JP2007244028A - Motor controller and electric power steering system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor controller in which disconnection can be detected with high precision without sacrifice of control stability. <P>SOLUTION: If such a state as a duty command value αx corresponding to that phase does not fall within a range (αLo≤αx≤αHi) corresponding to a threshold N0 for specifying a predetermined value Ith and a judgment object range sustains although the power supply voltage Vps is appropriate (Vps≥Vth) when a phase current value Ix is below the predetermined value Ith (Ix≤Ith) and the number of revolutions N falls within a disconnection judgment object range (N≤N0), a disconnection detecting section judges that disconnection occurred. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a motor control device and an electric power steering device.

  In recent years, electric power steering devices (EPS) using a motor as a drive source have been widely adopted as vehicle power steering devices. In many cases, the motor control device is provided with a disconnection detection function for detecting disconnection of a power supply line (a power line and a motor coil between a drive circuit that supplies drive power and a motor).

  That is, when the power supply line is disconnected, the motor stops or cannot stably generate torque, and a change in steering torque accompanying this causes deterioration in steering feeling. In view of this, it has a function of quickly detecting the occurrence of such disconnection of the power supply line and monitoring it promptly for failsafe.

Specifically, as disclosed in Patent Document 1, conventionally, in many motor control devices, such disconnection of the power supply line is detected based on whether or not the current deviation is within an appropriate range. That is, for example, in EPS in which current feedback is performed to generate a target assist torque, a deviation between the current command value and the detected actual current value occurs due to a state in which no current flows through the power supply line due to the occurrence of disconnection. Will increase. When the current deviation exceeds an appropriate range that can be taken during normal control, it is determined that a break has occurred in the power supply line.
JP 2000-177610 A

  However, in the disconnection detection based on such current deviation, a trade-off between the detection accuracy and the stability during normal control becomes a problem. That is, it goes without saying that the current deviation exists even during normal control, and therefore, when the actual current followability is low, the frequency of erroneous detection tends to increase. Therefore, in view of improving the accuracy of disconnection detection, it is desirable to increase the current response by setting the feedback gain as high as possible. However, on the other hand, there is a problem that it becomes more susceptible to noise as the current responsiveness becomes higher, and there is a possibility that abnormal noise and deterioration of steering feeling may be caused by a decrease in control stability due to this. is there. For this reason, in the above-described conventional technology, the disconnection detection accuracy cannot be increased due to the difficulty in balancing the disconnection detection accuracy and the control stability. In this respect, there is still room for improvement. It was.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a motor control device and an electric power steering device capable of detecting disconnection with higher accuracy without impairing control stability. Is to provide.

  In order to solve the above problems, the invention according to claim 1 is provided in the middle of a power supply path between a motor and a power source, and supplies a driving power to the motor, and the operation of the driving circuit. And control means for controlling the operation of the drive circuit to apply to the motor an applied voltage determined based on an actual current value energized to the motor, and the drive power Is a motor control device that detects disconnection of a power supply line to which power is supplied, wherein the control means supplies power when the actual current value is a predetermined value or less and the rotation speed of the motor is within a determination target range. It is determined that the disconnection has occurred when a state in which the applied voltage is not within a range corresponding to the predetermined value and the threshold value of the determination target range continues despite the voltage being appropriate. To

  According to the above configuration, disconnection can be detected as long as the current command is generated even if it is a little regardless of the current feedback gain. Then, by setting each threshold based on the motor NT characteristic, it is possible to eliminate the occurrence of erroneous detection. Therefore, more accurate disconnection detection can be performed without impairing control stability.

The gist of the invention described in claim 2 is that the control means uses an internal command value that defines the applied voltage as the applied voltage.
According to the above configuration, the detection accuracy can be further improved by eliminating the voltage detection error.

The gist of the invention described in claim 3 is that the continuation determination is made based on whether or not an integration time in a state not within the corresponding range within a predetermined time is equal to or greater than a predetermined threshold.
According to the above configuration, it is possible to perform disconnection detection with higher accuracy by eliminating the influence of disturbance such as detection error of each sensor.

