Diagnostic vehicle alignment system

A diagnostic vehicle alignment system includes an electronic controller for guiding a user through a series of diagnostic steps to determine probable causes for particular vehicle symptoms. Vehicle wheel alignment measuring instruments determine the alignment of at least one wheel of the vehicle. An input device is manually operable by a user for providing symptom identification and answers to diagnostic questions. A digital memory stores a set of possible causes for each selectable symptom and also stores diagnostic questions and an identification of diagnostic procedures. The stored diagnostic questions and procedures are preselected to eliminate possible causes of the selected symptom from consideration. A display is provided for displaying diagnostic questions and procedures to the user. The electronic controller is responsive to the selection of a particular symptom to cause the display to display diagnostic questions associated with that symptom to the user as well as the display of instructions to the user to perform diagnostic procedures, and the user uses the input device to interactively supply answers to the diagnostic questions and diagnostic procedure results to the electronic controller. The electronic controller is responsive to user provided input and to information from the vehicle wheel alignment measuring instruments to eliminate at least one possible cause of a symptom from consideration and identify any remaining possible causes of the symptom.

BACKGROUND OF THE INVENTION 
The present invention relates to vehicle alignment, and more particularly 
to vehicle alignment systems which assist in diagnosing vehicle alignment 
symptoms. 
Vehicle suspension and steering components are subject to wear, 
misadjustment, and failure. This results in various symptoms which, 
however, do not always unambiguously indicate the particular component 
which needs to be replaced or adjusted. Moreover, it is not always 
possible for the technician/user, particularly one who works on a great 
number of different models and makes of vehicles, to quickly and 
accurately determine the actual cause of any particular symptom. This 
results in increased repair time and costs and the possible replacement of 
undamaged parts. 
There are books available which may be used by the technician to diagnose a 
particular problem or symptom, but the books are not always available to 
the technician at the time they are needed. In addition, the books are 
bulky, are easily soiled, and generally are not a satisfactory solution. 
Various alignment equipment is available to the technician to assist in 
determining whether various alignment angles, such as toe, caster and 
camber are within specifications, but this information alone still does 
not always unambiguously define the cause of a particular symptom. Rather 
the currently available alignment equipment may direct the technician 
toward fixing a problem which is not actually the cause of the symptom 
complained of by the driver. When the symptom continues after the repair 
indicated by the alignment equipment, the driver will be dissatisfied. 
Such alignment equipment could be improved. 
SUMMARY OF THE INVENTION 
Among the various objects and features of the present invention is the 
provision of a vehicle alignment system which guides the technician 
through a process to diagnose the probable causes of vehicle symptoms. 
A second object is the provision of such a system which integrates 
information from the vehicle alignment system sensors. 
A third object is the provision of such a system which reduces the amount 
of knowledge required of the technician. 
A fourth object is the provision of such a system which reduces technician 
uncertainty. 
A fifth object is the provision of such a system which is usable with 
stored alignment measurements or with "live" alignment measurements, under 
control of the technician. 
A sixth object is the provision of such a system which includes asking the 
technician various diagnostic questions, as well as instructing the 
technician to perform various diagnostic procedures. 
A seventh object is the provision of such a system which provides 
additional information to the technician during the diagnostic process to 
facilitate the technician's job. 
An eighth object is the provision of such a system which informs the 
technician at all times concerning the current state of the diagnostic 
process and, upon request, the probable causes of the symptom. 
A ninth object is the provision of such a system which provides the 
technician with a list of probable causes of the symptom in order of 
probability. 
Other objects will be in part apparent and in part pointed out hereinafter. 
