JP4862423B2 - Vehicle state estimation and control device - Google Patents

Description

  The present invention relates to a road surface friction coefficient estimating device and a control device for stabilizing vehicle behavior.

Conventionally, a technique for estimating a road surface friction coefficient and using the estimated value for vehicle behavior control has been disclosed. In this technique, the road surface friction coefficient is estimated based on the lateral acceleration and yaw rate of the vehicle, the vehicle motion equation, and the like (see, for example, Patent Document 1).
JP 2003-118554 A

  However, in the above prior art, since the road surface friction coefficient is estimated based on the vehicle behavior such as yaw rate, it is estimated only after the influence of the vehicle behavior appears, and there is a problem that it takes time to estimate. there were.

  The present invention has been made paying attention to the above-mentioned problem, and its object is to provide a vehicle state estimation and control device capable of estimating a road surface friction coefficient before the influence of the road surface friction coefficient appears as a vehicle behavior. Is to provide.

To achieve the above object, the present invention, based on the vehicle state, the first tire lateral force sum for calculating a first tire lateral force sum of at least one of the two wheels of the two front wheels or two rear wheels of the vehicle Calculation means, tire slip angle calculation means for calculating the tire slip angle of the one of the two wheels, wheel load estimation means for estimating the wheel load of the one of the two wheels, and braking / driving reaction force of the one of the two wheels A braking / driving reaction force estimating means for estimating the second tire lateral force sum of the two wheels based on the estimated wheel load, estimated braking / driving reaction force, tire slip angle and road surface friction coefficient of the one of the two wheels . Second tire lateral force sum calculating means for calculating the above, search range setting means for setting a search range for the road surface friction coefficient of the one of the two wheels calculated by the second tire lateral force sum calculating means, and the search Starring based on the second tire lateral force summing units even during range From the second tire lateral force sum is, satisfies the difference is reduced condition that the first tire lateral force sum which is calculated on the basis of the first tire lateral force summing unit, a second tire lateral and search means for searching for a power sum, it was decided and a road surface friction coefficient estimation means you estimating the road surface friction coefficient of the 2 wheels of the one from the second tire lateral force sum which is the search.

  Therefore, by estimating the vehicle state based on the relationship between the braking / driving road surface reaction force and the lateral force generated on each wheel, the vehicle state can be estimated quickly before the change in the road surface friction coefficient appears as the vehicle behavior change. It is possible to realize advanced vehicle motion performance.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS The best mode for realizing a vehicle state estimation and control apparatus according to the present invention will be described below based on an embodiment shown in the drawings.

[System configuration]
The first embodiment will be described with reference to FIGS. FIG. 1 is a system configuration diagram of an electric vehicle in which four wheels are driven by independent electric motors. The electric vehicle is equipped with three-phase synchronous motors 3FL, 3FR, 3RL, and 3RR having permanent magnets provided on the rotor, and each motor 3FL to 3RR is connected to each wheel 2FL, 2FR via a speed reducer 4FL, 4FR, 4RL, 4RR. 2RL, 2RR. The output characteristics, reduction ratios, and wheel radii of the motors 3FL to 3RR, the reduction gears 4FL to 4RR, and the wheels 2FL to 2RR are all the same.

  The steering wheel 11 is connected to the steering rack 14 via a shaft, and the front wheels 2FL and 2FR are steered. Further, the turning angle δ of each of the wheels 2FL to 2RR is detected by the turning angle sensor 21 and output to the integrated controller 30.

  The integrated controller 30 is an arithmetic unit that calculates torque command values tTFL (left front wheel), tTFR (right front wheel), tTRL (left rear wheel), and tTRR (right rear wheel). In addition to the detection values from the yaw rate sensor 8, the turning angle sensor 21, the brake pedal sensor 22, the accelerator pedal sensor 23, the lateral acceleration sensors 24 and 25, the longitudinal acceleration sensor 26, and the vehicle slip angle sensor 29, the current motor 3FL The current rotation speed and output torque of ~ 3RR are input. Based on these input values, torque command values tTFL (left front wheel), tTFR (right front wheel), tTRL (left rear wheel), and tTRR (right rear wheel) for each motor 3FL to 3RR are calculated.

  Here, the vehicle body slip angle sensor 29 is a sensor of a type that detects the vehicle body side slip angle from the ratio of the two longitudinal filter speed detectors (detecting the vehicle longitudinal speed and the side slip speed by the ratio thereof, and is the center of the rear wheel shaft. (Point P in FIG. 3).

  The drive circuits 5FL to 5RR control the power running and regenerative torque of the motors 3FL to 3RR by controlling the electric power of the battery 6 based on the torque command values tTFL to tTRR from the integrated controller 30.

[Torque command value calculation control]
The integrated controller 30 calculates the torque command values tTFL to tTRR after estimating the road surface friction coefficient μ before the vehicle behavior such as the yaw rate is detected as the actual measurement value. More accurate motor control is performed by calculating torque command values tTFL to tTRR based on the estimated value of the road surface friction coefficient μ.

[Torque command value calculation control processing]
FIG. 2 is a main flowchart of a torque command value calculation control process executed by the integrated controller 30. These are executed at regular intervals, for example, every 5 ms. Hereinafter, each step will be described.

  In step S201, each sensor signal and data is captured. That is, the detected values of accelerator opening APS, brake pedal force BRK, steering angle STR, lateral acceleration YG1, YG2, longitudinal acceleration XG, and yaw rate γ are taken in, and the rotational speeds Nfl to Nrr and torque command values of the motors 3FL to 3RR are taken. The present value data of TFL to TRR and body slip angle β is taken in, and the process proceeds to step S202. The lateral accelerations YG1 and YG2 are two detection values of the two lateral acceleration sensors 24 and 25.

In step S202, the vehicle speed V is calculated by the following equation, and the process proceeds to step S203.
(Formula 1)
V = (Nfl / GG * R + Nfr / GG * R + Nrl / GG * R + Nrr / GG * R) / 4
Here, R is the radius of each wheel 2FL to 2RR, and GG is the reduction ratio of the reducers 4FL to 4RR.

  In step S203, the current vehicle state is estimated based on a vehicle state estimation routine and a road surface friction coefficient calculation routine described later, and the process proceeds to step S204.

  In step S204, motor torque command values TFL to TRR of the respective wheels 2FL to 2RR are calculated by calculation and transmission routine of each wheel motor torque command value, which will be described later, based on the vehicle state estimated in S203, and the driving circuits 5FL to 5RR are calculated. Output and end control.

[Vehicle condition estimation routine]
FIG. 3 is a diagram showing the relationship between the vehicle behavior parameters relating to the vehicle behavior estimation control in step S203 in the flow of FIG. In this embodiment, the vehicle behavior is estimated based on the road surface friction coefficient μ. Based on the steering angle STR, the brake pedal force BRK, and the lateral accelerations YG1 and YG2 detected by the turning angle sensor 21, the brake pedal sensor 22, and the lateral acceleration sensors 24 and 25, the turning angle δ, the braking / driving road surface reaction force Fx, The yaw moment MM and the lateral force YG are calculated, and the road surface friction coefficient μ is determined based on these.

