JP4802174B2 - Brushless motor control device and electric steering device - Google Patents

Description

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

Conventionally, when estimating the rotation angle of the magnetic pole of the rotor from a predetermined reference rotational position, for example, when the brushless motor is stopped, a pulse voltage that does not contribute to the rotation of the rotor is applied to the brushless motor, Based on the inductance obtained by Fourier transform from the current and voltage of the brushless motor at this time, from the inductance change according to the saliency of the rotor, the rotor angle indicating the rotor position, that is, the rotation of the magnetic pole of the rotor from the predetermined reference rotation position A method for estimating an angle is known (see, for example, Non-Patent Document 1).
Yamamoto, et al., “Initial magnetic pole position estimation method for surface magnet synchronous motor using pulse voltage”, IEEE Trans. IA, Vol. 125, no. 3,2005, p253-258

By the way, in the method according to the above prior art example, since it is necessary to perform complicated processing such as Fourier transform, it is difficult to reduce the time required for estimating the rotation angle. For example, in a brushless motor provided in an electric steering device, the driver's steering input cannot be appropriately assisted by the steering assist force generated from the brushless motor. There arises a problem that the driver feels uncomfortable with the steering feeling.
In addition, when applying a pulse voltage that does not contribute to the rotation of the rotor to the brushless motor, in order to reduce electromagnetic noise and vibration, a high frequency pulse voltage higher than the audible frequency is applied. Since the current change corresponding to the inductance change of the motor becomes extremely small, there arises a problem that it becomes difficult to improve the estimation accuracy of the rotation angle due to the error of the detection value detected by the current sensor or the like.

For example, the resistance _{R M} between the lines of the brushless motor 100 for electric power steering as shown in the equivalent circuit of FIG. 12 is a generally _R M = 20 (milliohms), the average value of the inductance _{L M} is generally _{L M} (mean value ) = 125 (μH). Then, the inductance _{L M} is the maximum value _{L Mmax,} as shown in FIG. 13 is generally _L Mmax = 150 _(μH), the minimum value _{L Mmin} is generally _L Mmin = 100 which changes when the rotor of the brushless motor 100 is rotated It is about (μH). However, FIG. 13 shows the line inductance variation of the 8-pole brushless motor 100 as shown in FIG. 3 described later.
Next, a method and problem will be described in which an AC voltage outside the audible frequency is applied to the brushless motor 100 to supply a current, and the inductance is estimated from the current. The brushless motor 100 in the equivalent circuit shown in FIG. 12, a current _{I M} at the time of applying a voltage _{V M} is indicated by the number (1) below. Substituting the above resistance value (R _M = 20 (mΩ)) and inductance value (L _M (average value) = 125 (μH)) into the following formula (1), the voltage V _M = 12 (V) and the frequency FIG. 14 shows a current waveform when a rectangular wave of f = 20 (kHz) is applied. If a thick solid line in the figure inductance _{L M} is the minimum value _{L Mmin,} the thin solid line shows the case inductance _{L M} is the maximum value _Mmax. The maximum difference between them is only 0.99 (A). The maximum operating current of the brushless motor 100 is approximately 85 (Arms) in terms of effective value and 120 (Arms) in terms of peak value. Since the current sensor needs to detect the peak value of the motor current, the input / output characteristics are ± 2.5 (V) per ± 125 (A) as shown in FIG.
On the other hand, the resolution of the AD converter required for taking in the detection voltage of the current sensor into the microcomputer is 10 (bits) per 5 (V). Therefore, the resolution of the current input to the microcomputer is 0.244 (A) per 1 (LSB).
Therefore, when 0.99 (A), which is the current change amount with respect to the inductance change amount, is read into the microcomputer, there is only 4 (LSB), and this value must be assigned to the rotation angle, so the resolution is low and the rotation is accurate. The angle could not be estimated.

  The present invention has been made in view of the above circumstances, and a brushless motor control device capable of quickly and accurately estimating the rotation angle of a brushless motor in a stopped state, and operating while ensuring desired silence. It is an object of the present invention to provide an electric steering device that can prevent a person from feeling uncomfortable with the steering feeling.

In order to solve the above-described problems and achieve the object, a brushless motor control device according to a first aspect of the present invention includes a rotor (for example, the rotor 63 in FIG. 3 of the embodiment) and a multi-phase stator winding. Brushless motor (eg, in FIG. 3 of the embodiment) having a stator (eg, stator 64 in FIG. 3 of the embodiment) having a wire (eg, stator winding 64a in FIG. 3 of the embodiment) Control of brushless motor provided with motor 31) and energization switching means (for example, PWM signal generation unit 87 and FET bridge 72 in FIG. 4 of the embodiment) for switching control of energization to the stator windings of each phase an apparatus, said plurality phase of the phase voltage and the midpoint voltage to the voltage detecting means for detecting the phase voltage which is the difference between (for example, a voltage sensor 77 and the first and second phases in FIG. 4 of the embodiment Pressure calculating section 88a, and 88b), and a voltage applying means for applying a predetermined AC voltage between predetermined line among the plurality of phases (for example, step S03 in FIG. 10 of the embodiment), the by the voltage applying means In a state in which the predetermined AC voltage is applied between predetermined lines of the plurality of phases, of the phases included between the lines to which the predetermined AC voltage is applied among the plurality of interphase voltages detected by the voltage detecting means . Estimating means (for example, step S04 to step S09 in FIG. 10 of the embodiment, rotation angle estimator 89 in FIG. 4) for estimating the rotation angle of the rotor based on the phase voltage ratio is provided.
Furthermore, in the brushless motor control device according to the second aspect of the present invention, the estimation means estimates the rotation angle of the rotor based on the phase voltage ratio and the phase voltage value to which the predetermined AC voltage is applied. .

