JP2012236531A - Electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric power steering device capable of accurately calculating a resistance value of a motor for imparting an assist force to a steering system.SOLUTION: The electric power steering device calculates an estimated induced voltage EXa by a disturbance observer based on an electric current value Im and a voltage value Vm, and also calculates the resistance value based on the electric current value Im and the voltage value Vm when the estimated induced voltage EXa falls within a predetermined range, and further corrects an arithmetic operation expression of the disturbance observer based on the voltage value Vm (the past voltage value) acquired before the last acquired voltage value Vm and the electric current value Im (the past electric current value) acquired before the last acquired electric current value Im.

Description

  The present invention relates to an electric power steering apparatus including a motor that applies assist force to a steering system.

As said electric power steering apparatus, the thing of patent document 1 is mentioned, for example.
In this device, in torque assist control in which torque is applied to the steering system by the motor, the motor is controlled using the rotational angular velocity ω of the motor calculated by the following equation (A).

ω = (Vm−R × Im) / Ke (A)

In the above, “Vm” represents a motor voltage value, “R” represents a motor resistance value, “Im” represents a motor current value, and “Ke” represents a counter electromotive force constant.

  The motor current and voltage are acquired when calculating the rotational angular velocity ω of the motor. The resistance value is calculated based on a map that defines the relationship between the motor current value and the resistance value.

JP 2004-66999 A

  In the electric power steering apparatus, since the estimation accuracy of the rotational angular velocity ω of the motor greatly affects the control of the motor for torque assist control, it is required to accurately estimate the rotational angular velocity ω.

  On the other hand, the resistance value of the motor is different for each motor. The reason is that the resistance value changes under the influence of at least one of the temperature of the motor itself and the ambient temperature. In addition, there are individual differences for each motor, and changes over time with the use of the motor.

  However, in the electric power steering apparatus of Patent Document 1, the difference in resistance value for each motor due to the above reasons is not taken into consideration, and therefore the resistance value calculated based on the map is the actual resistance value. There is a risk of a major departure from When the calculated resistance value is greatly deviated from the actual resistance value, the calculation accuracy of the rotational angular velocity ω of the motor is lowered.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an electric power steering apparatus capable of accurately calculating the resistance value of a motor that applies assist force to a steering system. It is in.

In the following, means for achieving the above object and its effects are described.
(1) According to the first aspect of the present invention, in the electric power steering apparatus including a motor that applies assist force to the steering system, a value indicating the magnitude of the current of the motor is a current value, and the magnitude of the voltage of the motor A voltage value is a value indicating the resistance, a resistance value is a value indicating the magnitude of the resistance of the motor, and the induced voltage of the motor is calculated by applying the current value and the voltage value to the induced voltage calculation means, When the induced voltage is within a predetermined range, the resistance value is calculated based on the current value and the voltage value, and the last acquired current value among the plurality of current values is used as a reference current value. The current value acquired before this reference current value is the past current value, and the voltage value acquired last among the plurality of voltage values is the reference voltage value, and the voltage acquired before this reference voltage value The value As a voltage value, and summarized in that to correct the induced voltage calculation means, based the at least one past current value and the previous voltage value.

  The induced voltage calculation means for calculating the resistance value of the motor includes terms of a motor current value, a voltage value, and an induced voltage. On the other hand, since the induced voltage changes as a part of the motor voltage, it is difficult to accurately estimate the induced voltage by separating it from the motor voltage. Therefore, in order to accurately calculate the resistance value of the motor, when the induced voltage is sufficiently small in relation to the estimated accuracy of the resistance value, that is, when the induced voltage is “0” or in the vicinity thereof, the resistance value of the motor Is preferably calculated.

  In the above invention, since the resistance value is calculated based on the current value and the voltage value, the change in the resistance value at that time during the operation of the electric power steering apparatus can be reflected in the control of the motor. Further, since the resistance value of the motor is calculated when the induced voltage is within a predetermined range, that is, when the induced voltage is sufficiently small, the estimation accuracy of the resistance value is increased. In addition, since the induced voltage is calculated based on at least one of the past current value and the past voltage value, that is, the induced voltage reflects at least one of the past current value and the past voltage value that affects the induced voltage of the motor. Therefore, the estimation accuracy of the induced voltage is increased.

  (2) The invention according to claim 2 is the electric power steering apparatus according to claim 1, wherein a period for acquiring the current value is a current acquisition period, and a period for acquiring the voltage value is a voltage. The gist is that at least one of the current acquisition cycle and the voltage acquisition cycle is shorter than the calculation cycle, where the acquisition cycle is the calculation cycle.

  In the above invention, in order to obtain the current value or voltage in a cycle shorter than the computation cycle, in comparison with the configuration for obtaining at least one of the current value and the voltage value for each computation cycle and calculating the induced voltage based on this, At least one of the current value and the voltage value acquired at a time closer to the calculation cycle this time can be reflected in the calculation of the induced voltage. For this reason, the estimation accuracy of the induced voltage is further improved.

  (3) The invention according to claim 3 is the electric power steering device according to claim 1 or 2, wherein the induction is based on at least one of the change pattern of the past current value and the change pattern of the past voltage value. The gist is to calculate a correction value for correcting the voltage calculation means.

  In the above invention, the change in the past current value or the change in the past voltage value is patterned, and the correction value of the induced voltage calculation means is calculated based on this pattern. This can be reflected in the calculation, thereby further increasing the estimation accuracy of the induced voltage.

  (4) The invention according to claim 4 is the electric power steering apparatus according to claim 3, wherein a disturbance observer is used as the induced voltage calculation means. In the calculation of the disturbance observer, the past current value and the past An intermediate variable is calculated based on a voltage value, and at least one of the past current value and the past voltage value used for calculating the intermediate variable is corrected as a correction term for correcting the induced voltage calculation means. The gist is to calculate the correction term.

  In the above invention, the correction value for correcting at least one of the past current value and the past voltage value is calculated, that is, the influence of the at least one value on the induced voltage is corrected by the correction value. The estimation accuracy of becomes higher.

  (5) The invention according to claim 5 is the electric power steering device according to claim 3 or 4, wherein a disturbance observer is used as the induced voltage calculation means, and the intermediate variable and the reference are used in the calculation of the disturbance observer. Calculating the induced voltage based on at least one of a current value and the reference voltage value, and as a correction term for correcting the induced voltage calculation means, the reference current value used for calculating the induced voltage and The gist is to calculate a correction term for correcting at least one of the reference voltage values.

  In the above invention, the correction value for correcting at least one of the reference current value and the reference voltage value is calculated, that is, the influence of the at least one value on the induced voltage is corrected by the correction value. The estimation accuracy of becomes higher.

  (6) The invention according to claim 6 is the electric power steering apparatus according to any one of claims 1 to 5, wherein an average value of the plurality of past voltage values is defined as a voltage average value, and the plurality of past Of the voltage values, the difference between the last acquired past voltage value and the voltage average value is a past voltage value difference, and the difference between the reference voltage value and the voltage average value is a reference voltage value difference. The gist is that at least one of the difference and the reference voltage value difference is used to calculate the induced voltage.

  In the electric power steering apparatus, since the voltage of the motor vibrates, the reference voltage value may not appropriately reflect the state of the motor. In the above invention, since at least one of the past voltage value difference and the reference voltage value difference is used in the calculation of the induced voltage, that is, since the magnitude of the past voltage value is reflected in the calculation of the induced voltage, the estimation of the induced voltage is performed. The accuracy is higher.

  (7) The invention according to claim 7 is the electric power steering apparatus according to any one of claims 1 to 6, wherein an average value of the plurality of past current values is defined as a current average value, and the plurality of past Of the current values, the difference between the past current value acquired last and the current average value is a past current value difference, and the difference between the reference current value and the current average value is a reference current value difference. The gist is that at least one of the difference and the reference current value difference is used for calculation of the induced voltage.

