Motor control device

This motor control devices provided with: a motor control unit which generates a command value on the basis of a motor drive command acquired from a PLC over a communication line; a drive unit which supplies motor drive voltage according to the command value; an interruption unit which interrupts transmission of the drive signal to the motor; a safety input unit which receives an emergency stop input operation over a control signal line; a reset input unit which receives a reset input operation; a determination unit which determines whether or not safety is maintained on the basis of input to the safety input unit; and a safety control unit which, when the safety input unit receives an emergency stop input operation, performs interruption processing of the drive signal through the interruption unit, and when the reset input unit receives a reset input operation, performs restart processing if safety is maintained.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a 371 application of the International PCT application serial no. PCT/JP2018/005951, filed on Feb. 20, 2018, which claims the priority benefits of Japan Patent Application No. 2017-030369, filed on Feb. 21, 2017. The entirety of the above-mentioned patent applications is hereby incorporated by reference herein and made a part of this specification.

TECHNICAL FIELD

The present invention relates to a motor control device that drives and controls a motor.

BACKGROUND ART

In recent years, a servo system has been used for, for example, positioning control of operating units in various machines at manufacturing sites. An example of such a servo system includes a system including a servo motor for operating various mechanical devices, an encoder attached to the servo motor, a servo driver for driving the servo motor, and a control device for outputting position command information or the like to the servo driver. Efforts to ensure the safety of workers together with cost reduction and improvement in productivity are becoming important requirements at manufacturing sites. Therefore, a servo system is also required to be suitable for corresponding safety standards.

A servo driver including a safe torque off (STO) function of interrupting a drive current that is supplied to a servo motor in response to an interrupting signal from the outside in order to ensure safety at the time of using the servo motor is known (Patent Literature 1). Further, it is necessary for a stop command to be reliably transferred to the servo driver when a user presses an emergency stop switch, and a safety controller is used for this purpose.

A configuration of a system of the related art with an STO function is illustrated inFIG. 9. In this system, a servo driver104, a standard programmable logic controller (PLC)105, and a safety PLC106are connected via a network line (a communication line)101, and the servo driver104drives a motor102on the basis of a drive command from the standard PLC105. The safety PLC106transfers a command regarding safety such as for emergency stopping to the servo driver104via the network line101. Further, an emergency stop switch107is connected to a safety controller109, and when the emergency stop switch107is pressed, a stop command is transferred from the safety controller109to the servo driver104via an external wiring (a control line). The emergency stop switch107has redundant contact portions in order to satisfy safety standards, and the safety controller109has a function of determining whether the emergency stop switch107has operated normally and maintains safety. The safety controller109does not permit a re-operation of the servo driver104even when the reset switch108is pressed in a case in which safety is not maintained.

CITATION LIST

Patent Literature

SUMMARY

Technical Problem

As described above, a method in which a servo driver acquires a stop command in the system of the related art includes two methods including a method of acquiring the stop command from the safety PLC via the network and a method of acquiring the stop command from the safety controller via external wiring. In the method of acquiring the stop command via a network, there is a problem that a network delay occurs and it takes time to stop the output. On the other hand, in the method of acquiring the stop command via external wiring, there is no problem of a network delay, but there is a problem that a safety controller separate from the servo driver is necessary and a system configuration or a control method therefor become complicated.

The present invention has been made in view of such problems, and an object of the present invention is to provide a motor control device capable of performing emergency stopping rapidly without causing deterioration in safety or complication of a system configuration.

Solution to Problem

In the present invention, a function of receiving an emergency stop signal, which is included in a safety controller of the related art, is incorporated into a motor control device in order to solve the above problems. With such a configuration, it is possible to realize both shortening of a time from generation of an emergency stop signal to stopping of output and simplification of a system configuration and a control method therefor.

