Feedback Design Method Research Articles

Designing Effective Visual Feedback for Facial Rehabilitation Exercises: Investigating the Role of Shape, Transparency, and Age on User Experience.

Facial expression recognition technology has been utilized both for entertainment purposes and as a valuable aid in rehabilitation and facial exercise assistance. This technology leverages artificial intelligence models to predict facial landmark points and provide visual feedback, thereby facilitating users' facial movements. However, feedback designs that disregard user preferences may cause discomfort and diminish the benefits of exercise. This study aimed to develop a feedback design guide for facial rehabilitation exercises by investigating user responses to various feedback design methods. We created a facial recognition mobile application and designed six feedback variations based on shape and transparency. To evaluate user experience, we conducted a usability test involving 48 participants (24 subjects in their 20s and 24 over 60 years of age), assessing factors such as feedback, assistance, disturbance, aesthetics, cognitive ease, and appropriateness. The experimental results revealed significant differences in transparency, age, and the interaction between transparency and age. Consequently, it is essential to consider both transparency and user age when designing facial recognition feedback. The findings of this study could potentially inform the design of more effective and personalized visual feedback for facial motion, ultimately benefiting users in rehabilitation and exercise contexts.

Learning-Based Adaptive Optimal Control for Flotation Processes Subject to Input Constraints

This article presents a learning-based adaptive optimal control approach for flotation processes subject to input constraints and disturbances using adaptive dynamic programming (ADP) along with double-loop iteration. First, the principle of the operational pattern is adopted to preset reagents’ addition based on the feeding condition. Then, this article leverages a deep learning model, which is composed of multiple neural layers to detect flotation indexes directly from the raw froth images. After that, the tracking error between the detected flotation indexes and the reference values can be minimized by using ADP-based double-loop iteration. Particularly, a policy-iteration (PI) method is utilized for the proposed learning-based ADP algorithm. In the inner loop, the optimal control problem is formulated as a linear quadratic regulator (LQR) problem using the low-gain feedback design method. In the outer loop, the design parameters, i.e., weighting matrices, are tuned automatically to satisfy the input constraints. Finally, the analytical results demonstrate that the proposed scheme can guarantee asymptotic tracking in the presence of actuator saturation and disturbances.

Robotic 3D printed lunar bionic architecture based on lunar regolith selective laser sintering technology

The lunar base is not only an experimental station for extraterrestrial space exploration but also a dwelling for humans performing this exploration. Building a lunar base presents numerous obstacles and requires environmental perception, feedback design, and construction methods. An integrated fabrication process that incorporates design, 3D printing workflow, and construction details to build a bionic, reconfigurable and high-performance lunar base prototype is presented in this paper. The research comprises the study of the lunar regolith 3D printing mechanism, the real-time control of powder laying and compaction procedure, and the development of a 3D printing tool end system. In this paper, many scientific questions regarding in situ fabrication on the lunar surface are raised and addressed with the proposal of a progressive optimization design method, the molding principle, and gradation strategy of lunar soil-polyaryletherketone (PAEK) hybrid powder, and the principle of dual-light field 3D laser printing. The feasibility of the technical strategy proposed in this paper is verified by the presented empirical samples.

Autonomous Parameter Design for Cascade-Structure Feedback Controller Based on Cooperative Optimization Method

This paper presents a cooperative optimization-based autonomous parameter design method for cascade-structure feedback (FB) controllers used in industrial precision servo systems. Designing fine parameters for a cascade-structure FB controller that realizes a wide control bandwidth is a nonconvex optimization problem owing to the nonlinear relations between the parameters. In conventional parameter design methods based on nonlinear optimization techniques, the obtained parameters strongly depend on the initial point, which requires considerable labor for trial and error-based initial point setting in industry. This paper aims to eliminate such annoyance in cascade-structure FB controller design by using the cooperative optimization technique with a simple initial parameter setting method. The effectiveness of the proposed method is verified through an example FB controller design for a galvanometer scanner, compared to a sequential quadratic programming-based parameter optimization method.

