DESIGN AND CONTROL OF AVARIABLE AUTOMOTIVE HYDRAULIC DAMPER USING CUCKOO SEARCH OPTIMIZED PID METHOD by Chan Kim Nam Thesis Supervisor: Prof. Wong Pak-Kin Department of Electromechanical Engineering, Faculty of Science and Technology In the automotive engineering, semi-active suspension (SAS) system has been one of the most attractive research projects and this topic is very challenging due to its highly nonlinearity and uncertainty in dynamic control. It is well known that the SAS system usually refers to the damping force control using a variable hydraulic damper (VHD). This research proposes a cuckoo search optimized proportional-integral–derivative (CS-PID) strategy for the electronic damping force control (EDFC) system based on the VHD in order to improve vehicles for different driving conditions and to improve the stability of handling and smoothness of driving. First, the quarter car dynamic model with air spring and VHD is developed. By constructing the detailed analytical model and describing the working process, the regulating mechanism and external characteristics of the VHD are presented. Subsequently, the CS-PID strategy is designed to generate the desired damping force according to the vehicle states in realtime, followed with the evaluation of the proposed strategy. Finally, the control system is constructed and experiments are carried out to verify the feasibility of the proposed strategy. Numerical results based on the analytical model reveal that the vehicle performance can be greatly improved with the proposed control strategy and experimental results show that the CS-PID strategy can be successfully implemented in the EDFC system with VHD.