JP4358070B2 - Body slip angle estimation method - Google Patents

Description

  The present invention relates to a vehicle body slip angle estimation method. In particular, the present invention relates to a vehicle body slip angle estimation method for estimating a vehicle body slip angle by recursively using an immediately preceding estimated vehicle body slip angle when calculating a current estimated vehicle body slip angle based on a vehicle dynamic model.

  Conventionally, when controlling the state of motion of a vehicle such as a turning motion, the optimal torque distribution of the vehicle using the angle (hereinafter referred to as slip angle β) formed by the traveling direction of the vehicle and the longitudinal axis (propeller shaft) of the vehicle. Control that improves exercise performance by performing control or the like is known. Conventionally, as a method of estimating the slip angle β, there is a method of estimating the slip angle by recursively using the previous estimated slip angle when calculating the current estimated slip angle based on the vehicle dynamic model. For example, Patent Document 1 describes a method for estimating a slip angle using a lateral force acting on a rear wheel in the lateral direction based on a tire dynamic model.

A lateral force acting on the rear wheels (hereinafter referred to as tire lateral force Y _r ) is calculated based on the tire dynamic model from the estimated road friction coefficient (hereinafter referred to as road surface μ) and the slip angle β estimated immediately before, and the yaw rate is calculated. A rotational angular velocity (hereinafter referred to as yaw rate r) around the vertical axis of the center of gravity of the vehicle detected by the sensor, a differential value r ′ thereof, and a vehicle speed (hereinafter referred to as vehicle speed V) detected by the vehicle speed sensor are expressed by the following equation (1). By substituting, the differential value in the time direction of the slip angle β (hereinafter, slip angle differential value β ′) is estimated.

β ′ = − 2 (L _f + L _r ) Y _r / mVL _f + Ir ′ / mVL _f −r−M / mVL _f
(1)
Where L _f is the distance from the vehicle center of gravity to the front wheel side axle, L _r is the distance from the vehicle center of gravity to the rear wheel side axle, Y _r is the tire lateral force, r ′ is the yaw rate differential value, m is the total mass of the vehicle, I is the yawing moment of inertia and M is the yawing moment.

The estimated slip angle derivative β ′ is integrated over time to estimate the current slip angle β, and the next tire lateral force Y _r is calculated by using the estimated current slip angle β recursively. A slip angle differential value β ′ and a slip angle β are estimated using the tire lateral force Y _r . In this way, the current slip angle β is calculated by using the previous slip angle β recursively.
JP 2003-306092 A

  As described above, the conventional vehicle body slip angle estimation method calculates the slip angle differential value β ′ and the slip angle β regardless of the value of the vehicle speed V. However, as shown in Equation (1), the vehicle speed V is included in the denominators of the first, second, and fourth terms. Therefore, when the vehicle speed V becomes low, the denominators of the first, second, and fourth terms are Since the value of the reciprocal of the vehicle speed V decreases and is increased by sensor noise and the like, the influence of sensor noise and the like becomes significant. When the speed is qualitatively low, the error of the slip angle differential value β ′ is growing. Also, the slip angle β, which is the integral value, includes a large error.

  Further, since the slip angle β is recursively calculated using the estimated value of the slip angle β immediately before that includes a large error, the lateral G acceleration is estimated using the slip angle differential value β ′. The error is superimposed and becomes large. Therefore, the sign of the slip angle differential value β ′ and the estimated value of the slip angle β is switched at a frequency of 3 Hz or higher, which cannot be considered as normal vehicle motion, and the slip angle differential value β ′ and the estimated value of the slip angle β are obtained. It diverges without being able to.

FIG. 7 is a diagram showing the divergence of the slip angle β. FIG. 7A shows the vehicle speed V on the vertical axis, time t on the horizontal axis, and FIG. 7B shows the slip angle β on the vertical axis and time t on the horizontal axis. FIG. 7C is a diagram showing the lateral acceleration estimated value G _{ye on} the vertical axis and the time t on the horizontal axis. As shown in FIG. 7A, the case where the vehicle speed is accelerated from zero and then decelerated is shown.

