JP2010214987A - Vehicular steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vehicular steering device capable of performing the turning control of wheels by adequately contributing the lateral acceleration generated according to the behavior change caused by the disturbance to be applied in the transverse direction of a vehicle. <P>SOLUTION: A target lateral acceleration computation unit 101 calculates the target lateral acceleration G<SP>*</SP>by multiplying a filter X(s) set based on the θ<SB>MA</SB>-G characteristic for achieving the target θ<SB>MA</SB>-γ characteristic by the steering angle θ<SB>MA</SB>. A feedforward computation unit 102 computes the feedforward control value δ<SB>ff</SB>based on the target lateral acceleration G<SP>*</SP>. A lateral acceleration deviation computation unit 103 calculates the deviation ΔG between the target lateral acceleration G<SP>*</SP>and the actual lateral acceleration G, and a PI control unit 104 computes the feedback control value Δδ<SB>fb</SB>according to the deviation ΔG. A target turning angle computation unit 105 calculates the target turning angle δ<SP>*</SP>by adding the control value δ<SB>ff</SB>to the control value Δδ<SB>fb</SB>. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a vehicle steering apparatus that enables stable running by steering control of wheels in response to a change in behavior of a vehicle, in particular, a behavior change due to a disturbance applied in a lateral direction.

  Conventionally, for example, as shown in Patent Document 1, a vehicle steering apparatus is known. In this conventional vehicle steering apparatus, the target behavior index value corresponding to the rotation operation angle of the operation member is calculated using the lateral acceleration and yaw rate of the vehicle and the weight ratio of these physical quantities, and generated in the vehicle. Using the detected lateral acceleration and yaw rate and the weight ratio of these detected values, a behavior index value corresponding to a change in the behavior of the vehicle due to a change in the steering angle is calculated. In the conventional vehicle steering apparatus, the target steering angle as a feedforward term corresponding to the target behavior index value, and the steering angle correction value as a feedback term corresponding to the deviation between the target behavior index value and the behavior index value Is the final target rudder angle, and the steering actuator is feedback controlled.

  Here, in the above-described conventional vehicle steering apparatus, regarding the transient response characteristics of the vehicle behavior with respect to the change in the steering angle, the lateral acceleration is dominant at the initial response, and the yaw rate is dominant thereafter, so the lateral acceleration is weighted. The ratio is set appropriately small. In this way, by setting the weighting ratio to the lateral acceleration to be small and performing compensation by feedback control, in the transient response of the lateral acceleration and yaw rate to the steering angle change, the speed response at a low vehicle speed is ensured at a high vehicle speed. To ensure the stability.

JP 2001-191937 A

  By the way, as a vehicle behavior change, for example, when steering control of a wheel is performed in response to a behavior change due to a lateral wind disturbance, the vehicle behavior is generally stabilized by feedback control using a lateral acceleration generated in the vehicle. It is said to be effective. In contrast, as described above, in the conventional vehicle steering apparatus, the behavior of the vehicle is stabilized by reducing the weighting ratio of the lateral acceleration, in other words, increasing the weighting ratio of the yaw rate.

  For this reason, for example, the desired stable behavior can be generated in a state where there is no side wind disturbance, but the contribution of the lateral acceleration may be small in the state where the side wind disturbance exists, and the effect of the feedback control may be reduced. There is. As a result, the behavior of the vehicle may not be stabilized. Therefore, it is necessary to stabilize the behavior of the vehicle by using the yaw rate generated in the vehicle, and to appropriately contribute the lateral acceleration generated in the vehicle in a state where a lateral wind disturbance exists. . However, if feedback control is performed by simply increasing the contribution of the lateral acceleration, the vehicle response may become too sensitive.

  The present invention has been made to cope with the above-described problem, and an object of the present invention is to control the steering of a wheel by appropriately contributing to the lateral acceleration generated along with the behavior change caused by the disturbance applied in the lateral direction of the vehicle. The object is to provide a vehicle steering system.

