Research on the drilling winch control system for clean sampling of Antarctic Subglacial Lakes

Abstract

Antarctica, with a large number of ice sheets, is among the last unexplored places on Earth. The subglacial lakes beneath these ice sheets have been isolated from the outside world for up to 35 million years, containing a diverse group of marine organisms and other materials. Its unique hydrological environment provides insights regarding microbial evolution and past climates on Earth, which have become central to interpreting the process of landscape evolution and assessments of possible future climate change. Clean sampling of subglacial lake water without introducing surface biological or other type of contamination has long been a goal of the international scientific community. The overlying ice thickness can reach thousands of meters and in conventional deep ice drilling, drilling fluids are employed while the boreholes exposed to the atmosphere. The only method for penetration is thermal drilling with the rate proportional to the vertical diameter of the drilling rig, which requires the drill body to be as thin as possible. The melted ice/water in the upper borehole will refreeze immediately once penetrating into the ice layers. Cables, thereby, need to be configured inside the drilling rig since separate cables from the external surface are not applicable in such cases. The drill rig comprises the motor-driven winch, outer surface heating system, control system as well as sampling system, totaling 600 kg in weight. Gear reducers are required during the cable lowering/lifting operations with a maximum outer diameter of the winch of 140 mm and a high-precision automatic synchronization between the reducers and cable lowering/lifting system is required. An automatic tension sensor along with a winch control system is designed to realize thee automatic synchronization between the gear reducers and the cable lowering/lifting system through servo control.