Numerical controller

Abstract

A numerical controller of the present invention includes a parameter setting unit which accepts settings of punch press parameters, an NC parameter calculating unit which calculates an axis control parameter in punch pressing based on the punch press parameters, a parameter storage unit which stores the punch press parameters and the axis control parameter, a command analyzing unit which analyzes a command block in the program to generate movement command data, an interpolating unit which generates interpolation data based on the movement command data, and an accelerating and decelerating unit which calculates a linear acceleration and deceleration time constant and a bell-shaped acceleration and deceleration time constant for use in axis control based on the punch press parameters, the axis control parameter, and a feed rate specified by the command block and performs post-interpolation acceleration or deceleration processing based on each of the calculated acceleration and deceleration time constants.

Claims

1. A numerical controller for controlling a machine which performs punch pressing based on a program, the numerical controller comprising a processor configured to: accept settings of punch press parameters regarding punch pressing; calculate an axis control parameter in punch pressing based on the accepted punch press parameters; store the punch press parameters and the axis control parameter; read and analyze a command block from the program to generate movement command data and output the generated movement command data; perform interpolation processing based on the movement command data to generate interpolation data and output the generated interpolation data; calculate a linear acceleration and deceleration time constant and a bell-shaped acceleration and deceleration time constant for use in axis control based on the stored punch press parameters and the axis control parameter and a feed rate specified by the command block, perform post-interpolation acceleration or deceleration processing on the interpolation data based on the calculated linear acceleration and deceleration time constant and the bell-shaped acceleration and deceleration time constant, and output the processed interpolation data to which the post-interpolation acceleration or deceleration processing is applied; and control an axis of the machine based on the outputted processed interpolation data, the processed interpolation data to which the post-interpolation acceleration or deceleration processing is applied.

2. The numerical controller according to claim 1, wherein the punch press parameters include at least a time taken for one punch, a reference pitch and a first target hit rate associated therewith, a minimum pitch and a second target hit rate associated therewith, and a maximum acceleration torque and a linear acceleration and deceleration time constant dependent on a structure of the machine.

3. The numerical controller according to claim 1, wherein the axis control parameter includes at least a torque waveform for adjusting the linear acceleration and deceleration time constant.

4. The numerical controller according to claim 1, wherein the processor is further configured to calculate the bell-shaped acceleration and deceleration time constant which is linear with respect to the linear acceleration and deceleration time constant.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The above and other objects and features of the present invention will become apparent from the following description of exemplary embodiments with reference to the accompanying drawings in which:

(2) FIG. 1 is a diagram depicting a relation between parameters for used in punch press controlled by a numerical controller of the present invention;

(3) FIG. 2 is a diagram for depicting feed rate-torque characteristics of a servo motor;

(4) FIG. 3 is a diagram for depicting a relation between acceleration torque and feed rate;

(5) FIG. 4 is a diagram for depicting calculation of a bell-shaped acceleration and deceleration time constant when a movement amount is small and a table axis arrived speed is short of a command speed;

(6) FIG. 5 is a diagram for depicting calculation of a bell-shaped acceleration and deceleration time constant when the movement amount is large and the table axis arrived speed is a command speed;

(7) FIG. 6 is a functional block diagram of a numerical controller according to an embodiment of the present invention;

(8) FIG. 7 is a flowchart of processing regarding parameter settings to be performed on the numerical controller of FIG. 6;

(9) FIG. 8 is a flowchart of control processing at the time of punch pressing to be performed on the numerical controller of FIG. 6;

(10) FIG. 9 is a diagram for depicting settings of speed, acceleration and deceleration time constant, and position gain achieved by positioning with optimum acceleration in punch pressing in a prior art technique;

(11) FIG. 10 is a diagram for depicting the technology disclosed in Japanese Patent Application Laid-Open No. 4-335410;

(12) FIG. 11 is a diagram for depicting a problem raised upon applied the technology of Japanese Patent Application Laid-Open No. 4-335410 to punch pressing;

(13) FIG. 12 is a diagram for depicting a problem when positioning with optimum acceleration in punch pressing in the prior art technique is used; and

(14) FIG. 13 is a diagram depicting a linear acceleration and deceleration time constant and bell-shaped acceleration and deceleration time constants automatically calculated by the numerical controller of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

(15) In the following, an embodiment of the present invention is described together with the drawings. First, each process in the numerical controller of the present invention is described.

