US5014227A
Expired / Lapsed
US
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Caster and steering axis inclination measurement technique
Assignee: SPX Technologies Inc
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Filing: 1989-07-17
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Granted: 1991-05-07
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Expires: 2009-07-17
Abstract
Abstract A wheel alignment system measures caster and steering axis inclination (SAI) by positioning the wheels at a right turn position and a left turn position. Toe, camber and inclination angle measurements are made for both wheels at both the left turn position and the right turn position. Based upon these measurements, caster and SAI are calculated either directly or through an iterative technique.
Inventors
- 👤 Michael J. Kling
- 👤 John M. Surwillo
- 👤 Peter A. Puetz
- 👤 Robert T. Braun
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 08:09
CPC Classifications
G; G01; G01B; G01B11/00; G01B11/26; G01B11/275; G01B11/2755; G01B2210/00; G01B2210/10; G01B2210/26; G01B2210/28; G01B2210/283
Claims Analysis
Total Claims: 27
Claim 1
Independent Claim
163 words
A method for accurately measuring caster and steering axis inclination (SAI) of left and right steerable wheels of a vehicle based upon measurements taken with the wheels in less than four different positions, the method comprising: mounting a left head unit on the left steerable wheel of the vehicle; mounting a right head unit on the right steerable wheel of the vehicle; turning the wheels to a first position; making toe, camber and inclination angle measurements for each of the wheels with the left head unit and the right head unit while the wheels are in the first position; turning the wheels to a second position; making toe, camber and inclination angle measurements for each of the wheels while with the left head unit and the right hand unit while the wheels are in the second position; and calculating caster and SAI of each wheel using the toe, camber and inclination angle measurements made for that wheel at the first and second positions.
Claim 2
Independent Claim
163 words
A method for accurately measuring caster and steering axis inclination (SAI) of left and right steerable wheels of a vehicle based upon measurements taken with the wheels in less than four different positions, the method comprising: mounting a left head unit on the left steerable wheel of the vehicle; mounting a right head unit on the right steerable wheel of the vehicle; turning the wheels to a first position; making toe, camber and inclination angle measurements for each of the wheels with the left head unit and the right head unit while the wheels are in the first position; turning the wheels to a second position; making toe, camber and inclination angle measurements for each of the wheels while with the left head unit and the right hand unit while the wheels are in the second position; and calculating caster and SAI of each wheel using the toe, camber and inclination angle measurements made for that wheel at the first and second positions.
Claim 3
Dependent Claim
101 words
The method of claim 1 wherein making toe, camber and inclination angle measurements while the wheels are in the first position includes producing a first set of left and right toe values (LT1 and RT1), left and right camber values (LC1 and RC1) and left and right inclination angle values (LS1 and RS1); and making toe, camber and inclination angle measurements while the wheels are in the second position includes producing a second set of left and right toe values (LT2 and RT2), left and right camber values LC2 and RC2) and left and right inclination angle values (LS2 and RS2).
Claim 4
Dependent Claim
57 words
The method of claim 2 wherein calculating caster and SAI for the left wheel is by an iterative technique using the following formulae: SAI=arctan((sin LS1-sin LS2-(cos LS2 cos LT2-cos LS1 cos LT1) tan CASTER)/(cos LS2 sin LT2-cos LS1 sin LT1)) CASTER=arctan((sin LC1-sin LC2-(cos LC2 cos LT2-cos LC1 cos LT1) tan SAI)/(cos LC2 sin LT2-cos LC1 sin LT1))
Claim 5
Dependent Claim
16 words
The method of claim 3 wherein the iterative technique is initiated with an initial approximate caster.
Claim 6
Dependent Claim
25 words
The method of claim 4 and further comprising: calculating initial approximate caster value (Approximate CASTER) by the following formula: Approximate CASTER=arctan((sin LC1-sin LC2)/(sin LT2-sin LT1))
Claim 7
Dependent Claim
57 words
The method of claim 2 wherein calculating caster and SAI for the right wheel is by an iterative technique using the following formulae: SAI=arctan((sin RS1-sin RS2-(cos RS2 cos RT2-cos RS1 cos RT1) tan CASTER)/(cos RS2 sin RT2-cos RS1 sin RT1)) CASTER=arctan((sin RC1-sin RC2-(cos RC2 cos RT2-cos RC1 cos RT1) tan SAI)/(cos RC2 sin RT2-cos RC1 sin RT1))
Claim 8
Independent Claim
17 words
The method of claim wherein the step of calculating the caster and SAI is an iterative process.
