Numerical control device and numerical control method

To dynamically change the acceleration without trial executions of a machining program, a numerical control device, which controls a motor on the basis of a machining program that specifies a path for a drive target of the motor, includes a changing unit that changes the acceleration of the motor under the control of the motor on the basis of the inertia ratio, the acceleration-deceleration factor that can be externally input, or the current value of the motor.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a National Stage of International Application No. PCT/JP2013/083522filed Dec. 13, 2013, the content of which are incorporated herein by reference in its entirety.

FIELD

The present invention relates to a numerical control device and a numerical control method.

BACKGROUND

Conventionally, in a case of machining a workpiece having a large inertia (weight) by numerically controlling a machine tool, a time constant according to the maximum inertia ratio is set in a numerical control device, and the time constant remains unchanged until the machining is finished. Therefore, when the inertia is reduced due to cutting or other machining, this makes an allowance for further accelerating or decelerating a motor. However, because the time constant remains fixed, the cycle time cannot be reduced. Accordingly, a function of selecting an optimal time constant according to the weight of a workpiece has been proposed (see, for example, Patent Literature 1).

CITATION LIST

Patent Literatures

SUMMARY

Technical Problem

According to the technique in Patent Literature 1 described above, however, a numerical control device initially operates a machine tool based on a machining program. At this time, the numerical control device estimates the weight of a workpiece, and derives an optimal time constant on the basis of the estimation result. The numerical control device records the derived time constant along with the machining program. When the numerical control device operates the machine tool again on the basis of the same machining program, this device uses the stored time constant to operate the machine tool. Therefore, there is a problem that each time the machining program or the weight of a workpiece is changed, estimation of the workpiece weight and derivation of the time constant are needed.

The present invention has been achieved to solve the above problems. An objective of the present invention is to provide cycle-time reduction effect, and vibration-suppression and overload prevention effects by means of estimating the inertia of a workpiece even while a program is being executed, and automatically changing the acceleration or the time constant to an optimal value on the basis of the estimation result while a machine tool is being operated. Further, another objective of the present invention is to provide a cycle-time reduction effect and vibration-suppression and overload prevention effects by automatically changing the acceleration or the time constant according to a state quantity other than the inertia of a workpiece, such as a load or an acceleration-deceleration factor.

The present invention has been achieved to solve the above problems and an objective of the present invention is to provide a numerical control device and a numerical control method that can dynamically change the acceleration without trial executions of a machining program.

Solution to Problem

In order to solve the problems and achieve the objectives, the present invention relates to a numerical control device that controls a motor according to a program that specifies a path for a drive target of the motor. The numerical control device includes: a changing unit that monitors a state quantity related to the motor while the motor is being controlled, and that changes an acceleration of the motor on the basis of the state quantity while the motor is being controlled.

Advantageous Effects of Invention

The numerical control device according to the present invention changes the acceleration of a motor on the basis of a state quantity of the motor even when the motor is being controlled. Therefore, it is possible to dynamically change the acceleration without trial executions of a machining program.

DESCRIPTION OF EMBODIMENTS

Exemplary embodiments of a numerical control device and a numerical control method according to the present invention will be explained below in detail with reference to the accompanying drawings. The present invention is not limited to the embodiments.

First Embodiment

FIG. 1is a diagram illustrating a configuration of a numerical control device according to a first embodiment. A numerical control device1is connected to an amplifier2. The amplifier2supplies a drive current to a motor3. A load4is connected as a drive target to the motor3. The motor3and the load4are called a “mechanical system5”. The mechanical system5includes one or more drive shafts (hereinafter, simply “shaft(s)”) that drive the same load4. The motor3and the amplifier2are each provided for each shaft.

The numerical control device1includes a program analysis unit10, a first interpolation unit11, a pre-interpolation acceleration-deceleration processing unit12, a second interpolation unit13, a parameter changing unit14, and a filtering unit15.

The program analysis unit10analyzes an externally-input machining program6and outputs the analysis result as analysis data. The machining program6is configured with the inclusion of a plurality of command blocks. The machining program6specifies at least a path for the drive target. The path specified by the machining program6is called a “command path”. The analysis data is necessary information for movement of each command block and it includes the movement amount of each shaft, command feed velocity, and command information (for example, a G code).

