Unbalanced Excitation Research Articles

Electromechanical Coupling Mechanism and Control Strategy for In-Wheel-Motor-Driven Electric Vehicles

This paper presents a control methodology for solving the vibration issues emerged in in-wheel motor electric vehicles (IWM-EVs). Unlike existing techniques and methods, the proposed investigation focuses on the electromechanical coupling effects between the subsystems in IWM-EV, which were considered as another negative effects bought by power integration. To this aim, an integrated model which describes the dynamic coupling process between electromagnetic excitation in motor and transient dynamics in vehicle is established and developed. The characteristics of the electromechanically motivated harassment are discussed and its coupling mechanism is analyzed. The key factors are extracted and adopted as the feedback signals in the design of control methods. The effectiveness verification is conducted within numerous practical scenario of vehicle dynamics. Theoretical analysis and simulation results reveal that the proposed approaches can prevent further enlargement of air-gap deformation and unbalanced electromagnetic excitation by cutting off the electromagnetic force outputting periodically, which are benefitted to attenuate the negative issues arisen by electromechanical coupling in IWM-EV. In addition, a more balanced outcome in vehicle dynamics is achieved by the independent-phase chopping method with a less side effect on output torque and speed tracking ability.

Highly efficient asymmetric optical transmission by unbalanced excitation of surface evanescent waves in a single—layer dielectric gradient metasurface

Asymmetric optical transmission has recently been demonstrated using Lorentz‒reciprocal devices with patterned photonic structures of linear materials by breaking spatial inversion symmetry. However, it is a huge challenge to fabricate such devices due to their sophisticated multilayer configurations. In this letter, we show that a simple single‒layer dielectric gradient metasurface (GM) enables high-efficiency asymmetric optical transmission under the oblique incidence. The underlying mechanism is ascribed to the unbalanced excitation of surface evanescent waves for forward and backward light. Our results provide strategies for creating compact, integrated and high performance asymmetric optical transmission devices.

Photoprotection and growth under different lights of Arabidopsis single and double mutants for energy dissipation (npq4) and state transitions (pph1).

Arabidopsis single and double mutants for energy dissipation (npq4) and state transitions (pph1, blocked in State II) show enhanced growth and flowers + siliques production under controlled low-light conditions. Non-photochemical quenching (NPQ) is a short-term regulation important to maintain efficient photosynthesis and to avoid photooxidative damages by dissipation of excess energy. Full activation of NPQ in plants requires the protonation of the PsbS protein, which is the sensor of the low lumenal pH triggering the thermal dissipation. State transitions are a second important photosynthetic regulation to respond to changes in light quality and unbalanced excitation of photosystems. State transitions allow energy redistribution between PSI and PSII through the reversible exchange of LHCII antenna complexes between photosystems thanks to the opposite action of the STN7 kinase and PPH1 phosphatase: phosphorylation of LHCII promotes its mobilization from PSII to PSI, while dephosphorylation has the opposite effect. In this work, we produced the pph1/npq4 double mutant and characterized some photosynthetic, growth and reproduction properties in comparison with wild-type and single-mutant plants in high- and low-light conditions. Results indicate that in high light, the pph1 mutant maintains good photoprotection ability, while npq4 plants show more susceptibility to photodamages. The pph1/npq4 double mutant showed a resistance to high-light stress similar to that of the single npq4 mutant. In low-light condition, the single mutants showed a significant increase of growth and flowering compared to wild-type plants and this effect was further enhanced in the pph1/npq4 double mutant. Results suggest that photosynthetic optimisation to improve crop growth and productivity might be possible, at least under controlled low-light conditions, by modifying NPQ and regulationof state transitions.