(Calculation of turning angle)
Since the vehicle in the present application is a front wheel steering type, the rear wheel turning angle is zero. Therefore, the values of the front wheel turning angles δfl and δfr corresponding to the steering angle STR are read from the steering angle-steering angle maps MAP_STRfl and MAP_STRfr of the front wheels and the rear wheels, and are calculated as follows.
(Formula 2)
δfl = MAP_STRfl (STR)
δfr = MAP_STRfr (STR)
δrl = 0
δrr = 0

(Calculation of braking / driving road surface reaction force)
The braking / driving road surface reaction forces Fxfl to Fxrr are estimated from the motor torque command values TFL to TRR and the rotational speed variation of each wheel 2FL to 2RR. As a specific estimation method, for example, a method disclosed in JP-A-6-98418 (Equation 11) is used. In particular, when using a mechanical brake, the front and rear wheel braking force maps are read from the brake pedal force BRK value, and the braking torque TBL_FBR (BRK) and TBL_RBR (BRK) are combined with the motor torque TFL to TRR. The driving road surface reaction forces Fxfl to Fxrr are calculated. Further, when the anti-skid braking system is operated, a braking torque decrease due to the system operation is detected, and the braking torque is corrected.

(Calculation of yaw angular acceleration and lateral acceleration)
FIG. 4 is a diagram showing the relationship between the lateral accelerations YG1 and YG2 and the vehicle behavior parameters, which are involved in the vehicle behavior estimation control in step S203 in the flow of FIG. The lateral force Fy is positive when the vehicle travels to the left. When the mounting positions of the lateral acceleration sensors 24 and 25 are the positions shown in FIG. 4, the yaw angular acceleration γ ′ (unit is rad / s ² , counterclockwise is positive) and the lateral acceleration YG (unit is the center of gravity). , M / s ² , where the vehicle left direction is positive) is obtained as follows.
(Formula 3)
γ '= (YG2-YG1) / L2
YG = YG1 + (YG2-YG1) * Lc / L2

(Calculation of lateral force and yaw moment)
From the yaw angular acceleration γ 'and the lateral acceleration YG value, the lateral force Fy and yaw moment MM acting on the vehicle are calculated using the vehicle yaw inertia design value I _γ [kgm ² ] and vehicle mass design value M [kg] Calculate as follows.
(Formula 4)
Fy = M * YG
MM = I _γ * γ '

ここでLf は前輪軸重心点距離[m]、Lr は後輪軸重心点距離[m]、Lt はトレッドベース距離(前後輪同一)[m]であり、それぞれ設計定数である。
上記数式５の第３項の影響は小さいものとして無視し、(Fyfl+Fyfr)および(Fyrl+Fyrr)を次のように求める。
（数式６）

ここでδfとして(δfl+δfr)/2を用い、δrとして(δrl+δrr)/2を用いることとし、(Fyfl+Fyfr)を第１前輪横力和Fy_f、(Fyrl+Fyrr)を第１後輪横力和Fy_rに代入する。 (Calculation of left and right lateral force sum of front and rear wheels)
As shown in FIG. 3, the lateral force generated at the left front wheel is Fyfl, the lateral force generated at the right front wheel is Fyfr, the lateral force generated at the left rear wheel is Fyrl, and the lateral force generated at the right rear wheel is Fyrr, If the left and right turning angles of the front wheels are equal (δfl = δfr = δf) and the left and right turning angles of the rear wheels are equal (δrl = δrr = δr), then Holds.
(Formula 5)

Here, Lf is the front wheel center of gravity distance [m], Lr is the rear wheel center of gravity center distance [m], and Lt is the tread base distance (same front and rear wheels) [m], which are design constants.
The influence of the third term of Equation 5 is ignored as being small, and (Fyfl + Fyfr) and (Fyrl + Fyrr) are obtained as follows.
(Formula 6)

Here, (δfl + δfr) / 2 is used as δf, (δrl + δrr) / 2 is used as δr, (Fyfl + Fyfr) is the first front wheel lateral force sum Fy_f, and (Fyrl + Fyrr) is the first. Substitute in the rear wheel lateral force sum Fy_r.

ここで、hは重心高[m]である。そして、これらの値に基づき、以下の式で各輪の輪荷重を演算する。
（数式９）

この方法以外に、センサを用いて検出した輪荷重値を用いても良い。 (Calculation of each wheel load)
The front wheel load Wf when the vehicle is stationary and the rear wheel load Wr (unit is N) when the vehicle is stationary are calculated by the following equations.
(Formula 7)
Wf = M * Lr / (Lf + Lr) /2*9.8
Wr = M * Lf / (Lf + Lr) /2*9.8
Next, the front-rear wheel load movement amount ΔWd and the left-right wheel load movement amount ΔWc are calculated as follows from the vehicle longitudinal acceleration XG and the lateral acceleration YG at the center of gravity obtained by Expression 5.
(Formula 8)

Here, h is the center of gravity height [m]. Based on these values, the wheel load of each wheel is calculated by the following equation.
(Formula 9)

In addition to this method, a wheel load value detected using a sensor may be used.

(Setting the road friction coefficient search range)
The estimation of the road surface friction coefficient μ uses a method of searching for and estimating a value that meets a condition from a certain fixed range, and therefore it is necessary to determine a fixed range to be searched in advance. Therefore, 0.05 is set as m_min as the minimum value of the search range, and 1.0 is set as m_max as the maximum value. Further, the search step width Δm of the search range is set to 0.05, for example.

(Search for road friction coefficient)
In order to perform highly precise vehicle control, the present application searches and estimates the road surface friction coefficient μ in each of the front wheels 2FL and 2FR and the rear wheels 2RL and 2RR. When searching for the road surface friction coefficient μ for the front wheels 2FL and 2FR, the first front wheel lateral force sum Fy_f (see Formula 6) calculated based on the front wheel lateral force Fyf and the yaw moment MM, and a road surface friction calculation routine for the front wheel position described later. Select the road friction coefficient μ that minimizes the difference between the second front wheel lateral force sums Fymf calculated based on the front wheel slip angles αfl, αfr and the front wheel braking / driving road surface reaction forces Fxfl, Fxfr, and estimate the front wheel road surface friction coefficient mf And

  Similarly, for the rear wheels 2RL and 2RR, the first rear wheel lateral force sum Fy_r (see Formula 6) calculated based on the rear wheel lateral force Fyr and the yaw moment MM and the road surface friction calculation routine for the rear wheel position described later are used. Select the road surface friction coefficient μ that minimizes the difference between the second rear wheel lateral force sum Fymr calculated based on the rear wheel slip angles αrl, αrr and the rear wheel braking / driving road surface reaction force Fxrl, Fxrr. The coefficient of friction is mr.

