JP4120488B2 - Vehicle steering control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention belongs to the technical field of a vehicle steering control device including a transmission ratio characteristic setting means that can variably set a transmission ratio characteristic according to a vehicle state or an operation state of an operation unit.
[0002]
[Prior art]
As this type of conventional technology, for example, when a lateral slip occurs in the vehicle, the inclination of the turning amount of the steered wheel with respect to the steering wheel operation amount (hereinafter referred to as steering gain) is increased. Some have been proposed for facilitating rehabilitation (see, for example, Patent Document 1).
[0003]
Conventionally, in order to reduce the driving load on the driver, the steering gain is increased at low speeds to reduce the steering angle at small turns, and at high speeds the steering gain is reduced to improve stability. Since it is effective to reduce the turning angle of the steered wheels, for example, the steering gain is made variable according to the vehicle speed.
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 11-291930
[Problems to be solved by the invention]
However, in the above prior art, when the steering gain is once increased at low speed and then returned to the original steering gain again, the turning angle of the steered wheels becomes zero even if the steering angle of the steering wheel becomes zero. There was a problem that a so-called neutral deviation occurred.
[0006]
The present invention has been made paying attention to the above-mentioned problem, and an object of the present invention is to prevent a neutral deviation when the inclination of the steering amount with respect to the operation amount is changed, and to obtain a smooth operability. An object of the present invention is to provide a steering control device for a vehicle.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, in the present invention, in the vehicle steering control device including the transmission ratio characteristic setting means capable of variably setting the transmission ratio characteristic according to the vehicle state or the operation state of the operation unit,
When the transmission ratio characteristic setting means changes the transmission ratio characteristic from the transmission ratio characteristic that turns the steering amount to zero when the operation amount is zero, and then returns to the original transmission ratio characteristic again, the operation amount decreases. Is a means for setting a transmission ratio characteristic that does not increase the inclination of the steering amount with respect to the operation amount.
[0008]
【The invention's effect】
Therefore, in the vehicle steering control device of the present invention, when the operation amount becomes zero, the changed transmission ratio characteristic is connected to the original transmission ratio characteristic that becomes the turning amount zero when the operation amount is zero. Steering amount is certainly zero, and neutral deviation can be prevented. In addition, since the transmission ratio characteristic that connects the changed transmission ratio characteristic and the original transmission ratio characteristic is a characteristic that does not increase the inclination of the turning amount with respect to the operation amount, the operation during a series of switchback operations can be realized smoothly. .
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment for realizing a vehicle steering control device of the present invention will be described based on a first example shown in the drawings.
[0010]
(First embodiment)
First, the configuration will be described.
FIG. 1 is an overall system diagram showing a vehicle steering control apparatus according to a first embodiment. The vehicle steering control device of the first embodiment includes a steering wheel (operation unit) 1, a steering angle sensor 2, a steering column 3, a gear ratio variable means (transmission ratio variable means) 4, and a turning angle sensor 5. And a steering gear 6, a side rod 7, steered wheels 8, vehicle state detection means 9, and a controller (transmission ratio characteristic setting means and transmission ratio control means) 10.
[0011]
The steering angle when the driver operates the steering wheel 1 is detected by the steering angle sensor 2 and transmitted to the controller 10. The controller 10 is also notified of physical quantities such as the vehicle speed and yaw rate detected by the vehicle state detection means 9 and the turning angle from the turning angle sensor 5. The controller 10 is based on this information and a reference gear ratio characteristic (= transmission ratio characteristic, see FIG. 3B) in which the inclination of the steered wheel with respect to the steering angle of the steering wheel 1 (hereinafter referred to as steering gain) is set in advance. Then, a gear ratio that is a ratio of the turning angle of the steered wheels 8 to the steering angle of the steering wheel 1 is calculated, and the gear ratio variable means 4 is controlled using this gear ratio as a set gear ratio.
