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Electric Mobility: What really drives the electric vehicle? | Chapter 6

Electric Mobility - Chapter Six
Electric Mobility - Chapter Six

Mobility Engineer 2030 | Electric Mobility - Chapter Six

Prof. Murugan was describing the historical evolution of EVs to his students before getting into the details of the electrical systems in an EV [1]. For all the attention that EVs receive today, they are not a modern development. Quite contrary to the buzz around them, they are close to two centuries old. According to the U.S Department of Energy, EVs were invented in the early part of the 18th century in Europe and in the U.S. It was Henry Ford’s Model T that gave a severe blow to EVs in the early 19th century. A petrol driven Model T was priced at $650, while an EV costed thrice that much. The price issue started more than a century back and continues even now. American customers liked long drives and the highways had come up in the U.S. Oil was cheap and internal combustion engine (ICE) driven vehicles became popular. The ‘70s saw a revival of interest in EVs when the price of crude oil shot up and original equipment manufacturers (OEMs) started looking at alternate fuels. Now, emission control and control of greenhouse gases has becoming the primary driver for the popularity of EVs.

Prof Murugan introduces the EV Battery

In an ICE vehicle, to vary the rpm (rotations per minute) and the torque or power delivered to the wheels, the amount of fuel sent to the engine should be controlled. In case of an EV, the flow of current in Amperes is the control lever for the motor rpm. Motors have a high range of rpm when compared to an engine. That explains why EVs do not have a complicated gear box like ICE vehicles for varying the speed and torque.

Prof. Murugan talking in front of a blackboard to a class of students
Prof. Murugan talking in front of a blackboard to a class of students

Among all sub-systems in an EV, the battery alone costs close to 40% of the total cost. It remains the single component that acts as a barrier for EVs to attain price parity with ICE vehicles. EVs will attain price parity when car makers can make it with the same profit margins as an ICE vehicle, without any government subsidies. The key parameters to measure the quality of a battery are its specific energy, specific power, safety, performance, life span and cost (Figure 2). Specific energy and specific power are the energy it can hold and the power it can deliver to the motor, for each kilogram of its mass. The lighter a battery, the more its specific energy and specific power.

Some materials are popular in battery usage. Lithium ion batteries (LiB) are the most popular batteries today. What is the reason for that? The reason is the high specific energy and specific power it has, when compared to other materials (Figure 2). The challenge with such batteries is the supply risk of the critical materials like Lithium and Cobalt. Almost all the Cobalt comes from Congo and Lithium comes from Argentina, Bolivia and Chile (ABC). These few countries hold up to 75% of the global supply of these materials and China has long-term trade agreements with the mines there. Every country is trying hard to come up with alternative materials for battery usage and reduce the dependence on China [2].

EV battery performance parameters
EV battery performance parameters

There are many materials available to make batteries. But Lithium ion batteries are popular. The reason is the high levels of specific power and specific energy.

Lithium ion batteries exhibit the highest levels of specific power and specific energy.
Lithium ion batteries exhibit the highest levels of specific power and specific energy.
Source: Visual Capitalist –The Battery Series https://www.visualcapitalist.com/critical-ingredients-fuel-battery-boom/

Kavya - the damsel in distress

Pavan came out of the classroom and opened WhatsApp to check for new messages. That’s a habit he is trying to get rid of but till date he is not able to. He saw messages from Kavya. And to his worry, there wasn’t one but seven new messages, all from Kavya. Kavya does ping him often but seven messages together! No, it’s rare and when she does, it’s not generally good news. Pavan opened the messages – quite worried. Big messages but the summary of it was that Dr. Rao, Kavya’s Dean, did not like the fact that she attended the EV conference skipping her regular attendance at college once more. He had warned Kavya of the consequences if the institute finds her attendance low. It might also mean she might not be allowed to sit for the final exam. This could jeopardize everything – Kavya already had a job offer but it would only materialize if she finished her graduation on time! The seven big messages were filled with Kavya’s worries, anxiety etc. Pavan knew something had to be done and done fast. He thought, if attendance is such a big issue why is it that his college is not warning him or any other students who are attending these external sessions or participating in activities.