(Calculation of road friction coefficient based on slip ratio: front wheels)
From the relationship between the slip ratios Sfl to Srr of each wheel and the braking / driving road surface reaction force Fx, the road surface friction coefficients mf0 and mr0 at the front wheels 2FL and 2FR and the rear wheels 2RL and 2RR based on the slip ratio S are estimated.
First, the front wheel slip road surface friction coefficient mf0 for the front wheels 2FL and 2FR is estimated. Here, based on the following equation, whether or not the slip angles αfl and αfr of the front wheels 2FL and 2FR are small is determined from the following condition, and mf0 is set.
| αfl + αfr | / 2 ≧ 0.5 / 180 * π
The front wheel slip angle αf is judged to be large, and the front wheel slip road surface friction coefficient mf0 = 1 is set.
αfl + αfr | / 2 <0.5 / 180 * π When the front wheel slip angle αf is judged to be small and large, the front wheel slip road surface friction coefficient mf0 is estimated based on the following formula (Formula 10)
m0_fl = MAP_FM (| Sfl |, | Fxfl / Wfl |)
m0_fr = MAP_FM (| Sfr |, | Fxfr / Wfr |)
Here, the slip ratios Sfl and Sfr of the front wheels 2FL and 2FR are obtained by the following equations.
(Formula 11)
Left front wheel: When V- (Nfl / GG * R) ≥ 0, Sfl = {V- (Nfl / GG * R)} / V
When V- (Nfl / GG * R) <0, Sfl = {V- (Nfl / GG * R)} / (Nfl / GG * R)
Right front wheel: When V- (Nfr / GG * R) ≥ 0, Sfr = {V- (Nfr / GG * R)} / V
When V- (Nfr / GG * R) <0, Sfl = {V- (Nfr / GG * R)} / (Nfr / GG * R)
MAP_FM is a characteristic map for the front wheels, and is a ratio of the slip ratios Sfl, Sfr and the road surface reaction forces Fxfl, Fxfr to the wheel loads Wfl, Wfr at the front wheels 2fl, 2fr. FIG. 5 shows an example of MAP_FM. Here, when the absolute value of the slip ratio is small (when there is neither a lock tendency nor a slip tendency), there is a wheel with an absolute value of the slip ratio Sf of 0.05 or less because the detection accuracy of the slip ratio is difficult to obtain sufficiently. In this case, the road surface friction coefficient mf0 is output as 1, and the road surface friction coefficient mf is not estimated.

(Calculation of road friction coefficient based on slip ratio: rear wheel)
For the rear wheels 2RL and 2RR, the rear wheel slip road surface friction coefficient mr0 at the rear wheels 2RL and 2RR is estimated in the same manner as the front wheels.
αrl + αrr | / 2 ≥ 0.5 / 180 * π Judge that rear wheel slip angle αr is large and set rear wheel slip road surface friction coefficient mr0 = 1
αrl + αrr | / 2 <0.5 / 180 * π | αrl + αrr | / 2 ≥ 0.5 / 180 * π Judge that the rear-wheel slip angle αr is small, the rear-wheel slip ratio Sr and the rear-wheel road surface reaction force Estimate rear wheel slip road friction coefficient mr0 based on Fxr (Formula 12)
m0_rl = MAP_FM (| Srl |, | Fxrl / Wrl |)
m0_rr = MAP_FM (| Srr |, | Fxrr / Wrr |)
Here, the slip ratios Srl and Srr of the rear wheels 2RL and 2RR are obtained by the following equations. MAP_RM is a map of the ratio of slip ratios Srl, Srr and road reaction forces Fxrl, Fxrr and wheel loads Wrl, Wrr at the rear wheels.
(Formula 13)
Left rear wheel: Srl = {V- (Nrl / GG * R)} / V when V- (Nrl / GG * R) ≥ 0
When V- (Nrl / GG * R) <0, Srl = {V- (Nrl / GG * R)} / (Nrl / GG * R)
Right rear wheel: When V- (Nrr / GG * R) ≥ 0, Srr = {V- (Nrr / GG * R)} / V
When V- (Nrr / GG * R) <0, Srr = {V- (Nrr / GG * R)} / (Nrr / GG * R)
Also in the case of the rear wheel, if there is a wheel having an absolute value of the slip ratio Sr of 0.05 or less, the rear wheel slip road surface friction coefficient mr0 is output as 1, and the rear wheel road surface friction coefficient mr is not estimated.

(Calculation of lateral force for each wheel)
1. Front wheel The front wheel slip road surface friction coefficient mf0 and the front wheel estimated road surface friction coefficient mf are compared. When mf> mf0, mf = mf0 is set. When mf ≦ mf0, mf remains as it is. This is due to the calculation of the road surface friction coefficient based on the slip ratio described above. When the tire slip angle is large and the slip ratio is minimal, the front wheel slip road surface friction coefficient mf0 = 1 is calculated, so mf ≦ mf0 and mf remains unchanged. Adopted. On the other hand, when the slip angle is small, the search for the estimated front wheel friction coefficient mf, which will be described later, does not go well, and mf = 1 is output, and the front wheel slip road friction coefficient mf0 outputs a value of 1 or less based on the aforementioned MAP. Therefore, mf> mf0 and mf = mf0 is adopted. In this way, the lateral forces Fyfl and Fyfr (see FIG. 3) of the front wheels 2FL and 2FR are calculated by the following equation based on the estimated front wheel friction coefficient mf. The calculation uses the tire characteristic map MAP_FT at the front wheels.
(Formula 14)
Fyfl = MAP_FT (Wfl, Fxfl, m_opt, αfl)
Fyfr = MAP_FT (Wfr, Fxfr, m_opt, αfr)
2. Rear wheel As with the front wheel, the rear wheel slip road surface friction coefficient mr0 based on the rear wheel slip ratio Sr is compared with the estimated rear wheel road surface friction coefficient mr, and if mr> mr0, mr = mr0. If mr ≦ mr0, mr remains unchanged. This is due to the calculation of the road surface friction coefficient based on the slip ratio described above. When the tire slip angle is large and the slip ratio is minimum, the front wheel slip road surface friction coefficient mr0 = 1 is calculated, so mr ≦ mr0 and mr remains unchanged. Adopted. On the other hand, if the slip angle is small, the search for the estimated front wheel friction coefficient mf, which will be described later, is not successful, and mr = 1 is output, and the front wheel slip road friction coefficient mr0 outputs a value of 1 or less based on the above-mentioned MAP. Therefore, mr> mr0 and mr = mr0 is adopted. Thus, based on the estimated rear wheel friction coefficient mr, the lateral forces Fyrl and Fyrr (see FIG. 3) of the rear wheels 2RL and 2RR are calculated by the following equations. The calculation uses a tire characteristic map MAP_RT at the front wheels.
(Formula 15)
Fyrl = MAP_RT (Wrl, Fxrl, m_opt, αrl)
Fyrr = MAP_RT (Wrr, Fxrr, m_opt, αrr)

[Vehicle behavior estimation control processing]
FIG. 6 is a routine of the vehicle state estimation control process executed in step S203 of FIG. Hereinafter, each step will be described.

  In step S401, each wheel turning angle δfl to δrr is calculated, and the process proceeds to step S402.

  In step S402, each wheel drive road surface reaction force Fxfl to Fxrr is calculated, and the process proceeds to step S403.

  In step S403, yaw moment MM and lateral force YG are calculated, and the process proceeds to step S404.

  In step S404, first front and rear wheel lateral force sums Fy_f and Fy_r are obtained, and the process proceeds to step S405.

  In step S405, the wheel loads Wfl to Wrr are calculated, and the process proceeds to step S406.

  In step S406, 0.05 is set as the minimum value m_min of the search range of the road surface friction coefficient μ, and 1.0 is set as the maximum value m_max. Further, the search step width Δm is set to 0.05, and the process proceeds to step S407.

  In step S407, the estimated road surface friction coefficient mf of the front wheels 2FL and 2FR is calculated, and the process proceeds to step S408. This step will be described later in the road friction calculation routine for the front wheel position.

