JP5511934B2 - Motor control device, motor control method, and electric power steering device - Google Patents

Description

  The present invention relates to a motor control device, a motor control method, and an electric power steering device, and more particularly to determination of an abnormal state.

  Conventionally, based on the polarity of the motor current detection value and the polarity of the motor current command value, it is determined whether the motor is in a power running operation state or a regenerative operation state. When the difference between the motor current command value and the motor current command value is equal to or greater than a predetermined judgment threshold value, it is determined as an abnormal state, and if it is determined as a regenerative operation state, the difference between the motor current detection value and the motor current command value is 2. Description of the Related Art A motor control device that determines an abnormal state when it is greater than or equal to a predetermined determination threshold is known (for example, see Patent Document 1).

  That is, in this motor control device, by setting the abnormality determination threshold value during the regenerative operation of the motor to be larger than the abnormality determination threshold value during the power running operation, while preventing erroneous determination of an abnormal state during the regenerative operation, the circuit element Appropriate protection is achieved.

Japanese Patent No. 4177387

However, the prior art has the following problems.
When the conventional motor control device is applied to, for example, an electric power steering device, the motor is forcibly rotated by an external force, such as the steering is returned to the neutral direction by a reaction force from the road surface, and the motor serves as a generator. May work.

  In this case, in order to prevent erroneous determination of the abnormal state due to the regenerative current returned to the power supply side, the abnormality determination threshold value during regenerative operation is larger than the current value that can flow when the motor operates as a generator. Or when the rotational speed of the motor is equal to or higher than a predetermined rotational speed at which the motor operates as a generator, it is necessary to prohibit abnormality determination. For this reason, there is a problem that the coverage of abnormality determination is lowered and the circuit elements may not be properly protected.

  The present invention has been made to solve the above-described problems, and improves an abnormality determination coverage while preventing an erroneous determination of an abnormal state due to a current flowing when a motor operates as a generator. Thus, an object is to obtain a motor control device, a motor control method, and an electric power steering device that can appropriately protect circuit elements.

A motor control device according to the present invention includes a plurality of switching elements, an H bridge circuit that drives a motor by turning on / off the plurality of switching elements, and a motor drive that outputs a drive signal to drive the plurality of switching elements. And a motor control unit for feedback controlling the motor drive unit so that the drive current matches the motor current command value. The motor control unit includes a current command value calculation unit that calculates a motor current command value, and, when the motor is operating as an electric motor , the drive current when the switching element that is PWM-driven is on It is detected on the power line or ground line of the circuit and output as the power running current detection value. , Or when the motor is operating as a generator, the motoring current detection unit does not detect the driving current, to detect the current direction from the magnitude relationship between the voltage across the motor, current direction detection for outputting the current direction detection value The current detection value for abnormality determination with the sign information of the energization direction detection value added to the power running current detection value and the sign of the current detection value for abnormality determination and the motor current command value match the difference between the abnormality determination for detecting the current value and the motor current command value, when at least a predetermined determination threshold, it is determined that the abnormal state of the motor or the motor drive unit generates an abnormality determination signal, the abnormality determination If the signs of the current detection value for the motor and the motor current command value do not match, when the current detection value for abnormality determination is equal to or greater than a predetermined threshold, it is determined that the motor or the motor drive unit is in an abnormal state and an abnormality determination signal is output. Living An abnormality determination unit that, and has a.

The motor control method according to the present invention includes a plurality of switching elements, an H bridge circuit that drives the motor by turning on / off the plurality of switching elements, and outputs a drive signal to drive the plurality of switching elements. A motor control device comprising: a motor drive unit; a motor current detection unit that detects a drive current flowing through the motor; and a motor control unit that feedback-controls the motor drive unit so that the drive current matches a motor current command value. A current command value calculation step for calculating a motor current command value, and a drive current when a PWM-driven switching element is on when the motor is operating as an electric motor. Is detected by the power supply line or ground line of the H-bridge circuit and output as a power running current detection value. If the switching element is off, or if the motor is operating as a generator, detects the current flowing does not detect the driving current, the motoring current detecting step for outputting a motoring current detection value, the voltage across the motor An energization direction detection step for detecting an energization direction from a magnitude relationship and outputting an energization direction detection value, and an operation for calculating a current detection value for abnormality determination by adding sign information of the energization direction detection value to the powering current detection value a step, when the sign of an abnormality determination for detecting the current value and the motor current command value are matched, the difference between the abnormality determination for detecting the current value and the motor current command value, when at least a predetermined determination threshold value, it is determined that the abnormal state of the motor or the motor drive unit generates an abnormality determination signal, when the sign of an abnormality determination for detecting the current value and the motor current command values do not match, the abnormality determination for detecting a current There are those with when equal to or greater than a predetermined threshold, the abnormality determining step of generating an abnormality judgment signal determines an abnormal state of the motor or the motor driving unit.

  An electric power steering device according to the present invention includes the motor control device.

According to the motor control device, the motor control method, and the electric power steering device according to the present invention, the abnormality determination unit supplies the energization input from the energization direction detection unit to the powering current detection value input from the powering current detection unit. The abnormality detection current detection value to which the sign information of the direction detection value is added is calculated, and the difference between the abnormality detection current detection value and the motor current command value input from the current command value calculation unit is equal to or greater than a predetermined determination threshold. If it is, it is determined that the motor or the motor drive unit is in an abnormal state and an abnormality determination signal is generated.
Therefore, it is possible to appropriately protect the circuit elements by improving the abnormality determination coverage while preventing erroneous determination of the abnormal state due to the current flowing when the motor operates as a generator.

