Rotor Control Research Articles

Noncontact Rotor Vibration Velocity Sensor and Its Application to Vibration Control of a Flexible Rotor on Active Magnetic Bearings

Noncontact Rotor Vibration Velocity Sensor and Its Application to Vibration Control of a Flexible Rotor on Active Magnetic Bearings

Research on the aerodynamic characteristics of electrically controlled rotor under Parallel Blade Vortex Interaction using Lattice Boltzmann Method

An electrically controlled rotor (ECR), also known as a swashplateless rotor, employs a trailing edge flap (TEF) system for primary rotor control instead of a swashplate, demonstrating the significant potential in rotor vibration and noise reduction. To investigate the aerodynamic characteristics of the blade flap segment of the ECR under parallel blade vortex interaction, an aerodynamic analysis model based on the lattice Boltzmann method (LBM) is established using the D3Q27 lattice model. The model is validated against experimental data of both the airfoil with trailing edge flap and conventional airfoil under vortex interaction, showing that the LBM can effectively predict variations in aerodynamic loads under both conditions. Based on this model, the effects of different flap deflection angles and miss distances on the aerodynamic characteristics of the ECR under parallel BVI are analyzed. The results indicate that under strong vortex interaction, a region of flow separation forms due to the entrainment effect of the vortex and adverse pressure gradient. The small-scale vortex structure upstream of the flap can also be observed and is believed to contribute to the unsteady flow phenomena such as vortex structure splitting, development, and separation on the upper surface of the flap. The different flap deflection angles mainly affect the scale and type of vortex structures developed on the flap upper surface. As the miss distance increases, the interaction effect is significantly weakened compared to strong vortex interaction. However, as the vortex moves downstream along the airfoil lower surface, it entrains vorticity from the lower surface, ultimately forming a negative pressure region on the lower surface of the flap. The different flap deflection angles will influence the structural characteristics during the downstream motion of the vortex, which changes the size of the negative pressure region, causing differences in the magnitude of the variations in aerodynamic parameters.

Reducing aerodynamic vibration of rigid rotors with retreating side active control avoidance

This paper proposes a new approach to eliminate aerodynamic lift oscillation, called the Dominant Sector Individual Blade Control (DS-IBC) method for rigid rotor helicopters. An Advancing Blade Concept (ABC) rotor model for aerodynamic analysis based on the free-wake method is applied. DS-IBC avoids applying active control on the rotor’s retreating side by employing and restricting active control inputs to a sector area of the rotor disc. Outside this sector, only primary collective and cyclic pitch control are used. Each blade takes turns entering the sector, creating a “relay” active control form to ensure continuous control inputs. The method also includes outer-trim and inner-trim iteration modules. Results show that DS-IBC can eliminate aerodynamic lift oscillation using much smaller control inputs than the sine-trim method. By focusing active control on the rotor’s advancing side, DS-IBC improves the effective lift-to-drag ratio and reduces the implementation difficulty of active rotor control for aerodynamic oscillation elimination, especially at a large lift-offset.

On the power and control of a misaligned rotor – beyond the cosine law

Abstract. We present a new model to estimate the performance of a wind turbine operating in misaligned conditions. The model is based on the classic momentum and lifting-line theories, considering a misaligned rotor as a lifting wing of finite span, and accounts for the combined effects of both yaw and uptilt angles. Improving on the classical empirical cosine law in widespread use, the new model reveals the dependency of power not only on the misalignment angle, but also on some rotor design parameters and – crucially – on the way a rotor is governed when it is yawed out of the wind. We show how the model can be readily integrated with arbitrary control laws below, above, and around the rated wind speed. Additionally, the model also shows that a sheared inflow is responsible for the observed lack of symmetry for positive and negative misalignment angles. Notwithstanding its simplicity and insignificant computational cost, the new proposed approach is in excellent agreement with large eddy simulations (LESs) and wind tunnel experiments. Building on the new model, we derive the optimal control strategy for maximizing power on a misaligned rotor. Additionally, we maximize the total power of a cluster of two turbines by wake steering, improving on the solution based on the cosine law.

