Integrated control of four-wheel-steering and torque vectoring

Since the development of first motor driven vehicle in 1769, the first occurrence of accident arise in 1770 . From that time engineers tried to find ways to build active safety systems in order to reduce accidents. The first active system was developed by Vehicle engineers in 1930 which was implemented in aerospace industry . This active system is called Antilock-Braking system (ABS). From 1978, it was mandatory that each vehicle contains this specific system. Contribution of this control logic is to reduce car crash and keep vehicle steerable during heavy brake.Today, numerous applications of active control system can be found in active steering, active suspension, active drive torque control. The roles of these systems are to maintain the stability and steer-ability of the vehicle as well as comfort of the driver and passengers. However, throughout the years researchers have found few limitations on each individual active control systems. Recently, intuitive methods, such as integrated control design technology, have been implemented and by these methods not only these limitations have been overcome but further improvement in terms of stability can be observed. The following, discuss some of the aforementioned applications of these systems. Integration control of active front steering(AFS) is the application of these systems with electronic stability program(ESP). This control logic uses AFS which adjusts front steering and is suitable in steady-state working condition. On the other hand ESP maintains the rotational stability of vehicle by generating brake force on each wheel. Combination of these two controllers can enhance the stability and handling of the vehicle. Another integrated control strategy is integration of active rear wheel steering and yaw moment ; this controller uses rear wheel steering that is well responded in terms of stability, however the improvement is limited in linear dynamic system. Therefore combining this strategy with direct yaw moment can improve handling and stability that cannot be achieved with rear wheel steering standalone. Another method of integration is combination of active suspension and AFS . In this situation active suspension optimizes vertical forces in order to maintain comfort and enhancement of handling and stability by taking into account the effect of yawrate and side-slip angle which are two main elements for defining stability.