AbstractIn this thesis, both theoretical and experimental research work has been carried out in the area of active suspensions for automotive application. A PC based digital control system and interfaces to an existing trailer with an active zero rate suspension system, sensors and electronics has been developed. The required control software has been written in C++. A nonlinear half (and quarter) car model with limited actuator bandwidth has been established for the two wheeled trailer with the active suspension. Various control strategies, namely PD, MIMO PID, LQG and Fuzzy Logic, have been implemented on the physical prototype. These controllers were simulated using the validated nonlinear model and implemented on the test rig. Experimental results have shown that the whole control system functions correctly and the methodology of these applications has been correct. The performance of these control strategies has been investigated mathematically and experimentally for the particular test rig in terms of ride comfort and handling. It has been shown that the MIMO PID performs the best. The effects of the nonlinearity and limited bandwidth of actuators were also investigated in the nonlinear model, which resulted in a novel explanation for the instability in test rig. A PC based active tuneable vibration absorber (ATVA) has been developed and built from concept to prototype. This system includes an accelerometer on the hub, an absorber tuned by a stepping motor, a PC computer and the relevant interfaces. The corresponding control strategy and software have also been developed for the ATVA. Experiments on a developed unsprung mass test rig and simulation have been used to evaluate the performance of the ATVA. It has been shown that the whole system including hardware, software and algorithm is effective and the developed ATVA can be a candidate to damp out hub vibration. The performance of the combination of the zero rate suspension and the ATVA has been predicted by simulating the trailer response under road profile inputs. The nonlinear half car model with MIMO PD) with sky hook damping and ATVA under white noise excitation was employed for this purpose. It has been shown that the combination can provide both ride comfort and handling. A PC based measurement system for identifying the transfer function of vehicle suspensions has also been developed from concept to the prototype. This work includes designing and building the measurement platform and interfaces to the PC computer, writing software for signal sampling and processing, and developing the test method and algorithm. Results from this system have been validated against two standard methods, a conventional hydraulic shaker and a quarter car test rig with swept sine wave excitation. The developed system has been proved to function correctly.
PublisherUniversity of Wolverhampton
TypeThesis or dissertation
DescriptionA thesis submitted in partial fulfilment of the requirements of the University of Wolverhampton for the degree of Doctor of Philosophy
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