Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Vehicle diagnosis or maintenance indication
Reexamination Certificate
2002-09-16
2004-04-27
Beaulieu, Yonel (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Vehicle diagnosis or maintenance indication
C701S037000, C356S138000
Reexamination Certificate
active
06728609
ABSTRACT:
FIELD OF THE DISCLOSURE
The disclosure generally relates to a method and system for determining an operational status of a steering system, and more specifically, to a method and system for determining and evaluating the operation of steering axes in a multiple-link steering system.
BACKGROUND
Steering systems are common in machines or vehicles for rotating or steering mechanical parts. For example, virtually every vehicle uses a steering system to steer the wheels. One important characteristic of a steering system is the steering axis around which mechanical parts or wheels rotate or pivot. For motor vehicles, an alignment process is used to determine and adjust parameters of the steering axis and the steering system. The parameters include camber, caster, steering axis inclination (SAI) and toe.
A camber angle is the inclination of the wheel plane viewed from the front with respect to the vertical plane. A camber angle is defined positive when the wheel leans outward at the top, and negative when it leans inward. Caster is the angle of the steering axis, viewed from the side of the vehicle, relative to the tire's vertical centerline. A caster angle is considered positive when the top of steering axis is inclined rearward and negative when the top of the steering axis is inclined forward. Steering axis inclination (SAI) is the angle between the steering axis, when viewed from the front of the vehicle, relative to the vertical line of the vehicle.
In order to measure these parameters, an operator may use a vision imaging system such as a computer-aided, three-dimensional (3D) machine vision that employs optical sensing devices, such as cameras, to determine the positions of various objects. Examples of such apparatus and methods are disclosed in U.S. Pat. No. 5,724,743, entitled “Method and Apparatus for Determining the Alignment of Motor Vehicle Wheels,” issued to Jackson, et al. on Mar. 10, 1998, and in U.S. Pat. No. 5,535,522, entitled “Method and Apparatus for Determining the Alignment of Motor Vehicle Wheels,” issued to Jackson, et al. on Jul. 16, 1996, each incorporated herein by reference.
These methods and systems work properly for vehicles using conventional steering systems. In a conventional steering system, each of the front wheels is connected to a knuckle. The knuckle has two ball joints: an upper ball joint connects to an upper link and a lower ball joint connects to a lower link. A steering link is connected to the knuckle via a pivot joint. The upper and lower ball joints work as pivot points. A driver uses a steering wheel that connects to the steering link to steer, or control the pivot of, the knuckle, which in turn pivots the wheels. As a result, the wheel pivots about a fixed steering axis extending from the upper ball joint to the lower ball joint.
FIG. 1
shows a multiple-link steering system
10
, a different type of steering system. In
FIG. 1
, a knuckle
12
is attached to the brake rotor
16
of front wheel. Knuckle
12
has three ball joints: an upper ball joint
22
and two lower ball joints
26
and
28
. An upper link
27
connects to knuckle
12
via upper ball joint
22
and to the chassis via two pivot hinges, forming a rigid triangle. A front lower link
32
connects to knuckle
12
via lower ball joint
28
and to the chassis via ball joint F. A rear lower link
34
connects to knuckle
12
via lower ball joint
26
and to the chassis via ball joint R. A steering link
14
is connected to knuckle
12
via another ball joint
24
. Similar to the conventional steering system, a driver uses a steering wheel that connects to steering link
14
to steer, or control the pivot of, knuckle
12
, which in turn pivots the wheel.
The chassis connections, and the interconnections of the linkage elements just described, constrain the motions of those elements relative to each other and the chassis. In particular, since the wheel is rigidly attached to knuckle
12
, which is attached to links
32
and
34
at joints
26
,
28
, and links
32
and
34
are attached to the chassis at joints F and R, joints
26
,
28
are constrained to move along arcs defined by this linkage. Due to this linkage, the position of joint
26
determines the position of
28
, and vice versa. These positions determine the position and orientation of knuckle
12
, and the wheel attached thereto, relative to the chassis. As steering link
14
moves from one position to another, joints
26
,
28
also move.
Lower links
32
,
32
may be parallel to each other in space. Thus, the extension lines FL, RL of lower links
32
,
34
do not necessarily intersect with each other. A pivot point may be defined as the midpoint of the two closest points on extension lines FL, RL of lower links
32
,
34
. Other definitions of pivot points may also be used.
FIGS. 1 and 2
show an example when the extension lines of lower links
32
,
34
intersect with each other. In this case, since the distance between the two lines is zero, the midpoint (the pivot point) is thus the same as the intersection point. In
FIG. 1
, a steering axis Xref about which the wheel pivots is defined as an axis passing through upper pivot point
22
and lower pivot point, which is the intersection
25
of lower links
32
,
34
.
Due to the movable linkage structure, the multiple link steering system does not have a fixed steering axis as that in conventional non-multiple-link steering systems. Rather, the multiple link steering system has a variable steering axis as the wheel turns. The change in the steering axis can be seen from
FIGS. 1 and 2
.
In
FIGS. 1 and 2
, the wheel is steered to a first direction and a second direction respectively. In
FIG. 2
, the steering axis of
FIG. 1
is marked as Xref, and the positions of two lower links of
FIG. 1
are marked as FL and RL respectively. Due to the structure of the movable linkages, when the wheel is steered from the first direction to the second direction, front lower link
32
moves from FL to line F′L′, and rear lower link
34
moves from line RL to line R′L′. As a result, the intersection of the two lower links shifts from point
25
to point
35
. The steering axis hence shifts from Xref to X
2
, which extends from ball joint
22
to point
35
, when the wheel is steered to the second direction. Accordingly, the steering axis of a multiple link steering system moves as the wheels are steered.
Other types of multiple-link steering systems are also available and have similar characteristics as illustrated in
FIGS. 1 and 2
. One type of multiple-link steering system has two upper links and only one lower link. Another type of multiple-link steering system has two links attached to both the upper and lower parts of the knuckle. The steering axes in these multiple-link steering systems also move as wheels are steered.
As steering axes in multiple-link steering systems move as wheels are steered, conventional methods for measuring parameters for a steering axis in non-multiple-link steering systems are not suitable for determining or evaluating steering axes in multiple link steering systems. Efforts have been devoted in establishing mathematical models for calculating the positional parameters of steering axes in a multiple-link steering system. However, such mathematical models are often complicated, and require a considerable amount of data and complex calculations. There is a need for a method and system that can easily evaluate the operation status of a multiple-link steering system, and without the need to know the exact positional parameters of the steering system. There is also a need to identify the existence of a multiple link steering system
SUMMARY
Diagnostic methods and systems are described to determine the existence and operational status of a multiple-link steering system for steering an object attached thereto. An exemplary diagnostic system includes a position determination system and a data processing system. The data processing system is coupled to the position determination system and configured to receive and proce
Dale, Jr. James L.
Glickman Stephen L.
Jackson David A.
Murray Patrick
Beaulieu Yonel
Snap-On Technologies Inc.
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