JP6069896B2 - Electric power steering device - Google Patents

Description

  The present invention relates to an electric power steering apparatus having functions of an automatic steering mode (parking support) and a manual steering mode, and applying an assist force by a motor to a steering system of a vehicle, and more particularly, steering control in an automatic steering mode. The present invention relates to an electric power steering apparatus having a vibration suppression function that improves the accuracy and steering feeling of (parking assist) and suppresses vibration of a steering wheel.

  An electric power steering apparatus that applies a steering assist force (assist force) to a vehicle steering mechanism by a rotational force of a motor is provided with a steering shaft or a rack shaft by a transmission mechanism such as a gear or a belt via a speed reduction mechanism. A steering assist force is applied to the vehicle. Such a conventional electric power steering device (EPS) performs feedback control of the motor current in order to accurately generate the torque of the steering assist force. In feedback control, the motor applied voltage is adjusted so that the difference between the steering assist command value (current command value) and the motor current detection value is small. The adjustment of the motor applied voltage is generally performed by PWM (pulse width). This is done by adjusting the duty of modulation) control.

  A general schematic configuration of the electric power steering apparatus will be described with reference to FIG. 1. A column shaft (steering shaft) 2 of the handle 1 is a speed reduction made up of a worm connected to a motor 20 and a worm wheel engaged with the worm. The mechanism 3, the universal joints 4 a and 4 b, the pinion rack mechanism 5, and the tie rods 6 a and 6 b are connected to the steered wheels 8 L and 8 R via the hub units 7 a and 7 b. The column shaft 2 is provided with a torque sensor 10 that detects the steering torque of the handle 1, and a motor 20 that assists the steering force of the handle 1 is connected to the column shaft 2 via the speed reduction mechanism 3. . The control unit (ECU) 30 that controls the electric power steering apparatus is supplied with electric power from the battery 13 and also receives an ignition key signal via the ignition key 11. The control unit 30 calculates a steering assist command value of an assist (steering assist) command based on the steering torque Tr detected by the torque sensor 10 and the vehicle speed Vel detected by the vehicle speed sensor 12, and obtains the steering assist command value. The current supplied to the motor 20 is controlled by the current control value E subjected to compensation or the like. The vehicle speed Vel can also be received from a CAN (Controller Area Network) or the like, and the column shaft 2 may include an intermediate shaft (intermediate shaft) that can be expanded and contracted on the output shaft side.

  FIG. 2 shows an example of an external appearance of an electric power steering apparatus having an intermediate shaft (lower shaft 40), and FIG. 3 shows a cross-sectional structure thereof. The input shaft 2a of the column shaft 2 is inserted into a cylindrical column 41, and the rear surface of the output shaft 2b is disposed with a gap of several minutes at the tip of the input shaft 2a. The output shaft 2b is further connected to a universal joint. It is connected to the lower shaft 40 which forms an intermediate shaft via 4a. A torsion bar 42 is disposed so as to penetrate through the output shaft 2b, and the torsion bar 42 is press-fitted into the distal end portion of the input shaft 2a. The torsion bar 42 and the output shaft 2b are fixed by a pin 43 on the distal end side. ing. The housing 45 connected to the column 41 is provided with a tilt lever 44 for adjusting the vertical position. There is a gap of several minutes between the input shaft 2a and the output shaft 2b. A torsion bar 42 is press-fitted into the tip of the input shaft 2a, and the torsion bar 42 is fixed to the output shaft 2b with a pin 43. Therefore, the twist amount (twist angle) of the handle can be detected using the torsion bar 42.

  The control unit 30 is built in the housing, and is mainly composed of a CPU (or MPU or MCU). FIG. 4 shows general functions executed by a program inside the CPU. Yes.

  The function and operation of the control unit 30 will be described with reference to FIG. 4. The steering torque Tr detected by the torque sensor 10 and the vehicle speed Vel from the vehicle speed sensor 12 are input to the steering assist command value calculation unit 31, and an assist map is displayed. The steering assist command value Iref is calculated using this. The calculated steering assist command value Iref is limited in output by the maximum output limiter 32 based on overheat protection conditions and the like, and the current command value I whose maximum output is limited is input to the subtractor 33. The part that generates the current command value I based on the steering torque Tr and the vehicle speed Vel forms a torque control unit.

