Rene Savelsberg

NVH Optimization of Range Extender Engines by Electric Torque Profile Shaping

Range extender operation in an electric vehicle should be imperceptible to the driver from a noise/vibration standpoint. Rolling torque compensation allows virtually vibration-free range extender engine operation by utilizing a balanced counter-rotating inertia that is geared to the cranktrain. The combustion process results in engine torque fluctuations that could cause gear rattle in such a system due to a combination of torque reversal and lash in the geared connection. This brief paper addresses the problem of gear rattle in a rolling torque compensation system. First, a preloaded split gear is introduced as a potential mechanical solution to eliminate the clearance in the gear contact zone. In addition, an approach for a mechatronic solution involving active shaping of the generator torque is introduced. This methodology includes measurement of the combustion engine torque via cylinder pressure indication data, calculation of allowable torque limits, and the determination of a generator torque profile to address gear rattle. A multicriteria cost function is introduced to determine the optimal torque within the established constraints. Variations of the cost function are investigated with respect to their impact on efficiency and range extender acoustics.

Variable step-size discrete dynamic programming for vehicle speed trajectory optimization

Predictive energy management has become a new focus of the automobile industry for its high potential of further reducing energy consumption. Based on previous works on predictive speed optimization using discrete dynamic programming (DDP), this paper introduces a novel approach of applying DDP with variable step size in stage variable discretization, which can realize a better tradeoff between precision and computational cost. In this approach, a “meshing” algorithm searches the points of interest (POI), such as speed limit change, traffic lights, and road curvatures, where changes in vehicle speed are expected. The algorithm increases the step-size resolution close to these points and reduces the resolutions in positions further away from POI, where the optimized vehicle speed is insensitive to the step size. With this approach, the position of POI can be precisely located to solve the DDP problem. In a test case with a relatively high density of POI, the computational cost is reduced by more than 53% by only sacrificing less than 1% of precision compared to a fixed step-size discretization with high resolutions. It can be expected that, with a lower density of POI, the computational cost will be reduced even further.

Road-to-rig-to-desktop: Virtual development using real-time engine modelling and powertrain co-simulation

By front-loading of the conventional vehicle testing to engine test bench or even further forward to offline simulations, it is possible to assess a large variation of powertrain design parameters and testing manoeuvres in the early development stages. This entails a substantial cost reduction compared to physical vehicle testing and hence an optimisation of the modern powertrain development process. This approach is often referred to as road-to-rig-to-desktop. To demonstrate the potential of this road-to-rig-to-desktop methodology as a seamless development process, a crank angle–resolved real-time engine model for a turbocharged gasoline engine was built with the simulation tool GT-POWER®. The model was validated with measurement data from an engine test bench and integrated into a vehicle co-simulation, which also includes a dual clutch transmission, the chassis, the environment and the automated driver. The most relevant functions of the engine and the transmission control systems were implemented in a Simulink-based software control unit. To verify the engine model in the transient vehicle simulation, two 900-s time windows from a 2-h real driving emission test, representing urban and motorway conditions, are simulated using the developed co-simulation platform. The simulation results are compared with the respective vehicle measurement data. The fuel consumption deviation caused by the combustion engine model is within 5%. The transient system behaviour and the dominant engine operation points could be predicted with a satisfying accuracy.

FEV ECObrid – a 48V mild hybrid concept for passenger car Diesel engines

Powertrain electrification is a key to compliance with future exhaust emission and CO2 limits. Besides conventional 12 V systems and high-voltage hybrid architectures, 48 V mild hybridization offers significant fuel economy potential and advanced emission control without the need for an entire powertrain redesign. The 48 V power net enables high recuperation capability, improved stop-start functionalities as well as electrical boosting by an electric compressor (e-Compressor) or belt-driven starter generator (BSG).