Topology design and size optimization of auxiliary units: A case study for steering systems

One opportunity for reducing the CO₂ emissions in an engine or hybrid driven vehicle is the hybridization of the auxiliary units. In this work three topologies for the steering system are modelled and optimized for sizing and control design, in order to investigate the fuel reduction potential. Depending of the class of the vehicle, in the case of heavy-duty trucks, gear driven steering systems can consume usually up to 2% of fuel. In hybrids, given two sources of energy, the engine and an electric machine, there is an implicit flexibility in choosing the topology for each auxiliary unit, e.g., the power steering. This leads to new requests on the development, connection of components and analysis of topologies that offer the lowest fuel consumption. The fuel improvement potential of steering systems is unknown, as well as the feasibility of other topologies in terms of control, cost or performance. To optimally choose the parameters of the novel topologies, mathematical descriptions of these power steering systems are built and validated. These models are then used to define the optimization problem and to determine the influence of the design parameters on fuel consumption. Simulations show considerable improvements at unit level if the conventional steering system topology is replaced with a novel one.