  The subtracting unit 33 obtains a deviation ΔI (= I−i) between the current command value I and the motor current i of the motor 20 being fed back, and the deviation ΔI is controlled and controlled by the current control unit 34 such as PI. The current control value E is input to the PWM control unit 35, the duty is calculated, and the motor 20 is driven via the motor drive circuit 36 by the PWM signal PS whose duty is calculated. The motor current i of the motor 20 is detected by the motor current detection circuit 37, and the motor current i is input to the subtractor 33 and fed back.

  The motor drive circuit 36 that controls the motor current i with the current control value E and drives the motor 20 uses a bridge circuit in which a semiconductor switching element (FET) and a motor are bridge-connected, and is based on the current control value E. The semiconductor switching element is ON / OFF controlled according to the determined duty of the PWM signal to control the motor current i.

  In such an electric power steering apparatus, in recent years, a vehicle having a parking assist function (parking assist) and switching between an automatic steering mode and a manual steering mode has emerged. Sets a target steering angle based on data such as a camera (image) and a distance sensor, and automatic control is performed according to the target steering angle.

  In WO 2008/146372 (Patent Document 1), a target sub steering angle or a target steering angle added by a sub steering angle superimposing mechanism is generated based on a steering wheel angle detection value from a steering wheel angle detection means and a transmission characteristic. Thus, the target sub steering angle and the sub steering angle detection value from the sub steering angle detection means match, or the target sub steering angle and the sub steering angle detection value from the sub steering angle detection means match, Target drive amount calculation means for calculating the target drive amount of the motor and motor drive means for driving the motor according to the target drive amount are provided, and the steered wheels are steered according to the steering of the driver's steering wheel.

WO 2008/146372 JP 2003-237607 A

  However, in the electric power steering device described in Patent Document 1, since the rate limiting process is not performed on the target steering angle, the driver's steering feeling is impaired when the target steering angle changes abruptly. turn into. In addition, since gain control according to the vehicle speed is not performed, there is a problem that precise control corresponding to the vehicle speed cannot be performed.

  Further, when the steering angle moves during the steering angle control in the automatic steering mode, a rotational vibration phenomenon may occur in the steering wheel due to the inertia and springiness of the steering wheel and the torsion bar. That is, in the case of the automatic steering mode, the operation is letting go, and the motor (20) → worm (3) → worm wheel (3) → output shaft (2b) → universal joint (4a) → intermediate shaft (40) → universal joint (4b) ) → Pinion rack mechanism (5) → Tie rods (6a, 6b) → Steering wheels (8L, 8R) in this order, torque is transmitted and the handle (1) rotates via the torsion bar (42). Rotational vibration due to. Further, road surface vibration (running vibration) is caused, and vibration enters the output shaft. As a measure for suppressing such vibrations, vibrations can be suppressed by adding a vibration current command value obtained by multiplying a torsion bar torsion angle derivative (torsion angular velocity) by a gain. For example, in Japanese Patent Application Laid-Open No. 2003-237607 (Patent Document 2), a torsion angle of a torsion bar provided between an input shaft connected to a handle and an output shaft engaged with a motor is detected using a torque sensor, A current command value is determined based on the twist angle and its differential value, and a vibration damping effect is obtained.

  However, in a vehicle having an automatic steering mode and a manual steering mode function, since the automatic steering mode is not the torque control but the steering angle control, the use of the torque sensor increases the load capacity. . Therefore, in the automatic steering mode, it is required to obtain a vibration damping effect efficiently without using the torque sensor, that is, by stopping the torque sensor.

  The present invention has been made under the circumstances described above, and an object of the present invention is to suppress vibration without using a torque sensor in an automatic steering mode in a vehicle having an automatic steering mode (parking support function) and a manual steering mode. It is possible to steer accurately according to the calculated target steering angle while obtaining the effect, and even if the target steering angle is abrupt steering, it can be smoothly steered. An object of the present invention is to provide an electric power steering device that can be brought close to the above.

