JP2013216278A - Grounding load estimation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a grounding load estimation device capable of accurately estimating a grounding load.SOLUTION: A lateral load moving amount and a longitudinal load moving amount of respective wheels are calculated from vehicle specifications, lateral acceleration, longitudinal acceleration, roll angle acceleration and pitch angle acceleration, and a grounding load of the wheels is calculated from the lateral load moving amount, the longitudinal load moving amount and the vertical acceleration of the wheels.

Description

  The present invention relates to a ground load estimation device.

  Conventionally, the steering stability of a vehicle has been improved by controlling the braking force / driving force of the vehicle in accordance with the behavior of the vehicle. In order to detect the behavior of the vehicle, for example, the behavior in the lateral direction of the vehicle is detected from a lateral acceleration sensor or the like, or the load sensor is provided on the vehicle and the ground load of each wheel is measured. However, even if the ground load is detected by these methods, the detection accuracy is limited, and it is not realistic to provide a large load sensor in the vehicle.

  Thus, it is known to estimate the ground contact load of the wheel based on the pitch moment of the vehicle (see, for example, Patent Document 1). In Patent Document 1, in order to estimate the ground load in consideration of not only the lateral behavior of the vehicle but also the behavior in the pitching direction of the vehicle, the ground contact load of the wheel in the vicinity of the limit behavior of the vehicle is appropriately estimated.

JP 2004-58960 A

  However, at present, in order to further improve the handling stability of a running vehicle, it is required to estimate the contact load of each wheel with higher accuracy by the vehicle contact load estimation device.

  Accordingly, an object of the present invention is to solve the above-described problems of the prior art and to provide a ground load estimation device capable of estimating the ground load with higher accuracy.

  The ground load estimation device of the present invention calculates the lateral load movement amount and the longitudinal load movement amount of each wheel from vehicle specifications, lateral acceleration, longitudinal acceleration, roll angular acceleration, and pitch angular acceleration, The ground contact load of the wheel is calculated from the lateral load movement amount and the longitudinal load movement amount of the wheel, and the vertical acceleration. In the ground load estimation apparatus of the present invention, the ground load can be estimated with higher accuracy by using the ground load using the roll angular acceleration and the pitch angular acceleration.

  The calculation of the contact load of the wheel is a load transfer ratio applied to the wheel in the initial state obtained by multiplying the contact load of the wheel by the vertical acceleration, the front-rear load movement amount, and the left-right load movement amount. It is preferable to calculate from the front load movement ratio. By estimating the ground load using these, the ground load can be estimated with high accuracy.

  In a preferred embodiment of the present invention, the vehicle specifications include vehicle weight, roll radius, roll center height, wheel base, roll inertia moment, pitch inertia moment, center of gravity height, and tread.

  According to the ground load estimation apparatus of the present invention, it is possible to achieve an excellent effect that the ground load can be estimated with higher accuracy.

The schematic diagram of the vehicle which has the ground load estimation apparatus of this embodiment. The flowchart for demonstrating the estimation method by the ground load estimation apparatus of this embodiment.

  The ground load estimation apparatus of the present invention will be described below.

  The vehicle 1 has a front drive shaft 3 to which power from the engine 2 is transmitted, and front wheels 4 r and 4 l provided on the front drive shaft 3. The vehicle 1 is further provided with rear wheels 5 r and 5 l on the rear shaft 6. The vehicle 1 includes a control unit 10 that performs integrated control of the vehicle 1.

  The ground load estimation device 11 of this embodiment is provided in the control unit 10 of the vehicle 1. The ground load estimation device 11 calculates and estimates the ground load of each wheel. A longitudinal acceleration sensor 21, a lateral acceleration sensor 22, and a vertical acceleration sensor 23 provided in the vehicle 1 are connected to the control unit 10. Furthermore, a roll rate sensor 24 and a pitch rate sensor 25 are connected to the control unit 10. Since these sensors are generally sensors mounted on a vehicle, they can be mounted on the vehicle easily.