  In order to achieve the above object, the present invention is characterized in that a steering handle operated to steer a vehicle, a steering actuator that steers wheels, a vehicle speed detection means that detects the vehicle speed of the vehicle, Lateral acceleration detection means for detecting actual lateral acceleration generated in the vehicle width direction; target lateral acceleration calculation means for calculating target lateral acceleration to be generated in the vehicle width direction of the vehicle body in response to an operation of the steering handle; Command value setting means for setting a command value according to the target lateral acceleration calculated by the target lateral acceleration calculation means, a command value set by the command value setting means, the detected actual lateral acceleration, and the calculated target In a vehicle steering apparatus comprising a steering control unit that drives the steering actuator to steer the wheel based on a deviation from a lateral acceleration, the target lateral acceleration calculation unit includes a front In computing the target lateral acceleration to achieve the operation target transmission characteristic is previously set represents the relationship between the yaw rate generated in the center of gravity around the body in response to the operation of the steering wheel.

  In this case, the target lateral acceleration calculating means is generated according to the steering of the wheel with respect to the transfer function of the yaw rate that represents the preset target transfer characteristic and is generated according to the operation of the steering handle. Multiplying the transfer function of the lateral acceleration divided by the transfer function of the yaw rate generated according to the wheel steering, and multiplying by the vehicle speed gain that changes according to the vehicle speed detected by the vehicle speed detecting means A target lateral acceleration according to the operation of the steering wheel may be calculated using a set filter.

  Further, in this case, the preset target transfer characteristic is a transfer characteristic representing a relationship between an operation of the steering handle at a predetermined vehicle speed of the vehicle and a yaw rate generated around the center of gravity of the vehicle body according to the operation. There should be.

  In this case, the target lateral acceleration calculating means may calculate a target lateral acceleration that realizes the preset target transfer characteristic when the vehicle speed is equal to or higher than the predetermined vehicle speed.

  According to these, the target lateral acceleration calculating means represents the relationship between the operation of the steering wheel and the yaw rate generated around the center of gravity of the vehicle body in accordance with this operation, and realizes a target lateral characteristic set in advance. Acceleration can be calculated. In this case, the preset target transfer characteristic may be determined using, for example, a transfer characteristic at an arbitrary vehicle speed among transfer characteristics that change according to the vehicle speed of the vehicle. Then, the command value setting means can calculate a command value (for example, a target turning angle of the wheel) according to the target lateral acceleration. Further, the steering control means feeds back the actual lateral acceleration to the target lateral acceleration to drive the actual lateral acceleration when the steering actuator is driven based on the command value to steer the wheel. The wheel can be automatically steered by driving the steer actuator so as to coincide with the acceleration.

  Therefore, when the wheels are steered by feedback control, the target lateral acceleration calculated so as to realize the target transmission characteristic of the yaw rate that is dominant in the transient response characteristic (frequency characteristic) of the vehicle behavior can be used. As a result, the lateral acceleration considering the frequency characteristics can be appropriately contributed in the feedback control, the vehicle behavior in the presence of disturbance is well stabilized, and the driver perceives a good steering feeling. can do.

1 is an overall system configuration diagram of a vehicle steering apparatus according to an embodiment of the present invention. It is a block diagram showing the steering control process performed by ECU for steering. FIG. 5 is a Bode diagram of a transfer function F _δg (s) / G _γ (V) * V. FIG. 6 is a Bode diagram of a transfer function F _δγ (s) / G _γ (V). It is a Bode diagram of transfer function γ (s) / θ _MA (s) when filter X (s) = 1. It is a step response diagram of transfer function γ (s) / θ _MA (s). It is a step response diagram showing a target θ _MA -γ characteristic. FIG. 8 is a step response diagram showing a θ _MA -G characteristic when the target θ _MA -γ characteristic of FIG. 7 is set.

  Hereinafter, a vehicle steering apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 schematically shows a system configuration of a vehicle steering apparatus according to an embodiment.

  This vehicle steering device mechanically includes a steering operation device 10 that is steered by a driver, and a steering device 20 that steers left and right front wheels FW1 and FW2 as steered wheels according to the steering operation of the driver. A separate steering-by-wire system is used. The steering operation device 10 includes a steering handle 11 as an operation unit that is rotated by a driver. The steering handle 11 is fixed to the upper end of the steering input shaft 12, and a steering reaction force electric motor 13 for generating a reaction force incorporating a speed reduction mechanism is assembled to the lower end of the steering input shaft 12.

  The steered device 20 includes a steered shaft 21 that extends in the left-right direction of the vehicle. The left and right front wheels FW1, FW2 are connected to both ends of the steered shaft 21 via tie rods 22a, 22b and knuckle arms 23a, 23b so as to be steerable. The left and right front wheels FW1 and FW2 are steered left and right by the displacement of the steered shaft 21 in the axial direction. On the outer periphery of the turning shaft 21, a turning electric motor 24 assembled in a housing (not shown) is provided. The rotation of the steered electric motor 24 is decelerated by the screw feed mechanism 26 and is converted into an axial displacement of the steered shaft 21. This steering electric motor 24 corresponds to the steering actuator of the present invention.

