JP2009296678A - Output estimating device, motor controller using the same, and motor control system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly safe and reliable motor control system at low cost. <P>SOLUTION: An output estimating device includes: a motor current detecting part 24 that detects a current value of the motor current for at least two phases of a three-phase synchronous motor 2; a current computer 25 that obtains, by computation, a motor current for three phases using the motor current for the two phases detected with the motor current detecting part 24; and an output estimating part 5 that estimates a torque output from the three-phase synchronous motor 2 from the motor currents 10a to 10c for three phase obtained with the current computer 25. The output estimating part 5 estimates the output from the three-phase synchronous motor 2 using the crest value of the motor current obtained by a square sum of the motor current for three phases obtained with the current computer 25. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an output estimation device that estimates the torque or thrust of a three-phase synchronous motor driven by sinusoidal driving by a simple method.

  In a system in which a motor is controlled by PWM (Pulse Width Modulation) control, digital control using a microprocessor is widely performed. In order to control the motor, it is necessary to detect the motor current and the rotor position information of the motor. In the digital control, the motor information is detected at every predetermined sampling period.

  The torque output by the surface permanent magnet synchronous motor used in the FA servo is proportional to the motor current, so the motor output is controlled by controlling the motor current value with PWM control. The torque to be controlled can be controlled.

  In a system product using such a motor, an effort is made to detect the torque output from the motor and to protect the system as a safety signal for the purpose of improving controllability and safety.

  Torque can be detected with high accuracy by using a strain gauge or eddy current detection type torque detector, but the system becomes large because it is mounted between the motor shaft and the load. Performance degradation due to is a problem. In order to solve this problem, as shown in FIG. 8, a method has been proposed in which torque is calculated from motor current and rotor position information (see, for example, Patent Document 1).

Moreover, although it is an example of an induction motor, the method of calculating | requiring by calculating a torque from the motor current and the line voltage of each phase is proposed (for example, refer patent document 2).
JP 2001-255220 A Japanese Patent Laid-Open No. 06-217585

  However, in the method of Patent Document 1, it is necessary to detect the position information of the rotor. However, the recent I / F between the motor control device and the rotor position detecting means (for example, a rotary encoder) is serial for line saving. In most cases, communication is performed, and rotor position information cannot be easily obtained from the outside. Moreover, attaching an encoder to the motor increases the cost.

  On the other hand, in the method of Patent Document 2, it is necessary to detect the line voltage of each phase. However, when PWM control is performed, a pulse-like waveform that is periodically coarse and dense is formed, and this waveform is shaped by a low-pass filter. However, when the voltage value is obtained, an error in amplitude or phase becomes large.

  The present invention solves the above-described conventional problems, and an object thereof is to provide an inexpensive, safe and reliable motor control system.

In order to solve the above-described problem, the output estimation device according to claim 1 is detected by a motor current detection unit that detects a current value of a motor current for at least two phases of a three-phase synchronous motor and the motor current detection unit. A current calculator for calculating a motor current for three phases using a motor current for two phases, and a torque output by the three-phase synchronous motor from a motor current for the three phases determined by the current calculator, or An output estimator for estimating thrust is provided, and the output estimator estimates the output using the peak value of the motor current obtained from the sum of squares of the motor current for three phases obtained by the current calculator.

  Further, in the output estimation device according to claim 2, the motor current detection unit detects a current value of the motor current for three phases, adds the motor currents for two phases, and the value obtained by reversing the sign and the remaining one. It is good also as a structure which compares with the electric current value of a phase, and determines with it being abnormal when a value differs.

  The output estimation device according to claim 3, wherein the estimated value obtained by the output estimation unit is input and compared with an output upper limit set value, and when the output upper limit set value is exceeded, the three-phase synchronous motor A command circuit that generates a command to stop the operation may be provided.

  The output estimation device according to claim 4 inputs the estimated value obtained by the output estimation unit, compares it with the output upper limit set value, and reduces the motor output when the output upper limit set value is exceeded. It is good also as a structure which provided the command circuit which produces | generates a command.

