JP2005239010A - Power steering device for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To properly restrain influence of lateral directional disturbance on steering, without reacting to a detecting error of a detecting means, in controlling the steering on the basis of a state quantity estimated by using an observer. <P>SOLUTION: This power steering device has an estimating means 32 for estimating by separating the lateral directional disturbance of a vehicle into lateral force disturbance ψ<SB>cw</SB>trying to move the vehicle in the lateral direction by lateral force and lateral gradient disturbance ψ<SB>rb</SB>acting on the vehicle by a lateral inclination of a road surface from a steering angle δ, a yaw rate γ, lateral acceleration G<SB>y</SB>and a vehicle speed V of the vehicle respectively detected by a steering angle detecting means 22, a yaw rate detecting means 23, a lateral acceleration detecting means 24 and a vehicle speed detecting means 25 on the basis of a steering-vehicle system model of the vehicle; and a control means 30 for compensating for quantity of steering assist torque by processing a correction quantity by a high-pass-filter by setting the correction quantity of the steering assist torque so as to restrain the lateral directional disturbance of the vehicle from an estimated result by the estimating means 32. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a vehicle power steering apparatus that controls a steering assist state of a vehicle in consideration of disturbance applied in a lateral direction to the vehicle.

When a car is running, steering is often affected by various disturbances. Focusing on this point, a technique for controlling the steering system of the vehicle according to the disturbance that the vehicle receives during traveling has been developed.
For example, in Patent Document 1, so-called disturbance suppression performance that prevents disturbances such as cross winds applied to the vehicle from affecting the steering operation of the driver can be improved by steering assist control using an electric power steering device. Things have been proposed.

  In this technique, in the control of the steering reaction force (corresponding to the steering assist force), the steering angle component T1 of the steering reaction force based on the steering angle (= the gain obtained by multiplying the steering angle) and the damping based on the steering angular velocity. A component T2 (= steering angular velocity multiplied by gain), a first vehicle behavior suppression component T3 based on vehicle yaw rate (= yaw rate multiplied by gain), and a second vehicle based on lateral acceleration of the vehicle. Calculate the behavior suppression component T4 (= lateral acceleration multiplied by gain) and the road surface component T5 (= steering reaction force multiplied by gain) based on the steering reaction force, as in the following equation: These steering reaction force components T1, T2, T3, T4, and T5 are added to determine the target steering reaction force Ts, and the output torque of the reaction force motor (corresponding to the steering assist electric motor), that is, the steering handle Steering reaction force for this target To return control to the steering reaction force Ts.

Ts = T1 + T3 + T4 + T5-T2
Further, in Patent Document 2, a low frequency component of disturbance is estimated by an observer, a steering torque amount necessary for suppressing the low frequency component of this disturbance is calculated based on this, and the steering torque is feedback-controlled. The technology is described.
JP-A-5-105100. JP 2003-81122 A

By the way, as described above, when the state quantity is estimated using the observer and the control is performed based on the state quantity, the control may not be properly performed due to the characteristics of the observer.
In other words, the observer reacts to the input low-frequency component but does not react to the high-frequency component, and has characteristics such as a so-called low-pass filter. For example, if there is a detection error inherent in the detection system, this is low. It is effectively processed by the observer as a frequency component. For this reason, if there is a detection error inherent in the detection system, even if no disturbance is actually applied, the observer performs an estimation process assuming that the disturbance is added, and as a result, based on an incorrect estimation of the observer. If the control is performed, the vehicle steering may be deflected.

  The present invention has been devised in view of the above-described problems. In the present invention, an amount of state is estimated using an observer and steering is controlled based on the estimated amount of state. An object of the present invention is to provide a power steering apparatus for a vehicle that can improve the active safety by performing a steering assist capable of suppressing the influence of a lateral disturbance on the vehicle.

