Sliding Mode Controller for Vehicle Body Roll Reduction Using Active Suspension System

In many designs of vehicle suspension anti-roll bars are used for body roll reduction (Cronje and Els, J Terramechanics 47:179–189, 2010; Her et al., IFAC Proc. 2013. https://doi.org/10.3182/20130904-4-JP-2042.00152). Such solutions are used in compact cars (C-segment), mid-size cars (D-segment), mid-size luxury car (E-segment) and even sports cars (S-segment). Antiroll bars are torsion bars connecting both sides of car suspension and they are connected with suspension arms. When car wheels move in vertical direction these torsion bars are twisted. Increasing torsional stiffness of front or rear suspension is the main role of sway bars. The use of these rods reduces tilting of the body while riding at high speed when the tilt of a car body is caused by the centrifugal force acting on the car. This force compress suspension spring with one side of the car, and extends on the other. The torque generated by the torsion bars reduce the difference in springs suspension. It reduces the compression of springs on one side of a car and extension on the other. Reduction of car body tilt improving handling and road holding and therefore improve safety. Antiroll bars also allow for the reduction of lateral vibrations caused by road roughness. During straight driving on equal road surface or under the same excitation of the wheels, the stabilizer doesn’t work. During overcoming high road irregularities, the force acting on one of a wheel is transferred to the other via the bar. Antiroll bars also allow for the reduction of lateral vibrations caused by road inequalities. This causes unwanted oscillations. This effect is more noticeable if angle stiffness of the stabilizer is higher. In order to avoid such phenomena, active anti-roll bars are used. The most commonly used solutions are two-part active disconnect anti-roll bar or just active antiroll bar. In case of a two-part disconnectable anti-roll bar a hydraulic actuator connected to the ends of the roll bars usually is used. In such case, wheels work independently of each other so that the reactions from one wheel are not transferred to the other. If necessary, the stabilizer is connected by means of an actuator and works just like the classic one. In an active stabilizer a hydraulic actuator connected to the ends of the antiroll rods usually is used. Controlling the pressure or flow rates of the oil gives wide possibilities for acting actively on the anti-swaying of the vehicle.