U.S. patent application number 09/847230 was filed with the patent office on 2001-11-01 for method for limiting endstop collisions in semi-active seat suspension systems.
Invention is credited to Clair, Kenneth A. St..
Application Number | 20010037169 09/847230 |
Document ID | / |
Family ID | 22743526 |
Filed Date | 2001-11-01 |
United States Patent
Application |
20010037169 |
Kind Code |
A1 |
Clair, Kenneth A. St. |
November 1, 2001 |
Method for limiting endstop collisions in semi-active seat
suspension systems
Abstract
A method for limiting endstop collisions when non-typical inputs
are experienced and also when the seat is leveled at a position
above or below the normal leveling zone limits. According to the
method of the invention a temporary or transient control method
referred to as rebound control method causes a large damping force
to be applied by the seat suspension system in response to
non-typically large inputs. The large damping force is applied
until a duration timer timesout. Also according to the invention, a
level control algorithm provides additional damping when the seat
is leveled outside the normal leveling zone. The degree of
additional damping provided is a function of the distance the seat
exceeds the normal leveling zone.
Inventors: |
Clair, Kenneth A. St.;
(Cary, NC) |
Correspondence
Address: |
Michael M. Gnibus
Lord Corporation
111 Lord Drive
PO Box 8012
Cary
NC
27512-8012
US
|
Family ID: |
22743526 |
Appl. No.: |
09/847230 |
Filed: |
May 2, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60200865 |
May 2, 2000 |
|
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|
Current U.S.
Class: |
701/37 ;
280/5.5 |
Current CPC
Class: |
B60G 2500/30 20130101;
B60G 2600/17 20130101; B60G 2800/164 20130101; B60N 2/0244
20130101; B60G 2600/02 20130101; B60N 2/501 20130101; B60G 2400/60
20130101; B60G 2204/45 20130101; B60N 2/505 20130101; B60N 2/502
20130101; B60G 17/01933 20130101; B60G 2400/202 20130101; B60N
2/544 20130101; B60N 2/0224 20130101; B60G 17/018 20130101; B60G
2600/1877 20130101; B60N 2/508 20130101; B60N 2/525 20130101; B60G
2400/252 20130101; B60G 2600/184 20130101; B60G 2200/345 20130101;
B60G 2800/162 20130101; B60N 2/522 20130101; B60G 2800/7022
20130101 |
Class at
Publication: |
701/37 ;
280/5.5 |
International
Class: |
B60G 017/00 |
Claims
I claim:
1. In a seat suspension system having a first endstop limit, a
second endstop limit and means for controlling the seat
displacement, a method for limiting endstop collisions, the method
comprising the steps of: (a) sensing the relative position of the
seat; (b) determining the relative seat velocity; (c) calculating a
control signal by multiplying the seat velocity by a gain factor;
and (d) transmitting the control signal to said displacement
control means to increase the damping to the required level.
2. The method of claim 1 further comprising the step of calculating
the relative change in position of the seat per unit time in step
(b).
3. The method of claim 1 wherein in step (b) the method further
comprising the steps of calculating the relative change in position
of the seat per unit time and taking the absolute value of the
relative change in seat position per unit time.
4. The method of claim 1 wherein the gain factor is a fixed
value.
5. The method of claim 1 wherein the gain factor is comprised of a
constant value multiplied by the deviation of the seat from a
normal leveling zone.
6. The method of claim 5 wherein the gain factor is of the greatest
magnitude when the seat is proximate one of the endstop limits.
7. The method as claimed in claim 1 wherein before step (c) the
method comprising the additional steps of determining the leveled
seat height; determining if the leveled seat height is within or
outside of a normal leveling zone.
8. The method as claimed in claim 7 wherein the method comprises
the steps of determining if the leveled seat height is greater than
the maximum normal leveling zone limit and determining if the
leveled seat height is less than the minimum normal leveling zone
limit.
