JP2005280688A - Behavior control device of vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve travelling stability of a vehicle at the time of turning acceleration and deceleration by effectively preventing deviation of the vehicle caused by a braking and driving force difference of left and right wheels at the time of rectilinear acceleration and deceleration of the vehicle and preventing unnecessary steering of a steering wheel at the time of the turning acceleration and deceleration of the vehicle. <P>SOLUTION: A yaw moment Mf working on the vehicle due to a longitudinal force difference of the left and right wheels is computed (S70, 80) when behavior control is not practiced, antiskid control or traction control is practiced and the vehicle is in the middle of turning (S30, 40, 50), a counter yaw moment Mc after correction is computed (S120) as a yaw moment Mg is added to a counter yaw moment Mc' (=-Mf) to set off the yaw moment Mf, and a steering angle of left and right front wheels is controlled so that the counter yaw moment Mc after the correction is given to the vehicle (S140 to 160). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a vehicle behavior control device, and more particularly to a behavior control device that controls the behavior of a vehicle by controlling the steering angle of a steered wheel.

  As one of behavior control devices for vehicles such as automobiles, for example, as described in Patent Document 1 below, a vehicle equipped with a steering device that can steer steering wheels independently of a driver's steering operation. There is already known a vehicle behavior control device that steers the steered wheels by the steering means so that the yaw moment acting on the vehicle is canceled by the difference in braking force between the left and right wheels during anti-skid control.

According to such a behavior control device, for example, when anti-skid control is performed on one of the left and right wheels, the difference in braking force between the left and right wheels increases, and the yaw moment due to the difference in braking force acts on the vehicle. The yaw moment due to the difference in braking force between the left and right wheels is canceled by turning the wheel.Therefore, without reducing the braking force of the wheel with the higher friction coefficient on the road surface, in other words, the vehicle deceleration and braking distance are reduced. Without sacrificing, the vehicle can be prevented from deflecting and the running stability of the vehicle can be improved.
Patent registration 2540742

  In general, when the vehicle turns, the ground contact load of the turning outer ring increases and the contact load of the turning inner ring decreases, so that the limit longitudinal force of the turning outer ring increases and the limit longitudinal force of the turning inner ring decreases. In the case of a vehicle in which the front / rear force of the wheel is automatically increased / decreased to prevent an excessive slip of the wheel, such as anti-skid control and traction control, the front / rear force of the outer turning wheel increases and the vehicle turns. The longitudinal force of the inner ring is reduced.

  Therefore, in the conventional behavior control apparatus as described above, when anti-skid control is performed during turning braking of the vehicle and a difference occurs in the braking force between the left and right wheels, it acts on the vehicle due to the difference in braking force between the left and right wheels. If the steering wheel is steered based on the braking force difference between the left and right wheels so that the yaw moment is canceled, the steering wheel is steered unnecessarily toward the inside of the turn, and the turning radius of the vehicle is reduced. There is a problem that it is easy. Conversely, if the traction control is executed during the acceleration of turning of the vehicle and there is a difference in the driving force between the left and right wheels, the difference in driving force between the left and right wheels will cancel out the yaw moment acting on the vehicle due to the difference in driving force between the left and right wheels. When the steered wheels are steered based on the above, the steered wheels are unnecessarily steered toward the outside of the turn, and there is a problem that the turning radius of the vehicle tends to increase against the driver's intention.

  The present invention has been made in view of the above-described problems in the conventional behavior control device that steers the steered wheels so that the yaw moment acting on the vehicle is canceled by the difference in braking / driving force between the left and right wheels. The main problem of the invention is that the vehicle caused by the braking / driving force difference between the left and right wheels during linear acceleration / deceleration of the vehicle by taking into account the difference in braking / driving force between the left and right wheels caused by load movement in the left / right direction during turning. This effectively prevents the steering wheel from turning to the inside or outside of the turn when the vehicle is turning and accelerating / decelerating. It is to improve the running stability of the vehicle during acceleration / deceleration.

  According to the present invention, the main problem described above is the structure of claim 1, that is, a turning means capable of turning the steered wheels independently of the driver's steering operation, and a means for estimating the longitudinal force of each wheel. Means for calculating a yaw moment due to the longitudinal force difference acting on the vehicle due to the difference in the longitudinal force between the left and right wheels, means for computing a yaw moment due to the load movement acting on the vehicle due to the load movement in the left-right direction of the vehicle, A counter yaw moment for at least partially canceling the force difference caused yaw moment is calculated, the counter yaw moment is corrected by the load movement caused yaw moment, and the corrected counter yaw moment acts on the vehicle. This is achieved by a vehicle behavior control device characterized by comprising steering control means for steering the steered wheels by the steering means.

