JP2011051537A - Electric power steering system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric power steering system in which estimation accuracy of an electric angle is improved when sensorless control is performed. <P>SOLUTION: A state determination unit 115 determines to be in a steering retaining state when the absolute value of differential values eu', ev', ew' of induced voltage even in only one phase is not more than a determination value A close to zero. When it is determined to be in the steering retaining state, a wire-wound resistance calculation unit 116 sets the arithmetical value of induced voltages eu, ev, ew generated in an electric motor 20 to zero, and calculates wire-wound resistances Ru, Rv, Rw from motor terminal voltages Vu, Vv, Vw and motor currents Iu, Iv, Iw. A wire-wound resistance correction unit 117 updates the wire-wound resistances Ru, Rv, Rw in an arithmetic expression stored in each phase induced voltage calculation unit 111 to the value calculated by the wire resistance calculation unit 116. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an electric power steering apparatus that drives and controls an electric motor based on a steering operation of a driver to generate a steering assist torque.

  Conventionally, an electric power steering device detects a steering torque applied to a steering wheel by a driver, calculates a target steering assist torque according to the detected steering torque, and obtains the target steering assist torque. Controls the amount of power applied to the motor. An electric power steering apparatus using a brushless motor as an electric motor has also been generalized. The brushless motor is energized to the U-phase, V-phase, and W-phase by inverter switching control. Therefore, when a brushless motor is used, a rotation angle sensor that detects the rotation angle (electrical angle) of the rotor is provided to control the phase of each phase.

  When the rotation angle sensor fails, the brushless motor cannot be controlled. Therefore, when the rotation angle sensor fails, the electrical angle is estimated based on the induced voltage (back electromotive force) generated in the brushless motor, and the brushless motor is driven using this estimated electrical angle (estimated electrical angle). An electric power steering device to be controlled is also known. The control of the brushless motor using the estimated electrical angle is called sensorless control.

  In sensorless control, the angular velocity is calculated from the induced voltage by utilizing the proportional relationship between the induced voltage generated by the brushless motor and the angular velocity. Then, the rotation angle of the brushless motor per cycle is obtained from the calculation cycle and angular velocity of the sensorless control, and the current electrical angle, that is, the current electrical angle, that is, by adding (or subtracting) this rotation angle to the electrical angle of the previous cycle. The estimated electrical angle is calculated. Such sensorless control is proposed in Patent Document 1, for example.

JP 2008-87756 A

  The value of the induced voltage can be calculated based on the current flowing through each phase of the brushless motor, the voltage applied to each phase, and the winding resistance value of each phase. However, the winding resistance value used for this calculation is a preset design value and may differ from the actual resistance value due to variations in individual motors, changes in ambient temperature, and the like. For this reason, the value of the induced voltage calculated may be different from the actual value, and in such a case, good estimation accuracy of the electrical angle cannot be obtained.

  An object of the present invention is to cope with the above-described problem, and is to improve the estimation accuracy of an electrical angle when performing sensorless control.

In order to achieve the above object, the present invention is characterized in that a steering torque sensor that detects a steering torque input from a steering handle to a steering shaft, an electric motor that is provided in a steering mechanism and generates a steering assist torque, and The rotation angle sensor for detecting the actual electric angle of the electric motor, the sensor abnormality detection means for detecting the abnormality of the rotation angle sensor, and the abnormality of the rotation angle sensor are detected by the sensor abnormality detection means. An electric angle estimating means for calculating an estimated electric angle of the electric motor, and a motor control value calculation for calculating a motor control value for generating a target steering assist torque according to the steering torque detected by the steering torque sensor And when the abnormality of the rotation angle sensor is not detected, based on the actual electrical angle and the motor control value. And an electric power provided with motor control means for driving and controlling the electric motor based on the estimated electric angle and the motor control value when an abnormality of the rotation angle sensor is detected. In the steering device,
The electrical angle estimating means includes a current sensor for detecting a current flowing in each phase of the electric motor, a voltage sensor for detecting a voltage applied to each phase of the electric motor, and each phase of the detected electric motor. Induced voltage calculation means for calculating an induced voltage generated in the motor based on a value of a current flowing through the motor, a voltage value applied to each phase of the electric motor, and a winding resistance value of each phase of the electric motor; , Estimated electrical angle computing means for computing the estimated electrical angle based on the induced voltage computed by the induced voltage computing means, and winding resistance computing means for computing the winding resistance value of each phase of the electric motor by computation And a winding resistance value correcting means for correcting the winding resistance value used for the calculation of the induced voltage by the induced voltage calculating means to the winding resistance value obtained by the winding resistance calculating means. .

  In the present invention, an electric angle (actual electric angle) of the electric motor detected based on the output signal of the rotation angle sensor and a target steering assist torque according to the steering torque detected by the steering torque sensor are generated. Based on the motor control value, the motor control means drives and controls the electric motor. For example, a brushless motor is used as the electric motor. When the rotation angle sensor fails, the rotation of the electric motor cannot be controlled. Therefore, in the present invention, the sensor abnormality detecting means for detecting the abnormality of the rotation angle sensor is provided, and when the abnormality of the rotation angle sensor is detected by the sensor abnormality detection means, the electric angle estimation means is the estimated electric motor. Calculate the corner. In this case, the motor control means drives and controls the electric motor based on the estimated electrical angle and the motor control value. That is, sensorless control is performed.

  The electrical angle can be estimated from an induced voltage generated by the electric motor. Therefore, the electrical angle estimating means includes an induced voltage computing means and an estimated electrical angle computing means, and the induced voltage computing means is connected to the current value flowing through each phase of the electric motor, the voltage value applied to each phase of the electric motor, and the electric motor. An induced voltage (induced voltage value) generated in the motor is calculated based on the winding resistance value of each phase of the motor, and an estimated electrical angle calculation means calculates an estimated electrical angle based on the induced voltage. The actual winding resistance value does not become a constant value due to variations in individual electric motors, ambient temperature, and the like. For this reason, when a preset design value is used as the winding resistance value used for the calculation of the induced voltage, the estimation accuracy of the electrical angle is not good, and the control performance of the electric motor is reduced. End up.

  Therefore, the electrical angle estimation means includes winding resistance calculation means and winding resistance value correction means, and the winding resistance calculation means obtains the winding resistance value of each phase of the electric motor by calculation, and corrects the winding resistance value. The winding resistance value used by the means for calculating the induced voltage is corrected (updated) to the winding resistance value obtained by the winding resistance calculation means. Therefore, the winding resistance value can be made to correspond to the variation of each electric motor and the ambient temperature, and the estimation accuracy of the electrical angle can be improved. As a result, the sensorless control performance of the electric motor is improved.

  According to another aspect of the present invention, the winding resistance calculation unit includes a state determination unit that determines whether or not the vehicle is in a state where an induced voltage generated by the electric motor is zero. When the state of the vehicle in which the induced voltage generated in the electric motor is detected by the means is detected, the current value flowing through the electric motor, the voltage value applied to the electric motor, and the winding resistance value are used. The winding resistance value is calculated by setting the induced voltage value in the relational expression representing the induced voltage to zero.

  The induced voltage generated in the electric motor can be calculated from a relational expression using a current value flowing through the electric motor, a voltage value applied to the electric motor, and a winding resistance value of the coil. Further, the induced voltage generated in the electric motor is not generated when the rotor of the electric motor is not rotating. Further, the current value flowing through the electric motor and the voltage value applied to the electric motor are known because they are detected by the current sensor and the voltage sensor. Therefore, in the present invention, when the state determination means determines whether the state of the vehicle in which the induced voltage generated by the electric motor is zero, and the state of the vehicle in which the induced voltage is zero is detected. In addition, the winding resistance value is set by setting the induced voltage value in the relational expression representing the induced voltage to zero using the current value flowing through the electric motor, the voltage value applied to the electric motor, and the winding resistance value. calculate. Therefore, when the state of the vehicle in which the induced voltage becomes zero is detected, the winding resistance value can be appropriately calculated by setting the induced voltage value in the relational expression to zero. The winding resistance value correcting means corrects the winding resistance value when the state of the vehicle in which the induced voltage generated by the electric motor is zero, that is, when the electric motor is not rotating, is detected. Therefore, the influence of the phase shift of the electric motor is not caused.

  Another feature of the present invention is that the state determination means determines whether or not the vehicle is in a steering-holding state when an abnormality of the rotation angle sensor is detected, or the vehicle is in a straight traveling state. It is to determine whether or not the vehicle is in a state where the induced voltage generated by the electric motor becomes zero.

