JP5309610B2 - Vehicle attitude control device and vehicle attitude control method - Google Patents

Description

  The present invention relates to a vehicle running attitude control device and a running attitude control method.

  Research has been conducted on vehicles that improve the running stability during turning by controlling the running posture of the vehicle independently of the operation of the driver. One such vehicle controls the driving force for each driving wheel. In such a vehicle, a desired yaw moment can be obtained by controlling not only the steering of the wheel but also the driving force for each driving wheel at the time of turning, and the tracing as desired can be performed.

In such a vehicle, when the target driving force cannot be obtained for some reason, for example, when the set target driving force exceeds the realizable range, the yaw moment that can be realized by the driving force control is the target yaw moment. It will be insufficient. In such a case, Patent Document 1 discloses a technique for obtaining a desired yaw moment by correcting and controlling the turning angle of the wheel independently of the steering wheel steering of the driver.
JP 2005-193752 A

  The present inventors have studied such a vehicle control method every day, and succeeded in completing a technique capable of obtaining a desired yaw moment with higher accuracy than the above-described conventional technology.

  As described above, the present invention has been made paying attention to such conventional problems, and a vehicle running attitude control device and a running attitude control method capable of obtaining a desired yaw moment more accurately than in the prior art. The purpose is to provide.

  The present invention solves the above problems by the following means. In addition, in order to make an understanding easy, although the code | symbol corresponding to embodiment of this invention is attached | subjected, it is not limited to this.

The present invention is an apparatus for controlling the attitude of a vehicle having wheels that can be steered independently of steering wheel steering by a driver, and is a driving force basic value setting that sets the driving force of driving wheels according to the driving state. It is determined whether or not the driving force set by the means (step S6) and the driving force basic value setting means is within a realizable range. Driving force limiting means (steps S8, S12) for limiting the force, and each wheel that suppresses a lateral force change and a moment change of the vehicle body caused by the driving force limitation when the driving force is limited by the driving force limiting means. Steering angle correction amount combination calculation means (step S11) for calculating a combination of the steering angle correction amounts of the wheels, wherein the steering angle correction amount combination calculation means has a lateral slip angle change amount of each wheel. Shadow The tire lateral force variation amount I index der representing the degree to which, based on the tire lateral force sensitivity divided by the side slip angle change amount, it calculates the combination of steering angle correction amount, characterized in that.

  According to the present invention, the combination of the steering angle correction amounts is calculated based on the tire lateral force sensitivity, which is an index representing the degree to which the side slip angle change amount of each wheel affects the tire lateral force change amount. The target course can be accurately traced even in a situation where one of the driving wheels cannot obtain the target driving force for a very short time.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings.

  First, in order to facilitate understanding of the present invention, the basic technical idea of the present invention will be described.

  By controlling the driving force of each driving wheel as well as the turning angle of the wheel when turning, there is a case where the desired driving force cannot be produced in a vehicle that obtains a desired yaw moment and controls the running posture. . For example, when turning, one of the driving wheels of the vehicle will step on a wet manhole and slip, and the target driving force cannot be obtained for a very short time. In such a case, a desired yaw moment can be obtained by correcting and controlling the turning angle of the wheels independently of the steering wheel steering of the driver.

The inventors of the present invention have focused on the fact that when the wheel is steered, the side slip angle of the tire changes, and when the side slip angle changes, the tire side force changes. That is, there is a relationship as shown in FIG. 1 among the driving force, lateral force, and slip angle of the tire. As shown in the enlarged view (FIG. 1B), when the tire is steered and the side slip angle increases by Δβ _i and the driving force Fx _i remains constant, the tire lateral force increases by ΔFy _i. .

  Such a relationship is also affected by the wheel load of the tire as shown in FIG.

As described above, the inventors of the present invention can control the yaw moment more accurately if the steering angle is corrected in consideration of the influence of the tire lateral force that changes as the side slip angle increases by Δβ _i by turning the tire. Has found out. That is, the change in the tire lateral force Fy _i affects the yaw moment M. Therefore, the present inventors determine the steering angle correction amount Δδ _i in consideration of the change in the tire lateral force Fy _i when the driving force Fx _i is limited due to slipping of the driving wheel. Thus, the desired yaw moment M is obtained. By doing so, it is possible to accurately trace the target course even in a situation where one of the driving wheels cannot obtain the target driving force for a very short time.

