JP5412360B2 - Electric power steering device - Google Patents

Description

  The present invention relates to an electric power steering apparatus.

2. Description of the Related Art In recent years, there has been proposed a technique for accurately detecting a drive current of an electric motor in an electric power steering apparatus that assists a driver's steering force with the power of an electric motor provided in a vehicle steering system.
For example, the electric power steering device described in Patent Document 1 is configured as follows. That is, a target current calculation means for inputting a steering torque and a traveling speed to command a supply current to a brushless motor for assisting a steering force, a current detection means for detecting a motor current, and a command value of the target current calculation means A drive control means for setting the supply voltage of the brushless motor from the deviation from the detection value of the current detection means, and a learning instruction for a correction value for the offset value of the current detected by the current detection means, determined by the command value of the target current calculation means Offset correction value learning determining means, reference voltage generating means for outputting a reference voltage in response to an instruction from the offset correction value learning determining means, and learning and storing an offset correction value from the motor current when the reference voltage is applied to offset the current detecting means Offset correction means for correcting the value.

JP 2002-29432 A

  In order to correct (learn) the offset correction value, it is desirable to correct the offset correction value while driving the electric motor for steering assistance, instead of stopping the driving of the electric motor for steering wheel steering assistance. .

  For this purpose, the present invention provides an electric motor that applies a steering assist force to a steering wheel, target current calculation means that calculates a target current to be supplied to the electric motor, and an actual current that is actually supplied to the electric motor. Output means for outputting a value corresponding to the output current, an actual current calculation means for calculating the actual current by correcting an offset of the output value from the output means using an offset correction value stored in advance, and the target current calculation means Voltage calculating means for calculating a target voltage applied to the electric motor based on the target current calculated by the actual current calculating means, and the target voltage calculated by the voltage calculating means to the electric motor. A motor driving means for applying and driving the electric motor; and a correction value correcting means for correcting the offset correction value based on the target voltage calculated by the voltage calculating means. When, an electric power steering apparatus comprising: a.

Here, it is preferable that the correction value correction unit corrects the offset correction value based on the target voltage calculated by the voltage calculation unit and the target current calculated by the target current calculation unit.
The electric motor is a three-phase brushless motor, the target current calculating means calculates a d-axis target current and a q-axis target current in a dq coordinate system, and the correction value correcting means is the voltage calculation. Based on the target voltage of the three-phase AC coordinate system calculated by the means, and the target current obtained by converting the d-axis target current and the q-axis target current calculated by the target current calculation means into a current of the three-phase AC coordinate system. It is preferable to correct the offset correction value.
The correction value correction means is a value obtained by multiplying the ratio of the offset to the amplitude of the target voltage in the three-phase AC coordinate system calculated by the voltage calculation means by the amplitude of the target current converted into the current in the three-phase AC coordinate system. It is preferable to correct the offset correction value by adding to the offset correction value stored in advance.

The electric motor is a three-phase brushless motor, and the correction value correction means corrects the offset correction value based on the target voltage calculated by the voltage calculation means and the interphase resistance of the electric motor. Is preferred.
Further, the correction value correction means adds a value obtained by dividing the target voltage of the three-phase AC coordinate system calculated by the voltage calculation means by the interphase resistance of the electric motor to the offset correction value stored in advance. Thus, it is preferable to correct the offset correction value.

  According to the present invention, the offset correction value can be corrected while driving the electric motor to assist the steering wheel. As a result, the steering feeling can be improved, and compatibility with an additional control function using a yaw rate sensor or a steering angle sensor can be achieved.

It is a figure showing the schematic structure of the electric power steering device concerning an embodiment. It is a schematic block diagram of the control apparatus of an electric power steering apparatus. It is a schematic block diagram of a target current calculation part. It is a schematic block diagram of a control part. It is a schematic block diagram of the offset correction part which concerns on 1st Embodiment. (A) is a figure which illustrates the electric current which actually flowed to three phases of an electric motor. (B) is a figure which shows the electric current calculated in the offset correction | amendment part in the state which the electric current which flowed like (a) is detected in the motor current detection part, and the offset error has generate | occur | produced. (C) is a figure which shows the electric current which the three-phase biaxial conversion part converted into the d-axis detection current and the q-axis detection current from the current calculated by the offset correction part as shown in (b). (A) is a figure which illustrates the electric current which actually flowed to three phases of an electric motor. (B) is a figure which shows the electric current calculated in the offset correction | amendment part in the state which the electric current which flowed like (a) is detected in the motor current detection part, and the offset error has generate | occur | produced. It is a figure which illustrates the d-axis target voltage and q-axis target voltage which were output from the d-axis PI control part and the q-axis PI control part. It is a figure which illustrates the U-phase target voltage and W-phase target voltage which were converted in the biaxial 3 phase conversion part. It is a flowchart which shows the procedure of the offset correction value calculation process which a correction current calculation part performs. It is a figure which shows schematic structure of the offset correction part which concerns on 2nd Embodiment.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
FIG. 1 is a diagram illustrating a schematic configuration of an electric power steering apparatus 100 according to an embodiment.
An electric power steering device 100 (hereinafter, also simply referred to as “steering device 100”) is a steering device for arbitrarily changing the traveling direction of a vehicle. In the present embodiment, the configuration applied to an automobile is used. Illustrated.

  The steering device 100 includes a wheel-like steering wheel (handle) 101 operated by a driver, and a steering shaft 102 provided integrally with the steering wheel 101. The steering device 100 includes an upper connecting shaft 103 connected to the steering shaft 102 via a universal joint 103a, and a lower connecting shaft 108 connected to the upper connecting shaft 103 via a universal joint 103b. . The lower connecting shaft 108 rotates in conjunction with the rotation of the steering wheel 101.

