JP2010124645A - Robot - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a robot capable of detecting an abnormality of a DC voltage output from a DC power supply accurately without increasing the number of samplings for determining that the DC current is abnormal. <P>SOLUTION: A second control circuit 26 controls the monitoring operation of a first control circuit 25 based on a deviation of a current rotating position of a motor 11 from a command value for rotating position which is known from a feedback value from an encoder 12. In the monitoring operation, the first control circuit 25 samples a voltage Vdet according to the DC voltage Vd in a predetermined period, and outputs an abnormal state signal Sb when the voltage values obtained by sampling are found to be abnormal voltage values for a predetermined number of times consecutively. The second control circuit 26 determines that the DC voltage Vd is abnormal when it is inputted with the abnormal state signal Sb. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a robot provided with a control circuit that monitors a DC voltage output from a DC power supply device for input to an inverter device that drives a motor.

In a device such as a robot equipped with a motor and its control circuit, there is a problem that the control of the motor cannot be performed correctly when an abnormality occurs in the DC voltage input to the inverter device for driving the motor, particularly when a voltage drop occurs. Occurs. For this reason, the direct current voltage is monitored based on a voltage value sampled at a predetermined period, and when a voltage abnormality is detected, abnormality handling control such as stopping the driving of the motor is performed (for example, Patent Document 1).
JP 2004-040880 A

  The robot is often used in an environment where various noises are generated. Due to the influence of such noise, there is a possibility that the DC voltage input to the inverter device will fluctuate temporarily. When the DC voltage fluctuates due to noise, the sampled voltage value temporarily becomes an abnormal value, and it may be erroneously detected that a voltage abnormality has occurred. As a countermeasure, a configuration is used in which it is determined that a voltage abnormality has occurred when the sampled voltage value is an abnormal value continuously for a predetermined number of times or more. According to this configuration, the accuracy of abnormality detection can be increased as the number of samplings for determining that a voltage abnormality has occurred.

  However, increasing the number of samplings increases the control load of the control circuit, and it is necessary to use a high-performance CPU in order to perform efficient control and ensure the operation efficiency of the robot. Since using a high-performance CPU leads to an increase in cost, it is not desirable to increase the number of samplings. Further, when the number of samplings is increased, when a voltage abnormality occurs, the time until the abnormality is detected becomes long, and there arises a problem that the abnormality handling control such as stopping the driving of the motor is delayed.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to accurately detect an abnormality in the DC voltage without increasing the number of samplings for determining that the DC voltage output from the DC power supply apparatus is abnormal. It is to provide a robot that can detect well.

  According to the first aspect, the second control circuit sets the deviation of the feedback value indicating the rotational speed or rotational position of the motor output from the encoder to the rotational speed command value or rotational position command value of the motor to zero. The drive of the motor by the inverter device is controlled so as to be close to each other. If this deviation is equal to or less than the first threshold value set to a value higher than the deviation when the motor drive is normally controlled, the motor drive is normally controlled. Conceivable. When the drive of the motor is normally controlled, there is a high possibility that the DC voltage output from the DC power supply device is normal. On the other hand, when the deviation exceeds the first threshold value, it is considered that the drive of the motor is not normally controlled. When the drive of the motor is not normally controlled, there is a high possibility that the DC voltage is not normal. In this means, paying attention to such a relationship, the DC voltage monitoring operation by the first control circuit is controlled as follows according to the value of the deviation.

  That is, the second control circuit stops the monitoring operation by the first control circuit during a period in which the deviation is equal to or less than the first threshold, and the deviation exceeds the first threshold. In a certain period, the monitoring operation by the first control circuit is executed. In this monitoring operation, the first control circuit samples the DC voltage output from the DC power supply device at a predetermined cycle, and the voltage value acquired by sampling is an abnormal value less than a predetermined threshold voltage continuously for a predetermined number of times. If it is, an abnormal state signal is output. When the abnormal state signal is input, the second control circuit determines that the DC voltage is abnormal.

