Linear Approach to ESP Control Logic Design 2006-01-1017
An Electronic Stability Program (ESP) control logic is designed. It is devoted to stabilize vehicle during cornering maneuvers. The aim of the activity is to obtain a feed forward (FF) control structure, capable of better performance than a previously developed closed loop one. The efficiency of ESP intervention is determined observing yaw rate peak reduction and oscillation damping time during step steer maneuver, together with vehicle side slip angle containment and longitudinal speed loss. A single track vehicle model is used to obtain two transfer functions describing vehicle and active system behavior. A third transfer function is derived from active vehicle frequency response that is the designer's target. The interaction between the transfer functions permits to design a feed forward control logic, which is then merged in a closed loop control structure in order to ensure fail safe conditions and control robustness. Final control logic is tested through simulation with a 10 degrees of freedom vehicle model. Results show that ESP intervention depends mainly on feed forward control and is quicker than the former system. Signals exchanged between vehicle on board sensors and ESP control unit are defined; active control output signals are quantified and physically realized through an analog output board. ESP innovative control logic is experimentally tested through a hardware in the loop brake system test bench. Pulse Width Modulation (PWM) valves actuation procedure is described. Feed forward logic is compared with other ESP in terms of influence on vehicle dynamics.