Design Procedure Of Control System Research Articles

ClosedLoop Control of Pulse-Density-Modulated Wireless Power Transfer with Fast MEPT

Efficient wireless power transfer (WPT) requires closedloop control to perform maximum efficiency point tracking (MEPT) against the dynamic changes of operating conditions. In this paper, we took the latest deltasigma pulse-density-modulated (PDM) WPT system as the plant and presented a systematic control design procedure. The WPT system was modeled by the reducedorder dynamic phasor method and further decoupled under the tuned condition. It was identified that the coupled resonators behave like a secondorder system, and its natural frequency is much lower than the resonant frequency. This was considered in the closedloop design to derive a suitable loop gain and ensure stability. The nonlinearity caused by the dualside PDM control is limited to a small inner loop so that the entire loop is linear and simple. Experimental results showed that the closedloop voltage regulation and MEPT took only about 10 ms after load stepping. The system DC output voltage was always tightly regulated, and the steadystate efficiency was very close to the theoretical maximum value under different coupling conditions.

Additive-state-decomposition-based model predictive tracking control for PMSM servo system with multiple disturbances

This paper presents an additive-state-decomposition-based model predictive tracking control and disturbance rejection method for a permanent magnet synchronous motor (PMSM) servo system subject to unknown parameter perturbations, unmodeled dynamics, and time-varying load torque. The basic idea of this method is to equivalently decompose the original system into a primary system for handling the tracking control subproblem and a secondary system for dealing with the robust stabilization subproblem. A model predictive controller is designed for the primary system to achieve high-accuracy tracking of the reference speed. As for the secondary system, a novel high-order generalized extended state observer (HGESO) is constructed to estimate the multiple disturbances simultaneously, and a state feedback control law incorporating a disturbance compensator is developed to eliminate the adverse effect of the multiple disturbances on the system output. By combining the control inputs of the two subsystems together, the control objectives of the original system can be achieved. Both the stability criterion and design procedure of the closed-loop control system are developed. Finally, hardware-in-the-loop-based comparative experiments are conducted to demonstrate that the proposed method effectively suppresses the influence of the multiple disturbances on motor speed tracking accuracy and that the control system has both satisfactory dynamic performance and robustness.

Model reference adaptive controllers with improved performance for applications in LCL-filtered grid-connected converters

This work presents a control strategy combining a direct Model Reference Adaptive Control (MRAC) with a robust state feedback for current control of grid-connected converters with LCL filters operating under grid impedance variations. The MRAC is based on a gradient law, providing properly current reference tracking and voltage disturbance rejection. The inclusion of a state feedback inner loop provides robust active damping of the filter resonance for an entire range of grid impedances. A systematic control design procedure is proposed, and the combination of both control actions in a multi-loop approach does not add significant computational complexity. The proposal allows to increase the MRAC gains adaptation dynamics, providing suitable responses under grid current reference variations and under typical grid voltage disturbances, including grid faults. Performance indexes as the grid-currents total harmonic distortion and the mean squared error are also improved. In addition, robust stability analysis based on Lyapunov functions are carried out for the inner control loop and for the outer control loop, considering the grid impedance uncertain and with unmodeled dynamics. The strategy is implemented in a commercial digital signal processor, and the compliance of the grid currents with the IEEE 1547 Std. is verified with controller hardware-in-the-loop and experimental results in a 5.4 kW prototype.

Transmission Power Policies for Energy-Efficient Wireless Control of Nonlinear Systems

We present an emulation-based controller and transmission policy design procedure for nonlinear wireless networked control systems. The objective is to ensure the stability of the closed-loop system, in a stochastic sense, together with given control performance, while minimizing the average power used for communications. The controller is designed by emulation, i.e., ignoring the network, and the transmission power is given by threshold policies. These policies involve waiting a given amount of time since the last successful transmission instant, as well as requiring that the measured wireless channel gain is above a given threshold, before attempting a new transmission. Two power control laws are investigated: i) a constant power and ii) a power level inversely proportional to the channel gain. We explain how to select the waiting time, the channel threshold and the power level to minimize the induced average communication power, while ensuring the desired control objectives.