As shown in FIGS. 7A and 7B, when the vehicle speed V is accelerated, when the vehicle speed V is decelerated between time t0 and time t1 when the vehicle speed reaches a certain level, the vehicle speed V is constant. There is a problem in that the sign of the estimated value of the slip angle β is switched at a frequency of 3 Hz or more from time t2 to time t3 when it is decelerated to diverge. Further, as shown in FIG. 7C, the lateral acceleration estimated value G _ye calculated using the slip angle differential value β ′ also diverges.

  Note that such divergence is not limited to the method of estimating the vehicle body slip angle using the equation (1), but the estimated vehicle body slip angle immediately before the current estimated vehicle body slip angle is calculated based on the vehicle dynamic model. The same occurs in other cases in which the vehicle body slip angle is estimated by recursively using.

  Using the slip angle β, the torque of the front and rear wheel electromagnetic actuators controls the movement of the vehicle, so when the slip angle β diverges, the control command value fluctuates greatly, increasing the frequency of operation of the electromagnetic actuator. There is a problem that the vehicle behavior is disturbed and the motion state of the vehicle cannot be satisfactorily controlled.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a vehicle body slip angle estimation method capable of preventing divergence.

According to the first aspect of the present invention, when the current estimated vehicle body slip angle is calculated based on the vehicle dynamic model, the differential value of the immediately preceding estimated vehicle body slip angle and the immediately preceding estimated vehicle body slip angle are recursively used. In a vehicle body slip angle estimation method for estimating a vehicle body slip angle, which is an angle formed between a traveling direction of a vehicle and a longitudinal axis of the vehicle, a step of detecting the speed of the vehicle body, and whether or not the vehicle body speed is equal to or less than a specified speed. A difference between the estimated value of the lateral acceleration and the lateral acceleration detected by the lateral acceleration sensor is zero. The vehicle mode is estimated using the step of estimating the friction coefficient of the road surface on which the vehicle is traveling, the estimated road friction coefficient and the immediately preceding estimated vehicle body slip angle. Calculating a lateral force acting on the rear wheel in a direction transverse to the vehicle based on the Le, when the speed of the vehicle is less than the prescribed speed, forcibly zeros the current estimated vehicle body slip angle differential value By preventing the divergence of the estimated vehicle body slip angle differential value, when the vehicle body speed exceeds the specified speed, based on the vehicle dynamics model, based on the lateral force, the vehicle body speed, the yaw rate, When the vehicle body slip angle differential value is estimated, and when the vehicle body speed is equal to or less than the specified speed, the zero set by the step of preventing the divergence is set as the current vehicle body slip angle, and the vehicle body speed is when There is greater than the prescribed speed, the integration interval including the current time, integrates the estimated vehicle body slip angle differential value time, ingredients and estimating a current vehicle slip angle Vehicle body slip angle estimating method characterized by the is provided.

According to a second aspect of the present invention, in the first aspect of the present invention, the specified speed includes a vehicle body speed, a constant specific to the vehicle body, a cornering power of the front wheels, a cornering power of the rear wheels, and an actual steering angle and a vehicle body slip angle. Based on the cornering power of the front wheel when the road surface friction coefficient is small at the vehicle body speed derived from the vehicle body speed derived from the vehicle body constant and the front wheel cornering power at which the vehicle body slip angle derived from the relationship between A set vehicle body slip angle estimation method is provided.

According to the first aspect of the present invention, the vehicle body slip angle immediately before the vehicle is used recursively, the current vehicle body slip angle differential value is used to estimate the current lateral acceleration, and the estimated lateral acceleration is further estimated. Is used to estimate the vehicle body slip angle differential value, but the vehicle body slip angle divergence tends to occur, but when the vehicle body speed is below the specified speed, the current estimated vehicle body slip angle differential value is forced to zero. In addition, when the current vehicle body slip angle is set to zero and the vehicle body speed is greater than the specified speed, the estimated vehicle body slip angle differential value is integrated over time in the integration interval including the current time, Since the vehicle body slip angle is estimated, the control amount of the vehicle motion state using the vehicle body slip angle does not diverge.