[0012]
Further, the controller 10 performs control for switching the gear ratio characteristic of the set gear ratio from the reference gear ratio characteristic to the gear ratio characteristic at the time of low gain (see L2 in FIG. 4) when the driver is performing steep steering. carry out. The gear ratio characteristic at the time of low gain is set so that the steering gain becomes smaller than the reference gear ratio characteristic at the same steering angle. When the driver's steep steering is finished, the set gear ratio is set again based on the reference gear ratio characteristics.
[0013]
Next, the operation will be described.
[Gear ratio characteristic setting control processing]
FIG. 2 is a flowchart showing the flow of the gear ratio characteristic setting control process executed by the controller 10 of the first embodiment apparatus. Each step will be described below.
[0014]
In step S201, signals (vehicle speed V, yaw rate ψ ′, steering angle θ) from the vehicle state detection means 9 and the steering angle sensor 2 are input, and the process proceeds to step S202.
[0015]
In step S202, it is determined whether the driver is performing steep steering. If YES, the process proceeds to step S208, and if NO, the process proceeds to step S203.
[0016]
In step S202, when any one of the following conditions is satisfied, it is determined that the driver is performing a sharp steering.
(1) The steering angle θ of the steering wheel 1 represents a periodic operation, and includes the neutral position of the steering wheel 1 in which the cycle, amplitude, and duration are each not less than a predetermined value and the vehicle is in a straight traveling state. If so.
(2) The difference between the estimated yaw rate ψ ^# 'estimated using the vehicle speed V, the steering angle θ, and the vehicle motion model, and the measured actual yaw rate ψ' exceeds a predetermined value.
(3) When the steering angular acceleration θ ′ is calculated based on the measured steering angle θ (steering angular acceleration calculating means), and the steering angular acceleration θ ′ becomes a predetermined value or more.
(4) The estimated yaw angular acceleration ψ ^# ″ is calculated using the vehicle speed V, the steering angle θ, and the vehicle motion model (estimated yaw angular acceleration calculating means), and the estimated yaw angular acceleration ψ ^# ″ exceeds a predetermined value. If it becomes.
(5) The yaw angular acceleration ψ ″ is calculated based on the yaw rate measurement value, and the yaw angular acceleration ψ ″ exceeds a predetermined value.
[0017]
In step S203, it is determined whether or not the gear ratio characteristic at the time of low gain is being switched to the reference gear ratio characteristic. If YES, the process moves to step S204, and if NO, the process moves to step S207.
[0018]
In step S204, it is determined whether or not the steering wheel 1 is being switched back. If YES, the process moves to step S206, and if NO, the process moves to step S205.
[0019]
In step S205, the gear ratio characteristic at the time of increase is set as the gear ratio characteristic of the set gear ratio, and this control is terminated. The gear ratio characteristic when the gear is increased is the characteristic obtained by connecting the characteristic from the same turning angle as the final turning angle in the reference gear ratio characteristic to the final turning angle set by the gear ratio characteristic at the time of low gain. Set as follows.
[0020]
In step S206, the gear ratio characteristic at the time of switching back is set as the gear ratio characteristic of the set gear ratio, and this control is terminated. The gear ratio characteristic at the time of switching back is set to have a relationship between the steering angle θ and the turning angle δ so as not to increase the steering gain Δδ / Δθ.
[0021]
In step S207, the reference gear ratio characteristic is set as the gear ratio characteristic of the set gear ratio (δ / θ), and this control is terminated. In this reference gear ratio characteristic, the relationship between the steering angle θ and the steering gain Δδ / Δθ is set, for example, as shown in FIG. Further, the steering gain Δδ / Δθ increases as the vehicle speed V increases, and is set so that the steered angle δ decreases as the vehicle speed V increases even at the same steering angle θ. Note that L1 in FIG. 3 (b) is a gear ratio characteristic diagram representing FIG. 3 (a) by the relationship between the steering angle θ and the turning angle δ.
[0022]
In step S208, the gear ratio characteristic at the time of low gain is set as the gear ratio characteristic of the set gear ratio δ / θ, and this control is terminated. Note that the gear ratio characteristic at the time of low gain is also set in advance similarly to the reference gear ratio characteristic.
