Design And Analysis Of An Articulating Portable Foot Restraint

Extravehicular activity is one of the key technologies of manned spaceflight project, by which astronauts can complete ground targets observation, on-orbit servicing and assembly of various spacecraft and large space facilities and other tasks. Astronauts required a reliable fixed way during extravehicular operations in microgravity environment and also need to complete real-time adjustment to adapt the job needs. For this requirement, the paper designed a practical articulating portable foot restraint, it can provide effective foot constraints for astronauts, and can complete on-orbit adjusting by foot movement. Articulating portable foot restraint is easier to carry with compact structure and its operation is simple and flexible.The articulating portable foot restraint is composed of a foot cleat, a position and attitude adjustment unit, a load limiter and an active worksite interface. The overall program design is proposed from the function to achieve: first the foot cleat and the active worksite interface implementation scheme were proposed to connect astronaut, foot restraint and workstation interface; The foot restraint is adjustable in 3 axes that is yaw, roll and pitch, and yaw and roll joints can realize on-orbit adjusting by feet moving and can complete self-locking, so two kinds of design scheme was put forward and the function principle and control method were implemented in detail, determine the dividing helical gear transmission scheme as a better solution, and one-handed operation lock-unlock institutions for pitch joint were put forward; finally, in order to prevent destruction when the device overloads, supporting and loading mechanism were proposed to bear all direction of loads and its elastic elements and support components were design and selected. Thereby the structure of each unit was integrated to form a final design.According to the design target parameters and mechanical properties of the joints, each part of the foot restraint was designed in detail. According foot restraint force situation and performance requirements, finite element analysis was used to make stress and strain analysis to key parts, checking their strength and stiffness. Yaw joint and pedal link mechanism were simulated to verify their angle and force situation. Load limiter simulation was carried out to get its angular displacement and contact force situation under loading. To provide a reference to the astronauts for use, the attitude adjustment range and angle corresponding of the foot restraint were analyzed, and so were the stability and motion interference of the overall structure.Experiments were made to verify the feasibility of the foot restraint through the methods of partially structural vacant and transverse to simulate microgravity environment. Optical test platform was built to measure joint angles and make real-time monitoring of movement, thus verifying all aspects of integrated performance of the foot restraint.