Robust Control of the Knee Joint Angle of Paraplegic Patients considering Norm-Bounded Uncertainties

A proposal for the knee position control design of paraplegic patients with functional electrical stimulation (FES) using control systems and considering norm-bounded uncertainties is presented. A state-space representation of the knee joint model of the paraplegic patient with its nonlinearity is also demonstrated. The use of linear matrix inequalities (LMIs) in control systems with norm-bounded uncertainties for asymptotic stability is analyzed. The model was simulated in the Matlab environment. The matrix K of state space feedback was obtained through LMIs

ELECTRONIC SYSTEM TO MEASURE PLANTAR FORCE DISTRIBUTION IN PATIENTS

This article describes an electronic system, projected to measure the force distribution under patients’ foot soles by instrumented soles with sensors. The system is basically composed of load cells installed in the soles, signal conditioning circuit, interfacing circuit and a computer, from which the measurement results can be read. It is possible to measure static and dynamic forces. Data visualization on the computer screen is displayed by a Visual Basic program. The system presents linear response with the applied force, small hysteresis, precision higher than 99.4%, in addition to its simple operation and handling. It could be used by sports and fitness professionals and other health area professionals to assist in the evaluation of specific programs that aim at increasing athletes’ performance

Sistema eletrônico para geração e avaliação de movimentos em paraplégicos

Foi implementado um sistema eletrônico de eletroestimulação funcional para geração e avaliação de movimentos nos membros inferiores de pessoas paraplégicas e hígidas. O sistema eletrônico é constituído por um estimulador elétrico neuromuscular, por uma plataforma de testes e por algoritmos de controle. O estimulador é de oito canais, independentes, controlado, com forma de onda de corrente de estimulação bifásica, retangular, com carga balanceada e capacidade de fornecer até 140 mA. O sistema pode operar com modulação por largura ou amplitude ou de pulso. Os parâmetros de estimulação podem ajustados e alterados com facilidade e agilidade por meio tela de do computador em um programa desenvolvido em LabVIEW. Foi necessária a implementação de uma plataforma de testes que contém os dispositivos necessários para gerar e aferir algumas grandezas, como estímulos elétricos controlados, deslocamento, velocidade e aceleração angular. A plataforma é composta por sensores, circuitos de condicionamento de sinais, software para o ajuste e controle dos parâmetros de eletroestimulação e também uma cadeira onde foi instalada toda a instrumentação. Utilizou-se DSP (Processador Digital de Sinais) e LabVIEW, juntamente com o eletroestimulador e sensores, para a implementação de controladores em malha fechada, PID (Proporcional Integral e Derivativo) e também Fuzzy Takagi-Sugeno, para estabelecer a posição da perna do na posição desejada, no movimento de extensão do joelho, de pessoas hígidas e paraplégicas. Foram realizados testes em malha aberta e malha fechada, com voluntários hígidos e paraplégicos. Modelos Fuzzy Takagi-Sugeno (TS) foram utilizados na modelagem e controle discreto do modelo matemático proposto por Ferrarin e Pedotti (2000). Foi proposta uma metodologia inédita para a...We have implemented an electronic system for functional electrical stimulation for generation and evaluation of movements in the lower limbs of paraplegic and healthy people. The electronic system comprises a neuromuscular electrical stimulator, a test platform and control algorithms. The eight-channel stimulator is independent, controlled, waveform for stimulating current biphasic, rectangular, and load-balanced ability to deliver up to 140 mA. The system can operate with width or amplitude modulation or pulse. The stimulation parameters can be easily and agility adjusted and changed through the computer screen in a program developed in LabVIEW. It was necessary to implement a test platform that contains the necessary devices to generate and measure some quantities such as controlled electrical stimulation, displacement, velocity and angular acceleration. The platform consists of sensors, signal conditioning circuits, software for adjustment of parameters and control of electrostimulation and also a chair where it was settled the instrumentation. We used DSP (Digital Signal Processor) and LabVIEW, together with the electrostimulator and sensors to implement a closed loop controllers, PID (Proportional Integral Derivative) and Fuzzy Takagi-Sugeno, to establish the position of the leg in a desired position, in the movement of knee extension in people. Tests were conducted in open and closed loop with healthy and paraplegic volunteers. Takagi-Sugeno (TS) fuzzy models were used for modeling and discrete control of the mathematical model leg proposed by Ferrarin e Pedotti (2000). We proposed a new methodology for the construction of local models considering the position, velocity and angular acceleration. The... (Complete abstract click electronic access below)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Sistema microcontrolado para medição de forças na região plantar e nos membros superiores de pacientes

