JP4443582B2 - Understeer suppression device - Google Patents

Description

  This invention detects understeer of the vehicle by detecting understeer of the vehicle (a phenomenon in which the lateral grip of the front wheel tire reaches the limit and causes the vehicle to slip excessively) caused by excessive steering on a slippery road surface. With regard to the device, in particular, the transmission control means changes the speed ratio to the low speed side (the side where the number of drive wheel revolutions per revolution of the prime mover is low) (hereinafter referred to as “shift down”), and the prime mover controller reduces the output of the prime mover. The present invention relates to a technique for suppressing understeer by automatically decelerating the vehicle and decelerating the vehicle.

  Conventionally, there has been proposed an understeer suppression device that detects understeer of a vehicle, automatically downshifts by a transmission controller and reduces motor output by a prime mover controller, and suppresses understeer by decelerating the vehicle. (For example, refer to Patent Document 1).

  In general, the force that can be generated in a vehicle tire is expressed using a friction circle as shown in FIG. FIG. 9 is an explanatory diagram showing the force that can be generated in the tire. In FIG. 9, the horizontal axis indicates the lateral force, the vertical axis indicates the driving force, the negative axis indicates the braking force, and the radius of the friction circle. Indicates the maximum friction force (determined by the vertical load and the road surface friction coefficient) that can be generated between the tire and the road surface.

  As is clear from FIG. 9, the frictional force used while the vehicle is traveling is represented by the vector sum of the driving braking force along the traveling direction and the lateral force perpendicular to the traveling direction. However, if both the driving braking force and lateral force are large, the driving braking force has priority over the lateral force, and the vector sum is always within the friction circle (the maximum value of the vector sum is limited to the radius of the friction circle). )

On the other hand, FIG. 10 is an explanatory diagram showing a friction circle at the time of understeering, and shows a front wheel friction circle when the front wheel drive vehicle during cornering is understeering.
During turning, the driving force for forward movement and the lateral force for turning are generated at the same time. However, as described above, the driving braking force has priority over the lateral force, or the vector sum Because the maximum value is limited to the radius of the friction circle (that is, even if the driving braking force is zero, the maximum lateral force is limited to the radius of the friction circle), the lateral force required for turning is sufficient. It is in a state that has not occurred.

In the above-mentioned conventional device, understeer of the vehicle is detected, downshift and motor output reduction are performed, and understeer is suppressed by decelerating the vehicle, but when excessive braking force is generated from the state of FIG. Since the braking force is prioritized over the lateral force, as shown in FIG. 11, the lateral force may further decrease, and as a result, understeer may be promoted. Although an example of a front-wheel drive vehicle is shown here, in the case of a rear-wheel drive vehicle as well, if excessive braking force is generated in the same manner, the lateral force of the rear wheel is reduced, and oversteer can be induced. There is sex.
JP 2003-31465 A

  In the conventional understeer suppression device, since understeer is detected by detecting the understeer of the vehicle, downshifting and reducing the motor output and decelerating the vehicle, for example, excessive braking force is generated from the state of FIG. Then, since the braking force has priority over the lateral force, the lateral force is further reduced as shown in FIG.

  The present invention has been made in order to solve the above-described problems. When detecting vehicle understeer, when decelerating the vehicle by downshifting and reducing the prime mover output, the gear ratio and the prime mover output are determined according to the locking tendency of the drive wheels. It is an object of the present invention to obtain an understeer suppressing device that can prevent understeer accurately by preventing excessive braking force from being generated.

