HYDRAULIC AUXILIARY AXLE STEERING CONTROL SYSTEM

Abstract

A hydraulic auxiliary axle steering control system is provided. In detail, there is provided a hydraulic auxiliary axle steering control system that can perform quick, precise, and safe control by changing an auxiliary axle steering control angle in accordance with a vehicle speed to problems with instability of driving, wear of tires, and a turning radius when a vehicle is driven at a low speed.

Claims

1. A hydraulic auxiliary axle steering control system, comprising: a sensor configured to steering of front wheels and a vehicle speed; an ECU configured to calculate and control a steering value of the auxiliary axle in accordance with the vehicle speed and steering of the front wheels; a motor and a hydraulic pump being able to be rotated in two directions to apply hydraulic pressure to a hydraulic cylinder; and a double rod cylinder configured to provide a driving force the auxiliary axle, wherein the ECU calculates and controls an auxiliary axle steering angle to linearly change in accordance with variation of a front-wheel steering angle when the vehicle speed is 30 km/h or less, and the ECU calculates and control the auxiliary axle steering angle to decrease to 0 in accordance with variation of the front-wheel steering angle in a period in which the vehicle speed increases from 30 km/h to 40 km/h, so it is possible to remove instability of driving, reduce wear of tires, and maximize turning in a narrow space by precisely controlling auxiliary axle steering according to front-wheel steering when the vehicle is driven at a low speed.

2. The hydraulic auxiliary axle steering control system of claim 1, wherein when the vehicle including a front-wheel first axle, a front-wheel second axle, a rear-wheel third axle, a rear-wheel fourth axle, and an auxiliary axle is turned left, in which a distance between the front-wheel first axle and a rear-wheel first axle is a first wheel base L1, a distance between the rear-wheel first axle and a rear-wheel second axle is a second wheel base L2, a distance between the rear-wheel second axle and the auxiliary axle is an auxiliary axle wheel base L3, a distance between center lines of two left and right tires of the auxiliary axis is an auxiliary axle tread L4, a center of the rear-wheel first axle and the rear-wheel second axle is a rear-axle center point G, a distance from a rotation center point to the rear-axle center point is L5, a front-wheel right steering angle is α1, and a front-wheel left steering angle is α1+α2, the ECU controls a left steering angel β1+β2 of the auxiliary axle as a following equation when the vehicle speed is 30 km/h or less $\beta 1+\beta 2=\mathrm{arc}\tan \left(\frac{\frac{L2}{2}+L3}{L5-\frac{L4}{2}}\right)$ and the ECU controls the left steering angel β1+β2 of the auxiliary axle as a following equation when the vehicle speed is larger than 30 km/h and is equal to or less than 40 km/h. $\beta 1+\beta 2\approx \left(\left(-1/10\right)\times \mathrm{Vx}+4\right)\mathrm{arc}\tan \left(\frac{\frac{L2}{2}+L3}{L5-\frac{L4}{2}}\right)$

3. The hydraulic auxiliary axle steering control system of claim 2, wherein the L5 is calculated as following equations by the ECU on the basis of the front-wheel right steering angle α1 and the front-wheel left steering angle is α1+α. $\begin{array}{c}L5=\tan \left(90°-\left(\alpha 1+\alpha 2\right)\right)\times \left(L1+\frac{L2}{2}\right)+\frac{L4}{2}\\ L5=\tan \left(90°-\alpha 1\right)\times \left(L1+\frac{L2}{2}\right)-\frac{L4}{2}\end{array}$

4. The hydraulic auxiliary axle steering control system of claim 1, wherein when the vehicle speed is 30 km/h or less, the ECU controls the auxiliary axle steering angel to 0 without a change in a period in which the front-wheel steering angle is minutely changed by up to ±2.

5. The hydraulic auxiliary axle steering control system of claim 2, wherein when the vehicle is turned right, the ECU calculates the auxiliary axle steering angle by changing a left steering angle from α1+α2 to α1 and changing a right steering angle from α1 to α1+α2.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The above and other objectives, features and other advantages of the present invention will be more clearly understood from the following detailed description when taken in conjunction with the accompanying drawings, in which:

[0031] FIG. 1 is a view of a hydraulic auxiliary axle steering control system;

[0032] FIG. 2 is a view showing control of a front-wheel steering angle and an auxiliary axle steering angle;

[0033] FIG. 3 is a view showing an auxiliary axle steering angle result according to variation of a front-wheel steering angle;

[0034] FIG. 4 is a view showing a dead zone test result of an auxiliary axle steering angle; and

[0035] FIG. 5 is a view showing output of an auxiliary axle steering angle according to a speed.

