Position Feedback Control Research Articles

Alternating Positive and Negative Feedback Control Model Based on Catastrophe Theories

In automatic control systems, negative feedback control has the advantage of maintaining a steady state, while positive feedback control can enhance some activities of the control system. How to design a controller with both control modes is an interesting and challenging problem. Motivated by it, on the basis idea of catastrophe theories, taking positive feedback and negative feedback as two different states of the system, an adaptive alternating positive and negative feedback (APNF) control model with the advantages of two states is proposed. By adaptively adjusting the relevant parameters of the constructed symmetric catastrophe function and the learning rule based on error and forward weight, the two states can be switched in the form of catastrophe. Through the Lyapunov stability theory, the convergence of the proposed adaptive APNF control model is proven, which indicates that system convergence can be guaranteed by selecting appropriate parameters. Moreover, we present theoretical proof that the negative feedback system with negative parameters can be equivalent to the positive feedback system with positive parameters. Finally, the results of the simulation example show that APNF control has satisfactory performance in response speed and overshoot.

Differential resistance based self-sensing recurrent neural network model for position estimation and control of antagonistic Shape Memory Alloy actuator

The paper presents the development and experimental investigation of recurrent neural network (RNN) based self-sensing position estimation (SSPE) model for shape memory alloy actuator (SMA). RNN is used as an estimator in the position feedback control loop to replace the external additional position sensor. The model was inspired by the physics-based analogy of the Mass-Spring-Damper (MSD) system for the antagonistic SMA wire actuator. Actuator displacement presents the hysteresis and non-linear dynamic relationship with observed differential resistance (sensing signal) during phase transformation. The resistance variation causes due to dissimilar resistivity between primary phases of SMA material. The RNN based estimation model was considered because it consists of memory elements for storing the processed information and feedback connections for dynamic modeling of the system. RNN was trained with input sensing signal and target displacement datasets. The estimation accuracy of the model was real-time evaluated during trajectory tracking of reference signals in the feedback control loop. A quantitative performance analysis is assessed in terms of correlation (ℛ), mean absolute error (MEA), and root mean square error (RSME) of the learned model along with the developed actuator system. The tracking results confirm the close agreement between estimated and measured displacement at a reasonable accuracy.

The Control Algorithm and Experimentation of Coaxial Rotor Aircraft Trajectory Tracking Based on Backstepping Sliding Mode

In view of the uncertainty of model parameters, the influence of external disturbances and sensor noise on the flight of coaxial rotor aircraft during autonomous flight, a robust backstepping sliding mode control algorithm for the position and attitude feedback control system is studied to solve the trajectory tracking problem of an aircraft in the case of unknown external interference. In this study, a non-linear dynamic model based on a disturbed coaxial rotor aircraft was established for an unknown flight. Then, a non-linear robust backstepping sliding mode controller was designed, which was divided into two sub-controllers: the attitude controller and the position controller of the coaxial rotor aircraft. In the controller, virtual control was introduced to construct the Lyapunov function to ensure the stability of each subsystem. The effectiveness of the proposed controller was verified through numerical simulation. Finally, the effectiveness of the backstepping sliding mode control algorithm was verified by flight experiments.

Anthocyanins: From Mechanisms of Regulation in Plants to Health Benefits in Foods.

Anthocyanins represent the major red, purple, and blue pigments in many flowers, fruits, vegetables, and cereals. They are also recognized as important health-promoting components in the human diet with protective effects against many chronic diseases, including cardiovascular diseases, obesity, and cancer. Anthocyanin biosynthesis has been studied extensively, and both biosynthetic and key regulatory genes have been isolated in many plant species. Here, we will provide an overview of recent progress in understanding the anthocyanin biosynthetic pathway in plants, focusing on the transcription factors controlling activation or repression of anthocyanin accumulation in cereals and fruits of different plant species, with special emphasis on the differences in molecular mechanisms between monocot and dicot plants. Recently, new insight into the transcriptional regulation of the anthocyanin biosynthesis, including positive and negative feedback control as well as epigenetic and post-translational regulation of MYB-bHLH-WD40 complexes, has been gained. We will consider how knowledge of regulatory mechanisms has helped to produce anthocyanin-enriched foods through conventional breeding and metabolic engineering. Additionally, we will briefly discuss the biological activities of anthocyanins as components of the human diet and recent findings demonstrating the important health benefits of anthocyanin-rich foods against chronic diseases.

