JP4438132B2 - Vehicle steering control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vehicle steering control device including a transmission ratio variable mechanism that changes a transmission ratio between a steering angle of a steering wheel and a turning angle of a steered wheel.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, there is known a vehicle steering control device including a transmission ratio variable mechanism that changes a transmission ratio between a steering angle of a steering wheel and a turning angle of a steered wheel. For example, Japanese Patent Laid-Open No. 5-139332 discloses a transmission ratio variable mechanism that changes the relationship between the steering angle of the steering wheel and the turning angle of the steered wheels according to the vehicle speed.
[0003]
[Problems to be solved by the invention]
In such a transmission ratio variable mechanism, when the transmission ratio is changed to the quick side according to a change in the running state of the vehicle such as a decrease in vehicle speed, the driving force of the transmission ratio variable mechanism is obtained when the steering angle is constant. Thus, the steered wheels are steered in the direction in which the steered angle increases. However, when the steered wheel is steered to the maximum steered angle, as shown in FIG. 7, even if the transmission ratio is gradually changed to G1, G2, and G3, Since the vehicle cannot be steered beyond that, the reaction force causes the driving force of the transmission ratio variable mechanism to act on the steering handle, causing the steering handle to return to the neutral side. If the force is applied in the direction in which the steering wheel is returned in this manner due to the change in the traveling state of the vehicle, the driver feels uncomfortable with steering.
[0004]
The present invention has been made to solve such a problem, and its purpose is to return the steering handle by the driving force of the transmission ratio variable mechanism even when the running state of the vehicle changes near the maximum turning angle. An object of the present invention is to provide a vehicle steering control device that can prevent an action in a direction.
[0005]
[Means for Solving the Problems]
A vehicle steering control device according to claim 1 is a vehicle steering control device including a transmission ratio variable mechanism that changes a transmission ratio between a steering angle of a steering wheel and a turning angle of a steered wheel. Steering angle detecting means for detecting the steering angle of the steering wheel, driving means for rotationally driving the transmission ratio variable mechanism, and driving means according to the detected steering angle based on the transmission ratio set according to the traveling state Control means for controlling the driving of the steering wheel when the turning angle of the steered wheel exceeds a predetermined steering angle , the change of the transmission ratio to the quick side or the slow side of the transmission ratio Among the changes to, a limiting means for limiting only the change to the quick side of the transmission ratio is provided.
[0006]
In a situation where the transmission ratio is changed to the quick side in accordance with a change in the running state of the vehicle, if the turning angle of the steered wheels exceeds the predetermined steering angle , the limiting means moves to the quick side of the transmission ratio. Only the change is limited, and the driving force of the transmission ratio variable mechanism is prevented from acting in the direction of returning the steering wheel.
[0007]
A vehicle steering control device according to claim 2 is a vehicle steering control device including a transmission ratio variable mechanism that changes a transmission ratio between a steering angle of a steering wheel and a turning angle of a steered wheel. Steering angle detecting means for detecting the steering angle of the steering wheel, driving means for rotationally driving the transmission ratio variable mechanism, and driving means according to the detected steering angle based on the transmission ratio set according to the traveling state and a control means for setting a control target value for the control means, when the turning angle of the steered wheels exceeds a predetermined steering angle, the control target value exceeding the predetermined steering angle change or of the changes of the predetermined said control target value does not exceed the steering angle, it is configured to include a limiting means for limiting changes only the control target value exceeding the predetermined steering angle.
[0008]
When the transmission ratio is changed to the quick side in accordance with a change in the running state of the vehicle, a control target value corresponding to the transmission ratio is set, and the drive unit of the transmission ratio variable mechanism is driven according to the control target value. . Therefore, when the turning angle of the steered wheels exceeds a predetermined steering angle , the transmission ratio is set in the same manner as in the normal state according to the traveling state of the vehicle, but the control exceeds the predetermined steering angle by the limiting means. By limiting only the change of the target value, the driving force of the transmission ratio variable mechanism is prevented from acting in the direction of returning the steering wheel.
[0009]
The vehicle steering control device according to claim 3 is the vehicle steering control device according to claim 1 or 2, wherein the limiting means performs the limiting process when the turning angle of the steered wheels becomes the maximum turning angle. To implement.
[0010]
If the turning angle of the steered wheels is steered to the maximum steered angle, the steered wheels may steer beyond that even when the transmission ratio is changed to the quick side and the control target value increases. Therefore, the driving force of the transmission ratio variable mechanism acts in a direction to return the steering wheel. Therefore, in the limiting means, the above-described limiting process is performed under the situation where the turning angle is the maximum turning angle.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the accompanying drawings.
