Mixed Sensitivity Research Articles

Multiple-Disturbance Rejection for High Precision Positioning of a VCM Servo Gantry

This paper presents an multiple disturbance rejection approach for rejecting narrow-band disturbances as well as norm-bounded random disturbances, with applications to high precision positioning of a Voice Coil Motor (VCM) actuated servo stage. An adaptive optimal phase filter design method is proposed for the rejection of frequency-varying narrow-band disturbances at unknown frequency range. With a parallel connection of the proposed adaptive filter, a robust H∞ controller can be synthesized with mixed sensitivity optimization for the purpose of both robust stability and rejection of norm-bounded random disturbances. The proposed control architecture is implemented to a VCM servo gantry to achieve high precision positioning in the presence of various disturbances.

Robust Two Degree-Of-Freedom Control for MIMO System with Both Model and Signal Uncertainties

In the study, a model inversion based two degree-of-freedom (DOF) controller is proposed to achieve optimal robust performance for multi-input-multi-output (MIMO) system with existence of both model and signal uncertainties. The original plant dynamics are modified by a pre-compensator and a post-compensator to obtain a diagonally dominant matrix, where the selected dynamics of the plant are contained within the diagonal entries. The inversion of the diagonal matrix, as a result, reflects the inversion of the plant dynamics within a specified frequency range. The feedback controller is designed using a standard H2 mixed sensitivity approach. The feedforward controller consists of plant inversion and a feedforward filter, which is optimized to balance the trade-off between nominal performance and robust performance under model uncertainty and signal uncertainty. A numerical example is used to demonstrate the improvement of the robust performance when using the optimal feedforward control.

21410 鉄道車両のアクティブサスペンションによる振動制御

A high speed railway vehicle is greatly affected by track irregularity. Vertical vibration of a high speed railway vehicle makes worse the ride comfort of passengers. This paper aims at reducing such vibration, especially the 1st mode bending vibration of carbody with the active suspension system. This system used the proposed method of designing a vibration control system. The controller was designed by applying the mixed sensitivity problem of H-infinity control theory. The numerical simulation results show that the ride comfort of passengers is improved by the active suspension.

Controller Design for Lateral Dynamics of Reusable Launch Vehicle by H-infinity Mixed Sensitivity approach

Abstract During reentry flight regime of a typical Reusable Launch Vehicle (RLV), there is rise in dynamic pressure which increases the coupling between yaw (directional) and roll (lateral) dynamics. High uncertainty on aerodynamic coefficients due to less number of wind tunnel tests, makes it essential to use robust control design techniques to design a controller for any new aerodynamic configuration of RLV. Control system design during critical flight regime of RLV using 'H-infinity Mixed Sensitivity' approach is addressed in this paper. The main bottle neck in using H-infinity approach is the lack of guidelines in finding weighting functions to achieve required time and frequency domain specifications. It is seen that the solution process becomes easier if the coupling and damping requirements are first addressed by designing the aileron to rudder interconnect (ARI) gain and roll-yaw rate gains using classical approach and then applying the H-infinity procedure on the plant model, updated with the designed ARI and rate gains, to shape the sensitivity and complementary sensitivity functions. This is the main contribution of our paper. This approach has resulted in highly robust controller against plant parameter perturbations. The yaw-roll coupling, which is the main problem, could also be eliminated to a greater extent.

H-infinity controller design for pneumatic servosystem: a comparative study

In recent times, pneumatic servosystems have received wide acceptance in industries and other special systems. Current researches focus on improving the disturbance rejection properties of pneumatic servosystems to work well in industrial environment. So far many controllers have been developed to control the system, of which the H∞ controller is found to guarantee robustness and performance. In this paper, design of robust H infinity controller is proposed for pneumatic servo system using different techniques such as mixed sensitivity function, loop shaping design using Glover-McFarlane method and optimal controller design based on solution of Riccati equations and comparative analysis is done with conventional PID controller tuned using Ziegler-Nichols method. Comparison with a well tuned PID controller shows the efficacy of H∞ controller designed using the proposed algorithms.