Specifically, a motor control device according to an aspect of the present invention includes a motor control unit, a drive unit, an interruption unit, a safety input unit, a reset input unit, a determination unit, and a safety control unit. The motor control unit generates a command value for driving the motor on the basis of a motor drive command acquired from a PLC via a communication line. The drive unit supplies a drive current for driving the motor to the motor according to the command value from the motor control unit. The interruption unit interrupts transfer of a drive signal to the motor.

The safety input unit receives an emergency stop input operation from a user via a control signal line different from the communication line. When the safety input unit receives the emergency stop input operation, the safety control unit executes a process of interrupting the drive signal.

The reset input unit receives a reset input operation from the user. The reset input unit may acquire a reset input signal from the safety PLC via the communication line, or may acquire a reset input signal via the control signal line different from the communication line. When the reset input unit receives the reset input operation and the safety is maintained, the safety control unit executes a re-activation process.

The determination unit determines whether safety is maintained on the basis of a change in a state of an input to the safety input unit. In the present disclosure, “safety is maintained” means a state in which security is secured and, more clearly, a state in which predetermined safety requirements are satisfied. Typically, a state in which no failure occurs in any of components is a state in which the predetermined safety requirements are satisfied, and thus, a state in which the safety is maintained.

The safety control unit executes a process of interrupting the drive signal through the interruption unit when the safety input unit receives the emergency stop input operation. An output of the drive signal to the motor is stopped through the interrupting process. Further, when the reset input unit receives the reset input operation and safety is maintained, re-activation processing is performed. The output of the drive signal to the motor is resumed through the re-activation process. Here, when the determination unit determines that safety is not maintained, the re-activation process is not performed even when there is the reset input operation, thereby preventing re-activation of the system in a state in which security cannot be secured.

With such a configuration, a function of securing safety regarding the emergency stop switch is provided in the motor control device, and the safety controller of the related art is not necessary. Therefore, since the stop command is acquired via the control signal line, it is possible to achieve rapid emergency stopping and prevent a system configuration from being complicated.

In the aspect, the input to the safety input unit may be duplexed as a first input and a second input, and the determination unit may determine that safety is maintained when a correlation between the first input and the second input satisfies a predetermined condition, and determine that safety is not maintained otherwise. An example of the “predetermined condition” is a correlation condition of the first input and the second input that is assumed to occur when no failure occurs in any component of the emergency stop switch. With such a configuration, even when a single failure occurs in the emergency stop switch, emergency stopping is possible, and re-activation in such a state can be prevented.

The reset input unit may receive a signal indicating that the user has performed the reset input operation from a safety PLC via the communication line. Since a rapid response is not required for the resetting process, no problem occurs even when the input is via the communication line, and an effect of reducing the number of terminals of the motor control device can be obtained by omitting the input via the control signal line. However, the reset input unit may receive the reset input operation from the user via a control signal line different from the communication line. Thus, the reset switch can be disposed near the emergency stop switch. Further, the reset input unit may receive the reset input operation via two systems, that is, via communication line and via a control signal line.

The motor control device according to the present aspect may further include a notification unit that notifies the safety PLC that the safety is not maintained. With this configuration, the safety PLC can perform a process such as notification of an error to the user.

Further, the notification unit may also notify the PLC of transition of an input to the safety input unit or an input to the reset input unit. With this configuration, the PLC can determine a component that has failed or a failure that has occurred on the basis of the transition of the input, and perform a process according thereto. This is a function that cannot be realized when the safety controller of the related art is adopted. This is because the safety controller of the related art only notifies the motor control device of a stop command or a re-activation command, and the motor control device is not notified of transition of the input to the safety input unit or the reset input unit.

It should be noted that the present invention can be understood as a motor control device having at least some of the above functions. The present invention can also be understood as a motor control system including the motor control device, the motor, and the PLC described above. Furthermore, the present invention can also be understood as a control method for executing at least some of the above processes. Further, the present invention can be understood as a computer program for causing a computer to execute this method, or a computer-readable storage medium storing this computer program non-temporarily. Each of the above means and processes can be combined with one another as far as is possible to constitute the present invention.

