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The problem of vehicle stability in emergency maneuvers has attracted a lot of research effort recently. Perhaps the most effective contributions made in this area were devoted to the control of vehicle yaw rate either by active steering or differential braking control systems. Each control technique has its own limitations that make it ineffective in some particular situations. This paper introduces a combined steering and braking control strategy using a fuzzy logic inference system. The proposed controller uses the estimated coefficient of friction (μ) to organize the combined control action. Computer simulation using a comprehensive vehicle model is used to illustrate the strengths and limitations of various control strategies.

High center of gravity vehicles need to be stiff in roll to prevent excessive roll angles when cornering. In some cases, there may be more roll compliance in the tires than in the suspension itself. For this reason, the conventional shock absorbers may not provide effective damping of the roll mode. The result is that wind gust and roadway unevenness disturbances can cause large swaying oscillations. Here a novel use of automatically steered wheel is proposed to augment the damping of the roll mode. Either the front wheels, the rear wheels or both can be steered using a simple feedback scheme using sensed roll rate. The scheme is effective in specific speed ranges and stabilizes the roll mode without introducing disturbance moments from roadway unevenness as shock absorbers do. There is a theoretical advantage to coordinated steering of both front and rear wheels but this level of complexity may not be practically justified.