Multi-objective Output Feedback Control Research Articles

Robust controller for artificial pancreas for patients with type-1 diabetes

The target of this paper is to design a simple and an efficient controller for artificial pancreas (AP) system for blood glucose (BG) regulation in type-1 diabetic mellitus (T1DM) patient. Bergman’s intravenous model is chosen for the controller design as the model is minimum ordered model of T1DM patient. A multi-objective output feedback controller has been designed for AP system considering robustness, disturbance rejection, and transient criterion. Considering H∞, pole-placement, and H2 constraints, a control algorithm has been developed and has been solved using linear matrix inequality (LMI) technique. As a testing platform of the intravenous model-based designed controller, UVa/Padova T1DM metabolic simulator has been chosen which uses subcutaneous insulin delivery method. The controller has been tested in the presence of unannounced meal disturbances. Experimental results show that the controller regulates BG level very efficiently with lesser amount of insulin and avoids hypoglycemia effect. In the presence of external noises like glucose sensor noise and insulin pump error, the robustness of the controller has been checked. The performance of the controller has been compared with compound internal model control (IMC) strategy reported earlier for same meal scenario. The designed multi-objective controller gives better performance metrices than compound IMC controller.

Multi-objective output feedback control strategy for a variable speed wind energy conversion system

This paper deals with the problem of sensorless output feedback control for wind energy conversion systems (WECSs). The considered system consists of a synchronous aero-generator connected to the grid through an AC/DC/AC converter. Maximum wind energy extraction is achieved by running the wind turbine generator in a variable-speed mode without using a wind velocity sensor. This work establishes a different approach to estimate the rotor position, speed, and turbine torque. Furthermore, the proposed technique aims to provide an on-line estimation of the grid voltage and pulsation, considered generally as accessible. To overcome these issues, a high gain observer is designed. It provides estimates of all state variables, only from the current and voltage measurements. An integral sliding mode controller is then synthesized based on the estimation provided by the observer, with the view of ensuring the MPPT objective. Several simulations show that all control objectives are achieved and the output feedback performances enjoy robustness properties.

Robust multi-objective blood glucose control in Type-1 diabetic patient.

In this study, an automatic robust multi‐objective controller has been proposed for blood glucose (BG) regulation in Type‐1 Diabetic Mellitus (T1DM) patient through subcutaneous route. The main objective of this work is to control the BG level in T1DM patient in the presence of unannounced meal disturbances and other external noises with a minimum amount of insulin infusion rate. The multi‐objective output‐feedback controller with H∞, H2 and pole‐placement constraints has been designed using linear matrix inequality technique. The designed controller for subcutaneous insulin delivery was tested on in silico adult and adolescent subjects of UVa/Padova T1DM metabolic simulator. The experimental results show that the closed‐loop system tracks the reference BG level very well and does not show any hypoglycaemia effect even during the long gap of a meal at night both for in silico adults and adolescent. In the presence of 50 gm meal disturbance, average adult experience normoglycaemia 92% of the total simulation time and hypoglycaemia 0% of total simulation time. The robustness of the controller has been tested in the presence of irregular meals and insulin pump noise and error. The controller yielded robust performance with a lesser amount of insulin infusion rate than the other designed controllers reported earlier.

Multi-objective and reliable output feedback control for spacecraft hovering

A multi-objective and reliable dynamic output feedback controller design method is proposed in this paper for spacecraft hovering around targets in circular orbits. The hovering process contains two steps namely, orbital transfer and hovering maintenance. Firstly, the dynamical model of spacecraft hovering is built and multi-objective output feedback control problems for the both steps are formulated. For orbital transfer control, we focus on fuel optimization and pole placement. And H2 performance, H∞ performance and pole placement are considered in hovering maintenance control. Then, sufficient conditions for guaranteed cost and pole placement are provided in the forms of nonlinear matrix inequalities. Using some changes of variables and Schur complement, the obtained sufficient conditions can be rewritten as linear matrix inequality constraints. Likewise, sufficient conditions for H2 control, H∞ control and pole placement are presented and transformed into linear matrix inequalities. Thus, the multi-objective controller design problems for both orbital transfer control and hovering maintenance are described as convex optimizations subject to linear matrix inequalities, respectively. Finally, numerical simulations are presented to illustrate the effectiveness and validity of the proposed dynamic output feedback controller design algorithms.