(16) <Calculation of Table Axis Operation Time t From Target Hit Rate and Press Time>

(17) In the numerical controller of the present invention, from target hit rates and their associated reference and minimum pitches set by a machine manufacturer, a table axis operation time t (msec) capable of achieving each target hit rate is found. The table axis operation time t (msec) per press block in a processing program capable of achieving the target hit rates can be calculated by Equation 1 below, when a target reference hit rate is h (times/msec), an execution time per press block capable of achieving the target hit rate is t.sub.b (msec), and a time taken for one punch is t.sub.p (msec), as depicted in FIG. 1.

(18) $\begin{array}{cc}{t}_b=\frac{1}{h},t=t_b-t_p,\mathrm{therefore},t=\frac{1}{h}-t_p& \left[\mathrm{Equation}1\right]\end{array}$
<Relation Between Acceleration Torque and Acceleration>

(19) A relation between acceleration torque and acceleration of a servo motor is generally represented by Equation 2 below, and a relation between rotation speed and axis delivering speed of the motor is generally represented by Equation 3 below.

(20) $\begin{array}{cc}\begin{array}{c}\begin{array}{c}\begin{array}{c}\begin{array}{c}\begin{array}{c}\begin{array}{c}{T}_a=V_m\frac{2}{60}\frac{1}{t_1}\left(J_M+\frac{J_L}{}\right)\\ T_a\text{:}\mathrm{acceleration}\mathrm{torque}\left(\mathrm{Nm}\right)\end{array}\\ V_m\text{:}\mathrm{motor}\mathrm{rotation}\mathrm{speed}\mathrm{at}\mathrm{rapid}\mathrm{feed}\left({\min }^{-1}\right)\end{array}\\ t_1\text{:}\mathrm{acceleration}\mathrm{and}\mathrm{deceleration}\mathrm{time}\mathrm{constant}\left(\sec \right)\end{array}\\ J_M\text{:}{\mathrm{rotor}}^{}s\mathrm{moment}\mathrm{of}\mathrm{inertia}\left({\mathrm{kgm}}^2\right)\end{array}\\ J_L\text{:}\mathrm{moment}\mathrm{of}\mathrm{inertia}\mathrm{of}\mathrm{load}\left({\mathrm{kgm}}^2\right)\end{array}\\ \text{:}\mathrm{mechanical}\mathrm{efficiency}\end{array}& \left[\mathrm{Equation}2\right]\\ \begin{array}{c}\mathrm{Vm}=V\frac{1}{P\frac{Z_1}{Z_2}}\\ \begin{array}{c}V\text{:}\mathrm{axis}\mathrm{feed}\mathrm{rate}\left(\mathrm{mm}/\min \right)\\ \begin{array}{c}P\text{:}\mathrm{ball}\mathrm{screw}\mathrm{pitch}\\ \frac{Z_1}{Z_2}\text{:}\mathrm{speed}\mathrm{reduction}\mathrm{ratio}\end{array}\end{array}\end{array}& \left[\mathrm{Equation}3\right]\end{array}$

(21) Based on these Equations 2 and 3, the relation between acceleration torque and acceleration of the servo motor can be represented by Equation 4 below. Since the terms other than T.sub.a and t.sub.1 in this Equation 4 are constant terms defined by the specifications of the machine, it can be found that table axis acceleration V/t.sub.1 and the acceleration torque T.sub.a have a proportional relation.

