JP2008087529A - Understeer suppression unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a low-cost and effective understeer suppression unit by means of only electromotive steering controller, engine controller and transmission controller provided in a light motor vehicle and a compact car. <P>SOLUTION: The understeer suppression unit includes a linear road-surface counterforce torque calculator 6, an estimated road-surface counterforce torque calculator 7, an understeer degree calculation means 8 and an execution processing selector 9. Based on a linear road-surface counterforce torque Talign_lin calculated from each sensor 1-5 in an electromotive steering controller 10 and an estimated road-surface counterforce torque Talign_est, an understeer degree US_Index is detected. When a symptom of understeer is detected, a driver is promoted to turn back the steering wheel through steering wheel turn-back processing using the electromotive steering controller 10, and further, the vehicle is automatically decelerated through deceleration processing using an engine controller 11 and a transmission controller 12. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention detects an understeer state (understeering degree) of a vehicle that is caused by excessive steering of a steering wheel on a slippery road surface in a vehicle equipped with a control device for electric power steering (hereinafter referred to as “electric power steering”). The present invention relates to an understeer suppression device that performs understeer suppression processing such as steering wheel turn-back acceleration processing and automatic deceleration processing.

Conventionally, a vehicle has been required to suppress an understeer state, and various countermeasures have been proposed.
The understeer state is a phenomenon in which the lateral grip of the front tire reaches a limit and causes excessive vehicle skidding, and is also called a drift-out state.

As a conventional understeer suppression device, a device that detects an understeer state of a vehicle based on a reference yaw rate and an actual yaw rate and performs understeer suppression control using a brake controller has been proposed (see, for example, Patent Document 1). .
However, in the conventional device described in Patent Document 1, since the understeer suppression control is executed after the lateral grip of the front wheel tire reaches the limit, and a certain degree of understeering occurs, the control effect of the understeering is performed. However, there was a problem that the driver of the vehicle was uncomfortable.

  Therefore, as another conventional device, when the grip degree in the lateral direction of the front tire is estimated and calculated, and the grip degree falls below a predetermined value, the brake controller, engine controller, and transmission controller are used to suppress understeer. An apparatus for performing control has also been proposed (see, for example, Patent Document 2).

In the case of Patent Document 2, understeer suppression control is executed using the estimated grip degree earlier than in the case of Patent Document 1, so that the control effect is large and the driver feels less uncomfortable. Is realized.
However, the conventional device of Patent Document 2 requires special sensor means for estimating the grip degree.

JP-A-6-99800 JP 2003-31465 A

In the conventional understeer suppressing device, when the yaw rate sensor and the lateral acceleration sensor are used to estimate the grip degree in the conventional device described in Patent Document 2, these sensors are very expensive. There was a problem of inviting up.
In addition, in order to estimate the grip level, it is necessary to execute processing such as steering friction torque estimation, self-aligning torque estimation, side force estimation, self-aligning torque origin gradient estimation and reference self-aligning torque estimation. There was a problem that a very expensive microcomputer with high capacity was required.

  Furthermore, in the technique described in Patent Document 2, when the grip level is reduced, it is necessary to perform understeer suppression control using a brake controller, but the brake controller is used when the driver does not step on the brake pedal. However, since the brake operation is very expensive and can be controlled by electronic control, there is a problem that the cost is increased.

By the way, in recent years, the majority of purchased vehicles by car users are relatively inexpensive vehicles called minicars and compact cars, and this class of vehicles has a small vehicle weight and requires the necessary steering assistance. Since the torque is relatively small and also has an effect of improving fuel efficiency, it is mainstream to use electric power steering rather than hydraulic power steering. In addition, this class of vehicles has a high need for cost reduction and cannot be equipped with expensive sensors, microcomputers and brake controllers, and therefore cannot be equipped with an understeer suppression device.
However, on the other hand, this class of vehicles has a low vehicle weight, so it is easy to fall into an understeer state on a slippery road surface, etc., but an inexpensive vehicle should be equipped even though an understeer suppression device is necessary. There was a problem that it was not possible.

  The present invention has been made to solve the above-described problems, and is inexpensively realized by using an engine controller, a transmission controller, and an electric power steering controller that are installed in the majority of light vehicles and compact cars. It is an object of the present invention to provide an understeer suppression device that realizes understeer suppression control, has a large control effect, and is less uncomfortable.

  An understeer suppressing device according to the present invention includes a vehicle speed detection unit that detects a vehicle speed of a vehicle, a steering angle detection unit that detects a steering angle of a steering wheel of the vehicle, a steering torque detection unit that detects a steering torque applied to the steering wheel, An electric motor for assisting a steering force applied to the steering wheel, a motor current detecting means for detecting a motor current flowing in the electric motor, a motor rotational speed detecting means for detecting a motor rotational speed of the electric motor, a vehicle speed and a steering angle; Linear road surface reaction torque calculation means for calculating a linear road surface reaction torque received by the vehicle based on the vehicle speed, and an estimated road reaction torque received by the vehicle based on the vehicle speed, steering torque, motor current, and motor rotation speed. Based on the estimated road surface reaction torque calculation means and the comparison between the linear road surface reaction torque and the estimated road surface reaction torque, the understeer degree of the vehicle is calculated. An understeer degree calculating means for calculating, an execution process selecting means for selecting an understeer suppression process to be executed based on the understeer degree, an electric power steering control means for controlling a steering assist torque output from the electric motor, and a vehicle engine An engine control means for controlling the output; and a transmission control means for transmitting the engine output to the drive wheels of the vehicle. The execution process selecting means is configured to perform electric power steering control when the understeering degree is a predetermined threshold value or more. At least one of a steering wheel turning-back acceleration process for suppressing steering assist torque using a means and a deceleration process using an engine control means or a transmission control means, and an electric power steering control means, an engine control means, and a transmission control means, By execution processing selection means And it executes the-option based on a result processing.

