JP3518587B2 - Steering control device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steering control device for controlling steering operation of steered wheels in response to steering wheel operation.

[0002]

2. Description of the Related Art An example of a conventional steering control device is disclosed in, for example, Japanese Patent Laid-Open No. 5-229442. In this steering control device, the operability of the steering wheel is improved by setting the control amount so as to increase the turning angle change amount of the steered wheels as the steering speed of the steering wheel increases. Also,
In order to prevent the yawing of the vehicle from becoming excessive and the behavior of the vehicle becoming unstable, the amount of change in the control amount with respect to the steering speed is suppressed in the situation where the steering speed is higher than a predetermined speed. We are trying to stabilize the behavior.

[0003]

As described above, in the prior art,
Since the amount of change in the turning angle is controlled according to the steering speed, if the steering wheel is kept in the steering holding state immediately after the sudden steering, the steering speed becomes 0, so the control amount corresponding to the steering speed suddenly becomes zero. Will approach. For this reason, when shifting to the steering holding state after such sudden steering, the steering angle of the steered wheels may suddenly change, and the driver may feel uncomfortable in steering.

The present invention has been made to solve such a problem, and an object thereof is to rapidly change the steered angle of steered wheels even when the steering wheel is kept in the steering-holding state immediately after the steered steering. It is an object of the present invention to provide a steering control device that prevents the above and improves the steering feeling.

[0005]

Therefore, a steering control device according to a first aspect of the present invention is a steering control device for controlling a steering operation of steered wheels in response to a steering wheel operation, and a detection means for detecting a steering angle of a steering wheel. And a steering angle control amount for changing the steered wheels based on a first control amount according to the steering angle and a second control amount according to the steering speed based on the detection result of the detection means. And a setting means for setting the steering angle control so that the change state of the steering angle control amount with respect to the change of the steering speed becomes slower when the steering speed decreases than when the steering speed increases. Set the amount.

The control means discriminates between an increase and a decrease of the steering speed, and when the steering speed decreases, the steering angle control amount is controlled so that the changing state of the steering angle control amount with respect to the change of the steering speed becomes slower. Set. As a result, even when the steering state is shifted to immediately after the sudden steering, the sudden change of the steered angle control amount is suppressed, and accordingly, the sudden change of the steered angle of the steered wheels is also suppressed.

In the steering control device according to the second aspect, the control means according to the first aspect sets the second control amount according to the steering speed to a smaller value when the steering speed decreases than when the steering speed increases. It is characterized by

Thus, when the steering speed is reduced, the second control amount corresponding to the steering speed is set to a smaller value,
It is possible to suppress a change in the steered angle of the steered wheels due to a sudden change in the second control amount.

In the steering control device according to a third aspect of the present invention, the control means according to the first aspect adds a predetermined control amount when the steering speed is reduced.

By thus adding the predetermined control amount when the steering speed is reduced, the turning angle control amount is set by adding the first control amount and the second control amount to the predetermined control amount. . As a result, the sudden change in the second control amount due to the decrease in the steering speed is canceled out, and as a result, the sudden change in the steering angle control amount can be suppressed.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.
Description will be given with reference to the accompanying drawings.

FIG. 1 shows the configuration of a steering apparatus 100 according to the embodiment.

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 type gear device 50, and steered wheels FW are provided on both sides of the rack shaft 51.
1, FW2 are connected.

The input shaft 20 is provided with an input angle sensor 21 for detecting the steering angle of the steering wheel 10 and the output shaft 40.
Is provided with an output angle sensor 41 for detecting the rotation angle of the output shaft 40. The rotation angle of the output shaft 40 corresponds to the stroke position of the rack shaft 51, and the stroke position of the rack shaft 51 corresponds to the steering angles of the steered wheels FW1 and FW2. Therefore, the output angle sensor 41 rotates the output shaft 40. By detecting the angle, the steered angles of the steered wheels FW1 and FW2 are detected.