Furthermore, in the brushless motor control device according to the third aspect of the present invention, the frequency of the predetermined AC voltage is a frequency other than an audible frequency.
Furthermore, in the brushless motor control device according to the fourth aspect of the present invention, the estimating means assumes that the phase voltage ratio is equal to the phase inductance ratio.

The electric steering apparatus according to the fifth aspect of the present invention includes a brushless motor control apparatus according to the first aspect or the second aspect, and steering torque detection means for detecting steering torque (for example, in FIG. 1 of the embodiment). The steering torque sensor 40), the steering torque detected by the steering torque detection means, and the rotation angle estimated by the estimation means are driven to control the brushless motor to assist the steering torque. Steering control means (for example, the control unit 73 in FIG. 4 of the embodiment) for generating auxiliary torque to be generated from the brushless motor.

According to the control device for a brushless motor according to the first aspect of the present invention, since the rotation angle is estimated based on the change in the ratio of phase voltage corresponding to the inductance change of the brushless motor, directly from the interphase voltage or the line voltage The change can be detected larger than the case of estimation, and the estimation accuracy is improved. And the estimation accuracy of a rotation angle can be improved compared with the case where a rotation angle is estimated according to the electric current change corresponding to the inductance change of a brushless motor, for example. Moreover, based on the ratio of the plurality of phase voltages, since estimating the rotational angle, for example, a case where an error of the inter-phase voltage is the power supply voltage due to fluctuation unstable energization switching section increases also, Oite the ratio of interphase voltage can offset the error in the inter-phase voltage, the estimation accuracy of the rotation angle, can be further improved.

Furthermore, according to the brushless motor control device of the third aspect of the present invention, unlike the prior art, since the current response is not used for the estimation of the rotation angle, the frequency of the applied voltage is set to a frequency higher than the audible frequency. In addition, there is no reduction in resolution as shown in FIG. 14 described above, and the rotation angle can be estimated with high accuracy, thereby ensuring desired silence.

In addition, according to the electric steering apparatus of the fifth aspect of the present invention, the apparatus configuration can be simplified and the apparatus can be reduced in size without the need for providing a rotation angle sensor such as a resolver. It is possible to improve the accuracy of the rotation angle while reducing electromagnetic noise and vibration when estimating the rotation angle of the brushless motor, and the driver feels uncomfortable with the steering feeling. Can be prevented.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of a brushless motor control device and an electric steering device according to the invention will be described with reference to the accompanying drawings.
The brushless motor control device 70 according to the present embodiment is mounted on an ECU (Electronic Control Unit) 50 of the electric steering device 1 as the vehicle steering device shown in FIG.

  As shown in FIG. 1, for example, the electric steering device 1 includes a steering shaft 3 connected to a steering wheel 2 of a vehicle and a universal shaft joint 4 connected to the steering shaft 3 to steering wheels (wheels) 5 and 5. The steering system includes a steering mechanism 7 housed in a housing 6 that constitutes a steering gear box, and a steering assist mechanism 8 that generates a steering assist force in the steering mechanism 7.

The steering mechanism 7 includes a rack and pinion mechanism 10, and a pinion shaft 11 of the rack and pinion mechanism 10 is connected to the universal joint 4.
The pinion 12 provided on the pinion shaft 11 and the rack 14 provided on the rack shaft 13 that can reciprocate in the vehicle width direction are meshed with each other.

The pinion shaft 11 is rotatably supported at its lower, middle, and upper portions by bearings 15 a, 15 b, and 15 c, for example, and the pinion 12 is provided at the lower end of the pinion shaft 11.
The rack shaft 13 is supported in a substantially cylindrical rack housing 6 a extending in the vehicle width direction of the housing 6 through a bearing 16 so as to be capable of reciprocating in the longitudinal direction of the shaft.

Both ends of the rack housing 6a have openings that open, and the end 13a of the rack shaft 13 protrudes from the opening.
A rack end plate 17 having an outer diameter larger than that of the rack shaft 13 is fixed to each end portion 13 a of the rack shaft 13, and a rack end head 18 is fixed to the rack end plate 17.
The rack end head 18 includes a ball joint 19, a tie rod 20 is connected to the ball joint 19, and a steering wheel (front wheel) 5 is linked to the tie rod 20.

On the outer peripheral surface near the opening at both ends of the rack housing 6a, an annular groove 6b protruding inward in the radial direction is formed.
An end of a bellows-shaped rack end cover 21 that can be expanded and contracted in the longitudinal direction of the rack shaft 13 is attached to the annular groove 6b of the rack housing 6a, and the end 13a of the rack shaft 13 and the rack end plate are mounted. 17, the rack end head 18, and the ball joint 19 are accommodated in a rack end cover 21, and the tie rod 20 penetrates the rack end cover 21 and protrudes outward.

The steering assist mechanism 8 includes a motor 31 including a brushless motor that generates a steering assist force for reducing the steering force by the steering wheel 2, a worm gear 32, and a worm wheel gear 33. The wheel gear 33 is accommodated in the housing 6 constituting the steering gear box.
The motor 31 is connected to a worm gear 32 that is pivotally supported by the housing 6, and the worm gear 32 meshes with a worm wheel gear 33 that is provided integrally with the pinion shaft 11. The worm gear 32 and the worm wheel gear 33 constitute a reduction mechanism, and torque generated by the motor 31 is boosted by the worm gear 32 and the worm wheel gear 33 and transmitted to the pinion shaft 11.