Self-Learning MAV Under Safety-Guaranteed Flight Test Environment

This paper presents a novel methodology for designing the flight control system of a micro aerial vehicle (MAV); it allows the MAV to learn how to fly by itself, without the risk of damage. The proposed methodology uses a magnetic levitation–based safety-guaranteed flight test environment and deep reinforcement learning techniques to avoid the current problems in flight control system design procedures, such as the reality gap issue of simulations, and the safety issues inherent to real flight testing. The safety-guaranteed flight test environment was achieved using a developed magnetic suspension and balance system, which dynamically adjusts magnetic forces interacting with a magnetically levitated MAV. As a result, the MAV can perform in either a free-flight condition for reinforcement learning or can be constrained for safety. This learning environment was developed to permit safe reinforcement learning of MAV, since trial-and-error-based learning typically makes the MAV unstable. In this regard, the MAV can learn to fly by itself based on trial and error, by interacting with the emulated free-flight test environment. Notably, the entire learning process can be conducted without numerical models for both the MAV itself and the flight environment, and the safety of the MAV is guaranteed, even when attempting undesirable actions that might cause the model to become unstable. By avoiding the modeling errors typical of computational simulations and preventing the risk of damage in real flight tests, this approach could enhance the use of reinforcement learning in the development of advanced flight control systems.

Controller Design of an Active Front-End Converter Keeping in Consideration Grid Dynamic Interaction

This paper presents a systematic control design procedure for an active front-end (AFE) converter connected to a power electronics embedded grid. A parametric model of the grid is firstly identified using the AFE itself to excite the system. This model is then integrated with AFE one in order to obtain a global system representation. Subsequently, a globally optimized local controller is synthesised for the AFE keeping in consideration interaction between the converter and the grid. The proposed method is finally tested experimentally and its performance is compared with a traditional Proportional-Integral (PI) controller in a dq synchronous reference frame.

Barrier Lyapunov function-based tracking control for stochastic nonlinear systems with full-state constraints and input saturation

This paper investigates the adaptive tracking control problem of stochastic nonlinear systems under the conditions of full-state constraints and input saturation. The barrier Lyapunov function (BLF) is applied to handle the full-state constraints. To deal with the input saturation, a distinctive method of introducing an auxiliary system is adopted. Then, a systematic controller design procedure is given by combining a novel radial basis function neural network (RBF NN) approximation approach with backstepping technique.By this way, an adaptive state-feedback controller with only one adaptive law is obtained, which renders the closed-loop system semi-globally uniformly ultimately bounded. Meanwhile, the tracking error is bounded by an explicit function of the design parameters and saturated input error. In addition, the full-states are not violated. Finally, a simple pendulum system and a numerical example are simulated to demonstrate the effectiveness of the proposed scheme.

U-Model and U-Control Methodology for Nonlinear Dynamic Systems

This study presents the fundamental concepts and technical details of a U-model-based control (U-control for short) system design framework, including U-model realisation from classic model sets, control system design procedures, and simulated showcase examples. Consequently, the framework provides readers with clear understandings and practical skills for further research expansion and applications. In contrast to the classic model-based design and model-free design methodologies, this model-independent design takes two parallel formations: (1) it designs an invariant virtual controller with a specified closed-loop transfer function in a feedback control loop and (2) it determines the real controller output by resolving the inverse of the plant U-model. It should be noted that (1) this U-control provides a universal control system design platform for many existing linear/nonlinear and polynomial/state-space models and (2) it complements many existing design approaches. Simulation studies are used as examples to demonstrate the analytically developed formulations and guideline for potential applications.

Global Stabilization of Discrete-Time Linear Systems Subject to Input Saturation and Time Delay

This article studies the problem of global stabilization of discrete-time linear systems subject to input saturation and time delay. The considered time-delay systems are first transformed into delay-free systems based on prediction technique. Then, by utilizing saturation functions technique, the corresponding global stabilizing controllers are proposed for two special discrete-time linear systems-a chain of integrators and oscillators, and explicit conditions guaranteeing stability are also given. Both current and delayed feedback information are utilized in the controller design, and some free parameters are also introduced into these controllers. These advantages can help improve the control performance significantly. Subsequently, a systematic control design procedure for globally stabilizing general discrete-time linear systems subject to multiple inputs and/or multiple inputs delays is proposed. The design procedure is in an explicit and recursive way with explicit conditions guaranteeing stability being given, and thus is easier to use than the existing one. Finally, the effectiveness of the proposed approaches are illustrated by three numerical examples.

Finite-Time Stabilization-Based Adaptive Fuzzy Control Design

This article is aimed at developing a finite-time adaptive fuzzy control strategy for a class of nonlinear strict-feedback systems. For the first time, a fast finite-time practical stability criteria is set up, which provides an effective approach to address the finite-time adaptive fuzzy control design. Furthermore, a systematic finite-time adaptive fuzzy control design procedure is developed by embedding that practical stability criteria. The closed-loop stability analysis shows that the tracking error converges to a small region around the origin in finite time. Meanwhile, all the signals in the closed-loop system are bounded. At last, the presented results are tested by a numerical example.

