Abstract
Research Objectives
The aim is to develop a non-linear variable structure control algorithm to continuous regulate the electric machines to replicate ABS and stability control features with electric machines. The research hypothesis assumes that due to the high actuation bandwidth of electric machines (i.e. up to 200Hz) compared with electrohydraulic system (up to 6-8Hz), the chassis dynamics and stability control features will dramatically improve the overall vehicle behavior on adverse situational environments (i.e. snow, black ice, split mu road surfaces etc.).
Methodology
My research utilizes both qualitative and quantitative methods. Initially, a variable structure control algorithm (i.e. Sliding Mode Control) is designed, implemented and tested on both virtual and experimental set up. This control software regulates, in continuous mode, the longitudinal wheel slip of an electrical vehicle. Fuzzy logic is employed to provide adaptive characteristics on the SMC for various road conditions.
Fuzzy logic is also employed to create ABS control software. Based on several simulation optimization studies and experimental data from a special instrumented vehicle, the fuzzy membership functions and the rule base structure are optimized for a wide operational bandwidth. The system is tested using CAE tools and experimental data. The last element is the comparison and quantification of the two methods as future strategies to control the motion of electric vehicles.
Results
Both Fuzzy Logic and Sliding Mode Control due to robustness on noise and model uncertainties provide very promising results on regulating the longitudinal wheel slip of electric vehicles on various road conditions. The results are based on experimental and simulation data for several braking conditions. The results indicates that electric machines is an enabler for more advanced motion control and the braking future of mobility will depend more on frictionless braking technology, as an active safety element.
Limitations of this study
The limitations of the study so far are the accurate determination of the speed over ground and the tyre-road adhesion coefficient in real time. Those two parameters are key elements on control perspective while the mechanical limitations of sub-components (i.e. compliance mountings, drive-shafts) and power electronics (i.e. inverters) restrict the actuation bandwidth of the next generation of ABS and active safety systems of electric machines.
What does the paper offer that is new in the field in comparison to other works of the author?
Develop adaptive capability of eABS with electric machine. This is an enabler of frictionless braking and opportunity to eliminate the friction brakes from the rear axle and thus reducing brakes emissions and drag.
Conclusions
Adaptive Sliding mode control (SMC) and Fuzzy-ABS are natural candidate x-by-wire actuation because of its applicability to the control of nonlinear systems as well as its established robustness in the presence of parametric and modelling uncertainties as well as disturbances. The evolution of electrification on vehicles challenges the standard control practices for x-by-wire vehicles and thus drives the appetite to modify ABS and active safety systems. The aforementioned control strategies provide a solid ground to introduce the frictionless braking technology on active safety electric vehicle attributes.
Key words : Brake by Wire; Frictionless braking; sliding mode control; fuzzy ABS