JPH11171036A - Vehicle steering control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the sudden change of steering angle which is caused when the transmission ratio characteristic is changed and reduce the sense of incompatibility of steering by providing a transfer means for transferring with lapse of time the transmission ratio characteristic when it is changed by a selecting means, to a changed transmission ratio settled under the transmission ratio characteristic. SOLUTION: A hear ratio map selecting part 71 stores plural kinds of gear ratio maps differed in changing characteristic of gear ratio, and selects a prescribed gear ratio map according to the shift operation of a user selecting switch 62 or the shift position detected by a shift position sensor 63. In a gear ratio setting part 75, a gear ratio according to vehicle speed V is set on the basis of the gear ratio map selected by the gear ratio map selecting part 71. In a gear ratio sudden change preventing part 72, the gear ratio map selected by the gear ratio map selecting part 71 is gradually transferred from the characteristic before change to the characteristic after change with the lapse of time. According to this, the gear ratio settled by a gear ratio variable mechanism can be prevented from being suddenly changed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle steering control device for controlling a transmission ratio of a steering amount of a wheel to a steering amount of a steering wheel.

[0002]

2. Description of the Related Art In a conventional steering apparatus, a transmission ratio variable mechanism for changing a transmission ratio of a steering amount of a wheel to a steering amount of a steering wheel is known. Generally, a variable transmission ratio control is performed in accordance with a vehicle speed. By doing so, the maneuverability and running stability according to the vehicle speed are ensured.

For example, the device disclosed in Japanese Patent Application Laid-Open No. 62-20757 is provided with a plurality of types of transmission ratio characteristics having different characteristics with respect to vehicle speed. Is selectable.

[0004]

However, when the driver switches the transmission ratio characteristics by operating the switch, the steering is immediately performed based on the new transmission ratio characteristics at the time of the switching operation. Depending on the driving conditions,
Even in a state where the steering wheel is maintained, the turning angle of the wheels may change suddenly, giving the driver a feeling of strange steering.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and an object of the present invention is to prevent a sudden change in the turning angle that may occur when the transmission ratio characteristic is switched, and to reduce the feeling of steering discomfort. It is an object of the present invention to provide a steering control device for a vehicle that reduces the amount of the vehicle.

[0006]

Accordingly, a vehicle steering control device according to a first aspect of the present invention is a vehicle steering control device for controlling a transmission ratio of a wheel turning amount to a steering amount of a steering wheel. A vehicle steering control device for controlling a transmission ratio of a turning amount of a wheel to a steering amount of a vehicle. Selecting means for selecting a ratio characteristic; and setting means for setting a transmission ratio in accordance with a driving state of the vehicle based on the transmission ratio characteristic selected by the selecting means. The setting means is selected by the selecting means. When the transmission ratio characteristic is changed, the transmission ratio is gradually changed to the transmission ratio set under the changed transmission ratio characteristic with time.

When there is a change in the transmission ratio characteristic selected by the selection unit, the transmission unit gradually changes over time so that the transmission ratio is set under the changed transmission ratio characteristic. A sudden change in the turning angle of the wheels is prevented.

According to a second aspect of the present invention, there is provided a vehicle steering control device comprising:
The setting means according to claim 1 further includes a shift stop means for stopping the transfer ratio shifting processing by the shift means according to the driving state of the vehicle.

[0009] As the driving state of the vehicle, for example, when the steering wheel is held at a constant steering angle position or when the vehicle is traveling at a constant speed, the vehicle is traveling stably. In such a driving state, if a change in the turning angle occurs in accordance with the change in the transmission ratio characteristic, the driver will strongly feel the steering discomfort. Therefore, in such an operation state, the shift of the transmission ratio is stopped by the shift stop unit even when the transfer ratio characteristic selected by the selection unit is changed.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described.
This will be described with reference to the accompanying drawings.

FIG. 1 shows a configuration of a steering device 100 including a steering control device according to a first embodiment.

The input shaft 20 and the output shaft 40 are connected via a gear ratio (transmission ratio) variable mechanism 30.
Is connected to a steering wheel 10. Output shaft 40
Is connected to a rack shaft 51 via a rack and pinion type gear device 50, and wheels FW1 and FW2 are connected to both sides of the rack shaft 51.

The variable gear ratio mechanism 30 includes a steering wheel 10.
Has a function of changing a gear ratio as a ratio of a steering amount of the wheels FW1 and FW2 to a steering amount of the motor, and a motor 31 is provided as a drive source for changing the gear ratio.

The drive control of the variable gear ratio mechanism 30 is performed by a steering control device 70. The steering control device 70 includes an input angle sensor 21 provided on the input shaft 20, an output angle sensor 41 provided on the output shaft 40, and a vehicle. A control signal is output to the motor 31 based on detection signals of a vehicle speed sensor 61 for detecting the speed of the vehicle, a user selection switch 62 for changing the gear ratio, and a shift position sensor 63 for detecting a shift position of the transmission. The set gear ratio of the variable gear ratio mechanism 30 is controlled.

