JP2011152612A - Robot control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a robot control device capable of securely stopping a robot within a predetermined time while maintaining the stopping control of the robot as much as possible. <P>SOLUTION: The robot control device includes: speed detectors 16a, 24 for detecting the action speed of the robot 2; a robot controller 12 for controlling the action of the robot 2; a speed comparator 16c for comparing the speed of the robot 2 detected by the speed detectors 16a, 24 with a comparison speed reducing from a maximum speed to zero in a first predetermined time after the robot controller 12 starts the stopping control of the robot 2; and power supply breakers 16d, 18 for cutting off power supply to the robot 2 when the speed of the robot 2 exceeds the comparison speed as the result of the comparison by the speed comparator 16c. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a robot control apparatus for stopping and controlling a robot in an emergency or the like.

  In robots such as multi-axis robots used as industrial robots, it is necessary to ensure safety by urgently stopping the robot in an emergency such as when people or obstacles enter the work area or malfunctions occur. is there. During an emergency stop of the robot, a plurality of stop modes are switched in accordance with the degree of danger, the work situation (such as an article holding situation) and the like. For example, in the IEC60204-1 and ISO10218-1 standards, when the stop command is received, the robot is stopped by interrupting the power supply to the robot, and when the stop command is received, the robot is controlled to stop. There are three categories: stop category 1 that cuts off the power supply after stopping, and stop category 2 that controls the stop of the robot when it receives a stop command and monitors the stop state of the robot while holding the power supply after stopping the robot. A plurality of stop modes are defined. Among these, when the robot is stopped by control as in the stop categories 1 and 2, it is necessary to stop the robot reliably within a predetermined time in order to ensure safety.

  As a configuration for reliably stopping the robot within a predetermined time when the robot is controlled to be stopped in this way, for example, a configuration as shown in Patent Document 1 below is known. According to the configuration of Patent Document 1, when a stop command is received, the robot is controlled to stop. However, if the speed of the robot under stop control exceeds the speed (initial speed) when the stop command is received, Shut off the power supply and stop the robot (switch the stop category from 1 or 2 to 0).

JP-T-2001-525263

  However, when a multi-axis robot is operated with linear interpolation (operation control in which the movement path of the robot tip is a straight line) or the like, the movement speed of each axis of the robot is Since the initial speed may be temporarily exceeded, when the operation speed of each axis of the robot is monitored in the configuration of the above-mentioned Patent Document 1, the stop category 0 is entered even though normal stop control is performed. May be switched. For example, if the brake is applied suddenly by shutting off the power supply while holding the article, it may cause problems such as scattering the article. Therefore, the robot is controlled as much as possible to apply an impact to the article. It is desirable to stop it (without holding the article). Therefore, it is desirable to maintain stop control as much as possible under the situation where the robot is controlled and stopped.

  In addition, when an abnormality that maintains a constant speed operation without decelerating in spite of receiving a stop command, in the configuration of Patent Document 1, the occurrence of the abnormality cannot be detected, and the stop category Since switching to 0 is not performed, there is a problem that the robot cannot be stopped within a predetermined time.

  The present invention has been made to solve the above-described problems, and provides a robot control device capable of reliably stopping a robot within a predetermined time while maintaining the stop control of the robot as much as possible. For the purpose.

  A robot control apparatus according to the present invention is a robot control apparatus that monitors the speed of a robot, a speed detector that detects an operation speed of the robot (hereinafter simply referred to as speed), a robot controller that controls the operation of the robot, A speed comparator that compares the speed of the robot detected by the speed detector with a comparative speed that decreases from the maximum speed to zero in a first predetermined time after the robot controller starts the stop control of the robot; And a power supply circuit breaker that cuts off the power supply to the robot when the speed of the robot exceeds the comparison speed as a result of the comparison by the speed comparator.