  According to the present invention, in order to effectively achieve the main problem described above, in the configuration of claim 1, the means for calculating the load movement-induced yaw moment has a large lateral acceleration of the vehicle. The load movement-induced yaw moment is calculated based on the lateral acceleration of the vehicle so that the magnitude of the load movement-induced yaw moment increases.

  According to the present invention, in order to effectively achieve the main problems described above, in the configuration according to claim 1 or 2, the steering control means is adapted to adjust the steering operation amount and predetermined steering characteristics of the driver. The provisional target rudder angle of the steered wheel is calculated based on the counter yaw moment after the correction, the target rudder angle of the steered wheel is calculated by correcting the temporary target rudder angle based on the corrected counter yaw moment, and the steered wheel is calculated based on the target rudder angle. The steering angle of the steered wheel is controlled by means (structure of claim 3).

  According to the configuration of the first aspect, the yaw moment due to the longitudinal force difference acting on the vehicle is calculated based on the difference between the longitudinal forces of the left and right wheels, and the yaw moment due to load movement acting on the vehicle due to the load movement in the lateral direction of the vehicle is calculated. The counter yaw moment for at least partially canceling the longitudinal force difference-induced yaw moment is calculated, the counter yaw moment is corrected by the load movement-induced yaw moment, and the corrected counter yaw moment acts on the vehicle. Since the steered wheels are steered by the steering means, the extra yaw moment caused by the difference in braking force between the left and right wheels due to left and right load movement is eliminated from the counter yaw moment, thus eliminating the extra yaw moment Steering wheels are made unnecessary by turning the steering wheels so that the later counter yaw moment acts on the vehicle. The vehicle can be prevented from being steered inwardly or outwardly during turning, thus effectively preventing vehicle deflection caused by a difference in braking / driving force between the left and right wheels during linear acceleration / deceleration of the vehicle. The running stability of the vehicle during turning acceleration / deceleration can be improved.

  According to the second aspect of the present invention, the load movement-induced yaw moment is calculated based on the lateral acceleration of the vehicle so that the magnitude of the load movement-induced yaw moment increases as the lateral acceleration of the vehicle increases. Therefore, the load movement-induced yaw moment is calculated so that the greater the difference in braking force between the left and right wheels due to the load movement in the left-right direction, the greater the magnitude of the load movement-induced yaw moment, thereby increasing the degree of turning of the vehicle and the lateral acceleration of the vehicle. The excess yaw moment can be surely reduced by the counter yaw moment even when the magnitude of is large.

  According to the configuration of the third aspect, the provisional target rudder angle of the steered wheels is calculated based on the driver's steering operation amount and predetermined steering characteristics, and the provisional target rudder angle is corrected based on the corrected counter yaw moment. Thus, the target rudder angle of the steered wheels is calculated, and the steered angle of the steered wheels is controlled by the steering means based on the target rudder angle, so that the vehicle travels when turning while reliably achieving a predetermined steering characteristic. Stability can be improved.

[Preferred embodiment of problem solving means]
According to one preferable aspect of the present invention, in the configuration according to any one of the first to third aspects, the steering means steers the steering wheel relative to the steering operator operated by the driver. The steering wheel is configured to be steered and driven independently of the driver's steering operation (preferred aspect 1).

  According to another preferred aspect of the present invention, in the configuration of claims 1 to 3, the steering control means has the same magnitude as the longitudinal force difference-induced yaw moment and has a reverse direction. Is configured to calculate the counter yaw moment (preferred aspect 2).

  According to another preferred aspect of the present invention, in the configuration of claims 1 to 3, the steering control means determines whether or not the vehicle is in a turning state, and when the vehicle is in a turning state. The steering wheel is steered by the steering means so that the corrected counter yaw moment acts on the vehicle, and when the vehicle is not in a turning state, the steering wheel is steered by the steering means so that the uncorrected counter yaw moment acts on the vehicle. It is comprised so that it may steer (the preferable aspect 3).

  According to another preferred aspect of the present invention, in the configuration of the first to third aspects, the vehicle behavior is controlled by controlling the braking / driving force of each wheel when the behavior of the vehicle is deteriorated. The steering control means has a behavior control means by controlling the braking / driving force to stabilize the steering wheel, and the steering control means controls the steering wheel so that the corrected counter yaw moment acts on the vehicle when the behavior control means is not operated. Is configured to steer (preferred aspect 4).