The transmission ratio variable mechanism 30 includes the steering handle 10.
Is a mechanical unit that controls the turning operation of the steered wheels FW1 and FW2 in response to the operation of the above, and includes a predetermined gear mechanism that connects the input shaft 20 and the output shaft 40 and a motor 31 that drives this gear mechanism. There is. By driving the gear mechanism by the motor 31, it has a function of transmitting the steering angle of the steering wheel 10 as the steering angle of the steered wheels FW1 and FW2 at a predetermined transmission ratio.

The drive control of the variable transmission ratio mechanism 30 is carried out by the steering control device 70. The steering control device 70 controls the input angle sensor 21 provided on the input shaft 20, the output angle sensor 41 provided on the output shaft 40, and the vehicle. The drive control of the transmission ratio variable mechanism 30 is performed by outputting the control current Is to the motor 31 based on each detection signal of the vehicle speed sensor 60 that detects the speed.

Here, the processing executed by the steering control device 70 will be described with reference to the flowchart of FIG.
In this case, the input angle θh changes as shown in FIG. 3 (a) while the steering wheel 10 is being held after the sudden steering, and the steering speed dθh / dt at that time is shown in FIG. 3 (b). The description will be made assuming the case of such changes.

This flowchart is started by turning on the ignition switch. First, the process proceeds to step (hereinafter, referred to as “S”) 102, and the input angle θh detected by the input angle sensor 21 is read. The input angle θh is output as positive on the right side and negative on the left side with the steering angle neutral position of the steering wheel 10 as a boundary.

In subsequent S104, the steering speed dθh / dt is set based on the input angle θh read in S102. At this time, the input angle θh read in S102 is differentiated or set based on the deviation from the input angle θh read in the previous routine and its time interval.

Then, in S106, a gain coefficient Ts that defines the gain of the steering speed dθh / dt is set. Here, a predetermined value is set as the gain coefficient Ts.

At 108, (dθh / dt) · Ts
Is calculated and the result is set as the differential angle Θ. As shown in FIG. 4, this is a process of obtaining the differential angle Θ based on the straight line having the inclination Ts that defines the gain coefficient Ts and the steering speed dθh / dt.

At S110, it is determined whether the differential angle | Θ | set at S108 is larger than the threshold | a |. During time t0 to t1 shown in FIG.
In No., the process proceeds to S112, and the output angle target value θpm as the steering angle control amount is set based on the following equation (1). In addition, in the formula (1), "G"
Indicates the steering angle of the steering wheel 10 by turning the steered wheels FW1, FW2.
The value of the transmission ratio that is transmitted as the steering angle of is shown and is a constant here.

Θpm = (1 / G) · (θh + Θ) (1) From the equation (1), θpm = (1 / G) · θh + (1
/G).THETA., And the first term on the right side is the first controlled variable and the second term is the second controlled variable.

After setting the output angle target value θpm in this way, the process proceeds to S114, where the output angle θp detected by the output angle sensor 41 is read. Then, the process proceeds to S116 and S1
The deviation e between the output angle target value θpm set in 12 and the output angle θp read in S114 is e = θpm−θp
Calculate as.

At S118, the control current Is for controlling the motor 31 is determined so that the deviation e is set to 0 without overshooting. As an example of this processing,
The control current Is can be determined by appropriately setting the parameters of PID control based on the equation of Is = C (s) · e. In addition, "s" in a formula is a Laplace operator.

In subsequent S120, the control current Is determined in S118 is output to the motor 31, the motor 31 is driven based on the control current Is, and this routine ends.

On the other hand, when the steering speed dθh / dt further increases and exceeds the time t1 shown in FIG. 3C, the differential angle Θ becomes larger than the threshold value a. Therefore, the previous S110
Then, it is determined to be “Yes”, the process proceeds to S122 and S108.
A process of replacing the value of the differential angle Θ set in step 1 with the threshold value a is performed. Therefore, in S122, guard processing is performed so that the differential angle Θ does not increase beyond the threshold value α. The steering speed dθh / dt set in S104
Is positive, the threshold value a is set to positive and the steering speed d
When θh / dt is negative, the threshold value a is set to a negative value.

In subsequent S124, the steering acceleration d ² θh /
It is determined whether dt ² = 0. This judgment can be performed as "whether the sign of the steering acceleration d ² θh / dt ² is inverted from positive to negative", or the logical sum of these judgments may be used.

