Dynamic Characteristics Optimization Research Articles

Optimal Design and Dynamic Characteristic Analysis of Double-Link Trapezoidal Suspension for 3WPYZ High Gap Self-Propelled Sprayer

A fast spraying speed, wide working area, and easy operation are the operational advantages of high-clearance boom sprayers. To address the issue of spray boom mechanical vibration affecting the spraying effect, a double-link trapezoidal boom suspension is designed for the 3WPYZ sprayer. This suspension can achieve passive vibration reduction, active balance, and ground profiling. The kinematic model of the boom suspension is established based on D’Alembert’s principle and the principle of multi-body dynamics, and the design factors affecting the stability of the boom are determined. Through orthogonal experimental design and virtual kinematics simulation, the influence of the boom length and orifice diameter of each part on the swing angle and the natural frequency of the boom suspension is investigated. Design-Expert 8.0.6 software is used to analyze and optimize the test results. The optimization results show that, when the connecting boom length LAB is 265 mm, the inner boom suspension boom length LAD is 840 mm, the outer boom suspension boom length LBC is 1250 mm, and the throttle hole diameter d is 4 mm; the maximum swing angle of the boom suspension is reduced by 53.02%. In addition, the natural frequency of the boom is reduced from 1.3143 rad/s to 1.1826 rad/s, and the dynamic characteristic optimization effect is remarkable. The modal analysis results show that the first sixth-order vibration test frequency of the boom sprayer suspension designed in this paper meets the requirements and avoids the influence of external factors. Field tests show that, when the sprayer is excited by the environment at 3.5° to 4°, the boom suspension can reduce the vibration transmitted by the body to a reasonable range. The static analysis shows that the structural design of this study reduces the stress at the connection of the end boom suspension, the maximum displacement, and the maximum stress of the inner boom suspension. The test results of the dynamic characteristics of the implement are basically consistent with the virtual model simulation test results, thus achieving the optimization objectives.

A VAM-based equivalent model for random vibration of composite sandwich plate with arrowhead-on cores

The composite sandwich plate with an arrowhead-on core (arrowhead-on CSP) is a new type of composite structure that has the advantages of a low weight, high specific strength, high specific stiffness, and negative Poisson’s ratio. In this study, the equivalent plate properties were obtained using the variational asymptotic method (VAM) to asymptotically analyze the energy functional stored in the unit cell. On this basis, a two-dimensional virtual equivalent model was constructed for random vibration analysis using the pseudo excitation method. To verify the accuracy and effectiveness of the equivalent model, the dynamic behaviors (free and random vibrations) of arrowhead-on CSPs under different conditions were analyzed. The power spectral density (PSD), the root mean square (RMS) values of the lateral displacement, velocity, and acceleration responses under a base acceleration excitation, and the modal effective mass fraction under vibrations were also investigated. Finally, the effects of the layup configuration of the composite facesheets and the geometric parameters of the arrowhead-on core on the dynamic characteristics of the equivalent plate were studied. The study revealed that the equivalent model was very efficient and accurate in free and random vibration analysis, which provided a reference for the dynamic characteristic optimization of arrowhead-on CSPs.

CFD-aided approach of modelling and dynamic characteristic optimization for a highly nonlinear auxiliary braking system

It is a considerable challenge to develop a mathematical method for modelling the coupling relationship between the control signal and braking performance in the design and optimization, especially with a highly nonlinear system. The present study thus establishes an integrated CFD-aided method, elaborately proposed based on a 1D/3D co-simulation to accomplish a goal of collaborative calculation between multi-physics fields, and conducting the braking and thermal properties that changes dynamically with the control signal. In particular, the 3D model is actually a multi-domain coupling CFD transient calculation, and the 1D model provides the dynamic boundary conditions. These results manifest some interesting issues, such as modelling the prediction interaction between the isolated control signal and dynamic braking capability. The synergies of the blade agitation and centrifugal force in the multi-phases development affect the oil-filling control and braking generation. The control pressure (Pair ) and throttle area (Aout ) are predominated in enhancing braking torque, shortening response time, and improving heat dissipation efficiency. The operations of Pair ≤ 3.2 bar and Aout ≥ 64π mm2 ensure a safe and reliable design and then optimize braking and control characteristics. The resulting maximum braking torque is 4070Nm, and the outlet oil temperature is reduced to 138°C.