Design and Optimal Control of Line of Sight Stabilization of Moving Target

The Line-of-Sight stabilization and tracking control based on gyro stabilized platform is required to isolate Line of sight from the movement and vibration of carrier and ensure pointing and tracking for target in electro-optical tracking system. This work describes the design of a high performance controller for an electromechanical target tracking system with an optical sensor for sighting. The control law has been obtained using a linear model of the electro mechanical system. The modelling of the system has been carried out using the experimental frequency response data. The PID adesigning of control system methodology has been used to design the controller and study the comparative analysis using both controller and optimized tuned performance is also seeing by using the designing the PID controller in different loop analysis and study responses of system by using step response and frequency response analysis by using the bode diagram so as to stabilize the line of sight stabilization and tracking control system. The mixed sensitivity optimisation problem has been posed and weighting functions are selected by using the gradient and dissent method having more numbers of iterations so that they not only encapsulate all the design goals but also accommodate the modelling uncertainties. A stabilising controller with excellent robustness properties has been obtained. Investigator has used MATLAB for the designing of controller and simulated the system for a required criterion of the system.

Quasipolynomial Approach to Simultaneous Robust Control of Time-Delay Systems

A control law for retarded time-delay systems is considered, concerning infinite closed-loop spectrum assignment. An algebraic method for spectrum assignment is presented with a unique optimization algorithm for minimization of spectral abscissa and effective shaping of the chains of infinitely many closed-loop poles. Uncertainty of plant delays of a certain structure is considered in a sense of a robust simultaneous stabilization. Robust performance is achieved using mixed sensitivity design, which is incorporated into the addressed control law.

Developments in the CSU-RAMS Aerosol Model: Emissions, Nucleation, Regeneration, Deposition, and Radiation

AbstractThe Colorado State University (CSU) Regional Atmospheric Modeling System (RAMS) has undergone development focused on improving the treatment of aerosols in the microphysics model, with the goal of examining the impacts of aerosol characteristics, scavenging, and regeneration processes, among others, on precipitation processes in clouds ranging from stratocumulus to deep convection and mixed-phase orographic clouds. Improvements in the representation of aerosols allow for more comprehensive studies of aerosol effects on cloud systems across scales. In RAMS there are now sub- and supermicrometer modes of sulfate, mineral dust, sea salt, and regenerated aerosol. All aerosol species can compete for cloud droplet nucleation, and they are regenerated via hydrometeor evaporation. A newly applied heterogeneous ice nuclei parameterization accounts for deposition nucleation and condensation and immersion freezing of aerosols greater than 0.5-μm diameter. There are also schemes for trimodal sea salt emissions and bimodal dust lofting that are functions of wind speed and surface properties. Aerosol wet and dry deposition accounts for collection by falling hydrometeors as well as gravitational settling of aerosols on water, soil, and vegetation. Aerosol radiative effects are parameterized via the Mie theory. An examination of the simulated impact of aerosol characteristics, sources, and sinks reveals mixed sensitivity among cloud types. For example, reduced aerosol solubility has little impact on deep convection since supersaturations are large and nearly all accumulation-mode aerosols activate. In contrast, reduced solubility results in reduced aerosol activation in precipitating stratocumulus. This leads to lower cloud droplet concentration, larger droplet size, and more efficient warm rain processes.

Three-objective optimization of a staggered herringbone micromixer

Shape optimization of a staggered herringbone micromixer (SHM) was performed using the three-dimensional numerical analysis of fluid flows and mixing of two fluids, surrogate modeling, and a multi-objective genetic algorithm. Two design variables related to dimensions of the grooves, i.e., depth and width, were chosen for optimization. Three performance parameters, i.e., the mixing index at the exit of the micromixer, overall friction factor, and mixing sensitivity, which is the mixing index at a specified axial location in upstream part of the micromixer, were employed as the objective functions. Surrogate modeling was performed for the objective functions using response surface approximation. Multi-objective genetic algorithm was used to find the Pareto-optimal solutions. Representative Pareto-optimal designs were analyzed using numerical analysis and a particle tracking method. The optimization results indicate that wide and deep grooves are desirable to promote faster mixing with a low pressure drop inside the SHM.

