JP2017147841A - Power conversion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology capable of suppressing a cost required for a motor drive system while satisfying safety performance required in the motor drive system.SOLUTION: An encoder I/F 114 acquires a first position signal and a second position signal having higher ability of error detection or correction than that of the first position signal, from an encoder 20 at different points of time. The encoder I/F 114 generates a first time stamp signal showing time at which the first position signal is acquired and a second time stamp signal showing time at which the second position signal is acquired. A safety microcomputer 122 determines presence/no presence of abnormality in communication of the second position signal. The safety microcomputer 122 generates first speed data from the first position signal and the first time stamp signal, generates second speed data from the second position signal and the second time stamp signal, and performs comparison using the first speed data, the second speed data, and a speed command signal supplied from a host controller.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power conversion device that drives a motor.

  Along with the growing demand for energy saving in the market, motor drive control systems (hereinafter referred to as motor drive systems) that are often used as power sources in factories and buildings have functions to adjust the speed and output of the rotor of the motor. A power converter is generally used. In this type of motor drive system, the introduction of a power conversion device achieves higher functionality while the system is becoming more complex. For this reason, there is an increased possibility of motor runaway or accidents due to failure of the power conversion device itself or accompanying peripheral devices, and there is a strong demand to prevent these runaways and accidents. Therefore, safety standards such as IEC 61508 and ISO 13849, which are international standards, have been established, and a safety function conforming to these safety standards has been provided in power converters. For example, regarding a safety function for a power conversion device that drives and controls a motor, specifications of safety functions such as safe torque-off and safe deceleration are defined in IEC 61800-5-2, which is an international standard. Each power converter manufacturer has developed a power converter based on the specifications of this safety function.

  Of these safety functions, the safety deceleration function monitors the speed of the rotor of the motor and decelerates the motor to the specified speed from the time when the deceleration command signal is input to the power converter to the specified time. Is required to. And when not decelerating normally, such as when deceleration is not carried out or when a prescribed speed is exceeded, it is required to forcibly cut off the output of the power converter. In order to realize such a safety deceleration function, means for accurately detecting a failure in the speed and position of the rotor of the motor (hereinafter simply referred to as the speed and position of the motor) is required. In general, an encoder is used to detect the speed and position of a motor.

  Here, when an abnormality occurs in the encoder, the speed and position of the motor cannot be normally detected, and the safety function cannot be normally functioned. For this reason, a technique for diagnosing the presence or absence of an abnormality in the encoder has been proposed.

  As an example, there is an ASIC (Application Specific Integrated Circuit) or CPU (Central Processing Unit) in the encoder or a duplex detection circuit. For example, the encoder is provided with two detection circuits and two ASICs. Each of the two ASICs independently compares the detection signals output from each of the two systems of detection circuits, and mutually diagnoses the comparison results in each ASIC. In addition, as another example, there is a duplex encoder in which a plurality of encoders are attached to a motor. In this case, another device different from the encoder compares the output of each encoder, thereby diagnosing the presence or absence of the encoder abnormality. As another example, a mode in which a part for monitoring the output of the encoder is provided in the motor drive system to enhance the diagnosis function for the presence or absence of the encoder abnormality is also conceivable.

  As another example, Patent Document 1 discloses a servo system having a controller, an encoder, a servo driver, and a safety unit. The servo driver of this servo system sends the speed command value supplied from the controller and the feedback value acquired from the encoder to the safety unit. The safety unit compares the speed command value with the feedback value. With the technique of Patent Document 1, it is possible to detect an abnormality in the feedback value acquired from the encoder, and it is possible to make the servo system safe without replacing the encoder with one having a safety function.

Japanese Patent No. 5367623

  By the way, a power converter device communicates with an encoder and acquires the output signal of an encoder. During communication between the encoder and the power converter, there is a possibility that an abnormality such as data bit corruption or erroneous data transmission may occur. In many cases, power converters such as servo amplifiers do not have a function for preventing such communication abnormalities so as to satisfy safety standards.

  When a function for preventing such communication abnormality is not provided in a form that satisfies the safety standard, as a countermeasure, a plurality of communication means for receiving the output signal of the encoder is installed in the power converter, and each communication means The received encoder output signal may be compared to diagnose whether there is an abnormality in communication with the encoder. However, when a plurality of communication means are provided in the power conversion device, the number of communication means increases, so that the board area necessary for installing the communication means increases and the cost for the communication means increases.

  The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide a technique capable of suppressing the cost of the motor drive system while satisfying the safety performance required in the motor drive system. To do.

  The power conversion device according to the present invention drives a motor. The power conversion device communicates with an encoder that detects the position of the rotor of the motor, and sends a first position signal and a second position signal having a higher error detection or correction capability than the first position signal. A safety circuit that determines whether there is an abnormality related to the encoder based on the communication means that is obtained from the encoder instead, the first position signal, the second position signal, and the speed command signal supplied from the host controller; Have.

