Electromechanical Coupling System Research Articles

Stiffness Modeling of Tooth Interior Fatigue and Tooth Flank Fracture and Their Fault Characteristics in Electromechanical Coupling Systems

Tooth flank fracture (TFF) and tooth interior fatigue fracture (TIFF) usually occur on case-harden gears in electromechanical coupling systems, both starting from the core caused by metal fatigue. The cracks propagate rapidly compared with the total life of a gear, so that it is necessary to detect and identify the faults in time when they take place in order to avoid danger. In this paper, the time-varying mesh stiffness model of two types of faults is established by the potential energy method and validating by the finite element method. Based on the stiffness model, the influence of faults on the electromechanical system and their fault characteristics are analyzed, which provides a theoretical basis for the health detection of electromechanical coupling systems. The results indicate that in the early stage of the three faults, i.e., tooth root fracture, tooth interior fatigue fracture, and tooth flank fracture, it is hard to discriminate the faults. But after the second stage, the faults can be distinguished by the vibration amplitude, frequency band components, and phase diagrams. The TFF can be discerned into different stages by frequency domains and phase diagrams. When the fracture occurs completely, three faults can be easily distinguished by the time domain and phase diagram. In the frequency domain, the TRF can also be distinguished from the other two faults by referring to the sideband component near the meshing frequency.

Analysis of electromechanical coupling vibration characteristics of motor-gear system based on bond graph theory

In recent years, there has been a growing demand in the field of engineering systems for research on the vibration response of motor-gear systems under non-steady state conditions. However, conventional modeling and simulation techniques are primarily restricted to systems within a single energy domain. When dealing with intricate electromechanical coupling systems, the modeling process becomes increasingly intricate. Consequently, this study adopts bond graph theory as the foundation for analyzing the vibration characteristics of motor-gear coupling systems. In addressing the vibration issue of the motor-gear transmission system, a nonlinear bond graph model is established that takes into account the time-varying mesh stiffness, static errors, and tooth surface friction, among other nonlinear factors. Then, according to the coupling relationship between motor mechanical systems and electrical systems, the electromechanical coupling dynamic model of the motor-gear system is established using the method of bond graph. In addition, the state equation of the system is derived based on the bond graph model. Finally, the system is simulated using 20-sim software, and the electromechanical coupled vibration characteristics of the simulation results are analyzed. This article lays the foundation for the design and analysis of motor-gear coupling systems and multi-energy domain complex systems.

A novel elastic strip suspension-based bi-directional electromagnetic wind energy harvester designed specifically for wind energy factories

In this study, we propose a novel parallel elastic strips suspended electromagnetic wind energy harvester (ESWEH) based on wind-induced vibration. Profiting galloping phenomena caused by wind flow, the hollow square tube is conceived to generate a significant transverse vibration, and two magnets are equipped on the hollow square tube to generate electrical energy utilizing the electromagnetic induction principle. The symmetrical design of the ESWEH enables it to harvest bi-directional wind energy, while this structure is easy to be assembled into an integrated energy harvesting factory to meet various power supply requirement. A theoretical model is developed to explain the operational mechanism of the proposed electromechanical coupling system. Further, a series of experiments are conducted in a wind tunnel to examine its power generation characteristics (including power-resistance, voltage-resistance) under a closed-circuit condition. The results of the experiments indicate that, when the wind velocity exceeds 2 m/s, the ESWEH equipped with both front and back attached fins produces a continuous and stable current output, with a voltage value exceeding 2.0 V and power exceeding 2.0 mW. Moreover, at an incoming wind velocity of 4 m/s, anaverage power of 7.8 mW is obtained, accompanied by a Root Mean Square (RMS) voltage of 3.2 V when connected to a resistance of 1.2 kΩ. In conclusion, the proposed ESWEH shows good performances in various aspects such as a simplified structure, efficiency-cost, low critical wind velocity and a high-power capacity. The experimental results further indicate that the proposed structure has potential application in construction of a stable power supplying system and wind energy factory for wireless sensors.

