Windup Phenomenon Research Articles

An anti-windup control strategy to actuator saturating input voltage for active magnetic bearing system

Purpose The active magnetic bearing is highly nonlinear and unstable system. In general most of physical systems, conventional PID control strategies are employed for their stable operation but the dynamics of the system are influenced by input voltage saturation that degrades the performance of the system. The conventional PID control scheme does not work properly alone. In such a situation, PID faces windup phenomenon that leads to instability in the system. To overcome this problem, an anti-windup control scheme leads to stable and smooth operation of active magnetic bearing system. Design/methodology/approach The proposed anti-windup control strategy is based on dynamic output feedback that is applied on linearized active magnetic bearing (AMB) system to stabilize and avoid the input voltage saturation effect in the actuator. Findings An anti-windup controller is designed for active magnetic bearing system in presence of input voltage saturation. The stability of AMB system with anti-windup controller is derived in sense of Lyapunov and expressed as linear matrix inequality problem for AMB system and the designed anti-windup controller also enlarges the region of attraction of considered AMB system. Originality/value T-S fuzzy technique is used for obtaining local linear model of nonlinear active magnetic bearing system for easy and simple implementation of anti-windup control scheme. In proposed methodology the region of attraction for anti-windup compensator is also discussed. The effectiveness of proposed method is verified by the numerical simulation results for considered active magnetic bearing system and domain of attraction or stability region of closed loop AMB system are also calculated using Eigen Value Optimization technique for both the cases such as with and without anti-windup controller. The comparative result and the contribution of proposed control strategy are also discussed.

Current Command Compensation for PM Servo Motor Considering Voltage Saturation Caused by Both Rapid Change in the Current Command and High‐Speed Rotation

SUMMARYThis paper proposes a new antiwindup method for PM (permanent magnet) servo motor control that compensates for the current commands based on both the amount of transient voltage saturation at high acceleration calculated from the proportional current control model and the amount of voltage saturation in the PI current controller at high speeds. Experimental results show that our proposed method can suppress the windup phenomenon and maintain stability under voltage saturation caused by high speed, high response, high acceleration, and severe voltage sag. Thus, the proposed method can improve the productivity of industrial machines, and is especially effective for PM servo motor control that has a large inductance, such as DDM (direct‐drive motors) and IPM (interior permanent magnet) motors.

Fast response Antiwindup PI speed controller of Brushless DC motor drive: Modeling, simulation and implementation on DSP

Most of the Brushless DC (BLDC) motors drive adopts proportional, integral and derivative (PID) controller and pulse width modulation (PWM) scheme for speed control. Hence, BLDC motor drive has strong saturation characteristics. The saturation results in a typical windup phenomenon. The paper presents an Antiwindup drive for BLDC motor. An Antiwindup controller (AWC) has been used in the paper. AWC has been modeled in MATLAB/Simulink and comparison has been done between conventional PI controller and AWC at different starting loads. Dynamic characteristics of the BLDC motor drive have been examined and results are presented and discussed in detail in this paper. Details of DSP based experimental validation of the simulated results are also presented here.

Anti-windup design for uncertain nonlinear systems subject to actuator saturation and external disturbance

Summary A novel anti-windup design method is provided for a class of uncertain nonlinear systems subject to actuator saturation and external disturbance. The controller considered incorporates both an active disturbance rejection controller as well as an anti-windup compensator. The dynamical uncertainties and external disturbance are treated as an extended state of the plant, and then estimate it using an extended state observer and compensate for it in the control action, in real time. The anti-windup compensator produces a signal based on the difference between the controller output and the saturated actuator output, and then augment the signal to the control to deal with the windup phenomenon caused by actuator saturation. We first show that, with the application of the proposed controller, the considered nonlinear system is asymptotically stable in a region including the origin. Then, in the case that the controller in linear form, we establish a linear matrix inequality-based framework to compute the extended state observer gain and the anti-windup compensation gain that maximize the estimate of the domain of attraction of the resulting closed-loop system. The effectiveness of the proposed method is illustrated by a numerical example. Copyright © 2016 John Wiley & Sons, Ltd.

