JP2008213709A - Vehicular steering angle presumption device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vehicular steering angle presumption device which accurately performs determination of the stationary state by all steering angle, based on a rotation speed of two-wheel, and also performs presumption of the steering angle as much as possible when it is not in the stationary state. <P>SOLUTION: The vehicular steering angle presumption device is provided with: a motor rotation angle sensor for detecting a motor rotation angle of the motor for giving steering assistant force to a steering system of the vehicle; a wheel rotation speed sensor for detecting a wheel rotation speed of left and right wheels of the vehicle; and a steering angle presumption means for presuming the steering angle of the steering system based on the wheel rotation speed from the wheel rotation speed sensor. A steering angle output means is provided, which presumes and outputs the actual steering angle by comparing the presumed steering angle presumed by the steering angle presumption means with a relative steering angle obtained by dividing the motor rotation angle by a speed reduction ratio of the steering system. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to a vehicle steering angle estimation device that estimates a steering angle (steering angle) of a vehicle using a vehicle wheel rotation speed and a rotation angle of a motor that applies a steering assist force to a steering system of the vehicle.

Many conventional vehicle steering angle estimation devices have been proposed, but many vehicle steering angle estimation devices estimate the steering angle only from the actual geometric relationship of the vehicle. For this reason, there is a problem that an error is likely to occur. As a vehicle steering angle estimating device that solves such a problem, there is one disclosed in Japanese Patent Laid-Open No. 2005-9827 (Patent Document 1). That is, each of the four wheels of the vehicle is provided with a wheel rotation speed sensor, and is a vehicle steering angle estimation device that estimates the steering angle of the vehicle based on the wheel rotation speed from each wheel rotation speed sensor. By comparing the relationship between the respective wheel rotation speeds, slip of the four wheels is detected.
JP-A-2005-9827

  However, in the thing of patent document 1, all the rotational speeds of four wheels are required, and there exists a problem that it cannot respond to the vehicle type which can be obtained only with the rotational speed of two wheels (front wheel or rear wheel). .

  The present invention has been made under the circumstances described above, and the object of the present invention is to accurately determine the steady state at all steering angles based on the rotational speed of the two wheels, and in the case where the steady state is not established. It is another object of the present invention to provide a vehicular rudder angle estimation device capable of estimating a rudder angle (steering angle) as much as possible. Another object of the present invention is to provide a high-performance electric power steering apparatus equipped with such a vehicle steering angle estimation apparatus.

  The present invention includes a motor rotation angle sensor that detects a motor rotation angle of a motor that applies a steering assist force to a vehicle steering system, a wheel rotation speed sensor that detects wheel rotation speeds of left and right wheels of the vehicle, and the wheel rotation speed. A steering angle estimation device for a vehicle comprising a steering angle estimation means for estimating a steering angle of the steering system based on a wheel rotation speed from a sensor. The object of the present invention is estimated by the steering angle estimation means. This is achieved by providing a steering angle output means for estimating and outputting an actual steering angle by comparing the estimated steering angle with a relative steering angle obtained by dividing the motor rotation angle by the reduction ratio of the steering system.

  Further, the object of the present invention is that the rudder angle output means obtains a difference 1 between the amount of change in the estimated rudder angle and the amount of change in the relative rudder angle, and when the difference 1 is a predetermined value 1 or less, By outputting the estimated steering angle as the steering angle of the vehicle, or the steering angle output means is obtained from the steering angular speed obtained by dividing the motor angular speed of the motor by the reduction ratio of the steering system and the estimated steering angle. When the difference 2 from the estimated steering angular velocity is obtained and the difference 2 is equal to or less than the predetermined value 2, the estimated steering angle is output as the steering angle of the vehicle.

  By incorporating the vehicle steering angle estimation device in the electric power steering device, a steering system with a good steering feeling can be achieved.

  According to the vehicle steering angle estimation device of the present invention, it is detected that the wheel is slipping by comparing the estimated steering angle obtained from the wheel rotational speed with the rotation angle information of the steering system motor. Using a relational expression that accurately reflects the ratio of the turning radius of each wheel in the steady state, it is possible to determine the steady state more accurately than in the conventional method, and to prevent erroneous estimation of the steering angle and to accurately measure the steering. The angle can be estimated.

  Provided is a high-performance electric power steering apparatus that can obtain steering angle information even if there is no steering angle detection means and is equipped with the vehicle steering angle estimation apparatus in an electric power steering apparatus and that has a good steering feeling. Can do.

