Active Control Strategy Research Articles

Pitch control for floating offshore wind turbines via model-dependent extended state observer-based active disturbance rejection control

Various types of disturbances bring significant challenges to the stable operation of floating offshore wind turbines. This paper formulates the pitch control of floating offshore wind turbines using a novel model-dependent extended state observer-based active disturbance rejection control, which can effectively estimate and compensate for total disturbances. Firstly, a Markov model is proposed to describe wind and wave combined external disturbances and the aerodynamic characteristics of floating offshore wind turbines. Then, an active disturbance rejection control is developed based on the constructed model-dependent extended state observer. The approach provided in this paper can adjust the pitch angle to ensure that the generator speed output tracks the desired reference value. Based on this, the multi verse optimization algorithm is introduced to optimize the parameters of the controller. Finally, the superiorities of the results presented in this paper are illustrated by a 5 MW floating offshore wind turbine model. Simulation results demonstrate that the model-dependent extended state observer-based active disturbance rejection control strategy can significantly adjust the pitch angle to guarantee the stable operation of floating offshore wind turbines under wind and wave combined external disturbances.

Study of a Cable‐Driven Hip Swimming‐Assisted Exoskeleton Utilizing Adaptive Active Control Strategy

ABSTRACTThe power‐assisted exoskeletons have a far‐reaching research significance. The adaptive active control strategy (AACS) of the exoskeleton allows the wearers to achieve personalized assistance tailored to their specific movement patterns and physical needs. However, due to the high requirements for waterproof design and the high difficulty in underwater AACS design, the researches on underwater power‐assisting exoskeletons are hardly to be seen. Therefore, this research proposes a cable‐driven hip swimming‐assisted exoskeleton (SAE) utilizing an AACS. SAE can generate adaptive power‐assisting guiding trajectories of thighs by underwater motion intention perception (UMIP) of the wearer. To achieve UMIP, a deep learning network is presented by combining conventional neural network, bidirectional long short‐term memory network, and attention mechanism (AM‐Dconvbilstm). SAE guides the wearer's thighs to move along the generated guiding trajectory by UMIP through the cables to conduct hip power assisting. The feasibility of the proposed AM‐Dconvbilstm on UMIP and the power‐assisting effect of designed SAE are tested on three elite swimmers by recording corresponding data from IMUs and a sports watch. According to the results of generated trajectories from SAE and actual trajectories from the wearer, the proposed AM‐Dconvbilstm model is verified to predict the wearer's hip motion intention accurately. The power‐assisting effect of SAE is also verified according to the sports watch's heart rate and average energy consumption. All the experiment results greatly validated the feasibility of the proposed AACS and designed SAE.

Flow characteristics analysis and combustion oscillation mitigation of a hydrogen industrial burner

With the promotion of carbon neutrality policies, hydrogen burners are widely used in the industrial field, and exploring the combustion characteristics and stable combustion technology of hydrogen industrial burners has important engineering application significance. This study investigates the flow characteristics and combustion oscillation mitigation of a specific hydrogen industrial burner for heating thermal oil through experiments and numerical simulations. The oscillating combustion with a frequency of 100 Hz is discovered during the field test. The dynamic characteristics are reproduced via large eddy simulation (LES), and the pressure amplitude is reduced by 22% via the active control strategy. LES results show that corner recirculation zone and main recirculation zone occur in the flame holding chamber, with maximum recirculation velocity and maximum temperature of −20 m/s and 2110 K, respectively. The unstable modes and key elementary reactions are revealed by modal analysis and eigen-analysis. The clustered neural network with horizons (CNNH) controller is constructed to suppress the combustion instability. The CNNH controller can effectively suppress the pressure oscillation by perturbing the inlet mass flow rate of main H2, reducing the peak amplitude in the frequency domain by 67%. By optimizing the controller parameters, the CNNH controller can be further applied to different scenarios of hydrogen industrial burners.

