JP2006224790A - Vehicular caster angle control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vehicular caster angle control device capable of correctly controlling the turning characteristic of a vehicle and the steering characteristic of a steering wheel. <P>SOLUTION: In a vehicle having a caster angle actuator to change the caster angles of right and left front wheels, an electronic control unit controls the caster angles of the right and left front wheels by the program control. In the program control, the target steering torque is calculated based on the yaw rate γ and the vehicle speed V, the detected actual steering torque MT is input, and the deviation thereof ΔMT*=ΔMT-MT is calculated (S11-S13). by multiplying the deviation ΔMT* by the coefficient k according to the detected cornering forces of the right and left front wheels, the caster angle changes Δθl, Δθr of the right and left front wheels are calculated (S14, S15). The electronic control unit changes the caster angles of the right and left front wheels by the caster angle changes Δθl, Δθr (S16). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a caster angle control device for a vehicle that includes a caster angle actuator that changes caster angles of left and right front wheels and controls caster angles of left and right front wheels.

2. Description of the Related Art Conventionally, as disclosed in Patent Documents 1 to 3 below, for example, a vehicle caster angle control device that variably controls a caster angle according to a vehicle motion state such as a vehicle speed and a steering angle is known. In this type of caster angle control device, control according to the lateral acceleration of the vehicle is added to improve the running stability of the vehicle when an external force such as a crosswind is generated.
JP-A-7-186676 Japanese Patent No. 2658529 Japanese Patent No. 2970367

  However, in the conventional vehicle caster angle control device, sufficient consideration is not given to the turning characteristics of the vehicle (understeer characteristics and oversteer characteristics) and the steering characteristics of the steering wheel. And the steering characteristics of the steering wheel are not necessarily controlled appropriately.

  The present invention has been made to address the above-described problems, and an object of the present invention is to provide a vehicle caster angle control device that accurately controls the turning characteristics of the vehicle and the steering characteristics of the steering wheel. is there.

  In order to achieve the above object, a feature of the present invention is that in a caster angle control device for a vehicle having a caster angle actuator for changing the caster angle of the left and right front wheels and controlling the caster angle of the left and right front wheels, the motion state quantity of the vehicle A state-of-motion amount detecting means for detecting a target steering torque, a target steering torque calculating means for calculating a target steering torque to be applied to the steering handle based on the detected amount of motion state, and a steering torque applied to the steering handle. Steering torque detection means for detecting, and caster angle control means for driving and controlling a caster angle actuator according to a difference between the calculated target steering torque and the detected steering torque to change and control the caster angles of the left and right front wheels. It is in having established.

  In the present invention configured as described above, when there is a difference between the target steering torque to be applied to the steering wheel and the actual steering torque based on the motion state quantity of the vehicle, the caster angles of the left and right front wheels are the difference. Will be changed according to By changing the caster angle, the moment acting around the kingpin shaft at the left and right front wheel positions is changed, the steering torque can be matched with the target steering torque, and the turning characteristics of the vehicle and the steering characteristics of the steering wheel are accurately controlled. The driver can steer the steering wheel with a steering torque that matches the motion state of the vehicle, and the steering performance of the vehicle is improved.

  Another feature of the present invention is further provided with cornering force detecting means for detecting the cornering forces of the left and right front wheels, respectively, and the caster angle control means determines whether the detected left and right front wheels are different from the difference between the target steering torque and the steering torque. In consideration of the cornering force, the caster angle of the left and right front wheels is changed and controlled. According to this, since the caster angle is changed and controlled in accordance with the cornering force of the left and right front wheels, the change amount of the caster angle is set more accurately in consideration of the influence of the road surface and the tire, and driving. The person can steer the steering wheel with a steering torque that is more suitable for the motion state of the vehicle.

