Yan Shaoze

Thermodynamic analysis of a space station remote manipulator with a harmonic drive that considers an integrated thermal protection layer

To eliminate anomalies and improve the performance of a space station remote manipulator (SSRM) used in a dynamically changeable thermal environment, we analyze the thermodynamic behavior of an SSRM that considers an integrated thermal protection system (ITPS). Solar radiative heat gain and loss become equally significant as conductive heat transfers through the interior of the SSRM on orbit. A thermodynamic model of the SSRM with a sandwich ITPS structure is established on the coupling between harmonic drive and changeable thermal environment. A motion precision is proposed to evaluate thermodynamic behavior under continuously changeable thermal circumstances. Simulation results indicate that the ITPS with a corrugated sandwich structure reduces the maximum amplitude of angular position errors to 41.6%, which helps improve the motion precision of the SSRM. The feasible regions for the SSRM in the Low Earth Orbit (LEO) and Geostationary Earth Orbit (GEO) are analyzed, which shows that the proportion of feasible region in LEO is significantly larger than that in GEO.

Reliability analysis of the solar array based on Fault Tree Analysis

The solar array is an important device used in the spacecraft, which influences the quality of in-orbit operation of the spacecraft and even the launches. This paper analyzes the reliability of the mechanical system and certifies the most vital subsystem of the solar array. The fault tree analysis (FTA) model is established according to the operating process of the mechanical system based on DFH-3 satellite; the logical expression of the top event is obtained by Boolean algebra and the reliability of the solar array is calculated. The conclusion shows that the hinges are the most vital links between the solar arrays. By analyzing the structure importance(SI) of the hinges FTA model, some fatal causes, including faults of the seal, insufficient torque of the locking spring, temperature in space, and friction force, can be identified. Damage is the initial stage of the fault, so limiting damage is significant to prevent faults. Furthermore, recommendations for improving reliability associated with damage limitation are discussed, which can be used for the redesigning of the solar array and the reliability growth planning.

A measurement method for distinguishing the real contact area of rough surfaces of transparent solids using improved Otsu technique

An experimental method of measuring the real contact area of transparent blocks based on the principle of total internal reflection is presented, intending to support the investigation of friction characteristics, heat conduction, and energy dissipation at the contact interface. A laser sheet illuminates the contact interface, and the transmitted laser sheet is projected onto a screen. Then the contact information is acquired from the screen by a camera. An improved Otsu method is proposed to process the data of experimental images. It can compute the threshold of the overall image and filter out all the pixels one by one. Through analyzing the experimental results, we describe the relationship between the real contact area and the positive pressure during a continuous loading process, at different loading rates, with the polymethyl methacrylate (PMMA) material. A hysteresis phenomenon in the relationship between the real contact area and the positive pressure is found and explained.

Simplified Analytical Method of Radial Shock Response of Satellite-rocket Separation Interface

The shock induced by satellite-rocket separation is one of the severe mechanical environments that the spacecraft has to experience.An axisymmetric circular ring vibration model is established to analyze the radial shock response of the satellite-rocket separation interface during separation process.By using this model validated by finite element analysis,the influence on the radial shock response concerning band pre-tightening force,structural parameter of the interface ring,mass of clamp band and fixture block are discussed.It is shown that the radial shock of the satellite-rocket separation interface increases with the increase of the pre-tightening force of clamp band.Considering the mass of the band and fixture block,the release time of the strain energy stored in the interface ring is prolonged.In ensuring the reliable satellite-rocket connection and separation,it is an effective means of decreasing the interface shock to reduce the pre-tightening force of clamp band and to delay the release time of strain energy of the interface connection structures.