Stability Of Control Scheme Research Articles

Pay load Stabilization for Offshore Cranes: A Unified Controller Based on Flatness

Crane-based handling operations represent a vital part of today's maritime sector. To guarantee both safe and efficient payload handling with ship cranes, payload oscillations induced by the sea swell have to be damped. Approaches for payload stabilization usually consider either vertical position control (Active Heave Compensation, AHC) or sway reduction (Anti Sway Control, ASC). In this paper, a unified control scheme for spatial payload stabilization is proposed, utilizing the differential flatness of the crane system. The presented framework inverts the nonlinear payload dynamics by means of the flat mapping, thus facilitating controller design. Furthermore, the approach provides a systematic way to include the sea disturbance in the controller. Redundancy of the considered knuckle boom crane is exploited to track secondary control objectives. A related cost function weighting the crane's manipulability is derived and used in an optimization-based target selector. The controller design is evaluated in simulation for varying sea disturbances. The results suggest good AHC and ASC capabilities, where the payload's position error is reduced up to 60% for light to medium sea states.

Iterative Contraction Stability Control Strategy for Planar Prismatic-Rotational Underactuated Robot

Iterative Contraction Stability Control Strategy for Planar Prismatic-Rotational Underactuated Robot

Adaptive fixed-time stabilization for a class of nonlinear uncertain systems.

Finite-time stability (FTS) has attained great interest in nonlinear control systems in recent two decades. Fixed-time stability (FxTS) is an improved version of FTS in consideration of its settling time independent of the initial values. In this article, the adaptive fixed-time stabilization issue is studied for a kind of nonlinear systems with nonlinear parametric uncertainties and uncertain control coefficients. Using the adaptive estimate and the adding one power integrator (AOPI) design tool, we propose a two-phase control strategy, which makes that the system states tend to the origin in fixed-time, and other signals are bounded on [0,+∞). We prove the main results by means of the recently developed fixed-time Lyapunov stability theory. Finally, we apply the proposed adaptive fixed-time stabilizing control strategy into the pendulum system, and the simulation results verify the efficacy of the presented method.

Coordination Stability Control Strategy for Four-wheel-independent-actuated Electric Vehicles

Coordination Stability Control Strategy for Four-wheel-independent-actuated Electric Vehicles

A layered roll stability control strategy for commercial vehicles based on adaptive model predictive control

Due to the high centre of mass, commercial vehicles are prone to ultimate rollover under extreme steering conditions. The rollover of commercial vehicles leads to serious traffic accidents and poses a threat to road traffic. In this paper, the mechanism of vehicle rollover is revealed by static equilibrium and phase plane analysis. Meanwhile, a robust roll angle observer is designed by combining Kalman filter and sliding mode observation. Considering the influence of wheel lifting on roll dynamics, a novel layered control strategy is proposed by employing engine torque limit, differential braking and active front-wheel steering. Moreover, the layered control of roll stability is realised by adaptive model predictive control with time-varying weights and constraints. To verify the validity and reliability of the proposed algorithm, the hardware-in-loop tests under typical driving conditions have been carried out. The results show that the proposed method can effectively restrain the divergence of roll state and prevent vehicle rollover.

Research on Landing Stability of Four-Legged Adaptive Landing Gear for Multirotor UAVs

Rotorcraft Unmanned Aerial Vehicles (UAVs) often need to take off and land under complex working conditions. The rugged terrains may cause the UAV to tilt during takeoff and landing and even cause rollover and other accidents in severe cases. In this paper, a new four-legged landing gear of multirotor UAVs with a passive cushioning structure is designed, aiming at the landing stability requirement of rotorcraft UAVs in complex terrains. The mathematical model of the landing gear dynamics is established in MATLAB/Simulink, and the drop test simulation is carried out under different landing terrain conditions. By comparing the simulation results of the drop test multibody dynamic model in Simcenter3D dynamics software, the adaptive landing and cushioning capacity of the landing gear and the accuracy of the mathematical model are verified. Combined with the landing stability criterion and control strategy of adaptive landing gear adjustment, the landing stability of adaptive landing gear under different slope angles of landing surface and horizontal velocities is studied. The landing stability boundary under different combinations of these two parameters is found.