Advantageous Effects of Invention

In the motor control device, it is possible to perform rapid emergency stopping without causing deterioration in safety or complication of a system configuration.

DESCRIPTION OF THE EMBODIMENTS

First Embodiment

FIG. 1is a schematic configuration diagram of a servo system in which a servo driver corresponding to a motor control device of the present invention is incorporated. The servo system includes a network1, a motor2, an encoder3, a servo driver4, a standard programmable logic controller (PLC)5, a safety PLC6, an emergency stop switch7, and a reset switch8. The motor2and the encoder3form a servo motor. The servo system is a system for driving the motor2, and the motor2is incorporated in various mechanical devices (for example, an arm and a conveying device of an industrial robot) (not illustrated) as an actuator for the devices. For example, the motor2may be an AC motor. The encoder3is attached to the motor2in order to detect an operation of the motor2. The encoder3generates a feedback signal indicating the detected operation of the motor2and transmits the feedback signal to the servo driver4. The feedback signal includes, for example, positional information on a rotational position (angle) of a rotational shaft of the motor2, and information on a rotational speed of the rotational shaft. A general incremental encoder or absolute encoder can be applied to the encoder3.

The servo driver4receives an operation command signal regarding an operation (motion) of the motor2from the standard PLC5through the network1(a communication line), and receives the feedback signal output from the encoder3. The servo driver4executes servo control on the driving of the motor2on the basis of the operation command signal from the standard PLC5and the feedback signal from the encoder3. Further, the servo driver4is also connected to the safety PLC6via the network1. Accordingly, the servo driver4performs monitoring of occurrence of an abnormality regarding the motor2or the servo driver4on the basis of the monitoring command signal received from the safety PLC6, and sends a result of monitoring to the safety PLC6.

Further, the servo driver4calculates a command value regarding the operation of the motor2on the basis of the operation command signal from the standard PLC5and the feedback signal from the encoder3. Further, the servo driver4supplies a drive current to the motor2so that the operation of the motor2follows the command value. It should be noted that AC power to be sent from the AC power supply11to the servo driver4is used for the supplied current. In the example, the servo driver4is of a type that receives a three-phase AC current, but may be of a type that receives a single-phase AC current.

The servo driver4also receives input operation signals of the emergency stop switch7and the reset switch8from the emergency stop switch7and the reset switch8via external wirings7aand8a(control signal lines). The servo driver4stops the supply of the drive current to the motor2when the operation signal of the emergency stop switch7is received. Further, the servo driver4determines whether the safety is secured regarding the emergency stop switch on the basis of transition of the input from the emergency stop switch7, and resumes the supply of the drive current to the motor2under the condition that the safety is secured when the operation signal of the reset switch is received.

Hereinafter, a more specific configuration of the servo driver4will be described.FIG. 2is a functional block diagram of the servo driver4. As illustrated inFIG. 2, the servo driver4includes a feedback processing unit41, a motor control unit42, an interruption unit43, a drive unit44, and an emergency stop unit50.

The feedback processing unit41generates a feedback value on the basis of the feedback signal from the encoder3. For example, when a pulse is output from the encoder3, the feedback processing unit41counts this pulse to calculate a rotational position or a rotational speed of a rotation shaft of the motor2, and generates a feedback value including a value indicating the position or the speed.

The motor control unit42receives the operation command signal from the standard PLC5and receives the feedback value from the feedback processing unit41. The motor control unit42generates a command value for executing position feedback control and speed feedback control on the basis of the operation command signal and the feedback value. For example, the motor control unit42generates a position command value and a speed command value under feedback control based on the operation command signal and the feedback value. It should be noted that a feedback scheme to be adopted in the feedback control is a scheme in which a servo loop suitable for a predetermined purpose (for example, conveyance of packages) of a mechanical device (for example, a conveyance device) in which the motor2is incorporated is formed, and can be appropriately designed. These command values generated by the motor control unit42are sent as drive signals to the interruption unit43.