  According to another preferred aspect of the present invention, in the configuration of claims 1 to 3, the vehicle controls the braking / driving force of the wheel when the acceleration slip or deceleration slip of the wheel is excessive. A wheel slip control means for reducing acceleration slip or deceleration slip is provided, and the steering control means has a corrected counter yaw moment acting on the vehicle when the vehicle is in a turning state and the wheel slip control means is operating. The steered means is configured to steer the steered wheels (preferred aspect 5).

  According to another preferred aspect of the present invention, in the configuration of the preferred aspect 4 or 5, the steering control means is configured to provide a provisional target rudder angle of the steered wheel based on a driver's steering operation amount and predetermined steering characteristics. And when the behavior control means is operating or when the wheel slip control means is not operating, the steering angle of the steered wheels is controlled by the turning means based on the provisional target steering angle (preferred aspect) 6).

  According to another preferred aspect of the present invention, in the configuration of the first to third aspects, the means for estimating the longitudinal force of each wheel estimates the driving force of each wheel and determines the braking force of each wheel. It is configured to estimate and to estimate the longitudinal force of each wheel as the sum of the driving force and the braking force (preferred aspect 7).

  According to another preferred aspect of the present invention, in the configuration of the above first to third aspects, the vehicle further includes braking / driving force distribution control means for controlling the distribution of braking / driving force of the wheels when the vehicle is turning accelerated / decelerated. And the steering control means is configured to steer the steered wheels by the steering means so that the corrected counter yaw moment acts on the vehicle when the braking / driving force distribution control means is not operating (preferred embodiment). 8).

  The present invention will now be described in detail with reference to the accompanying drawings.

  FIG. 1 is a schematic configuration diagram showing one embodiment of a vehicle behavior control device according to the present invention applied to a semi-steer-by-wire rear wheel drive vehicle equipped with a turning angle varying device functioning as an automatic turning device. is there.

  In FIG. 1, 10FL and 10FR respectively indicate left and right front wheels as driven steering wheels of the vehicle 12, and 10RL and 10RR respectively indicate left and right rear wheels as drive wheels of the vehicle. The left and right front wheels 10FL and 10FR, which are steering wheels, are rotated via a rack bar 18 and tie rods 20L and 20R by a rack-and-pinion type power steering device 16 driven in response to an operation of the steering wheel 14 by a driver. Steered.

  The steering wheel 14 is connected to a pinion shaft 30 of the power steering device 16 via an upper steering shaft 22 as a first steering shaft, a turning angle varying device 24, a lower steering shaft 26 as a second steering shaft, and a universal joint 28. Drive connected. In the illustrated embodiment, the turning angle varying device 24 is connected to the lower end of the upper steering shaft 22 on the housing 24A side, and is connected to the upper end of the lower steering shaft 26 on the rotor 24B side. An electric motor 32 for turning driving is included.

  Thus, the steering angle varying device 24 drives the lower steering shaft 26 to rotate relative to the upper steering shaft 22, so that the ratio of the steering angles of the left and right front wheels 10 FL and 10 FR, which are the steering wheels, with respect to the rotation angle of the steering wheel 14. In other words, it functions as a steering gear ratio variable device that changes the steering gear ratio, and also functions as an automatic steering device that drives the left and right front wheels 10FL and 10FR relative to the steering wheel 14 for the purpose of behavior control. Then, it is controlled by the steering control unit of the electronic control unit 34.

  In particular, the turning angle variable device 24 rotates the lower steering shaft 26 relative to the upper steering shaft 22 by the electric motor 32 so that the steering gear ratio becomes a gear ratio that achieves a predetermined steering characteristic in a normal state. At the time of auxiliary steering driving, the lower steering shaft 26 is actively rotated relative to the upper steering shaft 22 by the electric motor 32, so that the left and right front wheels 10FL and 10FR are automatically turned on without depending on the driver's steering operation. Steer.

  If an abnormality in which the lower steering shaft 26 cannot be driven to rotate relative to the upper steering shaft 22 occurs in the turning angle varying device 24, a lock device not shown in FIG. The relative rotation of the housing 24A and the rotor 24B is mechanically prevented so that the relative rotation angle of the lower steering shaft 26 with respect to 22 does not change.