A magnetostrictive steering torque sensor 40 that detects a steering torque (steering input) based on a change in magnetic characteristics caused by magnetostriction is provided between the intermediate bearing 15b and the upper bearing 15c in the pinion shaft 11. Has been placed.
The steering torque sensor 40 includes two magnetostrictive films 41 and 42 provided on the outer peripheral surface of the pinion shaft 11, two detection coils 43 and 44 disposed to face the magnetostrictive films 41 and 42, and each detection coil 43, 44. The detection circuits 45 and 46 are connected to the control circuit 44. Each of the detection circuits 45 and 46 converts an inductance change of the detection coils 43 and 44 caused by magnetostriction into a voltage change, and an ECU (Electric Control Unit). Output to 50. The ECU 50 calculates the steering torque that acts on the steering shaft 3 based on the outputs of the detection circuits 45 and 46.

  Then, the ECU 50 determines a target current to be supplied to the motor 31 in accordance with the magnitude of the steering torque detected by the steering torque sensor 40 (that is, the steering torque input from the steering wheel 2 by the driver). For example, by performing control such as PID control so that the current flowing through the target 31 matches the target current, an auxiliary torque corresponding to the steering torque is generated from the motor 31 and this auxiliary torque is transmitted to the pinion shaft via the speed reduction mechanism. 11 is transmitted. Thereby, the steering assist force by the motor 31 acts in the same direction as the steering input by the driver, and the steered wheels 5 are steered by the combined torque obtained by adding the assist torque of the motor 31 to the driver's steering torque.

For example, as shown in FIG. 2, the motor 31 is attached to the side portion of the housing 6 so as to protrude from the housing 6 with a bolt, and closes the side opening of the housing 6. The motor 31 is attached to the lid 61 with a bolt. A bottom cylindrical motor case 62, a rotor 63 provided around the rotation axis O, and having a permanent magnet 63 a, are arranged opposite to each other in the radial direction so as to cover the outer periphery of the rotor 63, and rotate the rotor 63. And a stator 64 having a plurality of stator windings 64a for generating a rotating magnetic field.
The stator 64 is accommodated in, for example, a motor case 62 by press fitting or the like, and an output shaft 65 disposed coaxially with the rotation shaft O is fixed to the inner peripheral portion of the rotor 63.
The lid 61 and the motor case 62 of the motor 31 support the output shaft 65 through two bearings 66 so as to be rotatable.

For example, as shown in FIG. 3, the stator 64 of the motor 31 includes a plurality of divided cores 64b arranged in an annular shape, an insulating bobbin 64c, and a stator winding 64a wound around the bobbin 64c in a multiple manner. And is accommodated by press-fitting or the like in a motor case 62 molded by press molding or the like.
The split core 64b is configured, for example, by laminating a plurality of substantially T-shaped silicon steel plates in the direction of the rotation axis O, and includes an outer yoke portion 64b1 and an inner teeth portion 64b2. On both end surfaces in the circumferential direction of the yoke portion 64b1, a convex portion protruding in the circumferential direction is provided on one end surface, and a concave portion in which the convex portion can be fitted is provided on the other end surface, and adjacent in the circumferential direction. An annular yoke is formed by fitting the convex portion of one yoke portion 64b1 of the divided cores 64b and 64b into the concave portion of the other yoke portion 64b1. The teeth portion 64b2 has a smaller circumferential width than the yoke portion 64b1, and protrudes from the yoke portion 64b1 toward the radially inward rotor 63. And the bobbin 64c which consists of insulating resin materials etc. is mounted | worn with the teeth part 64b2.

The rotor 63 of the motor 31 includes, for example, a permanent magnet 63a, a magnet cover 63b, a back yoke 63c, and an output shaft 65.
The substantially cylindrical back yoke 63c is configured, for example, by laminating a plurality of substantially annular silicon steel plates in the direction of the rotation axis O, the output shaft 65 is mounted on the inner peripheral portion, and a predetermined interval in the circumferential direction on the outer peripheral surface. A plurality of permanent magnets 63a are arranged. And the magnet cover 63b is arrange | positioned so that the outer peripheral surface of the some permanent magnet 63a may be covered.

The output shaft 65 of the motor 31 is connected to the worm shaft 32a of the worm gear 32 through a coupling 67, for example, as shown in FIG.
The worm shaft 32 a is arranged coaxially with the output shaft 65 of the motor 31 and is rotatably supported by the housing 6 via two bearings 68. Of the two bearings 68 mounted in the housing 6, one of the bearings 68 on the motor 31 side is restricted by the retaining ring 69 from moving toward the motor 31 in the longitudinal direction of the shaft.

  For example, as shown in FIG. 4, the motor control device 70 according to the present embodiment includes an FET bridge 72 that uses a battery 71 as a DC power source and a control unit 73, and is provided in the ECU 50.

