JP7199643B2 - vehicle steering system - Google Patents

Description

The present invention relates to a high-performance vehicle steering system that achieves a desired steering torque based on the torsion angle of a torsion bar or the like, is unaffected by road conditions, and is unaffected by changes in mechanical system characteristics over time.

An electric power steering system (EPS), which is one type of vehicle steering system, applies an assist force (steering assist force) to the steering system of a vehicle using the rotational force of a motor. The driving force of the controlled motor is applied as an assist force to the steering shaft or the rack shaft by a transmission mechanism including a speed reduction mechanism. Such a conventional electric power steering device performs feedback control of the motor current in order to generate an assist force accurately. Feedback control adjusts the voltage applied to the motor so that the difference between the steering assist command value (current command value) and the motor current detection value is reduced. modulation) control duty adjustment.

A general configuration of an electric power steering apparatus is shown in FIG. 6b and further through hub units 7a, 7b to steerable wheels 8L, 8R. The column shaft 2 having the torsion bar is provided with a torque sensor 10 for detecting the steering torque Ts of the steering wheel 1 and a steering angle sensor 14 for detecting the steering angle θh. 20 is connected to the column shaft 2 via the speed reduction mechanism 3 . A control unit (ECU) 30 that controls the electric power steering apparatus is supplied with power from a battery 13 and receives an ignition key signal via an ignition key 11 . The control unit 30 calculates the current command value of the assist (steering assistance) command based on the steering torque Ts detected by the torque sensor 10 and the vehicle speed Vs detected by the vehicle speed sensor 12, and compensates the current command value. is applied, the current supplied to the EPS motor 20 is controlled by the voltage control command value Vref.

The control unit 30 is connected to a CAN (Controller Area Network) 40 for exchanging various types of vehicle information, and the vehicle speed Vs can also be received from the CAN 40 . Also, the control unit 30 can be connected to a non-CAN 41 for transmitting/receiving communications other than the CAN 40, analog/digital signals, radio waves, and the like.

The control unit 30 is mainly composed of a CPU (including MCU, MPU, etc.), and general functions executed by programs inside the CPU are shown in FIG.

The functions and operations of the control unit 30 will be described with reference to FIG. 31. The current command value calculation unit 31 calculates a current command value Iref1, which is a control target value of the current supplied to the motor 20, using an assist map or the like based on the input steering torque Ts and vehicle speed Vs. The current command value Iref1 is input to the current limiter 33 via the adder 32A, the current command value Irefm whose maximum current is limited is input to the subtractor 32B, and the deviation I (= Irefm-Im) is calculated, and the deviation I is input to a PI (proportional integral) control unit 35 for improving steering operation characteristics. A voltage control command value Vref whose characteristics have been improved by the PI control unit 35 is input to the PWM control unit 36, and the motor 20 is PWM-driven via an inverter 37 as a driving unit. A current value Im of the motor 20 is detected by the motor current detector 38 and fed back to the subtractor 32B.

The compensation signal CM from the compensation signal generator 34 is added to the adder 32A, and the characteristics of the steering system are compensated by the addition of the compensation signal CM to improve convergence and inertia characteristics. . The compensation signal generator 34 adds the self-aligning torque (SAT) 343 and the inertia 342 in the adder 344, adds the convergence 341 to the addition result in the adder 345, and compensates the addition result of the adder 345. The signal is CM.

Thus, in the assist control of the conventional electric power steering device, the steering torque applied by the driver's manual input is detected by the torque sensor as the torsion torque of the torsion bar, and the assist current mainly corresponding to the torque is detected. to control the motor current. However, when the control is performed by this method, the steering torque may vary depending on the steering angle due to the difference in road surface conditions (for example, inclination). Steering torque may also be affected by variations in motor output characteristics due to long-term use.

In order to solve this problem, an electric power steering system as disclosed in Japanese Patent No. 5208894 (Patent Document 1) has been proposed. In the electric power steering apparatus of Patent Document 1, in order to provide an appropriate steering torque based on the tactile characteristics of the driver, the ratio between the steering angle and the steering torque is determined based on the relationship between the steering angle or the steering torque and the amount of response. The target value of the steering torque is set based on the relationship (steering reaction force characteristic map).

Japanese Patent No. 5208894

However, in the electric power steering apparatus of Patent Document 1, the steering reaction force characteristic map must be obtained in advance, and control is performed based on the deviation between the target value of the steering torque and the detected steering torque. Therefore, there is a possibility that the influence on the steering torque remains.

Also, in the assist control by the electric power steering device, when the steering wheel is returned to the neutral position to go straight from the steering wheel, when the steering wheel does not return smoothly to the neutral position and stops in the middle, It may exceed the position (overshoot). In such a state, the driver must perform corrective steering, which is a burden on the driver. A solution to this problem is also desired.

The present invention has been made in view of the circumstances described above, and an object of the present invention is to provide a steering wheel that is not affected by road conditions, is not affected by changes in the mechanical characteristics of the steering system due to aging, and is capable of adjusting the steering angle and the like. An object of the present invention is to provide a vehicle steering system capable of easily realizing equivalent steering torque. Another object of the present invention is to reduce the burden on the driver by allowing the steering wheel to return smoothly to the vicinity of the neutral position.

The present invention relates to a steering system for a vehicle, which includes at least a torsion bar having an arbitrary spring constant and a sensor for detecting the torsion angle of the torsion bar, and assists and controls a steering system by driving and controlling a motor. A target steering torque generator for generating a target steering torque, a converter for converting the target steering torque into a target torsion angle, and a motor current that causes the torsion angle to follow the target torsion angle A torsion angle control unit that calculates a command value, a manual input torque estimation unit that estimates a manual input torque to the steering wheel and obtains an estimated value of the manual input torque, and a differentiation that differentiates the steering angle and calculates the first angular velocity information. a steering wheel return compensating unit for obtaining a return compensation signal for steering wheel return compensation for compensating for steering wheel return using the first angular velocity information and the manual input torque estimated value; This is achieved by driving and controlling the motor based on the motor current command value reflecting the steering wheel return compensation.

Further, the above-described object of the present invention is achieved by the target steering torque generation section including the steering wheel return compensation section, and by outputting the return compensation signal as the target steering torque to reflect the steering wheel return compensation. Alternatively, by correcting the motor current command value according to the return compensation signal, by reflecting the steering wheel return compensation, or by causing the steering wheel return compensation unit to generate torque based on the magnitude of the manual input torque estimated value. A torque sensitive gain section for obtaining a sensitive gain is further provided, and the return compensation signal is obtained by multiplying and correcting the first angular velocity information by the torque sensitive gain, or the magnitude of the manual input torque estimated value. or the steering wheel return compensating section further includes a speed sensitive gain section that obtains the speed sensitive gain based on the magnitude of the first angular velocity information. and obtaining the return compensation signal by multiplying and correcting the first angular velocity information by the torque sensitive gain and the velocity sensitive gain, or the magnitude of the first angular velocity information changes from zero to a predetermined value. , the velocity sensitive gain increases as the magnitude of the first angular velocity information increases, and when the magnitude of the first angular velocity information exceeds the predetermined value, the magnitude of the first angular velocity information increases. or the steering wheel return compensating section further comprises a limiting section for limiting upper and lower limits of the return compensating signal; or The return compensator further comprises a target speed setting unit for obtaining a target speed for the steering angle, calculates second angular speed information from the first angular speed information and the target speed, and multiplies and corrects the second angular speed information. Alternatively, the target steering torque generating unit may obtain a first torque signal from the steering angle and the vehicle speed using a basic map and a damper gain map sensitive to the vehicle speed. and a hysteresis correction unit for obtaining a third torque signal having a hysteresis characteristic using the steering state and the steering angle. calculating the target steering torque from at least one of the first torque signal, the second torque signal and the third torque signal and the return compensation signal; or The target steering torque generating section uses a basic map section to obtain a first torque signal from the steering angle and vehicle speed using a basic map, and a damper gain map sensitive to vehicle speed based on third angular velocity information. and a hysteresis correction unit for obtaining a third torque signal having a hysteresis characteristic using the steering state and the steering angle. By calculating the target steering torque from at least one of the third torque signals, or by the characteristics of the basic map and the hysteresis correction section being vehicle speed sensitive, or by the target steering torque generation section. is further provided with a phase compensation section for performing phase compensation before or after the basic map section, and the first torque signal is obtained from the steering angle and the vehicle speed via the basic map section and the phase compensation section. By seeking, it will be achieved more effectively.