(22) $\begin{array}{cc}\mathrm{Ta}=V\frac{1}{P\frac{Z_1}{Z_2}}\frac{2}{60}\frac{1}{t_1}\left(J_M+\frac{J_L}{}\right)& \left[\mathrm{Equation}4\right]\end{array}$
<Registration of Feed Rate-torque Characteristics of Servo Motor>

(23) The servo motor has a predetermined feed rate-torque characteristics representing the relation between feed rate and torque (refer to FIG. 2). Features of these feed rate-torque characteristics (maximum acceleration torque T.sub.max, changing point F.sub.pc, and gradient A from the changing point) are registered in advance on a database so as to be linked to an allocated motor number of each servo motor. With the features of the feed rate-torque characteristics registered on the database in this manner, the feed rate-torque characteristics of each servo motor can be obtained only by designating a motor number. Note that for the use of a servo motor not registered on the database, the features of the feed rate-torque characteristics (maximum acceleration torque T.sub.max, changing point F.sub.pc, and gradient A from the changing point) may also be directly inputted. By allowing direct inputs, it is possible to flexibly support the use of a newly introduced servo motor, a servo motor of another manufacturer, and the like.

(24) <Calculation of Adjustment Torque Waveform for Linear Acceleration and Deceleration Time Constant>

(25) FIG. 3 depicts feed rate-torque characteristics of the servo motor. From FIG. 3, an upper-limit torque waveform of the feed rate-torque characteristics of the servo motor used in the punch press machine can be represented by Equation 5 below.

(26) $\begin{array}{cc}\{\begin{array}{ccc}{l}_p\left(f\right)=T_{\max }& f<F_{\mathrm{pc}}& \\ & & \left(A\text{:}\mathrm{gradient}\right)\\ l_p\left(f\right)=\mathrm{Af}+\left(T_{\max }-{\mathrm{AF}}_{\mathrm{pc}}\right)& f{F}_{\mathrm{pc}}& \end{array}& \left[\mathrm{Equation}5\right]\end{array}$

(27) And, by using Equation 5 above and the maximum offset load torque (maximum acceleration torque) T.sub.a (Nm) determined from the structure of the machine, an adjustment torque waveform l(f) for linearly controlling the linear acceleration and deceleration time constant and a changing point F.sub.c (mm/min) of the waveform can be represented by Equations 6 and 7 below. Note that the adjustment torque waveform l(f) is found from T.sub.a, the gradient A from the changing point F.sub.pc (mm/min) of l.sub.p(f), and a ratio X (%) with respect to the upper-limit torque waveform (this parameter is to prevent saturation of torque at the changing point F.sub.c onward).

(28) $\begin{array}{cc}\{\begin{array}{ccc}l\left(f\right)=T_a& \begin{array}{c}\mathrm{when}\mathrm{the}\mathrm{feed}\mathrm{rate}f\mathrm{is}\\ \mathrm{equal}\mathrm{to}\mathrm{or}\mathrm{smaller}\mathrm{than}{F}_c\end{array}& \\ l\left(f\right)=\mathrm{Af}+\frac{X}{100}\left(T_{\max }-{\mathrm{AF}}_{\mathrm{pc}}\right)& \begin{array}{c}\mathrm{when}\mathrm{the}\mathrm{feed}\mathrm{rate}f\\ \mathrm{is}\mathrm{larger}\mathrm{than}{F}_c\end{array}& \end{array}& \left[\mathrm{Equation}6\right]\\ F_c=\frac{T_a-\frac{X}{100}\left(T_{\max }-{\mathrm{AF}}_{\mathrm{pc}}\right)}{A}& \left[\mathrm{Equation}7\right]\end{array}$
<Calculation of Linear Acceleration and Deceleration Time Constant>

(29) The maximum toque T.sub.a at acceleration and deceleration and a maximum acceleration (linear acceleration and deceleration time constant t.sub.1m) are depend on the structure of the machine. However, since the upper-limit torque is decreased from the changing point F.sub.c of the adjustment torque waveform l(f), the linear acceleration and deceleration time constant has to be increased so that torque is not saturated. The linear acceleration and deceleration time constant t.sub.1 can be found by Equation 8 below, from the maximum torque T.sub.a, the adjustment torque waveform l(f), and the ratio X with respect to the upper-limit torque.