1 is a configuration diagram showing an electric power steering device to which a motor control device according to Embodiment 1 of the present invention is applied. FIG. It is a block block diagram which shows the motor control apparatus which concerns on Embodiment 1 of this invention with a peripheral device. It is explanatory drawing which shows the sample hold signal of the motor control apparatus which concerns on Embodiment 1 of this invention. It is explanatory drawing which shows the abnormality determination area | region in the motor control apparatus which concerns on Embodiment 1 of this invention. (A), (b) is explanatory drawing which shows the electricity supply path | route in case the DC motor is operate | moving as an electric motor in the motor control apparatus which concerns on Embodiment 1 of this invention. (A), (b) is explanatory drawing which shows each part waveform when the DC motor is operate | moving as an electric motor in the motor control apparatus which concerns on Embodiment 1 of this invention. (A), (b) is explanatory drawing which shows the electricity supply path | route in case the DC motor is operate | moving as a generator in the motor control apparatus which concerns on Embodiment 1 of this invention. (A), (b) is explanatory drawing which shows each part waveform when the DC motor is operate | moving as a generator in the motor control apparatus which concerns on Embodiment 1 of this invention. It is a flowchart which shows operation | movement of the abnormality determination part in the motor control apparatus which concerns on Embodiment 1 of this invention. (A), (b) is explanatory drawing which shows the electricity supply path | route in the conventional motor control apparatus. It is explanatory drawing which shows the abnormality determination area | region in the conventional motor control apparatus.

  Hereinafter, preferred embodiments of a motor control device, a motor control method, and an electric power steering device according to the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals. I will explain.

  The motor control device according to the present invention is a motor control device used for, for example, an electric power steering device for a vehicle, and the motor current detection value (driving current) matches the motor current command value. The current is feedback-controlled.

Embodiment 1 FIG.
1 is a configuration diagram showing an electric power steering apparatus to which a motor control apparatus according to Embodiment 1 of the present invention is applied. In FIG. 1, a DC motor (motor) 1 that generates steering assist torque is coupled to one end of a steering shaft 3 via a reduction gear 2, and a steering wheel 4 is connected to the other end of the steering shaft 3. ing. Further, the steering shaft 3 is provided with a torque sensor 5 that detects the steering torque of the steering wheel 4.

  Further, the controller (motor control device) 100 determines the steering assist torque based on the steering torque value detected by the torque sensor 5 and the vehicle speed value detected by the vehicle speed sensor 6 and drives the DC motor 1 by PWM. Thus, steering of the steering wheel 4 is assisted. The controller 100 is connected to a battery (power source) 7, an ignition key switch (IG) 8, and the like.

  FIG. 2 is a block configuration diagram showing the motor control device according to the first embodiment of the present invention together with peripheral devices. 2, the controller 100 includes a control computer (motor control unit) 10, a motor drive unit 20, an H bridge circuit 30, a motor current detection unit 40, a sample hold unit 50, and a voltage detection unit 60.

  The control computer 10 includes a current command value calculation unit 10a, a conduction direction command calculation unit 10b, an absolute value calculation unit 10c, a subtraction unit 10d, a current control unit 10e, a timer 10f, a PWM output unit 10g, a timing signal generation unit 10h, a power running current. It has the detection part 10i, the electricity supply direction detection part 10j, and the abnormality determination part 10k.

  The H-bridge circuit 30 is composed of four switching elements (Q1, Q2, Q3, Q4). Each switching element is turned on / off based on a drive signal (described later) input from the motor drive unit 20. The DC motor 1 is driven. Moreover, the voltage detection part 60 has the 1st voltage detection part 60a and the 2nd voltage detection part 60b.

Next, the function of each part of the controller 100 will be described.
The current command value calculation unit 10a performs a calculation according to predetermined characteristics based on the torque detection signal (steering torque value) of the torque sensor 5 and the vehicle speed detection signal (vehicle speed value) of the vehicle speed sensor 6, and drives the DC motor 1. Motor current command value I * is determined, and the determined motor current command value I * is output to the energization direction command calculation unit 10b, the absolute value calculation unit 10c, and the abnormality determination unit 10k.

  The energization direction command calculation unit 10b calculates the energization direction command value Dir * based on the sign of the motor current command value I * input from the current command value calculation unit 10a, and drives the calculated energization direction command value Dir * to the motor. To the unit 20. The energization direction command value Dir * is the energization direction command value Dir * = 1 when the motor current command value I *> 0, and the energization direction command value Dir * = 0 when the motor current command value I * = 0. When the command value I * <0, the energization direction command value Dir * = − 1 is calculated.

  The absolute value calculation unit 10c calculates the absolute value IMT = | I * | of the motor current command value I * input from the current command value calculation unit 10a, and outputs the calculated absolute value IMT to the subtraction unit 10d.

  The subtraction unit 10d calculates a current deviation ΔI (= IMT−IMS) between the absolute value IMT input from the absolute value calculation unit 10c and a powering current IMS (described later) input from the powering current detection unit 10i. The calculated current deviation ΔI is output to the current control unit 10e.

  The current control unit 10e performs a proportional-integral control calculation based on the current deviation ΔI input from the subtraction unit 10d, determines a voltage command value V * to be applied between the terminals of the DC motor 1, and determines the determined voltage command value V * Is output to the PWM output unit 10g.