According to the vehicle steering system of the present invention, the torsion angle follows the target torsion angle by controlling the target torsion angle obtained based on the target steering torque generated by the target steering torque generation unit. Thus, a desired steering torque can be realized, and an appropriate steering torque can be applied based on the steering feeling of the driver.

Furthermore, by estimating the manual input torque and compensating for the return of the steering wheel based on the estimated value of the manual input torque, the steering wheel can be accurately returned to the vicinity of the neutral position, and the load on the driver can be reduced.

1 is a configuration diagram showing an outline of an electric power steering device; FIG. FIG. 2 is a block diagram showing a configuration example inside a control unit (ECU) of the electric power steering device; FIG. 3 is a structural diagram showing an installation example of an EPS steering system and various sensors; It is a block diagram which shows the structural example (1st Embodiment) of this invention. FIG. 2 is a block diagram showing a configuration example (first embodiment) of a target steering torque generator; FIG. 5 is a diagram showing an example of characteristics of a basic map; FIG. 5 is a diagram showing an example of characteristics of a damper gain map; FIG. 5 is a diagram showing an example of characteristics of a hysteresis corrector; It is a block diagram which shows the structural example (1st Embodiment) of a steering wheel return compensation part. It is a schematic diagram of a handle and a torsion bar. FIG. 4 is a diagram showing a characteristic example of a torque sensitive gain map; 4 is a diagram showing an example of characteristics of a speed sensitive gain map; FIG. FIG. 5 is a diagram showing an example of setting upper and lower limit values in a limiter; 4 is a block diagram showing a configuration example of a twist angle control unit; FIG. It is a flowchart which shows the operation example (1st Embodiment) of this invention. 4 is a flowchart showing an operation example (first embodiment) of a target steering torque generator; 4 is a flow chart showing an operation example of a twist angle control unit; 4 is a graph showing an example of the time response of the steering wheel angle with and without steering wheel return compensation in a simulation showing the effect of the steering wheel return compensator. FIG. 7 is a block diagram showing a configuration example (second embodiment) of a steering wheel return compensator; 4 is a diagram showing an example of characteristics of a target speed setting map; FIG. 8 is a flow chart showing an operation example (second embodiment) of a target steering torque generator; It is a block diagram which shows the structural example (3rd Embodiment) of this invention. FIG. 11 is a block diagram showing a configuration example (third embodiment) of a target steering torque generator; It is a flowchart which shows the operation example (3rd Embodiment) of this invention. 9 is a flowchart showing an operation example (third embodiment) of a target steering torque generator; FIG. 11 is a block diagram showing a configuration example (fourth embodiment) of a target steering torque generation unit; It is a block diagram which shows the structural example (5th Embodiment) of this invention. It is a block diagram which shows the structural example (6th Embodiment) of this invention. FIG. 4 is a block diagram showing an example of insertion of a phase compensator; 1 is a configuration diagram showing an outline of an SBW system; FIG. It is a block diagram which shows the structural example (7th Embodiment) of this invention. It is a block diagram which shows the structural example of a target steering angle production|generation part. It is a block diagram which shows the structural example of a steering angle control part. FIG. 11 is a flow chart showing an operation example (seventh embodiment) of the present invention; FIG.

The present invention is a steering system for a vehicle, which is not affected by road surface conditions and which achieves steering torque equivalent to a steering angle or the like. A desired steering torque is realized by performing control so as to follow .

BEST MODE FOR CARRYING OUT THE INVENTION Below, embodiments of the present invention will be described with reference to the drawings.

First, an installation example of various sensors for detecting information related to an electric power steering device, which is one of the vehicle steering devices according to the present invention, will be described. FIG. 3 is a diagram showing an installation example of the EPS steering system and various sensors, and the column shaft 2 is provided with a torsion bar 2A. A road surface reaction force Fr and road surface information (friction coefficient) μ act on the steered wheels 8L and 8R. An upper angle sensor is provided on the handle side of the column shaft 2 with the torsion bar 2A interposed therebetween, and a lower angle sensor is provided on the steering wheel side of the column shaft 2 with the torsion bar 2A interposed therebetween. detects the steering wheel angle _θ1 and the _lower angle sensor detects the column angle θ2. The steering angle θh is detected by a steering angle sensor provided above the column shaft ₂ , and from the deviation of the steering wheel angle θ1 and the column angle θ2, the twist angle Δθ of the torsion bar and the torsion bar torque are obtained by the following equations 1 and ₂ . Tt can be obtained. Kt is the spring constant of the torsion bar 2A.

トーションバートルクＴｔは、例えば特開２００８－２１６１７２号公報で示されるトルクセンサを用いて検出することも可能である。なお、本実施形態では、トーションバートルクＴｔを操舵トルクＴｓとしても扱うこととする。

The torsion bar torque Tt can also be detected using a torque sensor disclosed in Japanese Patent Application Laid-Open No. 2008-216172, for example. In this embodiment, the torsion bar torque Tt is treated as the steering torque Ts.

Next, a configuration example of the present invention will be described.

FIG. 4 is a block diagram showing a configuration example (first embodiment) of the present invention. Steering by the driver is assist-controlled by a motor 20 in the EPS steering system/vehicle system 100. As shown in FIG. In addition to the steering angle θh, the target steering torque generator 200 that outputs the target steering torque Tref receives the vehicle speed Vs, the steering torque Ts, and the right-turn or left-turn steering state output from the right-turn/left-turn determination unit 400 . STs are entered. The target steering torque Tref is converted into a target twist angle Δθref by the conversion unit 500, and the target twist angle Δθref is input to the twist angle control unit 300 together with the twist angle Δθ of the torsion bar 2A. The torsion angle control unit 300 calculates a motor current command value Imc such that the torsion angle Δθ becomes the target torsion angle Δθref, and the EPS motor 20 is driven by the motor current command value Imc.

The right-turn/left-turn determination unit 400 determines whether the steering is right-turn or left-turn based on the motor angular velocity ωm, and outputs the determination result as the steering state STs. For example, when the motor angular velocity ωm has a positive value, it is determined as “right turn”, and when it has a negative value, it is determined as “left turn”. Instead of the motor angular velocity ωm, an angular velocity calculated by performing _a velocity calculation _on the steering angle θh, the steering wheel angle θ1, or the column angle θ2 may be used.

FIG. 5 shows a configuration example of the target steering torque generation section 200. The target steering torque generation section 200 includes a basic map section 210, a differentiation section 220, a damper gain section 230, a hysteresis correction section 240, a steering wheel return compensation section 250, and a multiplication section. A unit 260 and addition units 261 , 262 and 263 are provided. The steering angle θh is input to the basic map section 210 , differentiation section 220 , hysteresis correction section 240 and steering wheel return compensation section 250 . The steering state STs output from right-turn/left-turn determination section 400 is input to hysteresis correction section 240 . The steering torque Ts is input to the steering wheel return compensation section 250 , and the vehicle speed Vs is input to the basic map section 210 and the damper gain section 230 .

The basic map unit 210 has a basic map, and uses the basic map to output a torque signal (first torque signal) Tref_a having the vehicle speed Vs as a parameter. The basic map is adjusted by tuning. For example, as shown in FIG. 6A, the torque signal Tref_a increases as the steering angle θh magnitude (absolute value) |θh| increases as . In FIG. 6A, sign section 211 outputs the sign (+1, -1) of steering angle θh to multiplication section 212, and the magnitude of torque signal Tref_a is calculated from a map based on the magnitude of steering angle θh. and multiplied by the sign of the steering angle θh to obtain the torque signal Tref_a. Further, as shown in FIG. 6(B), the map may be constructed according to the positive and negative steering angles θh. can be Further, although the basic map shown in FIG. 6 is vehicle speed sensitive, it does not have to be vehicle speed sensitive.

Differentiating section 220 differentiates steering angle θh to calculate steering angular velocity ωh, which is angular velocity information (third angular velocity information), and steering angular velocity ωh is input to multiplying section 260 .