  According to such a configuration, the monitoring operation of the DC voltage is not executed during a period when the possibility that the DC voltage is normal is high. For this reason, even if the DC voltage having a normal voltage value temporarily fluctuates due to the influence of external noise or the like and becomes an abnormal voltage value, it is not determined that the DC voltage is abnormal. Therefore, erroneous detection of voltage abnormality due to the influence of noise can be prevented. On the other hand, the monitoring operation is performed during a period when the DC voltage is highly likely not normal. In the monitoring operation executed in this way, it is not necessary to increase the number of samplings for determining that the DC voltage is an abnormal value in order to remove the influence of noise. Therefore, it is possible to accurately detect an abnormality in the DC voltage without increasing the number of samplings. In addition, since the DC voltage monitoring operation is not always performed, the control loads of the first control circuit and the second control circuit are reduced accordingly, and the operation efficiency can be increased.

  According to the means described in claim 2, when the deviation exceeds the second threshold value set to a value higher than the first threshold value, the second control circuit immediately generates the DC voltage. Judge as abnormal. When the deviation is larger than the first threshold value, the possibility that the DC voltage is abnormal is further increased. In such a case, without performing the monitoring operation by the first control circuit, the second control circuit immediately determines that the DC voltage is abnormal, so that the subsequent abnormality response control can be executed promptly. it can.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 2 shows a system configuration of a general industrial robot. A robot system 1 (corresponding to a robot) shown in FIG. 2 includes a robot body 2, a controller 3 that controls the robot body 2, and a teaching pendant 4 connected to the controller 3.

  The robot body 2 is configured as an articulated type, and includes a base 5, a shoulder portion 6 supported by the base 5 so as to be turnable in the horizontal direction, and a lower arm 7 supported by the shoulder portion 6 so as to be turnable in the vertical direction. The upper arm 8 is supported on the lower arm 7 so as to be pivotable in the vertical direction, and the wrist 9 is supported on the upper arm 8 so as to be pivotable in the vertical direction. The wrist 9 includes a flange 10 that can be rotated (twisted) at the tip. Each axis provided in the robot body 2 is driven by a motor 11 or the like. An encoder 12 that outputs a pulse signal corresponding to the rotation state of the motor 11 is provided in the vicinity of the motor 11. Although not shown, a hand for gripping the work is attached to the flange 10.

  FIG. 1 is a block diagram showing an electrical configuration of a part related to the present invention in the robot system 1. In FIG. 1, the robot body 2 is provided with a motor 11 and an encoder 12. The motor 11 is an AC servo motor. The controller 3 drives a DC power supply 22 that rectifies and smoothes the AC supplied from the AC power supply 21, a voltage detection circuit 23 that detects the DC voltage Vd output from the DC power supply 22, and the motor 11. An inverter device 24, a first control circuit 25 that performs a monitoring operation of the DC voltage Vd, and a second control circuit 26 that controls these devices and circuits are provided.

  The DC power supply device 22 includes a rectifier circuit 27 and a smoothing capacitor 28. The rectifier circuit 27 has a known configuration in which a diode is connected in the form of a bridge. For example, each phase output of the single-phase 100 V AC power supply 21 is connected to the AC input terminal of the rectifier circuit 27. The DC output terminals of the rectifier circuit 27 are connected to DC power supply lines 29 and 30, respectively. A capacitor 28 is connected between the DC power supply lines 29 and 30.

  The voltage detection circuit 23 includes a series circuit of resistors 31 and 32. This series circuit is connected between the DC power supply lines 29 and 30. The voltage Vdet at the connection point of the resistors 31 and 32 is input to the first control circuit 25. The ratio of the resistance values of the resistors 31 and 32 is set so that the voltage Vdet is in a voltage range (for example, 0 V to +5 V) that can be input to the first control circuit 25.

  The inverter device 24 includes an inverter main circuit configured by three-phase full-bridge connection of six switching elements such as IGBTs (only two are shown in FIG. 1) between the DC power supply lines 29 and 30, and a drive circuit thereof. I have. A free-wheeling diode is connected between the collector and emitter of the IGBT. The gate signal is given to the gate of the IGBT from the drive circuit. The drive circuit drives each IGBT by outputting a gate signal that is pulse-width modulated based on the command signal Sa given from the second control circuit 26.

  The first control circuit 25 and the second control circuit 26 are mainly composed of a microcomputer including a CPU, a ROM, a RAM, an I / O, an A / D converter, and the like. The first control circuit 25 and the second control circuit 26 operate by receiving a power supply voltage (for example, +5 V) from the DC power supply lines 33 and 30. Therefore, the reference potential (ground) of the first control circuit 25 and the second control circuit 26 is common with the potential of the DC power supply line 30. The power supply voltage (+5 V) is generated by stepping down the DC voltage Vd of the DC power supply lines 29 and 30 by a power supply circuit (not shown).

