Robotic Systems and Applications
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Study on multi-axis sine vibration test control techniques
Get PDFThis paper describes several key aspects about multi-axis sine vibration test control techniques including the identification of the system frequency response function, synchronization of the input and output signals, the generation of the sinewave, the control algorithm, etc. A multi-axis sine vibration controller is developed based on these key techniques and the major framework of the controller is introduced. Finally, a dual axial experiment is carried out by the controller. The test results show the feasibility of the control algorithm and the good control strategy of the multi-axis sine vibration controller in which the key techniques are realized
Acoustic vibration response and power generation characteristics of airborne acoustic generator system
Get PDFAiming at the problem of insufficient power supply in modern intelligent fuze, it is of great theoretical significance and practical guidance to study the relationship between acoustic vibration response and power generation characteristics of airborne piezoelectric generators and maximum energy output. Theoretical analysis and experimental verification show that: 1. As long as the frequency of the acoustic wave induced by the flow coincides with the frequency of the acoustical modal in the cavity, a sinusoidal vibration excitation signal will be generated in the cavity; 2. With the increase of the flow rate, the frequency of the vibration signal coupled by the fluid sound source also increases. If the frequency of the acoustic wave is near the anti-resonance frequency of the piezoelectric vibrator, the displacement amplitude of the piezoelectric vibrator increases greatly. The maximum output open circuit voltage is the maximum power generated when the external circuit is connected; 3. The amplitude of the open circuit voltage of the electromechanical coupling output is linear with the amplitude of the displacement of the piezoelectric vibrator, the frequency is the same, the phase angle is the same, and the displacement and the exciting force of the piezoelectric vibrator have the characteristics of the same frequencies and backward phases, the maximum displacement of the piezoelectric vibrator is related to the amplitude of the exciting force and the angular frequency of the exciting force. This characteristic can be used to solve the piezoelectric stress factor under different initial conditions from the experimental point of view
On-site vibration test and dynamic response analysis of wind turbine of intertidal zone
Get PDFIn our study, the vibration signal of impulse response and attenuation response are extracted using the correlation function and power spectrum, and the natural frequency of wind turbine is determined. Compared with the rotation frequency of the blades of wind turbine which are 1p (one blade) and 3p (three blades), and wind vibration performance of the wind turbine is determined. The natural frequency of wind turbine is between the frequencies of one blade and three blades of wind turbine, which can avoid resonance phenomenon and meet the precision requirement for engineering application. The laws of acceleration and strain response along the wind turbine under ordinary wind load are obtained by installing acceleration sensor and strain gauge along the wind turbine. We found that the acceleration at the wind turbine top increases 10 times than that at the bottom. The acceleration influenced by tide is 1.14 times than that with no tide. The strain produced maximum value at the opening place of wind turbine and near the top, it should be paid attention in the engineering design
The control strength quantification analysis of outer pendulum rod for double inverted pendulum
Get PDFDue to the complexity of the dynamics characteristics of an inverted pendulum, and the problem that the linearization analyze method cannot satisfy the controlling requirement, a nonlinear dynamics analyze method was proposed. Through decoupling the dynamics model of a double inverted pendulum, the outer pendulum rod motion equation was derived. And then, aiming at the control strength function of outer pendulum rod, the qualitative and quantitative relationship between spatial position of pendulum rod and the control strength of outer rod, and the quantification relationship between dynamics parameters and the control strength of outer rod were separately analyzed. And the simulation verified the correctness of the analysis
Dynamic responses of base-isolated concrete liquid storage structure under two types of resonances
Get PDFOne important characteristic of base-isolated liquid storage structure (LSS) is that the vibration periods of structure and liquid are different, namely, there are two kinds of periods in the system. As a result, structure or liquid resonance may occurs under external excitation. In order to reflect the nonlinear characteristics of liquid sloshing, subsonic potential-based element is used to simulate the liquid. The governing equations of liquid field and fluid-structure interaction (FSI) equations are established; the initial and boundary conditions of liquid sloshing in dynamic coordinate system are obtained. Harmonic functions used to conduct time history analysis are generated by the first order vibration frequencies of structure and liquid respectively. The dynamic responses of base-isolated rectangular liquid storage structure (RLSS) under two types of resonance are studied comparatively. Results show that when the external excitation frequency is equal to the first order vibration frequency of isolated structure or liquid sloshing, wall tensile stress, structure displacement, base shear force and liquid sloshing wave height will appear resonance amplification phenomenon. The dynamic responses of structure itself caused by structure resonance are greater than that of liquid resonance; while the liquid sloshing wave height caused by liquid resonance is greater than that of structure resonance. Under structure resonance, the wall is prone to be cracked; and under liquid resonance, the liquid velocity field will become unusually violent, and liquid overflow will be caused easily
