Feedforward Control of Shape Memory Alloy Actuators Using Fuzzy-Based Inverse Preisach Model

This brief investigates a possible application of the inverse Preisach model in combination with the feedforward and feedback control strategies to control shape memory alloy actuators. In the feedforward control design, a fuzzy-based inverse Preisach model is used to compensate for the hysteresis nonlinearity effect. An extrema input history and a fuzzy inference is utilized to replace the inverse classical Preisach model. This work allows for a reduction in the number of experimental parameters and computation time for the inversion of the classical Preisach model. A proportional-integral-derivative (PID) controller is used as a feedback controller to regulate the error between the desired output and the system output. To demonstrate the effectiveness of the proposed controller, real-time control experiment results are presented.

Position control of shape memory alloy actuators using self tuning fuzzy PID controller

Shape Memory Alloy (SMA) actuators, which have the ability to return to a predetermined shape when heated, have many potential applications such as aeronautics, surgical tools, robotics and so on. Although the conventional PID controller can be used with slow response systems, there has been limited success in precise motion control of SMA actuators, since the systems are disturbed by unknown factors beside their inherent nonlinear hysteresis and changes in the surrounding environment of the systems. This paper presents a new development of a SMA position control system by using a self-tuning fuzzy PID controller. This control algorithm is used by tuning the parameters of the PID controller thereby integrating fuzzy inference and producing a fuzzy adaptive PID controller, which can then be used to improve the control performance of nonlinear systems. The experimental results of position control of SMA actuators using conventional and self-tuning fuzzy PID controllers are both included in this paper.

Internal model control for shape memory alloy actuators using fuzzy based Preisach model

This paper investigates a possible application of Preisach model to control shape memory alloy (SMA) actuators using an internal model control strategy. The developed strategy consists in including the Preisach hysteresis model of SMA actuator and the inverse Preisach model within the control structure. In this work, an extrema input hystory and a fuzzy inference is utilized to replace the classical Preisach model. This allows to reduce a large amount of experimental parameters and computation time of the classical Preisach model. To demonstrate the effectiveness of the proposed controller in improving control performance and hysteresis compensation of SMA actuators, experimental results from real time control are presented.

Trajectory Control of Electro Hydraulic Excavator using Fuzzy Self Tuning Algorithm with Neural Network

This paper presents the trajectory control of a 2DOF mini electro-hydraulic excavator by using fuzzy self tuning with neural network algorithm. First, the mathematical model is derived for the 2DOF mini electro-hydraulic excavator. The fuzzy PID and fuzzy self tuning with neural network are designed for circle trajectory following. Its two links are driven by an electric motor controlled pump system. The experimental results demonstrated that the proposed controllers have better control performance than the conventional controller.

Modelling and Control of Shape Memory Alloy Actuators by using Preisach Model, Genetic Algorithm and Fuzzy Logic

Shapememoryalloy (SMA) actuators, which have the ability to return to a predetermined shape when heated, have many potential applications in aeronautics, surgical tools, robotics and so on. Nonlinearity hysteresis effects existing in SMA actuators present a problem in the motion control of these smart actuators. This paper investigates the control problem of SMA actuators in both simulation and experiment. In the simulation, the numerical Preisachmodel with geometrical interpretation is used for hysteresis modeling of SMA actuators. This model is then incorporated in a closed loop PID control strategy. The optimal values of PID parameters are determined by using geneticalgorithm to minimize the mean squared error between desired output displacement and simulated output. However, the control performance is not good compared with the simulation results when these parameters are applied to the real SMA control since the system is disturbed by unknown factors and changes in the surrounding environment of the system. A further automated readjustment of the PID parameters using fuzzylogic is proposed for compensating the limitation. To demonstrate the effectiveness of the proposed controller, real time control experiment results are presented.