  Steering device 100 includes tie rods 104 connected to left and right front wheels 150 as rolling wheels, and rack shaft 105 connected to tie rods 104. Further, the steering device 100 includes a pinion 106 a that constitutes a rack and pinion mechanism together with rack teeth 105 a formed on the rack shaft 105. The pinion 106 a is formed at the lower end portion of the pinion shaft 106.

  The steering device 100 also has a steering gear box 107 that houses the pinion shaft 106. The pinion shaft 106 is connected to the lower connection shaft 108 via a torsion bar in a steering gear box 107. In the steering gear box 107, an example of a steering torque detecting means for detecting the steering torque of the steering wheel 101 based on the relative angle between the lower connecting shaft 108 and the pinion shaft 106, in other words, based on the torsion amount of the torsion bar. A torque sensor 109 is provided.

The steering device 100 includes an electric motor 110 supported by the steering gear box 107, and a speed reducing mechanism 111 that decelerates the driving force of the electric motor 110 and transmits it to the pinion shaft 106. Electric motor 110 according to the present embodiment is a three-phase brushless motor.
The steering device 100 includes a control device 10 that controls the operation of the electric motor 110. The control device 10 receives the output value of the torque sensor 109 and the output value of the vehicle speed sensor 170 that detects the vehicle speed Vc, which is the moving speed of the automobile.

  In the steering device 100 configured as described above, the steering torque T applied to the steering wheel 101 is detected by the torque sensor 109, and the control device 10 drives and controls the electric motor 110 in accordance with the detected torque. Torque generated by the motor 110 is transmitted to the pinion shaft 106. Thereby, the torque generated by the electric motor 110 assists the driver's steering force applied to the steering wheel 101.

Next, the control device 10 will be described.
The control device 10 includes a CPU 11 that performs arithmetic processing when controlling the electric motor 110, a ROM 12 that stores programs executed by the CPU 11, various data, and the like, and a RAM 13 that is used as a work memory for the CPU 11, and the like. An EEPROM (Electrically Erasable & Programmable Read Only Memory) 14 in which an offset value, which will be described later, is stored.
In the control device 10, the torque signal Td (see FIG. 2) obtained by converting the steering torque T detected by the torque sensor 109 described above into an output signal and the vehicle speed Vc detected by the vehicle speed sensor 170 are output signals. The converted vehicle speed signal v and the like are input.
FIG. 2 is a schematic configuration diagram of the control device 10 of the steering device 100.
The control device 10 calculates a target auxiliary torque based on the torque signal Td, and calculates a target current as an example of a target current calculation unit that calculates a target current necessary for the electric motor 110 to supply the target auxiliary torque. And a control unit 30 that performs feedback control and the like based on the target current calculated by the target current calculation unit 20.

Next, the target current calculation unit 20 will be described in detail.
FIG. 3 is a schematic configuration diagram of the target current calculation unit 20.
The target current calculation unit 20 includes a base current calculation unit 21 that calculates a base current that serves as a reference for setting the target current, an inertia compensation current calculation unit 22 that calculates a current for canceling the inertia moment of the electric motor 110, and And a damper compensation current calculation unit 23 for calculating a current for limiting the rotation of the motor. The target current calculation unit 20 includes a target current determination unit 25 that determines a target current based on outputs from the base current calculation unit 21, the inertia compensation current calculation unit 22, the damper compensation current calculation unit 23, and the like. Further, the target current calculation unit 20 includes a phase compensation unit 26 that performs phase compensation of the torque signal Td.

The target current calculation unit 20 converts the rotation speed Nm of the electric motor 110 calculated based on the torque signal Td, the vehicle speed signal v, and the angular velocity calculated by the motor angular velocity calculation unit 37 described later into an output signal. The rotation speed signal Nms is input.
Since signals from the vehicle speed sensor 170, the torque sensor 109, and the like are input to the control device 10 as analog signals, the analog signals are converted into digital signals by an A / D conversion unit (not shown), and the target current calculation unit 20 Have taken in.

  The base current calculation unit 21 calculates a base current based on the torque signal Ts obtained by phase compensation of the torque signal Td by the phase compensation unit 26 and the vehicle speed signal v from the vehicle speed sensor 170, and information on the base current is obtained. A base current signal Imb including the same is output. Note that the base current calculation unit 21, for example, creates a torque signal detected on a map indicating the correspondence between the torque signal Ts, the vehicle speed signal v, and the base current, which is previously created based on an empirical rule and stored in the ROM 12. The base current is calculated by substituting Ts and the vehicle speed signal v.

  The inertia compensation current calculation unit 22 calculates an inertia compensation current for canceling out the moment of inertia of the electric motor 110 and the system based on the torque signal Td and the vehicle speed signal v, and generates an inertia compensation current signal Is including information on this current. Output. Note that the inertia compensation current calculation unit 22 has been detected on a map indicating the correspondence between the torque signal Td, the vehicle speed signal v, and the inertia compensation current, which has been previously created based on empirical rules and stored in the ROM 12, for example. An inertia compensation current is calculated by substituting the torque signal Td and the vehicle speed signal v.

  The damper compensation current calculation unit 23 calculates a damper compensation current for limiting the rotation of the electric motor 110 based on the torque signal Td, the vehicle speed signal v, and the rotation speed signal Nms of the electric motor 110, and information on this current A damper compensation current signal Id including is output. The damper compensation current calculation unit 23 indicates the correspondence between the torque signal Td, the vehicle speed signal v, the rotation speed signal Nms, and the damper compensation current, which are previously created based on empirical rules and stored in the ROM 12, for example. A damper compensation current is calculated by substituting the detected torque signal Td, vehicle speed signal v, and rotational speed signal Nms into the map.