Pitch stability control of variable wheelbase 6WID unmanned ground vehicle considering tire slip energy loss and energy-saving suspension control

Acceleration on a ramp and emergency braking are common driving conditions for special vehicles. Due to the complex coupling between the suspension and the chassis structure, the body attitude maintenance and stability control face huge challenges. Aiming at the control problem of pitch stability of the existing six-wheel independent drive unmanned vehicle (6WID UGV) with variable wheelbase during acceleration and deceleration, this paper designs an interconnected active hydro-pneumatic suspension (IAHPS) that can autonomously adapt to the change of wheelbase. Based on this system, a pitch stability control strategy considering the lowest energy consumption of the chassis is proposed. Firstly, a PID-type sliding mode controller (SMC) is used in the upper controller to calculate the desired anti-pitching torque. The disturbance caused by the nonlinearity and uncertainty of the model is estimated by the extended state observer (ESO). Secondly, with the goal of minimizing the energy consumption of the suspension system, the PSO algorithm is used in the middle controller to decide the pressure of the two accumulators in IAHPS. Thirdly, the lower controller again uses the PSO algorithm to achieve wheel torque distribution to minimize tire slip energy loss; Finally, simulation tests in multiple scenarios verify the effectiveness of the designed layered control strategy in terms of the pitching stability control. Under random road and horizontal road, the energy consumption for active adjustment of suspension is reduced by 28.35% and 29.41% respectively; The total energy loss of tire slip is reduced by 65.16% and 41.52%.

Adaptive finite/fixed‐time stabilizing control for nonlinear systems with parametric uncertainty

AbstractThis article investigates the adaptive finite/fixed‐time stabilizing control problem for a class of uncertain nonlinear systems. Remarkably, the studied system allows the nonlinear parametric uncertainties. Compared with the existing results on adaptive finite/fixed‐time stabilizing control, the proposed state feedback stabilizing process consists of the first phase of steering the system states into a region of the fixed‐time stability in finite‐time and the second phase of further driving the states to the origin in fixed‐time, while the other signals in closed‐loop system are kept bounded. The adaptive finite/fixed‐time stabilizing control scheme is developed using a recursive design method, which is inspired by the adding‐a‐power‐integrator technique. The proof is based on the nonsmooth finite/fixed‐time Lyapunov stability theorem developed recently for nonlinear control systems. The angular set‐point stabilizing control of a pendulum system is used to demonstrate the effectiveness of the presented algorithm.

Evolutionary Game Analysis of the Regulatory Strategy of Third-Party Environmental Pollution Management

The “multiple-interaction” model of third-party management for environmental pollution has gradually replaced the traditional “command-and-control” model and become a new trend in governance. This new governance system is accompanied by a lack of regulatory capacity, a single reward and punishment mechanism, and frequent rent-seeking behavior, and other governance problems are becoming increasingly prominent. Based on the premise of limited rationality, considering the possible rent-seeking behavior of pollution control enterprises and professional environmental testing institutions, this paper constructs a tripartite evolutionary game model with pollution control enterprises, professional environmental testing institutions, and government regulatory departments as the main bodies. The evolutionary stabilization strategy of the three-party game is analyzed according to Lyapunov’s theory, and the system is optimized through a computational experimental simulation in MATLAB. The research results show that the government can effectively regulate the behavior of pollution control enterprises and professional environmental testing institutions by appropriately increasing the rewards and punishments, but excessive rewards are not conducive to increasing the government regulators’ own performance; the existing static reward and punishment mechanism of the government regulators fails to reward and punish the behavior of governance subjects in real time, and the linear dynamic punishment mechanism greatly increases the probability of rent-seeking behavior, neither of which is a stable control strategy for the system. The non-linear dynamic reward and punishment mechanism takes into account both dynamic incentives and dynamic constraints to make the system achieve the desired evolutionary stability strategy, i.e., pollution control enterprises follow regulations, professional environmental testing agencies refuse to seek rent, and the government actively regulates the system as the final evolutionary direction. The research findings and management implications provide countermeasures and suggestions for government regulators to improve the regulatory mechanism for the third-party management of environmental pollution.

