SYSTEME ASSURANT INDEPENDAMMENT LE GUIDAGE ET LA PROPULSION D'UN VEHICULE HORS ROUTE

INDEPENDENT STEERING AND PROPULSION SYSTEM FOR OFF ROAD VEHICLE

Abrégé anglais

TITLE
INDEPENDENT STEERING AND PROPULSION SYSTEM FOR OFF ROAD VEHICLE
ABSTRACT OF THE DISCLOSURE
A high mobility wheeled vehicle for transporting long loads,
such as trimmed tree trunks or whole trees, over roadless terrain.
The vehicle has front and rear quad wheel assemblies pivotally
connected to a centrally disposed elongated bed frame so as to
permit lateral rotation of these assemblies about a roll axis
disposed below and parallel to the longitudinal axis of the bed
frame. A linkage type roll control means interconnects the quad
wheel assemblies and the bed frame to proportionately control the
relative angular movement of the bed frame with respect to the
quad wheel assemblies. The roll control means includes a plurality
of interconnected links plus a pair of power extensible links for
selectively adjusting the steady state position of the vehicle
bed relative to the quad wheel assemblies in either direction.
The quad wheel assembly incorporates a unique mounting for
each of the wheels of the assembly which provides for individually
controlled motors for driving each wheel, individually controlled
brakes, and individually controlled, power actuated extensible
links for steering each wheel. Sensors are provided on each
wheel assembly which generate signals proportional to the rota-
tional velocity and direction of the wheel and proportional to
the turning angle of each wheel. A microprocessor receives all
such signals and compares same with a desired turning angle and
rotational velocity of the wheels in accordance with one of a
plurality of modes of operation of the vehicle selected by the

operator, and generates appropriate control signals to the
individually controlled wheels to adjust the turning motion and
the rotational velocity to that required to effect the desired
movement of the vehicle.

Revendications

The embodiments of the invention in which an exclusive
property or privilege is claimed are defined as follows:
1. The method of moving a multi-wheeled off-road vehicle
of the type having means for driving each wheel, an individual
steering means for turning each wheel about a radius on the
order of three feet, and an individual brake for each wheel,
under terrain conditions wherein movements of the vehicle by
wheel traction is impossible, comprising the steps of:
(1) locking each wheel against rotation
by application of the brake thereto; and
(2) turning all wheels on one side in
the same direction relative to the vehicle,
and concurrently turning all wheels on the
other side in the opposite direction.
2. The method of moving a multi-wheeled off-road vehicle
of the type having means for driving each wheel, an individual
steering means for turning each wheel about a radius on the order
of three feet, and an individual brake for each wheel, under
terrain conditions wherein movements of the vehicle by wheel
traction is impossible, comprising the steps of:
(1) locking each wheel against rotation
by application of the brake thereto;
(2) turning all wheels on one side in
the same direction relative to the vehicle,
and concurrently turning all wheels on the
other side in the opposite direction, and

(3) successively releasing the brakes on
each opposed pair of wheels and successively
repositioning each such pair of wheels in the
reverse direction relative to the vehicle.
3. The method of laterally moving a multi-wheeled vehicle
of the type having an individual drive motor for each wheel, an
individual steering means for turning each wheel about a radius
on the order of three feet, and an individual brake for each
wheel, comprising the steps of:
(1) turning all wheels on the vehicle
in the same direction relative to the
vehicle with the brakes off;
(2) turning all wheels on one side of
the vehicle with the brakes applied to
prevent rotation, and concurrently
(3) turning all wheels on the other
side of the vehicle in reverse direction to
their original movement with the brakes off
until all wheels reach a parallel position
to the vehicle, whereby the vehicle is
bodily laterally shifted.
4. The method defined in claim 3 plus continuing the last
mentioned turning movements beyond the said vehicle parallel
position but applying the brakes to lock the wheels on said other
side and releasing the brakes from the wheels on said one side
when the wheels pass their vehicle parallel positions.
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5. The method of laterally moving a multi-wheeled vehicle
of the type having an individual reversible traction motor for
each wheel, an individual steering means for turning each wheel
about a radius on the order of three feet, comprising the steps of:
(1) turning all wheels on the vehicle in the same
direction about their respective steering axes to
assume a skew steering mode, said turning being
accomplished without twisting of the wheel surfaces
against the supporting surface;
(2) applying traction power concurrently to
all wheels in the same direction to move the vehicle
body diagonally relative to its longitudinal axis;
(3) turning all wheels on the vehicle about their
respective steering axes in the opposite direction
to that accomplished in step (1) to assume a skew
steering mode reverse to that assumed in step (1),
said turning being accomplished without twisting of
the wheel surfaces against the supporting surface, and
(4) applying traction power concurrently to all
wheels in the direction opposite to that in step (2)
to move the vehicle body diagonally relative to its
longitudinal axis in the same lateral direction as
step (2) but the reverse longitudinal direction,
thereby effecting a bodily lateral movement of
the vehicle with little, if any, longitudinal
displacement of the vehicle.
6. The method defined in claim 5 wherein traction power
is applied to each wheel to assist the performance of steps (1)
and (3).
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7. The method according to claim 1 wherein the multi-
wheeled vehicle is of the type having an individual steering
actuator for turning each wheel between fixed angularly
limited positions and a microprocessor for controlling the
steering position of each wheel as a function of the posi-
tion of a selected master wheel; and skewing said vehicle
comprising the steps of selecting one of the rear wheels
as the master wheel whenever it is required to turn the
vehicle in a direction prohibited by the existing skew
position of the wheels, and turning said master rear wheel
in the direction opposite to the desired turn direction.
8. The method according to claim 1 wherein said multi-
wheeled off-road vehicle has laterally opposed pairs of
wheels;and braking said vehicle comprising the steps of
turning at least one laterally opposed pair of wheels in
opposite directions, whereby said pair of wheels function as
plows to resist movement of the vehicle.
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Description

" CROSS REFERENCE TO RELATED APPLICATIONS
~ This application is related to U.S. Patent No.
!1'4,153,265.
Certain of the structure disclosed in this application
is disclosed and claimed in my U.S. Patent No. 4,223,904.