Briefly, a diagnostic vehicle alignment system of the present invention 
includes an electronic controller for guiding a user through a series of 
diagnostic steps to determine probable causes for particular vehicle 
symptoms. Vehicle wheel alignment measuring instruments determine the 
alignment of at least one wheel of the vehicle and supply that information 
to the electronic controller. An input device is manually operable by a 
user to provide input from the user to the electronic controller. The 
input device, for example, is operable by the user to select and supply to 
the electronic controller an identification of a particular symptom which 
the user desires to diagnose. A digital memory is provided for storing a 
set of possible causes for each selectable symptom and for storing 
diagnostic questions and an identification of diagnostic procedures for 
each selectable symptom. The stored diagnostic questions and procedures 
are preselected to eliminate possible causes of the selected symptom from 
consideration. A display is operatively connected to the electronic 
controller for displaying diagnostic questions and procedures to the user, 
the electronic controller being responsive to the selection of a 
particular symptom to cause the display to display at least one diagnostic 
question associated with that symptom to the user. The input device is 
operable by the user to supply an answer to the diagnostic question or the 
results of the diagnostic procedure to the electronic controller.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Turning to the drawings, and more particularly to FIGS. 1 and 2, there is 
shown a diagnostic vehicle alignment system 11 of the present invention. 
Alignment system 11 includes a console 13 suitably mounted on a stand 15 
for use by a technician/user 17. Console 13 includes a set of manually 
operable input keys or switches 19(A-D) and a display 21. Display 21 is 
preferably a CRT computer monitor type display. 
Input keys 19 and display 21 are connected to a microcomputer 22 which 
functions as an electronic controller to control the operation of system 
11 and to guide technician 17 through the process of diagnosing vehicle 
symptoms. Any number of different microcomputers may be used in system 11, 
depending upon the other requirements of the system. Microcomputer 22 is 
also shown in FIG. 2 connected to a digital memory 23 and to a printer 24. 
It should be understood that memory 23 could be internal to microcomputer 
22, depending upon the particular microcomputer used. In addition, other 
peripheral devices, such as a CD ROM drive and the: like (not shown) could 
be connected to microcomputer 22 as desired. It is preferred that suitable 
alignment sensors 25 be operatively connected to microcomputer 22 for 
supplying alignment information to the microcomputer. The use of such 
sensors to measure alignment characteristics is, of course, well known. 
See, U.S. Pat. Nos. Re 33,144 to Hunter et al., and 4,381,548 to Grossman 
et al., the disclosures of which are incorporated herein by reference. 
System 11 is particularly suited for use by technician 17 in performing a 
diagnosis of vehicle alignment symptoms or problems. In the present 
invention the microcomputer works interactively with the technician to 
guide the diagnostic procedure and perform the diagnosis. This is done by 
means of display 21, which the microcomputer uses to present diagnostic 
questions and the identification of diagnostic procedures to the 
technician, and by means of input keys 19, which the technician uses to 
initially identify the symptom for the microcomputer, and to provide 
answers to the diagnostic questions. 
It should be noted that the bottom of display 21 contains four variable 
function blocks 29A-D (the display of which is controlled by microcomputer 
22). Function blocks 29A-D are disposed directly over corresponding 
switches 19A-D and display to the user the function of those switches at 
that particular time in the program which controls the operation of 
microcomputer 22. 
The diagnostic system of the present invention is capable of diagnosing 
vehicle problems based on information that it receives from the technician 
17, the sensors 25, and the customer and specifications databases. 
Database information is prestored in memory 23 for various makes and 
models of vehicles. 
The diagnostic system is an expert system that uses a knowledge base of 
information regarding vehicle alignment. A knowledge base is a set of 
rules and facts that, when used together, can diagnose problems. Rules are 
if--then constructs that hold knowledge such as "If there is feather edge 
tire wear, then there may be an excessive toe angle". The particular 
knowledge base of information is a matter of individual choice and forms 
no part of the present invention. Any such knowledge base is equally 
usable with the present invention. 
In overview, the diagnostic system interactively diagnoses problems by 
prompting the technician 17 through a series of questions displayed on CRT 
display 21. The system begins by asking the technician for a major symptom 
and then proceeds to narrow down the cause of the problem by asking a 
series of questions. Microcomputer 22 asks a minimum number of relevant 
questions. Before asking each question, microcomputer 22 considers the 
answers to all the preceding questions in order to determine the best 
question to ask next. The system, if desired, may also ask the technician 
to perform simple diagnostic procedures such as rotating tires in order to 
locate the cause of the problem. The diagnostic questions and the 
identification of diagnostic procedures are stored in memory 23 for use as 
needed in diagnosing a selected symptom. 
