H-infinity Controller Design Research Articles

Fixed-order H-infinity controller design for port-Hamiltonian systems

We present a new fixed-order H-infinity controller design method for potentially large-scale port-Hamiltonian (pH) plants. Our method computes controllers that are also pH (and thus passive) such that the resulting closed-loop systems is again passive, which ensures closed-loop stability simply from the structure of the plant and controller matrices. In this way, we can avoid computationally expensive eigenvalue computations that would otherwise be necessary. In combination with a sample-based objective function which allows us to avoid multiple evaluations of the H-infinity norm (which is typically the main computational burden in fixed-order H-infinity controller synthesis), this makes our method well-suited for plants with a high state–space dimension.In our numerical experiments, we show that applying a passivity-enforcing post-processing step after using well-established H-infinity synthesis methods often leads to a deteriorated H-infinity performance. By contrast, our method computes pH controllers, that are automatically passive and simultaneously aim to minimize the H-infinity norm of the closed-loop transfer function. Moreover, our experiments show that for large-scale plants, our method is significantly faster than the well-established fixed-order H-infinity controller synthesis methods.

Design and Analyse of Structured H-infinity Controller for Level Control of Nonlinear Quadruple Tank Systems

Industrial process systems operate by interacting with each other to fulfil an essential industrial task. The majority of processes have nonlinear dynamics and multiple-input multiple-output systems which make them even more difficult to design control schemes. In industrial process applications, level control is one of the important problems. This study computes a structured H-infinity controller for the level control of a nonlinear quadruple tank system. This study aims to design a simple (low-order) robust controller and compare its performance to the performance of the classical Proportional-Integral-Derivative (PID) controller. PID controllers are mostly used in industrial processes due to their simplicity of implementation. However, PID controllers have some disadvantages. One of these disadvantages is that PID controllers offer lower robustness than robust control schemes when the industrial process operates in the presence of disturbances. Simulations are conducted in MATLAB\Simulink environment. Furthermore, the performance of the proposed controller is compared with the PID controller in terms of error-dependent performance indices and time-domain specifications. The simulation results have shown that the proposed controller provides robust set-point tracking, good disturbance rejection, and handling of the parametric uncertainty properties for nonlinear quadruple tank systems in industrial processes.

Design and Validation of Pitch H-Infinity Controller for a Large Wind Turbine

In this study, a pitch H-infinity control algorithm was developed for variable-speed–variable-pitch (VSVP) wind turbines to improve the rotor standard deviation of the wind turbines under normal and extreme wind conditions. The pitch H-infinity control algorithm only uses H-infinity control in the blade pitch control loop in the rated power region, and conventional torque gain scheduling algorithms are applied in the partial power region. The performance of this controller was verified using simulations of a 5 MW wind turbine using the commercial aeroelastic simulation code Bladed. The performance of the pitch H-infinity controller was compared with that of the conventional proportional-integral (PI) control algorithm under three different operating conditions: normal operating conditions without sensor noise, normal operating conditions with sensor noise, and extreme operating conditions without sensor noise based on the wind turbine design standard by IEC. Based on the simulation results with two different wind speed regions, namely, the transition region and the rated power region, it was found that the proposed pitch H-infinity controller showed better rotor speed standard deviation performance in the three operating conditions and achieved lower standard deviations of the rotor speed and the electrical power without affecting the mean electrical power.

H-infinity controller design for robust speed control against disturbance and model uncertainty of DC motors

H-infinity controller design for robust speed control against disturbance and model uncertainty of DC motors

외란과 모델 불확실성이 존재하는 가변속 냉동시스템의 강인제어를 위한 H-infinity 제어기 설계

This paper describes the design of H-infinity controller for robust control of a variable speed refrigeration system. The suggested controller can ensure robustness against disturbance and model uncertainty by minimizing H-infinity norm of the transfer function from exogenous input to performance output and applying the small gain theorem. In particular, the controller was designed to simultaneously reduce the effects of disturbance and model uncertainty by formalizing these problems as a mixed sensitivity problem. In addition, an integrator was included to the controller to prevent the occurrence of steady state error. The validity of the proposed controller was demonstrated by computer simulations and real experiments. Moreover, the effectiveness of the proposed controller was confirmed by comparing its performance to the PI controller, which was tested under the same experimental conditions as the H-infinity controller.