  According to a fourth aspect of the present invention, the motor is a brushless motor having a three-phase motor coil, and the control means has a relationship between the actual current value and the rotational speed and the applied voltage for each phase. The gist is to determine the disconnection based on.

According to the said structure, since a disconnection detection is possible for every phase, the appropriate fail safe according to the disconnection state can be aimed at.
The gist of the invention described in claim 5 is an electric power steering device provided with the motor control device according to any one of claims 1 to 4.

  According to the present invention, it is an object to provide a motor control device and an electric power steering device capable of detecting disconnection with higher accuracy without impairing control stability.

Hereinafter, an embodiment in which the present invention is embodied in an electric power steering apparatus (EPS) will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of the EPS 1 of the present embodiment. As shown in the figure, a steering shaft 3 to which a steering wheel (steering) 2 is fixed is connected to a rack 5 via a rack and pinion mechanism 4. It is converted into a reciprocating linear motion of the rack 5 by the and pinion mechanism 4. The rudder angle of the steered wheels 6 is changed by the reciprocating linear motion of the rack 5.

  The EPS 1 includes an EPS actuator 10 that applies an assist force for assisting a steering operation to the steering system, and an EPS ECU 11 that controls the operation of the EPS actuator 10.

  The EPS actuator 10 of the present embodiment is a so-called rack-type EPS actuator in which a motor 12 that is a driving source thereof is arranged coaxially with the rack 5, and an assist torque generated by the motor 12 is a ball screw mechanism (not shown). Is transmitted to the rack 5 via. The motor 12 of the present embodiment is a brushless motor, and rotates by receiving supply of three-phase (U, V, W) driving power from the EPS ECU 11. The EPS ECU 11 as the motor control device controls the assist force applied to the steering system by controlling the assist torque generated by the motor 12 (power assist control).

  In the present embodiment, a torque sensor 14 and a vehicle speed sensor 15 are connected to the EPS ECU 11. The EPS ECU 11 executes the operation of the EPS actuator 10, that is, power assist control based on the steering torque τ and the vehicle speed V detected by the torque sensor 14 and the vehicle speed sensor 15, respectively.

Next, the electrical configuration of the EPS of this embodiment will be described.
FIG. 2 is a control block diagram of the EPS of this embodiment. As shown in the figure, the EPS ECU 11 is provided in the middle of a power supply path between a microcomputer 17 that outputs a motor control signal and a motor 12 and an in-vehicle power source (battery) 16, and the motor 12 is based on the motor control signal. And a driving circuit 18 for supplying three-phase driving power.

  The drive circuit 18 of this embodiment is a known PWM inverter in which three arms corresponding to each phase are connected in parallel with a pair of switching elements connected in series as a basic unit (arm). The output of the motor control signal defines the on-duty ratio of each switching element constituting the drive circuit 18. A motor control signal is applied to the gate terminal of each switching element, and each switching element is turned on / off in response to the motor control signal, so that the DC voltage of the in-vehicle power supply 16 is changed to three phases (U, V, W). ) To be supplied to the motor 12.

  More specifically, in the present embodiment, the EPS ECU 11 detects the current sensors 21u, 21v, 21w for detecting the respective phase current values Iu, Iv, Iw energized to the motor 12, and the rotation angle θ of the motor 12. A rotation angle sensor 22 is connected for this purpose. Then, the microcomputer 17 sends a motor to the drive circuit 18 based on the phase current values Iu, Iv, Iw and the rotation angle θ of the motor 12 detected based on the output signals of these sensors, and the steering torque τ and the vehicle speed V. Output a control signal.

  More specifically, the microcomputer 17 calculates a current command value Iq * that is a control target amount of assist force to be applied to the steering system, and a current command calculated by the current command value calculator 23. And a motor control signal output unit 24 that outputs a motor control signal based on the value Iq *. The current command value calculation unit 23 calculates a current command value Iq * based on the steering torque τ and the vehicle speed V detected by the torque sensor 14 and the vehicle speed sensor 15, and outputs the current command value Iq * to a motor control signal output unit. 24. The motor control signal output unit 24 includes the current command value Iq * calculated by the current command value calculation unit 23, the phase current values Iu, Iv, Iw detected by the current sensors 21u, 21v, 21w, and the rotation angle. The rotation angle θ detected by the sensor 22 is input. Then, the motor control signal output unit 24, based on these phase current values Iu, Iv, Iw, and the rotation angle θ, supplies a current amount (actual amount) supplied to the motor 12 to the current command value Iq * which is a control target amount. A motor control signal is output so as to follow the current value.