10 ~
SUMMARY OF THE INVENTION
Generally speaking, this invention relates to self-propelled
vehicles used primar;ly to transport long loads across roadless
I terrain. More specifically,- it relates to rubber tired vehicles
¦ that have wheel suspension mechanisms which provide balanced
I weight between its wheels and additionally permits adjustment of
¦l the steady state position of the main bed frame of the vehicle
relative to a longitudinal roll axis to permit compensation for
, the vehicle position when operating continuously on the side of a
20 ¦I hill, and also to facilitate unloading of the vehicle by a side
,l dumping action in either direction.
¦l In summary, the vehicle comprises an elongated bed frame
that forms the backbone of the vehicle. This frame is balanced
on the central portion of modular front and rear wheel assemblies,
i preferably each having four quadrilaterally spaced wheels. The
quad wheel suspension system is designed to provide a freedom of
movement of each wheel about mutually perpendicular roll and
pitcll axes that are vertically spaced one above the other. The
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quad wheel assemblies are pivotally mounted on the bed so as to
be movable about a roll axis which is parallel to and beneath the
I longitudinal axis of the main frame element. On the lower or
1 pitch axis of each quad wheel assembly, two walking beam me~bers,
¦ each carrying a pair of steerable wheels, are roc~ably mounted in
a balanced relationship. Thus the walking beams may rock about
¦I the pitch axis of the quad wheel assembly while the quad wheel
I assembly itself may pivot about the roll axis. A mechanical
¦ interconnection comprises a pair of tubular torque transmission
L0 I members that extend from one quad wheel assembly toward the other ¦
and are interconnected by a novel lin~age system which continuously
ad]usts the position of the longitudinal bed frame about the roll I
axis to lie intermediate the positions of the quad wheel assemblies.
I Additionally, the lin~age incorporates two power extensible links
~ by which the steady stat~ position of the longitudinal bed frame
~ member relative to the roll axis may be selectively ~etermined b~
i the operator.
¦ In accordance with the invention specifically clisclosed and
I claimed in my aforclnentioncd co-pending applicat;on, S.N.
I 9 ~ Sq , a unique mount;ng of ~ach wheel with respect
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to the wal~ing beam mcmber permits a driving motor and brake to
be incorpoL-ated in the wheel mounting mechanism for imparting
required rotational mov.nlents to the wheel and, additionally, an ¦
1 electrical or llydraulic actuator is also incorporated in the
,~ mo-nting to impart individuall~ controlled steering movements to
the particular wheel. ~dditionall~, sensors are pro~ided which
generate signals respectivel~T proportional to the rotational
velocity of the wheel and to the angle of turn of the particular
wheel. These sensor sigllals are inputs to a microprocessor and
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¦l are compared with the turning position and rotational velocity of
¦, the wheel required to effect a particular attitude and movement
¦ of the vehicle, and compensating signals are then fed to the
driving motor for the wheel and the turning actuator to cause the
' wheel velocity and wheel position to correspond to that required
to effect a desired attitude of the vehicle.
'i A vehicle equipped with this combination of features has
, numerous advantages over prior art off-road vehicles. The indi-
1~ vidual control of the veloci-ty and the turning angle of each
¦I wheel permits the vehicle to be manipulated through any selected
one of a plurality of unusual movements o-c attitudes, most of which
are completely incapable of accomplishmen-t by any vehicle equipped
with conventional driving and steering mechanisms. The vehicle
~ can, of course, proceed in a straight line, either for~ardly or
~ rearwardly. The microprocessor can be programmed to cause the
vehicle to turn according to the Ackerman principle which govexns
the turning of most conventional vehicles, but here the individual
colltrol of the rotational velocity ~nd turning angle of each
¦ wheel permits a prec;se ~ckerman turn to be accon~plished. All
¦ wheels of the vehicle can be simultaneously -turned a fixcd number
of degrees to cause the vehicle to boclily nlove in a path angularly
disposed with respect to its longitudinal axis. If the vehicle
is operating on a steep hillside, under treacherous conditions, a
number of opposed wheels of the vehicle can be turned at an a~gle
~5 l, opposing further movement in the direction of the hill slope and
~I thus providing a very effective braking of the vehicle. ~y
following a predetermined sequence of rotational, braking and
turning movements of each wheel of the vehicle, it is possible to
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nchieve a bodily lateral displacement of the vehicle when by some
misfortune it gets into a position on the rough terrain where it
can neither move forwardly or rearwardly. Similarly, when the
vehicle is mired in a bog or hung up on an obstacle such as a
high stump or a boulder, a series of turning movements of pairs
of the wheels can result in a bodily longitudinal displacement
of the vehicle. It necessarily follows that the ultimate flexi-
bility of movement of the vehicle is provided by the methods and
apparatus of thls invention.
Aoo~ng to a broad aspect, the invention relates to:
The metAod of ~oving a ~ulti~wheeled off-road ~ehicle
of the type having means for dri~ing each wheel, an individual
steering means for turning each wheel about a r~dius on the
other of three ~eet, and an individual ~rake for each wheel,
under terrain conditions wherein movements of the vehicle by
wheel traction is impossible, comprising the steps of:
(1) locking each wheel against rotation
by application of the brake thereto; and
(2) turning all wheels on one side in
the same direction relative to the vehicle,
and concurrently turning all wheels on the
other side in the opposite direction.
Aoo~ng to a further brcad a~x~t, the ~nvention relates to:
The method of laterally moving a multi-wheeled vehicle
! Of the type having an individual reversible traction motor for
each wheel, an individual steering means for turning each wheel
about a radius on the order of three feet, comprising the steps of
~1) turning all wheels on the vehicle in the same
direction about their respective steering axes to
assume a skew steering mode, said turning being
accompli~hed without twisting of the wheel surfaces
again~t the ~upporting surface;
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(2) applying traction power concurrently to
all wheels in the same direction to move the vehicle
body diagonally relative to its longitudinal axis;
(3) turning all wheels on the vehicle about their
respective steering axes in the opposite direction
to that accomplished in step (1) to assume a skew
steering mode reverse to that assumed in step (l),
said turning being accomplished without twisting of
the wheel surfaces against the supporting surface, and
(4) applying traction power concurrently to all
wheels in the direction opposite to that in step (2)
to move the vehicle body diagonally relative to its
longitudinal axis in the same lateral direction as
step (2) but the reverse longitudinal direction,
thereby effecting a bodily lateral movement of
the vehicle with little, if any, longitudinal
displacement of the vechicle.