Claim 9
Dependent Claim
35 words
The method of claim 1 wherein the first position is defined by a left toe-out angle of the left wheel, and the second position is defined by a right toe-out angle of the right wheel.
Claim 10
Dependent Claim
16 words
The method of claim 3 wherein the iterative technique is initiated with an initial approximate SAI.
Claim 11
Dependent Claim
79 words
The method of claim 2 wherein calculating caster and SAI for the left wheel is by a direct technique using the following formulae: SAI=arctan((A-BC)/(1-BD)) CASTER=arctan((C-AD)/(1-BD)) where A, B, C and D are defined as: A=(sin LS1 -sin LS2)/(cos LS2 sin LT2-cos LS1 sin LT1) B=(cos LS2 cos LT2-cos LS1 cos LT1)/(cos LS2 sin LT2-cos LS1 sin LT1) C=(sin LC1-sin LC2)/(cos LC2 sin LT2-cos LC1 sin LT1) D=(cos LC2 cos LT2-cos LC1 cos LT1)/(cos LC2 sin LT2-cos LC1 sin LT1)
Claim 12
Dependent Claim
80 words
The method of claim 2 wherein calculating caster and SAI for the right wheel is by a direct technique using the following formulae: SAI=arctan((A-BC)/(1-BD)) CASTER=arctan((C-AD)/(1-BD)) where A, B, C and D are defined as: A=(sin RS1-sin RS2)/(cos RS2 sin RT2- cos RS1 sin RT1) B=(cos RS2 cos RT2-cos RS1 cos RT1)/(cos RS2 sin RT2-cos RS1 sin RT1) C=(sin RC1- sin RC2)/(cos RC2 sin RT2-cos RC1 sin RT1) D=(cos RC2 cos RT2-cos RC1 cos RT1)/(cos RC2 sin RT2-cos RC1 sin RT1)
Claim 13
Independent Claim
313 words
An apparatus for measuring caster of left and right steerable wheels of a vehicle based upon measurements taken with the wheels in less than four different positions, the apparatus comprising: a left head unit for mounting to a left steerable wheel of a vehicle, the left head unit including: means for measuring left toe angles of the left wheel; means for measuring left camber angles of the left wheel; means for measuring left inclination angles of the left wheel; a right head unit for mounting to the right steerable wheel of a vehicle including the right head unit including: means for measuring right toe angles of the right wheel; means for measuring right camber angles of the right wheel; means for measuring right inclination angles of the right wheel; means connected to the left and right head units for collecting a first set of measurements from the means for measuring left toe angles and the means for measuring right toe angles, the means for measuring left camber angles and the means for measuring right camber angles, and the means for measuring left inclination angles and the means for measuring right inclination angles when the left and right wheels are steered to a first position; means connected to the left and right head units for collecting a second set of measurements from the means for measuring left toe angles and the means for measuring right toe angles, the means for measuring left camber angles and the means for measuring right camber angels, and the means for measuring left inclination angles and the means for measuring right inclination angles when the left and right wheels are steered to a second positions; and means connected to the left and right head units for providing outputs representative of the caster of the left and right wheels as a function of the first and second sets of measurements.
Claim 14
Independent Claim
313 words
An apparatus for measuring caster of left and right steerable wheels of a vehicle based upon measurements taken with the wheels in less than four different positions, the apparatus comprising: a left head unit for mounting to a left steerable wheel of a vehicle, the left head unit including: means for measuring left toe angles of the left wheel; means for measuring left camber angles of the left wheel; means for measuring left inclination angles of the left wheel; a right head unit for mounting to the right steerable wheel of a vehicle including the right head unit including: means for measuring right toe angles of the right wheel; means for measuring right camber angles of the right wheel; means for measuring right inclination angles of the right wheel; means connected to the left and right head units for collecting a first set of measurements from the means for measuring left toe angles and the means for measuring right toe angles, the means for measuring left camber angles and the means for measuring right camber angles, and the means for measuring left inclination angles and the means for measuring right inclination angles when the left and right wheels are steered to a first position; means connected to the left and right head units for collecting a second set of measurements from the means for measuring left toe angles and the means for measuring right toe angles, the means for measuring left camber angles and the means for measuring right camber angels, and the means for measuring left inclination angles and the means for measuring right inclination angles when the left and right wheels are steered to a second positions; and means connected to the left and right head units for providing outputs representative of the caster of the left and right wheels as a function of the first and second sets of measurements.