  A vehicle behavior control device 12 is connected to the ground load estimation device 11. The vehicle behavior control device 12 controls the behavior of the vehicle based on the ground load estimated by the ground load estimation device 11.

  Detection results from each sensor, that is, longitudinal acceleration, lateral acceleration, vertical acceleration, roll angular acceleration, and pitch angular acceleration are input to the ground load estimation device 11 of the control unit 10. The roll rate sensor 24 and the pitch rate sensor 25 detect angular velocities, and the roll angular velocity and the pitch angular velocity detected by the roll rate sensor 24 and the pitch rate sensor 25 are input to the ground load estimation device 11. The angular acceleration is derived from the angular velocity by the ground load estimation device 11. Note that the roll angular acceleration and the pitch angular acceleration may be derived from the acceleration detected by the roll rate sensor 24 and the pitch rate sensor 25 by another deriving unit and input to the ground load estimation device 11.

  The ground load estimation device 11 estimates the ground load on each wheel based on the input values from these sensors. A method of estimating the ground load performed by the ground load estimating device 11 will be described with reference to FIG.

  First, in step S1, the ground load estimation device detects an input value from a sensor. Proceed to step S2.

  In step S2, the ground load estimation device calculates and estimates the ground load of each wheel based on the following equation.

ここで、ΔＷ_ｌａｔ（ｔ）は時刻ｔにおける左右荷重移動量を、ΔＷ_ｌｏｎ（ｔ）は時刻ｔにおける前後荷重移動量を、Ａ_ｚ（ｔ）は時刻ｔにおける上下加速度を、Ｐ_ｆはフロント荷重移動比を示す。フロント荷重移動比Ｐ_ｆは、車両毎に予め規定される値である。 The first ground load W _FR (t) of the front wheel 4r is
(Formula 1)

Here, ΔW _lat (t) is the lateral load movement amount at time t, ΔW _lon (t) is the longitudinal load movement amount at time t, A _z (t) is the vertical acceleration at time t, and P _f is the front acceleration. Indicates the load transfer ratio. The front load movement ratio _Pf is a value defined in advance for each vehicle.

（式３）

である。
ここで、Ｔはトレッド、Ａ_ｙ（ｔ）は時刻ｔにおける横加速度であり、ｍは車両重量、ｈ_ｃｇは車両の重心高、ｈはロール半径、θ_ｒ（ｔ）は時刻ｔにおけるロール角、Ｉ_ｘはロール慣性モーメント、Ｌはホイール間距離（ホイールベース）、Ａ_ｘ（ｔ）は時刻ｔにおける前後加速度、θ_ｐ（ｔ）は時刻ｔにおけるピッチ角、Ｉ_ｙはピッチ慣性モーメントである。これらのうち、車両重量ｍ、車両の重心高ｈ_ｃｇ、ロール半径ｈ、ロール慣性モーメントＩ_ｘ、ピッチ慣性モーメントＩ_ｙは車両毎に予め規定される値である。 However,
(Formula 2)

(Formula 3)

It is.
Here, T is the tread, A _y (t) is the lateral acceleration at time t, m is the vehicle weight, h _cg is the height of the center of gravity of the vehicle, h is the roll radius, and θ _r (t) is the roll angle at time t. , I _x is the roll inertia moment, L is the distance between the wheels (wheel base), A _x (t) is the longitudinal acceleration at time t, θ _p (t) is the pitch angle at time t, and I _y is the pitch inertia moment. . Among these, the vehicle weight m, the center of gravity height h _{cg of the} vehicle, the roll radius h, the roll inertia moment I _x , and the pitch inertia moment I _y are values defined in advance for each vehicle.

後輪５ｒの第１接地荷重Ｗ_ＲＲ（ｔ）については、
（式５）

Similarly, for the first ground load W _FL (t) of the front wheel 4l,
(Formula 4)

Regarding the first ground load W _RR (t) of the rear wheel 5r,
(Formula 5)

である。 Regarding the first ground load W _RL (t) of the rear wheel 5l,
(Formula 6)

It is.

  Each of these equations is obtained from the following equation of motion.