In order to achieve the above target, a vehicle power steering apparatus according to the present invention is added to an actuator that is mounted on a vehicle and applies steering assist torque to a steering system, vehicle speed detection means that detects the vehicle speed of the vehicle, and the vehicle. A power steering device comprising: steering torque detection means for detecting steering torque; and control means for controlling the actuator based on detection information from the vehicle speed detection means and the steering torque detection means. Designed based on a steering angle detecting means for detecting a steering angle, a yaw rate detecting means for detecting the yaw rate of the vehicle, a lateral acceleration detecting means for detecting a lateral acceleration of the vehicle, and a steering-vehicle system model of the vehicle. By the observer, the vehicle speed detection means, the steering angle detection means, the yaw rate detection means, and the lateral acceleration detection means respectively detect them. From been a vehicle speed V of the vehicle steering angle δ and the yaw rate γ and lateral acceleration G _y, and a estimation unit that estimates a lateral disturbance of the vehicle, control means, vehicle speed detection means and the steering torque A basic control amount calculating means for calculating a basic control amount for controlling the actuator based on detection information from the detecting means, and an estimation result obtained by the estimating means so as to suppress a lateral disturbance of the vehicle. Correction amount calculation means for calculating a correction amount for correcting the steering assist torque, and calculation means for adding the correction amount calculated by the correction amount calculation means to the basic control amount calculated by the basic control amount calculation means; And a high-pass filter interposed between the correction amount calculation means and the calculation means.

An electric motor that is advantageous for carrying out fine steering assist control is suitable as the actuator.
Further, the estimation means is configured to detect a lateral disturbance of the vehicle by a lateral force disturbance φ _cw that attempts to move the vehicle in the lateral direction by a lateral force and a lateral gradient disturbance φ that acts on the vehicle by a lateral inclination of the traveling road surface. estimated separated into a _rb, the correction amount calculating means, the steering of imparting the estimation result by the estimating means, with said actuator so as to suppress the lateral force disturbance phi _cw primarily of lateral disturbance of the vehicle It is preferable to calculate the correction amount of the assist torque (claim 2).

The vehicle further includes steering angular velocity detecting means for detecting the steering angular velocity of the vehicle, the estimating means is configured to further estimate the yaw rate and lateral velocity of the vehicle, and the correction amount calculating means is configured to detect the steering angular velocity. A first correction torque is calculated from the steering angle, the steering angular velocity, the vehicle speed, and the yaw rate and lateral velocity estimated by the estimating means, the steering angle detecting means, and the vehicle speed detecting means, respectively. Calculating a second correction torque from the lateral force disturbance φ _cw and the lateral gradient disturbance φ _rb estimated by the means, and calculating a sum of the first correction torque and the second correction torque as a correction amount. (Claim 3).

Further, the correction amount calculating means calculates the first correction torque by multiplying each of the steering angle, the steering angular velocity, the yaw rate, and the lateral velocity by a gain set in accordance with the vehicle speed, The second correction torque is calculated by multiplying each of the force disturbance φ _cw and the lateral gradient disturbance φ _rb by a gain set in accordance with the vehicle speed, and the first correction torque and the second correction torque Is preferably calculated as a correction amount.

According to the vehicle power steering apparatus of the present invention, the estimation means estimates the lateral disturbance of the vehicle using the observer, and the control means determines the steering assist torque so as to suppress the lateral disturbance of the vehicle based on the estimation result. Therefore, the steering assist can be appropriately given.
At this time, in the control means, the basic control amount calculation means calculates a basic control amount for controlling the actuator based on the vehicle speed detection information and the steering torque detection information, and the correction amount calculation means calculates the lateral direction of the vehicle from the estimation result by the estimation means. Calculate the correction amount of the steering assist torque applied by the actuator so as to suppress the directional disturbance, process the calculated steering assist torque correction amount with a high-pass filter, and add to the basic control amount by the calculation means to correct To do.

  Therefore, for example, even if there is a detection error inherent in the detection system and the observer makes an estimation based on this detection error and the steering assist torque correction amount is erroneously calculated, Since the low-frequency component corresponding to the detection error inherent in the detection system is removed by the high-pass filter, the control based on the observer's erroneous estimation is prevented, for example, the vehicle steering may be deflected. Problems can be avoided and steering assist can be appropriately applied.

Further, the lateral disturbance of the vehicle is separated into a lateral force disturbance φ _cw that attempts to move the vehicle in the lateral direction by a lateral force and a lateral gradient disturbance φ _rb that acts on the vehicle by a lateral inclination of the traveling road surface. The correction amount calculation means estimates the correction amount of the steering assist torque applied by the actuator so as to suppress mainly the lateral force disturbance φ _cw among the lateral disturbances of the vehicle from the estimation result by the estimation means. By calculating, steering assist can be appropriately given.