  In the electric power steering apparatus, since the motor current vibrates, the reference current value may not appropriately reflect the state of the motor. In the above invention, since at least one of the past current value difference and the reference current value difference is used in the calculation of the induced voltage, that is, the magnitude of the past current value is reflected in the calculation of the induced voltage, the estimation of the induced voltage is performed. The accuracy is higher.

  (8) The invention according to claim 8 is the electric power steering device according to any one of claims 1 to 7, wherein a period for acquiring the current value is defined as a current acquisition period. The gist is to change the current acquisition period based on the change.

  By reducing the current acquisition period, it is possible to increase the estimation accuracy of the induced voltage. On the other hand, the calculation load increases as the current acquisition cycle is reduced. In the above invention, since the current acquisition cycle is changed based on the change in the current value that affects the estimation accuracy of the induced voltage, it is possible to balance the estimation accuracy of the induced voltage and the calculation load.

  (9) According to the ninth aspect of the present invention, in the electric power steering apparatus according to the eighth aspect, the current acquisition cycle when the amount of change in the current value per unit time is greater than a predetermined amount of change is obtained as a current acquisition. Let the period A be the current acquisition period B when the change amount of the current value per unit time is smaller than the predetermined change amount, and make the current acquisition period A smaller than the current acquisition period B. This is the gist.

  In the above invention, when the change amount of the current value is larger than the predetermined change amount, that is, when the influence of the change of the current value on the estimation accuracy of the induced voltage is estimated to be large, the current acquisition cycle is set small. For this reason, it can suppress that the estimation precision of an induced voltage falls.

  (10) The invention according to claim 10 is the electric power steering apparatus according to any one of claims 1 to 9, wherein a period for acquiring the voltage value is defined as a voltage acquisition period. The gist is to change the voltage acquisition cycle based on the change.

  It is possible to increase the estimation accuracy of the induced voltage by reducing the voltage acquisition period. On the other hand, the calculation load increases as the voltage acquisition period decreases. In the above invention, since the voltage acquisition cycle is changed based on the change of the voltage value that affects the estimation accuracy of the induced voltage, it is possible to balance the estimation accuracy of the induced voltage and the calculation load.

  (11) According to an eleventh aspect of the present invention, in the electric power steering apparatus according to the tenth aspect, the voltage acquisition cycle when the change amount of the voltage value per unit time is larger than a predetermined change amount is acquired as a voltage. Let the period C be a voltage acquisition period D when the amount of change in the voltage value per unit time is smaller than the predetermined amount of change, and make the voltage acquisition period C smaller than the voltage acquisition period D. This is the gist.

  In the above invention, when the change amount of the voltage value is larger than the predetermined change amount, that is, when the influence of the change of the voltage value on the estimation accuracy of the induced voltage is estimated to be large, the voltage acquisition cycle is set small. For this reason, it can suppress that the estimation precision of an induced voltage falls.

  (12) The invention according to claim 12 is the electric power steering device according to any one of claims 1 to 11, wherein the calculation of the induced voltage calculation means includes the plurality of past current values. And, when at least one of the plurality of past current values includes an abnormal value, a process of subtracting an abnormal correction value based on the abnormal value from the calculation term, and the plurality of past current values The gist is to perform a process of adding an average correction value based on an average value to the calculation term, and to use the calculation term after the execution of these processes for the calculation of the induced voltage.

  In the electric power steering apparatus, the current value may indicate an abnormal value. When the induced voltage is calculated including the current value as an abnormal value, the estimation accuracy may be reduced. In the above invention, when the abnormal value is included in the past current value, the abnormality correction value is subtracted from the calculation term, so that the influence of the abnormal value on the calculation of the calculation term is reduced. Moreover, since the average correction value is added to the calculation term as a substitute value for the abnormal correction value, that is, the average correction value closer to the actual past current value than the current value as the abnormal value is reflected in the calculation value. Thus, the estimation accuracy of the induced voltage is suppressed from decreasing.

  (13) The invention according to claim 13 is the electric power steering device according to any one of claims 1 to 11, wherein a disturbance observer is used as the induced voltage calculation means, a plurality of the past current values, Calculating an intermediate variable of the current calculation cycle based on the plurality of past voltage values, the reference current value, and a previous intermediate variable that is an intermediate variable calculated in the previous calculation cycle; an operation including the plurality of past current values A term is included in the previous intermediate variable, and when an abnormal value is included in at least one of the plurality of past current values used in the calculation of the previous intermediate variable, the abnormality correction value based on the abnormal value is After performing a process of subtracting from the calculation term and a process of adding an average correction value based on an average value of the plurality of past current values to the calculation term, and executing these processes And summarized in that the use of the calculation terms for the calculation of the intermediate variables of the current calculation cycle.

  In the above invention, when an abnormal value is included in at least one of the plurality of past current values used in the previous calculation of the intermediate variable, the abnormality correction value based on the abnormal value is subtracted from the calculation term, and an average of the plurality of past current values is obtained. The average correction value based on the value is added to the calculation term. Then, the calculation term obtained by these processes is used to calculate the intermediate variable of the current calculation cycle. Thereby, since the average correction value closer to the actual past current value than the current value as the abnormal value is reflected in the calculated value, it is possible to suppress the estimation accuracy of the induced voltage from being lowered.

  (14) The invention according to claim 14 is the electric power steering device according to claim 12 or 13, wherein an average value of the plurality of past current values is a past average value, and one of the plurality of past current values is When the difference from the past average value is larger than the determination value, one of the past current values is determined as the abnormal value.

  In the above invention, when the difference between one of the plurality of past current values and the past average value is larger than the determination value, one of the past current values is determined as an abnormal value, so that the abnormal value can be easily detected. it can.

The schematic diagram which shows typically the whole structure about the electric power steering apparatus of 1st Embodiment of this invention. The flowchart which shows the procedure of a resistance update process about the electric power steering apparatus of the embodiment. The graph which shows the relationship between the electric current value of a motor, and the calculation period of an estimated induced voltage about the electric power steering apparatus of the embodiment. The pattern diagram which shows the change pattern of the electric current value of a motor about the electric power steering apparatus of the embodiment. The table which shows the relationship between the change pattern of the electric current value of a motor, and a correction value about the electric power steering apparatus of the embodiment. The flowchart which shows the procedure of an induced voltage estimation process about the electric power steering apparatus of the embodiment. The graph which shows the relationship between the voltage value of a motor, and an average value about the electric power steering apparatus of 2nd Embodiment of this invention. The flowchart which shows the procedure of an induced voltage estimation process about the electric power steering apparatus of the embodiment. Regarding the electric power steering apparatus according to the third embodiment of the present invention, (A) is a graph showing a sampling period when the change in the motor current value is small, and (B) is a sampling period when the change in the motor current value is large. Graph showing. The graph which shows the change of the voltage value of a motor about the electric power steering apparatus of 4th Embodiment of this invention. The block diagram which shows the calculation process of an estimated induced voltage about the electric power steering apparatus of the embodiment.

(First embodiment)
A first embodiment of the present invention will be described with reference to FIGS.
The electric power steering apparatus 1 includes a steering angle transmission mechanism 10 that transmits the rotation of the steering wheel 2 to the steered wheels 3 and a force for assisting the operation of the steering wheel 2 (hereinafter referred to as “assist force”). An EPS actuator 20 to be applied and an electronic control unit 30 for controlling the EPS actuator 20 are provided. Furthermore, the electric power steering apparatus 1 is provided with a plurality of sensors for detecting the operating state of these apparatuses.

  The steering angle transmission mechanism 10 operates a steering shaft 11 that rotates together with the steering 2, a rack and pinion mechanism 12 that transmits the rotation of the steering shaft 11 to the rack shaft 13, a rack shaft 13 that operates the tie rod 14, and a knuckle. And a tie rod 14.

  The EPS actuator 20 includes a motor 21 that applies torque to the steering shaft 11 and a speed reduction mechanism 22 that reduces the rotation of the motor 21. As the motor 21, a motor 21 with a brush is employed. The rotation of the motor 21 is decelerated by the speed reduction mechanism 22 and transmitted to the steering shaft 11. At this time, torque applied from the motor 21 to the steering shaft 11 acts as an assist force.