According to the second aspect of the present invention, the specified speed is derived from a relational expression between the speed of the vehicle body, a constant specific to the vehicle body, the cornering power of the front wheels, the cornering power of the rear wheels, and the actual steering angle and the vehicle body slip angle. The vehicle body speed derived from the vehicle body constant and the front wheel cornering power at which the slip angle is zero is set based on the cornering power of the front wheel when the road surface friction coefficient is small. Divergence of the vehicle body slip angle can be effectively prevented on roads and the like.

  FIG. 1 is a diagram showing a schematic configuration of a power transmission device for a four-wheel drive vehicle based on a front engine / front drive (FF) vehicle in which the vehicle body slip angle estimation method of the present invention can be implemented. As shown in FIG. 1, the power transmission system includes a front differential device 6 in which power from an engine 2 disposed in front of the vehicle is transmitted from an output shaft 4a of the transmission 4, and power from the front differential device 6 is transmitted from the vehicle. It mainly includes a speed increasing device (transmission device) 10 that is transmitted through a propeller shaft 8 that is a front and rear shaft, and a rear differential device 12 to which power from the speed increasing device 10 is transmitted.

The front differential device 6 has a conventionally known structure, and the power from the output shaft 4a of the transmission 4 is transmitted to the left and right front wheel drive shafts 20 and 22 via the plurality of gears 14 and the output shafts 16 and 18 in the differential case 6a. By transmitting, each front wheel is driven. Torque control of the left and right wheels 29 _FR and 29 _FL of the front wheels is controlled by, for example, an electromagnetic actuator.

The rear differential device 12 includes a pair of planetary gear sets and a pair of electromagnetic actuators that respectively control the engagement of a multi-plate brake mechanism (multi-plate clutch mechanism). The left and right rear wheel drive shafts are controlled by controlling the electromagnetic actuator. The rear wheels 29 _RR and 29 _RL are driven by transmitting the power to the rear wheels 29 _RR and 29 _RL .

Wheel speed sensors 30 are provided for the front wheels 29 _FL and 29 _FR and the rear wheels 29 _RR and 29 _RL , respectively, and the rotational speed of each wheel is detected. The vehicle speed sensor 31 detects the vehicle speed (vehicle speed V) from each wheel speed detected by the plurality of wheel speed sensors 30 and outputs an electric signal corresponding to the vehicle speed V, for example, a voltage level.

The lateral acceleration sensor 33 detects a lateral acceleration G _y that is an acceleration applied to the vehicle in the lateral direction, and outputs an electrical signal corresponding to the magnitude of the detection result, for example, a voltage level. The yaw rate sensor 34 is, for example, an electrical signal according to the magnitude of the yaw rate r, such as a piezoelectric element or a gyro sensor that detects an angle change amount of the inclination angle with respect to the vehicle direction or the vertical direction in a horizontal plane, for example, Output voltage level.

  The yaw rate differential value calculation unit 36 time-differentiates the yaw rate r output from the yaw rate sensor 34 to calculate the yaw rate differential value r ′. The engine ECU 40 calculates drive torque and the like from the rotational speed of the engine 40.

FIG. 2 is an apparatus block diagram related to the control of the motion state of the vehicle. The vehicle body slip angle estimation device 38 is a vehicle body slip angle estimation method that estimates the vehicle body slip angle using the previous estimated vehicle body slip angle recursively when calculating the current estimated vehicle body slip angle based on the vehicle dynamic model. In this embodiment, as an example, the lateral acceleration G _y detected by the lateral acceleration sensor 33, the yaw rate r detected by the yaw rate sensor 34, and the yaw rate differential calculation unit 36 are calculated as an example. Based on the tire yaw rate differential value r ′ and the vehicle speed V detected by the vehicle speed sensor 32, the current slip angle β is estimated based on the tire dynamic model by using the estimated value of the previous slip angle β recursively.