[0012]
FIG. 1 shows a configuration of a steering apparatus according to the first embodiment.
[0013]
The input shaft 20 and the output shaft 40 are connected via a transmission ratio variable mechanism 30, and the steering handle 10 is connected to the input shaft 20. The output shaft 40 is connected to a rack shaft 51 via a rack and pinion gear device 50, and steered wheels FW are connected to both sides of the rack shaft 51.
[0014]
Further, since the steering angle of the steering handle 10 corresponds to the rotation angle of the input shaft 20, the input shaft 20 is provided with a steering angle sensor 21 that detects the steering angle θh as the rotation angle of the input shaft 20.
[0015]
The transmission ratio variable mechanism 30 is connected via a predetermined gear mechanism that connects the input shaft 20 and the output shaft 40, and this gear mechanism is driven by an actuator 31 configured by, for example, a servo motor, whereby the input shaft 20. A mechanism for changing the transmission ratio between the output shafts 40. The actuator 31 includes an operating angle sensor 32 that detects an operating angle of the actuator 31, and the detected operating angle θm is given to the steering control device 70. The actuator 31 is a mechanism that is locked after the control is finished by turning off the ignition switch, and the operating angle θm of the actuator 31 changes until the ignition switch is turned on. There is no.
[0016]
Assuming that the rotation angle of the output shaft 40 is the output angle θp, the actuator 31 rotates by the operating angle θm, so that the steering angle θh is increased to become the output angle θp, so that the steering angle θh, the operating angle θm, and the output The angle θp is expressed by the following equation (1). Accordingly, the output angle θp can be grasped based on the steering angle θh and the operating angle θm.
[0017]
θp = θh + θm (1)
Since the output angle θp corresponds to the stroke position of the rack shaft 51 and the stroke position of the rack shaft 51 corresponds to the turning angle of the wheel FW, the rotation of the wheel FW is based on the steering angle θh and the operating angle θm. The steering angle is detected.
[0018]
The drive control of the transmission ratio variable mechanism 30 is performed by the steering control device 70. In addition to the steering angle sensor 21 and the operating angle sensor 32, each detection signal of the vehicle speed sensor 60 that detects the vehicle speed is given to the steering control device 70, and the steering control device 70 transmits the transmission ratio based on these signals. In addition to setting G, the process of outputting the control signal Is set according to the transmission ratio G and the steering angle θh to the actuator 31 is repeated, and the drive control of the transmission ratio variable mechanism 30 is performed.
[0019]
Here, the control process performed by the steering control device 70 will be described along the flowchart of FIG.
[0020]
This flowchart is activated by turning on the ignition switch. First, the process proceeds to step (hereinafter, “S”) 100, the steering angle θh detected by the steering angle sensor 21, the operating angle θm detected by the operating angle sensor 32, and the vehicle speed sensor 60 detected. Each vehicle speed V is read.
[0021]
In the subsequent S200, the transmission ratio G setting process is performed, and the specific setting process will be described in detail later.
[0022]
In subsequent S300, a target operating angle θmm of the actuator 31 that is a control target is set. Since the steering angle θh, the transmission ratio G, and the output angle θp have the relationship of the following equation (2), the target operating angle θmm is defined by the equation (3) from the equations (1) and (2).
[0023]
θp = G · θh (2)
θmm = (G−1) · θh (3)
In the subsequent S400, the deviation e between the operating angle θm of the actuator 31 read in S100 and the target operating angle θmm set in S300 is calculated as e = θmm−θm, and in the subsequent S500, there is no overshoot. A control signal Is for controlling the actuator 31 is determined so that the deviation e is zero. As an example of this process, the control signal Is can be determined by appropriately setting parameters for PID control based on an arithmetic expression of Is = C (s) · e. Note that “(s)” in the expression is a Laplace operator.
[0024]
In subsequent S600, the control signal Is determined in S500 is output to the actuator 31, and the actuator 31 is driven based on the control signal Is.
[0025]
Thereafter, the process proceeds to S700, where it is determined whether the ignition switch (IG) has been turned off. If “No”, the process returns to S100, and the processes after S100 described above are performed until it is determined “Yes” in S700. Repeatedly executed.
[0026]
Here, the transmission ratio G setting process performed in S200 will be described with reference to the flowchart of FIG.