Other advsntages and ob~ects will become more apparent when
the following description is read with reference to the accompany-
ing drawings.
BRIE~ DESCRIPTION OF DRAWINGS
Figure 1 is a side elevational view of a complete vehicle
embodying the wheel suspension mechanism of this invention.
Figure 2 is a front elevational view of the vehicle of
Figure 1.
Figure 3 i8 a plan ~iew of the vehicle of Figure 1.
Figure 4 is an enlarged partial perspective view of the
~uspension mechanism for the quad wheel assemblies utilized in
the vehicle of Figure 1.
Figure S i8 an enlarged partial perspective view illustrating
the roll control linkage for the wheel suspensions incorporatedin the ~ehicle of Figure 1~
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Figure 6 is a block diagram of the control system embodying
this invention.
Figures 7a, 7b and 7c are schematic diagrams illustrating
the lateral shift mode of operation of the vehicle.
Figures 8a and 8b are schematic diagrams illustrating the
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traction shift mode of operation of the vehicle.
Figures 9a and 9b are schematic views illustrating the
operation of the vehicle in either of two braking modes.
~i Figure 10 is a schematic view illustrating an Ackerman
steering mode of a vehicle with the steering center located along'
~' a line that is perpendicular to the vehicle longitudinal axis and
j passes through the center of the vehicle.
¦, Figure 11 schernatically illustrates a modified Ackerman
, steering mode about a center located at the rear of the vehicle on
~ a line perpendicular to the vehicle longitudinal axis and passing
through the rear of the vehicle.
Figure 12 schematically illustrates a skew steering mode of
the vehicle in a right direction.
I Figure 13 schematically illustrates the turning of the
15 1 vehicle while in the skew steering mode.
¦ Figures 14a - 14f schematically illustrate a modified form
of lateral shift operation emplo~ing recurring cycles of skewed
movements.
~ .T~I`IFD DESCRIPTION OF INVENTIOrl
The vehicle illustrated in th~ dra~ings ls a transportation
vehicle such as one used Eor forwarding tree lengths from a
harvesting area in a forest to a landinc~ adjacent to a road.
I Referring particularly to Figures 1 - 3 of the drawings, it will
¦' be seen that the vehicle 20 is comprised of an elongated bed
1 frame assembly 21 including load-carrying cradle assemblies 22
I adapted to carry a plurality of tree lengths 23. Front and rear ¦
quad wheel assemblies 24, 26 are respectively attached to the bed
I frame assembly 21 by journals so as to be pivotally rnovable about,
! a longitudinal roll axis disposed parallel to and beneath the bed
¦~ frame assembly 21. A roll control linkage means 28 interconnects
the quad wheel assemblies with each other and with the elongated
Il' bed frame assembly so as to control their relative positions
! during operation over rough terrain. Preferably an engine unit !
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30 is located at the rear end of the vehicle, and an operator's
cab 31 is located at the front end.
The illustrated bed frame assembly 21 comprises an elongated
bed frame element 32 extending lengthwise along the ce~ter line
of the assembly. The bed frame 32 which serves as the backbone
of the vehicle may be a rectangular tube. A plurality of rigid
bed cross beams 38 extend laterally outwardly from the bed frame
structure in both directions to form the load-carrying cradles
~ 22. Upright side stakes 44 may be provided on the outer ends of
! the cross beams. The stakes, along one or both sides, may be
~ releasably mounted to permit sidewise dumping of the load on
¦ either side by appropriately tilting the bed frame assembly 21
¦ about the roll axis of the wheel suspension assemblies.
¦ In the drawings it will he noted that the front and rear
¦ quad wheel assemblies 24, 26 are substantially identical to one
another, so for the sake of brevity, the similar portions will be
described with respect to one of them only. Accordingly, attention
is directed to Figure ~ of the drawings wherein the details of
the front quad wheel assembly 24 are illustrated.
I The suspension system for the front quad wheel assembly
includes a main pivot block 46 which is pivotally suspended
beneath the tubular bed frame 32 between a pair of depending
blocks 32a, thus providing pivotal movement about a longitudinal I
I horizontal roll axis which is parallel to and slightly below the ¦
I axis of the tubular bedframe 32. Such pivotal mounting is not
;! shown but is entirely conventional. A torque transmission tube 94
¦ extends rearwardly from the main pivot block 46 and is co-movable
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therewith about the vehicle roll axis. A similar tube 95 extends j
forwardly from the rear quad wheel assembly and the adjacent ends
of tubes 94 and 95 are respectively interconnected by a roll
control linkage mechanism 28 to be hereinafter described.
The bottom portion of main pivot block 46 is provided with a
pair of laterally projecting horizontal pivot pins 46a which
respectively provide pivotal mounting for a pair of walking beams
48 which are of identical configuration except that they are
mounted in reversed positions on the pivot pins 46a. Each
walking beam 48 is of a generally truncated W-shaped configuration
in plan view including a central truncated V-shaped portion 48a
defining the bearing for the pivotal mounting on pin 46a and
identical angularly disposed arcuate end elements 48b which
provide mountings for steerable wheel units 58 of the quad wheel
assemblies. The ends of arm portions 48b are bifurcated as
indicated at 48c and the bifurcated ends are traversed by a
vertical pivot unit 48d which pivotally supports a central
cylindrical portion 50a of wheel spindle or drive housing 50. At ¦
its outer end, the axle hous;ng 50 terminates in a power driven
cylindrical hub 50b to which a wheel 58 is rigidly secured in
conventional fashion. The inner end of housing 50 defines a gear I
chamber 50c plus a mounting flange 50d for mounting an electricallly
or hydraulically driven reversible motor 54 by which the wheel 58 !
is driven. The gearing mechanism interconnecting the reversible
motor 54 with the wheel hub 50b may be entirely conventional and !
need not be described in detail. The extreme inner end of wheel
mounting housing 50 is provided with a pair of bifurcated lugs
50e which pivotally mount the apertured end of a steering ac-tuator
56. The other end of actuator 56 is pivotally mounted to the
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bottom portion 48e of the truncated W-shaped walking beam 48.
l~hile actuator 56 may be hydraulically operated, I prefer to
~ employ an electrically driven actuator and hence an actuator
Ii motor 57 is mounted on the actuator 56 and effects the extension
'. or retraction of actuator 56 to in turn effect a steering motion
of the associated wheel 58.
