JP5105184B2 - Vehicle steering system - Google Patents

Description

  The present invention relates to a vehicle steering apparatus provided with a reaction force means for applying a reaction force to an operation member for steering a vehicle.

  As a vehicle steering system, the mechanical coupling between the steering wheel and the steering mechanism is eliminated, the steering wheel operating angle is detected by a sensor, and the driving force of the steering actuator controlled according to the output of the sensor is steered. There has been proposed a steer-by-wire system that transmits to a mechanism (Patent Document 1). In the steer-by-wire system, the ratio of the steering angle of the steering wheel to the operation angle of the steering wheel (steering angle ratio) can be freely determined. Further, the turning angle control by the control of the steering actuator can be performed independently of the operation of the steering wheel, and thereby the vehicle behavior stabilization control by the steering control can be performed.

In the steer-by-wire system, a reaction force actuator for applying an operation reaction force to the steering wheel is provided. This reaction force actuator is controlled according to the operating angle of the steering wheel and the vehicle speed. As a result, an operation reaction force similar to that of a conventional vehicle steering apparatus in which the steering wheel and the steering mechanism are mechanically coupled is applied to the steering wheel.
JP 2001-213340 A JP 2006-2805 A

However, since the reaction force applied to the steering wheel from the reaction force actuator according to the operation angle does not necessarily correspond to the vehicle behavior, it is difficult to create a good steering feeling according to the driving situation. It was.
This problem is considered to be alleviated by adding a reaction force component proportional to the yaw rate representing the vehicle behavior to the operation reaction force.

However, in the region where the generated yaw rate is small, such as when the steering is started from the steering neutral position (straight-running state), the effect of the yaw rate proportional component is small. Therefore, the steering feeling still has room for improvement.
Accordingly, an object of the present invention is to provide a vehicle steering apparatus that can apply an operation reaction force according to vehicle behavior to an operation member, thereby contributing to an improvement in steering feeling. .

In order to achieve the above object, the invention described in claim 1 includes vehicle behavior detection means (16) for detecting a vehicle behavior (γ), and a change rate (γ of the vehicle behavior detected by the vehicle behavior detection means). ′), The vehicle behavior change rate calculating means (39), the operating angle detecting means (11) for detecting the operating angle (θ) of the operating member (1) for steering the vehicle, and the operating angle. Operation angle increase / decrease determination means (S1, S2, S5) for determining whether the magnitude of the operation angle detected by the detection means is increasing or decreasing, and reaction force means (19) for applying an operation reaction force to the operation member And the reaction force means for controlling the reaction force means to generate an operation reaction force including the reaction force component (T _{γ ′} ) corresponding to the change rate calculated by the vehicle behavior change rate calculation means. Force control means (S17 to S19), and the operation angle increase / decrease And a prohibiting means (S4) for prohibiting reaction force control by the reaction force control means based on the rate of change when it is determined by the determination means that the magnitude of the operation angle is decreasing. It is a steering device. The numbers in parentheses indicate corresponding components in the embodiments described later. The same applies hereinafter.

  According to this configuration, the operation reaction force applied from the reaction force means to the operation member includes a reaction force component corresponding to (for example, proportional to) the change rate (time change rate) of the vehicle behavior. For this reason, when the rudder starts to be turned from the rudder state, particularly when the turning from the midpoint of the operation angle starts, the operation reaction force corresponding to the change in the vehicle behavior (start of movement of the vehicle) is sufficiently applied to the operation member. be able to. Thereby, a steering feeling can be improved.

  Furthermore, in the present invention, it is determined whether the magnitude of the operation angle is increasing (steering away from the operation angle midpoint, forward steering) or decreasing (steering toward the operation angle midpoint, return steering). Is done. The magnitude of the operation angle tends to decrease. Therefore, when the return steering is performed, the reaction force control based on the change rate of the vehicle behavior is prohibited. At the time of return steering, the sign of the rate of change in vehicle behavior is opposite to the sign of the direction of vehicle behavior (for example, the direction of yaw rate). Therefore, when the reaction force control based on the vehicle behavior change rate is performed, the operation reaction force may be suddenly reduced, and a steering discomfort may occur. Therefore, in the present invention, it is decided to prevent the uncomfortable feeling of steering by prohibiting the reaction force control based on the vehicle behavior change rate during the return steering.

The vehicle behavior detecting means may detect a yaw rate (γ) of the vehicle as the vehicle behavior. In this case, it is preferable that the vehicle behavior change rate calculating means calculates a yaw acceleration (γ ′) that is a time differential value of the yaw rate.
The prohibiting means may be one that makes the reaction force component corresponding to the vehicle behavior change rate zero.
The reaction force control means further generates an operation reaction force including a reaction force component ( _Tγ ) corresponding to (for example, proportional to) the vehicle behavior calculated by the vehicle behavior calculation means from the reaction force means. Thus, the reaction force means may be controlled.