Next, the electric control device 30 that controls the rotational drive of the steering reaction force electric motor 13 and the steering electric motor 24 will be described. The electric control device 30 includes a steering angle sensor 31, a turning angle sensor 32, a vehicle speed sensor 33, and a lateral acceleration sensor 34. The steering angle sensor 31 is a steering angle detection means for detecting the steering angle of the steering handle 11 and is assembled to the steering input shaft 12 to detect the rotation angle from the reference point of the steering handle 11 to detect the steering angle θ _MA. A signal representing is output.

  The steered angle sensor 32 is a steered angle detecting means for detecting the steered angle of the steered wheels. The steered angle sensor 32 detects the amount of axial displacement from the reference point of the steered shaft 21, and turns the left and right front wheels FW1, FW2. A signal representing the steering angle δ is output. Here, the rotation angle of the rotor of the electric motor 24 for turning is a value corresponding to the amount of movement of the turning shaft 21 in the axial direction, that is, the amount of change in the turning angle δ. Therefore, the turning angle sensor 32 in the present embodiment includes a relative angle sensor (for example, a resolver sensor) that detects a rotation angle with respect to the reference position of the rotor of the electric motor 24 for turning, and an absolute angle sensor for giving the reference position. (For example, an encoder), and the turning angle δ is detected from the rotation angle of the turning electric motor 24 obtained by both sensors. The vehicle speed sensor 33 corresponds to the vehicle speed detection means of the present invention, and outputs a vehicle speed signal representing the vehicle speed V that is the traveling speed of the vehicle. The lateral acceleration sensor 34 corresponds to the lateral acceleration detecting means of the present invention, and outputs a signal representing the lateral acceleration G that is fixed to the vehicle body and works in the vehicle width direction.

Note that the steering angle θ _MA , the actual turning angle δ, and the lateral acceleration G described above can identify their directions. For example, the steering angle θ _MA is directed leftward with respect to the reference point, or acts leftward. It is represented by a positive value, and when it is directed rightward or acting rightward, it is represented by a negative value. In the present specification, when the magnitude relationship between detected values is discussed without distinguishing the direction, the magnitude of the absolute value is discussed.

  The electric control device 30 includes a steering reaction force electronic control unit (hereinafter simply referred to as a steering reaction force ECU) 35 and a steering electronic control unit (hereinafter simply referred to as a steering ECU). 36). Each of the steering reaction force ECU 35 and the steering ECU 36 includes a microcomputer including a CPU, a ROM, a RAM, and the like as main components. A steering angle sensor 31 and a vehicle speed are provided on the input side of the steering reaction force ECU 35. A sensor 33 is connected, and a steering angle sensor 31, a turning angle sensor 32, a vehicle speed sensor 33, and a lateral acceleration sensor 34 are connected to the input side of the steering ECU 36.

  A drive circuit 37 for driving and controlling the steering reaction force electric motor 13 is connected to the output side of the steering reaction force ECU 35, and the steering electric motor 24 is connected to the output side of the steering ECU 36. A drive circuit 38 for driving control is connected. In the drive circuits 37 and 38, current detectors 37a and 38a are provided for detecting drive currents flowing through the electric motors 13 and 24, respectively. The drive currents detected by the current detectors 37a and 38a are fed back to the steering reaction force ECU 35 and the steering ECU 36 in order to drive and control the electric motors 13 and 24, respectively.

  Next, the operation of the steering apparatus configured as described above will be described from reaction force control by the steering reaction force ECU 35.

The steering reaction force ECU 35 calculates a target steering reaction force torque T ^* based on the steering angle θ _MA detected by the steering angle sensor 31, and a control signal (for example, for example, a target steering reaction force torque T ^*) . By outputting a PWM control signal to the drive circuit 37, a drive current corresponding to the target steering reaction torque T ^* is caused to flow to the steering reaction force electric motor 13. Thereby, a steering reaction force equal to the target steering reaction force torque T ^* is applied to the steering handle 11 via the steering input shaft 12. Therefore, an appropriate reaction torque is applied to the turning operation of the steering handle 11 by the driver, and the driver can comfortably rotate the steering handle 11 while perceiving the steering reaction force. Such control of the steering reaction force torque is performed by the steering reaction force ECU 35 executing a control program stored in a ROM (not shown) or the like.

