Quarter Car Ride Model and Optimization Including a Suspension Mechanism

Abstract

In this study, a double wishbone suspension mechanism is modeled attached to a body representing a quarter-car. Quarter car models have been studied extensively in the literature using lumped parameter models usually represented as simple systems made of sprung masses, springs, dampers and unsprung masses. In reality suspension mechanisms consists of control arms, which contribute significantly to the response of the overall system. Considering more complex models system including suspension mechanism usually simulation software are used. The main purpose of this study is to derive and to develop the quarter car’s mathematical model including a suspension mechanism in matrix form, and to use this model simulating and investigating various types of studies. First a mathematical model of the double A arm suspension attached to a car mass is generated and the resulting computer simulations are obtained in MATLAB. Second the same model is created using Adams/View software to validate the mathematical model simulation results. In order to get the realistic responses of the suspension system to the road input, the spectral descriptions are used for generating artificial road profiles. Two types of optimization process are performed, one concerning the dimensional optimization of the mechanism (kinematic/geometric mechanism optimization), the other concerning the nonlinear characteristics of the suspension elements namely coil spring and viscous damper (dynamic ride optimization). In the kinematical optimization, the camber angular deviation and the roll center height are taken into account as the weighted objective function. Considering optimization of the nonlinear characteristics of the damper and the spring, the passenger comfort and the car handling measures are taken into account using ISO 2631 weighting standard. Finally, actuators are included in the model in order to increase the ride comfort by an active control scheme. Two actuators are inserted, one is under the driver seat the other is in the A arm mechanism to form an active suspension. A PID control scheme is used to increase ride comfort. These steps also show that, even though it is cumbersome to obtain the simulations of a realistic mathematical model of a commonly used system; once the simulation model is established, it is easy to perform several types of the studies at once.