In the motor control device 70, the motor 31 is driven by the FET bridge 72 in response to a control command output from the control unit 73.
For example, as shown in FIG. 5, the FET bridge 72 includes a bridge circuit formed by bridge connection using a plurality of FETs (for example, MOSFETs: Metal Oxide Semiconductor Field Effect Transistors), and the bridge circuit performs pulse width modulation. It is driven by the (PWM) signal.
The bridge circuit includes, for example, a high-side and low-side U-phase transistor UH, UL, a high-side and low-side V-phase transistor VH, VL, and a high-side and low-side W-phase transistor WH, WL that are paired for each phase. Each transistor UH, VH, WH has a drain connected to the battery 71 (+ B) to form a high side arm, and each transistor UL, VL, WL has a source grounded and a low side arm For each phase, the sources of the high-side arm transistors UH, VH, WH and the low-side arm transistors UL, VL, WL are connected to each other.

  The FET bridge 72 is a gate signal (that is, a PWM signal) that is a switching command that is output from the control unit 73 and is input to the gates of the transistors UH, VH, WH, UL, VL, and WL when the motor 31 is driven, for example. ), The DC power supplied from the battery 71 is converted into the three-phase AC power by switching the on (off) / off (off) state of each transistor paired for each phase. By sequentially commutating the energization to the winding 64a, AC U-phase current Iu, V-phase current Iv and W-phase current Iw are energized to the stator winding 64a of each phase.

Note that the booster circuit 74 includes, for example, a capacitor and a charge pump circuit composed of a transistor, and instructs a boost signal of the booster circuit 74 to switch the on (conductive) / off (shutoff) state of each transistor. Signal) is input from the control unit 73.
The booster circuit 74 boosts the gate voltages of the transistors UH, VH, and WH constituting the high side arm of the FET bridge 72.
Further, stator windings 64a and 64a between the battery 71 and the FET bridge 72 and the booster circuit 74, and any two phases (for example, U phase and V phase) of the FET bridge 72 and the motor 31 are used. Is provided with a relay 75b that is opened and closed by a relay drive circuit 75a. A relay drive signal for controlling the opening / closing operation of the relay 75b is input from the control unit 73 to the relay drive circuit 75a.

  The control unit 73 performs feedback control of current on the dq coordinates that form the rotation orthogonal coordinates. For example, the control unit 73 outputs a signal output from the steering torque sensor 40 according to the steering torque input from the steering wheel 2 by the driver. The target d-axis current Idc and the target q-axis current Iqc are calculated from the torque command Tqc and the like set accordingly, and the three-phase output voltages Vu, Vv, Vw is calculated, and a PWM signal as a gate signal is input to the FET bridge 72 according to the phase output voltages Vu, Vv, and Vw, and the phase currents Iu and Iv that are actually supplied from the FET bridge 72 to the motor 31 are calculated. , Iw and the d-axis current Id and the q-axis current Iq obtained by converting the detected values on the dq coordinates, the target d-axis current Idc and the target q-axis current Iqc, Each deviation is controlled to be zero.

For example, when the motor 31 is started, the control unit 73 compares each phase output voltage Vu, Vv, Vw with a carrier signal such as a triangular wave in order to pass a sinusoidal current, and each transistor of the FET bridge 72. A gate signal (that is, a PWM signal) for driving on / off of UH, VH, WH, UL, VL, WL is generated. Then, the DC power supplied from the battery 71 is converted into the three-phase AC power by switching the on (off) / off (off) state of each pair of transistors in the FET bridge 72 for each of the three phases. By sequentially commutating energization to each stator winding 64a of the three-phase motor 31, alternating U phase current Iu, V phase current Iv and W phase current Iw are energized to each stator winding 64a.
Note that the duty ratio of the PWM signal for turning on / off the transistors UH, UL and VH, VL and WH, WL by pulse width modulation (PWM), that is, a map (data) of the on / off ratio is controlled in advance. Stored in the unit 73.

  For this reason, the control unit 73 has at least any two of the phase currents Iu, Iv, Iw supplied from the FET bridge 72 to the stator windings 64a of each phase of the motor 31 (for example, the U-phase currents Iu, A detection signal (for example, U-phase detection current Ius, W-phase detection current Iws, etc.) output from a current sensor 76 that detects a W-phase current Iw and the like, and a rotor 63 of a motor 31 used in, for example, coordinate conversion processing, etc. Of each phase voltage Vu, Vv required to estimate the rotation angle θm (that is, the rotation angle of the magnetic pole of the rotor 63 from the predetermined reference rotation position and the rotation position of the output shaft 65 of the motor 31). , Vw (for example, U-phase voltage Vu, V-phase voltage Vv, etc.) and a midpoint voltage (midpoint voltage) Vn to which a plurality of stator windings 64a of motor 31 are connected are detected. That the detection signal output from the voltage sensor 77 (e.g., U-phase voltage Vu, V-phase voltage Vv, the middle point voltage Vn, etc.) and are inputted.

  The control unit 73 includes, for example, a target current setting unit 81, a current deviation calculation unit 82, a current control unit 83, a non-interference controller 84, a voltage correction unit 85, a dq-3 phase conversion unit 86, The PWM signal generator 87, first and second phase voltage calculators 88a and 88b, a rotation angle estimator 89, a rotation speed calculator 90, and a three-phase-dq converter 91 are configured. .

  The target current setting unit 81 determines the phase currents Iu, Iv, Iw supplied from the FET bridge 72 to the motor 31 based on the torque command Tqc and the rotation speed ωm of the motor 31 output from the rotation speed calculation unit 90. A current command for designating is calculated, and the current command is output to the current deviation calculation unit 82 as a d-axis target current Idc and a q-axis target current Iqc on rotating orthogonal coordinates.