In the present invention, as shown in FIG. 1, the turning radii of the four wheels fl, fr, rl, rr are Rfl, Rfr, Rrl, Rrr, the steering angles of the front wheels fl, fr are α _l , α _r , respectively, Is set to L, and the vehicle width (the distance between the centers of the left and right wheels) is set to E. The turning radius at the center of the front wheel axle is Rf, and the turning radius at the center of the rear wheel axle is Rr. As the wheel speed (wheel angular velocity) of each wheel fl, fr, rl, rr, if the left front wheel is ω _fl , the right front wheel is ω _fr , the left rear wheel is ω _rl , and the right rear wheel is ω _rr , It is known that the steering angle α (see FIG. 2) and the wheel speeds ω _fl , ω _fr , ω _rl , and ω _rr have the following relationship.

上記数１又は数２のいずれかで、車輪速ω_ｆｌ，ω_ｆｒ，ω_ｒｌ，ω_ｒｒから舵角αが一様に求められることになる。つまり、舵角αを推定することができる。また、左右それぞれの前後輪と、左右それぞれの舵角α_ｌ，α_ｒは以下の関係を持つ。

The steering angle α is uniformly obtained from the wheel speeds ω _fl , ω _fr , ω _rl , and ω _rr by either the above formula 1 or formula 2. That is, the steering angle α can be estimated. The left and right front and rear wheels and the left and right steering angles α _l and α _r have the following relationship.

図２に示すような前輪車軸中央の舵角αと、左前輪の舵角α_ｌ、右前輪の舵角α_ｒとの関係は車種により決まってくる。仮に以下の数５及び数６のような関係を持つとすれば、前記数１〜数４は共通の舵角αと車両の車軸距離L、車幅E（左右輪の中心間距離）とで成立することになる。なお、ｋ１は舵角と内輪舵角の比であり、ｋ２は舵角と外輪舵角の比である。
（数５）
左折のとき、 α_ｌ＝ｋ１・α
α_ｒ＝ｋ２・α
（数６）
右折のとき、 α_ｌ＝ｋ２・α
α_ｒ＝ｋ１・α

本発明では、車輪回転速度から求めた推定舵角を操舵系のモータの回転角情報と比較することにより、車輪がスリップしていることを検知するが、前輪（２輪）の回転速度しか検出できない車種を先ず例に挙げて説明する。

The relationship between the steering angle α at the center of the front wheel axle, the steering angle α _{l of} the left front wheel, and the steering angle α _r of the right front wheel as shown in FIG. Assuming that the following equations (5) and (6) are satisfied, the equations (1) to (4) are expressed by the common rudder angle α, the vehicle axle distance L, and the vehicle width E (the distance between the centers of the left and right wheels). It will be established. Here, k1 is a ratio between the rudder angle and the inner wheel rudder angle, and k2 is a ratio between the rudder angle and the outer wheel rudder angle.
(Equation 5)
When turning left, α _l = k1 ・ α
α _r = k2 · α
(Equation 6)
When turning right, α _l = k2 · α
α _r = k1 · α

In the present invention, the estimated rudder angle obtained from the wheel rotation speed is compared with the rotation angle information of the steering system motor to detect that the wheel is slipping, but only the rotation speed of the front wheels (two wheels) is detected. First, an example of a vehicle that cannot be described will be described.

  In a general electric power steering apparatus as shown in FIG. 3, a motor rotation angle sensor 3 that detects a motor rotation angle is attached to a motor 2 that applies a steering assist force to the steering system of the handle 1, A torque sensor 5 for detecting a steering torque is attached to the steering shaft 4 of the handle 1. The motor rotation angle from the motor rotation angle sensor 3 and the steering torque from the torque sensor 5 are input to a control unit (ECU) 6, and the control unit 6 calculates a steering assist command value based on the steering torque and drives the motor 2. Control. As a result, the motor 2 applies a steering assist force to the steering system via the speed reduction mechanism 7.

  In the present invention, the motor rotation angle detected by the motor rotation angle sensor 3 is inputted to the control unit 6, and the steering angle output means in the control unit 6 calculates the rotation angle of the steering shaft 4 from the motor rotation angle. Since the motor rotation angle and the rotation angle of the steering shaft 4 are passed through the reduction mechanism 7, the motor rotation angle change amount can be calculated by dividing the motor rotation angle by the reduction ratio. Therefore, the steering shaft rotation angle calculated by the steering angle output means in the control unit 6 is not an absolute steering angle but a relative change amount. In the present invention, the calculated steering shaft rotation angle is compared with the estimated steering angle estimated by the above equation (1).

