Browsing by Author "Laine, Sampo"
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Item Coupling with adjustable torsional stiffness(TEADUSTE AKADEEMIA KIRJASTUS, 2021) Kinnunen, Kalle; Laine, Sampo; Tiainen, Tuomas; Viitala, Risto; Seppänen, Alvari; Turrin, Tommaso; Kiviluoma, Panu; Viitala, Raine; Department of Mechanical Engineering; Mechatronics; Department of Mechanical EngineeringThis study presents a novel coupling design with adjustable torsional stiffness. Since the torsional stiffness of the coupling can be adjusted, it can potentially be applied to tune the torsional natural frequencies of rotating systems. The presented coupling design provides clear benefits compared to typical flexible element couplings. For applications with typical flexible element couplings with elastomeric inserts, the torsional stiffness can be adjusted by changing the elastomers. However, this often requires disassembly of the coupling, and the torsional stiffness adjustment has to be performed in large increments. In the presented coupling design, the torsional stiffness can be adjusted without disassembly. The torsional stiffness can be tuned to a wide range of stiffnesses and with arbitrarily small increments. The torsional stiffness of the coupling was determined by analytical calculations, FEM simulations and experimentally. In the experimental tests, the torsional stiffness range of the coupling was measured to be between 8–126 kNm/rad. Experimental measurements agree with the calculated and simulated stiffness values. The coupling design was considered to be successful, since the study confirmed that the torsional stiffness of the coupling can be adjusted to a wide range of different values.Item Effects of a variable frequency drive on torsional vibrations in electrical machines(2023-01-23) Hartikainen, Hannu; Laine, Sampo; Sähkötekniikan korkeakoulu; Hinkkanen, MarkoThis thesis deals with the identification of electromagnetic stiffness and damping. It is well known that electromagnetic stiffness and damping influence the torsional dynamics of an electric drivetrain. The electromagnetic stiffness and damping are obtained from a frequency response between the rotor angle and the electromagnetic torque, which could be identified or calculated analytically. However, the frequency response is usually only for a machine directly connected to the grid and does not include the effect of a variable frequency drive. The variable frequency drive is a common way to control the speed and torque of the machine. The main goal of this thesis is to develop a method that includes the effect of the variable frequency drive control on the frequency response. The identification method is based on a signal injection in time-domain simulations. The simulation model includes a discrete-time controller and a continuous-time motor model. In the simulation, an excitation signal is injected into the steady-state rotor speed, where the response is seen in the electromagnetic torque. The frequency response could be identified with the rotor speed and the electromagnetic torque spectra. The identification method is validated with analytical solutions of the frequency response from the literature. The validation includes one machine with three control methods for the variable frequency drive.Item Identification of mechanical impedance of an electric machine drive for drivetrain design(2023-05-15) Hartikainen, Hannu; Tiitinen, Lauri; Laine, Sampo; Hinkkanen, Marko; Department of Electrical Engineering and Automation; Department of Mechanical Engineering; Electric Drives; Mechatronics; Electric DrivesThis paper proposes a method for identifying mechanical impedance of an electric machine drive for drivetrain design and analysis. The mechanical impedance describes the dynamics of an electric machine as seen from its mechanical terminals. It depends not only on the electric machine but also on the control system, which should be taken into account when analyzing torsional vibrations. If the black-box input-output time-domain models of the electric machine and its control system are available, the mechanical impedance can be extracted from simulations. The proposed identification method is based on signal injection in time-domain simulations. At steady-state operating points, an excitation signal is injected into the rotor speed and the response is observed in the electromagnetic torque. The method is validated by comparing the identified mechanical impedances with the corresponding analytical solutions.Item Lateraalisen värähtelyanalyysin toteuttaminen pyörivän koneen suunnittelussa(2023-12-03) Kosonen, Marko; Laine, Sampo; Insinööritieteiden korkeakoulu; Viitala, RaineItem Method for Adjusting Torsional Natural Frequencies of Powertrains with Novel Coupling Design(MDPI AG, 2022-03) Kinnunen, Kalle; Laine, Sampo; Tiainen, Tuomas; Viitala, Raine; Department of Mechanical Engineering; MechatronicsTorsional vibrations are inherently present in every rotating powertrain. In resonant conditions, torsional vibrations can be significantly amplified. A typical method to reduce the torsional vibration particularly at resonance is to modify the torsional natural frequencies with the component design. Commonly, a straightforward method for the modification is the adjustment of the torsional stiffness of a coupling. This study presents a method to modify the torsional natural frequencies using a coupling design with continuously adjustable torsional stiffness. The presented coupling design is investigated with torsional analysis and experimental measurements. Torsional analysis was utilized to predict the effects of