JP2008067565A - Control method of electric motor, motor controller, and electric power steering system using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To continue steering assistance also by an electric power steering system without involving in deterioration of functions of electrical equipment, when a battery is abnormal. <P>SOLUTION: Electric energy Pw which can be currently generated by an alternator 26 is presumed from a rotating speed of an engine, then the remained electric energy which is secured for the electric equipment 27 to such an extent as deterioration of the functions is not caused is considered as power Pmax which can be supplied for an electric motor 12 to generate steering auxiliary force. When requested torque Treq in which steering torque T is limited according to motor characteristics is or more than torque Tmax which can be output and corresponds to the power Pmax which can be supplied, the requested torque Treq is limited to the torque Tmax which can be output, then steering auxiliary torque command value I<SB>M</SB><SP>*</SP>is computed based on the torque Tmax which can be output. Supposing that a d-axis target current value Id<SP>*</SP>equals to zero, a q-axis target current value Iq<SP>*</SP>which can generate the steering auxiliary torque command value I<SB>M</SB><SP>*</SP>is computed, then current values corresponding to the d-axis and q-axis current command values Id<SP>*</SP>, Iq<SP>*</SP>are supplied to the electric motor 12. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electric motor control method, a motor control device, and an electric power steering device using the same, which are supplied with power from a common power supply source with other electrical equipment.

Conventionally, an electric motor for a vehicle that detects steering torque input to the steering wheel and controls the rotation of the motor in accordance with the steering torque so as to apply assist force to the steering wheel turning operation. Power steering devices have been proposed.
In this type of electric power steering apparatus, the electric motor is driven and controlled by electric power supplied from a battery or an alternator that is operated by the rotational output of the engine. The battery and alternator are not only used for electric power steering devices, but also for car audio and car navigation, safe driving of vehicles such as engine starter motors, lamps, air conditioners, and in-vehicle electrical equipment that is indispensable for the vehicle interior environment. Is also supplying power.

If the battery voltage drops, it will affect the in-vehicle devices that are indispensable for the safe driving of these vehicles and the in-vehicle environment. By restricting the power supply, it is possible to secure power supply to highly necessary equipment (see, for example, Patent Document 1), and when a stationary operation is performed, to an electric motor A large current is supplied and the battery voltage drops accordingly, so a drop in the battery voltage is predicted, the idle is increased, and the current supply capability of the alternator is increased to avoid a drop in the battery voltage. Have also been proposed (see, for example, Patent Document 2).
JP 2003-170789 A JP 2001-253357 A

  By the way, in an electric power steering apparatus, it is difficult to reduce the output as an electric power steering apparatus with the increase in the size of an applied vehicle in recent years. For this reason, since a voltage abnormality has occurred in the battery, much of the output of the alternator is supplied to the electric power steering device when the output of the alternator covers the power supplied to the electric power steering device and various electrical equipment. However, there is a problem in that sufficient electrical power cannot be supplied to the electrical equipment, and in some cases, the electrical equipment may not be able to perform its functions sufficiently.

  Therefore, the present invention has been made paying attention to the above-mentioned conventional unsolved problems, and even when the battery voltage is lowered, the other electric equipment is operated while operating the electric motor. It is an object of the present invention to provide an electric motor control method, a motor control device, and an electric power steering device using the same.

  In order to achieve the above object, a control method for an electric motor according to claim 1 of the present invention is a control method for an electric motor that is operated by power supplied from a power supply source including at least power generation means, and the power generation means The power that can be supplied is estimated, and the output torque of the electric motor is limited according to the estimated power that can be supplied.

  According to a second aspect of the present invention, there is provided a motor control device for an electric motor that operates with power supplied from a power supply source including at least power generation means, and a target value of an output torque to be output by the electric motor. Torque target value detecting means for detecting the power, suppliable power estimating means for estimating the power that can be supplied by the power generating means, and the torque target value detecting means according to the suppliable power estimated by the suppliable power estimating means. Output torque limiting means for limiting the detected torque target value; and motor control means for driving and controlling the electric motor so as to generate torque equivalent to the torque target value limited by the output torque limiting means. It is characterized by.

  According to a third aspect of the present invention, in the motor control device according to the third aspect, the output torque limiting means determines the amount of power that can be distributed to the electric motor out of the supplyable power based on the supplyable power estimated by the supplyable power estimation means. The motor distribution amount estimation means for estimating is provided, and the torque target value is limited to a torque value equivalent to the motor distribution amount to the electric motor estimated by the motor distribution amount estimation means.

  According to a fourth aspect of the present invention, in the motor control device, the output torque limiting means corresponds to the motor distribution amount based on the motor distribution amount estimated by the motor distribution amount estimation means and the motor angular velocity detected by the motor angular velocity detection means. Output torque estimation means for estimating the torque generated from the electric motor when the electric power is supplied to the electric motor, and the torque target value detected by the torque target value detection means is used as the output torque estimation It is characterized by limiting to a threshold value set according to the output possible torque estimated by the means.

  According to a fifth aspect of the present invention, in the motor control device, the output torque limiting means estimates the amount of change in power supplied to the electric motor from the amount of change in the torque target value detected by the torque target value detecting means. A power change amount estimating means that, when the power change amount estimated by the power change amount estimating means is greater than or equal to a preset threshold value, a torque target value detected by the torque target value detecting means, The amount of change is limited to be equal to or less than the threshold value, and the limited value is set as a new torque target value.