In calculating the target steering reaction torque T ^* , for example, the spring reaction force torque component proportional to the steering angle θ _MA (or the lateral acceleration generated in the vehicle) and the steering angular velocity obtained by differentiating the steering angle θ _MA with respect to time. The friction reaction force torque component proportional to the magnitude of the torque and the viscous reaction force torque component proportional to the magnitude of the steering angular velocity are respectively calculated, and the torque components can be obtained by adding them up. The magnitude of the target steering reaction torque T ^* may be changed according to the vehicle speed V detected by the vehicle speed sensor 33. For example, when the detected vehicle speed V is low, the target steering reaction torque T ^* is small. When the detected vehicle speed V is high, the target steering reaction torque T ^* may be calculated to be large. Thus, the driver can easily steer the steering handle 11 during low-speed traveling, and the driver can steer the steering handle 11 while perceiving a firm reaction force torque during medium-high speed traveling. And good steering operability can be ensured.

  Next, turning angle control performed by the turning ECU 36 will be described. Since this turning angle control is related to the characteristic part of the present invention, it will be described in detail with reference to the functional block diagram of FIG. 2 showing functions realized by computer program processing in the steering ECU 36.

The steering ECU 36 includes a target lateral acceleration calculation unit 101. The target lateral acceleration calculation unit 101 inputs the steering angle θ _MA detected by the steering angle sensor 31 and the vehicle speed V detected by the vehicle speed sensor 33, and calculates the target lateral acceleration G ^* . Hereinafter, this calculation will be specifically described.

ここで、前記式１中のF_δγ(s)は下記式２で表されるように転舵角δを入力としヨーレートγを出力とする伝達関数であり、F_δg(s)は下記式３で表されるように転舵角δを入力とし横加速度Gを出力とする伝達関数である。

In general, the relationship between the lateral acceleration G and the yaw rate γ in the vehicle can be expressed by the following formula 1.

Here, the F _{[Delta] [gamma]} (s) of formula 1 is a transfer function that outputs an input yaw rate γ of the steering angle δ, as represented by the following formula _2, F δg (s) is the following formula 3 As shown, the steering angle δ is an input and the lateral acceleration G is an output.

なお、前記式４中のmは車両の質量を表し、L_fは車両重心点と前車軸間の距離を表す。また、前記式５中のL_rは車両重心点と後車軸間の距離を表す。また、前記式６中のI_zは車両のヨーイング慣性モーメントを表す。さらに、前記式４，６中のK_rは車両後輪のコーナリングパワーを表し、Lは車両のホイールベースを表す。 However, G _γ (V) in Equations 2 and 3 represents the steady gain of the steering angle δ−yaw rate γ set for each vehicle speed V, and ω _n (V) represents the vehicle speed set for each vehicle speed V. It represents the natural frequency (resonance frequency) of the response, and ζ represents the damping ratio of the response of the vehicle. Further, s in the above formulas 2 and 3 represents a Laplace operator. In addition, _Tr in the formula 2 is represented by the following formula 4, and T _y1 and T _y2 in the formula 3 are represented by the following formulas 5 and 6, respectively.

In Equation 4, m represents the mass of the vehicle, and L _f represents the distance between the vehicle center of gravity and the front axle. Further, L _r in formula 5 represents the distance between the vehicle center of gravity and the rear axle. Further, I _z in the equation 6 represents the yawing moment of inertia of the vehicle. Further, K _r in the formula 4, 6 represents a cornering power of the vehicle rear wheel, L is a wheelbase of the vehicle of the vehicle.

そして、前記式７を成立させるためのθ_MA−G特性は、前記式７を変形した下記式８によって表すことができる。

Here, in the present embodiment, a target steering angle θ _MA −yaw rate γ characteristic (hereinafter simply referred to as θ _MA −γ characteristic) is set, and a steering angle for realizing the target θ _MA −γ characteristic is set. theta _MA - characteristics of the lateral acceleration G (hereinafter, simply referred to as theta _MA -G characteristics) to calculate the target lateral acceleration G ^* based on. In this case, if the transfer function representing the target θ _MA -γ characteristic is F _MAγ (s) and the target yaw rate is γ ^* , based on the above equation 1, the following equation 7 is established.

