JP2008148535A - Motor controller and on-delay time setting method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor controller and an on-delay time setting method by which an on-delay time is set appropriately without excess or shortage based on a voltage command, a current command or a detection current, and by which the on-delay time is accurately compensated and vibration at rotation and at the stoppage of a motor is suppressed. <P>SOLUTION: The motor controller includes an on-delay time setting portion 16 which detects an intermediate phase in three phases of a three-phase motor based on the voltage command, and determines and sets the on-delay time of the intermediate phase based on a comparison result between the voltage command of the intermediate phase and a prescribed value set beforehand. The on-delay time setting portion 16 changes and sets the on-delay time of a phase other than the intermediate phase and the intermediate phase based on the comparison result. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a motor control device that drives a machine or the like with a servo motor, and a method for setting an on-delay time for switching a power transistor.

The first prior art has an on-delay compensation function for compensating for the influence of the on-delay time on the inverter output voltage, which is provided to prevent a short circuit of the power conversion elements (power devices) of the upper and lower arms of the voltage source inverter. The purpose is to improve the control performance by reducing the output voltage distortion due to the on-delay time (to reduce the error of the inverter output phase voltage due to the polarity of the phase current). Therefore, a compensation amount calculation circuit that changes the on-delay compensation amount according to the magnitude of the phase current detection value (for example, the u-phase current) is provided to enable stable compensation (see, for example, Patent Document 1).
FIG. 4 is an explanatory diagram for explaining the operation of the implementation configuration diagram in the first prior art.
The compensation amount calculation circuit is composed of, for example, a comparator having a hysteresis characteristic, and compares the U-phase phase current detection value iu with the constant hysteresis widths + iuhis and -iuhis as shown in FIG. If it is within the hysteresis width, the on-delay compensation amount -cp1 is output as shown in FIG. 4B, and if it is not the hysteresis width, the on-delay compensation amount -cp2 is output. On the other hand, if iu is negative and within the hysteresis width, the on-delay compensation amount cp1 is output as shown in FIG. 4B, and if it is not the hysteresis width, the on-delay compensation amount cp2 is output.
As described above, since the on-delay compensation amount is changed according to the detected phase current value, there is no overcompensation even when the phase current is small, and therefore an advantage that good control is possible can be obtained. -ing

The second prior art relates to an arm voltage pulse width detection circuit for an on-delay compensation circuit (also referred to as a dead time compensation circuit) used in an inverter, which improves detection delay, reduces influence of noise, gate The purpose is to reduce the number of external parts by making it possible to make an IC together with the drive circuit.In detecting the voltage pulse of the inverter arm used in the on-delay compensation circuit added to the switching pattern of the inverter, The on / off state of the diode interlocked with the on / off state of the inverter arm is detected (for example, see Patent Document 2).
FIG. 5 is a block diagram showing an embodiment in the second prior art.
Inverter arm on detection circuits C1 to C6 are provided for the upper and lower arm semiconductor switching elements S1 to S6 forming the inverter main circuit (a), and the upper arm semiconductor switching elements S1, S3, and S5 are detected. A level down circuit Dw1, Dw3, Dw5 for reducing the level of the circuit output is added, and the PWM pulse generated by the PWM pulse generator, the detection circuits C1 to C6, and the level down circuits Dw1, Dw3, Dw5 Is compared with the inverter arm voltage pulses V1 to V6 generated in Step 1, and the inverter arm voltage pulse width error due to the on-delay is compensated. In this way, when detecting the voltage pulse of the inverter arm, the on / off state of the diode that is linked to the on / off state of the inverter arm is detected. Therefore, in addition to the improvement of noise tolerance and the detection accuracy, the voltage pulse There is no need to insulate the upper and lower arms for detection, and there is no need for voltage-dividing resistors, so IC can be integrated (integrated), reducing the number of parts, saving space, and reducing costs. A high-performance circuit can be obtained.

The third prior art relates to a method of controlling a power transistor by PWM conversion using a triangular wave to control a motor current, and can compensate for an on-delay time relatively accurately, thereby causing current distortion and the like. The current control method is able to eliminate the on-delay time, and the compensation amount corresponding to the on-delay time is ΔV, and in the interval where the potential of the triangular wave increases with time, the phase of the positive high potential is turned on. The interval where the delay compensation amount is 0, the on-delay compensation amount of the intermediate potential phase is (−1/2) ΔV, the on-delay compensation amount of the negative potential phase is −ΔV, and the potential of the triangular wave decreases with time. Then, the on-delay compensation amount for the positive high potential phase is + ΔV, the on-delay compensation amount for the intermediate potential phase is (½) ΔV, and the on-delay compensation amount for the negative potential phase is zero. (For example, refer to Patent Document 3).
Japanese Patent Laid-Open No. 7-312875 (page 3, FIG. 2) Japanese Patent Laying-Open No. 2001-25265 (page 4, FIG. 1) JP 2004-032933 A (page 2-3, FIG. 2)

The first prior art has a problem that the on-delay compensation amounts cp1 and cp2 in the compensation amount calculation circuit 4 are set in advance and the compensation amount is compensated for the on-delay, so that the on-delay compensation cannot be performed completely. . On-delay compensation is performed according to the direction of the voltage command, etc., but the current direction of each phase in a three-phase motor has a direction flowing into each phase and a direction flowing out. Of the three phases, the current direction of two phases is one of the directions, but the other one phase is both directions. For this reason, when on-delay compensation is performed for a predetermined amount of on-delay compensation in accordance with the direction of the voltage command or the like, both directions cannot be fully compensated, and on-delay compensation itself does not include transistor switching, motor characteristics, etc. As a result, it is difficult to compensate accurately, and as a result, there has been a problem that it vibrates when rotating or stopping.
In the second prior art, on-delay compensation is added in conjunction with the on / off state of the inverter arm. As in the first conventional example, the amount of on-delay compensation is constant and in both directions as in the intermediate phase. There is a problem in that it cannot vibrate completely and it is difficult to compensate accurately, so that it vibrates at the time of rotation or stop.
In the third prior art, both the direction of flowing through the intermediate phase and the direction of flowing in are canceled together in one cycle of the carrier frequency. However, since the on-delay itself exists and is affected, it vibrates during rotation and when stopped. There was a problem.
The present invention has been made in view of such problems, and based on the voltage or current command or detection current, the on-delay time is appropriately set without excess or deficiency, and the on-delay time is accurately compensated. It is an object of the present invention to provide a motor control device and its on-delay time setting method that can suppress vibration during motor rotation and stop.

