Linear Dynamic Control Research Articles

Further Methods for Encrypted Linear Dynamic Controllers Utilizing Re-Encryption

Further Methods for Encrypted Linear Dynamic Controllers Utilizing Re-Encryption

Neural Predictor-Based Dynamic Surface Parallel Control for MIMO Uncertain Nonlinear Strict-Feedback Systems

We propose a neural predictor-based dynamic surface parallel control method for a class of uncertain nonlinear systems in this brief. The dynamics of the physical system is in the strict-feedback form and subject to multi-input, multi-output, and uncertain nonlinearities. The parallel control method is developed based on an ACP methodology, including three steps. Firstly, an artificial system to the physical system is developed using an echo state network-based neural predictor structure. Next, a high-order tuner-based computational experiment is developed to achieve online adaptive training of the echo state network. Finally, parallel execution is developed by using a second-order linear tracking differentiator-based dynamic surface control approach. The total closed-loop system can be proved to be input-to-state stable. The effectiveness of the proposed theoretical results is demonstrated by a simulation of trajectory tracking of an autonomous surface vehicle.

A Linear Iterative Controller for Software Defined Control Systems of Aero-Engines Based on LMI

Currently, most control systems of the aero-engines possess a central controller. The core tasks for the control system, such as control law calculations, are executed in this central controller, and its performance and reliability greatly impact the entire control system. This paper introduces a control system design named Software Defined Control Systems (SDCS), which features a controller-decentralized architecture. In SDCS, a network composed of a set of nodes serves as the controller, so there is no central controller in the system, and computations are distributed throughout the entire network. Since the controller is decentralized, there is a need for decentralized control tasks. To address this, this paper introduces a method for designing decentralized control tasks using periodic linear iteration. Each node in the network periodically broadcasts its own state and updates its next-step state as a weighted sum of its current state and the received current states of other nodes in the network. Each node in the network acts as a linear dynamic controller and maintains an internal state through information exchange with other nodes. We modeled the decentralized controller and obtained the model of the entire control system, and the workload of each obtained decentralized control task is balanced. Then, we obtained a parameter tuning method for each decentralized controller node based on Linear Matrix Inequalities (LMI) to stabilize the closed-loop system. Finally, the effectiveness of the proposed method was verified through digital simulation.

Data-driven dynamic relatively optimal control

We show how the recent works on data-driven open-loop minimum-energy control for linear systems can be exploited to obtain closed-loop control laws in the form of linear dynamic controllers that are relatively optimal. Besides being stabilizing, they achieve the optimal minimum-energy trajectory when the initial condition is the same as the open-loop optimal control problem. The order of the controller is N−n, where N is the length of the optimal open-loop trajectory, and n is the order of the system. The same idea can be used for obtaining a relatively optimal controller, entirely based on data, from open-loop trajectories starting from up to n linearly independent initial conditions.

Dynamic Controller That Operates Over Homomorphically Encrypted Data for Infinite Time Horizon

In this article, we present a dynamic feedback controller that computes the next state and the control signal over encrypted data using homomorphic properties of cryptosystems, whose performance is equivalent to the linear dynamic controllers over real-valued data. Assuming that the input as well as the output of the plant is encrypted and transmitted back to the controller, it is shown that the state matrix of any linear time-invariant controller can be always converted to a matrix of integer components. This allows the dynamic feedback controller to operate for infinite time horizon without decryption or reset of its internal state. For implementation in practice, we illustrate the use of a cryptosystem that is based on the Learning With Errors problem, which allows both multiplication and addition over encrypted data. It is also shown that the effect of injected random numbers during encryption for security can be maintained within a small bound by way of the closed-loop stability.

On the Stability of Linear Dynamic Controllers With Integer Coefficients

In this article, we show that linear dynamic controllers with integer coefficients are usually unstable. In fact, asymptotic stability can only be achieved if all controller eigenvalues are equal to zero. Moreover, for a fixed controller order, there exist only finitely many characteristic polynomials with integer coefficients that lead to marginally stable eigenvalues on the unit circle and we characterize these setups. The obtained results are, in particular, relevant to encrypted control, where (nontrivial) stable controllers with integer coefficients were on the “wish list.”