The first interpolation unit11generates and outputs interpolation data on the basis of the analysis data. In addition to the data that shows a movement amount per control cycle, the interpolation data also includes information that is to be used for generating a combined-velocity calculated value (described later), e.g., a terminal-point target velocity.

The parameter changing unit14monitors a state quantity related to the motor3while the motor3is being controlled and changes a parameter for driving the motor3on the basis of the state quantity and the analysis data while the motor3is under control.

In the first embodiment, the parameter to be changed by the parameter changing unit14is specifically an acceleration, and the state quantity is specifically an inertia ratio. The inertia ratio is a ratio of inertia of the mechanical system5relative to the inertia of the motor3. The inertia of the motor3is already known. In this example, the inertia ratio is estimated by the amplifier2. The parameter changing unit14obtains the inertia ratio from the amplifier2. It is possible to employ any method as an inertia-ratio estimating method as long as the inertia ratio is estimated while a machining program is being executed. It is possible, for example, to employ a method using recursive least squares as described in Patent Literature 2 or a method calculating the inertia ratio from the ratio between acceleration and torque while under acceleration or deceleration as an inertia-ratio estimating method. In this example, the acceleration can be a negative value.

The pre-interpolation acceleration-deceleration processing unit12performs an acceleration-deceleration process on a tangential velocity along a command path (i.e., a combined velocity) on the basis of the interpolation data and an acceleration (i.e., an acceleration set value) input from the parameter changing unit14. Specifically, when the acceleration set value is changed by the parameter changing unit14, the pre-interpolation acceleration-deceleration processing unit12calculates a combined velocity (i.e., the combined-velocity calculated value) so as to accelerate or decelerate the motor3at the changed acceleration set value. The pre-interpolation acceleration-deceleration processing unit12outputs the combined-velocity calculated value.

The second interpolation unit13interpolates the amount of movement of each shaft on the basis of the interpolation data and the combined-velocity calculated value, thereby generating a position command per control cycle. Specifically, for example, the second interpolation unit13generates each of the position commands such that the combined velocity on the basis of the position commands become identical to the combined-velocity calculated value. In other words, the second interpolation unit13generates each of the position commands to drive the motor3at a velocity obtained after the acceleration-deceleration process.

The filtering unit15performs a filtering process on the respective position commands so as to smooth the velocity waveform on the basis of each of the position commands. The filtering unit15outputs a position command after the filtering process to the amplifier2. The filtering process can be performed by any method as long as it can at least make the velocity waveform smooth. It is possible, for example, to employ a moving average filter as the filtering process.

The amplifier2drives the motor3in such a manner that the motor position or the position of the load4corresponds to an input position command.

FIG. 3is a flowchart explaining the changing process in the first embodiment.

First, the parameter changing unit14determines whether the interpolation mode is set to “pre-interpolation mode” (Step S11). The setting of the interpolation mode is described in the machining program6. By referring to the analysis data, the parameter changing unit14can determine whether the interpolation mode is set to “pre-interpolation mode”. The “pre-interpolation mode” is a mode for executing an acceleration-deceleration control before the interpolation. When the interpolation mode is not set to “pre-interpolation mode” (NO at Step S11), the parameter changing unit14finishes the changing process.

When the interpolation mode is set to “pre-interpolation mode” (YES at Step S11), the parameter changing unit14calculates an acceleration candidate value (Step S12). An acceleration candidate value A is calculated, for example, using the following equation (1).
A=A0*(J0/J)  (1)

In this equation, J is an inertia-ratio of the current value (i.e., the inertia-ratio obtained by the processing at Step S1). And, A0represents an acceleration reference value, and J0represents an inertia ratio when the acceleration reference value is set (i.e., an inertia-ratio reference value). The acceleration reference value A0and the inertia-ratio reference value J0are stored in the parameter changing unit14in advance. It is also possible to have a configuration that provides in the parameter changing unit14in advance a table in which the corresponding inertia ratios and accelerations are collated; and the parameter changing unit14refers to the table using the obtained inertia ratio as a search key so as to calculate an acceleration candidate value.

Subsequently, the parameter changing unit14calculates a residual distance Lm from the present position to a target position by using analysis data obtained from the program analysis unit10and by using a combined-velocity calculated value obtained from the pre-interpolation acceleration-deceleration processing unit12(Step S13). For example, the target position is specified in the machining program6and is therefore described in the analysis data. The parameter changing unit14calculates the deceleration-required distance Ld by using the acceleration candidate value (Step S14). The deceleration-required distance Ld is the distance required to reduce the velocity at the present position to the velocity at the target position.

