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Browsar Äldre organisation // Older organization efter Program "Automotive engineering (MPAUT), MSc"
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- PostA report on Objective Development of Damper Specification(2018) Adisesh, Ashrith; Agarwal, Rohit; Chalmers tekniska högskola / Extern; Chalmers University of Technology / ExternalDamping of the sprung and un-sprung masses of a vehicle through a suspension damper is crucial to obtain good comfort and handling characteristics. Damper tuning, which is predominantly based on subjective feedback and experience from engineers takes up a large amount of time and resources. Preliminary knowledge of the influence of dampers in different operating regions can provide a good starting point in the damper tuning process. This research thesis aims to develop objective metrics related to the response of simplified vehicle models and could provide information regarding the modifications in the damper specifications to achieve the desired response. Quarter-car models with linear, asymmetric and non-linear damper curves are simulated in the Matlab environment for step and swept sine inputs. The responses are further investigated to identify metrics of interest, by which the behaviour of the vehicle can be understood. For linear damper models, the poles of the system are analyzed and pole placement method is used to understand the behaviour of sprung and un-sprung masses when suspension parameters are varied. For asymmetric dampers, metrics which could help decide the required degree of asymmetricity between compression and rebound damping are presented. Finally, for non-linear dampers, the effect of damping force in different regions of operation is studied. A sensitivity analysis (Design of Experiments) is performed to identify the most influential variables corresponding to these metrics. With these results, the response of the model is studied to obtain the metrics of interest which can be attributed to the behaviour of the vehicle. Comparisons are presented to visualize the effects of different damper specifications by which an initial prediction could be made for the damper specifications. This outcome can potentially enhance the preliminary knowledge of the effects of damper tuning and thereby providing a better starting point for the damper development process.
- PostInvestigation of active anti-roll bars and development of control algorithm(2017) Gustafsson, Jacob; Agrawal, Harshit; Chalmers tekniska högskola / Extern; Chalmers University of Technology / ExternalActive anti-roll bars have recently found greater acceptance among premium car manufacturers and optimal application of this technology has emerged as an important field of research. This thesis investigates the potential of implementing active anti-roll bars in a passenger vehicle with the purpose of increasing customer value. For active anti-roll bars, customer value is defined in terms of vehicle’s ride comfort and handling performance. The objective with this thesis is to demonstrate this value through development of a control algorithm that can reflect the potential improvement in ride comfort and handling. A vehicle with passive anti-roll bars is simulated for different manoeuvres to identify the potential and establish a reference for the development of a control algorithm and for the performance of active anti-roll bars. While ride is evaluated using single-sided cosine wave and single-sided ramps, handling is evaluated using standardized constant radius, frequency response and sine with dwell manoeuvres. The control strategy developed implements a combination of sliding mode control, feed forward and PI-controllers. Simulations with active anti-roll bars showed significant improvement in ride and handling performance in comparison to passive anti-roll bars. In ride comfort, the biggest benefit was seen in the ability to increase roll damping and isolating low frequency road excitations. For handling, most significant benefits are through the system’s ability of changing the understeer behaviour of the vehicle and improving the handling stability in transient manoeuvres. Improvement in the roll reduction capability during steady state cornering is also substantial. In conclusion, active anti-roll bars are undoubtedly capable of improving both ride comfort and handling performance of a vehicle. Although the trade-off between ride and handling performance is significantly less, balance in requirements is critical to utilise the full potential of active anti-roll bars. With a more comprehensive control strategy, they also enable the vehicle to exhibit different driving characteristics without the need for changing any additional hardware.