Furthermore, the reaction force control means further generates an operation reaction force including a reaction force component (T _θ ) corresponding to the operation angle detected by the operation angle detection means from the reaction force means. The means may be controlled. The reaction force component corresponding to the operation angle may change in magnitude according to the vehicle speed (V). For example, the magnitude of the reaction force component preferably changes so as to increase as the vehicle speed increases.

The invention according to claim 2 further includes a steering motor (2) for applying a steering force to the steering mechanism, and a current detection means (25) for detecting a current of the steering motor, The reaction force control means controls the reaction force means so that an operation reaction force including a reaction force component (T _cur ) corresponding to the current detected by the current detection means is generated from the reaction force means. The vehicle steering apparatus according to claim 1.

  The current (load current) of the steering motor corresponds to (for example, proportional to) the force that the tire receives from the road surface. Therefore, by detecting this current by the current detection means and applying an operation reaction force including a reaction force component corresponding to the detected current to the operation member, an operation reaction force corresponding to the road surface condition can be given to the driver. it can. As a result, not only the vehicle behavior but also the road surface condition can be reflected in the operation reaction force, so that the operation reaction force according to the traveling state of the vehicle can be applied to the operation member. As a result, the steering feeling can be further improved.

According to a third aspect of the present invention, when the operation frequency of the operation member exceeds a predetermined threshold value (f _th ), the reaction force control means is more preferable than when the operation frequency is equal to or less than the threshold value. 3. The vehicle steering apparatus according to claim 1, further comprising a gain setting unit that sets a gain (G _{γ ′} ) of a reaction force component corresponding to the rate of change to be small.
When the steering input to the operation member is a high frequency as in the case of quickly operating the operation member to the left and right, there is a possibility that a delay in the generation of vehicle behavior (for example, yaw rate) with respect to steering may become a problem. In an extreme case, the change in the operation angle and the change in the vehicle behavior may be in opposite phases. In such a case, because the reaction force component corresponding to the vehicle behavior change rate may cause the operation reaction force to vibrate or diverge, there is a risk of deteriorating steering feeling. Therefore, in the present invention, when the operation frequency of the operation member exceeds a predetermined threshold, the gain of the reaction force component corresponding to the vehicle behavior change rate is reduced. Thereby, vibration or divergence of the operation reaction force can be prevented, and a good operation feeling can be maintained.

When the reaction force component corresponding to the vehicle behavior is included in the operation reaction force, when the operation frequency of the operation member exceeds the threshold value, the gain ( _Gγ ) for the reaction force component is also reduced. Is preferred.
When the reaction force component corresponding to the current of the steering motor is included in the operation reaction force, the gain (G _cur ) for the reaction force component when the operation frequency of the operation member exceeds the threshold value. Is preferably increased. As a result, the decrease in the reaction force component corresponding to the vehicle behavior and / or the vehicle behavior change rate can be compensated for, so that the steering feeling can be further improved.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is an illustrative view for explaining the configuration of a vehicle steering apparatus according to an embodiment of the present invention, and shows the configuration of a steer-by-wire system. The vehicle steering apparatus includes a steering wheel 1 as an operation member that a driver operates for steering, a steering actuator 2 that is driven according to a rotation operation of the steering wheel 1, and driving of the steering actuator 2. And a steering gear 3 that transmits force to the front left and right wheels 4 as steering wheels. There is no mechanical coupling between the steering wheel 1 and the steering mechanism 5 including the steering actuator 2 or the like such that the operating torque applied to the steering wheel 1 is mechanically transmitted to the steering mechanism 5. The wheel 4 is steered by driving and controlling the steering actuator 2 according to the operation amount (operation angle or operation torque) of the steering wheel 1.

  The steering actuator 2 is a steering motor configured by an electric motor such as a known brushless motor. The steering gear 3 has a motion conversion mechanism that converts the rotational motion of the output shaft of the steering actuator 2 into linear motion of the steering rod 7 (linear motion in the vehicle left-right direction). The movement of the steering rod 7 is transmitted to the wheel 4 via the tie rod 8 and the knuckle arm 9, and the toe angle (steering angle) of the wheel 4 changes. As the steering gear 3, a known one can be used, and the configuration is not limited as long as the movement of the steering actuator 2 can be transmitted to the wheels 4 so that the steering angle changes. In the state where the steering actuator 2 is not driven, the wheel alignment is set so that the wheel 4 can return to the straight steering position by the self-aligning torque.