  Next, the force acting on the vehicle will be described with reference to FIG.

  Consider the case where each wheel 1 to 4 is steered to the left.

The left front wheel 1 is steered by a steering angle δ ₁ [unit: rad] with respect to the vehicle longitudinal direction. At this time, the driving force is Fx ₁ [unit: N], and the tire lateral force is Fy ₁ [unit: N]. The steering angle δ _i (i = 1 to 4) is 0 when the rotational direction of each wheel coincides with the vehicle front-rear direction, and is counterclockwise when the vehicle is viewed from vertically above. The driving force Fx _i is positive when the vehicle is accelerated forward when the steering angle δ _i is all zero, and the tire lateral force Fy _i [unit: N] is left when the steering angle δ _i is all zero. The direction of acceleration in the direction is positive.

  The same applies to the right front wheel 2, the left rear wheel 3, and the right rear wheel 4. The subscript 2 is attached to the right front wheel, the subscript 3 is attached to the left rear wheel, and the subscript 4 is attached to the right rear wheel.

  The vehicle center of gravity G includes a vehicle longitudinal direction component Fx [unit: N] of the sum of tire forces, a vehicle lateral direction component Fy [unit: N] of the sum of tire forces, and a vehicle center of gravity around the vehicle center of gravity generated by the tire force of each wheel. The yaw moment M [unit: Nm] acts. The yaw moment M is positive in the counterclockwise direction when the vehicle is viewed from above.

  In FIG. 3, the tread length Lt [unit: m] of the front and rear wheels, the distance Lf [unit: m] from the vehicle center of gravity axis to the front wheel axle, and the distance Lr [unit: m] from the vehicle center of gravity axis to the rear wheel axle. , Wheel base length Ll = Lf + Lr [unit: m].

Referring now to FIG. 4, consider the force vehicle longitudinal direction component Fx _i of (tire forces) 'and the vehicle lateral component Fy _i' of the driving force generated in the wheel Fx _i and the tire lateral force Fy _i. 4A shows the case of the turning angle δ _i , and FIG. 4B shows the case of the turning angle δ _i + Δδ _i .

As shown in FIG. 4A, Fx _i ′ and Fy _i ′ when each wheel is turned by the steering angle δ _i are expressed by the following equations (1-1) and (1-2). However, Fx _i ′ is positive in the direction of accelerating the vehicle forward, and Fy _i ′ is positive in the direction of accelerating the vehicle in the left direction.

Then the driving force Fx _i wheel does not change, consider the tire lateral force variation amount DerutaFy _i when the steering angle of the wheel is Masa cut from [delta] _i in δ _i + Δδ _i. As shown in FIG. 4 (B), when the steering angle of each wheel is Masa cut from [delta] _i in _{δ i + Δδ i, Fx i} ', Fy i' is expressed by the following equation (2-1) and formula (2 It is expressed by 2).

Therefore, the driving force Fx _i of each wheel is not changed, Fx _i 'of variation ΔFx _i' when the steering angle of each wheel is Masa cut from [delta] _i to [delta] _i + .DELTA..delta _i have the formula (1-1 ) And equation (2-1) can be obtained by taking the difference between the sides, and the following equation (3-1) is obtained. The same 'amount of change ΔFy _i' Fy _i becomes the following equation can be obtained by taking the difference of sides s of formula (1-2) and (2-2) and (3-2). Note the formula (3-1) and (3-2) in .DELTA..delta _i is small, approximating the _{cosΔδ i ≒ 1, sinΔδ i ≒} Δδ i, Δδ i 2 ≒ 0.

The side slip angle β _{i of} each wheel and the tire lateral force Fy _i have the relationship shown in FIG.

Figure 1 is a view showing the relationship between the driving force Fx _i and the tire lateral force Fy _i when the there is no change in the wheel load W and the road surface friction coefficient mu. The horizontal axis is the driving force Fx _i, the vertical axis is the tire lateral force Fy _i. The sign of the side slip angle β _i is positive when the angle from the front-rear direction of the wheel to the direction of the wheel speed is counterclockwise when viewed from vertically above.