According to the present invention, the understeer state can be detected early from the sign stage by calculating the degree of understeer based on the road surface reaction torque (comparison between the linear road surface reaction torque and the estimated road surface reaction torque). .
In addition, when an indication of understeer is detected, the driver is prompted to switch back and the vehicle is automatically decelerated. Effective understeer suppression processing can be executed.
In addition, an electric power steering controller, an engine controller, and a transmission equipped in a light vehicle or a compact car are detected by using a sensor means included in a general electric power steering controller to detect understeer based on less arithmetic processing than in the past. By executing the understeer suppression process only by the controller, an inexpensive understeer suppression device can be realized without requiring a new expensive sensor or an expensive microcomputer.

Embodiment 1 FIG.
Hereinafter, the first embodiment of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a block diagram showing an understeer suppressing device according to Embodiment 1 of the present invention.

  In FIG. 1, the understeer suppression device includes various sensors including a steering angle sensor 1, a vehicle speed sensor 2, a steering torque sensor 3, a motor current sensor 4, and a motor rotation speed sensor, a linear road surface reaction force torque calculator 6, an estimated road surface reaction. Steering under the control of an arithmetic processing unit comprising a force torque computing unit 7 and an understeering degree computing unit 8, a suppression processing unit comprising an electric power steering controller 10, an engine controller 11 and a transmission controller 12, and an electric power steering controller 10 And an electric motor 20 that outputs an assist torque.

The steering angle sensor 1, the vehicle speed sensor 2, the steering torque sensor 3, the motor current sensor 4 and the motor rotation speed sensor 5 are provided in association with a vehicle steering system (not shown) including an electric power steering device.
A steering angle sensor 1 detects a steering angle θh of a vehicle handle (not shown), a vehicle speed sensor 2 detects a vehicle speed V of the vehicle, and a steering torque sensor 3 is applied to the handle by a driver of the vehicle. The steering torque Ts is detected.
The motor current sensor 4 detects a motor current Imtr flowing in an electric power steering electric motor (not shown), and the motor rotation speed sensor 5 detects a motor rotation speed ωmtr of the electric power steering electric motor.

The steering angle θh and the vehicle speed V from the steering angle sensor 1 and the vehicle speed sensor 2 are input to the linear road surface reaction force torque calculator 6.
The vehicle speed V, the steering torque Ts, the motor current Imtr, and the motor rotation speed ωmtr from the vehicle speed sensor 2, the steering torque sensor 3, the motor current sensor 4 and the motor rotation speed sensor 5 are input to the estimated road surface reaction force torque calculator 7. .

Based on the steering angle θh and the vehicle speed V, the linear road surface reaction torque calculator 6 calculates a linear road surface reaction torque Talign_lin received by the vehicle tire and inputs the linear road reaction torque torque Talign_lin to the understeer degree calculator 8.
The estimated road surface reaction torque calculator 7 calculates the estimated road surface reaction torque Talign_est received by the vehicle based on the steering torque Ts, the motor current Imtr, the motor rotational speed ωmtr, and the vehicle speed V, and inputs it to the understeer degree calculator 8. To do.
The road surface reaction force torque is a torque that attempts to return the tire in a straight direction when the steering wheel is steered.

The understeering degree calculator 8 calculates the vehicle understeering degree US_Index based on the comparison between the linear road surface reaction force torque Talign_lin and the estimated road surface reaction force torque Talign_est and inputs it to the execution processing selector 9.
The execution process selector 9 selects a process to be executed by any one of the electric power steering controller 10, the engine controller 11, and the transmission controller 12 based on the understeer degree US_Index.

Specifically, the execution process selector 9 uses the electric power steering controller 10 to assist the steering when the understeering degree US_Index indicates a value equal to or greater than a predetermined threshold Th1 (first threshold corresponding to an understeer sign). A steering wheel turning-back acceleration process for suppressing torque and a deceleration process using the engine controller 11 or the transmission controller 12 are selected.
Thereby, the electric power steering controller 10, the engine controller 11, and the transmission controller 12 execute processing based on the selection result by the execution processing selector 9.

The electric power steering controller 10 controls the steering assist torque output from the electric motor 20, and the electric motor 20 assists the steering force applied to the handle by the driver.
The engine controller 11 controls the engine output of the vehicle, and the transmission controller 12 transmits the engine output to the drive wheels of the vehicle.
The engine controller 11 and the transmission controller 12 control the driving torque and braking torque of the vehicle (generally called braking torque called engine brake).