Equation of motion of roll motion in the left-right direction:
(Formula 7)

ここで、ｋはロール剛性、ｃはロール減衰を示す。 Equation of motion indicating left-right load transfer:
(Formula 8)

Here, k represents roll rigidity, and c represents roll damping.

  Thereby, the left-right weighted movement amount described above can be obtained.

Also, the equation of motion of pitching motion in the front-rear direction:
(Formula 9)

Equation of motion showing back-and-forth load transfer:
(Formula 10)

  Thereby, the back-and-forth weighted movement amount described above can be obtained.

  As will be described in detail later, this equation of motion includes terms indicating roll stiffness and roll damping, but these terms indicating roll stiffness and roll damping are deleted as common terms. In the form, there is no term indicating a non-linear value from the expressions indicating the left and right load moving amounts and the front and rear load moving amounts. Thereby, in this embodiment, a contact load can be calculated | required more accurately.

  The ground load estimation unit is configured to determine the ground load of each wheel based on the above-described formulas based on the input value from the sensor input in step S1 and the value (vehicle specification) defined in advance for each vehicle. Ask for. Proceed to step S3.

  By the way, since the first grounding load of each wheel calculated in step S2 is the grounding load of each wheel alone, it is necessary to consider the grounding load of the entire wheel. Therefore, in order to obtain an accurate wheel ground load, in steps S3 to S15, when the value of the wheel ground load is negative, the ground load is applied to other wheels on the diagonal line. Because of this, the value of the ground contact load is added to other wheels existing on the diagonal line. Hereinafter, it demonstrates concretely by step S3-S15.

In step S3, first, it is determined whether or not the obtained first ground load W _FL (t) of the front wheel 4l is greater than zero. If larger (YES), the process proceeds to step S6. If smaller (NO), the process proceeds to step S4.

In step S4, the first ground load W _FL (t) of the front wheel 4l is substituted for the calculation ground load W _FL ′ of the front wheel 4l. Proceed to step S5.

In step S5, the first ground load W _FL (t) of the front wheel 4l is set to zero. Proceed to step S6.

In step S6, it is determined whether or not the determined first ground load W _FR (t) of the front wheel 4r is greater than zero. If larger (YES), the process proceeds to step S9. If smaller (NO), the process proceeds to step S7.

In step S7, the first ground contact load W _FR (t) of the front wheel 4r is substituted into the calculation ground load W _FR ′ of the front wheel 4r. Proceed to step S8.

In step S8, the first ground load W _FR (t) of the front wheel 4r is set to zero. Proceed to step S9.

In step S9, it is determined whether or not the first ground load W _RL (t) of the rear wheel 5l is greater than zero. If larger (YES), the process proceeds to step S12. If smaller (NO), the process proceeds to step S10.

In step S10, W _RL 'is substituted for the first contact load W _RL (t) of the rear wheel 5l to the calculation contact load of the rear wheel 5l. Proceed to step S11.

In step S11, the first ground load W _RL (t) of the rear wheel 5l is set to zero. Proceed to step S12.

In step S12, it is determined whether or not the first ground load W _RR (t) of the rear wheel 5r is greater than zero. If larger (YES), the process proceeds to step S15. If smaller (NO), the process proceeds to step S13.

In step S13, the first ground load W _RR (t) of the rear wheel 5r is substituted for the calculation ground load W _RR 'of the rear wheel 5r. Proceed to step S14.

In step S14, the first ground load W _RR (t) of the rear wheel 5r is set to zero. Proceed to step S15.

  In step S15, a second ground load that is a ground load of each wheel is calculated. That is, the contact load is accurately calculated by the following formula.

Second ground load of front wheel 4l = W _FL + W _FR '+ W _RL ' −W _RR '
Second ground load of front wheel 4r = W _FR + W _FL '−W _RL ' + W _RR '
The second ground load of the rear wheel _{5l = W RL + W FL '} -W FR' + W RR '
Second ground load of rear wheel 5r = W _RR −W _FL ′ + W _FR ′ + W _RL ′
In each equation, the value of the wheel (for example, the rear wheel 5r for the front wheel 4l) existing on the diagonal line is reduced, and the other values are added.