DETAILED DESCRIPTION OF THE INVENTION

[0036] The present disclosure may be modified in various ways and implemented by various exemplary embodiments, so that specific exemplary embodiments are shown in the drawings and will be described in detail.

[0037] However, it is to be understood that the present disclosure is not limited to the specific exemplary embodiments, but includes all modifications, equivalents, and substitutions included in the spirit and the scope of the present disclosure. Similar reference numerals are assigned to similar components in the following description of drawings.

[0038] It is to be understood that when one element is referred to as being “connected to” or “coupled to” another element, it may be connected directly to or coupled directly to another element or be connected to or coupled to another element, having the other element intervening therebetween. On the other hand, it should to be understood that when one element is referred to as being “connected directly to” or “coupled directly to” another element, it may be connected to or coupled to another element without the other element intervening therebetween.

[0039] Terms used in the present specification are used only to describe specific exemplary embodiments rather than limiting the present disclosure. Singular forms are intended to include plural forms unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” or “have” used in this specification, specify the presence of stated features, steps, operations, components, parts, or a combination thereof, but do not preclude the presence or addition of one or more other features, numerals, steps, operations, components, parts, or a combination thereof.

[0040] Unless defined otherwise, it is to be understood that all the terms used in the specification including technical and scientific terms has the same meaning as those that are understood by those who skilled in the art. It will be further understood that terms defined in dictionaries that are commonly used should be interpreted as having meanings that are consistent with their meanings in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0041] Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.

[0042] FIG. 2 is a plan view showing auxiliary axle steering angle control according to a front-wheel steering angle of a hydraulic auxiliary axle steering control system.

[0043] The embodiment of FIG. 2 is for a 4-axle freight vehicle, which includes a front-wheel first axle, a front-wheel second axle, a rear-wheel third axle, a rear-wheel fourth axle, and an auxiliary axle.

[0044] The distance between the front-wheel first axle and the rear-wheel first axle is a first wheel base L1, the distance between the rear-wheel first axle and the rear-wheel second axle is a second wheel base L2, the distance between the rear-wheel second axle and the auxiliary axle is an auxiliary axle wheel base L3, the distance between the center lines of two left and right tires of the auxiliary axis is an auxiliary axle tread L4, the center of the rear-wheel first axle and the rear-wheel second axle is a rear-axle center point G, and the distance from a rotation center point to the rear-axle center point is L5.

[0045] A front-wheel right steering angle is α1 and the front-wheel left steering angle is α1+α2.

[0046] An ECU of the auxiliary axle steering control system calculates and controls the left steering angle β1+β2 of the auxiliary axle as follows.

[0047] 1) when the speed of a vehicle is 30 km/h or less (Vx≤30 km/h), the ECU controls the left steering angel β1+β2 of the auxiliary axle as the following Equation 1.

[00003]$\begin{array}{cc}\beta 1+\beta 2=\mathrm{arc}\tan \left(\frac{\frac{L2}{2}+L3}{L5-\frac{L4}{2}}\right)& \left[\mathrm{Equation}1\right]\end{array}$

[0048] wherein L2 is a second wheel base, L3 is an auxiliary axle wheel base, and L4 is an auxiliary axle tread, which are eigenvalues of the vehicle input in the ECU in advance, and L5 is calculated as the following equation 2 by the ECU on the basis of the front-wheel right steering angle α1 or the front-wheel left steering angle α1+α2.

[00004]$\begin{array}{cc}\begin{array}{c}L5=\tan \left(90°-\left(\alpha 1+\alpha 2\right)\right)\times \left(L1+\frac{L2}{2}\right)+\frac{L4}{2}\\ L5=\tan \left(90°-\alpha 1\right)\times \left(L1+\frac{L2}{2}\right)-\frac{L4}{2}\end{array}& \left[\mathrm{Equation}2\right]\end{array}$

[0049] where the front-wheel right steering angle is α1 and the front-wheel left steering angle is α1+α2 are measured by a front-wheel angle sensor mounted on a front wheel and input to the ECU, and L1, L2, and L4 are eigenvalues of the vehicle input in the ECU in advance.

