inserting the spline interpolation as shown between the linear command and the circular arc command, the shock to the machine is reduced and the machining error is reduced without extending the machining time. Perform route control.

In FIG. 1, the coordinates of the switching point A are set to (0, 0), and the position of the end point C advanced by d2 to the circular interpolation from the position of the start point B, which is the spline interpolation up to the linear interpolation side by d1. Insert between. The distances d1, d
2 is the distance along the command path. The numerical control device performs the linear interpolation, the spline interpolation, and the circular interpolation, thereby realizing machining in which the acceleration continuously and smoothly changes.

Next, a method for obtaining a spline curve that defines a path for performing spline interpolation will be described with reference to FIG. Note that the example shown in FIG. 2 shows the case where the circular interpolation is performed subsequently to the linear interpolation as in the case shown in FIG. Generally, the spline curve is represented by a polynomial of degree n. Then, in the spline curve represented by the polynomial of degree n, the following three conditions must be satisfied in order for the acceleration to continuously and smoothly change between consecutive interpolation blocks.

(A) The spline curve passes through adjacent routes at its start point and end point. (B) The first-order differential vector of the spline curve is continuous with the route that is adjacent at the start point and the end point. (C) The second-order differential vector of the spline curve is continuous with the path that is adjacent at the start point and the end point.

The above conditions (a) to (c) are represented by six conditional expressions. If the degree of the n-th degree polynomial is 5, the coefficients of the polynomial are determined by the six conditional expressions without excess or deficiency. Therefore, hereinafter, a fifth-order polynomial represented by the following equation (1) is used as the n-th degree polynomial. f = At ⁵ + Bt ⁴ + Ct ³ + Dt ² + Et + F (1) From Expression (1), the positions in the X-axis direction and the Y-axis direction are the function fx and the function fy represented by the following expressions. fx = Axt ⁵ + Bxt ⁴ + Cxt ³ + Dxt ² + Ext + Fx (2) fy = Ayt ⁵ + Byt ⁴ + Cyt ³ + Dyt ² + Eyt + Fy (3) Here, in FIG. 2, the radius of the arc command is R and the spline interpolation is started. The end of the spline interpolation is set at a position returned by a distance of d1 along the command route and a position advanced by a distance of d2 along the command route. As a result, the coordinates of the point P on the circular arc according to the circular arc command becomes (Rsin
θ, R (1-cos θ)).

Further, if the spline parameter t is set so that t = 0 at the starting point A and t = 1 at the ending point C, the following equation approximately holds between the points A and C. (D1 + Rθ) / (d1 + d2) = t (4) where θ is an equation and is differentiated by t to obtain the following equation.

Θ = {(d1 + d2) · t−d1} / R (5) dθ / dt = (d1 + d2) / R (6) Therefore, the arc between point A and point C is a function g of θ.
The following equation is expressed by x (θ) and gy (θ).

Gx (θ) = Rsinθ (7) gy (θ) = R (1-cosθ) (8) In the above equations (7) and (8), the first derivative and the second derivative with respect to t are It becomes the following formula. gx (θ) ′ = dgx (θ) / dt = dgx (θ) / dθ · (dθ / dt) = Rcosθ · {(d1 + d2) / R} = (d1 + d2) · cosθ (9) gy (θ) ′ = Dgy (θ) / dt = dgy (θ) / dθ · (dθ / dt) = Rsinθ · {(d1 + d2) / R} = (d1 + d2) · sinθ (10) gx (θ) ”= dgx '(θ ) / Dt = dgx ′ (θ) / dθ · (dθ / dt) = − (d1 + d2) · sin θ · {(d1 + d2) / R} = − {(d1 + d2) ² / R} · sin θ ... (11) gy ( θ) ”= dgy ′ (θ) / dt = dgy ′ (θ) / dθ · (dθ / dt) = (d1 + d2) · cos θ · {(d1 + d2) / R} = {(d1 + d2) ² / R} · cos θ (12) The coordinates of the start point A of the spline curve are represented by (-d1,0), and the coordinates of the end point C Target is (R · sin (d2 / R), R ·
It is represented by (1-cos (d2 / R)).

When the condition (a) is applied to the functions of the above equations (2) and (3), the coordinates of the starting point A of the spline curve in FIG. 2 are (-d1,0) and the coordinates of the ending point C are ( R · sin (d2 / R), R · (1-cos (d2 /
R)), the following conditional expression (1
3) and (14) are obtained, and the following conditional expressions (15) and (16) are obtained from the condition of the end point C.