Study of the double closed-loop active disturbance rejection control strategy for the longitudinal motion of fully submerged hydrofoil craft

In the process of high-speed driving, the longitudinal motion of the hydrofoil craft has the characteristics of parameter uncertainty and strong coupling, which leads to poor stability of the hydrofoil craft and the problem of high precision requirement for disturbance wave data. Therefore, a control method based on active disturbance rejection control (ADRC) and double closed loop is proposed. The algorithm is under the condition of decoupling the ship’s motion attitude and realizes the internal and external double-loop active disturbance rejection control of pitch angle and heave displacement based on the high-order sliding mode observer (HSMO) with better adaptability. By designing the speed error integral sliding mode surface, the dynamic characteristics of the system have been improved., and improve overall hydrofoil stability at high speeds. Finally, based on the Unreal Engine 5 platform, a visual longitudinal motion control system of hydrofoil craft is constructed. The simulation results show that compared to the existing sliding control mode, this control method can reduce the heave displacement and pitch angle by about 50%, shorten the response time of real-time control of hydrofoil craft. The superiority and effectiveness of the control system were verified.

Active Control of Shimmy in Articulated Single-Axle Straddle-Type Monorail Train

The articulated single-axle straddle-type monorail train has many unique advantages, making it the preferred choice for medium-capacity urban rail transit. However, the issue of vehicle shimmy greatly restricts its promotion and application. In response to this issue, an active suspension control scheme is proposed, and the corresponding control algorithm is designed. Considering economic and feasible factors, a modification plan for the single-axle bogie without changing the original structure is proposed. A closed-loop feedback control strategy with lateral velocity and yaw rate as control objectives is designed, and a 114 degree-of-freedom dynamic model of a monorail train is established. Taking the skyhook damping control as the reference model, the SH-SMC (skyhook-sliding mode control) active control scheme is designed based on the sliding mode control theory. Considering practical applications, the control force distribution algorithm is further proposed. Through co-simulation of UM and Matlab, different control schemes are compared and analyzed. The results indicate that the SH-SMC active control scheme is more effective in suppressing the shimmy of single-axle monorail train, verifying the effectiveness of the SH-SMC active control scheme. It is of great significance for the further promotion and application of single-axle monorail trains in more cities.

Pressure Control of Multi-Mode Variable Structure Electro-Hydraulic Load Simulation System.

During the loading process, significant external position disturbances occur in the electro-hydraulic load simulation system. To address these position disturbances and effectively mitigate the impact of uncertainty on system performance, this paper first treats model parameter uncertainty and external disturbances as lumped disturbances. The various states of the servo valve and the pressures within the hydraulic cylinder chambers are then examined. Building on this foundation, the paper proposes a nonlinear multi-mode variable structure independent load port electro-hydraulic load simulation system that is tailored for specific loading conditions. Secondly, in light of the significant motion disturbances present, this paper proposes an integral sliding mode active disturbance rejection composite control strategy that is based on fixed-time convergence. Based on the structure of the active disturbance rejection control framework, the fixed-time integral sliding mode and active disturbance rejection control algorithms are integrated. An extended state observer is designed to accurately estimate the lumped disturbance, effectively compensating for it to achieve precise loading of the independent load port electro-hydraulic load simulation system. The stability of the designed controller is also demonstrated. The results of the simulation research indicate that when the command input is a step signal, the pressure control accuracy under the composite control strategy is 99.94%, 99.86%, and 99.76% for disturbance frequencies of 1 Hz, 3 Hz, and 5 Hz, respectively. Conversely, when the command input is a sinusoidal signal, the pressure control accuracy remains high, measuring 99.94%, 99.8%, and 99.6% under the same disturbance frequencies. Furthermore, the simulation demonstrates that the influence of sensor random noise on the system remains within acceptable limits, highlighting the effective filtering capabilities of the extended state observer. This research establishes a solid foundation for the collaborative control of load ports and the engineering application of the independent load port electro-hydraulic load simulation system.

Finite-time output consensus control of nonlinear uncertain multi-agent systems via extended state observer

This paper investigates the finite-time consensus problem for nonlinear uncertain multi-agent systems (MASs) affected by mismatched uncertainties and disturbances, as well as partial measurements. An active disturbance rejection control (ADRC) strategy that combines the backstepping technique with an extended state observer is proposed. Firstly, a finite-time state feedback controller is designed to ensure consensus when ignoring external disturbances. Secondly, a finite-time extended state observer (FTESO) is proposed for each agent to estimate the unavailable state and external disturbances, and a feedforward-feedback composite consensus controller is then developed. Furthermore, utilizing the homogeneous domination approach, we demonstrate that the proposed composite control strategy guarantees finite-time output consensus. Finally, the effectiveness of the proposed composite control strategy is illustrated using a multiple-manipulator system as an example.