Further, in the motor control device according to claim 6, when the torque target value is limited to a value smaller than this, the motor control means sets the d-axis current to the electric motor to zero and only the q-axis current. It is characterized by control.
The motor control device according to a seventh aspect is characterized in that the power supply source supplies power to the electric motor and other electrical equipment.
In the motor control device according to claim 8, the power supply source includes the power generation unit, a power storage unit charged by the power generation unit, and an abnormality detection unit that detects an abnormality of the power storage unit, The motor control means limits the torque target value detected by the target value detection means when the abnormality detection means detects an abnormality of the power storage means.

According to a ninth aspect of the present invention, there is provided an electric power steering apparatus according to any one of the first to eighth aspects, wherein the motor control apparatus is an electric motor that applies a steering assist force to a steering system. It is characterized by being applied as
Furthermore, the electric power steering apparatus according to claim 10, wherein the power generation means is an alternator that operates based on engine rotation output, and includes engine rotation speed detection means that detects the rotation speed of the engine, and the suppliable power The estimating means estimates the suppliable power of the alternator based on the engine speed detected by the engine speed detecting means.

According to the control method of the electric motor according to the first aspect of the present invention, the amount of power supplied to the electric motor can be adjusted according to the power that can be supplied by the power generation means.
According to the motor control device of the second aspect of the present invention, the electric motor is configured to limit the torque target value of the electric motor according to the electric power that can be supplied by the power generation means, and to generate the limited torque target value. Therefore, the amount of power supplied to the electric motor can be adjusted according to the power that can be supplied by the power generation means.

Further, according to the motor control device of the third aspect, since the torque target value is limited so as to generate a torque corresponding to the amount of power that can be distributed to the electric motor among the suppliable power that can be generated by the power generation means, The amount of power actually supplied to the electric motor can be kept within the range of power that can be distributed to the electric motor.
Further, according to the motor control device of the fourth aspect, the torque that can be output is estimated from the motor distribution amount that can be distributed to the electric motor and the motor angular velocity of the current electric motor, and the torque target value is output as the torque that can be output. Therefore, the amount of power actually supplied to the electric motor can be easily and accurately within the range of the amount of power that can be distributed to the electric motor.

  According to the motor control device of the fifth aspect, when the change amount of the electric power supplied to the electric motor is equal to or greater than a preset threshold value, the change amount of the torque target value is equal to or less than the threshold value. The torque target value is limited as described above, and the electric motor is driven and controlled using the limited value as a new torque target value, so that it is supplied to the electric motor resulting from the relationship between the fluctuation of the torque target value and the power generation capability of the power generation means. The fluctuation of the power supply voltage can be suppressed.

According to the motor control device of the sixth aspect, when the torque target value is limited, the d-axis current to the electric motor is set to zero, and so-called Id = 0 control for controlling only the q-axis current. Thus, the electric motor can be operated with high efficiency, and a decrease in output torque from the electric motor due to the limitation of the torque target value can be suppressed.
Moreover, according to the motor control apparatus which concerns on Claim 7, the electric power supply to an electric motor can also be performed, ensuring the electric power supplied to another electrical equipment according to the electric power which can be supplied of an electric power generation means.

  Further, according to the motor control device of the eighth aspect, even when the power generation means has a situation where it is necessary to cover the power supplied to the electric motor or the electrical equipment by the power generation output of the power generation means due to the abnormality of the power storage means. By limiting the torque target value of the electric motor according to the power that can be supplied, it is possible to supply sufficient power to other electrical equipment, and drive control of the electric motor while fully functioning the electrical equipment can do.

Moreover, according to the electric power steering apparatus of the ninth aspect of the present invention, since the electric power steering apparatus is applied as a motor control apparatus for an electric motor that applies a steering assist force to the steering system, the steering is performed within the range of power that can be supplied by the power generation means. Auxiliary force can be generated.
Furthermore, the electric power steering apparatus according to claim 10 can easily estimate the suppliable power of the alternator that is operated by the rotational output of the engine by using the engine speed.

Embodiments of the present invention will be described below.
First, a first embodiment will be described.
FIG. 1 is an overall configuration diagram showing an embodiment of the present invention.
FIG. 1 is an overall configuration diagram showing an embodiment in which the present invention is applied to an electric power steering apparatus. In the figure, reference numeral 1 denotes a steering wheel, which is applied to the steering wheel 1 from a driver. A steering force is transmitted to a steering shaft 2 having an input shaft 2a and an output shaft 2b. The steering shaft 2 has one end of the input shaft 2a connected to the steering wheel 1 and the other end connected to one end of the output shaft 2b via a steering torque sensor 3 as steering torque detecting means.

  The steering force transmitted to the output shaft 2 b is transmitted to the lower shaft 5 via the universal joint 4 and further transmitted to the pinion shaft 7 via the universal joint 6. The steering force transmitted to the pinion shaft 7 is transmitted to the tie rod 9 via the steering gear 8 and steers steered wheels (not shown). Here, the steering gear 8 is configured in a rack and pinion type having a pinion 8a connected to the pinion shaft 7 and a rack 8b meshing with the pinion 8a, and the rotational motion transmitted to the pinion 8a is linearly moved by the rack 8b. It has been converted to movement.