  The motor control device according to claim 5 is a motor control device that drives a three-phase synchronous motor by sinusoidal drive, and a motor current detection unit that detects a current value of a motor current of the three-phase synchronous motor; An output estimation unit for estimating the torque or thrust output from the three-phase synchronous motor from the three-phase motor current detected by the motor current detection unit, the output estimation unit detected by the motor current detection unit The output is estimated using the peak value of the motor current obtained from the sum of squares of the motor current for three phases.

  In addition, the motor control system according to claim 6 includes a command circuit provided with an output upper limit setting value outside the motor control device according to claim 5, and an estimated value obtained by the output estimation unit of the motor control device. Is input to the command circuit and compared with the output upper limit set value, and when the estimated value exceeds the output upper limit set value, the command circuit instructs the motor control device to stop the three-phase synchronous motor. Output.

  The motor control system according to claim 7 is a motor control system for driving a three-phase synchronous motor by sinusoidal drive, and detects a current value of a three-phase synchronous motor and a motor current of the three-phase synchronous motor. A motor control device having a first output estimation unit for estimating torque or thrust output from the three-phase synchronous motor from three-phase motor currents detected by one motor current detection unit; and outside the motor control device An output estimation device including a second output estimation unit that estimates torque or thrust output from the three-phase synchronous motor from three-phase motor currents detected by the provided second motor current detection unit; And a command circuit that inputs the estimated value obtained by the second output estimating unit and compares the estimated value with a preset setting value, wherein the command circuit determines that the difference between the two estimated values input is the set value. When there was example, it outputs a command for stopping the three-phase synchronous motor to the motor controller.

  According to the output estimation device of the first aspect, it is not necessary to detect the position information of the rotor or the mover, and the motor output can be easily estimated only by detecting the two-phase motor current. For this reason, it is not necessary to install a torque detector, and there is no deterioration in control performance due to the installation of the coupling and the increase in the shaft length, and an inexpensive motor control system can be constructed.

  According to the output estimation device of the second aspect, since the abnormality can be sequentially detected by the motor current for three phases, the reliability of the estimated output value is increased.

  Further, according to the output estimation device of the third aspect, since the system can be stopped when the estimated value exceeds the output upper limit set value, an inexpensive and highly safe motor control system can be constructed. .

  Further, according to the output estimation device of the fourth aspect, since it is possible to operate while reducing the motor output when the estimated value exceeds the output upper limit setting value, it is inexpensive with priority given to continuity of operation, A highly safe motor control system can be constructed.

  Further, according to the motor control device of the fifth aspect, since the configuration of the motor current detection unit can be shared, the configuration for output estimation can be provided at low cost.

  According to the motor control system of the sixth aspect, the three-phase synchronous motor can be stopped at the output value estimated by the motor control device, so that a cheaper and safer motor control system can be provided.

  Further, according to the motor control system of the seventh aspect, the estimated value obtained by the two output estimating units provided inside and outside the motor control device is compared to check the abnormal state, so that the safety is higher. A motor control system can be provided.

In a motor control device that drives a three-phase synchronous motor by sinusoidal drive, a motor current detector that detects a current value of a motor current of the three-phase synchronous motor, and a motor current for three phases detected by the motor current detector The output estimation unit for estimating the torque or thrust output from the three-phase synchronous motor is obtained from the sum of squares of the motor currents for the three phases detected by the motor current detection unit. The output is estimated using the peak value of the motor current. Hereinafter, specific embodiments will be described with reference to the drawings.
(Embodiment 1)
Embodiment 1 of the present invention will be described with reference to FIGS. FIG. 1 shows a block diagram of a motor control system equipped with an output estimation device (torque estimation device) outside the motor control device. The role of each block will be described below.

  In FIG. 1, reference numeral 1 denotes a motor control device that drives a motor by applying a voltage, 2 denotes a three-phase synchronous motor, and 3 denotes a position sensor.

  In the three-phase synchronous motor 2, a magnet is arranged on the rotor surface to generate magnet torque, a rotor is provided with a slit to generate only reluctance torque, or a magnet is arranged inside the rotor to generate magnet torque. That generate both torque and reluctance torque, and have been introduced into appropriate fields in consideration of efficiency, torque performance, and cost, which are characteristics of the motor.

