阅读说明：本技术 一种交流伺服控制系统 (Alternating current servo control system ) 是由 董直姜 张太猛 张太为 于 2020-05-11 设计创作，主要内容包括：一种交流伺服控制系统,用于控制交流伺服电机,包括：中央处理单元MCU、人机交互单元、接口单元,编码器和电机控制单元,中央处理单元MCU分别连接人机交互单元、接口单元和电机控制单元；编码器被安装于电机上,以反馈电机的动作；电机控制单元与编码器连接,用于根据编码器的反馈来生成转矩指令。根据本发明所述的交流伺服控制系统,既能及时地检测电机的失控,又能抑制误检测。(An ac servo control system for controlling an ac servo motor, comprising: the system comprises a central processing unit MCU, a man-machine interaction unit, an interface unit, an encoder and a motor control unit, wherein the central processing unit MCU is respectively connected with the man-machine interaction unit, the interface unit and the motor control unit; the encoder is arranged on the motor to feed back the action of the motor; the motor control unit is connected with the encoder and used for generating a torque command according to feedback of the encoder. According to the alternating current servo control system, the out-of-control of the motor can be detected timely, and the false detection can be restrained.)

1. An ac servo control system for controlling an ac servo motor, comprising:

the system comprises a central processing unit MCU, a man-machine interaction unit, an interface unit, an encoder and a motor control unit, wherein the central processing unit MCU is respectively connected with the man-machine interaction unit, the interface unit and the motor control unit;

the encoder is arranged on the motor to feed back the action of the motor;

the motor control unit is connected with the encoder and used for generating a torque command according to feedback of the encoder.

2. The ac servo control system according to claim 1, the motor control unit generating a torque command to control the motor in such a manner that a detected speed of the motor coincides with a command speed, the motor control unit comprising:

a torque command differentiation means for differentiating the torque command to obtain a torque command differentiation value;

the second-order differential unit is used for carrying out second-order differential on the detection speed of the motor to obtain motor jerk; and

the out-of-control detection unit is used for judging that the motor is in an out-of-control state if the abnormal state lasts for more than a specified time;

the abnormal state is a state in which the sign of the motor jerk does not coincide with the sign of the torque command differential value.

3. The AC servo control system of claim 2,

the runaway detection means resets the duration of the abnormal state to zero when the sign of the motor jerk matches the sign of the torque command differential value before the abnormal state continues for the predetermined time or longer.

4. The AC servo control system of claim 3,

the runaway detection means also determines that the motor is in an abnormal state if a first order differential value of the motor, that is, a sign of motor acceleration does not coincide with a sign of the torque command when the torque command is not 0 and a differential value of the torque command is 0.

5. The AC servo control system of claim 4,

the runaway detection means resets the duration of the abnormal state to zero when the sign of the motor acceleration matches the sign of the torque command when the torque command is not 0 and the differential value of the torque command is 0 before the abnormal state continues for the predetermined time or more.

6. The ac servo control system of claim 2, wherein

The torque command differentiating means and the second order differentiating means apply a low pass filter to an input signal to obtain a differential value.

7. The ac servo control system of any of claims 2 to 6, further comprising:

and an emergency stop means for stopping the motor by at least one of blocking current supply to the motor, using a dynamic brake, and setting the torque command to 0 when the runaway state of the motor is detected by the runaway detection means.

8. The AC servo control system of claim 1,

the human-computer interaction unit comprises an input display unit and a communication control unit, and the input display unit is connected with the MCU through the communication control unit.

9. The AC servo control system of claim 1,

the interface unit comprises a 485 bus interface, a CAN bus interface, an Ethercat bus interface and an M2/M3 bus interface.

10. A runaway state detection method of a motor performed in the ac servo control system of claims 1-9, the motor control unit generating a torque command to control the motor in such a manner that a detected speed of the motor coincides with a command speed, the runaway state detection method comprising the steps of:

differentiating the torque command to obtain a torque command differential value;

carrying out second-order differentiation on the detected speed of the motor to obtain motor jerk; and

and if the abnormal state that the motor jerk sign is inconsistent with the torque command differential value sign continues for more than a specified time, judging that the motor is in a runaway state.

