Meng F.M.,Chongqing University |
Meng F.M.,Shanghai Key Laboratory of Spacecraft Mechanism |
Zhang L.,Chongqing University |
Long T.,Chongqing University
Journal of Tribology | Year: 2017
Effects of groove textures on the performances for gaseous bubbles in the lubricant used for a textured journal bearing is studied under the consideration of thermal effect of lubricant. The Reynolds, energy, and Rayleigh-Plesset (RP) equations are solved simultaneously for simulating the behavior of the bubble. Numerical results show that the gaseous bubble radius shows a nonlinearly oscillation in a full cycle period, and high bubble pressure and temperature appear when the bubble collapses. Moreover, appropriately choosing groove length, width, or interval can reduce the maximum radius, collapse pressure, and collapse temperature of the bubble. There exists a critical groove depth minimizing the bubble pressure and temperature. © 2016 by The American Bryological and Lichenological Society, Inc.
Han L.,Shanghai Key Laboratory of Spacecraft Mechanism |
Peng F.,Shanghai Key Laboratory of Spacecraft Mechanism |
Chen M.,Shanghai Key Laboratory of Spacecraft Mechanism |
Yun W.,Shanghai Key Laboratory of Spacecraft Mechanism
Proceedings of the International Astronautical Congress, IAC | Year: 2016
After decades of human space activities, the increasing orbital debris becomes the No. 1 potential threat for the spacecraft. Active Debris Removal is an effective form of remediation. This paper puts forward a flexible and adaptive capture device based on octopus-inspired pneumatic soft robot for orbital debris removal, which is mainly made up of octopus-inspired tentacles and deployable arm. The device has functions with distant reaching, end position and pose adjusting, debris capturing and target recognition and measurement. The device can capture orbital debris reliably and nimbly with single tentacle bending or multi tentacles twining. Its tentacles are realized based on the mechanism of pneumatic soft robot, which can be compatible and adaptive with the irregularly shaped debris and absorb energy from the contact and impact. The deployable arm is driven by pneumatic actuation, so it is with light weight and high shrink ratio. Gecko-inspired biomimetic nano-sacle adhesive arrays are also used on the surface of the tentacle to ensure reliable grasping. According to the analysis of the task and bionics revelation, in this paper, the overall design of the capture device is presented, the solutions of some main subsystem are proposed, and some task simulations are carried out to validate the feasibility. Copyright © 2016 by the International Astronautical Federation (IAF). All rights reserved.
Li B.,Shanghai Key Laboratory of Spacecraft Mechanism |
Yang Y.,Shanghai University
Hangkong Xuebao/Acta Aeronautica et Astronautica Sinica | Year: 2015
In view of the multiple indexes and their interactive influences evaluating the structure performances of deployable and foldable panel antennas, the structure efficiency is introduced to the deployable structure optimization, and optimization on structure design is studied by the orthogonal experiment for a space deployable truss. The geometric design parameters are analyzed, and an optimal mathematic model is also built with goals of minimum mass and maximal structural stiffness. Aimed at the structure efficiency maximization, the structure optimization for the space deployable truss is calculated, and the design parameters of truss structure are obtained. It is found that the factors that influence structure efficiency such as mass and stiffness are considered synthetically, and the mass of optimized structure is reduced and the deployment stiffness is improved simultaneously. The most important influencing factor on the structure performance is l/w, and the minor influencing factor varies with different optimization goals. When p=90% the study indicates that area has an insignificant effect on the structure efficiency of a space deployable truss. The structure efficiency of the space deployable truss with variable cross-section is better than that of the one with unique cross-section. However, the space deployable truss with unique cross-section shows more economy under unique linkage dimensions.The proposed method can be helpful for the designer in evaluating the structure performances at the conceptual stage of design from the point of system design. © 2015, Press of Chinese Journal of Aeronautics. All right reserved.
Yun W.,Shanghai Key Laboratory of Spacecraft Mechanism |
Peng F.,Shanghai Key Laboratory of Spacecraft Mechanism
Proceedings of the International Astronautical Congress, IAC | Year: 2013
The new lightweight inflatable Entry/Re-entry decelerators (IED) technology has been demonstrated in several flight tests in Russia and America. This technology is designed to reduce the mass and cost of future entry/re-entry systems for Earth and planetary, which has been in the focus of on-going engineering activities in support to future interplanetary missions. This paper outlines the development and further application opportunities with the definition of an operational Satellite Download System and the Entry, Descent and Landing (EDL) on Mars, a scheme was then presented for a 360kg class Mars lander, which was executed in the form of a bladder of a conical shape. The preliminary system design, geometry and working principle of the entry and descent system was introduced. A simulation study was carried out to investigate dynamic properties of the lander structure. Key technologies associated with the entry and descent system were presented and the approaches to solve these key problems were given.
Zhang Z.,Xi'an Jiaotong University |
Miao J.,Shanghai Key Laboratory of Spacecraft Mechanism |
Wang X.,Shanghai Key Laboratory of Spacecraft Mechanism |
Wu W.,Xi'an Jiaotong University |
And 2 more authors.
Gaodianya Jishu/High Voltage Engineering | Year: 2014
In order to enhance the reliability of polyimide (PI) in complex engineering environments, we obtained the characteristics of surface flashover on polyimide under DC voltage in vacuum during electron beam irradiation through experiments. Besides, trap parameters of the tested samples before and after radiation were also measured using the thermally stimulated current (TSC) method. The results show that, the surface flashover voltage of sample under the radiation with electron energy of 0.5~20 keV is higher than that under no radiation. Higher electron energy leads to smaller positive charge density on dielectric surface and smaller relative dielectric constant, as well as larger trap, and consequently improves the uniformity of surface electric field and increases the flashover voltage. If the radiation electron energy remains the same, the flashover voltage would become lower with increasing beam density, number of initial electrons and leakage current.