  In the steering holding state or the straight running state of the vehicle, the induced voltage generated in the electric motor is zero because the rotor of the electric motor does not rotate. Therefore, in the present invention, the induced voltage generated by the electric motor becomes zero by determining whether or not the vehicle is in the steering holding state, or by determining whether or not the vehicle is in the straight running state. The situation can be detected appropriately.

  According to another feature of the present invention, the state determination means calculates a differential value of the induced voltage of each phase of the electric motor, and the absolute value of the differential value of the induced voltage of at least one phase is a steering determination criterion. When the value is equal to or less than the value, it is determined that the steering state is maintained.

  When the steering holding state is reached, the induced voltage value calculated by the induced voltage calculation means does not fluctuate (temporally fluctuate), so that the induced voltage differential value (time differential value) becomes zero. Therefore, in the present invention, the state determination means calculates the differential value of the induced voltage of each phase of the electric motor, and at least the absolute value of the differential value of the induced voltage of one phase is equal to or less than the steering determination reference value. It is determined that the steering is maintained. For this reason, it is possible to appropriately and easily detect the steered state by using the calculated value of the induced voltage in the sensorless control. In addition, the reference value for steering determination is a set value near zero that can be determined to be zero or a steering holding state in which no induced voltage is generated.

  According to another feature of the present invention, the state determination means calculates a differential value of the induced voltage of each phase of the electric motor, and the absolute value of the differential value of the induced voltage of all phases is a reference for determining steering. When the value is equal to or less than the value, it is determined that the steering state is maintained.

  According to the present invention, since the steered state is determined more strictly, the electrical angle estimation accuracy can be further improved.

  In another aspect of the present invention, the state determination unit includes a steering angle acquisition unit that acquires steering angle information indicating a steering angle of a steering wheel, and the steering angle derivative acquired by the steering angle acquisition unit is obtained. The steering angular velocity, which is a value, is calculated, and when the absolute value of the steering angular velocity is equal to or less than the reference value for steering determination, it is determined that the steering state is maintained.

  When the steering apparatus of the vehicle is provided with a steering angle sensor, it can be determined whether or not the vehicle is in the steering-holding state based on whether or not the steering angle is detected by the steering angle sensor. Therefore, in the present invention, the winding resistance calculating means calculates a steering angular velocity that is a differential value of the steering angle detected by the steering angle sensor, and the absolute value of the steering angular velocity is equal to or less than the reference value for steering determination. In this case, it is determined that the steering is maintained, and the winding resistance value is calculated. For this reason, the steering holding state can be detected appropriately and easily using the steering angle sensor. In addition, the reference value for steering determination is a set value near zero that can be determined to be zero or a steering holding state in which no induced voltage is generated.

  Another feature of the present invention is that the steering torque sensor detects an input side rotation angle and an output side rotation angle of a torsion bar inserted in the steering shaft, and is a difference between the two rotation angles. The steering torque input to the steering shaft is detected based on a twist angle, and the state determination means calculates a rotation angular velocity that is a differential value of the output side rotation angle or the input side rotation angle of the torsion bar. Then, when the absolute value of the rotational angular velocity is equal to or less than the reference value for steering determination, it is determined that the steering state is maintained.

  According to the present invention, since the steered state is determined based on the rotational angular velocity that is a differential value of the output side rotational angle or the input side rotational angle of the steering torque sensor using the steering torque sensor, the determination of the steered state is performed. Can be performed appropriately and easily. In addition, the reference value for steering determination is a set value near zero that can be determined to be zero or a steering holding state in which no induced voltage is generated.

  According to another aspect of the present invention, the state determination unit includes a wheel speed acquisition unit that acquires wheel speed information indicating the left and right wheel speeds, and the difference between the left and right wheel speeds acquired by the wheel speed acquisition unit. Is that the vehicle is in a straight-running state when the vehicle travels below the straight-running reference value.

  According to the present invention, since the straight running state of the vehicle is determined based on the left and right wheel speed difference, the determination is easy. The straight running determination reference value is a set value near zero that can be determined to be zero or a straight running state in which no induced voltage is generated.

  Another feature of the present invention is that the winding resistance computing means is a rotational angular velocity that is a differential value of a motor rotational angle detected by the rotational angle sensor when no abnormality is detected in the rotational angle sensor. When the absolute value of the rotational angular velocity is equal to or less than a near-zero determination reference value, the current value flowing through the electric motor, the voltage value applied to the electric motor, and the winding resistance value are used. A normal winding resistance calculating means for calculating the winding resistance value by setting the value of the induced voltage in the relational expression expressing the induced voltage to zero is provided.

  According to the present invention, the winding resistance value can be calculated and corrected before the abnormality of the rotation angle sensor is detected. For this reason, even when the abnormality of the rotation angle sensor actually occurs and the control is switched to the sensorless control, the electrical angle can be estimated with high accuracy from that point. As a result, it is possible to satisfactorily shift to sensorless control. Note that the zero vicinity determination reference value is a set value of the rotational angular velocity that is zero or a range in which no induced voltage is generated.

1 is a schematic configuration diagram of an electric power steering apparatus according to an embodiment of the present invention. It is a functional block diagram showing the process of the microcomputer of assist ECU. It is a flowchart showing an electrical angle estimation routine. It is a flowchart showing a winding resistance value correction routine. It is a flowchart showing a steering holding state determination subroutine. It is a graph showing an assist map. It is a circuit diagram of an electric motor. It is a flowchart showing the steering holding state determination subroutine as a 1st modification. It is a flowchart showing the steering holding state determination subroutine as a 2nd modification. It is a flowchart showing the steering holding | maintenance state determination subroutine as a 3rd modification. It is a flowchart showing the straight running determination subroutine as a 4th modification. It is a flowchart showing the winding resistance value correction | amendment routine as 2nd Embodiment.

  Hereinafter, an electric power steering apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a schematic configuration of an electric power steering apparatus for a vehicle according to the embodiment.

  The electric power steering apparatus includes a steering mechanism 10 that steers steered wheels by a steering operation of a steering handle 11, an electric motor 20 that is assembled to the steering mechanism 10 and generates a steering assist torque, and an electric motor 20 for driving the electric power steering apparatus. The motor drive circuit 30 and the electronic control device 100 that controls the operation of the electric motor 20 are provided as main parts. Hereinafter, the electronic control device 100 is referred to as an assist ECU 100.

  The steering mechanism 10 is a mechanism for turning the left and right front wheels FWL and FWR by a rotation operation of the steering handle 11, and includes a steering shaft 12 connected to the steering handle 11 so as to rotate integrally with the upper end. A pinion gear 13 is connected to the lower end of the steering shaft 12 so as to rotate integrally. The pinion gear 13 meshes with rack teeth formed on the rack bar 14 and constitutes a rack and pinion mechanism together with the rack bar 14. Knuckles (not shown) of the left and right front wheels FWL and FWR are steerably connected to both ends of the rack bar 14 via tie rods 15L and 15R. The left and right front wheels FWL and FWR are steered left and right according to the axial displacement of the rack bar 14 accompanying the rotation of the steering shaft 12 around the axis.

  An electric motor 20 is assembled to the rack bar 14. As the electric motor 20, a star (Y) -connected three-phase brushless DC motor is used. The rotating shaft of the electric motor 20 is connected to the rack bar 14 via the ball screw mechanism 16 so as to be able to transmit power, and the rotation gives the steering force to the left and right front wheels FWL and FWR to assist the steering operation. The ball screw mechanism 16 functions as a speed reducer and a rotation-linear converter, and decelerates the rotation of the electric motor 20 and converts it into a linear motion and transmits it to the rack bar 14.

  A steering torque sensor 21 is provided on the steering shaft 12. The steering torque sensor 21 includes, for example, resolvers 21a and 21b respectively assembled to an upper end portion (input side end) and a lower end portion (output side end) of a torsion bar 12a interposed in an intermediate portion of the steering shaft 12. The resolver 21a detects the rotation angle θt1 on the input side of the torsion bar 12a (for example, the rotation angle with respect to the reference angle position), and the resolver 21b detects the rotation angle θt2 on the output side of the torsion bar 12a (rotation angle with respect to the reference angle position). , And detection signals representing the detected rotation angles θt1 and θt2 are output to the assist ECU 100. The difference (θt1−θt2) between the two rotation angles θt1 and θt2 corresponds to the twist angle of the torsion bar 12a. Therefore, the assist ECU 100 detects the steering torque Tr acting on the steering shaft 12 using the difference (θt1−θt2) between the two rotation angles θt1 and θt2. As for the steering torque Tr, the operation direction of the steering wheel 11 is identified by positive and negative values. In the present embodiment, the steering torque Tr when the steering handle 11 is steered in the right direction is indicated by a positive value, and the steering torque Tr when the steering handle 11 is steered in the left direction is indicated by a negative value. Therefore, the magnitude of the steering torque Tr is the absolute value thereof. In this embodiment, the rotation angle of the torsion bar 12a is detected by a resolver, but it can also be detected by another rotation angle sensor such as an encoder.