When the interruption unit43receives an interrupting signal from the safety control unit53to be described below, the interruption unit43stops the drive unit44by not electrically passing the drive signal from the motor control unit42to the drive unit44to be described below. Accordingly, even when the motor control unit42transmits the drive signal, the output of the torque in the motor2is stopped. On the other hand, when the interrupting signal is not input to the interruption unit43, the interruption unit43passes the drive signal with a command value output from the motor control unit42to the drive unit44as it is. It should be noted that in the interruption unit43, two interrupting circuits are connected in series, and the two interrupting circuits are simultaneously interrupted when the interrupting signal is received. With this redundant configuration, it is possible to stop the transmission of the drive signal even when a failure occurs in any one of the interrupting circuits.

The drive unit44receives the drive signal from the motor control unit42via the interruption unit43. The drive circuit44includes, for example, a circuit including a semiconductor switching element such as an insulated gate bipolar transistor (IGBT), and generates a signal for turning on or off the switching element according to a PWM scheme on the basis of the drive signal from the motor control unit42, and turns on or off the switching element according to this signal. Accordingly, AC power is supplied to the motor2and the motor2is driven according to the drive signal. On the other hand, when the interruption unit43operates and the transfer of the drive signal to the drive unit44is interrupted, the output from the drive unit44is fixed to OFF. Accordingly, since the power supply to the motor2is stopped, the output of the torque from the motor2is stopped.

The emergency stop unit50is a functional unit for emergency stopping driving of the motor2at the time of an emergency, and includes a safety input unit51, a reset input unit52, a safety control unit53, a determination unit54, and a notification unit55.

The safety input unit51monitors the contacts of the emergency stop switch7. The emergency stop switch7may be any type such as a push button type, a foot type, or a rope type as long as the emergency stop switch7is a 2-channel emergency stop switch. The emergency stop switch7has two NC (normally closed) contacts, and when the user operates the emergency stop switch7, the two NC contacts are opened. The emergency stop switch7has a latching mechanism, and when the switch is operated, a state thereof is maintained and the NC contacts remain open. The safety input unit51acquires signals of two channels from the emergency stop switch7and, accordingly, receives an emergency stop input operation of the user. Hereinafter, the two-channel inputs are also referred to as a first safety input and a second safety input, respectively, as necessary. The safety input unit51sends the two-channel input to the safety control unit53to be described below.

The reset input unit52monitors contacts of the reset switch8. In order to re-activate the system after an emergency stop, a reset routine is required after the contacts of the emergency stop switch7are set to a position of closed. The reset switch8has a NO (normally open) contact, and the reset input unit52monitors this contact. The reset input unit52sends a reset input to the safety control unit53to be described below.

The safety control unit53controls transfer and interrupting of the drive signal to the servo driver4. The safety control unit53can be realized by a micro processor unit (MPU) executing a program, but may be realized by an application specific integrated circuit (ASIC).

The safety control unit53transmits the interrupting signal to the interruption unit43when it is determined that the safety of the system is not maintained (an interrupting process). Typically, when the emergency stop switch7is operated during the output of the drive signal to the motor2and there is a safety input to the safety input unit51, the safety input unit51transmits the interrupting signal to the interruption unit43according to the safety input and executes the interrupting process. Since the interruption unit43is redundant due to the serial connection of the interrupting circuits as described above, the interruption unit43can safely stop the transmission of the drive signal even when a failure occurs in one of paths. The safety control unit53also performs the interrupting process when the stop signal is received from the safety PLC6via the network1. Further, when a defect is detected in a component in the servo driver4or the motor2, the safety control unit53executes the interrupting process.