The control operations of the electric power steering controller 10, the engine controller 11 and the transmission controller 12 are general and will not be described in detail.
The steering angle sensor 1, the vehicle speed sensor 2, the steering torque sensor 3, the motor current sensor 4, and the motor rotation speed sensor 5 are all sensors included in a general electric power steering controller.

The specific operation according to the first embodiment of the present invention shown in FIG. 1 will be described below with reference to the flowchart of FIG.
The ECU (Electronic Control Unit) including the respective arithmetic units 6 to 8 and the execution process selector 9 in FIG. 1 is related to the various sensors 1 to 5 and the various controllers 10 to 12 in steps S1 to S1 in FIG. S12 is repeatedly executed.

  In FIG. 2, first, the steering angle sensor 1 detects the steering angle θh (step S1), the vehicle speed sensor 2 detects the vehicle speed V (step S2), and the steering torque sensor 3 detects the steering torque Ts (step S3). The motor current sensor 4 detects the motor current Imtr (step S4), and the motor rotation speed sensor 5 detects the motor rotation speed ωmtr (step S5).

  Next, the linear road surface reaction force torque calculator 6 calculates the linear road surface reaction force torque Talign_lin based on the steering angle θh and the vehicle speed V as shown in the following equation (1) (step S6).

However, in the equation (1), Kalign is a ratio of the road surface reaction force torque to the steering angle θh in a traveling region where the road surface reaction force torque is not saturated, and is a unique value for each vehicle.
Further, since the value of the ratio Kalign differs depending on the vehicle speed, it is determined in advance as a table value corresponding to each vehicle speed.

Next, the estimated road surface reaction torque calculator 7 calculates the estimated road surface reaction torque Talign_est based on the steering torque Ts, the motor current Imtr, the motor rotation speed ωmtr, and the vehicle speed V (step S7).
The specific calculation process of the estimated road surface reaction torque Talign_est is omitted here, but is well known, for example, as disclosed in Japanese Patent Nos. 3353770, 2003-312521, and 2005-324737. Techniques can be used.

  Next, the understeering degree calculator 8 calculates the understeering degree US_Index based on the deviation between the linear road surface reaction force torque Talign_lin and the estimated road surface reaction force torque Talign_est (Step S8). .

  The understeering degree US_Index obtained from the equation (2) indicates that the larger the value, the stronger the understeering state of the vehicle.

Here, the relationship between the steering angle θh and the understeer state (see the horizontal axis), the linear road surface reaction force torque Talign_lin, the road surface reaction force torque and the yaw rate (see the vertical axis) will be described with reference to the explanatory diagram of FIG. .
In FIG. 3, the relationship between the reference yaw rate and the actual yaw rate when the steering angle θh is increased from “0” in constant vehicle speed driving on the low friction coefficient road surface (see the upper row), and the linear road surface reaction force. The relationship between the torque Talign_lin and the road surface reaction torque (see the lower row) is shown.

In FIG. 3, as the steering angle θh is increased, the linear road surface reaction torque Talign_lin and the reference yaw rate (see solid line) increase linearly as the steering angle θh increases.
On the other hand, the road surface reaction force torque (see the two-dot chain line) saturates away from the value of the linear road surface reaction force torque Talign_lin when the steering angle θh is greater than or equal to the first steering angle θh1 (corresponding to the first threshold Th1). The deviation between the torques increases.

  When the steering angle θh further increases and becomes a region greater than or equal to the second steering angle θh2 (> θh1) (corresponding to the second threshold Th2), the actual yaw rate (see the alternate long and short dash line) is separated from the reference yaw rate value and saturated. However, the deviation between the two yaw rates increases. That is, as the steering angle θh increases, the degree of understeer US_Index increases and the understeer state of the vehicle becomes stronger.

  Here, in addition to the first threshold value Th1 corresponding to a sign of understeer, a second threshold value Th2 (described later) corresponding to mild understeer, and a third threshold value Th3 (described later) corresponding to moderate or higher understeer Are shown step by step.

  The road surface reaction force torque saturation occurs earlier than the actual yaw rate saturation by “θh2−θh1”. This is because, for example, the well-known document “Nakashima et al., A Vehicle State Detection Method Aligned Torque Using”. EPS, 05AC-46, 2005 SAE ".

In the present invention, the understeer degree US_Index corresponding to the understeer sign is calculated using a phenomenon in which the road surface reaction torque and the saturation threshold of the actual yaw rate are different.
Since the saturation mechanism of the road surface reaction torque (self-aligning torque) is also described in paragraphs [0006] to [0009] in the above-mentioned Patent Document 2, description thereof is omitted here.

  Returning to FIG. 2, following step S <b> 8, the execution process selector 9 selects a process to be executed in the current situation, and the understeering degree US_Index is equal to or greater than the first threshold Th <b> 1 for detecting an understeer sign. Is determined (step S9).

As described above, the first threshold value Th1 corresponding to the sign of understeer is that the road surface reaction force torque is separated from the linear road surface reaction torque value in FIG. 3 (and the actual yaw rate is not separated from the reference yaw rate). ) A criterion value for detecting a region.
If it is determined in step S9 that US_Index <Th1 (that is, NO), it is not an understeer sign state and there is no process to be executed, so no process (step S10) is selected, and the process returns to step S1.