  The dq coordinate forming the rotation orthogonal coordinate is, for example, a field magnetic flux direction of the permanent magnet of the rotor 63 is a d axis (field axis), and a direction orthogonal to the d axis is a q axis (torque axis). It rotates in synchronization with the rotation phase of 63. As a result, the d-axis target current Idc and the q-axis target current Iqc, which are DC signals, are given as current commands for the AC signal supplied from the FET bridge 72 to each phase of the motor 31.

  The current deviation calculator 82 calculates a deviation ΔId of the d-axis target current Idc and the d-axis current Id, and calculates a deviation ΔIq of the q-axis target current Iqc and the q-axis current Iq. a q-axis current deviation calculating unit 82b.

  The current control unit 83 includes, for example, a PID (proportional integral derivative) operation to control and amplify the deviation ΔId to calculate the d-axis voltage command value ΔVd, and to control and amplify the deviation ΔIq to q-axis. And a q-axis current PI controller 83b for calculating the voltage command value Vq.

  The non-interference controller 84 interferes between the d axis and the q axis based on, for example, the d axis current Id and the q axis current Iq and the d axis inductance Ld and the q axis inductance Lq stored in advance. In order to cancel the matching velocity electromotive force components and control the d-axis and the q-axis independently, a d-axis compensation term Vdc and a q-axis compensation term Vqc that cancel each interference component with respect to the d-axis and the q-axis are calculated.

  The voltage correction unit 85 includes a d-axis voltage calculation unit 85a that uses a value obtained by subtracting the d-axis compensation term Vdc from the d-axis voltage command value ΔVd as a d-axis voltage command value Vd, and a q-axis voltage command value ΔVq to q A q-axis voltage calculation unit 85b that uses a value obtained by subtracting the axis compensation term Vqc as a q-axis voltage command value Vq.

  The dq-3 phase converter 86 converts the d-axis voltage command value Vd and the q-axis voltage command value Vq on the dq coordinate according to the rotation angle θm corresponding to the rotation position of the motor 31 output from the rotation angle estimator 89. Then, it is converted into a U-phase output voltage Vu, a V-phase output voltage Vv, and a W-phase output voltage Vw, which are voltage command values on the three-phase AC coordinates that are stationary coordinates.

  For example, when the motor 31 is driven, the PWM signal generation unit 87 compares each phase output voltage Vu, Vv, Vw with a carrier signal such as a triangular wave in order to pass a sinusoidal current, and the FET bridge 72 A gate signal (that is, a PWM signal) for driving each transistor UH, VH, WH, UL, VL, WL on / off is generated.

  Further, the PWM signal generation unit 87, for example, at the time of estimation of the rotation angle when the motor 31 is stopped, responds to a command signal Vs output from a rotation angle estimator 89 described later, and each transistor UH, VH of the FET bridge 72. , WH, UL, VL, WL, a predetermined gate signal composed of pulses for driving on / off is output. This predetermined gate signal is a PWM frequency (for example, 20 kHz) when the motor 31 is driven as a predetermined rectangular wave, for example, a frequency outside the audible frequency, between phase terminals of the motor 31 (for example, between the U phase and V phase terminals). Or the like) is applied to the FET bridge 72 to apply a rectangular wave AC voltage having a predetermined voltage value (for example, 12 V) having twice the frequency (for example, 40 kHz).

  The PWM signal generator 87 is a signal for instructing the boosting operation of the booster circuit 74 (for example, a gate signal for switching on / off (shut off) state of each transistor of the charge pump circuit included in the booster circuit 74. Etc.) is output.

  The first and second inter-phase voltage calculation units 88a and 88b include operation amplifiers, and the first inter-phase voltage calculation unit 88a uses the U-phase voltage based on the phase voltages Vu and Vv and the midpoint voltage Vn detected by the voltage sensors 77. Vun (= Vu−Vn) is calculated, and the second inter-phase voltage calculation unit 88b calculates the V-phase voltage Vvn (= Vv−Vn).

First, when the value of the U-phase voltage Vun or the V-phase voltage Vvn is smaller than a predetermined value, the rotation angle estimator 89 generates no induced voltage due to the rotation of the motor 31, and the motor 31 stops. Estimated.
The rotation angle estimator 89 estimates the rotation angle θm of the motor 31 from the interphase voltages Vun and Vvn output from the first and second interphase voltage calculation units 88a and 88b, and outputs this estimated value as the rotation angle θm. .
Specifically, the rotation angle estimator 89 sets the transistors UH, VH, WH, UL, VL, WL of the FET bridge 72, for example, in FIG. 6A when estimating the rotation angle when the motor 31 is stopped. As shown in FIG. 6B, for example, the high-side U-phase transistor UH and the low-side V-phase transistor VL are turned on and the other transistors VH, WH, UL, WL are turned off. The U-phase-V phase of the motor 31 is driven by repeatedly driving two states of turning on the high-side U-phase transistor UH and turning off the other transistors VH, WH, UL, VL, WL. A command signal instructing application of an alternating voltage of a predetermined rectangular wave (for example, 40 kHz and 12 V) is output between the terminals. And based on the ratio (interphase voltage ratio) Vun / Vvn between the U-phase voltage Vun and the V-phase voltage Vvn when a predetermined rectangular wave is applied between the U-phase and V-phase terminals of the motor 31, for example, is set in advance. The rotation angle θm is acquired by map search for the predetermined first map.
The first map is a map showing a predetermined correspondence between the phase voltage ratio Vun / Vvn and the rotation angle θm, for example, as shown in FIG. 7, for example, 0 ° in electrical angle (edeg). In the range of 180 ° to 180 °, two values θ1 and θ2 of the rotation angle θm correspond to an appropriate single value of the interphase voltage ratio Vun / Vvn. For example, when the phase voltage ratio Vun / Vvn = 1.5, the rotation angles θm = θ1 (= 100 °) and θ2 (= 150 °) correspond to each other.