  The steering angle transmission mechanism 10 operates as follows. That is, when the steering 2 is operated, an assist force is applied to the steering shaft 11 and the shaft 11 rotates. The rotation of the steering shaft 11 is converted into a linear motion of the rack shaft 13 by the rack and pinion mechanism 12. The linear motion of the rack shaft 13 is transmitted to the knuckle through tie rods 14 connected to both ends of the rack shaft 13. And the rudder angle of the steered wheel 3 is changed with operation | movement of a knuckle.

  The steering angle of the steering 2 is determined with reference to when the steering 2 is in the neutral position. That is, the steering angle when the steering 2 is in the neutral position is set to “0”, and when the steering 2 rotates to the right or left from the neutral position, the steering angle increases according to the rotation angle from the neutral position.

  The steering state of the steering wheel 2 is classified into three types: a “rotation state”, a “neutral state”, and a “steering state”. “Rotating state” indicates a state in which the steering wheel 2 is rotating. The “neutral state” indicates a state in which the steering 2 is in the neutral position. The “steering state” indicates a state in which the steering 2 is in a position rotated rightward or leftward from the neutral position and is held at that position.

  The electric power steering apparatus 1 is provided with a torque sensor 31 for detecting the torque of the steering 2 and a vehicle speed sensor 32 for detecting the vehicle speed as a plurality of sensors. Each of these sensors outputs a signal corresponding to a change in the state of the monitoring target as follows.

  The torque sensor 31 outputs a signal (hereinafter, “output signal SA”) corresponding to the magnitude of torque applied to the steering shaft 11 by the operation of the steering 2 to the electronic control unit 30. The vehicle speed sensor 32 outputs a signal corresponding to the rotational angular velocity of the steered wheels 3 (hereinafter, “output signal SB”) to the electronic control unit 30. The vehicle speed sensor 32 is provided corresponding to each rear wheel.

The electronic control unit 30 calculates the following calculated values based on the output of each sensor.
Based on the output signal SA of the torque sensor 31, a calculated value (hereinafter referred to as “steering torque τ”) corresponding to the magnitude of torque input to the steering shaft 11 as the steering 2 is operated is calculated. Based on the output signal SB of the vehicle speed sensor 32, that is, based on the output signal SB output corresponding to each rear wheel, a calculated value (hereinafter referred to as “vehicle speed V”) corresponding to the traveling speed of the vehicle is calculated.

  Further, the electronic control unit 30 performs power assist control for adjusting the assist force based on a correction value of the vehicle speed V and the steering torque τ (hereinafter, “corrected steering torque τa”), the vehicle speed V, the corrected steering torque τa, and Steering torque shift control for calculating the corrected steering torque τa based on the rotational angular velocity ωm of the motor 21 is performed.

  The rotational angular velocity ωm used in the steering torque shift control is calculated based on the following equation (1) as a motor equation.

・「Ｖｍ」は、モータの電圧値（以下、「電圧値Ｖｍ」）を示す。
・「Ｉｍ」は、モータの電流値（以下、「電流値Ｉｍ」）を示す。
・「Ｒｍ」は、モータの抵抗値（以下、「抵抗値Ｒｍ」）を示す。
・「Ｋｅ」は、逆起電力定数を示す。

“Vm” indicates a voltage value of the motor (hereinafter, “voltage value Vm”).
“Im” indicates a current value of the motor (hereinafter, “current value Im”).
“Rm” represents a resistance value of the motor (hereinafter, “resistance value Rm”).
“Ke” indicates a back electromotive force constant.

  As the back electromotive force constant Ke, a value corresponding to the back electromotive force constant Ke unique to the motor 21 is used. The value of the back electromotive force constant Ke is set in advance and stored in the storage unit of the electronic control device 30. As the resistance value Rm, a value stored in the storage unit of the electronic control device 30 is used. This resistance value Rm is periodically updated.

The reason why the resistance value Rm of the motor 21 is updated is as follows.
The resistance value Rm of the motor 21 changes depending on the use for many years or the ambient temperature. For this reason, the actual resistance value Rm of the motor 21 may deviate from the value initially stored in the storage unit. For this reason, the resistance value Rm is updated in order to make the resistance value Rm stored in the storage unit close to the actual resistance value Rm.

The resistance value Rm is calculated as follows.
When the induced voltage is “0”, the resistance value at that time is expressed by Expression (2). Then, the actual resistance value Rm can be calculated based on the current value Im and the voltage value Vm.

誘起電圧ＥＸが略「０」と判定することができる状態を、抵抗値Ｒｍを算出することが可能な状態ということができるため、以降の説明では、この状態を「抵抗算出可能状態」という。

A state in which the induced voltage EX can be determined to be substantially “0” can be referred to as a state in which the resistance value Rm can be calculated. In the following description, this state is referred to as a “resistance calculation possible state”.

With reference to FIG. 2, the procedure of the resistance update process for updating the resistance value Rm of the motor 21 will be described. This process is repeatedly executed by the electronic control unit 30 at predetermined intervals.
In step S110, an induced voltage estimation process for calculating the induced voltage EX is executed. In step S120, resistance calculation availability determination processing is executed. In step S130, motor resistance calculation processing is executed. In the following description, the induced voltage EX calculated by the induced voltage estimation process is referred to as “estimated induced voltage EXa”.

  In the resistance calculation availability determination process, it is determined whether or not the estimated induced voltage EXa is smaller than the determination value VTA. When this determination is affirmative, it is determined that the motor 21 is in a resistance calculation enabled state. In this case, resistance update processing is performed. On the other hand, when the estimated induced voltage EXa is equal to or higher than the determination value VTA, it is determined that the motor 21 is not in a resistance calculation possible state. In this case, the resistance update process is not performed, and the resistance value Rm of the motor 21 at that time is maintained.

  In the motor resistance calculation process, the average value Iave of the current value Im of the motor 21 is calculated, the average value Vave of the voltage value Vm is calculated, and the resistance value Rm is calculated based on the equation (2). When the difference between the newly calculated resistance value Rm and the resistance value Rm stored in the storage unit exceeds the allowable value AX, the newly calculated resistance value Rm indicates the actual resistance of the motor 21. Remember as. On the other hand, when the difference between the newly calculated resistance value Rm and the resistance value Rm stored in the storage unit does not exceed the allowable value AX, the resistance value Rm stored in the storage unit is maintained.

Next, a method for calculating the estimated induced voltage EXa will be described.
Since the induced voltage EX is generated as a counter electromotive voltage with respect to the voltage between the terminals of the motor 21, the induced voltage EX cannot be detected independently. Therefore, the induced voltage EX is regarded as a disturbance in the control of the motor 21, and the induced voltage EX is calculated using a disturbance observer (induced voltage calculation means).

  The estimated induced voltage EXa is given by the following equation.

・「ξ」は、中間変数を示す。
・「Ｇ」は、オブザーバゲイン（固定値）。
・「Ｉｍ（ｎ）」は、ｎ周期目演算時のモータ２１の電流値（基準電流値）。
・「Ａ_１１」は、所定の行列定数。
・「Ａ_１２」は、所定の行列定数。
・「Ｂ_１」は、所定の行列定数。
・「Ｔｓ」は、推定誘起電圧ＥＸａの演算の演算周期。
・「Ｉｅ」は、単位行列。
・「ｎ」は、初回の演算をｎ＝１としてｎ周期目の演算回数を示す。
・「Ｖｍ（ｎ）」は、ｎ周期目演算時のモータ２１の電圧値。
・「Ｉｍ（ｎ）」は、ｎ周期目演算時のモータ２１の電流値。

“Ξ” represents an intermediate variable.
“G” is the observer gain (fixed value).
“Im (n)” is a current value (reference current value) of the motor 21 at the time of calculation in the nth cycle.
“A ₁₁ ” is a predetermined matrix constant.
“A ₁₂ ” is a predetermined matrix constant.
“B ₁ ” is a predetermined matrix constant.
“Ts” is the calculation cycle of the calculation of the estimated induced voltage EXa.
“Ie” is a unit matrix.
“N” indicates the number of calculations in the nth period, where n = 1 is the first calculation.
“Vm (n)” is the voltage value of the motor 21 at the time of the nth cycle calculation.
“Im (n)” is a current value of the motor 21 at the time of calculation in the nth cycle.