Flight Control Design for the Systematic Improvement of Ride Qualities

The reduction of rotor-induced vibrations has been a major concern in the history of helicopter engineering. This has led to the development of numerous countermeasures, which cause the vibration levels to decrease considerably. Recent findings have shown that the reduced level of rotor vibrations highlights the importance of turbulence for the ride qualities. The rejection of atmospheric disturbances is a key task of the flight control system (FCS). However, the FCS design is currently focused on stability and handling qualities rather than ride qualities. This work addresses this shortcoming by the introduction of a systematic control design procedure. The improvement of ride qualities is achieved by linking an existing discomfort criterion to parameters of the sensitivity function. This allows the systematic modification of these parameters according to their contribution to discomfort. The approach is embedded into a design framework for systematic compliance with stability and handling quality specifications. The procedure is applied to the control design of a light helicopter resulting in considerably improved ride qualities, while compliance with stability and handling quality specifications is maintained. This represents an important step towards a more comprehensive ride quality engineering for rotorcraft that goes beyond the reduction of rotor-induced vibrations.

Systematically Structured $H_2$ Optimal Control for Truss-Supported Segmented Mirrors

A systematic distributed optimal control design procedure is proposed for the rejection of wind load-induced disturbances on a truss-supported segmented mirror. The distributed nature of the controller is achieved by weighing of the interaction matrices between local (per-segment) controllers in a global ${\mathcal {H}_{2}}$ optimization. The procedure allows a tradeoff analysis between the controller implementation complexity versus the improved performance the extra communication brings. The procedure is demonstrated on a finite element model of a segmented mirror on a flexible supporting truss to which we apply the combined closed-loop performance and local controller interconnection structure optimization. The resulting set of controllers is compared to a set of baseline controllers including linear–quadratic–Gaussian control, singular value decomposition control, and a distributed controller where local controllers of neighboring segments communicate. The tradeoff analysis for the segmented mirror demonstrates that the communication between the local controllers can be greatly reduced without significantly compromising the rejection of wind-induced wavefront errors.

Low-order diving integrated guidance and control for hypersonic vehicles

A novel low-order integrated guidance and control (LOIGC) design model is deduced, and an original diving integrated guidance and control design approach is proposed in this paper. An analytical model between three-channel body rates and components of acceleration of the hypersonic vehicle in the ballistic frame is derived, and the commanded body rates can be directly obtained by analytic calculation. The LOIGC design model is conducted based on three dimensional (3D) relative dynamics between the hypersonic vehicle and target, and the direct relation with respect to line-of-sight (LOS) angles and control surface fin deflections of the hypersonic vehicle is established. Based on the LOIGC model, the design of six-degree-of-freedom (6DOF) guidance and control system for diving hypersonic vehicles can be converted into an output tracking problem of a low-order nonlinear system, and the commanded control surface fin deflections can be directly obtained by controlling derivatives of elevation and azimuth angles of line-of-sight between the hypersonic vehicle and target. In this paper, the system order and tuning parameters of the 6DOF guidance and control system are both decreased, and the design procedure of 6DOF guidance and control system is simplified. The process of calculating commands of angle of attack and bank angle based on desired guidance overloads, and the tracking loops with respect to Euler angles and body rates of the rotational system can also be omitted. In addition, the newly proposed method can improve the utilization of velocity measurements in the body frame of the hypersonic vehicle. Finally, the effectiveness and robustness of the newly proposed integrated guidance and control design approach are verified and investigated using a 6DOF generic hypersonic vehicle model.

U-neural network-enhanced control of nonlinear dynamic systems

Neural networks have been widely used as an approximation for nonlinear dynamic plants in control system design, but they are almost never used as a proper dynamic inverter, particularly with dynamic models available in advance. This study presents a universally feasible U-neural network (U-NN) structure to facilitate the designing control of all dynamic systems modelled with linear/nonlinear polynomial/state space equations. With the presented U-NN, this study proposes a procedure for a model independent control system design, U-control framework/platform. The procedure, against a traditional model based on control system design and a model free/data driven-based design (such as PID control, iterative learning control, and model free control), removes the boundaries of the linear/nonlinear and polynomial/state space model sets, where the model structures are universally treated within the new framework. Furthermore, this study analyses the U-control properties and gives a step-by-step implementation procedure. Several bench test examples demonstrate the effectiveness of the design procedure, as well as the routines in applications.

Robust approximation-free prescribed performance control for nonlinear systems and its application

ABSTRACTThis paper presents a robust prescribed performance control approach and its application to nonlinear tail-controlled missile systems with unknown dynamics and uncertainties. The idea of prescribed performance function (PPF) is incorporated into the control design, such that both the steady-state and transient control performance can be strictly guaranteed. Unlike conventional PPF-based control methods, we further tailor a recently proposed systematic control design procedure (i.e. approximation-free control) using the transformed tracking error dynamics, which provides a proportional-like control action. Hence, the function approximators (e.g. neural networks, fuzzy systems) that are widely used to address the unknown nonlinearities in the nonlinear control designs are not needed. The proposed control design leads to a robust yet simplified function approximation-free control for nonlinear systems. The closed-loop system stability and the control error convergence are all rigorously proved. Finally, comparative simulations are conducted based on nonlinear missile systems to validate the improved response and the robustness of the proposed control method.

