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Design of disturbance observers based on their implementability in industrial control systems. PhD David Tena
Abstract
PhD presentation. David Tena
... Other solutions [61][62][63][64][65][66][67][68][69] are characterized by linear or nonlinear phase responses, which lead to a time delay in the differentiated and integrated signals or imprecise response with respect to (periodic) signals with varying frequency. This, in turn, limits their applications in closed-loop control and real-time estimation and recovery of the state variables in, e.g., disturbance observer design [77][78][79][80][81][82][83][84][85]. ...
The design method and the time-variant FIR architecture for real-time estimation of fractional and integer differentials and integrals are presented in this paper. The proposed FIR architecture is divided into two parts. Small-phase filtering, integer differentiation, and fractional differential and integration on the local data are performed by the first part, which is time-invariant. The second part, which is time-variant, handles fractional and global differentiation and integration. The separation of the two parts is necessary because real-time matrix inversion or an extensive analytical solution, which can be computationally intensive for high-order FIR architectures, would be required by a single time-variant FIR architecture. However, matrix inversion is used in the design method to achieve negligible delay in the filtered, differentiated, and integrated signals. The optimum output obtained by the method of least squares results in the negligible delay. The experimental results show that fractional and integer differentiation and integration can be performed by the proposed solution, although the fractional differentiation and integration process is sensitive to the noise and limited resolution of the measurements. In systems that require closed-loop control, disturbance observation, and real-time identification of model parameters, this solution can be implemented.
En este trabajo se propone el análisis y diseño de predictores robustos de estructura _ja para su uso en el control de procesos con retardos puros, como alternativa al predictor de Smith y al observador de estados. Respecto al primero, se demuestra mejorar la robustez ante incertidumbre del modelo. Respecto al segundo, se reduce ampliamente el número de parámetros de ajuste, facilitando su implementación en plataformas industriales. Para el diseño, se plantea la minimización de varias normas del sistema mediante un problema de optimización con desigualdades matriciales y se obtienen los parámetros del predictor utilizando algoritmos de optimización. Finalmente, se desarrolla un ejemplo numérico de aplicación práctica.
In this work, we propose a Disturbance Observer (DOB) with a low pass filter with a single tuning parameter. The DOB can be added to a standard PI controller that is assumed to be controlling the system. Our DOB design can be applied to delayed and non-minimum phase systems and is decoupled from the PI control design. We analyse the impact of the DOB filter time constant in disturbance rejection performance, closed loop robustness and measurement noise amplification. The case of First Order plus Time Delay has been studied leading to a set of figures that highlight the trade-offs between those factors and can guide the designer. For arbitrary systems we propose simple rules and instructions for tuning the single parameter of the DOB, taking into account the trade-off between performance, robustness and noise amplification. Finally, we test our proposal experimentally in a real two-tank system setup.
In this work, we present a novel approach for fault detectors design and implementation in the case of actuator faults. Both the design and the implementation are focused on simplicity. The fault detector is based in an output observer that estimates the fault signal followed by a decision mechanism that detects the presence of a fault from the estimation. The observer consists of two transfer functions fed by the process manipulated variable and the sensor measurement. For the synthesis of the fault detector, we just need an input–output model of the process and two tuning parameters; one used in the observer, and the other in the decision mechanism. We present simple rules for the design considering the trade-off between the detection time, the minimum detectable fault and the false alarm rate. Our implementation method uses standard tools available in industrial control systems and we have applied it to a real two-tank system setup. The main contribution of this work is the simplicity of the design and implementation of the fault detector, making it suitable for process industry and for being managed by not experts in control systems. Another contribution is the a priori design based in intuitive engineering performance indices.
Multi-resonant disturbance observer design for a process industry distillation column under ambient temperature disturbances. Submitted for journal publication
- David Tena
- Ignacio Peñarrocha-Alós
David Tena and Ignacio Peñarrocha-Alós. Multi-resonant disturbance observer design for a process
industry distillation column under ambient temperature disturbances. Submitted for journal
publication (Control Engineering Practice), November 2021.
Actuator fault tolerant control proposal for pi controlled siso systems
- Ignacio Peñarrocha-Alós
- Ester Sales-Setién
- David Tena
Ignacio Peñarrocha-Alós, Ester Sales-Setién and David Tena. Actuator fault tolerant control
proposal for pi controlled siso systems. IFAC-PapersOnLinee, 51(24):680-687, 2018.
Comparison of leakage estimation strategies in a real industrial pipe network
- Ester Sales-Setién
- David Tena
- Ignacio Peñarrocha
Ester Sales-Setién, David Tena, and Ignacio Peñarrocha. Comparison of leakage estimation
strategies in a real industrial pipe network. IFAC-PapersOnLine, 50(1):13550-13555, 2017. 19th
World Congress of The International Federation of Automatic Control, IFAC World Congress 2017.