A steering assist mechanism 10 for transmitting a steering assist force to the output shaft 2b is connected to the output shaft 2b of the steering shaft 2. The steering assist mechanism 10 includes a reduction gear 11 connected to the output shaft 2b, and an electric motor 12 composed of, for example, a brushless motor as an electric motor that generates a steering assist force connected to the reduction gear 11. .
The steering torque sensor 3 detects the steering torque applied to the steering wheel 1 and transmitted to the input shaft 2a. For example, the steering torque sensor 3 is a torsion bar (not shown) in which the steering torque is interposed between the input shaft 2a and the output shaft 2b. It is configured to convert to a torsional angular displacement, and to detect this by converting the torsional angular displacement into a resistance change or a magnetic change.

The steering torque T detected by the steering torque sensor 3 is input to a controller 20 configured by, for example, an MCU (Micro Controller Unit) that controls the power steering device. The controller 20 detects the vehicle speed detected by the vehicle speed sensor 21. V is also input, and the controller 20 performs steering assist control processing in a known procedure based on the steering torque T and the vehicle speed V, and generates a steering assist force corresponding to the steering torque T and the vehicle speed V by the electric motor 12. A steering assist torque command value I _M ^* consisting of a current value for this is calculated, and a current value corresponding to this is supplied to the electric motor 12 to generate a steering assist force corresponding to the steering torque T and the vehicle speed V. In addition, the controller 20 monitors the abnormality of the battery 25 that supplies power to each part of the electric power steering apparatus, and if an abnormality of the battery 25 is detected, an engine (not shown) for charging the battery 25 is detected. The amount of electric power that can be supplied by the alternator 26 that operates by the rotation output is estimated, and the output torque of the electric motor 12 is limited according to the estimated supplyable electric power.
The battery 25 and the alternator 26 supply power to the controller 20 and also supply power to various audio equipment 27 such as a car audio and car navigation, an engine starter motor, a lamp, and an air conditioner.

FIG. 2 is a block diagram showing a functional configuration of the controller 20.
The controller 20, based on the steering torque T and vehicle speed V, the steering assist calculates a torque command value I _M ^* according to, steering assist torque command value I _M ^* and the angular velocity ω and the d-axis and q on the basis of the A current command value determination unit 31 that determines the current command values Id ^* and Iq ^* of the shaft, and a d-axis current command value Id ^* and a q-axis current command value Iq ^* determined by the current command value determination unit 31 in three phases A two-phase three-phase converter 32 that converts the current command values Iu ^* , Iv ^* , and Iw ^* , and a motor current detector 33 that detects the motor currents Iu, Iv, and Iw supplied to the phase coils of the electric motor 12; The motor currents Iu, Iv, and Iw detected by the motor current detection unit 33 are subtracted from the three-phase current command values Iu ^* , Iv ^* , and Iw ^* input from the two-phase / three-phase conversion unit 32, respectively. Current deviations ΔIu, ΔIv, ΔI Current control unit 34 for calculating voltage command values Vu, Vv, Vw by performing proportional-integral control on the phase current deviations ΔIu, ΔIv, ΔIw, and voltage command values Vu, A PWM control unit 35 that forms a pulse width modulation (PWM) signal for a switching element such as a field effect transistor constituting the inverter 36 based on Vv and Vw, and a pulse width modulation output from the PWM control unit 35 A motor current corresponding to the signal is output from the inverter 36 to the electric motor 12, and the electric motor 12 is driven and controlled.

  Further, the controller 20 differentiates the rotation angle θ from the motor rotation angle detection unit 37 and the motor rotation angle detection unit 37 that detects the rotation angle θ of the electric motor 12 constituted by a resolver, an encoder, and the like. A motor angular velocity calculation unit 38 that calculates 12 angular velocities ω, a battery monitoring unit 39 that detects battery terminal abnormality and output voltage abnormality of the battery 25, which will be described later, and detects battery abnormality, and the battery monitoring unit 39 detects abnormality. When this is done, the amount of power that can be output by the alternator 26 is estimated based on the engine speed Ne from the engine speed sensor 45, and based on this, the amount of power Pmax that can be supplied to the electric motor 12 is determined. A suppliable power determining unit 40 that outputs this to the current command value determining unit 31.

  The suppliable power determination unit 40 includes an alternator output estimation unit 40a that estimates the amount of electric power Pw that can be output by the alternator 26 based on the engine speed Ne detected by the engine speed sensor 45, and the alternator output estimation unit 40a. A motor output determination unit 40b that determines the suppliable power Pmax that can be supplied to the electric motor 12 based on the estimated outputable power amount Pw.

  The alternator output estimation unit 40a includes a table having the characteristics shown in the control map in FIG. 2 that represents the correspondence between the engine speed Ne and the amount of electric power Pw that can be output by the alternator 26 at the engine speed Ne. From this table, the power amount Pw corresponding to the detected engine speed Ne is specified. In the control map of FIG. 2, the horizontal axis represents the engine speed Ne, the vertical axis represents the power amount Pw, and the outputable power amount Pw increases as the engine speed Ne increases in a region where the engine speed Ne is low. And then increase sharply and then gradually increase as the engine speed Ne increases.

