Windup Phenomenon Research Articles

Change in Endogenous Pain Modulation Depending on Emotional States in Healthy Subjects: A Randomized Controlled Trial.

Chronic pain is a public health issue, leading to substantial healthcare costs and diminished quality of life for sufferers. While the role of anxiety in pain modulation has been extensively studied, the effects of other emotional states on the body's pain control mechanisms remain less understood. This study sought to explore how different emotions (happiness, anger, sadness, and interest) affect conditioned pain modulation (CPM) and the wind-up phenomenon in healthy adults. This randomized controlled, cross-over trial involved 28healthy participants aged 18-60. Participants watched video clips designed to induce specific emotions: happiness, anger, sadness, and interest. Emotional states were assessed using a 7-point Likert scale. Pain modulation was measured using CPM and the wind-up phenomenon. CPM was assessed with a hot water bath as the conditioning stimulus and pressure pain tolerance as the test stimulus. Wind-up was measured using pinprick needle stimulators and a visual analog scale. Data were analyzed using paired ttests to compare pre- and post-emotion induction values. Significant changes in emotional self-assessment values were observed for all emotions. Happiness increased CPM (4.6 ± 11.4, p = 0.04277), while sadness - 9.9 ± 23.1, p = 0.03211) and anger - 9.1 ±23.3, p = 0.04804) decreased it. Interest did not significantly alter CPM (- 5.1 ± 25.8, p = 0.31042). No significant effects were found for the wind-up phenomenon across any emotional states. This study shows that emotional states significantly affect the body's ability to modulate pain. Positive emotions like happiness enhance pain inhibition, while negative emotions such as sadness and anger impair it. These findings suggest that emotional modulation techniques could be integrated into pain management strategies to improve patient outcomes. Further research should explore a broader range of emotions and include objective measures to validate these results.

New anti‐windup Proportional‐Integral‐Derivative for motor speed control

AbstractThe proportional‐integral‐derivative (PID) was developed and recognized for its reliability. A PID controller is not only simple but also relatively cheap. However, the controller causes system performance degeneration over time due to the presence of windup in a motor speed control system. The windup phenomenon is caused by the saturated control state. Various anti‐windup methods were introduced to decrease a system's long settling time and extreme overshooting. Most anti‐windup techniques require integral switching between saturated and unsaturated states, whereby both versions of steady‐state integral proportional‐integral controller do not need integral switching mechanism. They possess a certain degree of decoupling between and tuning parameters and tested to allow a more comprehensive range of tuning in the absence of derivative control. This research investigated the impact of derivative control component on the tuning gain decoupling through hardware simulation. By integrating the derivative component, , the control system demonstrated an improved system stability and reduced overshoot. Result shows that the decoupling feature allows SIPIC01+D and SIPIC02+D controllers to produce performance with zero overshoot and short settling time. However, SIPIC01+D has better dynamical performance with fastest rise and settling time with no overshoot as compared to other anti‐windup controllers.

Adaptive anti‐windup output feedback control for nonlinear systems and its stability analysis

SummaryIn the practical application of adaptive control methods, a windup phenomenon for the systems with input saturation may occur because there exists an input restriction such as saturation of actuator in most actual systems due to physical reasons. In this paper, to alleviate the influence of the windup phenomenon by input saturation, we propose an output feedback exponentially passive (OFEP)‐based adaptive model recovery anti‐windup (AMRAW) control strategy for the stable nonlinear systems with input saturation. Moreover, in order to realize an augmented OFEP system for non‐OFEP nonlinear systems that do not satisfy the OFEP properties, a parallel feedforward compensator (PFC) is introduced, and a radial basis function (RBF) neural network (NN)‐based adaptive feedforward input is designed to attain accurate tracking performance for systems with the PFC. Furthermore, the detailed stability analysis of the proposed AMRAW control system is provided, and the performance of the proposed method is validated through appropriate numerical simulations.

Directional change and windup phenomena in LQR-controlled systems with actuator failure

Directional change and windup phenomena in LQR-controlled systems with actuator failure

Thermal Grill Illusion in Post-Stroke Patients: Analysis of Clinical Features and Lesion Areas.