Within housing 50, a suitable power actuated brake (not
1 shown) is also provided.
.l From the description thus far, it should be apparent that
I the steering movements of the wheels 58 about the respective
steering pin units 48d involve a much larger turning radius, from
one to four feet, depending on the size of the vehicle, than i~
customarily employed in wheeled vehicles. As will be described,
this large turning ràd.ius is of significant advantage in effec-
ting either a longitudinal or a lateral bodily displacement of
the entire vehicle through the combination of limited steering,
braking and rotational movements of the wheels in a selected
sequence. Obviously, both the wheel driving motors 54 and the
steering actl1ator motors 57 must have suficient power to effect
I the desired rotation of the wheels and steer.ing of the wheels
under the very adverse condi.tions encountered .in off-road oper- .
I ations. Such power may be suppl;ed :[rom a generator (not shown)
¦ driven by the engine 30.
I From the description thus far, it is also apparent that eac
I quad wheel assembly 24, 26 is suspended relative to the main bed
frame element 32 in such fashion that the bed frame may pivot
¦i rel.ative to the quad wheel assemblies about a roll axis which is ¦
l parallel to and slightly beneath the main bed frame element 32.
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¦, Concurrently, the wheels on each side of the quad wheel assembly
Il may freely move in a vertical plane about a horizontal pivot axis
defined by the walking beam pivot pin 46a. Moreover, due to the
! w shape of each walking beam 48, steering movements of each of
. the wheels up to a thirty degree (30) angle may be accomplished
', in either direction without interference with the suspension, the
main frame or load carrying cradles of the vehicle.
' The relative angular movement of the quad wheel assemblies
Jl 24, 26 with respect to each other and to the elongated bed frame
11 assembly 21 is regulated by a roll control linkage 28, centrally
located on the vehicle, that causes equal loading to be imposed
on each quad wheel assembly, and also causes the bed frame
assembly to be rotated proportionately, preferably one half the
total angular displacement between the front and rear quad wheel
j assemblies, as exists at any one time. Angular displacement
between the quad wheel assen~lies relative to the roll axis
obviously occurs during operation on uneven terrain or over
i boulders. The ground under the fxont quad wheel assembly may be
! laterally and possibly opposltely .inclined to the ground under
1I the rear quad wheel assembly, such as might occur while the
!I vehi.cle is traversing a d.itch at an angle.
Referring now to Fi~ure 5, the roll cont.rol linkage 28 will
! be described in greater detail. The rearward end of torque tube
! 94 and the forward end of torque tube 95 are suitably journaled
j in a depending frame block 32m and are disposed in spaced co~
axially aligned relationship approximately in the center o~ the
! elongated frame mem~er 32. Immediately above and between the
ends of the torque tubes 94, 95, the base member 32 is provided
with a pair of upstanding pivot ears 32f which support a pivot
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pin 32g which traverses the center portion of a transverse frame
tilt lever 33. On each end of frame tilt lever 33 a longitudinal
connecting lever 35 is mounted for pivotal movement about a
Il horizontal axis. Additionally, on each end of torque tubes 94
1 and 95 there are respectively rigidly secured primary transverse
¦i actuating levers 96 and 97 and the ends of these levers are in
1, general vertical alignment respectively with the ends of the
li connecting levers 35. A plurality of links 37 are provided
¦, respectively having their ends connected by a universal joint
¦I connection to the aligned ends of primary levers 96 and 97 and
I' the connecting levers 35. Thus, any pivotal movement of one of
¦ the quad wheel assemblies 24, 26 relative to the other will
result in a pivoting movement of the associated primary lever 96,
I 97 which in turn effects a tilting movement of the main tilt
I control lever 33 to shift the position of the main frame 32
approximately one half the amount of pivotal displacement of the '
quad wheel assembly relative to the roll axis. ~hus a very
I effective control of the movements of the main rame about the
¦ roll axis in response to much larger movements of the quad wheel l
~ assemblies is achieved and, in effect, the pivoted lever connection
control means 28 provi.de~s for ba.lancing the eE~ects of rotations
of the two quad wheel assembl.ies in op~-ositc dire~ctions about the
roll axis on the main frame assembly.
! Concurrently the roll control linkage eEfects a transfer of
, forces between the two quad wheel assemblies to equalize the
loading thereof during movements about the roll axis. I
A further feature of this vehicle suspension is the addi,ion¦
to the roll co~trol lever assemblage 28 of a pair of power
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'actuated stabilizing links which permit the operator to ad~ust
¦the static position of the tuhular main frame 32 relative to the
roll axis. Referring to Figure 5, such links may comprise the
~power actuated extensible elements 43 which are respectively
,connected between the extreme ends of the tilt control lever 33
and the bifurcated ends of lateral projections 32k, formed on the
depending block 32m, provided on the underside of the tubular bed
frame 32. As the one stabilizing link 43 is extended by the
llapplication of either hydraulic or electric power thereto, the
¦other link 43 is retracted so that the net effect is that the bed
¦frame 32 and the load supporting cradles or cross-beams 38 are
shifted angularly with respect about the roll axis. Thus, the
¦load may be maintained in a substantially horizontal position,
~even though the vehic~le is being operated continuously on a
hillside. This capability for adjusting the static angular
position of the load carrying cradles relative to the roll axis
provides additional stability to the vehicle and hence permits
larger loads to be safely carried along a relatively steep
hillside.
An extrerne extension of either link ~3 can efEect the
~dumping of the load on a selected side oE the vehicle.
The method and apparatus ~or individually con~rolling the
direction and speed oE rotation of each wheel and the turn angle
will now be described. Referrin~ to the control circuits sche-
matically illustrated in Figure 6, it will be noted that sensors
¦are incorporated within the wheel drivins mechanism in conven-
tional fashion so as to provide an electrical signal proportional
to the direction and velocity or rotation of the respective
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I wheel, Similarily, a turn angle sensor is incorporated in the
¦ steering linkage for each wheel to continuously generate a signal
I proportional to the turning angle of such wheel. Since these
¦¦ sensors are completely conventional, they are not shown in
detail.
