JP2006103348A - Steering force change device of vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steering force change device of a vehicle capable of applying appropriate auxiliary steering force and stabilizing behavior of the vehicle even when a tire is worn out or exchanged. <P>SOLUTION: A lateral force characteristic calculation part 12 calculates the lateral force characteristic of the tire based on a slip angle outputted from a slip angle calculation part 11. A cornering power calculation part 14 calculates the cornering power based on the lateral force characteristic outputted from the lateral force characteristic calculation part 12. A cornering power comparison part 15 compares the cornering power outputted the cornering power calculation part 14 with a predetermined cornering power initial value. An auxiliary steering force setting part 16 calculates the auxiliary steering force applying to a steering system based on the comparison result. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a vehicle steering force changing device that changes a steering force by supplementing a steering force of a vehicle.

  In a vehicle equipped with a power steering device, steering control is performed to add a predetermined torque to the steering angle operated by the driver to reduce the burden on the driver. In such steering control, for example, the vehicle speed and the steering speed are selected as detection characteristics, a target steering torque corresponding to the selected detection characteristics is set, and the difference between the actual steering torque and the target steering torque is set to zero. The steering is controlled. However, in performing the steering control, although the steering reaction force varies depending on the slip angle of the steered wheels, the above-described steering control may disturb the behavior of the vehicle.

  In response to such a problem, the steering reaction force control device disclosed in Japanese Patent Application Laid-Open No. 2003-154862 detects the side slip angle of the steered wheel with respect to the road surface and adds it to the steering means as the side slip angle increases. Control is performed to increase the steering torque. By performing such control, the behavior of the vehicle can be stabilized regardless of the influence of tire type, wear state, suspension type, vehicle weight, and the like.

A tire determining device disclosed in Japanese Patent Laid-Open No. 10-281944 has been conventionally used to calculate the lateral force of a tire. The tire determination device detects the lateral acceleration, yaw rate, vehicle speed, and the like of the vehicle, and calculates the tire slip angle and lateral force from the lateral acceleration, yaw rate, vehicle speed, and specification data. Further, the cornering power of the tire is calculated from the slip angle and the lateral force, and the grip performance of the tire is determined based on the cornering power.
Japanese Patent Laid-Open No. 2003-154962 JP-A-10-281944

  However, in the steering reaction force control device disclosed in Patent Document 1, the torque applied to the steering means is increased based on the side slip angle. For this reason, although it is possible to reduce the influence of the tire type, wear state, suspension type, vehicle weight, etc., there has been a problem that these influences cannot be eliminated. In particular, tire characteristics such as the type of tire and the state of wear often change depending on the traveling state of the vehicle, and the influence of the tire characteristics is inevitable. Therefore, there is a problem that it is difficult to apply an appropriate auxiliary steering force to the vehicle, and it is difficult to stabilize the behavior of the vehicle.

  Further, in the tire determination device disclosed in Patent Document 2, lateral force is calculated from vehicle lateral acceleration, yaw rate, vehicle speed, and vehicle specification data. However, this tire determination device has a problem that it is difficult to perform appropriate control because it cannot cope with changes in vehicle characteristics due to tire wear or replacement.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a vehicle steering control device that can provide an appropriate auxiliary steering force even when tires are worn or replaced, thereby stabilizing the behavior of the vehicle. It is in.

  A vehicle steering control device according to the present invention that has solved the above problems is a vehicle steering control device that performs steering control of a running vehicle. In the vehicle steering control device, a slip angle calculating means that calculates a slip angle of a running vehicle, A lateral force characteristic calculating means for obtaining a lateral force characteristic of a wheel with respect to a slip angle calculated by a slip angle calculating means in the vehicle based on a vehicle model formula; a steering torque detecting means for detecting a steering torque in a steering system of the vehicle; An auxiliary steering force is set based on an auxiliary steering force applying means for applying an auxiliary steering force to the steering system of the vehicle, a steering torque detected by the steering torque detecting means, and a lateral force characteristic obtained by the lateral force characteristic calculating means. Auxiliary steering force setting means, and the auxiliary steering force setting means includes a predetermined lateral force characteristic with respect to a predetermined slip angle and a lateral force characteristic calculating means. According to the difference between the fit was the lateral force characteristic is to set the assist steering force.

  In the vehicle steering control device according to the present invention, when setting the auxiliary steering force, the lateral force characteristic with respect to the preset auxiliary steering force and the lateral force characteristic obtained by the lateral force characteristic calculating means are determined according to the difference. Auxiliary steering force is set. For this reason, even when the tires are worn or replaced, an appropriate auxiliary steering force can be applied to the vehicle, and the behavior of the vehicle can be stabilized.

Here, the vehicle has steering direction determination means for determining whether the vehicle is in turning or in turning back,
The auxiliary steering force setting means is assisted based on a predetermined lateral force characteristic and a lateral force characteristic obtained by the lateral force characteristic calculating means when the steering direction determining means determines that the vehicle is turning or turning back. It can be set as the aspect which sets steering force.

  Thus, by using the preset lateral force specification at the time of cutting or returning, the auxiliary steering force can be set in accordance with the hysteresis set at the time of cutting and returning. Accordingly, since the steering characteristic having hysteresis can be obtained even after the auxiliary steering force is applied, the steering can be performed in a state where the uncomfortable feeling felt by the driver is reduced.