という伝達関数を用いて算出し、前記自動操舵モード及び手動操舵モードの切換指令に応じて前記切換部が切り換えられ、前記手動操舵モード時に、前記モータ電流指令値１に基づいて前記モータを駆動制御し、前記自動操舵モード時に、前記モータ電流指令値２に基づいて前記モータを駆動制御し、トルクセンサを停止すると共に、前記制振機能部によってハンドルの振動を抑制することにより達成される。
The present invention calculates a motor current command value 1 based on the steering torque and the vehicle speed, drives the motor based on the motor current command value 1 to perform assist control of the steering system, and includes an automatic steering mode and a manual steering mode. In the electric power steering apparatus having a function of switching between, the torsion angle of the torsion bar is detected based on the column shaft angular velocity, the estimated angular velocity of the torsion bar is calculated, and the control calculated based on the estimated angular velocity is calculated. A vibration suppression function unit for calculating a vibration current command value, a motor current command value calculated based on a target steering angle, an actual steering angle, the vehicle speed, and a motor angular velocity of the motor, and the vibration suppression current command value. Calculate the added motor current command value 2 and input the steering angle control unit having a vibration control function, the motor current command value 1 and the motor current command value 2 A switching unit for switching Te comprises a natural frequency of the torsion bar, the damping ratio respectively omega _n, and zeta, the column angular velocity, said torsion bar, respectively torsional angular velocity estimated value of omega _1, and omega _e, the system The vibration function unit calculates the torsional angular velocity estimated value.

And the switching unit is switched according to the switching command between the automatic steering mode and the manual steering mode, and the motor is driven and controlled based on the motor current command value 1 in the manual steering mode. In the automatic steering mode, the motor is driven and controlled based on the motor current command value 2, the torque sensor is stopped, and vibration of the steering wheel is suppressed by the vibration damping function unit.

Also, the object of the present invention is that the steering angle control unit is configured to multiply a rate limiter for facilitating a time change of the target steering angle , and a steering angle deviation between an output of the rate limiter and the actual steering angle by a proportional gain. And a proportional integration unit that multiplies and adds the integral gain; a speed unit that multiplies the motor angular velocity by a speed gain and subtracts it from the addition value of the proportional integration unit; and obtains the motor current command value 3; and the motor current command value 3 A vehicle speed unit that outputs a motor current command value 4 by multiplying a vehicle speed gain according to the vehicle speed, a vibration current command value is generated by inputting the motor angular velocity, and the vibration suppression command is added to the motor current command value 4. Or a vibration damping function unit that adds the current command value for output and outputs the motor current command value 2, or the vibration damping function unit divides the motor angular velocity by a reduction ratio to form a column shaft. Minute to output angular velocity A torsional angular velocity estimation unit that obtains a torsional angular velocity estimation value by functionally converting the column shaft angular velocity, and a damping gain that multiplies the torsional angular velocity estimation value by a damping gain and outputs the damping current command value by being constituted by the parts, or the steering angle control unit includes a rate limiter that facilitates the time variation of the target steering angle, proportional to the steering angle deviation between the actual steering angle and the output of the rate limiter A proportional integration unit that multiplies the gain and integral gain and adds them; a speed unit that multiplies the motor angular velocity by speed gain and subtracts it from the addition value of the proportional integration unit; and obtains the motor current command value 3; and the motor angular velocity The damping function unit that generates a damping current command value by inputting, adds the damping current command value to the motor current command value 3, and outputs a motor current command value 5, and the motor current command The value 5 is Or a vehicle speed unit that outputs a motor current command value 2 multiplied by a vehicle speed gain according to the speed, or the vibration damping function unit divides the motor angular speed by a reduction ratio to obtain a column shaft angular speed. A fractional part that outputs a function, a torsional angular speed estimation part that obtains a torsional angular speed estimated value by functionally converting the column shaft angular speed, and a phase that performs phase compensation on the torsional angular speed estimated value and outputs the vibration suppression current command value The rate limiter is configured by a compensation unit, or the rate limiter holds a past value of the target steering angle, and a difference between the target steering angle and the past value does not exceed a predetermined upper limit value. And a change amount setting unit that is set so as not to be less than a predetermined lower limit value , or if the input value is within a predetermined range at the final stage of the rudder angle control unit , it is output as it is And before If there is a limiter that outputs an upper limit value or a lower limit value within the predetermined range, a limiter for limiting the output is provided, and the motor current command value 2 is output from the limiter, which is achieved more effectively. The

  According to the electric power steering apparatus of the present invention, in a vehicle having an automatic steering mode (parking support function) and a manual steering mode, a target steering angle calculated from data such as a camera (image) and a distance sensor is taken into consideration for the vehicle speed. Therefore, the steering can be accurately performed with respect to the target steering angle, and the driver does not feel uncomfortable. In addition, since the abrupt target steering angle is controlled in a smooth manner, the driver will not feel uneasy even in automatic driving.

  Further, in the automatic steering mode, the torque sensor is stopped, and the damping current command value obtained by multiplying the torsion bar torsion angle derivative (torsion angular velocity) by the damping gain is added to the current command value for correction. Therefore, a vibration control effect can be obtained without using a torque sensor. Moreover, since the torque sensor value is not used, the control load capacity can be reduced.