[0027]
In S202, since the sum of the steering angle θh and the operating angle θm is the output angle θp (see equation (1)), the estimated value of the output angle θp obtained as the sum of the steering angle θh and the operating angle θm is the maximum output. It is determined whether it is larger than the angle θpmax. As an example, the maximum output angle θpmax is set to the output angle θp corresponding to the maximum turning angle at which the steered wheel FW can be steered.
[0028]
In the range where the sum of the steering angle θh and the operating angle θm is equal to or less than the maximum output angle θpmax, “No” is determined in S202, and the process proceeds to S204. Based on the map shown in FIG. A corresponding transmission ratio G is set. The transmission ratio G may be set according to the vehicle speed V, the steering angle θh, etc., in addition to being set according to the vehicle speed V.
[0029]
In subsequent S206, it is determined whether or not the correction flag is set to 1. In the initial state, since the correction flag F = 0, it is determined “No” and the process proceeds to S208, where the transmission ratio G set in this routine is set. The value is stored as Gold and the routine is terminated.
[0030]
On the other hand, if the sum of the steering angle θh and the operating angle θm is larger than the maximum output angle θpmax, “Yes” is determined in S202, and the process proceeds to S210. As in S204, the transmission ratio G corresponding to the vehicle speed V is determined. In the subsequent S212, it is determined whether G> Gold, that is, whether the transmission ratio G is changed to the quick side as compared with the transmission ratio Gold set in the previous routine.
[0031]
If “No” is determined in S212, the transmission ratio G is constant or changed to the slow side, and particularly when the transmission ratio G is changed to the slow side, as shown by the one-dot chain line in FIG. When the ratio is changed to the slow side from G1 to G4, the steering handle 10 can be further cut even if the steering angle θh is operated to the maximum turning angle of the steered wheels FW. Therefore, even if it is determined as “Yes” in S202, if the determination in S212 is “No”, there is no need to limit the set transmission ratio, so the process directly proceeds to S208, and S210. Is stored as the transmission ratio Gold set in the current routine.
[0032]
On the other hand, when the determination in S212 is “Yes”, the transmission ratio G is changed to the quick side, and the steering angle θh is already set to the steered wheel under the situation where “Yes” is determined in S202. Since the steering is steered to the maximum turning angle (per end) of the FW, if the transmission ratio G is changed to the quick side as it is, the steered wheels FW cannot be steered any further, and the reaction is transmitted by the reaction. A phenomenon occurs in which the driving force of the actuator 31 in the ratio variable mechanism 30 acts on the steering handle 10 and the steering handle 10 is returned to the neutral side. Therefore, if “Yes” is determined in S212, the process proceeds to S214, in which the transmission ratio Gold set in the previous routine is set again as the transmission ratio G to prohibit the change of the transmission ratio G, and in subsequent S216. Then, the correction flag F is set to 1 and the process proceeds to S208 described above.
[0033]
When the sum of the steering angle θh and the operating angle θm is larger than the maximum output angle θpmax, the processing of S210 to S216 is repeated. Thereafter, if “No” is determined in S202, the processing of S204 is performed again. However, if the transmission ratio G set in S204 is set as it is, a large deviation may occur in the transmission ratio G before and after the return.
[0034]
Therefore, after setting the transmission ratio G according to the vehicle speed V in S204, the process proceeds to S206, and since the correction flag F is set to 1 in S216, it is determined as “Yes” in S206, and the process proceeds to S218.
[0035]
In S218, the deviation between the transmission ratio G set in S204 and the transmission ratio Gold set in S214 and stored in S208 immediately after the return is set as a transmission ratio deviation Ge = G−Gold.
[0036]
In subsequent S220, it is determined whether or not the transmission ratio deviation Ge set in S218 is equal to or larger than the threshold value β (β> 0). If “Yes”, the process proceeds to S222 to reduce the transmission ratio deviation Ge. , Α is a predetermined constant (α> 0), a value obtained by adding the constant α to Gold is updated as the transmission ratio G set in the current routine, and the process proceeds to S208 described above. Therefore, while “Yes” is determined in S220, the transmission ratio Gold set in the previous routine is increased by a constant α for each routine.
[0037]
On the other hand, if “No” is determined in S220, the process proceeds to S224, and it is determined whether the transmission ratio deviation Ge is equal to or less than the threshold −β. If “Yes”, the process proceeds to S226, and this transmission is performed. In order to reduce the ratio deviation Ge, the value obtained by subtracting the constant α from Gold is updated as the transmission ratio G set in this routine, and the process proceeds to the above-described S208. Accordingly, while it is determined “Yes” in S224, the transmission ratio Gold set in the previous routine is decreased by a constant α for each routine.