  The steering shaft 12 is provided with a steering angle sensor 23 that detects the rotation angle of the steering handle 11. The steering angle sensor 23 outputs a detection signal representing the steering angle θh, which is the rotation angle of the steering handle 11, to the assist ECU 100. As for the steering angle θh, the operation direction of the steering wheel 11 is identified by a positive or negative value. In the present embodiment, the steering angle θh in the right direction from the neutral position of the steering handle 11 is indicated by a positive value, and the steering angle θh in the left direction is indicated by a negative value. Therefore, the magnitude of the steering angle θh is the magnitude of its absolute value. A value obtained by differentiating the steering angle θh with respect to time is used as the steering angular velocity ωh of the steering handle 11.

  The electric motor 20 is provided with a rotation angle sensor 22. The rotation angle sensor 22 is incorporated in the electric motor 20 and outputs a detection signal corresponding to the rotation angle position of the rotor of the electric motor 20, and is constituted by, for example, a resolver. The rotation angle sensor 22 outputs a detection signal indicating the rotation angle θm of the electric motor 20 to the assist ECU 100. The assist ECU 100 detects the electrical angle θe of the electric motor 20 from the rotation angle θm. The electric angle θe of the electric motor 20 has two types, that is, an electric angle detected by the rotation angle sensor 22 and an electric angle obtained by estimation which will be described later. The electrical angle detected by the angle sensor 22 is called an actual electrical angle θea, and the electrical angle obtained by estimation is called an estimated electrical angle θeb. In the present embodiment, a resolver is used as the rotation angle sensor 22, but other rotation angle sensors such as an encoder may be used.

  The motor drive circuit 30 comprises a three-phase inverter circuit composed of six switching elements 31 to 36 made of MOS-FET (Metal Oxide Semiconductor Field Effect Transistor). Specifically, a circuit in which a first switching element 31 and a second switching element 32 are connected in series, a circuit in which a third switching element 33 and a fourth switching element 34 are connected in series, a fifth switching element 35 and a first switching element A circuit in which 6 switching elements 36 are connected in series is connected in parallel, and a power supply line 37 to the electric motor 20 is drawn from between two switching elements (31-32, 33-34, 35-36) in each series circuit. Adopted.

  The motor drive circuit 30 is provided with a current sensor 38 that detects a current flowing through the electric motor 20. The current sensor 38 detects the current flowing in each phase (U phase, V phase, W phase), and outputs detection signals corresponding to the detected current values Iu, Iv, Iw to the assist ECU 100. Hereinafter, the measured three-phase current values are collectively referred to as a motor current Iuvw. The motor drive circuit 30 is provided with a voltage sensor 39 that detects the terminal voltage of the electric motor 20. The voltage sensor 39 detects the terminal voltage of each phase (U phase, V phase, W phase), and outputs detection signals corresponding to the detected voltage values Vu, Vv, Vw to the assist ECU 100. Hereinafter, the measured three-phase terminal voltages are collectively referred to as a motor terminal voltage Vuvw.

  As for each switching element 31-36 of the motor drive circuit 30, a gate is connected to assist ECU100, respectively, and a duty ratio is controlled by the PWM control signal output from assist ECU100. Thereby, the drive voltage of the electric motor 20 is adjusted to the target voltage. Incidentally, as indicated by circuit symbols in the figure, the MOSFETs constituting the switching elements 31 to 36 are parasitically structured with diodes.

  The assist ECU 100 includes a microcomputer including a CPU, a ROM, a RAM, and the like as a main part. The assist ECU 100 connects the steering torque sensor 21, the steering angle sensor 23, the rotation angle sensor 22, the current sensor 38, the voltage sensor 39, and the vehicle speed sensor 25 that detects the vehicle speed, and the steering torque Tr, the steering angle θh, and the rotation angle. Detection signals representing θm, motor currents Iu, Iv, Iw, motor terminal voltages Vu, Vv, Vw, and vehicle speed v are input. Then, based on the input detection signal, a command current (motor control value) that flows to the electric motor 20 is calculated so that an optimum steering assist torque according to the steering operation of the driver is obtained, and the command current flows. The duty ratio of each switching element 31 to 36 of the motor drive circuit 30 is controlled.

  Next, a power supply system of the electric power steering apparatus will be described. The electric power steering device is supplied with power from an in-vehicle power supply device 80. The in-vehicle power supply device 80 is configured by connecting in parallel a main battery 81 that is a general in-vehicle battery having a rated output voltage of 12V and an alternator 82 having a rated output voltage of 14V that is generated by the rotation of the engine. A power supply source line 83 and a ground line 84 are connected to the in-vehicle power supply device 80. The power supply source line 83 branches into a control system power line 85 and a drive system power line 86. The control system power supply line 85 functions as a power supply line for supplying power to the assist ECU 100. The drive system power supply line 86 functions as a power supply line that supplies power to both the motor drive circuit 30 and the assist ECU 100.

  An ignition switch 87 is connected to the control system power supply line 85. A main power relay 88 is connected to the drive system power line 86. The main power supply relay 88 is turned on by a control signal from the assist ECU 100 to form a power supply circuit to the electric motor 20. The control system power supply line 85 is connected to the power supply + terminal of the assist ECU 100, and includes a diode 89 on the load side (assist ECU 100 side) from the ignition switch 87 in the middle. The diode 89 is a backflow prevention element that is provided with the cathode facing the assist ECU 100 and the anode facing the in-vehicle power supply device 80, and allows energization only in the power supply direction.

  The drive system power line 86 is provided with a connecting line 90 branched from the main power relay 88 and connected to the control system power line 85 on the load side. This connection line 90 is connected to the assist ECU 100 side from the connection position of the diode 89 in the control system power supply line 85. A diode 91 is connected to the connecting line 90. The diode 91 is provided with the cathode facing the control system power line 85 side and the anode facing the drive system power line 86 side. Therefore, the circuit configuration is such that power can be supplied from the drive system power supply line 86 to the control system power supply line 85 via the connection line 90, but power cannot be supplied from the control system power supply line 85 to the drive system power supply line 86. . The drive system power supply line 86 and the ground line 84 are connected to the power supply input section of the motor drive circuit 30. The ground line 84 is also connected to the ground terminal of the assist ECU 100.

  Next, functions of the assist ECU 100 will be described with reference to FIG. FIG. 2 is a functional block diagram showing functions processed by program control of the microcomputer of the assist ECU 100. The assist ECU 100 includes an assist current command unit 101. As shown in FIG. 6, the assist current command unit 101 stores a basic assist map for setting the basic assist torque Tas according to the steering torque Tr and the vehicle speed v. The assist current command unit 101 inputs the steering torque Tr output from the steering torque sensor 21 and the vehicle speed v output from the vehicle speed sensor 25, and calculates the basic assist torque Tas by referring to this basic assist map. In this case, the basic assist torque Tas increases as the steering torque Tr increases and decreases as the vehicle speed v increases. The assist current command unit 101 receives the steering angle θh detected by the steering angle sensor 23 and calculates a compensation value Trt for the basic assist torque Tas. The compensation value Trt is, for example, for the return force to the basic position of the steering shaft 12 that increases in proportion to the steering angle θh and the rotation of the steering shaft 12 that increases in proportion to the steering angular velocity ωh obtained by time-differentiating the steering angle θh. Calculated as the sum of the return torque corresponding to the resistance force. The assist current command unit 101 sets the sum of the calculated basic assist torque Tas and the compensation value Trt as the target steering assist torque T *, and divides the target steering assist torque T * by the torque constant to obtain d−q A q-axis command current Iq * in the coordinate system is calculated. In calculating the target steering assist torque T *, the compensation value Trt may not be taken into account.

  The assist ECU 100 controls the rotation of the electric motor 20 by vector control described in a dq coordinate system in which the rotation direction of the electric motor 20 is the q axis and the direction orthogonal to the rotation direction is the d axis. The d-axis current does not act to generate the torque of the electric motor 20 and is used for field weakening control. In the present invention, since the field weakening control is not characterized, the assist current command unit 101 sets the d-axis command current Id * to zero (Id * = 0).