Numerical analysis of feedforward concepts for advanced control of organic Rankine cycle systems on heavy-duty vehicles

Organic Rankine cycle systems are the most promising technology to recover the waste heat from heavy-duty vehicles in an efficient and economical way, thus increasing their energy efficiency and reducing their environmental impact. A major challenge for an efficient and profitable integration of the organic Rankine cycle unit is presented by the highly transient nature of the waste heat during a driving cycle. In order to cope with the rapid fluctuations of the waste heat and to ensure safe operation, advanced control techniques have gained particular attention in the last decade. This paper presents novel high-order advanced feedforward control concepts for organic Rankine cycle units that improve the performance of classical proportional integral controllers. The proposed approach enables the use of high-order nonlinear models for feedforward control of organic Rankine cycle systems, therefore allowing for more accurate estimation of the desired control action. As a reference, a proportional integral controller with feedforward is presented, acting on the pump mass flow rate to control the degree of superheating at the turbine inlet, which is a key variable to ensure high power output and safe operation of the organic Rankine cycle system. Static, linear and nonlinear dynamic inversed-model feedforward controllers were integrated with a classical proportional integral controller and numerically evaluated under a realistic waste heat profile of a heavy-duty truck. The results suggest that the static and the linear feedforward concepts do not offer any advantages compared with the classical proportional integral controller, because they result in a higher absolute mean square tracking error and a higher cumulative controller effort. Instead, the high-order nonlinear dynamic inversed-model feedforward controller introduced in this work offers important advantages compared with the classical proportional integral controller by reducing the absolute root mean square tracking error from 10.8 K to 2.2 K without excessively increasing the controller cumulative effort (limited to 1.9%/s). On the contrary, the classical proportional integral controller could optimize only one of the objectives at the expenses of the other. The proposed control approach significantly improves the operation of the organic Rankine cycle unit, limiting the fluctuations of the degree of superheating and keeping this quantity within ±7 K of the desired set point. Thus, the novel feedforward concept will be highly beneficial in integrating classical proportional integral control of organic Rankine cycle units that involve highly transient heat sources.

Exponential stabilization of the problem of transmission of wave equation with linear dynamical feedback control

<p style='text-indent:20px;'>In this paper, we address exponential stabilization of transmission problem of the wave equation with linear dynamical feedback control. Using the classical energy method and multiplier technique, we prove that the energy of system exponentially decays.</p>

Adaptive Secure Output Consensus Tracking of Linear Multi-Agent Systems Via Dynamic Event-Triggered Impulsive Control Under Dos Attack

Adaptive Secure Output Consensus Tracking of Linear Multi-Agent Systems Via Dynamic Event-Triggered Impulsive Control Under Dos Attack

Resource-aware time-optimal control with multiple sparsity measures

The paper proposes a novel time-optimal control that is also sparse in both time and space domain to take account of resource constraints in networked control systems. The control problem is described as minimization of a weighted sum of the terminal time and the L0 norm of multi-input control for a linear time-invariant dynamical system, with state and control constraints. In particular, we treat the constraint on the number of actuations at each time, which is described as an ℓ0 norm constraint. Since the L0/ℓ0 optimization problem is highly non-convex, we propose to solve a convex relaxation using L1 and ℓ1 norms. We give sufficient conditions for the equivalence between the original L0/ℓ0 problem and the relaxed L1/ℓ1 problem. Based on the relaxation, we also propose a numerical computation method for the L1/ℓ1 problem by sequential linear programming. We show numerical examples to illustrate the effectiveness of the proposed control method.

Trajectory tracking of wheeled mobile robots using only Cartesian position measurements

The problem of trajectory tracking of nonholonomic wheeled mobile robots has been extensively studied in the last decades. Nevertheless, most of the control laws proposed in the literature assume full state measurements. Based on the flatness property of the robot’s kinematic model, we proposed a dynamic feedback linearization controller in combination with attitude and velocity observers. The proposed control-observer scheme requires only Cartesian position measurements and achieves asymptotic trajectory tracking. The stability analysis is carried out by means of Lyapunov’s theory and the properties of cascade time-varying systems. Experimental results are presented to show the performance of the proposed approach.