Experimental Investigation on Rotordynamic Characteristics and Rotor System Stability of a Novel Negative Dislocated Seal

Air‐induced force generated in seals is one key factor on the stability of the rotor system. In this paper, a novel negative dislocated seal (NDS) was developed in respect of dislocated bearing theory, to reduce hydrodynamic pressure effect and air‐induced force and improve rotor stability as well. A test rig was built to test rotordynamic characteristics and rotor stability of the NDS. The rotordynamic characteristics of seals were investigated based on the unbalanced synchronous excitation method, and seal‐rotor system stability was evaluated by the identification method with an electromagnetic bearing exciter. The effects of both rotating speed and inlet/outlet pressure ratio on the rotordynamic characteristics and rotor stability of both NDS and conventional cylindrical labyrinth seal were experimentally investigated. The results show that with the increasing rotating speed, inlet/outlet pressure ratio is promising to reduce the direct stiffness coefficients of seals and the logarithmic decrement rate of seal‐rotor system and enhance both cross stiffness and damping coefficient as well. Besides, the developed NDS effectively reduces cross‐stiffness coefficients and increases direct damping coefficients and the logarithmic decrement rate of the seal‐rotor system, relative to the conventional cylindrical seal. The proposed seal can effectively improve seal stability of turbomachinery.

Research on Improvement of Truck Vibration Based on Systematic G8D Method

In view of the common and difficult to solve vehicle vibration problem, taking a large truck manufacturing enterprise in China as an example, an improved model for solving truck vibration problem is established by using the G8D method, and the unbalanced excitation force of the wheel system is analysed. The coupling of the excitation frequency and the natural frequency of the system leads to the resonance phenomenon, as well as the inadequate damping function of the system, is the fundamental cause of the vibration problem. After verifying and implementing permanent correction measures at the same time at the three levels of components, devices, and the entire vehicle, the acceleration of the seat guide rails for the vibration performance of the truck reduces from the original state 1.04 m/s2 to 0.6 m/s2, a decrease of 42.3%, which reaches the best level of mainstream cars in the country and is close to the optimal level of 0.5 m/s2 among the same kinds of cars in Germany. Therefore, the improved model can improve the sustainability of product manufacturing, provide industry guidance for solving the quality problem of truck vibration, and provide a sustainable guarantee for social public transport safety.

Modeling and Experimental Study on the Micro-Vibration Transmission of a Control Moment Gyro

A control moment gyro (CMG) is the main source of vibration disturbance in the spacecraft. This paper presents a vibration mathematical model with 18 degrees of freedom by Lagrange energy method, for solving the problem that the transmission mechanism for the micro-vibration of the CMG is not clear. The parameters of the micro-vibration transmission model are identified by modal analysis, frequency response analysis, and dynamic-static unbalanced excitation analysis. The numerical simulation was performed to obtain the disturbance force of the CMG. The prototype was fabricated and an experimental system was established. The test results show that the numerical and experimental values of the disturbance force have highly consistent in accuracy, the maximum deviation is 4.77%. It demonstrates that the establishment of the micro-vibration transfer model of the CMG can predict its micro-vibration characteristics. This paper provides a sound theoretical basis and guidance for designing the CMG with ultra-low micro-vibration.

New backward whirl phenomena in intact and cracked rotor systems

Based on several published studies and relevant Campbell diagrams, it is well known that the passage through the critical backward whirl (BW) rotational speeds in rotor systems should theoretically precede the passage through the critical forward whirl (FW) rotational speeds. Theoretically, this means that the location of the zone/zones of the BW orbits should be captured before acquiring and exceeding the critical FW rotational speed under the effect of an unbalanced force excitation. However, for rotor systems that exhibit recurrent startup and coast down operations, the associated equations of motion take the form of linear time-varying (LTV) equations for which the traditional Campbell diagram is no longer valid for predicting the related critical FW and BW rotational speeds. Accordingly, herein, it is numerically and experimentally verified that new zones of BW rotational speeds appear immediately after the critical FW rotational speed is acquired and exceeded during startup and coast down operations in the cases of intact and cracked rotor systems. These numerical and experimental investigations have been carefully conducted to provide robust evidence about the appearance of these new BW zones. These discovered BW zones are found to be affected by the crack damage in the shaft and were accompanied with a stiffness asymmetry in the bearings. Unlike the case where the critical FW rotational speed is acquired and exceeded, the vibration during the case at which speeds acquire and exceed these new BW zones of rotational speeds was found to be associated with an abrupt reduction in whirl amplitudes to minimum values for both start-up and coast down operations.

