401 Microspine Gripping Mechanism for Asteroid Capture  

Ezekiel G . Merriam*, Andrew B . Berg**, Andrew Willig**, Aaron Parness**, Tim Frey+ and Larry L . Howell++ 

Abstract  

This paper details the development and early testing of a compliant suspension for a microspine gripper  device for asteroid capture or micro -gravity percussive drilling. The microspine gripper architecture is  reviewed, and a proposed microspine suspension design is presented and discussed. Prototyping methods  are discussed, as well as testing methods and results. A path forward is identified from the results of the testing completed thus far. Key findings include:   the microspine concept has been established as a valid  architecture and the compliant suspension exhibi ts the desired stiffness characteristics for good gripping  behavior. These developments will aid in developing the capability to grasp irregularly shaped boulders in micro -gravity . 

Introduction    Recent exploration efforts have been focused on Mars and near -earth asteroids. However, current mobility  technology (e.g. , wheeled vehicles and touch- and-go probes) are inadequate for detailed exploration of  sub-surface Martian caverns or the micro -gravit y environment of asteroids  [1]. Gravity -independent  microspine grasping mechanisms have  been demonstrated to have the necessary mobility to access these  difficult terrains. Proof -of-concept robots such as SpinyBot and Lemur IIB  have been shown to provide  climbing capability and gripping force in the presence of gravity, and have additionally been demonstrated   to function in inverted, harder -than- zero-g tests  [2]. 

A central element of these systems i s the mounting of spines to compliant suspensions  that permits the  system to conform to rough surfaces, placing a large fraction of many s pines in contact with the surface [3].  Many microspine grippers thus far demonstrated have  relied on polymer and elastomer flexure elements   (the part of the suspension that deflects to achieve motion) , which will not perform adequately in the space  environment. To advance the technology and enable missions in space, the flexure components of the  microspine must be converted to space- grade materials  that will function robustly in the space environment.    This paper details the current state- of-the-art of microspine graspers, discusses the current proposed  flexure system, and presents the testing methods used to validate the new flexure design. Results are discussed and design refinements are proposed.  

Background   Microspine grippers seek to imitate insects and arthropods that use the large numbers of small spines to climb surfaces  [3]. These spines engage with asperities on rough, hard surfaces to provide grip. Because  the number of spines is large, the load can be distributed among the spines so that the load on an individual  spine can be quite small and still in aggregate react  large forces  normal to the surface. In robots, these  spines can are mounted on an architecture of  hierarchical compliance:   robotic arms position the gripper  over the surface to be grasped, a linkage arm positions cassettes along macro contours of that surface,  and microspines opportunistically grasp local surface asperities to provide grip. The motion of an individual microspine allows it to conform to small -scale surface roughness, and is provided by a compliant  suspension.                                                          * Brigham Young University, Provo UT   ** Jet Propulsion Laboratory, California Institute of Technology , Pasadena CA   + Rochester Institute of Technology , Rochester NY   ++ Brigham Young University, Provo UT  

Proceedings of the 43rd Aerospace Mechanisms Symposium, NASA Ames Research Center, May 4-6, 2016