  In the power conversion device according to the present invention, the presence / absence of an abnormality in the encoder is determined based on the two types of position signals (first position signal and second position signal) and the speed command signal. For this reason, in this power converter device, the presence or absence of the abnormality regarding the encoder including the presence or absence of the abnormality of the communication between the encoder and the power converter device can be detected. For this reason, the power conversion device satisfies the safety performance required in the motor drive system even if the function for preventing abnormal communication between the encoder and the power conversion device is not provided in a form that satisfies the safety standard. . Moreover, in this power converter device, since a communication means acquires a 1st position signal and a 2nd position signal, it is not necessary to mount several communication means and the cost regarding installation of a communication means can be held down. In the power conversion apparatus, one position signal (specifically, the second position signal) of the two kinds of position signals is acquired from the encoder by communication with high error detection or correction capability. For this reason, in this power converter, compared with the conventional power converter, the presence or absence of a communication abnormality can be detected more reliably. Further, the encoder can generate the first position signal and the second position signal with one ASIC even if a plurality of ASICs are not mounted in the encoder. For this reason, if this power converter is used, it is not necessary to use an expensive safety-compatible encoder in which a plurality of ASICs are mounted in the encoder, and the cost of the encoder can be suppressed. In this power converter, the 1st position signal and the 2nd position signal are acquired from the same encoder. For this reason, if this power converter device is used, it is not necessary to attach a some encoder to a motor, and the cost concerning an encoder can be held down.

  Therefore, by using the power conversion device according to the present invention, it is possible to reduce the cost of the motor drive system while satisfying the safety performance required in the motor drive system.

1 is a block diagram showing a configuration of a motor drive system 1 including a power conversion device 10 according to an embodiment of the present invention. It is a figure which shows the structure of the communication frame of the 1st position signal which the encoder 20 in the motor drive system 1 produces | generates. It is a figure which shows the structure of the communication frame of the 2nd position signal which the encoder 20 in the motor drive system 1 produces | generates. 3 is a block diagram illustrating functions of a safety microcomputer 122 of the power conversion device 10. FIG. 4 is a flowchart showing the operation of the safety microcomputer 122.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
<Embodiment>
FIG. 1 is a block diagram showing a configuration of a motor drive system 1 including a power conversion device 10 according to an embodiment of the present invention. The motor drive system 1 includes a power conversion device 10 and an encoder 20. The power conversion device 10 is, for example, a servo amplifier or an inverter, and is a device that converts the power supplied from the AC power supply 40 and supplies the converted power to the motor 30 such as a servo motor or an induction motor, and drives and controls the motor 30. The encoder 20 is a device that detects the position (that is, the rotation angle) of the rotor of the motor 30. The output signal of the encoder 20 is sent to the power conversion device 10.

  A disk that rotates in the circumferential direction according to the rotation of the rotor is attached to the rotating shaft of the rotor of the motor 30. The encoder 20 detects the position of the rotor of the motor 30 by optically reading a code pattern corresponding to the angle drawn on the disk. The specific position detection method is not limited to the method of optically reading the code pattern. The encoder 20 has signal processing means for generating a first position signal and a second position signal which are output signals of the encoder 20 by performing signal processing on a signal representing the detection result of the rotor position of the motor 30. . The signal processing means is, for example, an ASIC or a CPU.

  FIG. 2 is a diagram illustrating a configuration of a communication frame of the first position signal generated by the ASIC of the encoder 20. The first position signal is a position signal mainly used for drive control of the motor. In the payload of the communication frame of the first position signal, position data that is a detection result of the position of the rotor of the motor 30 is stored. The position data is represented by 20 bits, for example. In the header of the communication frame of the first position signal, a communication command such as an acquisition command and a simple cyclic redundancy code used for cyclic redundancy check (CRC) are stored. Additional information of the other encoder 20 is stored in the footer of the communication frame of the first position signal. As described above, the communication frame of the first position signal has the same configuration as the communication frame of the output signal of the conventional encoder. The first position signal is a signal that does not satisfy a safety communication specification (for example, a specification related to safety communication defined by IEC) although a simple cyclic redundancy code is stored. For this reason, even though the first position signal can be used for motor drive control, it is not preferable to perform safety control using only the first position signal.