In this case, the amount of change in the steering shaft rotation angle calculated from the motor rotation angle is correct, but the absolute angle has an offset with respect to the actual steering angle. Therefore, the angle to be compared with the estimated rudder angle is not an absolute value, but must be a change from a certain common time point. When the difference Δθ in the amount of change in the rotation angle exceeds a predetermined value Δθ _th , the rudder angle is estimated with the wheel slipping, etc., so it is determined that the estimated rudder angle is unreliable and the estimated rudder angle is actually Do not output as rudder angle. Then, when the difference Δθ in the change amount of the rotation angle is smaller than the predetermined value Δθ _th and continues for a certain time, it is determined that the estimated steering angle can be trusted, and the estimated steering angle is output as the actual steering angle.

  FIG. 4 shows a specific flowchart to describe the operation of the first embodiment of the present invention.

First, as an initialization, the time counter (Cnt) is cleared to “0” (step S1), and the front wheel speeds ω _fl and ω _fr from the wheel rotation speed sensor and the motor rotation angle θ _m from the motor rotation angle sensor are read ( Step S2), the estimated steering angle θ _est = α _front is estimated according to Equation 1 (step S3). After _{obtaining the} estimated steering angle θ _est , it is determined whether or not the time Cnt counted by the time counter is “0” (step S4). If “0”, the motor rotation angle θ _m is determined as the initial motor rotation. After setting the angle θ _m0 and the estimated steering angle θ _est as the initial estimated steering angle θ _est0 , the process returns to step S2 (step S5). The initial motor rotation angle θ _m0 and the initial estimated steering angle θ _est0 are initial values at the start of estimation, respectively.

When the time Cnt is not “0” in step S4, the rudder angle estimation means subtracts the initial motor rotation angle θ _m0 from the motor rotation angle θ _m and steers the subtraction value (= θ _m −θ _m0 ). By dividing by the reduction ratio of the system, the rotation angle change amount Δθ, which is the absolute value of the value _obtained by subtracting the initial estimated steering angle θ _est0 from the estimated steering angle θ _est , is obtained from the value obtained by the division (step S10). . That is, the following equation 7 is performed to calculate the rotation angle change amount Δθ.
(Equation 7)
Δθ = | (θ _m −θ _m0 ) / reduction _ratio− (θ _est −θ _est0 ) |

Next, the rudder angle output means determines whether or not the calculated rotation angle change amount Δθ is equal to or _smaller than a predetermined value Δθ _th (step S11). When the change amount Δθ is larger than the predetermined value Δθ _th , the time of the time counter is cleared to “0” and the process returns to step S2 (step S12).

On the other hand, if the change amount [Delta] [theta] of the rotational angle in step S11 is less than the predetermined value [Delta] [theta] _th, the time measurement counter is incremented by "+1" (step S13), and whether the time Cnt exceeds the predetermined time C ₁ determined (step S14), and time Cnt is if it does not exceed the predetermined time _{C 1} returns to the step S2. When the time Cnt exceeds the predetermined time _{C 1} outputs the estimated steering angle theta _est as the steering angle theta (step S15).

  In this example, the steering angle θ is estimated and output based on the rotational speed of the front wheels (two wheels), but the steering angle θ can be estimated and output in the same manner only with the rear wheels (two wheels).

  Next, Embodiment 2 of the present invention will be described, taking as an example a vehicle type that can detect only the rotational speed of the front wheels (two wheels).

In the case of this example, the motor angular velocity ω _m is calculated by differentiating the motor rotation angle. The steering angular speed ω _r can be obtained by dividing the motor angular speed ω _m by the reduction ratio. In addition, the estimated rudder angular velocity ω _e can be obtained by differentiating the estimated rudder angle obtained in Equation 1, but the actual rudder angle output means is equivalent to differentiation by calculating the difference from the previous value. The effect of can be obtained. When the difference Δω _h between the rudder angular velocity ω _r and the estimated rudder angular velocity ω _e exceeds a predetermined value Δω _th , the rudder angle is estimated with the wheels slipping or the like. Judgment is made so that the estimated rudder angle is not output as the rudder angle. When the difference Δω _h between the rudder angular velocity ω _r and the estimated rudder angular velocity ω _e is smaller than the predetermined value Δω _th and continues for a certain time, it is determined that the estimated rudder angle can be trusted, and the estimated rudder angle is output as the rudder angle. Like that.

