•Developed a polynomial based dynamic expansion for cylindrical shell structure.•Evaluated the consistency of a set of measurements by using a modified Data.•Consistency Assessment Function ...(DCAF).•Identified the inconsistent data and modified them to be consistent.•Validated the technique by experimental data in either air or water.
A designated set of shape functions are created for cylindrical shell structures. The 1D Chebyshev polynomial is applied along the axial direction and the 1D harmonic basis along the circumferential direction. A 2D orthogonal space is formed on the cylindrical domain by combining the above two 1D bases and is used to develop the expansion function. A finite element model is not required for the expansion technique, nor are the boundary conditions or external forcing functions. Using these generated shape functions, the dynamic time response at some points on cylindrical shells structure can be expanded to obtain the information at a larger number of points. Only the measurement data, geometry, and coordinates of measured points are needed. The developed polynomial expansion technique is also extended to a Data Consistency Assessment Function (DCAF), which can assess the consistency of the data set and identify the inconsistent points. The inconsistent points can also be modified by using the polynomial expansion method. A cylindrical shell structure in either air or water medium is used to experimentally demonstrate the use of the developed shape functions for polynomial expansion and data consistency assessment and modification.
Data Consistency Assessment Function (DCAF) Chen, Yuanchang; Avitabile, Peter; Dodson, Jacob
Mechanical systems and signal processing,
July 2020, 2020-07-00, 20200701, Letnik:
141
Journal Article
Recenzirano
Odprti dostop
•Developed a Data Consistency Assessment Function (DCAF).•Evaluated the consistency of a set of measurements.•Identified the inconsistent data and modified them to be consistent.•Validated the ...technique by experimental data.
A Data Consistency Assessment Function (DCAF) is developed to check the consistency of a measurement or set of measurements to all of the data in the entire data set. The inconsistent data can be precisely spotted and identified, which are recognized as the poorly measured data and can also be modified to be consistent with the rest of the data with an expansion process. The data can be either mode shapes, dynamic time response, frequency response functions or strain fields. Depending on the particular situation, three forms of the data expansion approach can be selected to implement the DCAF: System Equivalent Reduction Expansion Process (SEREP) with finite element model, SEREP with experimental mode shapes, and polynomial expansion. Some academic and industrial structures are used as examples to study the application of DCAF. Experimental data are used to validate the technique.
Wind turbine design and operation will benefit from a better understanding of blade dynamics. Usually, only one surface or one side of a 3D structure is measured in Scanning Laser Doppler Vibrometer ...(SLDV) tests due to test setup and instrumentation limitations. However, in this work, we demonstrate an approach to overcome these limitations while also using an SLDV that provides high spatial resolution measurement. In the case of a wind turbine blade, only one surface is typically measured; however, it is beneficial to investigate both blade global modes and the relative motions of the two blade surfaces by using both numerical models and experimental tests. This work creatively develops both experimental and numerical approaches to investigate the dynamics and the relative motions of both surfaces of the wind turbine blade from global and local perspectives. On the experimental side, experimental modal testing is conducted on both surfaces of the wind turbine blade with a high spatial resolution 3D SLDV. The two surfaces of the wind turbine blade are measured and stitched together to build the blade experimental mode shapes of both surfaces. A total of over 1500 points are scanned from both surfaces of the blade in a non-contact fashion to obtain not only the global bending modes (flap-wise and edge-wise), the global torsional modes, but also the localized panel mode shapes. On the numerical side, a finite element model of the blade is developed to obtain the numerical mode shapes. The experimental mode shapes on either one surface or both surfaces of the blade are used to validate the blade finite element model. The mode shape correspondence between the model and the test is also identified. With the availability of both experimental and numerical mode shapes, localized panel modes of the wind turbine blade are observed and characterized, and as a result the numerical model is validated. This work provides useful case studies for the design and structural analysis of wind turbine blades based on both the experimental observations and the validation of numerical models typical of those used for blade design and blade structural analysis.
Instability caused by emergency braking and steering during ambulance operation would easily lead to a sharp rise of blood pressure in patient’s head, which would further cause a secondary injury to ...the patient. Furthermore, the vibration generated by uneven road would result in patient’s nausea and deterioration of patient’s condition. This article proposes a pitch–roll-interconnected hydro-pneumatic suspension system which can achieve the resistance control for pitch, roll, and bounce modes of ambulances to improve the stability and attenuate the vibration for the lying patients. The ambulance with pitch–roll-interconnected hydro-pneumatic suspension is characterized by 7 degrees of freedom dynamic model, in which the characteristics of pitch–roll-interconnected hydro-pneumatic suspension are explicitly formulized using hydrodynamic equation derivation. A motion-mode energy spectral density method is proposed to decouple the vibration energy for bounce, pitch, and roll modes in frequency domain. Subsequently, the parameter design approach incorporated with the suspension characteristic equations and motion-mode energy spectral density method is also presented to optimize the lying patient’s ride comfort and ambulance’s handling stability. The numerical simulation results show that the proposed pitch–roll-interconnected hydro-pneumatic suspension system can simultaneously provide pitch–roll–stiffness and damping without generating additional bounce-stiffness, resulting in superior ride comfort and handling stability compared to the conventional suspension.
Integrated motor-transmission (IMT) powertrain systems are widely used in future electric vehicles due to the advantages of their simple structure configuration and high controllability. In electric ...vehicles, precise speed tracking control is critical to ensure good gear shifting quality of an IMT powertrain system. However, the speed tracking control design becomes challenging due to the inevitable time delay of signal transmission introduced by the in-vehicle network and unknown road slope variation. Moreover, the system parameter uncertainties and signal measurement noise also increase the difficulty for the control algorithm. To address these issues, in this paper a robust speed tracking control strategy for electric vehicles with an IMT powertrain system is proposed. A disturbance observer and low-pass filter are developed to decrease the side effect from the unknown road slope variation and measurement noise and reduce the estimation error of the external load torque. Then, the network-induced delay speed tracking model is developed and is upgraded considering the damping coefficient uncertainties of the IMT powertrain system, which can be described through the norm-bounded uncertainty reduction method. To handle the network-induced delay and parameter uncertainties, a novel and less-conservative Lyapunov function is proposed to design the robust speed tracking controller by the linear matrix inequality (LMI) algorithm. Meanwhile, the estimation error and measurement noise are considered as the external disturbances in the controller design to promote robustness. Finally, the results demonstrate that the proposed controller has the advantages of strong robustness, excellent speed tracking performance, and ride comfort over the current existing controllers.
Time-delay feedback control can effectively broaden the damping frequency band and improve the damping efficiency. However, the existing time-delay feedback control strategy has no obvious effect on ...multi-frequency random excitation vibration reduction control. That is, when the frequency of external excitation is more complicated, there is no better way to obtain the best time-delay feedback control parameters. To overcome this issue, this paper is the first work of proposing an optimal calculation method that introduces stochastic excitation into the process of solving the delay feedback control parameters. It is a time-delay control parameter with a better damping effect for random excitation. In this paper, a 2 DOF one-quarter vehicle suspension model with time-delay is studied. First, the stability interval of time-delay feedback control parameters is solved by using the Lyapunov stability theory. Second, the optimal control parameters of the time-delay feedback control under random excitation are solved by particle swarm optimization (PSO). Finally, the simulation models of a one-quarter vehicle suspension simulation model are established. Random excitation and harmonic excitation are used as inputs. The response of the vehicle body under the frequency domain damping control method and the proposed control method is compared and simulated. To make the control precision higher and the solution speed faster, this paper simulates the model by using the precise integration method of transient history. The simulation results show that the acceleration of the vehicle body in the proposed control method is 13.05% less than the passive vibration absorber under random excitation. Compared with the time-delay feedback control optimized by frequency response function, the damping effect is 12.99%. The results show that the vibration displacement, vibration velocity, and vibration acceleration of the vehicle body are better than the frequency domain function optimization method, whether it is harmonic excitation or random excitation. The ride comfort of the vehicle is improved obviously. It provides a valuable tool for time-delay vibration reduction control under random excitation.
