The improvement of full vehicle semi-active suspension through kinematical model
1University of Oulu, Faculty of Technology, Department of Mechanical Engineering
|Online Access:||PDF Full Text (PDF, 2.4 MB)|
|Persistent link:|| http://urn.fi/urn:isbn:9514276124
|Publish Date:|| 2004-12-01
|Thesis type:||Doctoral Dissertation
|Defence Note:||Academic Dissertation to be presented with the assent of the Faculty of Technology, University of Oulu, for public discussion in Raahensali (Auditorium L10), Linnanmaa, on December 11th, 2004, at 12 noon.
Professor Matti Juhala
Doctor Hannu Lehtinen
Over recent years the progress in actuator and microelectronics technology has made intelligent suspension systems feasible. These systems are designed to reduce the drivers' exposure to harmful vibration, as well as to improve the handling properties of the vehicle. Due to widespread use of vehicles as an example of a true MIMO-system, a myriad of different control schemes and algorithms can be found in the literature for these systems. Linearized models are commonly used when the control algorithms are derived.
This thesis describes the development of a new analytical full vehicle model, which takes the essential kinematics of the suspension system into account, as well as a new approach to controlling the full vehicle vibration problem. The method of calculating the desired damping forces for each of the semi-active actuators is based on the skyhook theory and this new model is introduced.
The performance of the control schemes is evaluated with simulations in a virtual environment. For the excitation to the vehicle, standardized ISO-tracks, washboard tracks and single bump tracks were used. The performance between the two different semi-active control systems and the passive system are compared in terms of damping the vibration, variation of the dynamic tire load and demand for rattlespace.
The damping of vibration evaluates both the ability to suppress the vibration on heave, pitch and roll degrees of freedom and ability to reduce the drivers' exposure to harmful whole body vibration. The frequency distribution of the vibration was also reviewed. Variation of dynamic tire contact force is evaluated as an RMS-value and the demand for rattlespace is evaluated as a percentage value of the used rattlespace compared to the maximum free stroke provided by the suspension hardware.
As a result from this work, the theory and simulation results are presented. Also a new vehicle model, which takes the essential non-linearity caused by suspension kinematics into account, is presented including all the mathematics needed. The comparison between the passive and the semi-active concepts has been performed on the basis of simulation results. These results show that the novel semi-active concept reduces the driver's exposure to vibration induced by terrain undulations better than any earlier proposed version. Also variation of dynamic tire load is reduced with a novel concept, while it suffers a drawback in the demand for the rattlespace.
Acta Universitatis Ouluensis. C, Technica
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