FIG. 2 shows the configuration of the steering control device 70.

The steering control device 70 comprises a gear ratio map selection section 71, a gear ratio setting section 75, a gear ratio sudden change prevention section 72, a compensator 73, a motor drive circuit 74, and the like.

The gear ratio map selection section 71 stores a plurality of types of gear ratio maps having different gear ratio change characteristics. The gear ratio map selection section 71 performs a switching operation of the user selection switch 62 and a shift position sensor 63. A predetermined gear ratio map is selected in accordance with the shift position detected in.

For example, in the case where the user selection switch 62 switches between execution and non-execution of the variable gear ratio control,
In the case of selecting one of the gear ratio maps shown in FIGS. 3A and 3B in response to the switch operation and switching the change characteristic with respect to the vehicle speed V to a plurality of stages (here, three stages), FIG. 4 shows s1, s2, s corresponding to the switch operation.
One of the gear ratio maps shown as 3 is selected.

As an example of selecting the shift position corresponding to the shift position detected by the shift position sensor 63, the gear ratio map shown in FIG. 5 (b) is selected. In addition, it is also possible to detect the acceleration g applied to the vehicle and select the gear ratio map shown by s4 and s5 in FIG. 6 according to the magnitude of the acceleration g.

The gear ratio setting section 75 sets a gear ratio corresponding to the vehicle speed V based on the gear ratio map selected by the gear ratio map selection section 71.

When the gear ratio map selected by the gear ratio map selection unit 71 is changed, the gear ratio sudden change prevention unit 72 gradually shifts from the characteristics before the change to the characteristics after the change over time. It has a function of preventing a sudden change in the gear ratio set by the variable gear ratio mechanism 30.

Here, each process executed by the steering control device 70 will be described in order along the flowchart of FIG. 7 with reference to FIG.

The flowchart shown in FIG. 7 is started by turning on an ignition switch, and first proceeds to step (hereinafter, step is referred to as “S”) 102, where the vehicle speed V detected by the vehicle speed sensor 61 and the input angle sensor The shift position detected by the user selection switch 62 or the shift position sensor 63 is read in addition to the input angle θh detected by 21 and the output angle θp detected by the output angle sensor 41.

In the following S104, a predetermined gear ratio map is selected in the gear ratio map selection section 71 in accordance with the shift position detected by the user selection switch 62 and the shift position sensor 63 read in S102. A gear ratio Kv (V) corresponding to the vehicle speed V is set based on the gear ratio map selected in S104.

In S108, it is determined whether the gear ratio map selected in S104 has been changed from the gear ratio map selected in the previous routine. If “Yes” is determined in S108, the process proceeds to S110 to set the counter flag k to k = 0, and then proceeds to S112.
If “No” is determined in S108, S1 is performed as it is.
Proceed to 12.

In the gear ratio sudden change prevention unit 72, S1
Steps S12 to S120 are executed, and in S112, it is determined whether the value of the counter flag k is equal to a predetermined constant N. The constant N is a value set in advance for gradually shifting over time from the gear ratio map before the change to the gear ratio map after the change in N stages.

If "No" is determined in step S112, the process proceeds to step S114 to set Kvn = Kv (V), and then in step S116, the value of the counter flag k is incremented to k + 1.

In the following S118, the gear ratio Kv set in the current routine is calculated as follows: Kv = α · Kv + (1−α) · Kv
It is set by calculating as n. In the equation, “Kv” on the right side is the gear ratio set in the previous routine,
“Α” is a distribution constant preset to a value of 0 <α <1. Such a calculation process is a so-called filtering process. In the process of repeatedly executing such a filtering process for each routine, the gear ratio Kv, which is the calculation result of S118, gradually changes as α is set to a larger value. Then, after completing the process of S118, the process proceeds to S12.
Proceed to 2.

On the other hand, if it is determined "Yes" in S112, whether the filtering process is completed or S
This is a case where there is no change in the gear ratio map selected in 104. In such a case, the process proceeds to S120, and the process proceeds to S1.
After setting the gear ratio Kv (V) set in 06 as the gear ratio Kv set in this routine, the process proceeds to S122.

In S122, a target rotational position of the output shaft 40 according to the rotational operation of the steering wheel 10 is calculated. Specifically, the output angle target value θpm to be detected by the output angle sensor 41 is calculated as θpm = Kv · θh.

At S124, a deviation e between the output angle target value θpm calculated at S122 and the output angle θp detected by the output angle sensor 41 is calculated as e = θpm-θp.

