Analysis, modelling and robust control of automotive HID headlight systems

Automotive high intensity discharge (HID) lamps have received attention recently because of its significant improvement in vision and high luminous efficacy. The automotive headlight system usually consists of Xenon lamp and HID ballast. The modelling of Xenon type lamp requires programming of complex physical characteristic. The characteristic is nonlinear and highly dependent on temperature. Ageing study of the lamp allows the improvement in ballast design and illumination compensation. An ageing model is therefore necessary, but it requires the detailed study under the long term time-monitoring of the lamp. Another issue is the dimming control as it provides a flexible control of the lighting output. This thesis is focused on these two aspects: development of the electronic ballast circuit, and the new control methods to optimize the performance of the system. The study first begins with the comparison of a commerical available controller UCC2305 for the electronic ballast and a microprocessor controlled electronic ballast. The design method, theoretical analysis and experimental results are presented. A unified controller is then developed based on a flexible control platform dSPACE and it is realized by adaptive control method and PI control method. A 2-D spline interpolation model has been developed to present the characteristics of lamp. The model can then accurately represent the transient and steady states under various temperature control schemes. Under constant power control for the lamp, Passivity-based Control (PBC) controller of HID electronic ballast is examined. The dimming control for the HID lamp ballast is further investigated to include the relationship between the lamp power and various control parameters. Lastly, the lamp ageing measurement including voltage, current and lumen were made. A compensation has been proposed for the aged lamp in order to provide a consistent lumen output.