An understeer suppressing device according to the present invention includes an understeer detecting means for detecting understeer of a vehicle, a prime mover control means for controlling a prime mover output from the prime mover of the vehicle, and a transmission for controlling transmission of the prime mover output to the wheels of the vehicle and a gear ratio A control means and a drive wheel lock tendency detection means for detecting a lock tendency of the drive wheel of the vehicle, and when the understeer of the vehicle is detected by the understeer detection means, the transmission control means changes the gear ratio to the low speed side. An understeer suppressing device that performs at least one of a first deceleration control and a second deceleration control that reduces a prime mover output by a prime mover control means, wherein the understeer detection means includes a vehicle speed detection means that detects a vehicle speed of the vehicle. , Steering torque to detect steering torque by vehicle driver Output means, an electric motor for assisting the steering torque, motor current detection means for detecting the motor current of the electric motor, motor rotation speed detection means for detecting the motor rotation speed of the electric motor, vehicle speed, steering torque, and motor current Road surface reaction force torque calculating means for calculating an estimated road surface reaction force torque based on the motor rotation speed and a road surface reaction force torque reference change rate calculating means for calculating a road surface reaction force torque reference change rate based on the motor rotation speed and vehicle speed. The vehicle understeer is detected based on the comparison between the calculated value of the road surface reaction torque standard change rate and the differential value of the estimated road surface reaction torque, and the transmission control means is executing the first deceleration control. In addition, the gear ratio is controlled based on the output of the drive wheel lock tendency detecting means, and the prime mover control means performs the drive wheel lock during the execution of the second deceleration control. Based on the output of the direction detecting means, and controls the prime mover output.

  According to the present invention, when the vehicle understeer is detected, excessive braking force can be prevented and understeer can be suppressed accurately.

Embodiment 1 FIG.
Embodiment 1 of the present invention will be described below with reference to the drawings. 1 is a block diagram showing a schematic configuration of an understeer suppressing device according to Embodiment 1 of the present invention.
In FIG. 1, an understeer suppression device includes an electric power steering controller (understeer detection means) 1, a transmission controller (transmission control means) 2, a prime mover controller (prime mover control means) 3, and a drive wheel lock tendency detector. 4 is provided.
Each of the controllers 1 to 3 and the driving wheel lock tendency detector 4 are connected to a communication bus (for example, CAN) and can perform message communication with each other.

  An electric power steering controller (hereinafter abbreviated as “electric power steering controller”) 1 detects understeer of a vehicle (not shown). The prime mover controller 3 controls the prime mover output from the prime mover of the vehicle, and the transmission controller 2 controls the transmission of the prime mover output to the wheels of the vehicle and the gear ratio. The drive wheel lock tendency detector 4 detects the lock tendency of the drive wheels of the vehicle.

Next, an electric power steering controller (understeer detection means) 1 used in Embodiment 1 of the present invention will be described with reference to FIGS.
Here, a portion related to understeer detection is shown, and a portion related only to steering assist torque control is common and is omitted.

  In the understeer suppression device according to Embodiment 1 of the present invention, the transmission controller 2 or the prime mover controller 3 outputs the output of the drive wheel lock tendency detector 4 when the electric power steering controller 1 detects the understeer state of the vehicle. In response to this, vehicle deceleration control is performed.

That is, at the time of understeer detection, at least one of the first deceleration control for changing the gear ratio to the low speed side by the transmission controller 2 and the second deceleration control for reducing the motor output by the prime mover controller 3 is performed. Is called.
The transmission controller 2 controls the gear ratio based on the output of the drive wheel lock tendency detector 4 during the execution of the first deceleration control, and the prime mover controller 3 is executing the second deceleration control. In addition, the motor output is controlled based on the output of the drive wheel lock tendency detector 4.

3 is a functional block diagram showing a specific example of the electric power steering controller 1. FIG.
FIG. 2 is a block diagram showing a specific example of the electric power steering controller 1 used in Embodiment 1 of the present invention, and FIG. 3 is a flowchart showing the operation of the electric power steering controller 1. Here, only the portion related to understeer detection is shown, and the portion related to general steering assist torque control is not shown.
FIG. 4 is an explanatory diagram showing the relationship between the steering angle θh and the understeer state (horizontal axis), the reference road surface reaction force torque Talign_ref, the road surface reaction force torque, and the yaw rate (vertical axis).

  In FIG. 2, the electric power steering controller 1 includes a steering angle sensor 11, a vehicle speed sensor 12, a steering torque sensor 13, a motor current sensor 14, and a motor rotation speed sensor 15, a reference road surface reaction force torque calculator 16, A calculation processing unit including an estimated road surface reaction torque calculator (estimated road surface reaction torque calculation means) 17 and an understeer determination unit 18 and an electric motor (not shown) of a steering assist torque control system (electric power steering) are provided. Yes.