Next, the parameter changing unit14determines whether the residual distance Lm is longer than the deceleration-required distance Ld (Step S15). That is, at Step S15, the parameter changing unit14determines whether it is possible for a drive target to be moved to the target position at the acceleration candidate value. When the residual distance Lm is shorter than the deceleration-required distance Ld (NO at Step S15), the parameter changing unit14finishes the changing process. When the residual distance Lm is longer than the deceleration-required distance Ld (YES at Step S15), the parameter changing unit14outputs the acceleration candidate value as an acceleration set value to the pre-interpolation acceleration-deceleration processing unit12(Step S16), and then finishes the changing process.

FIGS. 4 and 5are diagrams illustrating examples of combined velocity waveforms. Solid lines101and103indicate a transition of the combined velocity according to the first embodiment. Dot-and-dash lines102and104indicate a transition of the combined velocity when the first embodiment is not applied.

As indicated by the solid line101, acceleration starts at an acceleration set value A1. At a time T1while under acceleration, a change in the inertia ratio is detected. In this example, the inertia ratio is decreased. As a result, the parameter changing unit14changes the acceleration set value A1to A2, which is greater than A1. The pre-interpolation acceleration-deceleration processing unit12calculates a combined-velocity calculated value using the acceleration set value A2at the time T1and later. Therefore, while under acceleration, the combined-velocity calculated value forms a velocity waveform with more abrupt acceleration. Due to this velocity waveform, for example while the machining program6is being executed, in a case where the inertia of a workpiece is significantly decreased due to cutting operations, the combined-velocity calculated value as illustrated inFIG. 4is automatically generated. Therefore, this makes it possible to generate a position command with a higher time-reduction effect when compared to the case where the acceleration set value A1is always used. In the same way, while under constant velocity and while under deceleration, a command with a higher time-reduction effect can also be generated.

As indicated by the solid line103inFIG. 5, acceleration starts at an acceleration set value A3. The inertia ratio is increased while under acceleration, and at a time T2while under acceleration, a change in the inertia ratio is detected. As a result, the parameter changing unit14changes the acceleration set value A3to A4, which is smaller than A3. The pre-interpolation acceleration-deceleration processing unit12calculates a combined-velocity calculated value using the acceleration set value A4at the time T2and later. Therefore, while under acceleration, the combined-velocity calculated value forms a velocity waveform with more moderate acceleration. Due to this velocity waveform, in a case where the inertia is increased by replacing a light-weight workpiece with a heavy-weight workpiece, the combined-velocity calculated value as illustrated inFIG. 5is generated. Therefore, a command with higher vibration-suppression and overload-prevention effects can be generated when compared to the case where the acceleration set value A3is always used. In the same way, while under constant velocity and under deceleration, a command with higher vibration-suppression and overload prevention effects can also be generated.

As described above, according to the first embodiment, the parameter changing unit14changes the acceleration of the motor3according to the inertia ratio as a state quantity of the motor3. Therefore, it is possible to reduce the cycle time when the inertia of a workpiece is decreased during machining. Further, it is possible to prevent the generation of vibrations and overloading when the inertia of a workpiece is increased during machining. That is, without changing the acceleration on the basis of the results of trial executions of the machining program6one or more times, it is possible to dynamically change the acceleration during the execution of the machining program6.

The parameter changing unit14calculates an acceleration candidate value according to the inertia ratio and determines whether it is possible for a drive target to be moved to a target position at the calculated acceleration candidate value. When the parameter changing unit14determines that it is possible for a drive target to be moved to a target position at the calculated acceleration candidate value, the parameter changing unit14changes the acceleration set value to this acceleration candidate value. This makes it possible to prevent a drive target from being moved to a position that is passed the target position.

The parameter changing unit14obtains the inertia ratio of the mechanical system5as a state quantity for changing the acceleration. It is also possible that the parameter changing unit14is configured to obtain the inertia of the mechanical system5(or the load4) from the amplifier2to convert the obtained inertia to an inertia ratio. It is also possible to configure the parameter changing unit14to change the time constant instead of changing the acceleration.