  The auxiliary steering force setting means generates a large auxiliary steering force when the difference between the predetermined lateral force characteristic with respect to a predetermined slip angle and the lateral force characteristic obtained by the lateral force characteristic calculating means is larger than a small difference. It can be set as the aspect to set.

  In this way, by setting a large auxiliary steering force when the difference between the predetermined lateral force characteristic with respect to the slip angle and the lateral force characteristic obtained by the lateral force characteristic calculating means is small, it is possible to set a more appropriate auxiliary steering force. Steering force can be applied.

  According to the vehicle steering control device of the present invention, an appropriate auxiliary steering force can be applied even when tires are worn or replaced, and the behavior of the vehicle can be stabilized.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, in each embodiment, the same number is attached | subjected to what has the same function and effect | action, and the overlapping description may be abbreviate | omitted. FIG. 1 is a block diagram of a vehicle steering control apparatus according to the present invention.

  As shown in FIG. 1, the steering control device 1 according to the present embodiment includes a control device 10. The control device 10 includes a slip angle calculation unit 11, a lateral force characteristic calculation unit 12, and a vehicle specification storage unit 13. The control device 10 includes a cornering power calculation unit 14, a cornering power comparison unit 15, an auxiliary steering force setting unit 16, and a steering force setting unit 17. Further, a steering torque sensor 2, a vehicle speed sensor 3, a yaw rate sensor 4, and a lateral acceleration sensor 5 are connected to the control device 10, and a steering force applying means (motor) 6 is further connected.

  The steering torque sensor 2 is attached to a steering rod, for example, and detects a steering torque when the driver operates the steering. The steering torque sensor 2 outputs the detected steering torque to the steering force setting unit 17 in the control device 10. The vehicle speed sensor 3 is attached to a vehicle body, for example, and detects the vehicle speed (vehicle speed). The vehicle speed sensor 3 outputs the detected vehicle speed to the slip angle calculation unit 11 in the control device 10.

  The yaw rate sensor 4 is attached to a part of the vehicle body, for example, and detects the yaw rate of the vehicle. The yaw rate sensor 4 outputs the detected yaw rate to the slip angle calculation unit 11 and the lateral force characteristic calculation unit 12 in the control device 10. The lateral acceleration sensor 5 is attached to a part of the vehicle body, for example, and detects the lateral acceleration (lateral G) of the vehicle. The lateral acceleration sensor 5 outputs the detected lateral acceleration to the slip angle calculation unit 11 and the lateral force characteristic calculation unit 12 in the control device 10. The steering force applying means 6 applies a steering force to the steering system of the vehicle based on the steering force output from the steering force setting unit 17 in the control device 10.

  The slip angle calculation unit 11 in the control device 10 calculates the slip angle of the vehicle based on the vehicle speed output from the vehicle speed sensor 3, the yaw rate output from the yaw rate sensor 4, and the lateral acceleration output from the lateral acceleration sensor 5. To do. The slip angle calculation unit 11 outputs the calculated slip angle to the cornering power calculation unit 14.

  The lateral force characteristic calculation unit 12 determines the vehicle specifications such as the yaw rate output from the yaw rate sensor 4, the lateral acceleration output from the lateral acceleration sensor 5, and the wheelbase and vehicle mass output from the vehicle specification storage unit 13. Based on this, the lateral force characteristics are calculated. The lateral force characteristic calculation unit 12 outputs the calculated lateral force characteristic to the cornering power calculation unit 14.

  The vehicle specification storage unit 13 stores a vehicle mass, a wheel base, a center of gravity position, a cornering power initial map corresponding to a tire that is mounted, and the like. The vehicle specification storage unit 13 outputs the stored vehicle mass, wheelbase, center of gravity position, and the like to the lateral force characteristic calculation unit 12, and outputs a cornering power initial map to the cornering power comparison unit 15.

  The cornering power calculation unit 14 creates these distribution maps based on the slip angle output from the slip angle calculation unit 11 and the lateral force characteristics output from the lateral force characteristic calculation unit 12, and performs cornering from the generated distribution map. Ask for power. The cornering power calculation unit 14 outputs the obtained cornering power to the cornering power comparison unit 15.

  The cornering power comparison unit 15 compares the cornering power initial value obtained from the cornering power initial map output from the vehicle specification storage unit 13 with the cornering power output from the cornering power calculation unit 14. The cornering power comparison unit 15 outputs the comparison result to the auxiliary steering force setting unit 16.

  The auxiliary steering force setting unit 16 stores a map indicating the relationship between cornering power and auxiliary steering torque. The auxiliary steering force setting unit 16 obtains the auxiliary steering torque by referring to the comparison result output from the cornering power comparison unit 15 in a map indicating the relationship between the cornering power and the auxiliary steering torque. Here, the auxiliary steering force unit 16 sets the auxiliary steering force to a negative value when the cornering power obtained by the cornering power calculation unit 14 is smaller than the initial value of the cornering power, and the cornering power calculation unit 14 When the obtained cornering power is larger than the cornering power initial value, the auxiliary steering torque is set to a positive value. Further, the absolute value of the auxiliary steering torque is set larger as the absolute value of the difference between the cornering power initial value and the cornering power characteristic calculation unit 14 is larger. The auxiliary steering force setting unit 16 outputs the obtained auxiliary steering force to the steering force setting unit 17.

  A steering torque is output from the steering torque sensor 2 to the steering force setting unit 17, and an auxiliary steering torque is output from the auxiliary steering force setting unit 16. The steering force setting unit 17 calculates a basic basic steering torque based on the steering force output from the steering torque sensor 2. Here, when the auxiliary steering torque is output from the auxiliary steering force setting unit 16, the auxiliary steering torque is added to the basic steering torque to calculate the steering torque.