Stabilizing feedback design for time delayed polynomial systems using kinetic realizations

A new stabilizing feedback design method is proposed in this paper for time delayed polynomial systems with a linear input structure. The task is to transform the open loop system to a time delayed complex balanced kinetic system by using a polynomial state feedback structure which guarantees stability with arbitrary time delays.It is shown that the required computations can be performed by simple linear programming, when the only goal is the semistability of the chosen equilibrium point. If one wants to achieve additionally the uniqueness of the closed loop equilibrium point to ensure local asymptotic stability, then the extended optimization problem requires the application of semidefinite programming. The existence of the solution and computability of the feedback do not depend on the magnitude of the delays.It is shown that involving additional monomials into the feedback beyond the ones contained in the open-loop model does not improve the solvability of the semistabilization problem, but it may ensure the uniqueness of the prescribed complex balanced equilibrium point. Thus, two variants of a systematic method are proposed to find appropriate extra monomials for the feedback. One of these requires to solve a linear programming optimization problem even in this extended case.

180 GHz high‐gain cascode power amplifier in a 130 nm SiGe process

A positive feedback gain-enhanced technique for power amplifiers has been introduced in this Letter. With the proposed circuit design method for optimal inductive feedback, a 180 GHz high-gain single-stage cascode power amplifier in a 130 nm SiGe process is implemented. The measurement results show a power gain of 10 dB and 20 GHz bandwidth with 110 mW dc power are achieved, and 6.5 dBm of output power referred to P 1dB and 3.5% collector efficiency are attained. The chip area of the power amplifier is only 0.50 × 0.48 mm2.

Design of a robust current controller for grid‐connected photovoltaic systems based on cascaded multilevel inverter

This work proposes a design method for robust state feedback H ∞ grid current controller applied to single-phase grid-connected photovoltaic (PV) systems. The proposed method achieved high system reliability even dealing with grid distorted voltages and other power quality issues. The robustness of the H ∞ controller was verified in the face of parametric uncertainties at the first-order output filter, and also a satisfactory disturbance rejection performance was achieved. The proposed design is based on linear matrix inequalities associated with constraints involving H ∞ optimisation and a pole placement analysis on the continuous-time domain. A discrete-time analysis is also presented in order to indicate the simplicity of its implementation by a microcontroller or similar devices. Based on the presented results and in order to validate the proposed controller, its robust performance was compared with two linear and well-known control methods: a classical PI controller, in terms of robustness; and a robust H ∞ resonant controller, regarding the power quality at the connection point with the grid-utility. Although the conclusions were listed regarding a low voltage PV grid-interactive multilevel power converter, the proposed H ∞ control design (and its concepts) can be applied to a great variety of renewable energy resources systems.

Robust composite nonlinear feedback control for uncertain robot manipulators

On the basis of the classical computed torque control method, a new composite nonlinear feedback design method for robot manipulators with uncertainty is presented. The resulting controller consists of the composite nonlinear feedback control and robust control. The core is to use the robust control for online approximation of the system’s uncertainty as a compensation term for the composite nonlinear feedback controller. The design method of the new controller is given, and the convergence of the closed-loop system is proved. The simulation results show that the proposed scheme can make the uncertain robot system have strong robustness and anti-interference ability.

Filter Cross-Feedback Control for Nutation Mode of Asymmetric Rotors With Gyroscopic Effects

The nutation mode is an obstacle to the stability improvement of a magnetic-bearing-supported rotor system with significant gyroscopic effects. This article explores a parameter design method of the filter cross feedback for the nutation mode suppression of asymmetric rotor systems supported by active magnetic bearings (AMBs). First, the coupled multi-input multi-output model of the asymmetric AMB rotor system is converted into an equivalent complex single-input single-output model. The equivalent transformation aims at easing the system analysis and extending the classical stability criterion to the complex coefficient frequency domain. Then, the double-frequency bode plot and the Nyquist criterion are used for analyzing the stability of the AMB rotor system and designing the parameters of the filter cross feedback exactly. Simulation results show that the designed filter cross-feedback method has a good performance for suppression of the nutation mode. Finally, the power spectrum level of the nutation component is below $-$ 60 dB after the filter cross-feedback method is implemented in the controller of a large-scale magnetically suspended turbomolecular pump. The experimental results validate the effectiveness of the proposed method.

Nonovershooting Cooperative Output Regulation of Linear Multiagent Systems by Dynamic Output Feedback

We consider the problem of cooperative output regulation for linear multiagent systems. A distributed dynamic output feedback design method is presented that solves the cooperative output regulation problem and also ensures that all agents track the desired reference signal without overshoot in their transient response.

