Tang Dewei

Study on rigid-body guidance synthesis of planar linkage ☆

Abstract In this paper, the guidance-line rotation method of rigid-body guidance is presented. The method effectively solves the rigid-body guidance synthesis problem for the given more than three coupler positions. Using this method, satisfactory four-bar linkages can be obtained such as crank–rocker mechanism, double-rocker mechanism and double-crank mechanism for the given four, five or more than five rigid-body positions. A set of software is developed to realize the automatic design and visualization of guidance synthesis for four-bar linkage, which proves the method to be feasible and effective.

Development of an Inchworm Boring Robot(IBR) for planetary subsurface exploration

This paper proposes a novel Inchworm Boring Robot(IBR) for implementing investigations of scientific targets such as geothermal gradient, chemical composition, mechanical properties of regolith in the planetary subsurface. The IBR consists of three modules: a drilling module, a discharging module and a propulsion module. Drilling module and discharging module were respectively used to break and transport the regolith. Propulsion module can make linear motion between drilling module and discharging module. Therefore, IBR can achieve inchworm movement according to the timing motion of above three modules. In this paper, the two key tools, drill and auger, were elaborately designed and tested to figure out its load characteristics for future prototype of IBR. Next, the prototype of IBR was developed based on the tools design and a novel proposed transmission scheme. Finally, boring experiments for IBR were conducted on the test platform. In these boring experiments, IBR successfully access to 510mm depth in the regolith simulant and these results show that it is feasible for IBR to make borehole and carry out the planetary subsurface exploration.

The study of normal force model for the flow of lunar dust particles

Lunar dust can cause mechanical clogging and seal failures in lunar events, so it is essential to study the contact state of lunar dust particles which stuck in the mechanisms. The soft ball model based on Hertz theory is commonly used in particle contact problem. However, the assumptions of soft ball model are not applicable to lunar dust particles with irregular shapes and rough surfaces. To solve the problem, the power function model and exponential function model were proposed based on discrete element theory and nonlinear models in the rock and soil mechanics. The nonlinear relationship between normal force and displacement was obtained by static load compression test and the experimental data were imported into MATLAB to finish curve fitting. The experimental results show that the nonlinear stress-strain relationship of lunar dust particles can be most accurately described by the power function model. Meanwhile, the concept of equivalent elastic coefficient was introduced to simplify the simulating process. The lunar dust particles can be modeled as smooth spherical particles and the nonlinear stress-strain relationship can be described by equivalent elastic coefficient. With the new method, the theoretical model can be simplified and the simulation efficiency can be improved without affecting the model accuracy.