  The steering force setting unit 17 sets the auxiliary steering torque to a negative value when the cornering power obtained by the cornering power calculation unit 14 is smaller than the initial value of the cornering power, and the cornering power obtained by the cornering power calculation unit 14 is When the cornering power is larger than the initial value, the auxiliary steering torque is set to a positive value. The absolute value of the auxiliary steering torque is set to be larger as the absolute value of the difference between the cornering power obtained by the cornering power calculation unit 14 and the initial value of the cornering power is larger.

  The steering force setting unit 17 outputs the steering force thus obtained to the steering force applying means 6. The steering force applying means 6 applies the steering force output from the steering force setting unit 17 to the steering system of the vehicle.

  A control procedure of the steering control device for a vehicle according to the present embodiment having the above configuration will be described. FIG. 2 is a flowchart showing a control procedure of the steering control device according to the present embodiment.

  As shown in FIG. 2, in the steering control device 1 according to the present embodiment, first, various measured values are read (S1). Here, the vehicle speed detected by the vehicle speed sensor 3, the yaw rate detected by the yaw rate sensor 4, and the lateral acceleration detected by the lateral acceleration sensor 5 are read. Next, in the slip angle calculation unit 11, the lateral speed obtained by integrating the vehicle speed output from the vehicle speed sensor 3, the yaw rate output from the yaw rate sensor 4, and the lateral acceleration output from the lateral acceleration sensor 5. Is used to calculate the slip angle (S2). The slip angle calculation unit 11 outputs the calculated slip angle to the cornering power calculation unit 14.

  The lateral force characteristic calculation unit 12 uses a vehicle model formula based on the yaw rate output from the yaw rate sensor 4, the lateral acceleration output from the lateral acceleration sensor 5, and the vehicle specifications output from the vehicle specification storage unit 13. A lateral force as a tire characteristic for each front and rear wheel of the tire is calculated using the following formulas (1) and (2) (S3). The lateral force characteristic calculation unit 12 outputs the lateral force thus obtained to the cornering power calculation unit 14. When determining the lateral force characteristics of each wheel, for example, the lateral force acting on each wheel is calculated by the following equations (1) and (2), assuming that the lateral force of the right wheel and the left wheel is the same. be able to.

mG = Y _f1 + Y _f2 + Y _r1 + Y _r2 (1)
However,
m: vehicle mass (inertial mass)
G: Lateral acceleration Y _f1 : Lateral force acting on the right front wheel Y _f2 : Lateral force acting on the left front wheel Y _r1 : Lateral force acting on the right rear wheel Y _r2 : Lateral force acting on the left rear wheel I = l _f (Y _f1 + Y _f2 ) −l _r (Y _r1 + Y _r2 ) (2)
However,
I: Yaw rate l _f : Distance between vehicle center of gravity and front wheel axis l _r : Distance between vehicle center of gravity and rear wheel axis In cornering power calculation unit 14, slip angle output from slip angle calculation unit 11 and lateral force characteristic calculation unit The lateral force output from 12 is plotted every few seconds, and a distribution map of slip angle and lateral force is created for each wheel (S4). After the distribution map is created, a tire characteristic map (lateral force characteristic map) of the tires mounted, for example, as shown in FIG. 3 is created based on the distribution chart (S5). The tire characteristic map is updated every time the vehicle travels a predetermined distance, for example, several thousand km. In this way, by updating the tire characteristic map every time the vehicle travels a predetermined distance, even if tire wear or the like occurs as the vehicle travels, it is possible to eliminate the influence of changes in tire characteristics.

  When the tire characteristic map is created in this way, the cornering power calculation unit 14 uses the calculated tire characteristic map together with the slip angle output from the slip angle calculation unit 11 and the lateral force output from the lateral force characteristic calculation unit 12 to calculate the cornering power. Output to the comparison unit 15. In addition, the cornering power comparison unit 15 outputs a cornering power initial map corresponding to the initial value of the tire being mounted from the vehicle specification storage unit 13.

  The cornering power comparison unit 15 determines whether or not the travel distance of the vehicle after updating the tire characteristic map is a predetermined distance L0, for example, less than several kilometers (S6). As a result, when the travel distance is less than L0, it is considered that the travel distance is small and the tire characteristics are not greatly changed from the initial value. In this case, the cornering power initial map is read as a tire characteristic map (S7). Further, the slip angle and tire characteristics at this time are referred to the cornering power initial map, and the obtained cornering power initial value Cp0 is output to the auxiliary steering force setting unit 16.

  The auxiliary steering force setting unit 16 stores a map indicating the auxiliary steering torque ΔT corresponding to the cornering power Cp as shown in FIG. Now, since the cornering power output to the auxiliary steering force setting unit 16 is the cornering power initial value Cp0 (= 0), the auxiliary steering torque ΔT becomes 0 (S8).

  On the other hand, when it is determined in step S6 that the travel distance is not less than L0, it is considered that the tire characteristics may have changed from the initial values. In this case, the cornering power comparison unit 15 calculates the cornering power Cp with reference to the slip angle and the lateral force in the tire characteristic map created by the cornering power calculation unit 14 (S9). When the cornering power Cp is calculated, an absolute value ΔCp of a difference between the calculated cornering power Cp and the cornering power initial value Cp0 obtained from the cornering power initial map is obtained, and whether or not the absolute value ΔCp exceeds a predetermined threshold value. Is determined (S10).

