Optimising EV Powertrains with Simulation for Efficiency and Performance

The automotive industry is accelerating toward an electrified future, and today, electric vehicles (EVs) have certainly taken centre stage in global transportation. EVs and their powertrains have rapidly evolved. EV powertrains are now at the top of these technological developments to enhance energy efficiency, cut carbon emissions, and improve vehicle performance. 

Global & Indian Perspective and Technology Drivers for EVs

The global transition to EVs isn’t just a trend but a reply to urbanization, climate change, and the growing demand for more sustainable transportation solutions. Governments around the world are setting ambitious targets for EV adoption. By 2030, the European Union aims to have at least 30 million electric cars on the road. China has already surpassed its target to increase the share of new energy vehicles (NEVs) to 20% by 2025, as it has already crossed 31% in 2023.

When it comes to India, the EV revolution is also gaining momentum. There are rising concerns over air pollution and energy security, and the country has set its sights on cutting its reliance on fossil fuels and adopting cleaner energy sources. Today, efficient, environmentally friendly transportation is becoming more critical than ever.

With increasing government regulations and rising consumer awareness, there is an increase in demand for radical innovation across the mobility ecosystem. The Indian government’s FAME (Faster Adoption and Manufacturing of Hybrid and Electric Vehicles) initiative backs EV manufacturing and infrastructure. However, several hurdles must be addressed quickly, including drivetrain efficiency, charging infrastructure, battery cost, payload improvement, better safety and security, and range anxiety. 

Developments in battery technology, power electronics, energy management systems, and, more importantly, powertrain optimization are some key technology drivers for EVs. Efficient powertrain systems are vital in making EVs more attractive, as they mean extended driving ranges, quicker acceleration, and better energy efficiency.

EV Powertrains 

The electric powertrain is a multi-disciplinary and hierarchical system with complex interactions between hardware design and software development. A classic EV powertrain comprises some key components. They are:

• Energy Storage System: The battery pack is the heart of the EV, as it stores electrical energy. Lithium-ion batteries are commonly used due to their high energy density.
• Electric Machine/Motor: Electrical energy is converted into mechanical energy to drive a vehicle.
• Power Electronics: Some inverters and converters control the power flow between the battery and the electric motor & provide a mechanism combining with embedded controls such that the powertrain responds to the driver demands at every time instance.
• Mechanical System/Transmission: EVs, unlike internal combustion engine (ICE) vehicles, use simpler transmissions. Electric motors have a wide torque range, which usually requires a single-speed gearbox. 
• Embedded system: Embedded systems are integral to the operation of EVs, enabling seamless communication, information processing, control, and management of various vehicle components.

Challenges in Powertrain Design & the Need for Optimization

With growing consumer expectations, regulatory requirements, and competition, EV drivetrains must be more efficient. The efficiency of the powertrain directly impacts the driving range of an EV.  Even today, apprehensions about the range and the accessibility of charging infrastructure continue to limit consumer adoption. Optimisation of the powertrain through simulation can ensure that EVs can handle increased payloads while maintaining optimal driving ranges.

Cybersecurity becomes paramount with an increased dependency on software to manage EV systems, especially battery management and critical powertrain components. Safeguarding EVs from potential cyber-attacks and ensuring the safety of software systems is very important. 
Benefits from Simulation and Modelling

The performance of EVs is affected by many requirements such as cost, speed, weight, acceleration, charging capabilities, and the range in which the vehicle can drive on a single charge. To meet these requirements, many tradeoffs must be made for each component that makes up the EV powertrain: the electric motors, battery pack, transmission, and power inverter.

Modeling and simulation play a vital role in most types of engineering designs, and EVs are no exception. Engineers obtain critical insight into the design and operation of each component of an EV, as well as the overall vehicle, through computer modeling and simulation. Simulation allows engineers to recognize inefficiencies, improve mechanisms, and forecast a powertrain's performance under numerous driving scenarios.

Simulation workflow for efficiency calculation of a high-performance electric powertrain

It is often encountered that a component designed in isolation exhibits the best in class component performance, but when integrated into a system, shows significantly subpar attributes. The complex interactions and interdependence between the components require component validation and design optimization on a system level. System validation and verification is an important milestone in product sign-off.

The traditional way of detailed system validation study is done after making physical prototypes of components and this makes any design change very expensive. Virtual validation and verifications, which can be done at an early stage, requires accurate representation of the components to ensure the accuracy in predictability of the system. Model Based Design can form the base of System simulation.

As the product design matures, more and more high-fidelity data generated which can be used to improve the system model. The advanced techniques such as Reduced order Modelling (ROM) have proven to develop very accurate model representations from geometric simulation data. For complex simulation, such as prediction of battery temperature over a drive cycle or estimating motor performance for a given driving scenario, the ROMs have proven to accelerate the simulation speed without compromising the accuracy.

There is as much software in current vehicles as the hardware. Model based software development is widely used to develop the control software. The Battery management System (BMS) is the most critical piece of software in electric drivetrain. The functionality and the safety of the battery is determined by how well BMS performs its functions. Another important software code is motor controller, which is responsible for efficient operation of the electric machine.

Apart from these, there are several vehicle level ECUs that manage the overall operation of the vehicle. These software algorithms, once implemented, need to be verified with the plant model through Model-in-loop (MiL), Software-in-loop (SiL) or Hardware-in-loop (HiL) interfaces. The accuracy of the plant model developed for these validations is very important to ensure the software integrity for various operating scenarios.

An example of the power of simulation in optimizing EV powertrains is the collaboration between Ansys and the TAG Heuer Porsche Formula E Team. Ansys Simulation tools were used to improve the performance of Porsche's first fully electric race car, the Porsche 99X Electric. The focus was refining the powertrain’s efficiency during high-performance driving, as in extreme race conditions. 
Perfecting powertrain design through Simulation is the key in attaining top performance in high-stakes environments, including motorsports. 

Future Outlook

Simulation leads the race in electric mobility to develop electrified powertrains that meet market expectations—be it for cost or performance. There is an increased focus on innovation, and market leaders will be those who can successfully change the way we move while reducing environmental impact. They will be defined by their speed and efficiency.  

Advancements in ML and AI mean even more powerful simulation tools, thus enabling real-time optimization of powertrain systems and cutting development times. With virtual replicas of powertrain systems, engineers can test and hone designs in a simulated environment, fast-tracking development and cutting costs. 

As the world moves towards a cleaner and more sustainable future, powertrain technologies must advance to meet the demands. Advanced simulation technologies will play a key role in helping in the progress of design, testing, and optimization. Manufacturers can, therefore, deliver vehicles that not only meet consumers' needs but also contribute to a more sustainable future.

Ankit Adhiya, is the Senior Manager Application Engineering at ANSYS India. Views expressed are the author's own.