Vehicle alignment system 11 operates in a plurality of modes. One mode is 
the diagnostic mode, described in detail herein. System 11 also includes 
an alignment mode, and may include such other modes as an inspection mode, 
etc. At any time in the diagnostic mode, the technician can ask system 11 
to produce a report on what it knows about the vehicle and what it can 
deduce from its knowledge, as described below. The report may be displayed 
on display 21, or printed on printer 24, or both. 
System 11 further keeps track of any information that it gathers during a 
particular diagnostic procedure or "Work Order". The technician may enter 
and exit from the diagnostic mode as desired. During the time the 
technician is exited from the diagnostic mode, microcomputer 22 maintains 
the answers to the questions that is has already asked the technician, so 
that upon re-entering the diagnostic mode that information is immediately 
available. Other information, such as sensor measurements from sensors 25 
which might change in the interim, is not saved. Sensor data is updated 
during the alignment mode, and the updated values are used upon 
re-entering the diagnostic mode. Of course, the sensor data could be 
acquired during the diagnostic mode itself, although this could complicate 
the diagnostic process if the sensor values were allowed to change during 
the diagnostic process itself. 
As briefly mentioned above, system 11 is not limited to information from 
the technician. It gathers information from databases, from the sensors 
and from the technician. Following are some examples of the types of 
information that the diagnostic system collects and typical sources of the 
information: 
______________________________________ 
Information Source 
______________________________________ 
Suspension type Spec. Database 
Steering System type 
Spec. Database 
Mileage Customer Database 
or by asking technician 
Vehicle Configuration 
From Spec. database 
or from technician 
How is the Vehicle being used 
Ask technician/customer 
Camber, Caster, Toe From the sensors or 
from saved job 
information 
What modifications have been made 
Ask technician 
to the vehicle 
______________________________________ 
The technician may enter the diagnostic mode from any of the "Primary" 
screens (not shown) in the vehicle alignment system. These Primary screens 
form no part of the present invention. Upon entering the diagnostic mode, 
microcomputer 22 causes the screen shown in FIG. 3 to be displayed on 
display 21 to technician 17. As shown in FIG. 3, in the diagnostic mode, 
microcomputer 22 first presents the technician with a hierarchical list of 
problems. The "2" symbol on this screen indicates that there are items at 
a lower level in the hierarchy. The "1" symbol indicates that the items at 
the lower level are currently displayed. 
At the bottom of the screen shown in FIG. 3, microcomputer 22 causes the 
display in blocks 29A-29D of the following: "Report", up-arrow, 
down-arrow, and "Diagnose Problem." By pressing the corresponding switch 
19A-19D associated therewith, the technician may move through the screen 
and move to other screens. For example, by pressing switch 19C associated 
with block 29C (the down-arrow in this part of the program), the 
technician moves down the list of problem types shown in FIG. 3. Likewise, 
pressing switch 19B (associated with the up-arrow) moves the indicator up 
the list of problem types. Once the desired problem type on the screen of 
FIG. 3 is highlighted, the user presses switch 19D (associated with 
"Diagnose Problem"), which results in microcomputer 22 causing the display 
of the subsequent screen, in this case the screen illustrated in FIG. 4. 
After the technician has selected a broad category of problems from the 
first list, he/she selects the precise problem or symptom from subsequent 
screens such as the one shown in FIG. 4. This is done by using switches 
19B and 19C to highlight the precise symptom on screen 21, and then using 
switch 19D to proceed with the diagnostic procedure. 
If desired, as shown in FIG. 4A, microcomputer 22 can aid the technician by 
displaying in a display block 29E the definition for each item as the 
technician moves through the list of items. For example, in FIG. 4A, the 
problem "memory steer" is highlighted and in display block 29E 
microcomputer 22 causes the display of the following definition: "Memory 
steer is a condition where the front wheels "remember" and seek a set 
position rather than returning to "straight ahead."" 
It should be understood that the legends in the display blocks 29 are under 
complete control of microcomputer 22. In addition to those legends shown, 
various alternative legends can be displayed by the microcomputer to enter 
different modes and to perform other functions. Of the legends displayed, 
the "Report" legend is used to produce a report of the problem, the known 
facts and the possible causes, as discussed in detail below. The function 
of the up-arrow and down-arrow legends has already been discussed. The 
"Diagnose Problem" legend, as discussed above, is used to begin the 
diagnostics process by further qualifying the problem or by prompting the 
technician with a definition of the problem. 