  In step S408, the estimated road surface friction coefficient mr of the rear wheels 2RL and 2RR is calculated, and the process proceeds to step S409. This step will be described later in the road friction calculation routine for the rear wheel position.

  In step S409, the front wheel slip road surface friction coefficient mf0 considering the slip ratio is estimated from the front wheel slip ratios Sfl and Sfr, and the process proceeds to step S410.

  In step S410, the rear wheel slip road surface friction coefficient mr0 is estimated from the rear wheel slip ratios Srl and Srr in consideration of the slip ratio, and the process proceeds to step S411.

  In step S411, it is determined whether the front wheel estimated road surface friction coefficient mf is larger than the front wheel slip road surface friction coefficient mf0 considering the slip ratio. If YES, the process proceeds to step S412. If NO, the process proceeds to step S413. .

  In step S412, the front wheel road surface friction coefficient mf is set to the front wheel slip road surface friction coefficient mf0 considering the slip ratio, and the process proceeds to step S413.

  In step S413, it is determined whether the estimated rear wheel road friction coefficient mr is larger than the rear wheel slip road friction coefficient mr0 considering the slip ratio. If YES, the process proceeds to step S414, and if NO, the process proceeds to step S414. Transition.

  In step S414, the rear wheel road surface friction coefficient mr is set to be the rear wheel slip road surface friction coefficient mr0 considering the slip ratio, and the process proceeds to step S415.

  In step S415, each wheel lateral force Fyfl to Fyrr is calculated, and this routine is terminated.

[Road friction calculation routine for front wheel position]
FIG. 7 is a flow related to the calculation of the road surface friction coefficient mf at the front wheel position in step S407 in the flow of FIG.
(Search initial value setting)
In order to search for the estimated value mf of the road surface friction coefficient μ, first, the front wheel road surface friction coefficient m_min at the start of the search is set. Next, m_min is set as the initial value of the candidate m_opt of the estimated front wheel surface friction coefficient mf. Also, a sufficiently large value (for example, 1000000) is input as J_opt (described later).

(Front wheel tire slip angle calculation)
The tire slip angles αfl and αfr of the front wheels 2FL and 2FR with respect to the vehicle slip angle β (the vehicle slip angle at the point P in FIG. 3) are calculated by the following equations. The relationship between the body slip angle β and the front tire slip angles αfl, αfr is roughly the following relationship: Chapter 3 (p.54) of “Automotive Movement and Control (Sankaido, Author: Masato Abe)” Is shown in In addition, the traveling direction of the center of the tire is a clockwise direction with respect to the direction of the tire rotation surface (see FIG. 3).
(Formula 16)
αfl = (V * β + (Lf + Lr) * γ) / (V-Lt * γ / 2)-δfl
αfr = (V * β + (Lf + Lr) * γ) / (V + Lt * γ / 2)-δfr

(Front wheel lateral force sum estimated value calculation)
Using the tire characteristic map, a second front wheel lateral force sum Fymf corresponding to the estimated front wheel friction coefficient m is calculated based on the following equation.
(Formula 17)
Second front wheel lateral force sum Fymf = MAP_FT (Wfl Fxfl, m, αfl) + MAP_FT (Wfr, Fxfr, m, αfr)

  Here, MAP_FT is inputted with data to output the lateral force generated by the front wheel tires 3FL and 3FR with respect to the wheel load, braking / driving road surface reaction force, road surface friction coefficient, and front wheel tire slip angles αfl and αfr. It is a map of 4 inputs and 1 output. The absolute value of the lateral force that is output is smaller as the road surface friction coefficient is smaller, and the absolute value of the lateral force that is output is smaller as the absolute value of the braking / driving road surface reaction force is larger.

(Minimization of difference between first and second front wheel lateral force sum)
A search is made for a combination of the road surface friction coefficient μ that minimizes the difference between the second front wheel lateral force sum estimated value Fymf and the first front wheel lateral force sum Fy_f. First, the value J of the function that outputs a smaller value is calculated as the values of the first and second front wheel lateral force sums Fy_f and Fymf are closer. Here, the following functions are used.
(Formula 18)
J = | 2nd front wheel lateral force sum Fymf-1st front wheel lateral force sum Fy_f |
Other (Formula 19)
J = (2nd front wheel lateral force sum Fymf-1st front wheel lateral force sum Fy_f) ²
And so on.

Here, if J is less than or equal to the stored J_opt, the second front wheel lateral force sum Fymf is the closest m to the first front wheel lateral force sum Fy_f among the road surface friction coefficients m so far. Judge. In that case, the evaluation value J_opt and the road surface friction coefficient candidate value m_opt are updated as follows. If it is more than J_opt, it is not updated.
(Formula 20)
J_opt = J, m_opt = m

  Further, the next search candidate value m of the road surface friction coefficient μ is updated to a value obtained by adding Δm. After the update, it is determined whether or not the search value m of the road surface friction coefficient μ exceeds the upper limit value m_max of the search range. If not, start again from the calculation of the front tire slip angles αfl, αfr. If the upper limit m_max is exceeded, set this search value m as a candidate value for the estimated value of the road surface friction coefficient μ. . If not, substitute m_opt for the front wheel road surface friction coefficient mf.

  That is, in this road surface friction coefficient search / estimation control, the road surface friction coefficient is changed in increments of Δm between the front wheel road surface friction coefficient ranges m_min to m_max. A front wheel road surface friction coefficient mf having a similar value of the first and second front wheel lateral force sums Fy_f and Fymf calculated using the tire characteristic map MAP_FT is extracted.

[Road friction calculation routine for front wheel position: processing]
FIG. 7 is a front wheel road surface friction coefficient search / estimation control processing routine. Hereinafter, each step will be described.

  In step S501, m_min is set as the road surface friction coefficient μ at the search start time, and the process proceeds to step S502.

  In step S502, m_min is set as the initial value of m_opt. Further, 1000000 is input to J_opt, and the process proceeds to step S503.

  In step S503, tire slip angles αfl and αfr of the front wheels 2FL and 2FR are calculated, and the process proceeds to step S504.

  In step S504, the second front wheel lateral force sum Fymf corresponding to the road surface friction coefficient m at the start of the search is read from the map, and the process proceeds to step S505.

  In step S505, the value J of the function that outputs a smaller value as the first and second front wheel lateral force sums Fy_f and Fymf are closer is calculated, and the process proceeds to step S506.

  In step S506, it is determined whether or not the function J is equal to or less than the stored J_opt. If YES, the process proceeds to step S507, and if NO, the process proceeds to step S508.

  In step S507, the evaluation value J_opt and the front wheel road surface friction coefficient candidate value m_opt are updated as J_opt = J, m_opt = m, and the process proceeds to step S508.

  In step S508, Δm is added to the next search candidate value m of the road surface friction coefficient μ, and the process proceeds to step S509.

  In step S509, it is determined whether or not the search value m of the road surface friction coefficient μ exceeds the search range upper limit value m_max. If YES, the process proceeds to step S510, and if NO, the process returns to step S503.

  In step S510, this search value m is set as a candidate value for the estimated value of the road surface friction coefficient μ, and this search value m is output as mf as a candidate value for the estimated value of the road surface friction coefficient μ to the aforementioned S407. Exit.