It is a lineblock diagram showing an outline of an electric power steering device. It is an external view which shows an example of an electric power steering device. It is sectional drawing which shows an example of an electric power steering device. It is a block diagram which shows the general structural example of a control unit. It is a block diagram which shows the example of whole structure of this invention. It is a block block diagram which shows an example of a steering angle control part. It is a block block diagram which shows an example of a rate limiter. It is a block diagram which shows the structural example of a variation setting part. It is a flowchart which shows the example of whole operation | movement of this invention. It is a flowchart which shows the operation example of the steering angle control part which concerns on this invention. It is a block block diagram which shows the other structural example of a steering angle control part.

  Even in a vehicle having the functions of the automatic steering mode (parking support function) and the manual steering mode, the road surface reaction force (SAT) transmitted to the steering system through the tire varies depending on the vehicle speed. Therefore, when the steering is automatically controlled to the calculated target steering angle in the automatic steering mode, the response of the steering angle varies depending on the vehicle speed. Therefore, in the present invention, the motor current command value for automatic control is adjusted according to the vehicle speed so as to reduce the influence of the road surface reaction force that the tire receives from the road surface. In the present invention, the target steering angle is smoothed by a rate limiter, and the response of the steering angle of the steering wheel can be reduced even when the target steering angle changes suddenly. Regardless of the vehicle speed, the vehicle can be moved accurately with respect to the target steering angle, which is safer for the driver.

  Furthermore, when the steering angle moves during the steering angle control in the automatic steering mode, vibration may occur in the steering wheel due to the inertia and springiness of the steering wheel system and the torsion bar, and the output may be caused by road surface vibration. Coming into the axis. Conventionally, vibration is suppressed by using a torque sensor to add a vibration current command value obtained by multiplying a torsion bar torsion angle derivative (torsion angular velocity) by a gain. In the present invention, without using a torque sensor, a motor angular velocity is detected by a rotation sensor directly connected to the output shaft, and a value obtained by dividing a reduction ratio from the motor angular velocity, that is, a column shaft angular velocity is used as an input, and the transfer function is used. An estimated angular velocity value of the torsion angle of the torsion bar is obtained, and an effective damping effect is obtained by a damping current command value based on the estimated torsion angle velocity value. Therefore, the torque sensor can be stopped and the control load capacity can be reduced.

  Embodiments of the present invention will be described below in detail with reference to the drawings.

  FIG. 5 shows an example of the overall configuration of the present invention. A rotation sensor 101 such as a resolver for detecting a motor rotation angle θs is connected to the motor 100, and the motor 100 includes an ECU 110 and an EPS (electrically driven) on the vehicle side. The drive is controlled via the ECU 120 on the power steering device side.

The vehicle-side ECU 110 is configured to output a switching command unit 111 that outputs a switching command SW for an automatic steering mode or a manual steering mode based on buttons, switches, and the like indicating a driver's intention, and signals from a camera (image), a distance sensor, and the like. And a target steering angle generator 112 that generates a target steering angle θt based on the above. Further, the actual steering angle θr detected by the steering angle sensor 102 provided on the column shaft and the vehicle speed Vel from the vehicle speed sensor 103 are input to the steering angle control unit 130 in the ECU 120 on the EPS side via the ECU 110. The rudder angle sensor 102 may be a rudder angle estimated value based on a column axis (including an intermediate shaft and a pinion axis), a rack and pinion rack displacement, and a wheel speed. The vehicle speed Vel can also be received from the CAN or the like. The switching command unit 111 is a signal for identifying that the vehicle enters the automatic steering mode, for example, a button or a switch provided on the dashboard or around the steering wheel. Alternatively, a switching command SW is output based on a vehicle state signal such as parking provided in the shift, and the switching command SW is input to the switching unit 122 in the ECU 120 on the EPS side. The target steering angle generation unit 112 generates a target steering angle θt by a known method based on data such as a camera (image) and a distance sensor, and the generated target steering angle θt is steered in the ECU 120 on the EPS side. Input to the angle controller 130.

  The ECU 120 on the EPS side outputs the motor current command value Itref calculated as described above based on the steering torque and the vehicle speed, the target steering angle θt, the actual steering angle θr, the vehicle speed Vel, and the motor angular speed ω. From the steering angle control unit 130 that calculates and outputs the motor current command value Imref for the steering angle automatic control based on the switching command, the switching unit 122 that switches the motor current command value Itref and Imref by the switching command SW, and the switching unit 122 A current control / drive unit 123 that drives and controls the motor 100 based on the motor current command value (Itref or Imref), and an angular velocity calculation unit 124 that calculates the motor angular velocity ω based on the motor rotation angle θs from the rotation sensor 101; It has.

