Blade Motion Research Articles

Experiments on Structurally Mistuned UHBR Open-Test-Case Fan ECL5/CATANA

Abstract The operational capabilities of turbofan engines encounter limitations due to instabilities arising from tightly coupled interactions among aerodynamics, acoustics, and structural mechanics. Modern fans and compressors exhibit non-synchronous vibration (NSV), leading to safety-critical blade oscillations. In contrast to self-excited phenomena such as flutter, NSV stems from the convection of aerodynamic disturbances that synchronize with blade eigenmodes. Understanding this phenomenon is challenging, as its intricate interaction patterns and the occurrence of flow separations constrain the predictive capabilities of current state-of-the-art methods. To establish a comprehensive benchmark dataset on the aeroelastic behavior of modern ultra-high bypass ratio (UHBR) architectures, the European CleanSky-2 project CATANA aimed to examine a carbon composite fan stage, ECL5, utilizing multiphysical instrumentation. Recently, experiments on a structurally tuned reference configuration were conducted, revealing high-amplitude NSV at multiple subsonic speedlines. The observed interaction modes and instability onset differed significantly from numerical predictions using both linearized Reynolds-averaged Navier–Stokes and unsteady Reynolds-averaged Navier–Stokes with prescribed harmonic blade motion. In an effort to enhance the dataset, two additional fan configurations with identical blade profile geometries were investigated: one featured a structurally mistuned rotor with approximately doubled frequency variation of all eigenmodes compared to the reference, and the other involved a case with locally increased tip clearance on individual blades. This paper presents the experimental results of a sensitivity study and explores the influence of structural mistuning and tip clearance variation associated with manufacturing tolerances. Contrary to the intended outcome, it will be demonstrated that the mistuned case exhibited higher blade vibration amplitudes than the reference case during NSV. Detailed instrumentation reveals that the mistuning pattern was effectively transferred to the rotating system, but aerodynamic mistuning, particularly concerning tip clearance, emerged as a dominant factor. The non-synchronous forced-response nature of NSV during highly throttled operation ultimately dictates the observed response levels under different conditions, necessitating a thorough analysis to evaluate the robustness of a specific configuration. These results contribute valuable insights to the open dataset for the ECL5 configuration, benefiting the research community. Particularly noteworthy is the detailed capture of blade-to-blade variations in this research, which will prove instrumental in validating numerical methods.

Rheology and structure of ceramic stereolithography slurries: Role of powder nature, dispersant, and orthogonal strain

AbstractWe investigate the rheological properties of ceramic slurries designed for laser stereolithography manufacturing in relation to their formulation, including the powder morphology, their volume fraction, and the concentration of dispersing agent. By combining dynamic strain sweep and Small‐Angle X‐ray Scattering (SAXS) experiments, we first illustrate that slurry viscosity follows an exponential trend with increasing particles content, with steeper increase observed for more aggregated particles. We then show that increasing the dispersant concentration up to an optimal value decreases slurry viscosity, as SAXS measurements reveal a reduction and homogenization in agglomerate size. Finally, we evidence that applying vertical oscillatory deformation during steady shear flow induces fluidization of the slurry. The shear viscosity exhibits a time–strain rate equivalence, enabling the generalization of this effect across a wide range of formulations. This methodology holds potential for industrial applications, where introducing vibration perpendicular to the scraping blade motion could improve the surface quality of the spread slurry prior to polymerization.

