Required Control Input Research Articles

Optimization-Free Fast Charging for Lithium-Ion Batteries Using Model Inversion Techniques

We propose a novel fast-charging control framework for lithium-ion (Li-ion) batteries that can leverage a class of models including the high-dimensional, electrochemical-thermal pseudo-two-dimensional model. The control objective is to find the highest battery current while fulfilling various operating constraints. Conventionally, computationally demanding optimization is needed to solve such a constrained optimal control problem when an electrochemical-thermal model is used, leading to practical difficulties in achieving low-cost implementation. Instead, this paper provides an optimization-free solution to Li-ion battery fast charging by converting the constrained optimal control problem into an output tracking problem with multiple tracking references. The required control input, i.e., the charging current, is derived by inverting the battery model. As a result, a nonlinear inversion-based control algorithm is obtained for Li-ion battery fast charging. Results from comparative studies show that the proposed controller can achieve performance close to nonlinear model predictive control but at significantly reduced computational costs and parameter tuning efforts.

A Quasi-Resonant Extended State Observer-Based Predictive Current Control Strategy for Three-Phase PWM Rectifier

In this letter, a quasi-resonant extended state observer-based predictive current control (QRESO-based PCC) strategy is proposed for three-phase pulse width modulation (PWM) rectifier. Specifically, the QRESO is utilized to estimate the predictive value of system total disturbance and grid current at time instant <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</i> +1 in the stationary <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">αβ</i> frame, and the required control input at time instant <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</i> +1 is then calculated based on the principle of deadbeat predictive control. The proposed control scheme can achieve robust control against to the electrical parameter variation, accommodate the measurement noise, and also assure the satisfactory steady-state and dynamic performance for the PWM rectifier. Besides, the stability analysis of QRESO and the whole current close-loop control system with the consideration of QRESO in the discrete-time domain are presented. Finally, several hardware-in-the-loop test results of the proposed control strategy are provided and compared with the model free predictive current control based on linear extended state observer and the generalized integrator-extended state observer-based PCC strategy, which validate the effectiveness and superiority of proposed QRESO-based PCC strategy.

Optimal Demand Response in a Residential PV Storage System Using Energy Pricing Limits

This article presents an optimal demand response (DR) control for a residential photovoltaic (PV) storage system using energy pricing limits. Unlike the existing literature, both energy buying and selling prices are considered in DR application for reducing the energy cost of the system. A method for determining buying price and selling price limits of the day using day-ahead predictions of energy price, load demand, and PV power profiles is proposed. To further reduce the energy cost of the system subbuying price limit is considered. A rule-based DR control for minimizing the energy cost of the system is proposed. The rules are formulated such that energy buying price and selling prices are limited to their corresponding price limits of the day with the flexible day-to-day management of battery energy storage system. For obtaining optimal results with rule-based control, required control inputs are determined optimally using genetic algorithm. The proposed method is tested in MATLAB. It is observed that energy cost savings of 34.09% and 5.4% are obtained on the day of more PV energy availability and less PV energy availability, respectively, based on the day-ahead operation. Further, the impact of uncertainties on the proposed DR control is discussed for real-time operation of the system.

Algebraic Criteria on Controllability and Positive-Controllability of Discrete-Time Bilinear Systems: Seeking Nonzero Entries

In this article, we consider controllability of discrete-time bilinear systems. A classical sufficient condition was obtained in this journal in 1973, which, unfortunately, is not algebraically verifiable, and the required control inputs to achieve state transition are unknown. However, based on a recently established notion, near-controllability, we propose a seeking nonzero entries approach to derive fully algebraically verifiable controllability criteria for discrete-time bilinear systems. More specifically, by our approach, the verification of controllability of the systems is transformed into the problem of seeking nonzero entries of a sequence of matrices generated by the two system matrices. In addition, the control inputs steering the controllable systems between any given pair of states can be easily computed by proposing two algorithms based on near-controllability. As applications, the seeking nonzero entries approach is generalized to construct arbitrary-finite-dimensional controllable discrete-time bilinear systems and also to prove positive-controllability of discrete-time bilinear systems, where algebraic criteria are obtained by the root locus theory and positive-near-controllability that is a new notion introduced in this article. Examples are provided to illustrate the obtained algebraic controllability criteria and algorithms.

Iterative feedforward control of toolface orientation with simulation and laboratory case studies

During slide drilling with a bent motor assembly, accurate toolface setting and control are critical challenges, and the performance depends a lot on the directional drillers' experience. An efficient and reliable controller is therefore needed to eliminate the variability in performance between drillers. However, low sampling frequency and large time delays make common feedback controllers often inoperative. In this paper, a model-based iterative feedforward controller is proposed, which makes use of a validated drillstring dynamics model to predict required control inputs. Axial and rotational movements are considered in the dynamics model, and a distributed nonlinear friction term is used. To remove the uncertainty within the model-based controller, a method of estimating section-wise friction parameters using surface torque curve and toolface orientation measurement is presented. Iterative execution of the proposed feedforward control is required to make sure that the control goal is achieved. Finally, laboratory experiments are designed to validate the proposed feedforward controller. Both simulation and experiment results demonstrate that the designed controller can achieve desired toolface orientation with bit off-bottom or on-bottom within a short time. The proposed method can save time in toolface setting, and further reduce the cost of directional drilling.

Optimally designed Lyapunov–Krasovskii terminal costs for robust stable–feasible model predictive control of uncertain time-delay nonlinear dynamical systems

This article details a new Model Predictive Control algorithm ensuring robust stability and control feasibility for uncertain nonlinear multi-input multi-output dynamical systems considering uncertain time-delay effects. The proposed control algorithm is based on construction of a Lyapunov–Krasovskii functional as terminal cost. Incorporation of this terminal cost into the Model Predictive Control optimization problem and calculation of the associated admissible set result in robust feasibility and robust stability of closed-loop system in presence of uncertain time-delay effects and bounded disturbance signals. The Lyapunov–Krasovskii functional term is constructed with respect to predicted sliding functions over the prediction horizon and considers the effects of dynamical variations over the prediction horizon in generation of control inputs. As dynamical variations are investigated in a sample-to-sample basis, feasible sliding regions are updated at each sample as well. Finally, based on expression of sliding functions as a combination of dynamical variations and input-based terms, required control inputs are calculated in the admissible bound by the optimization algorithm. Construction of control scheme on this basis permits straightforward calculation of robust stability and feasibility conditions for a general class of uncertain nonlinear system in finite prediction horizon whereas in the previous works, often-restrictive conditions were considered for the investigated dynamical systems. Numerical illustrations indicate precision and efficiency of control algorithm and improved stability and convergence rate for multivariable nonlinear dynamical systems considering uncertain time-delay effects. Finally, hardware-in-the-loop implementation indicates applicability of the proposed scheme in real-time control applications particularly in case appropriate compromises between optimality and calculation speed are considered.

A Simulated Inverted Pendulum to Investigate Human Sensorimotor Control.

Sensorimotor control regulates balance and stability as well as adaptation to the external environment. We introduce the use of a simulated inverted pendulum to study human sensorimotor control, demonstrating that this system introduces similar control challenges to human subjects as a physical inverted pendulum. Participants exhibited longer stabilization of the system as the pendulum length between the hand and the center of mass increased while the required control input varied in a non-monotonic, yet predictable manner. Finally, we show that the experimental results can be modelled as a PD controller with a time delay of $\tau = 140$ ms, matching the human visuomotor delay. Our results provide evidence of the importance of vision in a control of unstable systems and serve as a proof of concept of a simulated inverted pendulum.

Comparative performances of synchronisation between different classes of chaotic systems using three control techniques

This paper puts forward the comparative performances for synchronisation between (i) systems from different chaotic system families, (ii) systems from the Unified Chaotic System (UCS) family, (iii) a hyperchaotic and a chaotic systems and (iv) identical chaotic systems. Three different well-known control techniques, i.e. Nonlinear Active Control (NAC), Sliding Mode Control (SMC) and Adaptive Control (AC) are used for synchronisation between various pairs of chaotic and/or hyperchaotic systems. Performances of NAC, SMC and AC techniques are investigated and compared with synchronisation of different pairs of chaotic systems based on the error dynamics and required control inputs. The integral square error and required control energy measures are considered for comparison. Finally, a generalised view on the use of the control techniques for synchronisation is finally proposed. Moreover, a new chaotic system is proposed and its qualitative analysis is done to illustrate the chaotic behaviour of the system. The new system is used as an example of synchronisation. MATLAB simulation results are presented which reflect the successful achievement of the objectives.

Analysis of the crash of a transport aircraft and assessment of fuzzy-logic stall recovery

A turboprop transport Flight Data Recorder data indicates that attempt to recover from the stalled conditions has failed, even though the pitch angle is continuously pushed nose-down in accordance with the published stall-recovery technique. The present study is to examine the reasons for the angle of attack being increased in the first place and not being reduced after stall, even though the longitudinal control is set to nose-down. Fuzzy Logic models are used to preserve nonlinear and unsteady aerodynamic effects. It is found that the increasing angle of attack is initially caused by the nose-up pitching moment due to inertial coupling. In the subsequent nose-down control attempt for stall recovery, the stall angles of attack are still increasingly higher because the pitch rate relative to the rotating axes stays mostly positive. The present simulation study is based on a new method to be called “Fuzzy-Logic Dynamic Inversion,” where desired dynamics with reduced Euler angles and angular rates are specified; while the required control inputs in elevator, aileron and rudder are determined, all through Fuzzy Logic models. Results in elevator, aileron and rudder controls are illustrated to demonstrate the possibility of stall recovery and accident prevention. It is shown that if at the first sign of stall in icing and crosswind flight conditions, and the landing is aborted, stall recovery is possible by applying proper control inputs simultaneously about three control axes to reduce the moments of inertial coupling and the roll and pitch angles.

Incipient Actuator Fault Handling in Nonlinear Model Predictive Control

This paper presents a reconfigurable nonlinear model predictive control (NMPC) scheme for handling of incipient actuator faults in nonlinear plants. The scheme seeks to ensure recoverability from an incipient actuator fault in plants where the input redundancy is insufficient to stabilize the faulty system at the nominal operating point, thereby requiring transition to a safe control-invariant set. To this end, the proposed scheme takes into account an estimate of the decrease in remaining actuator capacity from the time of detection of an incipient actuator fault, and minimizes the required control input to steer the plant to the safe set. We provide conditions for stability and fault recoverability of the proposed scheme, and demonstrate its applicability on a numerical example with two CSTRs in series.

Optimized and decentralized pulse control of seismically excited steel structures

The idea of decomposing a centralized complicated system into several synchronous decentralized subsystems has been resulted into the development of decentralized control methods. In this study, a decentralized pulse control scheme is presented based on the theory of Inclusion Principle for steel systems comprising a multi-overlapping structure. The proposed control algorithm is basically an active control system that generates corrective pulses at each moment when the displacement or acceleration exceeds the predefined threshold. In order to evaluate the performance of proposed control system, a numerical study is conducted. The control system is implemented for two linear structural models of five- and twenty-story steel buildings. An optimization algorithm (PSO) is also used to determine the locations of required control inputs in the 20-story building. The results show that the proposed algorithm can substantially mitigate the structural response under different earthquake records (for 5-story model) and different subsystem configurations (for 20-story model).

A criterion for optimal sensor placement for minimizing spillover effects on optimal controllers

Optimal control techniques (LQG, H∞, etc.) offer several advantages for active vibration control, such as possibility of trade-off between achievable vibration attenuation and required control inputs, simultaneous suppression of multiple modes, unified and systematic controller design procedure for MIMO systems. However, a major limitation in their application has been the phenomena of spillover. For optimal controllers robustness to spillover is achieved by rolling-off controller response. In this paper, a novel criterion of sensors placement to minimize roll-off requirement, for given actuator locations, is proposed. As an illustration H∞ control is applied for suppressing first two modes of a slewing spacecraft. Comparison of results obtained for sensor location based on proposed criterion with those of collocated sensor location showed: (a) for a given controller order, performance characteristics similar to collocated control with improved robustness to spillover can be obtained by using the proposed criterion of sensor placement; (b) with proposed placement criterion robustness to spillover can be maintained with lower order controller as compared with the minimum controller order required for collocated control.

A root locus approach to near-controllability of a class of discrete-time bilinear systems with applications to Hermitian matrices

In this paper, a root locus approach is developed to investigate near-controllability of a class of discrete-time bilinear systems and new representations of Hermitian matrices are derived. The root locus approach has three merits: firstly, it makes the proof of near-controllability of the systems more simple; secondly, the control inputs that achieve the state transition can be computed in an explicit way and, meanwhile, the number of the required control inputs can be fixed; and thirdly, it leads to a more general conclusion on near-controllability. A numerical example is given to demonstrate the effectiveness of the root locus approach. Finally, the more general conclusion yields new representations of Hermitian matrices.

Global Adaptive Regulation of Uncertain Nonlinear Systems in Output Feedback Form

Minimum phase uncertain nonlinear systems in output feedback form are considered: they are subject to disturbances and/or uncertainties and are required to track reference signals. Both disturbances and references are generated by an exosystem whose model and order are uncertain. Assuming that the regulator problem has a solution, but with no a priori assumption on the required control input (e.g. no `immersion' assumption), a global robust error feedback regulator is explicitly computed which includes an adaptive internal model and a nonlinear stabilizing control, on the basis of known bounding functions for the uncertain system nonlinearities. The regulation error tends to a residual set which decreases as the reference input modeling error due to the internal model choice decreases. If the adaptive internal model can generate the required unknown control input, global asymptotic regulation is achieved.

Output transient trajectory shaping control for a class of nonlinear systems

SUMMARYThis paper presents a transient trajectory shaping (TTS) control method for the SISO strict feedback nonlinear systems. The TTS control refers to explicitly constraining the system output tracking error transient trajectories within predesigned time‐varying boundaries while they are converging to equilibrium. By this method, the boundaries of system output transient trajectories can be designed a priori according to the system transient control performance requirements in both symmetric and asymmetric ways. With a class of time‐varying boundary functions, control laws can be devised by utilizing the enhanced differential unbounded function techniques. Such control laws can ascertain that the system output tracking errors travel within their respectively predesigned time‐varying boundaries while converging to origin. To handle the control input exaggeration issue in TTS, input constraint control techniques are proposed to effectively reduce the required control input magnitude for second‐order systems. A numerical example is utilized to show the effectiveness of the proposed TTS control methods. Copyright © 2013 John Wiley &amp; Sons, Ltd.

Fuzzy compensator design against windup of a magnetic actuator during milling operation

A fuzzy anti-windup compensator is proposed and applied to the embedded cylindrical-array magnetic actuator to ensure the superior performance of spindle position regulation for milling machines under actuator saturation. Since embedded cylindrical-array magnetic actuator is a type of active magnetic bearing, the supplied coil current and the induced magnetic force are both limited by the maximum current and power output of the active magnetic bearing and the associated amplifier. Once the magnetic actuator is saturated, the required control input cannot be realized by an embedded cylindrical-array magnetic actuator and may lead to drastic tremble of the spindle position. In this work, an anti-windup compensator, based on a fuzzy logic algorithm, is therefore proposed to rectify the control input to an embedded cylindrical-array magnetic actuator. By employing commercial software, MATLAB/Simulink, and signal processing interface, Module DS1104 by dSPACE, the efficacy of the fuzzy anti-windup compensation is practically verified by intensive experiments.

Anti-windup embedded magnetic actuator applied for near-high-speed milling

A fuzzy anti-windup (AW) compensator is proposed and applied to the embedded cylindrical-array magnetic actuator (ECAMA) to ensure the superior performance of spindle position regulation for milling machines under actuator saturation. Since ECAMA is a type of active magnetic bearing (AMB), the supplied coil current and the induced magnetic force are both limited by the maximum current and power output of the AMB and the associated amplifier. Once the magnetic actuator is saturated, the required control input cannot be realized by ECAMA and may lead to drastic tremble of spindle position. In this work, an AW compensator, based on fuzzy logic algorithm, is therefore proposed to rectify the control input to ECAMA. By employing commercial software MATLAB/Simulink and signal processing interface, Module DS1104 by dSPACE, the efficacy of the fuzzy AW compensation is practically verified by intensive experiments.

Bicycle Design: A different approach to improving on the world human powered speed records

The current International Human Powered Vehicle Association world records for faired bicycles stand at 133.284km/h for the 200m flying start speed record and 91.562km for the hour record. Traditionally the recumbent bicycles that have been developed for breaking one of either of these records have been optimized around a specific, relatively small rider, enabling the overall size to be kept small. Creating the smallest frontal area possible and optimal aerodynamic shape were then the design goals. This paper discusses the development of the Velox recumbent bicycle, which has been designed using another approach. The power required to break either of the records depends mostly on air resistance. Therefore small riders have the advantage of allowing for smaller frontal areas, whilst larger riders are able to provide more power. Performance optimization, lead to a design based around an average 1.95m tall male rider for Velox. The aerodynamic shape of Velox was then developed around the above criterion and designed with CFD and validated with wind tunnel and road tests. Essential for the rider's performance is that the rider feels comfortable whilst riding the bicycle. Therefore the uncontrolled lateral dynamics and the required rider steer control input were investigated. The bicycle's geometry was optimized for low speed stability and the required control input.

Anti-Windup Compensation for Embedded Cylindrical-Array Magnetic Actuator

An Anti-Windup (AW) compensator is applied to the Embedded Cylindrical-Array Magnetic Actuator (ECAMA) to sustain the performance of spindle position regulation for milling machines under actuator saturation. Since ECAMA is a type of Active Magnetic Bearing (AMB), the maximum supplied coil current and the induced magnetic force are both limited by their extrema. Once the magnetic actuator is saturated, the required control input cannot be realized by the actuator as long as the magnitude of control input exceeds the upper limit of the actuator output. In this work, an AW compensator is therefore proposed and employed to compensate the output of PID controller to prevent saturation of ECAMA. By employing commercial software MATLAB/Simulink and signal processing interface, Module DS1104 by dSPACE, the efficacy of the AW compensation is practically verified by intensive experiments.

Robust Adaptive Regulation by Output Error Feedback for Uncertain Nonlinear Systems

AbstractMinimum phase uncertain nonlinear systems in output feedback form are considered: they are subject to disturbances and/or uncertainties and are required to track reference signals. Both disturbances and references are generated by an exosystem whose parameters are uncertain. Under the assumption that the regulator problem has a solution, but with no a priori assumption on the required control input (e.g. no ‘immersion’ assumption), a global robust error feedback regulator is designed. If its adaptive internal model can generate the required control input global asymptotic regulation is achieved, otherwise the regulation error tends to a residual set which decreases as the reference input modeling error decreases.