In other words, as the vehicle behavior caused by such as a side wind or Tetsuro, it can be grasped as a lateral force disturbance phi _cw, among lateral disturbance of the vehicle, primarily applying a steering assist torque to suppress the this lateral force disturbance phi _cw By doing so, the side slope disturbance φ _rb caused by the side slope of the road surface provided to enable smooth running on curved roads can be attributed to side winds, narrow roads, etc. without suppressing the effect. As the lateral force disturbance φ _cw affects the vehicle behavior and disturbs the steering, the influence can be suppressed.For example, while ensuring smooth running performance on a curved road, the influence of the lateral force disturbance on the steering is reduced. It becomes possible to suppress and improve active safety.

A first correction torque is calculated from the detected steering angle, rudder angular velocity, vehicle speed, estimated yaw rate, and lateral velocity, and the first correction torque is calculated from the estimated lateral force disturbance φ _cw and lateral gradient disturbance φ _rb . Steering assist can be appropriately performed by calculating 2 correction torques and calculating the sum of the first correction torque and the second correction torque as a correction amount.
Further, the first correction torque is calculated by multiplying each of the steering angle, the steering angular velocity, the yaw rate, and the lateral velocity by a gain set in accordance with the vehicle speed, and the lateral force disturbance φ _cw and the lateral gradient disturbance φ are calculated. By multiplying each of _rb by a gain set according to the vehicle speed to calculate the second correction torque, and calculating the sum of the first correction torque and the second correction torque as a correction amount, Steering assist can be performed more appropriately (claim 4).

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 to 9 show a vehicle power steering apparatus according to an embodiment of the present invention, which will be described with reference to these drawings.
As shown in FIG. 1, the power steering apparatus for a vehicle according to the present embodiment includes an electric motor (here, a DC motor) 11 as a steering actuator, detects the steering operation state of the vehicle and the state of the vehicle, and detects these. A target steering assist amount is set by an ECU (electronic control unit) 30 from the detection result, and the DC motor 11 is controlled so as to obtain this target steering assist amount.

  For example, as shown in FIG. 3, the DC motor 11 is a steering system (here, rack and pinion 3) including a steering wheel 1, a steering shaft 2, a rack and pinion 3, a tie rod 4, steering wheels (front wheels) 5L, 5R, and the like. ). Of course, this apparatus can be applied not only to the pinion type electric power steering but also to the case where a small motor is added to the hydraulic power steering or the rack assist type electric power steering.

Further, as means for detecting the steering operation state and the vehicle state, a steering wheel angular velocity sensor 21 as steering speed detection means (front wheel steering angular speed detection means) for detecting a steering angular speed (front wheel steering angular speed) ω _{f_s} , and a steering angle (front wheel) A steering angle sensor 22 as a steering angle detection means (front wheel steering angle detection means) for detecting δ _{f_s} , a yaw rate sensor (yaw angular velocity sensor) 23 as a yaw rate detection means for detecting the yaw rate γ _s of the vehicle, A lateral acceleration sensor 24 as a lateral acceleration detecting means for detecting the lateral acceleration G _{y_s} of the vehicle, a vehicle speed detecting means 25 for detecting the vehicle speed V, and a steering torque (input steering torque) _{Th_s} applied by the driver through the steering wheel (handle). And a steering torque detecting means (steering torque sensor) 26 for detecting.

The ECU 30 includes, as functional elements, a basic steering assist amount calculation unit (electric power steering control calculation unit) 31 as basic control amount calculation means for calculating a basic steering assist amount (basic assist torque) T _{m_base,} and a _{lateral force} applied to the vehicle. An observer 32 serving as an estimation means for estimating direction disturbance and the like, and a steering assist correction amount (assist torque correction amount) corresponding to a disturbance component applied to the steering system are calculated, and a steering assist amount (disturbance suppression control amount) is calculated accordingly. ) Is corrected. (Disturbance suppression correcting means) 33 is provided.