The target distribution torque setting device 42 includes the slip angle β estimated by the slip angle estimation device 38, the vehicle yaw rate r detected by the yaw rate sensor 34, the vehicle lateral acceleration G _y detected by the lateral acceleration sensor 33, and the vehicle speed. Based on the vehicle speed V detected by the sensor 32 and the drive torque calculated by the engine ECU 40, a target value of the distributed torque distributed to the left and right wheels 29 _FL , 29 _FR , 29 _RR , 29 _RL before and after the vehicle is set and calculated. The front and rear left and right wheel torques are output to the target distribution torque controller 44.

The target distribution torque control device 44 applies the left and right wheels 29 _FL , 29 _FR , 29 _RR , 29 _RL of the front and rear wheels so as to match the target torque based on the left and right wheel torque output from the target distribution torque control device 42. The current flowing through the corresponding electromagnetic actuator is controlled.

  FIG. 3 is a block diagram of the slip angle estimation device 38. The slip angle estimation device 38 includes a lateral acceleration estimation unit 50, a subtractor 52, a road surface μ initial setting unit 54, an adder 58, a tire lateral force calculation unit 60, a slip angle differential value calculation unit 62, and a slip angle differential value divergence prevention unit. 64, an integrator 66, and a slip angle divergence prevention unit 68.

The lateral acceleration estimation unit 50 substitutes the slip angle differential value β ′, the vehicle speed V, and the yaw rate r input from the slip angle differential value divergence prevention unit 64 into the following equation (2) to estimate the estimated lateral acceleration G _{ye of the} vehicle. Is output to the subtractor 52.

G _ye = V (r + β ′) (2)
Subtractor 52, the estimated lateral acceleration G _ye from the lateral acceleration G _y inputted from the lateral acceleration sensor 33 is inputted from the lateral acceleration estimation unit 50 is subtracted, and outputs the subtraction result to the PID regulator 54.

The PID controller 54 adjusts the initial value of the road surface μ so that the difference between the lateral acceleration G _y and the estimated lateral acceleration G _ye becomes zero by proportional / integral / derivative (PID) operation. The result is output to the adder 58. The road surface μ initial value calculation unit 56 calculates an initial value of the road surface friction coefficient μ and outputs the initial value to the adder 58. The adder 58 adds the adjustment value input from the PID adjuster 54 and the initial value of the road surface μ input from the road surface μ initial value calculation unit 56, and outputs the addition result μ to the tire lateral force calculation unit 60. .

Tire lateral force calculating section 60, the following equation is derived from the tire dynamic model (3), on the basis of (4), calculates the tire lateral force Y _r, and outputs the slip angle differential value calculation unit 62.

但し、式（３），（４）において、Ｗは接地重量であり、例えば、車両荷重の測定値を前後及び横加速度で補正した値あるいは懸架装置に設けたロードセルの出力から求めた値、Ｋはコーナリングパワーであり、予め設定された所定のマップ、例えば、摩擦係数μ及び接地荷重Ｗに応じて変化するコーナリングパワーのマップより求めた値、Ｘは前後力であり、例えば、加速度から推定、あるいは、制動液圧又はエンジン出力から求めた値、βは直前の推定スリップ角であり、スリップ角発散防止部６８より出力され、μは調整された路面μであり、加算器５８の出力である。

However, in the formulas (3) and (4), W is a ground contact weight, for example, a value obtained by correcting a measured value of the vehicle load with the longitudinal and lateral accelerations or a value obtained from an output of a load cell provided in the suspension device, K Is a cornering power, and is a value determined from a predetermined map set in advance, for example, a cornering power map that changes in accordance with the friction coefficient μ and the contact load W, X is a longitudinal force, for example, estimated from acceleration, Alternatively, the value obtained from the brake fluid pressure or the engine output, β is the immediately preceding estimated slip angle, and is output from the slip angle divergence prevention unit 68, μ is the adjusted road surface μ, and is the output of the adder 58. .