9. The method as claimed in claim 8 wherein if the leveled seat
height is greater than the maximum normal leveling zone limit, the
method comprising the additional step of subtracting the value of
the normal leveling zone maximum limit from the value of the
leveled seat height.
10. The method as claimed in claim 8 wherein if the leveled seat
height is less than the minimum normal leveling zone limit, the
method comprising the additional step of subtracting the value of
the leveled seat height from normal leveling zone minimum
limit.
11. The method of claim 5 comprising the Step of multiplying the
difference of claim 9 by the gain constant.
12. The method as claimed in claim 5 comprising the step of
multiplying the difference of claim 10 by the gain constant.
13. The method of claim 6 wherein the gain factor varies linearly
from a maximum normal leveling zone limit to the first endstop.
14. The method of claim 6 wherein the gain factor varies linearly
from a minimum normal leveling zone limit to the second
endstop.
15. The method as claimed in claim 6 wherein the gain factor is a
function of the distance the seat is outside the normal leveling
zone.
16. The method as claimed in claim 1 wherein before step (c) the
method comprising the additional step of determining if the seat
position is less than a minimum endstop detection threshold.
17. The method as claimed in claim 1 wherein before step (c) the
method comprising the additional step of determining if the seat
position is greater than the maximum endstop detection
threshold.
18. The method as claimed in claim 16 wherein the system includes a
timer, the method comprising the additional step of starting the
timer if the seat position is less than a minimum endstop detection
threshold.
19. The method as claimed in claim 17 wherein the system includes a
timer, the method comprising the additional step of starting the
timer if the seat position is greater than the maximum endstop
detection threshold.
20. The method as claimed in claim 18 wherein the gain factor is
set to zero if the timer is not running.
21. The method as claimed in claim 18 wherein if the timer limit is
exceeded the timer is halted and the gain factor is set to
zero.
22. The method as claimed in claim 7 wherein a sum value is set
equal to zero if the leveled seat height is within the normal
leveling zone.
23. The method as claimed in claim 18 wherein if the timer has not
exceeded a timer limit, the timer is incremented.
Description
CROSS REFERENCE
[0001] This application claims the benefit of Provisional
Application Ser. No. 60/200,865 filed May 2, 2000.
FIELD OF THE INVENTION
[0002] The invention generally relates to a method for limiting
endstop collisions in semi-active seat suspension systems, and more
particularly the invention relates to a method for limiting endstop
collisions by adjusting the seat damping gain when either the
system exceeds an endstop detection threshold or the seat is
leveled outside of a normal leveling limits.
BACKGROUND OF THE INVENTION
[0003] In semi-active control systems, such as semi-active seat
suspensions for example, the seat displacement control force
provided to the system by a damper is continually adjusted in
response to system inputs to provide isolation of high frequency
low amplitude disturbances and to also improve performance of the
seat suspension and comfort to the rider by limiting endstop
collisions. An end stop collision occurs when the mechanical system
in which the damper is connected hits the end stop, for example the
maximum mechanical limits of the extension and/or rebound strokes
when a sufficient transient load is encountered. If the system
velocity is high enough when the end stop collision occurs, a very
rapid impact results. The bottoming and topping out at an end stop
condition imparts unwanted stresses to the mechanical components in
the system and such collisions can be an annoyance to the driver.
More significantly, when a driver or other seat occupant
experiences endstop collisions, such collisions can effect the
physical health of the seat occupant.
[0004] Prior art semi-active control systems include a control
routine that serves to provide a damping force that is proportional
to the relative velocity of the seat or of another component of the
seat suspension system. U.S. Pat. Nos. 5,276,622 and 4,821,849
illustrate prior art semi-active control systems. In many
situations the tuning values applied to the system by the control
routines are selected to control the suspended seat over an
expected or typical range of inputs, rider weights, etc. These
selected tuning values are unique for each system and are selected
based on the particular damper design, installation kinematics, and
control system being used. In this way known semi-active systems
have attempted to provide the appropriate magnitude of damping
forces in response to typical inputs to limit endstop collisions.