The situation in which the determination of S124 is "No" is during the time t1 to t2 shown in FIG. 3C. In this case, the process proceeds to S112 and the guard process is performed in S122. Using the differential angle Θ, the above-described S112 to S1
20 processes are performed.

On the other hand, in the determination of S124, "Yes
s ”, that is, the situation in which it is determined that the steering acceleration d ² θh / dt ² = 0 is the state at time t2 in FIG. 3C, and the steering speed dθh / dt reverses from the increasing tendency to the decreasing tendency. is there.

Therefore, in this case, the routine proceeds to S126, where the differential angle Θ at the steering speed dθh / dt is Θ.
= A, the gain coefficient Ts is updated so that the differential angle Θ = a at the steering speed dθh / dt at this time, and is newly set as Ts = a / (dθh / dt).

In the following S128, the steering coefficient dθh / d at this time is calculated by using the gain coefficient Ts set in S126.
The differential angle Θ according to t is Θ = (dθh / dt) · Ts
Set as.

In subsequent S130, the output angle target value θpm is set using the differential angle Θ set in S128, based on the equation (1) shown above.

Thereafter, S132 to S138 are carried out in the same manner as S112 to S120 described above, and thereafter S14.
Go to 0.

At S140, the steering speed dθh / dt = 0
It is determined that the steering wheel is being held, and “N
In the case of “o”, it is considered that the steering speed dθh / dt is in the process of decreasing, and the process proceeds to S142.

In step S142, the input angle θh newly detected by the input angle sensor 21 is read, and in step S144, the input angle θh is read.
Based on the input angle θh read by 142, the steering speed dθ
Set h / dt.

Then, the process proceeds to S128 again, and in S128 in this situation, the steering speed dθh set in S144 is used by using the gain coefficient Ts updated in S126.
The differential angle Θ corresponding to / dt is Θ = (dθh / dt) ·
Set as Ts.

Thereafter, S1 is continued until it is judged "Yes" in S140, that is, the steering speed dθh / dt = 0.
The processing from 28 to S144 is repeatedly executed, and during this period, the differential angle Θ gradually decreases from Θ = a as the steering speed dθh / dt decreases, as shown at times t2 to t3 in FIG. 3C. Is set to.

Then, as shown at time t3, the steering speed d
When θh / dt = 0, it is determined to be “Yes” in S140, the routine is ended, and the processes of S102 and subsequent processes are started again.

The output angle target value θ set in this way
The transition of pm is shown by the solid line A in FIG. The dotted line B is the transition when the guard processing and the gain coefficient Ts are not updated at all when setting the differential angle Θ, and the alternate long and short dash line C
Is the transition when the guard process with the upper limit value of the differential angle Θ as a is performed when the steering speed dθh / dt increases and decreases. Focusing on the times t2 to t3 when the steering speed dθh / dt decreases, it can be seen that the change in the output angle target value θpm on the solid line A is suppressed as compared with the dotted line B and the alternate long and short dash line C. Therefore, by performing such processing, it is possible to prevent a phenomenon in which the steered angles of the steered wheels FW1 and FW2 suddenly change even when the steering handle 10 is kept in the steering-holding state immediately after the sudden steering. .

Next, FIG. 6A shows another embodiment.
~ It will be described along the flowchart of Fig. 5 with reference to Fig. 6D.

In this flowchart, S202 is replaced with S126 and S128 in the flowchart of FIG.
2 to S208, other processes are the same as those in the flowchart of FIG. 2, and the same processes as those in the flowchart of FIG.

In FIG. 5, in S124, the steering acceleration d ²
It is determined whether or not θh / dt ² = 0, and if “No” is determined, the steering speed dθh / dt tends to increase. In this case, the processing of S112 to S120 described above is performed. move on. If it is determined to be “Yes”,
The steering speed dθh / dt is being reversed from an increasing tendency to a decreasing tendency. In this case, the process proceeds to S202 and S
The value of the gain coefficient Ts set in 106 is updated and set to Ts ′ (Ts> Ts ′) that takes a smaller value than Ts.

