Abstract
As a novel power steering technology, Differential Drive Assisted Steering (DDAS) technology for the independent-wheel-drive electric vehicle has gradually appealed to researcher’s attention. However, the previous experimental results show that its assistance quality cannot be fully accepted due to its caused sensitive steering wheel torque fluctuation in actual work environment. According to the working principle of the DDAS system, it is founded that the road roughness, the front wheel alignment parameters and sensor noise are the main factors that influence the quality of assisted steering and driver’s road feel. Hence the three factors are added as interference into the ideal vehicle model. The simulation results and its comparison with the previous real vehicle tests confirm this causality between these factors considered and the steering wheel torque fluctuation of the DDAS system. Then a robust $H_{\infty }$ loop-shaping controller is designed to solve the issue caused by these inner interferences and outer noises. Simulations results validate the proposed controller and show better steering wheel torque performance than the traditional anti-windup PID controller published in the literature earlier. The proposed robust controller is further verified via real vehicle tests and the results are similar to the simulation results which can effectively suppress the steering wheel torque ripple, improve the anti-interference ability of DDAS system and greatly improve the driver’s road feel.
Highlights
Differential drive assisted steering (DDAS) system, which is based on the platform of the independent-wheel–drive (IWD) of electric vehicle (EV), makes full use of the difference of the torque output between the left and right front driving wheels, so that the steering assisted force can be achieved [1], [2]
The DDAS system eliminates the need of an additional electric motor for traditional power assisted steering and integrates its controller into the vehicle driving control unit and simplifies the configuration of the steering system
The concept of DDAS is proposed in recent years and many valuable achievements have been proposed
Summary
Differential drive assisted steering (DDAS) system, which is based on the platform of the independent-wheel–drive (IWD) of electric vehicle (EV), makes full use of the difference of the torque output between the left and right front driving wheels, so that the steering assisted force can be achieved [1], [2]. J. Wang et al.: Assistance Quality Analysis and Robust Control of Electric Vehicle With DDAS System on further application. J. Römer [4] studied the feasibility of a power steering system using wheel-individual drive torque at the front axle as well as the energy saving potential of DDAS system by using classical EPS look-up table and P controller while only converting the steering torque from EPS motor to the differential torques at the wheels. Similar to DDAS, different angular rotation speed output could achieve differential steering and Khan et al [14] designed control system using robust controller to alter differential angular rotation speed, which generated the steering effects and tracked the desired maneuvers with great stability. Various simulations and real vehicle tests are performed to validate its effectiveness
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