Design and performance evaluation of embedded micro stiffness sensor for On-Orbit service tools

Abstract

On-orbit service of the space station is a vital mission. The space station will be in orbit for many years, and parts would break down and instruments could fail in tight space. This research focuses on the needs of on-orbit maintenance operations in tight space and designs an end tool with embedded micro-sensors. The pressure & deformation sensing module is designed based on the principle of polyurethane flexible plate and metal strain film. The sensor module uses alloy as the housing to form a stiffness sensor, built into the end tool to achieve a single sensor envelope size in the range of 15*15*13 mm3. Calibration results indicate that the overall stiffness of this sensing unit is approximately 12000 N/mm, capable of sensing material stiffness within the range of 50 N/mm ∼ 12000 N/mm. Through multiple measurements and root mean square error (RMSE) analysis, it is shown that the uncertainty of different sensors is within the acceptable range compared with the standard data. The results of the fatigue test and simulated temperature test in the space station show that the performance of the stiffness sensor can meet the normal operation requirements in the space station environment. Comparisons with geometric dimensions, accuracy, sensitivity, and measurement precision show that the uncertainty between different position sensors, metal strain film sensors, and standard sensors does not exceed 1.8 %. The research results confirm the potential of this stiffness-sensing unit in future space missions and dexterous operations applications.