Vehicle speed control

A position control device for use in association with a foot pedal member controlling the fuel flow to an engine of a vehicle. The device includes an elongated and hollow chamber means and an actuator piston slidably disposed in the chamber means and movable between first and second positions therein. The first position represents a position of maximum fuel supply to the engine. Structure separately supporting the foot pedal member is provided for movement between first and second positions but permitting an operative connection of the foot pedal member to the actuator piston for movement along a path. A control device is provided for controlling the position of the actuator piston between the first and second positions and in response to vehicle speed and includes a yieldable resistance device for causing the actuator piston to resist a change in the position of the foot pedal member if an effort is made to alter the position of the foot pedal member toward the first position to increase the fuel supply to the engine and beyond the position of the actuator piston determined by the control means while simultaneously permitting an overpowering of the yieldable resistance device to effect a yieldable movement of the foot pedal member and the actuator piston together along the path to vary the fuel supply to the engine.

FIELD OF THE INVENTION 
This invention relates to a device for maintaining the rotative speed of a 
rotatable member at a selected value and, more particularly, relates to a 
speed control device for a vehicle powered by an engine in which fuel 
supplied thereto is controlled by the operator depressing and releasing a 
foot pedal member but that the speed of the vehicle can be maintained at a 
selected value through the application of a steady force to the foot pedal 
member. 
BACKGROUND OF THE INVENTION 
The standard cruise control is a device that allows the motorist to 
maintain a constant preselected vehicle speed without being required to 
depress the accelerator pedal. By automatically depressing the accelerator 
pedal to maintain a preselected velocity, cruise control eliminates the 
leg fatigue that can accompany sustained highway travel. This leg fatigue 
usually centers around the ankle and is the result of the varying amounts 
of accelerator pedal depression required of the motorist to maintain a 
fairly constant vehicle speed. 
There are some motorists who, while appreciating the speed control 
capability of cruise control, do not appreciate the means by which speed 
control is obtained. These motorists feel uncomfortable with a device that 
can pull the accelerator pedal into a depressed position. This discomfort 
is exacerbated by the lack of contact between the driver's foot and the 
accelerator pedal that is generally required for smooth and precise 
operation of cruise control. 
Another unattractive feature of cruise control use concerns a potential 
reduction in highway safety. When not using cruise control, most motorists 
are accustomed to the often-rehearsed lateral movement of the foot (or 
leg) when going from the accelerator pedal to the brake. An increase in 
reaction time regarding the execution of a braking response may occur when 
a motorist is using cruise control because: (1) the typical lateral 
response is no longer effective and (2) placement of the motorist's foot 
varies and must be determined each time a braking response is to be 
executed. This latency in the braking response is potentially dangerous. 
Still another feature of cruise control that incurs disfavor with some 
motorists is that its disengagement always requires a braking response or 
a button-pressing response. And engagement or re-engagement of cruise 
control always requires a button-pressing response. In heavy traffic, 
execution of these behavioral requirements is not only tedious but can 
prove potentially dangerous as well if the motorist delays disengaging the 
cruise control until absolutely necessary in the hope of avoiding the 
inconvenience entailed in temporarily reducing speed. 
DESCRIPTION AND BEHAVIOR ANALYSIS of Pat. No. 4 270 501 
In order to solve the highway speeding problem, a previous speed control 
invention, with a fixed speed setting (Pat. No. 4 270 501), was designed 
to achieve the following: (1) elimination of the relatively weak but 
frequent and prolonged behavior (accelerator pedal depression) entailed in 
unnecessary highway speeding (speeding in which the consequence is a 
relative reduction in the time to arrival) and (2) preservation of the 
relatively strong but infrequent and ephemeral behavior (accelerator pedal 
depression) entailed in necessary highway speeding (speeding in which the 
consequence is avoidance of an accident). 
The previous invention (Pat. No. 4 270 501) utilizes the systematic 
application of two behavioral principles to achieve speed control. These 
principles are punishment and reinforcement. Punishment functions to 
decrease the future probability of the behavior producing it, whereas 
reinforcement functions to increase the future probability of the behavior 
producing it. 
It has been experimentally shown that sufficiently increasing the force 
required to operate a manipulandum functions as punishment in that the 
reinforced behavior producing the increased force requirement will 
decrease in its future probability. Assuming a substantial force 
requirement has been imposed, it has also been experimentally shown that 
decreasing the imposed force required to operate a manipulandum functions 
as reinforcement in that the behavior producing the decreased force will 
increase in its future probability. Thus, increased force functions as 
punishment and decreased force functions as reinforcement. 
The previous invention (Pat. No. 4 270 501) eliminates the relatively weak 
behavior (accelerator pedal depression) involved in unnecessary highway 
speeding while preserving the relatively strong behavior (accelerator 
pedal depression) involved in necessary highway speeding through 
systematic manipulation of the accelerator pedal. Specifically, once the 
motorist exceeds a fixed velocity, increasing accelerator pedal resistance 
is a function of increasing vehicle speed. Once imposed, decreasing 
accelerator pedal resistance is a function of decreasing vehicle speed, 
with imposed accelerator pedal resistance terminating at the fixed 
velocity. As punishment, increasing accelerator pedal resistance will 
decrease the future probability of behavior producing the onset of and 
increases in unlawful highway vehicle speed. Once unlawful speeding has 
commenced, the reinforcement provided by decreasing accelerator pedal 
resistance will increase the future probability of behavior producing 
decreases in unlawful highway vehicle speed. The purpose of an increasing 
and decreasing range of accelerator pedal resistance values as opposed to 
a high single value of accelerator pedal resistance is to minimize 
potential problems with adaptation--the gradual strengthening of the leg 
and foot muscles due to prolonged exposure to increased force. By using a 
single value of imposed accelerator pedal resistance, it is possible for a 
motorist to accelerate to speeds well in excess of the fixed speed that is 
correlated with reinforcement (decreased accelerator pedal resistance). To 
illustrate, and as shown in FIG. 1, if the fixed velocity is 55 mph and a 
motorist is traveling at 70 mph, then only a decrease in speed to 55 mph 
will produce reinforcement (decreased pedal resistance). There is no 
reinforcement available to the speeding motorist who decreases speed to a 
velocity that is still in excess of 55 mph. Under these conditions, it 
might be expected that a determined motorist would accelerate to a fairly 
high unlawful speed (once speeding begins, further increases in speed are 
not differentially punished) and maintain that speed as long as possible 
before returning to 55 mph. With considerable practice sustaining a 
constant force, a motorist might find it easier to spend longer time 
periods traveling at unlawful highway speeds because of a gradual 
strengthening of the muscles (adaptation) involved in the execution of 
accelerator depression. Problems with adaptation can be rendered less 
likely if a system is designed to minimize the period of time that a 
speeding motorist spends at any increased value of accelerator pedal 
resistance. By using an increasing and decreasing range of accelerator 
pedal resistance values, the speeding motorist's behavior is brought under 
differential control. To illustrate, and as shown in FIG. 2, if a motorist 
is traveling at 70 mph and decreases vehicle speed to 65 mph, behavior 
producing the decrease in speed is differentially reinforced by decreasing 
accelerator pedal resistance. In fact, any decrease in unlawful vehicle 
speed will be reinforced since such a decrease is correlated with 
decreasing accelerator pedal resistance. This kind of differential 
procedure produces a smoother continual decline in unlawful vehicle speed 
that renders adaptation to increasing values of accelerator pedal 
resistance unlikely. 
In FIG. 3, the specific function relating increasing and decreasing 
accelerator pedal resistance to increasing and decreasing vehicle speed is 
negatively accelerated. This kind of function, as opposed to the linear 
function shown in FIG. 2, seems best suited to this particular application 
because the rate of decrease in accelerator pedal resistance (the 
magnitude of reinforcement) increases as unlawful speed decreases. 
Increasing the magnitude of reinforcement as vehicle speed decreases 
toward marginally unlawful speeds is desirable because the aversive 
stimulation (a motivational variable) is less at marginally unlawful 
speeds than substantially unlawful speeds. In other words, the way to 
compensate for the fact that decreases in higher accelerator pedal 
resistance values are more reinforcing than comparable decreases in lower 
values of imposed accelerator pedal resistance is to increase the rate of 
decrease (magnitude of reinforcement) in lower values of imposed 
accelerator pedal resistance. A negatively accelerated function satisfies 
these contingencies. 
Thus, the device of U.S. Pat. No. 4 270 501 did achieve the basic goal of 
discouraging the driver from speeding by requiring increasing pedal force 
as the vehicle exceeded the speed limit. However, the device did not 
address the critical problem of what happens when the driver travels at 
the 55 mph speed limit. There was an assumption that the driver could 
easily and conveniently sense the point at which the force increased, and 
use this point to raise and lower the pedal as required to maintain a 
constant speed. Experience and theory has shown this assumption to be 
invalid. 
