Multi-output Control Research Articles

Robust Air-to-Fuel Ratio and Boost Pressure Controller Design for the EGR and VGT Systems Using Quantitative Feedback Theory

This paper describes robust multi-input, multi-output controller for the exhaust gas recirculation (EGR) and variable geometry turbocharger (VGT) systems of passenger car diesel engines. The air-to-fuel ratio of the exhaust gas and boost pressure of the intake manifold were selected as performance indicators in this paper. To enable the online calibration of the controller, proportional-integral-derivative (PID) was used as a feedback controller. Using quantitative feedback theory (QFT), two control loops for air-to-fuel ratio and boost pressure were independently designed with linearized models and parameter uncertainties. The prefilters and PID gains of two control loops were designed for satisfying required robust stability and tracking performance using the QFT design framework. Furthermore, the problems originated from the cross-coupled dynamics between the EGR and VGT systems were mitigated by a static decoupler. Using the proposed design steps, PID and decoupler gains of the representative 15 engine operating points which are mainly used in New European Driving Cycle were obtained. The proposed controller was validated through various test conditions of engine experiments. From the step responses and transient experiments, it was demonstrated that the required robustness and tracking performance were successfully achieved.

Multi-input Multi-output Semi-active Fuzzy Control of Seismicexcited Building with Evolutionary Optimization Algorithms

In this study, a multi-input multi-output (MIMO) semi-active fuzzy control algorithm has been developed for vibration control of a seismically excited building structure. The MIMO fuzzy controller was optimized by evolutionary genetic algorithm. For numerical simulation, a five-story example building structure is used and two MR dampers are employed as semiactive control devices. For comparison purpose, a clipped-optimal control strategy based on acceleration feedback is employed for controlling MR dampers to reduce structural responses due to seismic loads. Numerical simulation results show that the MIMO fuzzy control algorithm can provide superior control performance to the clipped-optimal control algorithm. When the design method proposed in this study is applied, Pareto optimal solutions can be obtained in single optimization run. Therefore, an alternative solution can be easily selected by an engineer.

Enhanced ground-based vibration testing for aerodynamic environments

Typical methods of replicating aerodynamic environments in the laboratory are generally poor. A structure which flies “freely” in its normal operating environment, excited over its entire external surface by aerodynamic forces and in all directions simultaneously, is then subjected to a vibration test in the laboratory whilst rigidly attached to a high impedance shaker and excited by forces applied through a few attachment points and in one direction only. The two environments could hardly be more different. The majority of vibration testing is carried out at commercial establishments and it is understandable that little has been published which demonstrates the limitations with the status quo.The primary objective of this research is to do just that with a view to identifying significant improvements in vibration testing in light of modern technology. In this paper, case studies are presented which highlight some of the limitations with typical vibration tests showing that they can lead to significant overtests, sometimes by many orders of magnitude, with the level of overtest varying considerably across a wide range of frequencies. This research shows that substantial benefits can be gained by “freely” suspending the structure in the laboratory and exciting it with a relatively small number of electrodynamic shakers using Multi-Input–Multi-Output (MIMO) control technology. The shaker configuration can be designed to excite the modes within the bandwidth utilising the inherent amplification of the resonances to achieve the desired response levels. This free-free MIMO vibration test approach is shown to result in substantial benefits that include extremely good replication of the aerodynamic environment and significant savings in time as all axes are excited simultaneously instead of the sequential X, Y and Z testing required with traditional vibration tests. In addition, substantial cost savings can be achieved by replacing some expensive large shaker systems with a few relatively small shaker systems.

Integrated HCCI Engine Control Based on a Performance Index

The integrated control of a homogenous charge compression ignition (HCCI) combustion phasing, load, and exhaust aftertreatment system is essential for realizing high-efficient HCCI engines, while maintaining low hydrocarbon (HC) and carbon monoxide (CO) emissions. This paper introduces a new approach for integrated HCCI engine control by defining a novel performance index to characterize different HCCI operating regions. The experimental data from a single cylinder engine at 214 operating conditions is used to determine the performance index for a blended fuel HCCI engine. The new performance index is then used to design an optimum reference trajectory for a multi-input multi-output HCCI controller. The optimum trajectory is designed for control of the combustion phasing and indicated mean effective pressure (IMEP), while meeting catalyst light-off requirements for the exhaust aftertreatment system. The designed controller is tested on a previously validated physical HCCI engine model. The simulation results illustrate the successful application of the new approach for controller design of HCCI engines.