In the thermal grill illusion, participants experience a feeling similar to burning pain. The illusion is induced by simultaneously touching warm and cool stimuli in alternating positions. In post-stroke pain, central sensitization is caused by a variety of factors, including damage to the spinothalamic tract and shoulder pain. Because the thermal grill illusion depends on central mechanisms, it has recently been suggested that it may be a useful indicator of central sensitization. Therefore, we hypothesized that post-stroke patients who are more likely to experience central sensitization may also be more likely to experience a thermal grill sensation of pain and discomfort than the likelihood among those who are less likely to experience central sensitization. However, the effects of the thermal grill illusion in post-stroke patients have not yet been reported. In this pilot study, we conducted the thermal grill illusion procedure in post-stroke patients and analyzed the relationship between clinical somatosensory functions and thermal grill sensations. We also conducted brain imaging analysis to identify brain lesion areas that were associated with thermal grill sensations. Twenty patients (65.7 ± 11.9 years old) with post-stroke patients participated in this study. The thermal grill illusion procedure was performed as follows: patients simultaneously touched eight water-filled copper bars, with the water temperature adjusted to provide alternate warm (40°C) and cold (20°C) stimuli. Thermal grill sensation of pain and discomfort tended to be associated with the wind-up phenomenon in bedside quantitative sensory testing and thermal grill sensation of discomfort was also related to damage to the thalamic lateral nucleus. These findings suggest that the thermal grill illusion might measure central sensitization, and that secondary brain hyperactivity might lead to increased thermal grill sensations.

Model-based optimal and robust control of renewable hydrogen gas production in a fed-batch microbial electrolysis cell

Microbial electrolysis cell (MEC) is a fundamental type of bio-electrochemical system. MEC is a novel and emerging renewable energy technology that is based on biomass. The behavior of the MEC system is highly nonlinear due to the complexity of its dynamics. For the desired optimal production of hydrogen, feedback control of MEC processes is necessary. Due to the novelty of MEC, limited research is available on its control. Studies on linear model-based robust control of MEC processes are missing. In this article, we develop a nonlinear dynamic model for MEC, linearize this model, and calculate a linear time-invariant transfer function. Based on this linearization, a fixed-structure, optimal and robust controller is proposed to achieve a fast-settling time exhibiting no overshoot and having zero steady-state error. The robustness of the developed controller is evaluated for parameter uncertainty, measurement noise, and disturbance rejection. Batch biomass processes are fed only at the start of each process cycle. The output does not follow the desired response when the substrate or biomass is consumed. Then, the error accumulates, and it causes the control effort to increase unboundedly. The existing literature on control of fed-batch MEC processes does not consider this integral windup phenomenon. In this article, we also develop an anti-windup control strategy to eliminate the integral windup error and to avoid any possible instability or destruction. The overall conclusion of our study is that the developed robust controller achieves a faster and more robust response than the existing controllers. We provide an anti-integral windup solution to eliminate windup errors in feedback control of fed-batch MEC processes.

An anti-windup control strategy for discrete time-delay system based on triple Lyapunov functional

This paper addresses the design of a dynamic output feedback-based anti-windup compensator to mitigate the windup phenomenon for a discrete time-varying delayed system with input saturation to establish the asymptotic stability. Linear matrix inequalities–based stability conditions are derived locally and globally. The controller for the closed-loop system is designed to reduce the effect of external bounded disturbances by utilizing the linear matrix inequality approach. The novel triple Lyapunov–Krasovskii functional along with reciprocal convex inequality is used to solve the expressions contained in the forward difference of the functional and to maximize the basin of attraction. Finally, industrial examples are simulated to prove the effectiveness of the proposed criterion.

Integral Windup Resetting Enhancement for Sliding Mode Control of Chemical Processes with Longtime Delay

The effects of the windup phenomenon impact the performance of integral controllers commonly found in industrial processes. In particular, windup issues are critical for controlling variable and longtime delayed systems, as they may not be timely corrected by the tracking error accumulation and saturation of the actuators. This work introduces two anti-windup control algorithms for a sliding mode control (SMC) framework to promptly reset the integral control action in the discontinuous mode without inhibiting the robustness of the overall control system against disturbances. The proposed algorithms are intended to anticipate and steer the tracking error toward the origin region of the sliding surface based on an anti-saturation logistic function and a robust compensation action fed by system output variations. Experimental results show the effectiveness of the proposed algorithms when they are applied to two chemical processes, i.e., (i) a Variable Height Mixing Tank (VHMT) and (ii) Continuous Stirred Tank Reactor (CSTR) with a variable longtime delay. The control performance of the proposed anti-windup approaches has been assessed under different reference and disturbance changes, exhibiting that the tracking control performance in the presence of disturbances is enhanced up to 24.35% in terms of the Integral Square Error (ISE) and up to 88.7% regarding the Integral Time Square Error (ITSE). Finally, the results of the proposed methodology demonstrated that the excess of cumulative energy by the actuator saturation could reduce the process resources and also extend the actuator’s lifetime span.