[0023]
[Gear ratio characteristic setting control action]
As described above, FIG. 3A shows the relationship between the steering angle θ and the steering gain Δδ / Δθ, which is the increment of the turning angle δ, when the steered steering is not performed. From 0 to θ1, the steering gain Δδ / Δθ is constant, increases between θ1 and θ2, and is constant above θ2.
[0024]
A relationship between the steering angle θ and the turning angle δ is a reference gear ratio characteristic diagram as shown in FIG. As shown in the figure, in order to realize small steering angle steering with a small steering angle θ, the steering angle Δδ / Δθ is easy to handle in the steering angle region that is usually used frequently, and it is easy to handle, and the large steering angle region that is less frequently used. Then, the steering gain Δδ / Δθ is increased.
[0025]
In the relationship between the steering angle θ and the steering angle δ shown in FIG. 3, in order to realize a small steering angle steering, even in the region where the steering gain Δδ / Δθ with a steering angle of 0 to θ1 is small, the current general vehicle steering gain If it is greater than Δδ / Δθ, for example, if the vehicle is steered suddenly to avoid an obstacle, the vehicle behavior may change more than the driver expects. In the case of smooth steering, it is conceivable to reduce the steering gain Δδ / Δθ. At this time, in the flowchart shown in FIG. 2, the process proceeds from step S201 to step S202 to step S208.
[0026]
L2 in FIG. 4 is a gear ratio characteristic at the time of low gain. L1 is the reference gear ratio characteristic, and in the case of sudden steering, since the steering gain Δδ / Δθ is made small, the path of A is followed, and even if the steering angle is θa, the turning angle is δa Instead, it becomes δa ′.
[0027]
Let us consider a case where the normal steering is returned from this state, that is, the gear ratio characteristic of the set gear ratio is returned from the gear ratio characteristic at the time of low gain to the reference gear ratio characteristic.
[0028]
(When rounding up)
In the case of steering in a direction in which the steering angle is further increased from θa, the flow proceeds from step S201 to step S202 to step S203 to step S204 to step S205 in the flowchart shown in FIG.
[0029]
In other words, in step S205, the gear ratio characteristic of the set gear ratio indicates that the relationship between the steering angle and the steering angle after the steering angle θa ′ at which the turning angle of the reference gear ratio characteristic is δa ′ is (θa−θa ′). The offset is set so as to follow the relationship L2 connecting the Pa ′ point (θa ′, δa ′) and the subsequent points to the Pa point (θa, δa ′).
[0030]
Assuming that the steering angle is increased to θb, the relationship between the turning angle δ and the steering angle θ follows the route B and the turning angle becomes δb (point Pb). This is because, when normal steering is performed while maintaining a certain turning angle δ, if the vehicle's motion state is determined by the steering angle δ and the vehicle speed V, the steering in that motion state Although the absolute value | θ | of the angle θ is different from the normal value, it is better to set the change in the motion state with respect to the increase in the steering angle from that state to be the same as the steering gain Δδ / Δθ of the reference gear ratio characteristic. This is because it is easy for the driver to understand and does not cause a sense of incongruity.
[0031]
(When switching back)
Next, when the steering angle is decreased from the point Pb, the flow proceeds from step S201 to step S202 to step S203 to step S204 to step S206 in the flowchart shown in FIG.
[0032]
That is, in step S206, the gear ratio characteristic of the set gear ratio is set so as to be smoothly connected to the reference gear ratio characteristic L1. The gear ratio characteristic at this time is, for example, a characteristic that connects a tangent contact Pc drawn from the point Pb to the curve L1.
[0033]
As shown in FIG. 5, assuming that the Pd point returns from the Pb point to the L1 line, the steering gain Δδ / Δθ is once larger than the value between the Pb point and the Pd point when the steering angle is smaller than θd. Therefore, the steered angle δ with respect to the steering angle θ has a waved relationship, which may give the driver a feeling of strangeness.