varying the coupling stiffness to the torsional natural frequencies of a powertrain. The experimental measurements were conducted by attaching the adjustable stiffness coupling to the powertrain and measuring the change in the torsional natural frequencies while the torsional stiffness of the coupling was adjusted. The torsional natural frequencies were determined from the measurements by identifying the resonance induced torsional vibrations from the vibration response of the powertrain. The torsional vibrations were excited to the system by a load motor. The measurements showed that the first torsional natural frequency of the powertrain changed from 15.6 Hz to 43.0 Hz as the torsional stiffness of the coupling was adjusted. The results of the torsional analysis and the experimental measurements were compared to determine the performance of the realized coupling. The results indicated that the torsional natural frequencies determined by torsional analysis agree well with the experimentally measured results. The prediction errors were generally below ±5%, which is typically considered as a margin for accurate torsional analysis.Item Optimization Procedure and Toolchain for Roll Dynamic Geometry(MDPI AG, 2022-07) Tiainen, Tuomas; Laine, Sampo; Viitala, Raine; Department of Mechanical Engineering; MechatronicsIn rolls manufactured from first bent and then welded sheets of steel, the asymmetric distribution of mass due to the weld seam as well as imperfections of the geometry due to the bending may cause the roll cross-section roundness profiles to deform due to centrifugal forces when the roll is accelerated to rotate at its operating speed. This effect is known as the dynamic geometry of the roll. In previous research, it has been shown that it is possible to measure the dynamic geometry in operating speed and compensate for the deformation by grinding a suitable opposite geometry on the roll. This direct approach may work when only little material is removed. Such conditions apply especially for polymer coated rolls, where the dynamic geometry is mostly dependent on the geometry of the much stronger and denser steel body under the roll cover. This paper goes further to investigate the possibilities for compensating the dynamic geometry in cases where the amount of removed material is significant enough to have an effect on the dynamic geometry itself due to altered mass and stiffness. The paper presents a toolchain consisting of a parametric roll CAD model, finite element simulation of the dynamic geometry and a geometry optimization procedure based on minimizing a target function describing roundness errors in cross-sections of the roll. Results of simulation experiments for a case example indicate that the presented optimization procedure can be used to eliminate roundness errors related to dynamic geometry of the roll. Finally, the paper discusses the application of such a toolchain in the manufacturing of rolls.Item Paradigm shift in mechanical system design : toward automated and collaborative design with digital twin web(Springer, 2024-10-03) Ala-Laurinaho, Riku; Autiosalo, Juuso; Laine, Sampo; Hakonen, Urho; Viitala, Raine; Department of Mechanical Engineering; MechatronicsAnalyzing multi-vendor mechanical system designs requires a significant amount of manual work, resulting in a design paradigm where analysis is conducted only after the design is locked and components are selected. This leads to a suboptimal design with compatibility issues, over-dimensioned components, inferior performance, poor energy efficiency, and a lack of collaboration between OEMs (original equipment manufacturers) and system integrators. To overcome these issues, this paper proposes Co-Des (collaborative design) framework for automated and collaborative multi-vendor system design. The framework relies on standardized digital twin documents (DTD) of system designs, components, and analyses. The discoverability and distribution of these DTDs are enabled with digital twin web (DTW). Co-Des framework allows for finding suitable components for the design task by automatically running selected analyses employing component digital twins. In addition, OEMs can provide customized components for system integrators using the initial system design defined in the system design DTD. The use of the Co-Des framework was demonstrated with a windmill powertrain design use case, and the applicability of the automated assembly analysis for component selection was verified with performance measurements. The adoption of the proposed framework will lead to a paradigm shift from manual and siloed work relying on the exchange of PDFs to a more automated and collaborative design of mechanical systems. The adoption rate is defined by the willingness of system integrators to publish their initial system designs and OEMs their components as public digital twins.Item Roottorin dynaamisen taipuman mittaaminen venymäliuskoilla(2020-05-03) Laine, Sampo; Viitala, Risto; Insinööritieteiden korkeakoulu; Pietola, MattiItem Rotor resonance avoidance by continuous adjustment of support stiffness(Elsevier Ltd, 2024-05-15) Laine, Sampo; Haikonen, Sampo; Tiainen, Tuomas; Viitala, Raine; Department of Mechanical Engineering; Mechatronics; Department of Mechanical EngineeringThis paper presents a method to reduce lateral vibration amplitudes in large rotating machines. The method is based on avoiding resonances by altering the natural frequencies of the rotor system at each rotating speed during operation. While many research papers have considered altering support stiffness during crossing critical speeds, continuous adjustment