Empirical modeling of automotive damper curves and development of shape factors

Abstract

Automotive dampers are a complex system developed with integration of simple mechanisms. The system comprises of a cylinder filled with hydraulic fluid, a piston dividing cylinder into two chambers known as compression and rebound chambers; a coil spring in some case and nitrogen gas. When a vehicle moves, automotive Damper system deals with damping vibration and giving occupants a comfortable ride. While the system ensures a smooth ride by absorbing all the road vibration, hydraulic fluid inside the Damper system goes through various transformations. Changes and variations happen in properties like pressure and temperature inside the Damper system with time because of displacement of piston which leads to generation of heat which leads to change in damping coefficient. While calculating energy equation, it was observed that constant damping coefficient was used and was not a function of time. In a real world scenario this assumption is not correct because with changes in above mentioned properties, damping coefficient values are affected and they change constantly with time. Research was commenced on coming up with an empirical model that can give information regarding energy inside a Damper system, types of suspension behavior and various characteristics regarding Damper system for any range of velocities. A full-fledged Damper system empirical model will have various constants, parameters, shape factors and form factors. If these parameter values are obtained and used properly, they can give help determining the behavior of any Damper system, different settings that can be used to get required behavior by any Damper system. For a full-fledged empirical model, lots of efforts, resources and years of research will be required. So, to start with, an empirical model was worked upon that can act as a shape factor for any Damper system for given range of velocities. Any Damper system will give three different types of curves a progressive curve, a linear curve and a digressive curve. The three curve shows three kinds of suspension behavior which is required depending upon the application. Keeping this in mind, a model was created which was able to depict all three damper curves for certain range of values for both compression chambers and rebound chamber inside a damper. The model is a function of various trigonometric functions like sine, arctans, hyperbolic functions and property like velocity. There are constant parameters and changing their values will change shape of damper curve as per the requirement. Developed Empirical Model is able to fulfill the initial requirement of becoming a proper shape factor and can be used to predict behavior of Damper system for both compression and rebound chamber. Main reasons behind obtaining damper curves are the constant parameters associated with it. Those parameters can be related to any characteristics or properties associated with function and performance of a Damper system. Developed Empirical model acts as a foundation for next stage of research because once the shape factor is achieved; the parameters associated with it can be given a meaning based on Damper system's properties and characteristics.