  The q-axis command current Iq * and the d-axis command current Id * calculated in this way are output to the feedback control unit 102. The feedback control unit 102 calculates a deviation ΔIq obtained by subtracting the q-axis actual current Iq from the q-axis command current Iq *, and the q-axis actual current Iq is changed to the q-axis command current Iq * by proportional-integral control using the deviation ΔIq. The q-axis command voltage Vq * is calculated so as to follow. Similarly, a deviation ΔId obtained by subtracting the d-axis actual current Id from the d-axis command current Id * is calculated, and the d-axis actual current Id follows the d-axis command current Id * by proportional-integral control using the deviation ΔId. D-axis command voltage Vd * is calculated.

  The q-axis actual current Iq and the d-axis actual current Id are obtained by converting the detected values Iu, Iv, and Iw of the three-phase current actually flowing in the coil of the electric motor 20 into the two-phase current in the dq coordinate system. . Conversion from the three-phase currents Iu, Iv, Iw to the two-phase currents Id, Iq in the dq coordinate system is performed by the three-phase / 2-phase coordinate conversion unit 103. The three-phase / two-phase coordinate conversion unit 103 receives the electrical angle θe output from the electrical angle selection unit 122, and based on the electrical angle θe, the three-phase currents Iu, Iv, and Iw detected by the current sensor 38 are obtained. Conversion into two-phase currents Id and Iq in the dq coordinate system. The electrical angle selection unit 122 will be described later, but when the abnormality of the rotation angle sensor 22 is not detected, the actual electrical angle θea of the electric motor 20 is output as the electrical angle θe, and the abnormality of the rotation angle sensor 22 is detected. Is output, the estimated electrical angle θeb of the electric motor 20 is output as the electrical angle θe.

  The q-axis command voltage Vq * and the d-axis command voltage Vd * calculated by the feedback control unit 102 are output to the 2-phase / 3-phase coordinate conversion unit 105. The two-phase / three-phase coordinate conversion unit 105 converts the q-axis command voltage Vq * and the d-axis command voltage Vd * into the three-phase command voltages Vu * and Vv * based on the electrical angle θe output from the electrical angle selection unit 122. , Vw *, and the converted three-phase command voltages Vu *, Vv *, Vw * are output to the PWM control signal generator 106. The PWM control signal generator 106 outputs a PWM control signal corresponding to the three-phase command voltages Vu *, Vv *, Vw * to the switching elements 31 to 36 of the motor drive circuit 30. As a result, the electric motor 20 is driven, and a steering assist torque that follows the target steering assist torque T * is applied to the steering mechanism 10.

  The rotation detection signal output from the rotation angle sensor 22 is output to the actual electrical angle conversion unit 120 and the sensor abnormality detection unit 121. The actual electrical angle conversion unit 120 calculates the actual electrical angle θea of the electric motor 20 from the rotation detection signal output by the rotation angle sensor 22, and outputs the calculated actual electrical angle θea to the electrical angle selection unit 122. The sensor abnormality detection unit 121 detects an abnormality of the rotation angle sensor 22 based on the rotation detection signal output from the rotation angle sensor 22. When a resolver is employed as the rotation angle sensor 22, it is conceivable that the detection coil or the excitation coil in the resolver may be disconnected or cause an insulation failure. Therefore, the sensor abnormality detection unit 121 monitors the amplitude of the output signal of the detection coil, and determines that it is a sensor abnormality when the amplitude is out of the preset allowable range. In addition, since a pair of detection coils are provided such that the phase of the output signal is shifted by π / 2, an abnormality can be detected by comparing the two output signals. For example, when a sine wave signal is output from one detection coil and a constant value signal is output from the other detection coil, it is abnormal even when the combination of two output signals contradicts each other. It can be determined that there is. In this way, the sensor abnormality detection unit 121 determines whether or not the rotation angle sensor 22 is abnormal, and outputs a sensor abnormality determination signal F that indicates the presence or absence of an abnormality. For example, the sensor abnormality detection unit 121 sets the sensor abnormality determination signal F to “1” when it is determined that there is an abnormality, and sets the sensor abnormality determination signal F to “0” when it is determined that there is no abnormality. To do.

  When an abnormality occurs in the rotation angle sensor 22, the electrical angle cannot be detected, so that the rotation control of the electric motor 20 cannot be performed. Therefore, the assist ECU 100 includes an electrical angle estimation unit 110 so that the rotation control of the electric motor 20 can be continued even when the rotation angle sensor 22 is abnormal. The electrical angle estimation unit 110 starts to operate when the sensor abnormality determination signal F = 1 is input from the sensor abnormality detection unit 121. The electrical angle estimation unit 110 pays attention to its function. Each phase induced voltage calculation unit 111, induced voltage calculation unit 112, estimated angular velocity calculation unit 113, estimated electrical angle calculation unit 114, state determination unit 115, The winding resistance calculation unit 116 and the winding resistance value correction unit 117 are configured.

  Each phase induced voltage calculation unit 111 generates detection signals representing motor terminal voltages Vu, Vv, Vw output from the voltage sensor 39 and detection signals representing motor currents Iu, Iv, Iw output from the current sensor 38. The induced voltage eu, ev, ew generated in each phase of the electric motor 20 is calculated.

As shown in FIG. 7, when the induced voltage of the electric motor 20 is eu, the induced voltage of the V phase is ev, and the induced voltage of the W phase is ew, the induced voltages eu, ev, ew are expressed by the following formula (1). , (2), (3).
eu = Vu-Iu.Ru-Vm (1)
ev = Vv−Iv · Rv−Vm (2)
ew = Vw−Iw · Rw−Vm (3)
Here, Vm is a midpoint voltage, and Ru, Rv, and Rw are winding resistance values of the coils of each phase. The midpoint voltage Vm may be calculated as Vm = (Vu + Vv + Vw) / 3.

  Each phase induced voltage calculation unit 111 stores the above calculation formulas (1), (2), and (3) in a memory, and the motor terminal voltages Vu, Vv, The induced voltages eu, ev, ew are calculated by substituting the motor currents Iu, Iv, Iw detected by the current sensor 38 with Vw. In this case, to be precise, a voltage component (L · di / dt) due to the inductance L of the coil of each phase should be added. However, in the calculation of the induced voltage, the influence of the inductance L is very small. Is considered to be zero. The calculation may be performed in consideration of the voltage (L · di / dt) due to the inductance L.

Each phase induced voltage calculation unit 111 outputs the induced voltages eu, ev, and ew thus calculated to the induced voltage calculation unit 112. The induced voltage calculation unit 112 converts the three-phase induced voltages eu, ev, and ew input from the respective phase induced voltage calculation units 111 into the induced voltages ed and eq in the two-phase dq coordinate system, The induced voltage e generated in the electric motor 20 is calculated by 4).
e = √ (ed ² + eq ² ) (4)
The induced voltage e may be calculated from the sum of absolute values of the three-phase induced voltages eu, ev, and ew (e = | eu | + | ev | + | ew |).
The induced voltage calculation unit 112 outputs the calculation result of the induced voltage e to the estimated angular velocity calculation unit 113.

The estimated angular velocity calculation unit 113 estimates the angular velocity of the electric motor 20 using the proportional relationship between the induced voltage e generated in the electric motor 20 and the angular velocity, but it is necessary to determine the rotation direction of the electric motor 20. Therefore, the sign of the steering torque Tr detected by the steering torque sensor 21 is regarded as the rotation direction of the electric motor 20, and the estimated angular velocity ωm of the electric motor 20 is calculated by the following equation (5).
ωm = sign (Tr) · e / Ke (5)
Here, sign (Tr) represents the sign of the steering torque Tr (the direction of the torque acting on the steering shaft 12). If the steering torque Tr is a positive value or zero, sign (Tr) = 1 and the steering torque Tr is If it is a negative value, sign (Tr) = − 1. Ke is a motor induced voltage constant [V / (rad / s)] representing the relationship between the angular velocity of the electric motor 20 and the induced voltage. Therefore, the estimated angular velocity ωm takes a positive value when the electric motor 20 rotates in the right direction, and takes a negative value when the electric motor 20 rotates in the left direction.

  The rotation direction of the electric motor 20 may be detected by using the sign of the differential value of the rotation angle θt2 on the output side of the torsion bar 12a in the steering torque sensor 21 instead of the sign of the steering torque Tr. Also, the sign of the differential value of the steering angle θh detected by the steering angle sensor 23 can be used.

