Research On Gait And Structural Design Of Trinal-branch Robot Based On Trusses Of Space Station

The space environment is harsh,and the astronauts are very dangerous to complete the complex tasks such as observation and maintenance outside the space station.Space robots can replace astronauts on-orbit operations for a long time.For this reason,a large number of researches on space robots have been conducted at home and abroad.However,most space robots are still based on single-branch space robots,and some have mobile capabilities.Multi-branch space robots have more manipulators(branches),faster moving speeds,and can perform complicated operations such as moving while moving.There is currently no multi-branch robot system applied to a space station.In order to realize the mission of the future space station,it is necessary to design a robot capable of trussing the space station and reaching any position of the truss structure.In this paper,a trinal-branch climbing robot with 9 degrees of freedom and symmetrical structure is proposed for space station truss structure.Each branch has3 degrees of freedom.The axes of rotation of two joints far from the ends of the branches are parallel and perpendicular to each other.The axis of the inter-articular rod,the axis of rotation of the joint near the end of the branch coincides with the axis of the rod between the joints,and a dedicated holder is installed at the extreme ends of the three branches.The special holder installed at the end of the branch is composed of a space linkage mechanism,a crank-slider mechanism and a parallel four-bar mechanism.The principle is that the rotation of the rudder plate causes a change in the projection length of the space connecting rod in the axial direction of the rudder plate to drive the crank slide.The slider of the block mechanism translates and is clamped inwards by the crank slider mechanism and the driving clamp jaws of the parallel four-bar linkage mechanism,and can be used to move the robot in the space truss.The trinal-branch robot can use a ulnar gait,a circumgyrating gait,a rolling gait,a moving gait,and a feeding gait to perform load handling,rotation around the truss member,rapid movement,and movement between the truss members.A three-legged robot gait planning method was proposed for the trinal-branch robot structure.Several key attitudes of each gait of the robot were found during robot gait planning.The joints were rotated at the minimum angle between the key attitude transitions.The trapezoidal velocity curve is used for planning,and the restof the joints are controlled in a manner that is proportional to angular velocity and angular acceleration.The three-arm robot attitude conversion gait planning method proposed in this paper simplifies the kinematic analysis calculation,and lays the foundation for the trinal-branch robot motion trajectory planning,coordination operation and future space applications.