Here, when the current state of the wheel is the driving force Fx _i , the tire side force Fy _i , and the side slip angle β _i , an index representing the degree of influence of the side slip angle change amount Δβ _{i on} the tire side force change amount ΔFy _i . Is defined as tire lateral force sensitivity g _i (i = 1 to 4). That is, the tire lateral force sensitivity g _i is defined as the following equation (4). It is assumed that the side slip angle change Δβ _i and the tire side force change amount ΔFy _i are very small.

Therefore, when the side slip angle change amount Δβ _i and the tire side force change amount ΔFy _i are small, “g _i Δβ _i = ΔFy _i ”. It is possible to ignore the delays and camber angle change such as tire lateral force and steering adjustment mechanism, and the definitive and _{"g i Δβ i = ΔFy i ≒} g i Δδ i ", when the steering angle variation Δδ _i 'variation DerutaFx _i' of the front and rear vehicle direction component Fx _i and 'variation DerutaFy _i' of the vehicle lateral component Fy _i, the following equation from the equation (3-1) (3-2) (5-1) ( 5-2) can be obtained.

Therefore, according to the formula (5-1) (5-2), when the steering angle changes by .DELTA..delta _i, considering also the effect that the tire slip angle changes [Delta] [beta] _i, the tire lateral force changes DerutaFy _i In addition, the vehicle longitudinal direction component change amount ΔFx _i ′ and the vehicle lateral direction component change amount ΔFy _i ′ can be obtained.

  In the state of FIG. 3, the vehicle longitudinal component Fx of the sum of tire forces, the vehicle lateral component Fy of the sum of tire forces, and the yaw moment M around the center of gravity of the vehicle generated by the tire force of each wheel are as follows: (6-1) to (6-3).

Accordingly, when the steering angle change amount Δδ _i of each wheel is the vehicle front-rear direction component Fx, the vehicle lateral direction component Fy, and the change amounts ΔFx, ΔFy, ΔM of the yaw moment M are expressed by the following equations (7-1) to (7) (7-3).

  Therefore, the following equation (8) is obtained.

When Δδ ₁ is assumed to be known and Δδ ₂ , Δδ ₃ , and Δδ ₄ are solved, the following equation (9) is obtained.

Accordingly, when Υ ₁ ≠ 0, the steering angle change amount Δδ _{i of} each wheel that changes the vehicle longitudinal component Fx, the vehicle lateral component Fy, and the yaw moment M by ΔFx, ΔFy, and ΔM, respectively, around the current operating point. , Χ are given as arbitrary constants as shown in the following equation (10).

By applying the target vehicle longitudinal direction component change amount ΔFx, vehicle lateral direction component change amount ΔFy, and yaw moment change amount ΔM to the equation (10), the steering angle correction amount Δδ _{i of} each wheel can be obtained. And are taken into account equation (10), the also the tire slip angle variation [Delta] [beta] _i and the tire lateral force variation amount DerutaFy _i associated with the steering angle variation .DELTA..delta _i. Therefore, according to the equation (10), the steering angle change amount Δδ _i can be calculated more accurately. For example, if the vehicle longitudinal component change amount ΔFx is to be suppressed to zero based on the equation (10), “ΔFx = 0” may be set. In this way, changes in the longitudinal force, lateral force, and yaw moment can be suppressed by equation (10). Expression (10) is an expression for calculating _four components Δδ _{1 to} Δδ ₄ from the three components ΔFx, ΔFy, and ΔM, and a plurality of combinations (sets) of Δδ _{1 to} Δδ ₄ are obtained. Therefore, if the optimal solution is obtained from such combinations (sets) that minimize the sum of squares of Δδ _{1 to} Δδ ₄ , the steering angle correction amount can be reduced.

  The above is the basic technical idea of the present invention. Next, a specific system for realizing such a technical idea will be described.

  FIG. 5 is a diagram illustrating an example of a vehicle configuration.

  Vehicle 100 includes a left front wheel system 10, a right front wheel system 20, a left rear wheel system 30, a right rear wheel system 40, and a steering system 50.

  The left front wheel system 10 includes a left front wheel 1, an inverter 11, a motor 12, a driving force sensor 13, a steering actuator 14, and a steering angle sensor 15.