The safety control unit53stops the output of the interrupting signal to the interruption unit43when the reset switch8is operated (when the reset input signal is switched from OFF to ON), and resumes the output of the drive signal to the motor2(a re-activation process). However, a condition that the determination unit54determines that the safety of the system is secured is set in order to start the re-activation process and, in a case in which the security is not secured, the safety control unit53does not stop the output of the interrupting signal even when the reset switch8is operated.

The determination unit54is a sub-functional unit of the safety control unit53, and determines whether the safety of the servo driver4is secured. The determination unit54receives an operation signal (the first safety input and the second safety input) of the emergency stop switch7from the safety input unit51and an operation signal of the reset switch8from the reset input unit52, and determines whether or not the safety of the servo driver4is secured on the basis of a correlation between these signals.

A determination logic of the determination unit54will be described with reference toFIGS. 3A and 3B. The determination unit54first determines that security is secured when both the first safety input and the second safety input are closed within a time defined in advance, with an initial condition that the first safety input and the second safety input are open. When the user releases the emergency stop switch7, the two NC contacts are closed substantially simultaneously, but there is actually a slight time difference.

For example, after the first safety input is closed at time T1, the second safety input is closed at time T2, as illustrated inFIG. 3A. When a time difference Tdif=T2−T1is within a threshold time Tth, the determination unit54determines that the security is secured (valid) at time T2. It should be noted that the threshold time Tth is a maximum allowable value (for example, several milliseconds) of a difference between times at which the two contacts are closed when the emergency stop switch7has been released. On the other hand, when the difference between times at which the first safety input and the second safety input are closed (Tdif=T2′−T1inFIG. 3B) is greater than the threshold time Tth as illustrated inFIG. 3B, the determination unit54does not determine that the security is secured (kept invalid) even when the first safety input and the second safety input are both closed. When states of the two safety inputs are different, the determination unit54determines that the security is not secured (invalid).

The determination logic of the determination unit54will be further described with reference toFIG. 4. A determination in a state in which the security is secured, that is, a state in which the two safety inputs are both closed (after time T2inFIG. 4) will be described herein. The determination unit54determines that the security is not secured when the other safety input is open while one of the safety inputs remains closed, and continues to determine that the security is not secured even when the open safety input is then closed. In the example ofFIG. 4, the second safety input is open at time T3and is closed again at subsequent time T4in a state in which the first safety input remains closed. The determination unit54determines that the security is not secured at a time point of time T3. Further, both the safety inputs are closed at time T4, but one of the safety inputs remains closed, and thus, the determination unit54determines that the security is not secured. When both the safety inputs are both open at time T5to return to an initial state, and then, the safety inputs are both closed within the threshold time Tth, the determination unit54determines that the security is secured.

It should be noted that although only whether or not the emergency stop function is valid (a component does not fail and a safety standard is satisfied) is considered for simplification in determining whether the safety of the servo driver4is secured as described, other elements may be considered. For example, when a failure occurs in any component such as the interruption unit43or the encoder3, the determination unit54may determine that the safety of the servo driver4is not secured. In order to make such a determination, the determination unit54may be notified of a failure monitoring result of each component, and a monitoring method is also known. Detailed description thereof will be omitted.

When the determination unit54determines that the security is not secured, the notification unit55notifies the safety PLC6of the fact through an error notification via the network1. The error notification may simply indicate that security is not secured, but it is desirable to include more detailed information. For example, the notification unit55may notify the safety PLC6of transition of the input received by the safety input unit51or transition of the input received by the reset input unit52. The safety PLC6can use such information to determine a component that has failed or a failure that has occurred. For example, when one of the two safety inputs remains closed and the other is open, a determination can be made that the closed terminal fails (for example, short circuit), and a determination can be made that a defect has occurred even when a time difference from open to closed is greater than a threshold time. Further, when there is a reset input while the safety input remains open, a determination can be made that there is an error in a reset procedure. It should be noted that the notification unit55may perform failure analysis and notify the safety PLC6of a result thereof, instead of the safety PLC6being notified of the transition of the input and the safety PLC6performing the failure analysis.

OPERATION EXAMPLE

In a case in which there is no failure in the emergency stop switch7, the two NC contacts are both open when the emergency stop switch7is operated during driving of the motor2, and the safety control unit53executes the interrupting process in response thereto to stop the output of the drive signal to the motor2. Through the notification from the notification unit55, the safety PLC6can ascertain that the emergency stop has been performed since the emergency stop switch7has been operated, and notifies the user of the fact or a procedure for re-activation. In the re-activation, the user first releases the emergency stop switch7, and thus, both of the NC contacts change from open to closed. Thereafter, when the user operates the reset switch8, the safety control unit53executes the re-activation process to resume the output of the drive signal to the motor2. It should be noted that, even when the reset switch8is operated without releasing the emergency stop switch7, the safety control unit53does not execute the re-activation process. In this case, through the notification from the notification unit55, the safety PLC6can ascertain that the reset switch8is operated without releasing the emergency stop switch7, and notifies the user of the fact or a correct procedure of the re-activation.

Next, a case in which one channel or one safety input of the emergency stop switch7remains closed, for example, due to a short circuit between terminals is considered. When the emergency stop switch7is operated during driving of the motor2, a non-welded contact is open, and in response thereto, the safety control unit53executes the interrupting process to stop the output of the interrupting signal to the motor2. Through the notification from the notification unit55, the safety PLC6can ascertain that one of the contacts remains closed, that is, welding is occurring. Therefore, the safety PLC6notifies the user that the emergency stop switch7has failed. In this state, even when the user tries to re-activation and releases the emergency stop switch7, a condition that the two NC contacts both become open and then closed is not satisfied, and thus, the determination unit54can detect that a failure has occurred in the emergency stop switch7and determines that the security is not secured. Thereafter, even when the reset switch8is operated, the safety control unit53does not execute the re-activation process since the safety is not secured, and therefore, it is possible to prevent the re-activation in a state in which the emergency stop switch7fails. Although the welding is taken as an example herein, it is possible to similarly prevent the re-activation while the failure is left even in a case in which other failures such as short circuit or disconnection have occurred.

Advantage of Embodiment

According to the embodiment, since the input from the emergency stop switch7is received via the control signal line, no transmission delay via the network1occurs, and the output of the drive signal can be rapidly stopped after the emergency stop switch7is operated. Further, in the embodiment, since the safety of the emergency stop switch7can be secured in the servo driver4, the safety controller of the related art is not necessary, and a system configuration or a control method therefor is simplified.

Further, in the embodiment, since the servo driver4can directly acquire the inputs from the emergency stop switch7and the reset switch8, it is possible to transfer content of an error to the safety PLC6when the error has occurred. The safety PLC6can centrally manage error information and present, to the user, information such as a type of error that has occurred and an action to be taken for an error at any place including the emergency stop switch7. Therefore, troubleshooting is facilitated and convenience for users is improved.

Second Embodiment

A servo driver4according to a second embodiment will be described on the basis ofFIG. 5. Among functional units illustrated inFIG. 5, functional units substantially the same as the functional units illustrated inFIG. 2are denoted by the same reference numerals and detailed description thereof will be omitted.

In the modification example, a feedback processing unit41, a motor control unit42, an interruption unit43, and a drive unit44, which are functional units directly related to drive control of the motor2, are disposed on the main body side of the servo driver4. In this disposition, since the drive unit44is disposed under a higher voltage environment than the other functional units, a known appropriate insulation process is performed between the drive unit44and the other functional units. On the other hand, a safety control function of the emergency stop unit50based on inputs from an emergency stop switch7and a reset switch8is formed on a safety circuit board50A. In the modification example, a safety control unit57for performing an interrupting signal based on a stop signal from a safety PLC6is disposed on the main body side of the servo driver4. It should be noted that the modification example can be applied to the configuration of the modification example 1 described above.

