IFAC-PapersOnLine最新文献

This work extends list of recently published constrained automatic reset based controllers by optimizing one particular “problematic” solutions with the 4th-order output derivative. Although the proposal itself is derived for integral plus dead-time (IPDT) process models, thanks to the universality of the used ultra-local model, the field of applicability can be very wide and include a number of stable and unstable, linear and non-linear processes. With regard to the progress achieved in the design of generalized automatic reset controllers, the diversity of their various modifications and also with respect to the genius of original automatic reset and hyper reset controllers and their inventors, the contribution further discusses related terminological aspects, especially the misleading designation of these solutions by the term series PI and PID controllers, which was the source of many misunderstandings, problems and contributed to the significant lag in the further development of this type of control. Similar comments it also adds regarding the use of the term anti-reset-windup controller.

This paper proposes a data-driven method using a Fractional-Order Proportional-Integral-Derivative (FOPID) controller. The proposed method simultaneously obtains FOPID controller and reference model parameters to achieve tracking performance and specified robust stability from only one-shot closed-loop input-output data. The proposed control law is designed by solving an optimization problem, subject to the constraint condition of using the maximum value of the sensitivity function. Therefore, the proposed method provides trade-off design between tracking performance for the reference input and robust stability by selecting robust stability. By comparing numerical example results obtained for FOPID and integer-order controllers, it is shown that the use of the FOPID controller is effective in improving tracking performance for reference output.

This paper presents a novel constrained PID algorithm that performs almost the same as a constrained GPC tuned with a unit control horizon and an output soft constraint. The proposed approach computes the PID tuning parameters using the unconstrained GPC solution for first or second-order process models and uses a geometric approach, which avoids the use of an optimiser, to compute the final control action combining the PID tuning with a constraint-mapping law. Simulation results are used to illustrate the simplicity and good performance that can be obtained with the proposed approach, which is an interesting solution for PID applications in which output constraints are considered and low computation time of the control law is required.

In this paper, an attempt has been made to establish the existence and multiplicity of positive solutions for a class of nonlinear singular fractional differential equation subject to the non-local boundary conditions. We have shown that there exist countably many positive solutions with the help of fixed point index theory in a cone on a Banach space.

In this paper, the Infinite State Representation is applied to the fractional Lü chaotic system. Thanks to a finite dimension approximation, the original fractional order system is converted into a large dimension set of integer-order nonlinear equations whose initial conditions allow to test the butterfly effect of the equivalent chaotic system. This sensitivity to initial conditions is quantified thanks to Lyapunov exponents computed with an experimental technique. Then, the largest Lyapunov exponent is used as a fractional index to characterize the Infinite State Representation.

This paper mainly investigates the convective diffusion of non-Newtonian fluids in fractal main channels. The spatial fractional derivative constitutive equations of non-Newtonian fluids are coupled with the flow equations to derive the governing equations for fluid flow and heat transfer. The shifted Grünwald– Letnikov formula is used to obtain numerical solutions for the model. The effects of fractional derivatives, Reynolds number, and Prandtl number on fluid flow and heat transfer are analyzed.

Dynamic modeling of soft actuators is a challenging field of research mainly due to the nonlinear properties of the materials they are made of, as well as the infinite degrees of freedom that they exhibit. In this paper, the defection of an eccentric soft fluidic actuator is characterized in terms of the dynamic displacement using both integer and fractional order (FO) models. The actuator, which is cylindrical in shape, is made of a silicone polymer called polydimethylsiloxane (PDMS) from a water-soluble mold and a rod that, when placed eccentrically, allows to create the internal chamber of the actuator. Experimental results are presented to show that the best fitting is obtained with FO models. In fact, the dynamics of the actuator can be fully described with a two-parameter model, namely a fractional integrator of order of about 1.2 with a gain.

The morphological structure of retinal blood vessels plays an important role in diagnosing ophthalmic diseases such as glaucoma and diabetic retinopathy. Diabetic retinopathy is one of the leading causes of blindness worldwide. Because of the need to examine a large number of individuals on a daily basis, it is indeed challenging for ophthalmologists to analyze the complex retinal vasculature of every outpatient. Automated segmentation of retinal blood vessels can be of significant aid in this labor-intensive process. This work proposes an unsupervised approach for retinal blood vessel segmentation. Here, we enhance the performance of the B-COSFIRE filters for segmentation of the retinal vasculature by denoising a retinal image using a fractional filter derived from a left/forward weighted fractional integral prior to the vascular enhancement by B-COSFIRE filters. Also, we utilize hysteresis thresholding rather than a single global threshold to obtain the final segmented vessels enhanced by the B-COSFIRE filters. This helps to avoid the problem of nonuniform illumination and poor contrast in retinal images.