  According to the above configuration, the speed of the robot whose stop control has been started is detected by the speed detector and compared with the comparison speed. The comparison speed can be defined as the maximum time required for the robot to decelerate until it stops because the robot speed decreases from the maximum speed to zero in a predetermined time. Therefore, even when the speed of the robot temporarily increases, the speed is not more than the maximum speed as long as it is a normal operation, and does not exceed the comparison speed. That is, when the robot speed exceeds the comparison speed, it can be determined that an abnormality has occurred. In addition, since the comparison speed, which is the comparison target, also decreases with time, even if an abnormality occurs that maintains the constant speed operation without being decelerated despite receiving a stop command, the abnormality is reliably detected. be able to. When such an abnormality occurs, the power supply to the robot is cut off by the power supply breaker. Therefore, it is possible to reliably stop the robot within a predetermined time while maintaining the stop control of the robot as much as possible.

  The robot speed may be the speed of each axis of the robot, or may be an interpolation speed (for example, a linear speed) when the robot operation is interpolated by linear interpolation or the like.

  The power supply breaker may be configured to cut off the power supply to the robot when a time when the speed of the robot exceeds the comparison speed has passed for a second predetermined time or more. As a result, even when the speed of the robot temporarily exceeds the comparison speed due to erroneous speed detection, etc., the power supply to the robot will not be cut off unless the second predetermined time has elapsed. It can be performed.

  The comparison speed may be a monotonically decreasing function of time. Further, the comparison speed may be a linear function of time. According to this, it is possible to appropriately select the robot stop mode while reducing the amount of calculation for obtaining the comparison speed function.

  The speed detector may be configured to detect the speed of the robot by detecting an output from an encoder that detects rotation of a servo motor that drives the robot. When the speed detector detects the encoder output from the robot, the speed of the robot can be detected with high accuracy without providing a separate sensor or the like for detecting the speed.

  The power supply breaker may be configured to cut off the power supply to the robot when the speed of the robot becomes a predetermined stop speed or less. Accordingly, the robot can be surely stopped within a predetermined time while maintaining the stop category 1 stop control as much as possible.

  The power supply circuit breaker may be configured to maintain power supply to the robot even when the robot speed becomes zero as long as the speed of the robot does not exceed the comparison speed. Thereby, the robot can be surely stopped within a predetermined time while maintaining the stop control of the stop category 2 as much as possible.

  The present invention is configured as described above, and has an effect that the robot can be surely stopped within a predetermined time while maintaining stop control of the robot as much as possible.

It is a block diagram showing a schematic structure of a robot control device concerning one embodiment of the present invention. It is a flowchart which shows the flow of control in the robot control apparatus shown in FIG. It is a graph which shows the speed change of the robot at the time of stop control in the robot control apparatus shown in FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same or corresponding elements are denoted by the same reference symbols throughout the drawings, and redundant description thereof is omitted. FIG. 1 is a block diagram showing a schematic configuration of a robot control apparatus according to an embodiment of the present invention. As shown in FIG. 1, the robot control apparatus 1 of the present embodiment is applied to the operation control of the robot 2. In the present embodiment, an example in which one robot 2 is controlled as shown in FIG. 1 will be described, but the present invention can also be applied to a robot system in which one robot cell is configured by a plurality of robots.

  The robot 2 includes, for example, a manipulator 21 that can rotate around a plurality of axes, and a drive unit 23 of the manipulator 21. The drive unit 23 is provided with a plurality of servo motors 22 corresponding to the respective axes of the manipulator 21. Further, each motor shaft of the plurality of servo motors 22 is provided with an encoder 24 capable of detecting the respective rotation angle (amount). Note that the robot 2 is not limited to a manipulator, and may be in any form.

  The robot control apparatus 1 includes a servo amplifier 11 that operates the robot 2. The servo amplifier 11 is composed of, for example, a motor control device including a power converter capable of controlling output, and supplies power controlled in accordance with a control command from the robot controller 12 described later to a corresponding servo motor 22. By rotating this, the robot 2 (manipulator 21) is operated. A control command for the robot 2 is generated by the robot controller 12 and sent to the servo amplifier 11. Further, the output of the encoder 24 is input to the robot controller 12, and the robot 2 is feedback-controlled. Further, the robot controller 12 is configured to receive an external stop signal, which will be described later, and each servo motor according to an external stop command (stop signal, etc.) and the state of the robot 2 (control status). By controlling 22, the robot 2 is controlled to stop. Further, the servo amplifier 11 is configured to supply power from the power source 3 to the robot 2.