  As a result, when it is determined that the absolute value ΔCp of the difference between the cornering power Cp and the cornering power initial value Cp0 does not exceed the predetermined threshold value, the cornering power Cp is determined to be substantially equal to the cornering power initial value Cp0. it can. Therefore, in this case, the auxiliary steering force setting unit 16 sets the auxiliary steering torque ΔT to 0 (S8).

  On the other hand, when it is determined that the absolute value ΔCp of the difference between the cornering power Cp and the cornering power initial value Cp0 exceeds a predetermined threshold, a map indicating the auxiliary steering torque ΔT corresponding to the cornering power Cp is read (S11). The auxiliary steering torque ΔT is obtained by referring to the cornering power Cp in this map (S12).

  Thus, when the auxiliary steering torque ΔT is obtained in step S9 or step S12, the auxiliary steering force setting unit 16 outputs the auxiliary steering torque ΔT to the steering force setting unit 17, and the steering force setting unit 17 receives the steering. The steering torque detected by the torque sensor 2 is output. The steering force setting unit 17 calculates a basic steering torque based on the steering torque output from the steering torque sensor 2. Further, the basic steering torque is corrected based on the auxiliary steering torque ΔT output from the auxiliary steering force setting unit 16.

  The steering force setting unit 17 sets the steering torque using the following equation (3) (S13).

Steering torque T = basic steering torque T + auxiliary steering torque ΔT (3)
The steering torque T thus determined is output to the steering force applying means 6. The steering force applying means 6 applies the output steering torque to the vehicle steering system. In this manner, a predetermined steering torque is applied to the vehicle steering system.

  Thus, in the vehicle steering control apparatus according to the present embodiment, the lateral force of the tire is calculated, and the steering torque applied to the steering system is calculated using the lateral force of the tire. For this reason, even when there is tire wear or replacement and the tire characteristics change, an appropriate steering force can be applied. Therefore, steering control with stable behavior can be performed.

  Next, a second embodiment of the present invention will be described. FIG. 5 is a block diagram of a steering control device according to the second embodiment of the present invention.

  As shown in FIG. 5, the steering control device 20 according to the present embodiment includes a control device 21. The control device 21 includes a slip angle calculation unit 11, a vehicle specification storage unit 13, an auxiliary steering force setting unit 16, and a steering force setting unit 17 similar to those in the first embodiment. The control device 21 includes a tire characteristic calculation unit 22, a tire characteristic comparison unit 23, a braking assist force setting unit 24, and a braking force setting unit 25.

  Further, the steering torque sensor 2, the vehicle speed sensor 3, the yaw rate sensor 4, the lateral acceleration sensor 5, and the steering force applying means 6 are connected to the control device 21 as in the first embodiment. In addition, a brake sensor 7 and a braking force applying means 8 are connected to the control device 21.

  The brake sensor 7 is attached to a foot brake pedal (brake pedal), for example, and detects an operation amount when the driver operates the brake. The brake sensor 7 is connected to the braking force setting unit 25 in the control device 21 and outputs the detected brake operation amount to the braking force setting unit 25. The braking force applying means 8 is connected to the braking force setting unit 25 in the control device 21 and applies a brake corresponding to the braking force output from the braking force setting unit 25.

  A vehicle speed sensor 3, a yaw rate sensor 4, and a lateral acceleration sensor 5 are connected to the tire characteristic calculation unit 22 in the control device 21. In the tire characteristic calculation unit 22, tire characteristics such as a lateral force and a longitudinal force of the tire based on the vehicle speed output from the vehicle speed sensor 3, the yaw rate output from the yaw rate sensor 4, and the lateral acceleration output from the lateral acceleration sensor 5. Is calculated. The tire characteristic calculation unit 22 outputs the calculated tire characteristic to the tire characteristic comparison unit 23.

  Further, the tire characteristic calculation unit 22 outputs the slip angle calculated by the slip angle calculation unit 11. The tire characteristic calculation unit 22 creates these distribution maps based on the slip angle output from the slip angle calculation unit 11 and the calculated tire characteristics, and obtains the relationship between the slip angle and the tire characteristics from the created distribution map. . The tire characteristic calculation unit 22 outputs the obtained relationship between the slip angle and the tire characteristic to the tire characteristic comparison unit 23.

  Further, in the vehicle specification storage unit 13, there are tire characteristic initial maps (lateral force characteristic initial map and longitudinal force characteristic initial map) indicating the relationship between the slip angle corresponding to the initial value of the mounted tire and the tire characteristics. It is remembered. The vehicle specification storage unit 13 outputs the tire characteristic initial map to the tire characteristic calculation unit 22.

  A tire characteristic calculation unit 22 is connected to the tire characteristic comparison unit 23 in the control device 21. The tire characteristic comparison unit 23 compares the tire characteristic output from the tire characteristic calculation unit 22 and the initial value of the tire characteristic. Of these, the comparison result of the lateral force characteristics is output to the auxiliary steering force setting unit 16, and the comparison result of the longitudinal force characteristics is output to the braking auxiliary force setting unit 24.

  The auxiliary steering force setting unit 16 and the steering force setting unit 17 perform control according to the same procedure as in the first embodiment. In addition, the braking assist force setting unit 24 stores a map indicating the relationship between the longitudinal force characteristics of the tire characteristics and the corrected braking assist force. The braking assist force setting unit 24 obtains the corrected braking assist force by referring to the stored map for the comparison result of the longitudinal force characteristics output from the tire characteristic comparison unit 23. The braking assist force setting unit 24 outputs the obtained corrected braking assist force to the braking force setting unit 25.