(30) $\begin{array}{cc}\{\begin{array}{ccc}{t}_1=t_{1m}& \begin{array}{c}\mathrm{when}\mathrm{the}\mathrm{feed}\mathrm{rate}f\mathrm{is}\\ \mathrm{equal}\mathrm{to}\mathrm{or}\mathrm{smaller}\mathrm{than}{F}_c\end{array}& \\ t_1=\frac{T_a}{l\left(f\right)}{t}_{1m}& \begin{array}{c}\mathrm{when}\mathrm{the}\mathrm{feed}\mathrm{rate}f\\ \mathrm{is}\mathrm{larger}\mathrm{than}{F}_c\end{array}& \end{array}& \left[\mathrm{Equation}8\right]\end{array}$
<Calculation of Bell-shaped Acceleration and Deceleration Time Constants>

(31) Bell-shaped acceleration and deceleration time constants t.sub.2p and t.sub.2m are calculated from the above-calculated linear acceleration and deceleration time constant t.sub.1, the maximum allowable operation time t, and arrived speed. As depicted in FIG. 4, when a movement amount d is small and the table axis arrived speed is short of a command speed F, a bell-shaped acceleration and deceleration time constant t.sub.2 can be found as follows. That is, from FIG. 4, d=t.sub.0/2Ft.sub.0/2t.sub.1 holds. Therefore, when this equation is solved for a positioning time to only with the linear acceleration and deceleration time constant, t.sub.0=(4dt.sub.1/F) is obtained. Also, from t=t.sub.0+t.sub.2, t=(4dt.sub.1/F)+t.sub.2 is obtained. When this equation is solved for t.sub.2, t.sub.2=t(4dt.sub.1/F) is obtained, and therefore a bell-shaped acceleration and deceleration time constant with a reference pitch and a minimum pitch can be represented by Equation 9 below. Therefore, t.sub.2p and t.sub.2m can be calculated by Equation 10 below.

(32) $\begin{array}{cc}{t}_2=t-\sqrt{\frac{4{\mathrm{dt}}_1}{F}}& \left[\mathrm{Equation}9\right]\\ \begin{array}{c}{t}_{2p}=t-\sqrt{\frac{4d_p{t}_1}{F}}\\ t_{2m}=t-\sqrt{\frac{4d_m{t}_1}{F}}\end{array}& \left[\mathrm{Equation}10\right]\end{array}$

(33) Also, the bell-shaped acceleration and deceleration time constants t.sub.2p and t.sub.2m are calculated based on the above-described linear acceleration and deceleration time constant t.sub.1, maximum movable time t, and arrived speed. As depicted in FIG. 5, when the movement amount d is sufficiently large and the table axis arrived speed is the command speed F, the bell-shaped acceleration and deceleration time constant t.sub.2 can be represented by Equation 11 below. Therefore, t.sub.2p and t.sub.2m can be calculated by Equation 12 below.

(34) $\begin{array}{cc}{t}_2=t-\frac{d}{F}-t_1& \left[\mathrm{Equation}11\right]\\ \begin{array}{c}{t}_{2p}=t-\frac{d_p}{F}-t_1\\ t_{2m}=t-\frac{d_m}{F}-t_1\end{array}& \left[\mathrm{Equation}12\right]\end{array}$

(35) Then, with reference to the bell-shaped acceleration and deceleration time constants t.sub.2p and t.sub.2m with a table axis movement amount being the reference pitch d.sub.p and the minimum pitch d.sub.m, the bell-shaped acceleration and deceleration time constant is switched to the linear one in accordance with the table axis movement amount. An acceleration and deceleration time constant t.sub.2d (msec) with the movement amount d (mm) is calculated by Equation 13 below.