태양광 발전효율 증대를 위한 최대전력추종 시스템에서 Anti-windup 적용의 효과 분석

In this paper, application and comparative analysis of anti-windup method for improving the response of voltage control of MPPT method in photovoltaic generation system is proposed. In the case of MPPT, PI control can be mainly used to control a target voltage from a reference voltage that continuously changes according to changes in the surrounding environment for optimal control of PV power production. However, its PI controller has accumulated saturation of errors in the process of integrating the errors, so it is necessary to consider the integrator windup. This problem could affect the power production efficiency when performing MPPT control, so this paper sought to verify its effect by applying the follow-up anti-windup technique to MPPT control to improve the integral windup phenomenon. It could be confirmed from the results of the presented simulation that the application of the proposed algorithm mixed is more effective to improve the control performance of the photovoltaic system.

Skin Pain Sensation Under Mechanical Stimulus: Wind-Up and Ramp-Off

Abstract Researchers have been studying the pain sensation extensively in the past few decades. Quantitative simulation and theoretical modeling of pain sensation based on experimental results are necessary for pain research. Many theories have been proposed to explain the mechanism of pain from molecular, cellular, and neuron network perspectives. But some phenomena in pain sensation are not fully understood, including wind-up and ramp-off. This paper focused on the theoretical model of wind-up and ramp-off phenomena in the pain sensation. With the addition of the transduction model, the generation mechanism of wind-up and ramp-off is better explained. The simulations were carried out to analyze the skin pain sensation under the mechanical stimulus, consisting of four different parts: the mechanical model of skin, transduction, transmission, modulation, and perception. The stress distribution on the skin was obtained based on the elastic theory. And the modified Hodgkin and Huxley model and the mathematical model of gate control theory were utilized to analyze the process of transduction, modulation, and perception, respectively. The numerical experiments demonstrated the wind-up occurs with a frequent stimulus of 1 Hz and 2 Hz, and ramp-off appears with the withdrawal of constant mechanical stimulus, which could contribute to the understanding of the pain sensation mechanism.

Control oriented strategy to consider constraints of the deformable mirror M4 for the Mid-infrared ELT Imager and Spectrograph

The Mid-infrared ELT Imager and Spectrograph (METIS) will be equipped with a single conjugate adaptive optics (SCAO) system comprising the deformable mirror M4, the tip–tilt mirror M5, a wavefront sensor, and a modal controller implemented on real-time computers. To prevent any damage to M4 during operation and windup phenomena due to internal checks of M4, its absolute shape, time-discrete change of shape, and inter-actuator strokes are limited. Hence, we present a strategy to consider M4’s Cartesian constraints in the modal METIS-SCAO controller within this conceptual study. This strategy modifies the modal control error before it is fed into the SCAO controller considering the spatio-temporal and segmented characteristics of M4. Additionally, we present three different algorithms realizing this strategy. Furthermore, the presented strategy features the following characteristics, among others: add-on to a previously designed METIS-SCAO controller, no permanent trade-off between performance and constraint compliance, and application of numerically cheap approximating models. Moreover, we verify the functionality of the presented algorithms via standalone and closed loop simulations of the METIS-SCAO system. The simulations show that all presented algorithms work as intended and successfully enforce M4’s constraints. Therefore, the presented strategy and the three corresponding algorithms are applicable to the METIS-SCAO system.