Because known semi-active systems are tuned for typical system
inputs, when very large inputs outside the typical input range are
encountered, the large inputs can still produce endstop
collisions.
[0005] It is not practical to use prior art systems and methods to
tune a control system so that the system is able to sufficiently
damp the complete range of possible inputs to the seat suspension.
A system tuned for the complete range of system inputs would be
very heavy and expensive and would likely not meet the space,
weight and cost restrictions for the suspension. Additionally,
tuning a system for the complete range of possible inputs including
large inputs would degrade the ride over the routine or typical
inputs. Finally, when endstop collisions occur, the collisions
typically are unabated in known prior art systems, and as a result,
the suspension system may experience one or more additional endstop
collisions. Such endstop collisions are referred to by those
skilled in the art as rebounds.
[0006] Frequently, seat riders set their leveled seat height at an
extremely high or low position proximate the respective upper or
lower mechanical seat endstops. When the seat is set proximate the
upper and lower endstops and an input is experienced, the system
does not have sufficient time and distance to apply sufficient
damping force to prevent endstop collisions. As a result,
unintended and undesirable impacts with the mechanical endstops
occur. Because the seat is proximate the mechanical endstops, the
unintended and undesirable collisions occur even when a typical
input is applied to the system.
[0007] The foregoing illustrates limitations known to exist in
present semi-active devices and methods. Thus, it is apparent that
it would be advantageous to provide an alternative directed to
providing a large damping force in response to a non-typically
large input and also provides the best overall ride quality and
protection of the rider when the leveled seat height exceeds normal
bounds. Accordingly, a suitable alternative is provided including
features more fully disclosed hereinafter.
SUMMARY OF THE INVENTION
[0008] This is accomplished by the present invention which
generally relates to a method for limiting endstop collisions in
semi-active seat suspension systems, and more particularly the
invention relates to a method for limiting endstop collisions by
adjusting the damping gain factor when either the system exceeds an
endstop detection threshold or the seat is leveled outside of
normal leveling limits. Generally the seat suspension includes a
first endstop limit, a second endstop limit and means for
controlling the seat displacement, and the method for limiting
endstop collisions comprises the steps of: sensing the position of
the seat; determining the seat velocity; calculating a control
signal by multiplying the seat velocity by a gain factor; and
transmitting the control signal to said displacement control means
to increase the damping to the required level.
[0009] More specifically in one aspect of the present invention,
endstop collisions are limited by providing a temporary or
transient control method referred to as rebound control which
causes a large damping force to be applied by the seat suspension
system in response to non-typically large inputs which cause the
seat to cross or exceed an endstop detection threshold.
[0010] In another specific aspect of the invention, this is
accomplished by providing a level control algorithm that provides
additional level control when the seat is leveled outside the
normal leveling zone. The degree of additional level control or
gain factor supplied is a function of the distance the seat exceeds
the normal leveling zone. In this aspect of the present invention,
rider protection from end stop collisions is maximized.
[0011] The foregoing and other aspects will become apparent from
the following detailed description of the invention when considered
in conjunction with the accompanying drawing figures.
BRIEF DESCRIPTION OF THE DRAWING FIGURES
[0012] FIGS. 1a, 1b, and 1c are schematic representations of a seat
suspension system that utilizes the semi-active control system of
the present invention to limit endstop collisions.
[0013] FIG. 2 is a graphical representation of the changes in the
gain when the seat is located outside of the normal leveling
zone.
[0014] FIG. 3 is a schematic representation of the seat
displacement including the maximum and minimum endstop detection
threshold levels.
[0015] FIG. 4 is a schematic representation of a main control
algorithm that includes the rebound control and leveled seat height
control algorithms of the present invention.