The electric power steering control calculation unit 31 calculates a basic steering assist amount (basic assist torque) T _{m_base} based on the input steering torque _{Th_s} detected by the steering torque detection means 26 and the vehicle speed V detected by the vehicle speed detection means 25. To do.
In observer 32, based on the front wheel steering angle detecting means 22, the yaw rate detecting means 23, the lateral acceleration detecting means 24, a vehicle speed detecting means 25 in each detected the front wheel steering angle [delta] _{f_s,} yaw rate gamma _s, the lateral acceleration G _{y_s,} the vehicle speed V Lateral disturbance applied to the vehicle, etc. [Specifically, lateral force disturbance estimated value (estimated lateral force disturbance φ _cw trying to move the vehicle laterally by lateral force) φ _{cw_e} , lateral gradient disturbance estimation to estimate the value (running estimated value of the lateral gradient disturbance phi _rb acting on the vehicle by the lateral inclination of the road _surface) φ rb_e, lateral velocity estimate v _e, yaw rate estimated value gamma _e].

The correction unit 33 includes a steering assist correction amount calculation unit (disturbance suppression control calculation unit) 34 as a correction amount calculation unit for calculating a correction steering assist amount (correction assist torque) T _{m_add,} and correction to a basic assist torque T _{m_base} . When the correction steering assist amount T _{m_add} calculated by the addition unit 35 as a calculation means for adding the assist torque T _{m_add} and the steering assist correction amount calculation unit (disturbance suppression control calculation unit) 34 is output to the addition unit 35. A high-pass filter (band-pass filter) 36 that performs filtering so as to output only a high-frequency component is provided.

The steering assist correction amount calculation unit 34 includes a lateral force disturbance estimated value φ _{cw_e} , a lateral gradient disturbance estimated value φ _{rb_e} , a lateral speed estimated value v _e , a yaw rate estimated value γ _e estimated by the observer 32, and a front wheel steering angular speed detecting means. The disturbance component applied to the steering system based on the front wheel steering angular velocity ω _{f — s} detected at 21, the front wheel steering angle δ _{f — s} detected by the front wheel steering angular velocity detection means 21, and the vehicle speed V detected by the vehicle speed detection means 25. The correction assist torque T _{m_add} according to the _above is calculated.

That is, the steering assist correction amount calculation unit 34 multiplies the front wheel steering angular velocity ω _{f_s} by the gain K _ω to multiply the front wheel steering angular velocity correspondence correction amount (= K _ω ω _{f_s} ), and multiplies the front wheel steering angle δ _{f_s} by the gain K _δ. front wheel steering angle corresponding correction amount ₍₌ K δ δ _{f_s),} lateral velocity corresponding correction amount in the horizontal velocity estimate v _e is multiplied by a gain _{K v (= K v v e} ) a gain K to the yaw rate estimated value gamma _e yaw rate-dependent correction amount by multiplying the _r a (= K _r γ _e), respectively calculated through the adder unit 35, these correction amounts of added value _{T m_fb (= K ω ω f_s} + K δ δ f_s + K v v e + K _r γ _e ) is _defined as a feedback correction amount (first correction torque) for feedback correction of the basic assist torque T _{m_base} .

Also, the lateral force disturbance estimated value φ _{cw_e} is multiplied by the gain K _{Φ_cw} to _calculate a lateral disturbance corresponding correction amount (second correction torque) T _{m_cw} (= K _{Φ_cw} φ _{cw_e} ), and this correction amount T _{m_cw} is used as the basic assist torque. T _{m_base} is a feed forward correction amount for feed forward correction. As shown in FIG. 1, a lateral gradient disturbance corresponding correction amount (second correction torque) T _{m_rb} (= _{KΦ_rb} φ _{rb — e} ) is _obtained by multiplying the lateral gradient disturbance estimated value φ _{rb — e} by a gain K _Φ — _rb (= minute value). And the basic assist torque T _{m_base} may be feedforward corrected using this correction amount. However, basically, only the lateral force disturbance estimated value φ _{cw_e} is used (or mainly, the lateral force disturbance estimated value φ _{cw_e Therefore} , it is important to feed-forward correct the basic assist torque T _{m_base} so that the influence of the lateral disturbance is eliminated.

