JP2007168698A - Steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve contact avoiding capability to a front obstacle by making the utmost use of lateral force generated on a wheel. <P>SOLUTION: A wheel slip angle where the lateral force which is generated on the wheel gets maximum is stored as a target slip angle. When a front obstacle detecting sensor provided on a vehicle front part determines that a vehicle may contact with the front obstacle, a steering angle is calculated so as to make the wheel slip angle get to a target slip angle, thereby controlling steering. In case that lateral acceleration is generated to change load share of right and left wheels, the wheel slip angle where the lateral force gets maximum is changed. Therefore, steering is controlled by using the target slip angle according to a grounding load, thereby making the utmost use of the lateral force. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a steering device that steers wheels and avoids contact when a vehicle may contact a front obstacle while the vehicle is traveling.

Conventionally, as this type of steering device, for example, Patent Document 1 includes a collision risk determination unit that determines the risk of a vehicle colliding with an obstacle ahead based on the vehicle trajectory, and the risk of collision. There is known a four-wheel steering device that tries to avoid a collision by steering control when it is determined that there is. In this turning apparatus, when it is determined that there is a risk of collision, the avoidance locus of the vehicle is calculated, and the front and rear wheel turning ratio is calculated according to the avoidance locus. Then, the rear wheels are steered so that the ratio between the front wheel turning angle and the rear wheel turning angle becomes the calculated front and rear wheel turning ratio.
Further, for example, in Patent Document 2, in order to avoid collision with a front obstacle, a target yaw rate is calculated, and a steering angle of a front wheel or a rear wheel is controlled so that an actual yaw rate becomes a target yaw rate. Is also known.
JP-A-5-238403 Japanese Patent Laid-Open No. 2001-247023

However, in these steering devices, the lateral force generated on the wheels is not fully used for avoiding the collision with the obstacle, and the collision avoidance ability is inferior.
In other words, in the conventional apparatus, the collision avoidance in the lateral direction is performed by turning, and the rear wheel lateral force is obtained by generating the yaw rate. Will delay the lateral acceleration of the vehicle.
As described above, in the conventional apparatus, it is not considered to avoid the collision by making the maximum use of the lateral force generated on the wheel.

  An object of the present invention is to solve the above-described problem, and an object of the present invention is to improve the ability to avoid contact with a front obstacle by effectively using a lateral force generated on a wheel.

  In order to achieve the above object, the present invention is characterized by a steering actuator that adjusts the steering angles of the front and rear wheels, and a contact possibility determination that determines the possibility that the vehicle will contact a front obstacle while the vehicle is traveling Means, a turning angle calculating means for calculating a turning angle at which the lateral force generated on the wheel is maximized, and if it is determined that the vehicle may come into contact with the front obstacle, There is provided a turning angle control means for controlling the turning actuator so that the turning angle becomes the turning angle calculated by the turning angle calculation means.

  In the present invention configured as described above, when it is determined by the contact possibility determination means that the vehicle is likely to come into contact with a front obstacle during traveling, the turning angle control means includes the turning angle calculation means. The turning actuators are controlled to adjust the turning angles of the front and rear wheels so that the turning angle at which the lateral force (cornering force) generated on the wheels calculated by the above is maximized. That is, the steering actuators for the front and rear wheels are controlled using the turning angle at which the lateral force generated on the wheels is maximized as the target turning angle. Therefore, a large vehicle lateral acceleration is quickly generated by making maximum use of the lateral force generated on the front and rear wheels. As a result, the ability to avoid contact with the front obstacle is improved.

  Another feature of the present invention is that the turning angle calculation means calculates a wheel slip angle at which the lateral force generated on the wheel is maximum, and calculates the turning angle based on the slip angle. is there.

The lateral force (cornering force) generated on the wheel varies depending on the slip angle of the wheel. Therefore, the wheel slip angle at which the lateral force is maximized is obtained from the relationship between the lateral force and the wheel slip angle, and the turning angle is calculated so that the wheel slip angle can be obtained. Can generate power.
In determining the wheel slip angle at which the lateral force is maximized, for example, the wheel slip angle at which the lateral force is maximized from the relationship between the wheel slip angle and the wheel lateral force is stored in advance in the storage means as the target wheel slip angle. The stored target slip angle may be read out.