The parameter changing unit14as has been described here calculates an acceleration candidate value according to the equation (1). It is also possible to configure the parameter changing unit14to calculate an acceleration candidate value when the inertia ratio is increased in such a manner that the acceleration candidate value becomes smaller than the acceleration set value at that time point. It is also possible to configure the parameter changing unit14to calculate an acceleration candidate value when the inertia ratio is decreased in such a manner that the acceleration candidate value becomes higher than the acceleration set value at that time point. Furthermore, it is also possible to configure the parameter changing unit14to change the acceleration set value in either case where the inertia ratio is increased or where the inertia ratio is decreased.

In a case where the numerical control device1synchronously drives a plurality of shafts, the parameter changing unit14calculates an acceleration candidate value for each of the shafts. The parameter changing unit14then uses the minimum value of the acceleration candidate values for each of the respective shafts in order to perform the changing process.

Second Embodiment

FIG. 6is a diagram illustrating a configuration of a numerical control device according to a second embodiment. In the descriptions of the second and subsequent embodiments, constituent elements equivalent to those of the first embodiment are denoted with like names and reference signs and redundant descriptions thereof will be omitted.

A numerical control device1ais connected to the amplifier2. The amplifier2supplies a drive current to the motor3to which the load4is connected. The motor3and the load4constitute the mechanical system5. The numerical control device1aincludes the program analysis unit10, the first interpolation unit11, the pre-interpolation acceleration-deceleration processing unit12, the second interpolation unit13, a parameter changing unit14a, and a filtering unit15a.

The filtering unit15ais configured to be capable of externally changing the time constant (a time-constant set value) of a filtering process. The parameter changing unit14acan change the time-constant set value according to a state quantity. In this example, the state quantity indicates the inertia ratio in the same way as the first embodiment. As the time-constant set value is greater, the acceleration (more precisely, the absolute value of acceleration) becomes lower. As the time-constant set value is smaller, the acceleration (more precisely, the absolute value of acceleration) becomes higher. When the inertia ratio is increased, the parameter changing unit14acalculates a new time-constant set value such that the time constant becomes greater than the time-constant set value at that time point. When the inertia ratio is decreased, the parameter changing unit14acalculates a new time-constant set value such that the time constant becomes smaller than the time-constant set value at that time point.

FIG. 7is a flowchart explaining an operation of the parameter changing unit14aaccording to the second embodiment.

First, the parameter changing unit14adetermines whether the interpolation mode is set to “pre-interpolation mode” (Step S21). When the interpolation mode is set to “pre-interpolation mode” (YES at Step S21), processes identical to Steps S12to S16are performed at Steps S22to S26, respectively.

When the interpolation mode is not set to “pre-interpolation mode” (NO at Step S21), the parameter changing unit14arefers to a position command from the second interpolation unit13to determine whether rotations of the motor3are stopped (Step S27). When rotations of the motor3are not stopped (NO at Step S27), the parameter changing unit14afinishes the changing process.

When rotations of the motor3are stopped (YES at Step S27), the parameter changing unit14acalculates a time-constant set value (Step S28). A time-constant set value tc is calculated using the following equation (2), for example.
tc=tc0*(J/J0)  (2)

In this equation, tc0 represents a time-constant reference value, which is a value adjusted using the inertia-ratio reference value J0. The time-constant reference value is set in the parameter changing unit14ain advance.

Subsequently, the parameter changing unit14aoutputs the calculated time-constant set value tc to the filtering unit15a(Step S29), and then finishes the changing process.

As described above, according to the second embodiment, the parameter changing unit14acan change the acceleration by changing the time constant of the filtering process performed by the filtering unit15a.

In a case where the numerical control device1asynchronously drives a plurality of shafts, the parameter changing unit14acalculates the time-constant set value tc to each of the shafts. The parameter changing unit14then outputs the maximum value of the time-constant set values tc to the respective shafts to the filtering unit15a.

Third Embodiment

FIG. 8is a diagram illustrating a configuration of a numerical control device according to a third embodiment. A numerical control device1bis connected to the amplifier2. The amplifier2supplies a drive current to the motor3to which the load4is connected. The motor3and the load4constitute the mechanical system5. The numerical control device1bincludes the program analysis unit10, the first interpolation unit11, the pre-interpolation acceleration-deceleration processing unit12, the second interpolation unit13, a parameter changing unit14b, and the filtering unit15.