Dynamic Characteristic Analysis and Structural Optimization Design of the Large Mining Headframe

A large headframe is the core structure of a mine hoisting system. In the traditional design, only the static analysis under load is considered, resulting in the resonance phenomenon of the large headframe in later applications. In order to restrain the resonance phenomenon, a novel method for dynamic characteristic analysis and structural optimization design of a large headframe is proposed. First, the eigenfrequencies and vibration modes of the large headframe were obtained through modal analysis. The results showed that the numerical values of the multi-order eigenfrequencies of the system are relatively close. When subjected to alternating loads of similar frequencies, a large headframe is prone to the resonance phenomenon. Second, the steady-state vibration response of the large headframe was obtained through harmonic response analysis. The results showed that when the frequency of the alternating load is close to the first-order eigenfrequency, the vibration amplitude increases. Meanwhile, the fourth-order and the fifth-order eigenfrequencies are very close. When subjected to alternating loads of similar frequencies, the fourth-order and the fifth-order vibration modes of the headframe will be excited simultaneously. At this time, the headframe will have a strong resonance, which may cause structural damage and other problems. Finally, based on the above analysis, nine different structural optimization schemes are proposed in this paper. Through modal analysis and harmonic response analysis, the nine schemes were compared and analyzed, and the optimal scheme was eventually determined as scheme 9. The method proposed in this paper provides a new concept for the structural optimization design of a large mining headframe, and it has great significance for restraining the resonance phenomenon and ensuring the safety of mining operations.

Study on dynamic characteristic optimization of virtual inertia control for the grid-connected converters in DC micro grid

In order to reduce the transient time and voltage deviation due to voltage variation while increasing the system inertia of the DC microgrid, a new adaptive control method for the parameters of the grid-connected end is proposed. Firstly, a grid-connected converter control strategy mathematical model is established. Secondly, the influences of different control parameters on the dynamic characteristics of the system are studied. An adaptive equation based on the parameters of voltage deviation and voltage change rate of DC bus is proposed. Finally, through MATLAB/Simulink simulation, the simulation results of the traditional drooping control, the virtual inertial control with fixed parameters and the control strategy proposed in this paper are compared and analyzed. The result shows that the proposed control method has better dynamic characteristics.

Diversity and Regularity of Periodic Impact Motions of a Mechanical Vibration System with Multiple Rigid Stops

The mechanical model of a two-degree-of-freedom vibration system with multiple rigid stops was established, and the effects of the multiple rigid stops to dynamic characteristics of two mass blocks of the system were studied. The judgment conditions and differential equations of motion of the system masses impacting rigid stops were analyzed. Based on the multiparameter and multiobjective collaborative simulation analysis, the correlation between the dynamic characteristics of the vibration system and the model parameters is studied. The basic periodic and subharmonic impact motions are analyzed with emphasis on the influences of dynamical parameters on the mode diversity and the distribution characteristics, and the law of emergence and competition of various periodic impact motions on the parametric plane is revealed. The singular points, the hysteresis transition domains, and the accompanying codimension-two bifurcations, caused by the irreversibility of the transition between adjacent basic periodic impact motions in the low-frequency domain, are analyzed. The reasonable parameter matching range, associated with dynamic characteristic optimization of the system, is determined.

Angular velocity and contact force simulation of the spiral bevel gear meshing based on the hertz contact theory

To obtain the change tendency of the wheel’s angular velocity and tangential component of contact force with time of the pinion under the step input during spiral bevel gear meshing, the tooth flank equation of spiral bevel gear was constructed based on the Non-Uniform Rational B-splines curve. The three-dimensional model of the pinion and the wheel were built based on the tooth flank equation. The calculation equation and relative parameters set for the contact force of spiral bevel gear meshing were done based on the Hertz contact theory. A mating of spiral bevel gears was taken as an example for dynamics simulation and the simulation results show that the relative error rate of the angular velocity between simulation and theoretical calculation is 0.054%, and that the relative error rate of tangential component of the contact force between simulation and theoretical calculation is 4.82%. These findings provide the theoretical basis for dynamic characteristics optimization of the spiral bevel gears.

Dynamic Characteristic Optimization of Ball Screw Feed Drive in Machine Tool Based on Modal Extraction of State Space Model

The accurate prediction and research about the dynamic characteristic of machine tool during the design process are essential to develop high-performance machines. In order to consider the effect of mechanical modal characteristics on the whole dynamic performance and servo controller of ball screw feed drive fully, the modal characteristics of mechanical transmission are extracted and solved based on reduced state space matrix of ball screw feed system, which is also easy for integration with servo control model. On this basis, the step-by-step optimization method from the global to the local is proposed to optimize the servo controller and overall dynamic performance of ball screw feed drive. This step-by-step optimization method is as follows: first, the global initial optimal tuning of servo controller parameters under the influence of structure modal characteristics is originally realized through the analytic derivation of servo controller based on the extraction of state space modal characteristics. Second, the integrated model of the feed drive system is established. Finally, based on the above global optimization results, the overall dynamic performance, and the servo parameters of the feed drive system under the influence of the modal characteristics are further studied and optimized locally. Taking the ball screw feed drive studied in this paper like the example, its rise time and the settling time of step response are 0.089 and 0.104s before optimization, while these reduce to 0.038 and 0.092s after optimization. Its dynamic response performance after optimization is much better. The optimization result is also validated by the test: the rise time and the settling time by the test are 0.042 and 0.094s, which are close to that from the simulation. Also, the consistency of step response curves from experiment and simulation as well. All these show that: this prediction and optimization method of overall dynamic performance considering the modal characteristic influence of mechanical transmission fully is correct and reliable.