  The current value Im (n) is the last acquired among the stored current values Im and corresponds to the reference current value. The current value Im acquired before the current value Im (n) corresponds to the past current value. Vm (n) is the last acquired voltage value Vm stored, and corresponds to the reference voltage value. The voltage value Vm acquired before Vm (n) corresponds to the past voltage value.

  The disturbance observer calculates the estimated induced voltage EXa and the intermediate variable ξ (n) with a predetermined calculation cycle Ts. The estimated induced voltage EXa (n) includes an intermediate variable ξ (n) as a calculation element. The intermediate variable ξ (n) is based on the intermediate variable ξ (n−1) calculated at the previous calculation, and the voltage value Vm (n−1) and the current value Im (n−1) acquired at the previous calculation. Calculated.

  As described above, the estimated induced voltage EXa (n) is affected not only by the current value Im (n) at the time of the calculation but also by the current value Im and the voltage value Vm acquired before the time of the calculation. For this reason, the estimated induced voltage EXa can be made close to the actual induced voltage EX by shortening the calculation cycle and increasing the current value Im and the voltage value Vm. However, if the amount of information is increased, the computation processing of the computing device will not be in time, so there is a limit to shortening the computation cycle.

The relationship between the current value Im of the motor 21 and the calculation cycle Ts of the estimated induced voltage EXa will be described with reference to FIG.
As shown in the figure, the current value Im may fluctuate in a cycle shorter than the calculation cycle Ts of the estimated induced voltage EXa. In this case, if the current value Im is acquired only at the time of calculation, the change in the current value Im during the calculation cycle is not reflected in the estimated induced voltage EXa. Therefore, the estimated induced voltage EXa and the actual induced voltage are calculated. A deviation occurs from the voltage EX. As a result, it becomes difficult to accurately determine that the motor 21 is in the resistance calculation possible state, and the resistance value Rm becomes inaccurate.

  Therefore, the arithmetic expression (the above formulas (3) and (4)) of the estimated induced voltage EXa is corrected as follows using the correction value α and the correction value β.

補正値αと補正値βは、外乱オブザーバの演算式を補正するための値であり、所定演算時とこの演算時より後の所定演算時との間における電流値Ｉｍの変化パターンに関係する値として与えられる。

The correction value α and the correction value β are values for correcting the arithmetic expression of the disturbance observer, and are values related to a change pattern of the current value Im between a predetermined calculation and a predetermined calculation after this calculation. As given.

A method for determining a change pattern of the current value Im will be described with reference to FIGS.
In order to reflect the change in the current value Im during the calculation cycle in the calculation of the estimated induced voltage EXa, the sampling cycle of the current value Im is made shorter than the calculation cycle of the estimated induced voltage EXa. These current values Im are stored in the storage unit of the electronic control unit 30. Furthermore, the maximum value, the minimum value, the slope, the maximum value, and the minimum value of the current value Im are calculated based on the current value Im from the previous calculation time to the current calculation time, and the current is calculated based on these parameters. A change pattern of the value Im is determined.

Examples of patterns are given below.
As shown in FIG. 4, when there is one maximum value and one minimum value between the previous calculation and the current calculation, the change pattern of the current value Im is determined as the pattern A. When the maximum value is one between the previous calculation and the current calculation, the change pattern of the current value Im is determined as the pattern B. If there is one minimum value between the previous calculation and the current calculation, the change pattern of the current value Im is determined as the pattern C.

  As shown in FIG. 5, the correction value α and the correction value β are associated with a change pattern of the current value Im. Accordingly, the correction value α and the correction value β can be determined from the change pattern based on this table. Then, the estimated induced voltage EXa is calculated based on the above formulas (5) and (6) using the correction value α and the correction value β.

  The correction value α and the correction value β are calculated based on simulation. That is, the estimated induced voltage EXa is calculated by sufficiently shortening the calculation cycle of the estimated induced voltage EXa by a sufficiently high-speed and high-capacity calculation device that can follow the change in the induced voltage EX of the motor 21. These data are stored so that they can be reproduced as completely estimated data. On the other hand, the calculation cycle of the estimated induced voltage EXa is set relatively long, and the estimated induced voltage EXa is calculated by the above method using a plurality of types of patterns prepared in advance to obtain estimated data.

  Then, a correction value α and a correction value β are obtained for each pattern so that the complete estimation data and the estimation data are approximated. In this way, the correction value α and the correction value β for correcting the arithmetic expression of the disturbance observer so as to reduce the difference between the actual induced voltage EX and the estimated induced voltage EXa are obtained.

With reference to FIG. 6, the processing procedure of the induced voltage estimation processing will be described. Note that this processing is repeatedly executed by the electronic control device 30 every predetermined calculation cycle.
In step S210, the current value Im is acquired. In step S220, a parameter for determining a change pattern of the current value Im is calculated. That is, the maximum value, the minimum value, the slope, the maximum value, and the minimum value of the current value Im are calculated based on the accumulated data of the current value Im from the previous calculation time of the estimated induced voltage EXa to this point.

  In step S230, it is determined whether or not it is time to calculate the estimated induced voltage EXa. When it is time to calculate the estimated induced voltage EXa, the process proceeds to the next step. On the other hand, when it is not time to calculate the estimated induced voltage EXa, the process returns to step S210.

  In step S240, a change pattern of the current value Im is selected based on each parameter of the current value Im. In step S250, intermediate variable ξ and estimated induced voltage EXa are calculated using correction value α and correction value β corresponding to the selected pattern.

  Since the correction value α and the correction value β are values for correcting the arithmetic expression of the disturbance observer so as to reduce the difference between the actual induced voltage EX and the estimated induced voltage EXa, the correction value α and the correction value are corrected based on the change pattern. By determining the value β and using these values, the accuracy of the estimated induced voltage EXa can be increased. The correction value α and the correction value β are given as values corresponding to the change pattern of the current value Im sampled during the calculation cycle Ts, and the change pattern is identified by 1 during the calculation cycle Ts. Since it is performed once, the calculation load is not increased, so that the accuracy of the estimated induced voltage EXa can be increased without using a high-speed calculation device.

According to this embodiment, the following effects can be obtained.
(1) In the present embodiment, the resistance value Rm is calculated based on the current value Im and the voltage value Vm when the estimated induced voltage EXa is within a predetermined range, and the current value Im and the voltage value Vm acquired in the past are calculated. Based on this, the arithmetic expression is corrected.

  That is, since the resistance value Rm is calculated based on the current value Im and the voltage value Vm, the change in the resistance value Rm at that time can be reflected in the control of the motor 21 during the operation of the electric power steering apparatus 1. . Further, since the resistance value Rm is calculated when the estimated induced voltage EXa is within a predetermined range, that is, when the induced voltage EX is sufficiently small, the estimation accuracy of the resistance value Rm is increased.

  Further, since the estimated induced voltage EXa is calculated based on the current value Im and the voltage value Vm acquired in the past, that is, the past current value Im and the voltage value Vm that affect the estimated induced voltage EXa of the motor 21 are calculated. Since the estimated induced voltage EXa is calculated by reflecting it, the estimation accuracy of the estimated induced voltage EXa is increased.

  (2) In the present embodiment, the sampling period is made shorter than the calculation period. According to this configuration, the current value Im acquired at a time closer to the current calculation is compared with the configuration in which the current value Im is acquired at each calculation cycle and the estimated induced voltage EXa is calculated based on the current value Im. This can be reflected in the calculation of the voltage EXa. For this reason, the estimation accuracy of the estimated induced voltage EXa is further increased.

  (3) In the present embodiment, the correction value α and the correction value β for correcting the arithmetic expression are obtained based on the change pattern of the current value Im acquired in the past. In this configuration, the change in the past current value Im is patterned, and the correction value α and the correction value β of the arithmetic expression are selected based on the pattern. Therefore, the change in the past current value Im is calculated as the estimated induced voltage EXa. Thus, the estimation accuracy of the estimated induced voltage EXa is further improved.