The θ _MA -G characteristic for establishing the formula 7 can be expressed by the following formula 8 obtained by modifying the formula 7.

Therefore, considering the change in the steady gain due to the vehicle speed V, the filter X (s) can be expressed by the following Equation 9.

Then, the target acceleration calculation unit 101 uses the filter X (s) that is set based on the θ _MA -G characteristic that realizes the target θ _MA -γ characteristic, which is expressed by the above equation 9, and uses the target X Calculate the acceleration G ^* . That is, the target acceleration calculation unit 101 calculates the target lateral acceleration G ^* by multiplying the steering angle θ _MA input from the steering angle sensor 31 by the filter X (s). The target lateral acceleration calculation unit 101 corresponds to target lateral acceleration calculation means of the present invention.

Further, the steering ECU 36 includes a feed-forward calculation unit 102, a lateral acceleration deviation calculation unit 103, a PI control unit 104, and a target turning angle calculation unit 105 in order to calculate the target turning angle δ ^* . The target lateral acceleration G ^* calculated by the target lateral acceleration calculation unit 101 is input to the feedforward calculation unit 102 and the lateral acceleration deviation calculation unit 103. The feedforward calculation unit 102 inputs the target lateral acceleration G ^* and calculates the feedforward control value δ _ff of the turning angle using the following formula 10.

On the other hand, the lateral acceleration deviation calculating unit 103 feeds back and inputs the actual lateral acceleration G detected by the lateral acceleration sensor 34, and a deviation ΔG (= G ^* −G) between the target lateral acceleration G ^* and the actual lateral acceleration G. Calculate That is, the lateral acceleration deviation calculation unit 103 calculates a deviation ΔG from the actual lateral acceleration G that changes due to the influence of a disturbance such as a cross wind. The calculated deviation ΔG is input to the PI control unit 104. The PI control unit 104 calculates a turning angle feedback control value Δδ _fb by adding a proportional term proportional to the input deviation ΔG and an integral term obtained by integrating the deviation ΔG, as shown in Equation 11 below.

The feedforward control value δ _ff and the feedback control value Δδ _fb are input to the target turning angle calculation unit 105. The target turning angle calculation unit 105 adds the feedforward control value δ _ff and the feedback control value Δδ _fb to calculate the target turning angle δ ^* (= δ _ff + Δδ _fb ).

The steering ECU 36 further includes a turning angle deviation calculation unit 106, a target current calculation unit 107, a current deviation calculation unit 108, a PI control unit 109, and a PWM voltage generation unit 110. The target turning angle δ ^* calculated by the target turning angle calculation unit 105 is input to the turning angle deviation calculation unit 106. The turning angle deviation calculation unit 106 inputs a turning angle δ (hereinafter referred to as an actual turning angle δ) from the turning angle sensor 32, and a deviation Δδ between the target turning angle δ ^* and the actual turning angle δ. (= Δ ^* −δ) is calculated. The calculated deviation Δδ is input to the target current calculation unit 107.

The target current calculation unit 107 inputs a deviation Δδ between the target turning angle δ ^* and the actual turning angle δ, and calculates a target current i ^* proportional to the deviation Δδ. This target current i ^* is a target current value for energizing the electric motor 24. The target current i ^* is input to the current deviation calculation unit 108. The current deviation calculation unit 108 inputs the target current i ^* calculated by the target current calculation unit 107 and the actual current i flowing through the electric motor 24 detected by the current detector 38a, and the deviation Δi (= i) between the two. ^* -I) is calculated. The deviation Δi calculated by the current deviation calculation unit 108 is input to the PI control unit 109.

The PI control unit 109 calculates a target voltage v ^* for driving the electric motor 24 by adding a proportional term proportional to the inputted deviation Δi and an integral term obtained by integrating the deviation Δi. That is, the target voltage v ^* is calculated so that the deviation Δi becomes zero. The target voltage v ^* calculated by the PI control unit 109 is input to the PWM voltage generation unit 110. The PWM voltage generator 110 outputs a PWM control voltage signal corresponding to the target voltage v ^* to the drive circuit 38. The drive circuit 38 includes a switching element, and is, for example, an inverter circuit or an H bridge circuit. The drive circuit 38 turns on and off the switching element with a duty ratio corresponding to the PWM control voltage signal, and applies the target voltage v ^* to the electric motor 24. Accordingly, the left and right front wheels FW1 and FW2 are steered by the driving force of the electric motor 24.