Therefore, the control system is configured to suppress only the influence of the side wind disturbance among the side gradient disturbance and the side wind disturbance (also referred to as a side force disturbance) separated by the observer 32 estimation.
Then, in the steering assist correction amount calculation unit 34, the feedback correction by the feedback correction amount T _{m_fb} and the feed forward correction by the feed forward correction amount T _{m_cw} are _finalized by adding these values T _{m_add} (= T _{m_fb} + T _{m_cw} ). The correction assist torque is output, and feedback correction and feedforward correction are simultaneously performed by the correction assist torque _{Tm_add} .

  That is, as shown in FIG. 4, the road lateral slope on the curved road is generally provided to cancel the centrifugal force generated by turning the curve and facilitate turning on the curve. In addition, the lateral slope on the straight road is a small value of about 2 to 3%, but is provided for drainage. In the observer 32, the control system is configured so as to suppress only the influence of the lateral wind disturbance by excluding such a lateral gradient disturbance from the disturbance disturbance target among the lateral disturbances.

However, since the correction amount addition value T _{m_add} calculated by the steering assist correction amount calculation unit 34 is filtered by the high-pass filter 36 so as to output only a high-frequency component, each sensor type is _{included in} the correction amount addition value T _{m_add.} The amount corresponding to the detection error peculiar to is removed by the high-pass filter 36, and the correction amount addition value _{Tm_add} excluding this detection error is effectively output.

  In other words, as shown in FIG. 9, the observer reacts to the input low-frequency component but does not react easily to the high-frequency component, and has characteristics such as a so-called low-pass filter. Of these, the high frequency components are cut, and the estimation process is performed based on the medium and low frequency components. Therefore, when the state quantity changes suddenly or when noise enters the state quantity signal, the input data corresponding to these high-frequency components is substantially cut as shown in FIG. In this respect, abrupt control and control based on erroneous data such as noise can be prevented.

However, for example, if there is a detection error inherent in the detection system, this is effectively processed by the observer as a low-frequency component. Therefore, if there is a detection error inherent in the detection system, the observer does not actually add disturbance. However, it is estimated that the disturbance is added. In contrast, in the present apparatus, as shown in FIG. 9, the high-pass filter 36 cuts low frequency components such as the amount corresponding to the detection error specific to each sensor among the correction amount addition value T _{m_add.} Therefore, the final control amount is one that eliminates the influence of detection errors inherent in the detection system, and can prevent problems that cause deflection in the steering of the vehicle. It can be done.

When the estimation by the observer 32 is further described, the relationship of each variable related to the DC motor 11 can be modeled in a control block as shown in FIG.
The parameters in FIGS. 1 and 2 are shown in Table 1 below.

  From the relationship shown in FIG. 2, the following equation (A) is derived as an observer state equation.

In the above equation (A), the gains a ₁₁ , a ₁₂ , a ₂₁ , a ₂₂ , b ₁ , b ₂ are all determined according to the vehicle speed, and the gains l ₁₁ , l ₁₂ , l ₂₁ , l ₂₂ , l _{31 are determined.} , L ₃₂ , l ₄₁ , and l ₄₂ can be set to appropriate values by mathematical calculation in consideration of the frequency characteristics of the motor.
Thus, the observer 32, the front wheel steering angle [delta] _{f_s,} yaw rate gamma _s, the lateral acceleration G _{y_s,} as an input variable to each state quantity of the vehicle speed V, the lateral velocity estimated value v _e and yaw rate estimated value gamma _e and the lateral force estimated disturbance value Each state quantity of φ _{cw_e} and lateral gradient disturbance estimated value φ _{rb_e} can be estimated.

Here, the observer 32 for estimating the side gradient disturbance and the side wind disturbance will be described in more detail.
In designing the observer 32, it is necessary to construct a robust lateral control system, which is based on the following assumptions (a) to (d).
(A) The sensor signal assumes a steering angle, a steer torque, a yaw rate, and a lateral acceleration.
(B) Non-linearity of tire and suspension is not considered.
(C) Since a control system that is robust against lateral disturbance is designed, no driver operation is assumed (Th = 0).
(D) No yaw moment disturbance generated in the vehicle is assumed.