Identification of firefly algorithm-based fluctuation coefficient of the exciting torque for vehicle driveline

The unbalanced excitation force and torque generated by an engine that resonate with the natural frequency of drivetrain often causes vibration and noise problems in vehicles. This study aims to comprehensively employ theoretical modelling and experimental identification methods to obtain the fluctuation coefficients of engine excitation torque when a car is in different gear positions. The inherent characteristics of the system are studied on the basis of the four-degree-of-freedom driveline lumped mass model and the longitudinal dynamics model of vehicle. The correctness of the model is verified by torsional vibration test. The second order's engine torque fluctuation coefficients are identified by firefly algorithm according to the curves of flywheel speed in different gears under the acceleration condition of the whole open throttle. The torque obtained by parameter identification is applied to the model, and the torsional vibration response of the system is analysed. The influence of the key parameters on the torsional vibration response of the system is investigated. The study concludes that proper reduction of clutch stiffness can increase clutch damping and half-axle rigidity, which can help improve the torsional vibration performance of the system. This study can provide reference for vehicle drivetrain modelling and torsional vibration control.

Boosting and consolidating the proprioceptive cortical aftereffect by combining tendon vibration and repetitive TMS over primary motor cortex.

Tendon vibration of a limb elicits illusory movements in the direction that the vibrated muscle would be stretched, followed by a transient perception of movement in the opposite direction, that was demonstrated to correspond to a "cortical" aftereffect (Goodwin et al. Science 175:1382-1384, 1972). Primary motor cortex (M1) excitability of the non-vibrated antagonist muscle of the vibrated muscle increased during vibration and decreased thereafter. The cortical aftereffect is of interest when considering the possibility to use tendon vibration in rehabilitation for restoring unbalance activity between antagonistic muscles but, due to its short-lasting duration, has not been explored so far. We investigated the possibility to consolidate the cortical aftereffect by combining tendon vibration with a concomitant high-frequency 5-Hz repetitive transcranial magnetic stimulation (rTMS) protocol. The distal tendon of the flexor carpi radialis muscle (FCR) was vibrated and concomitantly a 2-min 5-Hz rTMS protocol was administered on the left hemi-scalp hot spot of the vibrated FCR or its antagonist muscle (extensor carpi radialis (ECR)). We found that this protocol induced a pattern of unbalanced M1 excitability between vibrated muscle and its antagonist with increased excitability of the FCR and decreased excitability of ECR cortical areas, which persisted up to 30min.

Integrated design of active suspension parameters for solving negative vibration effects of switched reluctance-in-wheel motor electrical vehicles based on multi-objective particle swarm optimization

As for the elastic layout of the direct-driven electric wheel system, the electromechanical coupling between the electromagnetic excitation of in-wheel driving motor and the weak damping system gives rise to negative vibration issues, which further deteriorate the dynamic performance of the electric vehicle. This paper presents a multi-objective optimization method for active suspension system to solve these issues by developing an integrated in-wheel motor electrical vehicles model. The unbalanced electromagnetic excitation from in-wheel driving motor is investigated by means of analytical and finite element methods. The Pareto solution set of optimal parameters are generated by the multi-objective particle swarm optimization method, and a comparison in vehicle dynamic performances is made to verify the targeted optimization method. The simulation results indicate that the optimized active suspension system attenuates the sensitivity of the vehicle system to electromagnetic excitation with a satisfactory balancing between vehicle ride comfort and stability as well as active suspension utilization.

Multi-objective optimization of active suspension system in electric vehicle with In-Wheel-Motor against the negative electromechanical coupling effects

Abstract This paper presents a multi-objective optimization control method of active suspension system for solving the negative vibration issues emerged from In-Wheel-Motor (IWM) in electric vehicles. An integrated model which considering electromechanical coupling between electromagnetic excitation in motor and transient dynamics in vehicle is established and developed. The characteristics of electromagnetic excitation are discussed and its influences on vehicle dynamics are analyzed. The key factors are formulated and selected as the objective criteria for multi-objective optimization approach. The Pareto solution set of optimal parameters in active suspension system is generated by Particle Swarm Optimization (PSO) method, a comparison in vehicle dynamic performances is made to verify the targeted optimization method. The simulation results indicate that the optimized active suspension system can effectively reduce the vertical component of unbalanced electromagnetic excitation by maintaining the relative eccentricity of driving motor in a reasonable interval meanwhile attenuate the sensitivity of the vehicle system to electromagnetic excitation. Furthermore, active suspension system also preserve dynamical advantages in vehicle by means of a balance between the ride comfort and the road holding. The proposed multi-objective optimization method of active suspension system demonstrates a potential application in engineering in order to solve vibration issues in electric vehicle with in wheel motor.