In order to solve the above problem, the present invention is configured as follows.
According to a first aspect of the present invention, a current control unit that performs current control based on a current command and a detected current, a PWM conversion circuit that performs PWM conversion on a voltage command that is an output signal of the current control unit, and outputs a PWM signal; A motor control device configured to set an on-delay time in the PWM signal to control a switching element to drive a three-phase motor, and to detect an intermediate phase among the three phases in the three-phase motor based on the voltage command An on-delay time setting unit that determines and sets an on-delay time of the intermediate phase based on a comparison result between the voltage command of the intermediate phase and a predetermined value set in advance, and the on-delay time setting unit includes: The on-delay time between the phase other than the intermediate phase and the intermediate phase is set based on the comparison result.
According to a second aspect of the present invention, the on-delay time setting unit in the first aspect of the invention sets a predetermined amount of on-delay time for a phase other than the intermediate phase, and the voltage command for the intermediate phase is When the intermediate phase is greater than a predetermined value, the predetermined amount of the on-delay time is set for the intermediate phase, and when the voltage command for the intermediate phase is equal to or less than the predetermined value, the intermediate phase has an on-delay time that is smaller than the predetermined amount of the on-delay time. It is to set.
According to a third aspect of the present invention, the on-delay time smaller than the predetermined amount of on-delay time in the second aspect of the invention is ½ of the predetermined amount of on-delay time.
According to a fourth aspect of the present invention, there is provided a current control unit that performs current control based on a current command and a detected current, a PWM conversion circuit that performs PWM conversion on a voltage command that is an output signal of the current control unit, and outputs a PWM signal. An on-delay time setting method for a motor control device for setting an on-delay time in the PWM signal, and detecting an intermediate phase in three phases in the three-phase motor based on the voltage command. The on-delay time setting process is performed to determine and set the on-delay time of the intermediate phase based on a comparison result between the voltage command of the intermediate phase and a predetermined value set in advance. In the setting process, the on-delay time between the phase other than the intermediate phase and the intermediate phase is set based on the comparison result.
According to a fifth aspect of the present invention, in the on-delay time setting process according to the fourth aspect of the invention, a predetermined amount of on-delay time is set for a phase other than the intermediate phase, and the voltage command for the intermediate phase is When the intermediate phase is greater than a predetermined value, the predetermined amount of the on-delay time is set for the intermediate phase, and when the voltage command for the intermediate phase is equal to or less than the predetermined value, the intermediate phase has an on-delay time that is smaller than the predetermined amount of the on-delay time. Set it.
According to a sixth aspect of the invention, the on-delay time smaller than the predetermined amount of on-delay time in the fifth aspect of the invention is ½ of the predetermined amount of on-delay time.
According to a seventh aspect of the present invention, a current control unit that performs current control based on a current command and a detected current, a PWM conversion circuit that performs PWM conversion on a voltage command that is an output signal of the current control unit, and outputs a PWM signal; In the motor control device that drives the three-phase motor by setting an on-delay time in the PWM signal to control the switching element, the voltage command for each phase in the three-phase motor and a predetermined value set in advance An on-delay time setting unit that determines and sets an on-delay time for each phase based on each comparison result, and the on-delay time setting unit determines an on-delay time for each phase based on each comparison result. Change and set.
According to an eighth aspect of the invention, the on-delay time setting unit in the seventh aspect of the invention sets a predetermined amount of on-delay time for each phase when the voltage command for each phase is smaller than the predetermined value. When the voltage command for each phase is equal to or greater than the predetermined value, an on delay time smaller than the predetermined amount of the on delay time is set for each phase.
According to a ninth aspect of the invention, an on-delay time smaller than the predetermined amount of on-delay time in the eighth aspect of the invention is ½ of the predetermined amount of on-delay time.
According to a tenth aspect of the present invention, there is provided a current control unit that performs current control based on a current command and a detected current, a PWM conversion circuit that performs PWM conversion on a voltage command that is an output signal of the current control unit, and outputs a PWM signal. An on-delay time setting method for a motor control device that sets an on-delay time in the PWM signal, based on a comparison result between a U-phase voltage command in the three-phase motor and a predetermined value set in advance. A U-phase on-delay time setting process for determining and setting time is performed, and an on-delay time is determined and set based on a comparison result between the V-phase voltage command and the predetermined value in the three-phase motor. A phase on delay time setting process is performed, and an on delay time is determined and set based on a comparison result between the W phase voltage command in the three phase motor and the predetermined value. And a phase-on delay time setting process, based on each phase of the comparison result, is to set by changing the phase of the on-delay time.
According to an eleventh aspect of the present invention, the on-delay time setting process for each phase in the tenth aspect of the present invention is performed when the voltage command for each phase is smaller than the predetermined value. When a fixed amount is set and the voltage command for each phase is equal to or greater than the predetermined value, an on delay time smaller than the predetermined amount of the on delay time is set for each phase.
According to a twelfth aspect of the present invention, an on-delay time smaller than the predetermined amount of on-delay time according to the eleventh aspect of the invention is ½ of the predetermined amount of on-delay time.