  In addition, another feature of the present invention is provided with load sharing fluctuation detecting means for detecting fluctuations in the ground load sharing of the left and right wheels, and the turning actuator can independently adjust the turning angles of the front, rear, left and right wheels. The turning angle calculation means is provided to calculate a turning angle corresponding to the change in the ground load sharing for each of the left and right wheels.

When vehicle lateral acceleration occurs, the ground load sharing between the left and right wheels changes, and the wheel slip angle that generates the maximum lateral force differs between the left and right wheels. Therefore, the turning angle calculation means calculates the turning angle of the front and rear left and right wheels (the turning angle that generates the maximum lateral force of the wheel) in consideration of the variation of the ground load sharing, thereby further effectively increasing the lateral angle. Force can be obtained, and contact avoidance ability is further improved.
In this case, for example, the turning angle calculation means detects the change in the ground load sharing based on the detection signal of the yaw rate sensor or the lateral acceleration sensor, and calculates the target wheel slip angle in consideration of the change in the ground load share. It may be.

  Hereinafter, a steering apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 schematically shows a turning device in a four-wheel independent turning vehicle according to the embodiment.

  This vehicle includes steering mechanisms 10A, 10B, 10C, and 10D for independently steering left and right front wheels Wfl and Wfr and left and right rear wheels Wrl and Wrr.

  The steered mechanisms 10A, 10B, 10C, 10D are assembled to the left and right front wheels Wfl, Wfr and the left and right rear wheels Wrl, Wrr, respectively, and integrally rotate about the vertical axis, and each wheel Wfl, Wfr, Wrl, Wrr. (Hereinafter, when these are generically referred to, they are simply referred to as wheels W.) knuckle 11a, 11b, 11c, and 11d are provided. Each knuckle 11a, 11b, 11c, 11d is supported by suspensions 12a, 12b, 12c, 12d. In this embodiment, a double wishbone type suspension is used, but other types such as a strut type suspension can also be adopted.

The suspensions 12a, 12b, 12c, and 12d include a pair of upper and lower suspension arms 12a1, 12b1, 12c1, and 12d1 that are pivotally supported on the left and right sides of the vehicle body BD so as to be swingable in the vertical direction and extend outward in the vehicle width direction.
The pair of upper and lower suspension arms 12a1, 12b1, 12c1, and 12d1 connect knuckles 11a, 11b, 11c, and 11d via ball joints 13a, 13b, 13c, and 13d provided at the front ends of the suspension arms 12a1, 12b1, 12c1, and 12d1, respectively. Wfr, Wrl, Wrr are supported so as to be rotatable around the vertical axis.
Although not shown, between the lower arm of the suspension arms 12a1, 12b1, 12c1, and 12d1 and the vehicle body BD, a spring device that absorbs an impact received from the road surface and enhances riding comfort, and a vertical vibration of the spring device. A shock absorber for generating a damping force.

  The knuckles 11a and 11b of the left and right front wheels Wfl and Wfr are extended rearward, and pins 14a and 14b are vertically fixed to the rear ends of the knuckles 11a and 11b, respectively, with the vertical direction as the axial direction. The knuckles 11c and 11d of the left and right rear wheels Wrl and Wrr are extended forward, and pins 14c and 14d are vertically fixed to the front end portions of the knuckles 11a and 11b with the vertical direction being the axial direction.

  Each pin 14a, 14b, 14c, 14d is driven in the vehicle width direction by the steering actuators 15a, 15b, 15c, 15d via the drive arms 16a, 16b, 16c, 16d. The steering actuators 15a, 15b, 15c, and 15d are housings 15a2, 15b2, and 15c2 that convert the electric motor and the rotation of the motor into linear motion to drive the pins 15a1, 15b1, 15c1, and 15d1 in the vehicle width direction. , 15d2 respectively. The pins 15a1, 15b1, 15c1, 15d1 protrude from guide holes 15a3, 15b3, 15c3, 15d3 provided in the housing 15a2, 15b2, 15c2, 15d2 along the vehicle width direction, and the guide holes 15a3, 15b3, 15c3 It is displaced in the vehicle width direction along 15d3. The drive arms 16a, 16b, 16c, and 16d are assembled so as to be rotatable around the axes of the pins 15a1, 15b1, 15c1, and 15d1 at the respective inner ends, and the pins 14a, 14b, 14c, and the like at the respective outer ends. It is assembled so as to be rotatable around the axis of 14d, and the pins 15a1, 14b, 14c, 14d and the knuckles 11a, 11b are swung on the horizontal plane by the displacement of the pins 15a1, 15b1, 15c1, 15d1 in the vehicle width direction. , 11c, 11d to steer each wheel Wfl, Wfr, Wrl, Wrr.