Centralised Multi-input Multi-output Controllers for Non-minimum Phase Systems

In the present work, the method of designing the centralised controllers for the minimum phase multivariable systems proposed by Vijay Kumar et al. is extended to non-minimum phase systems. The controller is designed based on the direct synthesis method. Inverse of process transfer function matrix in the direct synthesis method is approximated based on relative gain array concept. Maclaurin's series is applied to reduce it to a standard proportional and integral form. The method is further improved by using equivalent transfer function matrix derived from relative normalised gain array and relative average residence time array as process inverse transfer function matrix. Effective transfer function is the equivalent transfer function of gij(s) when all other loops are closed. The desired closed-loop transfer function should contain the process right half plane zero. Quadruple tank process with non-minimum phase behaviour is considered to analyse the performance of the proposed centralised controllers. The performance of centralised controllers is compared with a recently proposed decentralised controller.

Distributed H ∞ PID Feedback for Improving Consensus Performance of Arbitrary-delayed Multi-agent System

The H ∞ proportional-integral-differential (PID) feedback for arbitrary-order delayed multi-agent system is investigated to improve the system performance. The closed-loop multi-input multi-output (MIMO) control framework with the distributed PID controller is firstly described for the multi-agent system in a unified way. Then, by using the matrix theory, the prescribed H ∞ performance criterion of the multi-agent system is shown to be equivalent to several independent H ∞ performance constraints of the single-input single-output (SISO) subsystem with respect to the eigenvalues of the Laplacian matrix. Subsequently, for each subsystem, the set of the PID controllers satisfying the required H ∞ performance constraint is analytically characterized based on the extended Hermite-Biehler theorem. Finally, the three-dimensional set of the decentralized H ∞ PID control parameters is derived by finding the intersection of the H ∞ PID regions for all the decomposed subsystems. The simulation results reveal the effectiveness of the proposed method.

Performance-controlled server consolidation for virtualized data centers with multi-tier applications

Modern data centers must provide performance assurance for complex system software such as multi-tier web applications. In addition, the power consumption of data centers needs to be minimized to reduce operating costs and avoid system overheating. Various power-efficient performance management strategies have been proposed based on dynamic voltage and frequency scaling (DVFS). Virtualization technologies have also made it possible to consolidate multiple virtual machines (VMs) onto a smaller number of active physical servers for even greater power savings, but at the cost of a higher overhead. This paper proposes a performance-controlled power optimization solution for virtualized server clusters with multi-tier applications. While most existing work relies on either DVFS or server consolidation in a separate manner, our solution utilizes both strategies for maximized power savings by integrating feedback control with optimization strategies. At the application level, a novel multi-input–multi-output controller is designed to achieve the desired performance for applications spanning multiple VMs, on a short time scale, by reallocating the CPU resources and conducting DVFS. At the cluster level, a power optimizer is proposed to incrementally consolidate VMs onto the most power-efficient servers on a longer time scale. Empirical results on a hardware testbed demonstrate that our solution outperforms pMapper, a state-of-the-art server consolidation algorithm, by having greater power savings and smaller consolidation overheads while achieving the required application performance. Extensive simulation results, based on a trace file of 5415 real servers, demonstrate the efficacy of our solution in large-scale data centers.

New Extendable Single-Stage Multi-input DC–DC/AC Boost Converter

This paper presents a new extendable single-stage multi-input dc-dc/ac boost converter. The proposed structure comprises of two bidirectional ports in the converter's central part to interface output load and battery storage, and several unidirectional input ports to get powers from different input dc sources. In fact, the proposed topology consists of two sets of parallel dc-dc boost converters, which are actively controlled to produce two independent output voltage components. Choosing two pure dc or two dc-biased sinusoidal values as the converter reference voltages, situations of the converter operating in two dc-dc and dc-ac modes are provided, respectively. The proposed converter utilizes minimum number of power switches and is able to step up the low-level input dc voltages into a high-level output dc or ac voltage without needing any output filter. The converter control system includes several current regulator loops for input dc sources and two voltage regulator loops for generating the desired output voltage components, resulting in autonomously charging/discharging the battery to balance the power flow. Due to the converter inherent multi-input multioutput control system, the small signal model of the converter is extracted and then the pole-placement control strategy via integral state feedback is applied for achieving the converter control laws. The validity and effectiveness of the proposed converter and its control performance are verified by simulation and experimental results.