The target current determination unit 25 includes a base current signal Imb output from the base current calculation unit 21, an inertia compensation current signal Is output from the inertia compensation current calculation unit 22, and a damper compensation current output from the damper compensation current calculation unit 23. A q-axis target current calculation unit 251 that calculates a q-axis target current Iqc in the dq coordinate system based on the signal Id is provided. The target current determination unit 25 calculates a d-axis target current Idc in the dq coordinate system based on the q-axis target current Iqc calculated by the q-axis target current calculation unit 251 and the angular velocity of the electric motor 110. A magnetic current calculation unit 252 is included. For example, the q-axis target current calculation unit 251 previously creates a compensation current obtained by adding the inertia compensation current to the base current and subtracting the damper compensation current based on an empirical rule, and stores the compensation current in the ROM 12. The q-axis target current Iqc is calculated by substituting it into a map indicating the correspondence between the compensation current and the q-axis target current Iqc.
The target current determination unit 25 then includes a signal including information on the q-axis target current Iqc calculated by the q-axis target current calculation unit 251 and a signal including information on the d-axis target current Iqc calculated by the field current calculation unit 252. Are output to the control unit 30.

Next, the control unit 30 will be described in detail.
FIG. 4 is a schematic configuration diagram of the control unit 30.
The control unit 30 includes a motor drive control unit 31 that controls the operation of the electric motor 110 and a motor drive unit 32 as an example of a motor drive unit that drives the electric motor 110. The control unit 30 also includes a motor current detection unit 33 that detects an actual current that actually flows through the electric motor 110, an offset correction unit 34 that corrects an offset of the current detected by the motor current detection unit 33, and an offset correction. A three-phase two-axis conversion unit 35 that converts the three-phase alternating current corrected by the unit 34 into a current in the dq coordinate system. The control unit 30 also calculates a rotation angle of the electric motor 110 (hereinafter also referred to as “motor angle θ”), and a motor angle θ calculated by the motor angle calculation unit 36. And a motor angular velocity calculation unit 37 that calculates an angular velocity of the electric motor 110 (hereinafter also referred to as “motor angular velocity”).

The motor drive control unit 31, the motor drive unit 32, and the offset correction unit 34 will be described in detail later.
The motor current detection unit 33 detects a U phase actual current that is a current that actually flows in the U phase of the electric motor 110, and a W current that actually flows in the W phase of the electric motor 110. A W-phase current detection unit for detecting a phase actual current. The U-phase current detection unit and the W-phase current detection unit detect the motor current flowing in each phase as a voltage signal from voltages generated at both ends of a so-called shunt resistor connected to the U-phase and W-phase of the electric motor 110, respectively. This is a circuit that amplifies and outputs a detected voltage signal with a known operational amplifier. As described above, the motor current detection unit 33 is an example of an output unit that outputs a value corresponding to the actual current actually supplied to the electric motor 110.

  The three-phase two-axis conversion unit 35 includes a U-phase correction current Iua ′ and a W-phase obtained by correcting the U-phase detection current Iua and the W-phase detection current Iwa detected by the motor current detection unit 33 by the offset correction unit 34. The correction current Iwa ′ and the motor angle θ calculated by the motor angle calculation unit 36 are input. Then, the three-phase two-axis conversion unit 35 converts the U-phase correction current Iua ′ and the W-phase correction current Iwa ′ into d-axis detection currents that are values in the dq coordinate system according to the following formulas (1) and (2). It converts to Ida and q-axis detection current Iqa, and outputs the converted d-axis detection current Ida and q-axis detection current Iqa. The dq coordinate system is a rotation orthogonal coordinate system including a d axis and a q axis that rotate in synchronization with the rotor (permanent magnet) of the electric motor 110, and the d axis is along the direction of the magnetic flux formed by the rotor. The q-axis is an axis along the direction of the torque generated by the motor M.

  The motor angle calculation unit 36 calculates the motor angle θ based on the output signal of the resolver provided in the electric motor 110. This motor angle θ is an angle of the rotor (field) with respect to the position of the U-phase armature winding of the electric motor 110. The motor angular velocity calculator 37 calculates the motor angular velocity based on the motor angle θ calculated by the motor angle calculator 36.

Next, the motor drive control unit 31 and the motor drive unit 32 will be described in detail.
The motor drive control unit 31 subtracts the d-axis detection current Ida calculated by the three-phase two-axis conversion unit 35 from the d-axis target current Idc calculated by the target current determination unit 25 of the target current calculation unit 20. a d-axis subtractor 41d, and a q-axis subtractor 41q that subtracts the q-axis detected current Iqa calculated by the three-phase two-axis converter 35 from the q-axis target current Iqc calculated by the target current determiner 25. have.

  Further, the motor drive control unit 31 performs PI (proportional integration) so that the d-axis target current Idc and the d-axis detection current Ida coincide with each other based on the deviation (Idc−Ida) calculated by the d-axis subtraction unit 41d. The q-axis target current Iqc and the q-axis detection current Iqa are controlled based on the deviation (Iqc−Iqa) calculated by the d-axis PI control unit 42d that calculates the d-axis target voltage Vdc and the q-axis subtraction unit 41q. And q-axis PI control unit 42q for performing q (proportional integration) control so as to match q and calculating q-axis target voltage Vqc.