Impedance modelling and stability analysis of modular multilevel converter with different types of grid‐forming control schemes

With the increasing penetration of power electronics, grid-forming modular multilevel converters (MMCs) have attracted great attention in the upcoming MMC-based high-voltage direct current transmission (HVDC) projects. Power synchronization control (PSC) and direct power control (DPC) are two typical grid-forming control schemes for MMCs. This paper sets out to investigate the impedance-based stability characteristics of PSC-MMC and DPC-MMC. Utilizing the harmonic state space (HSS), equivalent impedance models of PSC-MMC and DPC-MMC are developed with the consideration of complete controllers and MMC internal dynamic characteristics. Impedance shaping effects of the major controllers are further analyzed to identify the frequency bands where the MMCs have negative resistive impedance characteristics. Finally, potential instability phenomena of the interconnected system are shown through the case studies, and the virtual impedance method is introduced as the stabilization control scheme. The electromagnetic transient simulation results based on PSCAD/EMTDC verify the accuracy of the impedance models and the effectivity of the stabilization control scheme.

Small-Gain Approach to Fuzzy Adaptive Control for Interconnected Systems With Unmodeled Dynamics

This article presents a new stabilizing control scheme for a class of interconnected nonlinear systems subjected to unmodeled dynamics and immeasurable states. Fuzzy logic systems are applied to approximate the unknown functions, and a fuzzy-based state observer is constructed. The interconnection of the overall system is completely compensated via the cyclic-small-gain condition theorem, and the small-gain theorem is introduced to overcome the unmodeled dynamics in each subsystem. Furthermore, assumptions from prior literature are relaxed, and computing burden is reduced through the design of less adaptive laws. This article proves that under the designed control scheme, the closed-loop systems are controlled to be input-to-state practically stable and that all signals are guaranteed to be semiglobally uniformly ultimately bounded. Finally, this article’s simulation section illustrates the effectiveness of the proposed approach through an example derived from a practical system model.

Asynchronous H∞ Continuous Stabilization of Mode-Dependent Switched Mobile Robot

Four-wheeled steerable mobile robots have been widely used in industrial fields. However, robust tracking control is hard to achieve with a fixed maneuver mode. Based on a novel internal coupled sliding mode control (ICSMC) method, this study handles the above challenge by constructing a mode-dependent switched mobile robot (MSMR), and then designing an asynchronous <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$H_{\infty}$ </tex-math></inline-formula> continuous stabilization control scheme. This method governs the system behaviors to perform adaptive-mode allocations asynchronously and smoothly. First, a unified expression of MSMR is formulated, which regards the maneuver modes as optional subsystems. Then, with the coupled sliding surfaces and modified reaching law, an enhanced chattering-free ICSMC technique is established to optimize continuous control inputs for each subsystem. Moreover, using a surveillant criterion that depicts the energy decaying rate, an evaluation rule is built to distinguish the mismatched subsystems and then realize autonomous mode switching for the concerned MSMR. Utilizing piecewise Lyapunov functional technique and mode-dependent average dwell time, new sufficient conditions are derived for global exponential stability and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$H_{\infty}$ </tex-math></inline-formula> performance. Comparative experiments implemented on the developed MSMR are carried out to verify the effectiveness of the proposed control scheme.

Evolutional solid phase and solid-liquid interface uranium immobilization mechanisms by nanoscale zero-valent iron and enhanced uranium stability control strategy