  On the other hand, if it is determined in step S9 that US_Index ≧ Th1 (that is, YES), the execution process selector 9 performs the steering switch back acceleration process (step S11) by the electric power steering controller 10 as the understeer suppression process to be executed. And vehicle deceleration processing (step S12) by the engine controller 11 and the transmission controller 12 are selected.

As a result, the electric power steering controller 10 executes a handle turning-back acceleration process according to step S11.
Further, the engine controller 11 and the transmission controller 12 execute a vehicle deceleration process in accordance with step S12.
Thereafter, the processing routine of FIG. 2 is terminated, and the process returns to step S1.

  In step S11, the steering switch back acceleration process by the electric power steering controller 10 is realized by suppressing the steering assist torque output from the electric motor 20 for electric power steering. More specifically, the electric motor 20 This is realized by suppressing the supply current to the.

  In step S12, the deceleration process by the engine controller 11 is realized by suppressing the amount of intake air to the engine (not shown), stopping the fuel injection, or changing the ignition timing. Processing is realized by downshifting or the like.

  Further, for convenience of explanation, the understeer suppressing device is configured as shown in FIG. 1, but the steering angle sensor 1, the vehicle speed sensor 2, the steering torque sensor 3, the motor current sensor 4 and the motor rotation speed sensor 5 are all general. These are various sensors included in the electric power steering controller. The linear road surface reaction torque calculator 6, the estimated road surface reaction torque calculator 7, the understeer degree calculator 8, and the execution processing selector 9 are all software in the ECU. Realized by arithmetic processing.

Therefore, the actual hardware configuration is expressed as shown in FIG.
FIG. 4 is a block diagram showing an actual hardware configuration example of the understeer suppressing device of FIG. 1. The same components as those described above (see FIG. 1) are denoted by the same reference numerals as those described above, and detailed description thereof is omitted.
In FIG. 4, the electric power steering control ECU 100 includes the functions of the above-described electric power steering controller 10 as well as the functions of the various computing units 6 to 8 and the execution processing selector 9.

The electric power steering control ECU 100 is connected to an engine control ECU 110 and a transmission control ECU 120 via a communication bus.
The engine control ECU 110 and the transmission control ECU 120 correspond to the engine controller 11 and the transmission controller 12 described above, respectively.

As shown in FIG. 4, the engine control ECU 110 and the transmission control ECU 120 are connected to the electric power steering control ECU 100 via a communication bus, and the arithmetic processing by software is executed by the electric power steering control ECU 100, and the selection result of the execution processing selector 9 is It transmits to engine control ECU110 and transmission control ECU120.
As a result, an understeer suppressing device having the above function can be realized without adding a new ECU.

  As described above, the understeer suppression device according to the first embodiment of the present invention includes the linear road surface reaction torque based on the various sensors 1 to 5, the electric motor 20 that assists the steering force, the vehicle speed V, and the steering angle θh. A linear road surface reaction torque calculator 6 for calculating Talign_lin; an estimated road surface reaction torque calculator 7 for calculating an estimated road surface reaction torque Talign_est based on the vehicle speed V, the steering torque Ts, the motor current Imtr, and the motor rotational speed ωmtr; The understeering degree calculator 8 for calculating the understeering degree US_Index of the vehicle based on the comparison between the linear road reaction force torque Talign_lin and the estimated road reaction force torque Talign_est, and the understeering suppression process to be executed based on the understeering degree US_Index are selected. Execution process selector 9 And an electric power steering controller 10 that controls the steering assist torque, an engine controller 11 that controls the engine output, and a transmission controller 12 that transmits the engine output to the drive wheels of the vehicle. When the understeering degree US_Index indicates a value equal to or greater than a predetermined threshold value (first threshold value) Th1, the steering wheel switchback acceleration process using the electric power steering controller 10 (step S11), the engine controller 11 or the transmission controller 12 is selected, and the electric power steering controller 10, the engine controller 11, and the transmission controller 12 execute processing based on the selection result by the execution processing selector 9.

Therefore, by calculating the understeering degree US_Index based on the road surface reaction torque (deviation between the linear road surface reaction torque Talign_lin and the estimated road surface reaction torque Talign_est), the understeer state of the vehicle can be detected early from the sign. .
In addition, when a sign of understeer is detected, the driver is prompted to switch back the steering wheel and the vehicle is automatically decelerated. Effective understeer suppression processing can be executed.

In addition, since the understeer can be detected by using various sensors 1 to 5 included in the general electric power steering controller 10 and with less arithmetic processing than the conventional device, an inexpensive understeer suppressing device is realized. Can do.
Furthermore, since the understeer suppression process is executed only by the electric power steering controller 10, the engine controller 11 and the transmission controller 12 included in the light vehicle or the compact car, a new sensor and an expensive microcomputer are not required, and it is inexpensive. An understeer suppressing device can be realized.

Embodiment 2. FIG.
In the first embodiment, the understeer suppression process to be executed is selected in consideration of only the first threshold Th1 for detecting an understeer sign. However, as shown in FIG. 5, the first threshold Th1 higher than the first threshold Th1 is selected. The understeer suppression process to be executed may be selected step by step in consideration of the two threshold Th2.