The slip angle differential value calculating unit 62 converts the lateral force balance formula and the vertical moment balance formula to the lateral force Y _f acting on the front tire and the lateral force Y _r acting on the rear tire. The slip angle differential value β ′ is calculated by substituting into the following equation (7) obtained by eliminating the lateral force Y _f acting on the front tire from the following equations (5) and (6) described based on the above equation. .

mV (r + β ′) = − 2Y _f −2Y _r (5)
_{Ir '= - 2Y f L f} + 2Y r L r + M ··· (6)
β ′ = − 2 (L _f + L _r ) Y _r / mVL _f + Ir ′ / mVL _f −r−M / mVL _f
(7)
Where L _f is the distance from the vehicle center of gravity to the front wheel side axle, L _r is the distance from the vehicle center of gravity to the rear wheel side axle, Y _r is the tire lateral force, r ′ is the yaw rate differential value, m is the total mass of the vehicle, I is the yawing moment of inertia and M is the yawing moment.

  The slip angle differential value divergence prevention unit 64 prevents the divergence of the slip angle differential value β ′ output from the slip angle differential value calculation unit 62, and when the vehicle speed V is equal to or less than a specified speed, the slip angle differential value. β ′ is forcibly reset to zero, and the slip angle differential value β ′ input from the slip angle differential value calculation unit 62 when the vehicle speed V is larger than the specified speed is reset. Is output to the integrator 66 and the lateral acceleration estimation unit 50.

  When controlling the motion state such as the turning motion of the vehicle body, when the slip angle of the vehicle body is used, its purpose is mainly used to detect unstable behavior during traveling. For this reason, it is important that the slip angle can be estimated at an accuracy higher than the vehicle speed at which the vehicle body behavior may be disturbed.

  By resetting the slip angle to prevent divergence at a low speed at which the influence of behavioral disturbance is small, the estimation accuracy can be tolerated as compared with the case where the slip angle diverges.

  As a characteristic of the vehicle, the vehicle body slip angle β can be theoretically calculated by the following equation (8).

但し、βはスリップ角、ｍは車体重量、Ｌはホイールベース寸法、Ｌ_fは重心から前輪側車軸までの距離、Ｌ_rは重心から後輪側車軸までの距離、Ｖは車体速度、Ｋ_fは前輪のコーナリングパワー、Ｋ_rは後輪のコーナリングパワー、δ₀は実舵角である。

Where β is the slip angle, m is the vehicle body weight, L is the wheel base dimension, L _f is the distance from the center of gravity to the front wheel side axle, L _r is the distance from the center of gravity to the rear wheel side axle, V is the body speed, and K _f the front wheel cornering power, K _r is the rear wheel cornering power, [delta] ₀ is the actual steering angle.

The vehicle speed that is important for vehicle control is the portion where the slip β is zero or less from the equation (8). The vehicle speed V ₀ where the slip angle is zero is given by the following equation (9).

式（９）より速度Ｖ₀は車体固有の定数とＫ_rから求まる。Ｋ_rは路面の摩擦係数が小さいときに小さくなる特徴があるので一般に雪道のように滑り易い路面にて速度Ｖ₀が小さくなる。

From equation (9), the speed V ₀ is obtained from a constant specific to the vehicle body and K _r . K _r is the velocity V ₀ at easily skid as generally canal snow because of the small features when the road friction coefficient is small becomes small.

  Since the lowest road surface friction coefficient in which the vehicle is used is a snowy road or the like, a speed region in which the slip angle β is accurately estimated above the speed on the road surface may be defined. The specified speed here is the vehicle speed obtained as described above, and is generally 5 to 10 kmh or less, although it varies depending on the characteristics of the vehicle.

  The integrator 66 integrates the slip angle differential value β ′ input from the slip angle differential value divergence prevention unit 64 with the time axis, and outputs the integral value β to the slip angle divergence prevention unit 68. The slip angle divergence prevention unit 68 prevents the divergence of the slip angle β output from the integrator 66, and forcibly resets the slip angle β to zero when the vehicle speed V is equal to or lower than the specified speed. When the reset slip angle β is greater than the specified speed, the slip angle β input from the integrator 66 is output to the tire lateral force calculation unit 60.