Fx (0) = − d1 (13) fy (0) = 0 (14) fx (1) = R · sin (d2 / R) (15) fy (1) = R {1− cos (d2 / R)} (16) Next, when the condition (b) is applied to an expression obtained by first-order differentiation of the functions of the expressions (2) and (3), expressions (9) and (10) are obtained. From the condition of the starting point A, the following conditional expressions (17) and (1
8), the following conditional expression (19) from the condition of the end point C,
Get (20). Note that θ at the point C is θ = d2 / R
It is. fx ′ (0) = d1 + d2 (17) fy ′ (0) = 0 (18) fx ′ (1) = (d1 + d2) · cos (d2 / R) (19) fy ′ (1) = (d1 + d2) ) .Sin (d2 / R) (20) Next, the function fx and the function fy of the above equations (2) and (3).
When the above condition (c) is applied to the expression obtained by quadratic differentiation, the following conditional expressions (21) and (22) are obtained from the condition of the starting point A using the expressions (11) and (12), and the condition of the end point C is obtained. From the following conditional expressions (23) and (24) are obtained.

Fx ″ (0) = 0 (21) fy ″ (0) = 0 (22) fx ″ (1) = − {(d1 + d2) ² / R} · sin (d2 / R) (23) ) Fy ″ (1) = {(d1 + d2) ² / R} · cos (d2 / R) (24) Therefore, using the conditional expressions (13) to (24), the coefficients Ax to Fx and the coefficient Ay to By obtaining Fy, the spline function fx and the function fy can be determined.

The processing by the spline interpolation is performed by, for example, FIG.
As shown in, the linear interpolation block is performed by inserting spline interpolation between the circular interpolation block and between the circular interpolation block and the linear interpolation block.
In the above example, the area between the linear interpolation block and the circular interpolation block is shown as an example, but the same applies to other interpolation blocks between interpolation blocks in which the acceleration direction of the tool path is discontinuous. You can

FIG. 4 is a block diagram illustrating the configuration of a control system to which the route control system of the present invention is applied. Processor 2
Reference numeral 01 denotes a processor that controls the NC device 1 as a whole, reads a system program stored in the ROM 202 via the bus 200, and controls the NC device 1 according to the system program. The RAM 203 stores temporary calculation data, display data, various data input by the operator via the CRT / MDI unit 70, and parameters necessary for control. The CMOS memory 204 is backed up by a battery (not shown), and is configured as a non-volatile memory that retains a stored state even when the power of the NC device 1 is turned off. The CMOS memory 204 stores a machining program input via the interface 205, a machining program input from the CRT / MDI unit 70 via the interface 208, and the like.
In addition, the ROM 202 is pre-written with a system program for executing processing such as edit mode processing and spline interpolation processing required for creating and editing a machining program.

The interface 205 is an interface for an external device connectable to the NC device 2,
Various input / output means, external storage device, and external device 72
Is connected. The NC device 1 uses this interface 2
A machining program or the like can be read from an external device via 05, and the edited machining program can be output to an external storage device or an output device. Further, the servo parameter automatic adjusting apparatus of the present invention can input / output an adjusting program and servo information to / from the NC apparatus 1 by connecting to the interface 205.

A PMC (programmable machine, controller) 206 controls an auxiliary device on the machine tool side, for example, an actuator such as a robot hand for tool change, by a sequence program built in the NC device 1. That is, the sequence program converts into a signal required by the auxiliary device according to the M function, S function, and T function instructed by the machining program, and outputs the signal from the I / O unit 207 to the auxiliary device. This output signal activates auxiliary devices such as various actuators. Further, it receives signals from the machine tool main body, the limit switches on the auxiliary device side, various switches of the operation panel arranged on the machine tool main body, performs necessary processing, and then passes the signals to the processor 201.

Data signals such as the current position of each axis of the machine tool, an alarm, a servo parameter, a movement command value to each axis at the time of simulation and servo information are sent to the CRT / MDI unit 70 and displayed on the display. CRT
The / MDI unit 70 is a manual data input device including a processor, a memory, a display, a keyboard, etc., and the interface 208 receives the data from the CRT / MDI unit 70 and transfers it to the processor 201.
Further, the CRT / MDI unit 70 includes the processor 20
The display processing is executed based on the data sent from No. 1 and displayed on the display. Interface 20
9 is connected to the manual pulse generator 71 and receives a pulse from the manual pulse generator 71. Manual pulse generator 71
Is mounted on the operation panel of the machine tool main body and is used for precise positioning of the movable part of the machine tool by controlling each axis by distributing pulses based on manual operation.