[Rear surface friction calculation routine]
FIG. 8 is a flow related to the calculation of the road surface friction coefficient mr at the rear wheel position in step S408 in the flow of FIG. As with the front wheels, the rear wheel road surface friction coefficient m_min at the start of the search is set for the rear wheels, and m_min is set as an initial value of the candidate m_opt for the estimated front wheel road surface friction coefficient mf. Also, a sufficiently large value (for example, 1000000) is input as J_opt (described later).

(Rear wheel tire slip angle calculation)
Similar to the front wheels, the tire slip angles αrl and αrr of the rear wheels 2RL and 2RR with respect to the vehicle slip angle β (the vehicle slip angle at the point P in FIG. 3) are calculated by the following equations.
(Formula 21)
αrl = (V * β + (Lf + Lr) * γ) / (V-Lt * γ / 2)-δrl
αrr = (V * β + (Lf + Lr) * γ) / (V + Lt * γ / 2)-δrr

(Rear wheel lateral force sum estimated value calculation)
Using the tire characteristic map, the second rear wheel lateral force sum Fymr corresponding to the estimated rear wheel friction coefficient m is calculated based on the following equation.
(Formula 22)
Second rear wheel lateral force sum Fymr = MAP_RT (Wrl Fxrl, m, αrl) + MAP_RT (Wrr, Fxrr, m, αrr)

  Here, MAP_RT is a map of the lateral force of the rear wheel tires 3RL, 3RR with respect to the wheel load, braking / driving road surface reaction force, road surface friction coefficient, and tire slip angles αrl, αrr. The absolute value of the lateral force that is output is smaller as the road surface friction coefficient is smaller, and the absolute value of the lateral force that is output is smaller as the absolute value of the braking / driving road surface reaction force is larger.

(Minimization of the difference between the first and second rear wheel lateral force sums)
A search is made for a combination of the road surface friction coefficient μ that minimizes the difference between the second rear wheel lateral force sum estimated value Fymr and the first rear wheel lateral force sum Fy_r. First, the value J of the function that outputs a smaller value as the values of the first and second rear wheel lateral force sums Fy_r, Fymr are closer is calculated.
(Formula 23)
J = | 2nd rear wheel lateral force sum Fymr-1st rear wheel lateral force sum Fy_r |
Other
J = (second rear wheel lateral force sum Fymr-first rear wheel lateral force sum Fy_r) ²
And so on. If J is less than or equal to the stored J_opt, the second front wheel lateral force sum Fymf is determined to be m closest to the first front wheel lateral force sum Fy_f among the road surface friction coefficients m up to that point. . In that case, the evaluation value J_opt and the road surface friction coefficient candidate value m_opt are updated as follows. If it is more than J_opt, it is not updated.
(Formula 24)
J_opt = J, m_opt = m

  Further, the next search candidate value m of the road surface friction coefficient μ is updated to a value obtained by adding Δm, and it is determined whether or not the search value m of the road surface friction coefficient μ exceeds the upper limit value m_max of the search range. If not exceeded, the calculation is performed again from the calculation of the rear wheel tire slip angles αrl and αrr. If the upper limit m_max is exceeded, the search value m is set as a candidate value for the road surface friction coefficient μ. If not, m_opt is substituted for the rear wheel road surface friction coefficient mr.

  That is, as with the front wheels, the first and second rear wheel lateral force sums Fy_r, Fymr calculated using the tire characteristic map MAP_FT are changed in increments of Δm between the road surface friction coefficient ranges m_min to m_max in the rear wheels. The rear wheel road surface friction coefficient mr with a close value is extracted.

  Note that the road surface friction coefficient m_opt is updated using a condition that the difference between the first and second lateral force sums (Fy_f, Fy_r) and (Fymf, Fymr) at the front and rear wheels is the smallest. However, depending on the required detection accuracy of the road surface friction coefficient, it is considered that the difference between the lateral force sum calculated using the tire characteristic map and the detected lateral force sum falls within the predetermined range is small, and the road surface friction coefficient m_opt May be updated.

[Rear surface friction calculation routine: processing]
FIG. 8 is a rear wheel road surface friction coefficient search / estimation control processing routine. Hereinafter, each step will be described.

  In step S501, m_min is set as the road surface friction coefficient μ at the search start time, and the process proceeds to step S502.

  In step S502, m_min is set as the initial value of m_opt. Further, 1000000 is input to J_opt, and the process proceeds to step S503.

  In step S553, tire slip angles αfl and αfr of the rear front wheels 2RL and 2RR are calculated, and the process proceeds to step S554.

  In step S554, the second rear wheel lateral force sum Fymr corresponding to the road surface friction coefficient m at the start of the search is read from the map, and the process proceeds to step S555.

  In step S555, the value J of the function that outputs a smaller value as the first and second front wheel lateral force sums Fy_r and Fymr are closer is calculated, and the process proceeds to step S506.

  In step S506, it is determined whether or not the function J is equal to or less than the stored J_opt. If YES, the process proceeds to step S507, and if NO, the process proceeds to step S508.

  In step S507, the evaluation value J_opt and the front wheel road surface friction coefficient candidate value m_opt are updated as J_opt = J, m_opt = m, and the process proceeds to step S508.

  In step S508, Δm is added to the next search candidate value m of the road surface friction coefficient μ, and the process proceeds to step S509.

  In step S509, it is determined whether or not the search value m of the road surface friction coefficient μ exceeds the search range upper limit value m_max. If YES, the process proceeds to step S510, and if NO, the process returns to step S503.

  In step S560, this search value m is set as a candidate value for the estimated value of the road surface friction coefficient μ, and this search value m is output as mf as a candidate value for the estimated value of the road surface friction coefficient μ to S407 described above. Exit.

[Motor torque command value calculation control]
In the motor torque command value calculation control in step S204 of FIG. 2, first, the target driving force tTD of the vehicle is read from the vehicle speed-accelerator opening degree map MAP_tTD (see FIG. 8).

Next, motor torque command values tTFL to tTRR for the respective wheels fl to rr are calculated based on the following equation. Note that tU is determined by reading the V-tU map of FIG. 9 based on the target driving force vehicle speed and the steering amount STR.
(Formula 25)
Left front, rear wheel tTFL, tTRL = tTD * R / GG / 4-tU * R / GG / 4
Right front, rear wheel tTFR, tTRR = tTD * R / GG / 4 + tU * R / GG / 4
Here, GG is a reduction ratio in the reducers 4FL to 4RR. The yaw rate γ and the vehicle lateral acceleration YG may be corrected so as to have a desired transient response, and there is no particular limitation. For the correction method, refer to Chapter 8 of “Automotive Movement and Control (Sankaido, Author: Masato Abe)”.

  With respect to the calculated motor torque command values tTFL to tTRR, the driving torque of each wheel fl to rr is redistributed so that the lateral force Fy, yaw moment MM, and longitudinal acceleration XG of the vehicle do not change. Specifically, based on the estimated wheel load W of each wheel, the tire slip angle α, the estimated turning angle δ, and the estimated road friction coefficient μ, it is regenerated according to the sensitivity k of the lateral force YG to the longitudinal acceleration (longitudinal force) XG. To distribute. Motor torque command values tTFL to tTRR of the respective wheels fl to rr after the redistribution are output to the motor drive circuit.