As shown in FIG. 6, when the line connecting the point Pb and the origin O does not intersect L1, it may be returned to the origin without passing on L1.
[0034]
Further, when the reference gear ratio characteristic is set to an angular relationship in which a plurality of straight lines are connected as shown in FIG.
[0035]
As described above, the case where the steering is suddenly performed from the neutral position has been described. However, the same processing can be performed when the steering is suddenly performed from a position that is not neutral. In FIG. 8, when steering is performed at a steering speed that is determined not to be abrupt, and suddenly increases from the state at the point Pd on L1, the steering gain Δδ / Δθ becomes small without shifting on L1. Reach Pa point. From there, when the steering speed is increased at a non-steep steering speed, L1 is shifted on (L2) shifted by (θa−θa ′), for example, reaches Pb + point, and Pb which is a contact point from Pa to L1 in steering in the return direction -It moves toward a point.
[0036]
In addition, when sudden return steering is performed from the Pd point, the vehicle moves on L1 and passes the neutral point. This is because the sudden steering on the return side requires that the turning angle δ suddenly change in the zero direction, and further obtains the turning angle δ of the opposite sign, and the steering gain Δδ / Δθ is somewhat large. However, since the turning angle δ is always zero when the steering angle θ is zero, the turning angle δ does not occur more than the driver's expectation unlike the increase side.
[0037]
As described above, even if steering is performed once such as obstacle avoidance and deviates from the relationship between the normal steering angle θ and the turning angle δ, it always returns smoothly to the origin at the time of switchback steering. Neutral deviation does not occur.
[0038]
In addition, as shown in FIG. 9, the vehicle turns as it is without going through the state where the steering angle θ becomes zero from the state where the steering is once performed to avoid the obstacle and deviates from the relationship between the normal steering angle and the turning angle. Even when the operation is continued, while the increase / return operation is continued, the relationship gradually approaches the relationship L1 between the normal steering angle θ and the turning angle δ ((1) → (2) in FIG. 9). (→→ 3 →→ 4 ▼ → 5 →→ 6)).
[0039]
Further, since the turning angle δ at a certain steering angle θ does not become larger than the turning angle δ when the set gear ratio is the reference gear ratio characteristic, the steering gain Δδ / Δθ is excessively increased. Can be prevented.
[0040]
Next, the effect will be described.
In the vehicle steering control device of the first embodiment, the effects listed below can be obtained.
[0041]
(1) At the time of switching back, the gear ratio characteristic of the set gear ratio is set so as to follow the tangent line drawn from the Pb point (θb, δb) on L2 in FIG. 4 to L1, so the steering gain Δδ / Δθ The operation during a series of switchback operations can be smoothly realized.
[0042]
(2) When the gear ratio is increased, the gear ratio characteristic of the set gear ratio is offset by (θa−θa ′) and the gear ratio characteristic after the steering angle θa ′ at which the turning angle of L1 in FIG. Is set so as to follow the relationship L2 connecting the Pa 'point (θa', δa ') and beyond to the Pa point (θa, δa'), so that the behavior change of the vehicle with respect to the steering increment is changed to the original gear ratio characteristic. By making it the same as the steering gain Δδ / Δθ in L1, the driver does not feel uncomfortable.
[0043]
(3) Even when the steering angle of the steering wheel 1 is on one side without exceeding the neutral position, the gear ratio characteristic is gradually changed from the gear ratio characteristic at the time of low gain to the reference gear ratio characteristic every time switching back and back is repeated. Can be returned to.
[0044]
(Other examples)
The embodiment of the present invention has been described based on the first example. However, the specific configuration of the present invention is not limited to the first example, and the design can be changed without departing from the gist of the invention. Is included in the present invention.
[0045]
For example, in the first embodiment, a configuration in which the operation unit (steering wheel) and the steering unit (steering gear) are mechanically coupled by the steering column is shown. The present invention can also be applied to a steering-by-wire system that is not mechanically connected.
