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In this paper, the adaptive second order sliding mode (SOSM) controller is designed for two input - two output (TITO) uncertain nonlinear systems and the robustness properties are ensured in the presence of uncertainties and bounded external disturbances. The objective is to design a controller that ensure stability and path tracking despite the effects of coupling. To this end, the system model is divided into two subsystems, and the coupling effects between such subsystems are considered as uncertainties. The sliding mode approach with PI sliding surface is used to remove the offset and converge the steady state error to zero. To avoid chattering phenomenon, Second order sliding mode method is proposed. Using adaptive switching gain, a new method is presented which unlike other methods, does not require the upper bound of the system uncertainties in the design procedure. Robustness properties against system uncertainties and external disturbances is shown by the Lyapunov stability theorem. Finally, the proposed method is used to control azimuth and elevation angle of as a laboratory helicopter with two degrees of freedom. Simulation results show performance of the algorithm in the presence of perturbations.

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In this paper the conventional structure of dual-axis sun tracker is modified based on new mechanical and electrical detectors which are proposed to reduce both the angular error and power consumption. Automatic adjustment of the azimuth, latitude and altitude angle for the photovoltaic panels improves the performance of converting solar energy to the electrical energy, throughout all the seasons. In other words, both the north-worth and east-west angular error is continuously minimized until that the panel’s surface is solarized with the maximum energy. Post-Fabrication results show that the proposed control circuit and two actuators consume the average power of less than 10mWatt alongside the 13-hour of a summer day. The external power source is no longer required because the received power is saved in a battery in order to provide the power of the control circuit. The ratio of the required energy to the saved energy is optimized to around 0.13%. Measurement results confirm that the total Watt-hour during a summer day is improved around 60 percent in comparison to the case that a fixed panel is used. Design of the mechanical objects are performed using CATIA software such that endure up to 1200Watt panel array.