  Another feature of the present invention is that target stability factor calculation means for calculating a target stability factor of the vehicle based on the detected motion state quantity, and stability factor detection for detecting the stability factor of the vehicle. The caster angle control means includes a difference between the target steering torque and the steering torque, in addition to a difference between the calculated target stability factor and the detected stability factor. It is to change control.

  Here, the stability factor represents a turning characteristic (understeer characteristic and oversteer characteristic) of the vehicle. Therefore, in this case as well, the caster angle is changed and controlled in accordance with the actual turning characteristics of the vehicle according to the change in the vehicle speed, so that the driver can steer with the steering torque that matches the motion state of the vehicle. The steering wheel can be steered.

a. First Embodiment Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 schematically shows an entire caster angle control device for a vehicle according to the first embodiment.

  The vehicle steering apparatus includes a steering torque sensor 13 and left and right front wheel cornering force sensors 14 and 15 in addition to a yaw rate sensor 11 and a vehicle speed sensor 12 that detect a motion state quantity of the vehicle. The yaw rate sensor 11 detects a yaw rate γ generated in the vehicle. The yaw rate γ represents a clockwise yaw rate generated when the vehicle turns right, and represents a counterclockwise yaw rate generated when the vehicle turns left. The vehicle speed sensor 12 detects a traveling speed (vehicle speed) V of the vehicle.

  The steering torque sensor 13 is connected to the steering handle at the upper end and is assembled to the steering shaft for steering the left and right front wheels FWl and FWr by rotation around the axis, and the torque applied to the steering shaft, that is, the steering applied to the steering handle. Torque MT is detected. The left and right front wheel cornering force sensors 14, 15 are composed of strain sensors assembled to the respective bearing units of the left and right front wheels FWl, FWr, and detect the left and right front wheel cornering forces Ff1, Ffr received by the left and right front wheels FWl, FWr from the road surface, respectively. To do. As the left and right front wheel cornering force sensors 14 and 15, known ones disclosed in, for example, Japanese Patent Application Laid-Open Nos. 2004-142577 and 2004-155261 can be used. Further, the left and right front wheel cornering forces Ff1 and Ffr represent a right cornering force when the vehicle is turning right, and a left cornering force when the vehicle is turned left.

  These sensors 11 to 15 are connected to an electronic control unit 20 whose main component is a microcomputer comprising a CPU, a ROM, a RAM and the like. The electronic control unit 20 controls to change the caster angles θl and θr of the left and right front wheels FWl and FWr by repeatedly executing the caster control program shown in FIG. 2 every predetermined short time.

  The electronic control unit 20 is connected to left and right front wheel caster angle actuators 31 and 32, respectively. The left and right front wheel caster angle actuators 31 and 32 are provided between the lower arm and the vehicle body that support the left and right front wheels FWl and FWr so as to be swingable with respect to the vehicle body, and by moving the lower arm back and forth with respect to the vehicle body, The caster angles θl and θr of the front wheels FWl and FWr are changed. As these left and right front wheel caster angle actuators 31 and 32, known ones shown in, for example, JP-A-7-186676, Japanese Patent No. 2658529, Japanese Patent No. 2970367, and the like can be used. These left and right front wheel caster angle actuators 31 and 32 are assembled with left and right front wheel caster angle sensors 33 and 34, respectively. The left and right front wheel caster angle sensors 33 and 34 detect the caster angles θl and θr of the left and right front wheels FWl and FWr, respectively, corresponding to the operation amounts of the left and right front wheel caster angle actuators 31 and 32.

  Next, the operation of the first embodiment configured as described above will be described. When an ignition switch (not shown) is turned on, the electronic control unit 20 starts execution of the caster angle control program of FIG. 2 in step S10. After the start of step S10, the electronic control unit 20 determines in step S11 the yaw rate γ, the vehicle speed V, the steering torque MT from the yaw rate sensor 11, the vehicle speed sensor 12, the steering torque sensor 13, and the left and right front wheel cornering force sensors 14, 15. The left and right front wheel cornering forces Ff1 and Ffr are input.