The various sensors 11 to 15 are provided in association with a vehicle steering system (not shown) including an electric power steering device.
A steering angle sensor 11 detects a steering angle θh of a handle (not shown) operated by a driver of the vehicle, and a vehicle speed sensor (vehicle speed detection means) 12 detects a vehicle speed V of the vehicle and detects a steering torque sensor ( (Steering torque detecting means) 13 detects a steering torque Ts applied to the steering wheel by the driver.
A motor current sensor (motor current detection means) 14 detects a motor current Imtr flowing in the electric motor, and a motor rotation speed sensor (motor rotation speed detection means) 15 detects a motor rotation speed ωmtr of the electric motor.

The steering angle θh and the vehicle speed V from the steering angle sensor 11 and the vehicle speed sensor 12 are input to the reference road surface reaction force torque calculator 16.
The vehicle speed V, the steering torque Ts, the motor current Imtr, and the motor rotation speed ωmtr from the vehicle speed sensor 12, the steering torque sensor 13, the motor current sensor 14, and the motor rotation speed sensor 15 are input to the estimated road surface reaction force torque calculator 17. .

The reference road surface reaction torque calculator 16 calculates a reference road surface reaction torque Talign_ref based on the steering angle θh and the vehicle speed V, and inputs it to the understeer determination unit 18.
The estimated road surface reaction force torque calculator 17 calculates an estimated road surface reaction force torque Talign_est based on the vehicle speed V, the steering torque Ts, the motor current Imtr, and the motor rotation speed ωmtr and inputs the calculated road surface reaction force torque Talign_est to the understeer determination unit 18.
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 understeer determination unit 18 determines whether or not the vehicle is understeer based on a comparison between the reference road surface reaction force torque Talign_ref and the estimated road surface reaction force torque Talign_est, and outputs an understeer determination result.

Hereinafter, the operation of the electric power steering controller 1 will be described with reference to FIGS. 3 and 4. The electric power steering controller 1 periodically executes the operation flow of FIG.
In FIG. 3, first, the steering angle sensor 11 detects the steering angle θh (step S1), the vehicle speed sensor 22 detects the vehicle speed V (step S2), and the steering torque sensor 13 detects the steering torque Ts (step S3). ), The motor current sensor 14 detects the motor current Imtr (step S4), and the motor rotation speed sensor 15 detects the motor rotation speed ωmtr (step S5).

  Next, the reference road surface reaction force torque calculator 16 calculates the reference road surface reaction force torque Talign_ref 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 V, it is obtained in advance as a table value Kalign (V) corresponding to each vehicle speed V.

Next, the estimated road surface reaction torque calculator 17 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 processing of the estimated road surface reaction torque Talign_est is not described here, but a known method (for example, Japanese Patent No. 3353770, Japanese Patent Application Laid-Open No. 2003-312521, Japanese Patent Application Laid-Open No. 2005-324737). Reference) can be used.

  Next, the understeer determination unit 18 calculates the understeering degree US_Index as in the following equation (2) based on the road surface reaction force torque deviation between the reference road surface reaction force torque Talign_ref and the estimated road surface reaction force torque Talign_est ( Step S8).

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

Here, the relationship between the steering angle θh and the understeer state (refer to the horizontal axis), the standard road surface reaction force torque Talign_ref, the road surface reaction force torque and the yaw rate (refer to the vertical axis) will be described with reference to the explanatory diagram of FIG. .
FIG. 4 shows the relationship between the reference yaw rate and the actual yaw rate when the steering angle θh is increased from zero in constant vehicle speed driving on a low friction coefficient road surface (see the upper row), the reference road surface reaction force torque Talign_ref, and It shows the relationship with the road surface reaction torque (see the lower part).

In FIG. 4, when the steering angle θh is increased, the reference road surface reaction force torque Talign_ref and the reference yaw rate (see the solid line) increase linearly as the steering angle θh increases.
On the other hand, the road surface reaction torque (see the two-dot chain line) saturates away from the value of the reference road surface reaction torque Talign_ref when the steering angle θh is equal to or greater than the first steering angle θh1, and the road surface reaction force between the two torques. The torque deviation (understeering degree US_Index = | standard road surface reaction torque Torig_ref−road surface reaction torque |) increases.