Technical Field

The invention belongs to the technical field of digital control, and relates to a drive control technology of an alternating current servo motor, which is particularly used for detecting the out-of-control of the motor.

Background

The ac servo motor enters an out-of-control state in the reverse direction of the acceleration command due to erroneous wiring or the like. There are generally two methods known in the art for detecting such an out-of-control condition:

(1) when the servo motor is in acceleration, if the acceleration direction of the servo motor is different from a torque instruction to the servo motor, the servo motor is judged to be in an out-of-control state. However, this method causes erroneous detection when the motor is operated by an offset or unbalanced load.

(2) And monitoring the speed after the servo motor starts accelerating, comparing the speed with the displacement speed, and updating the displacement speed and detecting the out-of-control of the servo motor if the speed is higher than the displacement speed. However, this method cannot detect runaway until the motor speed exceeds the peak speed, and especially in the case of a large inertial load, runaway detection takes time. Further, false detection may occur when an oscillation in which control is unstable occurs due to gain setting of the controller.

Disclosure of Invention

The invention aims to detect out-of-control of a motor in time and inhibit error detection.

In order to solve the above technical problems, the present invention discloses an ac servo control system for controlling an ac servo motor, including: the system comprises a central processing unit MCU, a man-machine interaction unit, an interface unit, an encoder and a motor control unit, wherein the central processing unit MCU is respectively connected with the man-machine interaction unit, the interface unit and the motor control unit; the encoder is arranged on the motor to detect the action of the motor; the motor control unit is connected with the encoder and used for generating a torque command according to feedback of the encoder.

In the present invention, the sign of the jerk of the motor is compared with the sign of the torque command differential value, and if the signs do not match for a predetermined time or longer, it is determined that the motor is out of control.

Specifically, a motor control unit according to the present invention generates a torque command to control a motor so that a detected speed of the motor matches a command speed, the motor control unit including: a torque command differentiation means for differentiating the torque command to obtain a torque command differentiation value; the second-order differential part is used for carrying out second-order differential on the detection speed of the motor so as to obtain motor jerk; and a runaway detection means for determining that the motor is in a runaway state if an abnormal state in which the sign of the motor jerk does not coincide with the sign of the torque command differential value continues for a predetermined time or longer.

When there is an unbalanced load or the like, there is a possibility that the torque command does not match the sign of the motor acceleration even in a normal operation, but the torque command differential value and the sign of the motor jerk match as long as they are in a normal operation. Therefore, the motor control unit of the present invention can detect the runaway of the motor without fail and quickly even in the presence of an unbalanced load.

The runaway detection means of the present invention compares the torque command differential value with the sign of motor jerk at predetermined time intervals, and can determine that the motor is in a runaway state if the result of determination that the torque command differential value does not match the sign of motor jerk is repeatedly detected a predetermined number of times. For example, when the predetermined time is 10 milliseconds, the symbol match/mismatch is determined every 1 millisecond, and when 10 consecutive times are mismatches, it is determined that the state is out of control.

Preferably, the runaway detection means in the present invention determines that the motor is in the abnormal state even when the first order differential value of the motor, i.e., the sign of the motor acceleration does not match the sign of the torque command when the torque command is not 0 and the differential value of the torque command is 0.

A situation in which the torque instruction value is saturated in runaway is assumed. At this time, the torque command differential value becomes 0, and runaway cannot be detected depending on the sign comparison between the torque command differential value and the motor jerk. Therefore, if the torque command is not 0 and the torque command differential value is 0, the runaway can be detected from the sign of the motor acceleration and the sign of the torque command.

Since the state in which the motor acceleration does not match the torque command is not normally operated despite the saturation of the torque, the determination based on the signs of the motor acceleration and the torque command does not cause erroneous detection even when the torque is saturated.

