In this study, we demonstrated a way to suppress spasticity at a metameric site and to increase walking speed effectively by applying surface ES on the muscle-tendon junction of spastic gastrocnemius muscles.
The wheelchair developed in this study, although not absolutely superior to the joystick-controlled method, should still provide a better alternative for people with disabilities unsuited to traditional input devices.
This paper presents the modeling, controller design and a steady-state analysis algorithm for a wind-driven induction generator system. An output feedback linear quadratic controller is designed for the static synchronous compensator (STATCOM) and the variable blade pitch in a wind energy conversion system (WECS) in order to reach the voltage and mechanical power control under both grid-connection and islanding conditions. A tworeference-frame model is proposed to decouple the STATCOM real and reactive power control loops for the output feedback controller. To ensure zero steady-state voltage errors for the output feedback controller, the integrals of load bus voltage deviation and dc-capacitor voltage deviation are employed as the additional state variables. Pole-placement technique is used to determine a proper weighting matrix for the linear quadratic controller such that satisfactory damping characteristics can be achieved for the closedloop system. Effects of various system disturbances on the dynamic performance have been simulated, and the results reveal that the proposed controller is effective in regulating the load voltage and stabilizing the generator rotating speed for the WECS either connected with or disconnected from the power grid. In addition, proper steady-state operating points for an isolated induction generator can be determined by the proposed steady-state analysis algorithm. Constant output frequency control using the derived steady-state characteristics of the isolated induction generator is then demonstrated in this paper.
The variation in source impedance and solar irradiation effects on photovoltaic (PV) system control performance is investigated. A proportional-resonant (PR) controller in a stationary frame in place of a proportional-integral controller in a synchronous frame was adopted to modulate a single-phase grid-tied inverter for PV systems. Although the PR controllers have gained some momentum lately due to advantages such as instantaneous tracking capability and low-cost computational resources, the tracking performance may decline due to changes in source impedance and solar irradiation where the conventional PR design rule is void. To adapt PR controllers over diverse operating conditions without incurring excessive tracking error, a one-dimensional optimization (ODO) algorithm that dictates the quality of the tracking performance is proposed to search for an appropriate factor χ between the real part of dominant and nondominant eigenvalues for the PV systems. The control gains of the PR controller can be then altered in light of the optimal χ through a simple algebraic conversion. The experimental results confirm the performance of the proposed strategy.
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