KR100892480B1 - System for presuming self-alignment torque - Google Patents

Abstract

A steering self aligning torque calculating system is provided to control steering precisely by calculating vehicles self aligning torque. A steering self aligning torque calculating system comprises: a sensor unit(10); a transversal speed observer(20) designed in order to calculate traversal speed; and a steering self-alignment torque observer(30) calculating the steering self-alignment torque of the vehicle. The sensor unit comprises a yaw rate sensor(11), a steering angle sensor(12) and a vehicle speed sensor(13). The steering self-alignment torque observer uses values measured in the sensor unit and the present traversal speed calculated in the transversal speed observer.

Description

Steering Restoration Torque Estimation System {System for Presuming Self-Alignment Torque}

The present invention relates to a system capable of estimating steering restoration torque, which is the torque that causes the wheel to return to its original straight state when the steering wheel is rotated for curve driving.

Recently, development of a lane departure suppression system or a lane keeping system has been actively conducted to reduce driver fatigue and prevent traffic accidents due to carelessness or immature driving.

Such a system performs automatic control so that the vehicle normally follows a certain lane, but should allow manual control of the driver's steering angle if the driver has an active intention to change lanes. In this case, a torque sensor installed in a column or a rack is used to determine whether the driver wants to change lanes.

However, since the measured value in the torque sensor is the sum of the actual steering torque applied to the steering wheel and the self-alignment torque (TS) caused by the lateral movement of the vehicle, the measured value in the torque sensor The driver's intention judgment was incorrect. In particular, since the steering restoration torque is a physical quantity having a strong nonlinearity that varies with the vehicle speed, its inaccuracy is further increased.

Therefore, for proper steering control in accordance with the driver's intention, it is necessary to accurately measure the steering restoration torque applied by the driver. However, steering restorative torque cannot be measured using a sensor and must be estimated from other physical quantities.

The present invention has been proposed to solve this problem, and an object thereof is to provide a steering restoration torque estimation system capable of estimating vehicle restoration torque for precise steering control.

Steering reconstruction torque estimation system according to the present invention for achieving the above object, the sensor unit including a yaw rate sensor, a steering angle sensor and a vehicle speed sensor; Between the yaw rate value measured by the yaw rate sensor, the steering wheel angle multiplied by the steering gear ratio measured by the steering angle sensor, the vehicle speed measured by the vehicle speed sensor, and the measured yaw rate value and the estimated yaw rate value fed back It is designed to estimate the lateral velocity using the error multiplied by the observer gain, the observer gain is scheduled according to the vehicle speed, and the estimated lateral velocity when the error converges within a certain range, and the current lateral velocity of the vehicle. A lateral velocity observer that assumes to be; And a steering restoration torque observer for estimating the current steering restoration torque of the vehicle according to the vehicle speed by using the values measured by the sensor unit and the current lateral velocity estimated by the lateral speed observer.

Preferably, the gain value is scheduled for each constant vehicle speed section, the transverse speed observer is designed according to the following equation.

Meanwhile, the steering restoration torque estimation system according to the present invention may be commonly applied to a vehicle that is subjected to steering control by a motor, which requires precise steering control.

According to the steering restoration torque estimation system having the above-described structure, when the steering wheel is rotated according to the driver's active intention, the steering restoration torque value is estimated to enable precise steering control, thereby improving the driver's riding comfort and driving safety. We can plan.

Hereinafter, a steering restoration torque estimation system according to a preferred embodiment of the present invention will be described with reference to the accompanying drawings.

In order to enable automatic driving, a sensor that can recognize road conditions and lanes, a controller that calculates input road information and outputs an appropriate control amount (speed, steering, brake, etc.), and an actuator that executes these control amounts is required. Do.

1 is a conceptual diagram illustrating a movement path during driving of a vehicle.