Total serum IL-12 and IL-12p40, but not IL-12p70, are increased in the serum of older subjects; relationship to CD3(+)and NK subsets

Interleukin 12 (IL-12), a central cytokine acting on T and natural killer (NK) cells, directs proliferation of activated T lymphocytes towards a Th1 phenotype. The heterodimeric molecule IL-12p70, equates with IL-12 biological activity, while IL-12p40 may antagonize IL-12 and inhibit cytotoxic T lymphocyte (CTL) generation in vitro. This study characterizes age-related changes in serum total IL-12, IL-12p70 and IL-12p40 relating them with CD3(+), NK and related subsets from subjects, aged 30-96 years. Total IL-12, IL-12p40 and the IL-12p40/IL-12p70 ratio, but not IL-12p70, increased significantly with age (P

Age-related reference intervals for lymphocyte subsets in whole blood of healthy individuals

Enumeration of various lymphocyte subsets is used widely in the diagnosis and monitoring of various disease states. With the development of flow cytometric technology and whole blood analysis, methodologies have become more sensitive. It is therefore important to establish reference intervals in normal, healthy individuals using these techniques to give a better indication of the border between health and disease. Since some lymphocyte subpopulations are known to change with age, we have enumerated common subsets in healthy individuals from all decades of adult life, including nonagenarian subjects. We report reference intervals for these subsets in each age group, which will be of use in diagnosis and disease monitoring, particularly in elderly subjects, the most rapidly expanding group within the population today.

Changes in lymphocyte subsets, interleukin 2, and soluble interleukin 2 receptor in old and very old age

In this study, the changes in some of the cellular components of the immune system and the activity of the cytokine interleukin 2, important for immune activation and lymphocyte proliferation, were measured in a large cross-sectional study of all age groups including octogenarian and nonagenarian subjects. In 206 apparently well community-living subjects, the absolute lymphocyte count and T and B cell numbers fell a little in old and very old subjects. Within the T cell compartment, helper/inducer CD4+ T cells, together with their subsets identified as 'naive' (CD4+/CD45RA+) and 'memory' (CD4+/CD45RO+) cells, also showed a decline with increased age. The suppressor/cytotoxic CD8+ subset showed no age-related change. The levels of the cytokine interleukin 2 were very low in octogenarian and nonagenarian subjects, while the soluble interleukin 2 receptor levels increased with increasing age. The interleukin 2 levels were associated with number and percentage of the 'memory' (CD4+/CD45RO+) subset of T cells which mediates the host response to previously met antigens. Since the interleukin 2 values were very low in the oldest groups and were associated with a reduced 'memory' (CD4+/CD45RO+) compartment, this suggests a possible mechanism of why the very elderly subject is more susceptible to morbidity and mortality from infectious or other agents.

Distinguished algebraic semantics for t-norm based fuzzy logics:Methods and algebraic equivalencies

This paper is a contribution to Mathematical fuzzy logic, in particular to the algebraic study of t-norm based fuzzy logics. In the general framework of propositional core and ?-core fuzzy logics we consider three properties of completeness with respect to any semantics of linearly ordered algebras. Useful algebraic characterizations of these completeness properties are obtained and their relations are studied. Moreover, we concentrate on five kinds of distinguished semantics for these logics-namely the class of algebras defined over the real unit interval, the rational unit interval, the hyperreals (all ultrapowers of the real unit interval), the strict hyperreals (only ultrapowers giving a proper extension of the real unit interval) and finite chains, respectively-and we survey the known completeness methods and results for prominent logics. We also obtain new interesting relations between the real, rational and (strict) hyperreal semantics, and good characterizations for the completeness with respect to the semantics of finite chains. Finally, all completeness properties and distinguished semantics are also considered for the first-order versions of the logics where a number of new results are proved. © 2009 Elsevier B.V. All rights reserved.

Lymphocyte subsets in conjunctival mucosa-associated-lymphoid-tissue after exposure to retinal-S-antigen

Purpose: To evaluate the immune cell subsets in conjunctival mucosa-associated-lymphoid-tissue (C-MALT) following challenge with antigen. Methods: Ten adult female Lewis rats were studied. Five rats received one drop (5 µL) of retinal S-antigen (500 µg/mL in phosphate buffered saline, PBS) instilled into the lower fornix twice daily for 10 consecutive days. Five rats received PBS only and served as controls for the experiment. Two days after the last instillation the animals were sacrificed and the orbital contents prepared for immunohistological staining. A panel of monoclonal antibodies was used: CD5, CD4, CD8, CD25, and CD45RA. The number of positive cells were counted in sections of epibulbar, forniceal, and tarsal conjunctiva. Results: There was a significant increase in the number of CD8 T lymphocytes in the conjunctiva of animals receiving retinal S-antigen when compared to control animals. Conclusion: Conjunctival instillation of retinal S-antigen causes an immune response in the C-MALT with a significant increase in the CD8 T lymphocyte subset in this tissue. This response may be involved in the induction of tolerance to the encountered antigen.