Coordination of Steer Angles, Tyre Inflation Pressure, Brake and Drive Torques for Vehicle Dynamics Control 2013-01-0712
During vehicle operation, the control objectives of stability, handling, energy consumption and comfort have different priorities, which are determined by road conditions and driver behavior. To achieve better operation characteristics of vehicle, coordinated control of vehicle subsystems is actively used. The fact of more active vehicle subsystems in a modern passenger car provides more flexibility for vehicle control and control algorithm development. Since the modern vehicle can be considered as over-actuated system, control allocation is an effective control technique to solve such kind of problem.
This paper describes coordination of frictional brake system, individual-wheel drive electric motors, active front and rear steering, active camber mechanisms and tyre pressure control system. To coordinate vehicle subsystems, optimization-based control allocation with dynamic weights is applied. The influence of different weights (subsystem restriction) on criteria of vehicle dynamics (RMSE of yaw rate, sideslip angle, dynamic tyre load factor) and energy consumption and losses (consumed/recuperated energy during maneuver, longitudinal velocity decline, tyre energy dissipation) were analyzed. Based on this analysis, the optimal solution was selected. The proposed control strategy is based on the switching between optimal criteria related to vehicle safety and energy efficiency during vehicle motion. Dynamic weights were utilized to achieve this switching.
The simulation-based analysis and evaluation of both variants was carried out using a nonlinear vehicle model with detailed models of actuators. The test maneuver is ‘Sine with Dwell’. Both variants of control allocation guarantees vehicle stability of motion and good handling. Meanwhile, proposed variant demonstrates slightly higher longitudinal velocity at the end of maneuver and higher amount of recuperated energy up to 15%; however, tyre dissipation energy increased to 5% compared to optimal solution from simulation-based analysis.