This paper analyzes for the first time a two-loop sliding-mode control (SMC) of a high-order converter supplying a constant power load (CPL). The converter is a single-switch quadratic buck structure (QBC) interfacing a domestic 380 V DC bus to a CPL requiring a regulated voltage of 48 V DC. The converter is unstable in the absence of control and even after the insertion of an inner loop based on SMC of the input inductor current. The addition of an appropriate linear outer loop establishing the reference to the inner loop stabilizes the system and provides output voltage regulation. The regulated QBC shows a fast recovery of the output voltage with negligible overshoot in response to step-type changes of the output power or the input voltage. It is also shown that the implemented regulator for CPL supply can be used directly in the case of a constant current load (CCL) or a constant resistance load (CRL) resulting in similar performance to the CPL case. PSIM simulations and experimental results in a 400 W prototype are in good agreement with theoretical predictions.

Robust control techniques for power converters are becoming more attractive because they can meet with most demanding control goals like uncertainties. In this sense, the Takagi-Sugeno (T-S) fuzzy controller based on linear matrix inequalities (LMI) is a linear control by intervals that has been relatively unexplored for the output-voltage regulation problem in switching converters. Through this technique it is possible to minimize the disturbance rejection level, satisfying constraints over the decay rate of state variables as well as the control effort. Therefore, it is possible to guarantee, a priori, the stability of the large-signal converters in a broad operation domain. This work presents the design of a fuzzy control synthesis based on a T-S fuzzy model for non-minimum phase dc-dc converters, such as boost and buck-boost. First, starting from the canonical bilinear converters expression, a Takagi-Sugeno (T-S) fuzzy model is obtained, allowing to define the fuzzy controller structure through the parallel distributed compensation technique (PDC). Finally, the fuzzy controller design based on LMIs is solved for the defined specification in close loop through MATLAB toolbox LMI. Simulations and experimental results of a 60 W prototype are presented to verify theoretical predictions.

This work presents the synthesis of fuzzy controls based on Linear Matrix Inequality (LMI) for DC-DC converters. Concretely, the paper proposes a linear-piecewise continuous control for a buck-boost converter which optimizes the decay rate of state variables under pole placement constraints and duty-cycle limitation. Based on a Takagi-Sugeno model of a buck-boost converter for a determined interval of operation, the paper describe the LMIs which take into account quadratic stability, closed-loop pole region and control signal bound. The procedure derives the control law by solving the LMI set using standard optimization algorithms on MATLAB. Some simulations illustrate and verify the correctness of proposed control design method, also a comparison with a common linear control law is provided.

According to statistical data provided by the National Administrative Department of Statistics (DANE), during 2005, 29.32% of Colombias disabled population had problems with their legs related to moving or walking. In order to contribute and help these people, medical science and engineering have been working together to provide solutions that can improve the quality of life of injured people. In this sense, it is possible to design and implement electromechanical devices to assist and facilitate movements in rehabilitation processes. Such devices can keep detailed records of movements performed, patient history, speed, force, muscle interaction, among others; also allows physiotherapists to have complete control of rehabilitation processes, improving it and offering a lot more possible treatments by analyzing the summarized collected data. Rehabilitation focused exoskeletons work as guide and support in physical therapy, those make sure that the treated patient performs correctly all its exercises, in case that the patient cannot perform the movement by himself such devices helps the patient to finish the exercise, improving the effectiveness of the therapy and reducing the time it takes to recover lost faculties. As a contribution to rehabilitation processes, this paper proposes the design of an exoskeleton by considering biome-chanical models involving the most possible characteristics of the human body to reduce the differences between the mathematical model and the real behavior of the body segments; That proposed model is used to constraint and design a controller in master-slave configuration to assist and ensure soft movements improving rehabilitation processes involving flection and extension movements in the sagittal plane of the lower limbs.