There is shown in Figure 6 a propulsion and steering control
system for controlling the direction, speed of rotation and turn
angle for each wheel of the vehicle. There is provided for the
operator a steering wheel 201, a control panel 202 and a throttle
or speed selector 203. Information with respect to the positions
of the steering wheel 201 and the speed selector 203 is provided
to a microprocessor 204 to control respectively the turn angle of
the vehicle and the speed of the vehicle The control panel
generates information to the microprocessor concerning the desired
steering, rotational speed and braking condition of each wheel of
the vehicle to accomplish a desired movement or attitude of the
vehicle. The microprocessor uses the inputted information to
generate control signals to a propulsion motor, brake and a steer-
ing motor for each of the wheels of the vehicle.
There is shown a wheel 205 which represents any one of the
eight vehicle wheels. The wheel 205 is mechanically coupled to a
propulsion motor 206 which controls the direction and speed of
rotation of the wheel. The propulsion motor 206 corresponds to
the reversible motor 54 shown in Figure 4. A tachometer 207 is
2S ¦ mechanically coupled to the propulsion motor 206 to generate a
! speed signal having a polarity which represents the direction of
¦¦ rotation of the wheel and a magnitude which represents the speed
¦l of rotation of the wheel. The tachometer 207 could be replaced
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by a pair of sensors, one of which generates a signal repre- I
senting the direction of rotation and the other of which generates
a signal representing the speed of rotation of the wheel. The
output signal generated by the tachometer 207 is converted from
analog to digital form by an analog-to-digital converter 208 and
generated as a digital actual wheel speed signal to the micro-
processor 204. The microprocessor 204 program has a speed
program portion 209 to integrate the difference between a speed
reference signal S and the actual speed signal A to generate a
speed error signal SE to a digital-to-analog converter 210. The ¦
converter 210 generates an analog speed error signal to a motor
controller 211 which receives power from a source (not shown) to
control the speed and direction of rotation of the propulsion
motor 206.
The wheel 205 is also mechanically coupled to a steering
motor 212 which controls the turn angle of the wheel. A shaft
encoder 213 is mechanically coupled to the steering motor
212 output shaft to generate a s.ignal indicating the wheel
position for the wheel 205 to the microprocessor 204. The
microprocessor 204 i5 programmed to integrate the difference
between a steering position reference signal P and the wheel
position signal W rom the shaft encoder 213 to generate a
steering position error signal PE to a digital-to-analog converte:
214. The converter 214 generates an analog output signal to a
motor controller 215 which receives power from a source (not
shown) to control the steering motor 212 to determine the turn
angle of the wheel 205. The motor 212 corresponds to the actuator
motor 57 of Figure 4. A synchro transmitter 216 is mechanically
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¦¦coupled to the shaft encoder 213 and receives an excitation
~¦signal from a source (not shown) to generate a wheel position
ll signal to a synchro receiver 217 to provide an indication of .he
¦I,turn angle of the wheel 205 to the operator of the vehicle as
,iwill be discussed. The elements 205-209 and 211-217 are duplicated
,, for each of the eight vehicle wheels but are not shown in Figure
¦l 6 in order to simplify the schematic.
When the vehicle is in one of the s-teering modes, a selected
Il one of the front or rear wheels is designated as the master ~heel
1I for the purpose of prov.iding a reference for the steering sys.em.
¦! A shaft encoder 218 is mechanically coupled to the steering wheel
¦1 201 to generate a steering wheel position signal SW to the
mi.croprocessor 204. The microprocessor 204 selects as the
master wheel, the w~eel at the corner in the direction of travel
1 and the direction of the turn. Thus, in a forward direction of
travel and a front steer steering mode, the right front wheel
j becomes the master wheel. The wheel position signal W for the
right front wheel is one of the inp~lts to the steering progra~
219 of the microprocessor program. This wheel position signal is
I outputted from the steering program 219 as a master wheel position
signal ~. The microprocessor 204 is programmed to integrate the
!I difference between the s-teering wheel position signal SW from the
¦ shaft encoder 218 and the master wheel position signal MW from
¦ the steering program 219 to yenerate a master wheel position
I error signal ME to the steering program 219. The steering pro~ram
¦! 219 substitutes the master wheel error signal ME for the steering
~l position error signal PE for the selected master wheel. Thus,
il
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113~72
l l
the master wheel is being controlled in accordance with the
steering wheel position while each of the other wheels is being
controlled in accordance with an associated steering position
reference signal,the generation of which will be discussed below. !
A second shaft encoder 221 is mechanically coupled to the
first shaft encoder 218 by a spring coupling 222, The spring
coupling 222 allows the steering wheel 201 to be turned a small
, distance to the right or left and be automatically returned to
¦ the center position when the steering wheel 201 is released when
~ no steering motion is desired. The shaft encoder 221 is mechani- ¦
cally coupled to a steering wheel motor 223 to generate a steering,
wheel motor position signal MP to the microprocessor 204. The
microprocessor 204 iQ programmed to generate a steering wheel
position error signal SWE which is the integral of the difference ¦
between the master wheel position signal MW and the steering
¦ wheel motor position signal MP. This steering wheel position
error signal SWE is generated to a digital-to-analog converter
224 which generates an analog control signal to a motor con-
troller 225 which receives power from a source (not shown) to
I control the position of the steering wheel motor 223. Thus, if
¦ the steering wlleel 201 is turned and maintained in that position,
¦ the microprocessor 204 will generate the master wheel position
¦ error signal ME to turn the wheel which is selected as the
I master wheel to change the value of the wheel position signal W
I generated by the corresponding shaft encoder similar to the shaft
1,' encoder 213. The microprocessor 204 responds to the change in
¦ the wheel position signal W to change the steering wheel position i
li error signal SWE thus effecting the rotation o~ the steering
I
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i
i 11~3~7Z9
! wheel motor 223. The steering wheel motor 223 rotates to a
li position corresponding to the position of the steering wheel 201.
¦~ The rate of turning of the steering wheel motor 223 will be
!I proportional to the force exerted by the operator on the steering
wheel 201. Thus, the steering feedback circuit is a human
engineering feature which provides the operator a feel for the
I position and rate of steering of the vehicle. This steering f
¦ feedback feature can also be utilized when the system is in one
Il of the traction modes. The microprocessor can generate its own
¦I master wheel position error signal ME such that the position of
the steering wheel is automatically chanyed to correspond to the
i controlled position of the master wheel.