  A brake pedal operation amount is output from the brake sensor 7 to the braking force setting unit 25, and a corrected braking assist force is output from the braking assist force setting unit 24. The braking force setting unit 25 calculates a basic basic braking force based on the operation amount of the brake pedal output from the brake sensor 7. Here, when the corrected braking assist force is output from the braking assist force setting unit 24, the corrected braking assist force is added to the basic braking force to calculate the braking force.

  The braking force setting unit 25 outputs the braking force thus obtained to the braking force applying means 8. The braking force applying means 8 brakes the vehicle with the braking force output from the braking force setting unit 25. About the other point, it has the same structure about the member same as said 1st embodiment.

  A control procedure of the steering control device for a vehicle according to the present embodiment having the above configuration will be described. FIG. 6 is a flowchart showing a control procedure of the steering control device according to the present embodiment, and FIG. 7 is a flowchart showing a procedure following FIG.

  As shown in FIG. 6, first, the auxiliary steering torque ΔT and the corrected braking assist force ΔBA are set to 0, and various measured values are read (S21). Here, the vehicle speed detected by the vehicle speed sensor 3, the yaw rate detected by the yaw rate sensor 4, and the lateral acceleration detected by the lateral acceleration sensor 5 are read. Next, in the slip angle calculation unit 11, the lateral speed obtained by integrating the vehicle speed output from the vehicle speed sensor 3, the yaw rate output from the yaw rate sensor 4, and the lateral acceleration output from the lateral acceleration sensor 5. Is used to calculate the slip angle (S22). The slip angle calculation unit 11 outputs the calculated slip angle to the tire characteristic calculation unit 22.

  In the tire characteristic calculation unit 22, based on the yaw rate output from the yaw rate sensor 4, the lateral acceleration output from the lateral acceleration sensor 5, and the vehicle specifications output from the vehicle specification storage unit 13, the above equation (1) And the lateral force as the tire characteristic for each front and rear wheel of the tire is calculated using the equation (2) (S23). Further, by comparing the longitudinal acceleration of the vehicle obtained by differentiating the vehicle speed and the angular acceleration of the tire, the longitudinal force as the tire characteristic for each front and rear wheel of the tire is calculated (S23).

  The tire characteristic calculation unit 22 plots the slip angle output from the slip angle calculation unit 11 and the calculated lateral force every few seconds, and creates a distribution diagram of the slip angle and the lateral force for each wheel ( S24). Further, the slip angle output from the slip angle calculation unit 11 and the calculated longitudinal force are plotted every few seconds, and a distribution diagram of the slip angle and the longitudinal force is created for each wheel (S24).

  Once the distribution map is created, a tire characteristic map of the tire that is mounted is created based on these distribution charts (S25). The tire characteristic map is created for each of a lateral force characteristic map indicating the relationship between the slip angle and the lateral force and a longitudinal force characteristic map indicating the relationship between the slip angle and the longitudinal force. These tire characteristic maps are updated every time the vehicle travels a predetermined distance, for example, several thousand km, as in the first embodiment. In this way, by updating the tire characteristic map every time the vehicle travels a predetermined distance, even if tire wear or the like occurs as the vehicle travels, it is possible to eliminate the influence of changes in tire characteristics.

  When the tire characteristic map is thus created, the tire characteristic calculation unit 22 outputs the tire characteristic map to the tire characteristic comparison unit 23 together with the slip angle output from the slip angle calculation unit 11 and the calculated tire characteristic. In addition, the tire characteristic comparison unit 23 outputs a lateral force characteristic initial map and a longitudinal force characteristic initial map corresponding to the initial value of the mounted tire.

  The tire characteristic comparison unit 23 determines whether or not the travel distance of the vehicle after updating the tire characteristic map is a predetermined distance L0, for example, less than several km (S26). As a result, when it is determined that the travel distance is less than L0, it is considered that the travel distance is small and the tire characteristics are not greatly changed from the initial value. In this case, the tire characteristic initial map is read as the tire characteristic map, and the initial value of the tire characteristic is calculated.

  The lateral force characteristic initial value Fy0 is calculated by referring to the slip angle in the lateral force characteristic initial map as the tire characteristic initial map (S27). The calculated lateral force characteristic initial value Fy0 is output from the tire characteristic comparison unit 23 to the auxiliary steering force setting unit 16. Further, the front-rear force characteristic initial value Fx0 is calculated by referring to the slip angle in the front-rear force characteristic initial map as the tire characteristic initial map (S28). The calculated longitudinal force characteristic initial value Fx0 is output from the tire characteristic comparison unit 23 to the braking assist force setting unit 24.

  The auxiliary steering force setting unit 16 stores a map indicating the auxiliary steering torque ΔT corresponding to the lateral force characteristic Fy of the vehicle, for example, as shown in FIG. The lateral force characteristic Fy output to the auxiliary steering force setting unit 16 is the lateral force characteristic initial value Fy0. Accordingly, the auxiliary steering torque ΔT is kept unchanged at 0. The braking assist force setting unit 24 stores a map indicating the corrected braking assist force ΔBA corresponding to the vehicle longitudinal force characteristic Fx as shown in FIG. The longitudinal force characteristic output to the braking assist force setting unit 24 is the longitudinal force characteristic initial value Fx0. Therefore, the corrected braking assist force ΔBA remains 0 without being changed.