  The timer 10f generates a triangular wave signal serving as a PWM carrier signal by an up / down counter, and outputs the generated PWM carrier signal to the PWM output unit 10g and the timing signal generation unit 10h.

  The PWM output unit 10g compares the voltage command value V * input from the current control unit 10e with the PWM carrier signal (triangular wave signal) input from the timer 10f to drive the DC motor 1 by PWM. A PWM signal Dt is generated, and the generated PWM signal Dt is output to the motor drive unit 20.

  The motor drive unit 20 includes an energization direction command value Dir * input from the energization direction command calculation unit 10b, a PWM signal Dt input from the PWM output unit 10g, and an abnormality determination signal ERR ( And a drive signal for driving the H bridge circuit 30 is generated, and the generated drive signal is output to the H bridge circuit 30.

  Specifically, when the abnormality determination signal ERR = 0 (normal state) and the energization direction command value Dir * = 1, the motor driving unit 20 performs the normal rotation switching elements (Q1, Q4) is PWM driven by the PWM signal Dt, and a signal for turning off the reverse switching elements (Q2, Q3) is generated as a drive signal.

  Further, when the abnormality determination signal ERR = 0 (normal state) and the energization direction command value Dir * = − 1, the motor driving unit 20 performs the forward rotation switching elements (Q1, Q4) constituting the H bridge circuit 30. Is turned off, and a signal for PWM driving the reverse switching elements (Q2, Q3) with the PWM signal Dt is generated as a drive signal.

  Further, when the abnormality determination signal ERR = 1 (abnormal state) or the energization direction command value Dir * = 0, the motor drive unit 20 transmits all the switching elements (Q1, Q2, Q3) constituting the H bridge circuit 30. , Q4) is generated as a drive signal.

  The motor current detection unit 40 measures the potential difference between both ends of the shunt resistor R inserted between the low potential side of the H bridge circuit 30 and the ground (current flowing through the power supply line of the H bridge circuit 30 or the bus of the ground line). Then, the drive current Im flowing through the DC motor 1 via the H bridge circuit 30 is detected, and the detected drive current Im is output to the sample hold unit 50. Note that when the sign of the detected drive current Im is positive, it indicates that a current flows from the low potential side of the H bridge circuit 30 toward the ground.

  The timing signal generation unit 10 h generates a sample hold signal at the timing of the valley peak value of the PWM carrier signal (triangular wave signal) input from the timer 10 f and outputs the generated sample hold signal to the sample hold unit 50. For example, as shown in FIG. 3, the sample hold signal is a pulse signal composed of a pulse having a predetermined width centered on the peak value on the valley side of the PWM carrier signal (triangular wave signal).

  The sample hold unit 50 samples and holds the drive current Im input from the motor current detection unit 40 based on the sample hold signal input from the timing signal generation unit 10h, and supplies the sample hold current Im2 to the power running current detection unit 10i. Output.

  The power running current detection unit 10i extracts the power running current IMS from the sample hold current Im2 input from the sample hold unit 50 by a method described later, and outputs the extracted power running current IMS to the subtraction unit 10d and the abnormality determination unit 10k.

  The first voltage detection unit 60a is applied to a series connection point between the forward switching element Q1 and the reverse switching element Q3 constituting the H-bridge circuit 30 based on the sample hold signal input from the timing signal generation unit 10h. The sample voltage VM + is sampled and held, and the sample hold voltage Vm + is output to the energization direction detector 10j.

  The second voltage detector 60b is applied to the series connection point of the reverse switching element Q2 and the forward switching element Q4 that constitute the H-bridge circuit 30 based on the sample hold signal input from the timing signal generator 10h. The sample voltage VM− is sampled and held, and the sample hold voltage Vm− is output to the energization direction detector 10j.

  The energization direction detection unit 10j detects the energization direction detection value Dir based on the magnitude relationship between the sample hold voltage Vm + input from the first voltage detection unit 60a and the sample hold voltage Vm− input from the second voltage detection unit 60b. ^ Is calculated, and the calculated energization direction detection value Dir ^ is output to the abnormality determination unit 10k.

  The conduction direction detection value Dir ^ is the conduction direction detection value Dir ^ = 1 when Vm +> Vm-, the conduction direction detection value Dir ^ = 0 when Vm + = Vm-, and the conduction direction detection value when Vm + <Vm-. Calculated as Dir ^ =-1.

  Abnormality determination unit 10k is an abnormality in which the sign information of energization direction detection value Dir ^ input from energization direction detection unit 10j is added to powering current (powering current detection value) IMS input from powering current detection unit 10i. The determination current detection value IMS2 is calculated.

  Further, the abnormality determination unit 10k has a relationship between the calculated abnormality detection current detection value IMS2 and the motor current command value I * input from the current command value calculation unit 10a in the abnormality regions 1 to 4 shown in FIG. When a value within the range is indicated, it is determined that the DC motor 1 or the motor drive unit 20 is in an abnormal state, and when a value outside the range of the abnormal region 1 to 4 is indicated, it is determined as a normal state.

  In addition, the abnormality determination unit 10k generates an abnormality determination signal ERR = 1 when it is determined as an abnormal state, and generates an abnormality determination signal ERR = 0 when it is determined as a normal state. The determination signal is output to the motor drive unit 20.