  In this manner, the ground load estimation device 11 of the present embodiment calculates the second ground load in consideration of the load of the entire wheel after obtaining the first ground load that is the load of each wheel alone. Then, the behavior of the vehicle 1 is controlled by the vehicle behavior control device 12 according to the ground load calculated by the ground load estimation device 11.

  In such a contact load estimation device 11 of this embodiment, when obtaining the contact load of each wheel, a longitudinal acceleration sensor 21, a lateral acceleration sensor 22, and a vertical acceleration sensor 23, which are general-purpose sensors, are provided without newly providing sensors. The estimation can be performed using the roll rate sensor 24 and the pitch rate sensor 25.

  The ground load estimation device 11 of the present embodiment has high accuracy by obtaining the ground load of each wheel from roll angular acceleration and pitch angular acceleration. That is, the contact load estimation formula does not include linearity such as roll rigidity and roll attenuation, and does not include a formula whose numerical value is changed depending on the roll angle. As described above, the equation of motion used when calculating the contact load estimation formula includes a non-linear term, but the formulas (1) and (4) to (4) are final contact load estimation formulas. (6) includes only values having linearity. As described above, the ground load estimation device 11 according to the present embodiment performs estimation using only values having linear characteristics such as the roll inertia moment and the pitch inertia moment among the vehicle specifications. The estimation can be performed, and the characteristics and stability of the system can be analyzed by the transfer function.

  Further, in the ground load estimation device 11 of this embodiment, since the ground load of each wheel is obtained from the longitudinal acceleration, lateral acceleration, vertical acceleration, roll angular acceleration, and pitch angular acceleration, what force is applied to which wheel. It can be detected. For example, after determining the ground contact load of each wheel, it is possible to clarify the cause of variation such as load movement due to lateral acceleration occupying most of the load movement in the ground load. Therefore, the suspension control can be corrected according to the variation factor.

  Further, in the ground load estimation device 11 of the present embodiment, when obtaining the first ground load, from the vehicle specifications, lateral acceleration, longitudinal acceleration, vertical acceleration, roll angular acceleration, and pitch angular acceleration, Since the ground contact load of the wheel is estimated, each value can be easily detected from the sensor, and the ground load can be detected with higher accuracy than the case where the calculation is not performed using the angular acceleration. Thus, in the ground load estimation apparatus 11 of this embodiment, the stability of the vehicle can be improved.

  In the present embodiment, the vehicle uses the engine 2 as a drive source, but is not limited to this. For example, the present invention can be applied to an electric vehicle such as an electric vehicle or a hybrid vehicle.

DESCRIPTION OF SYMBOLS 1 Vehicle 2 Engine 3 Front drive shaft 4r, 4l Front wheel 5r, 5l Rear wheel 6 Rear shaft 10 Control part 11 Ground load estimation apparatus 12 Vehicle behavior control apparatus 21 Longitudinal acceleration sensor 22 Lateral acceleration sensor 23 Vertical acceleration sensor 24 Roll rate sensor 25 Pitch rate sensor

Claims (3)

From the vehicle specifications, lateral acceleration, longitudinal acceleration, roll angular acceleration, and pitch angular acceleration, the lateral load movement amount and the longitudinal load movement amount of each wheel are calculated,
A grounding load estimation device that calculates a grounding load of a wheel from a lateral load movement amount and a longitudinal load movement amount of the wheel and a vertical acceleration.   The calculation of the contact load of the wheel is a load transfer ratio applied to the wheel in the initial state obtained by multiplying the contact load of the wheel by the vertical acceleration, the front-rear load movement amount, and the left-right load movement amount. 2. The ground load estimation device according to claim 1, wherein the ground load estimation device is calculated from a front load movement ratio.   The ground load estimation according to claim 1 or 2, wherein the vehicle specifications are vehicle weight, roll radius, roll center height, wheel base, roll inertia moment, pitch inertia moment, center of gravity height, and tread. apparatus.

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