  The steering wheel 1 is connected to a rotating shaft 10 that is rotatably supported on the vehicle body side. The rotary shaft 10 is provided with a reaction force actuator 19 that generates a reaction force torque (operation reaction force) acting on the steering wheel 1. The reaction force actuator 19 can be constituted by an electric motor such as a brushless motor having an output shaft integrated with the rotary shaft 10.

  An elastic member 30 is provided between the vehicle body and the rotating shaft 10 to provide elasticity in a direction to return the steering wheel 1 to the straight steering position. The elastic member 30 can be constituted by, for example, a spring that gives elasticity to the rotary shaft 10. When the reaction force actuator 19 does not apply torque to the rotary shaft 10, the steering wheel 1 returns to the straight steering position by the elasticity of the elastic member 30.

  In order to detect the operation angle (rotation angle) θ of the steering wheel 1, an angle sensor 11 that detects the rotation angle of the rotary shaft 10 is provided. In addition, a torque sensor 12 that detects torque transmitted by the rotary shaft 10 is provided in order to detect an operation torque Th that the driver of the vehicle acts on the steering wheel 1. Furthermore, a steering angle sensor 13 for detecting a steering angle (steering angle of the steering mechanism 5) δ of the vehicle is provided. The steering angle sensor 13 is constituted by, for example, a potentiometer that detects the operation amount of the steering rod 7 corresponding to the steering angle δ. A speed sensor 14 for detecting the vehicle speed V, a lateral acceleration sensor 15 for detecting the lateral acceleration Gy of the vehicle, and a yaw rate sensor 16 for detecting the yaw rate γ of the vehicle are provided.

These angle sensor 11, torque sensor 12, rudder angle sensor 13, speed sensor 14, lateral acceleration sensor 15 and yaw rate sensor 16 are respectively connected to a control device 20 constituted by a computer. The control device 20 controls the steering actuator 2 and the reaction force actuator 19 via the drive circuits 22 and 23.
FIG. 2 shows a control block diagram of the control device 20. The driver applies an operation torque Th to the steering wheel 1 and the reaction force actuator 19 applies a reaction force torque Tm. An operation angle θ as an operation amount of the steering wheel 1 is detected by the angle sensor 11 and input to the control device 20.

The control device 20 includes, as function processing means realized by software processing, a turning angle setting unit 31, a target yaw rate setting unit 32, a yaw rate deviation calculation unit 33, a turning angle correction value calculation unit 34, and a setting rotation. A steering angle correction unit 35, a target current calculation unit 36, a reaction force setting unit 37, a gain multiplication unit 38, and a yaw acceleration calculation unit 39 are provided.
The turning angle setting unit 31 uses the transfer function K _δ (V) to obtain a turning angle setting value δ _FF ^* corresponding to the operation angle θ and the vehicle speed V. This turning angle set value δ _FF ^* is provided to the set turning angle correction unit 35. Thus, the steered angle setting unit 31 has a function as a steered angle feedforward control value setting means for determining the steered angle set value δ _FF ^* (steered angle value) according to the steering state. .

The target yaw rate setting unit 32 obtains a target yaw rate γ ^* as a vehicle behavior target value using the transfer function K _γ (V) based on the operation angle θ and the vehicle speed V. This target yaw rate γ ^* is given to the yaw rate deviation calculation unit 33.
The yaw rate deviation calculator 33 subtracts the actual yaw rate γ of the vehicle 100 detected by the yaw rate sensor 16 from the target yaw rate γ ^* to obtain these deviations Δγ.

The turning angle correction value calculation unit 34 uses a transfer function C _FB (s) (where s is a Laplace operator) to obtain a turning angle correction value δ _FB ^* corresponding to the yaw rate deviation Δγ. This turning angle correction value δ _FB ^* is provided to the set turning angle correction unit 35.
Set turning angle correcting section 35 obtains a target steering angle [delta] ^* by correcting the steering angle set value [delta] _FF ^* at turning angle correction value [delta] _FB ^*. In this way, the vehicle behavior stabilization control that feeds back the yaw rate γ detected by the yaw rate sensor 16 and leads the yaw rate of the vehicle 100 to the target yaw rate γ ^* is performed. That is, if the absolute value of the yaw rate deviation Δγ is large, the absolute value of the steering angle correction value δ _FB ^* (steering angle correction value) increases accordingly, and the steering is performed regardless of the driver's operation of the steering wheel 1. Active steering control for changing the angle is performed.

