Self-localization is one of the most important aspects for using mobile robots in unstructured environments. In this paper, the authors introduce a new approach for a self-localization and navigation unit for mobile p...Self-localization is one of the most important aspects for using mobile robots in unstructured environments. In this paper, the authors introduce a new approach for a self-localization and navigation unit for mobile platforms in extraterrestrial environments, based on the authors＂ successful results in self-localization of forestry machines on earth. The presented approach is developed from a highly modular concept, which allows a simple but efficient adaption to specific applications by just substituting some scenario dependent components. In this paper, the authors will explain the general concept and the terrestrial implementation so far. On this basis, the authors will demonstrate and discuss the necessary adaptions to the general concept in order to handle the different conditions on extraterrestrial surfaces.展开更多
To enhance the reliability and to extend service life of packing rings, tribological and sealing perfor- mances are investigated based on the experimental results. Friction force, leakage rate and power consumption of...To enhance the reliability and to extend service life of packing rings, tribological and sealing perfor- mances are investigated based on the experimental results. Friction force, leakage rate and power consumption of three materials of pressure packing seals are measured in a refitted vertical gas compressor. The rings are made of common filled polytetrafiuroethylene （Filled PTFE）, PTFE reinforced with 30% mass fraction carbon fiber （30%CF^PTFE）, and carbon-carbon composites infiltrated with PTFE （C/C＋PTFE）, respectively. It is found that packing rings will periodically vibrate with the periodic vibration of pressure packing after the travel direction of motion abruptly turns to the reverse direction. Furthermore, the amplitude of vibration slows down with the increasing crank angle. Approximate value of friction force is available by multiple-point fast Fourier transformation （FFT） employed to process the experimental results by reducing the impact of vibration to a great extent. Of three materials of rings employed in experiments, Filled PTFE presents minimal leakage rate accom- panied with maximum power consumption. And 30%CF＋PTFE exhibits minimum friction power and moderate leakage rate. As for C/C＋PTFE, its high mechanical and thermal properties are favorable factors to enhance the ability of operating under high pressure and velocity and to improve the wear resistance. Unfortunately, this also leads to a large leakage rate. Comprehensive consideration should be taken into to evaluate the availability, reliability and service life for a type of packing ring under dry running conditions.展开更多
文摘Self-localization is one of the most important aspects for using mobile robots in unstructured environments. In this paper, the authors introduce a new approach for a self-localization and navigation unit for mobile platforms in extraterrestrial environments, based on the authors＂ successful results in self-localization of forestry machines on earth. The presented approach is developed from a highly modular concept, which allows a simple but efficient adaption to specific applications by just substituting some scenario dependent components. In this paper, the authors will explain the general concept and the terrestrial implementation so far. On this basis, the authors will demonstrate and discuss the necessary adaptions to the general concept in order to handle the different conditions on extraterrestrial surfaces.
文摘To enhance the reliability and to extend service life of packing rings, tribological and sealing perfor- mances are investigated based on the experimental results. Friction force, leakage rate and power consumption of three materials of pressure packing seals are measured in a refitted vertical gas compressor. The rings are made of common filled polytetrafiuroethylene （Filled PTFE）, PTFE reinforced with 30% mass fraction carbon fiber （30%CF^PTFE）, and carbon-carbon composites infiltrated with PTFE （C/C＋PTFE）, respectively. It is found that packing rings will periodically vibrate with the periodic vibration of pressure packing after the travel direction of motion abruptly turns to the reverse direction. Furthermore, the amplitude of vibration slows down with the increasing crank angle. Approximate value of friction force is available by multiple-point fast Fourier transformation （FFT） employed to process the experimental results by reducing the impact of vibration to a great extent. Of three materials of rings employed in experiments, Filled PTFE presents minimal leakage rate accom- panied with maximum power consumption. And 30%CF＋PTFE exhibits minimum friction power and moderate leakage rate. As for C/C＋PTFE, its high mechanical and thermal properties are favorable factors to enhance the ability of operating under high pressure and velocity and to improve the wear resistance. Unfortunately, this also leads to a large leakage rate. Comprehensive consideration should be taken into to evaluate the availability, reliability and service life for a type of packing ring under dry running conditions.