  The switching unit 122 switches between a manual steering mode that is torque control by the torque control unit 121 and an automatic steering mode that is parking assistance by the rudder angle control unit 130 based on a switching command SW from the switching command unit 111 of the ECU 110. The motor current command value Itref is output in the manual steering mode, and the motor current command value Imref is output in the automatic steering mode. The current control / drive unit 123 includes the subtracting unit 33, the current control unit 34, the PWM control unit 35, and the motor drive circuit 36 described above.

  The details of the steering angle control unit 130 are configured as shown in FIG. 6, the target steering angle θt is smoothed by the rate limiter 140, and the smoothed target steering angle θtm is added to the subtraction unit 131. . The rate limiter 140 corresponds to a case where the target steering angle θt changes suddenly, and smoothly changes within the range of a predetermined time change rate. The target limiter smoothed from the rate limiter 140 is The angle θtm is output. The actual steering angle θr is subtracted and input to the subtracting unit 131, and the steering angle deviation θd that is the subtraction result (= θtm−θr) of the subtracting unit 131 is added and input to the adding / subtracting unit 136 via the proportional gain (Kp) unit 132. At the same time, the signal is added to the addition / subtraction unit 136 via the integration (1 / s) unit 133 and the integration gain (Ki) unit 134. The integral gain Ki has the effect of reducing the steady-state deviation, and the proportional gain unit 132, the integral unit 133, the integral gain unit 134, and the addition / subtraction unit 136 constitute a proportional integration unit.

  Further, the motor angular speed ω is subtracted and input to the adder / subtractor 136 via the speed gain (Kd) unit 135, and the current command value Iref1 as the addition / subtraction result of the adder / subtractor 136 is input to the vehicle speed gain (Kv) unit 137 that is sensitive to the vehicle speed Vel. Is done. The speed gain Kd has an effect of suppressing overshoot, and the speed gain unit 135 and the addition / subtraction unit 136 constitute a speed unit. The current command value Iref2 that has been gain (Kv) adjusted by the vehicle speed gain unit 137 is input to the adding unit 153.

The motor angular velocity omega, are input are converted to the column shaft angular velocity omega _c the fractional portion 150 that is divided (1 / n) at the speed reduction ratio n of the speed reduction mechanism 3, column shaft angular velocity omega _c denominator quadratic transfer function entered twisted angular velocity estimate omega _e is estimated angular velocity estimator 151 twisted to the estimated torsion angular velocity estimate omega _e is converted to vibration-suppression current command value Irefb1 through the damping gain portion 152 of the gain Kc And input to the adder 153. The adding unit 153 corrects the current command value Iref2 by adding the damping current command value Irefb1, and the corrected current command value Iref3 is limited by the limiter 138 to be output as a motor current command value Imref. . The fraction unit 150, the torsional angular velocity estimation unit 151, the vibration suppression gain unit 152, and the addition unit 153 constitute a vibration suppression function unit.

The rate limiter 140 smoothes and outputs when the target steering angle θt changes abruptly, and has a configuration as shown in FIG. 7, for example. That is, the target steering angle θt is added to the subtracting unit 141, and the steering angle θt1, which is a result of subtraction from the past value, is set by the variation setting unit 142 as the variation θt2. The change setting unit 142 sets the difference θt1 between the past value from the holding unit (Z ⁻¹ ) 144 and the input (θt), and the addition result of the change θt2 and the past value in the adder 143 is used as the target steering angle. Output as θtm. The change setting unit 142 prevents the change from exceeding the set upper limit and lower limit, and obtains a difference from the input (target steering angle) θt every calculation cycle T to set the change. When the value is outside the upper and lower limits of the unit 142, the output θtm is changed stepwise as shown in FIG. 8 by repeatedly adding the difference to the past value, and finally the output θtm is changed. It is made to coincide with the target steering angle θt. When the difference from the input (target steering angle) θt is within the upper and lower limits of the change setting unit 142, the change θt2 = difference θt1 is output and added to the past value, so that the result is output. θtm and input (target steering angle) θt coincide. As a result, even if the target steering angle θt changes abruptly, the target steering angle θt that changes abruptly can be changed smoothly, preventing sudden current changes (= rapid steering) and It plays a function to reduce the anxiety of autonomous driving.