The yaw rate deviation calculating unit 33 and the turning angle correction value calculating unit 34 function as steering angle feedback control value setting means for setting a turning angle correction value δ _FB ^* (steering angle correction value) according to the vehicle behavior, Further, a target yaw rate setting unit 32 is added to the vehicle behavior stabilization control means for stabilizing the vehicle behavior.
The target current calculation unit 36 obtains the target current value i ^* corresponding to the target turning angle δ ^* using the transfer function C _δ (s). By controlling the steering actuator 2 so that this target current value i ^* is achieved, the turning angle δ of the steering mechanism 5 is brought close to the target turning angle δ ^* .

The yaw acceleration calculator 39 obtains yaw acceleration (yaw rate differential value) γ ′ by differentiating the yaw rate detected by the yaw rate sensor 16 with respect to time. The yaw acceleration γ ′ is given to the reaction force setting unit 37.
The reaction force setting unit 37 includes an operation angle θ detected by the angle sensor 11, a vehicle speed V detected by the speed sensor 14, a yaw rate γ detected by the yaw rate sensor 16, and a yaw acceleration calculated by the yaw acceleration calculation unit 39. Based on γ ′, a target reaction force torque basic value T _obj is obtained. The target reaction force torque Tm ^* is obtained by multiplying the target reaction force torque basic value T _obj by the torque gain K _T corresponding to the operation torque Th detected by the torque sensor 12. The reaction force actuator 19 is controlled based on the target reaction force torque Tm ^* .

Thus, the reaction force actuator 19 operates to apply a reaction force torque Tm corresponding to the operation angle θ, the vehicle speed V, the yaw rate γ, and the yaw acceleration γ ′ to the steering wheel 1. Thereby, the bilateral servo system which returns the external force added to the steering mechanism 5 side to the steering wheel 1 is comprised.
FIG. 3 is a functional block diagram for explaining a more detailed configuration of the reaction force setting unit 37. The reaction force setting unit 37 includes a first reaction force component generation unit 41, a second reaction force component generation unit 42, a third reaction force component generation unit 43, a gain setting unit 46, and an addition unit 47. Yes.

The first reaction force component generation unit 41 generates an operation angle reaction force component T _θ (V) corresponding to the operation angle θ and the vehicle speed V. Second reaction force component generating unit 42 generates a yaw rate reaction force T _gamma corresponding to the yaw rate gamma. The third reaction force component generator 43 generates a yaw acceleration reaction force component T _{γ ′} corresponding to the yaw acceleration _{γ ′} . The gain setting unit 46 sets the gain G _{γ ′} of the yaw acceleration reaction force component T _{γ ′} with respect to the yaw acceleration γ ′ according to the operation angle θ and the yaw acceleration γ ′. Therefore, the third reaction force component generation unit 43 generates the yaw acceleration reaction force component T _{γ ′} corresponding to the gain G _{γ ′} set by the gain setting unit 46. The adding unit 47 includes an operation angle reaction force component T _θ (V), a yaw rate reaction force component T _γ, and a yaw acceleration reaction force component generated by the first, second, and third reaction force component generation units 41, 42, and 43. T _{γ ′} is added to generate a target reaction force torque basic value T _obj (= T _θ (V) + T _γ + T _{γ ′} ).

FIG. 4A is a diagram illustrating a setting example of the operation angle reaction force component T _θ (V) by the first reaction force component generation unit 41, and FIG. 4B is a diagram illustrating the yaw rate reaction force component T _γ by the second reaction force component generation unit 42. FIG. 4C is a diagram illustrating a setting example of the yaw acceleration reaction force component T _{γ ′} by the third reaction force component generation unit 43. In each figure, only the characteristic curve of the positive region of the parameter (θ, γ, γ ′) is shown, but the characteristic of the negative region of each parameter is represented by a point-symmetric curve with respect to the origin in each figure. Is done.

As shown in FIG. 4A, the operation angle reaction force component T _θ corresponding to the operation angle _θ is determined so as to increase as the absolute value of the operation angle θ increases and to increase as the vehicle speed V increases. Absolute value is lower range of the operation angle theta, i.e., the operation angle range around the steering angle midpoint, rises sharply the operation angle reaction force component T _theta, the operation angle range away from the operation angle around the midpoint, the steering angle reaction force T _theta has become a characteristic which rises slowly.

Further, as shown in FIG. 4B, the yaw rate reaction force component Tγ corresponding to the yaw rate _γ is determined to be proportional to the yaw rate γ, for example.
Further, as shown in FIG. 4C, the yaw acceleration reaction force component T _{γ ′} corresponding to the yaw acceleration _{γ ′} is determined to be proportional to the yaw acceleration γ ′, for example. In this case, the yaw acceleration reaction force component T _{γ ′} can be expressed as T _{γ ′} = γ ′ × G _{γ ′} using the above-described gain G _{γ ′} .