Influence of location of measurement point on evaluation of human perception of vibration
Get PDFHuman perception of vibration is very subjective parameter which depends among others on age, sex or even nationality. There are three main methods of assessment of human perception of vibration according to national standards which differ from each other. All three methods are clearly described in this paper and their advantages and disadvantages are shown. Evaluation methods are helpful in diagnosis and design of the building when they are used properly. One of interesting aspect of quality of measurements is localization of measurement points. The choice of localization of measurement points could have significant influence on result of evaluation of human response to vibration. International and national standards are compatible in this matter – measurement points should be localized in the place of human vibration perception. It means that should be located in the middle of the floor. Sometimes it is difficult to determine the exact center of the floor, especially when building has irregular construction. In this paper influence of localization of measurement point on human perception of vibration is investigated and center zone in which measurement results are proper is determined. In-situ measurements were made to investigate the problem of localization of human vibration perception in buildings
Defect elimination in torsional harmonic reducer based on harmonic resonance
Get PDFThis paper will introduce the torsional vibration test method and signal analysis for a harmonic reducer in industrial robot. The harmonic reducer is generally applied to the fifth and sixth axes of the industrial robots, and the torsional vibration will affect the mechanical performance. To understand the torsional vibration condition of the harmonic reducer, the test device is set up through loading the corresponding moment of inertia. In the study, the curve of torsional characteristic is obtained, and it can be used to assess the mechanical performance; Using zoom spectrum technology on harmonic resonance, the characteristic frequency is identified in detail. The manufacturing defect of the harmonic reducer is diagnosed based on characteristic frequencies of its transmission, and defect elimination is successfully realized by adjustment of components in the harmonic driver; Some nonlinear vibration characteristics caused by stiffness with time periodic dependent, including bi-spectrum and harmonic resonance, etc., are investigated. The experimental results show that the test and analysis of torsional vibration have positive significance for the online quality assembly assurance of harmonic reducer
Dynamics research of a flywheel shafting with PMB and a single point flexible support
Get PDFFlywheel energy storage system (FESS) is new advanced machinery which is intended for electric power storage and release. A FESS, which is suitable for the small flywheel, was developed with a permanent magnet bearing (PMB) and a single point flexible support, and its friction loss is very low. By means of the Lagrange theory, a dynamic model was established. The Campbell diagram, mode shapes, modal damping ratios and critical speeds were designed after the flywheel data at different operating speeds was obtained by numerical simulation. Based on the excitation test and single freedom vibration theory, the stiffness and damping coefficient of the upper and lower damper was measured. The influences of damper dynamic parameters on modes of flywheel rotor bearing system were discussed in detail. The comparison between the calculated unbalance response and the experimental response indicates that the dynamic model is appropriate. The results showed that the lower damper absorbed vibration energy of the flywheel rotor, which increased vibration of the damping body. And the bigger damping coefficient had better vibration absorption effect. The developed FESS is simple, stable and efficient in structure
An intelligent bearing fault diagnosis method based on the AFEEMD and 1D CNNs
Get PDFTo process the non-stationary vibration signals and improve accuracy of bearing fault diagnosis, this paper presents a novel intelligent fault diagnosis method based on the adaptive fast ensemble empirical mode decomposition (AFEEMD) and one-dimensional convolutional neural networks (1D CNNs). First, the AFEEMD algorithm is utilized to decompose the raw signals into intrinsic mode functions (IMFs). Then, the time and frequency statistic features of the first several IMFs are analyzed to form feature vector, which are used as the input of 1D CNNs to identify the bearing fault. The performance of the proposed method is validated using the dataset from the Case Western Reserve University (CWRU). Compared with the traditional back propagation neural network (BPNN), the results show that the proposed AFEEMD-1D CNNs method not only can obtain higher accuracy and achieve more reliable performance, but also can improve the generalization performance. Due to the end-to-end feature learning capacity, it can be extended to other machinery for fault diagnosis
Electromagnetic buffering considering PM eddy current loss under intensive impact load
Get PDFThe intensive impact load will generate a huge acceleration in the primary part of the Electromagnetic buffers (EMBs), resulting in an instantaneous increase in the eddy current loss of the permanent magnet (PM). In this paper, the PM eddy current loss is taken into account in the electromagnetic buffering under intensive impact load. The reason why the eddy current damping force differs between two different buffer stages is analyzed. The experimental results signify that the model considering the PM eddy current loss is more accurate