  The first control circuit 25 samples the input voltage Vdet at a predetermined period, and performs a monitoring operation of the DC voltage Vd between the DC power supply lines 29 and 30 based on the voltage value obtained by this sampling. When the first control circuit 25 determines that the DC voltage Vd is the above-described abnormal voltage value in the monitoring operation, the first control circuit 25 outputs the abnormal state signal Sb to the second control circuit 26.

  The encoder 12 outputs a pulse signal Sc (feedback value) corresponding to the rotational position of the motor 11. The second control circuit 26 receives the pulse signal Sc and the rotational position command value θr of the motor 11 given from the outside. The second control circuit 26 has a configuration for detecting the current rotational position θ of the motor 11 based on the pulse signal Sc. The second control circuit 26 calculates a deviation Δθ of the current rotational position θ with respect to the rotational position command value θr of the motor 11, outputs a command signal Sa so that the deviation Δθ approaches zero, and the motor by the inverter device 24. 11 is feedback-controlled.

  By such feedback control, even if the DC voltage Vd slightly varies, the duty ratio of the gate signal is changed based on the command signal Sa, and the motor 11 is normally driven. However, when the DC voltage Vd becomes a voltage value (abnormal voltage value) less than a predetermined voltage value, the motor 11 cannot be driven normally even if the duty ratio of the gate signal is 100%.

  The second control circuit 26 outputs a voltage monitoring execution command Sd or a voltage monitoring stop command Se to the first control circuit 25 according to the value of the deviation Δθ. The first control circuit 25 executes or stops the monitoring operation of the DC voltage Vd based on these commands Sd and Se. When the abnormal state signal Sb is output from the first control circuit 25, the second control circuit 26 determines that the DC voltage Vd is an abnormal voltage value and stops driving the motor 11, for example. Execute.

Next, control for determining the abnormality of the DC voltage Vd in the robot system 1 will be described with reference to FIGS.
FIG. 3 is a flowchart showing the control content of the second control circuit 26. FIG. 4 is a flowchart showing the control contents of the first control circuit 25. FIG. 5 is a diagram showing the relationship between the deviation Δθ and the state of the monitoring operation of the DC voltage Vd. In the present embodiment, the first threshold value shown in FIG. 5 is set to a value slightly higher than the maximum value of the deviation Δθ that is assumed when the drive of the motor 11 is normally controlled. . Further, the second threshold value is set to a value higher than the maximum value (for example, a value that is twice or more the first threshold value). A period T1 and a period T3 in FIG. 5 are periods in which the driving of the motor 11 is normally controlled. In addition, the period T2, the period T4, and the subsequent period are periods in which the driving of the motor 11 is not normally controlled.

  First, the control contents of the second control circuit 26 will be described with reference to FIGS. When the drive of the motor 11 is normally controlled as in the periods T1 and T3, the deviation Δθ of the current rotational position θ with respect to the rotational position command value θr of the motor 11 is within the range of the first threshold value from zero. Fits in. As described above, when the deviation Δθ is less than the first threshold value (“YES” in step S1), the second control circuit 26 monitors the voltage for causing the first control circuit 25 to stop the monitoring operation. A stop instruction Se is output (step S2). Therefore, during the periods T1 and T3, the monitoring operation of the DC voltage Vd by the first control circuit 25 is stopped (voltage monitoring state = OFF).

  When the drive of the motor 11 is not normally controlled as in the periods T2 and T4, the deviation Δθ is equal to or greater than the first threshold value. In this case, however, the deviation Δθ is less than the second threshold value. Thus, when the deviation Δθ is greater than or equal to the first threshold value and less than the second threshold value (“NO” in step S1 and “YES” in step S3), the second control circuit 26 Then, a voltage monitoring execution command Sd for causing the first control circuit 25 to execute the monitoring operation is output (step S4). Therefore, during the periods T2 and T4, the monitoring operation of the DC voltage Vd by the first control circuit 25 is executed (voltage monitoring state = ON).

  In the periods T2 and T4 during which the monitoring operation by the first control circuit 25 is executed, the second control circuit 26 determines whether or not the abnormal state signal Sb has been received (step S5). When the abnormal state signal Sb is received (YES), it is determined that the DC voltage Vd between the DC power supply lines 29 and 30 is abnormal (step S6), and the driving of the motor 11 is stopped.