Accordingly, it is an object of the present invention to provide a speed 
control system utilizing driver participation (accelerator pedal 
depression) and at the same time eliminating the ankle fatigue that can 
accompany sustained highway travel. 
A further object of the present invention is to provide a speed control 
system, as aforesaid, to preserve the same response requirements as those 
entailed in operating a motor vehicle without a speed control device. 
A further object of the present invention is to provide a speed control 
system to render its operation convenient in heavy as well as light 
traffic. 
It is a further object of this invention to provide a device for 
maintaining the speed of rotation of a rotatable member at a selected 
value while simultaneously employing the subject matter disclosed in the 
aforementioned U.S. Pat. No. 4 270 501, namely, increasing the resistance 
to foot pedal depression as the vehicle speed increases above a 
preselected value and decreasing the resistance to foot pedal depression 
as the vehicle speed decreases toward the aforementioned preset value. 
It is a further object of this invention to provide a single housing 
structure, small in size, to house the various elements for effecting both 
the increase and decrease in resistance to foot pedal depression and 
effecting a maintaining of the speed of a rotatable member at a value 
selected by the operator. 
A further object of the invention is to provide a speed maintaining device 
and an operator constraining device, as aforesaid, in the aforesaid 
compact housing structure, the components of which housed therein being of 
durable construction and easy maintenance. 
A further object of the invention is to provide a compact housing 
arrangement, as aforesaid, which is capable of easy in-the-field 
installation on a vehicle in a location closely adjacent the accelerator 
pedal to thereby occupy a minimum of space as required in vehicle 
constructions today. 
SUMMARY OF THE INVENTION 
The objects and purposes of the invention are met by providing a position 
control device for use in association with a foot pedal member controlling 
the fuel flow to an engine of an automobile. The device includes an 
elongated and hollow chamber means and an actuator piston slidably 
disposed in the chamber means and movable between first and second 
positions therein. Structure separately supporting the foot pedal member 
is provided for movement between first and second positions but permitting 
an operative connection of the foot pedal member to the actuator piston 
for movement along a common path. A control device is provided for 
controlling the position of the actuator piston between the first and 
second positions and in response to vehicle speed and includes a yieldable 
resistance device for causing the actuator piston to resist a change in 
the position of the foot pedal member if an effort is made to alter the 
position of the foot pedal member beyond the position of the actuator 
piston determined by the control means while simultaneously permitting an 
overpowering of the yieldable resistance device to effect a yieldable 
movement of the foot pedal member and the actuator piston together along 
the common path to vary the fuel supply to the engine. 
The objects and purposes of the invention are further met by providing the 
aforementioned invention, both apparatus and the method use thereof, in an 
automobile environment wherein the speed of the automobile is maintained 
at a selected value. 
The objects and purposes of the invention are further met by providing a 
speed control device for a vehicle which is equipped with structure for 
increasing and decreasing the resistance to accelerator pedal depression 
in response to the speed of the vehicle above a preselected value set by 
the operator.

DETAILED DESCRIPTION 
The present invention maintains a preselected vehicle speed by limiting the 
motorist's degree of accelerator pedal depression to the position required 
to maintain the preselected vehicle speed. The motorist can depress the 
accelerator pedal beyond the position that maintains the preselected speed 
by overriding the force utilized to maintain pedal position control (for 
example, 12 pounds, as depicted in FIG. 4). Pedal position control and 
thus the preselected velocity will be maintained if the motorist exerts 
any force less than the force utilized to maintain pedal position control 
but more than the force provided by the return spring. (Actually, if the 4 
pound force generated by the average return spring (not shown) of the 
accelerator pedal is added to the 12 pound force (in the above example) 
used for position control, a total greater than 16 pounds is required of 
the motorist to depress the accelerator pedal beyond the controlled 
position.) When the motorist is traveling at speeds below the preselected 
speed, the accelerator pedal functions in the usual manner by providing a 
back force of approximately 4 pounds via the return spring. 
FIGS. 5 and 6 show how the application of position control technology to 
the present invention differs from its application to cruise control. The 
operational range of the position control system shown in FIG. 5 is 
represented in the circled area of FIG. 4, beginning with the accelerator 
pedal fully depressed at 53 mph and extending in a linear fashion with 
increasing speed until reaching a fully extended position at 56 mph. The 
present invention operates to move the accelerator pedal toward an 
extended position when vehicle speed exceeds the preselected speed, 
whereas cruise control allows the normal return spring to move the 
accelerator pedal toward an extended position when vehicle speed exceeds 
the preselected speed. And the present invention allows the motorist's 
foot to move the accelerator pedal toward a depressed position when 
vehicle speed falls below the preselected speed, whereas cruise control 
moves the accelerator pedal toward a depressed position when vehicle speed 
falls below the preselected speed. It is evident that while both the 
present invention and cruise control allow the motorist to travel at a 
constant speed, the means by which speed control is obtained require a 
different application of the technology involving control of accelerator 
pedal position. 
The present invention, like cruise control, can eliminate the ankle fatigue 
often accompanying sustained travel. When operating a motor vehicle not 
equipped with a speed control device, motorists generally rest the heel of 
the foot on the floor while the rest of the foot is in full contact with 
the accelerator pedal. Varying amounts of accelerator pedal depression are 
required of the motorist to maintain a constant speed when encountering 
varying road gradients and changing wind conditions. The motorist varies 
accelerator pedal depression by foot movements pivotal at the ankle. With 
the present invention, the heel of the motorist's foot need not rest on 
the floor during accelerator pedal operation. Instead, the motorist now 
has the option of placing the foot, including the heel, on the accelerator 
pedal so that the accelerator pedal literally functions to support the 
foot. If a motorist attempted this in a vehicle not equipped with this 
invention, the weight of the foot would provide a force greater than the 
counterforce provided by the 4 pound return spring of the accelerator 
pedal. The accelerator pedal would become almost completely depressed, and 
the speed of the vehicle would become far too great. If a motorist's foot 
is placed on the accelerator pedal of a vehicle equipped with the present 
invention, the weight of the motorist's foot will depress the accelerator 
pedal only far enough to maintain the selected velocity. As the vehicle 
moves uphill, the weight of the motorist's foot will further depress the 
accelerator pedal to the new position required to maintain the selected 
velocity. As the vehicle moves downhill, the accelerator pedal will 
automatically move the motorist's foot toward an extended position to 
maintain the selected velocity. Thus, this invention, like cruise control, 
eliminates ankle fatigue by automatically maintaining a preselected 
velocity; however, this invention, unlike cruise control, achieves speed 
control in conjunction with driver participation. 
As already noted, various behavioral requirements can render operation of 
cruise control tedious in heavy traffic when vehicle speed must be 
frequently reduced. The present invention is designed to minimize the 
behavioral responses required for its operation in heavy traffic. When a 
reduction in vehicle speed below the controlled speed becomes necessary, 
the motorist simply reduces the amount of accelerator pedal depression 
(unless an abrupt reduction is required, in which case the brake would 
obviously be applied). When desiring to resume traveling at the controlled 
speed, the motorist depresses the accelerator pedal until the preselected 
velocity is obtained, at which point the accelerator pedal will once again 
position itself (and the motorist's foot) so as to maintain that velocity. 
Thus, unlike cruise control, the present invention may be operated in 
heavy traffic without proving tedious for the motorist. In fact, once a 
preselected velocity has been chosen, the responses required to operate 
the present invention in heavy traffic (or any traffic, for that matter) 
are exactly the same as those required in normal vehicle operation. The 
only response requirement entailed in operating the present invention is 
choosing the velocity at which one wishes to travel. 
The present invention may be combined with the previous invention (Pat. No. 
4 270 501) to produce an improved speed control system. That is, the 
device of Pat. No. 4 270 501 has only one function, namely, controlling 
the force required to depress the pedal. This combination is inventively 
accomplished by replacing the steep initial slope of imposed accelerator 
pedal resistance values between 55 and 56 mph shown in FIG. 3 with the 
position control system shown in FIGS. 4 and 5 to produce the improved 
speed control system shown in FIG. 10. The reason for this change is that 
smoother operation at the preset speed can be obtained by position and 
force control as opposed to using force control only. 
The improved speed control system will function as follows. At 55 mph, the 
accelerator pedal will resist further depression by positioning itself and 
the motorist's foot so as to maintain 55 mph. (Position control actually 
operates across a narrow speed range in which the accelerator pedal may be 
fully depressed at 53 mph and is fully extended at 56 mph if the travel 
speed is set for 55 mph.) The position control may be overridden if the 
motorist depresses the accelerator pedal with a force greater than the 12 
pound constant utilized to maintain the position control. When the 
position control is overridden, the vehicle will accelerate in speed. When 
this occurs, position ceases to be a factor as increasing accelerator 
pedal resistance is imposed as a function of increases in vehicle speed. 
Once accelerator pedal resistance has been imposed, decreasing accelerator 
pedal resistance is a function of decreasing vehicle speed. Only when 
vehicle speed has been reduced below 56 mph (but remains above 53 mph) 
will position control resume operation. 