  The inverter 11 supplies the output power of the battery 9 to the motor 12. Further, the inverter 11 outputs the regenerative power of the motor 12 to the battery 9.

  The motor 12 drives the left front wheel 1 with electric power supplied through the inverter 11. Further, electric power is regenerated by the braking force of the left front wheel 1.

  The driving force sensor 13 detects the driving force of the left front wheel 1. The detection signal is transmitted to the controller 7.

  The steering actuator 14 steers the left front wheel 1.

  The steering angle sensor 15 detects the steering angle of the left front wheel 1. The detection signal is transmitted to the controller 7.

  The basic configuration of the right front wheel system 20, the left rear wheel system 30, and the right rear wheel system 40 is the same as that of the left front wheel system 10. In addition, in order to distinguish each system, the code | symbol of the 20th series is attached | subjected about a right front wheel system. The left rear wheel system will be numbered in the thirty range. The right rear wheel system will be marked with the number forty.

  The steering system 50 includes a steering wheel 5 and a steering angle sensor 51. The present embodiment is a so-called steer-by-wire system in which the steering system and the steered wheels are not mechanically connected. The steering angle sensor 51 detects the steering angle of the steering wheel 5. The detection signal is transmitted to the controller 7.

  The acceleration sensor 71 detects the longitudinal acceleration and the lateral acceleration of the vehicle. The detection signal is transmitted to the controller 7.

  The yaw rate sensor 72 detects the yaw rate of the vehicle. The detection signal is transmitted to the controller 7.

  The accelerator pedal position sensor 73 detects the depression amount of the accelerator pedal. The detection signal is transmitted to the controller 7.

  The brake pedal position sensor 74 detects the depression amount of the brake pedal. The detection signal is transmitted to the controller 7.

  Based on various signals, the controller 7 controls the motors 12 to 42 to control the driving force of the wheels 1 to 4 and also controls the steering actuators 14 to 44 to control the turning angles of the wheels 1 to 4. . The controller 7 includes a microcomputer having a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), and an input / output interface (I / O interface). The controller 7 may be composed of a plurality of microcomputers.

  Below, the concrete control logic of the controller 7 is demonstrated along a flowchart.

  FIG. 6 is a flowchart of the main routine.

  The controller 7 repeatedly executes the following processing every predetermined time (for example, 10 milliseconds).

In step S1, the controller 7 detects the accelerator depression amount AP, the brake depression amount BP, the steering angle θ, and the turning angle δ _i of each wheel.

  In step S2, the controller 7 detects the vehicle speed V. Specific contents will be described later.

In step S3, the controller 7 calculates the basic value δ _i ^# of the turning angle of each wheel. A specific calculation method will be described later.

In step S4, the controller 7 calculates the side slip β _{i of} each wheel. A specific calculation method will be described later.

In step S5, the controller 7 calculates a target value Fx ^* of the front-rear direction target static driving force. A specific calculation method will be described later.

In step S6, the controller 7 calculates a driving force basic value Fx _i ^# distributed to each wheel. A specific calculation method will be described later.

  In step S7, the controller 7 calculates the upper limit value Fxi_max and the lower limit value Fxi_min of the driving force of each wheel. The lower limit value is considered because there is braking (regeneration). A specific calculation method will be described later.

Step controller 7 in S8, determines whether the drive force basic value Fx _i ^# to allocate to each wheel is in the range of the upper limit value Fx _i _ _max and the lower limit value Fx _i _ _min. If it is within the range, the process proceeds to step S9, and if it is out of the range, the process proceeds to step S10.

In step S9, the controller 7 sets the driving force basic value Fx _i ^# to the driving force command value Fx _i ^***, and sets the turning angle basic value δ _i ^# to the turning angle command value δ _i ^*** . .

  In step S10, the controller 7 calculates the vehicle longitudinal direction component variation ΔFx, the vehicle lateral direction component variation ΔFy, and the yaw moment variation ΔM. A specific calculation method will be described later.

In step S11, the controller 7 calculates a turning angle correction value Δδ _i for each wheel. A specific calculation method will be described later.