  For example, when the state in which the drive of the motor 11 is not normally controlled continues for a long period of time, the deviation Δθ becomes equal to or larger than the second threshold value as in the period after the period T4 (in step S3, “ NO "). In such a case, the possibility that the DC voltage Vd between the DC power supply lines 29 and 30 is an abnormal value is extremely high. Therefore, the second control circuit 26 immediately determines that the DC voltage Vd is abnormal without outputting the voltage monitoring execution command Sd (voltage monitoring state = OFF) (step S6), and drives the motor 11. Stop.

  Next, the control contents of the first control circuit 25 will be described with reference to FIGS. The first control circuit 25 starts the monitoring operation of the DC voltage Vd when the voltage monitoring execution command Sd is given from the second control circuit 26. In this monitoring operation, the first control circuit 25 detects the DC voltage when the voltage value obtained by sampling the voltage Vdet is an abnormal voltage value (voltage value lower than the threshold voltage Vth) continuously for a predetermined number of times (N times). It is determined that Vd is abnormal, and an abnormal state signal Sb is output. The variable c in FIG. 4 is for counting the predetermined number of times, and the initial value is set to zero (c = 0).

  For example, when the voltage monitoring execution command Sd is given from the second control circuit 26 at the start of the period T2, the control of the contents shown in FIG. 4 is started (START). In step U1, a voltage value obtained by sampling voltage Vdet (hereinafter referred to as voltage value Vdet) is compared with threshold voltage Vth. This threshold voltage Vth is set to a value slightly higher than the voltage value Vdet when the voltage value of the DC voltage Vd reaches the lower limit of the range in which the inverter 11 can drive the motor 11 normally.

  If the voltage value Vdet is equal to or higher than the threshold voltage Vth (“NO” in step U1), the process proceeds to step U3 while keeping the variable c as the initial value (step U2). In step U3, it is determined whether or not a voltage monitoring stop command Se is given. When the voltage monitoring stop command Se is given (“YES” in step U3), the monitoring control of the DC voltage Vd is ended (END). When the voltage monitoring stop command Se is not given (“NO” in step U3), the process returns to step U1.

  On the other hand, when the voltage value Vdet is less than the threshold voltage Vth (“YES” in step U1), the process proceeds to step U4, and the variable c is incremented (c = c + 1). In the following step U5, it is determined whether or not the variable c is N or more. If the variable c is less than N (“NO” in step U5), the process proceeds to step U3. Thereafter, steps U1, U4, U5, and U3 are repeated until the voltage monitoring stop command Se is given or the voltage value Vdet becomes equal to or higher than the threshold voltage Vth, and the variable c is sequentially incremented. If the voltage value Vdet becomes equal to or higher than the threshold voltage Vth on the way, the process proceeds to step U2, and the variable c is returned to the initial value (c = 0). When the variable c is greater than or equal to N, it is determined that the voltage value Vdet has been continuously lower than the threshold voltage Vth N times (“YES” in step U5), and an abnormal state signal Sb is output (step U6). The monitoring control of Vd is terminated (END).

As described above, according to the present embodiment, the following effects can be obtained.
The second control circuit 26 stops the monitoring operation by the first control circuit 25 during a period in which the deviation Δθ is equal to or smaller than the first threshold, and the deviation Δθ exceeds the first threshold. In a certain period, the monitoring operation by the first control circuit 25 is executed. In this monitoring operation, the first control circuit 25 samples the voltage Vdet corresponding to the DC voltage Vd at a predetermined period. The first control circuit 25 outputs an abnormal state signal Sb when the voltage value Vdet acquired by sampling is an abnormal voltage value that is less than the threshold voltage Vth for N consecutive times. When the abnormal state signal Sb is input, the second control circuit 26 determines that the DC voltage Vd is abnormal.

  According to such a configuration, the monitoring operation of the DC voltage Vd is not executed during a period in which the DC voltage Vd is likely to be normal. Therefore, even if the DC voltage Vd having a normal voltage value temporarily fluctuates due to the influence of external noise or the like and becomes an abnormal voltage value, the DC voltage Vd is not determined to be abnormal. That is, erroneous detection of voltage abnormality due to the influence of noise can be prevented. On the other hand, the monitoring operation is performed during a period when the DC voltage Vd is likely not normal. In the monitoring operation executed in this way, in order to remove the influence of noise, it is necessary to increase the predetermined number N (the number of samplings for determining that the DC voltage Vd is abnormal) in step U5 in FIG. Absent. Therefore, in the monitoring operation, an abnormality in the DC voltage Vd can be accurately detected with the same number of samplings as in the prior art.