Robust adaptive speed control of uncertain hybrid electric vehicle using electronic throttle control with varying road grade

The design objective of this paper is to apply various control techniques to control the speed of a hybrid electric vehicle (HEV) using an electronic throttle control system (ETCS). The DC servo motor is used for controlling the angular position of the throttle valve. A proportional-integral-derivative (PID), a self-tuning fuzzy PID (STF-PID) controller and a model reference adaptive system (MRAS) with a sliding mode (SM) adaptation mechanism are used for controlling the speed of the nonlinear vehicle. The integral error performance indices (IEPI) such as the integral of the absolute error (IAE), the integral of the square of error (ISE) and the time domain performance specifications such as overshoot (OS), settling time (ST) and rise time (RT) are taken into consideration for the performance analysis of HEV. The robust H∞ controller using mixed sensitivity approach is designed and implemented for the linearized HEV. The robust stability of uncertain HEV with H∞ controller using Kharitonov’s theorem is analyzed, and the stability margin of the linearized vehicle system is determined. These control techniques are developed to achieve the robust performance of the throttle controlled HEV with the target to achieve a wide range of speed, fuel economy, reduced pollution and improved efficiency.

Research on control strategy for differential steering system based on H mixed sensitivity

The differential steering system (DSS) of electric wheel vehicle gets rid of the restrictions of traditional steering system completely. As an ideal steering technology, it not only realizes the perfect combination of the road feel and the steering portability, but also realizes the harmony and unification between the steering maneuverability and safety. The structure and basic theory of the DSS of electric wheel vehicle are discussed in this paper. Based on these, the dynamic model of the steering system is built. Considering of the uncertainties and disturbances existing in the model, the H∞ mixed sensitivity control theory is applied to achieve better tracking performance and road feel in the process of steering. Then, a H∞ mixed sensitivity controller is designed to restrain the effect of the road disturbance and model uncertainties. The simulation results indicate that the DSS with the designed controller can effectively restrain the effect of noises and disturbances caused by random motivation from road, torque sensor measurement and model parameter uncertainty, and enable the driver to obtain satisfactory road feel.

Aeroelastic analysis and active flutter control of nonlinear lattice sandwich beams

Nonlinear aeroelastic characteristics of sandwich beams with pyramidal lattice core are investigated, and the active flutter control of the nonlinear structural system is also studied using the piezoelectric actuator/sensor pair. In the structural modeling, Reddy’s third-order shear deformation theory is applied. Aerodynamic pressure is evaluated by the supersonic piston theory. Hamilton’s principle and the assumed mode method are used to derive the equation of motion. The proportional feedback and the optimal H∞ control methods are performed to design the controller. In the robust control, the uncertainty caused by omitting the nonlinear terms of the control equation is taken into account, and the mixed sensitivity method is used to solve the problem. The nonlinear aeroelastic property of the sandwich beam is analyzed and is compared with that of the equivalent isotropic beam with the same weight to show the superior aeroelastic characteristics of the lattice sandwich beam. Controlled vibration responses under the two different controllers are calculated and compared. Simulation results show that the robust controller is much more effective than the proportional feedback controller in the flutter suppression of the nonlinear sandwich beam.

