ON A RIDE CONTROL ALGORITHM FOR HEAVE, PITCH AND ROLL MOTIONS OF A MOTOR VEHICLE (ACTIVE, SEMI-ACTIVE, OPTIMAL, AUTOMOTIVE, DYNAMICAL SYSTEM)

An analytical and numerical study of a multi-degree of freedom passenger car incorporating Passive, Active and Semi-active Suspension is performed. The model includes rigid body translational and rotational modes. This constitutes an extension of the state-of-the-art, since previous investigations of semi-active suspensions were restricted to jounce vibration control (exclusive of roll). The vibrations of the four-wheeled vehicle are induced by deterministic and random inputs at the left and right track. With the above model, an investigation of the influence of active and semi-active damping on vehicle ride quality control is performed, and comparison with the conventional passive suspension by means of computer simulation is made. The resulting optimal active control problem belongs to the class of partially controllable and partially observable systems. The optimal active suspension structure is derived using a linear quadratic regulator approach. A switching function which modifies the active control strategy to a semi-active nonlinear control process is employed and a comprehensive, interactive digital computer optimization code is developed. Simulation results in the time and frequency domain show that the semi-active damper is superior than the conventional passive one, with performance approaching that of a fully active system. Specifically the root mean square passenger seat acceleration is reduced by 57% using semi-active damper and 87% using active damper control. The penalty cost associated with these ride comfort improvements is an increase of the secondary and primary suspensions deflections. In contrast to the fully active, the semi-active suspension requires no other power supply than that for signal processing and valve activation. Based on the results of this research it is anticipated that superior vibration isolation of active and semi-active suspensions has a potential for nearly equivalent ride quality performance between a subcompact car and a full-size car.; The study intends to explicitly show the effects of active and semi-active suspension control on the response characteristics of the coupled vibration modes relative to random excitation.