A damper gain section 230 outputs a damper gain DG to be multiplied by the steering angular velocity _ωh . The multiplication result of the steering angular velocity _ωh and the damper gain DG in the multiplier 260 is input to the adder 262 as a torque signal (second torque signal) Tref_b. The damper gain _DG is obtained according to the vehicle speed Vs using a vehicle speed sensitive damper gain map of the damper gain section 230 . The damper gain map has a characteristic of gradually increasing as the vehicle speed Vs increases, as shown in FIG. 7, for example. The damper gain map may be variable according to the steering angle θh. The damper gain section 230 and the multiplication section 260 constitute a damper calculation section.

Based on the steering angle θh and the steering state STs, the hysteresis correction unit 240 calculates a torque signal (third torque signal) Tref_c according to Equation 3 below. In Equation 3 below, x=θh, y=Tref_c, a>1, c>0, and _Ahys is the hysteresis width.

右切り操舵から左切り操舵、左切り操舵から右切り操舵へ切り替える際に、最終座標（ｘ１，ｙ１）の値に基づき、切り替え後の数３の“ｂ”に以下の数４を代入する。これにより、切り替え前後の連続性が保たれる。

When switching from right-turn steering to left-turn steering and from left-turn steering to right-turn steering, the following equation 4 is substituted for "b" in equation 3 after switching based on the values of the final coordinates (x1, y1). This maintains continuity before and after switching.

上記数４は、上記数３中のｘにｘ１を、ｙ_Ｒ及びｙ_Ｌにｙ１を代入することにより導出することができる。

Equation 4 above can be derived by substituting x1 for x and y1 for _yR and _yL in Equation 3 above.

Any positive number greater than 1 can be used as "a". For example, when Napier's number "e" is used, Equations 3 and 4 become Equations 5 and 6 below.

数５及び数６においてＡ_ｈｙｓ＝１［Ｎ・ｍ］、ｃ＝０．３と設定し、０［ｄｅｇ］から開始し、＋５０［ｄｅｇ］、－５０［ｄｅｇ］の操舵をした場合の、ヒステリシス補正されたトルク信号Ｔｒｅｆ＿ｃの線図例を図８に示す。即ち、ヒステリシス補正部２４０からのトルク信号Ｔｒｅｆ＿ｃは、０の原点→Ｌ１（細線）→Ｌ２（破線）→Ｌ３（太線）のようなヒステリシス特性となる。

Set A _hys = 1 [N m] and c = 0.3 in Equations 5 and 6, start from 0 [deg], and steer +50 [deg] and -50 [deg], An example diagram of the hysteresis-corrected torque signal Tref_c is shown in FIG. That is, the torque signal Tref_c from the hysteresis correction unit 240 has hysteresis characteristics such as the origin of 0→L1 (thin line)→L2 (dashed line)→L3 (thick line).

The coefficient A _hys representing the output width of the hysteresis characteristic and the coefficient c representing the roundness may be variable according to the vehicle speed Vs and/or the steering angle θh.

The steering wheel return compensator 250 estimates the manual input torque applied to the steering wheel 1 by the driver using the steering angle θh and the steering torque Ts, and based on the estimated manual input torque (manual input torque estimated value) Tse A return compensation signal Tref_d for compensating for steering wheel return is calculated. When the steering wheel 1 is released from the turned state, the steering wheel 1 may stop on the way without returning to the neutral position, so a return compensation signal Tref_d for returning the steering wheel to the vicinity of the neutral position is calculated.

FIG. 9 shows a configuration example of the steering wheel return compensator 250. As shown in FIG. The steering wheel return compensation section 250 includes a manual input torque estimation section 251, a torque sensitive gain section 252, a speed sensitive gain section 253, a limiting section 254, a differentiation section 255, absolute value sections 256A and 256B, and multiplication sections 257A and 257B.

The manual input torque estimator 251 calculates the manual input torque estimated value Tse using the steering angle θh and the steering torque Ts. Here, a method for estimating manual input torque will be described. FIG. 10 shows the relationship between the manual input torque Th to the steering wheel 1, the steering angle θh, and the torsion bar torque Tt. FIG. 10 is a schematic representation of the handle 1 and the torsion bar 2A. When the driver's manual input torque Th is applied to the steering wheel 1, the steering wheel 1 rotates at the steering angle θh, and a torsion bar torque Tt proportional to the torsion angle Δθ of the torsion bar is generated in the direction opposite to the rotation. . From this relationship, since the torsion bar torque Tt is treated as the steering torque Ts in this embodiment, the following relational expression (7) holds between the manual input torque Th, the steering angle θh, and the steering torque Ts.

ここで、Ｊｈは慣性モーメント、Ｄｈは減衰係数である。上記数７を手入力トルクＴｈについて解くと下記数８が得られる。

Here, Jh is the moment of inertia and Dh is the damping coefficient. Solving Equation 7 above for the manual input torque Th yields Equation 8 below.

よって、慣性モーメントＪｈ及び減衰係数Ｄｈを予め求めておくことにより、操舵角θｈ及び操舵トルクＴｓを用いて、手入力トルクＴｈを求めることができる。実際には、上記数８は連続系で表されているので、離散系に変換して求めることになる。連続系から離散系への変換は、既存の方法、例えば、単純には微分演算を差分演算として行う等により行う。また、数８には微分演算が含まれており、高周波の微分ノイズが現れやすくなるので、ローパスフィルタ（ＬＰＦ）等によるフィルタ処理を行う。以上のことより、手入力トルク推定部２５１は、入力した操舵角θｈ及び操舵トルクＴｓを用いて、予め求められた慣性モーメントＪｈ及び減衰係数Ｄｈを含む数８を離散系に変換した演算処理を行い、その演算結果に対してＬＰＦ等によるフィルタ処理を施すことにより、手入力トルク推定値Ｔｓｅを算出する。なお、数８による演算処理とフィルタ処理とを分けずに、両方を含んだ離散系の演算処理で手入力トルク推定値Ｔｓｅを算出しても良い。また、微分ノイズが軽微な場合、フィルタ処理を省略しても良い。

Therefore, by obtaining the moment of inertia Jh and the damping coefficient Dh in advance, the manual input torque Th can be obtained using the steering angle θh and the steering torque Ts. Actually, since the above Equation 8 is expressed in a continuous system, it is converted into a discrete system to obtain it. Transformation from a continuous system to a discrete system is performed by an existing method, for example, simply performing a differential operation as a differential operation. In addition, equation 8 includes a differential operation, and since high-frequency differential noise tends to appear, filter processing using a low-pass filter (LPF) or the like is performed. As described above, the manual input torque estimator 251 uses the input steering angle θh and steering torque Ts to perform arithmetic processing in which Equation 8 including the moment of inertia Jh and the damping coefficient Dh obtained in advance is converted into a discrete system. The manual input torque estimated value Tse is calculated by subjecting the calculation result to filter processing using an LPF or the like. It should be noted that the manual input torque estimated value Tse may be calculated by a discrete system calculation process including both without separating the calculation process and the filter process according to Equation 8. Also, if the differential noise is slight, filtering may be omitted.

The reason for using the manual input torque estimate will be explained. For example, if the steering torque Ts is used when the driver releases the steering wheel after turning it, a slight delay occurs before the torsion of the torsion bar is eliminated, and the steering torque Ts is immediately released. cannot be zero. By combining the manual input torque estimation and the torque sensitive gain, which will be described later, the steering wheel return function can be quickly and strongly effective only when the manual input torque is near zero.

Similar to the differentiating unit 220, the differentiating unit 255 differentiates the steering angle θh to calculate a steering angular velocity ωh1, which is angular velocity information (first angular velocity information). Note that the differentiation unit 220 may be shared and the differentiation unit 255 may be omitted.

The absolute value units 256A and 256B output the magnitude (absolute value) of the input data. The absolute value unit 256A outputs the absolute value of the manual input torque estimated value Tse, and the absolute value unit 256B outputs the absolute value of the steering angular velocity ωh1. Output each.

The torque sensitive gain section 252 uses the torque sensitive gain map to find the torque sensitive gain Gt corresponding to the magnitude of the manual input torque estimated value Tse. The torque sensitive gain map has a characteristic that the torque sensitive gain Gt gradually decreases as the magnitude of the manual input torque estimated value Tse increases, as shown in FIG. 11, for example.

