PRIOR ART
Techniques for lowering the overall fuel consumption using knowledge of the upcoming road-behaviour are under development. Several ways have been proposed in recent studies. The knowledge of future road condition is needed to increase the coordinated operation of vehicle auxiliary systems to decrease fuel consumption. In the area of power train control proposes an adaptable cruise control system & shift advisory system, for stop and go situations on a congested road. Using values for required engine torque, gear and slope of road, a reduction of the fuel consumption can be improved.
OBJECT OF THE INVENTION
This novel system focuses on the accessibility and processing of elevation and slope data for roads traveled by trucks & buses. It is to be used primarily for applications with shift advisor and predictive algorithms. Ways to estimate road slope have been proposed in many papers. Some of the cases, road slope is measured by GPS. Some of them talk about the use of pressure sensor to get the barometric pressure drop to estimate the road slope. One other way to predict road slope by monitoring the engine torque.

The method proposed in this system is extremely simple, low cost and uses existing components of the vehicle to predict the road slope. This system not only gives the estimation of road slope but also gives information about the trajectory of the road as the vehicle moves.
DESCRIPTION OF THE DRAWINGS
Fig-1 illustrates the tubular level sensors.
Fig-2 is the block diagram of microcontroller.
Fig-3 illustrates the level of two sensors, when the vehicle is on plane
road.
Fig-4,5 & 6 illustrates the level of two sensors, when the vehicle is on
gradient road.
DESCRIPTION OF THE INVENTION
In the present invention the basic principle behind this method is the level difference in the both edges of fuel tank due to the slope. There are two tubular level sensors fitted in the tank both equidistance from the tank walls and tank centerline shown in fig - 1. The sensor has a plastic float, which travels with the fuel level. Float (4) is connected to a resistive wire (2) (Nicrome). Based on the level and hence the float position sensor output resistance changes which is direct measurement of the level. This resistive output of both the sensors can be converted into corresponding voltage by circuit diagram below. A linier relationship can be established

between level and voltage output and can be programmed into the microcontroller shown in fig -2.
When vehicle is traveling on plane road without any gradient, level will be same for both the sensors which is illustrated in flg-3. As per circuit diagram, if the output of the sensors were same the resultant output would be zero.
If there is a gradient on the road the level will also show the same gradient in reverse direction. The sensors will correspondingly give different readings, which can be calibrated, in terms of angles in degrees shown in fig-4, 5 8B 6
Minimum and maximum detection angles as per the invention; tan A = H/L A = tan x (H/L)
L is a constant and can be set at appropriate value.
Hence "A" is directly related to the H, which is the level difference between the float positions.
Minimum & maximum value of "A" which can be detected:
From the experiences in STC project, Fuel level sensor can detect 2 mm of the height displacement.
Hmin = 2 mm
For having the resolution of 0.2 degree of slope the sensor separation length should be
tan (0.2)= 2/L

Lmin= 2/tan (0.2)
Lmin= 573 mm (approx)
For 573 mm separation, the maximum angle that can be detected with 350 mm height tank
Tan A = 350/573
A = 32° approx
For our 212 Ltr rectangular tank, we can detect from 0.2° to 32°-

WE CLAIM:
1. An apparatus for real time road slope estimation of the roads traveled by vehicles, which vehicles have a fuel tank comprising:-
a) a fuel tank,
b) two tubular level sensors fitted within the tank both equidistant from
the tank wall and tank center line,
c) a plastic float on each sensor adapted to travel with the fuel level in the two edges of the fuel tank,
d) a resistance wire (2) connected to the float (4),
e) a control circuit to convert the output resistance of two sensors into corresponding voltages,
f) the said sensors plastic float travel with the fuel level, thereby providing the levels at the two edges of the tank,
g) a micro controller programmed for linear relationship between the voltage outputs and the slope gradient,
h) the said sensors output resistance is based on the float position at one edge and thereby is based on fuel level on that corresponding edge of the fuel tank,
i) the said micro controller is programmed for the linear relationship between the voltage outputs 8B and the road gradient,

(-) such that when level is same for both sensors in a plane surface of the road, and the output of two sensors are same, which means resultant output which is difference of the two outputs is zero, and
(-) such that when level is different for both sensors in a gradient surface, and the output of two sensors are different which means resultant output which is difference of the two outputs is above or below zero value.
2. An apparatus for real time road slope estimation of the roads traveled by vehicles, wherein the detection angle of the road gradient is computed from the distance between sensors and level difference between the sensor floats, wherein L is the distance between sensors in the tube, H is the level difference between the two float positions and A is the detection angle based on H & L, wherein tan A = H/L and A- tan -1 (H/L).
3. An apparatus for real time road slope estimation of the roads traveled by vehicles, wherein minimum 85 maximum detection angles of the road gradient is computed from values of the distance between sensors and level difference between the sensors for a selected fixed level difference between the two sensors and selected minimum resolution of degree of slope desired to be detected.

4. An apparatus for real time road slope estimation of the roads traveled
by vehicles, as illustrated in Fig. 1-6.
5. An apparatus for real time road slope estimation of the roads traveled
by vehicles, as substantially described in the accompanying complete
specification.