[0016] FIG. 5 is a schematic representation of the rebound control
algorithm of the present invention.
[0017] FIG. 6 is a schematic representation of the level control
algorithm of the present invention.
DETAILED DESCRIPTION
[0018] Now turning to the drawings wherein like parts are referred
to by the same numbers in the several views, the present invention
method most generally relates to a method for limiting endstop
collisions in semi-active seat suspensions and the method is
represented generally in FIGS. 2-6. As referred to hereinafter the
term endstop shall refer to the end of permissible seat
displacement. FIGS. 1a, 1b and 1c schematically illustrate a
typical seat suspension system adapted for use in combination with
the control method of the present invention where the seat is shown
at different heights. The present invention, senses the seat
position relative to the maximum and minimum endstop limits for
suspension system 10 which supports seat 12 which might be a truck
seat for example, and if the system approaches the endstop either
when the seat is at an extreme leveled height or after an endstop
collision has occurred, the gain supplied to the system is adjusted
to rapidly increase the damping supplied by unit 40. The method of
the present invention serves to greatly decrease travel to the
endstop limits and thereby provides a more comfortable ride to the
driver or passenger occupying seat 12.
[0019] The seat 12 includes a mechanical multibar linkage 14 with
first and second links 21 and 22 shown in FIGS. 1a-c. The linkage
is shown in FIGS. 1a-c is shown in two-dimensions for illustrative
purpose, and it should be understood that the linkage includes
additional members not shown in the Figures. The linkage 14 is
exemplary and it should also be understood that the linkage may be
comprised of any suitable means for movably joining the seat and
suspension system. The links 21 and 22 include respective fixed
location ends 15 and 16 typically rotatably fixed at the back of
the seat, and linearly moveable ends 17 and 18 at the front of the
seat. See FIGS. 1a-1c. The linearly movable ends of links move in a
fixed linear path or track 23 and 24 and the rotatable ends 15 and
16 are fixed by a conventional connection that permits the ends 15
and 16 to be rotatable displaced. A pivotal connection 20 joins the
links 21 and 22 and other members (not shown) comprising the
linkage 14. The mechanical linkage is of conventional design well
known to one skilled in the art and therefore further description
of the linkage is not required.
[0020] A spring 60 is conventionally coupled to the mechanical
linkage 14 at a suitable location and the spring serves to adjust
the leveled height of the seat. The spring may be any suitable well
known spring such as a mechanical coil spring or an air spring. The
leveled seat height is the height that the seat assumes when it is
unaffected or substantially unaffected by vibratory disturbances.
The leveled seat height is selected by the rider for comfort, ease
of reaching vehicle controls such as the steering wheel, brake,
clutch and throttle pedal and also personal preference dictates the
ultimate leveled seat height. The leveled height is controlled by
increasing or decreasing the force supplied by spring 60 by
respectively decreasing or increasing the spring height. The change
in height may be effected in a number of ways such as by
mechanically adjusting the coil spring endpoints or by releasing
air from or introducing air into the air spring.
[0021] A conventional position sensor 30 is connected to link 21
and serves to sense the position of the link 21, and the position
sensor is electrically connected to controller 70 which in turn is
connected to conventional magnetorheological (MR) damper 40. The
damper 40 is connected to link 22. The damper 40 may contain any
suitable field responsive material including magnetorheological
(MR) fluid as indicated. The damper serves to control the
displacement of the seat during operation. The electrical signals
are supplied to the damper during system operation to provide
damping sufficient to prevent the system from reaching the maximum
and minimum endstop limits. The damper 40 may be comprised of any
suitable controllable damper such as a servo valve controlled
damper for example.
[0022] A conventional microprocessor based controller 70 for
processing the sensor signals and actuating the method of the
present invention may be located in the same control housing as
sensor 30 as shown in FIGS. 1a, 1b, and 1c. The controller is
electrically connected to the memory 50. However the controller and
sensor may be discrete components that are not collocated in the
same housing. The control method 200 operates using conventional
microprocessor based technology well known to one skilled in the
art and therefore further detailed description of the
microprocessor technology is not required.
