Stabilization of Automotive Vehicles Using Active Steering and Adaptive Brake Control Allocation

Abstract

Abstract-In this work a dynamic control allocation approach is presented for an automotive vehicle yaw stabilization scheme. The stabilization strategy consists of a high level module that deals with the vehicle motion control objective (yaw rate reference generation and tracking), a low level module that handles the braking control for each wheel (longitudinal slip control and maximal tire-road friction parameter estimation) and an intermediate level dynamic control allocation module that generates the longitudinal slip reference for the low level brake control module and commands front wheel steering angle corrections. The control allocation design is such that the actual torque about the yaw axis tends to the desired torque calculated form the high level module, with desirable distribution of control forces satisfying actuator constraints and minimal control effort objectives.Conditions for uniform asymptotic stability are given for the case when the control allocation includes adaptation of the tire-road maximal friction coefficients, and the scheme has been implemented in a realistic non linear multi body vehicle simulation environment. The simulation cases show that the yaw control allocation strategy stabilizes the vehicle in extreme maneuvers where the non linear vehicle yaw dynamics otherwise (without active braking or active steering) becomes unstable in the sense of over-or under steering.The control allocation implementation is efficient and suitable for low cost automotive electronic control units.

Control allocation—A survey

“…Tires have highly nonlinear characteristics with saturations at high longitudinal and lateral slips, which may lead to nonlinear effector models, e.g. (Tjønnås & Johansen 2010). Nonlinearities are discussed further in Section 4 when describing application domains.…”

“…The dynamic adaptive nonlinear control allocation method is studied for yaw stabilization in (Tjønnås & Johansen 2010) (see section 3.3), where a combination of braking and frontwheel steering is used for actuation. Estimation of maximum tire-road friction coefficient is an integral part of the adaptive control allocation strategy.…”

“…Using polyhedral approximation of the friction ellipsoids, a quadratic programming approach is taken to allocation error minimization in (Schofield, Hägglund & Rantzer 2006). In (Alberding, Tjønnås & Johansen 2009), the dynamic nonlinear control allocation approach of (Tjønnås & Johansen 2010) is extended to include rollover prevention objectives.…”

Study on electronic stability program control strategy based on the fuzzy logical and genetic optimization method

“…1 The TCS system was designed to maximize the contact forces between the tires and the road during braking and acceleration. 2 TCS controls the output torque of the driving wheels to control the tires' longitudinal force. This is not available in the braking condition.…”

“…[5][6][7] ESP is introduced to control the yaw motion and prevent oversteering and understeering. 2 Direct yaw moment has a higher ability to stabilize the vehicle motion than active steering control. 8 This article introduces the rear wheel steer angle to maintain sideslip angle in an ideal range and then combines the additional yaw moment and rear wheel steer angle to improve the lateral movement stability.…”