Integrated Braking Control for Electric Vehicles with In-Wheel Propulsion and Fully Decoupled Brake-by-Wire System

Abstract

This paper introduces a case study on the potential of new mechatronic chassis systems for battery electric vehicles, in this case a brake-by-wire (BBW) system and in-wheel propulsion on the rear axle combined with an integrated chassis control providing common safety features like anti-lock braking system (ABS), and enhanced functionalities, like torque blending. The presented controller was intended to also show the potential of continuous control strategies with regard to active safety, vehicle stability and driving comfort. Therefore, an integral sliding mode (ISM) and proportional integral (PI) control were used for wheel slip control (WSC) and benchmarked against each other and against classical used rule-based approach. The controller was realized in MatLab/Simulink and tested under real-time conditions in IPG CarMaker simulation environment for experimentally validated models of the target vehicle and its systems. The controller also contains robust observers for estimation of non-measurable vehicle states and parameters e.g., vehicle mass or road grade, which can have a significant influence on control performance and vehicle safety.

Reconfigurable Slip Vectoring Control in Four In-Wheel Drive Electric Vehicles

“…"Upper" controls are computed accordingly to the desired speed and yaw-rate references so that total driving longitudinal force and yaw-moment, such as Direct Yaw Moment Control (DYC) [27][28][29][30]55], are provided. For the upper motion control strategy several possible techniques could be considered: Sliding-Mode Control (SMC) [13,20,28,[31][32][33][34], robust loop shaping [35,36], PI control [9,10], Model Predictive Control (MPC) [15,17,37,55], controllers based on energy and optimal efficiency allocation [17,27,[38][39][40][41][42]56]. Then, since an in-wheel electric motor can be controlled to track either a torque [2] or a speed reference [8,9], two kinds of CA of the upper control could be implemented: torque or speed.…”

“…The PI control approach is a convenient tool for Wheel Slip Control (WSC) [20] and TC, as also discussed in [17]. Most importantly, the reason behind the proposed speed/slipcontrol approach is properly linked to the online load estimation capability, which enforces the independence of the controller from the wheel PMF model knowledge (this aspect is treated in the next Section 3.2).…”

“…For this reason, ISMC solutions are introduced to make the WSC continuously actuated. Since the actual wheel torque can be estimated without information about vehicle velocity and wheel conditions, such as road friction coefficient and nominal vertical load (road-and-load), by [57], a good applicability on EVs is allowed by PI schemes for continuous WSC [9], also providing intrinsic filtering properties [20].…”

“…Distributed Electric Powertrain (EP) configurations offer redundancy and enhance the maneuverability, since Traction Control (TC) [11,[16][17][18] and ABS [11,12,19,20] devices can be improved in cooperation with IWMs. Most importantly, the vehicle yaw-motion can be continuously controlled by bidirectional differential torques in a configuration with distributed IWMs: this is a technological advantage in comparison to conventional ESC [9], which acts with on/off negative torques by electromechanical brakes [21].…”

Wheel Slip Control Applied to an Electric Tractor for Improving Tractive Efficiency and Reducing Energy Consumption

“…Sliding mode control (SMC) and incremental proportional-integral (IPI) control were compared in [20] to achieve travel reduction in electric tractors, but the slippage of traction wheels was not analyzed in detail. Similarly, integral sliding mode (ISM) and proportional-integral (PI) control applied in wheel slip control are compared in [21] in terms of simulation results only. In turn, the focus in [22] is given to estimating the optimum slip that leads to the maximum traction and low soil disturbances in unmanned electric tractors, whereas an online slip control algorithm based on SMC is proposed.…”