JP6447141B2 - Robot emergency stop method, robot control device - Google Patents

Description

  The present invention relates to a robot emergency stop method and a robot control apparatus.

  Industrial robots have a non-stop function for urgently stopping a robot when some abnormality occurs. When executing such an emergency stop function, the robot control device does not suddenly turn off the power, but stops it while controlling its behavior so that excessive current does not flow and smoothly stops. Stop control is performed (for example, refer to Patent Document 1).

Japanese Patent Laid-Open No. 1-270779

  By the way, in the case of an industrial robot, in order to prevent an excessive force from being applied to the workpiece during the operation of the robot, the motor current may be limited during normal operation. In such a state where current is limited, it is assumed that there is not enough current to operate according to the command value. In such a situation, the motor operates slightly behind the command value. It will be. That is, when the motor current is limited, the command angle that is an angle given as the command value may deviate from the actual angle that is the actual motor angle.

  When the command angle deviates from the actual angle, the motor operates to reach the command angle. For this reason, there is a possibility that the motor does not operate as intended by the stop control in an attempt to continue the operation so far, even though the stop control is performed.

  For example, in the case of a robot having a plurality of motors, a motor whose command angle does not deviate from the actual angle starts to decelerate quickly when stop control is started, while the command angle and real angle deviate. The motor being operated may continue to operate even when the stop control is started.

  In addition, when the current is limited, it may be impossible to secure the current required for deceleration during emergency stop. In that case, the deceleration time until the motor stops increases, and the motor The distance that the arm or the like driven by the movement moves also becomes long.

  In this way, a motor that is limited in current during normal operation may not be able to immediately decelerate, that is, shift to stop operation during an emergency stop. May show different behaviors and may cause vibrations on the arm or contact with a workpiece, peripheral devices, etc. without stopping at the assumed stop position due to a long deceleration time. That is, there is a possibility that stop control for the robot cannot be performed promptly and smoothly during an emergency stop.

  The present invention has been made in view of the above circumstances, and an object thereof is to quickly and smoothly perform stop control at the time of emergency stop in a robot in which the motor current may be limited during normal operation. It is an object to provide a robot emergency stop method and a robot control device.

  In the robot emergency stop method according to the first aspect of the present invention, in a robot that may limit the motor current during normal operation, when performing stop control, a release step of releasing the current limit on the motor, and the stop control To correct the command angle given to the motor in order to maintain the continuity of the motor operating state before and after releasing the current limit, and stop using the command angle corrected in the correction step And a stop step for performing the control.

  In this case, the motor whose current is limited during normal operation is released during emergency stop. As a result, a current required for stop control can be secured, and an increase in deceleration time can be prevented. Therefore, the robot can be quickly stopped, and it is possible to prevent contact with a workpiece or a peripheral device without stopping at the assumed stop position.

  Further, the command angle given to the motor to perform the stop control at the time of emergency stop is corrected so that the continuity of the operation state of the motor is maintained. For this reason, the robot operates to start the stop control from the operation state before the stop control is started (more strictly, a state in which a current limit is applied immediately before the emergency stop operation or the like is performed). Even if the amount of operation increases suddenly due to the increase in the amount of current in the state (the state where the current limit is released), the occurrence of vibrations is suppressed and the actual stop control is completed during an emergency stop. The time until it can be shortened. The stop of the robot is not stopped until the hand is moved to the target position and the robot stops at that position, that is, does not vibrate.

  Then, starting the stop control with the corrected command angle as an initial value, that is, starting the stop control in a state where the continuity of the motor operation state is maintained. The posture does not change suddenly. This can prevent the arm from vibrating. Further, since the stop control is started with the corrected command angle as an initial value, the behavior of the robot during the stop control can be controlled as intended.

Thus, in a robot that may limit the motor current during normal operation, stop control during an emergency stop can be performed quickly and smoothly.
In the invention according to claim 2, in the correction step, the actual angle, which is the actual angle of the motor before the current restriction is released, is set to the initial value of the command angle given to the motor in order to perform stop control. Thus, the command angle is corrected so that the continuity of the angle is maintained before and after the restriction of the current is released.

  When the command angle is not corrected, if the actual angle immediately before the stop control is different from the command angle given for the stop control, the motor will try to reach the given command angle. To do. That is, it takes a long time to actually start the stop control. On the other hand, by correcting the command angle as in the present invention, the motor starts decelerating from the current actual angle when stop control is started. Thereby, time until stop control is started can be shortened, and it can prevent contacting with a work, a peripheral device, etc.