Multi-objective output feedback control for autonomous spacecraft rendezvous

In this paper, the problem of robust output feedback control for a class of spacecraft rendezvous systems is investigated, which contains parameter uncertainty, external disturbance, poles assignment, H∞-norm, variance and input constraints. The aim of this problem is to design a dynamic output feedback controller such that the closed-loop poles are placed within a specified disc, the H∞ norm of the transfer function from disturbance to output is ensured to be less than a prespecified disturbance attenuation level, the steady-state variance for each state of spacecraft rendezvous system is guaranteed to be less than the prespecified individual upper bound, and the actual control input is confined into a certain range simultaneously. Based on the Lyapunov theory, the existence conditions of such controller are derived in terms of linear matrix inequalities (LMIs). An illustrative example is given to demonstrate the effectiveness of the proposed control design method.

Multi-model approaches to three-axis missile autopilot design under aerodynamic roll angle uncertainty

The problem of designing a robust three-axis missile autopilot that operates under aerodynamic roll angle uncertainty is addressed in this article. A finite number of local state-space models over an aerodynamic roll angle envelope are developed as a multi-model to represent uncertainty bounds. Two design methods with multi-objective output-feedback control are proposed. In the first approach, a classical three-loop autopilot structure is slightly modified for the multivariable autopilot design. The optimal gains in the autopilot structure are automatically obtained by using a co-evolutionary optimization method that addresses competing specifications and constraints. In the second approach, the mixed H2/ H∞ performance criteria are guaranteed by multi-objective control synthesis via optimization techniques. Both design approaches are used in non-linear simulations with variations in the aerodynamic roll angle to provide satisfactory performance as a three-axis missile autopilot.

LuGre model-based friction compensation and positioning control for a pneumatic actuator using multi-objective output-feedback control via LMI optimization

This paper deals with a high-friction pneumatic actuator positioning technique based on a LuGre friction closed-loop observer dynamics. The main purpose of the technique is to establish the stability condition by using the passivity of interconnected linear and nonlinear subsystems dealing with the varying and uncertain parametrization of friction modeling and exogenous bounded inputs resulting from the force-loop dynamics. With this formulation, we succeed in designing a full-order dynamic feedback which ensures exponential stabilization and additional multi-objective constraints (an H ∞ criterion and a closed-loop pole location). These conditions are expressed in terms of linear matrix inequalities (LMIs). The formulation is therefore numerically tractable via LMI optimization. The performances are validated experimentally on a pneumatic plant operating under a high level of friction. The robust LuGre model-based friction compensator is experimentally compared to other friction compensation and position control schemes.

Multi-objective output-feedback control for microsatellite attitude control: An LMI approach

Mixed H 2 / H ∞ output-feedback controller with pole placement constraints against the internal uncertainty of moment-of-inertia variation and space environmental disturbances is proposed for mircosatellite attitude control. The multi-objective controller is designed based on linear model of attitude dynamics. The H ∞ performance takes into account both robustness stability against moments-of-inertia uncertainty and the disturbance rejection aspect. H 2 performance takes into account the LQG aspect which avoids the undesirable wheels’ saturation effect. In addition, the closed-loop poles can be forced into some sector of the stable half-plane to obtain well-damped transient responses. The problem is then reduced to a convex optimization involving linear matrix inequalities (LMIs), so it can be efficiently solved. The simulation results demonstrate that the presented mixed H 2 / H ∞ control system is robust stable and optimal in the sense of H 2 norm, and has good steady-state and dynamic performances against the parameter uncertainties and various disturbances for the microsatellite attitude control system.

Multiobjective Output Feedback Control of a Class of Stochastic Hybrid Systems with State-Dependent Noise

This paper deals with dynamic output feedback control of continuous-time active fault tolerant control systems with Markovian parameters (AFTCSMP) and state-dependent noise. The main contribution is to formulate conditions for multiperformance design, related to this class of stochastic hybrid systems, that take into account the problematic resulting from the fact that the controller only depends on the fault detection and isolation (FDI) process. The specifications and objectives under consideration include stochastic stability,ℋ2andℋ∞(or more generally,stochastic integral quadratic constraints) performances. Results are formulated as matrix inequalities. The theoretical results are illustrated using a classical example from literature.

A Multi-Objective Output-Feedback Controller for Systems with Friction

In this paper, we develop a full-order dynamic output feedback positioning tracking for servo-systems with friction, based on LuGre friction observer dynamics with fixed model parameters. To this end, we use the position and velocity measurements. The compensator design is appropriately built to ensure a global asymptotic stabilization of the tracking error dynamics under a specific pole clustering. And, we take into account some H2 cost performance to offer an optimal control structure. The subsequent stated controller matrices are found by using the Linear Matrix Inequality approach. Simulation results illustrate the effectiveness of the proposed compensator.