Here, formulas for estimating the torsional angular velocity ω _e from the column shaft angular velocity ω will be described below. However, the moment of inertia of the handle is J, the spring constant of the torsion bar is k, the viscous friction coefficient of the torsion bar is c, the column shaft rotation angle is θ ₁ , the handle rotation angle is θ ₂ , the column shaft angular velocity is ω ₁ , and the handle angular velocity Is ω ₂ .

  First, the equation of motion for the rotation of the handle is as follows.

次に数１をラプラス変換し、ｓをラプラス演算子として、Θ_１（ｓ）（Θ_１（ｓ）はθ_１（ｔ）のラプラス変換表現）に対するΘ_２（ｓ）（Θ_２（ｓ）はθ_２（ｔ）のラプラス変換表現）の伝達関数を求める。そして、Ω_１＝ｓ・Θ_１、Ω_２＝ｓ・Θ_２であることを考慮すると、コラム軸角速度Ω_１（ｓ）（Ω_１（ｓ）はω_１（ｔ）のラプラス変換表現）に対するハンドル角速度Ω_２（ｓ）（Ω_２（ｓ）はω_２（ｔ）の伝達関数）の伝達関数を求めることができる。即ち、数１をラプラス変換すると、下記数２となる。

Next, the Laplacian transformation is performed on Formula _{1, and} s ₁ is the Laplace operator, and Θ ₂ (s) (Θ ₂ (s)) for Θ ₁ (s) (where Θ ₁ (s) is the Laplace transform representation of θ ₁ (t)). Finds the transfer function of the Laplace transform representation of θ ₂ (t). And considering that Ω ₁ = s · Θ ₁ and Ω ₂ = s · Θ ₂ , the column axis angular velocity Ω ₁ (s) (where Ω ₁ (s) is a Laplace transform representation of ω ₁ (t)) A transfer function of the steering wheel angular velocity Ω ₂ (s) (Ω ₂ (s) is a transfer function of ω ₂ (t)) can be obtained. That is, when Laplacian transformation is performed on Formula 1, the following Formula 2 is obtained.

(Equation 2)
Js ² Θ ₂ = k (Θ ₁ −Θ ₂ ) + cs (Θ ₁ −Θ ₂ )
When formula 2 is arranged, the following formula 3 and formula 4 are obtained.

(Equation 3)
(Js ² + cs + k) Θ ₂ = (cs + k) Θ1

上記数４に基づいて、Ω_１からΩｅ（ｓ）（Ωｅ（ｓ）はωｅ（ｔ）のラプラス変換表現）を求めると、下記数５のようになる。

Based on the equation 4, the _{Ω 1 Ωe (s) (Ωe} (s) is the Laplace transform representation of ωe (t)) when seek is as the following equation 5.

上述のような数式関係が成立するため、下記数６が成立する。

Since the above mathematical relationship is established, the following equation 6 is established.

従って、分数部１５０及び捩れ角速度推定部１５１によって数６から捩れ角速度推定値ω_ｅを得ることができる。捩れ角速度推定値ω_ｅをゲイン倍（Ｋｃ）した電流値を電流指令値に加算することで、操舵系に設けられるトーションバーのバネ特性、ハンドルの重量によるマスバネによる振動の発生を抑制することができる。

Therefore, the torsional angular velocity estimated value ω _e can be obtained from the equation 6 by the fractional unit 150 and the torsional angular velocity estimating unit 151. By adding the twist current value gain multiple (Kc) the angular velocity estimate omega _e to the current command value, the spring characteristics of the torsion bar provided in the steering system, is possible to suppress the generation of vibration due to mass-spring due to the weight of the handle it can.

  In such a configuration, an example of the operation will be described with reference to the flowchart of FIG.

  When the operation of the steering system starts, torque control by the torque control unit 121 is performed (step S1), and the motor 100 is driven by the current control / drive unit 123 using the motor current command value Itref (step S2). The above operation is repeated until the switching command SW is output from the switching command unit 111 (step S3).

  When the automatic steering mode for parking assistance is entered and a switching command SW is output from the switching command unit 111, the target steering angle θt is input from the target steering angle generation unit 112 (step S4), and the actual steering angle θr is output from the steering angle sensor 102. Is input (step S5), the vehicle speed Vel is input from the vehicle speed sensor 103 (step S6), the motor angular velocity ω is input from the angular velocity calculation unit 124 (step S7), and the motor current command value Imref is calculated by the rudder angle control unit 130. It is generated (step S100).