In subsequent S204, the steering coefficient dθh / d at this time is used by using the gain coefficient Ts set in S202.
The differential angle Θ according to t is Θ = (dθh / dt) · Ts
Set as. When the gain coefficient Ts set in S202 is used as described above, the differential angle Θ is the gain coefficient Ts updated at time t2 as shown in FIG. 6C.
Depending on the amount of decrease of, the value is set smaller than before update,
After time t2, as the steering speed dθh / dt decreases,
It changes as shown by the alternate long and short dash line.

In subsequent S206, it is determined whether or not the differential angle | Θ | set in S204 is less than or equal to the threshold value | a |. During time t2 to t4 shown in FIG.
Since the differential angle | Θ | set in step 1 is larger than the threshold value | a |, it is determined as "No", and the process proceeds to S208.

In S208, a guard process is performed in which the value of the differential angle Θ set in S204 is replaced with the threshold value a. Also in this case, the threshold value a is set to be positive when the steering speed dθh / dt set in S104 is positive, and the threshold value a is set when the steering speed dθh / dt is negative.
Is set to a negative value. Then, in subsequent S130, S
Using the differential angle Θ set in 208, the output angle target value θpm is set based on the equation (1) shown above, and S1 is set.
The processing shifts to 32 and thereafter.

At time t4, the differential angle Θ set in S204 becomes Θ = a, and as a result, S20.
It is determined to be “Yes” in 6, and the process proceeds to S130. Therefore,
From time t4 to time t3, the differential angle Θ set in S204 is set as it is, and during this time, the differential angle Θ is set as shown in FIG.
As shown at time t4 to t3 in (c), the steering speed d
The differential angle Θ is set to gradually decrease from Θ = a as θh / dt decreases.

The output angle target value θ set in this way
The transition of pm is shown by the solid line D in FIG. The dotted line E is the transition when the guard process and the update of the gain coefficient Ts are not performed at the time of setting the differential angle Θ, and the one-dot chain line F
Reduces the gain coefficient Ts to a smaller value T at time t2.
This is a transition when updated to s'. Also in this case, focusing on the times t2 to t3 when the steering speed dθh / dt decreases, it can be seen that the change in the output angle target value θpm on the solid line D is suppressed as compared to the dotted line E and the alternate long and short dash line F. . Therefore, by performing such processing, it is possible to prevent a phenomenon in which the steered angles of the steered wheels FW1 and FW2 suddenly change even when the steering handle 10 is kept in the steering-holding state immediately after the steered steering. .

FIG. 8A shows still another embodiment.
~ It demonstrates according to the flowchart of FIG. 7 with reference to FIG. Note that in the flowchart of FIG.
The same processes as those in the flowchart in FIG.

In FIG. 7, in step S124, the steering acceleration d ²
It is determined whether or not θh / dt ² = 0, and if “No” is determined, the steering speed dθh / dt tends to increase. In this case, the processing of S112 to S120 described above is performed. move on. If it is determined to be “Yes”,
The steering speed dθh / dt is being reversed from the increasing tendency to the decreasing tendency, and in this case, the process proceeds to S302.

In S302, the value of the gain coefficient Ts set in S106 is updated, and T which takes a smaller value than Ts is updated.
Set to s '(Ts>Ts'). At the same time, a predetermined value K is set to the addition angle Θ ′ to be added when setting the output angle target value θpm.

In the following S304, the steering coefficient dθh / d at this time is calculated using the gain coefficient Ts set in S302.
The differential angle Θ according to t is Θ = (dθh / dt) · Ts
Set as.

When the gain coefficient Ts set in the previous S302 is used, the differential angle Θ is not updated before time t2 as shown in FIG. 8C in accordance with the decrease amount of the updated gain coefficient Ts. Is set to a value smaller than that at time t2
After that, as the steering speed dθh / dt decreases, the transition is made as shown by the alternate long and short dash line. For convenience of explanation, in FIG. 8C, after the time t2, the value obtained by adding the addition angle Θ'to the differential angle Θ is shown, but as described above, after the time t2, the addition angle Θ'is always added. Therefore, the added angle Θ ′ remains even after the time t3 when the differential angle Θ = 0.