  Next, the electronic control unit 20 calculates the target steering torque MT * corresponding to the input yaw rate γ and vehicle speed V with reference to the target steering torque table in step S12. The target steering torque table is provided in the ROM of the electronic control unit 20, and stores a target steering torque MT * that increases as the yaw rate γ increases as shown in FIG. Further, the target steering torque MT * shows a larger absolute value as the vehicle speed V increases with respect to the same yaw rate γ. Instead of using the target steering torque table, the target steering torque MT * that changes in accordance with the yaw rate γ and the vehicle speed V is stored in advance as a function, and the yaw rate γ and The target steering torque MT * corresponding to the vehicle speed V may be calculated. This target steering torque MT * represents the target value of the steering torque applied to the steering wheel by the driver in the current movement state of the vehicle (in this case, the movement state of the vehicle determined according to the yaw rate γ and the vehicle speed V). .

After the process of step S12, the electronic control unit 20 calculates a deviation ΔMT between the calculated target steering torque MT * and the input steering torque MT by executing the calculation of the following equation 1 in step S13.
ΔMT = MT * −MT Equation 1

Next, in step S14, the electronic control unit 20 calculates the coefficient k according to the following equation 2 using the input left and right front wheel cornering forces Ff1 and Ffr.
k = a · (Ffl + Ffr) ... Formula 2
It should be noted that “a” in Equation 2 is a positive constant determined in advance according to vehicle characteristics.

Next, in step S15, the electronic control unit 20 uses the calculated coefficient k and steering torque deviation ΔMT to set the caster angle change amounts Δθl and Δθr of the left and right front wheels FWl and FWr according to the following equations 3 and 4, respectively. calculate.
Δθl = k · ΔMT Equation 3
Δθr = k · ΔMT Equation 4

  In step S16, the electronic control unit 20 inputs the caster angles θl and θr from the left and right front wheel caster angle sensors 33 and 34, and the caster angles θl and θr are changed from the caster angles θl and θr before the control is started. The left and right front wheel caster angle actuators 31 and 32 are driven and controlled until they change by the change amounts Δθl and Δθr, respectively. Since the left and right front wheel caster angle actuators 31 and 32 change the caster angles θl and θr of the left and right front wheels FWl and FWr according to this drive control, the caster angles θl and θr of the left and right front wheels FWl and FWr are the caster angle change amounts before the start of control. Changes by Δθl and Δθr. After the process of step S16, the electronic control unit 20 once ends the execution of the caster angle control program in step S17. Then, every time a predetermined short time elapses, the electronic control unit 20 repeatedly executes the caster angle control program described above, and continues to change the caster angles θl and θr of the left and right front wheels FWl and FWr.

  If the actual steering torque MT is smaller than the target steering torque MT * to be applied to the steering wheel in accordance with the motion state of the vehicle, the caster angles θl and θr are large. It is controlled to become. As a result, the moments around the kingpin shaft at the positions of the left and right front wheels FWl and FWr are increased, and in order to obtain the same vehicle motion state as described above, the driver needs to operate a steering torque larger than the above on the steering wheel. is there. On the contrary, if the actual steering torque MT is larger than the target steering torque MT * to be applied to the steering wheel in accordance with the motion state of the vehicle, the caster angles θl and θr are controlled to be small. As a result, the moment around the kingpin axis at the positions of the left and right front wheels FW1 and FW2 is reduced, and in order to obtain the same vehicle motion state as described above, the driver only has to operate the steering wheel with a steering torque smaller than that described above. . As a result, the driver's steering torque is controlled so as to match the target steering torque suitable for the vehicle's movement state, and the turning characteristics of the vehicle and the steering characteristics of the steering wheel become accurate, and the driver's movement state of the vehicle Since the steering wheel can be steered with a steering torque suitable for the vehicle, the steering performance and running performance of the vehicle are improved.

