The Structural Design Of Planetary Sampling Arm And Its Trajectory Planning

The exploration of outer space is a hot topic in the current research, and the planetary sampling research is a very important part of it. In this paper, the lightweight low-power structural design of planetary sampling arm and its trajectory planning is mainly researched, which is a exploratory study under the background of the mars exploration program and the lunar exploration project in China.Firstly, the overall structural design is determined according to the task requirement, the designed sampling arm has four degrees of freedom which are all rotary joints. The joints are linked by the hollow rod, each joint mechanical structure is designed. The mast is replaced with triangle structure to support navigation camera in the designed sampling arm, then a mechanical locking device is designed to ensure the stability of triangle structure. The design reduces the weight and energy consumption substantially. The interference and collision in the motion of sampling arm is checked by the simulation software. The strength and stiffness is also analyzed by the finite element software. The results show that the design meets the requirements.Secondly, the kinematic model is established according to the designed mechanical structure of sampling arm. The forward kinematic model is established by D-H parameter method, the motion workspace is solved based on the forward kinematic model. The inverse kinematic model is established by algebraic method. The kinematics simulation is conducted by Robotics ToolBox to verify the correctness of the kinematic model.Thirdly, the trajectory planning algorithm of is analyzed based the established kinematic model. The trajectory planning in the joint space by cubic polynomial interpolation and five polynomial interpolation is analyzed and simulated. The simulation results show that, the cubic polynomial interpolation has smaller calculation, but it can’t ensure the continuity of angular acceleration; the five polynomial interpolation can ensure the continuity of angular acceleration, but it has larger calculation. The trajectory planning in the Cartesian space by space linear and arc interpolation is analyzed and simulated.Fourthly, the 3D motion simulation software is developed in the Windows platform by Visual C++ 6.0. The overall framework of software is set up by MFC, than 3D simplified model is drew by OpenGL, the kinematic model and the trajectory planning algorithm are added into the software. The simulation software effectively verify the correctness of the kinematic model and the trajectory planning algorithm. It can also visualize the simulation animation of trajectory planning, which provides a great reference for debugging of physical prototype.Finally, the debugging experiment of sampling arm physical prototype is carried on. The hard platform of sampling arm is set up which includes the link of controller、drivers and motors. The communication between the controller and the motion simulation software is realized so that the data solved by the simulation software can be sent to the controller to control motor. The experiment of the trajectory planning in the Cartesian space by space linear and arc interpolation is realized. The results of experiment further verify the correctness of the kinematic model and the trajectory planning algorithm.