  In the invention according to claim 3, in the correction step, the speed of the motor before canceling the current limit is obtained based on the actual angle that is the actual angle of the motor, and a new command angle that is the obtained speed is calculated. By setting the calculated new command angle to the initial value, the command angle is corrected so that the continuity of the speed is maintained before and after the restriction of the current is released.

  This prevents the speed of the motor from changing before and after releasing the current limit, that is, before and after starting the stop control. Therefore, the behavior of the motor is prevented from changing greatly before and after the current restriction is released, and the arm can be prevented from vibrating.

  In the invention according to claim 4, in the correction step, the torque of the motor before canceling the current limit is obtained based on the actual angle that is the actual angle of the motor, and a new command angle that becomes the obtained torque is calculated. By setting the calculated new command angle as an initial value, the command angle is corrected so that the continuity of torque is maintained before and after the limitation of current is released.

  As a result, the torque of the motor is prevented from changing before and after releasing the current limit, that is, before and after starting the stop control. Therefore, the behavior of the motor is prevented from changing greatly before and after the current restriction is released, and the arm can be prevented from vibrating.

In the invention according to claim 5, in the correction step, the internal state of the integrator is also corrected so that the continuity of the torque of the robot is maintained before and after the restriction on the current is released.
In the case of the first to fourth aspects of the present invention, the continuity of the operation state at the time of starting the stop control is maintained, but it is assumed that the internal state of the control system has changed greatly after the stop control is started. May move outside. Therefore, by maintaining the continuity of the internal state of the integrator of the control system, the robot can be controlled as intended even after the stop control is started.

  According to a sixth aspect of the present invention, there is provided a robot control apparatus that executes the steps of the robot emergency stop method according to any one of the first to fifth aspects. Thus, similarly to the first to fifth aspects of the invention, in a robot that may limit the motor current during normal operation, stop control during an emergency stop can be performed quickly and smoothly.

The figure which shows the structure of the robot system of one Embodiment typically. The figure which shows the functional block of the control device typically Diagram showing the flow of emergency stop processing by the control device

Hereinafter, a plurality of embodiments of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the site | part substantially common in each embodiment, and the detailed description is abbreviate | omitted.
(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. 1 to 3.

  As shown in FIG. 1, the robot system 1 of this embodiment includes a control device 2 and a robot 3 controlled by the control device 2. In this embodiment, a vertical articulated robot is assumed as the robot 3, and a plurality of motors 4 are provided in the robot. Each motor 4 is provided at a joint portion or the like of the robot 3 and drives an arm.

  The control device 2 is composed of a microcomputer (corresponding to control means) having a CPU, ROM, RAM, and the like (not shown), and controls the robot system 1 according to a computer program stored in the ROM.

  As shown in FIG. 2, the control device 2 includes a command value generation unit 10 (command value generation means) and a control signal generation unit 11 (control signal generation means). The command value generation unit 10 and the control signal generation unit 11 are realized in software by a computer program executed by the control unit of the control device 2.

  The command value generation unit 10 generates a command value for instructing the angle (rotation angle) and speed (rotation speed) of the motor 4 in order to control the posture of the robot 3. In the case of this embodiment, the command value is an angle command for commanding the angle of the motor 4.

  Based on the command value generated by the command value generation unit 10, the control signal generation unit 11 generates a control signal to be given to the drive circuit 12 (drive means) that drives the motor 4. Note that the control of the motor 4 for operating the robot 3 can be performed in the same manner as in the prior art, and a detailed description thereof will be omitted here, but the control signal generator 11 includes a speed control system and a position control system. Angle detection means such as an encoder that detects the rotation angle of the motor 4 while detecting the current by the current detection means 13 such as a shunt resistor that detects the current supplied to the motor 4 side, which is a control system having a multiple structure. Based on the speed / angle of the motor 4 detected at 14, a control signal for controlling the motor 4 is generated. The angle detection unit 14 also functions as a speed detection unit that detects the speed of the motor 4 based on the detected change in the angle of the motor 4.