Another improvement over Pat. No. 4 270 501 is the addition of increments 
and decrements in imposed accelerator pedal resistance as a function of 
increments and decrements in accelerator pedal depression once a specified 
velocity is exceeded. (See FIG. 7 for example.) Accelerator pedal 
resistance occurring as a function of accelerator pedal depression once a 
specified velocity is exceeded is to be superimposed on the increasing and 
decreasing range of accelerator pedal resistance that occurs as a function 
of increases and decreases in unlawful speed as described in Pat. No. 4 
270 501. The purpose of the additional acceleratorpedal-depression-based 
accelerator pedal resistance concerns a potential problem already 
discussed--adaptation on the part of the motorist to imposed accelerator 
pedal resistance. 
Under certain conditions a motorist may change the degree of accelerator 
pedal depression without generating a corresponding change in vehicle 
speed. For example, this situation may occur when a motorist encounters 
varying road gradients after establishing vehicle speed on a horizontal 
road. The changes in momentum that result when a motorist encounters 
changes in road gradients can counterbalance the effects of changed engine 
output that accompanies changes in accelerator pedal depression. Another 
situation in which accelerator pedal depression can be changed without 
changing the established speed involves changing wind conditions. 
Variations in head winds and tail winds can result in the maintenance of 
the established speed despite changes in accelerator pedal depression. 
The importance of a differential system of accelerator pedal control has 
been discussed above as a safeguard in reducing the likelihood of 
adaptation to imposed accelerator pedal resistance. It was noted that an 
advantage of the differential system is that behavior producing any 
increase or decrease in unlawful highway vehicle speed generated, 
respectively, punishment (increased accelerator pedal resistance) and 
reinforcement (decreased accelerator pedal resistance). 
Behavior producing increases and decreases in accelerator pedal depression 
is, of course, critical in effecting corresponding increases and decreases 
in unlawful highway vehicle speed (or any vehicle speed). In fact, changes 
in accelerator pedal depression once unlawful speeding begins are so 
important that each change should alter imposed accelerator pedal 
resistance even if vehicle speed has not been altered. This is because 
behavior that generates changes in accelerator pedal depression is at the 
very least precursory to behavior that will effect changes in unlawful 
highway vehicle speed. 
Imposing a supplementary source of punishment (increases in accelerator 
pedal resistance) as a function of behavior producing increases in 
accelerator pedal depression once highway speeding begins will render less 
likely behavior effecting increases in unlawful highway vehicle speed. And 
providing a supplementary source of reinforcement (decreases in 
accelerator pedal resistance) as a function of decreases in accelerator 
pedal depression will render more likely behavior effecting decreases in 
unlawful highway vehicle speed. Thus, the range of increases and decreases 
in accelerator pedal resistance occurring as a function of respective 
increases and decreases in unlawful highway vehicle speed is to be 
concurrently supplemented by a range of increasing and decreasing 
accelerator pedal resistance imposed as a function of respective increases 
and decreases in accelerator pedal depression. 
It should be noted that the values of imposed accelerator pedal resistance 
occurring as a function of unlawful highway speed are substantially 
greater than the values of imposed accelerator pedal resistance occurring 
as a function of accelerator pedal depression once unlawful highway speed 
begins. The correlation between increasing and decreasing accelerator 
pedal resistance and increases and decreases in unlawful highway speed 
might under some conditions prompt the motorist to gauge current unlawful 
highway vehicle speed according to the value of accelerator pedal 
resistance currently imposed. Stated differently, imposed accelerator 
pedal resistance occurring as a function of unlawful highway speed may 
occasionally be utilized by the motorist much like a speedometer--to 
quickly determine the approximate vehicle speed. Subsequent driving 
behavior (such as when to cut back in after passing a vehicle on a hill) 
may be partially controlled by the speed-based accelerator pedal 
resistance urging against the motorist's foot. Any stimulus that can even 
briefly exert control in the fashion of a speedometer must reflect vehicle 
speed as accurately as possible. A stimulus such as accelerator pedal 
resistance as a function of accelerator pedal depression once highway 
speeding begins is only loosely correlated with increases and decreases in 
unlawful highway speed and thus would not be a reliable indicator of 
unlawful highway speed. By using relatively high values of speed-based 
accelerator pedal resistance and relatively low values of 
accelerator-pedal-depression-based accelerator pedal resistance, the 
saliency of the former will render speedometer control by the latter 
unlikely. 
Thus, and relating the foregoing discussion to the conventional cruise 
control, an actuator in the conventional cruise control pulls directly on 
the throttle lever through a separate cable. This actuator need only act 
in one direction, since there is a return spring which returns the 
throttle to idle. If the driver wishes to travel faster, he can push the 
pedal down further, which simply puts slack in the cable. He cannot let up 
on the throttle, however, without disengaging the cruise control. 
In the inventive device, the driver must push down on the pedal for it to 
move at all; but if he tries to exceed the pedal position which will just 
maintain the desired set speed, then the actuator pushes back on the 
driver's foot. The manner in which this is accomplished will be explained 
in further detail below. 
FIG. 8 illustrates in schematic form the general concept of the invention 
as it is applied to a powered vehicle, such as an automobile 10. The 
automobile has a floorboard 11 extending generally at an angle to join 
with a fire wall 12 extending vertically between a passenger compartment 
13 and an engine compartment 14. A throttle control 16 operates to control 
the movement of a fuel control linkage 17 having a foot pedal member such 
as the accelerator pedal 18 pivotally mounted on a lever arm 19 which is 
pivotally mounted on a bracket 21 fastened to the fire wall 12. The lever 
arm 19 is, in this embodiment, a two-arm lever, the arm 22 having the 
accelerator pedal 18 mounted thereon and the arm 23 having a cable 24 
fastened thereto, which cable extends through an opening 26 in the fire 
wall 12 and is connected to the throttle linkage on the internal 
combustion engine for the vehicle, not illustrated. A pulling on the cable 
in the direction of the arrow 27 will generally cause more fuel to be used 
by the engine of the automobile 10 to increase the velocity of the 
automobile when it is in gear and being driven on a roadway. A movement of 
the cable 24 in the opposite direction will generally cause less fuel to 
be used by the engine to cause a decrease in the velocity of the 
automobile. If desired, a not illustrated spring can be provided to pull 
the cable 24 leftwardly to continually urge the accelerator pedal 18 to 
its most raised position thereby providing the engine with a minimum of 
fuel so that the carburetor setting for the automobile will maintain the 
engine in an idle operation. 
The aforementioned throttle control structure for the internal combustion 
engine is conventional and does not form a part of the invention. 
A pedal movement resisting device 30 includes a piston-cylinder assembly 
28, is provided for controlling the resistance to depression of the 
accelerator pedal 18 in direction A. This assembly 28 includes a cylinder 
29 having a closed end 31 and an open end 32. An actuator piston 33 is 
slidably mounted in the cylinder 33 and has a piston rod 34 fastened 
thereto on a side of the piston 33 remote from the closed end 31 and 
projecting through an opening 36 in the floorboard 11. In this particular 
embodiment, the piston rod 34 has a recess 37 in the free end thereof. A 
linkage arm 38 is, in this particular embodiment, pivotally secured to the 
arm 22 of the lever 19 and projects through the opening 36 in the 
floorboard 11 and is received in the recess 37 in the free end of the 
piston rod 34. It will be noted that if the accelerator pedal 18 is moved 
in the direction of the arrow A, the linkage arm 38 will bottom out in the 
recess 37 to urge the piston 33 toward the closed end 31 against whatever 
pressure force may be present in the cylinder 29 resisting such movement. 
The pedal movement resisting device also includes a control unit 39 (the 
specific subject matter of which is illustrated in FIG. 13), which is 
housed in a moisture resistant housing structure, not illustrated. The 
control unit 39 is responsive to electrical signals which will be 
described in detail below. One of the electrical signals is generated by a 
pedal position sensor 41 which supplies an electrical signal through a 
connecting line 42 to indicate the actual position of the piston 33 in the 
cylinder 29. A further signal is provided through lines 43 and 44 to the 
control unit 39 and indicate the actual speed of the vehicle through a 
vehicle speed transducer 46. A pressure transducer 47 is provided for 
generating an electrical signal transmitted through connecting line 48 to 
the control unit 39 to indicate the actual pressure generated by a servo 
pump 49. In this particular embodiment, the servo pump 49 is driven by the 
rotating speedometer cable through a connection schematically illustrated 
in FIG. 8 but described in more detail in relation to FIGS. 15 to 20. The 
servo pump 49 has a pair of check valves 51 and 52, the check valve 51 
closing on a compression stroke of the piston 53 while the check valve 52 
becomes opened. Similarly, on the downstroke of the piston 53, the check 
valve 52 becomes closed and the check valve 51 becomes open to facilitate 
the entry of air into the compression chamber 54. Pressurized air from the 
servo pump 49 is transmitted through a conduit 56 to the closed end 31 of 
the cylinder 29. The pressure transducer 47 communicates with the conduit 
56 through a conduit 57 to provide a feedback signal through the 
electrical connecting line 48 to the control unit 39 thereby indicating 
the actual pressure in the conduit 56 generated by the servo pump 49. In 
order to effect an acceleration of the vehicle, the operator must depress 
the foot pedal 18 in the direction of the arrow A. Additional fuel will be 
supplied to the engine to accelerate the vehicle. As shown in the graph of 
FIG. 10, the operator must initially overcome a 4-pound force pushing up 
on the accelerator pedal 18 in a direction opposite to the arrow A. The 
normal resistance to pedal depression is generally around 4 pounds and is 
caused by various springs acting on the throttle linkage system. Normal 
operation of the accelerator occurs at speeds below 53 miles per hour. 