Design and integration studies of a diagnostics slim cassette concept for DEMO

The diagnostics slim cassette (DSC) is a concept currently proposed for DEMO to host the microwave reflectometry diagnostic in a dedicated poloidal section, for the feedback control of plasma position and shape, also providing the radial edge density profile at several poloidal angles. This DSC, which is expected to house up to 100 antennas and waveguides, is to be integrated with the breeding blanket (BB) segments. Moreover, it is being designed with remote handling compatibility in mind to facilitate a ‘fast’ exchange by remote maintenance (RM) when needed, fulfiling one of the aims of the work package diagnostic and control. In this approach the pre-assembled (banana-shaped) DSC modules are inserted/removed from the upper port (UP) of the vacuum vessel (VV), at least when the BB segments are replaced. Here the main constraints related to the integration of the DSC with the BB, the UP and the equatorial port are identified and discussed in detail, with a strong focus on the required RM operations inside the VV (in-vessel), providing solutions that can be adapted to present and future blanket and UP designs.

Fuzzy logic aided PPF controller design to active vibration control of a flexible beam

This paper presents a fuzzy-logic-based observer and a positive position feedback controller to reduce a standard beam's free vibrations using a piezoelectric actuator. It is aimed that fuzzy-logic-based observer is used as feed-through and improves the overall performance of the PPF controller. For this aim, the cantilever beam and a piezoelectric patch are initially numerically modeled using the finite element method considering the close loop control algorithm. The displacement and strain responses results are compared with the experimental model. Then, two controllers are applied to the designed system: positive position feedback (PPF) and fuzzy-logic-based positive position feedback (FLBPPF). The uncontrolled and controlled system responses are investigated and compared in terms of the linear strain and tip displacement results. Using the FLBPPF controller, the settling times of controlled systems are decreased by about 20.7% and 41.6% regarding the linear strain and tip displacement response compared to the PPF controller.

Suppress the vibration of a nonlinear dynamical system subjected to external force using a positive position feedback control.

Suppress the vibration of a nonlinear dynamical system subjected to external force using a positive position feedback control.

Iterative Sliding Mode-Based Output Feedback Control for the Dynamic Positioning of Ships

Abstract Because the velocities of a ship are unmeasured, a novel iterative sliding mode (ISM)-based output feedback control scheme is proposed for the dynamic positioning (DP) of a ship subjected to external environmental disturbances. First, the finite-time state observer is addressed, guaranteeing that estimated errors converge to a small neighborhood of zero in finite time with high precision. Furthermore, based on the outputs of the state observer, an ISM function is given. Then, the output feedback control scheme is designed for the DP of the ship with two remarkable features: (1) an integral item of the sign function exists in the control scheme, which inherently eliminates the chattering of the traditional sliding mode control (SMC), and (2) an integral term of the sliding mode is added to the control scheme, which is helpful in strengthening the transient response with lower overshooting. Finally, simulation studies and quantitative analysis are carried out to demonstrate the superior advantages of the proposed control scheme compared to the proportional-integral-derivative (PID) control scheme and the traditional SMC scheme.

Design of Low Leakage 9T SRAM Cell with Improved Performance for Ultra-Low Power Devices

In this paper, a 9T SRAM cell with low power (LP9T) and improved performance has been proposed. This cell is free from half-select issue and works with single-ended read and differential write operation in the sub-threshold region. To evaluate the relative performance, the obtained characteristics of LP9T SRAM cell are compared with other state-of-the-art designs at 45-nm technology node. The read and write power dissipation of LP9T SRAM cell is reduced by [Formula: see text] and [Formula: see text] as compared to Conv.6T SRAM cell. In proposed cell, leakage power is reduced by [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text] as compared to conventional 6T (Conv.6T), low power (LP8T), transmission gate 8T(TG8T), transmission gate 9T (TG9T), Schmitt trigger 9T (ST9T), and positive feedback control 10T (PFC10T) SRAM cells. This reduction in leakage power is attributed to stacking effect. LP9T SRAM cell also exhibits significant improvement in read/write access time as compared to all considered cells. Also, the read and write energy of proposed cell is lowest among all considered cells. The LP9T SRAM cell has [Formula: see text] and [Formula: see text] higher read and write stability as compared to Conv.6T SRAM cell. Proposed SRAM cell has the highest value of ON to OFF current ratio ([Formula: see text]) which signifies the highest bit-cell density among all considered cells. The LP9T SRAM cell occupies [Formula: see text] large area as compared to Conv.6T SRAM cell. The overall quality of SRAM cell is calculated through the electrical quality metric (EQM). It is observed that LP9T SRAM cell has the highest value of EQM in comparison to considered cells at 0.3[Formula: see text]V supply voltage.