  (4) In the present embodiment, in the disturbance observer calculation, the intermediate variable ξ is calculated based on the past current value Im and the past voltage value Vm. Then, in the disturbance observer, a correction value α for correcting a term (see formula (6)) constituted by the past current value Im and the past voltage value Vm is based on the change pattern of the past current value Im. Ask. Further, the influence of the past current value Im and the past voltage value Vm on the estimated induced voltage EXa is corrected by the correction value α. Thereby, since past information can be reflected in the calculation of the estimated induced voltage EXa, the estimation accuracy of the estimated induced voltage EXa can be further increased.

  (5) In this embodiment, in the disturbance observer calculation, the estimated induced voltage is calculated based on the intermediate variable ξ and the current value Im (reference current value) used for the current calculation. Then, in the disturbance observer, a correction value β for correcting the term of the current value Im (see Expression (5)) used for calculating the estimated induced voltage EXa is obtained based on the past change pattern of the current value Im. Then, the influence of the past current value Im and the past voltage value Vm on the estimated induced voltage EXa is corrected by the correction value β. Thereby, since past information can be reflected in the calculation of the estimated induced voltage EXa, the estimation accuracy of the estimated induced voltage EXa can be further increased.

(Second Embodiment)
A second embodiment of the present invention will be described with reference to FIGS.
The electric power steering apparatus 1 according to the present embodiment is modified as follows from the configuration of the first embodiment. That is, in order to improve the calculation accuracy of the estimated induced voltage EXa, in the first embodiment, the change pattern of the current value Im is grasped based on the data of the current value Im during the calculation cycle of the estimated induced voltage EXa, and this pattern. Based on the above, the arithmetic expression of the estimated induced voltage EXa is corrected.

  On the other hand, in this embodiment, the calculation accuracy of the estimated induced voltage EXa is increased by correcting the influence of the vibration of the voltage value Vm. Hereinafter, a detailed change from the configuration of the first embodiment that occurs with this change will be described. In addition, about the structure which is common in the said 1st Embodiment, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

With reference to FIG. 7, the fluctuation of the voltage value Vm will be described.
The estimated induced voltage EXa is calculated based on the voltage value Vm and the current value Im as shown in the above formulas (3) and (4). However, since the voltage value Vm vibrates, if a value away from the average value of the voltage value Vm is used when calculating the induced voltage EX, an error occurs between the estimated induced voltage EXa and the actual induced voltage EX. . When such calculation is repeated, the estimated induced voltage EXa greatly deviates from the actual induced voltage EX. Therefore, when calculating the estimated induced voltage EXa, the arithmetic expression of the estimated induced voltage EXa is corrected based on the average value of the past voltage values Vm. Hereinafter, a specific correction method will be described.

The induced voltage estimation process will be described with reference to FIGS.
In step S310, the current value Im is acquired. Next, in step S320, the voltage average value Vmat of the voltage value Vm from the (n−m1−m2) period to the (n−m1) period before is calculated.

  In step S330, it is determined whether or not the estimated induced voltage EXa is being calculated. That is, it is determined whether or not the elapsed time from the previous calculation is the calculation cycle of the estimated induced voltage EXa. When the estimated induced voltage EXa is being calculated, the process proceeds to the next step. On the other hand, if it is before the calculation of the estimated induced voltage EXa, the process returns to step S310.

In step S340, the difference (past voltage value difference) between the voltage average value Vmat of the voltage value Vm and the voltage value Vm (n-m1) before the (n−m1) period is calculated, and based on this difference, the following An intermediate variable ξ is calculated using equation (7), and an estimated induced voltage EXa is calculated using the value of the intermediate variable ξ. The equation (7) is obtained by adding the correction term “E ₁ · {Vmat−Vm (n−m1)}” to the above equation (4).

・「Ｅ１」は補正定数。
・「Ｖｍ（ｎ−ｍ１）」は、（ｎ−ｍ１）周期目演算時の電圧値Ｖｍ。

• “E1” is a correction constant.
“Vm (n−m1)” is a voltage value Vm at the time of (n−m1) period calculation.

  Thus, when calculating the intermediate variable, a value based on the difference between the voltage average value Vmat, which is the past voltage value Vm, and the voltage value Vm close to the current calculation is added as a correction term. That is, when the difference between the voltage value Vm close to the time of calculation and the voltage average value Vmat is large, the value of the correction term becomes large, so that the intermediate variable ξ is greatly corrected. On the other hand, when the difference between the voltage close to the time of calculation and the voltage average value Vmat is small, the value of the correction term becomes small, so that the intermediate variable ξ is hardly corrected. Thereby, since the calculation error resulting from the vibration of the voltage value Vm is reduced as a whole, an increase in the difference between the estimated induced voltage EXa and the actual induced voltage EX is suppressed.

According to the electric power steering apparatus 1 of the present embodiment, in addition to the effects (1) to (5) according to the first embodiment, the following effects can be further achieved.
(6) In the present embodiment, the past voltage value difference is used to calculate the estimated induced voltage EXa. In general, since the voltage of the motor 21 vibrates, the voltage value Vm acquired for use in the calculation may not appropriately reflect the state of the motor 21.

  In the above configuration, since the past voltage value difference is used in the calculation of the estimated induced voltage EXa and the magnitude of the past voltage value Vm is reflected in the calculation of the estimated induced voltage EXa, the estimation accuracy of the estimated induced voltage EXa becomes higher. .

(Third embodiment)
A third embodiment of the present invention will be described with reference to FIG.
The electric power steering apparatus 1 according to the present embodiment is modified as follows from the configuration of the first embodiment. That is, in order to improve the accuracy of the induced voltage EX, in the first embodiment, the change pattern of the current value Im is grasped based on the data of the current value Im during the calculation cycle of the estimated induced voltage EXa and based on this pattern. Thus, the arithmetic expression of the estimated induced voltage EXa is corrected. In order to obtain the change pattern, the current value Im is sampled at a predetermined cycle.

  On the other hand, in the present embodiment, the sampling period (current acquisition period) of the current value Im is changed according to the rate of change of the current value Im. Hereinafter, a detailed change from the configuration of the first embodiment that occurs with this change will be described. In addition, about the structure which is common in the said 1st Embodiment, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

The sampling period with respect to the rate of change of the current value Im is changed as follows. In the following description, the current change amount per unit time of the current value Im is defined as the change rate.
As shown in FIG. 9A, when the rate of change of the current value Im is within a specified value BX (predetermined change amount), the sampling period is set to the current acquisition period B. In this case, the maximum value of the difference between the current value Im by sampling and the actual current value Im between the previous sampling and the current sampling is an error D1.

  As shown in FIG. 9B, when the rate of change of the current value Im exceeds a specified value BX (predetermined change amount), the sampling period is set to a current acquisition period A shorter than the current acquisition period B. In this case, the maximum value of the difference between the current value Im by sampling and the actual current value Im between the previous sampling and the current sampling becomes an error D2. On the other hand, when the sampling period is maintained at the current acquisition period B, the maximum difference in the actual current value Im between the previous sampling and the current sampling is an error D3. This error D3 is larger than the error D2.

The relationship between the calculation cycle Ts of the estimated induced voltage EXa and the sampling cycle of the current value Im is set as follows.
When the current acquisition cycle B is set to a length that can complete the calculation process by the disturbance observer within the current acquisition cycle B, the calculation of the estimated induced voltage EXa is executed in the same cycle as the current acquisition cycle B. That is, the sampling current acquisition cycle B and the calculation cycle Ts of the estimated induced voltage EXa coincide.

  When the current acquisition cycle A is set to a length within which the calculation process by the disturbance observer cannot be completed within the current acquisition cycle A, the estimated induced voltage EXa is calculated at a cycle different from the sampling current acquisition cycle A. . That is, if the sampling current acquisition cycle A is shorter than the calculation cycle Ts of the estimated induced voltage EXa, only data accumulation of the current value Im is performed during the current acquisition cycle A. Then, when calculating the estimated induced voltage EXa, the calculation formula of the estimated induced voltage EXa is corrected using the data accumulated as in the first embodiment.