The estimated angular velocity calculation unit 113 outputs the calculation result of the estimated angular velocity ωm to the estimated electrical angle calculation unit 114. The assist ECU 100 performs various arithmetic processes with a predetermined short calculation cycle by the microcomputer. The electrical angle estimation unit 110 also calculates the estimated electrical angle θeb at this calculation cycle. In this case, the estimated electrical angle calculation unit 114 stores the estimated electrical angle θeb (n−1) calculated at the calculation timing one cycle before, and based on the estimated angular velocity ωm input from the estimated angular velocity calculation unit 113, An electrical angle Δθe obtained by rotating the rotor of the electric motor 20 during one calculation cycle is obtained, and this electrical angle Δθe is added to the estimated electrical angle θeb (n−1) calculated immediately before. θeb (n) is calculated.
θeb (n) = θeb (n−1) + Δθe (6)
Δθe = Kf · ωm
Here, Kf is a constant for obtaining the electrical angle (rad) at which the electric motor 20 rotates during one calculation cycle from the angular velocity (rad / s), and corresponds to the calculation cycle (s).

  In this case, the initial value of the estimated electrical angle θeb (n−1) is a value immediately before the abnormality of the rotation angle sensor 22 is detected by the sensor abnormality detection unit 121. The estimated electrical angle calculation unit 114 receives and updates the actual electrical angle θea output from the actual electrical angle conversion unit 120 from when no abnormality of the rotation angle sensor 22 is detected, and outputs the sensor abnormality detection unit 121. When it is detected that the sensor abnormality determination signal F to be switched to “1” representing the abnormality of the rotation angle sensor 22, the actual electrical angle θea immediately before the abnormality detection is set to the estimated electrical angle θeb (n−1), and Calculation of the estimated electrical angle θeb (n) is started. After that, since the calculated estimated electrical angle θeb (n) is used as the estimated electrical angle θeb (n−1) in Equation (6) in the next calculation cycle, the estimated electrical angle θeb (n) is used as the estimated electrical angle. As the angle θeb (n−1) is sequentially stored and updated.

  The estimated electrical angle calculation unit 114 outputs the calculated estimated electrical angle θeb to the electrical angle selection unit 122. The electrical angle selection unit 122 inputs the actual electrical angle θea and the estimated electrical angle θeb, reads the sensor abnormality determination signal F from the sensor abnormality detection unit 121, and the sensor abnormality determination signal F indicates that the rotation angle sensor 22 is abnormal. In the case of “1” indicating this, the estimated electrical angle θeb is selected and output as the electrical angle θe. When the sensor abnormality determination signal F is “0” indicating that the rotation angle sensor 22 is normal, the actual electrical angle θea is selected and output as the electrical angle θe.

  As described above, the induced voltage e for calculating the estimated electrical angle θeb calculates the motor currents Iu, Iv, Iw, the motor terminal voltages Vu, Vv, Vw, and the winding resistance values Ru, Rv, Rw. Calculated using as a parameter. Among these, the motor currents Iu, Iv, Iw and the motor terminal voltages Vu, Vv, Vw are accurate because they are detected by the current sensor 38 and the voltage sensor 39. On the other hand, the winding resistance values Ru, Rv, and Rw are predetermined design values, and may differ from actual resistance values due to variations in individual electric motors 20, changes in ambient temperature, and the like.

  Therefore, in this embodiment, the actual winding resistance values Ru, Rv, and Rw are obtained by calculation, and the calculated winding resistance values Ru, Rv, and Rw in the equations (1) to (3) are calculated as actual winding values. Correction (update) to the line resistance values Ru, Rv, Rw.

  When the rotor of the electric motor 20 is not rotating, no induced voltage is generated in each phase of the electric motor 20. Therefore, when the state of the vehicle in which the induced voltage in each phase is zero is detected, the values of the induced voltages eu, ev, ew in the calculations in the equations (1) to (3) are set to zero, and the motor current Winding resistance values Ru, Rv, Rw can be calculated from Iu, Iv, Iw and motor terminal voltages Vu, Vv, Vw.

  When the sensor abnormality determination signal F = 1 is input from the sensor abnormality detection unit 121, the state determination unit 115 starts determining whether the vehicle is in a state where the induced voltage generated by the electric motor 20 is zero. In the present embodiment, the state determination unit 115 inputs the three-phase induced voltages eu, ev, ew calculated by the respective phase induced voltage calculation units 111, and the time differential values eu ′ of the induced voltages eu, ev, ew. , Ev ′, ew ′ are calculated, and the rotor of the electric motor 20 is in a steered state where the rotor of the electric motor 20 is not rotating when the magnitude (absolute value) of the differential value is not more than the near-zero determination value even in one phase. Is determined.

The state determination unit 115 outputs to the winding resistance calculation unit 116 a state determination signal SS indicating whether or not the steering state is maintained. The state determination signal SS is set to “1” when it is determined that the steering state is maintained, and is set to “0” when it is not determined that the steering state is maintained. The winding resistance calculation unit 116 does not operate while the state determination signal SS output from the state determination unit 115 is “0”. When the state determination signal SS becomes “1”, that is, when the steered state is detected, the motor currents Iu, Iv, Iw detected by the current sensor 38 and the motor terminal voltage Vu detected by the voltage sensor 39 are detected. , Vv, Vw are read, the induced voltages eu, ev, ew in equations (1) to (3) are set to zero, and the motor terminal voltages Vu, Vv, Vw and motor currents Iu, Iv, Iw From the above, winding resistance values Ru, Rv, Rw are calculated as in the following equations (6), (7), (8).
0 = Vu−Iu · Ru−Vm → Ru = (Vu−Vm) / Iu (7)
0 = Vv−Iv · Rv−Vm → Rv = (Vv−Vm) / Iv (8)
0 = Vw−Iw · Rw−Vm → Rw = (Vw−Vm) / Iw (9)

  The winding resistance calculation unit 116 outputs the calculated winding resistance values Ru, Rv, Rw to the winding resistance value correction unit 117. The winding resistance value correcting unit 117 uses the winding resistance values Ru, Rv, and Rw of the equations (1), (2), and (3) stored in each phase induced voltage calculating unit 111 as the winding resistance calculating unit. The winding resistance values Ru, Rv, and Rw calculated by 116 are corrected. That is, the winding resistance values Ru, Rv, and Rw in the expressions (1), (2), and (3) are replaced (updated) with the winding resistance values Ru, Rv, and Rw calculated by the winding resistance calculation unit 116. . The winding resistance values Ru, Rv, and Rw are stored as design values that are set in advance as initial values, but are updated and stored as new values every time the steering holding state is detected by this correction processing. It will be.

  Here, the electrical angle estimation process and the winding resistance value correction process will be described with reference to flowcharts. FIG. 3 shows an electrical angle estimation routine, and FIG. 4 shows a winding resistance value correction routine. Both routines are executed by the electrical angle estimation unit 110 of the assist ECU 100. However, the electrical angle estimation routine includes the phase induced voltage calculation unit 111, the induced voltage calculation unit 112, the estimated angular velocity calculation unit 113, and the estimated electrical speed. The winding resistance value correction routine is executed by the angle calculation unit 114, and is executed by the state determination unit 115, the winding resistance calculation unit 116, and the winding resistance value correction unit 117. The electrical angle estimation routine and the winding resistance value correction routine are stored as a control program in the ROM of the assist ECU 100, and after the ignition switch 87 is turned on, the sensor abnormality determination signal F output from the sensor abnormality detection unit 121. Is activated when F = 1, and is repeatedly executed at a predetermined short calculation cycle.

  First, the electrical angle estimation routine will be described. When the electrical angle estimation routine starts, the motor terminal voltages Vu, Vv, Vw output from the voltage sensor 39 are read in step S11, and the motor currents Iu, Iv, Iw output from the current sensor 38 are read in step S12. In step S13, the steering torque Tr detected by the steering torque sensor 21 is read. Subsequently, in step S14, induced voltages eu, ev, ew of the respective phases of the electric motor 20 are calculated using the above-described equations (1), (2), (3). Subsequently, in step S15, the induced voltage e of the electric motor 20 is calculated using the above-described equation (4). In step S16, the estimated angular velocity ωm is calculated using the above-described equation (5). Subsequently, in step S17, the estimated electrical angle θeb (n) is calculated using the above-described equation (6).

  After calculating the estimated electrical angle θeb (n) in step S17, the electrical angle estimation unit 110 temporarily ends the electrical angle estimation routine. At this time, the electrical angle estimator 110 outputs the calculated estimated electrical angle θeb (n) to the electrical angle selector 122 and also calculates the estimated electrical angle θeb (n) to the estimated electrical angle θeb ( Store as n-1). Then, while the sensor abnormality determination signal F output from the sensor abnormality detection unit 121 is F = 1, the electrical angle estimation routine is executed at a predetermined calculation cycle.

