Next Generation Integrated Vehicle Dynamics and Controls
The increasing number of active chassis systems leads to a higher need for control integration: coordinating the vehicle actuators in a supervised way has the potential of enhancing the vehicle performance in terms of handling and power efficiency while addressing the possible conflicts between the different actuators, thus reducing implementation cost of active systems thanks to better reusability, ease of configuration and calibration. This research presents the development of a multi-layered control framework for vehicles equipped with an electric drivetrain, independent braking, and active steering actuators. The control architecture is decomposed into two parts: an abstract layer that defines controls at the wheel level and which does not require precise knowledge of the actuators equipped on the vehicle, and an application layer that coordinates the actuators to follow the wheel control requests. A simplified tire model is developed to model the coupling behavior between the longitudinal and lateral tire forces; the abstract layer utilizes multivariable control methods in conjunction with the simplified tire model to define optimal wheel controls. Similarly, a control allocation is implemented in the application layer to coordinate the brake and drivetrain actuators. The distribution of actuator commands is made invisible at the wheel torque level by cleverly using the Smith-McMillan decomposition of a redundant system, simplifying the controller design by dissociating the actuator allocation problem from the control problem while ensuring internal stability and good robustness properties. Simulations with a high-fidelity vehicle model validate the control framework. Several actuator configurations are considered to highlight the reusability of the control architecture. Results show that the control architecture provides a unified framework for the vehicle's longitudinal, lateral, and yaw control.