  Further, the motor drive control unit 31 uses the d-axis target voltage Vdc and the q-axis target voltage Vqc calculated by the d-axis PI control unit 42d and the q-axis PI control unit 42q as the U-phase target voltage in the three-phase AC coordinate system. A V-axis target voltage Vvc from the U-phase target voltage Vuc and the W-phase target voltage Vwc converted by the two-axis three-phase converter 51 that converts the Vuc and the W-phase target voltage Vwc. And a V-phase target voltage calculation unit 52 for calculating. The biaxial three-phase converter 51 converts the U-phase target voltage Vuc and the W-phase target voltage Vwc according to the following formulas (3) and (4). V-phase target voltage calculation unit 52 calculates V-phase target voltage Vvc by subtracting U-phase target voltage Vuc and W-phase target voltage Vwc from zero (Vvc = − (Vuc + Vwc)).

このように、ｄ軸ＰＩ制御部４２ｄ、ｑ軸ＰＩ制御部４２ｑ、２軸３相変換部５１およびＶ相目標電圧算出部５２が、目標電流算出部２０が算出した目標電流とオフセット補正部３４が算出した実電流とに基づいて電動モータ１１０に印加する目標電圧を算出する電圧算出手段として機能する。

In this way, the d-axis PI control unit 42d, the q-axis PI control unit 42q, the 2-axis three-phase conversion unit 51, and the V-phase target voltage calculation unit 52 have the target current and offset correction unit 34 calculated by the target current calculation unit 20. Functions as a voltage calculation means for calculating a target voltage to be applied to the electric motor 110 based on the calculated actual current.

  The motor drive control unit 31 is further electrically driven based on the U-phase target voltage Vuc, the V-phase target voltage Vvc, and the W-phase target voltage Vwc calculated by the biaxial three-phase conversion unit 51 and the V-phase target voltage calculation unit 52. A PWM signal generation unit 60 that generates a PWM (pulse width modulation) signal for PWM driving the motor 110 and outputs the generated PWM signal is provided.

Next, the motor drive unit 32 will be described in detail.
The motor drive unit 32 is a so-called inverter, and includes, for example, six independent transistors (FETs) as switching elements. Three of the six transistors are a positive line of a power source, an electric coil of each phase, The other three transistors are connected to the electric coil of each phase and the negative side (ground) line of the power source. Then, the driving of the electric motor 110 is controlled by driving the gates of two transistors selected from the six and switching the transistors.

<First Embodiment>
Next, the offset correction unit 34 will be described in detail.
FIG. 5 is a schematic configuration diagram of the offset correction unit 34 according to the first embodiment.
As shown in FIG. 5, the offset correction unit 34 uses an offset correction value (hereinafter referred to as an offset correction value for the U-phase detection current) used to correct the offset of the output value from the motor current detection unit 33 (see FIG. 4). Iuo, and the offset correction value for the W-phase detection current is Iwo.) A correction value correction unit 341 as an example of a correction value correction unit for correcting the correction, and a correction value storage unit that stores the offset correction values Iuo and Iwo 342. The correction value correction unit 341 will be described in detail later. The correction value storage unit 342 is configured using a partial area of the EEPROM 14 described above. In the case where the control device 10 has a flash memory, a part of the flash memory may be used.

  Further, the offset correction unit 34 corrects the offset value of the output value from the motor current detection unit 33 using the offset correction values Iuo and Iwo stored in the correction value storage unit 342, thereby correcting the U-phase correction current Iua ′, A correction current calculation unit 343 that calculates the W-phase correction current Iwa ′ is provided. The correction current calculation unit 343 multiplies the value obtained by subtracting the offset correction values Iuo and Iwo from the output value from the motor current detection unit 33 by a predetermined coefficient, thereby obtaining a U-phase correction current Iua ′ and a W-phase correction current. Iwa ′ is calculated. As described above, the correction current calculation unit 343 is an example of an actual current calculation unit that calculates the actual current by correcting the offset of the output value from the motor current detection unit 33 using the offset correction values Iuo and Iwo stored in advance. is there.

The U-phase correction current Iua ′ and the W-phase correction current Iwa ′ calculated by the offset correction unit 34 are values obtained by detecting the U-phase actual current and the W-phase actual current that actually flow in the U-phase and the W-phase of the electric motor 110. It becomes.
However, if the offset correction values Iuo and Iwo used by the correction current calculation unit 343 deviate from appropriate values due to the temperature characteristics of the motor current detection unit 33, the U-phase correction current Iua ′ calculated by the offset correction unit 34 is used. , A so-called offset error occurs between the W-phase correction current Iwa ′ and the U-phase actual current and the W-phase actual current, which may cause a difference between the target current and the actual current of the electric motor 110. Since electric motor 110 according to the present embodiment is a three-phase brushless motor, the difference between the target current and the actual current is a ripple-like difference.

  FIG. 6A is a diagram illustrating current actually flowing in the three phases of the electric motor 110. FIG. 6B shows the current calculated by the offset correction unit 34 in a state where the current flowing as shown in FIG. 6A is detected by the motor current detection unit 33 and an offset error has occurred. FIG. 6C shows the current obtained by converting the current calculated by the offset correction unit 34 into the d-axis detection current Ida and the q-axis detection current Iqa as shown in FIG. FIG. Note that the V-phase current in FIG. 6B shows the same curve as in FIG. 6A for reference.