  When the steering angle θh further increases and becomes a region greater than or equal to the second steering angle θh2 (> θh1), the actual yaw rate (see the one-dot chain line) saturates away from the reference yaw rate value, and the yaw rate deviation between both yaw rates (Standard yaw rate-actual yaw rate) increases. That is, as the steering angle θh increases, the degree of understeer US_Index increases and the understeer of the vehicle becomes stronger.

  As shown in FIG. 4, the road surface reaction torque saturation occurs earlier than the actual yaw rate by “θh2−θh1”. This is, for example, known from the publication “Nakajima et al., A Vehicle ST-ate”. Detection Method Based on EST-imimated Aligning Torque using EPS, 05AC-46, 2005 SAE ". Therefore, in the first embodiment of the present invention, this phenomenon is used to detect the degree of understeer.

  Further, the saturation mechanism of the road surface reaction torque is also described in the above-mentioned Patent Document 1 (Japanese Patent Laid-Open No. 2003-31465, paragraphs “0006” to [0009]), and is therefore omitted. The road surface reaction torque in Form 1 is synonymous with the self-aligning torque described in Patent Document 1).

  Returning to FIG. 3, following step S8, the understeer determiner 18 determines whether the vehicle is understeered by determining whether the understeering degree US_Index exceeds a predetermined threshold Th_us (step S9), and step S9. Is transmitted to the transmission controller 2 and the prime mover controller 3 (step S10, step S11), and the process of FIG.

That is, if it is determined in step S9 that US_Index ≦ Th_us (that is, NO), a determination result indicating that there is no understeer is transmitted (step S10), and the processing routine of FIG. 3 ends.
On the other hand, if it is determined in step S9 that US_Index> Th_us (that is, YES), a determination result indicating understeer is transmitted (step S11), and the processing routine of FIG. 3 ends.

Next, the operation of the transmission controller 2 used in Embodiment 1 of the present invention will be described with reference to FIG. Since the configuration of the transmission controller 2 is common, it is omitted.
FIG. 5 is a flowchart showing the operation of the transmission controller 2. The transmission controller 2 periodically repeats the operation flow of FIG.

In FIG. 5, the transmission controller 2 first receives the understeer determination result transmitted from the electric power steering controller 1 (step S21), and determines whether or not the determination result indicates understeer (step S22). .
If it is determined in step S22 that there is no understeer (that is, NO), normal processing (transmission control according to the accelerator pedal depression amount, vehicle speed, etc.) is performed (step S23), and the current processing in FIG.

On the other hand, if it determines with understeering (namely, YES) in step S22, 1st deceleration control (steps S24-S27) with respect to a vehicle will be performed.
First, a drive wheel lock tendency value DL transmitted from the drive wheel lock tendency detector 4 (details will be described later) is received (step S24), and it is determined whether or not the drive wheel lock tendency value DL exceeds a threshold value Th_lock. (Step S25).

If it is determined in step S25 that DL ≦ Th_lock (that is, NO), the gear ratio is shifted down by a predetermined amount to the low speed side (step S26), and the process of FIG.
On the other hand, if it is determined in step S25 that DL> Th_lock (that is, YES), the gear ratio is changed (shifted up) by a predetermined amount to the high speed side (step S27), and the process of FIG. .

  As a result, the transmission controller 2 repeats the first deceleration control (steps S24 to S27) while the understeer of the vehicle continues, and the drive wheel lock tendency value DL does not exceed the threshold Th_lock. Since the gear ratio is changed by a predetermined amount toward the lower speed side, an appropriate braking force can be generated.

Next, the operation of the prime mover controller 3 used in Embodiment 1 of the present invention will be described with reference to FIG. In addition, about the structure of the motor | power_engine controller 3, since it is common, it abbreviate | omits.
FIG. 6 is a flowchart showing the operation of the prime mover controller 3. The prime mover controller 3 periodically executes the operation flow shown in FIG. In FIG. 6, steps S31 to S35 are processes corresponding to steps S21 to S25 described above (see FIG. 5).

The motor controller 3 first receives the understeer determination result transmitted from the electric power steering controller 1 (step S31), and determines whether or not the determination result indicates understeer (step S32).
If it is determined in step S32 that there is no understeer (that is, NO), normal processing (primary motor output control according to the accelerator pedal depression amount, prime mover state, etc.) is performed (step S33), and the current processing of FIG. 6 is performed. finish.