  The power steering device 16 may be either a hydraulic power steering device or an electric power steering device. However, the power steering device 16 is generated by the auxiliary steering driving of the front wheels by the steering angle varying device 24 and transmitted to the steering wheel 14. A rack coaxial type electric motor having, for example, an electric motor and a conversion mechanism such as a ball screw type that converts the rotational torque of the electric motor into a reciprocating force of the rack bar 18 so that an auxiliary steering torque for reducing the force torque is generated. A power steering apparatus is preferable.

  The braking force of each wheel is controlled by controlling the pressure Pi (i = fl, fr, rl, rr) in the wheel cylinders 40FL, 40FR, 40RL, 40RR, that is, the braking pressure, by the hydraulic circuit 38 of the braking device 36. It has become so. Although not shown in the drawing, the hydraulic circuit 38 includes an oil reservoir, an oil pump, various valve devices, and the like, and the braking pressure of each wheel cylinder is normally driven in response to the depression operation of the brake pedal 42 by the driver. It is controlled by the master cylinder 44 and individually controlled by the electronic control unit 34 as will be described in detail later if necessary.

  In the illustrated embodiment, the upper steering shaft 22 is provided with a steering angle sensor 50 for detecting the rotation angle of the upper steering shaft as a steering angle θ. The steering angle variable device 24 includes a housing 24A and A rotation angle sensor 52 that detects the relative rotation angle of the rotor 24B as the relative rotation angle θre of the lower steering shaft 26 with respect to the upper steering shaft 22 is provided, and the output of these sensors is supplied to the electronic control unit 34.

  The electronic control unit 34 also includes a signal indicating the vehicle lateral acceleration Gy detected by the lateral acceleration sensor 54, a signal indicating the vehicle yaw rate γ detected by the yaw rate sensor 56, and the wheel speed sensors 58FL to 58RR. A signal indicating the wheel speed Vwi (i = fl, fr, rl, rr) of the wheel, a signal indicating the braking pressure Pi of each wheel detected by the pressure sensors 60FL-60RR, the throttle opening φ and the engine from the engine controller 62 A signal indicating the rotational speed Ne is input.

  Although not shown in detail in FIG. 1, the electronic control unit 34 is a steering control unit that controls the steering angle varying device 24, a braking force control unit that controls the braking force of each wheel, and the behavior of the vehicle. Each control unit includes a CPU, a ROM, a RAM, and an input / output port device, which include a microcomputer connected to each other via a bidirectional common bus. Good. Further, the steering angle sensor 50, the rotation angle sensor 52, the lateral acceleration sensor 54, and the yaw rate sensor 56 are respectively set to the steering angle θ, the relative rotation angle θre, and the lateral acceleration when the vehicle is steered, steered, or turned in the left turn direction. Gy and yaw rate γ are detected.

  As will be described later, the electronic control unit 34 normally calculates a steering gear ratio Rg for achieving a predetermined steering characteristic based on the vehicle speed V, and based on the steering angle θ and the steering gear ratio Rg indicating the steering operation amount of the driver. The provisional target rudder angle δst is calculated, and the turning angle varying device 24 is controlled so that the rudder angle of the left and right front wheels becomes the provisional target rudder angle δst. The front wheels 10FL and 10FR are steered.

  The electronic control unit 34 also obtains a target braking pressure Pti (i = fl, fr) for each wheel by multiplying the master cylinder pressure Pm by a predetermined pressure increase coefficient Ki (i = fl, fr, rl, rr) during normal braking. , Rl, rr) and control so that the braking pressure Pi becomes the target braking pressure Pti, but when anti-skid control (ABS control) or traction control (TRC control) described later is executed or braking force control When the target braking pressure Pti for behavior control by is calculated, the braking pressure of each wheel is controlled with priority on those controls.

  The electronic control unit 34 calculates the vehicle body speed Vb and the braking slip amount SBi (i = fl, fr, rl, rr) of each wheel based on the wheel speed Vwi of each wheel in a manner known in the art. When the braking slip amount SBi becomes larger than the reference value for starting anti-skid control (ABS control) and the anti-skid control start condition is satisfied, the braking slip amount of the wheel is increased until the anti-skid control end condition is satisfied. Anti-skid control is performed by controlling the braking pressure Pi of the wheel so as to be within a predetermined range.

  When the electronic control unit 34 performs anti-skid control for only one of the left and right wheels, the left and right wheels are adjusted by matching the braking force of the wheel on the opposite side to the wheel with the braking force of the wheel on the anti-skid control side. No so-called low select control is performed to prevent the braking force difference between the two from becoming excessive.