The axis control circuits 210 to 214 are the processor 2
In response to the movement command of each axis from 01, the command of each axis is output to the servo amplifiers 220 to 224. Servo amplifier 22
Receiving this command, 0 to 224 drive the servomotors 50 to 54 of the machine tool axis. A servo coder for each axis has a pulse coder for position detection built in, and the position signal from this pulse coder is fed back by pulse train or serial transfer. In some cases, a linear scale can be used as the position detector. Further, in the case of a pulse train, the velocity data can be formed by F / V (frequency / velocity) conversion, and in the case of serial data, the velocity data can be obtained by obtaining the difference in absolute position. In FIG. 4, description of the position signal feedback and the velocity feedback is omitted.

Further, the spindle control circuit 215 receives a spindle rotation command to the machine tool and outputs a spindle speed signal to the spindle amplifier 226. Spindle amplifier 22
6 receives the spindle speed signal and rotates the spindle motor 60 of the machine tool at the commanded rotation speed. A position coder 61 is coupled to the spindle motor 60 by a gear or a belt, and the position coder 61 outputs a feedback pulse in synchronization with the rotation of the spindle, and the feedback pulse is read by the processor 201 via the interface 230.

The position feedback signal, the speed feedback signal, the current from the axis control circuit, the feedback pulse, etc. can be used as servo information in the automatic adjustment of the servo parameters of the present invention. A feedback current is fed back from the motor to the axis control circuit via a servo amplifier.

The above-mentioned NC device has the same structure as a conventionally known numerical control device, and its details are omitted. Next, a flow in the case where the numerical control device inserts a spline interpolation block during execution of the input machining program and performs machining with the inserted interpolation block will be described with reference to the flowchart of FIG.

In the machining program, when a spline interpolation block is already inserted between interpolation blocks whose accelerations are discontinuous, and the numerical controller performs machining according to the machining program, the machining is performed according to the flowchart of FIG. Here, the processed block is indicated by the index i, and the final block is the block N.

First, the index i is determined and set to "1". This index is used for reading the block in the machining program (step S1). Step S2
Then, in step S3, the continuous block i and block i + 1 are read out. Then, the commands of the consecutive block i and block i + 1 that have been read are compared,
It is determined whether or not the direction of the acceleration applied to the tool is changed by the command (step S4).

If it is determined in step S4 that the direction of the acceleration applied to the tool is not changed by the commands of the consecutive blocks, it is not necessary to insert the spline interpolation between the two blocks, so the command of block i is executed ( Step S
5), "1" is added to the index i (step S6).
It is determined whether or not the index i obtained by adding 1 exceeds the final block N (step S7). If the index i exceeds the final block N, it is determined that the final machining process is in progress, and the final Execute block i and end (step S
8).

When the final block N is not exceeded in step S7, it is determined that the block is being processed, the process returns to steps S2 and S3, the next continuous block is read, and the above steps are repeated. Further, in the judgment of the step S4, if the direction of the acceleration applied to the tool changes between the commands of the read continuous block i and block i + 1, the spline function is obtained (step S9), and the block i is executed. Spline interpolation based on the spline function obtained later (step S10) is executed (step S11). When obtaining the spline function, as described above, the conditional expression (13)
To (24), the coefficients Ax to Fx and the coefficient Ay to
By finding Fy, the spline function fx and the function fy are determined. At this time, the values of d1 and d2 required for determining the spline function can be stored in advance in the memory, or can be set by inputting from the input means as needed.

When the CPU in the numerical control device has a function of spline interpolation, the spline interpolation is executed by obtaining an interpolation value according to the spline function obtained by using the function. If the CPU does not have the function of spline interpolation, the value of the spline function is calculated at each predetermined minute interval Δt to obtain the position coordinates, and a linear block of minute straight lines connecting the position coordinates is generated. You can also

After execution of the spline interpolation, the process returns to step S6 and continues the processing. Next, the procedure for inserting the spline interpolation block into the machining program in the automatic programming of the numerical controller will be described with reference to the flowchart of FIG. Here, the processed block is indicated by the index i, and the final block is the block N.

First, the index i is determined and set to "1". This index is used for reading the block in the machining program (step T1). Step T2
Then, in step T3, consecutive block i and block i + 1 are read out. Then, the commands of the consecutive block i and block i + 1 that have been read are compared,
It is determined whether or not the direction of the acceleration applied to the tool is changed by the command (step T4).

In step T4, if the direction of the acceleration applied to the tool is not changed by the instruction of the consecutive blocks, it is not necessary to insert the spline interpolation between the two blocks, so "1" is added to the index i. (Step T5). It is determined whether or not the index i obtained by adding 1 exceeds the final block N (step T6). If the index i exceeds the final block N, it is determined that the editing of the machining program is completed, and the processing is executed. To finish.

In step T6, if the final block N is not exceeded, there are still blocks to be processed, so the process returns to steps T2 and T3.
Read the next consecutive block and repeat the process. When the direction of the acceleration applied to the tool changes between the commands of the read continuous block i and block i + 1 in the determination of the step T4, a spline function is obtained to generate a spline interpolation block (step T7). , And returns to step T5.

