How can vehicle dynamics testing and validation be improved for electric and hybrid vehicles?

1 Battery weight and distribution

One of the main differences between EVs and HEVs and conventional vehicles is the presence of a large and heavy battery pack, usually located in the lower part of the vehicle. This affects the vehicle's center of gravity, mass, and inertia, which in turn influence its dynamic behavior. For example, a lower center of gravity can improve the vehicle's stability and cornering, but a higher mass can increase the braking distance and the tire wear. Therefore, it is important to test and validate how the battery weight and distribution affect the vehicle dynamics in various scenarios, such as straight-line driving, lane change, emergency braking, and rollover. Some of the methods that can be used for this purpose are computer simulations, laboratory experiments, and field tests, using appropriate sensors, models, and control strategies.

2 Regenerative braking

Another feature of EVs and HEVs is the ability to recover some of the kinetic energy that would otherwise be wasted as heat during braking, and convert it into electrical energy that can be stored in the battery. This is called regenerative braking, and it can reduce the fuel consumption and the emissions of the vehicle. However, regenerative braking also affects the vehicle dynamics, especially the brake balance, the brake feel, and the brake stability. For example, regenerative braking can reduce the brake force applied by the hydraulic system, which can result in a longer pedal travel and a softer pedal feel. It can also cause a difference in the braking torque between the front and rear axles, which can affect the vehicle's yaw stability and steering response. Therefore, it is essential to test and validate how regenerative braking interacts with the conventional braking system, and how it can be optimized and coordinated to achieve the best performance and safety. Some of the techniques that can be used for this purpose are brake-by-wire systems, adaptive brake controllers, and driver feedback systems.

3 Electric power steering

A third aspect of EVs and HEVs that impacts the vehicle dynamics is the electric power steering (EPS) system, which replaces the hydraulic power steering (HPS) system used in most conventional vehicles. EPS uses an electric motor to assist the driver in steering the vehicle, which can reduce the fuel consumption and the emissions of the vehicle. However, EPS also affects the vehicle dynamics, especially the steering feel, the steering feedback, and the steering stability. For example, EPS can provide a more precise and responsive steering control, but it can also reduce the natural feedback from the road surface and the tire forces. It can also introduce some disturbances and noises in the steering system, which can affect the vehicle's handling and comfort. Therefore, it is important to test and validate how EPS influences the vehicle dynamics, and how it can be calibrated and tuned to match the driver's preferences and expectations. Some of the tools that can be used for this purpose are steering torque sensors, steering angle sensors, and steering assist maps.

4 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?