Experimental implementation of an active synthesis of a gyroscopic-nonreciprocal acoustic metamaterial

Experimental realization of a new class of active Nonreciprocal Gyroscopic Meta-Material (NGMM) is presented. The proposed active NGMM system consists of a one-dimensional acoustic cavity provided with piezoelectric boundaries that act as sensors and actuators. These active boundaries are integrated with linear dynamic control capabilities that virtually synthesize a gyroscopic control action in order to generate desirable non-reciprocal characteristics of tunable magnitude and phase shift. The dynamics of a prototype of the NGMM cell are identified experimentally and the theoretical characteristics of the virtual gyroscopic controller are predicted for various control gains for both forward and backward propagations. The theoretical predictions are validated experimentally using a dummy NGMM cell to act as a physical dynamic controller. Such a preferred arrangement is coupled with analog controllers in order to enable fast execution of the controller and, in turn, enhance the bandwidth of its operating frequency. The time and frequency response characteristics of the NGMM cell are measured for different control gain and the behavior is evaluated for both forward and backward propagations. The obtained experimental results are found to be in close agreement with the theoretical predictions. The presented concept, controller design, and implementation of the NGMM can be extended to various critical structures to achieve realistic acoustic diode configurations in a simple and programmable manner.

Stabilization of a Class of Fractional Order Systems With Both Uncertainty and Disturbance

This paper investigates the stabilization problem of fractional order systems with both model uncertainty and external disturbance. By combining the linear feedback control method, the dynamic feedback control method, and the uncertainty and disturbance estimator (UDE)-based control method, respectively, two new UDE-based control methods are developed. Using these methods, the fractional order systems can be stabilized by three steps. In the first step, the linear feedback and dynamic feedback controllers are designed to stabilize the nominal fractional order systems. The second step is to design a UDE-based fractional order controller to estimate the model uncertainty and external disturbance. In the third step, the two controllers are combined into a new controller to realize the stabilization of those fractional order systems. Finally, a numerical example is given to verify the correctness and validity of the proposed methods.

Dynamic models and control system design for heated channels in a Canadian SCWR

The proposed Canadian SCWR is based on the concept of the CANDU reactor. However, the dynamic characteristics of the SCWR significantly differ from the CANDU reactor because of the special heat transfer phenomenon of the supercritical water in the fuel bundle. Thus, it is important to design a control system to maintain the SCWR operating at the required operating point when it is subjected to disturbances. The transient CFD simulations of the heated channels in a Canadian SCWR are conducted in order to obtain the dynamic relationship between the inputs and outputs of the SCWR. Then, the linear dynamic control models are constructed by the system identification technique based on the dynamic relationship between the inputs and outputs obtained from the CFD simulations. The linear dynamic models are validated using the results from the full scale non-linear CFD simulations. Based on the linear dynamic models, a closed-loop control system, which consists two PID controllers, is designed. The performance evaluation of the proposed control system is also carried in this work.

Численный метод проверки робастного качества управления для линейных одномерных динамических систем управления

Численный метод проверки робастного качества управления для линейных одномерных динамических систем управления

Active synthesis of a gyroscopic-nonreciprocal acoustic metamaterial

A class of active nonreciprocal metamaterials is developed to control the flow and distribution of energy along periodic dynamical systems. Such a development constitutes a radical departure from the currently available approaches where the non-reciprocities are generated either by utilizing various physical sources of passive nonlinearities, gyroscopic circulators, spatiotemporal modulation, or active control of nonlinear systems. The proposed active Nonreciprocal Gyroscopic Meta-Material (NGMM) cell consists of a one-dimensional acoustic duct provided with linear dynamic control capabilities that virtually synthesize a gyroscopic control action that generates non-reciprocal characteristics of tunable magnitude and direction. The controller is designed in order to enable the spatial control and redistribution of the wave propagation energy flow along the acoustic duct. During this entire process, the system behaves in a linear fashion. Numerical examples are presented to demonstrate the basic features, non-reciprocal behavior, as well as the energy flow characteristics. The presented concept and controller design of the NGMM can be extended to various critical structures to achieve realistic acoustic diode configurations in a simple and programmable manner.