FIG. 5 is a flowchart for explaining processing by the gain setting unit 46. The gain setting unit 46 determines whether the operation angle θ is greater than or equal to zero (step S1). When the operation angle θ is equal to or greater than 0, the gain setting unit 46 further determines whether the yaw acceleration γ ′ is equal to or greater than 0 (step S2). When the yaw acceleration γ ′ is greater than or equal to 0 (step S2: YES), that is, when the operation angle θ and the yaw acceleration γ ′ have the same sign, the gain setting unit 46 corresponds to the characteristics shown in FIG. 4C. A gain G _{γ ′} (> 0) is generated (step S3). Therefore, the third reaction force component generation unit 43 generates the yaw acceleration reaction force component T _{γ ′} (= γ ′ × G _{γ ′} ) corresponding to the yaw acceleration _{γ ′} .

On the other hand, when the yaw acceleration γ ′ is less than 0 in step S2 (step S2: NO), that is, when the operation angle θ and the yaw acceleration γ ′ have different signs, the gain setting unit 46 sets the gain G _{γ. '} Is set to 0 (step S4). Therefore, the yaw acceleration reaction force component T _{γ ′} generated by the third reaction force component generation unit 43 becomes zero.
When the operation angle θ is a negative value (step S1: NO), the gain setting unit 46 determines whether the yaw acceleration γ ′ is 0 or more (step S5). When the yaw acceleration γ ′ is 0 or more (step S5: YES), that is, when the operation angle θ and the yaw acceleration γ ′ have different signs, the gain setting unit 46 sets the gain G _{γ ′} to 0 ( Step S4). Therefore, the yaw acceleration reaction force component T _{γ ′} generated by the third reaction force component generation unit 43 becomes zero.

On the other hand, when the yaw acceleration γ ′ is a negative value (step S5: NO), that is, when the operation angle θ and the yaw acceleration γ ′ have the same sign, the gain setting unit 46 is shown in FIG. 4C. A gain G _{γ ′} (> 0) corresponding to the characteristic is generated (step S3). Therefore, the third reaction force component generation unit 43 generates the yaw acceleration reaction force component T _{γ ′} (= γ ′ × G _{γ ′} ) corresponding to the yaw acceleration _{γ ′} .

The operating angle θ and the yaw acceleration γ ′ have different signs in the case of return steering in which the steering wheel 1 is operated toward the operating angle midpoint (θ = 0), that is, the magnitude of the operating angle θ | θ When | is decreasing. During forward steering in which the steering wheel 1 is operated in a direction away from the operation angle midpoint, and during steering while the operation angle θ of the steering wheel 1 is maintained, that is, the magnitude | θ | of the operation angle θ tends to increase. At times (including when there is no increase / decrease), the operation angle θ and the yaw acceleration γ ′ have the same sign (both including the case of zero). Therefore, at the time of return steering, the gain G _{γ ′} becomes zero, and accordingly, the yaw acceleration reaction force component T _{γ ′} becomes zero. Thereby, the reaction force control corresponding to the yaw acceleration γ ′ is prohibited during the return steering.

FIG. 6 is a flowchart for explaining the flow of processing related to reaction force control, and shows processing that is repeatedly executed by the control device 20 at predetermined control cycles. The control device 20 includes an operation angle θ detected by the angle sensor 11, an operation torque Th detected by the torque sensor 12, a vehicle speed V detected by the speed sensor 14, and a yaw rate γ detected by the yaw rate sensor 16. (Step S11). The yaw acceleration calculation unit 39 generates the yaw acceleration γ ′ by differentiating the yaw rate γ with respect to time (step S12). Further, the gain setting unit 46 generates a gain G _{γ ′} based on the operation angle θ and the yaw acceleration γ ′ (step S13). The details of this process are as shown in FIG.

The first reaction force component generation unit 41 generates the operation angle reaction force component T _θ (V) according to the characteristics of FIG. 4A based on the operation angle θ and the vehicle speed V (step S14). Based on the yaw rate γ, the second reaction force component generation unit 42 generates the yaw rate reaction force component T _γ according to the characteristics of FIG. 4B (step S15). Based on the yaw acceleration γ ′, the third reaction force component generation unit 43 generates a yaw acceleration reaction force component T _{γ ′} according to the characteristics of FIG. 4C (step S16). These are added together by the adding unit 47 to generate a target reaction force torque basic value T _obj (step S17). The target reaction force torque basic value T _{obj is} multiplied by the torque gain K _T by the gain multiplication unit 38 to generate the target reaction force torque Tm ^* in consideration of the operation torque Th (step S18). . The reaction force actuator 19 is driven so that the target reaction force torque Tm ^* matches the torque generated by the reaction force actuator 19 (step S19).