  Specifically, in the present embodiment, the motor control signal output unit 24 generates a motor control signal by current feedback control in the d / q coordinate system. That is, in the motor control signal output unit 24, the phase current values Iu, Iv, and Iw are input to the three-phase / two-phase conversion unit 25 together with the rotation angle θ, and the three-phase / two-phase conversion unit 25 performs d / q It is converted into a d-axis current value Id and a q-axis current value Iq in the coordinate system. The current command value Iq * output from the current command value calculation unit 23 is input to the subtractor 26q as the q-axis current command value together with the q-axis current value Iq, and the d-axis current value Id is the d-axis current command value. It is input to the subtractor 26d together with Id * (Id * = 0). Then, the d-axis current deviation ΔId and the q-axis current deviation ΔIq calculated in the subtractors 26d and 26q are respectively input to the corresponding F / B control units 27d and 27q, and the F / B control units 27d and 27q are The d-axis voltage command value Vd * and the q-axis voltage command value Vq * are calculated by multiplying the d-axis current deviation ΔId and the q-axis current deviation ΔIq by a predetermined F / B gain (PI gain). The d-axis voltage command value Vd * and the q-axis voltage command value Vq * calculated by the F / B control units 27d and 27q are input to the two-phase / three-phase conversion unit 28 together with the rotation angle θ. The three-phase conversion unit 28 converts the voltage into three-phase voltage command values Vu *, Vv *, and Vw *. Then, the PWM command value generation unit 29 generates duty command values αu, αv, αw corresponding to these voltage command values Vu *, Vv *, Vw *, and the PWM output unit 30 outputs the duty command values αu, A motor control signal having an on-duty ratio indicated by αv and αw is output.

  In addition to the current command value calculation unit 23 and the motor control signal output unit 24, the microcomputer 17 of the present embodiment includes a power supply line between the drive circuit 18 and the motor 12, that is, motor coils 32u and 32v for each phase. , 32w and a disconnection detector 34 for detecting disconnection of the power lines 33u, 33v, 33w connecting the motor coils and the drive circuit 18.

  More specifically, in the present embodiment, the disconnection detection unit 34 is provided with an internal command that defines the voltage applied to the motor 12 together with the phase current values Iu, Iv, and Iw that are actual current values that are supplied to the motor 12. The duty command values αu, αv, αw for each phase, the power supply voltage Vps, and the rotation speed N of the motor 12 are input as values. In the present embodiment, the rotational speed N is calculated based on the rotational angular velocity ω obtained by differentiating the rotational angle θ (unit: [RPM]). Then, the disconnection detection unit 34 detects the disconnection of the power supply line based on these input state quantities, and if it is determined that the disconnection has occurred, the disconnection detection unit 34 notifies the current command value calculation unit 23 to that effect. The disconnection detection signal shown is output. As a result, the motor 12 is promptly stopped to achieve failsafe.

(Disconnection detection)
Next, an aspect of disconnection detection in the disconnection detection unit will be described.
As described above, in disconnection detection based on current deviation, there is a trade-off relationship between the detection accuracy and stability during normal control, and it is difficult to balance this at a high level. There is a problem that can not be raised.

  In consideration of this point, in the present embodiment, the disconnection detecting unit 34 determines that the phase current value Ix of each phase is equal to or less than a predetermined value Ith (Ix ≦ Ith) and the rotation speed N is within the target range for disconnection determination (N ≦ N0). When the power supply voltage Vps is appropriate (Vps ≧ Vth), the duty command value αx corresponding to the phase is a range (αLo) corresponding to the predetermined value Ith and the threshold value N0 that defines the determination target range. When the state not in (≦ αx ≦ αHi) continues, it is determined that a disconnection has occurred. The “X” indicates one of the three phases U, V, and W. And the disconnection detection part 34 performs the said disconnection detection for every phase.

