JPS61113562A - Steering angle control unit for car - Google Patents

Abstract

PURPOSE:To improve steering stability by preventing variation in movement characteristics from being generated even when a load change applied to wheels occurs at driving and braking. CONSTITUTION:A microcomputer 1 calculates the steering angle target value deltaR by inputting the car speed V sensed by a car speed sensor 3, the steering amount thetaS of a steering handle 8 sensed by a handle steering amount sensor 2, the output TF of a front wheel torque sensor 16, and the output TR of a rear wheel torque sensor 17. The front wheel torque sensor 16 senses the front wheel driving torque that is sent from a center differential gear 6 to a front wheel differential gear 14 and the rear wheel torque sensor 17 senses the rear driving torque that is sent from the center differential gear 6 to a rear wheel differential gear 15. A rear wheel steering device 5 performs the steering control of rear wheels based on the data of the rear wheel angle target value deltaR assigned from the microcomputer 1.

Description

[Detailed description of the invention] (Industrial application field) These 9 inventions are normal! The 2-wheel steering vehicle or 1 can be used as a steering device for a 4-wheel steering vehicle, and is particularly capable of freely controlling the motion performance of the vehicle during steering, and controlling the drive and driving performance of the vehicle.
Vehicle steering angle control system that allows proper control during braking! Regarding.

(Prior art) Conventional vehicles equipped with mechanical link steering devices steer the front wheels in response to the amount of steering from the steering wheel, and the motion variables associated with steering are:
The dynamic performance is uniformly determined by the vehicle specifications of the vehicle, and is unique to each vehicle type.

For this reason, for example, even if you try to make a sedan car have the driving performance of a sports car, the vehicle specifications of the sports car are determined by the body structure and tire characteristics of the sports car, so it cannot be called a sedan car after all. Due to the body structure, it was difficult to freely change the dynamic performance.

Therefore, the applicant has developed a vehicle steering system in which the desired vehicle specifications are set in advance, and the driving performance obtained based on the vehicle specifications is achieved by electronically controlling the wheel steering angle. We are proposing a control device.

For example, when a sedan car is to have the driving performance of a sports car, the vehicle specifications of the sports car are stored as the target vehicle specifications, and the steering amount and vehicle speed of the steering wheel and the target vehicle opening λ source are stored. Find the target value of the motion variable C, for example, yaw angular acceleration, from the equation of motion using
The vehicle is configured to calculate a wheel steering angle to achieve a motion variable (corresponding to a motion variable in a sports car) and steer the wheels to this steering angle.

This means that even a sedan car can have the same driving performance as a sports car.

(Problems to be Solved by the Invention) By the way, the inventors of the present application further researched the above-mentioned device and found the following improvements.

In other words, when the vehicle is running at a constant speed, there is no load movement and the driving force only resists air resistance and tire rolling resistance, so the tire characteristics are hardly affected and the dynamic characteristics are Although it does not change, when the vehicle is driving (when driving force is applied to the tires) or braking, the load movement and tire characteristics (particularly the cornering force of the wheels) change, and the dynamic characteristics change.
However, in the device according to the above-mentioned prior application, the target vehicle specifications are fixed, and control based on calculations based on this is performed in accordance with steady running conditions, and changes in dynamic characteristics that occur when driving and braking the vehicle are Not considered. The present invention aims to solve this problem.

(Means for Solving the Problems) □In order to solve the above problems, the present invention includes the means shown in FIG. 1.

- The motion variable target value calculating means 102 calculates the steering amount 08 of the main steering wheel detected by the steering wheel steering amount detecting means 10G and the vehicle speed V detected by the vehicle speed detecting means 101.
The target value of the vehicle motion variable corresponding to is determined based on the vehicle motion equation using desired vehicle specifications.

The wheel steering angle target value calculation means 108 calculates a wheel steering angle target value δ of at least one of the front wheels and the rear wheels to realize the motion variable target value M based on the motion variable target value M and the vehicle specifications of the host vehicle. The wheel steering means 104 steers the wheel corresponding to the wheel steering angle target value δ to the target value δ.