In the third embodiment, as a state quantity for converting a parameter, a current value that is output from the amplifier2to the motor3is used. The parameter changing unit14bconverts the current value to a load value of the motor3. The load value of the motor3is proportional to the square of the current value. The load value becomes greater as the acceleration is higher. Further, the load value becomes greater as the inertia ratio is higher. For example, in an attempt to drive the load4having a large inertia at a high acceleration, the motor3is overloaded. When the motor3is overloaded, there is a possibility for the motor3or the mechanical system5to be defective. In the parameter changing unit14b, an overload threshold Xth for determining whether the motor3is overloaded is set in advance. Upon detecting an overload, the parameter changing unit14bchanges the acceleration set value.

FIG. 9is a flowchart explaining an operation of the parameter changing unit14baccording to the third embodiment.

The changing process in the third embodiment is performed in the same manner as in the first embodiment. In the changing process in the third embodiment, an acceleration candidate value is calculated, that is at least smaller than the acceleration set value having been set immediately before. It is also possible that, as an acceleration candidate value, a predetermined value is used, which is set to a degree that does not overload the motor3.

Conventionally, when an overload is detected, a procedure to stop the operation is adopted. Therefore, the work time is increased. According to the third embodiment, the parameter changing unit14bchanges the acceleration set value according to the load value. Due to the third embodiment, even when a light-weight workpiece is replaced with a heavy-weight workpiece for example, the acceleration is switched over while under acceleration before the motor3is overloaded. This makes it possible to prevent an overload, and eliminate the need for the procedure to stop the operation due to an overload.

It is also possible to configure that, upon detecting an overload, the parameter changing unit14bchanges the time constant of the filtering process in the filtering unit15. Specifically, upon detecting an overload, the parameter changing unit14bchanges the time constant to a greater value.

Further, it is also possible to configure that, when the load value is increased, the parameter changing unit14bchanges the acceleration set value to a smaller value. It is also possible to configure that, when the load value is decreased, the parameter changing unit14bchanges the acceleration set value to a greater value. Furthermore, it is also possible that, when the load value is increased, the parameter changing unit14bchanges the time constant to a greater value. It is also possible that, when the load value is decreased, the parameter changing unit14bchanges the time constant to a smaller value.

Fourth Embodiment

FIG. 10is a diagram illustrating a configuration of a numerical control device according to a fourth embodiment. A numerical control device1cis connected to the amplifier2c. The amplifier2csupplies a drive current to the motor3to which the load4is connected. The motor3and the load4constitute the mechanical system5. The numerical control device1cincludes the program analysis unit10, the first interpolation unit11, the pre-interpolation acceleration-deceleration processing unit12, the second interpolation unit13, a parameter changing unit14c, and the filtering unit15.

In the fourth embodiment, an acceleration-deceleration factor is used as a state quantity for changing the acceleration set value. In this example, the amplifier2ccalculates and outputs an acceleration-deceleration factor. Upon detecting a change in the acceleration-deceleration factor, the parameter changing unit14cperforms the changing process. It is also possible to configure that the acceleration-deceleration factor is input from a device other than the amplifier2c. For example, a user can manually input the acceleration-deceleration factor through an operating panel.

The changing process in the fourth embodiment is performed in the same manner as in the first embodiment. In the changing process in the fourth embodiment, the parameter changing unit14cmultiplies the acceleration reference value A0by the acceleration-deceleration factor to define the obtained value as an acceleration candidate value.

As described above, according to the fourth embodiment, the parameter changing unit14cchanges the acceleration to a value obtained by multiplying a predetermined acceleration reference value by an externally-input acceleration-deceleration factor. Due to this calculation, it is possible to change the acceleration according to the acceleration-deceleration factor even while under the execution of the machining program6.

It is also possible to configure that the parameter changing unit14cchanges the time constant of the filtering process in the filtering unit15according to the acceleration-deceleration factor. For example, when the value of acceleration-deceleration factor is larger than 1, the parameter changing unit14cchanges the time constant to a value smaller than the time constant at that time point. For another example, when the value of acceleration-deceleration factor is smaller than 1, the parameter changing unit14cchanges the time constant to a value greater than the time constant at that time point. Further, it is also possible to configure that a time-constant factor is externally input to the parameter changing unit14c, and according to the input time-constant factor, the parameter changing unit14cchanges the time constant of the filtering process in the filtering unit15. That is, the parameter changing unit14ccomputes a new time constant on the basis of the externally-input parameter and the time constant that is set at that time point, and then updates the time constant that is set at that time point to the new time constant.