  Subsequently, the abnormality determination process in the motor control device according to the first embodiment of the present invention will be specifically described with reference to the explanatory diagrams of FIGS. 5 to 8 and the flowchart of FIG. 9.

  First, the current detection operation by the motor current detection unit 40 will be described. FIG. 5 is an explanatory diagram showing an energization path when the DC motor 1 operates as an electric motor in the motor control apparatus according to Embodiment 1 of the present invention. FIG. 6 is an explanatory diagram showing waveforms of respective parts when the DC motor 1 is operating as an electric motor in the motor control apparatus according to Embodiment 1 of the present invention.

  FIG. 7 is an explanatory diagram showing an energization path when the DC motor 1 operates as a generator in the motor control apparatus according to Embodiment 1 of the present invention. FIG. 8 is an explanatory diagram showing waveforms of respective parts when the DC motor 1 is operating as a generator in the motor control apparatus according to Embodiment 1 of the present invention. 5 to 8, (a) shows the forward rotation driving time, and (b) shows the reverse rotation driving time.

  When the DC motor 1 is operating as an electric motor, when the switching element driven by PWM is on, current flows through the energization path A shown in FIGS. 5A and 5B, and when it is off. A current flows through the energization path B shown in FIGS. 5 (a) and 5 (b).

  At this time, as shown in FIGS. 6A and 6B, the drive current Im detected by the motor current detection unit 40 is the same value during forward rotation drive and during reverse drive, but PWM drive is performed. When the switching element is on (FIG. 6 (i)), the drive current Im is in the positive direction, and when it is off (FIG. 6 (ii)), the drive current Im is in the negative direction.

  On the other hand, when the DC motor 1 is operating as a generator, regardless of whether the switching element that is PWM-driven is on or off, it is always shown in FIGS. 7 (a) and 7 (b). Current flows through the energization path.

  At this time, as shown in FIGS. 8A and 8B, the drive current Im detected by the motor current detection unit 40 becomes the same value during forward rotation drive and during reverse drive, and is PWM driven. Regardless of whether the switching element is on or off, the drive current Im is always in the negative direction (FIGS. 8 (i) and (ii)).

  That is, when the switching element that is PWM-driven is on, when the drive current Im is in the positive direction, it indicates that the DC motor 1 is operating as an electric motor, and when it is in the negative direction, the DC motor 1 is It shows that it is operating as a generator.

  Next, operations of the sample hold unit 50 and the power running current detection unit 10i will be described. When the DC motor 1 operates as a generator, the current flowing through the DC motor 1 is a normal operation and should not be determined as abnormal. Therefore, in Embodiment 1 of the present invention, abnormality determination is performed based on the current that flows when the DC motor 1 operates as an electric motor.

  Therefore, the sample hold unit 50 and the power running current detection unit 10i extract the current that flows when the DC motor 1 is operating as an electric motor from the drive current Im detected by the motor current detection unit 40.

  First, the sample hold unit 50 samples and holds the drive current Im based on the sample hold signal generated by the timing signal generation unit 10h (a signal synchronized with the timing at which the PWM driven switching element is turned on). Thus, the drive current when the PWM-driven switching element is on is extracted (sample hold current Im2 in FIGS. 6 and 8).

  Subsequently, the power running current detection unit 10i determines that IMS = Im2 when Im2 ≧ 0, based on the sample hold current Im2 (drive current when the PWM-driven switching element is on) extracted by the sample hold unit 50. When Im2 <0, IMS = 0 and a powering current IMS that is a current that flows when the DC motor 1 is operating as an electric motor is extracted (powering current IMS in FIGS. 6 and 8).

  Next, operations of the first voltage detection unit 60a, the second voltage detection unit 60b, and the energization direction detection unit 10j will be described. As described above, the drive current Im detected by the motor current detection unit 40 has the same value during forward rotation drive and during reverse drive. That is, it is not possible to detect the energization direction of the motor current MI flowing through the DC motor 1 based on the drive current Im.

  Therefore, in the first embodiment of the present invention, the energization direction is detected from the magnitude relationship between the voltages at both ends of the DC motor 1. In addition, the abnormality determination in the first embodiment of the present invention is performed based on the current that flows when the DC motor 1 is operating as an electric motor, so the first voltage detection unit 60a and the second voltage detection unit 60b. And the energization direction detection part 10j detects the energization direction of the electric current which flows, when the DC motor 1 is operate | moving as an electric motor.

  First, the first voltage detection unit 60a and the second voltage detection unit 60b are based on the sample hold signal (signal synchronized with the timing at which the PWM-driven switching element is turned on) generated by the timing signal generation unit 10h. By sampling and holding the voltage (VM +, VM−) across the DC motor 1, the voltage across the DC motor 1 when the PWM driven switching element is on is detected (Vm + in FIGS. 6 and 8). Vm-).

  Subsequently, the energization direction detection unit 10j determines the energization direction detection value Dir when VM +> VM− based on the voltages (Vm +, Vm−) detected by the first voltage detection unit 60a and the second voltage detection unit 60b. When ^ = 1, VM + = VM−, the energization direction detection value Dir ^ = 0, and when VM + <VM−, the energization direction detection value Dir ^ = − 1 is calculated (FIG. 6). , Energization direction detection value Dir ^) of FIG.

  Next, operation | movement of the abnormality determination part 10k is demonstrated along the flowchart of FIG. FIG. 9 is a flowchart showing an operation of abnormality determination unit 10k in the motor control apparatus according to Embodiment 1 of the present invention.

