Model‐free online tuning of controller parameters using a globalized local search algorithm

In an earlier work, the authors proposed a globalized bounded Nelder‐Mead algorithm with deterministic restarts and a linearly growing memory vector. It was shown that the algorithm was a favorable option for solving multimodal optimization problems like controller tuning because of the greater probability of finding the global minimum and lesser numerical cost. Therefore, the algorithm was successfully used for model‐based offline tuning of sliding mode controller parameters for a servo‐pneumatic position control application. However, such offline tuning requires a sufficiently adequate system model, which, in some applications, is difficult to attain. Moreover, it is not generally appreciated as an essential requirement for controller tuning by the end user like the industry. An improvement in performance of optimization algorithm for tuning is expected if it relies on measurements coming directly from an actual physical system and not just its mathematical model. Therefore, in this paper, we apply the aforementioned algorithm for model‐free online optimization of controller parameters. The application involves the programmatic control of a real‐time interface of a physical system by the algorithm for data flow and logical decisions for optimization. For comparison with the results of the model‐based offline tuning suggested in earlier work, the sliding mode controller parameters are tuned online for the same position control application. The experimental results reveal that the system performance with controller parameters tuned online using the algorithm compares favorably to the one with model‐based offline tuning especially at higher priority level for accuracy. The improvement in system performance amounts to 21%.     

Modified whale optimization algorithm for fractional‐order multi‐input SSSC‐based controller design

In this paper, the design of a fractional‐order (FO) multi‐input–single‐output (MISO)–type static synchronous series compensator (SSSC) is proposed with a goal to improve the power system stability using modified whale optimization algorithm (MWOA). The proposed MWOA achieves an appropriate balance between exploitation and exploration stages of the original whale optimization algorithm. The performance of MWOA is validated by employing the benchmark test functions and further contrasted with whale optimization algorithm and other heuristic algorithms like gravitational search algorithm, particle swarm optimization, differential evolution, and fast evolutionary programming algorithms to demonstrate its strength. The proposed FO MISO SSSC controller is optimized by the MWOA technique and tested under single‐machine infinite bus system and further extended to a multi‐machine framework. To demonstrate the superiority of MISO‐type SSSC controller, the results obtained from it are compared with particle swarm optimization and differential evolution–based conventional single‐input–single‐output structured SSSC controllers. The comparison of results of MWOA with that of other methods validates its superiority in the present context.     

Robust reliability method and reliability‐based performance optimization for non‐fragile robust control design of dynamic system with bounded parametric uncertainties

An efficient robust reliability method for non‐fragile robust control design of dynamic system with bounded parametric uncertainties is presented systematically, in which the uncertainties existing in the controlled plant and controller realization are taken into account simultaneously in an integrated framework. Reliability‐based design optimization of non‐fragile robust control for parametric uncertain systems is carried out by optimizing the H₂ and H_∞ performances of the closed‐loop system, with the constraints on robust reliabilities. The non‐fragile robust controller obtained by the presented method may possess a coordinated optimum performance satisfying the precondition that the system is robustly reliable with respect to the uncertainties existing in controlled plant and controller. Moreover, the robustness bounds of uncertain parameters can be provided. The presented formulations are within the framework of linear matrix inequality and thus can be carried out conveniently. It is demonstrated by a numerical example that the presented method is effective and feasible. Copyright © 2016 John Wiley & Sons, Ltd.     

New registration algorithm for determining 3D knee kinematics using CT and single‐plane fluoroscopy with improved out‐of‐plane translation accuracy

To understand the kinematic effects of surgery, arthroplasty or conservative treatments, a noninvasive system to capture accurate 3D imaging of functional activities in prospective, controlled studies is required. To provide such a technique, a new algorithm was developed to register 3D CT data of normal bones to the same bones in a 2D fluoroscopy frame. The algorithm produces a digitally reconstructed radiograph (DRR) from the CT data and then filters this to produce an edge‐enhanced image. The resulting image is then registered with an edge‐enhanced version of the fluoroscopy frame using a new similarity measure called Cross‐Correlation Residual Entropy (CCRE). The system was evaluated by implanting tantalum beads into three cadaveric knees to act as fiducial markers. The knees were flexed between 0° and 70°, and single‐plane fluoroscopy data of the knees were acquired. CT data of the femur and tibia were then individually registered to the fluoroscopy images. No significant measurement bias was observed, and the standard deviation of the error in bead positions was 0.38 mm for in‐plane translation and 0.42 degrees for rotation. To determine the accuracy of the registration algorithm for out‐of‐plane translations, fluoroscopy frames were scaled in size by fixed increments; the average standard deviation of the errors for out‐of‐plane translation was 0.65 mm. The ability to obtain such accurate 3D motion data from a noninvasive technique will enable prospective, longitudinal, and controlled studies of reconstruction surgery, and conservative management of joint pathologies. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:334–340, 2010     