A velocity sensitive gain section 253 uses a velocity sensitive gain map to obtain a velocity sensitive gain Gv corresponding to the magnitude of the steering angular velocity ωh1. For example, as shown in FIG. 12, the speed-sensitive gain map shows that the speed-sensitive gain Gv increases rapidly as the steering angular speed ωh1 increases within a range from 0 to a predetermined value ω0. , and in a range exceeding a predetermined value ω0, it gradually decreases as the magnitude of the steering angular velocity ωh1 increases.

The steering angular velocity ωh1 output from the differentiating section 255 is multiplied by the speed sensitive gain Gv in the multiplication section 257A, and the multiplication result is multiplied by the torque sensitive gain Gt in the multiplication section 257B to calculate the return compensation signal Tref_d0. .

The limiting unit 254 limits the upper and lower limits of the return compensation signal Tref_d0 and outputs the return compensation signal Tref_d. By limiting the upper and lower limits of the return compensation signal Tref_d0, output of abnormal values is suppressed. As shown in FIG. 13, the upper limit value and the lower limit value for the return compensation signal are set in advance. Otherwise, return compensation signal Tref_d0 is output as return compensation signal Tref_d.

The characteristics of the torque sensitive gain map and speed sensitive gain map are not limited to the curvilinear characteristics shown in FIGS. 11 and 12, but may be linear characteristics or may be defined by functions. Further, in cases such as when the steering wheel return can be appropriately compensated only by multiplication of the torque sensitive gain Gt from the torque sensitive gain section 252, the speed sensitive gain section 253 and the accompanying absolute value section 256B and multiplication section 257A can be omitted. . Furthermore, the limiter 254 can be omitted when the return compensation signal does not become an abnormal value or when the output of the abnormal value is suppressed by other means.

The return compensation signal Tref_d and the torque signals Tref_c, Tref_b, and Tref_a obtained as described above are successively added by adders 263, 262, and 261, and the final addition result is output as the target steering torque Tref.

The steering angular velocities ωh and ωh1 calculated by the differentiating units 220 and 255 are obtained by differentiating the steering angle θh. , LPF processing may be performed appropriately. Alternatively, the differential operation and LPF processing may be performed using a high-pass filter (HPF) and gain. Further, the steering angular velocities ωh and ωh1 are calculated by performing differentiation and LPF processing on the steering wheel angle θ1 detected by the _upper angle sensor or the column angle θ2 detected by the _lower angle sensor instead of the steering angle θh. You can The motor angular velocity ωm may be used as the angular velocity information instead of the steering angular velocities ωh and ωh1, in which case the differentiating sections 220 and 255 are not required. In this embodiment, the steering wheel return compensation section 250 is provided in the target steering torque generation section 200. However, the steering wheel return compensation section 250 is removed from the target steering torque generation section 200, and the addition section is placed after the target steering torque generation section. is provided, and the output from the target steering torque generating section and the return compensation signal from the steering wheel return compensation section are added by the adding section to obtain the target steering torque Tref.

The conversion unit 500 has a characteristic of -1/Kt obtained by inverting the sign of the reciprocal of the spring constant Kt of the torsion bar 2A, and converts the target steering torque Tref into the target twist angle Δθref.

The torsion angle control unit 300 calculates the motor current command value Imc based on the target torsion angle Δθref and the torsion angle Δθ. FIG. 14 is a block diagram showing a configuration example of the torsion angle control unit 300. The torsion angle control unit 300 includes a torsion angle feedback (FB) compensation unit 310, a torsion angular velocity calculation unit 320, a speed control unit 330, and an output limiter 350. and a subtractor 361 . The target torsion angle Δθref output from the conversion unit 500 is added to the subtraction unit 361 , and the torsion angle Δθ is subtracted to the subtraction unit 361 and input to the torsion angular velocity calculation unit 320 .

The torsion angle FB compensator 310 multiplies the deviation Δθ ₀ between the target torsion angle Δθref and the torsion angle Δθ calculated by the subtraction unit 361 by a compensation value C _FB (transfer function) to obtain the torsion angle Δθ outputs a target torsional angular velocity ωref that follows. The compensation value CFB may be a simple gain _Kpp or a generally used compensation value such as a PI control compensation value. The target torsional angular velocity ωref is input to the velocity controller 330 . The torsion angle FB compensation section 310 and the speed control section 330 allow the torsion angle Δθ to follow the target torsion angle Δθref, thereby realizing a desired steering torque.

The torsion angular velocity calculator 320 calculates a torsion angular velocity ωt by differentiating the torsion angle Δθ, and the torsion angular velocity ωt is input to the velocity controller 330 . Pseudo-differentiation using HPF and gain may be performed as the differential operation. Alternatively, the torsion angular velocity ωt may be calculated by another means or other than the torsion angle Δθ and input to the velocity control section 330 .

Speed control unit 330 calculates a motor current command value Imca such that torsional angular velocity ωt follows target torsional angular velocity ωref by IP control (proportional leading PI control). The difference (ωref−ωt) between the target twist angular velocity ωref and the twist angular velocity ωt is calculated by the subtraction unit 333, the difference is integrated by the integration unit 331 having the gain Kvi, and the integration result is added to the subtraction unit 334. be. The torsional angular velocity ωt is also input to the proportional section 332 , subjected to proportional processing by the gain Kvp, and subtracted and input to the subtracting section 334 . The subtraction result of the subtraction unit 334 is output as the motor current command value Imca. Note that the speed control unit 330 performs PI control, P (proportional) control, PID (proportional-integral-derivative) control, PI-D control (differential-preceding PID control), model matching control, and model reference control, instead of IP control. The motor current command value Imca may be calculated by a commonly used control method such as control.

Motor current command value Imca from speed control unit 330 is input to output limiting unit 350 .

Output limiter 350 limits the upper and lower limits of motor current command value Imca and outputs motor current command value Imc. Similar to the limiting section 254 in the steering wheel return compensating section 250, an upper limit value and a lower limit value for the motor current command value Imca are preset and limited. Note that the output limiter can be omitted.

In such a configuration, an operation example of this embodiment will be described with reference to the flow charts of FIGS. 15 to 17. FIG.

When the operation is started, the right-turn/left-turn determination unit 400 receives the motor angular velocity ωm, determines whether the steering is right-turned or left-turned based on the sign of the motor angular velocity ωm, and uses the determination result as the steering state STs. It is output to the target steering torque generator 200 (step S10).

The target steering torque generator 200 receives the steering angle θh, the steering torque Ts, and the vehicle speed Vs along with the steering state STs, and generates a target steering torque Tref (step S20). An example of the operation of the target steering torque generator 200 will be described with reference to the flowchart of FIG.

The steering angle θh input to the target steering torque generation unit 200 is supplied to the basic map unit 210, the differentiation unit 220, the hysteresis correction unit 240, and the steering wheel return compensation unit 250, the steering state STs is supplied to the hysteresis correction unit 240, and the steering torque Ts is supplied to the steering wheel. The vehicle speed Vs is inputted to the basic map section 210 and the damper gain section 230 of the return compensation section 250 (step S21).

Basic map unit 210 generates torque signal Tref_a corresponding to steering angle θh and vehicle speed Vs using the basic map shown in FIG. ).

The differentiating section 220 differentiates the steering angle θh to output the steering angular velocity _ωh (step S23), and the damper gain section 230 outputs the damper gain DG according to the vehicle speed Vs using the damper gain map shown in FIG. S24). The multiplier 260 multiplies the steering angular velocity _ωh and the damper gain DG to calculate the torque signal Tref_b, and outputs it to the adder 262 (step S25).

The hysteresis correction unit 240 performs hysteresis correction by switching the calculations of Equations 5 and 6 according to the steering angle θh and the steering state STs (step S26), generates a torque signal Tref_c, and outputs it to the addition unit 263 ( step S27). Although the hysteresis widths A _hys , c, x1 and y1 in Equations 5 and 6 are set and held in advance, b and b′ are calculated in advance from Equation 6, and b and b′ are calculated instead of x1 and y1. may be held.