Feedback Stabilization of a 1-D Linear Reaction–Diffusion Equation With Delay Boundary Control

The goal of this paper is to design a stabilizing feedback boundary control for a reaction–diffusion partial differential equation (PDE), where the boundary control is subject to a constant delay while the equation may be unstable without any control. For this system, which is equivalent to a parabolic equation coupled with a transport equation, a prediction-based control is explicitly computed by splitting the infinite-dimensional system into two parts: a finite-dimensional unstable part and a stable infinite-dimensional part. A finite-dimensional delayed controller is computed for the unstable part, and it is shown that this controller stabilizes the whole PDE. The proof is based on an explicit expression of the classical Artstein transformation combined with an adequately designed Lyapunov function. A numerical simulation illustrates the constructive feedback design method.

Neutrosophic state feedback design method for SISO neutrosophic linear systems

The indeterminacy of parameters in actual control systems is inherent property because some parameters in actual control systems are changeable rather than constants in some cases, such as manufacturing tolerances, aging of main components, and environmental changes, which present an uncertain threat to actual control systems. Therefore, these indeterminate parameters can affect the control behavior and performance. Then, a neutrosophic number (NN) z = d + eI consists of its determinate term d and its indeterminate term eI for d, e ∈ R (R is all real numbers and I denotes indeterminacy). In fact, NN implies a changeable interval depending on the indeterminate range of I ∈ [IL, IU] and easily expresses determinate and/or indeterminate information. Unfortunately, NNs are not introduced into the modeling, analysis, and design of uncertain control systems with interval/determinate parameters in existing literature so far. To develop a new neutrosophic design method, this study firstly introduces neutrosophic state space models and the neutrosophic controllability and observability in indeterminate linear systems. Then, a neutrosophic state feedback design method is established for achieving a desired closed-loop state equation or a desired control ratio for single-input single-output (SISO) neutrosophic linear systems. Finally, the proposed control design method is used for a numerical example with NN parameters, and the simulation results demonstrate that the designed state feedback control system can reach the desired system tracking performance requirements. Meanwhile, the obtained state feedback design result demonstrates its effectiveness and robustness.

Static output feedback fault tolerant control using control allocation scheme

SummaryThis paper describes two novel schemes for fault tolerant control using robust suboptimal static output feedback design methods. These schemes can also be employed as actuator redundancy management for overactuated uncertain linear systems. In contrast to many existing methods in the literature that assume the control input matrix (i) is not of full‐rank such that it can be factorized into two matrices and (ii) it does not involve uncertainty, these schemes can be applied to systems whose control input matrix cannot be factorized and/or involve uncertainty. The so‐called virtual control, in these schemes, is calculated using suboptimal ‐based static output feedback design schemes constructed to be robust against uncertainties emanating from inherent input matrix uncertainty and visibility of the control allocator to the controller. Then, using two proposed control allocation schemes (fixed and on‐line), the obtained virtual control signal is redistributed among remaining (redundant or nonfaulty) set of actuators. As the proposed schemes are modular‐based, they can be employed as real‐time fault tolerant control schemes with no need to reconfigure the controller in the case of actuator faults or failures. The effectiveness of the proposed schemes is discussed and compared with numerical examples.

Design of Freeform Illumination Optics

AbstractFreeform optics constitutes a new technology that is currently driving substantial changes in illumination design. It liberates designers and engineers from restrictions of optical surface geometry, enabling them to achieve compact, lightweight, and efficient illumination systems with excellent optical performance. Freeform optics is currently used widely for both fundamental research and practical applications. This Review focuses on the design of freeform illumination optics, which is a key factor in advancing the development of illumination engineering. The design methods of freeform illumination optics can be divided into two groups: zero‐étendue algorithms based on ideal source assumption and design algorithms for extended light sources. The zero‐étendue algorithms include ray mapping method, Monge–Ampère equation method, and supporting quadric method. The algorithms for extended sources include illumination optimization, feedback design, and simultaneous multiple surfaces method. The characteristics and limitations of these design methods are illustrated and a summary of these methods with future outlooks is also given.