  As described above, by changing the sampling period in accordance with the rate of change of the current value Im, it is possible to suppress an increase in deviation between the actual current value and the acquired current value Im. In addition, when sampling is performed at a cycle shorter than the estimated induced voltage EXa, only data accumulation is performed, so that an excessive calculation load is suppressed.

According to the electric power steering apparatus 1 of the present embodiment, in addition to the effects (1) to (5) according to the first embodiment, the following effects can be further achieved.
(7) In the present embodiment, the current sampling period (current acquisition period) of the motor 21 is changed based on the change in the current value. It is possible to increase the estimation accuracy of the estimated induced voltage EXa by reducing the current sampling period. On the other hand, the calculation load increases as the current sampling period is reduced. In the above configuration, since the sampling period is changed based on the change in the current value Im that affects the estimation accuracy of the estimated induced voltage EXa, the estimated accuracy of the estimated induced voltage EXa and the calculation load can be balanced. .

  (8) In the present embodiment, the current sampling period when the current change rate is larger than the specified value BX is defined as the current acquisition period A, and the current sampling period when the current change rate is smaller than the specified value BX. As the current acquisition cycle B, the current acquisition cycle A is made smaller than the current acquisition cycle B. Thereby, it can suppress that the estimation precision of the estimation induced voltage EXa falls.

(Fourth embodiment)
A fourth embodiment of the present invention will be described with reference to FIGS. 10 and 11.
The electric power steering apparatus 1 according to the present embodiment is modified as follows from the configuration of the first embodiment. That is, in order to improve the calculation accuracy of the estimated induced voltage EXa, in the first embodiment, the change pattern of the current value Im is grasped based on the data of the current value Im during the calculation cycle of the estimated induced voltage EXa, and this pattern. Based on the above, the arithmetic expression of the estimated induced voltage EXa is corrected.

  In contrast, in the present embodiment, when the voltage value Vm is an abnormal value, the arithmetic expression of the estimated induced voltage EXa is corrected in consideration of the abnormal value. Hereinafter, a detailed change from the configuration of the first embodiment that occurs with this change will be described. In addition, about the structure which is common in the said 1st Embodiment, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

With reference to FIG. 10, the fluctuation of the voltage value Vm will be described.
The estimated induced voltage EXa is calculated based on the voltage value Vm and the current value Im as shown in the above formulas (3) and (4). However, the voltage value Vm may include noise that is not caused by the rotation state of the motor 21. For example, the voltage value Vm changes instantaneously due to abnormal movement of the stator.

  The abnormal value of the voltage value Vm reduces the estimation accuracy of the estimated induced voltage EXa. For this reason, it is preferable to exclude this abnormal value when calculating the estimated induced voltage EXa. However, whether or not the voltage value Vm is an abnormal value cannot be determined unless it is compared with the voltage values Vm before and after the time when the abnormality of the voltage value Vm occurs. For this reason, conventionally, since the abnormal value has not been removed, the abnormal value is reflected in the estimated induced voltage EXa.

  Therefore, in the present embodiment, an abnormal value of the voltage value Vm is detected based on information before the estimated induced voltage EXa is calculated, and when the voltage value Vm is an abnormal value, the estimated induced voltage EXa is calculated. Correction that excludes a portion to which the voltage value Vm that is abnormal at the time of calculation contributes is performed. Hereinafter, correction of the arithmetic expression of the estimated induced voltage EXa will be described.

First, the contribution of the voltage value Vm given to the intermediate variable ξ will be described.
In order to simplify the equation (4) for the intermediate variable ξ, the equation (8) is used. When Expression (8) is expanded based on Expression (8), the item of ξ (n) is expressed as Expression (9).

・「Ｃ」は、Ｔｓ・Ｇ・Ａ_１２＋Ｉｅを示す。
・「Ｄ１」は、Ｔｓ・Ｇ・Ｂ_１を示す。
・「Ｄ２」は、Ｔｓ・Ｇ・（Ａ_１１・Ｉｅ−Ｇ・Ａ_１２）を示す。
・「ξ（ｎ＋１）」は、今回演算周期の中間変数（今回中間変数）を示す。
・「ξ（ｎ）」は、前回演算周期の中間変数（前回中間変数）を示す。

“C” represents Ts · G · A ₁₂ + Ie.
“D1” indicates Ts · G · B ₁
“D2” indicates Ts · G · (A ₁₁ · Ie-G · A ₁₂ ).
“Ξ (n + 1)” indicates an intermediate variable (current intermediate variable) of the current calculation cycle.
“Ξ (n)” indicates an intermediate variable (previous intermediate variable) of the previous calculation cycle.

すなわち、中間変数ξには、演算時の電圧値Ｖｍおよび電流値Ｉｍだけではなく、過去の電圧値Ｖｍおよび過去の電流値Ｉｍの値が反映される。例えば、（ｎ−ｍ）周期の電圧値Ｖｍ（ｎ−ｍ）は、中間変数ξ（ｎ＋１）に対してＡ^ｍ・Ｃ１・Ｖｍ（ｎ−ｍ）の影響を与える。

That is, the intermediate variable ξ reflects not only the voltage value Vm and current value Im at the time of calculation but also the past voltage value Vm and past current value Im. For example, the voltage value Vm of (n-m) cycles (n-m) has an effect of ^A m · C1 · Vm to the intermediate variable ξ (n + 1) (n -m).

If, when the value of the voltage value Vm (n-m) were ^outliers, A m · C1 · Vm the (n-m) and an abnormal correction value HX, the voltage value Vm of the abnormal correction value HX the timing By substituting with a value based on the average value (average correction value HY), the difference between the estimated induced voltage EXa and the actual induced voltage EX can be reduced.

  Specifically, the abnormal value is detected from the past voltage value Vm data. Then, an average value of the voltage value Vm (hereinafter, “past average value Vma”) in a period before and after the time when the abnormal value is acquired is calculated. Then, the arithmetic expression of the estimated induced voltage EXa is corrected based on the difference between the abnormal value and the past average value Vma.

A disturbance observer that performs the above correction will be described with reference to FIG.
The calculation unit A surrounded by the alternate long and short dash line is a block diagram of the above formulas (3) and (4). That is, the intermediate variable ξ (n) and the estimated induced voltage EXa (n) are calculated based on the current value Im and the voltage value Vm input from the left in the figure. Z ⁻¹ stores the intermediate variable ξ calculated by the previous calculation process.

  The calculation unit B surrounded by the alternate long and short dash line in FIG. 7 detects the abnormal voltage value Vm and calculates the correction value HA. Specifically, the calculation unit B calculates a voltage average calculation for calculating an average value of the voltage value Vm (n) for a predetermined period, a voltage latch process for temporarily storing the voltage value Vm (n), and a voltage value Vm. An abnormality determination for determining whether or not is abnormal, a calculation value latch process for storing a predetermined calculation value, and a correction calculation for calculating the correction value HA from these values are executed.

  In the voltage averaging process, the data from the voltage value Vm (n−m−z) to the voltage value Vm (n−m + z) among the voltage value Vm acquired corresponding to the calculation process of the estimated induced voltage EXa is stored. The average value of these data is calculated as the past average value Vma.

  In the voltage latch process, data used for the voltage averaging process is stored. That is, data from the voltage value Vm (n−m−z) to the voltage value Vm (n−m + z) is stored. Then, a voltage value Vm (nm) that is an intermediate value is selected.

  In the abnormality determination, the past average value Vma is compared with a value in the middle of the value stored in the voltage latch process, that is, the voltage value Vm (nm), and the absolute value of the difference exceeds the determination value CX. Determine whether or not. When the absolute value of the difference between the past average value Vma and the voltage value Vm (nm) exceeds the determination value CX, it is determined that the voltage value Vm (nm) is abnormal. On the other hand, when the absolute value of the difference between the past average value Vma and the voltage value Vm (nm) is equal to or smaller than the determination value CX, it is determined that the voltage value Vm (nm) is not abnormal. Further, the past average value Vma and the voltage value Vm (nm) at the time of this determination are stored for calculation of the correction value HA.