  First, the abnormality determination unit 10k includes the motor current command value I * determined by the current command value calculation unit 10a, the power running current IMS detected by the power running current detection unit 10i, and the energization direction detected by the energization direction detection unit 10j. The detection value Dir ^ is read (steps S1 to S3).

  Subsequently, the abnormality determination unit 10k determines whether or not the energization direction detection value Dir ^ is smaller than 0 (step S4).

  In step S4, when it is determined that the energization direction detection value Dir ^ is smaller than 0 (that is, Yes), the abnormality determination unit 10k sets the sign of the energization direction detection value Dir ^ with respect to the powering current IMS. In addition, the abnormality determination current detection value IMS2 (= -IMS) is calculated (step S5).

  On the other hand, in step S4, when it is determined that the energization direction detection value Dir ^ is 0 or more (that is, No), the abnormality determination unit 10k determines the energization direction detection value Dir ^ with respect to the power running current IMS. A sign is added to calculate the abnormality detection current detection value IMS2 (= IMS) (step S6).

  Here, when the DC motor 1 operates as an electric motor, the abnormality detection current detection value IMS2 becomes a current value (IMS2 in FIG. 6) that matches the motor current MI flowing through the DC motor 1, and the DC motor 1 Is operating as a generator, the signal indicates 0 (IMS2 in FIG. 8).

  Next, abnormality determination unit 10k determines whether the polarity of motor current command value I * is the same as the polarity of current detection value IMS2 for abnormality determination (step S7).

  If it is determined in step S7 that the polarities of the two are the same (that is, Yes), the abnormality determination unit 10k determines that the motor current MI flowing through the DC motor 1 is forward with respect to the motor current command value I *. Therefore, the abnormality determination process in the forward direction is performed (step S8).

  At this time, the abnormality determination unit 10k compares the abnormality detection current detection value IMS2 with the motor current command value I *, and the value of | IMS2 | − | I * | is equal to or greater than the first determination threshold TH1 (in FIG. 4). It is determined whether the region is within the abnormal region 1 or the abnormal region 3 (step S8).

  If it is determined in step S8 that | IMS2 | − | I * | ≧ TH1 (that is, Yes), the current detection value IMS2 for abnormality determination is obtained even though the DC motor 1 is operating as an electric motor. This is a state in which the motor current command value I * is overshooting by the first determination threshold value TH1 or more. Therefore, the abnormality determination unit 10k regards the abnormality occurrence state of the DC motor 1 (wiring abnormality state such as a ground fault), generates a temporary abnormality determination signal, and proceeds to step S9.

  Subsequently, the abnormality determination unit 10k generates a final abnormality determination signal ERR = 1 by regarding the temporary abnormality determination signal as a final abnormality determination state when the temporary abnormality determination signal continues for a predetermined time (predetermined period) T1. The output of the drive signal from the motor drive unit 20 is shut off (step S9). Thereby, switching elements Q1-Q4 etc. in H bridge circuit 30 can be protected from an excessive ground fault current.

  It should be noted that the abnormality determination unit 10k does not consider the final abnormality determination state until the predetermined time T1 elapses, generates a final abnormality determination signal ERR = 0, and determines whether or not the predetermined time has elapsed. Determination is made (step S10), and after a predetermined time has elapsed (that is, Yes), the process returns to step S1.

  On the other hand, if it is determined in step S8 that | IMS2 | − | I * | <TH1 (that is, No), the abnormality determination unit 10k is in a normal state, so the abnormality determination signal ERR = 0 and the process proceeds to step S10. After a predetermined time has elapsed, the process returns to step S1.

  As described above, by generating the final abnormality determination signal ERR = 1 when the temporary abnormality determination signal continues for the predetermined time T1, | IMS2 | − | I * | ≧ The case where the relationship of TH1 is satisfied can be excluded, and the abnormality occurrence state can be reliably detected.

  On the other hand, if it is determined in step S7 that the polarities of the two are different (that is, No), the abnormality determining unit 10k causes the motor current MI flowing through the DC motor 1 to be in the reverse direction with respect to the motor current command value I *. In the reverse direction, an abnormality determination process is performed (step S10).

  At this time, abnormality determination unit 10k determines whether or not | IMS2 | is greater than or equal to second determination threshold value TH2 (within the range of abnormal region 2 or abnormal region 4 in FIG. 4) for current detection value IMS2 for abnormality determination. It is determined whether or not (step S11).

  If it is determined in step S11 that | IMS2 | ≧ TH2 (ie, Yes), the abnormality detection current detection value IMS2 is equal to the motor current command value I, even though the DC motor 1 is operating as an electric motor. In the opposite direction to *, the second determination threshold value TH2 is overshot. Therefore, the abnormality determination unit 10k regards the abnormality occurrence state of the DC motor 1 (wiring abnormality state such as a ground fault), generates a temporary abnormality determination signal, and proceeds to step S12.

  Subsequently, when the temporary abnormality determination signal continues for a predetermined time T2, the abnormality determination unit 10k regards it as a final abnormality determination state and generates a final abnormality determination signal ERR = 1. The output of the drive signal from is cut off (step S12). Thereby, switching elements Q1-Q4 etc. in H bridge circuit 30 can be protected from an excessive ground fault current.