Target sensitivity study of density transition-injected electrons in laser wakefield accelerators

While plasma-based accelerators have the potential to positively impact a broad range of research topics, a route to application will only be possible through improved understanding of their stability. We present experimental results of a laser wakefield accelerator in the nonlinear regime in a helium gas jet target with a density transition produced by a razor blade in the flow. Modifications to the target setup are correlated with variations in the plasma density profile diagnosed via interferometry and the shot-to-shot variations of the density profile for nominally equal conditions are characterized. Through an in-depth sensitivity study using particle-in-cell simulations, the effects of changes in the plasma density profile on the accelerated electron beams are investigated. The results suggest that blade motion is more detrimental to stability than gas pressure fluctuations, and that early focusing of the laser may reduce the deleterious effects of such density fluctuations. Published by the American Physical Society 2024

On Hysteresis In A Variable Pitch Fan Transitioning To Reverse Thrust Mode And Back

Abstract A novel hysteresis phenomenon during the transition to and back from the reverse thrust mode in a Variable Pitch Fan (VPF) is identified and characterised in this work. This is done by using a three-dimensional (3D) fully transient Unsteady Reynolds averaged Navier?Stokes (URANS) with the transitioning fan blade aerofoils simulated by an adaptation of the mesh displacement method. The VPF is modelled to be transitioning in a modern 40000 lbf geared high bypass ratio turbofan engine architecture at "Approach Idle" engine power setting in a typical twin-engine airframe with the flaps, slats, and spoilers set for an aircraft touchdown airspeed of 140 knots. The transition to reverse thrust mode involves flow starvation into the engine, formation of recirculation zones in the bypass duct and the establishment of the reverse stream, all of which occurs in the opposing presence of the free stream flow at aircraft touchdown velocity. The transition back to forward flow mode involves the gradual re-establishment of the free stream which is opposed by the presence of the reverse stream within the engine. It is quantified that in the transition to reverse thrust, the blockage develops with a larger time delay than the disappearance of the blockage during the transition back due to the interplay of the temporal dynamics of fan blade motion and flow field response. The hysteresis phenomena described in this work are critical in properly developing control schedules to adapt for potential bi-stable flow field development during the landing run.

An experimental and numerical investigation into the influence of wind effects on wind turbines with tubular towers

This study delves into investigating the profound impact of wind loads on the structural integrity of wind turbines. To comprehensively assess the influence of wind loads, a two-pronged approach was adopted: first, a meticulously crafted 1/100 scale model was employed within a wind tunnel, and second, advanced numerical simulations based on computational fluid dynamics (CFD) were conducted. Moreover, the study takes into account the intricate factor of turbine proximity in the wind tunnel setup. The design of the tower structure takes into consideration an array of loads, including lateral and gravitational forces. Notably, a substantial load arises from the rotational force generated by blade motion, which exerts its effects on the structure. Calculations of this force were executed using ABAQUS software. This multifaceted analysis involves the application of angular velocity to the blades, subsequently enabling the computation of time-dependent support reactions via dynamic numerical analysis employing the Newmark method. Furthermore, the study encompasses the determination of static equivalent forces. It is noteworthy that the maximum displacement experienced by the structure coincides with the initial phase of blade movement.

Influence of rotation speed and frequency on the decision of Columba livia domestica (homing pigeon) to cross the rotor-swept area of paper blades mimicking a wind turbine

Abstract To reduce bird collisions with wind turbines, automatic detection systems have been developed to slow the blades down when a bird is approaching. We experimentally tested whether blade rotational speed (i.e., number of rotations per min) and frequency (i.e., number of times a blade passes a point per min) affected the decision time (i.e., time to take-off), path choice (i.e., the position in the aviary), and decision to cross the rotor-swept area in Columba livia domestica (rock dove [domestic variety]; aka homing pigeon; hereafter, pigeon). We used a homemade device with paper blades, mimicking the movement of wind turbine blades. We adjusted the paper blade dimensions and achromatic contrast with the background to match the visual capabilities of pigeons, increasing the probability of detection. Pigeons were less likely to cross the rotor-swept area at higher speeds and frequencies, independent of their decision time. When pigeons crossed the rotor-swept area (43 out of 160 trials), 63% collided with the blades, regardless of blade speed or frequency. Pigeons chose to avoid the rotor-swept area after they had travel half the distance to the wind turbine. Pigeons were not better able to avoid the rotor-swept area when blades were rotating at low speed and/or frequency and often collided with the blades. Thus, slowing blades to a low rotational speed may not reduce collisions with some species and a complete turbine shutdown may be necessary. The feasibility and economic costs of regular complete shutdowns after the deceleration triggered by the automatic detection systems need further investigation.