  Actually, even if a current as shown in FIG. 6A flows in each phase of the electric motor 110, the U-phase correction current Iua ′ and the W-phase correction calculated by the offset correction unit 34 due to the offset error. As shown in FIG. 6B, the current Iwa ′ is shifted from the U-phase actual current and the W-phase actual current shown in FIG. Further, a difference occurs between the d-axis detection current Ida and the q-axis detection current Iqa output from the three-phase two-axis conversion unit 35 and the actual d-axis current and q-axis current of the electric motor 110, and FIG. As shown in c), a primary nipple of the motor electrical angle is generated.

FIG. 7A is a diagram illustrating current actually flowing through the three phases of the electric motor 110. FIG. 7B shows the current calculated by the offset correction unit 34 in a state where the current flowing as shown in FIG. 7A is detected by the motor current detection unit 33 and an offset error has occurred. FIG. Note that the V-phase current in FIG. 7B shows the same curve as in FIG. 7A for reference.
Actually, even if a current having an offset as shown in FIG. 7A flows in each phase of the electric motor 110 due to the influence of the offset error, the offset correction unit 34 calculates the offset error. The U-phase correction current Iua ′ and the W-phase correction current Iwa ′ have values with no offset as shown in FIG. 7B.

The d-axis detection current Ida and the q-axis detection current Iqa output from the three-phase two-axis conversion unit 35 are subjected to PI control by the d-axis PI control unit 42d and the q-axis PI control unit 42q, respectively, and the d-axis target The voltage Vdc and the q-axis target voltage Vqc are output.
FIG. 8 is a diagram illustrating the d-axis target voltage Vdc and the q-axis target voltage Vqc output from the d-axis PI control unit 42d and the q-axis PI control unit 42q. FIG. 8A shows the case where no offset error occurs in the value calculated by the offset correction unit 34, that is, the U-phase correction current Iua ′ and the W-phase correction current Iwa ′ calculated by the offset correction unit 34. The d-axis target voltage Vdc and the q-axis target voltage Vqc output from the d-axis PI control unit 42d and the q-axis PI control unit 42q in the case of the values shown in FIG. FIG. 8B shows the case where an offset error has occurred in the value calculated by the offset correction unit 34, that is, the U-phase correction current Iua ′ and the W-phase correction current Iwa ′ calculated by the offset correction unit 34. The d-axis target voltage Vdc and the q-axis target voltage Vqc output from the d-axis PI control unit 42d and the q-axis PI control unit 42q in the case of the values shown in FIG.
As seen from the output voltages from the d-axis PI control unit 42d and the q-axis PI control unit 42q, when there is no offset error in the d-axis detection current Ida and the q-axis detection current Iqa, as shown in FIG. In addition, the d-axis target voltage Vdc and the q-axis target voltage Vqc are flat values. In contrast, when an offset error occurs in the d-axis detection current Ida and the q-axis detection current Iqa, the ripple is suppressed by the PI control, but the d-axis target voltage Vdc and the q-axis target voltage Vqc include As shown in FIG. 8B, a ripple corresponding to the offset error occurs.

The d-axis target voltage Vdc and the q-axis target voltage Vqc, which are output values from the d-axis PI control unit 42d and the q-axis PI control unit 42q, are converted by the two-axis three-phase conversion unit 51, and the U-phase target voltage Vuc. , W phase target voltage Vwc is output.
FIG. 9 is a diagram illustrating the U-phase target voltage Vuc and the W-phase target voltage Vwc converted by the two-axis three-phase conversion unit 51. 9A shows a U-phase target voltage obtained by converting the d-axis target voltage Vdc and the q-axis target voltage Vqc, which are flat values as shown in FIG. It is a figure which shows Vuc and W phase target voltage Vwc. FIG. 9B shows a U-phase target obtained by converting the d-axis target voltage Vdc and q-axis target voltage Vqc in which ripples are generated as shown in FIG. It is a figure which shows the voltage Vuc and the W-phase target voltage Vwc.
When viewed from the U-phase target voltage Vuc and the W-phase target voltage Vwc, which are output values from the biaxial three-phase conversion unit 51, when the d-axis target voltage Vdc and the q-axis target voltage Vqc are flat values, There is no offset in the phase target voltage Vuc and the W phase target voltage Vwc. That is, the maximum value and the minimum value of the d-axis target voltage Vdc and the q-axis target voltage Vqc are the same value. On the other hand, when the d-axis target voltage Vdc and the q-axis target voltage Vqc are rippled as shown in FIG. 8B, as shown in FIG. An offset occurs in the voltage Vuc and the W-phase target voltage Vwc. That is, the maximum value and the minimum value of the d-axis target voltage Vdc and the q-axis target voltage Vqc are different values.

  Then, based on the U-phase target voltage Vuc and the W-phase target voltage Vwc in which an offset occurs as shown in FIG. 9B, the PWM signal generation unit 60 generates a PWM signal, and based on the generated PWM signal. If the motor drive unit 32 controls the driving of the electric motor 110, the target current is not supplied to the electric motor 110, which may cause deterioration of steering feeling, sound, and vibration. Therefore, in the offset correction unit 34 according to the present embodiment, the correction value correction unit 341 calculates and corrects the optimum offset correction values Iuo and Iwo according to the situation, thereby suppressing such an event.

Hereinafter, the correction value correction unit 341 will be described in detail.
As a result of intensive studies, the present inventors have determined the amplitude, offset amount, and offset correction values Iuo and Iwo of the U-phase target voltage Vuc and the W-phase target voltage Vwc, which are output values from the biaxial three-phase converter 51. And found that there is a relationship. That is, it has been found that the effect of the offset error in the offset correction unit 34 appears as an offset amount of the U-phase target voltage Vuc and the W-phase target voltage Vwc. This is as shown in FIG. 6 (a), FIG. 6 (b) and FIG. 9 (b).
Therefore, in the correction value correction unit 341 according to the present embodiment, in consideration of such matters, the offset is corrected based on the U-phase target voltage Vuc, the W-phase target voltage Vwc, the d-axis target current Idc, and the q-axis target current Iqc. The correction values ΔIuo and ΔIwo of the correction values Iuo and Iwo are calculated, new offset correction values Iuo and Iwo are calculated based on the calculated correction values ΔIuo and ΔIwo of the offset correction values, and stored in the correction value storage unit 342. .