Next, the effect when steering control is performed as described above will be described. Now, when both sides of the equation 3 are divided by G _γ (V) * V and a Bode diagram of F _δg (s) / G _γ (V) * V is expressed, the frequency characteristics are as shown in FIG. That is, as apparent from FIG. 3 (a), the gain changes as the frequency and the vehicle speed V increase, and as shown in FIG. 3 (b), there is a frequency characteristic in which the phase delay increases at a certain frequency. On the other hand, when both sides of the equation 2 are divided by G _γ (V) and a Bode diagram of F _δγ (s) / G _γ (V) is represented, the frequency characteristics shown in FIG. 4 are obtained. That is, as is clear from FIG. 4 (a), the gain characteristic changes as the vehicle speed V increases at a certain frequency, and the phase delay increases as the frequency increases as apparent from FIG. 4 (b). Have

In addition, in the functional block diagram of FIG. 2 in which the transfer function F _δγ (s) and the transfer function F _δg (s) having such frequency characteristics are used and the lateral acceleration G is fed back to control the turning angle, When the filter X (s) = 1, that is, in the case of a normal vehicle to which the filter X (s), which is a feature of the present invention is not applied, a transfer function having the steering angle θ _MA as an input and the lateral acceleration G as an output. G (s) / θ _MA (s) is constant. At this time, the transfer function γ (s) / θ _MA (s) with the steering angle θ _MA as an input and the yaw rate γ as an output is γ (s) / G (s), which is very vibrational when the vehicle speed V is high. become. That is, the Bode diagram of the transfer function γ (s) / θ _MA (s) when the filter X (s) = 1 is expressed as shown in FIG. 5, and the gain at a certain frequency as the vehicle speed V increases. The phase advance at a certain frequency increases. Then, when the step response of the transfer function γ (s) / θ _MA (s) in this case is shown, it can be understood that as the vehicle speed V increases, the amplitude increases and becomes oscillating as shown in FIG. .

On the other hand, when the filter X (s) determined by the equation 9 is adopted, the target lateral acceleration G ^* is calculated based on the θ _MA -G characteristic that realizes the target θ _MA -γ characteristic. Is done. That is, the target lateral acceleration G ^* that realizes the target θ _MA −γ characteristic is calculated by arbitrarily setting F _MAγ (s) in the _equation (9). For this reason, for example, when the θ _MA −γ characteristic is made constant in the entire vehicle speed range, the transfer function F _δγ (s) at a certain vehicle speed Va as shown in the θ _MA −γ characteristic (step response) shown in FIG. | Set F _MAγ (s) as the θ _MA −γ characteristic with _{V = Va} as the target. Then, by calculating the target lateral acceleration G ^* using the filter X (s) having F _MAγ (s) set in this way, the θ _MA -G characteristic realizes the target θ _MA -γ characteristic. For example, as shown in FIG. 8, the θ _MA -G characteristic (step response) has a tendency to gradually converge with the passage of time, although the magnitude of the amplitude varies depending on the vehicle speed V.

Therefore, according to the present embodiment, the target lateral acceleration G ^* is calculated based on the θ _MA −G characteristic that realizes the target θ _MA −γ characteristic, and the turning angle is calculated using the target lateral acceleration G ^*. Feedback control can be performed. Thereby, in the feedback control of the turning angle using the lateral acceleration G, it is possible to use the target lateral acceleration G ^* in consideration of the θ _MA -G characteristic, that is, the frequency characteristic, which realizes the target θ _MA -γ characteristic. Therefore, it is possible to suppress the sensitive response of the vehicle to ensure a good steering feeling and to stably realize the original disturbance stabilization control.

  The implementation of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the object of the present invention.

For example, in the above embodiment, the transfer function F _δγ (s) | _{V = Va} at a certain vehicle speed Va is set to F _MAγ (s) as the target θ _MA -γ characteristic. The target lateral acceleration G ^* was calculated using the filter X (s) having F _MAγ (s) set in this way. As a result, the vibration (resonance) of the transfer function γ (s) / θ _MA (s) can be suppressed particularly when the vehicle speed V is high.