Hierarchical Modeling and Dynamic Analysis of Hoist System in Electric Mining Shovel

The hoist system of electric mining shovel (EMS) always encounters excessive vibration in present work. However, the shortage of suitable dynamic model has been the bottleneck of reducing vibration. In order to analyze the vibration of the EMS hoist system, a coupled dynamic model is proposed using the hierarchical modeling method, which contains couplings of bolt, bear, coupling, rope, and gear mesh. The components were equivalent to mass elements with several nodes corresponding to their structure. Considered helical gears and motors, a dynamic gear transmission model with couplings of bending, torsion, and axes was developed. Based on the dynamic model, the modal characteristics were calculated, and the vibration modes were classified to five types. Under the ripple drive torque simulated by Simulink, the dynamic characteristics of the hoist system in time domain and frequency domain were obtained using numerical integration with the Runge–Kutta method in Matlab. At last, the model validity was verified by contrasting the responses under actual test and the model. The dynamic model and study results can provide support for dynamic characteristic evaluation and dynamic optimization of the EMS hoist system.

Dynamic Characteristic Optimization for Transmission Mechanism of UHV Circuit Breaker

Dynamic Characteristic Optimization for Transmission Mechanism of UHV Circuit Breaker

Effects of Tuned Rail Damper on Track Dynamic Characteristics Optimization

Egg-III system track is widely used in the vibration-abatement-sections of Beijing Metro, while DTVI2 fastener track is a common used form that frequently applied in the sections without vibration reduction requirements. These two railway track forms are favored in the field of urban rail transit for the respective superiorities. Recently after several months of operation, a series of abnormal problems occur, including rail corrugation problem on Egg-III fasteners section and clips fracture problem on DTVI2 rail fastening section. To provide a feasible solution for both problems, the presented paper introducing the laboratory tests which were conducted to optimize the dynamic properties of Egg-III fastener track and DTVI2 fastener track using the device of Tuned Rail Damper (‘TRD’ for short).The tests were carried out on the experimental platform in Beijing Jiaotong university, which provides dynamic testing conditions for varying track forms. To evaluate the effects of TRD on track dynamic properties, tests of direct frequency response function, vibration decay rate and vibration acceleration level were done for Egg-III system track and DTVI2 fastener track (installed/uninstalled with TRD).Experimental results indicate that TRD obviously optimizes the dynamic characteristics of both Egg-III system track and DTVI2 fastener track. The optimization effects are listed as follows: (1) The resonance peaks of frequency response function curve are significantly reduced and moved in the range of 100-400Hz, which is identified as the cause of the rail corrugation occurred on Egg-III system track sections. (2) The vertical and transverse vibration decay rates on Egg-III system are obviously increased with TRD， suppressing the vibration transited along the rail. (3) Vibration reduction ability of Egg-III system track is not weakened with TRD, but strengthened up to 1.2-6 times at most frequencies. (4) The amplitudes of frequency response function curve are reduced when TRD was installed on the rail of DTVI2 fastener track. (5) The vertical and transverse vibration decay rates of DTVI2 fastener track are raised markedly with TRD, that the vibration energy transmitted to rail fastening clips is reduced.

Integrated approach of the dynamic characteristics optimization for spacecraft’s technical systems on the exploratory tests

Integrated approach is the process connecting various project, theoretical and testing procedures. It is provided by the specific series-parallel combination of the mentioned operations. This paper shows that using results of the previous procedures on the further algorithm stages of exploratory tests and product verification is expedient. At that, the necessary correcting of engineering solutions in corresponding procedures is conducted simultaneously. Then, results of each procedure are used in the fixed sequence. It provides maximum attainable optimality of the designed system.

Dynamic Characteristics Optimization of Joint Interface of Machine Tool Based on Porous Oily Materials

The joint interface plays a significant role in machine tools and other machineries. A novel type of joint which consists of oily porous material was proposed in the paper. A test system for identifying the unit area dynamic characteristic parameters of Fe-based joint interfaces were represented. The stiffness and damping parameters were compare to the conversional structures. The result showed that the joint which contains an oil film interlayer formed by porous and steel was superior to the joint with non-media formed by steel in stiffness and damping characteristics. In the case of the same preload, the former’s stiffness is increased by about 50 %, and the damping is increased about five to six times.