Auxiliary‐function‐based double integral inequality approach to stability analysis of load frequency control systems with interval time‐varying delay

A new approach is presented for the stability problem of one-area and multi-area load frequency control (LFC) scheme with time delays in this study. Novel stability criteria with delay dependency in terms of linear matrix inequalities for LFC systems are derived by an augmented Lyapunov–Krasovski functional with triple integral terms. The LFC design takes the interval time-varying communication delays into account and the load disturbance is mathematically modelled as a norm-bounded non-linear function. This study suggests a new class of inequality for double integral of quadratic functions via intermediate auxiliary functions, which produce more tighter bounds than what Wirtinger's double integral inequality produces. Case studies are carried out to illustrate the validity of the proposed delay-dependent proportional–integral-based output feedback design method.

Gain-scheduled static output feedback control for saturated LPV systems with bounded parameter variations

This paper presents a new design method for gain-scheduled static output feedback (SOF) controllers of saturated LPV (linear parameter varying) systems. Our solution is based on a special SOF scheme in conjunction with specific congruence transformations. The regional design is established through an effective treatment of nonlinear effects introduced by the saturations in the closed loop. Using parameter-dependent Lyapunov functions, the control design is reformulated as a parameter-dependent LMI optimization with a single line search parameter. Then, by an equivalent polytopic transformation, tractable design conditions are derived for constrained LPV systems with a broad class of parametric dependencies. In particular, it is proved that the new method generalizes some well-known results based on linear matrix equalities while reducing the design conservatism. Moreover, explicit rank constraints on state–space system matrices are not required. A physically motivated example is given for illustration purposes.

H∞ Optimal Performance Design of an Unstable Plant under Bode Integral Constraint

This paper proposed the H∞ state feedback and H∞ output feedback design methods for unstable plants, which improved the original H∞ state feedback and H∞ output feedback. For the H∞ state feedback design of unstable plants, it presents the complete robustness constraint which is based on solving Riccati equation and Bode integral. For the H∞ output feedback design of unstable plants, the medium‐frequency band should be considered in particular. Besides, this paper presents the method to select weight function or coefficients in the H∞ design, which employs Bode integral to optimize the H∞ design. It takes a magnetic levitation system as an example. The simulation results demonstrate that the optimal performance of perturbation suppression is obtained with the design of robustness constraint. The presented method is of benefit to the general H∞ design.

Semi-global stabilization by an output feedback law from a hybrid state controller

This article suggests a design method of a hybrid output feedback for SISO continuous systems. We focus on continuous systems for which there exists a hybrid state feedback law. A local hybrid stabilizability and a (global) complete uniform observability are assumed to achieve the stabilization of an equilibrium with a hybrid output feedback law. This is an existence result. Moreover, assuming the existence of a robust Lyapunov function instead of a stabilizability assumption allows to design explicitly this hybrid output feedback law. This last result is illustrated for linear systems with reset saturated controls.

Ultimate bound minimisation by state feedback in discrete-time switched linear systems under arbitrary switching

We present a novel state feedback design method for perturbed discrete-time switched linear systems. The method aims at achieving (a) closed-loop stability under arbitrary switching and (b) minimisation of ultimate bounds for specific state components. Objective (a) is achieved by computing state feedback matrices so that the closed-loop subsystem evolution matrices generate a solvable Lie algebra (namely, they are all upper triangular in a common coordinate basis). Previous results derived an iterative algorithm that computes the required feedback matrices, and established conditions under which this procedure is possible. Based on these conditions, objective (b) is achieved by exploiting available degrees of freedom in the iterative algorithm.

Design Method of Adaptive Full Order Observer With or Without Estimated Flux Error in Speed Estimation Algorithm

The performance of adaptive full order observer for sensorless induction motor drives can be improved further though it has been researched for many years. In this paper, two different design methods for improving the speed estimation stability and robustness are proposed: 1) In classical speed estimation algorithm used in adaptive full order observer, the estimated rotor flux error is neglected. A robust design method of feedback gains with classical speed estimation algorithm is proposed. Compared with existed three main design methods of feedback gains, the stability of speed estimation and estimated speed error are improved. 2) A robust speed estimation algorithm with estimated rotor flux error and the corresponding feedback gains are proposed in this paper. Through Lyapunov's theorem, the stability of proposed speed estimation algorithm is proved. The stability of flux estimation and estimated speed error can be improved much more. Finally, the feasibility of two proposed methods is verified by experiments.