  Thereafter, the switching unit 122 is switched by the switching command SW from the switching command unit 111 (step S10), and the motor 100 is driven by the current control / drive unit 123 using the motor current command value Imref from the steering angle control unit 130. (Step S11), the process returns to Step S3. The drive control based on the motor current command value Imref is repeated until the switching command SW is changed from the switching command unit 111.

  The generation of the motor current command value Imref is performed by the steering angle control unit 130, and the generation operation of the motor current command value Imref in the steering angle control unit 130 is as shown in the flowchart of FIG.

  That is, the target steering angle θt is input to the rate limiter 140 (step S101), and the rate limiting operation as described above is executed by the rate limiter 140 (step S102). Further, the actual steering angle θr is input from the rudder angle sensor 102 (step S103), “θtm−θr” is subtracted by the subtraction unit 131 (step S104), and the steering angle deviation θd as the subtraction value is a proportional gain unit. The value is multiplied by Kp at 132 and added to the adder / subtractor 136 (step S105). Further, the steering angle deviation θd is multiplied by Ki with the integration unit 133 and the integration gain unit 134 and added to the addition / subtraction unit 136 (step S106). The motor angular velocity ω is input from the angular velocity calculation unit 124 (step S107), multiplied by the speed gain Kd by the speed gain unit 135, and subtracted and input to the addition / subtraction unit 136 (step S108), and the motor current as the addition / subtraction result of the addition / subtraction unit 136 The command value Iref1 is input to the vehicle speed sensitive gain unit 137 (step S109). Further, the vehicle speed Vel is input from the vehicle speed sensor 103 (step S110), the vehicle speed sensitive vehicle speed gain unit 137 multiplies the motor current command value Iref1 by the vehicle speed gain Kv (step S111), and the motor current command value Iref2 is added to the addition unit 153. Is input.

Further, the motor angular velocity omega column shaft angular velocity omega ₁ is calculated by being 1 / n times is input to the fractional portion 150 (step S112), the torsion angular velocity estimation unit column shaft angular velocity omega ₁ is represented by the number 5 151, the torsional angular velocity estimation value ω _e is estimated (step S113). The estimated torsional angular velocity value ω _e is multiplied by the damping gain Kc by the damping gain unit 152 (step S114), and the obtained damping current command value Irefb1 is added to the motor current command value Irrer2 by the adding unit 153 (step S115). The upper limit value of the current command value Iref3, which is the added value, is limited by the limiter 138 (step S116), and is output as the motor current command value Imref.

  Note that the rate limiter 140 may be a primary or secondary low-pass filter in addition to the above-described configuration. Further, the integrating unit 133 may be a primary phase delay compensator or a primary low-pass filter.

FIG. 11 shows another configuration example of the rudder angle control unit 130 (steering angle control unit 130A). The phase compensation unit 154 performs phase compensation on the torsion angular velocity estimation value ω _e from the torsion angular velocity estimation unit 151. . That is, the phase compensator 154 has a function of “kc · (T ₂ · s + 1) / (T ₁ · s + 1)” with time constants T ₁ and T ₂ . The damping current command value Irefb2 that is the output of the phase compensation unit 154 is added to the current command value Iref1 by the adding unit 153, and the current command value Iref4 that is the added value is input to the vehicle speed sensitive vehicle speed gain unit 137. The current command value Iref5 from the vehicle speed gain unit 137 is input to the limiter 138, and the motor current command value Imref whose upper and lower limits are limited by the limiter 138 is output.

1 Handle 2 Column shaft (input shaft 2a, output shaft 2b)
DESCRIPTION OF SYMBOLS 3 Deceleration mechanism 10 Torque sensor 12 Vehicle speed sensor 13 Battery 20,100 Motor 30 Control unit 31 Steering assistance command value calculating part 32 Maximum output limiting part 34 Current control part 35 PWM control part 36 Motor drive circuit 37 Motor current detection circuit 40 Lower shaft (Intermediate shaft, intermediate shaft)
41 Column 42 Torsion bar 101 Rotation sensor 102 Rudder angle sensor 103 Vehicle speed sensor 110 ECU on the vehicle side
111 switching command unit 112 target steering angle generation unit 120 ECU on EPS side
121 torque control unit 122 switching unit 123 current control / drive unit 124 angular velocity calculation unit 130, 130A steering angle control unit 132 proportional gain (Kp) unit 134 integral gain (Ki) unit 135 speed gain (Kd) unit 137 vehicle speed gain (Kv) ) Part 138 limiter 140 rate limiter 142 change setting part 150 fraction part 151 torsion angular velocity estimation part 152 damping gain (Kc) part 154 phase compensation part