  Further, the absolute values | Δθl | and | Δθr | of the caster angle change amounts Δθl and Δθr are set to smaller values as the left and right front wheel cornering forces Ff1 and Ffr are larger. According to this, the greater the influence by the road surface, the smaller the change amount of the caster angles θl and θr, so that the caster angle change amounts Δθl and Δθr are set more accurately in consideration of the influence of the road surface and the tire. Thus, the driver can steer the steering wheel with a steering torque that is more suitable for the motion state of the vehicle.

b. Second Embodiment Next, a second embodiment of the vehicle caster angle control device according to the present invention will be described. The second embodiment is characterized by considering the stability factor and independently controlling the caster angles θl and θr of the left and right front wheels FWl and FWr.

  As shown by a broken line in FIG. 1, the caster angle control device according to the second embodiment includes a steering angle sensor 41, a lateral acceleration sensor 42, and left and right rear wheels in addition to the caster angle control device according to the first embodiment. Cornering force sensors 43 and 44 are provided. Further, the electronic control unit 20 repeatedly executes the caster angle control program of FIG. 4 every predetermined short time instead of the caster angle control program of FIG. Other configurations are the same as those in the first embodiment.

  The steering angle sensor 41 is assembled to a steering shaft to which a steering handle is connected, and detects the steering angle δ of the left and right front wheels FWl and FWr by detecting the rotation angle around the axis of the steering shaft. Alternatively, the left and right front wheels FWl and FWr are connected to both ends, and the axial displacement of the rack bar that steers the left and right front wheels FWl and FWr is detected by the axial displacement. The steering angle δ may be detected. The steering angle δ also represents the right turn of the vehicle, that is, the right steering angle of the left and right front wheels FWl and FWr, and the left turn of the vehicle, that is, the left steering angle of the left and right front wheels FWl and FWr. .

  The lateral acceleration sensor 42 detects a lateral acceleration Gy generated in the vehicle. The lateral acceleration Gy is also positive when the vehicle is turning right and negative when the vehicle is turning left. Similar to the left and right front wheel cornering force sensors 14 and 15, the left and right rear wheel cornering force sensors 43 and 44 are each composed of a strain sensor assembled to each of the left and right rear wheel bearing units, and the left and right rear wheels receive from the road surface. The rear wheel cornering forces Fr1 and Frr are detected. The left and right rear wheel cornering forces Fr1 and Frr also represent the right cornering force when the vehicle is turning right, and the left cornering force when the vehicle is turning left as a negative.

  Next, the operation of the second embodiment configured as described above will be described. When an ignition switch (not shown) is turned on, the electronic control unit 20 starts execution of the caster angle control program of FIG. 4 in step S20. After the start of step S20, in step S21, the electronic control unit 20 controls the steering angle sensor in addition to the yaw rate γ, the vehicle speed V, the steering torque MT, and the left and right front wheel cornering forces Ff1 and Ffr in the first embodiment. 41, the steering angle δ of the left and right front wheels FWl and FWr, the lateral acceleration Gy, and the left and right rear wheel cornering forces Fr1 and Frr are input from the lateral acceleration sensor 42 and the left and right rear wheel cornering force sensors 43 and 44.

  Next, in step S22, the electronic control unit 20 calculates the target steering torque MT * corresponding to the yaw rate γ and the vehicle speed V in the same manner as in step S12 of the first embodiment. Next, in step S23, the electronic control unit 20 executes the calculation of the above equation 1 in the same manner as the processing of step S13 of the first embodiment, thereby calculating the calculated target steering torque MT * and the input steering torque. MT deviation ΔMT (= MT * −MT) is calculated.

