scholarly journals Dynamic Performance of Planetary Gear Joint for Satellite Antenna Driving Mechanism Considering Multi-Clearance Coupling

Energies ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 815
Author(s):  
Jianchao Han ◽  
Lei Liang ◽  
Yang Zhao
Keyword(s):  
Coupling Effect ◽  
Dynamic Performance ◽  
Planetary Gear ◽  
Analytical Models ◽  
Radial Clearance ◽  
Driving Mechanism ◽  
Tracking Accuracy ◽  
Satellite Antenna ◽  
Dynamic Errors ◽  
Stiffness And Damping

Dynamic pointing and tracking accuracy are the most relevant indicators of dynamic performance for the satellite antenna driving mechanism. Multi-clearance coupling in the joints will incur high-frequency vibration and dynamic errors of the system. Joints of existing analytical models are generally oversimplified as planar revolute hinges, which ignore the coupling effect of multi-clearance. It cannot proficiently predict the dynamic behavior of the driving mechanism with multi-clearance on the orbit. To address this problem, a typical 2K-H planetary gear joint model with multi-clearance coupling has been developed by considering radial clearance, backlash, tooth profile error, time-varying meshing stiffness, and damping. A dynamic model of a typical dual-axis driving mechanism is established to analyze the dynamic characteristics of multibody systems with planetary gear joints. The effects of rotational speed, radial clearance, backlash, and their coupling on the dynamic performance of the dual-axis driving mechanism under different driving modes are explored by numerical simulations. The results show that the coupling of radial clearance and backlash in joints have a significant influence on the dynamic performance of the system. Appropriate clearance design avails the dynamic pointing accuracy and tracking accuracy of the dual-axis driving mechanism.

scholarly journals Vibration Characteristics Analysis of Planetary Gears with a Multi-Clearance Coupling in Space Mechanism

Energies ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2687 ◽  
Author(s):  
Huibo Zhang ◽  
Chaoqun Qi ◽  
Jizhuang Fan ◽  
Shijie Dai ◽  
Bindi You
Keyword(s):  
Rotational Velocity ◽  
Dynamic Performance ◽  
Planetary Gear ◽  
Vibration Characteristics ◽  
Radial Clearance ◽  
Nonlinear Dynamic Model ◽  
Planetary Gears ◽  
Light Load ◽  
Characteristics Analysis ◽  
Gear Systems

Multi-clearance is the main cause for the performance and reliability decline of complicated mechanical systems. The increased clearance could induce contacts and impacts in joints, and consequently affect control accuracy. A nonlinear dynamic model of planetary gears with multi-clearance coupling is proposed in the current study to investigate the mechanism of influence of clearance on the dynamic performance. In addition, the coupling relationship between radial clearance and backlash is integrated into the multi-body system dynamics. The vibration characteristics of planetary gears with the changes of rotational velocity, clearance size and inertia load are explored. The numerical simulation results show that there are complex coupling relations in planetary gear systems, due to the multi-clearance coupling. The phenomenon of system resonance may occur with the changes of rotational velocities and clearances’ sizes. Multi-clearance coupling can significantly increase the resonant response of planetary gear systems in empty-load or light-load states.

scholarly journals Dynamic Simulation of Crank-group Driving Mechanism with Clearance

2016 ◽  
Vol 12 (02) ◽  
pp. 35
Author(s):  
Yansong Liu ◽  
Jujiang Cao
Keyword(s):  
Angular Velocity ◽  
Dynamic Simulation ◽  
Dynamic Characteristics ◽  
Dynamic Performance ◽  
Driving Mechanism ◽  
Practical Applications ◽  
Dynamic Simulation Model ◽  
Processing Errors ◽  
Stiffness And Damping ◽  
D Model

The crank-group driving mechanism includes a group of redundant constraints. This mechanism can move as a driving mechanism under ideal conditions, but it may be stuck because of the processing errors in practical applications. So, some clearances are reserved between the pin hole and the pin to ensure that the crank-group driving mechanism can achieve normal movement, but these clearances inevitably affect the dynamic performance of the output member. In this paper, the dynamic simulation model of the crank-group driving mechanism is established by NX/Motion Simulation which is based on the 3-D model of planar link mechanism. The comparative analysis is made about the dynamic characteristics of the mechanism which is influenced by different clearances, different angular velocity, different damping, and make a qualitative analysis how the clearances affects the dynamic performance of the output member. The simulation results also show that appropriately increasing the angular velocity, increasing stiffness and damping of the components can effectively inhibit the adverse influences of clearance on the dynamic characteristics of the mechanism.