  Thus, since abnormality is judged with the same sampling number as the past, the increase in the control load of the 1st control circuit 25 can be suppressed. Furthermore, since the monitoring operation of the DC voltage Vd is not always performed, the control load of the first control circuit 25 is reduced accordingly. Further, the control in which the second control circuit 26 acquires the deviation Δθ is a control that has been conventionally used when the motor 11 is feedback-controlled. Thus, since the second control circuit 26 diverts the control originally performed to the monitoring control of the DC voltage Vd, the control load can be suppressed to the same level as in the past. For this reason, the overall control load of the first control circuit 25 and the second control circuit 26 is reduced, and the operation efficiency can be increased. Even when the rotation of the motor 11 is stopped, the deviation Δθ is equal to or less than the first threshold value. Thus, when the rotation of the motor 11 is stopped, it is not necessary to monitor the DC voltage Vd. In such a case, it is possible to suppress performing a useless monitoring operation.

  The second control circuit 26 immediately determines that the DC voltage Vd is abnormal when the deviation Δθ exceeds the second threshold value set to a value higher than the first threshold value. When the deviation Δθ is larger than the first threshold value, the possibility that the DC voltage Vd is abnormal is further increased. In such a case, without performing the monitoring operation by the first control circuit 25, the second control circuit 26 immediately determines that the DC voltage Vd is abnormal, so that the subsequent abnormality response control is promptly executed. can do.

The present invention is not limited to the embodiment described above and illustrated in the drawings, and the following modifications or expansions are possible.
The encoder 12 may be configured to output a pulse signal (feedback value) corresponding to the rotation speed of the motor 11. In that case, the 2nd control circuit 26 should just be equipped with the structure which detects the present rotational speed of the motor 11 based on the pulse signal according to rotational speed. The second control circuit 26 only needs to have a configuration for calculating a deviation of the current rotational speed with respect to the rotational speed command value of the motor 11 given from the outside. The encoder referred to in the present invention only needs to output a feedback value indicating the rotational speed or rotational position of the motor 11, and may be a speed sensor that detects the rotational speed of the motor 11, for example.

  The motor 11 may be another type of motor such as an induction motor or a DC motor. When a DC motor is used as the motor 11, an AC / DC converter may be mounted to generate a DC voltage that is applied to the DC motor.

The electric block diagram of the robot system which shows one Embodiment of this invention Perspective view showing the configuration of the robot system Flow chart showing control contents of second control circuit Flow chart showing control contents of first control circuit Diagram showing the relationship between deviation and DC voltage monitoring operation status

Explanation of symbols

  In the drawings, 1 is a robot system (robot), 2 is a robot body, 11 is a motor, 12 is an encoder, 22 is a DC power supply device, 24 is an inverter device, 25 is a first control circuit, and 26 is a second control circuit. Indicates.

Claims (2)

A robot body having a shaft driven by a motor;
A DC power supply,
An inverter device for driving the motor by inputting a DC voltage output from the DC power supply device;
A first control circuit that performs a monitoring operation of the DC voltage based on a voltage value obtained by sampling the DC voltage at a predetermined period;
An encoder that outputs a feedback value indicating the rotational speed or rotational position of the motor;
The drive of the motor by the inverter device is controlled so that the deviation of the feedback value with respect to the rotational speed command value or rotational position command value of the motor approaches zero, and the DC voltage monitoring operation by the first control circuit A second control circuit for controlling
The first control circuit is in an abnormal state in the second control circuit when the voltage value acquired by the sampling in the monitoring operation is an abnormal voltage value less than a predetermined threshold voltage continuously for a predetermined number of times. Output signal,
In the period in which the second control circuit is equal to or less than a first threshold set to a value higher than the value of the deviation when the drive of the motor is normally controlled. The monitoring operation by the first control circuit is stopped, and the monitoring operation by the first control circuit is executed in a period in which the deviation exceeds the first threshold, and the abnormality A robot characterized by determining that the DC voltage is abnormal when a status signal is input.   The second control circuit immediately determines that the DC voltage is abnormal when the deviation exceeds a second threshold value set to a value higher than the first threshold value. The robot according to claim 1.

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