A novel projected Fletcher‐Reeves conjugate gradient approach for finite‐time optimal robust controller of linear constraints optimization problem: Application to bipedal walking robots

For finite‐time optimal robust control problem of bipedal walking robot, a class of global and feasible projected Fletcher‐Reeves conjugate gradient approach is proposed based on an online convex optimization algorithm. The optimal robust controllers are solved by projected Fletcher‐Reeves conjugate gradient approach. The approach can rapidly converge to a stable gait cycle by selecting an initial gait. Under some suitable conditions, we provide a rigorous proof of global convergence and well‐defined properties for projected Fletcher‐Reeves conjugate gradient approach. To demonstrate the effectiveness of the bipedal walking robot, we will conduct numerical simulations on the model of 3‐link robot with nonlinear, impulsive, and underactuated dynamics. Furthermore, to indicate the availability of high‐dimensional robotic system, the main result is illustrated on a nonlinear impulsive model of a bipedal walking robot through simulations via finite‐time optimal robust controller. Numerical results show that the projected Fletcher‐Reeves conjugate gradient approach is feasible and effective for bipedal walking robots. Therefore, it is reasonable to infer that the optimal robust control approach can be used in practical systems.     

Distributed controller design and performance optimization for discrete‐time linear systems

This article addresses the problem of distributed controller design for linear discrete‐time systems. The problem is posed using the classical framework of state feedback gain optimization over an infinite‐horizon quadratic cost, with an additional sparsity constraint on the gain matrix to model the distributed nature of the controller. An equivalent formulation is derived that consists in the optimization of the steady‐state solution of a matrix difference equation, and two algorithms for distributed gain computation are proposed based on it. The first method consists in a step‐by‐step optimization of said difference matrix equation, and allows for fast computation of stabilizing state feedback gains. The second algorithm optimizes the same matrix equation over a finite time window to approximate asymptotic behavior and thus minimize the infinite‐horizon quadratic cost. To assess the performance of the proposed solutions, simulation results are presented for the problem of distributed control of a quadruple‐tank process, as well as a version of that problem scaled up to 40 interconnected tanks.     

Discrete‐time proportional and integral observer and observer‐based controller for systems with both unknown input and output disturbances

In this paper, a novel discrete proportional and integral observer is proposed for estimating the system state, input and output disturbances at the same time. Compared with the previous results, the proposed observer has an advantage in handling output disturbances. A simulated numerical example is given to demonstrate the efficiency. By using the estimates of the state and disturbance, an observer‐based controller with disturbance accommodation is designed to ensure the system stability and to satisfy the specified performance index. A simulated study of a reduced‐order gas turbine discrete model is given to illustrate the design approach, and encouraging simulation results are obtained. Copyright © 2007 John Wiley & Sons, Ltd.     

Robust fixed‐order H2 controller for micro air vehicle—design and validation

Design and real‐time validation of a robust fixed‐order H₂ optimal controller for micro aerial vehicle, named Sarika‐2, is presented. Strengthened discrete optimal projection equations, which approximate the first‐order necessary optimality condition, are used for the controller design. Effect of low‐frequency gust disturbance and high‐frequency sensor noise is alleviated through the output sensitivity and control sensitivity minimization. The novelty of this paper is that a single robust H₂ controller, which is designed at the central operating point, ensures simultaneous stabilization of the radio‐controlled aircraft over the entire cruise speed range of 16–26 m/s. The controller is implemented on a digital‐signal‐processor‐based flight computer, and subsequently, it is validated through the real‐time hardware‐in‐loop‐simulation. The responses obtained from the hardware‐in‐loop‐simulation compares well with those obtained from the off‐line simulation. Copyright © 2006 John Wiley & Sons, Ltd.     