The runaway state detection means may regard, as the same abnormal state, an abnormal state in which the differential value based on the torque command does not coincide with the motor jerk, and an abnormal state in which the differential value based on the torque command is not coincident with the motor acceleration when the torque command is saturated, and may determine that the motor has run away when any one of the states is satisfied for a predetermined time or longer.

Alternatively, the runaway state detection means may regard the two runaway states as different ones, and determine that the motor has run away when one of the conditions continues continuously for a predetermined time or longer.

The runaway detector in the present invention may reset the duration of the abnormal state to zero when the sign of the motor jerk matches the sign of the torque command differential value before the abnormal state continues for the predetermined time or longer. In the present invention, before the abnormal state continues for the predetermined time or more, when the torque command is not 0 and the differential value of the torque command is 0, the runaway detector may reset the duration of the abnormal state to zero if the sign of the motor acceleration matches the sign of the torque command.

With this configuration, it is possible to eliminate erroneous detection due to symbol inconsistency that occurs sporadically or due to symbol inconsistency caused by noise or the like.

Preferably, the torque command differentiating means and the second order differentiating means apply a low-pass filter to an input signal to obtain a differential value. If the band of the differentiating section is not limited, the higher the frequency, the higher the gain becomes, and the larger the noise becomes, so that erroneous detection is more likely to occur. By providing the differentiating section with a low-pass filter to limit the band of the differentiated signal, erroneous detection due to noise caused by differentiation can be suppressed.

Preferably, the motor control unit of the present invention further includes: and an emergency stop means for stopping the motor by at least one of blocking current supply to the motor, using a dynamic brake, and setting the torque command to 0 when the runaway state of the motor is detected by the runaway detection means.

According to this configuration, when the runaway of the motor is detected, the motor can be immediately stopped.

Preferably, the human-computer interaction unit of the invention comprises an input display unit and a communication control unit, wherein the input display unit is connected with the central processing unit MCU through the communication control unit.

It is also preferred that the interface unit of the present invention comprises a 485 bus interface, a CAN bus interface, an Ethercat bus interface, and an M2/M3 bus interface.

The present invention discloses a motor control unit applied to the ac servo control system, which generates a torque command to control a motor in such a manner that a detected speed of the motor coincides with a command speed, the motor control unit including: and a runaway state detection means for determining that the motor is in an abnormal state if a sign of a motor jerk, which is a second order differential value of the detected speed of the motor, does not coincide with a sign of a differential value of the torque command, and determining that the motor is in a runaway state if the abnormal state continues for a predetermined time or longer.

The present invention can be understood as a motor control unit having at least a part of the above-described functions. The present invention can also be understood as a control method for executing at least a part of the processing. Furthermore, the present invention can also be understood as a computer program for causing a computer to execute the method or a computer-readable storage medium that stores the computer program non-temporarily. The components and processes described above can be combined with each other as much as possible to constitute the present invention.

Technical effects

The motor control unit can not only timely detect the out-of-control of the motor, but also inhibit the false detection.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below.

Fig. 1 is a schematic diagram of the connection between the drive control system and the ac servo motor according to the present invention.

Fig. 2 is a block diagram of a motor control unit in the first embodiment.

Fig. 3 is a flowchart of the runaway state detection process in the first embodiment.

Fig. 4A to 4E are diagrams illustrating detection of a runaway state when a wiring is erroneously connected in the first embodiment.

Fig. 5A to 5E are diagrams illustrating detection of a runaway state when an external disturbance occurs in the first embodiment.

Fig. 6 is a block diagram of a motor control unit in the second embodiment.

Fig. 7 is a flowchart of the runaway state detection process in the second embodiment.

Fig. 8A to 8E are diagrams illustrating the runaway state detection processing in the second embodiment.

Detailed Description

The technical solution in the embodiments of the present invention is clearly and completely described below with reference to the drawings in the embodiments of the present invention.