In step S126, a target current value Im serving as a drive current for the motor 31 is determined so that the deviation e becomes zero without overshooting. This processing is executed by the compensator 73. As an example of the processing, Im = C (s)
The target current value Im can be determined by appropriately setting the parameters of the PID control based on the arithmetic expression of e. Note that “s” in the expression is a Laplace operator.

In S128, the motor drive circuit 74 drives the motor 31 according to the target current value Im determined in S126.

By repeatedly performing the processing of S102 to S128, even when the gear ratio map is changed, the gear ratio map set in the pre-change gear ratio map is used as the changed gear ratio map. The gear ratio Kv gradually changes over time according to the magnitude of the distribution constant α and the constant N up to the set gear ratio, and it is possible to prevent a sudden change in the gear ratio.

Next, a second embodiment will be described with reference to FIG.

In the second embodiment, the following processing is performed between S116 and S118 in the flowchart (FIG. 7) shown in the first embodiment.

After finishing the process of S116, the process proceeds to S200, in which the change speed | dθh / dt | of the input angle θh is set to a predetermined value ε.
1 and the speed of change of the vehicle speed V | dV / dt |
Is smaller than a predetermined value ε2.

When | dθh / dt | <ε1, it can be considered that the steering wheel 10 is kept in a constant steering position (steering state), and | dV / dt | <
In the case of ε2, it can be considered that the vehicle is traveling at a substantially constant speed (constant speed state). When the gear ratio map change operation is performed during such a steady running, the wheels FW1, FW are maintained in spite of being in the steering maintaining state and the constant speed state.
The steering angle of No. 2 may change, giving the driver a feeling of steering discomfort.

Therefore, if "Yes" in S200, that is, if it is determined that the vehicle is traveling normally, the process proceeds to S202, and the value of α is set to 1. After that, proceed to S118,
A filtering process represented by Kv = α · Kv + (1−α) · Kvn is executed. Since α = 1 is set in S202, the gear ratio Kv set by the filtering process is set in the previous routine. The value of the gear ratio Kv thus set is set as it is. Therefore, even when a gear ratio map change operation is performed, the process of shifting the set gear ratio is stopped during steady running. As a result, even when the gear ratio map changing operation is performed, the gear ratio is kept constant during steady running, so that it is possible to avoid a situation in which the driver feels unnatural steering due to a change in the turning angle.

On the other hand, if "No" in S200, that is, if it is determined that the vehicle is not traveling normally, the flow proceeds to S204, in which the value of α is set to a predetermined value α0. Filtering processing is performed.

By executing steps S200 to S202 in this manner, when a gear ratio map change operation is performed while the vehicle is traveling in the steering-holding state and the constant-speed state, the gear ratio map accompanying the change of the gear ratio map is changed. The transfer process can be stopped.

[0042] In S200, instead of the exemplified determination condition in S200 of FIG. 8, the vehicle speed V may be determined whether a large (V> V _0?) Than the predetermined value V _0. In this case, S
"Yes" at 200, i.e. at high speeds the vehicle speed V is greater than V ₀ is fixed value of α 1, the migration process of the gear ratio due to change of the gear ratio map during high speed running is stopped . Also, the logical OR of the determination of “V> V ₀ ?” And the determination illustrated in S200 of FIG.
The determination condition of S200 may be used.

Next, a third embodiment will be described with reference to the flowchart shown in FIG.

The flowchart shown in FIG. 9 is started by turning on the ignition switch, and first proceeds to S302, where the vehicle speed V detected by the vehicle speed sensor 61, the input angle θh detected by the input angle sensor 21, the output angle sensor In addition to the output angle θp detected at 41, the shift position detected by the user selection switch 62 and the shift position sensor 63 are read.

In subsequent S304, a predetermined gear ratio map is selected in the gear ratio map selection section 71 in accordance with the shift position detected by the user selection switch 62 and the shift position sensor 63 read in S302.

In S306, it is determined whether the gear ratio map selected in S304 has been changed from the gear ratio map selected in the previous routine.

If "Yes" is determined in S306, the process proceeds to S308, where the gear ratio set based on the vehicle speed V in the gear ratio map before the change is K0 (V), and the gear ratio map in the changed gear ratio map is lower. The gear ratio set based on the vehicle speed V at K1
(V).

In the following S310, the value of the interpolation coefficient β used for the interpolation processing executed in the subsequent S318 is set to 0,
Proceed to S312. If “No” is determined in S306, the process proceeds directly to S312.

In S312, it is determined whether or not the value of the interpolation coefficient β is 1, and if “No”, the flow proceeds to S314, in which the change speed | dθh / dt | of the input angle θh is smaller than a predetermined value ε1 and , It is determined whether the change speed | dV / dt | of the vehicle speed V is smaller than a predetermined value ε2.