[0050] In the period of the vehicle speed is increased or decreased between 0 km/h and 30 km/h, the steering angel β1+β2 of the auxiliary axle according to variation of the front-wheel steering angles α1 and α2 is linearly changed, and variation of the auxiliary axle steering angle is almost 0 in the period in which the front-wheel steering angles are minutely changed by about ±2°.

[0051] 2) when the speed of a vehicle is larger than 30 km/h and equal to or smaller than 40 km/h (30 km/h<Vx<40 km/h), the ECU controls the left steering angel β1+β2 of the auxiliary axle as the following Equation 3.

[00005]$\begin{array}{cc}\beta 1+\beta 2\approx \left(\left(-1/10\right)\times \mathrm{Vx}+4\right)\mathrm{arc}\tan \left(\frac{\frac{L2}{2}+L3}{L5-\frac{L4}{2}}\right)& \left[\mathrm{Equation}3\right]\end{array}$

[0052] where L2, L3, and L4 are eigenvalues of the vehicle input in advance in the ECU, and L5 is calculated as the following Equation 4 by the ECU.

[00006]$\begin{array}{cc}\begin{array}{c}L5=\tan \left(90°-\left(\alpha 1+\alpha 2\right)\right)\times \left(L1+\frac{L2}{2}\right)+\frac{L4}{2}\\ L5=\tan \left(90°-\alpha 1\right)\times \left(L1+\frac{L2}{2}\right)-\frac{L4}{2}\end{array}& \left[\mathrm{Equation}4\right]\end{array}$

[0053] When the vehicle speed is larger than 30 km/h and equal to or smaller than 40 km/h, the speed Vx is also input to the ECU and the left steering angel β1+β2 of the auxiliary axle is calculated. Further, in a period in which the vehicle speed is increased from 30 km/h to 40 km/h, the auxiliary axle steering angel β1+β2 according to variation of the front-wheel steering angles α1 and α2 decreases to 0.

[0054] 3) When the vehicle speed is larger than 40 km/h (40 km/h<Vx), the steering angels β1 and β1+β2 of the auxiliary axle are 0.

[0055] That is, when the speed of the vehicle increases over 40 km/h with heavy freight thereon, a problem is generated with the driving stability of the vehicle and there is a possibility of turnover, so the steering angles of the auxiliary axle are controlled to be 0.

[0056] 4) When a (front-wheel steering) direction is changed.

[0057] FIG. 2 shows the case in which the vehicle is turned left, and when the vehicle is turned right, the current left steering angle is changed to α1 from α1+α2 and the right steering angle is changed to α1+α2 from α1.

[0058] According to the present disclosure, the control relationship of the auxiliary axle steering angles β1 and β2 according to the front-wheel steering angles were optimally designed through dynamic analysis and tests of the auxiliary axle steering angles according to the front-wheel steering angles α1 and α2 at a vehicle speed of 0 km/h˜40 km/h.

[0059] FIG. 3 shows test result data of variation of the right steering angle of the auxiliary axle according to variation of the front-wheel right steering angle when the vehicle speed is 10 km/h, 20 km/h, 25 km/h, and 30 km/h.

[0060] According to the result, when the vehicle speed is increased or decreased in the range of 0 km/h to 30 km/h, variation (12˜3) of the auxiliary axle steering angles are linear to variation (−40˜−10) of the front-wheel steering angles.

[0061] That is, when steering angle control is performed in accordance with the above equations while the vehicle speed changes between 0 km/h and 30 km/h, the variation of the auxiliary axle steering angles according to the variation of the front-wheel steering angles can be considered as being stable.

[0062] FIG. 4 shows the result of an auxiliary axle steering angle test according to the front-wheel steering angles when the vehicle speed is 30 km/h. According to the result, it can be seen that the auxiliary axle steering angles are not changed while the front-wheel steering angles are minutely changed by about ±2°.

[0063] FIG. 5 shows a test result of an auxiliary axle steering angle according to a speed. It was found that the auxiliary axle steering angle is maintained at a predetermined level when the vehicle speed is 0 km/h˜30 km/h, and then the auxiliary axle steering angle decreases to 0 when the vehicle speed increases to 30 km/h˜40 km/h. That is, it can be seen that an equation wad derived such that the auxiliary axle steering angle decreases to a stable level when the vehicle speed is changed to 30 km/h˜40 km/h.