Physics-based dynamic simulation opportunities with digital twins

Abstract This paper aims to provide a viewpoint on the exploitation of physics-based dynamic simulation in product development and discrete manufacturing products. The dynamics models can be represented with computationally light models when the product and its dynamics are well known and thereby analyzing the performance e.g., with AI methods rapidly and accurately. The recent developments with methodologies, sensor development, measuring techniques and increased computing capacity are making the simulation world closer to reality and the ability for real-time operation simulations paralleled to the real system. This enables the exploitation of the digital twin paradigm at full capacity together with high-maturity digital twin models

Investigation of material combinations for axially-laminated synchronous machine

Abstract High-speed electric machines are special types of electric machines which aim for compact, direct-driven high-speed applications and highly efficient operation, especially, when gearbox can be avoided. Design of these types of machines is highly iterative combining multiphysics optimization and leads to custom types of machines which fulfill the application-specific requirements. Synchronous Reluctance Machines (Syn-RMs) might have an axially-laminated solid rotor structure, which combines magnetic and non-magnetic layers rigidly bonded to each other by vacuum brazing, hot isostatic pressing, soldering, explosion welding or even by additive manufacturing. In the study five non-magnetic materials and nine magnetic materials are cross compared and the results show clear differences in performance, efficiency and physical properties of the rotor when made of different material combinations, and thereby can suggest the best pairs when application-specific performance criteria are known. The study is carried out on a 12 kW machine with a maximum speed of 24000 rpm

Estimation of unmeasurable vibration of a rotating machine using Kalman filter

Abstract Rotating machines are typically equipped with vibration sensors at the bearing location and the information from these sensors is used for condition monitoring. Installing additional sensors may not be possible due to limitations of the installation and cost. Thus, the internal condition of machines might be difficult to evaluate. This study presents a numerical and experimental study on the case of a rotor supported by four rolling element bearings (REBs). As such, the study resembles a complex real-life industrial multi-fault scenario: a lack of information, uncertainties, and nonlinearities increase the overall complexity of the system. The study provides a methodology for modeling and analyzing complicated systems without prior information. First, the unknown model parameters of the system are approximated using measurement data and the linearized model. Thereafter, the Unscented Kalman Filter (UKF) is applied to the estimation of the vibration characteristics in unmeasured locations. As a result, the estimation of unmeasured vibration characteristics has a reasonable agreement with the rotor whirling, and the estimated results are within a 95% confidence interval. The proposed methodology can be considered as a transfer learning method that can be further used in other identification problems in the field of rotating machinery

Electric vehicles’ powertrain systems architectures design complexity

Abstract Strict emission regulations and energy scarcity have ushered in a new era of automotive technology. Utilizing electric power as a second source of energy or an alternative to fossil fuel energy has been the center of attention for decades. Implementing electric energy in vehicles’ powertrain systems requires new system architecture and rigorous methods for decision-making in a multi-disciplinary design procedure. Accordingly, the challenge is to define the design requirements and the economic feasibility of the final product

Materials applicable to an Axially-Laminated Synchronous Reluctance Machine considering mechanical and electromagnetic aspects

Abstract High-speed electric machines aim for compact, direct-driven elevated speed applications and highly efficient operation, especially when a gearbox can be avoided. The design of these types of machines is highly iterative, combining multiphysics optimization and leading to custom types of machines that fulfill the application-specific requirements. The Axially Laminated Synchronous Reluctance Machine (ALASynRM) with a solid rotor is one of the motor types that can be considered for high-speed applications. An axially laminated solid rotor structure combines magnetic and nonmagnetic layers rigidly bonded to each other by vacuum brazing, hot isostatic pressing, soldering, explosion welding, or even additive manufacturing. In this study, six nonmagnetic materials and nine magnetic materials are cross-compared. The results show clear differences in performance, efficiency, and physical properties of the rotor when made of different material combinations and can thereby suggest the best pairs when the application-specific performance criteria are known. The study is carried out on a 12 kW machine with a maximum speed of 24000 rpm

Active magnetic bearing positioning in the conceptual design phase of a high-speed electric machine