  Thus, by forcibly resetting the estimated value of the slip angle differential value β ′ and the estimated value of the slip angle β to zero at a vehicle speed equal to or less than the specified speed, the vehicle speed is The divergence due to approaching 0 can be prevented, and unnecessary estimated portions below the specified speed can be cut, and the torque distribution output by the target distribution torque controller 44 can be stabilized.

  FIG. 4 is a flowchart showing a vehicle body slip angle estimation method. FIG. 5 is a flowchart showing a vehicle body slip angle differential value divergence prevention method. FIG. 6 is a flowchart of the vehicle body slip angle divergence prevention method. Hereinafter, the vehicle body slip angle estimation method of the present invention will be described with reference to FIGS.

In step S2 in FIG. 4, the lateral acceleration estimation unit 50 substitutes the previous slip angle differential value β ′, vehicle speed V, and yaw rate r estimated in step S14, which will be described later, into the above equation (2). The estimated lateral acceleration _Gye of the vehicle is calculated. In step S4, the subtractor 52 subtracts the estimated lateral acceleration G _ye from the lateral acceleration G _y.

In step S6, the PID controller 54 adjusts the initial value of the road surface μ so that the difference between the lateral acceleration G _y and the estimated lateral acceleration G _ye becomes zero by a proportional / integral / derivative (PID) operation. The adjustment value of is calculated. In step S8, the adder 58 adds the adjustment value input from the PID adjuster 54 and the initial value of the road surface μ input from the road surface μ initial value calculation unit 56, and outputs an estimated value of the road surface μ.

In step S10, the tire lateral force calculation unit 60 substitutes the estimated value of the previous slip angle β calculated in step S18 into the above formulas (3) and (4) derived from the tire dynamic model. , and calculates the lateral force Y _r acting on the rear tires.

In step S12, the slip angle differential value calculation unit 62, the horizontal acting a balance type vehicle lateral force and the vehicle vertical axis moment equilibrium equation, the lateral force Y _f and a rear wheel tire acting on the front tire From the above equations (5) and (6) described based on the force Y _r , the yaw inertia moment I is calculated by eliminating the lateral force Y _f acting on the front tire, and the above equation (7) The slip angle differential value β ′ is calculated by substituting into.

  In step S30 in FIG. 5, the slip angle differential value divergence preventing unit 64 determines whether or not the vehicle speed V is equal to or less than a specified speed. If the vehicle speed V is less than the specified speed, the process proceeds to step S32. If the vehicle speed is not less than the specified speed, the process returns to step S16 in FIG. In step S32, the estimated value of the slip angle differential value β 'is forcibly set to zero, and the process returns to step S16 in FIG.

  In step S16 in FIG. 4, the integrator 66 integrates the slip angle differential value β ′ calculated in step S14 on the time axis, and outputs the integral value β to the slip angle divergence prevention unit 68. In step S40 in FIG. 6, the slip angle divergence prevention unit 68 determines whether or not the vehicle speed V is equal to or less than a specified speed.

  If the vehicle speed V is less than the specified speed, the process proceeds to step S42. If the vehicle speed V is not less than the specified speed, the process returns to step S2 in FIG. In step S42, the estimated value of the slip angle β is forcibly set to zero, and the process returns to step S2 in FIG. The above steps S2 to S18 are repeatedly executed.

As described above, the slip angle differential value β ′ and the estimated value of the slip angle β can be prevented from diverging. This slip angle β is set by the target distribution torque setting device 42 to set the target value of the distribution torque distributed to the left and right wheels 29 _FL , 29 _FR , 29 _RR , 29 _RL before and after the vehicle, and further, target distribution torque control Based on the left and right wheel torque output from the target distribution torque control device 42, the device 44 is provided corresponding to the left and right wheels 29 _FL , 29 _FR , 29 _RR , 29 _RL of the front and rear wheels so as to match the target torque. Since the current flowing through the electromagnetic actuator is controlled, divergence of the electromagnetic actuator command value can be prevented, behavioral disturbance due to divergence can be avoided, and good control of the vehicle motion state can be prevented.