Feed-hopper level estimation and control in cone crushers

This paper describes a novel feed-hopper level estimation and control scheme for addressing the known problem of unreliable and occasionally corrupted feed-hopper level measurement in a cone crusher. The approach involves estimating the feed-hopper level with an adaptive time-variant state estimator. The proposed adaptive scheme delivers asymptotically unbiased feed-hopper level estimates, despite using an inherently biased state estimator with biased measurement(s) and/or model, and therefore addresses the common pitfall of state estimators.The paper details the entire control system design procedure, from the fundamental theory, through dynamic modeling and estimator/controller tuning, to the design validation and control performance evaluation. The performance of the proposed scheme is evaluated through extensive full-scale tests in various production scenarios, including process start-up, level setpoint changes, and mass flow disturbance rejection.The full-scale tests revealed a number of benefits compared to the straightforward level control implementation. These benefits include the possibility of recovering from a temporary loss of measurement signal, smaller control effort, and increased system robustness due to an increased ability to withstand measurement errors. Therefore, the proposed scheme will enable more consistent size reduction and provide protection against performance degradation and process down-time.

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.

D-SEND#2の制御系設計

This paper is concerned with flight controller design of D-SEND#2. D-SEND is a project to demonstrate a low sonic boom aerodynamic design concept. In the #2 part of this project, an unpowered test vehicle is lifted to an altitude of 30km by a balloon from which it then separates. After the separation, the vehicle's on-board flight control computer selects a target Boom Measurement System (BMS) according to the separation point. The vehicle then autonomously flies to the selected BMS and establishes prescribed sonic boom measurement flight conditions. The design of the GNC system for D-SEND#2 project is exceptionally challenging since 1) there is no nominal trajectory, 2) there is only limited control available to meet various requirements, 3) the flight envelope is quite wide, and 4) the development time is short. Dynamic inversion method and time-scale separation technique are applied to deal with these problems, and a systematic controller design procedure is presented. The controller is designed with this procedure and evaluated through linear analysis and Monte-Carlo simulations which shows it has sufficient performance and safety margines. This controller design method is confirmed to be a practical method for UAVs.

Relative Degrees and Adaptive Feedback Linearization Control of T–S Fuzzy Systems

This paper presents a new study on the relative degrees of single-input and single-output T–S fuzzy systems in general noncanonical forms, and proposes a feedback linearization-based control design method for such systems. The study extends the system relative degree concepts, commonly used for the control of nonlinear systems, to general T–S fuzzy systems, derives various relative degree conditions for general T–S fuzzy systems, and establishes the relative degree dependent normal forms. A feedback linearization-based control design framework is developed for general T–S fuzzy systems using its normal form, to achieve closed-loop stability and asymptotic output tracking under relaxed design conditions. A new adaptive feedback linearization-based control scheme for T–S fuzzy systems in general noncanonical forms with parameter uncertainties is designed and analyzed. Some extensions of relative degrees and their possible application to robust adaptive control for noncanonical form T–S fuzzy systems are also demonstrated. An illustrative example is presented with simulation results to demonstrate the control system design procedure and to show the effectiveness of the proposed control scheme.

A general U-block model-based design procedure for nonlinear polynomial control systems

ABSTRACTThe proposition of U-model concept (in terms of ‘providing concise and applicable solutions for complex problems’) and a corresponding basic U-control design algorithm was originated in the first author's PhD thesis. The term of U-model appeared (not rigorously defined) for the first time in the first author's other journal paper, which established a framework for using linear polynomial control system design approaches to design nonlinear polynomial control systems (in brief, linear polynomial approaches → nonlinear polynomial plants). This paper represents the next milestone work – using linear state-space approaches to design nonlinear polynomial control systems (in brief, linear state-space approaches → nonlinear polynomial plants). The overall aim of the study is to establish a framework, defined as the U-block model, which provides a generic prototype for using linear state-space-based approaches to design the control systems with smooth nonlinear plants/processes described by polynomial models. For analysing the feasibility and effectiveness, sliding mode control design approach is selected as an exemplary case study. Numerical simulation studies provide a user-friendly step-by-step procedure for the readers/users with interest in their ad hoc applications. In formality, this is the first paper to present the U-model-oriented control system design in a formal way and to study the associated properties and theorems. The previous publications, in the main, have been algorithm-based studies and simulation demonstrations. In some sense, this paper can be treated as a landmark for the U-model-based research from intuitive/heuristic stage to rigour/formal/comprehensive studies.