scholarly journals Dynamic positioning accuracy of dual-axis drive mechanism of satellite antenna with multi-clearance coupling

2018 ◽  
Vol 198 ◽  
pp. 06002
Author(s):  
Chaoqun Qi ◽  
Huibo Zhang ◽  
Bindi You ◽  
Jizhuang Fan ◽  
Shijie Dai
Keyword(s):  
Dynamic Model ◽  
Rotational Speed ◽  
Radial Clearance ◽  
Driving Mechanism ◽  
Dynamic Positioning ◽  
Nonlinear Dynamic Model ◽  
Positioning Accuracy ◽  
Satellite Antenna ◽  
Drive Mechanism ◽  
Axis Drive

The dual-axis drive mechanism of satellite antenna as a typical multi-joint aerospace mechanism consists of azimuth axis and pitch axis. The multi-clearance contained within those drive joint cause contact and impact in joint, and consequently affect the dynamic positioning accuracy. A nonlinear dynamic model of planetary gears with multiple clearances couplings is proposed to investigate the influence mechanism of clearances on the dynamic performances. The nonlinear factors such as radial clearance, backlash and time-varying meshing stiffness of the bearing are considered in the model. And the dynamic model of double-axis driving mechanism of satellite antenna with multi-clearance coupling is established. Then positional and rotational speed error curves of antenna reflector at different rotational speed are respectively analyzed. The numerical simulation results show that the influence of multi-clearance coupling on the dynamic positioning accuracy of double-axis drive mechanism of satellite antenna is remarkable.

Theoretical and Experimental Study on Dynamic Coefficients and Stability for a Hydrostatic/Hydrodynamic Conical Bearing

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
Guo Hong ◽  
Lai Xinmin ◽  
Cen Shaoqi
Keyword(s):  
Dynamic Performance ◽  
Flow Equation ◽  
Operating Conditions ◽  
Fluid Film ◽  
Radial Clearance ◽  
Stability Parameters ◽  
Damping Coefficients ◽  
Conical Bearing ◽  
The Stability ◽  
Stiffness And Damping

This paper presents a theoretical study and experimental method to recognize the dynamic performance (stiffness and damping coefficients) of an externally pressurized deep/shallow pockets hybrid conical bearing compensated by flat capillary restrictors. The equations governing the flow of fluid film in the conical bearing together with the pressure boundary condition and the restrictor flow equation are solved by using the finite element method. A delicate test rig is constructed and bearings having a big end diameter of 97 mm, a length of 90 mm, and a radial clearance of 0.02–0.025 mm are analyzed. It is assumed that the fluid film force of the hydrostatic/hydrodynamic conical bearing is characterized by a set of linear stiffness and damping coefficients. The experiment used the impulse excitation method to recognize these coefficients and established their characteristics under different operating conditions. Numerical results are compared with the experimental results. The stability parameters of hybrid conical, hydrodynamic, and hydrostatic bearings are compared. The results show that the hybrid conical bearing has the advantages of high load carrying capability and high stability under small eccentricity.

Experimental Response of a Rotor Supported on Rayleigh Step Gas Bearings

2005 ◽  
Author(s):  
Xuehua Zhu ◽  
Luis San Andre´s
Keyword(s):  
High Speed ◽  
Damping Ratio ◽  
Dynamic Performance ◽  
Radial Clearance ◽  
Large Magnitude ◽  
Gas Bearings ◽  
Rotor Surface ◽  
Stiffness And Damping ◽  
Rapid Deployment ◽  
Damping Capability

