Optimal Gear Shifting for Green Environment


The problem of efficient gear automation according to speed and load of and on vehicle is discussed in this article with the aim of minimizing the fuel consumption of the engine and also reduce the air pollution and saving precious fossil fuel, which is going to be determined by rules of fuzzy logic, mechanics and geometry, The simulation of gear shifting is done with tools of “matlab fuzzy inference system” and further implement and usage of this technology in traffic control and global positioning system management is also to be presented, all of this system will need a special type of sensing device to determine the actual load on a car or truck.


The biggest problem the world is facing is environmental change and increasing fossil fuel prices and both of these problems play a major role in an automobile, the amount of fuel using by a vehicle and the amount of carbon emission by automobile depends on the vehicle gearbox. In this article first part going to differentiate the multi-gear vehicle and single gear vehicle and the functioning of the gear changing in a vehicle with graphical explanation with mechanical and thermodynamically process of generation of power torque and speed.

Part 1

We come across the name of multi-gear vehicle like any motorbike or carex: hero splendor having and single gear vehicle scooters like Honda active or hero maestros A multi-gear vehicle has a number of gears of which one can be selected according to the speed and torque requirement, while in single gear vehicle there is only one gear.

Fig. 1: Multi-gear system

At the point of contact of the tire to the surface, its speed is the value of the change in position of that point with respect to the road surface and torque is the value of force applied by the contact point on the surface multiplied by the radius of the tire.

Torque = force * radius

Fig. 2: The torque of the vehicle

This force value is determined by the capacity of the engine and internal gear size, For example if the engine capacity is 1232 cc and 54 kW it means that the engine can provide maximum of 54 KW which means no of times the piston in cylinder goes up and down multiple into value of gas (1232cc in this case ) is equal to power of engine.

(Volume of the cylinder) * (number of rotation) = power eq2 for this case1232 * (number of rotation) = power

Fig. 3: Gear System

There is a third relation which is a general rule of mechanics

Speed * force = power;

In a circular motion, the force is actually torque

Speed * torque = power —– eq3

From Eq. 2 and 3

(Volume of the cylinder)*(number of rotation) = speed*torque

Here the volume of a cylinder is always constant as it’s the depends on the construction of cylinder size which means the,

Speed * torque = k * n, (let n= no of rotation)

Which means that speed multiplied by torque is directly propositional to the no of rotation of piston in a time unit the no of rotation is always depends on the amount of acceleration provided by the accelerator of the vehicle, suppose we have fixed the accelerator at a particular value

The Speed * torque = constant

Which means it is to be increased torque value should come down and if the speed decreases torque value will get an increase which means,

Speed = c / torque (for particular value of acceleration)

And hence, Speed is inversely proportional to the torque.

From here we can discuss the use of gear, suppose a there are two bikes running one on a plane road and one on a mountain road in an upward direction. Now due to gravitational force the bike going on mountain road needs more torque then the other bike, for this requirement different types of gears are required in a vehicle which can convert one torque and speed to other torque and speed value.

When an input gear is small and output gear is of large size the speed will be large and torque will be low and when the output gear of smaller size then that of the input gear the speed will be low and the torque will be high. So when a vehicle with only single gear runs on a mountain road and a plane road there torque and speed requirements are different but it cannot be fulfilled in this type in this case the rings of the gear starts slipping on the shaft of an engine and start wasting the use of full energy.

*Note this shaft and gear connection is a very vast automobile engineering topic and needs to read separately.
But in the case of a multi-gear vehicle, this torque speed requirement can be achieved with the help of changing the gear.


In this article, the approach of efficient gear determination will be discussed which will be found through fuzzy logic. A fuzzy logic is a type of logic that recognizes more than simple true and false values. With fuzzy logic, propositions can be represented with degrees of truthfulness and falsehood. For example, the statement, today is sunny, might be 100% true if there are no clouds, 80% true if there are a few clouds, 50% true if it’s hazy and 0% true if it rains all day. Fuzzy logic has proved to be particularly useful in expert system and other artificial intelligence applications.

The Fuzzy system works on three inputs. In actual practice, these will be sensed by sensors fitted into the vehicle. But for this work, which is just the software simulation, they are interactively entered by the user through the command window. The program asks the user to enter the values of the slope, road quality, and traffic conditions on the command prompt and works using the inputs provided by the user to simulate the decision process. The rule set has 27 fuzzy rules, in addition to traditional classical logic rules. The rules use linguistic variables. One example rule is:

If ((The slope of the road is flat) && (The quality of the road is good in terms of bumps per unit length) && (The traffic is clear)) Then (Selected Gear is “High”)
Another rule could be
If ((The slope of the road is steep) && (The quality of the road is poor in terms of bumps per unit length) && (The traffic is dense)) Then (Selected Gear is “Low”).

The machine fault used for study is shown in Fig. 2. We can use that for fault diagnosis of gearbox all of the tractors. It consists of:

  1. Test rig for the rotational machine.
  2. On-line signal acquisition system.
  3. Signal analysis.

It was made of five main parts:

  1. mechanical parts,
  2. pneumatic parts,
  3. hydraulic parts,
  4. lubrication system, and
  5. electrical and electronic parts,

that each one of them was formed of many subsets. A variable speed AC motor (30 kW) with speed up to 3000 rpm is the drive (details of electromotor are given in Table 1). A piezoelectric accelerometer (ATLPC 259 model, Made in England, Fig. 3) is mounted on the flat surface Gearbox and is connected to the PLC (programmable logic controller). A variable load establisher system beside rotation of Gearbox. Eight shock absorbers (Fig. 4) under the base of the testbed to cancel out vibrations.

Fig. 5: Load Variation

The proposed method here is to the determination of preferred gear with the help of fuzzy logic we have taken this assumption for the implementation of fuzzy logic which is as follow. With this assumption, we tried to simulate the fuzzy inference system in Matlab 13a version with the Mamdani rule and here the speed load and gearbox and result graph of the system.

Here the speed is classified in 4 ways as shown in figure

Load on vehicle: this load on the vehicle is a typical thing to understand its depends on actual weight on the vehicle and also the load due to movement with respect to the gravitational force
This eq of motion of a car can be written as:

F – Mgsin(θ) – mgcos(θ) * µ

Where µ is the value of the friction coefficient

Here the load can be written as Load =mgsin(θ)+mgcos(θ)*u

This load is needed to be calculated by a special type of sensor as it requires the actual value of weight on car and the amount of angle of the road.

Once the value of load is calculated it doesn’t need to recalculate but the value of angle change again and again but it could also be calculated with any GPS device

The value of gear is 4 for this demo

A gear is always an integer value so as can be seen in the figure


As you can see there are two dialler input which is going to decide the actual gear, the fuzzy logic takes input in fractional value and also gives output in fractional value as you can see the output here can be any of the infinite value between 1 to 4, so these value needed to be interpreted in practical form which is done by a Matlab code given in later column

Fig. 5: An optimal value

This slide is actually 3 dimensional surface graph of the gear changing pattern where input 1 is speed and input 2 is load and the vertical axis is the gear value, this is the Matlab code which is going the fuzzy value to the actual gear output, there is requirement of a special electronic circuit to make this transformation possible which can take this output from this code and make this happens in the real circuit and then in the gearbox.


The fuzzy inference system developed here for optimal gear shifting very flexible, which will optimize the oil consumption and emission of carbon from the vehicle. As a future work, this can integrate with the traffic system and GPS for optimal gear shifting in busy traffic conditions. Even the rule set may be varied to cater to the needs of different scenarios.

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