  In addition, the steering apparatus includes a steering handle 31 that is turned by a driver to steer the wheels Wfl, Wfr, Wrl, and Wrr. The steering handle 31 is fixed to the upper end of the steering shaft 32, and a reaction force actuator 33 including an electric motor and a speed reduction mechanism is connected to the lower end of the steering shaft 32. The reaction force actuator 33 applies a reaction force to the turning operation of the steering handle 31 by the driver.

  The vehicle further includes a steering control device 40 for controlling the steering actuators 15a, 15b, 15c, 15d and the reaction force actuator 33. The steering control device 40 is configured by a microcomputer as a main part, and includes a steering angle sensor 41, wheel steering angle sensors 42a, 42b, 42c, 42d, a steering torque sensor 43, a vehicle speed sensor 44, a yaw rate sensor 45, a lateral acceleration. The sensor 46 and the front obstacle detection sensor 47 are connected. Further, the steering control device 40 includes drive circuits 50a, 50b, 50c, and 50d for driving the respective steering actuators 15a, 15b, 15c, and 15d, and a reaction force actuator 33 that applies a steering reaction force to the steering handle 31. A drive circuit 51 for driving is connected.

The steering angle sensor 41 is assembled to the steering shaft 32 connected to the steering handle 31, detects the rotation angle from the neutral position of the steering handle 31, and outputs it as the steering angle θ. The steering torque sensor 43 also detects torque applied to the steering handle 31 by being assembled to the steering shaft 32 and outputs the detected torque as steering torque T.
The wheel steering angle sensors 42a, 42b, 42c, 42d (hereinafter simply referred to as the wheel steering angle sensor 42) are referred to as the steering actuators 15a, 15b, 15c, 15d (hereinafter collectively referred to as the wheel steering angle sensors 42). The actual turning angles δf1, δf2, δr1, δr2 from the neutral position of each wheel Wfl, Wfr, Wrl, Wrr (hereinafter referred to simply as actual rotation) (Referred to as steering angle δ).

Note that the steering angle θ and the actual turning angle δ represent a neutral position as “0”, a left rotation angle as a positive value, and a right rotation angle as a negative value. The steering torque T represents a torque applied in the left direction as a positive value and a torque applied in the right direction as a negative value.
The vehicle speed sensor 44 detects and outputs the vehicle speed V. The yaw rate sensor 45 detects and outputs the yaw rate γ of the vehicle. The lateral acceleration sensor 46 detects and outputs the lateral acceleration Gy of the vehicle.
As the front obstacle detection sensor 47, a millimeter wave radar is used. The front obstacle detection sensor 47 is provided in a bumper or the like in front of the vehicle, irradiates the front of the vehicle while scanning radio waves in the horizontal direction, receives radio waves reflected on the front obstacle surface, and receives obstacles. Presence / absence, direction, distance, relative speed, etc. are detected. Note that the front obstacle sensor is not limited to the millimeter wave radar, and may capture an image with a CCD camera or the like.

  The turning control device 40 stores in advance a target turning angle table of each wheel Wfl, Wfr, Wrl, Wrr corresponding to the steering angle θ and the vehicle speed V as a target turning angle table, and this target turning during traveling. The target turning angle of each wheel Wfl, Wfr, Wrl, Wrr is calculated with reference to the angle table. The steering actuators 15a, 15b, 15c, and 15d are feedback-controlled according to deviations from the actual steering angles δf1, δf2, δr1, and δr2 detected by the wheel steering angle sensors 42a, 42b, 42c, and 42d. Each wheel Wfl, Wfr, Wrl, Wrr is set as a target turning angle.