As the vehicle speed approaches 53 miles per hour, the pressure forces 
acting on the piston 33 in the cylinder 39 will suddenly be adjusted to 
cause the piston to move upwardly in the cylinder in a direction opposite 
the arrow A so that the piston will become oriented in the proper location 
as determined by the pedal position indicator 41 and in accordance with 
the indicated speed of the vehicle. If the operator continues to depress 
the accelerator pedal in a manner to cause the vehicle to exceed the 53 
mph speed limit, it must be done by a force in excess of 12 pounds (see 
FIG. 10). The pedal movement resisting device 30 which includes the servo 
pump 49 and related circuitry in the control circuit 39 will control a 
pair of solenoid valves 58 and 59 to accurately control the pressure of 
the compressed air in the conduit 56. As illustrated in FIG. 10, the force 
required by the operator to exceed the 55 mph speed limit will instantly 
jump upwardly which the vehicle operator will immediately take note of by 
reason of the extra effort required to depress the accelerator pedal. 
However, the vehicle operator may continue to override the system by 
providing a greater force on the accelerator pedal to enable the vehicle 
to accelerate to speeds in excess of 55 mph. The vehicle operator will 
also take note of the fact that greater and greater forces will be applied 
to the accelerator pedal 18 in a direction opposite the arrow A as the 
vehicle speed continues to increase. Assuming the vehicle operator desires 
to operate the vehicle at about 55 mph, the vehicle operator must then 
control the accelerator pedal by applying a force thereto in the direction 
of the arrow A. That is, the force applied to the accelerator pedal in the 
direction of the arrow A and the position of the accelerator pedal, or at 
least the position of the piston 33, are controlled by the control circuit 
39 so that the piston 33 can only raise the pedal by pushing up on the 
driver's foot through a lost-motion link represented by the linkage arm 
38. In order for the position action for the accelerator pedal to be 
realized, the driver must push down on the pedal 18 at least hard enough 
so that the piston rod 34 is contacted. Thus, the piston rod 34 will push 
back to raise the pedal and give way to a depression of the pedal. The 
pedal force applied by the operator must always exceed the reverse force 
applied to the piston 33. In this case, and as illustrated in FIG. 10, the 
reverse force is assumed to be approximately 12 pounds if the vehicle 
operator desires to operate the vehicle under the speed limit of 56 mph 
and above 53 mph. If the vehicle speed should accelerate due to the 
vehicle moving, for example, down a hill, it will be necessary, in order 
to maintain the speed of the vehicle as close as possible to the 55 mph 
speed limit, to reduce the distance "X" indicated by the pedal position 
sensor 41. This is accomplished without the operator varying the force 
applied to the accelerator pedal by holding the solenoid 59 deenergized so 
that the servo pump 49 will supply pressurized air to the conduit 56 to 
push out on the piston 33 to thereby raise the accelerator pedal 18 in a 
direction opposite the arrow A. The reason for this is that the ball check 
member 61 in the check valve 51 will be urged by the spring 62 into 
engagement with the ball seat normally provided for the check ball 61. 
Thus, on suction strokes of the piston 53, air will be drawn past the ball 
61. On pressure strokes of the servo pump 49, the ball check member 61 
will close and the ball check member 63 of the check valve 52 will open 
against the urging of the spring 64 to supply pressurized air to the 
conduit 56. The increase in pressure will also be detected by the pressure 
transducer 47 which will transmit an appropriate electrical signal at 48 
to the control unit 39. If, for example, the vehicle encounters a hill and 
it is desired to travel up the hill without losing speed, it will be 
necessary for the operator to continue to hold a generally steady foot 
force on the accelerator pedal and without experiencing any greater than 
normal return force (i.e. the 12-pound force mentioned above). This can be 
accomplished by energizing the solenoid 58 to retract the ball-like check 
member 66 away from the seat normally provided therefor so that 
pressurized air can be bled from the conduit 56 through the conduit 67 to 
the atmosphere. If, of course, the vehicle speed exceeds the 55 mph limit, 
the solenoid 58 will immediately become closed so that the pressure in the 
conduit 56 can be activated to instantly inform the operator that the 
vehicle speed has attained the desired speed limit value of 55 mph through 
the sensation felt through the foot. It will, of course, be recognized 
that if the solenoid 59 is energized, the armature 68 thereof will hold 
the ball check member 61 away from the seat provided therefor to prevent 
any compression from being developed within the chamber 54. In other 
words, the servo pump will be instantly deactivated. However, the pressure 
in the conduit 56 will remain due to a closing of the ball check members 
63 and 66. Thus, on a normal roadway extending generally horizontally, the 
servo pump can continue to function but will be rendered inactive due to 
an opening of the ball check member 61 by activation of the solenoid 59. 
During the course of the above set forth operative sequence, it will be 
immediately recognized that if the operator removes the foot from 
engagement with the accelerator pedal 18, the vehicle will immediately 
respond thereto by effecting a decrease in the supply of fuel to the 
engine and if conditions are appropriate, the vehicle would begin to slow 
down. Further, the characteristic of FIG. 10 will be realized if an 
attempt is made to violate the characteristic of FIG. 9. 
FIGS. 15 to 20 illustrate a compact housing structure which is to be 
mounted in the general location indicated by the location of the 
piston-cylinder assembly 28 in FIG. 8. That is, it is to be mounted on the 
floorboard 11 and project away therefrom on a side of the floorboard 11 
remote from the accelerator pedal 18. The housing 71 has plural side walls 
72, 73, 74 and 75 and a pair of end walls 76 and 77. The housing 71 is 
divided into two compartments, namely, a pumping chamber 78 corresponding 
to the cylinder 29 set forth above in regard to FIG. 8 and pressure 
transducer chamber 97 described in more detail below. The pumping chamber 
78 has slidably disposed therein a piston member 79, which piston member 
has a piston rod 81 secured thereto. The piston 79 and the piston rod 81 
correspond, of course, to the piston 33 and piston rod 34 mentioned above 
in regard to FIG. 8. The piston rod 81 has a recess 82 in the free end 83 
thereof. The piston rod 81 projects through an opening 84 provided in the 
end wall 86 of the chamber 78 remote from the end wall 76. In this 
particular embodiment, the opening 84 is defined by a sleevelike 
projection 87 extending outwardly from the end wall 86. The piston rod 81 
has mounted on a side thereof an elongated strip of conductive material 88 
on which slidably rides a pair of electrical contacts 89. Only one such 
electrical contact 89 is shown in FIG. 15. It is to be understood that the 
electrically conductive material 88 is generally U-shaped with each 
contact 89 slidably engaging a leg of the U-shaped electrically conductive 
material 88. One contact 89 is connected to ground and the other contact 
is connected to the control circuit 39 through the conductor 42 (FIG. 8). 
The circuit 39 will be described in more detail below and in regard to 
FIG. 13. It can be stated that when the piston rod 81 is fully extended, 
the contacts 89 will be adjacent each other at the bight portion of the 
U-shaped conductive material 88 so that virtually no resistance will be 
presented between the contacts 89. On the other hand, when the piston rod 
81 is fully retracted, the contacts will be adjacent the free ends of the 
legs of the U of the conductive material 88 and a maximum of electrical 
resistance will be presented between the contacts 89. This arrangement 
will be utilized to indicate the position of the piston 79 and piston rod 
81 relative to the cylindrical chamber 78. 
The side walls 73 and 75 of the housing 71 have axially aligned openings 
therein, each of which is encircled by an externally threaded coupling 91 
and 92. The speedometer cable member 93 from a vehicle driven component of 
the automobile is connected to the coupling member 91 as schematically 
illustrated in FIG. 15. The other speedometer cable member 94 is coupled 
to the other coupling 92 and delivers speed and odometer information to 
the speedometer and odometer visible to the driver of the vehicle. As 
illustrated in FIGS. 16 and 17, a disk 96 is rotatably supported in the 
housing 71 particularly in the chamber 97 immediately adjacent the 
aforedescribed pumping chamber 78. A bearing member 98 is rotatably 
mounted in the coupling member 91 and the disk 96 is connected to the 
rotatable member of the bearing member. The rotatable member in the 
bearing member is coupled to the driving member in the speedometer cable 
93. The disk 96 also has a crank pin 99 thereon which is coupled to a 
further disk 101 rotatably supported on the rotatable member in the other 
coupling member 92. Thus, a rotation of the disk 96 will also result in a 
simultaneous rotation of the disk 101 and thence a driving of the 
rotatable member in the speedometer cable 94 drivingly coupled thereto. 