Underwater vehicle guidance control design within the DexROV project: preliminary results

Abstract: The paper addresses the guidance control design of the motion controller for an underwater Remotely Operated Vehicle (ROV) within an European Commission H2020 research project called DexROV. Given a kinematics model of an ROV possibly subject to an ocean current, the problem consists in designing a guidance control law able to realize, within a common and unified framework, several basic control loops denoted as “primitives”. The problem is rather standard when considering such primitives individually, but it becomes more challenging when aiming at designing a single general solution able to realize several different primitives according on how the reference signal for the controller is assigned. Moreover, the proposed guidance loop is required to operate in the presence of delays. The proposed solution builds on standard techniques leading to a Proportional - Integral (PI) controller with an adaptive gain selection rule to cope with integrator wind-up phenomena due to vehicle velocity saturation. The designed solution is numerically tested and analysed through simulations accounting for simplified, yet realistic, sensor models including stochastic noise and delays.

Gain Tuning of Fuzzy PID Controllers for MIMO Systems: A Performance-Driven Approach

A new methodology for tuning the scaling factors, or gains, of fuzzy proportional-integral-derivative controllers, by taking explicitly into account the closed-loop system performance is proposed in this study. The solution is obtained by solving a nonlinear constrained optimization problem, considering a set of constraints on the scaling factors of the Mamdani-type fuzzy system, and on the plant's inputs and outputs. Two distinct approaches are presented, which are associated with the optimization being carried out offline or in real time. The offline tuning scheme assumes the system dynamics described by a nonlinear model, while for the real-time implementation, the plant's dynamics is locally approximated by a linear model, with the underlying parameters recursively updated. In order to cope with rather stringent sampling time requirements, the constrained online optimization problem is implemented based on the grid computing paradigm. Given the adaptive nature of the real-time scheme, time-varying dynamics and unknown disturbances can be accommodated in such a way that the closed-loop performance is effectively maximized, while avoiding wind-up phenomena induced by the integrator term. The proposed tuning methodologies are assessed on a benchmark three-tank system and compared against a conventional-based tuning approach. Results from experiments illustrate the feasibility of the proposed approaches and also all the relevance in optimal control systems based on Mamdani-type fuzzy controllers.

A Detailed Governor-Turbine Model for Heavy-Duty Gas Turbines With a Careful Scrutiny of Governor Features

Due to substantial use of gas turbines and their highly dynamic behavior, they have a profound impact on electrical grid. Although the control philosophies of various turbines are almost the same, there are some nuances in governor systems. As long as these details affect system response in extremely dynamic phenomena such as load rejection, they should be included in models. In this paper, the governor system is subjected to careful scrutiny; tasks of controllers are classified schematically and some special features such as back-tracing and feed-forward are discussed. The turbine is also modeled and a function is developed to calculate turbine exhaust gas temperature. The proposed governor-turbine model is validated by test results and a comparative analysis shows that the back-tracing method prevents wind-up phenomenon and the feed-forward method improves stability and response time.

Spinal cord stimulation attenuates temporal summation in patients with neuropathic pain.

Evidence has shown that electrical stimulation at the dorsal columns attenuated the "wind-up" phenomenon in dorsal horn neurons in nerve-injured rats. This study was aimed to test the effect of spinal cord stimulation (SCS) on temporal summation (TS), the clinical correlate of the wind-up phenomenon in patients with radicular leg pain. Eighteen patients with SCS implants were tested both 30 minutes after SCS activation ("ON") and 2 hours after turning it off ("OFF"), in a random order. Temporal summation was evaluated in the most painful site in the affected leg and in the corresponding area in the contralateral leg by applying a tonic painful heat stimulus (46.5°C; 120 seconds) and simultaneous recording of the perceived heat pain intensity. Patients were also requested to report their clinical pain intensity (0-100 numerical pain scale) during SCS "ON" and "OFF". The Wilcoxon signed rank test was used in the comparisons between SCS "ON" and "OFF". Spinal cord stimulation activation significantly attenuated clinical pain intensity (from 66 ± 18 to 27 ± 31, P < 0.001). In the nonpainful leg, SCS activation failed to produce an effect on TS (24 ± 20 vs 21 ± 24 in SCS "OFF" and "ON", respectively; P = 0.277). In contrast, a significant decrease in the magnitude of TS in the affected leg was observed in response to SCS activation (from 32 ± 33 to 19 ± 24; P = 0.017). These results suggest that attenuation of TS, which likely represents suppression of hyperexcitability in spinal cord neurons, is a possible mechanism underlying SCS analgesia in patients with neuropathic pain.