The Design and Performance of Feedback Controllers for the Attenuation of Road Noise in Vehicles

Active noise control systems offer a potential method of reducing the weight of acoustic treatments in vehicles and, therefore, of increasing fuel efficiency. The commercialisation of active noise control has not been widespread, however, partly due to the cost of implementation. This paper investigates the design and performance of feedback road noise control systems, which could be implemented cost-effectively by using the car audio loudspeakers as control sources and low-cost microphones as error sensors. Three feedback control systems are investigated, of increasing complexity: a single-input single-output (SISO) controller; a SISO controller employing weighted arrays of error sensors and control sources; and a fully-coupled multi-input multi-output (MIMO) controller. For each of the three controllers robustness and disturbance enhancement constraints are defined and by formulating the three controllers using an Internal Model Control (IMC) architecture, and using frequency discretisation, the constrained optimisation problems are solvable using sequential quadratic programming. The performance of the three controllers and the associated design methods are first evaluated in a simulated environment, which allows the physical limits on performance to be understood. Finally, to validate the results in the simulated environment, the performance of the three controllers has been calculated using data measured in a car cabin and it has been shown that the fully-coupled MIMO controller is able to achieve significant low frequency road noise control, at the expense of increased implementation complexity compared to the SISO and SISO weighted transducer arrays feedback controllers

Polynomial accessibility condition for the multi-input multi-output nonlinear control system

The paper presents a computation-oriented necessary and sufficient accessibility condition for the set of nonlinear higher- order input-output differential equations. The condition is presented in terms of the greatest common left divisor of two polynomial matrices, associated with the system of input-output equations. The basic difference from the linear case is that the elements of the polynomial matrices belong to a non-commutative polynomial ring. The condition found provides a basis for finding the accessible representation of the set of input-output equations, which is a suitable starting point for the construction of an observable and accessible state space realization. Moreover, the condition allows us to check the transfer equivalence of two nonlinear systems.

Advanced Control Education: Optimal & Robust MIMO Control of a Flexible Beam Setup

This paper discusses and illustrates core aspects in control education (prerequisites, working conditions, course structure) necessary to empower students of general engineering disciplines to understand and apply advanced optimal and robust control concepts. The results of a master thesis on the robust and optimal control of a flexible beam laboratory setup are presented and related to the skills formed during the undergraduate studies. Optimal and robust control design methods are utilized for active damping of bending vibrations of a simply supported thin structural aluminium beam. For this purpose a multi-input multi-output (MIMO) control system setup is used, comprising four collocated piezo patch actuators and sensors acting in longitudinal direction. An electrodynamic shaker introduces a disturbance force in the direction of oscillation. The design plant is obtained by a measurement-data-driven system identification. Also, finite element based modelling is carried out. The suitability of Linear-Quadratic Gaussian (LQG) control with modal weighting, mixed-sensitivity ℋ∞ control and D(G)K-synthesized control for improving disturbance rejection of the experimental control system setup is investigated and compared.

Improved delay-dependent stability conditions for MIMO networked control systems with nonlinear perturbations.

This paper provides improved time delay-dependent stability criteria for multi-input and multi-output (MIMO) network control systems (NCSs) with nonlinear perturbations. Without the stability assumption on the neutral operator after the descriptor approach, the new proposed stability theory is less conservative than the existing stability condition. Theoretical proof is given in this paper to demonstrate the effectiveness of the proposed stability condition.

Multi-Input Multi-Output (MIMO) Control System with a State Equation for Fusion Reactors

Multi-Input Multi-Output (MIMO) Control System with a State Equation for Fusion Reactors

Multi-Input Multi-Output Control of Consumable DE-GMAW

A novel and high efficient consumable double-electrode gas metal arc welding (consumable DE-GMAW) method has been introduced. Because of the coupled welding parameters, a multi-input multi-output (MIMO) control scheme was proposed and tested, which controlled the bypass arc by adjusting the bypass wire feed speed, and controlled the base metal current by adjusting the bypass current. Then, the welding experiment has been carried out. The results showed that the MIMO control scheme was effective. The base metal current was controlled at a nearly constant level and the welding process was stable. Also a good weld appearance was obtained.

Nonlinear aeroservoelastic analysis of a controlled multiple-actuated-wing model with free-play

In this paper, the effects of structural nonlinearity due to free-play in both leading-edge and trailing-edge outboard control surfaces on the linear flutter control system are analyzed for an aeroelastic model of three-dimensional multiple-actuated-wing. The free-play nonlinearities in the control surfaces are modeled theoretically by using the fictitious mass approach. The nonlinear aeroelastic equations of the presented model can be divided into nine sub-linear modal-based aeroelastic equations according to the different combinations of deflections of the leading-edge and trailing-edge outboard control surfaces. The nonlinear aeroelastic responses can be computed based on these sub-linear aeroelastic systems. To demonstrate the effects of nonlinearity on the linear flutter control system, a single-input and single-output controller and a multi-input and multi-output controller are designed based on the unconstrained optimization techniques. The numerical results indicate that the free-play nonlinearity can lead to either limit cycle oscillations or divergent motions when the linear control system is implemented.