Plural permanent magnet members 102 are fixedly provided around the 
periphery of the disk 96 as illustrated in FIG. 16. 
A crank arm 103 is journaled to the crank pin 99. Since the crank pin 99 is 
oriented adjacent the periphery of the disk 96, the crank arm 103 will be 
caused to be moved accordingly therewith. Radially aligned with the disk 
96, particularly the crank pin portion 99 thereof is a cylindrical chamber 
104 having a piston 106 slidably disposed therein. The free end of the 
crank arm 104 is connected through a spherical socketlike joint 107 so 
that upon a rotation of the disk 96, the piston 106 will be driven for 
reciprocal movement within the cylindrical chamber 104. Thus, the driven 
member in the speedometer cable 93 will effectively drive the disk 96 for 
rotation and effect a reciprocation of the piston 103 within the 
cylindrical chamber 104. This servo pump corresponds to the servo pump 49 
described above and has been correspondingly referenced in FIG. 16. 
A mounting plate 111 is provided in the chamber 97 and extends generally 
parallel to but spaced from the side wall 72. A cylindrical sleeve 112 is 
fastened to the mounting plate 111 on a side thereof remote from the side 
wall 72. The cylindrical sleeve 112 is radially aligned with the radial 
plane of the disk 96. An inflatable diaphragm is secured to the 
cylindrical sleeve 112. The inflatable diaphragm 113 corresponds to the 
pressure transducer 47 illustrated in FIG. 8. A conduit 113 supplies 
pressurized air from the servo pump 49 to the inflatable diaphragm 113 and 
corresponds to the conduit 57 illustrated in FIG. 8. The inflatable 
diaphragm 113 is oriented between the cylindrical sleeve 112 and the 
peripheral surface of the disk 96 as illustrated in FIGS. 16 and 17. A 
3501T Hall effect transducer 116 is secured to the surface of the 
inflatable diaphragm 113 on a side thereof remote from the cylindrical 
sleeve 112. The Hall effect transducer 116 is oriented so that it is 
closely adjacent the peripheral surface of the disk 96, particularly the 
permanent magnets 102 provided thereon. Thus, every time one of the 
magnets embedded in the disk 116 passes by the Hall effect transducer, its 
output voltage varies in a cyclic manner. The specific function performed 
by the Hall effect transducer will be described in more detail below in 
relation to the operation of the circuit illustrated in FIG. 13. 
As illustrated in FIGS. 19 and 20, the electromagnet solenoids 58 and 59 
are also provided in the housing 71, particularly in the chamber 97. The 
check valve arrangement is normally closed as indicated by the valve 
member 61 resting against the seat provided therefor. The armature 68 is 
pulled downwardly within the solenoid 59 upon energization thereof against 
the urging of the spring 62, which in this particular embodiment is a leaf 
spring instead of the coil spring schematically illustrated in FIG. 8. A 
check valve 52 controls the flow of pressurized air to the conduit 56. The 
solenoid valve 58 is normally closed and maintains the pressure within the 
conduit 56. However, when the solenoid 58 is energized, the armature 66 
will be retracted to bleed pressurized air from the conduit 56 out to the 
atmosphere in direction of the arrow B illustrated in FIG. 20. 
CIRCUIT OF FIG. 20 
Referring to FIG. 8, the function of the control unit 39 is to control the 
position and/or operating force of the accelerator pedal. Control of 
position can be considered the primary function; control of the force is 
in the form of an override of the position control. That is, the position 
control will permit whatever force is necessary to be applied to achieve 
the specified position, up to where the force required exceeds its 
specified limit. 
The force and position are controlled by a pneumatic actuator, i.e. the 
piston 33 (79) and piston rod 34 (81) that can only raise the pedal, by 
pushing up on the driver's foot through a lost-motion link to the 
accelerator pedal 18. This is a primary safety feature. In order for the 
position action to be realized, the driver must, as stated above, push 
down on the pedal 18 at least hard enough so that the actuator 33, 34 is 
contacted. Thus, the actuator 33, 34 will push back at a speed of at least 
53 mph to raise the pedal, and give way to depressing the pedal; this 
situation will always be assumed in what follows unless otherwise stated. 
The force action of FIG. 10 comes into operation when the driver pushes on 
the pedal with a force that exceeds the limit as determined by the 
existing vehicle speed and other factors as depicted by FIG. 9. The 
actuator 33, 34 then gives way until the force is at or below the limit. 
This means that the driver's foot force is always equal to or overpowers 
the position control at speeds of 53 mph or greater. 
The position and force are primarily functions of vehicle speed. They are 
also functions of time. The force is in addition a function of the pedal 
position. 
Position Control 
Basically, the position of the pedal is specified by the vehicle speed in 
such a way as to keep the speed itself as constant as possible. Thus, when 
the speed is close to but below 53 mph, the pedal 18 should be fully 
depressed, since the speed is too low. When the speed goes above 53 mph, 
the pedal is raised linearly with the speed (decreasing the value of 
dimension "X" in FIG. 8), so that the pedal is fully raised at 56 mph. See 
FIG. 9, showing pedal position vs. speed. This is essentially the same 
action the driver takes as he acts to control the speed himself, and is 
exactly the same principle used by many, but not all, vehicle cruise 
controls. The details as to how this is accomplished are as follows. 
Referring to the circuit diagram of FIG. 13, upper left corner, information 
as to the vehicle speed is obtained from the rotation of the servo pump 
flywheel or disk 96, which is driven by the speedometer cable 93 (FIG. 
15). Every time one of the magnets 102 embedded in the flywheel 96 passes 
by the 3501T Hall effect transducer 116, its output voltage, V.sub.hal, 
varies in a cyclic manner. This cyclic variation is passed through 
capacitors C1 and C2, and appears as the voltage V".sub.hal, at the input 
to the LM2917 frequency-to-voltage (F-V) converter 118. (The intermediate 
voltage V'.sub.hal is used for force control described below.) Voltage 
V".sub.hal will cycle symmetrically about ground due to the effect of R1 
in conjunction with C2. The Hall device 116 also requires a ground 
connection and a 7.56 v supply voltage. Capacitor C5 acts to supply the 
varying current required by the Hall device 116, thus reducing the current 
variation needed from the 7.56 v source. 
The action of the F-V converter 118 is to convert a frequency into a 
proportional voltage V.sub.spd, at the output of the charge pump of the 
F-V converter. C4 acts to average the current pulses produced by the 
charge pump and convert them to a voltage. A large value of capacitance 
for C4 can reduce the residual ripple in the V.sub.spd voltage but cannot 
eliminate it entirely; C4 cannot be too large or V.sub.spd will not 
respond to dynamic variations in vehicle speed fast enough. R2 determines 
the calibration of this voltage and is such that 0.05 v equals 1 mph, so 
that 2.8 v is equivalent to 56 mph. See FIG. 11. 
V.sub.spd is applied to the non-inverting junction of operational amplifier 
(op amp) U9 in the F-V converter. The voltage on the inverting junction of 
op amp U9, V'.sub.spd, is kept at an initial, or nominal, 2.8 v by the 
action of the 7.56 v reference voltage acting through R8 and R9. (The 7.56 
v reference is part of the F-V converter package, and is obtained by use 
of zener D6 to establish the voltage, and R7 connected to the 12 v 
filtered battery voltage to supply the current required by the 7.56 v 
reference.) The actual value of V'.sub.spd depends on V.sub.con, acting 
through R6 and V".sub.pos acting through R10. V'.sub.spd is 2.8 v when 
V.sub.con is zero v and V".sub.pos is 9 v, the nominal values for these 
quantities. 
It will first be shown how V.sub.con can be made to vary as a function of 
V.sub.spd in a certain desired manner. This is achieved by the action of 
op amp U9. (Q4 is simply used to boost the output current capability of 
U9, and will not be referred to further.) 
The action of U9 is to make V.sub.con vary as a function of V.sub.spd by 
the "feedback" effect of V.sub.con acting through R6 on V'.sub.spd so as 
to keep V'.sub.spd equal to V.sub.spd. When V.sub.spd rises above 2.8 v, 
so that V'.sub.spd is less than V.sub.spd, the reaction of U9 is to raise 
its output, V.sub.con. This is due to the relationship between the summing 
junction voltages of an op amp and its output, and is the reason for the 
use of the terms "inverting" (-) junction and "non-inverting" (+) 
junction. The action of V.sub.con through R6 causes V'.sub.spd to rise as 
V.sub.con rises. This continues until V'.sub.spd is again equal to 
V.sub.spd, so that an equilibrium is reached. R6 has a relatively large 
value, so that V.sub.con must increase from zero to 12 v as V'.sub.spd 
increases very little, from 2.8 v to 3.2 v; this corresponds to an 
increase in the vehicle speed from 56 to 64 mph. This assumes that 
V".sub.pos remains constant at 9 v. The resistance values are such that 
the graph of FIG. 12 results. This total range of values for V.sub.con is 
only important for other purposes, however; for position control, 
V.sub.con changes over a very limited range, as will be explained shortly. 