Next, the contact avoidance turning control that is a feature of the present invention will be described.
FIG. 2 shows a contact avoidance turning control routine executed by the turning control device, and is stored as a control program in a storage element (not shown) of the turning control device 40.
This contact avoidance steering control routine is activated by an ignition-on operation and is repeatedly executed at a predetermined short cycle.

When this control routine is started, first, parameters necessary for this control are read (S11). In the present embodiment, the vehicle speed V detected from the vehicle speed sensor 44, the steering angle θ detected from the steering angle sensor 41, and the actual turning angles δf1, δf2 detected from the wheel steering angle sensors 42a, 42b, 42c, 42d. , Δr1, δr2, the yaw rate γ detected from the yaw rate sensor 45, the lateral acceleration Gy detected from the lateral acceleration sensor 46, and the output signal output from the forward obstacle detection sensor 47 are read.
Subsequently, it is determined whether or not the vehicle is required to perform emergency avoidance steering control in the lateral direction with respect to the obstacle ahead (S12). That is, it is determined whether or not there is a possibility that the vehicle is in contact with a front obstacle.
For example, the relative distance L and the relative speed Vs between the host vehicle and the front obstacle are calculated from the output signal of the front obstacle detection sensor 47. Then, based on the relative distance L, the relative speed Vs, and the vehicle speed V detected by the vehicle speed sensor 44, the possibility of contact with the front obstacle is determined.

In general, as the relative distance L between the host vehicle and the front obstacle increases, the possibility that the host vehicle contacts the front obstacle decreases. When the host vehicle and the front obstacle are traveling at substantially the same speed, that is, when the relative speed Vs is small, the possibility that the host vehicle is in contact with the front obstacle is low, and the relative speed Vs is As the speed increases, the braking stop distance Ls of the host vehicle increases by the relative speed Vs, and the possibility that the host vehicle contacts the front obstacle increases.
Therefore, the degree of possibility of contact with the front obstacle can be expressed by a value of Ls / L, where Ls is the braking stop distance of the vehicle according to the relative speed Vs.
In addition, as the vehicle speed V increases, the distance traveled per unit time increases, and if the brake operation or steering wheel operation is delayed due to the driver's carelessness, the stop distance of the vehicle is increased by the distance corresponding to the delay, and the vehicle is The possibility of coming into contact with a front obstacle increases.

Therefore, the degree X of possibility of contact with the front obstacle is determined as follows.
X = f (V, Vs) · Ls / L
Here, f (V, Vs) is a weighting coefficient according to the own vehicle speed V and the relative speed Vs, and is set so as to increase as the relative speed Vs increases and as the own vehicle speed V increases. Yes.
Therefore, the degree X is calculated based on each sensor output, and the calculated degree X is compared with a preset reference value X0. When the degree X is larger than the reference value X0, the vehicle comes into contact with a front obstacle. Judge that there is a possibility.

Returning to the description of the control routine of FIG. 2, the determination in step S12 is “NO”, that is, there is no possibility that the vehicle will come into contact with the front obstacle, and the vehicle avoids the emergency avoidance in the lateral direction with respect to the front obstacle. If it is determined that steering control is not necessary, the control routine is temporarily exited.
This control routine is repeatedly executed at a predetermined cycle. Then, the above-described processing is repeated, and the determination in step S12 is “YES”, that is, there is a possibility that the vehicle may come into contact with the front obstacle. If it is determined that rudder control is necessary, the process proceeds to step S13.

In step S13, the vehicle traveling direction is confirmed. Here, based on the yaw rate γ from the yaw rate sensor 45, the lateral acceleration Gy from the lateral acceleration sensor 46, and the vehicle speed V from the vehicle speed sensor 44, it is determined whether the vehicle is moving in the left or right direction with respect to the front obstacle. .
Subsequently, the process proceeds to step S14, and the turning angle at which the lateral force (cornering force) of each wheel Wfl, Wfr, Wrl, Wrr in the traveling direction is maximized is calculated.
Here, calculation of the turning angle δ at which the lateral force of the wheel W is maximized will be described in detail.