Reliability calculation and error analysis of VSV adjustment mechanism motion accuracy

The adjustable stator vane (VSV) adjustment mechanism of an aircraft engine was taken as the research object, and a kinematic model with kinematic pair clearance was established. Considering the randomness of factors such as drive error, dimensional error and assembly clearance, a VSV adjustment mechanism motion accuracy reliability model considering the failure correlation of each stator blade motion accuracy was established. The BP neural network proxy model was introduced, and the Monte Carlo method was used to calculate the reliability of the mechanism, and the variation law of the reliability with the number of stator blades and the failure threshold was given. By comparing with the system model with independent unit failure assumptions and the fully correlated system model, the rationality of the mechanism system motion accuracy reliability model considering failure correlation was verified. Finally, a method for estimating the reliability error of the complex system caused by the proxy model error was proposed, and it was proved that the reliability calculation result of the VSV adjustment mechanism is accurate and reliable.

Comprehensive study of vortices interaction and blades height effect in a Darrieus vertical axis wind turbine with J‐type blades

AbstractThere is a growing demand to improve the performance of vertical axis wind turbines to facilitate their commercialization for application in urban areas. This study utilizes a 3D numerical analysis to examine the influence of different vortices generated on turbine efficiency with straight and J‐type blades. The numerical simulation of this study employs the Reynolds‐Averaged Navier–Stokes equations and ‎sliding ‎mesh techniques ‎to more accurately model the rotational motion of blades about the turbine axis in relation to the ‎wind. Comparing the output ‎torque and the flow field at different span‐wise sections, the J‐type blades achieve better ‎performance at mid‐spans where the effect of stall vortices is dominant. Conversely, the lower ‎performance of J‐type blades is seen at tip spans due to stronger tip vortices. Investigations also ‎reveal the criticality of the downwind region on the overall performance at high tip speed ratios. It is observed that by ‎increasing the height, the tip vortices are limited to the tip sections, and stall vortices expand further ‎along the blade. At TSR = 1, the improvement by J‐type blades rises from 10% at a height of 0.8 m to 44% ‎at 3 m. The growth in height at lower wind speeds becomes more beneficial. Compared to the straight blades, the self‐starting ‎generated torque by J‐type blades for heights of 0.8, 1.2, and 1.6 m, are improved by 15.6%, ‎‎26.9%, and 34.7%, respectively. Overall, it is concluded that by increasing the blade height, the superiority ‎of the J‐type blade becomes more noticeable as the blade mainly contributes to suppressing the stall ‎vortices effect where the tip vortices effect is not presented. ‎

On modeling added mass and circulation terms with fast potential-flow methods for oscillating-foil propulsors

The design of cycloidal thrusters and other oscillating foil propulsors requires fast tools that provide accurate estimates of propulsor hydrodynamic performance and mechanical loads. Potential-flow theory coupled with empirical formulae that account for viscous effects is the best choice for fast multi-parameter optimization. Within this context, oscillating foils are usually approximated as thin wings with flow solutions derived from small-disturbance theory. Added mass (non-circulatory) effects may be relevant even under such assumptions. They can be easily included in the flow equations assuming that the foil is a flat plate heaving and pitching. However, for blade motions involving complex trajectories like those in Voith Schneider propellers, the foils describe cycloidal loops, and the assumption of small pitch angles is no longer valid. Therefore, a more accurate modeling of added mass and circulatory terms is required.This paper presents extensions to a previous model, which allows for a more precise representation of the added mass terms in the potential flow equations, combining low computational cost and accurate modeling. The results show clear improvement in the evolution foil forces in time when the new approach is used. The extensions are especially needed for the simulations of foils describing complex paths with large variations of pitch angle. Applications to transverse-axis cycloidal propulsors are presented as well as to unconventional counter-flapping propulsors that have recently appeared in the scientific literature. Validation of the method with RANS computations is provided.

