  The four-wheel independent drive and four-wheel independent steering
(4WID-4WIS) configurations enhance control flexibility and dynamic performance
potential for more integrated electric vehicles. This paper comprehensively
analyzes the impacts of four key factors on tire force control allocation:
vertical load estimation, actuator dynamic characteristics, tire force
constraints, and wheel steering precision at handling limits. The study
demonstrates that precise vertical load estimation enhances lateral force
allocation accuracy. Additionally, the self-compensating effect of lateral tire
forces minimizes the impact of small deviations in vertical load estimation on
tire force control allocation. A novel control allocation method considering
actuator dynamics is introduced, effectively improving yaw rate response and
reducing tracking errors. Considering tire-road adhesion and actuator rate
constraints, an innovative method to calculate the real-time attainable tire
force volume is proposed based on the tire slip ratio and slip angle.
Feedforward control with bump steer compensation is implemented to improve
wheel steering precision and lateral tire force control accuracy.
Matlab/Simulink and Carsim co-simulation results emphasize the importance of
these key factors' individual impacts and combined effects. This analysis
offers valuable insights for developing advanced tire force control allocation
strategies in 4WID-4WIS electric vehicles.