~, The operator control panel 202 is utilized for displaying
' wheel position information and generating switchiny si~nals to
I control the operation of the wheels. Each wheel position siynal
from the corresponding synchro transmitter .is an input to a
synchro receiver which is coupled to a wheel position display
device. For example, the wheel position si~nal ~rom the synchro
I transmitter 216 is an input to thc synchro receiver 217 which
, receives its excitation f.rom a source (not shown). The synch.ro
¦I receiver 217 is coupled to an appropriate d:isplay device 226
jl which indicates the wheel position of the corresponding wheel
205. Although not shown, each wheel rnay be similarly coupled to
Il a display device on the control panel 202.
25 l~ The control panel 202 also includes controls for the steeriny
1' modes, traction modes and the braking mode operation of the
¦, vehicle. Each of these steering modes is selected through the
I
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7z9
actuation of a control button such as a push button 227 for
selecting an Ackerman steering mode with a center to the right or !
left of the vehicle (Figure 10); a push button 231 for selec~ing
a modified Ackerman steering mode about a center laterally spaced
l, from the rear or front of the vehicle (Figure 11); a push button,
, 228 for selecting a right skew steering mode (Figure 12); and a
i push button 229 for selecting a left skew steering mode (not
shown). The vehicle can be operated in either the forward or
I; reverse direction in each of the steering modes and a push buttonl
1 232 is provided for selecting the forward direction of travel whi~e
j a push button 233 is provided for selecting the reverse direction
¦ of travel. The vehicle can also be operated in either of two
traction modes which~are a lateral shift and a -traction shift
and respectively produce a bodily lateral movement of the vehicle !
and a bodily longitudinal movement (Figs. 7a, 7b, 7c, 8a and 8b).¦
The lateral shift mode is performed in either the left direction !
I by actuating a push button 234 or in the right direction by
¦ actuatin~ push button 235. AEter the direction of shift is
¦ selected, a push button 236 is actuated to initiate th~ automatic
¦ cycling of the lateral shift mode. In the traction shift mode,
I either a fortiard shiEt can be selected by actuating a push button
¦~ 237 or an aft shift can be selected by actuating a push hutton
¦l 238. After the traction shift direction has been selected, a
~¦ push button 23~ can be actuated to initiate automatic cycling in
I the traction shift mode. In the braking mode, (Figures 9a and
9b) the actuation of a push button 241 will automatically brake
I all of the vehicle wheels and the actuation of a push button 242
jj will automatically brake a program~ed selected number of all o~
Il l
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Il 113~729
the wheels. The operation of the vehicle in each of the steering,
traction and braking modes will be discussed below.
The steering mode switching siynals, the traction mode
switching signals and the braking mode switching signals, generated
by the actuation of selected push buttons on the control panel
202, are inputs to the microprocessor 204. In any of the steering
.,modes of operation, the steering mode switching signals provide
information to a steering proyram portion 243 of the program in
¦! the microprocessor 204. The steering program 243 generates a
llsteering position reference signal P for each of the seven wheels
jlnot selected as the master wheel. These steering position re~erence
signals can be genera-ted either by entering the turn angle of the
master wheel into an equation to generate the position reference
¦values for each of the o~her seven wheels or by selecting the
Iposition reference value in accordance with the turn angle of the
¦Imaster wheel from a set of data stored in a memo.ry 244. The
memory 244 can be included in the microprocessor 204 or can be a
~separate element coupled to the microprocessor 204 to generat~
~,data in response to control siclnals. In either case, a new set
l¦of seven steeri.ng pOSitiOIl reference signals will be genera-ted
each time the master wheel position changes by a predetermlned
¦amount typical.ly equal to the xesolution of the shaft encoder
!!213.
!¦ The magnitudes of the speed reference signals S are deter-
i'.mined by the position of the speed selector 203 which is mechanically
icoupled to a shaft encoder 245 to generate a throttle position
signal to the microprocessor 204. A speed program portion 246 of
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li3~)7Zg
the program of the microprocessor 204 utilizes the speed selector
signal to generate the speed reference signal S for the master
I wheel. The speed program 246 then generates a speed reference
¦~ signal S for each of the wheels in accordance with either an
I equation in the program or a set of relationships stored in the
memory 244. A new set of speed reference signals are generated
each time the position of the speed selector 203 changes by a
I predetermined amount, typically equal to the resolution of the
I tachometer 207.
¦ Each wheel has an associated brake and all of the brakes are
actuated simultaneously by the operator. As shown in Figure 6,
the wheel 205 is mechanically coupled to a brake 247 which in
I turn is mechanically coupled to an associated brake actuator 248.j
The brake actuator is normally controlled by the operator from a
control means (not shown) which generates an operator actuation
signal. This signal can be generated by conventional means such
as a hydraulic or electric brakin~ system control. As will be ,l
discussed be]ow, when the vehicle is in one of the traction modes¦
I of operation, the brake for each of the wheels is automatically
cycled. The microproce~sor 204 is prograrnmed to respond to the
braking mode switching signals to generate an appropriate brake
signal to each of the brake actuators, such as the brake actuator
1 248, to automat;cally control the vehicle brakes.
In summary the vehicle control system shown in Figure 6
provides for the operator selection of one of four steering
modes, one of two traction modes and one of two braking modes to
control the vehicle. In the steering modes, the microprocessor
204 is responsive to the position of the steering wheel 201 to
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307Z9
i
I control the turn angle of the selected master wheel and the turn
¦ angle of each of the other wheels in accordance with the turn
¦ angle of the master wheel. The relative speed of each wheel is
l! also automatically controlled by the microprocessor 204 and the
1l absolute speeds in accordance with the position of the speed
selector 203 and, when the vehicle is in a steering mode, in
. accordance with the turn angle relationship of the other wheels
to the master wheel. The microprocessox 204 is programmed to
~ either solve equations for the steering position reference
1.0 I signals and the speed reference signals or to select the values
j for these signals from data stored in the memory 244. It will be
¦ apparent from the succeeding discussions of the operational modes
of the vehicle that in some modes a symmetry exists such that
more than one wheel can be controlled with the same steering
¦ position error signal or the same speed error signal. These
situat.ions can be taken into account to reduce the size of the
memory 244 where the equations are stored or the stored data
approach is taken to generating the steering position reference
l and speed reference signals. It will also be apparent that the
'i microprocessor 204 can be replaced by a plurality of microprocessors
¦l including one for each wheel in order to decrease the response
li time of the system to a change in any mode of operation~ turn
¦ angle and/or vehic.le speed. Furthermore, although the wheel
¦j speed and steer.ing position for each wheel is controlled in
il accordance with the integral of the difference between a refer-
~, ence signal and an actual value signal, such control could be in
jl addition proportional or differential in accordance with well-
', known control techniques.