  After the process of step S23, the electronic control unit 20 calculates a target stability factor Kh * corresponding to the input yaw rate γ and vehicle speed V with reference to the target stability factor table in step S24. The target stability factor table is provided in the ROM of the electronic control unit 20. As shown in FIG. 5, the target stability factor table is kept almost constant in a region where the absolute value | γ | of the yaw rate γ is small, and the absolute value | A target stability factor Kh * that is slightly increased as the absolute value | γ | increases in a large region of γ | is stored. Further, the target stability factor Kh * shows a large positive value as the vehicle speed V increases with respect to the same yaw rate γ. Instead of using the target stability factor table, the target stability factor Kh * that changes according to the yaw rate γ and the vehicle speed V is stored in advance as a function, and the yaw rate is calculated by executing the calculation using this function. A target stability factor Kh * corresponding to γ and the vehicle speed V may be calculated. The target stability factor Kh * represents an ideal value for the vehicle in the current movement state of the vehicle (in this case, the movement state of the vehicle determined according to the yaw rate γ and the vehicle speed V).

Next, in step S25, the electronic control unit 20 calculates the current vehicle body slip angle β by executing the integral calculation of the following equation 5 using the input lateral acceleration Gy, vehicle speed V, and yaw rate γ.
β = ∫ (Gy / V−γ) dt Equation 5

なお、前記式６中の係数ａ1，ａ2，ｂ1，ｂ2，ｃ1は、車両の特性に応じて予め決められた定数である。 Next, in step S26, the electronic control unit 20 calculates the calculated vehicle body slip angle β, the input yaw rate γ, the vehicle speed V, the steering angle δ of the left and right front wheels FWl and FWr, and the left and right front and rear wheel cornering forces Ff1, Ffr, The current stability factor Kh is calculated by executing the calculation of Equation 6 below using Fr1 and Frr.

Note that the coefficients a1, a2, b1, b2, and c1 in Equation 6 are constants determined in advance according to the characteristics of the vehicle.

Next, the electronic control unit 20 calculates the deviation ΔKh between the calculated target stability factor Kh * and the stability factor Kh by executing the calculation of the following expression 7 in step S27.
ΔKh = Kh * −Kh Equation 7

  Next, in step S28, the electronic control unit 20 refers to the caster angle change amount tables for the left and right front wheels FWl and FWr, respectively, and inputs the steering angle δ, the calculated steering torque deviation ΔMT, and the stability factor. The caster angle change amounts Δθl and Δθr of the left and right front wheels FWl and FWr are calculated based on the deviation Kh, respectively.

  The caster angle change amount table for the left front wheel FWl is, as shown by a solid line in FIG. 6, for the right turn of the vehicle, the caster angle change amount Δθl that gradually decreases in the negative region as the steering torque deviation ΔMT increases. I remember it. Further, as shown by the broken line in FIG. 6, this caster angle change amount table stores a caster angle change amount Δθl that gradually increases in the positive region as the steering torque deviation ΔMT increases as the vehicle turns left. Yes. The absolute value | Δθl | of the caster angle change amount Δθl for the right turn and the left turn shows a smaller value as the stability factor deviation ΔKh becomes larger than the steering torque deviation ΔMT showing the same value. . Further, the rate of change of the caster angle change amount Δθl for turning left is greater than the rate of change of the absolute value | Δθl | of the caster angle change amount Δθl for turning right. The caster angle change amount table for the right front wheel FWr is the same as the caster angle change amount Δθl for the left turn of the left front wheel FWl (broken line in FIG. 6) as shown in the solid line in FIG. The caster angle change amount Δθr that changes depending on the characteristics is stored. The caster angle change amount table for the right front wheel FWr is the same as the caster angle change amount Δθl for the right turn of the left front wheel FWl (solid line in FIG. 6) for turning the vehicle left as indicated by a broken line in FIG. The caster angle change amount Δθr that changes depending on the characteristics is stored.