The controller 7 in step S12, when the driving force basic value Fx _i ^# exceeds the upper limit value Fx _i _ _max is an upper limit value Fx _i _ _max to the driving force command value Fx _i ^***, driving force basic value Fx _i ^# is at below the lower limit Fx _i _ _min sets the lower limit value Fx _i _ _min to the driving force command value Fx _i ^***. Further, the turning angle correction value Δδ _i is added to the turning angle basic value δ _i ^# to set the turning angle command value δ _i ^*** .

  In step S13, the controller 7 controls the driving force and the turning angle of each wheel based on the command value.

  FIG. 7 is a flowchart of a vehicle speed detection subroutine.

  In step S21, the controller 7 detects the rotational speeds ω1 to ω4 of the respective wheels.

  In step S22, the controller 7 calculates the speeds V1 to V4 of each wheel based on the following equations (11-1) to (11-4).

  In step S23, the controller 7 calculates the vehicle speed V based on the following equation (12).

  FIG. 8 is a flowchart of a subroutine for calculating the basic value of the turning angle of each wheel.

In step S31, the controller 7 calculates a basic value δ _i ^# of the turning angle of each wheel based on the following equations (13-1) to (13-4).

  FIG. 9 is a flowchart of a subroutine for calculating the side slip of each wheel.

  In step S41, the controller 7 obtains the yaw rate γ by integrating the value obtained by dividing the yaw moment M by the yaw inertia moment I of the vehicle. That is, the yaw rate γ is calculated by the following equation (14).

  In step S42, the controller 7 calculates the time differential value β ′ of the side slip angle of the vehicle based on the following equation (15).

  In step S43, the controller 7 integrates the time differential value β ′ of the side slip angle of the vehicle to calculate the side slip angle β of the vehicle as in the following equation (16).

In step S44, the controller 7 calculates the side slip β _{i of} each wheel based on the following equations (17-1) to (17-4).

  FIG. 10 is a flowchart of a subroutine for calculating the target value of the longitudinal target static driving force.

In step S51, the controller 7 obtains the driving force Fax ^* by applying the accelerator depression amount AP and the vehicle speed V to the characteristic map shown in FIG. 11A stored in the ROM in advance through simulation or experiment.

In step S52, the controller 7 obtains the braking force Fbx ^* by applying the brake depression amount BP to a characteristic map as shown in FIG. 11B stored in the ROM in advance through simulation or experiment.

In step S53, the controller 7 calculates the longitudinal target static driving force Fx ^* based on the following equation (18).

  FIG. 12 is a flowchart of a subroutine for calculating a driving force basic value to be distributed to each wheel.

  In step S61, the controller 7 obtains the left / right driving force difference ΔF by applying the vehicle speed V and the steering angle θ to the characteristic map shown in FIG. 13 stored in the ROM in advance through simulation or experiment.

In step S62, the controller 7 calculates a driving force basic value Fx _i ^# to be distributed to each wheel based on the following equations (19-1) to (19-4).

  FIG. 14 is a flowchart of a subroutine for calculating the upper limit value and the lower limit value of the driving force of each wheel.

In step S71, the controller 7 calculates the road surface friction coefficient μ _i of each wheel. As an example of the calculation method, for example, as described in Japanese Patent Application Laid-Open No. 11-78843, a technique capable of estimating a road surface friction coefficient gradient, which is a gradient of a friction coefficient between a tire and a road surface, As described in Japanese Utility Model Publication No. 10-114263, as a physical quantity that can be handled equivalently to a road surface friction coefficient gradient, there is a technique of estimating based on a braking torque gradient or a driving torque gradient with respect to a slip speed. .

In step S72 the controller 7 calculates the wheel load W _i for each wheel. A specific calculation method will be described later.

  In step S73, the controller 7 calculates the upper limit value Fxi_max and the lower limit value Fxi_min of the driving force of each wheel based on the following equations (20-1) and (20-2).

  FIG. 15 is a flowchart of a subroutine for calculating the wheel load of each wheel.

  In step S721, the controller 7 obtains a vehicle longitudinal component αx and a lateral component αy of acceleration based on the longitudinal component Fx and the lateral component Fy of the tire force.

Step controller 7 in S722 calculates the wheel load W _i for each wheel based on the following equation (21-1) - (21-4).