Claim 15
Dependent Claim
49 words
The apparatus of claim 12 wherein the means for providing outputs includes: means for calculating caster and SAI values for each wheel based upon an iterative process using the first and second sets of measurements; and means for providing the output based upon the calculated caster and SAI values.
Claim 16
Dependent Claim
72 words
The apparatus of claim 13 wherein the first set of measurements include left and right toe values (LT1 and RT1), left and right camber values (LC1 and RC1) and left and right inclination angle values (LS1 and RS1), and wherein the second set of measurements include left and right toe values (LT2 and RT2), left and right camber values (LC2 and RC2), and left and right inclination angle values (LS2 and RS2).
Claim 17
Dependent Claim
105 words
The apparatus of claim 14 wherein the means for calculating calculates caster and SAI for the left wheel according to the following formulae: SAI=arctan((sin LS1-sin LS2-(cos LS2 cos LT2-cos LS1 cos LT1) tan CASTER)/(cos LS2 sin LT2-cos LS1 sin LT1)) CASTER=arctan((sin LC1-sin LC2-(cos LC2 cos LT2-cos LC1 cos LT1) tan SAI)/(cos LC2 sin LT2-cos LC1 sin LT1)) and calculates caster and SAI for the right wheel according to the following formulae: SAI=arctan((sin RS1-sin RS2-(cos RS2 cos RT2-cos RS1 cos RT1) tan CASTER)/(cos RS2 sin RT2-cos RS1 sin RT1)) CASTER=arctan((sin RC1-sin RC2-(cos RC2 cos RT2-cos RC1 cos RT1) tan SAI)/(cos RC2 sin RT2-cos RC1 sin RT1))
Claim 18
Dependent Claim
25 words
The apparatus of claim 15 wherein the means for calculating uses an initial approximate caster value for each wheel in calculating caster and SAI values.
Claim 19
Dependent Claim
34 words
The apparatus of claim 16 wherein the means for calculating calculates the initial approximate caster values by the following formulae: Approximate left CASTER=arctan((sin LC1-sin LC2)/(sin LT2-sin LT1)) Approximate right CASTER=arctan((sin RC1-sin RC2)/(sin RT2-sin RT1))
Claim 20
Dependent Claim
150 words
The apparatus of claim 14 wherein the means for calculating calculates caster and SAI for the left wheel according to the following formulae: SAI=arctan((A-BC)/(1-BD)) CASTER=arctan((C-AD)/(1-BD)) where A, B, C and D are defined as: A=(sin LS1- sin LS2)/(cos LS2 sin LT2-cos LS1 sin LT1) B=(cos LS2 cos LT2-cos LS1 cos LT1)/(cos LS2 sin LT2-cos LS1 sin LT1) C=(sin LC1-sin LC2)/(cos LC2 sin LT2-cos LC1 sin LT1) D=(cos LC2 cos LT2-cos LC1 cos LT1)/(cos LC2 sin LT2-cos LC1 sin LT1) and calculates camber and SAI for the right wheel according to the following formulae: SAI=arctan((A-BC)/(1-BD)) CASTER=arctan((C-AD)/(1-BD)) where A, B, C and D are defined as: A=(sin RS1- sin RS2)/(cos RS2 sin RT2-cos RS1 sin RT1) B=(cos RS2 cos RT2-cos RS1 cos RT1)/(cos RS2 sin RT2-cos RS1 sin RT1) C=(sin RC1- sin RC2)/(cos RC2 sin RT2-cos RC1 sin RT1) D=(cos RC2 cos RT2-cos RC1 cos RT1)/(cos RC2 sin RT2-cos RC1 sin RT1)
Claim 21
Dependent Claim
26 words
The apparatus of claim 15 wherein the means f or calculating uses an initial approximate SAI value for each wheel in calculating caster and SAI values.