  FIG. 3 is a diagram illustrating a configuration of a communication frame of the second position signal generated by the ASIC of the encoder 20. The second position signal is a position signal used for safety control. In the payload of the communication frame of the second position signal, position data that is a detection result of the position of the rotor of the motor 30 is stored. The position data of the second position signal is the same as the position data of the first position signal. The header of the communication frame of the second position signal includes a communication command such as an acquisition command, a sequence number that is updated every time communication is performed, and an identifier that can be clearly determined as a communication partner. And a unique ID and a cyclic redundancy code such as 8 bits or 16 bits are stored. The cyclic redundancy code of the second position signal has a larger number of bits than the simple cyclic redundancy code of the first position signal. The footer of the communication frame of the second position signal stores minimum information necessary for communication. As described above, the communication frame of the second position signal is configured to store more information used for error detection or correction in the header than the communication frame of the first position signal. For this reason, the second position signal is a position signal having higher error detection or correction capability than the first position signal. The second position signal has higher safety in communication than the first position signal, and satisfies the safety communication specification.

  As shown in FIG. 1, the power conversion device 10 includes a control board 11, a power supply board 15, a main circuit 13, and a safety option 12.

  The main circuit 13 includes a switching element such as an IGBT (Insulated Gate Bipolar Transistor). This switching element is turned on / off according to the gate signal. The main circuit 13 outputs a current according to on / off of the switching element to the motor 30. The motor 30 operates according to the current supplied from the main circuit 13.

  The control board 11 is provided with each element for driving and controlling the motor 30. Specifically, the control board 11 includes a command signal terminal block 111, a motor control microcomputer 112, a PWM LSI (Pulse Width Modulation Large Scale Integration) 113, and an encoder interface (hereinafter, the interface is referred to as I / F) 114. Has been implemented.

  The command signal terminal block 111 receives various command signals (for example, a speed command signal) from a host controller (not shown) and delivers them to the motor control microcomputer 112. The motor control microcomputer 112 is a control calculation unit that performs calculations for driving and controlling the motor 30 based on various command signals supplied from the host controller via the command signal terminal block 111. The motor control microcomputer 112 performs the calculation and generates a control signal (for example, a voltage command signal). The PWM LSI 113 generates a PWM signal by pulse width modulating the carrier signal based on the control signal supplied from the motor control microcomputer 112. The generated PWM signal is output to the gate drive circuit 14 mounted on the power supply substrate 15.

  The gate drive circuit 14 includes, for example, a photocoupler. In the state where the gate stop signal is not given, the gate drive circuit 14 turns on the power supply of the photocoupler, and outputs the PWM signal supplied from the PWM LSI 113 of the control board 11 to the main circuit 13 as a gate signal. On the other hand, when the gate drive circuit 14 receives the gate stop signal, the photocoupler is turned off and stops outputting the gate signal to the main circuit 13. Further, the gate drive circuit 14 outputs a gate stop state signal indicating whether or not the output of the gate signal is stopped to the safety option 12.

  The encoder I / F 114 is a communication unit that communicates with the ASIC of the encoder 20 according to serial communication based on a standard such as RS485. The encoder I / F 114 communicates with the encoder 20 and acquires the first position signal and the second position signal from the encoder 20 while changing the time. That is, the timing at which the encoder I / F 114 acquires the first position signal is different from the timing at which the encoder I / F 114 acquires the second position signal.

  Here, in the encoder 20, the first mode in which the first position signal and the second position signal are generated at the same timing, and the first position signal and the second position signal are generated at different timings. Two aspects of the second aspect are conceivable.

  In the first aspect, for example, the encoder I / F 114 transmits the request signal to the encoder 20 at a predetermined frequency (such as the frequency similar to the frequency of communication when acquiring the output signal of the encoder in the conventional power converter). To do. When the encoder 20 receives the request signal, the encoder 20 detects the position of the rotor of the motor 30 at the reception timing. The ASIC of the encoder 20 stores the position data as the position detection result in the communication frame of FIG. 2 to generate the first position signal, and stores the position data as the position detection result in the communication frame of FIG. Thus, the second position signal is generated. That is, in this aspect, the position data of the first position signal and the position data of the second position signal are the same data detected at the same timing. Then, the ASIC of the encoder 20 transmits the first position signal to the power conversion device 10 and transmits the second position signal to the power conversion device 10 after the transmission of the first position signal is completed. The power conversion device 10 acquires the first position signal and the second position signal thus generated at the same timing from the encoder 20 while changing the time.

  In the second mode, for example, the encoder I / F 114 transmits a request signal for the first position signal to the encoder 20 at a predetermined frequency. The encoder 20 detects the position of the rotor of the motor 30 at the timing at which the request signal for the first position signal is received. The ASIC of the encoder 20 stores the position data, which is the position detection result, in the communication frame of FIG. 2 and generates a first position signal. Then, the ASIC of the encoder 20 transmits the first position signal to the power conversion device 10. In this way, the power conversion device 10 acquires the first position signal from the encoder 20. Thereafter, the encoder I / F 114 transmits a request signal for the second position signal to the encoder 20. The encoder 20 detects the position of the rotor of the motor 30 at the timing at which the request signal for the second position signal is received. The ASIC of the encoder 20 stores the position data that is the position detection result in the communication frame of FIG. 3 and generates a second position signal. That is, in this aspect, the position data of the first position signal and the position data of the second position signal are different data detected at different timings. Then, the ASIC of the encoder 20 transmits the second position signal to the power conversion device 10. The power conversion device 10 acquires the first position signal and the second position signal generated at different timings in this way from the encoder 20 while changing the time.