  Therefore, if the vehicle is in a right turn state, the electronic control unit 20 determines the right turn state based on the input steering angle δ, and according to the calculated steering torque deviation ΔMT and stability factor deviation Kh. Then, the caster angle change amount Δθl for the left front wheel FWl according to the characteristic indicated by the solid line in FIG. 6 is calculated. Further, the electronic control unit 20 calculates the caster angle change amount Δθr for the right front wheel FWr according to the characteristics shown by the solid line in FIG. 7 according to the calculated steering torque deviation ΔMT and stability factor deviation Kh. . On the other hand, if the vehicle is in a left turn state, the electronic control unit 20 determines this left turn state based on the input steering angle δ, and according to the calculated steering torque deviation ΔMT and stability factor deviation Kh, The caster angle change amounts Δθl and Δθr for the left and right front wheels FWl and FWr according to the characteristics indicated by the broken lines in FIGS.

  Instead of using this caster angle change amount table, caster angle change amounts Δθl and Δθr that change according to the steering angle δ, the steering torque deviation ΔMT, and the stability factor deviation Kh are stored in advance as functions, The caster angle change amounts Δθl and Δθr corresponding to the steering angle δ, the steering torque deviation ΔMT, and the stability factor deviation Kh may be calculated by executing a calculation using this function.

  Then, in step S29, the electronic control unit 20 inputs the caster angles θl and θr from the caster angle sensors 33 and 34 in the same manner as in step S16 of the first embodiment, while the left and right front wheels FWl and FWr are The caster angles θl and θr are changed by the caster angle change amounts Δθl and Δθr from the caster angles θl and θr before the start of control. After the processing of step S29, the electronic control unit 20 once ends the execution of the caster angle control program in step S30. Then, every time a predetermined short time elapses, the electronic control unit 20 repeatedly executes the caster angle control program described above, and continues to change the caster angles θl and θr of the left and right front wheels FWl and FWr.

  By the control by the caster angle control program as described above, when the vehicle turns right, the caster angle θl of the left wheel FWl on the outer turning wheel side is controlled to become smaller as the steering torque deviation ΔMT becomes larger (FIG. 6). (See the solid line). Further, the caster angle θr of the right wheel FWl on the turning inner wheel side is controlled to increase as the steering torque deviation ΔMT increases (see the solid line in FIG. 7). That is, when the vehicle turns right, the caster angle θr of the right wheel FWr that is the inner turning wheel is larger than the caster angle θl of the left wheel FWl that is the outer turning wheel, and the difference θr−θl has a large steering torque deviation ΔMT. It is controlled to become larger as the time goes. On the other hand, when the vehicle turns left, the relationship between the left and right wheels FWl and FWr is reversed from that in the right turn, so that the caster angle θf of the left wheel FWl that is the turning inner wheel is the caster angle of the right wheel FWr that is the turning outer wheel. The difference θl−θr is larger than θr, and is controlled to increase as the steering torque deviation ΔMT increases (see the broken line in FIGS. 6 and 7).

  As a result, also in this second embodiment, if the actual steering torque MT is smaller than the target steering torque MT * that should be applied to the steering wheel in accordance with the motion state of the vehicle, the turning characteristic of the vehicle is on the understeer characteristic side. Changed to On the contrary, if the actual steering torque MT is larger than the target steering torque MT * to be applied to the steering wheel in accordance with the motion state of the vehicle, the turning characteristic of the vehicle is changed to the oversteer characteristic side. Therefore, also in this second embodiment, the driver's steering torque is controlled to match the target steering torque suitable for the vehicle's motion state, and the turning characteristics of the vehicle and the steering characteristics of the steering wheel become accurate, The driver can steer the steering wheel with a steering torque that matches the motion state of the vehicle, and the steering performance of the vehicle is improved.