Uranium is a carbon dioxide free nuclear energy, and uranium-contained wastewater poses serious chronic health effects toward human. Nanoscale zero-valent iron (nZVI) separates uranium from wastewater with ultrafast kinetic, high capacity and selectivity. However, the dynamic interfacial uranium binding mechanisms and its stability, controlled by the phase transformation of nZVI, is important but poorly understood. After 120 h reaction, the fresh nZVI was oxidized and transformed to ferrihydrite and then lepidocrocite and hematite. Analysis for the structures and valence states of U, Fe species indicated that the dominate U(VI) uptake mechanism changed from Fe0 induced reduction to adsorption as nZVI transformed to iron (oxyhydr)oxides. Density functional theory calculation revealed that uranyl formed corner-sharing configurations on the surface of iron nanoparticles, and some uranium ions prefer to incorporate into the structure of lepidocrocite than hematite during the crystallization processes of ferrihydrite. Meanwhile, 100 ∼ 10000 μg/L uranyl ions were quickly captured, the residual uranium could be maintained at ∼9.31 μg/L and the content of uranium in reacted iron nanoparticles reached ∼24.16 wt%. Interestingly, the oxidization reduction potential (Eh) was a potential parameter to control uranium immobilization in the CSTR system, and the Eh control strategy could be used to increase the fraction of U(IV)/U(V), sparingly soluble and highly stable, higher than 90 %. The findings augment our understanding of U-nZVI reactions and guide nZVI technology to remedy real uranium-contained wastewater.

System Identification of Heterogeneous Multirotor Unmanned Aerial Vehicle

An energy efficient heterogeneous multirotor unmanned aerial system (UAS) is presented in this paper, wherein, the aerodynamical characteristics of both helicopter and quadrotor are obtained in a single multirotor design. It features the energy efficiency and endurance of a helicopter, while keeping the mechanical simplicity, control and maneuverability of a quadrotor; employing a single large central rotor to get majority of the lift and four small arm canted rotors for control. Developing the stable and robust control strategy requires the accurate model of system. Due to the added mechanical complexities of the new design including the existence of couplings and gyroscopics, the modelling through the dynamic equations of the multirotor would not be possible in providing accurate results. Therefore, precise system modelling is required for the development of stable and robust control strategy. This paper proposes a novel system identification method with the objective to experimentally estimation of the precise dynamic model of the heterogeneous multirotor. The approach comprises of the utilization of input excitation signals, frequency sampling filter and derivation of transfer functions through complex curve fitting method. To validate the accuracy of the obtained transfer functions, the experimentally auto-tuned PID controllers are implemented over the transfer functions. Custom designed fight controller is used to experimentally implement the proposed idea. Presented results demonstrate the efficacy of the proposed approach for heterogeneous multirotor UAS.

Analysis of the Stability and Optimal Control Strategy for an ISCR Rumor Propagation Model with Saturated Incidence and Time Delay on a Scale-Free Network

The spread of rumors in the era of new media poses a serious challenge to sustaining social order. Models regarding rumor propagation should be proposed in order to prevent them. Taking the cooling-off period into account in this paper, a modified ISCR model with saturated incidence and time delay on a scale-free network is introduced. The basic reproduction number R0, which does not depend on time delay τ, is given by simple calculation. The stability of the rumor-free and rumor-endemic equilibrium points is proved by constructing proper Lyapunov functions. The study of the ISCR rumor-spreading process acquires an understanding of the impact of many factors on the prevalence of rumors. Then, the optimal control strategy for restraining rumors is studied. Numerous sensitivity studies and numerical simulations are carried out. Based on the saturated incidence and time delay, results indicate that the effect of time delay plays a significant part in rumor propagation on a scale-free network.

Research on Hierarchical Stability Control Strategy Based on Model Predictive Control for Multi-axis H-Type Distributed Drive Electric Vehicles

Research on Hierarchical Stability Control Strategy Based on Model Predictive Control for Multi-axis H-Type Distributed Drive Electric Vehicles

A Zeno-Free Event-Triggered Control Strategy for Asymptotic Stabilization of Switched Affine Systems

This article investigates the event-triggered control problem for switched affine systems (SASs). The presence of affine terms brings many difficulties on the exclusion of triggering Zeno behavior when ensuring asymptotic stability. We propose an event-triggered control strategy dynamically updated with triggering to solve this problem, in which the triggering condition is associated with the affine terms and given with a time-varying term that is updated at triggering instants. Based on the triggering strategy, the controllers for subsystems and a switching rule are designed to achieve asymptotic stability of the resulting closed-loop system. Moreover, due to the special feature of event-triggered SASs, a new method for proving the exclusion of Zeno behavior is given. Finally, the developed results are illustrated by an electric circuit example.