The user may instruct the microcomputer at any time (by a switch not shown) 
to display other legends. These legends for the particular screens shown 
in FIGS. 4 and 4A include a set of legends "Job Management", "Vehicle 
Specs", "Vehicle Measurements", and "Vehicle Inspection" for instructing 
the microcomputer to move to the primary screens for those functions. It 
should be understood that the diagnostic mode is fully integrated with 
these other functions. In particular, the technician/user is able to move 
to various modes of the aligner which may have some effect on the 
diagnostics. For example, in the Vehicle Specs mode, the technician may 
access the specification database. If the technician changes the 
specifications of a vehicle, the diagnosis may change. That is, 
measurements that once were within specifications, may now fall out of 
specifications. Or a technician may recall a vehicle with a different 
suspension type which may lead to a different diagnosis. 
Similarly, in the Vehicle Measurements mode, the technician may observe 
measurements from sensors 25 attached to the vehicle. In this mode, he/she 
may make adjustments to the vehicle. Any changes that the technician makes 
in this mode is reflected subsequently in the diagnostic mode. 
Likewise, in the Vehicle Inspection mode, the technician inspects a vehicle 
in order to produce a report of what parts of the vehicle are worn or 
damaged. If the fact that a part is worn is relevant to the problem that 
is being diagnosed, microcomputer 22 will recognize the fact that the 
technician identified the worn part in the Inspection mode, and will use 
that information subsequently in the diagnostic mode. 
Additional legends such as "Clear All Answers" and "Help" are also 
displayable. Pressing "Clear all Answers" causes the microcomputer to 
clear all answers to all the questions that the technician has answered to 
that point in the procedure. The "Help" legend is self-explanatory. 
After the technician has identified a problem in the initial hierarchical 
list of problems, the system may need to qualify the problem further. For 
example, if the technician selects Tire Wear, microcomputer 22 may qualify 
the type of tire wear with a screen like that shown in FIG. 5. 
In this type of screen various types of wear are illustrated in selectable 
panes 31A-31G. The technician uses switches 19A (associated with "Next 
Picture") and 19B (associated with "Previous Picture") to highlight the 
pane which best illustrates the state of wear, and then uses switch 19C 
(associated with "Select Picture") to select that particular pane. 
Although this feature is illustrated with respect to tire wear, it should 
be appreciated that it is applicable as well to other types of wear and 
symptoms. 
After the technician has selected a problem or symptom through the use of 
screens like those of FIGS. 4, 4A, and/or 5, microcomputer 22 causes the 
display on display 21 of a screen that defines the problem (see FIG. 6). 
This screen lets the technician decide if he/she wants a printed checklist 
or interactive diagnosis. If the technician selects "Print Checklist" by 
pressing switch 19A, microcomputer 22 will cause printer 24 to print out a 
printed report that can be used to diagnose the car without the computer. 
The report can also be used to talk to the customer without the aid of the 
computer, or to use in a road test of the vehicle. 
If the technician selects "Diagnose" (presses switch 19B), microcomputer 22 
will cause the display of diagnostic questions and instruct the technician 
to perform diagnostic procedures. Whenever possible, microcomputer 22 will 
cause the display of diagnostic questions using pictures, such as 
illustrated in FIG. 7. These pictures are preferably actual photographs of 
the portion of the vehicle in question, although line art may also be 
used. As can be seen in FIG. 7, these diagnostic question screens with 
pictures include not only a picture and a diagnostic question, but also 
some indication (the box 35 in FIG. 7) highlighting the part to be 
inspected. The technician at this point has the option to back up one 
screen in the procedure (by pressing switch 19A), answering the question 
"yes" (by pressing switch 19B), answering the question "no" (by pressing 
switch 19C), or by answering the question as "unknown" (by pressing switch 
19D). 