  As shown in FIG. 3, the lateral force CF of the wheel W changes according to the wheel slip angle α (the angle of the wheel direction with respect to the traveling direction of the wheel). In this case, the wheel lateral force CF has a characteristic that when the wheel slip angle α is small, it increases as the slip angle α increases, but decreases with a predetermined slip angle α0 as a boundary. Therefore, in the present embodiment, the wheel slip angle α0 at which the maximum wheel lateral force CFmax is obtained is stored as a target wheel slip angle α * in the storage element in the steering control device 40, and at the time of obstacle contact avoidance, The turning angle is controlled so that the actual wheel slip angle α becomes the target wheel slip angle α *.

Further, the relationship between the wheel lateral force CF and the wheel slip angle α also changes depending on the ground load of the wheel W. Therefore, when a lateral acceleration Gy is generated in the vehicle at the time of avoiding contact, the load sharing on the left and right wheels W varies due to the load movement, and the wheel lateral force CF changes.
FIG. 4 shows a state in which the ground load balance is biased toward the left wheel Wfr, Wrr due to load movement, and FIG. 4A is steered so that the maximum lateral force is generated in each wheel Wfl, Wfr, Wrl, Wrr. Represents the wheel maximum lateral force CFflmax, CFfrmax, CFrlmax, CFrrmax and wheel slip angles αfl0, αfr0, αrl0, αrr0, and (b-1), (b-2), (b-3), (b-4) Represents the relationship between the wheel lateral forces CFfl, CFfr, CFrl, CFrr of each wheel Wfl, Wfr, Wrl, Wrr and the wheel slip angles αfl, αfr, αrl, αrr in this load balance.

In this case, when the ground contact load of the wheel W changes, the slip angle α0 at which the wheel lateral force CF becomes maximum also changes slightly.
Therefore, in the present embodiment including the four-wheel independent steering mechanism, the wheel having the maximum wheel lateral force CFfl, DFfr, CFrl, CFrr according to the variation of the ground load for each wheel Wfl, Wfr, Wrl, Wrr. Slip angles αfl0, αfr0, αrl0, αrr0 are set as target wheel slip angles αfl *, αfr *, αrl *, αrr *.
The ground load may be detected by providing a ground load sensor for each wheel Wfl, Wfr, Wrl, Wrr. However, in this embodiment, the left and right ground load is shared by the detection signal γ of the yaw rate sensor 45. Guess.
Then, for each wheel Wfl, Wfr, Wrl, Wrr, target slip angles αfl *, αfr *, αrl *, αrr * corresponding to the yaw rate γ are stored in advance in a reference table or the like, and a reference table is obtained from the detected yaw rate γ. The target slip angles αfl *, αfr *, αrl *, αrr * are determined with reference to FIG.

In this contact avoidance turning control routine, the target turning angles δfl *, δfr *, δrl *, and δrr * of the four wheels are finally calculated and controlled. The calculation is performed as follows.
First, the slip angle β of the vehicle body is obtained by the following formula.
β = ∫ (Gy / V−γ) dt
Gy: lateral acceleration, V: vehicle speed, γ: yaw rate Next, the actual wheel slip angles αfl, αfr, αrl, αrr are obtained by the following equations.
αfl = β + af · γ / V−δfl
αfr = β + af · γ / V−δfr
αrl = β-ar · γ / V-δrl
αrr = β-ar · γ / V-δrr
af: distance between the center of gravity of the vehicle and the front axle, ar: distance between the center of gravity of the vehicle and the rear axle, δfl: actual steering angle of the left front wheel, δfr: actual steering angle of the right front wheel,
δrl: Actual turning angle of left rear wheel, δrr: Actual turning angle of right rear wheel

Next, deviations Δαfl, Δαfr, Δαrl, Δαrr between the actual wheel slip angles αfl, αfr, αrl, αrr and the target wheel slip angles αfl *, αfr *, αrl *, αrr * are obtained by the following equations.
Δαfl = αfl * −αfl
Δαfr = αfr * −αfr
Δαrl = αrl * −αrl
Δαrr = αrr * -αrr
Finally, the target turning angles δfl *, δfr *, δrl *, δrr * are calculated by adding the wheel slip angle deviations Δαfl, Δαfr, Δαrl, Δαrr to the actual turning angles δfl, δfr, δrl, δrr. .
δfl * = δfl + Δαfl
δfr * = δfr + Δαfr
δrl * = δrl + Δαrl
δrr * = δrr + Δαrr