!1
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113~7Z9
OPERATIONAL MOD~S
If the operator pushes button 227, the vehicle can then be~
steered in the conventional Ackerman steering mode about a steer-
! ing center located either to the right or left of the vehicle on I
I a line drawn perpendicular to the vehicle longitudinal axis and
through the center of the vehicle (Figure 10). Actuation of push
button 231 selects a modified Ackerman steering mode, with the
steering center located at a point laterally spaced on either
side of the vehicle but on a line intersecting the vehicle longi-
tudinal axis at either the front or the rear portion of the
vehicle (Figure 11).
The actuation of push button 228 selects a right skew
steering mode as illustrated in Figure 12.
Skew steering has long been advocated as a means for per-
mitting multi-wheeled off-road vehicles to avoid obstructions
that would be encountered if the vehicle progressed forwardly or
rearwardly wh:ile making ordinary turns. In skew steering, all of
the wheels of the vehicle are concurrently turned in the sarne
direction by the ~ame amount so that when traction forces are
applied to the wheels, the vehicle moves along a path which is
angularly disposed relative to the longitudinal axis of the
vehicle, for example, as illustrated in Figure 12.
Assuming that in ~igure 12 the wheels are already turned
counter-clockwise to the maximum degree permitted by the steering
mechanism, then the utilization of prior art controls for the
application of steering and propulsion forces to the vehicle
would indicate that the vehicle in Figure 12 coul~ in no manner

~; ( ~ l
. 113(~7Z
¦ be turned to the left if such action were necessary to avoid an
obstruction that would be encountered if the vehicle continued
on the original skewed path. With the control system of this
invention, the vehicle may be readily steered to the left, as
¦ illustrated in Figure 13, by merely selecting either of the rear j
¦ wheels of the vehicle as the master wheel and then executing an
Ackerman turn by turning those and the other rearward wheels
clockwise and thereby achieve a left turn of the vehicle accord-
ing to the Ackerman principle about a turning point which is
located along a line passing through the steering axes of~the
rear wheels and perpendicular to the longitudinal axis of the
vehicle.
At the same time, the vehicle may be steered to the -i~ht
from the skewed steering mode illustrated in Figure 12 by merely
selecting either of the front wheels as the master wheel and
executing an Ackerman-type turn about the turnillg point located
on a.line passing through the steerin9 axes of the two front
wheels and perpendicular to the lonyitudi.nal axis of the vehicle.
It is there:Eor appa.rent that a control systCm emhodyi.ng
this invention prov.ides aclditional flexibility for skew steering
of the vehicle. The same flexi.bil.i.t~ is prov:ided when button
229 is actuated to select a left skew steerin~ mode (not shown)
which permits the vehicle to be steered in either direction in
~n Ackerman fashion even while the wheels are in the skewed
p~sitio~.
In the braking modes illustrated in Figures 9a and 9b, the
actuation of push button 241 will cause all of the vehicle wheels
to be turned with all wheels on one side turned opposite to those
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11307Z9
¦ on the other so that the wheels are effectively positioned to
¦ block any longitudinal movement of the vehicle as illustrated in
Figure 9a. If it is desired to apply the braking mode only to
' a selected number of the wheels, for example, the four inner~ost
! wheels so as to provide for some de~ree of steering control of
the two ends of the vehicle, then the actuation of push button
~ 242 will effect the simultaneous turning of the four inner wheels !
¦ with the wheels on opposite:sides of the vehicle being turned
oppositely to their full extent, resultin~ in the configuration
I of the Fiyure 9b where the vehicle is effectively braked against
longitudinal progress by the inner wheels but, if the vehicle
continues to move, such as under snow conditions on a steep hill-
side, steering control may still be exerted by the operator
through ~ontrolling the forward and rearward pairs of wheels
re~pectively.
Still another advantage of the mechan;sm and control
system for the steering of the vehicle in accordance with the
invention is provided by operating the vehicle in a lateral shift
I mode. By way of background, those skilled in the art will rec-
I ognize that any vehicle which is capable of skew steering can be
laterally shifted by first movirly the vehicle along a path
I representating the ma~imum skew to the riyht and then twisting
¦ the wheels in place against the restraining forces of the ground
I on which they are in contact to re-position the wheels in their
I maxim~n reversed skewed position and then reversing the direction
of travel of the vehicle. The vehicle thus moves in a saw-tooth
p ttern involving both a longit~dinal and a lateral component of
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11307Z9
motion ut the longitudinal component is effe tively cancelled
out after each complete cycle of the above described two skewed
movements.
A lateral shift mode of operation of the vehicle embodying
¦ this invention does not require the twisting of all the tires of ¦
the vehicle against the ground surface in order to achieve the
re-arrangement of the wheels from the maximum right skewed posi-
tion to the maximum left skewed position. Instead, lateral shift
of the vehicle may be accomplished in either of two manners, the
first of which is illustrated by Figures 7a, 7b, and 7c and the
second by Figures 14a through 14f.
The lateral shift mode of operation schematically illus-
trated in Figures 7~a, 7b and 7c is employed wllen forward or
rearward movement of the vehicle is impeded, for example, by
boulders or trees, or due to the wheels being mired in a bog and
having no traction, so as to prevent an~ significant forward or
rearward movement of the vehicle by wheel rotation. The lateral
shit mode of operation is selected by actuating either push
button 234 or 235, depending upon whether a shi~t of the vehicle
to the left or right is clesired, and then actua~ion of push butto]
236 causes the automatic cycling of the wheels of the vehicle
b~ the micro-processor. In this modification, the micro-processo
204 is programmed to first turn all of the wheels on the vehicle
to their maximum turned position in either a clockwise or counter
clockwise direction, counter-clockwise being illustrated in
Fig~lre 7a. During this turning movement, the wheels are free to ¦
rotate so that if they are in a bog, the turning movement can
~evertheless be accomplished, because no reliance is placed on
¦ the traction of the wheels against the particular terrain on which
they est.