H-infinity controller design for chatter suppression in machining based on integrated cutting and flexible structure model

This paper describes a feedback controller design for chatter suppression in machining based on combined flexible structure and cutting force models. To deal with time-delayed feedback effects from cutting forces, a linear time-delay control system is introduced that satisfies an H∞ norm-bound criterion. A corresponding set of linear matrix inequalities (LMIs) is derived from a delay-dependent Lyapunov–Krasovskii functional (LKF) and used to synthesize controllers that can achieve stable operation for specified material removal rates. Experiments on a hardware-in-the-loop flexible structure test-bed show that the LKF-LMI H∞ controller gives significant improvements in stability regions compared with robust (non-time-delay) controller designs, confirming the method’s potential for machining vibration control.

Application of robust H-infinity controller in transition flight modeling of autonomous VTOL convertible Quad Tiltrotor UAV

PurposeThis paper aims to provide a mathematical modeling and design of H-infinity controller for an autonomous vertical take-off and landing (VTOL) Quad Tiltrotor hybrid unmanned aerial vehicles (UAVs). The variation in the aerodynamics and model dynamics of these aerial vehicles due to its tilting rotors are the key issues and challenges, which attracts the attention of many researchers. They carry parametric uncertainties (such as non-linear friction force, backlash, etc.), which drives the designed controller based on the nominal model to instability or performance degradation. The controller needs to take these factors into consideration and still give good stability and performance. Hence, a robust H-infinity controller is proposed that can handle these uncertainties.Design/methodology/approachA unique VTOL Quad Tiltrotor hybrid UAV, which operates in three flight modes, is mathematically modeled using Newton–Euler equations of motion. The contribution of the model is its ability to combine high-speed level flight, VTOL and transition between these two phases. The transition involves the tilting of the proprotors from 90° to 0° and vice-versa in 15° intervals. A robust H-infinity control strategy is proposed, evaluated and analyzed through simulation to control the flight dynamics for different modes of operation.FindingsThe main contribution of this research is the mathematical modeling of three flight modes (vertical takeoff–forward, transition–cruise-back, transition-vertical landing) of operation by controlling the revolutions per minute and tilt angles, which are independent of each other. An autonomous flight control system using a robust H-infinity controller to stabilize the mode of transition is designed for the Quad Tiltrotor UAV in the presence of uncertainties, noise and disturbances using MATLAB/SIMULINK. This paper focused on improving the disturbance rejection properties of the proposed UAV by designing a robust H-infinity controller for position and orientation trajectory regulation in the presence of uncertainty. The simulation results show that the Tiltrotor achieves transition successfully with disturbances, noise and uncertainties being present.Originality/valueA novel VTOL Quad Tiltrotor UAV mathematical model is developed with a special tilting rotor mechanism, which combines both aircraft and helicopter flight modes with the transition taking place in between phases using robust H-infinity controller for attitude, altitude and trajectory regulation in the presence of uncertainty.

Event-Triggered H-Infinity Controller Design of Nonlinear Networked Cascade Control System

Nonlinearity is ubiquitous in practical industrial production, so this paper investigates the problems of modeling, $H_{\infty }$ control and stabilization for a class of nonlinear networked cascade control systems (NCCSs) under an event-triggered scheme, which makes the system have more practical application value. Firstly, aiming at a kind of typical nonlinear system in industrial production, a new mathematical model is established by adding networked cascade control system and event-triggered scheme. The collaborative design method of primary and secondary controller parameters and event-triggered parameters is completed utilizing linear matrix inequality (LMI). Secondly, based on ensuring its stability, combined with $H_{\infty }$ control, the system’s disturbance is suppressed, making the system more universal. Finally, the feasibility and effectiveness of the proposed method in the nonlinear networked cascade control system has verified by a marine boiler liquid level cascade control system.