  The motor output determination unit 40b is configured by a multiplier or the like, and multiplies the power amount Pw from the alternator output estimation unit 40a by a gain equivalent to a margin, and outputs this as suppliable power Pmax. The gain corresponding to the margin is used to calculate the amount of power that can be supplied to the electric motor 12 out of the amount of power Pw that is output from the alternator 26 when the battery 25 is unable to supply predetermined power. For example, the gain is set according to the amount of electric power necessary for the electrical equipment 27 to fully perform its function. That is, when the battery 25 can no longer supply predetermined power, only the power supplied from the alternator 26 covers the power of the electric motor 12 and the electrical equipment 27. At this time, the output of the alternator 26 Most of the electric motor 12 is not used, but the electric motor 12 is supplied with electric power capable of exhibiting the function of the electric device 27 and also supplied to the electric motor 12. Is set to a possible gain.

Then, the suppliable power Pmax determined in this way and the control switching command Sc for switching the calculation method of the current command value in the current command value determination unit 31 when the abnormality of the battery 25 occurs are represented by the current command value. It outputs to the determination part 31.
The current command value determination unit 31 is a current command value for generating a steering assist torque corresponding to the steering torque T based on the steering torque T from the steering torque sensor 3 and the vehicle speed V from the vehicle speed sensor 21. A steering assist torque command value calculation unit 31a that calculates a certain steering assist torque command value I _M ^* , and a steering assist torque command value I _M ^* and a motor angular velocity calculation unit 38 that are calculated by the steering assist force torque command value calculation unit 31a. Is provided with a d-q axis current calculation unit 31b that calculates a d-axis current command value Id ^* and a q-axis current command value Iq ^* based on the motor angular velocity ω calculated in step (b).

The steering assist torque command value calculation unit 31a uses, for example, the vehicle speed V as a parameter based on the steering torque T from the steering torque sensor 3 and the vehicle speed V from the vehicle speed sensor 21, and the steering torque T and the steering assist torque command. in known procedures using unillustrated control map or the like showing a correspondence between the value I _M ^*, and sets the steering assist torque command value I _M ^*, the smaller the steering torque T is large steering assist torque command value I _M ^* increases and and as the steering assist torque command value I _M ^* becomes smaller when the vehicle speed V is high, determines the steering assist torque command value I _M ^*.

The dq axis current calculation unit 31b is a steering assist torque command value calculation unit when a control switching instruction is not issued by the control switching command Sc from the suppliable power determination unit 40, that is, when the battery 25 is normal. a steering assist torque command value _I ^{M *} corresponding to the d-axis current command value Id ^* and the q-axis current command value Iq ^* from 31a is calculated by known procedures. For example, when the target value of the steering assist torque generated by the electric motor 12 according to the steering assist torque command value I _M ^* is T (I _M ^* ), the steering assist torque T (I _M ^* ) and the electric motor Since the command power amount, which is a command value of the power consumed by the electric motor 12, expressed by a multiplication value of the angular velocity ω of 12, is balanced with the output power amount from the electric motor 12, the following equation (1) is obtained. be able to.
T (I _M ^* ) × ω = (3/2) × (ed · Id ^* + eq · Iq ^* ) (1)
Therefore, the d-axis current command value Id ^* and the q-axis current command value Iq ^* can be calculated from the equation (1). In the equation, ed and eq are counter electromotive voltages on the d-axis and the q-axis, respectively.

On the other hand, when a control switching instruction is issued by the control switching command Sc from the suppliable power determining unit 40, the electric motor is actually based on the suppliable power Pmax input from the suppliable power determining unit 40 together with the control switching command Sc. torque output from 12, to be smaller than the steering assist torque command value I _M ^* equivalent torque, and calculates the q-axis current command value Iq ^*. At this time, the d-axis current command value Id ^* is set to Id ^* = 0, so-called Id = 0 control generally used as a control method of the SPM synchronous motor is performed, and the electric motor 12 is operated with high efficiency.

FIG. 3 is a flowchart illustrating an example of a processing procedure of calculation processing for determining the d-axis and q-axis current command values Id ^* and Iq ^* in the current command value determination unit 31.
First, in step S1, a torque limiting process according to the motor characteristic for limiting the steering torque T according to the motor characteristic of the electric motor 12 is performed on the steering torque T from the steering torque sensor 3. Specifically, as shown in the flowchart of FIG. 4, first, in step S1a, the motor angular velocity ω calculated by the motor angular velocity calculation unit 38 and the motor characteristic diagram shown in the flowchart of FIG. The output torque Tmmax of the electric motor 12 that can be output at the angular velocity ω is specified. In the motor characteristic diagram shown in the flowchart of FIG. 4, the horizontal axis represents the output torque Tm of the electric motor 12, and the vertical axis represents the motor angular velocity ω.

  Next, the process proceeds to step S1b, where the steering torque T from the steering torque sensor 3 is compared with the motor output torque Tmmax specified in step S1a, and if the steering torque T is smaller than the motor output torque Tmmax (T <Tmmax), step S1b is performed. In S1c, the steering torque T is set as the required torque Treq as it is. However, if the steering torque T is equal to or greater than the motor output torque Tmmax (T ≧ Tmmax), the process proceeds to Step S1d, and the motor output torque Tmmax is set as the required torque Treq. Set. That is, in the limiting process according to the motor characteristics, the steering torque T is limited to the motor output torque Tmmax determined by the motor characteristics. If the required torque Treq is calculated in this way, the process returns to FIG. 3 and proceeds to step S2.