  FIG. 16 is a flowchart of a subroutine for calculating the vehicle longitudinal direction component variation ΔFx, the vehicle lateral direction component variation ΔFy, and the yaw moment variation ΔM.

In step S101, the controller 7 obtains an amount ΔFx _i that is limited when the driving force basic value Fx _i ^# distributed to each wheel exceeds the upper limit value Fxi_max or the lower limit value Fxi_min by the following equation (22-1). Similarly, ΔFy _i and ΔM are obtained by the following equations (22-2) and (22-3).

  In step S102, the controller 7 obtains the vehicle longitudinal component variation ΔFx, the vehicle lateral component variation ΔFy, and the yaw moment variation ΔM by the following equations (23-1) to (23-3).

  FIG. 17 is a flowchart of a subroutine for calculating a turning angle correction value for each wheel.

In step S111, the controller 7 calculates the turning angle correction value Δδ _i of each wheel based on the above-described equation (10).

According to the present embodiment, as described above, when the driving wheel Fs _i is limited due to slipping of the driving wheel, the steering angle correction amount Δδ is also considered in consideration of the change in the tire lateral force Fy _i. By determining _i , a desired yaw moment M is obtained while suppressing changes in vehicle behavior due to changes in tire lateral force. By doing so, it is possible to accurately trace the target course even in a situation where one of the driving wheels cannot obtain the target driving force for a very short time.

  Without being limited to the embodiments described above, various modifications and changes are possible within the scope of the technical idea, and it is obvious that these are also included in the technical scope of the present invention.

  For example:

(1) Although the turning angle correction value Δδ _i of each wheel is calculated based on the equation (10) above, the equation (10) is based on the assumption that the side slip angle change Δβ _i is minute. Therefore, also in using the equation (10), the vehicle front-rear direction component change amount ΔFx, the vehicle lateral direction component change amount ΔFy, and the yaw moment change amount ΔM obtained in step S10 are further differentiated to some extent to obtain a turning angle correction value Δδ. _i is calculated, and further, the turning angle correction value Δδ _i is calculated in consideration of changes in the vehicle longitudinal direction component variation ΔFx, the vehicle lateral direction component variation ΔFy, and the yaw moment variation ΔM due to the influence thereof, and so on. By repeating this, the turning angle correction value Δδ _i of each wheel can be calculated more accurately. If it is difficult to perform such a calculation in real time, a case assumed in advance may be calculated and stored in the controller.

  (2) It is preferable to obtain a plurality of combinations of the steering angle correction amounts and to calculate an optimum combination of the steering angle correction amounts from them.

  For example, in the above equation (10), the following equation (24) is obtained as “ΔFx = ΔFy = ΔM = 0”.

Then from the set (combination) of the .DELTA..delta _i, may be selected a combination square sum of .DELTA..delta _i is minimized. When the above combination exists, all the vehicle behaviors Fx, Fy, and M can be maintained.

  (3) A turning angle correction amount calculation formula may be used so that “ΔFx: ΔFy: ΔM = Rx: Ry: Rm”.

  In this case, the following equation (25) is derived.

  Then, the change amount Δβ ′ of the differential value of the side slip angle of the vehicle is expressed by the following equation (26).

  Therefore, if “Rx: Ry: Rm = cosβ: sinβ: 0”, the change amount Δβ ′ of the differential value of the side slip angle of the vehicle becomes zero, and the change in the vehicle behavior reduces the driver's uncomfortable feeling. Can be changed. Therefore, it is possible to adjust how the vehicle behavior changes when the driving force restriction is applied, and to improve the driving performance of the driver.

  Since β is very small, it may be simply “Rx: Ry: Rm = 1: β: 0”.

  (4) The above embodiment has been described on the assumption that the steering angles of the four wheels are independently controlled. For example, in a vehicle in which the steering angles of the front left and right wheels are physically linked, The present invention can also be applied to a vehicle having only three adjustable wheels, that is, a front wheel (left and right are linked), a rear left wheel, and a rear right wheel.

In this case, in the above equation (8), if “Δδ ₁ = Δδ ₂ = Δδ _f ” (where Δδ _f is the amount of change in the front wheel steering angle δ _f ), the following equation (27) is obtained.