The first embodiment:

fig. 1 is a schematic diagram of the connection between the drive control system and the ac servo motor according to the present invention.

An ac servo control system for controlling an ac servo motor, comprising: the system comprises a central processing unit MCU, a man-machine interaction unit, an interface unit, an encoder and a motor control unit, wherein the central processing unit MCU is respectively connected with the man-machine interaction unit, the interface unit and the motor control unit; the encoder is arranged on the motor to feed back the action of the motor; the motor control unit is connected with the encoder and used for generating a torque command according to feedback of the encoder.

Fig. 2 is a schematic block diagram of a motor control unit incorporated with the present invention and applied to the above-described ac servo control system. The motor control unit 1 has the following functions: a torque command is generated in such a manner that the speed of the motor 2 coincides with a speed command from the central processing unit MCU to control the motor 2, and runaway of the motor 2 is detected. The motor 2 is incorporated in various mechanical devices (not shown) as an actuator of the devices (for example, an arm of an industrial robot or a conveying device). The motor 2 is, for example, an ac motor. The encoder 3 is attached to the motor 2 to detect the operation of the motor 2. The encoder 3 contains position information on the rotational position (angle) of the rotating shaft of the motor 2, information on the rotational speed of the rotating shaft, and the like. As the encoder 3, a general incremental encoder, an absolute encoder, or the like can be used.

A more specific configuration of the motor control unit 1 will be explained. The motor control unit 1 includes a speed command input unit 11, a speed control unit 12, a current controller 13, a speed detector 14, a torque command differentiator 15, a second-order differentiator 16, a comparator 17, a runaway state detection unit 18, and a motor stop unit 19. In these configurations, the torque command differentiator 15, the second order differentiator 16, the comparator 17, and the runaway state detection unit 18 are functional units for detecting runaway of the motor 2.

The speed command input unit 11 receives a command speed of the motor 2 from the central processing unit MCU. The speed detector 14 acquires the actual speed of the motor 2 based on the feedback signal from the encoder 3. The speed control unit 12 generates a torque command so that the command speed matches the detected speed. The current controller 13 turns on/off a switching element such as an Insulated Gate Bipolar Transistor (IGBT) based on a torque command to supply ac power to the motor 2.

The torque command differentiator 15 receives the torque command generated by the speed control unit 12, and calculates a differential value (first order differential value) thereof. Hereinafter, the output of the torque command differentiator 15 is referred to as a torque command differential value.

The second order differentiator 16 receives the actual speed of the motor output from the speed detector 14, and calculates a second order differentiation value thereof. Hereinafter, the output of the motor actual speed second order differentiator 16 is referred to as a motor jerk.

The comparator 17 receives the torque command differential value from the torque command differentiator 15 and the motor jerk from the second-order differentiator 16, and determines whether or not the signs of these values match. The comparison result by the comparator 17 is input to the runaway state detection portion 18.

The runaway state detection portion 18 determines whether the motor 2 is in a runaway state using the comparison result made by the comparator 17. Specifically, the runaway state detection unit 18 determines that the motor 2 is in the runaway state when the torque command differential value does not match the motor jerk sign, and determines that the abnormal state continues for a predetermined time or longer. In fig. 2, only the comparison result of the comparator 17 is input to the runaway state detection unit 18, but actually, a torque command value or a motor actual speed is also input, and the runaway state detection of the motor 2 is also performed using these pieces of information. The details of the runaway state detection process will be described below with reference to a flowchart.

The motor stop unit 19 receives a signal indicating that the runaway state is detected from the runaway state detection unit 18, and then emergently stops the motor 2. The motor stopping unit 19 stops the motor 2 by, for example, one of blocking the supply of current from the current controller 13 to the motor 2, using a dynamic brake (regenerative brake), and setting a torque command to zero, or a combination of a plurality of these.

