What are the best methods to measure and optimize the center of gravity of electric and hybrid vehicles?

1 Why CG matters

The CG of a vehicle influences how it behaves on the road, especially when cornering, braking, or accelerating. A lower and more central CG improves the vehicle's agility, responsiveness, and stability, as it reduces the body roll, pitch, and yaw motions. A higher and more offset CG increases the risk of rollover, understeer, or oversteer, as it creates more lateral and longitudinal forces on the tires and suspension. Therefore, it is important to design and optimize the CG of electric and hybrid vehicles to achieve the desired performance and safety characteristics.

2 How to measure CG

There are several methods to measure the CG of a vehicle, depending on the level of accuracy and complexity required. One of the simplest methods is to use a set of scales and a level platform to measure the weight and height of each wheel. By applying some basic physics equations, the CG location can be calculated from the weight distribution and the wheelbase and track dimensions. Another method is to use a tilt table or a ramp to measure the angle at which the vehicle starts to tip over. By knowing the vehicle's weight and dimensions, the CG height can be determined from the tilt angle. A more advanced method is to use a kinematic and compliance (K&C) test rig, which can measure the CG location and the suspension characteristics of the vehicle under various loading conditions.

4 How to test CG

The CG of a vehicle can be tested by performing various dynamic tests on a track or a simulator. These tests can evaluate how the CG affects the vehicle's handling, stability, and performance under different driving scenarios. Some of the common tests are steady-state circular test, slalom test, lane change test, brake test, and acceleration test. These tests can measure parameters such as lateral acceleration, yaw rate, steering angle, braking distance, and acceleration time, which can indicate the vehicle's behavior and response to the driver's inputs. By comparing the test results with the CG measurements and the design objectives, the vehicle's dynamics can be analyzed and improved.