Internal model based robust inversion feedforward and feedback 2DOF control for LPV system with disturbance

To reduce the adverse effects on the control performance and disturbance rejection caused by system uncertainty, a novel internal model based robust inversion feedforward and feedback 2DOF control approach was proposed for LPV system with disturbance. The proposed control approach combines the internal model control and robust inversion based 2DOF control, it utilizes internal model based control to reject external disturbance, utilizes robust inversion 2DOF control to enhance the control resolution and guarantee the system control performance. At first, a LMI synthesis approach for LPV system model identification and a disturbance compensator optimization design method which could minimize H∞ norm of output error caused by disturbance are presented. Then, combined with internal loop for disturbance compensation, a robust inversion feedforward controller is designed by robust inversion approach and the feedback controller which could render the requirements of reference signal tracking performance and robustness satisfied is obtained by the H∞ mixed sensitivity synthesis approach. Finally, atomic force microscopy (AFM) vertical positioning simulation experiments are conducted and the experiment results showed that the proposed control approach could achieve better output performance and disturbance rejection compared with conventional internal model based control and robust inversion based 2DOF control approach.

Sensitivity of the squark flavor mixing to the CP violation of K, [formula omitted] and [formula omitted] mesons

We study the sensitivity of the squark flavor mixing to the CP violating phenomena of K, B0 and Bs mesons in the framework of the split-family scenario, where the first and second family squarks are very heavy, O(10) TeV, on the other hand, the third family squark masses are at O(1) TeV. In order to constrain the gluino-sbottom-quark mixing parameters, we input the experimental data of the CP violations of K, B0, and Bs mesons, that is ϵK, ϕd, and ϕs. The experimental upper bound of the chromo-EDM of the strange quark is also input. In addition, we take account of the observed values ΔMB0, ΔMBs, the CKM mixing |Vub|, and the branching ratio of b→sγ. The allowed region of the mixing parameters are obtained as |δ13dL(dR)|=0∼0.01 and |δ23dL(dR)|=0∼0.04. By using these values, the deviations from the SM are estimated in the CP violations of the B0 and Bs decays. The deviation from the SM one is tiny in the CP asymmetries of B0→ϕKS and B0→η′K0 due to the chromo-EDM of the strange quark. On the other hand, the CP asymmetries Bs→ϕϕ and Bs→ϕη′ could be largely deviated from the SM predictions. We also predict the time dependent CP asymmetry of B0→K0K¯0 and the semi-leptonic CP asymmetries of B0→μ−X and Bs→μ−X. We expect those precise measurements at Belle II, which will provide us interesting tests for the squark flavor mixing.

Robustness of Improving Active Maglev Motorized Spindle Equilibrium Position

The equilibrium position of active maglev motorized spindle had great influence on the industrial processing accuracy, in order to improve the performance of active maglev motorized spindle and processing accuracy, a new control method and control device of active maglev was put forward based on H ∞ mixed sensitivity. Firstly, a mathematical model was established among the electromagnetic force on the rotor, control current and position displacement of the rotor center. Secondly, the H ∞ mixed sensitivity control method was used, the selection method of weighting function was discussed and H ∞ robust controller was designed, the experimental results showed that for active maglev motorized spindle, the designed controller had better static and dynamic performance, position precision, so that the robustness of the motorized spindle equilibrium position was further improved, which met the requirement of high precision industrial process. DOI: http://dx.doi.org/10.11591/telkomnika.v11i9.3263

Investigation of Robust Combination Control for Elastic Vehicle Based on Reduced-Order Model

Putting forward with an integrated flight and aeroelasticity control method of elastic air vehicle and aiming at the reduction errors introduced during combination dynamic model reduction, the paper adopts mixed sensitivity H∞ control to design low-order combination control law that satisfies its robustness based on reduced-order model. Against to the wide reduced-order error bounds that may influence control performance, the two-circuit design method is used, and combined with inner-circuit suboptimal feedback design, error bounds of equivalent model are greatly narrowed. Without any orders extra added to the controllers, the outer-circuit robust controller designed on that basis will effectively improve the performance of the system, significantly superior to the single circuit design method. It is shown in simulation results that such low-order combination law will not only provide satisfactory robustness and performance, but will also effectively suppress the occurrence of servo flutter, while the greatly-reduced orders will be helpful for the realization of projects.