Torsional vibration characteristics analysis and adaptive fixed‐time control of wind turbine drivetrain

AbstractThe drivetrain has an important impact on the stability and reliability of wind turbines operating in complex conditions, which belongs to the electromechanical coupling system. This work studies the two domains of research on drivetrain vibration analysis and control method in detail. The electromechanically coupled torsional vibration model is first established by considering the air gap magnetic field energy of the PMSG. Preliminary analysis in terms of Hamiltonian energy indicates that there is sufficient energy to sustain the exciting oscillation behaviors. Moreover, to reduce the vibration amplitude caused by wind speed or torsional stiffness, a novel adaptive fixed‐time control method is proposed to solve the issue of wind turbine drivetrain chaotic oscillation with uncertainties and disturbances. Furthermore, the proposed method not only can prevent the jumping and bifurcation of torsional vibration from happening, but also there are the advantages of the control scheme with high accuracy, fast convergence rate and strong robustness. For the fair comparison, three different control methods have been used to demonstrate the superiority of the control scheme by the simulation results. The research results can provide a theoretical basis for the parameter design and control of wind turbine drivetrain.

Broadband energy harvesting in a two-degree-of-freedom nonlinear system without internal resonance

In this paper, we propose a novel two-degree-of-freedom (TDOF) nonlinear energy harvester without internal resonance to realize broadband harvesting characteristic. To show the performance, a TDOF nonlinear electromagnetic harvester is designed. The electromechanical coupling system is established and solved by adopting the harmonic balance method. The modulation equations are constructed, the first-order harmonic solutions of the system are obtained and the frequency response curves of the displacement and current are plotted. The advantage of the proposed harvester is compared to the conventional single-degree-of-freedom (SDOF) nonlinear model and the corresponding TDOF linear system, the results achieve that the proposed scheme can enhance the bandwidth of the harvesting energy. Furthermore, the influences of system parameters on the response are discussed. The accuracy of the first-order harmonic results is revealed by numerical simulations. To further demonstrate the accuracy of analytical solutions, the finite element simulation is constructed in ANSYS finite element analysis (FEA) software. The performance predictions from the analytical solutions are compared with results from FEA. It is convincingly demonstrated that periodic solutions have a degree of good consistency for the behavior of frequency response curves.

A New Performance Optimization Method for Linear Motor Feeding System

The linear motor feeding system is a typical electromechanical coupling system. Conventional characteristic analyses of electromechanical coupling often overlook the influence of flexible deformation in critical components of the linear motor feeding system. Moreover, when employing genetic algorithms to optimize servo system PID control parameters, slow convergence, nonconvergence, or premature convergence problems may arise. To address these issues, this paper proposes a new performance optimization method for a linear motor feeding system. The method uses a combination of “multi-body theory + finite element” to accurately account for the flexible deformation of critical components of the feeding system, establishes a rigid–flexible electromechanical coupling model of the linear motor feeding system, and optimizes the PID parameters of the established model with an improved adaptive genetic algorithm. Simulation results demonstrate that, when utilizing an adaptive genetic algorithm to optimize the rigid–flexible electromechanical coupling model and a control system model that disregards flexible body deformation, the system achieves stability in 0.02 s and 0.027 s with overshoots of 13% and 27%, respectively. These outcomes confirm the accuracy and importance of considering flexible body deformation in the optimization performance of a linear motor feeding system. At the same time, the time required to reach the steady state of the rigid–flexible electromechanical coupling model optimized by the adaptive genetic algorithm is shortened from 0.035 s to 0.02 s. The sinusoidal signal response curve of the optimized system does not exhibit any peak overshoot compared with that of the nonoptimized system, and the response speed is also faster. These results demonstrate the effectiveness of the rigid–flexible electromechanical coupling model optimized by the nonlinear adaptive genetic algorithm. The displacement response curves of the linear motor feeding system under different workbench loads are obtained through experiments and compared with those obtained from simulations to verify the established model and the correctness of the proposed method.