•Hybrid DIC-EFG method is used to obtain the accurate full-field strain and SIF.•Tests and sensitivity analysis validated the accuracy and stability of the method.•The method of establishing meshless ...model based on DIC speckle image is simple.•The proposed method is able to implement without knowing the load and constraints.
A Hybrid DIC–EFG Method combining Digital Image Correlation (DIC) and Element-free Galerkin (EFG) method is proposed to characterize the strain field and study the fracture performance of a crack by evaluating the stress intensity factor (SIF). The full-field displacement data is measured by DIC. The meshless calculation model is developed by using the speckle image coordinate. Then the displacement data is imported into the model and strain is calculated by the EFG method. The SIF is obtained based on the J-integral method. A static tensile test with a quasi-static cyclic load is conducted on a Compact Tensile specimen (CT specimen) to experimentally validate the accuracy and stability of proposed method. The proposed method can effectively predict the strain at the crack tip, which is a great challenge for the DIC measurement. Compared with the reference ASTM standard, the proposed method can obtain the SIF accurately without knowing the geometry, load and boundary condition of the structure.
A frequency-based modeling approach has been developed for the vehicle fitted with Hydraulically Interconnected Suspension (HIS) system. This frequency-based model has fewer degrees of freedom (DOF) ...than the reference time-based model. Several physical parameters of HIS system are selected to analytically investigate their effects on several indicators of vehicle roll, pitch and bounce modes, such as roll and pitch angular acceleration, vertical acceleration, and tire ground force. The HIS system parameters are also coordinately tuned and optimized to meet the ride comfort requirement. The full vehicle drop test is conducted for the experimental validation. The analytical results of the proposed model have a good agreement with the measurements.
Vehicles driving on the road continuously suffer low-frequency and high-intensity road excitation, which can cause the occupant feelings of tension and dizziness. To solve this problem, a ...three-degree-of-freedom vehicle suspension system model including vehicle seat is established and a linear function equivalent excitation method is proposed. The optimization of the random excitation is transformed into the optimization of constant force in a discrete time interval, which introduces the adaptive weighted particle swarm optimization algorithm to optimize the delay and feedback gain parameters in the feedback control of time delay. In this paper, the stability switching theory is used for the first time to analyze the stability interval of 3-DOF time-delay controlled active suspension, which ensures the stability of the control system. The numerical simulation results show that the algorithm can reduce vertical passenger acceleration and vehicle acceleration, respectively, by 13.63% and 28.38% on average, and 29.99% and 47.23% on random excitation, compared with active suspension and passive suspension based on inverse control. The effectiveness of the method to suppress road random interference is verified, which provides a theoretical reference for further study of suspension performance optimization with time-delay control.
To reduce seat vibration caused by uneven road surfaces, the time-delay feedback control into the seat suspension system was introduced and an active seat suspension control method based on ...time-delay feedback was proposed in this paper. A three-degree-of-freedom (3-DOF) suspension model with time-delay feedback control was established. The time-delay independent stability region and critical stability curve of the system were derived using the method of characteristic root and stability switching. The effect of feedback control parameters on system vibration was investigated in the stability region. The seat acceleration (SA), body acceleration (BA), suspension dynamic deflection (SDD), and tire dynamic displacement (TDD) were used as multi-objective optimization functions and the optimal values of feedback control parameters were obtained based on the particle swarm algorithm (PSO) with above optimization functions. The numerical simulation was conducted to validate the proposed model. The simulated results show that the time-delay feedback control can significantly suppress the vibration response of the seat and effectively improve the suspension performance under different road excitation compared with the passive suspension. It can be seen that the active seat suspension with time-delay control significantly improve ride comfort and handling stability of the vehicle, which can be used as a reference for the active control technology of vehicle suspension.
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