  As described above, the servo amplifier 11 performs operation control and power supply control of each servo motor 22 of the robot 2 based on the control command from the robot controller 12.

  In a power supply path between the power supply 3 and the servo amplifier 11, a power supply switch 13 that executes or cuts off power supply from the power supply 3 to the servo amplifier 11 is provided. As the power supply switch 16, for example, a magnet contactor or the like is applicable.

  The robot control apparatus 1 according to the present embodiment includes a safety unit 14 that cuts off the power supply to the robot 2 based on the encoder output of the robot 2 and an external stop command. The safety unit 14 receives an output from the encoder 24 of the drive unit 23, performs an interface (I / F) 15 that performs filtering and the like, and an arithmetic unit that performs an operation related to the speed of the robot 2 based on the encoder output acquired by the interface 15 16, a storage unit 17 that stores various data, and a power supply cutoff circuit 18 that switches the power supply switch 13 from the power supply state to the power cutoff state based on the result calculated by the arithmetic unit 16.

  The safety unit 14 includes, for example, a microcomputer, and the arithmetic unit 16 uses, for example, a CPU of the microcomputer. Further, for example, an internal memory of this microcomputer is used for the storage device 17. The arithmetic unit 16 and the storage unit 17 are connected to each other. The storage device 17 stores a control program. Furthermore, the storage device 17 stores various data. The computing unit 16 performs processing and control such as computation by reading and executing the control program stored in the storage unit 17. Specifically, the computing unit 16 performs a process including a speed comparison calculation based on an external stop command and an encoder output of the robot 2 captured by the interface 15, and stores these processing results in the storage unit 17. Alternatively, the power supply cutoff circuit 18 is controlled based on the processing result.

  In the present embodiment, the configuration in which the safety unit 14 is provided separately from the robot controller 12 is described. However, the robot controller 12 may have a configuration in which the safety unit 14 is provided. 12 may function as the safety unit 14.

  Here, the stop command from the outside includes a normal stop command by a normal stop operation and an emergency stop command in an emergency. The normal stop command by the normal stop operation includes, for example, a signal input from a remote control unit (not shown) such as a computer arranged away from the robot 2, and the robot 2 receiving the normal stop command For example, it is stopped by stop control of stop category 2. In this case, when receiving the normal stop command, the robot controller 12 controls the stop of the robot 2 and monitors the stop state of the robot 2 while holding the power supply after the robot 2 stops.

  The emergency stop command may be an emergency stop command generated when an emergency stop button (not shown) provided near the robot 2 or the corresponding control panel is operated, or an intrusion sensor such as a light curtain. An intrusion detection signal or the like generated when it is detected that a human body or the like has entered a predetermined range around the robot 2 is included. The robot 2 that has received the emergency stop command is stopped, for example, by stop control of stop category 1 or stop category 0. For example, when an emergency stop button is operated, stop control is performed with stop category 0, and when the intrusion sensor detects intrusion, stop control is performed with stop category 1. In this case, upon receiving an emergency stop command, the robot controller 12 immediately shuts off the power supply to the robot 2 in response to the emergency stop command and stops the robot 2, or stops the robot 2 by controlling the robot 2 to stop. The power supply is cut off later.

  Even in the case of an emergency stop command from the same transmission source, the stop category may be switched depending on the situation of the robot 2 (control mode, whether or not an object is gripped, etc.).

  The computing unit 16 functions as a speed detection unit 16 a that detects the speed of the robot 2 based on the encoder output of the robot 2 captured by the interface 15. The speed of the robot 2 means the operation speed of the robot 2, specifically, the moving speed of each part (link (arm member), hand (tool), etc.) of the manipulator 21. That is, the encoder 24 and the speed detector 16a constitute a speed detector. Further, the calculator 16 also functions as a comparison speed function calculation unit 16b that calculates a comparison speed function such that the speed of the robot 2 decreases from the maximum speed to 0 in a predetermined time (first predetermined time). The computing unit 16 also detects the speed of the robot 2 detected by the speed detector from the start of the deceleration of the robot by the robot controller 12, and the comparison speed based on the comparison speed function calculated by the comparison speed function calculation unit 16b. It also functions as a speed comparison unit 16c that compares the two. That is, the comparison speed function calculation unit 16b and the speed comparison unit 16c constitute a speed comparator. Further, the arithmetic unit 16 may be a power supply cutoff unit 16d that controls the power supply cutoff circuit 18 to cut off the power supply to the robot 2 when the speed of the robot 2 exceeds the comparison speed in the speed comparator. Function. That is, the power supply cutoff unit 16d and the power supply cutoff circuit 18 constitute a power supply breaker.