Mathematical Model of the Dynamic Action of the Controlled Vibration Exciter on the Processed Medium of Mixer with Toroidal Working Container

Vibration mixers are technological machines that are meant for mixing of different processed medium. A driving force in such machines is realizing by oscillation exciter. In this article, the constructive scheme of the vibration mixer is introduced. Such a mixer has the toroidal working container and is equipped with controlled mechanical centrifugal unbalanced exciters of oscillations with a vertically located unbalanced shaft. The work principle of one of the possible configurations in this exciter is considered and provided. One inflexible and two mobile unbalances are strengthen on its unbalanced shaft. The mobile unbalances by means of independent external action, that is caused by mechanism for managing of mobile unbalances, have an opportunity to change synchronously its positions on the unbalanced shaft directly in time of mixer’s work. The centrifugal inertia forces of inflexible and mobile unbalances make the dynamic wrench that consists of the main vector 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 and the main moment 
 
 and rotates with unbalanced shaft. It is determined that the value of the main vector 
 
 and the main moment 
 
 evaluate the dynamic action of this vibration exciter to the mixer’s working container. The mathematical model of the dynamic action of oscillator exciter on the processed medium of mixer with the toroidal working container is received. Depending on the value of turn angle of mobile unbalances from its starting positions exciter: a) staying in the dynamic balance state; b) is generating the translation force field; c) generates the wrench force field of this or that direction. These opportunities of controlled vibration exciter firmly provide anfractuous circulative motion of the processed medium on the volume of the mixer’s working container. Using of controlled exciter also leaves out the transfers through intermediate resonance frequencies. As its starting and stopping happen in a dynamic balance state, so it leaves out the possibility of manifestation of the “Sommerfeld’s effect” that is harmful for the driven motor, improves the constructive availability of the vibration mixer and increases its efficiency and life duration.

Коливання привода вібраційних машин з дебалансними збудниками

Коливання привода вібраційних машин з дебалансними збудниками

Investigation on a No Trial Weight Spray Online Dynamic Balancer

In order to suppress the spindle vibration with high efficiency and high precision, a no without trial weight spray online balance method is proposed in this paper. By analyzing the relationship between the unbalanced excitation and the unbalanced response of the spindle, the relationship between the dynamic influence coefficient and the system model is studied. A high‐speed spindle finite element analysis model was established, and the dynamic influence coefficient matrix was identified. A no trial weight spray online dynamic balancing system was developed, which has the advantages of without trial weight and high‐precision loading. A new type of integrated balancing terminal that was formed using 3D printing technology was first proposed by our research group, and its advantages in various aspects are significantly higher than traditional assembly balanced terminals. The experimental verification of the without trial weight spray online dynamic balancing system was performed on a high‐speed spindle test stand. Experiments show that the no trial weight spray online balancing method proposed in this paper can achieve high‐efficiency and high‐precision vibration suppression, greatly reducing balance time and cost of the spindle. At the same time, the online balance test also verified the reliability of the integrated balanced terminal.

Обґрунтування параметрів та моделювання руху двомасової мобільної вібраційної системи з двома дебалансними віброзбудниками

Обґрунтування параметрів та моделювання руху двомасової мобільної вібраційної системи з двома дебалансними віброзбудниками

Performance analysis of self-excited induction generator for different excitation and loading condition in wind turbine application

To ensure the complete control of AC machine, state analysis is highly required during the dynamic modelling. In this paper, a mathematical model of the self-excited induction generator (SEIG) is developed to analyse its operation in wind energy systems. A generalised steady state model using d-q stationary reference frame of such a three phase SEIG has been developed. The model has been analysed for balanced and unbalanced excitation condition. Moreover, the effect of wind speed and pitch angle in generator response is observed. Eventually, the model is tested for static and dynamic loads. The analysis of the results could help to determine the efficiency solutions for the system to supply isolated areas even when the loads are unbalanced. The derived equations and developed model are verified through the simulation results of MATLAB simulator.