Parametric excitation analysis for system performance of piezoelectric energy harvesters

Capitalizing on the advantages of parametric excitation and real-life low frequency vibration, the steady-state response of piezoelectric energy harvesting system composing of a cantilever beam with a tip mass and horizontal excitation at the fixed end is investigated. By applying Hamilton's principle, the nonlinear partial differential equation of a cantilever bimorph piezoelectric energy harvesting system with an additional tip mass is derived and analyzed. The cantilever is modeled as an axially non-elongated Euler Bernoulli beam with geometric and damping nonlinearities. By using the Galerkin method, the nonlinear partial differential equation is reduced to an electromechanical coupling system that governs a cantilever piezoelectric energy harvesting system with a tip mass under parametric excitation. The first-order resonance response of this harvesting system is studied by using the method of multiple scales. The analytical response expressions and first-order amplitude functions for vertical displacement, output voltage and output power are derived and analyzed. The influence of different impedance and tip mass on the piezoelectric energy harvesting system performance is summarized and concluded. For the parametric excitation system, the load resistance shows significant influence on the initial threshold of the piezoelectric energy harvesters under parametric excitation. For a short circuit, the initial threshold increases with increasing load resistance. For an open circuit, the initial threshold decreases with increasing load resistance. For an open circuit resistance or a short circuit resistance under parametric excitation, an increase in the end block mass effectively reduces the resonance frequency of the piezoelectric energy harvesters. Consequently, the energy harvesting bandwidth is increased, and the harvesting effect of the piezoelectric energy harvesters is enhanced. In this paper, a more accurate and practical theoretical model is established to predict the electromechanical coupling behavior of cantilever piezoelectric energy harvester under parametric excitation. Using this approach, it is possible to complement parametric and direct excitation such that the advantages of parametric excitation can be achieved. It is also significant to improve the energy conversion efficiency of energy harvesting system.

Dynamic Characteristics of Electromechanical Coupling and Fuzzy Control of Intelligent Joints for Robot Drive and Control

Abstract In this technical brief, the resonance problem of a robot joint is analyzed. By establishing the electromechanical coupling dynamic equation of the robot joint, the natural vibration characteristics of the electromechanical coupling system are calculated, and the resonance is analyzed by combining the modal energy and Campbell diagram. It is found that when the meshing frequency coincides with the seventh- and eighth-order natural frequencies, resonance is easy to occur. The influence of different parameters on natural characteristics is analyzed. The increase of torsional stiffness and meshing stiffness will increase the natural frequency. Different control algorithms will have different impacts on the transmission system, and fuzzy control is better than double closed-loop control.

Impact of electromechanical coupling of main drive system of cold rolling mill on amplitude-frequency characteristics

Main drive mechanical system of a cold rolling mill was simplified to a three-inertia model, and natural frequency of mechanical system was obtained by using Matlab simulation. Combining the main motor speed control system and the mechanical system into an electromechanical coupling system, it was found that natural frequencies of mechanical components in coupled system are different from those of the independent mechanical system. The proportional control coefficient (P value) of the speed loop would affect amplitude of system at resonance point, whereas frequency of resonance point was rarely changed and the integral control coefficient (I value) almost had no effect on the amplitude-frequency characteristics. The notch filter whose limit frequency is the resonance frequency has the best vibration suppression effect. The load observer completely suppressed torsional vibration of motor but amplified torsional vibration of gears and rolls.

Brake Pressure Estimation of the Integrated Braking System Considering Vehicle Dynamics

The integrated braking control system (IBC) has become one of the most popular brake-by-wire (BBW) solutions due to its compactness and versatility. Accurate monitoring of wheel cylinder pressure in real time is the basis for brake pressure control, and pressure estimation is a low-cost and reliable method. However, the IBC is an electromechanical hydraulic coupling system that has significant nonlinear behaviors; moreover, vehicle dynamics also have a critical impact on the accuracy of pressure estimation. To solve this problem, this paper proposes a novel adaptive extended Kalman filter (EKF) approach that combines a hydraulic model and a single-wheel model. This novel strategy has better estimation than the hydraulic model when the pressure is accurately estimated by the single-wheel model, while when the single-wheel model is not accurate, the EKF degrades to the hydraulic model. Finally, vehicle experimental data under high- and low-mu braking are collected. The pressure estimation error of the EKF is within 0.4 MPa in the low-mu road and 2 MPa in the high-mu road. It is proven that the proposed pressure estimation strategy is highly effective.