  The correction value correction unit 341 uses the d-axis target current Idc and the q-axis target current Iqc calculated by the target current determination unit 25 of the target current calculation unit 20 as the U-phase target current Iuc and the W-phase in the three-phase AC coordinate system. A biaxial three-phase converter 341a (see FIG. 5) that converts the target current Iwc, and a correction value calculator 341b that calculates offset correction values Iuo and Iwo based on output values from the biaxial three-phase converter 341a; It has. The biaxial three-phase conversion unit 341a converts the U-phase target current Iuc and the W-phase target current Iwc according to the following equations (5) and (6).

  The correction value calculation unit 341b determines the amplitude and offset amount of the U-phase target voltage Vuc and the U phase for one electrical angle rotation of the electric motor 110 when a preferable condition for calculating the optimum offset correction value Iuo is satisfied. A correction value ΔIuo of the offset correction value Iuo of the U-phase detection current Iua is calculated based on the amplitude of the target current Iuc and the following equation (7). Then, a new offset correction value Iuo is calculated by adding the calculated correction value ΔIuo to the previous offset correction value Iuo. (Iuo ← Iuo + ΔIuo)

ここで、Ｉｕｃｐ，Ｖｕｃｐは、電動モータ１１０の電気角１回転分における、Ｕ相目標電流Ｉｕｃの振幅，Ｕ相目標電圧Ｖｕｃの振幅であり、
Ｉｕｃｐ＝Ｉｕｃｍａｘ−Ｉｕｃｍｉｎ、
Ｖｕｃｐ＝Ｖｕｃｍａｘ−Ｖｕｃｍｉｎ、
である。
また、Ｖｕｃｏは、電動モータ１１０の電気角１回転分における、Ｕ相目標電圧Ｖｕｃのオフセット量であり、Ｖｕｃｏ＝（Ｖｕｃｍａｘ＋Ｖｕｃｍｉｎ）／２である。

Here, Iucp and Vucp are the amplitude of the U-phase target current Iuc and the amplitude of the U-phase target voltage Vuc for one electrical angle rotation of the electric motor 110,
Iucp = Iucmax-Iuccmin,
Vucp = Vucmax−Vuccmin,
It is.
Further, Vuco is an offset amount of the U-phase target voltage Vuc for one electrical angle rotation of the electric motor 110, and Vuco = (Vucmax + Vucmin) / 2.

  Further, the correction value calculation unit 341b includes the amplitude and offset amount of the W-phase target voltage Vwc for one electrical angle rotation of the electric motor 110 when a preferable condition for calculating the optimum offset correction value Iwo is satisfied, Based on the amplitude of the W-phase target current Iwc and the following equation (8), a correction value ΔIwo of the offset correction value Iwo of the W-phase detection current is calculated. Then, a new offset correction value Iwo is calculated by adding the calculated correction value ΔIwo to the offset correction value Iwo so far. (Iwo ← Iwo + ΔIwo)

ここで、Ｉｗｃｐ，Ｖｗｃｐは、電動モータ１１０の電気角１回転分における、Ｗ相目標電流Ｉｗｃの振幅，Ｗ相目標電圧Ｖｗｃの振幅であり、
Ｉｗｃｐ＝Ｉｗｃｍａｘ−Ｉｗｃｍｉｎ、
Ｖｗｃｐ＝Ｖｗｃｍａｘ−Ｖｗｃｍｉｎ、
である。
また、Ｖｗｃｏは、電動モータ１１０の電気角１回転分における、Ｗ相目標電圧Ｖｗｃのオフセット量であり、Ｖｗｃｏ＝（Ｖｗｃｍａｘ＋Ｖｗｃｍｉｎ）／２である。

Here, Iwcp and Vwcp are the amplitude of the W-phase target current Iwc and the amplitude of the W-phase target voltage Vwc for one electrical angle of the electric motor 110,
Iwcp = Iwcmax−Iwcmin,
Vwcp = Vwcmax−Vwcmin,
It is.
Vwco is an offset amount of the W-phase target voltage Vwc for one electrical angle rotation of the electric motor 110, and Vwco = (Vwcmax + Vwcmin) / 2.

  As preferable conditions for calculating the optimum offset correction values Iuo and Iwo, there can be considered a condition relating to a target current described below and a condition relating to the angular velocity of the electric motor 110. The condition relating to the target current is that the average value of the q-axis target current Iqc in a predetermined period is equal to or greater than a predetermined value, the fluctuation range of the period is equal to or less than a predetermined value, and the d-axis target current It can be exemplified that Idc is zero. This is because in such a case, it is considered that the drive of the electric motor 110 is stable. Further, the condition regarding the angular velocity of the electric motor 110 exemplifies that the average value of the motor angular velocity in a predetermined period is equal to or less than a predetermined value and the fluctuation range of the period is equal to or less than a predetermined value. be able to. This is because in such a case, it is considered that the drive of the electric motor 110 is stable.