  Next, the winding resistance correction routine (FIG. 4) will be described. The winding resistance value correction routine is executed in parallel with the electrical angle estimation routine (FIG. 3). When the winding resistance value correction routine is started, first, in step S20, a steering holding state determination process is performed. This steered state determination process is executed by the state determination unit 115 along the steered state determination subroutine shown in FIG. When the steering holding state determination subroutine is started, the state determination unit 115 first reads the induced voltages eu, ev, and ew calculated by the respective phase induced voltage calculation units 111 in step S201. Subsequently, in step S202, time differential values eu ', ev', ew 'of the induced voltages eu, ev, ew are calculated. Since the electrical angle estimation unit 110 performs various calculation processes at a predetermined short calculation cycle, here, the induced voltages eu (n−1) and ev () read from the respective phase induced voltage calculation units 111 one cycle before. n−1), ew (n−1) and the difference between the induced voltages eu (n), ev (n), ew (n) read from each phase induced voltage calculation unit 111 (eu (n) − eu (n-1), ev (n) -ev (n-1), ew (n) -ew (n-1)) are calculated as differential values eu ', ev', ew '.

  Subsequently, in step S203, it is determined whether or not the absolute value of the differential value eu ′ of the U-phase induced voltage is equal to or less than the zero vicinity determination value A. In step S206, the state determination signal SS is set to “1”. On the other hand, if the absolute value of the differential value eu ′ of the U-phase induced voltage exceeds the near-zero determination value A, in step S204, the absolute value of the differential value ev ′ of the V-phase induced voltage is determined to be near zero. It is determined whether or not the value is A or less. When the absolute value of the differential value ev ′ of the V-phase induced voltage is equal to or less than the near-zero determination value A, it is determined that the steering state is maintained, and the state determination signal SS is set to “1” in step S206. . On the other hand, if the absolute value of the differential value ev ′ of the V-phase induced voltage exceeds the near-zero determination value A, the absolute value of the differential value ew ′ of the W-phase induced voltage is determined to be near zero in step S205. It is determined whether or not the value is A or less. When the absolute value of the differential value ew ′ of the W-phase induced voltage is equal to or less than the near-zero determination value A, it is determined that the steering is maintained, and the state determination signal SS is set to “1” in step S206. . On the other hand, if the absolute value of the differential value ew ′ of the W-phase induced voltage exceeds the near-zero determination value A, it is determined that the steering is not maintained, and the state determination signal SS is set to “0” in step S207. To "". That is, when the absolute values of the differential values eu ′, ev ′, ew ′ of the induced voltage of at least one of the three phases are equal to or less than the near-zero determination value A, it is determined that the steering is maintained. Thus, when the state determination signal SS is set, the steering state determination subroutine is exited, and the processing from step S21 of the winding resistance value correction routine of FIG. 3 is performed. In the initial stage when the induced voltages eu (n-1), ev (n-1)) and ew (n-1) are not detected, the time differential value cannot be obtained, so it is determined that the steering state is not maintained. In the next calculation cycle, eu (n), ev (n), ew (n) read this time are induced voltages eu (n-1), ev (n-1), ew (n) one cycle before. Used as -1).

  Returning to the description of the winding resistance correction routine of FIG. The processing from step S21 to step S24 is executed by the winding resistance calculation unit 116. In step S21, the winding resistance calculation unit 116 determines whether or not the steering is maintained based on the state determination signal SS. When it is not in the holding state (SS = 0), the winding resistance value correction routine is temporarily ended as it is. When the steering is maintained (SS = 1), the motor terminal voltages Vu, Vv, Vw output from the voltage sensor 39 are read in step S22, and the motor current Iu output from the current sensor 38 is read in step S23. , Iv, Iw are read. Subsequently, in step S24, the winding resistance values Ru, Rv, Rw are calculated using the above-described equations (7), (8), (9). In this case, when the motor currents Iu, Iv, Iw are smaller than the dead band setting value, and when the motor terminal voltages Vu, Vv, Vw are smaller than the dead band setting value, the winding resistance value of the corresponding phase Should not be calculated. This is because, when the motor currents Iu, Iv, Iw and the motor terminal voltages Vu, Vv, Vw are small, calculation errors of the winding resistance values Ru, Rv, Rw may increase. Therefore, the dead zone set value is set to a boundary value in a range where it is determined that calculation errors of the winding resistance values Ru, Rv, and Rw occur.

  The subsequent processing from step S25 is executed by the winding resistance value correction unit 117. In step S25, the winding resistance value correcting unit 117 determines whether the winding resistance values Ru, Rv, and Rw are within the design range (R1 or more and R2 or less). The winding resistance values Ru, Rv, and Rw should be within the expected range (within the design range), although they vary depending on individual variations and the environmental temperature. Therefore, when the winding resistance values Ru, Rv, Rw calculated in step S24 are out of the design range, the reliability of the calculation result is low. Accordingly, the winding resistance value correcting unit 117 calculates the arithmetic expressions (1), (2), and (2) stored in each phase induced voltage calculating unit 111 only when the winding resistance values Ru, Rv, and Rw are within the design range. The winding resistance values Ru, Rv, Rw in (3) are corrected (updated) to the winding resistance values Ru, Rv, Rw calculated in step S24. If the winding resistance values Ru, Rv, Rw are outside the design range, the winding resistance value correction routine is temporarily terminated without correcting the winding resistance values Ru, Rv, Rw.

  The winding resistance value correction routine is repeatedly executed at a predetermined short calculation cycle. Therefore, even when the winding resistance values Ru, Rv, and Rw are different from the design values (initial values) due to individual differences of the electric motor 20, the winding resistance values Ru, Rv, and Rw are corrected to appropriate values. Even if the ambient temperature of the electric motor 20 changes, the winding resistance values Ru, Rv, and Rw are sequentially corrected following the change. Furthermore, when calculating the winding resistance value, a steering state where no induced voltage is generated in each phase is detected, and when this steering state is detected, an arithmetic expression (motor current, motor terminal voltage and winding resistance is detected). To calculate the winding resistance value by setting the induced voltage value of each phase to zero in the relational expression that represents the induced voltage of each phase). It can be carried out. In addition, since the state where the absolute value of the differential value of the induced voltage of each phase is equal to or less than the near-zero determination value A is determined as the steered state, the determination accuracy is good.

  As a result, according to the present embodiment, the estimation accuracy of the electrical angle can be improved. As a result, the sensorless control performance of the electric motor 20 is improved. Further, since the winding resistance values Ru, Rv, and Rw are corrected when the electric motor 20 is not rotating, the influence of the phase shift of the electric motor 20 does not occur.

  Next, the 1st modification regarding a steering hold state determination process is demonstrated. FIG. 8 shows a flowchart executed instead of the steering holding state determination subroutine (FIG. 5) in the above-described embodiment. In this modification, when all of the time differential values eu ′, ev ′, ew ′ of the induced voltages eu, ev, ew of each phase are close to zero, it is determined that the steering state is maintained. . Hereinafter, regarding the modification, when the process is the same as that of the above-described embodiment, the same step symbols are attached to the drawings, and only a brief description is given.

  When the steered state determination subroutine of the first modification is started, the state determination unit 115 reads the induced voltages eu, ev, ew calculated by the respective phase induced voltage calculation units 111 in step S201, and in step S202. The differential values eu ′, ev ′, ew ′ are calculated. Subsequently, in step S203, it is determined whether or not the absolute value of the differential value eu ′ of the U-phase induced voltage is equal to or less than the near-zero determination value A. If it is determined “Yes”, in the subsequent step S204. If the absolute value of the differential value ev ′ of the V-phase induced voltage is equal to or less than the near-zero determination value A, and if “Yes” is determined, the W-phase induced voltage is further determined in step S205. It is determined whether or not the absolute value of the differential value ew ′ is equal to or less than the zero vicinity determination value A. If “Yes” is determined in step S205, that is, if the absolute values of the differential values eu ′, ev ′, and ew ′ of the induced voltages of the respective phases are all equal to or less than the zero vicinity determination value A, step S206 is performed. , It is determined that the steering is maintained, and the state determination signal SS is set to “1”. On the other hand, if the absolute value of the differential values eu ′, ev ′, ew ′ of the induced voltage exceeds the near-zero determination value A even in one phase, it is determined in step S207 that the steering state is not maintained, and the state determination signal Set SS to “0”.

  According to the first modified example, since the determination of the steered state is strictly performed, the calculation accuracy of the winding resistance values Ru, Rv, Rw can be further improved. For this reason, the estimation accuracy of the electrical angle can be further improved, and the sensorless control performance of the electric motor 20 is improved.

  Next, the 2nd modification regarding a steering hold state determination process is demonstrated. FIG. 9 shows a flowchart executed instead of the steering holding state determination subroutine (FIG. 5) in the above-described embodiment. In the second modification, the state determination unit 115 is configured to input the steering angle θh detected by the steering angle sensor 23 instead of the induced voltages eu, ev, ew of the respective phases (FIG. 2 is indicated by a broken line).