FIG. 7 is a diagram illustrating an example of temporal changes in the operation angle θ (FIG. 7A), the yaw rate γ (FIG. 7B), and the yaw acceleration γ ′ (FIG. 7C). More specifically, the time change of each value when the steering wheel 1 is operated in the direction of rightward operation angle θ> 0) and held for a while and then returned to the operation angle midpoint is shown. In response to the operation of the steering wheel 1, the operation angle θ rises to a positive value, is held at a constant value for a while, and then returns to zero. The yaw rate γ changes slightly after the operation angle θ, rises to a positive value, is held at a constant value for a while, and then returns to zero. The yaw acceleration γ ′ takes a positive value when the yaw rate γ rises, becomes zero when the yaw rate γ is constant, and takes a negative value when the yaw rate γ falls back to zero (shown by hatching in FIG. 7C). .) Since the sign of the operation angle θ and the yaw acceleration γ ′ is different during the period in which the yaw acceleration γ ′ is negative (the period in which the magnitude of the operation angle | θ | tends to decrease due to the return steering), the yaw acceleration γ The gain _{Gγ ′} of _′ is set to 0 (step S4 in FIG. 5), and the yaw acceleration γ ′ during this period does not contribute to the reaction force control.

As described above, according to this embodiment, in addition to the yaw rate reaction force component T _γ corresponding to the yaw rate γ representing the vehicle behavior, the yaw acceleration reaction force component corresponding to the yaw acceleration γ ′ (change rate of the vehicle behavior). T _{γ ′} is included in the target reaction force torque basic value T _obj . As a result, reaction torque that more accurately reflects the vehicle behavior can be applied to the steering wheel 1. Specifically, an operation reaction force corresponding to the vehicle behavior can be applied to the steering wheel 1 immediately after the steering is started from the steering holding state, particularly in a period in which the steering is started from the midpoint of the operating angle (straight traveling state). . Thereby, the steering feeling in the vicinity of the midpoint of the operating angle can be improved, and a feeling closer to that of the combined steering device can be realized.

On the other hand, during reverse steering, the yaw acceleration γ ′ has a sign opposite to that of the yaw rate γ. For this reason, when the reaction force control based on the yaw acceleration γ ′ is performed, the operation reaction force may rapidly decrease. Therefore, in this embodiment, during the return steering, the yaw acceleration reaction force component T _{γ ′} corresponding to the yaw acceleration _{γ ′ is set} to zero, and the reaction force control based on the yaw acceleration γ ′ is prohibited. Thereby, it is possible to prevent a sense of incongruity from being generated when performing return steering from the state in which the rudder is cut and maintained to the operation angle midpoint.

FIG. 8 is a functional block diagram for explaining a structure for reaction force control in the vehicle steering apparatus according to the second embodiment of the present invention, and a reaction force that can be used in place of the structure of FIG. The configuration of the setting unit 37A is shown. 8, portions corresponding to the configuration shown in FIG. 3 are denoted by the same reference numerals as those in FIG.
In this embodiment, a current detection circuit 25 (indicated by a two-dot chain line in FIG. 1) for detecting a drive current (motor current, load current) of the steering actuator 2 (steering motor), and the steering wheel 1 And an operation frequency detection unit 26 for detecting the operation frequency.

The reaction force setting unit 37A includes a fourth reaction force component generation unit 44 in addition to the configuration shown in FIG. The fourth reaction force component generator 44 generates a current reaction force component T _cur corresponding to the motor current detected by the current detection circuit 25. This current reaction force component T _cur is added in the adder 47 together with other reaction force components T _θ (V), T _γ and T _{γ ′} . Accordingly, in this embodiment, the target reaction force torque basic value T _obj = T _θ (V) + T _γ + T _{γ ′} + T _cur is expressed.

The current detection circuit 25 detects a drive current supplied from the drive circuit 22 to the steering actuator 2. For example, the operation frequency detection unit 26 calculates the frequency of the output signal of the angle sensor 11 and is a function processing unit realized by software processing by the control device 20.
Gain setting unit 46, in this embodiment, the gain G _gamma of the yaw rate reaction force T _{gamma, 'gain} G _gamma' of the yaw acceleration reaction force T _gamma, and sets the gain G _cur current reaction force component T _cur It is like that. More specifically, the gains G _γ , G _{γ ′} and G _cur are variably set according to the operation frequency f detected by the operation frequency detection unit 26. Further, the gain G _{γ ′} of the yaw acceleration reaction force component G _{γ ′} is further set to zero at the time of return steering by the processing according to the flowchart of FIG.