In step S <b> 2, it is determined whether the control switching command Sc is input from the suppliable power determining unit 40, that is, whether the battery monitoring unit 39 has detected an abnormality in the battery 25. If no battery abnormality is detected, the process proceeds to step S3, and the required torque Treq limited in the process of step S1 is set as the target steering torque T ^* . Next, the routine proceeds to step S4, where the steering assist torque command value I _M ^* is calculated by a known procedure based on the target steering torque T ^* and the vehicle speed V, and then the routine proceeds to step S5, where the steering assist torque command value I _M ^{Based on *} and the motor angular velocity ω, command values are calculated in the dq-axis coordinate system by a known procedure, and d-axis and q-axis current command values Id ^* and Iq ^* are calculated.

  On the other hand, when it is determined in the process of step S2 that control switching is instructed by the control switching command Sc from the suppliable power determining unit 40 and abnormality is occurring in the battery 25, the process proceeds from step S2 to step S6. The suppliable power Pmax that is the amount of power of the alternator 26 that can be supplied to the electric motor 12 out of the output power of the alternator 26 from the suppliable power determination unit 40 is divided by the motor angular velocity ω, and the suppliable power Pmax is electric. When it is supplied to the motor 12, it is converted into a torque Tmax that can be output by the electric motor 12 (Tmax = Pmax / ω).

Next, the routine proceeds to step S7, where the required torque Treq limited in step S1 is compared with the outputtable torque Tmax calculated in step S6. When the required torque Treq is smaller than the outputtable torque Tmax, the torque is supplied from the alternator 26. the power, a steering assist torque corresponding to the steering torque T is determined that can be sufficiently generated, the process proceeds to step S3, and sets the required torque Treq as the target steering torque T ^*, the target steering torque T ^* The d-axis and q-axis current command values Id ^* and Iq ^* that can be generated are calculated (steps S4 and S5).

On the other hand, when the required torque Treq is greater than or equal to the outputtable torque Tmax in step S7, the process proceeds to step S8, and after setting the outputable torque Tmax as the target steering torque T ^* , the process proceeds to step S9.
In this step S9, the steering assist torque command value I _M ^* is calculated from the target steering torque T ^* and the vehicle speed V in the same procedure as the processing in step S4, and then the process proceeds to step S10, where the d-axis and q-axis are shifted. Current command values Id ^* and Iq ^* are calculated.

In step S10, an abnormality occurs in the battery 25, the required torque Treq is larger than the torque Tmax equivalent to the suppliable power Pmax, and it is difficult to generate a torque equivalent to the required torque Treq. Is limited to the torque Tmax that can be output. Therefore, Id = 0 control is performed to perform control with the d-axis current set to zero to achieve high-efficiency operation. That is, the d-axis current command value Id ^* = 0, and the q-axis current command value Iq ^* is calculated by a known procedure from the steering assist torque command value I _M ^* and the motor angular velocity ω.

Next, the operation of the first embodiment will be described.
Now, when the battery 25 is operating normally, power is supplied from the battery 25 to the electric motor 12 and various electrical equipment 27, and audio equipment, air conditioning equipment, and various lamps are activated, and safe driving is performed. As well as being secured, the interior environment of the vehicle is kept good. At this time, the alternator 26 is actuated by the rotation of the engine (not shown), and the battery 25 is charged by the power generation output. Therefore, the output voltage of the battery 25 is kept substantially constant, and is supplied to the electric motor 12 and the electrical equipment 27. Stable power supply.

Further, when the battery 25 is normal, no control switching instruction is issued from the suppliable power determining unit 40, so the current command value determining unit 31 proceeds from step S1 in FIG. 3 to step S3 through step S2. The required torque Treq, which is the steering torque T limited according to the output characteristics of the electric motor 12, is set as the target steering torque T ^*, and the d-axis and q-axis current command values Id ^* that can generate the target steering torque T ^{* .} It calculates the Iq ^* (step S4, S5). As a result, a steering assist torque corresponding to the steering torque T is generated from the electric motor 12, and the driver can perform light steering.

  If an abnormality occurs in the battery 25 from this state, this is detected by the battery monitoring unit 39, and the suppliable power determining unit 40, based on the engine rotational speed Ne at this time, from the 26 output characteristic map of the alternator, The amount of electric power Pw that can be output at present by the alternator 26 is estimated, and of this, the suppliable power Pmax that can be supplied to the electric motor 12 is estimated. Since a battery abnormality has occurred, a control switching instruction is issued, so that the current command value determination unit 31 proceeds from step S2 to step S6 in FIG. 3 and outputs suppliable power Pmax to the electric motor 12. It converts into possible torque Tmax, and this output possible torque Tmax is compared with required torque Treq.

At this time, the steering is not so much performed, and the required torque Treq falls below the outputable torque Tmax corresponding to the suppliable power Pmax, and a torque corresponding to the required torque Treq is generated within the range of the outputtable torque Tmax. Since it is possible, the process proceeds from step S7 to step S3, where the required torque Treq is set as the target steering torque T ^*, and control is performed so as to generate a steering assist force according to this. For this reason, even when an abnormality occurs in the battery 25, sufficient power supply to the electric motor 12 is continued by the power generation output of the alternator 26, and the driver can perform light steering. In addition, since various types of electrical equipment 27 are supplied with power to such an extent that the functionality of the electrical equipment 27 does not deteriorate, the functions of the various electrical equipment 27 are not impaired.

