Framework for the Evaluation of Wheel Torque Blending Algorithms

Electric vehicle power train concepts with wheel-hub or close-to-wheel propulsion open up a whole new area of vehicle control possibilities. The DLR robotic concept vehicle ROMO allows the evaluation of these possibilities using integrated chassis control. With its electric drive train it is possible to recuperate kinetic energy during braking process. Using only the electric motors for braking, an increased mass of electric drives & energy storage would be necessary in order to comply to legal passenger vehicle braking regulations. Therefore, the combination of friction based brake and electric motor brake can be advantageous. In this paper, object oriented models (Modelica) of a permanent magnet synchronous machine driven electro-hydraulic disc brake and an in-wheel direct driven traction motor are presented. Furthermore, two torque blending algorithms of an electro-hydraulic disc brake and an in-wheel permanent magnet synchronous machine are evaluated. One algorithm is based on a dynamic control allocation using real-time capable quadratic programming, the other is a feed forward control based on heuristic considerations. Finally, four comparison methods are presented and applied to evaluate the performance of the used torque blending.