  The encoder I / F 114 may acquire the second position signal by performing communication regarding the second position signal between the communication regarding the first position signal acquired at a predetermined frequency. The communication frequency regarding the first position signal and the communication frequency regarding the second position signal may be the same or different. In the case of the second aspect described above, for example, the second position signal is acquired twice after the first position signal is acquired and before the request signal of the next first position signal is transmitted. As described above, the communication frequency related to the first position signal and the communication frequency related to the second position signal can be changed.

  When the encoder I / F 114 acquires the first position signal, the encoder I / F 114 generates a first time stamp signal indicating the time when the first position signal is acquired. The encoder I / F 114 delivers the acquired first position signal and the generated first time stamp signal to the motor control microcomputer 112. Further, when the encoder I / F 114 acquires the second position signal, the encoder I / F 114 generates a second time stamp signal indicating the time when the second position signal is acquired. The encoder I / F 114 delivers the acquired second position signal and the generated second time stamp signal to the motor control microcomputer 112.

  Upon receiving the first position signal, the first time stamp signal, the second position signal, and the second time stamp signal from the encoder I / F 114, the motor control microcomputer 112 sends these signals to the safety option 12. . Further, the motor control microcomputer 112 sends the speed command signal supplied from the host controller to the safety option 12. Thus, the motor control microcomputer 112 also serves to output these signals to the safety option 12. The motor control microcomputer 112 refers to the position data of the first position signal when performing a calculation based on a command signal for driving and controlling the motor 30.

  The safety option 12 outputs a gate stop signal and outputs a gate signal to the gate drive circuit 14 when an abnormality is detected in the motor drive system 1 or when an operator presses an emergency stop button. It is a safety circuit that performs safety control to stop output. As an example of an abnormality in the motor drive system 1, an abnormality relating to the encoder 20 such as an abnormality of the encoder 20 itself or an abnormality in communication between the encoder 20 and the power conversion device 10 can be given. The safety option 12 is a means for determining whether there is an abnormality related to the encoder 20. Such determination of the presence / absence of an abnormality is realized by executing a program stored in a storage device (not shown) by the safety option 12.

  In the power conversion device 10, the safety option 12 may be duplicated by adding a circuit having the same configuration as the safety option 12. In this case, each of the two safety options 12 independently determines whether there is an abnormality in the encoder 20 and mutually diagnoses the result in each safety option 12.

  The safety option 12 includes a safety-related signal terminal block 121, a safety microcomputer 122, and an emergency stop circuit 123.

  The safety-related signal terminal block 121 receives an emergency stop signal (for example, a signal generated by pressing the emergency stop button) from an external circuit (not shown), and delivers it to the safety microcomputer 122 and the emergency stop circuit 123. The safety-related signal terminal block 121 receives a safety signal from an external circuit (not shown) and delivers it to the safety microcomputer 112. Examples of the safety signal include a safety signal for realizing a safety function for safety torque off, a safety signal for realizing a safety function for deceleration stop, a safety signal for realizing a safety function for speed limitation, and the like. The safe torque off is a safety function that immediately shuts off the gate of the switching element of the main circuit 13. The deceleration stop is a safety function in which the motor 30 is decelerated to stop the motor 30 as soon as possible, and the safety torque is turned off near the stop. The speed limit is a safety function that decelerates the motor 30 to a preset speed.

  The safety microcomputer 122 acquires an emergency stop signal and a safety signal output from the safety-related signal terminal block 121 and a gate stop state signal output from the gate drive circuit 14. In addition, the safety microcomputer 122 acquires the speed command signal, the first position signal, the first time stamp signal, the second position signal, and the second time stamp signal output from the motor control microcomputer 112. The safety microcomputer 122 is a circuit that determines the presence or absence of an abnormality in the motor drive system 1 based on these signals and outputs an emergency stop command to the emergency stop circuit 123 when it is determined that there is an abnormality.

  The emergency stop circuit 123 outputs a gate stop signal to the gate drive circuit 14 when an emergency stop signal output from the safety-related signal terminal block 121 or an emergency stop command output from the safety microcomputer 122 is supplied. Circuit.