Swirling flow axial injection control in a Francis turbine: An LES study

This study investigates an active control strategy to suppress the precessing vortex core (PVC) and aims to extend the stable operation range of Francis turbine air model. Large-eddy simulation (LES) is used to analyze swirling flow under partial load conditions with axial jet injection within a narrow range of injection flow rates (1 to 5% of the main flow rate). The geometry, flow parameters and control technique are adopted from the experimental work of Litvinovet al. (2023). The effectiveness of the injection is assessed by analyzing the time-averaged velocity and fluctuations, wall pressure pulsations signal and its azimuthal decomposition. Additionally, the influence of axial injection on pressure fluctuations induced by the PVC and instantaneous pressure isosurfaces are examined. The results show that 3% injection flow rate most effectively mitigates the PVC dynamics while not causing other instabilities to occur. On the contrary, jets of 4% and 5% flow rate induce additional perturbations. Proper orthogonal decomposition of the pressure field is applied in this manuscript to reveal coherent structures of the swirling flow in cases without injection and with 3 and 5% jet flow rates.

Flatness-based nonlinear internal model control with disturbances compensation via improved extended state observer for remotely operated vehicle

This paper proposes an improved Active Disturbance Rejection Control (ADRC) scheme for nonlinear control-affine systems, achieving superior robustness/ performance trade-offs. By leveraging the flatness property within a closed-loop structure, Nonlinear Internal Model Control (NLIMC) is employed as a model-based controller utilises partial plant knowledge to enhance control performance and eliminate static tracking errors. Subsequently, an improved Extended State Observer (IESO) is incorporated with NLIMC to address unmodelled dynamics, disturbances, and parameter uncertainties in addition to the full state's estimation. The IESO's added hyperbolic function dynamic ensures higher sensitivity and accuracy compared to conventional linear ESOs, especially in case of large errors. Control performances are evaluated through a Remotely Operated Vehicle (ROV) application. Numerical simulations have been carried out and the results confirm its effectiveness and superiority compared to Ocean Disturbance Observer-based Double-loop Sliding Mode Controller (ODSMC) and the linear ADRC.

A LiDAR-Based Active Yaw Control Strategy for Optimal Wake Steering in Paired Wind Turbines

In this study, we investigate a yaw control strategy in a two-turbine wind farm with 3.5 MW turbines, aiming to optimize power management. The wind farm is equipped with a nacelle-mounted multi-plane LiDAR system for wind speed measurements. Using an analytical model and integrating LiDAR and SCADA data, we estimate wake effects and power output. Our results show a 2% power gain achieved through optimal yaw control over a year-long assessment. The wind predominantly blows from the southwest, perpendicular to the turbine alignment. The optimal yaw and power gain depend on wind conditions, with higher turbulence intensity and wind speed leading to reduced gains. The power gain follows a bell curve across the range of wind inflow angles, peaking at 1.7% with a corresponding optimal yaw of 17 degrees at an inflow angle of 12 degrees. Further experiments are recommended to refine the estimates and enhance the performance of wind farms through optimized yaw control strategies, ultimately contributing to the advancement of sustainable energy generation.

Active boundary control of spinning beams with elastic constraints using piezoelectric stack actuator

A spinning beam structure is usually subjected to severe vibration. To suppress this vibration, piezoelectric stacking actuators are installed on the boundary of the spinning beam. Here, an active boundary control model for the vibration of spinning beam structures with elastic constraints is established. The dynamic equation of motion of the coupled system is derived by combining the Lagrange equation with the modified Fourier series method. An active control strategy is used to suppress the vibration of the spinning beam with elastic constraints. The vibration suppression effect of the proposed method under different spinning speeds and different elastic boundary conditions is discussed. It is proven that the current active control scheme can quickly suppress the vibration of the spinning beam structure with elastic constraints. The present control method can provide a new way to suppress the vibrations of spinning beam structures with nonideal boundaries in practical engineering.

Active disturbance rejection control with adaptive RBF neural network for a permanent magnet spherical motor

In response to the issues of low tracking accuracy and poor robustness in the trajectory tracking control of a permanent magnet spherical motor (PMSpM), an active disturbance rejection control (ADRC) scheme combining neural networks is put forward in this research. The unknown total disturbance is approximated by employing a radial basis function (RBF) neural network, with weights updated by an adaptive law and compensated for through the nonlinear feedback loop. This approach addresses the problem of performance degradation of the extended state observer under severe total disturbance, thereby ensuring accurate tracking of the PMSpM. Comparative simulations are accomplished to evaluate the performance of the RBF-ADRC scheme in enhancing disturbance rejection capability and robustness. Experimental results from the planar circular motion experiment on the PMSpM test platform validate the application value of the scheme.