  Further, the difference between the caster angles θl and θr of the left and right wheels FWl and FWr when the vehicle is turning to the right θr−θl (> 0) and the difference between the caster angles θl and θr of the left and right wheels FWl and FWr when the vehicle is turning left θl−θr (> 0) is controlled to decrease as the stability factor deviation ΔKh (= Kh * −Kh) increases. Here, the fact that the stability factor deviation ΔKh is large (that is, a positive value) means that the steering characteristic of the vehicle is on the oversteer side. Conversely, a small stability factor deviation ΔKh (ie, a negative value) means that the steering characteristic of the vehicle is on the understeer side. As a result, the actual steering torque MT becomes smaller or larger than the target steering torque MT *, and the steering torque deviation ΔMT becomes positive or negative. Therefore, it decreases as the stability factor deviation ΔKh increases. Thus, by controlling the difference θr−θl (or θl−θr) between the caster angles θl and θr, the steering torque and the steering characteristics (oversteer characteristics and understeer characteristics) of the vehicle can be controlled at the same time. Performance is improved.

  Although the first and second embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments and modifications thereof, and various modifications can be made without departing from the object of the present invention. It can be changed.

  For example, in the first and second embodiments, the motion state of the vehicle is estimated using the yaw rate γ and the vehicle speed V. However, since the turning state of the vehicle is also observed by the lateral acceleration Gy, the lateral acceleration Gy can be employed instead of the yaw rate γ.

1 is an overall schematic diagram of a vehicle caster angle control device according to first and second embodiments of the present invention. FIG. It is a flowchart which shows the caster angle control program which concerns on 1st Embodiment and is performed by the electronic control unit of FIG. It is a graph which shows the relationship between yaw rate (gamma), vehicle speed V, and target steering torque Tr *. It is a flowchart which shows the caster angle control program which concerns on 2nd Embodiment and is performed by the electronic control unit of FIG. It is a graph which shows the relationship between the yaw rate (gamma), the vehicle speed V, and the target steering stability factor Kh *. It is a graph which shows the relationship between steering torque deviation (DELTA) MT for left front wheels, stability factor deviation (DELTA) Kh, and caster angle change amount (DELTA) (theta) l. It is a graph which shows the relationship between steering torque deviation (DELTA) MT for right front wheels, stability factor deviation (DELTA) Kh, and caster angle change amount (DELTA) theta.

Explanation of symbols

FWl, FWr ... front wheel, 11 ... yaw rate sensor, 12 ... vehicle speed sensor, 13 ... steering torque sensor, 14, 15, 43, 44 ... cornering force sensor, 20 ... electronic control unit, 31, 32 ... caster angle actuator, 33, 34 ... Caster angle sensor, 41 ... Rudder angle sensor, 42 ... Lateral acceleration sensor.

Claims (3)

In a caster angle control device for a vehicle having a caster angle actuator for changing the caster angle of the left and right front wheels, and controlling the caster angle of the left and right front wheels,
A movement state quantity detecting means for detecting a movement state quantity of the vehicle;
Target steering torque calculating means for calculating a target steering torque to be applied to the steering wheel based on the detected motion state quantity;
Steering torque detection means for detecting the steering torque applied to the steering wheel;
Caster angle control means is provided for driving and controlling the caster angle actuator according to the difference between the calculated target steering torque and the detected steering torque to change and control the caster angles of the left and right front wheels. A vehicle caster angle control device. The vehicle caster angle control device according to claim 1, further comprising cornering force detection means for detecting cornering forces of the left and right front wheels, respectively.
The caster angle control device for a vehicle changes and controls the caster angle of the left and right front wheels in consideration of the difference between the target steering torque and the steering torque and the detected cornering force of the left and right front wheels. . The vehicle caster angle control device according to claim 1, further comprising a target stability factor calculation means for calculating a target stability factor of the vehicle based on the detected motion state quantity,
A stability factor detecting means for detecting the stability factor of the vehicle,
The caster angle control means changes and controls the caster angles of the left and right front wheels by adding the difference between the calculated target stability factor and the detected stability factor to the difference between the target steering torque and the steering torque. A caster angle control device for a vehicle.

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