methods have received less attention. Continuous on-line adjustment of the natural frequencies of a rotor system is possible to a large range by adjusting the support stiffness of the bearing housings. The optimal foundation stiffness tuning policy can be defined utilizing a rotordynamic model or experimental measurements, effectively creating a resonance-free operating speed region, where vibrations are drastically reduced. It is shown through full-scale experimental laboratory tests, that the subcritical and supercritical response of the rotor system is significantly decreased during run-up and run-down with the optimal foundation stiffness tuning strategy. The developed method can be applied to reduce vibrations in any rotating machinery, where a variable foundation stiffness control can be installed. Moreover, this on-line foundation stiffness tuning strategy could also be applied in combination with resonance crossing methods involving stiffness manipulation.Item Rotordynamic Investigation of Roll Bouncing Phenomenon in Two-Drum Winder(2023) Rytömaa, Samuli; Laine, Sampo; Viitala, Raine; Department of Mechanical Engineering; Okada, Masafumi; MechatronicsIn paper manufacturing, the vibration caused by roll bouncing is one of the factors limiting the productivity of a two-drum winder. As paper roll rotational speed intersects with natural frequencies of the winder system during the winding cycle, resonance occurs leading to roll bouncing and high vibration levels. To help understand the phenomenon, a simulation model of a two-drum winder is investigated. The model includes the unbalance, changing rotational speed and increasing paper roll diameter. The model is based on finite-element method, including the rotordynamic effects. An example winder geometry is used to demonstrate the simulation capabilities using modal and forced response analysis. The results indicate that the model is capable of capturing the roll bouncing problem and agrees qualitatively with previous research. The model can be used to improve winder designs and therefore increase their productivity.Item Torque estimation for maritime powertrains using convex optimization(2023-08-21) Hakonen, Urho; Manngård, Mikael; Laine, Sampo; Insinööritieteiden korkeakoulu; Viitala, RaineThis thesis studies the estimation of shaft torque for maritime powertrains using convex optimization. Understanding the unknown external forces affecting the maritime powertrain is important to ensure safe and reliable operation, and to further improve the condition monitoring procedures and design requirements for the mechanical components of the system. The aim of this thesis is to show that through mathematical modeling, simulations and convex optimization, the unknown input torque and the torsional response of the powertrain can be reconstructed using measurements close to the driving motor. The studied convex optimization problem is the regularized least-squares problem. Four subclasses of the regularized least-squares problem are considered, including Tikhonov regularization, ell1 regularization, H-P trend filtering and ell1 trend filtering. The purpose of the regularization methods is to improve the conditioning of the least-squares problem, and to enforce desired structure in the estimate. The estimation of torque is studied using simulations and measurements from experiments conducted using a small-scale maritime thruster testbench. The regularization methods are used for estimating the driving motor and propeller input torques simultaneously. The estimated inputs and the testbench model are used to reconstruct the states of the testbench, yielding an estimate of the shaft torque. Estimates of the shaft torque are compared to verification measurements from the propeller shaft of the testbench. The results show that convex optimization can be used to estimate the propeller shaft torque with measurements near the driving motor of the testbench. The torque estimation method is flexible enough to handle a large class of excitations, and it can be directly modified to include other regularized least-squares problems. Overall, out of the four considered regularization methods, the H-P trend filter performs best, producing smooth and accurate torque estimates. A benefit of the H-P trend filter is that it has an analytical solution, thus, it is computationally efficient. As the external torques affecting maritime powertrains can be assumed to vary smoothly, this thesis proposes the H-P trend filter as a robust method for estimation of shaft torque in maritime powertrains.Item Torsional vibrations in electric powertrains(2021-08-23) Laine, Sampo; Holopainen, Timo; Insinööritieteiden korkeakoulu; Viitala, RaineThe vast majority of the electricity in the world is produced by powertrains with electric generators, and a large proportion of the produced electricity is consumed by powertrains driven by an electric motor. Even the smallest performance increases in the design processes and operation of these machines can thus lead to massive improvements in the overall efficiency of the use of electrical energy. Simulation and design phase analysis of electric powertrains requires consideration of the mechanical and electromagnetic effects in the powertrains. In the present study, a holistic analysis method is presented for torsional vibration analysis of electric powertrains. The purpose of the torsional vibration analysis is to prevent problems related to excess vibrations in the machine system. Introducing an electric machine on a powertrain adds electromagnetic stiffness and damping to the system. Furthermore, electric motors may act as