Performance analysis of self-excited induction generator for different excitation and loading condition in wind turbine application

To ensure the complete control of AC machine, state analysis is highly required during the dynamic modelling. In this paper, a mathematical model of the self-excited induction generator (SEIG) is developed to analyse its operation in wind energy systems. A generalised steady state model using d-q stationary reference frame of such a three phase SEIG has been developed. The model has been analysed for balanced and unbalanced excitation condition. Moreover, the effect of wind speed and pitch angle in generator response is observed. Eventually, the model is tested for static and dynamic loads. The analysis of the results could help to determine the efficiency solutions for the system to supply isolated areas even when the loads are unbalanced. The derived equations and developed model are verified through the simulation results of MATLAB simulator.

Vibration signal modeling of a localized defective rolling bearing under unbalanced force excitations

Vibration signal modeling of a localized defective rolling bearing under unbalanced force excitations is carried out in this paper. A mass-spring-damping system with eight degrees of freedom is derived to consider the transverse vibrations and high frequency resonances of the rotor and bearing pedestals. External excitations come from the unbalanced mass and self-weight of the rotor. Due to the Hertz contact and bearing clearance, the dynamic model is coupled by the nonlinear stiffness. The inner/outer race defects are localized and modeled by additional contact deformations. The Runge-Kutta method is utilized to solve the nonlinear coupled differential equations and vibration signals with and without defects are obtained. Through envelope analysis, the fault characteristic frequencies of inner/outer raceway defects with and without unbalanced force excitations are presented. Detailed comparisons show that the unbalanced force excitations have significant influence on the fault characteristic frequencies. Finally, dynamic tests on a typical rotor-bearing system are conducted to verify the theoretical results.

On the rational dynamic modes of vibrating machines with an unbalanced vibration exciter of limited power

The aspects of choosing the design parameters of a vibrating machine made according to the scheme of a series two-mass vibrating system, as well as of the modes of its oscillations excited by two synchronously rotating unbalanced vibration exciters with a drive of limited power, are considered. The limitations on possible modes of oscillation excitation caused by taking the designed features of the vibration exciter into account are determined. At the specified masses and stiffnesses of a vibrating system, as well as for the specified parameters of oscillations of the actuating element, the rational values of the parameters of vibration exciter and the damping in the components of the vibrating system and dynamic modes, which are characterized by low expenditures of energy and a small dynamic effort transmitted to the foundation of the machine, are determined. The oscillation modes in which changing the mass of the actuating element leads to the smallest changes of the amplitudes of its oscillations are determined.

Effects of thermo hydrodynamic (THD) floating ring bearing model on rotordynamic bifurcation

This paper introduces a numerical scheme for simulating instabilities of a nonlinear rotordynamic system including thermal effects in the fluid film bearings. The method utilizes shooting/arc-length continuation, and simultaneous, finite element based solutions of the variable viscosity Reynolds equation and the energy equation. This provides a means to investigate the effects of the thermo-hydrodynamic THD model on bifurcations and nonlinear rotordynamic stability. A “Jeffcott” type rigid rotor is modeled as supported on double-layered fluid film, floating ring bearings (FRB). The FRB are known to produce highly nonlinear forces as functions of relative and absolute internal displacements and velocities. Both autonomous (free vibration) and non-autonomous (mass unbalanced excitation) cases and algorithms are presented. The computational workload and execution time required for determining coexisting periodic solutions is significantly reduced by employing deflation and parallel computing methods. The THD model nonlinear responses and bifurcation diagrams are compared with isoviscous model results for various lubricant supply temperatures. The autonomous case, THD model orbit sizes and onset of Hopf and saddle–node bifurcations for coexisting steady state responses, may have significant differences relative to the isothermal model results. The onset of Hopf bifurcation is strongly dependent on thermal conditions, and the saddle–node bifurcation points are significantly shifted compared to the isothermal model. This tends to increase the likelihood of bifurcation from a machine operators standpoint. In the non-autonomous case, large unbalance forces create sub-synchronous and quasi-periodic responses at low spin speeds. The responses stability and onset of bifurcations of these responses are highly reliant on the lubricant supply temperature.