  The electronic control unit 34 calculates the vehicle body speed Vb and the acceleration slip amount SAi (i = fl, fr, rl, rr) of each wheel based on the wheel speed Vwi of each wheel in a manner known in the art. When the acceleration slip amount SAi becomes larger than the reference value for starting traction control (TRC control) and the traction control start condition is satisfied, the acceleration slip amount of the wheel is within a predetermined range until the traction control end condition is satisfied. Traction control is performed by controlling the braking pressure Pi of the wheel so as to be inside.

  The electronic control unit 34 also includes a spin state quantity SS indicating the degree of vehicle spin and a drift-out state quantity DS indicating the degree of vehicle drift-out based on the vehicle state quantity such as the lateral acceleration Gy of the vehicle that changes as the vehicle travels. And the target braking pressure Pti (i = fl, fr, rl, rr) for each wheel for stabilizing the behavior of the vehicle based on the spin state amount SS and the drift-out state amount DS is calculated. By controlling the braking pressure Pi to be equal to the target braking pressure Pti, behavior control is performed by controlling the braking force that stabilizes the behavior of the vehicle.

  The above-described behavior control by the anti-skid control, the traction control, and the braking force control itself does not form the gist of the present invention, and these controls are executed in any manner known in the art. Good.

  Further, when the vehicle is turning, the behavior control by the braking force control is not executed, and the anti-skid control or the traction control is executed, the electronic control device 34 calculates the longitudinal force Fxi of each wheel by estimation. The yaw moment Mf due to the longitudinal force difference acting on the vehicle is calculated from the difference in the longitudinal force between the left and right wheels, and the yaw moment Mg due to the load movement acting on the vehicle due to the load movement in the lateral direction of the vehicle is calculated. The corrected counter yaw moment Mc is calculated by adding the load movement-induced yaw moment Mg to the counter yaw moment Mc 'for canceling the yaw moment, and the corrected counter yaw moment Mc is calculated based on the corrected counter yaw moment Mc. Calculate the corrected turning angle Δδt of the left and right front wheels to give Mc to the vehicle, and the provisional target steering angle δst It calculates the left and right front wheels of the target steering angle .DELTA.t by correcting at .DELTA.t, controls the steering angle of the left and right front wheels by the turning angle varying apparatus 24 on the basis of the target steering angle .DELTA.t.

  Next, a vehicle behavior control routine based on the steering angle control of the left and right front wheels achieved by the electronic control unit 34 in the illustrated embodiment will be described with reference to the flowchart shown in FIG. The control according to the flowchart shown in FIG. 2 is started by closing an ignition switch not shown in the figure, and is repeatedly executed at predetermined time intervals.

First, at step 10, a signal indicating the steering angle .theta. Is read, and at step 20, the steering gear ratio Rg is calculated from the map corresponding to the graph shown in FIG. At the same time, a provisional target rudder angle δst of the left and right front wheels for achieving a predetermined steering characteristic is calculated according to the following formula 1.
δst = θ / Rg (1)

  The provisional target rudder angle δst is the sum of the rudder angle δw (= θ / Rgo) corresponding to the driver's steering operation and the control turning angle δc for achieving a predetermined steering characteristic. Further, the steering characteristic itself does not form the gist of the present invention, and the steering gear ratio Rg may be calculated in an arbitrary manner known in the art, for example, to improve the transient response of the vehicle to the steering. It may be changed by the steering speed.

  In step 30, it is determined whether or not behavior control based on braking force control, that is, spin suppression control or drift-out suppression control is being executed. If an affirmative determination is made, the process proceeds to step 60, and a negative determination is made. When the operation is performed, the process proceeds to step 40.

  In step 40, it is determined whether or not anti-skid control is being performed for any of the wheels. If an affirmative determination is made, the process proceeds to step 70. If a negative determination is made, the process proceeds to step 50. .

  In step 50, it is determined whether or not the traction control is being executed for the left rear wheel or the right rear wheel, which are driving wheels. If a negative determination is made, in step 60, the target rudder of the left and right front wheels is determined. After the angle δt is set to the provisional target rudder angle δst, the process proceeds to step 160. When an affirmative determination is made, the process proceeds to step 70.