[Brief description of the drawings]
FIG. 1 is an overall system diagram showing a vehicle steering control apparatus according to a first embodiment;
FIG. 2 is a flowchart showing a flow of a gear ratio characteristic setting control process executed by a controller 10 of the first embodiment apparatus.
FIG. 3 is a diagram (a) showing a relationship between a steering angle and a steering gain in a reference gear ratio characteristic, and a reference gear ratio characteristic diagram (b).
FIG. 4 is a gear ratio characteristic diagram at the time of low gain.
FIG. 5 is a non-recommended gear ratio characteristic diagram.
FIG. 6 is a diagram showing an example of a gear ratio characteristic at the time of switching back.
FIG. 7 is a diagram illustrating an example of a gear ratio characteristic.
FIG. 8 is a diagram illustrating the operation of the first embodiment.
FIG. 9 is a diagram illustrating the operation of the first embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Steering wheel 2 Steering angle sensor 3 Steering column 4 Gear ratio variable means 5 Steering angle sensor 6 Steering gear 7 Side rod 8 Steering wheel 9 Vehicle state detection means 10 Controller

Claims (3)

A transmission ratio variable means capable of arbitrarily changing a transmission ratio, which is a ratio of a steered amount of a steered portion that steers a wheel to an operation amount of an operating unit operated by a driver;
A transmission ratio characteristic setting means capable of variably setting a transmission ratio characteristic which is a characteristic of the transmission ratio according to a vehicle state or an operation state of the operation unit;
A transmission ratio control means for outputting a control command for changing the transmission ratio to the transmission ratio variable means based on at least a set transmission ratio characteristic;
In a vehicle steering control device comprising:
When the transmission ratio characteristic setting means changes the transmission ratio characteristic from the transmission ratio characteristic that turns to zero when the manipulated variable is zero, and then returns to the original transmission ratio characteristic again, the manipulated variable decreases. Includes a transmission ratio characteristic that does not increase the gradient of the steering amount with respect to the operation amount. A transmission ratio variable means capable of arbitrarily changing a transmission ratio, which is a ratio of a steered amount of a steered portion that steers a wheel to an operation amount of an operating unit operated by a driver;
A transmission ratio characteristic setting means capable of variably setting a transmission ratio characteristic which is a characteristic of the transmission ratio according to a vehicle state or an operation state of the operation unit;
A transmission ratio control means for outputting a control command for changing the transmission ratio to the transmission ratio variable means based on at least a set transmission ratio characteristic;
In a vehicle steering control device comprising:
When the transmission ratio characteristic setting means changes the transmission ratio characteristic from the transmission ratio characteristic that turns the steering amount to zero when the operation amount is zero, and then returns to the original transmission ratio characteristic again, the operation amount increases. Is characterized in that a transmission ratio characteristic is set by connecting a characteristic from the same turning amount as the final turning amount in the original transmission ratio characteristic to the final turning amount set by the changed transmission ratio characteristic. A vehicle steering control device. A transmission ratio variable means capable of arbitrarily changing a transmission ratio, which is a ratio of a steering amount of a steering unit that steers a wheel with respect to an operation amount of an operation unit operated by a driver;
A transmission ratio characteristic setting means capable of variably setting a transmission ratio characteristic which is a characteristic of the transmission ratio according to a vehicle state or an operation state of the operation unit;
A transmission ratio control means for outputting a control command for changing the transmission ratio to the transmission ratio variable means based on at least a set transmission ratio characteristic;
In a vehicle steering control device comprising:
When the transmission ratio characteristic setting means changes the transmission ratio characteristic from the transmission ratio characteristic that turns to zero when the operation amount is zero, and then returns to the original transmission ratio characteristic again,
If the operation amount is decreasing, set a transmission ratio characteristic that does not increase the inclination of the steering amount with respect to the operation amount,
When the manipulated variable is increasing, the final turning amount set by the changed transmission ratio characteristic is connected to the characteristic from the same turning amount as the final turning amount in the original transmission ratio characteristic. A vehicle steering control device characterized by setting a ratio characteristic.

Images