Vehicle turn speed control

A vehicle turn speed control and method therefor having an engine control unit which receives input from at least one speed sensor and at least one angle sensor, calculates the vehicle turn radius, calculates the ratio of the vehicle speed divided by the vehicle turn radius, compares the ratio of the vehicle speed divided by the turn radius with a reference value and outputs a signal to a brake motor which is connected to the vehicle brakes and which will apply the brakes when the calculated ratio of vehicle speed to turn radius exceeds the reference ratio of turn speed.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a vehicle control system. More particularly, the 
invention relates to a method and apparatus for controlling the turning 
speed of a vehicle. Most particularly, the present invention relates to a 
method and apparatus for controlling the turning speed of the vehicle by 
determining the ratio of the vehicle speed divided by the turn radius, and 
applying pressure to the brakes of the vehicle to slow the vehicle if said 
ratio is greater than predetermined design criteria expressed as a 
reference ratio. 
2. Description of the Prior Art 
The present invention uses speed sensors and angle sensors in conjunction 
with an engine control module or engine control unit and a brake motor to 
apply the vehicle brakes under certain pre-determined conditions. While 
the various components have been used in various ways in the prior art, 
there is no combination showing total vehicle turn speed control. 
The U.S. Pat. No. 5,407,023 to Yamashita et al., shows the use of angle 
sensors and wheel speed sensors, together with a controller, in a manner 
such that the amount of slip of the driving wheels converges on a target 
value when the amount of slip of the driving wheels exceed a predetermined 
threshold value. When the vehicle is making a turn, the amounts of slip of 
the driving wheels is calculated, and the calculated amounts of slip are 
corrected with correction values for correcting the amounts of slip of the 
inner and outer driving wheels taking into account the difference between 
the wheel speed of the inner driving wheel and that of the outer driving 
wheel during turning. 
The U.S. Pat. No. 5,289,100 to Craig L. Joseph shows a propulsion system 
whereby when a vehicle is making a turn, an inside motor provides an 
electric current to a D.C. bus to supply additional power to an outside 
motor. Speed and steering signals operate the electric motors and control 
the speed of an engine and an alternator which supplies power to the D.C. 
bus. 
The U.S. Pat. No. 5,383,531 to Yoshioka et al. shows a turn control system 
for a four wheel drive vehicle which includes an accelerating transmission 
for driving the right and left steerable wheels at a greater average 
velocity than the right and left non-steerable wheels. 
None of the above prior art shows a system which controls the speed of a 
vehicle based on a comparison of the ratio of the vehicle speed divided by 
the turn radius with a reference ratio of turn speed. The speed of the 
vehicle is controlled in turns so that it does not exceed such reference 
ratio, which is a predetermined design limit supplied by the auto 
manufacturer. Thus, those skilled in the art continued to search for a 
satisfactory system to prevent vehicles from being driven around corners 
at excessive speeds. 
SUMMARY OF THE INVENTION 
A vehicle turn speed control is provided having an engine control unit or 
engine control module which receives inputs from at least one speed sensor 
and at least one angle sensor calculates the vehicle turn radius, 
calculates the ratio of the vehicle turn radius divided by the vehicle 
speed, compares the ratio of turn radius divided by vehicle speed with a 
reference ratio, and outputs a signal to a brake motor which is connected 
to the vehicle brakes and which will apply the brakes when the limit turn 
speed is exceeded. 
In one embodiment of the invention, the engine control unit and brake motor 
may be dedicated to the vehicle speed control system of the present 
invention. 
In another embodiment of the present invention, the engine control unit may 
be the same as found in almost every vehicle equipped with an automatic 
braking system (ABS). Several inputs will need to be added. One input will 
be added for a speed sensor. Another input will be added for the turn 
angle. A third input will be provided to receive the predetermined design 
values represented by the reference ratio of limit turn speed. One output 
will be added for controlling a brake motor. 
The brake motor may be such as found in any vehicle having an ABS brake 
control system, or a separate brake motor may be added if the system is 
used on vehicles without ABS brake systems. 
Therefore, it is an object of the present invention to provide a vehicle 
turn speed control which prevents accidents from occurring during normal 
driving conditions when the operator of a motor vehicle attempts to go 
around a corner at a speed faster than the safe speed for which the 
vehicle was designed to take a particular corner. 
Further objects and advantages of this invention will be apparent from the 
following description and appended claims, reference being made to the 
accompanying drawings forming a part of the specification, wherein like 
reference characters designate corresponding parts in the several views.

It is to be understood that the present invention is not limited to its 
application to the details of construction and arrangement of parts 
illustrated in the accompanying drawings, since the invention is capable 
of other embodiments, and of being practiced or carried out within the 
scope of the claims. Also it is to be understood that the phraseology and 
terminology employed herein is for the purpose of description, and not of 
limitation. 
DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIG. 1 there is shown a motor vehicle, generally designated by 
the numeral 20, in which the construction of the present invention has 
been embodied. In the embodiment shown, the motor vehicle 20 is a front 
drive vehicle having an engine 21 driving the front wheels 22 through two 
halves of a split drive shaft 23. Rear wheels 24 are mounted for rotation 
on solid axle 25. Although a front wheel drive motor vehicle is 
illustrated, it can easily be understood that the present invention may be 
used with any drive arrangement having any number of driven 22 and 
non-driven wheels 24. 
Regardless of the drive arrangement, the present invention will utilize at 
least one speed sensor 26, preferably associated with a driven wheel 22, 
and at least one angle sensor 27. The angle sensor 27 detects the turning 
angle of the steering wheel 28a as it turns steering shaft 28. 
Referring now to FIGS. 1 and 2, the signals from the speed sensor 26 and 
the angle sensor 27 are input to an engine control unit or module 30. The 
engine control unit or module 30 may be a dedicated module operating only 
the vehicle turn speed control system of the present invention, or, as 
found in many vehicles, it may be such as an engine control unit having an 
engine control section for effecting the fuel injection control and the 
ignition timing control of a modern internal combustion engine. It is only 
necessary to add the speed sensor and angle sensor inputs to existing 
engine control units to adopt them for use in the system of the present 
invention. It is also necessary to supply an additional input for the 
design values or reference value input supplied by the motor vehicle 
manufacturer, to be discussed hereinafter. 
As shown in FIG. 2 the engine control unit 30 will supply an output to a 
brake motor 35 which is hydraulically connected to the well known disc 
brake systems 36. 
Referring now to FIG. 3, at the supplying of a suitable start signal by 
means well known in the art, the system will begin operation (box 100). 
The system will first read the vehicle speed (V.sub.S)from the speed 
sensor 26, and the turn angle theta .vertline..theta..vertline. from the 
turn angle sensor 27. The system also reads the reference ratio of turn 
speed (R.sub.S) 31 supplied for the particular vehicle by the vehicle 
manufacturer (box 102). 
The system will then calculate the turn radius (R.sub.T)(box 104) by linear 
interpolation from the following Table 1. An example of the relationship 
between the steering angle .vertline..theta..vertline. and the turn radius 
(R.sub.T) of the vehicle is shown in the following table: 
______________________________________ 
.vertline..theta..vertline. 
R.sub.T 
(degree) (m) (ft) 
______________________________________ 
15.degree. 150 492 
30.degree. 85 279 
85.degree. 30 98 
175.degree. 15 49 
255.degree. 10 33 
340.degree. 8 26 
425.degree. 6 20 
510.degree. 5 16 
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Next, the system will calculate a ratio based on the vehicle speed divided 
by the turn radius (box 105) and will compare that value to the reference 
ratio or limit turn speed (box 106). If the calculated ratio is not 
greater than the reference ratio, no action will be taken, and the system 
will loop back to box 102 and begin the loop of reading the values, 
calculating the turn radius and ratio, and making the comparison. Nothing 
is done until the ratio of the vehicle speed over the turn radius exceeds 
the reference ratio. 
At this point the system gives a control output signal 108 which opens the 
brake valve 110 in the brake motor 35 which results in an increase in 
braking pressure (box 112) which will reduce the speed of the motor 
vehicle. 
When the return (box 116) is reached the system will cycle back to the 
start at box 100. The vehicle speed will continue to be reduced until the 
ratio of the vehicle speed divided by the turn radius is no longer greater 
than the design reference ratio (box 106), at which time the control 
signal 108 will cease to be supplied to the brake motor 35, and the brake 
valve will close. This will result in no further pressure being applied by 
the brake motor 35 through the calipers 38 to the discs 37, and the 
control of the vehicle again will be with the vehicle operator. 
It should be understood that the system is primarily intended for use on 
dry pavement. In other words, the design reference values give the maximum 
turn speed for the vehicle for a particular speed on dry pavement. Thus, 
the system is not intended to operate under wet or snowy conditions when 
the vehicle speed will be much slower than the speed of operation on dry 
pavement, and thus the system would not operate unexpectedly in adverse 
weather conditions. However, the system is particularly advantageous under 
normal driving conditions on city cross roads, where there are no speed 
limit signs such as are normally found on curves, to guide the driver as 
to what a safe speed is. Under these conditions, the system will operate 
and will prevent turnover accidents which frequently occur by virtue of 
drivers trying to take corners within the city limits at too great a 
speed. 
Therefore, by carefully analyzing the operation of motor vehicles under 
turning conditions on a wide variety of road surfaces a novel vehicle turn 
speed control has been developed.