Integrated Rudder/Fin Concise Control Based on Frequency Domain Analysis

This paper describes a concise robust controller design of integrated rudder and fin control system in use of the closed loop gain shaping algorithm (CGSA) strategy. Compared with the arbitrary selection of weighting function in integrated rudder and fin H ∞ mixed sensitivity control design procedures, the CGSA methods provided a relatively more straightforward and concise design method. Simulations were described that the overall performance of each CGSA rudder and fin control loop and the interaction between them. Hence, it can be concluded that the integrated rudder and fin CGSA control scheme is very suitable to present and indeed feasible for future practical application. DOI: http://dx.doi.org/10.11591/telkomnika.v11i7.2834 Full Text: PDF

A colorimetric assay optimization for high-throughput screening of dihydroorotase by detecting ureido groups

Dihydroorotase (DHOase) is the third enzyme in the de novo pyrimidine biosynthesis pathway and is a potential new antibacterial drug target. No target-based high-throughput screening (HTS) assay for this enzyme has been reported to date. Here, we optimized two colorimetric-based enzymatic assays that detect the ureido moiety of the DHOase substrate, carbamyl-aspartate (Ca-asp). Each assay was developed in a 40-μl assay volume using 384-well plates with a different color mix, diacetylmonoxime (DAMO)–thiosemicarbazide (TSC) or DAMO–antipyrine. The sensitivity and color interference of both color mixes were compared in the presence of common HTS buffer additives, including dimethyl sulfoxide, reducing agents, detergents, and bovine serum albumin. DAMO–TSC (Z′-factors 0.7–0.8) was determined to be superior to DAMO–antipyrine (Z′-factors 0.5–0.6) with significantly less variability within replicates. An HTS pilot screening with 29,552 compounds from four structurally diverse libraries confirmed the quality of our newly optimized colorimetric assay with DAMO–TSC. This robust method has no heating requirement, which was the main obstacle to applying previous assays to HTS. More important, this well-optimized HTS assay for DHOase, the first of its kind, should make it possible to screen large-scale compound libraries to develop new inhibitors against any enzymes that produce ureido functional groups.

Voltage Control of Multiterminal VSC-HVDC Transmission Systems for Offshore Wind Power Plants: Design and Implementation in a Scaled Platform

This paper deals with multiterminal voltage source converter (VSC) HVDC transmission systems for the connection of offshore wind power plants to the main land ac grid. A droop-based control scheme is considered. The droop controllers have been designed base on a mixed sensitivity criterion by solving a convex optimization problem with linear matrix inequalities. The system is analyzed by means of simulations and experimentally in a scaled platform. Simulations show the control performance during a wind speed change and a voltage sag in the main ac grid. Experimental results include wind power changes (increase and decrease) and an eventual VSC loss (both considering grid-side and wind farm VSC loss). In all the cases, the simulation and the experimental results have shown a good system performance.

Atopy phenotypes in the Childhood Asthma Prevention Study (CAPS) cohort and the relationship with allergic disease

Atopy in early life is heterogeneous in timing of onset, remission and persistence and in the nature of specific sensitization to allergens. However, this heterogeneity is not well characterized. Our aim was to define longitudinal phenotypes of atopy between ages 1.5 and 8years, and to assess the relationship of the atopy phenotypes to the risk of asthma, eczema and rhinitis at 8years of age. We used latent class analysis (LCA) to define atopy phenotypes using data from skin prick tests that were performed at 1.5, 3, 5 and 8years in participants in the Childhood Asthma Prevention Study (CAPS). Four phenotypes were defined: late mixed inhalant sensitization; mixed food and inhalant sensitization; house dust mite (HDM) monosensitized; and no atopy. All three atopic phenotypes were associated with asthma, eczema and rhinitis, but the strongest association, particularly for asthma, was with the mixed food and inhalant sensitization phenotype. We have used a LCA model to define atopy phenotypes empirically. The finding of a strong association between the mixed food and inhalant sensitization class and the presence of asthma and poor asthma control at age 8years implies that food sensitization in early life may be of greater significance for subsequent risk of asthma than previously thought.