Reliable gas bearings will enable the rapid deployment of high speed oil-free micro-turbomachinery. This paper presents analysis and experiments of the dynamic performance of a small rotor supported on Rayleigh step gas bearings. Comprehensive tests demonstrate that Rayleigh step hybrid gas bearings exhibit adequate stiffness and damping capability in a narrow range of shaft speeds, up to ∼ 20 krpm. Rotor coast down responses were performed with two test bearing sets with nominal radial clearance of 25 μm and 38 μm. A near-frictionless carbon (NFC) coating was applied on the rotor to reduce friction at liftoff and touchdown. However, the rotor could not lift easily and severe rubbing occurred at shaft speeds below ∼ 4,000 rpm. The tests show that the supply pressure raises the rotor critical speed and decreases the system damping ratio, while only affecting slightly the rotor-bearing system onset speed of instability. Whirl frequencies are nearly fixed at the system natural frequency (∼ 120 Hz) with subsynchronous amplitude motions of very large magnitude that prevented rotor operation above ∼ 20 krpm. The geometry of the Rayleigh steps distributed on the rotor surface generates a time varying pressure field, resulting in a sizable 4X super synchronous component of bearing transmitted load. Predictions show the synchronous stiffness and damping coefficients decrease with shaft speed. Predicted threshold speeds of instability are much lower than measured values due to the analytical model limitations assuming a grooved stator. The predicted synchronous responses to imbalance correlate well with the measurements. The Rayleigh step gas bearings are the most unreliable rigid bearing configuration tested to date.

Measurement of frequency characteristics of disturbance torque in the process of satellite antenna rotation

2020 ◽  
Vol 64 (1-4) ◽  
pp. 1563-1569
Author(s):  
Bo Gao ◽  
Minglong Xu
Keyword(s):  
Real Time ◽  
Signal Transmission ◽  
Frequency Characteristics ◽  
Structural Vibration ◽  
Driving Mechanism ◽  
Satellite Antenna ◽  
Satellite Applications ◽  
Study Characteristics ◽  
Satellite Signal ◽  
Disturbance Torque

As an important equipment for satellite signal reception and transmission, the satellite antenna needs to be rotated in real time to achieve real-time tracking of the target and complete signal transmission during applications. Antenna driving mechanism is generally composed of motor and other components, which will cause some structural vibration during rotation. For high-stability satellite applications, the vibration disturbance torque is a major factor affecting the satellite stability. In order to study characteristics of the disturbance torque, the disturbance data from the antenna under different rotation conditions should be measured. In this paper, the frequency characteristics of disturbance torque of a rotating satellite antenna using stepper motor as driving motor is tested and discussed.

The Surface Roughness Effect on the Dynamic Stiffness and Damping Characteristics of the Hydrostatic Thrust Spherical Bearings: Part 5 of 5 — Clearance Type of Bearings

2007 ◽  
Author(s):  
Ahmad W. Yacout
Keyword(s):  
Surface Roughness ◽  
Capillary Tube ◽  
Dynamic Stiffness ◽  
Dynamic Performance ◽  
Major Effect ◽  
Design Parameters ◽  
Compressibility Effect ◽  
Damping Coefficients ◽  
Stiffness And Damping ◽  
Fluid Compressibility

This study has theoretically analyzed the surface roughness, centripetal inertia and recess volume fluid compressibility effects on the dynamic behavior of a restrictor compensated hydrostatic thrust spherical clearance type of bearing. The stochastic Reynolds equation, with centripetal inertia effect, and the recess flow continuity equation with recess volume fluid compressibility effect have been derived to take into account the presence of roughness on the bearing surfaces. On the basis of a small perturbations method, the dynamic stiffness and damping coefficients have been evaluated. In addition to the usual bearing design parameters the results for the dynamic stiffness and damping coefficients have been calculated for various frequencies of vibrations or squeeze parameter (frequency parameter) and recess volume fluid compressibility parameter. The study shows that both of the surface roughness and the centripetal inertia have slight effects on the stiffness coefficient and remarkable effects on the damping coefficient while the recess volume fluid compressibility parameter has the major effect on the bearing dynamic characteristics. The cross dynamic stiffness showed the bearing self-aligning property and the ability to oppose whirl movements. The orifice restrictor showed better dynamic performance than that of the capillary tube.