On the other hand, if it is determined in step S32 that the vehicle is understeered (that is, YES), second deceleration control (steps S34 to S37) is performed on the vehicle.
First, the driving wheel lock tendency value DL transmitted from the driving wheel lock tendency detector 4 is received (step S34), and it is determined whether or not the driving wheel lock tendency value DL exceeds a threshold value Th_lock (step S35).

If it is determined in step S35 that DL ≦ Th_lock (that is, NO), the motor output is reduced by a predetermined amount (step S36), and the process of FIG.
On the other hand, if it is determined in step S35 that DL> Th_lock (that is, YES), the motor output is increased by a predetermined amount (step S37), and the process of FIG.

  Thus, the prime mover controller 3 repeats the second deceleration control (steps S34 to S37) while the understeer of the vehicle continues, and the driving wheel lock tendency value DL does not exceed the threshold Th_lock. Since the prime mover output is reduced by a predetermined amount, an appropriate braking force can be generated.

Next, the drive wheel lock tendency detector 4 used in Embodiment 1 of the present invention will be described with reference to FIGS.
FIG. 7 is a block diagram showing a specific example of the drive wheel lock tendency detector 4. In FIG. 7, the drive wheel lock tendency detector 4 includes a drive wheel lock tendency value calculator 41 that calculates a drive wheel lock tendency value DL, and wheel speed sensors 42 to 45 that detect the wheel speed of each wheel of the vehicle. I have.

  The driving right wheel speed sensor 42 detects the driving right wheel speed VFR, the driving left wheel speed sensor 43 detects the driving left wheel speed VFL, and the non-driving right wheel speed sensor 44 detects the non-driving right wheel speed VRR. The left wheel speed sensor 45 detects the non-drive left wheel speed VRL and inputs each detected value to the drive wheel lock tendency value calculator 41.

FIG. 8 is a flowchart showing the operation of the drive wheel lock tendency detector 4. The drive wheel lock tendency detector 4 periodically and repeatedly executes the operation flow of FIG.
In FIG. 8, first, the wheel speed sensors 42 to 45 detect wheel speeds VFR, VFL, VRR, and VRL (step S41).

  Subsequently, the drive wheel lock tendency value calculator 41 calculates the drive wheel lock tendency value DL using the wheel speeds VFR, VFL, VRR, and VRL as shown in the following equation (3) (step S42).

  Finally, the drive wheel lock tendency value calculator 41 transmits the calculated value of the drive wheel lock tendency value DL to the transmission controller 2 and the prime mover controller 3 (step S43), and ends the process of FIG. .

As described above, according to the first embodiment of the present invention, the electric power steering controller (understeer detection means) 1, the transmission controller 2, the prime mover controller 3, and the drive wheel lock tendency detector 4 are provided. When the understeer of the vehicle is detected by the understeer detector 1, the first deceleration control for changing the gear ratio to the low speed side by the transmission controller 2 and the second deceleration for reducing the prime mover output by the prime mover controller 3 The electric power steering controller 1 is a vehicle speed sensor 12 that detects a vehicle speed V of a vehicle, and a steering torque sensor 13 that detects a steering torque Ts by a driver of the vehicle. An electric motor for assisting the steering torque Ts, and a motor current sensor 14 for detecting the motor current Imtr of the electric motor; A motor rotation speed sensor 15 that detects a motor rotation speed ωmtr of the electric motor, an estimated road surface reaction force torque calculation that calculates an estimated road surface reaction force torque Talign_est based on the vehicle speed V, the steering torque Ts, the motor current Imtr, and the motor rotation speed ωmtr. And a road surface reaction force torque reference rate change rate calculating means for calculating a road surface reaction force torque reference change rate Talign_rate_ref based on the motor rotational speed ωmtr and the vehicle speed V, and a calculated value and an estimate of the road surface reaction force torque reference change rate Talign_rate_ref. Based on the comparison with the differential value Talign_rate_est of the road surface reaction torque, the vehicle understeer is detected, and the transmission controller 2 outputs the output of the drive wheel lock tendency detector 4 (drive wheel) during the execution of the first deceleration control. Based on lock tendency value DL) Since the prime mover controller 3 controls the speed change ratio and controls the prime mover output based on the output of the drive wheel lock tendency detector 4 (drive wheel lock tendency value DL) during execution of the second deceleration control, The reduction of the lateral force due to the braking force can be prevented, and understeer can be suppressed accurately.