  The abnormality determination unit 10k does not consider the final abnormality determination state until the predetermined time T2 elapses, and generates a final abnormality determination signal ERR = 0 and determines whether or not the predetermined time has elapsed. Determination is made (step S10), and after a predetermined time has elapsed (that is, Yes), the process returns to step S1.

  On the other hand, if it is determined in step S11 that | IMS2 | <TH2 (that is, No), the abnormality determination unit 10k is in a normal state, so the abnormality determination signal ERR = 0 and the process proceeds to step S10, and a predetermined time has elapsed. Later, the process returns to step S1.

  Thus, by generating the final abnormality determination signal ERR = 1 when the temporary abnormality determination signal continues for a predetermined time T2, the relationship of | IMS2 | ≧ TH2 is temporarily satisfied due to the influence of noise or the like. It is possible to reliably detect an abnormality occurrence state.

  Further, as described above, since the standby process of step S10 is inserted in the path returning to step S1, the processes shown in steps S1 to 9 and 10 to 11 are executed in a predetermined cycle (predetermined period). Can be managed.

As described above, according to the first embodiment, the abnormality determination unit obtains the sign information of the energization direction detection value input from the energization direction detection unit with respect to the powering current detection value input from the powering current detection unit. When the added abnormality detection current detection value is calculated and the difference between the abnormality detection current detection value and the motor current command value input from the current command value calculation unit is equal to or greater than a predetermined determination threshold, It is determined that the motor drive unit is in an abnormal state, and an abnormality determination signal is generated.
Therefore, it is possible to appropriately protect the circuit elements by improving the abnormality determination coverage while preventing erroneous determination of the abnormal state due to the current flowing when the motor operates as a generator.

  Specifically, according to the motor control device according to the first embodiment of the present invention, the current (powering current IMS) that flows when the DC motor 1 operates as an electric motor and the magnitude of the voltage across the DC motor 1 are increased or decreased. An abnormality determination current detection value IMS2 is calculated based on the energization direction detection value Dir ^ calculated based on the relationship, and the calculated abnormality determination current detection value IMS2 is compared with the motor current command value I *. The configuration is such that the determination is performed. Therefore, it is possible to always perform abnormality determination.

  That is, in the conventional motor control device, in order to prevent an erroneous determination of an abnormal state due to a current flowing when the motor operates as a generator, for example, the abnormality determination process is stopped when the rotational speed of the motor is equal to or higher than a predetermined value. It was necessary to take measures to prevent misjudgment.

  Here, the problem of the above-described conventional motor control device will be specifically described with reference to FIGS. FIGS. 10A and 10B are explanatory views showing energization paths in the conventional motor control device. FIG. 11 is an explanatory diagram showing an abnormality determination region in a conventional motor control device.

  In the conventional motor control device, as shown in FIG. 10, the current flowing through the motor is detected bidirectionally by detecting the motor current based on the voltage across the shunt resistor inserted in series with the motor wire. doing. Therefore, for example, during power running, the current flowing through the motor is detected through the energization path A shown in FIGS. 10A and 10B, and during regenerative operation, the current of B shown in FIGS. 10A and 10B is detected. A current flowing through the motor is detected through the energization path.

  That is, in the conventional motor control device, regardless of power running operation or regenerative operation, the current flowing to the motor is detected bidirectionally, and the abnormality determination is performed by comparing the detected motor current detection value with the motor current command value. .

  Therefore, when used in applications where the motor is forced to rotate by an external force and the motor may operate as a generator, an erroneous determination of an abnormal state due to the current flowing through the motor when the motor operates as a generator In order to prevent this, it is necessary to set the abnormality determination threshold value during the regenerative operation to a value larger than the current value that can flow when the motor operates as a generator. As a result, as shown in FIG. 11, the abnormality determination coverage in the regenerative operation region is reduced.

  Also, considering that the motor operates as a generator when the counter electromotive voltage generated by the rotation of the motor exceeds the power supply voltage, the counter electromotive voltage is equal to or higher than a predetermined motor rotation speed equal to the power supply voltage. In some cases, it is necessary to prohibit abnormality determination. In this case, the abnormality determination cannot be performed at a speed higher than the predetermined motor rotation speed, so that the abnormality determination coverage in the motor high rotation range is lowered.

  On the other hand, in Embodiment 1 of this invention, when the DC motor 1 operate | moves as a generator, it becomes the structure which does not detect the electric current which flows into a motor. Therefore, there is no possibility of erroneous determination of an abnormal state due to a current flowing when operating as a generator, and abnormality determination can always be performed.

  Further, the failure determination condition and the determination threshold are switched according to the polarities of the abnormality detection current detection value IMS2 and the motor current command value I * so that the determination threshold TH2 can be appropriately set when the polarities are different. I have to. Therefore, it is possible to ensure a higher abnormality determination coverage than the conventional motor control device.

  That is, in the conventional motor control device, in order to prevent an erroneous determination of an abnormal state due to a current that flows when the motor operates as a generator, the determination threshold value TH2 when the polarity is different is used when the motor operates as a generator. It was necessary to set it larger than the current flowing through the. On the other hand, in the motor control device according to the first embodiment of the present invention, since the current flowing through the motor is not detected when the DC motor 1 operates as a generator, the determination threshold TH2 when the polarity is different is used. Can be set appropriately.