Adaptive neuro-fuzzy inference system based active force control with iterative learning for trajectory tracking of a biped robot

ABSTRACT We investigate the integration of the active force control (AFC) scheme and the adaptive neuro-fuzzy inference system (ANFIS) as an intelligent controller algorithm to address trajectory-tracking problems in robotic systems, The AFC-ANFIS model exploits iterative learning (IL) to improve the tracking performance based on its trained model. The ANFIS parameters are tuned using both particle swarm optimisation (PSO) and beetle antennae search (BAS) algorithms. The simulation results of two different robots, i.e. a five-link biped robot and a PUMA 560 robot arm, indicate that the proposed AFC-ANFIS controller performs well for trajectory tracking and disturbances rejection. The AFC-ANFIS performance is evaluated and compared with those from other controllers using the average tracking error (ATE) metric. The comparative results reveal that AFC-ANFIS offers a viable approach with a rapid training process to undertaking trajectory tracking and disturbance rejection tasks.

Active constrained motion control for a robot-assisted endoscope manipulator in pediatric minimal access surgery.

Robot-assisted laparoscopic surgery has three main system requirements: safety, simplicity, and intuitiveness. However, accidental movement of the endoscope due to body fatigue and misunderstanding of the verbal orders between the surgeon and assistant will contribute to highly unexpected tool-tissue interactions, particularly in pediatric minimal access surgery with restricted working space. This study introduces a compact, lightweight endoscope manipulator with a mechanical remote-center-motion function. Using a custom-designed human-machine interface, the surgeon can intuitively control the movement of the endoscope manipulator over their view. In addition, an active constrained motion control algorithm is proposed to generate a forbidden-region constraint for avoiding collisions between the endoscope tip and surrounding organs in a pediatric abdominal cavity with restricted space. Simulations and experiments demonstrate the performance of the proposed compact endoscope manipulator and the active constrained surface tracking control scheme.

Fixed-time active fault-tolerant control for a class of nonlinear systems with intermittent faults and input saturation

In this paper, the problem of fixed-time active fault-tolerant control is studied for systems with sector-bounded nonlinearities, intermittent faults, and input saturation. Since intermittent faults appear and disappear randomly, a fixed-time scheme is considered in the active fault-tolerant control algorithm, composed of detection, isolation, estimation, and the control unit. Utilizing homogeneity-based observers, the fixed-time state estimation is available in the presence of unknown but bounded disturbances, and a fault diagnosis unit is proposed. An input saturation compensator is introduced to analyze the effect of input saturation, and its auxiliary variables are used in the reconfigurable control law. The fault-tolerant controller, which is constructed via the information provided by the fault diagnosis unit and saturation compensator, has two switching modes. As a consequence, intermittent faults are compensated via the designed active fault-tolerant control method and the system reaches practical stability with the entire convergence time bounded in a fixed time. Finally, the example of a heat control system is exploited to demonstrate the effectiveness of the developed active fault-tolerant control scheme.

Study on Dynamic Characteristics of Single-Span Rotor Under Cross-Coupling Stiffness Control on Non-drive End

Abstract The sealing-induced cross-coupling stiffness (CCS) often decreases the rotordynamic stability of turbomachinery. In our previous study, an active negative CCS control strategy applied between two bearings in the middle of the rotor was validated to enhance the stability of the rotor system. In this paper, a different approach was taken by applying both positive and negative CCS control strategies to the non-drive end, aiming to investigate their effects on rotordynamic stability using a rotordynamic model. The model represented a single-span centrifugal compressor rotor with CCS at the seal node. The logarithmic decrements and unbalance response of the rotor system were compared under different CCS applications at the non-drive end and in the span. The results demonstrate that applying both positive and negative CCS at the non-drive end can improve system stability, but the positive CCS strategy has limitations, and its applicability is not as extensive as Negative CCS. A “critical stiffness” phenomenon emerges when the rotor system is actively stabilized at the non-drive end, resembling critical resonance. Furthermore, when components like seals introduce cross-coupling stiffness out of the span, they contribute to system stabilization. These findings provide valuable insights into actively enhancing the stability of rotor systems.