R5 is present to ensure that V.sub.con can be pulled down to zero volts 
when this is needed. 
By adjusting R8, the 56 mph onset point, where V.sub.con starts to 
increase, can be changed. For instance, V.sub.con can be made to increase 
from zero to 12 v for a vehicle speed of 60 to 68 mph by reducing R7. 
Also, if V".sub.pos remains constant, but at 3 v instead of 9 v, then 
V.sub.con increases from zero to 12 v for a vehicle speed of 53 to 61 mph. 
The 8 mph speed interval (56 mph to 64 mph) will remain essentially 
constant. Capacitor C6 acts to reduce the ripple voltage on V.sub.con due 
to the ripple voltage on V.sub.spd, by providing a low impedance path 
around R6 at high frequencies. 
V.sub.spd and V.sub.con are also used for force control, as explained 
later. For position control, V.sub.con is only used about a very limited 
range of values to switch the solenoid valves on and off. This is achieved 
as follows. 
Assuming that voltage comparator U2 (used for force control) is an open 
circuit, resistor R4 simply passes through the voltage, so that V'.sub.con 
=V.sub.con, and this voltage appears on the inverting junctions of 
comparators U7 and U8. The combination of R4 and C11 add additional 
filtering on any high frequency ripple voltage not removed by filter C6. 
R36, R37 and R38 establish 0.9 v and 1.2 v on the non-inverting junctions 
of U8 and U7, respectively. 
Now assume that V'.sub.con is less than 0.9 v. The voltage on the inverting 
junction is lower than the voltage on the non-inverting junction of both 
U8 and U7. Therefore the action of both U8 and U7 is to disconnect their 
outputs from ground via an internal switching transistor, and the 12 v 
through R39 and R40 will raise the outputs of U8 and U7 to be at or near 
12 v. Power MOSFET transistors Q3 and Q2 therefore conduct, and solenoid 
coils L2 and L1 are then energized. Coil L2 controls the retract solenoid 
valve 58, with the coil being energized meaning that the valve connecting 
the conduit 56 to atmosphere is open. The actuator 33, 34 will retract due 
to the force of the operator's foot and therefore the pedal is depressed 
to increase the distance "X". Coil L1 controls the extend solenoid, with 
the coil being energized meaning that the intake valve to the servo pump 
is held open and no air is pumped to the actuator. 
If V'.sub.con is between 0.9 v and 1.2 v, the output of U8 switches to 
ground, Q3 stops conducting, L2 is deenergized and the retract solenoid 
valve 58 closes. The air in the conduit 56 is therefore trapped, so the 
actuator 33, 34 is prevented from moving. Coil L1 remains energized as 
before so that the ball check 61 is spaced from the seat therefor. 
If V'.sub.con is more than 1.2 v, the output of U7 switches to ground, Q2 
stops conducting, L1 is deenergized and the extend solenoid 59 no longer 
holds the intake valve 61 of the servo pump 49 open. The servo pump 49 
therefore pumps air into the conduit 56 so that the actuator 33, 34 will 
extend and the pedal 18 be pushed upwards. Coil L2 is still de-energized 
at this point. 
R35 and R42 have very large resistance values, and create a small "positive 
feedback" or latching action on U7 and U8, so that these devices do not 
tend to switch up and down due to any residual ripple voltage or noise 
that is present on the input junctions. 
The important point about the previous paragraphs is that the pedal will be 
depressed if V'.sub.con (and therefore V.sub.con) is less than 0.9 v and 
raised if V'.sub.con is greater than 1.2 v, and this corresponds to 
V.sub.spd being 2.83 v and 2.84 v respectively. This is a very narrow 
range of voltage and corresponds to the speed being between 56.6 mph and 
56.8 mph. For many purposes, we can ignore this range and consider that 
the net effect is for the pedal to be depressed if the speed is below a 
reference speed of 56.7 mph, and raised if it is above the reference 
speed. The purpose of the 0.2 mph "dead spot" will be explained shortly. 
The next step is to finally show how the above characteristics combine with 
other circuitry to control the pedal position in the desired manner. 
All of the above assumes that V".sub.pos remains constant at 9 v, but it 
actually varies as the pedal position "X" varies. This occurs due to the 
variation of V'.sub.pos, which in turn varies with V.sub.pos, which in 
turn varies with R3, the resistance associated with the position 
transducer measuring the pedal position. When the pedal is fully down 
(X=2"), V.sub.pos is at ground. As the pedal moves up, V.sub.pos increases 
as R3 interposes its increasing resistance between ground and the 
non-inverting junction of U5. This voltage rise occurs due to the fixed 
resistor R15 between the junction and 7.56 v. When the pedal is fully up 
(X=0), V.sub.pos is 1 v. The variation of V.sub.pos between the two 
voltage extremes is to a good approximation a linear function of the pedal 
position. The resistance elements R13 and R16 associated with U5 make it 
act as an amplifier and buffer for V.sub.pos, resulting in the voltage 
V'.sub.pos. As V.sub.pos varies from zero to 1 v, V'.sub.pos varies 
proportionately from zero to 6 v. For later purposes, it should be noted 
that this implies the following formula; V'.sub.pos =6-3X. 
U5 is a comparator, like U7 and U8, but is used as an op amp, like U9. It 
is characterized by the op amp attempting to keep the inverting junction 
voltage equal to the non-inverting junction voltage by appropriate changes 
in its output. R14 is required to energize the action of U5, enabling it 
to put out the required voltage level. R11 performs the same function for 
U6. 
V'.sub.pos is fed to U6 and results in the output V".sub.pos by the action 
of C7, R43, R24 and R12. If V'.sub.pos does not change too quickly, 
V".sub.pos varies from 5 to 7 v (6.+-.1 v of the voltage is expressed as a 
steady component plus and minus a symmetrically varying component), as 
V'.sub.pos varies from zero to 6 v (3.+-.3 v), i.e. a reduction by a 
factor of three in the range of variation, with an added bias of 3 v on 
the steady component of the voltage due to the effect of R24 being 
connected to 7.56 v. (The added bias is actually 5 v instead of 3 v, since 
the gain reduction of 3 v implies that V".sub.pos would be 1.+-.1 v 
without the bias.) If V'.sub.pos varies smoothly and quickly but in a 
cyclic manner between 0 and 6 v, V".sub.pos tends to vary through a 3 to 9 
v range (6.+-.3 v), i.e. a range of variation equal to the 3.+-.3 v 
variation of V'.sub.pos. If V'.sub.pos has settled down at zero v but then 
jumps up to 6 v, V".sub.pos starts out at 5 v, jumps up to 11 v but then 
settles gradually down to 7 v; if V'.sub.pos then jumps back to zero v, 
V".sub.pos jumps from 7 down to 1 v, but then gradually increases to 5 v. 
This provides the necessary transition between the two modes of operation. 
For purposes of initial explanation, we shall first examine what occurs 
when the second of the above cases results, and V".sub.pos varies through 
a 3 to 9 v range. (V'.sub.pos is also used for force control, as explained 
later, and explains why some of the specific circuitry is used.) 
It was previously established that, if the speed is less than 56.6 mph, 
V.sub.spd is less than 2.83 v, V.sub.con drops proportionately to less 
than 0.9 v so that V'.sub.spd will remain equal to V.sub.spd. At the same 
time, the pedal is depressed due to the effect of V.sub.con on the 
solenoid valves. This was all based on assuming that V".sub.pos remained 
at 9 v, but as the pedal is depressed, this voltage actually reduces, as 
has just been described. The effect of a reduction in this voltage is to 
attempt to reduce V'.sub.spd, because of the connection to V".sub.pos 
through R10. This is another example of "feedback". Due to the action of 
U9, this must cause V.sub.con to again rise, eventually to just above 0.9 
v, and the result of this is to cause the pedal to stop moving. It should 
be evident that, as the speed, and thus V.sub.spd, drops to lower and 
lower values, a series of conditions will exist, where the pedal will be 
increasingly depressed as the speed is reduced. Full depression of the 
pedal causes a drop in V".sub.pos from 9 to 3 v (a change in X from zero 
to 2"), and the value of R10 is such that this must have resulted from a 
drop in V'.sub.spd from 2.83 v to 2.68 v. Since V.sub.spd is equal to 
V'.sub.spd during all this, the vehicle speed must have dropped from 56.6 
mph to 53.6 mph. This is exactly the characteristic as shown by the graph 
of FIG. 9, that we initially stated we wanted to achieve. (Note that 
V.sub.con is always equal to 0.9 v at each equilibrium condition.) 