Then, the correction value calculation unit 341b calculates the offset correction values Iuo and Iwo according to the procedure described below.
FIG. 10 is a flowchart illustrating a procedure of offset correction value calculation processing performed by the correction value calculation unit 341b. The correction value calculation unit 341b periodically executes this offset correction value calculation process, for example, every 2 ms.
First, the correction value calculation unit 341b acquires the d-axis target current Idc, the q-axis target current Iqc, and the motor angular velocity (step 1001). Thereafter, it is determined whether or not the target current condition is satisfied (step 1002). This is a process for determining whether or not the above-described conditions regarding the target current are satisfied. For example, the average value, the maximum value, and the minimum value of the q-axis target current Iqc in the period from 100 ms before the current time to the current time are calculated. A process for determining whether the calculated average value is equal to or greater than a predetermined value, the deviation between the maximum value and the minimum value is equal to or less than a predetermined value, and whether the d-axis target current Idc is zero. It is.

  If the condition regarding the target current is satisfied (Yes in Step 1002), it is determined whether or not the motor angular velocity condition is satisfied (Step 1003). This is a process for determining whether or not the above-described conditions regarding the angular velocity of the electric motor 110 are satisfied. For example, the average value, the maximum value, and the minimum value of the motor angular velocity in a period from 100 ms to the present time are calculated. In this process, it is determined whether or not the calculated average value is equal to or less than a predetermined value and the deviation between the maximum value and the minimum value is equal to or less than a predetermined value.

  If the motor angular velocity condition is satisfied (Yes in step 1003), the U-phase target current Iuc, which is correction value calculation data used to calculate the correction values ΔIuo and ΔIwo of the offset correction values Iuo and Iwo, W phase target current Iwc, U phase target voltage Vuc and W phase target voltage Vwc are acquired (step 1004). Thereafter, it is determined whether or not the acquisition of the correction value calculation data in step 1004 has been completed for one electrical angle of the electric motor 110 (step 1005). This is because the electrical angle of the electric motor 110 has made one rotation while the target current condition and the motor angular speed condition are satisfied from the time when the correction value calculation data is first acquired after the target current condition and the motor angular speed condition are satisfied. Is determined based on the output value of the motor angle calculation unit 36.

If the electric motor 110 has completed one electrical angle (Yes in Step 1005), the correction values ΔIuo and ΔIwo of the offset correction values Iuo and Iwo are calculated (Step 1006). This is calculated by calculating the amplitude and offset amount of the U-phase target voltage Vuc and the amplitude of the U-phase target current Iuc based on each correction value calculation data acquired in step 1004 for one electrical angle rotation. This is a process of calculating by substituting the value into the equation (7). Further, based on each correction value calculation data acquired in step 1004 for one electrical angle rotation, the amplitude and offset amount of the W-phase target voltage Vwc and the amplitude of the W-phase target current Iwc are calculated and calculated. Is calculated by substituting into the equation (8). For example, when performing the so-called peak hold in which the maximum value and the minimum value of each correction value calculation data acquired in step 1004 are stored in the storage area, the maximum value and the minimum value are substituted into the above-described formula, and Iucp , Vucp, Iwcp, Vwcp, Vuco, Vwco are calculated.
Then, new offset correction values Iuo and Iwo are calculated by adding the correction values ΔIuo and ΔIwo calculated in step 1006 to the previous offset correction values Iuo and Iwo. (Iuo ← Iuo + ΔIuo, Iwo ← Iwo + ΔIwo) (step 1007).

On the other hand, if the condition regarding the target current is not satisfied (No in Step 1002), or if the motor angular velocity condition is not satisfied (No in Step 1003), the correction value calculation data is initialized (Step 1008). In other words, if either the target current condition or the motor angular speed condition is not satisfied while the acquisition of correction value calculation data for one electrical angle of the electric motor 110 is not completed, step 1004 in the flow up to now is performed. This is a process of erasing the correction value calculation data acquired and stored in step.
The correction value calculation unit 341b thus calculates and corrects (updates) the offset correction values Iuo and Iwo. Then, the correction current calculation unit 343 corrects the offset value of the output value from the motor current detection unit 33 using the corrected (updated) offset correction values Iuo and Iwo, thereby correcting the U-phase correction currents Iua ′ and W-phase. A correction current Iwa ′ is calculated.

  As described above, the offset correction unit 34 according to the present embodiment uses the U-phase target voltage Vuc and the W-phase target that are used to control the driving of the electric motor 110 to assist the operation of the steering wheel 101. Based on the voltage Vwc, the U-phase target current Iuc, and the W-phase target current Iwc, offset correction values Iuo and Iwo are calculated and updated. Therefore, the offset correction values Iuo and Iwo can be set to optimum values while driving the electric motor 110 to assist the operation of the steering wheel 101. Therefore, for example, by forcibly stopping the driving of the electric motor 110 for assisting the operation of the steering wheel 101 and supplying the electric motor 110 with a voltage for correcting the offset correction value, the offset correction value is obtained. Compared to correcting the above, the operation of the steering wheel 101 can be assisted for a longer period of time. That is, the control dead zone of the steering device can be reduced, and the steering feeling can be improved. In addition, compatibility with an additional control function using a yaw rate sensor or a rudder angle sensor is possible.

  Note that the induced voltage Vue of the electric motor 110 may be taken into account when calculating the correction values ΔIuo and ΔIwo of the offset correction values Iuo and Iwo. In other words, the induced voltage Vue is calculated by multiplying the average value Mspd of the motor angular velocity for one electrical angle of the electric motor 110 in step 1005 by the induced voltage constant Ke (Vue = Mspd × Ke). Then, the offset correction value Iuo is calculated using the following equation (9) instead of the above equation (7), and the offset correction value Iwo is calculated using the following equation (10) instead of the above equation (8). Should be calculated.