Vehicle specification correction means 106 includes driving/braking information detection means 1
Based on the information regarding at least one of driving and braking of the vehicle detected in step 05, among the vehicle specifications of the own vehicle used in the wheel steering angle target value calculating means 102, the vehicle-factor that is involved in the cornering force of the wheels is determined. at least one of
Correct one.

(Function) Since the motion variable target value X determined by the motion variable target value calculation means 102 is determined based on desired vehicle specifications, for example, when the vehicle equipped with the device of the present invention is a sedan , if the vehicle specifications of a sports car are used, the motion variable target value M determined thereby is realized by the wheel steering angle target value calculation means 108 and the wheel steering means 104, and as a result, the own vehicle is determined to be a sports car. It will have equivalent exercise performance. .

In addition, the vehicle specification correction means 106 corrects at least one of the vehicle specifications that are involved in wheel gonaring among the i specifications used by the motion variable target value calculation means 102. Control is performed so that the motion characteristics are appropriate even when the vehicle is driven or moved.

(Embodiment) FIG. 2 shows the configuration of an embodiment of the present invention. In this example,
This is an example applied to a four-wheel drive type four-wheel steered vehicle.

The output of the engine 13 is distributed by the center differential 6 to a front wheel differential 14 and a rear wheel differential 15, thereby driving front wheels 9, 10 and rear wheels 11, 12. Moreover, the center differential 6 is an electronically controlled center differential,
Through the movement of a front-rear distribution controller (not shown), the clutch pressure of the rear-wheel electromagnetic clutch in the center differential 6 is controlled, and the amount of driving force distributed between the front and rear wheels is variably set.

The microcomputer receives the vehicle speed V detected by the vehicle speed sensor 8, the steering amount θ of the steering wheel 8 detected by the steering wheel steering amount sensor 2, the output TF of the front wheel torque sensor 6, and the output TR of the rear wheel torque sensor 7. is input to calculate one rear wheel steering angle target value δR.

The front wheel torque sensor 16 is a torque sensor that detects the front wheel drive torque sent from the center differential 6 to the front wheel differential 14, and similarly, the rear wheel torque sensor 7 detects the front wheel drive torque sent from the center differential 6 to the rear wheel differential 15. It detects wheel drive torque.

The 8 wheel rotation fle device 5 adjusts the rear wheel 1 based on the data of the rear wheel steering angle target value δR given from the microcomputer.
This is a device that performs steering control of 1.12.

The front wheels 9 , 10 are steered by the mechanical link type steering device 4 , and the steering angle is proportional to the amount of steering of the steering wheel 8 .

The rear wheels 11, 12 are steered by a hydraulic steering device 7, which has a configuration as shown in FIG. 3, for example. .8
8 and whose both ends are connected to tie rods (as shown) is moved in the axial direction by creating a difference between the working oil pressures of left and right hydraulic chambers 34 and 35, thereby steering the wheels.

In addition, within the central chamber 87, repulsion plates δ8 and 89, which are biased in left and right opposite directions by the spring 36, are loosely fitted onto the shaft 31, and this is caused by the hydraulic pressure of the left and right hydraulic chambers 34,35. □ is for returning the first shaft 81 to its original neutral position when it is pulled out.

The rear wheel steering device 5 includes a solenoid driver 21, a control pulp z2, an oil pump 26, and one oil tank 27.

The control pulp 2z is the hydraulic steering device 7
It is provided with oil passages 28, 29 communicating with the left and right hydraulic chambers 84, 85, and is provided with a spool pulp 25 that adjusts the amount of hydraulic oil flowing into these oil passages 28, 29. This spoon
・Levalp 25 has electromagnetic solenoids 28 and 24 on the left and right ends.
It is loosely fitted into the left and right hydraulic chambers 84.8 and moves in the axial direction depending on the magnitude of the magnetic force of the electromagnetic solenoids 28 and 24
Adjust the amount of actuation fFji given to 5.

The solenoid driver 21 supplies a current signal proportional to the rear wheel steering angle target value δR given from the microcomputer 1 to either the left or right electromagnetic solenoids 28 and 24. In this case, control is performed by switching the electromagnetic solenoid that applies current to the left or right depending on the steering direction of the wheels.

FIG. 4 is a 70-chart showing the processing executed by the microcomputer 1. The operation of this embodiment will be explained below along with the explanation of this 70-chart.