A specific operation according to the second embodiment of the present invention will be described below with reference to the flowchart of FIG. 5 together with FIGS.
The configuration of the understeer suppressing device according to Embodiment 2 of the present invention is as shown in FIGS.
Further, in FIG. 5, the same processing (steps S1 to S11) as described above (see FIG. 2) is denoted by the same reference numeral and detailed description is omitted.

  First, after the arithmetic processing based on the detection information from the various sensors 1 to 5 is executed in steps S1 to S8, the execution processing selector 9 compares the understeering degree US_Index with the first threshold Th1 in step S9. If it is determined that US_Index <Th1, no processing (step S10) is selected, and the process returns to step S1.

On the other hand, if it is determined in step S9 that US_Index ≧ Th1, the execution process selector 9 subsequently causes the understeer degree US_Index to be greater than or equal to the first threshold Th1 and less than the second threshold Th2 (corresponding to the understeer predictor region). It is determined whether or not the value is indicated (step S9A).
Note that the second threshold value Th2 corresponding to mild understeer is a determination reference value for detecting a region where the actual yaw rate is slightly separated from the reference yaw rate in FIG. 3 as described above.

If it is determined in step S9A that Th1 ≦ US_Index <Th2 (that is, YES), the execution process selector 9 performs a handle switchback acceleration process by the electric power steering controller 10 as a process to be executed for the understeer sign state. Is selected (step S11A).
As a result, the electric power steering controller 10 executes a handle switching back acceleration process and returns to step S1.

On the other hand, if it is determined in step S9A that US_Index ≧ Th2 (that is, NO), the execution process selector 9 performs an engine controller 11 or a transmission controller 12 as a process to be executed for a slight or higher understeer state. The vehicle deceleration process is selected (step S12A).
As a result, the engine controller 11 or the transmission controller 12 executes a vehicle deceleration process, and returns to step S1.

  As described above, in the understeer suppressing device according to the second embodiment of the present invention, the execution processor 9 has the first threshold Th1 corresponding to the understeer as the predetermined threshold and the degree of understeering than the first threshold Th1. When at least two threshold values including a second threshold value Th2 having a high US_Index are set and the understeering degree US_Index indicates a value that is greater than or equal to the first threshold value Th1 and less than the second threshold value Th2, the steering wheel switchback acceleration process is selected, When the understeering degree US_Index indicates a value equal to or greater than the second threshold Th2, the deceleration process is selected.

Therefore, when an indication of understeer is detected, first, in step S11A, the driver is prompted to turn back the steering wheel by reducing the assist torque from the electric motor 20, so that understeering can be suppressed by turning back the steering wheel of the driver.
As a result, when understeer is suppressed by the driver's steering wheel turning-back process, the automatic deceleration process of the vehicle in step S12A is not executed, so that the driver does not feel uncomfortable due to the deceleration. Therefore, it is possible to realize an understeer suppressing device with less discomfort than in the case of 1.
Further, when an understeer state that is mild or more is detected, the vehicle is automatically decelerated in step S12A, so that the understeer state can be reliably suppressed.

Embodiment 3 FIG.
In the second embodiment (see FIG. 5), the steering wheel turning-back acceleration process (step S11A) is selected when an understeer sign is detected, but an alarm 13 is provided as shown in FIG. As shown in FIG. 7, the notification process (step S13) may be selected when an understeer sign is detected.

The specific operation according to the third embodiment of the present invention will be described below with reference to the block diagram of FIG. 6 and the flowchart of FIG. 7 together with FIG.
6 and 7, the same parts as those described above (see FIGS. 1 and 5) are denoted by the same reference numerals as those described above, and detailed description thereof is omitted.

In the understeer suppressing device according to Embodiment 3 of the present invention shown in FIG. 6, the execution process selector 9A corresponds to the execution process selector 9 described above (see FIG. 1).
Therefore, the understeer suppressing device according to Embodiment 3 of the present invention has the same configuration as that described above (see FIG. 1) except that the alarm 13 is added.
The notification device 13 is configured to notify the driver, for example, by voice or light when an understeer sign is detected.
In FIG. 7, the operation according to the third embodiment of the present invention is different from the above (see FIG. 5) only in step S11A.

  In this case, when the understeering degree US_Index indicates a value that is greater than or equal to the first threshold Th1 and less than the second threshold Th2 (understeer sign), the execution process selector 9A selects the notification process by the notification unit 13 Then (step S13), thereby the notification device 13 executes notification processing.

  On the other hand, when the understeering degree US_Index indicates a value equal to or larger than the second threshold value (understeering state of lighter or greater), the execution process selector 9A selects the vehicle deceleration process by the engine controller 11 or the transmission controller 12 ( In step S12A), the engine controller 11 and the transmission controller 12 thereby execute a deceleration process.