  On the other hand, when it is determined in step S26 that the travel distance is not less than L0, the tire characteristic output from the tire characteristic calculation unit 22 is compared with the tire characteristic map to obtain the lateral force characteristic Fy (S29). The absolute value of the difference between the lateral force characteristic Fy and the lateral force characteristic initial value Fy0 (hereinafter referred to as “lateral force characteristic difference absolute value”) ΔFy is calculated, and the lateral force characteristic difference absolute value ΔFy has a predetermined threshold value. It is determined whether it exceeds (S30). As a result, when it is determined that the lateral force characteristic difference absolute value ΔFy exceeds a predetermined threshold value, the tire characteristic comparison unit 23 outputs the lateral force characteristic difference absolute value ΔFy to the auxiliary steering force setting unit 16. The auxiliary steering force setting unit 16 refers to the output lateral force characteristic difference absolute value ΔFy in the map shown in FIG. 8 to obtain the auxiliary steering torque ΔT with respect to the lateral force characteristic difference absolute value ΔFy (S31).

  Further, the tire characteristic comparison unit 23 compares the tire characteristic output from the tire characteristic calculation unit 22 with the tire characteristic map to obtain the longitudinal force characteristic Fx (S32). An absolute value ΔFx of the difference between the longitudinal force characteristic Fx and the longitudinal force characteristic initial value Fx0 (hereinafter referred to as “absolute longitudinal force characteristic difference absolute value”) is calculated, and the longitudinal force characteristic difference absolute value ΔFx has a predetermined threshold value. It is determined whether or not it exceeds (S33). As a result, when it is determined that the longitudinal force characteristic difference absolute value ΔFx exceeds a predetermined threshold, the tire characteristic comparison unit 23 outputs the longitudinal force characteristic difference absolute value ΔFx to the braking assist force setting unit 24. The braking assist force setting unit 24 obtains a corrected braking assist force ΔBA for the longitudinal force characteristic difference absolute value ΔFx by referring to the output longitudinal force characteristic difference absolute value ΔFx in the map shown in FIG. 9 (S34).

  Thereafter, the auxiliary steering force setting unit 16 outputs the obtained auxiliary steering torque ΔT to the steering force setting unit 17. Further, the braking assist force setting unit 24 outputs the obtained corrected braking assist force ΔBA to the braking force setting unit 25.

  Then, the steering force setting unit 17 sets the steering torque using the above equation (3) (S35). The steering torque T thus determined is output to the steering force applying means 6. The steering force applying means 6 applies the output steering torque to the vehicle steering system. In this manner, a predetermined steering torque is applied to the vehicle steering system.

  The braking force setting unit 25 calculates the braking force using the following equation (4) (S36).

Braking force BA = basic braking force BA + corrected braking assist force ΔBA (4)
The braking force BA thus obtained is output to the braking force applying means 8. The braking force applying means 8 applies the output steering torque to the vehicle. In this way, a predetermined braking force is applied to the vehicle.

  As described above, in the vehicle steering control device according to the present embodiment, the lateral force and the longitudinal force are calculated as the tire characteristics, and the steering torque applied to the steering system and the vehicle are braked using the lateral force of the tire. The braking force is calculated. For this reason, even if there is wear or replacement of the tire and the tire characteristics change, appropriate steering force and braking force can be applied. Therefore, steering control with stable behavior can be performed.

  Subsequently, a third embodiment of the present invention will be described. FIG. 10 is a block diagram of the steering control device according to the third embodiment.

  As shown in FIG. 10, the steering control device 30 according to the present embodiment includes a control device 31. The control device 31 includes a slip angle calculation unit 11, a lateral force characteristic calculation unit 12, a vehicle specification storage unit 13, an auxiliary steering force setting unit 16, and a steering force setting unit 17 similar to those in the first embodiment. Yes. In addition, the control device 21 includes a lateral force characteristic comparison unit 32 and a steering direction determination unit 33.

  A lateral force characteristic calculation unit 12, a vehicle specification storage unit 13, and an auxiliary steering force setting unit 16 are connected to the lateral force characteristic comparison unit 32 in the control device 31. The lateral force characteristic comparison unit 32 compares the lateral force characteristic output from the lateral force characteristic calculation unit 12 and the initial value of the lateral force characteristic, and outputs the comparison result to the auxiliary steering force setting unit 16. The auxiliary steering force setting unit 16 sets the auxiliary steering force based on the output comparison result.

  A slip angle calculation unit 11 and a steering angle sensor 9 are connected to the steering direction determination unit 33. The steering angle sensor 9 is attached to, for example, a steering rod of the steering system, detects a steering angle in the steering system, and outputs the detected steering angle to the steering direction determination unit 33. The steering direction determination unit 33 determines the steering direction based on the steering angular velocity obtained from the steering angle output from the steering angle sensor 9 and the slip angle output from the slip angle calculation unit 11. The steering direction determination unit 33 outputs the determination result of the steering direction to the lateral force characteristic comparison unit 32. About the other point, it has the same structure about the member same as said 1st embodiment.

  A control procedure of the vehicle steering control apparatus according to the present embodiment having the above-described configuration will be described. FIG. 11 is a flowchart showing a control procedure of the steering control device according to the present embodiment.