First, each variable shown in FIG. 1 will be described, where δ _f is the wheel angle of the vehicle, υ is the lateral velocity of the vehicle, γ (Gamma) is the yaw rate of the vehicle, and x is the initial traveling direction of the vehicle. where y is the transverse direction of the vehicle, V is the vehicle speed, and β is the side slip angle, and is the angle of rotation at the center of gravity of the vehicle, depending on the steering wheel angle of the front wheels of the vehicle. Here, the wheel angle δ _f may be expressed as the product of the steering angle δ rotating at the steering wheel and the steering gear ratio n. For example, when the steering gear ratio n is 18: 1, the wheel angle δ _f is 1 ° when the steering angle δ of the steering wheel is 18 °.

Looking at the motion path of the vehicle for estimating the steering restoration torque with reference to Figure 1, the lateral motion of the vehicle starting cornering can be modeled using the force balance equation and the moment balance equation as follows. However, it is assumed that the cornering force is constant.

Looking at the force balance equation (y direction), the force balance due to the cornering force acting on the wheel can be formulated as in Equation 1 below. In addition, since the side slip angle may be expressed as Equation 2 below, Equation 1 may be expressed as Equation 3 when Equation 1 is summarized with respect to lateral velocity and yaw rate.

[Equation 1]

[Formula 2]

[Equation 3]

here,

m: vehicle mass,

C _f : cornering power of the front wheel, that is, the value of the cornering force for the side slip angle,

C _r : cornering power of the rear wheel, that is, the value of the cornering force for the side slip angle,

_f is the distance from the center of the vehicle to the front axle, and

l _r : Distance from vehicle center to rear axle.

Next, to derive the moment equilibrium equation of the system, the moment equilibrium due to the rotation of the vehicle center can be formulated as shown in Equation 4 below, if Equation 4 is summarized with respect to the yaw rate and the lateral velocity is shown in Equation 5.

[Equation 4]

[Equation 5]

Where I is the vehicle center rotational moment of inertia.

Steering restorative torque is the torque generated because the cornering force of the cornering force is behind the ground center, and this restorative torque is generated in the direction of reducing the side slip angle during turning. .

Here, the steering restoration torque Ts may be modeled linearly as shown in Equation 6 below, and Equation 6 may be expressed again as shown in Equation 7 based on Equation 2.

[Equation 6]

[Formula 7]

here,

ξ: trail length of the front wheel, that is, how long the front wheel touches the ground,

k _f : The cornering stiffness of the front wheel, ie the drag received by the front wheel from the ground during rotation.

Looking at Equation 7 in detail, three variables (wheel angle δ _f , yaw rate γ, and transverse velocity υ) are required to calculate steering restoration torque Ts using Equation 7. At this time, the wheel angle δ _f can be calculated using the steering gear ratio n and the steering angle δ, which is a measured value of the steering angle sensor, and the yaw rate γ can be directly measured using the yaw rate sensor. The measurement of the direction velocity υ is quite difficult.

Conventionally, the lateral velocity (υ) is calculated using the measured value of the lateral acceleration sensor. However, since the measured amount in the lateral acceleration sensor is the sum of the lateral acceleration component and the yaw rate vehicle speed, the lateral acceleration sensor It is difficult to calculate the lateral velocity using.

Therefore, one embodiment according to the present invention is to design an observer that can estimate the precise lateral speed using the wheel angle and yaw rate.

2 is a conceptual diagram of a steering restoration torque estimation system according to the present invention.

2, the steering restoration torque estimation system includes a sensor unit 10, a lateral velocity observer 20, and a steering restoration torque observer 30.

The sensor unit 10 includes a yaw rate sensor 11, a steering angle sensor 12, and a vehicle speed sensor 13. More specifically, the yaw rate sensor 11 measures the yaw rate γ of the vehicle, the steering angle sensor 12 measures the steering angle δ of the steering wheel, and the vehicle speed sensor 13 measures the vehicle speed V of the vehicle. Measure

The lateral velocity observer 20 may be designed through the following equations (Equations 8 to 12).

First, in the case of a general time invariant control system, the state equation may be expressed as Equation 8 below. In addition, the output equation may be expressed as a measurable yaw rate, such as Equation 10.

Equation 8

[Equation 9]

Here, the elements in the determinant are as follows.