  As described above, the understeer suppressing device according to the third embodiment of the present invention includes the notification device 13 that performs notification processing based on the selection result of the execution processing selector 9A, and the execution processing selector 9A has a predetermined value. As threshold values, at least two threshold values including a first threshold value Th1 corresponding to an indication of understeer and a second threshold value Th2 having an understeering degree US_Index higher than the first threshold value Th1 are set, and the understeering degree US_Index is equal to or greater than the first threshold value Th1. And when the value less than 2nd threshold value Th2 is shown, the alerting | reporting process (step S13) by the alerting | reporting device 13 is selected, and when understeering degree US_Index shows the value more than 2nd threshold value Th2, deceleration process (step S12A). ) Is selected.

Therefore, when an understeer sign is detected, the alarm 13 is first driven to notify the driver that the understeer sign is present, so that the driver turns back the steering wheel or decelerates the vehicle. Understeer can be suppressed.
In addition, when understeer is suppressed by the driver's operation in response to the alarm device 13, the automatic deceleration process (step S12A) of the vehicle is not executed, and therefore, more than in the case of the above-described second embodiment. An understeer suppressing device with less discomfort can be realized.

Embodiment 4 FIG.
In the third embodiment (see FIG. 7), when understeering that is light or more (second threshold Th2 or more) is detected, vehicle deceleration processing (step S12A) by the engine controller 11 or the transmission controller 12 is performed. However, instead of this, the steering switch back acceleration process by the electric power steering controller may be executed, or the steering switch back acceleration process by the electric power steering controller 10 may be executed as well as the deceleration process. Good.

Hereinafter, a fourth embodiment of the present invention will be described with reference to FIG. 8 together with FIG. 3 and FIG.
In the fourth embodiment of the present invention, the deceleration process and the steering wheel turn-back acceleration process are executed when a slight understeer is detected.

FIG. 8 is a flowchart showing the operation according to the fourth embodiment of the present invention. When understeer of a slight degree (second threshold Th2) or more is detected, not only the deceleration process (step S12B) but also the stage of the understeering degree US_Index. Correspondingly, a processing routine in the case where the steering switch back acceleration processing (step S11B) by the electric power steering controller 10 is executed is shown.
In FIG. 8, the same components as those described above (see FIG. 7) are denoted by the same reference numerals as those described above, and detailed description thereof is omitted.

The execution process selector 9B (not shown) according to the fourth embodiment of the present invention is only partially different in function from the execution process selector 9A described above (see FIG. 6).
In this case, in addition to the first threshold Th1 and the second threshold Th2, the execution process selector 9B sets a third threshold Th3 (see FIG. 3) for detecting an understeer that is medium or higher, and is mild (second threshold Th2). For the above-described understeer, the steering wheel turning-back acceleration process (step S11B) is selected, and for the moderate (third threshold Th3 or more) understeer, the deceleration process (step S12B) is selected.

  In FIG. 8, the execution process selector 9B first sets the understeering degree US_Index to a value that is equal to or greater than the first threshold value Th1 and less than the second threshold value Th2 (predictive state of understeer) in steps S9 and S9A. In the case of showing, the notification process by the notification unit 13 is selected (step S13), whereby the notification unit 13 executes the notification process.

On the other hand, if it is determined in step S9A that US_Index ≧ Th2 (that is, NO), then the execution process selector 9B determines whether or not the understeering degree US_Index indicates a value less than the third threshold Th3 ( Step S9B).
Note that the third threshold Th3 for understeer detection of medium or higher is a determination reference value for detecting a region where the actual yaw rate is relatively far from the reference yaw rate in FIG.

If it is determined in step S9B that US_Index <Th3 (that is, YES), the execution process selector 9B performs a process to be executed for a mild understeer state (greater than or equal to the second threshold Th2 and less than the third threshold Th3). Then, the steering switch back acceleration process by the electric power steering controller 10 is selected (step S11B).
As a result, the electric power steering controller 10 executes the steering wheel turn-back acceleration process by reducing the assist torque from the electric motor 20, and returns to step S1.

On the other hand, if it is determined in step S9B that US_Index ≧ Th3 (that is, NO), the execution process selector 9B performs the engine controller 11 and the transmission controller as processes to be executed for a moderate or higher understeer state. 12 is selected (step S12B).
As a result, the engine controller 11 or the transmission controller 12 executes a vehicle deceleration process, and returns to step S1.

  As described above, the understeer suppressing device according to the fourth embodiment of the present invention includes the alarm 13 (see FIG. 6), and the execution process selector 9B includes the first threshold Th1 corresponding to the understeer sign, and the first threshold Th1. A second threshold Th2 having a higher understeering degree US_Index than the first threshold Th1 (corresponding to mild understeering), and a third threshold Th3 having a higher understeering degree US_Index than the second threshold Th2 (corresponding to moderate or higher understeering) When the understeering degree US_Index indicates a value not less than the first threshold Th1 and less than the second threshold Th2, the notification process (step S13) by the notification unit 13 is selected, and the understeering degree US_Index is selected. Indicates a value greater than or equal to the second threshold Th2 and less than the third threshold Th3, Bundle switchback promotion processing to select (step S11B), understeer degree US_Index is to indicate a third threshold value Th3 or more values, selects the deceleration processing (step S12B).

  Therefore, when an understeer sign is detected, the driver 13 is first driven to notify the driver that the understeer sign is in the same manner as in the third embodiment, so the driver switches back the handle. Alternatively, understeer can be suppressed by decelerating the vehicle.