The process shown in FIG. 4 is repeatedly executed every predetermined time period Δ, and initialization is performed when the ignition switch is turned on and power is supplied.

In the process of step 201, the steering wheel steering amount sensor 2,
Vehicle speed sensor 8, front wheel drive torque sensor 16t ([[dynamic h
from the lux sensor 17 to the microcomputer 1. Steering wheel steering amount input to 08, vehicle speed v1, front wheel drive torque T
Each data of y-rear wheel drive torque TH is read.

In the process of step 202, a vehicle having desired driving performance is set as a target vehicle (for example, in the case of a sedan car, a sports car is set as the target vehicle), and the vehicle specifications of this target vehicle are stored in advance in the memory. Therefore, processing to read them is performed.

In this embodiment, the target vehicle is the own vehicle. That is,
For example, if the vehicle in which the device of this embodiment is installed is a sedan type, the target vehicle will be a sedan equipped with a conventional mechanical link type steering device, and the unique structure and tire characteristics of the own vehicle will be used. The aim is to achieve the exercise performance determined by the above using electronic control. and,
As will be described later, the present invention also attempts to appropriately control the corner 1J force in response to changes in the driving force of the vehicle.

The vehicle specifications read in step 202 are shown below.

□: Yaw inertia of the target vehicle - Ml: Vehicle weight of the target vehicle Lo: Wheel pace of the target vehicle, "Fl" Distance between the front axle and center of gravity of the target vehicle LR1 "Distance between the rear axle and center of gravity of the target vehicle □To work□=Inertia around the kingpin of the target vehicle Ks□:' Steering rigidity DK of the target vehicle □: Steering system viscosity coefficient ξ of the target vehicle: Trail No. of the target vehicle: Steering gear ratio KFl of the target vehicle ``Target vehicle Cornering power of the front wheels of the target vehicle KR□: Cornering power of the rear wheels of the target vehicle.In the next step 208, the target motion variable (
In this embodiment, calculation is performed to obtain the yaw angular acceleration.

This calculation is performed according to the following formula.

Engineering Kl″a71-NIK81(θB-N1aF1)”
DK1'F1 ”'”1'F1 ”−”−(”
) Ml(y, + p, V) -20yu + 201
1 ------- (j)IZ19'l = 2LFIC
F1 ""R1'R1-""""(')βFl-δ
, H(÷,” LF1?,)/V −−−−−(4)
βR, −−(y, −LR1÷,)/V −−−−−(
li)'Fl = KF□β1r, '------
(6) Here, δ: Front wheel steering angle of the target vehicle (the target vehicle is a two-wheel steering angle
÷ : Yaw rate ψ1 of the target vehicle : Yaw angular acceleration of the target vehicle yo : Lateral velocity y of the target vehicle : Lateral acceleration βFl of the target vehicle ``Slip angle of the front wheels of the target vehicle・βR1' Side slip angle CFl of rear wheels of target vehicle ``Cornering force CR1 of front wheels of target vehicle: Cornering force of rear wheels of target vehicle = ψ: Yaw angular acceleration target value.

The above equations (1) to (3) are equations of motion for the target vehicle, and to solve these equations, four integral operations are required for each Δ. An appropriate integration method is used depending on the required integration precision, such as the rectangular integration method expressed by -A(t)+Δt-1(1) or the Runge-Kutta method.

The yaw angular acceleration target = value ψ obtained in this way is the yaw angular acceleration of the target vehicle corresponding to the steering wheel steering amount θ8 and the vehicle speed V, and these motion variables of the target vehicle are calculated by the own vehicle. This is the aim of this embodiment.

Next, a calculation is performed to determine the rear wheel steering angle to achieve the above-mentioned angular acceleration target value 9, but in this embodiment, before that, in order to perform appropriate control in response to changes in the driving force of the vehicle. processing is executed.

That is, in the process of step 204, based on the front wheel drive torque Ty and rear wheel drive torque TR read in step 201, the load movement amount ΔW and the driving force moving to the tire contact points of the front and rear wheels (this is expressed as " Tire ground point driving force
) QF and QR are calculated, and further, through the process of step 205, the cornering power (ideal value) of the front and rear wheels is calculated from the above ΔW e Qy * QR
, calculate KR.