  FIG. 2 is a flowchart showing a flow of control in the robot control apparatus shown in FIG. First, when power is supplied from the power source 3 to the servo amplifier 11, the power supply switch 13 is turned on so that the robot 2 can be operated. In this state, the servo amplifier 11 controls each servo motor 22 of the robot 2 based on a control command from the robot controller 12. Thereby, the operation of the robot 2 is controlled.

  In such an operation state of the robot 2, the arithmetic unit 16 of the safety unit 14 monitors whether or not an external stop command is input (step S1), as shown in FIG. When an external stop command is input (Yes in step S1), the computing unit 16 determines whether to control and stop the robot 2 based on the stop command and / or the control status of the robot 2, that is, It is determined whether or not the stop category is other than 0 (step S2).

  When the stop category is other than 0 (Yes in step S2), in order to control and stop the robot 2, the calculator 16 functions as the comparison speed function calculation unit 16b and calculates the comparison speed function. Specifically, a comparison speed function is calculated such that the speed of the robot 2 decreases from the maximum speed to 0 in a predetermined time (first predetermined time) based on the capability of the servo motor 22 of the robot 2 (step S3). .

FIG. 3 is a graph showing changes in the speed of the robot during stop control in the robot control apparatus shown in FIG. In the present embodiment, a case where the robot 2 is moving at constant speed will be described as an example. The comparison speed function f (t) is defined as t ₀ when the arithmetic unit 16 of the safety unit 14 receives the stop command, from time t ₁ after elapse of a predetermined time from t ₀ to time t ₂ after elapse of the predetermined time. The speed of the robot 2 is calculated as a function that makes the maximum speed V _m 0. In the present embodiment, the comparison speed function f (t) is a monotone decreasing function, and more specifically, a linear function. Specifically, the comparison speed function is exemplified as f (t) = − (V _m / (t ₂ −t ₁ )) t + V _m · t ₂ / (t ₂ −t ₁ ) (1).

In the present embodiment, the entire comparison speed function f (t) is calculated based on the time t ₀ when the calculator 16 receives the stop command. However, the present invention is not limited to this. A comparison speed function to which a plurality of parameters can be substituted may be stored in advance, and the parameter of the comparison speed function may be calculated and substituted based on the time t ₀ when the stop command is received. Specifically, after receiving the stop command, the preparation time T _p (the time from time t ₀ to time t ₁ ) required for the robot 2 to actually start the stop operation and the robot 2 decelerates from the maximum speed. start to leave set before stopping the (necessary) maximum stop time allowed T _{m (time} from time t ₁ to time t ₂₎ in advance, and these preparation time T _p and the maximum stop time T _m it may be calculated to compare speed function f (t) on the basis of the time t ₀ which has received the stop instruction. That is, f (t) = − (V _m / t _m ) t + V _m obtained by substituting t ₁ = t ₀ + T _p , t ₂ = t ₀ + T _p + T _m in the above formula (1) as a comparison speed function. _{· (t 0 + T p +} T m) / t m may be used. As described above, the comparison speed function f (t) can be determined based only on the time t _{0 when the} stop command is received.

When the preparation time T _p elapses from the time t _{0 when the} stop command is received and the time t ₁ is reached (after the comparison speed function is calculated), the robot controller 12 starts the stop control of the robot 2 via the servo amplifier 11. (Step S4). The stop control of the robot 2 may be controlled such that the speed of each axis of the manipulator 21 (rotational speed of each servo motor 22) is reduced, or the tip of the manipulator 21 is interpolated such as linear interpolation or circular interpolation. When operating by calculation, control may be performed so that the linear moving speed or the circular arc moving speed at the tip of the manipulator 21 decreases.

