The phase change in shape memory alloys (SMA) is highly nonlinear, and the development of advanced positioning applications for SMA actuators benefits from the availability of good models of this behaviour. One phenomenological model for SMA transformation kinetics is Madill's model, which has recently been extended to include the effect of timevarying stress. This extension allows for the modelling of stress disturbances and the simulation and prediction of stress-strain behaviour. In this work, we couple the phase kinetics of the extended model with a series-based mechanical model which includes both shape memory and superelastic behaviour. This coupled model is inverted and used to investigate different control architectures for sine tracking and stress disturbance rejection for an SMA actuator with constant load. Open-loop model-inverse feedforward control is compared with simple PI feedback and the combination of feedforward plus feedback. The results show in particular that using complicated inverse models does not always bring the expected increase in performance, and that other limitations of SMA actuators can negate the benefit of model-inverse feedforward.

This paper intends to compare controllers used for non-isolated (transformer less) interleaved double dual boost (IDDB) converter which provide high voltage gain and can be used for high-power applications. A control subsystem is required to improve dynamic behaviour of converter and to have a better output response. In most cases small signal model of converter is obtained which are linearized at an operating point to derive a controller which cannot take uncertainties into consideration. Robust control and Nonlinear control methods are probably areas which can handle uncertainties and non-linearities effectively. Conventional linear quadratic regulator (LQR) controller cannot assure stability if system is highly uncertain. A convex model of converter dynamics is obtained taking uncertainties into account. To apply LQR control in uncertain converter case linear matrix inequalities(LMIs) are used to optimize the performance index.A comparative study of LMI-LQR control, LQR Controller and PID controller is done.

No abstract