As described above, calculating the target lateral acceleration G ^* using the filter X (s) having F _MAγ (s) favorably changes the characteristics at high speeds. The filter X (s) may be another definition. In this case, as shown in FIG. 3, the frequency characteristic of F _δg (s) / G _γ (V) * V is such that the gain magnitude at a low frequency and the gain magnitude at a high frequency at a certain vehicle speed Vb. I can understand that they are replaced. Based on the change in this characteristic, for example, when the vehicle speed V is less than the vehicle speed Vb, the filter X (s) is _converted to X (s) = F using the transfer function F _δg (s) | _{V = Vb} for the lateral acceleration at the vehicle speed Vb. _δg (s) | _{V =} and _Vb, the transfer function F _{[Delta] [gamma]} (s) related to a yaw rate of the vehicle speed Vb when the vehicle speed V is equal to or greater than the vehicle speed _{Vb | F MAγ (s) =} F δg (s) with _{V = Vb} | It is also possible to carry out such that _{V = Vb and the} filter X (s) is determined according to the above equation 9. As a result, it is possible to suppress changes in the lateral acceleration G at low speeds below the vehicle speed Vb, and at medium and high speeds above the vehicle speed Vb, particularly sensitive to changes in vehicle behavior due to a large gain of the θ _MA −G characteristic in the high frequency range. It is possible to suppress the change in yaw rate γ as well as to suppress the fluctuation. Further, by changing the filter X (s) with the vehicle speed Vb as a boundary, it is possible to suppress the uncomfortable feeling perceived by the driver along with the change.

  Furthermore, in the present embodiment, a steering-by-wire type steering device is employed. However, the present invention can also be applied to a gear ratio variable steering device that can freely adjust the steering gear ratio. Even in this case, the same effect as in the above embodiment can be expected.

  DESCRIPTION OF SYMBOLS 10 ... Steering operation device, 11 ... Steering handle, 20 ... Steering device, 24 ... Electric motor for steering, 30 ... Electric control device, 31 ... Steering angle sensor, 32 ... Steering angle sensor, 33 ... Vehicle speed sensor, 34 DESCRIPTION OF SYMBOLS ... Lateral acceleration sensor, 35 ... Steering reaction force ECU, 36 ... Steering ECU, 101 ... Target lateral acceleration calculating part, 102 ... Feed forward calculating part, 103 ... Lateral acceleration deviation calculating part, 104 ... PI control part, 105 ... Target turning angle calculation unit, 106 ... Steering angle deviation calculation unit

Claims (4)

A steering handle that is operated to steer the vehicle, a steering actuator that steers the wheels, vehicle speed detection means that detects the vehicle speed of the vehicle, and a lateral that detects the actual lateral acceleration generated in the vehicle width direction of the vehicle body. In accordance with the target lateral acceleration calculated by the target lateral acceleration calculating means, the target lateral acceleration calculating means for calculating the target lateral acceleration to be generated in the vehicle width direction of the vehicle body according to the operation of the steering handle, Command value setting means for setting the command value, the command value set by the command value setting means, and the deviation between the detected actual lateral acceleration and the calculated target lateral acceleration. In a steering apparatus for a vehicle provided with steering control means for driving and steering the wheels,
The target lateral acceleration calculating means represents a relationship between an operation of the steering handle and a yaw rate generated around the center of gravity of the vehicle body in accordance with the operation, and calculates a target lateral acceleration that realizes a preset target transfer characteristic. A vehicle steering apparatus characterized by calculating. In the vehicle steering apparatus according to claim 1,
The target lateral acceleration calculating means includes
The transfer function of the lateral acceleration generated in response to the steering of the wheel is expressed as the transfer function of the wheel in response to the yaw rate transfer function generated in response to the operation of the steering handle. A filter that is set by multiplying a transfer function of a yaw rate generated according to the rudder and multiplying by a vehicle speed gain that changes according to the vehicle speed detected by the vehicle speed detecting means is used. A vehicle steering apparatus characterized by calculating a target lateral acceleration according to an operation. In the vehicle steering apparatus according to claim 1,
The preset target transfer characteristic is:
A vehicle steering apparatus characterized by a transmission characteristic representing a relationship between an operation of the steering handle at a predetermined vehicle speed and a yaw rate generated around a center of gravity of the vehicle body in response to the operation. In the vehicle steering apparatus according to claim 3,
The target lateral acceleration calculating means includes
A vehicle steering apparatus that calculates a target lateral acceleration that realizes the preset target transmission characteristic when the vehicle speed is equal to or higher than the predetermined vehicle speed.

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