Therefore, according to this equation (27), Δδ _f , Δδ ₃ , Δδ ₄ for realizing ΔFx, ΔFy, ΔM can be obtained.

  In order to reduce the uncomfortable feeling that the driver feels due to changes in vehicle behavior, it is only necessary to keep the amounts of change in the longitudinal force, lateral force, and yaw moment at a constant ratio, that is, ΔFx: ΔFy: ΔM at a constant ratio. In this way, if ΔFx: ΔFy: ΔM is maintained at a constant ratio, it can be considered that there are two vehicle behaviors to be maintained. Therefore, even in a vehicle having only three steered angle elements that can be independently controlled, the number of vehicle behaviors to be maintained is exceeded. Therefore, the target course can be accurately traced within the range that does not make the driver feel uncomfortable.

  In the case of the equation (27), it is preferable to selectively maintain the lateral force and the yaw moment as the important vehicle behavior when turning. Then, ΔFx in equation (27) is omitted and the following equation (28) is obtained.

  According to this equation (28), even a vehicle having only three steered angle elements that can be controlled independently exceeds the number of vehicle behaviors to be maintained. By selectively maintaining lateral force and yaw moment as the vehicle behavior to be maintained in this way, the target course can be accurately traced even in a vehicle having only three steerable angle elements that can be controlled independently. .

  (5) Vehicles whose steering angles of the rear left and right wheels are also physically linked, that is, there are only two sets of wheels that can independently adjust the steering angle, front wheels (left and right linked) and rear wheels (left and right linked). The present invention can be applied even to a vehicle.

In this case, in the above equation (28), if “Δδ ₃ = Δδ ₄ = Δδ _r ” (where Δδ _r is the amount of change in the front wheel steering angle δ _r ), the following equation (29) is obtained.

Therefore, according to the equation (29), Δδ _f and Δδ _r for realizing ΔFy and ΔM can be obtained.

  Further, by maintaining the change amounts of the lateral force and the yaw moment at a constant ratio, that is, by maintaining ΔFy: ΔM at a constant ratio, it is possible to reduce a sense of incongruity felt by the driver due to a change in vehicle behavior. Thus, if ΔFy: ΔM is maintained at a constant ratio, it can be considered that there is only one vehicle behavior to be maintained. Therefore, even a vehicle having only one steerable angle element that can be controlled independently exceeds the number of vehicle behaviors to be maintained. Therefore, the target course can be accurately traced within the range that does not make the driver feel uncomfortable.

(6) In the above description, the upper limit value Fxi_max and the lower limit value Fxi_min of the driving force of each wheel are calculated based on the road surface friction coefficient μ _i and the wheel load W _i of each wheel. The upper and lower limits of the driving force of each wheel may be obtained, and the upper and lower limits may be set as Fxi_max and Fxi_min, respectively. Specifically, a map (FIG. 18) for determining the relationship with the maximum output Ptmax [unit: W] that can suppress motor overheating from the current motor temperature is preset from the temperature of each motor, and from this Ptmax What is necessary is just to obtain | require like following Formula (30-1) (30-2).

It is a figure which shows the relationship between the driving force of a tire, lateral force, and a slip angle. It is a figure which shows the relationship between the driving force of a tire, lateral force, and a slip angle by the difference in wheel load. It is a figure explaining the force which acts on a vehicle. It is a figure explaining the force which acts on a wheel. It is a figure which shows an example of a vehicle structure. It is a flowchart of a main routine. It is a flowchart of a subroutine of vehicle speed detection. It is a flowchart of the subroutine which calculates the basic value of the steering angle of each wheel. It is a flowchart of the subroutine which calculates the side slip of each wheel. It is a flowchart of the subroutine which calculates the target value of the front-back direction target static driving force. It is a figure which shows an example of the characteristic of an accelerator depression amount and a driving force, and the characteristic of a brake depression amount and a braking force. It is a flowchart of the subroutine which calculates the driving force basic value distributed to each wheel. It is a figure which shows the relationship between a vehicle speed and a steering angle, and a right-and-left driving force difference. It is a flowchart of the subroutine which calculates the upper limit and lower limit of the driving force of each wheel. It is a flowchart of the subroutine which calculates the wheel load of each wheel. 10 is a flowchart of a subroutine for calculating a vehicle longitudinal direction component change amount ΔFx, a vehicle lateral direction component change amount ΔFy, and a yaw moment change amount ΔM. It is a flowchart of the subroutine which calculates the turning angle correction value of each wheel. It is a figure which shows the relationship between the temperature of a motor, and a maximum output.