Then, the rotation angle estimator 89 performs a map search for a predetermined second map set in advance, for example, based on the V-phase voltage Vvn when a predetermined rectangular wave is applied between the U-phase and V-phase terminals of the motor 31. Thus, one of the two values θ1 and θ2 of the rotation angle θm searched by the first map is selected.
This second map is a map showing a predetermined correspondence between, for example, the V-phase voltage Vvn and the rotation angle θm. For example, as shown in FIG. 8, the second map has an electrical angle (edeg) of 0 ° to 180 °. Within the range, two values φ1 and φ2 of the rotation angle θm correspond to an appropriate single value of the V-phase voltage Vvn.
In order to obtain an accurate rotation angle θm even if the battery voltage (that is, the power supply voltage of the FET bridge 72) fluctuates, the battery voltage Vb is detected, and the detected V-phase voltage Vvn is corrected using this value. The second map is searched using the corrected V-phase voltage Vvn to obtain two values φ1 and φ2 of the rotation angle θm. Therefore, a voltage follower circuit 71a having an operational amplifier is provided between the rotation angle estimator 89 and the battery 71 (+ B), for example, and the output of the voltage follower circuit 71a is a rotation angle. It is input to the estimator 89.
For example, if the V-phase voltage Vvn when the phase-to-phase voltage ratio Vun / Vvn = 1.5 is Vvn = 2.3, the rotation angle satisfying this is the rotation angle θm = φ1 (= 100 °), φ2 (= 175 °) corresponds.
At this time, a value θ1 (= 100 °) at which the search result of the first map is equal to the search result of the second map is selected as the estimated value of the rotation angle θm.

In the energization switching by the FET bridge 72, for example, when the U-phase and V-phase stator windings 64a are energized, the magnitudes of the currents flowing through the U-phase and V-phase stator windings 64a are equal. Therefore, the interphase voltage ratio Vun / Vvn is equal to the impedance ratio Zun / Zvn as shown in the following formula (2). Since each of the impedances Zun (= Run + j · ω · Lun) and Zvn (= Rvn + j · ω · Lvn) has a sufficiently high angular frequency ω (ω = 2πf, f = 40 kHz), each winding resistance Since Run and Rvn are sufficiently smaller than the reactances (ω · Lun) and (ω · Lvn), the interphase voltage ratio Vun / Vvn is substantially equal to the interphase inductance ratio Lun / Lvn.
The interphase inductances Lun, Lvn, and Lwn are caused by the saliency of the motor 31 and have a phase difference of 120 ° in electrical angle (edeg) as shown in FIG. 9, for example, according to the rotation angle θm. 1 cycle of this change is 180 ° in electrical angle (edeg).
In FIG. 9 showing the inductance change of the motor 31, for example, the average value of the interphase inductances Lun, Lvn, and Lwn is about 72 μH, and the interphase inductances Lun, Lvn, and Lwn are the minimum value (for example, 58 μH) and the maximum value. (For example, 86 μH).
Therefore, the rotation angle θm can be detected from the interphase voltage ratio Vun / Vvn approximated to the interphase inductance ratio Lun / Lvn.

For example, with respect to the winding resistance Run (for example, 10 mΩ) of the motor 31 and the angular frequency ω (for example, 2π × 40 × 10 ³ rad / sec), the winding resistance Run (= 10 × 10 ⁻³ Ω). << impedance ω · Lun (= 18100 × 10 ⁻³ Ω), and the winding resistance Run can be ignored as shown in the above formula (2).
Further, since the impedances Zun and Zvn are relatively high with respect to the voltage of the battery 71, the magnitude of the current flowing through the U-phase and V-phase stator windings 64a (for example, about 0.1 A) is relative. It is possible to prevent unnecessary torque from being generated in the motor 31 due to energization of a rectangular wave applied between the phase terminals of the motor 31 when the rotation angle is estimated.

  Further, the rotation angle estimator 89, for example, in a driving state in which the rotational speed ωm of the motor 31 is equal to or higher than a predetermined speed, the U-phase voltage Vun or the V-phase voltage Vvn is a predetermined value due to an induced voltage caused by the rotation of the motor 31 In this case, it is estimated that the motor 31 is rotating, and the rotation angle θm is estimated based on the induced voltage that varies according to the magnetic pole position of the rotor 63. Detailed description is omitted.

  At this time, the rotation speed calculation unit 90 calculates the rotation speed ωm (= dθm / dt) from the rotation angle θm output from the rotation angle estimator 89.

  The three-phase-dq conversion unit 91 outputs the detection signals of the phase currents Iu and Iw detected by the current sensors 76 and 76, that is, the U-phase detection current Ius and the W-phase detection current Iws, and the rotation angle estimator 89. Based on the rotation angle θm, the d-axis current Id and the q-axis current Iq on the rotation coordinate based on the rotation phase of the motor 31, that is, the dq coordinate, are calculated.