Reliably estimating the impact of an active control strategy in a building

Conventional measurement and verification (M&V) methods rely on a pre-/post-intervention analysis that generally take a long time (2 years) to estimate energy savings. Further, results are often affected by changes in building performance that are unrelated to the intervention but that occur over that timeframe. This paper describes a new method which applies to interventions that are easily switchable, such as active control strategies, and which overcomes these limitations. It uses a switchback design that randomly and frequently switches building operations between baseline and intervention strategies at fixed time intervals (e.g., daily). The method uses sequential testing to evaluate pre-defined stopping criteria using measurements obtained by that point in time. Upon satisfying all criteria, the analyst reports savings with an associated uncertainty. The paper demonstrates the method by evaluating a control strategy developed by a software-as-a-service company in a case study building in Chicago, IL, USA. It provides guidance on randomization and blocking, selection of meaningful stopping criteria, implementation of sequential evaluation, and annual weather normalization. The results show that all pre-defined thresholds were satisfied after 45 weeks and the method reliably detected an annual average power savings of 7 kW (±5 kW at 90 % confidence), or 11 % annual energy savings when weather normalized. This result was obtained faster and more robustly than conventional methods, and remained consistent with estimates derived from a further 15 weeks of data. The supplementary material includes example software code to apply this method to other case studies and replicate this analysis.

Research on a Bridge Hybrid Isolation Control System Based on PID Active Control and Genetic Algorithm Optimization

A bridge hybrid isolation system, integrating both active and passive control strategies, is proposed and investigated to enhance seismic performance. The system is modeled as a two-layer structure, with the upper layer subjected to active control via a Proportional–Integral–Derivative (PID) controller, and the lower layer employing a conventional passive base isolation system. The displacement response of the superstructure is minimized by the control forces generated by the PID controller, which also accounts for the reaction forces transmitted to the lower isolation layer. To optimize the controller’s performance, a genetic algorithm is implemented for real-time tuning of the PID parameters. Numerical simulations, conducted using the Newmark method, are employed to assess the influence of active control on the lower isolation system. The results reveal that, while active control increases the peak displacement of the superstructure to some extent, it significantly prolongs the structural period, thus enhancing the system’s overall seismic resilience and stability.

Active Support Pre-Synchronization Control and Stability Analysis Based on the Third-Order Model of Synchronous Machine

When traditional grid-forming converters directly participate in the grid-connected operation of the power grid, due to the lack of a pre-synchronization control system, the voltage amplitude and initial phase on both sides of the grid-connected point will deviate, resulting in voltage and current distortion during grid-connected mode. An active support phase-locked loop free pre-synchronization control strategy based on the third-order model of a synchronous generator is proposed to address the grid-connected problem of the grid-forming converter mentioned above. First, a model of active support control with frequency integral feedback at small signal levels was constructed. The root locus method was employed to examine how system parameters affect the stability of the active support control system. Second, by adding phase pre-synchronization controllers and amplitude pre-synchronization controllers to the active frequency loop and excitation voltage loop of the third-order model, it was ensured that the frequency, phase, and voltage amplitude of the unit are consistent with the power grid, achieving a fast and smooth grid-connected mode of the unit. Finally, by using a DC source to simulate all types of new energy power generation equipment, the active support pre-synchronization control system based on the three-order model of synchronous generator is built in the MATLAB/Simulink simulation environment, and the accuracy and effectiveness of the control strategy in this paper is verified.

Effects of Perforated Plates on Shock Structure Alteration for NACA0012 Cascade Configurations

To alleviate the shock boundary layer interaction adverse effects, various active or passive flow control strategies have been investigated in the literature. This research sheds light on the behavior of perforated plates as passive flow control techniques applied to NACA0012 airfoils in cascade configurations. Two identical perforated plates with shallow cavities underneath are accommodated on the upper and lower surfaces of each airfoil in the cascade arrangement. Six different cascade arrangements, including a baseline configuration with no control applied, are additively manufactured, with different perforated plate orifice sizes in the range of 0.5–1.2 mm. A high-speed wind tunnel with Schlieren optical diagnosis and wall static pressure taps is used to investigate the changes in the shock waves pattern triggered by the perforated plates. Steady 3D density-based numerical simulations in Ansys FLUENT are conducted for further analysis and validation. In the cascade configuration, the perforated plates alter the shock structure, and the strong normal shock wave is replaced by a weaker X-type shock structure. Eventually, a 1% penalty in overall total pressure loss is induced by the perforated plates because of the negative loss balance between the reduced shock losses and the enhanced viscous losses. Further studies on perforated plate geometrical features are needed to improve this outcome in a cascade arrangement.