The tire grounding point driving force QF and QR of the front and rear wheels above are as follows:
It can be obtained as follows.

Front and rear wheel drive torque Ty *TR is front wheel differential 14,
Since the torque is transmitted to the rear wheel differential 15, the front wheels 9,
10 and rear wheel 11. The drive torque (sum of left and right wheels) TFHt TRH transmitted to IB is TyH- if the gear ratio of front wheel differential 14 and rear wheel differential 15 is My v NR.
My −T, −(o)TRH= NR−
TR...(10) Represented by:

Here, the above T and T are applied to the wheels from the road surface FIi
R ■ Torque seen, i.e. front and rear wheel grounding point driving force Qy
e If it is balanced with QR, then Qlr −
T, H/ro-(11) Winter QR-TRH/ro °-(1m) (However,
ro is the tire diameter) Therefore, if we use the relational expressions (9) to (1m) above,
Based on the above front and rear wheel drive torques T, , and TR, the front and rear tire ground point driving forces QF and QR are determined.

In addition, the load movement amount ΔW is the height of the center of gravity of the vehicle body.

If the wheel pace is (all actual values for the own vehicle), then -(QF+QR) HG/L ・-(18
).

Next, the calculation of the cornering power of the front and rear wheels, and KR will be explained.

Here, the cornering power KF of the front and rear wheels.

KR usually changes in proportion to the wheel load, as shown in FIG. 5, and changes with a characteristic called a friction circle with respect to driving force and braking force, as shown in FIG. 6.
j In this way, when driving and braking, the accompanying load transfer occurs, and the cornering power of the front and rear wheels is 1KF,
Since KR varies, the driving characteristics, especially the cornering force, change.

Therefore, if the cornering power Ky e KR is set to a fixed value, the equation of motion used in the calculation of the rear wheel steering angle target value aR, which will be described later, is only for constant speed driving, and if the vehicle body turning motion is controlled by the determined JR. , This means that even if the motion characteristics are appropriate when driving at a constant speed, they are no longer appropriate when driving or braking.

Therefore, in this embodiment, the cornering power KF is determined according to the characteristics shown in FIGS.

By correcting KR, we are trying to control the cornering power KF of the front and rear wheels to below 0 so that it has appropriate dynamic characteristics even when driving.

The formula for calculating KR is shown below. Here, KFO is the cornering power of the front wheels when driving at a constant speed.
``Rear wheel cornering power WFO when driving at constant speed'' Front wheel static load RO'' Rear wheel static load.

Next, in the process of step 206, since the vehicle specifications of the own vehicle [1] except for the cornering power Ky*KR of the front and rear wheels are stored in advance in the memory, a process is performed to read them. . The following vehicle specifications unique to the own vehicle are used.

1-inertia of the snow vehicle: Vehicle weight and weight: Wheel pace of the vehicle L1'! ``Distance between the front axle and the center of gravity of the own vehicle'' Rli ``Distance between the rear wheel and the center of gravity of the own vehicle IK, : Inertia around the kingpin of the own vehicle Ksi ``Steering rigidity of the own vehicle DKl'' Steering system viscosity coefficient ξ of the own vehicle , : Trail N of own vehicle, : Steering gear ratio of own vehicle Here, in this example, since the target vehicle is the own vehicle, the 1 target vehicle trend and the vehicle specifications unique to the own vehicle are the same. In other words, “Zl −”Z□m Is
”= Ml * Ls-LX e LFl-LFl #
LRs ”” LRl t 2 ”” 1Kl t
KSs -KSt t DK2-DKxlξ3-ξ□
, N, -N□.

Then, in the process of the next step 20, the vehicle specifications unique to the own vehicle, the yaw angular acceleration target value ψ obtained in the step 203, and the cornering power Ky t of the front and rear wheels obtained in the step 205 are calculated. From KR, a calculation is performed to obtain a target steering angle value δR for the rear wheels of the own vehicle. This operation is performed according to the following formula.

