This study applies nonlinear model predictive control (NMPC) to the torque-vectoring and front-to-total anti-roll moment distribution control of a four-wheel-drive electric vehicle with in-wheel-motors, a brake-by-wire system, and active suspension actuators. The NMPC cost function formulation is based on energy efficiency criteria, and strives to minimize the power losses caused by the longitudinal and lateral tire slips, friction brakes, and electric powertrains, while enhancing the vehicle cornering response in steady-state and transient conditions. The controller is assessed through simulations using an experimentally validated high-fidelity vehicle model, along ramp steer and multiple step steer maneuvers, including and excluding the direct yaw moment and active anti-roll moment distribution actuations. The results show: i) the substantial enhancement of energy saving and vehicle stabilization performance brought by the integration of the active suspension contribution and torquevectoring; ii) the significance of the power loss terms of the NMPC formulation on the results; and iii) the effectiveness of the NMPC with respect to the benchmarking feedback and rule based controllers.
Abstract-Fully electric vehicles are rapidly gaining user and market interest worldwide, due to their zero direct emissions, appealing driving experience and fashionable perception. Unfortunately, cost, range and reliability have not reached the desired targets yet. Since consumers are prone to spend money to have a more reliable system, Design-for-Reliability will be a useful tool for the Design of tomorrow's EVs, justifying part of the increased cost for these products. In this work, a vertical model-based approach to design-for-Reliability of power converters for EVs is presented, paying special attention to thermally-induced aging. The design starts from various driving cycles, properly assembled to describe the vehicle mission, then load profiles for the converters are found and the resulting thermal stress is quantified. The converter lifetime can be estimated, taking into account also parameter dispersion, and requirements for the active thermal control of the parts modeled achieved, thus giving practical information to the system designers.
The on-state voltage of MOSFETs is a convenient and powerful temperature-sensitive electric parameter (TSEP) to determine the junction temperature, thus enabling device monitoring, protection, diagnostics and prognostics. The main hurdle in the use of the on-state voltage as a TSEP is the per-device characterization procedure, to be carried out in a controlled environment, with high costs. In this paper we compare two novel techniques for MOSFET junction temperature estimation: controlled shoot-through and direct heating by resistive heaters embedded in two Kapton (polyimide) films. Both allow in-place characterization of the TSEP curve with the device mounted in its final circuit and assembly, including the working heat sink. The two methods are also validated against the conventional procedure in a thermal chamber.
The paper deals with the development of fast and lightweight vehicle dynamics models oriented to the vehicle electrification. Two models are created, as they are concerned with different accuracy levels. The first one is very essential: it consists of three dynamics, that is full vehicle, front wheels and rear wheels; regularised Coulomb friction model is adopted. The second model is more advanced since it comprehends the vertical dynamics due to the suspension system and tyre friction model comes from Pacejka's theory. The dynamics models are subsequently compared with a very sophisticated and accurate model developed thanks to Chrono::Engine (C::E): because C::E is a powerful and reliable software, this process can be considered as a first validation of the more essential vehicle descriptions. Afterwards, models are connected to an electric powertrain to evaluate the effects of the different mechanical models with respect to the same electric system; this also aims to estimate the characteristic quantities of the electric domain.
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