  As shown in FIG. 11, in the steering control device according to this embodiment, first, various measured values are read (S41). Here, the vehicle speed detected by the vehicle speed sensor 3, the yaw rate detected by the yaw rate sensor 4, and the lateral acceleration detected by the lateral acceleration sensor 5 are read. Next, in the slip angle calculation unit 11, the lateral speed obtained by integrating the vehicle speed output from the vehicle speed sensor 3, the yaw rate output from the yaw rate sensor 4, and the lateral acceleration output from the lateral acceleration sensor 5. Is used to calculate the slip angle (S42). The slip angle calculation unit 11 outputs the calculated slip angle to the lateral force characteristic calculation unit 12.

  In the lateral force characteristic calculation unit 12, based on the yaw rate output from the yaw rate sensor 4, the lateral acceleration output from the lateral acceleration sensor 5, and the vehicle specifications output from the vehicle specification storage unit 13, (1) The lateral force as the tire characteristic for each front and rear wheel of the tire is calculated using the equations (2) and (2).

  On the other hand, in the steering direction determination unit 33, either the left or right direction is determined based on the steering angular velocity obtained by differentiating the steering angle output from the steering angle sensor 9 and the slip angle output from the slip angle calculation unit 11. The steering direction is determined as to whether cutting or reversing is performed (S44). When determining the steering direction, the right side is positive and the left side is negative.When the steering angular velocity is positive and the slip angle is positive, the right side is cut.When the steering angular velocity is negative and the slip angle is positive, the right side is turned back. When the positive and slip angles are negative, the left side is turned back, and when the steering angular velocity is negative and the slip angle is negative, the left side is cut. The steering direction determination unit 33 outputs the determination result of the steering direction to the lateral force characteristic calculation unit 12.

  The lateral force characteristic calculation unit 12 plots the slip angle output from the slip angle calculation unit 11 and the calculated lateral force into the steering directions output from the steering direction determination unit 33 every few seconds, and each steering direction. A total of four slip angles and lateral force distribution maps are created for each wheel (S45).

  In addition, when the lateral force characteristic calculation unit 12 creates a distribution map of the slip angle and the lateral force with respect to each steering direction, a tire characteristic map (lateral A force characteristic map) is created (S46). The tire characteristic map is updated every time the vehicle travels a predetermined distance, for example, several thousand km. In this way, by updating the tire characteristic map every time the vehicle travels a predetermined distance, even if tire wear or the like occurs as the vehicle travels, it is possible to eliminate the influence of changes in tire characteristics.

  After creating the tire characteristic map in this way, the lateral force characteristic calculation unit 12 displays the calculated tire characteristic map for each steering direction along with the slip angle output from the slip angle calculation unit 11 and the calculated lateral force. 32. Further, the lateral force characteristic comparison unit 32 outputs a lateral force characteristic initial map for each steering direction corresponding to the initial value of the mounted tire from the vehicle specification storage unit 13.

  The lateral force characteristic comparison unit 32 determines whether or not the travel distance after updating the lateral force characteristic map is a predetermined distance L0, for example, less than several kilometers (S47). As a result, when the travel distance is less than L0, it is considered that the travel distance is small and the tire characteristics are not greatly changed from the initial value. In this case, the lateral force characteristic initial map is read as the tire characteristic map (S48). Further, the slip angle and lateral force characteristics at this time are referred to the lateral force characteristic initial map, and the obtained lateral force characteristic initial value Fy0 is output to the auxiliary steering force setting unit 16. Here, since the lateral force output to the auxiliary steering force setting unit 16 is the lateral force characteristic initial value Fy0 (= 0), the auxiliary steering torque ΔT becomes 0 (S49).

  On the other hand, when it is determined in step S37 that the travel distance is not less than L0, it is considered that the tire characteristics may have changed from the initial values. In this case, the lateral force characteristic comparison unit 32 refers to the tire characteristic map created by the lateral force characteristic calculation unit 12 with reference to the steering direction, slip angle, and lateral force, and determines the lateral force characteristic Fy corresponding to the steering direction. Calculate (S50). After calculating the lateral force characteristic Fy, an absolute value of a difference between the calculated lateral force characteristic Fy and the initial lateral force characteristic value Fy0 obtained from the initial lateral force characteristic map is obtained, and this absolute value exceeds a predetermined threshold value. Whether or not (S51).

  As a result, when it is determined that the absolute value of the difference between the lateral force characteristic Fy and the lateral force characteristic initial value Fy0 does not exceed a predetermined threshold value, the lateral force characteristic Fy is substantially equal to the lateral force characteristic initial value Fy0. It can be judged that there is. Therefore, in this case, the auxiliary steering force setting unit 16 sets the auxiliary steering torque ΔT to 0 (S49).

  On the other hand, when it is determined that the absolute value of the difference between the lateral force characteristic Fy and the initial lateral force characteristic value Fy0 exceeds a predetermined threshold, a map indicating the auxiliary steering torque ΔT corresponding to the lateral force characteristic Fy is read (S52). ). A map indicating the auxiliary steering torque ΔT corresponding to the lateral force characteristic is prepared for each steering direction. For this reason, the auxiliary steering torque ΔT is obtained by referring to the lateral force characteristic Fy in the map corresponding to the steering direction (S53). The auxiliary steering torque ΔT is changed more greatly at the time of turning or turning back than at other times.

