Analytical and Experimental Dynamic Analysis of A Four Wheeler Vehicle With Semi Active Suspension System

Abstract

Advances in the automobile industries in several engineering aspects have opened up never ending challenges and scopes. One such interesting challenge is to achieve better ride quality which intends to provide more comfort to the passengers. The road profile randomness is not uniform around the globe. Therefore, achieving a good ride comfort has always been a task for researchers over the years. A key component responsible for ride quality is the suspension system of the vehicle, a major combination of spring and damper. The nature and magnitude of energy dissipation from the damper provides suitable ride quality to the vehicle. Passive dampers provide constant response against any kind of road disturbances since the fluid properties cannot be altered with any external input. Hence, replacing passive damping medium with semi-active medium will provide added advantage to the suspension system in providing greater ride comfort. Magneto-rheological (MR) fluid is one such smart fluid which is known for its semi-active nature when the external magnetic field is varied. This research study deals with synthesis of magnetorheological fluid and its application in damper of a light motor vehicle. In the primary part of this study, a passive damper was extracted from the suspension system of the commercially available light motor vehicle. This passive damper was characterized in the dynamic testing machine (DTM) to understand the dynamic response of the damper towards varying cyclic input. The damping force response from the passive damper was considered as the benchmark for development of MR fluid damper particular for the test vehicle. A quarter car model was developed using the MATLAB/ Simulink and the response of the passive damper characterization was employed in the damping element of the model. As a preliminary study of the MR fluid damper, a small stroke MR damper was designed and developed. For this purpose, an MR fluid was prepared in-house and used as the damping medium in the MR damper. This prototype was then characterized using dynamic testing machine subjected to different amplitude, frequency and DC current inputs. A mathematical model was established which could iv relate the damping force and the current which was then used in quarter car simulation. Based on the above preliminary works, a prototype MR damper with actual scale was then designed using optimization technique under certain geometrical constraints. The designed MR damper piston was analyzed by using finite element magnetic methods (FEMM) to verify the magnetic flux development in the fluid flow gap. MR fluid as the damper fluid was synthesized in-house using electrolytic iron particle (EIP) and paraffin oil. Rheological study of the synthesized MR fluid was conducted to analyze the shear stress as well as viscosity variation against the shear rate and the current inputs. The developed MR damper was then characterized under various dynamic and DC current inputs to study the force versus displacement nature. The hysteresis of the damper was mathematically represented using parametric modeling technique called Kwok model. The parameters of the model were determined for each condition by using optimization method. This model was then used in quarter car simulation to analyze the effect of suspension under off-state, constant current and through skyhook control. The validation of this simulation was carried out by using the suspension with MR damper in a quarter car test rig and the deviation in the results was analyzed. As an important part of this research work, the suspension with the developed MR damper was tested on-road by using a test vehicle. The passive damper in the front suspension of the test vehicle was replaced with MR damper and the suspension was tested at two different velocities. Also, the ride comfort at different conditions was analyzed. As an extended part of the study, a control logic involving single sensor technique was developed. The performance of developed control was tested using the quarter car set up and the comparison of the responses through different current inputs was also presented.