ACADO toolkit—An open‐source framework for automatic control and dynamic optimization

In this paper the software environment and algorithm collection ACADO Toolkit is presented, which implements tools for automatic control and dynamic optimization. It provides a general framework for using a great variety of algorithms for direct optimal control, including model predictive control as well as state and parameter estimation. The ACADO Toolkit is implemented as a self‐contained C++ code, while the object‐oriented design allows for convenient coupling of existing optimization packages and for extending it with user‐written optimization routines. We discuss details of the software design of the ACADO Toolkit 1.0 and describe its main software modules. Along with that we highlight a couple of algorithmic features, in particular its functionality to handle symbolic expressions. The user‐friendly syntax of the ACADO Toolkit to set up optimization problems is illustrated with two tutorial examples: an optimal control and a parameter estimation problem. Copyright © 2010 John Wiley & Sons, Ltd.     

H∞ control for linear switched systems with time‐varying delay and dead‐zone inputs via an adaptive memory controller

This paper deals with the problem of robust H_∞ control for linear switched systems with time‐varying delay and dead‐zone inputs. First, a new state‐dependent switching law is proposed for the switched system with stable and unstable subsystems. Based on the proposed switching law and using the scaled small gain theorem, a more general stability criterion for the switched delay systems is established. Second, an adaptive memory controller is proposed for the switched system with dead‐zone inputs. With the help of a two‐term approximation of the time‐varying delay, the proposed memory controller only depends on the bounds of the time‐varying delay. Sufficient conditions on the existence of the desired controller are formulated in terms of linear matrix inequalities. Three examples are provided to illustrate the effectiveness of the proposed methods. Copyright © 2016 John Wiley & Sons, Ltd.     

Robust reliable guaranteed cost control for uncertain T‐S fuzzy neutral systems with interval time‐varying delay and linear fractional perturbations

The robust reliable guaranteed cost control for Takagi–Sugeno fuzzy systems with interval time‐varying delay is considered in this paper. Some free weighting matrices and non‐negative terms are provided to improve the conservativeness of our main results. An LMI optimization approach is applied to solve the problems of robust reliable guaranteed cost control and minimization of cost function. Copyright © 2014 John Wiley & Sons, Ltd.     

Guaranteed cost control for switched LPV systems via parameter and state‐dependent switching with dwell time and its application

This paper is concerned with the problem of guaranteed cost control for switched linear parameter‐varying (LPV) systems. A parameter and state‐dependent switching law with dwell time is designed. The guaranteed cost control problem for switched LPV systems is still solvable even though this problem for each subsystem is unsolvable. First, a sufficient condition ensuring the solvability of the guaranteed cost control problem for switched LPV systems is presented via multiple parameter‐dependent Lyapunov functions. Then, the parameter‐dependent controller is designed, such that the closed‐loop system is asymptotically stable with the guaranteed cost index. Finally, the effectiveness of the proposed control design scheme is illustrated by its application to an aero‐engine. Copyright © 2016 John Wiley & Sons, Ltd.     

Standard preoperative use of nonopioid multi‐modal medications for patients undergoing mastectomy with immediate reconstruction and the effect on postoperative opioid needs

Standardized nonopioid preoperative protocol effects perioperative opioids. Combined use of acetaminophen, pregabalin, celecoxib, and transdermal scopolamine (APCS), in mastectomy with immediate subpectoral reconstruction procedures. Retrospective (2014‐2017) cohort study (n = 305) examined treatment groups; APCS, no treatment (NONE), and partial combination APCS (OTHER), employing multivariable gamma regression models controlling preoperative and perioperative variables, examining postoperative opioid use (oral morphine equivalents, OME) and hospital stay (hours, LOS). APCS group had a 25% statistical reduction in OME total vs OTHER, a 12% statistical reduction in LOS vs OTHER, and 11% statistical reduction in LOS vs NONE. Standardized nonopioid preoperative protocol provides insight into perioperative opioid use.     

Rapid and simple detection of foot‐and‐mouth disease virus: Evaluation of a cartridge‐based molecular detection system for use in basic laboratories