[0023] The damper 40 serves to control the displacement of the seat
during operation. The electrical signals are supplied to the damper
during system operation to provide damping sufficient to prevent
the system from reaching the maximum and minimum endstop limits 90
and 91.
[0024] The control method 200 includes at least three subroutines:
main ride control algorithm 500, rebound control algorithm 300 and
level control algorithm 400. The main seat or ride control routine
500 is not described in detail herein. See FIG. 4. The main ride
control routine controls the seat during typical inputs and the
present invention controls the seat damping when non-typical inputs
or endstop collisions are experienced. The main ride control
algorithm 500 may be comprised of the control method described in
U.S. Pat. No. 5,276,622 for "System for Reducing Suspension
End-Stop Collisions" or U.S. Pat. No. 4,821,849 for "Control Method
and Means for Vibration Attenuating Damper" which control a seat
suspension system when it experiences typical inputs.
[0025] FIG. 4 schematically illustrates the control algorithm of
the present invention 200 for limiting endstop collisions in
semi-active seat suspension system. As indicated above, in addition
to main control routine 500, the algorithm 200 comprises a rebound
control algorithm 300 and level control algorithm 400 and
algorithms 300 and 400 are graphically illustrated in FIGS. 5 and 6
respectively. As the algorithm 200 is executed both algorithms are
continuously and rapidly executed. Sensor 30 continuously monitors
the leveled seat height and also the proximity of the seat to
maximum and minimum endstop detection thresholds 100 and 101 to
determine the branches or sections of algorithms 300 or 400 to be
executed to limit endstop collisions.
[0026] In algorithm 200 the position sensor 30 continuously
monitors the change in position of link 21 over time. See Step 201.
The change in position of link 21 over time represents the relative
velocity of the seat 12. See Step 202. In Step 203, the leveled
seat height is sensed by sensor 30. The sensed relative seat
position and relative seat velocity are provided to algorithms 300
and 400 when they are executed. Additionally, the values for
maximum seat position and minimum seat position are supplied to the
controller and are used to calculate the distance to the end stop
limit 90 or 91. In Step 204, the algorithm 200 determines if the
seat is within the predetermined normal leveling zone (hereinafter
"NLZ") for the particular seat model and manufacturer. When the
leveled seat height is outside the normal leveling zone or NLZ, the
level of damping applied to the seat is increased pursuant to the
logic of level control routine 400. When it is determined that the
seat has traveled past either a maximum or minimum endstop
detection threshold 100 or 101, the level of damping applied to the
seat is increased pursuant to the logic of rebound control routine
300.
[0027] Turning to the rebound control routine 300 shown in FIG. 5,
in Step 301 the seat position is compared to the minimum and
maximum detection thresholds 100 and 101 and if the seat position
exceeds either threshold limit the gain applied to the damper
control signal is significantly increased to rapidly increase
damping supplied by damper 40 and thereby prevent residual endstop
collisions. As the description proceeds the terms minimum detection
threshold and maximum detection threshold may also be referred to
in abbreviated form respectively as MINDT and MAXDT.
[0028] FIG. 3 schematically illustrates the range of displacement
for suspension system 10 as well as the approximate locations of
the maximum and minimum endstop detection thresholds 100 and 101
relative to respective maximum and minimum endstops 90 and 91. Also
see FIGS. 1a, 1b and 1c which identify endstop positions 90 and 91.
The rebound control routine 300 increases the gain supplied to the
damper control signal when the seat suspension experiences
non-typical disturbances that cause the seat to move past either
threshold 100 or 101 and such non-typical disturbances may even
produce endstop collisions. The routine 300 does not effect the
gain applied to the damper control signal when the seat position is
located between the threshold boundaries along position 102. It
should be understood that although the endstops 90 and 91 are shown
oriented vertically relative to each other in FIG. 3, the endstops
may be oriented relatively horizontally as shown in FIGS. 1a, 1b
and 1c.