  In this manner, when the auxiliary steering torque ΔT is obtained in step S49 or step S53, the auxiliary steering force setting unit 16 outputs the auxiliary steering torque ΔT to the steering force setting unit 17. The steering torque detected by the torque sensor 2 is output. The steering force setting unit 17 calculates a basic steering torque based on the steering torque output from the steering torque sensor 2. Further, based on the auxiliary steering force output from the auxiliary steering force setting unit 16, the basic steering torque is corrected using, for example, the above equation (3) (S54).

  The steering torque T thus determined is output to the steering force applying means 6. The steering force applying means 6 applies the output steering torque to the vehicle steering system. In this manner, a predetermined steering torque is applied to the vehicle steering system.

  Thus, in the vehicle steering control apparatus according to the present embodiment, the lateral force of the tire is calculated, and the steering torque applied to the steering system is calculated using the lateral force of the tire. For this reason, even when there is tire wear or replacement and the tire characteristics change, an appropriate steering force can be applied. Therefore, steering control with stable behavior can be performed.

  Also, when setting the auxiliary steering force in accordance with the lateral force of the tire, the left and right cutting and turning back, which are the steering direction, are taken into account, and when turning or turning back, the auxiliary steering is more effective than at other times. The force (auxiliary steering torque) is increased. For this reason, when it is determined at the time of turning or when turning back, the auxiliary steering force can be set in accordance with the hysteresis set at the time of turning and turning back by largely changing the auxiliary steering force. . Accordingly, since the steering characteristic having hysteresis can be obtained even after the auxiliary steering force is applied, the steering can be performed in a state where the uncomfortable feeling felt by the driver is reduced.

  The preferred embodiment of the present invention has been described above, but the present invention is not limited to the above embodiment. For example, in the second embodiment, the auxiliary steering force is obtained from the lateral force characteristics of the tire and the corrected braking assist force is obtained from the longitudinal force. However, the auxiliary steering force is obtained from the cornering power and corrected by the longitudinal force. It is also possible to obtain a braking assist force. In the third embodiment, the steering direction is detected when the auxiliary steering force is obtained from the lateral force characteristic of the tire. However, the steering direction is detected when the auxiliary steering force is obtained from the cornering power. It can also be.

It is a block block diagram of the steering control apparatus which concerns on 1st embodiment. It is a flowchart which shows the control procedure of the steering control apparatus which concerns on 1st embodiment. It is a tire characteristic map which shows the relationship between the slip angle of a tire, and lateral force. It is a map which shows the magnitude | size of the auxiliary | assistant steering torque corresponding to a cornering power. It is a block block diagram of the steering control apparatus which concerns on 2nd embodiment. It is a flowchart which shows the control procedure of the steering control apparatus which concerns on 2nd embodiment. It is a flowchart which shows the procedure following FIG. It is a map which shows the magnitude | size of the auxiliary | assistant steering torque corresponding to the lateral force of a tire. It is a map which shows the magnitude | size of the correction | amendment braking assistance force corresponding to the front-back force of a tire. It is a block block diagram of the steering control apparatus which concerns on 3rd embodiment. It is a flowchart which shows the control procedure of the steering control apparatus which concerns on 3rd embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1,20,30 ... Steering control apparatus 2,21,31 ... Steering torque sensor, 3 ... Vehicle speed sensor, 4 ... Yaw rate sensor, 5 ... Lateral acceleration sensor, 6 ... Steering force provision means, 7 ... Brake sensor, 8 ... Braking force applying means, 9 ... steer angle sensor, 10 ... control device, 11 ... slip angle calculation unit, 12 ... lateral force characteristic calculation unit, 13 ... vehicle specification storage unit, 14 ... cornering power calculation unit, 15 ... cornering power Comparison unit, 16 ... auxiliary steering force setting unit, 17 ... steering force setting unit, 22 ... tire characteristic calculation unit, 23 ... tire characteristic comparison unit, 24 ... braking auxiliary force setting unit, 25 ... braking force setting unit, 32 ... sideways Force characteristic comparison unit, 33... Steering direction determination unit.

Claims (3)

In a vehicle steering control device that performs steering control of a running vehicle,
Slip angle calculating means for calculating the slip angle of the vehicle during traveling;
Lateral force characteristic calculating means for obtaining a lateral force characteristic of a wheel with respect to a slip angle calculated by the slip angle calculating means in the vehicle based on a vehicle model formula in the vehicle;
Steering torque detection means for detecting steering torque in the steering system of the vehicle;
An auxiliary steering force applying means for applying an auxiliary steering force to the steering system of the vehicle;
An auxiliary steering force setting means for setting the auxiliary steering force based on the steering torque detected by the steering torque detection means and the lateral force characteristics obtained by the lateral force characteristic calculation means;
Have
The auxiliary steering force setting means sets the auxiliary steering force in accordance with a difference between a predetermined lateral force characteristic with respect to the predetermined slip angle and a lateral force characteristic obtained by the lateral force characteristic calculating means. A vehicle steering control device. Steering direction determination means for determining whether the vehicle is in turning or in turning back;
The auxiliary steering force setting means is based on a predetermined lateral force characteristic when the steering direction determining means determines that it is in turning or returning, and a lateral force characteristic obtained by the lateral force characteristic calculating means. The vehicle steering control device according to claim 1, wherein auxiliary steering force is set.   The auxiliary steering force setting means has a large auxiliary steering force when a difference between a predetermined lateral force characteristic for the predetermined slip angle and a lateral force characteristic obtained by the lateral force characteristic calculating means is larger than a small difference. The vehicle steering control device according to claim 1, wherein the vehicle steering control device is set.

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