Highly contagious transboundary animal diseases such as foot‐and‐mouth disease (FMD ) are major threats to the productivity of farm animals. To limit the impact of outbreaks and to take efficient steps towards a timely control and eradication of the disease, rapid and reliable diagnostic systems are of utmost importance. Confirmatory diagnostic assays are typically performed by experienced operators in specialized laboratories, and access to this capability is often limited in the developing countries with the highest disease burden. Advances in molecular technologies allow implementation of modern and reliable techniques for quick and simple pathogen detection either in basic laboratories or even at the pen‐side. Here, we report on a study to evaluate a fully automated cartridge‐based real‐time RT ‐PCR diagnostic system (Enigma MiniLab^®) for the detection of FMD virus (FMDV ). The modular system integrates both nucleic acid extraction and downstream real‐time RT ‐PCR (rRT ‐PCR ). The analytical sensitivity of this assay was determined using serially diluted culture grown FMDV , and the performance of the assay was evaluated using a selected range of FMDV positive and negative clinical samples of bovine, porcine and ovine origin. The robustness of the assay was evaluated in an international inter‐laboratory proficiency test and by deployment into an African laboratory. It was demonstrated that the system is easy to use and can detect FMDV with high sensitivity and specificity, roughly on par with standard laboratory methods. This cartridge‐based automated real‐time RT ‐PCR system for the detection of FMDV represents a reliable and easy to use diagnostic tool for the early and rapid disease detection of acutely infected animals even in remote areas. This type of system could be easily deployed for routine surveillance within endemic regions such as Africa or could alternatively be used in the developed world.     

H2 ∕ H ∞ control for discrete TDS with application to networked control systems: Periodic and asynchronous communication

This paper is concerned with the design of mixed H₂ ∕ H _∞ controllers for discrete‐time delay systems and networked control systems. The controllers are obtained by solving a constrained optimization problem. Those constraints are suitably transformed into linear matrix inequalities, in such a way that the problem is solved using available algorithms. The stability is ensured resorting to the Lyapunov–Krasovskii theory. Additionally, the paper investigates an asynchronous event‐based sampling policy that allows a reduction of the bandwidth usage and the energy consumption. The relation between the boundedness of the stability region and the threshold that triggers the events is studied. The robustness and performance of the proposed technique is showed by numerical simulations. Copyright © 2013 John Wiley & Sons, Ltd.     

Exact penalty functions for optimal control problems I: Main theorem and free‐endpoint problems

In this two‐part study, we develop a general approach to the design and analysis of exact penalty functions for various optimal control problems, including problems with terminal and state constraints, problems involving differential inclusions, and optimal control problems for linear evolution equations. This approach allows one to simplify an optimal control problem by removing some (or all) constraints of this problem with the use of an exact penalty function, thus allowing one to reduce optimal control problems to equivalent variational problems and apply numerical methods for solving, eg, problems without state constraints, to problems including such constraints, etc. In the first part of our study, we strengthen some existing results on exact penalty functions for optimisation problems in infinite dimensional spaces and utilise them to study exact penalty functions for free‐endpoint optimal control problems, which reduce these problems to equivalent variational ones. We also prove several auxiliary results on integral functionals and Nemytskii operators that are helpful for verifying the assumptions under which the proposed penalty functions are exact.     

Exercise Studies in Patients With Rotary Blood Pumps: Cause,Effects, and Implications for Starling‐Like Control of Changes in Pump Flow

This multicenter study examines in detail the spontaneous increase in pump flow at fixed speed that occurs in exercise. Eight patients implanted with the VentrAssist rotary blood pump were subjected to maximal and submaximal cycle ergometry studies, the latter being completed with patients supine and monitored with right heart catheter and echocardiography. Maximal exercise studies conducted in each patient at three different pump speeds on separate days established initially the magnitude and consistency of increases in pump flow that correlated well with changes in heart rate. However, there was considerable variation, coefficients of variation for mean heart rate and pump flow being 47.9 and 49.3%, respectively. Secondly, these studies indicated that increasing pump flows caused significant improvements in maximal exercise capacity. An increase of 2.1 L/min (35%) in maximum blood flow caused 12 W (16%) further increase in achievable work, 1.26 (9.3%) mL/kg/min in maximal oxygen uptake, and 2.3 (23%) mL/kg/min in anaerobic threshold. Mean increases in lactate were 0.85 mm (24%), but mean B‐type natiuretic peptide fell by 126 mm , (?78%). From submaximal supine exercise studies, multiple linear regression of pump flow on factors thought to underlie the spontaneous increase in pump flow indicated that it was associated with increases in heart rate (P = 0.039), pressure gradient across the left ventricle (P = 0.032), and right atrial pressure (P = 0.003). These changes have implications for the recently reported Starling‐like controller for pump flow based on pump pulsatility values, which emulates the Starling curve relating pump output to left ventricular preload. Unmodified, the controller would not permit the full benefits of this effect to be afforded to patients implanted with rotary blood pumps. A modification to the pump control algorithm is proposed to eliminate this problem