FIG. 9 is a diagram for explaining the characteristics of the current reaction force component T _cur generated by the fourth reaction force component generation unit 44. The current reaction force component T _cur is determined so as to be proportional to the drive current detected by the current detection circuit 25. Since the drive current of the steering actuator 2 corresponds to the load of the steering actuator 2 and is therefore an index representing the input from the road surface transmitted from the road surface to the steering mechanism 5, the current reaction force component _Tcur is It corresponds to the input from the road surface. That is, by _adding the current reaction force component _Tcur to the target reaction force torque, input from the road surface can be transmitted to the driver via the steering wheel 1, and the driver obtains information on the road surface condition from the steering wheel 1. be able to.

FIG. 10 is a diagram for explaining the gain setting according to the operation frequency f detected by the operation frequency detection unit 26. In this embodiment, the gains G _γ (f) and G _{γ ′} (f) of the yaw rate reaction force component T _γ , the yaw acceleration reaction force component T _{γ ′} and the current reaction force component T _cur (however, gain during forward steering) G _cur (f) is variably set according to the operating frequency f.

The gains G _γ (f) and G _{γ ′} (f) corresponding to the yaw rate reaction force component T _γ and the yaw acceleration reaction force component T _{γ ′} are constant values within a predetermined frequency threshold f _th (for example, 2 Hz). In the range exceeding the frequency threshold f _th , the frequency is set to be smaller as it is higher (decrease linearly in the example of FIG. 10), and to be the lower limit LL at the predetermined frequency f ₁ (> f _th ). .
Current reaction force T _cur gain corresponding to G _cur is set to a constant value in a range of frequency threshold value f _th, a range exceeding the frequency threshold value f _th, frequency higher increases (in the example of FIG. 10 Linearly increases), and is set to have an upper limit _UL at a predetermined frequency f ₁ .

FIG. 11 is a flowchart for explaining the flow of processing related to reaction force control, and shows processing that is repeatedly executed by the control device 20 every predetermined control cycle. In FIG. 11, the same reference numerals are assigned to steps in which the same processing as each step shown in FIG. 6 is performed.
The control device 20 includes an operation angle θ detected by the angle sensor 11, an operation torque Th detected by the torque sensor 12, a vehicle speed V detected by the speed sensor 14, and a yaw rate γ detected by the yaw rate sensor 16. Then, the drive current detected by the current detection circuit 25 is taken in (step S21). The yaw acceleration calculation unit 39 generates the yaw acceleration γ ′ by differentiating the yaw rate γ with respect to time (step S12). Further, the operation frequency detection unit 26 obtains, for example, the fluctuation frequency of the operation angle θ as the operation frequency f (step S22).

Furthermore, the gain setting unit 46 sets the gains G _γ , G _{γ ′} and G _cur according to the characteristics of FIG. 10 based on the operation frequency f (step S23). Further, the gain setting unit 46 executes the processing according to FIG. 5 based on the operation angle θ and the yaw acceleration γ ′, and sets the gain G _{γ ′} to zero if the steering is being returned (step S13).
The first reaction force component generation unit 41 generates the operation angle reaction force component T _θ (V) according to the characteristics of FIG. 4A based on the operation angle θ and the vehicle speed V (step S14). Based on the yaw rate γ, the second reaction force component generation unit 42 generates the yaw rate reaction force component T _γ according to the characteristics of FIG. 4B (step S15). The slope in the characteristic line in FIG. 4B corresponds to the gain _Gγ . Based on the yaw acceleration γ ′, the third reaction force component generation unit 43 generates a yaw acceleration reaction force component T _{γ ′} according to the characteristics of FIG. 4C (step S16). The slope of the characteristic line in FIG. 4C corresponds to the gain G _{γ ′} . Further, the fourth reaction force component generation unit 44 generates a current reaction force component T _cur according to the characteristics of FIG. 9 (step S24). The slope in the characteristic line in FIG. 9 corresponds to the gain G _cur .

These are added together by the adding unit 47 to generate a target reaction force torque basic value T _obj (step S17). The target reaction force torque basic value T _{obj is} multiplied by the torque gain K _T by the gain multiplication unit 38 to generate the target reaction force torque Tm ^* in consideration of the operation torque Th (step S18). . The reaction force actuator 19 is driven so that the target reaction force torque Tm ^* matches the torque generated by the reaction force actuator 19 (step S19).

Thus, in this embodiment, the operation reaction force including the current reaction force component T _cur corresponding to the drive current of the steering actuator 2 is applied to the steering wheel 1. Thereby, input information from the road surface to the steering mechanism 5 can be transmitted to the driver via the steering wheel 1. Therefore, the driver can obtain information on road surface conditions. Thereby, it is possible to obtain a steering feeling that is more approximate to the combined steering device. In addition, in order to transmit road surface information to the driver, there is no need to add sensors such as an axial force sensor for detecting the axial force received by the steering gear 3 and a stress sensor for detecting the stress generated in the tire. Therefore, an increase in cost can be suppressed and the size of the apparatus is not increased.