Improved model-free fractional-order intelligent proportional–integral fractional-order sliding mode control with anti-windup compensator

In addition to the difficulty of system modeling, every physical system faces actuator saturation, making the real control different from the controller output (desired control input). When this occurs, the controller output does not regulate the system properly and errors occur as a result of incorrect updating. This is known as the windup phenomenon. In the event that the controller is configured to override actuator saturation, it can lead to a failure in the controller’s performance, such as large overshoots, high response time, and even system instability in the worst case. Therefore, in this paper, a new robust model-free controller method is proposed. It is a combination of four nonlinear control techniques, namely model-free controller, fractional-order sliding mode controller, fractional integral–proportional (PI) controller, and anti-windup compensator, which gives rise to the new model-free controller algorithm called hybrid fractional-order intelligent PI fractional sliding mode controller with an anti-windup compensator termed (MF-FOiPI-FOSMC-AW). However, to illustrate the effectiveness of the new proposed MF-FOiPI-FOSMC-AW method, simulation and experimental results compared to classical PI and iPI controllers (with and without an anti-windup compensator) on a hydraulic system are presented in the presence or absence of external disturbances for different types of references. Finally, simulation is conducted through an experimental comparison of the proposed approach with other strategies such as the classical anti-windup PI controller and the anti-windup intelligent PI controller, which is carried out for this purpose.

Systematic mitigation of gain scheduling induced windup phenomena

Abstract In this paper, we discuss the systematic design of gain scheduling controllers for nonlinear systems. We discuss control signal blending induced windup phenomena and employ an extended Model-Recovery Anti-Windup (MRAW) scheme to mitigate them. Combining control signal blending with MRAW allows to build gain scheduling controllers without imposing the common slow variation assumption regarding the scheduling vectors. In addition, the approach offers a higher flexibility in the choice of the sub-controllers compared to classical approaches and convex optimization allows for a very efficient design of the anti-windup networks.

Anti windup GPC speed controller for induction machine based on Youla parametrization

Abstract In the induction motor indirect vector control system, because of its physical limitations, the large step change in the speed command and/or load would eventually cause the so-called “integral windup phenomenon” which causes unexpected behavior of the system. To counteract this problem, an anti- windup generalized predictive speed control method is proposed by using the Youla parametrization. As first step, the design of an initial GPC controller based on its polynomial equivalent structure is required. Then, thanks to the Youla parametrization, this controller is retuned considering two specifications. The first is a frequency specification on the quadratic component of stator current response to the speed reference. And the second is a time domain constraint on the measured speed response to the speed reference. These constraints are formulated within a convex optimization framework. The simulation results proved the efficiency of the present design method.

Research on a New Adaptive Integral Sliding Mode Controller Based on a Small BLDC

A new adaptive saturation Integral Sliding Mode Controller (ADSA-ISMC) is presented to solve the speed fluctuation problem caused by a small brushless DC motor (S-BLDC) under variable load. First, according to the characteristics of S-BLDC and Kalman filter, a Kalman-based S-BLDC load disturbance observer is established, and an adaptive integrated sliding mode controller (AD-ISMC) is constructed based on the motor load obtained by the observer. Then, we introduce the saturation function into the input error link of the traditional integral sliding mode function, to propose a new ADSA-ISMC to improve the windup phenomenon produced by the integral sliding mode controller and prove the stability and convergence of the controller by the Lyapunov method. Finally, the experimental results show that the Kalman load disturbance observer can observe the motor load disturbance well. In addition, when a load of S-BLDC changes, many speed control performance indexes of ADSA-ISMC are significantly better than SMC and AD-ISMC. Theoretical analysis and experimental results show that the ADSA-ISMC proposed in this paper shows excellent control performance in S-BLDC speed control.

Conditioned-based robust nonlinear control of plug-in hybrid electric vehicle with saturated control actions

Plug-in hybrid electric vehicles (PHEVs) are considered to be a better choice than conventional hybrid electric vehicles due to environmental concerns. There are two main subsystems in the PHEVs power system namely: integrated charging unit (ICU) and hybrid energy storage system (HESS). In this work three energy sources fuel cell (FC), battery and ultra-capacitor (UC) are considered. Keeping in view of different challenging aspects like actuator limits and nonlinear nature of power conditioning circuits in ICU and HESS, design of robust nonlinear controller is still a challenge. Conventional Supertwisting Algorithm (STA) based controller exhibits wind-up effects when control signal is saturated which deteriorates the dynamic response of the controller. In order to resolve this issue, conditioning technique is used to propose conditioned Supertwisting algorithm (CSTA) based controller which mitigates the wind-up phenomenon when the control signal is saturated and exhibits better dynamic performance in the presence of external disturbances. Moreover, energy management algorithm in HESS is also presented in which State of Charge (SoC) of the battery and UC is taken as a decisive factor for the execution of rule-based strategy. Asymptotic stability of the system is proved using Lyapunov stability criterion. Simulations are performed in Matlab/Simulink ODE 45 environment which show the comparison of the proposed controller with conventional STA-based controller. The results show better performance of proposed controller when the control signals are saturated but at the same time conventional STA does not exhibit good response due to integrator wind-up. For the real-time control of PHEV, hardware in loop (HIL)-based experimental verification is also done.