[Motor torque command value calculation control process]
FIG. 10 is a motor torque command value calculation control processing routine. Hereinafter, each step will be described.

  In step S601, the target driving force tTD is calculated, and the process proceeds to step S602.

  In step S602, motor torque command values tTFL to tTRR for the wheels 2FL to 2RR are calculated, and the process proceeds to step S603.

  In step S603, the drive torque of each wheel fl to rr is reallocated, and the process proceeds to step S604.

  In step S604, motor torque command values tTFL to tTRR for the respective wheels fl to rr are output, and this routine ends.

[Effect of the embodiment of the present application]
(1) First lateral force sum calculating means for calculating the first front wheel lateral force sum Fy_f and the first rear wheel lateral force sum Fy_r based on the vehicle state, and the road surface friction coefficient at the front wheels 2FL, 2FR and the rear wheels 2RL, 2RR. Vehicle state estimation means for estimating mf, mr, initial value m_min of estimated road surface friction coefficient m in front wheels 2FL, 2FR and rear wheels 2RL, 2RR are set, front wheel slip angles αfl, αfr and rear wheel slip angles αrl, αrr Based on the vehicle angle, the initial value m_min of the road surface friction coefficient in the front wheels 2FL and 2FR or the rear wheels 2RL and 2RR, the front wheel slip angles αfl and αfr, and the rear wheel slip angles αrl and αrr. 2 front wheel lateral force sum Fymf and second rear wheel lateral force sum Fymr. The vehicle state estimating means includes a first front wheel lateral force sum Fy_f and a second front wheel lateral force sum Fymf. The estimated front wheel road surface friction coefficient mf is estimated so that the difference between the first and second rear wheels lateral force sum Fy_r and Fymr is So as to be small, it was decided to estimate the estimated rear-wheel road surface friction coefficient mr.

  As a result, the estimation uses the characteristic that the lateral force of the tire changes according to the road friction coefficient and the slip angle of the tire, and the change in the lateral force Fy due to the change in the road friction coefficient μ appears as a change in vehicle behavior. It is possible to estimate the road surface friction coefficient μ immediately before, and it is possible to realize a high vehicle motion performance.

  (2) Lateral acceleration sensors 24 and 25 for detecting the lateral acceleration of the vehicle, vehicle lateral force estimating means for estimating the vehicle lateral force FX based on the detected lateral accelerations YG1 and YG2, and detected lateral acceleration YG1, Based on YG2, yaw moment estimating means for estimating yaw moment γ ', front wheel load calculating means for calculating loads Wfl to Wrr of each wheel 2FL to 2RR, and braking / driving reaction force Fxfl to Fxrr for each wheel 2FL to 2RR The braking / driving reaction force estimating means for estimating, the vehicle speed detecting means for detecting the vehicle speed V, the yaw rate sensor 8 for detecting the yaw rate γ, and the turning angle sensor 21 for calculating the turning angles δfl to δrr of the wheels 2FL to 2RR. The first front wheel lateral force sum calculating means calculates the first front wheel lateral force sum Fy_f based on the estimated vehicle lateral force Fx and the estimated yaw moment γ ′, and the front wheel slip angles αfl and αfr are the vehicle speed V and the yaw rate. Calculated based on γ and front wheel turning angle δfl, δfr, the second front wheel lateral force summation The means is to calculate the second front wheel lateral force sum Fymf based on the initial value m_min of the front wheel road surface friction coefficient m, the front wheel loads Wfl, Wfr, the front wheel braking / driving reaction forces Fxfl, Fxfr, and the front wheel slip angles αfl, αfr. .

  By using the characteristic that the tire lateral force Fy changes according to the road surface friction coefficient μ and the front wheel slip angle αfl, αfr, the relationship between the front wheel estimated braking / driving road surface reaction force Fxmf and the second front wheel lateral force sum Fymf is obtained. By performing the estimation based on this, the road surface friction coefficient μ can be estimated at a high speed.

  (3) The inventions of (1) and (2) above are also applied to the rear wheels, and the road surface friction coefficient mr for the rear wheels 2RL and 2RR and the road surface friction coefficient mf for the front wheels 2FL and 2FR are obtained by different calculations. Thus, for example, even in a driving situation in which the road surface friction coefficient is switched (for example, a driving situation in which the road surface is switched from an asphalt road surface to a compressed snow road surface), the road surface friction coefficient mf, mr is applied to the front wheels 2FL, 2FR and the rear wheels 2RL, 2RR. The vehicle behavior can be highly controlled by appropriately distributing the driving force according to the respective road surface friction coefficient and tire condition.

(4) The second lateral force calculation means may be a means for calculating in consideration of a dynamic factor of lateral force generation delay with respect to the input of each wheel slip angle αfl to αrr. In this case, the transfer characteristic of response delay is T (s) (s is a differential operator), and the map reference value in steps S504, S554, and S415 is subjected to the first-order delay process of T (s) by the following formula: Is calculated as the tire lateral force.
(Formula 26)
T (s) = 1 / (kt / V s + 1)
Here, kt is a constant that determines the time constant of the first-order lag. By performing the first-order lag processing, it is possible to further improve the estimation accuracy of the road surface friction coefficient in a transient state where each wheel slip angle αfl to αrr is changing.

  (5) The integrated controller 30 is mounted on a vehicle that can independently distribute braking force or driving force to a plurality of wheels, and when one of the wheels 2FL to 2RR cannot sufficiently obtain the braking / driving road surface reaction force Fx. The braking / driving force is redistributed based on the estimated value m of the estimated road surface friction coefficient μ. Thus, the drive torque of each wheel 2FL to 2RR is redistributed so that the lateral force Fy, yaw moment MM, and longitudinal acceleration XG of the vehicle do not change with respect to the calculated motor torque command values tTFL to tTRR. This makes it possible to further stabilize the vehicle behavior.

  A second embodiment will be described with reference to FIG. Since the basic configuration is the same as that of the first embodiment, only different points will be described. In the first embodiment, the road surface friction coefficient mf of the front wheels and the road surface friction coefficient mr of the rear wheels are estimated. In the second embodiment, the road surface friction coefficient m is estimated on the assumption that the road surface friction coefficients of the four wheels are the same value m. Different.

[Vehicle Behavior Estimation Control Processing in Embodiment 2]
FIG. 12 is a flowchart of the vehicle behavior establishment control process in the second embodiment. The tire slip angle average values αf and αr of the front wheels and the rear wheels are compared, and if the front wheel side slip angle αf is large, the front wheel road surface friction coefficient mf is selected as the road surface friction coefficient m. Similarly, if the rear wheel side slip angle αr is large, the rear wheel road surface friction coefficient mr is selected as the road surface friction coefficient m. In other words, the road surface friction coefficient m is calculated by placing importance on the road surface friction coefficient (mf or mr) of the wheel having the larger tire slip angle.
Steps S401 to S410 and step S415 are the same as the flowchart of the vehicle behavior estimation control process (FIG. 6) of the first embodiment.