In the steering wheel return compensating section 250, the steering torque Ts is inputted to the manual input torque estimating section 251, and the steering angle θh is inputted to the manual input torque estimating section 251 and the differentiating section 255, respectively. The manual input torque estimating unit 251 uses the input steering angle θh and steering torque Ts as well as the preset moment of inertia Jh and damping coefficient Dh to convert Equation 8 into a discrete system and filter processing using the LPF. , the manual input torque estimated value Tse is calculated (step S28), and the manual input torque estimated value Tse is input to the absolute value unit 256A. The differentiation unit 255 differentiates the steering angle θh to calculate the steering angular velocity ωh1 (step S29), and the steering angular velocity ωh1 is input to the absolute value unit 256B and the multiplication unit 257A. The absolute value section 256A calculates the absolute value of the manual input torque estimated value Tse and outputs it to the torque sensitive gain section 252, and the absolute value section 256B calculates the absolute value of the steering angular velocity ωh1 and outputs it to the speed sensitive gain section 253. (Step S30). The torque sensitive gain section 252 uses a torque sensitive gain map having characteristics as shown in FIG. 11 to determine a torque sensitive gain Gt corresponding to the absolute value of the manual input torque estimated value Tse (step S31). The velocity sensitive gain section 253 uses a velocity sensitive gain map having characteristics as shown in FIG. 12 to determine a velocity sensitive gain Gv corresponding to the absolute value of the steering angular velocity ωh1 (step S32). The torque sensitive gain Gt is input to the multiplier 257B, and the speed sensitive gain Gv is input to the multiplier 257A. The multiplier 257A multiplies the steering angular velocity ωh1 by the speed sensitive gain Gv, the multiplier 257B multiplies the multiplication result by the torque sensitive gain Gt (step S33), and outputs the multiplied result as the return compensation signal Tref_d0. The return compensation signal Tref_d0 is input to the limiting unit 254, and the limiting unit 254 limits the upper and lower limit values of the return compensation signal Tref_d0 with preset upper and lower limit values, and outputs the return compensation signal Tref_d to the addition unit 263 ( step S34).

Then, the addition unit 263 adds the return compensation signal Tref_d and the torque signal Tref_c, the addition unit 262 adds the torque signal Tref_b to the addition result, and the addition unit 261 adds the torque signal Tref_a to the addition result. Then, the target steering torque Tref is calculated (step S35).

The target steering torque Tref generated by the target steering torque generation unit 200 is input to the conversion unit 500, where it is converted into the target torsion angle Δθref (step S40). The target twist angle Δθref is input to the twist angle control section 300 .

The torsion angle control unit 300 inputs the torsion angle Δθ together with the target torsion angle Δθref, and calculates the motor current command value Imc (step S50). An operation example of the twist angle control section 300 will be described with reference to the flowchart of FIG.

The target torsion angle Δθref input to the torsion angle control unit 300 is input to the subtraction unit 361, and the torsion angle Δθ is input to the subtraction unit 361 and the torsion angular velocity calculation unit 320 (step S51).

The subtraction unit 361 calculates the deviation _Δθ0 by subtracting the torsion angle Δθ from the target torsion angle Δθref (step S52). The deviation Δθ ₀ is input to the torsion angle FB compensator 310, and the torsion angle FB compensator 310 multiplies the deviation Δθ ₀ by the compensation value C _FB to compensate for the deviation Δθ ₀ (step S53), and obtains the target torsion angular velocity ωref is output to the speed control unit 330 .

The torsion angular velocity calculation unit 320 having received the torsion angle Δθ calculates a torsion angular velocity ωt by differential calculation with respect to the torsion angle Δθ (step S54), and outputs the torsion angular velocity ωt to the speed control unit 330 .

In the speed control unit 330, the difference between the target torsional angular velocity ωref and the torsional angular velocity ωt is calculated by the subtracting unit 333, the difference is integrated (Kvi/s) by the integrating unit 331, and added to the subtracting unit 334 (step S55). ). Furthermore, the torsional angular velocity ωt is proportionally processed (Kvp) by the proportional portion 332, the proportional result is subtracted and input to the subtractor 334 (step S55), and the motor current command value Imca, which is the subtraction result of the subtractor 334, is output.

Motor current command value Imca is input to output limiter 350 . The output limiter 350 limits the upper and lower limits of the motor current command value Imca by preset upper and lower limits (step S56), and outputs the motor current command value Imc (step S57).

Based on the motor current command value Imc output from the torsion angle control unit 300, the motor is driven to perform current control (step S60).

Note that the order of data input and calculation in FIGS. 15 to 17 can be changed as appropriate.

The effect of the steering wheel return compensation (handle wheel return compensation) by the steering wheel return compensator in this embodiment will be described based on simulation results.

In the simulation, by applying a manual input torque of 4 Nm, the steering angle θh was maintained at about 50 degrees for about 1 second from the start of operation, and then the hands were released (manual input torque: 0 Nm). Simulate the time response of the steering wheel angle (upper angle of the torsion bar) with and without steering wheel return compensation by the steering wheel return compensator.

FIG. 18 shows the simulation results, where FIG. 18(A) is the simulation result when there is no steering wheel return compensation, and FIG. 18(B) is the simulation result when there is steering wheel return compensation. From FIG. 18(A), it can be seen that when there is no steering wheel return compensation, the steering wheel angle after releasing exceeds 0 deg, overshoots to about -11 deg, and then stays at about -3 deg. In this case, the driver feels that the appearance is unpleasant, and since the vehicle has deviated from straight running, the driver must perform corrective steering. This corrective steering becomes a load for the driver.

On the other hand, when there is steering wheel return compensation, it can be seen from FIG. 18(B) that the steady-state deviation is improved to about 0 deg with almost no overshoot after the hand is released. With this improvement, it is possible to maintain a state close to straight-ahead running, and the appearance of the vehicle does not make the driver feel uncomfortable, so there is no burden on the driver.

In the steering wheel return compensator 250 of the first embodiment, a target speed corresponding to the steering angle θh is set, and a compensation value corresponding to the deviation between the target speed and the steering angular speed ωh1 is obtained. can be strengthened. FIG. 19 shows a configuration example (second embodiment) of a steering wheel return compensator equipped with this function. A target speed setting unit 258 and a subtraction unit 259 are added to the steering wheel return compensation unit 650 of the first embodiment shown in FIG. A speed setting unit 258 sets a target speed ωref according to the steering angle θh.

The target speed setting unit 258 has a target speed setting map that defines target speeds according to steering angles. For example, as shown in FIG. 20, the target speed setting map is such that when the steering angle is zero, the target speed is also zero. has the property of growing. A target speed setting unit 258 inputs a steering angle θh, obtains a target speed ωref for the steering angle θh based on a target speed setting map, and subtracts the target speed ωref from the target speed ωref to a subtraction unit 259 . The steering angular velocity ωh1 outputted from the differentiating part 255 is added to the subtracting part 259, and the steering angular velocity deviation ωhc (second angular velocity information) is calculated by subtracting the target velocity ωref from the steering angular velocity ωh1. The calculated steering angular speed deviation ωhc is multiplied by the speed sensitive gain Gv and the torque sensitive gain Gt in multipliers 257A and 257B, respectively. For example, it is assumed that the steering angle θh is positive and the target speed ωref is more negative than the steering angular speed ωh1. At this time, the steering angular velocity deviation ωhc becomes a positive value, and the return compensation signal Tref_d also becomes a positive value. Since the return compensation signal Tref_d becomes a positive value, the target torsion angle Δθref is obtained so as to return the steering wheel to the neutral position against the road surface reaction force, and the steering wheel return is improved. On the other hand, when the steering angular velocity deviation ωhc is negative, the speed of returning to the neutral position is moderated, and overshoot can be suppressed. In FIG. 20, the characteristics of the target speed setting map are symmetrical with respect to the origin, but they may be asymmetrical depending on the characteristics of the vehicle. In addition, linear characteristics may be used instead of curvilinear characteristics, and characteristics may be expressed by mathematical expressions.

In the operation example of the second embodiment, the operation of the target speed setting unit 258 and the subtraction unit 259 is added to the operation example of the target steering torque generation unit 200 in the first embodiment shown in FIG. .