(36) $\begin{array}{cc}\{\begin{array}{cc}{t}_{2d}=t_{2m}& \left(\mathrm{when}d<d_m\right)\\ t_{2d}=\frac{t_{2p}-t_{2m}}{d_p-d_m}d& \left(\mathrm{when}{d}_{m}d{d}_p\right)\\ t_{2d}=t_{2p}& \left(\mathrm{when}{d}_p<d\right)\end{array}& \left[\mathrm{Equation}13\right]\end{array}$

(37) In the numerical controller of the present invention, the linear acceleration and deceleration time constant t.sub.1 and the bell-shaped acceleration and deceleration time constant t.sub.2d are calculated through the above operation process, and by using these values, table axis movement control is performed.

(38) FIG. 6 is a functional block diagram of the numerical controller according to an embodiment of the present invention. A numerical controller 1 of the present embodiment includes a parameter setting unit 10, an NC parameter calculating unit 11, a parameter storage unit 12, a command analyzing unit 13, an interpolating unit 14, an accelerating and decelerating unit 15, and a servo control unit 16.

(39) The parameter setting unit 10 accepts settings of various parameters for use in processing by a punch press inputted based on operator's operation from a display/MDI unit (not depicted) included in the numerical controller 1. Examples of various parameters of the punch press include the time t.sub.p taken for one punch, the reference pitch d.sub.p and the target hit rate h.sub.p associated therewith, the minimum pitch d.sub.m and the target hit rate h.sub.m associated therewith, and the maximum acceleration torque T.sub.a and the linear acceleration and deceleration time constant t.sub.1m dependent on the structure of the machine.

(40) Also, the parameter setting unit 10 accepts, as required, settings of the feed rate-torque characteristics of the servo motor based on the operator's operation.

(41) Based on the settings of the various parameters for use in processing by the punch press set by the parameter setting unit 10, the NC parameter calculating unit 11 calculates the adjustment torque waveform l(f) for the linear acceleration and deceleration time constant by following the above-described calculation procedure, and stores, in the parameter storage unit 12, the calculated adjustment torque waveform l(f) for the linear acceleration and deceleration time constant together with the various parameters set by the parameter setting unit 10.

(42) The command analyzing unit 13 analyzes a block of a process command included in a program read from memory not depicted to generate data regarding a movement command, and outputs the generated data regarding the movement command to the interpolating unit 14.

(43) Based on the data regarding the movement command input from the command analyzing unit 13, the interpolating unit 14 generates interpolation data obtained by interpolation calculation of points on a command route specified by the data regarding the movement command at an interpolation cycle, and outputs the generated interpolation data and an arrived speed included in the data regarding the movement command to the accelerating and decelerating unit 15.

(44) Based on the arrived speed input from the interpolating unit 14, the various parameters stored in the parameter storage unit 12, and the adjustment torque waveform l(f) for the linear acceleration and deceleration time constant, the accelerating and decelerating unit 15 calculates the linear acceleration and deceleration time constant t.sub.1 and the bell-shaped acceleration and deceleration time constants t.sub.2p and t.sub.2m, and further calculates the bell-shaped acceleration and deceleration time constant t.sub.2d. Then, based on the calculated linear acceleration and deceleration time constant t.sub.1 and the bell-shaped acceleration and deceleration time constant t.sub.2d, the accelerating and decelerating unit 15 performs post-interpolation acceleration or deceleration processing on the interpolation data input from the interpolating unit 14 to calculate a speed for each drive axis at every interpolation cycle, and outputs, to the servo control unit 16, interpolation data after acceleration or deceleration processing to which the calculation result is applied.

(45) Then, based on the output from the accelerating and decelerating unit 15, the servo control unit 16 controls the servo motor 2 which controls each axis to be controlled.

(46) FIG. 7 is a flowchart of processing regarding parameter settings to be performed on the numerical controller 1 of the present invention.