Steady-State Integral Proportional Integral Controller for PI Motor Speed Controllers

The output of the controller is said to exceed the input limits of the plant being controlled when a control system operates in a non-linear region. This process is called the windup phenomenon. The windup phenomenon is not preferable in the control system because it leads to performance degradation, such as overshoot and system instability. Many anti-windup strategies involve switching, where the integral component differently operates between the linear and the non-linear states. The range of state for the non-overshoot performance is better illustrated by the boundary integral error plane than the proportional–integral (PI) plane in windup inspection. This study proposes a PI controller with a separate closed-loop integral controller and reference value set with respect to the input command and external torque. The PI controller is compared with existing conventional proportional integral, conditional integration, tracking back calculation, and integral state prediction schemes by using ScicosLab simulations. The controller is also experimentally verified on a direct current motor under no-load and loading conditions. The proposed controller shows a promising potential with its ability to eliminate overshoot with short settling time using the decoupling mode in both conditions.

1P1-X02 最大筋力を考慮した筋骨格システムの位置制御

This paper proposes a set-point control method for a musculoskeletal system considering maximum muscular force. In our previous work, the set-point control method for a musculoskeletal system was proposed which combines a feedforward control with a sensory feedback control including a considerable time-delay. However, the maximum output force of each muscle have not been considered though it sometimes induces a wind-up phenomenon because of the saturation of the muscular force. The ratio function to determine the ratio of feedforward and feedback control inputs is newly introduced in this paper to prevent such a wind-up phenomenon without the saturation of muscular force, and generate more sophisticated reaction motion even if disturbances are added on the end-point during movement. Numerical simulation results are shown to demonstrate the effectiveness of the proposed method.

Convergence-based Analysis of Robustness to Delay in Anti-windup Loop of Aircraft Autopilot

The windup phenomenon is interpreted as a consequence of the convergent property absence for system with a saturation. This makes it possible to use the frequency-domain criterion for analysis of anti-windup augmentation in the case of stable and marginally stable plants. Based on this approach, robustness of the systems with respect to time delay in the anti-windup loop is examined and the approach for an optimal choice of the static anti-windup gain is proposed. An application of the convergence-based anti-windup control strategy to aircraft flight control for the case of time-delay in the anti-windup loop is described and studied by simulations.

A New Anti-Windup PI Controller for Direct Torque Control System

Speed controller in induction motor direct torque control (DTC) system usually adopts the traditional PI controller. But the traditional PI controller has characteristic of nonlinear saturation, what will make the control performance of actual system become worse. In order to improve system control performance, this paper adopts a new type Anti-Windup PI controller, This method separately control the integral state by feed backing the output of the integrator to the input port of the integrator according to whether the controller output is saturated or not, which can make the system leaving saturation as soon as possible. As a result, the overshoot and settling time of the system are reduced. Simulation and experimental results show that this method can significantly suppress the integral windup phenomenon as well as reduce the overshoot and shorten the settling time. The new Anti-Windup PI controller has a better performance than the traditional PI controller.

Anti-Windup变结构自适应PID控制在航空相机位角控制系统的应用

The integral Windup phenomenon from a position angle control system in the aviation camera is more likely to happen when a big travel is given, which will affect the dynamic performance of the camera. To improve the dynamic response performance of the position-angle control system on this condition, this paper proposes a method based on the Anti-Windup variable structure adaptive PID control to design the position angle control system. A primary and secondary cascade dual loop was used to control the position of a position-angle mirror, and a variable structure adaptive PID control based on the Anti-Windup was adopted to control the compensation in the speed inner loop. The PID tuning method based on real-coded genetic algorithm was taken to tune the initial PID control parameters of speed inner loop, and the optimal index of parameter selection used punishment function to eliminate the overshoot. As mentioned above, the position-angle control system is able to achieve satisfactory performance in a large position given. Experiments show that the control strategy based on the Anti-Windup variable structure adaptive PID control avoids the position angle mirror coming into a saturation in the back stage after auto-focusing, increases the adjust time of back stage by 35.7% and improves the return performance of the position angle mirror.