Robust Control and Optimization for Autonomous and Connected Vehicle Platoons with Vehicle-to-Vehicle Communication Delay

Recent advances in vehicle-to-vehicle (V2V) communication technologies enable autonomous vehicle platoons to better utilize the information of other members in the platoon to achieve the desired longitudinal intervehicular spacing specifications. However, most existing studies adopt a fixed time headway hw, and do not take into account the effects of V2V communication delay on the desired design specifications for the platoons. Moreover, for stability analysis, the commonly adopted Routh-Hurwitz approach usually needs a lot of computation time, which will significantly reduce the efficiency and flexibility of the platoons in real-time applications. In order to overcome the aforementioned issues with the existing results on autonomous vehicle platoons, this paper investigates the robust control and optimization problem for a platoon of autonomous and connected vehicles subject to V2V communication delay and uncertain parasitic actuation lag under a constant time headway policy (CTHP). First, by employing the Padé approximation approach, the spacing error propagation transfer function, from the preceding vehicle to the following vehicle, under immediate predecessor’s acceleration, velocity, and position feedback control mechanism is derived. In addition, in order to improve the computation efficiency, a signature method is utilized for the Hurwitz stability analysis. Then the string stability analysis for attenuating the spacing propagation error along the platoon is performed. Both lower and upper bounds for the time headway hw as well as the admissible sets for controller gains are achieved for Hurwitz stability and string stability. Comparative simulation results are finally provided to demonstrate the effectiveness of the proposed design scheme.

Resveratrol protects human nucleus pulposus cells from degeneration by blocking IL-6/JAK/STAT3 pathway

BackgroundNucleus pulposus cells’ (NPCs’) degeneration is mainly responsible for the intervertebral disc degeneration (IDD), which is closely related to inflammatory response. Among the major proinflammatory factors that are related to NPCs’ degeneration, interleukin-6 (IL-6) and its downstream JAK/STAT3 pathway have received recent attention. The goal of our study is to figure out whether or how resveratrol (RSV) can protect NPCs from degeneration by affecting IL6/JAK/STAT3 pathway.MethodsDifferent concentrations of RSV were added to NPCs’ mediums. Cell viability was measured by MTT assay and crystal violet staining. Cell cycle and apoptosis were analyzed by flow cytometry. Protein expression level was determined by western blot. mRNA expression level was measured by qPCR.ResultsOur study showed that RSV improved NPCs’ cell viability. It also inhibited cell apoptosis and cell cycle arrest, which were accompanied by the increased expression level of heat shock protein 90 (HSP90) and N-Cadherin. What’ more, RSV also improved the NPCs’ degeneration which was reflected in the increase of extracellular matrix (collagen II, Aggrecan). Moreover, RSV significantly attenuated the level of IL-6 secretion, which was accompanied by less phosphorylation of the transcription factors Janus kinase 1 (JAK1) and signal transducer and activator of transcription 3 (STAT3).ConclusionRSV exerted its protective effect on HNPCs’ degeneration by improving cell survival and function. The possible mechanism may be associated with the suppression of JAK/STAT3 phosphorylation and the decreased IL-6 production, which could be explained by a blockage of the positive feedback control loop between IL-6 and JAK/STAT3 pathway.

Time-delayed positive position feedback control of nonlinear vibrations of continuous rotating shafts

The objective of the present study is to suppress the large amplitudes of a continuous spinning shaft under an active vibration control. For this purpose, the Positive Position Feedback (PPF) control with time-delays are applied to the system via Macro-Fiber-Composite (MFC) sensors and actuators. The nonlinear dynamics of the system is explored analytically utilizing the perturbation method in the primary and one-to-one internal resonances. The steady state solutions of the system and controller in the Cartesian and polar forms are obtained. The effects of the controller gains and time delays on the stability and loci of bifurcations of the system are investigated. The controller shows its feasibility in controlling the system vibrations. Also, it is demonstrated that by increasing the controller gain coefficients the minimum amplitude regions of the system are increased. Furthermore, the safe boundary of the loop delays is studied. The results of the analytical approach are in good agreement with the numerical results of the original system of equations.