  FIG. 4 is a block diagram showing functions of the safety microcomputer 122. The safety microcomputer 122 includes a speed command signal acquisition unit 503, a position signal acquisition unit 501, a position speed conversion unit 502, a speed comparison unit 504, a safety communication processing unit 505, a position speed conversion unit 506, an emergency stop command output unit 508, a motor. It includes a control microcomputer communication unit 509, a safety signal monitoring unit 507, an emergency stop signal monitoring unit 510, a gate stop state signal monitoring unit 511, a self-diagnosis processing unit 512, a mutual diagnosis processing unit 513, and an initialization related processing unit 514. These parts of the safety microcomputer 122 are functions realized by the safety microcomputer 122 executing a program.

  FIG. 5 is a flowchart showing the operation of the safety microcomputer 122. When the power is turned on, the safety microcomputer 122 reads the program, operates as each functional unit shown in FIG. 4, and sequentially performs the processes of steps S101 to S108 shown in FIG. Thereafter, the safety microcomputer 122 periodically repeats the processes of steps S101 to S108. The operation of the safety microcomputer 122 will be described with reference to FIGS.

  First, the self-diagnosis processing unit 512 performs self-diagnosis as to whether a runaway or abnormality of itself (that is, the safety microcomputer 122) occurs (step S101). For example, the self-diagnosis processing unit 512 acquires a result of measuring the temperature of the safety microcomputer 122 and determines whether or not the temperature measurement result is equal to or higher than a predetermined temperature. If the temperature detection result is equal to or higher than the predetermined temperature, the self-diagnosis processing unit 512 causes the emergency stop command output unit 508 to perform an emergency stop because there is a high possibility that the safety microcomputer 122 will run out of heat and errors in various processing results increase. A command is output to cause the emergency stop circuit 123 to output a gate stop signal (omitted in the flowchart of FIG. 5). When the safety microcomputer 122 is duplicated, in addition to the self-diagnosis by the self-diagnosis processing unit 512, the mutual diagnosis processing unit 513 of the safety microcomputer 122 determines whether there is an abnormality in the safety microcomputer 122. A diagnosis is performed mutually with step 122 (step S101). If there is an abnormality in any of the safety microcomputers 122, the mutual diagnosis processing unit 513 that has detected the abnormality causes the emergency stop command output unit 508 to output an emergency stop command and outputs a gate stop signal to the emergency stop circuit 123. (Omitted in the flowchart of FIG. 5).

  Next, the speed command signal acquisition unit 503 acquires a speed command signal from the motor control microcomputer 112 (step S102). The speed command signal acquisition unit 503 delivers the acquired speed command signal to the speed comparison unit 504.

  Next, the position signal acquisition unit 501 acquires a first position signal from the motor control microcomputer 112 (step S103). The position signal acquisition unit 501 extracts position data (hereinafter referred to as first position data) stored in the communication frame of the acquired first position signal, and sends the first position data to the position / velocity conversion unit 502. hand over.

  Next, the safety communication processing unit 505 acquires a second position signal from the motor control microcomputer 112 (step S104). The safety communication processing unit 505 determines whether there is a communication abnormality in the second position signal based on the data stored in the header of the communication frame of the acquired second position signal. For example, the safety communication processing unit 505 determines whether or not the unique ID stored in the header is a preset identifier, or uses a cyclic redundancy code of 8 bits or 16 bits stored in the header. Redundancy check (CRC) is performed. When the unique ID of the second position signal is not a preset identifier, the safety communication processing unit 505 has a high possibility that the communication of the second position signal is an erroneous transmission. Judge that there was an abnormality. Since the second position signal stores a cyclic redundancy code having a larger number of bits than the cyclic redundancy code of the first position signal, the safety communication processing unit 505 compares the first position signal with the first position signal. It is possible to detect an error in the position signal 2 with high accuracy. When the safety communication processing unit 505 detects an error by CRC using the cyclic redundancy code stored in the second position signal, the safety communication processing unit 505 determines that there is an abnormality in communication of the second position signal. In addition, when an error is detected by CRC, the safety communication processing unit 505 performs a process of correcting the error of the second position signal. In addition, when an error is detected by CRC, the safety communication processing unit 505 transmits the sequence number stored in the second position signal to the encoder 20 via the encoder I / F 114, and the first corresponding to the sequence number. Second position signal retransmission may be requested.

  In addition, when there is an abnormality in communication in the second position signal (for example, when an error is detected by CRC), the safety communication processing unit 505 abnormally sets a value (for example, 1) indicating that an abnormality has occurred in communication. An abnormality flag signal stored in the flag (hereinafter simply referred to as an abnormality flag signal) is output to the emergency stop command output unit 508. When no abnormality is found in the communication in the second position signal, the safety signal processing unit 505 uses the position data (hereinafter referred to as second position data) stored in the communication frame of the acquired second position signal. The second position data is extracted and transferred to the position / velocity conversion unit 506.