Specifically, the drive wheel lock tendency detector 4 can calculate the drive wheel lock tendency value DL as shown in Equation (3) based on at least the vehicle wheel speeds VFR, VFL, VRR, and VRL. .
The understeer detector 1 includes a vehicle speed sensor 12, a steering torque sensor 13, an electric motor, a motor current sensor 14, a motor rotation speed sensor 15, and an estimated road surface reaction force torque calculator 17. Understeer of the vehicle can be detected based on the calculated value of the reaction force torque Talign_est.

The electric power steering controller 1 according to the first embodiment calculates the estimated road surface reaction force torque Talign_est and the reference road surface reaction force torque Talign_ref in order to detect understeer, and sets the absolute value of the deviation between the two as the understeer degree US_Index. When the understeering degree US_Index exceeds a predetermined threshold Th_us, the understeer state is determined. However, the understeer determination method based on the estimated road surface reaction force torque Talign_est is not limited to this.
For example, the ratio of the estimated road surface reaction torque Talign_est and the standard road surface reaction torque Talign_ref may be used as the understeer degree US_Index.

  Further, the estimated road surface reaction force torque Talign_est calculated as described above is time-differentiated to obtain an “estimated road surface reaction torque torque change rate (differential value) Talign_rate_est”, and road surface reaction force torque reference change rate calculation means is provided. The “road surface reaction force torque reference change rate Talign_rate_ref” may be calculated by the following equation (4).

However, in Formula (4), ωh is a steering wheel steering speed, which is a value obtained by multiplying the motor rotation speed ωmtr by a gear ratio. Further, Kalign (V) is a table value similar to that in Expression (1).
That is, in the electric power steering controller (understeer detection means) 1, the road surface reaction force torque reference rate change rate calculation means calculates the road surface reaction force torque reference change rate Talign_rate_ref based on the motor rotational speed ωmtr and the vehicle speed V.
In this case, the understeering degree US_Index is expressed by the following equation (5).

Thereby, understeer can be detected based on the saturation phenomenon of the road surface reaction torque as in the first embodiment. This is because, when the road surface reaction torque is saturated, a difference occurs between the road surface reaction torque reference change rate Talign_rate_ref and the estimated road surface reaction torque differential value Talign_rate_est.
In addition, according to this method, the steering angle sensor 11 (see FIG. 2) is not necessary, so that the manufacturing cost of the understeer suppressing device can be reduced.

  Further, by using a known technique (for example, see JP-A-6-99800), a reference yaw rate calculated from a steering wheel angle and a vehicle speed V is compared with an actual yaw rate detected by a yaw rate sensor to detect understeer. May be.

  In the first embodiment, the drive wheel lock tendency detector 4 calculates the drive wheel lock tendency value DL according to the expression (3) based on the detected values of the wheel speeds VFR, VFL, VRR, and VRL. As a method of detecting the lock tendency value DL, other known methods may be used as long as the lock tendency of the driving wheel can be detected. For example, the left and right drive wheel lock tendency values DL_FR and DL_FL can be detected by the following equations (6) and (7) using the respective wheel speeds.

  Further, if a sensor such as an acceleration sensor is used in addition to the wheel speed sensors 42 to 45, the driving wheel locking tendency can be detected with higher accuracy.

  Further, in the first embodiment, as shown in FIGS. 5 and 6, when the vehicle understeer is detected, the first deceleration control (shift down) by the transmission controller 2 and the first deceleration by the prime mover controller 3 are performed. Although both control (motor engine output reduction) are executed, only one of the first and second deceleration control may be executed.

  Further, the transmission controller 2 may be a stepped transmission or a CVT (Continuously Variable Transmission) as long as the transmission ratio is changed to a low speed side during traveling to generate a braking force on the vehicle. Either of these may be used.