  The position sensor 3 requires a CS sensor that detects only the magnetic pole position (commutation) of the rotor, high-accuracy positioning control, and high responsiveness and robustness in the FA and automobile fields. Detectors such as a rotary encoder having a resolution of 17 bits or more and a resolver having a resolution of 10 bits or more per rotation are used. Further, the I / F between the position sensor 3 and the motor control device 1 is often based on serial communication for the purpose of wire saving.

The motor control device 1 drives the motor by controlling the timing of applying a voltage to the motor based on the rotor position information from the position sensor 3, and is often equipped with current control. A shunt resistor is arranged to convert the motor current into a voltage, and the converted voltage value is converted into digital data by an A / D converter.

  FIG. 2 shows a three-phase motor current waveform diagram, which is a sine wave having a phase difference of 2 / 3π radians, and U-phase, V-phase, and W-phase motor currents are represented by Iu, Iv, Iw, θre. Is the electrical angle, and A is the peak value of the sine wave, the motor current detects a two-phase current, and the remaining one phase can be obtained by calculation from Equation 1 below. In many cases, the structure is different.

  The motor current is converted into q-axis current Iq and d-axis current Id by the three-phase / two-phase conversion from the following formula 2 together with the rotor position information from position sensor 3, and the q-axis and d-axis currents are commanded. The motor torque is controlled by controlling the current so as to match the value.

  In order to obtain the torque output by the motor with the above configuration, it can be obtained by calculating the following Equation 3 or Equation 4.

  Here, Pn is the number of pole pairs of the motor, Φfa is the maximum value of the number of armature winding interlinkage magnetic fluxes linked to the winding for one phase, Φfa is obtained by converting Φfa to 3 phase / 2 phase, Φfad = Sqrt (3/2) · Φfa.

  In this case, the electrical angle θre of the rotor is necessary. However, since the information of the position sensor 3 is connected to the motor control device 1 by serial communication, it is difficult to detect the information of the position sensor 3 by an external system. is there.

  In order to solve this problem, a motor current detector 24 (configured by a current detector 4a, a current detector 4c, and an AD converter 6), a current calculator 25, and an output estimator 5 are provided outside the motor control device 1. An output estimation device is provided.

The current detector 4a and the current detector 4c detect a current flowing through the motor winding and convert it into a voltage, and a CT (Current Transfer) or a resistor is used. The motor current converted into a voltage value by the current detector 4a and the current detector 4c is converted into a digital signal by the AD converter 6.

  The current calculator 25 adds the two-phase motor currents detected as digital signals by the AD converter 6 and obtains the remaining one-phase current by a method of sign inversion (see Equation 1).

  The output estimation unit 5 uses the three-phase motor current obtained by the current calculator 25 and obtains an estimated value of the output torque as follows. A three-phase sine wave signal having a peak value of 1 and a phase difference of 2 / 3π radians has the characteristic shown in the following Expression 5.

  When the peak value of the three-phase motor current is A and is expressed as the above-described expression 1, the expression 1 can be converted into the following expression 6 using the characteristic of the expression 5.

  Thus, the peak value of the motor current can be obtained from the detected instantaneous value of the motor current without using the electrical angle θre. The torque of the motor can be easily obtained by calculating the following Expression 7 from this peak value.

  Here, Pn is the number of pole pairs of the motor, and Φfa is the maximum value of the number of armature winding linkage magnetic fluxes linked to the windings for one phase, which is a known number determined by the drive motor.

  The motor current detection unit 24 is configured to detect a motor for two phases, but may detect a motor current for three phases. In this case, the calculation of the current calculator 25 is not necessary.

According to the output estimation apparatus of the first embodiment, the torque output from the three-phase synchronous motor can be estimated by detecting the two-phase motor current and performing simple arithmetic processing without requiring the rotor position information. As described above, since the output abnormality can be detected without using the torque detector, the safety of the system can be ensured.
(Embodiment 2)
In the first embodiment, the motor current detector detects the motor current for two phases, but in the second embodiment, the motor current for three phases is detected. For this reason, the calculation of the current calculator in the first embodiment becomes unnecessary. Hereinafter, the difference will be mainly described.