  Next, the position / velocity conversion unit 502 receives the first position data from the position signal acquisition unit 501 and acquires the first time stamp signal from the motor control microcomputer 112. The position / velocity conversion unit 502 generates first speed data represented by the first position signal from the first position data and the first time stamp signal (step S105). Specifically, the position / velocity conversion unit 502 stores the first position data and the first time stamp signal in the register each time it acquires the position data. The position / velocity conversion unit 502 calculates the difference between the position represented by the newly acquired first position data and the position represented by the previous first position data acquired immediately before and stored in the register. Next, the position / velocity conversion unit 502 calculates the difference between the time indicated by the newly acquired first time stamp signal and the time indicated by the previous first time stamp signal acquired immediately before and stored in the register. Is calculated. Next, the position / velocity conversion unit 502 divides the calculated position difference by the calculated time difference. The position / velocity conversion unit 502 passes the division result calculated in this way to the speed comparison unit 504 as first speed data.

  Next, the position / velocity conversion unit 506 receives the second position data from the safety communication processing unit 505 and acquires the second time stamp signal from the motor control microcomputer 112. The position / velocity conversion unit 506 generates second speed data represented by the second position signal from the second position data and the second time stamp signal (step S105). The position / velocity conversion unit 506 may perform the same calculation as the position / velocity conversion unit 502. Specifically, the position / velocity conversion unit 506 calculates the difference between the position represented by the current second position data and the position represented by the previous second position data from the time represented by the current second time stamp signal and the previous time. Is divided by the time difference represented by the second time stamp signal. The position / velocity conversion unit 502 delivers the division result calculated in this way to the speed comparison unit 504 as second speed data.

  Next, the speed comparison unit 504 receives the speed command signal received from the speed command signal acquisition unit 503, the first speed data received from the position / speed conversion unit 502, and the second speed received from the position / speed conversion unit 506. A comparison using the data is performed to determine whether there is an abnormality related to the encoder 20 (step S106). When at least one of the first speed data and the second speed data does not match the speed command signal, the speed comparison unit 504 regards that an abnormality relating to the encoder 20 has occurred (S106: Yes), and an abnormality flag The signal is output to the emergency stop command output unit 508.

  When the acquisition frequency of the first position signal and the second position signal is different, the difference result of the first position signal and the difference result of the second position signal are different. In this case, since the generation interval of the first time stamp signal and the generation interval of the second time stamp signal are different, the difference result of the first time stamp signal and the difference result of the second time stamp signal are also different. . However, even in this case, the result of dividing the difference result of the first position signal by the difference result of the first time stamp signal and the result of dividing the difference result of the second position signal by the second time stamp signal is If there is no abnormality in the first position signal and the second position signal without considering the transmission delay or the like, they should be the same. For this reason, even if the acquisition frequency of a 1st position signal and a 2nd position signal differs, the speed comparison part 504 can compare three signals.

  Further, when the first position signal and the second position signal are generated at the same timing (in other words, when the first position data and the second position data are the position detection results at the same timing). ) The speed comparison unit 504 may compare the first speed data, the second speed data, and the speed command signal as they are. On the other hand, when the first position signal and the second position signal are generated at different timings (in other words, when the first position data and the second position data are position detection results at different timings). ), The speed comparison unit 504 interpolates the first speed data and the second speed data on the time axis, respectively, and the first speed data (interpolated first speed data) and the second at the same timing. The speed data (interpolated second speed data) may be compared with the speed command signal. In this way, even if the first position signal and the second position signal represent positions at different timings, speed comparison can be performed accurately.

  Further, when the acquisition frequencies of the first position signal, the second position signal, and the speed command signal are different, until all three types of signals of the first speed data, the second speed data, and the speed command signal are obtained, What is necessary is just to repeat the step before the comparison process (step S106) in the speed comparison unit 504. And the speed comparison part 504 should just perform a comparison process with the frequency match | combined with the signal with little acquisition frequency. Alternatively, when the acquisition frequencies are different, each speed data may be interpolated on the time axis, and the speed data with a low acquisition frequency may be compared using the interpolated speed data. This is because the comparison based on the three types of signals of the first position signal, the second position signal, and the speed command signal can be performed.

  Upon receiving the abnormality flag signal from the speed comparison unit 504, the emergency stop command output unit 508 outputs an emergency stop command to the emergency stop circuit 123 (step S108). The emergency stop command output unit 508 causes the motor control microcomputer communication unit 509 to output a diagnostic signal indicating that an abnormality has occurred in the motor drive system 1 along with the output of the emergency stop command. The motor control microcomputer 112 recognizes that an abnormality has occurred in the motor drive system 1 by receiving the diagnostic signal output from the motor control microcomputer communication unit 509.

  If the first speed data, the second speed data, and the speed command signal match in step S106, the speed comparison unit 504 determines that an abnormality relating to the encoder 20 has not occurred (S106: No). .

  After the speed comparison unit 504 determines that an abnormality relating to the encoder 20 has not occurred, the emergency stop signal monitoring unit 510 determines whether an emergency stop signal has been supplied via the safety-related signal terminal block 121 ( Step S107). When the emergency stop signal is supplied (S107: Yes), the emergency stop signal monitoring unit 510 outputs an abnormality flag signal to the emergency stop command output unit 508. Then, the emergency stop output unit 508 that has received the abnormality flag signal from the emergency stop signal monitoring unit 510 outputs an emergency stop command to the emergency stop circuit 123 (step S108). The emergency stop signal monitoring unit 510 also checks whether there is an abnormality in communication related to the supply of the emergency stop signal. The emergency stop signal monitoring unit 510 outputs an abnormality flag signal to the emergency stop command output unit 508 when there is an abnormality in communication related to the supply of the emergency stop signal.

  When the emergency stop signal is not supplied and when there is no abnormality in the communication related to the supply of the emergency stop signal (S107: No), the series of processing ends.

  Although omitted in the flowchart of FIG. 5, it is possible to confirm whether there is an abnormality in communication related to the supply of the safety signal and whether there is an abnormality in communication related to the supply of the gate stop state signal. good. For example, when the determination result in step S107 is No, the safety signal monitoring unit 507 determines whether there is an abnormality in communication related to the supply of the safety signal. The safety signal monitoring unit 507 outputs an abnormality flag signal to the emergency stop command output unit 508 when there is an abnormality in the communication related to the supply of the safety signal. When there is no abnormality in the communication related to the supply of the safety signal, the gate stop state signal monitoring unit 511 determines whether there is an abnormality in the communication related to the supply of the gate stop state signal. The gate stop state signal monitoring unit 511 outputs an abnormality flag signal to the emergency stop command output unit 508 when there is an abnormality in communication related to the supply of the gate stop state signal. The emergency stop output unit 508 that has received the abnormality flag signal from the safety signal monitoring unit 507 or the gate stop state signal monitoring unit 511 outputs an emergency stop command to the emergency stop circuit 123. On the other hand, if there is no abnormality in the communication related to the supply of the gate stop state signal, the series of processes is terminated.

  The initialization-related processing unit 514 is a functional unit that operates when various setting values used in the functional units of the safety microcomputer 122 are initialized.

  As described above, the power conversion device 10 according to the present embodiment obtains the first position signal and the second position signal having a higher error detection or correction capability than the first position signal at different times. I / F 114. In addition, the power conversion device 10 includes a safety microcomputer 122 that determines whether there is an abnormality in the encoder based on the first position signal, the second position signal, and the speed command signal supplied from the host controller. Have. In other words, power converter 10 determines whether there is an abnormality in encoder 20 based on two types of position signals (a first position signal and a second position signal) and a speed command signal. Therefore, the power conversion device 10 can detect the presence or absence of an abnormality related to the encoder 20 including the presence or absence of a communication abnormality between the encoder 20 and the power conversion device 10. For this reason, even if the power converter 10 is not provided with a function that prevents an abnormality in communication between the encoder 20 and the power converter 10 in a form that satisfies the safety standards, the safety required in the motor drive system 1 Satisfy performance. Further, in the power conversion device 10, since the encoder I / F 114 acquires the first position signal and the second position signal, there is no need to install a plurality of encoder I / Fs 114, and the cost associated with the installation of the encoder I / F 114 is eliminated. Can be suppressed. In addition, the power conversion apparatus 10 acquires one position signal (specifically, the second position signal) of the two types of position signals from the encoder 20 by communication with high error detection or correction capability. For this reason, in the power converter device 10, the presence or absence of communication abnormality can be detected more reliably than in the conventional power converter device. Further, the encoder 20 can generate the first position signal and the second position signal with one ASIC even if a plurality of ASICs are not mounted in the encoder 20. For this reason, if the power converter 10 is used, it is not necessary to use an expensive safety-compatible encoder in which a plurality of ASICs are mounted in the encoder 20, and the cost of the encoder 20 can be suppressed. Further, in the power conversion device 10, the first position signal and the second position signal are acquired from the same encoder 20. For this reason, if the power converter device 10 is used, it is not necessary to attach a plurality of encoders 20 to the motor 30, and the cost of the encoder 20 can be suppressed.

  Therefore, by using the power conversion device 10 of the present embodiment, it is possible to reduce the cost of the motor drive system 1 while satisfying the safety performance required in the motor drive system 1.