  As shown in FIG. 5, the actual steering system is composed of a mechanical system and a DC motor system. The inertial system is composed of a steering wheel, a DC motor, and a tire, and the elastic system is composed of a torsion bar and a tire. Here, when a differential equation is built around the kingpin, the following equations (1) to (3) are obtained.

Here, [delta] _f the front wheel actual steering angle, alpha is the steering wheel angle (the column axis), T _s is the self-Alai Schimmelpenninck torque from the road surface, T _m is the additional torque of the DC motor, T _h is the driver torque (torque sensor value ). The system parameters I _s , C _s , N _t , N _m , and K _t are described in Table 1 above.
Here, the front wheel actual steering angle δ _f can be measured from the driver torque _Th and the steering wheel angle α, which are sensor values.

  When the previous equation (2) is modified, the following equation (4) is obtained.

Furthermore, here, a two-wheel model as shown in FIG. 6 is a vehicle model. If the front wheel actual steering angle δ _f is defined as a system input, the equation of motion of the vehicle system of this model can be described as follows.

Here, v is the lateral velocity of the vehicle, γ is the yaw rate of the vehicle, and φ is a lateral disturbance element. The system parameters I _s , C _s , N _t , N _m , and K _t are listed in Table 1 above.
The above equations (5) and (6) showing differential equations representing the lateral movement and yaw movement of the vehicle are generally well known.
As described above, the lateral disturbance φ is _{composed of} the lateral force disturbance φ _cwe and the lateral gradient disturbance φ _rb (see the following formula).

These lateral force disturbance φ _cw and lateral gradient disturbance φ _rb are given as external inputs to equation (5), but cannot be directly measured. Therefore, as a countermeasure against these lateral disturbances, as shown in FIG. 7, a control method is used in which the disturbance is estimated by an observer, and the controller (control command system in the ECU 30) approximately cancels the influence of the disturbance by a feedforward loop. I took it. This method is equivalent to integral control when the disturbance is a constant value. A lateral acceleration sensor value, which is an output signal to be measured, is expressed by a vehicle state quantity and a lateral gradient disturbance φ _rb as shown in the following equation, but does not include the lateral force disturbance φ _cw . Note that the controller 30 feeds back each state quantity of the vehicle for disturbances other than lateral disturbances to suppress the influence of the disturbances.

By the way, the detection value G _{y — s} of the G sensor is expressed by the equation (8a) on the flat road s having no right and left gradient, but is a disturbance φ _rb having a lateral gradient. Is included, equation (8b) is obtained.

The above equation (8a) indicates that the two lateral disturbances φ _cw and φ _rb can be separated, and the equations (5), (6), (7), and (8b) are arranged as follows: The equation of state is obtained.

Here, in order to design an observer that simultaneously estimates the unknown state quantity v and the lateral disturbances φ _cw and φ _rb , two lateral disturbances φ _cw and φ _rb are expanded as state quantities as shown in the following equation. Define the model.

In the above equations (11) and (12), the rank (rank [C CA... CA ⁿ⁻¹ ] ^T ) of the coefficient matrices A and C (lower equations) of v, γ, φ _cw and φ _rb is the number of states. (Type of state quantity) Since n is satisfied, it is observable, and unknown state quantity v and unknown disturbances φ _cw and φ _rb can be estimated by an observer. Here, v, γ, φ _cw , and φ _rb are estimation results, and L shown in the following equation (13) is an estimated gain matrix.

A block diagram of such an observer is schematically shown in FIG.
In the linear robust control, when a fourth-order differential equation is applied as a control target model, the fourth-order model is obtained by using two state variables of the steering system model, the front wheel actual steering angle δ _f , the front wheel actual steering angular velocity ω _f and the vehicle. It is composed of two state variables of the system, the lateral velocity v and the yaw rate γ. Here, the lateral disturbances φ _cw and φ _rb are given to the controlled object as external inputs. Note that the driver torque in the previous equation (1) is assumed to be zero (T _h = 0).

  The robust control system includes a state feedback loop and a disturbance suppression feedforward loop. The state feedback loop ensures sufficient system response and stability. The disturbance suppression feedforward loop suppresses the influence of the crosswind disturbance in the steady state. The control input in equation (14) is determined by the following equations (15) to (17).