According to the first to sixth aspects of the present invention, instead of simply setting the preset on-delay time of each transistor for each phase, the phase is changed according to the state of each phase voltage command in the three-phase motor. Since an appropriate on-delay time is determined and set for each time, more accurate on-delay compensation can be achieved, the effect of on-delay is reduced, and smooth and highly accurate current control closer to each phase voltage command (current command) is performed. be able to. Further, vibration during motor rotation or stop can be suppressed, and stable motor control can be performed.
According to the seventh to twelfth aspects of the present invention, instead of simply setting the preset on-delay time of each transistor for each phase, it depends on the magnitude of the absolute value of each phase voltage command in the three-phase motor. As a result, an appropriate on-delay time is determined and set for each phase, so that more accurate on-delay compensation can be achieved, the effect of on-delay is reduced, and each phase voltage command (current command) is smoother and more accurate. Current control can be performed. Further, vibration during motor rotation or stop can be suppressed, and stable motor control can be performed.

  Hereinafter, specific examples of the method of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic configuration diagram showing the configuration of the motor control device of the present invention. In the figure, 1 is a motor control device, 11 is a position or speed control unit, 12 is a current control unit, 13 is a PWM conversion circuit, 14 is an inverter unit, 15 is an FB signal processing unit, 2 is a motor (motor), 3 A position detector 16 such as an encoder is an on-delay time setting unit. A configuration in which the motor 2 is driven in accordance with the position detection signal or the speed detection signal that is output from the command and the FB signal processing unit 15 (the motor control device 1, the position or speed control unit 11) is input. Since the current control unit 12, the PWM conversion circuit 13, the inverter unit 14, the FB signal processing unit 15, the motor (electric motor) 2, the position detector 3 such as an encoder, etc. are obtained by a well-known technique, a detailed description will be given. Omitted.
The part in which the present invention is different from the prior art is a part provided with an on-delay time setting unit 16, and the on-delay time setting unit 16 does not simply set the on-delay time uniformly for each phase, but a three-phase motor. The intermediate phase in the three phases is detected, and the voltage command of the intermediate phase is compared with a predetermined value, and in addition to the on-delay time setting for the phases other than the intermediate phase, according to the comparison result An appropriate on-delay time is set for the intermediate phase.

FIG. 2 is a flowchart showing the processing procedure of the on-delay time setting method of the present invention. The on-delay time setting method of the present invention will be described in order with reference to this figure.
(Step 1) A phase located in the middle of the three phases in the three-phase motor is detected, and the process proceeds to Step 2. In detection, the magnitudes of the three-phase voltage commands may be compared with each other to detect an intermediate phase among the three phases.
(Step 2) It is determined whether or not the detected voltage command of the intermediate phase is equal to or less than a predetermined value set in advance. If it is equal to or less than the predetermined value, the process proceeds to Step 3; Here, the predetermined value set in advance is a relatively small current value, for example, about 20 to 30% of the rated current value of the motor.
(Step 3) When the voltage command of the intermediate phase is equal to or less than a predetermined value set in advance, the on-delay time of the intermediate phase is set to a half of the preset normal on-delay time (predetermined amount of on-delay time), and the switching processing procedure Exit. Here, the normal on-delay time (predetermined amount of on-delay time) is an on-delay time in which the upper and lower transistors are not short-circuited under any conditions, and is determined by the specifications of the transistors to be used. The reason why the on-delay time of the intermediate phase may be half of the normal on-delay time (predetermined amount of on-delay time) is that when the transistor is less than the predetermined value which is a relatively small current value, it takes time to extinguish the transistor used. This is because no extra on-delay time is required.
(Step 4) If the voltage command of the intermediate phase is larger than a predetermined value set in advance, the on-delay time of the intermediate phase is set as a normal on-delay time, and the switching processing procedure is ended.
In this way, instead of simply setting a preset transistor on-delay time for each phase, an appropriate on-delay time is set for each phase according to the state of each phase voltage command in the three-phase motor. Since it is determined and set, accurate on-delay compensation can be performed, and smooth and highly accurate control closer to each phase voltage command (current command) can be performed. Note that the current direction other than the intermediate phase is one of the direction flowing into the phase and the direction flowing out, and the switching element switches in either direction, so the on-delay time may be a predetermined amount. Under the influence of switching of two phases other than the phase, both the upper switching element and the lower switching element are ignited, and since the current flows in both directions, the influence increases, so the on-delay time is smaller than a predetermined amount. There is a need to.