When the stop control of the robot 2 is started, the arithmetic unit 16 of the safety unit 14 functions as the speed detection unit 16a and detects the output from each encoder 24 corresponding to the operation of each servo motor 22 of the robot 2. Thus, the speed of the robot 2 is detected (step S5). As for the speed of the robot 2, the speed of each axis of the manipulator 21 (the rotational speed of each servo motor 22) may be detected as it is as the speed of the robot 2, or the speed detection unit 16a performs an interpolation calculation such as linear interpolation or circular interpolation. Then, the speed of the robot 2 may be detected by calculating the interpolation speed such as the linear speed or arc speed of the tip of the manipulator 21 from the speed of each axis. The detected speed of the robot 2 (hereinafter referred to as “detected speed”) is temporarily stored in the storage unit 17. Further, the maximum speed V _m of the robot 2 used for the above-described comparison speed function f (t) may be a speed calculated for each axis of the manipulator 21 or may be an interpolation speed calculated by an interpolation calculation.

  The computing unit 16 also functions as the speed comparison unit 16c, and the detected speed of the robot 2 detected in step S5 and the comparison speed that is a dependent variable of the comparison speed function f (t) (the comparison speed function at the time t). f (t) value) (step S6). When the detection speed of the robot 2 exceeds the comparison speed (Yes in step S6), the arithmetic unit 16 functions as the power supply cut-off unit 16d, opens the power supply switch 13, and starts from the power supply 3 to the servo amplifier 11 (robot 2). The power supply cutoff circuit 18 is controlled so as to cut off the power supply to the power supply (step S7). That is, when the detection speed of the robot 2 exceeds the comparison speed, the stop category is switched to 0.

On the other hand, if the detected velocity of the robot 2 does not exceed the comparison speed (No in step S6), and calculator 16 determines whether the speed detected speed of the robot 2 is predetermined (stop speed) V _s or less (Step S8). If the detected speed of the robot 2 is greater than the stop speed _{V s} (No in step S8), and continues the deceleration control (step S6). When the detected speed of the robot 2 becomes equal to or lower than the stop speed V _s (Yes in step S8), the computing unit 16 determines whether the stop category is 1 based on the stop command and / or the control status of the robot 2. Is determined (step S9).

  When the stop category is 1 (Yes in step S9), the calculation unit 16 functions as the power supply cutoff unit 16d, opens the power supply switch 13, and supplies power from the power source 3 to the servo amplifier 11 (robot 2). Cut off. Thereby, the robot 2 can be surely stopped within a predetermined time while maintaining stop control of the stop category 1 as much as possible.

Even when the detected speed of the robot 2 is equal to or lower than the stop speed V _s , if the stop category is not 1 (that is, if the stop category is 2), the computing unit 16 does not perform power supply cutoff control. The power supply to the robot 2 is maintained (No in step S9). Thereby, the robot 2 can be reliably stopped within a predetermined time while maintaining the stop control of the stop category 2 as much as possible. Further, although not shown, the computing unit 16 continuously detects the speed from the output from each encoder 24, and cuts off the power supply to the robot 2 when the detected speed of the robot 2 becomes 0 or more. Control as follows.

  As described above, according to the above configuration, the speed of the robot 2 that has started to decelerate based on the stop command is detected by the speed detector and compared with the comparison speed according to the comparison speed function f (t). The comparison speed function f (t) is a function that decreases the speed of the robot 2 from the maximum speed to 0 in a predetermined time, and is defined as the maximum time required for the robot 2 to decelerate until it stops. can do. Therefore, even when the speed of the robot 2 temporarily increases, the speed is not more than the maximum speed as long as it is a normal operation (shown in FIG. 3A), and the comparison speed according to the comparison speed function f (t). Not exceed. That is, when the speed of the robot 2 exceeds the speed according to the comparison speed function f (t), it can be determined that an abnormality has occurred.