In many instances, microcomputer 22 causes the display of diagnostic 
questions without the aid of pictures, as shown in FIG. 8. In addition to 
the answer display blocks for the screens of FIGS. 7 and 8 discussed 
above, the microcomputer may at the technician's request also cause the 
display of the following legends "Report" (which results in the production 
of a report of the problem, the known facts and the possible causes), 
"Return To Problem List" (which results in returning to the main problem 
diagnostic screen), and "Restart Diagnosis" (which results in the clearing 
of all answers for the current diagnosis). If the technician choses to 
return to the main screen, he/she may at that point diagnose another 
problem or reenter the diagnosis for the current problem. 
Microcomputer 22 will often need measurement information. It obtains this 
information from sensors 25 in the conventional way during the alignment 
mode. Microcomputer 22 also, when using measurement information, informs 
the technician of this fact by the display of a screen such as that shown 
in FIG. 9. For example, if the microcomputer requires left front camber 
information during a diagnosis, then display 21 informs the technician of 
the fact that left front camber information is being used, along with the 
results of the camber measurement. 
The technician would usually press switch 19D to Continue with the 
diagnosis when he/she sees such a screen. However the technician could 
press switch 19B (associated with the legend "Modify Values") to change 
the camber value, the specification, or the tolerance. If the technician 
pressed "Modify Values," the screen would change to an edit screen, in 
which the technician uses a tab key (not shown) to move between the camber 
value, the specification, and the tolerance. The technician could change 
any of the values before pressing switch 19D to continue. The diagnostic 
system would use the altered values as it tries to determine the cause of 
the problem. If the technician alters the specification or the tolerance, 
the modified values will only be used within the diagnostic mode of system 
11. 
Once microcomputer 22 has reached a diagnosis, it displays a report to the 
technician, such as that shown in FIG. 10. The technician may also produce 
this report at any time by selecting "Report" from the soft keys on any 
diagnostic screen. The technician may view this report on screen 21 or 
print it on printer 24 (by pressing switch 19A). The report presents all 
the facts known by the system and all the possible cause of the problem in 
order of decreasing probability. 
System 11 is able to diagnose a finite set of problems. For each of the 
problems there will be a finite number of causes that the diagnostic 
system understands. For example the diagnostic system is able to handle 
problems such as the following: 
Pull Left/Right 
Centerline Steering Error 
Shimmy 
Vibration 
Hard Steering 
Loose Steering 
etc. 
For the "Pull Left/Right" problem, the diagnostic system will understand a 
fixed number of causes, such as: 
Uneven tire pressure 
Uneven tread wear 
Mismatched tires 
Uneven Camber 
Uneven caster 
Brake drag 
Setback 
Suspension/frame sag 
Tire conicity 
Unbalanced power assist 
Bent spindle 
Bent strut 
Worn suspension components (front/rear) 
Rear suspension misalignment 
In performing the actual diagnosis, microcomputer 22 operates using a 
process of elimination. When the technician first identifies the problem, 
microcomputer 22 considers all of the potential causes for the problem as 
"Possible Causes." If the technician requests a report before he/she had 
answered any questions about a problem, then microcomputer 22 reports all 
of the potential causes of a problem as "Possible Causes". As the 
technician answers questions and performs diagnostic procedures, and as 
the diagnostic system gathers measurement information, the number of 
possible causes is reduced. Microcomputer 22 asks questions that will 
eliminate each possible cause in an effort to determine a single cause of 
the problem. 
Note that the present system is not limited to use with sensors 25. For 
example, the technician could perform a diagnosis on a vehicle, by 
inspecting it "off of the rack" without measurement information. The 
technician could answer any of the questions that do not involve 
measurements. Microcomputer 22 is able to eliminate many of the possible 
causes and provide a useful list of the remaining possible causes for the 
technician. 
In some instances it is possible that the diagnostic system of the present 
invention will not be able to identify the cause of the problem. 
Microcomputer 22 in that case tries to eliminate all of the causes of a 
problem that it can. If all the possible causes programmed in 
microcomputer 22 are eliminated, then it reports to the technician that 
the cause of the problem is unknown. 
In the event that a second diagnosis is performed on the same vehicle, 
microcomputer 22 re-asks all questions relevant to any problem even if the 
questions have already been asked for another problem. 
In view of the above, it will be seen that the various objects and features 
of the present invention are achieved and other advantageous results 
obtained. It will be understood that the various embodiments of the 
present invention described herein are illustrative only and are not to be 
taken in a limiting sense.