  That is, as shown in FIG. 3, for example, when a disconnection occurs in the U-phase power supply line, the U-phase phase current value Iu is naturally “0”. It is considered that the actual current value (q-axis current value) does not follow Iq *. Therefore, the U-phase duty command value αu rises (or falls) beyond the range (αLo ≦ αx ≦ αHi) corresponding to the actual actual current value (Iu = 0). In this case, the “corresponding range” is set including detection errors of the current sensors 21u, 21v, and 21w.

  That is, as shown in FIG. 4, according to the motor NT characteristic (rotational speed-torque characteristic), the rotational speed N of the motor, the applied voltage Vap, and the torque generated by the motor (that is, the actual current value I) are When any two of these elements are determined, the remaining elements are also uniquely determined. For this reason, when the rotation speed N is within the determination target range (N ≦ N0) and the actual current value I is equal to or smaller than the predetermined value I0 (I ≦ I0), the applied voltage Vap to the motor is always the predetermined value. It is within the range of the predetermined voltage V0 (V ≦ V0) corresponding to I0 and the threshold value N0 of the determination target range.

  Here, when three-phase driving power is supplied, the actual current value I corresponds to the q-axis current value Iq. Therefore, the predetermined value Ith serving as the threshold value of the phase current value Ix can be obtained by the formula Ith = I0 / √ (3/2). If the power supply voltage Vps is within an appropriate range, the duty command value αx, which is an internal command value that defines the applied voltage Vap, should be within the range (αLo ≦ αx ≦ αHi) corresponding to the predetermined voltage V0. If this condition is not satisfied, it can be estimated that a disconnection has occurred in the power supply line of the phase.

  Note that “N0”, “I0 (Ith)”, and “V0 (αLo and αHi)” that are threshold values for the rotation speed N, the actual current value I (phase current value Ix), and the applied voltage Vap (duty command value αx) are: What is necessary is just to set arbitrarily according to the motor NT characteristic shown in FIG. That is, firstly, a range to be determined is set in consideration of the rotational speed at which the influence of disconnection is likely to be significant, and a value near zero is set as a predetermined value Ith that is a threshold value of the phase current value Ix. Then, the threshold values αLo and αHi of the duty command value αx corresponding to this are set. Alternatively, the predetermined value Ith of the phase current value Ix and the threshold values αLo and αHi of the duty command value αx are set in consideration of the detection error of each value. Then, a threshold value N0 of the rotation speed N may be set so as to correspond to this.

Next, a disconnection detection processing procedure by the disconnection detection unit will be described.
As shown in FIG. 5, the disconnection detection unit 34 first determines whether or not a measurement flag described later is set (measurement flag ON) (step 101). If not set (step 101: NO), initialization of each measurement counter (ta = 0, tb = 0) is executed (step 102). If it is determined in step 101 that the measurement flag has already been set (step 101: YES), that is, if the state estimated to be a disconnection state is being counted, the processing in step 102 is performed. Is not executed.

 Next, the disconnection detector 34 determines whether the phase current value Ix (absolute value thereof) is equal to or less than a predetermined value Ith (step 103), whether the rotational speed N is equal to or less than a threshold value N0 (step 104), and whether the power supply voltage Vps is It is sequentially determined whether it is within the appropriate range (step 105). When all of these determination conditions are satisfied (| Ix | ≦ Ith and N ≦ N0 and Vps ≧ Vth, steps 103, 104, 105: YES), the duty command value αx corresponding to the phase is subsequently set. It is determined whether or not the phase current value Ix is in a range (αLo ≦ αx ≦ αHi) corresponding to the predetermined value Ith of the phase current value Ix and the threshold value N0 of the rotational speed N (step 106).