このように、電動モータ１１０の誘起電圧Ｖｕｅを考慮してオフセット補正値Ｉｕｏ，Ｉｗｏの補正値ΔＩｕｏ，ΔＩｗｏを算出することで、より精度高く補正値ΔＩｕｏ，ΔＩｗｏを算出することができ、オフセット補正値Ｉｕｏ，Ｉｗｏをより適切な値にすることが可能となる。

Thus, by calculating the correction values ΔIuo and ΔIwo of the offset correction values Iuo and Iwo in consideration of the induced voltage Vue of the electric motor 110, the correction values ΔIuo and ΔIwo can be calculated with higher accuracy, and the offset correction is performed. It becomes possible to make the values Iuo and Iwo more appropriate values.

<Second Embodiment>
FIG. 11 is a diagram illustrating a schematic configuration of the offset correction unit 34 according to the second embodiment.
Hereinafter, differences from the first embodiment will be described, and the same components will be denoted by the same reference numerals and detailed description thereof will be omitted.
The correction value correction unit 341 according to the second embodiment is characterized in that the correction values ΔIuo and ΔIwo of the offset correction values Iuo and Iwo are calculated using the interphase resistance RM of the electric motor 110.
That is, the correction value ΔIuo of the offset correction value Iuo is calculated using the following equation (11) instead of the above equation (7), and the following equation (12) is used instead of the above equation (8). A correction value ΔIwo of the offset correction value Iwo is calculated.
ΔIuo = Vuco / RM (11)
ΔIwo = Vwco / RM (12)

  Also in the offset correction unit 34 according to the second embodiment configured as described above, the U-phase target voltages Vuc, W used for controlling the driving of the electric motor 110 to assist the operation of the steering wheel 101. Based on the phase target voltage Vwc, the offset correction values Iuo and Iwo are calculated and updated. Therefore, the offset correction values Iuo and Iwo can be set to optimum values while driving the electric motor 110 to assist the operation of the steering wheel 101. Therefore, for example, by forcibly stopping the driving of the electric motor 110 for assisting the operation of the steering wheel 101 and supplying the electric motor 110 with a voltage for correcting the offset correction value, the offset correction value is obtained. Compared to correcting the above, the operation of the steering wheel 101 can be assisted for a longer period of time. That is, the control dead zone of the steering device can be reduced, and the steering feeling can be improved. In addition, compatibility with an additional control function using a yaw rate sensor or a rudder angle sensor is possible.

  As described above, the correction value correction unit 341 according to the second embodiment uses the U-phase target voltage Vuc, the W-phase target voltage Vwc and the interphase resistance RM to correct the correction values ΔIuo and ΔIwo of the offset correction values Iuo and Iwo. Therefore, the U-phase target current Iuc and the W-phase target current Iwc, which are target currents in the three-phase AC coordinate system, are not used. Therefore, the correction value correction unit 341 according to the second embodiment may not include the biaxial three-phase conversion unit 341a.

DESCRIPTION OF SYMBOLS 10 ... Control apparatus, 20 ... Target current calculation part, 25 ... Target current determination part, 30 ... Control part, 31 ... Motor drive control part, 32 ... Motor drive part, 33 ... Motor current detection part, 34 ... Offset correction part, DESCRIPTION OF SYMBOLS 100 ... Electric power steering apparatus, 101 ... Steering wheel (handle), 110 ... Electric motor

Claims (6)

An electric motor that gives steering assist force to the steering wheel;
Target current calculation means for calculating a target current to be supplied to the electric motor;
Output means for outputting a value corresponding to the actual current actually supplied to the electric motor;
An actual current calculating means for correcting the offset of the output value from the output means by using an offset correction value stored in advance and calculating the actual current;
Voltage calculating means for calculating a target voltage to be applied to the electric motor based on the target current calculated by the target current calculating means and the actual current calculated by the actual current calculating means;
Motor driving means for driving the electric motor by applying the target voltage calculated by the voltage calculating means to the electric motor;
Correction value correction means for correcting the offset correction value based on the target voltage calculated by the voltage calculation means;
An electric power steering apparatus comprising:   The correction value correction unit corrects the offset correction value based on the target voltage calculated by the voltage calculation unit and the target current calculated by the target current calculation unit. Electric power steering device. The electric motor is a three-phase brushless motor,
The target current calculation means calculates a d-axis target current and a q-axis target current in a dq coordinate system,
The correction value correction means converts the target voltage of the three-phase AC coordinate system calculated by the voltage calculation means, the d-axis target current and the q-axis target current calculated by the target current calculation means into currents of the three-phase AC coordinate system. The electric power steering apparatus according to claim 2, wherein the offset correction value is corrected based on the converted target current.   The correction value correcting means is a value obtained by multiplying the ratio of the offset to the target voltage amplitude of the three-phase alternating current coordinate system calculated by the voltage calculating means by the target current amplitude converted into the current of the three-phase alternating current coordinate system, The electric power steering apparatus according to claim 3, wherein the offset correction value is corrected by adding the offset correction value to a previously stored offset correction value. The electric motor is a three-phase brushless motor,
2. The electric power steering apparatus according to claim 1, wherein the correction value correction unit corrects the offset correction value based on a target voltage calculated by the voltage calculation unit and an interphase resistance of the electric motor. .   The correction value correction unit adds a value obtained by dividing the target voltage of the three-phase AC coordinate system calculated by the voltage calculation unit by the interphase resistance of the electric motor to the offset correction value stored in advance. The electric power steering apparatus according to claim 5, wherein the offset correction value is corrected.

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