Hybrid rayleigh–van der pol–duffing oscillator: Stability analysis and controller

The current study examines the hybrid Rayleigh–Van der Pol–Duffing oscillator (HRVD) with a cubic–quintic nonlinear term and an external excited force. The Poincaré–Lindstedt technique is adapted to attain an approximate bounded solution. A comparison between the approximate solution with the fourth-order Runge–Kutta method (RK4) shows a good matching. In case of the autonomous system, the linearized stability approach is employed to realize the stability performance near fixed points. The phase portraits are plotted to visualize the behavior of HRVD around their fixed points. The multiple scales method, along with a nonlinear integrated positive position feedback (NIPPF) controller, is employed to minimize the vibrations of the excited force. Optimal conditions of the operation system and frequency response curves (FRCs) are discussed at different values of the controller and the system parameters. The system is scrutinized numerically and graphically before and after providing the controller at the primary resonance case. The MATLAB program is employed to simulate the effectiveness of different parameters and the controller on the system. The calculations showed that NIPPF is the best controller. The validations of time history and FRC of the analysis as well as the numerical results are satisfied by making a comparison among them.

Vibration reduction of a non-linear ship model using positive position feedback controllers

Vibration reduction of a non-linear ship model using positive position feedback controllers

Feedback attitude control of spacecraft using two single gimbal control moment gyros

In this paper, feedback attitude control of an underactuated spacecraft with two single gimbal control moment gyros (SGCMGs) is considered. For a two-SGCMG system in an arbitrary configuration, a feedback control method based on a real-time optimization approach is proposed. Here, the gimbal angle trajectories as the solution to the minimum-time control are parameterized by the time polynomials, and their coefficients are modified at each sampling period. Numerical simulations are performed to demonstrate the validity of the proposed method as well as a certain robustness against unmodeled dynamics. Furthermore, the experimental verification is also conducted to demonstrate the actual effectiveness.

Waypoint following dynamics of a quaternion error feedback attitude control system

Closed-loop attitude steering is a concept for implementing an attitude trajectory by using a conventional quaternion error feedback controller to track the time-varying attitude reference, rather than to simply regulate to a desired orientation. This is done by sampling the reference input and executing the maneuver as a sequence of closely spaced regulating commands that are read out from the spacecraft’s command buffer. The idea has been employed in practice to perform zero-propellant maneuvers on the International Space Station and minimum-time maneuvers on NASA’s TRACE space telescope as well as NASA’s Lunar Reconnaissance Orbiter (LRO). A challenge for operational implementation of the idea is the limited capacity of a space vehicle’s command storage buffer, which is normally not designed with attitude tracking in mind. One approach to mitigate the problem is to downsample-and-hold the attitude commands so that the attitude control system (ACS) regulates to a series of waypoints. This article explores the waypoint following dynamics of a quaternion error feedback control law for such an approach. It is shown that downsample-and-hold induces a ripple between downsamples that causes the satellite angular rate to significantly overshoot the desired limit. Analysis in the z-domain is carried out in order to understand the phenomenon. An interpolating Chebyshev-type filter is proposed that allows the desired attitude trajectory to alternatively be encoded in terms of a small set of filter coefficients. Using the interpolating filter, the continuous-time reference trajectory can be reconstructed and issued at the ACS rate but with significantly reduced memory requirements. The ACS of the LRO is used as an example to illustrate the behavior of a practical ACS.

Trajectory tracking of a bouncing ball in a triangular billiard by unfolding and folding the billiard table

In this paper, a feedback control law is proposed to solve the asymptotic tracking problem for a ball bouncing in a triangular billiard. This controller is designed by firstly transforming the billiard table into a surface on which the ball moves without experiencing any impact, i.e. by reflecting the billiard table rather than the ball trajectory and designing a position feedback controller based on such an unfolded billiard table. Furthermore, it is shown how such an infinite-billiard table can be mapped to the surface of a torus, thus leading to bounded trajectories of the ball.