Fig. 3 is a flowchart showing a flow of the runaway state detection process performed by the runaway state detection unit 18. The processing shown in fig. 3 is executed periodically, and the execution interval thereof may be arbitrary, and may be set to, for example, about 1 ms.

First, as a precondition for the runaway state detection, the runaway state detection unit 18 confirms that the motor detection speed is equal to or higher than the first threshold value in step S11 and that the torque command is equal to or higher than the second threshold value in step S12. The determination in step S11 is to confirm that the motor is operating, and a sufficiently small value is set as the first threshold value. The determination in step S12 is for avoiding erroneous detection, and a value of, for example, about 10% of the rated torque is set as the second threshold value.

If it is determined in any of steps S11 and S12 that the determination is not satisfied (no in S11 or no in S12), the routine proceeds to step S17, where the runaway state detection unit 18 resets the abnormality duration time for counting the continuation of the abnormal state to zero.

If both the determinations at steps S11 and S12 are satisfied (yes at S11 and yes at S12), the routine proceeds to step S13, where the runaway state detector 18 determines whether or not the torque command differential value and the motor jerk are different in sign. This determination is made based on the output from the comparator 17.

If the torque command differential value is not equal to the motor jerk sign (yes at S13), the routine proceeds to step S14, and the runaway state detector 18 increments the abnormality duration. On the other hand, if the torque command differential value matches the motor jerk sign (no at S13), the routine proceeds to step S17, and the runaway state detector 18 resets the abnormality duration to zero.

In step S15, the runaway state detection unit 18 determines whether or not the abnormality duration is equal to or greater than a third threshold. The third threshold value is a time period during which the motor can be determined to be out of control when the torque command differential value does not match the motor jerk sign for the predetermined time period or longer. As the third threshold value, for example, 10ms (the value of the counter is 10) can be used.

If the abnormality duration is less than the third threshold value (no at S14), the runaway state detection unit 18 remains the determination and ends the process. On the other hand, if the abnormality duration is equal to or longer than the third threshold (yes at S14), the process proceeds to step S16, and the runaway state detector 18 determines that the motor 2 is in the runaway state. When the runaway of the motor 2 is detected, an emergency stop measure of the motor 2 is implemented by the motor stop portion 19.

The runaway state detection processing in a specific case will be described with reference to fig. 4A to 4E and fig. 5A to 5E.

Fig. 4A to 4E are diagrams showing a torque command value, a motor acceleration, a motor speed, a torque command differential value, and a motor jerk when the motor control unit 1 and the motor 2 are connected to each other. At this time, the direction of the torque command is opposite to the rotation direction of the motor, and the speed control loop constitutes positive feedback. Therefore, the torque command increases with time, and the speed of the motor 2 also increases in the reverse direction.

In the present embodiment, the runaway of the motor 2 can be detected quickly regardless of the magnitude of the load inertia of the motor. This is because, in the present embodiment, the condition that the motor speed exceeds the peak speed is not a condition for detecting the runaway but a condition that the sign of the torque command differential value does not match the sign of the motor jerk. Since the sign of the torque command differential value and the sign of the motor jerk are different from each other immediately after the motor is driven (T1), the runaway of the motor can be detected at T2 after the predetermined time has elapsed from T1.

Fig. 5A to 5E are diagrams showing a torque command value, a motor acceleration, a motor speed, a torque command differential value, and a motor jerk when external disturbances such as an unbalanced load are present, respectively. In this example, the following is assumed: the motor held by the brake or the like releases the holding state after the start of driving, and acceleration is generated due to unbalanced load.

When an unbalanced load exists, the torque command and the motor acceleration may not have the same sign. In the illustrated example, the sign of the torque command does not match the sign of the motor acceleration between the period from T6 to T7 to the period from T3 after driving. Therefore, if the runaway detection is performed based on the signs of the torque command and the motor acceleration as in the conventional technique, there is a possibility that the false detection occurs.