The foregoing would correspond to a situation where the vehicle encounters 
a steep hill, causing the vehicle to slow down; the pedal will therefore 
be depressed until the engine is able to develop enough power to maintain 
speed. 
It should be evident that when the top of the hill is reached and a 
downgrade is encountered that the vehicle will speed up, V.sub.con will 
rise to more than 1.2 v, the actuator 33, 34 will cause the pedal to rise, 
and essentially the same relationship between pedal position and speed 
will be achieved for the case of increasing speed, except that V.sub.con 
remains at 1.2 v rather than 0.9 v. 
Since X cannot go below zero or above 2", variations in V.sub.spd above 
56.6 or below 53.6 mph are responded to by variations in V.sub.con, as 
previously described for constant V".sub.pos. 
The purpose of the 0.3 v dead spot, where V.sub.con can cause the pedal to 
neither raise nor lower, is to keep the solenoid valves from being cycled 
continuously once the proper relationship between pedal position and speed 
is achieved. This will extend the life of the mechanical components. As 
stated before, this dead spot corresponds to a change in V.sub.spd of 0.01 
v, which is a speed range of only 0.2 mph. There is a corresponding 
variation in pedal position, where the pedal can be moved without causing 
a reaction from the control circuit. This amounts to only a 0.4 v 
variation in V".sub.pos, and this corresponds to 0.133 inches of pedal 
travel. 
If the dead spot is too small, it is still possible for the solenoid valves 
to continuously cycle. The tendency to do this is measured by the "gain" 
of the combination of coil drive, solenoid valve and actuator, and is 
determined as follows. The actuator moves the pedal down at a range of +2 
inches per second when V'.sub.con is 0.9 v, and moves the pedal up at -2 
inches per second when V'.sub.con is 1.2 v. The total change in pedal 
speed is 4 inches/second, and the change in voltage is 0.3 v. The gain is 
therefore 4/0.3 or 13.3 inches/second per volt. With the other gains 
involved, this results in a "loop gain" of 30/seconds, a quantity that is 
used by those familiar with "feedback control theory" to analyze dynamic 
behavior of control devices such as the position control. 
We can now state what happens when the pedal position varies slowly enough 
so that, instead of V".sub.pos being equal to V'.sub.pos +3 v, the 
variation in V".sub.pos is only one third as much; V".sub.pos =V'.sub.pos 
/3+5. The pedal will go from full down at 54.6 mph full up at 55.6 mph, as 
V".sub.pos varies from 7 down to 5 v. Instead of there being a 3 mph speed 
variation, there is then only a 1 mph variation. This is desirable from 
the point of view of very accurate control over the speed, and will be the 
situation that occurs except when there are very sudden changes in 
operating conditions. The dead spot in pedal travel is therefore reduced 
to 0.044 inches. The reason for having the larger speed variation at all 
has to do with the stability of control; if the speed range remains small 
for quick variations in speed (loop gain equal to 90/seconds), the vehicle 
speed may cycle about the desired point instead of settling down. 
To summarize, position control is accomplished by the following steps: 
1. A voltage analog of the vehicle speed, V.sub.spd, is created; 
2. A control voltage, V.sub.con, is then created, which causes the pedal to 
move up or down based on whether a certain reference speed (56.7 mph when 
V".sub.pos is 9 v) is exceeded or not; and 
3. A voltage analog of the pedal position, V.sub.pos, is created and used 
to vary V.sub.con in such a way as to establish the desired relationship 
between pedal position and vehicle speed. 
Force Control 
Basically, the force on the pedal is limited to a maximum specified level 
by controlling the air pressure in the actuator. In this embodiment, the 
piston area of the actuator is 1 inch.sup.2, so that the conversion factor 
is "1 psi equals 1 pound of force". If the driver exerts enough force to 
urge the pedal down against the throttle return spring, but not enough to 
exceed this maximum, then the position control circuit maintains the pedal 
position as previously described. Only if he tries to overpower the 
position control does the force control come into action. 
The force control circuit consists of three parts: the first part generates 
a voltage which corresponds to the actual pressure in the actuator; the 
second part generates a voltage which corresponds to the maximum allowable 
pressure; the third part compares these two voltages and changes the 
voltage V'.sub.con so that it is no longer equal to V.sub.con. This latter 
action is done in such a way that the pressure is prevented from exceeding 
the maximum specified pressure. 
Generation of the actual pressure voltage will be described first. The 
voltage V'.sub.hal will cyclically vary as V.sub.hal varies due to the 
coupling of C1. The effect of diode D1 will be to shift the level of this 
voltage so that its minimum value will always dip to -0.5 v with respect 
to ground. This voltage is then averaged by the action of R17 and C9 and 
appears as V.sub.prs on the non-inverting junction of U1. 
The Hall effect transducer 116 is mounted on a diaphragm 113 whose interior 
is supplied with the pressure to be measured. When this pressure 
increases, the diaphragm 113 expands, moving the Hall device 116 closer to 
the magnets 102 on the flywheel 96. The magnetic field seen by the Hall 
device 116 thus increases and this causes a greater excursion in the 
voltages V.sub.hal and thus V'.sub.hal. Since V'.sub.hal is always 
reference to -0.5 v, this greater excursion will result in a predictable 
increase in the average voltage V.sub.prs. The result is that at zero psig 
(atmospheric pressure) V.sub.prs is 1 v, and at 50 psi pressure above 
this, V.sub.prs is 2 v. Between these two extremes V.sub.prs is to a good 
approximation a linear function of the pressure. 
The action of U1 in conjunction with R18, R20 and R44 is to act as an 
amplifier, buffer and bias shift of V.sub.prs, such that the output of U1, 
V'.sub.prs, represents the pressure with a calibration of 0.15 v/psi and 
measuring zero volts at 14 psig (28.7 psia). In other words, V'.sub.prs 
=0.15(P-14), where P is the pressure in psi. Capacitor C8 filters the 
ripple voltage that remains on V.sub.prs. R21 supplies the necessary 
current and voltage for U1 to operate. 
Calibration is achieved in the following manner. As initially installed, 
due to tolerances, the Hall device 116 will cause V'.sub.prs to have a 
gain that differs from 0.15 v/psi, and to have a bias at 14 psig. The 
physical distance of the Hall device 116 from the magnets 102 at 14 psig 
is first adjusted to eliminate the bias. The adjustment of the Hall device 
116 is facilitated by the fact that its center grounding terminal is 
soldered to the surface of the metal diaphragm in such a way that it acts 
as a mounting leg 117 (FIGS. 16 and 17) which can be bent to adjust the 
distance. The value of V'.sub.prs at 14 and 50 psi is then measured, with 
R19 not installed. A value of R19 is calculated which will give the 
correct gain, and this is installed. It may be necessary to readjust the 
bias or to repeat the entire procedure one or more times before both the 
gain and bias are satisfactory, since adjustment of one somewhat affects 
the other. 
Generation of the maximum pressure voltage will now be described. The 
voltage V.sub.mps at the non-inverting junction of U3 is generated so as 
to represent the maximum pressure as implied by the vehicle speed. This is 
obtained by applying V.sub.spd through R27 and V.sub.con through R25; in 
combination with R45, the resistors have values such that 1.413V.sub.mps 
is equal to the sum V.sub.spd +0.1V.sub.con. The voltage V.sub.spd 
+0.1V.sub.con -1.4 is the voltage which represents the desired maximum 
pressure function, with a conversion factor of 0.1 v/psi. (The 1.413 
factor is necessary for later purposes.) With V.sub.spd and V.sub.con 
being functions of speed according to the graphs of FIGS. 11 and 12, the 
graph of FIG. 10 results. This is the basic force function. The value of 
this function above 56 mph, where the steeper gain starts, is the only 
part that will actually be used. The main characteristic is that there is 
a steep force gradient from 56 to 64 mph, and a less steep gradient beyond 
64 mph. 
A superimposed change in the force due to the pedal position has been 
referred to. This is the same as if a spring were installed in the 
actuator, urging the piston downward, and for this reason is referred to 
as a pseudo spring force. It is intended that this spring have a rate of 6 
lb/in. This is accomplished as follows. V'.sub.pos is applied to the 
inverting junction of U3 through R26, at the same time as the output of U3 
is connected to this junction through R22. The values of these resistors 
are such that V.sub.mpsx is equal to the sum V.sub.spd +0.1V.sub.con 
-0.2V'.sub.pos -1.6. As with 1.413V.sub.mps, V.sub.mpsx represents a 
pressure function with a conversion factor of 0.1 v/psi. The bias of 1.6 v 
is provided by the use of 7.56 v supplied through R29. Since V'.sub.pos as 
previously noted can be represented by the formula 6-3X, we can state that 
the quantity V.sub.mpsx is equal to the sum V.sub.spd +0.1V.sub.con 
+0.6X-2.8. In other words, the pressure function of FIG. 10 has added to 
it an additional voltage equal to 0.6 v/inch pedal motion. This represents 
6 lb/in pedal force, and is the desired relationship. The purpose of the 
bias is so that the value of V.sub.mpsx is zero when the maximum pressure 
is 14 psi (which occurs at 56 mph, V.sub.spd =2.8, V.sub.con =X=0); this 
value can be changed by changing R29. To summarize, V.sub.mpsx =V.sub.spd 
+0.1V.sub.con +0.6X-2.8. This represents the maximum pressure where the 
voltage is zero when the pressure is 14 psig and the gain is 0.1 v/psi. In 
other words; V.sub.mpsx =0.1(P.sub.max -14), where P.sub.max is the 
maximum allowable pressure. Note that the op amp voltage cannot be less 
than zero; if a negative voltage is called for by the equation, the 
voltage will actually be zero. 