Explanation of symbols

1 left front wheel 2 right front wheel 3 left rear wheel 4 right rear wheel Step S1 Steering amount detecting means Step S6 Driving force basic value setting means Steps S8 and S12 Driving force limiting means Step S11 Steering angle correction amount combination calculating means

Claims (9)

A device for controlling the posture of a vehicle having wheels that can be steered independently of steering wheel steering by a driver,
Driving force basic value setting means for setting the driving force of the driving wheel according to the driving state;
It is determined whether or not the driving force set by the driving force basic value setting means is within a realizable range. When the driving force exceeds the realizable range, the driving force is limited to the realizable driving force. Means,
Steering angle correction amount combination calculation that calculates a combination of steering angle correction amounts for each wheel that suppresses changes in lateral force and moment of the vehicle body caused by the driving force limitation when the driving force is limited by the driving force limiting means. Means,
Have
The steering angle correction amount combination calculation means, the tire lateral force sideslip angle variation of the wheel divided by the side slip angle variation of the tire lateral force variation amount I index der representing the degree of influence on the tire lateral force variation Calculate the rudder angle correction amount combination based on the sensitivity,
A vehicle attitude control device. The rudder angle correction amount combination calculating means calculates a rudder angle correction amount combination based on tire lateral force sensitivity at a limited driving force.
The vehicle attitude control device according to claim 1. When there are three or more wheels that can be steered,
The rudder angle correction amount combination calculating means obtains a plurality of rudder angle correction amount combinations, and calculates an optimum rudder angle correction amount combination from them.
The vehicle attitude control device according to claim 1 or 2, wherein The rudder angle correction amount combination calculating means calculates a combination with the smallest sum of squares of the respective rudder angle correction amounts as an optimal combination.
The vehicle attitude control device according to claim 3. When there are three or more wheels that can be steered,
The rudder angle correction amount combination calculating means calculates a rudder angle correction amount combination so as to suppress a change in the longitudinal force of the vehicle body caused by the driving force limitation.
The vehicle attitude control device according to any one of claims 1 to 4, wherein the vehicle attitude control device is characterized in that: Vehicle behavior change amount setting means for setting a ratio of the longitudinal force change, the lateral force change, and the moment change according to a driving state;
The rudder angle correction amount combination calculating means calculates a rudder angle correction amount combination that realizes the ratio set by the vehicle behavior change amount setting means.
The vehicle attitude control device according to any one of claims 1 to 5, wherein When there is no combination of steering angle correction amounts that realizes the ratio set by the vehicle behavior change amount setting means, the ratio of the longitudinal force change, the lateral force change, and the moment change according to the driving state. Change the
The vehicle attitude control device according to claim 6. The vehicle behavior change amount setting means sets the ratio of the longitudinal force change, the lateral force change, and the moment change to cosβ: sinβ: 0.
The vehicle attitude control device according to claim 6 or 7, characterized by the above. A method of controlling the attitude of a vehicle having wheels that can be steered independently of steering wheel steering by a driver,
A driving force basic value setting step for setting the driving force of the driving wheel according to the driving state;
It is determined whether or not the driving force set in the driving force basic value setting step is within a realizable range, and when the driving force exceeds the realizable range, the driving force is limited to the realizable driving force. Process,
Steering angle correction amount combination calculation for calculating a combination of steering angle correction amounts for each wheel so as to suppress changes in lateral force and moment of the vehicle body caused by the driving force limitation when the driving force is limited in the driving force limiting step. Process,
Have
The steering angle correction amount combination calculation step, a tire lateral force sideslip angle variation of the wheel divided by the side slip angle variation of the tire lateral force variation amount I index der representing the degree of influence on the tire lateral force variation Calculate the rudder angle correction amount combination based on the sensitivity,
And a vehicle attitude control method.

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