Applications of Sensor Data
Vehicle Dynamics Control
The three for our application most important signals coming from the LPMS-CU IMU were the accelerations in x (longitudinal, direction of travel) and y (lateral, direction of the front and rear axle) direction, as well as the rotation rate around the z-axis (vertical direction), further called the yaw rate of the car.
These signals were important inputs for our vehicle dynamics control system. The signal from the IMU has important influences in both, torque vectoring and traction control, as well as several smaller control algorithms used to maximise the performance of the race car.
Furthermore, some points are described, where the signals from the IMU were used in the vehicle dynamics control system:
1. Weight transfer calculation: One important thing to know for calculating the maximum torque which can be used by the tire is the force in z direction at every tire. To calculate this value, we use the accelerations in x and y direction to determine the chassis movement, and to calculate the forces on every single tire.
2. Mu estimator: We are able to adjust the used friction coefficient to calculate the possible deliverable forces of the tires. Depending on the track and the outer conditions, the friction coefficient (mu) is increased or decreased. For this calculations we need the absolute force which is acting on the car in x-direction, which can be calculated by the longitudinal acceleration and the mass of the car.
3. Torque vectoring: The yaw rate is the most important value for our torque vectoring system. By using a simplified vehicle model, we calculate the optimal yaw rate for every corner at every time. This calculated value is then compared to the actual measured value by the IMU, and an occurring error is corrected by an adjusted torque distribution on every wheel.
Data Analysis
Furthermore, the data coming from the IMU was very important for data analysis. One example of the usage of the signals is the G-G-Plot, a classical way to look at the performance of the system car and driver.