He went to Prof. Murugan’s cabin and asked him upfront about this. Prof. Murugan explained him the intentions under the New Education Policy (NEP) 2020 [3] and the National Innovation and Startup Policy (NISP) 2019 [4]. He said the two policies were rolled out to develop and support the innovative and entrepreneurial mindset of students and faculty members. While the NEP specifically emphasizes on experiential learning, the NISP talks about special encouragement to students for pursuing new projects outside their regular curriculum. Pavan’s institute followed the principles underlined by these two new policies. Pavan became very excited – it seemed there was a way out for Kavya. Rather than replying over WhatsApp, he called her on the phone. He told Kavya to have a meeting with Dr. Rao. She should first understand his concerns over her attendance. He also shared what Prof. Murugan told him about the NEP and the NISP. Kavya felt very relieved. But she knew this one-on-one talk was never going to be easy. Nevertheless she should definitely give it a try!

Bharath explains Electrical / Electronic Architecture of EV

Bharath had now started focusing on the EV product architecture to make in the upcoming factory. He posed a technical challenge to his team, “How do we design the vehicle electrical/electronic (E/E) architectures such that it is easy to shift from the current ICE technology to the next-gen EV technology”? The automotive industry increasingly uses the term “ E/E architecture” that refers to the convergence of electronics hardware, network communications, software applications and wiring into one integrated system that controls an ever-increasing number of vehicle functions in the areas of vehicle control, body and security, infotainment, active safety, and other comfort, convenience, and connectivity functionality [5].

The electrical architecture in the ICE vehicle has played a very limited role - control low voltage distribution, head lights, display, cooling, cranking systems etc. It did not control the flow of the power or energy in the vehicle. The vehicular subsystems such as air conditioning systems, electric steering, seat controls, anchor break, air bags, wipers, headlights, USB charging ports, etc. are powered using low voltage electric supply (from an alternator coupled to the engine and from a battery). Going forward, Bharath strongly felt that the vehicle electrical architecture should be designed to be flexible and modular, so that it can easily adopt drivetrain electrification using present platforms.

Bharath holding an electronics circuit board in his hand in front of his team
Bharath holding an electronics circuit board in his hand in front of his team

Bharath recollected his discussion with an EV expert Dr Mhaskar [6]. He emphasized the need to consider power delivery path for components which use other than the electrical system (breaks, suspension control, steering, cooling), the electrical power demand of various sub-systems (e.g. infotainment systems, power windows, air-conditioning), the drive cycle-based torque / power requirements for all operating modes and the overall energy supply and management needs (including charging and regeneration capability utilization). We also need to consider technical specifications for products (e.g. opportunity of charging, quick charging, gradient, standards, drive cycle efficiency), the interaction with the external world (e.g. communication, bi-directional power transfer), adoption of different energy sources (e.g. fuel cell, battery & its combination) and the overall weight and volume of various components (battery, traction, air compressor). The cost, reliability and other key parameters related to technology maturity (e.g. use of silicon carbide-based system for inverters), the safety related parameters (e.g. use dual energy sources while powering auxiliary systems such as battery management system, traction control system & vehicle safety system), communication system layer (e.g. CAN for inter ECU communication, gateways for communications with the external world (charging infrastructure)) and the wiring harness and its placement (e.g. HV and LV system and its routing) are also important considerations for the electrical architect [6].

EVs need at least three types of energy conversion units: DC/DC converter, typically from high voltage to 12 V to power the low-voltage electronics. DC/AC traction inverter to drive the electric motors, typically three-phase, which supply the power to the wheels. AC/DC converters for recharging vehicle batteries both during braking energy recovery and from standard residential or high-power charging stations (for fast charging). The use of silicon carbide (SiC) for power electronics in EVs helps to increase the efficiency and range of such vehicles, while reducing the weight and cost of the entire vehicle and thus increasing the power density of control electronics [7].

Bharath concluded that the electrical architecture of an electric and connected vehicle needs to be reliable, efficient, fault tolerant, safety- as well as EMI/EMC compliant and it should allow the user to realize all operating modes of EVs. It has to handle the complexity of technology and vehicle features for electrification, ADAS, connected systems and for a number of ECUs, which are interconnected by various vehicle network topologies with a distributed functionality. The electrical architecture is typically designed considering control features such as traction control, body and chassis control, on board charger control, battery management system (BMS) control, auxiliary power system control, communication Interface control, controls required for standard and safety compliance etc [6].