Analyzing dynamic stall on tubercle mounted VAWT blades: A simplistic experimental approach using an oscillating rig

Leading-edge tubercles, inspired by the flippers of humpback whales, are widely adopted passive flow control devices to enhance the aerodynamic performance of various lifting surfaces. This experimental study investigates the implementation of sinusoidal and triangular tubercles on H-type Vertical Axis Wind Turbine blades to analyze their effects on dynamic stall characteristics. Experimental tests were conducted using a specially designed oscillating rig to replicate blade motion at different reduced frequencies. The results reveal that tubercle blades exhibit a lower stall angle and maximum normal force compared to the baseline configuration. Moreover, the dynamic stall characteristics of tubercle blades are notably smoother, leading to reduced hysteresis losses. A variation in the tubercle amplitude-wavelength ratio further decreases hysteresis, albeit at the cost of reduced normal force generation. At the highest tested reduced frequency of 0.065, tubercles reduce hysteresis by up to 38%. Despite the reduction in normal force, tubercles effectively mitigate the effects of dynamic stall vortices, resulting in smoother stall behavior. The observed reduction in hysteresis can contribute to enhancing the turbine’s lifespan and increasing power production efficiency. This experimental approach provides a cost-effective alternative to more expensive methods for studying dynamic stall characteristics.

Comparison of aerodynamic and aeroacoustic characteristics of fixed-pitch and variable-pitch rotors

This research conducts a comparative analysis of the aerodynamic and aeroacoustic characteristics of fixed-pitch and variable-pitch controlled multirotors [i.e., revolution per minute (RPM) and collective pitch control]. The study encompasses single-, twin-, and quad-rotor configurations under hovering flight conditions. The unsteady blade motion is modeled as a function of RPM and pitch, fluctuating with frequency and amplitude. To comprehensively account for wake interaction effects, a free-wake vortex lattice method combined with acoustic analogy is utilized. The findings reveal that unsteady blade motion and wake interaction effects cause fluctuations in thrust and tip vortex trajectory. The thrust and tip vortex behavior exhibited greater instability in response to RPM fluctuations than to pitch fluctuations. Consequently, the axial unsteady loading noise was more pronounced under RPM fluctuations compared to pitch fluctuations. In both twin- and quad-rotor configurations, the wake interaction significantly influenced the characteristics of thrust and tip vortex behavior. In addition, spectral analysis demonstrated that the frequencies of unsteady blade motion and wake interaction determine the frequencies of thrust and tip vortex fluctuations as well as unsteady loading noise.

Interference mechanism of trailing edge flap shedding vortices with rotor wake and aerodynamic characteristics

A robust Reynolds-Averaged Navier-Stokes (RANS) based solver is established to predict the complex unsteady aerodynamic characteristics of the Active Flap Control (AFC) rotor. The complex motion with multiple degrees of freedom of the Trailing Edge Flap (TEF) is analyzed by employing an inverse nested overset grid method. Simulation of non-rotational and rotational modes of blade motion are carried out to investigate the formation and development of TEF shedding vortex with high-frequency deflection of TEF. Moreover, the mechanism of TEF deflection interference with blade tip vortex and overall rotor aerodynamics is also explored. In non-rotational mode, two bundles of vortices form at the gap ends of TEF and the main blade and merge into a single TEF vortex. Dynamic deflection of the TEF significantly interferes with the blade tip vortex. The position of the blade tip vortex consistently changes, and its frequency is directly related to the frequency of TEF deflection. In rotational mode, the tip vortex forms a helical structure. The end vortices at the gap sides co-swirl and subsequently merge into the concentrated beam of tip vortices, causing fluctuations in the vorticity and axial position of the tip vortex under the rotor. This research concludes with the investigation on suppression of Blade Vortex Interaction (BVI), showing an increase in miss distance and reduction in the vorticity of tip vortex through TEF phase control at a particular control frequency. Through this mechanism, a designed TEF deflection law increases the miss distance by 34.7% and reduces vorticity by 11.9% at the target position, demonstrating the effectiveness of AFC in mitigating BVI.