In step 70, Ji is the wheel inertia moment, Vwdi is the wheel rotational angular velocity, R is the wheel effective radius, Txi is the wheel braking torque Tbi (negative value) and drive torque Tdi (positive value). ), The longitudinal force (braking / driving force) Fxi (i = fl, fr, rl, rr) of each wheel is calculated according to the following equation 2.
Ji ・ Vwdi ＝ R ・ Fxi + Txi
Fxi = (Ji · Vwdi−Txi) / R (2)

  The rotational angular velocity Vwi of the wheel is calculated as a differential value of the wheel velocity Vwi. The braking torque Tbi is calculated based on a master cylinder pressure Pm detected by a pressure sensor (not shown) and a pressure-braking torque conversion coefficient determined by the specifications of the braking device 36. Further, the drive torque Tdi is calculated based on the throttle opening φ and the engine speed Ne inputted from the engine control device 62, and based on the engine torque Te and a constant determined by the specifications of the drive system. Calculated. Further, the braking torque Tbi and the driving torque Tdi may be directly detected by, for example, a force sensor.

In step 80, the yaw moment Mf due to the longitudinal force difference acting on the vehicle due to the longitudinal force difference between the left and right wheels is calculated based on the longitudinal force Fxi of each wheel based on the longitudinal force Fxi of each wheel with T as the tread of the vehicle. .
Mf = {(Fxfr + Fxrr)-(Fxfl + Fxrl)} (T / 2) (3)

In step 90, Fzlo and Fzro are the total ground load of the left front and rear wheels and the total ground load of the right front and rear wheels when the vehicle is stationary, respectively, M is the vehicle weight, and H is the height of the center of gravity of the vehicle. As a result, the total ground load Fzl of the left front and rear wheels and the total ground load Fzr of the right front and rear wheels are calculated according to the following equations 4 and 5. The ground loads Fzl and Fzr are calculated based on the lateral acceleration Gy of the vehicle, but may be calculated based on the ground load of each wheel detected by a load sensor, for example.
Fzl = Fzlo-M ・ Gy ・ H / T (4)
Fzr = Fzro + M ・ Gy ・ H / T (5)

In step 100, Kg is the acceleration of gravity and Fx is the sum of the longitudinal force Fxi of each wheel, and the load movement-induced yaw moment Mg acting on the vehicle by the load movement in the left-right direction of the vehicle is calculated according to the following equation (6). The
Mg = Fx {(Fzr-Fzl) / (Fzr + Fzl)} (T / 2)
= Fx (Gy · H) / Kg (6)

  In step 110, for example, whether or not the vehicle is in a turning state is determined by determining whether or not the absolute value of the vehicle yaw rate γ is greater than or equal to a reference value γo (positive constant). When the determination is made, the routine proceeds to step 120, and when the negative determination, that is, the determination that the vehicle is substantially in a straight traveling state or a stopped state is performed, the processing proceeds to step 130.

In step 120, if the counter yaw moment for canceling the yaw moment due to the longitudinal force difference is Mc ′ (= −Mf), the counter yaw moment is corrected to the load yaw moment due to load movement added to Mc ′. The counter yaw moment Mc as the counter yaw moment is calculated according to the following equation (7), and in step 130, the counter yaw moment Mc is set to -Mf.
Mc = Mc '+ Mg
= -Mf + Mg (7)

  In step 140, the corrected turning angle Δδt is applied to the technical field as the turning angle of the left and right front wheels to be increased or decreased in order to apply the counter yaw moment Mc to the vehicle by turning the left and right front wheels based on the counter yaw moment Mc. In step 150, the target steering angle δt of the left and right front wheels is calculated as the sum of the provisional target steering angle δst and the corrected steering angle Δδt. In step 160, the left and right front wheels are calculated. The steered angle of the left and right front wheels is controlled by controlling the steered angle varying device 24 so that the steered angle becomes the target steered angle δt.

  Thus, according to the illustrated embodiment, in step 20, the steering gear ratio Rg for achieving a predetermined steering characteristic is calculated based on the vehicle speed V, and the steering angle .theta. Based on the gear ratio Rg, the provisional target rudder angle δst is calculated. In normal times, in steps 60 and 160, the steering angle variable device 24 is set so that the rudder angle of the left and right front wheels becomes the same target rudder angle δt as the provisional target rudder angle δst. Thus, the left and right front wheels 10FL and 10FR are steered with predetermined steering characteristics in accordance with the driver's steering operation.

  On the other hand, when the behavior control by the control of the braking force is not executed, the anti-skid control or the traction control is executed, and the vehicle is turning, a negative determination is made in step 30, and step 40 is executed. Alternatively, an affirmative determination is made at 50, the longitudinal force Fxi of each wheel is calculated by estimation at step 70, and the yaw moment due to the longitudinal force difference acting on the vehicle due to the difference between the longitudinal forces of the left and right wheels at step 80. Mf is calculated, and in steps 90 and 100, the load movement-induced yaw moment Mg acting on the vehicle by the load movement in the left-right direction of the vehicle is calculated.