  Next, when the duty command value αx is not within the above range (step 106: NO), the disconnection detection unit 34 sets a measurement flag (measurement flag ON, step 107), and increments the first counter (ta = ta + 1). Step 108). Then, it is determined whether or not the counter value ta of the first counter is equal to or greater than a predetermined threshold value t1 (step 109). If the counter value ta is equal to or greater than the predetermined threshold value t1 (ta ≧ t1, step 109: YES) ), A disconnection flag is set, that is, it is determined that a disconnection has occurred in the power line of the relevant phase (step 110).

  On the other hand, if any of the above conditions of Step 103 to Step 106 is not satisfied (| Ix |> Ith or N> N0 or Vps <Vth, or αx ≦ αLo or αx ≧ αHi, any of Steps 103, 104, 105) Is “NO” or step 106 is “YES”), the disconnection detection unit 34 does not execute the processing of step 107 to step 110. If the counter value ta does not reach the predetermined threshold value t1 in step 109 (ta <t1, step 109: NO), the process of step 110 is not executed.

  In this case, the disconnection detection unit 34 increments the second counter (tb = tb + 1, step 111). Then, it is determined whether or not the counter value tb of the second counter is equal to or greater than a predetermined threshold value t0 (step 112). If the counter value tb is equal to or greater than the threshold value t0 (tb ≧ t0, step 112: YES). Turns off the measurement flag (measurement flag OFF, step 113). If the counter value tb is smaller than the threshold value t0 (tb <t0, step 112: NO), the process of step 113 is not executed.

  That is, in the present embodiment, the disconnection detection unit 34 executes the processing of the above-described steps 101 to 113 at predetermined intervals, and within a predetermined time corresponding to the threshold value t0 for the counter value tb of the second counter. When the count value ta of the first counter, which is the accumulated time in a state in which all the conditions of Step 103 to Step 106 are satisfied, is equal to or greater than a predetermined threshold value t1, a disconnection occurs. When the counter value ta of the first counter does not reach the predetermined threshold value t1 within a predetermined time corresponding to the threshold value t0, the measurement flag is turned off and a series of disconnection detection determinations are performed again.

As described above, according to the present embodiment, the following features can be obtained.
(1) When the phase current value Ix of each phase is equal to or less than a predetermined value Ith (Ix ≦ Ith) and the rotation speed N is within the target range for disconnection determination (N ≦ N0), the disconnection detection unit 34 Although Vps is appropriate (Vps ≧ Vth), the duty command value αx corresponding to the phase is not within the range (αLo ≦ αx ≦ αHi) corresponding to the predetermined value Ith and the threshold value N0 that defines the determination target range. When the state continues, it is determined that a disconnection has occurred.

  According to the above-described configuration, disconnection can be detected as long as the current command value Iq * is generated even if it is a little, regardless of the current feedback gain. Then, by setting each threshold based on the motor NT characteristic, it is possible to eliminate the occurrence of erroneous detection. In addition, by using the duty command value αx, which is an internal command value that defines the applied voltage Vap, as a parameter instead of the applied voltage Vap, voltage detection errors can be eliminated and detection accuracy can be further improved. it can. Therefore, more accurate disconnection detection can be performed without impairing control stability. Furthermore, since the disconnection can be detected for each phase, an appropriate fail-safe according to the disconnection state can be achieved.

  (2) The disconnection detecting unit 34 is an integrated time in a state (step 106: NO) that satisfies all the above-described steps 103 to 106 within a predetermined time corresponding to the threshold value t0 for the counter value tb of the second counter. When the counter value ta of the first counter is greater than or equal to a predetermined threshold value t1, a disconnection occurs. Thereby, it is possible to detect the disconnection with higher accuracy by eliminating the influence of disturbance such as detection error of each sensor.

In addition, you may change this embodiment as follows.
In the present embodiment, the present invention is embodied in an electric power steering device (EPS), but may be embodied in other motor control devices.

In the present embodiment, the motor drive device of the brushless motor is embodied, but the motor drive device of a motor with a brush may be embodied.
In this embodiment, the duty command value αx, which is an internal command value that defines the applied voltage Vap, is used as a parameter as a proxy variable of the applied voltage Vap. However, a voltage command value Vx * may be used. Further, the applied voltage Vap may be measured and used.