  When the steered state determination subroutine of the second modified example is started, the state determination unit 115 reads the steering angle θh detected by the steering angle sensor 23 in step S211, and in step S212, converts the steering angle θh to time. The steering angular velocity ωh is calculated by differentiation. Subsequently, in step S213, it is determined whether or not the absolute value of the steering angular velocity ωh is equal to or less than the near zero determination value B. If the absolute value of the steering angular velocity ωh is equal to or less than the near-zero determination value B, in step S206, it is determined that the steering is maintained, and the state determination signal SS is set to “1”. On the other hand, if the absolute value of the steering angular velocity ωh exceeds the near-zero determination value B, it is determined in step S207 that the steering is not being held, and the state determination signal SS is set to “0”.

  According to the second modified example, the steered state can be detected appropriately and easily using the steering angle sensor 23.

  Next, a third modified example related to the steered state determination process will be described. FIG. 10 shows a flowchart executed instead of the steering holding state determination subroutine (FIG. 5) in the above-described embodiment. In the third modification, the state determination unit 115 is configured to input the rotation angle θt2 detected by the resolver 21b of the steering torque sensor 21 instead of the induced voltages eu, ev, ew of the respective phases. (Indicated by a broken line in FIG. 2).

  When the steered state determination subroutine of the third modification is started, the state determination unit 115 reads the rotation angle θt2 detected by the resolver 21b of the steering torque sensor 21 in step S221, and in the subsequent step S222, the rotation angle The rotational angular velocity ωt2 is calculated by differentiating θt2 with respect to time. Subsequently, in step S223, it is determined whether or not the absolute value of the rotational angular velocity ωt2 is equal to or less than the near zero determination value C. If the absolute value of the rotational angular velocity ωt2 is equal to or less than the near zero determination value C, in step S206, it is determined that the steering is maintained, and the state determination signal SS is set to “1”. On the other hand, if the absolute value of the steering angular velocity ωh exceeds the near zero determination value C, it is determined in step S207 that the vehicle is not in the steered state, and the state determination signal SS is set to “0”.

  According to the third modified example, it is possible to appropriately and easily detect the steered state using the resolver 21b of the steering torque sensor 21. Note that the rotation angle θt1 detected by the resolver 21a may be used instead of the resolver 21b.

  Next, a fourth modification will be described. The winding resistance values Ru, Rv, and Rw must be calculated in a vehicle state where the induced voltage generated by the electric motor 20 is zero. Therefore, in the above-described embodiment and the first to third modifications, the steered state is detected as the vehicle state, but in the fourth embodiment, the straight traveling state is detected as the vehicle state. Therefore, in the fourth modification, the state determination unit 115 inputs the right wheel speed vR and the left wheel speed vL detected by a wheel speed sensor (not shown) instead of the induced voltages eu, ev, and ew of each phase. (Shown by a broken line in FIG. 2).

  FIG. 11 is a flowchart showing a straight traveling determination subroutine executed in place of the steered state determination subroutine (FIG. 5) in the above-described embodiment. In the fourth modification, step S20 of the main routine of FIG. 4 is a straight running determination process, and the determination in step S21 is a determination as to whether or not the vehicle is in a straight running state.

  When the straight traveling determination subroutine is started, the state determination unit 115 calculates the right wheel speed vR and the left wheel speed vL detected by the wheel speed sensors of the left and right front wheels (or the left and right rear wheels) in step S231. Read. Subsequently, in step S232, a wheel speed difference ΔvRL (= vR−vL) between the right wheel speed vR and the left wheel speed vL is calculated. Subsequently, it is determined whether or not the absolute value of the wheel speed difference ΔvRL is equal to or less than a zero vicinity determination value D. If the absolute value of the wheel speed difference ΔvRL is less than or equal to the near zero determination value D, it is determined in step S234 that the vehicle is running straight, and the state determination signal SS is set to “1”. Conversely, if the absolute value of the wheel speed difference ΔvRL exceeds the near-zero determination value D, it is determined in step S235 that the vehicle is not in the straight running state, and the state determination signal SS is set to “0”. If either the right wheel speed vR or the left wheel speed vL read in step S231 is a value near zero, it is determined that the vehicle is stopped and the process proceeds to step S235.

  According to the fourth modification, it is possible to determine the state in which the induced voltage is zero in the electric motor 20 by determining the straight running state of the vehicle, and the determination is easy.

  Next, a second embodiment will be described. In the above-described embodiment (hereinafter referred to as the first embodiment) and the four modified examples, when the abnormality of the rotation angle sensor 22 is detected, the winding resistance value of the electric motor 20 is obtained by calculation, and this is obtained. The winding resistance value is updated as the winding resistance value in the calculation formula for calculating the induced voltage. However, in the second embodiment, when the abnormality of the rotation angle sensor 22 is not detected, The winding resistance value is updated. Hereinafter, processing to be added to the first embodiment (including modifications) will be described.

  FIG. 12 shows the second embodiment, which is performed by the electrical angle estimation unit 110 (particularly, the winding resistance calculation unit 116 and the winding resistance value correction unit 117) when no abnormality is detected in the rotation angle sensor 22. It is a flowchart showing a winding resistance value correction routine. This winding resistance value correction routine is started when a sensor abnormality determination signal F with F = 0 (no abnormality) is output from the sensor abnormality detection unit 121 after the ignition switch 87 is turned on, and a predetermined short calculation is performed. It is executed repeatedly in a cycle. Then, when the ignition switch 87 is turned off, or when the sensor abnormality determination signal F is switched to F = 1 (abnormality exists), the process ends. In the second embodiment, the winding resistance calculation unit 116 is configured to input the rotation angle θm detected by the rotation angle sensor 22 (indicated by a broken line in FIG. 2).

  When the winding resistance value correction routine of the second embodiment is started, first, in step S31, the rotation angle θm detected by the rotation angle sensor 22 is read. Subsequently, in step S32, the rotational angle θm is differentiated with respect to time to calculate the rotational angular velocity ωma. Since the electrical angle estimation unit 110 performs various arithmetic processes at a predetermined short calculation cycle, here, the rotation angle θm (n−1) read one cycle before and the rotation angle θm (n) read this time. (Θm (n) −θm (n−1)) is calculated as the rotational angular velocity ωma. Hereinafter, this rotational angular velocity ωma is referred to as an actual rotational angular velocity ωma to distinguish it from the estimated angular velocity ωm.

  The electric motor 20 does not generate an induced voltage when the rotor is not rotating. That is, no induced voltage is generated when the rotational angular velocity becomes zero. Therefore, in step S33, it is determined whether or not the absolute value of the actual rotational angular velocity ωma is equal to or less than the near zero determination value E. This near-zero determination value E is a value of a rotational angular velocity at which it can be determined that no induced voltage is generated in the electric motor 20, and is set to zero or a value close to zero. If the absolute value of the actual rotational angular velocity ωma exceeds the near-zero determination value E, it cannot be said that no induced voltage is generated in the electric motor 20, and therefore the winding resistance value correction routine is temporarily terminated.

  On the other hand, when the absolute value of the actual rotational angular velocity ωma is equal to or less than the near-zero determination value E, it can be said that no induced voltage is generated in the electric motor 20, and therefore, the processing from step S34 is performed. The processing of step S34 to step S38 corresponds to the processing of step S22 to step S26 of the winding resistance value correction routine (FIG. 4) in the first embodiment. That is, the motor terminal voltages Vu, Vv, Vw output from the voltage sensor 39 are read in step S34, the motor currents Iu, Iv, Iw output from the current sensor 38 are read in step S35, and in step S36, Winding resistance values Ru, Rv, and Rw are calculated using equations (7), (8), and (9). If the winding resistance values Ru, Rv, and Rw are within the design range (R1 or more and R2 or less) (S37: Yes), they are stored in each phase induced voltage calculation unit 111 in step S38. The winding resistance values Ru, Rv, and Rw in the calculated equation are corrected (updated) to the winding resistance values Ru, Rv, and Rw calculated in step S36.

  According to the second embodiment, since the winding resistance values Ru, Rv, and Rw are corrected before the abnormality of the rotation angle sensor 22 is detected, the abnormality of the rotation angle sensor 22 actually occurs and the sensorless control is performed. Even in the case of switching, the electrical angle can be estimated with high accuracy from that point. As a result, it is possible to satisfactorily shift to sensorless control. Note that the processing of steps S31 to S36 is executed by the winding resistance calculation unit 116, and the processing of steps S37 and S38 is executed by the winding resistance value correction unit 117.

  The electric power steering apparatus according to the present embodiment has been described above. However, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the object of the present invention.