Control of Helicopter Using Virtual Swashplate

This article presents a virtual swashplate mechanism for a mini helicopter in classic configuration. The propeller bases are part of a passive mechanism driven by main rotor torque modulaton, this mechanism generates a synchronous and opposite change in the propellers angle of attack, then the thrust vector tilts. This approach proposes to control the 6 degrees of freedom of the aircraft using two rotors. The main rotor controls vertical displacement and uses torque modulation and swing-hinged propellers to generate pitch and roll moments and the horizontal displacement while the yaw moment is controlled by the tail rotor. The dynamic model is obtained using the Newton-Euler approach and robust control algorithms are proposed. Experimental results are presented to show the performance of the proposed virtual swashplate in real-time outdoor hover flights.

Helicopter rotor in a propeller slipstream: Aerodynamic and rotor blade flapping responses

During helicopter air-to-air refueling the helicopter's rotor can engage the tanker aircraft's wing and flap end tip vortices and the slipstream of its propellers. The tip vortices represent a swirl around an axis that is essentially parallel to the rotor longitudinal axis. The slipstream of the propellers includes a strong air jet downstream that can cover a significant amount of the helicopter's main rotor. This phenomenon was recently treated analytically for a rigid rotor by means of blade-element momentum theory and the rotor control angles required to reject the disturbance were computed. In this article, the rotor blade flapping is introduced as degree of freedom. It is shown that the rotor coning is affected by the slipstream position with respect to the rotor hub. Without retrim, the largest amount of coning and cyclic flapping occurs for slipstream positions on the retreating side of the rotor.

Power performance of a model floating wind turbine subjected to cyclic pitch motion: A wind tunnel study

Wind tunnel experiments were performed with a miniature floating wind turbine model to study the effects of cyclic pitch motion on its power performance. The cyclic pitch motion was prescribed by two key parameters: pitch frequency and amplitude. The power performance of the turbine model was investigated at a frequency range of 0.1 − 5.0Hz and an amplitude range of 0 − 30°. Both the mean and time variation of the power production were analyzed, and the effects of the pitch parameters, i.e., the pitch amplitude and frequency, were investigated and discussed. The results show a clear periodicity of power variation and its dependence on pitch frequency and amplitude. For relatively small pitch frequencies (0.5 − 3.0Hz), the mean power and periodic power variation can be predicted based on the uniform and steady flow assumption. Compared to the power output in the baseline case of no pitch dynamics, cyclic pitch motions were found to cause higher power fluctuations, which were contributed by both the pitch motion and flow turbulence. Finally, the temporal variation of the free-rotation speed, used as an indicator of available aerodynamic power, is found to be periodic when the turbine is under cyclic pitch motion. This suggests the possibility of applying dynamic rotor control strategies to maximize power production.

Spring-Damped Underactuated Swashplateless Rotor on a Bicopter Unmanned Aerial Vehicle

The stabilisation capabilities of unmanned aerial vehicles (UAVs) with bicopter underactuated swashplateless rotors are highly sensitive to motor-induced vibration. Due to the requirement of the active control of underactuated swashplateless rotors, conventional designs are limited in reducing vibration through control optimisation. A solution with customized passive spring-damping structures on a unique underactuated swashplateless rotor of a tiltrotor bicopter platform is presented. The implementation of this structure effectively reduces the self-coherent vibration in flights. As a result, a higher level of control authority has been achieved without setting excessive low-pass filtering for vibration. Experimentally obtained inertial measurement unit (IMU) data, rotor speed, rotor tilt angle, and the cyclic stator response are presented for comparison with Simulink model predictions.