Here, [K _ω , K _δ , K _v , K _γ ] is a state feedback gain, which is obtained by LG control theory. The state feedback loop is mainly aimed at stabilizing the system. The front wheel actual steering angular velocity ω _f can be calculated from the additional voltage and current of the motor. The front wheel actual steering angle δ _f is obtained from the previous equation (4).
As described above, v, φ _cw and φ _rb are estimated from the disturbance observer. On the other hand, the disturbance suppression feedforward loop aims to reduce the influence of the lateral force disturbance φ _cw , and specifically feedforward gain so that the steady value of the yaw rate generated by the estimated lateral force disturbance φ _{cw_e} is zero. Determine. When determining this feedforward gain k _ff , it is assumed that φ _rb = 0 in equation (14).

  From the above assumption, the following equation of state (18) is obtained.

  In the steady state (dx / dt = 0), the equation (18) is transformed into the following equation (19).

Here, δ _fss , v _ss , and γ _ss are steady values of δ _f , v, and γ with respect to φ _cw . Therefore, the following equation (20) that directly solves this equation is obtained.

In order to make the steady value of the yaw rate generated by the lateral force disturbance φ _cw zero, attention can be paid to the row of γ _{ss in} equation (20), and the following equations (21a) and (21b) can be transformed.

Therefore, the feedforward gain k _ff (= K _{Φ_cw} ) is obtained from the following equation (22).

Since the vehicle power steering apparatus according to the embodiment of the present invention is configured as described above, the steering assist correction means (the steering assist correction amount calculation unit 34 and the calculation unit 35) 33 corrects the front wheel steering angular velocity corresponding correction. the amount ₍₌ K ω ω _{f_s),} front wheel steering angle corresponding correction amount ₍₌ K δ ω _{f_s),} lateral velocity corresponding correction amount (= K _{v v e),} the yaw rate corresponding correction amount adding value (= K _r γ _e) the basic assist torque T _{M_base} well as the feedback correction by _{T m_fb (= K ω ω f_s} + K δ ω f_s + K v v e + K r γ e), basic by lateral disturbance corresponding correction amount _{T m_cw (= K Φ_cw φ cw_e} ) Since the assist torque T _{m_base} is feed-forward corrected, the steering assist torque is applied by controlling the electric motor so as to suppress the lateral disturbance (lateral wind disturbance, etc.) φ _cw from which the lateral gradient disturbance is removed from the lateral disturbance. Therefore, while ensuring smooth running performance on curved roads, it is possible to improve the active safety by suppressing the influence of cross wind disturbance on the steering.

Further, the correction amount addition value T _{m_add} calculated by the steering assist correction amount calculation unit 34 is filtered by the high-pass filter 36 so as to output only a high-frequency component, so that each sensor type is _{included in} the correction amount addition value T _{m_add.} The amount corresponding to the detection error peculiar to is removed by the high-pass filter 36, and the correction amount addition value _{Tm_add} excluding this detection error is effectively output.

  Therefore, for example, there is a detection error inherent in the sensor system, and the observer makes an erroneous estimation based on this detection error, and as a result, the steering assist torque correction amount includes a detection error. The low-frequency component corresponding to the detection error inherent in the detection system in the steering assist torque correction amount is removed by the high-pass filter, so that control based on an erroneous estimation of the observer is prevented. Problems such as the occurrence of deflection can be avoided, and steering assist can be appropriately applied.

Although the embodiments of the present invention have been described above, the present invention is not limited to such embodiments, and various modifications can be made without departing from the spirit of the present invention.
For example, each gain _{Kω, Kδ, K v, K} r, the K? _{_Cw,} as it is possible to improve the stability and steering feeling of the system, it is important to appropriately set according to the vehicle speed.

It is a block diagram which shows the function structure of the power steering apparatus for vehicles as one Embodiment of this invention. It is a block diagram of the observer which estimates the state quantity of the motor control system concerning the power steering device for vehicles as one embodiment of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram illustrating a vehicle power steering device as one embodiment of the present invention. It is a figure explaining the horizontal direction disturbance to the vehicle which drive | works, (a) is a typical top view of the vehicle which drive | works, (b) is a typical rear view of the vehicle which drive | works. It is a mimetic diagram showing a steering system model concerning one embodiment of the present invention. It is a mimetic diagram showing a vehicle system model concerning one embodiment of the present invention. It is a block diagram explaining steering control concerning one embodiment of the present invention. It is a block diagram of an observer explaining steering control concerning one embodiment of the present invention. It is a graph which shows the output characteristic of the controlled variable by the observer and high pass filter concerning one Embodiment of this invention.