  Further, the control signal generation unit 11 includes a limiting unit 15 (limiting unit) and a correcting unit 16 (correcting unit) in relation to the present invention. The limiter 15 limits the current supplied to the motor 4 side. Here, since the torque of the motor 4 is proportional to the current, limiting the current is equivalent to limiting the torque. The limiter 15 limits the current to the motor 4 that is required to limit the current in order to prevent an excessive force from being applied to the workpiece or the like during the operation of the robot 3. For this reason, in the case of the robot 3 including the plurality of motors 4 as described above, the motor 4 that is limited to the current during the operation and the motor 4 that is not limited may be mixed.

  Although the details will be described later, the restriction unit 15 needs to stop the robot 3 urgently, for example, when an emergency stop switch is operated or when an emergency stop command is received from a host system. At the time of emergency stop, the current limit of the motor 4 is released. For this reason, during an emergency stop, the motor 4 can be operated with a larger current than during normal operation. As the current increases, the torque that the motor 4 can output increases as described above.

Although the details will be described later, the correction unit 16 corrects the command angle for the motor 4 for which the current restriction has been released at the time of an emergency stop.
Next, the operation of the above configuration will be described.

  The robot 3 may limit the current of the motor 4 as described above, and in that case, the command angle and the actual angle may deviate as described above. Therefore, if an emergency stop operation is performed in a state where the command angle and the actual angle are deviated, the motor 4 that is limited in current may continue to operate in an attempt to reach the command angle.

  At this time, when a plurality of motors 4 are provided, the motor 4 whose current is not limited may stop immediately, while the motor 4 whose current is limited may continue to operate. Further, when the current is limited, there is a possibility that the current necessary for decelerating in the stop control cannot be secured. In this case, the deceleration time of the motor 4 becomes long, and the arm etc. The distance traveled also becomes longer.

  As a result, there is a possibility that a problem may occur at the time of an emergency stop, such as the arm touching a workpiece or the robot 3 being in an unintended posture and touching a peripheral device or the like. Further, when the robot 3 comes into contact with a peripheral device or the like, it may be necessary to perform a calibration operation or the like, which may affect not only during an emergency stop but also after an emergency stop. However, if the current limit is simply released, the current may change abruptly, and the behavior of the motor 4 may also fluctuate and the arm may vibrate.

  Therefore, as described below, the control device 2 corrects the command angle based on the actual angle of the motor 4 so that the current of the motor 4 may be limited during normal operation. Stop control at the time of stop is performed quickly and smoothly.

  The control device 2 executes an emergency stop process shown in FIG. 3 at the time of an emergency stop such as when an emergency stop switch is operated or an emergency stop command is received. In this emergency stop process, the control device 2 first acquires the actual angle of the motor 4 (S1), and corrects the command angle based on the acquired actual angle (S2). The process in step S2 corresponds to a correction process.

  Since the control device 2 is based on the premise that the motor 4 operates in accordance with the command value, the initial value of the command angle when starting deceleration by the stop control is normal before the emergency stop. The commanded command angle is set as it is. That is, if the command angle before the emergency stop is α, the initial value of the command angle is also set to α.

  However, in the case of the motor 4 that limits the current as described above, even if the command angle before the emergency stop is α, the actual angle may be deviated from α, for example, β. is there. In this case, if α is set as the initial value of the command angle, the motor 4 tries to operate from the actual angle (β) to the initial value (α) of the command angle. Nevertheless, there is a possibility that the motor 4 performs an extra operation against the intention.

  Therefore, the control device 2 of the present embodiment corrects the initial value of the command angle with the actual angle of the motor 4. More specifically, the control device 2 corrects the command angle by setting the actual angle of the motor 4 to the initial value of the command angle.

  When the command angle is corrected, the control device 2 releases the current limitation (S3), and performs stop control based on the corrected command angle (S4). In step S4, the control device 2 starts the stop control from the corrected command angle, that is, the actual angle of the motor 4 immediately before the emergency stop in the present embodiment. For this reason, before and after the emergency stop, the motor 4 starts deceleration by the stop control without changing its angle. The process in step S3 corresponds to a release process, and the process in step S4 corresponds to a stop process.

  In step S3, the current restriction is released, so that more current can be used by the motor 4, and current, that is, torque of the motor 4 is prevented from being insufficient in the stopping process of step S4. Is done. In the stop step of step S4, the stop control is started in a state where the initial value of the command angle when starting the stop control and the actual angle of the motor 4 coincide. As a result, the motor 4 is prevented from performing an extra operation as described above, and the deceleration can be started as quickly as possible. Furthermore, in step S4, stop control, that is, control for stopping while controlling the behavior of the robot 3, is performed, so that the vehicle can be decelerated smoothly.