Este trabalho descreve um sistema eletrônico implementado com o objetivo de monitorar os esforços exercidos pelos membros superiores e inferiores de pacientes. O sistema é constituído por transdutores, circuitos de condicionamento de sinais, circuito de comunicação e um software para a aquisição de dados, além da visualização em um microcomputador. São descritos dois tipos de transdutores, construídos com extensômetros metálicos, um para conexão em muletas e o outro projetado para ser inserido em palmilhas. Os fundamentos teóricos necessários para o projeto destes transdutores são apresentados, bem como os esquemas dos circuitos implementados. É descrita a metodologia utilizada para a determinação das características estáticas e dinâmicas dos transdutores. Estes apresentaram respostas lineares, excelente repetibilidade, e faixa dinâmica que atende às finalidades do projeto. Foi desenvolvido um software com interface gráfica contendo várias telas que possibilitam diferentes análises e armazenamento de informações. Utilizando o sistema, foram realizadas, com êxito, medições de forças exercidas pelos membros inferiores e superiores de pacientes normais e hemiplégicos.This work describes the development of a computer-based system able for monitoring forces acting on patients’ upper and lower limbs. The system consists of insoles and crutches instrumented with load cells, signal conditioning circuits, data acquisition system, and a computer. The results of the static and dynamic measurements can be presented in the screen of a computer through graphs and tables, and stored in a data base, to follow-up the development of a patient treatment. The program was developed in Visual Basic, and the communication uses the USB port. All transducers presented linear response, small hysteresis, excellent repeatability and resolution. Static and dynamic measurements performed with the transducers are presented as well as the visualization of the forces exerted on the plantar area and upper limbs of healthy and hemiplegic patients.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Realimentação derivativa e modelo fuzzy Takagi-Sugeno paracontrole da articulação do joelho de pacientes paraplégicos com o uso de acelerômetros

Feedback control systems have been used to move the muscles and joints of the limbs of paraplegic patients. The feedback signal, related to the knee joint angle, can be obtained by using an electrogoniometer. However, the use of accelerometers can help the measurements due the facility of adhering these devices to the skin. Accelerometers are also very suitable for these applications due their small dimensions and weight. In this paper a new method for designing a control system that can vary the knee joint angle using Functional Electrical Stimulation (FES) is presented, as well as a simulation with parameters values available in the literature. The nonlinear control system was represented by a Takagi-Sugeno fuzzy model and the feedback signals were obtained by using accelerometers. The design method considered all plant nonlinearities and was efficient and reliable to control the leg position of a paraplegic patient with the angle of the knee ranging from 0° to 30°, considering electric stimulation at the quadriceps muscle. The proposed method is viable and offers a new alternative for designing control systems of the knee joint angle using more comfortable sensors for the patients

Robust T-S Fuzzy Control of Electrostimulation for Paraplegic Patients considering Norm-Bounded Uncertainties

This manuscript presents a Takagi–Sugeno fuzzy control for a mathematical model of the knee position of paraplegic patients using functional electrical stimulation (FES). Each local model of the fuzzy system is represented considering norm-bounded uncertainties. After obtaining the model of FES with norm-bounded uncertainties, the fuzzy control strategy is designed through the solution of linear matrix inequalities (LMIs) using the conditions available in the literature, which consider these norm-bounded uncertainties. The strategy considers decay rate and constraints on the input signal. The model is simulated in the Matlab environment using the numerical parameters measured by experimental tests from a paraplegic patient

Measurement of orthovoltage X-ray intensity with a lithium niobate transducer

A microcontrolled instrument for measuring the energy fluence rate (or intensity) of X-ray pulses in the orthovoltage range of 120 to 300 kV is described. The prototype instrument consists of a pyroelectric sensor, a low-noise highsensitivity current-to-voltage converter, a microcontroller and a digital display. The response of the instrument is nonlinear with the intensity of the radiation. The precision is better than 3%. The equipment is inexpensive, rugged, simple to construct and has good long-term stability. © 2009 Springer-Verlag

Digital controller design considering hardware constraints: application in a paraplegic patient

INTRODUCTION: A methodology was developed for implementing closed-loop control algorithms and for evaluating the behavior of a system, considering certain component restrictions used in laboratory implementation. METHODS: Mathematical functions representing a model of the biological system were used for knee extension/flexion movements. A Proportional Integral Derivative (PID) controller and another one using the root locus method were designed to control a patient’s leg position by applying functional electrical stimulation (FES). The controllers were simulated in Matlab and ISIS Proteus. After the simulations were performed, the codes were embedded in a microcontroller, and tests were conducted on a paraplegic volunteer. To the best of the authors’ knowledge, this is the first time that ISIS Proteus software resources have been used prior to implementing a closed-loop system designed to control the leg position of patients. RESULTS:This method obviates the application of initial controller tests directly to patients. The response obtained in the experiment with a paraplegic patient complied with the specifications set in terms of the steady-state error, the settling time, and the percentage overshoot. The proposed procedure was successfully applied for the implementation of a controller used to control the leg position of a paraplegic person by electrical muscle stimulation. CONCLUSION:The methodology presented in this manuscript can contribute to the implementation of analog and digital controllers because hardware limitations are typically not taken into account in the design of controllers.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES