Closed-loop Control Configurations Research Articles

Development of an innovative test machine for tyre, wheel and suspension systems for automotive and industrial vehicles

Reliability and efficiency of automotive and industrial vehicles are strongly affected by the behaviour of the components involved in the interaction with the ground. For this reason, components like tyres, wheels and suspension systems are physically tested, for performance and durability assessment. Anyway, standard test machines are generally designed for testing only one specific component.The aim of this work is the design of an innovative test machine, able to perform different kinds of tests, for tyre, wheel and suspension system components, on a unique bench. The machine is a flat track type, better fit than traditional drum types in simulating real tyre-to-ground contact conditions. The core of the machine is a Gough-Stewart platform, where the flat track is fixed, which is moved by six hydraulic actuators to reproduce multiple work configurations, for extended time periods or numerous test block repetitions. After the preliminary design phase, the machine components were subjected to topology optimization and modal analysis by FEM, to reduce weights and avoid any issues related to the expected working frequencies. Given the quality of the results achieved, currently, the software design for closed-loop control configuration is under development, for the machine prototype next construction.

Direct Power Based Control Strategy for DAB DC-DC Converter With Cooperative Triple Phase Shifted Modulation

The cooperative triple-phase-shifted modulation (CTPS) for the isolated dual-active bridge (DAB) DC-DC converter has the advantages of zero dual-DC side flow back currents and best current characteristics. However, the mathematical model and corresponding closed-loop control configuration of the DAB converter driven by CTPS are not presented so far. In order to solve this problem, in this paper, the average state space model of the DAB converter driven by CTPS is established for the first time. It is proven that the DAB converter driven by CTPS is a zero-order system and it is not necessary to construct an inner inductor current closed-loop control loop in the entire closed-loop control configuration of DAB converter. Furthermore, the average power model is derived. Two control strategies based on the resulted average power model when the DAB converter is connected to DC microgrid or a pure resistive load are proposed to realize the precise control of the transfer power or the output voltage, respectively. The detailed experimental results verify the correctness of the established mathematical model and the closed-loop control strategies.

Small-Signal Modeling and Closed-Loop Control of Bidirectional Buck-Boost Current-Fed Isolated DC–DC Converter

The bidirectional buck-boost current-fed isolated dc–dc converter (B3CFIdc) has the advantages of low current stress, high efficiency, and wide power/voltage conversion range. The linear models of buck mode and boost mode of B3CFIdc are originally derived using state-space averaging method. The dual-closed-loop control configuration with the inductor current and output voltage is designed. In order to ensure the stability of both operation modes at the same time, the parameters of the controllers are designed using the method of Hurwitz criterion plus frequency response. The asymptotic stability of the operating conditions with periodic switching between the two modes caused by the periodic fluctuation of input voltage is verified using the linear switching theory. The detailed experimental results verify the correctness of the built small-signal models and the feasibility of the designed closed-loop control configuration and the design rule of the controller parameters.

Fault-Tolerant Economic Model Predictive Control for Wind Turbines

The operational cost of wind turbines (WT) is remarkably incurred in fatigue loads induced by torsional vibration within the drive-train subsystem and fore-aft bending of the tower subsystem. Under closed-loop control configuration, actuator faults in pitch subsystem and converter subsystem proliferate these fatigue loads, thereby, severely affect the economic operation of WT. In this paper, we present a novel active fault-tolerant control (FTC) methodology for WT, which minimizes the economic cost of WT by achieving the two broad objectives: power maximization and fatigue reduction, possibly under the effect of torque bias faults in converters. The proposed FTC system is composed of two modules: fault detection and diagnosis (FDD), and controller reconfiguration (CR). We develop the CR module using a model-predictive control (MPC) technique where the primary issue is that the constraint set is not convex in decision variables. The novelty of the proposed scheme lies in transforming the original nonconvex optimization problem into a convex problem using some new decision variables. We also develop the FDD module using an unknown-input-residual generator and a suitably designed estimation filter to extract the complete information of the fault. This fault information is subsequently used to reconfigure in real-time the constraints of the MPC to ensure system availability. The effectiveness of the developed scheme is demonstrated on a 2-MW wind turbine system.

Enhanced control of activated sludge process using predetermined set-points

The performance of activated sludge process (ASP) is evaluated by the effluent quality which is determined by five different variables of the treated wastewater such as ammonia, total nitrogen, COD, BOD5 and TSS. To keep these five variables within the limits as per environmental regulations, nitrate and nitrite concentration (SNO) in the second anoxic reactor and the dissolved oxygen concentration (SO) in the last aerobic reactor of the ASP should be maintained at prescribed levels. To do that, a closed-loop control configuration is required and proper set-points for these closed-loop control configurations are needed. In this paper, the optimal values of controller set-points are determined for nitrogen removal in the activated sludge process. Effluent quality limits have been considered to evaluate the optimal set-points for the Indian climatic conditions. Once the optimal set-points are determined, PI controllers are used to control SNO in the second anoxic reactor and SO in the last aerobic reactor of the ASP. Further, feed-forward control is incorporated to minimize the effect of disturbances, which enters along with the influent. No case studies of BSM1 model have been reported in the literature for the Indian wastewater. In this work, the dynamic simulation of an activated sludge process is performed using the data collected from the sewage treatment plant, located in India. The results of the simulation showed that feed-forward with PI control strategy, ASP can be efficiently controlled without any effluent violations, when compared to BSM1.

Non-linear control of a hydraulic piezo-valve using a generalised Prandtl–Ishlinskii hysteresis model

The potential to actuate proportional flow control valves using piezoelectric ceramics or other smart materials has been investigated for a number of years. Although performance advantages compared to electromagnetic actuation have been demonstrated, a major obstacle has proven to be ferroelectric hysteresis, which is typically 20% for a piezoelectric actuator. In this paper, a detailed study of valve control methods incorporating hysteresis compensation is made for the first time. Experimental results are obtained from a novel spool valve actuated by a multi-layer piezoelectric ring bender. A generalised Prandtl–Ishlinskii model, fitted to experimental training data from the prototype valve, is used to model hysteresis empirically. This form of model is analytically invertible and is used to compensate for hysteresis in the prototype valve both open loop, and in several configurations of closed loop real time control system. The closed loop control configurations use PID (Proportional Integral Derivative) control with either the inverse hysteresis model in the forward path or in a command feedforward path. Performance is compared to both open and closed loop control without hysteresis compensation via step and frequency response results. Results show a significant improvement in accuracy and dynamic performance using hysteresis compensation in open loop, but where valve position feedback is available for closed loop control the improvements are smaller, and so conventional PID control may well be sufficient. It is concluded that the ability to combine state-of-the-art multi-layer piezoelectric bending actuators with either sophisticated hysteresis compensation or closed loop control provides a route for the creation of a new generation of high performance piezoelectric valves.

Tuning algorithms for fractional order internal model controllers for time delay processes

ABSTRACTThis paper presents two tuning algorithms for fractional-order internal model control (IMC) controllers for time delay processes. The two tuning algorithms are based on two specific closed-loop control configurations: the IMC control structure and the Smith predictor structure. In the latter, the equivalency between IMC and Smith predictor control structures is used to tune a fractional-order IMC controller as the primary controller of the Smith predictor structure. Fractional-order IMC controllers are designed in both cases in order to enhance the closed-loop performance and robustness of classical integer order IMC controllers. The tuning procedures are exemplified for both single-input-single-output as well as multivariable processes, described by first-order and second-order transfer functions with time delays. Different numerical examples are provided, including a general multivariable time delay process. Integer order IMC controllers are designed in each case, as well as fractional-order IMC controllers. The simulation results show that the proposed fractional-order IMC controller ensures an increased robustness to modelling uncertainties. Experimental results are also provided, for the design of a multivariable fractional-order IMC controller in a Smith predictor structure for a quadruple-tank system.

Performance Evaluation of Three PID Controller Tuning Algorithm on a Process Plant

Accurate tuning of controller in industrial process operation is prerequisite to system smooth operation which directly reduce process variability, improved efficiency, reduced energy costs, and increased production rates. Performance evaluation of a model based PID controller tuning algorithm on a chemical process plant is presented in this paper. The control action of three different PID controller tuning algorithms namely; Hagglund-Astrom, Cohen and Coon, and Ziegler-Nichols on the process plant was examined in a closed loop control configuration under normal operating condition and in the face of disturbance. LabVIEW software was used to model a chemical process plant from open loop control test data. The time domain response analysis of the controllers shows that each tuning algorithm exhibit different time response. Ziegler-Nichols algorithm shows the best performance with fastest rise time, settling time and was able to restore the system back to normal operating condition in a short time when subjected to disturbance compare to Cohen & Coon controller and Hagglund-Astrom algorithm settings.

ToMFIR-based incipient fault detection and estimation for high-speed rail vehicle suspension system

High requirements on safety and reliability of the high-speed railway vehicle suspension (HRVS) system demand accurate detection and estimation of various incipient faults as early as possible under closed-loop control configurations. Firstly, a dynamic model of the suspension system for a three-car CRH2 multiple unit is set up, under which the external disturbances (i.e., track irregularities) and the actuator faults are further modeled. Then, an improved total measurable fault information residual (ToMFIR) based fault detection and estimation method is proposed, in which the restriction on fault type in the original method is removed. Finally, the obtained theoretical results are applied to a CRH2 HRVS simulation system. Results show that the proposed method can detect and estimate several frequent incipient faults effectively, outperforming the conventional observer-based or output residual-based fault detection and estimation methods.

Control of CSR PWM Outer Current Loop Based on Fuzzy Algorithm

This paper expounds the double closed-loop control configuration which is composed by the AC inner current control loop and the DC outer current loop of the CSR PWM rectifier ,and the functions of the inner current loop and the outer current control loop are pointed out. To improve the control performance ,a current controller whose DC outer current loop is designed by the fuzzy algorithm is used. The DC outer current loop error fuzzy variable E’s membership functions is researched ,and also the Rate of change of the current error fuzzy variable EC and the fuzzy variable Δi which is exported by fuzzy controller. Their influences to the control performance are considered. After the simulation experiments, it shows that the DC outer current loop fuzzy control is feasible and effective. The performance of the outer current control loop can be improved.

Functional electrical stimulation-based cycling assisted by flywheel and electrical clutch mechanism: A feasibility simulation study

A new assist mechanism, represented by a flywheel and an electrical clutch, is developed and evaluated, in simulation studies, to assist paralysed legs during functional electrical stimulation (FES)-based cycling exercise in a closed-loop control configuration. The flywheel is engaged and disengaged, by the clutch, to assist or retard the cycling when necessary. The flywheel engages with the crank to absorb the surplus energy, produced by stimulating the leg, store it as kinetic energy and slow down the movement. Also, it engages again to use the same stored energy to assist the leg and speed up the cycling. A comparative assessment of FES-cycling, using fuzzy logic control, is carried out with and without the new assist mechanism. Clinically recorded data is used to derive a force-drop indicator for assessment purposes. Although the stimulation intensity is slightly increased, the indicator showed 14%–17% muscle fatigue delay with the new mechanism as compared with cycling without assistance. This mechanism is promoting prolonged FES-cycling and increased work rate for paraplegics by delaying the occurrence of muscle fatigue.

ChemInform Abstract: Synthetic Mammalian Gene Networks as a Blueprint for the Design of Interactive Biohybrid Materials

AbstractReview: 83 refs.

Synthetic mammalian gene networks as a blueprint for the design of interactive biohybrid materials

Synthetic biology aims at the rational design and construction of devices, systems and organisms with desired functionality based on modular well-characterized biological building blocks. Based on first proof-of-concept studies in bacteria a decade ago, synthetic biology strategies have rapidly entered mammalian cell technology providing novel therapeutic solutions. Here we review how biological building blocks can be rewired to interactive regulatory genetic networks in mammalian cells and how these networks can be transformed into open- and closed-loop control configurations for autonomously managing disease phenotypes. In the second part of this tutorial review we describe how the regulatory biological sensors and switches can be transferred from mammalian cell synthetic biology to materials sciences in order to develop interactive biohybrid materials with similar (therapeutic) functionality as their synthetic biological archetypes. We develop a perspective of how the convergence of synthetic biology with materials sciences might contribute to the development of truly interactive and adaptive materials for autonomous operation in a complex environment.

Optimal grade transition and selection of closed-loop controllers in a gas-phase olefin polymerization fluidized bed reactor

To satisfy the diverse product quality specifications required by the broad range of polyolefin applications, polymerization plants are forced to operate under frequent grade transition policies. Commonly, the optimal solution to this problem is based on the minimization of a suitable objective function defined in terms of the changeover time, product quality specifications, process safety constraints and the amount of off-spec polymer, using dynamic optimization methods. However, considering the great impact that a given control structure configuration can have on the process operability and product quality optimization, the time optimal grade transition problem needs to be solved in parallel with the optimal selection of the closed-loop control pairings between the controlled and manipulated variables. In the present study, a mixed integer dynamic optimization approach is applied to a catalytic gas-phase ethylene-1-butene copolymerization fluidized bed reactor (FBR) to calculate both the “best” closed-loop control configuration and the time optimal grade transition policies. The gPROMS/gOPT computational tools for modelling and dynamic optimization, and the GAMS/CPLEX MILP solver are employed for the solution of the combined optimization problem. Simulation results are presented showing the significant quality and economic benefits that can be achieved through the application of the proposed integrated approach to the optimal grade transition problem for a gas-phase polyolefin FBR.

A New Measurement System for Advanced Modelling and Identification for Robot Control

Abstract This paper presents a new real time position and orientation measurement system, based on the laser-tracking-principle for external dynamic measurements of robot behaviour in 6 degrees of freedom. The system uses a laser interferometer and highly accurate laser rotary encoders to determine the position of the robot’s end-effector. The orientation is measured using an advanced picture processing system. The described system allows measurements that help to improve the mechanical construction and the identification of the parameters of the internal model of the robot. Additionally since the position of the robot’s end-effector is computed in real time, it can be fed back to the robot’s motion controller resulting in a closed loop control configuration.

Aircraft Engine Control Mode Analysis

This paper describes the control mode analysis procedure that is used to establish closed-loop control requirements for advanced aircraft propulsion systems. The procedure utilizes anticipated variations in engine component performance, engine deterioration, and control tolerances in a statistical analysis to establish corresponding variations in engine output performance and safety parameters. Potential closed-loop control configurations are evaluated by this process, compared, and the best configuration selected for implementation into control law and schedule designs. A byproduct of the analysis is the establishment of engine design and performance margins. The paper will describe typical engine variational models used in this process, the General Electric COMET program designed to automate the analysis, and typical mode study results based on a current augmented turbofan engine.