Thus, when the abnormality is occurring in the battery 25, the driver performs a relatively large steering operation, the required torque Treq becomes a relatively large value, and when this exceeds the outputable torque Tmax, the process proceeds from step S7 to step S8. migrated, possible output torque tmax is set as the target steering torque ^{T *.}
Then, a current command value is calculated according to the target steering torque T ^* thus limited (steps S9 and S10), the d-axis current command value is set to Id ^* = 0, and the q-axis current command value Iq ^*. Is calculated and set to a value capable of generating a torque corresponding to the target steering torque T ^* . The electric motor 12 is driven and controlled in accordance with the d-axis and q-axis current target values Id ^* and Iq ^* .

  At this time, an abnormality has occurred in the battery 25, and the total amount of electric power supplied to the electric motor 12 and various electric equipments 27 has decreased, but the electric motor is secured while ensuring the electric power supplied to the electric equipment 27. Since the electric power supply to 12 is restricted, the electric motor 12 can be operated to generate a steering assist force while avoiding a significant decrease in the function of the various electrical equipment 27. As described above, since the amount of power supplied to the electric motor 12 is limited, the generated steering assist force is suppressed, but the steering assist force is suppressed, but the steering assist force can be generated. Therefore, although there is some possibility that the driver feels that the steering assist force is insufficient, the driver can continue to perform light steering.

At this time, although the target steering torque T ^* is limited to the output possible torque Tmax, Id = 0 control of the electric motor 12 is performed so as to achieve high efficiency operation. Obtainable.
Further, the motor output determination unit 40b calculates the suppliable power Pmax by multiplying the power amount Pw that can be output by the alternator 26 by a gain equivalent to a margin, and the electric power Pw at the alternator 26 is Since the amount of power supplied to the electric motor 12 is reduced while securing the supply power for the device 27, the electric motor 12 and the electrical equipment 27 can be operated without significant deterioration in their functions. it can.

  In addition, although the motor output determination unit 40b has been described with respect to the case where the motor output determination unit 40b is set with the suppliable power Pmax by multiplying the gain corresponding to the margin, for example, the power amount Pw that can be output by the alternator 26 And the minimum amount of electric power required to execute the function that should be realized at least by the electrical equipment 27, and the remaining electric power is ensured and the remainder is set as electric power that can be supplied to the electric motor 12. May be.

Next, a second embodiment of the present invention will be described.
The second embodiment is the same as the first embodiment except that the processing in the steering assist torque command value calculation unit 31a of the current command value determination unit 31 is different. The detailed explanation is omitted.
In the second embodiment, the steering assist torque command value calculation unit 31a detects the abnormality of the battery 25, the electric motor 12 side with respect to the torque limit value Treq limited according to the output characteristics of the motor. The output fluctuation suppression process is performed to suppress fluctuations in the power supply voltage accompanying fluctuations in the amount of supplied power requested in step (b).

FIG. 5 is a block diagram illustrating a functional configuration of a processing unit that performs output fluctuation suppression processing in the steering assist torque command value calculation unit 31a. That is, the multiplier 101 that multiplies the required torque Treq and the motor angular speed ω to convert the motor required output Pm corresponding to the required torque Treq, the delay circuit 102 that receives the motor required output Pm that is the output of the multiplier 101, The subtracter 103 that subtracts the motor request output Pm (n−1) at the previous sampling time that is the output of the delay circuit 102 from the motor request output Pm (n), and the motor that is the output of the subtractor 103. A rate limiter 104 that suppresses the change amount of the motor request output Pm according to the change amount dPm / dt of the request output Pm, and a target motor request output Pm ^* that is a motor request output whose change amount is limited by the rate limiter 104 is 1 And a multiplier 105 that multiplies / ω (ω is a motor angular velocity) and converts it to a fluctuation suppression torque Tm ^* .

In the rate limiter 104, as shown in the control map in FIG. 5, when the absolute value of the change amount dPm / dt of the motor request output Pm is larger than a preset threshold value ΔPlim, the change amount dPm / dt is set to ΔPlim. Restrict to. That is, when the change amount dPm / dt of the motor request output Pm is equal to or less than the threshold value ΔPlim, the motor request output Pm is set as the target motor request output Pm ^* as it is. On the other hand, when the change amount dPm / dt of the motor request output Pm is larger than the threshold value ΔPlim, a value obtained by adding the threshold value ΔPlim to the previous target motor request output Pm ^* (n−1) is set as a new target motor request output Pm ^*. (N).

Then, the steering assist torque command value calculation unit 31a calculates the steering assist torque command value I _M ^* based on one of the required torque Treq and the fluctuation suppression torque Tm ^* according to the control switching command Sc, and performs control. When no control switching instruction is issued by the switching command Sc and no abnormality has occurred in the battery 25, the steering assist torque command value I _M ^* is calculated based on the required torque Treq, and the control switching instruction is issued by the control switching command Sc. cage, when an abnormality in the battery 25 occurs, calculates a steering assist torque command value I _M ^* using the change inhibition torque Tm ^*.