  In the operation value latch processing, a value corresponding to the sum of the term of the current value Im and the term of the voltage value Vm in the equation (4), that is, the value of the following equation (10) is stored. Equation (10) corresponds to a calculation term including a plurality of past current values.

補正演算では、異常判定で電圧値Ｖｍ（ｎ−ｍ）が異常である旨判定したとき、式（１０）の値に、以下式（１１）に与えられる補正値ＨＡを加えて、当該式（１０）の値を補正する。すなわち、式（４）に補正値ＨＡを加えた補正式を外乱オブザーバの演算式とする。

In the correction calculation, when it is determined in the abnormality determination that the voltage value Vm (nm) is abnormal, the correction value HA given in the following expression (11) is added to the value of the expression (10), and the expression ( The value of 10) is corrected. That is, a correction formula obtained by adding the correction value HA to the formula (4) is used as a disturbance observer calculation formula.

・「γ」は、補正定数。
・「γ・Ｃ^ｍ・Ｄ_１・Ｖｍａ（ｎ−ｍ）」は、平均補正値ＨＹ。
・「γ・Ｃ^ｍ・Ｄ_１・Ｖｍ（ｎ−ｍ）」は、異常補正値ＨＸ。

・ "Γ" is a correction constant.
“Γ · C ^m · D ₁ · Vma (nm)” is an average correction value HY.
“Γ · C ^m · D ₁ · Vm (nm)” is an abnormality correction value HX.

The disturbance observer operates as follows.
The voltage value Vm is stored by the voltage latch process. On the other hand, an average value of voltage values Vm (past average value Vma) is calculated by voltage averaging processing. Then, whether or not the voltage value Vm is abnormal is determined by the abnormality determination. When it is determined that the voltage value Vm is abnormal, the correction value HA is calculated by the correction calculation, and the estimated induced voltage EXa is calculated by correcting the value of the above equation (10) with the correction value HA.

  As described above, when an abnormal value is detected in the voltage value Vm, the term reflecting the voltage value Vm, which is the abnormal value, is subtracted when calculating the intermediate variable ξ. By adding the past average values Vma in the preceding and subsequent periods, the influence of abnormal values can be reduced. For this reason, a decrease in the estimation accuracy of the estimated induced voltage EXa based on the abnormal value of the voltage value Vm is suppressed.

According to the electric power steering apparatus 1 of the present embodiment, in addition to the effects (1) to (5) according to the first embodiment, the following effects can be further achieved.
(9) In the present embodiment, in the calculation of the estimated induced voltage EXa, a calculation term (formula (10)) including a plurality of past current values Im is used. When an abnormal value is included in the plurality of past current values Im, the abnormality correction value HX based on the abnormal value is subtracted from the calculation term, and the average correction value HY based on the average value of the plurality of past current values is obtained. Add to the above operation term. Then, the operation term corrected in this way is used for calculating the estimated induced voltage EXa.

  Thereby, since the average correction value HY closer to the actual past current value Im than the current value Im as an abnormal value is reflected in the calculated value, it is suppressed that the estimation accuracy of the estimated induced voltage EXa is lowered. .

  (10) In the present embodiment, the following correction is performed on a calculation term (equation (10)) including a plurality of past current values Im among the intermediate variable ξ (n−1) that is an element of the disturbance observer. That is, when an abnormal value is included in a plurality of past current values Im used to calculate the previous intermediate variable ξ (n−1), an abnormal correction value HX based on the abnormal value is subtracted from the operation term, and a plurality of past An average correction value HY based on the average value of the current values is added to the calculation term. Then, the calculation term after executing these processes is used to calculate the intermediate variable ξ (n) of the current calculation cycle. Thereby, since the average correction value HY closer to the actual past current value Im than the current value Im as the abnormal value is reflected in the calculated value, the estimation accuracy of the estimated induced voltage EXa is suppressed from being lowered.

  (11) In this embodiment, when the difference between one of a plurality of past current values and the past average value Vma is larger than the determination value CX, one of the past current values is determined as an abnormal value. In this configuration, when the difference between one of the past current values Im and the past average value Vma is larger than the determination value CX, the current value Im is determined as an abnormal value. Can be detected.

(Other embodiments)
In addition, the embodiment of the present invention is not limited to the embodiment exemplified in each of the above-described embodiments, and can be implemented by changing it as shown below, for example. The following modifications are not applied only to the above-described embodiment, and different modifications can be combined with each other.

  In the first embodiment, the resistance value Rm is periodically updated, but the value stored in the storage unit is used regardless of the magnitude of the current value Im. However, the resistance value Rm depends on the current value Im. Therefore, when the rotational angular velocity ωm is calculated, the resistance value Rm may be further corrected based on the current value Im. This correction can be performed using, for example, a map indicating the relationship between the resistance value Rm and the current value Im.

  In the first embodiment, whether or not the estimated induced voltage EXa is smaller than the determination value VTA as a determination condition for determining whether or not the motor 21 is in a resistance-computable state (hereinafter, “first condition”). However, instead of this, it can be determined as follows. That is, in addition to the first condition, the fact that the rate of change of the current value Im is smaller than the determination value ITA is added as a second condition, and when both conditions are satisfied, it is determined that the motor 21 is in a resistance-calculatable state. By adding the conditions in this way, it is possible to determine the resistance calculation possible state more accurately.

  In the first embodiment, the calculation formula of the estimated induced voltage EXa is corrected based on the change pattern of the current value Im. On the other hand, the arithmetic expression of the estimated induced voltage EXa can be corrected based on the change pattern of the voltage value Vm. In this case, the sampling period of the voltage value Vm is made shorter than the calculation period of the estimated induced voltage EXa. Further, the arithmetic expression of the estimated induced voltage EXa may be corrected based on the change pattern of the current value Im and the change pattern of the voltage value Vm.

In the first embodiment, the term including the past voltage value Vm and the past current value Im is corrected by the correction value α as shown in Expression (6), but instead of this correction method, the past Only the term of the voltage value Vm (“Ts · G · B ₁ · Vm (n−1)”) may be corrected. Further, only the term of the past current value Im (“Ts · G · (A ₁₁ · Ie−G · A ₁₂ )”) may be corrected.

  In the first embodiment, as in equation (5), the term including the current value Im used for the current calculation is corrected by the correction value β. Instead of this correction method, the following correction may be performed. it can. For example, when the term of the voltage value Vm used for the current calculation is included in the calculation formula of the estimated induced voltage EXa, the term including the voltage value Vm may be corrected. Further, both the term including the current value Im and the term including the voltage value Vm may be corrected.

In the second embodiment, the intermediate variable ξ is calculated based on the equation (7) obtained by adding the item E ₁ · {Vmat−Vm (n−m1)} to the equation (4). The equation (7) can be modified as follows. That is, the additional items are E ₁ · {ε 1 · Vmat−ε 2 · Vm (n−m 1)}, and ε 1 and ε 2 are values between 0 and 1, respectively. In this configuration, ε1 and ε2 can be set so that the value of the estimated induced voltage EXa approaches the actual induced voltage EX by changing the weight of the voltage value Vm (n−m1) and the voltage average value Vmat. Therefore, the estimated induced voltage EXa can be set to a more accurate value.

  In the second embodiment, the intermediate variable ξ is set based on the difference between the voltage average value Vmat that is the average value of the voltage values Vm in the past predetermined period and the last voltage value Vm (n−m1) in the predetermined period. to correct. On the other hand, the intermediate variable ξ may be corrected based on the difference (reference voltage value difference) between the voltage average value Vmat and the voltage value Vm (n) calculated this time.

  In the second embodiment, the intermediate variable ξ is corrected based on the average value of the past voltage value Vm in order to consider the vibration of the voltage value Vm. In such a correction method, the current value Im vibrates. It can also be applied to cases. That is, the intermediate variable ξ can be corrected based on the average value (current average value) of past current values Im. Further, when both the voltage value Vm and the current value Im vibrate, correction according to the second embodiment may be performed for each.