  In the motor control device according to the first embodiment of the present invention, the drive current Im and the voltage across the DC motor 1 are sampled and held based on the sample and hold signal generated by the timing signal generator 10h. . Therefore, the information on the power running current IMS detected by the power running current detection unit 10i and the conduction direction detection value Dir ^ detected by the conduction direction detection unit 10j can be reliably synchronized. Thereby, the current (= abnormality determination current detection value IMS2) that flows when the DC motor 1 operates as an electric motor can be accurately obtained, and highly reliable abnormality determination can be realized.

  Further, the both-ends voltage (VM +, VM−) of the DC motor 1 is sampled based on the sample hold signal (signal synchronized with the timing at which the PWM driven switching element is turned on) generated by the timing signal generator 10h. Using the held information (Vm +, Vm−), the energization direction detection value Dir ^ is calculated. Therefore, even when the duty of the PWM signal Dt is small and the average potential difference between the voltages at both ends of the DC motor 1 is small, the energization direction can be detected with high accuracy and a highly reliable abnormality determination can be realized. .

  The abnormality determination unit 10k generates a final abnormality determination signal ERR = 1 when the abnormal state continues for a predetermined time. Therefore, it is possible to reliably detect an abnormal state by excluding a temporary abnormal state due to the influence of noise or the like.

  Further, according to the abnormality determination signal ERR = 1 from the abnormality determination unit 10k, the motor driving unit 20 turns off all the switching elements (Q1, Q2, Q3, Q4) and stops driving the motor. Therefore, the generation of abnormal torque of the motor can be reliably suppressed.

  In addition, according to the electric power steering control apparatus according to Embodiment 1 of the present invention, the determination threshold value TH2 when the polarities are different is appropriately set without considering the current flowing when the DC motor 1 operates as a generator. By doing so, the abnormality determination coverage of the reverse assist region can be improved. Therefore, it is possible to realize a highly reliable electric power steering control device that can reliably detect a dangerous failure mode in which the DC motor 1 rotates due to a power fault or ground fault of the motor terminal.

  That is, in this electric power steering apparatus, when the DC motor 1 rotates due to an abnormal motor current, a torque in a direction opposite to the motor output torque is detected by the torque sensor 5, and the current command value calculation unit 10a detects the motor. A current command value having a reverse polarity with respect to the current is generated. Therefore, by appropriately setting the determination threshold TH2 and expanding the areas of the abnormal area 2 and the abnormal area 4 shown in FIG. 4, it is possible to reliably detect a dangerous failure mode in which the DC motor 1 rotates.

  In the first embodiment, the sample hold signal is generated by the timing signal generator 10h. However, the present invention is not limited to this, and the same effect can be obtained even if the PWM signal Dt is used as the sample hold signal. it can. In this case, since the port for outputting the sample hold signal from the timing signal generator 10h and the control computer 10 is not necessary, the configuration can be further simplified.

  In the first embodiment, the driving current Im is sampled and held by the sample hold unit 50 based on the sample hold signal generated by the timing signal generation unit 10h. However, the present invention is not limited to this. That is, using the AD converter in the control computer 10 instead of the sample hold unit 50, the same effect can be obtained even if the drive current Im is AD converted at the timing when the switching element driven by PWM is turned on. be able to. In this case, the sample hold unit 50 is not necessary, and the cost can be reduced.

  Similarly, instead of sampling and holding the both-ends voltage (VM +, VM−) of the DC motor 1 by the first voltage detection unit 60a and the second voltage detection unit 60b, respectively, the AD converter in the control computer 10 is used to perform PWM. A similar effect can be obtained by AD-converting the voltages (VM +, VM−) across the DC motor 1 at the timing when the driving switching element is turned on. In this case, the sample and hold function in the first voltage detection unit 60a and the second voltage detection unit 60b is not necessary, so that the cost can be reduced.

  In the first embodiment, the motor current detection unit 40 measures the potential difference between both ends of the shunt resistor R inserted between the low potential side of the H bridge circuit 30 and the ground, and the H bridge circuit 30 is However, the present invention is not limited to this. That is, a configuration in which the shunt resistor R is inserted between the high potential side of the H bridge circuit 30 and the battery 7 and the potential difference between both ends of the shunt resistor R may be measured.

  In the first embodiment, the motor current detection unit 40 detects bidirectional current detection (a current flowing from the low potential side of the H bridge circuit 30 toward the ground is detected as a positive current value, and the H bridge circuit is connected to the ground. The current flowing toward the low potential side of 30 is detected as a negative current value), and only the positive current value is extracted by the powering current detection unit 10i to calculate the powering current IMS. It is not limited to.

  That is, the motor current detection unit 40 detects a one-way current (a current flowing from the low potential side of the H bridge circuit 30 toward the ground is detected as a positive current value, and from the ground toward the low potential side of the H bridge circuit 30. The same effect can be obtained even if the configuration is such that the flowing current is detected as 0). In this case, since the power running current detection unit 10i is not necessary, the configuration can be further simplified.

  In the first embodiment, the motor current detection unit and the power running current detection unit 10i share the shunt resistor R inserted between the low potential side of the H bridge circuit 30 and the ground. The shunt resistor may be provided individually.

  That is, similarly to Patent Document 1 described above, a motor current detection unit is configured to measure the potential difference between both ends of the shunt resistor inserted at the position shown in FIG. The power running current detector 10i may be configured to detect the power running current based on the potential difference between both ends of the shunt resistor R inserted between the low potential side of the bridge circuit 30 and the ground.