Dynamic Characterization of an Integral Squeeze Film Bearing Support Damper for a Supercritical CO2 Expander

2017 ◽  
Author(s):  
Bugra Ertas ◽  
Adolfo Delgado ◽  
Jeffrey Moore
Keyword(s):  
High Speed ◽  
Dynamic Performance ◽  
Mechanical Impedance ◽  
Squeeze Film ◽  
Fluid Inertia ◽  
Inertia Effects ◽  
Damping Behavior ◽  
Impedance Testing ◽  
Stiffness And Damping ◽  
Onset Of Cavitation

The present work advances experimental results and analytical predictions on the dynamic performance of an integral squeeze film damper (ISFD) for application in a high-speed super-critical CO2 (sCO2) expander. The test campaign focused on conducting controlled orbital motion mechanical impedance testing aimed at extracting stiffness and damping coefficients for varying end seal clearances, excitation frequencies, and vibration amplitudes. In addition to the measurement of stiffness and damping; the testing revealed the onset of cavitation for the ISFD. Results show damping behavior that is constant with vibratory velocity for each end seal clearance case until the onset of cavitation/air ingestion, while the direct stiffness measurement was shown to be linear. Measurable added inertia coefficients were also identified. The predictive model uses an isothermal finite element method to solve for dynamic pressures for an incompressible fluid using a modified Reynolds equation accounting for fluid inertia effects. The predictions revealed good correlation for experimentally measured direct damping, but resulted in grossly overpredicted inertia coefficients when compared to experiments.

Numerical analysis of the dynamic performance of aerostatic thrust bearings with different restrictors

2018 ◽  
Vol 233 (3) ◽  
pp. 406-423 ◽  
Author(s):  
Hailong Cui ◽  
Yang Wang ◽  
Xiaobin Yue ◽  
Yifei Li ◽  
Zhengyi Jiang
Keyword(s):  
Load Capacity ◽  
Dynamic Stiffness ◽  
Dynamic Performance ◽  
Dynamic Mesh ◽  
Eccentricity Ratio ◽  
Thrust Bearings ◽  
Stiffness And Damping Coefficient ◽  
Stiffness And Damping ◽  
The Impact ◽  
The Relationship

This study utilizes a dynamic mesh technology to investigate the dynamic performance of aerostatic thrust bearings with orifice restrictor, multiple restrictors, and porous restrictor. An experiment, which investigates the bearing static load capacity, was carried out to verify the calculation accuracy of dynamic mesh technology. Further, the impact of incentive amplitude, incentive frequency, axial eccentricity ratio, and non-flatness on the bearing dynamic performance was also studied. The results show incentive amplitude effect can be ignored at the condition of amplitude less than 5% film thickness, while the relationship between dynamic characteristics and incentive frequency presented a strong nonlinear relationship in the whole frequency range. The change law of dynamic stiffness and damping coefficient for porous restrictor was quite different from orifice restrictor and multiple restrictors. The bearing dynamic performance increased significantly with the growth of axial eccentricity ratio, and the surface non-flatness enhanced dynamic performance of aerostatic thrust bearings.

Trajectory Synthesis and Redundancy Resolution for High Speed Point to Point Motions of Redundant Robot Manipulators

1997 ◽  
Author(s):  
W. Kim ◽  
J. Rastegar
Keyword(s):  
High Speed ◽  
Degrees Of Freedom ◽  
Robot Manipulator ◽  
Robot Manipulators ◽  
Dynamic Performance ◽  
High Harmonic ◽  
Harmonic Excitation ◽  
Redundancy Resolution ◽  
Tracking Accuracy ◽  
Point To Point

Abstract Trajectory synthesis for robot manipulators with redundant kinematic degrees-of-freedom has been studied by numerous investigators. Redundant manipulators are of interest since the redundant degrees-of-freedom can be used to improve the local and global kinematic and dynamic performance of a system. As a robot manipulator is forced to track a given trajectory, the required actuating torques (forces) may excite the natural modes of vibration of the system. Noting that manipulators with revolute joints have nonlinear dynamics, high harmonic excitation torques are generally generated even though such harmonics have been eliminated from the synthesized trajectories and filtered from the drive inputs. In this paper, a redundancy resolution method is developed based on the Trajectory Pattern Method (TPM) to synthesize trajectories such that the actuating torques required to realize them do not contain higher harmonic components with significant amplitudes. With such trajectories, a robot manipulator can operate at higher speeds and achieve higher tracking accuracy with suppressed residual vibration. As an example, optimal trajectories are synthesized for point to point motions of a plane 3R manipulator.

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