The electric steering device 1 according to this embodiment has the above-described configuration. Next, the operation of the electric steering device 1, particularly, the process of estimating the rotation angle θm of the motor 31 in a stopped state will be described.
First, for example, in step S01 shown in FIG. 10, it is determined whether or not the ignition switch of the vehicle is turned on (IG ON).
If this determination is “YES”, the flow proceeds to step S 02.
On the other hand, when the determination result is “NO”, the process does not proceed.

In step S02, it is determined whether or not the motor 31 is in a stopped state.
For example, as described above, when the value of the U-phase voltage Vun or the V-phase voltage Vvn is smaller than a predetermined value, an induced voltage due to the rotation of the motor 31 is not generated, and the motor 31 is stopped. Is determined.
If this determination is “NO”, the flow proceeds to the end, and the series of processing is ended.
On the other hand, if the determination is “YES”, the flow proceeds to step S03.
In step S03, application of a predetermined rectangular wave AC voltage is started between the phase terminals of the motor 31 (for example, between the U-phase and V-phase terminals).
In step S04, the U-phase voltage Vun (= Vu−Vn) and the V-phase voltage Vvn (= Vv−) calculated based on the phase voltages Vu and Vv and the midpoint voltage Vn detected by the voltage sensors 77. Vn) is obtained.

In step S05, the interphase voltage ratio Vun / Vvn is calculated.
In step S06, two values θ1 and θ2 of the rotation angle θm are acquired by map search for the first map based on the interphase voltage ratio Vun / Vvn.
In step S07, two values φ1 and φ2 of the rotation angle θm are acquired by map search for the second map based on the V-phase voltage Vvn.
In step S08, a value equivalent to one of the two values φ1 and φ2 is set as the estimated value of the rotation angle θm from the two values θ1 and θ2.
In step S09, the application of the predetermined rectangular wave AC voltage is terminated, and the series of processes is terminated.

As described above, according to the brushless motor control apparatus 70 according to the present embodiment, when estimating the rotation angle when the motor 31 is stopped, each of the motor 31 corresponding to changes in the interphase inductances Lun, Lvn, and Lwn. Since the rotation angle θm is estimated on the basis of the change in the ratio between the interphase voltages Vun and Vvn, the change can be detected larger than in the case of directly estimating from the interphase voltage or the line voltage, and the estimation accuracy is improved. For example, the estimation accuracy of the rotation angle θm can be improved as compared with the case where the rotation angle θm is estimated according to the current change corresponding to the change in the interphase inductances Lun, Lvn, and Lwn of the motor 31. In addition, since the rotation angle θm is estimated based on the interphase voltage ratio Vun / Vvn, the error between the interphase voltages Vun and Vvn increases due to, for example, unstable output voltage of the battery 71. However, in the interphase voltage ratio Vun / Vvn, errors in the interphase voltages Vun and Vvn can be offset, and the estimation accuracy of the rotation angle θm can be further improved.
Furthermore, since the present invention does not estimate the rotation angle θm using the current response unlike the prior art, it is outside the audible frequency between the phase terminals of the motor 31 (for example, between the U-phase and V-phase terminals). Even when a voltage of a predetermined rectangular wave having a frequency of 1 is applied, there is no reduction in resolution as shown in FIG. 14 described above, and the rotation angle can be accurately estimated, thereby ensuring the desired quietness. Can do.

  In addition, according to the electric steering device 1 according to the present embodiment, it is possible to simplify the device configuration and reduce the size of the device without the need for providing a rotation angle sensor such as a resolver, and to improve the vehicle mountability. In addition, the overhang of the motor 31 with respect to the housing 6 constituting the steering gear box (for example, the distance to the pinion shaft 11) can be reduced, and the housing 6 is vibrated by vibration generated when the motor 31 is driven. Moment can be reduced, and vibration caused by driving of the motor 31 can be reduced. Furthermore, it is possible to improve the estimation accuracy of the rotation angle while reducing electromagnetic noise at the time of estimating the rotation angle of the motor 31, and to prevent the driver from feeling uncomfortable with the steering feeling.

In the above-described embodiment, the rotation angle estimator 89 estimates the rotation angle θm based on the interphase voltage ratio Vun / Vvn. However, the present invention is not limited to this. For example, the rotation angle estimator 89 rotates based on the line voltage ratio Vuv / Vwu. The angle θm may be estimated.
In the brushless motor control device 70 according to this modification, for example, as shown in FIG. 11, the rotation angle estimator 89 receives detection signals output from the voltage sensors 77 that detect the phase voltages Vu, Vv, and Vw. Have been entered.

The rotation angle estimator 89 calculates the line voltages Vuv (= Vu−Vv) and Vwu (= Vw−Vu), and the line voltage ratio Vuv / Vwu is substantially equal to the line inductance ratio Luv / Lwu. By using this, the rotation angle θm is obtained by a map search for a third map showing a predetermined correspondence between the line voltage ratio Vuv / Vwu and the rotation angle θm.
This third map is a map showing a predetermined correspondence between the line voltage ratio Vuv / Vwu and the rotation angle θm, for example, within a range of 0 ° to 180 ° in electrical angle (edeg). The two values α1 and α2 of the rotation angle θm correspond to an appropriate single value of the line voltage ratio Vuv / Vwu.
Then, the rotation angle estimator 89 uses the line voltage Vuv or the line voltage Vwu and the rotation to select one of the two values α1 and α2 of the rotation angle θm searched by the third map. The rotation angle θm is acquired by map search for the fourth map showing a predetermined correspondence with the angle θm.
The fourth map is a map showing a predetermined correspondence between the line voltage Vwu and the rotation angle θm, and the line voltage Vwu is within a range of 0 ° to 180 ° in electrical angle (edeg). Two values β1 and β2 of the rotation angle θm correspond to an appropriate single value.
Of the two values α1 and α2 of the rotation angle θm retrieved by the third map, a value equivalent to one of the two values β1 and β2 of the rotation angle θm corresponding to the line voltage Vwu is set as the rotation angle. Select as the estimated value of θm.
In order to obtain an accurate rotation angle θm even if the battery voltage (that is, the power supply voltage of the FET bridge 72) fluctuates, the battery voltage Vb is detected, and the detected line voltage Vwu is corrected using this value. The fourth map is searched using the corrected line voltage Vwu to obtain two values β1 and β2 of the rotation angle θm. Therefore, a voltage follower circuit 71a having an operational amplifier is provided between the rotation angle estimator 89 and the battery 71 (+ B), for example, and the output of the voltage follower circuit 71a is the rotation angle. It is input to the estimator 89.