  In addition, when understeer is suppressed by the operation of the driver in response to the alarm device 13, the steering wheel turning-back acceleration process (step S11B) and the vehicle automatic deceleration process (step S12B) are not executed. Fewer understeer suppression devices can be realized.

Further, even when a slight understeer is detected, first, the driver is prompted to turn back the steering wheel in step S11B, so that understeer can be suppressed by the steering wheel turning back of the driver.
Further, when understeer is suppressed by turning back the steering wheel of the driver, the automatic deceleration process (step S11B) of the vehicle is not executed, so that the driver does not feel uncomfortable due to the deceleration. As a result, it is possible to realize an understeer suppressing device with less discomfort.

In the third and fourth embodiments, the notification device 13 using voice or light is used as the notification device. However, the notification device 13 is not limited to the notification device, and for example, the electric power steering controller 10 functions as the notification device. You may let them.
In this case, since it is not necessary to provide the alarm device 13, further cost reduction can be realized.

  As specific notification processing by the electric power steering controller 10, for example, the steering assist torque is vibrated to vibrate the steering wheel by vibrating the supply current to the electric motor 20, or the supply to the electric motor 20 is performed. It is conceivable to increase the steering assist torque by rapidly increasing the current, thereby giving the driver a feeling of lack of road reaction force.

In the first to fourth embodiments, the understeer degree US_Index is calculated based on the deviation between the linear road surface reaction force torque Talign_lin and the estimated road surface reaction force torque Talign_est as shown in Expression (2). The calculation formula is not limited to the formula (2), and another calculation formula based on a comparison between the linear road surface reaction force torque Talign_lin and the estimated road surface reaction force torque Talign_est may be used.
For example, a differential value of a deviation between the linear road surface reaction force torque Talign_lin and the estimated road surface reaction force torque Talign_est may be used, or a ratio between the linear road surface reaction force torque Talign_lin and the estimated road surface reaction force torque Talign_est may be used. .

  In the second and fourth embodiments, in order to realize the understeer suppression process with less uncomfortable feeling for the driver, when the understeer degree US_Index is increased, first, the driver is prompted to perform the steering wheel return by the steering wheel return acceleration process. Although the automatic deceleration process of the vehicle is executed only when understeer is not suppressed even by turning back the steering wheel of the driver, the stepwise execution order of the process may be set in reverse.

  In other words, when priority is given to automatic understeer suppression processing in order to prevent the driver from performing a steering wheel turning-back operation as much as possible, when the understeering degree US_Index increases, first, an understeer sign state (or a mild understeering state) In the state), the automatic deceleration process of the vehicle is selected and executed, and only when the understeer is not suppressed by the deceleration process (or the moderate or higher understeer state), the driver may be prompted to switch back the steering wheel. .

In this way, even if the execution order of understeer suppression processing is reversed, compared to the case where understeer suppression control is executed after understeering occurs as in the conventional device, early and effective understeer suppression processing is realized. can do.
Moreover, while using various sensors with which the general electric power steering controller 10 is provided, and detecting understeer with less arithmetic processing than the conventional device, the electric power steering controller 10 with which a light vehicle or a compact car has Since the understeer suppressing process is executed only by the engine controller 11 and the transmission controller 12, an inexpensive understeer suppressing device can be realized without requiring a new sensor or an expensive microcomputer.

In the first, second, and fourth embodiments, as an understeer suppression process, a steering wheel turning back acceleration process using the electric motor 20 by the electric power steering controller 10 and a deceleration using the engine controller 11 or the transmission controller 12 are performed. The process is selected, but at least one of the steering wheel return acceleration process and the deceleration process may be selected.
Similarly, in the third embodiment (see FIG. 7), the deceleration process (step S12A) is selected in the mild understeer state. However, instead of the deceleration process, at least one of the steering wheel return acceleration process and the deceleration process is selected. Processing may be selected.

It is a block block diagram which shows the understeer suppression apparatus which concerns on Embodiment 1 of this invention. It is a flowchart which shows operation | movement of the understeer suppression apparatus which concerns on Embodiment 1 of this invention. It is explanatory drawing which shows the relationship between the steering angle by this Embodiment 1, and a linear road surface reaction torque, a road surface reaction torque, a yaw rate, and an understeer state. It is a block diagram which shows the hardware structural example of the understeer suppression apparatus which concerns on Embodiment 1 of this invention. It is a flowchart which shows operation | movement of the understeer suppression apparatus which concerns on Embodiment 2 of this invention. It is a block block diagram which shows the understeer suppression apparatus which concerns on Embodiment 3 of this invention. It is a flowchart which shows operation | movement of the understeer suppression apparatus which concerns on Embodiment 3 of this invention. It is a flowchart which shows operation | movement of the understeer suppression apparatus which concerns on Embodiment 4 of this invention.