U3 was assumed to be able to respond to the voltages on its summing 
junctions. This can only happen if there is a source of sufficient current 
and voltage attached to its output. This will occur if the current flow 
through D2 due to R32, which is attached to 12 v, is not otherwise used 
up. Noting that U3 and U4 have their outputs connected together, if the 
output of U4 is not internally grounded, then the current due to R32 can 
indeed be used to generate V.sub.mpsx. This in turn is related to what the 
output of U4 would be if its output weren't connected to U3. This output 
voltage is designated as V.sub.tim, and this voltage will actually exist 
if the output of U3 is not internally grounded. It should thus be evident 
that V.sub.max, the actual output of U3 and U4, will be either V.sub.mpsx 
or V.sub.tim, whichever is smaller. 
Just as V.sub.mpsx represents the maximum allowable pressure on the basis 
of speed and pedal position, V.sub.tim represents the maximum pressure on 
the basis of time. The reasons for having the maximum pressure depend on 
time are as follows. Assume that the driver has been driving along, 
pressing just hard enough on the pedal so that the position control 
function will be active. The vehicle will maintain a speed of 54.6 to 55.6 
mph, depending on the amount of pedal depression needed to cause the 
engine to put out sufficient power to overcome the various loads on the 
drive train. The driver then attempts to pass a vehicle he has caught up 
with, and for various reasons he really needs to speed up significantly. 
Assuming the pressure control works as intended, he will immediately have 
to exert a force of 14 pounds, just to exceed the pedal position called 
for by the position control function. As his speed increases to 64 mph, 
the force he has to exert would have to significantly increase if it were 
to be in accordance with the graph of FIG. 10. This is not desirable, 
since this is legitimate speeding, and the driver's attention may be 
diverted, from the task of safely passing the other vehicle, to what is 
happening to the force on his foot. 
The passing phenomenon is marked by the fact that it takes place over a 
limited time interval. What is needed is for the force to remain constant 
at 14 pounds for 30 seconds and then increase gradually, if such is 
indicated by the value of V.sub.mpsx, over another 60 seconds. This is 
indicated in FIG. 14 and is accomplished as follows. 
We shall first explain the variation with time of V.sub.int, the voltage on 
the non-inverting junction of U4. Due to the connection to v.sub.con 
through R34, V.sub.int is normally equal to V.sub.con. For pedal position 
control, V.sub.con is in the range of 0.9 to 1.2 v, as it is used to 
trigger the solenoid valves. If the speed increases to 60 mph, V.sub.con 
increases to 6 v. Due to the action of C10, V.sub.int rises only slowly, 
taking 30 seconds to reach 1.6 v and about another 60 seconds to reach 2.5 
v; this can be described mathematically as roughly corresponding to an 
"integrating" action. The reaction of U4 to V.sub.int is determined by 
gain resistors R31 and R33 and bias resistor R30; when V.sub.int is 1.6 v 
or less, V.sub.tim is zero; when V.sub.int is 2.5 v, V.sub.tim is 3.6 v. 
Between these extremes, the relationship is a linear one. Now, just as 
V.sub.mpsx corresponds to a maximum pressure, so does V.sub.tim. When 
V.sub.tim is zero, the corresponding pressure is 14 psi, and when 
V.sub.tim is 3.6 v, the corresponding pressure is 50 psi. This is based on 
an 80 mph maximum speed so that v.sub.spd =4.0 V.sub.con =12, X =2; 
therefore the equation for V.sub.mpsx gives 3.6 v. 
Realizing that the real maximum pressure is V.sub.tim or V.sub.mpsx, 
whichever is smaller, the maximum pressure will first be determined by 
V.sub.tim, which is held at zero volts or 14 psi for 30 seconds while 
V.sub.int builds up to 1.6 v. The maximum pressure then increases linearly 
with time, up to 50 psi or whatever is called for by the speed as 
indicated by V.sub.mpsx. The actual voltage that exists on the output of 
U3 and U4 will be designated V.sub.max. 
If the passing speed is less than 60 mph, V.sub.max will take longer to 
build up. If it is greater than 60 mph, V.sub.max buildup will take less. 
This is desired since a lower passing speed means a longer passing time 
and vice versa. Once the passing procedure is completed and the speed is 
brought back down to 56 mph, V.sub.con will drop down to the normal 0.9 to 
1.2 v range. Since V.sub.int is now smaller, current can flow through 
diode D3, discharging C10 rapidly at least until V.sub.int is no more than 
0.5 v higher than V.sub.con. This provides for rapid reset of the time 
delay and will allow the driver to perform another passing procedure 
without encountering excessive resistance. The final 0.5 v drop in 
V.sub.int must be discharged through R34 over about 30 seconds time, which 
means that if the driver immediately speeds again, the delay before the 
pressure starts to build up is eliminated; this prevents him from using 
such a procedure to defeat the purpose of the deaccelerator. 
We are now ready to describe the part of the force control circuit which 
compares the maximum pressure voltage with the actual pressure voltage and 
acts to limit the actual pressure to the maximum. 
V.sub.max will appear at the non-inverting junction of U2, with an added 
bias of 0.5 v due to D2; thus the voltage at this junction never drops 
below 0.5 v. V'.sub.prs is applied to the inverting junction through R23, 
and the output of U2 is fed back through R28. If U2 is able to generate 
the required output as implied by these connections, the resistance values 
can be chosen such that; V'.sub.con =3(V.sub.mpsx -0.667V'.sub.prs) +1.5. 
If the pressure equivalents for V.sub.mpsx and V'.sub.prs are substituted; 
V'.sub.con =0.3(P.sub.max -P) +1.5. This will turn out to be the desired 
relationship; it means that V'.sub.con decreases by 0.3 v for every psi 
that the actual pressure exceeds the maximum, and that it operates with a 
bias of 1.5 v. 
Assume that V'.sub.con drops below 0.9 v in accordance with the equation 
just given, because P rises above 16 psi and P.sub.max is at 14 psi. U8 
goes high, which ultimately causes the pressure in conduit 56 to connect 
to atmosphere as previously explained. Since the driver holds the pedal at 
a certain position, the air pressure P will drop instead of the pedal 
moving downward. When this pressure reaches 16 psi, the value of 
V'.sub.con rises to 0.9 v. In accordance with the circuits just described, 
the connection to atmosphere is again closed, and the pressure then stops 
changing. Conversely, if the pressure drops below 15 psi, V'.sub.con is 
above 1.2 v, the servo pump ports air to the conduit 56, increasing the 
pressure. We thus have another feedback loop, in which the pressure is 
maintained between 15 and 16 psi when P.sub.max is 14 psi. The 1 to 2 psi 
apparent discrepancy between the actual and maximum pressure does not 
actually exist, since the ultimate intent was to control the initial 
pressure to an average of 15.5 psi, and the 14 psi number has been used 
merely for clarity of explanation. It should be evident that the circuits 
will act to control the pressure to 1 to 2 psi above P.sub.max for any 
value of P.sub.max. 
All the above assumes that V'.sub.con can be controlled by U2; this means 
that V.sub.con must be above 1.2 v, since flow of current through R4 is 
the source of current for the operation of U2. This situation will always 
be associated with the driver overpowering the position control. 
The 1 psi dead spot in the control of the pressure serves the same purpose 
as the dead spot in the position control; if the dead spot is too small, 
the solenoid valves may cycle continuously. The gain which measures the 
tendency to do this is determined as follows. The pressure increases at 
+30 psi/sec when V'.sub.con is 0.9 v, and reduces at -30 psi/sec when 
V'.sub.con is 1.2 v. The total change in pressure rate is 60 psi/sec, and 
the voltage change is 0.3 v. The gain is therefore 200 psi/sec per volt. 
With a stated gain of 0.3 v/psi ior the rest of the loop, this results in 
a loop gain of 60/sec. 
Although a particular preferred embodiment of the invention has been 
disclosed in detail for illustrative purposes, it will be recognized that 
variations or modifications of the disclosed apparatus, including the 
rearrangement of parts, lie within the scope of the present invention.