Lu S.,Chongqing University |
Zhang Y.,Chongqing University |
Shi J.,Shanghai Key Laboratory of Spacecraft Mechanism
Chinese Control Conference, CCC | Year: 2016
This paper presents a novel Fault Tolerant Control (FTC) method for Electric Vehicle (EV) with wheel hub motors and by-wire steering system, in order to improve the vehicle safety and directional stability in case of steering failure. The driving force of this Four Wheel Independent Drive (FWID) EV was generated from four in-wheel motors using by-wire technology. The main objective is to track the desired motion to turn around even the steering breaks down. A dynamic vehicle model with the function of four-wheel driving and front-wheel steering is established. The transient dynamic behaviors of steering failure cases are conducted by comparing with the normal cases. Based on functional redundancy of over-actuated chassis, the potential of fault tolerant control by independent braking was analyzed. Subsequently, a sliding mode based motion controller is designed for generalizing the desired yaw moments. According to the concept of tire usages, an optimal control allocation strategy based on Non-linear quadratic programming is implemented to deal with the steering failure by driving/braking torque allocation. Numerical simulations have been conducted to verify the proposed FTC algorithm. The result suggests that steering failure could be effectively covered by driving/braking torque allocation for the functional redundancy of over-actuated chassis system. © 2016 TCCT.
Li B.,Shanghai Key Laboratory of Spacecraft Mechanism |
Li R.-X.,Shanghai Key Laboratory of Spacecraft Mechanism
Mocaxue Xuebao/Tribology | Year: 2011
In this paper, the transmission behaviors and tribological properties of the solid and grease lubricated XB1-60-150 harmonic drivers were studied under a range of temperature and overload condition. The results showed that in the temperature range of -50°C to 40°C and overload condition below 150%, both the solid and grease lubricated harmonic drivers exhibited good transmission behaviors. The transmission efficiency of the grease lubricated harmonic driver was better than that of the solid lubricated one. However, the solid lubricated harmonic driver showed more stable transmission efficiency under different temperatures and loads. After running 1.5 × 105 r of the wave generator, a strip examination of the two harmonic drivers using an optical microscope revealed that the surface of the flexspline and the circular spline was in a good condition with no signs of inordinate wear. The lubrication in this area had thus been fully effective. In addition, the effects of temperature, lubrication mode and load on transmission behavior of the harmonic driver were analyzed with an orthogonal design method for multi-factor analysis. The analysis results showed that the influence order of the tested factors were ranked as temperature > lubrication type > load condition.
Li B.,Shanghai Key Laboratory of Spacecraft Mechanism
Jixie Gongcheng Xuebao/Journal of Mechanical Engineering | Year: 2012
Thermal-vacuum tests are performed to evaluate the transmission performance of solid and grease lubricated XB1-60-150 harmonic drive. The effects of ambient temperature, output load, lubrication type, and operation time on the transmission performance of the harmonic drive are investigated based on orthogonal design method for multi-factor analysis, when the transmission efficiency is taken into account as an evaluation index. The transmission performance of the solid and grease lubricated harmonic drivers is studied under a range of temperature and rated load condition. The relationship of transmission efficiency of those to temperature and operation time is analyzed. After running 1.5×10 5 r of the wave generator, the morphologies of the gear teeth and the inner surface of the flexspline under different lubrication type are analyzed by using an optical microscope. It is found that the most important influencing factor on the transmission performance is temperature and the least important influencing factor is operation time. Lubrication type and output load are less important factors. In the temperature range of -40°C to 60°C, the transmission efficiency of grease lubricated harmonic drive is better, however, the solid lubricated harmonic drive shows obviously more stable transmission efficiency. The gear teeth and the inner surface of both the solid and grease lubricated harmonic drivers' flexspline show distinct traces of sliding movement after thermally-cycled test. © 2012 Journal of Mechanical Engineering.
Zhu C.-Y.,Fudan University |
Shao J.-M.,Shanghai Key Laboratory of Spacecraft Mechanism |
Na S.,Fudan University |
Tang G.-A.,Fudan University |
Tang G.-A.,Shanghai Key Laboratory of Spacecraft Mechanism
Zhendong yu Chongji/Journal of Vibration and Shock | Year: 2012
According to natural frequencies and modal damping parameters of a solar array system, an input shaper based on zero-displacement algorithm was designed and used to suppress residual vibration after attitude adjustment of the solar array. Through dynamics response simulation of the finite element model of the solar array, it was verified that the shaped rotation angle input function to drive the attitude adjustment of the solar array can suppress the residual vibration, and has a better robustness. At last, this results was verified experimentally with a scaled model of the solar array.
Li Y.,Xidian University |
Qiu Y.Y.,Xidian University |
Peng F.J.,Shanghai Key Laboratory of Spacecraft Mechanism
Applied Mechanics and Materials | Year: 2012
There are some problems in the control for a large flexible spacecraft on orbit such as the coupling, destabilization, and performance of the control system. To solve the problems, an active tuned mass damper (ATMD) is developed utilizing the piezoelectricity smart material, and an optimal output feedback control strategy is proposed based on the positive position feedback (PPF) method. The numerical simulations show that the developed ATMD/PPF method can suppress the flexible structural vibration induced by disturbances effectively. Using the method, the stability of the control system can be ensured and a good performance can be maintained even in case that the ATMD is in failure. © (2012) Trans Tech Publications.