Explanation of symbols

11 DC motor 21 Front wheel rudder angular velocity detection means (steering angular velocity detection means)
22 Front wheel rudder angle detecting means (steering angle detecting means)
23 Yaw rate detection means 24 Lateral acceleration detection means 25 Vehicle speed detection means 26 Steering torque detection means 30 Electronic control unit (ECU) as control means
31 Basic control amount setting unit (electric power steering control calculation unit) or basic control amount calculation means 32 Estimation means (observer)
33 Correction means (disturbance suppression correction means)
34 Steering assist correction amount calculation section (disturbance suppression control calculation section) or correction amount calculation means 35 Addition section (calculation means)
36 High-pass filter (band-pass filter)

Claims (4)

An actuator mounted on a vehicle for applying steering assist torque to a steering system, vehicle speed detection means for detecting the vehicle speed of the vehicle, steering torque detection means for detecting steering torque applied to the vehicle, vehicle speed detection means, A power steering device comprising control means for controlling the actuator based on detection information from the steering torque detection means,
Steering angle detection means for detecting the steering angle of the vehicle;
Yaw rate detecting means for detecting the yaw rate of the vehicle;
Lateral acceleration detecting means for detecting lateral acceleration of the vehicle;
Steering of the vehicle—By the observer designed based on the vehicle system model, the vehicle speed V of the vehicle detected by the vehicle speed detecting means, the steering angle detecting means, the yaw rate detecting means, and the lateral acceleration detecting means and the steering are respectively detected. An estimation means for estimating a lateral disturbance of the vehicle from the angle δ, the yaw rate γ, and the lateral acceleration G _y ;
The control means includes
Basic control amount calculating means for calculating a basic control amount for controlling the actuator based on detection information from the vehicle speed detecting means and the steering torque detecting means;
Correction amount calculating means for calculating a correction amount for correcting the steering assist torque applied by the actuator so as to suppress lateral disturbance of the vehicle from the estimation result by the estimating means;
Arithmetic means for adding the correction amount calculated by the correction amount calculation means to the basic control amount calculated by the basic control amount calculation means;
A power steering apparatus for a vehicle, comprising a high-pass filter interposed between the correction amount calculation means and the calculation means. The estimation means includes a lateral force disturbance φ _cw that attempts to move the vehicle in a lateral direction by a lateral force, and a lateral gradient disturbance φ _rb that acts on the vehicle due to a lateral inclination of the traveling road surface. Estimated separately,
The correction amount calculating means calculates a correction amount of the steering assist torque applied by the actuator so as to suppress mainly the lateral force disturbance φ _cw among the lateral disturbances of the vehicle from the estimation result by the estimating means. A vehicle power steering device. A steering angular velocity detecting means for detecting a steering angular velocity of the vehicle;
The estimating means is configured to further estimate the yaw rate and lateral velocity of the vehicle;
The correction amount calculating means includes a steering angle, a steering angular speed, a vehicle speed detected by the steering angular speed detecting means, the steering angle detecting means, and the vehicle speed detecting means, respectively, a yaw rate and a lateral speed estimated by the estimating means. Is calculated from the lateral force disturbance φ _cw and the lateral gradient disturbance φ _rb estimated by the estimation means, and the first correction torque and the second correction torque are calculated. 2. The power steering apparatus for a vehicle according to claim 1, wherein the sum of the torque and the torque is calculated as a correction amount. The correction amount calculating means calculates the first correction torque by multiplying each of the steering angle, the steering angular velocity, the yaw rate, and the lateral velocity by a gain that is set according to the vehicle speed, and the lateral force disturbance described above. The second correction torque is calculated by multiplying each of φ _cw and lateral gradient disturbance φ _rb by a gain set in accordance with the vehicle speed, and the sum of the first correction torque and the second correction torque The power steering apparatus for a vehicle according to any one of claims 1 to 3, wherein the correction amount is calculated as a correction amount.

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