In step S461, a road surface friction coefficient m is calculated as a value between mf and mr. The front tire slip angle average value αf (= (αfl + αfr) / 2) and the rear wheel tire slip angle average value αr (= (αrl + αrr) / 2) are obtained.
Here, if | αf | and | αr | have the same value, the road surface friction coefficient m is calculated as follows by taking a weighted average of | αf | and | αr |.
When | αf | = | αr |, m = (mf + mr) / 2
On the other hand, when the values of | αf | and | αr | are different from each other, the road surface friction coefficient m is calculated as follows according to the magnitude relationship.
If | αf |> | αr |, m = mf
If | αf | <| αr |, m = mr
After calculating the road surface friction coefficient m, the process proceeds to step S462.

  In step S462, using the road surface friction coefficients mf0 and mr0 information calculated in steps S409 and S410, the front and rear wheel road friction coefficients mf and mr are calculated as the minimum values of m, mf0 and mr0, and step S415 Migrate to

[Effect of Example 2]
In the second embodiment, the vehicle state estimating means compares the absolute value of the front wheel slip angle | αf | with the absolute value of the rear wheel slip angle | αr | and the intermediate value (mf + mr) / 2 of the road surface friction coefficient. When the absolute value of the front wheel slip angle | αf | is larger, the road surface friction coefficient m of each wheel is set to a value closer to the front wheel road surface friction coefficient mf than the intermediate value (mf + mr) / 2. If the absolute value of the rear wheel slip angle | αr | is larger, the road surface friction coefficient m of each wheel is set closer to the rear wheel road surface friction coefficient mr side than the intermediate value (mf + mr) / 2. It was decided to. That is, the tire slip angle average values αf and αr of the front wheels and the rear wheels are compared, and if the front wheel side slip angle αf is large, the front wheel road surface friction coefficient mf is selected as the road surface friction coefficient m. Similarly, if the rear wheel side slip angle αr is large, the rear wheel road surface friction coefficient mr is selected as the road surface friction coefficient m.

  Even if the tire slip angle average value αf, αr of either the front or rear wheels is not so large, and the difference in the value of the tire lateral force Fyf, Fyr is small, the estimation accuracy of the road surface friction coefficient cannot be obtained sufficiently, The estimation accuracy of the road surface friction coefficient can be improved with more opportunities by estimating the road surface friction coefficient value on the wheel having the larger slip angle average values αf and αr among the front and rear wheels.

  In the second embodiment, m is the road surface friction coefficient of the larger wheel among the average slip angle values αf and αr of the front and rear wheels, but other methods may be used to determine the road surface friction coefficient m. Listed below.

(Example 2-1)
The vehicle state estimating means sets a value between the front wheel road surface friction coefficient and the rear wheel road surface friction coefficient and including the front wheel and rear wheel road surface friction coefficients as the road surface friction coefficient of each wheel. That is, the road surface friction coefficient mf, mr of the front and rear wheels, the front and rear wheel tire slip angle average values αf, αr, and the coefficients Km1, Km2 may be obtained as follows.
(Formula 27)
m = (Km1 * | αf | * mf + | αr | * mr) / (Km1 * | αf | + | αr |)
Here, the values of Km1 and Km2 are determined based on the fact that the tire slip angle (αv) at which the lateral force change with respect to the road surface friction coefficient becomes large differs between before and after. For example, when αv is smaller for the front wheels than for the rear wheels (when a smaller tire slip angle shows a lateral force change characteristic with respect to the road surface friction coefficient), Km1> 1 is set according to the degree. On the other hand, when αv is larger on the front wheels than on the rear wheels (when the tire slip angle has a larger lateral force change characteristic with respect to the road surface friction coefficient), Km1 <1 is set according to the degree. Similarly, the value of Km2 may be determined based on the fact that the magnitude of the tire lateral force at which the lateral force change with respect to the road surface friction coefficient increases differs between the front and rear.

(Example 2-2)
Instead of using the slip angles αfl to αrr of each wheel as in the second embodiment, the following calculation may be performed based on the magnitudes of the first front and rear wheel lateral force sums Fy_f and Fy_r.
(Formula 28)
m = (Km2 * | Fy_f | * mf + | Fy_r | * mr) / (Km2 * | Fy_f | + | Fy_r |)
As in Example 2-1, Km1 and Km2 are coefficients.

(Example 2-3)
Further, the turning angle sensor 21 further detects the steering angle STR of the steering wheel 11, and the vehicle state estimation means determines whether the steering wheel 11 is in the increased state or the switched back state based on the detected steering angle STR. If it is determined that it is in an increased state, a value closer to the front wheel road surface friction coefficient mf than the rear wheel road surface friction coefficient mr is set as the road surface friction coefficient m. A value close to the rear wheel road surface friction coefficient mr may be set as the road surface friction coefficient m. When turning the steering wheel 11, the front wheel slip angle αf tends to be larger than the rear wheel slip angle αr, and when turning back the steering wheel 11, the front wheel slip angle αf is greater than the rear wheel slip angle αr. Taking advantage of the tendency to decrease first, the road surface friction coefficient m is calculated according to the steering operation amount STR as follows.
When | STR | is increasing, m = mf
When | STR | tends to decrease m = mr
When there is no change in | STR | m = (mf + mr) / 2

  By taking into account the tire characteristics before and after (difference in cornering stiffness, etc.), any one of the methods of Example 2-1 to Example 2-3 can be selected as appropriate to obtain the same effects as those of Example 2. it can.

(Other examples)
As mentioned above, although the steering device of the present invention has been described based on the embodiments, the specific configuration is not limited to these, and the design of the steering device is not limited unless it deviates from the gist of the invention according to each claim of the claims. Changes and additions are allowed.

  For example, a vehicle that steers rear wheels may be used. In this case, the rear wheel steering angles δrl and δrr calculated in step S401 in FIG. 6 are not always set to 0, but are determined according to the detected value of the rear wheel steering angle.

  Regarding the steering of the front wheels, the system may be a system in which the relationship between the steering operation angle and the front wheel turning angle can be made variable while mechanically connecting the steering handle and the front wheel turning system. Further, a so-called steer-by-wire system in which the steering handle and the front wheel steering system are electronically connected may be used, and in this case, the front wheel steering angle detection values are used as the front wheel steering angles δfl and δfr calculated in step S401. Use it.

  Further, the drive mode to which the present invention can be applied is not limited to that in which the four wheels are independently motor driven as shown in FIG. The drive source may be an engine, or any of front wheel drive, rear wheel drive, and four wheel drive. A hybrid vehicle using both an engine and a motor may be used, and similar effects can be obtained by appropriately changing the embodiment according to the drive mode of the drive source.

Further, in addition to using the vehicle slip angle sensor 29 described in the first embodiment, the calculating means for the second front wheel lateral force sum Fymf and the calculating means for the second rear wheel lateral force sum Fymr are used for slipping the front wheel or the rear wheel. The slip angle of the vehicle body may be detected by calculating the second front wheel lateral force sum Fymf or the rear wheel lateral force sum Fymr in consideration of the dynamic factors of the lateral force generation delay with respect to the angles αf and αr. For example, an observer using output signals of two lateral acceleration sensors and a yaw rate sensor may be configured, and the vehicle slip angle at the center of gravity G may be estimated. Based on this β, the vehicle slip angle b at point P in FIG. 3 is estimated using the following equation.
(Formula 29)
b = (V * β-Lr * γ) / V

It is a system block diagram of the electric vehicle which drives 4 wheels with an independent electric motor. It is a main flowchart of a torque command value calculation control process. It is a figure which shows the relationship between a vehicle body slip angle and each vehicle behavior parameter. It is a figure which shows the relationship between a lateral acceleration and each vehicle behavior parameter. It is a map of the ratio of slip ratio and road surface reaction force / wheel load. It is a routine of a vehicle state estimation control process. It is a search / estimation control processing routine for a front wheel road surface friction coefficient. It is a search / estimation control processing routine for a rear wheel road surface friction coefficient. It is a vehicle speed-accelerator opening degree map. It is a vehicle speed-steering angle map. It is a motor torque command value calculation control processing routine. 7 is a routine of a vehicle state estimation control process in Embodiment 2.

