In many robotic applications, pneumatic actuators are not adequate for tracking control tasks given the poor performance obtained with traditional control techniques like PID controllers. In this paper we show that the so-called Active Disturbance Rejection Control Structure (ADRCS), combined with a discontinuous observer and standard or robust algorithms in the controller block, provides a good solution to regulation and tracking control problems of pneumatic actuators. The discontinuous observer estimates the velocity, and whose discontinuous nature permits to estimate also the disturbances affecting the system, allowing to use a very simple model of the actuator and avoiding an off-line parameter identification. To analyze the observer ability to estimate the disturbances, we test three different algorithms in the controller block, the standard PD and two discontinuous controllers proposed elsewhere. The performance of the closed loop system is evaluated through experimental results using a performance index based on an 2 norm, for constants and sinusoidal references. Also, we compare the performance of the proposed algorithms with the controllers with those using the same control algorithm but not including the disturbance compensation, showing the important effect of the disturbance estimation included in the ADRCS on the overall controller performance.
<p>Se propone una estrategia para resolver el problema de seguimiento de trayectorias en actuadores neumáticos inciertos y con medición parcial del vector de estado. La estrategia se basa en la estructura de control con compensación activa de perturbaciones (ADRC), que está formada por un observador de estado, un filtro pasa bajas y un controlador. En esta propuesta se utiliza un observador de estado discontinuo que estima el vector de estado completo y, utilizando el concepto del control equivalente, permite estimar los términos de perturbación presentes en la planta. El filtro pasa bajas se encarga de recuperar el control equivalente a partir de un término discontinuo del observador. Finalmente, el controlador tiene la estructura básica PD con un término adicional, que corresponde a las perturbaciones estimadas, y que tiene como fin compensar las perturbaciones reales en la planta. El rendimiento del sistema en lazo cerrado se evalúa mediante un índice de desempeño basado en la norma L2.</p>
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