FIG. 3 is a flowchart showing the processing procedure of the on-delay time setting method of the present invention in the second embodiment. The on-delay time setting method of the present invention will be described in order with reference to this figure. In addition, the structure which implements this method is the same as that of Example 1 in FIG.
(Step 11) In a three-phase motor (U phase, V phase, W phase), it is determined whether or not the absolute value of the U phase voltage command is greater than or equal to a predetermined value. If it is smaller than the value, the process proceeds to step 13. Here, the predetermined value set in advance is a command with a sufficiently large voltage command, and is set to, for example, about half of the rated current value of the motor.
(Step 12) If the absolute value of the U-phase voltage command is equal to or greater than a predetermined value, the U-phase on-delay time is set to half of a preset normal on-delay time (predetermined amount of on-delay time) Proceed to step 14. Here, the normal on-delay time (predetermined amount of on-delay time) is an on-delay time in which the upper and lower transistors are not short-circuited under any conditions, and is determined by the specifications of the transistors to be used. In this case, the reason why the half of the normal on-delay time (predetermined amount of on-delay time) is sufficient is, for example, in the state where the magnitude of the three-phase voltage command is U phase> V phase>, W phase, When current flows from the U phase of the motor to the V and W phases, the U phase upper diode flows even if the U phase upper transistor is extinguished, and even if the U phase lower transistor is fired there, This is because no current flows. On the other hand, even if the U-phase lower side is extinguished and the U-phase upper transistor is extinguished, current does not flow immediately after the U-phase upper diode is extinguished so that it does not conduct.
(Step 13) If the absolute value of the U-phase voltage command is smaller than a predetermined value, the U-phase on-delay time is set to a normal on-delay time (predetermined amount of on-delay time). Proceed to
(Step 14) to (Step 19) For the V phase and the W phase, as in (Step 11) to (Step 13) in the U phase, the magnitude of the absolute value of the voltage command is compared with a predetermined value set in advance. Then, the on-delay time is set based on the comparison result, and the switching processing procedure is terminated.
In this way, instead of simply setting a preset transistor on-delay time for each phase, it is appropriate for each phase according to the magnitude of the absolute value of each phase voltage command in the three-phase motor. Since the on-delay time is determined and set, accurate on-delay compensation can be performed, and smooth and highly accurate control closer to each phase voltage command (current command) can be performed.
Further, instead of the voltage command in the first and second embodiments, a current command or a detected current (current feedback) may be used.

The block diagram which shows the structure of the motor control apparatus of this invention The flowchart which shows the process sequence of the on-delay time setting method in 1st Example of this invention. The flowchart which shows the process sequence of the on-delay time setting method in 2nd Example of this invention. Explanatory drawing for demonstrating operation | movement of the implementation block diagram in 1st prior art The block diagram which shows embodiment in 2nd prior art

Explanation of symbols

1 Motor control device 2 Motor (electric motor)
3 Position detector 11 Position or speed control unit 12 Current control unit 13 PWM conversion circuit 14 Inverter unit 15 FB signal processing unit 16 On-delay time setting unit

Claims (12)

A current control unit that performs current control based on a current command and a detected current; and a PWM conversion circuit that outputs a PWM signal by PWM-converting a voltage command that is an output signal of the current control unit, and is on-delayed to the PWM signal In a motor control device that sets a time and controls a switching element to drive a three-phase motor,
Based on the voltage command, an intermediate phase in the three phases of the three-phase motor is detected, and based on a comparison result between the voltage command of the intermediate phase and a predetermined value, the on-delay time of the intermediate phase is determined. It has an on-delay time setting section to determine and set,
The motor control device, wherein the on-delay time setting unit sets an on-delay time between a phase other than the intermediate phase and the intermediate phase based on the comparison result. The on-delay time setting unit sets a predetermined amount of on-delay time for a phase other than the intermediate phase,
If the voltage command of the intermediate phase is larger than the predetermined value, the predetermined amount of on-delay time is set in the intermediate phase,
2. The motor control device according to claim 1, wherein an on-delay time smaller than a predetermined amount of the on-delay time is set in the intermediate phase when the voltage command of the intermediate phase is equal to or less than the predetermined value.   The motor control device according to claim 2, wherein an on-delay time smaller than the predetermined amount of on-delay time is ½ of the predetermined amount of on-delay time. A current control unit that performs current control based on a current command and a detected current; and a PWM conversion circuit that outputs a PWM signal by PWM-converting a voltage command that is an output signal of the current control unit, and is on-delayed to the PWM signal In the on-delay time setting method of the motor control device for setting the time,
An intermediate phase detection process for detecting an intermediate phase in the three phases in the three-phase motor based on the voltage command,
On-delay time setting processing for determining and setting the on-delay time of the intermediate phase based on a comparison result between the voltage command of the intermediate phase and a predetermined value set in advance,
An on-delay time setting method for a motor control device, wherein the on-delay time setting process sets the on-delay time between a phase other than the intermediate phase and the intermediate phase based on the comparison result. The on-delay time setting process sets a predetermined amount of on-delay time for a phase other than the intermediate phase,
If the voltage command of the intermediate phase is larger than the predetermined value, the predetermined amount of on-delay time is set in the intermediate phase,
5. The on-delay time setting for a motor control device according to claim 4, wherein when the intermediate-phase voltage command is equal to or less than the predetermined value, an on-delay time smaller than a predetermined amount of the on-delay time is set for the intermediate phase. Method.   6. The on-delay time setting method for a motor control device according to claim 5, wherein an on-delay time smaller than the predetermined on-delay time is ½ of the predetermined on-delay time. A current control unit that performs current control based on a current command and a detected current; and a PWM conversion circuit that outputs a PWM signal by PWM-converting a voltage command that is an output signal of the current control unit, and is on-delayed to the PWM signal In a motor control device that sets a time and controls a switching element to drive a three-phase motor,
An on-delay time setting unit configured to determine and set an on-delay time of each phase based on each comparison result between the voltage command of each phase in the three-phase motor and a predetermined value set in advance;
The motor control device, wherein the on-delay time setting unit changes and sets the on-delay time of each phase based on the comparison results. The on-delay time setting unit sets a predetermined amount of on-delay time for each phase when the voltage command for each phase is smaller than the predetermined value,
8. The motor control device according to claim 7, wherein when the voltage command for each phase is equal to or greater than the predetermined value, an on delay time smaller than a predetermined amount of the on delay time is set for each phase.   9. The motor control device according to claim 8, wherein an on-delay time smaller than the predetermined on-delay time is ½ of the predetermined on-delay time. A current control unit that performs current control based on a current command and a detected current; and a PWM conversion circuit that outputs a PWM signal by PWM-converting a voltage command that is an output signal of the current control unit, and is on-delayed to the PWM signal In the on-delay time setting method of the motor control device for setting the time,
A U-phase on-delay time setting process for determining and setting an on-delay time based on a comparison result between a U-phase voltage command in the three-phase motor and a predetermined value set in advance;
A V-phase on-delay time setting process for determining and setting an on-delay time based on a comparison result between the V-phase voltage command and the predetermined value in the three-phase motor;
Based on a comparison result between the W-phase voltage command and the predetermined value in the three-phase motor, a W-phase on-delay time setting process is performed to determine and set an on-delay time,
An on-delay time setting method for a motor control device, wherein the on-delay time of each phase is changed and set based on the comparison result of each phase. The on-delay time setting process for each phase sets a predetermined amount of on-delay time for each phase when the voltage command for each phase is smaller than the predetermined value,
11. The on-delay time setting method for a motor control device according to claim 10, wherein when the voltage command for each phase is equal to or greater than the predetermined value, an on-delay time smaller than a predetermined amount of the on-delay time is set for each phase. .   12. The on-delay time setting method for a motor control device according to claim 11, wherein an on-delay time smaller than the predetermined on-delay time is ½ of the predetermined on-delay time.

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