Improved Neutral-Point Voltage Balancing Control With Time Delay Compensation and Antiwindup Loop for a Three-Level NPC Inverter

This article proposes an improved neutral-point voltage balancing control (NPVBC) with time delay compensation and an antiwindup loop based on a dynamic change limit for a three-level neutral-point clamped (NPC) voltage-source inverter. NPVBC is essential for a three-level NPC inverter since it has a separate dc link. In an NPVBC based on the carrier-based pulsewidth modulation (CBPWM), the neutral-point (NP) voltage is regulated by synthesizing the NP current. The conventional NP voltage balancing controller is designed as a proportional-integral controller; however, time delays due to the digital control and pulsewidth modulation, and antiwindup loop were not considered despite the fact that digital control delay disturbs the accurate synthesis of NP current and the windup phenomenon may appear on the regulator since synthesizable NP current range can be limited by operating condition. To solve these problems, this article proposes improvement methods for NPVBC with digital delay compensation and an antiwindup loop based on CBPWM. Analysis on the effect of digital delay is described, and the time delays compensation method is proposed. Furthermore, an NP voltage balancing controller with an antiwindup loop is proposed along with an analysis of the synthesizable NP current range. With the proposed method, NP voltage ripples can be reduced, and control stability of the NPVBC can be greatly improved by preventing the windup phenomenon that may occur when the inverter output is insufficient. To verify the proposed methods, simulations and experiments, including elevator tower test, were conducted, and the results verify the effectiveness of the proposed methods.

Development of an Antiwindup Technique for a Cascade Control System.

A cascade control system comprising the primary and secondary controllers suffers from a cascade-type integral windup problem in which the output saturation of the secondary control loop can considerably increase the integral part of the primary control loop. In this paper, we present a new predictive antiwindup technique that can completely eliminate the possibility of secondary controller output saturation, resulting in no cascade-type integral windup phenomenon. The proposed method does not require any type of process models; thus, its implementation is simple and straightforward, which is a very favorable advantage compared to the model-based antiwindup techniques from the practical viewpoint. Our simulation confirms that the proposed method can completely remove the primary controller’s cascade-type integral windup resulting from the saturation of the secondary controller output. Further, the proposed method exhibited good control performance without needing any type of process model for the various types of processes and controllers. Our experimental study successfully demonstrated that there are no problems in applying the proposed method to real plants.

Torque control of a series elastic actuator using an ultrasonic motor with angular‐velocity saturation

AbstractA series elastic actuator (SEA) using an ultrasonic motor (USM) and an elastic element has attracted attention as a compact actuator with high torque–weight ratio and high force control performance. However, an elastic element in a SEA often causes mechanical vibrations. To suppress these vibrations, studies implemented the state feedback of the motor‐ and load‐side angles. However, as the controller has many integrators, the control system becomes unstable when the angular‐velocity of the USM is saturated. Therefore, in this study, integrators in the controller were reduced in number. Furthermore, a limit error feedback controller was designed to suppress the windup phenomenon caused by the integrators. The frequency analysis using a describing function showed that stability is guaranteed even if the angular‐velocity is saturated. In addition, the experimental results indicate that an overshoot of the torque response is suppressed.

Anti-Windup PID Controller by ITAE Tuning Rule for Steam Distillation System

In control engineering system, the PID controller is more prefer compared to the other controller. It very simple and easy to develop. Unfortunately, PID controller exhibit a weakness once spike at wind-up region. The wind-up problem is always happen due to inability of compensator to control the phenomenon. The main cause is created in controller design phase; neglect a nonlinearities dynamic. The issue can be solved by implementation of additional integral feedback compensation in order to minimize the effect of windup situation. The wind-up phenomenon can cause high overshoot, long settling time and loss productivity yield. This objective of this research to improve windup situation using backcomputation method tuning by Integral Time Absolute Error (ITAE) tuning rule. The propose ITAEProportional-Integral-Derivative integrated AntiWindup (ITAE-PID-AW) controllers revealed better performances compared to the ITAE-ProportionalIntegral-Derivative (ITAE-PID) controller.