Effect of baffles on efficiency of darrieus vertical axis wind turbines equipped with J-type blades

This study investigates the effects of incorporating baffles in J-type bladed vertical axis wind turbines. The objectives are to analyze the behavior of vortices and their impact on turbine performance and to explore various locations for placing the baffles along the J-type blades. The 3D numerical simulations of the current study applies the sliding mesh techniques to better model the rotational motion of blades about the turbine axis with respect to the wind. The results show that mounting zero-thickness baffles over the tips of the blades effectively reduces vortex leakage, minimizes tip vortices, and increases the pressure differential across the sides of J-type blades leading to a significant improvement of the turbine performance. At low tip speed ratios (TSRs) of 0.5, 0.75 and 1, in particular, the torque generation in comparison with conventional NACA0021 straight bladed turbines has been improved by up to 49.5 %, 38.2 %, and 28 %, respectively. Considering a wide range of TSRs, on average, the implementation of baffles results in a 17.5 % increase in torque generation. The effect of the baffle thickness on generated vortices and their evolution along the course of flow is also investigated to show how the zero-thickness baffles improves the blade aerodynamics.

Wind Tunnel Experiments on Parallel Blade–Vortex Interaction with Static and Oscillating Airfoil

This study aims to experimentally investigate the effects of parallel blade–vortex interaction (BVI) on the aerodynamic performances of an airfoil, in particular as a possible cause of blade stall, since similar effects have been observed in literature in the case of perpendicular BVI. A wind tunnel test campaign was conducted reproducing parallel BVI on a NACA 23012 blade model at a Reynolds number of 300,000. The vortex was generated by impulsively pitching a second airfoil model, placed upstream. Measurements of the aerodynamic loads acting on the blade were performed by means of unsteady Kulite pressure transducers, while particle image velocimetry (PIV) techniques were employed to study the flow field over the blade model. After a first phase of vortex characterisation, different test cases were investigated with the blade model both kept fixed at different incidences and oscillating sinusoidally in pitch, with the latter case, a novelty in available research on parallel BVI, representing the pitching motion of a helicopter main rotor blade. The results show that parallel BVI produces a thickening of the boundary layer and can induce local flow separation at incidences close to the stall condition of the airfoil. The aerodynamic loads, both lift and drag, suffer important impulsive variations, in agreement with literature on BVI, the effects of which are extended in time. In the case of the oscillating airfoil, BVI introduces hysteresis cycles in the loads, which are generally reduced. In conclusion, parallel BVI can have a detrimental impact on the aerodynamic performances of the blade and even cause flow separation, which, while not being as catastrophic as in the case of dynamic stall, has relatively long-lasting effects.

Computational investigations of Ka-226T helicopter coaxial rotor aerodynamics in the vortex ring state

The vortex ring states are observed when the rotor is flowed at positive angles of attack. For the main rotor, these conditions are realized during a steep descent of the helicopter at low speeds. The rotor vortex ring states are affected by significant phenomena related to the behavior of its aerodynamics, including negative phenomena. The latter is, firstly, referred to decrease in rotor thrust, increase in the required power, pulsations of thrust and torque, unsteady flapping blade motion, etc. In terms of helicopter piloting, it means a sharp loss of altitude, increase in the control force, a high level of vibration, defocusing attenuation of rotor spinning cone, as well as controllability deterioration. All these factors determine the relevance of research on these modes and the importance of solving a problem of defining their boundaries. Recently, due to the rapid development of computer technologies and computational models, it has become practical to perform numerical research of the rotor aerodynamics in vortex ring states. The paper presents the study results of Ka-226T helicopter coaxial rotor aerodynamics in steep descent modes in the field of vortex ring states. The angles of rotor attack αВ = 90...30° and the range of vertical descent velocities Vу = 0...26 m/s are considered. The original nonlinear bladed vortex model of the rotor developed at the Moscow Aviation Institute (MAI) was used. The total and distributed aerodynamic rotor characteristics were calculated. The shapes of the vortex wake and the rotor flow patterns were analyzed. The boundaries of the vortex ring states in velocity coordinates “Vx − Vу” were constructed according to various criteria reflecting the known features of these states. The results obtained significantly complement the existing experience of experimental and numerical research in this field.