Robust H-infinity control of two novel MEMS force sensors

This paper presents the design and implementation of a robust H-infinity controller on two novel MEMS force sensors. The novel microelectromechanical system (MEMS) sensors incorporated a mechanism that permits tuning of the device’s mechanical stiffness and has been used for the characterization of micro-cantilever and biological tissues. To ensure stability and guaranteed performances, certain specifications such as error tracking, command moderation, disturbance rejection, and robustness in presence of uncertainties, were made and the H-infinity control technique was employed to synthesize robust controllers for the two force sensors. Finally, this robust controller, integral, and PID controllers were implemented on the real systems and their performance in closed-loop were compared.

Design of H-infinity Controller for VTOL Tiltrotor Unmanned Aerial Vehicle

Design of H-infinity Controller for VTOL Tiltrotor Unmanned Aerial Vehicle

Dynamic tracking control of an SMA wire actuator based on model matching

Wires of shape memory alloys (SMAs) contract in response to heat, and are used as actuators because of this ability. However, as this deformation is accompanied by hysteresis, SMA actuators cannot be described as a linear time invariant (LTI) system. In this article, we demonstrate a method for modelling SMA wire actuators that is valid in the full displacement range, to be applied in linear control systems. To this end, we describe the response of the SMA actuators as a first-order lag system, using a model matching method. The time constant used in this first-order lag system is selected based on observations of the limited range below the austenite onset temperature. Analysis of the step response of the SMA actuator established that a PI controller alone is unable to approximate this first-order lag system properly. Hence, with our technique, a PI-controlled SMA actuator is considered as a plant, to which we apply H-infinity control design, which improves the approximation to the first-order lag system. This improvement was verified through a comparison of the transfer functions of the H-infinity-based system and a solely PI-controlled system. We also consider self-sensing by measuring the resistance of the SMA actuator directly, instead of using a load cell to observe the force induced by actuator deformation. Based on these results, we are able to demonstrate that the effect of self-sensing on the closed-loop characteristic is within the permissible range, suggesting that the creation of compact self-sensing actuators is viable.

Design of Distributed Multi-Actuator Systems with Incomplete State Information for Vibration Control of Large Structures

In this paper, we investigate the design and performance of static feedback controllers with partial-state information for the seismic protection of tall buildings equipped with incomplete multi-actuation systems. The proposed approach considers a partially instrumented multi-story building with an incomplete system of interstory force–actuation devices implemented on selected levels of the building, and an associated set of collocated sensors that measure the corresponding interstory drifts and interstory velocities. The main elements of the proposed controller design methodology are presented by means of a twenty-story building equipped with a system of ten interstory actuators arranged in three different layouts: concentrated, semi-distributed and fully-distributed. For these control configurations, partial-state controllers are designed following a static output-feedback H-infinity controller design approach, and the corresponding frequency and time responses are investigated. The obtained results clearly indicate that the proposed partial-state controllers are effective in mitigating the building seismic response. They also show that a suitable distribution of the instrumented stories is a relevant factor in the control system performance.

Integrated multiple-model adaptive fault identification and reconfigurable fault-tolerant control for Lead-Wing close formation systems

ABSTRACTThis paper investigates the attitude and position tracking control problem for Lead-Wing close formation systems in the presence of loss of effectiveness and lock-in-place or hardover failure. In close formation flight, Wing unmanned aerial vehicle movements are influenced by vortex effects of the neighbouring Lead unmanned aerial vehicle. This situation allows modelling of aerodynamic coupling vortex-effects and linearisation based on optimal close formation geometry. Linearised Lead-Wing close formation model is transformed into nominal robust H-infinity models with respect to Mach hold, Heading hold, and Altitude hold autopilots; static feedback H-infinity controller is designed to guarantee effective tracking of attitude and position while manoeuvring Lead unmanned aerial vehicle. Based on H-infinity control design, an integrated multiple-model adaptive fault identification and reconfigurable fault-tolerant control scheme is developed to guarantee asymptotic stability of close-loop systems, error signal boundedness, and attitude and position tracking properties. Simulation results for Lead-Wing close formation systems validate the efficiency of the proposed integrated multiple-model adaptive control algorithm.