Further, in this embodiment, in the range where the operation frequency exceeds the threshold value f _{th, 'gain} G _gamma of, G _gamma' yaw rate reaction force T _gamma and yaw acceleration reaction force T _gamma is reduced. As a result, even when steering is performed to quickly turn left and right, the phase of the operation reaction force does not reverse due to the response delay of the yaw rate, and vibration and divergence can be suppressed or prevented. Further, decrease of the yaw rate reaction force T _gamma and yaw acceleration reaction force T _{gamma 'is,} because it is compensated by the increase in current reaction force component T _cur, the driver, while feeling a sufficient response, performs a steering operation be able to.

As mentioned above, although embodiment of this invention was described, this invention can also be implemented with another form. For example, in the above-described embodiment, the return steering is determined by examining the signs of the operation angle θ and the yaw acceleration γ ′. However, the return steering is determined when the signs of the yaw rate γ and the yaw acceleration γ ′ do not match. It can also be configured.
In the above-described embodiment, the steer-by-wire system is taken as an example, but the same control is performed with a variable gear in which the relationship between the operation angle and the steering angle is variable between the steering wheel and the steering wheel. The present invention can also be applied to a ratio type steering device (see Patent Document 2). In this case, the steering wheel and the steering wheel are not necessarily mechanically separated from each other, and may be mechanically coupled to each other via a variable transmission ratio unit, for example.

  In addition, various design changes can be made within the scope of matters described in the claims.

It is an illustration figure for demonstrating the structure of the steering apparatus for vehicles which concerns on one Embodiment of this invention. FIG. 2 is a control block diagram according to the embodiment of FIG. 1. It is a functional block diagram for demonstrating the structure of a reaction force setting part. 4A is a diagram illustrating a setting example of an operation angle reaction force component, FIG. 4B is a diagram illustrating a setting example of a yaw rate reaction force component, and FIG. 4C is a diagram illustrating a setting example of a yaw acceleration reaction force component. It is a flowchart for demonstrating the setting of the gain of the reaction force component corresponding to a yaw acceleration. It is a flowchart for demonstrating the flow of the process relevant to reaction force control. It is a figure which shows an example of the time change of an operation angle (FIG. 7 (a)), a yaw rate (FIG. 7 (b)), and a yaw acceleration (FIG. 7 (c)). It is a functional block diagram for demonstrating the structure for reaction force control in the steering apparatus for vehicles which concerns on 2nd Embodiment of this invention. It is a figure for demonstrating the characteristic of an electric current reaction force component. It is a figure for demonstrating the gain setting according to the operation frequency. It is a flowchart for demonstrating the flow of the process relevant to reaction force control in the said 2nd Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Steering wheel, 2 ... Steering actuator, 5 ... Steering mechanism, 11 ... Angle sensor, 16 ... Yaw rate sensor, 19 ... Reaction force actuator, 37 ... Reaction force setting part, 39 ... Yaw acceleration calculating part

Claims (3)

Vehicle behavior detection means for detecting the behavior of the vehicle;
Vehicle behavior change rate calculating means for obtaining a change rate of the vehicle behavior detected by the vehicle behavior detecting means;
An operation angle detection means for detecting an operation angle of an operation member for steering the vehicle;
An operating angle increase / decrease determining means for determining whether the operating angle detected by the operating angle detecting means is increasing or decreasing;
Reaction force means for applying an operation reaction force to the operation member;
A reaction force control means for controlling the reaction force means so that an operation reaction force including a reaction force component corresponding to the change rate calculated by the vehicle behavior change rate calculation means is generated from the reaction force means;
A vehicle that includes a prohibiting unit that prohibits reaction force control by the reaction force control unit based on the change rate when the operation angle increase / decrease determination unit determines that the magnitude of the operation angle is decreasing. Steering device. A steering motor for applying a steering force to the steering mechanism;
A current detection means for detecting the current of the steering motor; and
The reaction force control means controls the reaction force means so that an operation reaction force including a reaction force component corresponding to the current detected by the current detection means is generated from the reaction force means. The vehicle steering apparatus according to claim 1.   The reaction force control means reduces the gain of the reaction force component corresponding to the change rate when the operation frequency of the operation member exceeds a predetermined threshold than when the operation frequency is equal to or less than the threshold. The vehicle steering apparatus according to claim 1, further comprising gain setting means for setting.

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