If "No" in S314, that is, if it is determined that the vehicle is not running normally, the process proceeds to S316,
The value of the interpolation coefficient β is updated by adding Δβ to the interpolation coefficient β,
Proceed to S318. Note that Δβ is a value preset to a value of 0 <Δβ <1.

In step S318, the gear ratio Kv set in this routine is set using the interpolation coefficient β updated in step S316.
Is calculated as Kv = β · K1 (V) + (1−β) · K0 (V) to execute the interpolation processing.

When such an interpolation process is repeatedly executed for each routine, β = 0 immediately after the change of the gear ratio map, so that the gear ratio becomes Kv = K0 (V), and the gear ratio map before the setting is changed. Gear ratio based on the interpolation coefficient β
Is gradually increased by Δβ, so that K
The value of 1 (V) gradually becomes dominant. Then, when the interpolation coefficient β becomes 1, “Y
es ”, the process proceeds to S320, and Kv = Kv (V)
And the gear ratio map is completely switched.

Further, similarly to the second embodiment, S314
If the answer is "Yes", that is, if it is determined that the vehicle is traveling normally, the process proceeds to S322, where the value of the interpolation coefficient β is set to the interpolation coefficient β determined in the previous routine. Therefore, in subsequent S318, the value of the interpolation coefficient β does not change, so that the gear ratio Kv is set to the same value as in the previous routine.
The gear ratio shifting process is stopped.

After the processing of S318 is executed, S324
Steps S330 to S330 are executed, but this processing is the same as the processing of S122 to S128 in FIG. 7 described above, and a description thereof will be omitted.

In each of the embodiments described above, when the gear ratio map is changed, a method for gradually shifting over time so that the gear ratio is set based on the changed gear ratio map is adopted. Although the filtering process and the interpolation process are illustrated, for example, with the change of the gear ratio map, 1
It is also possible to preliminarily set a limit value ΔK of the variable ratio of the gear ratio that can be changed in the routine, and to perform a guard process for guarding the value of the gear ratio set for each routine with the limit value ΔK. .

[0056]

As described above, according to the steering control apparatus for a vehicle according to the first aspect, the transition that gradually shifts with time so as to become the transmission ratio set under the changed transmission ratio characteristic. Since the means is provided, it is possible to prevent a sudden change in the steering angle due to a change in the transmission ratio characteristic, and in this case, it is possible to sufficiently reduce the steering discomfort felt by the driver.

According to the vehicle steering control device of the second aspect, since the shift stop means for stopping the shift processing of the transmission ratio by the shift means according to the driving state of the vehicle is provided, for example, the vehicle is driven at a constant speed. It is possible to avoid the occurrence of a steering discomfort such as a change in the turning angle of the wheels during a steady running state in which the vehicle runs and the steering is maintained.

[Brief description of the drawings]

FIG. 1 is a configuration diagram schematically showing a configuration of a steering device provided with a steering control device.

FIG. 2 is a block diagram illustrating a configuration of a steering control device.

FIGS. 3A and 3B are explanatory diagrams each showing a modified example of a gear ratio map.

FIG. 4 is an explanatory diagram showing a modified example of a gear ratio map.

FIGS. 5A and 5B are explanatory diagrams each showing a modified example of a gear ratio map.

FIG. 6 is an explanatory diagram showing a modified example of a gear ratio map.

FIG. 7 is a flowchart illustrating a process according to the first embodiment.

FIG. 8 is a flowchart illustrating a process according to the second embodiment.

FIG. 9 is a flowchart illustrating a process according to a third embodiment.

[Explanation of symbols]

Reference Signs List 10 steering wheel, 20 input shaft, 21 input angle sensor, 30 gear ratio variable mechanism, 40 output shaft, 41 output angle sensor, 70 steering control device, 71 gear ratio map selection unit (selection means) ), 72: gear ratio sudden change prevention unit (transition means, transition stop means), 75: gear ratio setting unit (setting means), 100: steering device.

Claims (2)

[Claims] 1. A vehicle steering control device for controlling a transmission ratio of a turning amount of a wheel to a steering amount of a steering wheel, wherein a plurality of transmission ratio characteristics differing in a change characteristic of the transmission ratio with respect to a driving state of a vehicle. Selecting means for selecting one of the transmission ratio characteristics, and setting means for setting the transmission ratio in accordance with the driving state of the vehicle based on the transmission ratio characteristic selected by the selection means, A setting unit configured to shift the transmission ratio, which is set under the changed transmission ratio characteristic, with time when the transmission ratio characteristic selected by the selection unit is changed; Steering control device. 2. The vehicle steering control device according to claim 1, wherein the setting unit further includes a shift stop unit that stops a shift process of the transmission ratio by the shift unit according to a driving state of the vehicle.