FIG. 21 shows a flowchart of an operation example of the target steering torque generator in the second embodiment. The steering angle θh input to the steering wheel return compensating section 650 is input to the target speed setting section 258 in addition to the manual input torque estimating section 251 and the differentiating section 255 . After the steering angular velocity ωh1 is calculated by the differentiating section 255 (step S29), the steering angular velocity ωh1 is input to the absolute value section 256B and the subtracting section 259. FIG. The target speed setting unit 258 having input the steering angle θh obtains the target speed ωref for the steering angle θh using a target speed setting map having characteristics as shown in FIG. 20 (step S29A), and subtracts the target speed ωref. Subtraction is input to the unit 259 . The subtractor 259 calculates the steering angular velocity deviation ωhc by subtracting the target speed ωref from the steering angular velocity ωh1 (step S29B), and the steering angular velocity deviation ωhc is input to the multiplier 257A. After that, the same operation as the operation example of the target steering torque generation unit 200 in the first embodiment is performed (from step S30).

Note that the order of data input and calculation in FIG. 21 can be changed as appropriate.

In the first embodiment, steering wheel return compensation is performed by treating the return compensation signal calculated by the steering wheel return compensation section as the target steering torque. It can be carried out. FIG. 22 shows a configuration example (third embodiment) of the present invention in this case, and FIG. 23 shows a configuration example of the target steering torque generation section in the third embodiment. Compared with the target steering torque generator 200 in the first embodiment shown in FIG. 4 and the first embodiment shown in FIG. A steering wheel return compensation unit 750 is provided outside the target steering torque generation unit 700, and the return compensation signal Imh output from the steering wheel return compensation unit 750 is subtracted and input to a newly provided subtraction unit 770. , the motor current command value Imc from the torsion angle control unit 300 is additionally input to the subtraction unit 770 in addition to the return compensation signal Imh. Since the target steering torque generation section 700 does not have a steering wheel return compensation section, the steering torque Ts that was input only to the steering wheel return compensation section is not input.

The target steering torque generation unit 700 has a configuration in which the steering wheel return compensation unit 250 and the addition unit 263 are removed from the target steering torque generation unit 200 in the first embodiment, and the other components are the target steering torque generation unit 200. The torque signal Tref_c output from the hysteresis correction unit 240 is input to the addition unit 262 . Note that the target steering torque generation unit 700 may be configured by at least one of the basic map unit 210 , the damper calculation unit (damper gain unit 230 and multiplication unit 260 ), and the hysteresis correction unit 240 .

The steering wheel return compensator 750 has the same configuration as the steering wheel return compensator 250 in the first embodiment shown in FIG. However, the steering wheel return compensation unit 750 outputs a return compensation signal Imh treated as a current command value. Therefore, the torque sensitive gain map of the torque sensitive gain section and the speed sensitive gain map of the speed sensitive gain section in the third embodiment are modified from the maps in the first embodiment. That is, the mode of change is the same as that of each map in the first embodiment, but the maximum gain value and the like are adjusted so that the return compensation signal is treated as the current command value.

The motor current command value Imc is corrected by subtracting the return compensation signal Imh from the motor current command value Imc in the subtractor 770, and the corrected motor current command value Imc is output as the motor current command value Imcc.

The operation of the third embodiment differs from the operation of the first embodiment in that the operation in the target steering torque generation section and the return compensation signal output from the steering wheel return compensation section are related.

24 and 25 respectively show a flowchart of an operation example of the third embodiment and a flowchart of an operation example of the target steering torque generator 750 in the third embodiment. As shown in FIG. 25, the target steering torque generation unit 750 performs the same operation as the target steering torque generation unit 200 in the first embodiment until generation of the torque signal Tref_c in the hysteresis correction unit 240 (step S27). Torque signal Tref_c is input to adder 262 . After that, steps S28 to S34 in the target steering torque generation unit 200 are not performed, the addition unit 262 adds the torque signal Tref_c and the torque signal Tref_b, and the addition unit 261 adds the torque signal Tref_a to the addition result. A steering torque Tref is calculated (step S35A).

After generating the target steering torque (step S20A), calculation of the target torsion angle Δθref (step S40) and torsion angle control (step S50) are executed, and the motor current command value Imc output from the torsion angle control unit 300 is subtracted. An addition input is provided to the unit 770 .

On the other hand, in the steering wheel return compensation section 750, the return compensation signal Imh is calculated by the same operation as the steering wheel return compensation section 250 in the first embodiment (step S50A), and the return compensation signal Imh is subtracted and input to the subtraction section 770. .

The subtraction unit 770 subtracts the return compensation signal Imh from the motor current command value Imc, outputs the motor current command value Imcc, drives the motor based on the motor current command value Imcc, and carries out current control (step S60). ).

Note that the order of data input and calculation in FIGS. 24 and 25 can be changed as appropriate.

The target speed setting unit 258 of the second embodiment is added to the steering wheel return compensation unit 750 of the third embodiment, and the return compensation signal Imh is generated with the same configuration as the steering wheel return compensation unit 650 shown in FIG. It is also possible to calculate

The return compensation signal may be treated as the target twist angle, and the target twist angle Δθref may be corrected by subtracting the return compensation signal from the target twist angle Δθref output from the conversion unit 500 to compensate for steering wheel return. Also in this case, the torque sensitive gain map and the speed sensitive gain map of the steering wheel return compensation section are adjusted so that the return compensation signal is treated as the target torsion angle.

The target steering torque generation unit 200 in the first embodiment includes a basic map unit 210, a damper calculation unit (damper gain unit 230 and multiplication unit 260), a hysteresis correction unit 240, and a steering wheel return compensation unit 250. Only the steering wheel return compensator 250 may be provided. FIG. 26 shows a configuration example (fourth embodiment) of the target steering torque generator in this case. In target steering torque generation section 800, return compensation signal Tref_d output from steering wheel return compensation section 250 is output as target steering torque Tref. Note that the target steering torque generation section may be configured by combining at least one of the basic map section 210 , the damper calculation section, and the hysteresis correction section 240 and the steering wheel return compensation section 250 . Also, a configuration including only the steering wheel return compensation section 650 in the second embodiment, or a configuration in which at least one of the basic map section 210, the damper calculation section and the hysteresis correction section 240 and the steering wheel return compensation section 650 are combined may be employed.

A current command value (hereinafter referred to as "assist current command value") calculated based on the steering torque in a conventional EPS is added to the motor current command value Imc or Imcc in the first to fourth embodiments, for example. 2 or a current command value Iref2 obtained by adding the compensation signal CM to the current command value Iref1 output from the current command value calculation unit 31 shown in FIG.

FIG. 27 shows a configuration example (fifth embodiment) in which the above contents are applied to the first embodiment, and FIG. 28 shows a configuration example (sixth embodiment) in which the above contents are applied to the third embodiment. The assist control unit 150 is composed of the current command value calculation unit 31, or the current command value calculation unit 31, the compensation signal generation unit 34, and the addition unit 32A. In the fifth embodiment, the assist current command value Iac output from the assist control unit 150 (corresponding to the current command value Iref1 or Iref2 in FIG. 2) and the motor current command value Imc output from the torsion angle control unit 300 are Add by 160. In the sixth embodiment, the adder 160 adds the assist current command value Iac and the motor current command value Imcc output from the subtractor 770 . Then, the current command value Ic, which is the addition result of the adding section 160, is input to the current limiting section 170, and the motor is driven based on the current command value Icm with the maximum current limited, and current control is performed.

In the target steering torque generating section including the basic map section 210 in the first to sixth embodiments, the phase compensating section 270 that performs phase compensation may be inserted before or after the basic map section 210 . That is, the configuration of the region R surrounded by the dashed lines in FIGS. 5 and 23 may be changed to the configuration shown in FIG. 29(A) or (B). The target steering torque generator is not limited to the above configuration as long as it is based on the steering angle.

Although the present invention is applied to a column-type EPS in FIGS. 1 and 3, the present invention is not limited to an upstream-type EPS such as a column-type EPS, and can also be applied to a downstream-type EPS such as a rack and pinion. Furthermore, in terms of performing feedback control based on the target torsion angle, it is also applicable to a steer-by-wire (SBW) reaction force device or the like that includes at least a torsion bar (arbitrary spring constant) and a torsion angle detection sensor. An embodiment (seventh embodiment) in which the present invention is applied to an SBW reaction device having a torsion bar will be described.