Explanation of symbols

3 fl to 3 rr Wheel 4 fl to 4 rr Reducer 5 fl to 5 rr Drive circuit 6 Battery 8 Yaw rate sensor 11 Steering wheel 14 Steering rack 21 Steering angle sensor 22 Brake pedal sensor 23 Accelerator pedal sensor 24, 25 Lateral acceleration sensor 26 Longitudinal acceleration sensor 29 Car body Slip angle sensor 30 Integrated controller

Claims (9)

Based on the vehicle state, and the first tire lateral force sum calculation means for calculating a first tire lateral force sum of at least one of the two wheels of the two front wheels or two rear wheels of the vehicle,
Tire slip angle calculating means for calculating the tire slip angle of the one of the two wheels;
A wheel load estimating means for estimating a wheel load of the one of the two wheels;
Braking / driving reaction force estimating means for estimating the braking / driving reaction force of the one of the two wheels;
Second tire lateral force sum calculation for calculating the second tire lateral force sum of the one two wheels based on the estimated wheel load, estimated braking / driving reaction force, tire slip angle and road surface friction coefficient of the one two wheels Means,
Search range setting means for setting a search range for the road surface friction coefficient of the one of the two wheels calculated by the second tire lateral force sum calculation means;
Wherein among the second tire lateral force sum which is calculated on the basis of the search range in the A and the second tire lateral force summing units, first which is calculated based on the first tire lateral force summing units A search means for searching for a second tire lateral force sum, which satisfies a condition that a difference between the tire lateral force sum and the tire lateral force sum is reduced;
A road surface friction coefficient estimation means you estimating the road surface friction coefficient of the one of the two wheels from the second tire lateral force sum which is the search,
A vehicle state estimation device. The vehicle state estimation device according to claim 1,
The first tire lateral force summing unit calculates a first tire lateral force sum of the other two wheels,
It said tire slip angle calculating means calculates a tire slip angle of the other two wheels,
The load estimating means estimates a wheel load of the other two wheels;
The braking / driving reaction force estimating means estimates the wheel load of the other two wheels,
The second tire lateral force summing unit calculates a second tire lateral force sum of the other two wheels,
The search range setting means sets a search range for the road surface friction coefficient of the other two wheels calculated by the second tire lateral force sum calculation means,
State estimating device for a prior km surface frictional coefficient estimation means vehicle and estimates a road surface friction coefficient of the two-wheel of the other. In the vehicle state estimation device according to claim 1 or 2,
Lateral acceleration detecting means for detecting the lateral acceleration of the vehicle;
Vehicle lateral force estimation means for estimating vehicle lateral force based on the detected lateral acceleration;
A yaw moment estimating means for estimating a yaw moment based on the detected lateral acceleration;
Vehicle speed detection means for detecting the vehicle speed;
A yaw rate detecting means for detecting the yaw rate;
A turning angle calculating means for calculating a turning angle of each wheel;
Vehicle slip angle detecting means for detecting the slip angle of the vehicle body,
With
The first tire lateral force sum calculation means calculates the first tire lateral force sum on the basis of the estimated vehicle lateral force and the estimated yaw moment,
It said tire slip angle calculating means calculates the vehicle speed, yaw rate, vehicle slip angle, and the tie Yasu slip angle based on the steering angle of each wheel,
The second tire lateral force sum operation means, the search value for each wheel road surface friction coefficient, wherein the wheel load, the second tire lateral force sum on the basis of the respective wheel braking driving reaction force, and the tire slip angle A vehicle state estimation device characterized by: The vehicle state estimation device according to any one of claims 1 to 3,
Slip ratio detecting means for detecting the slip ratio of the one of the two wheels;
A slip road surface friction coefficient estimating means for calculating a slip road surface friction coefficient of the one two wheels based on the braking / driving reaction force of the one two wheels and the slip ratio of the one two wheels;
With
The road surface friction coefficient estimation unit, when the tire slip angle of said one of the two wheels is smaller than a predetermined value, characterized in that estimating the slip road surface friction coefficient of the one of the two-wheel as the road surface friction coefficient before Symbol each wheel A vehicle state estimation device. The vehicle state estimation device according to any one of claims 2 to 4,
It said tire slip angle calculating means calculates a tire slip angle of one and the other two wheels,
The second tire lateral force sum operation means, said one and the other based on dynamic elements of the lateral force generated delay with respect to the tire slip angle of 2 wheels, tire lateral force sum or the other of two-wheel prior Symbol hand A vehicle state estimation device characterized by calculating a tire lateral force sum of the two wheels. The vehicle state estimation device according to any one of claims 2 to 5,
The road surface friction coefficient estimating means estimates the road surface friction coefficient of one of the two wheels and the road surface friction coefficient of the other two wheels , and is between the road surface friction coefficient of the one two wheels and the road surface friction coefficient of the other two wheels. a value, and a value comprising該Ichi Ho及 beauty other road surface friction coefficient, the state estimation apparatus for a vehicle and estimating the road surface friction coefficient of each wheel. The vehicle state estimation device according to claim 6,
The road surface friction coefficient estimating means compares the calculated absolute value of one tire slip angle with the calculated absolute value of the other tire slip angle and calculates an intermediate value between the one and the other road surface friction coefficients. And
When the absolute value of the one tire slip angle is larger, the road surface friction coefficient of each wheel is estimated as a value closer to the one road surface friction coefficient side than the intermediate value,
When the absolute value of the other tire slip angle is larger, the road surface friction coefficient of each wheel is estimated as a value closer to the other road surface friction coefficient side than the intermediate value. apparatus. The vehicle state estimation device according to claim 7,
One wheel is one and the other two are the other,
Steering angle detection means for detecting the steering angle of the steering wheel for performing one steering,
The road surface friction coefficient estimating means determines whether the steering is in an increased state or a switched back state based on the detected steering angle;
When it is determined that the state is increased, the road friction coefficient is estimated to be a value closer to the one road friction coefficient than the other road friction coefficient,
A vehicle state estimation device characterized by estimating, as a road surface friction coefficient, a value closer to the other road surface friction coefficient than the one road surface friction coefficient when it is determined as a switchback state. In a vehicle control device comprising braking / driving force distribution control means for distributing braking / driving force to each wheel based on an estimated value of the vehicle state,
The vehicle state estimation device according to any one of claims 1 to 7, as means for estimating the state estimated value,
The braking / driving force distribution control means, when a certain wheel cannot obtain a target braking / driving road surface reaction force, based on the calculated value of the tire slip angle of each wheel and the estimated value of the road surface friction coefficient, A vehicle control device that redistributes the braking / driving force of the vehicle.

Images