Performance improvement of the stochastic-resonance-based tri-stable energy harvester under random rotational vibration

In this paper, the stochastic-resonance-based tri-stable energy harvester (TEH) is proposed to enhance harvesting performance under random rotational vibration. An electromechanical coupled system interfaced with a standard rectifier circuit driven by colored noise is considered. The stationary probability density function (SPDF) of the harvester is obtained by the improved stochastic averaging. Then, with the adiabatic approximation theory, the analytical expression of signal-to-noise ratio (SNR) for the TEH is deduced to characterize stochastic resonance (SR). To enhance direct current (DC) power delivery from a rotational TEH, the influences of system parameters on SR is discussed. The obtained results suggest that there are damping-induced resonance and noise-intensity-induced SR in the tri-stable system. The TEH has higher harvesting performance under the optimal SR. That is, the optimal parameter combinations can induce optimal SR and maximize harvesting performance. Thus, the stochastic-resonance-based TEH can be optimized to enhance energy harvesting through choosing the optimal parameter.

Vibration Characteristics of the Dual Electric Propulsion System of Vessels under Electromechanical Coupling Excitation

An electromechanical coupling driving system is a commonly used system for large overloading ships. In this paper, a dual input electromechanical coupling model, including an inverter power supply, three-phase induction motor, fixed-axis gear, and load, is established. The influences of the gear error, inverter, and coupling stiffness on the vibration characteristics of the system are studied, and the influences of each parameter on the vibration characteristics are analyzed. The inverter power supply part considers the constant voltage–frequency ratio control and sinusoidal pulse width modulation, as well as the inverter. The motor part uses the dynamic motor model based on the equivalent circuit. The fixed-axis gear section uses a translation–torsion model with time-varying mesh stiffness and damping. The mechanical part and the motor part are coupled with the load torque of the motor. The results show that the greater the error of the gear, the greater the vibration of the system, and the rotation frequency error is the main factor. Secondly, by comparing the influence of error value and accuracy difference on vibration, we found that when an accuracy difference exists, the dominant factor of system vibration is the accuracy difference. Thirdly, the use of an inverter also increases the vibration of the electromechanical coupling system. Finally, we found that the lower stiffness of the elastic coupling reduced the vibration of the system.

Torque Ripple Suppression Strategy of Electromechanical Coupling System of Hybrid Electric Towing Vehicle Based on Feedforward Control

Aiming at the problem of output torque ripple of power split engine motor power system coupled with planetary gear train, based on the dynamic model of the system, the torque ripple suppression algorithm considering coupling device and engine instantaneous torque observer based on engine instantaneous torque are designed. In order to solve the problem that a single control method fails to meet the steady-state performance and response time at the same time, a torque ripple suppression strategy of electromechanical coupling system based on feedforward control is proposed. Combined with the modeling of GT-power and MATLAB / Simulink platform, the rated operating points are simulated in coordinated driving mode and input split mode respectively. The results show that the control strategy can reduce the output torque ripple of the ring gear by 25.46% and 19.34% respectively in coordinated driving mode and input split mode. The control strategy can reduce the output torque ripple by 14.30% and speed ripple by 37.32% in the dynamic condition of PTO intervention.

Dynamic characteristic analysis of a multi-power coupling transmission system considering non-torque loads

The multi-power coupling transmission system (MPCTS) is an electromechanical coupling system, which typically use two or more induction motors to provide its driving torque. It is used in various industrial applications, such as cutter header driving systems of tunnel boring machinery, and yaw systems of wind turbines. In practical engineering applications, the loads borne by the MPCTS are very complex, including both torque loads and non-torque loads. Its dynamic characteristics are affected by both the gear transmission system and the drive motors. For this study, an electromechanical coupling dynamic model of the MPCTS, coupled with a gear transmission system, induction motor, and non-torque load, was constructed to analyze its dynamic characteristics under a non-torque load condition. The results showed increased offsets from the gear vibration equilibrium position, as well as deterioration in system load-sharing characteristics from increases in non-torque load and rotational speed. However, the influence of the non-torque load was significantly greater than that of the rotational speed.

