Lateral motion control for four-wheel-independent-drive electric vehicles using optimal torque allocation and dynamic message priority scheduling

In this paper, the vehicle lateral motion control of four-wheel-independent-drive electric vehicles (4WID-EVs) with combined active front steering (AFS) and direct yaw moment control (DYC) through in-vehicle networks is studied. As a typical over-actuated system, a 4WID-EV requires a control allocation algorithm to achieve the generalized control efforts. In this paper, a quadratic programming (QP) based torque allocation algorithm is proposed with the advantage of equally and reasonably utilizing the tire-road friction of each wheel. It is also well known that the in-vehicle network and x-by-wire technologies have considerable advantages over the traditional point-to-point communications, and bring great strengths to complex control systems such as 4WID-EVs. However, there are also bandwidth limitations which would lead to message time-delays in in-vehicle network communications and degradation of control performance. The paper also proposes a mechanism to effectively utilize the limited network bandwidth resources and attenuate the adverse impact of in-vehicle network-induced time-delays, based on the idea of dynamic message priority scheduling. Simulation results from a high-fidelity vehicle model show that the proposed control architecture with the torque allocation algorithm and message dynamic-priority scheduling procedure can effectively improve the vehicle lateral motion control performance, and significantly reduce the adverse impact of the in-vehicle network message time-delays in the simulated maneuvers.