Equation 10

Referring to Equation 9, the lateral velocity v of the vehicle can be expressed by the equation, but should be estimated because it is a state variable that cannot be measured. Therefore, we want to design the state observer 20 for the lateral velocity v.

The lateral velocity observer 20 may be specifically expressed through Equations 11 and 12.

[Equation 11]

Equation 12

는 추정 요레이트이며,

는 추정 횡방향 속도이다.here,

Is the estimated yaw rate,

Is the estimated lateral velocity.

)는 추정 출력값과 실제 측정 출력값간의 차이인 출력오차이며 더욱 상세하게는 실제로 측정된 요레이트와 추정된 요레이트의 차이값으로 표현된다. Equation 11 is a general state observer. Specifically, the estimated error (

) Is an output error that is the difference between the estimated output value and the actual measured output value, and more specifically, the difference between the actually measured yaw rate and the estimated yaw rate.

Equation 12 may be expressed using Equations 8 to 11. Referring to Equation 12, the yaw rate and the lateral velocity can be estimated when the estimation error converges within a certain error range.

Here, L1 and L2, which are gain values of the estimated error, have different values according to the vehicle speed and are scheduled according to the vehicle speed measured by the vehicle speed sensor 13. Here, it is obvious that the gain value may have a separate value for each vehicle speed section.

The steering restoration torque observer 30 calculates the steering restoration torque Ts by using the value transmitted from the sensor unit 10 and the lateral velocity value estimated by the lateral velocity observer 20 according to Equation 7.

3 is a conceptual diagram of a steering control system using the estimated steering restoration torque. 3 illustrates how steering control is performed using the steering restoration torque estimated in FIG.

1 is a conceptual diagram illustrating a movement path during driving of a vehicle.

2 is a conceptual diagram of a steering restoration torque estimation system according to the present invention.

3 is a conceptual diagram of a steering control system using the estimated steering restoration torque.

<Description of the symbols for the main parts of the drawings>

10: sensor unit 11: yaw rate sensor

12: Steering Angle Sensor 13: Vehicle Speed Sensor

20: lateral velocity observer 30: steering restoration torque observer

Claims (4)

A sensor unit 10 including a yaw rate sensor 11, a steering angle sensor 12, and a vehicle speed sensor 13; The yaw rate value measured by the yaw rate sensor 11, the wheel angle obtained by multiplying the steering gear ratio by the steering angle measured by the steering angle sensor 12, the vehicle speed measured by the vehicle speed sensor 13, and the measurement yaw rate It is designed to estimate the lateral velocity using the error multiplied by the observer gain multiplied by the error between the value and the estimated yaw rate value, and the observer gain is scheduled according to the vehicle speed and the estimated transverse when the error converges within a certain range. A lateral speed observer 20 for estimating the directional speed as the current lateral speed of the vehicle; And A steering restoration torque observer 30 for estimating the current steering restoration torque of the vehicle according to the vehicle speed by using the values measured by the sensor unit 10 and the current lateral velocity estimated by the lateral speed observer 20. Steering recovery torque estimation system comprising a .; The system of claim 1, wherein the gain value is scheduled for each constant vehicle speed section. The method of claim 2, wherein the lateral velocity observer 20 is designed based on the following formula,

here,

,

,

,

,

,

,

: Estimated yaw rate, γ: measured urine rate,

= Estimated transverse velocity, δ _f : wheel angle (where wheel angle is the product of steering angle (δ) and steering gear ratio), V: vehicle speed, m: vehicle mass, C _f : cornering power of the front wheel, C _r : cornering power of the rear wheels, _f is the distance from the center of the vehicle to the front axle, l _r : distance from the center of the vehicle to the rear axle, I: vehicle center rotational moment of inertia, L1 and L2 is a steering recovery torque estimation system, characterized in that the gain value of the observer. The steering restoration torque calculated by the steering restoration torque observer 30 is expressed by the following equation,

Where ξ is the trail length of the front wheel, i.e. the length of the front wheel touching the ground, and k _f is the steering stiffness of the front wheel, ie the drag received from the ground during rotation. Torque estimation system.

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