Clinical and neurological characteristics of patients with somatic referred back pain at the lumbosacral level

Referred pain is a painful sensation in the peripheral regions during pathological processes in deep tissues or viscera. There are two types of referred pain: 1) somatic referred pain (from spinal structures to adjacent areas); 2) visceral referred pain (from pelvic and abdominal viscera). Patients and methods. The investigation enrolled 80 patients with nonspecific chronic and subacute lumbosacral spine pain. All the patients underwent standard neurological examination. Pain intensity was determined on a visual analog scale (VAS) using the DN4, PainDETECT, and short-form McGill questionnaires; the wind-up phenomenon was evaluated; the degree of muscular tonic syndrome was estimated applying the Khabirov questionnaire. The health-activity-mood (HAM), SF-36, and Roland-Morris questionnaires were used to assess quality of life. Results. Somatic referred pain was found in 62% of the examinees. In these patients, the clinical picture showed a set of characteristics for neuropathic (allodynia (31%), hyperesthesia (12%), and nociceptive (grades 1 and 2 muscular tonic syndrome 41 and 59%, respectively) pain; a high wind-up index was noted in 89% of the patients.

Permanent-magnet synchronous motor velocity control based on second-order integral sliding mode control algorithm

In this paper, a novel second-order integral sliding mode control (SOSMC) algorithm is proposed to accomplish velocity control of the permanent-magnet synchronous motor (PMSM) so that the performance can be improved. An integral manifold is utilized to reduce the static error during the sliding mode movement phase to improve the control precision, and a new SOSMC law is achieved by a Lyapunov function approach so the system convergence is guaranteed. The presented method can not only eliminate the system chattering problem successfully but also improve the performance of the PMSM control system. Meanwhile, in order to solve the problem of the windup phenomenon of the PMSM control system, an anti-windup control method is proposed in the PMSM control system. The simulation experimental results are given to indicate that the proposed method is effective and can improve the performance of the PMSM control system such as fast response, high robustness and speed tracking precision, etc.

Interaction of the adenosine A1 receptor agonist N6-cyclopentyladenosine (CPA) and opioid receptors in spinal cord nociceptive reflexes

AimsWe previously observed that the adenosine A1 receptor agonist N6-cyclopentyladenosine (CPA) is a very effective antinociceptive agent on intact but not on spinalized adult rats with inflammation. Since a close connection between opioid and adenosine A1 receptors has been described, we studied a possible relationship between these systems in the spinal cord. Main methodsCPA-mediated antinociception was challenged by the selective adenosine A1 receptor antagonist 8-cyclopentyl-1, 3-dimethylxanthine (CPT) and by the opioid receptor antagonist naloxone on male adult Wistar rats with carrageenan-induced inflammation. Withdrawal reflexes activated by noxious mechanical and electrical stimulation were recorded using the single motor technique in intact and sham-spinalized animals. Key findingsCPA was very effective in intact and sham spinalized rats but not in spinalized animals. Full reversal of CPA antinociception was observed with i.v. 1mg/kg of naloxone but not with 20mg/kg of CPT i.v. in responses to noxious mechanical and electrical stimulation. CPT fully prevented CPA from any antinociceptive action whereas naloxone did not modify CPA activity. These results suggest a centrally-mediated action, since CPA depressed the wind-up phenomenon which is derived of the activity of spinal cord neurons. SignificanceThe present study provides strong in vivo evidence of an antinociceptive activity mediated by the adenosine A1 receptor system in the spinal cord, linked to an activation of opioid receptors in adult animals with inflammation.

Assessment of the wind-up phenomenon in the equine nociceptive trigeminal system

Repeated sub-threshold nociceptive electrical stimulation resulting in temporal summation of the limb nociceptive withdrawal reflex is a well-established non-invasive model to investigate the wind-up phenomenon in horses. Due to structural similarities of the trigeminal sensory nucleus to the dorsal horn of the spinal cord, temporal summation should be evoked by repeated transcutaneous electrical stimulation of trigeminal afferents. To evaluate this hypothesis repeated transcutaneous electrical stimulation was applied to the supraorbital and infraorbital nerves of 10 horses. Stimulation intensities varied between 0.5 and 1.3 times the trigemino-cervical reflex threshold defined for single stimulation. Evoked electromyographic activity of the orbicularis oculi, splenius and cleidomastoideus muscles was recorded and the signals analysed in the previously established epochs typical to the early and late component of the blink reflex and to the trigemino-cervical reflex. Behavioural reactions were evaluated with the aid of numerical rating scale.The nociceptive late component and the trigemino-cervical reflex were not elicited by sub-threshold intensity repeated transcutaneous electrical stimulation. Furthermore, the median reflex amplitude for the 10 horses showed a tendency to decline over the stimulation train so temporal summation of afferent trigeminal inputs could not be observed. Therefore, the modulation of trigeminal nociceptive processing attributable to repeated Aδ fibre stimulations seems to differ from spinal processing of similar inputs as it seems to have an inhibitory rather than facilitatory effect. Further evaluation is necessary to highlight the underlying mechanism.

