Abstract
Model uncertainties and exogenous disturbances are inherent
phenomena in chemical plants that degrade performance and lead
to poor-quality products. To mitigate these issues, this paper
addresses disturbances by exploiting the differential flatness
property (DFP) of the nonlinear continuous stirred tank reactor
(NCSTR). A two-degree-of-freedom (2DOF) control design was
implemented, incorporating flatness-based feedforward and
feedback controllers. This design leverages the differential
flatness method for effective stabilization and tracking
performance. A robust feedback tracking control strategy
integrating a disturbance observer (DO) and a simple feedback
controller was implemented to form a flatness active disturbance
rejection control (FADRC) scheme. The B-spline technique was
used for trajectory generation to enhance the performance of the
proposed control strategy. Additionally, constraints were handled
symbolically rather than numerically by designing B-spline curves
for the system's flat output. This approach ensures a feasible
open-loop reference trajectory that satisfies the feedback
controller's states and input constraints. A comparison was
conducted between the switching function-based (SF) trajectory
and the B-spline (Bs) designed reference trajectory regarding
their impact on system tracking performance, smoothness, and
robustness to disturbances. A detailed analysis evaluated tracking errors, control effort, and disturbance rejection capabilities under
both trajectory designs. The proposed flatness-based ADRC
methodology efficiently managed exogenous disturbances and
constraints on the input of a nonlinear plant.
phenomena in chemical plants that degrade performance and lead
to poor-quality products. To mitigate these issues, this paper
addresses disturbances by exploiting the differential flatness
property (DFP) of the nonlinear continuous stirred tank reactor
(NCSTR). A two-degree-of-freedom (2DOF) control design was
implemented, incorporating flatness-based feedforward and
feedback controllers. This design leverages the differential
flatness method for effective stabilization and tracking
performance. A robust feedback tracking control strategy
integrating a disturbance observer (DO) and a simple feedback
controller was implemented to form a flatness active disturbance
rejection control (FADRC) scheme. The B-spline technique was
used for trajectory generation to enhance the performance of the
proposed control strategy. Additionally, constraints were handled
symbolically rather than numerically by designing B-spline curves
for the system's flat output. This approach ensures a feasible
open-loop reference trajectory that satisfies the feedback
controller's states and input constraints. A comparison was
conducted between the switching function-based (SF) trajectory
and the B-spline (Bs) designed reference trajectory regarding
their impact on system tracking performance, smoothness, and
robustness to disturbances. A detailed analysis evaluated tracking errors, control effort, and disturbance rejection capabilities under
both trajectory designs. The proposed flatness-based ADRC
methodology efficiently managed exogenous disturbances and
constraints on the input of a nonlinear plant.
Keywords
Active disturbance rejection control
B-spline
Flatness Control
trajectory design