According to the embodiment described above, the following effects can be obtained.
The control device 2 corrects the command angle given to the motor 4 to perform stop control at the time of emergency stop so that the continuity of the operation state of the motor 4 is maintained before and after releasing the current restriction. A stop control process including (S2), a release step (S3) for releasing the current restriction on the motor 4, and a stop step (S4) for starting stop control with the command angle corrected in the correction step as an initial value. The emergency stop method to be executed is adopted. By adopting such an emergency stop method, when the stop control is performed, the current limit of the motor 4 is released, so that a larger amount of current can be used by the motor 4. Thereby, it is suppressed that the current is insufficient (torque is insufficient) during deceleration. Therefore, it is possible to secure a current necessary for the stop control and prevent the deceleration time from becoming long.

  Further, since the restriction on the current is released, even if there is a motor 4 that has a plurality of motors 4 and the current is not restricted during normal operation, the current is restricted during normal operation. Only the applied motor 4 is prevented from continuing to operate. Furthermore, even if the current is limited during normal operation and the command angle may deviate from the actual angle, stop control is started with the initial value of the command angle corrected to the actual angle during an emergency stop. Therefore, deceleration can be started quickly, and the deceleration time can be prevented from becoming longer.

  In addition, the command angle given to the motor 4 to perform stop control at the time of emergency stop is corrected so that the continuity of the operation state of the motor 4 is maintained. In the case of the present embodiment, in the correction step, the actual angle that is the actual angle of the motor 4 before releasing the current limit is set to the initial value of the command angle given to the motor 4 in order to perform stop control. Thus, since the motor 4 starts decelerating from the current actual angle when the stop control is started, the time until the stop control is started can be shortened.

  Since the stop control is started with the corrected command angle as an initial value, that is, the stop control is started in a state where the continuity of the operation state of the motor 4 is maintained, the robot when the stop control is performed. The posture does not change suddenly. As a result, it is possible to prevent the arm from vibrating, and the stop control is started with the corrected command angle as an initial value. Therefore, the behavior of the robot 3 during the stop control can be controlled as intended. it can.

  Thus, it is possible to prevent the motor 4 from performing an extra operation as described above and the arm from vibrating when starting the stop control. Further, it is possible to prevent the braking distance that the arm or the like driven by the motor 4 moves from being increased, and to stop the robot 3 promptly. Further, since the vibration of the arm is suppressed, the control for suppressing the vibration is unnecessary, and the time until stopping can be shortened.

  Further, since the stop control is performed, that is, the robot 3 is stopped while controlling the behavior of the robot 3, the robot 3 can be smoothly stopped. Therefore, in the robot 3 that may limit the current of the motor 4 during normal operation, stop control during an emergency stop can be performed quickly and smoothly.

Moreover, the control apparatus 2 provided with the control means which performs each of these processes can perform stop control at the time of emergency stop quickly and smoothly.
Further, if the robot 3 comes into contact with a peripheral device or the like, it is necessary to perform a calibration operation or the like before restarting. However, according to the emergency stop method of the present embodiment, contact with the peripheral device or the like is prevented. Therefore, it is possible to suppress an increase in work after an emergency stop, and it is possible to provide benefits to the user not only during an emergency stop but also after an emergency stop.

  Note that the correction step (S2) and the release step (S3) described above may be performed at the same time, or the order may be switched. That is, the execution order of the correction process and the cancellation process may be any as long as they are performed before the stop control (S4) is started.

(Second Embodiment)
Hereinafter, a second embodiment of the present invention will be described. Note that the configuration of this embodiment and the flow of emergency stop processing are the same as those in the first embodiment, and will be described with reference to FIGS.

  In the present embodiment, the method for correcting the command angle in step S2 of the emergency stop process shown in FIG. 3 is different from that in the first embodiment. The control device 2 according to the present embodiment uses the following two methods that can maintain the continuity of the operation state of the motor 4 in step S2 in which the command angle is corrected based on the actual angle of the motor 4 acquired in step S1. Either way, the command angle is corrected. Hereinafter, the first method is referred to as Method A for convenience, and the second method is referred to as Method B for convenience.