However, the torque command differential value and the sign of the motor jerk coincide during all periods. Therefore, the present embodiment can prevent the false detection of the motor runaway despite the motor runaway not being detected even when there is an external disturbance such as an unbalanced load.

As described above, according to the present embodiment, the runaway can be detected quickly regardless of the load inertia of the motor, and erroneous detection when the external disturbance occurs can be suppressed.

Second embodiment

In the second embodiment, the runaway of the motor can be detected even when the torque command is saturated. Fig. 6 is a diagram showing the configuration of the motor control unit 1 according to the present embodiment. Among the functional units shown in fig. 6, those substantially identical to those shown in fig. 2 are denoted by the same reference numerals, and detailed description thereof will be omitted.

The motor control unit 1 of the present embodiment includes a first order differentiator 20 and a comparator 21, compared with the first embodiment.

The first order differentiator 20 receives the actual motor speed output from the speed detector 14 and calculates a first order differentiation value thereof. Hereinafter, the output of the first order differentiator 20 is referred to as a motor acceleration.

The comparator 21 receives the torque command value from the speed control unit 12 and the motor acceleration from the first-order differentiator 20, and determines whether or not the signs of these values match. The comparison result by the comparator 21 is input to the runaway state detection portion 18.

The runaway state detection unit 18 in the present embodiment receives the comparison result of the comparator 21 and the torque command differential value from the torque command differentiator 15 in addition to the comparison result of the comparator 17. The runaway state detection process of the runaway state detection unit 18 according to the present embodiment will be described with reference to fig. 7.

In the flowchart of fig. 7, the same reference numerals are given to those substantially identical to the processing shown in fig. 3, and detailed description thereof is omitted. In the present embodiment, when both the determinations at steps S11 and S12 are satisfied, the runaway state detector 18 determines whether or not the torque command differential value is zero at step S18. If the torque command differential value is not zero (no at S18), the routine proceeds to step S13 to make the same determination as in the first embodiment. That is, if the torque command differential value differs from the motor jerk in sign, it is determined as an abnormal state and the abnormality duration is incremented, and if not, the abnormality duration is reset to zero.

On the other hand, if the torque command differential value is zero (yes at S18), the process proceeds to step S19. In step S19, the runaway state detection unit 18 determines whether or not the torque command value and the motor acceleration have different signs using the comparison result by the comparator 21. A state in which the rotation direction of the motor is opposite to the command although the torque command is saturated cannot be said to be a normal state. Therefore, if the signs are different, it is determined that the state is abnormal, and the process proceeds to step S14 to increment the abnormality duration. On the other hand, if the signs match, it is determined that the state is not an abnormal state, and the process proceeds to step S17, where the abnormality duration is reset to zero. The subsequent processing is the same as in the first embodiment.

Fig. 8A to 8E are diagrams showing a torque command value, a motor acceleration, a motor speed, a torque command differential value, and a motor jerk when the torque command is saturated in the case where the motor control unit 1 and the motor 2 are erroneously connected. The differential value of the torque command differs from the sign of the motor jerk due to miswiring. Here, it is assumed that: the time until the torque command is saturated (time T7 to T8) is shorter than the threshold time for runaway detection. After T8, the differential value of the torque command becomes zero, and the motor jerk also becomes zero along with this, so that the runaway detection based on the signs of these values cannot be performed. However, in the present embodiment, when the torque command differential value is zero, the sign of the torque command and the sign of the motor acceleration may be compared to detect runaway of the motor.

As described above, in the present embodiment, even when the torque command is saturated, the runaway of the motor can be reliably detected.

In the present embodiment, the runaway state detection unit 18 determines that a runaway state has been established when either the affirmative determination at step S13 or the affirmative determination at step S19 have continued for a predetermined time or longer. However, the runaway state detection unit 18 may regard the affirmative state at step S13 and the affirmative state at step S19 as different abnormal states, and may determine that the runaway state is present if any one of the abnormal states continues for a predetermined time or longer.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.