FIG. 6 is a flowchart illustrating an example of a processing procedure of the current command value determination unit 31 according to the second embodiment. In addition, the same code | symbol is provided to the same process as the electric current command value determination part 31 in the said 1st Embodiment.
That is, when the battery 25 is normal, it is the same as in the first embodiment, and after limiting the steering torque T according to the motor characteristics (step S1), the d-axis corresponding thereto and the current command value of the q-axis Id ^* and calculates the Iq ^* (step S2 to S5).

  On the other hand, if a battery abnormality has occurred, the process proceeds from step S2 to step S20, and the output suppression variation process shown in FIG. 7 is performed on the required torque Treq limited in accordance with the motor characteristics. That is, first, in step S21, the required motor torque Preq and the motor angular velocity ω are multiplied to calculate the required motor output Pm required for the electric motor 12 to generate a torque equivalent to the required torque Treq. It is determined whether or not the absolute value of the change amount dPm / dt is equal to or greater than the threshold value ΔPlim (step S22).

The threshold value ΔPlim is a value that is set according to the output characteristics of the alternator 26. In order to cause the electric motor 12 to generate a steering assist torque that corresponds to the current required torque Treq, this threshold value ΔPlim is used. Even if it is supplied to the electric motor 12, the power supply voltage is set to a value that can be regarded as small, and is set according to the output characteristics of the alternator 26.
When the absolute value of the change amount dPm / dt of the motor request output Pm is smaller than the threshold value ΔPlim, that is, the amount of change in the motor request output Pm is small, and the steering assist torque corresponding to the request torque Treq is generated. If it is predicted that the power supply voltage will not fluctuate even if the electric power is supplied to the electric motor 12, the process proceeds to step S23, and the motor request output Pm calculated in step S21 is directly used as the target motor request. Set as output Pm ^* .

On the other hand, the absolute value of the change amount dPm / dt of the motor required output Pm is equal to or greater than the threshold value ΔPlim, the amount of change in the motor required output Pm is large, and electric power is generated to generate the steering assist torque corresponding to the required torque Treq. When power supply to the motor 12 is performed, when it is predicted that the power supply voltage fluctuates, the process proceeds to step S24, and the threshold value ΔPlim is set to the previous value Pm ^* (n−1) of the target motor request output Pm ^*. The added value is set as the current target motor request output Pm ^* (n).
Then, the process proceeds to step S25, the target motor required output Pm ^* set in step S23 or step S24 is divided by the motor angular velocity ω, and a fluctuation suppression torque Tm ^* , which is a torque corresponding to the motor required output Pm ^* , is calculated. To do.

Then, returning to FIG. 6, the process proceeds to step S <b> 6, and after the suppliable power Pmax determined by the suppliable power determination unit 40 is converted into the outputable torque Tmax, the process proceeds to step S <b> 7 a, The variation suppression torque Tm ^* is compared. If the variation suppression torque Tm ^* is equal to or greater than the outputtable torque Tmax, the process proceeds to step S8, where the outputable torque Tmax is set as the target steering torque T ^* . That is, the fluctuation suppression torque Tm ^* is limited to the outputtable torque Tmax. On the other hand, when the fluctuation suppression torque Tm ^* is smaller than the outputtable torque Tmax, the process proceeds to step S8a, and the fluctuation suppression torque Tm ^* is set as the target steering torque T ^* as it is.

Then, using the target steering torque ^{T *} that is set by the processing in step S8 or step S8a to calculate the steering assist torque command value _I ^{M *} (step S9), and the d-axis current command value, as ^Id * = 0, the steering calculating the corresponding auxiliary torque command value _I ^{M *} q-axis current command value Iq ^*.
Therefore, in this second embodiment, for example, when sudden steering is performed, as shown by a broken line in FIG. Since the power fluctuation increases, the power fluctuation to be supplied to the electric motor 12 also increases.

Here, when an abnormality has occurred in the battery 25, the power supplied to each part is covered mainly by the output of the alternator 26. Depending on the output characteristics of the alternator 26, the fluctuation of the power supplied to the electric motor 12 is varied. There is a possibility that the power supply voltage fluctuates.
However, when the fluctuation amount of the steering torque T is large and the electric power fluctuation to be supplied to the electric motor 12 is predicted to be large, the electric power fluctuation amount is set to be equal to or less than the threshold value ΔPlim as shown by a solid line in FIG. Since it is limited, fluctuations in the power supply voltage that accompany changes in the amount of power supplied to the electric motor 12 can be suppressed.

  Therefore, even when an abnormality occurs in the battery 25, as in the first embodiment, power is supplied to each part without significant functional deterioration of the electric motor 12 and the various electrical devices 27. In addition, even when the power supply fluctuation is large, such as when sudden steering is performed, it is possible to suppress fluctuations in the power supply voltage and perform stable power supply.

  In each of the above embodiments, the case where the power supplied to the electric motor 12 is limited when an abnormality occurs in the battery 25 has been described. However, the present invention is not limited to this, and the case where the battery 25 is normal. It is also possible to apply. For example, when using the car audio, car navigation, air conditioning equipment, lights, etc., when the steering wheel 1 is steered, the electric motor 12 as shown in the first or second embodiment. By limiting the power supply to the power supply, fluctuations in the power supply voltage due to the electric power steering device can be suppressed.