  Further, since the comparison speed according to the comparison speed function f (t) to be compared also decreases with time, as shown in FIG. 3B, the robot 2 is not decelerated despite the stop command. Even when an abnormality that maintains constant speed operation occurs, the abnormality can be reliably detected. Furthermore, in this embodiment, since the comparison speed function f (t) is a linear function, the stop mode of the robot 2 is appropriately selected while reducing the amount of calculation for obtaining the comparison speed function f (t). be able to. When such an abnormality occurs, the power supply to the robot 2 is interrupted by the power supply interrupter configured by the arithmetic unit 16 and the power supply interrupting circuit 18. Therefore, it is possible to reliably stop the robot 2 within a predetermined time (first predetermined time) while maintaining the stop control of the robot 2 as much as possible.

  In addition, since the speed of the robot 2 is detected by detecting the encoder output from the robot 2, the speed of the robot 2 can be detected with high accuracy without providing a separate sensor or the like for detecting the speed.

In the present embodiment, as shown in FIG. 3B, the computing unit 16 that functions as the power supply cutoff unit 16d has a predetermined time (second predetermined time) T when the detection speed of the robot 2 exceeds the comparison speed. The power supply to the robot 2 is cut off when _i or more have elapsed. As a result, even if the detection speed of the robot temporarily exceeds the comparison speed due to erroneous detection of the speed or the like, the power supply to the robot 2 is not cut off unless the predetermined time T _i elapses. Control can be performed.

  In the present embodiment, the comparison speed function f (t) is calculated by the calculator 16 of the safety unit 14 in accordance with the stop signal. However, the present invention is not limited to this, and for example, another controller ( For example, the calculation may be performed by the robot controller 12 or the like, and the calculation result may be stored in the storage unit 17 of the safety unit 14. Alternatively, the comparison speed function f (t) may be calculated every time a stop command is received from the outside, or the comparison speed function f (t) calculated in advance may be stored in the storage unit 17. Good. When stored in advance, the time axis of the comparison speed function f (t) is calculated as a function that makes t = 0 when the robot 2 starts to decelerate.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various improvements, changes, and modifications can be made without departing from the spirit of the present invention.

  The robot control apparatus of the present invention is useful for reliably stopping the robot within a predetermined time while maintaining the stop control of the robot as much as possible.

DESCRIPTION OF SYMBOLS 1 Robot controller 2 Robot 3 Power supply 11 Servo amplifier 12 Robot controller 13 Power supply switch 14 Safety unit 15 Interface 16 Calculator 16a Speed detector (speed detector)
16b Comparison speed function calculation part 16c Speed comparison part (speed comparator)
16d Power supply cutoff unit (Power supply breaker)
17 Memory 18 Power supply cut-off circuit (Power supply breaker)
21 Manipulator 22 Servo motor 23 Drive unit 24 Encoder (speed detector)

Claims (7)

In the robot controller that monitors the speed of the robot,
A speed detector for detecting the operation speed of the robot (hereinafter simply referred to as speed);
A robot controller for controlling the operation of the robot;
A speed comparator that compares the speed of the robot detected by the speed detector with a comparison speed that decreases from a maximum speed to zero in a first predetermined time after the robot controller starts the stop control of the robot;
A robot control apparatus comprising: a power supply circuit breaker that cuts off power supply to the robot when the speed of the robot exceeds the comparison speed as a result of comparison by the speed comparator.   2. The robot control device according to claim 1, wherein the power supply circuit breaker interrupts power supply to the robot when a time when the speed of the robot exceeds the comparison speed exceeds a second predetermined time.   The robot control apparatus according to claim 1, wherein the comparison speed is a monotonously decreasing function of time.   The robot control apparatus according to claim 3, wherein the comparison speed is a linear function of time.   The robot control apparatus according to claim 1, wherein the speed detector detects the speed of the robot by detecting an output of an encoder that detects rotation of a servo motor that drives the robot.   The robot control apparatus according to any one of claims 1 to 5, wherein the power supply interrupter interrupts power supply to the robot when the speed of the robot becomes equal to or lower than a predetermined stop speed. 6. The power supply circuit breaker according to claim 1, wherein the power supply circuit breaker maintains power supply to the robot even when the speed of the robot becomes zero as long as the speed of the robot does not exceed the comparison speed. Robot controller.

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