First, the entire SBW system including the SBW reaction force device will be described. FIG. 30 is a diagram showing a configuration example of the SBW system in correspondence with the general configuration of the electric power steering apparatus shown in FIG. In addition, the same code|symbol is attached|subjected to the same structure, and detailed description is abbreviate|omitted.

The SBW system does not have an intermediate shaft that is mechanically connected to the column shaft 2 at the universal joint 4a, and is a system that transmits the operation of the steering wheel 1 to the steering mechanism consisting of the steerable wheels 8L, 8R, etc. by electrical signals. . As shown in FIG. 30, the SBW system includes a reaction device 60 and a drive device 70, and a control unit (ECU) 50 controls both devices. The reaction force device 60 detects the steering angle θh with the steering angle sensor 14, and at the same time, transmits the motion state of the vehicle transmitted from the steered wheels 8L, 8R to the driver as reaction torque. The reaction torque is generated by the reaction force motor 61 . Some SBW systems do not have a torsion bar in the reaction force device, but the SBW system to which the present invention is applied has a torsion bar, and the torque sensor 10 detects the steering torque Ts. do. Also, the angle sensor 74 detects the motor angle θm of the reaction force motor 61 . The driving device 70 drives a driving motor 71 in accordance with the steering of the steering wheel 1 by the driver, applies the driving force to the pinion rack mechanism 5 via the gear 72, and passes through the tie rods 6a and 6b to drive the driving motor 71. The direction wheels 8L and 8R are steered. An angle sensor 73 is arranged near the pinion rack mechanism 5 to detect the turning angle θt of the steered wheels 8L, 8R. In order to cooperatively control the reaction force device 60 and the drive device 70, the ECU 50 controls the vehicle speed Vs and the like from the vehicle speed sensor 12 in addition to information such as the steering angle θh and the turning angle θt output from both devices. A voltage control command value Vref1 for driving and controlling the reaction force motor 61 and a voltage control command value Vref2 for driving and controlling the driving motor 71 are generated.

The configuration of the seventh embodiment in which the present invention is applied to such an SBW system will be described.

FIG. 31 is a block diagram showing the configuration of the seventh embodiment. In the seventh embodiment, control of the torsion angle Δθ (hereinafter referred to as “torsion angle control”) and control of the turning angle θt (hereinafter referred to as “turning angle control”) are performed to control the reaction force device. It is controlled by angle control, and the driving device is controlled by steering angle control. Note that the driving device may be controlled by other control methods.

In the torsion angle control, the torsion angle Δθ follows the target torsion angle Δθref calculated through the target steering torque generation unit 200 and the conversion unit 500 using the steering angle θh and the like by using the same configuration and operation as in the first embodiment. control such as The motor angle θm is detected by the angle sensor 74 , and the motor angular velocity ωm is calculated by differentiating the motor angle θm by the angular velocity calculator 951 . A steering angle θt is detected by an angle sensor 73 . Further, in the first embodiment, the processing in the EPS steering system/vehicle system 100 is not described in detail, but the current control unit 130 includes the subtraction unit 32B, the PI control unit 35, and the PWM control shown in FIG. Based on the motor current command value Imc output from the torsion angle control unit 300 and the current value Imr of the reaction force motor 61 detected by the motor current detector 140, by the same configuration and operation as the unit 36 and the inverter 37, Current control is performed by driving the reaction force motor 61 .

In the steering angle control, the target steering angle θtref is generated based on the steering angle θh in the target steering angle generation section 910, and the target steering angle θtref is input to the steering angle control section 920 together with the steering angle θt. be. The turning angle control section 920 calculates a motor current command value Imct that makes the turning angle θt equal to the target turning angle θtref. Then, based on the motor current command value Imct and the current value Imd of the drive motor 71 detected by the motor current detector 940, the current control unit 930 controls the drive motor 71 with the same configuration and operation as the current control unit 130. 71 is driven to perform current control.

FIG. 32 shows a configuration example of the target turning angle generator 910. As shown in FIG. The target steering angle generator 910 includes a limiter 931 , a rate limiter 932 and a corrector 933 .

A limiting unit 931 limits the upper and lower limits of the steering angle θh and outputs the steering angle θh1. Similar to the limiting section 254 in the steering wheel return compensating section and the output limiting section 350 in the torsion angle control section 300, upper and lower limits for the steering angle θh are set in advance and limited.

A rate limiter 932 limits the amount of change in the steering angle θh1 by setting a limit value to avoid a sudden change in the steering angle, and outputs a steering angle θh2. For example, if the amount of change is the difference from the steering angle θh1 one sample before, and the absolute value of the amount of change is greater than a predetermined value (limit value), the steering angle θh1 is added or subtracted and output as the steering angle θh2. If it is equal to or less than the limit value, the steering angle θh1 is directly output as the steering angle θh2. Instead of setting a limit value for the absolute value of the amount of change, an upper limit value and a lower limit value may be set for the amount of change to limit the amount of change. You may make it restrict|limit with respect to a rate.

A correction unit 933 corrects the steering angle θh2 and outputs a target steering angle θtref. For example, using a map that defines the characteristics of the target turning angle θtref with respect to the steering angle θh2 magnitude |θh2| Ask for Alternatively, the target steering angle θtref may be obtained simply by multiplying the steering angle θh2 by a predetermined gain.

A configuration example of the turning angle control section 920 is shown in FIG. The turning angle control section 920 has the same configuration as the configuration example of the torsion angle control section 300 shown in FIG. Enter θt. In the turning angle control unit 920, a turning angle feedback (FB) compensation unit 921, a turning angular velocity calculation unit 922, a speed control unit 923, an output limiter 926, and a subtraction unit 927 correspond to the twist angle FB compensation unit 310 and the twist angle FB compensation unit 310, respectively. Angular velocity calculator 320 , velocity controller 330 , output limiter 350 , and subtractor 361 have the same configurations and perform the same operations.

With such a configuration, an example of operation of the seventh embodiment will be described with reference to the flow chart of FIG.

When the operation starts, the angle sensor 73 detects the steering angle θt, the angle sensor 74 detects the motor angle θm (step S110), the steering angle θt is sent to the steering angle control unit 920, and the motor angle θm is the angular velocity. They are input to the calculation unit 951 respectively.

The angular velocity calculation unit 951 differentiates the motor angle θm to calculate the motor angular velocity ωm, and outputs it to the right-turn/left-turn determination unit 400 (step S120).

Thereafter, the same operations as steps S10 to S60 shown in FIG. 15 are executed to drive the reaction force motor 61 and carry out current control (steps S130 to S170).

On the other hand, in steering angle control, the target steering angle generator 910 inputs the steering angle θh, and the steering angle θh is input to the limiter 931 . The limiting unit 931 limits the upper and lower limits of the steering angle θh with preset upper and lower limits (step S180), and outputs the result to the rate limiting unit 932 as the steering angle θh1. The rate limiter 932 limits the amount of change in the steering angle θh1 by a preset limit value (step S190), and outputs it to the correction unit 933 as the steering angle θh2. The correction unit 933 corrects the steering angle θh2 to obtain the target turning angle θtref (step S200), and outputs the target turning angle θtref to the turning angle control unit 920 .

The turning angle control unit 920, which receives the turning angle θt and the target turning angle θtref, calculates the deviation Δθt ₀ by subtracting the turning angle θt from the target turning angle θtref in the subtraction unit 927 (step S210). The deviation Δθt ₀ is input to the turning angle FB compensator 921, and the turning angle FB compensator 921 multiplies the deviation Δθt ₀ by a compensation value to compensate for the deviation Δθt ₀ (step S220), and obtains the target turning angular velocity. ωtref is output to the speed controller 923 . The steering angular velocity calculator 922 inputs the steering angle θt, calculates the steering angular velocity ωtt by differential calculation with respect to the steering angle θt (step S 230 ), and outputs it to the speed controller 923 . Speed control unit 923 calculates motor current command value Imcta by IP control in the same manner as speed control unit 330 (step S240), and outputs it to output limiting unit 926. FIG. The output limiter 926 limits the upper and lower limits of the motor current command value Imcta by preset upper and lower limits (step S250), and outputs the motor current command value Imct (step S260).

