Powertrains and Electric Vehicles: An Introduction for Mechanical and Electrical Engineers - Part 2

Powertrains and Electric Vehicles: An Introduction for Mechanical and Electrical Engineers

This is part two of a three-part series, you can read part one - here. An Engine Control is also known as an Engine Control Unit (ECU) or an Engine Control Module (ECM). It is an electronic component that monitors and controls an automobile's engine to ensure that the right flow and mixture ratio of air and fuel enters into the engine to deliver the required torque.

Evolution of Engine Controls   

The braking or the brake adjustment you would do on a bicycle is one of the most primitive forms of calibration or controls with regard to automotive engineering principles. But thanks to modern technology, we have since improved our methods of control and calibration. 

Initially, carburetors and magnetos were widely used to supply fuel, but today we use a completely electronically controlled engine. 

The engine control module is the brain that tells you how much of the fuel and air should come, and when the injection should take place. It also dictates the engines' air to fuel ratio. In the end, the entire game plan of engine controls is to figure out how to ensure proper and accurate torque delivery using all of this information.

We have come a long way from purely mechanical controls to mechatronic controls, which are a fusion of mechanical and electronic systems. Before we dive deeper into this, let us look at how much of a regular automobile is occupied with electronic systems.

The Expanse and Share of Electronic Systems in an Automobile

The share of electronics systems in the modern automobile has grown multifold, not just in the aspect of powertrains but also in other areas like; ADAS (Automatic Driver Assistance System ), Collision systems, lighting systems, and entertainment and infotainment systems. 

• Lighting
• Collision avoidance
• Engine and emission management
• Multi-zone automatic climate control
• Electrochromic glass
• Auto-distance cruise control
• Anti-lock Braking System (ABS)
• Navigation and a trip computer
• Entertainment
• Infotainment
• Airbag deployment system
• Rain-sensing automatic windshield wipers
• Tire pressure monitors
• Active suspension
• Traction control

A large fraction of automotive control systems in modern automobiles are electronic. Hence, let us first have a glance at automotive controls before jumping into the former.

Why Do We Use Automotive Controls? 

Purely mechanical systems are very limited in the amount of information they can provide to the user. For example, a mechanical system may indicate that a valve has been displaced but would not inform you of the precise amount by which it has moved.

Plus, a purely mechanical system will not provide information on how much torque should be delivered when the accelerator of a car is engaged by a certain amount or how much air and fuel should reach the engine. 

Due to these limitations, most mechanical systems are now transforming into mechatronic systems as the electronics systems advance.  

Accuracy Improvement, Lesser Failures, and Better Error Prediction 

Decreasing the scope of errors is crucial in the automotive sector. Better error prediction methodologies and improvements in accuracy can minimize failures and increase fuel efficiency. The ability of electronic sensors to understand the environment and provide accurate feedback makes this possible.

Preemptive Control and Response 

Preemptive control and response are critical in the automobile sector rather than a reactive response. This essentially means that you should be prepared for the future by analyzing and gaining substantial insight from past data. Automotive control systems provide this data, thereby improving the performance and safety of vehicles.

Automotive Electronics 

Now that you have a good idea of automotive controls, here is what you should know about automotive electronics to understand the concept better.

Improvements in vehicle controls go hand in hand with developments in electronics. One modern high-end car uses more lines of code than Facebook and Android combined. This goes to show how much device intelligence goes into making a smart automotive product.

Modern vehicles are equipped with better sensors that provide nearly perfect data acquisition for improved vehicle diagnostic methods and accurate failure detection. 

The world now realizes the value of automotive electronics. The share of electronics and electrical controls in the automotive sector has been on a rapid rise since the mid-1990s and is expected to grow to 50% by 2030. 

Intra-Vehicle Networks 

When you have so many electronics in a single product, it's challenging for them to be able to communicate with each other. This is where vehicle networks come into play.

Different types of controllers, like powertrain and body controllers, can interact with each other through intra-vehicle networking.  

CAN is the most important network protocol that is used in the car, and the Ethernet is predominantly used for diagnostics. Other networks include FlexRay for high performance and LIN for many multimedia fiber-optic interactions. 

Now, let us see how hybrid vehicles and their control mechanism fit into all of this.

Hybrid Vehicle Control 

The complexity of hybrid vehicle controls is more than that of a purely electric vehicle because of the presence of both internal combustion (IC) engine components as well as electric vehicle motor components.  

The whole game plan of hybrid electric vehicle controls is to blend the realm of IC engines and electric motors into a seamless and fluid working model.  

The vehicle pedals are a means of sending driver input to the electric propulsion subsystem that works in unison with the energy source subsystem and the auxiliary subsystem to produce the required output.  

There are different types of hybrid systems. The most common and primitive one is the start/stop hybrid system, which was a massive hit in the Indian market because it solved the problem of wasting a lot of fuel in traffic lights.  

Another hybrid concept is the starter-generator concept wherein a motor acts as a generator that is either connected to the engine or between the engine and the transmission. This adds to your electric torque. 

Parallel, Series and Power-Split Hybrids 

There are different types of hybrids.

Series Hybrid 

Advantages: 

• High efficiency in engine operation.
• Simple drive train.

Disadvantages: 

• Requires a large motor.
• Energy conversion losses.

Parallel Hybrid 

Advantages: 

• Minimal design changes from a conventional vehicle.
• Less energy conversion.

Disadvantages: 

• The engine cannot operate at its best efficiency.
• Low efficiency of automatic transmission.

Power-Split Hybrid 

Advantages: 

• Combines the benefits of series and parallel hybrids.

Disadvantages: 

• Design and control are more complex than the other two HEV types.

Conclusion 

As complexity in design increases, complexities in control systems also increase. Hence, it is up to the manufacture to decide which type of control systems is best suited for which automobile and which market.  

You can read the third and final part of this three-part series - here

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