  The above operation will be described with reference to the flowchart of FIG.

First, the time counter (Cnt) as initialized to "0" cleared (step S20), and the front wheel speed omega _fl and omega _fr from the wheel rotation speed sensor, reads the motor rotation angle theta _m from the motor rotational angle sensor ( In step S21), the rudder angle estimating means estimates an estimated rudder angle θ _est = α _front according to Equation 1 (step S22). After determining the estimated steering angle theta _est, it subtracts the previous value of the motor rotational angle theta _m from a motor rotation angle theta _m, dividing the subtracted value (= θ _m -θ _m previous value) at the speed reduction ratio of the steering system Then, from the value obtained by the division, a rotational speed change Δω _h that is an absolute value of a value obtained by subtracting the previous value of the estimated steering angle θ _est from the estimated steering angle θ _est is obtained (step S23). That is, the following equation 8 is performed to calculate the rotation speed change amount Δω _h .
(Equation 8)
Δω _h = | (θ _m −θ _m previous value) / reduction ratio− (θ _est −θ _est previous value) |

Next, the rudder angle output means determines whether or not the calculated rotation speed change amount Δω _h is equal to or less than a predetermined value Δω _th (step S24), and the rotation speed change amount Δω _h. There is greater than a predetermined value [Delta] [omega _th is a time counter time is cleared to "0" returns to the step S21 (step S25).

On the other hand, if the change amount [Delta] [omega _h of the rotation speed in step S24 is equal to or less than a predetermined value [Delta] [omega _th is a time counter is incremented by "+1" (step S26), whether the time Cnt exceeds the predetermined time C ₂ It determines (step S27), if the time Cnt has not exceeded the predetermined time _{C 2} returns to the step S21. When the time Cnt exceeds the predetermined time _{C 2} outputs the estimated steering angle theta _est as the steering angle theta (step S28).

  In this example, the steering angle θ is estimated from the rotational speed of the front wheels (two wheels). However, the steering angle θ can be estimated and output in the same manner only with the rear wheels (two wheels). Further, the rotation speed may be obtained by differentiation of the rotation angle.

  The vehicle steering angle estimation device of the present invention can be applied to a vehicle such as an automobile optimally because the steady state can be accurately determined for all steering angles. Further, even in a non-steady state, the steering angle can be estimated as much as possible, which is effective for the vehicle device.

It is a figure for demonstrating the principle of this invention. It is a figure for demonstrating a steering angle. It is a lineblock diagram showing an example of a general electric power steering device. It is a flowchart which shows the operation example (Embodiment 1) of this invention. It is a flowchart which shows the operation example (Embodiment 2) of this invention.

Explanation of symbols

1 Handle 2 Motor 3 Motor rotation angle sensor 4 Steering shaft 5 Torque sensor 6 Control unit 6
7 Deceleration mechanism fl, fr Front wheel rl, rr Rear wheel L Axle distance E Vehicle width (distance between centers of left and right wheels)

Claims (4)

A motor rotation angle sensor that detects a motor rotation angle of a motor that applies a steering assist force to the steering system of the vehicle, a wheel rotation speed sensor that detects wheel rotation speeds of the left and right wheels of the vehicle, and wheels from the wheel rotation speed sensor In a vehicle steering angle estimation device comprising a steering angle estimation means for estimating a steering angle of the steering system based on a rotational speed, the estimated steering angle estimated by the steering angle estimation means, the motor rotation angle A steering angle estimation device for a vehicle comprising a steering angle output means for estimating and outputting an actual steering angle by comparing with a relative steering angle divided by a reduction ratio of a steering system. The rudder angle output means obtains a difference 1 between the change amount of the estimated rudder angle and the change amount of the relative rudder angle, and when the difference 1 is equal to or less than a predetermined value 1, the estimated rudder angle is steered by the vehicle. The vehicle steering angle estimation device according to claim 1, which is output as a corner. The steering angle output means obtains a difference 2 between a steering angular speed obtained by dividing a motor angular speed of the motor by a reduction ratio of the steering system and an estimated steering angular speed obtained from the estimated steering angle, and the difference 2 is a predetermined value 2 The vehicle steering angle estimation device according to claim 1, wherein the estimated steering angle is output as the steering angle of the vehicle when the following is true. An electric power steering apparatus comprising the vehicle steering angle estimation apparatus according to any one of claims 1 to 3.

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