H-Infinity Controller Design for the Switched Reluctance Machine

H-Infinity Controller Design for the Switched Reluctance Machine

H-Infinity Control Design Considering Packet Loss as a Disturbance for Networked Control Systems

H-Infinity Control Design Considering Packet Loss as a Disturbance for Networked Control Systems

H-infinity controller design for active magnetic bearings considering nonlinear vibrational rotordynamics

H-infinity controller design for active magnetic bearings considering nonlinear vibrational rotordynamics

H-infinity Backpressure Controller for High Response Engine Exhaust Throttles

Modern engine exhaust restriction valves can be applied not only as retarders. A suitable pressure generation can assist the aftertreatment system (exhaust gas temperature management) and raw emission control as well. To provide these functionalities the exhaust backpressure has to be controlled arbitrarily. In this paper a model-based controller design is demonstrated to minimize calibration effort. A first engineering principle based, mean-value, nonlinear model was described and converted into linear parameter-varying (LPV) form. To satisfy the demands of the above applications the controller needs to be a high dynamic, stabilizing, tracking controller which is robust in the whole relevant engine operation range. The exhaust processes of the individual cylinders generate comparable amplitude pressure oscillations to the expected control accuracy. To fulfill the above requirements and manage the challenge of the exhaust pressure waves an H-infinity controller design method was chosen. In order to handle the saturation of the control signal a high gain anti-windup was applied. Seeking for the lowest possible computational demand the controller order reduction was proposed based on Hankel singular values. Finally the controller performance was demonstrated and evaluated in software-in-the-loop simulations.

H-Infinity Control for Pitch-Roll AR.Drone

This paper describes the design and implementation of H-infinity controller applied to the AR.Drone to follow a given trajectory. The trajectory will be achieved by using two control signals, pitch and roll. Pitch and roll of the AR.Drone models are obtained by assuming that the transfer function of internal control for pitch and roll is the second order system. Two schemes of H-infinity controller designed for pitch and roll. H-infinity control for x-position has exogenous input of the x-reference, xref, control input of pitch value, exogenous output in the form of x-position and process output as error x. While H-infinity control for y-position has exogenous input of y-reference, yref, control input in the form of roll value, exogenous output of y-position and process output as error y. The results of simulation and implementation show that drone can follow multiple references of trajectories given.

非线性时滞奇异系统的鲁棒同时H<sub>∞</sub>控制

针对一组具有不确定性状态非线性的时滞奇异系统鲁棒H∞控制问题进行研究。基于Lyapunov-Krasovskii泛函和线性矩阵不等式(LMI)以及非线性不确定向量函数范数有界的条件下，得到自由奇异系统的稳定性判据，进而有状态反馈控制下闭环非线性时滞奇异系统的正则、无脉冲、稳定的充分条件。给出带有不确定性具有扰动的非线性时滞闭环系统的H∞控制器的构造方法。最后，给出仿真算例说明本文方法的可行性。 This paper considers the problems of robust simultaneous H-infinity control for nonlinear singular systems with uncertain state time-delay. The stabilization criterion for singular systems is derived by Lyapunov-Krasovskii functional, linear matrix inequality (LMI) and nonlinear uncertain vector function with norm bounded, then the sufficient condition of closed-loop nonlinear singular systems with time-delay is gained to guarantee regular, impulse-free, stable. The H-infinity controller design approach is given for nonlinear uncertain singular closed-loop systems with time-delay and distur-bance. Finally, a numerical example is presented to illustrate the feasibility of the proposed results.

Observer-based state feedback H-infinity control for networked control systems

The observer-based H-infinity controller design problem is considered for the networked control systems with uncertain network-induced delays and packet dropouts. The system states are reconstructed by introducing an observer and an augmented system model with time-varying delays is established. Based on the delay-dependent Lyapunov stability theory, a sufficient condition is proposed to ensure that the closed-loop system is asymptotically stable with a guaranteed H-infinity performance level r. Since the obtained condition is nonlinear, the singular value decomposition method is applied to convert the nonlinear inequalities into LMIs. The delay-dependent approach shows a less conservative result than the delay-independent approach. A numerical example is given to demonstrate the high validity and merit of the proposed approach.