  Furthermore, the prime mover to be controlled by the prime mover controller 2 may be either an internal combustion engine or an electric motor. For example, if the prime mover is an internal combustion engine, deceleration control can be performed by suppressing the amount of supplied air or fuel, or changing the ignition timing, and if the prime mover is an electric motor, supply to the motor is possible. The output can be reduced by suppressing the current.

It is a block diagram which shows schematic structure of the understeer suppression apparatus which concerns on Embodiment 1 of this invention. It is a block block diagram which shows the specific example of the electric power steering controller which concerns on Embodiment 1 of this invention. It is a flowchart which shows operation | movement of the electric power steering controller which concerns on Embodiment 1 of this invention. It is explanatory drawing which shows the relationship between the steering angle by this Embodiment 1, a reference | standard road surface reaction torque, a road surface reaction torque, a yaw rate, and an understeer. It is a flowchart which shows operation | movement of the transmission controller which concerns on Embodiment 1 of this invention. It is a flowchart which shows operation | movement of the motor | power_engine controller which concerns on Embodiment 1 of this invention. It is a block block diagram which shows the specific example of the driving wheel lock tendency detector which concerns on Embodiment 1 of this invention. It is a flowchart which shows operation | movement of the driving wheel lock tendency detector which concerns on Embodiment 1 of this invention. It is explanatory drawing which shows the general friction circle for demonstrating the subject which this invention tends to solve. It is explanatory drawing which shows the general friction circle for demonstrating the subject which this invention tends to solve. It is explanatory drawing which shows the general friction circle for demonstrating the subject which this invention tends to solve.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Electric power steering controller (understeer detection means), 2 Transmission controller, 3 Motor controller, 4 Drive wheel lock tendency detector, 11 Steering angle sensor (steering angle detection means), 12 Vehicle speed sensor (vehicle speed detection means), 13 Steering torque sensor (steering torque detection means), 14 Motor current sensor (motor current detection means), 15 Motor rotation speed sensor (motor rotation speed detection means), 16 Reference road surface reaction force torque calculator (Reference road surface reaction force torque calculation means) ), 17 Estimated road surface reaction torque calculator (estimated road surface reaction torque calculation means), 18 Understeer determination unit, 41 Drive wheel lock tendency value calculator, 42 to 45 Wheel speed sensor, DL drive wheel lock tendency value, Imtr motor Current, Ts Steering torque, Talign_est Estimated road surface reaction torque, US_Index Understeering degree, V vehicle speed, ωmtr motor rotation speed.

Claims (2)

Understeer detecting means for detecting understeer of the vehicle;
Prime mover control means for controlling the prime mover output from the prime mover of the vehicle;
Transmission control means for controlling transmission and transmission ratio of the motor output to the vehicle wheel;
Driving wheel lock tendency detecting means for detecting the lock tendency of the drive wheel of the vehicle,
When the understeer of the vehicle is detected by the understeer detecting means, a first deceleration control for changing the transmission gear ratio to a low speed side by the transmission control means, and a second for reducing the prime mover output by the prime mover control means. An understeer suppression device that performs at least one of the deceleration control of
The understeer detecting means includes
Vehicle speed detecting means for detecting the vehicle speed of the vehicle;
Steering torque detection means for detecting steering torque by a driver of the vehicle;
An electric motor for assisting the steering torque;
Motor current detecting means for detecting a motor current of the electric motor;
Motor rotation speed detection means for detecting the motor rotation speed of the electric motor;
Estimated road surface reaction force torque calculating means for calculating an estimated road surface reaction force torque based on the vehicle speed, the steering torque, the motor current, and the motor rotation speed;
Road surface reaction force torque reference change rate calculating means for calculating a road surface reaction force torque reference change rate based on the motor rotation speed and the vehicle speed;
Based on the comparison between the calculated value of the road surface reaction torque standard change rate and the differential value of the estimated road reaction torque, the vehicle understeer is detected,
The transmission control means controls the speed ratio based on the output of the drive wheel lock tendency detection means during execution of the first deceleration control,
The under-steer suppressing device, wherein the prime mover control means controls the prime mover output based on an output of the drive wheel lock tendency detection means during execution of the second deceleration control.   2. The understeer suppression device according to claim 1, wherein the drive wheel lock tendency detecting unit detects the drive wheel lock tendency based on at least a wheel speed of the vehicle.

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