In each of the above embodiments, the case where the motor control device according to the present invention is applied to an electric power steering device has been described. However, the present invention is not limited to this, and power is supplied from a power supply source including an alternator. Even an electric motor control device that operates can be applied.
In each of the above embodiments, the alternator 26 corresponds to the power generation means, the battery 25 corresponds to the power storage means, and the battery 25 and the alternator 26 correspond to the power supply source.

3 corresponds to the torque target value detection means, the suppliable power determination unit 40 corresponds to the suppliable power estimation means, and the processing from step S6 to step S8 in FIG. 3 corresponds to the output torque limiting means. And the processes of steps S4 and S5 and steps S9 and S10 correspond to the motor control means.
Further, corresponding to the motor distribution amount estimating means of the motor output determining section 40b of the suppliable power determining section 40, the process of step S6 in FIG. 3 corresponds to the output possible torque estimating means.
Further, step S21 and step S22 in FIG. 7 correspond to the power change amount estimating means.
Further, the battery monitoring unit 39 corresponds to the abnormality detecting means, and the engine speed sensor 45 corresponds to the engine speed detecting means.

It is a schematic block diagram which shows one Embodiment at the time of applying this invention to an electric power steering apparatus. It is a functional block diagram which shows the specific structure of the controller of FIG. It is a flowchart which shows an example of the process sequence of the arithmetic processing in the electric current command value determination part in 1st Embodiment. It is a flowchart which shows an example of the process sequence of the motor characteristic limitation process of FIG. It is a block diagram which shows the function structure of the process part which performs the output fluctuation suppression process in 2nd Embodiment. It is a flowchart which shows an example of the process sequence of the arithmetic processing in the electric current command value determination part in 2nd Embodiment. It is a flowchart which shows an example of the process sequence of the output fluctuation suppression process of FIG. It is explanatory drawing with which it uses for operation | movement description of 2nd Embodiment.

Explanation of symbols

3 Steering torque sensor 12 Electric motor 20 Control unit 21 Vehicle speed sensor 25 Battery 26 Alternator 27 Electrical equipment 31 Current command value determination unit 37 Motor rotation angle detection unit 39 Battery monitoring unit 40 Supplyable power determination unit

Claims (10)

A method for controlling an electric motor that operates with power supplied from a power supply source including at least power generation means,
A method for controlling an electric motor, wherein power that can be supplied by the power generation means is estimated, and a command power amount that is a command value of power consumed by the electric motor is limited according to the estimated power that can be supplied. In a motor control device for an electric motor that operates with power supplied from a power supply source including at least power generation means,
Torque target value detection means for detecting a target value of output torque to be output by the electric motor;
Suppliable power estimating means for estimating the power that can be supplied by the power generating means;
Output torque limiting means for limiting the torque target value detected by the torque target value detection means according to the supplyable power estimated by the supplyable power estimation means;
A motor control device comprising: motor control means for driving and controlling the electric motor based on a torque target value restricted by the output torque restriction means. The output torque limiting unit includes a motor distribution amount estimation unit that estimates a power amount that can be distributed to the electric motor among the supplyable power based on the supplyable power estimated by the supplyable power estimation unit,
3. The motor control device according to claim 2, wherein the torque target value is limited to a torque value corresponding to a motor distribution amount to the electric motor estimated by the motor distribution amount estimation means. The output torque limiting unit is configured to supply power corresponding to the motor distribution amount to the electric motor from the motor distribution amount estimated by the motor distribution amount estimation unit and the motor angular velocity detected by the motor angular velocity detection unit. An outputable torque estimating means for estimating a torque generated from the electric motor;
4. The motor control according to claim 3, wherein the torque target value detected by the torque target value detecting means is limited to a threshold value set in accordance with the outputable torque estimated by the outputable torque estimating means. apparatus. The output torque limiting means includes power change amount estimation means for estimating a change amount of power supplied to the electric motor from a change amount of the torque target value detected by the torque target value detection means,
When the power change amount estimated by the power change amount estimating means is greater than or equal to a preset threshold value, the torque target value detected by the torque target value detecting means is determined so that the change amount is less than or equal to the threshold value. 5. The motor control device according to claim 2, wherein the limited value is set as a new torque target value. 6.   3. The motor control unit according to claim 2, wherein when the torque target value is limited to a value smaller than this, the d-axis current to the electric motor is set to zero and only the q-axis current is controlled. 6. The motor control device according to any one of items 5.   The motor control apparatus according to any one of claims 2 to 6, wherein the power supply source supplies power to the electric motor and other electrical equipment. The power supply source includes the power generation means and a power storage means charged by the power generation means,
An abnormality detection means for detecting an abnormality of the power storage means,
The said motor control means performs the restriction | limiting with respect to the torque target value detected by the said target value detection means, when the abnormality of the said electrical storage means is detected by the said abnormality detection means. The motor control device according to any one of the above.   An electric power steering apparatus, wherein the motor control apparatus according to any one of claims 1 to 8 is applied as a motor control apparatus for an electric motor that applies a steering assist force to a steering system. The power generation means is an alternator that operates according to the rotational output of the engine,
An engine speed detecting means for detecting the engine speed;
The electric power steering apparatus according to claim 9, wherein the suppliable power estimating means estimates the suppliable electric power of the alternator based on the engine speed detected by the engine speed detecting means.

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