Feedforward decoupling vibration control of an unbalanced maglev rotor subjected to base excitation

ABSTRACT The maglev rotor installed on a moving base is subjected to both the unbalanced force of the rotor itself and the base excitation caused by external interferences. The interaction between the maglev rotor and the moving base gives rise to a combination of challenges. Specifically, the base excitation can propagate to the rotor, inducing vibration, while the unbalanced vibration can reciprocally transmit to the base, thereby augmenting the complexity of the base vibration. This paper introduces a feedforward decoupling control approach to address the base excitation vibration of the maglev rotor, utilising the base acceleration as the reference signal. The foundation of the feedforward controller model for countering base excitation vibration is constructed through the utilisation of inverse system principles and system identification techniques. The resultant decoupling model is engineered to facilitate decentralised control of the rotor across four radial directions. Simultaneously, to mitigate the impact of rotor unbalance on the base acceleration reference signal used by the feedforward controller, the least mean square (LMS) adaptive filtering algorithm is employed. This strategy facilitates unconstrained rotation of the rotor around its inertial axis, thereby reducing the unbalanced inertial forces and enabling isolated control of both base excitation vibration and rotor unbalance-induced vibration in the maglev system. An experimental device is constructed to validate the effectiveness of the proposed control methodology. The experimental results show that the maximum vibration amplitude of the maglev rotor decreases by 47% ~71% after the control method is applied.

Nonlinear vibration characteristics of an aeroengine cantilever flexible rotor considering interference fit and unbalance

Aeroengine power turbine rotor is a typical nonlinear rotor system, in which the interference connection between long shaft and short shaft has a prominent influence on the coupling vibration of the system, especially at high speed, the nonlinear stiffness change of interference contact is more obvious. Therefore, the paper considers the change of the contact characteristics of the long shaft and the short shaft of the turbine rotor, and the nonlinear restoring force of the bearing to analyze the dynamic characteristics of the rotor. Firstly, according to the theory of elasticity, the contact parameters under different speed states are calculated, the contact stiffness model under interference fit is established, and the relationship between contact stiffness and speed is analyzed. Secondly, according to the Hertz contact theory, a bearing nonlinear restoring force model considering time-varying characteristics is established. Finally, the dynamic model of the bearing-flexible rotor coupling considering interference contact is established. The influence of contact parameters and unbalance parameters on the nonlinear vibration characteristics of the rotor is analyzed by amplitude-frequency curve, bifurcation diagram, time-domain waveform, spectrum diagram, trajectory diagram and Poincaré diagram. In addition, the simulation results are compared with the experiment results of the rotor test rig to verify the accuracy of the established dynamic model. By analyzing the influence of different parameters such as interference magnitude, unbalance position, unbalance magnitude and unbalance couple on the nonlinear vibration of the rotor, the basis for the design and vibration control of the cantilever turbine rotor is provided.

A minimum objective function trim procedure for VTOLs noise reduction

The present paper proposes a novel approach for multi-rotor acoustic nuisance mitigation based on the identification of optimal control settings. This strategy is possible thanks to the peculiarity of multi-rotor systems (like, for instance, those involved in urban air mobility applications) to have redundant controls. The idea is to take full advantage of the control redundancy by defining the control settings that guarantee the desired steady-state flight conditions while, at the same time, optimizing selected target functions such as performance or noise emissions. To this aim, the trim problem is recast into a constrained cost function minimization problem. Since the objective is to reduce as much as possible the noise disturbance of trimmed VTOL, an aeroacoustic tool based on the chordwise-compact form of the Farassat 1A formulation for the evaluation of noise radiation is suitably coupled with a trim solver. The numerical investigations consider quadcopter and hexacopter configurations in level flight at several advancing speeds. Comparisons of the proposed minimum-noise trim strategy with two other trim strategies based on the minimization of rotor torque and control effort prove its capability to provide an overall reduction of noise throughout the entire velocity range examined.