Research on Dynamic Characteristics Optimization via Analytical Modeling for Typical Rotational Electromagnetic System

As an analytical method with lumped parameters, the magnetic equivalent circuit method is usually constrained by its incapability of flux leakage and magnetic saturation compared with finite element (FE) method. We propose a new approach introducing compensation matrix C m×n to combine both methods. It requires a certain number of feature points by FE to compensate flux leakage at different positions and saturation extents at different coil currents, result precision within 5% and only second time consumed. Then, the approach is applied in dynamic modeling, design refinement, and performance optimization, where repetitive calculation of electromagnetic character is needed, and the results indicate the feasibility of the approach.

Dynamic characteristics optimization for a whole vertical machining center based on the configuration of joint stiffness

Joint stiffness often has a significant effect on the dynamic characteristics of the whole machine tool. In this paper, a joint stiffness configuration method is developed to optimize the dynamic characteristics of a whole vertical machining center, in which the premise is considering the joint characteristics to create the accurate finite element model (FEM) of the whole machine tool. Identifying the joints parameters including the contact stiffness and damping of the linear guides, bolts, ball screws, and bearings is conducted. Vibration test and finite element simulation are implemented to verify the accuracy of the FEM which is created based on the identified joints parameters by comparing the tested and simulated frequency-response functions (FRFs). With these tested and simulated results, taking the dynamic flexibility at the spindle nose to measure the dynamic characteristics of the whole machine tool, vibration modes, and joints related to a higher modal flexibility and elastic energy distribution ratio can be determined to be the weak modes and joints respectively. Optimization aiming to decrease the modal flexibility is conducted by adopting the orthogonal experiment method to instruct the simulations to predict how stiffness of the weak joints affected the dynamic characteristics of the whole vertical machining center. Thus, an optimal joint stiffness configuration can be obtained by using the range analysis and fuzzy similar preference ratio method to analyze the simulated results. Redoing the simulation with the optimal configuration, results indicate that modal flexibility of each weak mode is decreased obviously. The decreased modal flexibilities and dynamic responses verify that the optimal configuration method is feasible to provide a way for improving the dynamic characteristics of the whole machine tool.

Dynamic Analysis of Less-Teeth Gear Transmission System

According to the less-teeth gear design theory, the FEM model of less-teeth gear system was established, and its dynamic contact characteristic was analyzed, then dynamic contact simulation was realized. Laws of contact area, contact stress and tooth stress change over time were got, which can be used for the gear profile modification and dynamic characteristics optimization design of the less-teeth gear system.

Study on Nonlinear Dynamic Characteristic of Gearbox Based on Explicit Dynamic

Considering the drawbacks of existing dynamics research of gearbox system, the dynamic analysis method based on perfectly elastic body is presented. A certain type of marine gearbox is taken as investigation object based on Abaqus/Explicit dynamic finite element program, the dynamic contact nonlinear model of gearbox system is established considering the coupling effect of each component, dynamic simulation of the gearbox system is carried out. The results show that, in the gearbox coupling model, the coupling effects among the bearing, the housing and the gears cause the dynamic characteristic of the gear transmission system more complex, which exacerbates shock effect of the gearbox, the model which considered coupling among the components is closer to the real working condition. The research has certain reference value for gearbox dynamic characteristic optimization.

Dynamic Characteristics Analysis and Optimization Design of Spindle Box with FEA

The simplified finite element modal was established with ANSYS aiming to study the spindle box. The changing regularity of the first 6-order natural frequency of spindle box was studied after the static and modal analysis. Shape optimization design was carried out by taking the maximum deformation of the direction of X，Y，Z as the objective function. The results show that the structure of spindle box after optimization can effectively reduce the maximum deformations of the direction of X，Y，Z，and has better static and dynamic characteristics.

Modal Analysis of Electronic Power Steering Based on Finite Element Method

With the application of the software Pro / Engineer, the 3-D model of automobile Electric Power steering system is built. The pre-processing and post-processing of the model are carried in I-DEAS software, while PERMAS solver is used to calculate. The structure design and dynamic characteristic optimization of the model are researched, and on the basis of natural frequencies analysis, several design improvement schemes are brought forward. The optimum scheme is generated through comparison.

Modal Analysis of Electronic Power Steering Based on Finite Element Method

With the application of the software Pro / Engineer, the 3-D model of automobile Electric Power steering system is built. The pre-processing and post-processing of the model are carried in I-DEAS software, while PERMAS solver is used to calculate. The structure design and dynamic characteristic optimization of the model are researched, and on the basis of natural frequencies analysis, several design improvement schemes are brought forward. The optimum scheme is generated through comparison.