Reducing the Tuning Effort of a Steer-Torque-Manager for Vehicle Lateral Control

Abstract: A lot of research and development in the automotive industry today is focusing on active safety and driver assistance functions. On the market there are already car models with the ability to provide autonomous steering and behind next door stands the fully autonomous vehicles. The steering functionality is often referred to as Lane Keeping or lateral control. When its operation is verified in one vehicle it needs to be introduced into the following vehicles models as efficiently as possible. Aspects like vehicle dynamics together with system and component responses require the need for tuning and modification for each new vehicle model. One software component in the steering functionality that needs extensive tuning is the module determining the steer torque request that is sent to the Electric Power Steering (EPS). This component is referred to as the Steer-Torque-Manager (STM). In this thesis an investigation takes place regarding how the tuning effort of the STM can be reduced with help from model-based development and what the requirements for this are. To achieve this two virtual vehicle models including a steering system model are evaluated against physical measurements from a Volvo XC90. The first one is a model created in the software CarMaker and Simulink and the second one is a co-simulation model between Adams and Simulink. To evaluate the significance of certain parameters and settings a sensitivity analysis is performed. With the objective to evaluate if the existent STM controller can be modified to allow more rapid tuning a Two-Degree-Of-Freedom (2-DOF) controller, an Internal ModelControl (IMC) controller and a Self-Tuning Regulator (STR) are implemented and evaluated. The results show that the accuracy of the co-simulation model is sufficient to make it useful in the design and tuning of the STM and that the characteristics of the torsion bar, steering columnand steering wheel has a large impact on the system response. From the control investigation it can be concluded that the 2-DOF controller has the ability to simplify the tuning and slightly improve the performance, while the IMC controller decreases the performance and the STR suffers from implementation issues.