Vortex-induced vibrations of wind turbines: From single blade to full rotor simulations

Vortex-induced vibrations (VIVs) of wind turbine blades are a phenomenon that cannot be predicted sufficiently accurate by low fidelity methods. High fidelity methods, such as computational fluid dynamics (CFD) coupled to a structural solver come at a high computational cost. Most studies of the phenomenon have so far focused on analysis of single blades. For these cases, the so-called forced-motion method of prescribing the blade motion according to structural modeshapes has proven effective.In this article, VIVs of the IEA 10 MW reference turbine is studied in a fluid–structure interaction setup, where the structural dynamics of the full turbine are represented in the structural solver and the full rotor aerodynamics are simulated in the CFD solver. Due to the high computational cost this study is limited to only a single case with the rotor in bunny configuration, 80 degrees pitch and 90 degrees yaw. Also the purely structural power dissipation of the full turbine is studied to enable full rotor forced-motion in future work. A blade tip amplitude of roughly 17 meters is reached in the full turbine simulations, which is a significantly larger limit cycle amplitude than what would be reached in a corresponding isolated single blade simulation. The analysis also shows that forced-motion simulations combining three single blades vibrating according to the structural modeshape would be feasible. It is further observed, that the power injection or extraction close to the blade tip may change drastically at very large amplitudes compared to lower amplitudes.

Numerical investigation of elastomeric solid cutting: Enhancing cut initiation for minimally invasive biological tissue cutting

Abstract Minimizing tissue damage during blade cutting is vital for optimal surgical outcomes. However, the elastomeric properties of tissues require that they be considerably deformed before cut initiation, resulting in physical damage. Thus, the blade indentation depth required for cut initiation must be reduced by enhancing the cut-initiation ability of a process. In this study, factors that influence the cut initiation of elastomeric solids are identified by investigating the tensile stress states beneath the blade that trigger cut initiation. Finite element simulations are used to analyze interfacial interactions between the blade and workpiece and their relation to the stress states. Results show that the distribution of the in-plane stretch of the workpiece surface along the blade surface plays a key role in determining the stress states and the resulting cut-initiation ability. The effects of process parameters, including interfacial friction, blade tip geometry, blade motion, and workpiece size, are examined and discussed by analyzing the corresponding in-plane surface stretch distribution. This study offers a fundamental understanding of cut initiation in elastomeric solid cutting for improving surgical cutting tasks.

Approach Distances of Scottish Golden Eagles Aquila chrysaetos to Wind Turbines According to Blade Motion Status, Wind Speed, and Preferred Habitat