When the target turning angles δfl *, δfr *, δrl *, δrr * are calculated in this way, the steering actuators 15a, 15b, 15c, and 15d are driven and controlled in the next step S15, and the wheel turning angles are set. Set the target turning angle δfl *, δfr *, δrl *, δrr *.
As a result, the wheels Wfl, Wfr, Wrl, and Wrr are steered in the direction in which the lateral force is maximized, and the lateral acceleration is quickly obtained to move from the front obstacle in the lateral direction.
Subsequently, in step S16, it is determined whether or not avoidance from the front obstacle is completed, and the processing from step S11 is repeated until the avoidance is completed.
In this case, the wheel slip angles αfl, αfr, αrl, αrr decrease as the vehicle moves in the lateral direction. By repeating this process, the four wheels Wfl, Wfr, Wrl, Wrr always obtain the maximum lateral force. The turning angle δfl *, δfr *, δrl *, δrr * is adjusted every moment.

According to the contact avoidance turning control routine of the present embodiment described above, during the period in which it is determined that there is a possibility of contact with the front obstacle, the four wheels independently make the lateral force maximum. Because the angle is controlled, a large vehicle lateral acceleration can be quickly generated by making maximum use of the lateral force CF generated on the four wheels W. As a result, the occurrence of lateral acceleration of the vehicle is not delayed unlike the conventional apparatus, and the ability to avoid contact with the front obstacle is improved.
In addition, it is possible to easily generate the maximum lateral force on the wheel by obtaining the wheel slip angle that maximizes the lateral force, calculating the turning angle so that the wheel slip angle can be obtained, and performing the turning control. Can do.
Furthermore, even if the balance between the left and right ground loads changes due to the occurrence of vehicle lateral acceleration, the target slip angle is calculated in consideration of the variation in the ground loads, so that the contact avoidance capability is further enhanced. In addition, since the change in the balance of the ground load is estimated by the detected yaw rate value γ, it is not necessary to newly provide a special sensor such as a ground load sensor, and the cost is not increased.

As mentioned above, although the steering apparatus of this embodiment was demonstrated, this invention is not limited to the said embodiment, A various change is possible unless it deviates from the objective of this invention.
For example, in the present embodiment, contact avoidance steering control is applied to a four-wheel independent steering device, but the steering of a type in which left and right front wheels and left and right rear wheels are connected to independently steer front and rear wheels. It can be applied to the device. As an example, a steering apparatus according to the second embodiment will be described below.

FIG. 5 shows a schematic configuration of the steering apparatus as the second embodiment. In this steering device, the following configuration is provided in place of the steering actuator 15 in the above-described embodiment (referred to as the first embodiment). Accordingly, in the following description, the same components as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.
This steering apparatus includes a steering mechanism 20A for front wheel steering and a steering mechanism 20B for rear wheel steering.
The steering mechanism 20A for front wheel steering is configured such that the vehicle center side ends of the left and right drive arms 16a and 16b are swingably connected to both ends of the rack bar 22A by pins 21a and 21b. The output of the turning actuator 23A is configured to be transmitted to the rack bar 22A via a pinion gear 25A provided on the output shaft 24A. In this case, the rotational force of the steering actuator 23A is converted into a force in the axial direction of the rack bar 22A, and the front wheels Wfl and Wfr are steered left and right via the knuckles 14a and 14b. The steering actuator 23A is driven and controlled by the drive circuit 27A by a control signal from the steering control device 40. The output shaft 24A is provided with a wheel steering angle sensor 26A that detects the rotation angle and outputs it as the actual turning angle δ.