Explanation of symbols

  1 operation angle sensor (steering angle detection means), 2 vehicle speed sensor (vehicle speed detection means), 3 steering torque sensor (steering torque detection means), 4 motor current sensor (motor current detection means), 5 motor rotation speed sensor (motor rotation) Speed detection means), 6 linear road surface reaction force torque calculator (linear road surface reaction torque calculation means), 7 estimated road surface reaction torque calculator (estimated road surface reaction torque calculation means), 8 understeer degree calculator (understeer degree calculation) Means), 9, 9A execution process selector (execution process selection means), 10 electric power steering controller (electric power steering control means), 11 engine controller (engine control means), 12 transmission controller (transmission control means), 13 Alarm (notification means), Talign_lin Linear road surface reaction torque, Talign_est The road surface reaction force torque, US_Index understeer degree.

Claims (7)

Vehicle speed detecting means for detecting the vehicle speed of the vehicle;
Steering angle detection means for detecting the steering angle of the steering wheel of the vehicle;
Steering torque detection means for detecting steering torque applied to the steering wheel;
An electric motor for assisting a steering force applied to the steering wheel;
Motor current detecting means for detecting a motor current flowing in the electric motor;
Motor rotation speed detection means for detecting the motor rotation speed of the electric motor;
Linear road reaction force torque calculating means for calculating linear road reaction force torque received by the vehicle based on the vehicle speed and the steering angle;
Based on the vehicle speed, the steering torque, the motor current, and the motor rotation speed, estimated road surface reaction force torque calculating means for calculating an estimated road surface reaction torque received by the vehicle;
An understeer degree calculating means for calculating an understeer degree of the vehicle based on a comparison between the linear road reaction force torque and the estimated road reaction force torque;
Execution process selection means for selecting an understeer suppression process to be executed based on the degree of understeer;
Electric power steering control means for controlling steering assist torque output from the electric motor;
Engine control means for controlling the engine output of the vehicle;
Transmission control means for transmitting the engine output to the drive wheels of the vehicle,
The execution process selection means, when the understeer degree shows a value greater than or equal to a predetermined threshold, a steering wheel return acceleration process for suppressing the steering assist torque using the electric power steering control means, and the engine control means or Selecting at least one of deceleration processing using the transmission control means;
The electric power steering control unit, the engine control unit, and the transmission control unit execute processing based on a selection result by the execution processing selection unit. The execution process selection means includes:
As the predetermined threshold, at least two thresholds including a first threshold corresponding to a sign of understeer and a second threshold having a higher degree of understeer than the first threshold are set.
When the degree of understeer indicates a value that is greater than or equal to the first threshold value and less than the second threshold value, the steering wheel switchback promoting process is selected,
2. The understeer suppressing device according to claim 1, wherein the deceleration process is selected when the degree of understeer indicates a value equal to or greater than the second threshold value. The execution process selection means includes:
As the predetermined threshold, at least two thresholds including a first threshold corresponding to a sign of understeer and a second threshold having a higher degree of understeer than the first threshold are set.
When the degree of understeer is not less than the first threshold value and less than the second threshold value, the deceleration process is selected,
2. The understeer suppressing device according to claim 1, wherein when the understeer degree indicates a value equal to or greater than the second threshold value, the steering wheel switchback promoting process is selected. Comprising notification means for executing notification processing based on a selection result of the execution processing selection means;
The execution process selection means includes:
As the predetermined threshold, at least two thresholds including a first threshold corresponding to a sign of understeer and a second threshold having a higher degree of understeer than the first threshold are set.
If the degree of understeer indicates a value that is greater than or equal to the first threshold value and less than the second threshold value, the notification process by the notification unit is selected,
2. The understeer suppressing device according to claim 1, wherein when the understeer degree indicates a value equal to or greater than the second threshold value, at least one of the steering wheel switchback acceleration process and the deceleration process is selected. Comprising notification means for executing notification processing based on a selection result of the execution processing selection means;
The execution process selection means includes:
The predetermined threshold value includes at least 3 including a first threshold value corresponding to an indication of understeer, a second threshold value having a higher understeer level than the first threshold value, and a third threshold value having a higher understeer level than the second threshold value. Set two thresholds,
If the degree of understeer indicates a value that is greater than or equal to the first threshold value and less than the second threshold value, the notification process by the notification unit is selected,
When the degree of understeer indicates a value that is greater than or equal to the second threshold value and less than the third threshold value, the steering wheel switchback promoting process is selected,
2. The understeer suppressing device according to claim 1, wherein the deceleration process is selected when the degree of understeering is greater than or equal to the third threshold value. Comprising notification means for executing notification processing based on a selection result of the execution processing selection means;
The execution process selection means includes:
The predetermined threshold value includes at least 3 including a first threshold value corresponding to an indication of understeer, a second threshold value having a higher understeer level than the first threshold value, and a third threshold value having a higher understeer level than the second threshold value. Set two thresholds,
If the degree of understeer indicates a value that is greater than or equal to the first threshold value and less than the second threshold value, the notification process by the notification unit is selected,
When the understeer degree indicates a value that is greater than or equal to the second threshold value and less than the third threshold value, the deceleration process is selected,
2. The understeer suppressing device according to claim 1, wherein when the understeering degree indicates a value equal to or greater than the third threshold, the steering wheel switchback promoting process is selected.   The understeer according to any one of claims 4 to 6, wherein the informing means executes the informing process by vibrating or increasing the steering assist torque by the electric power steering control means. Suppression device.

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