  FIG. 3 is a block diagram of the output estimation apparatus according to the second embodiment. In FIG. 3, the output estimation device installed outside the motor control device 1 includes a motor current detection unit 24a (consisting of three current detectors 4a-4c and an AD converter 6a) and an output estimation unit 5a. The motor currents for the three phases detected by the current detectors 4a-4c are input to the AD converter 6a and converted into digital signals, respectively.

  The three-phase motor current converted into the digital signal is input to the output estimation unit 5a, and the detected three-phase is detected using the property that the sum of the three-phase sine wave signals having a phase difference of 2 / 3π radians becomes zero. Add all the motor currents in minutes.

      If the calculation result is within the detection error range, the output estimation unit 5a obtains an estimated value of the output torque as in the first embodiment. On the other hand, if the calculation result is outside the detection error range, a motor abnormality or a CT, resistor, or AD converter abnormality is assumed. In this case, it is determined that the system is abnormal.

  The detection error can be obtained from the accuracy of CT, resistor, AD converter, and variation in the number of armature winding linkage magnetic fluxes linked to the motor windings. Since it is about 5 to 10%, the detection error range may be set to 10 to 15%. This variation range is accurate to within a few percent with a method in which a measuring instrument is connected to the outside such as a torque detector, but is the same variation with methods that calculate from current and voltage, or methods that use current and rotor position information. Since this is a factor, the output estimation accuracy of this method is at a level that can be used sufficiently.

According to the output estimation apparatus of the second embodiment, it is possible to easily detect CT output abnormality, resistor short circuit / resistance change abnormality, and current detection abnormality caused by AD converter failure.
(Embodiment 3)
Embodiment 3 of the present invention will be described. The difference from the first and second embodiments is that a command circuit is newly provided, and this point will be mainly described.

  FIG. 4 is a block diagram of the motor control system in the third embodiment. In FIG. 4, the command circuit 22 receives the estimated torque output from the output estimation unit 5c, and outputs a command to the motor control device 1 to drive or stop the motor. In order to determine whether to drive / stop, the command circuit 22 is set with a maximum allowable torque in advance.

  The command circuit 22 compares the maximum allowable torque and the estimated torque value of the output estimating unit 5c, and issues a command to stop the three-phase synchronous motor when the relationship | torque estimated value |> | maximum allowable torque | Output.

  Further, the command circuit 22 compares the maximum allowable torque with the estimated torque value of the output estimating unit 5c, and when the relationship of | torque estimated value |> | maximum allowable torque | A command for reducing the limit value may be output to the motor control device 1.

According to the present embodiment, the output torque of the three-phase synchronous motor is limited to the maximum allowable torque with a simple configuration, and the system can be stopped when an abnormality that exceeds the maximum allowable torque occurs. Further, by giving a command for further reducing the output torque of the three-phase synchronous motor, an inexpensive and highly safe system can be constructed.
(Embodiment 4)
Embodiment 4 of the present invention will be described. The difference from the first and second embodiments is that the motor current detection unit and the output estimation unit are provided not in the motor control device 1 but in the motor control device 1.

  FIG. 5 is a block diagram of a motor control device according to the fourth embodiment. In FIG. 5, the motor current detection unit 24b installed in the motor control device 1 is composed of three current detectors 12a-12c and an AD converter 14, and each role is the same as in the first and second embodiments. Therefore, explanation is omitted.

  The three-phase motor current detected by the motor current detection unit 24b is added to the detected three-phase motor current using the property that the sum of the three-phase sine wave signals is zero by the output estimation unit 21. To do.

  If the calculation result is within the detection error range, the torque estimation is calculated using Expressions 6 and 7 as in the first embodiment, and the output torque is estimated. If the calculation result is outside the detection error range, it is assumed that the motor is abnormal, or that the CT, resistor, or AD converter is abnormal. In this case, it is determined that the system is abnormal. Since the detection error range is about ± 5 to 10% as described above, the detection error range may be set to 10 to 15%.

  In the present embodiment, the three-phase motor current is detected by the motor current detection unit. However, as in the first embodiment, at least two current detectors provided in a general motor control device are used. It is good also as a structure which detects only the motor current for two phases.