Optimal control of wave cycloidal rotors with passively morphing foils: An analytical and numerical study

In this paper we perform an analytical and numerical study of the performance of a wave cycloidal rotor in irregular waves, with passively morphing foils and variable rotational velocity control. The performance is measured in two ways: Mechanical power, and fatigue damage in a sample stress hot spot located at the fixed end of the hydrofoils. We consider different strategies seeking to both maximise power extraction and reduce fatigue damage. To maximise power, we consider both constant and variable rotational speed. To mitigate fatigue damage, we consider, for the first time, morphing foils in the context of a wave cycloidal rotor. By testing these control strategies in isolation and in combination, and with the aid of high performance computations, we find that variable rotational speed, in combination with morphing foils, offers the best compromise to enhance power production with a reduced structural penalty on the sample stress hot spot. Hence, in this work, we demonstrate that novel control strategies, such as those proposed in this work, can hold the key in reducing the levelised cost of energy and accelerate the commercialisation of the next generation of lift-based wave energy converters.

Vibration Control of Base-Excited Rotors Supported by Active Magnetic Bearing Using a Model-Based Compensation Method

Active magnetic bearings (AMBs) are a type of mechatronics product widely used in high-speed rotating machinery. Considerable research has been conducted on the vibration rejection of the AMBs-rotor systems at the base standstill. However, little attention has been paid to the case where the rotor operates under base excitations, such as turbines mounted on ships with wave excitation. The increased rotor vibration caused by base excitations is a great challenge to operational safety. To address this issue, a base acceleration feedforward compensation (BAFC) algorithm was proposed in this paper. Using the online base excitation data and the dynamic model of the rotor system, the proposed model-based algorithm determines the optimal compensation current in real time. Further, to reject the decreased compensation performance due to inaccurate modeling, a method for correcting the compensation error has been presented. Moreover, the effect of controller parameters on system stability was explored to avoid parametric instability during base excitations. By employing the BAFC algorithm in the experiments, the rotor vibration was reduced considerably under both the harmonic and random base excitations with a maximum vibration reduction of 85%, demonstrating the remarkable effectiveness of the BAFC algorithm.

Non destructive control of permanent magnet rotors in a perspective of electric motor circularity

This work presents an innovative non destructive control process in order to guide for the end of life (re-use or recycling) of permanents magnets (PM) rotors of electric motors. The process is based on the measurement of the external field produced by the PM rotors. A Finite Element model of the rotor and its environment has been used to simulate a process of classification of the geometry of PM rotors, crucial information for the disassembling of the PM. Firstly, using a finite element model, we were able to investigate the field distribution outside the rotor of the magnetic flux density for different PM rotors designs. From this information, we can set up a classification methodology, based on the Central Voronoi Tessellation (CVT) method, which can help to identify how the PM are inserted within the rotor. This information can be very useful to choose PM disassembling process that should be applied.

Parameter effect on the novel swashplateless rotor control

To achieve underactuated control, a novel swashplateless rotor configuration of asymmetric inclined hinges which can be driven by periodic sinusoidal torque is studied, hopefully eliminating the conventional swashplate mechanism and multiple actuators. Therefore, the traditional mechanism can be intelligently replaced by software. However, high-frequency torque variation will invariably result in vibration noise and energy loss.Thus it is critical to properly design the swashplateless rotor in order to achieve a control process with less torque variation. As a result, in both numerical simulation and experiments, we performed sensitivity analyses on related design parameters such as hinge eccentricity, hinge inclined angle, and wingtip hammer position. The parameter effect on swashplateless rotor control was discovered through the analyses, and the basic law of its design was obtained.

Optimizing Grid Stability through the Integration of Wind Energy

It has become increasingly apparent that wind energy can contribute to reducing carbon emissions and reducing fossil fuel reliance. In spite of this, wind's intermittent nature makes it challenging for grids to maintain stability. The objective of this paper is to review the current state of wind energy integration, highlighting key research findings on the potential of wind power, turbine performance, and approaches to enhance grid stability. A particular part of the research focuses on the modelling of DFIG systems, which includes the rotor control mechanism as well as the grid control mechanism at the grid side of the generator. Voltage fluctuations, transients in the power system, and reactive power management are among the technical challenges associated with wind power integration. SFCLs (Superconducting Fault Current Limiters) are also explored in the paper as innovative solutions for improving grid stability. As a result of simulations, it is demonstrated that SFCLs can mitigate power deviations and improve overall system stability to an extremely high degree.

