Analysis and Comparison of One-Pedal Driving Strategies for Electric Vehicles from Consumption and Comfort Point of View

One-pedal driving is the idea of applying with the same accelerator pedal both traction and regenerative braking which has emerged thanks to the regeneration capabilities and the potential of implementing complicated control systems in electric vehicles. In this thesis a model-based design approach was used to provide a virtual model in MATLAB & Simulink capable of analyzing and comparing different one-pedal strategies for electric vehicles. The study was mainly carried out on an electrified old version of Fiat Panda. In the beginning, the vehicle had only a simple on/off electric braking with constant level of regeneration which could be activated either by slightly pushing the brake pedal or releasing the accelerator pedal but without any possibility to modulate the magnitude. The first step was to study different levels of regeneration and compare the two modes of activation. 40% regeneration with respect to the maximum regenerative torque was chosen as the trade-off considering both energy recuperation and comfort issues while being able to follow a desired reference cycle. Besides, both activation modes gave the same results. Next, by implementing the real control logic instead of the primarily ideal one in the Simulink model and also tuning some parameters that were initially obtained by calculations, this virtual model was validated with four experimental data sets which were acquired with different regeneration levels. Regarding the consumption values, simulations’ errors on average became lower than 6% with respect to the experimental results whereas with ideal control and calculated coefficients they were first in the range of 12% to 37%. Additionally, simulated current and electrical power profiles became much closer to those seen in the real experiments. The following step was to employ this validated virtual model in order to implement, analyze and compare more complicated control strategies that could realize one-pedal driving. Targets to be investigated were mainly energy consumption, comfort issues regarding foot activity between pedals and deceleration profiles while being able to follow precisely a desired reference cycle. Two different strategies which were studies previously done by others and one which was designed and developed during this thesis, in addition to the basic on/off braking were chosen to be investigated, compared and modified if necessary, to be adapted to the aforementioned vehicle. For all of the strategies capable of following some standard reference cycles only using regenerative braking (no exploitation of hydraulic brakes) electrical energy consumption was almost the same. However, regarding comfort huge success was achieved by reducing the number of accelerator pedal releases noticeably e.g. from more than 160 times with the simplest on/off strategy in WLTP Class 3 cycle down to less than 10 times with two of the strategies. Additionally, deceleration profiles were shown to be differently acting on the longitudinal comfort in each strategy. With the basic on/off electric braking repetitive activation of regenerative braking with high deceleration values occurs for most of the velocity range with minimum possibility to modulate it through accelerator pedal positioning. On the other hand, more complicated strategies have maximum deceleration in the mid velocity range and they give more flexibility in modulating the deceleration values with wider exploitation of accelerator pedal positioning.