Abstract The optimization of high-speed active magnetic bearing rotor layout concerning the effect of external disturbance is studied. The centrifugal loads and related strain forces in the HS rotors limit the maximum rotational speed and AMB capacity, bandwidth, and location limit control of dynamics. Additionally, external synchronous disturbances, i.e., unbalance forces, rotor runout, application forces from the impeller, and static forces cause adverse effects on active control and pose limitations. Therefore, to achieve a sub-critical rotor, the dimensions of electric machine components, such as bearings, seals, and impellers affect each other and have to be constrained. The proposed method examines the effect of disturbances and locations and resulting dynamic limitations at the conceptual design phase. This enables the design of the AMBs and component layout to the application demands. The method uses maximum singular values to examine the effects of disturbances on bearing forces and rotor displacements at key locations

Method for mechanical design of squirrel cage slitted solid rotor

Abstract The design of high-speed machines requires extensive multidisciplinary approach to achieve a high-performance machine. The design process is highly iterative, and analytical methods can accelerate it with faster design iterations at low computational efficiency to find the optimum parameters at conceptual stage. In this study, an analytical design method for obtaining rotor mechanical limits is developed for squirrel-cage slitted high-speed induction machine rotors. In high-speed electric machines, the design is made specifically to meet the application requirements and the objective is to reach a high efficiency. This means that the design needs to be made often from the scratch and existing designs can rarely be used as a starting point. The method developed in this study enables rapid design iterations, especially considering the mechanical limits in the conceptual and layout design phase. The proposed analytical design method is validated with three different case studies

Dynamics of high-power multi-rotor system

Abstract Typically, active magnetic bearings have been applied to high-speed rotors in medium to high power range to replace ball, roller, and oil-film bearings. They require less maintenance and provide number of unique benefits owing to contactless suspension and active control. Integrated compressor or turbines result in predictable rotor dynamics. This allows use of model-based controllers. The model-based centralized controllers outperform decoupled transfer function controllers, but they do require accurate plant models. For integrated wheels on a single rotor the control models comprise a rigid rotor and lowest frequency bending modes. The bending mode parameters related to node locations can be identified yielding controllers tuned to the applications. This work introduces drive train modelling and magnetic levitation control of 2 MW rotor and external load with flexible coupling. The model-based control is tested in the experimental setup and drive train frequency responses are compared to the modelled multi-rotor drive train dynamics

Design of thick-lamination rotor configuration for a high-speed induction machine in megawatt class

Abstract Solid rotors are preferred choice of topology for high-speed applications due to their robustness against high centrifugal forces at high speeds, ease of manufacturability, and higher temperature range. However, for peripheral speeds lower than 200 m/s, laminated rotor structure is preferred because of lower eddy current losses resulting in higher efficiency. However, laminated rotors are complex to manufacture, sensitive to temperature and have vibration and mechanical integrity related issues. As a compromise between these two designs in terms of mechanical strength and efficiency, this study investigates a radial flux 2 MW, 15 krpm induction motor rotor core made of thick laminations. The baseline dimensions of the thick-lamination rotor design are calculated using analytical equations considering aspects such as mechanical stresses, rotordynamics, and bearing parameters. Lastly, the lamination to lamination contact behavior under unbalance load is analyzed for a simplified model and their effect on natural frequencies is studied

Mechanical properties of welded ultrahigh-strength S960 steel at low and elevated temperatures

Abstract New ultrahigh-strength steels have been developed to meet the need for better performance, load bearing capacity, safety and weight saving. However, the design guidelines are incomplete, especially regarding the design of welded ultrahigh-strength steel components in fluctuating operating conditions. This reduces usability and can cause serious safety risks when the welded structures are in use. The heat input and cooling rate have a significant effect on the microstructure and mechanical properties of the ultrahigh-strength steels. Therefore, a model to predict the strength and microstructure, based on welding parameters, is required for designers to create safer solutions in engineering design. In this study, a 6 mm thick S960 low alloy ultrahigh-strength steel was welded using gas metal arc welding (MAG) and laser welding. The effects of welding heat input and operating temperature on the tensile properties, hardness, microstructure, and fracture mechanism of the welded specimens were investigated. The effects of operating temperature on the mechanical properties of welded joints were investigated by performing tensile tests between temperatures of −80 °C and + 400 °C. The unwelded base material was also tested in the same temperature range. The results showed a ductile fracture mechanism in all the samples regardless of the test temperature and welding heat input. However, the tensile strengths and elongations increased when the test temperature drops to −80 °C from room temperature. In addition, mathematical predictions for the strength and elongation properties, and grain sizes in heat-affected zones, as a function of temperature and welding heat input were proposed