  In step 110, an affirmative determination is made, and in step 120, the corrected yaw moment Mc due to load movement is added to the counter yaw moment Mc 'for canceling the yaw moment due to the longitudinal force difference. The moment Mc is calculated, and in step 140, the corrected turning angle Δδt of the left and right front wheels for applying the corrected counter yaw moment Mc to the vehicle based on the corrected counter yaw moment Mc is calculated. The target steering angle δt of the left and right front wheels is calculated by correcting the provisional target steering angle δst with the corrected steering angle Δδt. In step 160, the steering angle varying device 24 calculates the target steering angle δt of the left and right front wheels based on the target steering angle δt. The rudder angle is controlled.

  Therefore, according to the embodiment shown in the figure, when the vehicle is turning, the behavior control by the braking force control is not executed and the anti-skid control is executed, the vehicle turns due to the braking force difference between the left and right wheels. The left and right front wheels 10FL and 10FR are unnecessarily steered to the inside of the turn due to the turning angle corresponding to the yaw moment Mf caused by the longitudinal force difference acting in the acceleration direction, and the turning of the vehicle due to this It is possible to reliably prevent the radius from becoming unnecessarily small.

  Further, according to the illustrated embodiment, when the vehicle is turning, the behavior control by the braking force control is not executed, and the traction control is executed, the vehicle is turned by the difference in driving force between the left and right rear wheels. The left and right front wheels 10FL and 10FR are unnecessarily steered to the outside of the turn due to the turning angle corresponding to the yaw moment Mf due to the longitudinal force difference acting in the restraining direction, and the driver's Contrary to the intention, the turning radius of the vehicle can be reliably prevented from becoming unnecessarily large.

  In particular, according to the illustrated embodiment, even when the vehicle is turning and the anti-skid control or the traction control is being executed, when the behavior control by the braking force control is being executed, an affirmative determination is made at step 30. Since steps 40 to 150 are not executed, in a situation where the braking force of each wheel is actively controlled to stabilize the behavior of the vehicle, it is based on the difference between the front and rear force of the left and right wheels by the behavior control. Therefore, it is ensured that the unnecessary front-rear force difference-induced yaw moment Mf is calculated, the left and right front wheels 10FL and 10FR are steered unnecessarily, and the stabilization of the vehicle behavior is hindered due to this. Can be prevented.

  Further, according to the illustrated embodiment, it is determined whether or not anti-skid control or traction control is being executed in steps 40 and 50, respectively, and whether or not the vehicle is turning in step 110. When the anti-skid control or the traction control is executed and the vehicle is in the turning state, steps 120, 140, and 150 are executed, so that the determination of steps 40, 50, and 110 is not performed. Compared to the case, it is possible to reduce the possibility that the counter yaw moment Mc ′ is unnecessarily added and corrected by the load movement-induced yaw moment Mg.

  Further, according to the illustrated embodiment, the steering gear ratio Rg for achieving a predetermined steering characteristic is calculated in step 20, and the steering angle θ and the steering gear ratio Rg indicating the steering operation amount of the driver are calculated. Based on the corrected counter yaw moment Mc in steps 120, 140 and 150, the provisional target rudder angle δst is calculated based on the corrected counter yaw moment Mc to the vehicle. Is calculated and the target steering angle δt of the left and right front wheels is calculated by correcting the provisional target steering angle δst with the corrected steering angle Δδt, so that at the time of turning acceleration / deceleration while reliably achieving the predetermined steering characteristics The running stability of the vehicle can be improved.

  Although the present invention has been described in detail with reference to specific embodiments, the present invention is not limited to the above-described embodiments, and various other embodiments are possible within the scope of the present invention. It will be apparent to those skilled in the art.

  For example, in the above-described embodiment, the turning angle varying device 24 as the turning means does not depend on the driver's steering operation by rotating the lower steering shaft 26 relative to the upper steering shaft 22. The left and right front wheels 10FL and 10FR are automatically steered. However, as long as the steerable means can steer the steered wheels independently of the driver's steering operation, for example, a type that expands and contracts the tie rods 20L and 20R. The steering angle variable device and the steer-by-wire type steering device may be of any configuration known in the art, and the steering means steers the rear wheels as auxiliary steering wheels. It may be.

  In the above embodiment, the counter yaw moment Mc 'for canceling the longitudinal force difference-induced yaw moment is -Mf, that is, the magnitude is the same as that of the longitudinal force difference-induced yaw moment Mf and the direction is opposite. Although it is the yaw moment, the magnitude of the counter yaw moment Mc ′ may be smaller than the magnitude of the yaw moment Mf resulting from the longitudinal force difference.