The circuit board50A is configured to be removable from the main body via a slot4aprovided on the main body side of the servo driver4. Therefore, when the circuit board50A is incorporated into a main body of the servo driver4through the slot4a, electrical contacts of the circuit board4A and the main body side of the servo driver4are designed so that the interruption unit43receives the interrupting signal from the safety control unit.

Thus, it is possible to realize an optimal configuration according to system requirements by enabling the safety control function based on the emergency stop switch7and the reset switch8to be removed. For example, in a case in which emergency stop can be performed at a sufficiently high speed on the basis of the stop signal from the safety PLC6, addition of the safety circuit board50A is unnecessary and costs can be reduced.

Modification Example

In the above embodiment, independent power supplies are supplied to two inputs from the emergency stop switch7and one input from the reset switch8and a failure can be reliably detected when the failure has occurred. However, six terminals are required for the servo driver4, leading to an increase in a size of the device. Therefore, the number of terminals of the servo driver4may be reduced to three by adopting a configuration in which a common power supply is supplied to three inputs as illustrated inFIG. 6.

Further, a situation in which a signal is not OFF may occur due to a short circuit between channels even when the emergency stop switch7is operated and the two NC contacts are open. In order to detect such a failure, a test pulse output terminal may be provided, a short OFF pulse may be regularly transmitted, and it may be checked whether the OFF pulse returns. When the OFF pulse returns, a circuit can be diagnosed as being normal, and when the OFF pulse does not return, it can be diagnosed as a short circuit failure of wirings.

Further, the reset switch8may be connected to the safety PLC6and the reset signal may be input to the servo driver4via a network as illustrated inFIG. 7, instead of the input from the reset switch8being input to the servo driver4via the control signal line. Since high-speed responsiveness is not required for a reset operation, no severe problem occurs even when a delay due to transmission via the network occurs. On the other hand, there is an advantage that miniaturization can be realized by reducing the number of input terminals of the servo driver4. In this case, a configuration in which a reset circuit can be added to the servo driver4is also effective since a system configuration can be made flexible.

Further, although operating the reset switch8after the emergency stop switch7is released is required in order to perform the re-activation after emergency stop in the above description, a configuration in which the re-activation is performed without the operation of the reset switch8may be adopted according to a required safety standard.

Modification Example 2

Although the servo driver4as a motor control device of the present invention is illustrated in the above example, the servo driver40illustrated inFIG. 8can also be adopted as the motor control device in place of the aspect. It should be noted that an induction motor or the like can be illustrated as the motor2driven and controlled by the servo driver40.FIG. 8is a diagram illustrating functional blocks of the servo driver40. As illustrated inFIG. 8, the servo driver40includes a plurality of functional units. Among the functional units, the functional units substantially the same as the functional units included in the servo driver4illustrated inFIG. 2are denoted with the same reference numerals, and detailed description thereof will be omitted. Specifically, the servo driver also includes a feedback processing unit41, a motor control unit42, an interruption unit43, a drive unit44, and an emergency stop unit50, and also includes an operation instruction unit46.

The operation instruction unit46generates the operation command signal for driving the motor2on the basis of a request operation given by the user via an input device (not illustrated) in advance. Therefore, no operation command signal is provided from an external device (for example, the standard PLC5) to the servo driver40, and the servo driver40drives and controls the motor2according to a predetermined feedback scheme on the basis of the feedback signal from the encoder3and the operation command signal from the operation instruction unit46. Alternatively, the operation command signal may be provided from the external device to the servo driver40. In the servo driver40configured in this manner, the emergency stop process can be performed on the basis of the safety input from the emergency stop switch7by the determination unit54included in the emergency stop unit50, and the torque output from the motor2can be stopped by the operation of the interruption unit43, as in the servo driver4described above.