The output angle target value θ set in this way
The transition of pm is shown by the solid line G in FIG. The dotted line H represents the transition when the guard processing and the update of the gain coefficient Ts are not performed at the time of setting the differential angle Θ. Also in this case,
Focusing on the times t2 to t3 when the steering speed dθh / dt decreases, it can be seen that the change in the output angle target value θpm in the solid line G is suppressed as compared with the dotted line H.

In each of the embodiments described above, the transmission ratio G is described as a constant, but the transmission ratio G can be set according to the vehicle speed V based on the map shown in FIG. 9, for example.

Further, in the above-described embodiment, the steering control device having the variable transmission ratio mechanism is illustrated as the device for controlling the steering operation of the steered wheels FW1 and FW2 in response to the operation of the steering wheel 10. However, the steering handle 10 and the steered wheels FW1 and FW2 are not limited to these.
Can be mechanically separated from each other, and can be applied to a steering control device that performs steering control of the steered wheels FW1 and FW2 based on the driving force of the actuator.

[0057]

According to the steering control device according to each of the claims, in the setting means, the change state of the turning angle control amount with respect to the change of the steering speed becomes slower when the steering speed decreases than when the steering speed increases. As described above, the steered angle control amount is set, so that a sudden change in the steered angle control amount is suppressed even when the steering state is shifted to immediately after the steered steering, thereby suppressing a sudden change in the steered angle of the steered wheels. As a result, the steering feeling can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a steering device according to an embodiment.

FIG. 2 is a flowchart showing a process executed by a steering control device.

FIG. 3A is a diagram showing an example of transition of an input angle θh,
(B) is a diagram showing a transition of the steering speed dθh / dt corresponding to (a), (c) is a diagram showing a transition of the set differential angle Θ, and (d) is a transition of the output angle target value θpm. It is a figure.

FIG. 4 is a steering speed dθh / d according to a gain coefficient Ts.
6 is a map showing the relationship between t and the differential angle Θ.

FIG. 5 is a flowchart showing a process executed by the steering control device.

FIG. 6A is a diagram showing an example of a transition of an input angle θh,
(B) is a diagram showing a transition of the steering speed dθh / dt corresponding to (a), (c) is a diagram showing a transition of the set differential angle Θ, and (d) is a transition of the output angle target value θpm. It is a figure.

FIG. 7 is a flowchart showing a process executed by the steering control device.

FIG. 8A is a diagram showing an example of transition of an input angle θh,
(B) is a diagram showing a transition of the steering speed dθh / dt corresponding to (a), (c) is a diagram showing a transition of the set differential angle Θ, and (d) is a transition of the output angle target value θpm. It is a figure.

FIG. 9 is a map defining a relationship between a vehicle speed V and a transmission ratio G.

[Explanation of symbols]

10 ... Steering handle, 21 ... Input angle sensor, 30 ... Transmission ratio variable mechanism, 41 ... Output angle sensor, 100 ... Steering device.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor, Kawago, Toko, Toyota City, Toyota, Aichi Prefecture, 1 Toyota Town, Ltd. (56) References JP-A-6-278625 (JP, A) JP-A-5 -58313 (JP, A) JP-A 6-1254 (JP, A) JP-A 4-159178 (JP, A) JP-A 5-229442 (JP, A) (58) Fields investigated (Int.Cl) . ^7, DB name) B62D 6/00

Claims (3)

(57) [Claims] 1. A steering control device for controlling a turning operation of steered wheels in response to a steering wheel operation, comprising: a detection means for detecting a steering angle of a steering wheel; and a steering angle based on a detection result of the detection means. First responded
The control device further includes setting means for setting a turning angle control amount for changing the steered wheels based on the control amount and the second control amount according to the steering speed, and the setting means is configured to increase the steering speed when the steering speed increases. On the other hand, the steering control device that sets the steering angle control amount so that the change state of the steering angle control amount with respect to the change in the steering speed becomes slower when the steering speed decreases. 2. The control means sets the second control amount according to the steering speed to a smaller value when the steering speed is decreased than when the steering speed is increased. Steering control device. 3. The control means, when the steering speed is reduced,
The steering control device according to claim 1, wherein a predetermined control amount is added.