Therapeutic effects and mechanism of ferulic acid and icariin in mammary gland hyperplasia model rats via regulation of the ERK pathway

BackgroundFerulic acid (FA) and icariin (ICA), as the active compounds derived from Angelica sinensis and Epimedium brevicornum Maxim, respectively, have been shown to promote blood circulation, regulate menstruation, exhibit anti-inflammatory effects, and modulate estrogen levels. The aim of this study was to elucidate the possible mechanism of FA, ICA, and FA-ICA on estrogen-induced mammary gland hyperplasia (MGH) in rats.MethodsHematoxylin and eosin (HE) staining was performed to record the pathological changes in breast tissue, and enzyme-linked immunosorbent assay (ELISA) was utilized to determine the serum levels of luteinizing hormone (LH), PRL (prolactin), testosterone (T), estradiol (E2), follicular stimulating hormone (FSH), and progesterone (P). The message RNA (mRNA) expression levels of extracellular signal-regulated kinase 1 (ERK1), extracellular signal-regulated kinase 2 (ERK2), estrogen receptor (ER), and progesterone receptor (PR) were detected by real-time reverse transcription-polymerase chain reaction (RT-PCR) analysis. Furthermore, ER, phosphorylated-ER, PR, p-PR, ERK1/2, and p-ERK1/2 protein factors in the ERK signaling pathway were evaluated by Western blotting. Simultaneously, changes in breast height, diameter, body weight, and organ index were all recorded.ResultsWe found that FA and ICA could modulate the degree of breast swelling, and reduce the body weight, thymus index, and uterus index. Furthermore, it could also block the pathological changes of MGH, including the number of mammary lobules, and the proliferation or expansion of acini and ducts. Moreover, treatment with FA and ICA remarkably down-regulated the serum expression levels of LH, PRL, T, and E2, as well as the mRNA expression levels of ERα, PR, ERK1, and ERK2. Additionally, protein levels of ERα, p-ERα, PR, p-PR, ERK1/2, and p-ERK1/2 in breast tissue were down-regulated, however the serum content of FSH and P was up-regulated.ConclusionsOur outcomes revealed that FA and ICA might potentially inhibit ERα, PR, ERK1/2, and their phosphorylated proteins via the ERK signaling pathway, thus indicating a positive feedback control for the degree of breast hyperplasia.

Finite‐time fault‐tolerant output feedback attitude control of spacecraft formation with guaranteed performance

AbstractThis article examines the problem of finite‐time fault‐tolerant output feedback attitude control for spacecraft formation system with guaranteed performance, in the presence of uncertainties, external disturbances, actuator faults, and input saturation. First, a neural network (NN) based finite‐time observer is established for follower spacecraft to observe its angular velocity, where the NN is utilized to approximate the unknown uncertainties. Furthermore, based on the information from the angular velocity observer, backstepping procedure, and barrier Lyapunov function technique, a distributed finite‐time controller with only attitude measurement is proposed. Unlike the existing finite‐time control scheme, the tracking errors keep inside their predefined feasible regions with guaranteed transient and steady‐state performance. A theoretical proof shows that the finite‐time stability of the closed‐loop system can be achieved. Finally, numerical simulation results are presented to illustrate the effectiveness and fine performance of the proposed finite‐time observer and controller for the attitude control system.

Nonlinear vibration control of smart plates using nonlinear modified positive position feedback approach

In this paper, nonlinear vibration control of a plate is investigated using a nonlinear modified positive position feedback method that is applied through a piezoelectric layer on the plate. Based on the classical theory of displacement and strain relations with von Karman, intended equations of motion for the smart plate have been obtained. In this model, transverse vibrations are studied and stimulations are performed for the primary resonance. Boundary conditions of the smart plate are simply supported. The plate is thickness symmetrical. Using the Galerkin method the temporal nonlinear equations governing the system have been found. Then, the free and forced vibrations of the structure with the nonlinear modified positive position feedback controller have been solved using the Method of Multiple Scales to obtain an analytical solution. Results show that this controller reduces the amplitude of the vibration by inducing an increase in the damping coefficient. In addition, this provides a higher level of suppression in the overall frequency domain response by increasing the compensator gain. Finally, the results of the analytical solution for the closed-loop nonlinear modified positive position feedback controller are presented and compared with the result of the conventional positive position feedback controller and nonlinear integral resonant controller. The results show that the performance of the nonlinear modified positive position feedback controller is better than other controllers and significantly reduces the vibration amplitude.