  Further, in the above-described embodiment, even when the vehicle is in a turning state and the anti-skid control or the traction control is executed, when the behavior control by the braking force control is executed, steps 40 to 150 are executed. However, in the case of a vehicle in which braking / driving force distribution control is performed to control the distribution of braking / driving force between at least the left and right wheels during acceleration / deceleration of turning of the vehicle, the braking / driving force distribution control is executed. It is preferable that the steps 40 to 150 are not executed even during the operation.

  Further, in the above-described embodiment, when the behavior control by the braking force control is executed, the steps 40 to 150 are not executed, but the behavior control by the braking force control or the braking / driving force distribution is performed. When the control is being executed, the counter yaw moment Mc ′ may be corrected based on the yaw moment generated by the control.

  In the above-described embodiment, the steering gear ratio Rg for achieving a predetermined steering characteristic is calculated based on the vehicle speed V, and provisional based on the steering angle θ indicating the driver's steering operation amount and the steering gear ratio Rg. The target rudder angle δst is calculated, and normally, the rudder angle of the left and right front wheels is controlled to become the provisional target rudder angle δst. When the vehicle is in a turning state and anti-skid control or traction control is being executed, the provisional target rudder angle The steering angle of the left and right front wheels is controlled with the target steering angle δt as a value corrected by the correction steering angle Δδt for applying the counter yaw moment Mc to the vehicle. , 150 is omitted, and it is not necessary to apply the counter yaw moment Mc to the vehicle, that is, a negative determination is made in step 30, or in steps 40 and 50 When a positive determination is made Te may be modified to relative rotational angle by the turning angle varying apparatus 24 is controlled to zero.

  In the above-described embodiment, the behavior control is such that the braking force of each wheel is controlled and the vehicle's behavior is controlled by applying a required yaw moment to the vehicle. It may be performed by controlling the braking force and driving force of the wheels.

  Further, in the above-described embodiment, the vehicle is a rear wheel drive vehicle in which the rear wheels are driven by an engine. However, the present invention may be applied to a front wheel drive vehicle or a four wheel drive vehicle. The present invention may be applied to a vehicle in which driving wheels are driven by corresponding driving devices, such as a motor type vehicle.

It is a schematic block diagram which shows one Example of the vehicle behavior control apparatus by this invention applied to the semi steer-by-wire type rear-wheel drive vehicle provided with the turning angle variable apparatus which functions as an automatic turning apparatus. It is a flowchart which shows the steering angle control routine of the left-right front wheel in an Example. It is a graph which shows the relationship between the vehicle speed V and steering gear ratio Rg.

Explanation of symbols

DESCRIPTION OF SYMBOLS 16 Power steering device 14 Steering wheel 24 Steering angle variable device 34 Electronic control device 36 Braking device 44 Master cylinder 50 Steering angle sensor 52 Rotation angle sensor 54 Lateral acceleration sensor 56 Yaw rate sensor 58FL-58RR Wheel speed sensor 60FL-60RR Pressure sensor 62 Engine control device

Claims (3)

  The steering means that can steer the steered wheels independently of the driver's steering operation, the means for estimating the longitudinal force of each wheel, and the longitudinal force difference-induced yaw moment acting on the vehicle due to the longitudinal force difference between the left and right wheels Means for calculating, means for calculating the load movement-induced yaw moment acting on the vehicle by load movement in the left-right direction of the vehicle, and calculating a counter yaw moment for at least partially canceling the yaw moment due to the longitudinal force difference. A steering control unit that corrects the counter yaw moment with the load movement-induced yaw moment, and steers the steered wheels by the steering unit so that the corrected counter yaw moment acts on the vehicle. A vehicle behavior control device.   The means for calculating the load movement-induced yaw moment calculates the load movement-induced yaw moment based on the lateral acceleration of the vehicle so that the magnitude of the load movement-induced yaw moment increases as the lateral acceleration of the vehicle increases. The vehicle behavior control device according to claim 1. The steering control means calculates a provisional target rudder angle of a steered wheel based on a driver's steering operation amount and predetermined steering characteristics, and corrects the provisional target rudder angle based on the corrected counter yaw moment. The vehicle behavior control device according to claim 1 or 2, wherein a target steering angle of the wheel is calculated, and the steering angle of the steering wheel is controlled by the turning means based on the target steering angle.

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