IK! δy4-N2KS, (#, -N, δmouth)” D
Kl”F””ξ,CF!-(16)M,(is”fsV
) = 20ys44C1**+ (17) β2. −δ
Ffi"(3'l + L ha ÷,) /'V - (1
8) a, , -xFsβFl,
-(19)ORs -(LlrsCys-+vine I, m
) / LRI = (1G) βR1 = 0R11
/ KRs ” ”’ ””However, ψ2−ψ. .

here, δys: Front wheel steering angle of own vehicle ψ,: own vehicle's yaw rate : Lateral speed of own vehicle y: lateral acceleration of own vehicle β: Side slip angle of front wheels of own vehicle βHm　Slip angle of rear wheels of own vehicle It is.

Equations (16) and t(17) above are the equations of motion of the own vehicle, and the integral operation used to solve these equations uses the integral method used in step 808. The rear wheel steering angle target value δR is input to the rear wheel steering device 5 through the process of the next step 208.

The rear wheel steering device 6 supplies hydraulic pressure necessary for steering the rear wheels 11, 12 to a given rear wheel steering angle target value δR to the hydraulic steering 7, thereby controlling the rear wheels 11, 12.
The steering is carried out. Due to the operation of 1' or more, the actual eye-angular acceleration ψ of the own vehicle becomes
The yaw angular acceleration is also equal to the target value 9 during driving (acceleration), and even if the tire load changes due to changes in driving force, the target motion characteristics can always be achieved.

The effects of this will be explained in more detail. Now, a vehicle equipped with this implementation-device is traveling at high speed (loo1@/h),
“Assume that the steering wheel 8 is continuously steered left and right as shown in FIG. 7(m).

At this time, if the vehicle is running at a constant speed, the steering wheel steering amount #8 and the car i! ! yaw angle acceleration corresponding to v) is calculated, and the rear wheel steering angle target value δ to realize this ¥nF is calculated.
R is calculated. As a result, the yaw rate of the vehicle body changes as shown in FIG. 7(B).

Next, if the same steering wheel is operated at the same speed (loOJ*/14) as in the constant speed driving state while accelerating (with driving force applied), the yaw angle acceleration target The value is the same as 1''9;o when traveling at a constant speed, and a rear wheel steering angle target value δR for realizing this is determined.

Here, the cornering power of the front and rear wheels Ky * KR
When is fixed, the actual cornering power of the own vehicle changes as described above, so as shown in Fig. 7 (
0), the S yaw rate gain decreases as shown by the single-dot chain #iIA, and the steering response becomes slower than when traveling at a constant speed.

On the other hand, as in this example, when the driving force changes, □
Correspondingly, by changing the cornering powers Ky and KR used for calculating the rear wheel steering angle target value δR in the same manner as the actual cornering power change, the yaw angular acceleration target value ψ is determined. will be faithfully realized. That is, as shown in Actual IIA in FIG. 7(0), the yaw rate change is the same as the change characteristic during constant speed running shown in FIG. 7(B). This indicates that the motion characteristics do not change due to changes in the driving force.

In the above embodiment, an example was shown in which the cornering power Kye KR is corrected in response to a change in driving force, but if the correction is similarly performed during braking, the motion characteristics can be further stabilized.

In this case, to detect changes in braking force, for example, an acceleration sensor that detects acceleration in the longitudinal direction of the vehicle body is used to detect changes in driving force.
This can be achieved by detecting changes in braking force.

Further, if such an acceleration sensor is used, it can be applied not only to a four-wheel drive vehicle as in the above embodiment, but also to a normal two-wheel drive vehicle.

Further, in the above embodiment, an example of the configuration was shown in which the steering angle of the rear wheels was controlled to change the maneuverability, but this may be one in which the front wheels or both the front wheels and the rear wheels are controlled. These cases can be realized by slightly modifying the equation of motion used for calculation and vehicle specifications.

Furthermore, in the above embodiment, an example was shown in which the yaw angular acceleration ψ is determined as the target motion variable =
It is also possible to obtain other motion variables, such as centripetal G.

1. In the above embodiment, the driving force for the front and rear wheels is determined from the driving torque transmitted to the front and rear wheel differentials 14 and 15, but this is different from the engine, transmission, and propeller shaft. It may be determined by detecting the drive torque at any point in the drive train consisting of the allencial gear drive shaft. Also, the braking force can be detected by detecting the fluid in the brake mask cylinder or the wheel cylinder of each wheel. A configuration in which detection is performed based on pressure changes is also conceivable.