Study and Evaluation a New Predictive Control Method for Speed and Stator Current Control of Induction Motor

It is clear that modern industries rely heavily on electric motors, especially induction motors. These motors convert electrical energy into mechanical energy. The distinction in the performance of the induction motor lies in that it is powerful when exposed to various operational and environmental variables, and it is also inexpensive. However, there are many traditional disadvantages that appear during the operation of the induction motor in its non-linear mechanical properties in addition to the difficulty in regulating the speed of the motor. In this paper , we present a new control method for controlling the stator current and speed of induction motor based on current control with speed control technique. The present model is based on conventional predictive controller development with a structure which is similar to rotor control and the direct torque control .It has double loops and both loops will use the prediction power. The inner loop controls the stator current based on Finite Control Set - Model Predictive Control (FCS-MPC) and the outer loop controls the speed to maximize the dynamic response of the loop. The MATLAB software has been used to implement the controller circuit. The obtained simulation results indicates that the presented control method has comparable performance to conventional controllers with some reduction in the overshoot and fast response interval.

Design of Unmanned Helicopter Distributed Electric Tail Rotor Controller Based on Improved Active Disturbance Rejection Control

Design of Unmanned Helicopter Distributed Electric Tail Rotor Controller Based on Improved Active Disturbance Rejection Control

Summary to the article ”Complications that arise when sidetracking at the Gunashli field and ways to solve them”

As it is not economically feasible to construct gravity based fixed offshore platform (FOP) for drilling new wells in the “Guneshli” field, the sidetracking using the wells that have stopped producing is important. In this regard, it is necessary to examine the well stock at the field, select unproductive wells, and when using their bores, it is important to continue and increase with sidetracking. For a faster and easier result, first of all it is necessary to choose wells, the production casing which are equipped with diameters of 168 or 178 mm. In such wells, it will be possible to reach the design horizon with a smaller drilling passage by performing cutting operations at lower intervals. As a result, such wells are cheaper and more economically efficient. When performing cutting work on casing with 178 mm diameter, it is possible to drill and expand wells with a relatively large diameter, that is, with a diameter of 127 mm. This, in turn, made it possible to carry out major workover and well remedial work in the future. To eliminate failures and complications that arose during the drilling process, specific conclusions were drawn and it was proposed that when choosing an interval for opening a window, it was necessary to clarify the well configuration.The window opening should be smooth, and after cutting the casings, the cut part should be smoothed out by processing several times. Considering the limited productivity and large pressure losses when drilling small-diameter wells, drilling should be carried out not using a downhole drilling motor, but using a Rotor control system (RCS), one of the latest achievements of new technology. In order to prevent possible absorption and contamination of the well layers, wells should be drilled with solutions based on hydrocarbons or polymer potassium with the addition of necessary materials. If intensive absorption often occurs during drilling, the effectiveness of the measures taken is unsatisfactory, only in such cases should drilling be carried out with a bit with a diameter of 142.9 mm with the addition of materials that prevent absorption, without expanding the wellbore.

Twin Rotor Control via Second Order Sliding Modes

The control problem of a twin rotor system is considered in this study. Since the twin rotor system has highly nonlinear and coupled dynamics, a second order sliding mode controller is proposed which reduces chattering. An estimation for the equivalent part of the controller is also proposed. The classical sliding controller is also calculated and adapted to the twin-rotor system to compare. The numerical results presented that the designed controller achieved superior performance than the classical sliding mode controller in terms of reference tracking and chatter attenuation.