  For example, in the present embodiment, as the initial value of the estimated electrical angle θeb (n−1), the value of the actual electrical angle θea immediately before the abnormality of the rotation angle sensor 22 is detected is used. A value may be used. This is because even if the initial estimated electrical angle is different from the actual electrical angle, the rotational position of the rotor is synchronized with the estimated electrical angle for control while the electric motor 20 is rotating. .

  In this embodiment, the winding resistance value is corrected when an abnormality of the rotation angle sensor 22 is detected. However, the winding resistance value is corrected only when the abnormality of the rotation angle sensor 22 is not detected. A configuration for performing correction, for example, a configuration for performing a winding resistance value correction routine shown in FIG.

  In the present embodiment, the rack assist type electric power steering device that applies the torque generated by the electric motor 20 to the rack bar 14 has been described. However, the torque generated by the electric motor is determined by the steering shaft 12 (from the torsion bar 12a). It may be a column assist type electric power steering device applied to the output side.

  In addition, the structure which consists of the electrical angle estimation part 110 in this embodiment, the current sensor 38, and the voltage sensor 39 corresponds to the electrical angle estimation means of this invention. In addition, the configuration including each phase induced voltage calculation unit 111 and the induced voltage calculation unit 112 in the present embodiment corresponds to the induced voltage calculation unit of the present invention, and includes the estimated angular velocity calculation unit 113 and the estimated electrical angle calculation unit 114. The configuration corresponds to the estimated electrical angle calculation means of the present invention. Further, the configuration comprising the state determination unit 115 and the winding resistance calculation unit 116 in the present embodiment corresponds to the winding resistance calculation means of the present invention, and the winding resistance value correction unit 117 corrects the winding resistance value of the present invention. Corresponds to means. Further, the state determination unit 115 in the present embodiment corresponds to a state determination unit of the present invention. The assist current command unit 101 in this embodiment corresponds to the motor control value calculation means of the present invention, and includes a feedback control unit 102, a three-phase / two-phase coordinate conversion unit 103, a two-phase / three-phase coordinate conversion unit 105, and a PWM. The configuration comprising the control signal generator 106 and the motor drive circuit 30 corresponds to the motor control means of the present invention. In the second embodiment, the winding resistance calculator 116 that executes the winding resistance correction routine shown in FIG. 12 corresponds to the normal winding resistance calculator of the present invention. Further, the near zero determination values A, B, and C in the present embodiment are set to zero or a near zero setting value that can be determined to be a steered state where no induced voltage is generated. Corresponds to the value. Further, the near zero determination value D in the present embodiment is a set value near zero that can be determined to be zero or a straight traveling state in which no induced voltage is generated, and corresponds to the reference value for straight traveling determination of the present invention. .

  DESCRIPTION OF SYMBOLS 10 ... Steering mechanism, 11 ... Steering handle, 12 ... Steering shaft, 12a ... Torsion bar, 21 ... Steering torque sensor, 21a, 21b ... Resolver, 22 ... Rotation angle sensor, 23 ... Steering angle sensor, 25 ... Vehicle speed sensor, 30 DESCRIPTION OF SYMBOLS ... Motor drive circuit, 38 ... Current sensor, 39 ... Voltage sensor, 100 ... Electronic control unit (assist ECU), 101 ... Assist current command part, 102 ... Feedback control part, 103 ... Three-phase / two-phase coordinate conversion part, 105 ... 2 phase / 3 phase coordinate conversion unit, 106 ... PWM control signal generation unit, 110 ... electrical angle estimation unit, 111 ... each phase induced voltage calculation unit, 112 ... induced voltage calculation unit, 113 ... estimated angular velocity calculation unit, 114 ... Estimated electrical angle calculation unit, 115 ... state determination unit, 116 ... winding resistance calculation unit, 117 ... winding resistance value correction unit, 120 ... actual electrical angle conversion , 121 ... sensor abnormality detection unit, 122 ... electrical angle selection section.

Claims (9)

A steering torque sensor for detecting a steering torque input from the steering handle to the steering shaft;
An electric motor provided in the steering mechanism for generating steering assist torque;
A rotation angle sensor for detecting an actual electrical angle of the electric motor;
Sensor abnormality detecting means for detecting abnormality of the rotation angle sensor;
An electrical angle estimating means for calculating an estimated electrical angle of the electric motor when an abnormality of the rotation angle sensor is detected by the sensor abnormality detecting means;
Motor control value calculating means for calculating a motor control value for generating a target steering assist torque according to the steering torque detected by the steering torque sensor;
When the abnormality of the rotation angle sensor is not detected, the electric motor is driven and controlled based on the actual electrical angle and the motor control value, and when the abnormality of the rotation angle sensor is detected, the estimated electrical angle and An electric power steering apparatus comprising: motor control means for driving and controlling the electric motor based on the motor control value;
The electrical angle estimation means includes
A current sensor for detecting a current flowing in each phase of the electric motor;
A voltage sensor for detecting a voltage applied to each phase of the electric motor;
Induction generated in the motor based on the detected current value flowing in each phase of the electric motor, the voltage value applied to each phase of the electric motor, and the winding resistance value of each phase of the electric motor Induced voltage calculation means for calculating a voltage;
Estimated electrical angle computing means for computing the estimated electrical angle based on the induced voltage computed by the induced voltage computing means;
Winding resistance calculating means for calculating the winding resistance value of each phase of the electric motor by calculation;
Winding resistance value correction means for correcting the winding resistance value used by the induced voltage calculation means for calculation of the induced voltage to the winding resistance value obtained by the winding resistance calculation means, Electric power steering device. The winding resistance calculation means is
A state determining means for determining whether or not the vehicle is in a state where the induced voltage generated by the electric motor is zero;
When a state of the vehicle in which an induced voltage generated in the electric motor is zero is detected by the state determination means, a current value flowing through the electric motor, a voltage value applied to the electric motor, and the winding resistance value 2. The electric power steering apparatus according to claim 1, wherein the winding resistance value is calculated by setting the value of the induced voltage in the relational expression representing the induced voltage to zero using.   The state determination means determines whether or not the steering angle is maintained when abnormality of the rotation angle sensor is detected, or determines whether or not the vehicle is in a straight traveling state. 3. The electric power steering apparatus according to claim 2, wherein it is determined whether or not the vehicle is in a state where an induced voltage generated by the electric motor is zero.   The state determination means calculates a differential value of the induced voltage of each phase of the electric motor, and when the absolute value of the differential value of the induced voltage of at least one phase is equal to or less than the reference value for determining the steering, The electric power steering apparatus according to claim 3, wherein the electric power steering apparatus is determined to be present.   The state determination means calculates the differential value of the induced voltage of each phase of the electric motor, and when the absolute value of the differential value of the induced voltage of all phases is equal to or less than the reference value for steering determination, The electric power steering apparatus according to claim 4, wherein the electric power steering apparatus is determined to be present. The state determination means includes
Steering angle acquisition means for acquiring steering angle information representing the steering angle of the steering wheel;
Steering angular velocity, which is a differential value of the steering angle acquired by the steering angle acquisition means, is calculated, and when the absolute value of the steering angular velocity is equal to or less than the reference value for steering determination, it is determined that the steering state is maintained. The electric power steering apparatus according to claim 3. The steering torque sensor detects an input-side rotation angle and an output-side rotation angle of a torsion bar inserted into the steering shaft, and based on a torsion angle of the torsion bar, which is a difference between both rotation angles, The input steering torque is detected,
The state determination means calculates a rotation angular velocity that is a differential value of the output-side rotation angle or the input-side rotation angle of the torsion bar, and when the absolute value of the rotation angular velocity is equal to or less than a reference value for holding determination, The electric power steering apparatus according to claim 3, wherein the electric power steering apparatus is determined to be in a state. The state determination means includes
Wheel speed acquisition means for acquiring wheel speed information representing the left and right wheel speeds,
4. The electric power steering according to claim 3, wherein when the difference between the left and right wheel speeds acquired by the wheel speed acquisition means is equal to or less than a reference value for determining straight running, the vehicle is judged to be in a straight running state. apparatus. The winding resistance calculation means is
When an abnormality of the rotation angle sensor is not detected, a rotation angular velocity that is a differential value of the motor rotation angle detected by the rotation angle sensor is calculated, and an absolute value of the rotation angular velocity is equal to or less than a near-zero determination reference value. In this case, the value of the induced voltage in the relational expression representing the induced voltage is set to zero using the current value flowing through the electric motor, the voltage value applied to the electric motor, and the winding resistance value. The electric power steering apparatus according to any one of claims 1 to 8, further comprising a normal winding resistance calculation means for calculating the winding resistance value.

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