Furthermore, it is also possible to configure that at least two types of state quantities that are the inertia ratio, the current value of the motor3, and the acceleration-deceleration factor, are input to the parameter changing unit14c. Specifically, a determination condition and a priority are set to each type of the state quantities. Step S2corresponds to a determination condition for the inertia ratio. Step S33corresponds to a determination condition for the current value. A determination condition for the acceleration-deceleration factor is that the parameter changing unit14cdetects a change in the acceleration-deceleration factor. It is possible that, when respective determination conditions for two or more types of state quantities are satisfied simultaneously, the parameter changing unit14cchanges the acceleration or the time constant according to the highest-priority state quantity. For example, in a case where a determination condition for the inertia ratio of the mechanical system5, and a determination condition for the current value are satisfied simultaneously, when it is desired to assign a higher priority to stable operation, then the acceleration or the time constant is changed on the basis of the current value. Therefore, the vibration-suppression and overload-prevention effects can be obtained. The acceleration is then changed according to the inertia ratio of the mechanical system5, and therefore the time-reduction effect can be obtained.

Fifth Embodiment

FIG. 11is a diagram illustrating a configuration of a numerical control device according to a fifth embodiment. A numerical control device1dis connected to the amplifier2. The amplifier2supplies a drive current to the motor3to which the load4is connected. The motor3and the load4constitute the mechanical system5. The numerical control device1dincludes the program analysis unit10, the first interpolation unit11, the pre-interpolation acceleration-deceleration processing unit12, the second interpolation unit13, a parameter changing unit14d, and the filtering unit15.

In the fifth embodiment, the parameter changing unit14dcan perform a resetting process when a specific external signal is input to the parameter changing unit14d, or when it reads a specific auxiliary code command. The resetting process is a process of resetting the acceleration set value to a predetermined value. As an external signal for the resetting process, it is possible to employ any signal such as a reset signal, a single block signal, or a feed hold signal. An auxiliary code command for the resetting process is described in the machining program6. The program analysis unit10describes the auxiliary code command described in the machining program6to analysis data. The parameter changing unit14dcan read the auxiliary code command from the analysis data.

For example, when an auxiliary code command for tool replacement is given, the inertia is changed due to the tool replacement. Therefore, at the time of the next operation, the inertia is estimated to switch over the acceleration. As an acceleration in the operation when the inertia is estimated, the acceleration set value before the switchover is used. Therefore, there is a possibility of the occurrence of an overload or oscillations depending on the acceleration set value. According to the fifth embodiment, when a tool-replacement command is given, the parameter changing unit14ddetermines whether to perform the resetting process on the basis of an auxiliary code command given along with the tool-replacement command. When the parameter changing unit14ddetermines to perform the resetting process, it switches over the acceleration to the predetermined acceleration. An acceleration, which has been found in advance not to cause vibrations or an overload, is predetermined. This makes it possible to suppress an overload and oscillations at the time of tool replacement.

It is also possible to configure that the parameter changing unit14dperforms a time-constant resetting process when a specific external signal is input to the parameter changing unit14d, or when it reads a specific auxiliary code command. The time-constant resetting process is a process of resetting the time-constant set value to a predetermined value.

Further, it is also possible to configure that, when the parameter changing unit14dreads a specific operation command, it stops switching over the acceleration or the time constant during the operation period according to the specific operation command. For example, there is an operation such as synchronized tapping or threading, in which a switchover in acceleration is not desired. In this case, a user can add an auxiliary code for stopping the switchover in acceleration before such an operation as described, and also add an auxiliary code for starting the switchover in acceleration after such an operation as described. Upon reading the auxiliary code, the parameter changing unit14dstops or starts switching over the acceleration.

Further, it is also possible that a specific operation command is configured to be capable of being defined in the machining program6, or being set in the parameter changing unit14d, in advance as stopping the switchover in acceleration or time constant during the execution period of the specific operation command. Upon reading the specific operation command, the parameter changing unit14dstops switching over the acceleration or the time constant.

Each functional block that constitutes the numerical control device according to the first to fifth embodiments can be implemented by either hardware or software, or by a combination of both. “Implementing each functional block by software” refers to, in a computer that includes a computation device and a storage device, storing a program module that corresponds to a constituent element in the storage device, and executing the program module stored in the storage device by the computation device, thereby implementing a function of the constituent element.

REFERENCE SIGNS LIST