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1 11307Z9
¦ Once having achieved this pcsition, the automatic sequencing
¦ control by the micro-processor 204 applies the brakes to all of
the wheels on the side of the vehicle opposite the desired lateral¦
! shift direction, here the left side of the vehicle, while at the
I same time imparting a turning movement to the wheels to turn them
to their straight forward position relative to the vehicle, as
illustrated in Figure 7b. Concurrently, all wheels on the right
side of the vehicle are turned in the same direction to their
i straight forward steering position with the wheel rotation un-
restrained or with traction power applied to assist such turning,
as illustrated in Figure 7b, resulting in a bodily lateral shift
of the vehicle. At this point the automatic sequencing control
applies the brakes to the wheels on the side toward which movement
is desired, release~ the brakes on the opposite side wheels, but
continues the clockwise turning movements of all wheels to the
extreme position illustrated in Figure 7c, resulting in more
bodily lateral movement.
If additional lateral movement is required, the braking and
turning sequence is repeated, but the wheels are now turned in
counter-clockwise direction.
In the second form of lateral shift of the vehicle which may
be accomplished by utilizat;on o-f the structure and controI system
of the invention, the sequence of wheel positions is illustrated
by Figures 14a through 14f. This second form cannot be utilized
¦ in a bog because some degree of wheel traction is required. In
Figure 14a, which is presumed to be the starting position, all
of the wheels are parallel to the longitudinal axis of the
vehicle. In the first step of the sequence, the wheels
.' ;
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, ~1307Z9
on both sides of the vehicle are concurrently traction actuated
and turned through the maximum steering angle to assume the
positions shown in Figure 14b. It should be noted that this motion
of the wheels does not produce any shift of the body of the vehicle,
~represented by the bloc~ V.
In the next step, all of the opposed pairs of wheels are
concurrently rotated by the application of traction power thereto
to, in effect, achieve rearward mGvement of the vehicle according
Ito a skew steering mode. Since it is presumed that the longitu-
Idinal freedom of the vehicle is quite limited, this ~ovement is
generally on the order of less t~an a full rotation of the wheel,
say from thirty (30) to si~ty (60) degrees. The vehicle then
assumes the position shown in ~igure 14c wherein the body V of thei
'vehicle has been sh fted both laterally to the right and longi-
tudinally rearwardly, assuming that the top of the page represents!
a forward motion of the vehicle. In this and other views, the
dotted square indicates the initial position of the vehicle. Fror
this point, the wlleels are t-lrned in the reverse direction with
the traction bra]ies rele;lcsed, and with ~oth tr~ction power and
steering power appl;ecl, t]~e~~e~y ac;s-lmillc~ t.he position shown in
Figure 14d wherein it will bc~ nc-ted that a~3clin no lateral or lonsi-
¦tudillal movement of the }-c-ct~ of tl)e \~e]liClt-' has heen accomp]ished.
The wlleels are no~ Osit;c1~ec~ fc~- s~e~ steeril-1c3 in the o~posite
Idirection than in FiCJ~ll^e 1~1 alld acJain, traction power is applied ¦
1l to rotate the wheels in a for~al-cl direction from thirty to sixty
dcgrees, assllining the pOSit:iOII of Pic3ure 14e, where it will be
noted that tl-e body ~r of t l~e ~el-i cle has been additionall~ shifted
to the right but retul-r.ed to a lollgitudinal position slightly for;;ard
!
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1130'729
` .
I ,1.
of the initial position of Figure 14a. Traction power and
steering power are then applied to concurrently shift all wheels ¦
counter-clockwise to the position shown in Figure 14f, which
again has no effect on the position of the vehicle body V.
~ At this point the wheel positions are identical to that
shown in Figure 14b and the cycle can be repeated if further
lateral shift of the vehicle body is desired.
I In the aforedescribed description of the second traction
¦ shift mode, and, in fact, in any of the skew steering modes, it
I is assumed that the steering mechanism for the vehicle is such
as to hold the vehicle wheels in a desired steering position,
once such position has been selected by the micro-processor. ~his
may be accomplished either by through the utilization of ~rrev~rsible
gearing to effect the steering of the wheels or through the
utili2ation of a brake which is effective to hold the steering
mechanism for each wheel in a selected position according to the '
energization signals received from the micro-processor 204. Such¦
braking action for the steering mechanism is entirely conventiona~
and hence has not been illustrated in the drawin~s.
¦ It will also be apparent to those skilled in the art tilat ,
the micro-processor 204 will be programmed to provide either of
the two types of traction shift operations heretofor described.
The electrical connections for effecting such alternative selec-
I tion are entirely conventional and have not been illustrated in
¦ the drawings.
A similar sequencing of braking and turning movements of
the wheels may be employed in the traction shift mode, as illus- ¦
trated in Figures 8a and 8b, to effect the forward or rearward
bodily movement of the vehicle when ordinary wheel traction
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1 1~307Z9
¦cannot supply such or when the vehicle has become immobilized.
¦ ~uch a condition can occur as a result of miring the vehicle in
la bog or hanging it up on high stumps or boulders, and usually
Irequires a towing vehicle of similar size to effect a recovery.
IIn the control sequence, which is initiated by actuating push
¦ button 237 or button 238, depending upon whether a forward ~r
aft movement of the vehicle is desired, all brakes of the vehicle
wheels are applied and all of the wheels are concurrently turned
Ito a toe-in position relative to the vehicle frame with all wheels
¦on one side being turned in the opposite direction to the turn-
ing movement of the wheels on the other side as illustrated in
Figure 8a. This motion alone effects a degree of bodily longi-
¦ tudinal shift of the vehicle from its original position. In the
next step of the aut~omatic sequencing, opposed pairs of wheels
are turned in se~uence first one pair and then the next pair,
from their position shown in Figure 8a to their position shown in
Figure 8b but the wheels of each such pair are permitted to freely
rotate or with power applied; but no bodily displacement of the
vehicle occurs due to the restraining position of the other wheels
The braking and turning cycle can t}lC?1- be repeated, and a further
longit~ldinal shiEt of the vehicle body is eEfected.
In any of the aforedescribed movements wherein a limited
bodily lateral movement of th~ w}leels relative to the c3round would
appear to be re~uired, such can be absorbed by flexure of the huge
low pressure tires which are mounted on such wheels.
~lany modifications of this invention will be apparent to
those skilled in the art and it is intended that the scope of he
invention be determined solely by the appended claims.
li !
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