[0029] Again turning to rebound control algorithm 300, the absolute
value of the velocity calculated in Step 202 is taken in Step 302.
If in Step 301 it is determined that the leveled seat height is
either less than the minimum endstop detection threshold (MINDT)
101 or the leveled seat height is greater than the maximum endstop
detection threshold (MAXDT) 100, the timer is started in Step 303
and then in Step 305 the absolute value of the velocity calculated
in Step 302 is multiplied by a predetermined gain factor stored in
memory 50. The gain constant may be a factor of two or three. The
predetermined gain factor is the multiplication factor that has
been determined as the suitable value for the particular seat
suspension in use. By maximizing the multiplied gain factor
residual endstop collisions, are prevented. In Step 304 the rebound
gain factor is obtained from memory 50, and in Step 305 the product
of the absolute value of the seat velocity (identified as E in Step
305) is multiplied by the gain factor (identified as F in Step
305). The product obtained in Step 305 represents the rebound
control signal required to limit endstop collisions and in Step 306
the rebound control signal is sent to damper 40 to control the
motion of seat 12. The routine 300 then returns to Step 201 to
again determine the position of the seat. Ultimately, the damping
forces applied during a non-typical input event may be two or three
times greater than the damping forces applied during typical input
events. If after the rebound control signal is sent to the damper
the seat still has exceeded the MINDT or MAXDT values, the timer is
again restated in Step 303 and Steps 305 and 306 are executed as
previously described.
[0030] The product calculated in Step 305 is one component of the
control signal that is ultimately transmitted to damper 40. The
rebound control signal calculated in Step 305 is added with other
component control signals in the control sum Step 205 of algorithm
200 to arrive at a control signal value. For example, the control
signal of Step 306 may be summed with component signals received
from main ride routine 500 and the level control routine 400
described hereinbelow. The summed rebound control signal of Step
205 is applied to damper 40 as the damper control signal.
[0031] If in Step 301 it is determined that the seat position has
not exceeded either of the detection thresholds 100 or 101, the
algorithm will not apply the gain factor to the rebound control
signal. The gain factor is momentarily set equal to zero. If the
MINDT and MAXDT values have not been exceeded and the routine timer
is running in Step 307, the routine 300 compares the actual timer
value to the predetermined timer limit retrieved from memory 50 in
Step 309. If the actual time has exceeded the timer limit, (usually
about one second) then the timer is stopped in Step 310 and the
gain factor is momentarily set to zero. In Step 307 if the timer is
not running the gain factor is momentarily set to zero in Step 313.
When Steps 313 and 311 are executed the product in Step 305 will be
zero so that the rebound control algorithm component summed in Step
205 will also be zero.
[0032] If in Step 308 the timer has not exceeded its predetermined
limit, the timer is incremented in Step 312 and the routine
proceeds to the production of the rebound control signal in Step
305 as previously described hereinabove.
[0033] Although the rebound control routine 300 of the present
invention is shown and described as controlling the gain factor
when the seat exceeds either the maximum or minimum threshold
detection limits it should be understood that the system may only
effect the gain when one of the endstop detection thresholds is
exceeded plus a finite time interval. For example the gain may only
need to be considered when the minimum endstop detection threshold
is exceeded. In such a situation the seat occupant's weight in
combination with the stored energy of the compressed spring will
force the seat back towards the opposite endstop thus requiring a
significant increase in the supplied damping to prevent a collision
with endstop 90. Conversely when the seat is at the height of its
travel, the spring 60 is fully extended and has no stored energy
making is less critical to significantly increase damping supplied
by damper 40.