<Method A: Method of maintaining speed continuity as an internal state>
In the case of Method A, the control device 2 pays attention to the speed as the internal state of the control system, and in the emergency stop process, sets a new command angle that maintains the continuity of the speed of the motor 4 before and after releasing the current restriction. The obtained command angle is set to an initial value, and stop control is started.

  Usually, the control system of the robot 3 has a multiple structure of a speed control system and a position control system as described in the first embodiment. At this time, an integral element is generally used for the speed control system in order to obtain an I-type (integration type) servo system. Therefore, in this embodiment, a position proportional / velocity proportional integral control system will be described. Note that the configuration of the control system may be other than the position proportional / velocity proportional integral control system, and in this case, the present invention can be applied based on the same concept as the present embodiment. The same applies to Method B described later.

First, the command angle is r, the actual angle of the motor 4 is y, the command speed is w, the actual speed of the motor 4 is y _d (differential value of the actual angle y), the position proportional gain of the control system is K _PP , and the speed proportional gain Is K _VP , the speed integral gain is K _VI , and the torque command (that is, current command) is τ, the position proportional / velocity proportional integral control system can be expressed by the following equations (1) and (2). .

Now, in a situation where available sufficient current not applied is limited to the current, the integral control of the speed control system, the command speed w and the actual speed y _d is equal. In contrast, in a situation where current limit is applied, without obtain sufficient acceleration in the case where the current is insufficient, the actual speed y _d is smaller than the commanded speed w. In this case, in order to maintain the continuity of the speed system when releasing the emergency stop limit current comprises a command speed w and the actual speed y _d may be corrected command angle r to match.

  From the above equation (1), the command angle r can be expressed as the following equation (3).

Then, in order to obtain the command angle r of the command speed w and the actual speed y _d are the same, the (3) may be substituted into relationship w = y _d to the equation, the following (4) be determined by the formula Can do.

  If r obtained from the equation (4) is set as the initial value of the command angle for emergency stop, stop control can be performed while maintaining the continuity of the speed system. Specifically, in step S2 shown in FIG. 3, the command angle is corrected based on equation (4), the current limit is released in step S3, and stop control is performed based on the corrected command angle in step S4. Good.

  Thereby, at the time of an emergency stop, stop control can be performed while maintaining continuity of speed, and it is possible to prevent the speed from changing suddenly. Since the speed is prevented from changing suddenly, unintended operations such as a sudden change in the moving speed of the arm can be prevented. Further, since the speed changes continuously, an extra speed change does not occur and it is possible to prevent the deceleration time from becoming long.

<Method B: Method for maintaining continuity of torque (current) as an internal state>
In the case of method B, the control device 2 pays attention to the torque (current) as an internal state of the control system, and in the emergency stop process, a new continuity of the torque of the motor 4 is maintained before and after the restriction of the current is released. A command angle is obtained, the obtained command angle is set to an initial value, and stop control is started.

Assuming that the torque command before canceling the current limit is τ ₀ and the state quantity of the integrator is x _i0 , the control system can be expressed by the following equations (5) and (6). Then, from the relationship between these equations (5) and (6) and the above equation (3), equation (7) is obtained as the command angle r to be corrected.

  If r obtained from the equation (7) is set as the initial value of the command angle at the time of emergency stop, the stop control can be performed while maintaining the torque continuity.

  That is, the control device 2 corrects the command angle based on the equation (7) in step S2 shown in FIG. 3, cancels the current limit in step S3, and performs stop control based on the corrected command angle in step S4. Do.

  Thereby, at the time of an emergency stop, stop control can be performed while maintaining the continuity of the torque, and it is possible to prevent the torque from changing suddenly. Since the torque is prevented from changing suddenly, unintended operations such as a sudden increase in the force applied to the workpiece and a large change in the arm speed can be prevented.

Note that if the torque is saturated when the current restriction is released, and if it is saturated only by the output of the integrator, τ0 and K _VI x _i0 are equal to each other. The expression is the same as the expression (3) described above.

  Similar to the first embodiment, the stop control at the time of an emergency stop is performed promptly and smoothly by correcting the command angle by paying attention to the internal state of the control system as in these methods A and B. be able to.

(Third embodiment)
Hereinafter, a third embodiment of the present invention will be described.
The present embodiment is a method for correcting the state quantity of the integrator of the control system when correcting the command angle, and the continuity of the torque of the control system of the robot 3 before and after the current restriction is released. The state quantity of the integrator is also corrected so as to be maintained. The technique of this embodiment is used in combination with correction for maintaining the continuity of the operation state of the motor 4 in the first to third embodiments. Specifically, when the command angle is corrected in step S2 of the emergency stop process shown in FIG. 3, the state quantity of the integrator is also corrected.