Output feedback controller for trajectory tracking of robot manipulators without velocity measurements nor observers

The main contribution of this study is the design of a trajectory tracking controller using output feedback applied to robot manipulators. The given controller does not need velocity measurements for its implementation and to achieve the tracking control objective. The structure of the proposed scheme consists of a proportional gain plus a dynamic gain resulting from a first-order system. The dynamic gain is not motivated by any observer nor estimator to approach the joint velocity. The dynamic linear controller has three tunable gain parameters for the one degrees-of-freedom (DOF) systems and two gain matrices for the nDOF lagrangian systems. These gains can be tuned following the conditions given in the stability analysis. An adaptive estimator of the viscous friction coefficient is added to robustify the closed-loop design; the analysis for the estimator is presented for one DOF systems and nDOF manipulators. The closed-loop stability analyses are developed by using Lyapunov's theory. The performance of the proposed control structure is illustrated and compared with other controllers such as the PID controller and the first-order sliding mode algorithm via numerical simulations. Moreover, real-time experiments are carried out in a two DOF SCARA robot manipulator.

Automated procedure for self-assessment and forecast of organizational maturity of university division

The main goal of the article is to support the process of ensuring the effectiveness of organization management. For this, the task of self-assessment according to organizational maturity levels is being solved. The methodological basis of the study is the ISO 9004-2010 standard, the technical implementation of the processes of self-assessment of organizational maturity is performed using the ELMA business process management system. The directorate of the Institute of Informatics and Telecommunications (IITC), Reshetnev Siberian State University of Science and Technology served as an object of study. The process of self-assessment of the organization according to maturity level was implemented. It is shown that the maturity of the organization is on average at level 2 (“Managed”) and is characterized by integrity, without failures for individual components. The developed approach in accordance with the purpose of the standard ISO 9004-2010 can be used both in higher education institutions and for the management of a machine-building enterprise. In addition, the article solves the problem of predicting indicators of organizational maturity of an enterprise as a linear dynamic control system in discrete time. It is shown that such a model adequately reproduces the behavior of the system of an educational institution business processes’ maturity indicators.

Optimization control for dynamic vibration absorbers and active suspensions of in-wheel-motor-driven electric vehicles

This study addresses the challenges of ride comfort improvement and in-wheel-motor vibration suppression in in-wheel-motor-driven electric vehicles. First, a mathematical model of a quarter vehicle equipped with a dynamic vibration absorber and an active suspension is developed. Then, a two-stage optimization control method is proposed to improve the coupled dynamic vibration absorber–suspension performance. In the first stage, a linear quadratic regulator controller based on particle swarm optimization is designed for the dynamic vibration absorber to suppress the in-wheel-motor vibration, in which the dynamic vibration absorber parameters and linear quadratic regulator controller weighting factors are optimally matched by using the particle swarm optimization algorithm. In the second stage, a finite-frequency H∞ controller is designed in the framework of linear matrix inequality optimization for the active suspension to improve vehicle ride comfort. Suspension performance factors, including suspension working space and road-holding ability, are taken as constraints in both stages. The proposed method simultaneously improves vehicle ride comfort and suppresses in-wheel-motor vibration. Finally, the effectiveness and superiority of the proposed method are illustrated through comparison simulations.

Horizontal Stabilator Utilization for Post Swashplate Failure Operation on a UH-60 Black Hawk Helicopter

A flight simulation model for the UH-60 Black Hawk, based on Sikorsky's GenHel model, is modified to simulate a locked failure of a main rotor swashplate servo actuator, which is compensated by using the stabilator as a redundant control effector. Steady-state trim analysis is performed to demonstrate feasibility of trimmed flight in various conditions with different locked servo actuator positions for the forward, aft, and lateral actuators. A model-following, linear dynamic inversion controller is implemented and modified to account for locked actuator position. Postfailure, the controls are reconfigured to partially reallocate the control authority in the longitudinal axis from the main rotor longitudinal cyclic to the stabilator. This is done by manipulation of only the control allocation relating pilot stick inputs to servo actuator positions, whereas the feedback control gains and mechanical rigging between servo actuators and rotor pitch controls remain identical to the baseline. Flight simulation results demonstrate the ability of this reallocation to compensate for locked failure of the forward main rotor swashplate servo actuator, as well as the ability of the aircraft to decelerate from cruise at 120 kt to 50 kt, slower than the published safe rolling landing speed of 60 kt. A similar range of locked positions of the forward and aft actuators is demonstrated to be feasible for aircraft recovery using control of the stabilator. Feasibility of aircraft recovery for locked positions of the lateral servo actuator is also considered, as well as the effect of variation in gross weight, speed of actuator locking, and delays in fault detection and identification.