Actuator Limitations in Spatial Temperature Control of SOFC

A high performance multi-input multi-output feedback controller has been developed to minimize solid oxide fuel cell (SOFC) spatial temperature variation during load following. Cathode flow rate and its inlet temperature are used to minimize spatial temperature variations in the SOFC electrode electrolyte assembly for significant load perturbations. We focus on control design in the presence of nonideal actuation. This includes the effects of fuel processing delays, cathode inlet thermal delays, and parasitic power associated with the blower supplying air to the cathode. The controller, based on energy-to-peak minimization synthesis, is applied to a dynamic model of an anode-supported coflow planar SOFC stack. The results indicate that many of the problems associated with realistic and imperfect actuation can be addressed with relatively standard control synthesis modifications, but fuel flow delays can compromise power following significantly. Finally, a strategy that relies primarily on partial internal reformation for power following addresses many of the difficulties associated with reformer delays.

Robust flutter suppression for a 2-dimensional wing-store system

In this paper, a new scheme is proposed to model the flow speed uncertainties in an aeroelastic system. Compared with the traditional method, the new scheme is based on a signal transformation so as to reduce the dimension of the mathematical model of the flow speed uncertainties. Thus, the robust flutter controller can be designed easily via the reduced-order model of the aeroelastic system. To illustrate the procedure of proposed scheme, the dynamic equation of a two-dimensional wing-store aero-servo-elastic system with flow speed uncertainties is modeled by using the proposed scheme. The aerodynamic forces of the wing section and the store are computed through the use of doublet lattice approach and slender-body aerodynamic theory, respectively. To suppress the flutter instability of the wing-store aeroelastic system with flow speed uncertainties, the trailing-edge control surface is used as a control input and a single-input and multi-output (SIMO) controller is designed via the robust control theory. Numerical results indicate that, with the proposed scheme, the robust flutter control law is efficient and the flutter boundary of aeroelastic system can be greatly expanded.

Overcoming passivity violations: closed‐loop stability, controller design and controller scheduling

Control of systems that have had their passive input–output map partially violated is the motivation of this study. The hybrid passivity/finite-gain systems framework is specifically well suited to systems that have experienced a passivity violation. The focus of this study is the extension and application of the hybrid passivity/finite-gain systems framework to a multi-input multi-output (MIMO) control problem. Calculation of the hybrid passivity/finite-gain parameters in a linear time-invariant (LTI) MIMO context is considered. Additionally, we show that a set of hybrid very strictly passive/finite-gain (VSP/finite-gain) controllers gain-scheduled in a particular way also possesses hybrid VSP/finite-gain properties. To synthesise hybrid VSP/finite-gain controllers a frequency-weighted optimal control scheme is used to parameterise controllers that are then constrained and optimised within a numerical optimisation framework. The theoretical contributions of this work are validated experimentally using a two-link flexible manipulator apparatus. Results highlight the utility of the hybrid passivity/finite-gain framework, the scheduling scheme and controller design method.

MIMO PREDICTIVE PID CONTROL: A PRACTICAL APPROACH FOR QUADRUPLE TANK

In this paper, predictive control has been implemented by several methods in a most simplified manner for quadruple tank system, i.e., a multi-input multi-output control problem. Quadruple tank system is a nonlinear system which can be adjusted to obtain two different class of system i.e., minimum and nonminimum phase, therefore tuning for each phase of system has to be tackled separately. Control system design has been obtained by manual proportional-integral controller, traditional generalized predictive control, predictive proportional-integral-derivative on the basis of generalized predictive control, predictive iterative learning control and finally adaptive predictive proportional-integral-derivative control has been developed successfully. Stability and performance of the each control system design has also been discussed.

Power Control for GPU Clusters in processing large-scale streams

Many emerging online data analysis applications require Large-scale streams data processing. GPU cluster is becoming a significantly parallel computing scheme to handling large-scale streams data tasks. However power optimization is a challenging issue. In this paper, we present a novel power consumption control model to shift power budge among nodes in the cluster based on their real workload needs, while capping redundancy energy and controlling the total power budge of the cluster to keep or below a constraint imposed by its power supplies. Our controller is very suitable to the dynamic workloads task model and designed based on an Multi-Input_Multi-Output control theory. We analyze the power consumption behaviors of GPU cluster and the variation of workload. The detailed control problem formulation is presented and analyzed in theory. We finally conduct simulation experiments on a physical cluster to compare our controller with two state-of-the-art controllers. The experimental results demonstrate that our proposed controller outperforms the other controllers by having more accurate control and more stability.