Quarter car rig for software function development of fully active suspension and continuously controlled dampers

Abstract

Electric vehicles require a delicate balancing act by manufacturers. When engineers try to increase the ride comfort, ease of handling can be hurt and vice versa. Engineers in the automotive industry use computer-aided simulation extensively to find the right balance between comfort and handling. However, applying that requires training and extensive knowledge to get the best performance and results. Nowadays, fully active suspension (FAS) is a solution which can improve balance between ride comfort and handling. Currently, there’s lot of competition going on in an automotive market, especially because of electric vehicles. Checking the effect of FAS in the early development phase of the car will be helpful to achieve the right balance between ride comfort and handling. Early in the vehicle development projects, real vehicle prototypes are missing or lacking correct suspension geometry and/or FAS and CCD actuators. Virtual prototypes (simulation models) are also not available. Like the quarter car model, a test rig that takes approximately 1/4 of the sprung mass and unsprung mass where different suspension geometries can be used. Such test rig will be a good initial approach to understand the behavior of the vehicle. Therefore, this thesis involves the work to design a modular test rig for a quarter car that can be used on one poster in an existing 4-poster rig. The motion of the poster will be such that it will consider only the vertical dynamics of a car. In the first step, a conceptual model of a rig has been designed by combining a tire, a suspension geometry, Linear Motion Guide (LM Guide), and all the necessary required components to fix the testrig to the ground. After performing analysis on Tire Testrig in Adams Car and considering the complexity, it has been decided to keep a tire stationary instead of rolling. Considering the motion dynamics, caged type LM guide has been chosen which can take optimum forces in radial direction and has a better rolling resistance than other models. Then, a CAD geometry of a test rig has been developed using Catia-Teamcenter Integration tool with the aim to build a rig that can be used for various suspension geometries. The modularity of a testrig is required as various platforms have different mounting points, characteristics of a wheel, etc. While performing different load cases and test run the testrig, various instrumentation as well as production sensors will be used to measure the different signals coming out from the test run. The test rig which involves FAS and CCD can be validated either on a simulation level or by comparing with passive components on a 4-poster test rig. A simulation model which can exactly emulate the behavior or the functions of the physical quarter car testirg has been developed with the help of Adams software. Results from the simulation model accurately represents the realworld phenomenon. There are many benefits of having a Quarter Car Testrig. Some of them involves tuning the controller of an active damper, to iterate springs with different stiffness values to achieve the required targets. Additionally, we can fix the inhouse built software package on the testrig to validate the system. In such a way we can have more mature products during development phase through various iterations, and testing. This might help us becoming more decisive in a way and reduce little bit of time required considering the overall planning