  In this case, motor current control is performed based on the motor current detection value detected by the motor current detection unit, and the abnormality determination unit 10k performs abnormality determination based on the power running current detected by the powering current detection unit 10i. The same effect as in the first embodiment can be obtained while configuring a current control system similar to the conventional one.

  DESCRIPTION OF SYMBOLS 1 DC motor, 2 reduction gear, 3 steering shaft, 4 steering wheel, 5 torque sensor, 6 vehicle speed sensor, 7 battery, 10 control computer (motor control part), 10a current command value calculating part, 10b energization direction command calculating part, 10c absolute value calculation unit, 10d subtraction unit, 10e current control unit, 10f timer, 10g PWM output unit, 10h timing signal generation unit, 10i power running current detection unit, 10j energization direction detection unit, 10k abnormality determination unit, 20 motor drive unit , 30 bridge circuit, 40 motor current detection unit, 50 sample hold unit, 60 voltage detection unit, 60a first voltage detection unit, 60b second voltage detection unit, 100 controller.

Claims (9)

An H-bridge circuit including a plurality of switching elements and driving a motor by turning on / off the plurality of switching elements;
A motor drive unit that outputs a drive signal and drives the plurality of switching elements;
A motor current detector for detecting a drive current flowing in the motor;
A motor control unit including a motor control unit that feedback-controls the motor drive unit so that the drive current matches a motor current command value,
The motor controller is
A current command value calculation unit for calculating the motor current command value;
When the motor is operating as an electric motor, the drive current when the switching element that is PWM driven is on is detected by the power supply line or the ground line of the H bridge circuit, and is output as a powering current detection value In addition, when the switching element is off, or when the motor is operating as a generator, a power running current detector that does not detect a drive current ;
An energization direction detection unit that detects an energization direction from a magnitude relationship between both end voltages of the motor and outputs an energization direction detection value;
The abnormality detection current detection value with the sign information of the energization direction detection value added to the powering current detection value is calculated, and the signs of the abnormality determination current detection value and the motor current command value match. If the difference between the motor current command value and the abnormality determination for detecting the current value, when at least a predetermined determination threshold value, the abnormality determination signal is determined to be abnormal condition of the motor or the motor drive unit When the sign of the current detection value for abnormality determination and the motor current command value does not match, when the current detection value for abnormality determination is equal to or greater than a predetermined threshold, the motor or the motor drive unit An abnormality determination unit that determines an abnormal state and generates an abnormality determination signal . The abnormality determination unit includes a first determination threshold used when the abnormality detection current detection value and the motor current command value have the same polarity as the predetermined determination threshold, and the abnormality determination current detection value. The motor control apparatus according to claim 1, further comprising: a second determination threshold value used when the polarities of the motor current command value and the motor current command value are different. At least one switching element among the plurality of switching elements including the forward switching element and the reverse switching element constituting the H bridge circuit is PWM-driven,
The energization direction detection unit is configured to apply an energization direction of the motor based on a voltage applied to a series connection point between the forward rotation switching element and the reverse rotation switching element during a period in which the PWM driven switching element is turned on. The motor control device according to claim 1 or 2. Among the plurality of switching elements constituting the H-bridge circuit, at least one switching element is PWM-driven,
The power running current detector detects a power running current flowing from a power source to the H bridge circuit based on a current flowing through a power source line of the H bridge circuit or a bus line of a ground line during a period when a switching element driven by PWM is turned on. The motor control device according to any one of claims 1 to 3, wherein the motor control device is detected. The motor control device according to any one of claims 1 to 4, wherein the abnormality determination unit generates a final abnormality determination signal when the abnormality determination signal continues for a predetermined period. The motor control device according to any one of claims 1 to 5, wherein the motor driving unit stops driving the motor when the abnormality determination signal is generated. The motor control device according to any one of claims 1 to 6, wherein the motor current detection unit and the power running current detection unit are shared. An H-bridge circuit including a plurality of switching elements and driving a motor by turning on / off the plurality of switching elements;
A motor drive unit that outputs a drive signal and drives the plurality of switching elements;
A motor current detector for detecting a drive current flowing in the motor;
A motor control method that is executed by a motor control device including a motor control unit that feedback-controls the motor drive unit so that the drive current matches a motor current command value,
A current command value calculating step for calculating the motor current command value;
When the motor is operating as an electric motor, the drive current when the switching element that is PWM driven is on is detected by the power supply line or the ground line of the H bridge circuit, and is output as a powering current detection value In addition, when the switching element is off, or when the motor is operating as a generator, a power running current detection step that does not detect a drive current ;
An energization direction detection step of detecting an energization direction from a magnitude relationship between both end voltages of the motor and outputting an energization direction detection value;
A calculation step for calculating an abnormality determination current detection value to which the sign information of the energization direction detection value is added to the powering current detection value;
When the case where the sign of said motor current command value and the abnormality determination for the current detection values match, the difference between the motor current command value and the abnormality determination for the current detection value is equal to or greater than a predetermined determination threshold value The abnormality determination signal is generated by determining that the motor or the motor driving unit is in an abnormal state, and if the sign of the abnormality detection current detection value and the motor current command value does not match, the abnormality determination current An abnormality determination step of determining an abnormal state of the motor or the motor drive unit and generating an abnormality determination signal when the detected value is equal to or greater than a predetermined threshold value . An electric power steering device comprising the motor control device according to any one of claims 1 to 7.

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