  The slip angle estimation method according to the present invention is a method for estimating the current slip angle β from the vehicle speed V based on a tire dynamic model and using the estimated value of the previous slip angle β recursively. In the present embodiment, the case of the slip angle estimation method shown in FIG. 3 has been described, but as another example, for example, the integration in FIGS. 4 to 6, FIG. The slip angle differential value divergence prevention unit 64 and the slip angle divergence prevention unit 68 can be applied before and after the device 43 in the same manner as in FIG.

It is the schematic which shows the power transmission system of a four-wheel drive vehicle. It is a block diagram concerning the movement state control of a vehicle. It is a functional block diagram of the vehicle body slip angle estimation apparatus by embodiment of this invention. It is a flowchart which shows the vehicle body slip angle estimation method by embodiment of this invention. 3 is a flowchart illustrating a vehicle body slip angle differential value divergence prevention method according to an embodiment of the present invention. 5 is a flowchart illustrating a vehicle body slip angle divergence prevention method according to an embodiment of the present invention. It is a figure which shows the divergence of a slip angle.

Explanation of symbols

10 Speed increaser (transmission)
12 Rear differential devices 24, 26 Rear axle 32 Vehicle speed sensor 33 Lateral acceleration sensor 34 Yaw rate sensor 36 Yaw rate differential value calculation unit 38 Car body slip angle estimation device 50 Lateral acceleration estimation unit 54 PID adjuster 60 Tire lateral force calculation unit 62 Slip angle differential unit Value calculation unit 64 Slip angle differential value divergence prevention unit 66 Integrator 68 Slip angle divergence prevention unit

Claims (2)

When calculating the current estimated vehicle body slip angle based on the vehicle dynamics model, the vehicle traveling direction and the longitudinal axis of the vehicle are recursively calculated using the differential value of the immediately preceding estimated vehicle body slip angle and the immediately preceding estimated vehicle body slip angle. In the vehicle body slip angle estimation method for estimating the vehicle body slip angle that is an angle between
Detecting the speed of the vehicle body;
Determining whether the speed of the vehicle body is a specified speed or less;
Estimating the lateral acceleration using the immediately preceding estimated vehicle body slip angle differential value;
Estimating the friction coefficient of the road surface on which the vehicle is traveling so that the difference between the estimated value of the lateral acceleration and the lateral acceleration detected by the lateral acceleration sensor becomes zero;
Calculating a lateral force acting on a rear wheel in a lateral direction with respect to the vehicle based on the vehicle model using the estimated road friction coefficient and the immediately preceding estimated vehicle body slip angle;
When the speed of the vehicle is less than the prescribed speed, by forced to zero the current estimated vehicle body slip angle differential value to prevent divergence of the estimated vehicle body slip angle differential value, the speed of the vehicle is the prescribed Estimating a current vehicle body slip angle derivative based on the lateral force, the vehicle body speed, and the yaw rate based on the vehicle dynamic model when exceeding a speed ;
When the speed of the vehicle body is less than or equal to the specified speed, the zero set by the step of preventing divergence is set as a current vehicle body slip angle, and when the speed of the vehicle body is greater than the specified speed , Integrating the estimated vehicle body slip angle derivative over time in an integration interval including time, and estimating the current vehicle body slip angle;
A vehicle body slip angle estimation method comprising: The specified speed is the vehicle body speed, the vehicle-specific constant, the cornering power of the front wheels, the cornering power of the rear wheels, and the vehicle body slip angle derived from the relational expression between the actual steering angle and the vehicle body slip angle is zero. The vehicle body slip angle estimation method according to claim 1, wherein the vehicle body speed derived from the inherent constant and the cornering power of the front wheel is set based on the cornering power of the front wheel when the road surface friction coefficient is small .

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