The method of obtaining the spline function is similar to the above, using the conditional expressions (13) to (24) to obtain the coefficients Ax to F.
The spline function fx and the function fy are determined by obtaining x and the coefficients Ay to Fy. At this time, the values of d1 and d2 required for determining the spline function can be stored in the memory in advance as described above, or can be set by inputting them from the input means as needed.

Next, FIGS. 7 to 12 show the simulation results of the tool path and the acceleration for each axis when the spline interpolation of the present invention is applied. 7 and 8
Is the tool path and acceleration when d1 = 0.15 mm and d2 = 1 mm, and in FIGS. 9 and 10, d1 =
FIG. 11 and FIG. 12 show the tool path and the acceleration when 0.3 mm and d2 = 2 mm, and d1 = 0.45 m in FIGS.
It is a tool path and acceleration when m and d2 = 3 mm. 7, 9 and 11, the tool path and the command path are shown by comparison, and the error amount from the command path is multiplied by 10. In addition, FIGS. 8, 10, and 12 represent the acceleration in the Y-axis direction, and represent the acceleration when the linear interpolation and the circular interpolation according to the command are performed, and the acceleration when the spline interpolation is performed.

According to the above simulation results, the insertion of the spline interpolation according to the present invention causes the acceleration path to continuously and smoothly change, although the path deviates slightly from the command path. The deviations from the command path are d1 and d
2, and as shown in the simulation result, when the size of d1 and d2 is increased, the shift amount increases, but the acceleration change becomes smoother. Therefore, by selecting the magnitudes of d1 and d2 to appropriate values, it is possible to smooth the acceleration change and reduce the machining error while keeping the deviation amount from the command path within the allowable range. For example, the deviation amount from the command path and the acceleration change with respect to the magnitudes of d1 and d2 are obtained in advance, and the magnitudes of d1 and d2 are selected according to the allowable amount of error set at the machining location. It can be carried out.

[0042]

As described above, according to the present invention,
In the path control method of the numerical control device, when the acceleration direction of continuous machining commands is discontinuous, inserting a spline interpolation between both machining commands reduces shock to the machine and reduces machining error. In addition, it is possible to perform path control without extending the processing time.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a relationship between interpolation blocks in a route control method of the present invention.

FIG. 2 is a diagram for explaining a method of obtaining a spline curve that defines a path for performing spline interpolation.

FIG. 3 is a diagram illustrating a block of spline interpolation.

FIG. 4 is a block diagram illustrating a configuration of a control system to which the route control system of the present invention is applied.

FIG. 5 is a flowchart for explaining a flow when processing is performed using an interpolation block.

FIG. 6 is a flowchart for explaining a procedure for inserting a block for spline interpolation into a machining program.

FIG. 7 is a simulation result of a tool path when the spline interpolation of the present invention is applied.

FIG. 8 is a simulation result of Y-axis acceleration when the spline interpolation of the present invention is applied.

FIG. 9 is a simulation result of a tool path when the spline interpolation of the present invention is applied.

FIG. 10 shows Y when the spline interpolation of the present invention is applied.
It is a simulation result of the acceleration of the axis.

FIG. 11 is a simulation result of a tool path when the spline interpolation of the present invention is applied.

FIG. 12 shows Y when the spline interpolation of the present invention is applied.
It is a simulation result of the acceleration of the axis.

FIG. 13 is a diagram for explaining a path error of a processing path.

[Explanation of symbols]

 1 NC device (numerical control device) 70 CRT / MDI unit 200 Bus 201 CPU 202 ROM 203 RAM 204 CMOS

Claims (5)

[Claims] 1. A route control method for a numerical control device, wherein in a route control method for a numerical control device, spline interpolation is inserted between the machining commands when the acceleration directions of successive machining commands are discontinuous. method. 2. The numerical control according to claim 1, wherein the spline interpolation passes a machining command path that is adjacent at both end points of the spline interpolation, and the velocity and acceleration at the both end points are continuous. Device routing method. 3. A path control system in a numerical control device, wherein the numerical control device is configured such that when the acceleration directions of continuous machining blocks of a machining program are discontinuous,
3. The route control method for a numerical controller according to claim 1, wherein a block for performing spline interpolation is automatically inserted between both machining blocks to perform machining. 4. In a route control method in a numerical control device, a machining program for controlling the numerical control device is
The machining program is generated by automatically inserting a block for performing spline interpolation between both machining blocks when the acceleration direction due to the machining blocks continuous in the machining program is discontinuous. The route control system of the numerical control device described in 2. 5. The path control method of the numerical controller according to claim 1, wherein the spline interpolation is formed by a combination of minute linear blocks.