a source of torsional excitation. As is often done in practical analysis, consideration of the electric motor only as an ideal torque source may render these influences unnoticed. The modelling methods proposed in this study rely on the torsional shaft-line finite element method, and equivalent circuit models of the electric machines. Parameters of the mechanical models can typically be determined from the dimensions of the powertrain. The electrical properties may not be measurable from the physical system, however, model identification methods can be applied. The present study includes an implementation of the modelling tools for torsional vibration analysis of electric powertrains, published as an open-source library. Furthermore, a programming interface is presented for sharing the electric machine models in a way that preserves the high accuracy of the model, without compromising intellectual property related to the design of the machine. The theoretical influence of the electromagnetic effects was studied with simplified electromechanical models. The present study is limited to induction motors, which are a commonly used motor type in industrial applications. The results show that in certain situations, the electromagnetic effects may considerably affect the lowest natural frequencies of the system. According to the results, consideration of the electromagnetic effects is especially important in powertrains with small stiffness, connecting an electric machine with small inertia to a relatively large inertia load. Verification measurements were conducted on a laboratory powertrain to inspect the modelling capacity of the implemented methods. In this case, the influence of the analysis implied that the electromagnetic effects were negligible. Comparison of the results of the modelling and the results of the measurements suggests that the critical speeds of the system can be closely estimated.Item Transient torsional vibration analysis in arctic maritime propulsion systems(2024-05-09) Häggman, Oliver; Laine, Sampo; Insinööritieteiden korkeakoulu; Viitala, RaineAzimuth thrusters are widely used in maritime vessels, especially those operating in Arctic waters. These thrusters increase maneuverability, which is critical in harsh Arctic environments. However, component failures have been found in the thrusters. A common source of failure is torsional vibrations. Studying torsional vibrations through simulations is more cost-efficient and less laborious than measuring the vibrations in full-scale thrusters with sensors. In this thesis, transient torsional vibrations are simulated in a small-scale Azimuth thruster test bench. A simulation model is established using a finite number of lumped inertia elements. The model is represented mathematically in discrete-time state-space form. Simulations are conducted for a step, an impulse, and an ice-load excitations. The simulated torque response is compared with measurements from previous research. The simulated torque responses show similar trends to the measured responses. However, some differences are noteworthy. The simulated torque for all three excitations has a negative DC offset. In addition, the amplitude of the simulated responses is lower and decays faster. Possible reasons for this are incorrect damping parameters in the model and different controller parameters compared to the experiments. The highest amplitude peak in the frequency spectrum of the simulated torque response corresponds with measurements. However, two amplitude peaks are missing in the impulse response and one in the step response. This indicates that the simulation model might be more damped than the test bench. The simulated torque responses seem to correspond quite well with the measurements. Similar differences are seen for all three excitations, with an exception in the Fourier analysis. This indicates that the model is precise and has the potential to be tuned for better accuracy. Future research could be to optimize the damping parameters to see if they improve the prediction capability of the model.Item Vääntövärähtelyanalyysin toteuttaminen laivan voimansiirron suunnittelussa(2023-09-13) Nieminen, Eetu; Laine, Sampo; Insinööritieteiden korkeakoulu; Viitala, RaineItem Wire rope isolator identification and dynamic modeling for small amplitude vibrations(Elsevier BV, 2024-11-01) Rytömaa, Samuli; Malmi, Olli; Laine, Sampo; Keinänen, Jarkko; Viitala, Raine; Department of Mechanical Engineering; Mechatronics; Vibrol OyWire rope isolators are used in variety of applications to protect sensitive equipment from vibration. The nonlinear hysteretic behavior of steel wires provides advantages when compared to linear vibration isolators. This study proposes an amplitude dependent stiffness and damping model for low amplitude vibrations under axial loading, where the parameters can be determined with an experimental procedure. Comprehensive experimental results of forced vibration tests with varying loading, frequency and preload were considered in the model identification. Amplitude dependent stiffness and loss energy models were determined from the test data, and the effect of the preload and loading frequency on the model parameters were studied. It is shown, that the effect of preload and frequency is not evidently clear, while the effect of vibration amplitude is more significant. The mathematical model was further verified against measurements from base excitation loading. The proposed model can be used to study the effectiveness of the selected wire rope isolator configurations in chosen application, and to effectively perform dynamic design studies.