[0034] Now turning to the level control algorithm 400 shown
schematically in FIG. 6, the level control algorithm serves to
prevent endstop collisions when the seat is leveled at a position
that is outside a predetermined normal leveling zone or NLZ for the
particular seat in use. In Steps 204a and 204b the routine 400
determines if the seat has been leveled at a height that is outside
of the normal leveling zone NLZ identified as 113 in FIG. 3.
[0035] The seat position sensed by sensor 30 in Step 201 is sent to
the controller and in Step 202 the derivative of the position or
the change in position per unit time. The absolute value of the
velocity calculated in Step 202 is taken in Step 403.
[0036] In Step 402, the leveled seat height is computed using a
suitably tuned low pass filter of conventional design is compared
with the normal leveling zone maximum limit 103 and the normal
leveling zone minimum limit 104 in respective Steps 404a and 404b.
See FIG. 6. The maximum and minimum limits are shown in FIG. 2. If
in Step 404a it is determined that the leveled seat height is in
zone 110 and is therefore above limit 103 and the NLZ as shown in
FIG. 2, Step 405a determines where in the zone 110 the leveled seat
height is located. If in Step 404b it is determined that the
leveled seat height is in zone 112 and is therefore below limit 104
and below the NLZ, Step 405b determines where in the zone 112 the
leveled seat height is located. In respective Steps 405a and 405b
the difference between the leveled height and the above normal
minimum and the below normal maximum values are taken. The
difference calculated in Step 405a and 405b is summed in Step 406
with other calculated values. If in Steps 404a or 404b it is
determined that the leveled height is within the NLZ, the sum is
set equal to zero in Step 411.
[0037] In Step 407 the non-NLZ gain is read from memory 50. The
stored gain is a predetermined constant value for the particular
seat in use. In Step 408 the non-NLZ gain is multiplied by the
value of the deviation from the NLZ to arrive at the gain factor.
As shown in FIG. 2, the gain factor calculated in Step 408
increases as the seat approaches the endstop limit once the seat
enters either the above normal leveling zone 110 (above point C) or
the below normal leveling zone 112 (below point B). The value of
the gain factor is constant in the NLZ, between points B and C, in
FIG. 2. The gain factor is at a maximum value at the endstops 90
and 91 also identified as points A and D in FIG. 2. The gain factor
increases substantially linearly in zones 110 and 112 between
points C and D and B and A respectively.
[0038] FIG. 2 illustrates a linearly increasing gain factor as the
leveled seat height is at increasing distances from the NLZ maximum
limit or is at decreasing distance from the NLZ minimum limit. It
should be noted that any non-linear function, such as a squared
relationship could be implemented to increase the gain factor. An
example of a non-linear function is represented in dashed font in
FIG. 2.
[0039] By maximizing the gain factor at the endstop collision, the
tendency for a rebound collision with the opposite endstop will be
minimized. Turning to FIG. 6, in Step 408 the non-NLZ gain constant
(identified as G in Step 407) is multiplied with the sum arrived at
in Step 406 (identified as H in Step 406) and this product
(identified as J in Step 408) is the gain factor. The gain factor
is in turn multiplied with the absolute value of the relative seat
velocity (identified as K in Step 403) to arrive at the non-normal
leveling zone control signal that is transmitted to damper 40. The
signal of Step 410 is summed in Step 205 as previously
described.
[0040] By algorithm 400 when a seat is leveled outside a predefined
normal leveling zone for the seat, the algorithm will adjust the
applied gain factor according to the relationship of FIG. 2 so that
endstop collisions that are a result of leveling the seat proximate
the endstops will be limited. In this way, the increased damping
force is a preventative measure for limiting endstop collisions
[0041] While I have illustrated and described a preferred
embodiment of my invention, it should be understood that this is
capable of modification, and I therefore do not wish to be limited
to the precise details set forth, but desire to avail myself of
such changes and alterations as fall within the purview of the
following claims.
* * * * *