[0038]
If β>Ge> −β, the transmission ratio deviation Ge is processed to be eliminated, the process proceeds to S228, the correction flag F is reset to 0, and the process proceeds to the previous S208. Thereby, the value of the transmission ratio G set in S204 is stored as it is as the transmission ratio Gold set in the current routine.
[0039]
In S <b> 200, the transmission ratio G change prohibition process is performed as described above, whereby the driving force of the transmission ratio variable mechanism 30 can be prevented from acting in the direction of returning the steering handle 10. Also, when the transmission ratio G value is restored from the restricted value to the normal setting value, a process of gradually restoring it over time has been adopted to prevent sudden changes in the setting transmission ratio immediately after the restriction is released. can do.
[0040]
In the first embodiment described above, the case where the maximum output angle θpmax is set as the output angle θp corresponding to the maximum turning angle at which the steered wheels FW can be steered is exemplified, but the maximum output angle θpmax is appropriately set. It is possible to set the output angle θp corresponding to the turning angle near the maximum turning angle. Moreover, while the sum of the steering angle θh and the operating angle θm is larger than the maximum output angle θpmax, the process for prohibiting the change of the transmission ratio G to the quick side is exemplified, but the present invention is not limited to this example. For example, while the sum of the steering angle θh and the operating angle θm is larger than the maximum output angle θpmax, the change of the transmission ratio G including the slow side and the quick side may be prohibited. It is sufficient if the change to the quick side can be prohibited.
[0041]
Next, a second embodiment will be described.
[0042]
In the first embodiment described above, the case where the setting of the transmission ratio G is limited when the estimated output angle θp is larger than the maximum output angle θpmax is exemplified. However, the output angle θp is greater than the maximum output angle θpmax. Even in a large case, the same effect can be achieved by setting the transmission ratio G as usual and limiting the target operating angle θmm of the actuator 31.
[0043]
Therefore, a setting process example of the target operating angle θmm performed in S300 of FIG. 2 will be described along the flowchart of FIG. In this case, in S200, the transmission ratio G corresponding to the vehicle speed V is set based on the map shown in FIG.
[0044]
First, in S302, it is determined whether the estimated value of the output angle θp obtained as the sum of the steering angle θh and the operating angle θm is larger than the maximum output angle θpmax.
[0045]
Assuming that the steering wheel FW is steered up to the maximum turning angle, when the transmission ratio G is changed when the steering angle θh is constant, the target operating angle θmm set from the equation (3) is also obtained. Will change. Therefore, a process for making the target operating angle θmm constant is performed by correcting the value of the steering angle θh. This is a process of substantially changing the neutral position (N point) of the steering angle θh. If “Yes” in S302, the process proceeds to S304, and the N point correction value θNe for correcting the neutral position of the steering angle θh is set. It is set based on the following equation (4).
[0046]
θNe = θh− (θpmax / G) (4)
FIG. 6 shows θNe, θh, and (θpmax / G). When the transmission ratio G5 is changed to the transmission ratio G6 on the quick side in the situation where the steering wheel FW is steered to the maximum turning angle at the transmission ratio G5, the steering angle and the steering are set by setting the N point correction value θNe. The relationship with the corner is a relationship indicated by a dotted line as G6 ′.
[0047]
In subsequent S306, the target operating angle θmm is set based on the following equation (5).
[0048]
θmm = (θh−θNe) · (G−1) (5)
In this way, while the output angle θp estimated in S302 is larger than the maximum output angle θpmax, even when the transmission ratio G is changed by S302 and S304, the target operating angle θmm becomes a constant value. Therefore, it is possible to prevent the driving force of the transmission ratio variable mechanism 30 from acting in the direction in which the steering handle 10 is returned.
[0049]
Further, when it is determined “No” in S302, the process returns from such a restriction process. In this case as well, if the neutral position of the steering angle θh is immediately returned to the original position, the set target operating angle θmm is set. Therefore, the N point correction value | θNe | is gradually reduced.
[0050]
Therefore, if “No” in S302, the process proceeds to S308, and the value of the N point correction value θNe set in the previous routine is read. In S310, the value of the N point correction value θNe read in S308 is a predetermined threshold. It is determined whether or not the value is γ (γ> 0) or more. If “Yes” in this determination, the process proceeds to S 312, where δ is set as a predetermined constant (δ> 0), and the value obtained by subtracting the constant δ from the N point correction value θNe is updated as the N point correction value θNe. The process proceeds to S306.