According to the present embodiment, it is possible to estimate the torque output from the three-phase synchronous motor with an inexpensive configuration including only the motor control device.
(Embodiment 5)
Embodiment 5 of the present invention will be described. The difference from the fourth embodiment is that a command circuit is provided outside the motor control device to monitor the output abnormality of the three-phase synchronous motor, and this point will be mainly described.

  FIG. 6 is a block diagram of a motor control system according to the fifth embodiment. In FIG. 6, the command circuit 22 outputs to the motor control device 1 a command to drive or stop the three-phase synchronous motor 2. For the determination of driving / stopping, the maximum allowable torque is set in the command circuit 22 in advance, and the relationship of | torque estimated value |> | maximum allowable torque | When established, the three-phase synchronous motor is stopped.

  Alternatively, when the relationship of | torque estimated value |> | maximum allowable torque | is established by comparing the maximum allowable torque with the estimated torque value estimated by the output estimating unit 5c, the command circuit 22 determines the three-phase synchronous motor. A command to lower the torque limit value to the motor control device 1 may be output. Further, the command circuit 22 may be provided inside the motor control device 1.

According to the present embodiment, since the motor control device estimates the output torque, it is possible to limit the output of the three-phase synchronous motor with a simpler configuration, and when an abnormality that exceeds the maximum allowable torque occurs, the system Can be stopped. Alternatively, it is possible to provide an inexpensive and highly safe motor control system by giving a command to reduce the output of the three-phase synchronous motor.
(Embodiment 6)
Embodiment 6 of the present invention will be described. The difference from Embodiments 1 to 5 is that an output estimation unit and a motor current detection unit are provided both inside and outside the motor control device, and this point will be mainly described.

  FIG. 7 is a block diagram of a motor control system according to the sixth embodiment. In FIG. 7, both the estimated torque value 23 obtained by the torque estimating unit 21 inside the motor control device 1 and the estimated torque value 11 obtained by the torque estimating unit 5 a installed outside the motor control device 1 are commanded together. Input to the circuit 22a.

The command circuit 22a first compares the input torque estimate value 11 with the torque estimate value 23. If the difference is outside the detection error range, the command circuit 22a determines that there is an abnormality and stops the system. To the unit 16. If the difference is within the detection error range, the maximum allowable torque set in advance in the command circuit 22a is compared with the estimated torque values estimated by the torque estimating unit 5a and the torque estimating unit 21, and the | torque estimated value | If the relationship> | maximum allowable torque | is satisfied, the motor is stopped. Since the detection error range is about ± 5 to 10% as described above, the detection error range may be set to 10 to 15%.

  Similarly, the maximum allowable torque set in advance in the command circuit 22a is compared with the estimated torque values estimated by the torque estimating unit 5a and the torque estimating unit 21, and the relationship of | torque estimated value |> | maximum allowable torque | When the above is established, a command to reduce the torque limit value to the motor may be output to the motor control device 1.

  According to the present embodiment, the results of the motor current detector and the torque estimator installed inside and outside the motor control device 1 are compared by the command circuit to check the abnormal state. Can be configured.

  The above-described first to sixth embodiments are configured to estimate the torque (rotation system) output by the three-phase synchronous motor. However, the thrust (direct current) output by the three-phase synchronous linear motor is obtained in the same manner. Dynamic system) can be estimated.

  In addition, the torque equation of a synchronous motor including an IPM motor (Internal Magnet Synchronous Motor) in which a magnet is arranged inside the rotor and a synchronous reluctance motor (Synchronous Reluctance Motor) having no magnet in the rotor and having a slit is as follows. It is represented by the following formula 8.

  Here, Ld is a d-axis inductance, Lq is a q-axis inductance, and β is a phase angle when the q-axis phase is 0 radians. In the case of a synchronous motor with a surface magnet structure, the maximum torque is obtained when the phase angle β is 0 radians. In the case of a synchronous reluctance motor, the phase angle β is π / 4 radians, and in the case of an IPM motor, the values of Ld and Lq. The phase angle for generating the maximum torque differs depending on Since Ld and Lq are known numbers, and the phase angle β at which the maximum torque is output can be calculated from these known numbers, the output can be estimated in the same manner for IPM motors and synchronous reluctance motors.