Understanding drivers underlying birds’ responses to operational wind turbines is essential for robust wind farm proposal assessments, especially for large raptors with life history traits engendering sensitivity to impacts from two potential adverse effects: fatality through collision with rotating turbine blades and functional habitat loss through avoidance of turbines. The balance between these two potential effects represents opposing extremes on a continuum and is influenced by several factors. Collisions have an obvious impact on survival, but the impacts of avoidance may be more insidious and potentially more significant for a population. It is reasonable to conclude that collisions are less likely when blades are motionless. Consequently, turbine shutdown systems (TSSs, “shutdown on demand” or “curtailment”), instigated as raptors approach operational turbines, may provide mitigation against collisions. By contrast, if avoidance is most likely, this could be independent of blade motion, and TSSs/curtailment would provide no mitigation against habitat loss. For birds tending to wariness of turbines, therefore, it is important to understand if it is conditional on blade motion. Scottish golden eagles show a strong propensity to avoid (be wary of) turbines, subject largely to the suitability of habitat at and surrounding turbine locations. A previous Scottish study found that approach distances to turbines by non-territorial eagles were unaffected by blade motion but were closer at higher wind speed. Here, we analyse movement data from a GPS-tagged territorial eagle and non-territorial eagles responding to the motion status (and wind speed) of turbines at another Scottish wind farm. Eagles’ approach distances to turbines were only weakly affected by blade motion but were closer at higher wind speed. We again found that habitat suitability in and around turbine locations was strongly influential on eagles’ approach distance to turbines. Our confirmation that blade motion had little effect on Scottish golden eagles’ wariness of turbines suggests that for eagles that are prone to avoid turbines, their wariness is a response to turbines per se, and not blades’ movement. In our study system, and others where avoidance is the predominant response, curtailment of turbines’ operation on birds’ close approaches, or making turbine blades more obvious, should, therefore, have little material influence on functional habitat loss impacts. If true, this has important implications for wind farm designs and any proposed mitigation.

Blade tip timing for multi-mode identification based on the blade vibration velocity

Blade Tip Timing (BTT) is a widely employed non-contact measurement technique for monitoring turbomachinery blade vibrations. The conventional BTT method typically involves computing the expected time of arrival (TOA) and subtracting it from the actual TOA to derive the time difference, subsequently used to calculate blade-tip displacement. However, calculating the expected TOA introduces computational errors. Moreover, obtaining blade-tip vibration displacement under variable rotational speeds necessitates pre-processing to remove trend terms caused by speed fluctuations. To address these challenges, this study introduces a paradigm shift by replacing the traditional displacement-based blade-tip timing (D-BTT) with velocity-based blade-tip timing (V-BTT). Specifically, this approach utilizes the angular information between adjacent sensors and the measured TOA to extract the blade-tip vibration velocity through a Taylor series expansion, thus eliminating the calculating of the expected TOA and improving the computational efficiency. Building upon this methodology, a compressed sensing model for undersampled vibration velocity is established and solved using the Block-OMP algorithm, enabling vibration parameter identification without relying on prior information. By providing a superior representation of mid-frequency components of blade-tip vibration, V-BTT facilitates precise identification of higher-order vibration parameters in multi-mode blade motion. Finally, the efficacy of the proposed method is confirmed through numerical simulations and experiments involving multi-mode blades. The experimental results reveal that the relative errors of the first two modal frequencies for the five blades identified using vibration velocity are all below 0.5%, affirming the method's accuracy. Compared to the traditional D-BTT method, the V-BTT approach reduces the need for trend removal, eliminates calculation errors associated with the expected TOA, and, most importantly, enhances the accuracy of multi-mode frequency identification.

Enhanced grip force estimation in robotic surgery: A sparrow search algorithm-optimized backpropagation neural network approach.

The absence of an effective gripping force feedback mechanism in minimally invasive surgical robot systems impedes physicians' ability to accurately perceive the force between surgical instruments and human tissues during surgery, thereby increasing surgical risks. To address the challenge of integrating force sensors on minimally invasive surgical tools in existing systems, a clamping force prediction method based on mechanical clamp blade motion parameters is proposed. The interrelation between clamping force, displacement, compression speed, and the contact area of the clamp blade indenter was analyzed through compression experiments conducted on isolated pig kidney tissue. Subsequently, a prediction model was developed using a backpropagation (BP) neural network optimized by the Sparrow Search Algorithm (SSA). This model enables real-time prediction of clamping force, facilitating more accurate estimation of forces between instruments and tissues during surgery. The results indicate that the SSA-optimized model outperforms traditional BP networks and genetic algorithm-optimized (GA) BP models in terms of both accuracy and convergence speed. This study not only provides technical support for enhancing surgical safety and efficiency, but also offers a novel research direction for the design of force feedback systems in minimally invasive surgical robots in the future.