  In this embodiment, the accumulated time in a state where the duty command value αx within the predetermined time is not within the range corresponding to the predetermined value Ith and the threshold N0 that defines the determination target range (αLo ≦ αx ≦ αHi) is equal to or greater than the predetermined threshold. The continuation determination is performed by determining whether or not there is, but the determination is not limited to this, and it may be simply performed by determining whether or not the continuation has continued for a predetermined time.

  Further, when the admittance Y is obtained from the phase current value Ix, the power supply voltage Vps, the voltage command value Vx, and the rotational angular velocity ω based on a well-known motor voltage equation, and this admittance falls below a predetermined threshold (| Y | It is good also as a structure which determines with being in a disconnection state to <Yth). Specifically, the admittance Y can be obtained by an equation of Y = Ix / ((Vx−Vps) / (2−k × ω)). Note that the actual applied voltage Vap may be used as the voltage command value Vx. Further, an inductance may be used instead of the admittance Y. And it cannot be overemphasized that a more accurate detection can be performed by considering a continuation condition like the said embodiment.

Next, technical ideas other than the claims that can be understood from the above embodiments will be described.
(Additional remark 1) It is provided in the middle of the electric power supply path between a motor and a power supply, The drive circuit which supplies drive power to the motor, The control means which controls the operation of the drive circuit, The control means, Motor control for controlling the operation of the drive circuit so as to apply to the motor an applied voltage determined based on an actual current value supplied to the motor, and detecting disconnection of the power supply line to which the drive power is supplied A device that determines the actual current value, the power supply voltage, the applied voltage, and the rotational angular velocity admittance of the motor based on a well-known motor voltage equation, and is disconnected when the admittance falls below a predetermined threshold. A motor control device characterized in that

The schematic block diagram of an electric power steering device (EPS). The block diagram which shows the electric constitution of EPS. The wave form diagram which shows transition of each state quantity at the time of disconnection generation | occurrence | production. Explanatory drawing which shows the relationship between a motor NT characteristic and a disconnection detection. The flowchart which shows the process sequence of a disconnection detection.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Electric power steering apparatus (EPS), 10 ... EPS actuator, 11 ... EPS ECU, 12 ... Motor, 17 ... Microcomputer, 18 ... Drive circuit, 32u, 32v, 32w ... Motor coil, 33u, 33v, 33w ... Power line, 34 ... Disconnection detection unit, I ... Actual current value, Iu, Iv, Iw, Ix ... Phase current value, I0, Ith ... Predetermined value, N ... Number of rotations, N0 ... Threshold value, Vap ... Applied voltage, Vu *, Vv * , Vw *, Vx * ... voltage command value, αu, αv, αw, αx ... duty command value, V0 ... predetermined voltage, αHi, αLo ... threshold value, ta, tb ... counter value, t0, t1 ... threshold value.

Claims (5)

A drive circuit that is provided in the middle of a power supply path between the motor and a power supply and that supplies drive power to the motor; and a control unit that controls the operation of the drive circuit, the control unit energizing the motor A motor control device for controlling the operation of the drive circuit to apply to the motor an applied voltage determined based on an actual current value to be detected and detecting disconnection of a power supply line to which the drive power is supplied. ,
When the actual current value is equal to or less than a predetermined value and the number of rotations of the motor is within the determination target range, the control unit determines that the applied voltage is the predetermined value and the A motor control device characterized by determining that the disconnection has occurred when a state not within a range corresponding to a threshold value of a determination target range continues. The motor control device according to claim 1,
The control means uses an internal command value defining the applied voltage as the applied voltage;
A motor control device. In the motor control device according to claim 1 or 2,
The continuation determination is performed based on whether or not an integration time in a state not within the corresponding range within a predetermined time is equal to or greater than a predetermined threshold value. In the motor control device according to any one of claims 1 to 3,
The motor is a brushless motor having a three-phase motor coil,
The motor control device according to claim 1, wherein the control unit determines the disconnection based on a relationship between the actual current value and the rotation speed and the applied voltage for each phase.   An electric power steering device comprising the motor control device according to any one of claims 1 to 4.

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