CONSTRUCTION OF SELF-TUNING SUSPENS10N SYSTEMS OF VEHICLES USING FUZZY THEORY

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This investigation presents the construction of self-tuning active and semi-active suspension systems of vehicles using fuzzy theory. The construction is classified into active syspension systems for large-sized buses, and semi-active suspension systems for compact passenger cars. It is carried out by the simulation study using personal computers, and its effectiveness is shown by the field testing and the experiment. The active suspension system is derived by choosing the fuzzy control rules and the membership functions for the input and output variables where the vertical and rotary accelerations and velocities of the vehicle body are denoted as the input variables. The defuzzified value of the output variable is obtained by using the product-sum-gravity method. A self-tuning suspension system, which can adaptively tune the control structure according to the variation of the road input, is constructed where the membership function for the output variable is changed by the measurement … More of the input variable. Two kinds of approaches to improve the suspension performance is proposed. The first is the construction of preview control obtained by measuring the road input advanced from the front wheel. The second is the construction of dynamic absorbers fitting to the front and rear axes. The dynamic absorbers reduce the vibration with the frequencies generated by the Lime difference between the front and rear wheels. While, the semi-active suspension system is derived by choosing the fuzzy control rules where the suspension stroke and the time increment are denoted as the input variables, and the damping force is done as the output one. AS the selection of the damping force needs about 10 ms. at least and it leads the performance degradation, the fuzzy control rules are constructed by considering the time delay. The effectiveness of the semi-active suspension is shown by the field testing, and the pneumatic active suspension system is experimentally obtained by a quarter car model. Less