  Note that the line voltages Vuv (= Vu−Vv), Vvw (= Vv−Vw), and Vwu (= Vw−Vu) according to this modification are as described in the following formula (3), for example. The magnitude is multiplied by √3 with respect to each interphase voltage Vun, Vvn, Vwn in the form, and the phase is delayed by (π / 6).

  The present embodiment relates to a brushless motor having a permanent magnet 63a in the rotor 31, but the present invention uses the fact that the inductance changes according to the rotation angle θm of the rotor 31 to estimate the rotation angle at the time of stopping. In order to solve the problem, the present invention is not limited to a brushless motor, but can be applied to a synchronous reluctance motor or an SR motor whose inductance changes in accordance with the rotation angle θm of the rotor.

It is a lineblock diagram of the electric steering device concerning one embodiment of the present invention. It is a lineblock diagram of the steering auxiliary mechanism of the electric steering device concerning one embodiment of the present invention. It is the sectional view on the AA line shown in FIG. It is a block diagram of the control apparatus of the brushless motor which concerns on one Embodiment of this invention. It is a block diagram of FET bridge | bridging shown in FIG. FIG. 5 is a diagram illustrating an on (conduction) / off (cutoff) state of each transistor of the FET bridge illustrated in FIG. 4. It is a graph which shows the correspondence of the voltage ratio Vun / Vvn and rotation angle (theta) m which concern on one Embodiment of this invention. It is a graph which shows the correspondence of the interphase voltage Vvn and rotation angle (theta) m which concern on one Embodiment of this invention. It is a graph which shows the correspondence of each phase inductance Lun, Lvn, Lwn and rotation angle (theta) m which concerns on one Embodiment of this invention. It is a flowchart which shows the operation | movement of the electric steering apparatus which concerns on one Embodiment of this invention, especially the process which estimates rotation angle (theta) m of the motor of a stop state. It is a block diagram of the control apparatus of the brushless motor which concerns on the modification of one Embodiment of this invention. It is an equivalent circuit of the brushless motor which concerns on an example of a prior art. It is a graph which shows the line inductance fluctuation | variation of the brushless motor which concerns on an example of a prior art. It is a graph which shows the electric current waveform at the time of applying a predetermined rectangular wave to the brushless motor which concerns on an example of a prior art. It is a graph which shows the input-output characteristic of the current sensor which concerns on an example of a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Electric steering apparatus 31 Motor 40 Steering torque sensor (steering torque detection means)
63 Rotor 64 Stator 64a Stator winding 70 Brushless motor control device 72 FET bridge (energization switching means)
73 Control unit (steering control means)
77 Voltage sensor (voltage detection means)
87 PWM signal generator (energization switching means)
88a First interphase voltage calculation section (voltage detection means)
88b Second interphase voltage calculation section (voltage detection means)
89 Rotation angle estimator (estimator)
Step S03 Voltage applying means Step S04 to Step S09 Estimating means

Claims (5)

A brushless motor control device comprising: a brushless motor including a rotor and a stator having a plurality of phases of stator windings; and energization switching means for switching and controlling energization of the stator windings of each phase,
Voltage detecting means for detecting a phase voltage which is the difference between the phase voltage and the midpoint voltage of said plurality of phases,
Voltage applying means for applying a predetermined AC voltage between predetermined lines of the plurality of phases;
In a state where the predetermined AC voltage between predetermined line among the plurality of phases by the voltage applying means is applied, a line predetermined AC voltage is applied among the plurality of the inter-phase voltage detected by said voltage detecting means A brushless motor control device comprising: an estimation unit configured to estimate a rotation angle of the rotor based on a phase voltage ratio between phases included therebetween. 2. The brushless motor control device according to claim 1, wherein the estimation unit estimates a rotation angle of the rotor based on a ratio of the interphase voltages and an interphase voltage value to which the predetermined AC voltage is applied. The brushless motor control device according to claim 1 or 2 , wherein the frequency of the predetermined AC voltage is a frequency other than an audible frequency. The brushless motor control device according to any one of claims 1 to 3, wherein the estimation means sets the ratio of the interphase voltage equal to the ratio of the interphase inductance. The brushless motor control device according to any one of claims 1 to 4 ,
Steering torque detection means for detecting steering torque;
The brushless motor is driven and controlled according to the steering torque detected by the steering torque detection means and the rotation angle estimated by the estimation means, and auxiliary torque for assisting the steering torque is supplied from the brushless motor. An electric steering apparatus comprising: a steering control means for generating the electric steering apparatus.

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