Variable-model SMA-driven spherical robot

In this paper, we introduce a bionic spherical robot. This research has been inspired by the muscular organs and modularity of organisms such as starfish and octopuses. The robot that we fabricated uses five soft feet to crawl like a starfish, and the robotic feet are driven by the shape memory alloy springs. The robotic spherical structure and the soft feet were fabricated by 3 D printing. The robotic feet were made of silicone gel; these feet could bend upward and downward to help the robot to crawl on the ground and roll down a slope. The shell separation module installed inside the robot could divide the robot into two identical modules, and this smart structure could enhance the robotic flexibility in a small space. We performed force analysis and robotic simulation, and the results verified the feasibility of the model. The robot can switch between rigidity and softness by using human control. Three types of gaits have been proposed for controlling robotic movement and improving robotic flexibility in movement; these include rolling, crawling, and avoiding obstacles. The results of this study indicate that the variable-model design of the robot is an effective way to enhance the flexibility of soft robots.     

A micro-adjusting attitude mechanism for autonomous drilling robot end-effector

Drilling end-effector is a key unit in autonomous drilling robot. The perpendicularity of the hole has an important influence on the quality of airplane assembly. Aiming at the robot drilling perpendicularity, a micro-adjusting attitude mechanism and a surface normal measurement algorithm are proposed in this paper. In the mechanism, two rounded eccentric discs are used and the small one is embedded in the big one, which makes the drill＇s point static when adjusting the drill＇s attitude. Thus, removal of drill＇s point position after adjusting the drill attitude can be avoided. Before the micro-adjusting progress, four non-coplanar points in space are used to determine a unique sphere. The normal at the drilling point is measured by four laser ranging sensors. The adjusting angles at which the motors should be rotated to adjust attitude can be calculated by using the deviation between the normal and the drill axis. Finally, the motors will drive the two eccentric discs to achieve micro-adjusting progress. Experiments on drilling robot system and the results demonstrate that the adjusting mechanism and the algorithm for surface normal measurement are effective with high accuracy and efficiency.     

Study on the general principle of normal circular-arc gear transmission

As a typical engineering application of basic principle of Bertrand conjugate surfaces, the general principle of normal circular-arc gear transmission, including paralleled-axis, intersected-axis and crossed-axis, is systematically studied. The research method, from datum surface to the directrix, is presented. The types of datum surfaces and the directrixes of all kinds of transmissions and the method to generate tooth flank of normal circular-arc gear are developed, and the investigation on the noninterference condition is performed by the curvature axis. Three typical normal circular-arc gear transmissions as loxodromic-type, geodesic-type and hyperboloidal-type under the condition of intersected-axis and crossed-axis are proposed.