(47) [Step SA01] The parameter setting unit 10 accepts various parameters, by operator's operation, for use in processing by a punch press such as the time t.sub.p taken for one punch, the reference pitch d.sub.p and the target hit rate h.sub.p associated therewith, and the minimum pitch d.sub.m and the target hit rate h.sub.m associated therewith, and settings such as the maximum acceleration torque T.sub.a and the linear acceleration and deceleration time constant t.sub.1m dependent on the structure of the machine, and then outputs these parameters and settings to the NC parameter calculating unit 11.

(48) [Step SA02] The parameter setting unit 10 accepts, as required, settings of the feed rate-torque characteristics of the servo motor by operator's operation, and outputs the settings to the NC parameter calculating unit 11.

(49) [Step SA03] The NC parameter calculating unit 11 calculates the adjustment torque waveform l(f) for the linear acceleration and deceleration time constant based on the various setting values set by the operator at steps SA01 and SA02, and stores the calculated adjustment torque waveform l(f) for the linear acceleration and deceleration time constant in the parameter storage unit 12 together with the various setting values set at steps SA01 and SA02.

(50) FIG. 8 is a flowchart of a control process effected at the time of punch pressing to be performed on the numerical controller 1 of the present invention.

(51) [Step SB01] The command analyzing unit 13 reads a block from a program stored in memory not depicted.

(52) [Step SB02] The command analyzing unit 13 analyzes the block read at step SB01 to generate data regarding a movement command, and outputs the generated data regarding the movement command to the interpolating unit 14.

(53) [Step SB03] The interpolating unit 14 performs interpolation processing on the data regarding the movement command generated at step SB02 to generate interpolation data, and outputs the generated interpolation data and a feed rate (arrived speed) specified by the data regarding the movement command to the accelerating and decelerating unit 15.

(54) [Step SB04] The accelerating and decelerating unit 15 calculates the linear acceleration and deceleration time constant t.sub.1 based on the arrived speed input from the interpolating unit 14, the various parameters stored in the parameter storage unit 12, and the adjustment torque waveform l(f) for the linear acceleration and deceleration time constant.

(55) [Step SB05] The accelerating and decelerating unit 15 calculates the bell-shaped acceleration and deceleration time constants t.sub.2p and t.sub.2m based on the linear acceleration and deceleration time constant t.sub.1 calculated at step SB04 and the various parameters stored in the parameter storage unit 12.

(56) [Step SB06] The accelerating and decelerating unit 15 determines whether the bell-shaped acceleration and deceleration time constants t.sub.2p and t.sub.2m calculated at step SB05 are both equal to or larger than 0. When both are equal to or larger than 0, the procedure proceeds to step SB08. When either one of them is smaller than 0, the procedure proceeds to step SB07.

(57) [Step SB07] The accelerating and decelerating unit 15 outputs an alert that a target hit rate cannot be achieved, and interrupts the processing.

(58) [Step SB08] The accelerating and decelerating unit 15 calculates the bell-shaped acceleration and deceleration time constants t.sub.2d based on the bell-shaped acceleration and deceleration time constants t.sub.2p and t.sub.2m calculated at step SB05 and the various parameters stored in the parameter storage unit 12.

(59) [Step SB09] The accelerating and decelerating unit 15 performs post-interpolation acceleration or deceleration processing on the interpolation data input from the interpolating unit 14 based on the linear acceleration and deceleration time constant t.sub.1 calculated at step SB04 and the bell-shaped acceleration and deceleration time constant t.sub.2d calculated at step SB08, and outputs the processing result to the servo control unit 16.

(60) [Step SB10] The servo control unit 16 controls the servo motor 2 which controls each axis to be controlled, based on the output from the accelerating and decelerating unit 15.

(61) [Step SB11] Whether the program has ended is determined. If the program has ended, the processing ends. If the program has not ended, the procedure proceeds to step SB01.

(62) While the embodiment of the present invention has been described above, the present invention is not restricted to the examples of the above-described embodiment, and can be implemented by other embodiments by adding modifications as appropriate.