  In power converter 10, safety microcomputer 122 performs the operation which generates the 1st speed data from the 1st position signal, and the operation which generates the 2nd speed data from the 2nd position signal. That is, in the power converter 10, since the speed calculation related to the safety control is performed only by the safety microcomputer 122, the speed calculation related to the safety control is performed in two places (for example, the motor control 112 microcomputer and the safety microcomputer 122), There are few circuits responsible for the speed calculation. For this reason, in the power converter 10, compared with the aspect which performs the speed calculation in multiple places, generation | occurrence | production of the abnormality in the calculation process of the speed calculation and a calculation result can be reduced, and safety can be improved.

  In the power conversion device 10, the safety microcomputer 122 determines whether there is an abnormality related to the encoder 20. For this reason, in the power conversion device 10, the transmission path of the first and second position signals from the encoder 20 to the safety microcomputer 122 (for example, a cable between the encoder 20 and the encoder I / F 114 or an encoder I / F 114 is connected). It is possible to detect the occurrence of communication abnormality in an integrated circuit to be realized.

  In addition, the encoder I / F 114 performs serial communication with the encoder 20 and acquires the first position signal and the second position signal from the encoder 20 by changing the time. For this reason, in this embodiment, it is possible to send the first position signal and the second position signal to the safety microcomputer 122 through the same transmission path. From this, it can be said that if the power conversion device 10 is used, it is not necessary to mount a plurality of encoder I / Fs 114, and the cost related to the installation of the encoder I / F 114 can be suppressed.

  In the power conversion device 10, since the second position signal having high error detection or correction capability is acquired from the encoder 20, the speed comparison unit 504 not only detects the presence / absence of communication abnormality with the encoder 20. The safe communication processing unit 505 can also detect it. For this reason, compared with the conventional power converter, the presence or absence of the abnormality of the communication can be detected more reliably.

  Further, in the power conversion device 10, the encoder I / F 114 may acquire the first position signal and the second position signal at different frequencies. If the first position signal and the second position signal are acquired at different frequencies, the execution frequency of the speed comparison unit 504 and the execution frequency of the safety communication processing unit 505 change, and thus the power converter 10 is used. The presence or absence of the communication abnormality can be detected with the reliability suitable for the motor drive system.

  Further, the safety option 12 of the power conversion device 10 provides a stop signal (specifically, a gate stop signal) for stopping power supply to the motor 30 when the safety microcomputer 122 determines that there is an abnormality related to the encoder 20. Output from the emergency stop circuit 123. For this reason, if the power converter 10 is used, even if abnormality regarding the encoder 20 occurs, the motor 30 can be stopped reliably and danger can be avoided.

<Other embodiments>
Although one embodiment of the present invention has been described above, other embodiments are conceivable for the present invention. For example:

(1) The functions of the motor driving microcomputer 112, the PWM LSI 113, and the encoder I / F 114 may be integrated into a single integrated circuit such as a SoC (System on Chip).

  DESCRIPTION OF SYMBOLS 1 ... Motor drive system, 10 ... Power converter, 20 ... Encoder, 30 ... Motor, 40 ... AC power supply, 11 ... Control board, 12 ... Safety option, 13 ... Main circuit, 14 ... Gate drive circuit, 15 ... Power supply board , 111 ... command signal terminal block, 112 ... motor control microcomputer, 113 ... PWMLSI, 114 ... encoder interface, 121 ... safety related signal terminal block, 122 ... safety microcomputer, 123 ... emergency stop circuit.

Claims (5)

A power converter for driving a motor,
The encoder communicates with an encoder for detecting the position of the rotor of the motor, and changes the first position signal and the second position signal having a higher error detection or correction capability than the first position signal at different times. Communication means obtained from
A safety circuit that determines the presence or absence of an abnormality related to the encoder based on the first position signal, the second position signal, and a speed command signal supplied from a host controller;
The power converter characterized by having. The communication means includes
A first time stamp signal indicating a time when the first position signal is acquired;
Generating a second time stamp signal indicating the time when the second position signal was acquired;
The safety circuit is
Generating first velocity data based on the first position signal and the first time stamp signal;
Generating second velocity data based on the second position signal and the second time stamp signal;
The power converter according to claim 1, wherein comparison is performed using the first speed data, the second speed data, and the speed command signal. Control arithmetic means for performing an operation for driving and controlling the motor based on various command signals supplied from a host controller,
The speed command signal supplied from the host controller, the first position signal and the second position signal acquired by the communication means, the first time stamp signal generated by the communication means, and the The power conversion device according to claim 2, further comprising a control calculation unit that outputs a second time stamp signal to the safety circuit. The power converter according to any one of claims 1 to 3, wherein the communication unit acquires the first position signal and the second position signal at different frequencies. The said safety circuit outputs the stop signal which stops the electric power supply to the said motor, when it judges that there exists abnormality regarding the said encoder. The claim of any one of Claim 1 to 4 characterized by the above-mentioned. Power conversion device.

Images