E/E Architecture - Evolution and Future Trends

Bharath encouraged his team to study the evolution of the vehicle architecture over the years [8]. The integration of electrical and mechanical systems occurred in the late 1950s with the advent of basic cruise control. In the ’60s, there were audio and lighting enhancements; in the ’70s, new emissions controls spurred advances in E/E architecture; and by the ’90s, managing the complexity of the electrical/electronic architecture was becoming an issue for OEMs. In the early 2000s, data and communication protocols drove new product requirements, and in the past decade, OEMs have focused on features and regulations governing occupant safety, driver distraction and fuel economy, which have led to adoption of high-voltage powertrains and systems.

Past: Vehicle E/E architecture of the past had up to 150 electronic control units (ECU's). Most of this ECU's had an embedded microcontroller which controlled actuators, processed sensor signals, controlled mechanical operations (like ignition/injection control) and executed electronic functions (like auto-parking, air-bag trigger). Each function had its own electronic control unit. These ECU's were connected by wiring harnesses and there existed limited interactions between the different ECU’s [9].

Present: Vehicle E/E architectures of today have moved towards more centralized systems with dedicated domain control units (DCUs) or Domain ECU’s. Several functions are combined into a domain ECU to reduce the number of individual ECUs, consolidate functions and simplify the wire harness. Infotainment and driver assistance are expected to be the forerunners [9].

Future: The future server-based vehicle architecture is characterized by a few servers for centralized high-performance-computing. These servers will be closely connected and on the cloud for regular updates as well as for off-vehicle computations. Sensors and actuators are controlled by the central vehicle servers through standardized interfaces. There will be an intermediate step of a server-based vehicle architecture with additional ZONE ECUs and some remaining ECUs for safety-critical applications with strong real-time or latency requirements. The Zone ECU's bridge the sensors and actuators of today to the vehicle servers and thus help to reduce the wire harness as they are placed at different zones of the vehicle [9].

E/E architectures will have to accommodate advances in automated driving, expanded infotainment, 5G connectivity and increased vehicle electrification. The conventional approach of introducing new ECU with their own power, processing, data and connectivity for each new function will no longer work; it will not scale to accommodate all of the new requirements for computing power, data processing and power distribution. The rise of battery electric vehicles (BEVs) gives automotive OEMs the opportunity to start fresh and create a new E/E architecture — an architecture that considers the power and data needs of every electrical device in the vehicle and meets those needs in the most streamlined and integrated way possible. Bharath reiterated that if we get it right, then will have a competitive advantage in delivering a better digital user experience [5].

As Bharath completed his discussion and walked back to his office, he met Dr Sharma on the way. He requested Bharath to join him for lunch. On the way, he asked Bharath if had seen the morning news. He said one of their competitors had made an announcement that had caught the eye of the media, analysts, policy makers and consumers alike. He said he will explain to Bharath during lunch. Bharath was more focused on his meeting today and missed the news Dr Sharma was talking about. What was it that was so serious and had caught everyone’s attention?

Note:

All opinions and points-of-view expressed above are those of the authors and do not represent that of any other individual or organization.

References:

  1. The History of the Electric Car - https://www.energy.gov/articles/history-electric-car

  2. The New Materials that are shaping the Future of Mobility - http://autocomponentsindia.com/the-new-materials-that-are-shaping-the-future-of-mobility/

  3. National Education Policy - https://www.education.gov.in/sites/upload_files/mhrd/files/NEP_Final_English_0.pdf

  4. National Innovation and Startup Policy 2019 for Students and Faculty - https://mic.gov.in/assets/doc/startup_policy_2019.pdf

  5. What is an Electrical / Electronic Architecture, Aptiv, 2021

  6. Electric Architecture – the backbone of an electric vehicle, Dr Uday Mhaskar, KPIT

  7. Silicon Carbide for the success of Electric Vehicles - https://www.powerelectronicsnews.com/silicon-carbide-for-the-success-of-electric-vehicles/

  8. Evolution of Vehicle Architecture, Aptiv (2018)

  9. Future Automotive E / E Architecture, Arun Shankar, IEEE Publication

Connect with Authors on LinkedIn:

Dr Shankar Venugopal | Ramachandran S | Sayantan Mukherjee

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