The automotive industry is undergoing a significant transformation as it shifts toward electrification and sustainability. Among the innovations driving this change are in-wheel electric motors, which offer a unique approach to vehicle design and performance. These systems integrate the motor directly within the wheel hub, potentially simplifying vehicle architecture by minimizing the need for traditional components, such as transmissions and driveshafts. This design not only aims to simplify manufacturing, but also addresses weight management, which is critical for maintaining vehicle handling and performance.
As manufacturers look to create adaptable and modular vehicle platforms, in-wheel motors present an opportunity for increased flexibility in design and production efficiency. While challenges remain, including concerns about cost and the impact of unsprung weight on driving dynamics, advancements in materials and engineering solutions are being explored to mitigate these issues.
In this context, we spoke with Marko Lehtimäki, co-founder and CEO of Donut Lab, to gain insights into the evolving role of in-wheel electric motors.
Key takeaways:
- Integration and design: In-wheel electric motors are designed to be housed within the wheel hub, which can simplify vehicle architecture by potentially reducing the number of mechanical components, such as transmissions and driveshafts.
- Weight management: The weight of in-wheel motors is crucial for vehicle performance. Donut Lab's motors weigh under 40 kilograms, which is intended to minimize the impact on unsprung mass and maintain vehicle handling characteristics. This weight management is essential for achieving optimal driving dynamics.
- Cost factors: There are concerns regarding the cost of in-wheel motors. Donut Lab claims that their motors can contribute to lowering total drivetrain costs, as they utilize fewer materials while providing comparable performance to other in-wheel motors in the market.
- Impact on vehicle architecture: The use of in-wheel motors could facilitate modular vehicle designs, allowing manufacturers to create adaptable platforms that can be used across different vehicle types. This modularity may lead to efficiencies in production and design flexibility.
The following is an edited transcript of the conversation.
S&P Global Mobility: How do you see the role of in-wheel electric motors evolving in the context of the global push toward electrification and sustainability in the automotive industry?
Marko Lehtimäki: In-wheel electric motors are designed to simplify electric vehicle construction by integrating the motor directly within the wheel hub, which may reduce the need for components, such as transmissions and driveshafts. Our flagship motor produces 845 hp and weighs 88 pounds. This configuration aims to improve efficiency and performance. The potential benefits of in-wheel motors include lighter vehicle designs and the possibility of aiding automakers in meeting electrification objectives.
What do you believe are the biggest barriers to widespread adoption of in-wheel electric motors, and how can the industry collaboratively address these challenges?
The primary challenge with in-wheel motors is their weight, as excessive weight can negatively impact driving dynamics due to increased unsprung mass. Research indicates that adding up to 40 kilograms of weight in the wheel may not significantly affect handling for professional drivers, but exceeding this weight can lead to performance issues.
Donut Lab's motors are designed to weigh less than 40 kilograms, which is intended to address concerns related to unsprung mass. Additionally, there are considerations regarding cost; Donut Lab claims that their motors can reduce overall drivetrain costs compared to competitors. They also assert that their motors are competitively priced due to the use of fewer materials while maintaining similar performance levels.
How does the unsprung mass of in-wheel motors influence suspension design, and what engineering solutions are being developed to mitigate any adverse effects on ride quality?
Additional weight in the wheels can affect vehicle handling and ride quality. To address this issue, we are using lightweight materials and compact designs to reduce motor mass. We aim to limit concerns related to unsprung weight with its motor designs. We are developing advanced suspension technologies and active damping systems to mitigate potential challenges related to ride quality, with the goal of maintaining comfort and performance in vehicles.
What advancements in battery technology are necessary to fully realize the potential of in-wheel electric motors, particularly regarding energy density and charging capabilities?
To maximise the full benefits of our in-wheel motors, batteries must store more energy without increasing size or weight. We anticipate improvements through solid-state battery technology and advanced chemistries, offering higher energy density and faster charging.
These advancements will mean vehicles equipped with our motors achieve longer ranges and quicker recharge times, further increasing their appeal. However, with the current battery technology, the in-wheel motors are already better in every way when compared to traditional electric motors. There is no reason for original equipment manufacturers to wait.
How do you foresee the evolution of in-wheel electric motor technology impacting future vehicle architectures, particularly in relation to modular design and manufacturing processes?
Donut Lab’s in-wheel motors are inherently suited to modular vehicle design. Integrating motors into wheels allows vehicles to adopt simplified, flexible platforms. Carmakers can scale production efficiently, tailor vehicles to diverse needs, and streamline manufacturing processes. Our motors already reflect this versatility, supporting a range of vehicles from scooters to trucks, showcasing the potential for modular and adaptable automotive architectures. The flatbed design that can be achieved by removing the entire drivetrain gives automotive designers a whole new canvas from which to build something beautiful.
As the electric vehicle market matures, what innovations do you predict will emerge in motor technology that could redefine performance standards and consumer expectations?
Future motors will become lighter, more powerful and smarter. Donut Lab is leading this initiative with motors that deliver industry-leading power-to-weight and torque-to-weight ratios. Next, we see innovations in intelligent motor controls, advanced cooling methods and new lightweight composite materials pushing performance even further. This will enhance responsiveness, handling and driving range, raising expectations for electric vehicle performance, and we plan to lead in this area in future as well.
How do you envision the integration of in-wheel electric motors with emerging technologies such as autonomous driving and smart city infrastructure?
Our in-wheel motors provide precise control over each wheel individually, providing up to ten times the accuracy of other electric motors. This— makes them a good fit for autonomous vehicles and smart city integration. Vehicles equipped with Donut Lab motors could communicate with smart infrastructure, optimising driving behaviour for safety, efficiency and smooth traffic flow. We believe our technology will play a role in creating cleaner, smarter urban environments, supporting autonomous driving capabilities and fully connected transportation ecosystems.