The motor current command value Imct is input to the current control unit 930 , and the current control unit 930 controls the drive motor 71 based on the motor current command value Imct and the current value Imd of the drive motor 71 detected by the motor current detector 940 . 71 is driven to perform current control (step S270).

Note that the order of data input and calculation in FIG. 34 can be changed as appropriate. Further, like the speed control unit 330 in the torsion angle control unit 300, the speed control unit 923 in the steering angle control unit 920 is not IP control, but PI control, P control, PID control, PI control, P control, PI control, and PI control. control, etc., can be realized, and any one of P, I, and D control may be used, and follow-up control in the steering angle control unit 920 and the twist angle control unit 300 is generally used. You can do it with a control structure that has As for the turning angle control section 920, if it has a control configuration in which the actual angle (here, the turning angle θt) follows the target angle (here, the target turning angle θtref), it is used in the vehicle device. The control configuration is not limited, and for example, a control configuration used in industrial positioning devices, industrial robots, and the like may be applied.

In the seventh embodiment, as shown in FIG. 30, one ECU 50 controls the reaction device 60 and the driving device 70. You can set it. In this case, the ECUs transmit and receive data through communication. The SBW system shown in FIG. 30 does not have a mechanical connection between the reaction force device 60 and the drive device 70. However, when an abnormality occurs in the system, the column shaft 2 and the steering mechanism are connected by a clutch or the like. The present invention can also be applied to an SBW system having a mechanical torque transmission mechanism that mechanically couples at . In such an SBW system, when the system is normal, the clutch is turned off to disengage mechanical torque transmission, and when the system is abnormal, the clutch is turned on to enable mechanical torque transmission.

The torsion angle control unit 300 in the above-described first to seventh embodiments and the assist control unit 150 in the fifth and sixth embodiments directly calculate the motor current command value Imc and the assist current command value Iac. However, before calculating them, the motor torque to be output (target torque) may be calculated first, and then the motor current command value and the assist current command value may be calculated. In this case, in order to obtain the motor current command value and the assist current command value from the motor torque, the generally used relationship between the motor current and the motor torque is used.

The diagrams used above are conceptual diagrams for qualitatively explaining the present invention, and the present invention is not limited to these. Moreover, although the above-described embodiment is a preferred example of the present invention, it is not limited to this, and various modifications can be made without departing from the gist of the present invention. Also, any mechanism having an arbitrary spring constant between the handle and the motor or reaction motor may be used without being limited to the torsion bar.

The main object of the present invention is to calculate a return compensation signal and implement steering wheel return compensation using the return compensation signal. It does not have to be limited to departments.

1 steering wheel 2 column axis (steering shaft, steering wheel axis)
2A torsion bar 3 speed reduction mechanism 10 torque sensor 12 vehicle speed sensor 14 steering angle sensor 20 motors 30, 50 control unit (ECU)
31 current command value calculators 33, 170 current limiter 34 compensation signal generators 38, 140, 940 motor current detector 60 reaction force device 61 reaction force motor 70 drive device 71 drive motor 72 gears 73, 74 angle sensor 100 EPS steering system/vehicle system 130, 930 current control unit 150 assist control unit 200, 700, 800 target steering torque generation unit 210 basic map unit 211 encoding unit 230 damper gain unit 240 hysteresis correction unit 250, 650, 750 steering wheel return compensation unit 251 Manual input torque estimating unit 252 Torque sensitive gain unit 253 Speed sensitive gain unit 254, 931 Limiting unit 258 Target speed setting unit 270 Phase compensation unit 300 Torsion angle control unit 310 Torsion angle feedback (FB) compensation unit 320 Torsion angular velocity calculation unit 330, 923 Speed control units 350, 926 Output limiting unit 400 Right-turn/left-turn determination unit 500 Conversion unit 910 Target turning angle generation unit 920 Turning angle control unit 921 Turning angle feedback (FB) compensation unit 922 Turning angular velocity calculation unit 932 Rate limiter 933 Corrector

Claims (13)

A steering system for a vehicle, which includes at least a torsion bar having an arbitrary spring constant and a sensor for detecting the torsion angle of the torsion bar, and assists and controls a steering system by driving and controlling a motor,
a target steering torque generator that generates a target steering torque;
a conversion unit that converts the target steering torque into a target twist angle;
a torsion angle control unit that calculates a motor current command value that causes the torsion angle to follow the target torsion angle;
A manual input torque estimating unit that estimates a manual input torque to a steering wheel and obtains an estimated manual input torque value, and a differentiating unit that differentiates a steering angle and calculates first angular velocity information, wherein the first angular velocity information and a steering wheel return compensator for obtaining a return compensation signal for steering wheel return compensation for compensating for steering wheel return using the manual input torque estimated value;
A steering system for a vehicle, wherein the motor is driven and controlled based on the motor current command value reflecting the steering wheel return compensation by the return compensation signal. 2. The steering system for a vehicle according to claim 1, wherein the target steering torque generation unit includes the steering wheel return compensation unit, and outputs the return compensation signal as the target steering torque to reflect the steering wheel return compensation. 2. The vehicle steering system according to claim 1, wherein the steering wheel return compensation is reflected by correcting the motor current command value using the return compensation signal. The handle return compensator is
further comprising a torque sensing gain unit that obtains a torque sensing gain based on the magnitude of the manual input torque estimated value;
4. The vehicle steering system according to claim 1, wherein the return compensation signal is obtained by multiplying and correcting the first angular velocity information by the torque sensitive gain. 5. The vehicle steering system according to claim 4, wherein the torque sensitive gain decreases as the magnitude of the manual input torque estimated value increases. The handle return compensator is
further comprising a velocity sensitive gain unit that obtains a velocity sensitive gain based on the magnitude of the first angular velocity information;
6. The vehicle steering system according to claim 4, wherein the return compensation signal is obtained by multiplying and correcting the first angular velocity information by the torque sensitive gain and the speed sensitive gain. When the magnitude of the first angular velocity information is from zero to a predetermined value, the velocity sensitive gain increases as the magnitude of the first angular velocity information increases, and the magnitude of the first angular velocity information increases to the predetermined value. 7. The steering system for a vehicle according to claim 6, wherein the velocity sensitive gain decreases as the magnitude of the first angular velocity information increases after exceeding . The handle return compensator is
8. The steering system for a vehicle according to claim 1, further comprising a limiter for limiting upper and lower limits of said return compensation signal. The handle return compensator is
Further comprising a target speed setting unit for determining a target speed for the steering angle,
9. The vehicle control system according to any one of claims 1 to 8, wherein second angular velocity information is calculated from said first angular velocity information and said target velocity, and said return compensation signal is obtained by multiplying and correcting said second angular velocity information. direction device. The target steering torque generation unit
a basic map unit that obtains a first torque signal from the steering angle and the vehicle speed using the basic map;
a damper calculation unit that obtains a second torque signal based on third angular velocity information using a damper gain map sensitive to vehicle speed;
a hysteresis correction unit that obtains a third torque signal having a hysteresis characteristic using the steering state and the steering angle;
3. A vehicle steering system according to claim 2, wherein said target steering torque is calculated from at least one of said first torque signal, said second torque signal and said third torque signal and said return compensation signal. The target steering torque generation unit
a basic map unit that obtains a first torque signal from the steering angle and the vehicle speed using the basic map;
a damper calculation unit that obtains a second torque signal based on third angular velocity information using a damper gain map sensitive to vehicle speed;
a hysteresis correction unit that obtains a third torque signal having a hysteresis characteristic using the steering state and the steering angle;
4. A vehicle steering system according to claim 3, wherein said target steering torque is calculated from at least one of said first torque signal, said second torque signal and said third torque signal. 12. The vehicle steering system according to claim 10, wherein the characteristics of the basic map and the hysteresis correction unit are vehicle speed sensitive. The target steering torque generation unit
further comprising a phase compensation unit that performs phase compensation before or after the basic map unit;
13. The vehicle steering system according to claim 10, wherein the first torque signal is obtained from the steering angle and the vehicle speed via the basic map section and the phase compensation section.

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