  In the third embodiment, the sampling period is divided into two stages, but the number of the divisions may be three or more. In this case, the error between the actual current value Im and the acquired current value Im can be further reduced.

  In the third embodiment, the cycle is changed for sampling the current value Im, but the cycle may be changed for sampling the voltage value Vm. For example, the voltage acquisition cycle when the rate of change of the voltage value Vm is larger than a specified value DX (predetermined change amount) is the voltage acquisition cycle C, and the rate of change of the voltage value Vm is smaller than the specified value DX (predetermined change amount). When the voltage acquisition cycle is the voltage acquisition cycle D, the voltage acquisition cycle C is made smaller than the voltage acquisition cycle D.

  In the fourth embodiment, the relationship between the change pattern of the current value Im, the correction value α, and the correction value β is obtained by simulation. However, the disturbance observer of the same embodiment is applied to the actual motor 21 to correct the correction value α. And the correction value β may be obtained.

  In each of the above embodiments, the estimated induced voltage EXa is calculated using the disturbance observer, but the disturbance observer is not limited to the model. That is, if the disturbance observer is derived by modeling the motor equation with the induced voltage EX as a disturbance element, the disturbance observer can be adopted as a calculation method for calculating the estimated induced voltage EXa.

  In each of the above embodiments, the resistance update process is applied to the electric power steering apparatus 1 including the brushed motor as the motor 21 of the EPS actuator 20, but the resistance update process is also applied to the electric power steering apparatus 1 including the brushless motor. Can be applied.

  In the above embodiment, the present invention is applied to the column-type electric power steering apparatus 1, but the present invention can also be applied to the pinion type and rack assist type electric power steering apparatus 1. Also in this case, the effect according to the effect of the embodiment can be obtained by adopting the configuration according to the embodiment.

  DESCRIPTION OF SYMBOLS 1 ... Electric power steering device, 2 ... Steering, 3 ... Steering wheel, 10 ... Steering angle transmission mechanism (steering system), 11 ... Steering shaft, 12 ... Rack and pinion mechanism, 13 ... Rack shaft, 14 ... Tie rod, 20 ... EPS actuator, 21 ... motor, 22 ... deceleration mechanism, 30 ... electronic control device, 31 ... torque sensor, 32 ... vehicle speed sensor.

Claims (14)

In an electric power steering apparatus including a motor that applies assist force to a steering system,
A value indicating the magnitude of the motor current is a current value, a value indicating the voltage of the motor is a voltage value, a value indicating the resistance of the motor is a resistance value, and the current value and the Calculating an induced voltage of the motor by applying a voltage value to the induced voltage calculation means;
Calculating the resistance value based on the current value and the voltage value when the induced voltage is within a predetermined range;
In addition, a current value acquired at the end of the plurality of current values is set as a reference current value, a current value acquired before the reference current value is set as a past current value, and a current value acquired before the reference current value is set at the end of the voltage values. Using the acquired voltage value as a reference voltage value and the voltage value acquired before this reference voltage value as a past voltage value, the induced voltage calculation means is corrected based on at least one of the past current value and the past voltage value An electric power steering device. The electric power steering apparatus according to claim 1, wherein
The period for acquiring the current value is a current acquisition period, the period for acquiring the voltage value is a voltage acquisition period, the period for calculating the induced voltage is an operation period, and the current acquisition period and the period An electric power steering device, wherein at least one of the voltage acquisition cycles is shorter than the calculation cycle. In the electric power steering apparatus according to claim 1 or 2,
An electric power steering apparatus, wherein a correction value for correcting the induced voltage calculation means is calculated based on at least one of the change pattern of the past current value and the change pattern of the past voltage value. In the electric power steering device according to claim 3,
Using a disturbance observer as the induced voltage calculation means;
In the calculation of the disturbance observer, calculating an intermediate variable based on the past current value and the past voltage value;
And a correction term for correcting at least one of the past current value and the past voltage value used for calculating the intermediate variable is calculated as a correction term for correcting the induced voltage calculation means. Steering device. In the electric power steering device according to claim 3 or 4,
Using a disturbance observer as the induced voltage calculation means;
In the calculation of the disturbance observer, calculating the induced voltage based on an intermediate variable and at least one of the reference current value and the reference voltage value;
And a correction term for correcting at least one of the reference current value and the reference voltage value used for calculation of the induced voltage is calculated as a correction term for correcting the induced voltage calculation means. Steering device. In the electric power steering device according to any one of claims 1 to 5,
An average value of the plurality of past voltage values is defined as a voltage average value, and a difference between the last acquired past voltage value and the voltage average value among the plurality of past voltage values is defined as a past voltage value difference, and the reference voltage value And the difference between the voltage average value and the reference voltage value difference,
An electric power steering device, wherein at least one of the past voltage value difference and the reference voltage value difference is used for calculation of the induced voltage. In the electric power steering device according to any one of claims 1 to 6,
An average value of a plurality of past current values is defined as a current average value, and a difference between the past current value acquired last among the plurality of past current values and the current average value is defined as a past current value difference, and the reference current value And the difference between the current average value and the reference current value difference,
An electric power steering device, wherein at least one of the past current value difference and the reference current value difference is used for calculating the induced voltage. In the electric power steering device according to any one of claims 1 to 7,
The electric power steering apparatus characterized in that the current acquisition period is changed based on a change in the current value, with a period for acquiring the current value as a current acquisition period. The electric power steering apparatus according to claim 8,
The current acquisition cycle when the change amount of the current value per unit time is larger than a predetermined change amount is defined as a current acquisition cycle A, and the change amount of the current value per unit time is smaller than the predetermined change amount The electric power steering apparatus, wherein the current acquisition cycle is set to be a current acquisition cycle B, and the current acquisition cycle A is made smaller than the current acquisition cycle B. In the electric power steering device according to any one of claims 1 to 9,
An electric power steering apparatus, wherein a period for acquiring the voltage value is set as a voltage acquisition period, and the voltage acquisition period is changed based on a change in the voltage value. The electric power steering apparatus according to claim 10,
The voltage acquisition cycle when the amount of change in the voltage value per unit time is larger than a predetermined amount of change is defined as a voltage acquisition cycle C, and the amount of change in the voltage value per unit time is smaller than the predetermined amount of change. The electric power steering apparatus, wherein the voltage acquisition cycle is set to a voltage acquisition cycle D, and the voltage acquisition cycle C is made smaller than the voltage acquisition cycle D. In the electric power steering device according to any one of claims 1 to 11,
In the calculation of the induced voltage calculation means, a calculation term including the plurality of past current values is used,
In addition, when at least one of the plurality of past current values includes an abnormal value, a process of subtracting an abnormality correction value based on the abnormal value from the calculation term, and an average based on an average value of the plurality of past current values An electric power steering apparatus characterized in that a process of adding a correction value to the calculation term is performed, and the calculation term after executing these processes is used for calculation of the induced voltage. In the electric power steering device according to any one of claims 1 to 11,
Using a disturbance observer as the induced voltage calculation means;
Calculating an intermediate variable of the current calculation cycle based on the plurality of past current values, the plurality of past voltage values, the reference current value, and a previous intermediate variable that is an intermediate variable calculated in the previous calculation cycle;
An arithmetic term including the plurality of past current values is included in the previous intermediate variable;
In addition, when an abnormal value is included in at least one of the plurality of past current values used in the calculation of the previous intermediate variable, a process of subtracting an abnormal correction value based on the abnormal value from the calculation term; A process of adding an average correction value based on an average value of past current values to the calculation term is performed, and the calculation term after executing these processes is used for calculation of an intermediate variable of the current calculation cycle. Electric power steering device. The electric power steering apparatus according to claim 12 or 13,
When the average value of the plurality of past current values is a past average value, and the difference between one of the plurality of past current values and the past average value is larger than a determination value, one of the past current values is set as the abnormal value. An electric power steering device characterized by determining as follows.

Images