  Similarly, the rear wheel steering mechanism 20B is configured such that the vehicle center side ends of the left and right drive arms 16c and 16d are swingably connected to both ends of the rack bar 22B by pins 21c and 21d, and is decelerated with an electric motor. The output of the steering actuator 23B comprising the mechanism is configured to be transmitted to the rack bar 22B via a pinion gear 25B provided on the output shaft 24B. In this case, the rotational force of the steering actuator 23B is converted into a force in the axial direction of the rack bar 22B, and the rear wheels Wrl and Wrr are steered left and right via the knuckles 14c and 14d. The steering actuator 23B is driven and controlled by the drive circuit 27B by a control signal from the steering control device 40. Further, the output shaft 24B is provided with a wheel steering angle sensor 26B that detects the rotation angle and outputs it as the actual turning angle δ.

In the steering device of the second embodiment, the slip angle at which the maximum lateral force is generated is stored on the front wheel side and the rear wheel side as in the contact avoidance steering control described above, and the contact avoidance steering is performed. At times, the turning angle is controlled so that this slip angle is obtained.
For example, as shown in FIG. 6, the characteristics of the wheel lateral force CF with respect to the wheel slip angle α are different between the front wheel side and the rear wheel side. Therefore, considering the two-wheel model, the wheel slip angles αf0 and αr0 at which the maximum wheel lateral forces CFfmax and CFrmax are obtained are stored as target wheel slip angles αf * and αr * separately for the front wheel side and the rear wheel side. It is used in the contact avoidance turning control described above.
That is, the calculation of the turning angle in step S14 of the contact avoidance turning control routine of the first embodiment is performed for each of the front wheels and the rear wheels without being performed for each of the four wheels. In this case, as in the first embodiment, the vehicle body slip angle β, the front and rear wheel actual wheel slip angles αf and αr, the front and rear wheel target wheel slip angles αf * and αr *, and the front and rear wheel target turning angles δf *, δr * is calculated and steered.

  In the second embodiment, although the target slip angle is not adjusted for the left and right load movement, as in the first embodiment, the wheel lateral force CF is utilized to the maximum to quickly generate a large vehicle lateral acceleration. And the ability to avoid contact with a front obstacle can be improved.

It is a whole lineblock diagram of a steering device concerning an embodiment of the present invention. It is a flowchart showing a contact avoidance steering control routine. It is a characteristic view showing the relationship between a wheel slip angle and a wheel lateral force. It is explanatory drawing showing a wheel slip angle and a wheel lateral force generation condition. It is a whole block diagram of the steering apparatus which concerns on 2nd Embodiment. It is a characteristic view showing the relationship between the wheel slip angle and lateral force in the front and rear wheels.

Explanation of symbols

10A, 10B, 10C, 10D, 20A, 20B ... Steering mechanism, 11a, 11b, 11c, 11d ... Knuckles, 12a, 12b, 12c, 12d ... Suspension, 15a, 15b, 15c, 15d, 23A, 23B ... Steering Actuator, 40 ... Steering control device, 41 ... Steering wheel steering angle sensor, 42a, 42b, 42c, 42d, 26A, 26B ... Wheel steering angle sensor, 44 ... Vehicle speed sensor, 45 ... Yaw rate sensor, 46 ... Lateral acceleration sensor, 47 ... Front obstacle detection sensor, Wfl, Wfr, Wrl, Wrr ... Wheel.

Claims (3)

A steering actuator that adjusts the steering angles of the front and rear wheels,
Contact possibility determination means for determining the possibility of the vehicle contacting a front obstacle while the vehicle is running;
A turning angle calculation means for calculating a turning angle at which the lateral force generated on the wheel is maximum;
When it is determined that the vehicle may come into contact with the front obstacle, the turning actuator is controlled so that the turning angle of the front and rear wheels becomes the turning angle calculated by the turning angle calculation means. And a turning angle control means.   The steered angle calculating means according to claim 1, wherein the steered angle calculating means obtains a slip angle of a wheel that produces a maximum lateral force on the wheel, and calculates the steered angle based on the slip angle. apparatus. While equipped with load sharing fluctuation detection means for detecting fluctuations in the ground load sharing of the left and right wheels,
The steering actuator is provided so that the turning angles of the front, rear, left and right wheels can be adjusted independently,
The steered device according to claim 2, wherein the steered angle calculating means calculates a steered angle according to a change in the ground load sharing for each of the left and right wheels.

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