Saturation in Engineering Simulation

The wind-up effect is a phenomenon known mostly from implementing PI(D) controllers in real operation when saturation of the manipulated variable may occur and cause worse control results. Nowadays many publications exist on this topic where several anti wind-up mechanisms are presented and discussed. However, the wind-up phenomenon, i.e. the problem of continued integration after the output has become limited (saturated), is a problem appearing not only in connection with numerically calculated control actions of digital controllers, but also in computer models of controlled plants. In this field, existence of the wind-up effect is somehow missed. Results and conclusions obtained by such inaccurate simulation may be misleading. Surprisingly, occurrence of this situation is not so rare, because use of amplitude limiting blocks in simulation is considered to be the only necessary precaution. In education of many control engineers, information about wind-up effect in simulation is not sufficiently pointed out. In models of higher than first order, the same approach as the one used the filed of PI(D) controllers is not always correct. The publications focused on the solutions for this case seem to be rare, if any exist. This paper presents one possible approach to wind-up and anti wind-up mechanism in modeling and simulations.

Nonlinear problems in control of manufacturing systems

Nowadays, production control problems has been widely studied and a lot of valuable approaches have been implemented. This paper addresses the problem of tracking the uncertain demand in case of uncertain production speeds. The uncertainties are described by deterministic inequalities and the performance is analyzed in from of the worst-case scenario. First, simple mathematical models are introduced and the control problem is formulated. In continuous-time, the cumulative output of a manufacturing machine is the integral of the production speed over time. At the same time, the production speed is bounded from below and above, and hence the manufacturing process can be modeled as an integrator with saturated input. Since the cumulative demand (which is the reference signal to track) is a growing function of time, it is natural to consider control policies that involve integration of the mismatch between the current output and current demand. In the simplest consideration it results in models similar to a double integrator closed by saturated linear feedback with an extra input that models disturbances of a different nature. This model is analyzed and particular attention is devoted to the integrator windup phenomenon: lack of global stability of the system solutions that correspond to the same input signal. As a systematic design procedure to prevent the windup phenomenon we present observer based techniques with full and reduced-order observers. The next part of the paper deals with a similar control problem in discrete-time under the surplus-based policy: each machine in the production network tracks the demand trying to keep the downstream buffer at some specified safe level. The performance of manufacturing networks with different topologies is analyzed via the second Lyapunov method, while the disturbances are modeled by deterministic inequalities. The nature of the approach leads to performance analysis in the form of a worst case scenario and allows to find a trade-off between the inventory for each machine in the system and the demand tracking accuracy. The final part of the paper illustrates how to make the theoretical findings operational with the experimental setup called Liquitrol. The experimental setup consists of a number of water tanks and pumps that can be interconnected via flexible piping. Due to its flexibility and mobility, the setup allows not only to verify theoretical results via experiments, but it also can be used in an educational process to illustrate different phenomena in tandem and re-entrant manufacturing networks.

Design Method of Limitation Compensator Maintaining Response Performance for PI Speed Control System of SPMSM

It is important to use a robust servo system to improve the performance of motion control systems for several industry applications. Generally, a speed servo system has a controller with an integrator, such as a PI controller. When its output variable is saturated by current and voltage limits, a wind-up phenomenon and an unstable response often occur. We have already proposed an anti-windup algorithm considering voltage saturation for servo systems, and it regulates the current response smoothly and stably. However, the motor speed response exhibits a large overshoot caused by current saturation.This paper proposes an anti-windup algorithm considering motor dynamics and current saturation for speed servo system of surface permanent magnet synchronous motor. The experimental results show that the speed servo system employing the proposed algorithm regulates the motor speed smoothly and stably.