EVs are more popular every year, as they offer many benefits over conventional cars, such as lower emissions, lower running costs, and higher performance. However, EVs also pose some unique challenges for engineers and designers, especially when it comes to suspension systems.
Suspension systems are essential for any vehicle, as they provide comfort, stability, and safety for the occupants and the vehicle itself. They do this by absorbing and dissipating the forces generated by the road surface, such as bumps, potholes, and curves. Suspension systems also affect the handling and steering of the vehicle, as well as its aerodynamics and efficiency.
However, EVs have different characteristics than conventional cars that require different approaches to suspension design. For example, EVs have heavier batteries that increase the weight and lower the center of gravity of the vehicle. They also have different weight distribution and torque delivery than internal combustion engine (ICE) vehicles. Moreover, EVs have less noise and vibration than ICE vehicles, which means that any imperfection in the suspension system can be more noticeable and annoying for the driver and passengers.
Therefore, EV suspension systems need to be optimized for these specific conditions while also meeting the expectations of customers who demand high levels of comfort and performance. In addition, EV suspension systems need to take advantage of the opportunities offered by electrification, such as energy regeneration and active control.
Let's explore some of the latest developments and innovations in EV suspension systems and how they are evolving to meet the needs and demands of the future.
Energy Regeneration
One of the most promising features of EV suspension systems is their ability to regenerate energy from the wheel movement and use it to recharge the battery. This can improve the range and efficiency of EVs and reduce their environmental impact. Several technologies have been developed or proposed, such as:
- Michelin Active Wheel: This technology was one of the first suspension systems designed exclusively for EVs. It consists of two electric motors integrated into each wheel: one for propulsion and one for active suspension control. The system eliminates the need for many conventional components, such as a gearbox, clutch, transmission shaft, universal joint, and anti-roll bar. The system also recovers energy from braking and suspension movement and feeds it back to the battery.
- A regenerative suspension system: This technology was developed by a team led by Professor Lei Zuo from the Advanced Energy Technology and Research Center at Stony Brook University. A regenerative suspension system can recover 100 to 400 watts of kinetic energy from a passenger car traveling at 100 km/h. The system uses an electric generator coupled to a conventional suspension system with steel springs and hydraulic shock absorbers.
- Convert kinetic energy from the vertical suspension movement: This technology was patented by Intertronic Gresser GmbH in 2014. It is a regenerative suspension system that converts a large percentage of the kinetic energy from the vertical suspension movement and the body acceleration into electricity using coupled linear generators. The company claimed that this system could increase the range by 50 percent in relation to the battery storage capacity.
- Captures energy from a bump: This technology was revealed by a patent filed by BMW in 2022. A regenerative suspension system captures energy generated by the wheel movement as it absorbs the shock from a bump. The energy is then sent to a generator unit that converts it into usable electricity to charge the battery.
Active Control
Another feature that can enhance EV suspension systems is active control. This means that the suspension system can adjust its parameters in real-time according to the road conditions, driving style, and vehicle mode. This can improve EVs' comfort, handling, stability, and safety.
Some examples of active control technologies are:
- Bose Ride System: This technology was developed by Bose Corporation, known for its audio products. It is an active suspension system that uses linear electromagnetic motors instead of traditional springs and dampers. The system can sense road irregularities and adjust the force applied to each wheel up to 1000 times per second. The system can reduce vertical movement by up to 90 percent and lateral movement by up to 50 percent.
- ZF sMOTION: This technology was developed by ZF Friedrichshafen AG, a leading supplier of automotive components. It is an active suspension system that uses electric actuators instead of hydraulic or pneumatic ones. The system can control the vehicle's vertical, roll, and pitch movements independently. The system can also adapt to different driving modes: comfort, sport, or off-road.
- ClearMotion: ClearMotion Inc., a startup founded by MIT graduates, developed this technology. It is an active suspension system that uses software and hardware to create a smooth ride. The system uses sensors, actuators, and algorithms to predict and counteract road disturbances. The system can also create different ride sensations, such as soft, firm, or dynamic.