Claims (7)

A function of calculating a motor current command value 1 based on the steering torque and the vehicle speed, driving the motor based on the motor current command value 1 to assist control of the steering system, and switching between an automatic steering mode and a manual steering mode. In the electric power steering apparatus having
A vibration damping function that detects a torsion angle of the torsion bar based on the column shaft angular velocity, obtains an estimated angular velocity value of the torsion angle of the torsion bar, and calculates a vibration suppression current command value calculated based on the estimated angular velocity value And
A motor current command value 2 obtained by adding the motor current command value calculated based on the target steering angle, the actual steering angle, the vehicle speed, and the motor angular velocity of the motor and the vibration suppression current command value is calculated, and vibration suppression Rudder angle control unit having a function;
A switching unit for inputting and switching the motor current command value 1 and the motor current command value 2;
_Let the natural frequency and damping ratio of the torsion bar be ω _n and ζ , respectively .
The column angular velocity and the estimated torsional angular velocity of the torsion bar are respectively ω ₁ and ω _e ,
The vibration suppression function unit calculates the torsional angular velocity estimated value.

Using the transfer function
The switching unit is switched in response to a switching command between the automatic steering mode and the manual steering mode, and the motor is driven and controlled based on the motor current command value 1 in the manual steering mode. Drive control of the motor based on the motor current command value 2, stop the torque sensor,
An electric power steering apparatus characterized in that vibration of a steering wheel is suppressed by the vibration damping function unit. The rudder angle control unit is a rate limiter that smoothes the time change of the target steering angle, and a proportionality that a steering angle deviation between the output of the rate limiter and the actual steering angle is multiplied by a proportional gain and an integral gain. An integration unit; a speed unit that multiplies the motor angular velocity by a speed gain and subtracts it from the addition value of the proportional integration unit to obtain a motor current command value 3; and the motor current command value 3 is multiplied by a vehicle speed gain according to the vehicle speed. A vehicle speed section for outputting a motor current command value 4 and a motor angular velocity are input to generate a damping current command value, and the damping current command value is added to the motor current command value 4 The electric power tearing device according to claim 1, further comprising a vibration damping function unit that outputs a motor current command value 2. The vibration damping function unit divides the motor angular velocity by a reduction ratio and outputs a column shaft angular velocity, a torsion angular velocity estimation unit that obtains a torsion angular velocity estimation value by functionally converting the column shaft angular velocity, and the torsion The electric power steering apparatus according to claim 2, further comprising: a damping gain unit that multiplies an estimated angular velocity value by a damping gain and outputs the damping current command value. The rudder angle control unit is a rate limiter that smoothes the time change of the target steering angle, and a proportionality that a steering angle deviation between the output of the rate limiter and the actual steering angle is multiplied by a proportional gain and an integral gain. An integration unit, a speed unit that multiplies the motor angular velocity by a speed gain and subtracts it from the addition value of the proportional integration unit to obtain a motor current command value 3, and generates the vibration suppression current command value by inputting the motor angular velocity The damping function unit that adds the damping current command value to the motor current command value 3 and outputs the motor current command value 5; and the motor current command value 5 is multiplied by a vehicle speed gain according to the vehicle speed. The electric power tearing device according to claim 1, further comprising a vehicle speed unit that outputs the motor current command value 2. The vibration damping function unit divides the motor angular velocity by a reduction ratio and outputs a column shaft angular velocity, a torsion angular velocity estimation unit that obtains a torsion angular velocity estimation value by functionally converting the column shaft angular velocity, and the torsion The electric power steering apparatus according to claim 4, further comprising: a phase compensation unit that performs phase compensation on the estimated angular velocity value and outputs the vibration suppression current command value. The rate limiter holds a past value of the target steering angle, and a difference between the target steering angle and the past value does not exceed a predetermined upper limit value and does not become less than a predetermined lower limit value. The electric power steering apparatus according to any one of claims 2 to 5, further comprising a change setting unit set to A limiter is provided in the final stage of the rudder angle control unit to output the input value as it is if it is within a predetermined range, and to output the upper limit value or the lower limit value of the range if it is outside the predetermined range. The electric power steering apparatus according to any one of claims 2 to 6, wherein the motor current command value 2 is output from the limiter.

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