[0051]
If “No” is determined in S310, the process proceeds to S314, and it is determined whether the value of the N point correction value θNe read in S308 is equal to or less than a predetermined threshold value −γ (−γ <0). . If “Yes” in this determination, the process proceeds to S316, the value obtained by adding the constant δ to the N point correction value θNe is updated as the N point correction value θNe, and the process proceeds to the above-described S306.
[0052]
If “No” in the determination of S314, γ>θNe> −γ. In this case, the process proceeds to S318, where the N point correction value θNe is set to 0, and the steering angle θh is shifted by N points. Is processed, and the process proceeds to S306 described above. Therefore, in this case, in S306, the target operating angle θmm is set in the above equation (3), and thereafter, the N point correction value θNe = 0 is processed until it is determined “Yes” in S302. .
[0053]
In the second embodiment described above, the case where the neutral position of the steering angle θh is corrected when the estimated output angle θp is larger than the maximum output angle θpmax has been described. However, the estimated output angle θp is the maximum. Even when the transmission angle G is changed to the slow side even when the output angle is larger than the output angle θpmax, the target operating angle θmm is set as usual, and the process of S304 is performed only when the transmission angle G is changed to the quick side. good.
[0054]
【The invention's effect】
As described above, according to the vehicle steering control device of the first aspect, when the turning angle of the steered wheels exceeds a predetermined range, the limiting means for restricting the change of the transmission ratio to the quick side is provided. Even if the set transmission ratio changes when the steering handle is steered to the maximum turning angle of the steered wheels, the driving force of the transmission ratio variable mechanism acts in the direction to return the steering handle. This can be prevented.
[0055]
According to the vehicle steering control device of the second aspect, since the configuration including the limiting means for limiting the change of the control target value when the turning angle of the steered wheels exceeds the predetermined range, the steering handle The direction in which the drive force of the variable transmission ratio mechanism returns the steering handle even when the control target value changes with the change in the set transmission ratio while the steering wheel is steered to the maximum turning angle (per end) Can be prevented.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an overall configuration of a steering device.
FIG. 2 is a flowchart showing a control process executed by the steering control device.
FIG. 3 is a flowchart showing a transmission ratio setting process.
FIG. 4 is a map that defines the relationship between vehicle speed V and transmission ratio G;
FIG. 5 is a flowchart showing processing for setting a target operating angle.
FIG. 6 is an explanatory diagram showing a relationship between a steering angle and a turning angle when an N point correction value θNe is set.
FIG. 7 is an explanatory diagram showing a relationship between a steering angle and a turning angle at each transmission ratio.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 20 ... Input shaft, 21 ... Steering angle sensor, 30 ... Transmission ratio variable mechanism 31 ... Actuator, 32 ... Operating angle sensor, 40 ... Output shaft 60 ... Vehicle speed sensor, 70 ... Steering control device

Claims (3)

A vehicle steering control device including a transmission ratio variable mechanism that changes a transmission ratio between a steering angle of a steering wheel and a turning angle of a steered wheel,
Steering angle detection means for detecting a steering angle of the steering wheel;
Drive means for rotationally driving the transmission ratio variable mechanism;
Control means for performing drive control of the drive means according to the detected steering angle based on the transmission ratio set according to the running state,
The control means, when the turning angle of the steered wheels exceeds a predetermined steering angle , of changing the transmission ratio to the quick side or changing the transmission ratio to the slow side, A vehicle steering control device comprising limiting means for limiting only changes to the side. A vehicle steering control device including a transmission ratio variable mechanism that changes a transmission ratio between a steering angle of a steering wheel and a turning angle of a steered wheel,
Steering angle detection means for detecting a steering angle of the steering wheel;
Drive means for rotationally driving the transmission ratio variable mechanism;
Control means for setting a control target value for the drive means according to the detected steering angle based on the transmission ratio set according to the running state,
Wherein, when the turning angle of the steered wheels exceeds a predetermined steering angle, does not exceed changed or the predetermined steering angle of the control target value exceeding the predetermined steering angle of the control target value A vehicle steering control device comprising limiting means for limiting only the change of the control target value exceeding the predetermined steering angle among the changes.   3. The vehicle steering control device according to claim 1, wherein the restricting unit performs a restricting process when a turning angle of the steered wheel reaches a maximum turning angle. 4.

Images