Hydrodynamic piezoelectric energy harvesting with topological strong vortex by forced separation

Inspired by the fish tail, we propose a piezoelectric energy harvester based on flow induced vibration with topological strong vortex by forced separation for low-velocity water flow. Observed using computational fluid dynamics, the high surface curvature at the up and down edges of the elliptic cylinder forces the boundary layer to separate and forms strong vortex squeezed on the bluff body. The extended Hamilton’s principle is used to derive the governing equation of the electromechanical coupling system and the Galerkin procedure is introduced to calculate the analytical output of the energy harvester. An experimental study with macro fiber composite in a circulating open U-shaped channel is conducted. The output voltage for the elliptic cylinder with an aspect ratio of 2.5 under the water velocity of 0.45 m/s is 38.4 V, 21.5 times higher than that for the circular cylinder. The hydrodynamic negative and positive damping determined by the shape of the bluff body balance the energy pumped in and dissipated in a period and fix its phase portraits at a stable limit cycle, resulting in the self-excited vibration of the bluff body. Optimal resistance analysis shows that changing parameters of the bluff body such as reducing its mass or increasing its length also improves the energy harvesting efficiency. The results are helpful for the optimal design of energy harvesters at low water velocity.

Active Vibration Control on a Smart Composite Structure Using Modal-Shaped Sliding Mode Control

Abstract This article proposes an active modal vibration control method based on a modal sliding mode controller applied to a smart material composite structure with integrated piezoelectric transducers as actuators and sensors. First, the electromechanical coupled system is identified using a modal reduced-order model. The sliding surface is based on the modal-filtered states and designed using a general formulation allowing the control of multiple vibration modes with multiple piezoelectric sensors and actuators. The performance and stability of the nonlinear controller are addressed and confirmed with the experimental results on a composite smart spoiler-shaped structure. The nonlinear switching control signal based on the modal-shaped sliding surface improves performances of the linear part of the control while maintaining not only stability but also robustness. The attenuation level achieved on the target modes on all piezoelectric sensors starts from −14 dB up to −22 dB, illustrating the strong potential of nonlinear switching control methods in active vibration control.

1Pb3-3 Differential Forms for the Application to Electromechanical Coupling Systems

1Pb3-3 Differential Forms for the Application to Electromechanical Coupling Systems

Control synchronization of three eccentric rotors driven by motors in space considering adaptive fuzzy sliding mode control algorithm

In this paper, to obtain ideal dynamic behavior of vibration screen, control synchronization of three eccentric rotors (ERs) driven by motors in space vibration system is investigated by employing the adaptive fuzzy sliding mode control (AFSMC) algorithm. First, the dynamic model of the vibration system is established, and the motion equation of the electromechanical coupling system is derived via Lagrange equation. Then, the synchronization controllers of three ERs are systematically designed with the combination of AFSMC algorithm and master–slave control (MSC) structure, and the stability of the control system is verified by Lyapunov theory. Additionally, in comparison with the conventional sliding mode control (SMC) algorithm, the superiority and feasibility of the proposed AFSMC strategy are confirmed through numerical simulation in MATLAB/Simulink. Moreover, the robustness of the control system is demonstrated in the simulation via changing the motor velocities and structure parameters. The research result shows that the proposed adaptive strategy can effectively control the ERs to implement the desired in-phase synchronization motion, and the control method possesses commendable efficacy in reducing chattering, enhancing control accuracy, eliminating overshoot, and resisting parameter perturbation.

Bifurcation Analysis of a Fractional-Order Delayed Rolling Mill’s Main Drive Electromechanical Coupling System

This work is focused on a rolling mill’s main drive electromechanical coupling system. Firstly, we equip electromechanical coupling system with fractional-order time delay. Secondly, we, respectively, derive the conditions for occurrence of Hopf bifurcation around equilibriums E 0 0 , 0 , 0 , 0 and E 1 x 1 ∗ , 0 , x 3 ∗ , 0 . It is found that the fractional order α and time delay τ in the system play an important role on the system stability. Finally, numerical simulations are given to verify the analytic results.

Low frequency vibration suppression of a moderate thick cabin structure by multiple piezoelectric patches shunted with RL-double negative capacitance circuits

Multiple piezoelectric patches shunted with RL-double negative capacitances circuits, which are bonded on the bulkhead, are proposed to control the resonant response of multiple low frequency modes of a moderate thick cabin structure. Dynamic modeling of the electromechanical coupling system of the cabin structure and the piezoelectric shunt circuit is established by employing the three-dimensional finite element. Optimum tuning strategy is based on the trial and error method. It is shown that the proposed approach is effective in enhancing the generalized electromechanical coupling coefficient and controlling the low frequency modes that exhibits coupled deformation of the bulkhead and cabin structure.