This paper presents a nonlinear, robust control algorithm for accurate positioning of a single degree of freedom rotary manipulator actuated by Shape Memory Alloy (SMA). A model for an SMA actuated manipulator is presented. The model includes nonlinear dynamics of the manipulator, a constitutive model of Shape Memory Alloy, and electrical and heat transfer behavior of SMA wire. This model is used for open and closed loop motion simulations of the manipulator. Experiments are presented that show results similar to both closed and open loop simulation results. Due to modeling uncertainty and nonlinear behavior of the system, classic control methods such as Proportional-Integral-Derivative control are not able to present fast and accurate performance. Hence a nonlinear, robust control algorithm is presented based on Variable Structure Control. This algorithm is a control gain switching technique based on the weighted average of position and velocity feedbacks. This method has been designed through simulation and tested experimentally. Results show fast, accurate, and robust performance of the control system. Computer simulation and experimental results for different stabilization and tracking situations are also presented.

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A review of different approaches to setpoint, trajectory tracking, and path following control for autonomous underactuated surface vessels is presented in this work. The review is focused on rigorous control approaches developed using planar autonomous surface vessel models over approximately the last two decades. The controllers are categorized into setpoint, trajectory tracking, and path following approaches with further classification into discontinuous and smooth timevarying control laws for the setpoint control approaches. An overview of the formulation, advantages, and disadvantages of each approach is presented. Although much progress has been made in autonomous underactuated surface vessel control, there remains a need for the evolution of these approaches to achieve robust, real-time control laws that can be implemented on actual autonomous Unmanned Surface Vessel (USV) platforms in the presence of high sea states and external disturbances in uncertain and unstructured environments.