NME3521 Modelling of Electromechanical Systems: HEV Analysis

This project provides a comprehensive analysis of hybrid electric vehicles (HEVs), exploring their design, components, and operational characteristics. The document begins with an introduction to HEVs, highlighting their advantages over traditional internal combustion engine (ICE) vehicles and pure electric vehicles (EVs). It explains the combination of combustion engines and electric motors, which enables HEVs to achieve both extended driving ranges and reduced emissions. The analysis includes discussions on mild and full HEV configurations, detailing features such as auto idle-off and regenerative braking. The document presents equations for calculating average power and energy dissipation during braking, and graphs illustrating the NEDC vehicle driving cycle are provided. These graphs show the interplay between ICE and electric motor usage, battery voltage fluctuations, and energy recovery through regenerative braking. Furthermore, the project delves into energy efficiency calculations, power train configurations, and the flow of power from both ICE and electric motors. The conclusion emphasizes the promising future of HEVs, while also acknowledging the technical challenges associated with their widespread adoption, such as high manufacturing costs and battery-related issues. Finally, it suggests measures to promote HEVs, including the establishment of charging infrastructure.

Hybrid Electric Vehicle
Introduction
Machines, as the definition goes, are meant to make work easier. Therefore, cars, just like any
other machine, are supposed to conveniently move you from one location to another.
Manufacturers take into consideration cost, efficiency and environmental pollution caused by
emissions when designing and manufacturing cars. Sadly, most cars are fitted with fossil fuel
engines which for ages have been main component of pollution due to emissions. And pure
electric vehicles, despite being emission free, do not have ability to go over long distances and
cannot provide power to vehicles of internal combustion engines. (Pistoia, 2010)
So the invention of hybrid electric vehicle has been a great stride forward. HEV combines both
combustion engines and electric motor engines. This ensures that the HEV vehicle can drive as
far as you would want and at the same time emit just a fraction of harmful gases; just as ICE
powered vehicles emit. For instance for shorter trips such as running errands electric motors are
used, and while driving in highways over considerable distances one should opt for combustion
engines so as not to deplete batteries. (Liu, 2013)
The hybrid electric vehicle balances when to use either of the engines.
Analysis
The hybrid electric vehicle has been engineered in mainly two formats; mild and full. They have
similar basic features:
 Auto idle off
 Regenerative breaking that is energy is recovered through generator while decelerating
 Battery can provide additional power in times of high demand driving.
Average power can be found by the equation;
And the energy that is being dissipated when braking by deceleration can be calculated using the
formula;

The following graphs are for the NEDC vehicle driving cycle that I worked in part two of the
assignment.
The graph starts with the positive spike signaling the start of the ICE using stored energy
in the battery. And in addition the battery gives additional when the NEDC vehicle starts
accelerating.
And after around 100 seconds some battery power starts to be recovered from the running
engine so the power becomes negative. And this is shown by sharp spikes throughout the
whole cycle showing energies being recovered as the car brakes and stops. The ICE is
switched off and restarted and the cycles repeated.

The NEDC vehicle starts with a positive spike as the engine receives power and
accelerates. Negatives at 100, 250 and other points shows power recovered as the
vehicles brakes and decorates.
The cycles continue showing positive and negatives spikes for the whole cycle as the
processes are repeated.
The battery voltage of the NEDC vehicle starts at 375 volts. The voltages oscillates about
the equilibrium of 375 volts. This goes down showing some spikes which signals the start
of recharging the battery and cycles and spikes above equilibrium shows the voltage that
is being drawn from the battery.

In the driving mode sufficient amount of electric energy can be recovered through
regenerative breaking and cruising for it meet the energy requirements for acceleration.
(Denton, 2016) Energy efficiency can be given by;
(AW + AL) x y1 + EW+EL > CR x y2+DR
This is,
FE = (ICE only % *ICE FE + hybrid use %*lab tested FE)/100
The energy stored in the battery at time t can be denoted E(t) and evolves according to the
differential equation;
E( t)=fs ps (t)
where Ps (t) is the electrical flowing into the battery.
The balance of power at the wheels gives the equation;
Pw (t)+P(t)+ P(t)=0
Power Train
Power from both ICE and electric motors

Figure showing a sketch of a combined ICE and electric motors
Power flows from the internal combustion engine, via the secondary drive shaft, via the
transmission, and then to the tires. Powers also from both electric motors, to the transmission,
and then to the primary drives shaft and the tires. (Husain, 2011) The overrunning clutches 3, 4,
and 5 are engaged and solenoid clutch 2 is engaged. Others are disengaged.
Conclusion

In regard to the future of vehicles, HEV’s star is shining bright. With the earth running out of
fossil fuels in less than a century due to depletion of earth deposits, the world might remain with
only one option and that’s turning to hybrid electric cars and vehicles.
HEV has numerous benefits among them reducing overdependence on petroleum fuels, ensuring
energy security, reduced emissions to the atmosphere aligns HEV with climate change mitigation
strategies and ensures clean air to the populace due to reduced emission.
But despite the above benefits, HEV has its own shortcomings. They include; first there a few
technical challenges that will need to be overcome before the HEV vehicles are universally
accepted and mass roll out starts. Technical glitches include high cost of manufacturing, faster
charging facilities, physical size of batteries, long charging time and many more. In addition,
HEV cars are only clean at the point use but will be more meaningful if use electricity produced
using clean source instead of fossil fuel generating stations.
Measures should be put in place among them increasing hybrid electric vehicles in transport
sector globally, introduction of wind generated and solar generated charging centers at
workplaces, homes and even charging centers just like we have petrol stations all over the world.
References
Denton, T. (2016). Electric and Hybrid Vehicles. New York: Routledge.
Husain, I. (2011). Electric and Hybrid Vehicles: Design Fundamentals. London: CRC Press.
Liu, W. (2013). Introduction to Hybrid Vehicle System Modeling and Control. Toronto: John Wiley and
Sons.

Pistoia, G. (2010). Electric and Hybrid Vehicles: Power Sources, Models, Sustainability, Infrastructure and
the Market. Tokyo: Gianfranco Pistoia.