  The output estimation device and motor control device of the present invention can estimate the output of a three-phase synchronous motor without the position information of the rotor or mover, and are useful for ensuring safety in a rotary and linear motion motor control system. It is.

Block diagram of output estimation apparatus according to Embodiment 1 Explanatory drawing of the motor current waveform of the first embodiment Block diagram of output estimation apparatus according to Embodiment 2 Block diagram of motor control system in Embodiment 3 Block diagram of motor control apparatus in embodiment 4 Block diagram of motor control system in Embodiment 5 Block diagram of motor control system in Embodiment 6 Main part block diagram of torque estimation device in conventional example

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Motor controller 2 Three-phase synchronous motor 3 Position sensor 4a, 4b, 4c Current detector 5, 5a, 5c Output estimation part 6, 6a AD converter 7a, 7b, 7c Motor detection current (analog value) of each phase
8a, 8b, 8c Motor current of each phase 9 Position information serial communication data 10a, 10b, 10c Motor detection current of each phase (digital value)
12a, 12b, 12c Current detector (in the motor controller)
14 AD converter (in the motor controller)
15 Position detection circuit (in the motor controller)
16 Motor control unit 17 Motor drive circuit 18 PWM signal for each phase 20 Position information 21 Output estimation unit (in motor control device)
22, 22a Command circuit 23 Estimated torque value 24, 24a, 24b Motor current detector 25 Current calculator 26a, 26b I / F data

Claims (7)

A motor current detector for detecting a current value of a motor current for at least two phases of the three-phase synchronous motor;
A current calculator for calculating a motor current for three phases using a motor current for two phases detected by the motor current detector;
An output estimation unit for estimating the torque or thrust output by the three-phase synchronous motor from the motor current for three phases obtained by the current calculator;
The output estimation unit estimates an output using a peak value of a motor current obtained from a square sum of motor currents for three phases obtained by the current calculator.   The motor current detection unit detects the current value of the motor current for three phases, adds the motor current for two phases, compares the value obtained by inverting the sign, and the current value of the remaining one phase. The output estimation apparatus according to claim 1, wherein the output is determined to be abnormal.   An estimated value obtained by the output estimating unit is input and compared with an output upper limit set value, and when the output upper limit set value is exceeded, a command circuit is provided that generates a command to stop the three-phase synchronous motor. The output estimation apparatus according to claim 1 or 2.   The estimated value calculated | required in the said output estimation part is input, compared with an output upper limit setting value, and the command circuit which produces | generates the instruction | command which reduces a motor output when the said output upper limit setting value is exceeded is provided. The output estimation apparatus according to claim 2. In a motor control device that drives a three-phase synchronous motor with sinusoidal drive,
A motor current detector for detecting a current value of the motor current of the three-phase synchronous motor;
An output estimation unit for estimating the torque or thrust output by the three-phase synchronous motor from the motor current for the three phases detected by the motor current detection unit;
The output estimation unit estimates the output using a peak value of a motor current obtained from a square sum of motor currents for three phases detected by the motor current detection unit. A command circuit provided with an output upper limit set value outside the motor control device according to claim 5,
When the estimated value obtained by the output estimating unit of the motor control device is input to the command circuit and compared with the output upper limit set value, and when the estimated value exceeds the output upper limit set value,
The command circuit is a motor control system that outputs a command to stop the three-phase synchronous motor to the motor control device. In a motor control system that drives a three-phase synchronous motor with sinusoidal drive,
A three-phase synchronous motor,
First output estimation for estimating the torque or thrust output by the three-phase synchronous motor from the three-phase motor current detected by the first motor current detector that detects the current value of the motor current of the three-phase synchronous motor. A motor control device having a section;
An output comprising a second output estimating unit for estimating the torque or thrust output by the three-phase synchronous motor from the motor current for three phases detected by the second motor current detecting unit provided outside the motor control device. An estimation device;
A command circuit for inputting estimated values obtained by the first and second output estimating units and comparing the estimated values with a preset set value;
The command circuit outputs a command to stop the three-phase synchronous motor to a motor control device when a difference between two input estimated values exceeds the set value.

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