Numerical modelling of the impact of leakage under divertor baffle in WEST

In WEST experimental campaign C5, the divertor pumping capability has been improved by sealing the space between the divertor outer baffle and the vacuum vessel. It is expected that the degree of baffle leakage influences the transport of neutral particles inside the main chamber, which affects the detachment onset. Knowing the exact impacts of leakage and understanding the physical processes behind it are helpful for the study and control of plasma detachment. We investigate the impact of leakage by performing transport simulations through SOLEDGE-EIRENE code considering several cases with different leakage levels. Starting from the basic simulation case, non-constant radial transport coefficients obtained by the feedback control method are applied to achieve a better match with the experimental one (#54903) in L-mode. Based on the basic case, the evolution of plasma regimes from sheath limited regime to detached one in different wall geometries has been studied by ramping the upstream density. The numerical results show that the cases with closed or reduced leakage under the baffle have better performance in trapping the neutral particles and higher neutral pressure near the baffle. The neutral compression ratio is increased by a factor up to 4, leading to more significant momentum and power dissipation in the divertor, thus lowering the detachment threshold in n e,sep by up to 16%. At the same time, a much higher gas puff rate by a factor up to 22 is needed to maintain an equivalent n e,sep level in the case without or reduced leakage. For all the cases here, there exist characteristic parameters on which the baffle closure has no obvious influence on their value when plasma starts to detach. The evolution of radiator height as a function of target temperature shows no sensitivity to the leakage, which gives some insight into the stable detachment control strategy in the future. Finally, simulation results are compared with available neutral pressure measurements from WEST campaigns to verify the predictions from the simulation. • The impact of wall geometry (characterized by different sizes of leakage under the divertor baffle) on detachment properties in WEST is investigated using SOLEDGE-EIRENE transport code. • Radial non-constant transport coefficients obtained by the feedback control method are applied in the simulation, allowing a better match with experimental results in L-mode. • The case with less leakage has better performance in trapping the neutral particles and has higher neutral pressure near the target, leading to greater power dissipation in the divertor, thus decreasing the detachment threshold in upstream separatrix density. • The evolution of the radiation front and the sensitivity of the detachment process to multiple parameters under the influence of leakage have been investigated. • Simulation results are compared with available neutral pressure measurements from WEST campaigns to verify the predictions from the simulation with respect to the impact of leakage.

A novel test technology for a standardized stability control system and its test platform

The stability control system is the second defense line of the power system, and the test before applying the stability control system is a key link to ensure the performance of the system. Since the configuration and strategy of the standardized stability control system are related through the setting of fixed value items, it is necessary to comprehensively consider the coupling between different application scenarios, different operation modes, and different stability control strategies to verify the functions of each device. Starting from the design concept and function of the standardized stability control system, this paper introduces the test scheme of the standardized stability control system from three aspects: monomer test, static test, and strategy verification test. Besides, the test platform of the stability control system based on RTDS is built, which lays the foundation for the stability control test and ensures that the standardized stability control system meets the requirements of regulations and specifications.

Coordinated control of heterogeneous vehicle platoon stability and energy-saving control strategies

This work presents an overall control strategy for heterogeneous vehicle platoons to minimize energy consumption and improve transportation efficiency by sustaining the string stability of the platoon on signalized arterials under external perturbations. First, the stability criterion is derived by analyzing the string stability of multi-time-lag heterogeneous platoon based on the intelligent driver model (IDM). The optimal model of vehicle platoon consumption is reconstructed to reduce the optimization variables to simplify the solution process. Then, by combining the reconstructed optimal control model with stability, a stable eco-driving model is established for a heterogeneous vehicle platoon consisting of multiple purely electric intelligent connected vehicles (ICVs) and human-driven vehicles (HVs). The overall speed control strategy is proposed by combining the vehicle platoon stability and energy consumption for nonlinear optimization analysis. The platoon is made to pass through the signal intersection with the highest efficiency and the lowest energy consumption to achieve a balance of stability and energy saving. Third, the overall model is optimally solved by a global optimization algorithm, and the numerical simulation has clearly validated the performance of the proposed driving control strategy.