Claim 22
Independent Claim
150 words
A method for accurately measuring caster of left and right steerable wheels of a vehicle, the method comprising: mounting measurement devices on the left and right steerable wheels; turning the wheels to a first left turn position in which the left steerable wheel is toed-out; making toe, camber and inclination angle measurements for each of the wheels using the measurement devices while the wheels are in the first position; turning the wheels to a second right turn position in which the right steerable wheel is toed-out; making toe, camber and inclination angle measurements for each of the wheels using the measurement devices while the wheels are in the second; calculating caster of each wheel using only two sets of measurements, which comprise the toe, camber and inclination angle measurements made for that wheel at the first and second positions; and providing outputs representative of the caster calculated for each wheel.
Claim 23
Independent Claim
150 words
A method for accurately measuring caster of left and right steerable wheels of a vehicle, the method comprising: mounting measurement devices on the left and right steerable wheels; turning the wheels to a first left turn position in which the left steerable wheel is toed-out; making toe, camber and inclination angle measurements for each of the wheels using the measurement devices while the wheels are in the first position; turning the wheels to a second right turn position in which the right steerable wheel is toed-out; making toe, camber and inclination angle measurements for each of the wheels using the measurement devices while the wheels are in the second; calculating caster of each wheel using only two sets of measurements, which comprise the toe, camber and inclination angle measurements made for that wheel at the first and second positions; and providing outputs representative of the caster calculated for each wheel.
Claim 24
Dependent Claim
97 words
The method of claim 20 wherein making toe and camber measurements while the wheels are in the first position includes producing a first set of left and right toe values (LT1 and RT1), left and right camber values (LC1 and RC1), and left and right inclination angle values (LS1 and RS1); and making toe and camber measurements while the wheels are in the second position includes producing a second set of left and right toe values (LT2 and RT2), left and right camber values (LC2 and RC2), and left and right inclination angle values (LS2 and RS2).
Claim 25
Independent Claim
196 words
An apparatus for measuring caster of left and right steerable wheels of a vehicle, the apparatus comprising: means for measuring toe angles of the left and right wheels; means for measuring camber angle of the left and right wheels; means for measuring inclination angle of the left and right wheels; means for prompting user to steer the wheels to a first position and then to a second position; means for collecting and storing a first set of measurements from the means for measuring toe angles, the means for measuring camber angles and the means for measuring inclination angle when the left and right wheels are steered to the first position; means for collecting and storing a second set of measurements from the means for measuring toe angles, the means for measuring camber angles and the means for measuring inclination angle when the left and right wheels are steered to the second position; means for calculating caster and SAI values for each wheel based solely upon the stored first and second sets of measurements; and means for providing outputs representative of the caster of the left and right wheels based upon the calculated caster and SAI values.
Claim 26
Independent Claim
196 words
An apparatus for measuring caster of left and right steerable wheels of a vehicle, the apparatus comprising: means for measuring toe angles of the left and right wheels; means for measuring camber angle of the left and right wheels; means for measuring inclination angle of the left and right wheels; means for prompting user to steer the wheels to a first position and then to a second position; means for collecting and storing a first set of measurements from the means for measuring toe angles, the means for measuring camber angles and the means for measuring inclination angle when the left and right wheels are steered to the first position; means for collecting and storing a second set of measurements from the means for measuring toe angles, the means for measuring camber angles and the means for measuring inclination angle when the left and right wheels are steered to the second position; means for calculating caster and SAI values for each wheel based solely upon the stored first and second sets of measurements; and means for providing outputs representative of the caster of the left and right wheels based upon the calculated caster and SAI values.
Claim 27
Dependent Claim
72 words
The apparatus of claim 22 wherein the first set of measurements include left and right toe values (LT1 and RT1), left and right camber values (LC1 and RC1), and left and right inclination angle values (LS1 and RS1), and wherein the second set of measurements include left and right toe values (LC2 and RT2), left and right camber values (LC2 and RC2), and left and right inclination angle values (LS2 and RS2).
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