When the command angle before canceling the current limit is r ₀ , the command speed is w ₀ , and the state quantity of the integrator is x _i0 , the torque command before and after canceling the current limit is If τ0 and the torque command after release are τ, they can be expressed by the following equations (8) and (9).

In this case, when correcting the torque command τ ₀ and the released torque command so that τ is equal, the relationship of the following equation (10) is established.

And from this equation (10), the state amount x _i integrator after releasing the limitation of the current, obtained as following equation (11).

Further, the command speed w ₀ is obtained as the following equation (12) from the relationship of the above equation (1).

From these formulas (11) and (12), the state quantity x _i of the integrator after releasing the current limit can be finally expressed by the following formula (13).

When applying the state quantity x _i of the integrator after releasing the current restriction to the method of matching the command angle described in the first embodiment with the actual angle, the expression (13) is expressed by the expression (1). From the relationship, it can be expressed as the following equation (14).

  Further, when applied to the method for maintaining the continuity of the speed system described in the method A of the second embodiment, the equation (13) is expressed as the following equation (15) from the relationship of the equation (4). Can do.

In any case, by correcting the integrator state quantity x _i , it is possible to prevent the torque from becoming discontinuous when the current limit is released. This eliminates the discontinuity of torque after the start of stop control, and reduces the risk of unintended operations due to the discontinuity of torque when performing stop control. it can.

  In addition, when applied to the method for maintaining the continuity of torque described in the method B of the second embodiment, since the continuity of torque is already maintained by the method, the method of the present embodiment is substantially effective. Is not effective. That is, equation (13) can be expressed as the following equation (16) from the relationship between equations (7) and (8), which means that the state quantity of the integrator is not corrected.

x _i = x _i0 (16)
(Other embodiments)
The present invention is not limited to the configuration exemplified in the above-described embodiment, and can be arbitrarily modified, combined, and expanded without departing from the gist thereof.

  In the embodiment, a vertical articulated robot having a plurality of motors 4 is exemplified as the robot 3, but a horizontal articulated robot or a rectangular coordinate robot may be used. Moreover, you may provide the one motor 4 like a linear motion type short axis robot. That is, the present invention can be applied to any robot having a motor whose current may be limited during normal operation regardless of the number of motors provided.

  In the drawings, 1 is a robot system, 2 is a control device (control device for a robot), 3 is a robot, and 4 is a motor.

Claims (6)

In a robot that may limit the motor current during normal operation, it is an emergency stop method for the robot to perform stop control to stop while controlling its behavior at the time of emergency stop,
When performing the stop control, a release step of releasing the current limit for the motor;
A correction step for correcting the command angle given to the motor to perform the stop control so that the continuity of the operation state of the motor is maintained before and after releasing the restriction of the current;
A stop step of starting the stop control with the command angle corrected in the correction step as an initial value;
An emergency stop method for a robot characterized in that   In the correction step, by setting an actual angle, which is an actual angle of the motor before releasing the current limit, to an initial value of the command angle given to the motor to perform the stop control, The robot emergency stop method according to claim 1, wherein the command angle is corrected so that the continuity of the angle is maintained before and after the restriction is released.   In the correction step, the speed of the motor before releasing the current limit is calculated based on the actual angle that is the actual angle of the motor, a new command angle that is the calculated speed is calculated, and the calculated new 2. The emergency stop method for a robot according to claim 1, wherein the command angle is corrected so that the continuity of the speed is maintained before and after releasing the restriction of the current by setting the command angle to an initial value. .   In the correction step, the torque of the motor before canceling the current limit is calculated based on the actual angle that is the actual angle of the motor, a new command angle that is the calculated torque is calculated, and the calculated new 2. The emergency stop method for a robot according to claim 1, wherein the command angle is corrected so that the continuity of the torque is maintained before and after releasing the restriction of the current by setting the command angle to an initial value. .   5. The internal state of the integrator is also corrected in the correction step so that the continuity of the torque of the robot is maintained before and after the current restriction is released. 6. Emergency stop method for robots.   6. A robot control apparatus that executes each step in the emergency stop method for a robot according to claim 1.

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