Also, among the calculations used in the above example, formula (11) for calculating the tire grounding point driving force QF t QB of the front and rear wheels.
, (is) does not take into account the amount of driving torque T and T consumed by the increase in FHRH rotation of the wheels, so the wheel acceleration ωF of the front wheels and the wheel acceleration ωR of the rear wheels are detected, and QF − (TFH” Engineering F”F) / rO-(221)
QR= (THH-IB”H) / ro-(114)
By determining QF t qR from the following equation, a more accurate tire ground contact driving force Qy * QR can be determined. however,
1 In the above formula (18) ) (+14), I is the inertia of the front wheels (left and right wheel cloth), and IR is the inertia of the rear wheels (
Left and right wheel cloth).

Further, in the above embodiment, the cornering power KF is determined based on the tire characteristics shown in FIGS. 5 and 6.

Although we have shown an example of correcting KR, it is also possible to use the data team to calculate non-linear load-dependent characteristics, such as those obtained by actually measuring the characteristics of the tires to be mounted, as well as more detailed driving and braking force-dependent characteristics. It is also possible to give it in the form of a pull @ In addition, the vehicle specifications to be corrected are not limited to the cornering power as in the above example, but may be other vehicle specifications as long as they are related to cornering brake loss. It is also possible to make the correction symmetric.

1 In the above embodiment, an example was shown in which one target vehicle was set as the own vehicle, but this means that if a vehicle of a different type from the own vehicle is set as the target vehicle, the driving performance of the own vehicle is It can be the target vehicle's motion performance. For example, if one's own vehicle is a sedan and the target vehicle is a sports car, it is possible to have the same driving performance as a sports car even though the body structure is of the sedan type.

(Effects of the Invention) As explained in detail above, the present invention changes the original vehicle specifications of the own vehicle, such as the body structure, by controlling the wheel steering angle by calculation using desired vehicle specifications. It is possible to provide the desired exercise performance without having to

In addition, even if the load applied to the wheels changes during drive or control operations, there will be no fluctuation in the motion characteristics, making it possible to always faithfully achieve the target motion characteristics.
It can contribute to improving steering stability.

[Brief explanation of drawings]

Fig. 1 is a block diagram of the present invention. Fig. 2 is a block diagram of an embodiment of the present invention. Fig. 8 is a block diagram of the front wheel steering device, rear wheel steering device, and hydraulic steering device in Fig. 2. , FIG. 4 shows the processing executed by the microcomputer in FIG.
0-chart, FIG. 5 is a diagram showing the wheel load dependence characteristics of cornering power, FIG. 6 is a diagram showing the driving force and braking force dependence characteristics of cornering power, and FIG. 7 is the example device shown in FIG. 2. FIG. 2 is a diagram showing the motion characteristics of a vehicle equipped with a 100...Handle steering amount detection means 101...Vehicle speed detection means IH...Motion variable target value calculation means lo8...Wheel steering angle target value calculation means 104--Wheel turning means 105-...Drive - Braking information detection means 106...Vehicle specification correction means 1...Microcomputer 2--Handle steering amount sensor a...Vehicle speed sensor 5...Rear wheel steering device 6.
... Center differential 7 ... Hydraulic steering device 8 ... Steering handle

Claims (1)

[Scope of Claims] 1. Steering wheel steering amount detection means for detecting the steering amount of the steering wheel; vehicle speed detection means for detecting vehicle speed; and said detection based on the equation of motion of the vehicle using desired vehicle specifications. a motion variable target value calculating means for calculating a target value of a motion variable of the vehicle corresponding to a steering wheel steering amount and a vehicle speed; Wheel steering angle target value calculation means for calculating a target value of a wheel steering angle of at least one of a front wheel and a rear wheel to realize the above-mentioned wheel steering angle, and steering a wheel corresponding to the determined wheel steering angle target value to the target value. a wheel steering means for detecting vehicle driving/braking; a driving/braking information detecting means for detecting information regarding at least one of driving or braking of the vehicle; and based on the vehicle driving/braking information detected by the driving/braking information detecting means, Vehicle specification correction means for correcting at least one of the vehicle specifications related to the cornering force of the wheels among the vehicle specifications of the host vehicle used by the wheel steering angle target value calculation means. Rudder angle control device.